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PubMed2000

Time trends in biological fertility in Britain.

BACKGROUND: There is evidence of a decline in semen quality in some countries, including Britain, in recent decades. This retrospective cohort study examined the hypothesis that biological fertility had also declined. The trend in couple fertility was assessed by means of time to pregnancy (TTP--a sensitive and validated measure of fertility. METHODS: A representative sample of the British population aged 16-59 years was surveyed. TTP was obtained for all births conceived after unprotected intercourse that began during 1961-93, excluding contraceptive failures. The sample size was 1540. FINDINGS: In contrast to the original hypothesis, this study found that fertility has increased; the rising trend was accompanied by slight dips during 1976-80 and 1986-90. These results were consistent between male and female respondents, and undiminished by adjustment for possible confounding factors. A stronger and more consistent relation was found with the year when unprotected intercourse started (a period effect) than with the year of birth of either partner (a birth cohort effect). INTERPRETATION: The findings could not be explained by trends in age at first birth, increased treatment of subfertility, or changes in oral contraceptive use. If a decline in male fertility has occurred, it has been more than compensated for by a countervailing increase in couple fertility.

Adolescent↗
PubMed1990

Ethnic fertility differentials in Peninsular Malaysia and Singapore.

Differences in fertility between the three major ethnic groups (Malays, Chinese and Indians) in Peninsular Malaysia and Singapore have existed since before the onset of fertility decline in the late 1950s and remain today, although the relative positions and the actual differences have changed due to the varying rates of decline. By 1987, the Malays experienced the highest fertility and the Chinese the lowest in both countries but in Singapore the Malay fertility was lower than the Chinese fertility in Peninsular Malaysia. The fertility differentials will lead to changes in the ethnic composition in both countries but more so in Peninsular Malaysia.

Adolescent↗
PubMed2000

The fertility impact of temporary migration in China: a detachment hypothesis.

This paper expands the migration-fertility linkage literature by examining the fertility impact of temporary migration in Hubei, China. The central hypothesis is that temporary migration affects migrants' fertility through a detachment process: The separation of temporary migrants' actual residence from their de jure residence creates a loophole in family planning administration, weakening the social control over their fertility. The analysis of annual order-specific births since 1979 suggests that temporary migrants exhibit significantly higher probabilities of having a second birth than permanent migrants and nonmigrants once type of residence is controlled for: rural-rural temporary migrants have the highest fertility among all groups examined. The results lend support to the detachment hypothesis while indicating a strong antinatal impact of urban residence. Rural-urban temporary migrants are not the ones to blame for increases in outplanning births in contemporary China, but their fertility would have been lower if there had been no detachment. Rural-rural temporary migrants are actually the escapees of the one-child-per-family policy.

Asia↗
PubMed1988

World system status, techno-economic heritage, and fertility.

The relevance of world system/dependency theory, and ecological-evolutionary theory for the population processes of currently developing nations is explored and evaluated by testing hypotheses drawn from models of fertility and fertility decline implied by them. Despite the preliminary and necessarily limited nature of the tests and measures, some support is found for hypotheses drawn from boh perspectives. Techno-economic heritage is found to affect fertility change directly, and world system status and techno-economic heritage are each found to affect fertility level and fertility change through independent effects on intervening variables. In addition, a significant interaction effect of techno-economic heritage and world system status on fertility level is found.

Birth Rate↗
PubMed1991

[Estimates of natural fertility in rural Tokugawa Japan].

"This paper estimates the value of [natural fertility] and [the degree of parity-specific fertility control] in rural Tokugawa Japan mainly using [the Coale-Trussell model]. What we gained through this analysis is 1) the level of natural fertility in rural Tokugawa Japan was very low compared to the pre-transition level of England, [and] 2) in spite of this low level fertility, parity-specific fertility control was not practiced.... We can say that rural Tokugawa Japan since the second half of [the] seventeenth-century was in a 'natural fertility regime'...." (SUMMARY IN ENG)

Asia↗
PubMed1994

[Analysis of the results obtained in fertilization in vitro according to the degree and type of teratospermia].

