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PubMed2001

Antifertility effects of estradiol in adult male rats.

The dose-related effects of estradiol 17-beta at the doses 0.1 pg, 10 microg, 100 microg, 200 microg, 300 microg, 400 microg, 1,000 microg/kg/day were determined on sperm motility, potency, fertility parameters, serum levels of LH, FSH, PRL and testosterone, weights of testes and accessory sex organs, weights of pituitary and adrenal glands. The drug was administered daily via sc route for a period of 60 days. Dose-related effects on fertility parameters of the estradiol-treated male rats were ascertained by allowing them to mate with normal cycling female rats. Estradiol at 0.1 microg/kg/day dose significantly reduced sperm motility with no effects seen on potency or fecundity, serum LH, FSH, PRL or testosterone, weights of testes and accessory sex organs while pituitary weight increased. Estradiol at 10 microg/kg/day dose significantly reduced motility, serum LH, FSH, weights of testes and accessory sex organs, while pituitary weight increased with no effects seen on potency, fecundity, PRL or testosterone. Estradiol at 100-1,000 microg/kg/day dose significantly reduced motility, potency and fecundity, serum LH, FSH and testosterone, weights of testes and accessory sex organs while serum PRL and the weights of pituitary and adrenal glands increased significantly. Histology of the testes revealed disorganization of the cytoarchitecture in the seminiferous tubules, vacuolation, absence of lumen and compartmentalization of spermatogenesis. Estradiol withdrawal, testosterone propionate at 100 pg/kg/day or antiestrogen (tamoxifen citrate) at 400 microg/kg/day prevented the histological changes. It is conduded that estradiol reduces sperm motility even at a low dose. Low doses (<10 microg/kg/ day) appear to maintain whilst high doses (>10 microg/kg/day) reversibly disrupt spermatogenesis. Prevention of disruption by testosterone or antiestrogen indicates crosstalk between androgen and estrogen receptors in Sertoli cells. Loss of potency and fecundity also suggests effects on crosstalk between these receptors in other male reproductive organs.

Animals↗
PubMed2005

Cross protection studies with Eimeria maxima strains.

The purpose of this study was to determine whether differences in fecundity of Eimeria maxima isolates were related to their abilities to elicit cross-protective immunity. Immunizations were initiated by low-dose gavages of sporulated oocysts to day-old broiler chicks under conditions that allowed parasite recycling, and chickens were challenged with homologous and heterologous strains. Immunization efficacies were measured using a protective index calculated from weight gain, gross lesion score, plasma carotenoid, and NO2- + NO3- data. A 4x4 cross- immunization study of four E. maxima strains (designated A-D) showed that strain A, which displayed the lower fecundity, provided no cross-protection against the other three strains. Following several maintenance passages, the fecundity of strain A was increased to that of strain C, and infection with strain A oocysts was able to provide cross-immune protection against challenge with strain C. This study indicates that parasite fecundity is important in providing good immune stimulation, and should be carefully monitored when characterization of the unique immune potentials of Eimeria strains is undertaken.

Animals↗
PubMed2005

Ecological implications of parasites in natural Daphnia populations.

In natural host populations, parasitism is considered to be omnipresent and to play an important role in shaping host life history and population dynamics. Here, we study parasitism in natural populations of the zooplankton host Daphnia magna investigating their individual and population level effects during a 2-year field study. Our results revealed a rich and highly prevalent community of parasites, with eight endoparasite species (four microsporidia, one amoeba, two bacteria and one nematode) and six epibionts (belonging to five different taxa: Chlorophyta, Bacillariophyceae, Ciliata, Fungi and Rotifera). Several of the endoparasites were associated with a severe overall fecundity reduction of the hosts, while such effects were not seen for epibionts. In particular, infections by Pasteuria ramosa, White Fat Cell Disease and Flabelliforma magnivora were strongly associated with a reduction in overall D. magna fecundity. Across the sampling period, average population fecundity of D. magna was negatively associated with overall infection intensity and total endoparasite richness. Population density of D. magna was negatively correlated to overall endoparasite prevalence and positively correlated with epibiont richness. Finally, the reduction in host fecundity caused by different parasite species was negatively correlated to both parasite prevalence and the length of the time period during which the parasite persisted in the host population. Consistent with epidemiological models, these results indicate that parasite mediated host damages influence the population dynamics of both hosts and parasites.

