AS10 AGA ABSTRACTS

• G3328 REGIONAL LINGUAL MECHANICS DURING SWALLOWING: A SYNERGISTIC MODEL INVOLVING INTRINSIC AND EXTRINSIC MUSCLE ACTIVITY. VI Napadow, Q Chen, VJ Wedeen, ILl Gilbert. Department of Mechanical Engineering, Massachusetts Institute of Technology, Department of Radiology, Beth Israel Deaconess Medical Center, and NMR Center and Department of Radiology, Massachusetts General Hospital. Boston, MA.

The tongue is comprised of a core region of orthogonally aligned intrinsic fibers surrounded by a longitudinal sheath, and extrinsic muscles that are located in the posterior region of the organ and oriented in the inferior and superior directions. The extent to which intrinsic and extrinsic muscles contribute to lingual deformation during complex physiological motion is presently unknown. Our goal was to quantify regional lingual strain associated with the function phases (early and late accommodation, propulsion) of normal swallowing. METHODS: Subjects (n=7) were imaged with a Siemens Vision 1.5T MRI scanner using a single shot gradient echo pulse sequence. Strain was represented as deformations of discrete deforming elements, defined by the application of supersaturated magnetized bands in the x and y directions. Subjects initiated dry swallows following a sound corresponding to tag application, and imaging was performed after a delay of 200-700 msec. Tissue mechanics were depicted graphically as color-coded 2D strain maps and as octahedra whose axes corresponded to the 3D strain properties for each element. RESULTS: During early accommodation, the anterior tongue showed positive (expansion) anterior-posterior (AP) strain (peak 0.521), while the midtongue showed negative (contractile) superior- inferior (SI) strain (peak -0.117). During late accommodation, the anterior tongue displayed increased positive AP and SI strain (peak 0.782) and the posterior tongue displayed decreased negative SI strain (peak -0.258). During propulsion, posterior displacement of the tongue was associated in the mid- sagittal plane with positive strain (peak 0.631) directed in the posterior and superior directions. CONCLUSION: Deglutitive accommodation is a function of intrinsic muscle contraction in the anterior tongue and extrinsic muscle contraction in the posterior tongue (consistent with the genioglossus and hyoglossus). Propulsion is associated with posterior passive stretch in the midline, consistent with contraction of the laterally inserted styloglossus. Lingual deformation during swallowing can be conceived of as a synergism involving varying mechanical contributions of intrinsic and extrinsic muscles. This research was supported in part by a grant from Ross Products Division, Abbott Laboratories, Columbus, Ohio.

• G3329 GLUCAGON-LIKE PEPTIDE-1 (GLP-1) IS A POWERFUL INHIBITOR OF GASTRIC EMPTYING IN MAN. E N~isl.und 1, S Skogar 2, P Gryb[ick 3, H Jacobsson 3, JJ Hoist 4, PM Hellstr~Sm 3. IDivision of Surgery, Danderyd Hospital, Karolinska Institute, 2Dept of Hepatology and Gastroenterology, and 3Radiology, Karolinska Hospital, Stockholm, Sweden; 4Dept of Medical Physiology, University of Copenhagen, Copenhagen, Denmark.

Background: Glucagon-like peptide-1 (GLP-1) is released after food intake and has been proposed as a candidate for the "ileal brake" in man. Previous studies on GLP-1 and gastric emptying have examined the emptying of liquids. The aim of this study was to assess the effect of GLP-1 on gastric emptying of solids and to assess the amount of nutrients emptied to the intestine are needed for a release of GLP-I. Methods: After an overnight fast, gastric emptying was studied in six male normal weight subjects (BMI _+SE 23.9 -+ 1.1 kg/m 2) for 180 min after ingestion of a 310 kcal 99rnTc-labeled omelet. At the start of the meal intravenous GLP-1 (0.75 pmol/kg min) or saline (randomized double blind) was administered for the duration of the study period. Scintigraphic acquisitions and plasma samples for the analysis of GLP-1, glucose, insulin and peptide YY (PYY) were obtained every 5 min for 50 min, every ten rain for 70 rain and finally once at 180 min after the meal. Results: Infusion of GLP-1 results in an prolongation the lag phase (90 rain) and slower emptying rate of solid meal. Peak plasma GLP-1 concentrations of biologically active GLP-1 were higher during GLP-1 infusion (Mean _+ SE, 17.8 _+ 1.5 vs 12.3 _+ 1.4 pmol/L). Plasma PYY and glucose concentrations were lower during GLP-1 infusion. During saline infusion a significant elevation (+2 SD over fasting values) of plasma GLP-1 concentrations was observed after a emptying time of (mean --. SE) 15.7 -+ 2.9 min at which 10 ± 2.4% of the meal or 31 _+ 7.4 kcal had emptied.

Saline (n=6) GLP-1 (n=6) p value Lag phase (90) (rnin) 16.4 (10.2-43.4) T50 (rain) 71.3 (43.6-89.4) Emptying rate (%/rain) 0.85 (0.62-1,33)

91.5 (75.5-133.2) p=0.03 226.1 (144.8-420.8) p=0.03 0.34 (0.12-0.56) p=0.03

Data shows as median (range), Wilcoxon signed rank test for matched pairs.

