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Biomedical subjects

L Sportelli

Publications and source records attributed to L Sportelli.

34 records · Page 2Linked to original sources
PubMed1987

Effect of gamma irradiation on membranes of normal and pathological erythrocytes (beta-thalassemia).

The influence of ionizing radiation on the membrane of human normal erythrocytes has extensively been studied and a variety of effects including changes in the cation fluxes [3, 9] or in non-electrolytes permeability [5, 6, 11], in membrane fluidity, in peroxidation of unsaturated lipids as well as chemical composition or structural modifications [4, 7, 8] has been observed. However, only few studies deal with the effects of ionizing radiation on pathological red blood cells. In this work, we have investigated by means of electron spin resonance (ESR) spectroscopy the effects of 60Co gamma-radiation on the normal and homozygous beta-thalassemic human erythrocyte membranes [12, 13].

Cell Membrane Permeability↗
PubMed1987

Alteration of membrane conductivity and fluidity in human erythrocyte membranes and erythrocyte ghosts following gamma-irradiation.

Alterations of electrical properties of human erythrocyte membranes induced by gamma irradiation have been studied by means of conductivity measurements in the frequency range from 10 KHz to 100 MHz. The results clearly demonstrate the role played by haemoglobin in the structural modification of the membrane produced by gamma irradiation. Further support for this point of view has been derived from electron spin resonance measurements carried out on the same samples, labelled with different spin labels which probe the outer half layer of membrane at different penetration levels.

Cobalt Radioisotopes↗
PubMed1980

Effects of pulsed electric fields on rat liver homogenate paramagnetic species.

Rat liver homogenate has been submitted to pulsed electric fields at different intensities and exposition times. Among the paramagnetic species present in the samples only the mitochondria free radical is affected by pulsation, as revealed by electron spin resonance spectroscopy. In parallel a variation in the respiratory activity of mitochondria is registered.

Animals↗
PubMed1979

1H NMR study on the interaction of cupric ion with ribonuclease A.

The reassignment of the 1H NMR C-2 histidine signals of the bovine pancreatic ribonuclease A has required a revision of the 1H NMR data on the role of the different histidines in their interaction with the Cu2+. The results of our measurements carried out at p2H 5.5 and 7.0 reduce the importance of His-12 as main site of interaction. At p2H 5.5 a very strong binding site involves His-119, while a weaker one contains certainly His-105. On the contrary, at p2H 7.0 the histidines 105 and 119 seem to possess binding constants of the same order of magnitude and in addition they provide stronger ligands for the Cu2+ than His-12. The comparison with X-ray data in the crystal shows numerous analogies. Finally, preliminary results on the competitive inhibition effect between the Cu2+ and 2',3'-cytidine monophosphoric acid are discussed.

Animals↗
PubMed1977

ESR an optical absorption studies on the copper(II) interaction with small peptides containing aromatic amino acids.

The interaction of Cu(II) with di- and tripeptides each containing phenylalanine, tryptophan or histidine in the amino acid chain has been investigated by means of electron spin resonance (ESR) and optical absorption spectroscopy. Cu(II) complexes of dipeptides and tripeptides exhibit different magnetic and optical parameters. Dipeptide complexes have larger gparallel-values and smaller A parallel values than tripeptide complexes. When compared to dipeptide complexes, the d-d band of the central metal ion is blue shifted for tripeptide complexes. There are no significant difference in the behavior of Cu(II) peptide complexes containing phenylalanine or tryptophan. Complexes of histidine containing peptides, however, show modified spectra caused by the participation of the imidazole nitrogen in the coordination to Cu(II). The imidazole nitrogen seems to coordinate in-plane with other coordinating atoms or in an axial position depending on the kind of peptide.

Chelating Agents↗
PubMed1976

ESR and optical absorption studies on the copper (II) interaction with aromatic amino acids.

Electron spin resonance and optical absorption studies have been done in order to investigate the interaction between Cu2+ and aromatic amino acids in aqueous solution at 77 K and at room temperature as well. Depending on the concentration each aromatic amino acid can form two different kinds of complexes with Cu2+ which can be characterized by its ESR pattern. Additional information was obtained from optical d-d and CT transitions.

Amino Acids↗
PubMedDate not supplied

On the influence of aromatic residues on the interaction of copper (II) with small peptides containing aromatic amino acids: ESR and optical studies.

The complexation behaviour of Cu(II) with di- and tripeptides containing the aromatic amino acids phenylalanine or typtophan has been investigated at different pH-values and compared with results obtained with di- and triglycine. The results obtained by means of ESR and optical absorption spectroscopy show an influence of the two different aromatic entities on the magnetic and optical parameters. A significant decrease of the g11-value and, concomittantly, an increase of the energy of the d-d transition was measured when an aromatic entity is present in the peptide. A possible explanation for this observation is given.