Animals↗
PubMed1992

Therapeutic donor insemination: a prospective randomized trial of fresh versus frozen sperm.

OBJECTIVE: We evaluated the efficacy of fresh versus frozen sperm in therapeutic donor insemination. STUDY DESIGN: Fifty-seven women underwent 72 courses of treatment (a maximum of six therapeutic donor insemination cycles--three fresh and three frozen) totaling 198 cycles. Each woman served as her own control and was prospectively randomized to receive a single, timed insemination of either fresh or frozen sperm. RESULTS: Fecundity was 20.6% for fresh sperm cycles and 9.4% for frozen (p less than 0.03, by chi 2 analysis). Fresh cervical cap insemination fecundity was 20.3%; frozen was 7.8% (p less than 0.03, by chi 2 analysis). Fresh intrauterine insemination fecundity was 21.2%; frozen was 15.8% (p = 0.63, by chi 2 analysis). Fresh 3-month life-table pregnancy rates were 48% +/- 10%; frozen rates were 22% +/- 8% (p = 0.05 by Breslow analysis). Survival analysis with fixed covariates showed a positive association with the use of fresh sperm (p = 0.04). CONCLUSION: Cycle fecundity was significantly greater with fresh sperm in women undergoing cervical cap insemination or intrauterine insemination and in women undergoing only cervical cap insemination. These results have important implications for contemporary management of patients undergoing therapeutic donor insemination with frozen sperm.

Adult↗
PubMed1992

Trichinella spiralis: dose dependence and kinetics of the mucosal immune response in mice.

The role of the mucosal immune response in helminth infections is not clear. In this study, the dose dependence and kinetics of the mucosal immune response to Trichinella spiralis were determined in experimentally infected Swiss Webster and BALB/c mice. The primary mucosal isotype was sIgA, although IgG was also detected, and primary infections with 10 and 150 larvae produced an anamnestic response on challenge. The mucosal and systemic immunoglobulin responses were dose dependent in both primary and challenge infections. The fecundity and length of worms and the rate of expulsion from the gut were determined on Day 6 postchallenge in Swiss Webster mice. Adult worm recovery and fecundity were reduced by greater than 50% and worm length by 28% in mice infected and challenged with 10 larvae and by 90, 85, and 35%, respectively, in mice infected and challenged with 150 larvae. The rate of expulsion was correlated with the size of both primary and challenge doses and a reduction in fecundity was correlated with the size of the primary dose only. The reduction in worm length did not differ significantly between the infection doses, but the trend was similar to that for expulsion. In BALB/c mice the expulsion response was dissociated from a reduction in fecundity and worm length, the latter two being positively correlated with sIgA levels, supporting a role for sIgA and/or IgG in these effects. However, expulsion does not appear to be dependent on the mucosal immunoglobulin response.

Animals↗
PubMed1985

Hookworm burdens and faecal egg counts: an analysis of the biological basis of variation.

The relationships between various measures of faecal egg output and hookworm burdens were investigated in 84 villagers from West Bengal with mixed Necator americanus and Ancylostoma duodenale infections. The pattern of day to day variability in egg counts from individuals can be characterized by the linear relationship between the logarithms of the variances and means. Egg output is shown to be non-periodic in long runs of day-to-day records. The distribution of worm numbers per host is well described by the negative binomial probability model, and the relationship between per capita egg output and worm burden is non-linear where egg output declines as parasite burden rises. Density-dependent effects on fecundity are shown to act at comparatively low worm burdens in relation to the range of observed parasite loads. Egg output measures are shown to be qualitative as opposed to quantitative measures of worm burdens as a consequence of inherent sampling heterogeneity and variability induced by biological processes, such as density-dependent depression of parasite fecundity. The analyses suggest that it is possible, on the basis of egg counts, to discriminate between individuals with low and high hookworm burdens. The intrinsic per capita fecundities of the two species of hookworms are shown to be similar, but density-dependent constraints on egg production by N. americanus appear to be more severe than those acting on A. duodenale. This observation may help explain why A. duodenale appears to produce larger numbers of eggs per unit of time than N. americanus. The regulatory role of density-dependent fecundity and aggregated distributions of worm numbers per person are discussed in relation to the over-all transmission dynamics of hookworm parasites.

