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PubMed2005

Population genetics of complex life-cycle parasites: an illustration with trematodes.

Accurate inferences on population genetics data require a sound underlying theoretical null model. Organisms alternating sexual and asexual reproduction during their life-cycle have been largely neglected in theoretical population genetic models, thus limiting the biological interpretation of population genetics parameters measured in natural populations. In this article, we derive the expectations of those parameters for the life-cycle of monoecious trematodes, a group comprising several important human and livestock parasites that obligatorily alternate sexual and asexual reproduction during their life-cycle. We model how migration rates between hosts, sexual and asexual mutation rates, adult selfing rate and the variance in reproductive success of parasites during the clonal phase affect the amount of neutral genetic diversity of the parasite (effective population size) and its apportionment within and between definitive hosts (using F-statistics). We demonstrate, in particular, that variance in reproductive success of clones, a parameter that has been completely overlooked in previous population genetics models, is very important in shaping the distribution of the genetic variability both within and among definitive hosts. Within definitive hosts, the parameter F(IS) (a measure of the deviation from random mating) is decreased by high variance in clonal reproductive success of larvae but increased by high adult self-fertilisation rates. Both clonal multiplication and selfing have similar effects on between-host genetic differentiation (F(ST)). Migration occurring before and after asexual reproduction can have different effects on the patterns of F(IS), depending on values of the other parameters such as the mutation rate. While the model applies to any hermaphroditic organism alternating sexual and clonal reproduction (e.g. many plants), the results are specifically discussed in the light of the limited population genetic data on monoecious trematodes available to date and their previous interpretation. We hope that our model will encourage more empirical population genetics studies on monoecious trematodes and other organisms with similar life-cycles.

Animals↗
PubMed2000

Influence of sexual stimulation on sperm parameters in semen samples collected via masturbation from normozoospermic men or cryptozoospermic men participating in an assisted reproduction programme.

To evaluate the influence of sexual stimulation via sexually stimulating videotaped visual images (VIM) on sperm function, two semen samples were collected from each of 19 normozoospermic men via masturbation with VIM. Two additional samples were collected from each man via masturbation without VIM. The volume of seminal plasma, total sperm count, sperm motility, percentage of morphologically normal spermatozoa, outcome of hypo-osmotic swelling test and zona-free hamster oocyte sperm penetration assay, and markers of the secretory function of prostate were significantly larger in semen samples collected via masturbation with VIM than masturbation without VIM. The improved sperm parameters in the samples collected via masturbation with VIM may reflect an enhanced prostatic secretory function and increased loading of the vas deferens at that time. In a similar protocol, two semen samples were collected via masturbation with VIM from each of 22 non-obstructed azoospermic men. Semen samples from these men had been occasionally positive in the past for a very small number of spermatozoa (cryptozoospermic men). Two additional samples were collected from each cryptozoospermic man via masturbation without VIM. The volume of seminal plasma, total sperm count, sperm motility, and a marker of the secretory function of prostate were significantly larger in semen samples collected via masturbation with VIM. Fourteen out of the 22 men were negative for spermatozoa in both samples collected via masturbation without VIM. These men demonstrated spermatozoa in both samples collected via masturbation with VIM. Six men with immotile spermatozoa in both samples collected via masturbation without VIM exposed motile spermatozoa in both samples collected via masturbation with VIM. High sexual stimulation during masturbation with VIM results in recovery of spermatozoa of greater fertilizing potential both in normozoospermic and cryptozoospermic men. The appearance of spermatozoa after masturbation with VIM in the vast majority of cryptozoospermic men is of clinical significance in programmes applying intracytoplasmic sperm injections for the management of severe male infertility and obviates the need for testicular biopsy.

Biomarkers↗
PubMed2004

Model parameters and outbreak control for SARS.

Control of the 2002-2003 severe acute respiratory syndrome (SARS) outbreak was based on rapid diagnosis coupled with effective patient isolation. We used uncertainty and sensitivity analysis of the basic reproductive number R0 to assess the role that model parameters play in outbreak control. The transmission rate and isolation effectiveness have the largest fractional effect on R0. We estimated the distribution of the reproductive number R0 under perfect isolation conditions. The distribution lies in the interquartile range 0.19-1.08, with a median of 0.49. Even though the median of R0 is <1, we found that 25% of our R0 distribution lies at R0 > 1, even with perfect isolation. This implies the need to simultaneously apply more than one method of control.

