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Biomedical subjects

V Viti

Publications and source records attributed to V Viti.

53 records · Page 3Linked to original sources
PubMed1985

Interaction of tryptophan with lecithin liposomes: NMR and turbidity studies.

A study on the interactions between tryptophan (Trp) and dipalmitoylphosphatidyl choline (DPPC) liposomes conducted with the NMR technique and taking turbidity measurements is reported. Trp is shown to be incorporated into the bilayer only when interaction occurs above gel-liquid transition. Disappearance of turbidity changes at the phase transition temperatures are shown to occur with Trp incorporation. 1H and 13C NMR relaxation times T1 of DPPC are seen to be reduced. Acyl chain signal intensity is shown to decrease and the corresponding line-width to increase as a function of Trp concentration. DPPC 31P [1H] Nuclear Overhauser Effect (NOE) is depressed by the presence of Trp above gel-liquid transition temperature whereas NOE remains high below phase transition temperature when Trp is present in the bilayer. Effects are shown to be the same in both H2O and in 2H2O. A membrane modification that may account for the previously observed inhibition of polysaccharide induced cell aggregation is hypothesized.

Kinetics↗
PubMed1984

Gamma-irradiation effects on phosphatidylcholine multilayer liposomes: calorimetric, NMR, and spectrofluorimetric studies.

Chemical and structural modifications in multilayer liposomes of synthetic phosphatidylcholine induced by gamma irradiation are investigated with different techniques. Fluorescence anisotropy of the DPH probe and differential scanning calorimetry reveal a broadening of the main lipid transition and the disappearance of pretransition. Fluorescence anisotropy is shown to be higher in the irradiated sample and particularly so at low temperatures. NMR and TLC results show that lysolecithin and palmitic acid are formed with a consequent change in bilayer organization. The possibility that these modifications may account for the permeability variations observed in irradiated natural membranes is discussed.

Calorimetry, Differential Scanning↗
PubMed1983

Effect of lipophilic vitamins on the erythrocyte membrane. 31P NMR and fluorescence studies.

Structural changes induced by the fat-soluble vitamins A, D3, E and K1 in natural membranes were studied by 31P NMR and fluorescence anisotropy on erythrocyte ghosts; the occurrence of cell fusion following vitamin addition was detected by optical microscopy of intact cells. Vitamins A, E and K1, which produce cell fusion, also induce the formation of configurational phases other than the bilayer and increase, at a different extent for the different vitamins, membrane fluidity. Vitamin D3, on the contrary, induces aggregation without fusion, paralleled by bilayer phase stabilization and microviscosity increase. A correlation between fusion phenomena and structural variations in the bilayer organization is therefore suggested.

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↗
PubMedDate not supplied

Continuous quality improvement in radiotherapy: the role of the "Istituto Superiore di Sanità" in its application over the national territory.

The "Laboratorio di Fisica" of the "Istituto Superiore di Sanità" has undertaken some initiatives to tackle the problem of patients' radiation protection in relation to the issues of radiotherapy, both with respect to the promulgation of new National and European laws and directives and to the extremely rapid and innovative technological developments involved in this field. First, interdisciplinary study groups were organized to identify the aspects on which recommendations to be applied at the national level could be based, and to provide for their development. Second, a national plan was launched for continuous quality improvement in radiotherapy, intended as a program of controls and correctives implemented in radiotherapy to ensure its compliance with predefined standards together with its continuous improvement. Within this plan, a group of experts coordinated by the "Istituto Superiore di Sanità" has promoted two different intercomparisons of dosimetry to evaluate the differences between the measured dose and the calculated dose 1) with reference to a water phantom and 2) during a simulated treatment of rectal cancer in a plastic phantom.

Academies and Institutes↗