Franz J. Ingelfinger

Peer review in biomedical publication

Abstract The conventional reviewing system of American biomedical journals determines where and when an author may publish, and hence may affect his career. Yet the systems effectiveness in validating reports, or the cost of such validation, has been little studied. Problems are inadequate review, unrealistic editorial expectation of what reviewers can do, and bias. Expert reviewers frequently disagree. Thus concurrence between two reviewers of each of some 500 papers submitted to the New England Journal of Medicine was only moderately better than a chance result. Costs of the reviewing system include time and effort involved, the possible violation of confidentiality, and occasional suppression of the novel advance. Despite deficiencies, the reviewing system is important to maintain standards. It could be improved if studies of its operation were carried out, if reviewers were better indoctrinated, if the work load of reviewers were lessened, if reviews were signed, and if the reviewing process were more rewarding to reviewers.

A Method for Studying Absorption of Water and Solute from the Human Small Intestine

Summary A triple-lumen intubation technique is described whereby absorption or secretion of water, electrolytes, and other solutes can be studied within specific and defined test segments of the human small intestine. The technique allows correction for endogenous water and solute that enter the test segment from digestive secretions. Experiments that were carried out to test the precision of the method have demonstrated the technique to have a high degree of accuracy when 1-hr study periods are used.

Intestinal absorption of sucrose in man: interrelation of hydrolysis and monosaccharide product absorption.

Disaccharides are hydrolyzed by their specific enzymes present in the intestinal mucosa (1-3). Although some current textbooks still state that these enzymes are secreted into the intestinal lu-men (4-7), the concentrations of monosaccharide products free in intestinal contents during disac-charide absorption in vitro (8-10) have been found insufficient to support the concept of intraluminal hydrolysis. In addition, the low disaccharidase activity of intestinal contents during the absorption process in vivo (11-13) strongly suggests that the disaccharide either enters the cell before being hydrolyzed or else is hydrolyzed at the cell surface by mucosa-bound enzyme. The released monosaccharide products presumedly are then transported across the intestinal cell (8, 14, 15). Little information is available that relates disac-charide hydrolysis to absorption of the component monosaccharides. Wilson and Vincent (14) commented on the accumulation of monosaccharides in the mucosal medium during the process of disac-charide absorption in hamster gut sac preparations, and Dahlqvist and Thomson have reported that large amounts of free fructose accumulate intra-luminally during sucrose absorption in the intact rat (16). Despite these findings in animals, Dahlqvist and Borgstr6m found little free intra-luminal monosaccharides during the process of disaccharide absorption in man (12). It was recently demonstrated, however, that appreciable amounts of the hydrolysis products accumulate intraluminally during the process of sucrose absorption in man and that these monosaccharides appear to move back from their mucosal site of hy-drolysis to the lumen (13). The present work is concerned with the relation of hydrolysis of sucrose to the absorption of its monosaccharide components, glucose, an actively absorbed monosaccharide (14, 15, 17), and fructose, which is passively absorbed (14, 15). Methods Thirty-two normal young subjects were studied on 105 occasions by use of a double-lumen tube placed at various levels of the intestine (13, 18). Polyethlene glycol 4000 (PEG) was used as the nonabsorbable water-soluble marker and was determined by a modification of Hyd&is method (19). Sucrose solution or an equivalent mixture of glucose and fructose made isotonic with NaCl (290 ± 10 mOsm per L) was infused at 15 ml per minute through the proximal orifice of the tube. In some studies , galactose was also infused. Intestinal samples were collected by siphonage from the distal orifice, which was located 15 or 30 cm from the site of infusion. The initial 30 minutes of an infusion period allowed steady state conditions to be approached so that, thereafter, concentration of PEG and the …

HYDROGEN AND METHANE PRODUCTION IN MAN

For many years it has been known that hydrogen and methane are produced by bacteria and that these gases may be present in high concentration in flatus. Recently, Nielsen has developed methods to measure hydrogen and methane in expired air,l and Calloway has related the breath hydrogen concentration to the ingestion of certain foods.2 There are, however, few data on the site and rate of formation of H2 and CH4 in man. In our studies a constant-infusion technique ordinarily used for the study of intestinal absorption of liquids was modified to obtain quantitative data on human intestinal gas production.

