Search PubMed⌕ Search

Biomedical subjects

J C Allen

Publications and source records attributed to J C Allen.

At least 289 records · Page 16Linked to original sources
PubMed1973

Isolation and characterization of the antigen of Neisseria gonorrhoeae.

The beta antigen of Neisseria gonorrhoeae has been isolated from the alkaline-extracted gonococcal endotoxin by ion exchange, molecular sieve, and powder block electrophoretic chromatography. Hemagglutination inhibition studies indicate that the preparation is essentially free of common enterobacterial and gonococcal alpha antigen. Analysis of the isolated antigen by immunodiffusion and acrylamide gel electrophoresis reveal only one detectable component. Chemical studies indicate that the antigen is an acidic glycoprotein composed primarily of four major amino acids: alanine, glutamic acid, glycine, and proline. The antigen has an s(20,w) of 8.55, and spectral analysis in the ultraviolet and visible range reveals a single absorption peak at 217 nm.

Amino Acids↗
PubMed1972

Renal sodium-potassium-activated adenosine triphosphatase and sodium reabsorption.

The role of renal Na(+),K(+)-ATPase in sodium reabsorption was further examined in dogs in which digoxin, a specific inhibitor of the enzyme system, was infused into one renal artery in doses ranging from 0.4 to 0.9 mug/kg/min (low dose) and from 1.0 to 4.0 mug/kg/min (high dose). A significant natriuresis occurred with both dose ranges which was accompanied by inhibition of Na(+),K(+)-ATPase of cortex and medulla in the infused kidney. Despite over 90% enzyme inhibition in many experiments, at least 80% of the filtered sodium continued to be reabsorbed. The per cent change in enzyme activity correlated with the rate of digoxin administration and the total dose administered but not with changes in sodium excretion. Changes in medullary Na(+),K(+)-ATPase activity, however, bore a direct relationship to alterations in fractional solute free water reabsorption (T(c) (H2O)). Inhibition of cortical enzyme activity alone was not associated with natriuresis, suggesting that medullary enzyme activity must be depressed for increased sodium excretion to occur during digoxin infusion. In high-dose experiments, significant inhibition of cortical and medullary enzyme in the contralateral control kidney was also observed, but natriuresis did not occur. In these experiments the rate at which digoxin reached the control kidney rose progressively but never equaled the rates in the directly infused kidney with either dose. Nevertheless, it is clear that under certain circumstances enzyme inhibition of either cortex or medulla need not be accompanied by natriuresis. We conclude that the major role of renal Na(+),K(+)-ATPase is in sodium reabsorption in the medulla (ascending limb of Henle's loop) and that it has a relatively small role in proximal sodium reabsorption. The kidney can rely on other sodium reabsorptive mechanisms depending on the rate of enzyme inhibition, so that natriuresis may not occur at all if depression in activity occurs "slowly." The nature of these mechanisms is not clear.

Adenosine Triphosphatases↗