SEARCH · PubMed Health

Results for “Reproductive Period”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18Linked to original sources

PubMed1996

Seasonal variation in levels of prostaglandins D2, E2 and F2(alpha) in the brain of a mammalian hibernator, the Asian chipmunk.

Seasonal changes in the in vivo levels of the prostaglandins (PGs) PGD2, PGE2, and PGF2(alpha) were measured in the brain of the male Asian chipmunk, Tamias asiaticus (n = 111), which underwent hibernation during the period between November and March. The mean level of PGD2 ranged from 36.0 to 85.2 pg/g tissue from June to October and remained essentially unchanged (80.5 pg/g tissue) in December. However, the mean PGD2 level rose significantly to 128.6 pg/g tissue in February, and returned to 75.2 pg/g tissue in the following April, suggesting a correlation between PGD2 and hibernation phenomenon. While PGE2 level did not vary significantly throughout the year, PGF2(alpha), which appeared to be the most abundant among the three prostanoids, showed a marked circannual rhythm with a trough of 51.6 pg/g tissue in July, rising to 391.6 pg/g tissue in February and reaching the peak value of 492.7 pg/g tissue in April, the reproduction period.

Animals↗

PubMedDate not supplied

The pattern of reproductive life in a Berber population of Morocco.

Reproductive patterns were studied from data collected in 1,450 Berber households in the province of Marrakesh, Morocco in 1984. Women aged 45-49 years had a mean of 8.9 pregnancies to achieve 5.7 living children. Social influences on fertility rates show the importance of tradition, particularly through time-dependent variables such as age at marriage, waiting time to first birth, interbirth intervals, and duration of breastfeeding. Birth control does not appear to affect the tempo of fertility; rather, its main use is to bring the reproductive period to a close. The comparison of two subsamples of women separated by a 25-year interval indicates an actual acceleration of the tempo of fertility by the reduction of waiting time to first birth and of interbirth intervals. The supposed ongoing process of demographic transition is not clearly observed in this population.

Adolescent↗

PubMed1987

Pineal gland and ocular influences on turkey breeder hens. 2. Body weight, feed intake, and egg characteristics.

Yearling Large White turkey breeder hens underwent pinealectomy (PX), bilateral ocular enucleation (EX), or both and were then photo-induced into reproductive activity. During the subsequent 20-week reproductive period, data were recorded for body weight, change in body weight, feed intake, egg weight, eggshell thickness, and percent settable eggs. A significant interaction between PX and EX treatments did not occur for any of the parameters of this study. Absolute body weight, feed intake, shell thickness, and percent settable eggs were not significantly affected by PX during the study, but PX significantly increased egg weights. Feed intake was significantly reduced by EX, but other parameters were not affected. Both PX and EX reduced body weight losses typically observed in breeder hens during an in-season egg laying cycle. It was concluded that the pineal gland and the eyes can influence body weight changes, egg size, or feed intake in breeder turkey hens during a reproductive cycle.

Animals↗

PubMed2001

Seasonal and age-related changes in blood parasite prevalence in Dark-eyed Juncos (Junco hyemalis, Aves, Passeriformes).

We determined seasonal changes in blood parasite infections in a free-living population of Dark-eyed Juncos (Junco hyemalis) breeding in interior Alaska (65 degrees N; 148 degrees W). The common parasites found in blood smears were Leucocytozoon fringillinarum (56%), Trypanosoma avium (33%), and Haemoproteus fringillae (9%). In males, parasite prevalences were relatively high at arrival on breeding grounds and increased during the breeding season. Intensity of infection with Leucocytozoon also increased between spring and summer, and then decreased at the time of migration (September). This decrease did not occur in adult females. Elevated prevalences during the breeding season probably reflected the addition of new cases via vector activity to positive status resulting from spring relapse. We observed neither an association between parasite species nor a consistent relationship between parasite intensity and body condition. To further study relationships between reproductive system activity and parasite infections, we compared prevalences in adult males that were undergoing their first cycle of gonadal development and regression (males in their second calendar year, or SY) with those of older males (males in their third or more calendar year, i.e., after-second-year males or ASY). Circulating testosterone concentrations declined in both groups between arrival on breeding grounds (end of April-early May) and the end of the reproductive period (July), and they were higher in May in ASY than in SY males. At the peak of the breeding season (June), ASY males also had a higher parasite prevalence than SY males. This difference may have resulted from immunosuppressive effects of gonadal hormones and/or from behavioral differences between SY and ASY males such that older males were exposed to more insect vectors than younger males. .

