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Biomedical subjects

M Salazar

Publications and source records attributed to M Salazar.

At least 55 records · Page 3Linked to original sources
PubMed1996

Structure of chimeric duplex junctions: solution conformation of the retroviral Okazaki-like fragment r(ccca)d(AATGA).d(TCATTTGGG) from Moloney murine leukemia virus.

We have determined the solution structure of the synthetic chimeric duplex r(ccca)d(AATGA).d(TCATTTGGG) by two-dimensional NMR, distance geometry, restrained molecular dynamics, and full relaxation matrix simulation of the two-dimensional nuclear Overhauser effect spectra at various mixing times. The chimeric strand of this duplex consists of the last four residues of the tRNA(Pro) primer for (-) strand DNA synthesis of Moloney murine leukemia virus and the first five residues of the (-) strand DNA produced by extending this primer; the complementary DNA strand corresponds to the (+) strand product from this template. The hybrid section of this chimeric duplex assumes a structure similar to that found for pure hybrid duplexes of mixed sequence, while the DNA section assumes a conformation closer to B-form DNA. There is significant distortion of the duplex at the hybrid-DNA junction which is manifested in marked changes in the helical parameters buckle, roll, and tip, changes in glycosidic torsion angles, and changes in the backbone torsion angles delta, epsilon, and zeta. The sugar conformations also undergo large changes, from heteromerous puckers in the hybrid section to a more B-form in the DNA section. Furthermore, the intrastrand phosphate separation in the chimeric strand is more typical of A-form duplexes in the RNA section but more like B-form duplexes in the DNA section. In the DNA section the minor groove width changes gradually from B-form at the periphery and approaches hybrid-like dimensions closer to the junction. The structural discontinuities act synergistically to produce a bend of 18 +/- 3 degrees at the junction. The global structure of this sequence is similar to that previously found in the chemically analogous Okazaki fragment r(gcg)d(TATACCC).d(GGGTATACGC) in solution. Such structure homology suggests a possible link between structure and function with respect to the recognition and cleavage of the junction RNA residues in both retroviral chimeras and Okazaki fragments during reverse transcription and normal DNA replication.

Base Sequence↗
PubMed1996

Antifertility effects of (+)-S-2-amino-6-iodoacetamidohexanoic acid (2-AIHA) in female rats.

(+)-S-2-amino-6-iodoacetamidohexanoic acid (AIHA), an irreversible inhibitor of the ornithindecarboxylase and extrahepatic arginase enzymatic activities with antineoplasic properties, was evaluated for antifertility activity in pregnant rats by oral administration at different periods of gestation. Our results showed that doses of 10 and 20 mg/kg of AIHA orally administered produced a contraceptive effect when it was administered from days 2 to 5, and 8 to 12 of gestation, respectively. The gestation time was slightly shortened when AIHA was applied from day 15 until labor. No sign of external malformations in fetuses was observed. On the other hand, AIHA did not affect the total length of oestrous cycle at the same dosage level used to interrupt pregnancy. In ovariectomized immature rats, neither changes in uterine weight, premature vaginal opening, or cornified cells were found. However, AIHA enhanced the estradiol-induced increase in uterine weights when both were concomitantly administered.

Abortifacient Agents↗
PubMed1996

Effect of Spirulina maxima consumption on reproduction and peri- and postnatal development in rats.

Spirulina maxima, an edible micro-organism useful in human nutrition, was examined for its effect on general reproductive performance and for peri- and postnatal toxicity in rats at levels of 0, 10, 20 and 30% (w/w) incorporated into the diet. There was no reduction in body weight gain in males or females and no deaths or clinical signs of toxicity. Treatment was not associated with any adverse effect on any measure of reproductive performance, including male and female fertility and duration of gestation. There was no increase in the number of abnormal pups at caesarean section or at birth. S. maxima consumption did not result in adverse effects on developmental markers of the pups.

Animals↗
PubMed1996

Evidence for a dopaminergic involvement in the natriuretic action of centrally administered renin.

Intracerebroventricular (IVT) administration of renin (R) to conscious male hydrated rats induces an increase in sodium excretion. The involvement of brain dopaminergic neurons in the renal action of IVT-R was investigated. Renin-induced natriuretic action was prevented by domperidone and by inhibition of tyrosine hydroxylase activity with alpha-methyl-p-tyrosine treatment. In addition, this effect was absent following selective central dopaminergic denervation with 6-hydroxydopamine (IVT) in combination with desmethylimipramine (IP). Our results suggest that renin acts centrally, at least in part, via an interaction with endogenous dopamine systems.

Animals↗
PubMed1996

Comparison of HLA-A antigen typing by serology with two polymerase chain reaction based DNA typing methods: implications for proficiency testing.

