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Biomedical subjects

G Curatola

Publications and source records attributed to G Curatola.

At least 55 records · Page 3Linked to original sources
PubMed1993

Use of Laurdan fluorescence in studying plasma membrane organization of polymorphonuclear leukocytes during the respiratory burst.

The changes in plasma membrane polarity of polymorphonuclear leukocytes (PMN) during the activation of the respiratory burst were investigated by measuring the steady-state fluorescence emission spectra of 2-dimethylamino(6-lauroyl) naphthalene (Laurdan), which is known to be incorporated at the hydrophobic-hydrophilic interface of the bilayer, displaying spectral sensitivity to the polarity of its surroundings. Laurdan shows a marked steady-state emission blue shift in nonpolar solvents, with respect to polar solvents. Our results show a blue shift of the fluorescence emission spectra of Laurdan during activation of PMN with phorbol myristate acetate or N-formyl-methionyl-leucyl-phenylalanine. These results suggest that the activation of the respiratory burst of PMN is accompanied by a decrease in polarity in the hydrophobic-hydrophilic interface of the plasma membrane.

2-Naphthylamine↗
PubMed1993

Parathyroidectomy and blood pressure in hemodialysis patients.

To assess whether parathyroidectomy (PTx) affects blood pressure (BP) in hemodialysis (HD) patients, we studied 11 uremics on HD treatment for 8.2 +/- 0.9 years who underwent successful PTx. As the control group, we selected 11 HD patients not submitted to PTx, matched with the study group for sex, age, years on HD, dialysis procedure and BP values. In the controls, BP and body weight did not change during the 2 years of observation. In the patients, BP remained stable in the year before PTx. PTx caused a progressive reduction in BP in 7 of the 11 patients. The fall was significant from the 3rd quarter onward (mean BP values before PTx: 139/82 mm Hg, 1 year after PTx: 122/75 mm Hg). The magnitude of the hypotensive effect of PTx was related to the pre-PTx systolic BP value (r = -0.70, p = 0.016). PTx also caused a significant progressive increase in body weight (1.56 +/- 0.57 kg 1 year after PTx). In conclusion, PTx causes BP fall in HD patients regardless of whether their preintervention values are normal or increased. The BP reduction occurs in concomitance with a consistent increase in body weight. BP variations are clinically relevant and may be related to the post-PTx calcium efflux from the vessel wall.

Alkaline Phosphatase↗
PubMed1993

Changes of plasma lipids and erythrocyte membrane fluidity in psoriatic children.

Psoriasis has been associated with an abnormal plasma lipid metabolism, and changes of erythrocyte membrane lipid composition and fluidity have been shown in adult patients. To investigate whether the alterations of plasma lipids appear also in pediatric patients, we have studied plasma lipids and lipoproteins in 15 prepubertal children affected by mild-to-moderate psoriasis with respect to healthy controls. The patients showed higher levels of plasma total cholesterol (4.44 +/- 0.78 versus 4.03 +/- 0.58 mmol/L), a significant increase of cholesterol associated with HDL (1.39 +/- 0.26 versus 1.13 +/- 0.28 mmol/L, p = 0.02), and a significant decrease of the ratio LDL cholesterol to HDL cholesterol (1.73 +/- 0.6 versus 2.46 +/- 0.8, p = 0.02). By using fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, we have shown a significant increase in fluidity in erythrocyte membrane of psoriatic children that was associated with a slight, but not significant, decrease in the cholesterol to protein ratio (422 +/- 127 versus 503 +/- 117 nmol/mg). No significant changes of phospholipid fatty acid composition have been shown, in disagreement with previous studies in adult patients. Our results support the relation between childhood psoriasis and plasma lipid changes, which are likely related to the slight compositional changes in erythrocytes. However, the observed abnormalities are expressed differently in children than in adults.

Apolipoproteins↗
PubMed1993

Physico-chemical properties of copper-oxidized high density lipoprotein: a fluorescence study.

