A review of the mechanisms and evidence for typical and atypical twinning.

The mechanisms responsible for twinning and disorders of twin gestations have been the subject of considerable interest by physicians and scientists, and cases of atypical twinning have called for a reexamination of the fundamental theories invoked to explain twin gestations. This article presents a review of the literature focusing on twinning and atypical twinning with an emphasis on the phenomena of chimeric twins, phenotypically discordant monozygotic twins, mirror-image twins, polar body twins, complete hydatidiform mole with a coexistent twin, vanishing twins, fetus papyraceus, fetus in fetu, superfetation, and superfecundation. The traditional models attributing monozygotic twinning to a fission event, and more recent models describing monozygotic twinning as a fusion event, are critically reviewed. Ethical restrictions on scientific experimentation with human embryos and the rarity of cases of atypical twinning have limited opportunities to elucidate the exact mechanisms by which these phenomena occur. Refinements in the modeling of early embryonic development in twin pregnancies may have significant clinical implications. The article includes a series of figures to illustrate the phenomena described.

Genital tract abnormalities among female sex workers who douche with lemon/lime juice in Nigeria.

Vaginal douche products have been associated with cervical cancer. We examined female sex workers (FSWs) in Nigeria who douche with lemon or lime juice and compared the findings with that of nonusers. We obtained Pap smears and performed colposcopy of the vulva, vagina and cervix. A total of 374 FSWs comprising 81 Lemon users (LUs) and 293 non lemon users (NLUs) were examined. Their mean age was 27.8 +/- 6.7 (range 16-63) years. At colposcopy, 17 (4.5%) had genital warts [LUs 5 (6.2%); NLUs 12 (4.1%); p=0.43], 61 (16.3%) had suspected squamous intraepithelial lesions (SILs) [LUs 17 (21.0%); NLUs 44 (15.0%); p=0.20] and 65 (17.4%) had other findings. Pap smear cytology showed that 87 (24.6%) had SILs [LUs 26 (33.3%); NLUs 61 (22.1%); p=0.03]. Lemon/lime use was associated with cervical dysplasia after controlling for HIV status (Adjusted OR=1.8; 95% CI, 1.0-3.0). Our data suggests an association between the practice of douching with citrus juice and cervical dysplasia.

Topical oestrogen keratinises the human foreskin and may help prevent HIV infection.

With the growing incidence of HIV, there is a desperate need to develop simple, cheap and effective new ways of preventing HIV infection. Male circumcision reduces the risk of infection by about 60%, probably because of the removal of the Langerhans cells which are abundant in the inner foreskin and are the primary route by which HIV enters the penis. Langerhans cells form a vital part of the body's natural defence against HIV and only cause infection when they are exposed to high levels of HIV virions. Rather than removing this natural defence mechanism by circumcision, it may be better to enhance it by thickening the layer of keratin overlying the Langerhans cells, thereby reducing the viral load to which they are exposed. We have investigated the ability of topically administered oestrogen to induce keratinization of the epithelium of the inner foreskin. Histochemically, the whole of the foreskin is richly supplied with oestrogen receptors. The epithelium of the inner foreskin, like the vagina, responds within 24 hours to the topical administration of oestriol by keratinization, and the response persists for at least 5 days after the cessation of the treatment. Oestriol, a cheap, readily available natural oestrogen metabolite, rapidly keratinizes the inner foreskin, the site of HIV entry into the penis. This thickening of the overlying protective layer of keratin should reduce the exposure of the underlying Langerhans cells to HIV virions. This simple treatment could become an adjunct or alternative to surgical circumcision for reducing the incidence of HIV infection in men.

Foetal age determination and development in elephants.

Elephants have the longest pregnancy of all mammals, with an average gestation of around 660 days, so their embryonic and foetal development have always been of special interest. Hitherto, it has only been possible to estimate foetal ages from theoretical calculations based on foetal mass. The recent development of sophisticated ultrasound procedures for elephants has now made it possible to monitor the growth and development of foetuses of known gestational age conceived in captivity from natural matings or artificial insemination. We have studied the early stages of pregnancy in 10 captive Asian and 9 African elephants by transrectal ultrasound. Measurements of foetal crown-rump lengths have provided the first accurate growth curves, which differ significantly from the previous theoretical estimates based on the cube root of foetal mass. We have used these to age 22 African elephant foetuses collected during culling operations. Pregnancy can be first recognized ultrasonographically by day 50, the presumptive yolk sac by about day 75 and the zonary placenta by about day 85. The trunk is first recognizable by days 85-90 and is distinct by day 104, while the first heartbeats are evident from around day 80. By combining ultrasonography and morphology, we have been able to produce the first reliable criteria for estimating gestational age and ontological development of Asian and African elephant foetuses during the first third of gestation.

