Biomedical subjects

R Fiorini

Publications and source records attributed to R Fiorini.

At least 19 recordsLinked to original sources

PubMed1997

Partition of the organochlorine insecticide lindane into the human sperm surface induces membrane depolarization and Ca2+ influx.

The effects of the insecticide lindane (the gamma-isomer of 1,2,3,4,5,6-hexachlorocyclohexane) on membrane potential, cytosolic free Ca2+ concentration ([Ca2+]i) and surface biophysical properties were studied in human spermatozoa. The insecticide induces rapid, transient and reproducible membrane depolarization and opening of voltage-dependent Ca2+ channels leading to an increase in [Ca2+]i. In contrast with the effect in somatic cells, lindane did not affect gamma-aminobutyric acid receptor-linked Cl- currents. Ca2+ and K+ currents were found to drive lindane-induced membrane depolarization and repolarization respectively, whereas Na+ and Cl- fluxes appear not to have a role in the phenomenon. The insecticide was still able to produce membrane depolarization both in the combined absence of extracellular Ca2+ and Na+ and in high-K+ buffer, suggesting that lindane alters the membrane dipole potential. In agreement with this, Laurodan and Prodan fluorescence spectroscopy revealed that lindane partition into the sperm plasma membrane lowers water molecular dynamics in the uppermost region of the membrane external leaflet, probably as the result of reordering of water dipoles. We propose that the first effect of lindane partitioning into the sperm plasma membrane is a change in the membrane dipole potential, which results in the activation of membrane-located Ca2+-influx pathways.

2-Naphthylamine↗

PubMed1997

Role of guanine nucleotides as endogenous ligands of a kainic acid binding site population in the mammalian cerebellum.

An endogenous inhibitor of the membrane binding of kainic acid was extracted from pig brain tissue and purified. The substance was identified as GMP by structural analysis: Most likely it corresponds to an inhibitor previously extracted from the rat brain. The nucleotide is active as an inhibitor for kainate binding on goldfish brain synaptosomes, probably owing to direct displacement on receptor sites; it is also active on a low-affinity kainate site population in membranes from rat cerebellum. The interaction of GMP with the latter sites leads to a concentration-dependent kainate binding increase or inhibition, thus demonstrating that these sites can bind the nucleotide and cooperatively increase their affinity. Other guanine nucleotides show interaction with these sites, by either an increase (GTP) or inhibition (cyclic GMP or GDP) of kainate binding. These findings support the view that a guanine nucleotide is the endogenous ligand of a receptor in the mammalian cerebellum similar to the kainate binding protein present with high density in the cerebellum of lower vertebrates, whose function is probably connected to the role of the glial cells in this zone.

Animals↗

PubMed1996

Platelet plasma membrane in subjects with primary nocturnal enuresis: effect of desmopressin.

Plasma membrane fluidity of platelets (PLT) obtained from subjects with primary nocturnal enuresis (PNE) and healthy controls was investigated before and after addition of desmopressin (DDAVP). Membrane fluidity was studied by measuring steady-state fluorescence anisotropy of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3, 5-hexatriene incorporated into PLT plasma membrane. Our results show an increase in membrane fluidity at the surface level of PLT from subjects with PNE. Moreover, the addition of DDAVP induces a stable and significant decrease of membrane fluidity in both groups. These results suggest alterations of the lipid order in the exterior part of the PLT plasma membrane from patients with PNE.

Adolescent↗

PubMed1994

Polymorphonuclear leukocyte-generated oxygen metabolites decrease beat frequency of human respiratory cilia.

We investigated the effect of polymorphonuclear leukocyte (PMN)-generated oxygen metabolites on the ciliary beat frequency. PMNs were incubated with human respiratory cilia obtained by nasal brushing. The oxidative metabolism was stimulated by opsonized zymosan, and ciliary beat frequency was evaluated before and after activation of PMNs. Ciliary beat frequency was studied using video microscopy. Our results demonstrate a significant decrease in ciliary beat frequency after activation of PMNs. This effect was reduced by catalase. These data suggest that the PMN-generated oxygen metabolites, particularly H2O2, decrease beat frequency of human respiratory cilia.

Ascorbic Acid↗

PubMed1994

A sensitive detection of neutrophil activation by fluorescence quenching of membrane inserted singlet oxygen probe.

