Search PubMed⌕ Search

Biomedical subjects

M Salazar

Publications and source records attributed to M Salazar.

At least 73 records · Page 4Linked to original sources
PubMed1995

Evaluation of the teratological potential of the new antihypertensive 5-methoxytryptamine, beta-methylcarboxylate hydrochloride (indorenate) in mice.

5-Methoxytryptamine, beta-methylcarboxylate hydrochloride (indorenate), a new antihypertensive agent, was examined for teratogenic-embryotoxic effects in the mouse at doses of 0 (control), 10, 20, 40, and 80 mg/kg/day. The compound was administered by gastric intubation on days 6-15 of gestation. On day 17, the dams were sacrificed, the number of live, dead, and resorbed fetuses recorded and mean pup weight determined. Teratological evaluation was carried out by visual inspection, alizarin red staining of the skeleton and Wilson's sections. Signs of overtoxicity in mothers were found in the high-dose groups. There were no differences between control and indorenate-treated groups in the number of implantations, live fetuses or anomalies. However, an embryotoxic effect was observed at 40 and 80 mg/kg, shown by increased resorptions and lower weight of pups at the higher dose.

5-Methoxytryptamine↗
PubMed1994

A human opsin-related gene that encodes a retinaldehyde-binding protein.

The ligand-binding property of a cytoplasmic membrane-bound protein from bovine retinal pigment epithelium (RPE) has been demonstrated. The putative RPE-retinal G protein coupled receptor (RGR) covalently binds both all-trans- and 11-cis-retinal after reduction by sodium borohydride. The 32-kDa receptor binds all-trans-retinal preferentially, rather than the 11-cis isomer. The amino acid sequence of the opsin-related protein in humans is 86% identical to that of bovine RGR, and a lysine residue, analogous to the retinaldehyde attachment site of rhodopsin, is conserved in the seventh transmembrane domain of RGR in both species. The human gene that encodes the novel retinaldehyde receptor spans 14.8 kb and is split into seven exons. The structure of the gene is distinct from that of the visual pigment genes. These findings support the notion that the rgr gene represents the earliest independent branch of the vertebrate opsin gene family. A second form of human RGR in retina is predicted by alternative splicing of its precursor mRNA. This RGR variant results from the alternative use of an internal acceptor splice site in the second intron of the human gene, and it contains an insertion of four amino acids in the connecting loop between the second and thrid transmembrane domains. Since RGR binds all-trans-retinal preferentially, one of its functions may be to catalyze isomerization of the chromophore by a retinochrome-like mechanism.

Amino Acid Sequence↗
PubMed1994

The solution structure of the r(gcg)d(TATACCC):d(GGGTATACGC) Okazaki fragment contains two distinct duplex morphologies connected by a junction.

Okazaki fragments are important intermediates in DNA replication. Chimeric duplexes that are structurally equivalent to Okazaki fragments also occur during reverse transcription of RNA retroviruses. Such duplexes consist of an RNA-DNA chimeric strand base-paired to a pure DNA strand; hence they have a hybrid duplex "left half" covalently linked to a "right half" that is pure DNA. We have determined the solution structure of the synthetic Okazaki fragment r(gcg)d(TATACCC):d(GGGTATACGC) by means of two-dimensional NMR, restrained molecular dynamics and full relaxation matrix simulation of the two-dimensional nuclear Overhauser effect spectra at various mixing times. The large negative x-displacement and large positive inclination in the hybrid section of the duplex are structural characteristics similar to those found in pure hybrid duplexes. However, the DNA sugar puckers and the width and depth of the minor groove in the pure DNA section are more like B-form DNA, especially beyond the junction. Thus, this Okazaki fragment duplex assumes a conformation in solution that is a chimeric mixture of hybrid-form (H-form) and B-form structures and the overall molecule cannot be classified as either an A-form or a B-form duplex. The co-existence of these two different conformations in a single duplex gives rise to a structural discontinuity with a bend of approximately 18.1 (+/- 0.4) degrees at the junction between the hybrid and DNA segments that may be important for reverse transcriptase binding and RNase H cleavage of such molecules. Despite the fact that the solution structure is quite different from the all A-form structure reported recently for the exact same molecule in the crystalline state, a surprising number of local helical parameters were found to be quite similar to those reported for the crystal structure.

