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Biomedical subjects

C Vargas

Publications and source records attributed to C Vargas.

At least 55 records · Page 3Linked to original sources
PubMed1998

Cerebrospinal fluid levels of non-neurotransmitter amino acids in patients with Alzheimer's disease.

We measured the CSF levels of 21 and the plasma levels of 24 amino acids in 37 patients with Alzheimer's disease (AD) and in 32 matched controls. We used an ion-exchange chromatography method. When compared with controls, AD patients had lower CSF levels of phosphoserine, citrulline, alfa-aminobutyric acid, methionine, and ethanolamine; and higher CSF levels of threonine, serine, lysine, histidine and arginine. However, when expressed relative to CSF protein, CSF levels of serine, lysine, histidine, and arginine, were normal. AD patients had higher plasma levels of phosphoserine, threonine, citrulline, hydroxyproline, and proline; and lower plasma levels of alfa-aminobutyric acid, methionine, leucine and ethanolamine. The CSF/plasma ratios of phosphoserine, serine, citrulline, alfa-aminobutyric acid and arginine were significantly lower in AD patients than those of controls. CSF amino acid levels were not related with the duration and severity of the disease.

Aged↗
PubMed1998

Dissimilar effects of lithium and valproic acid on GABA and glutamine concentrations in rat cerebrospinal fluid.

1. This study compared the effects of the antimanic drugs, lithium and valproic acid, on GABA and glutamine CSF concentration and on head-shakes during hyponatremia. 2. Hyponatremic and normonatremic rats were treated with 2 mEq/kg lithium and 360 mg/kg valproic acid. Behavioral observation was conducted for 120 min after which blood and CSF collection were performed under anesthesia. 3. Peritoneal dialysis with glucose induced moderate hyponatremia and doubled glutamine CSF concentrations. Both lithium and valproic acid significantly increased GABA CSF levels in normonatremic and hyponatremic animals. Valproic acid induced head-shakes and increased CSF glutamine concentration. 4. The results suggest that both antimanic drugs have similar effects on GABA, but lithium is preferred if the increase in glutamine concentration poses a problem, either in the presence or absence of hyponatremia.

Animals↗
PubMed1998

Characterization of the genes for the biosynthesis of the compatible solute ectoine in the moderately halophilic bacterium Halomonas elongata DSM 3043.

The ectoine synthesis genes of the moderately halophilic bacterium Halomonas elongata DSM 3043 have been precisely located in a 2.8-kb EcoRI region of a cosmid clone previously isolated (CANOVAS, D., VARGAS, C., IGLESIAS-GUERRA, F., CSONKA, L. N., RHODES, D., VENTOSA, A., NIETO, J. J.: Isolation and characterization of salt-sensitive mutants of the moderate halophile Halomonas elongata and cloning of the ectoine synthesis genes. J. Biol. Chem. 272, 25794-25801, 1997). This region was sequenced and three open reading frames were found corresponding to the genes ectA (encoding the diaminobutyric acid acetyl transferase), ectB (encoding the diaminobutyric acid aminotransferase) and ectC (encoding the ectoine synthase). These three genes were able to restore the salt tolerance of two H. elongata mutants defective in the synthesis of ectoine (strains CHR62 and CHR63). However, the H. elongata ectoine synthesis genes did not confer to Escherichia coli the ability to synthesize ectoine. Transposon insertion in the salt-sensitive mutant strain CHR63 was exactly mapped within the ectC gene. Moreover, sequences homologous to the H. elongata ect region have been found in a number of moderately halophilic bacteria belonging to the genera Halomonas and Chromohalobacter.

Acetyltransferases↗
PubMed1998

Sulfation of nod factors via nodHPQ is nodD independent in Rhizobium tropici CIAT899.

