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PubMed2003

The kinetics of monospermic and polyspermic fertilization in free-spawning marine invertebrates.

The equation of Vogel et al. (1982) is widely used in fertilization studies of free-spawning marine invertebrates to predict the percentage of viable eggs that will be fertilized at any specified levels of gamete concentration and contact time. Here, the random collision model that underlies the Vogel et al. equation is extended to distinguish between monospermic and polyspermic fertilization, and separate equations for the percentages of monospermic and polyspermic fertilization are obtained. These equations provide an explanation for empirical observations which have shown a decreased percentage of successful egg development at high sperm concentrations. Comparison is made with an earlier heuristic attempt (Styan, 1998) to predict the extent of polyspermic fertilization, and it is found that this earlier method can underestimate the percentage of polyspermic fertilization by up to 10 percent. Moreover, the approach used here retains the flexibility to model changes in sperm concentration due to dispersal mechanisms, and is able to model different mechanisms for the block to polyspermy.

Animals↗
PubMed1994

Varicocele related testicular atrophy and its predictive effect upon fertility.

Varicoceles are the most common reversible cause of male factor infertility, yet approximately 80% of men with varicoceles are fertile. Therefore, it is unclear whether all adolescents should undergo prophylactic varicocelectomy to prevent future infertility or whether a subgroup of patients who are at increased risk for future infertility can be identified and treated. Testicular size discrepancy or hypotrophy of the testis associated with a unilateral varicocele has been suggested as an indication for prophylactic varicocelectomy in adolescents. We examined 946 men attending a urological clinic for complaints other than infertility to determine whether testis size discrepancy was predictive of infertility in men with left varicoceles. A left varicocele was detected on physical examination in 211 men, of whom 173 (82%) had been able to father children and 38 (18%) had never fathered children. A group of 630 men without palpable varicoceles served as controls, including 528 (84%) with a history of fertility. Testicular size was measured using an orchidometer and the average testicular volume difference was obtained by subtracting left from right testicular volume. The mean testicular volume difference for the fertile men without varicoceles (1.6 +/- 0.3 ml.) was significantly lower than the fertile men with varicoceles (3.1 +/- 0.4 ml.) (p < 0.05) and infertile men with varicoceles (2.5 +/- 0.6 ml.) (p < 0.05). There was no significant difference between fertile and infertile men with varicoceles. This study confirms prior reports that the majority of men with left varicoceles are able to father children and that varicoceles cause significant ipsilateral testicular atrophy/hypotrophy. However, we were unable to demonstrate a correlation between loss of testicular volume and fertility status in men with left varicoceles. Further study is needed to identify the clinical parameters predictive of future infertility in adolescents with varicoceles.

Adolescent↗
PubMed1994

Early antibody response following vasectomy is related to fertility after vasovasostomy in glucocorticoid-treated and untreated Lewis rats.

The influence of treatment with a glucocorticoid on antisperm antibodies and fertility after vasectomy and vasovasostomy was studied in Lewis rats. Animals received a bilateral vasectomy followed 4 weeks later by bilateral vasovasostomy. Treatment with methylprednisolone for two months beginning at the time of the vasovasostomy resulted in a decrease in antisperm antibodies compared with nontreated vasovasostomized animals, but there was no difference in fertility between treated and nontreated vasovasostomized groups. However, when fertile vasovasostomized animals from treated and nontreated groups were compared with infertile vasovasostomized animals, antisperm antibodies were found to be significantly lower in fertile rats 2, 4 and 8 weeks after vasectomy, while antibodies did not differ between fertile and infertile animals at the end of the study (12 weeks). The observation that differences in antisperm antibodies appeared shortly after vasectomy, preceding either vasovasostomy or treatment, suggests that changes occurring very early after vasectomy have far-reaching effects and are among the factors that influence future fertility after vasovasostomy.

Analysis of Variance↗
PubMed2001

Fertility sparing treatment for in situ and early invasive adenocarcinoma of the cervix.

