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PubMed1998

Does moderate alcohol consumption affect fertility? Follow up study among couples planning first pregnancy.

OBJECTIVE: To examine the effect of alcohol consumption on the probability of conception. DESIGN: A follow up study over six menstrual cycles or until a clinically recognised pregnancy occurred after discontinuation of contraception. SUBJECTS: 430 Danish couples aged 20-35 years trying to conceive for the first time. MAIN OUTCOME MEASURES: Clinically recognised pregnancy. Fecundability odds ratio: odds of conception among exposed couples divided by odds among those not exposed. RESULTS: In the six cycles of follow up 64% (179) of women with a weekly alcohol intake of less than five drinks and 55% (75) of women with a higher intake conceived. After adjustment for cycle number, smoking in either partner or smoking exposure in utero, centre of enrolment, diseases in female reproductive organs, woman's body mass index, sperm concentration, and duration of menstrual cycle, the odds ratio decreased with increasing alcohol intake from 0.61 (95% confidence interval 0.40 to 0.93) among women consuming 1-5 drinks a week to 0.34 (0.22 to 0.52) among women consuming more than 10 drinks a week (P=0.03 for trend) compared with women with no alcohol intake. Among men no dose-response association was found after control for confounders including women's alcohol intake. CONCLUSION: A woman's alcohol intake is associated with decreased fecundability even among women with a weekly alcohol intake corresponding to five or fewer drinks. This finding needs further corroboration, but it seems reasonable to encourage women to avoid intake of alcohol when they are trying to become pregnant.

Adult↗
PubMed1994

On some stochastic models of open birth interval.

"In this paper, a set of two probability models have been derived to describe the variation in the length of open birth interval of women having given birth to a child during the last 'T' years of their current reproductive age. The first model is derived by assuming the reproduction process as steady-state, the second is obtained by varying the fecundability parameter involved in the first model after the last birth. These models are applied to the three sets of data, one collected from [the Indian] Varanasi-survey, 1969-70 and the other two generated from the data on age-specific fertility rates using the life table technique. The biological parameters such as fecundability and secondary sterility have been estimated using some simple procedure of estimation."

Asia↗
PubMed1993

Age and infertility in a micronesian atoll population.

The relationship between female age and infertility is examined using a single-island Micronesian population case. Demographic data, derived primarily from reproductive history interviews, show that a significant age-associated decline in marital reproductive performance is absent before women reach their late thirties in this population but a substantial decline is present once women reach their forties. Ethnographic data support the demographic inference that couples are maintaining relatively high levels of conjugal coital activity with both advancing female age and increasing marital duration. Thus coital activity levels appear to be an important factor in the maintenance of fertility in this group before the mid-thirties but decreases in fecundability after this age are due primarily to reductions in fecundity, not to declines in coital activity. The description of the Butaritari case lends support to Underwood's (1990) suggestion that a "Micronesian pattern" of reproductive performance may exist for the region's atoll-based populations and underscores the promise of further investigations of these special cases in the fields of demography and reproductive ecology.

Adolescent↗
PubMed1995

Proximate determinants of fertility in eastern Uttar Pradesh.

Our main objective here is to examine and discuss the effects of some sociocultural and economic factors on the proximate determinants of fertility in rural areas of eastern Uttar Pradesh (population more than 40 million persons). The region is known for its present demographic trends because the crude birth, death, and infant mortality rates are among the highest for India. The determinants considered are age at marriage of female, postpartum amenorrhea (PPA), fecundability and sterility, and menopause. The sociocultural and economic factors studied are caste, education, breast-feeding status, and social status of the currently married females in the reproductive age group. The study population is predominantly Hindu, among whom caste is a strong indicator of socioeconomic conditions. The average age of the female at return marriage (RM) is below 18 years in each religion or caste group but has been increasing over time. Median durations of breast feeding and PPA differ significantly among various socioeconomic and demographic subgroups. These are longest in scheduled castes and shortest in upper-caste Hindus. As the social status of the household increases, the median durations of breast feeding and PPA decrease. The estimates of fecundability consistently decrease with age, whereas those of sterility increase with age after 35 years. The smallest estimate of sterility is 4%, corresponding to the 25-30-year age group in each religion or caste group. Occurrence of menopause is rare before age 35, and it increases with the age of the female irrespective of religion or caste. However, the risk is minimum for females in upper castes and maximum for those in scheduled castes.

