Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
the management of parkinson 's disease ( pd ) is often enhanced by complementary rehabilitation strategies , such as exercise .
for example , studies of resistance [ 13 ] and endurance [ 47 ] exercise training have improved balance , gait , postural stability , and physical function and reduced falling in people with pd .
tai chi , a traditional chinese martial art that involves meditation and slow , graceful movements , is often recommended to reduce stress , improve mood , flexibility , physical function , and balance [ 810 ] .
studies of tai chi in people with chronic disease including parkinson 's disease and old people have supported the potential for benefit , with gains in the quality of life , postural stability , gait , physical function , immune function , cardiometabolic disease risk factors , and other health - related parameters [ 4 , 1119 ] . however , research on the effectiveness of tai chi is contradictory due to inconsistencies in the implementation of the tai chi movements , limited samples , and the lack of randomized control trials .
the purpose of this study is to investigate the effects of a randomized control trial of therapeutic tai chi training on improving the motor function and physical function of parkinson 's disease patients .
all participants gave informed consent in accordance with the procedures of the parkinson 's disease center and the sports medicine center of the asan medical center .
the participants of this study were 24 clinically stable patients with diagnosed idiopathic parkinson 's disease recruited from the parkinson 's disease center in asan medical center in seoul , republic korea .
eligible participants met the following inclusion criteria : ( 1 ) hoehn - yahr stage 1 or 2 and ( 2 ) stable drug regimen .
volunteers were excluded from the study if they had ( 1 ) severe cognitive impairment , ( 2 ) concomitant severe neurologic , cardiopulmonary , or orthopedic disorders , ( 3 ) specific contraindications to exercise , or ( 4 ) they had recently participated in any physiotherapy or rehabilitation program .
the volunteers were screened for inclusion and exclusion criteria based upon the medical history and physical examination .
participants were randomized to either a twelve - week intervention of therapeutic tai chi ( ttc ) or a non - exercise control group ( see figure 1 ) .
the ttc group visited the clinic 2 times a week and performed home - based activity 1 time per week for 12 weeks .
each ttc session started with a 10-minute stretching exercise warm - up , followed by 30 minutes of tai chi exercises , and ending with 10 minutes of meditation and 10 minutes of stretching exercise cool - down .
the exercise was performed within the intensity ranges of 11 to 15 ( light to somewhat hard ) on the borg ratings of perceived exertion ( rpe ) scale .
study outcome measures were obtained at baseline ( prerandomization ; one week prior to the start of the program ) and within one week following the end of the 12-week intervention .
the outcome measures included several test of physical function ( lateral stance , agility , tandem gait , timed up and go , and six - minute walk ) and the unified parkinson 's disease rating scale ( updrs ) sections 13 .
all the tests were performed in the same order , at the same time of day , and when the participant felt best .
the participant stands with hands on hips with eyes closed ; when ready , the participant stands on the foot of choice for as long as possible , with the knee of the other leg flexed to 90 degrees .
when a light comes on , they jump up as fast as possible in response to a single light stimulus .
the tandem gait test   was used to assess balance , appendicular coordination , and gait , which involves multiple sensory and motor systems .
the participant walks in a straight line while touching the heel of one foot to the toe of the other with each step . for the timed up and go test , the participant was seated in an arm chair ( 45  cm high ) with their back against the chair . on a signal
, they stand up , walk 3 meters as quickly and safely as possible , turn around , walk back to the chair , and sit down with their back against the chair .
the six - minute walk test   was applied as a test of cardiorespiratory endurance for daily physical activities .
this test measures the distance that can be walked at a self - paced velocity on a flat hard surface over a period of six minutes .
an analysis of variance ( anova ) for repeated measures with one between factor ( treatment group ; ttc versus control ) and one within factor ( time ; pre- and postintervention ) was used to evaluate the effects of the intervention .
a total of 11 participants were randomized to the ttc and 11 participants to the control condition .
two subjects in the control group did not complete the study for personal reasons unrelated to the study .
as shown in table 3 , significant changes were observed in the mentation , behavior , and mood subscale and the motor subscale of the updrs , with no significant main effects on the activities of daily living scale ( adl ) , balance , or reaction time .
however , there were significant interactions between time and intervention group on the updrs activities of daily living subscale ( figure 2 ) .
however , as shown in figures 3 and 4 , there were significant ( p < 0.05 ) interaction effects for balance ( one - leg standing test ) and reaction time ( light stimulus ) .
in this study , we investigated the motor and nonmotor effects of therapeutic tai chi exercise training on participants with pd .
the findings of our study showed modest effectiveness of tai chi training on people with parkinson 's disease , with significant interaction effects for balance , reaction time , and adls .
these findings support that tai chi is effective in improving some aspects of motor function , most notably reaction time and balance .
in addition , pd participants reported an improvement in their ability to engage in their activities of daily living .
exercise therapy has a major role in the rehabilitation of the patients with parkinson 's disease [ 26 , 27 ] .
regular physical activity may increase the functional ability and enhance the capacity for independent living by decreasing the need for assistance with the activities of daily life .
in addition , exercise may achieve the goal of neuroprotection , slow disease progression , and postpone disabilities [ 28 , 29 ] .
several cohort studies have described the functional achievements of moderately affected parkinson 's disease participants who have undergone intensive standardized exercise training [ 3033 ] .
however , burini et al .   reported in a study with a crossover design that a 7-week tai - chi and aerobic exercise training did not affect the severity of neurological signs and symptoms as assessed by the updrs or have any significant impact of training on the attendant disability .
.   showed that physical therapy is mainly focused on mobility rather than various neurologic symptoms such as rigidity and tremor .
reported that some aspects of the mobility and balance functions were positively affected by tai chi exercise .
however , assessing the mobility and balance function by only one item , such as the walking function , is not very representative of the spectrum of the motor signs and symptoms .
furthermore , there is little attention toward non - motor symptoms such as fatigue mood and health quality of life , all of which may be altered by exercise [ 27 , 3740 ] . in a recently published clinical trial ,
li et al .   found beneficial effects of tai chi exercise on balance , physical function , and falls , suggesting that tai chi is an appropriate physical activity for patients with parkinson 's disease and it might be useful as a therapeutic exercise . the ability to balance is related to the control of the center of gravity within the base of support .
koller and huber   found that the balance impairment in older adults with a longer duration of pd does not usually respond to levodopa ; 38% of the persons with pd experience fall , 13% fall more than once per week , and some studies have reported that pd patients fall repeatedly throughout the day .
persons with pd are 5 times more likely to suffer falls - related injuries such as hip fractures than healthy older adults .
reaction time for agility was measured in the present study and improved with ttc training .
ttc training has benefits for postural stability in elderly people , including patients with pd , likely by acting on a number of sensorimotor systems that contribute to postural control [ 12 , 43 , 44 ] .
this improvement combined with the observed improved agility performance confirms the separate observations of previous studies showing that ttc training results in better balance capacity , proprioception function , and muscle strength [ 11 , 4547 ] .
while our study and other studies have shown enhanced balance and agility resulting from tai chi , further work is needed to confirm that these improvements in fall risk factors actually result in fewer falls , as there are somewhat contradictory findings in the literature [ 19 , 45 , 48 ] .
physical function refers to the assessment of the capability to complete a specific task rather than assessing the physiologic - derived attributes , and it is believed to reflect the ability to carry out activities of daily living . in the present study , we assessed the physical function with the timed up and go , tandem gait , and six - minute walk tests .
the timed up and go test showed no significant change after training , which is in contrast to the findings of li et al . .
these differences may be due to differences in the programs of tai chi , the wider range of disease severity in the study by li et al . , or the smaller numbers of participants in our study .
the timed up and go test largely depends on the muscular power and strength of the quadriceps and the hip extensor muscles to arise from a chair [ 49 , 50 ] .
it may be that our version of tai chi does not substantially improve lower extremity power .
the results of the tandem gait test and the six - minute walk test were also not changed after 12 weeks of ttc training .
poor performance on the tandem gait and six - minute walk could result from several potential factors , including poor cardiorespiratory fitness and gait or balance abnormalities [ 23 , 51 ] .
many of the pd participants likely had poor cardiorespiratory fitness and inadequate levels of physical activity , as shown by garber and friedman .
consistent with this finding , all of the participants in this study had below normal results on the six - minute walk test , suggesting that poor cardiorespiratory fitness , gait , and/or balance may have been an important determinant of performance .
other studies of tai chi have not shown an improvement in cardiorespiratory fitness , and our results are consistent with these previous findings .
this study investigated motor function and the severity of motor and non - motor symptoms and signs .
these motor and nonmotor symptoms and signs were not improved after treatment , although self - reported engagement in activities of daily living was enhanced by tai chi exercise .
ttc training involves splitting up complex movements into simple motor tasks and incorporating simultaneous movements , which is also beneficial for parkinson disease patients .
thus , this study lends additional evidence for tai chi as a complementary treatment for people with parkinson 's disease  one that will allow them to engage more fully in their activities of daily living .
further studies are needed that will consider the effects of various components of a tai chi program and also to help to identify the intensity , duration , and frequency of tai chi exercise to attain optimal benefits .
further , the influence of various medication and dietary factors may moderate the effects of exercise , and this has also not been studied .