OBJECTIVE: To explore the outcome and long-term follow-up of fertility sparing surgery for cervical adenocarcinoma in situ and early invasive adenocarcinoma. METHODS: Between 1985 and 1996, all women with adenocarcinoma in situ (AIS) and stage I adenocarcinoma were identified. Data were abstracted from clinical records and pathology reviewed. RESULTS: One hundred thirty three women with stage I adenocarcinoma of the cervix were treated. Twenty subjects met the criteria for International Federation of Gynecology and Obstetrics stage IA1 lesions. Fourteen subjects were treated with radical hysterectomy, whereas two were treated with simple hysterectomy. Because of the desire to preserve fertility, four women with adenocarcinoma were treated with cervical conization alone, and three women have gone on to deliver viable infants. Forty-two women with adenocarcinoma in situ were identified, of whom 20 were treated with fertility sparing surgery (conization). Five women treated with conization had positive margins recurring in two, and one developed an invasive adenocarcinoma 5 years after conization. None of the women with adenocarcinoma treated with cervical conization have developed recurrent disease after a median follow-up of 48 months. Cone margin status was predictive of residual disease at hysterectomy. CONCLUSION: Women with adenocarcinoma in situ and negative margins may be treated with conservative, fertility sparing surgery. Education is essential regarding the risks of residual/recurrent disease because subjects can develop lethal recurrent disease. The fertility sparing management of invasive stage IA1 adenocarcinoma of the uterine cervix may also be entertained among women who desire future fertility and have negative margins of resection.

Adenocarcinoma↗
PubMed1998

MacLeod revisited: sperm count distributions in 374 fertile men from 1971 to 1994.

OBJECTIVES: There has been an enormous amount of interest as to whether sperm counts are declining over time. We sought to compare a contemporary group of fertile men to those from the MacLeod study of 1951 to ascertain whether sperm counts in fertile men have changed over time. METHODS: We obtained sperm count data from 374 fertile men who banked sperm in Minnesota prior to vasectomy from 1971 to 1994 and compared them to sperm count distributions from the 1000 fertile men of MacLeod's study. Semen analyses were performed as per World Health Organization guidelines using identical techniques in both the present and MacLeod studies. RESULTS: The contemporary group had a mean sperm count of 102 +/- 81 x 10(6)/mL (median 85 x 10(6)/mL) compared to 107 +/- 74 x 10(6)/mL (median 90 x 10(6)/mL) for MacLeod's data. There are no significant differences in mean or median sperm counts or sperm count distributions between the groups. CONCLUSIONS: We find remarkable similarities in sperm count distributions in cohorts of fertile men from 1951 and 1971 to 1994. Sperm counts in fertile men have not changed appreciably in the 40 years since MacLeod's report.

Fertility↗
PubMed2001

The effects of age, season and fertility status on plasma and intratesticular insulin-like growth factor I concentration in stallions.

The purposes of this study were to establish the basal plasma and testicular insulin-like growth factor-I (IGF-I) values for stallions ranging in age from 6 months to 23 years and to determine if IGF-I could be used as a marker for declining fertility. Blood and testes were obtained from 28 light horse stallions and colts. Of the 28 stallions, 22 were considered fertile and were categorized by age (<2 y, 5 to 10 y, 11 to 15 y, and 16 to 23 y); 12 age-matched stallions were grouped as to fertility status (fertile, subfertile, infertile); and all 28 stallions were grouped as to season of castration (breeding season vs. non-breeding season). In colts less than 2 years of age, IGF-I concentrations in plasma and testicular extracts were higher (P < 0.01) than in the other age groups and were higher in the breeding season than in the non-breeding season (P < 0.01). No significant differences in plasma or testicular extract concentrations of IGF-I were found among fertility groups. The results of this study demonstrate that plasma and testicular IGF-I levels are high in stallions younger than 2 years of age and then decline and plateau in stallions older than 5 years of age, suggesting that IGF-I may be involved in testicular development. The results allude to a possible seasonal effect on IGF-I production. However, it is difficult to separate true seasonality and the effect of age as only those stallions less than 2 years old exhibited variation between seasons. The IGF-I does not appear to have a direct relationship with declined fertility in the stallions tested, suggesting that IGF-I may not be a reliable biomarker for the diagnosis of subfertility and infertility.

Aging↗
PubMed2002

Effect of sperm survival and CTC staining pattern on in vitro fertilization of porcine oocytes.