Base Sequence↗
PubMed1994

Major histocompatibility complex class II alleles and haplotypes and blood groups of four Amerindian tribes of northern Colombia.

MHC class II alleles and haplotypes were determined from unrelated individuals and families of the Arhuaco (n = 107), Kogi (n = 42), Arsario (n = 18), and Wayú (n = 88) tribes located in the northern part of Colombia. Class II DRB, DQA1, and DQB1 alleles were determined by PCR-SSO and PCR-RFLP based methods. Four haplotypes, [DRB1*0407, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*0403, DRB4*0101, DQA1*03, DQB1*0302]; [DRB1*1402/1406, DRB3*0101, DQA1*0501, DQB1*0301]; and [DRB1*0802, DQA1*0401, DQB1*0402], were observed among these four tribes. In addition to these haplotypes, the Wayú Indians showed a frequency of 21.3% for the [DRB1*1602, DRB5*02, DQA1*0501, DQB1*0301] haplotype, 13.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0302] haplotype, and 8.1% for the [DRB1*0411, DRB4*0101, DQA1*03, DQB1*0402] haplotype. Red cell antigen typing was used to calculate genetic admixture. The Kogi and Arsario showed no genetic admixture while the Arhuaco tribe showed admixture with genes of African origin and the Wayú showed admixture with Caucasians as well as genes of African origin. These findings were confirmed by the MHC class II allele and haplotype data obtained, as alleles and haplotypes of Caucasian and African origin were detected in the Wayú and Arhuaco and not in the Kogi or Arsario. These studies will be important in disease association and transplantation studies for Amerindian and colombian populations and for correlating genetic traits with the anthropologic and linguistic data available in order to better understand the Amerindian populations.

Alleles↗
PubMed1994

Evaluation of the toxic and teratogenic potential of the anticonvulsant drug 4-hydroxy, 4-ethyl, 4-phenylbutyramide in mice.

The toxicity profiles of the phenyl alcohol amides: 4-hydroxy, 4-ethyl, 4-phenylbutyramide (HEPB) and two lower homologous: 3-hydroxy, 3-ethyl, 3-phenylpropionamide (HEPP) and 2-hydroxy, 2-ethyl, 2-phenylacetamide (HEPA) were studied in mice. TD50 value was determined by oral administration and LD50 by oral and intraperitoneal routes. The results indicate that HEPP is less toxic than the others, both of which had very similar toxicity. Furthermore, the teratogenic potential of HEPB was investigated in mice after oral administration. The compound was administered on days 6-15 of gestation at doses of 0, 5, 25, 50 or 100 mg/kg of weight. On day 17 of pregnancy the mice were sacrificed and the pups examined. An increase of body weight in both mothers and fetuses was observed at 25 and 50 mg/kg and a decrease was found in mothers receiving 100 mg/kg, as a sign of maternal toxicity. Considering the litter data, embryotoxicity and fetotoxicity were only shown at the highest dose. However, the HEPB treatment did not result in malformations of live fetuses or resorptions when the implantations were considered as the individual entity.

Abnormalities, Drug-Induced↗
PubMed1994

Genetic control of the decline of natural killer cell activity in aging mice.

NK cell activity declines with age and is strain dependent. We investigated the age associated decline of NK cell activity in the HW26C strain of mice. The bilineal congenic strain HW26C which contains a segment of chromosome 4 of BALB/cBy introduced onto the C57BL/6By (B6) background was used to investigate the decline of NK cell activity with age. Our experiments showed that there is a significant decline of NK cell activity in old (18-26 months) HW26C mice as compared to the B6. By contrast, the NK cell frequency determined using a surface marker for NK cells, NK1.1, did not show any significant difference with age. It appears therefore, that the decline in NK activity during aging is a reflection of loss of lytic activity rather than an actual decline in the number of NK cells and the responsible gene(s) resides in chromosome 4.

