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Biomedical subjects

C Rodriguez

Publications and source records attributed to C Rodriguez.

At least 199 records · Page 11Linked to original sources
PubMed1989

Blockade of endothelin-induced contractions by dichlorobenzamil: mechanism of action.

Contractions of intact rat aortic rings induced by endothelin were totally inhibited by the amiloride analogue dichlorobenzamil (DCB) at concentrations known to block Na-Ca exchange (IC50 = 30 microM). Amiloride (100 microM) was ineffective. Ca-channel blockers and a K-channel opener elicited only partial inhibition. These results could indicate that the Na-Ca exchanger plays an important role in endothelin-induced contractions. Endothelin, however, had no effect on the kinetics of the exchanger, and, in addition, contractions also occurred in Na-depleted vessels. The endothelin-induced contractions produced by Ca release from intracellular pools were also completely inhibited by DCB. In fact, the latter compound was found to block contractions induced by Ca itself in the presence of Ca ionophore or detergent. We conclude that DCB acts directly on Ca-induced activation of myofilaments in smooth muscle.

Amiloride↗
PubMed1989

Comparative functional study of colostral macrophages from mothers delivering preterm and at term.

Number and function of milk macrophages (MM) from 30 healthy mothers delivering preterm (mean gestational age 33 weeks) were compared with those obtained from 92 mothers with term delivery. The average concentration of MM in colostrum did not differ in the two groups: 0.55 x 10(6)/ml (preterm) and 0.42 x 10(6)/ml (term). Preterm MM showed the same activity as term MM in all three assayed functions (phagocytosis, chemotaxis and IL-1 secretion). Phagocytic activity, and impaired migratory motility and IL-1 secretion were significantly increased both in preterm and term MM in comparison with the activity in less mature blood monocytes. Thus it appears that preterm MM are, like term MM, a fully mature tissue macrophage population and therefore we suggest that with regard to MM both preterm and term colostrum are comparable, at least in the gestational age tested.

Cell Count↗
PubMed1989

Evaluation of a competitive antibody enzyme immunoassay for specific diagnosis of Chagas' disease.

A competitive enzyme immunoassay based on the use of a monoclonal antibody (MAb) specific for "component 5" of Trypanosoma cruzi was evaluated. The antigenicity and immunogenicity of this component has been observed in natural and experimental infections. The studies were conducted in an area of Bolivia where mixed infections with Leishmania braziliensis are frequent and present a problem in the accurate diagnosis of T. cruzi infections. The specificity and sensitivity of this assay as compared to the indirect immunofluorescence and ELISA tests were demonstrated. The present test has proved to be more specific than the immunofluorescence and ELISA tests.

Animals↗
PubMed1989

Expression of cytoskeletal proteins in glial cells of dorsal root ganglia.

The localization of S-100 protein-, glial fibrillary acidic protein- and vimentin-like immunoreactivity has been studied in dorsal root ganglia of the rat using monoclonal antibodies. A positive reaction for both S-100 protein-like and vimentin-like was found in satellite and Schwann cells. In addition, some large and intermediate sized neurons also result S-100 protein-like immunoreactivity. No positive reaction for glial fibrillary acidic protein-like was observed. The authors discuss these results.

Animals↗
PubMed1989

Cathepsin D in erythroid cells.

We have detected, solubilized, and purified to near-homogeneity a membrane-bound acid protease from rabbit reticulocytes. Chemical, physical, immunological, and catalytic characterization demonstrate that the enzyme is cathepsin D. With cytochrome b5 as substrate, the enzyme shows a surprisingly high pH optimum and is stimulated by ATP and DPG. Possible roles for the protease include protein processing of microsomal enzymes, degradation of subcellular organelles, and destruction of excess hemoglobin chains. The possible role of cathepsin D in protein processing of microsomal enzymes will be best assessed by the molecular biological approaches described in the following two presentations.

Adenosine Triphosphate↗
PubMed1989

The erythrocyte density test (EDT) and erythrocyte creatine concentration (ECE) as laboratory indexes of perinatal hypoxia.

To study the influence of gestational age and asphyxia on the behaviour of EDT and ECE a group of cuban control and asphyxiated newborns was investigated. A total number of 203 newborns at the age of 0-3 days of life, all with adequate weight for gestational age, were classified into 4 groups according to their gestational age, the 1 min and 5 min Apgar score and the presence of meconium stained amniotic fluid and/or respiratory distress syndrome immediately after birth. In the group of asphyxiated newborns higher values for both parameters were found when they were compared with the respective control groups (p less than 0.05). These techniques could help the neonatologists to more precisely identify newborns with severe perinatal asphyxia and to improve the prognosis of the outcome.

Asphyxia Neonatorum↗
PubMed1988

Iron deficiency anemia and steady-state work performance at high altitude.

