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At least 775 records · Page 43Linked to original sources
PubMed1985

Circannual rhythms of ground squirrels: role of the hypothalamic paraventricular nucleus.

Female golden-mantled ground squirrels, maintained in an LD 14:10 photoperiod at 23 degrees C, sustained lesions of the paraventricular nucleus (PVN) or sham operations. Body weight and reproductive status were recorded weekly pre- and postoperatively. Bilateral lesions of the PVN did not eliminate, phase-shift, or otherwise disrupt the circannual rhythms of body mass or reproduction. Absolute levels of body weight were unaffected by PVN ablation. The PVN is not an essential component of the oscillatory system that generates circannual cycles in ground squirrels.

Animals↗
PubMed1984

Changes in gonadotrophin, lipid and cholesterol levels during annual reproductive cycle in the freshwater teleost, Cirrhinus mrigala (Ham.).

Pituitary gonadotrophin started increasing with gonadosomatic index from preparatory phase but increase in serum gonadotrophin became evident from prespawning phase. However, their peaks were noticed in spawning phase. During other phases of reproductive cycle their values were low except for female pituitary gonadotrophin potency which remained comparatively high during postspawning phase. An increase in ovarian and decrease in testicular lipid started from preparatory phase which continued till spawning phase. Liver lipid in either sex decreased during prespawning and spawning phases. Lipid level was low in ovary but was high in testis and liver during the remaining period of the year. Liver cholesterol was low during spawning and high in prespawning phase whereas serum cholesterol was low during prespawning and spawning phases and remained high during other and peak was recorded during spawning phase. Testicular cholesterol was low during preparatory and postspawning phases and high during the rest of the period of reproductive cycle.

Animals↗
PubMed1988

Djungarian hamsters exhibit reproductive responses to changes in daylength at extreme photoperiods.

In seasonally breeding species, an animal's photoperiodic history (the daylength or photoperiod previously experienced) influences the reproductive response to new photoperiods. However, this has only been examined over a relatively narrow range of photoperiods. We assessed whether Djungarian hamsters (Phodopus sungorus) respond to daylength changes at extremely long and extremely short photoperiods. To determine the extent and temporal sequence of reproductive responses to photoperiod changes, ultrasonography was employed to determine serial changes in testis weight in individual animals; serial changes in body weight and pelage color were also assessed. Male animals (60-day-old) shifted from 6 h of light/day (6L) to 10L showed partial testicular recrudescence and darkening of the coat. In control animals remaining in 6L, testes remained small, and coat color continued to lighten. Animals shifted from 20L to 16L showed partial and transient testicular regression, whereas testes remained large in control animals remaining in 20L. There were no significant differences in body weight between control and experimental animals in either study. These findings indicate that Djungarian hamsters respond reproductively to changes in photoperiod at extreme daylengths, but the magnitude of the response appears to be dependent on the absolute daylength.

Animals↗
PubMed2006

Adenomyosis and reproduction.

Evidence has been provided that pelvic endometriosis is significantly associated with uterine adenomyosis and that the latter constitutes the major factor of infertility in such conditions. Furthermore, it has become evident that both adenomyosis and endometriosis constitute a pathophysiological and nosological entity. Mild peritoneal endometriosis of the fertile woman and premenopausal adenomyosis of the parous and non-parous woman, as well as adenomyosis in association with endometriosis of the infertile woman, constitute a pathophysiological continuum that is characterized by the dislocation of basal endometrium. Due to the postponement of childbearing late into the period of reproduction, premenopausal adenomyosis might increasingly become a factor for infertility in addition to adenomyosis associated with endometriosis of younger women. In any event, the presence or absence of uterine adenomyosis should be examined in a sterility work-up.

Adult↗
PubMed1977

Effects of postnatal corticosterone treatment on reproductive development in the rat.

