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The canine stomach empties meat as particles smaller than 0.5 mm. The present work was undertaken to determine whether fed liver enters the human intestine predominantly as small particles. In both human and canine subjects, a triple lumen (OD = 4 mm) tube was positioned with the ports beyond the ligament of Treitz, two attached to a Crosby bubble trap with 1.2-mm holes. The bubble trap effectively sampled only particles smaller than 0.8 mm. Polyethylene glycol and 0.1–0.5-mm particles of 51 Cr-chicken liver were perfused at a constant rate through the 3rd port, 25 cm proximal to the bubble trap. It was assumed that small particles of liver entering the perfused segment from above would be sampled in the same proportions as the perfused 51 Cr-liver particles, so the amount passing the bubble trap could be calculated from recovery of 51 Cr. Both dogs and humans were fed 60 g of steak + 30 g of 99m Tc-chicken liver in 10 mm cubes, + 100 ml H 2 O. In validation experiments in dogs and humans, there were good correlations between calculated recovery from the bubble trap and actual recovery. In humans, the rate at which aspiratable ( 99m Tc-chicken liver passed the bubble trap was compared with the rate at which 99m Tc-chicken liver particles of all sizes entered the bowel, as determined by measuring gastric emptying of 99m Tc with a gamma camera. When 5 human subjects were fed 10-mm cubes of 99m Tc-chicken liver, 76 ± 7% of the liver left the stomach in 3 h, while 72 ± 5% passed the jejunal sampling site as aspirable particles. When the same subjects ate the liver as aspiratable, 0.4-mm particles on another day, 66 ± 8% left the stomach in 3 h, while 58 ± 4% passed through the jejunum as aspiratable particles. By contrast, when 1.2–1.7-mm particles of 99m Tc chicken liver were instilled into the proximal duodenum, little liver could be aspirated from the jejunum. The findings indicate the human stomach, like the dog stomach, allows only small particles of meat to pass into the gut.

Since the chain length dependency of fatty acid-induced pancreatic exocrine secretion parallels that of fatty acid-induced inhibition of gastric emptying, similar mechanisms of action may be involved. An earlier study suggested that binding of calcium might mediate fatty acid-induced inhibition of gastric emptying. This study investigated possible mediation of fatty acid-induced pancreatic secretion by calcium binding. Pancreatic secretory response to intraduodenal administration of dodecanoate and various calcium chelators (sodium EDTA, calcium-saturated EDTA, sodium dodecyl sulfate, sodium dioctyl sulfosuccinate, and sodium taurocholate) was studied in three dogs equipped with chronic pancreatic fistulae. Calcium affinity of the various test solutions was quantitated by titrating aliquots of perfusate against a standard CaCl2 solution. Sodium EDTA was found to be the most potent calcium binder (pKc 8.3); sodium dodecanoate, sodium dodecyl sulfate, and sodium dioctyl sulfosuccinate were moderate calcium binders (pKc 7.3, 7.2, 6.9, respectively), whereas sodium taurocholate and calcium-saturated EDTA were poor calcium binders. Sodium dodecanoate evoked brisk bicarbonate output (0.6-1.6 mEq/15 min). Minimal secretory responses were observed in response to all other agents tested. These findings suggest that calcium binding is not involved in mediation of fatty acid-induced pancreatic bicarbonate secretion.

Present concepts on the gastric emptying of solid materials derive from experiments with plastic spheres now known to be emptied differently than food. Accordingly, experiments were undertaken with radiolabeled chicken liver to assess (a) the size of meat particles passed by the normal canine stomach and (b) the effeds of ulcer surgery on the rate of emptying and the size of emptied meat particles. Control or ulcer-operated dogs were prepared with chronic duodenal fistulas from which chyme was collected after a standard meal of beefsteak + radioliver + water. Collected chyme was sieved over a stack of sieves of decreasing pore size, and the percent of radioactivity recovered on each sieve was determined each postcibal hour for 5 hr. Control dogs emptied the meal slowly, and virtually all recovered meat was emptied in particles ʩ 2.0 mm. Dogs with vagotomy (V), pyloroplasty (P), vagotomy + pyloroplasty (V + P), or antrectomy with end-toend (A-BI) or end-to-side (A-BII) gastroduodenostomy did not empty the meal faster than the control dogs. In all ulcer-operated dogs except those with P, there were significant upward shifts in the size of meat particles emptied from the stomach; but changes were marked only in dogs with V + P or ABII. Although the experiments verify the antral sieving mechanism noted in earlier work with plastic spheres, the trituration of solid food is probably more complex than previously envisioned.