Adolescent↗
PubMed2006

Health disparities and infertility: impacts of state-level insurance mandates.

OBJECTIVE: To determine whether important racial, ethnic, or socioeconomic status (SES) health disparities exist in infertility, impaired fecundity, or infertility treatment. DESIGN: Four waves of the National Survey of Family Growth (NSFG) were pooled. Measures were compared across various race/ethnicity, education, and age groups. PARTICIPANT(S): Data for 31,047 women 15-44 years old from the NSFG were pooled. INTERVENTION(S): Outcomes were compared by whether the women's states of residence had a mandate in place (at least 1 year before the interview) to compel insurers to cover or offer to cover infertility treatment. MAIN OUTCOME MEASURE(S): Infertility status, impaired fecundity, ever having sought infertility treatment. RESULT(S): Infertility is more common for non-Hispanic black women, non-Hispanic other race women, and Hispanic women than for non-Hispanic white women, and both infertility and impaired fecundity are more common for high school dropouts and high school graduates with no college than for 4-year college graduates, and for older women compared with women 29 and younger. Older women, non-Hispanic white women, and women who are more educated (with at least some college) are more likely to have ever received treatment. No evidence has been found that the racial, ethnic, or education disparities are ameliorated by the health insurance mandates. CONCLUSION(S): Racial, ethnic, and educational disparities exist in infertility status and treatment, and educational disparities in impaired fecundity. More study of the impact of infertility treatment mandates on these disparities is needed.

Adolescent↗
PubMed2005

Extinction in relation to demographic and environmental stochasticity in age-structured models.

The demographic variance of an age-structured population is defined. This parameter is further split into components generated by demographic stochasticity in each vital rate. The applicability of these parameters are investigated by checking how an age-structured population process can be approximated by a diffusion with only three parameters. These are the deterministic growth rate computed from the expected projection matrix and the environmental and demographic variances. We also consider age-structured populations where the fecundity at any stage is either zero or one, and there is neither environmental stochasticity nor dependence between individual fecundity and survival. In this case the demographic variance is uniquely determined by the vital rates defining the projection matrix. The demographic variance for a long-lived bird species, the wandering albatross in the southwestern part of the Indian Ocean, is estimated. We also compute estimates of the age-specific contributions to the total demographic variance from survival, fecundity and the covariance between survival and fecundity.

Age Factors↗
PubMed2000

The influence of self-fertilization and pairing on life-history traits in the freshwater snail Bulinus forskalii (Gastropoda, planorbidae).

This study analyses the basic reproductive biology of the schistosonie-vector snail Bulinus forskalli. This hermaphroditic species can self-fertilize. Variation of the mating system was analysed in two populations from Cameroon in a three-step experiment. (i) The fecundity (number of eggs and of egg capsules) of isolated virgin individuals from both populations was followed over a month, as well as the survival of offspring from these individuals. Estimates of these parameters were intermediate. Our results also indicate that inbreeding depression has a maximum value of about one-half in both populations. No difference was observed between populations for both the overall fecundity of adults and survival of offspring. (ii) Individuals were then paired either within, or between populations over three successive days, and the number of copulations recorded. Copulations were observed in all situations, including between-population pairs. No significant dlifference in the number of copulations per pair was detected. However, this value decreased with time, and reciprocal copulations were significantly less numerous between than within populations. (iii) Individuals that successfully copulated as female in (ii) were isolated, and their fecundity was followed over 3 weeks. The fecundity of individuals that had been maintained isolated over the whole experiment served as a control. No significant difference was on the whole detected. Our results collectively suggest that the individuals from the two populations studied are rather selfers, confirming that B. forskalii is a preferentially selfing species. There is also some pre-zygotic isolation against crosses between populations.

Animals↗
PubMed1992

Superovulation with human menopausal gonadotropins in the treatment of infertility associated with minimal or mild endometriosis: a controlled randomized study.

