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C Vargas

Publications and source records attributed to C Vargas.

At least 19 recordsLinked to original sources
PubMed2000

Production and biochemical characterization of an alpha-amylase from the moderate halophile Halomonas meridiana.

Extracellular amylase production by the moderate halophile Halomonas meridiana was optimized and the enzyme was characterized biochemically. The highest amylase production was achieved by growing H. meridiana cultures in media with 5% salts and starch, in the absence of glucose until the end of the exponential phase. The amylase exhibited maximal activity at pH 7.0, being relatively stable in alkaline conditions. Optimal temperature and salinity for activity were 37 degrees C and 10% NaCl, respectively. Moreover, activity at salinity as high as 30% salts was detected. Maltose and maltotriose were the main end products of starch hydrolysis, indicating an alpha-amylase activity.

Culture Media↗
PubMed2000

Upregulation of BDNF mRNA and trkB mRNA in the nigrostriatal system and in the lesion site following unilateral transection of the medial forebrain bundle.

We have performed unilateral transection of the medial forebrain bundle (MFB) and studied BDNF mRNA and trkB mRNA levels at different postlesion times in the nigrostriatal system by means of in situ hybridization. BDNF mRNA levels were transiently induced in the substantia nigra pars compacta at 1 day postaxotomy. The disposition of BDNF mRNA expressing cells at this postlesion time in substantia nigra mimicked that of the dopaminergic neurons expressing the mRNA for the dopamine transporter. TrkB mRNA levels remained unaltered in the ventral mesencephalon at the different postlesion times examined-1 to 14 days. In contrast, trkB mRNA levels were significantly induced in the striatum at the longer postlesion time examined-14 days-when all neurodegenerative events are completed. It is becoming apparent that nigral BDNF mRNA levels are anterogradely transported to its target tissue in striatum. However, following axotomy, the lesion site represents a second potential target for BDNF action. Consequently, we also analyzed the pattern of mRNA expression for BDNF and trkB at the lesion site where dopaminergic axons are disconnected. There, we found notable inductions of both BDNF mRNA and trkB mRNA levels at 4 days postaxotomy. BDNF mRNA expressing cells were confined at the site of axotomy, which coincided precisely to that showing induction of trkB mRNA. Altogether, our results anticipate promising trophic roles of BNDF in the injured nigrostriatal system.

Animals↗
PubMed2000

Anaerobic degradation of fluorinated aromatic compounds.

Anaerobic enrichment cultures with sediment from an intertidal strait as inoculum were established under denitrifying, sulfate-reducing, iron-reducing and methanogenic conditions to examine the biodegradation of mono-fluorophenol and mono-fluorobenzoate isomers. Both phenol and benzoate were utilized within 2-6 weeks under all electron-accepting conditions. However, no degradation of the fluorophenols was observed within 1 year under any of the anaerobic conditions tested. Under denitrifying conditions, 2-fluorobenzoate and 4-fluorobenzoate were depleted within 84 days and 28 days, respectively. No loss of 3-fluorobenzoate was observed. All three fluorobenzoate isomers were recalcitrant under sulfate-reducing, iron-reducing, and methanogenic conditions. The degradation of the fluorobenzoate isomers under denitrifying conditions was examined in more detail using soils and sediments from different geographic regions around the world. Stable enrichment cultures were obtained on 2-fluorobenzoate or 4-fluorobenzoate with inoculum from most sites. Fluoride was released stoichiometrically, and nitrate reduction corresponded to the values predicted for oxidation of fluorobenzoate to CO2 coupled to denitrification. The 2-fluorobenzoate-utilizing and 4-fluorobenzoate-utilizing cultures were specific for fluorobenzoates and did not utilize other halogenated (chloro-, bromo-, iodo-) benzoic acids. Two denitrifying strains were isolated that utilized 2-fluorobenzoate and 4-fluorobenzoate as growth substrates. Preliminary characterization indicated that the strains were closely related to Pseudomonas stutzeri.

Anaerobiosis↗
PubMed2000

Cloning and expression of alpha-amylase from the hyperthermophilic archaeon Pyrococcus woesei in the moderately halophilic bacterium Halomonas elongata.

