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J L Ramirez

Publications and source records attributed to J L Ramirez.

At least 37 records · Page 2Linked to original sources
PubMed1997

Characterization of an interspersed repetitive DNA element in the genome of Trypanosoma cruzi.

We report the molecular characterization of a middle repetitive DNA sequence, named C6, isolated from the Trypanosoma cruzi genome. C6 appears to be a composite repeated element since 3 subregions may be defined within it on the basis of sequence similarities with other T. cruzi genomic sequences. Sequences homologous to C6 are interspersed in the genome and can be mapped out on most chromosomal bands of different T. cruzi. strains. The copy number of the C6 element is about 1000 per haploid genome. Given the species specificity and different genomic distribution of C6 homologous sequences among the T. cruzi strains the C6 element could be a useful probe for diagnosis and typing of parasites. C6 is a polymorphic marker with potential as a tool for physical mapping of the T. cruzi genome.

Animals↗
PubMed1997

Influence of exogenous insulin before breeding on conception rate and litter size of sows.

We conducted two experiments on commercial farms to evaluate the effect of insulin administered to primiparous sows before postweaning estrus on subsequent reproductive performance. On the day after weaning in Exp. 1, 138 crossbred primiparous sows were assigned to receive saline or insulin (.4 IU/kg BW) once daily at the time of feeding for four consecutive days. Treatment did not affect interval from weaning to estrus (5.1 +/- .2 d) or percentage in estrus by 7 d after weaning (92.6%). Farrowing rate at second parity was increased by insulin (76.7 and 92.3% for saline and insulin treatments, respectively; P < .01). Litter sizes at second parity were not affected by insulin treatment. Experiment 2 was conducted on a different commercial farm using 491 primiparous crossbred sows. They were treated similarly to those in Exp. 1 with saline or insulin after weaning, except that treatment duration of 2 d of saline or insulin was included. Treatment did not affect the interval from weaning to estrus (overall, 9.2 +/- .5 d), percentage in estrus by 7 d after weaning (79.1%) or farrowing rate (90.2%). However, the number of total pigs born in the second litter for sows mated within 7 d after weaning was increased (P < .05) by one pig in sows treated with insulin for 4 d (10.3 +/- .3 pigs) compared with 2 d (9.1 +/- .3) and with saline (2 d and 4 d grouped together: 9.3 +/- .1). Third-parity litter size was not adversely affected by treatments applied before the second litter. In conclusion, manipulation with a metabolic hormone such as insulin may improve postweaning fertility by affecting aspects of ovarian follicle development or pregnancy establishment.

Analysis of Variance↗
PubMed1996

Restriction fragment length polymorphisms of constant region genes of immunoglobulin lambda chains in Venezuelan patients with systemic lupus erythematosus.

Previous studies suggest a potential association between human immunoglobulin (Ig) genes and susceptibility to systemic lupus erythematosus (SLE). Ig allotypic determinants seem to confer an increased risk for the disease in various ethnic patient populations. In this study we have examined the pattern of restriction fragment length polymorphisms (RFLP) of constant region lambda (C lambda) light chain genes in a group of 78 Venezuelan patients with SLE and 70 healthy controls. The frequency of the 8-kb allele and the 8/8 genotype was significantly lower in normal Venezuelan controls as compared to healthy British Caucasians (P = 0.0002 and 0.0007 respectively). In turn, Venezuelan controls showed a higher frequency of the 18-kb allele and the 18/18 genotype (P = 0.0002 and 0.0052 respectively). However, there were no statistically significant differences in either parameter between Venezuelan SLE patients and healthy controls. Our study argues against a role for lambda light chain constant region genes in predisposition to SLE.

Autoimmune Diseases↗
PubMed1996

Somatostatin increases growth hormone (GH) secretion in a subpopulation of porcine somatotropes: evidence for functional and morphological heterogeneity among porcine GH-producing cells.