Polyspermy in pig oocytes fertilized in vitro remains unacceptably high. In this study, we evaluated the effects of gamete coincubation time, and determined if the proportion of capacitated spermatozoa would be predictive of the fertilizing ability of frozen-thawed semen in vitro. Cumulus-oocyte complexes were collected from slaughterhouse prepubertal gilt ovaries and matured in vitro for 44 h in TCM199, with EGF, FSH, cysteamine and follicular fluid. Fertilization was induced with 2 x 10(5) frozen-thawed spermatozoa/ml in TBM. Penetration of oocytes as well as polyspermic fertilization occurred 2 h after insemination. A strong correlation between penetration and polyspermic fertilization rates has been demonstrated, but there was no correlation between the proportion of capacitated spermatozoa, as assessed by chlortetracycline staining, at the time of insemination and fertilization rates. We also compared the results of IVF in three IVF media: TBM, m199 and TALP. Penetration and polyspermy were very different in these three media: 71 +/- 19% and 25 +/- 13% in TBM, 37 +/- 11% and 6 +/- 2% in m199, 10 +/- 2% and 0% in TALP, respectively. Nevertheless, survival of spermatozoa or modifications of the capacitation status were not different in these media after 6 h incubation. We concluded that survival and capacitation characteristics of the semen used for IVF could not be predictive of the IVF results. It seems necessary to act at the oocyte level to control both variability between replicates and the incidence of polyspermy. Improving the spermatozoa penetration blocking system of the oocytes and reducing the number of sperm-binding sites on the zona pellucida (ZP) are our further objectives.

Animals↗
PubMed2003

Buffalo and cattle hybrid embryo development is decreased by caffeine treatment during in vitro fertilization.

Water buffalo are renowned for difficulties in the implementation of assisted reproductive technologies, with both males and females being problematic. In this study, we used cattle oocytes to assess the effect of treatments with heparin and caffeine on buffalo spermatozoa and subsequent fertilization and embryo development in vitro. There was no significant difference between buffalo and bovine spermatozoa in the events associated with fertilization. Fertilization of cattle oocytes with buffalo spermatozoa resulted in 7.8% of oocytes developing into hybrid embryos. A difference in the developmental capability of hybrid embryos compared with the cattle control was observed. This has not been previously reported. The subsequent transfer of a limited number of hybrid embryos did not produce a viable pregnancy. However, control treatments in this experiment also failed to achieve pregnancy, so objective data is not available to provide conclusions about the developmental competence of the buffalo and cattle hybrid embryos. Optimal spermatozoa capacitation treatments achieved 61% fertilization and 21% zygote cleavage into two cell embryos. There was no significant difference in fertilization or development due to heparin or spermatozoa concentrations. However, treatment of buffalo and cattle spermatozoa with caffeine significantly decreased embryo cleavage but also tended to decrease embryo development to the blastocyst stage. These studies suggest that problems with reproduction in buffalo may reside with biological mechanisms associated with the oocyte that are often complicated by poor male reproductive performance. Selection for bull fertility would prevent some of these complications.

Animals↗
PubMed2004

Capacity of boar spermatozoa to bind zona pellucida proteins in vitro in relation to fertilization rates in vivo.

The purpose of this study was to determine variation among boars in the percentage of sperm in an ejaculate that express enhanced binding of zona pellucida proteins during treatment for capacitation in vitro, and to determine whether this relates to fertilizing ability in vivo. Ejaculates (n=35) were collected from 12 boars. A sample of each ejaculate was treated for capacitation in vitro. During incubation, the zona binding ability of spermatozoa was assessed at regular intervals with fluorescein-conjugated solubilized zona pellucida proteins (FITC-sZP) and propidium iodide, using a flow cytometer. After incubation, a percentage of the sperm had enhanced FITC-sZP binding. The percentage of viable sperm with enhanced FITC-sZP binding, expressed as a percentage of the total sperm population, increased rapidly over the first 60 min and thereafter reached a plateau after 120-180 min. Averaged over all ejaculates, the percentage at 180 min was 46% (range 27-61%); this percentage was significantly different among boars. However, the variation between ejaculates within a boar was relatively small. There was no significant boar effect on the rate at which the percentage of viable cells with enhanced FITC-sZP binding reached the maximum. In ejaculates (n=14) from four boars (selected from the group of 12), we investigated the increase in the percentage of viable sperm with enhanced sZP binding during treatment for capacitation in vitro in relation to the ability to fertilize in vivo. Sows (n=44) were inseminated 4 h after ovulation with a suboptimal insemination dose (0.5x10(9) spermatozoa). Time of ovulation was determined using transrectal ultrasonography and sows were killed at 120 h after ovulation. The percentage of fertilized oocytes, embryo development, and numbers of accessory spermatozoa were determined. The percentage of spermatozoa that were viable and showed enhanced sZP binding after 180 min of incubation was 48 +/- 12% (range 28-56%). The percentage of fertilized oocytes was 85 +/- 27% and 64% of the sows had 100% fertilized oocytes. The percentage of sows with 100% fertilized oocytes correlated well (P< or =0.05, R2=0.98) with the percentage of viable spermatozoa with enhanced FITC-sZP binding after capacitation in vitro.

