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Biomedical subjects

M Torres

Publications and source records attributed to M Torres.

At least 163 records · Page 9Linked to original sources
PubMed1996

T lymphocytic and immature macrophage alveolitis in active pulmonary tuberculosis.

The phenotype of bronchoalveolar cells from 11 healthy subjects and from affected and unaffected lungs of 15 patients with pulmonary tuberculosis (PTB) was determined. An immature macrophage alveolitis was found in the affected lung and the unaffected lung versus controls as determined by morphology and peroxidase activity. T lymphocytic alveolitis also was found in the affected but not the unaffected tuberculous lung compared with healthy controls. The majority of alveolar lymphocytes in unaffected and affected PTB lungs were T cells expressing the alpha beta T cell receptor. Alveolar T cells from both unaffected and affected lungs were activated, as determined by increased expression of CD69 and HLA-DR. Interleukin-2 receptor (IL-2R alpha) expression was, however, unchanged on alveolar lymphocytes from affected lung and was decreased in the unaffected lung. Thus, activated T lymphocytes and immature macrophages in the tuberculous lung are basic to the local immunopathogenesis of PTB.

Adult↗
PubMed1996

Low dose alpha interferon therapy can be effective in chronic active hepatitis C. Results of a multicentre, randomised trial.

BACKGROUND: There is some controversy concerning the efficacy of low dose alpha interferon therapy in chronic hepatitis C. AIMS: To evaluate the effectiveness of treatment with low doses of alpha interferon in chronic hepatitis C. PATIENTS: One hundred and forty one patients with anti-HCV positive chronic active hepatitis C from six hospitals were enrolled in the study. METHODS: Patients were randomised to treatment with 5 MU (group A) or 1.5 MU (group B) injections. The dose was reduced in responders from group A or increased in non-responders from group B to maintain treatment with the minimal effective dose. Patients were treated for 48 weeks and followed up for 24 additional weeks with no treatment. Normalisation of alanine aminotransferase (ALT) was used to evaluate response. RESULTS: A sustained response was seen in eight patients from group A (12%) and in 15 (21%) from group B. This difference was not statistically significant. Increasing the dose of interferon led to sustained response in only five of 58 patients (9%) from group B who did not respond to 1.5 MU injections. In contrast, 15 of 21 patients (71%) in whom ALT remained normal with 1.5 MU injections developed a sustained response. By multivariate analysis sustained response seemed associated with young age and was more frequent in patients with genotype 3 HCV infection. Sustained response was preceded by a rapid normalisation of ALT and was inversely related to the amount of alpha interferon necessary to maintain ALT at low values during treatment. CONCLUSIONS: Some patients with chronic hepatitis C are very sensitive to alpha interferon and can be successfully treated with low doses. Treatment with higher doses may be effective in a minority of patients who do not respond to low doses.

Alanine Transaminase↗
PubMed1996

Pax2 contributes to inner ear patterning and optic nerve trajectory.

During gestation, the paired box-containing gene Pax2 is expressed in the mid-hindbrain area, developing eye and inner ear. We generated Pax2 null mutant mice, which show the requirement of Pax2 for the establishment of axonal pathways along the optic stalks and ventral diencephalon. In mutant brains, the optic tracts remain totally ipsilateral due to agenesis of the optic chiasma. Furthermore, Pax2 mutants show extension of the pigmented retina into the optic stalks and failure of the optic fissure to close resulting in coloboma. In the inner ear, Pax2 mutants show agenesis of the cochlea and the spiral ganglion, i.e., the parts of the organ responsible for auditory function and in whose primordium Pax2 is expressed. Our results identify Pax2 as a major regulator of patterning during organogenesis of the eye and inner ear and indicate its function in morphogenetic events required for closure of the optic fissure and neural tube.

Animals↗
PubMed1996

Dysgenesis of cephalic neural crest derivatives in Pax7-/- mutant mice.

