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Biomedical subjects

R Fioravanti

Publications and source records attributed to R Fioravanti.

11 recordsLinked to original sources
PubMed1989

[Substances with antibacterial and antifungal activity. VII. Synthesis and microbiologic activity of new derivatives of 1,5-diarylpyrrole].

The synthesis and antifungal activities of new 1,5-diarylpyrrole derivatives are reported. Antimicrobial data in comparison with pyrrolnitrin show that N-methylpiperazinylamides exhibit very poor activity against Candida albicans and Candida sp. while acid and ester derivatives are inactive. Vice-versa many acid or amide derivatives show interesting antibacterial activity. The results obtained are discussed on the basis of structure-activity relationships.

Anti-Bacterial Agents↗
PubMed1988

Chemotherapeutic agents with an imidazole moiety. II. Synthesis and biological activities of new 1,4-diarylimidazoles.

The synthesis, antifungal and pharmacological activities of new 1,4-diarylimidazoles are reported. Antimicrobial data in comparison with antifungal antibiotic pyrrolnitrin pointed out that the 1,4-diaryl-2-mercaptoimidazole derivatives were inactive and all 1,4-diarylimidazoles exhibited a weak antifungal activity. Some compounds showed a selective activity against strains of Candida sp. Instead pharmacological data did not evidence any significant antiinflammatory activity. The tested compounds were prepared by reacting appropriate phenacylanilines with potassium thiocyanate in acidic medium to afford 1,4-diaryl-2-mercapto imidazoles which were then transformed into title compounds by treatment with nitric acid.

Animals↗
PubMed1984

Extrinsic charge movement in the squid axon membrane. Effect of pressure and temperature.

The absorption of the lipophilic anions dipicrylamine (DPA-) and tetraphenylborate (TPhB-) by the lipid matrix of the squid axon membrane, and the kinetics of their translocation, were studied by the charge pulse relaxation technique. The axons were treated with tetrodotoxin (TTX) and 4-aminopyridine to block the ionic currents responsible for nerve excitation. At high enough concentrations of absorbed ions (approximately 10(-12) mol/cm2) the membrane voltage relaxation following a brief current pulse consisted mainly of two exponential components, whose time constants and relative amplitudes were used for estimating the translocation rate constant, K, and the density of absorbed ions, N. These measurements were performed at different hydrostatic pressures in the range 1-100 MPa (approximately 1,000 atm), and at different temperatures in the range 5 degrees C-20 degrees C. Both K and N were found to be little affected by pressure. The pressure dependence of K indicated that the translocation of lipophilic ions across the nerve membrane involves activation volumes of the order of 5 cm3/mol. In all experiments the passive membrane resistance was little affected by pressures up to 80 MPa. However, above 100 MPa it fell dramatically to low values, presumably because of phase separation phenomena between the membrane components. The temperature dependence of K, both for DPa- and TPhB-, implied an activation energy for ion translocation of the order of 60 kJ/mol, close to that measured in artificial lipid bilayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1978

Action of extracellular pH on Na+ and K+ membrane currents in the giant axon of Loligo vulgaris.

Voltage-clamp currents and resting membrane potential of squid giant axons have been studied at extracellular pH varying between 4 and 10. The membrane currents, analyzed according to the Hodgkin-Huxley equations, showed that sodium permeability, PNa(E), and potassium conductance gK(E), curves were shifted toward positive voltages by different amounts and slightly depressed as the external pH was lowered. Under the same conditions, taum(E) and taun(E) were found to be enhanced and shifted to a larger extent in the same direction. The rate constants alpham and alphan were shifted substantially toward positive voltages, but betam and betan changed hardly at all. The shift of the alpham(E) curve was analyzed in terms of a fixed surface charge model; it indicates that unspecific negative groups with an approximate pKa of 4.5 are located in the vicinity of sodium active sites with an average charge separation of 8 A. A similar figure is obtained for the potassium system from the shift of the alphan(E) curve.

Animals↗
PubMed1975

Fluorescence polarization studies of squid giant axons stained with N-methylanilinonaphthalenesulfonates.

The polarized components of the extrinsic fluorescence of squid giant axons stained with 2,6-MANS or 1,8-MANS were studied. The polarization properties of the fluorescence changes associated with voltage-clamp pulses were found to be very different from those of the static fluorescence, supporting the notion that the optical changes involve highly oriented membrane adsorbed fluorophores. The theoretical expectations according to this hypothesis are discussed in detail. The experimental results are in good agreement with the theory assuming that possible probes reorientations are soley due to the action of the applied electric field upon the probes electric dipole. The quantitative analysis of the data for 2,6-MANS provides a fairly accurate determination of the orientation of the membrane bound 2,6-MANS molecules responsible for the fluorescence changes. Such orientation appears to be independent of the membrane face exposed to staining. The data for 1,8-MANS indicate a very different orientation of this isomer. The results suggest a profitable use of extrinsic fluorophores for studies of the structural organization of nerve membranes.

Anilino Naphthalenesulfonates↗
PubMed1972

Analysis of responses in visual cells of the leech.

1. Potentials were recorded from the cytoplasm and from the vacuole of leech photoreceptors. Since the vacuole is lined with microvilli and is connected to the outside by narrow channels, the potential drops between vacuole and outside measure the current through the microvillar membrane.2. In darkness, the potential of the cytoplasm with respect to the outside is about - 45 mV while the potential of the vacuole is approximately zero.3. Following illumination the negativity of the cytoplasm decreases and the vacuole becomes negative relative to the outside.4. For dim intensities, the response to a flash of light may grow proportionately more than the intensity of the flash. This is probably due to development of a depolarizing local response.5. The resistance from the cytoplasm to the outside was about 150 MOmega in darkness and decreased to approximately 40 MOmega at the peak of the response to a bright flash (on average). Corresponding measurements from the vacuole gave 50 MOmega in darkness and 35 MOmega at the peak of the response.6. Charging curves produced by steps of constant currents applied to the cytoplasm or to the vacuole include two time constants (about 5 and 50 msec on average). The longer time constant decreases greatly with bright illumination.7. The results are consistent with the interpretation that the response to light is brought about by an increase of conductance of the microvillar membrane.

Action Potentials↗
PubMedDate not supplied

Chemotherapeutic agents with an imidazole moiety. III. Synthesis and microbiological activity of new 1,4-diarylimidazole and 1,4-pyrrolimidazolphenylene derivatives.

New 1,4-diarylimidazole and 1,4-pyrrolimidazol-phenylene derivatives were prepared in attempt to deepen S.A.R. study on chemotherapeutic agents with an imidazole moiety. Antimicrobial data in comparison with antifungal antibiotic pyrrolnitrin showed that all tested compounds are practically inactive against blastomycetes but some derivatives exhibited selective activity against strains of gram-negative bacteria. The results obtained are discussed on the basis of structure-activity relationships.

Anti-Bacterial Agents↗