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Biomedical subjects

S Díaz

Publications and source records attributed to S Díaz.

At least 19 recordsLinked to original sources
PubMed1992

Alterations in the cell wall of Saccharomyces cerevisiae induced by the alpha sex factor or a mutation in the cell cycle.

We performed experiments in parallel to study the rate of synthesis of cell wall polysaccharides and the activity of glycosyl transferases in Saccharomyces cerevisiae after arrest of a cdc 28 mutant in G1 phase by either addition of alpha-factor or transfer to the non-permissive temperature. Both effectors brought about similar time-dependent increases in the rate of synthesis and deposition of the cell wall polysaccharides chitin, glucan and mannan. These changes in cell wall composition were accompanied by an increase in the specific activities of glucan and chitin synthetases. This increase was inhibited by cycloheximide suggesting that it represented de novo enzyme biosynthesis and not enzyme activation. Our data are consistent with the notion that both alpha-factor and the cdc 28 mutation affect the same stage-specific function that controls the temporal expression of glycosyl transferases.

Cell Cycle↗
PubMed1992

Relative contributions of anovulation and luteal phase defect to the reduced pregnancy rate of breastfeeding women.

OBJECTIVE: To evaluate the contribution of anovulation and luteal phase defects to lactational infertility. DESIGN: Prospective longitudinal follow-up. SETTING: Outpatient clinic. SUBJECTS: Forty-nine women fully nursing and amenorrheic on day 75 postpartum and 25 cycling, interval non-nursing women. INTERVENTIONS: Plasma prolactin, luteinizing hormone, estradiol (E2), and progesterone (P) levels twice a week up to the second postpartum menses. MAIN OUTCOME MEASURES: Ovulation rate and endocrine profile of the menstrual cycles. RESULTS: Ovulation rates were 37% and 97% at 6 and 12 months postpartum; 67% of ovulations occurred in amenorrhea. The luteal phase was shorter, and E2 and P levels were lower in lactating women than in non-nursing women. These parameters were closer to normal in the second cycle than the first, in spite of active nursing. The risk of ovulation and pregnancy in amenorrhea was 27.7% and 0.9% at month 6 postpartum. After the first menses, these risks were 93% and 7%, respectively. CONCLUSION: The abnormal endocrine profile of the first luteal phase offers effective protection to women who ovulate during lactational amenorrhea within the first 6 months after delivery. Later luteal phases are improved and women are at risk of pregnancy.

Adolescent↗
PubMed1991

Clinical trial with 3-keto-desogestrel subdermal implants.

The study was done to assess the clinical performance and in vivo steroid release rate of 3-keto-desogestrel subdermal implants designed to deliver 5 different doses of the progestin. Volunteers were healthy women of proven fertility who provided blood samples at scheduled intervals during treatment. No pregnancy occurred in 514 woman-months in users of implants delivering 30 and 40 micrograms per day of 3-keto-desogestrel. Three pregnancies, one ectopic, were observed in 109 woman-months recorded with implants delivering 20 micrograms per day or less. Ovulation was inhibited, as judged by depressed progesterone levels, in 57 of 59 (97%) blood samplings in women whose 3-keto-desogestrel plasma levels were greater than 0.28 nmol/L and in 39 of 75 (52%) of cases with lower levels. Users of 4 cm implants manufactured by The Population Council, New York, showed mean levels above 0.28 nmol/L until 18 months of use. Levels achieved with 4.4 cm implants manufactured by Organon, Oss, Holland, were less consistent. No changes were observed in the plasma lipoprotein pattern or clinical chemistry during treatment. The main complaint was the occurrence of bleeding irregularities, particularly with the lower doses. Ovarian cysts found during pelvic examination in 11 (22%) subjects disappeared spontaneously within 7-90 days. 3-keto-desogestrel implants releasing around 40 ug/day and providing plasma levels around 0.28 nmol/L afford efficient contraceptive protection.

Adolescent↗
PubMed1991

Contraceptive efficacy of lactational amenorrhea in urban Chilean women.

The contraceptive efficacy of breastfeeding was assessed in 236 healthy urban women who were followed at monthly intervals during the first postpartum year. Proportional hazard models were used to evaluate the influence of time postpartum, menstrual status and breastfeeding pattern upon the risk of pregnancy. Time and menstrual status had a highly significant effect on this risk. Those women who remained in amenorrhea had cumulative probabilities of pregnancy of 0.9% and 17% at 6 and 12 months postpartum, respectively. In those who recovered menstrual cycles, the risk rose to 36% and 55% at 6 and 12 months, respectively. Milk supplementation also increased significantly the risk when considered alone but not when time and/or menstrual status were included in the analysis. However, amenorrheic women who introduced bottle feeding, had a higher risk of pregnancy after 6 months postpartum than those who remained fully nursing. The analysis was unable to detect a significant influence of the nursing frequency. The results confirm that lactational amenorrhea is an effective contraceptive during the first six months postpartum. The first postpartum bleeding marks a great increase in the risk of pregnancy. Supplementation also increases the risk, particularly in amenorrheic women.

