PubMed HealthSearch

Biomedical subjects

F H Stewart

Publications and source records attributed to F H Stewart.

17 recordsLinked to original sources

Commentary: the quest for women's prophylactic methods--hopes vs science.

The companion article by Rosenberg and Gollub in this issue summarizes data from 10 observational studies and concludes that female-controlled contraceptive methods, under typical conditions, are comparable to condoms in preventing sexually transmitted diseases and should be merchandized as such. While we agree that chemical and mechanical contraceptives provide protection against some sexually transmitted diseases, we think the authors have overstated the scientific case for these methods, especially in comparison with the condom. We think the current data remain inconclusive regarding the absolute protection of spermicides against the human immunodeficiency virus and their level of protection--relative to that of the condom--against other sexually transmitted diseases. Three reasons account for our differences: the limitations in the comparative data; the reported adverse effects of spermicides on vaginal conditions, including genital ulcers; and the relative value of condoms, even under typical conditions, in preventing sexually transmitted diseases. For these reasons, we would currently counsel both women and men who practice high-risk sexual behaviors to use condoms as their first line of defense. If this is unacceptable, the female barriers become a fallback position to protect against bacterial sexually transmitted diseases.

Condoms

A guide to interpreting contraceptive efficacy studies.

Results of trials of various birth control methods and contraceptive products may provide misleading data and engender unrealistic expectations regarding efficacy. An analysis of published efficacy-trials reveals numerous fallacies in their design, performance, and reporting. Consequently, family planning clinicians find it virtually impossible to make valid comparisons among the methods or products. This article reviews the definitions and measures that have been used to assess contraceptive efficacy, describes and illustrates some of the flaws that confound interpretation and comparison of studies, and presents a set of recommendations for future studies. A summary table providing comparative failure rates for all methods of contraception is included.

Confounding Factors, Epidemiologic

Variant endothelial cells. Fibronectin as a transducer of signals for migration and neovascularisation.

A morphologic and growth control variant of bovine aortal endothelial cells has been isolated and shown to synthesise factor VIII antigen (McAuslan and Reilly '79). The variant also possesses the endothelial surface markers angiotensin converting enzyme and alpha 2-microglobulin. The normal cell synthesises fibronectin and deposits it underneath the cells; the variant also synthesises fibronectin. At least three times more fibronectin is distributed over the upper cell surface of variants. This correlates with the three-fold increased binding of the replication inhibitor Con A and suggests a role of fibronectin in endothelial cell growth control. When stimulated to migrate by CuII ions, the variant leaves deposits of fibronectin in its trail; in contrast, migrating normal cells do not, but they do redistribute their surface fibronectin. As revealed by scanning electron microscopy, variant cells are unusual in that they grow over or under cultured normal endothelial cells. It is proposed that during the process of neovascularisation, variant cells have a special function as lead cells that lay down fibronectin on which an endothelium can become established.

Animals

Reduced dose of Rh immunoglobulin following first trimester pregnancy termination.

The efficacy and safety of a 50-microgram dose of Rh immune globulin for prevention of Rh isosensitization following first trimester vacuum abortion are evaluated in this study. A total of 1027 women undergoing abortion at three outpatient facilities participated in the study; 755 (73.5%) completed follow-up serologic screening 6 months after termination of pregnancy. None showed serologic evidence of Rh sensitization at the time of followup. No serious adverse reactions to the drug were observed.

Abortion, Induced

The photodecomposition of tryptophan peptides.

Aqueous solutions of the four tryptophan peptides, Ala-Trp-Val, Val-Trp-Ala, Ala-Ala-Trp-Val and Ala-Gly-Trp-Leu, have been irradiated with the light of wavelength greater than 295 nm. The major changes were destruction of the tryptophan residue, liberation of ammonia and the formation of photoproducts of increased molecular weight. Up to 40% of Ala-Ala-Trp-Val and Ala-Gly-Trp-Leu were converted to products with molecular weights ranging from two to four times those of the original tetrapeptides. Most of the yellow material formed during irradiation in air was present in the high molecular weight fractions. Irradiation of Ala-Gly-[14C]Trp-Leu gave the following identifiable photoproducts: Ala-Gly-Asp-Leu, Ala-Gly-(N'formyl)Kyn-Leu, Ala-Gly-Oia-Leu, and ammonia, where Kyn means kynurenine and Oia, beta-(3-oxindolyl)alanine.

Amino Acid Sequence

Contraceptive failure in the United States: an update.

This report provides an update of the authors' previous estimates of first-year probabilities of contraceptive failure for all methods of contraception. Estimates are provided of failure during typical use (which includes both incorrect and inconsistent use) and during perfect use (correct use at every act of intercourse). The difference between these two probabilities provides a measure of how forgiving of imperfect use each method is. These revisions are prompted by recent studies that provide the first estimates of failure during perfect use for periodic abstinence and the cervical cap, by more complete evaluations of implants, and by the appearance of the Copper T 380A and disappearance of other IUDs from the US market. Also provided is a more complete explanation of how the previous estimate of the probability of becoming pregnant while relying solely on chance should be interpreted, and this estimate is revised slightly downward.

Clinical Trials as Topic