The modifications of the physico-chemical properties of the high density lipoprotein (HDL) before and after in vitro induced oxidation by copper ions have been studied using the fluorescence polarization (Pf) of the phosphatidylcholine derivative of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) and of the cationic derivative (TMA-DPH). We have observed that HDL oxidation is associated with a decrease of the molecular order at the lipoprotein surface as demonstrated by the increase in Pf with respect to untreated HDL. Moreover in oxidized HDL the polarity-sensitive probe laurdan has shown a decrease of the polarity in its microenvironment. It has been suggested that a decrease in HDL fluidity would inhibit cholesterol reverse transport from peripheral tissues in form of HDL core cholesteryl esters. Peroxidation of HDL, if occurring in vivo, could contribute to the progress of atherogenesis by decreasing cholesterol efflux from peripheral tissues.

Copper↗
PubMed1992

Alterations in erythrocyte membrane fluidity in children with trisomy 21: a fluorescence study.

Membrane fluidity of erythrocytes obtained from 15 children with trisomy 21 and 20 healthy controls were studied by measuring steady-state fluorescence anisotropy and fluorescence lifetime of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) incorporated in hemoglobin-free erythrocyte membranes. Our results demonstrate a significant decrease in DPH fluorescence anisotropy and a significant increase in TMA-DPH fluorescence anistropy in erythrocytes from subjects with trisomy 21. No significant differences between the two groups were observed in the fluorescence lifetime of DPH and TMA-DPH. These data suggest an increase in membrane fluidity in the interior part of the membrane and a decrease in fluidity at the lipid-water interface region. This could be in part attributed to an increased oxidative damage in trisomy 21.

Adolescent↗
PubMed1992

Lower susceptibility of low density lipoprotein to in vitro oxidation in diabetic patients.

The susceptibility to peroxidative stress of low density lipoprotein (LDL), induced by incubation with CuSO4, has been studied in eleven diabetic patients and eleven control subjects. Our results suggest that oxidized LDL (OX-LDL) of diabetic patients have a significant higher reactivity to 2,4,6-trinitrobenzene sulfonic acid (TNBS) than controls, that indicates a lower susceptibility of LDL to oxidative stress. Furthermore using the fluorescence polarization (Pf) of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its phosphatidylcholine derivative (DPH-PC) we have shown that peroxidation induces a decrease of fluidity in OX-LDL of controls and diabetic patients, both at the lipoprotein surface, where is localized DPH-PC and at the interface between lipoprotein surface and core which is probed by DPH.

Adult↗
PubMed1992

Interaction of a phosphatidylcholine derivative of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) with lymphocytes.

In this study we have demonstrated a transfer of a phosphatidylcholine derivative of 1,6-diphenyl-1,3,5-hexatriene (DPH-PC) from self-quenched lipid vesicles to intact lymphocytes. Membrane labeling was followed measuring the time dependent reexpression of fluorescence. The results of fluorescence quenching by 2,4,6-trinitrobenzene sulfonate and the decrease of fluorescence polarization values during incubation at 37 degrees C, suggest that the probe could remain localized at level of the plasma membrane until 20-30 minutes. DPH-PC is identical to the natural phospholipid with respect to head group structure and polarity therefore we suggest that under appropriate experimental conditions, it could represent an useful tool to study the physico-chemical properties of specific phospholipid domains in the plasma membrane of intact cells.

Animals↗
PubMed1991

Effect of PAF on erythrocyte membrane heterogeneity: a fluorescence study.

The effect of platelet activating factor, PAF, on the erythrocyte membrane heterogeneity was investigated by measuring the steady-state fluorescence anisotropy and fluorescence decay of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) incorporated in hemoglobin-free erythrocyte membranes. PAF induced a significant increase of the lipid order in the exterior part of the membrane and a decrease in membrane heterogeneity. These results indicate that PAF may cause changes in the physico-chemical structure of the erythrocyte membrane.

Diphenylhexatriene↗
PubMed1991

Evaluation of antiepileptic drug effect on membrane fluidity.