Adult↗
PubMed1991

Mechanism of action of progesterone as contraceptive for lactating women.

Progesterone vaginal rings releasing 5-15 mg/day were tested as a contraceptive for lactating women. Progesterone plasma levels achieved ranged from 10 to 20 nmol/L. Pregnancy rates at the end of the year were less than 1% and 39% in treated (n = 210) and untreated (n = 236) nursing women, respectively. Around 70% of treated and 30% of untreated women were amenorrheic at 8 months post partum. The endocrine profile during the first 8 months post partum was assessed in 36 treated and 28 untreated nursing women. Pre- and postsuckling prolactin (PRL) levels were measured at 1600 hr at fortnightly intervals and E2 determinations and ovarian ultrasound were performed twice a week. Prolactin increases in response to suckling and postsuckling PRL levels were higher, E2 levels were lower, and follicular growth was arrested at earlier stages in progesterone-treated than in untreated women. The pattern observed in progesterone-treated women was similar to that in prolonged lactational amenorrhea. This suggests that progesterone increases the sensitivity of the breast-hypothalamic-pituitary system to suckling and reinforces the mechanism of lactational infertility.

Breast Feeding↗
PubMed1991

Early difference in the endocrine profile of long and short lactational amenorrhea.

The endocrine profiles associated with long and short lactational amenorrhea were assessed in a longitudinal study in which morning blood samples were drawn in 48 women from the first postpartum month until the recovery of ovulation and in a cross-sectional study in which the samples were drawn throughout 24 h at the end of the third postpartum month in 10 fully nursing and amenorrheic women. PRL, LH, FSH, estradiol (E2), progesterone, cortisol, and dehydroepiandrosterone sulfate were measured. In both studies we detected a smaller PRL increase in response to suckling (P less than 0.001) and higher E2 levels (P less than 0.001) in nursing women who ovulated within 6 months postpartum compared to those in women who did not. Such differences were observed early after delivery when all women were fully nursing and amenorrheic. These results suggest some probable sources of variability in the duration of lactational amenorrhea in our population. The greater PRL response to suckling associated with longer amenorrhea may be due to higher sensitivity of the breast-hypothalamus-pituitary system or a stronger suckling stimulus in this group. Differences in plasma E2 levels between longer and shorter periods of amenorrhea may reflect dissimilar endogenous production, intake, or clearance of estrogens.

Adult↗
PubMed1990

Clinical assessment of treatments for prolonged bleeding in users of Norplant implants.

The effectiveness of three drugs in controlling prolonged bleeding in the first year of NORPLANT implants use was tested. The drugs were levonorgestrel (L-Ng, 0.03 mg twice a day for 20 days), ethinylestradiol (EE, 0.05 mg per day for 20 days) and ibuprofen (Ib, 800 mg three times a day for 5 days) and were given orally. A control group received a placebo (PL, one pill of lactose for 20 days). Treatment should start each time a woman experienced eight consecutive days of bleeding or spotting. The 183 volunteers were not aware of the drug administered. A daily record of bleeding and spotting and of treatment intake was maintained. One-hundred-forty women completed the study period; 60 never used the prescribed treatment. Women treated with the three test drugs had significantly fewer bleeding and spotting days during the treated month and also throughout the study year than women using the placebo. The mean number of bleeding plus spotting days per actually treated subject in the first year was 77, 94, 101 and 129 days for the EE, Ib, L-Ng and PL groups, respectively. The administration of EE might help in the management of prolonged bleeding during the first year of NORPLANT implants use.

Administration, Oral↗
PubMed1989

A longitudinal study on cortisol, prolactin and thyroid hormones in users of Norplant subdermal implants or a copper T device.

A longitudinal study was undertaken to assess PRL, cortisol, TSH, T3 and T4 levels in NORPLANT implant users (n = 22) and Copper T users (n = 20). Participants were healthy women with no contraindication for hormonal contraception. Samples were drawn at 0930 to 1000 h twice pretreatment and at month 2, 4, 6, 12, 24 and 36 after insertion. At the second treatment month, a second sample was obtained at 1600 h to assess cortisol diurnal variation. Hormones were measured by RIA. Values for all hormones were similar in Norplant and Copper T users. No significant changes occurred throughout the study period. Elevated PRL levels (greater than 500 mU/1) were found in three women from each group before and during treatment but no clinical evidence of hyperprolactinemia was detected. The results of this study reassure that long-term use of NORPLANT implants do not impair plasma levels of cortisol, prolactin and thyroid hormones.