Pax7 is a member of the paired box containing gene family. Its expression pattern suggests a function in cephalic neural crest derivatives, skeletal muscle and central nervous system development. To understand the role of Pax7 during mouse embryogenesis, we used the homologous recombination technique in embryonic stem cells and generated Pax7-/- mice. Homozygous animals are born but die shortly afer weaning. They exhibit malformations in facial structures involving the maxilla and nose. Our analysis suggests that the observed phenotype is due to a cephalic neural crest defect. No obvious phenotype could be detected in the central nervous system and skeletal muscle. Functional redundancy between Pax7 and Pax3 is discussed.

Animals↗
PubMed1996

Effects of short-term zinc supplementation on cellular immunity, respiratory symptoms, and growth of malnourished Equadorian children.

OBJECTIVE: To assess the effect of zinc supplementation on respiratory tract disease, immunity and growth in malnourished children. DESIGN: A randomized double-blind placebo-controlled trial. SETTING: A day-care center in Quito, Ecuador. SUBJECTS: Fifty children (12-59 months old) recruited by height-for-age and weight-for-age deficit. INTERVENTIONS: Twenty-five children (supplemented, S group) received 10 mg/day of zinc as zinc sulfate, and 25 (nonsupplemented, NS group) received a placebo during 60 days. All were also observed during a 60-day postsupplementation period. Two children of the S group dropped out. Daily the clinical presence of cough, respiratory tract secretions, and fever, was recorded. On days 0,60 and 120, the cutaneous delayed-type hypersensitivity (DTH) to multiple antigens, and anthropometric parameters were assessed. On days 0 and 60 serum zinc levels were also measured. RESULTS: On day 60, DTH was significantly larger (20.8 +/- 7.1 vs 16.1 +/- 9.7 mm), and serum zinc levels were significantly higher (118.6 +/- 47.1 vs 83.1 +/- 24.5 micrograms/dl) in the S group than in the NS group (P <0.05 for each). The incidence of fever [relative risk (RR): 0.30, c.i. = 0.08- 0.95, P =0.02], cough (RR): 0.52, c.i. = 0.32-0.84, P = 0.004) and upper respiratory tract secretions (RR):0.72, c.i. = 0.59-0.88, P = 0.001) was lower in the S group than in the NS group at day 60. At the end of the postsupplementation observation period (day 120), the incidence of fever and upper respiratory tract secretions was the same in both the S and NS groups. The incidence of cough was higher at day 120 in the S group than in the NS group (RR): 2.28, c.i. = 1.37-3.83, P = 0.001). CONCLUSIONS: This study supports a role for zinc in immunity, and immunity to respiratory infections, while pointing out the need for larger studies.

Adjuvants, Immunologic↗
PubMed1996

Effect of cyclic GMP-increasing agents nitric oxide and C-type natriuretic peptide on bovine chromaffin cell function: inhibitory role mediated by cyclic GMP-dependent protein kinase.

Both sodium nitroprusside (SNP), a nitric oxide (NO) generator, and C-type natriuretic peptide (CNP) have been found to raise cGMP levels in bovine chromaffin cells in a time- and concentration-dependent manner. The effect of these compounds on catecholamine secretion and calcium influx has also been studied, and both compounds were found to produce a slowly developing inhibitory effect on acetylcholine- or depolarization-stimulated catecholamine secretion and calcium increases without affecting the spontaneous release or the basal intracellular Ca2+ concentration. These inhibitory effects were observed only at high doses of acetylcholine or high levels of extracellular potassium and required concentrations of SNP or CNP very similar to those that increased cGMP levels. Preincubation with 100 microM zaprinast, a cGMP-phosphodiesterase inhibitor able to increase cGMP levels, mimicked the inhibitory effects of SNP and CNP. We investigated the effect of the soluble guanylate cyclase inhibitor methylene blue and the cGMP-dependent protein kinase (PKG) inhibitor 8-(4-chlorophenylthio)-guanosine 3',5'-cyclic monophosphorothioate, Rp isomer, on inhibition by SNP or CNP. Although methylene blue (10 microM) partially prevented the inhibitory effect of SNP, it did not do so for that produced by CNP, thus indicating that SNP acts through cGMP produced by the NO-activated guanylate cyclase. 8-(4-Chlorophenylthio)-guanosine 3',5'-cyclic monophosphorothioate, Rp isomer totally reversed both the SNP and CNP inhibitory effects. These results suggest that the activation of PKG mediates the inhibition induced by SNP and CNP. We successfully measured the PKG activity from cells preincubated with SNP or CNP, and our results show that this enzymatic activity increased with a time dependence very similar to the increase in the cGMP levels. Our results indicate that NO and CNP peptide inhibit secretagogue-stimulated catecholamine release via activation of soluble and particulate isoforms of the guanylate cyclase, respectively, presumably by inhibition of calcium entry through voltage-activated calcium channels. This inhibitory effects seems to be mediated by activation of the PKG.

