PubMed Health⌕ Search

Biomedical subjects

G Castillo

Publications and source records attributed to G Castillo.

At least 37 records · Page 2Linked to original sources
PubMed1995

Inhibitory effect of sodium ursodeoxycholate on basal and stimulated short-circuit current across the isolated toad skin.

The effect of sodium ursodeoxycholate (U) on short-circuit current (SCC), an index of basal and stimulated net ion transport across isolated skins of Bufo arenarum toads, was tested. U inhibited basal SCC when added to the epidermal side of the skins. The inhibitory effect was reversible after rinsing the preparation during 60 min. U also inhibited the natriferic response to oxytocin, db-cAMP and theophylline by 82%, 49% and 47%, respectively. Inhibition of SCC by exposure to U was reversed by the polyene antibiotic nystatin. In turn, SCC induced by nystatin in the amiloride-treated skin was insensitive to U and blocked by ouabain, a Na+, K(+)-ATPase inhibitor. These results strongly suggest that the effect of U is exerted at the apical membrane of sodium transporting cells, and rule out the existence of an additional site of inhibitory action of U.

Action Potentials↗
PubMed1995

Opioid availability in Latin America: the declaration of Florianopolis.

Between March 27 and 29, 1994, a group of representatives of 32 palliative care programs from eight Latin American countries met under the auspices of the World Health Organization (WHO) Palliative Care Program for Latin America in Florianopolis, Brazil. The participants included physicians, nurses, psychologists, volunteers, drug regulators, hospital administrators, and representatives from the pharmaceutical industry. A comprehensive report by David Joranson (University of Wisconsin-Madison) was followed by a general discussion moderated by Jan Stjernsward, Chief of the Cancer Unit, World Health Organization, and by Eduardo Bruera, Coordinator of the WHO Cancer Pain and Palliative Care Program for Latin America. A number of issues related to opioid availability were identified and discussed. This declaration summarizes the main conclusions of the meeting. The attendants would like to encourage the widest possible distribution of this document.

Analgesics, Opioid↗
PubMed1995

Metabolic inhibition and chloride transport in isolated toad skin.

1. When added to the Na(+)-containing solution bathing the isolated toad skin, dinitrophenol (DNP, an uncoupler of oxidative phosphorilation) caused decreases in the baseline values of short circuit current (SCC) and transepithelial conductance (G). 2. DNP also inhibited the increases in SCC and G caused by theophylline, whether added prior to the xanthine, or after the effect of the latter was fully developed. 3. In skins exposed to theophylline and bathed in Cl(-)-free (sulfate Ringer's) solution, the changes in SCC and G had a similar time course (t1/2 > 15 min). In the presence of Cl- (skins bathed in Ringer's solution), SCC decreased with a similar rate, whereas the rate of the decrease in G was greater (t1/2 < 15 min). 4. DNP also decreased the SCC induced by a Cl- concentration gradient in skins exposed to theophylline (SCCg) with a time course similar to its effect on the theophylline-increased G in the presence of Cl-. DNP was effective irrespective of the presence of ambient Na+. 5. A similar difference was observed in skins bathed in CIR and exposed to forskolin. In contrast to theophylline, however, forskolin partially overcame the inhibition of G brought about by DNP; no such recovery was observed in SCC. 6. In contrast to its influence on the responses to theophylline and forskolin, DNP failed to prevent either the increase in G or the onset of SCCg in skins exposed to dibutyryl cyclic AMP. 7. Rotenone, an inhibitor of the electron-transport chain, significantly decreased SCC and G in the unstimulated skin. It also prevented the SCC response to theophylline, and decreased it if added after the effects of the xanthine were fully developed, but failed to modify the increase in G brought about by theophylline. The time course of SCC inhibition by rotenone was similar to that caused by DNP. 8. Ouabain, an inhibitor of Na+,K(+)-ATPase, decreased SCC in the theophylline-stimulated skin, without affecting G. 9. We conclude that, whereas integrity of oxidative energy metabolism is necessary to sustain SCC in the isolated toad skin, it is not a strict requirement for the increase of Cl(-)-dependent G activated by cAMP. 10. The effect of DNP on Cl(-)-dependent G activated by cAMP is probably exerted at the cAMP generation step, by inhibition of adenyl cyclase and/or a decrease in the availability of ATP.

