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M L Barcellona

Publications and source records attributed to M L Barcellona.

At least 19 recordsLinked to original sources
PubMed1994

Heat shock proteins following rat cerebral ischemic/reperfusion episode: effect of ketamine.

This paper reports the influence of ketamine on HSP70 expression, during an ischemic/reperfusion episode, in rat cerebral cortex and hippocampus. The results indicate that ketamine, injected 1h before the surgical treatment, increases HSP70 cellular concentration in both ischemic and sham-operated animals. The HSP70 levels, after the transient ischemic episode, are higher in ketamine treated than in urethane-treated animals respect to the control levels. After reperfusion an increase of HSP70 levels is observed; this induction is maintained for at least 22h, irrespective of the anaesthetic drug treatment. Comparing the cerebral areas examined, the hippocampus exhibits higher protein levels than those of the cerebral cortex.

Animals↗
PubMed1991

A molecular approach to 4',6-diamidine-2-phenylindole (DAPI) photophysical behaviour at different pH values.

The photophysical mechanisms which determine the spectral properties and decay rates of 4',6-diamidine-2-phenylindole (DAPI) in solution and in association with nucleic acids have not yet been fully elucidated. We have performed steady-state and time-resolved fluorescence experiments on DAPI in a wide pH range to investigate the hypothesis that different ground-state conformations are responsible for the photophysical properties of the probe. Several excited-state mechanisms are investigated and it is concluded that among the proposed models, the hypothesis of ground-state heterogeneity with rapid interconversion among conformations is the only one consistent with the experiments in the entire pH range investigated.

DNA↗
PubMed1990

Time-resolved fluorescence of DAPI in solution and bound to polydeoxynucleotides.

Fluorescence decay studies, obtained by multifrequency phase-modulation fluorometry, have been performed on DAPI in solution and complexed with natural and synthetic polydeoxynucleotides. DAPI decay at pH 7 was decomposed using two exponential components of 2.8 and 0.2 ns of lifetime values, respectively. The double exponential character of the decay was maintained over a large pH range. Phase- and modulation-resolved spectra, collected between 420 and 550 nm, have indicated at least two spectral components associated with the two lifetime values. This, plus the observation of the dependence of the emission spectrum on the excitation wavelength, suggests a lifetime heterogeneity originating from ground-state molecular conformers, partially affected by pH changes. DAPI complexed with natural polydeoxynucleotides retained most of the features of DAPI decay in solution, except for the value of the long lifetime component that was longer (approximately 4 ns) and the relative fractional fluorescence intensities of the two components that were inverted. AT polymers/DAPI complexes show single exponential decay. Solvent shielding when DAPI is bound to DNA changes the indole ring solvation and stabilizes the longer lifetime decay component. For poly(GC)/DAPI complex, the decay was similar to that of free DAPI in solution, proving the dependence on the polydeoxynucleotides sequence the different types of binding and the reliability of the fluorescence method to solve them.

Animals↗
PubMed1990

The fluorescence properties of a DNA probe. 4'-6-Diamidino-2-phenylindole (DAPI).

Steady-state and dynamic fluorescence measurements have been performed on DAPI in solution and in complexes formed with a number of synthetic and natural polydeoxynucleotides. The decay of DAPI in buffer at pH 7 was decomposed using two exponentials having lifetime values of approximately 2.8 ns and 0.2 ns. The double exponential character of the decay was maintained over a large pH range from 3 to 9. At pH 1 the short component dominated, whereas at pH 12, only the long component was detectable. Two distinct spectra were associated with the two lifetime components; the short component was shifted to the red. The short lifetime component occurs in the presence of water. In water the excitation spectra depended on the emission wavelength and there was no viscosity dependence of the two forms. To explain these results we propose that there is a ground state conformer in which preferential solvation of the indole ring allows proton transfer in the excited state. DAPI complexed with polydeoxynucleotides retained most of the features of the decay of DAPI in solution. However, the complexes with fully AT-containing polymers stabilized the longer lifetime form of DAPI because the stronger binding enhanced solvent shielding. A gradual increase of the short lifetime component, which monitors dye solvent exposure, was obtained as the AT content was decreased. For polyd(GC) the decay was similar to that of free DAPI.

