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Biomedical subjects

C Ramos

Publications and source records attributed to C Ramos.

At least 145 records · Page 8Linked to original sources
PubMed1994

The behavior of bacteria designed for biodegradation.

Mineralization of organic molecules by microbes is essential for the carbon cycle to operate. The massive mobilization of compounds stored in natural resources, or the introduction of xenobiotics into the biosphere, leads to unidirectional fluxes, which result in the persistance of a number of chemicals in the biosphere, and thus constitute a source of pollution. Molecular biology offers the tools to optimize the biodegradative capacities of microorganisms, accelerate the evolution of "new" activities, and construct totally "new" pathways through the assemblage of catabolic segments from different microbes. Although the number of genetically engineered microbes (GEMs) for potential use in biodegradation is not large, these recombinant microbes function in microcosms according to their design. The survival and fate of recombinant microbes in different ecological niches under laboratory conditions is similar to what has been observed for the unmodified parental strains. rDNA, both on plasmids and on the host chromosome, is usually stably inherited by GEMs. The potential lateral transfer of rDNA from the GEMs to other microbes is significantly diminished, though not totally inhibited, when rDNA is incorporated on the host chromosome. The behavior and fate of GEMs can be predicted more accurately through the coupling of regulatory circuits that control the expression of catabolic pathways to killing genes, so that the GEMs survive in polluted environments, but die when the target chemical is eliminated.

Bacteria↗
PubMed1994

Cardiac development in the dogfish (Scyliorhinus canicula): a model for the study of vertebrate cardiogenesis.

We have studied the cardiac development of the dogfish (Scyliorhinus canicula) in six serially sectioned embryos ranging from 14 to 40 mm in total length. Our preliminary results show some significant similarities with the cardiac development of higher vertebrates, in spite of about 400 millions years of divergent evolution. The dogfish cardiac tube is composed of endocardium and myocardium separated by a thick layer of cardiac jelly. Large clefts form in the atrial and ventricular myocardium before the cardiac jelly disappears. These clefts seem to be related to the origin of the intertrabecular sinusoids. Myocardial pores in the sinus venosus and atrium might allow the flow of some cardiac jelly to the subepicardial space. Two atrioventricular and three conal endocardial cushions are formed by epithelial-mesenchymal transformation. The atrioventricular and conal valves seem to develop from these cushions, while the sinoatrial valve seems to derive from two transversal infoldings of the cardiac wall. The epicardium forms from mesothelial cells proceeding first from the liver and sinus venosus lining, and then from the developing septum transversum. A subepicardial space appears early and it is populated by mesenchymal cells which seem to proceed at least partly from the epicardium. These subepicardial cells apparently form capillary-like structures some of which coalesce in large annular veins around the atrioventricular and conoventricular grooves. The veins connect with ventricular sinusoids and the sinus venosus lumen.

Animals↗
PubMed1994

[Interphasic in situ fluorescent hybridization (FISH) in 4 cases of myeloid neoplasias with chromosome 7 changes].

The use of FISH as a complement to the conventional cytogenetic studies is of great help in attaining a better characterisation of the chromosome anomalies present in haematological malignancies, such as chromosome 7 monosomy. A study was carried out in three cases of acute non-lymphoblastic leukaemia and a myelodysplastic syndrome with chromosome 7 involvement, as shown by conventional cytogenetic studies. The Cocktail probe for chromosome 7 (DZ1, DZ2) was used (Oncor) in performing in situ hybridation. A monosomic cell line for chromosome 7, undetected by conventional techniques, was disclosed with this procedure in two of the cases. In the remaining two patients the monosomy of chromosome 7 was confirmed, although at percentages different from those attained with the conventional methods.

Chromosomes, Human, Pair 7↗
PubMed1994

[Campylobacter jejuni and HIV infection].

OBJECTIVE: To evaluate the characteristics of the Campylobacter jejuni infection in HIV positive patients. DESIGN: We report all cases appeared in our hospital between September 1991 and October 1992 with: HIV infection, chronic diarrhoea and C. jejuni in stool culture. Epidemiologic factors, other opportunist infections, immunologic situation, clinical symptomatology, antibiotic sensitivity and evolution are recorded. RESULTS: Six patients, 4 men and 2 women, with an average age of 38 years were recorded. They have different risk factors (drug abusers, sexual behaviour and haemophilia). Chronic liver disease and other opportunist infections of the gastrointestinal tract were the most important facts in past history. CD4 count were directly related with the severity of the illness. Quantitative or qualitative disorders of B lymphocytes or immunoglobulins were not found. All of term suffered from chronic diarrhoea with fever in four of them and bacteremia in 2 patients. First generation cephalosporins resistance in one occasion. A good evolution occurred in 3 patients, another had a relapse and bacteremia appeared in 2 patients whose CD4 count were lower of 100/mm3, have AST, ALT changes and other concomitant gastrointestinal infections. CONCLUSION: C. jejuni infection of the gastrointestinal tract results in chronic diarrhoea with a higher incidence than expected in HIV positive patients. The severity is directly related with CD4 count, and the existence of concomitants infections of the gastrointestinal tract or chronic liver disease. Antibiotic resistance to macrolide is possible, especially in chronic and severe forms.