By speeding the fragmentation of meat, peptic digestion might accelerate gastric emptying. To examine this possibility, mongrel dogs prepared with chronic duodenal fistulas were fed steak and 99mTc-labeled chicken liver, measuring 99mTc in all chyme exiting from the stomach out the duodenal fistula allowed quantitation of the gastric emptying of 99mTc-liver. Emptying was studied during relatively uninhibited gastric propulsion when the proximal bowel was perfused with chyme or fat. When chyme was diverted, the speed of emptying varied with peptic activity in the stomach--that is, it was increased by orogastric perfusion with acid-pepsin (vs. a control perfusion of pH 7 buffer) or, alternately, was decreased from the unperfusion stomach by i.v. cimetidine (vs. i.v. saline). By contrast, no effect of altering peptic conditions was observed when chyme was allowed access to the proximal bowel (the more normal situation), or when the duodenum was perfused with fat. We conclude that duodenal inhibition may override the effect of peptic digestion on the emptying of liver. We postulate that inhibition of gastric contractions limits the grinding of liver into particles susceptible to peptic digestion.

The influence of gastric emptying of nutrients on plasma cholecystokinin and pancreatobiliary functions is poorly understood. We therefore temporally related the emptying of fat, protein, and glucose of a mixed meal to release of the gut hormones cholecystokinin, pancreatic polypeptide, and peptide YY and outputs of trypsin, lipase, bilirubin, and bile salts. Five healthy volunteers with a multilumen duodenal tube ingested a mixed meal with phase-specific markers for the aqueous phase, liquid fat, solid fat, and solid protein phases. Duodenal passage was determined by intraduodenal infusion of a second set of phase-specific nonabsorbable markers. Plasma cholecystokinin levels and pancreatobiliary secretions rose to a maximum at 30-60 min and then gradually declined (p less than 0.01) despite continued entry of protein and fat into the duodenum throughout the whole 4-h experimental period. High levels of both pancreatic polypeptide and peptide YY were observed in the last 2 h of the experiment. Release of factors capable of inhibiting cholecystokinin release and subsequently pancreatobiliary secretion may be responsible for the observed time-course.

This study was undertaken to answer two questions: (a) does antrectomy disturb sieving or grinding of solid food, or both, and (b) how abnormal are jejunal flows and concentrations of pancreatic enzymes and bile salts after a meal of solid food. Six normal subjects and 9 subjects with truncal vagotomy plus antrectomy were intubated with a triple-lumen tube attached to a bubble trap sited in the jejunum, 60 cm from the stomach. All subjects ate a meal of 100 ml of H2O, 60 g of beefsteak, and 30 g of 99mTc-liver diced into 10-mm cubes. By previously validated techniques, the tube-bubble trap system allowed comparison of the rate of passage of 99mTc-liver particles smaller than 1 mm through the jejunum with the rate of entry of all sizes of eaten 99mTc-liver into the intestine described by gamma camera. The tube system also measured concentrations and rates of passage of enzymes and bile salts. 99mTc-liver emptied very rapidly from the stomach in the first 50 min in most subjects with truncal vagotomy plus antrectomy and thereafter emptied slowly, while in the normal subjects there was a 30 min lag before a steady, slow rate of emptying. Nearly 30% of the 99mTc-liver that emptied into the intestine in the subjects with truncal vagotomy plus antrectomy was larger than 1 mm, but in the normal subjects less than 3% of the liver entered the intestines as larger particles. In this study with a solid meal, jejunal flows in the subjects with truncal vagotomy plus antrectomy were lower than normal, and concentrations of bile salts and pancreatic enzymes were close to normal.

