Testosterone influences basal metabolic rate in male house sparrows: a new cost of dominance signalling?

Sexually selected signals of individual dominance have profound effects on access to resources, mate choice and gene flow. However, why such signals should honestly reflect individual quality is poorly understood. Many such signals are known to develop under the influence of testosterone. We conducted an experiment in male house sparrows in which testosterone was manipulated independently during two periods: before the onset of the breeding season and prior to the autumn moult. We then measured the effects of these manipulations on basal metabolic rate and on the size of the chest bib, a sexually selected signal. The results demonstrate that testosterone simultaneously affects both signal development and basal metabolic rate in the house sparrow (Passer domesticus). This evidence, therefore, supports a novel conclusion: that testosterone-dependent signals act as honest indicators of male quality possibly because only high-quality individuals can sustain the energetic costs associated with signal development.

Transcutaneous male sterilization.

PIP: This report reviews and summarizes the results of current animal and human research studies for each of the 3 approaches to transcutaneous sterilization: intratesticular injection of chemical agents to affect spermatogenesis; intraepididymal injection of chemical agents to affect sperm transport; and obstruction of the vas lumen by the intravasal injection of chemical (sclerosing) agents or by electrocoagulation of the vas lumen. Wiebe and Barr evaluated the effects of the direct injection of aqueous 1, 2, 3-trihydroxypropane (THP; glycerol), a normal component of living cells, into the testes of Sprague-Dawley rats. Spermatogenesis was inhibited by a direct and local action of THP on the seminiferous tubules. The only other intratesticular method that has been investigated is the use of ultrasonic energy. Although the injection of sclerosing agents directly into the epididymis is technically simpler than injection into the vas lumen, the intraepididymal approach to nonsurgical sterilization has been evaluated in only 3 studies. The advantages of intraepididymal over intravasal injections are that the cauda epididymis is easily palpated and intraluminal placement of the needle in the epididymis is not necessary. The appeal of the intraepididymal approach to transcutaneous sterilization is that it is easier to inject a chemical into the epididymis than into the vas lumen. Limitated evaluations of the intraepididymal injection of chemical agents has shown this to be an unsatisfactory approach to male sterilization. Whether improved results can be obtained with other chemical agents remains to be evaluated. Numerous chemical agents have been injected into the vasa of rats, dogs, and rabbits to evaluate their effects in producing vas occulsion. A table lists the agents that have been evaluated. Only 2 chemical agents are known to have been tested in man: 3.6% formaldehyde in 90% ethanol and 4% formaldehyde in 90% ethanol and a carbolic acid, n-butyl alpha cyanoacrylate mixture. The mode of action of all of the sclerosing agents tested is thought to be similar: they produce local necrosis and fibrosis and vasal closure through scarring. A main objective in choosing a chemical agent for use in human sterilization procedures is to select one that has minimal toxic effects and will produce a minimal amount of damage if injected onto structures other than the vas. The transcutaneous intravasal sterilization procedure developed by the Chinese and which has been widely and successfully used since 1972 is described. To further advance the electrocoagulation procedure developed by Schmidt in 1966, bipolar electrodes have been developed. Black, at the Marie Stopes Clinic in the UK, is currently investigating a transcutaneous electrocoagulation procedure. Black believes that improvement of the electrodes and some changes in the technique of performing the electrocoagulation will result in an effective procedure.^ieng

Advances in sterilization equipment.

From the array of sterilization procedures that are safe, simple and effective, the service provider must select procedures that fit his or her logistical criteria, which include the cost and maintenance of equipment, availability of supplies, and training of the requisite personnel. In this paper, these criteria are discussed for each of the various sterilization procedures. Information about female sterilization equipment for conventional postpartum laparotomy, minilaparotomy, colpotomy, laparoscopy, and culdoscopy is presented, together with facts about the related tubal occlusion techniques. The standard ligation techniques for male sterilization are compared with the newer electrocoagulation and thermocoagulation methods. A variety of methods for both female and male sterilization that are in the research stage are also mentioned. It is concluded that, from a programmatic point of view, vasectomy and postpartum ligation via laparotomy are the optimal sterilization procedures. For women who have not recently been pregnant, minilaparotomy with a standard tubal ligation technique is recommended, except in large teaching hospitals where laparoscopy can be performed efficiently.

Workshop on present and future IUDs.

PIP: The purpose of the workshop was to review current and experimental IUDs as to effectiveness, complications, and clinical problems. The IUD is not for every woman and has had some failures. All types of IUDs have been associated with complications and side effects. Concerning the status of experimental IUDs, no inert devices have yet been demonstrated to have significant advantages over others already available. The T-Cu-200 and the 7-Cu-200 seem as good as any others, for example . Nor have drug-releasing IUDs yet proved better than other available IUDs. All prospective IUD users should be informed that the IUD is not 100% effective and has potential complications and side effects. Moreover, it is recommended that the International Federation of Fertility Societies establish a committee to define appropriate terminology, advise which IUDs warrant evaluation, delineate guidelines regarding IUD research, and promote pertinent IUD research.^ieng

Male sterilization in El Salvador: A preliminary report.

The expectation that male sterilization would not be an acceptable method of fertility control to the Latin American male has not been upheld in the initial phases of male sterilization programs in Colombia, Costa Rica, Guatemala, and El Salvador. On the contrary, in all of these programs and also at the Asociación Demográfica Salvadoreña, a free-standing, non-profit family planning clinic in San Salvador, the initial success has been impressive, with 180 men accepting sterilization during the first two years (February, 1972 to February, 1974). All sterilizations were performed by excising a 10-15 mm segment of each vas and ligating each vas end. Procedures were performed on an outpatient basis using a local anesthetic. Follow-up examinations were conducted at one week and three months after the procedure. Although complications were reported by 24.0% of the subjects at the one-week follow-up, the complications were minor: most were scrotal infections not requiring antibiotic therapy. Rates of complications were low for subjects returning for a three-month examination and semen test. Only one subject had a positive semen test.