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At least 1,171 records · Page 65Linked to original sources
PubMed2004

Environmental anti-androgens and male reproductive health: focus on phthalates and testicular dysgenesis syndrome.

The amount of research into endocrine disruption has exploded over the past decade and a re-evaluation of the state of research in this area is timely. There are debates about whether human male reproductive health is really declining and whether endocrine disrupting chemicals play any role in the perceived decline. Most data currently conclude that there are wide geographical variations in semen quality and in the incidence of testicular cancer, cryptorchidism and hypospadias. This review aims to give a brief overview of the issues surrounding the perceived decline in human male reproductive health and the importance of the hormonal environment for the development of the testis and reproductive tract. The consequences for the male reproductive tract of abnormal androgen levels or action are discussed with reference to environmental anti-androgenic compounds. The in vivo data on several anti-androgenic compounds that have been administered to pregnant rodents during the period of male reproductive tract development are assessed with attention to the effects on the male offspring. Finally, the data on in utero phthalate administration are discussed in detail to illustrate the similarities between the effects of some phthalate esters and the human male reproductive tract disorders which comprise testicular dysgenesis syndrome (TDS).

Androgen Antagonists↗
PubMed1994

Prolactin injection, a new contraceptive method: experimental study.

"Prolactin injection" is presented as a new contraceptive method. The method was tested in dogs. The dogs in the test group were injected with prolactin (PRL) in a dose of 600 micrograms/kg of body weight weekly for 6 months. During this period, the testicles, semen, reproductive hormones, renal function, and serum sodium and potassium were examined periodically. Testicular biopsy was obtained after 3 and 6 months of PRL injection. These investigations were repeated during the 6 months following withdrawal of the drug. Sperm count decreased to azoospermia in 3 months after PRL administration with decrease of sperm motility and increase of abnormal forms. Testicular biopsy showed degenerated seminiferous tubules. Reproductive hormones, renal function, and serum sodium and potassium revealed insignificant change (P > 0.05). Dog mating during the period of PRL administration induced no pregnancy. After 3 months of drug withdrawal, the sperm count normalized and dog mating produced pregnancy; offsprings showed no anomalies. The study demonstrates that PRL administration has the potential to be developed as a reversible male contraceptive.

Analysis of Variance↗
PubMed1986

Corticosterone-binding proteins and behavioral effects of high plasma levels of corticosterone during the breeding period in the pied flycatcher.

In the pied flycatcher there exists an anomaly in the relationship between cortical histology and plasma levels of corticosterone during the breeding period. In an attempt to study this anomaly, binding capacity and binding affinity of plasma corticosterone-binding proteins (CBP) were studied in free-living pied flycatchers during the early and late parts of the breeding period. Binding capacity of CBP showed a significant decrease with the progress of the breeding season in both males and females. During the early parts of the breeding season binding capacity was significantly higher in males than in females. No difference between sexes was observed during the nestling period. In males there also was a seasonal decrease in the binding affinity of CBP. The results show that there is a good relationship between periods with high plasma levels of corticosterone and its binding capacity in the blood. A second study showed that an experimentally increased plasma level of corticosterone during the nestling period drastically reduced reproductive success. Parents given silastic implants containing corticosterone fed their nestlings less frequently and produced significantly fewer fledglings than did controls. Unlike the control birds, the body weight of the corticosterone-implanted birds did not decrease during the nestling period. Birds given corticosterone implants in which one small hole had been punched, in order to facilitate diffusion of corticosterone, all abandoned their territories and, consequently, these parents produced no fledglings. Thus, the results show that an elevation of plasma levels of corticosterone in adult pied flycatchers during the nestling period affects parental as well as territorial behavior.

Animals↗
PubMed2005

Fertility signaling--the proximate mechanism of worker policing in a clonal ant.

