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Biomedical subjects

J W Robinson

Publications and source records attributed to J W Robinson.

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

The response of the dog colon mucosa one hour's ischaemia.

Segments of dog colon were subjected to one hour's ischaemia, and their morphology and function were studied either immediately after the ischaemia or 24 hours later. As functional tests, net sodium transport across the mucosa in vitro, the transport capacity in vitro for sugars and amino-acids, tissue respiration, lactate production, and the liberation of acid phosphatase were applied. Immediately after the ischaemia, all parameters differed significantly from the control mucosa: net sodium transport was abolished; amino-acid and sugar uptake, oxygen consumption and lactate production were reduced; and lysosomal enzyme release was increased. All parameters, except sugar uptake, had normalised 24 hours after the trauma. Histological examinations revealed much variation in the lesions occurring after the ischaemia, varying from slight epithelial desquamation to considerable mucosal destruction. In most cases, the mucosa had almost normalised 24 hours later. Morphometric analysis revealed decreased mean mucosal thickness immediately after the trauma, though 24 hours later, there was again no significant difference with the control group.

Acid Phosphatase↗
PubMed1975

Active amino-acid and sugar uptake by gall bladder epithelium in dog, guinea-pig and man.

Slices of dog gall bladder are capable of accumulating amino-acids and sugars against considerable concentration gradients across the luminal membrane of the cell. The epithelium of the common bile duct also absorbs these substrates. The transport systems are sodium-dependent, saturable and inhibited by ouabain and metabolic poisons. The specificity of the mechanisms is more reminiscent of kidney than of intestinal transport. Glycine is preferentially transported across dog gall bladder from the mucosa to the serosa, but the net flux is small. It is concluded that the contraluminal membrane of the epithelial cell might be relatively impermeable to the amino-acid. concentrative uptake also occurs in guinea-pig gall bladder; however it appears to be practically non-existent in rabbit tissue. Human gall bladders, obtained at random from the operating room, also displayed active accumulation. The gall bladder epithelium is remarkably resistant to anoxia. Furthermore, following obstruction of the common bile duct for 2 weeks in dogs, the gall bladder is still able to concentrate amino-acids and sugars, but the extent of the uptake is significantly reduced.

Amino Acids↗
PubMed1975

New characteristics of harmaline inhibition of intestinal transport systems.

Harmaline strongly inhibits the uptake of phenylalanine by slices of guinea-pig intestine in vitro. The lowest concentration having a significant effect is 0.1 mM. The drug also inhibits the unidirectional flux of phenylalanine from the mucosal to serosal face of the tissue provided it is added to the solution bathing the mucosal surface. The unidirectional flux of sodium from the mucosa to the serosa was similarly reduced. Ion and water absorption in the perfused dog intestine in vivo is also diminished in the presence of harmaline. These results support the hypothesis, previously proposed in view of the rapid onset of harmaline inhibition of sodium-dependent uptake mechanisms in a variety of tissues, that harmaline interacts with the sodium-site of non-electrolyte carrier complexes. The effect of harmaline on phenylalanine uptake by the intesting is duplicated by other psychotropic indole analogues. The actions of harmine and harnalol are similar to that of harmaline, despite great differences in the liposolubility of the different compounds. N:N-dimethyl-tryptamine is equally inhibitory, but serotonin is inactive. Mescaline and lysergic acid diethylamide also inhibit phenylalanine transport, but to a much lesser extent than harmaline.

Alkaloids↗
PubMed1975

Function and structure of the mucosa of continent ileostomy reservoirs in dogs.

Continent ileostomy reservoirs were constructed in dogs. Nine to 29 days after formation of the pouches, they were excised together with a loop of adjacent ileum for biochemical and morphological assessment. The villous and epithelial cell heights were reduced, whereas villous width and mitotic index were increased. The mucosa of the pouch was able to absorb phenylalanine and Beta-methyl-glucoside against a concentration gradient, although this absorptive capaciti was lower than that of normal ileum. Similar considerations applied to oxygen consumption. The results indicate that the mucosa of the pouch undergoes transformation, but the intergrity of the epithelial layer is maintained.

Acid Phosphatase↗