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Biomedical subjects

A Ramos

Publications and source records attributed to A Ramos.

At least 199 records · Page 11Linked to original sources
PubMed1996

Detection and identification of human pathogenic Leishmania and Trypanosoma species by hybridization of PCR-amplified mini-exon repeats.

A single pair of PCR primers within a conserved region of the mini-exon repeat was used to amplify the repeats from 10 species of pathogenic Leishmania belonging to four major clinical groups and also from three species of Trypanosoma. Oligonucleotide hybridization probes for the detection and identification of the PCR-amplified repeats were constructed from alignments of mini-exon intron and intergenic sequences. The probes generated from mini-exon intergenic regions of the L. (V.) braziliensis, L. (L.) donovani, and L. (L.) mexicana species hybridized specifically to their cognate groups without discriminating between the species within the groups. The probes for L. (L.) major and L. (L.) aethiopica were species-specific, while the L. (L.) tropica probe also hybridized with the L. (L.) aethiopica mini-exon repeat. The mini-exon intron-derived probes for T. cruzi, T. rangeli, and T. brucei were species-specific. This method involving the detection of specific PCR-amplified products produced using a single primer set represents a novel sensitive and specific assay for multiple trypanosomatid species and groups.

Animals↗
PubMed1996

Completely allogeneic spleen cells induced cytolytic neonatal tolerance to alloantigens, but failed to establish allo-helper interactions with host T cells.

The injection of spleen cells from F1 mice into-newborns from a parental strain results in the establishment of cytolytic tolerance to donor alloantigens and the development of a lupus-like disease. This syndrome is the consequence of the recognition by alloreactive host CD4+ T cells of discordant major histocompatibility complex (MHC) class II antigens on semi-allogeneic donor B cells. We have analysed whether completely allogeneic spleen cells are as able as semi-allogeneic spleen cells to induce cytolytic tolerance to donor alloantigens and to co-operate with alloreactive T cells for autoantibody production. BALB/c mice were injected at birth with Thy-1-depleted spleen cells from (C57BL/6 x BALB/c)F1 or C57BL/6 mice, either alone or in combination. Cytolytic tolerance was always induced, as manifested by persistence of chimerism and acceptance of skin allografts. However, only F1 semi-allogeneic B cells were activated by alloreactive host T cells to produce anti-DNA IgG antibody. The deficient co-operation between BALB/c CD4+ T cells and completely allogeneic C57BL/6 B cells was confirmed after neonatal injection of (C57BL/ 6 x BALB/c)F1(Igha) spleen cells together with C57BL/6(Ighb) spleen cells. These mice developed anti-DNA antibodies bearing only the Igha allotype. Similar results were observed in experiments of allogeneic interaction in vitro, in which BALB/c CD4+ T cells were cocultured with either (C57BL/6 x BALB/c)F1 or C57BL/6 B cells. The present results demonstrate that completely allogeneic spleen cells efficiently induced cytolytic unresponsiveness to donor alloantigens, but B cells contained in this spleen cell population were unable to establish allo-helper interactions with alloreactive CD4+ T cells, suggesting that cytolytic and helper T-cell interactions involved in alloreactivity may be different.

Animals↗
PubMed1996

Immunoglobulin G subclass measurements in recurrent aphthous stomatitis.

We have measured serum levels of IgG subclasses and total IgG, IgA and IgM in a group of 34 recurrent aphthous stomatitis (RAS) patients. At the time of blood collection, 23 of the 34 patients had active oral lesions. The remaining 11 patients were at an inactive stage. All measurement were performed in the Beckmann 360 Array Protein System. Serum levels of IgG2 subclass were significantly lower (P < 0.05) in the whole group of patients (34) when compared to the control group. This relationship was still significant (P < 0.05) when only the 11 patients without active oral lesions were considered but disappeared in patients at an active stage. We conclude that low serum levels of IgG2 may play a role in the pathogenesis of RAS, just as in other recurrent infectious diseases, and that serum levels of this immunoglobulin subclass, as well as total IgA, may undergo transient changes, depending on the different periods of activity and quiescence of the disease.

Adolescent↗
PubMed1996

Serum levels of CD14 in neonatal sepsis by Gram-positive and Gram-negative bacteria.