Aging↗
PubMed1994

Genetic typing of the DQA1*4 alleles by restriction enzyme digestion of the PCR product obtained with the DQ Alpha Amplitype kit.

The three DQ Alpha 4 alleles, 4.1 (0501), 4.2 (0401), and 4.3 (0601) cannot be distinguished with the reverse dot blot DQ Alpha Amplitype Kit. A previous report (Yunis, I. et al., Tissue Antigens, Vol. 39, 1992, pp. 182-186) indicated that the typing of these three alleles can be accomplished by endonuclease digestion of the PCR product that is produced following amplification with the DQ Alpha primers with Fok I and Rsa I. We report here the use of this method to type the DQA1*0401, 0501 and 0601 alleles in the PCR product obtained with the DQ Alpha-Amplitype Kit. We have analyzed the PCR product obtained in over 200 forensic samples. We have found that in all of these cases, it is possible to assign a type to those samples that type as DQ Alpha 4 with the Amplitype Kit. Furthermore, we have found the technique to be useful in some cases where it has not been previously possible to distinguish individuals or samples that have the DQ Alpha 4 allele and type identically with respect to all other DQ Alpha alleles.

Alleles↗
PubMed1993

Major histocompatibility complex susceptibility genes for dermatitis herpetiformis compared with those for gluten-sensitive enteropathy.

Dermatitis herpetiformis (DH) shares some clinical features and major histocompatibility complex (MHC) markers with gluten-sensitive enteropathy (GSE). We compared MHC haplotypes in 27 patients with DH, 35 patients with GSE, and normal controls. As in GSE, the frequencies of two extended haplotypes, [HLA-B8, SC01, DR3] and [HLA-B44, FC31, DR7], were increased in patients with DH. Distributions of fragments of extended haplotypes, consisting of some but not all of the elements of complete extended haplotypes, were analyzed to attempt to localize a susceptibility gene. Besides complete extended susceptibility haplotypes, (DR3, DQ2) and (DR7, DQ2) fragments were most common in GSE. In contrast, DH showed only a few such fragments but many instances of the fragment (SC01). The differences in distribution of these fragments in the two diseases were highly significant (P < 0.002). HLA-DQ2 and DR3 had the highest odds ratios for GSE, but the highest odds ratio for DH was for the complotype SC01. These findings suggest that the MHC susceptibility gene for DH is between class II and complotype regions, closest to the complotype, whereas that for GSE is in the class II region.

Celiac Disease↗
PubMed1993

Structure of a DNA:RNA hybrid duplex. Why RNase H does not cleave pure RNA.

The solution structure of the DNA:RNA hybrid duplex d(GTCACATG):r(caugugac) has been determined by means of two-dimensional nuclear Overhauser effect (2D-NOE) spectra, restrained molecular dynamics and full-relaxation matrix stimulation of the 2D-NOE spectra. The DNA:RNA hybrid duplex assumes neither an A-form nor a B-form structure in solution, but an intermediate heteromerous duplex structure. The sugars of the RNA strand have a normal N-type C3'-endo conformation, but the DNA strand sugars have neither N-type nor S-type conformations; instead, they have an unexpected intermediate O4'-endo conformation. The negative x-displacement, as well as the small rise and positive inclination of the base-pairs, resembles A-form morphology but the minor groove width is intermediate between that of A-form and B-form duplexes. Both the DNA and RNA strands show prominent sequence-dependent variations in their helical parameters. Combined analysis of NOE and J-coupling data indicates that the DNA sugars are not in a dynamical two-state equilibrium. The detailed three-dimensional structure of this DNA:RNA hybrid molecule leads to a proposed model for its interaction with RNase H. Several specific structural features of the enzyme complexed with the hybrid duplex appear to explain the mechanism whereby RNase H discriminates between DNA:RNA hybrid duplexes and pure RNA:RNA duplexes.

Base Sequence↗
PubMed1993

The DNA strand in DNA.RNA hybrid duplexes is neither B-form nor A-form in solution.