An extracellular alpha-amylase gene from the hyperthermophilic archaeon Pyrococcus woesei has been cloned and sequenced. The 1.4-kb protein-coding sequence is identical to that of the corresponding alpha-amylase gene of the closely related species P. furiosus. By using a shuttle cloning vector for halophilic bacteria, the P. woesei alpha-amylase was expressed in the moderate halophile Halomonas elongata, under the control of a native H. elongata promoter. The hyperthermophilic amylase activity expressed in the halophilic host was recovered completely in the crude membrane fraction of cell homogenates, suggesting the formation of inclusion bodies or that the secretion machinery of H. elongata may fail to recognize and release the pyrococcal alpha-amylase to the extracellular medium. However, thermal stability, metal ion interactions, optimal temperature and pH values for the crude and purified recombinant alpha-amylase were comparable with those of the native pyrococcal enzyme. The P. woesei amylase activity expressed in H. elongata was consistently detected in the cells upon growth on a wide range of NaCl concentrations (0.7-2.5 mol l-1). To our knowledge, this is the first report on the expression of an archaeal gene (P. woesei alpha-amylase) in a moderate halophilic host which serves as a cell factory able to grow under extreme salt conditions and with very simple nutritional requirements.

Base Sequence↗
PubMed1999

An antitumor promoter from Moringa oleifera Lam.

In the course of studies on the isolation of bioactive compounds from Philippine plants, the seeds of Moringa oleifera Lam. were examined and from the ethanol extract were isolated the new O-ethyl-4-(alpha-L-rhamnosyloxy)benzyl carbamate (1) together with seven known compounds, 4(alpha-L-rhamnosyloxy)-benzyl isothiocyanate (2), niazimicin (3), niazirin (4), beta-sitosterol (5), glycerol-1-(9-octadecanoate) (6), 3-O-(6'-O-oleoyl-beta-D-glucopyranosyl)-beta-sitosterol (7), and beta-sitosterol-3-O-beta-D-glucopyranoside (8). Four of the isolates (2, 3, 7, and 8), which were obtained in relatively good yields, were tested for their potential antitumor promoting activity using an in vitro assay which tested their inhibitory effects on Epstein-Barr virus-early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA). All the tested compounds showed inhibitory activity against EBV-EA activation, with compounds 2, 3 and 8 having shown very significant activities. Based on the in vitro results, niazimicin (3) was further subjected to in vivo test and found to have potent antitumor promoting activity in the two-stage carcinogenesis in mouse skin using 7,12-dimethylbenz(a)anthracene (DMBA) as initiator and TPA as tumor promoter. From these results, niazimicin (3) is proposed to be a potent chemo-preventive agent in chemical carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Differential upregulation of aquaporin-4 mRNA expression in reactive astrocytes after brain injury: potential role in brain edema.

Astrocytes and aquaporin-4 (AQP4) play a significant role in brain ion homeostasis. Consequently the regulation of AQP4 mRNA in the CNS after different neurological insults was of interest. A single intrastriatal injection of ringer or quinolinic acid strongly induced AQP4 mRNA in the striatum, specially at the core of the lesion. Colocalization studies demonstrated that AQP4 mRNA induction was restricted to hypertrophic astrocytes. The extent of striatal AQP4 mRNA induction did not correlate with neuronal degeneration, but it did with extravasation of Evans blue dye as a marker of BBB disruption. Distant lesions were additionally induced by either 6-OHDA or a knife cut in the medial forebrain bundle (MFB). The former, but not the latter, induced a high AQP4 mRNA expression in the lesioned substantia nigra. However, axotomy of the MFB induced a high AQP4 mRNA expression at the lesion site. We conclude that the induction of AQP4 mRNA expression is related to disruption of the blood-brain barrier and under brain edema conditions this water channel plays a key role in the reestablishment of the brain osmotic equilibrium.

Animals↗
PubMed1999

A model for dengue disease with variable human population.

A model for the transmission of dengue fever with variable human population size is analyzed. We find three threshold parameters which govern the existence of the endemic proportion equilibrium, the increase of the human population size, and the behaviour of the total number of human infectives. We prove the global asymptotic stability of the equilibrium points using the theory of competitive systems, compound matrices, and the center manifold theorem.

Aedes↗
PubMed1999

Analysis of the replication region of the cryptic plasmid pHE1 from the moderate halophile Halomonas elongata.

The basic replicon of the narrow-host-range plasmid pHE1 from the moderately halophilic bacterium Halomonas elongata ATCC 33174 has been identified and characterized. The replicon consists of a 1.7-kb DNA fragment, which contains the genetic information required for autonomous replication and stable maintenance. Analysis of its sequence revealed the presence of two ORFs which seem to form one transcription unit. ORF1 encodes a replication initiator protein (RepA), which has a high degree of homology to the theta-replicase (RepA) protein of ColE2 plasmid and to the RepA proteins of a family of replicons from gram-positive and gram-negative bacteria, also related to ColE2. The product encoded by ORF2 showed a certain similarity to the RepB proteins of the same family of replicons and perhaps represents the pHE1 RepB function. Deletion analysis suggests that the pHE1 origin of replication (ori) is located in an 800-bp region upstream of repA. A third putative gene, incA, was found on the complementary strand to the leader region of the repA mRNA. This, together with the presence in the 5' untranslated region of the repA mRNA of inverted repeats that could form stable stem-loop structures, suggests that the incA gene encodes a small antisense RNA. A possible control mechanism for pHE1 replication is proposed, involving an RNA molecule which sequesters the translational initiation region of the replication protein RepA. The basic replicon characterized here shows very interesting properties that should allow it to be used in the construction of cloning and expression vectors for moderate halophiles.