Age Factors↗

PubMed2006

Jekyll and Hyde, the p53 protein, pleiotropics antagonisms and the thrifty aged hypothesis of senescence.

Antagonistic pleiotropy theory holds that ageing is a not selected trait, and only the consequence of genes fixed in evolution by their reproductive advantage early in life, but with harmful effects in the post reproductive period. Although the existence of antagonistic pleiotropic genes has been controversial, recent molecular approaches seem to confirm them. One of the proposed examples is p53, a gene that plays a pivotal role in the cell stress response. It has been pointed that p53 driven programs, apoptosis and cellular senescence, protect organisms from cancer early in life, but promote ageing phenotype in older members. On the other hand, recent evidences suggest that ageing is not a random program, but a carefully orchestrated one. Accordingly, the antagonistic pleiotropy theory as well as the ageing purpose must be updated. In this issue the p53 candidature to be an antagonistic pleiotropic gene is revisited. Moreover, it has been postulated that these kinds of genes could be actively selected by both effects, and not only by their reproductive advantage early in life, because they improve fitness and they contribute to structure ageing, a program that optimise the energy availability in the post reproductive state.

Aged↗

PubMed1983

[Medical genetic study of the population or Turkmenia. II. The population structure of the inhabitants of the rural soviet Izgant, Geok-Tepe District, Ashkhabad Province].

This report is devoted to the populational description of the Ashkhabad district. Examination of one of the typical agricultural villages (Izgant of the Ashkhabad district) gave the main parameters of the population. The total number of the inhabitants studied is 1596, the proportion of the studied is 56%, the average family size for the parent with completed reproduction period being 5.47, the average generation time - 33 to 38, the gametic index - 0.67 and the inbreeding coefficient - 0.002267. The distribution of some markers (ABO, MN, Hp, Rh, Pp) have been studied. A rather low coefficient of inbreeding, as a result of the absence of geographical isolation, may account for incidence of autosomal recessive disorders.

Adolescent↗

PubMed1984

Seasonal reproductive endocrine profiles in two wild mammals: the red fox (Vulpes vulpes L.) and the European badger (Meles meles L.) considered as short-day mammals.

The annual cycle of the testicular function (testis and epididymis weights and plasma testosterone levels) were considered in relation to seasonal variations in plasma LH and prolactin concentrations in two wild European mammals: the badger and the fox. Phase relationships were established between the annual prolactin cycles and daylight duration. The influence of castration on the seasonal variations in plasma LH levels was also studied. The resumption of activity in the testicular function occurs during autumn for both species. The reproduction period begins in winter but it is over by the beginning of spring for the fox whereas for the badger it lasts until early summer. In the same way, the annual cycle of the gonadotrophic function which, in the fox, presents only one maximum at the end of autumn, is bimodal in the badger with one maximum in January and a second in June. On the other hand, both species have a similar annual prolactin cycle, which shows an increase from the winter solstice onwards, in synchronization with the increase in daily light duration. The highest prolactin levels are measured in spring followed by a decrease during summer. This result calls into question the role played by prolactin in the regulation of the testicular function in as far as the two species have an annual reproductive cycle of the 'short-day' type (onset of activity occurring before the winter solstice) but show seasonal prolactin variations similar to those described for 'long-day' species.

Animals↗

PubMed1999

Seasonal changes in mRNA levels of gonadotropin and thyrotropin subunits in the goldfish, Carassius auratus.

Seasonal changes in the mRNA levels of glycoprotein alpha, gonadotropin (GTH) Ibeta and IIbeta, and thyrotropin (thyroid-stimulating hormone (TSH)) beta subunits in the pituitary of goldfish were quantified by Northern blot analysis and laser densitometry. Reproductive development and thyroid activity were monitored by measuring gonadosomatic index, plasma GTH II, testosterone (T), estradiol, 11-ketotestosterone, and thyroid hormones (T4 and T3). Plasma GTH II and steroids showed characteristic increases, while plasma thyroid hormones levels, in general, decreased in association with the reproductive period. In females, the mRNA levels of the alpha, GTH Ibeta, and GTH IIbeta subunits increased synchronously during early spawning period (April) and then decreased during ovarian regression (August). In males, the levels of the alpha and GTH IIbeta subunits showed changes similar to those in females, but the GTH Ibeta mRNA levels showed only a small increase during the late spawning period (May). In both sexes, TSHbeta mRNA levels were high during winter to early spring (February and April) and low during late spring to summer (May and August). These results suggest that in goldfish the gonadotropins may be synthesized synchronously in order for asynchronous gametogenesis to take place. Additionally, the data suggest a negative feedback relationship between synthesis of the TSHbeta subunit and the thyroid hormones.

