Percussion as a way of life.
Explore the source record for details and available documents.
Animal Rights↗
Biomedical subjects
R V Short
Publications and source records attributed to R V Short.
Male germ cell transplantation in rats: apparent synchronization of spermatogenesis between host and donor seminiferous epithelia.
Primordial germ cells (PGC) and gonocytes from male Sprague-Dawley rat fetuses and neonates were transplanted via the rete testis into the lumen of the seminiferous tubules of recipient adult Long Evans rats. The donor germ cells apparently differentiated into mini-tubules or irregular segments of seminiferous epithelium within the lumen of the host seminiferous tubules, and exhibited qualitatively normal spermatogenesis in 10 out of 16 recipients. The stage of spermatogenesis of the intraluminal epithelium was synchronized closely with that of the adjacent seminiferous tubule epithelium, suggesting that the spermatogenic cycle is regulated locally by the intraluminal microenvironment. Male germ cell transplantation provides an interesting new tool for investigating the control of spermatogenesis.
Animals↗
Monozygotic triplets in the mare.
Explore the source record for details and available documents.
Animals↗
Darwin, have I failed you?
Explore the source record for details and available documents.
Attitude of Health Personnel↗
Human reproduction in an evolutionary context.
Explore the source record for details and available documents.
Anthropology↗
Women's reproductive cancers in evolutionary context.
Reproductive experiences for women in today's affluent Western nations differ from those of women in hunting and gathering societies, who continue the ancestral human pattern. These differences parallel commonly accepted reproductive risk factors for cancers of the breast, endometrium and ovary. Nutritional practices, exercise requirements, and body composition are nonreproductive influences that have been proposed as additional factors affecting the incidence of women's cancers. In each case, these would further increase risk for women in industrialized countries relative to forager women. Lifestyles and reproductive patterns new from an evolutionary perspective may promote women's cancers. Calculations based on a theoretical model suggest that, to age 60, modern Western women have a breast cancer risk as much as 100 times that of preagricultural women.
Biological Evolution↗
What the breast does for the baby, and what the baby does for the breast.
Breastfeeding is nature's effective method of child-spacing, provided that feeding is exclusive and prolonged. Yet, its popularity has been limited in modern societies for a range of cultural, social and medical reasons. It is a matter of surprise and regret that no medical specialty has claimed overall 'ownership' of the physiology, function, pathology and management of this conspicuous organ, the female breast. The breast has major benefits for the baby in protecting against debilitating diarrhoea, necrotising enterocolitis and certain allergies, as well as providing highly specific nutritional requirements for the human neonate. It is less widely appreciated that, in addition to its major child-spacing benefits for the mother, breastfeeding also provides major protection against the development of breast cancer, up to 50% reduction in incidence in one study. Few other measures can approach this.
Breast Feeding↗
Contraceptives of the future in the light of HIV infection.
The AIDS and sexually transmissible disease pandemics have helped to focus the world's attention on the need for good protection against transmission of infections during sexual intercourse. Most of the highly effective modern contraceptives provide only limited protection against STD transmission, although recent progress with the development of loose-fitting plastic male condoms and new spermicides gives some hope. Urgent attention must continue to be given to contraceptives with STD protective qualities which are under the woman's control. Refinements of the female condom and vaginal sponges with new spermicides and microbicides may be a step in this direction.
Acquired Immunodeficiency Syndrome↗
Fertility control in laboratory rats and mice after feeding with the antigestagen RU486.
The intermittent use of an antigestagen could prove to be a very effective way of controlling the fertility of rats and mice in the wild. This concept was tested by giving paraffin wax blocks containing cereal grains and the antigestagen Mifepristone, RU486 (150 mg kg-1 block) to male and female laboratory rats and mice in a series of free-choice feeding experiments. There was no significant difference in the consumption of blocks with or without RU486, showing that it was completely palatable to rats and mice, and no aversion developed following refeeding. The average consumption of RU486 by rats was 11 mg kg-1 day-1; mice consumed 37 mg kg-1 day-1. All the females showed persistent oestrous vaginal smears throughout the treatment. When male and female rats and mice were given continuous access to treated paraffin blocks for 30 days, no conceptions occurred. At the end of this time, there was a significant increase in ovarian weight in the treated rats and mice, but no difference in testicular weight. Treated blocks were given to rats for 3 days every 21 days for a total of 115 days. Four dead litters were produced following the first antigestagen treatment on day 21, but no more litters were produced and no treated rats were pregnant when autopsied on day 115. Mice were initially treated for 3 days every 21 days, but some animals continued to produce live young on this schedule. The treatment period was therefore reduced to 3 days every 18 days and no more litters were produced and none of the treated females was pregnant at autopsy.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Fertility control in wild mice after feeding with RU486 or methyl testosterone.