Animals↗
PubMed2004

Bull semen in vitro fertility after cryopreservation using egg yolk LDL: a comparison with Optidyl, a commercial egg yolk extender.

Low-density lipoproteins (LDL) have been previously isolated and identified as the cryoprotective fraction of yolk. The effect of LDL on sperm motility after freezing-thawing has been reported, but no study has been made to assess the effect of LDL on bull semen fertility. The aim of this study was to evaluate the fertility of bull semen cryopreserved in the presence of LDL. Motility of semen cryopreserved in LDL was analyzed and compared to semen cryopreserved with Optidyl, a commercial extender containing egg yolk. To evaluate the fertilizing ability of semen, we used in vitro fertilization test, whereas acrosome and plasma membrane integrity were also evaluated. The percentage of motile spermatozoa was two fold higher after freezing in LDL than in Optidyl 54.4% versus 30.2% (P < 0.05). The cleavage rate was significantly higher after fertilization with semen frozen in LDL than with Optidyl 63.0% versus 54.8% (P < 0.05). No significant difference was observed on the blastocyst rate after in vitro culture. Integrity of the acrosome and the plasma membrane were maintained in both extenders. In conclusion, LDL preserve bull semen quality and fertilizing ability, allowing also better semen motility, after the freeze-thaw process.

Acrosome↗
PubMed1998

Evaluation of fluids from cystic follicles for in vitro maturation and fertilization of bovine oocytes.

Follicular cysts are defined as cystic structures derived from unovulated follicles. The formation of the cysts appears to be related to failure of the oocyte to resume meiosis. The aim of this study was to evaluate in the bovine: 1) the ability of the fluid from cystic follicles to promote in vitro oocyte maturation and fertilization, 2) the predictive value of the morphology of oocytes derived from cystic follicles on the ability of the follicular fluid to promote in vitro maturation/fertilization as well as the oocytes to undergo maturation and fertilization. In Experiment 1, the ability of fluid from cystic (and normal) follicles from live and slaughtered cows (to promote) in vitro maturation and fertilization of bovine cumulus-oocyte-complexes (COC's) was assessed by cumulus expansion, sperm penetration, male pronucleus formation and polyspermy rates. Concentrations of progesterone (P4) and estradiol-17 beta (E2) were measured in the fluid from cystic follicles collected from live and slaughtered cows. In Experiment 2, we investigated the relationship of the morphology of COC's from cystic follicles, and the effect of the follicular fluids on oocyte maturation as well as P4 and E2 concentrations. In Experiment 1, although sperm penetration and male pronucleus formation were inhibited significantly by fluid from some cystic follicles collected from live and slaughtered cows, there were no significant differences in sperm penetration, male pronucleus formation and polyspermy rates between fluid from cystic follicles collected from live cows, from slaughtered cows and from control groups, regardless of the P4/E2 ratio. In Experiment 2, the morphology of cumulus-oocyte complexes from cystic follicles varied and the pronucleus formation of oocytes after in vitro fertilization was abnormal. On the other hand, the male pronucleus formation rates were not significantly different between the cystic follicular fluids and control, regardless, of the P4/E2 ratio. The results of this study suggest that many of the bovine follicular fluids from cystic follicles possess the ability to induce cumulus expansion, nuclear maturation and male pronucleus formation following in vitro maturation and fertilization of bovine oocytes. The morphology of the cumulus-oocytes complexes from cystic follicles seems not to relate to the ability of the cystic follicular fluids to induce oocyte maturation, and oocytes from cystic follicles possess the ability to form male pronucleus even though most were abnormal after in vitro fertilization.

Animals↗
PubMedDate not supplied

Natural fertility in northeastern Mexico.

