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PubMed1977

[Patterns in the cellular organization of ovule growth in the pine, Pinus silvestris L. II. Growth processes in nucellus and integument].

The dynamics of growth processes was studied in the integument and nucellus of Pinus silvestris during the year of fertilization. The growth of two parts of the nucellus and integument under study is described by an S-shaped curve but the dynamics of growth processes and the ratio of cell reproduction and elongation differ in each tissue. The growth of micropylar part of the nucellus and integument proceeds, mainly at the expense of cell proliferation. At the first stages of growth the cell size remains constant, then during a short period the reproduction and elongation of cells occur simultaneously, and after the fertilization the growth proceeds at the expense of cell elongation only, since the cell division arrests completely. In the part of nucellus concrescent with the integument, the mitotic activity disappears still prior to fertilization and the growth proceeds, mainly, at the expense of cell elongation. Differences in the cell size are observed both between tissues and between different regions of the same tissue. The larges nuclei are situated in the micropylar part of nucellus. The nuclear size suffers insignificant changes during the growth of the tissues under study.

Growth↗
PubMed1987

Annual cycle of liveweight and reproductive changes of farmed male fallow deer (Dama dama) and the effect of daily oral administration of melatonin in summer on the attainment of seasonal fertility.

Entire bucks (N = 7) exhibited pronounced liveweight gains over spring and summer months (October-February), to reach a peak mean weight of 59.8 kg, and rapid liveweight losses over the rutting period (April-May) with a minimum mean liveweight of 54.2 kg. Mean neck girth and serum testosterone levels increased during late summer (January-March) and peaked at 387 mm and 12 ng/ml respectively immediately before the onset of the rut (April). Thereafter both measures declined during winter and spring months (June-December). Bucks castrated prepubertally (N = 11) exhibited similar but less pronounced changes in mean liveweight and neck girth, in the absence of any change in testosterone secretion. Peak mean testicular diameter of entire bucks (39 mm) occurred immediately before the rut and was followed by testicular regression over winter and spring months (June-November), such that the testes attained their minimum mean size of 18 mm diameter in early summer (November). Motile spermatozoa were absent from ejaculates collected in summer (November 1983, 1984; January 1984). However, ejaculates collected pre-rut (late March), immediately post-rut (June) and in early spring (September) contained successively increasing numbers of motile spermatozoa. A further 14 polled, entire bucks were given orally 5 mg (N = 7; Group A) or 20 mg (N = 7; Group B) melatonin at 15:30 h daily from 1 December 1983 to 14 January 1984 (45 days). Seven control bucks (Group C) received vehicle ration only. The measurements taken for bucks in Groups A and B were not significantly different (P greater than 0.1) on any sampling date and the data for these 2 groups were pooled. Mean serum testosterone concentrations and mean ejaculate volume were not significantly different between melatonin-treated and control bucks on any sampling date, although other measures exhibited significant differences (P less than 0.05) at various treatment or post-treatment dates: melatonin-treated bucks showed a transiently greater increase in neck muscle development during and immediately after treatment, a slight retardation of liveweight gain between 45 and 75 days after treatment, an earlier peak in maximum mean testicular diameter and an earlier onset of sperm presence in ejaculates.

Animals↗
PubMed1999

Impact of market value on human mate choice decisions.

Mate choice strategies are a process of negotiation in which individuals make bids that are constrained by their status in the market place. Humans provide an unusual perspective on this because we can measure their explicitly expressed preferences before they are forced to make any choices. We use advertisements placed in newspaper personal columns to examine, first, the extent to which evolutionary considerations affect the level of competition (or market value) during the reproductively active period of people's lives and, second, the extent to which market value influences individual's willingness to make strong demands of prospective mates. We show that female market value is determined principally by women's fecundity (and, to a lesser extent, reproductive value), while male market value is determined by men's earning potential and the risk of future pairbond termination (the conjoint probability that the male will either die or divorce his partner during the next 20 years). We then show that these selection preferences strongly influence the levels of demands that men and women make of prospective partners (although older males tend to overestimate their market value).