Paraffin blocks containing either no steroid, 150 mg RU486 kg-1, 500 mg methyl testosterone kg-1 or 1500 mg methyl testosterone kg-1 were fed to wild mice (Mus musculus) in addition to the standard laboratory diet in four large (3 m x 3 m) outdoor pens for six months over the summer. The RU486 bait was provided for only 3 days every 18 or 21 days, whereas the methyl testosterone bait was available continuously. From a foundation stock of 20 mice (nine male, eleven female) in each pen, the population had increased to 253 (control), 72 (RU486), 249 (low methyl testosterone concentration) and 103 (high methyl testosterone concentration) at the end of six months, when 17%, 4%, 32% and 13% of the mature females were pregnant in the respective treatment groups. There was little evidence of an increase in the incidence of injuries in the androgen-treated animals. Daily estimation of water consumption in the pens proved to be a good non-invasive way of monitoring population growth during the course of the experiment. Intermittent feeding with a low concentration of RU486 appeared to be much more successful in inhibiting reproduction than continuous feeding with a high concentration of methyl testosterone, and it therefore offers a new method for controlling feral mouse populations.
Animals↗
Use of an oestrogen, androgen or gestagen as a potential chemosterilant for control of rat and mouse populations.
Three synthetic steroids were evaluated as potential chemosterilants for rodent control. Ethinyl oestradiol, methyl testosterone or Org 5933, a synthetic gestagen, were incorporated into paraffin blocks containing cereal grains and offered to laboratory rats and mice in addition to their standard laboratory diet. Ethinyl oestradiol (50 mg kg-1 paraffin block) was highly unpalatable to female rats, and the amount of steroid ingested was not sufficient to interfere with their oestrous cycles or inhibit ovulation. Methyl testosterone (5000 mg kg-1 paraffin block), although not as palatable as untreated blocks, was effective in inducing almost immediate infertility in female rats and mice at an ingested dose of about 35 micrograms g-1 body weight day-1. This infertility persisted throughout the duration of treatment, and lasted for several weeks after the cessation of treatment. Male rats became infertile after 3 months of treatment owing to suppression of spermatogenesis. Female rats developed a specific aversion to methyl testosterone when they were pregnant or lactating; it was therefore not possible to masculinize the brains of their female offspring. In mice, the androgen treatment induced high levels of aggression in the females so that they fought with males and with one another. One female died of her wounds. Org 5933 (4 mg kg-1 paraffin block) was highly palatable to female rats and mice, and at doses of about 420 ng g-1 body weight day-1 was effective in inhibiting ovulation in rats within 3 to 4 days after the start of treatment. This infertility persisted throughout the duration of treatment, and the animals conceived within 5 days of cessation of treatment. A dose of about 930 ng g-1 body weight day-1 was not completely effective in inhibiting ovulation in mice, but females that became pregnant during treatment gave birth to dead young. When the gestagen was given to female rats and mice in the last few days of pregnancy, the duration of gestation was significantly prolonged, and most young were born dead; some of the females also died in labour. The gestagen did not appear to inhibit lactogenesis, since the few animals that gave birth to live young reared them normally for the first 5 days of life. These results show that either methyl testosterone or Org 5933 in paraffin blocks could perhaps be used as a chemosterilant for the control of rat and mouse populations.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Lactational infertility in family planning.
The contraceptive effect of breast-feeding is the single most important determinant of human population growth rates in traditional societies without access to modern forms of contraception; lactational amenorrhoea is Nature's contraceptive. Even today, breast-feeding still prevents more pregnancies than all modern forms of contraception in many developing countries. Afferent neural inputs from the nipple pass via the spinal cord to the hypothalamus, where they cause a local release of beta endorphin. This acts to depress GnRH secretion, thereby inhibiting pituitary gonadotrophin secretion, ovarian follicular development, ovulation and menstruation. The hypothalamic beta endorphin release also inhibits dopamine production, resulting in increased pituitary prolactin secretion. The higher the suckling frequency, the more beta endorphin that is released and hence the longer the duration of lactational amenorrhoea. Lactational amenorrhoea can be relied up to give over 98% contraceptive protection to breast-feeding women in the first 6 months postpartum, regardless of their nutritional status or the time of first supplement introduction to the baby. This is because the first postpartum menstruation usually precedes the first ovulation during these early months. Once menstruation has resumed, lactation's contraceptive effect can no longer be relied upon, even though the woman continues to breast-feed. In breast-feeding women whose amenorrhoea extends beyond 6 months, there is an increasing tendency for the first ovulation to precede the first menstruation, thereby decreasing the reliability of lactational amenorrhoea as a contraceptive. Nevertheless, many women who continue to breast-feed may still have up to 1-2 years of good contraceptive protection from prolonged lactational amenorrhoea.(ABSTRACT TRUNCATED AT 250 WORDS)
Amenorrhea↗
The control of rodent populations.
