117,321 research outputs found
The effect of acute glutathione treatment on sorbitol level in erythrocytes from diabetic patients
No full textThis study evaluated the effect of acute intravenous glutathione (GSH) infusion on red blood cell (RBC) sorbitol levels in 21 diabetic subjects and 6 normal controls of similar age and body mass index (Kg/m2). All patients received 1,200 mg of GSH in 500 ml of isotonic saline solution during one-hour intravenous administration. At the end of acute infusion of GSH, sorbitol concentration decreased from 20.90 ± 1.16 to 16.24 ± 0.81 nmol/g Hb (p < 0.001) in RBCs of diabetic subjects. No significant changes were observed in controls. These data support the hypothesis that GSH depletion, by reducing glycolytic flux to pyruvate, may enhance the rate of glucose metabolism through the polyol pathway and worsen the metabolic imbalance of diabetic tissues. The administration of exogenous GSH could interrupt this vicious circle
Helix-Specific Interactions Induce Condensation of Guanosine Four-Stranded Helices in Concentrated Salt Solutions
No full textAbstractDeoxyguanosine-5′-monophosphate in water self-associates into stable structures, which include liquid-crystalline hexagonal and cholesteric phases. The structural unit is a four-stranded helix, composed of stacked Hoogsteen-bonded guanosine quartets. By using the osmotic stress method, we recently measured the force between helices in KCl solutions up to 2M. In addition to the long-range electrostatic force, a short-range hydration repulsive contribution was recognized. The hydration repulsion is exponential, and shows a decay length independent from the ionic strength of the solution. Here, we report that more concentrated KCl solutions cause condensation of the guanosine helix in a hexagonal phase with constant equilibrium separation of ∼7Å between helix surfaces. Long-range attraction, which induces the self-assembly, and short-range repulsion, which prevents the contact between the helices, are implied. By using osmotic stress, the force needed to push helices closer from the spontaneously assumed position has been measured. The attractive force was then estimated as a difference between the net force and the repulsive contribution, revealing an exponential decay length about two times larger than that of the short-range repulsion. The agreement with the helix interaction theory introduced recently by Kornyshev and Leikin (Kornyshev, A. A., and S. Leikin, 1997. Theory of interaction between helical molecules. J. Phys. Chem. 107:3656–3674) suggests that the repulsive and attractive forces originate from helix-specific interactions
Relationship between glutathione and sorbitol in erythrocytes from diabetic patients.
No full textRed blood cell (RBC) concentrations of sorbitol and reduced glutathione (GSH) were evaluated in 29 type II diabetic subjects and eight normal controls. In erythrocytes from diabetic subjects, sorbitol levels were higher (18.7 ± 1.33 v 11.2 ± 0.7 nmol/g hemoglobin [Hb], P < .001) and GSH levels were lower (5.48 ± 0.19 v 8.33 ± 0.24 μmol/g Hb, P < .01) than in nondiabetics. RBC sorbitol levels were positively correlated with fasting blood glucose (r = .57, P < .001) but not with HbA(1c) (r = .16, P = NS). RBC GSH levels showed a negative correlation with fasting blood glucose (r = - .35, P < .05) and with HbA(1c) (r = -.34, P < .05) and a significant negative correlation with RBC sorbitol levels (r = -.62, P < .001). Stepwise regression analysis highlighted the fact that the hyperglycemia-dependent increase in RBC sorbitol was significantly influenced by GSH concentrations (partial F = 14.6, P < .001). These data suggest the hypothesis that the hyperglycemia-induced enhanced activity of the polyol pathway leads to GSH depletion and, in turn, GSH depletion, reducing the glycolytic flux to pyruvate, enhances the rate of glucose metabolism through the polyol pathway. The overall effect is a progressive worsening of metabolic pseudohypoxia and depletion of GSH, resulting in lower defense against oxidative stress
Reply to “Comment on ‘Optical determination of flexoelectric coefficients and surface polarization in a hybrid aligned nematic cell’ ”
No full textA. Mazzulla, F. Ciuchi, and J. Roy Sambles, Physical Review E, Vol. 68, article 023702 (2003). "Copyright © 2003 by the American Physical Society."In their Comment [G. Barbero and L. R. Evangelista, Phys. Rev. E 68, 023701] on our paper [A. Mazzulla, F. Ciuchi, and J. R. Sambles, Phys. Rev. E 64, 021708 (2001)], Barbero and Evangelista conclude that the procedure followed by us to fit the reflectivity data from the half leaky guided mode technique is questionable. In the absence of a model that is able to reproduce the experimentally obtained tilt angle profiles, their argument is unsubstantiated. To further refute their arguments, we also illustrate and discuss additional experimental data (that were not shown in our paper) that strongly support our conclusions
Magnetic and dielectric properties of cobalt ferrite/titania composites
No full textIn order to develop materials with both magnetic and dielectric properties, recently a lot of researchers concentrate their work to process and study composite ceramics with both magnetic and dielectric phases. Cobalt ferrite Co Fe2O4 and TiO2 are good candidates for this type of composites as they have good magnetic and dielectric properties respectively.