Previous results demonstrate that porcine somatotropes can be separated by density gradient centrifugation into low density (LD) and high density (HD) subpopulations. In rat, two analog somatotrope subpopulations differ morphologically and functionally. In an attempt to determine whether morphological differences were also present within LD and HD porcine somatotropes, we undertook a quantitative electron microscope study of the subcellular organelles of immunoidentified LD and HD somatotropes. In addition, to test for the existence of functional differences, cultures of separated HD and LD subpopulations were treated for 4 h with or without 10 microM GRF-(1-29) and/or 100 microM somatostatin (SRIF), and porcine GH release and intracellular content were evaluated using a homologous enzyme immunoassay. Morphometric results demonstrate that LD somatotropes are smaller in size (P < 0.05) and contain fewer secretory granules (P < 0.05) and more rough endoplasmic reticulum (P < 0.05) than HD somatotropes. In terms of secretion, LD somatotropes showed a classical response; GRF increased GH release 1.7-fold (n = 6; P < 0.05) over the control value, whereas treatment with SRIF alone did not affect basal GH release in this subpopulation, but partially blocked GRF-induced GH release. HD somatotropes responded to GRF with a similar 1.7-fold increase in GH release. However, SRIF administered alone or in combination with GRF exerted a paradoxical stimulatory effect on HD somatotropes (2.15- and 2.12-fold over control value, respectively; n = 6; P < 0.05). These results demonstrate that the porcine somatotrope population is composed of two major subpopulations that display a distinctive pattern of ultrastructural organization and a markedly divergent secretory response to in vitro SRIF treatment.

Animals↗
PubMed1996

Follow-up of a human accidental infection by Leishmania (Viannia) braziliensis using conventional immunologic techniques and polymerase chain reaction.

The results of a two-year follow-up study of an accidental human infection with Leishmania (Viannia) braziliensis are presented. Western blots, indirect immunofluorescence, and intradermal reaction assays were not able to detect the infection before week 18 postinfection, whereas using the polymerase chain reaction (PCR) on blood samples, parasite DNA was detected at week 8. All test results, except the intradermal reaction followed the cure process and 12 weeks after the last chemotherapy injection (week 36 postinfection), all were negative. However, a year after cure, the PCR became positive again and has remained so for two years. To determine in which blood cell fraction the parasite was evident, enriched lymphocyte and monocyte fractions were assayed by the PCR. These results are discussed in the context of persistent infections.

Accidents↗
PubMed1993

Isolation of two pyruvate kinase activities in the parasitic protozoan Leishmania mexicana amazonensis.

Using phosphocellulose affinity chromatography we were able to separate two pyruvate kinase (EC 2.7.1.40) activities in the parasitic protozoan Leishmania mexicana amazonesis. One activity (PYK1) showed hyperbolic kinetics and was decreased by fructose 2,6-bisphosphate, whereas the second activity (PYK2) showed sigmoidal kinetics for the substrate phosphoenolpyruvate and was activated by fructose 2,6-bisphosphate. Molecular sieve chromatography (Sephacryl S-400) of PYK1 produced a single peak of apparent molecular mass around 200,000, while PYK2 eluted at a position corresponding to M(r) 55,000.

Animals↗
PubMed1993

Repetitive sequences in the ribosomal intergenic spacer of Trypanosoma cruzi.

A fragment of Trypanosoma cruzi ribosomal intergenic spacer (IGS) located at 6.7 kb from the 3' end of the 24S rRNA gene was analyzed. This IGS fragment is characterized by the presence of three types of repetitive elements (designated Spacer Repetitive Elements, SRE), short direct repeats (5-6 bp) and chi-like recombinational sequences. SRE elements are composed of relatively short repeats (43-145 bp) which show variabilities consisting of nucleotide changes, insertions and deletions. SRE-1 element (145 bp) has a short oligo(dA) tail at the end of the repeat and can be found flanked by other SRE elements. SRE elements are species-specific, suggesting that probes based on them may be diagnostic for Trypanosoma cruzi.

Animals↗
PubMed1993

Detection of human papillomavirus-related oral verruca vulgaris among Venezuelans.

A sensitive in situ hybridization test under low stringency conditions (LCS) with a set of digoxigenin-labeled human papillomavirus mixed probes (D-L HPV MP) revealed a positive reaction in 8 of 10 cases of oral verruca vulgaris (OVV). Ages ranged from 5 to 37 years with a mean of 14.5 years. 50% of all cases were located intraorally on the hard palate, followed in frequency by the commissures. These preliminary findings provide evidence of the role of HPV in OVV from a sample of the Venezuelan population. We show that in situ hybridization conducted under LSC is useful in HPV detection (regardless of the type) and the digoxigenin-labeling system is a rapid, relatively easy and specific method. In addition, this technique permits the retrospective evaluation of routinely processed material, thus widening the investigative spectrum for HPV.