In eusocial insects, the ability to regulate reproduction relies on cues that signal the presence of fertile individuals. We investigated the variation of cuticular hydrocarbons (CHCs) with reproductive status in Platythyrea punctata, an ant, in which all workers are capable of producing daughters from unfertilized eggs (thelytoky). Who reproduces is determined through dominance and worker policing. New reproductives, which developed their ovaries after separation from an old reproductive for a short period of time, were attacked by nonreproductives upon reintroduction into their colony. In contrast, aggression against new reproductives with fully developed ovaries, which had been separated over a longer period, was initiated by fights between old and new reproductives. CHC profiles varied with ovarian development. New reproductives were only attacked when they expressed a CHC profile similar to old reproductives, but not when it was similar to that of nonreproductives. CHCs appear to signal the fertility of individuals and induce policing behavior towards surplus reproductive workers.

Aggression↗
PubMed1976

[Reproductive death and population kinetics of survived hamster cells in vitro during 48 hours following x-ray doses up to 800 Rad. II].

By means of a quantitative analysis, the time dependency of the number of dead cells and the resulting statement of cell numbers are compared with colony survival curves and with the distribution of colony sizes. The obtained periodical variation of reproductively killed cells is analyzed through population kinetics and is reduced to the number of those among the irradiated cells which show radiation-induced lethal reproductive damage. Therefrom, together with both sorts of interphase-dead cells, the dose dependency of the three lethal fractions results, taking into consideration the quantitative cellular statement. The formation of maxima of reproductively killed cells at the intervals of generation time until F3-generation is explained by an autosynchronization of partly lethally injured cell populations. From colony size distributions a linear dose dependency of the mean colony size group can be derived; this is discussed in connection with DNA double strand breaks regarded as a possible cause of reproductive lethal damages. The data obtained concerning the development of a cell population with radiation damages are evaluated by the construction of phylogenetic schedules for every 300 rd and 500 rd. By this means, the underlying population kinetics is being revised quantitatively.

Animals↗
PubMed2002

Sex differences in lipid metabolism during reproduction in free-living tree lizards (Urosaurus ornatus).

Understanding the relationship between energy metabolism and signals that regulate reproduction may provide insight into the coordination of the energetically costly behavioral and physiological events that occur during reproduction. Significant changes in the utilization of stored lipids may occur during reproduction and the patterns of utilization observed often differ between females and males. Changes in levels of stored lipid reserves have been described extensively in animals from many taxa, but detailed biochemical analyses of alterations in the enzymes and substrates regulating lipid metabolism during periods of active reproductive effort rarely have been performed. In addition, few studies have compared males and females from the same population during the same reproductive season. In this study we examined lipid metabolism in free-living female and male tree lizards across a single reproductive season. We measured lipid stores, circulating lipid substrates, and the activities of enzymes regulating lipid storage and release in both liver and adipose tissue. Overall, females and males showed significant variation in abdominal fat body mass, liver total lipid, the activity of an enzyme regulating fat storage (DGAT) in both of these tissues, and circulating free fatty acids across the reproductive season. In females, total fat body mass, adipose DGAT, liver lipid, and liver DGAT significantly varied across reproductive stage, with vitellogenic and Gravid females often at opposite extremes. In males, fat body mass and liver fat varied across reproductive stage (without significant variation in DGAT in either tissue), as did circulating glycerol and free fatty acids. Correlations among sex steroid hormone levels and lipid metabolism variables suggested a role for these hormones in producing the patterns observed in each sex and in the observed sex differences lipid metabolism.

Acyltransferases↗
PubMed1992

A possible role of prostaglandin E2 in reproduction of the male water frog, Rana esculenta. In vivo and in vitro studies.

Plasma prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), androgens and estradiol-17 beta were measured in the male water frog, Rana esculenta, during the annual sexual cycle. In vivo experiments were carried out to study the effects of PGE2 and PGF2 alpha on plasma sex steroids during the following periods: prereproduction (April), reproduction (May), postreproduction (June) and recovery (October). In the same months, in vitro experiments were performed to evaluate the effects of these two prostaglandins (PGs) on testicular release of sex steroids. The PGE2 plasma levels peaked in April. PGE2 treatment in vivo increased androgens in April and October, while PGF2 alpha increased estradiol-17 beta in June and October. In in vitro experiments, PGE2 increased androgens in April, while PGF2 alpha increased estradiol-17 beta in October. These results suggest that PGE2 could induce the breeding activity, probably through androgens synthesis. PGF2 alpha could interrupt the breeding, through estradiol-17 beta secretion.

