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Biomedical subjects

C Rodríguez

Publications and source records attributed to C Rodríguez.

At least 181 records · Page 10Linked to original sources
PubMed1993

Circadian rhythmicity in the GABAergic system in the suprachiasmatic nuclei of the rat.

The participation of GABAergic mechanisms in the regulation of circadian rhythmicity by the suprachiasmatic nuclei (SCN) has been suggested from different lines of evidence. Little is known, however, whether GABA synthesis, release, uptake or content within the SCN may show a circadian pattern. The present results show that the activity of the GABAergic system within the SCN region of the rat exhibits circadian rhythmicity, which is manifested by correlative changes of the GABA content and the glutamic acid decarboxylase activity under the light/dark cycle, and by changes in the GABA content in animals kept under constant darkness.

Animals↗
PubMed1993

Essential role of tumor necrosis factor-alpha in the differentiation of human tonsil in vivo induced B cells capable of spontaneous and high-rate immunoglobulin secretion.

Human tonsils contain B cells capable of spontaneous and high-rate immunoglobulin (Ig) secretion in vitro. These cells are in vivo induced mature B cells, and, as such, they provide and adequate model for studying tonsil B cell differentiation. The present report analyzes the effect of a variety of factors on purified tonsil B cells capable of spontaneous IgG secretion in fetal calf serum (FCS)-containing and serum-free supplemented cultures. Tumor necrosis factor-(TNF) alpha was found to be important for these B cells to reach the high-rate IgG-secreting stage, as is indicated by the following findings: (a) none of the factors used modified tonsil B cell IgG secretion in FCS-containing cultures; (b) TNF-alpha (5-20 ng/ml), but not other cytokines or factors including interleukin (IL)-6, was capable of restoring missing IgG production in serum-free supplemented cultures of tonsil B cells; and (c) IgG secretion in FCS-containing cultures was inhibited by the addition of blocking anti-TNF-alpha antibodies, but not anti-IL-6 antibodies, and this inhibition could be specifically reversed by exogenous TNF-alpha. TNF-alpha was actively produced by tonsil B cells (range 120-750 pg/ml) in the presence, but not in the absence, of FCS. The TNF-alpha inductive effect occurred during the first 12 h of culture and did not require DNA synthesis. These results indicate that the early and endogenous generation of TNF-alpha seems to be essential for tonsil in vivo induced B cells to differentiate into the high-rate Ig-secreting stage.

B-Lymphocytes↗
PubMed1993

Development and androgen regulation of the secretory cell types of the Syrian hamster (Mesocricetus auratus) Harderian gland.

The secretory cell types of the hamster Harderian glands were studied in both male and female Syrian hamsters. As previously demonstrated, female hamsters showed a single secretory cell type (type I), while male hamsters displayed two secretory cell types (type I and type II). Type-II cells were observed after the first month of age correlating with the increase in testosterone levels. The administration of testosterone to adult female hamsters resulted in a marked increase in the percentage of type-II cells without a significant increase in the number of mitotic figures. Very low levels of serum testosterone were able to maintain the percentage of type-II cells. Castration of male hamsters produced a decrease in the percentage of type-II cells. This drop correlated with the reduction in serum testosterone levels. The chronic administration of a luteinizing hormone-releasing hormone agonist to male Syrian hamsters induced a significant reduction in both serum luteinizing hormone and testosterone. However, the percentage of type-II cells was similar to that of control hamsters suggesting that very low levels of circulating testosterone are able to maintain the percentage of type-II cells. In a final experiment male Syrian hamsters were treated with the antiandrogen cyproterone acetate. No changes were observed in the percentage of type-II cells, whereas serum luteinizing hormone and testosterone levels were significantly modified. We concluded that (1) type-II cells differentiate from type-I cells; (2) gonadal androgens are the major factor controlling this differentiation; and (3) the disappearance of type-II cells after androgen deprivation occurs through holocrine and apocrine mechanisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗
PubMed1993

Therapeutic consultation: a necessary adjunct to independent drug information.

1. A therapeutic consultation service was implemented in 1984 to complement other methods of information and education on drug therapy for prescribers. 2. Up to 1991, 1,620 enquiries were received, 65% from our hospital and an increasing proportion from primary care (10%), other hospitals (6%), family planning centres (4%), and other sources (14%). 3. More than two-thirds (67%) were consultative enquiries, as opposed to demands for factual information, which needed knowledge of medical aspects of the case and clinical expertise. 4. 85% of enquiries were answered with a written report including relevant references and as conclusive as possible recommendations. 5. More discussion of therapeutic consultation is needed, and aspects for discussion are suggested.

Drug Information Services↗
PubMed1993

[Transmural electrical stimulation in the reticular groove of adult cattle].