Serology has been routinely used for class I HLA typing for the selection of donors for allotransplantation. However, serology is not adequate for the assignment of all class I specificities especially when testing non-Caucasians subjects and it is necessary to adopt new strategies for routine testing. At the present time the extent of incorrect serologic HLA-A assignments in clinical testing is not known. The polymerase chain reaction (PCR) based techniques have become useful standard clinical typing methods of HLA class II alleles but most laboratories still use serology for class I typing. In this report we have compared two PCR based techniques, PCR amplification with sequence-specific primers (PCR-SSP) and PCR amplification and subsequent hybridization with sequence-specific oligonucleotide probes (PCR-SSOP), for the assignment of HLA-A specificities in 56 blood samples from patients and families serologically typed for HLA-A. This side-by-side comparison of PCR methods showed 100% correlation between them. However, serology showed 7.1% misassignments and, in an additional panel of 19 cells where serology produced equivocal results, the PCR-SSP and SSOP methods identified the correct HLA-A specificity. Our results emphasize the need to complement routine serologic testing of HLA specificities with a small number of primers designed to test HLA-A34, A36, A43, A66, A74 and A80, that are not detected with high precision by serology. We concluded that the PCR-SSP and -SSOP methods can be used in routine HLA-A typing of patients and donors for transplantation with a greater precision than serology.

HLA-A Antigens↗
PubMed1996

New HLA-DR haplotypes containing the DRB6 pseudogene.

An unexpected probe reaction pattern was observed in two samples during HLA-DR typing by PCR-Sequence Specific Oligonucleotide Probes. In order to confirm the unusual typings, samples were analyzed by PCR-Sequence Specific Primers, cloning, and nucleotide sequencing of the second exon of the HLA-DRB-genes. The confirmed DR, DQ phenotype for one sample was DRB1*0701, DRB4*01, DRB5*0101, DRB6*0201, DQB*0602, DQB1*0202. The phenotype of other sample was DRB1*1602, DRB1*1302, DRB3*0301, DRB6*0101, DQB1*0501, DQB1*0502. The first sample has the novel combination of DRB1*0701 with DRB5*0101 and DRB6*0201. The second sample has either DRB6*0101 together with DRB1*1602 in absence of any DRB5 allele or DRB6*0101 together with DRB1*1302, DRB3*0301. We postulate that the most likely haplotype in sample #1 is DRB1*0701; DRB5*0101, DRB1*0602 which could have arisen from gene conversion. The most likely haplotype in sample #2, DRB1*1602, DRB6*0101, DQB1*0502 would have arisen from an homologous recombination event.

HLA-DR Antigens↗
PubMed1996

MHC class II alleles and haplotypes in patients with pemphigus vulgaris from India.

Pemphigus vulgaris (PV) is a blistering disease of the skin and mucous membranes characterized by an autoantibody response against a keratinocyte adhesion molecule, desmoglein 3, causing acantholysis and blister formation. We compared high resolution MHC class II alleles and haplotype frequencies (HLA-DRB, DQA1 and DQB1) in 37 patients with PV to 89 haplotypes of normal relatives from New Delhi and Ahmedabad. We found that PV patients had significantly increased frequencies of DRB1*1404 (P < 0.0001), DQA1*0101 (P = 0.001), and DQB1*0503 (P < 0.0001). These associations were due to the increased frequencies of the haplotype HLA-DRB1*1404, DRB3*0202, DQA1*0101, DQB1*0503 in patients compared to control haplotypes (p < 0.0001). Also, patients from Ahmedabad had a significant increase in HLA-DQB1*0302 (p = 0.03). An identical amino acid sequence (Leu-Leu-Glu-Arg-Arg-Arg-Ala-Glu), in positions 67-74 of the beta domain of DRB alleles is restricted to some DR14 alleles. Therefore, there are three possible explanations for class II allele involvement in autoantibody in PV patients with class II haplotypes marked by HLA-DR14. First, the class II alleles could be markers for an unidentified susceptibility gene in linkage disequilibrium with them. Second, the primary association could be with DQB1*0503 and the association with HLA-DR14 alleles would be the result of linkage disequilibrium. Third, the HLA-DRB1 locus susceptibility could involve a specific amino acid sequence in the third hypervariable region shared by several HLA-DR14 alleles.

Alleles↗
PubMed1996

High incidence of hepatitis C virus infection in hemodialysis patients in units with high prevalence.