Animals↗
PubMed1995

[Comparison between digoxin and atenolol in chronic atrial fibrillation].

The benefits of digoxin in patients with atrial fibrillation may be reduced due to its limited effect on atrioventricular conduction. The aim of this work was to compare digoxin and atenolol on functional class, resting and exercise heart rate and exercise capacity in patients with atrial fibrillation. Thirteen subjects with this condition, normal echocardiographic left ventricular function and size, a resting heart rate less than 80 beats/min and with no contraindication for beta blocker or digoxin use were studied. Patients were randomly assigned to receive initially digoxin 0.25 mg o.d. or atenolol 100 mg o.d. in a double blind fashion. The doses were adjusted to obtain a heart rate between 60 and 80 beats/min at the end of the first week of treatment. After two weeks of treatment, outcomes were assessed, patients were left without treatment for one week and crossed over to the other drug after that. Resting heart rates achieved with digoxin and atenolol were similar (67 +/- 11 and 65 +/- 23 beats/min respectively). However, maximal exercise heart rates and maximal exercise time were higher during digoxin treatment (166 +/- 23 vs 135 +/- 27 beats/min and 9.95 +/- 1.68 vs 8.5 +/- 2 min respectively). NYHA functional class deteriorated in three patients receiving atenolol. We conclude that atenolol achieves a better control of heart rate during exercise but also reduces maximal exercise capacity.

Adult↗
PubMed1995

In vitro growth of Vibrio cholerae in cholera stool fluid leads to differential expression of virulence factors.

We report on the physiological response of Vibrio cholerae upon growth on bacteria-free intestinal fluids prepared from feces of individuals in the acute phase of cholera. Sterilized stool fluids supported growth of V. cholerae to reach 0.3-0.4 O.D. units (600 nm) at 37 degrees C. Scanning electron microscopy showed vibrios to be slender and elongated as compared to bacteria in synthetic media. Growth in stool fluid apparently induced expression of several immunoreactive proteins using cholera convalescent sera. Supernatants of fluid-grown vibrios had undetectable cholera toxin (CT) concentrations. Soluble hemagglutinins and soluble proteases were much less reduced when compared to cultures in Syncase or AKI media while cell-associated mannose-sensitive hemagglutinin (MSHA) was expressed at good levels. Lack of production of CT in fluid devoid of tissue may be due to absence of stimulating elements in intact intestine. Alternatively, culturing V. cholerae in stool fluid might resemble a late proliferation stage where downregulation of toxin might occur. Irrespectively, concomitant production of other virulence factors represents a phenomenon of differential regulation by fluid. Efforts are now underway to determine if this response depends upon factors in stool fluid acting through known genetic regulatory cascades or other. Attempts are also geared to identify fluid-induced proteins and their genes.

Biological Factors↗
PubMed1994

Oxytocic effect of trypsin on the isolated rat uterus.

To study the oxytocic effect of trypsin, we measured the force of isometric contraction in uteri isolated from estrogenized rats exposed to trypsin (8.8 x 10(-10) to 1.7 x 10(-6) mol/L) either alone or in the presence of receptor antagonists to angiotensin II [saralasin ([Sar1,Ala8]angiotensin II) or DuP 753 (losartan)] or to kinins (D-[Arg0,Hyp3,Thi5,8,D-Phe7]-bradykinin). We found that saralasin or DuP 753, but not the kinin antagonist, displaced the dose-response curve to the right. Exposure to exogenous angiotensin I desensitized the preparation to further doses of either angiotensin I or II or trypsin, without altering the effects of oxytocin or bradykinin. Enalaprilat (an angiotensin I converting enzyme inhibitor) or pepstatin A (a renin inhibitor) also displaced the dose-response curve to trypsin to the right, without altering the effects of oxytocin or angiotensin II. Our results indicate that the response to trypsin is mediated by an agent produced from a substrate present in the uterus and acting on the angiotensin II type 1 receptor and are consistent with both renin and angiotensin I converting enzyme being involved in its mechanism of action, thus supporting the notions that the renin-angiotensin system may be important in the late stages of pregnancy and that serine proteases existing in the uterus may contribute to its activation.

