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S Rodríguez

Publications and source records attributed to S Rodríguez.

At least 37 records · Page 2Linked to original sources
PubMed2001

Highly stereoselective reagents for beta-keto ester reductions by genetic engineering of baker's yeast.

While whole cells of baker's yeast (Saccharomyces cerevisiae) are a convenient biocatalytic reducing agent for a wide variety of carbonyl compounds, mixtures of stereoisomeric alcohols are often observed since the organism contains a large number of reductase enzymes with overlapping substrate specificities but differing stereoselectivities. We sought to improve the performance of baker's yeast for beta-keto ester reductions by using recombinant DNA techniques to alter the levels of three enzymes known to play important roles in these reactions (fatty acid synthase, Fasp; aldo-keto reductase, Ypr1p; alpha-acetoxy ketone reductase, Gre2p). A complete set of "first-generation" yeast strains that either lack or overexpress each of these three enzymes was created and tested for improvements in stereoselective reductions of a series of beta-keto esters. On the basis of these results, multiply modified ("second-generation") strains were created that combined gene knockout and overexpression in single strains. In some cases, these additional modifications further improved the stereoselectivities of beta-keto ester reductions, thereby making several beta-hydroxy ester building blocks readily available by reactions that can be performed by nonspecialists. This work also revealed that additional yeast proteins participate in reducing beta-keto esters, and further progress using this strategy will require either additional genetic manipulations or the expression of yeast reductases in hosts that lack enzymes with overlapping substrate specificity.

Alcohol Oxidoreductases↗
PubMed2001

Detection of errors in dinucleotide repeat typing by nondenaturing electrophoresis.

This study shows that consideration of minor bands (heteroduplex, shadow, and faint bands) associated with allele bands in nondenaturing polyacrylamide gel electrophoresis (PAGE) after polymerase chain reaction (PCR) is effective for detecting PCR processing errors that lead to mistyping of heterozygotes as homozygotes. Notably, we show that minor bands in native gels are highly effective for detecting allele dropout and preferential amplification in PCR amplification of dinucleotide repeats. These findings are based on an analysis of Mendelian inheritance patterns in families, and the reproduction of heterozygous band patterns by mixing homozygous DNAs before PCR, for a total of six (AC)n repeats located on human chromosome 11p15. To investigate the utility of our approach, a large population sample of 405 unrelated individuals was genotyped for each (AC)n repeat using minor bands as internal quality controls. Genotype frequencies at each of the six loci were in close agreement with Hardy-Weinberg proportions, which suggests that there were few genotyping errors. Our observations add to the evidence indicating that minor bands in native gels are of diagnostic value in the genotyping of dinucleotide repeats.

Acrylic Resins↗
PubMed2001

Population analysis of an unusual NOR-site polymorphism in brown trout (Salmo trutta L.).

A population analysis of an unusual NOR-site polymorphism previously detected in brown trout (Salmo trutta L.) from North-western Spain was carried out in 225 individuals from 20 native populations from this area. The analysis performed has permitted us to reveal: (i) the ubiquity of this phenomenon in most river basins from NW Spain, 13 extra-NORs not observed in standard trout being detected; (ii) the rDNA constitution of all extra-NORs, as confirmed by CMA3-staining and rDNA-FISH, and their capability to constitute their own nucleolus; (iii) the constant location of extra-NORs within individuals and their stable transmission across generations; and (iv) the telomeric location of Ag-NORs, which were randomly distributed in the karyotype of S. trutta, mostly in the heterozygous condition. Repetitive sequences in the IGS or scattered along rDNA units, rather than chromosome rearrangements, could play an important role in the dispersion of NORs. The polymorphism described seems to have a single geographical origin, since a positive correlation was demonstrated between the degree of polymorphism and geographical distance to a central point of the river basin where the phenomenon showed a higher intensity. The distribution of NOR-site variation as compared with allozyme variation in the populations studied, showed significant statistical differences. Selection against high copy number, or mutation due to changes in NOR location, could be acting on this polymorphism to explain the observed distribution. The high dispersion of NOR-site variants within and among populations suggests the transposition phenomenon responsible for NOR jumping could be still active.