Fluorescence emission intensity of 1,3-diphenylisobenzofuran incorporated in polymorphonuclear granulocytes plasma membranes was investigated in basal conditions and during stimulation with different activators. Phorbol myristate acetate, known as the most effective "oxygen burst" inducer, produced a larger decrease in 1,3-diphenylisobenzofuran fluorescence intensity than 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet activating factor) and N-formyl-methionyl-leucyl-phenylalanine, known as weak stimulants of oxygen uptake. Diphenyl iodonium an inhibitor of leukocyte NADPH oxidase, and the singlet oxygen selective trap alpha-terpinene inhibited the quenching effect of phorbol myristate acetate on 1,3-diphenylisobenzofuran fluorescence. These data suggest formation of singlet oxygen in activated leukocytes and demonstrate that measurement of 1,3-diphenylisobenzofuran fluorescence intensity provides a new sensitive method of detection of neutrophils activation.

Benzofurans↗

PubMed1993

Effect of PAF on human lymphocyte membranes: a fluorescence study.

We have studied the effect of platelet-activating factor (PAF) on the physico-chemical organization of human lymphocyte plasma membranes by measuring the steady-state fluorescence anisotropy and the fluorescence decay of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) incorporated in lymphocyte plasma membranes. PAF induced a time-limited and significant increase of the lipid order in the exterior part of the membrane and a decrease in membrane heterogeneity. These changes were blocked in the presence of PAF antagonist L-659,989. The results indicate that the observed changes in the physico-chemical properties of the lymphocyte plasma membranes may be attributed to a PAF-receptor interaction.

Cell Membrane↗

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

Membrane fluidity of polymorphonuclear leukocytes from children with primary ciliary dyskinesia.

Plasma membrane fluidity and heterogeneity of polymorphonuclear leukocytes (PMN) were investigated in seven children with primary ciliary dyskinesia (PCD) and 17 healthy controls. Membrane fluidity and heterogeneity were studied by measuring the steady state fluorescence anisotropy and fluorescence decay of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) incorporated into PMN plasma membrane. Our results show an increase in membrane fluidity at the surface level of PMN from patients with PCD. Distribution analysis of TMA-DPH lifetime values indicate an increase in membrane heterogeneity in subjects with PCD. The observed changes in the physicochemical properties of the membrane could lead to alterations in the function of PMN from children with PCD.

Chemotaxis, Leukocyte↗

PubMed1993

[Oxidative metabolism in polymorphonuclear granulocytes of children with trisomy 21].

In response to certain stimuli, polymorphonuclear leukocytes (PMNs) undergo an oxidative burst during which a series of reactive oxygen metabolites are generated. The importance of the release of these oxygen metabolites by polymorphonuclear leukocytes, is recognized to be a key event in the function of these cells during infection and inflammation. We have evaluated the release of reactive oxygen species during the activation of respiratory burst (RB) of PMNs obtained from children with trisomy 21 using chemiluminescence techniques. As chemiluminogenic probes we have employed lucigenin and luminon that are know to be sensitive to the superoxide anion and the H2O2-myeloperoxidase-halide system of PMNs, respectively. Activated PMNs from children with trisomy 21 exhibited a low level of superoxide and a reduced activity of H2O2-myeloperoxidase-halide system compared to the control group. No significant difference in extracellular H2O2 release was observed. It seems likely that alterations in the enzymatic activities of the Cu/Zn-Superoxide dismutase and myeloperoxidase induce imbalance in the release of reactive oxygen species in activated PMNs from children with trisomy 21. This imbalance could be on the basis of the increased oxidative injury reported in trisomy 21.

Child↗

PubMed1992

Diabetes mellitus induces red blood cell plasma membrane alterations possibly affecting the aging process.

Various alterations of red blood cell (RBC) plasma membrane appear both in diabetes mellitus and during the physiological aging process. Diabetes mellitus decreases RBC life-span; therefore, it may change the plasma membrane by acting through its effect on the aging process. In order to clarify the issue, RBCs from normal subjects and insulin-dependent diabetic patients were fractionated in five subpopulations of different mean age (fraction 1: early young RBC, fraction 5: mature RBC). Thereafter, plasma membranes were prepared and enzymatic activities, membrane fluidity and lipid peroxidation were evaluated. NA+, K(+)-ATPase activity decreased during aging and it was higher in all RBC subpopulations from normal subjects in comparison to diabetic patients. Next, lipid peroxidation and fluidity increased during aging in both the study groups; in this case, however, in all subpopulations, except for that from fraction 1, RBCs from diabetic patients showed higher membrane fluidity and lipid peroxidation in comparison to normal subjects. Data herein reported suggest that diabetes mellitus affects the plasma membrane independently of (lipid peroxidation and fluidity) or dependently on (Na+, K(+)-ATPase) its effect on aging. In the case of lipid peroxidation and fluidity diabetes mellitus seems to affect the membrane by decreasing RBC life span, whereas in the case of Na+K(+)-ATPase it seems to alter this enzymatic activity which in turn might affect RBC aging. Acetylcholinesterase activity decreased during aging in RBCs from normal subjects, but it increased in RBCs from diabetic patients; RBC subpopulation from fraction 1, on the other hand, showed similar values in normal subjects and diabetic patients. In this case the effect of diabetes mellitus appears only during aging.

