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At least 649 records · Page 36Linked to original sources
PubMed1995

[Toxicology of reproduction and development. Pregnancy and periods of risks from drugs].

The authors discuss the possibilities of drug interference with the reproductive system and especially during various stages of pregnancy: from the sequence of neurochemical events that condition the release of pituitary gonadotrophines at the level of the central nervous system to late events that may occur during development. After listing the periods of risk, drug-induced changes in the conceptus are illustrated on the basis of data registered in the literature. In this context, it is stressed that the dysmorphogenic effect is limited to the period of differentiation and organogenesis whereas it is becoming more and more obvious that drugs may also have variable effects on other stages of pregnancy where frequently they have specific pharmacodynamic actions on the fetus. The knowledge of these effects may be useful in order to avoid untoward actions on pregnancy or on embryo, fetus, neonate or postnatal development, but may also create a basis for in utero drug treatments of fetal pathologies.

Central Nervous System↗
PubMed1982

Effectiveness of photoperiod stimulation on reproductive performance of sheep housed continuously indoors on an accelerated breeding schedule.

Over five breeding periods, the reproductive performance (fertility, prolificacy and fecundity) of three strains of sheep housed continuously indoors was measured. The sheep were maintained as two separate flocks, A and B, with similar genetic background on an eight month accelerated breeding schedule under one of three lighting regimes, abrupt, contracted or constant, to induce ovarian activity. Overall fertility to one estrus was 59%. For flock A, fertility was greatest under the contracted lighting regime and lowest under the constant lighting regime; the opposite was true for flock B. Among the three strains, fertility was lowest for the Dam 2 strain in flock A. Prolificacy averaged 1.8 lambs per ewe lambing and was similar under each of the three lighting regimes. Fecundity (averaging 106%), the number of lambs born per 100 ewes exposed to rams, generally followed the pattern of fertility.

Animals↗
PubMed1989

Temporal relationships of neuropathologic conditions caused by perinatal asphyxia.

The neuropathologic conditions in 120 perinatal deaths attributed to fetal or newborn asphyxia were examined. Central nervous system necrosis was present in 16 of these deaths. The approximate time of asphyxial insult was established by determining the duration of the process, based on the findings of neuronal necrosis, macrophage response, or an astrocyte response, in conjunction with clinical data. The time of the asphyxial insult for the 16 perinatal deaths was as follows: antepartum fetal asphyxia, two cases; antepartum-intrapartum fetal asphyxia, five cases; intrapartum fetal asphyxia, four cases; and neonatal asphyxia, five cases. These observations indicate that an asphyxial insult may occur in the antepartum period, in the prodromal period of preterm labor, in the intrapartum period, and in the neonatal period. Five to ten percent of the asphyxial insults in each reproductive time period were initially sublethal, allowing necrosis of the brain of the fetus or newborn to develop.

Asphyxia Neonatorum↗
PubMed2000

Quantification of rainbow trout (Oncorhynchus mykiss) estrogen receptor-alpha messenger RNA and its expression in the ovary during the reproductive cycle.

This study developed a quantitative reverse transcription-polymerase chain reaction (RT-PCR) method to measure estrogen receptor-alpha (ERalpha) mRNA in the rainbow trout (Oncorhynchus mykiss). Using RT-PCR, and primers based on the known ERalpha DNA sequence in this species, cDNA sequences representing most of the protein coding region were obtained from ovary poly A(+) RNA. Using these DNA sequences as probes in Northern blot hybridizations confirmed that a single transcript of 4.2 kilobases in poly A(+) RNA could be detected in liver and ovary RNA. For the quantitative RT-PCR assay an internal standard RNA molecule was produced to control for inherent inter-tube differences in amplification efficiency and permit accurate quantification of ERalpha mRNAs. The quantitative RT-PCR assay proved to be highly specific for ERalpha mRNA with a detection limit of 6.9 fg, which corresponds to 273 fg ERalpha mRNA/microg total RNA. The quantitative RT-PCR assay was used to measure the levels of ERalpha mRNA in ovaries of rainbow trout at different stages of reproductive development. Ovarian ERalpha mRNA expression was found during two distinct periods of reproductive development, in pre-vitellogenic ovaries of fish with ovarian follicle diameters (OFDs) </=100 microm and in mid-vitellogenic ovaries with OFDs >1000 microm. ERalpha mRNA could not be detected in the ovaries of fish with OFDs >100 microm but </=1000 microm. The highest levels of ERalpha mRNA were found in late vitellogenic ovaries of fish with OFDs >2000 microm.

