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Biomedical subjects

G Castillo

Publications and source records attributed to G Castillo.

At least 37 records · Page 2Linked to original sources
PubMed1997

Down-regulation of the mdr gene by thyroid hormone during Xenopus laevis development.

The developmental regulation of mdr in Xenopus laevis has been investigated. Xe-mdr expression was first detected in the early tadpole stage just prior to the onset of feeding and increased during intestinal development, with a sharp decline at metamorphosis. Xe-mdr expression was found to be localized specifically to the epithelial cells lining the intestinal tract. When premetamorphic tadpoles were treated with 5 nM triiodothyronine to induce metamorphosis, a significant decrease in mdr message and protein was observed after 3 days, a time at which the primary epithelium remained intact. Furthermore, in thyroid-hormone treated primary cultures of brush border epithelial cells, a reduction in mdr message also was observed. These results demonstrate that the Xe-mdr gene is developmentally regulated and suggest a role for thyroid hormone in this process. This is the first report of a naturally occurring substance that can down-regulate mdr gene expression in vivo.

Animals↗
PubMed1997

Opioid availability in Latin America: the Santo Domingo report progress since the Declaration of Florianopolis.

The World Health Organization (WHO) has indicated that opioid analgesics are insufficiently available, particularly in developing countries, due to a variety of reasons, including legislative, educational, and policy issues. In its effort to promote the rational use of medical opioids and the adequate treatment of patients with cancer, WHO has sponsored a meeting of Latin American representatives every 2 years, which includes health professionals and government regulators. During March 24-27, 1996, a group of 86 representatives of cancer pain relief and palliative care programs from nine Latin American countries met in Santo Domingo under the auspices of the WHO Palliative Care Program for Latin America. For the first time since the First Latin American Meeting, government regulators were present to help address the issue of opioid availability from their perspective. During the meeting, issues pertaining to cancer pain, opioid availability, and palliative care were discussed. This report summarizes some of the events and presents a summary of the conclusions of an earlier meeting in 1994, as described in the Declaration of Florianopolis, and presents its follow-up, The Santo Domingo Report, generated following the 1996 meeting.

Analgesics, Opioid↗
PubMed1996

Isocratic high-performance liquid chromatographic method for quantitative determination of lysine, histidine and tyrosine in foods.

A method for the quantitative determination of lysine, histidine and tyrosine in foods based on pre-column derivatization with 5-dimethylaminonaphthalene-1-sulfonyl chloride (DnsCl) and reversed-phase liquid chromatography has been developed. Derivatization conditions, including DnsCl concentration, time, temperature, and buffer solution were studied. To establish the reliability of the proposed liquid chromatographic (LC) method, the precision and accuracy of the analyses were evaluated using samples of casein and lysozyme.

Caseins↗
PubMed1996

Amebiasis of the penis.

Penile amebiasis is rarely a recognized entity because the penis is not the usual site of presentation for amebiasis. Homosexual men have a higher risk of acquiring the lesion. Amebic ulcers resemble cutaneous lesions arising from squamous cell carcinoma, chancroid, primary syphilis, granuloma inguinale, and many other causes. An amebic ulcer should be suspected in a patient with balanoposthitis that resists antibiotic therapy. Biopsy is fundamental to isolate the trophozoites to confirm the diagnosis. Metronidazole and hydrochloric emetine are still the treatment of choice. This diagnosis should especially be considered in cases of lesions detected in patients who practice anogenital sex or who are immunocompromised.

Adolescent↗
PubMed1995

A homologue of the mammalian multidrug resistance gene (mdr) is functionally expressed in the intestine of Xenopus laevis.

P-glycoprotein is an integral membrane protein that functions in multidrug resistance (MDR) cells as a drug efflux pump to maintain intracellular concentrations of antitumor drugs below cytotoxic levels. A homologue of the mammalian mdr gene has been isolated and characterized from Xenopus laevis (Xe-mdr). The cDNA was isolated from a tadpole cDNA library using the full length mouse mdrlb cDNA as a probe. The Xe-mdr encodes a protein that is 66% identical to the mouse mdrlb and 68% identical to the human mdrl. The predicted structure of the Xe-mdr gene product identifies twelve membrane spanning domains and two ATP binding sites both of which are the hallmark of the ABC (ATP binding cassette) transporters. Xe-mdr mRNA is expressed as a single message of 4.5 kb and is found predominantly in the intestine. Xe-mdr message is increased 3- to 4-fold in the ileum compared to the rest of the small intestine. In situ hybridization of sequential sections from the small intestine localized the expression of the Xe-mdr to the cells lining the lumenal epithelium. Brush border membrane vesicles prepared from the small intestine of Xenopus laevis effluxed vinblastine in an ATP-dependent manner. Efflux was decreased by verapamil, a known inhibitor of P-glycoprotein function. These studies indicate that the structure of Xe-mdr has been conserved and suggest that the protein has a role in maintaining the function of the normal intestine in Xenopus.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
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↗