BACKGROUND: The aims of this study were as follows: 1) to describe the fertility of a sample of Mexican women (> or =45 years of age, married, not using any family planning methods, and residing in the Mexican state of Nuevo León); 2) to determine whether or not the distribution of completed family size fits the negative binomial distribution, as in other populations studied in the world, and 3) to assess the association between fertility and 10 explanatory variables. METHODS: A sample of 410 women was interviewed at and selected from seven medical units of the Instituto Mexicano del Seguro Social (IMSS). The women were grouped by their year of birth (1896-1925 and 1926-1955) and birthplace [persons whose four grandparents were born in northeastern Mexico (NE) and outside northeastern Mexico (Not-NE)]. A binomial negative distribution analysis was assessed. Multiple linear regression was used to assess association between fertility (transformed by the use of inverse hyperbolic sines) and 10 explanatory variables, including age at marriage, heterozygosity, individual admixture, wife's education, husband's education, wife's occupation, husband's occupation, and couple's residence zone, birth year, and birthplace. RESULTS: Completed fertility was only associated with age at marriage. This population showed a fertility pattern similar to those described in Venezuelan and Brazilian populations in 1950 and 1940, respectively. CONCLUSIONS: We conclude that before worldwide family planning programs, fertility was determined mainly by natural selection forces.

Adolescent↗
PubMed2000

The use of databases to manage fertility.

Dairy farming now needs more records to be kept for quality assurance as well as for management. Herd fertility management is best brought about through the use of computerised records for each animal that integrate fertility, health and production. The development of dairy information systems over the last 25 years has allowed the creation of databases that give rise to "standards" of performance and "interference levels". These databases are of limited use for research unless the coding system has a structure and definition that works across herds. There is an increasing need to incorporate carefully coded disease records into these databases as there is increasing concern about welfare, zoonoses, assurance and the environment. Rules can be determined for satisfactory fertility so interference at an early stage is cost-effective. Integrated indices have been developed (using databases) that incorporate the costs of wastage caused by poor fertility, thus highlighting the priorities for management. Databases are best operated near to the farm, either in the veterinarian's office or on-line in the farm office. Databases can be made into expert systems that deliver high standards of fertility management. A checklist is included that can be followed to analyse the causes of poor fertility in a dairy herd.

Animals↗
PubMed2001

Double fertilization in flowering plants: discovery, study methods and mechanisms.

The double fertilization of flowering plants was discovered a century ago. The cytology of the gametes is now well known. However the description of the fertilization steps is still poor and most of the cellular and molecular mechanisms involved are unknown. Recent research using in vitro fertilization demonstrated that the early steps of fertilization share some homology with those in animal species. In particular, gamete fusion is followed by a cytosolic calcium increase in the fertilized egg as well as a calcium influx. Further understanding of fertilization also comes from the analysis of mutants isolated in Arabidopsis thaliana. Important new ideas have already emerged from these studies such as the importance of the female gametophyte in embryo development, and an early silencing of the male genome during the first days following gamete fusion.

Arabidopsis↗
PubMedDate not supplied

An assessment of fertility in boron-exposed Turkish subpopulations.

Relationships between elevated boron intake and fertility were sought by comparing reproduction in the residents of two Turkish villages with high levels of boron in their drinking water (one with 8.5 to 29 mg B/L and the other with 2.05 to 2.5 mg B/L), with three nearby villages with more typical low boron levels (0.03 to 0.40 mg B/L). The two high boron villages were designated as Region I, and the three villages with low boron in the drinking water were designated Region II. In addition to exposure to elevated boron in drinking water, 28.3% of the probands in Region I were employed in borate mining or processing, whereas in Region II, 11.7% were so employed. An observational study was carried out in which the authors compared the reproductive history of families living in Region I with families living in Region II by identifying married adults (referred to as probands) who were able to provide information about their and their spouses' family pedigrees covering three generations. Probands were identified by home visits and, if ever married, accepted for ascertainment. Evidence of fertility was birth of a living child, and data were obtained about the fertility of the proband generation, their parents' and also their childrens' generations. In high-boron villages (Region I), 159 three-generation kindreds containing 1068 families were ascertained and, in low-boron villages (Region II), 154 three-generation kindreds containing 610 families were ascertained. In Region 1, 96% of marriages produced at least one child, with primary infertility estimated at 2.34% compared with 96% and 2.62%, respectively, for Region II. There was no significant difference in fertility either between Region I and Region II or between the villages within the Regions. The fertility figures are not different from similar measures of fertility in other parts of Turkey. In Region I, the gender ratio (M:F) of offspring was 0.89, whereas in the Region II villages the gender ratio was 1.04 (NS, chi2 = 1.335, P > 0.05). It is concluded that at the elevated boron drinking water levels studied, a boron-related effect on reproduction was not found.