Sherlock Holmes was recently hospitalized for Crohn’s disease by his friend and personal physician Dr. Watson. When the famous detective asked what he was having for.lunch, Watson replied, “It’s elemental, my dear Holmes!” The elemental diet (ED) has been introduced into clinical practice as one approach to improve the nutritional status of malnourished patients. It is an almost ancient observation that starved and malnourished individuals are less able to cope with the ravages of illness than are their well-fed counterparts. Many sufferers of both acute and chronic diseases may develop protein-calorie malnutrition as an outcome of their disease.’ Although these patients differ from those with starvation in that their premorbid nutritional status was usually adequate, it is often assumed that this disease-acquired malnutrition-will be associated with additional adverse effects. By this reasoning, correction of nutritional deficiency might benefit the patient. Based on these assumptions, an entire technology has arisen to support catabolic patients nutritionally. These techniques employ both parenteral (not to be further considered) and enteral routes. Enteral nutrition can be supplied through a variety of means, most commonly natural food. In the past three decades, a different type of diet has been developed, in which the nutritional elements are individually added to produce a predefined mixture. The first planned human application of these diets was for the use of. astronauts on prolonged space voyages, where the problems of storage, ingestion, and waste disposal were considerably more pressing than they are on the earth’s surface.’ For this reason, they came to be called “space diets.” With their application to the nutritional support of terrestrials, however, these diets became known as “elemental” or “chemically defined.”

Using conscious dogs with chronic gastrointestinal fistulas, we studied the intestinal transit of radiolabeled liver particles relative to the transit of a liquid phase marker, polyethylene glycol. All studies were performed during a "fed" intestinal motility pattern induced by feeding or by intestinal perfusion with a fat-containing solution. Median transit times were determined from duodenum to fistulas at the midintestine, or at the terminal ileum, by recovery of polyethylene glycol and radiolabel in effluent from the fistulas. We also sized recovered particles of liver to determine the extent of digestion or fragmentation, or both, in transit. After a steak meal, when liquid flows were very low, the liquid marker and small (0.5-0.7 mm) and large (2-3 mm) particles moved through the proximal intestine together at a slow rate. When intestinal liquid flows were progressively increased from 2 to 24 ml/min by intestinal perfusion, transit was progressively accelerated; but 2-mm particles moved at 25%-20% of the rate of polyethylene glycol or 0.5-mm particles. Increasing transit with increasing flows was associated with decreasing digestion or fragmentation of liver particles. Under most conditions, 2-mm particles were well digested or fragmented than 0.5-mm particles. We conclude that fluid flows have a major effect on transit and digestion of food particles in the small intestine.

In previous studies, liquid fat has been used to determine the effect of bile diversion on fat absorption. Since protein digests, in addition to bile salts, are capable of solubilizing lipids, we hypothesized that fat incorporated in the protein-rich matrix of solid food would be less sensitive to bile diversion than fat ingested as an oil or liquid. Using (3H)glycerol triether as a nonabsorbable fat recovery marker, we determined how much (14C)triolein was absorbed from solid (chicken liver) and liquid (margarine) dietary sources. After a standard liquid/solid meal with either the chicken liver or margarine labeled, midintestinal chyme was collected for 6 hr, extracted, and counted for 14C and 3H activity. Zero, eighty, or one hundred percent of endogenous bile was diverted. Fat absorption from both chicken liver and margarine was nearly complete by midintestine with 0% diversion and was little affected by diversion of 80% of bile. Complete biliary diversion significantly decreased fat absorption from margarine (87.9 +/- 4.4 to 37.2 +/- 9.2%, P less than 0.05) but reduced (14C)triolein absorption from chicken liver less consistently and insignificantly (78.8 +/- 6.9 to 43.9 +/- 10.6%). These data indicate that fat absorption is not solely dependent on bile and supportmore » the hypothesis that fat ingested in a cellular matrix is less dependent on bile than liquid fat. Using these same animals but with the midintestinal cannulas plugged to expose the distal intestine to unabsorbed luminal nutrients, we also demonstrated that bile diversion of an initial meal reduced food consumption at a meal offered 3 hr later.« less