The purpose of this study is to measure soluble CD14 (sCD14) levels in sera from newborn with sepsis, to compare it with other markers, and to study its evolution in Gram-negative and Gram-positive sepsis. Forty normal newborns were included (26 were full term and 14 were preterm infants), 20 babies had a positive blood culture (11 Gram-positive and 9 Gram-negative) and 16 cases were suspected of having sepsis based on clinical and laboratory findings, but a negative blood culture. Interleukin-6 (IL-6), sCD14, and tumour necrosis factor-alpha (TNF alpha) were measured by enzyme immunoassay, and fibronectin (FN) and C-reactive protein (CRP) by radial immunodiffusion. Neonates with a positive blood culture had increased levels of sCD14 (3.20 +/- 1.26 micrograms ml-1, p < 0.001), CRP (69 +/- 46 micrograms ml-1, p < 0.001) and IL-6 (134 +/- 150 pg ml-1, p < 0.001), and decreased values of FN (12.3 +/- 6.6 mg ml-1, p < 0.001). TNF alpha levels were also high (160 +/- 37 pg ml-1), but this increase was not statistically significant. Newborn infants suspected of having sepsis but a negative blood culture had similar but milder abnormalities. Soluble CD14 levels correlated with CRP values; however, there was no correlation between sCD14, TNF alpha and IL-6. Neonates with sepsis by Gram-positive bacteria had lower sCD14 levels than patients with Gram-negative sepsis (2.63 +/- 1.2 versus 4.04 +/- 1.0 micrograms ml-1, p < 0.05). In conclusion, the sCD14 level is increased in newborn infants with sepsis, and this is higher in infections by Gram-negative bacteria, suggesting a different contribution of monocyte and macrophage cells. In contrast, IL-6, TNF alpha, CRP and FN values are similar in infections by Gram-positive and Gram-negative bacteria.

Biomarkers↗
PubMed1996

Citrate and Sugar Cofermentation in Leuconostoc oenos, a (sup13)C Nuclear Magnetic Resonance Study.

(sup13)C nuclear magnetic resonance spectroscopy was used to investigate citrate-glucose cometabolism in nongrowing cell suspensions of the wine lactic acid bacterium Leuconostoc oenos. The use of isotopically enriched substrates allowed us to identify and quantify in the end products the carbon atoms derived from each of the substrates supplied; furthermore, it was possible to differentiate between products derived from the metabolism of endogenous carbon reserves and those derived from external substrates. Citrate-sugar cometabolism was also monitored in dilute cell suspensions for comparison with the nuclear magnetic resonance results. A clear metabolic shift of the end products from glucose metabolism was observed when citrate was provided along with glucose: ethanol was replaced by acetate, and 2,3-butanediol was produced. Reciprocally, the production of lactate and 2,3-butanediol from citrate was increased in the presence of glucose. When citrate was cometabolized with glucose, a 10-fold reduction in the intracellular concentration of glucose-6-phosphate was observed, a result in line with the observed citrate-induced stimulation of glucose consumption. The presence of citrate provided additional pathways for NADP(sup+) regeneration and allowed the diversion of sugar carbon to reactions in which ATP was synthesized. The increased growth rates and maximal biomass yields of L. oenos growing on citrate-glucose mixtures resulted from increased ATP synthesis both by substrate-level phosphorylation and by a chemiosmotic mechanism.

Journal Article↗
PubMed1996

Genital chlamydial infection among women in Nicaragua: validity of direct fluorescent antibody testing, prevalence, risk factors and clinical manifestations.

OBJECTIVE: To validate the performance of a direct fluorescence antibody (DFA) test and to determine the prevalence, risk factors and clinical manifestations of cervical chlamydia infection in different groups of women in Nicaragua. STUDY POPULATION: 926 women, 863 routine clinic attenders (mean age 27 years) and 63 sex workers (mean age 25 years) attending health centres in León, Corinto, Matagalpa and Bluefields. METHODS: Cervical specimens were examined using the Syva MicroTrak test system with a cut-off of 10 or more elementary bodies (EBs). The DFA results were validated by a one-step polymerase chain reaction (PCR) assay. Discordant results were further examined in nested PCR assays directed at two different target genes. An interviewer-administered questionnaire and a standard gynaecological examination were completed. RESULTS: Sensitivity of DFA was 80.1%, specificity 98.3%, and positive and negative predictive values 62.5% and 99.3%, respectively. Values were lower in locations where samples thawed because of electricity breaks and higher among sex workers. The majority of discordant results was confirmed as positive in nested PCR assays. Prevalence of cervical chlamydia infection based on positivity in DFA and/or PCR ranged from 2% among routine clinic attenders aged 35 years or older, to 8% among adolescent clinic attenders, and to 14% among sex workers. Among routine clinic attenders, young age (odds ratio [OR] 3.6, 95% confidence intervals [95% CI] 1.4-8.9 for women aged 15-19 years as compared with 1 in women 25 years of age or older) and use of oral contraceptives (OR 4.0, 95% CI 1.7-9.6) were the only statistically significant risk factors identified in multivariate logistic regression analysis. Presence of mucopurulent cervical discharge (OR 5.9, 95% CI 3.0-11.5) and presence of ectropion (OR 2.6, 95% CI 1.1-6.5) were the clinical signs independently associated with infection. CONCLUSIONS: Our results indicate that the DFA test was sensitive and specific while the performance of the PCR assay depends on adequate storage of samples. Genital C trachomatis infection is a common health problem among women in Nicaragua. The wide implementation of syndromic STD management algorithms together with health education programmes aimed at young people is the most promising approach to control STD in Nicaragua.