Adolescent↗
PubMed1980

Fat and fertility: demographic implications of differential fat storage.

Anthropologists interested in human nutrition have become intrigued by the possibility of a link between nutritional status, fat stores, and fertility. Frisch (1978) and Frisch and McArthur (1974) have hypothesized such a link, based on studies of body composition at menarche and menstrual dysfunction in anorectics. This review indicates that both over- and undernutrition may interfere with reproductive function, but probably do so only when extreme. Evidence for fat as a regulator of fecundity is conflicting and is best documented for age at puberty. Effects of fat on birth interval (a demographically more significant parameter) are confounded by the influence of lactation. A review of hormonal and metabolic patterns in obesity and inanation indicate similarities between these conditions and general or psychological stress. It is suggested that fat is better seen as an indicator of systemic function than as a single independent factor. The adaptive value of fat for human populations may lie in its ability to enhance work performance as much as in its influence on fecundity.

Age Factors↗
PubMed1989

Fertility change in Costa Rica 1960-84: analysis of retrospective lifetime reproductive histories.

Lifetime reproductive histories of a 1984-85 nationally representative sample of 870 women aged 25-59 years provided data to describe the evolution of fertility, contraception, breast-feeding, and natural fecundability in Costa Rica between 1960 and 1984. The contraceptive prevalence rate increased from 23% in 1965 to 58% in 1975 and 66% in 1984. Duration of breast-feeding was stable during the 1960s, decreased in the early 1970s, and increased after about 1976. Fecundability among women who did not practise contraception was lower than expected and declined between 1960 and 1975, probably because of selection effects. Despite a high consistency between estimations from the reproductive histories and other sources of data, some suggestion of omissions of short periods of contraceptive use in the distant past was detected. The survey may have reduced recall errors by using a calendar that summarizes major life events together. The analysis demonstrated the feasibility and usefulness of asking for lifetime reproductive histories in fertility surveys in developing countries.

Adult↗
PubMed1993

Seasonality of reproductive function and weight loss in rural Nepali women.

Menstrual and hormonal disturbances have been reported in thin, dieting and exercising Western women, and also recently in rural African women. A study of salivary progesterone profiles was undertaken in a Nepali population to examine whether seasonal increases in workload and changes in energy balance influenced ovarian function. Women's energy expenditure levels were moderately heavy in the winter and very heavy in the monsoon, and body mass fluctuated by -2.8 to +4.8 kg. Samples were collected from 24 normally menstruating women in two seasons, each individual serving as her own control. Progesterone levels were significantly depressed in the monsoon relative to winter for women who lost weight, but not for women who gained weight, indicating that energy imbalance is associated with a loss of fecundity. No differences in body mass index were found between women who lost or gained weight. Progesterone levels were age-dependent, and the degree of hormonal disturbance between age-groups was related to weight loss. The study demonstrates seasonal changes in the fecundity of hard-working Nepali women and a direct link between ovarian function and weight loss (negative energy balance), which is independent of current nutritional status.

Adolescent↗
PubMed2026

A horizontally transferred bacterial gene for pantothenic acid biosynthesis regulates diapause and reproduction in the spider mite Amphitetranychus viennensis.

Horizontal gene transfer (HGT) has contributed substantially to the evolution of arthropod genomes, yet the functional significance of many horizontally acquired genes remains poorly understood. The hawthorn spider mite, Amphitetranychus viennensis, is a devastating agricultural pest whose high fecundity and overwintering diapause afford its exceptional ecological resilience. Through a genome-wide screen, we identified 37 high-confidence horizontally transferred genes (HTGs) in A. viennensis. Among these candidates, we prioritized AvPBL, a gene encoding pantothenate-β-alanine ligase, for functional characterization because it controls the rate-limiting step of a distinctly non-metazoan pantothenic acid (vitamin B5) biosynthesis pathway. RNAi-mediated suppression of AvPBL significantly reduced transcript abundance and endogenous pantothenic acid levels, triggering a 23.7% reduction in cumulative fecundity and severely compromising the mites' ability to enter winter diapause. Importantly, exogenous pantothenic acid supplementation rescued these reproductive and diapause defects, directly linking the observed phenotypes to the disruption of pantothenic acid biosynthesis. Our results demonstrate that the horizontally transferred bacterial gene AvPBL has been functionally integrated into the endogenous metabolic network of A. viennensis, playing a critical role in vitamin B5 biosynthesis, reproduction, and diapause regulation. These findings provide direct evidence that horizontally acquired metabolic genes can shape key life-history traits and drive adaptive evolution in arthropods.