Communicable Disease Control↗
PubMed1994

[Compared dynamics of Triatoma infestans cohorts in residential environment].

Triatoma infestans is an insect with a high colonization capacity, capable of maintaining populations near saturation levels in different environments. However, it has a great lability in its population parameters when exposed to variable environmental conditions. The aim of this work was to explore the response of two cohorts with 4 initial egg densities, in two environmental conditions ("shelter" at 24 +/- 2.7 degrees C and 73 +/- 7% of relative humidity and "room" at 16.9 +/- 2.1 degrees C and 69.8 +/- 5% of relative humidity), similar to those commonly found in houses at Santiago, Chile. The proportion of fertile egg was higher in shelter conditions (93.7 vs 74.6%). Survival curves were similar in both environments and mortality was not influenced by density or maturity of individuals. Maturation was retarded in both environment, specially in the colder one, compared to constant environments. It is concluded that maturation of T infestans is the most affected parameter in the unprotected environment. Even though, considering the insect's longevity, its reproductive function is probably accomplished. The great lability of T. infestans population parameters, suggests that the finding of favorable microenvironments is essential for their survival.

Animals↗
PubMed2003

Estrogen receptors in the spinal cord, sensory ganglia, and pelvic autonomic ganglia.

Until relatively recently, most studies of the effects of estradiol in the nervous system focused on hypothalamic, limbic, and other brain centers involved in reproductive hormone output, feedback, and behaviors. Almost no studies addressed estradiol effects at the spinal cord or peripheral nervous system level. Prior to the mid-1960s-1970s, few studies examined neural components of reproductive endocrine organs (e.g., ovary or testis) or the genital organs (e.g., uterus or penis) because available data supported endocrine regulation of these structures. Over the last two decades interest in and studies on the innervation of the genital organs have burgeoned. Because of the responsiveness of genital organs to sex steroid hormones, these neural studies seeded interest in whether or not autonomic and sensory neurons that innervate these organs, along with their attendant spinal cord circuits, also are responsive to sex hormones. From the mid-1980s there has been a steady growth of interest in, and studies of the neuroanatomy, neurochemistry, neural connectivity, and neural functional aspects in reproductive organs and the response of these parameters to sex steroids. Thus, with the growth of probes and techniques, has come studies of anatomy, neurochemistry, and circuitry of sex hormone-responsive neurons and circuits in the spinal cord and peripheral nervous system. This review focuses on estrogen receptors in sensory, autonomic, and spinal cord neurons in locales that are associated with innervation of female reproductive organs.

Animals↗
PubMed1991

Reproductive hazards of fire fighting. I. Non-chemical hazards.

Fire fighters are regularly exposed to chemical and non-chemical agents that have known or suspected adverse effects on reproductive health. Although chemical agents have received some attention, non-chemical hazards such as heat, noise, and physical exertion have only recently been examined for their reproductive effects. There is evidence that heat, noise, and physical exertion may affect various endpoints of reproductive health, including fertility, fetal loss, and growth parameters of the offspring. In particular, hyperthermia, a major fire fighting hazard, has been shown to impair male fertility and may also be teratogenic. Further study of the potential reproductive effects of this and other common non-chemical agents in the fire environment is needed to ensure the reproductive health of male and female fire fighters.

Animals↗
PubMed2001

Embryo selection by the first cleavage parameter between 25 and 27 hours after ICSI.