Answer:
objective .
 the purpose of the study was to investigate the effects of a 12-week program of therapeutic tai chi on the motor function and physical function of idiopathic parkinson 's disease patients ( pds ) .
 methods . the participants were 22 clinically stable pds in hoehn - yahr stages 1 - 2 randomly assigned to a therapeutic tai chi group ( ttc , n = 11 ) or a control group ( con , n = 9 ) .
 two subjects in control group did not complete the study for personal reasons .
 ttc was performed three days a week ( 60  min / session ) .
 motor symptoms by the updrs were assessed , and tests of physical function were administered before and after the 12-week trial . results .
 the ttc group , as compared to the con group , showed changes in the mentation , behavior , mood , and motor scales of the updrs ( p < 0.05 , p < 0.01 , resp . ) , with no significant main effects on the activities of daily living scale ( adl ) .
 however , there was a significant interaction between the time and intervention group on adl ( p < 0.05 ) .
 there were no significant main effects for any of the physical function variables .
 there were significant interaction effects in balance and agility ( p < 0.05 , resp . ) . conclusions .
 this study showed that ttc training had modest positive effects on the functional status of parkinson 's disease patients .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
retinoblastoma ( rb ) is the most common intraocular malignant tumor in childhood , with an incidence of 1 in 15000 live births .
it may affect one eye ( unilateral rb ) or both ( bilateral rb ) during the first five years of life .
although   extensive epidemiologic studies have been done to study   this tumor , the results have been more often misinterpreted at   the expense of mutation theory which has prevailed until recently in spite of the outstanding evidence against it . in the present review
the authors analyze the most relevant epidemiological issues concerning retinoblastoma , in the light of recent developments highlighting the role of aneuploidy and genetic instability   in the pathogenesis of this eye cancer .
the most important studies to investigate the pathogenesis of retinoblastoma began with a paper published by knudson in 1971 , when the author , after investigating the age distribution and laterality of a cohort of 48  rb patients , concluded that the disease could be inherited and formulated the so - called  two - hit theory  in order to explain its pathogenesis . in reality , no clues about the inheritance of retinoblastoma could be deducted from such a small sample .
in fact , in his first report on this matter , knudson referred to earlier , smaller series showing that , in retinoblastoma survivors with bilateral disease , the proportion of affected offspring closely approximated   50% , as in dominant ( mendelian ) inheritance . from an original , mathematical analysis of the above data , knudson inferred that retinoblastoma is caused by two sequential ( two hit ) mutational events . according to this hypothesis , in the dominantly inherited form of the disease ,
one mutation is inherited via the germinal cells and the second spontaneously occurs in somatic cells of the retina and other tissues of the body . on the contrary , in the nonhereditary form
the different timing and cell type involved by the two mutations determines the different clinical phenotype , with all bilateral and a minority of the unilateral cases being classified as hereditary , and the remaining unilateral cases being included in the sporadic group ( table 1 ) . during the following forty years of epidemiological , clinical , genetic , and biological research in this field , with the discovery of the rb1 as the prototype tumor suppressor gene , the medical establishment agreed on the pathogenetic  two - hit  theory which was further expanded by knudson , in many other scientific articles and review papers [ 624 ] .
this generated the widespread conviction that rb is caused by two mutational events leading to the loss or inactivation of both alleles of the rb1 gene , as still believed by some authors .
as mentioned above , the original input into the possible genetic derivation of retinoblastoma was based on limited evidence showing an apparently dominant mendelian distribution of the disease in the offspring of bilaterally affected individuals , thus allowing knudson to conclude that bilateral rb is inherited through the germ cells .
minimum or no disagreement   had been appeared on this account in the literature during the last four decades . in an attempt to elucidate this issue ,
we have performed an analysis of the distribution of the disease in the offspring of unilaterally affected rb survivors , referred to the department of ophthalmology
we discovered that in a total of 16 children born to 12 unilaterally affected patients , 8 ( 50% ) were healthy and 8 ( 50% ) affected with rb ( table 2 ) . using the reasoning of knudson
, it would be easily concluded that the unilateral disease phenotype is inherited and not sporadic , and this would be in sharp contrast with the current knowledge according to which bilateral rb is  always  hereditary and unilateral rb is  almost always  sporadic .
it was reported by knudson   and confirmed by others   that about 10% of all rb cases do have a  positive family history  . in other words , the family history of the  index  case offers at least one other affected member , either a parent or another close relative . in this case , it is assumed that the events leading to the inactivation of the rb1 gene run in the family , and therefore the first
hit  is transmitted through the germline , exactly what happens in bilateral rb , but with one difference ; bilateral rbs , which after knudson are all to be considered  hereditary  , are also assumed to have inherited the  first hit  through a mutation in one of the parent 's germ cells , but they are the only affected members in their families .
we should therefore be reasoning that , since familial rbs share the same pathogenetic mechanism with bilateral ( hereditary ) rb , the vast majority of these cases should show the bilateral phenotype . to be more accurate ,
we could make a calculation of the percentage of familial rbs carrying the unilateral phenotype . as a matter of fact
, table 1 shows that the unilateral phenotype accounts for about 1/3 of all hereditary cases ( or about 30% ) , and since familial rb represents the 10% of all rbs , it comes out that rbs carrying the unilateral phenotype , within the familial group , should not be more than 3% ( i.e. , the 30% of the 10% ) . as a matter of fact , a meta - analysis of a cohort of 3584 patients ( table 3 ) , reported by us elsewhere [ 4 , 5 ] , reveals that on a total of 344 ( 9.5% ) familial cases , 83 ( 24% ) show the unilateral phenotype , instead of the predicted 3% , a rather unexplainable figure , in the light of the predictions made by the
in 1986 , potluri and coworkers observed that the association of rb with the constitutional chromosome 13q deletion syndrome and the finding of 13q deletions or monosomy 13 in rb cells in individuals with normal constitutional karyotypes seemed to suggest that chromosome 13q could contain a gene responsible for tumor development in retinoblastoma .
although the authors themselves acknowledged that other chromosome abnormalities , in addition to those involving chromosome 13 , are evident in retinoblastoma ( additional copies of 1q material in 44% of cases , isochromosome 6p , in 45% of cases , monosomy 16 , in 18% of cases , marker 1p+ , in 13% of cases , and homogeneously staining regions and double minutes , in 9% of cases ) , further investigations on this matter stressed the role of 13q deletions in the genesis of rb , thus reinforcing the belief that the loss or inactivation of the rb1 was the only responsible for rb to develop .
but it is well known that retinoblastoma is only one among many different tumors associated with deletions of chromosome 13 .
cancers linked with these deletions include chronic lympocytic leukaemia ( cll ) , chronic myeloproliferative disorders , multiple myeloma , hepatocellular carcinoma ( hcc ) , nasopharyngeal carcinoma , benign and low - grade malignant lipomatous tumors , bladder cancer , malignant mesothelioma , and prostate cancer .
the same pleiomorphism in the phenotypic expression of cancers associated with rb1 gene mutations   is therefore evident in 13q deletion syndrome .
but the most important consideration to be made about the association of 13q deletion syndrome and rb concerns the evident discrepancy existing between the expected and the real number of bilateral tumors among the patients affected by this genetic disorder . as a matter of fact
, the 13q deletion syndrome must be confirmed by the cytogenetic analysis of peripheral blood lymphocytes , and it is   due to a
deletion of the long arm of chromosome 13 which involves , by definition , the rb1 gene locus . since the  constitutional  deletion of the rb1 gene can only be present if transmitted through the germ cells of one parent , it follows that all patients affected by 13q deletion syndrome and retinoblastoma belong to the  hereditary  group of knudson 's and must , therefore , express the bilateral disease phenotype .
it happens , however , that this assumption does not fit the clinical reality . in table 4 a series of 13 cases of 13q deletion syndrome and retinoblastoma referred to us over the last four decades is reported .
of these patients , only 4 had the bilateral disease phenotype , while the remaining 9 were unilaterally affected ( table 4 ) .
the mean age at diagnosis in this group , which is about 10 months , further reinforces the assumption that they must belong to the  hereditary  group   of knudson 's , but the unilateral disease phenotype is unexplainably high . in the light of the  two hit  theory ,
the data summarized above do not have any   rationalization , and the only plausible conclusion is that the assumptions made   in regard to the role of the rb1 gene in retinoblastoma are incorrect .
clinical epidemiology is a leading discipline in the understanding of disease pathogenesis and etiology , but , as any other scientific endeavor , it relies on the correct interpretation of the available data .
the proper analysis of data , in turn , relies not only on the individual researcher 's skill but also on social , economic , and political environment in which the data are analyzed .
the presumed genetic origin of rb and its relationship with the rb1 gene represent a clear example of how an entire body of prominent researchers may fail to question a flawed pathogenetic hypothesis ( i.e. , the  two - hit  theory ) , for the sake of personal , academic , or other interests .
it was not by chance that we had to approach many different scientific journals to have access to the medical community about the role of aneuploidy and genomic instability in the genesis of rb [ 4 , 5 , 39 ] .
we are still optimistic , however , because our alternative pathogenetic explanation has finally appeared in recent ophthalmologic literature .