Thirty-seven young adult male highland residents at 3,600-4,100 m in La Paz, Bolivia, performed short-duration cycle ergometry at 60, 80, and 100% of maximal voluntary O2 consumption (VO2max). Three groups of subjects representing the high-altitude population mean hemoglobin (Hb), the 10th percentile Hb, and below the 1st percentile were examined to test the hypothesis that the relationship of exercise performance to Hb concentration is similar to those relationships established at low altitude. Anemic individuals (n = 8) had 23% lower voluntary VO2max and 28% lower maximal work loads compared with controls (n = 17) or marginally anemic subjects (n = 12) although the relationship of VO2 to work load was similar. Anemic individuals maintained significantly higher arterial O2 partial pressures and Hb saturations during heavy exercise (90 +/- 0.5 vs. 85 +/- 0.6%) in conjunction with a greater heart rate up to maximal effort. A significantly decreased erythrocyte 2,3-diphosphoglycerate (2,3-DPG)-to-Hb molar ratio (0.70 +/- 0.04 vs. 1.12 +/- 0.06), suggestive of a left-shifted dissociation curve in anemics, is in contrast to the expected right-shifted curve. Moderate anemics were similar to controls. Anemic individuals did not differ in arterial lactate concentration from controls at absolute work loads; anemics had significantly lower arterial lactate concentrations at maximal effort than controls with no differences in the work load-to-lactate relationship. In conclusion, O2 transport during exercise at high altitude seems unaffected by the Hb concentrations as low as the 10th percentile of the population mean.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Tumor necrosis factor expression in human epithelial tumor cell lines.

Tumor necrosis factor (TNF) is a monokine with in vitro cytotoxicity for some but not all tumor cells. The basis for sensitivity and resistance to the antitumor effects of this agent remains unclear. The present studies have monitored the effects of TNF on 14 epithelial tumor cell lines. Eleven of these cell lines were resistant to the growth inhibitory effects of TNF (50% inhibitory concentration greater than 1,000 U/ml). 12 of the 14 tumor cell lines has detectable levels of high affinity cell surface TNF binding sites, thus suggesting that resistance was not often due to the absence of cell surface TNF receptors. Northern blot analysis demonstrated that three of the eleven resistant cell lines expressed detectable levels of TNF mRNA. Furthermore, both sensitive and resistant epithelial tumor cells had the capacity to express TNF transcripts in the presence of the protein synthesis inhibitor, cycloheximide. Finally, the presence of TNF expression at the RNA level is shown to be associated with the production of a TNF-like protein in the resistant Ov-D ovarian carcinoma cells. These findings suggest that certain human epithelial tumor cell lines inherently resistant to TNF also express this cytokine.

Animals↗
PubMed1988

Impaired production and lack of secretion of interleukin 1 by human breast milk macrophages.

Interleukin 1 (IL-1) production by human breast milk macrophages (HMMø) in response to bacterial lipopolysaccharides (LPS) was investigated in 49 healthy mothers and compared with that of blood monocytes (HMo). IL-1 activity in 24 h HMMø culture supernatants was in most cases below the assay detection limits and much smaller than that of stimulated HMo (72 +/- 17 u/ml). Intracellular IL-1 activity in response to LPS in HMMø raised from less than 2 +/- 1 u/ml to 19 +/- 12 u/ml and was similar to that found in stimulated HMo (16 +/- 4 u/ml). Neither the low IL-1 production by HMMø nor its release into supernatants could be increased by stimulating with higher LPS concentrations (40-400 micrograms/ml) or when longer culture times were assayed (24-72 h). Inhibiting the production of prostaglandins by adding indomethacin to HMMø cultures, caused no effect either on IL-1 production or on its secretion to supernatants. The presence of inhibitors for the IL-1 thymocyte proliferative assay, in supernatants from HMMø, was excluded by mixing experiments with a known amount of IL-1. Thus, we conclude that HMMø produce four or five times less IL-1 than HMo in response to LPS stimulus. Furthermore, HMMø are completely unable to release the IL-1 produced.

Adolescent↗
PubMed1988

Liquid-chromatographic determination of free and total 3,4-dihydroxyphenylglycol and 3-methoxy-4-hydroxyphenylglycol in urine.

We describe the conjoint measurement in urine of the alcoholic catecholamine metabolites 3,4-dihydroxyphenylglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG). The method involves extraction with ethyl acetate and back-extraction into acetic acid (MHPG), followed by adsorption onto alumina (DHPG). The separation is performed by reversed-phase liquid chromatography with column switching and amperometric detection. Total (free plus conjugated) compounds are determined after a 24-h enzymatic hydrolysis. Twelve-hour excretion values for normal and hypertensive subjects are given, together with results obtained for patients with pheochromocytoma, chemodectoma, and congenital dopamine-beta-hydroxylase deficiency. The assay is sensitive, reproducible, and free of interferences, and may lead to a better understanding of overall catecholamine metabolism in health and disease.

