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B H Ginsberg

Publications and source records attributed to B H Ginsberg.

16 recordsLinked to original sources
PubMed1992

An overview of minimally invasive technologies.

Self-measurement of blood glucose is an integral part of diabetes mellitus therapy. As many as 65% of diabetic people (4-5 million people) perform some degree of self-monitoring and approximately 20-30% do so frequently. Most patients consider this the most onerous part of their diabetes therapy. It requires obtaining blood, frequently in public, and is usually the most painful part of therapy, being significantly more painful than insulin self-administration. Patients therefore are anxious for a less-invasive method for glucose measurement. Methods exist or are being developed for minimally invasive glucose monitoring, which use body fluids other than blood (e.g., sweat and saliva), subcutaneous tissue, or blood measured less invasively. Sweat and saliva are relatively easily obtained but their glucose concentration lags significantly behind blood glucose. Methods to increase sweating have been developed and seem to increase the timeliness of the sweat glucose measurement. Subcutaneous glucose measurement seems to lag only a few minutes behind blood glucose and may actually be a better measurement of the critical values of glucose concentrations in brain, muscle, and other tissue. Glucose can be measured by noninvasive or minimally invasive methods, such as those making skin or mucous membranes permeable to glucose or those placing a reporter molecule in the subcutaneous tissue. Needle-type sensors have been improved in accuracy, size, and stability and can be placed into the subcutaneous tissue or peripheral veins to monitor blood glucose with miniature instruments.

Blood Glucose Self-Monitoring↗
PubMed1991

Insulin sensitivity is increased in Friend erythroleukemia cells enriched in polyunsaturated fatty acid.

Increases in membrane lipid unsaturation and drug-induced increases in membrane fluidity have been shown to be associated with increases in insulin receptor concentration in animals, cultured cells, and liposomes. In the current study, we have examined the effect of increased membrane fatty acid unsaturation on insulin action. Friend Erythroleukemia cells were grown with exogenous polyunsaturated fatty acids for three days. After growth in medium supplemented with fatty acids, the unsaturation index of the phospholipids increased from 1.08 to 1.92, and this was associated with a significant decrease in anisotropy, as measured by fluorescence polarization. When measured at 15 degrees C, insulin receptor number rose from 9000 to 22,000 per cell with increased fatty acid unsaturation. The affinity for insulin in the polyunsaturated fatty acid treated cells decreased, however, resulting in similar amounts of insulin binding at low insulin concentrations but more binding at high insulin concentrations when compared to control cells. In contrast, binding of IGF-I was not influenced by increased membrane fatty acid unsaturation. When measured at 37 degrees C there were no changes in binding of insulin or IGF-I. Internalization of insulin was identical in control cells and in cells with increased membrane fatty acid unsaturation. Thymidine incorporation, an insulin-dependent function in these cell, was measured in control and fatty acid treated cells. In control cells, insulin increased thymidine incorporation by 80%, with an ED50 of about 5 nM. In cells treated with polyunsaturated fatty acids, the insulin stimulated thymidine incorporation was slightly higher and the ED50 was about 0.2 nM. In contrast, there was no increase in the sensitivity or responsiveness of fatty acid treated cells to IGF-I. We conclude that increased membrane fatty acid unsaturation greatly influences insulin binding and biological sensitivity, but not that of IGF-I. At low insulin levels, there was a greater insulin bioeffectiveness, despite the same or lower insulin binding, suggesting more efficient coupling of the insulin-effector complex.

Animals↗
PubMed1990

Ethanolamine metabolism in cultured bovine aortic endothelial cells.