Answer:
retinoblastoma ( rb ) is considered to represent the prototype of cancer linked to the sequential loss or inactivation of both alleles of a so - called  tumor suppressor gene  , the rb1 gene .
 the pathogenetic mechanism behind this tumor was first hypothesized by knudson in 1971 and further confirmed by others   who identified the rb1 gene whose loss or inactivation was claimed to be responsible for the disease .
 however , after about four decades of continuous research in the field of molecular biology , the evidence behind the role of the rb1 gene in rb appears to be seriously flawed in the light of epidemiological , biological , and clinical evidences .
 this editorial summarizes the inconsistencies on this subject .
 nevertheless , the molecular biology establishment still adheres to the biased view of the genetic origin of rb and other cancers , and hardly any alternative explanations are taken into account .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
desktop computer and laptop use is becoming common , and computing - related musculoskeletal
 symptoms are considered important health problems in university students and office
 workers1,2,3,4 .
previous studies have indicated that improper sitting posture
 during visual display terminal ( vdt ) work ( e.g. , desktop computer or laptop use ) can induce
 musculoskeletal disorders , especially low - back pain3 ,
 4 ) .
carter and banister3
 suggested that increased tension in ligaments and discs during a slumped sitting posture may
 lead to low - back pain .
cross - legged sitting , a commonly adopted posture during daily living and vdt work , has been
 reported to induce a slumped sitting posture5 , 6 .
lee et al.5 showed that the cross - legged sitting
 position leads to a greater slumped posture compared with an upright sitting posture during
 vdt work . to prevent the unwanted slumped posture , it is crucial to identify factors that
 contribute to slumped posture during cross - legged sitting .
limited hip flexion range of
 motion ( rom ) could be one possible risk factor for excessive lumbar flexion . because the
 lumbar spine and hip joint are connected via the pelvis
, limited hip flexion can cause
 greater lumbar flexion through pelvic posterior tilt during the trunk flexion - related
 posture7 .
although it seems reasonable that limited hip flexion rom leads to greater lumbar flexion
 during the cross - legged sitting posture , no study has investigated how hip flexion rom
 influences the kinematics of the lumbar spine in the cross - legged posture during vdt work .

furthermore , previous studies have not determined whether greater lumbar flexion during vdt
 work with a cross - legged sitting posture changes trunk muscle activities as measured by
 electromyography ( emg ) .
only one emg study revealed decreased emg activity in the internal
 oblique ( io ) muscles during the static cross - legged sitting posture compared with the static
 normal sitting posture8 .
thus , the aim of
 the present study was to compare the lumbar flexion angle and trunk muscle activity in
 individuals with and without limited hip flexion rom during vdt work with a cross - legged
 sitting position .
all subjects showed
 right - leg dominance and performed computer work more than 20 hours per week .
measurements of
 the right hip flexion rom were used to classify subjects into the experimental or control
 groups . according to previous findings9
,
 sufficient hip flexion rom was defined as more than 120 of hip flexion , and limited hip
 flexion rom was defined as 110 in this study .
subjects with more than 120 of right hip
 flexion rom ( one female , six males ) were classified into the control group , and subjects
 with no more than 110 of right hip flexion rom ( eight males ) were classified into the
 experimental group .
subjects were excluded if they had acute low - back pain , orthopedic
 damage , or lower extremity injury during the last 6 months .
in addition , individuals with
 hip flexion rom between 110 and 120 were also excluded in this study .
the inje university
 faculty of health science human ethics committee approved this study , and each subject
 signed an informed consent form before participation . to measure hip flexion rom ,
subjects were placed in the supine position on a table , and an
 examiner passively flexed the right hip of subjects until further hip flexion was limited by
 firm end feel9 .
the fulcrum of a
 goniometer was placed on the greater trochanter , and the proximal and distal arms were
 aligned with the lateral midlines of the pelvis and femur , respectively .
the lumbar flexion angle was measured using eight vicon mx - t10 motion capture systems
 ( vicon motion systems ltd . ,
three reflective
 markers were placed on the bilateral anterior superior iliac spines and on the midpoint
 between the bilateral posterior superior iliac spines for the pelvic segment .
additionally ,
 four reflective markers were attached to the first and second lumbar spinous processes and
 3  cm bilaterally from the second lumbar spinous process for the lumbar segment .
the lumbar
 flexion angle was calculated by assessing the anterior rotation of the lumbar segment with
 respect to the pelvic segment using the cardan angle10 .
the trunk muscle activity of the bilateral rectus abdominis ( ra ) ,
 external oblique ( eo ) , and io muscles was recorded using a synchronized surface emg system
 ( delsys inc . ,
prior to attachment of the electrodes , skin preparation was
 performed by shaving the hair and cleansing with an alcohol swab .
each electrode was
 attached along the direction of the muscle fiber based on placements suggested by
 criswell11 .
emg signals were acquired
 at a sampling rate of 1,000  hz with a bandwidth of 20450  hz and converted into
 root - mean - square ( rms ) data . to normalize emg data of the trunk muscles , reference voluntary
 contraction ( rvc ) data of trunk muscles
were collected when subjects were seated on a chair
 in a comfortable sitting posture with 90 of hip and knee flexion for 40 s. the rvc maneuver
 was repeated three times , and the mean value of the average muscle activity for the middle
 30  s of the three trials was used to normalize trunk muscle activity . prior to vdt work , a laptop ( xnote r400 , lg , seoul , korea ) was placed on a 73-cm - high desk ,
 and subjects sat on a height - adjustable chair without a backrest with 90 of hip and knee
 flexion .
the examiner confirmed the 90 hip and knee flexion position using a goniometer .
 for vdt work with a cross - legged sitting posture ,
subjects were instructed to cross the
 right leg over the left by putting the right knee on the left knee5 , 8 . following
 cross - legged sitting ,
subjected performed typing work in which they copied some text
 provided on the monitor by the korean version of hansoft .
the subjects typed for 1  min for
 each trial , and three test trials were conducted with 30-s rest periods between trials .
the
 average values of the lumbar flexion angle and emg activity of the trunk muscles for the
 middle 40  s of each trial were collected , and the mean values of three test trials were used
 for data analysis .
the subjects characteristics ( age , height , weight , hip flexion rom ) , lumbar flexion angle
 and trunk muscle activity during vdt work with cross - legged sitting in the experimental and
 control groups were compared using independent t - tests .
, chicago , il , usa ) was used , and the statistical significance level
 was set at p = 0.05 .
the general characteristics of the subjects in the control group ( mean age 25.1
 1.5  years ; mean weight 62.6  5.7  kg ; mean height 171.9  6.9  cm ) and the experimental group
 ( mean age 23.6  1.5  years ; mean weight 67.4  4.1  kg ; mean height 175.1  4.5  cm ) were not
 significantly different ( p > 0.05 ) , except for the hip flexion rom ( 123.6  2.4
 versus 102.5  3.8 ; p < 0.001 ) .
the lumbar flexion angle was significantly greater in the experimental group compared with
 the control group during vdt work with cross - legged sitting ( p = 0.017 ) ( table 1table 1 .
comparison of the lumbar flexion angle and trunk muscle activity between the two
 groups during visual display terminal work with cross - legged sittingvariablemean  sdcontrol groupexperimental grouplumbar flexion ( )15.2  7.023.3  4.3*right ra activity ( % rvc)101.2  5.9100.5  8.2right eo activity ( % rvc)98.7  6.2113.3  30.4right io activity ( % rvc)91.4  7.9109.4  22.3left ra activity ( % rvc)101.3  7.1101.7  8.2left eo activity ( % rvc)98.3  5.0115.3  35.0left io activity ( % rvc)99.8  10.897.2  11.3rvc , reference voluntary contraction ; ra , rectus abdominis ; eo , external oblique ; io ,
 internal oblique . *
however , there were no significant differences in emg measures of trunk
 muscle activity between the control and experimental groups ( p > 0.05 ) .
rvc , reference voluntary contraction ; ra , rectus abdominis ; eo , external oblique ; io ,
 internal oblique . *
in the present study , the subjects with limited hip flexion rom showed greater lumbar
 flexion compared with subjects with sufficient hip flexion rom during vdt work with
 cross - legged sitting ; however , these differences in hip flexion rom did not influence emg
 activity in trunk muscles .
the lumbo - pelvic - hip complex is connected via a kinematic link termed the lumbo - pelvic
 rhythm7 , 12 . during forward bending ,
the lumbar spine is flexed anteriorly with
 respect to the pelvis , while the pelvis is flexed anteriorly on the femur12 .
when lumbar flexion is limited , greater
 hip flexion is required with pelvic anterior tilt throughout the lumbo - pelvic rhythm7 . in other words ,
greater lumbar flexion is
 caused throughout the pelvic posterior tilt when hip flexion is limited .
the results of our
 study imply that greater lumbar flexion compensated for insufficient hip flexion in subjects
 in the experimental group during vdt work with cross - legged sitting . despite significant differences in lumbar flexion between the experimental and control
 groups , emg activity in the trunk muscles was not significantly different between the two
 groups .
snijders et al.8
 reported that the cross - legged sitting position decreased emg activity in io muscles due to
 increased stability in the sacroiliac joint .
the cross - legged sitting posture is performed
 by the combined motion of hip flexion and adduction .
increased tension in the biceps
 femoris , gluteus maximus and piriformis by hip flexion and abduction influences sacroiliac
 joint compression and tension in the sacrotuberous ligament , which can contribute to
 increased stability in the sacroiliac joint13,14,15 .

although the hip flexion angle may have been influenced by differences in hip flexion rom in
 subjects in this study , sufficient hip adduction may have been possible for all subjects
 during vdt work with cross - legged sitting .
we suggest that the sacroiliac joint compression
 by hip adduction during cross - legged sitting may not differ between subjects with and
 without limited hip flexion rom , resulting in the absence of significant differences in emg
 activity in trunk muscles between the two groups .
first , our study included a small sample size ;
 therefore , it is difficult to generalize our results .
however , a previous study by lee et al.5 showed that trunk kinematics were immediately changed after assuming
 a cross - legged sitting posture during vdt work , and the trunk flexion angle then did not
 significantly change for 30  min .
based on previous findings , we consider that the kinematic
 data of the lumbar spine and emg data of the trunk muscles during vdt work with cross - legged
 sitting for short periods may provide meaningful information for individuals who prefer
 cross - legged sitting .