Animals↗
PubMed2005

Isolation and characterization of two cytochrome P450 aromatase forms in killifish (Fundulus heteroclitus): differential expression in fish from polluted and unpolluted environments.

Populations of killifish (Fundulus heteroclitus) persist in many different highly polluted environment indicative of adaptation or tolerance. In this study, we sought to determine whether long term, multigenerational exposures to environmental contaminants has affected reproductively relevant genes and biological processes. A homology cloning strategy was used to isolate the killifish cytochrome P450 aromatase (P450arom, estrogen synthetase) cDNAs. Consistent with previous fish studies, killifish were found to have two P450arom forms, which segregated into A- and B-gene clades and were differentially expressed in brain (B >> A) and ovary (A >> B). Comparison of killifish from highly polluted (New Bedford Harbor, NBH) and unpolluted (Scorton Creek, SC) environments revealed no site-related differences in P450arom coding sequences or in overall tissue distribution patterns. As measured by real-time quantitative PCR (QPCR) analysis, however, P450arormB (a known marker of estrogen effect) was approximately two-fold higher in the brain of NBH than of SC fish, a difference seen in reproductively active and inactive males and females. Providing further evidence of exposure to estrogen-like pollutants or metabolites in NBH, vitellogenin (vtg) mRNA and protein were elevated in seasonally active and inactive males, and in reproductively inactive females, when compared to SC fish. By contrast, during the period of reproductive activity, NBH females had a lower gonadosomatic index, lower plasma estrogen, a decreased hepatosomatic index, and reduced vtg expression as compared to SC females, indicating that the female hypothalamic-pituitary-gonadal (HPG)-liver axis is impaired in the polluted environment. As measured by a decrease in plasma androgen (but not GSI), the male HPG axis was impaired in reproductively active NBH versus SC fish. In agreement with reports that NBH killifish are resistant to dioxin-like chemicals (DLC) that activate arylhydrocarbon receptor (AhR) signaling, ovarian P450aromA (a marker of dioxin-like effect in zebrafish embryos) did not differ in SC and NBH fish. In conclusion, the killifish population at the NBH Superfund site maintains a level of reproductive competence in the face of evidence of exposure to estrogen-like pollutants and endocrine disruption.

Amino Acid Sequence↗
PubMed1997

African bats: evolution of reproductive patterns and delays.

Patterns of reproduction in African bats can be compared in three taxon-based groups: fruit bats (Megachiroptera), freetailed bats (Microchiroptera: Molossidae) and the nonmolossid Microchiroptera. In the fruit bats and nonmolossid Microchiroptera there is a trend from either seasonal or aseasonal polyestry, with prolonged or continuous spermatogenesis in the tropics, towards seasonal monestry and seasonal spermatogenesis at more temperate latitudes. Reproductive delays (sperm storage, delayed implantation and delayed development) are rare at tropical latitudes, but are the norm in the nonmolossid Microchiroptera away from the tropics. The molossids are mostly polyestrous at tropical and temperate latitudes, although the duration of the reproductive season decreases with increasing latitude. The molossids appear to have escaped the constraints that affect reproduction of the other Microchiroptera. We propose that this may be due to their flight capabilities and foraging behavior, which give them access to year-round food, and to the thermal characteristics of their roots. We suggest that the ancestral reproductive pattern of the Chiroptera was probably aseasonal or seasonal polyestry, as seen in extant tropical species, and therefore that reproductive cycles have evolved from the polyestrous to the monestrous condition. Short periods of reproductive delay occur in some species of tropical bats; we suggest that these reproductive delays originally were not adaptations to temperate latitudes but rather to the long dry season, which is characteristic of African tropical latitudes. With the move away from the tropics, selective pressures, acting on the timing of lactation and spermatogenesis, would have ensured that these processes continued to occur in the warm wet season, and that the length of the reproductive delay increased. This model accommodates the probable evolutionary origin of bats and links the evolution and development of reproductive delays to the differences in climate that occur with changes in latitude. There is evidence that mate choice and sperm competition may be important to modern bats, but we believe that they need not be involved as causal factors in the evolution of reproductive delays, which can be adequately explained using purely energetic arguments.