A variety of radionuclide-labeled, solid foods have been used to measure gastric emptying. Implicit is the idea that the nuclide label identifies the rate of emptying of meal contents. The present studies tested whether different foods empty from the human stomach at different rates. Eight volunteers were fed meals of 200 ml of water + 213 g of beef stew + 52 g of chicken liver, with half the liver as 0.25-mm particles and half as 10-mm chunks, labeled with 99mTc and 113In, respectively, or the reverse. Another 8 subjects ingested 200 ml of water + 75 g of noodles, labeled with 123I, + 30 g of liver, labeled with 113m In. Gastric emptying of each radionuclide was determined for 3 h by measuring the decline of counts in the gastric region of interest, using an Ohio Nuclear S410 gamma camera interfaced to a DEC computer. In each case, appropriate corrections were made for nuclear decay, down-scatter from 113mIn, and septal penetration. Seven of 8 subjects emptied 0.25-mm liver particles more quickly than 10-mm chunks of liver, while 1 subject emptied the two sizes of liver at the same rate. The t1/2 for the 0.25-mm liver was 70 ± 10 min; and for the 10-mm liver, 117 ± 19 min (p

The present study examines peptide YY responses to regional intestinal perfusion of fatty acids of different chain length--dodecanoate and oleate. Six dogs with chronic gastric, duodenal, and jejunal fistulas were studied. Proximal perfusates were administered into the duodenum and diverted through an intestinal fistula placed 45 cm beyond the duodenal cannula. Distal perfusates were administered into the caudal stoma of this intestinal stoma. Peptide YY responses to proximal, distal, and whole-gut perfusion were compared. Proximal perfusion with oleate or dodecanoate failed to release peptide YY. In contrast, distal and whole-gut perfusion with either fatty acid produced significant increases that were of similar magnitude. Immunocytochemical studies demonstrated that peptide YY cells predominated in the canine ileocolonic mucosa and decreased progressively in an orad direction. We conclude that peptide YY release is not dependent on fatty acid chain length and that the duodenum does not play a dominant role in peptide YY release. As such, peptide YY release differs from that of its cousin pancreatic polypeptide and may result at least in part from direct stimulation of the peptide YY cell in the ileocolonic mucosa.

Many believe that intragastric deactivation of lipase accounts for the frequent failure of orally ingested pancreatic enzymes to normalize fat absorption in patients with pancreatic insufficiency. To test this hypothesis, we measured fat absorption from a large test meal in six patients with pancreatic insufficiency after we had instilled Viokase directly into the postcibal duodenum in two doses, one to deliver lipase at about 10% of normal secretory rates and the other at four times this rate. Direct duodenal instillation of neither the low nor the high dose of Viokase, nor the low dose of Viokase plus sodium bicarbonate, normalized fat absorption from the test meal; none of these duodenal instillations significantly improved fat absorption over that after the test meal plus orally ingested Viokase. Despite these various treatments, the patients excreted an average of 25.5 g of dietary fat as opposed to 2.1 g excreted by six normal subjects after the same meal. We conclude that more than just intragastric destruction of lipase underlies the frequent failure of orally ingested pancreatin to normalize fat absorption in pancreatic insufficiency.