Animals↗
PubMed2001

Spectrum of nonrandom associations between microsatellite loci on human chromosome 11p15.

Most evidence about nonrandom association of alleles at different loci, or gametic disequilibrium, across extensive anonymous regions of the human genome is based on the analysis of overall disequilibrium between pairs of microsatellites. However, analysis of interallelic associations is also necessary for a more complete description of disequilibrium. Here, we report a study characterizing the frequency and strength of both overall and interallelic disequilibrium between pairs of 12 microsatellite loci (CA repeats) spanning 19 cM (14 Mb) on human chromosome 11p15, in a large sample (810 haplotypes deduced from 405 individuals) drawn from a single population. Characterization of disequilibrium was carried out, taking into account the sign of the observed disequilibria. This strategy facilitates detection of associations and gives more accurate estimates of their intensities. Our results demonstrate that the incidence of disequilibrium over an extensive human chromosomal region is much greater than is commonly considered for populations that have expanded in size. In total, 44% of the pairs of microsatellite loci and 18% of the pairs of alleles showed significant nonrandom association. All the loci were involved in disequilibrium, although both the frequency and strength of interallelic disequilibrium were distributed nonuniformly along 11p15. These findings are especially relevant since significant associations were detected between loci separated by as much as 17-19 cM (7 cM on average). It was also found that the overall disequilibrium masks complicated patterns of association between pairs of alleles, dependent on their frequency and size. We suggest that the complex mutational dynamics at microsatellite loci could explain the allele-dependent disequilibrium patterns. These observations are also relevant to evaluation of the usefulness of microsatellite markers for fine-scale localization of disease genes.

Base Sequence↗
PubMed2001

A programmed ependymal denudation precedes congenital hydrocephalus in the hyh mutant mouse.

Hydrocephalic hyh mice are born with moderate hydrocephalus and a normal cerebral aqueduct. At about the fifth postnatal day the aqueduct becomes obliterated and severe hydrocephalus develops. The aim of the present investigation was to investigate the mechanism of this hydrocephalus, probably starting during fetal life when the cerebral aqueduct is still patent. By use of immunocytochemistry and scanning electron microscopy, mutant (n = 54) and normal (n = 61) hyh mouse embryos were studied at various developmental stages to trace the earliest microscopic changes occurring in the brains of embryos becoming hydrocephalic. The primary defect begins at an early developmental stage (E-12) and involves cells lining the brain cavities, which detach following a well-defined temporo-spatial pattern. This ependymal denudation mostly involves the ependyma of the basal plate derivatives. There is a relationship between ependymal denudation and ependymal differentiation evaluated by the expression of vimentin and glial fibrillary acidic protein. The ependymal cells had a normal appearance before and after detachment, suggesting that their separation from the ventricular wall might be due to abnormalities in cell adhesion molecules. The process of detachment of the ventral ependyma, clearly visualized under scanning electron microscope, is almost completed before the onset of hydrocephalus. Furthermore, this ependymal denudation does not lead to aqueductal stenosis during prenatal life. Thus, the rather massive ependymal denudation appears to be the trigger of hydrocephalus in this mutant mouse, raising the question about the mechanism responsible for this hydrocephalus. It seems likely that an uncontrolled bulk flow of brain fluid through the extended areas devoid of ependyma may be responsible for the hydrocephalus developed by the hyh mutant embryos. The defect in these embryos also includes loss of the hindbrain floor plate and a delayed in the expression of Reissner fiber glycoproteins by the subcommissural organ.

Animals↗
PubMed2001

[Prevalence of nutritional anemia in women of reproductive age. Costa Rica. National nutrition survey, 1996].