The role of extracellular ethanolamine in phospholipid synthesis was examined in cultured bovine aortic endothelial cells. Serine and ethanolamine were both readily accumulated by these cells and incorporated into phospholipid. Exposing cells to extracellular ethanolamine for 4-6 weeks had no effect on cell growth, yet increased the phosphatidylethanolamine content of these cells by 31% as compared to control cells. The intracellular content of ethanolamine was measured by high performance liquid chromatography, and results showed that the ethanolamine-treated cells contained a significantly greater amount of free ethanolamine compared to control cells (0.62 +/- 0.07 nmol/mg of protein versus 0.27 +/- 0.05 nmol/mg of protein, respectively). Ethanolamine-treated cells also had decreased accumulation and incorporation into lipid of [3H]ethanolamine throughout a 48-h incubation and increased K'm and V'max parameters of ethanolamine transport as compared to control cells. Studies were also done to examine the effect of ethanolamine on the generation of free ethanolamine from phosphatidylserine. In pulse-chase experiments with [3H]serine, a physiological concentration of ethanolamine (25 microM) decreased the amount of 3H-labeled phosphatidylethanolamine produced from 3H-labeled phosphatidylserine by 12 h as compared to the amount of 3H-labeled phosphatidyl-ethanolamine produced in the absence of ethanolamine in the chase incubation. Furthermore, ethanolamine-treated cells accumulated 20% less labeled ethanolamine in the aqueous pool from [3H]serine after 24 h of incubation than did control cells. These results can be explained by isotope dilution with the ethanolamine pool that accumulates in these cells with time when exposed to media supplemented with a physiological concentration of ethanolamine and by an effect of ethanolamine on ethanolamine generation from phosphatidylserine. The results show that an extracellular source of ethanolamine significantly influences the phospholipid metabolism of cultured bovine aortic endothelial cells.

Animals↗
PubMed1988

Effect of increased glucose levels on Na+/K+-pump activity in cultured neuroblastoma cells.

Neuroblastoma cells were used to analyze the effect of elevated glucose levels on myo-inositol metabolism and Na+/K+-pump activity. The activity of the Na+/K+ pump in neuroblastoma cells is almost totally sensitive to ouabain inhibition. Culturing neuroblastoma cells in 30 mM glucose caused a significant decrease in Na+/K+-pump activity, myo-inositol metabolism, and myo-inositol content, compared to cells grown in the presence of 30 mM fructose. Glucose supplementation also caused a large intracellular accumulation of sorbitol. The aldose reductase inhibitor sorbinil prevented the abnormalities in myo-inositol metabolism and partially restored Na+/K+-pump activity in neuroblastoma cells cultured in the presence of elevated glucose levels. These results suggest that the accumulation of sorbitol by neuroblastoma cells exposed to elevated concentrations of extracellular glucose causes a decrease in myo-inositol metabolism and these abnormalities are associated with a reduction in Na+/K+-pump activity.

Aldehyde Reductase↗
PubMed1987

Amino acid and putative neurotransmitter transport in human Y79 retinoblastoma cells. Effect of insulin and insulin-like growth factor.

The binding of insulin and insulin-like growth factor I (IGF-I) and their effect on amino acid and neurotransmitter transport was studied in cultured human Y79 retinoblastoma cells. Y79 cells possess specific receptors for both insulin and IGF-I. Insulin binding to Y79 cells is characterized by a curvilinear Scatchard plot suggesting a two-site or two-affinity binding system. In contrast, IGF-I binding has a linear plot indicative of a one-site, one-affinity binding system. The uptake of glycine, a putative neurotransmitter in the retina occurs by a specific transport system in Y79 cells, independent of the uptake of other neutral amino acids. The uptake of glycine was increased 25-50% by either insulin or IGF-I. The response to insulin or IGF-I on glycine uptake is gradual and concentration dependent. The accumulation of other amino acids and putative retinal neurotransmitters by Y79 cells was not significantly affected by insulin of IGF-I. In addition, the activity of Na+/K+-ATPase was not influenced. The analysis of high affinity glycine uptake indicates that insulin and IGF-I are stimulating glycine transport by increasing the V'max without significantly affecting the K'm. Further analysis suggests that insulin and IGF-I are causing a recruitment of additional glycine transporters at the cell surface or activating otherwise nonfunctional transporters by an unexplained mechanism. Because of the implication that glycine responds as a neuroactive amino acid in Y79 cells these studies suggest that insulin and IGF-I may influence neuroactivity in the human retina by regulating the transport of glycine.