Amphitetranychus viennensis↗
PubMed1986

Fertility, infertility and generation replacement.

Throughout most of human history 'natural fertility' and life expectations of about 35 years kept population numbers reasonably balanced; but the achievement of life expectations of 75 or more years destroyed this 'natural' system. As longevity increased amongst Western peoples, explosive growth rates were only prevented by increasingly efficient checks on fertility. Today, these checks are so universal and so efficient in Australia and in many other Western countries that 'intrinsic' levels of fertility are below generation replacement level. Changes in fecundity were not a significant factor in this demographic revolution; at least 10-12% of couples remain without issue, but the prime cause of the change is the evolution of the two-child family, a process which now involves only about a sixth of a couple's fecund married life. For the rest of their years most couples are now voluntarily infertile. Correction of involuntary sterility is important to individual couples but has little significance in terms of generation replacement.

Adolescent↗
PubMed2000

Accounting for unreported and missing intercourse in human fertility studies.

In prospective studies of human fertility that attempt to identify days of ovulation, couples record each day whether they had intercourse. Depending on the design of the study, couples either (I) mark the dates of intercourse on a chart or (II) mark 'yes' or 'no' for each day of the menstrual cycle. If protocol I is used, intercourse dates that couples fail to record are indistinguishable from dates of no intercourse. Consequently, estimates of day-specific fecundability are biased upwards. If protocol II is used, data from menstrual cycles with missing intercourse information must be discarded in order to fit current fertility models. We propose methods to account for unreported and missing intercourse under the assumption that the missingness mechanism is independent of time conditional on the unobservable true intercourse status. We use probit mixture models to allow for heterogeneity among couples, both in fecundability and in the missingness and non-reporting mechanisms. Markov chain Monte Carlo (MCMC) techniques are used for Bayesian estimation. The methods are generally applicable to the analysis of aggregated Bernoulli outcomes when there is uncertainty in whether a given trial, out of a series of trials, was completed. We illustrate the methods by application to two prospective fertility studies. Published in 2000 by John Wiley & Sons, Ltd.

Algorithms↗
PubMed1999

Action and pharmacokinetics of a novel insect growth regulator, halofenozide, in adult beetles of aubeonymus mariaefranciscae and leptinotarsa decemlineata

Topical application of halofenozide on adults of the Colorado potato beetle (CPB), Leptinotarsa decemlineata, and Aubeonymus mariaefranciscae (AMF) exhibited its effects in a different way in the two coleopterans. In CPB, the fecundity was strongly affected, whereas the main effect in AMF was a drastic decrease of the progeny survival. The rate of penetration of labeled halofenozide through the cuticle followed a similar pattern in CPB and AMF, whereas the rate of excretion was much more rapid in AMF. The extremely slow excretion of the product in CPB suggested that this fact must contribute to the prolonged action of halofenozide on fecundity at its highest dose of 20 &mgr;g per adult. Retention of halofenozide in the reproductive system of males of AMF and CPB was low, whereas high levels of radioactivity were recovered in females (ovaries + eggs). Comparing females of both coleopterans, CBP retained a higher amount than AMF. Moreover, treated CPB adults showed a rapid cessation of oviposition due to distorted ovaries, detrimental oocyte growth, and loss of oviposition due to the fact that yolk protein synthesis and/or incorporation into eggs was reduced. In AMF, the development of the progeny was strongly affected, and more than 80% of first-instar larvae died after egg hatching in the first 25 days after the treatment, due to premature molting and inhibition of ecdysis. Cross sections of intoxicated first larval instars of AMF originating from adults that were topically treated with halofenozide showed the presence of a double cuticle and these larvae could not shed the old cuticle. Arch. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗
PubMed2003

Demographic and life-history patterns in a population of ring-tailed lemurs (Lemur catta) at Beza Mahafaly Reserve, Madagascar: a 15-year perspective.

