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Biomedical subjects

M Beltrame

Publications and source records attributed to M Beltrame.

At least 37 records · Page 2Linked to original sources
PubMed1989

Specific recognition of cruciform DNA by nuclear protein HMG1.

Cruciform DNA, a non-double helix form of DNA, can be generated as an intermediate in genetic recombination as well as from palindromic sequences under the effect of supercoiling. Eukaryotic cells are equipped with a DNA-binding protein that selectively recognizes cruciform DNA. Biochemical and immunological data showed that this protein is HMG1, an evolutionarily conserved, essential, and abundant component of the nucleus. The interaction with a ubiquitous protein points to a critical role for cruciform DNA conformations.

Animals↗
PubMed1988

Pharmacokinetics of a new oral antibacterial agent, ofloxacin, in dentistry and oral surgery.

The new oral antibacterial agent, ofloxacin, was administered for prophylactic purposes to a group of 12 patients with dental and oral inflammatory processes requiring oral surgery. Drug concentrations in serum, saliva and gingival mucosa were assayed at different times after administration of the drug. Good serum, salivary and gingival mucosal tissue concentrations were achieved.

Adult↗
PubMed1987

Intracellular chromium reduction.

Two steps are involved in the uptake of Cr(VI): (1) the diffusion of the anion CrO4(2-) through a facilitated transport system, presumably the non-specific anion carrier and (2) the intracellular reduction of Cr(VI) to Cr(III). The intracellular reduction of Cr(VI), keeping the cytoplasmic concentration of Cr(VI) low, facilitates accumulation of chromate from extracellular medium into the cell. In the present paper, a direct demonstration of intracellular chromium reduction is provided by means of electron paramagnetic (spin) resonance (EPR) spectroscopy. Incubation of metabolically active rat thymocytes with chromate originates a signal which can be attributed to a paramagnetic species of chromium, Cr(V) or Cr(III). The EPR signal is originated by intracellular reduction of chromium since: (1) it is observed only when cells are incubated with chromate, (2) it is present even after extensive washings of the cells in a chromium-free medium; (3) it is abolished when cells are incubated with drugs able to reduce the glutathione pool, i.e., diethylmaleate or phorone; and (4) it is abolished when cells are incubated in the presence of a specific inhibitor of the anion carrier, 4-acetamido-4'-isothiocyanatostilbene-2-2'-disulfonic acid.

Animals↗
PubMed1985

Cytosolic Ca2+ homeostasis in Ehrlich and Yoshida carcinomas. A new, membrane-permeant chelator of heavy metals reveals that these ascites tumor cell lines have normal cytosolic free Ca2+.

The intracellularly trappable fluorescent Ca2+ indicator quin-2 was used to measure free cytosolic Ca2+, [Ca2+]i, in the two highly dedifferentiated tumor cell lines, Ehrlich and Yoshida ascites carcinomas. It was found that these carcinoma cells can trap quin-2 similarly to normal cells, but [Ca2+]i was apparently significantly lower than in any normal cell tested previously with this method. By using a new lipid-soluble heavy metal chelator TPEN (N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine), which crosses artificial and natural membranes, it was found that endogenous heavy metals are responsible for partially quenching quin-2 fluorescence trapped inside the cells. Although the quenching of intracellular quin-2 fluorescence is quantitatively more relevant in these ascites carcinomas, TPEN was effective also in normal cells like lymphocytes and granulocytes. Both in the normal and especially in the malignant cell lines [Ca2+]i can be grossly underestimated at low intracellular quin-2 concentrations. Endogenous heavy metal quenching is thus a potential source of artifact when [Ca2+]i is measured with quin-2. When corrected for quin-2 fluorescence quenching by intracellular heavy metals, [Ca2+]i and basic regulatory mechanisms of [Ca2+]i homeostasis in Ehrlich and Yoshida carcinomas are similar to those of nontransformed cells.

Aminoquinolines↗
PubMed1985

Effects of chromium(VI) and chromium(III) on energy charge and oxygen consumption in rat thymocytes.

The cytotoxic effects of chromium compounds in two oxidation states have been studied in rat thymocytes. endogenous nucleotide levels and oxygen consumption were examined as relevant parameters of the physiological state of the cell. Incubation of rat thymocytes with Cr(VI) produced a marked unbalance of endogenous purine nucleotide pool and a parallel decrease in oxygen consumption. A close correlation between the reduction of oxygen consumption and ATP level in rat thymocytes treated with increasing concentrations of Cr(VI) has been found. In rat thymocytes permeabilized with digitonin and in isolated rat liver mitochondria both Cr(VI) and Cr(III) showed, at different range of concentrations, a marked inhibition of maximal oxygen consumption rate (uncoupled respiration). The effects observed were depending on chromium oxidation state and on different mitochondrial sites of substrate oxidation.

Adenosine Diphosphate↗
PubMed1979

Labelling of cardiolipin in vitro.

A method for labelling the polar head groups of cardiolipin is described. Labelling was carried out on sonicated cardiolipin/water suspensions. The free hydroxyl group of cardiolipin was oxidised with an excess of p-(diazonium) benzenesulfonic acid (DABS) and then reduced with NaB3H4. Isopropanol was oxidised in the presence of DABS to test the reactivity of the diazonium salts, and the reaction product was analysed by means of gas-chromatography. Labelled cardiolipin, identified by thin-layer chromatography (TLC), was chromatographically pure and identical to untreated cardiolipin. The hydrolysis of cardiolipin confirmed that the labelling was at the level of polar head groups.

Cardiolipins↗
PubMed1977

Cation transport in cytochrome oxidase reconstituted vesicles.

Cation translocation across the membrane of cytochrome oxidase reconstituted vesicles may be followed with a simple spectrophotometric method. Cytochrome oxidase reconstituted vesicles, supplemented with ascorbate and cytochrome c. induce large spectral changes of the positive dye safranine, reversed by uncouplers and inhibitors of respiration. The dye is probably accumulated in the inner space of the vesicles, where it reaches high concentrations and aggregates. The spectral shifts and the absorbance changes, due to aggregation, are proportional to the amount of the dye taken up and depend on the respiratory control. In the presence of potassium, valinomycin causes an inhibition, whereas nigericin stimulates the dye uptake. The data are discussed in terms of electrical potential dependent fluxes.

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone↗