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Results for “Fecundability”

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At least 631 records · Page 35Linked to original sources
PubMed1993

Sexual maturation and seasonal changes in plasma levels of sex steroids and fecundity of wild Norway rats selected for reduced aggressiveness toward humans.

Parameters of sexual maturation and reproductive function were compared in two groups of Norway rats, one selected for reduced aggressiveness towards man and the other for aggressiveness. It was found that selection for reduced aggressiveness produced an acceleration of sexual maturation as judged by earlier vaginal opening in the female and presence of mature spermatozoa in the testes of the male as well by earlier prepubertal increase in plasma testosterone in the male. In domesticated adults, seasonal variations in the parameters of the reproductive function narrowed; they showed neither the winter decrease in sexual activity nor the marked fall in plasma testosterone and estradiol exhibited by their aggressive counterparts.

Aggression↗
PubMed1985

Lifetime breeding studies in fully fed and dietary restricted female CFY Sprague-Dawley rats. 1. Effect of age, housing conditions and diet on fecundity.

The capacity of female CFY Sprague-Dawley rats to bear multiple litters when breeding was commenced at increasing ages was assessed under the following conditions: continuous housing with male (GC), intermittent breeding of group (GI) and individually housed (I) fully fed animals, restriction of food intake (DR), refeeding of dietary restricted rats (DRA). The percentage of females pregnant, number of litters produced and total litter size were assessed. The number of litters or percent pregnant was unaffected by individual housing but there was a significantly greater decline in total litter size with increasing age of mother when compared to (GI) rats. The slope of the regression line in (I) was identical to that for (GC) females and may reflect the burden of continuous breeding or the stress of individual housing. Both litter size and overall fertility were decreased by dietary restriction but these females did retain their capacity to breed as late as 937 days in contrast to 720 days for any group of fully fed animals. There was no decline in litter size with increasing age in (DR). Returning (DR) rats to full feeding resulted in a rate of decline in litter size identical to that for (GI). All groups of (DRA) produced a maximum of three litters, commencement of breeding at 750 days resulting in production of a litter as late as 952 days.

Aging↗
PubMed1995

Dietary calorie restriction in the Emory mouse: effects on lifespan, eye lens cataract prevalence and progression, levels of ascorbate, glutathione, glucose, and glycohemoglobin, tail collagen breaktime, DNA and RNA oxidation, skin integrity, fecundity, and cancer.

The Emory mouse is the best model for age-related cataract. In this work we compare the effects of feeding a control diet (C) with a diet restricted (R) by 40% relative to C animals. In the R animals, median lifespan was extended by 40%. The proportion of R mice with advanced cataract was lower than C mice as early as 5 months of age. The mean grade of cataract was lower in R animals, beginning at 11 months and continuing until the end of the study. Ascorbate levels in R plasma and liver were 41-56% of C animals. There was no difference between diet groups with respect to lens ascorbate. Aging was associated with a decrease in ascorbate in lenses and kidneys in C and R mice. By 22 months, R animals had 48% higher liver glutathione levels than C mice. Liver glutathione levels were maximal at 12 months. Plasma glucose levels were > 27% lower in R animals at 6.5 and 22 months, and there was a 14% increase in glucose levels upon aging for both diet groups. In R mice, glycohemoglobin levels were 51% lower and tail collagen breaktime was decreased by 40%, even in younger animals. Collagen breaktime increased > 360% upon aging for both diet groups. Rates of production of urinary oxo8dG and oxo8G were higher in R animals compared with C animals, and increased upon aging. C animals exhibited more cancer and dermatological lesions, but less tail tip necrosis and inflamed genitals than R mice. These data allow evaluation of several theories of aging.

Animals↗
PubMed1992

Superovulation of a low fecundity sheep breed using a porcine gonadotrophin extract with a defined LH content (Pluset).