PURPOSE: The objective of this study was to assess first embryo cleavage (FEC) 25-27 h after intracytoplasmic sperm injection (ICSI) as a parameter for the embryo selection process. METHODS: From January 1998 to December 1999, a total of 670 patients were subjected to the ICSI programme at the Centre for Human Reproduction, Sinhá Junqueira Maternity Foundation, and the FEC parameter was evaluated in three situations. RESULTS: In the first, a total of 300 zygotes were analyzed on the basis of a score (16-18 h after ICSI) and observed for the presence or absence of FEC (25-27 h after ICSI). A significant (p < 0.02) presence of FEC was observed in zygotes with a score of 15 (ideal score). In the second, a total of 200 patients were selected and divided into two groups matched for age and laboratory performance. Group I (n = 100) was subjected to transfer of embryos with the absence of FEC only (since in this cycle no embryos with FEC were detected within 25-27 h after ICSI) and Group II (n = 100) was subjected to transfer of embryos with the presence of FEC only. The age of Group I patients (33.8 +/- 4.2 years) did not differ significantly (p = 0.50) from that of Group II patients (33.5 +/- 4.3 years). The number of embryos transferred was similar (p = 0.07) for Group I (2.7 +/- 1.1) and Group II (2.9 +/- 0.88). In Group II, the 17.5% implantation rate was significantly higher (p < 0.01) than the 5.9% rate obtained for Group I. The pregnancy rate for Group II was significantly higher (p < 0.01) (33%) than that for Group I (12%). The incidence of abortion was 16.6% in Group I as compared with 6% in Group II. In the third situation, we observed the frequency of embryos with FEC in 36 patients whose implantation rate was 100% (ideal result) and obtained a value of 82%. CONCLUSIONS: The data suggest that the presence of the FEC parameter that was evaluated 25-27 h after ICSI could be used to select embryos with a higher implantation power. The data reported here may justify routine analysis of embryos with FEC for the process of embryo selection after ICSI.

Adult↗
PubMed1975

Natural selection and age-structured populations.

This paper studies the properties of a new class of demographic parameters for age-structured populations and analyzes the effect of natural selection on these parameters. Two new demographic variables are introduced: the entropy of a population and the reproductive potential. The entropy of a population measures the variability of the contribution of the different age classes to the stationary population. The reproductive potential measures the mean of the contribution of the different age classes to the Malthusian parameter. The Malthusian parameter is precisely the difference between the entropy and the reproductive potential. The effect of these demographic variables on changes in gene frequency is discussed. The concept of entropy of a genotype is introduced and it is shown that in a random mating population in Hardy-Weinberg equilibrium and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the covariance in entropy and reproductive potential. This result is an information theoretic analog of Fisher's fundamental theorem of natural selection.

Age Factors↗
PubMed2000

[Evaluation of coagulation and fibrinolysis systems in women at peri- and postmenopausal age qualified for hormone replacement therapy].

OBJECTIVE: The aim of the study was to evaluate coagulation and fibrinolysis systems in peri- and postmenopausal women who were qualified for hormone replacement therapy. MATERIALS AND METHODS: In sixty eight peri- and postmenopausal women qualified for hormone replacement therapy under study some coagulation and fibrinolysis parameters were measured in serum--platelet count, prothrombin time, prothrombin ratio, INR, APTT, thrombin time (TT), fibrinogen, D-dimers, TAT, factor VII, activity of antithrombin III, activity of protein C and protein S, PAI-1 and t-PA concentration. Controls were 26 healthy, reproductive women. RESULTS: Out of fifteen examined coagulation and fibrinolysis parameters in six cases there were statistically significant differences between menopausal women and controls:--APTT and TT were shortened (but within normal range) in menopausal group than in controls;--concentration of fibrinogen in menopausal group (also within normal range) was higher than in controls;--activity of factor VII was risen (and outside normal range) in the examined group in comparison to the controls;--activity of protein S was lower in menopausal than in reproductive women;--also concentration of t-PA was lower in the examined group. CONCLUSIONS: 1. Differences in the values of coagulation and fibrinolytic parameters between the menopausal and reproductive groups of women may testify to the increased risk of thrombus formation in women at peri- and postmenopausal age. 2. Impaired fibrinolysis (low t-PA, high PAI-1) together with the rise in activity of factor VII can contribute to the development of ischaemic heart disease in menopausal women.

Adult↗
PubMed1996

Role of delivery on serum iron-related parameters in Macaca fascicularis females.

Few data exist on the iron status and metabolism in macaques, which are considered optimal models for the study of reproductive biology and anemia. The delivery influence on the hematological parameters of iron metabolism was investigated in adult Macaca fascicularis females during late pregnancy and at 6 weeks postpartum follow-up. No significant differences were detected for each parameter by one-way analysis of variance. A decrease of all parameters was observed at delivery. During the following weeks, however, the hematological values progressively came back to normal. In conclusion, notwithstanding the increased need of iron faced during pregnancy, a balanced diet, including iron, does not allow the development of either iron deficiency or sideropenic anemia.

Animals↗
PubMed1997

Parameters of linear-quadratic radiation dose-effect relationships: dependence on LET and mechanisms of reproductive cell death.