Reproductive development was studied in rats in which corticosterone (25 mg/100 g body wt) mixed with an equal amount of cholesterol was implanted i.p. at Days 3, 6, 12 or 18 after birth. Vaginal perforation in rats treated on Days 12 or 18 was advanced by 10 days but reproductive function in the treated animals was generally disrupted. A variable incidence of persistent vaginal oestrus was observed in adult females given implants on Days 3 and 6, and of prolonged vaginal dioestrus in those treated on Days 12 or 18. All treated females had lordosis quotients lower than those of untreated controls, the effect being most pronounced at the earlier ages of treatment. The results are believed to indicate two periods in reproductive development which are differentially affected by corticosterone.

Aging↗
PubMed1996

Responses in the hypothalamic monoaminergic system activity in ewes to beta-endorphin, CRF and their antagonists.

This article reviews data concerning the action of opioidergic and monoaminergic system on LHRH secretion. Generally, in anestrous ewes beta-endorphin and/or corticoliberin significantly change extracellular concentrations of monoamine metabolites in the MBH-ME, but in estrous ewes both beta-endorphin and CRF alters also dopamine, noradrenaline and serotonin levels. Responses of catecholaminergic and serotoninergic system in the MBH-ME to naloxone or CRF-antagonist depend, to a large degree, on the phase of reproduction. In anestrous ewes subjected to stressful stimuli an opiate receptor blocker, naloxone, and CRF-antagonist attenuate the stress - induced activity of catecholaminergic and serotoninergic system in the MBH-ME; in non-stressed animals they suppress only serotoninergic system activity in this structure. No clear explanation can be offered now for either differences in response of catecholaminergic and serotoninergic system in the MBH to beta-endorphin and CRF in various periods of reproduction or for differences in the responses of these systems to CRF antagonist and naloxone in non-stressed and stressed ewes. It has been suggested that the responses in monoaminergic system activity are highly dependent upon the physiological state of the animal and that beta-endorphin and corticoliberin may indirectly modulate LHRH and other hypothalamic hormone secretion by monoaminergic systems.

Animals↗
PubMed2005

Using gonadotropin-releasing hormone (GnRH) and GnRH analogs to modulate testis function and enhance the productivity of domestic animals.

Gonadotropin releasing hormone (GnRH) controls the activity of the gonadotrope cells of the pituitary gland and, as a consequence, is a critical component of the endocrine cascade that determines the growth, development, and functional activity of testicular tissue. The use of GnRH and GnRH analogs is common in domestic animal production systems. Although GnRH and GnRH analogs are most commonly used to control the fertility and reproductive events in female animals, GnRH agonists and antagonists are increasingly used to modulate the fertility, behavior, and productivity of male animals as well. This review will focus on recent advances in this use of GnRH agonists and antagonists.

Animals↗
PubMed1994

Reproductive function and contraception in the postpartum period.

The postpartum period is a time of major cellular and hormonal change enabling the return of pelvic organs and the hypothalamic-pituitary-ovarian axis to the nonpregnant state. Breast-feeding modifies this change and maintains the endocrine profile and uterine endometrium in a "static" state. In nonlactating women, menstruation returns on average by day 55 to 60 postpartum and ovulation returns on average by day 40 to 50 postpartum. Breast-feeding prolongs the return of menstruation to some 8 to 15 months postpartum and the first ovulation on average was between 30 to 40 weeks postpartum. However, in breast-feeding women, the return of menstruation and ovulation can be quite variable and is influenced by the pattern of breast-feeding, in particular, the intensity and pattern of suckling. There is concern that breast-feeding, although an effective contraceptive on a wide population scale, is unpredictable for the individual. An overall pregnancy rate of 2 to 10 per cent during lactational amenorrhea has been reported. Barrier methods, intrauterine contraceptive devices, and progestogen-only contraceptives are some of the highly effective and most commonly used additional methods of contraception by lactating women. Other methods of contraception during this period include the use of periodic abstinence and combined oral contraceptives. This paper provides an overview of postpartum reproductive function in relation to breast-feeding and the use of contraception in this unique period.

