Ascertaining accurate blood pressure.
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Arm↗
Biomedical subjects
S W Peterson
Publications and source records attributed to S W Peterson.
Phylogenetic relationship within Fusarium sambucinum Fuckel sensu lato, determined from ribosomal RNA sequences.
Partial ribosomal RNA nucleotide sequences were determined for 11 strains of Fusarium sambucinum Fuckel sensu lato to assess by molecular genetic means, Nirenberg's recent morphotaxonomic interpretation which split the species into three distinct taxa: F. sambucinum sensu stricto, F. torulosum, and one other species, as yet unnamed (Fusarium species nova). Four sequence patterns were identified among the 11 strains. Two sequences that varied at one site were found among strains of F. sambucinum, strains of F. torulosum and Fusarium sp. nov. showed no intraspecific variation. Interspecific comparisons revealed nucleotide sequence differences of 3-9 substitutions in the ca. 240 nucleotide rRNA segment examined. Although interspecific differences are not large in terms of percent nucleotide substitution, they are much larger than the observed intraspecific variation and support the morphological interpretation distinguishing three taxa. When the data were analysed using parsimony and bootstrapping, the three taxon tree was well supported. The phylogenetic arrangement of these strains is congruent with secondary metabolite profile similarities.
Base Sequence↗
Osteomyelitis caused by Neosartorya pseudofischeri.
The first case of osteomyelitis caused by Neosartorya pseudofischeri is reported. The patient, a 77-year-old male with a history of silicosis and tuberculosis, on X-ray examination revealed lytic lesions of L2 and L3 vertebrae suspicious for metastatic lesions. Histologic examination of biopsy specimens from vertebral bodies showed short, distorted, extra- and intracellular, hyaline hyphal fragments. The culture from the biopsy tissue produced numerous, evanescent asci containing eight ellipsoidal ascospores with two distinctive equatorial bands ca. 1 micron wide. When examined by a scanning electron microscope, ascospores exhibited a convex surface ornamented with raised flaps of tissue, in shape resembling triangular projections or long ridge lines. The conidial state (anamorph) was identified as Aspergillus thermomutatus on the basis of conidial columns which were smaller and less tightly packed as well as of a lighter shade of green than those observed in Aspergillus fumigatus. On the basis of the morphologic features of the ascospores, the teleomorph was identified as N. pseudofischeri.
Aged↗
Membrane electrical properties associated with insulin receptor downregulation in human erythrocytes.
This study investigated the alterations in the electrical properties of human erythrocytes that occur during the insulin-induced internalization of insulin receptors (downregulation). Using a dielectric relaxation technique based on the Maxwell-Wagner effect, the data indicate a steady decrease over time in membrane conductivity, membrane permittivity, and conductivity of the cytosol in erythrocytes that have been stimulated to undergo downregulation by the addition of insulin. We hypothesize that variations in active transport properties as well as changes in membrane lipids and/or proteins occur during the process of insulin-induced downregulation of insulin receptors.
Cell Membrane↗
Cytoskeletal oxidative changes lead to alterations of specific cell surface receptors.
Electron acceptors in biological systems, termed "oxidants", have been associated with numerous cytopathic conditions. In particular, oxygen-derived free radicals have been shown to induce various subcellular oxidative injuries which can lead to different types of pathologies. It has also been suggested that oxidative stress induced by xenobiotics can determine specific subcellular alterations in in vitro models. An oxidative imbalance in cells seems in fact to affect intracellular functions including the expression of some growth factor surface receptors. In this work, we observed a specific early alteration of the microfilament system and the microtubular network induced in K562 cells by oxidative stress. In particular, we hypothesize that oxidative imbalance could lead to an impairment of the expression of these receptors, such as transferrin receptors, via a modification of the cytoskeleton. This could represent a general mechanism by which a modification of receptor regulation can lead to cell aging, injury or death.
Cell Membrane↗
Human erythrocyte insulin receptor processing is affected by the oxidizing agent menadione.