Adult↗
PubMed1998

Only long sperm are fertilization-competent in six sperm-heteromorphic Drosophila species.

Males of many species exhibit sperm heteromorphism, in which multiple morphologies of sperm are produced in a common testis (see references in [1]). Polymegaly, a form of sperm heteromorphism, is found in the Drosophila obscura group and is characterized by the production of two size classes of nucleated sperm that differ only in head and tail lengths [1,2]. Both the length and the ratio of sperm types produced is species-specific [1,3-5], and each sperm type develops in its own bundle deriving from a single stem cell [4]. Previous studies suggested that both types of sperm are fertilization-competent on the basis of similar ultrastructure [6], DNA content [6], nuclear protein transition during spermatogenesis [7], and storage in females [3-5]. However, a previous study demonstrated that only long sperm fertilize eggs [3]. Here, we extend this study to examine fertilization in six obscura group species using anti-sperm antibodies and digital deconvolution microscopy. Consistent with the previous study, we found that all eggs were fertilized by only the long sperm type, even in polyspermic eggs. Moreover, sperm entry and position during and following fertilization were similar to other Drosophila groups [3,8-10]. Thus, polymegaly and its maintenance appear to have arisen independently of fertilization processes per se.

Animals↗
PubMed2003

Fertility concerns and sexual behavior in adolescent girls with polycystic ovary syndrome: implications for quality of life.

OBJECTIVE: To examine the fertility concerns and sexual behavior of adolescent girls with polycystic ovary syndrome (PCOS) as compared to healthy adolescent girls and the effect of these concerns on health-related quality of life. DESIGN AND SETTING: A cross-sectional study of adolescent girls with PCOS (n = 97) and healthy comparisons (n = 186) was conducted at an urban, hospital-based adolescent medicine practice. Participants completed the Child Health Questionnaire Version CF-87 as a measure of health-related quality of life and a general health history questionnaire that included items regarding sexual activity, contraception, fertility concerns, and severity of illness. Findings were evaluated using multivariate logistic and linear regression models. RESULTS: Healthy subjects were 2.8 times more likely to have had sexual intercourse than PCOS participants, though the mean age at initiation of sexual intercourse among sexually active girls was not significantly different between the two groups. Severity of illness and the worry about fertility were not associated with odds of being sexually active. Girls with PCOS were 3.4 times more likely to be worried about their ability to become pregnant than comparisons and concern about future fertility was associated with significant reductions in quality of life. CONCLUSION: Adolescents with PCOS are more concerned about fertility than their healthy peers and this concern may affect their overall quality of life. The finding that more than a third of the adolescents with PCOS in this study were sexually active underscores the importance of providing ongoing counseling on fertility issues, contraception, and STD prevention in the care of adolescent girls with PCOS.

Adolescent↗
PubMed2001

Natural selection at the MJD locus: phenotypic diversity, survival and fertility among Machado-Joseph Disease patients from the Azores.

Machado-Joseph Disease (MJD) is an autosomal dominant neurodegenerative disorder of adult onset, associated with the expansion of a (CAG)n tract in the coding region of the causative gene, localized on 14q32.1. Machado-Joseph Disease shows non-Mendelian features typical of other triplet repeat disorders, including clinical heterogeneity, variable age at onset and anticipation. Three phenotypes have been proposed (clinical types 1, 2 and 3). Type 1 is associated with early age at onset and a high repeat number of the CAG sequence, and Types 2 and 3 have later onset and lower numbers of CAG repeats. This paper investigates whether there is selection against the MJD gene, acting through differential survival. nuptiality and fertility associated with clinical type and age at onset. The study sample comprised 40 MJD patients from the Azores (Portugal) having fully documented reproductive histories and known dates of death. The proportion of married patients of each clinical type increased from 0.22 among Type 1 patients, to 0.40 in Type 2 and 0.95 in Type 3. Age at onset and length of survival were also associated with marital status, with the married cases having later mean age at onset and longer mean survival time. In the whole sample, clinical type was associated with fertility, with significantly fewer children born to Type 1 patients. Among married patients clinical type was not associated with age at marriage, reproductive span or number of children. No reduction of fertility was detected among married patients in whom the onset of MJD was below the age of 50. The authors' interpretation of these results is that the high-repeat CAG haplotypes associated with early age at onset and clinical Type 1 are selected against through reduced survival and fertility. The fertility component of selection is mediated by nuptiality rather than marital fertility.

Adolescent↗