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Biomedical subjects

R Rivera

Publications and source records attributed to R Rivera.

At least 19 recordsLinked to original sources
PubMed1992

Influence of age and parity on the development of the human breast.

Breast cancer is heavily influenced by the reproductive history of the individual. Pregnancy has a protective effect which is attributed to differences in the degree of differentiation of the breast. The purpose of this work was to determine whether the quantity and the type of parenchymal structures present in the human breast were related to the age and parity history of a woman. Fifty-one human breast samples were obtained from bilateral or unilateral reduction mammoplasties performed in 40 parous women ranging in age from 18 to 57 years, and 11 nulliparous women ranging in age from 14 to 54 years. An average of 100 grams of tissue/specimen were processed for whole mount. A total of 650 slides were examined and 31,222 structures were classified and counted under the light microscope. The following mammary structures were identified: terminal structures (TS), and lobules (LOB) type 1, 2, and 3. Results were plotted for the total patient population and separately for nulliparous and parous women against age. The total patient population contained similar proportions of LOb1, 2, and 3 between ages 14-18, with a reduction of percentage of Lob1 and increase in Lob3 between ages 23 to the middle forties, when Lob3 decreased and Lob1 increased to 70%. Lob2 and TS did not exhibit significant changes throughout the period of life analyzed. When analyzed separately it was found that the breasts of nulliparous women were predominantly composed of Lob1, fewer Lob2, with Lob3 almost completely absent, whereas parous women had a high frequency of Lob3, which were the predominant structures until the fourth decade of life.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Evaluating the readability of informed consent forms used in contraceptive clinical trials.

The readability level of informed consent forms used in clinical trials on contraceptives was determined. Three different formulas for measuring readability were used. Some forms received relatively high scores by all three methods. The most common problems associated with high readability scores were the use of 'unfamiliar' words, long words and long sentences. At present all forms used must be readable, using the SMOG formula, at a grade 6 level or less.

Clinical Trials as Topic↗
PubMed1992

Interactions between intrauterine contraceptive device use and breast-feeding status at time of intrauterine contraceptive device insertion: analysis of TCu-380A acceptors in developing countries.

OBJECTIVE: This paper is a reassessment of earlier findings from a preliminary analysis of data from a multicenter international trial regimen on breast-feeding and non-breast-feeding women in which events related to insertion, expulsion, and removal of the TCu-380A intrauterine contraceptive device (ParaGard 380) were investigated. STUDY DESIGN: Performance of the TCu-380A through 12 months after insertion was compared with life-table rate analysis, chi 2, Fisher exact test, or Student's t test. Variables were events reported during intrauterine contraceptive device insertion and events throughout the 12 months of study participation by breast-feeding status. RESULTS: Breast-feeding among intrauterine contraceptive device users was associated with fewer insertion-related complaints and lower removal rates for bleeding and pain. No uterine perforations were reported throughout the study. CONCLUSION: Differences in the performance of the TCu-380A intrauterine contraceptive device suggest physiologic effects associated with lactational amenorrhea. The TCu-380A intrauterine contraceptive device is a viable option for women breast-feeding at the time of intrauterine contraceptive device insertion.

Adult↗
PubMed1992

Field tests of an acephate baiting system designed for eradicating undesirable honey bees (Hymenoptera: Apidae).

Field evaluations were made of a baiting system designed for use by regulatory agencies in suppressing populations of undesirable feral honey bees, Apis mellifera L. (e.g., bees posing hazards [especially Africanized bees] and colonies infested with parasitic mites). Bees from feral or simulated feral (hived) colonies were lured with honey and Nasonov pheromone components to feeders dispensing sucrose-honey syrup. After 1-3 wk of passive training to feeders, colonies were treated during active foraging by replacing untreated syrup with syrup containing 500 ppm (mg/liter) acephate (Orthene 75 S). In four trials using hived colonies on Grant Terre Island, LA., 21 of 29 colonies foraged actively enough at baits to be treated, and 20 of the 22 treated were destroyed. In the lower Rio Grande Valley of Texas (two trials at each of two trials), treatments killed 11 of 16 colonies (6 of 10 hived; 50 of 6 feral). Overall results showed that all 11 colonies that collected greater than 25 mg acephate died, whereas 3 of 10 colonies receiving less than 25 mg survived. Delivering adequate doses required a minimum of approximately 100 bees per target colony simultaneously collecting treated syrup. The system destroyed target colonies located up to nearly 700 m away from baits. Major factors limiting efficacy were conditions inhibiting foraging at baits (e.g., competing natural nectar sources and temperatures and winds that restricted bee flight).