A cosmid from the Rhizobium tropici CIAT899 symbiotic plasmid, containing most of the nodulation genes described in this strain, has been isolated. Although this cosmid does not carry a nodD gene, it confers ability to heterologous Rhizobium spp. to nodulate R. tropici hosts (Phaseolus vulgaris, Macroptilium atropurpureum, and Leucaena leucocephala). The observed phenotype is due to constitutive expression of the nodABCSUIJ operon, which has lost its regulatory region and is expressed from a promoter present in the cloning vector. Thin-layer chromatography (TLC) analysis of the Nod factors produced by this construction shows that it is still capable of synthesizing sulfated compounds, suggesting that the nodHPQ genes are organized as an operon that is transcribed in a nodD-independent manner and is not regulated by flavonoids.

Bacterial Proteins↗
PubMed1998

Synthesis of glycine betaine from exogenous choline in the moderately halophilic bacterium halomonas elongata

The role of choline in osmoprotection in the moderate halophile Halomonas elongata has been examined. Transport and conversion of choline to betaine began immediately after addition of choline to the growth medium. Intracellular accumulation of betaine synthesized from choline was salt dependent up to 2.5 M NaCl. Oxidation of choline was enhanced at 2.0 M NaCl in the presence or absence of externally provided betaine. This indicates that the NaCl concentration in the growth medium has major effects on the choline-betaine pathway of H. elongata.

Journal Article↗
PubMed1997

Isolation and characterization of salt-sensitive mutants of the moderate halophile Halomonas elongata and cloning of the ectoine synthesis genes.

The moderate halophile Halomonas elongata Deustche Sammlung für Mikroorganismen 3043 accumulated ectoine, hydroxyectoine, glutamate, and glutamine in response to osmotic stress (3 M NaCl). Two Tn1732-induced mutants, CHR62 and CHR63, that were severely affected in their salt tolerance were isolated. Mutant CHR62 could not grow above 0.75 M NaCl, and CHR63 did not grow above 1.5 M NaCl. These mutants did not synthesize ectoine but accumulated ectoine precursors, as shown by 13C NMR and mass spectroscopy. Mutant CHR62 accumulated low levels of diaminobutyric acid, and mutant CHR63 accumulated high concentrations of N-gamma-acetyldiaminobutyric acid. These results suggest that strain CHR62 could be defective in the gene for diaminobutyric acid acetyltransferase (ectB), and strain CHR63 could be defective in the gene for the ectoine synthase (ectC). Salt sensitivity of the mutants at 1.5-2.5 M NaCl could be partially corrected by cytoplasmic extracts of the wild-type strain, containing ectoine, and salt sensitivity of strain CHR62 could be partially repaired by the addition of extracts of strain CHR63, which contained N-gamma-acetyldiaminobutyric acid. This is the first evidence for the role of N-gamma-acetyldiaminobutyric acid as osmoprotectant. Finally, a cosmid from the H. elongata genomic library was isolated which complemented the Ect- phenotype of both mutants, indicating that it carried at least the genes ectB and ectC of the biosynthetic pathway of ectoine.

Amino Acids, Diamino↗
PubMed1997

Decreased cerebrospinal fluid levels of neutral and basic amino acids in patients with Parkinson's disease.

We measured the CSF levels of 21, and the plasma levels of 26, amino acids in 31 patients with Parkinson's disease (PD) and in 45 matched controls. We used an ion-exchange chromatography method. When compared to controls, PD patients had lower CSF levels of taurine, alanine, valine, leucine, isoleucine, ethanolamine, citrulline, ornithine, lysine, histidine, arginine, and alpha-aminobutyric acid. PD patients not treated with levodopa or with dopamine agonists had higher CSF tyrosine and phenylalanine levels than those not treated with these drugs and also than controls. PD patients had higher plasma levels of phosphoserine, threonine, methionine, tyrosine, sarcosine and alpha-aminoadipic acid, and lower plasma levels of valine, leucine, and tryptophan, than controls. The CSF/plasma ratio of many of these amino acids was significantly lower in PD patients than those of controls, suggesting that PD patients might have a dysfunction in the transport of neutral and basic amino acids across the blood-brain barrier.

