Biomedical subjects

K D Price

Publications and source records attributed to K D Price.

4 recordsLinked to original sources

PubMed2001

Hyperglycemia-induced ascorbic acid deficiency promotes endothelial dysfunction and the development of atherosclerosis.

Dehydroascorbic acid, the oxidized form of vitamin C, is transported into mammalian cells via facilitative glucose transporters and hyperglycemia inhibits this process by competitive inhibition. This inhibited transport may promote oxidative stress and contribute to the increase in atherosclerotic cardiovascular disease observed in patients with diabetes mellitus. This review explores the importance of this proposed mechanism in light of current research. For example, recent reports suggest that administration of antioxidants, such as vitamin C, may slow atherogenesis by improving endothelium-dependent vasodilation in individuals with abnormal glucose and lipid metabolism, perhaps by preventing the oxidation of nitric oxide, an important regulator of vasomotor tone. Endothelial dysfunction plays a key role in the development of atherosclerosis and endothelial cells may be particularly affected by hyperglycemia-induced ascorbic acid deficiency as they line the interior of blood vessels. In addition, we discuss evidence of several other mechanisms by which vitamin C status may affect the development of atherosclerotic cardiovascular disease, particularly its inverse relationship to multiple cardiovascular disease risk factors and indicators. Given these factors, vitamin C administration is recommended during periods of both acute and chronic hyperglycemia to help preserve endothelial function.

Animals↗

PubMed1999

A four-dimensional view of assembly of a morphogenetic protein during sporulation in Bacillus subtilis.

We report the use of a fusion to the green fluorescent protein to visualize the assembly of the morphogenetic protein SpoIVA around the developing forespore during the process of sporulation in the bacterium Bacillus subtilis. Using a deconvolution algorithm to process digitally-collected optical sections, we show that SpoIVA, which is synthesized in the mother cell chamber of the sporangium, assembled into a spherical shell around the outer surface of the forespore. Time-lapse fluorescence microscopy showed that this assembly process commenced at the time of polar division and seemed to continue after engulfment of the forespore was complete. SpoIVA remained present throughout the late stages of morphogenesis and was present as a component of the fully mature spore. Evidence indicates that assembly of SpoIVA depended on the extreme C-terminal region of the protein and an additional region that directly or indirectly facilitated interaction among SpoIVA molecules. The N- and C-terminal regions of SpoIVA, including the extreme C terminus, are highly similar to the corresponding regions of the homologous protein from the distantly related endospore-forming bacterium Clostridium acetobutylicum, attesting to their importance in the function of the protein. Finally, we show that proper localization of SpoIVA required the expression of one or more genes which, like spoIVA, are under the control of the mother cell transcription factor sigmaE. One such gene was spoVM, whose product was required for efficient targeting of SpoIVA to the outer surface of the forespore.

Amino Acid Sequence↗

PubMed1997

A Bacillus subtilis gene encoding a protein similar to nucleotide sugar transferases influences cell shape and viability.

Bacillus subtilis gene ypfP, which is located at 196 degrees on the genetic map, shows similarity to both the monogalactosyldiacylglycerol synthase gene of Cucumis sativus, which encodes a galactosyltransferase, and the murG genes of B. subtilis, Escherichia coli, Haemophilus influenzae, and Synechocystis sp. strain PCC6803, which encode N-acetylglucosaminyltransferases involved in peptidoglycan biosynthesis. Cells containing a null mutation of ypfP are shorter and rounder than wild-type cells during growth in Luria-Bertani medium and glucose minimal medium. In addition, the mutant cells preferentially undergo lysis when grown on solid Luria-Bertani medium.

Acyltransferases↗

PubMed1996

Hyperglycemia-induced latent scurvy and atherosclerosis: the scorbutic-metaplasia hypothesis.

Latent scurvy is characterized by a reversible atherosclerosis that closely resembles the clinical form of this disease. Acute scurvy is characterized by microvascular complications such as widespread capillary hemorrhaging. Vitamin C (ascorbate) is required for the synthesis of collagen, the protein most critical in the maintenance of vascular integrity. We suggest that in latent scurvy, large blood vessels use modified LDL--in particular lipoprotein(a)--in addition to collagen to maintain macrovascular integrity. By this mechanism, collagen is spared for the maintenance of capillaries, the sites of gas and nutrient exchange. The foam-cell phenotype of atherosclerosis is identified as a mesenchymal genetic program, regulated by the availability of ascorbate. When vitamin C is limited, foam cells develop and induce oxidative modification of LDL, thereby stabilizing large blood vessels via the deposition of LDL. The structural similarity between vitamin C and glucose suggests that hyperglycemia will inhibit cellular uptake of ascorbate, inducing local vitamin C deficiency.

Animals↗