Angiotensin I↗
PubMed1992

Biochemical and genetic characterization of the multidrug resistance phenotype in murine macrophage-like J774.2 cells.

The development of multidrug resistance (MDR) in malignant tumors is a major obstacle to the treatment of many cancers. MDR sublines have been derived from the J774.2 mouse macrophage-like cell line and utilized to characterize the phenotype at the biochemical and genetic level. Two isoforms of the drug resistance-associated P-glycoprotein are present and distinguishable both electrophoretically and pharmacologically. Genetic analysis has revealed the presence of a three-member gene family; expression of two of these genes, mdr1a and mdr1b, is associated with MDR whereas the expression of the third, mdr2, is not. Studies of these three genes have revealed similarities and differences in the manner in which they are regulated at the transcriptional level, and have suggested that post-transcriptional effects may also be important.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Variability of proteoglycan expression in the isolated rat glomerulus.

The sulphation of proteoglycans in freshly isolated rat glomeruli was studied by biosynthetic labelling with [35S]sulphate. At least 75% of the observed sulphation requires de novo synthesis of core protein and proceeds at a constant rate over at least 40 h. Heparan and dermatan sulphate proteoglycans (HSPG and DSPG, respectively) are the two major species produced, with only minor amounts (less than 5%) of chondroitin sulphate labelled under these conditions. Several factors affect the population distribution of labelled material. When glomeruli were obtained from rats 6 weeks of age, HSPG accounted for 75 +/- 9% of tissue proteoglycan sulphated over 16 h. When older rats (12-14 weeks) were used, only 32 +/- 10% of label was associated with HSPG, DSPG accounting for the remainder. Production of HSPG is sulphate-dependent, increasing relative to DSPG with increasing sulphate, up to physiological concentrations. However, the net charge-density of sulphated material is conserved even at the lowest concentrations of sulphate. This may reflect the importance of electrostatic properties in the function of glomerular proteoglycans. The production of HSPG increases relative to DSPG with time following isolation and this effect is more dramatic in glomeruli from younger rats. However, reciprocal changes in production of HSPG and DSPG sustain a constant rate of sulphation. This phenomenon may arise from interdependency of the glomerular epithelial and mesangial cells with respect to regulation of proteoglycan synthesis.

Age Factors↗
PubMed1990

Functional expression of murine multidrug resistance in Xenopus laevis oocytes.

The development of multidrug resistance (MDR) is associated with the overproduction of a plasma membrane glycoprotein, P glycoprotein. Here we report the functional expression of a member of the murine mdr family of proteins and show that Xenopus oocytes injected with RNA encoding the mouse mdr1b P glycoprotein develop a MDR-like phenotype. Immunological analysis indicated that oocytes injected with the mdr1b RNA synthesized a protein with the size and immunological characteristics of the mouse mdr1b P glycoprotein. These oocytes exhibited a decreased accumulation of [3H]vinblastine and showed an increased capacity to extrude the drug compared to control oocytes not expressing the P glycoprotein. In addition, competition experiments indicated that verapamil, vincristine, daunomycin, and quinidine, but not colchicine, can overcome the rapid drug efflux conferred by the expression of the mouse P glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1988

Molecular cloning and expression in E. coli of a Salmonella typhi porin gene.

Immunoscreening of a Salmonella typhi cosmid library in E. coli allowed the detection of clones producing a 36 kDa porin from S. typhi. The gene is efficiently expressed in an E. coli porin-less mutant and the protein is exported to the outer membrane envelope. Two clones which markedly differ in their level of expression have been isolated.

Bacterial Outer Membrane Proteins↗
PubMed1986

Hyporeninemic hypoaldosteronism in children with chronic renal failure.