AIDS-Related Opportunistic Infections↗
PubMed1994

Synaptophysin and neurofilament expression in neurons infected with dengue virus.

The expression of two genes encoding the neuronal specific proteins synaptophysin and high molecular weight neurofilaments was investigated in primary cell cultures of embryonic mouse brain infected with dengue virus type 2, using immunocytochemistry and Western blot analysis with monoclonal antibodies. The viral infection leads to a 20-fold induction in the expression of the mentioned synaptogenesis-related proteins. These results suggest a correlation between virus infection and neuropathology of immature neurons in vivo.

Animals↗
PubMed1993

T-DNA transfer to maize cells: histochemical investigation of beta-glucuronidase activity in maize tissues.

Agrobacterium tumefaciens is routinely used to engineer desirable genes into dicotyledonous plants. However, the economically important graminaceous plant maize is refractory to tumor induction by inoculation with virulent strains of A. tumefaciens. Currently, the only clearcut evidence for transferred DNA (T-DNA) transport from Agrobacterium to maize comes from agroinfection. To study T-DNA transfer from Agrobacterium to maize cells in a virus-free system, we used here the beta-glucuronidase (GUS; EC 3.2.1.31) gene as a marker. GUS expression was observed with high efficiency on shoots of young maize seedlings after cocultivation with Agrobacterium carrying the GUS gene. Agrobacterium virulence mutants, incapable of transferring T-DNA to dicot tissue, were shown to be deficient in eliciting GUS expression in maize. Hence, expression of the T-DNA-located GUS gene in maize cells is strictly dependent on Agrobacterium-mediated DNA transfer. Histochemical staining of maize shoots revealed GUS expression located mainly in the leaves and the coleoptile.

Journal Article↗
PubMed1993

Isolation of a mutant allele that deregulates the threonine biosynthesis in Saccharomyces cerevisiae.

We have cloned the yeast allele HOM3-R2, that codes for a mutant aspartate kinase which is insensitive to feedback inhibition by threonine, by gap-repair. A strain carrying this allele in a multicopy plasmid, or integrated into the genome, accumulates 14-times and 8-times more threonine than the wild-type, respectively. The sequence of the mutant allele differs from that of the wild-type in a single base pair change, namely a G by an A, at position 1355 in the open reading frame. The fact that the presence of this mutant allele in a cell induces threonine overproduction points to aspartate kinase as the key enzyme in the regulation of threonine biosynthesis in yeast.

Alleles↗
PubMed1993

Comparison between lung parenchyma and bronchoalveolar lavage collagenolytic activity.

We have evaluated, in an experimental model of silicosis in guinea pigs, if the presence of collagenolytic activity in bronchoalveolar lavage (BAL) fluid reflects the collagen catabolism in lung parenchyma. We measured simultaneously BAL collagenase activity, using as substrate [3H]type I collagen, and lung collagenolytic activity by the tissue pellet assay. Animals (n = 30) were instilled intratracheally with 50 mg of quartz DQ-12 and sacrificed 15, 30, and 60 days after silica administration. Guinea pigs instilled with saline solution were used as controls. Our results showed that lung parenchymal collagenolytic activity was present in all experimental and normal guinea pigs. There were no statistical differences between silicotic and normal animals at 15 and 30 days. At 60 days, however, a significant decrease in tissue collagenolytic activity was observed in silicotic animals (161 +/- 100 vs. 400 +/- 152 units of collagenase activity; p < 0.001). In contrast, BAL collagenolytic activity was revealed only in 7 of 10 silicotic animals at 15 days and 30 days, and in 4 of 10 at 60 days. Normal guinea pigs did not exhibit BAL collagenase activity. BAL and tissue collagenase activity from each experimental animal were analyzed by straight line regression and no significant relationship was observed (r = 0.082; p = 0.87). This suggests that BAL collagenolytic activity does not reflect lung tissue collagen turnover.

Animals↗
PubMed1993

Genetic analysis of the virD operon of Agrobacterium tumefaciens: a search for functions involved in transport of T-DNA into the plant cell nucleus and in T-DNA integration.