Many drugs and chemicals have been shown to induce modifications of the physicochemical properties of cellular membranes. In this study we investigated the changes in fluidity of erythrocyte membrane from epileptic patients under different pharmacological treatments, with respect to healthy controls, by using trimethylammonium-1,6-diphenyl-1,3,5-hexatriene (TMA-DPH) fluorescence polarization. The increase in TMA-DPH fluorescence polarization values observed in epileptic patients indicated a decrease in membrane fluidity. Since the analysis of erythrocyte membrane composition did not reveal significant differences between the two groups studied, a correlation with membrane lipoperoxide content was tried, as different drugs and chemicals elicit in vivo alterations resulting in peroxidation of membrane lipids. Therefore the presence of peroxidation products in the blood and the possible correlation with membrane lipoperoxide were studied. Although a direct causal linkage cannot be proved we can hypothesize that exogenous compounds such as antiepileptic drugs could modify membrane fluidity by increasing membrane lipid peroxidation. Moreover the increase of peroxidative products in the blood could indicate that the peroxidative damage might propagate through the formation of new free radical species. The possibility of using erythrocyte membrane as a model system to analyze antiepileptic drug side effects is advanced.

Adolescent↗
PubMed1991

Erythrocyte membrane fluidity and changes in plasma lipid composition: a possible relationship in childhood obesity.

We have studied plasma lipid patterns and erythrocyte membrane fluidity in 60 obese children and 20 normal children. Plasma levels of total cholesterol and associated low-density lipoproteins were significantly increased in 20 obese patients with respect to controls. A significant decrease in membrane fluidity, measured as an increase in the fluorescence polarization value of the probe 1,6-diphenyl-1,3,5-hexatriene, associated with an increase in the cholesterol/protein ratio has been shown in obese patients. The study of the correlation between erythrocyte membrane fluidity and plasma cholesterol has indicated that significant changes in fluidity and membrane lipid composition also occur in erythrocytes of obese patients with normal plasma lipid levels. These findings confirm that the erythrocyte membrane responds very early to modifications of plasma lipoproteins and suggest that in childhood obesity a modified transfer of cholesterol from plasma to erythrocyte membrane may take place.

Adolescent↗
PubMed1991

Alterations in membrane fluidity of diabetic polymorphonuclear leukocytes.

Plasma membrane fluidity of polymorphonuclear leukocytes was investigated in 28 patients with insulin dependent diabetes mellitus and 30 healthy controls. Membrane fluidity was measured by steady-state fluorescence anisotropy of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) incorporated into the plasma membrane. The fluorescence anisotropy values in resting (unstimulated) polymorphonuclear leukocytes from diabetic subjects were significantly higher than those of controls (0.318 +/- 0.003 vs 0.287 +/- 0.003, P less than 0.001). The addition of the respiratory burst stimulus phorbol myristate acetate induced a stable increase in fluorescence anisotropy values in both groups. Fluorescence anisotropy values of stimulated polymorphonuclear leukocytes from the diabetic and control groups were not significantly different (P greater than 0.05). These data demonstrate a decrease in plasma membrane fluidity of resting polymorphonuclear leukocytes obtained from diabetic subjects. This finding could be in part explained by an increase in their basal respiratory burst activity.

Child↗
PubMed1991

Mechanism of hypercalciuria in essential hypertension and in primary nephrolithiasis.

We have studied the metabolic response to changes in calcium in 15 hypercalciuric essential hypertensives, in 8 normotensive hypercalciuric stone formers and in 11 normotensive healthy subjects matched for age and sex. At variance with hypercalciuric stone formers, at low calcium intake hypercalciuric hypertensives did not appropriately reduce urinary calcium excretion and developed mild hypocalcemia. Furthermore, the PTH response to calcium deprivation was not appropriately enhanced in these patients. The data indicate that different mechanisms prevail in these two forms of hypercalciuria: the renal in essential hypertension and the intestinal in urolithiasis.

Adult↗
PubMed1990

Changes of fluorescence anisotropy in plasma membrane of human polymorphonuclear leukocytes during the respiratory burst phenomenon.

Steady state fluorescence anisotropy (rs) of TMA-DPH was measured to study the effect of respiratory burst activation with PMA, FMLP, and PAF on the physico-chemical structure of PMNs plasma membrane. Our results show a significant increase in rs during the respiratory burst activation. In the presence of NADPH-oxidase inhibitor DPI, only PAF induces changes in rs values. This suggests a non-specific effect of PAF on plasma membrane. Azide, which induces a supranormal release of H2O2, fails to increase the basal rs value after activation. Moreover, the catalase does not abolish the increase in rs induced upon activation. This rules out the possibility that changes of rs during the respiratory burst activation are attributed mainly to H2O2 release. We conclude that multiple processes accompanying the respiratory burst activation are responsible for the changes in the physico-chemical properties of PMNs plasma membrane.