We compared the gastric, pancreatic, and biliary secretory responses to a liquid test meal and the rates of gastric emptying of liquid and solid test meals in six patients at least 1 year after parietal cell vagotomy with eight unoperated subjects, one with duodenal ulcer disease and seven normal control subjects. Parietal cell vagotomy decreased gastric acid secretion to one third of normal, but total trypsin and bile salt secretion during the first 150 postcibal minutes were normal. The liquid test meal emptied from the stomach faster after parietal cell vagotomy, the pattern of emptying being exponential in the vagotomy patients and linear in the normal subjects. The rate of gastric emptying of a liquid meal, although faster than normal, was less precipitous after parietal cell vagotomy than after truncal vagotomy plus drainage or subtotal gastrectomy, and trypsin and bile salt concentrations were not diluted to abnormal levels, as occurs after these other procedures. Furthermore, emptying and dispersion of solid food remained normal after parietal cell vagotomy. These findings probably explain, at least in part, the decreased incidence of postprandial dumping and diarrhea that accompanies parietal cell vagotomy compared with the other popular operations for duodenal ulcer.

Microspheres of pancreatin should empty from the stomachs of patients with pancreatic insufficiency as fast as food. The present study was undertaken in 26 healthy subjects to identify the size of spheres that would empty from the stomach with food and to determine whether different meals alter this size. Spheres of predefined sizes were labeled with 113mIn or 99mTc. Using a gamma-camera, we studied the concurrent gastric emptying of spheres labeled with 113mIn and of chicken liver labeled with 99mTc in 100-g, 154-kcal or 420-g, 919-kcal meals, or the concurrent emptying of 1-mm vs. larger spheres. One-millimeter spheres emptied consistently (p less than 0.01, paired t-test) faster than 2.4- or 3.2-mm spheres when ingested together with either the 420- or 100-g meals. Thus, in the 1-3-mm range of diameters, sphere size was a more important determinant of sphere emptying than meal size. Statistical analyses indicated that spheres 1.4 +/- 0.3 mm in diameter with a density of 1 empty at the same rate as 99mTc-liver. Our data indicate some commercially marketed microspheres of pancreatin will empty too slowly to be effective in digestion of food.

T he Invitations to Enquiry are one of several teaching aids brought forth in the past decade to aid the high school biology teacher in teaching biology as inquiry. As reported by Joseph J. Schwab the Invitations to Enquiry are designed to "... bring to the student small samples of the operation of enquiry." As expressed by Schwab, to teach biology as enquiry the biology student must be shown that knowledge arises from the interpretation of data and that the interpretation and search for data progress on the basis of concepts and assumptions that change as knowledge grows. The Invitations to Enquiry present to the biology student samples of biological data from which the stident is expected to participate in enquiry by drawing conclusions from the given data, or proposing new hypotheses based on the gained knowledge or proposing hypotheses to account for the data given. By reading, teacher directed class discussion and student participation many examples of the processes of biological investigation become familiar to the student. This article contains the results of a year long study in which an assessment was made of the effectiveness of the Invitations to Enquiry in promoting the understanding of science, critical thinking ability, and academic achievement in biology. This study was conducted using 46 first year high school biology students enrolled in two of the writer's BSCS Yellow Version classes at Niles Township High School, North Division, Skokie, Illinois. The two classes studied were heterogeneous groups of regular track biology students that did not differ significantly in their vocabulary comprehension, mathematics comprehension or IQ scores. Before the first day of school one class was randomly designated to be the experimental group and receive the presentation of the "invitations." Each class during the course of the year would meet with the instructor 40 minutes on 3 days of the week and 80 minutes on the other 2 days. An attempt was made to control the type of subject material that was presented to each class. Identical laboratory exercises and laboratory write-ups were assigned to each class. In addition, the quizzes and examinations administered throughout the year were identical. Schwab suggests that the various "invitations" be presented in one or all of the following manners. (1) As independent learning experiences being covered during a certain period each week. (2) In conjunction with related laboratory exercises or (3) In conjunction with classroom work with the "invitation" selected to match the subject under study. It was decided to present the experimental class with one "invitation" each week for the duration of the school year. No attempt was made to correlate the subject of the "invitation" with the classroom topic under study. Each "invitation" was presented as a separate entity and no special attempt was made to relate it to the current classroom topic. However, as the school year progressed many of the "invitations" presented were naturally discussed in a context related to a class studied biological topic. In the course of the school year a total of thirty-one "invitations" were presented to the experimental class. As listed in the Biology Teachers' Handbook, the "invitations" presented to the experimental group were taken from group I