Animals↗
PubMed1992

[Clinical course characteristics of gastric cancer 1958-1990].

The clinical, surgical and histopathologic characteristics of patients with gastric cancer were compared among 3 consecutive periods from 1958 to 1990. A significant increase in the frequency of location at the upper third of the stomach, a greater proportion of resectable lesions, an increasing tendency towards extended total gastrectomy and a significant increase in the frequency of undifferentiated or diffuse carcinoma were observed. A change in pathogenetic factors along the years may be involved in the differences described.

Adult↗
PubMed1992

Oral tolerance impairment in mice with staphylococci-induced wasting syndrome.

The effects of staphylococci-induced experimental wasting disease on the immune response of 1 month old CD1 mice were investigated. Animals were separated into different subgroups in order to study their cellular immune competence. Malnutrition of wasted mice was associated with anorexia, diarrhea and weakness. Footpad-injected splenic cells produced normal graft vs. host (GvH) reactions in the popliteal lymph nodes of F1 hybrids. In other experiments, the SRBC intragastric feeding of wasted mice did not cause a tolerant anti-erythrocyte humoral immune response. Three weeks after the staphylococci injections, convalescent erythrocyte-fed wasted mice exhibited an anti-SRBC PFC production similar to that observed in non-tolerant immunized control healthy mice. In return, healthy SRBC-fed control mice showed the specific attenuation of antibody response characteristics of oral tolerance. Differences were found between the immune competence of the undernourished staphylococci-treated wasted mice and those shown by other authors in protein-depleted mice.

Administration, Oral↗
PubMed1992

[The propedeutic course given at the School of Medicine and the academic performance of the students that passed it].

A report of the results of the Propedeutic Course in the Medical School of the University of Panama is informed. This course was established by the Academic Council, at the request of the Medical School, to diminish the registration form 280 to 180 students, taking into account the low academic performance of the students with the lowest grades in the Admission Process. The study showed that the correlation indices of the students in the Propedeutic Course and in the first regular semester was low. The study also showed that the number of students from the Propedeutic Course who repeated or were separated from the school, was higher than those from the regular semester.

Curriculum↗
PubMed1979

Factors influencing better results in operation for postinfarction ventricular aneurysms.

A series of 66 consecutive patients operated on for postinfarction ventricular aneurysm is reviewed with regard to the factors influencing the progressive decline of mortality (3.2% in the last 31 patients seen). The method of myocardial protection has a significant influence on mortality, which was 45% in patients operated on with aortic cross-clamping under conventional hypothermia and 5% in patients operated on under profound local hypothermia. Associated revascularization with vein bypass graft was performed in 28 patients, without mortality. The technique of aneurysmectomy adapted to the extension and location of the fibrotic scar is described, with exclusion of the septal portion of the aneurysm in 85% of the patients. In 36 patients who had postoperative cardiac catheterization, this technique produced normal ejection fraction and near normal left ventricular volumes

Angiocardiography↗
PubMed1978

Circulatory responses to systemic infusions of estrone and estradiol-17alpha in nonpregnant, oophorectomized ewes.

Uterine arterial blood flow dose-response curves to systemic infusions of either estrone (E1) or estradiol-17alpha (E2alpha) were determined in ten oophorectomized, nonpregnant ewes. Maximum uterine blood flow occurred with 5 microgram per kilogram of E1 and greater than or equal to 20 microgram per kilogram of E2alpha. Total uterine blood flow measured with isotope-labeled microspheres rose more than tenfold following 30 microgram per kilogram of either estrogen, as did blood flow to the myometrium, endometrium, and uterine caruncles (p less than 0.05). Distribution of uterine blood flow was unaltered. Cervical and vaginal blood flows increased ten-to twenty-fold with E1 and E2alpha, while mammary gland blood flow rose 54 and 77 per cent. Significant increases in adrenal and thyroid blood flows were documented. The only significant decrease in blood flow occurred in the pancreas (- 13 percent; p less than 0.05) following E2alpha infusion. At the dose studied, E1 and E2alpha are potent vasodilators of reproductive tissues, especially the cervix and vagina. As they appear to be the major estrogens during ovine pregnancy, it is likely they participate in the preparation of these tissues for parturition.

Animals↗