Search PubMed⌕ Search

Biomedical subjects

C Alonso

Publications and source records attributed to C Alonso.

At least 325 records · Page 18Linked to original sources
PubMed1987

Antitrypanosomal action of cis-diamminedichloroplatinum (II) analogs.

The present report deals with the alterations produced by cis-diamminedichloroplatinum (II) (DDP), and 2 of its analogs: cis-Pt(II)(tranylcypromine)2Cl2 and cis-Pt(II)(benzothiazole)2Cl2 in cultured epimastigote forms of Trypanosoma cruzi. Studies have been performed at the ultrastructural level and the inhibitory effect of these complexes on macromolecule synthesis, evaluated by 3H-thymidine, 3H-uridine, and 3H-leucine incorporation, has been investigated. DDP at concentrations of 50 and 100 micrograms/ml does not inhibit significantly the incorporation of radioactive precursors, but a clear decrease was observed with the 2 analogs. Eight hours of treatment at a concentration of 10 micrograms/ml rendered in all 3 cases an increase in autophagic vacuoles and lipids as well as an abnormal condensation of the nucleus chromatin.

Animals↗
PubMed1987

Mode of action of intercalating drug, cis-Pt(II)(DDH)Cl2, cis-Pt(II)(DDH) (metafluorobenzoic)2, and cis-Pt(II)(DDH)(mucubromic)2, on Trypanosoma cruzi.

The trypanocidal activity of three new compounds derived of the antineoplastic drug cis-diamminodichloroplatinum(II) (DDP) has been studied over epimastigote forms of Trypanosoma cruzi. The electron microscopy indicated that, in the treated animals, the nuclear chromatin is distributed in the nucleus in a lax form and that the number of lipidic vacuoles increases largely. This action is more significant when cis-Pt(II)1,2-diaminocyclohexane is used. In addition this compound causes a destabilization of the DNA double helix with a decrease of melting temperature. The three compounds inhibit the incorporation of leucine, uridine and thymidine, although the thymidine uptake is the most significantly affected.

Animals↗
PubMed1985

Immunofluorescence localization of DNA:RNA hybrids in Drosophila melanogaster polytene chromosomes.

Sites of transcriptional activity in the whole set of Drosophila melanogaster polytene chromosomes have been localized by means of fluorescent antibodies against DNA:RNA hybrid molecules and compared with results on 3H-uridine incorporation obtained earlier. The majority of large and small puffs with intensive 3H-uridine incorporation demonstrate bright fluorescence. Moreover, bright fluorescence is also observed for a large number of small puffs though the intensity of 3H-uridine incorporation is low. Some prominent puffs with high levels of 3H-uridine incorporation show weak fluorescence. Condensed bands, as a rule, do not show fluorescence. The regions that look like interbands under the light microscope are not real interbands, but consist of minibands visible only in the electron microscope (EM). However, a region that has been previously studied by EM and proven to be a real interband between two thick dark bands (100B3-100B4-5) showed fluorescence. These data support previous suggestions indicating a substantial contribution of transcriptional products from small puffs and interbands to the whole transcriptional system of polytene chromosomes.

Animals↗
PubMed1985

Locations of Z-DNA in polytene chromosomes.

In polytene chromosomes of Drosophila hydei and D. melanogaster, Z-DNA was identified in varying distribution after different conditions for fixation were used. When salivary glands were fixed and squashed in 50% acetic acid alone, Z-DNA was found in the less dense DNA regions, such as interbands, some puffs, and a few of the less dense bands. Prefixation that combined ethanol and acetic acid exposure led to prominent immunofluorescent staining of the bands, generally but not strictly correlating with the total DNA content. Separate exposure to ethanol and acetic acid did not cause this band to stain, but if residual ethanol was present after ethanol fixation, subsequent exposure to acid did cause it. Under the more selective acid fixation conditions, Z-DNA reactivity was seen in portions of certain ecdysone-inducible puffs in the induced but not in the resting state; in other inducible regions, the Z-DNA immunoreactivity was not changed on induction. Z-DNA was also identified in polytene chromosomes within isolated nuclei that had been frozen and fixed in ethanol without exposure to acid; this Z-DNA was present in regions of low DNA density.

Acetates↗
PubMed1984

Trypanosoma cruzi induces changes in the nucleic acids content of host Hela cells "in vitro".