The structure of the DNA.RNA hybrid (GTCACATG).(caugugac), where lowercase letters designate RNA residues, has been determined on the basis of J-coupling analysis and 2D-NOE studies. The central hexamer in this sequence has been previously studied [Reid, D. G., Salisbury, S. A., Brown, T., Williams, D. H., Vasseur, J.-J., Rayner, B., & Imabach, J.-L. (1983) Eur. J. Biochem. 135, 307-314] via one-dimensional NOE methods and circular dichroism studies. Contrary to their results, we find that this duplex does not assume a B-form conformation in solution. Instead, the RNA residues retain their C3'-endo (A-form) conformation, as indicated by the absence of H1'-H2' couplings and by strong H6/H8 to (n-1) H2'NOEs. The sugars of the DNA residues, on the other hand, do not assume an A-form (or a B-form) conformation but an intermediate conformation in the O4'-endo range (P approximately 72-110 degrees), as indicated by the presence of strong H1'-H4' NOEs, medium-strength H2"-H3' COSY cross peaks, strong H3'-H4' DQF-COSY cross peaks, and H1'-H2' coupling constants that are of approximately the same magnitude as the H1'-H2" coupling constants. These results suggest that the RNA strand not only retains its N-type structure but also exerts an influence on the conformation of the DNA strand. Our results provide strong evidence that DNA.RNA hybrid duplexes do not assume an all-C2'-endo B-type conformation; neither do they assume an all-C3'-endo A-type conformation in solution. Furthermore, although not the main focus of this study, a comparison of the longitudinal relaxation times of the DNA and RNA residues indicates the need for extended relaxation delays in two-dimensional NMR spectra of hybrid duplexes, as has been previously observed for DNA.RNA chimeric duplexes (Wang, A. C., Kim, S.-G., Chou, S.-H., Orban, J., Flynn, P., & Reid, B. R. (1992) Biochemistry 31, 3940-3946).

Base Sequence↗
PubMed1993

Sugar conformations at hybrid duplex junctions in HIV-1 and Okazaki fragments.

We have carried out a solution study of the local conformation in a hybrid-chimeric duplex of the [sequence: see text] type (where r and D represent RNA and DNA). The object of this study was to investigate the sugar conformations at the internal junction in the hybrid-DNA octamer duplex (gccaCTGC). (GCAGTGGC)--where the lower-case letters represent RNA residues. Such duplexes represent good models for Okazaki fragments in which RNA primers are covalently extended into DNA strands during DNA replication of the lagging strand. Furthermore, this particular sequence occurs during HIV-1 retrovirus reverse transcription. The chimeric RNA-DNA strand and the complementary pure DNA strand chosen for this study result from the priming of (-)-strand DNA synthesis by tRNA(Lys) and subsequent (+)-strand DNA synthesis by reverse transcriptase prior to HIV-1 retrovirus integration. Despite the unusual specificity of the RNase H activity of reverse transcriptase, which cleaves the RNA c-a phosphodiester rather than the junction a-C linkage, we found no major structural differences among the RNA c-a phosphodiester rather than the junction a-C linkage, we found no major structural differences among the RNA sugar conformations--all RNA sugars were found in the normal C3'-endo A-form conformation. Instead, we find that the first DNA residue of the chimeric strand (5C) assumes a sugar conformation in the C4'-exo to O4'-endo range (P = 54-90 degrees). Furthermore, the hybrid segment of this duplex is more heteronomous than previously assumed for duplexes of the [sequence: see text] type.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1993

Genetics of life span in mice.

