Duodenal infusion of different nutrients and the site of gaseous stimulation influence intestinal gas dynamics

OBJECTIVE: Excessive intestinal gas can be involved in postprandial abdominal symptom generation, but whether the small bowel influences intestinal gas dynamics, depending on the ingested meal, remains to be demonstrated. We compare the intestinal response to a proximal and distal small intestinal gas challenge during different duodenal nutrient components. MATERIAL AND METHODS: We randomly studied 32 healthy subjects, twice, on different days with a gas mixture infused at 12 ml/min either directly into the proximal jejunum or into the ileum; during duodenal lipids, amino acids, glucose, at 1 kcal/min each, or saline (n=8 for each group). Gas evacuation was monitored continuously and abdominal perception and girth changes were assessed. RESULTS: In response to the jejunal gas challenge, duodenal lipids delayed intestinal gas clearance more potently than amino acids (733+/-26 ml and 541+/-108 ml final gas retention; p<0.001), but when gas was directly infused into the ileum the retained volumes were much smaller (271+/-78 ml and 96+/-51 ml; p<0.001). During duodenal glucose, intestinal gas clearance following jejunal or ileal gas infusion was not significantly influenced. Abdominal perception in response to the jejunal and ileal gas challenge only increased slightly during duodenal lipids (2.0+/-0.3 score and 2.3+/-0.6 score; p<0.05 versus control). CONCLUSION: Postprandial intestinal gas clearance is hampered by duodenal lipids and amino acids but not by glucose. Specific inhibitory effects are more pronounced when gas is infused into the jejunum, which underlines the importance of the small intestine in postprandial gas retention.     

Effect of High- and Low-Caloric Mixed Liquid Meals on Intestinal Gas Dynamics

High-caloric meals can evoke postprandial abdominal complaints involving disturbances in intestinal gas balance. We aimed to determine the influence of the caloric content of meals on intestinal gas dynamics. Eight healthy subjects (five women, three men; age range, 25–43 years) underwent paired studies with low (1 kcal/min)- and high (3 kcal/min)-caloric meal infusion 35% fat, (45% carbohydrate, 20% protein) into the duodenum in random order and proximal jejunal gas infusion. Gas evacuation, perception, and abdominal girth were assessed. The low-caloric meal caused neither gas retention (–7 ± 58 ml) nor girth changes (0 ± 0 mm). In contrast, the high-caloric meal led to significant gas retention (705 ± 56 ml) and increased abdominal perimeter (7 ± 1 mm; P < 0.001 vs. the low-caloric meal for both). Thus, a high caloric load of nutrients arriving at the duodenum modulates both intestinal gas transit and abdominal perimeter. This work was supported by Research Fund of the Mannheim Faculty of Clinical Medicine Grant 098200/99-245, University of Heidelberg, and the Else-Kroener Fresenius Foundation.     

Influence of body posture on intestinal transit of gas

BACKGROUND: Patients describe that body posture may affect their abdominal bloating, distension, and flatulence, but whether changes in position have objectively demonstrable effects, either beneficial or deleterious, has not been investigated. Aim: To determine the effect of body posture, upright versus supine, on intestinal transit of gas loads. SUBJECTS: Eight healthy subjects without gastrointestinal symptoms. METHODS: In each subject a gas mixture was continuously infused into the jejunum (12 ml/min) for three hours, and gas evacuation, clearance of a non- absorbable gaseous marker, perception, and abdominal girth were measured. Paired studies were randomly performed in each subject on separate days in the upright and supine positions. RESULTS: In the upright position, intestinal gas retention was much smaller than when supine (13 (52) ml v 146 (75) ml retention at 60 minutes, respectively; p<0.05), and clearance of the gas marker was expedited (72 (10)% clearance v 49 (16)% at 60 minutes, respectively; p<0.05). The gas challenge test was well tolerated both in the upright and supine positions without abdominal distension. CONCLUSION: Body posture has a significant influence on intestinal gas propulsion: transit is faster in the upright position than when supine.     

