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Biomedical subjects

S Gálvez

Publications and source records attributed to S Gálvez.

At least 19 recordsLinked to original sources
PubMed2000

Molecular Mechanisms in Root Nodule Development.

Under nitrogen-limiting conditions, bacteria from the family Rhizobiaceae establish a symbiosis with leguminous plants to form nitrogen-fixing root nodules. These organs require a coordinated control of the spatiotemporal expression of plant and bacterial genes during morphogenesis. Both plant and bacterial signals are involved in this regulation in the plant host. Plant genes induced during nodule development, the so-called nodulin genes, have been extensively characterized. Products of several of these genes show homologies to known regulators of signal transduction pathways in other plant or animal systems. Initial functional analysis of the molecular mechanisms implicated in nodulation have been undertaken using model legumes. Insertion mutagenesis and transgenic technologies to modify nodulin gene expression, as well as pharmacologic approaches, have been used to analyze molecular mechanisms involved in morphologic responses induced by the bacterial symbiont in the plant. G protein-mediated transduction mechanisms have been implicated, and the nin transcription factor appears to be required for early steps in nodule development. ENOD40, a gene coding for an RNA that contains only short ORFs, seems to be closely tied to nodule primordium formation. In addition, a vascular-associated Krüppel-like transcription factor and small Rab type G-proteins affect bacteroid differentiation and the function of the nitrogen-fixing zone. These initial results presage a wealth of information that will be obtained from the application of genomic approaches to legumes.

Journal Article↗
PubMed2000

Oxygen regulation of a nodule-located carbonic anhydrase in alfalfa.

Control of the permeability to oxygen is critical for the function of symbiotic nitrogen fixation in legume nodules. The inner cortex (IC) seems to be a primary site for this regulation. In alfalfa (Medicago sativa) nodules, expression of the Msca1 gene encoding a carbonic anhydrase (CA) was previously found to be restricted to the IC. We have now raised antibodies against recombinant Msca1 protein and used them, together with antibodies raised against potato leaf CA, to demonstrate the presence of two forms of CA in mature nodules. Each antibody recognizes a different CA isoform in nodule tissues. Immunolocalization revealed that leaf-related CAs were localized primarily in the nitrogen-fixing zone, whereas the Msca1 protein was restricted exclusively to the IC region, in indeterminate and determinate nodules. In alfalfa nodules grown at various O(2) concentrations, an inverse correlation was observed between the external oxygen pressure and Msca1 protein content in the IC, the site of the putative diffusion barrier. Thus Msca1 is a molecular target of physiological processes occurring in the IC cells involved in gas exchange in the nodule.

Blotting, Western↗
PubMed1999

Are isocitrate dehydrogenases and 2-oxoglutarate involved in the regulation of glutamate synthesis?

In plants, nitrogen assimilation into amino acids relies on the availability of the reduced form of nitrogen, ammonium. The glutamine synthetase-glutamate synthase pathway, which requires carbon skeletons in the form of 2-oxoglutarate, achieves this. To date, the exact enzymatic origin of 2-oxoglutarate for plant ammonium assimilation is unknown. Isocitrate dehydrogenases synthesize 2-oxoglutarate. Recent efforts have concentrated on evaluating the involvement of different isocitrate dehydrogenases, distinguished by co-factor specificity and sub-cellular localization. Furthermore, several observations indicate that 2-oxoglutarate is likely to be a metabolic signal that regulates the coordination of carbon:nitrogen metabolism. This is discussed in the context of recent advances in bacterial signalling processes.

Journal Article↗
PubMed1998

Mitochondrial localization of a NADP-dependent [corrected] isocitrate dehydrogenase isoenzyme by using the green fluorescent protein as a marker.

In this work, we describe the isolation of a new cDNA encoding an NADP-dependent isocitrate dehydrogenase (ICDH). The nucleotide sequence in its 5' region gives a deduced amino acid sequence indicative of a targeting peptide. However, even if this cDNA clearly encodes a noncytosolic ICDH, it is not possible to say from the targeting peptide sequence to which subcellular compartment the protein is addressed. To respond to this question, we have transformed tobacco plants with a construct containing the entire targeting signal-encoding sequence in front of a modified green fluorescent protein (GFP) gene. This construct was placed under the control of the cauliflower mosaic virus 35S promoter, and transgenic tobacco plants were regenerated. At the same time, and as a control, we also have transformed tobacco plants with the same construct but lacking the nucleotide sequence corresponding to the ICDH-targeting peptide, in which the GFP is retained in the cytoplasm. By optical and confocal microscopy of leaf epiderm and Western blot analyses, we show that the putative-targeting sequence encoded by the cDNA addresses the GFP exclusively into the mitochondria of plant cells. Therefore, we conclude that this cDNA encodes a mitochondrial ICDH.