Over 15 field seasons (1987-2001), we collected census and life-history data on a population of individually identified ring-tailed lemurs at the Beza Mahafaly Reserve, Madagascar. No significant difference was found in population size over the study period, though a marked decline in the population occurred following a 2-year drought. The population rebounded rapidly after the immediate postdrought period. There was nearly a complete replacement of individuals over the study period. Average group size is 11.5 animals, and adult male to female sex ratio is 0.92. Most females reproduce annually, and the average fecundity rate is 84.3%. The greatest variability in fecundity is found among old females. We suggest that ring-tailed lemur females follow an "income breeding" strategy, i.e., females use maximum resources during reproduction rather than relying on fat stores, as do "capital breeders." Infant mortality to 1 year of age in a nondrought year is 52%, higher than infant mortality in small to medium-sized anthropoids. The oldest known female was 18 years old in 2001. We suggest that 18-20 years may represent the maximum life-span for wild ring-tailed lemurs. Because males regularly emigrate from the population, we have no data regarding male life-span; however, there is some indication that males do not survive as long as females. Group fission has occurred three times: twice from one parent group living in the driest area of the reserve, with the most dispersed food resources. We suggest that the reproductive strategy that has evolved in this species, wherein females reproduce early in life and annually until old age, is a response to the unusual climate and environmental conditions under which Lemur catta has evolved.

Animals↗
PubMed2002

Effect on growth and reproduction of hormone immersed and masculinized fighting fish Betta splendens.

To produce all-male progenies in the fighting fish, Betta splendens, six groups of fry were subjected to discrete immersion treatment at different 17alpha-methyltestosterone (MT) doses (viz. 100, 200, 500, 700, 900, and 1,000 microg/l) for a constant duration (3 hr/day) and frequency (second, fifth, and eighth day after hatching). The treatment at 900 microg/l led to 98% masculinization and 71% survival at sexual maturity. Treated groups, which showed significant deviation from the 1:1 sex ratio, were classified into two different series: S1 and S2. The groups that showed nearly cent-percent masculinization were classified as S1, and the other groups were classified as S2. The S1 males showed remarkably slower growth and attained 3.5 cm total length compared to 6.0 cm attained by a normal male. The S2 males attained 5.4 cm total length. Apart from these morphological defects, both S1 and S2 males suffered functional (decreased sperm count and sperm motility) and behavioral defects (incomplete embracing during mating) in their reproductive ability, leading to approximately 50% and 30% reduction in fecundity per mating, respectively. The cumulative fecundity loss suffered by the S1 male during its active reproductive phase is discussed. When normal and sex-reversed males were presented, a female preferred the former. Progeny testing of the sex-reversed males showed the occurrence of 12.75% males, indicating the possible role of autosomal genes in the sex determination mechanism of this species. Discrete immersion treatment at optimal/super-optimal doses ensured not only a higher percentage of masculinization, but also a higher frequency of homogametic males (XX).

Animals↗
PubMed2006

Differential aphicidal effects of chitinase inhibitors on the polyphagous homopteran Myzus persicae (Sulzer).

Four chitinase inhibitors, cyclo-(Proline-Tyrosine), cyclo-(Histidine-Proline), allosamidin and psammaplin A, were selected for in vitro feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions. Artificial diets were used to provide chitinase inhibitors at 10, 50 and 100 microg mL(-1) to M. persicae. Except for cyclo-(Proline-Tyrosine), which did not modify aphid demographic parameters, chitinase inhibitors induced differential aphicidal effects on M. persicae. At all doses, cyclo-(Histidine-Proline) induced significant effects affecting daily fecundity, intrinsic rate of natural increase (r(m)) and doubling time of population. When compared with the control diet, allosamidin decreased nymph survival and daily fecundity, increasing the doubling time of population from 1 to 1.5 days. Psammaplin A was the most toxic inhibitor when delivered via artificial diet, as it induced the death of all aphids reared at 50 and 100 microg mL(-1). The results demonstrate the potential use of chitinase inhibitors as aphid management tools.

Acetylglucosamine↗
PubMed2001

Assessing human fertility using several markers of ovulation.