The syndrome of hyporeninemic hypoaldosteronism (SHH) is not infrequent in adults with chronic renal failure caused by chronic tubulointerstitial nephritis, but it has been reported rarely in children. We present a systematic study of the interrelation between renal excretion of potassium and the renin-aldosterone axis in 23 children with CRF of different and unselected causes. Twenty children with chronic renal failure never had hyperkalemia, and both renin and aldosterone were normally stimulated by intravenous administration of furosemide, whereas three patients had moderate hyperkalemia (serum potassium concentration between 5.3 and 5.6 mEq/L) and failed to raise plasma renin activity and aldosterone values in response to furosemide. There three patients with SHH had lower basal and stimulated values of fractional potassium excretion than did patients with normokalemic chronic renal failure. Fractional potassium excretion was curvilinearly related to glomerular filtration rate (GFR), but in all three patients with SHH it was lower than expected for the level of GFR present. Fractional sodium excretion was also related to GFR, but no abnormalities were found. Two patients had hyperchloremic metabolic acidosis. After furosemide administration, they excreted an acid urine with low ammonium content, features characteristic of type 4 or hyperkalemic renal tubular acidosis. Prostaglandin E2 excretion was also significantly related to GFR, and appeared appropriate in two patients with SHH. The identification of three patients with SHH among 23 with chronic renal failure of unselected causes suggests that this entity is not rare in childhood.

Child↗
PubMed1986

Hyperkalemic distal renal tubular acidosis in salt-losing congenital adrenal hyperplasia.

Functional indices of distal urinary acidification were assessed in two male infants, aged 1 and 3 months, with salt-losing congenital adrenal hyperplasia. In both cases the diagnosis was sustained by the presence of elevated plasma levels of 17-hydroxyprogesterone, hyponatremia, hyperkalemia, metabolic acidosis and increased plasma renin activity. Both patients were unable to lower urinary pH below 5.9 either during acute ammonium chloride-induced acidosis or after i.v. administration of furosemide. One patient also failed to decrease urine pH below 5.5 and to increase urinary potassium excretion during sodium sulfate infusion. Oral sodium bicarbonate loading was given to both patients but failed to induce a significant increase in the urine minus blood PCO2 gradient. This gradient remained low also after neutral phosphate administration. Repeated studies after acute administration of fludrocortisone in one case or after prolonged administration of hydrocortisone in the other resulted in complete normalization of all functional studies. We conclude that salt-losing congenital adrenal hyperplasia can lead to hyperkalemic distal renal tubular acidosis in early infancy. The defective renal secretion of hydrogen ion and potassium is probably related to the abolishment of the negative potential difference in the cortical collecting tubule induced by the impaired reabsorption of sodium.

Acidosis, Renal Tubular↗
PubMed1984

Production of soluble and cell-associated fibronectin by cultured keratinocytes.

Fibronectin has been demonstrated in epithelial cell types in culture, but published studies of keratinocytes have shown patterns of fibronectin produced by cells grown in medium with serum, which contains fibronectin. Since plasma fibronectin can bind to cells in vitro, cells grown in serum-supplemented media could show artifactual patterns of cell-associated fibronectin. To study insoluble fibronectin produced by keratinocytes, we plated cells in the absence of feeder layers in medium lacking fibronectin. Medium conditioned by metabolically labeled keratinocytes was studied by immunoprecipitation and by extraction with gelatin-Sepharose. Cells grown in fibronectin-free medium were labeled using affinity-purified anti-fibronectin antibody and fluorescein-conjugated antirabbit IgG. Keratinocytes produced soluble fibronectin, since both immunoprecipitation and adsorption to gelatin-Sepharose detected 35S-methionine-labeled material which comigrated with human plasma fibronectin on sodium dodecyl sulfate polyacrylamide gels. Demonstration of insoluble, cell-associated fibronectin was enhanced in Triton X-100-extracted cells and was seen in subcellular fibrillar arrays at both physiologic and reduced Ca++ concentrations, but in intracellular locations only at physiologic Ca++ concentrations. When cells grown in 1.1 mM Ca++ were removed with Triton X-100, diffusely distributed fibrillar fibronectin remained on the surface of the coverslip. Asymmetric "tracks" of fibronectin left by sparsely plated cells suggested movement. Fibronectin is deposited by keratinocytes on the culture surface and may be modulated by culture conditions.

Animals↗