OBJECTIVE: To determine the efficacy of superovulation with buserelin acetate, human menopausal gonadotropins (hMG), and human chorionic gonadotropin (hCG) in the treatment of infertility associated with minimal or mild endometriosis. DESIGN: Prospective, randomized, controlled study. SUBJECTS: Forty-nine infertile women with a laparoscopic diagnosis of endometriosis stage I (n = 29) or II (n = 20) according to the revised American Fertility Society classification, randomly assigned to three superovulation cycles (n = 24) or 6 months' expectant management (n = 25). MAIN OUTCOME MEASURES: Cycle fecundity rates and cumulative pregnancy rates (CPR) in the two groups. RESULTS: Nine pregnancies were obtained in the superovulation-treated patients and six in the nontreated ones. The cycle fecundity rates and CPR were 0.15% and 37.4% after three superovulation cycles and 0.045% and 24% after 6 months of expectant management (P less than 0.05 and P = not significant, respectively). The women who did not achieve a pregnancy after three cycles of superovulation were followed for a total of 50 months during which no therapy was given. One pregnancy started in this period (cycle fecundity rate = 0.020). One spontaneous abortion occurred in each group. Three treated patients had multiple pregnancies, and four had ovarian hyperstimulation syndrome. CONCLUSION: Superovulation seems to be associated with a better cycle fecundity rate but not a better CPR than expectant management in infertile women with endometriosis stages I and II. The efficacy and side effects of this therapeutic approach should be evaluated in larger series.

Adult↗
PubMed2000

Predicting amphipods' brood size variation in brackish environments: an empirical model for Corophium multisetosum Stock, 1952 (Corophiidae) in Ria de Aveiro (NW Portugal).

Data on fecundity of Corophium multisetosum from Areão (Ria de Aveiro, Portugal) are analysed by non linear regression to quantify the relationship between brood size (N(e)) and head length (L(h), in mm), water temperature (T, in degrees Celsius) and salinity (S, in psu). The aim of the analysis is to obtain a simple line N(e)=a+bL(h), in which the slope (b) and the y intercept (a) are functions of salinity and/or temperature on each sampling occasion. The equation N(e)=(-2.940-8.027S)+(-89.431+18.171S+12.904T-0.368T(2))L(h) explains 64% of the variability of brood size throughout the breeding period. The model predicts an optimal temperature around 18 degrees C and a very low fecundity at low salinities. The graphical comparison of the lines obtained by the model and by a usual linear regression illustrates its potential usefulness to predict fecundity changes. The authors suggest that the observed variation in the fecundity of other brackish-water amphipods can be described and predicted using similar models.

Journal Article↗
PubMed2000

Effect of periodical starvation on the life history of Brachionus plicatilis O.F. Müller (Rotifera): a possible strategy for population stability.

To estimate the changes in the life history of the rotifer Brachionus plicatilis O.F. Müller under starvation, we carried out an individual culture and determined the effects of periodical food deprivation on its asexual reproductive characteristics such as lifespan, reproductive period, age at first egg and offspring production, and lifetime fecundity (total number of offspring produced in her lifetime). Rotifers were fed for 1-3 h daily, and were then starved until the next day. Control animals were fed throughout their lifespan. Starved rotifers matured and produced their first offspring at an older age than the control animals. The periodical starvation resulted in a decrease in the lifetime fecundity to less than half that of the non-starved control. The reproductive period and lifespan were 2-3 times longer in the starved animals than in the control animals. The negative relationship between lifespan and lifetime fecundity is interpreted as a trade-off in an alternative life-history strategy of rotifers under starved conditions. The great decrease in fecundity and extension of lifespan enables rotifers to compensate to keep the population in equilibrium.

Journal Article↗
PubMed2001

New evidence of the copepod maternal food effects on reproduction.

