The role of the gut in albumin catabolism. II. Studies in enterectomized rabbits

Using I¹³¹-albumin tracer methods, albumin breakdown rates were estimated in 7 rabbits following extensive gastrointestinal resection, including 5 with nearly complete enterectomy, 1 with total gastroenterectomy, and 1 with gastrectomy only, and in 4 sham operated rabbits. Breakdown rates in the resected animals varied from 48 to 187 per cent of the corresponding controls, with an average of 96 per cent. It is concluded that no more than one-half, and probably much less, of albumin breakdown occurs in the gastrointestinal tract.

The absorption of fat by intestine of golden hamster in vitro

Everted sacs of intestine from golden hamsters were incubated at 37°C for at least 1 hour in vitro with emulsified lipid after removal of both pancreatic lipase and bile salts. The fine structure of intestinal epithelium is well preserved under these conditions. Absorption of fat by the intestinal mucosa in vitro closely resembles lipid absorption in vivo, as observed by both light and electron microscopy. The physiological significance of these observations is discussed. Tubular elements of the agranular endoplasmic reticulum are often strikingly abundant in the apical cytoplasm of intestinal absorptive cells. These have a role in the intracellular transport of fat since they frequently contain droplets of lipid derived from the incubation medium. The rate of fat accumulation in the epithelium appears to be proportional to the concentration in the medium.

Effect of structural analogues on intestinal accumulation of glycine

Glycine uptake (1 x 10–3 m) by hamster intestinal segments in vitro was studied after 20 min of incubation both in the absence and presence of various analogues (5 x 10–3 m). A variety of chemical relatives of glycine with modifications of the —COOH, —NH2, or α-hydrogen groups or with double modifications (such as ethanol) were without effect on glycine accumulation. Thus under these conditions glycine could not be displaced by its analogues. Three compounds, however, all α-amino acids, were effective in depressing glycine uptake (allylglycine, α-phenylglycine, l-alanine). Data are presented showing that two of these inhibitors are themselves transported and hence likely competed with the amino acid transport system. α-Aminoisobutyric acid and N-methylglycine, both known to be transported by the gut, did not interfere with glycine accumulation. In addition to oxalic acid, other succinic dehydrogenase inhibitors (hydrocinnamic acid, glutaric acid, malonic acid at 5 x 10–3 m) were without major depressant effect on glycine accumulation by this system.

Relationship of host antibody to fluctuations of Escherichia coli serotypes in the human intestine

Robinet, Harriette G. (Walter Reed Army Institute of Research, Washington, D.C.). Relationship of host antibody to fluctuations of Escherichia coli serotypes in the human intestine. J. Bacteriol. 84:896-901 1962.-A study was undertaken to determine the relationship of host antibody to the changes which take place among Escherichia coli serotypes present in the intestine. A survey of six healthy persons examined for E. coli monthly for 6 months reaffirmed the periodic fluctuations of antigenic types. Serotypes were studied from each individual and their appearance and maintenance or disappearance closely followed. Representative strains were chosen each month and used to prepare a heated sodium hydroxide lipopolysaccharide extract for sensitizing human group O Rh-negative red blood cells for the hemagglutination test. These antigens were tested with the sera drawn from each of the six individuals at the time monthly cultures were made. Results showed that antibody levels for each serotype remained basically constant over the 6-month period. Titer levels tended to be characteristic of the host rather than related to the E. coli bacteria, as shown by tests with serotypes both from the individual's own intestinal tract and from other individuals in the study. High normal antibody levels for autologous E. coli serotypes did not act as a deterrent to the ability of the organisms to establish themselves in the bowel, nor did antibody titer for E. coli strains determine whether they would continue as residents over several months or depart as transient flora.

Formation of a reticuloendothelial-depressing substance in the ischemic intestine

The phagocytic index of the reticuloendothelial system of normotensive assay dogs was determined by measuring the clearance of carbon particles from the blood. These animals were cross-transfused with portal venous blood from experimental dogs bled to a mean arterial pressure of 40 mm Hg for 90 min. The superior mesenteric artery of the experimental animal was perfused at a normal rate of 8.8 ml/kg/min in half of the experiments and at a rate of 3.2 ml/kg/min (equivalent to rates prevailing in hemorrhagic hypotension) in the remaining experiments. Statistical comparison showed a significantly greater ( P < 0.01) depression of reticuloendothelial activity in the group with lower flows. The results strongly suggest that a humoral reticuloendothelial-depressing substance is formed in the ischemic intestine of dogs subjected to hemorrhagic hypotension.

Histamine and 5-hydroxytryptamine in the intestinal tract of germ-free animals, animals harbouring one microbial species and conventional animals

Histamine and 5-hydroxytryptamine were determined in the intestinal tract of germfree and conventional rats and mice. Comparable histamine data were collected in Clostridium perfringens mono-associated rats, while 5-hydroxytryptamine determinations were extended to include the chicken. In rats and mice harbouring an intestinal microflora, bacterial formation of histamine occurs mainly in the caecum. Compared to values found in germ-free animals, histamine levels in the wall of the small intestine of the conventional animal tend to be higher, though in the rat the data are not consistent. Mono-association (harbouring of one microbial species) of germ-free rats with a histamine-producing strain of Clostridium perfringens resulted in high histamine concentrations in the caecal contents, but failed to increase the histamine levels in the wall of the small intestine. 5-Hydroxytryptamine levels in the intestinal wall in the presence of an intestinal flora were generally lower than those in germ-free animals. Modification of the flora by dietary administration of penicillin to mice partly abolished its depressing effect.