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The WHO Task Force on Vaccines for Fertility Regulation. Its formation, objectives and research activities.
HUMAN REPRODUCTION. 1991 Jan; 6(1):166-72.The WHO Task Force on Vaccines for Fertility Regulation is one of several Task Forces, consisting of international, multidisciplinary groups of scientists and clinicians collaborating in research on specific goals, established in 1972. Its accomplishments are reviewed here. The Task Force convened a meeting in 1974 to select criteria for tissues and molecules capable of mounting antifertility responses. These molecules had to be restricted to the target tissue, sequestered in the reproductive tract, present transiently, and chemically characterized. Some of the antigens considered were sperm enzymes and membranes, as well as a data bank of sera naturally immunized against sperm. Other were anti-ovum and placenta molecules such as zona pellucida, the SP-1 placental antigen, and the placental hormones chorionic somatotrophin and human chorionic gonadotropin (hCH). Trophoblast-derived monoclonal antibodies and gene libraries are being screened. Anti-hCH is the vaccine composed of a portion of the beta subunit complexed to a carrier antigen, diphtheria toxoid, in a water- oil emulsion with an adjuvant has been tested in a phase I clinical trial in 1986-1988. A Phase II trial is being planned to see if the immune response in women is large enough to be capable of preventing pregnancy. Further improvements in the vaccine are being envisioned, such as incorporation of the peptide carrier conjugate and immune stimulant into biodegradable microspheres, hopefully to produce a longer-lasting immunity and a more stable vaccine. While the WHO Task Force on Vaccines for Fertility Regulation has been forced to cut back on some avenues of research, its success has stimulated other centers to take up several important projects, e.g. the sperm LDH and zona pellucida vaccines.
[Regulation of implantation as a contraceptive method] La regulacion de la implantacion como metodo anticonceptivo.
Gaceta Medica de Mexico. 1980 Jul; 116(7):318-28.Implantation of a fertilized ovum requires physiological and structural modifications in the endometrial tissue. Several mechanisms are currently being studied to modify or inhibit the implantation process: 1) a decrease in the secretion of luteinizing hormone; 2) action on endometrial progesterone receptors; 3) changes in prostaglandin secretion; 4) modifications of the surface of the ovum by utilizing antibodies against the pellucid zone; and 5) modification of the endometrial surface so to hinder the adhesion process. Most studies in this field are sponsored by the WHO, and they are all still at an experimental stage.
Injectable progestogens - officials debate but use increases. Les progestatifs injectables : les autorites en debattent, mas l'usage s'en repand.
Population Reports. Series K: Injectables and Implants. 1975 Mar; (1): p.A report on the status of the injectable contraceptive agents, Depo-Provera (depot medroxyprogesterone acetate) and Norigest is presented. Depo-Provera is distributed in 64 countries, though it is not available in the U.S., the United Kingdom, and Japan. The drug is usually administered in single 150 mg injections every 3 months, and doses of 300-400 mg every 6 months have been studied. The contraceptive effect of Depo-Provera is primarily through its ability to inhibit ovulation. Norigest exerts its effect by altering the cervical mucus. The suppression of ovulation is most likely caused by action on the hypothalamus-pituitary axis, resulting in inhibition of the luteinizing hormone surge. Depo-Provera causes an atrophic endometrium, while Norigest has varying endometrial effects. The reported pregnancy rates for Depo-Provera are usually less than 1%, while those for Norigest are slightly higher. Most method failures occur either shortly after the 1st injection or at the end of an injection interval. Menstrual disorders have been the primary reason for discontinuation. The injectables can cuase shorter or longer cycles, increased or decreased menstrual flow, and spotting. Depo-Provera users experience increased amenorrhea with continued use, while normal cycles increasingly reappear in Norigest users. Cyclic estrogen therapy has been effective in treating excessive or irregular bleeding and amenorrhea. Long-acting estrogen injections have been administered in combination with Depo-Provera or Norigest, though the studies are limited in number. Weight gain of up to 9 pounds has been reported for users of Depo-Provera. Some researchers have found that Depo-Provera raises blood glucose levels, while others have reported it does not. No adverse effects have been reported for injectables on blood clotting, adrenal or liver function, blood pressure, lactation, and metabolic or endocrine functions. The continuation rate for Depo-Provera is reportedly higher than that for oral contraceptives. Generally, 60% of the acceptors will use the method for at least 1 year. Effective counseling on the menstrual alterations resulting from injectables can increase continuation of the method. The return of fertility in Depo-Provera users usually requires 13 months from the time of the last injection, while the afertile period in Norigest users is about 6 months from the time of the last injection. Instances of fetal masculinization as a result of Depo-Provera use have not occurred. The possibility that Depo-Provera can cause cervical carcinoma in situ has not been substantiated by the evidence; doubt about this possible association has prevented its approval as a contraceptive method in the U.S. Although Depo-Provera and Norigest have caused breast nodules in laboratory animals, there is no evidence to suggest that this effect would occur in human. Despite the advantages of injectables, family planning officials have been reluctant to permit its unrestricted use, primarily because it cannot be withdrawn guickly enough if problems arise and because the actual effect on fertility is not yet known. Nonetheless, the use of Depo-Provera has increased in recent years. The IPPF and the U.N. Fund for Population Activities currently supply the drug.