Pancreatic exocrine secretion is regulated by a complex interaction of meal-stimulated neurohormonal reflexes. Pancreatic enzyme output must be reduced to less than 10 per cent of normal before fat absorption is appreciably impaired, proving that the pancreas secretes a large surplus of enzymes. Surgical therapy does not improve pancreatic exocrine insufficiency, and partial pancreatic resection frequently precipitates steatorrhea in patients with chronic pancreatitis. Therefore, pancreatic resection should be undertaken cautiously in patients who do not yet have clinically evident exocrine insufficiency. In most patients, oral pancreatic enzymes will control diarrhea secondary to steatorrhea. In others, concurrent administration of an H2 blocker is required to reduce gastric acidity and prevent enzyme inactivation in the stomach. Formulations with an acid-resistant coating are also effective in some patients. However, complete normalization of fat absorption with restoration of body weight and nutritional well-being requires careful management of multiple dietary and behavioral factors, as well as long-term follow-up. Unfortunately, this appears to be an elusive goal, as many patients with chronic pancreatitis continue to die of malnutrition.

With an inhibitor assay technique rates of passage of salivary and pancreatic isoamylase through the jejunum were measured in six healthy volunteers after different liquid, intragastric meals. In all subjects and in 13/17 experiments, more than 2500 units of salivary amylase were passed over 200 postcibal minutes. Salivary amylase comprised 13.8 +/- 3.9% (mean +/- SEM) of the total amylase and appeared predominantly as single, distinct peak. The inhibitor method was validated by isoelectric focusing (r = 0.988; P less than 0.001; N = 7). The frequency of detection of salivary amylase in gastric or jejunal samples fell as gastric pH fell below 3.0. In vitro, amylase was inactivated in gastric juice as pH fell between 3.8 and 3.3. Salivary amylase accounted for 11% of total amylase output in a normal and 27% in an achlorhydric subject after a hamburger meal. We conclude that amylase should not be measured in postprandial studies of pancreatic secretion in humans without correction for salivary amylase.

Little is known about how gastric and pancreatobiliary responses differ after intake of elemental diets from responses to polymeric food. We therefore compared pancreatic and biliary secretions after gastric instillation of albumin (7 g%, with dextrose 21 g%) with an elemental diet in 6 healthy volunteers. The elemental diet contained amino acids (7 g%, with dextrose 21 g%) in the same molar composition as the albumin. Furthermore, we studied the effect of a pure intragastric dextrose solution (21 g%) on pancreatobiliary secretions, as glucose constitutes a major component of elemental diet formulas. The various pancreatobiliary responses were tested against a maximal i.v. cholecystokinin stimulus. The dextrose, amino acid, and albumin meals emptied at similar rates, and gastric emptying was completed within 3 h. Similar pancreatobiliary responses were observed after the albumin and amino acid meals, but response to both the amino acid and albumin meals was smaller than to the intravenous cholecystokinin stimulus. The glucose meal caused a marked and sustained stimulation of pancreatobiliary outputs, which did not differ significantly from the other test meals. However, lower cholecystokinin levels were observed after the glucose meal compared with distinct cholecystokinin release after the albumin and amino acid meals. We conclude first that there are no major differences in secretory responses between elemental (amino acid) and polymeric (protein) meals and second, that intragastric pure glucose meals strongly stimulate pancreatobiliary secretions. The marked pancreatic and biliary responses to intragastric dextrose cannot be fully explained on the basis of cholecystokinin release, suggesting that this response is probably mediated by neural mechanisms.

Treating pancreatic exocrine insufficiency with orally administered pancreatic enzymes is more difficult than is usually imagined.1 The goals of therapy are to prevent weight loss and muscle wastin...