Adult↗
PubMed1989

Circadian variation of basal plasma prolactin, prolactin response to suckling, and length of amenorrhea in nursing women.

The circadian pattern of plasma PRL levels and the PRL response to suckling were examined at various times during the first postpartum year and related to the length of lactational amenorrhea. Ten healthy women whose infants were breast-fed exclusively and who were amenorrheic 3 months postpartum were studied 3, 6, and 9-11 months postpartum. The women and their babies were admitted to a metabolic unit for 48 h. On the second day, blood samples were drawn at 2-h intervals for 26 h starting at 0800 h and also 10 and 30 min after the initiation of six of the nursing episodes. During the three postpartum periods, there was a circadian rhythm of basal plasma PRL concentrations; the peak concentrations occurred between 2400-0600 h. Suckling induced a significant rise in plasma PRL levels at all hours except 0800 h. There was a positive correlation between the duration of the nursing episode and the suckling-induced PRL increase at 30 min. Both the basal plasma PRL levels and the PRL responses to suckling diminished with time after delivery. This trend was less evident at 0400 h and was not fully explained by changes in the nursing pattern. The five women in whom menstrual cycles resumed before day 180 postpartum had lower basal and suckling-induced plasma PRL levels than the women who had amenorrhea for a longer period. This difference was present in the third month, when all women were amenorrheic and fully nursing and when the frequency and duration of nursing episodes and infant growth rates were similar. The results indicate that comparable nursing patterns may be associated with different plasma PRL levels, which are associated with different lengths of lactational amenorrhea. An early difference in the sensitivity of the breast-hypothalamus-pituitary system to suckling may explain the differences in the duration of lactational amenorrhea, which are not dependant on the breastfeeding pattern. The magnitude of the PRL response to suckling may predict the likelihood of recovering ovarian function during lactation.

Adult↗
PubMed1989

[Long-term follow-up of women treated with contraceptive implants of levonorgestrel Norplant].

This report describe the long-term follow-up of 376 women who received Norplant implants in the period october 1974 through may 1979. One-hundred-and-ten subjects received replacement implants after variable lengths of use of the first set. The average levonorgestrel plasma levels declined steadily through eight years of use of Norplant capsules (r = -937). Values were 0.35 ng/ml, 0.29 ng/ml and 0.22 ng/ml at treatment years 1, 5 and 8, respectively. Levonorgestrel plasma levels after replacement with a second set of implants were similar to those observed after the first insertion, either when placed in the same site as the first set or in a different area. The levonorgestrel half-life after implant removal was 42 +/- 16 h (X +/- S.E.) and only trace amounts are detected after 96 h. Nineteen pregnancies occurred during 18,530 woman-months of use of the first set of implants, eleven of them during years 6 through 8 of treatment. The Pearl Index for the first years of Norplant implants use was 0.63. No pregnancy has occurred in 5.020 woman-months observed during treatment with a second set of capsules. Fifty-six women (14.9%) out of 376 acceptors of the first implant and 12 (10.9%) out of 110 acceptors of the replacement implants were terminated for other medical reasons, mainly side effects commonly associated with hormonal contraception. Removals for bleeding problems occurred in 5.6% and 3.6% of the acceptors of the first and second implant, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Estradiol plasma levels during long-term treatment with Norplant subdermal implants.

Estradiol-(E2) plasma levels were assessed in forty-seven women treated for one through seven years with the same set of Norplant implants. Each woman was subjected to one (n = 34), two (n = 11) or three (n = 2) sampling runs. At each sampling run, blood samples were drawn every third or fourth day during 5 or 6 consecutive weeks. Sampling runs were classified as ovulatory (n = 11), anovulatory (n = 49) or uncertain (n = 1) according to progesterone levels. Controls were Copper T users (n = 8), all classified as ovulatory. No significant differences were found for the mean E2 levels between Norplant users and Copper T users and between ovulatory and anovulatory cases. The mean of the peak E2 value found in each sampling run was significantly higher in anovulatory Norplant subjects than in the control group. The mean of the minimum E2 level observed was significantly lower in Norplant cases than in Copper T users. A single woman from the Norplant group and none from the Copper T group had all E2 values below 370 pmol/l. The inhibition of the reproductive function induced by Norplant implants is associated with a wider range of E2 circulating levels. None of the values observed at the extremes should cause serious concerns. High peaks are transitory and opposed by the antiestrogenic effect of levonorgestrel. Persistent low levels which could be associated with a hypoestrogenic state were observed in a single case.

Adult↗