Sites of symptomatic gas retention during intestinal lipid perfusion in healthy subjects

BACKGROUND: Gas pooling within the gut may produce abdominal symptoms but the segment of the intestine responsible for gas retention is unknown. Our aim was to determine the role of the proximal and distal bowel in symptomatic gas accumulation using an experimental model of gas retention triggered by intraluminal lipids. SUBJECTS: Sixteen healthy subjects. METHODS: A gas mixture (N2, O2, and CO2 in venous proportions) was infused into the intestine at12 ml/min for three hours and gas evacuation was continuously measured via an anal cannula connected to a barostat. Abdominal perception and girth changes were measured at 10 minute intervals. Lipids (1 kcal/min) were simultaneously perfused either into the duodenum (n = 8) or into the ileum (n = 8). Each subject was studied twice on separate days, with gas infused into the jejunum or ileum. RESULTS: Duodenal lipids produced retention of gas infused into the jejunum (646 (62) ml) but the volume retained was much smaller when gas was infused directly into the ileum (262 (90) ml; p<0.05). The effects on gas retention were even more pronounced during ileal perfusion of lipids (1546 (184) ml during jejunal gas infusion and 847 (142) ml during ileal gas infusion; p<0.05). Abdominal distension correlated with the volume of gas retained (r = 0.87; p<0.001). Healthy subjects tolerated gas retention, and significant symptoms (score 3.7 (0.8)) developed only during jejunal gas infusion plus ileal lipid perfusion when gas retention was very large. CONCLUSION: Intraluminal lipids induce intestinal gas retention, predominantly acting on the proximal small bowel.     

Impaired small bowel gas propulsion in patients with bloating during intestinal lipid infusion

OBJECTIVE: In healthy individuals, intraluminal lipids delay intestinal gas clearance, and this reflex is exaggerated in patients with irritable bowel syndrome (IBS). Our aim was to determine the site of action of abnormal lipid-induced reflexes in IBS. METHODS: In six patients with (IBS) predominantly complaining of bloating and in six healthy subjects, a mixture of gas (N2, O2, and CO2 in venous proportions to minimize diffusion) was infused (12 mL/min) either into the jejunum or into the ileum for 2 h, with simultaneous perfusion of lipids (0.5 kcal/min) into the proximal duodenum. Rectal gas evacuation was measured by a barostat. Abdominal perception (by a 0-6 scale) and girth changes were measured at 15-min intervals. The effects of jejunal versus ileal gas infusion were compared by paired tests in random order on separate days. RESULTS: IBS patients exhibited significant gas retention during infusion of gas into the jejunum (398 +/- 90 mL vs-210 +/- 105 mL in health, p < 0.05) but not during ileal infusion (-79 +/- 87 mL vs-79 +/- 78 mL in health, NS; p < 0.05 vs jejunal infusion). Gas retention during jejunal gas infusion in IBS patients was associated with significant abdominal distension (11 +/- 3 mm girth increment vs 0 +/- 1 mm during ileal gas infusion and 1 +/- 1 mm in health, p < 0.05 for both) and abdominal symptoms (3.6 +/- 0.6 score vs 2.6 +/- 0.7 score during ileal gas infusion and 1.6 +/- 0.5 score in health, p < 0.05 for both). CONCLUSIONS: In IBS patients intraluminal lipids impair intestinal gas clearance because of upregulated reflex inhibition of small bowel transit, without appreciable colonic effects.     

Physical activity and intestinal gas clearance in patients with bloating

BACKGROUND: Patients complaining of abdominal bloating have impaired tolerance and clearance of intestinal gas loads. Mild exercise enhances intestinal clearance and prevents retention of intestinal gas loads in healthy subjects. Our aim was to evaluate the putative beneficial effects of physical activity in patients with abdominal bloating. METHODS: In eight patients complaining of bloating, seven with irritable bowel syndrome, and one with functional bloating, according to Rome II criteria, a gas mixture was continuously infused (12 mL/min) into the jejunum for 120 min with simultaneous duodenal lipid perfusion (1 kcal/min). Gas evacuation, perception (0-6 scale), and abdominal girth were measured at 15-min intervals. Paired studies were randomly performed in the supine position during intermittent pedaling (5 min with 3-min rest intervals at 40 rpm and 0.15 kp load) versus rest (as control). RESULTS: During rest, a significant proportion of the gas infused was retained in the gut (45 +/- 9%, P < 0.01 vs basal), but retention was significantly lower during exercise (24 +/- 7%, P < 0.05 vs rest). Gas retention during rest was associated with significant abdominal symptoms (3.6 score; P < 0.01 vs basal), and symptoms also improved during exercise (2.8 score, P < 0.05 vs rest). During the test, patients developed abdominal distension, which was related to the volume of gas retained (r = 0.68, P < 0.05). CONCLUSION: Mild physical activity enhances intestinal gas clearance and reduces symptoms in patients complaining of abdominal bloating.     