1-Methyl-3-isobutylxanthine↗
PubMed1996

[Reference values in the diagnosis of anemia in the elderly].

OBJECTIVES: To analyze the usefulness of some reference values for erythropoiesis in the elderly. Methods. A total of 226 individuals older than 65 years (139 females and 87 males) were studied with measurements of hemoglobin (Hb), corpuscular indexes, red blood cell distribution index, serum iron level, ferritin and creatinine. Plasma erythropoietin (EPO) was determined in 72 cases. Values were grouped according to age, younger (126) and older than 76 years (100), and sex. RESULTS: Hb was lower in males older than 76 years than in individuals younger than 76 years but this differences was not observed among women. Serum iron level was low in 13.3% of individuals. Creatinine was higher among males than among women and higher among males younger than 76 years than in males older than 76 years. EPO was higher among the elderly patients than in young adults (p < 0.001), keeping no relationship with age. CONCLUSIONS: With the exception of EPO, the usual reference values for erythropoiesis in the adults can be used for the elderly patients. Despite differences in EPO compared with adults, the quantitation of this finding is useless for the diagnosis of anemia in the elderly.

Aged↗
PubMed1996

Vital status in the National Panel Survey of Black Americans: a test of the National Death Index among African Americans.

To test the specificity of the National Death Index (NDI), information was submitted on 157 randomly selected respondents from the National Panel Survey of Black Americans (NPSBA) who were known to be living as of 1992. Information also was submitted for 153 known deceased respondents from the panel survey to test the sensitivity of the NDI. The NDI was very sensitive; however, specificity was somewhat less impressive. Although we found the NDI/NPSBA match to be highly accurate, there was a nontrivial number of false positives.

Black or African American↗
PubMed1996

Effect of fluorescent powder on Lutzomyia longipalpis (Diptera: Psychodidae) and a simple device for marking sand flies.

A simple device for marking phlebotomine sand flies with fluorescent powders is described and tested; the design of the new device is characterized by separate compartments for sand flies and powder. The effect of fluorescent powder on survival and mobility of the sand fly Lutzomyia longipalpis was compared using our device (method A) and a single-container method (method B). Mortality within 1 h of powder application was negligible for method A (0.9%), but was 19.8% for method B; in addition, method B also reduced sand fly mobility. Adherence of excess powder to the sand flies observed with method B was responsible for the negative effects observed during the marking process. In field releases, however, recapture rates were the same for each method. Neither sand fly mobility or survival were adversely affected if appropriate quantities (method A) of fluorescent powder were applied to the exoskeleton of these insects.

Animals↗
PubMed1996

[Natural history of human immunodeficiency virus infection in a cohort of Chilean patients].

We characterized clinical manifestations and the risk to develop AIDS in a cohort of 32 patients infected with human immunodeficiency virus without AIDS A multivariate analysis was performed to determine association between the progression of infection and control variables (socioeconomic level, age, sex and sexual preferences) and causal variables (psycho-social changes, significant clinical events, stress scoring and sexual activity). The cumulative AIDS incidence, defined as a CD4 lymphocyte count below 200 cells/cm3 was 50% at 6.5 years and 82% at 8 years. Using clinical criteria to define AIDS, 50% developed the disease at 8 years of follow up. Among studied factors, only age (faster progression at higher age) and time of evolution were associated with progression in stages before AIDS, the most frequent diseases were acute diarrhea, sexual transmission diseases, oral candidiasis, sinusitis and varicella zoster infections. The reduction; of CD4 lymphocytes-below 200 cells/cm3 always preceded the symptoms of the disease. Two patients have remained more than eight years without clinical or immunological deterioration.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Comparison of the cervical cytology test using the PAPNET method and conventional microscopy.