Previous work has indicated that a chemoselective resistance controls gastric emptying. By use of meals of glucose or oleate, which were shown to empty spontaneously from dogs' stomachs half as fast as saline, we sought to locate this resistance by studying flow under controlled pressures in various regions of the gastrointestinal tract. In intact dogs, gastric outflow of glucose or oleate rose one-third as fast as outflow of saline as gastric pressure was raised, and this increased resistance to outflow of nutrients was unaffected by truncal vagotomy and pyloroplasty. In fistula dogs, gastroduodenal outflow rose linearly with gastroduodenal pressure gradients; outflow was markedly inhibited in a dose-related manner by intestinal oleate but not glucose. Inhibition by oleate was abolished by pyloroplasty. Glucose or oleate flowed into the small bowel from a barostat only slightly slower than saline. However, there was a strong inhibition of intestinal inflow of all three meals by gastric distension, an effect unaltered by truncal vagotomy. The findings suggest that gastric emptying is controlled by complex interactions among pressures and resistances, both within and beyond the stomach.

The primary objective of this study was to define the pH conditions under which supplemental pancreatic enzyme preparations must function in the upper gastrointestinal tract. The hypothesis was that normal or greater acid output in patients with cystic fibrosis (CF), combined with low pancreatic bicarbonate output, results in an acidic duodenal pH, compromising both dosage-form performance and enzyme activity. Gastrointestinal pH profiles were obtained in 10 CF and 10 healthy volunteers under fasting and postprandial conditions. A radiotelemetric monitoring method, the Heidelberg capsule, was used to continuously monitor pH. Postprandial duodenal pH was lower in CF than in healthy subjects, especially in the first postprandial hour (mean time greater than pH 6 was 5 min in CF, 11 min in healthy subjects, P less than 0.05). Based on the dissolution pH profiles of current enteric-coated pancreatic enzyme products, the duodenal postprandial pH in CF subjects may be too acidic to permit rapid dissolution of current enteric-coated dosage forms. However, the pH was above 4 more than 90% of the time on the average, suggesting that irreversible lipase inactivation in the duodenum is not likely to be a significant limitation to enzyme efficacy. Overall results suggest that slow dissolution of pH-sensitive coatings, rather than enzyme inactivation, may contribute to the failure of enteric-coated enzyme supplements to normalize fat absorption.

• One hundred cases of pancreatic abscess were identified at five hospitals affiliated with UCLA between 1973 and 1985. Patients were included if a pancreatic mass or phlegmon followed an episode of pancreatitis, if the clinical impression was pancreatic abscess, and if drainage cultures were positive. Less than three Ranson's signs were present on admission in 72% of patients. The admission temperature was less than 38.3°C in 71% of patients, and 27% of patients never had a fever. Abdominal tenderness was absent in 40% of patients. The admission amylase concentrations and white blood cell counts were normal in 36% and 23% of patients, respectively. Extensive debridement, external drainage, and a low threshold for reoperation were the mainstays of surgical therapy. Twenty patients (20%) died, but Ranson's signs did not predict outcome. Pancreatic abscess may have an insidious presentation. A high index of suspicion, early computed tomographic scanning, and diagnostic needle aspiration may be necessary to establish this diagnosis. (Arch Surg1988;123:1067-1072)

Polyporphyre and polycyanine are polymeric dyes which were recently described as useful markers for intestinal perfusion studies. The dyes were examined in this study in regard to their suitability for postcibal studies. In comparison with polyethylene glycol (PEG) 4000, a widely used nonabsorbable marker, both dyes were quantitatively adsorbed to cooked liver particles. This in vitro finding was confirmed in dogs with midgut fistulas. After a meat meal, we observed complete uptake of polycyanine to food particles. Polycyanine furthermore showed color instability below pH 3. These results indicate that the dyes are inferior to PEG 4000 when solid food is present in the intestinal lumen.