Impaired transit and tolerance of intestinal gas in the irritable bowel syndrome

BACKGROUND: Patients with irritable bowel syndrome (IBS) frequently complain of excessive gas but their fasting volume of intestinal gas is apparently normal. We hypothesised that the pathophysiological mechanism involved may be impairment of intestinal gas transit. AIM: To investigate intestinal gas transit and tolerance in IBS patients compared with healthy subjects. METHODS: A gas mixture (N(2), O(2), and CO(2) in venous proportions) was infused into the jejunum of 20 patients with IBS and 20 healthy controls at 12 ml/min for four hours. Gas evacuation, initially flatus from the anus (two hours) and then intrarectally (two hours), was continuously recorded. Symptom perception (0-6 scale) and abdominal distension were measured at 10 minute intervals. RESULTS: After two hours of external gas (flatus) collection, 18 of 20 IBS patients had developed gas retention (>400 ml), increased gastrointestinal symptoms (score >3), or abdominal distension (>3 mm girth increment) compared with only four of 20 control subjects. During intrarectal gas collection, 13 of 17 patients still exhibited abnormal responses. CONCLUSION: A large proportion of patients with IBS can be shown to have impaired transit and tolerance of intestinal gas loads. This anomaly may represent a possible mechanism of IBS symptoms, specifically pain and bloating.     

Impaired reflex control of intestinal gas transit in patients with abdominal bloating

BACKGROUND: Patients with abdominal bloating and distension exhibit impaired transit of intestinal gas which may lead to excessive gas retention and symptoms. Furthermore, we have previously shown that intestinal gas transit is normally accelerated by rectal distension. We hypothesise that in patients with functional bloating this modulatory mechanism fails and impairs gas transit. METHODS: In 12 healthy subjects and eight patients with abdominal bloating we compared, by paired studies, the effect of rectal versus sham distension on intestinal gas transit. Gas was infused into the jejunum (12 ml/min) for three hours with simultaneous perfusion of lipids into the duodenum (Intralipid 1 kcal/min) while measuring evacuation of gas per rectum. RESULTS: In healthy subjects, duodenal lipid infusion produced gas retention (409 (68) ml) which was prevented by rectal distension (90 (90) ml; p<0.05 v sham distension). In contrast, rectal distension in patients with abdominal bloating failed to reduce lipid induced gas retention (771 (217) ml retention during rectal distension v 730 (183) ml during sham distension; NS; p<0.05 v healthy controls for both). CONCLUSION: Failure of distension related reflexes impairs intestinal gas propulsion and clearance in patients with abdominal bloating.     

Effects of physical activity on intestinal gas transit and evacuation in healthy subjects

PURPOSE: To determine the effects of mild physical activity on intestinal gas transit and clearance. METHODS: In 8 healthy adults, a gas mixture was infused continuously into the jejunum (12 mL/min) for 120 minutes with simultaneous duodenal lipid perfusion (1 kcal/min). Gas evacuation, perception of abdominal sensations (on a scale of 0 [none] to 6 [pain]), and abdominal girth were measured at 15-minute intervals during rest and intermittent pedalling, with subjects in a supine position. RESULTS: Mean (+/- SD) intestinal gas retention was lower during exercise than at rest (-84 +/- 303 mL vs. 143 +/- 219 mL, P <0.05). Gas retention during rest was associated with significant abdominal distension (8 +/- 6 mm, P <0.01 vs. basal), which was decreased with exercise (3 +/- 7 mm, P <0.05 vs. rest). The gas challenge test was well tolerated both during exercise and rest (perception score: 0.6 +/- 0.5 vs. 0.9 +/- 0.4, P = 0.25). CONCLUSION: In healthy subjects, gut transit of intraluminal gas is enhanced by mild physical activity.     