Adult↗
PubMed1997

Identification of a promoter region on the Halomonas elongata cryptic plasmid pHE1 employing the inaZ reporter gene of Pseudomonas syringae.

A native promoter located on the cryptic plasmid pHE1 from the moderate halophile Halomonas elongata was identified employing a promoterless ice nucleation gene inaZ of Pseudomonas syringae by direct subcloning and assaying for ice nucleation activity. The presence of the promoter was verified by inserting the corresponding intact or deleted pHE1 fragment in the promoter analysis vector pKK232-8 upstream of the promoterless cat or inaZ gene. Only constructs carrying the intact pHE1 fragment gave CAT phenotype (chloramphenicol resistance) or ice nucleation activity, respectively. Comparative evaluation of the sequence analysis data of the intact and deleted fragment suggested the localization of an Escherichia coli-type promoter region.

Base Sequence↗
PubMed1997

Expression of 5-HT7 receptor mRNA in rat brain during postnatal development.

The present study is the first one to demonstrate the expression of 5-HT7 receptor mRNA by in situ hybridization during postnatal development. No quantitative developmental changes in the 5-HT7 gene expression was observed in neocortex, pyramidal layers of CA1 and CA2, dentate gyrus, most of thalamic nuclei, mammillary region, superior colliculus and central gray. However, in retrosplenial cortex, subiculum and medial habenula an increase of labeling is observed between postnatal days (PN) PN15 and PN21. Striatum showed a transient expression during the first stages of development to be undetectable in adults. CA3 pyramidal cell layer, intramediodorsal thalamic nucleus and lateral habenula displayed a high mRNA expression at PN5 and PN8 which decreased throughout development but it was still present in adults. A possible non-neurotransmitter trophic function of 5-HT mediated through 5-HT7 receptors could be suggested.

Animals↗
PubMed1997

Salt-Sensitive and Auxotrophic Mutants of Halomonas elongata and H. meridiana by Use of Hydroxylamine Mutagenesis

The killing action and induced mutagenicity inhydroxylamine (HA)-treated cells of two moderately halophilic species of thegenus Halomonas, H. elongata and H. meridiana, wereinvestigated. A high sensitivity of H. elongata and especially ofH. meridiana to HA was found. The efficiency of the mutagenicityobtained with the HA treatment was tested at different salinities. Optimalexperimental conditions for HA mutagenesis of these two moderate halophileswere determined. A clear, efficient mutagenicity of both H. elongataand H. meridiana after HA mutagenesis was achieved. The optimalprocedures yielded a number of useful auxotrophic mutants of H.elongata as well as different salt-sensitive mutants of H.elongata and H. meridiana for further studies. Some of theselatter mutants appeared to be affected in the synthesis of compatiblesolutes.

Journal Article↗
PubMed1996

Neurotransmitter amino acids in cerebrospinal fluid of patients with Parkinson's disease.

We measured the CSF and plasma levels of glutamate, glutamine, aspartate (only in plasma), asparagine, glutamine, glycine and GABA in 31 patients with Parkinson's disease and in 45 matched controls. We used an ion-exchange chromatography method. When compared to controls, PD patients had similar CSF levels of glutamate, glutamine, asparagine, and glycine higher CSF GABA levels higher plasma levels of glutamine, asparagine, and glycine, and lower plasma levels of aspartate. The CSF levels of the amino acids measured were not correlated with the clinical features of PD. Our results that CSF GABA levels are not decreased in PD as previously suggested.

Aged↗
PubMed1996

The cytochrome bc1 complex but not CycM is necessary for symbiotic nitrogen fixation by Rhizobium leguminosarum.

