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At least 901 records · Page 50Linked to original sources
PubMed1991

Follicle-stimulating hormone pulse amplitude decreases with the onset of the breeding season in the mare.

The relationship between daily mean FSH concentrations in serum and the pattern of FSH detected by frequent sampling for 12-h periods (samples every 15 min) was examined in five mares during the transition into the breeding season. The five mature anestrous mares were exposed to a natural increase in daylength. Blood samples were collected daily from February 1 until the first ovulation of the breeding season (April 14 +/- 3.7 days, Mean +/- SEM). Periods of frequent blood collection were performed every two weeks. Blood samples were obtained daily by jugular venipuncture or jugular cannula (frequent samples). Mean daily concentrations of FSH in serum determined by RIA decreased during seasonal transition. Patterns of FSH in serum detected by frequent sampling were pulsatile. FSH pulse amplitude decreased during seasonal transition, and the decrease in amplitude was associated with the decrease in mean serum FSH concentrations. This decrease in FSH pulse amplitude may reflect an involvement of a follicular product from developing follicles or a change in hypothalamic stimulation of pituitary FSH release.

Activity Cycles↗
PubMed1995

Diagnosing senescence: inferring evolutionary causes from phenotypic patterns can be misleading.

Based on the predictions of two theories for the evolution of senescence, the 'antagonistic pleiotropy' and the 'mutation accumulation' theory, an age-specific increase in mortality and a decrease in fecundity are widely used criteria to diagnose senescence in natural, and laboratory populations. In this study we question the reliability of these criteria. Using a simple model we show that similar phenotypic patterns result from optimal life histories without senescence. With a tradeoff between reproduction and period survival, optimal life histories produce patterns of increasing mortality and decreasing fecundity as organisms age, even if the tradeoff does not deteriorate with age, so that we are not forced to invoke genetic effects such as antagonistic pleiotropy or accumulation of deleterious mutations to explain such patterns. Furthermore, if optimal life history theory is applied to senescent organisms, phenotypic patterns can result that are usually not associated with senescence. We conclude that the reliability of a diagnosis of senescence based on phenotypic patterns and the comprehension of the phenomenon senescence depends critically on understanding to what extent tradeoffs are determined by the effects of segregating genes.

Aging↗
PubMed2004

Large-scale geographical variation confirms that climate change causes birds to lay earlier.

Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long-term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.

Animals↗
PubMed2006

Blind population genetics survey of tropical rainforest trees.

Rainforest tree species can be difficult to identify outside of their period of reproduction. Vascular tissues from Carapa spp. individuals were collected during a short field trip in French Guiana and analysed in the laboratory with nuclear and chloroplast markers. Using a Bayesian approach, > 90% of the samples could be assigned to one of two distinct clusters corresponding to previously described species, making it possible to estimate the genetic structure of each species and to identify cases of introgression. We argue that this blind procedure represents a first-choice rather than a fallback option whenever related taxa are investigated.

Bayes Theorem↗
PubMedDate not supplied

The influence of LH and/or FSH on Leydig and Sertoli cell morphology after testicular involution in the Djungarian hamster, Phodopus sungorus, induced by hypophysectomy or short photoperiods.

In the Djungarian hamster, Phodopus sungorus, the morphological alterations of Sertoli and Leydig cells were investigated under the influence of gonadotropins (LH and/or FSH) after testicular regression induced either by hypophysectomy or photoinhibition. Stimulation with LH or LH/FSH lead to a redifferentiation of morphological features of Leydig cells such as nuclear structure, smooth endoplasmic reticulum and size of cell and nucleus area within 7 days of hormone treatment. Similarly, stimulation with FSH or LH/FSH caused redifferentiation of Sertoli cell nuclear structure, rough endoplasmic reticulum and nuclear size within 7 days. Incomplete restoration of Leydig and Sertoli cell morphology was observed under FSH and LH treatment respectively. In both Leydig and Sertoli cells combined LH and FSH application resulted in an increased response in respect to morphological redifferentiation, possibly indicating paracrine regulatory mechanisms. In all groups treated an intact blood-testis barrier (BTB) was reestablished after a minimum of 7 days, indicating that the existence of the blood-testis barrier is not dependent on specific gonadotropin supply but on the developmental stage of the seminiferous epithelium. Sham-operated animals showed increased cell and nucleus area of Leydig cells in comparison to photostimulated animals. After testicular involution as well as after LH or FSH treatment there were no significant morphological differences between hypophysectomized and photoinhibited animals in respect to the documented ultrastructural and morphometrical characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Differences in bone mineral content and density between male and female budgerigars (Melopsittacus undulatus) during the non-reproductive season.