Potential HIV-1 target cells in the human penis.

OBJECTIVES: To study the distribution of HIV-1 receptors and degree of keratinization in the human penis. DESIGN: Formalin-fixed penises were obtained from nine uncircumcised cadavers. Foreskins were obtained from 21 healthy adult men undergoing elective circumcision for social reasons. Uncircumcised penises were obtained within 24 h of death from eight men. All tissues were stained for keratin and HIV-1 receptors. METHODS: Penises from nine formalin fixed cadavers aged 64-80 years were obtained from the Department of Anatomy, University of Melbourne. Foreskins were obtained from 21 men aged 18-64 years following circumcision performed at either the Freemason's or Mercy Private Hospitals, Melbourne, Australia. Fresh penile necropsy specimens from eight uncircumcised men aged 23-63 years were obtained from the Victorian Institute of Forensic Medicine, Melbourne. The degree of keratinization was scored, and the distribution of HIV-1 susceptible cells was mapped in the glans penis, penile urethra, urethral meatus, frenulum and foreskin. RESULTS: Cells with HIV-1 receptors were present in all penile epithelia, but Langerhans' cells were most superficial in the inner foreskin and frenulum. The inner foreskin had a significantly thinner keratin layer (1.8 +/- 0.1 units), than the outer foreskin (3.3 +/- 0.1), or glans penis (3.3 +/- 0.2), P < 0.05. CONCLUSIONS: Superficial Langerhans' cells on the inner aspect of the foreskin and frenulum are poorly protected by keratin and thus could play an important role in primary male infection. These findings provide a possible anatomical explanation for the epidemiologically observed protective effect of male circumcision.

Sperm immobilizing properties of lemon juice.

The aim of this study was to evaluate the sperm-immobilizing properties of lemon juice to determine if they are consistent with its traditional contraceptive use. It was found that lemon juice supernatant (LJS) has high osmolality (550-60 mOsm) and low pH (2.2-2.6) and that addition of LJS to semen to give a final concentration of 20% v/v reduced the pH from around 8.4 to 4.1. This acidification was associated with irreversible cessation of all sperm movements within 1 minute. In conclusion, lemon juice should be further evaluated for acceptability, safety, and efficacy as a topical vaginal contraceptive agent.

Sexual differentiation in three unconventional mammals: spotted hyenas, elephants and tammar wallabies.

The present review explores sexual differentiation in three non-conventional species: the spotted hyena, the elephant and the tammar wallaby, selected because of the natural challenges they present for contemporary understanding of sexual differentiation. According to the prevailing view of mammalian sexual differentiation, originally proposed by Alfred Jost, secretion of androgen and anti-Mullerian hormone (AMH) by the fetal testes during critical stages of development accounts for the full range of sexually dimorphic urogenital traits observed at birth. Jost's concept was subsequently expanded to encompass sexual differentiation of the brain and behavior. Although the central focus of this review involves urogenital development, we assume that the novel mechanisms described in this article have potentially significant implications for sexual differentiation of brain and behavior, a transposition with precedent in the history of this field. Contrary to the "specific" requirements of Jost's formulation, female spotted hyenas and elephants initially develop male-type external genitalia prior to gonadal differentiation. In addition, the administration of anti-androgens to pregnant female spotted hyenas does not prevent the formation of a scrotum, pseudoscrotum, penis or penile clitoris in the offspring of treated females, although it is not yet clear whether the creation of masculine genitalia involves other steroids or whether there is a genetic mechanism bypassing a hormonal mediator. Wallabies, where sexual differentiation occurs in the pouch after birth, provide the most conclusive evidence for direct genetic control of sexual dimorphism, with the scrotum developing only in males and the pouch and mammary glands only in females, before differentiation of the gonads. The development of the pouch and mammary gland in females and the scrotum in males is controlled by genes on the X chromosome. In keeping with the "expanded" version of Jost's formulation, secretion of androgens by the fetal testes provides the best current account of a broad array of sex differences in reproductive morphology and endocrinology of the spotted hyena, and androgens are essential for development of the prostate and penis of the wallaby. But the essential circulating androgen in the male wallaby is 5alpha androstanediol, locally converted in target tissues to DHT, while in the pregnant female hyena, androstenedione, secreted by the maternal ovary, is converted by the placenta to testosterone (and estradiol) and transferred to the developing fetus. Testicular testosterone certainly seems to be responsible for the behavioral phenomenon of musth in male elephants. Both spotted hyenas and elephants display matrilineal social organization, and, in both species, female genital morphology requires feminine cooperation for successful copulation. We conclude that not all aspects of sexual differentiation have been delegated to testicular hormones in these mammals. In addition, we suggest that research on urogenital development in these non-traditional species directs attention to processes that may well be operating during the sexual differentiation of morphology and behavior in more common laboratory mammals, albeit in less dramatic fashion.