Origin of gas retention and symptoms in patients with bloating

BACKGROUND & AIMS: Patients reporting abdominal bloating exhibit impaired tolerance to intestinal gas loads. The aim of this study was to identify the gut compartment responsible for gas retention. METHODS: In 30 patients predominantly reporting abdominal bloating (24 with irritable bowel syndrome and 6 with functional bloating) and 22 healthy subjects, gas (nitrogen, carbon dioxide, and oxygen) was infused into the intestine for 2 hours while measuring rectal gas outflow. First, in 12 patients and 10 healthy subjects, gas transit (24 mL/min jejunal infusion labeled with 74 MBq bolus of 133 Xe) was measured by scintigraphy. Second, in groups of patients and healthy subjects, the effects of gas infusion (12 mL/min) in the jejunum versus ileum, jejunum versus cecum, and jejunum versus sham infusion (n=6 each) were compared by paired tests. RESULTS: In patients, total gut transit of gas was delayed (50% clearance time, 33 +/- 4 min vs 23 +/- 4 min in healthy subjects; P <.05) owing to impaired small bowel transit (50% clearance time, 20 +/- 2 min vs 12 +/- 3 min in healthy subjects; P <.05), whereas colonic transit was normal (50% clearance time, 13 +/- 2 min vs 11 +/- 2 min in healthy subjects; not significant). Furthermore, jejunal gas infusion in patients was associated with gas retention (329 +/- 81 mL vs 88 +/- 79 mL in healthy subjects; P <.05), whereas direct ileal or colonic infusion was not (61 +/- 103 mL and -143 +/- 87 mL retention, respectively). CONCLUSIONS: In patients reporting bloating, the small bowel is the gut region responsible for ineffective gas propulsion.     

Intestinal gas distribution determines abdominal symptoms

BACKGROUND: Patients with functional gut disorders manifest poor tolerance to intestinal gas loads but the mechanism of this dysfunction is unknown. AIM: Our aims were firstly, to explore the relative importance of the amount of intestinal gas versus its distribution on symptom production, and secondly, to correlate gut motility and perception of gas loads. SUBJECTS: Fourteen healthy subjects with no gastrointestinal symptoms. METHODS: In each subject a gas mixture was infused (12 ml/min) either into the jejunum or rectum for one hour during blocked rectal gas outflow, and subsequently gas clearance was measured over one hour of free rectal evacuation. We measured abdominal perception, distension, and gut tone by duodenal and rectal barostats. RESULTS: Similar magnitude of gas retention (720 ml) produced significantly more abdominal symptoms with jejunal compared with rectal infusion (perception score 4.4 (0.4) v 1.5 (0.5), respectively; p<0.01) whereas abdominal distension was similar (15 (2) mm and 14 (1) mm girth increment, respectively). Jejunal gas loads were associated with proximal contraction (by 57 (5)%) and colonic loads with distal relaxation (by 99 (20)%). CONCLUSION: The volume of gas within the gut determines abdominal distension whereas symptom perception depends on intraluminal gas distribution and possibly also on the gut motor response to gas loads.     

Colonic gas transit in patients with bloating: the effect of an electromechanical stimulator of the abdominal wall

Background

The aim of our study was to evaluate gas retention, abdominal symptoms and changes in girth circumference in females with bloating using an active or sham abdominal wall mechanical stimulation.

Methods

In 14 female patients, complaining of bloating (11 with irritable bowel syndrome and 3 with functional bloating according to the Rome III criteria) a gas mixture was continuously infused into the colon for 1 h (accommodation period). Abdominal perception and girth were measured. At the beginning of the 30-min period of free rectal gas evacuation (clearance period), an electromechanical device was positioned on the abdominal wall of all patients. The patients were randomly assigned to an active or a sham stimulation protocol group. Gas retention, perception and abdominal distension were measured at the end of the clearance period.

Results

All patients tolerated the volume (1,440 ml) of gas infused into the colon. Abdominal perception and girth measurements was similar in both groups during the accommodation period. At the end of the clearance, the perception score and the girth changes in the active and sham stimulation groups were similar (2.8 ± 2.0 vs. 1.4 ± 1.2, p = 0.2 and 4.9 ± 4.5 vs. 2.8 ± 2.3 mm, p = 0.3 active vs. sham, respectively). Furthermore, the mechanical stimulation of the abdominal wall did not significantly reduce gas retention (495 ± 101 ml vs. 566 ± 55, active vs. sham, p = 0.1).