Breast Feeding↗
PubMed1982

Photoperiodicity and circannual levels of LH, FSH, and testosterone in normal and castrated male, white-tailed deer.

To establish the relation between photoperiodicity and the levels of LH, FSH, and testosterone (T) in plasma, three intact and three castrated adult male white-tailed deer were sampled once a month for 2-3 years. The rang of average LH levels in controls varied between 0.8 and 2.0 ng/mL; the levels in castrates were considerably higher, 3.4 to 8.9 ng/mL. Average levels of FSH varied in controls between 25 and 112 ng/mL and in castrates between 141 and 240 ng/mL. A significant correlation between the seasonal time course of LH and FSH was found in castrated, but not in intact bucks. In castrates both gonadotropins exhibit two major elevations coinciding with spring and fall equinoxes in March and September. The seasonal time course of FSH in castrates correlates highly with seasonal levels of FSH in controls. However, the time course of the LH curve in controls is substantially different from the curve in castrates, presumably owing to feedback mechanisms. A possible role of testicular estradiol in this feedback is discussed. In controls, peak T levels are reached in December, i.e., 3 months after maximum levels of FSH and 5 months after peak levels of LH were detected. It appears that male deer undergo two periods of reproductive stimulation (one in the spring, the other in the fall). However, the organism responds with the full range of gonadal and behavioral mechanisms leading to the initiation of the rut only during the fall.

Animals↗
PubMed1993

Effect of maternal aging on transgene heritability in transgenic founder mice derived from zygotes microinjected with retroviral long terminal repeat-containing recombinant deoxyribonucleic acid.

To determine the stability of artificially introduced recombinant DNA in the mouse germline throughout the reproductive life, founder mice derived from fertilized eggs injected with retroviral long-terminal-repeat-containing recombinant DNAs were mated with congenic FVB/N mice. Tail DNA of all progeny were screened and restriction fragment patterns of the transgenes were examined. Litter size and percentage of transgene transmission at various reproductive age periods were analyzed. Microinjection of 1737 eggs with four different recombinant DNAs resulted in 12 female and 11 male transgenic mice; 2 males were sterile and the remaining 21 mice served as founders to produce 1087 F1 progeny. With increasing parental age, litter size decreased generally. The percentage of progeny inheriting the transgenes declined markedly with increasing aging of 4 female founders; this aging effect was not observed in male founders (p < 0.005). No apparent change in transgenes was detected in progeny from late reproductive stages.

Aging↗
PubMed1976

[Variations in cerebral neurosecretion during the reproductive cycle of a viviparous insect, Glossina fuscipes fuscipes (Diptera, Muscidae)].

The neurosecretory A cells of the pars intercerebralis of the viviparous fly Glossina fuscipes fuscipes present important changes during the genital cycle. A slight release of neurosecretory products occurs at the moment of the first ovulation and at the hatching. An important discharge takes place just before the larviposition and the second ovulation.

Animals↗
PubMed1999

[Food effects on some reproductive aspects of rainbow trout, Oncorhynchus mykiss, in a Venezuelan fish farm].

Samples of rainbow trout, Oncorhynchus mykiss, were fed with three different dried diets, labeled D1, D2 and D3, the first ones were expanded and the last one pelleted type food. Their protein content ranged from 36% to 42%, and only D1 diet presented a pigment in its composition. The gonodasomatic index (GSI) as well as the gonadial development showed a different behavior in males and females for all the samples tested. A continuous sperm production was observed in males fish, while in female fish the GSI showed a tendency to increase through the whole study, and they showed a reproductive rest period on july 92. Fish relative fecundity and egg diameter were similar in all cases. The gonodial maduration age was shorter for the female that were fed with D1 and D2, while the 50% of the trout population that got D3 had a gonodial maduration period two months longer. For all trouts tested the fertility was low with a maximum value of 49%. The hatchery from the tested trouts with D2 intakes had a mortality value of 62%. Meanwhile, those with D1 and D3 intakes showed mortality values of 36% and 43% respectively.