Adolescent↗
PubMed1993

What is a chromosome like in Leishmania?

Hereby, we present evidences of the presence of centromeric proteins in Leishmania mexicana. These proteins were partially purified and used to bind Leishmania DNA. The protein-DNA complex was immunoprecipitated and the DNA extracted, like in the human sample. Two major fragments of 1.2 and 2.2 Kbp, respectively, were resolved in agarose gel electrophoresis. A model of chromosomal structure and chromosomal segregation in Leishmania is presented.

Animals↗
PubMed1993

Fructose 2,6 bisphosphate promotes the monomer-tetramer conservation of Leishmania mexicana amazonensis pyruvate kinase type two.

The enzyme pyruvate kinase of Leishmania mexicana amazonensis presents two forms with different kinetic properties and behavior for the heterotrophic activator fructose 2,6 bisphosphate. Pyruvate kinase 1, which is isolated as a tetramer, is inhibited by this metabolite. The second activity, Pyruvate kinase 2, is activated by fructose 2,6 bisphosphate, which promotes the monomer-tetramer conversion of this enzyme.

Animals↗
PubMed1993

Homogeneous restriction fragment length polymorphism analysis of the ribosomal DNA repeating unit in New World Leishmania.

We have studied the Sau 3AI restriction length polymorphisms (RFLP) of the non-transcribed ribosomal spacer of Leishmania isolates from the mexicana and braziliensis complexes, using cloned sequences of Leishmania garnhami and Leishmania braziliensis. The L. garnhami probe produced very complex but conserved patterns in the homologous organisms, and these were shared by all the mexicana complex isolates at intermediate stringency conditions. The small subunit rRNA coding region within the probe also revealed a polymorphic Sau 3AI site exclusive of the braziliensis isolates. The braziliensis probe, containing only spacer sequences, yielded simple and very homogeneous patterns in all braziliensis isolates regardless of their geographical origin. Two main groups are identified in the New World isolates by the RFLP analysis in coincidence with the accepted mexicana and braziliensis complexes.

Animals↗
PubMed1993

Differential turn-over of beta-tubulin during the cell differentiation of Trypanosoma cruzi.

We investigated the expression of beta-tubulin during the differentiation of non-infective epimastigotes to infective metacyclics of Trypanosoma cruzi to underlay some of the regulatory mechanisms of the gene expression in this pathogenic parasite. Given the strong evolutionary conservation of tubulin, it was possible to study its translational and transcriptional products with heterologous probes. Quantitative Western blotting with specific monoclonal antibodies against beta-tubulin revealed an increase in the relative amounts of this protein in metacyclics with respect to epimastigotes. Pulse-chase experiments with radioactive methionine followed by immunoprecipitation and polyacrylamide gel electrophoresis showed that beta-tubulin has a slower degradation in metacyclics, which may contribute to its relative higher abundance in these parasite forms. In contrast with these results, both in vitro translation of poly (A+) mRNA in a wheat germ system and Northern blots of total and poly (A+) mRNA with a heterologous DNA probe from Leishmania enriettii, revealed a significant decrease (5 fold) in the specific transcripts of beta-tubulin in the metacyclics with respect to epimastigotes. It thus appeared that after differentiation of T. cruzi the translational machinery for a key protein such as beta-tubulin is shut off by a decrease in its specific message. The protein levels of this protein are maintained, however, by a compensatory mechanism that involves a slower turn-over of the synthesized protein.

Animals↗
PubMed1992

In situ hybridization with digoxigenin-labelled DNA probes for the detection of human papillomavirus-induced focal epithelial hyperplasia among Venezuelans.

An in situ hybridization assay with digoxigenin-labelled probes was used to detect the presence of human papillomavirus (HPV) sequences in ten related Venezuelan patients with the diagnosis of focal epithelial hyperplasia. The samples displayed HPV sequences in all cases. Further restriction analysis in four of the patients suggested the presence of HPV-13 in oral lesions.