Amino Acids↗
PubMed1985

Mitogenic activity of glia maturation factor. Interaction with insulin and insulin-like growth factor-II.

The mitogenic activity of glia maturation factor (GMF) was tested on sparse-cultured cells. GMF stimulates the growth rate of normal astroblasts and fibroblasts grown in the presence of fetal calf serum (FCS), and raises the saturation density of the cells over what is imposed by the corresponding serum concentrations. GMF has no mitogenic effect in the complete absence of serum. The mitogenicity of GMF is also demonstrable in defined media where certain serum components are present. In particular, GMF in combination with the defined medium N2 partially mimics the proliferative effect of serum alone. Insulin, an ingredient of N2, can substitute for the complete N2 formula. Insulin-like growth factor-II (IGF-II), in turn, can substitute for insulin. The interaction of GMF with insulin or IGF-II can be demonstrated in a sequential manner, suggesting that GMF is a competence factor. Since insulin is required at a concentration well above the physiologic serum level, and must be used at a dose 1000 times higher than IGF-II, we suspected that insulin acts on IGF-II receptors. This was substantiated by the demonstration of IGF-II receptors and the absence of detectable insulin receptors on the astroblasts. The combined effect of IGF-II and GMF mimics the combined effect of 10% FCS and GMF, in both growth rate and saturation density.

Animals↗
PubMed1985

Demonstration of receptors for insulin-like growth factor-II on human T-lymphocytes.

Primary human T-lymphocytes that have been mitogen activated in chemically defined medium demonstrate cell surface receptor for insulin-like growth factor-II (IGF-II). In contrast resting T-lymphocytes demonstrate little or no IGF-II receptor. Receptors appear within 24 hours of mitogen activation with maximal binding occurring at 72 hours. After this point IGF-II binding declines. Receptor binding of IGF-II to T-lymphocytes does not show a sharp pH dependence but is maximal above pH 7. Insulin does not compete for IGF-II binding sites and proinsulin competes only weakly, suggesting that this is a type 2 IGF receptor and not an insulin receptor. Furthermore, anti-insulin antibodies do not inhibit IGF-II from binding to activated T-lymphocytes indicating divergent binding domains on the two peptide hormones. IGF-II demonstrates stimulating action on T-lymphocyte proliferation probably mediated by binding of IGF-II to this receptor.

Cells, Cultured↗
PubMed1985

Anomalous glucose and insulin responses in patients with insulinoma. Caveats for diagnosis.

Two patients with insulinomas had unusual glucose and insulin-secretory dynamics in response to prolonged fasting. In patient 1, low insulin values persisted throughout three separate supervised fasts without a steady rise in the insulin-glucose ratio. In patient 2, a rising insulin-glucose ratio during a fast returned to normal after a documented catecholamine surge following a transient hypoglycemic episode. While patient 1 had clearly elevated proinsulin values of 52% to 57%, patient 2 had a near-normal value of 23%. The diagnosis of an insulinoma can usually be made by obtaining simultaneous glucose and insulin values during a prolonged supervised fast. Rarely, however, anomalous results may be obtained during supervised fasts of patients with insulinoma, and a broader range of diagnostic tests will be required to establish the correct diagnosis.

Adenoma, Islet Cell↗
PubMed1979

Reconstitution of the solubilized insulin receptor in phospholipid vesicles.

The insulin receptor was solubilized from turkey erythrocyte membranes by extraction with 1% beta-octylglucopyranoside. Insulin binding was enhanced when the solubilized material was reconstituted in phospholipid vesicles. The affinity of the reconstituted vesicles for various insulins was similar to that of the intact membranes: porcine insulin greater than proinsulin greater than desoctapeptide insulin. A curvilinear Scatchard plot was obtained for insulin binding to the reconstituted system at 15 degrees C. A high affinity association constant of 1.4 x 10(9) M-1 was obtained from the Scatchard plot. This is a four-fold increase over the value for the turkey erythrocyte membrane, which contains more highly saturated phospholipids. This suggests that the insulin receptor may be sensitive to the lipid composition of the membranes in which it is embedded.