From August 1994 to June 1995, laboratories in 28 Mexican states and the Federal District submitted a total of 10098 diagnosed Pap test slides to Mexico's National Institute of Epidemiologic Diagnosis and Reference (INDRE) for reexamination by conventional methods and also by the automated PAPNET system in Suffern, New York, U.S.A. The aim was to determine the degree of agreement obtained by these various methods. Most of the slides examined (at least 78%) yielded negative results or merely indicated an inflammatory process; 8% to 14% indicated mild or moderate cervical dysplasia; and 2% to 3% indicated conditions ranging from severe dysplasia to invasive cervical cancer. Comparison of the state laboratory and INDRE diagnoses yielded a Kappa correlation coefficient of 0.62, near the lower limit of agreement, the agreement being poorest in cases where it was necessary to distinguish between degrees of abnormality. Although state laboratory underestimation appeared lowest with respect to cases of atypia and of mild, moderate, and severe dysplasia (between 12% and 20%), these percentages are alarming because it is at these stages that the patient may be treated to prevent evolution to carcinoma. While the Kappa correlation coefficient was better (0.80) when the INDRE and PAPNET diagnoses were compared, PAPNET showed only limited ability to distinguish between various pathologic alterations, and the percentages of underestimates (false negatives) obtained with PAPNET were also high. Overall, the results indicate a need to improve the quality of cervical cytology diagnoses at state public health laboratories in Mexico through stepped-up training and supervision. They also indicate that the use of PAPNET involves greater difficulty than does manual microscopic examination of cervical smears, and that a way still needs to be found to detect and review the false negative results generated by PAPNET before approving use of this technology.

Adolescent↗
PubMed1995

Activation of mitogen-activated protein kinase by heat shock treatment in Drosophila.

Heat shock treatment of Drosophila melanogaster tissue culture cells causes increased tyrosine phosphorylation of several 44 kDa proteins, which are identified as Drosophila mitogen-activated protein (MAP) kinases. Tyrosine phosphorylation occurs within 5 min, and is maintained at high levels during heat shock. It decreases to basal levels during recovery, concurrent with the repression of heat shock transcription and heat-shock-protein synthesis. The increased MAP kinase tyrosine phosphorylation is parallelled by increased MAP kinase activity. At least two MAP kinases, DmERK-A and DmERK-B, are identified whose tyrosine phosphorylation increases during heat shock. Thus MAP kinase activation is an immediate early response to heat shock, and its increased activity is maintained throughout heat shock treatment. Protracted MAP kinase activation may contribute to heat shock transcription factor phosphorylation and the numerous metabolic alterations that constitute the heat-shock response.

Animals↗
PubMed1995

Lipopolysaccharide stimulates the tyrosine phosphorylation of mitogen-activated protein kinases p44, p42, and p41 in vascular endothelial cells in a soluble CD14-dependent manner. Role of protein tyrosine phosphorylation in lipopolysaccharide-induced stimulation of endothelial cells.

Vascular endothelial cell (EC) injury or activation by LPS plays a critical role in the pathogenesis of Gram-negative meningitis and endotoxic shock. EC do not express membrane CD14, but respond to LPS in a soluble CD14-dependent manner. The signal transduction mechanisms involved in LPS-induced EC responses are largely unknown. We used bovine and human brain microvessel EC (BBMEC, and HBMEC) to study LPS-induced protein tyrosine phosphorylation. LPS rapidly induced the tyrosine phosphorylation of several proteins in BBMEC and HBMEC, which was detectable by 5 to 15 min, reached a maximum by 30 min, and declined by 60 to 90 min. The increase in tyrosine phosphorylation was apparent following stimulation with LPS at 0.1 ng/ml and was dose dependent up to 100 ng/ml. Similar changes in tyrosine phosphorylation were induced by smooth and rough LPS as well as lipid A, but not by the inactive lipid A analogue, Rhodopseudomonas sphaeroides diphosphoryl lipid A. Pretreatment of EC with the tyrosine kinase inhibitor, herbimycin A, inhibited LPS-stimulated protein tyrosine phosphorylation and LPS-mediated lactic dehydrogenase release from BBMEC and IL-6 release from HBMEC in a dose-dependent manner. Three proteins with apparent m.w. of 44, 42, and 41 kDa were predominant among the LPS-induced tyrosine phosphoproteins, and they were identified as mitogen-activated protein kinase isoforms ERK1, ERK2, and p38, respectively. LPS-induced protein tyrosine phosphorylation in HBMEC and BBMEC was soluble CD14 dependent, since pretreatment of these cells with anti-hCD14 mAb inhibited the LPS-induced tyrosine phosphorylation of p44, p42, and p41. Additionally, LPS induced a mobility shift in p44 and p42 mitogen-activated protein kinase isozymes, which was inhibited by herbimycin A pretreatment of the EC. These findings demonstrate for the first time that increased protein tyrosine phosphorylation and activation of mitogen-activated protein kinases occur rapidly after LPS stimulation of EC in the presence of soluble CD14. Our data also suggest that a herbimycin-sensitive step, presumably a tyrosine kinase, is involved in mediating LPS-induced human EC activation and IL-6 secretion.

