PubMed Health⌕ Search

Biomedical subjects

A Randolph

Publications and source records attributed to A Randolph.

22 records · Page 2Linked to original sources
PubMed1979

In vitro proliferation of endothelial cells from kitten retinal capillaries.

When microvessel (predominantly capillary) fragments freshly isolated from the retinas of young kittens are incubated in tissue culture medium, we observe the slow outgrowth of cells that appear to be derived from the capillary endothelium. The cells grow as a monolayer with a tightly packed, mosaic-like array. Electron microscopy of these cells reveals "tight junctions" (zonulae occludentes) resembling those found in the endothelium of intact capillaries. The availability of in vitro preparations of retinal capillary endothelial cells should facilitate investigations of the causes of abnormal endothelial cell proliferation in various diseases and of factors that modify cell junctions and capillary permeability in the retina. Since we have previously demonstrated proliferation in culture of intramural pericytes ("mural cells") from retinal capillaries, it should now be possible to carry out compratative studies of biochemical and functional properties of retinal capillary pericytes and endothelial cells.

Animals↗
PubMed1977

Regional blood flow to the stomach and small intestine in ponies.

Studies on regional blood flow to the stomach and small intestine were performed in 9 anesthetized ponies. Carbonized microspheres (15 +/- 5 micron in diameter) labeled with 85Sr were injected into the left atrium to determine blood flow distribution. In 4 ponies, the regional flows to mucosal-submucosal layers of the stomach and the small intestine were also measured. The nonglandular region of the stomach received the least blood per 100 g of tissue, and the duodenum received the greatest. The regional blood flow to the duodenum was significantly higher than that to the glandular stomach region, jejunum, and ileum.

Animals↗
PubMedDate not supplied

Evolution of phosphofructokinase--gene duplication and creation of new effector sites.

Phosphofructokinases (PFK; EC 2.7.1.11) are tetrameric enzymes that have a key role in the regulation of glycolysis; as such, they are subject to allosteric activation and inhibition by various metabolites. Eukaryotic PFKs are about twice the size of prokaryotic enzymes and are regulated by a wider repertoire of effectors: for example, the subunit molecular weights of rabbit muscle (RM) PFK and Bacillus stearothermophilus (Bs) PFK are 82,000 and 36,000, respectively. Both enzymes are activated by ADP (or AMP), but RM-PFK is also activated by fructose bisphosphates (FBP) and inhibited by ATP and citrate. This, together with other evidence, has led to speculation that mammalian PFKs have evolved by duplication of a prokaryotic gene, although previous peptide analysis failed to reveal internal homology in RM-PFK. Here we demonstrate clear homology among the N- and C-halves of RM-PFK and Bs-PFK, thus establishing an evolutionary relationship by series gene duplication and divergence. Furthermore, detailed knowledge of the Bs-PFK structure provides the basis for inferences concerning the structural organization of RM-PFK and the evolution of new effector sites in the enzyme tetramer.

Amino Acid Sequence↗