Acetylcholinesterase↗

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↗

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

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↗

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

Steady state fluorescence polarization and Fourier transform infrared spectroscopy studies on membranes of functionally senescent human erythrocytes.

Human erythrocytes were separated using Percoll/Albumin density gradient centrifugation into 5 subpopulations which represent cell subpopulations of different ages. The physico-chemical properties of the membranes and their lipid extracts, prepared from the 5 subpopulations, were studied by 1,6-diphenyl-1,3,5-hexatriene fluorescence polarization and by Fourier Transform Infrared Spectroscopy respectively. The fluorescence polarization data show a decrease of membrane fluidity in the youngest erythrocyte fraction and the infrared spectroscopy reveals a lower degree of unsaturation of the lipids from this fraction. Changes of membrane fluidity among the 5 erythrocyte subpopulations is assigned to the variations of the degree of unsaturations of lipids rather than to variations of cholesterol content.

Adult↗

PubMed1989

Effect of cholesterol on membrane microheterogeneity: a study using 1,6-diphenyl-1,3,5-hexatriene fluorescence lifetime distributions.

The effect of cholesterol on microheterogeneity of liposomes obtained from saturated and unsaturated phospholipids was studied by measuring the fluorescence decay of 1,6-diphenyl-1,3,5-hexatriene (DPH). Data obtained by frequency domain fluorometry have been analyzed either by discrete exponential or continuous lifetime distribution approaches. In egg phosphatidylcholine liposomes, the addition of cholesterol increases the lifetime value or the centre of the lifetime distribution. At high cholesterol concentration, good fits are obtained using a monomodal distribution analysis or single exponential component. At low cholesterol concentration an additional short component of low fractional intensity must be included to obtain a good fit. In dipalmitoylphosphatidylcholine, the addition of cholesterol decreases the long lifetime component centre value both in the gel and in the liquid-crystalline state. The DPH lifetime value is sensitive to the dielectric constant of the probe microenvironment, and cholesterol has been shown to modify water penetration in the bilayer. Using this information our data indicate that cholesterol affects the polarity of the microenvironment in liposomes of unsaturated phosphatidylcholine and saturated phosphatidylcholine in different ways. Although the major conclusions of this paper are obtained using changes of the distribution centre upon cholesterol addition, there are also preliminary indications that the lifetime distribution width decreases as cholesterol is added. We have interpreted this observation as being due to the homogenizing effect of cholesterol.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1989

Modifications of erythrocyte membrane fluidity of in vivo functionally aged human erythrocytes.

The process of red blood cell senescence in the blood stream results in many changes in their physical and biochemical properties. In this work we have studied the physico-chemical state of erythrocyte membranes prepared from 5 subpopulations of erythrocytes of different age by using the fluorescence technique. Membrane fluidity has been evaluated by the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and a further study of the fluorescence decay of this probe has been performed by multifrequency phase and modulation fluorometry. DPH fluorescence polarization is significantly increased in the membranes prepared from the youngest fraction of erythrocytes, indicating a decreased fluidity without any significant change in DPH fluorescence decay.

Erythrocyte Aging↗

PubMed1988

Increased membrane heterogeneity in stimulated human granulocytes.

TMA-DPH fluorescence decay in human PMN before and after stimulation with FMLP was studied using frequency domain fluorometry. Membrane heterogeneity was assessed by the width of the continuous distributions of lifetime values of Lorentzian shape used to describe the fluorescence decay. In non-stimulated granulocytes TMA-DPH fluorescence decay is characterized by two distributions of lifetime values centered at 6.5 and 1.0 ns and full width at half maximum of 0.3 and 1.2 ns, respectively. Within 15 min after stimulation, the center values of the two distribution components were 5.1 and 0.8 ns and the distribution width was 0.8 and 0.6 ns, respectively. These results indicate changes of membrane domain organization which can be ascribed to compositional changes and redistribution of membrane components.

Cell Membrane↗