Conclusions

An external mechanical massage of the abdominal wall did not improve intestinal gas transit, abdominal perception and abdominal distension in our female patients complaining of functional bloating.     

Gastric distension and duodenal lipid infusion modulate intestinal gas transit and tolerance in humans

OBJECTIVE: Patients with unexplained abdominal complaints often attribute their symptoms to intestinal gas and indicate that symptoms are exacerbated by ingestion of a meal. However, the mechanisms responsible are unknown. Our aim was to analyze the specific influence of two meal-related factors, gastric distension, and intestinal nutrients, on intestinal gas dynamics and tolerance. METHODS: In 35 healthy subjects, gas evacuation and perception of jejunal gas infusion (12 ml/min) were measured for 3 h, during simultaneous duodenal infusion of saline, as control, lipids at 1 Kcal/min, or gastric distension. RESULTS: Infusion of lipids into the duodenum induced gas retention (584 +/- 154 ml, p < 0.05 vs 161 +/- 86 ml after saline infusion) without perception (2.2 +/- 0.5 score), whereas gastric distension induced perception (score 5.6 +/- 0.4, p < 0.05 vs score 1.9 +/- 0.4 after saline) without gas retention (7 +/- 205 ml). CONCLUSIONS: Different meal-related factors exert specific effects on intestinal gas dynamics and tolerance, and these mechanisms may interact to produce postprandial gas symptoms.     

Prokinetic effects in patients with intestinal gas retention

BACKGROUND & AIMS: We have previously shown that patients with irritable bowel syndrome (IBS) have impaired transit of intestinal gas loads. Because abnormal gas retention can be experimentally reproduced in healthy subjects by pharmacological inhibition of gut motility, we hypothesized that impaired gas transit and retention can be reciprocally corrected by pharmacologically stimulating intestinal propulsion. METHODS: In 28 patients with abdominal bloating (14 IBS, 14 functional bloating) and in 14 healthy subjects, gas evacuation and perception of jejunal gas infusion (12 mL/min) were measured. After 2 hours, in 20 patients we tested the effect of intravenous neostigmine (0.5 mg) vs. intravenous saline administered blindly and randomly at a 1-hour interval. RESULTS: After 2 hours of gas infusion, patients with IBS and functional bloating alike exhibited significant gas retention (418 +/- 86 mL), abdominal symptoms (2.7 +/- 0.5 score), and objective distention (8 +/- 2 mm girth increment), in contrast to healthy controls, who experienced none (46 +/- 102 mL retention, 0.4 +/- 0.3 symptom score, and 3 +/- 1 mm distention; P < 0.05 for all). Neostigmine produced immediate clearance of gas retained within the gut (603 +/- 53 mL/30 minutes vs. 273 +/- 59 mL/30 minutes after saline; P < 0.05) and by 1 hour reduced gas retention (by 373 +/- 57 mL), abdominal symptoms (by 1.1 +/- 0.5 score), and distention (by 6 +/- 1 mm; P < 0.05 for all), whereas intravenous saline produced no effects. CONCLUSIONS: In patients with intestinal gas retention, pharmacological stimulation of intestinal propulsion improves gas transit, abdominal symptoms, and distention.     

Alterations in rat intestinal transit by morphine promote bacterial translocation

Translocation of enteric microorganisms from the intestinal tract to extraintestinal sites has been proposed as an early step in the development of gram-negative sepsis. This study examined the role of altered bowel transit in influencing intestinal bacteriostasis and bacterial translocation using morphine as a pharmacologic inhibitor of such transit. In the first experiment, either normal saline (N=8) or morphine sulfate (20 mg/kg;N=8) was injected subcutaneously. Two hours later, morphine (7.5 mg/kg) was infused subcutaneously for an additional 22 hr; control animals received saline alone. After completion of this regimen, a volume of 0.2 ml of 2.5 mM FITC dextrans (10,000 daltons) were injected intraduodenally in each group. The bowel was removed 25 min later, divided into 5-cm segments, and the content of dextrans measured. Small bowel propulsion was expressed as the geometric center of the distribution of dextrans throughout the intestine (in percentage length of small bowel). Gut propulsion was significantly reduced after morphine treatment as compared to controls (32.8±8.2% vs 55.8±4.0%;P<0.01). In 16 additional rats, saline or morphine was again administered as described. After 24 hr, samples were obtained from the mesenteric lymph node (MLN) complex, blood, spleen, liver, duodenum, jejunum, ileum, and cecum for standard bacteriology. The bacterial counts increased significantly in each intestinal segment following morphine treatment. Microorganisms translocated to the MLN complex in 5, and to distant sites in four of eight morphine-treated animals, respectively. Translocation to the MLN complex occurred in only one of eight controls (P<0.05); no translocation to distant sites occurred in control animals. We conclude that the morphine-induced prolongation in bowel transit promotes bacterial translocation secondary to an overgrowth of enteric bacteria in the intestinal lumen.Supported by NIH grant GM 38529 and the DFG grant Ru 387/1-2.     