DNA↗
PubMed1989

Fluorescence lifetime distributions of DNA-4',6-diamidino-2-phenylindole complex.

Time-resolved fluorescence of 4',6-diamidino-2-phenylindole (DAPI) complexes show that for a homogeneous polymer (polyd(AT) or polyd(A).polyd(T)) at high P/D (phosphate/dye) ratio, a single exponential component adequately describes the fluorescence decay. For the AT polymers at low P/D ratio or for native DNA, the decay cannot be described by a single-exponential term. A continuous distribution of lifetime values of Gaussian shape gives a good fit to the decay data. We propose that the lifetime distribution method for the analysis of the fluorescence decay of DNA-DAPI complexes provides a useful method of characterizing the microheterogeneity of site binding.

DNA↗
PubMed1987

DAPI-pUC8 complex: a tool to investigate biological effects of nucleic acid-drug interaction.

A complex consisting of pUC8, a 1.8 Md plasmid, and 4'-6-diamidino-2-phenylindole, a DNA-binding agent, has been performed in vitro under different conditions of ionic strength, and used to transform competent cells. A strong interference with the plasmid-coded activities, related to the P/D ratio where at the DNA-drug complex was formed, was shown to occur. Since the compound does not inhibit the uptake process neither affects plasmid activity once dissociated at high ionic strength, it is likely to be acting from inside the cell while still in the form of a DNA-adduct. This system is proposed as a useful tool to investigate the effects on target genes of drugs endowed with DNA sequence specificity.

Circular Dichroism↗
PubMed1986

DNA-4'-6-diamidine-2-phenylindole interactions: a comparative study employing fluorescence and ultraviolet spectroscopy.

DAPI is a drug that interacts with double-stranded nucleic acids, binding preferentially to A + T base pairs. The interaction is not intercalative, therefore providing a useful model for mimicking the effect of functional molecules in modifying specific sites, namely, A + T segments, of significance in gene expression. Knowledge of the nature of such interaction has been enriched by additional information obtained from comparative analysis of the data acquired by uv spectroscopy and fluorescence. Two classes of binding sites, defined by different apparent affinity constants and numbers of binding sites, are evident. All types of interaction are dependent on the nucleic acid/dye ratio and on the ionic strength of the medium.

Binding Sites↗
PubMed1985

Interaction of DAPI with double-stranded ribonucleic acids.

The interaction of DAPI with natural and synthetic double-stranded polyribonucleotides was studied with different optical and calorimetric methods. The results were similar to those obtained previously with double-stranded polydeoxynucleotides, i.e. two interaction modes, the first of which shows high affinity for AU clusters and consequent strong fluorescence enhancement. The results suggest caution in the use of DAPI as selective fluorescent staining agent for DNA in the presence of RNA. A narrow groove binding model with hydrogen bonds between DAPI and AU pairs is proposed. An intercalation mechanism can be excluded because of the non planarity of DAPI molecule.

Calorimetry↗
PubMed1985

Interaction of papaverine with covalently closed DNA.

Cyclic nucleotides influence viral replication and papaverine, as an inhibitor of phosphodiesterase, also affects the replication of both DNA and RNA viruses through an increase in cAMP levels. Moreover in vitro papaverine affects neither protein synthesis nor several polymerases, while it inhibits DNA synthesis. Static fluorescence studies on the interaction of the drug with ColE1 plasmid covalently closed DNA indicate that the drug binds to the nucleic acid, probably by intercalation. A comparison between the binding characteristics of Papaverine and Actinomycin D is also reported.

Bacteriocin Plasmids↗
PubMed1983

Interaction of diamidino-2-phenylindole (DAPI) with natural and synthetic nucleic acids.

The interaction of DAPI with natural and synthetic polydeoxynucleotides of different base content and sequences was studied with circular dichroism, ultracentrifugation, viscosity and calorimetry. All the polymers show two types of binding. The strength of the interaction and its resistance to ionic strength are related to the content of AT clusters in the chain. On the other hand, sedimentation measurements rule out an intercalation mechanism. A model of DAPI interaction with DNA, similar to that displayed by distamycin and netropsin, is proposed.

Animals↗
PubMed1983

Effect of undernutrition on some enzymes of purine metabolism in different regions of developing rat brain.

