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Biomedical subjects

M R Thompson

Publications and source records attributed to M R Thompson.

At least 73 records · Page 4Linked to original sources
PubMed1978

Hepatic inactivation of gastrins of various chain lengths in dogs.

In dogs with gastric fistulae and with transposition of the portal vein and the inferior vena cava, we studied secretion of acid in response to portal or systemic venous infusion of a series of progressively longer fragments of the carboxyl terminal portion of human gastrin. Pentagastrin, G6, G7, G8, G9, G10, G13, G17, and G34 were studied. Potency by portal venous infusion relative to systemic venous infusion was used as an index of hepatic inactivation. Fragments with eight or fewer amino acid residues were more than 90% inactivated by hepatic transit. Fragments with nine or more amino acid residues were more resistant to hepatic inactivation than shorter fragments. For fragments with 7 to 17 amino acid residues, increasing the chain length was accompanied by progressive increase both in hepatic resistance to inactivation and in potency for stimulation of acid secretion, suggesting that resistance to hepatic inactivation may be a major determinant of potency.

Animals↗
PubMed1977

Biological properties of Shigella flexneri 2A toxin and its serological relationship to Shigella dysenteriae 1 toxin.

A toxin extracted from heat-inactivated, alkaline-treated Shigella flexneri 2a showed biological properties similar to those of Shigella dysenteria 1 toxin. The S, flexneri 2a toxin was lethal to mice, enterotoxic for ileal loops of rabbits, and cytotoxic for HeLa cells. A serological relationship between S. flexneri 2a and S. dysenteriae 1 toxin was shown with cross neutralization tests.

Antigens, Bacterial↗
PubMed1976

Ultrastructure and elemental composition of dormant and germinating Diplodia maydis spores.

The ultrastructure of Diplodia maydis spores was studied in thin sections with a transmission electron microscope. Storage vacuoles were evenly distributed in the two cells. Some of the vacuoles that contained a dense osmiophilic sphere(s) were surrounded by a membrane, and had membranous aggregates around their periphery. The sport wall was composed of an electron-dense layer and an electron-translucent layer. An inner cytoplasmic membrane was present. Dormant and germinating spores were studied with scanning electron microscopy and also with a Si (Li) energy-dispersive X-ray analyzer. The dormant spore was ovate and usually two-celled with a central septum. Germination proceeded via a germ tube from the side of one end of the cell. Of several methods for preparation of specimens for X-ray analysis studied, freeze-dried spores mounted on carbon stubs and then further carbon coated gave the best results. X-ray analyses revealed that spore populations contained large amounts of Si, P, Cl, and K, smaller amounts of S and Ca, and trace amounts of Mg and Al. Analyses of single spores revealed high K and Cl and low P and Mg at one end of the cell with concomitant low K and Cl and high P and Mg in the central portion and other end of the cell. In two-celled germinating spores, high K and Cl occurred in the end of the nongerminating spore cell, whereas the germinating cell contained high P and Mg and low K and Cl. X-ray image maps revealed that K and Cl were located together at one end of the spore.

Calcium↗
PubMed1976

Gastric mucosal lesions produced by intravenous infusion of aspirin in cats.

Aspirin was given by continuous intravenous infusion to 35 intact cats for 7 days in doses ranging from 25 to 200 mg kg-1 day-1. Gastric mucosal lesions occurred in 50 to 70% of the animals in the various dosage groups, including deep ulcers in 20%. All of the ulcers were in antral mucosa near its border with oxyntic mucosa. The incidence of lesions, including ulcers, showed no apparent relation to the dose of aspirin. With all but the highest dose, plasma salicylate levels were within or below what is regarded as the therapeutic range for man. Asprin, 100 mg kg-1 day-1, was given for 7 days to 4 cats with pouches containing all of the antral mucosa plus some oxyntic mucosa. One or more deep ulcers occurred in the antral mucosa of the pouches in each of these 4 cats. The electrical potential difference across the mucosa did not decrease, and net fluxes of hydrogen ions out of the pouch and of sodium ions into the pouch did not increase during the 7 days of aspirin administration despite the occurrence of ulcers in the pouches. It is concluded that intravenous aspirin, in doses giving plasma levels within or below the therapeutic range for man, causes gastric mucosal lesions including deep ulcers within 7 days in cats. These lesions occur without the changes in electrical potential difference and hydrogen and sodium fluxes that are regarded as characteristic of the "broken barrier."

Animals↗
PubMed1976

Studies on the acid secretion that occurs during injury to the gastric mucosa.

When pouches of the oxyntic glandular mucosa in dogs were irrigated with 4mM dithiothreitol in acid solution the mucosa shed plasma and secreted acid. There was a linear relationship between the net addition of H+ to the lumen and the amount of plasma shed, suggesting that the mechanisms of acid secretion and plasma shedding were closely related. Atropine, metiamide, and PGE2 only partially inhibited the acid secretion. The three drugs also reduced the plasma shedding and may be useful in the management of protein-losing gastropathy in man.

Animals↗
PubMed1975

A study of protein-sodium dodecyl sulfate complexes by transient electric birefringence.

The method of transient electric birefringence has been applied to study the conformation of protein-sodium dodecyl sulfate complexes. A model of a deformable prolate ellipsoid has been proposed for the protein-dodecyl sulfate complex. This model is compared to the models proposed by J. A. Reynolds and C. Tanford (1970), J. Biol. Chem. 245, 5161) and K. Shirahama, K. Tsujii, and T. Takagi (1974, J. Biochem. 75, 309). Differences between these latter two models are resolved by the model presented here. In addition, it has been demonstrated that protein molecular weights may be obtained from the slow relaxation time for transient electric birefringence of protein-dodecyl sulfate complexes.

Animals↗
PubMed1975

Hydrodynamic structure of bovine serum albumin determined by transient electric birefringence.

Birefringence relaxation studies on bovine serum albumin (BSA) reveal transient decay described by a double exponential process. The values of the relaxation times lead to estimation of the size of the equivalent ellipsoid of revolution for BSA. Previous measurements of transient birefringence for BSA have shown a single relaxation process, since the apparatus used in obtaining those data was not fast enough to detect the faster relaxation process.

Animals↗
PubMed1975

Titration of sodium channels in canine gastric mucosa.

Net Na+ flux from mucosa to lumen, potential difference, and volume and plasma protein outputs were measured in vagally denervated, separated pouches of the dog's oxyntic or pyloric glandular mucosa when the pouches were irrigated with Na+-free solutions whose pH ranged from 1.5 to 12.2. The apparent permeability to Na+(P'Na) was calculated. P'Na is lowest when the mucosa is bathed with acid and increases 2- to 3-fold when the pH is raised to 10. In the range of pH 10.0--11.2 P'Na is greater by an order of magnitude, but volume output is small, and no plasma proteins are shed. When the pH is above 11.2 there is an abrupt increase in P'Na, and the mucosa sheds a large volume of fluid containing plasma proteins. The change effected by raising the pH to the range of 10.0--11.2 occurs within 10 sec, and it is reversible. The change effected by raising the pH above 11.2 also occurs within 10 sec, and it is partly reversible.

Animals↗