Response to intraluminal gas in irritable bowel syndrome

Our aim was to evaluate the response to intraluminal gas in irritable bowel syndrome and to determine whether this response was consequent upon disordered motility or altered perception. We evaluated 10 patients who satisfied the clinical criteria for the diagnosis of irritable bowel syndrome and 10 healthy controls. An eight-lumen perfused catheter assembly was positioned to monitor motor activity in the duodenum and proximal jejunum; a separate side port in the distal duodenum permitted gas infusion. Subjects recorded symptoms of abdominal pain, bloating, and nausea throughout the study, using a visual analog scale. Following an overnight fast and a 60-min basal recording period in the fasted state, subjects ate a standard meal; 60 min later, sham gas was administered for 20 min, followed by the actual infusion of nitrogen gas at 40 ml/min. Subjects were randomized to receive atropine (7 µg/kg) or placebo intravenously during the period of actual gas infusion. Patients with irritable bowel syndrome described more pain (score, mean±se, control versus irritable bowel: 0.22±0.16 vs 1.65±0.5,P<0.01) and nausea (0.25±0.21 vs 1.45±0.64,P<0.04) during sham gas; motility indices were similar in both groups. During active gas, irritable bowel syndrome patients reported more pain (0.40±0.39 vs 2.94±1.16,P<0.03); motility indices at all sites were similar in both groups. Symptom severity in irritable bowel syndrome subjects randomized to receive atropine was similar to control subjects during active gas infusion; motility indices were similar. We conclude that irritable bowel syndrome patients are more sensitive to intraluminal gas. This does not appear related to an exaggerated motor response, but may reflect heightened central perception.Supported in part by a grant from the University of Nebraska Hospital.Presented, in part, at the annual meeting of the American Gastroenterological Association, Boston, Massachusetts, May 1993, and has appeared in abstract form. Gastroenterology 104:A 511, 1993.     

Absorption and motility of the bypassed human ileum

The authors assessed absorption and motility of the human ileum after a prolonged period of disuse. In eight patients with ulcerative colitis, a manometric-catheter assembly was placed via the ileostomy into the unused portion of distal ileum two months after ileal pouch-anal anastomosis and temporary diverting loop ileostomy. The distal ileum was perfused at 5 ml/min with an isosmotic solution of either sodium chloride or ileal chyme diluted with sodium chloride for three hours before and three hours after a meal on two consecutive days. Absorption was measured, single and clustered pressure waves were identified and quantitated with the aid of a computer program, and a motility index was calculated. Mean absorption ± S.E.M. of both perfusates was poor on day 1 (–10±2 ml/25 cm × 30 min), and the meal induced no ileal motor response. By day 2, however, absorption of both perfusates was much improved (–1±2 ml/25 cm × 30 min; P<0.05), and the number of discrete clustered contractions and the motility index now clearly increased after the meal (2.6±0.6 vs. 7.2±1.0 clustered waves/hr; 7.5±0.5 vs. 9.7±0.2 motility units/30 min;P<0.05).The conclusion was that absorption and motility of the human ileum were impaired after two months of disuse, but that ileal absorption and motility improved one day after the introduction of isosmotic ileal perfusates.Supported in part by USPHS NIH Grants DK34988, DK18278 and DK07198, and the Mayo Foundation.     

