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Biomedical subjects

F Castelli

Publications and source records attributed to F Castelli.

At least 91 records · Page 5Linked to original sources
PubMed1990

Calcium ion influence on thermotropic behaviour of dipalmitoylphosphatidylcholine-vitamin D3 systems.

An analysis of Ca2+ influence on the thermotropic behaviour of different phosphatidylcholine-vitamin D3 mixtures was carried out by differential scanning calorimetry technique (DSC). A competitive effect between Ca2+ and vitamin D3 on the membrane fluidity was detected. The observed shifts of the gel-liquid crystal transition temperature were correlated with the mole fraction of vitamin D3 dissolved within the lipid bilayer as well as with the Ca2+ concentration in the surrounding medium. These shifts were rationalized on the ground of a simple microscopic model through the calculation of the internal pressure exerted by the adsorbed Ca2+ on the lipid matrix by the Clapeyron equation. The experimental results and the obtained equations accord with each other and support the idea of micro-domain formation richer in one lipid component. The extent of such lateral phase separation of the lipid components seems to be favoured by the adsorption of Ca2+ at the membrane-water interface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Effect of teicoplanin and vancomycin on Staphylococcus aureus ultrastructure.

Morphological changes induced by teicoplanin and vancomycin on Staphylococcus aureus have been comparatively evaluated. The most pronounced structural damages were found on the cell wall which was uniformly thickened on bacteria exposed to teicoplanin while it was of irregular thickness and often absent around the cells in those exposed to vancomycin. The inhibitory action of teicoplanin on proteoglycan polymerization but not on nucleic acid and protein synthesis indicates that the effect in the wall is due to the accumulation at this level of proteoglycan soluble precursors continuously produced by the cell. The different effects induced by vancomycin on cell wall morphology can also be related to the compatibility of this antibiotic in altering cytoplasmatic membrane function and ribonucleic acid synthesis.

Anti-Bacterial Agents↗
PubMed1990

Ultrastructural features of host-parasite interactions in "in vitro" cultures of Plasmodium falciparum.

We carried out an electron-microscopy study on in vitro cultures of Plasmodium falciparum, whose general ultrastructural features are consistent with previous reports. In addition, whorled membrane-vesicles systems involving parasite and host-cells, never described to our knowledge up to now. As far as the parasite is concerned, these membraneous systems appear to be related to its growth and its connection with the external medium, with the possible involvement of Maurer's clefts. As for the erythrocyte, surface vesicles prove to be related to plasmodial infection in long-term in vitro culture. Richness in membranous structures of the complex host-parasite varies according to the metabolic demand of the plasmodium (i.e. on the life-cycle stage) and is influenced by external factors, possibly being a marker of drug action.

Animals↗
PubMed1989

Ultrastructure of Plasmodium falciparum "in vitro". II. Morphological patterns of different quinolines effects.

In the present morphological study, we used electron microscopy (EM) to evaluate the activity of three quinolines upon Plasmodium falciparum strains cultured in vitro. The drugs (namely chloroquine, mefloquine and a new active substance, SF6606) showed common cellular targets (i.e. feeding process, protein synthesis, membrane formation and utilisation) but gave rise to different morphological features. EM as a tool is able to reveal a variety of drug-induced alterations, but it does not seem to supply evidence of a definite mechanism of action. Nevertheless, our observations suggest that each drug acts via several mechanisms, possibly linked to different degrees of parasite susceptibility.

Animals↗
PubMed1989

Ultrastructure of Plasmodium falciparum "in vitro". I. Base-line for drug effects evaluation.

A chloroquine-sensitive and a chloroquine-resistant strain of Plasmodium falciparum were examined in drug-free culture. Apart from the presence of knobs on the erythrocytes infected with sensitive parasites, no major differences between the two strains were observed. Nevertheless, the parasites of each strain show a variety of morphological features, some of which are quite similar to drug-induced alterations concerning cytoplasmic organelles, feeding process, and host-parasite interactions.

Animals↗
PubMed1988

Lifetime and quenching of tryptophan fluorescence in whiting parvalbumin.

The fluorescence lifetime of the single tryptophan in whiting parvalbumin has been measured by time-correlated single-photon counting. In the presence of saturating calcium, greater than 2 mol/mol of protein, the decay of fluorescence is accurately single exponential with a lifetime of 4.6 ns (0.1 M KCl, 20 mM borate, 1 mM dithiothreitol, 20 degrees C, pH 9). Upon complete removal of calcium from parvalbumin with ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid the emission decay becomes biphasic, and a second more rapid decay process with a lifetime of 1.3 ns comprising approximately 18% of the fluorescence emission at 350 nm is observed. The fluorescence emission of the calcium-saturated form is not measurably quenched by iodide. In contrast, upon complete removal of calcium, the fluorescence is completely quenchable as shown by extrapolation of the data to infinite iodide concentration. These results indicate that there is a large increase in the accessibility of the tryptophan residue in the protein to solvent upon removal of calcium. Stern-Volmer plots of the quenching data are nonlinear and indicate that there is more than one quenchable conformation of the calcium-free protein. The lifetime and quenching results are consistent with the presence of significant concentrations of only two stoichiometric species, apoparvalbumin and parvalbumin--Ca2, at partial occupancy of the calcium binding sites.

Animals↗
PubMed1988

[Imported malaria in Lombardia. A second review of hospitalized cases in 1981-1985].