In 1996, The Ministry of Health and Inciensa conducted the latest National Nutrition Survey, to provide support and guidance to the national policies, plans and programs in the field of food and nutrition. The present paper reports the results for the prevalence of anemia estimated in a total of 884 women of reproductive age, in three areas: metropolitan area, other urban areas and rural areas. Anemia was determined through measurements of hemoglobin, plasma ferritin and plasma folates. In addition, hemoglobin patterns were determined by electrophoresis. The cutt-off points used were those recommended by the WHO. Anemia was present in 18.6% of the women. Severe to moderate deficiency of iron (< 12 ng/dl) and of folates (< 6 ng/dl) were found in 43.2 and 24.7% of women respectively, with statistically significant differences by area of residence. The magnitude of the problem for anemia can be classified as mild, for iron deficiency as severe, and for folate deficiency as moderate. In conclusion, Anemia represents a public health problem for Costa Rica that has remained constant throughout the last decade. In women of reproductive age, iron deficiency is the main cause of Anemia, followed by folates deficiency, and in a small percentage hemoglobinopathies. Intestinal parasites are not longer a mayor cause of Anemia. Prevalence of Anemia is influenced by place of residence, but not by age. In summary, despite the favorable health conditions present in Costa Rica, the prevalence of Anemia and of iron deficiency are similar to those of the Latin-American region. To improve this situation, public health interventions are necessary.

Adolescent↗
PubMed2001

[Prevalence of anemia, iron and folate deficiency in children 7 years smaller. Costa Rica, 1996].

In 1996, were studied in Costa Rica 961 children with ages between one and six years, with representation for metropolitan, urban and rural zones of the country. The classification approaches applied were emitted by the Pan-American Health Organization and the World Health Organization. The preschooler population presented in the national environment a prevalence of anemia of 26.3% (children from 1 to 4 years with hemoglobin < 11.0 g/dL and those from 5 to 6 years old with hemoglobin < 12.0 g/dL). The prevalence of Iron depletion (Ferritin < 12 ng/mL) and iron deficiency (Ferritin < 24 ng/mL) were 24.4% and 53.8%, respectively. The folate deficiency (< 6.0 ng/mL) was 11.4%. The iron deficiency was higher in children smaller than 4 years, being the maximum deficiency in the 1 year-old (75%). More than 40% of the preschool children presented sub-clinical deficiency of iron; of them, 10% showed severe deficiency of iron without presence of anemia. The children from the rural area presented the highest prevalence of anemia and iron depletion, while the metropolitan area met more frequency with iron deficiency. The nutritional anemias still constitute a moderate problem of public health in Costa Rica. The main cause is iron deficiency, associated in small proportion with folate deficiency and other factors associated with the erythropoiesis.

Anemia↗
PubMed2000

Hydrocephalus induced by immunological blockage of the subcommissural organ-Reissner's fiber (RF) complex by maternal transfer of anti-RF antibodies.

Stenosis of the cerebral aqueduct seems to be a key event for the development of congenital hydrocephalus. The causes of such a stenosis are not well known. Overholser et al. in 1954 (Anat Rec 120:917-933) proposed the hypothesis that a dysfunction of the subcommissural organ (SCO) leads to aqueductal stenosis and congenital hydrocephalus. The SCO is a brain gland, located at the entrance of the cerebral aqueduct, that secretes glycoproteins into the cerebrospinal fluid that, upon release, assemble into a fibrous structure known as Reissner's fiber (RF). By the permanent addition of new molecules to its rostral end, RF grows and extends along the aqueduct, fourth ventricle, and central canal of the spinal cord. The immunological blockage of the SCO-RF complex has been used to test Overholser's hypothesis. The following was the sequence of events occurring in pregnant rats that had been immunized with RF glycoproteins: the mother produced anti-RF antibodies and transferred them to the fetus through the placenta and to the pup through the milk, and the antibodies reached the brain of the fetus and pup and blocked the SCO-RF complex. This resulted in a permanent absence of RF that was followed by stenosis of the cerebral aqueduct, and then by the appearance of hydrocephalus. The latter was patent until the end of the 6-month observation period. The chronic hydrocephalic state appeared, in turn, to induce new alterations of the SCO. It is concluded that a selective immunological knock out of the SCO-RF complex leads to hydrocephalus.

Animals↗
PubMed2000

Determination of the phospholipid/lipophilic compounds ratio in liposomes by thin-layer chromatography scanning densitometry.