Insulin-induced down-regulation of erythrocyte insulin receptors is a simplified model that can provide useful information on the cell surface regulative phenomena and on role of the plasma membrane and cytoskeleton in such physiological processes. Oxidative imbalance was examined since it was shown to play an important role in numerous cellular pathologies as well as in cell aging. Specifically, the free radical inducer menadione was used in order to evaluate if this compound is able to modify (and in which manner) the down-regulation process. Biochemical, biophysical, and ultrastructural approaches were used. The results obtained seem to indicate that menadione-induced oxidative damage was able to decrease the insulin-induced down-regulation process, as measured by binding assays. This effect was accompanied by slight alterations in plasma membrane ultrastructure and insignificant variations in plasma membrane lipid composition. In addition, the decrease in membrane order, measured by electron paramagnetic resonance, which was shown to usually occur during the process of down-regulation, was not observed. In contrast, cytoskeletal protein assembly, as previously shown in other in vitro systems, appeared to be remarkably altered. Such changes in specific cytoskeletal elements could lead to the decrease of down-regulation phenomenon induced by menadione. Changes in electrophoretic pattern of some cytoskeletal proteins (e.g., spectrin) reinforce this hypothesis. Considering the importance of free radicals in cell injury, data reported here could represent a specific example of a general mechanism by which cell surface receptor expression and recycling can be modified by changes in some intracellular molecule redox status and cell ionic homeostasis.
Actin Cytoskeleton↗
Changes in erythrocyte membrane lipid composition affect the transient decrease in membrane order which accompanies insulin receptor down-regulation.
We have recently demonstrated, using electron paramagnetic resonance (EPR) spectroscopy, that insulin receptor internalization in response to insulin incubation (down-regulation) in human erythrocytes is accompanied by a transient decrease in membrane order, as measured by the 2T' parallel order parameter. Since membrane lipids play such an important role in receptor internalization, we investigated the possible effects that an alteration of the normally-occurring lipid profile might have on down-regulation and the concomitant transient decrease in membrane order. Consequently, human erythrocytes enriched with cholesterol and erythrocytes from cirrhotic patients were examined, because both of these groups of cells have a higher cholesterol/phospholipid molar ratio (CH/PL) than controls. The 5-nitroxystearate spin label, which inserts into the lipid bilayer of cell membranes, was used to monitor changes in 2T' parallel for a 3-h period at 37 degrees C. We report here that both cholesterol-enriched and cirrhotic erythrocytes do not down-regulate, as demonstrated by binding assays, and that they do not show the typical transient decrease in membrane order observed in controls. The results seem to indicate that a more ordered membrane inhibits internalization of the insulin receptor in erythrocytes, and that an increase in membrane disorder is necessary for insulin receptor down-regulation.
Cholesterol↗
Isolation, preservation, and taxonomy.
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Databases, Bibliographic↗
Effect of intravenous polyunsaturated phosphatidylcholine infusion on insulin receptor processing and lipid composition of erythrocytes in patients with liver cirrhosis.
The aim of this study was to determine whether insulin receptor processing capabilities of human erythrocytes could be improved by changing the cell membrane lipid composition using an intravenous infusion of polyunsaturated phosphatidylcholine. Thirteen cirrhotics were submitted to the i.v. infusion of phosphatidylcholine (2 g day-1 for 3 days). Both erythrocyte lipid composition and insulin receptor processing ability were examined at the beginning of the study and at 0, 3 and 11 days after the end of the treatment. This treatment decreased the erythrocyte cholesterol to phospholipid molar ratio and increased the proportion of polyunsaturated fatty acids (mainly linoleic acid) immediately after the end of the treatment. The proportion of arachidonic acid increased immediately in the phosphatidylserine class and, a few days later, also in phosphatidylethanolamine. The phospholipid class distribution did not show any relevant modification in the course of the study. Surface insulin receptors, which generally were up-regulated in the untreated subject (-7.1 +/- 20.4%), showed an improvement in down regulation capabilities that appeared to be well correlated with the changes in lipid composition of cell membranes induced by i.v. infusion of polyunsaturated phosphatidylcholine. The confirmation of these findings also in target cells for insulin may open new perspectives in the treatment of diabetes mellitus.
Adult↗
Altered insulin receptor processing and membrane lipid composition in erythrocytes of cirrhotic patients.
