Association of Escherichia coli with the small intestinal epithelium. II. Variations in association index and the relationship between association index and enterosorption in pigs

The association between small intestinal epithelium and enteropathogenic Escherichia coli (EEC) was studied in ligated intestinal loops of pigs and rabbits. The association indexes (degree of association) for each of two porcine EEC strains varied widely among pigs and independently of each other. Significant litter-to-litter variations in association indexes among colostrum-deprived newborn pigs were interpreted to be the result of congenital resistance to association with specific EEC in some pigs. Since enterosorption occurred in loops with low association indexes, it was not necessary for EEC to establish a high association index for them to cause enterosorption in ligated intestinal loops. Two strains of EEC which are enteropathogenic for humans caused enterosorption in ligated loops in pigs 3 weeks old or less but not in 6-week-old pigs.

Association of Escherichia coli with the small intestinal epithelium. I. Comparison of enteropathogenic and nonenteropathogenic porcine strains in pigs

Two enteropathogenic strains of Escherichia coli (EEC) differed from a nonenteropathogenic strain of E. coli (NEEC) in their association with porcine small intestinal epithelium. The EEC characteristically were found along villi from tip to base and contiguous to the brush border. They were not in crypts. In contrast, the NEEC characteristically remained in the central lumen near the tips of villi and was only occasionally contiguous to the brush border. No organisms were detected within epithelial cells. The difference in distribution between EEC and NEEC was apparent in ligated jejunal loops 45 min postexposure. The association between host and bacterial cells was most consistently demonstrated on frozen sections of intestine, as other histological techniques removed many bacteria. However, cellular details of the association were best demonstrated in chemically fixed tissues.

The role of intraluminal sodium in glucose absorption in vivo

Active glucose absorption is thought to depend on a gradient of sodium ion concentration across the brush border membrane of intestinal epithelial cells. This concept is generally accepted, although its validity has never been adequately evaluated in the human small intestine in vivo. According to this hypothesis, the rate of glucose absorption should decrease markedly if the luminal sodium concentration is markedly reduced, and glucose absorption against a concentration gradient should cease entirely if luminal sodium is lower than intracellular sodium concentration. In the present series of experiments we were not able to show an important role of intraluminal sodium concentration in the active absorption of glucose from the human, rat, and dog ileum in vivo. Specifically, glucose absorption was minimally reduced or not reduced at all when intraluminal sodium concentration was reduced from 140 to as low as 2.5 mEq/liter. The discrepancy between our results and those of previous workers whose data suggest that removal of intraluminal sodium should markedly inhibit active glucose absorption is not entirely clear, but there are a number of differences in experimental design between most previous studies and our own. Although our data show that active glucose absorption proceeds at a near normal rate even when lumen sodium concentration is reduced below 3 mEq/liter, our results do not disprove the sodium gradient theory because of the theoretic possibility that the microclimate adjacent to the brush border has a high concentration of sodium even when luminal sodium concentration is markedly reduced. The validity of the sodium gradient hypothesis would appear to be critically dependent on such a microclimate.

Purification, morphology and partial characterization of a reovirus-like agent associated with neonatal calf diarrhea

Studies have been conducted on a virus which has recently been implicated as an etiological agent in widely disseminated cases of calf diarrhea. The virus was isolated from feces and intestinal mucosa from experimentally infected calves and from cell cultures which had been inoculated with material from infected calves. The virus was purified by differential centrifugation, nuclease treatment, extraction with Genetron 113 and cesium chloride (CsC1) gradient. Purified and non-purified samples were studied by electron microscopy. Both types of preparations contained unenveloped particles approximately 64 nm in diameter with a hexagonal core region 36 nm in diameter. Subunits of the capsids appeared to be arranged in accordance with cubic synmetry. Essential lipids were not associated with the virus. The buoyant density of purified virus was 1.359. Viral nucleic acid was determined by chemical methods to be ribonucleic acid (RNA). The morphology and some chemical characteristics appear to be similar to those of the reovirus group. However, the exact classification of this virus and its relationship to other groups remains to be established.

The mouse intestinal microflora with emphasis on the strict anaerobes

The various components of the intestinal microflora in the mouse become established according to a definite time sequence; the strict anaerobes are the last groups of bacteria to reach their maximum population levels, 14-16 days after birth. The multiplication of these strict anaerobes in the mouse intestine seems to depend upon the prior multiplication of other bacterial species, and coincides with the ingestion of food other than maternal milk. These two conditioning factors may correspond to the establishment of a suitably reduced Eh potential and to the provision of certain metabolites. Once established, the strict anaerobes constitute by far the largest percentage of the total intestinal microflora; most of them are associated in a viable form with the mucosa. In normal animals they persist at very high levels throughout the life span. However, their populations can be drastically reduced by dietary manipulation of the animal, by administration of vancomycin, or by certain disease processes of the intestine. The strict anaerobic bacteria seem to play an important, and perhaps essential role in the maintenance of the anatomic structures and physiological functions of the intestine. They also seem to hold in check several species of intestinal bacteria, in particular the coliform bacilli.

Failure to isolate mycoplasmas from upper samll intestine of man

A screening investigation for mycoplasmas in upper small intestine was carried out in 65 patients, normal or affected by either biliary tract disorders or malabsorptive states. Mucosal biopsies, duodeno-jejunal fluid aspirates and biliary secretions were cultured for mycoplasma growth on appropriate media. Serological studies were performed to detect antimycoplasma antibodies. Both cultural and serological findings were consistently negative. It is suggested that the upper small intestine and biliary tract are not inhabited by mycoplasmas in either normal or pathological conditions.