Adolescent↗
PubMed1992

Differential response of amphibian PRL and TSH pituitary cells to in vitro TRH treatment.

Hypophysial prolactin (PRL) and thyrotropin (TSH) cells of Rana perezi were examined after treatment in vitro with synthetic thyrotropin-releasing hormone (TRH). Ultrastructural morphometry applied to PRL and TSH immunoidentified cells estimated the volume density (Vv) of the secretory granules (SG), rough endoplasmic reticulum (ER), and Golgi complex (GC) as well as the numerical density (Nv) of the granules. Hemipituitaries were cultured in a superfusion system with or without 100 ng TRH/ml for 4, 14, or 24 hr. PRL cells showed significant degranulation (42%) of medium size SG after 14 hr of stimulation, whereas the biosynthetic machinery (ER and GC) was significantly developed after 4 hr of TRH culture (increase of Vv of GC, 1.5-fold, and ER, 1.3-fold, in comparison to the control). Most of these changes remained after 24 hr of TRH treatment. Compared with controls, TRH-treated TSH cells differed only after 24 hr when SG showed degranulation (40%), mainly of the medium size ones, and Vv of GC (1.6-fold) and ER (1.3-fold) increased. These results suggest that TRH acts directly on amphibian PRL and TSH cells stimulating hormonal synthesis and release. The time courses of responses to TRH differed in that PRL cells gave an immediate response while TSH cells gave a more delayed reaction.

Animals↗
PubMed1991

Assessment of delta virus infection in Venezuelan high-risk population for hepatitis B virus.

HDV infectivity particularly related to sexual activity has been difficult to establish. We investigated the prevalence of HDV in a high risk urban male population currently evaluated for HIV infection. Fourth-eight homosexual or bisexual men (96% positive for HIV) being routinely followed in the outpatient clinic, 40 sera obtained randomly from male homosexuals and 24 HBsAg carriers were examined by ELISA and Western Blot. HDV RNA was assessed by slot-blot after hybridization with cDNA probe from a recombinant plasmid (pS-1). [None of the 48 male subjects or from a recombinant plasmid (pS-1).] None of the 48 male subjects or from the randomly selected homosexuals tested positive for anti-HDV. HDV RNA searched in a selected group of sera from either high risk population or from HBsAg carriers proved also to be negative. We suggest that factors other than HBV chronic bearing and/or sexual promiscuity should be associated with HDV spread.

Adult↗
PubMed1988

Estrogen induces estrus unaccompanied by a preovulatory surge in luteinizing hormone in suckled sows.

The objective was to determine if progressive changes occurred in incidence of estrus and patterns of luteinizing hormone (LH) after estradiol benzoate (EB) administration at three stages of lactation. Estradiol benzoate (800 micrograms) was injected at the beginning of the second (7.8 +/- 0.3 days, range 7-8, n = 4), third (15.6 +/- 0.3 days, range 15-16 days, n = 5), or fourth (23.3 +/- 0.5 days, range 22-24, n = 4) wk of lactation. Interval to estrus (h) and proportion in estrus (in parentheses) were 72 (1/4), 88.5 (4/5), and 99 (4/4; pooled SEM = 3.5) for the second, third, and fourth weeks, respectively. Only one animal ovulated during lactation (third week). This animal had a progesterone concentration of 17 ng/ml 1 wk after estrus and an LH concentration above 2.0 ng/ml for 72 through 90 h after EB. In other sows, LH remained less than 1.0 ng/ml after EB. Patterns of LH after EB in sows treated during the fourth week of lactation were increased to a maximum of 0.76 ng/ml by 120 h after EB, which was greater than for those treated during the second or third week (maxima of 0.38 and 0.32 ng/ml, respectively; pooled SEM = 0.07; p less than 0.05). Concentrations of LH in sows that exhibited estrus were greater both before and after treatment than in sows that did not exhibit estrus after EB (p less than 0.05). By 2 wk after weaning, 8 sows had ovulated (6 of these exhibited estrus), and there were no effects of stage of lactation on these responses. We concluded that the behavioral responsiveness to EB increased as lactation progressed. The increased LH in sows treated during the fourth week indicated a partial recovery of the positive feedback response to EB. These data suggested that separate mechanisms caused behavioral and gonadotropin responses to EB in lactating sows.

Animals↗