Insulin binding and insulin receptor down-regulation characteristics were evaluated, as well as cholesterol and phospholipid levels in erythrocytes from 22 patients with liver cirrhosis. These parameters were correlated with clinical characteristics and with scores related to severity of the liver injury. Nine healthy subjects were studied as a control group. It was observed that insulin binding was generally greater in patients than in controls because of an increase in surface insulin receptor numbers, rather than from a change in receptor affinities. In cirrhotic patients, the erythrocyte insulin receptors did not undergo the normal down-regulation process but, in most cases, increased in response to insulin incubation. The alterations in insulin processing characteristics were more frequent in patients with alcoholic cirrhosis and more severe liver impairment and correlated with the changes in the lipid composition of erythrocyte membranes. In particular, an increase in the cholesterol to phospholipid molar ratio and a decrease in polyunsaturated fatty acid content of phospholipids in erythrocyte membranes of cirrhotic patients was associated with impairments in insulin receptor processing. Similar changes in insulin receptor processing were observed when the molar ratio of cholesterol to phospholipid in normal erythrocytes was modified in vitro by incubation with cholesterol-rich liposomes.
Adult↗
Human erythrocyte insulin receptor down-regulation is accompanied by a transient decrease in membrane order.
Insulin receptor internalization in response to insulin incubation (down-regulation) has been shown to occur in human erythrocytes as well as in human erythrocyte ghosts. It is also known that changes in cell membrane events can be detected with electron paramagnetic resonance (EPR) spectroscopy using spin labels. In the present study, changes in erythrocyte membrane order during down regulation as measured by the 2T'II parameter were investigated using EPR. The spin label, 5-nitroxystearate, which inserts into the lipid bilayer of cell membranes, was used. Changes in 2T'II at 37 degrees C were followed over a 3 h time period. A transient decrease in erythrocyte membrane order began within 30 min of the start of insulin incubation and reached a minimum level of 52.5 Gauss (G) within 90 min. This represented nearly a 2 G decrease from the zero incubation time value. Membrane order returned to the initial value by 2.5 h. These time-related changes in membrane order corresponded well with the insulin receptor internalization process as followed by surface binding assays. Surface insulin binding began to decrease within 30 min of the start of insulin incubation, and was reduced to 30% of control values within 2 h. Similar correlations between membrane order and receptor internalization were observed at 23 degrees C. Erythrocytes incubated with denatured insulin, and ATP-depleted erythrocytes incubated with native insulin, did not down-regulate their insulin receptors. Under these conditions, these erythrocytes also did not exhibit the transient decreases in membrane order. These findings are consistent with the hypothesis that an increase in membrane disorder is part of the mechanism of insulin receptor down-regulation.
Adenosine Triphosphate↗
Phylogenetic relationships among species of the genus Issatchenkia Kudriavzev.
The phylogenetic relatedness of Issatchenkia spp. was estimated from partial rRNA sequences in two regions of the large subunit and one region of the small subunit. I. terricola was the most divergent species of the genus, differing from other members by 18% nucleotide differences in the highly variable 25S-635 region. These data indicate Issatchenkia to be the most divergent ascomycetous yeast genus presently known.
Base Sequence↗
Phylogenetic relationships among species of Sterigmatomyces and Fellomyces as determined from partial rRNA sequences.
Sequence comparisons of selected regions from small (18S) and large (25S) subunit rRNAs were used to examine species relationships in the anamorphic yeast genera Sterigmatomyces, Fellomyces, Tsuchiyaea, and Kurtzmanomyces. On the basis of sequence similarity, the genus Sterigmatomyces is comprised of Sterigmatomyces halophilus and Sterigmatomyces elviae, while the genus Fellomyces contains three recognized species, Fellomyces fuzhouensis, Fellomyces penicillatus, and Fellomyces polyborus. Tsuchiyaea wingfieldii and Kurtzmanomyces nectairii are well separated from the other species which we examined. Comparison with selected teleomorphs indicated that the genus Fellomyces is closely related to the genus Sterigmatosporidium, whereas the genus Sterigmatomyces exhibited somewhat closer relatedness with the genus Leucosporidium. Impacting on our estimates of relatedness was the finding that nucleotide substitution in the rRNA regions which we examined seems relatively constant only among closely related species.
Base Sequence↗
Influence of the carbohydrate moiety on the growth inhibitory activity and adhesiveness of 3T3 cell plasma membranes.
Treatment of 3T3 cell plasma membranes with glycosidase enzymes decreased their ability to inhibit cell growth and also decreased their binding to 3T3 cells. This suggests that carbohydrate is required for complete function of inhibitory activity and that inhibition is associated with membrane adhesion.