Animals↗

PubMed2004

Modeling the invasion of recessive Bt-resistant insects: an impact on transgenic plants.

There is a growing public concern on ecological and evolutionary consequence of the use of genetically modified organisms. We study the impact of Bt-resistant pests on genetically modified Bt crops. We develop and analyse a conceptual reaction-diffusion model of the Bt crop-Bt-susceptible insects-Bt-resistant insects to simulate the invasion of Bt-resistant insects. We show by means of computer simulations that there is a key parameter, which we define as the growth number that characterizes the insects' fitness. We also show that the Bt-resistant insect invasion can lead to inhomogeneity in plant and insect spatial distributions. The plant biomass is found to be essentially dependent on the duration of the Bt-resistant insect reproduction period. There are two types of this dependence. One of them exhibits, respectively, higher plant biomass in comparison with another. The ambiguity in the response of the Bt crop-Bt-susceptible insects system to the invasion of Bt-resistant insects can lead to serious complications in attempts to regulate the dynamics of the system.

Animals↗

PubMed1981

Testosterone-dependent changes in vivo and in vitro in the structure of the renal glomeruli of the teleost Gasterosteus aculeatus L.

During the reproductive period of the male stickleback, structural and functional changes of the kidney take place, both in the glomeruli and in the renal tubule cells. The structural changes in the glomeruli involve almost all glomerular components and point to a reduction of the glomerular filtration rate. The purpose of this study was to investigate whether these changes are controlled by testosterone, indirectly or directly. In vivo experiments demonstrated that exposures of immature castrates for 8 days to methyltestosterone leads to activation of mesangial cells and podocytes, to slight expansion of mesangial matrix and slight thickening of basal lamina. Observations on cultured renal tissue showed that two androgens, 11-ketotestosterone and methyltestosterone, are also able to stimulate the secretory activity of podocytes and mesangial cells in vitro. The results therefore indicate, that most glomerular changes in male sticklebacks during the reproductive season are directly effected by testosterone.

Animals↗

PubMed2006

[Study on the association between hantavirus infection and Rattus norvegicus].

OBJECTIVE: To further understand the association of hantavirus (HV) harbored and transmitted in wild brown rats. METHODS: Rattus norvegicus (n = 570) were trapped in 10 sites in Beijing. RT-PCR was used to test rodent lung samples for hantavirus infection. Unconditional multivariate logistic regression analysis was performed, with PCR positive as the dependent variable and the characteristics of Rattus norvegicus population as independent variables. RESULTS: The overall HV prevalence in Rattus norvegicus was 9.1% (52/570). Significant association between HV infection in Rattus norvegicus and some biological characteristics of host population was observed. Adult Rattus norvegicus had a higher HV prevalence than juveniles. Males in the reproduction periods and rats with wounds were more likely to be infected with HV than others. CONCLUSION: It was further confirmed that there existed parallel transmission of HV in Rattus norvegicus hosts. Aggression might be the primary mode of HV transmission among male Rattus norvegicus.

Aggression↗

PubMed1981

Reproduction and growth of progeny of female mice mated after treatment with crufomate.

Effects on reproduction and litter growth were studied for two successive reproductive periods (RP)--interval between caging females with males and whelping--in female mice treated dermally with crufomate at 100 or 50 mg/kg on days 35 and 21 before caging with untreated males. Each treatment with crufomate caused about 50% reversible inhibition of cholinesterase activity without inducing any signs of toxicity. The higher dose reduced the conception rate and the number of litters and young born and weaned during the two RPs. It also reduced the lactation index, weaning weight of males and females, and mature weight of males in the first litter. The lower dose prolonged the gestation period and reduced the lactation index and the number of litters and young weaned in the first RP and conception rate and number of litters and young born and weaned in the second RP. The lower dose reduced the weaning and mature weights of the first litter and mature weight of males in the second litter. The higher dose reduced the body weight and the lower dose increased the adrenal weight of the treated females.