Amino Acid Sequence↗
PubMed1995

Activation of NO:cGMP pathway by acetylcholine in bovine chromaffin cells. Possible role of Ca2+ in the down-regulation of cGMP signaling.

The production of cyclic GMP (cGMP) induced by acetylcholine and other stimuli was studied in bovine chromaffin cells. Acetylcholine increased intracellular cGMP in a transitory (peak at 2 min) and concentration-dependent manner (estimated half maximal increase, EC50 = 61 +/- 5 microM). NG-nitro-L-arginine methyl ester (NAME) inhibited such a rise in cGMP with a half maximal inhibitory concentration (IC50) of 231 +/- 55 microM. The acetylcholine-induced increase in cGMP was also inhibited by a calmodulin antagonist (calmidazolium, 30 microM) and by the absence of extracellular calcium. Other agents that strongly increased cytosolic calcium concentration ([Ca2+]i) as acetylcholine did, such as the nicotinic-agonist, 1,1-dimethyl-4-phenylpiperazinium (DMPP), high-KCl (50 mM), and ionomycin, also caused a rise in cGMP in cultured bovine chromaffin cells. Veratridine, an activator of sodium channels, produced a slowly developing calcium increase and no significant cGMP production. The muscarinic-agonist, muscarine, failed to increase cytosolic calcium, and was the weakest stimulator of cGMP production. cGMP formation, induced by sodium nitroprusside (SNP, 100 microM) and by C-type natriuretic peptide (CNP, 100 nM), was inhibited by 30-40% by increasing [Ca2+]i with ionomycin. This inhibition was abolished by calmidazolium (30 microM) and by the absence of calcium in the extracellular medium. In conclusion, bovine chromaffin cells synthesize nitric oxide (NO) to activate guanylate cyclase in response to several stimuli, which increase [Ca2+]i. Moreover, the increase in [Ca2+]i also stimulates a Ca2+/calmodulin phosphodiesterase, which could down-regulate the levels of cGMP in these cells.

Acetylcholine↗
PubMed1995

Constitutive N-myc gene expression inhibits trkA mediated neuronal differentiation.

The effect of constitutively expressed N-myc gene on nerve growth factor (NGF) induced neuronal differentiation was investigated. B104, a rat central nervous system-derived cell line and its N-myc gene expressing derivative lines (C6, C7) (Bernards et al., 1986), were stably transfected with the trkA proto-oncogene and independent clones for each cell line were analysed. NGF induced phosphorylation of the trkA receptor, activated a cascade of cellular intermediaries such as phospholipase C gamma 1 and ERK proteins, and stimulated c-fos gene transcription in all trkA-expressing clones. NGF-mediated neuronal differentiation was observed solely in trkA-expressing B104-derived clones and was characterized by reduced cell growth, activation of NGF-regulated genes, and downregulation of the endogenous low-affinity NGF receptor gene (gp75NGFR). No such phenotypical changes occurred in trkA-expressing C6 or C7-derived clones following NGF treatment. These results are consistent with the hypothesis that constitutive expression of N-myc inhibits exit from cell cycle and blocks neuronal cell differentiation.

Animals↗