The prevalence of hepatitis C virus (HCV) infection was evaluated in 227 hemodialysis patients from four units in Caracas, Venezuela, by using different second- and third-generation enzyme immunoassays (EIAs) and immunoblot assays. HCV antibodies were detected in 162 patients (71%) by the recombinant-based second-generation assays (Abbott and Ortho) and in 161 patients by the synthetic peptide-based EIA (UBI). Of the 162 HCV antibody-positive serum samples, 161 were confirmed to be positive by RIBA 3. HCV RNA was detected in 49 of 68 (72%) of the seropositive patients and in 5 of 21 (24%) of the seronegative ones. HCV RNA was not always correlated with an increase in alanine aminotransferase (ALT) levels. Among 20 patients positive for HCV RNA and for HCV antibodies (without any hepatitis B virus [HBV] marker), only 10 had elevated ALT levels. The possible interference of HBV for HCV replication was evaluated. No significant difference was found between the presence of HCV RNA and the presence of any HBV serological markers. The possible routes of transmission of HCV in hemodialysis patients are multiple, and some of them are still controversial. Of the HCV-positive patients, 30% received a blood transfusion, significantly more than the 15% found for the HCV-negative group. However, blood transfusions alone could not account for the high incidence observed in this group of patients (38% from 1994 to 1995). In conclusion, about one-quarter of the apparently non-HCV-infected patients were probably seroconverting, ALT may not be a useful indicator of HCV infection in hemodialysis patients, and nosocomial transmission of HCV may play a role in the spread of HCV in this group.

Alanine Transaminase↗
PubMed1995

The major histocompatibility complex region marked by HSP70-1 and HSP70-2 variants is associated with clozapine-induced agranulocytosis in two different ethnic groups.

Genes of the major histocompatibility complex (MHC) have been associated with susceptibility to drug-induced adverse reactions. We previously found that clozapine-induced agranulocytosis (CA) is associated with the HLA-DRB1*0402, DRB4*0101, DQB1*0302, DQA1*0301 haplotype in Ashkenazi Jewish patients and with the HLA-DRB1*1601, DRB5*02, DQB1*0502, DQA1*0102 haplotype in non-Jewish patients. In the present study, we tested the hypothesis that the variants of the heat-shock protein 70 (HSP-70) encoded by the HSP-70 loci located within the MHC region and known to be involved in apoptosis and regulation of cell proliferation could play an important role in molecular mechanisms of CA. First, we analyzed HSP70-2 polymorphism in risk-associated haplotypes from HLA homozygous cells and normal individuals and confirmed that the HSP70-2 9-kb variant was associated invariably with DR4 (HLA-DRB1*0402, DQB1*0302) and DR2 (HLA-DRB1*01601, DQB1*0502, DQA1*0102 and HLA-DRB1*1501, DQB1*0602) haplotypes, which were the haplotypes found increased in Jewish and non-Jewish patients with CA, respectively. The 9.0-kb variant was also found to be associated with HLA-B44, DRB1*0401 and HLA-B44, DRB1*07 haplotypes. Second, in patients with CA (12 Ashkenazi Jewish and 20 non-Jewish patients), HSP70-1 A and HSP70-2 9.0-kb variants were associated with the MHC haplotypes found by us to be markers of susceptibility to CA. The clozapine-treated control group had an excess number of HSP70-1 C and HSP70-2 8.5-kb variants, consistent with genetic resistance to CA associated with those variants. This finding supports our hypothesis that a dominant gene within the MHC region (marked by HSP70-1 and HSP70-2), but not necessarily HLA, is associated with CA in two different ethnic groups.

Agranulocytosis↗
PubMed1995

HLA associations in clozapine-induced agranulocytosis.

We previously reported preliminary results of association of clozapine-induced agranulocytosis (CA) with HLA-B38, DR4, DQ3 in five Ashkenazi Jewish patients and with HLA-DR2, DQ1 in four non-Jewish patients. In the present study, 31 additional patients with CA, 10 Ashkenazi Jewish, and 21 of non-Jewish ancestry, were studied. HLA alleles and haplotypes were compared among 52 patients (33 Ashkenazi Jewish, 19 non-Jewish) matched for ethnic background and clinical status. Our results show two associations and define the HLA allele markers for the Ashkenazi Jewish and non-Jewish haplotypes associated with CA. The most important markers for susceptibility for CA in Ashkenazi Jewish patients were DRB1*0402, DQB1*0302, and DQA1*0301, and in non-Jewish patients, HLA-DR*02, DQB1*0502, and DQA1*0102. HLA-DRB1*011 and DQB1*0301 were underrepresented in Ashkenazi Jewish patients when compared with controls. We hypothesize that genes of the major histocompatability complex, other than class I and class II, are responsible for CA; among them are the variants of the heat-shock proteins 70 or the tumor necrosis factor loci.

Adult↗
PubMed1995

Anti-inflammatory activity of the bark of Hippocratea excelsa.

