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Biomedical subjects

G A Castro

Publications and source records attributed to G A Castro.

At least 91 records · Page 5Linked to original sources
PubMed1975

Lethality of disrupted intestinal lamina propia cells for Trichinella spiralis in vitro.

The possible direct role of inflammatory cells in resistance to Trichinella spiralis was studied by observing the effects of lamina propria cells from the small intestine (LP cells) of immunized rats on various stages of the parasite. Effects produced by physically disrupted cells were compared to those produced by intact cells on worms exposed to phytohemagglutinin or immune serum. LP cells were isolated from the rat intestine by collagenase digestion of everted gut segments that were previously denuded of epithelium by treatment with hyaluronidase. Disrupted cells, but not intact ones, selectively killed T. spiralis juvenile and adult worms in vitro, whereas larvae were unaffected by similar treatment. Attempts to identify the lethal component of disrupted cells led to an evaluation of the enzyme, peroxidase. Mucosal peroxidase is localized in LP cells and its activity increases several-fold during intestinal trichinosis. It is presumed to be myeloperoxidase, a particulate-bound enzyme of myeloid-derived leukocytes that functions as part of a potent antimicrobial system in combination with H2O2 and a halide. Results indicated that the vermicidal component of LP cells was associated with the pellet fraction of disrupted centrifuged LP cells, but was not linked to a peroxidase-H2O2-halide system.

Animals↗
PubMed1975

Structural and hormonal alterations in the gastrointestinal tract of parenterally fed rats.

This study examines the effect of prolonged absence of oral food intake on structural parameters of the gastrointestinal tract in rats maintained nutritionally by intravenous feeding for up to 3 weeks. During this time, their body weights increased by 22%. Controls fed a nearly isocaloric oral diet were sham operated and harnessed in the same manner as their parenterally fed counterparts. Parenteral feeding resulted in a significant decrease in the weights (per 100 g body weight) of the oxyntic gland area of the stomach, small intestine, and pancreas. The weights of the spleen, testes, kidneys, and antral region of the stomach were unaltered. In the small intestine there was a significant loss of DNA and a near doubling of the RNA:DNA ratio in the parenterally fed animals. In the absence of an oral diet antral gastrin levels decreased to one-thirtieth of the control level. The following conclusions are suggested by these results. First, the oral intake and/or physical presence of food within the gastrointestinal tract are necessary for structural maintenance of some tissues of that tract. Second, the disproportionate decrease in weight that occurs in certain tissues is apparently unrelated to the absence of nutrients which might normally be utilized directly from the lumen. Third, maintenance of normal tissue stores of the hormone, gastrin, is dependent on stimuli provided by oral ingestion and the presence of food in the gastrointestinal tract.

Animals↗
PubMed1975

Action of gastrin on gastrointestinal structure and function.

In previous communications we have reported using the rat fed by total parenteral nutrition to examine the effects of the absence of food from the gut on functional and structural parameters of the gastrointestinal tract. In the current study three groups of animals were fed parenterally; one received a continuous infusion of pentagastrin equal to about one-half the D50 for acid secretion, another received a comparable infusion of histamine, and a third group was given only the liquid diet. These animals were compared to orally fed sham operated controls. The parenterally fed animals had significantly lower levels of antral and serum gastrin. When compared to whole body weight, the weights of the oxyntic gland area of the stomach, the pancreas, and the small intestine were significantly lower. In addition, the total and specific activities of the disaccharidase enzymes were significantly reduced. Pentagastrin prevented both the decreases in weights of the gastrointestinal tissues and the decreases in dissaccharidase activity. Histamine was without effect. We conclude that pentagastrin prevents the changes in gastrointestinal structure and function caused by the absence of food from the gut and that the trophic action of gastrin is necessary for the maintenance of the functional and structural integrity of the gastrointestinal tract.

Animals↗