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Results for “Reproductive Period”

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At least 307 records · Page 17Linked to original sources

PubMed1989

Estradiol receptor in the lizard liver (Podarcis s. sicula). Seasonal changes and estradiol and growth hormone dependence.

This study shows that in the liver of the oviparous lizard, Podarcis s. sicula, the estrogen receptor (ER) level increases during the reproductive period (spring) when vitellogenesis occurs. This phenomenon interested both unfilled and filled ER present in the cytosolic and nuclear fractions. The increase in unfilled cytosolic and filled nuclear receptor was positively correlated to the plasma level of vitellogenin. The level of liver ER approximated that of mammalian liver ER and, therefore, it is higher than that reported for the liver of several nonmammalian species. At electrofocusing, liver ER distributes in two pH ranges (pH 6.5-7.5 and 8.0-8.8, respectively). The first form predominated in nuclei of reproductive females or of spayed estrogenized females and could represent the activated form of receptor. Ovariectomy was followed by a decrease in liver ER which can be induced in spayed females by estradiol administration. Pituitary growth hormone (GH) seemed to exert a synergic effect on estradiol liver estrogen receptor regulation. In lizards treated both with estradiol and GH, in fact, there was a significant increase in nuclear filled ER rather than an increase in the level of total nuclear ER.

Animals↗

PubMedDate not supplied

Evidence for a circadian oscillation in the gonadal response of the tropical weaver bird (Ploceus philippinus) to programmed photoperiod.

The effect of an asymmetrical skeleton photoperiod scheduleee was studied on the gonadal development in a tropical finch, the weaver bird (Ploceus philippinus). The schedul comprised a short nonstimulatory primary photoperiod of 6 hrs and a secondary much shorter lightperiod given as a 15-min light pulse at different times in the dark period. The light pulse 11 hrs after the basic period resulted in gonadal stimulation, while light pulse in contimuation with the basic period or 8, 14 or 21 hrs after the basicperiod was not stimulatory. The "photoinducible phase" was much more precisely outlined by shifting the birds from an 8-h to a 10-h pulse, and from an 11-h to 12-h pulse and was found to be very short, lasting about an hour falling between 11 and 12 hrs after the primary light period. The short photoinducible phase may be of an adaptive value since in the tropics the difference between the shortest and the longest daylength is also rather small (3 hrs and 15 min at Varanasi, 25degrees N). Clearly the weaver bird possesses a fine time-measuring device involving an endogenous circadian rhythm in photosensitivity. In nature, spermatogenesis in this bird also begins in March when the daylength exceeds 11 hrs (thus perhaps coinciding with the photoinducible phase). In rather small, photoperiod may not serve as a cue to trigger seasonal reproductive periodicity, it seems that photoperiod can act as a Zeitgeber for the initiation of spermatogenesis in the weaver bird at least.

Animals↗

PubMed2001

[Fish larvae association in a Mexican Caribbean bay].

Interannual ichthyoplankton variation, was analyzed in Bahía de la Ascensión, Mexico, during December of four consecutive years (1994-1997). A total of 32 families, 35 genera and 21 species of fish larvae were identified. The most abundant fish larvae were the Gobiidae followed by the Callionymidae, Clupeidae and Tetraodontidae. Larval diversity was low when compared with other periods ("dry" and "rainy"). Three spatial associations (internal, medium and external) were found in December 1994 and 1995. In 1996-1997, stations of the inner and outer parts of the bay were mixed. The dominant families characterized most of the faunal associations. Egg density was highest in the external zone of the bay, whereas larvae were most abundant in the inner area. Major factors affecting the fish larval assemblages during December (1994-1997) in Bahía de la Ascensión seem to be related to the nursery areas location and to the tropical fishes reproductive period.

Animals↗

PubMed1978

[Plasma proteins in young and adult Spermestes c. cucculatus (Swainson) (Aves - Ploceidae - Estrildinae)].

The blood plasma of Spermestes c. cucullatus (Swainson) analysed electrophoretically on agar shows seven fractions. Immunoelectrophoresis against an antispermestes rabbit serum reveals 16 fractions. Individual variation of the plasma protein fractions is very low, as is also the case for the mobility of the fractions. With age, the alpha-globulins disappear gradually. In the newly hatched bird, the protein variations are more pronounced than in adults. Most important are the lower relative content of albumin and a corresponding relatively higher content of beta- and gamma-globulins. There seems to exist a slight sexual dimorphism in albumin level, which is higher in males than in females. During the reproduction period, both sexes show a fall of the relative concentration of albumin. Injections of gonadotropine hormone produce an increase of the plasma-proteins level and a marked decrease of the relative concentration of albumin. The overall figure is comparable with that of birds in natural breeding condition.