Androgens↗
PubMed2003

Cost minimization by helpers in cooperative vertebrates.

When parents invest heavily in reproduction they commonly suffer significant energetic costs. Parents reduce the long-term fitness implications of these costs through increased foraging and reduced reproductive investment in the future. Similar behavioral modifications might be expected among helpers in societies of cooperative vertebrates, in which helping is associated with energetic costs. By using multivariate analyses and experiments, we show that in cooperative meerkats, Suricata suricatta, helping is associated with substantial short-term growth costs but limited long-term fitness costs. This association forms because individual contributions to cooperation are initially condition dependent, and, because when helpers invest heavily in cooperation, they increase their foraging rate during the subsequent nonbreeding period and reduce their level of cooperative investment in the subsequent reproductive period. These results provide a unique demonstration that despite significant short-term costs, helpers, like breeders, are able to reduce the fitness consequences of these costs through behavioral modifications.

Animals↗
PubMed1987

Effect of pinealectomy on thyroid hormone (T4 and T3) levels in plasma during annual reproductive cycle in the freshwater catfish, Clarias batrachus.

Thyroxine and triiodothyronine (T3) were measured by radioimmunoassay in serum and thyroid gland of the freshwater teleost Clarias batrachus. Pinealectomy increased the glandular levels of the thyroid hormones but decreased the plasma levels of T4 concomitantly with the increase of T3 levels. Most of the effects of pinealectomy on thyroid hormones were restricted to the gonadal development periods. Pinealectomy has shown no significant impact on thyroid hormones during the other periods of the reproductive cycle. Thus, it appears that the pineal gland is inhibitory to thyroid hormones during gonadal development and maturation.

Animals↗
PubMed1999

Disruption of androgen-regulated male reproductive development by di(n-butyl) phthalate during late gestation in rats is different from flutamide.

Gestational and lactational exposure to di(n-butyl) phthalate (DBP) at >/=250 mg/kg/day disrupts male rat reproductive development and function. Although this indicates an antiandrogenic mechanism, DBP and its biologically active metabolite do not interact with the androgen receptor (AR) in vitro. In the present study, we compared the effects of DBP and the antiandrogen flutamide using a shorter exposure during the prenatal period of male sexual differentiation in rats. Pregnant CD rats received DBP at 0, 100, 250, or 500 mg/kg/day po (n = 10) or flutamide at 100 mg/kg/day po (n = 5) from Gestation Days 12 to 21. In F1 males, DBP (500 mg/kg/day) and flutamide caused hypospadias; cryptorchidism; agenesis of the prostate, epididymis, and vas deferens; degeneration of the seminiferous epithelium; and interstitial cell hyperplasia of the testis. Flutamide and DBP (250 and 500 mg/kg/day) also produced retained thoracic nipples and decreased anogenital distance. Interstitial cell adenoma occurred at 500 mg DBP/kg/day in two males. The only effect seen at 100 mg DBP/kg/day was delayed preputial separation. In contrast to flutamide, DBP caused a low incidence of prostate agenesis and hypospadias with no vaginal pouch. The low incidence of DBP-induced intraabdominal testes contrasted with the high incidence of inguinal testes seen with flutamide. Thus prenatal male sexual differentiation is a sensitive period for the reproductive toxicity of DBP. A no observed adverse effect level was not established and the lowest observed (adverse) effect level was 100 mg/kg/day. Flutamide and DBP disrupted the androgen signaling necessary for male sexual differentiation but with a different pattern of antiandrogenic effects. DBP is an example of an environmental antiandrogen that disrupts androgen-regulated male sexual differentiation without interacting directly with the AR, as does flutamide.