Adolescent↗
PubMed1996

Factors influencing distant tele-evaluation in cytology, pathology, conventional radiology and mammography.

The present paper summarizes our 1 year's experience with the use of static high resolution videophones (9600 bauds transmission rate, lossless compression, 512 x 512 spatial resolution). The images (n = 610) belong to regular videoconsultation in cytology (160 images), (160 images), pathology (226 images), conventional radiology (50 images) and mammographies (174 images). The results showed an exponential relationship between agreement with 'gold standards' (true diagnosis of the case based on pathology, surgery and follow-up) and the time of training on screen diagnosis (r = 0.9726, P < 0.01) that increases (r = 0.983, P < 0.004) when the screen diagnosis training within the specific topic is examined. Conversely, no significant correlation is found when medical experience itself is considered (r = 0.31, P nonsignificant). Sufficient diagnostic response has been achieved after 1 year of training on screen diagnosis within a specific topic.

Cell Biology↗
PubMed1995

Specific dinucleoside polyphosphate cleaving enzymes from chromaffin cells: a fluorimetric study.

This article presents a fluorimetric study of the main properties of the enzymes dinucleoside tetraphosphate (asymmetrical) hydrolase or dinucleoside tetraphosphatase (Ap4Aase, EC 3.6.1.17) and dinucleoside triphosphate hydrolase or dinucleoside triphosphatase (Ap3Aase, EC 3.6.1.29), both present in adrenal medulla cytosolic extracts. Diethenoadenosine polyphosphates, epsilon-(ApnA), are used as artificial fluorogenic substrates. Ap4Aase exhibits a molecular mass around 20 kDa and neutral optimum pH (7.0-7.5). It requires Mg2+ and preferentially hydrolyzes substrates with four phosphate groups. Km for epsilon-(Ap4A) is 1.3 microM and Ki for Ap4A and Gp4G are 1 and 0.2 microM respectively. Km for Ap4A determined by HPLC is 1.6 microM. epsilon-(Ap5A) and epsilon-(Ap6A) are hydrolyzed at reduced rates. This enzyme is inhibited by Zn2+, F- and very strongly by Ap4 and epsilon-Ap4. Ca2+ cannot replace Mg2+, but behaves as inhibitor in its presence. The substrate analogs dinucleoside triphosphates Ap3A, G;3G, m7Gp3G and m7Gp3A and the periodate-oxidized nucleotides o-(Ap4A), o epsilon-(Ap4A), o-Ap4 and o epsilon-Ap4 behave as inhibitors. Ap3Aase exhibits a molecular mass around 30 kDa and neutral optimum pH (7.0-7.5). It requires Mg2+ or Ca2+, but retains a low measurable activity around 10% in the absence of these divalent cations. It only hydrolyzes substrates with three phosphate groups. Km for epsilon-(Ap3A) is 11 microM and Ki for Ap3A and Gp3G are 20 and 22 microM, respectively. Km for Ap3A determined by HPLC is 16 microM. m7Gp3G and m7Gp3A are also good substrates for triphosphatase.

Acid Anhydride Hydrolases↗
PubMed1995

Use of fluorogenic substrates for detection and investigation of ectoenzymatic hydrolysis of diadenosine polyphosphates: a fluorometric study on chromaffin cells.

A set of procedures to assay and investigate ectoenzymatic hydrolysis of diadenosine polyphosphates (ApnA) in both intact cell or plasma membrane preparations is described. Procedures are based on the use of the fluorogenic ApnA analogs, epsilon-(ApnA), as artificial substrates. It is shown that these fluorogenic analogs behave as excellent substrates of the ectoenzyme present in cultured chromaffin cells. The ectoenzyme hydrolyzed all epsilon-(ApnA) tested (n = 2-6), always producing epsilon-AMP and epsilon-Ado 5'(n - 1) phosphate moieties. These released nucleotide moieties were then further catabolized up to epsilon-Ado by other ectonucleotidases. Epsilon-(Ap4A) hydrolysis by cultured cells displayed Km and Vmax values of 4.1 +/- 1.5 microM and 13.2 +/- 1.3 pmol/min x 10(6) cells, respectively, as measured by continuous fluorometric assays and 3.5 +/- 1.6 microM and 10.0 +/- 1.9 pmol/min x 10(6) cells by chromatographic-fluorometric assays. Using plasma membranes, values of 2.5 +/- 0.8 microM and 669 +/- 59 pmol/min x mg protein for Km and Vmax, respectively, were obtained through continuous fluorometric assays. ApnA and GpnG behaved as competitors and Ki values for these dinucleotides ranged between 0.7 and 3.5 microM. The ectoenzyme was activated by Mg2+ and Ca2+ and achieved maximal activity in the pH range 8.5-9.0.