An analysis of mammalian cell radiation-dose survival curves, based on the linear-quadratic formalism, is shown to yield insights in the various components of damage that contribute to cell reproductive death. RBE-LET relationships of single-track lethal damage, sublethal damage, potentially lethal damage and DNA double-strand breaks are compared. Single-track lethal damage is derived to be composed of two components: (1) damage that remains unrepaired in an interval between irradiation and assay for proliferative capacity, with a very strong dependence on LET, and (2) potentially lethal damage that is only weakly dependent on LET, similar to sublethal damage and DNA double-strand breaks. The results of this analysis lead to new interpretations of published experimental results and to suggestions for applications in radiotherapy.

Cell Death↗
PubMed2004

Effects of an antisense oligonucleotide inhibitor of human ICAM-1 on fetal development in rabbits.

The potential for reproductive toxicity of an antisense oligonucleotide designed to inhibit ICAM-1 was evaluated as part of the safety assessment for this compound. The human active ICAM-1 inhibitor (ISIS 2302) is not pharmacologically active in rabbits. Female rabbits were treated once daily on Day 6 through 18 of gestation. Rabbits were treated with 0, 1, 3, and 9 mg/kg ISIS 2302 by daily i.v. injection. Reproductive indices evaluated included estrus cycling, litter parameters, fetal development, and fetal body weight. Concentrations of oligonucleotide in plasma following the last dose, and in selected maternal target organs, placenta, and fetal tissues at scheduled necropsy were also measured. Maternal toxicity was evident as a decreased maternal body weight gain, decreased food consumption, and scant feces at doses > or =3 mg/kg. Increased spleen to body weight ratio and increased mononuclear cell infiltrates were indicative of a proinflammatory effect of ISIS 2302 at the 9 mg/kg dose level. Despite the maternal toxicity, there were no changes in litter parameters or fetal development in rabbits treated with ISIS 2302. The only change was a decrease in fetal body weight at the 9 mg/kg dose level, which was attributed to the maternal toxicity observed. Maternal liver and kidney contained dose-dependent concentrations of oligonucleotide, but there was relatively little or no oligonucleotide measured in placenta or fetal tissues. Thus, there was no dose-dependent exposure and maternal toxicity to ISIS 2302, but no reproductive toxicity in rabbits, and exposure of fetus or pups is negligible.

Animals↗
PubMed2003

Comparing data on the reproduction of Varroa destructor.

Varroa destructor reproductive success is considered an important character for determining the resistance of honey bees to this mite parasite. However, most of the published data are not comparable due to the different methods of ascertaining and reporting reproduction. A recently published technique that involves reconstructing mite families in older worker brood gives repeatable and reliable parameters. This methodology was used to compare various categories of reproduction of approximately 1,000 V. destructor females in each of three studies on Africanized bees in Brazil and Mexico and European bees in England. The most objective and useful measure was the determination of the number of viable females per female that had invaded the worker brood in singly infested cells, which was denominated the "effective reproduction rate". Viable females are those that can reach the adult stage and have a mate available. The effective reproduction rate in worker brood was 0.64, 0.73 and 1.01 in Brazil, Mexico and England, respectively. Standardization of reproduction determination techniques would make published data comparable and much more useful.

Animals↗
PubMed2003

The mitochondrial genome in embryo technologies.

The mammalian mitochondrial genome encodes for 37 genes which are involved in a broad range of cellular functions. The mitochondrial DNA (mtDNA) molecule is commonly assumed to be inherited through oocyte cytoplasm in a clonal manner, and apparently species-specific mechanisms have evolved to eliminate the contribution of sperm mitochondria after natural fertilization. However, recent evidence for paternal mtDNA inheritance in embryos and offspring questions the general validity of this model, particularly in the context of assisted reproduction and embryo biotechnology. In addition to normal mt DNA haplotype variation, oocytes and spermatozoa show remarkable differences in mtDNA content and may be affected by inherited or acquired mtDNA aberrations. All these parameters have been correlated with gamete quality and reproductive success rates. Nuclear transfer (NT) technology provides experimental models for studying interactions between nuclear and mitochondrial genomes. Recent studies demonstrated (i) a significant effect of mtDNA haplotype or other maternal cytoplasmic factors on the efficiency of NT; (ii) phenotypic differences between transmitochondrial clones pointing to functionally relevant nuclear-cytoplasmic interactions; and (iii) neutral or non-neutral selection of mtDNA haplotypes in heteroplasmic conditions. Mitochondria form a dynamic reticulum, enabling complementation of mitochondrial components and possibly mixing of different mtDNA populations in heteroplasmic individuals. Future directions of research on mtDNA in the context of reproductive biotechnology range from the elimination of adverse effects of artificial heteroplasmy, e.g. created by ooplasm transfer, to engineering of optimized constellations of nuclear and cytoplasmic genes for the production of superior livestock.