The determination of the ratio of phospholipid/lipophilic compounds in liposomes was achieved after thin-layer chromatography (TLC) by measuring the spot intensities of dipalmitoyl phosphatidylcholine and the lipophilic compound. The liposome components under study were separated on one TLC plate, developed in two steps, and detected after charring the plate with specific visualization reagents. The method shows good reproducibility and provides a simple way to quantify the level of lipophilic compound incorporated in the liposome bilayer.

Chromatography, Gas↗
PubMed2000

Portable data acquisition system for EKG measurements in marine environments.

In the present paper, an electronic prototype designed to acquire electrocardiographic signals from marine mammals has been developed. The system consists of a portable device that allows the on-line acquisition of EKG signals through a parallel port interface that is connected to a laptop computer. The EKG waveform, the voltage level, the bandwidth and the most relevant information from this type of signals is stored and analysed under real-time conditions by means of specifically implemented software. The whole system has been successfully tested to obtain the EKG from captive dolphins. The characteristics of the equipment presented here, with its low cost, size and energy requirements accomplish a portable system suitable for the acquisition of this type of signals in conductive media such as the seawater.

Animals↗
PubMed2000

Characterization of Gibberella fujikuroi complex isolates by fumonisin B1 and B2 analysis and by RAPD and restriction analysis of PCR-amplified internal transcribed spacers of ribosomal DNA.

Twenty nine isolates of Fusarium spp. (twenty four of them belonging to the Gibberella fujikuroi complex) isolated from banana and corn from different geographical regions were analyzed for their ability to produce fumonisins B1 and B2 and for genetic relatedness using random amplified polymorphic DNA (RAPD) and restriction analysis of PCR amplification products of the 5.8s ribosomal DNA-intervening internal transcribed spacer regions (ITS I-5.8S-ITS II). For RAPD analysis, six of twenty oligonucleotide primers were selected after testing with five Fusarium spp. isolates and used to characterize 24 additional isolates. DNA fragments from the 29 isolates of Fusarium spp., which were approximately 560 bp, were amplified with the universal primers ITS1 and ITS4. The restriction enzymes HaeIII, MboI, HpaII and MspI were useful for distinguishing the isolates. The RAPD analysis permitted to find interspecific differences among the isolates of Fusarium spp., between isolates with low and high capacity of fumonisin production and among isolates from different hosts. The restriction fragment length polymorphism (RFLP-PCR) analysis permitted to distinguish among different species of Fusarium. In combination with morphological analysis, the results of this research may find an application for the diagnosis of unknown Fusarium spp. and, particularly, for the characterization of fumonisin-producing isolates, which may be very useful in the food technology field.

Carboxylic Acids↗
PubMed2000

Construction and characterization of a nonproliferative El Tor cholera vaccine candidate derived from strain 638.

In recent clinical assays, our cholera vaccine candidate strain, Vibrio cholerae 638 El Tor Ogawa, was well tolerated and immunogenic in Cuban volunteers. In this work we describe the construction of 638T, a thymidine auxotrophic version of improved environmental biosafety. In so doing, the thyA gene from V. cholerae was cloned, sequenced, mutated in vitro, and used to replace the wild-type allele. Except for its dependence on thymidine for growth in minimal medium, 638T is essentially indistinguishable from 638 in the rate of growth and morphology in complete medium. The two strains showed equivalent phenotypes with regard to motility, expression of the celA marker, colonization capacity in the infant mouse cholera model, and immunogenicity in the adult rabbit cholera model. However, the ability of this new strain to survive environmental starvation was limited with respect to that of 638. Taken together, these results suggest that this live, attenuated, but nonproliferative strain is a new, promising cholera vaccine candidate.

Amino Acid Sequence↗
PubMed2000

Pairing affinities of the B- and G-genome chromosomes of polyploid wheats with those of Aegilops speltoides.