Acid Anhydride Hydrolases↗
PubMed1995

Overexpression of PKC zeta in NIH3T3 cells does not induce cell transformation nor tumorigenicity and does not alter NF kappa B activity.

Signal transduction is the major mechanism by which cells communicate among themselves through extracellular stimuli. Among the different structural components involved in signal transduction, protein kinases are one of the key elements in the process. Protein kinase C is a multimember family of kinases which has been involved in the regulation of diverse cellular functions. Regulation of cell growth in fibroblasts has been reported to be one of such functions. In particular the PKC zeta isoenzyme has been postulated to be transforming to NIH3T3 cells (Berra et al., 1993) and to serve as an effector for Ras proteins through the regulation of the NF kappa B transcription factor (Dominguez et al., 1993) and direct interaction (Díaz-Meco et al., 1994). We have investigated the effects of overexpressing the mouse wild-type PKC zeta in NIH3T3 cells. When compared to the parental NIH3T3 cells, we have found (1) no significant effect on cell morphology; (2) no difference in growth properties in the absence of serum or in the presence of individual growth factors such as insulin, phorbol esters or PDGF; (3) no growth in soft agar nor tumorigenic activity in nude mice. In addition cells stably overexpressing the PKC zeta kinase did not interfere or amplify the induction of NF kappa B activity by tumor necrosis factor alfa (TNF-alpha) nor altered NF kappa B activity in transient expression of cells treated with TNF-alpha. Thus, mammalian PKC zeta is most likely not directly involved in the regulation of cell proliferation in fibroblasts nor affects directly or indirectly the activation of NF kappa B.

3T3 Cells↗
PubMed1995

CD4+ T cells determine the ability of spleen cells from F1 hybrid mice to induce neonatal tolerance to alloantigens and autoimmunity in parental mice.

Spleen cells from F1 hybrid mice injected into newborn parental mice induce a state of cytolytic unresponsiveness to the corresponding alloantigens. However, these mice develop a transient autoimmune syndrome characterized by the production of multiple autoantibodies and glomerulonephritis. Previous reports indicated that the depletion of F1 donor T cells, shortly prior the injection into parental mice, does not interfere with any of these events. Here, we have explored whether the continuous absence of T cells in F1 mice influences the ability of their spleen cells to induce neonatal tolerance to alloantigens and the associated autoimmune manifestations. Our results revealed that spleen cells from athymic (BALB/c x C57BL/6) F1 hybrid (CB6F1) nu/nu mice or from euthymic CB6F1 mice depleted from birth of CD4+ T cells, but not of CD8+ T cells, are unable to induce neonatal tolerance to alloantigens and autoimmune manifestations. By contrast, the partial reconstitution of T cells in CB6F1 nu/nu mice, after the neonatal graft of a syngeneic thymus, restored the capacity of spleen cells from these mice to induce tolerance and autoimmunity when injected into newborn BALB/c mice. These results demonstrate that the functional defect of spleen cells from athymic CB6F1 nu/nu mice to induce neonatal tolerance to alloantigens is directly related to the long-term absence of mature CD4+ T cells. Interestingly, a new increase in the titers of anti-DNA Ab was observed when spleen cells from athymic CB6F1 nu/nu mice were injected into adult BALB/c mice that had been tolerized at birth with normal CB6F1 spleen cells. This finding indicates that B cells from CB6F1 nu/nu mice recover their capacity to interact with alloreactive Th2 cells when they are placed into mice having functional CD4+ T cells. These data indicate that the continuous absence of CD4+ T cells causes a reversible functional defect in F1 spleen cells that determines their inability to induce neonatal tolerance and autoimmunity.

Animals↗
PubMed1995

A new technique for laparoscopic repair of hypertrophic pyloric stenosis.

Since 1987, pyloric traumamyoplasty, a technique for the resolution of hypertrophic pyloric stenosis, has been used in 111 patients. Continuous prensile force is applied with Babcock intestinal clamps, with consequent rupture of the muscular layer, without disruption of the mucosa. Because this is a simple procedure that requires introduction of only one noncutting instrument, it has now been applied laparoscopically in 17 patients. Twelve were under 30 days of age; seven weighed less than 3.5 kg. The hospital stay averaged 1.8 days, and the average surgical time was less than 30 minutes. Only two trocar incisions were made in each case--one for the laparoscope video camera and lamp, the other for a modified Babcock clamp. There were no deaths and no complications related to the pyloric repair procedure. The authors conclude that laparoscopic pyloric traumamyoplasty is an attractive alternative for the management of hypertrophic pyloric stenosis.

Female↗