Animal Feed↗
PubMed1975

[Cyclic reproductive activity in bathyal and abyssel deep-sea fishes].

A female of the rare Brotulid fish Cataetyx laticeps has been caught; it contained a great number of larvae all of the same size. Growth marks can be noticed on its otoliths as well as on those of various species caught to the depth of 4 700 m. They are indications of a cyclic activity in the abyssal depths.

Animals↗
PubMed1996

Correlation of fecundability and serum estradiol after danazol treatment in patients with advanced endometriosis.

OBJECTIVE: To examine the relationship between pregnancy incidence and the level of serum E2 during danazol therapy. DESIGN: Danazol was given by 200 mg four times daily for 3 months. Serum E2 level was checked after completing the therapy, but before stopping medication. Patients then were advised to conceive at the appropriate time over a 6-month period. SETTING: Reproductive and Endocrine Laboratory of the Department of Obstetrics and Gynecology, Keelung Chang Gung Memorial Hospital, Keelung, Taiwan. PATIENTS: Infertile women with invasive endometriosis receiving conservative surgery and danazol treatment. INTERVENTIONS: Serum E2 is checked before medication and at the end of danazol therapy, but before stopping medication. MAIN OUTCOME MEASURES: Whether pregnancy is related to the change of serum E2 caused by danazol therapy. RESULTS: There were 24 pregnancies in 38 patients with invasive endometriosis after treatment. Pregnant patients had significantly lower serum E2 levels as compared with the nonpregnant patients. CONCLUSIONS: After conservative surgery for invasive endometriosis associated with infertility, the therapeutic period of danazol treatment could be shortened to 3 months. Because there is significant correlation of fecundability and serum E2 after danazol medication, serum E2 could be a guideline for predicting pregnancy or for prolonging or changing of treatment after danazol therapy.

Danazol↗
PubMed2002

Longitudinal analysis of length growth in the chimpanzee (Pan troglodytes).

The adolescent growth spurt in linear dimension in humans is considered to be unique among mammals, but few comparative studies have been done, even on chimpanzees. Growth of the summed length of crown to rump, thigh, and leg was studied longitudinally in 12 chimpanzees. We took body weight growth and reproductive maturation into consideration. Reproductive maturation was monitored by the swelling of sexual skin and menarche in females, and by testicular development in males. We applied two relationships found in humans between body length growth and the environment to the chimpanzees. The first relationship was the robustness of the growth spurt, meaning that the spurt is absent only in individuals under the most severe environmental pressure. Subjects maturing in a favorable or even mediocre environment are anticipated to show the growth spurt. The second relationship was catch-up growth, where, when the environment is ameliorated, growth may be accelerated to attain the target size. Catch-up growth at the end of the juvenile period may mimic the adolescent growth spurt. Results showed that subjects living under favorable conditions did not exhibit a growth spurt, and that it was only the subjects who had delayed growth in the juvenile period that showed a spurt in adolescence, the period when reproductive maturation occurred. Although we have concluded that chimpanzees do not have an adolescent growth spurt, except in cases of catch-up growth, this does not mean that they have a different growth pattern from that of humans. The absence of a growth spurt may be associated with adaptations to chimpanzee patrilineal society, where adolescent males are incorporated into the adult hierarchy at a low rank.

Animals↗
PubMed1988

Mammalian reproductive strategies: genes, photoperiod and latitude.

This paper considers how and why natural selection might promote or block the photoperiodic regulation of a mammal's reproduction. The factors most important in making this decision would seem to be the following: life expectancy, length of the female's cycle, feeding strategy, the presence or absence of survival mechanisms like hibernation, and the nature of the seasonal challenges offered by the mammal's habitat. A speculative scheme is offered for the potential utility of this type of regulation dependent upon life expectancy and latitude of residence.

Animals↗