Aging↗

PubMed2001

The effect of litter size before weaning on subsequent body development, feed intake, and reproductive performance of young rabbit does.

An experiment was performed to study the effect of litter size before weaning on subsequent body development and composition, feed intake, and reproductive performance of young rabbit does with the objective to improve reproductive performance. Litter size (LS) before weaning (treatment) was 6, 9, or 12 kits. After weaning (30 d), 58 female kits per treatment (in two successive replicates) were reared and fed for ad libitum intake to 14.5 wk of age (end of rearing). At 14.5 wk of age, receptive does were inseminated. Nonreceptive and nonpregnant does were inseminated at 17.5 wk of age. The experiment ended when the second litter was weaned. Part of the animals was slaughtered to determine body composition at the end of the experiment (replicate one) and at the end of rearing (replicate two). At weaning, BW differed among treatments (P < 0.05; 855, 773, and 664 +/- 15 g for LS6, 9, and 12, respectively). Compensatory growth was observed. At the end of rearing, LS12 does were smaller (P < 0.05) than LS9 and LS6 does (3,524, 3,778, and 3,850 +/- 48 g, respectively). After first lactation, no difference in BW among treatments was found. Compared with LS6, empty body weight (BW minus gut, bladder, and uterus content) of LS12 contained more (P < 0.05) nitrogen (32.5 vs 31.1 +/- 0.3 g/kg), more (P < 0.05) ash (30.7 vs 28.3 +/- 0.6 g/kg), and less (P < 0.05) fat (168.6 vs 200.2 +/- 8.6 g/kg). No differences in body composition among treatments were found at the end of the experiment. During rearing, LS12 had the lowest (P < 0.05) daily feed intake (152, 164, and 169 +/- 2 g/d for LS12, 9, and 6, respectively). During the reproductive period, no differences in feed intake among treatments were found. Kindling rate (the number of kindlings per number of inseminations) was not influenced by treatment. In the first parity, total litter size (number of alive and stillborn kits) was lower (P < 0.10) for LS12 than for LS9 (6.4 vs 8.6 +/- 0.5, respectively). When first mating was delayed by 3 wk, an increased (P < 0.05) total litter size was found regardless of treatment (7.5 and 9.4 +/- 0.3 for 14.5, and 17.5 wk, respectively). Decreasing litter size before weaning from nine to six kits did not alter future reproductive performance. Based on results of this study, it seems advisable to perform a limited standardization level (at nine kits) after kindling and postpone first mating to an older age (17.5 wk) to improve reproductive performance.

Animal Husbandry↗

PubMed2005

Impact of oilseed rape expressing the insecticidal serine protease inhibitor, mustard trypsin inhibitor-2 on the beneficial predator Pterostichus madidus.

Abstract Insect-resistant transgenic plants have been suggested to have deleterious effects on beneficial predators feeding on crop pests, through transmission of the transgene product by the pest to the predator. To test this hypothesis, effects of oilseed rape expressing the serine protease inhibitor, mustard trypsin inhibitor -2 (MTI-2), on the predatory ground beetle Pterostichus madidus were investigated, using diamondback moth, Plutella xylostella as the intermediary pest species. As expected, oilseed rape expressing MTI-2 had a deleterious effect on the development and survival of the pest. However, incomplete pest mortality resulted in survivors being available to predators at the next trophic level, and inhibition studies confirmed the presence of biologically active transgene product in pest larvae. Characterization of proteolytic digestive enzymes of P. madidus demonstrated that adults utilize serine proteases with trypsin-like and chymotrypsin-like specificities; the former activity was completely inhibited by MTI-2 in vitro. When P. madidus consumed prey reared on MTI-2 expressing plants over the reproductive period in their life cycle, no significant effects upon survival were observed as a result of exposure to the inhibitor. However, there was a short-term significant inhibition of weight gain in female beetles fed unlimited prey containing MTI-2, with a concomitant reduction of prey consumption. Biochemical analyses showed that the inhibitory effects of MTI-2 delivered via prey on gut proteolysis in the carabid decreased with time of exposure, possibly resulting from up-regulation of inhibitor-insensitive proteases. Of ecological significance, consumption of MTI-2 dosed prey had no detrimental effects on reproductive fitness of adult P. madidus.