Animals↗
PubMed1997

Influence of breeding season and reproductive status on male reproductive characteristics in the common mole-rat, Cryptomys hottentotus hottentotus.

The effects of breeding season and reproductive status on male reproduction were investigated in the common mole-rat (Cryptomys hottentotus hottentotus), a co-operatively breeding rodent that exhibits seasonal reproduction and a reproductive division of labour. Testicular anatomical and histological morphometrics, and selected sperm parameters were studied in 50 males from 17 wild caught colonies. Males exhibited no apparent manifestation of season on testicular activity: spermatogenesis and sperm quality (motility and percentage normal morphology) were similar in the reproductively active and inactive periods. This maintenance of reproductive activity during the non-reproductive period is essential in C. h. hottentotus males, as this period coincides with the period of maximal dispersal opportunities. Such reproductive activation in dispersing males may aid intersexual recognition, and assist pair-bond formation or successful assimilation into foreign colonies, thereby facilitating later outbreeding. Consequently, outbreeding opportunities may be important determinants of reproductive activity in male common mole-rats, moderating seasonal effects. Reproductive and non-reproductive males revealed no differences in any of the testicular or sperm parameters studied. The absence of a physiologically well-defined suppression of reproduction in male common mole-rats is more typical of social suppression in male mammals.

Animals↗
PubMed2007

Prenatal testosterone exposure permanently masculinizes anogenital distance, nipple development, and reproductive tract morphology in female Sprague-Dawley rats.

In mammals, abnormal increases in fetal androgens disrupt normal development of the female phenotype. Due to the recent concern regarding environmental androgen-active chemicals, there is a need to identify sources of fetal androgen variation and sensitive developmental markers for androgenic activity in female rats. Anogenital distances (AGD), nipple retention, reproductive tract, and external genitalia are morphological parameters organized by prenatal androgens and are predictive of altered masculinized/defeminized phenotype in adult female mice and rats. The objectives of this study were to (1) characterize the natural prenatal androgen environment of rats including the magnitude of the intrauterine position (IUP) effect, (2) characterize the permanent effects of prenatal androgen exposure on female rats, and (3) determine the ability of AGD and areolas to predict these permanent androgenic alterations in female rats. Untreated male fetal rats had higher tissue testosterone (T) concentrations than females in the amniotic fluid, reproductive tract, gonad, and fetal body. The intrauterine position (IUP) of male and female fetuses did not affect T concentrations or AGD in male or female rats at gestational day (GD) 22. Female offspring exposed to 0, 1.5, and 2.5 mg/kg/day testosterone propionate (TP) on GDs 14-18 displayed increased AGD at postnatal day (PND) 2 and decreased nipples at PND 13 and as adults. TP-induced changes in neonatal AGD and infant areola number were reliable indicators of permanently altered adult phenotype in female rats. Further, females in the two high-dose groups displayed increased incidences of external genital malformations and the presence of prostatic tissue, not normally found in female rats.

Abnormalities, Drug-Induced↗
PubMed2007

Colour variation and alternative reproductive strategies in females of the common lizard Lacerta vivipara.

Within-sex colour variation is a widespread phenomenon in animals that often plays a role in social selection. In males, colour variation is typically associated with the existence of alternative reproductive strategies. Despite ecological conditions theoretically favourable to the emergence of such alternative strategies in females, the social significance of colour variation in females has less commonly been addressed, relative to the attention given to male strategies. In a population of the common lizard, females display three classes of ventral colouration: pale yellow, orange and mixed. These ventral colours are stable through individual's life and maternally heritable. Females of different ventral colourations displayed different responses of clutch size, clutch hatching success and clutch sex-ratio to several individual and environmental parameters. Such reaction patterns might reflect alternative reproductive strategies in females. Spatial heterogeneity and presence of density- and frequency-dependent feedbacks in the environment could allow for the emergence of such alternative strategies in this population and the maintenance of colour variation in females.

Animals↗