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Biomedical subjects

N Kalant

Publications and source records attributed to N Kalant.

At least 55 records · Page 3Linked to original sources
PubMed1978

Diabetic glomerulosclerosis: current status.

Current information on the nature, pathogenesis and treatment of diabetic glomerulosclerosis is reviewed. The fundamental lesion is one of the glomerular basement membrane, a complex layer of collage-like and other peptides; thickening of this membrane, seen microscopically, is due to the presence of an increased amount of membrane material of normal composition. There is little reliable evidence relating the frequency of glomerulosclerosis to the quality of control of the diabetic state, but indirect evidence from patients with secondary diabetes and from a variety of studies in animals indicates strongly that the glomerular lesion is a consequence of the abnormal metabolic state and can be prevented by adequate treatment of the diabetes. A concept of the pathogenesis of the glomerular lesions and renal failure is presented, but there remain large gaps in knowledge of the mechanisms involved. Treatment of chronic renal failure by maintenance renal dialysis and renal transplantation is not as successful in persons with diabetes as in those without this condition; however, the results appear to be improving, and transplantation particularly holds much promise.

Animals↗
PubMed1978

Effect of exercise on glucose and insulin utilization in the forearm.

Glucose and insulin utilization by forearm muscle was examined at rest and during exercise. Care was taken to have a steady state with regard to arterial plasma concentrations for 1 hr prior to as well as during the measurements. At rest, insulin uptake was linearly related to arterial insulin concentration. During exercise with no change in arterial plasma concentration of either glucose or insulin, there was an increase in uptake of both substances, and the relation of insulin uptake to concentration became exponential. It is hypothesizes that the latter phenomenon is due to an increase in cellular uptake of insulin by a mechanism independent of membrane receptors.

Adult↗
PubMed1977

Cytoplasmic compartmentation of glucose 6-phosphate.

When rat diaphragm, intact or homogenized, was incubated with [14C]glucose, the initial specific activity of the fructose 6-phosphate was higher than that of glucose 6-phosphate (glc-6-P). This relationship was also found when the cytosol was incubated with the labeled glucose. The early time course of production of glc-6-P from glucose and its removal provide evidence that newly synthesized glc-6-P does not equilibrate rapidly with the total pool of this metabolite and is preferentially removed by isomerization. It is concluded that glc-6-P is functionally compartmented within the cytoplasm.

Animals↗
PubMed1977

D-Glucose uptake and insulin binding by the human adipose cell plasma membrane as a function of its polypeptide composition.

A preparation of plasma membranes isolated from human omental lipocytes is composed of about 15 major polypeptide components including three major glycoproteins with an apparent molecular weight range from 100000 to 23 000, as determined by sodium dodecyl sulfate - polyacrylamide gel electrophoresis. Extraction of this membrane preparation with sodium iodide or 2,3-dimethylmaleic anhydride solubilized 50 and 70% of the membrane protein, respectively, resulting from the extensive extraction of protein from all but two of the major membrane polypeptide components. This removal of protein did not affect the membrane's stereospecific D-glucose-uptake activity but did reduce its total specific [125I]insulin-binding activity by 46-67%. The binding of [125I]insulin to its specific receptor on lipocyte plasma membranes was detected at physiologic concentrations of the hormone and could be competitively displaced by increasing concentrations of native insulin. The kinetic behaviour of this reaction was approximated by Scatchard analysis, and both the affinity and binding capacity of the plasma membrane for insulin were increased at lower temperatures. These results suggest that D-glucose transport in human adipose tissue is mediated by an intrinsic component of the hydrophobic structure of the lipocyte plasma membrane, and represent a partial purification of this component. In addition, these studies demonstrate and characterize the binding of insulin to the plasma membrane isolated from human lipocytes. A quantitative study of this binding reaction may provide further understanding of the mechanisms underlying the decreased insulin responsiveness characteristic of human diabetes.

Adipose Tissue↗
PubMed1977

A radioreceptor assay for serum insulin.

A method is described for the measurement of insulin in serum by RRA with normal human sRRA. The sensitivity of the assay is similar to that of a commonly used immunoassay. There is no detectable interference from somatomedin or NSILA, whereas proinsulin has only about 5% of the activity of insulin in the assay. There is a high degree of correlation between the results of immunoassay and the RRA over the physiological range of serum insulin. However, the greater ability to differentiate between insulin and proinsulin, together with greater ability of receptor binding to exclude altered (biologically inactive) insulin, present advantages of this assay over the RIA, which may be significant in abnormal situations.

Binding, Competitive↗
PubMed1975

Insulin control of hepatic glucose production.

Insluin injected intravenously caused a rapid, marked decrease in hepatic glucose secretion in the rabbit, as determined by an isotope-dilution procedure. This was associated with a decrease in the concentrations of gluconeogenic intermediates from phosphoenolpyruvate to triose phosphates, inclusive, compatible with inhibition of gluconeogenesis at phosphoenolpyruvate carboxykinase. The concentration of glucose 6-phosphate was unaltered but that of hepatic glucose was reduced. The specific activities of the hexose phosphates, relative to that of liver glucose, were the same in control and insulin-treated animals. These observations can be explained by a decrease in the activity of glucose-6-phosphatase. It is concluded that this enzyme is a control point for hepatic glucose production and is inhibited by insulin. In the rat, insulin produced a rapid fall in blood sugar. The hepatic glucose output remained normal despite a fall in hepatic glucose 6-phosphate concentration during the initial period of insulin action. This suggests that glucose-6-phosphate returned to normal with no change in the rate of glucose production. The data suggest that in the rat, insulin produces a transient increase in glucose-6-phosphatase activity.

Adenine Nucleotides↗
PubMed1975

Relation between insulin and glucose flux rates in the dog.

A constant infusion isotope dilution procedure for measurement of plasma insulin flux rates was performed in acutely eviscerated dogs receiving an infusion of nonlabeled insulin; the calculated rate of insulin flux corresponded closely to that of the administered rate, thus validating the isotope dilution procedure. Flux rates of insulin and glucose were measured simultaneously at different steady levels in intact dogs. There was a linear relationship between plasma insulin concentration and insulin flux rate. In each animal there was also a linear relationship between glucose flux rate and insulin concentration, and between rates of glucose flux and insulin flux, but there was considerable inter-animal variation in the slope of the regression lines.

Animals↗
PubMed1972

Phospholipid of the rat glomerular basement membrane in experimental nephrosis.

Phospholipids were found to be a constant component of rat glomerular basement-membrane preparations. The concentration fell during preparation of basement membrane by sonication of whole glomeruli, but then remained constant despite continued sonication. The proportions of the individual phospholipids were different from those of whole renal tissue or of isolated glomeruli. The basement-membrane preparations had no (Na(+)+K(+))-activated adenosine triphosphatase activity, an enzyme that is bound to plasma membranes. The concentration of lipid P was decreased on exposure in vivo or in vitro to antiserum against basement membrane; 7 days after injection of antiserum there was a change in the phospholipid composition, with a relative increase in phosphatidylcholine and a decrease in sphingomyelin content. The metabolic turnover rate of the lipid P remaining in the membrane was normal, as determined by (32)P incorporation. The loss of phospholipid was associated with decreases in the relative concentrations of hydroxyproline, hydroxylysine and glycine, and relative increases in proline, lysine, serine, threonine and valine. Administration of aminonucleoside and daunomycin produced proteinuria but did not cause a decrease in lipid P. Anticollagen and anti-lymphocyte sera that attached to the basement membrane but failed to produce proteinuria, also failed to affect the phospholipid content.

Adenosine Triphosphatases↗