Animals↗

PubMedDate not supplied

A laboratory study on the possible use of Helisoma duryi in the biological control of Bulinus africanus, intermediate host of Schistosoma haematobium.

In order to evaluate the possible use of Helisoma duryi as biological competitor of Bulinus africanus, life-tables were compiled for these two snail species maintained either in the presence of each other, or separately. Population parameters were calculated from these life-tables and it was found that H. duryi had a higher innate capacity of increase, net reproduction rate and growth rate as well as a longer lifespan and reproductive period than Bu. africanus. Furthermore, the biological potential of Bu. africanus was found to be adversely affected in the presence of H. duryi. It was concluded that the latter might be capable of replacing Bu. africanus in certain freshwater habitats and that field trials ought to be undertaken in South Africa.

Animals↗

PubMed2005

Reproductive biology of Astyanax janeiroensis (Osteichthyes, Characidae) from the Ubatiba river, Maricá, RJ, Brazil.

Aspects of the reproductive biology of Astyanax janeiroensis in the Ubatiba river in Maricá, RJ, Brazil were evaluated in order to ascertain whether the strategy adopted by the species is causally related to environmental variables. Specimens were collected on a monthly basis from October 1994 to September 1995, through electrofishing. The Sex ratio was not significantly different from the expected frequency of 1:1 (G = 1.29; p > 0.50); nonetheless, considering three standard length classes, significantly larger numbers of females were recorded for the higher SL class (G = 11.07; p < 0.01). Size at first maturation showed no significant differences between sexes. Length-weight ratio analyses showed negative allometry for males and isometry, for females. Length structure was significantly different between sexes, suggesting that females are larger than males (D = 0.027, p < 0.01). Reproductive specimens were recorded during nine months of the annual cycle. Seasonal variations of reproductive specimens belonging to two different standard length classes displayed an asynchronous behavior, with larger specimens having a longer reproductive period and smaller ones reproducing for fewer months during the annual cycle. High values of fecundity (F), varying from 3169 to 18714 oocytes, were recorded for fish of 9.1 and 10.2 cm lengths, respectively. The correlation between weight and number of oocytes/unit of weight was positive, indicating that larger specimens produced more eggs.

Animals↗

PubMed2004

Genetic and demographic structure in a population of Ctenomys lami (Rodentia-Ctenomyidae).

The variability at eight microsatellite loci was analyzed in 88 individuals of Ctenomys lami, a species of tuco-tucos. Initially considered as three subpopulations, the estimated Fst values ranged from 0.0007 to 0.0589. Additionally, a Bayesian approach presented probabilities of 0.9933 for the existence of only one population. A Fis value of 0.19 could indicate an incipient structure. Sexual dimorphism was observed. The reproductive period was short and a seasonal pattern was observed with sex ratio of 1:1 during all seasons. Presence of recent bottleneck is described suggesting further research in this population to assess more complete and detailed data.

Age Distribution↗

PubMed2002

Demographic responses of the polychaete Dinophilus gyrociliatus to chromium exposure.

The effects of chromium on the life history and demography of Dinophilus gyrociliatus (Polychaeta) were studied on a control and three treated cohorts kept in artificial seawater enriched with nominal concentrations of chromium at 1.0, 1.4, and 1.6 microg/ml. Survival and fecundity were significantly reduced by chromium. Fecundity was higher in the chromium treatments than in the control group at the beginning of the reproductive period; however, overall, the highest fecundity was observed in the control. Life expectancy, net growth rate, and generation time were also significantly reduced by chromium. The population growth rate (lambda) was higher in the treated animals than in the controls. The differences in lambda between the treated animals and the controls (deltalambda) were almost completely due to the differences in the life tables observed during the first three weeks of life. The differences in survival between the treated and control animals did not contribute to deltalambda. The contribution to deltalambda of the slight increase in age-specific fecundity in the early reproductive events compensated for the marked decrease in overall fecundity in the treated animals. The complex effects of chromium enrichment on D. gyrociliatus underline the importance of analyzing both individual and population responses when assessing the effects of pollutants on organisms. Our results confirm that D. gyrociliatus might serve as an indicator species in confined areas of polluted seawater such as lagoons and harbors.