Answer:
[ purpose ] the purpose of this study was to compare the lumbar flexion angle and
 electromyography ( emg ) measurements of trunk muscle activity in individuals with and
 without limited hip flexion range of motion ( rom ) during visual display terminal ( vdt )
 work with cross - legged sitting .
 [ subjects ] the 15 participants included a control group
 with sufficient hip flexion rom ( n = 7 ) and an experimental group with limited hip flexion
 rom ( n = 8) . [ methods ] all subjects performed vdt work with cross - legged sitting .
 the
 lumbar flexion angle was measured using a three - dimensional motion capture system , and the
 trunk muscle activity was recorded using a surface emg system during vdt work with
 cross - legged sitting .
 the differences in trunk flexion angle and trunk muscle activity
 between the two groups were analyzed using independent t - tests .
 [ results ] the lumbar
 flexion angle was significantly greater in the experimental group than the control group ,
 although trunk muscle activity did not differ between the two groups .
 [ conclusion ] these
 findings suggest that limited hip flexion leads to greater lumbar flexion during
 cross - legged sitting .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
vero e6 cells were infected with 100 focus - forming units of ebov expressing enhanced green fluorescent protein . after a 1-h incubation , the inoculum was removed and replaced with media ( dulbecco s modified eagle 's medium with 2% fetal bovine serum , penn / strep , l - glutamine ) containing chloroquine ( sigma , st .
the supernatant was collected on days 1 , 3 , 5 , 7 , and 9 after infection and media replaced with fresh drug .
viral rna was extracted from the supernatant and quantified by real - time quantitative reverse transcription pcr as previously described ( 10 ) .
concurrently , cell viability was assayed by using cell titer96 aqueous one solution ( promega , madison , wi , usa ) according to the manufacturer s instructions .
ec was determined by using prism6 ( graphpad software , san diego , ca , usa ) . when added 1 h after infection , chloroquine at 5 g / ml and 25 g / ml reduced the viral loads by 0.61 and 1.07 logs , respectively ( peak reduction observed on day 5 ) , without any significant cytotoxicity ( figure 1 ) .
analysis of the data from day 5 resulted in an ec50 of 1.77 g / ml and an ec90 of 23.34 g / ml , concentrations that are comparable with previous data ( 8) ; however , reductions in viral loads at these concentrations at other time points were negligible .
although concentrations of > 50 g / ml of chloroquine reduced viral loads by 24 logs starting on day 3 , this decrease was accompanied by a high level of cytotoxicity ( > 50% ) that was evident both in the cytotoxicity assay and microscopically resulting in poor selectivity of chloroquine .
viral loads from supernatants derived from vero cells infected with ebola virus expressing enhanced green fluorescent protein and treated with chloroquine at the indicated concentrations ( 0 , 5 , 25 , 50 , 100 , and 200 g / ml ) .
six - week - old balb / c mice or syrian hamsters ( both from harlan , indianapolis , in , usa ) were inoculated intraperitoneally with 100 50% lethal dose of ma ebov .
the mouse ( 11 ) and the hamster ( 12 ) are well - established disease models of ebov infection .
treatment groups ( mice and hamsters ) received 90 mg / kg of chloroquine alone ( intraperitoneally ) .
an additional group of hamsters received 50 mg / kg of chloroquine ( intraperitoneally every 24 h ) in combination with 2.5 mg / kg doxycycline ( gavage every 12 h ) and 50 mg / kg azithromycin ( intraperitoneally every 24 h ) .
after inoculation , animals were monitored at least twice daily and euthanized by using a humane endpoint scoring criteria as approved by the animal care and use committee at rocky mountain laboratories ( hamilton , mt , usa ) .
two of 3 mock - challenged mice did not survive because of chloroquine ( 90 mg / kg ) treatment alone ( figure 2 , panel a ) . only 2 of 9 mice infected with ma ebov and treated with
chloroquine survived , and 1 of 9 mice infected with ma ebov and treated with vehicle survived . with median survival of 7 , 8 , and 8 d for mock - challenged / chloroquine - treated mice , ma ebov  infected / chloroquine - treated mice , and ma ebov  infected / vehicle - treated mice , respectively , treatment had no significant effect on survival .
this dose , although previously stated as the maximum tolerated dose in mice ( 8) , was not well tolerated by the animals in this study and clearly did not improve survival in animals challenged with ma ebov .
survival of ma ebov - inoculated mice ( a ) and hamsters ( b ) treated with cq ( 90 mg / kg ) .
c ) survival of ma ebov  infected hamsters treated with a combination of cq ( 50 mg / kg ) , doxycycline ( 2.5 mg / kg ) , and azithromycin ( 50 mg / kg ) .
combo , combination of chloroquine , doxycycline , and azithromycin ; cq ,  chloroquine ; ebov , ebola virus ; ma , mouse - adapted .
when the same dose ( 90 mg / kg ) of chloroquine was given to hamsters challenged with ma ebov , the study had to be terminated on day 2 after treatment .
nearly all the treated animals , in both the ma ebov and the mock - challenged groups , died of acute toxicity after administration of chloroquine intraperitoneally , typically within 30 min after treatment ( figure 2 , panel b ) . in a separate study , hamsters were treated with chloroquine ( 50 mg / kg ) in combination with doxycycline ( 2.5 mg / kg ) and azithromycin ( 50 mg / kg ) to additionally provide broad - spectrum antimicrobial drug coverage .
reperfusion injury of the gut after ebov disease , which would subsequently result in bacterial sepsis , has been suspected as a possible cause of death .
thus , broad - spectrum antimicrobial drugs were proposed to help in this regard . in this study
, no toxicity was observed in the mock - challenged group as a result of the combination treatment .
however , treatment had no effect on survival ; no combination - treated or vehicle - treated groups survived , and median survival times were comparable ( figure 2 , panel c ) .
despite some activity of chloroquine against ebov in vitro , we observed no benefit to its administration in the mouse and hamster models . in the mouse model ,
a dose of 90 mg / kg resulted in toxicity but did not alter survival ; therefore , higher concentrations of chloroquine in the mouse would not be expected to be possible . in the hamsters ,
this dose was already lethal on its own . in the hamster model at a lower dose ( 50 mg / kg ) combined with doxycycline and azithromycin  which together provide broad - spectrum antimicrobial coverage , in addition to doxycycline having a small antiviral effect against ebov
previous anecdotal reports of the incidental use of chloroquine in patients with filovirus infections also do not support any benefit from its use ( 13,14 ) .
together , these data suggest that chloroquine is unlikely to provide any protection from ebov infection in humans .
given its in vitro activity against many different viruses and its longstanding use in humans , chloroquine has been put into multiple clinical trials . during dengue virus infection ,
viremia did not decrease ( 15 ) , and chloroquine neither prevented influenza virus infection ( 7 ) nor improved outcome of chikungunya virus infection ( 6 ) despite promising in vitro activity against these viruses .
when taken together with previous findings for other less pathogenic viruses , the clinical use of chloroquine seems unlikely to provide any benefit for either prophylaxis or treatment of ebov .
moreover , chloroquine has a small therapeutic window ; dosing for treatment of acute malaria is 15 mg / kg , and lethality starts at 50 mg / kg .
thus , current preclinical data do not support the continued consideration of chloroquine for use against ebov infections in humans .

Answer:
the antimalarial drug chloroquine has been suggested as a treatment for ebola virus infection .
 chloroquine inhibited virus replication in vitro , but only at cytotoxic concentrations . in mouse and hamster models
 , treatment did not improve survival .
 chloroquine is not a promising treatment for ebola .
 efforts should be directed toward other drug classes .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
one of them is that development is the increase in production , promoting the health and therapeutic services level , and eliminating problems .
therefore , development as it is considered by people and national institutions is a complicated and multidimensional process that requires changes in social structure , accelerating economic growth , reducing inequality , eradicating poverty , establishing social justice and equality , and environment stability .
therefore , in order to achieve development , identifying developed and undeveloped regions is of great importance in the first step ( 1 ) . codifying and establishing development and success strategies in implicational and executive plans , studying and recognizing capabilities and shortcomings and deficiencies , determining development levels in regions based on a set of appropriate indexes are inevitable requirements through which executive managers will become enable to identify development strategies based on needs and specific conditions in each and propose plans consistent with the conditions in each region ( 2,3 ) . assessing and evaluating and determining priorities help executive managers meet necessary needs more quickly .
health and therapy section is one of the sections in which prioritizing for meeting needs regarding resources limitation is essential ( 4 ) .
inequality and its dimensions are indexes of underdevelopment because in fact countries are considered developed that have high economic and social indexes and the distribution of incomes and revenues and facilities is rather equal in them while in undeveloped countries the amounts of these indexes are low and there is inequality in their distributions ( 5 ) .
numerous indexes are considered for assessing development level with the limitations in a time interval or period and place range .
there has been a lot of efforts to define and design an appropriate instrument which is an indicator of the socioeconomic status of people in a society ( 7 , 8) .
for example , australian researchers believe that using an index such as the validity of residency place for determining the socioeconomic status of individuals is very questionable .
therefore , it is necessary to use different indexes for determining the socioeconomic status . among these different development indexes ,
health care index is one of the most important indexes of progress and development in any country due to its significant role in providing the society s health and the success of national development programs depends highly on achieving these aims ( 9 ) .
a transient look at the health indexes in the country in the past decade shows the fast growing trend of the promotion of the indexes on one hand and inequalities in some indexes in different regions and provinces in the country on the other hand .
it is necessary that in iran like in any developing country , special attention should be paid to the development of health and therapy section in order to improve the country s development status and position among other countries in the world since development in this section is the prerequisite for the development in other sections of the society . nowadays , the issue of development is a big concern in many countries . in other words , development is nothing more than making the living status and conditions more satisfying for people ( 10 ) .