The effect of undernutrition on the activity of some enzymes involved in purine metabolism, ie, adenosine aminohydrolase, adenylate aminohydrolase, and inosine phosphorylase in cerebral hemispheres, cerebellum, and brain stem of rats at different days of postnatal development was studied. Adenosine aminohydrolase, adenylate aminohydrolase, and inosine phosphorylase were assayed by radiochemical methods which involve the measurement of the radioactive products formed, ie, inosine, IMP, and hypoxanthine, respectively. The results obtained indicate that undernutrition affects the activity of the enzymes which control the concentration of purine nucleotides to a different degree in the three brain regions examined.

AMP Deaminase↗
PubMed1983

Effect of undernutrition on some enzymes involved in the salvage pathway of purine nucleotides in different regions of developing rat brain.

The effect of undernutrition on the activity of two key enzymes of purine salvage pathway, namely hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) and adenine phosphoribosyltransferase (APRTase), in cerebral hemispheres, cerebellum and brain stem of rats at different days of postnatal development was studied. The activity of HGPRTase and of APRTase is significantly lower in all brain regions of undernourished animals at 5 days after birth; between 10 and 15 days of age there is a recovery of the enzymatic activity which is particularly evident in the cerebellum. Successively both enzymatic activities decrease reaching at 30 days of age values quite similar to those of controls. These results indicate that undernutrition during fetal and postnatal development, impairs and delays the activity of the enzymes of purine salvage pathway.

Adenine Phosphoribosyltransferase↗
PubMed1982

De novo biosynthesis of nucleotides and of nucleic acids in different regions of developing rat brain: effect of undernutrition.

The effect of undernutrition on the de novo biosynthesis of nucleic acids in cerebral hemispheres, cerebellum, and brain stem of rats at different days of postnatal development was studied. The experiments were carried out in vitro by measuring the incorporation of [14C]-formate into the adenine nucleotide of the acid-soluble fraction of RNA and DNA, as well as into the thymine of DNA. The results obtained indicate that undernutrition during fetal and postnatal development impairs the de novo synthesis of the purine nucleotides of RNA and DNA at 5 days of age and delays it thereafter in the various brain regions examined, particularly in the cerebellum.

Adenine↗
PubMed1981

Reactivity of gastric (H+ + K+)-ATPase to N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline.

The K+-dependent ATPase and p-nitrophenyl phosphatase activity of, and formation of phosphoenzyme by, hog parietal cell membranes were inhibited in a time- and concentration-dependent manner by the carboxyl-activating reagent, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The kinetics of inactivation was pseudo first order and was similar to the EEDQ-catalyzed incorporation of [14C]glycine ethyl ester. The most likely mechanism is the EEDQ-dependent formation of inter- and intramolecular amide bonds. Cross-linking between the subunits of the ATPase occurs with EEDQ treatment. The presence of K+ on the luminal face of the enzyme is able to prevent EEDQ inhibition of K+ ATPase activity (but not intermolecular cross-linking), whereas ATP enhanced the rate of inactivation. EEDQ reaction with the enzyme therefore allows investigation of K+- and ATP-dependent states of the enzyme.

Adenosine Triphosphatases↗
PubMed1981

[Intermolecular interactions between fluorescent probes bound to linear DNA].

Intermolecular interactions of fluorescent probes bound to linear DNA. Several fluorescent probes can be widely used in determining the base content, the geometry and the possible conformational transitions of linear and circular DNAs in solution. Data are presented showing that Tb3+ and DAPI bind independently to DNA and can therefore be used to monitor the G+C and A+T content of the nucleic acid respectively.

Amidines↗
PubMed1980

The interaction of K+ with gastric parietal cells and gastric ATPase.

The gastric H+ secretion in isolated cell requires K+ and is ATP dependent. There is also evidence in the cell system for Na+ inhibition of H+ secretion. The isolated gastric ATPase also shows K+ activation and inhibition by K+ or Na+ located on the ATP binding side of the enzyme, which corresponds to the cytoplasmic face of the enzyme. Gastric vesicles are activated in terms of transport activity by internal K+, and this site, inhibited by reagents that modify carboxyl groups, is required for enzyme turnover and transport.

Adenosine Triphosphate↗