The aim of this study was to determine the efficiency of a porcine pituitary gonadotrophin extract with a defined pLH content in the superovulation of sheep. Estrus was synchronized in 61 Polish Mountain ewes with intravaginal fluorogestone acetate sponges. Twenty-four hours before the sponges were removed, the ewes underwent different superovulatory treatments: Group I 250 IU of pFSH with 250 IU of pLH (n=19); Group II 500 IU of pFSH with 500 IU of pLH (n=19); and Group III 750 IU of pFSH and 750 IU of pLH (n=18). Gonadotrophine was administered intramuscularly twice a day over a 3-day period in decreasing dosages. A control group of ewes (n=5) was treated with saline. In most of the ewes estrus began about 20 hours after sponges were removed. All the ewes were bred naturally every 12 hours. Superovulation was confirmed in 75% of the treated animals. The ewes receiving 250 IU each of pFSH and pLH produced an average of 7.6 +/- 3.1 corpora lutea (CL), 6.3 +/- 2.4 ova and 4.3 +/- 4.1 transferable embryos. Group II (500 IU of pFSH and pLH) produced 8.5 +/- 4.0 CL, 7.6 +/- 4.1 ova, and 4.1 +/- 2.9 transferable embryos. Group III (750 IU each of pFSH and pLH) produced 8.3 +/- 5.2 CL, 7.5 +/- 5.5 ova and 5.2 +/- 5.1 transferable embryos. The mean embryo recovery rate was 87% for all three groups. Differences in superovulatory response and embryo recovery rate among the groups were not statistically significant (P>0.05).

Journal Article↗
PubMed1991

High fecundity of amenorrhoeic women in embryo-transfer programmes.

There is uncertainty over whether the steady decline in human fertility with increasing maternal age is due to quality of the oocyte or of the endometrium. To clarify the issue age-related implantation and pregnancy rates in two embryo-transfer programmes were examined in relation to embryo quality and type of menstrual cycle. In both the UK and the US programmes rates were higher in previously amenorrhoeic (acyclic) women than in eugonadal women, irrespective of age and number of embryos replaced. Oocyte quality, as determined by age of oocyte donor, in-vitro growth of embryo, and proportion of defective embryos in culture, did not contribute to the difference, nor did type of cycle during therapy. If a uterus that has not been subjected to regular menstrual cycles is a favourable factor, a period of induced amenorrhoea might be beneficial for infertile women.

Amenorrhea↗
PubMed1983

Reduced fecundity of vitamin D deficient rats.

1. Female rats fed on a vitamin D deplete (D-) diet for 90 days prior to mating gave birth to litters having significantly fewer young than females fed a diet containing vitamin D (2.2 IU/g, D + diet). 2. Neither age nor body weight of females had a significant influence on litter size. 3. Serum calcium and phosphorus levels in D+ and D- dams were not significantly different, nor were serum calcium and phosphorus levels and bone ash of D+ and D- weanlings. 4. The level of 25-hydroxyvitamin D3 [25(OH)D3], the main circulating form of vitamin D, was low in D- dams and was not detected in D- weanlings. 5. These data suggest that vitamin D is required for reproduction in the rat.

Animals↗
PubMed1991

The agonist (d-leu-6,des-gly-10)-LHRH-ethylamide does not protect the fecundity of rats exposed to high dose unilateral ovarian irradiation.

Attempts to protect the ovary from the toxic effects of radiation and chemotherapy are relevant to the management of the young patient with cancer. Previous studies in a variety of animal species with several types of agonists of GnRH have shown promise in affording gonadal protection using indirect indices of reproductive function. The current investigations are based on these observations. Female rats were treated with (d-leu-6,des-gly-10) LHRH-ethylamide (GnRHa) from day 22 to day 37 of life. Sham-irradiation or unilateral irradiation of the left ovary was performed on day 30. The animals were mated following resumption of cycles and sacrificed on day 21 of pregnancy. There was no significant effect of ovarian artery ligation. Radiation reduced ovarian function ipsilateral to the radiation. GnRHa alone did not affect reproductive performance significantly. GnRHa and radiation combined resulted in no reproductive protection but augmented the damage done to the ipsilateral ovarian weight and to numbers of corpora lutea and fetuses. Under these experimental circumstances the agonist provided no protection.

Animals↗
PubMed2004

Fecundity genes in sheep.

Since 1980 there has been increasing interest in the identification and utilisation of major genes for prolificacy in sheep. Mutations that increase ovulation rate have been discovered in the BMPR-1B, BMP15 and GDF9 genes, and others are known to exist from the expressed inheritance patterns although the mutations have not yet been located. In the case of BMP15, four different mutations have been discovered but each produces the same phenotype. The modes of inheritance of the different prolificacy genes include autosomal dominant genes with additive effects on ovulation rate (BMPR-1B; Lacaune), autosomal over-dominant genes with infertility in homozygous females (GDF9), X-linked over-dominant genes with infertility in homozygous females (BMP15), and X-linked maternally imprinted genes (FecX2). The size of the effect of one copy of a mutation on ovulation rate ranges from an extra 0.4 ovulations per oestrus for the FecX2 mutation to an extra 1.5 ovulations per oestrus for the BMPR-1B mutation. DNA tests enable some of these mutations to be used in genetic improvement programmes based on marker assisted selection.

Animals↗