Amino Acid Sequence↗
PubMed1998

Eucalypt NADP-dependent isocitrate dehydrogenase. cDNA cloning and expression in ectomycorrhizae.

NADP-dependent isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots of Eucalyptus globulus subsp. bicostata ex Maiden Kirkp. during colonization by the ectomycorrhizal fungus Pisolithus tinctorius Coker and Couch. To investigate the regulation of the enzyme expression, a cDNA (EgIcdh) encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The putative polypeptide sequence of EgIcdh showed a high amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH protein lacks an amino-terminal targeting sequence and shows highest similarity to plant cytosolic ICDHs, it probably represents a cytoplasmic isoform. RNA analysis showed that the steady-state level of EgIcdh transcripts was enhanced nearly 2-fold in ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity. Indirect immunofluorescence microscopy indicated that NADP-ICDH was preferentially accumulated in the epidermis and stele parenchyma of nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of cytosolic NADP-ICDH in ectomycorrhizae is discussed.

Amino Acid Sequence↗
PubMed1996

Identification of a tobacco cDNA encoding a cytosolic NADP-isocitrate dehydrogenase.

A cDNA which encodes a specific member of the NADP-dependent isocitrate dehydrogenase (ICDH) multi-isoenzyme family has been isolated from a tobacco cell suspension library, and the expression pattern of ICDH transcripts examined in various plant tissues. To assign this cDNA to a specific ICDH isoenzyme, the major, cytosolic ICDH isoenzyme of tobacco leaves (ICDH1) was purified to homogeneity and its N-terminus as well as several tryptic peptides, representing 30% of the protein, were sequenced. The comparison of these amino acid sequences with the deduced protein sequence of the cDNA confirmed that this clone encodes for ICDH1. The total ICDH specific activity and protein content were higher in vascular-enriched tobacco leaf tissue than in deveined (depleted in midrib and first-order veins) leaves. Taking advantage of antibodies raised against either ICDH1 or the chloroplastic ICDH2 isoenzyme from tobacco cell suspensions, an immuno-cytochemical approach indicated that the ICDH1 isoenzyme, located in the cytosolic compartment of tobacco leaf cells, is responsible for this expression pattern. This observation was confirmed by northern blot analyses, using a specific probe obtained from the 3' non-coding region of the ICDH1 cDNA. A comparison of ICDH protein sequences shows a large degree of similarity between eukaryotes (> 60%) but a poor homology is observed when compared to Escherichia coli ICDH (< 20%). However, it was found that the amino acids implicated in substrate binding, deduced from the 3-dimensional structure of the E. coli NADP-ICDH, appear to be conserved in all the deduced eukaryotic ICDH proteins reported until now.

Amino Acid Sequence↗
PubMed1995

Purification and characterization of a fully active recombinant tobacco cytosolic NADP-dependent isocitrate dehydrogenase in Escherichia coli: evidence for a role for the N-terminal region in enzyme activity.

The recently isolated full-length NADP-dependent isocitrate dehydrogenase (ICDH) cDNA encoding the tobacco cytosolic isoenzyme has been cloned into the expression vector pET8c and used to transform Escherichia coli strain BL21 (DE3). The recombinant protein was purified to electrophoretic homogeneity and used to raise polyclonal antibodies. Its kinetic properties were found to be identical to those of the cytosolic ICDH isoenzyme purified from tobacco cell cultures. The recombinant and the endogenous bacterial ICDH could be easily distinguished by their different behaviors during anion-exchange column chromatography and immunological response. An incomplete ICDH-encoding cDNA clone, encoding a protein lacking the first 36 amino acids at the N-terminus, was cloned into the expression vector pKK233-2 and used to transform ICDH-lacking E. coli cells (strain 2004). The truncated, recombinant ICDH produced by the bacteria was found to be inactive.