 a lot of studies have been done about ranking the level of health indexes of development using statistical methods and mathematical patterns . in a research ,
regions of portugal were assessed and ranked regarding development using factor and cluster analysis techniques in the time intervals of 1991 and 1995 ( 11 ) . in studies by soares et al . ( 11 ) in portugal and yanis and andriant ( 12 ) , regions are ranked using health and economy indexes by factor analysis and clustering and fuzzy logic models . despite all criticisms to using quantitative models in city issues since 1970 , mathematic models can give a clearer picture and understanding of city phenomena if they are established and codified in simple frameworks with limited number of variables .
standardized score and moriss s models are among quantitative models for assessing and ranking regions .
standardized score model is used for comparing indexes and obtaining a single index from the combinatory results of the indexes .
in fact , the standardized score model can uncover main differences among regions regarding the determined indexes ( 13 ) .
morris model is also introduced as a model for ranking regions in terms of development by civil program of the united nations organization which is the most recent official model applied at an international level and is capable of being developed , replaced , and applied in the planning environments with various different scales .

therefore , for achieving this goal and establishing social equality , it is necessary to rank regions and identify their degree or level of development regarding health and therapy indexes , determining capabilities , shortcomings , and deficiencies .
the present study addresses the analysis of development levels in cities in tehran province regarding health infrastructural indexes using standardized score and morris inequality models .

 the present study is applied or pragmatic based on its aim and descriptive based on its nature . in this study ,
the cities in tehran were ranked based on health indexes in 2012 using standardized score and morris models .
the studied geographic scope was tehran province and the statistical population was 14 cities in tehran .
after studying the experts articles and opinions , 10 indexes were selected as health indexes including the ratio of active medical and therapeutic institutions to a population of one thousand individuals , the ratio of beds at active medical and therapeutic institutions to a population of one thousand individuals , the ratio of health therapeutic and medical centers to a population of one thousand people , the ratio of governmental public health and medical institutions to active health and medical institutions , the ratio of daily medical and therapeutic centers to active health medical and therapeutic centers , the ratio of 24-hour health medical and therapeutic centers to active health medical and therapeutic centers , the ratio of laboratories to a population of one thousand individuals , the ratio of pharmacies to a population of one thousand individuals , the ratio of radiology centers to a population of one thousand individuals , and the ratio of rehabilitation centers to a population of one thousand individuals .
the required data were gathered from the statistics center and tehran university of medical sciences using a researcher - made information list including items and questions about the name of the cities , the number of active medical and therapeutic institutions , available beds , the number of health and medical therapeutic centers , the number of governmental public health medical and therapeutic centers , the number of daily health medical and therapeutic centers , the number of 24-hour health medical and therapeutic centers , the number of laboratories , the number of pharmacies , the number of radiology centers , the number of rehabilitation centers , and the population of the cities . after the completion of the lists , the development in cities was ranked and calculated using morris inequality and standardized score models in excel in 2010 .
the calculations in the two methods are as follows :

 first , the indexes were standardized based on the city using standardized score model , as follows :

 which , ssij is standardized score of index i for city j , xij is amount of index i for the city j , x is mean of indexes and is standard deviation of the index i.

 then , the standardized score of each of the studied indexes in each city are added up together and the result is divided by the total number of indexes .
the obtained score is the average of the standardized score or the development index of any city that makes the comparison regarding development status possible as a single index :

 which , ssi is the index for city j and n is the number of considered indexes .

 in morris model , the development status or position of each region among other regions is determined based on the selected indexes using the gathered information for each region .
this method is used for reporting human resource development by the united nations and the obtained index is the evidence showing countries ranking regarding human resource development . in this method ,
the deviation of the numerical values of the index i in any region or area from the minimum of the index i among the regions or areas is divided by the range of the changes of that index , and the degree of the inconsistency or inequality of the numerical value of the index in relation to the dispersion index of its changes or variation range is computed ( r = x ( max ) - x ( min ) i ) .

( 3)miiij = xijx(min)ix(max)ix(min)i

 which , miiij is the value of morris inequality index for i index in the region or neighborhood j , xij is the numerical value of the index i in the region or neighborhood j , x(min)i is the lowest value of the index i and x(max)iis the highest value of the index i.

 in the next step , the mean of the numerical values of morris inequality index for indexes in each region or neighborhood is applied as the criteria for determining the ranking or development status from the highest value ( the first ranking ) to the lowest ( the last ranking ) :

 which , miii is development index for region or neighborhood j , and n is the number of considered indexes .

in addition , for determining the developmental gap in health and therapy section in cities , 5 classifications of developed , rather developed , intermediately developed , less developed , and undeveloped were considered .
then , for determining the distance between cities in 5 levels , first the range of changes in scores was obtained using a formula and then the distance between levels was calculated by b formula and as a result the cities were classified in 5 groups .

 based on the standardized score model , rey city has the best , and pishva city has the worst condition in terms of health indexes ( table 1 ) .

based on the standard score model , 28% of the cities were placed in developed group and 43% of the cities were in undeveloped group ( table 2 ) .

based on morris inequality model , rey has the best state and pishva has the worst state ( table 3 ) .

 based on morris inequality model , 28% of the cities were placed in developed group and 43% of the cities were placed in undeveloped group ( table 4 ) .

 the first step for developing health and therapy section and reducing the gap regarding health among different regions is to achieve a thorough understanding of the condition of the healthcare sector in the region .
indexes of development in developing countries are not distributed equally in the regions and geographical zones .
one of the main indexes of development is health index or in other words , the degree to which a society benefits from the health and therapeutic services and facilities .
the developmental gap of these indices can be easily observed in the provinces and cities in the country .

the findings showed that regarding the rate of development in the health sector , there is a deep development gap among the cities in tehran and the distribution of health services and facilities in the cities of the province seems unbalanced and unequal.for determining the development of cities in the standardized model , five levels of highly developed , developed , developing , deprived , and very deprived were considered.based on standardized score and morris inequality , only 28% of the cities were placed in the developed countries and this is in line with the results obtained by tofighi et al ( 14 ) and mirvis ( 15 ) .
therefore , planners and policy makers should focus their efforts to find the cause of the gap in development.given the values of tables ( 1 ) and ( 3 ) , rey city has maintained its superiority over other cities and was considered as the developed city and pishva got the last ranking for the development of health indexes.the noticeable point is that tehran is in the third ranking despite the fact that it is the capital city which indicates that the geographical location can not be considered as the factor influencing the development of a city and this was confirmed in other studies ( 14).bahadori et al .
( 16 ) also investigated the ranking of the health structural indexes in golestan province using scalogram method.the results showed that there is a large gap regarding the benefits of the health structural indexes among the cities in golestan province.aqqala city with 97 points enjoyed the most and azad city with 41 points enjoyed the lowest level of the benefits of health structural indexes respectively . in this study ,
in the studies by nastaran ( 17 ) and zarabi in isfahan ( 18 ) , amini in all the provinces in the country ( 19 ) and taghvaee in all the provinces in the country ( 20 ) , similar results were obtained about the gap in enjoying the health structural indexes .
therefore , it is suggested that officials , authorities , and planners pay attention to eliminating the mentioned problems , achieving growth and equal regional development , balancing the pattern of the distribution of health services and facilities , and decentralization of them in some cities ( 21 ) .
the distribution of health services and facilities should be done based on the level or degree of underdevelopment in cities . in general , ranking the country s cities and provinces in health sector makes it possible for the related authorities to make more accurate planning , identify strengths and weaknesses , and prioritize resources adapted to the needs of each city and province . in summary
, the results showed that statistical methods are effective tools for ranking and determining the status of development in the health sector .
the results of this study concerning the allocation of the health sector resources would be useful for health planners and policy makers .

 structural indexes have always been considered as one of the main factors influencing health status and life.thus , to achieve a fair , balanced , and equal state of health in the province , it is suggested to make plans and take actions based on facts and the development situation of provinces and cities in order to reduce the gap in accessing and enjoying health facilities and services among the cities.furthermore , it is suggested that in the first stages of city development , authorities need to focus on short term policies and equity in access and pay attention to the development of necessary services in developing and deprived cities over a medium and long term plan .

Answer:
background : one of the main indexes of development is health index or the degree to which a
 society enjoys health and therapeutic services . the present study was done with the aim to analyze
 development levels in cities in tehran regarding health infrastructural index using the standardized
 score and morris model .

 methods : this is a descriptive and pragmatic study which ranks 14 cities in tehran province using
 the standardized score and morris models based on 10 selected health indexes . the required data
 were gathered using a researcher - made information list and the information gathered from the statistics
 center and tehran university of medical sciences .
 the data were analyzed using excel software .

 results : the development coefficient in the studied cities varies from 0.595 to -0.379 so that rey
 city has the highest level of development and pishva city has the lowest level of development among
 the studied cities . the more number of the cities ( 43% ) was among the rather undeveloped group and
 none of the cities ( 0% ) was in the rather developed group .