Amino Acid Sequence↗
PubMed1999

Genetic organization of the mobilization region of the plasmid pHE1 from Halomonas elongata.

The mobilization (mob) region of the non-self transmissible 4.2-kb plasmid pHE1 from the moderately halophilic bacterium Halomonas elongata ATCC 33174 has been identified and characterized. Analysis of the sequence revealed the presence of four open reading frames (mobCABD) which show a complex organization with two of them (mobB and mobD) entirely overlapped by a third (mobA). The deduced proteins appeared to have a high degree of homology to Mob proteins of CoIE1 and closely related plasmids. To assess the functionality of the mob region, the hybrid vector pHS134 was constructed, consisting of the complete plasmid pHEI, the E. coli vector pKS(-) and a streptomycin-resistance gene for positive selection in Halomonas. Vector pHS134 was found to be mobilizable from E. coli to H. elongata assisted by pRK600. Upstream of the mob genes, an oriT region with a putative nick sequence highly homologous to that of CoIE1 plasmids was identified. To our knowledge, this is the first mobilizable plasmid found in moderate halophiles. This property, together with its small size, the availability of its complete sequence, and its broad host range in moderately halophilic strains, makes pHE1 a good candidate for the construction of cloning and expression vectors for these extremophiles.

Amino Acid Sequence↗
PubMed1999

Gut mucosal atrophy after a short enteral fasting period in critically ill patients.

PURPOSE: The purpose of this study was to evaluate the presence of gut mucosal atrophy and changes in mucosal permeability in critically ill patients after a short fasting period. MATERIALS AND METHODS: Fifteen critically ill patients underwent a period of enteral fasting of at least 4 days (mean 7.8 days). We took the following measurements the day before initiating enteral nutrition: indirect calorimetry, serum albumin, prealbumin, and lymphocyte count. We also performed a duodenal endoscopic biopsy with histopathological and mucosal morphometric analysis including villus height and crypt depth. The lactulose-mannitol test was performed to assess gut permeability. A total of 28 healthy volunteers served as controls for duodenal biopsy or lactulose-mannitol test. Clinical data, such as length of fasting, severity score, and previous parenteral nutritional support, were recorded. RESULTS: We found gut mucosal atrophy, expressed as a decrease in villus height and crypt depth, in patients compared with controls. The patients also exhibited an abnormal lactulose-mannitol test. Morphometric changes did not correlate with permeability. Further, we found no correlation between the results of the lactulose-mannitol test and of mucosal morphometry with clinical data. CONCLUSIONS: We found that a short period of enteral fasting was associated with significant duodenal mucosal atrophy and abnormal gut permeability in critically ill patients.

Adult↗
PubMed1999

Role of Ngamma-acetyldiaminobutyrate as an enzyme stabilizer and an intermediate in the biosynthesis of hydroxyectoine.

Strain CHR63 is a salt-sensitive mutant of the moderately halophilic wild-type strain Halomonas elongata DSM 3043 that is affected in the ectoine synthase gene (ectC). This strain accumulates large amounts of Ngamma-acetyldiaminobutyrate (NADA), the precursor of ectoine (D. Cánovas, C. Vargas, F. Iglesias-Guerra, L. N. Csonka, D. Rhodes, A. Ventosa, and J. J. Nieto, J. Biol. Chem. 272:25794-25801, 1997). Hydroxyectoine, ectoine, and glucosylglycerate were also identified by nuclear magnetic resonance (NMR) as cytoplasmic organic solutes in this mutant. Accumulation of NADA, hydroxyectoine, and ectoine was osmoregulated, whereas the levels of glucosylglycerate decreased at higher salinities. The effect of the growth stage on the accumulation of solutes was also investigated. NADA was purified from strain CHR63 and was shown to protect the thermolabile enzyme rabbit muscle lactate dehydrogenase against thermal inactivation. The stabilizing effect of NADA was greater than the stabilizing effect of ectoine or potassium diaminobutyrate. A (1)H NMR analysis of the solutes accumulated by the wild-type strain and mutants CHR62 (ectA::Tn1732) and CHR63 (ectC::Tn1732) indicated that H. elongata can synthesize hydroxyectoine by two different pathways-directly from ectoine or via an alternative pathway that converts NADA into hydroxyectoine without the involvement of ectoine.