Adrenal Glands↗

PubMed1994

Is corticosterone involved in the reproductive processes of the male lizard, Podarcis sicula sicula?

Corticosterone (B) and testosterone (T) plasma levels and the effects of short (1-48 min) and long (6-192 hr) confinement stress during the various phases of the reproductive period of the male lizard, Podarcis sicula sicula, were studied; in addition, the in vitro effects of B on the T secretion by testis and adrenals were evaluated. Plasma B was highest during the mating phase and plasma T was highest during the aggressive phase. Confinement stress caused an increase of B plasma levels within 12 min of capture and a decrease in plasma T within 48 min of capture; B increase and T decrease continued for 48 hr, but, after 192 hr of confinement, the levels of these two steroids became similar to those found a few minutes after capture. The basal release of T by the tests and of B and T by adrenals mirrored the trends seen in the systemic circulation. In in vitro experiments B treatment decreased T by testis and adrenal tissue release in aggressive and mating phases. These data suggest that B could involved in the reproduction of P. s. sicula by acting on T synthesis to reduce aggressive behavior and allow breeding.

Aggression↗

PubMed1994

Relationships among GnRH, substance P, prostaglandins, sex steroids and aromatase activity in the brain of the male lizard Podarcis sicula sicula during reproduction.

The release of PGF2 alpha and PGE2, progesterone, androgens and oestradiol in vitro, and the aromatase activity in the brain of the male lizard Podarcis sicula sicula during three different phases of the reproductive period were evaluated. In addition, the effects of salmon GnRH, substance P, salmon GnRH antagonist, substance P antagonist, PGF2 alpha, PGE2 and acetylsalicylic acid on the release of prostaglandins and sex steroids and on aromatase activity in the brain were evaluated during the same three phases. PGF2 alpha, oestradiol and aromatase activity were higher during the refractory phase, androgens during the fighting phase, and progesterone during the mating phase, while PGE2 was lower during the refractory phase. Treatment with salmon GnRH increased PGF2 alpha, oestradiol and aromatase activity, but decreased the amount of androgens released. Substance P decreased PGF2 alpha, oestradiol and aromatase activity, but increased the amount of androgens released. PGF2 alpha increased oestradiol and aromatase activity, but decreased the amount of androgens released. Acetylsalicylic acid decreased PGF2 alpha, oestradiol and aromatase activity, but increased the amount of androgens released. These data suggest that salmon GnRH and substance P have different roles in reproductive processes, with opposite mechanisms, in the central nervous system of this male lizard: salmon GnRH seems to be involved in regulating the refractory phase, while substance P plays a role in regulating the fighting phase.

Androgens↗

PubMed2000

Hormonal correlates of reproductive seasonality in wild female hanuman langurs (Presbytis entellus).

To date, it is not known whether the seasonal occurrence of sexual behavior and mating in free-ranging Hanuman langurs at Ramnagar, Nepal, is correlated with seasonal changes in female ovarian function, and, if so, which factor(s) triggers the onset of the reproductive period. Using noninvasive fecal hormone analysis in combination with behavioral observations, this study was carried out to: 1) investigate and characterize seasonal patterns of ovarian cyclicity and timing of conception in wild langur females living in a highly seasonal habitat; and 2) examine the relationship between seasonal patterns of ovarian cyclicity, behavioral estrus, and female physical condition. Behavioral data and fecal samples were collected during a total period of 14 months from nine females living in a multi-male group. Physical condition of the females was assessed monthly by visual inspection, using a seven-fold scale. Ovulatory cycles and timing of conceptions were identified by the measurement of immunoreactive pregnanediol glucuronide (iPdG) in extracted feces. Hormone profiles in individual females revealed a clearly seasonal distribution in the occurrence of ovulatory cycles, which were restricted to the period from July to October. The distribution of female estrus behavior showed a similar seasonal pattern, and in total 88.2% of all estrus periods observed in the focal females were accompanied by ovulation. Onset of ovarian cycles as well as mating activities were strongly correlated with the onset of the rainy season. Females conceived, on average, in their second ovulatory cycle (pregnancy length: 211.6 +/- 3.4 days), with timing of conception being confined to the months when animals showed an improved physical condition. Collectively the present data clearly suggest that in seasonally-breeding langurs at Ramnagar, ecological conditions (rainfall, food availability, and quality) influence the onset of ovulations and timing of conceptions.