Chromosome pairing at metaphase I was studied in different interspecific hybrids involving Aegilops speltoides (SS) and polyploid wheats Triticum timopheevii (AtAtGG), T. turgidum (AABB), and T. aestivum (AABBDD) to study the relationships between the S, G, and B genomes. Individual chromosomes and their arms were identified by means of C-banding. Pairing between chromosomes of the G and S genomes in T. timopheevii x Ae. speltoides (AtGS) hybrids reached a frequency much higher than pairing between chromosomes of the B and S genomes in T. turgidum x Ae. speltoides (ABS) hybrids and T. aestivum x Ae. speltoides (ABDS) hybrids, and pairing between B- and G-genome chromosomes in T. turgidum x T. timopheevii (AAtBG) hybrids or T. aestivum x T. timopheevii (AAtBGD) hybrids. These results support a higher degree of closeness of the G and S genomes to each other than to the B genome. Such relationships are consistent with independent origins of tetraploid wheats T. turgidum and T. timopheevii and with a more recent formation of the timopheevi lineage.

Animals↗
PubMed2000

Chromosome structure of Triticum timopheevii relative to T. turgidum.

The chromosome structure of four different wild populations and a cultivated line of Triticum timopheevii (2n = 28, AtAtGG) relative to Triticum turgidum (2n = 28, AABB) was studied, using genomic in situ hybridisation (GISH) and C-banding analysis of meiotic configurations in interspecific hybrids. Two wild accessions and the cultivated line showed the standard C-banding karyotype. The other two accessions are homozygous for translocation 5At/3G and translocations 1G/2G and 5G/6G. GISH analysis revealed that all the T. timopheevii accessions carry intergenome translocations 6At/1G and 1G/4G and identified the position of the breakpoint in translocation 5At/3G. C-banding analysis of pairing at metaphase I in the hybrids with T. turgidum provides evidence that four species-specific translocations (6AtS/1GS, 1GS/4GS, 4GS/4AtL, and 4AtL/3AtL) exist in T. timopheevii, and that T. timopheevii and T. turgidum differ in the pericentric inversion of chromosome 4A. Bridge plus acentric fragment configurations involving 4AL and 4AtL were identified in cells at anaphase I. This result suggests that the paracentric inversion of 4AL from T. turgidum does not exist in T. timopheevii. Both tetraploid species have undergone independent and distinct evolutionary chromosomal rearrangements. The position, intercalary or subdistal, of the breakpoints in species-specific translocations and inversions contrasts with the position, at or close to the centromere, of intraspecific translocations. Different mechanisms for intraspecific and species-specific chromosome rearrangements are suggested.

Anaphase↗
PubMed1999

Improving the stereoselectivity of bakers' yeast reductions by genetic engineering.

[formula: see text] The stereoselectivities of bakers' yeast catalyzed reductions of beta-keto esters can be manipulated by genetic design. Strains in which two major beta-keto ester reductases are either knocked out or overexpressed have been constructed. The former approach results in whole cell biocatalysts with reversed stereoselectivity from unmodified bakers' yeast while the latter shows useful improvements in stereoselectivity. These results indicate that the "designer yeast" approach can provide useful biocatalysts for these transformations.

Catalysis↗
PubMed1999

ANTI-INFLAMMATORY ACTIVITY OF PHYCOCYANIN EXTRACT IN ACETIC ACID-INDUCED COLITIS IN RATS.

The anti-inflammatory effect of c-phycocyanin extract was studied in acetic acid-induced colitis in rats. Phycocyanin (150, 200 and 300 mg kg-1 p.o.) was administered 30 min before induction of colitis with enema of 1 ml of 4% acetic acid per rat. Twenty-four hours later myeloperoxidase (MPO) activity was determined as well as histopathological and ultrastructural studies were carried out in colonic tissue. Phycocyanin substantially reduced MPO activity which was increased in the control colitis group. Also, histopathological and ultrastructural studies showed inhibition in inflammatory cell infiltration and reduction to some extent in colonic damage in rats treated with phycocyanin. The probable role of antioxidative and the scavenging properties of phycocyanin against reactive oxygen species in the anti-colitic effect is discussed in this paper. To our knowledge this is the first report on the anti-inflammatory effect of phycocyanin in an experimental model of colitis.(c) 1999 The Italian Pharmacological Society.

Journal Article↗