 conclusion : regarding the findings , there is a big gap and difference regarding enjoying health and
 therapeutic infrastructural indexes among the cities in tehran province .
 therefore , it is suggested
 that development - oriented plans consistentent with development levels should be implemented in
 these cities .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
catheter - based radiofrequency ablation ( rfa ) delivered during endoscopic retrograde cholangiopancreatography ( ercp ) has recently emerged as a possible therapeutic option within the bile duct 1
 2
 3
 4 .
intrabiliary extension of neoplasm remains an important challenge in the endoscopic eradication of complex ampullary lesions 5
 6 , and rfa may represent a viable treatment adjunct for this problem .
recently , the use of rfa at the ampulla and within the distal bile duct has been described 7
 8 .
herein we present 4 cases assessing the technical feasibility , safety , and treatment outcomes of rfa employed at the time of ercp to treat ampullary lesions with intraductal extension .
the study was conducted at the medical university of south carolina ( musc ) from july 1 , 2014 through october 1 , 2015 .
after institutional review board approval , we retrospectively identified eligible adult subjects through the musc endoscopy report database ( endoworks , olympus america , center valley , pa ) by searching for reports that contained the keywords  radiofrequency ablation ( rfa )  and  endoscopic retrograde cholangiopancreatography ( ercp )  .
we excluded patients who underwent rfa of a stricture not associated with an ampullary lesion .
all procedures were performed by an experienced pancreaticobiliary endoscopist under general anesthesia using a side - viewing duodenoscope .
ampullary resection was performed either en bloc or in piecemeal fashion by delivering electrosurgical current through a snare with or without prior submucosal lift .
intraductal extension of the lesion was assessed cholangiographically ( fig .  1 ) and/or visually ( fig .  2 ) . in some cases , a biliary sphincterotomy extension and papillary balloon dilation
was performed to expose the inside of the terminal bile duct for assessment and therapy .
ablative therapy was delivered using a standard argon plasma coagulation ( apc ) probe ( erbe usa inc . ,
mariette , ga ) at a flow rate of 1.0  l / min to 1.2  l / min and 30 to 40 maximum watts ( w ) and/or the habib endohpb rfa bipolar cautery probe ( emcision united kingdom , london , united kingdom ) at 10  w for 60 to 90 seconds , extrapolating from manufacturer s recommendations of 7 to 10  w    120 seconds 9 .
given the proximity to the pancreatic orifice and the benign nature of the target lesions , a shorter duration of treatment was chosen . in general , apc was reserved for treating exposed target tissue in the duodenum or very distal duct , whereas rfa was reserved for treating hidden or difficult to access tissue within the duct .
all patients undergoing rfa received a temporary pancreatic stent ( 5 fr , 2    5  cm ) and rectal indomethacin to reduce the risk of post - ercp pancreatitis ( pep ) , as well as a plastic endobiliary prostheses to prevent biliary obstruction and cholangitis .

cholangiogram showing a filling defect in the distal bile duct ( arrow ) representing bulky intraductal extension of an ampullary adenoma .

endoscopic view of the papilla after ampullectomy demonstrating intraductal extension of the adenoma ( arrow ) .
technical success was defined as the ability to successfully position the rfa probe across the biliary orifice and deliver thermal energy to the region of the papilla and terminal bile duct , resulting in coagulation of the visualized target areas .
clinical success was defined as endoscopic absence of polypoid or adenomatous - appearing tissue at the treatment site and histologic absence of neoplasm based on extensive follow - up biopsies from the papilla , pancreaticobiliary septum , biliary orifice , and distal bile duct .
when the distal bile duct was not fully exposed by prior sphincterotomy , a pediatric biopsy forceps was introduced into the distal duct to acquire tissue .
patient demographics , procedure indications , and treatment outcomes are listed in table  1 .
four eligible patients were identified , all of whom were men with a mean age of 63 years ( range 54    84 ) .
three patients ( 75  % ) had a history of familial adenomatous polyposis ( fap ) .
three patients were treated for ampullary adenoma and 1 for ampullary adenoma with a focus of adenocarcinoma ( he declined surgical evaluation ) .
fap , familial adenomatous polyposis ; lgd , low - grade dysplasia ; hgd , high - grade dysplasia ; imc , intramucosal cancer ; apc , argon plasma coagulation ; rfa , radiofrequency ablation ; pep , post - endoscopic retrograde cholangiopancreatography pancreatitis ; eus , endoscopic ultrasound
 video 1 presents a synopsis of 2 representative cases .
all rfa procedures were technically successful , resulting in a perceptible tissue effect ( fig .  3 ) .
rfa was performed immediately following endoscopic resection in 1 case and during a subsequent session in the remaining cases .
the mean number of rfa sessions per patient was 1.5 ( range 1    3 ) .
all patients were discharged uneventfully after the procedure without any immediate adverse events ( aes ) .
one patient developed obstructive jaundice due to a fibro - inflammatory bile duct stricture at the level of prior rfa that manifested 3 days after biliary stent removal ( approximately 6 weeks after the rfa ) and has required ongoing endobiliary stent therapy in excess of 3 months .
3 patients had visual and histologic evidence of complete eradication ; the patient with a focus of adenocarcinoma who declined surgery developed overt invasive ampullary cancer .

video 1 this footage consists of 2 video clips demonstrating catheter - based rfa of intraductal ampullary adenoma
although endoscopic ampullectomy is the preferred treatment for noninvasive ampullary lesions with a success rate reported as high as 92  % 10 , biliary extension of neoplasm represents a significant obstacle to endoscopic eradication .
exposure and eversion of the adenoma through a biliary sphincterotomy to allow resection or ablation has been described in amenable cases 5
 11
 12 .
however , broad adenomatous involvement of the distal bile is associated with limited treatment success ( <  50  % ) and has been considered an indication for surgical resection 5 .
based on its ease of use and the ability to precisely position the probe within the distal duct , radiofrequency ablation may represent the first viable treatment adjunct for this challenging scenario .
to date , only single case reports of rfa for benign ampullary lesions have been described ; we aimed to expand our understanding of this technology by presenting our experience in 5 patients .
catheter - based rfa was technically successful in all cases , and based on short - term follow up in a small sample , may be safe and clinically effective .
however , because rfa induces thermal injury and subsequent necrosis of the bile duct wall and beyond , several safety concerns exist .
first , while rfa has been associated with a favorable safety profile when applied to malignant biliary strictures 1
 2
 3
 4 , it remains unclear whether rfa in the intra - pancreatic portion of the bile duct without the protective buffer of a surrounding tumor  especially in the vicinity of the pancreatic orifice  will be associated with an increased risk of pancreatitis . until additional data on the risk of post - ercp pancreatitis in this context
if the pancreatic and biliary orifices are in close proximity , especially if adenoma appears to involve the pancreaticobiliary septum , it may be best to perform the rfa adjacent to a guidewire which has already been placed in the pancreatic duct ( subsequently guaranteeing pancreatic access for stent placement ) rather than adjacent to a plastic pancreatic stent which may be damaged or even fractured during rfa .
another safety concern is the development of clinically important post - rfa biliary strictures that occurred in 1 of our patients , akin to what has been observed in the esophagus after rfa of barrett s epithelium 13 .
this concern is particularly relevant in the context of benign ampullary disease in which patients do not typically undergo long - term stent placement , as is the case when rfa is performed for palliation of malignant strictures . along these lines , until additional data are available , we have attempted to minimize rfa across the cystic duct takeoff to avoid thermal injury - related obstruction of the cystic duct , which has intentionally been induced by electrohydraulic lithotripsy to treat refractory bile leak 14 .   in our series
, rfa appears to have provided effective adjunctive therapy in all 4 cases of benign pathology but was ineffective in the setting of early adenocarcinoma , underscoring the concept that surgical resection remains first - line therapy for ampullary cancer ( our patient declined surgery and chemoradiation ) . despite the apparent effectiveness for benign lesions , it is important to consider that intrabiliary extension is often nodular in nature , leading to heterogeneous contact between the rfa probe and the target tissue ; this may lead to incomplete therapy and/or an increased risk of buried neoplasm as is the concern when rfa is used to treat nodular barrett s esophagus .
moreover , it can be technically challenging to ensure circumferential contact of the probe and the target tissue within a dilated bile duct , even when luminal air is suctioned to induce collapse of the duct around the probe . in these cases , a balloon - based rfa device that flattens nodular tissue and maximizes treatment contact may be of value .
an additional consideration is that the proximal extent of neoplasm is often difficult to assess cholangiographically and the role of cholangioscopy to guide probe placement should be further explored .
prospective studies are necessary to evaluate these issues and determine the long - term effectiveness of this modality .   in summary , catheter - based rfa after endoscopic resection of ampullary lesions that extend up the bile duct is technically feasible .
concerns regarding injury to the pancreas and bile duct as well as incomplete treatment of nodular target tissue exist and will be addressed by additional clinical experience and research .

Answer:
background and study aims : catheter - based radiofrequency ablation ( rfa ) delivered during endoscopic retrograde cholangiopancreatography ( ercp ) may represent a viable treatment option for intraductal extension of ampullary neoplasms , however , clinical experience with this modality is limited .
 after ampullary resection , 4 patients with intraductal extension underwent adjunctive rfa of the distal bile duct .
 all patients received a temporary pancreatic stent to reduce the risk of pancreatitis , as well as a plastic biliary stent to prevent biliary obstruction .
 three patients were treated for adenoma and 1 for adenoma with a focus of adenocarcinoma . during a short follow - up period , 3 patients experienced complete eradication of the target lesion , whereas the patient with a focus of adenocarcinoma had progression to overt invasive cancer .
 there were no immediate adverse events .
 one patient developed a post - rfa bile duct stricture , which has required additional endoscopic therapy .
 catheter - based rfa of ampullary lesions that extend up the bile duct is technically feasible . additional research is necessary to understand the risks and long - term benefits of this technique .


Question:
You will be shown the title of a chemistry paper, together with sections excerpted from the body of the paper. The paper sections may include HTML tags like `<p>` and `</p>`; please ignore these. Your task is to write an abstract for the paper. Your response should include the abstract and no other text.

Title:
Isolation and X-ray characterization of palladium–N complexes in the guanylation of aromatic amines. Mechanistic implications

Paper sections:
Introduction

N-Arylguanidines are important compounds with interesting biological activities [1,2] such as fungicides [3] and also in supramolecular chemistry as complementary partners of carboxylate and nitro groups [4][5][6][7]. Some of these guanidines are commercially used as antifouling agents in marine paints and in the formulation of protective surface coatings [8][9][10]. N-Arylguanidines can be obtained by aniline insertion into the corresponding carbodiimide [11][12][13][14][15][16][17][18]. This nucleophilic addition can be efficiently catalyzed by palladium salts [19], such as PdCl 2 or Pd(OAc) 2 in homogenous phase. Also recently we have reported that palladium nanoparticles supported on magnesia can be a solid catalyst for this process [20]. Working with PdCl 2 (NCCH 3 ) 2 in dichloromethane we were able to isolate two types of palladium complexes with iodoaniline and guanidine, respectively, (see Scheme 1) that give some clue about the reaction mechanism of the catalytic process.