Amino Acids, Diamino↗
PubMed1999

[Daily mortality in Santiago and its relationship with air pollution].

BACKGROUND: Santiago de Chile, due to meteorological and topographic factors, is one of the most polluted cities in the world. The adverse effects of contamination on health are relatively well known, but they may be overvalued. AIM: To evaluate the short term effects of exposure to air pollution on mortality of people over 65 years old. MATERIAL AND METHODS: Daily mortality data in Santiago, from 1988 to 1993, was obtained from the National Statistics Institute. Daily concentrations of contaminants in Santiago and meteorological variables, were obtained from SESMA the Metropolitan Environmental Health Services. An association between contamination and mortality due to respiratory or cardiovascular diseases in subjects over 65 years old was searched, using temporal series analysis. RESULTS: There was a significant association between air pollution, meteorological variables on the same and previous days and mortality. PM10 had the strongest association with mortality. The relative risk of a 100 micrograms/m3 increment in PM10 was 1.052 for the elderly, 1.025 for cardiovascular and 1.061 for respiratory mortality. The relative risk of SO2 was 1.006 for all deaths and 1.017 for respiratory deaths. The figures for O3 were 1.015 for all deaths and 1.008 for cardiovascular deaths. CONCLUSIONS: This work confirms a consistent association between air pollution and daily mortality, specially for particulate matter, even for levels below Chilean norms.

Aged↗
PubMed1999

Adaptation of the differential display RT-PCR technique to isolate sugarcane genes induced by plant association with endophytic nitrogen-fixing bacteria.

Differential Display RT-PCR is a powerful technique that has been used to isolate differentially expressed genes. This technique was first described by Liang & Pardee, in 1992. Afterwards, several modifications were introduced in the original version, including a simplification described by Sokolov & Prockop, in 1994. In this work, we describe an adaptation of the Sokolov & Prockop technique, in order to isolate sugarcane genes induced by plant association with endophytic nitrogen-fixing bacteria. Several modifications were introduced: the use of oligo-dT primer in the first strand cDNA synthesis, replicates of the PCR reactions, analysis of the amplified fragments on silver stained polyacrilamide gel and confirmation of cloning the differentially amplified selected band prior to its molecular characterisation. The methodology established was successfully used to identify a large number of differentially amplified sugarcane cDNAs. So far, one of these cDNAs was already isolated and characterized.

DNA, Complementary↗
PubMed1998

Chronic administration of propionic acid reduces ganglioside N-acetylneuraminic acid concentration in cerebellum of young rats.

Elevated levels of propionate comparable to those of human propionic acidaemia were achieved in the blood of young rats by injecting subcutaneously buffered propionic acid (PPA) twice a day at 8-h intervals from the 6th to the 28th day of life. A matched group of animals (controls) was treated with the same volumes of saline. The animals were weighed and sacrificed by decapitation at 28, 35 or 60 days of age. Cerebellum and cerebrum were weighed and their protein and ganglioside N-acetylneuraminic acid (G-NeuAc) contents determined. Body, cerebral and cerebellar weights were similar in both groups, suggesting that PPA per se neither alters the appetite of the rats nor causes malnutrition. Brain protein concentration was also not affected by chronic administration of PPA, in contrast to G-NeuAc concentration which was significantly reduced in the cerebellum. Since ganglioside concentration is closely related to the dendritic surface and indirectly reflects synaptogenesis, our results of an important ganglioside deficit in the brain of PPA-treated animals may be related to the neurologic dysfunction characteristic of propionic acidaemic patients.

Animals↗
PubMed1998

Analysis of a dengue disease transmission model.

A model for the transmission of dengue fever in a constant human population and variable vector population is discussed. A complete global analysis is given, which uses the results of the theory of competitive systems and stability of periodic orbits, to establish the global stability of the endemic equilibrium. The control measures of the vector population are discussed in terms of the threshold condition, which governs the existence and stability of the endemic equilibrium.

Aedes↗
PubMed1998

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

We measured the CSF and plasma levels of glutamate, glutamine, aspartate (only in plasma), asparagine, glutamine, glycine and GABA in 37 patients with Alzheimer's disease and in 32 matched controls. We used an ion-exchange chromatography method. When compared to controls, AD patients had higher CSF glutamate and glycine levels, higher plasma levels of aspartate and glycine, and lower plasma levels of asparagine and GABA. When expressed relative to CSF proteins, CSF levels of glutamate and glycine remained higher, and CSF asparagine levels were lower in AD patients than in controls. The CSF levels of the amino acids measured were not correlated with the clinical features of AD with the exception of plasma GABA levels with duration of the disease. Our results might suggest a possible pathogenetic role of neurotransmitter amino acids in AD.

Aged↗
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↗