Biomedical subjects

T Rojas

Publications and source records attributed to T Rojas.

5 recordsLinked to original sources

PubMed1997

[Endometrial interference of synthetic estrogens in fertility regulation.Is it necessary to interfere with the antiovulatory mechanism at the central nervous system level in order to obtain contraception?].

For some time the anti-ovulatory activity of certain estrogen/progestagen preparations was the main approach in fertility control. Up to date a drastic dosage reduction of both steroid hormones has been accomplished ameliorating the side effects on the one hand, and being active compounds as contraceptives, in the other. Currently, there are a wide variety of oral contraceptives available with a variety of estrogen doses combined with different progestagens. The estrogen content is a high as 80 micrograms and as low as 20 micrograms, moreover, such formulations are prescribed beginning the 1st or the 5th day of the menstrual cycle. By studying plasma and endometrial samples simultaneously obtained from chronic oral contraceptive users taking either 30 micrograms or 50 in such pills; a 17-beta-estradiol pattern was attained as that seen during follicular maturation in the ovulatory cycle only women under the lower dose of synthetic estrogen. However, in the endometrium such a cyclicity did not take place; in parallel circulating progesterone in both groups never reach levels greater than 5.0 ng/ml. Results offer to find a local critical period during the ovulatory menstrual cycle to achieve with much lower hormonal dosages a different approach in future methods of contraception.

Contraception↗

PubMed1995

Psychological considerations in colonoscopy.

In summary, psychological issues around the colonoscopy procedure have not yet been fully studied or even formulated. The framework taken here is to consider psychological preconditions to disease, psychological barriers to screening, and ways to maximize the psychological strength of patients when presenting serious diagnoses. Two common themes are present in this review. First, the idea of hopelessness and loss of personal control is present throughout the research in terms of personality predispositions, decisions to seek care, and outcome of disease when present. Physicians need to address the question, what can I do to maximize the hopefulness of this person before, during, and after screening? Are we encouraging an optimistic perspective in the lives of others? The second theme is closely related and that is the critical nature of the patient/physician relationship in all stages of health/illness behavior. It is often the positive, empathic strength of this relationship that affects patient behavior and ultimately the patient's medical outcome. Future research as well as physician self-examination and increased knowledge in this area are truly important. It is in this way that the procedure of colonoscopy truly becomes part of the total patient care.

Colonoscopy↗

PubMed1990

Sinefungin as treatment for American Leishmania in sensitive BALB/c and resistant C57BL/6 mice.

Using inbred BALB/c and C57BL/6 mice as animal models for American cutaneous leishmaniasis, we evaluated the inhibitory effect of sinefungin on foot-pad infection produced by 5 different Leishmania isolates. When treatment was initiated a few days, or even 2 weeks, after infection, an obvious leishmanicidal effect was detected on mice infected with Leishmania mexicana or L. braziliensis isolates, which lasted at least 50 weeks for all isolates studied. The optimal dose schedule was 4 mg/kg body weight/day, injected ip for 10 consecutive days; lower doses produced only a short leishmanistatic effect. The optimal dose found was 50-fold lower than the LD50. In vitro studies using Leishmania-infected murine peritoneal macrophages showed sinefungin as a powerful inhibitory drug, mean ED50 for the several Leishmania isolates studied being 50 ng/ml. No correlation was found between in vitro sensitivity of culture promastigotes and in vivo sensitivity to sinefungin of an American Leishmania isolate.

Adenosine↗

PubMed1987

American Leishmania spp: formycin B treatment of cutaneous leishmaniasis in mice.

Using foot-pad infection of female C57BL/6, DBA/2J and NMRI-IVIC mice as an animal model for American cutaneous leishmaniasis (ACL), we evaluated the inhibitory effect of Formycin B (FoB) on the infection produced by 7 different Leishmania isolates. When treatment was initiated some days, or even some weeks, after infection a significant leishmanistatic effect was detected on mice infected with all Leishmania isolates, which reached 30-55 weeks for some isolates. The optimal dose schedule was 1.25 mg/kg body weight/day, injected intraperitoneally for 20 consecutive days. Significant differences in the sensitivity of various Leishmania spp. to FoB were found, either in vivo, or in vitro where a high [3H]FoB incorporation rate was found only for certain Leishmania isolates. The low toxicity of this drug and the sensitivity of the 7 Leishmania isolates tested suggest that FoB could be useful in the treatment of ACL.

Animals↗

PubMed1987

Biological activity of analogs of guanine and guanosine against American Trypanosoma and Leishmania spp.

The growth inhibitory effects of six guanine and guanosine analogs, 3-deazaguanine (compound 1); 3-deazaguanosine (compound 2); 6-aminoallopurinol (compound 3); 9-beta-xylofuranosyl guanine (compound 4); a ribosylated derivative of compound 3, 6-aminopyrazolo(3,4-d)pyrimidin-4-one (compound 5); and 5-aminoformycin B (compound 6), were tested against some pathogenic members of the family of American Trypanosomatidae. Compounds 1 and 2 were highly active against Trypanosoma cruzi, Trypanosoma rangeli, and American Leishmania spp. in in vitro culture forms. Both compounds also showed antiprotozoal activity in T. cruzi-infected mice, with the optimal dose being about 30 mg/kg of body weight per day given as 10 consecutive doses. Compound 3 was the most active compound in vitro, inhibiting all of the American Trypanosomatidae culture forms tested. It was also highly inhibitory in mice that were acutely infected with T. cruzi, with the optimal dose being about 10 mg/kg of body weight per day. Ribosylation of compound 3 resulted in a derivative that showed decreased inhibitory activity on Trypanosomatidae multiplication. Compound 6 was highly inhibitory of in vitro multiplication of American Leishmania and T. rangeli but had no effect on T. cruzi epimastigotes and on mice that were acutely infected with T. cruzi. Compound 4 showed only a slight effect on T. cruzi epimastigotes.

Animals↗