Previous studies suggested that the food-containing canine stomach retains large, nondigestible spheres until all food has emptied; but it is not known whether there is a threshold size or a gradation of sizes that will empty along with food. Further, nothing is known of the effects of such parameters as density, shape, and surface energy on the emptying of nondigestible particles of any given size. To answer these questions 6 dogs with chronic duodenal fistulas were studied. Radiolabeled food and spheres were collected from the fistulas to compare the rate of gastric emptying of the spheres with that of the food. After a standard test meal of 99mTc-labeled liver, steak, and water, diverted chyme was collected over a stack of sieves in 30-min fractions over 5 postcibal hours. The percent of fed spheres and fed 99mTc-labeled liver in each collection was counted, and liquid chyme was returned to the distal duodenum. Spheres with a density of 1 emptied progressively faster as sphere diameters were decreased from 5 to 1 mm; but 0.015-mm spheres emptied at about the same rate as those with diameters of 1 mm. Emptying of the spheres became similar to emptying of the 99mTc-labeled liver at about 1.6 mm. Spheres with densities less than 1 or greater than 1 emptied more slowly than spheres of the same size with a density of 1, whereas paper squares emptied the same way as spheres of comparable size and density. Surface energy did not affect emptying. The findings indicated that both sphere size and density affect their emptying in the presence of food.

In two groups of dogs, we studied average rates of gastric emptying of 0.15 M NaCl, 0.6 M glucose, or 0.04 M oleate liquid meals while gastric pressures were controlled by a barostat and compared this emptying to spontaneous gastric emptying of the same three meals. In the first group of dogs, this comparison was made before and after truncal vagotomy + pyloroplasty (TVP); and in the second group, before and after antrectomy, first with gastroduodenostomy (A-BI) and then with Roux-Y bypass (A-RY). Under barostatically controlled gastric pressures, gastric emptying of oleate and glucose remained slower than emptying of saline before as well as after TVP or A-BI and A-RY. However, all operations accelerated initial spontaneous emptying, compressing differences between half-emptying times of the three meals. We conclude postfundic resistances remain after TVP or antrectomy but may act too late to alter rapid initial emptying.

A PROJECT TO INTRODUCE biology students to the impact of biology upon society, entitled Societal Enrichments in High School Biology, has been introduced at Cedar Falls (Iowa) High School. Brief individualized exercises have been designed to give the student an opportunity to discover the growing influence of the biological sciences on the world's cultural, economic, political, and social systems. To date, forty enrichment exercises have been developed around six controversial areas

Although hospitalizations and deaths attributable to peptic ulcer have decreased notably during the past decade, it is not certain whether this decrease is because of reduced incidence of new cases or changes in other factors, such as the severity of the disease. Several genetic traits associated with peptic ulcer have been recognized. Hyperpepsinogenemia I is the most prevalent. Peptic ulcer is a heterogeneous group of disorders with multiple genetic and environmental causes. One manifestation of the diversity of ulcer disease is the variety of physiologic abnormalities seen in patients. The use of endoscopy has enabled more reliable evaluation of new treatments. Histamine H2-receptor antagonists are the dominant mode of treatment, but increasing attention is being given to agents that enhance the resistance of the mucosa to injury, such as prostaglandins. Because of the lower frequency of side effects, proximal gastric vagotomy is gradually replacing truncal vagotomy with drainage. The possibility that endoscopic treatments, such as laser coagulation, may reduce mortality from bleeding ulcers is being investigated.

Variations of water vapor in the troposphere are calculated from simultaneous airborne measurements of radio refractive index and temperature obtained respectively with a microwave refractometer and an aerograph employing a sensitive bead thermistor. The partial pressure of water vapor is calculated from the well-known equation Figure 1. where n is the refractive index; T is temperature, °K; and P is total atmospheric pressure mb. The method is applied to the investigation of the horizontal and vertical structure of water vapor associated with a thin inversion layer found near 9800 ft pressure altitude. Evidence is offered for the vertical stability and absence of turbulent mixing of the air in the region of the inversion. When the reflection coefficient of the observed layer at radio wave lengths of 600 and 72 cm is computed at a range of 200 mi beyond the horizon, better than an order of magnitude agreement is obtained between the calculated and observed path losses at this range.