Results and Discussion

In order to provide further support to the mechanistic proposal for the C-N insertion promoted by palladium(II) suggested by us [20], in the present report we describe the study of palladium-catalyzed guanylation of three additional anilines (1a-c) Scheme 1: Isolation of trans-dichlorobis(4-iodoanilino-ĸN)palladium(II) and trans-dichlorobis [1,3-diisopropyl-2-(4-iodophenyl)guanidino-ĸN(aryl)]palladium(II) complexes formed by reaction of PdCl 2 (MeCN) 2 with 4-iodoaniline (upper row) or with 4-iodoaniline and N,N'-diisopropylcarbodiimide (lower reaction).

Scheme 2: Isolation of trans-dichlorobis [1,3-diisopropyl-2-(aryl)guanidino-ĸN(aryl)]palladium(II) complexes (4a-c) by reaction of PdCl 2 (MeCN) 2 with anilines 1a-c and N,N'-diisopropylcarbodiimide (2). Dashed lines indicate the formation of trans-dichlorobis(anilino-ĸN)palladium(II) complexes (3a-c) as primary intermediates during the reaction, and their subsequent reaction with 2 to led 4a-c.

with N,N'-diisopropylcarbodiimide (2). For these reactions we have been able to characterize three palladium complexes of the type of bis(anilino)Pd(II) (3a-c) as well as three palladium complexes of the type of bis(guanidino)Pd(II) (4a-c) (Scheme 2) whose structures have been characterized by singlecrystal X-ray structural analysis, as well as to obtain evidence for the intermediacy of these complexes in the catalytic process. Overall the present data reinforce the previous proposal for the mechanism of aniline guanylation.

When a stoichiometric (2:2:1) mixture of anilines 1a-c and carbodiimide 2 with PdCl 2 (MeCN) 2 is stirred at 60 °C in CH 2 Cl 2 , evolution at initial reaction times of a solid precipitate is observed (Scheme 2). Filtration of these precipitates and subsequent washing with CH 2 Cl 2 renders three solids whose combustion analysis is in accordance with the percentages expected for dichlorobis(anilino-ĸN)palladium(II) (3a-c) (see Supporting Information File 1, experimental section). IR spectra of complexes 3a-c show the characteristic absorption peaks due to the coordinated anilines 1a-c (see Supporting Information File 1, Figures S1-S3); these are compatible with the proposed structure for these intermediates. Complex 3a derived from 1a has been recently characterized by single-crystal X-ray diffraction [21] showing similar coordination to trans-dichlorobis(4- iodoaniline-ĸN)palladium(II) complex recently published by us [20]. Compounds 3a-c were also characterized by solid state 13 C NMR spectroscopy that gave spectra showing carbon peaks compatible with the proposed structure (see Supporting Information File 1, Figures S4-S6).

After prolonging the reaction time, the initially evolved precipitate undergoes dissolution indicating that it has been transformed under the reaction conditions. At this stage, filtering of the transparent orange-red (4a,b) and red (4c) solutions followed by subsequent addition of ethyl ether or toluene and slow solvent evaporation at ambient temperature allows the formation of crystals with suitable quality for a crystallographic diffraction study. The structures of these intermediates solved by X-ray analysis showed that these compounds corresponding to trans-dichlorobis[arylguanidino-ĸN(aryl)]palladium(II). Figure 1, Figure 2 and Figure 3 present ORTEP views of complexes 4a-c as well as selected views along some crystallographic axes (see Tables S1-S3 and also Figures S7, S11 and S15 in Supporting Information File 1, and for full details of the crystallographic data see Supporting Information File 2).

Besides X-ray crystal structure analysis, palladium complexes 4a-c were also characterized by NMR spectroscopy, ESIMS and combustion analysis (see experimental section in Supporting Information File 1). 1 H, 13    Similar reactions were carried out mixing anilines 1a-c and N,N'-diisopropylcarbodiimide (2), but in this case in the presence of only a catalytic amount of PdCl 2 (NCCH 3 ) 2 (4 mol %) (Scheme 3). Under these conditions no evidence for the formation of palladium complexes (3a-c) and (4a-c) could be obtained due to the low amount of palladium and no solid precipitates were observed. In contrast, in the presence of catalytic amounts of palladium, formation of the corresponding N-arylguanidines was observed in almost quantitative yield. These guanidines 5a-c formed by nucleophilic attack of anilines 1a-c to N,N'-diisopropylcarbodiimide (2) catalyzed by palladium were fully characterized by analytical and spectro-  scopic data (see Supporting Information File 1, experimental section).

Structure of guanidine 5a was confirmed by single-crystal X-ray analysis, Figure 4 shows the corresponding ORTEP for compound 5a as well as some views of the crystal packing (see also Supporting Information File 1, Table S4 and Figure S20 and for full details of crystallographic data see Supporting Information File 2). Beside X-ray crystal analysis of guanidine 5a, guanidines 5a-c were also characterized by 1 H, 13 C and 19 F NMR spectroscopy and combustion analysis (see Figures Overall the information obtained from the experiments performed in the presence of a large palladium excess, in which two kinds of palladium complexes have been detected and isolated, with the formation of guanidines under conditions in which a catalytic amount of palladium is present, allows us to make reasonable mechanistic proposals. Thus, upon contacting anilines 1a-c and PdCl 2 (MeCN) 2 , a rapid formation of dichlorobis(anilino-ĸN)palladium(II) (3a-c) complexes should take place. These palladium complexes will interact with the N,N'-diisopropylcarbodiimide (2) giving rise to the dichlorobis(guanidino-ĸN)palladium(II) (4a-c) complexes. When Pd is used in catalytic amounts, cleavage of this bis(guanidino-ĸN) complex by aniline will form another dichlorobis(anilino-ĸN)palladium(II) (3a-c) completing one cycle and liberating guanidines 5a-c as free products of this catalytic reaction with high yields and selectivities (see Scheme 4). In this mechanism the rate determining step will be the attack of dichlorobis(anilino-ĸN)palladium(II) (3a-c) to the N,N'-diisopropylcarbodiimide (2) (Scheme 4).

In this process, coordination of nitrogen to palladium should strongly reduce the nucleophilicity of the corresponding nitrogen atom and, therefore, the attack at the carbodiimide would be significantly slowed down compared to free uncoordinated aniline. However, this negative effect of palladium coor- dination to aniline should be overcompensated by coordination of carbodiimide to palladium in close proximity to aniline in fixed geometry as indicated in the presumed intermediates 6a-c. There are precedents in the literature [22] showing that palladium(II) can interact weakly with accumulated carbodiimide bonds, but this type of complex is typically very labile and difficult to isolate under the reaction conditions due the presence of an aniline excess, and for this reason we have been unable to isolate labile intermediates 6a-c. This preassociation between complexes 3a-c and carbodiimide 2 to form intermediates 6a-c would make easier the key step of C=N insertion leading to guanidines (Scheme 4).

Alternatively, it can be also envisioned that the acidity of hydrogen atoms bonded to nitrogen in intermediates 3a-c increases sufficiently to protonate the nitrogen atom of the carbodiimide that subsequently would be activated to accept the nucleophilic attack of the resulting anilide anion or aniline (see Scheme 4). This mechanism would be similar to that accepted for peptide-bond formation mediated by carbodiimides [23][24][25][26]. It can also be possible that these two steps, i.e., protonation and nucleophilic attack occur in a quasi-concerted manner around the intermediates 6a-c.

Conclusion

In conclusion, we show the possibility to isolate and characterize palladium complexes by performing some reactions using large amounts of palladium salts. The structures of these complexes shed light onto the reaction mechanism of the palladiumcatalyzed reaction. In this case, we have applied this methodology to isolate and characterize bis(anilino)-and bis(guanidino)palladium complexes that are proposed to be reaction intermediates, together with the still not isolated aniline-carbodiimide palladium complex 6, in the mechanism of the guanylation of anilines. Our study opens the way to apply a similar methodology to study the reaction mechanism of other catalytic reactions.

Answer: In the context of palladium-catalyzed guanylation of anilines herein, we have been able to characterize and isolate bis(anilino) and bis(guanidino)Pd(II) complexes using reaction conditions under which stoichiometric amounts of palladium salts are used. Characterization of these palladium complexes strongly supports a mechanistic proposal for the catalytic guanylation of anilines using PdCl 2 (NCCH 3 ) 2 as catalyst that involves the intermediacy of these Pd(II) complexes.