Diurnal rhythmicity of absorption of a lipid compound (vitamin K-1)in vivo in the rat

The possibility of rhythmicity in the intestinal absorption of lipids was explored by assessing the absorption of vitamin K-1 by the unanesthetized rat at 6pm, 12 and 6am, and 12pm. A marked variability in the absorption rate of vitamin K-1 was found throughout the 18-hr period. The highest rates of absorption occurred at midnight (139.8±.22 and 134.4±9.1 pmol/min/10 cm of jejunum and ileum, respectively). The lowest rates of absorption occurred at 6am (54.5±1 and 81.4±7.4 pmol/min/10 cm of jejunum and ilenum, respectively). Absorption rates at noon were not different from absorption at 6am but an initial increase in absorption was noted at 6pm. Synchronization of the absorptive rate with time is most likely related to the time of feeding and not to changes in the pattern of illumination. The possibility of marked diurnal variability in the absorption rate should be considered in the design and execution of intestinal absorption experiments.     

Trophic effects of neurotensin in massive bowel resection in the rat

The trophic effect of the administration of exogenous neurotensin on the intestinal mucosa was studied in rats following an 80% bowel resection. Villus length and mucosal DNA content were assessed in the jejunal and ileal mucosa of the remnant intestine 14 days after resection. The data obtained in an 80% resected control group (80% group) and an experimental group receiving an infusion of neurotensin (300 µg/kg/day) for 14 days subcutaneously (80%+NT group) were compared. The results indicate that the administration of exogenous neurotensin (80%+NT) increases villus length (jejunum: 920±77 vs 861±25 µm and ileum length: 975±23 vs 875±99 µm) to an extent greater than that observed in the 80% resected group not receiving exogenous neurotensin. The levels of mucosal DNA per milligram of protein increased significantly in both groups but was paradoxically less in the 80%+NT group than in the 80% resection group (jejunum: 8±0.56 vs 10.18±0.80; ileum; 8.63±0.43 vs 10.05±0.46). These data suggest that the administration of exogenous neurotensin to the rat potentiates the growth of intestinal villi and accelerates the intestinal trophic response seen following massive bowel resection. The increase in circulating enteroglucagon levels noted after neurotensin administration (80%+NT: 547±48 pg/ml vs 80%: 341±41 pg/ml) suggests that some of the trophic effects of neurotensin may be mediated, at least in part, by enteroglucagon. These data also suggest a potential role for the use of neurotensin in the initial treatment of individuals with short bowel syndrome.     

Qualitative Changes in Enteric Flora and Short-Chain Fatty Acids After Intestinal Resection

Our aim was to determine the effect ofintestinal transection and resection on the prevalenceof enteric flora and evaluate whether any such changesalter luminal SCFA and lactic acid content. Dogsunderwent either 50% proximal (PR, N = 6) or distal (DR,N = 7) resection, distal resection with bypass of theileocecal junction (DRBP, N = 9) or midpoint transectionalone performed to serve as the appropriate control for luminal sampling for either proximal (PTC,N = 6) or distal (DTC, N = 7) resection. Studies wereperformed every four weeks for 12 weeks. Both jejunumand ileum had >10⁵/ml aerobic bacteria,most commonly E. coli. Streptococcal species were more commonin the normal jejunum than ileum but were found in theileal remnant after PR. Significant (>10⁵)anaerobic growth occurred infrequently in the jejunum, and DR did not increase anaerobic growth injejunum unless DRBP was performed (93% vs 62% DR, 45%DTC, 20% normal jejunum, P < 0.05). Clostridiumspecies increased significantly in the jejunal remnant after DRBP. Significant anaerobic growthoccurred infrequently in normal ileum but increasedafter PR (89% vs 50% PTC, P < 0.05). Flora normallyfound in the jejunum tended to increase in the ileumafter PR. Jejunal SCFA increased after DRBP (3126± 577 mug/ml vs 1600 ± 301 DTC, P <0.05) but not DR (1791 ± 321 mug/ml). Significant(>105) anaerobic bacterial growth was associated withincreased SCFA content (2717 ± 381 vs 1029± 170 mug/ml, P < 0.05) and the presence oflactic acid (30% vs 5%, P < 0.05), but there was nocorrelation between the presence of specific bacteriaand SCFA and lactic acid. Following resection of theproximal small intestine, the intestinal remnant tendsto assume the bacteriologic characteristics of theresected segment. Following a distal resection, the presence of an intact ICJ protects against theproliferationof a flora characteristic of the distalintestine; resection with bypass of the ICJ results inthe appearance of coliforms in the jejunal remnant. These changes in enteric flora do not correlatewith content of specific SCFA and lactic acid in thesmall intestine.