The ethanol extract of the plant Hippocratea excelsa was examined for its anti-inflammatory effects using several animal models. It produced significant inhibition of carrageenan-induced paw edema and reduced the weight of cotton pellet-induced granuloma at doses of 25-100 mg/kg. The extract was found to exert a protective effect on heat-induced erythrocyte lysis at concentrations of 25, 50 and 100 micrograms/ml. In chronic models of formaldehyde and adjuvant arthritis, its anti-arthritic activity was found to be less than that of phenylbutazone (PNB). It may be inferred that the ethanol extract is effective against both exudative-proliferative and chronic phases of inflammation.

Animals↗
PubMed1995

Life-span, T-cell responses, and incidence of lymphomas in congenic mice.

Survival, T-cell functions, and postmortem histopathology were studied in H-2 congenic strains of mice bearing H-2b, H-2k, and H-2d haplotypes. Males lived longer than females in all homozygous and heterozygous combinations except for H-2d homozygotes, which showed no differences between males and females. Association of heterozygosity with longer survival was observed only with H-2b/H-2b and H-2b/H-2d mice. Analysis using classification and regression trees (CART) showed that both males and females of H-2b homozygous and H-2k/H-2b mice had the shortest life-span of the strains studied. In histopathological analyses, lymphomas were noted to be more frequent in females, while hemangiosarcomas and hepatomas were more frequent in males. Lymphomas appeared earlier than hepatomas or hemangiosarcomas. The incidence of lymphomas was associated with the H-2 haplotype--e.g., H-2b homozygous mice had more lymphomas than did mice of the H-2d haplotype. More vigorous T-cell function was maintained with age (27 months) in H-2d, H-2b/H-2d, and H-2d/H-2k mice as compared with H-2b, H-2k, and H-2b/H-2k mice, which showed a decline of T-cell responses with age.

Animals↗
PubMed1995

DNA duplexes flanked by hybrid duplexes: the solution structure of chimeric junctions in [r(cgcg)d(TATACGCG)]2.

Hybrid duplexes and chimeric duplexes containing hybrid segments linked to pure DNA (or pure RNA) segments are involved in transcription and replication, as well as reverse transcription. A complete understanding of the mechanism of these processes requires detailed information on such duplexes and the junctions between duplexes of differing structure. Using two-dimensional NMR, restrained molecular dynamics and mechanics, and back-calculation refinement against the nuclear Overhauser effect spectra at various mixing times, we have determined the solution structure of the chimeric duplex [r(cgcg)d-(TATACGCG)]2 containing a pure DNA segment in the center of a hybrid duplex. The solution structure differs from the previously determined X-ray structure of the analogous duplex [r(gcg)d(TATACGC)]2, which was found to be A-form throughout [Wang, A.H.-J., et al. (1982) Nature 299, 601-604]. The basic features of the solution structure are (a) the RNA residues are all A-form with C3'-endo sugar conformations, (b) the central DNA segment is B-form, (c) the transition from A-form RNA sugar conformations to B-form DNA sugar conformations involves only the dT5 base step, and (d) although the sugar conformations of the DNA residues A6-G12 are closer to B-form, the basic helical properties of the peripheral RNA.DNA hybrid segments are closer to typical A-form than to B-form.

Base Sequence↗
PubMed1995

Normal HBsAg presentation and T-cell defect in the immune response of nonresponders.

Lymphocytes from nonresponders to HBsAg fail to proliferate in vitro in the presence of HBsAg-pulsed antigen presenting cells. We studied four pairs of major histocompatibility complex (MHC)-matched, mixed lymphocyte reaction-negative individuals discordant for HBsAg response. For each pair, responder lymphocytes proliferated in the presence of nonresponder antigen-pulsed antigen presenting cells. Responder and nonresponder antigen presenting cells were equally effective. There was no evidence for inhibition of responder T-cell proliferation by nonresponder lymphocytes or antigen presenting cells. The defect is thus in the helper T cells of nonresponders and not in the antigen processing or binding of processed peptides to MHC molecules on antigen presenting cells.

Adult↗
PubMed1995

Advances in HLA genetics.

The major histocompatibility complex (MHC) is a genetic system of over 70 known genes that occupies the midportion of the short arm of the sixth chromosome (C6p) and spans about 4 million base pairs of DNA. The high-resolution typing of class I and class II MHC genes and the identification of genes between and near them has increased the definition of the genetic basis of immune responses and diseases of unknown etiology such as autoimmune diseases in man. Although there are many more genetic systems that participate in the rejection of tissues and in the immune response, the MHC plays a central role in tissue compatibility and immune response against cancer and infectious diseases. In this paper, the authors review evidence about the role of HLA polymorphism in the pathogenesis and development of cancer, infectious diseases, autoimmune diseases and transplantation.

Animals↗