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Biomedical subjects

H W Moon

Publications and source records attributed to H W Moon.

At least 127 records · Page 7Linked to original sources
PubMed1975

Induction of heat-labile enterotoxin synthesis in enterotoxigenic Escherichia coli mitomycin C.

Introduction of heat-labile toxin (LT) synthesis in enterotocigenic strains of Escherichia coli by mitomycin C (MTC) was demonstrated. Six enteropathogenic strains which produce LT were inducible, exhibiting an 896-fold increase in LT when compared to ininduced cultures. On the other hand, four nonenteropathogens and three other pathogens which produce only the heat-stable toxin were not induced to produce LT. Gel filtration chromatography, antibody neutration, and heat lability studies suggest that the toxin synthesized in the presence of MTC is the same as the toxin synthesized in the absence of MTC.

Chloramphenicol↗
PubMed1975

Age-dependent resistance to transmissible gastroenteritis of swine. III. Effects of epithelial cell kinetics on coronavirus production and on atrophy of intestinal villi.

Coronavirus titers in small intestine, degree of villous atrophy and apparent rates of regeneration of intestinal villi were compared in newborn, 3-week-old and adult pigs for 1 week after they were exposed to the transmissible gastroenteritis virus of swine. The response within the newborn group was homogeneous, resulting in high virus titers, maximal villous atrophy and comparatively slow regeneration. In general, virus titers were lower, villous atrophy was less severe and regeneration more rapid in both older groups than in the newborn pigs. However, the response varied greatly in the older groups. The 3-week-old group was divided into two populations. The major population had low virus titers and developed partial villous atrophy, whereas the minor population had marked villous atrophy and virus titers comparable to those of the newborn pigs. These observations support the hyposthesis that the accelerated replacement of villous epithelium in the small intestine of pigs during the first 3 weeks contributes to the innate age-dependent resistance to transmissible gastroenteritis. The accelerated replacement of villous epithelial cells in older pigs contributes to resistance in two ways. The increased proliferative capacity of crypt epithelium results in a more rapid regeneration of atrophic villi; and the comparatively young villous absorptive cells resulting from accelerated replacement produce less virus per cell than the older ones of the newborn pig.

Age Factors↗
PubMed1975

Epithelial cell migration in the small intestine of sheep and calves.

Replacement of villous epithelium in the small intestine of sheep and calves was studied by tritiated thymidine (3-H-TdR) autoradiography. Sheep were less than 1 day old, 3 weeks old, 3 months old, or more than 1 year old, and calves were less than 1 day old or 3 months old. In both species, there was marked variation in the location of labeled epithelial cells on villi among individuals from the same age group studied at the same time after administration of a single intravenous dose of 3-H-TdR. Labeled epithelial cells were confined to the proximal half of the villi at 48 hours after thymidine exposure in the animals, except some 3-month-old individuals from both species. Labeled epithelial cells had reached or were near the tips of the villi in these individuals at 48 hours. In both species, villi were longer and crypts were shorter in the newborn animals than in the older animals. The data were interpreted to indicate that replacement times were well in excess of 48 hours in neonates from both species and decreased somewhat with age.

Age Factors↗
PubMed1975

Effect of age on epithelial cell migration in small intestine of chickens.

Villous length, crypt depth, epithelial cell migration rate, and replacement time were studied by autoradiography of histologic sections of small intestine from normal chickens exposed to tritiated thymidine (3-H-TdR). The results indicated that villi and crypts elongate, and epithelial cell migration accelerates between 1 day and 6 months of age. Epithelial replacement time seemed to increase with age of the chickens. Replacement was nearly complete in the 1-day-old group of chickens 5 days after thymidine exposure. In contrast, at this same time, replacement was only approximately 75 and 50% complete in the 3-week-old and 6-month-old groups of chickens, respectively.

Age Factors↗
PubMed1974

Detection of heat-labile Escherichia coli enterotoxin with the use of adrenal cells in tissue culture.

Cell-free culture filtrates of heat-labile enterotoxin-producing strains of Escherichia coli are capable of inducing morphological changes and steroidogenesis in monolayer cultures of adrenal cells. These tissue culture changes are simiar to those induced by cholera enterotoxin and cannot be effected by culture filtrates of other enterotoxigenic or enteropathogenic types of bacteria. The results of the tissue culture studies correlated well with those done in the standard intestinal-loop systems and suggest that this tissue culture system could be used to significantly aid epidemiological and molecular studies with heat-labile Escherichia coli enterotoxin.

Adrenal Gland Neoplasms↗
PubMed1973

Age dependent resistance to transmissible gastroenteritis of swine (TGE). I. Clinical signs and some mucosal dimensions in small intestine.

Pigs were exposed to transmissible gastroenteritis (TGE) virus when three days old or when 21 days old. Diarrhea was earliest in onset, most frequent, most profuse and most prolonged in the youngest group. Pigs exposed when three days old also had a higher case fatality rate than those exposed when 21 days old. The histological response of both groups to exposure was atrophy of villi and hyperplasia of crypts in jejunum and ileum. However, from days three to seven post-exposure, when most fatalities occurred in the younger group, atrophy of villi was both more intensive and extensive in the younger group. Hyperplasia of crypts was also greater and more prolonged in the younger group. Regeneration of atrophic villi was more rapid in jejunum than ileum in both groups. Results were interpreted to indicate two populations, with different rates of regeneration, in the 21-day old group. Based on this interpretation, regeneration of villi was more rapid in one population from the 21-day old group than in the three-day old group. The length of villi and depth of crypts in control pigs varied longitudinally (i.e. from site to site) in the intestine, within each age group. Length of villi and depth of crypts in control pigs also varied with age.

Age Factors↗
PubMed1973

Age dependent resistance to transmissible gastroenteritis of swine (TGE). II. Coronavirus titer in tissues of pigs after exposure.

Coronavirus titers were compared in various tissues of three-day old and 21-day old pigs after exposure to the virus of transmissible gastroenteritis (TGE). Pigs in both groups that did not die from TGE were necropsied at intervals from one to 15 days post-exposure, and their tissues assayed for viral content. Viral titers were much higher in the small intestines of the younger pigs. Viral isolations were obtained from several tissues of the younger pigs but only from the small intestines of pigs infected at 21 days of age. Levels of viral neutralizing antibodies in the serums of both age groups were comparable at similar post-exposure intervals.

Age Factors↗
PubMed1972

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.

Animals↗
PubMed1972

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.

Adsorption↗