Following Tn5 mutagenesis of Rhizobium leguminosarum biovar viciae, two mutants in one complementation group were identified as being unable to fix nitrogen in pea nodules. Spectroscopic analysis revealed that the mutants had lowered levels of c-type cytochromes and cytochromes aa3, but increased levels of cytochrome d. Cells of the mutants were greatly reduced in their ability to oxidize the artificial electron donor N,N,N',N'-tetramethyl-p-phenylenediamine but membranes prepared from them had increased levels of succinate- and NADH-dependent respiration. NADH oxidation by the mutants was insensitive to the respiratory inhibitor antimycin A, that targets the cytochrome bc1 complex. Molecular analysis of the mutants revealed that they were affected in the cytochrome bc1 complex. One of the mutants contained Tn5 in a gene homologous to that encoding cytochrome c1, and in the other the Tn5 was in DNA homologous to that encoding the cytochrome b component of the cytochrome bc1 complex. Haem staining revealed that haem proteins of M(r)31,000 and M(r)23,000 were absent from membranes from the mutants whereas an additional soluble c-type cytochrome protein of M(r)23,000 was present. We conclude that the larger of these two haem proteins corresponds to cytochrome c1 and, in its absence, the protein of M(r)23,000 does not remain associated with the membrane. Formation of this M(r)23,000 component was specifically blocked in a third respiratory-defective mutant which contained Tn5 in a region of DNA showing homology to a Bradyrhizobium Japonicum gene previously shown to encode the membrane-bound c-type cytochrome CycM. Although the cytochrome bc1 complex is essential for symbiotic nitrogen fixation, the other membrane-bound c-type cytochrome (CycM) is not.

Amino Acid Sequence↗
PubMed1996

Cerebrospinal fluid nitrate levels in patients with Alzheimer's disease.

It has been suggested that nitric oxide could be implicated in the pathogenesis of Alzheimer's disease (AD). Recently Kuiper et al. reported decreased CSF nitrate levels (oxidation product that provides an indirect estimation of nitric oxide) in AD patients, assessed with a colorimetric method. However other group, using a microplate version of the Griess reaction, did not confirm these findings. We studied the CSF and plasma levels of nitrate with kinetic cadmium-reduction method in 32 AD patients and 36 matched controls. The CSF and plasma nitrate levels did not differ significantly between the two study groups. CSF and plasma nitrate levels did not correlate with age at onset and duration in the patient group. These data suggest that CSF and plasma levels of nitrate are apparently unrelated with the risk for AD.

Aged↗
PubMed1996

Lithium and valproate combined administration: acute behavioural effects and drug plasma levels.

Drug plasma concentrations and behavioural effects of acute combined administration of lithium and valproic acid were studied in normonatraemic and hyponatraemic rats. Hyponatraemia was induced two hours before drug administration and behavioural observations lasted for two additional hours. Blood was collected by the end of the behavioural observation. The higher doses of valproic acid (360 mg/kg) or lithium (2 mEq/kg) induced more head-shakes and higher plasma concentration than 180 mg/kg of valproic acid or lithium 1 mEq/kg, respectively. Valproic acid and lithium administered separately induced more head shakes and higher drug plasma levels in hyponatraemic rats than in normonatraemic animals. Combined administration of valproic acid (180 mg/kg) and lithium (2 mEq/kg) produced a supra-aditive effect in head-shakes. The drug interaction between lithium and valproic acid induced a decrease in valproic acid plasma level and an increase in lithium plasma levels.

Analysis of Variance↗
PubMed1996

Osmoprotectants in Halomonas elongata: high-affinity betaine transport system and choline-betaine pathway.