Abnormalities, Drug-Induced↗
PubMed1990

Photoperiod and temperature interaction in the determination of reproduction of the edible snail, Helix pomatia.

Snails were kept in self-cleaning housing chambers in an artificially controlled environment. Mating was frequent under long days (18 h light) and rare under short days (8 h light) regardless of whether the snails were kept at 15 degrees C or 20 degrees C. An interaction between photoperiod and temperature was observed for egg laying. The number of eggs laid (45-50/snail) and the frequency of egg laying (90-130%) were greater in long than in short days (16-35/snail and 27-77%) but a temperature of 20 degrees C redressed, to some extent, the inhibitory effect of short days. At both temperatures only long photoperiods brought about cyclic reproduction over a period of 16 weeks, confirming the synchronizing role of photoperiod on the neuroendocrine control of egg laying in this species of snail.

Animals↗
PubMed1979

Steroid synthesizing cellular sites in the ovary of the domestic pigeon Columba livia (Gmelin): a histochemical study.

The ovary of the domestic pigeon, Columba livia, has been assayed histochemically for the localization of delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta-HSDH), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSDA), 11 beta-hydroxysteroid dehydrogenase (11 beta-HSDH), glucose-6-phosphate dehydrogenase (G6P-DH) and NADH-diaphorase activities during different periods of the reproductive cycle. delta 5-3 beta-HSDH, 17 beta-HSDH, 11 beta-HSDH, G6P-DH and NADH-diaphorase activity was found in the theca interna of growing, atretic and postovulatory follicles, the granulosa of ovulatory, atretic and postovulatory follicles, and interstitial gland cells during the pre-incubation and the laying periods. During the incubation and squab feeding periods only delta 5-3 beta-HSDH, G6P-DH and NADH-diaphorase activities were observed in the above mentioned cells. The steroidogenic potential of atretic follicles depends upon the type of atresia a follicle undergoes.

Animals↗
PubMed2004

Effects of triclosan on the early life stages and reproduction of medaka Oryzias latipes and induction of hepatic vitellogenin.

Triclosan (2,4,4'-trichloro-2'-hydroxydiphenyl ether) is widely used as antibacterial agent in various industrial products, such as textile goods, soap, shampoo, liquid toothpaste and cosmetics, and often detected in wastewater effluent. In this study, the effects of TCS on the early life stages and reproduction of medaka (Oryzias latipes) were investigated. The 96-h median lethal concentration value of TCS for 24-h-old larvae was 602 microg/l. The hatchability and time to hatching in fertilized eggs exposed to 313 microg/l TCS for 14 days were significantly decreased and delayed, respectively. An assessment of the effects of a TCS 21-day exposure period on the reproduction of paired medaka showed no significant differences in the number of eggs produced and fertility among the control and 20, 100 and 200 microg/l TCS treatment groups. However, concentrations of hepatic vitellogenin were increased significantly in males treated with TCS at 20 and 100 microg/l. In the F(1) generations, although the hatching of embryos in the 20 microg/l treatment showed adverse effects, there was no dose-response relationship between hatchability and TCS treatment levels. These results suggest that TCS has high toxicity on the early life stages of medaka, and that the metabolite of TCS may be a weak estrogenic compound with the potential to induce vitellogenin in male medaka but with no adverse effect on reproductive success and offspring.

Animals↗
PubMed2000

The menopause transition and the aging process: a population perspective.

The menopause transition period, extending from active reproductive capacity with well-characterized hormone profiles through reproductive senescence, has been less well studied than any other period of the life span except extreme old age. Yet, for the gerontologist, this is an important period to understand for at least two reasons. First, during this period changes in the neuroendocrine system and ovary may provide a model for the study of other aging-related processes. Second, specific characteristics of this transitional period (including duration, intensity, and age at menopause) may be considered "aging", and influence short-term health and quality-of-life status, as well as life expectancy. In addition to discussing the menopause transition in terms of age and culture, we include some of the theories and conceptual models that can influence the nature and interpretation of information from this time period, and its ultimate impact on health and health practice.

Aging↗