It is known that female birds increase medullary mineral stores in long bones shortly before egg laying. Here, we present results from two groups of budgerigars, in both of which females had significantly higher bone mineral contents and densities, as measured by peripheral quantitative computed tomography of the tibiotarsus, during a reproductively dormant period. The results could indicate that female birds can accumulate mineral stores outside of the breeding season.

Animals↗
PubMed2005

Male sexual function improves after ileal pouch anal anastomosis.

PURPOSE: Restorative Proctocolectomy and Ileal Pouch Anal Anastomosis has become the gold standard surgical therapy for the majority of patients with mucosal ulcerative colitis. However sexual functional disturbances after this procedure can be a concern for patients. Therefore the aim of this study was to determine the outcome of sexual-function related quality of life in male patients undergoing restorative proctocolectomy. METHODS: One hundred and twenty-two male patients who underwent restorative proctocolectomy with ileal pouch anal anastomosis between 1995 and 2000 were evaluated by the validated International Index of Erectile Function (IIEF) scoring instrument. This index scale examines sexual function in five categories. These are erectile function, orgasmic function, sexual desire, intercourse satisfaction and overall satisfaction. The IIEF instrument was administered after surgery and then scores before and after RP/IPAA were evaluated and compared. The significance of age at the time of the surgery, type of surgery, type of anastomotic technique (mucosectomy vs stapled) and septic complications on sexual functional outcome were also investigated. RESULTS: Mean age at the time of the surgery was 39.9 +/- 11.5 years. The mean follow-up period (time between pouch surgery and IIEF completed) was 3.6 +/- 1.8 years. There was statistically significant improvement in 4 of 5 categories of sexual function (erectile function, sexual desire, intercourse satisfaction, and overall satisfaction) where patients had improved scores after surgery compared to prior to surgery. The mean erectile function score increased pre to post surgery by 2.12 points (P = 0.02), which indicates better sexual results. Anastomotic technique and septic complication did not influence the results, however, older age had a negative impact on results. CONCLUSIONS: Despite some adverse sexual functions, male patients who undergo RP/IPAA for the surgical management of their colitis may preserve or improve their overall sexual functional outcome.

Adult↗
PubMed1994

The prevalence of polycystic ovaries on ultrasound scanning in a population of randomly selected women.

Polycystic ovaries (PCO) diagnosed by ultrasound have been commonly reported amongst healthy women. The study aimed to determine the prevalence of PCO in a population of women from the community, and to relate it to clinical and endocrinological data. Twelve hundred women chosen randomly from electoral rolls were invited to take part in the study. Two hundred and fifty five women (21%) who met eligibility criteria greed to participate and 183 women 916%) finally completed the study. Seventy two women did not attend. An ultrasound scan and blood tests were taken on day 5-9 of their menstrual cycles. Data about their menstrual periods and reproductive history was collected. The prevalence of PCO was 21% (39 of 183). No differences existed between women with PCO and normal ovaries with respect to uterine size, body mass index, luteinizing hormone levels, serum hormone binding globulin levels and fertility status. Hirsutism (Ferriman Gallwey score > 7), elevated testosterone levels and irregular menstrual cycles were significantly more frequent amongst women with PCO. Mean ovarian volume was larger in women with PCO irrespective of the use of hormonal contraception. Fifty nine per cent of women with PCO had irregular menstrual cycles or elevated Ferriman Gallwey scores or both. There was no detectable effect of PCO on parity or miscarriage although only 70% of women with PCO had evidence of an adequate ovulation compared to 95% of women with normal ovaries.

Female↗
PubMedDate not supplied

Identification of a seasonal elevation in daytime melatonin levels associated with the rut in fallow bucks (Dama dama): the effect of day length and exogenous melatonin.