Failure of female reproductive capacity in the copepod Calanus helgolandicus was related to number and combination of the phytoplankton species in the diets. The maternal food effects were detectable at different levels: fecundity, oogenesis and hatching. Fecundity and hatching were normal with two single (ca. Isochrysis galbana and Prorocentrum minimum) and one mixed (Phaeodactylum tricornutum+Dunaliella tertiolecta+Pavlova lutherii+I. galbana+P. minimum) diets. With the single P. lutherii diet, fecundity decreased, but hatching remained optimal. The daily egg production and hatching rates decreased significantly in females fed the other single P. tricornutum, D. tertiolecta and mixed (P. tricornutum+D. tertiolecta+P. lutherii+I. galbana) diets, or starved. The fecundity decrease coincided with gonad atresia, which was reversible when P. tricornutum and P. lutherii diets were replaced by P. minimum diet. It was irreversible when D. tertiolecta was replaced by P. minimum, leading to female sterilization expressed by the deterioration of OS3 and OS2 oocytes, as a function of the feeding duration. We assume that atresia of female gonads was caused by the limitation of essential nutrients in food, such as fatty acids, which induced catabolism and recycling of yolk reserves and thus, maintenance of gonad integrity and low spawning rates. With the D. tertiolecta diet, abnormally high increase of ornithine concentrations in eggs showed that the ornithine metabolism and polyamine pathway were affected during oogenesis, leading atresia of oocytes to be deeply disturbed and followed up by necrosis of the gonads.

Journal Article↗
PubMed2003

Effects of zinc exposure on the polychaete Dinophilus gyrociliatus: a life-table response experiment.

A life-table response experiment (LTRE) was performed in order to study the effects of enhanced zinc on the survival, fecundity and demographic indices of Dinophilus gyrociliatus (Polychaeta). A control group and three treated cohorts kept in artificial seawater enriched with nominal concentrations of zinc at 0.25, 0.50 and 1.00 microg Zn/ml, respectively, were considered. Zinc marginally affected survival but had a strong impact on the reproduction of D. gyrociliatus. Zinc enrichment had no effect on age at maturity, whereas it induced a slight increase in fecundity during the early reproductive phases at 0.50 and 1.00 microg Zn/ml, and a sharp decrease in fecundity from the 20th day of life at all levels of metal enrichment tested. Treated groups were characterised by a marked reduction of the net growth rate (R0) and a decrease in generation time (T) with respect to the control groups, but no effect on life expectancy (e0) or on population growth rates (lambda) was observed. R0 and lambda, which are the most commonly used indices of fitness, were not equally susceptible to zinc. Lambda appears less sensitive to stress induced by metal enrichment with respect to R0 and other life history traits like age-specific fecundity. D. gyrociliatus appears to be an appropriate bioindicator species in LTRE to assess the consequences of environmental heavy metals on individual life-history and population dynamics.

Animals↗
PubMedDate not supplied

A follow-up study of male exposure to welding and time to pregnancy.

The aim of this study was to estimate whether male welding has an impact on couple fecundability (the probability of conceiving in a menstrual cycle). A sample of Danish couples without previous reproductive experience was recruited nationwide by postal letters to members of the union of metal workers and three other trade unions. Among 430 included couples, 201 males were metal workers and 130 were welders. The couples were followed for a maximum of six menstrual cycles from termination of birth control until a clinical pregnancy was detected. Compared with nonwelding metal workers the fecundability odds ratio (OR) of male exposure to welding was 0.86 (95% confidence interval [CI] 0.58-1.28). An interaction between male smoking and welding was found; within smokers the OR for welding was 0.40 (95% CI 0.17-0.95) and within nonsmokers it was 1.22 (95% CI 0.74-1.99). Previous welding exposure was negatively related to fecundability among smokers (OR 0.84 per year with mild steel welding, OR 0.76 per year with stainless steel welding). No significant results were found when comparing with an external group of nonmetal workers. Decreased fecundability among smoking welders attributable to both current and previous welding exposure is possible, but these findings were the results of subanalyses that were not part of the a priori hypothesis.

Adult↗
PubMed1981

Reversibility of the effects of the host immune response on the intestinal phase of Trichinella spiralis in the mouse, following transplantation to a new host.