New cobalt ferrite/titania (CFO/TO) ceramics composites were prepared by conventional solid state reaction with a CFO/TO ratio ranging from 2 to 8. Composition, crystalline structure and microstructure of the sintered ceramic composite bodies were investigated and the phases content volume percentage were determined. Dielectric permittivity ( real part of permittivity and dielectric losses) and magnetic permeability (real part of permeability and magnetic losses) were measured at room temperature in a range of frequency from 100 Mhz-1 GHz. Dielectric and magnetic properties were analyzed as function of the microscopic structure (SEM analysis) and phase compositions (XRD analysis). The formation of the ternary compound (FCTO) was found in composites with the TO/CFO bigger than 3
Polaronic and nonadiabatic phase diagram from anomalous isotope effects
No full textIsotope effects (IEs) are powerful tools to probe directly the dependence of many physical properties on lattice dynamics. In this Letter we investigate the onset of anomalous IEs in the spinless Holstein model by employing the dynamical mean field theory. We show that the isotope coefficients of the electron effective mass and of the dressed phonon frequency are sizable also far away from the polaronic crossover and mark the importance of nonadiabatic lattice fluctuations. We draw a nonadiabatic phase diagram in which we identify a novel crossover, not related to polaronic features, where the IEs attain their largest anomalies
Reply to “Comment on ‘Optical determination of flexoelectric coefficients and surface polarization in a hybrid aligned nematic cell’ ”
No full textIn their Comment [G. Barbero and L. R. Evangelista, Phys. Rev. E 68, 023701] on our paper [A. Mazzulla, F. Ciuchi, and J. R. Sambles, Phys. Rev. E 64, 021708 (2001)], Barbero and Evangelista conclude that the procedure followed by us to fit the reflectivity data from the half leaky guided mode technique is questionable. In the absence of a model that is able to reproduce the experimentally obtained tilt angle profiles, their argument is unsubstantiated. To further refute their arguments, we also illustrate and discuss additional experimental data (that were not shown in our paper) that strongly support our conclusions
Progressive deterioration of beta-cell function in non-obese type 2 diabetic subjects. Post-prandial level of plasma C-peptide is an indication of insulin dependency.
No full textThe purpose of the present study was to characterize secondary failure (SF) to oral hypoglycaemic agents by assessment of threshold insulin-secretion values in relation to diabetes duration. One hundred and forty-seven nonobese diabetic patients, 35 to 80 years of age, with disease duration ranging from 1 to 36 years, were studied. Beta-cell function was assessed by meal-stimulated (ΔCP) and glucagon-stimulated (ΔaCP) C-peptide concentrations. The quality of glycaemic control was considered good if mean daily blood glucose was less than 8.5 mmol/l. One group with good (NOb-GC) and another with poor control (NOb-SF) were established. Mean daily glycaemia was negatively correlated with ΔCP or ΔaCP (r = -0.703 vs r = -0.696; p <0.001) more than with basal C-peptide (r = -0.453; p<0.001). A close positive correlation between meal-stimulated (ΔCP) and glucagon-stimulated (ΔaCP) C-peptide concentrations was observed {r = 0.869; p<0.001). Residual beta-cell function (ΔCP and ΔaCP) was significantly correlated with known disease duration in both groups (GC : r = -0.693 and SF: r = -0.680 ; p < 0.001). Nonobese patients with SF showed early impaired secretion during the first years of disease, meal-stimulated ΔCP being below 0.350 mmol/l. The most useful result in this study was the incremental value of C-peptide (ΔCP), which showed minimal overlapping between the two groups. Basal, postprandial or postglucagon absolute values were less discriminating. The daily profile allowed measurement of both glycaemic control and insulin production after a regular meal. The validity of this measurement was confirmed by the strong correlation between meal-stimulated and glucagon-stimulated ΔC-peptide concentrations. This parameter is a useful physiological marker of secondary failure
Is type 2 diabetes mellitus a different disease in non-obese and obese patients?
No full textThe main purpose of this work was to study the possible differences in insulin secretion in a large group of type 2 diabetic patients in relation to diabetes duration, obesity, and the presence of secondary failure after treatment with oral hypoglycemic agents. RESEARCH DESIGN AND METHODS - There were 147 nonobese and 215 obese type 2 diabetic subjects, aged 35-80 years, investigated in a cross-sectional descriptive study. Subjects were grouped according to whether glycemic control was good (mean blood glucose <8.5 mmol/l) or poor. β-Cell function was assessed by measuring meal-stimulated insulin and C-peptide concentrations, as the mean of the three postprandial increments above the premeal value. RESULTS - Basal C-peptide concentrations were significantly higher in obese than nonobese patients of both groups. The mean of meal-stimulated C-peptide concentrations was also significantly higher in obese than nonobese patients with good glycemic control, but not in the secondary failure groups. In nonobese and obese patients considered separately, a significant negative correlation between the mean of daily blood glucose and meal-stimulated C-peptide was observed (r = -0.705 and r= -0.679, respectively, P < 0.001) and the residual β-cell function was significantly correlated with the known duration of diabetes and metabolic control, but not with BMI, in both groups. CONCLUSIONS - On average, obese diabetic subjects showed higher meal-stimulated C- peptide than nonobese subjects only in well-controlled groups. In both obese and nonobese patients, an inverse association between meal-stimulated insulin secretion and duration of diabetes was observed. In obese patients, as in nonobese patients, the lower β-cell function seems likely to be the major pathogenetic factor in the appearance of secondary failure, while being overweight plays only a minor role, thus showing that type 2 diabetes is the same disease in obese and nonobese patients
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