Age Factors↗

PubMed1993

Effects of tamoxifen and CV 205502 on the morphology and the evolution of the noncancerous mouse mammary gland.

Tamoxifen (TAM, 0.01 mg/animal, three times a week) and the experimental prolactin-lowering CV 205502 (CV, 1 microgram/animal, daily) were administered prophylactically, alone or combined, to virgin C3H/Sy mice during the early period of promotion in this spontaneous mammary carcinogenesis system (end of 2nd-5th month of age), in order to study their influence on the morphology and evolution of the noncancerous mammary gland during therapy and after treatment cessation. During TAM administration the epithelial cells of the growing part of the gland exhibited myoepithelial- and, late in the treatment period, apoptotic-like features instead of the secretory ones expected, accompanied by intense basement membrane alterations, thickening of the surrounding connective tissue and arrested adipocyte maturation. These effects reversed progressively after drug withdrawal. The epithelial alterations were more intense and longer lasting in the TAM+CV-group, while growth arrest of the glands was observed in both groups parallel to the degree and the duration of these morphological changes. In these groups, tumor incidence was diminished, as expected, but the tumors that developed late after treatment cessation were of low histological differentiation. The above morphological observations show that TAM inhibits noncancerous mammary gland growth during the reproductive period by altering stromal and epithelial differentiation, effects that reverse progressively after treatment discontinuation and are potentiated by a prolactin-lowering agent in this animal study.

Adipocytes↗

PubMed2000

Experimental study of suspension-feeding activity in the serpulid polychaete Ditrupa arietina (O.F. Müller).

As time spent feeding can be an index of the feeding intensity, we attempted to describe the filtering activity in the suspension-feeding polychaete Ditrupa arietina. This description was based on the detection of the opening of the gill-crown by an automated image analysis system. The common pattern of activity could be described as the succession of filtering events and resting periods of which the number and the mean duration differed greatly from one worm to another. Filtering activity in D. arietina was neither a continuous process nor even a process having a particular rhythm. Within a same batch of worms, total filtration durations could represent between 12.5 and 87.5% of the total experimental time. Despite a strong inter-individual variability, our results showed the existence of pronounced seasonal variations in the activity of the gill-crown. In May, worms spent less than 25% of time feeding compared to more than 50% during the rest of year. These temporal changes appeared to result from the physiological state of the worms (reproductive period and ageing) at the time of the experiment.

Journal Article↗

PubMed1993

Induced abortion among the Pati Rabha women of Boko area, Kamrup district, Assam.

"Acceptance of induced abortion as a device of family planning among the Pati Rabha of Boko area [India] was studied. Out of 345 couples, practising various family planning devices, 86 (24.93%) accepted induced abortion. Of the total 629 conceptions of these 86 women, 137 (21.78%) conceptions were terminated by induced abortion.... The highest percentage (18.24%) of the induced abortion was done at the 6th order of pregnancy, 62.79% of the women accepted the induced abortion only once in their reproductive period. Most (91.86%) of the acceptors were illiterate and all of them were house wives." Consideration is given to the use of traditional methods of inducing abortions.

Abortion, Induced↗

PubMed1985

Incidence of a circadian cycle of photosensitivity in the regulation of the annual testis cycle in the mink: a short-day mammal.

Like the birds or long-day mammals studied up until now the photoregulation of the annual testicular cycle in the mink, a short-day mammal, depends on phase relationships existing between the daily cycle of alternating period of light-dark and the circadian cycle of photosensitivity. Our results show, however, that the characteristics of photoresponse in the mink are exactly the opposite of those of long-day animal species. For long-day species light has a stimulating effect on the central machinery of gonadotropic control (LH-RH) whereas in the mink, the secretion of gonadotropins is induced by short days. Interpreted according to this hypothesis, the sexual cycle of the mink under natural photoperiodic conditions is also explained by seasonal gonadotropic stimulation beginning after the autumn equinox when in our latitudes daily light duration is less than 12 hr. However, the end of the reproduction period which, in nature, seems to be the result of the inhibition of the gonadotropic function by long days could, in fact, be the result of a more complex mechanism. Different inhibiting mechanisms already shown in long-day animals could also be involved during this phase of the sexual cycle in the mink.