Explore the source record for details and available documents.
Animals↗
Steroid hormone content of the gonads of the tammar wallaby during sexual differentiation.
The gonads of the tammar wallaby, Macropus eugenii, are sexually indifferent at birth (Day 0) despite the fact that phenotypic sexual differentiation has already commenced as evidenced by the presence of a scrotum in males and mammary anlagen in females. The seminiferous cords of the testis first become clearly recognizable on Day 2 of pouch life, and ovarian differentiation is recognizable by Day 10. To monitor the endocrine development of the gonads during sexual differentiation of the urogenital tract, we measured the steroid hormone content in 92 pools of gonads from male and female tammar pouch young from the day of birth to 206 days of pouch life. Progesterone, estradiol, and dihydrotestosterone concentrations were low (less than 0.05 ng/mg protein) in both ovaries and testes at all stages examined, and testosterone concentrations were uniformly low in ovaries. Testosterone concentrations in testes were low on Days 0-4, averaging about 0.2 ng/mg protein; they rose by Days 5-10 to an average of 0.9 ng/mg protein, remained elevated until about Day 40, and thereafter fell to values similar to those in the ovaries. The phallus and urogenital sinus were able to convert testosterone to dihydrotestosterone from the earliest stages examined (Days 10 and 11). Thus in the tammar wallaby, as in eutherian mammals, testosterone is the androgen secreted by the developing testis, and dihydrotestosterone is formed in certain androgen target tissues.(ABSTRACT TRUNCATED AT 250 WORDS)
Age Factors↗
Contraceptive effects of extended lactational amenorrhoea: beyond the Bellagio Consensus.
We have recorded the duration of lactational anovulation and amenorrhoea in a well-nourished group of Australian women who breastfed their babies throughout the study. The data enabled us to compare the theoretical cumulative probability of conception among breastfeeding women who had unprotected intercourse irrespective of their menstrual status with that of those who had unprotected intercourse only during lactational amenorrhoea. Breastfeeding alone is not an effective form of contraception, since all the women in our study resumed normal ovulation while still breastfeeding. However, among women who have unprotected intercourse only during lactational amenorrhoea but adopt other contraceptive measures when they resume menstruation, only 1.7% would have become pregnant during the first 6 months of amenorrhoea, only 7% after 12 months, and only 13% after 24 months. Thus for our women it would be possible to extend the Bellagio Consensus Conference guidelines which stated that lactational amenorrhoea can only be relied on as a contraceptive for the first 6 months post-partum in women who are fully or almost fully breastfeeding. The lactational amenorrhoea method can be relied on for excellent contraceptive protection in the first 6 months of breastfeeding, irrespective of when supplements are introduced into the baby's diet; for women who continue to breastfeed the method can also give good protection for up to 12 months post partum. Once menstruation has returned, other forms of contraception are essential to prevent pregnancy.
Amenorrhea↗
Mammary glands in male marsupials. 2. Development of teat primordia in Didelphis virginiana and Monodelphis domestica.
Young and adults of both sexes of two didelphid marsupials, Didelphis virginiana and Monodelphis domestica, were examined externally for evidence of mammary gland development. Female young possessed teat numbers typical of adult females (13-15 in D. virginiana; 11-13 in M. domestica). Male young showed variable teat numbers which were always low compared with females, with the majority possessing 2-4 in anterior positions. Teats were also present in adult males of both species, in similar numbers and locations to those of young males. There are no previous reports of the presence of teats in any adult male marsupials. No mammary primordia in males have been recorded at any stage of development in the most thoroughly studied Australian marsupials. Our findings strengthen the view that there is a dichotomy between the two marsupial lineages in the regulation of male mammary gland expression.
Aging↗