Acetylglucosaminidase↗
Insulin causes insulin-receptor internalization in human erythrocyte ghosts.
The effect of incubation with insulin on insulin-receptor internalization by erythrocyte ghosts was investigated. The number of surface insulin receptors decreased by 30-40% after incubation of ghosts with insulin. Total insulin-receptor binding to solubilized ghosts was the same in insulin-incubated and control ghosts, whereas insulin binding to an internal vesicular fraction was substantially increased in insulin-incubated ghosts. Our findings suggest that erythrocyte-ghost insulin receptors are internalized to a vesicular compartment in response to incubation with insulin.
Adenosine Triphosphate↗
Insulin stimulates choline acetyltransferase activity in cultured embryonic chicken retina neurons.
The effect of insulin on the appearance of the enzyme choline acetyltransferase (ChoAcT; acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6) in embryonic chicken retina neurons cultured in defined medium was studied. In the presence of a minimal level of insulin (1 ng/ml), ChoAcT activity increased with time in culture. A correspondence between the insulin concentration in the defined medium (1-100 ng/ml) and both the rate of increase and maximum attained level of ChoAcT activity was observed. Maximal ChoAcT activity was 2- to 3-fold greater in cells cultured in the presence of 100 ng of insulin per ml than in cells cultured in the presence of 1 ng of insulin per ml. To elicit maximum ChoAcT activity, insulin at 100 ng/ml was required in the medium for only the first 4 days of the culture period, at which time insulin could be reduced to maintenance levels (10 ng/ml) without affecting ChoAcT activity. Insulin binding assays performed during a 7-day culture period revealed that irrespective of the insulin concentration in the medium during culture, cell-surface insulin receptors decreased by approximately 90% between 4 and 7 days in culture. This decrease in insulin binding corresponded to the observed decrease in the sensitivity of ChoAcT activity to insulin. Our findings suggest that insulin plays a role in mediating cholinergic differentiation in the embryonic chicken retina.
Animals↗
Insulin receptor processing as a function of erythrocyte age. A kinetic model for down-regulation.
The effects of cell aging on insulin binding and on insulin receptor processing in human erythrocytes were studied. Erythrocytes were found to exponentially lose equal proportions of both high and low affinity receptors as a function of age. The affinities of remaining surface receptors did not change significantly. The maximum extent of insulin receptor down-regulation that could be induced decreased linearly with age over the range studied. Together with dose-response and time course studies, these age-related changes in insulin binding and receptor down-regulation were used to develop a kinetic model in which receptor internalization is a function of surface receptor concentration. The ability of the model to predict the behavior of a heterogeneous population suggests that changes in receptor processing with age may be attributed to changes in the surface receptor concentration.
Dose-Response Relationship, Drug↗
Insulin binding and insulin action in cultured fibroblasts: significant differences between a phosphoglucose isomerase-deficient mutant and the parental strain.
The interrelationships of hexose feeding and insulin action were studied in the Chinese hamster fibroblast cell lines 023 and DS-7. The latter, derived from 023 and deficient in phosphoglucose isomerase, has been used to map the metabolic requirements for aldohexose-mediated down-regulation or "curbing" of hexose transport. We have characterized insulin binding and the response to insulin in both cell lines to determine if the insulin-mediated stimulation of transport is similarly dependent on hexose metabolism. DS-7 cells exhibited 5-6 times as many high-affinity insulin binding sites as the parental strain. Apart from this difference, 023 and DS-7 cells showed comparable insulin binding characteristics, which are similar to those observed in other cell types. Insulin at a concentration of 1 microgram/ml (167 nM) was found to stimulate 3-O-methylglucose uptake by approximately equal to 50% in glucose-fed cells of both lines. In neither line did glucose starving significantly alter insulin binding or the insulin-induced stimulation of transport. Feeding with mannose or fructose was found to increase both parameters in 023 cells but had no effect on DS-7 cells. The increase in hexose uptake with the administration of insulin or with glucose starving was shown to be due to an increase in Vmax. Our studies suggest that insulin binding and effect are not regulated by hexose metabolism in the same manner as in the curbing process and insulin induces the recruitment of a transporter pool that is insensitive to hexose curbing.
3-O-Methylglucose↗