The timing of the seasonal reduction in voluntary food intake and hormonal changes associated with the rut were investigated in mature fallow bucks subjected to artificial long-day exposure with and without superimposed melatonin-releasing implants. Circulating testosterone profiles and the period of inappetence, signalling the onset of the period of reproductive activity in untreated bucks under natural photoperiod, were phase-advanced in both treatment groups. In the long-day treated group, these profiles were phase-advanced by 1 week, while in the long-day + melatonin group, the phase advance was 6 weeks compared to the controls. Circulating daytime melatonin, elevated in all three groups, corresponds with seasonal changes in circulating testosterone levels associated with the rut. Prolactin profiles followed ambient photoperiod, being high during natural or artificial long days and low during natural short days. Exogenous melatonin administered during long-day exposure initiated a rapid and reversible decrease in circulating prolactin levels. The elevation in plasma melatonin could not be separated temporally from the seasonal testosterone peak by exposure to long days or to exogenous melatonin. However, this daytime melatonin profile was abolished by the ablation of circulating testosterone following immunization against luteinizing hormone releasing hormone (LHRH). The presence of this endogenous melatonin during daylight was observed only during the rut, as measured in two radioimmunoassays and confirmed by mass spectrometry. It is likely that both testosterone and melatonin influence the onset of the seasonal rut in fallow bucks.

Animals↗
PubMedDate not supplied

Variability and comparison of hyporheic water temperatures and seepage fluxes in a small Atlantic salmon stream.

Ground water discharge is often a significant factor in the quality of fish spawning and rearing habitat and for highly biologically productive streams. In the present study, water temperatures (stream and hyporheic) and seepage fluxes were used to characterize shallow ground water discharge and recharge within thestreambed of Catamaran Brook, a small Atlantic salmon (Salmo salar) stream in central New Brunswick, Canada. Three study sites were instrumented using a total of 10 temperature sensors and 18 seepage meters. Highly variable mean seepage fluxes, ranging from 1.7 x 10(-4) to 2.5 cm3 m(-2) sec(-1), and mean hyporheic water temperatures, ranging from 10.5 degrees to 18.0 degrees C, at depths of 20 to 30 cm in the streambed were dependent on streambed location (left versus right stream bank and site location) and time during the summer sampling season. Temperature data were usefulfor determining if an area of the streambed was under discharge (positive flux), recharge (negative flux), or parallel flow (no flux) conditions and seepage meters were used to directly measure the quantity of water flux. Hyporheic water temperature measurements and specific conductance measurements of the seepage meter sample water, mean values ranging from 68.8 to 157.9 microS/cm, provided additional data for determining flux sources. Three stream banks were consistently under discharge conditions, while the other three stream banks showed reversal from discharge to recharge conditions over the sampling season. Results indicate that the majority of the water collected in the seepage meters was composed of surface water. The data obtained suggests that even though a positive seepage flux is often interpreted as ground water discharge, this discharging water may be of stream water origin that has recently entered the hyporheic zone.The measurement of seepage flux in conjunction with hyporheic water temperature or other indicators of water origin should be considered when attempting to quantify the magnitude of exchange and the source of hyporheic water.

Animals↗
PubMed1984

Women, labour and fertility: population growth in nineteenth century Java.

The sharp increase in Java's population after 1830 is usually explained in terms of higher living standards and consequent lower mortality resulting from Dutch colonization, but there is little historical evidence supporting such an interpretation and much to refute it. An alternative view is that Java's population growth after 1830 was due to increasing fertility. The major constraint to Javanese fertility prior to this period has been extended periods of postpartum abstinence, the length of which was determined by the duration of breastfeeding, because people believed semen had deleterious effects on breast milk. In 1830 a system of forced cultivation of export crops was imposed by the Dutch rulers and greatly increased the amount of labor which Javanese households required to reproduce themselves. The arduous work women began to undertake made it increasingly difficult to breastfeed their children. As the average period of breastfeeding fell, the average period of postpartum abstinence declined and fertility increased.

Agriculture↗
PubMed1972

Circadian involvement in termination of the refractory period in two sparrows.

Endogenous daily rhythmicity is involved in the short-day photoperiodic response of breaking the refractory period in both white-crowned and golden-crowned sparrows. Under a modified "coincidence model," short-day photoperiodic induction occurs when light is noncoincident with a specific phase of an internal rhythm.

Animals↗