Thymic involution that occurs earlier in some individuals than others may be the result of complex interactions between genetic factors and the environment. Such interactions may produce defects of thymus-dependent immune regulation associated with susceptibility to developing autoimmune diseases, malignancy, and an increased number of infections associated with aging. The major histocompatibility complex may be important in determining profiles of cause of death and length of life in mice. Genetic influences on life span involve interactions between loci and allelic interactions during life which may change following viral infections or exposure to other environmental factors. We have used different experimental protocols to study the influence of H-2 on life span and found that interactions between genetic regions, are inconsistent, particularly when comparing mice infected or not infected with Sendai virus. Genes important for life span need to be studied against many genetic backgrounds and under differing environmental conditions because of the complexity of the genetics of life span. Several genetic models were used to demonstrate that the MHC is a marker of life span in backcross and intercross male mice of the H-2d and H-2b genotypes in B10 congenic mice. Females lived longer than males in backcross and intercross mice, while males lived longer than females in B10 congenics. H-2d was at a disadvantage for life span in backcross mice of the dilute brown and brown males exposed to Sendai infection, but intercross mice not exposed to Sendai virus of the same genotype were not at a disadvantage. H-2d mice were not disadvantaged when compared to H-2b in B10 congenics that had not been exposed to Sendai virus infection but the reverse was true when they were exposed. Overall, all our studies suggest that genetic influences in life span may involve interactions between loci and many allelic interactions in growing animals or humans. These genetic influences on life span may vary after they are exposed to infections or other environmental conditions. This paper emphasizes the need to use several genetic models, especially animals that have been monitored for infections, to study the genetics of life span.

Animals↗
PubMed1993

Modulation of 5HT1A receptors in the hippocampus and the raphe area of rats treated with clonazepam.

1. Clonazepam is one of the most potent benzodiazepines known to decrease the activity of the central serotonergic systems. The acute and subchronic administration of clonazepam reduced serotonin (5HT) turnover rate in the hippocampus of the rat, as determined by the ratio of the monoamine and its metabolite, 5-hydroxyindoleacetic acid. 2. The modulation of 5HT binding sites and 5HT1A receptors by the administration of clonazepam for various periods of time were studied in the hippocampus and the raphe area by experiments with radioligands. 3. The density of [3H]5HT recognition sites increased in the hippocampus of clonazepam-treated rats in a dose- and time-dependent manner. This increase was impaired by the simultaneous administration of the 5HT agonist 5-methoxy-N,N-dimethyltryptamine. The affinity of this binding did not significantly change. This observation might indicate an increase in some of the 5HT receptors or an increase of the uptake site. 4. The binding parameters for [3H]DPAT, Bmax and Kd, decreased in the hippocampus but not in the raphe area of clonazepam-treated rats. It seems that the presynaptic reduction in 5HT function, resulting in the decrease of its availability at the synaptic space, modifies the corresponding 5HT recognition sites. 5. These changes could be related to the anxyolitic activity or the withdrawal symptoms of benzodiazepines.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Association of diarrhea and low serum retinol in Peruvian children.

To examine the relationship between acute diarrhea and vitamin A status, a study was conducted in 137 children (72 with diarrhea and 65 illness-free control subjects) in the city of Lima, Peru. Serum retinol was measured spectrophotometrically in samples collected in 1987 and kept frozen until they were analyzed simultaneously in 1989. Serum retinol was significantly lower in the children with diarrhea (mean +/- SD: 0.51 +/- 0.48 mumol/L) than in those without diarrhea (1.00 +/- 0.32 mumol/L; 1 mumol/L retinol = 28.6 micrograms/dL). The multivariate estimate of the effect of diarrhea (-0.464 mumol/L) in a model that incorporated age, sex, and acute malnutrition (ie, weight-for-height) as confounding variables was essentially the same as the unadjusted difference (-0.492 mumol/L). Thus, this model showed that the retinol concentration in the serum depends greatly on the presence of diarrhea. These findings suggest that diarrhea, as has been shown for other infections, may lead to lower circulating retinol concentrations and perhaps to its depletion.

Child↗
PubMed1993

HLA-DQA1, DQB1 and DPB1 alleles on HLA-DQ2- and DQ9-carrying extended haplotypes.