Animals↗
PubMed1979

Decrease in insulin receptors during Friend erythroleukemia cell differentiation.

The Friend erythroleukemia cell has an insulin receptor with all the properties of mammalian insulin receptors: rapid, reversible, and saturable binding of insulin; specific for insulin and insulin analogs; inversely proportional to temperatures; sharply pH dependent (optimum = 8.0); and demonstrated ligand-induced accelerated dissociation consistent with negative cooperativity. There were 17,200 sites per cell. After induction by dimethylsulfoxide, 80% of the cells became benzidine positive (i.e., contained hemoglobin). The receptor concentration dropped to 4300 sites per cell, while the remaining receptors retained all the initial binding characteristics. This loss of receptors could not be attributed directly to either dimethylsulfoxide or changes in cell size. Thus, during the process of differentiation, the concentration of insulin receptors in the Friend erythroleukemia cell decreases.

Animals↗
PubMed1978

Properties and partial purification of the detergent-solubilized insulin receptor: a demonstration of negative cooperativity in micellar solution.

Turkey erythrocytes possess insulin receptors with binding properties very similar to those of mammalian insulin receptors. In the present study, the insulin receptor of the avian erythrocyte has been solubilized in Triton X-100, extensively characterized and partially purified, and its properties compared to those of the membrane-bound receptor. The solubilized insulin receptor has a Stokes radius of 70 A and an apparent molecular weight of 300 000 in 0.05% Triton. The binding of insulin to the soluble receptor was very similar to the binding observed with the membrane-bound receptor. Thus, binding was markedly temperature dependent for both the soluble and membrane-bound forms, although the kinetics of binding were slower with the soluble receptor. Both forms of the receptor also showed a sharp pH optimum; however, solubilization produced a shift from maximal binding at pH 7.8 to pH 7.3. The soluble receptor also retained insulin analog specificity, ion sensitivity and negative cooperativity. The soluble receptor did not appear to degrade either bound or free insulin. On DEAE-cellulose chromatography the receptor eluted as a single peak. The specific activity of this partially purified preparation was 25--30 pmol/mg protein (about 500-fold enrichment over crude extract and 5-fold over highly purified membranes). Extensive attempts to purify further the receptor by gel filtration, carboxymethyl-cellulose chromatography and affinity chromatography resulted in either a very low yield or only modest enrichment. Purification was also complicated because the receptor was easily denatured; about 40% of the activity was lost after a 90-min exposure to 3 M urea or pH 4.5. These data suggest that the insulin receptor retains its properties in the absence of the lipid bilayer of the membrane. Complete purification will be difficult due to a lack of stability under a number of conditions.

Animals↗
PubMed1977

The insulin receptor of the turkey erythrocyte: similarity to mammalian insulin receptors.

Avian erythrocytes possess insulin receptors which have binding properties that are virtually identical to those of the well studied mammalian insulin receptors. The affinity for porcine insulin was identical for the turkey and mammalian receptors over the entire range of insulin concentrations, as was the affinity of each of four insulin analogues which differed 300-fold in biological potency. Insulin induced acceleration of dissociation (i.e., the negatively cooperativite site-site interaction) was indistinguishable over a 10(6) range of insulin concentrations. Sharp pH dependence of binding was identical for turkey and mammalian receptors. The effects of temperature on association, dissociation and steady state binding were also identical. Thus, although birds and mammals have evolved separately for 300 million years there has been little change in the properties of the insulin receptor over this time period.

Allosteric Regulation↗
PubMed1976

The insulin receptor of the turkey erythrocyte. Characterization of the membrane-bound receptor.

The insulin receptor of the turkey erythrocyte has previously been shown to be very similar to that of the mammalian insulin receptors. As a first step in the isolation of this receptor a highly purified plasma membrane fraction has been prepared. The binding characteristics of the purified membrane-bound receptor were identical to those found with intact erythrocytes, but the membrane preparation had very little insulin-degrading activity. Isolation of the membrane by the methods described gave a 100-fold purification of the insulin receptor with 67% yield.

Animals↗