Africa↗
PubMed1987

Familial acanthosis nigricans. A longitudinal study.

The triad of hyperandrogenism, insulin resistance and acanthosis nigricans (HAIR-AN) is known to have a familial tendency. In order to better understand the natural history and possible treatment of this disorder, we studied the clinical course of two families in which all female progeny were affected. A rapid progression of the HAIR-AN syndrome was apparent during the peripubertal period and early reproductive years. Beyond this period, the progression of HAIR-AN appeared quite variable. Rapid weight gain was a major stimulant for increasing insulin resistance and hyperandrogenemia. In the one subject with a postmenarcheal onset of the syndrome, prolonged weight reduction was associated with an improvement in the dermatologic manifestation as well as in the hyperandrogenism and insulin resistance. Oral contraceptives appear to improve the dermatologic symptoms of the HAIR-AN syndrome.

Acanthosis Nigricans↗
PubMed1991

Influence of thyroidectomy on reproductive responses of male domestic turkeys (Meleagris gallopavo).

1. The influence of age at thyroidectomy on reproductive activity of male turkeys was investigated. 2. Thyroidectomy of 53-week-old male domestic turkeys that had been reproductively active for 25 weeks resulted in undetectable plasma thyroxine concentrations, termination of semen production and testicular regression. Daily light-dark treatment was 14L:10D before and after thyroidectomy. 3. Thyroidectomy of 28-week-old, reproductively inactive, males maintained on a daily light-dark cycle of 8L:16D resulted in increased semen volumes following photostimulation with 14L:10D at 32 weeks of age. Semen quality was not affected, while plasma thyroid hormone concentrations were undetectable. The moult and termination of semen production that occurred in response to changing the daily light-dark cycle from 14L:10D to 8L:16D near the end of the study were inhibited by thyroidectomy. 4. The requirement for the thyroid glands in the reproductive processes of male turkeys changes either with age or after an extended period of reproductive activity.

Animals↗
PubMed1979

Seasonal reproductive inefficiency in large pig breeding units in Britain.

The reproductive performance of five large, intensive pig breeding units was monitored over a period of 930 days. During this time three periods of reproductive inefficiency were noted, these mainly involving animals served during the summer months of July and August. Manifestations of this inefficiency were returns of oestrus, abortions and animals reaching 95 days of presumed gestation not-in-pig. It is suggested that ambient temperature stress, a hitherto unidentified arbortifacient factor, and a seasonal tendency towards suboestrus may have been contributory factors.

Abortion, Veterinary↗
PubMed2000

Reproductive character displacement and speciation in periodical cicadas, with description of new species, 13-year Magicicada neotredecem.