Adrenal Gland Neoplasms↗
PubMed1987

Miliary tuberculosis and adult respiratory distress syndrome.

Although, miliary tuberculosis is an unusual cause of severe acute respiratory failure, we describe nine patients with miliary tuberculosis who developed adult respiratory distress syndrome. This complication occurred in seven patients despite treatment with antituberculous drugs. In two patients who developed the syndrome, miliary tuberculosis was diagnosed only at postmortem. The presence of pulmonary hypertension in all cases and disseminated intravascular coagulation in seven cases suggests a possible pathophysiologic relationship with severe pulmonary vascular damage. The high mortality rate (88.8%) was associated with nonpulmonary organ system failure. Miliary tuberculosis should be considered in patients with adult respiratory distress syndrome of unknown etiology, and simple diagnostic procedures such as sputum, bronchial brushing, and gastric examination should be followed by invasive diagnostic procedures to confirm this etiology. Since untreated miliary tuberculosis is usually fatal, early recognition of this disease is of great importance, and specific therapy may play a lifesaving role.

Adult↗
PubMed1987

Induction of tumor necrosis factor expression and resistance in a human breast tumor cell line.

Tumor necrosis factor (TNF) is a polypeptide cytokine that is cytotoxic to some but not all tumor cells. The basis for resistance to the cytotoxic effects of this agent remains unclear. We have studied the development of TNF resistance in human ZR-75-1 breast carcinoma cells. ZR-75-1 cells have undetectable levels of TNF RNA and protein. However, TNF transcripts are transiently induced in these cells by exposure to recombinant human TNF. This induction of TNF RNA is associated with production of TNF-like protein in cell lysates and culture supernatants. Stable resistance to TNF-induced cytotoxicity develops when ZR-75-1 cells are exposed to increased concentrations of TNF. The TNF-resistant cells, designated ZR-75-1R, continuously express TNF transcripts and a TNF-like protein. Furthermore, ZR-75-1R cell supernatants contain cytotoxic activity that is abrogated by polyclonal antibody against TNF. The ZR-75-1R cells also possess TNF receptors that are occupied or down-regulated by the TNF-like protein. These findings thus suggest that (i) TNF induces TNF transcripts and production of a TNF-like protein in ZR-75-1 cells and (ii) resistance to TNF-induced cytotoxicity is associated with stable TNF expression.

Breast Neoplasms↗
PubMed1986

Routine analysis of catecholamines and metabolites in urine by a liquid chromatographic column switching system.

A reversed-phase liquid chromatographic technique including a column switching system has been adapted for the routine measurement of catecholamines and their metabolites (14 compounds) in urine. From 1 ml of urine all the compounds and the internal standards were obtained according to combined extraction procedures involving organic solvent, anionic and weakly cationic resins. Finally four extracts (catecholamines, methoxamines, acidic and neutral derivatives) had to be chromatographed throughout a wholly automated apparatus. For each run, the column switching system determined the analytical columns to be used to obtain the separation of the compounds from interferences due to other co-extracted endogenous substances, while the analysis times remained between 20 and 40 min. Such a system allowed the rapid clean-up of columns (in direct- and back-flush mode) carried out between two consecutive injections. By coupling on-line fluorimetric and electrochemical detections the specificity of the technique could be checked, since the ratio of the responses of both detectors was an index of the purity of the peaks. Finally the advanced automation of the equipment allowed weekly the evaluation of catecholamines and the whole range of their known metabolites in 36 urine samples.

Catecholamines↗
PubMed1986

Effects of calcium channel blockers on gastric emptying and acid secretion of the rat in vivo.

Experiments were designed to evaluate the effects of three calcium channel blockers (verapamil, diltiazem and cinnarizine) on gastric emptying and secretion in the rat. Pretreatment with the calcium blockers delayed gastric emptying of phenol red in a dose-dependent manner. Verapamil was the most effective of the agents tested. Verapamil and diltiazem inhibited gastric acid secretion in the pylorus-ligated rat without affecting pepsin output. Cinnarizine was ineffective in this model. When the perfused lumen of the anaesthetized rat was used, verapamil was found to inhibit responses to carbachol or histamine more than those to pentagastrin. Further, we found a greater sensitivity to verapamil for basal compared with vagal-stimulated (2-deoxy-D-glucose) acid secretion. Neither diltiazem nor cinnarizine modified gastric acid secretion in this experimental model. These findings are discussed in relation to the role of extracellular calcium in gastric motility and secretion, and the existence of a regional and functional selectivity for calcium blockers is proposed.

Anesthesia↗