Use of lemon or lime juice douches in women in Jos, Nigeria.

OBJECTIVE: To describe the use of lemon/lime juice for douching by female sex workers (FSWs) and family planning clients (FPCs) in Jos, Nigeria. METHOD: A total of 300 sexually active women comprising 200 FSWs and 100 FPCs were interviewed in June 2004 to determine the mode and rationale for the use of lemon/lime juice for sex. RESULT: Majority of the women 167/300 (55.7%, 95% CI = 50-61%) i.e. 163/200 (81.5%, 95% CI = 75-87%) FSWs, 4/100 (4%, 95% CI = 1-10%) FPCs used vaginal lemon/lime douches. Lime juice was used by 105/167 (62.8%, 95% CI = 55-70%), lemon juice by 30/167 (18%, 95% CI = 12-25%) or a mixture by 18/167 (10.8%, 95% CI = 7-25%). The juice was used either neat 44/167 (26%, 95% CI = 20-34%) or diluted in water 75/167 (45%, 95% CI = 37-53%) either before or after sex. Nineteen per cent (32/167) found the juice painful. Over half of the women believed that it protected them from pregnancy and/or sexually transmitted infections; they did not know their HIV status. Eighty-six per cent would recommend it to others, and 71% would be willing to take part in a study to evaluate its safety and efficacy. CONCLUSION: Lemon and lime juice are widely used for douches among women at high risk of HIV transmission. There is an urgent need to determine whether or not this practice promotes or prevents HIV infection.

Fetal lung development in the elephant reflects the adaptations required for snorkeling in adult life.

The adult elephant is unique among mammals in that the pleural membranes are thickened and the pleural cavity is obliterated by connective tissue. It has been suggested that this peculiar anatomy developed because the animal can snorkel at depth, and this behavior subjects the microvessels in the parietal pleura to a very large transmural pressure. To investigate the development of the parietal pleura, the thickness of the endothoracic fascia (ET) was measured in four fetal African elephants of approximate gestational age 111-130 days, and the appearances were compared with those in human, rabbit, rat and mouse fetuses of approximately the same stage of lung organogenesis. The mean thicknesses of ET in the elephant, human, rabbit, rat and mouse were 403, 53, 29, 27 and 37 microm, respectively. This very early development of a thick parietal pleura in the elephant fetus is consistent with the hypothesis of a long history of snorkeling in the elephant's putative aquatic ancestors.

Successful intra- and interspecific male germ cell transplantation in the rat.

The lumen of the seminiferous tubules has hitherto been regarded as an immunologically privileged site. We report here the birth of young following transplantation of stem spermatogonia from Long-Evans rats to the seminiferous tubules of Sprague-Dawley rats after treatment with the immunosuppressive agent cyclosporin. Follicle-stimulating hormone was also given to stimulate Sertoli cell proliferation, and testosterone to stimulate the recovery of spermatogenesis. Donor germ cells underwent normal spermatogenesis, and progeny were repeatedly produced from the donor germ cells as demonstrated by microsatellite paternity analysis. In addition, donor germ cells from the cryptorchid testes of LacZ mice were also able to colonize the seminiferous tubules of Sprague-Dawley rats using this protocol. Morphologically normal rat and mouse spermatozoa were present in the epididymis and vas deferens of the recipient rats. This highlights the potential for transplantation of male germ cells between different species.

Mammalian mitogenomic relationships and the root of the eutherian tree.

The strict orthology of mitochondrial (mt) coding sequences has promoted their use in phylogenetic analyses at different levels. Here we present the results of a mitogenomic study (i.e., analysis based on the set of protein-coding genes from complete mt genomes) of 60 mammalian species. This number includes 11 new mt genomes. The sampling comprises all but one of the traditional eutherian orders. The previously unrepresented order Dermoptera (flying lemurs) fell within Primates as the sister group of Anthropoidea, making Primates paraphyletic. This relationship was strongly supported. Lipotyphla ("insectivores") split into three distinct lineages: Erinaceomorpha, Tenrecomorpha, and Soricomorpha. Erinaceomorpha was the basal eutherian lineage. Sirenia (dugong) and Macroscelidea (elephant shrew) fell within the African clade. Pholidota (pangolin) joined the Cetferungulata as the sister group of Carnivora. The analyses identified monophyletic Pinnipedia with Otariidae (sea lions, fur seals) and Odobenidae (walruses) as sister groups to the exclusion of Phocidae (true seals).