Acoustic mate-attracting signals of related sympatric, synchronic species are always distinguishable, but those of related allopatric species sometimes are not, thus suggesting that such signals may evolve to "reinforce" premating species isolation when similar species become sympatric. This hypothesis predicts divergences restricted to regions of sympatry in partially overlapping species, but such "reproductive character displacement" has rarely been confirmed. We report such a case in the acoustic signals of a previously unrecognized 13-year periodical cicada species, Magicicada neotredecim, described here as a new species (see Appendix). Where M. neotredecim overlaps M. tredecim in the central United States, the dominant male call pitch (frequency) of M. neotredecim increases from approximately 1.4 kHz to 1.7 kHz, whereas that of M. tredecim remains comparatively stable. The average preferences of female M. neotredecim for call pitch show a similar geographic pattern, changing with the call pitch of conspecific males. Magicicada neotredecim differs from 13-year M. tredecim in abdomen coloration, mitochondrial DNA, and call pitch, but is not consistently distinguishable from 17-year M. septendecim; thus, like other Magicicada species, M. neotredecim appears most closely related to a geographically adjacent counterpart with the alternative life cycle. Speciation in Magicicada may be facilitated by life-cycle changes that create temporal isolation, and reinforcement could play a role by fostering divergence in premating signals prior to speciation. We present two theories of Magicicada speciation by life-cycle evolution: "nurse-brood facilitation" and "life-cycle canalization."

Acoustic Stimulation↗
PubMed2006

Thyroid hormone profile during annual reproductive cycle of diploid and triploid catfish, Heteropneustes fossilis (Bloch).

Triploid fishes generally show sterility along with retarded gonadal development and aneuploid gametes. In teleosts, thyroid hormones influence seasonal adaptations and annual events such as reproduction. In addition, thyroid hormone deposition in matured ova is important for reproductive success as the role of thyroid hormones in early development and metamorphosis is well established. The present study deals with measurements of free and total thyroxine (T4) and triiodothyronine (T3) in the plasma of triploid and diploid catfish Heteropneustes fossilis (Bloch) in a complete reproductive cycle. Accumulations of total T4 and T3 within the oocytes have also been measured during the spawning period from fishes of both ploidy groups. No difference of plasma free hormones was noticed between the diploids and triploids of both the sexes in any period of reproductive cycle, although, seasonal variations were noted in both the groups. A significant decrease in the total thyroid hormone levels was noticed in plasma of the diploids in the spawning period compared to triploid fish. During the same period, accumulation of THs was significantly higher in the oocytes of diploids than that of the triploids. Thyroid gland structure also revealed a higher state of activity in the female diploids than the triploids during spawning period. Lower activity of thyroid tissue, higher levels of THs in plasma, and lower accumulation of maternally derived hormones in the oocytes of triploid females during spawning period may be associated with sterility of triploids.

Animals↗
PubMed1990

Cyclic variations in nitrogen uptake rate in soybean plants: uptake during reproductive growth.

Net uptake of NO3- by non-nodulated soybean plants [Glycine max (L.) Merr. cv. Ransom] growing in flowing hydroponic culture was measured daily during a 63 d period of reproductive development between the first florally inductive photoperiod and [unknown word] seed growth. Removal of NO3- from a replenished solution containing 1.0 mol m-3 NO3- was determined by ion chromatography. Uptake of NO3- continued throughout reproductive development. The net uptake rate of NO3- cycled between maxima and minima with a periodicity of oscillation of 3 to 7 d during the floral stage and about 6 d during the fruiting stage. Coupled with increasing concentrations of carbon and C : N ratios in tissues, the oscillations in net uptake rates of NO3- are evidence that the demand for carbohydrate by reproductive organs is contingent on the availability of nitrogen in the shoot pool rather than that the demand for nitrogen follows the flux of carbohydrate into reproductive tissues.

Biological Transport↗
PubMedDate not supplied

Examination of mink (Mustela vison) fed a sulphuric acid preserved fish silage during lactation and growth period. II. Production and pathologic studies correlated to results of clinical-chemical studies.