An in vitro study of the smooth muscle of the fore third of the reticular groove bottom was carried out in adult bovines, to determine the most favorable parameters for electrical transmural stimulation (ETS). The mechanical activity of the preparations was registered isometrically and the electric stimuli were applied by means of ring-shaped platinum electrodes. Results show that the response of this tissue to ETS is of a phasic and synchronic nature in accordance with the stimulus. The parameter values necessary to produce a homogeneous, quantifiable and reproducible response were the following: Supermaximum voltage 70-100 V, frequency 30 Hz, pulsing time 4 ms, stimulus time 5 s and intervals between each stimulus 4 min. The intervals among stimuli where 3 min long to establish the frequency curves of 2, 6, 10, 20 and 30 Hz.

Animals↗
PubMed1993

Comparison of three methods to obtain upper small bowel contents for culture.

In this study of 27 patients with dyspepsia, we compared three methods for obtaining upper small bowel contents for culture: 1) the Enterotest or string capsule method, 2) duodenal intubation using a closed polyethylene tube filled with water that had been boiled for sterilization and removal of dissolved oxygen, and 3) brushing of duodenal mucosa with a cytology brush protected by a sheath (the last two done during endoscopy). In 12 of the 27 patients, duplicate intubations and brushings were performed. The samples obtained were cultured aerobically. Parameters used to compare the three methods were: the contribution of each method to the diagnosis of upper small bowel bacterial overgrowth (USBBO), agreement between the methods in diagnosis of USBBO and in detailed microbiological findings, and the reproducibility of diagnosis of USBBO and of microbiological findings in duplicate intubation and brushing. Intubation and brushing were highly reproducible and superior to the Enterotest in all of the tested parameters. Intubation and brushing are equally efficacious, but intubation is preferred because of the slight cost advantage, ease of specimen processing, and the ability to obtain anaerobic specimens.

Adult↗
PubMed1992

Low prevalence of gastric metaplasia in the duodenal mucosa in Peru.

We compared the prevalence of gastric metaplasia of the duodenal mucosa (GM) and its characteristics in 204 Peruvian patients from a low socioeconomic level with the corresponding prevalence reported in dyspeptic patients from a developed country, the United Kingdom. Gastric metaplasia was significantly less prevalent in the Peruvian than in the United Kingdom series. However, when present, GM was not significantly different in extent or frequency of colonization by Helicobacter pylori or association with active duodenitis, despite a higher prevalence of H. pylori-associated gastritis. Hypochlorhydria was markedly more frequent in the Peruvian than in the United Kingdom series. The finding of a low prevalence of H. pylori-colonized GM in patients with previously reported low prevalence of duodenal ulcer gives further support to a pathogenic link between both conditions.

Adolescent↗
PubMed1992

Human germinal centre B cells inhibit mitogen-induced proliferation of mantle zone B cells.

Lymphoid follicles are the main B-cell areas in peripheral lymphoid tissues. These structures commonly consist of germinal centre (GC) and mantle zone (MZ) regions. In the present work, human tonsillar B cells belonging to these two compartments were purified by a combination of density centrifugation and separation techniques involving the recognition by monoclonal antibodies of specific surface molecules followed by panning and magnetic bead selection. These purified populations were identified as GC and MZ cells by three different criteria: (1) GC cells showed the phenotype IgD- CD20+bright CD38+ CD44- and peanut agglutinin (PNA)+, and MZ cells were IgD+ CD20+dim CD38- CD44+ and PNA-; (2) morphologically, MZ cells appeared as small resting lymphocytes whereas GC cells consisted of large blastic cells of the germinal centre; (3) functionally, most GC, but not MZ, cells underwent apoptosis early in culture. The isolation of GC and MZ cells allowed the study of their proliferative response. As a result of these studies, GC cells were demonstrated to inhibit the proliferation of MZ cells in response to B-cell mitogens (Staphylococcus aureus Cowan I and anti-mu plus BCGF) in a concentration-dependent way; 50% inhibition was reached at a GC/MZ cell ratio of 1/2. This effect did not require GC-cell DNA synthesis since similar results were obtained with irradiated GC cells. Neither was it due to a non-specific toxic effect since GC cells did not alter the proliferative response of autologous T cells to mitogens (phytohaemagglutin and anti-CD3). The inhibition required cellular contact between GC and MZ cells, and was not restricted by histocompatibility barriers. These data suggest the possible existence of a new regulatory pathway within peripheral B-cell areas.

Antibodies, Monoclonal↗
PubMed1992

Glucose utilization and insulin action in adult rats submitted to prolonged food restriction.