Animals↗

PubMed2004

The implications of body fat mass and fat distribution for cognitive function in elderly women.

OBJECTIVE: To investigate how body fat mass, an established source of endogenous estrogen after menopause, influences cognitive impairment in elderly women. RESEARCH METHODS AND PROCEDURES: Study participants were 5607 generally healthy postmenopausal women with mean age of 63.8 years at baseline followed for an average of 7.3 years. Cognitive function assessed at follow-up using the short Blessed test was related to baseline body weight, the yearly change in weight, and follow-up measures of body fat depots assessed by DXA. Cognitive function was also related to various surrogates of lifetime estrogen exposure. RESULTS: Women with the worst cognitive performance (score >or= 9) at follow-up were the ones who lost the most body weight and revealed the lowest central fat mass (CFM). The association of weight loss with worse cognitive performance was apparent across all age groups except for those more than 80 years old. In the multivariate logistic model, the risk of cognitive impairment was 18% lower in women in the second quartile of CFM (p = 0.14), 32% lower in the third (p = 0.01), and 48% lower in the fourth (p < 0.001) compared with those in the first quartile. CFM showed significant correlation with the simultaneously measured serum estradiol (r = 0.25; p < 0.001). Cognitive score showed an inverse linear relationship with the duration of reproductive period and bone mineral density assessed at follow-up. DISCUSSION: These findings argue for a protective association of body fat mass with cognitive impairment in elderly women. This association seems to involve a more prominent exposure to endogenous estrogens.

Adipose Tissue↗

PubMedDate not supplied

[The role of riboflavin and pantothenic acid in the reproductive function of swine].

Results of the experiment have shown that in order to increase multiple pregnancy and quality of piglets the ration of sows during pubescence and in the reproductive period must contain not less than 5-6 mg of riboflavin and 20-22 mg of pantothenic acid per one feed unit. That level can be ensured either by addition of synthetic preparation of riboflavin (4-4.5 mg) and calcium d-pantothenate (10-15 mg), or by inclusion of about 5% of the fodder yeast mass into complete-ration combined feed.

Animal Nutritional Physiological Phenomena↗

PubMed1996

[The ultrastructural characteristics of olfactory receptor cells with different levels of sensitivity].

Structural and functional properties of the animals olfactory analyzer were studied on different stages of their life. Attention was drawn to defining the correlations between the ultrastructure of primary sensory cells, their sensitivity and realization of adaptive behavior in fish in diverse reproductive period stages. Structural organization in fish olfactory cells appearing during spawning aim both to activate these cells to provide specific receptor function during intercourse and to urgently abolish it when transitioning to paternal behaviour. Not only central mechanisms of nervous system but also reorganizations of peripheral chemoreceptive apparatus are of great importance, which is demonstrated for the first time.

Animals↗

PubMed1996

Fat body of the frog Rana esculenta: an ultrastructural study.

In the frog, the fat body is the largest body lipid deposit and is associated with the gonad. The aim of the present work was to investigate the fine structure of the fat body at different periods of the annual cycle and during prolonged starvation. Results indicate that fat body cells of Rana esculenta caught in autumn and after winter hibernation resemble mammalian adipocytes of white adipose tissue and contain markers of adipose tissue, such as S-100 protein and lipoproteinlipase. However, unlike mammalian adipocytes, fat body adipocytes consistently show small lipid droplets associated with their single, large lipid deposits, a lack of a definite external lamina, and the presence of cellular prolongations and spicula at their surfaces. Transmission and scanning electron microscopy in association with lanthanum tracer experiments suggest that in fat body adipocytes a vesicular-tubular system connects the cytoplasm and the interstitial space. In June (i.e., during the reproductive period), fat body adipocytes appear to have lost much of their lipid deposit and adjacent adipocytes show interdigitation of their plasma membranes and prominent Golgi complexes. In starved frogs, fat body cells can be almost devoid of lipid and in regression to a near-mesenchymal state. Nevertheless, these fat bodies still contain lipoproteinlipase activity (approximately 45% of that found in lipid-filled ones), indicating persistent adipose differentiation of the cells therein. Results presented here show that the R. esculenta fat body is an adipose organ undergoing reversible extreme changes in adipocyte fat content, which are associated with definite ultrastructural features. The fat body represents a suitable model for studying adipose tissue under different and extreme physiological conditions.

Adipocytes↗