The transferred DNA (T-DNA) is transported from Agrobacterium tumefaciens to the nucleus and is stably integrated into the genome of many plant species. It has been proposed that the VirD2 protein, tightly attached to the T-DNA, pilots the T-DNA into the plant cell nucleus and that it is involved in integration. Using agroinfection and beta-glucuronidase expression as two different very sensitive transient assays for T-DNA transfer, together with assays for stable integration, we have shown that the C-terminal half of the VirD2 protein and the VirD3 protein are not involved in T-DNA integration. However, the bipartite nuclear localization signal, which is located within the C terminus of the VirD2 protein and which has previously been shown to be able to target a foreign protein into the plant cell nucleus, was shown to be required for efficient T-DNA transfer. virD4 mutants were shown by agroinfection to be completely inactive in T-DNA transfer.

Agrobacterium tumefaciens↗
PubMed1993

[Ulcerative colitis and HIV infection].

UNLABELLED: FUNDAMENTAL: The difficulties to raise to a correct diagnosis in patients with human immunodeficiency virus infection and diarrhea, and the few cases reported of ulcerative colitis in the context of HIV infection. OBJECTIVE: Description of 2 cases of ulcerative colitis in patients with HIV infection and the possibility of immunopathogenic relationship between them. MATERIAL AND METHODS: The clinic history of the patients, the anatomopathological diagnosis after the colon biopsy and the determination of CD4 cells. RESULTS: In case 1 the low level of CD4 cells didn't stop the aggressivity of ulcerative colitis. However, in both cases there was a good evolution of colitis after treatment although AIDS. CONCLUSION: It is necessary to study more cases of inflammatory bowel disease in patients with HIV infection to determine the influence of the level of CD4 cells in the enteropathy's evolution.

Adult↗
PubMed1993

[The intracellular increase of ionized calcium depends on factors present in the blood of patient with preeclampsia].

In previous works our group has demonstrated that intracellular concentration of calcium ionized is greater in patients with pre-eclampsia than in normotense pregnant patients, and that these figures correlate with arterial pressure. Both indicators become normal six weeks after delivery. With the idea of searching the possible participation of soluble factors in the plasma, in increasing free, intracellular calcium, eight pre-eclamptic patients, were studied; the patients were diagnosed by the criteria of the American College of Gynecologists and Obstetricians. As a control group, eight normotense pregnant patients, were included; they were paired by age, chronological and gestational. To measure transmembrane calcium flow, platelets from healthy males, were used. The platelets were incubated during 0, 15, 30 and 60 minutes in sera of pre-eclamptic patients, or of normotensive pregnant patients, marked with Ca. The differences in calcium transportation, were evaluated with variance analysis of Kruskall Wallis. Calcium transportation was greater when the platelets were incubated in pre-eclamptic patients sera, Md = 1.475 +/- 0.311 nanomoles than when were incubated in normotensive women sera, Md = 0.9725 +/- 0.58 nanomoles, p < 0.02. This finding suggests that in pre-eclamptic patients serum, exists some factor that facilitates the entrance of calcium to the cell, that provokes an increase in free calcium concentration, and it participates in the gestational hypertension.

Adult↗
PubMed1992

Gonadal hormones determine sex differences in timing of incubation by doves.

Male and female ring doves express a sexually dimorphic pattern of incubation. The dimorphism is temporal rather than motoric. The male incubates for a block of time in the middle of the day and the female incubates the rest of the time. The present study explored the role of gonadal hormones in the control of the temporal dimorphism. Female-female pairs incubated their eggs, but it could not be predicted which of the partners would be sitting on the nest at any given time. Male-male pairs did not incubate and instead destroyed the nests that were provided and displayed aggressive behavior. Some intact males incubated when paired with gonadectomized males, although the castrates tended to ignore the nest. In contrast, when castrated birds were given heterotypical hormonal replacement therapy, they and their same-sex partners incubated the eggs that had been provided, with the gonadectomized birds sitting at a time appropriate to the hormonal state. The results indicate that gonadal hormones influence not only the expression of incubation behavior, but also its phase and duration.

Animals↗
PubMed1992

Overproduction of threonine by Saccharomyces cerevisiae mutants resistant to hydroxynorvaline.