Dysphagia Produced by a Contractile Ring in the Lower Esophagus

Summary 1.In six male patients complaining of dysphagia, the responsible disorder appeared to be an annular esophageal constriction situated 0.5-2.5 cm. above the diaphragm. The constriction did not produce dysphagia unless it happened to trap a solid morsel of food, thereby occluding the esophageal lumen. 2.Anamnestic, radiologic, physiologic and pathologic evidence indicated that the annular constriction was not caused by a fibrous band, inflammatory stricture, cardiospasm (or achalasia), or diaphragmatic hernia. 3.If the claim of several anatomists is correct that a physiologic sphincter exists in the esophagus 1-2 cm. above the diaphragmatic hiatus, the constriction ring may be identified tentatively as an overactive inferior esophageal sphincter.

Sugar absorption tests, with special reference to 3-0-methyl-d-glucose and d-xylose.

Excerpt Tests employing glucose have limited value in the diagnosis of malabsorption because factors other than absorption influence glucose blood levels following an oral dose of this sugar (1). T...

Mechanism of Belching: Effects of Gastric Distension With Air

Summary The mechanisms of belching and gastroesophageal reflux have been studied by recording radiologically and manometrically the effects of distending the human stomach with air. After a slight initial rise, intragastric pressure plateaued in the face of continued injection of air, suggesting that both gastric and abdominal cavities relax receptively in response to increased gastric volume. At inconstant time intervals after gastric pressure had reached a plateau, either simple gastroesophageal reflux or reflux with belching occurred in most but not all subjects. During simple reflux, the gastroesophageal barrier opened widely and a common gastroesophageal cavity was established. The esophagus was then emptied of air by a secondary peristaltic wave, returning air to the stomach and reestablishing the competency of the gastroesophageal barrier. No sensations were experiencedduring simple reflux, which appeared to be the result of an involuntary mechanism not involving somatic muscles. Belching, on the other hand, appeared to require contraction of somatic musculature, usually superimposed on antecedent or simultaneous opening of the gastroesophageal barrier, and resulting in the expulsion of air from a common gastroesophageal cavity.

CONTROVERSY IN INTERNAL MEDICINE

CONTROVERSY IN INTERNAL MEDICINE , CONTROVERSY IN INTERNAL MEDICINE , کتابخانه مرکزی دانشگاه علوم پزشکی ایران

The effect of 5-hydroxytryptamine on intestinal motor function in man

Abstract The effect of 5-hydroxytryptamine (serotonin) on intestinal motility has been investigated by means of balloon kymography in thirty-seven studies in thirty-four healthy persons. In twenty-six studies intravenous injection of 5-HT was followed by increased intestinal tone, in five it was followed by decreased tone, and in 6 no effect was noted. The intestinal response to 5-HT was affected by drugs as follows: (1) potentiated by antihistaminics; (2) inhibited by a benzyl analog of serotonin; (3) inhibited by anticholinergic drugs (methantheline and atropine); and (4) unaltered by ganglionic blockade by hexamethonium. The available pharmacologic evidence suggests that 5-HT stimulates intestinal motor activity through cholinergic nerves at a site distal to the ganglionic synapse.

The role of sodium in intestinal glucose absorption in man

The effect of luminal sodium on intestinal glucose absorption at a variety of glucose concentrations was studied with a segmental perfusion technique in normal subjects. Uphill glucose transport was inhibited with sodium-free perfusions with either mannitol or Tris-HCl as the osmotic replacement of sodium (P < 0.01-P < 0.001). This effect did not appear to be the result of solvent drag, as increasing net water absorption without supplying sodium to the lumen did not increase glucose absorption. Downhill glucose transport (infusion concentrations of 6.0-27.8 mmoles/liter), on the other hand, was not affected by the absence of sodium in the infusion solution. Glucose concentrations of upper intestinal fluid after normal carbohydrate meals were usually found to exceed serum concentrations; thus, downhill glucose absorption, with, at most, a very limited dependence upon intraluminal sodium concentration, may account for a significant part of normal carbohydrate absorption.