Glucose tolerance and insulin effects on glucose production and utilization by various tissues were studied in 70-day-old anesthetized rats submitted to food restriction from the fetal stage. Basal and glucose-induced plasma insulin levels were reduced in food-restricted rats without alterations in glucose tolerance. Insulin action was quantified by using the euglycemic-hyperinsulinemic clamp technique. Glucose turnover rates were measured by using D-[6-3H]glucose. Exogenous insulin failed to decrease glucose production in food-restricted rats. Weight-related whole body glucose utilization was higher in restricted rats than in controls both in the basal (21.9 +/- 0.7 vs. 9.4 +/- 0.6 mg.min-1.kg-1) and hyperinsulinemic states (37.5 +/- 1.1 vs. 14.0 +/- 1.2 mg.min-1.kg-1). Local glucose utilization by peripheral tissues was estimated by a 2-deoxy-D-[1-3H]glucose technique. In both basal and hyperinsulinemic conditions glucose utilization was increased in various adipose and muscle tissues of the food-restricted rats as compared with the controls. Thus we conclude that food restriction leads to an increase in the insulin-mediated glucose uptake by various peripheral tissues and to insulin resistance in the liver.

Adipose Tissue↗
PubMed1992

[The cholera epidemic in Panama 1991].

The authors studied the epidemiology of the outbreak of cholera (due to Vibrio cholerae 01, Inabe serotype) which occurred in Panama in 1991, during which 1179 probable cases were reported, with 292 hospitalizations, 29 deaths and 51 confirmed cases. There was an average of 24.7% hospitalizations and a 2.5% mortality. The epidemic involved 21 of 24 "corregimientos' in Darién, 2 of 4 in San Blas, 5 of 15 in Panama East, 3 of 40 in Colón and one of 19 in the metropolitan area of Panama City. The incidence of infected patients was seen in infants less than 1 year old and in children 1 to 4 years of age. Taking into account the population in each 'corregimiento', it can be said that less than 1% of the population was infected, but that in San Blas, where few communities have aqueduct and latrines, 10% of the population was infected.

Age Factors↗
PubMed1991

Helicobacter pylori and progressive gastric pathology that predisposes to gastric cancer.

Evidence is presented suggesting that infection by Helicobacter pylori triggers and continuously contributes to the pathophysiology of progressive gastric changes that can ultimately lead to gastric cancer. In Peru, especially in population groups of low socioeconomic status, infection by H. pylori begins earlier in life and is more prevalent and persistent than in developed countries. The infection produces a destructive lesion of the mucinous surface epithelium which probably enables other aggressive luminal factors to cause further mucosal damage. As a consequence, active chronic gastritis appears. The gastritis is of the superficial type at the beginning but may progressively change to atrophic. Chronic atrophic gastritis is found more frequently and at a younger age in dyspeptic patients with low socioeconomic status--that is, in patients having higher prevalence of persistent infection by H. pylori since earlier in life. When chronic atrophic gastritis becomes severe and extensive, hypochlorhydria ensues. Hypochlorhydria favors the appearance of bacterial overgrowth, nitrites, and N-nitroso compounds in the gastric lumen. N-nitroso compounds, because of their mutagenic-carcinogenic properties, probably induce gastric premalignant lesions like intestinal metaplasia and dysplasia of the gastric mucosa. Oral bismuth therapy apparently reverses H. pylori-associated gastric dysplasia. It is proposed that future programs designed for the control of gastric cancer would be incomplete if they do not include further evaluation of the many effects of infection by H. pylori on the gastric mucosa and of cost-effective methods to eradicate the infection.

Age Factors↗
PubMed1991

[Multiple primary pulmonary carcinomas].

Three cases of multiple simultaneous primary lung carcinomas are presented, in which diagnosis was established by post-surgery pathological exam. In all three cases, chest X-ray showed pulmonary masses suggestive or clinical malignancy, and pre-surgery pathological diagnosis or squamous lung carcinoma. During thoracotomy or in the resected segment, a second lesion we confirmed which made resection necessary being this second lesion classified as lung adenocarcinoma.

Adenocarcinoma↗
PubMed1991

[Subleukemic acute monophagocytic leukemia. A biological phenotype close to malignant histiocytosis].

An 80 year-old woman presented subleukaemic acute monoblastic leukaemia (AML-M5a). Her bone marrow showed invasion by highly dysplastic histio-monocytic cells of great size and wide cytoplasm, with intense phagocytic activity (erythrophagocytosis was frequently seen), and with abnormal karyotype (50XX, +8, +8, +16, +21). The different malignant and reactive features of the mononuclear phagocytic system are commented, along with the haemophagocytic activity of the histio-monocytic cells in different states. The cytogenetic anomalies more frequently found in AML-M5 are also dealt with as compared to this patient's. The case reported here seems to correspond to subleukaemic acute "monophagocytic" leukaemia, with a biologic phenotype close to that of malignant histiocytosis.

Aged↗
PubMed1991

[Autoimmune phenomena in the elderly].

We analyzed sera from 102 subjects older than 65 years of age with no clinical evidence of autoimmune disorders, inflammatory diseases or pharmacological interventions. Positive titers for antinuclear antibodies were found in 18.6%, anti-smooth muscle fibre in 16.6%, and rheumatoid factor in 11.8%. These values were significantly higher than those of a control group of healthy younger adults (p < 0.0001). Anti mitochondrial antibodies were present in 1% (NS). Thus, a greater proportion of autoimmune phenomena is demonstrated in the elderly.

Age Factors↗