Conclusion: Infusion of GLP-1 at the start of a meal prolongs the lag phase and slows the emptying phase of solid gastric emptying. The L-cells releasing GLP-1 into the blood are very sensitive, requiring only small amounts of nutrients released into the small intestine for GLP-1 release.

GASTROENTEROLOGY Vol. 114, No. 4

• G3330

INFLUENCE OF MENTAL STRESS AND RECTAL DISTENSION ON TONIC AND PHASIC MOTOR ACTIVITY OF THE LEFT COLON. MG Naumann. S Schneider, U Scholz*, U Frankenberger, B Wiedenmann, M Karans. Depts. of Medicine (Div. of Gastroenterology) and Neurology*, University Hospital Charit6, Humboldt-University, Berlin, Germany.

We have recently shown that rectal distension causes a decrease in tone of the left colon (Gastroenterology 112:A797,1997). The neural pathways of this recto-colonic inhibitory reflex are not yet known. Therefore, we studied whether neural input from the CNS affects this reflex by applying mental stress. Methods: In 8 healthy, fasted volunteers (4 men, 4 women, 20-32 years) a barostat assembly was placed endoscopically via guide wire in the distal colon 30 cm above the anal verge. Colonic tone and phasic activity were recorded as volume changes of the balloon at an operating pressure set at 2mmHg above the minimum distending pressure using a computerised barostat. After determination of the perception thresholds for rectal balloon distension the following stimuli were applied in random order: 1. Submaximal rectal distension (50ml under pain threshold) 2. Mental stress by arithmetic tasks 3. Rectal distension and mental stress, simultaneously. Stress effects were controlled by cardiovascular parameters. The tone was expressed as baseline volume and the phasic activity as motor index (MI = no of contractions x contraction amplitudes). Results: (x _+ SD) Rectal distension led to a significant decrease in colonic tone, whereas mental stress had no significant effect. The combination of mental stress and rectal distension led to a significant decrease in sigmoid tone although this decrease was less marked than with rectal distension alone. Phasic activity was significantly higher during combined mental stress and rectal distension than during rectal distension alone. The volume changes for tone and the MI for phasic activity are given in the table:

Rectal mental stress rectal distension distension and mental stress

Tone: Volume change (ml) 32.25 ± 17.81"* 11.13 ± 24.57 16.5 :t: 16.19"

Phasic activity (/vii) Control 50.63 ± 50.84 55.19 ± 44.63 89,5 + 78.04 Stimulus 16.75 + 26.47 58.25 ± 44.6 83.5 ± 70.63

(* p < 0.05, ** p < 0.01 vs resp. control periods)

Conclusions: Mental stress has no significant effects on basal colonic tone or phasic activity. However, during simultaneous rectal distension the stress stimulus caused a significant increase in phasic activity and a tendency towards reduction of the decrease in colonic tone. This suggests a central component in the regulation of recto-colonic reflexes.

• G3331 FACTORS ASSOCIATED WITH HEALTH CARE SEEKING IN IRRITABLE BOWEL SYNDROME. MK Newcomer. MJ Shaw, TJ Beebe, SA Adlis, NJ Talley, Park Nicollet Clinic, Minneapolis, Minnesota and University of Sydney, Penrith, Australia.

A number of factors have been suggested to influence health care seeking in patients with irritable bowel syndrome (IBS), including type and severity of abdominal symptoms, and psychosocial factors, such as anxiety, depression, or illness behavior. The relative importance of these factors is unknown. Objective: Examine factors associated with health care seeking behavior for IBS in a large community sample. Methods: A random age and sex-stratified population sample of 1800 subjects were selected in the Minneapolis, MN area. They were mailed a questionnaire which included: a valid, self-report bowel disorders survey, SF-36 health survey, hospital anxiety and depression scale (HAD), pain index scale, psychosomatic symptom and comorbid illness checklists, and a 3 item measure of patient concern regarding their symptoms. 52 subjects were excluded due to non-deliverable address, deceased, mentally disabled, or language difficulties. Bivariate analyses were used to identify significant factors which were then examined in logistic regression analyses. Results: A total of 1238 subjects (71%) completed the questionnaire; 21% (254 subjects) met > 2 or more Manning criteria for IBS, (65% female, mean age 46). 29% (73 subjects) had sought medical care for abdominal complaints in the prior 12 months. Utilizing stepwise logistic regression analysis, male gender (p --- 0.03), decreased SF-36 - physical functioning summary scores (p = 0.01), more intense pain experience (p = 0.002), and concern for a serious or fatal illness (p = 0.009) was associated with an increased likelihood of seeking medical care. Anxiety or depression, or a decreased SF-36 mental functioning summary score was not associated with increased heaithcare seeking. The presence of one or more non-digestive comorbid illnesses did not increase the likelihood of seeking medical care. A significant amount of the variance was explained by this model. Conclusion: The results of the present study demonstrate that in a large, randomly selected community sample, more intense pain experience and concern for a serious or fatal illness were most strongly associated with seeking medical care. Psychological disturbance or psychosocial functioning, as measured by commonly used surveys, did not predict health care seeking. Supported in part with an unrestricted grant from Astra-Merck, Inc.