Earlier and present experiments have shown detrimental influence of sulphuric acid preserved fish in mink feed on production parameters, early kit growth and kit mortality. Comparison of the production parameters with clinical-chemical parametres and pathological-anatomical findings give a picture of the tolerated amount of sulphuric acid preserved fish silage in the mink feed during different production periods. It seems that the animals tolerate only small amounts of sulphuric acid preserved fish silage (5-8 per cent) in the total feed during the stress periods of reproduction, lactation and early kit growth but higher amounts (20-30 per cent) during late growth period, where the need of feed is high.

Animal Feed↗
PubMed1981

Control of seasonal reproduction in sheep and goats by light and hormones.

Seasonal variations of reproductive ability have been demonstrated in male and female sheep and goats. For the female, there is a distinct breeding season. Whilst there are large breed differences in the duration of the sexual season, oestrous cycles generally start when daylength is decreasing and end when daylength is increasing. In some breeds, ovulation without oestrus occurs during the non-breeding season. Although males are able to mate all the year round, seasonal variations occur in the weight of the testis and seminal vesicles and in the fructose concentration of the seminal vesicles. Sexual behaviour and semen characteristics also show seasonal variations. These seasonal variations in males and females are related to hormonal levels. FSH and LH concentrations in the pituitary are reduced to 50% during the non-breeding season. In the peripheral blood, LH concentrations vary throughout the year whilst prolactin concentrations follow the pattern of daylength. Steroid hormones and their feedback actions at the hypothalamo-pituitary axis play a role in the regulation of seasonal reproduction. Three different ways are proposed to overcome these seasonal variations. (1) Males can be introduced into a flock of females before the onset of the breeding season. This leads to induction of ovulation and oestrus, although the first ovulation is frequently followed by a short luteal phase. Teasing does not necessitate contact or sight and is only effective after a period of isolation of the females from the males. (2) Oestrus and ovulation may be induced during the anoestrous period by hormonal treatments. Inducers of LH release have to be associated with a progestagen treatment; PMSG is still the most efficient inducer of LH release. Artificial insemination is useful in this context to avoid subfertility due to seasonal variations of the male. (3) The period of reproduction may be controlled by artificial light regimens. There is a photoinducible period in the circadian cycle of the ewe and it may soon be practical to breed out of season by timed exposure of ewes to short periods of light during the normal hours of darkness.

Animals↗
PubMed2004

Associations between fish reproductive cycle and the dynamics of metazoan parasite infection.

The parasite fauna of the stone loach (Barbatula barbatula) was investigated monthly from May to December 2001. Four parasite species were recorded: Gyrodactylus spp. (Monogenea), Tylodelphys clavata (Digenea), Proteocephalus sagittus (Cestoda), and Raphidascaris acus (Nematoda). The changes in the seasonal dynamics of parasite infection were investigated throughout the 8 months. The potential effect of the reproductive investment of the host, measured by gonad mass and gonado-somatic index (GSI), on the parasite infection was tested against the prediction that, during periods of high reproductive investment (beginning of the breeding period or forming gonads after breeding), the fish are more susceptible to parasite infection. Differences between parasite loads between genders were also hypothesized. Seasonal differences in infection were observed for all parasite species studied. The values of GSI showed a pattern of energy accumulation in the pre-reproductive period and at the beginning of breeding, a decrease during breeding, and an increase in the post-breeding period. A similar pattern was observed for parasite abundance, a strong or weak increase in spring and/or autumn and a decrease during summer (July and August). Positive correlations between the abundance of Gyrodactylus spp. and R. acus and both gonad mass and GSI were found in females after eliminating the effect of fish weight. Our results suggest that stone loach females are more susceptible to parasite infection in periods of higher reproductive investment. The main factor determining the infection of T. clavata was fish size. The abundance of P. sagittus was positively correlated with GSI in the total fish sample with no detectable effect of sex or fish weight. The increase in cestode infection in spring supports the hypothesis that the parasite life cycle could by synchronized with the beginning of host reproduction, probably induced by increasing fish hormone levels in the spring.

Animals↗