We carried out a research on hospitalized cases of imported malaria in Lombardy in the period 1981-1985 to characterize the risk factors and the clinical features of this phenomenon and to identify its trend in comparison with the previous quinquennium (Carosi et al., 1983). 1) Prevalent factors of risk are: the P. falciparum etiology (68%), the african origin of the strains, the work motivated travelling (56%) and a long period of stay (56%) in the summer-autumnal season (62%). On the contrary, in the previous quinquennium, short periods of stay during winter season prevailed. 2) As far as the chemoprophylaxis is concerned, it has been adopted in 55% of the cases, but only in 14 cases it was correct. In 52% of the cases, symptoms were noted within 20 days of re-entry, and in 17% of the cases they started abroad. In 62% of the cases a correct diagnosis was made within 10 days from the onset of symptoms and in 72% fever disappeared within 48 hours after therapy. Data show an inversion of the trend of the previous quinquennium and evidentiate a wider use of chemoprophylaxis and a more effective therapeutic action by the Sanitary Structure in Lombardy. The Authors stress the need for improvement in malaria control programs by Italian industries working in Developing Countries (roads and dams construction) and the increasing prophylactic problems related to che widespread extent of chloroquine resistant P. falciparum strains in Africa. Our causistry shows the outcome of 14 falciparum malaria cases in spite of correct chloroquine chemoprophylaxis.

Adult↗
PubMed1986

Intracellular killing of Brucella melitensis within mouse peritoneal macrophages: influence of treatment with rifampicin. An ultrastructural study.

The aggregation and condensation of ribosomes and the disjunction of the cell-wall membranous system are the ultrastructural alterations caused by rifampicin on B. melitensis cultured in Brucella-Broth medium. Our ultrastructural researches carried out on mouse peritoneal macrophages infected with B. melitensis and treated with rifampicin (1 microgram/ml) have demonstrated that vacuoles containing B. melitensis which had been damaged by the drug fuse with lysosomes. On the contrary vacuoles containing undamaged and viable Brucellae showed markedly impaired lysosomal fusion.

Animals↗
PubMed1986

Alterations due to ampicillin and rifampicin in S. sanguis and S. aureus isolated from dental plaque. An electron microscopic study.

In this work we analysed the ultrastructural changes in S. aureus and S. sanguis after exposure to rifampicin and ampicillin respectively. S. aureus grown in the presence of rifampicin showed ultrastructural changes that can be summarized as follows: the peripheral cell-wall increased to three to five times the normal thickness; the cross-walls were considerably (two to ten times) thicker than normal; after 8 h of exposure a complete lysis occurred. S. sanguis grown in the presence of ampicillin showed ultrastructural changes that can be summarized as follows: aggregation and condensation of ribosomes; alterations of division with the presence of asynchronous septa; in some bacterial cells a prominent bulge was observed at one pole of the cell; after 8 h of exposure a complete lysis occurred.

Ampicillin↗
PubMed1985

Life cycle of P. carinii in the lung of immuno-compromised hosts: an ultrastructural study.

We describe the ultrastructural features of interstitial pneumonia and life cycle of P. carinii in the lung of immuno-compromised hosts. The hyperplasia and edema of alveolar lining cells appear to be largely responsible for the extensive desquamative alveolitis which characterizes the histopathologic features of P. carinii in the lung of immuno-compromised hosts. The ultrastructural data concerning the ameboid trophozoite, particularly the presence of lobopodies and the reduplication by binary fission, associated with cyst forming capacity, suggest that P. carinii can be reasonably placed within the Protozoa.

Animals↗
PubMed1985

Clinical study with cefoxitin in paediatrics.

A trial of cefoxitin was performed on 25 children needing urgent and accurate antibiotic therapy before laboratory test results could be made available. Cefoxitin proved to be highly active in the treatment of infections of bacterial origin. It was therefore found suitable for use in the clinical situation where the urgency of the need for treatment differs from theoretical practice.

Bacterial Infections↗
PubMed1985

Toxoplasma gondii: in vivo and in vitro immunological and ultrastructural patterns of a human low virulent strain.

The AA. analyze the ultrastructural and immunological patterns of a low virulent strain of T. gondii cultured in vitro on A-9 cells line (PV-H1C-83). The tissue culture method described here is highly recommended to study the immunological aspects of experimental toxoplasmosis. Biological tests' results and the time courses of serological tests are also similar to those obtained from mice infected with cerebral tissue containing cysts. The low virulent strain (PV-H1C-83), when cultured in vitro, is able to induce the formation of large parasitophorous vacuoles, in which the EM investigation shows a typical cyst wall enveloping numerous bradyzoites.

Animals↗
PubMed1984

An improved method for increasing the sensitivity of direct agglutination test (D.A.T.) to the detection of IgM and IgG anti-toxoplasma antibodies.

The present investigation has shown that the antibody titers obtained by IgG-IFA correlate well with 2-ME-DA (correlation coefficient 0.927, p less than 0.001). These results are obtained when the antibody titers are expressed as IU/ml. Buffer without 2-ME and purification of IgM fractions by simple gel-filtration method seem to be necessary conditions for detecting IgM antibodies by DA test in adult patients. Therefore the DA with these micromodifications has a specificity and sensitivity similar to those of IgG and IgM-IFA tests and would be convenient for laboratories that perform large scale surveys during pregnancy.

Adult↗