DQA1, DQB1 and DPB1 alleles were investigated in a large panel of samples carrying HLA-DQ2- and HLA-DQ9-bearing extended haplotypes. Every instance of the [HLA-B8, SCO1, DR3, DQ2a] and [HLA-B18, F1C30, DR3, DQ2b] extended haplotypes carried the DQA1*0501 allele, while every instance of [HLA-B44, FC31, DR7, DQ2c], [HLA-B47, FC91,0, DR7, DQ2c] and [HLA-B57, SC61, DR7, DQ2d] carried the DQA1*0201 allele. All HLA-DR3, DQ2 and HLA-DR7, DQ2 extended haplotypes carried the DQB1*0201 allele. Every example of [HLA-B57, SC61, DR7, DQ9] carried the DQB1*0303 allele. Several associations between the DPB1 alleles and some HLA-DQ2- and DQ9-carrying extended haplotypes were identified. HLA-DPw2-encoding alleles, DPB1*0202 (50%, p < 0.001) and 0201 (30%), were found on the [HLA-B18, F1C30, DR3, DQ2b] extended haplotype. Every instance of the [HLA-B57, SC61, DR7, DQ9] extended haplotype carried the DPB1*0401 allele. Also, we have confirmed the associations of the DPB1*0101 and DPB1*0401 alleles with the [HLA-B8, SC01, DR3, DQ2a] extended haplotype. The analysis of homozygous typing cells carrying the [HLA-B44, FC31, DR7, DQ2c] extended haplotype showed that the DPB1*0401 and 0201 alleles were present at similar frequencies (37.5%), while the DPB1*1101 allele was found in only 25% of these haplotypes analyzed. Our results suggest that the constancy of the DNA of the HLA-B, DR, DQ regions may extend to the DP region and that the extent of such fixity varies, perhaps as the result of ethnic variability of the population studied.

Alleles↗
PubMed1993

Unrelated donor matching for bone marrow transplantation.

We found that in our laboratory the MLC was interpretable in most cases, in spite of patient disease state and shipping blood from unrelated donors over great distances. Our data clearly show that DRB1 allele typing was a good predictor of MLC reactivity and we believe that MLC testing in DRB1 allele mismatched unrelated pairs is not informative. However, our data suggest that MLC testing in DRB1 allele matched unrelated pairs is informative, because many such pairs produced weak but significant allostimulation. These weak MLC reactions may guide improvements in matching unrelated donors for BMT. For example, our MLC data suggest that it is important to match unrelated donors at DRB3 alleles for BMT.

Alleles↗
PubMed1992

Solution structure of [d(GCGTATACGC)]2.

The solution structure of the alternating pyrimidine-purine DNA duplex [d(GCGTATACGC)]2 has been determined using two-dimensional nuclear magnetic resonance techniques and distance geometry methods. Backbone distance constraints derived from experimental nuclear Overhauser enhancement and J-coupling torsion angle constraints were required to adequately define the conformation of the inter-residue backbone linkages and to avoid underwinding of the duplex. The distance geometry structures were further refined by back-calculation of the two-dimensional nuclear Overhauser enhancement spectra to correct spin-diffusion distance errors. Fifteen final structures for [d(GCGTATACGC)]2 were generated from the refined experimental distance bounds. These structures all exhibit fully wound B-form geometry with small penalty values (< 1.5 A) against the distance bounds and small pair-wise root-mean-square deviation values (typically 0.6 A to 1.5 A). The final structures exhibit positive base-pair inclination with respect to the helix axis, a marked alternation in rise and twist, and are shorter and wider than classical fiber B-form DNA. The purines were found to adopt a sugar pucker close to the C-2'-endo conformation while pyrimidine sugars exhibited significantly lower pseudorotation phase angles in the C-1'-exo to C-2'-endo range. The minor groove cross-strand steric clashes at pyrimidine-purine steps that would exist in pure B-DNA are attenuated by an increased rise at these steps (and an increased roll angle at TpA steps). Concomitantly the backbone torsion angles of the pyrimidine moieties have larger gamma values, larger epsilon values, and smaller zeta values than the purines. The structures generated by distance geometry methods were also compared with those obtained from restrained molecular dynamics with empirical force-field potentials. The results indicate that the nuclear magnetic resonance/distance geometry approach alone is capable of elucidating most of the salient structural features of double-stranded helical nucleic acids in solution without resorting to empirical energy potentials and without using any structural assumptions from crystallographic data.

Base Sequence↗