Copper↗
PubMedDate not supplied

Paramagnetic species in beta-thalassemic sera: an ESR study.

Homozygous beta thalassemic sera show an electron spin resonance (ESR) signal at g approximately equal to 6 which is not present in normal and heterozygous sera. The signal arises from high spin heme groups exhibiting a departure from tetragonal symmetry toward rhombic. Binding by a serum protein is very likely responsible for such a distortion. In contrast with other authors' findings, we report that heme-human albumin complex shows a similar rhombic distortion. The observed ESR signal at g approximately equal to 6 is then attributed to this complex.

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

Conductivity of normal and pathological human erythrocytes (homozygous beta-thalassemia) at radiowave frequencies.

The conductivity of normal and homozygous beta-thalassemic erythrocyte suspensions has been measured over the frequency range from 5 KHz to 100 MHz in the temperature interval from 5 to 45 degrees C. The electrical parameters of the membrane, i.e., the capacitance CM and the conductance GM per unit surface have been calculated from an expression given by Hanai for the conductivity of a suspension of ellipsoidal particles covered with a shell. Some interesting differences between the normal and pathological state are evidentiated.

Electric Conductivity↗
PubMedDate not supplied

Effect of extracellular alkali metal salts on the electric parameters of human erythrocytes in normal and pathological conditions (homozygous beta-thalassemia).

The conductivity of human erythrocyte cells dispersed in various uni-univalent electrolyte solutions (NaCl, KCl, LiCl, CsCl; 0.15 M) have been measured in the frequency range from 10 KHz to 100 MHz at five temperatures between 5 and 45 degrees C. The results were analyzed in the light of the theory of conductivity polarization of a suspension of ellipsoidal particles-covered with two confocal shells. Differences in the electrical parameters of the membrane between normal and homozygous beta-thalassemic cells have been evidentiated.

Electric Conductivity↗
PubMedDate not supplied

Isotopic effect on the kinetic of thermal denaturation of ceruloplasmin.

The kinetics of thermal denaturation of ceruloplasmin in water and in water with different percentage of D2O in the temperature range 25-85 degrees C, following the optical density change of the 610 nm charge transfer band of the protein has been investigated. A temperature Tt approximately equal to 65 degrees C above which an irreversible denaturation process of the protein active site takes place has been found. The kinetics of the denaturation process of the protein are fitted by two first order reactions, which have been assigned to a different thermal denaturation behaviour of the two Cu2+ type I sites existing in the protein. Addition of D2O to the protein solution affects the two kinetics in a different way, i.e. the rate of one of them is increased whilst that of the other is decreased. The different effect of D2O on the kinetics of disruption of the two copper sites is discussed in terms of different location and degree of hydrophobicity of the two Cu2+ type I sites.

Ceruloplasmin↗
PubMedDate not supplied

Effect of inhalation anesthetics on spin-labeled cholesterol containing DPPC vesicles.

We have investigated by means of electron spin resonance (ESR) spectroscopy the influence of three inhalation anesthetics, i.e. halothane, chloroform and diethyl ether, on the interfacial and hydrophobic region as well of 38 mol% cholesterol containing DPPC unilamellar vesicles. The study has been carried out in the temperature range 25-45 degrees C. The variation of the order parameter, S, vs temperature of the lipid phase indicates that with this content of cholesterol the characteristic gel----liquid crystalline main phase transition of DPPC, normally occurring at Tt approximately 41 degrees C, disappears. When halothane and chloroform are added to the vesicles suspension up to [DPPC]/[anesthetic] molar ratio of 1:1 the main phase transition, as detected with the stearic acid spin label I (12,3), reappears again and it results down shifted at Tt approximately 35 and 39 degrees C, respectively. In presence of diethyl ether, instead, the main phase transition is not observable also at the highest concentration of anesthetic used. Moreover, halothane and chloroform affect similarly the hydrophobic core of cholesterol + DPPC vesicles which, in turn, results to be different from the action exerted by diethyl ether in the same region. The ESR findings are discussed in terms of competitive effects shown by cholesterol and inhalation anesthetics. Moreover, the interfacial region of CHOL + DPPC vesicles results to be the target of anesthetics.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

Thermal behaviour of lymphocyte membrane: ESR investigation.

The order parameter, S, of the plasma membrane of in toto human peripheral blood lymphocytes was obtained by electron spin resonance spectroscopy in the temperature range 25-41 degrees C. This membrane is completely in the liquid crystalline state above 31 degrees C. In presence of the antigen ETB from Staphylococcus aureus at the concentration of 4 micrograms/3 x 10(7) cells an overall decrease of the order parameter for this membrane is observed. The decrease of S is followed by an upwards shift at about 35 degrees C of the temperature of the liquid crystalline state.

Cell Membrane↗