The nucleic acid content of parasitized, non-parasitized Hela, cells, infected with metacyclic forms of Trypanosoma cruzi, was measured during 7 days of parasitization by means of histochemical techniques. Hela cells were first exposed to the parasite for 12 hrs. and then parasites were removed from the culture medium. Measurements of nuclear RNA + DNA content indicate that the three types of cells behave during 7 days of subsequent culture as three different populations. Similar results were obtained when only nuclear DNA was determined. DNA of parasitized cells increased dramatically compared to control and non-parasitized cells. This increase however was not observed in cells derived from non-parasitized cells, which were infected with trypomastigotes from the first parasitization cycle.

Animals↗
PubMed1983

Fractionation by micrococcal nuclease digestion of Drosophila embryo chromatin: isolation of a fraction enriched in two major nonhistone proteins.

Limited digestion of Drosophila melanogaster embryo nuclei with mitochondrial nuclease, followed by selective solubilization in 0.1 M NaCl, yields a soluble nucleoprotein fraction (S3) enriched in two dominant protein bands of apparent molecular weight of 44000 and 48000. The analysis of the nucleosome monomer and multimer peaks, separated on sucrose gradients after slight digestion with micrococcal nuclease, shows that these proteins are associated with chromatin subunits, and that they are principally found in the subnucleosome region of fraction S3. This doublet is tentatively identified as a member of the noncanonical HMG of Drosophila. The thermal denaturation and the circular dichroism spectra of the fraction soluble in 0.1 M NaCl (S3) and insoluble fraction (P3) show that both fractions are also structurally different.

Animals↗
PubMed1982

In situ immunofluorescent visualization of chromosomal transcripts in polytene chromosomes.

The induction and distribution of chromosomal transcripts in the polytene chromosomes of D. melanogaster and D. hydei has been investigated by indirect immunofluorescence using an antiserum directed against DNA/RNA hybrids. The fluorescence was intense and occurred in most of the chromosomal subdivisions when the chromosomes were exposed to denaturing conditions and then allowed to reanneal. The extent of hybrid formation depended both on the extent of DNA denaturation and on the maintenance of RNA integrity. Fluorescence was absent from chromosomes treated with pancreatic RNase before denaturation. The velocity of the chromosomal DNA/RNA hybridization reaction and the effects of the initiation inhibitor of RNA synthesis, DRB, suggest that in order to hybridize the RNA has to be located in its transcriptional compartment. Even though overall patterns of fluorescence seem to be similar during a developmental stage, variations were observed, particularly some correlated with puff induction after ecdysone stimulation.

Animals↗
PubMed1982

[Glutamate dehydrogenase from rat brain. Properties of the enzyme when acting in the direction of glutamate degradation].

Several aspects on regulation of rat brain glutamate dehydrogenase when the enzyme catalyses the reaction of glutamate degradation have been studied. The 2-oxo-glutarate is a competitive inhibitor against glutamate and NADH competes with NAD. The enzyme seems to have three sites of binding for glutamate, two of them bind the alpha and gamma carboxylic groups and the other the NH2-group of glutamate. Between the binding of two -COO- groups, the site on the enzyme which binds the gamma -COO- group of glutamate seems to be more important than the alpha one.

Allosteric Regulation↗
PubMed1982

[Regulation of transcription in eukaryotic cells: chromosomal transcription].

In situ hybridization of the endogenous chromosomal RNA to the chromosomal DNA allowed us to detect that most of the subregions of the salivary gland polytene chromosomas of Drosophila melanogaster transcribe RNA although at different rates. The DNA melting curves of two chromosomal subregions showed that there should be some correlation between the rate of transcription and the macromolecular architecture of the nucleoprotein.

Animals↗
PubMed1981

Isolation of a structural gene mapping to subregions 63F of Drosophila melanogaster and 90B of D. hydei polytene chromosomes.

We have isolated by molecular cloning techniques a structural gene that maps to subregion 63F of Drosophila melanogaster chromosome 3L. This locus being one of the early chromosomal targets for ecdysone stimulation, may be induced to puff by the hormone. The gene is on a plasmid vector and it has been designated as pDm 63F. This recombinant molecule also maps to the early ecdysone inducible subregion 90B of Drosophila hydei chromosome 4. The cytological inspection of large number of chromosomal sets after in situ hybridization of the cloned DNA, locates the cloned sequence between bands 63F 2-4 according to Bridges map. Similarly, in Drosophila hydei the cloned DNA maps between subdivisions 90B 2-4 according to Berendes' map. In situ hybridization of the pDm 63F cloned DNA, directed to the nascent RNA rather than to the DNA, shows two to three times more silver grains over the corresponding regions when puffed than in the resting stage. There are however quantitative differences attending to the transcriptional activity of homologous loci in both species. By RNA excess hybridization we have found that the cellular concentration of the 63F cloned mRNA is bout 2 times higher in hormone stimulated total larval tissues than in non-stimulated ones.

Animals↗