Amino Acid Sequence↗
PubMed1995

Cloning and expression analysis of the cytosolic NADP(+)-dependent isocitrate dehydrogenase from potato. Implications for nitrogen metabolism.

A full-length cDNA (icdh-1) encoding a cytosolic NADP(+)-dependent isocitrate dehydrogenase (ICDH-1) from potato (Solanum tuberosum L.) has been isolated. Analysis of the deduced protein sequence revealed considerable homologies with the corresponding proteins from other eukaryotes such as tobacco, alfalfa, soybean, cattle, pig, and yeast. The gene was transcribed in all tissues tested, with the highest amount of icdh-1 transcript being found in green tissues, in flowers, and in roots. In leaves, enzyme activities were dependent on the age, with fully mature leaves showing the highest level of RNA expression and enzyme activity. This observation may indicate that NADP(+)-dependent ICDH is not only involved in amino acid biosynthesis via the glutamine synthetase/glutamine oxoglutarate aminotransferase cycle but also in cycling, redistribution, and export of amino acids. The latter assumption has been strengthened by our finding of a preferential expression of NADP(+)-dependent ICDH in leaf veins. Under in vivo conditions, the expression pattern paralleled the enzyme activity, indicating coarse control on the RNA level. Experiments carried out with detached leaves revealed an influence of light, nitrate, and sucrose on icdh-1 transcript levels and in some cases also on NADP(+)-dependent ICDH activity. In darkness, nitrate or sucrose induced icdh-1 mRNA expression. Leaves kept under starvation conditions exhibited a decrease of their protein content, whereas icdh-1 expression and ICDH activity increased significantly.

Amino Acid Sequence↗
PubMed1993

[APS-2: comparative study on populations of critical patients in Chile, United States and New Zealand].

Between 1988 and 1991, the Acute Physiologic Score (APS-2) was applied to 1000 critically ill patients admitted to an intensive care unit of a general hospital in Chile. Its predictive capacity was assessed and compared with two series from United States and New Zealand. The mean admission APS-2 in Chilean patients was 12.8 and there was a progressive increase in mortality with elevating scores; no patient with an APS-2 over 30 survived. Admission APS-2 scores in USA and New Zealand were 10.7 and 14.2. Overall mortality in Chilean patients was 28%, compared with 12% in USA and 15% in New Zealand. Within different score ranges, mortality was higher in Chilean patients than those from USA or New Zealand. It is concluded that the assessment of admission APS-2 score underlying diagnosis, physiologic age and previous health status of a patient may help to predict the success of intensive care.

Adult↗
PubMed1992

Familial Creutzfeldt-Jakob disease in Chile is associated with the codon 200 mutation of the PRNP amyloid precursor gene on chromosome 20.

We have found the codon 200Lys mutation in 6 Chilean CJD families, including a family in the rural case cluster in Chillán. Thus, all 3 of the known clusters of CJD, in Slovakia, Libyan-born Israeli Jews, and Chile, are linked to the presence of the same mutation. The phenotypic features of the disease in these families are similar to those reported for other clustered or individual families elsewhere in the world. The heterogeneous genetic composition of the Chilean population interpreted in light of historical migration patterns suggests that the mutation may have entered Chile by Jewish emigration from Spain.

Adult↗
PubMed1991

Creutzfeldt-Jacob disease associated with the PRNP codon 200Lys mutation: an analysis of 45 families.

200Lys mutation in the human PRNP coding region has been identified in 45 of the 55 CJD-affected families thus far presented to our NIH laboratory. These codon 200Lys families have a total of 87 patients, and originate from 7 different countries: Slovakia, Poland, Germany, Tunisia, Greece, Libya, and Chile. Forty-seven patients were neuropathologically verified, and brain tissue from 14 patients transmitted disease to experimental primates. The mutation was found by direct sequencing in 4 patients, and it was detected by restriction endonuclease analysis with BsmA 1 and/or the single nucleotide extension reaction in 36 other patients and 45 of 109 first degree relatives (1 parent, 14 siblings, and 30 children). The mutation is associated with all known geographical clusters of CJD (Slovakia, Libyan Jews, Chile) in which the annual mortality rate is tens or hundreds of times higher than the world average of 1 per million. All patients originating from the cluster areas carried the mutation, but it was seen in only 1 of 103 unrelated control individuals from the same areas, and in none of 102 controls from other areas, indicating a strong association between the mutation and disease. The penetrance of the mutation was estimated to be 0.56. Branches of some families migrating from cluster areas to other countries continue to have CJD over several generations, suggesting that CJD in these families is a genetic disorder, in which the 200Lys mutation is responsible for the disease.