The osmoregulatory pathways of the moderately halophilic bacterium Halomonas elongata DSM 3043 have been investigated. This strain grew optimally at 1.5 to 2 M NaCl in M63 glucose-defined medium. It required at least 0.5 M NaCl for growth, which is a higher concentration than that exhibited by the H. elongata type strain ATCC 33173. Externally provided betaine, choline, or choline-O-sulfate (but not proline, ectoine, or proline betaine) enhanced the growth of H. elongata on 3 M NaCl-glucose-M63 plates, demonstrating the utilization of these compounds as osmoprotectants. Moreover, betaine and choline stimulated the growth of H. elongata DSM 3043 over the entire range of salinity, although betaine was more effective than choline at salinities below and above the optimum. We found that H. elongata DSM 3043 has at least one high-affinity transport system for betaine (K(m) = 3.06 microM and Vmax = 9.96 nmol of betaine min(-1) mg of protein(-1)). Competition assays demonstrated that proline betaine and ectoine, but not proline, choline, or choline-O-sulfate, are also transported by the betaine permease. Finally, thin-layer chromatography and 13C-nuclear magnetic resonance analysis showed that exogenous choline was taken up and transformed to betaine by H. elongata, demonstrating the existence of a choline-glycine betaine pathway in this moderately halophilic bacterium.

Betaine↗
PubMed1995

Isolation of cryptic plasmids from moderately halophilic eubacteria of the genus Halomonas. Characterization of a small plasmid from H. elongata and its use for shuttle vector construction.

Three cryptic plasmids have been isolated from moderately halophilic eubacteria belonging to three species of the genus Halomonas. These three plasmids were designated pHE1 (4.2 kb, isolated from H. elongata ATCC 33174), pHI1 (48 kb, isolated from "H. israelensis" ATCC 43985), and pHS1 (ca. 70 kb, isolated from H. subglaciescola UQM 2927). Because of its small size, the plasmid pHE1 was selected for further characterization and construction of a shuttle vector for Halomonas strains. pHE1 was cloned into pBluescript KS and a detailed restriction map was constructed. Hybridization experiments excluded the existence of sequences homologous to pHE1 in total DNA from other strains of the genus Halomonas. Moreover, no DNA homology with pMH1, the only plasmid described so far from moderate halophiles, was found. Since pHE1 appeared to be unable to replicate in Escherichia coli cells, a number of mobilizable pHE1-derived hybrid plasmids were constructed that could be selected and maintained both in E. coli and in H. elongata. Finally, an improved shuttle vector, pHS15, was generated. The vector pHS15 contains an origin of replication from E. coli as well as one from H. elongata, a streptomycin resistance gene for positive selection in moderate halophiles, a number of unique restriction sites commonly used for cloning, and the mobilization functions of the broad host range IncP plasmid RK2. The vector pHS15 was readily mobilized by the RK2 derivative pRK2013 to all Halomonas strains tested so far. This is the first report on the development of a cloning vector useful for moderately halophilic eubacteria.

Genetic Vectors↗
PubMed1995

Influence of salt concentration on the susceptibility of moderately halophilic bacteria to antimicrobials and its potential use for genetic transfer studies.

The influence of salinity on the susceptibility of 13 moderately halophilic collection strains belonging to the genera Chromohalobacter, Deleya, Halomonas, Vibrio, and Volcaniella to 10 common antimicrobials has been studied. Three different patterns of tolerance were found when salinity was varied from 10 to 1% (wt/vol) total salts in the testing media. The first one included the responses to ampicillin and rifampicin, where only minimal effects on the susceptibility were found. All moderate halophiles showed a high sensitivity to rifampicin regardless of the salt concentration. In the second group, including the responses to the aminoglycosides gentamycin, kanamycin, neomycin, and streptomycin, a remarkable and gradual increase of the toxicity was detected at lower salinities. Thirdly, the highest heterogeneity was found for the rest of antimicrobials assayed (trimethoprim, nalidixic acid, spectinomycin, and tetracycline), where the effect of salinity was moderate and dependent on both the individual strain and the antimicrobial tested. The data presented here should facilitate genetic studies on moderate halophiles. Thus, they simplify the design of selection media for genetic exchange experiments. Besides, by using low-salinity media, genes encoding resistance to a number of antimicrobials, especially to aminoglycosides, can be used as genetic markers for plasmids or transposons to be transferred to these extremophiles.

Anti-Bacterial Agents↗