Adult↗
PubMed1990

The contraceptive needs of midlife women.

For those women who have not been contraceptively sterilized, midlife is a period of waning fertility. However, the occurrence of anovulatory menstrual cycles is unpredictable. Contraceptive methods also become increasingly contraindicated, both medically and physiologically. This article reviews the physiology of waning fertility and midlife contraceptive options, and discusses implications for helping women meet their contraceptive needs throughout the perimenopausal period.

Adult↗
PubMedDate not supplied

Reproductive and developmental toxicity of natural and depleted uranium: a review.

Although the biokinetics, metabolism, and chemical toxicity of uranium are well known, until recently little attention was paid to the potential toxic effects of uranium on reproduction and development in mammals. In recent years, it has been shown that uranium is a developmental toxicant when given orally or subcutaneously (SC) to mice. Decreased fertility, embryo/fetal toxicity including teratogenicity, and reduced growth of the offspring have been observed following uranium exposure at different gestation periods. The reproductive toxicity, maternal toxicity, embryo/fetal toxicity, and postnatal effects of uranium, as well as the prevention by chelating agents of uranium-induced maternal and developmental toxicity are reviewed here. Data on the toxic effects of depleted uranium on reproduction and development are also reviewed.

Abnormalities, Drug-Induced↗
PubMed1994

Effect of exogenous prostaglandin F2 alpha in clinically normal postparturient dairy cows with a palpable corpus luteum.

In 228 clinically normal cows with a palpable corpus luteum 20 to 40 days after parturition and a mean 305-day mature equivalent milk production of 8,970 kg, prostaglandin F2 alpha was administered in a randomized, controlled clinical trial to determine whether such treatment enhanced their subsequent reproductive performance. Although the treatment reduced median time to first breeding by 4.5 days (P = 0.0025) from 57.0 days, median time to conception was not significantly different between the treatment and nontreated control group (87.0 vs 88.5 days) and conception rate by 110 days after parturition was not significantly different (64.7 vs 69.6%). Use of prostaglandin was associated with a significant (P = 0.0459) decrease in conception rate at first breeding from 42.0 to 29.3%. This study suggested that prostaglandin treatment of cows with a normal reproductive tract and a palpable corpus luteum at a median of 25 days after parturition does not enhance their reproductive performance and thus is not cost-effective.

Animals↗
PubMed2000

Fitness, reproduction and longevity among European aristocratic and rural Finnish families in the 1700s and 1800s.

The life histories of two socio-economically different groups of humans comprising birth cohorts from the 1700s and 1800s were investigated. It was discovered that fertility selection was greater among European aristocrats and mortality selection greater among rural Finns. The life history of the rural Finns involved shorter female life spans, a considerably longer period of reproduction, higher juvenile mortality, a greater total production of offspring and slightly higher individual fitness. In a comparison of parental cohorts, it was discovered that longevity and progeny survival improved significantly from the 1700s to the 1800s. Out of the three factors investigated, longevity was found to influence reproduction and fitness more than socio-economic group or birth cohort. The reproductive efficacy and fitness of women increased along with their life span. However, reproductive success and fitness were lower among women with the longest life span (over 80 years). Among men, reproductive success improved consistently along with the increase in longevity. When birth intervals were examined, it was discovered that the sex of previous offspring did not influence the interval between births.

Adult↗
PubMed1983

Influence of photoperiod, nutrition and water availability on reproduction of male California voles (Microtus californicus).

Male California voles were maintained in long (14L:10D) or short photoperiods (10L:14D) for 10 weeks and fed a standard diet of rabbit chow and water ad libitum. One additional group in each photoperiod received the standard diet plus supplements of spinach 3 times weekly. A fifth group was housed in 14L:10D and fed the standard diet, but for 10 weeks water availability was restricted to several hours each morning. Testes and seminal vesicles were heaviest in long-day voles fed spinach supplements and lightest in short-day voles fed only the standard diet; the latter animals manifested reduced testicular spermatogenesis. Testicular weights were also depressed in voles with restricted access to water. It is suggested that photoperiods that simulate those of winter induce regression of the reproductive organs of male California voles but the availability of green vegetation counteracts the inhibitory effects of short daylengths.