Africa↗
PubMed1990

[Prolonged hospitalization in the intensive care unit: a worthless effort?].

Hospitalization of a patient in critical care unit for over a month is exceptional and often raises the question of an irreversible disease process. From 2715 consecutive patients admitted to an intensive care unit in the last 4 years we identified 20 patients remaining in the unit for over a month. Acute pancreatitis and septic abortion were the most common diagnosis at admission. Overall mortality in this series was 30%. None of the complications developing or the therapeutic procedures used in the first 3 weeks predicted the outcome. In contrast, the presence of respiratory failure, septic shock, requirement of ventilation or parenteral nutrition at day 30 was highly associated with mortality.

Adolescent↗
PubMed1985

Familial clustering of the ataxic form of Creutzfeldt-Jakob disease with Hirano bodies.

A family cluster of the ataxic form of Creutzfeldt-Jakob disease with one probable and two autopsy proven cases that occurred in a single generation between 1974 and 1982 is reported. The clinical characteristics of the cases are closely similar to those of kuru patients, with a fair correlation between the prominent truncal ataxia and the intense devastation of the cerebellar cortex most marked in the vermis. Pathologically, the marked hippocampal involvement rarely seen in typical transmissible Creutzfeldt-Jakob disease and the finding of Hirano bodies in the Ammon's horn without specific Alzheimer's senile changes are noteworthy features.

Caudate Nucleus↗
PubMed1984

Computed tomography findings in 15 cases of Creutzfeldt-Jakob disease with histological verification.

Computed tomography (CT) was normal in twelve of fifteen patients with definite Creutzfeldt-Jakob disease. In two patients CT showed mild sulcal widening, while marked ventricular enlargement and moderate cortical atrophy were seen in a patient who had both Creutzfeldt-Jakob disease and normal pressure hydrocephalus. No correspondence was observed between CT findings, severity of the clinical picture and postmorten gross brain examination. According to these results, a normal CT in a demented patient should suggest Creutzfeldt-Jakob disease. Conversely, CT is of value for the diagnosis of other potentially reversible illnesses clinically resembling Creutzfeldt-Jakob disease.

Adult↗
PubMed1983

Familial Creutzfeldt-Jakob disease in Chile.

Of the 87 cases of Creutzfeldt-Jakob disease (CJD) ascertained in Chile since 1931, 39 are familial accounting for 45% of all cases, and 25% of the 51 definite cases. There are 11 affected families with an average of 3.5 affected members per family, and a rate of occurrence consistent with autosomal dominant transmission. There is no evidence for maternal lineage, and age at death is not significantly different from that of sporadic cases. About half of the cases died around the same age, suggesting some form of vertical transmission. Three pairs of affected members in 3 different families died at the same time, possibly indicating common exposure to CJD agent. The study of absolute death intervals and temporal and spatial separations between affected members suggests minimum incubation periods ranging from 2 to 37 years, assuming case-to-case transmission. CJD occurring in a woman related by marriage to one of the affected families strongly argues for horizontal transmission. The high proportion of familial CJD observed in Chile is probably the result of both a genetically determined susceptibility to the CJD virus, and a high degree of case ascertainment. However, the present study leaves unanswered the mode of transmission of the agent within the affected families.

Adult↗
PubMed1980

Serial EEG findings in 27 cases of Creutzfeldt-Jakob disease.

Serial EEG examination was performed in a series of 27 cases of Creutzfeldt-Jakob disease observed in Chile in the period 1960 to 1977. The pattern of EEG disturbances is described in the different stages of the disease and compared with those previously reported. In the fully developed stage of the disease, 94% of the EEGs (25 of 27 patients) showed a characteristic periodic aspect. The progressive disappearance of the superficial periodic activity is tentatively explained in one patient submitted to stereo EEG.

Adult↗