Adult↗
PubMed1990

Interaction of the herbicide atrazine with model membranes. I: Physico-chemical studies on dipalmitoyl phosphatidylcholine liposomes.

Atrazine (2-chloro-4 ethylamino-6-(isopropylamino)-s-triazine) is one of the most widely used herbicides. Fourier transform infrared spectroscopy, differential scanning calorimetry and fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and of its derivative 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) were used to study the interaction of atrazine with dipalmitoyl phosphatidylcholine liposomes used as a model for biological membranes. The results show that atrazine does not perturb the hydrophobic core of the lipid bilayer and suggest that the herbicide localizes near the glycerol backbone of the lipid.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Interaction of the herbicide atrazine with model membranes. II: Effect of atrazine on fusion of phospholipid vesicles.

The effect of atrazine on Ca2+ induced fusion of cardiolipin(CL) and phosphatidylserine (PS) vesicles is studied by Tb3+/dipicolinic acid fluorescence and turbidity measurements. The interaction of herbicide with CL and PS membranes is studied by DPH fluorescence polarization. At low concentrations the pesticide partially inhibits fusion, especially in CL vesicles. Higher concentrations of atrazine decrease inhibition of fusion in CL, while fusion is slightly increased in PS. The Ca2(+)-induced increase of turbidity is not affected by atrazine in both PS and CL aggregation experiments. DPH polarization measurements show a perturbation only of the membrane hydrophobic core of PS, in presence of Ca2+. It is hypothesized that this biphasic effect shown by low and high atrazine concentrations on Ca2(+)-induced fusion of vesicles is due to a different localization of the pesticide in the membrane.

Atrazine↗
PubMed1990

Phosphatidic acid affects structural organization of phosphatidylcholine liposomes. A study of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) fluorescence decay using distributional analysis.

The fluorescence decay of 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) was used to study micro-heterogeneity of 1,2-dimyristoyl-3-sn-phosphatidylcholine (DMPC) liposomes and to characterize the effect of phosphatidic acid on the correlation between fluorescence microheterogeneity and membrane permeability. The fluorescence decay, measured using multifrequency phase fluorometry, has been analyzed either by using a model of discrete exponential components or a model of continuous distribution of lifetime values. Both analyses have shown that TMA-DPH decay is characterized by two components: a long one of about 9 ns and a short one of about 5 ns. In the gel phase, at variance with previous DPH studies, the short component was associated with a large fractional intensity. The distributional analysis showed changes of lifetime values and width in correspondence to the calorimetric transitions. The presence of egg phosphatidic acid increased both long lifetime values and distributional width. The use of TMA-DPH as a probe to evaluate membrane heterogeneity using the distributional width is discussed. The effect of phosphatidic acid on the membrane surface and in the hydrophobic core has been related to its structural properties and to its role in water penetration.

Calorimetry↗
PubMed1990

Effects of intramembrane particle aggregation on erythrocyte membrane fluidity: an electron spin resonance study in normal and in dystrophic subjects.

Mobilization and aggregation of intramembrane particles (IMPs) are physiological events observed in various cells. In erythrocyte membranes, aggregation of IMPs can be induced by the exposure of partially desprectrinized erythrocyte membranes to acidic pH. We investigated the association between IMPs aggregation, protein mobility, and membrane fluidity in erythrocyte membranes of healthy controls and Duchenne muscular dystrophy (DMD) patients by using electron spin resonance and specific spin labels for membrane proteins and lipids. In erythrocyte membranes of control subjects, the partial spectrin removal induced a decreased segmental motion of protein spin label indicating an increase of protein-protein interactions. Stearic acid spin labels 5- and 16-(N-oxyl-4,4'-dimethyloxazolidine) showed that the treatment induces an increase of membrane fluidity. In DMD patients, both treated and untreated erythrocyte membranes showed changes of membrane fluidity when compared to those of the controls. Our results suggest that defects in the interactions between skeletal proteins and/or between membrane and skeleton components may contribute to the alterations of erythrocyte membranes in DMD.

Electron Spin Resonance Spectroscopy↗