Animals↗
PubMed2004

Prevalence of induced abortion in a reproductive lifetime.

The period total first abortion rate (TFAR) has been used to estimate the proportion of women who will experience an induced abortion in their reproductive lifetime. It is a hypothetical measure as age-specific rates currently existing will change with time. Instead, a cohort TFAR has been calculated for women born around 1955 using legal-abortion reports in South Australia to calculate first abortion rates for each year of age from 15 years to 44 years for 1971-2000, respectively, and summing these. Yearly fertility rates were also calculated for this cohort to further describe their reproductive experience. Yearly first abortion rates were also calculated for later cohorts born in 1960-1980. The 1955 cohort TFAR was 288.1 per 1,000 women aged 15-44 years. Cumulative first abortion rates at specific ages were higher for subsequent cohorts (e.g., 309.6 per 1,000 at age 40 years for the 1960 cohort). Thus, about 29% of South Australian women born around 1955 and exposed to legal abortion throughout their reproductive lifetime experienced an induced abortion. This proportion would be higher for later cohorts of women born in 1960-1980 (e.g., at least 31% for those born in 1960).

Abortion, Induced↗
PubMed1993

The relationship of plasma thyroid hormone and prolactin concentrations to egg laying, incubation behavior, and molting by female turkeys exposed to a one-year natural daylength cycle.

To determine relationships to egg laying, incubation behavior and molting, plasma thyroxine (T4), triiodothyronine (T3), and prolactin levels of 20 female domestic turkeys were determined throughout a one-year cycle of natural daylengths. Endocrine changes were analyzed relative to periods of reproductive and molting cycles. Data were also analyzed relative to termination of lay after division into two groups based on the presence (I, n = 7) or absence (NI, n = 13) of incubation behavior. Plasma T4 levels of the flock increased to a peak and subsequently decreased during the onset of lay period from February to April. Plasma T4 generally increased throughout the decline of lay period from April to July and molting period from July to October, and then reached greatest levels at the end of the molting period. Plasma T3 reached a peak early in the onset of lay and decreased rapidly during the remainder of that period. Plasma T3 remained depressed during the decline of lay, increased throughout molting, and attained greatest levels as molt was completed. Prolactin was low throughout the prelay period and sharply increased midway through the onset of lay. Prolactin increased to a marked peak during the decline of lay, and then rapidly decreased as egg laying was terminated. Relative to NI birds, egg laying was terminated earlier and prolactin levels were markedly greater during and following the termination of lay in I birds. Plasma T4 and T3 were generally lower in I birds during the molting period which followed the termination of lay and their molt was delayed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Reproductive ecology of the blue crab, Callinectes danae Smith, 1869 in the Conceição Lagoon system, Santa Catarina Isle, Brazil.

Abundance of ovigerous females, size of the first gonadal maturation and the possible migration, route of the blue crab Callinectes danae from the Conceição Lagoon system, Santa Catarina Isle, Brazil, are described. This lagoon is connected with the coastal area through a canal. A total of 1,124 crabs was caught during a 19 month sampling period. The reproduction and recruitment of juveniles occurred all year-round, with two peaks of abundance (February and September), correlated with the presence of ovigerous females (June and January). The mean carapace width at which the crabs attained gonadal maturity for the first time was 9.4 cm in males and 8.4 cm in females. The Conceição Lagoon is a growth, reproduction, and spawning area for the species. However, egg eclosion occurs outside the lagoon following migration of ovigerous females to the open sea. After hatching the eggs, some females return to the lagoon, but males stay there for most of their life cycle.

Animals↗
PubMedDate not supplied

Reproductive responsiveness to short photoperiod develops postnatally in male golden hamsters.