In this work, we isolated and characterized mutants that overproduce threonine from Saccharomyces cerevisiae. The mutants were selected for resistance to the threonine analog alpha-amino-beta-hydroxynorvalerate (hydroxynorvaline), and, of these, the ones able to excrete threonine to the medium were chosen. The mutant strains produce between 15 and 30 times more threonine than the wild type does, and, to a lesser degree, they also accumulate isoleucine. Genetic and biochemical studies have revealed that the threonine overproduction is, in all cases studied, associated with the presence in the strain of a HOM3 allele coding for a mutant aspartate kinase that is totally or partially insensitive to feedback inhibition by threonine. This enzyme seems, therefore, to be crucial in the regulation of threonine biosynthesis in S. cerevisiae. The results obtained suggest that this strategy could be efficiently applied to the isolation of threonine-overproducing strains of yeasts other than S. cerevisiae, even those used industrially.

Aspartate Kinase↗
PubMed1992

Production of collagenase and tissue inhibitor of metalloproteinases by fibroblasts derived from normal and fibrotic human lungs.

Several experiments have demonstrated low collagenolytic activity during the development of pulmonary fibrosis. In order to determine if fibroblasts play a role in this alteration, procollagenase and tissue inhibitor of metalloproteinases (TIMP) were quantified in fibroblasts derived from 12 human lung specimens (normal = 6, idiopathic pulmonary fibrosis [IPF] = 6). Under basal conditions, three cell strains from normal and three from fibrotic lung specimens did not synthesize collagenase and a similar number of normal and IPF-derived fibroblast strains produced the enzyme. However, the rate of enzyme synthesis among normal and fibrotic collagenase producing fibroblasts exhibited significant differences. Thus, whereas normal fibroblasts produced more than 300 ng/ml, fibrotic lung fibroblasts secreted approximately half of this amount (115 +/- 67 ng/ml). Phorbol myristate acetate (PMA) enhanced collagenase production in all of the 12 lung fibroblast lines tested. In four IPF fibroblasts, PMA increased collagenase secretion close to those of normal stimulated lung fibroblasts; however, a lower induction was observed in cell strains from two fibrotic lung specimens. There was a wide variation in TIMP production both in normal and fibrotic lung fibroblasts, and no statistically significant difference was observed. Under basal conditions, TIMP levels ranged from 329 to 16,911 ng/ml in normal lung cells, and from 377 to 17,557 in fibrotic lung fibroblasts. PMA induced a severalfold increase in all cell lines. These results suggest that there are subpopulations of lung fibroblasts with different potential to produce collagenase and TIMP in vitro, and that the predominance of low collagenase-producing subsets may contribute to the development of fibrosis.

Adult↗
PubMed1992

Collagenase-inhibitory activity in deposit and resorption phases of guinea pig carrageenin granuloma.

The levels of collagenase inhibitor, both free and bound to metalloproteinases, were evaluated at 7 days [deposit phase (DP)] and 14 days [resorptive phase (RP)] of evolution of the subcutaneous carrageenin-induced granuloma in the guinea pig. The level of free collagenase inhibitor was considerably higher in the supernatant of DP granulomas (7.95 +/- 1.53 U/mg protein) as compared to that of RP granulomas (2.53 +/- 0.41 U/mg protein). When the samples were heated at acid pH to release the inhibitor from metalloproteinase-inhibitor complexes, free inhibitor was recovered in both phases. However, the units of recovered collagenase inhibitor were several fold higher in all RP granulomas in comparison with DP granulomas (6.88 +/- 2.46 vs 1.5 +/- 0.53). Therefore, DP and RP tissues exhibited similar total amount of tissue inhibitor. By HPLC, collagenase inhibitor activity was localized in a fraction consistent with the size of TIMP. These results suggest a different balance of collagenase and collagenase inhibitor during the evolution of the granuloma; an excess of inhibitor over metalloproteinases appears to predominate during the phase of collagen accumulation contrasting with an inverse situation when the granuloma is healing.

Animals↗
PubMed1992

Structure and expression of the human pseudoautosomal gene XE7.

The human pseudoautosomal region comprises a 2.6 megabase segment of the distal short arms of the X and Y chromosomes. Complete DNA sequence homology between the two sex chromosomes is found in this region, and is believed to be important in mediating X-Y pairing in male meiosis. The only known functional genes in this region are MIC2 and CSF2R; in addition a pseudoautosomal location has been proposed for a genetic locus controlling stature. Here we report the structure of a recently identified pseudoautosomal gene, XE7, and its expression in human tissues. Analysis of genomic and cDNA clones shows that alternative RNA splicing results in the production of two predicted protein isoforms, one containing 385 amino acids and the other with 695 residues. The smaller polypeptide is a truncated version of the larger, and results from the inclusion of a cassette exon that introduces an in-frame stop codon into the mRNA. The XE7 gene appears to be ubiquitously expressed, and the production of both protein isoforms is predicted in each of several tissues examined.

Alternative Splicing↗