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
anterior cervical discectomy and fusion is a commonly performed surgery for the treatment of spondylosis , radiculopathy , myelopathy , and trauma .
esophageal perforation is an exceedingly rare complication following anterior cervical discectomy and fusion ( acdf ) .
the incidence of these complications ranges from 0.02 to 1.52% although is higher when it is a result of trauma . we describe a case of a 24-year - old man who underwent acdf and corpectomy following a motor vehicle accident who developed delayed onset aspiration pneumonia and dysphagia requiring surgical repair of an esophageal perforation . to the best of our knowledge
there has been no prior literature discussing airway management in patients who underwent esophageal repair for perforation following cervical spine surgery .
we believe this paper will provide a deeper understanding to the intensivist in regards to postoperative airway management in this type of patient .
a 24-year - old man presented to an outside hospital following a motor vehicle accident with cervical spine fractures of c5 - c7 , anterolisthesis of c6 and associated spinal cord transection with resulting quadriplegia .
the patient was taken to the operating room and underwent anterior cervical decompression and fusion ( acdf ) of c5 - 7 , c6 corpectomy with polyetheretherketone ( peek ) cage and c4 - t1 posterior fusion [ figure 1a ] .
postoperatively the patient did well and was discharged to a rehabilitation center at our institution .
lateral cervical x - ray shows c4-t1 posterior fusion with c5-c7 acdf and peek cage at the level of c6 with no apparent hardware defects ( a ) ct neck demonstrated air surrounding the implant at c6 as well as the anterior fusion plate ( b ) barium swallow study showed a posterior esophageal barium leak at c5-c6 and a te - fistula .
the contents of the fistula are seen tracking inferiorly t1 and is seen anterior to the fusion plate ( c ) barium swallow study done ten days postoperatively shows resolution of perforation ( d ) approximately four months following his surgeries the patient began to develop increased sputum production , cough and fever .
, the aspiration was thought to be due to the patient 's poor pulmonary clearance from his immobility and quadriplegia . while on antibiotic therapy for aspiration pneumonia the patient developed acute dysphagia .
computed tomography ( ct ) scan demonstrated air surrounding the implant at c6 as well as the anterior fusion plate [ figure 1b ] .
barium swallow revealed an esophageal defect with contrast tracking down the prevertebral space to the level of t1 anterior to the cervical fusion plate as well as a tracheo - esophageal fistula [ figure 1c ] .
the patient underwent removal of the anterior plate , which was visualized in the pharyngoesophagus during intraoperative video - assisted laryngoscopy , removal of peek cage and placement of antibiotic impregnated bone cement , primary repair in conjunction with a sternocleidomastoid muscle flap being placed on the esophageal defect [ figure 2 ] .
postoperatively , the patient remained intubated with the ngt to remain in place for one week .
the patient was extubated over a soft 22-french exchange catheter without incident and repeat barium swallow study demonstrated resolution of the esophageal perforation [ figure 1d ] .
anterior cervical discectomy and fusion ( acdf ) has been the mainstay treatment of patients with radiculopathy or myelopathy attributed to cervical spine disease , particularly herniated nucleus pulposus . in the trauma
setting , vertebral body fracture may require corpectomy in which acdf is typically performed in conjunction with posterior instrumentation .
esophageal perforation is a more rare and potentially life threatening complication occurring in 0.02 - 1.52% of patients .
identifying patients with esophageal perforation can be difficult as the clinical presentation and initial onset is highly variable .
presentation with dysphagia , choking , aspiration , pain , fever or subcutaneous emphysema can all be postoperative complaints typically seen in up to 9.5% of patients .
the placement of an anterior cervical plate improves fusion rates and reduces risk of graft migration .
additionally , chronic compression of the esophagus against the anterior cervical plate during swallowing can result in pressure necrosis and eventually perforation and fistula formation .
diagnosis of esophageal perforation can be challenging due to the delayed and variable clinical presentation .
in addition to computed tomography ( ct ) scan , upper endoscopy , barium contrast studies , and bronchoscopy are the most informative studies to determine the location and extent of perforation . proper management of esophageal perforation is very important as its associated mortality rate is high . a conservative approach including nil per os ( npo ) , with temporal parenteral nutrition by either ng or peg tube and broad - spectrum intravenous antibiotics may be appropriate in a very select group of patients where perforation is incidentally found and are asymptomatic .
spontaneous healing of these injuries may take four to twelve weeks however , this conservative approach is associated with a 20 - 45% rate of abscess formation .
the use of a sternocleidomastoid ( scm ) muscle flap has been considered the gold standard to achieve and maintain perforation closure as without it esophageal sutures will invariably fail .
the scm is a highly mobile and vascularized medium that can improve antibiotic delivery , wound healing and provides a physical barrier between the esophagus and the cervical spine .
important considerations when extubating is the degree of healing following esophageal perforation repair , mallampati grade , as well as the possible need and risks of reintubation in an airway emergency . although most reports describe waiting approximately 10 - 14 days postoperatively before resuming oral feeds , our patient was successfully extubated and tolerated oral feeds suggesting this period of time to be sufficient for would healing . in our patient ,
although rare , esophageal perforation can occur following accidental esophageal intubation and is of clear concern in patients who underwent esophageal repair .
risk of perforation is higher when inexperienced individuals attempt intubation , difficult intubation requiring multiple attempts , as well as in emergency scenarios . when the patient has satisfied all weaning parameters and has a present cuff leak we strongly recommend that an experienced anesthesiologist be present for extubation and have all appropriate airway devices available including a fiberoptic bronchoscope .
the more rigid and thicker bougie should be avoided due to their risk of trauma .
a small hole should be made in the facemask such that the exchange catheter may pass through while the patient receives 8 - 10 l of oxygen for typically 30 - 60 minutes .
this will allow for a more controlled and safer reintubation in the event the patient fails extubation and therefore reduce the potential risk of reperforation .
greater vigilance is required in the event reintubation is required as perforation of the surgical repair site is of great concern .
therefore , it is our recommendation that an experienced anesthesiologist be present for extubation and that all appropriate airway devices are available including a fiberoptic bronchoscope .

Answer:
anterior cervical discectomy and fusion ( acdf ) is a commonly performed surgery for the treatment of spondylosis , radiculopathy , myelopathy , and trauma to the cervical spine .
 esophageal perforation is a rare yet serious complication following acdf with an incidence of 0.02 to 1.52% .
 we describe a case of a 24-year - old man who underwent acdf and corpectomy following a motor vehicle accident who subsequently developed delayed onset esophageal perforation requiring surgical intervention .
 we believe that the detailed review of the surgical management of esophageal perforation following cervical spine surgery will provide a deeper understanding for the intensivist in regards to postoperative airway management in these types of patients .
 careful extubation over a soft flexible exchange catheter should take place to help reduce the risk of perforation in the event reintubation is required .


Question:
You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
a 35-year - old female presented with a painless , slowly growing
 mass in the right inferior orbit for the past four years .
she did
 not complain of diminution of visual acuity , diplopia or field
 defect . on examination , visual acuity in both eyes
the right side demonstrated a solid , non - tender ,
 freely mobile mass in the inferior orbit , which became more
 prominent on applying pressure on the upper part of the globe .

the mass measured approximately 20 mm  15 mm and the
 size did not vary with valsalva maneuver , ocular movements
 or posture .
slit - lamp
 and fundus examination of the eye showed normal anterior
 and posterior segments .
b - scan ultrasonography revealed an extraconal ,
 homogenous lesion in the inferior part of the right orbit .

computed tomography revealed a non - enhancing well-
 defined homogenous mass measuring 20 mm  12 mm in the
 right inferior orbit which was displacing the inferior rectus
 and inferior oblique muscle upwards .
the mass was separate
 from the above - mentioned muscles and produced no globe
 indentation or displacement [ figure 1a ] .
a provisional diagnosis of orbital dermoid was made and
 the patient was taken up for an excision biopsy .
peroperative findings were of a smooth , well - encapsulated
 mass with no attachments to the surrounding muscles .
on histopathological examination , the gross specimen
 consisted of a smooth well - encapsulated solid mass measuring
 25 mm in the greatest diameter [ figure 1b ] .
microscopically , a
 biphasic pattern of tumor cells was seen with areas of closely
 packed spindle cells having fusiform nuclei and eosinophilic
 cytoplasm ( antoni a ) admixed with looser myxoid tissue
 having ovoid cells ( antoni b ) . at places ,
these tumors cells
 were arranged in palisades and this arrangement of cells
 is referred to as verocay bodies .
orbital
 schwannoma is a tumor of adulthood usually presenting
 between 20 to 70 years of age .
schwannomas are usually
 asymptomatic when small and may produce progressive ,
 painless proptosis on enlargement
. a variable combination
 of signs and symptoms may be present due to the variable
 origin and location of the tumor in the orbit.2 displacement
 of the globe is related to the site of the tumor mass .
most
 schwannomas arise from branches of either the supraorbital
 or supratrochlear nerves and hence produce downward
 displacement of the globe .
less commonly , the tumor may arise
 from the infraorbital nerve and produce upward displacement
 of globe .
larger tumors may produce diplopia , particularly
 when they arise from the orbital portion of the third , fourth
 or sixth nerve .
the growth of the tumor may
 cause compression of the optic nerve with papilledema or
 optic atrophy .
surgical excision is the treatment of choice and
 the tumor should be removed intact at the earliest to prevent
 compression of the optic nerve.3 incomplete excision can lead
 to recurrence or even intracranial extension .
highly cellular
 tumors have greater chance of recurrence and malignant
 transformation . therefore an early treatment is indicated
 to avoid the complications related to progressive growth of
 the tumor . in our patient , we were successful in achieving
 the above objectives with timely and complete excision of
 the tumor .
orbital schwannoma arising from the infraorbital nerve
 is rare and clinical diagnosis is often difficult .
extensive
 literature search revealed only a few case reports of an orbital
 schwannoma arising from the infraorbital nerve.4 - 10 our
 patient presented with the tumor in this uncommon location .

a solitary schwannoma , though rare , should be considered
 as a preoperative differential diagnosis of a unilateral slow-
 growing orbital mass in an adult and prompt management
 is warranted to prevent development of vision - threatening
 complications .

Answer:
a rare case of unilateral orbital schwannoma arising from the
 infraorbital nerve is presented .
 an excision biopsy with complete
 removal of the mass in the inferior orbit was performed .
 a
 definitive diagnosis was made on histopathological examination .

 the clinical and histological features of schwannoma are
 discussed . a need for early removal of such tumors
 is
 recommended to prevent complications .