The development of the reproductive response to short photoperiod in golden hamsters was examined by monitoring testis size in hamsters that were either: raised on 14L:10D from birth; raised on 6L:18D from birth; or born on 14L:10D and transferred to 6L:18D at either 1, 2, 3, 4, 5, 6, 7, 9, or 12 weeks of age. Testis growth occurred between 3 and 7 weeks of age at similar rates in all groups. Testicular regression occurred in all groups exposed to short days; the time of regression depended on the age of the animals when they were first transferred to 6L:18D. Testicular regression began at about 10 weeks of age in all groups transferred to 6L:18D between birth and 5 weeks of age. In contrast, regression began at 11.2, 13.3, 15.6, and 18.2 weeks of age in hamsters transferred to 6L:18D at 6, 7, 9, and 12 weeks of age, respectively. These results suggest that the reproductive system of male hamsters is refractory to the inhibitory effects of short days on reproductive function until 5 to 6 weeks of age. Thereafter, exposure to short days initiates testicular regression in hamsters within 5 to 7 weeks.

Aging↗
PubMedDate not supplied

Reproductive adaptations to a large-brained fetus open a vulnerability to anovulation similar to polycystic ovary syndrome.

During the ovarian or menstrual cycle, prior to ovulation, many female primates exhibit a relatively prolonged follicular phase and terminate the postovulatory luteal phase with menstrual bleeding. The prolonged follicular phase is a trait that distinguishes primate from nonprimate species. It enables extended estrogen-induced proliferation and growth of the uterine endometrium prior to progesterone-induced maturation during the luteal phase to accommodate a potential pregnancy with a rapidly invading placenta. Progressive development of both an extended duration of estrogen-induced, preimplantation endometrial proliferation and a rapidly invading placenta across the Primate order may well have been necessary to accommodate differentiation and growth of an increasingly large fetal brain. Prolongation of the follicular phase in primates has also led to the isolation of the final stages of follicle selection (growth deviation of the dominant follicle from its contemporaries) solely within the follicular phase and thus outside the protection of luteal phase progesterone inhibition of pituitary luteinizing hormone (LH) secretion. Such primate reproductive characteristics put the latter stages of ovarian follicle selection at risk of exposure to excessive pituitary secretion of LH. Excessive secretion of LH during follicle selection could result not only in impaired follicle development, excessive ovarian androgen secretion, and ovulation failure, but also in excessive estrogenic stimulation of the uterine endometrium without intervening menstrual periods. Such reproductive abnormalities are all found in a single, prevalent infertility syndrome afflicting women in their reproductive years: polycystic ovary syndrome (PCOS). We propose that successful female reproductive adaptations to accommodate the growth demands of large-brained primate fetuses have facilitated a particular vulnerability of higher primates to hypergonadotropic disruption of ovulatory function, as found in PCOS.

Adaptation, Biological↗
PubMed2007

Growing out of a caste--reproduction and the making of the queen mole-rat.

Naked mole-rats have a eusocial colony structure consisting of non-reproductive workers and a reproductively active caste where a single, dominant queen and 1-3 males produce all of the offspring. Well-established queens have elongated bodies that characterize their caste. Worker females retain the ability to transform into queens, however the trigger and time course for this physical transformation remain a mystery. Here, we show a direct link between periods of pregnancy and vertebral lengthening in nascent queens. Adult female mole-rats were paired with a male and radiographed weekly for two and a half years to track the growth of the lumbar vertebrae as the mole-rats became sexually mature and experienced pregnancies. The lumbar vertebrae of breeding females grew at an increased rate during each pregnancy but growth rates returned to normal between pregnancies and during extended periods without reproduction. The rate of lumbar lengthening was reduced to normal rates in older, established queens experiencing pregnancies. Our results imply that the length of a new queen mole-rat is proportional to the number of pregnancies experienced and suggest that hormones related to pregnancy may play the critical role in bone growth associated with caste transformation.

Age Factors↗