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Biomedical subjects

M G Tozzi-Ciancarelli

Publications and source records attributed to M G Tozzi-Ciancarelli.

28 records · Page 2Linked to original sources
PubMed1989

Human erythrocyte damage at the initial stages of oxidative stress.

Specific fluorescent probes have been used to monitor changes in erythrocyte membranes in the first stages of the hemolytic process induced by irradiation with visible light in the presence of protoporphyrin IX. Although no change, or even a slight increase of fluorescence anisotropy, occurred with two probes having a preferential binding to membrane proteins, such as fluorescamine and 3-pyrene maleimide, the fluorescence anisotropy of two lipophilic probes, namely diphenyl-hexatriene and anilino-naphthalene sulfonate, underwent a substantial decrease upon irradiation. Concomitantly, a dramatic decrease of ATPase activity and an increase of thiobarbituric-reacting substances were observed in erythrocyte membranes. Instead, there was no effect on the activities of the intracellular enzymes glucose-6-phosphate dehydrogenase and pyruvate kinase. These findings are consistent with the hypothesis that protoporphyrin-sensitized irradiation induces, primarily in the erythrocyte membrane, the peroxidation of the lipid component, which results in an increase of the fluidity of the bilayer. Hemolysis eventually occurs because of an osmotic imbalance resulting from the combination of increased passive diffusion and decreased active ion transport.

Cytoplasm↗
PubMed1989

In vitro and in vivo effects of erythrocyte phototherapy on newborns.

The photodynamic action of the bilirubin is associated with severe consequences observed during 'in vitro' irradiation of the erythrocytes. This paper is designed to evaluate the bilirubin photodynamic effects which occur 'in vitro' and 'in vivo' on erythrocytes in healthy and jaundiced infants. The in vitro bilirubin sensitized photoreaction damages the erythrocytes mainly at the membrane level. In particular, a dramatic decrease of ATPase activity and an increased susceptibility to lipid peroxidation, expressed as malondialdehyde production, were observed. For in vivo studies, specific fluorescent probes have been used to verify probable changes on the functional architecture of the erythrocyte membrane in the phototherapy-treated infants. Our results showed that specific areas of the membrane are differently affected, mainly at lipid/protein interface. Although the role of the erythrocyte membrane is an important factor of the hemorheological behavior, the measurement of blood viscosity and erythrocyte aggregation and filtration did not show significant alterations during the overall time of phototherapy.

Adenosine Triphosphatases↗
PubMed1989

Fluorescence studies of the aged erythrocyte membranes.

The most important purpose of this research is to characterize by means of fluorescence polarization the structural and functional changes which occur in the membrane of the human erythrocytes during aging process. Our results provide evidence of a significant increase of membrane fluidity in the deep lipid core and in the lipid/protein boundary, in the aged erythrocytes. These features are associated with a rigidity of the membrane surface, as revealed by the anisotropy increase of a specific probe suitable for monitoring the membrane protein behaviour. These modifications could be considered as one of the mechanisms which contribute to alter erythrocyte rheological properties sufficiently to be recognised and removed within circulation.

Erythrocyte Aging↗
PubMed1989

PPIX induced photohemolysis of erythrocytes partially-depleted of cholesterol.

The protoporphyrin IX (PPIX)-sensitized hemolysis of erythrocytes depleted of cholesterol was investigated. From 20% to 30% of the total membrane cholesterol was removed from cells by incubation with old autologous plasma or by means of interaction with L-alpha-phosphatidylcholine dipalmitoyl (DPPC) liposomes. As expected, after this treatment, the cells show an overall increase in membrane fluidity revealed by means of specific fluorescent probes. The same cells are more susceptible to the photohemolysis induced by PPIX excited by visible light, but gave no lysis in the absence of the sensitizer. As a consequence, the primary oxidative damage which is produced during irradiation can be possibly assigned to the phospholipidic and/or proteic moiety instead of the steroidal moiety.

Anilino Naphthalenesulfonates↗
PubMed1988

Controlled human RBC modifications affecting the binding of cationic liposomes.

Cationic liposomes were prepared either by sonication or by detergent dialysis and used to deliver the antioxidative enzyme glutathione peroxidase into human erythrocytes in vitro. The enrichment ability of these two preparations was similar, amounting to about 30% of the control cells. The lysis of enzyme-treated erythrocytes induced by photoirradiation in the presence of PPIX was compared with that of cells incubated with empty liposomes. Erythrocytes enriched with GPX appear to be more resistant toward photohemolysis. Pre-treatment of cells with neuraminidase or proteinase K suggests that: a) sialic acid seems to be essential for the cell-liposome fusion process, no enrichment being found with the neuraminidase-treated cells; b) hydrolysis of the outer membrane proteins leads to an increased fragility with respect to controls even in GPX-enriched cells. These results were confirmed by extrinsic fluorescence polarization experiments, using isolated erythrocyte membranes and specific fluorescent probes.

Endopeptidase K↗
PubMed1985

Photodynamic damage induced by bilirubin on human platelets: possible relevance to newborn pathology.

Several reports have appeared showing the possibility of bilirubin-sensitized photodamage. We have extended these observations to platelets. In the presence of 300 microM bilirubin the in vitro irradiation of isolated platelets or platelet-rich plasmas with visible light induced significant lysis as determined by the release of lactate dehydrogenase (LDH). The extent of LDH release was a function of irradiation time, being about 20% after 2 h of irradiation. A loss membrane-bound ATPase activity was also observed at earlier times, indicating that membrane damage was preliminary to the lytic effect. The release of beta-thromboglobulin, induced by close cell-to-cell contact, was lower in bilirubin- and light-treated platelets with respect to controls. Our results suggest that bilirubin may act as a photodynamic agent producing some damage on human blood platelets.

Adenosine Triphosphatases↗
PubMedDate not supplied

Erythrocyte membrane fluidity in subjects affected with reversible ischemic attacks (RIA).

It is well recognized that in subjects with cerebrovascular disease (CVD), changes in hemorheological properties may occur in about 50% of the patients. This paper concerns a study on microhemorheological perturbations of the erythrocyte membranes in a group of 20 RIA's patients, treated with Pentoxifylline. At the admission of the subjects to the study a trend to an increased whole blood viscosity and erythrocyte aggregation was associated to alterations of membrane fluidity analyzed by means of the fluorescent probes in the patients with respect to the controls. At the end of pharmacological treatment and wash-out, our data indicate a clear modification in erythrocyte membrane which results improved. Our results underline how the improvement of the erythrocyte membrane fluidity, induced by pentoxifylline, is a basic factor of blood flow in the microcirculation.

Erythrocyte Membrane↗
PubMedDate not supplied

In vitro effects of alloplastic biomaterials on the functional features of human erythrocytes and platelets.

In vitro experiments were performed to evaluate the biocompatibility of metallic plates used in reconstructive maxillofacial surgery, analyzing the effect of titanium, nickel-chromium-molybdenum and stainless steel plates on some functional features of human erythrocytes and platelets, being rheological properties and platelet responsiveness pivotal for the perfusion of the tissues surroding the metallic implants. Our data underline that the tested plates are not responsible for significant alterations of the erythrocyte rheological features and of platelet reactivity.

Biocompatible Materials↗