On day 10 of a primary infection of Trichinella spiralis in NIH mice, when adult worms were in the process of being expelled, their fecundity was markedly depressed. Upon transplantation to new host mice, the worms were able to establish successfully in their usual position in the anterior small intestine, even if originally recovered from the large intestine of mice expelling their worms, and these worms fully recovered their fecundity after 7 days in recipients. On day 5 of secondary and tertiary infections, immediately before loss of worms began, the adult worms were stunted and had a depressed fecundity. However, such worms, when transplanted, were able to establish in normal numbers and in a normal position in the intestine of recipient mice. Additionally, these worms were found to have developed a fecundity, and grown to a length, comparable to that of normal worms, but slightly less than that of control worms transplanted from day 7 of a primary infection, after 7 days in a new host. Electron microscopy showed that worms taken at the time of expulsion in primary and tertiary infections showed structural abnormalities, including large quantities of lipid in intestinal cells and somatic musculature and decreased quantities of stored glycogen. Upon transplantation to new host mice, these worms were found to have recovered a normal ultrastructural appearance within 7 days, although there was still evidence of a slightly elevated lipid and depressed glycogen content. It is concluded that immune expulsion of T. spiralis from mice does not involve irreversible damage to the worms.

Animals↗
PubMed1995

Energy restriction and severe zinc deficiency influence growth, survival and reproduction of Heligmosomoides polygyrus (Nematoda) during primary and challenge infections in mice.

The objectives of this study were (1) to determine the impact of severe zinc deficiency on the establishment, growth, survival and reproduction of Heligmosomoides polygyrus in the laboratory mouse, during both primary and challenge infection protocols, and (2) to determine whether the observed effects resulted from zinc deficiency per se, or from the accompanying energy restriction. Three diet groups were used: zinc-sufficient (Zn+:60 mg zinc/kg diet), zinc-deficient (Zn-:0.75 mg zinc/kg diet) and energy restricted (ER:60 mg zinc/kg diet pair fed to Zn- mice). Neither Zn- nor ER influenced the establishment of the parasite during a primary infection. However, both significantly influenced the early development of the parasite. The proportion of adult worms recovered 9 days post-infection (p.i.) was highest in Zn- mice, intermediate in ER mice and lowest in Zn+ mice. Worms were also distributed more distally in the intestine of the Zn- mice and worm survival was highest in Zn- mice, intermediate in ER mice and lowest in Zn+ mice at both 4 and 5 weeks p.i. Although the length of female worms was reduced in Zn- mice, neither per capita fecundity nor egg viability was affected by zinc deficiency. Energy restriction, on the other hand, significantly reduced worm fecundity at 5 weeks post-primary infection, but had no effect on egg viability. Zinc concentration of adult H. polygyrus was similar among dietary groups. The effects of zinc deficiency and energy restriction were also investigated 4 and 5 weeks after a challenge infection. Whereas strong host resistance was evident in Zn+ and ER mice, based on comparison of worm numbers between challenged mice and primary infection controls, no evidence of resistance was detected in Zn- mice. As in the primary infection, female worms were shorter in Zn- mice than in ER and Zn+ mice, and energy restriction but not zinc deficiency significantly affected per capita fecundity. However, in contrast to the primary infection, ER mice had elevated rather than reduced fecundity. This study demonstrates a complex interaction between H. polygyrus and zinc and energy restriction, and highlights the importance of controlling for reduced food intake in nutrition-infection studies.

Animals↗
PubMed2003

Oviposition model of overwintered adult Tetranychus urticae (Acari: Tetranychidae) and mite phenology on the ground cover in apple orchards.

The phenology of overwintered Tetranychus urticae was studied on the ground cover in apple orchards in the early season, and an oviposition model of overwintered adults was developed. The movement of overwintered adults from trees to ground cover started from mid-March and continued until mid-April. One life cycle from eggs to new adults (the 1st generation adults) on the ground cover was from late March to early May. The longevity and fecundity of overwintered T. urticae were affected largely by temperature. The longevity ranged from 46.6 days at 10 degrees C to 6.5 days at 35 degrees C. The total fecundity was minimum (0.2 eggs) at 10 degrees C and maximum (45.5 eggs) at 25 degrees C. The relationship between total fecundity and temperature was described well by a nonlinear equation. The cumulative age-specific oviposition rate was described well by the two-parameter Weibull function. The overall adult survival exhibited a reverse logistic curve. Three temperature-dependent components, age-specific cumulative oviposition rate, temperature-dependent total fecundity and age-specific survival rate functions, were incorporated into an oviposition model. The oviposition model simulation described the occurrence pattern of eggs laid by overwintered T. urticae on the ground cover in apple orchards relatively well.

Animals↗