In modelling human fertility one ideally accounts for timing of intercourse relative to ovulation. Measurement error in identifying the day of ovulation can bias estimates of fecundability parameters and attenuate estimates of covariate effects. In the absence of a single perfect marker of ovulation, several error prone markers are sometimes obtained. In this paper we propose a semi-parametric mixture model that uses multiple independent markers of ovulation to account for measurement error. The model assigns each method of assessing ovulation a distinct non-parametric error distribution, and corrects bias in estimates of day-specific fecundability. We use a Monte Carlo EM algorithm for joint estimation of (i) the error distribution for the markers, (ii) the error-corrected fertility parameters, and (iii) the couple-specific random effects. We apply the methods to data from a North Carolina fertility study to assess the magnitude of error in measures of ovulation based on urinary luteinizing hormone and metabolites of ovarian hormones, and estimate the corrected day-specific probabilities of clinical pregnancy. Published in 2001 by John Wiley & Sons, Ltd.

Algorithms↗
PubMed2001

Effects of Cu+2 and pH on the fitness of Ceriodaphnia dubia (Richard 1894) (Crustacea, Cladocera) in microcosm experiments.

An important disturbance of anthropogenic origin frequently occurring in freshwater ecosystems is a rise in the concentration of heavy metals in solution, among which copper stands out due to its known toxicity. However, the study of the chemical behavior of copper in solution is highly dependent on pH. In this study, the effect of ionic copper on the fitness of Ceriodaphnia dubia was assessed in microcosm experiments under different conditions of Cu+2 and pH. Two groups of experiments were conducted: effects on survival and fecundity, and effects on population dynamics. In the former, both pH and copper concentrations were manipulated. On the other hand, only the concentration of biologically available ionic copper was manipulated whereas pH was maintained constant in the population dynamics experiments. There was an agreement between both sets of experiments in terms of their results, showing important toxic effects of copper as evidenced through significant differences between controls and treatments in survival and fecundity. Mean age of first reproduction was delayed, and both the number of neonates produced per female and number of broods decreased with the increase in the concentration of copper. R0 was always lower at pH 6 than at pH 8 and was negatively related to the increment in the concentration of copper under either pH. A significant effect on population dynamics at 5 micrograms l-1 of copper sulfate was found and the extinction of the population at 20 micrograms l-1 of copper sulfate. New values of toxicity from copper are proposed, and the potential effects that an increment in copper could have on the communities that occupy a central position in aquatic food webs are discussed.

Animals↗
PubMed2005

Variation in the response of juvenile and adult gastropods (Lymnaea stagnalis) to cyanobacterial toxin (microcystin-LR).

Owing to the increasing public health problem related to the proliferation of toxin-producing cyanobacteria in aquatic ecosystems, we have investigated the response of the pond snail Lymnaea stagnalis exposed to 33 microg/L microcystin-LR for 6 weeks, through its life traits (survival, growth, fecundity) and locomotion; uptake of microcystin-LR was also quantified in the snail body tissues. To study the potential plasticity of the response related to the development stage, snails were exposed to the toxin as sexually immature and mature. According to our results, microcystin-LR accumulated in snail tissues at a higher level in juveniles (7.96 ng/g fresh weight) versus adults (2.17 ng/g fresh weight). Whatever the age, survival, growth, and locomotion were not affected by the toxin, and fecundity of polluted adults was reduced by half. These results are discussed in terms of negative effects of aqueous microcystin-LR occurrence on the dynamics of natural populations of gastropods.

Age Factors↗
PubMed1998

Primary and secondary sex ratio manipulation by zebra finches.

Wild zebra finches, Taeniopygia guttata, breed opportunistically when there is sufficient food available, often rapidly mobilizing their reproductive systems in response to an ephemeral boom in grass seed production. For females in captivity, fecundity, attractiveness to mates and survival to reproduction are all correlated with their fledging weight. By contrast, for males, only attractiveness is related to fledging weight; the relationship between fledging weight and male mortality is much weaker and that for male fecundity is unknown. Previous work thus suggests that how much food nestlings receive will have a profound impact on their reproductive success, and that this effect may be more marked for females than for males. I manipulated the food available to domesticated breeding zebra finches to test Trivers & Willard's (1973, Science, 179, 90-92) hypothesis of adaptive sexual investment. When food availability was restricted, clutch sex ratios were significantly more male biased than when food was available in excess. Within clutches, daughters hatched sooner than sons and first-hatched chicks fledged at higher weights than those that hatched last. Chick mortality was female biased when food availability was low but male biased when food availability was unrestricted. I compared the song output of brothers of differing weight at independence, but found no significant difference between them. These data suggest that zebra finches manipulate both their primary and secondary sex ratios in relation to food availability to invest adaptively in sons and daughters, and support Trivers & Willard's hypothesis. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