Animals↗

PubMed2000

Inhibin in the testis and adrenal gland of the male lacertid, Podarcis sicula Raf.: a light immunocytochemical study.

Inhibin is a glycoproteic hormone mostly produced by the gonads. Through a feedback at the pituitary level, it selectively inhibits the release of follicle-stimulating hormone. In mammals, inhibin has been found also in some extragonadal tissues such as placenta, pituitary, adrenal, spleen, kidney, brain and spinal cord. At present, no information is available about the existence of inhibin in reptiles. The aim of the present work is to localise, through immunocytochemical methods, the sites of inhibin production in male lizards during the main phases of the reproductive cycle: the culmination phase (April-June), the early regressive phase (early July), the maximal regressive phase (August) and the winter stasis (January). In the testis, immunostaining is mainly localised in the Leydig cells during the early regressive phase, while it is observed in the Sertoli cells during the maximal regressive phase. In the epididymis, the immunostaining is present only during the reproductive period at the level of secreting cells and inside its ducts. In the adrenal gland, after immunostaining, both chromaffin and steroidogenetic tissues are inhibin-positive during the whole spermatogenetic cycle, though with variable intensity throughout the year: cross-reaction appears more evident from January to April (winter stasis and culmination phase) and weaker in June. However, in captive animals, the reaction persists in chromaffin cells, but disappears in steroidogenetic cells. The functional meaning of the presence of inhibin as a factor in the local regulation of spermatogenesis is discussed.

Adrenal Glands↗

PubMed1998

Epidemiological aspects of centipede (Scolopendromorphae: Chilopoda) bites registered in greater S. Paulo, SP, Brazil.

INTRODUCTION: The lack of basic knowledge on venomous arthropods and the benignity of the clinical manifestations contribute to the centipede bite victims' not being taken to a treatment reference center, leading to underestimation of the number of cases and minimizing the possibility of a broader epidemiological view. An inventory of the centipede bite occurrences in Greater S. Paulo, Brazil, and the therapeutic methods employed, by the main Brazilian medical center for the notification of poisoning by venomous animals, is presented. METHOD: All patient cards of the period 1980-1989 have been checked as to place, month and time of occurrence; sex, age, affected part of the body, signs and symptoms have been observed, as well as the therapeutic methods employed. The centipedes that caused the accidents were identified at the Arthropods Laboratory. RESULTS: It was registered 216 accidents, with a 69% predominance of the Greater S. Paulo and in only 63% of the cases (136) was the agent brought in by the victim for identification. The genera most frequently represented were Cryptops (58%), Otostigmus (33%) and Scolopendra (4%). Of the 136 cases, 87% showed erythema, edema, hemorrhage, burns, cephalalgia, and intense pain. There was a predominance of accidents in the warm rainy season, in the morning and for females between 21 and 60 years of age. Hands and feet were the parts of the body most affected. The benign evolution of the clinical picture (54%) made therapeutical treatment unnecessary. Only the victims of Scolopendra and Otostigmus (46%) were medicated with anesthetics (51%), analgesics (25%), antihistamines and cortisone (24%). CONCLUSION: The reproductive period of the centipedes, associated with their sinanthropic habits, contributes to the greater incidence of accidents in urban areas in the warm rainy season. Only patients bitten by Scolopendra and Otostigmus require therapeutical treatment.

Adult↗

PubMed1991

Reproductive cycle and heavy metals in the organs of red mullet, Mullus barbatus (L.), from the northwestern Mediterranean.

Concentrations of the heavy metals Cd, Cu, Fe Mn, V and Zn have been measured in the principal tissues of the red mullet, Mullus barbatus (L.), during a complete sexual cycle. By comparison of metal levels during the reproductive and non-reproductive periods, it was found that concentrations as well as total amounts of Cu, Mn and Zn in liver and gonads of male and female mullets were dependent upon the stage of the sexual cycle. No relationship with the sexual cycle was noted for these metals measured in muscle, kidney, spleen or pyloric caecum. Because of the observed variation in liver and gonad metal concentrations, these tissues appear to be poor indicators of ambient levels of metals in the surrounding waters. However, muscle may prove useful as an indicator tissue owing to its apparent independence of effects of the sexual cycle.

Animals↗