The aim of this study was to evaluate the consequences of sperm morphology abnormalities on fertilization capacity. We selected 115 couples who consulted for in vitro fertilization at the Salengro Maternity Ward (Lille, France). Teratospermia was > 40% in all. The mean rate of cleavage was 23% and was significantly lower than in a population which had had in vitro fertilization for a tube indication (63%, p < or = 0.001). In addition, this level was significantly correlated with teratospermia (p < or = 0.05). The ROC method demonstrated that above the threshold of 74% teratospermia, fertilization decreases significantly. We distinguished several types of abnormal morphology and demonstrated a weak correlation between head abnormalities and the rate of cleavage, a stronger correlation between abnormalities of the intermediary piece and rate of cleavage and finally the absence of any correlation between flagella abnormalities and the rate of fertilization. Teratospermia is therefore an important factor in evaluating fertilization capacity. A better selection of normal spermatoids could improve the chance of success in cases of male sterility.

Adult↗
PubMed1998

Fertility levels, trends, and differentials in sub-Saharan Africa in the 1980s and 1990s.

This study presents an assessment of fertility trends in 23 countries of sub-Saharan Africa. It examines trends and differentials in proximate determinants and fertility preferences. Findings from the Demographic and Health Surveys for these countries over a period of 15 years show that desired family size has decreased significantly. Two-thirds of the countries examined show evidence of fertility decline, a particularly rapid decline in the cases of Kenya and Zimbabwe. Areas with higher education for women and lower child mortality experienced larger reductions in fertility and desired family size. Contraceptive use far exceeds other proximate determinants in explaining these changes. The striking regularity in fertility reduction across all ages indicates that contraception is practiced mostly for birth spacing and that contraceptive methods have gained wide acceptance among younger cohorts. Good prospects are seen for further intensification of fertility declines in East Africa and urban West Africa. However, low levels of education and high child mortality make rapid changes unlikely in rural West Africa.

Adolescent↗
PubMed1994

Determinants of racial fertility differentials in some urban areas of South Africa.

Results of a survey of some urban areas in the Pretoria-Witwatersrand-Vereenining region show differential impacts of proximate and socioeconomic factors on the fertility of urban blacks and whites. Timing of starting and ending of childbearing and the reproductive behaviour of women who have never been married account for the major differences in fertility levels. White women confine their childbearing career to the 20-39 age range, while black women utilise the entire 15-49 age range. The fertility level is quite high among black women who have never been married (in contrast to never married white women). With the exception of breast-feeding, racial patterns in other proximate determinants of fertility do not suggest the observed racial differentials in fertility.

Adolescent↗
PubMedDate not supplied

Tunisia WFS [World Fertility Survey].

Tunisia, the smallest North African country in size, has recently published the results of its part of the World Fertility Survey (WFS) taken in 1978. About 1/2 of this Missouri-sized country consists of arid and semiarid desert, with well-irrigated fertile areas in the north. The country, which has a population of about 7 million, must import large quantities of food each year and also suffers from widespread unemployment. In 1964, the government was among the earliest to announce a policy to reduce the rate of population growth and Tunisia now has 1 of the lowest birth rates of the African continent (33 births/1000 population) although it is still moderately high. Part of the reason for the birth rate decline has been a risking age at marriage; the legal minimum was fixed at 17 years for women and 20 for men by a 1964 law. The Tunisia WFS indicates that, of women 20-24 in 1978, 56% had not yet married, a large increase from the 27% of 1966. The mean age at 1st marriage for females was 24 in 1978, very high by less developed country standards. It may be that the fertility-lowering impetus from rising age at marriage has been spent (this measure cannot rise indefinitely): Tunisia's total fertility rate (TFR), the average number of children/woman, dropped from 7.1 children in 1966 to 5.7 in 1976, but the decrease has tapered off somewhat since. The TFR appears to have dropped to 5.2 as of 1981. When asked how many children they would like to have, the women surveyed gave 4.2 children, on average, as their "ideal" number. This number is, of course, considerably above that needed to ultimately stop population growth (about 2.1-2.5 children/woman). Contraceptive use in Tunisia is quite high by developing country standards; much of this is due to the efficient network of government-sponsored clinics. About 44% of the women exposed to pregnancy were practicing an efficient form of family planning with the pill or sterilization accounting for most of that number (22 and 20% respectively). Nonetheless, traditions which still favor 3-5 children and some possible loss of momentum from a rising age at marriage may cause future fertility declines to be slower than in the recent past. Tunisia does present an interesting case of a country maintaining a government program to reduce population growth as an overall part of the country's development efforts.

Africa↗
PubMedDate not supplied

The impact of development and population policies on fertility in India.

This article examines the impact of development and population policies on fertility decline and regional variations in India during the 1970s. Indicators of development at the household level include female literacy and education, infant mortality, and poverty; at the village level they include availability of such social services as schools, medical facilities, and transportation and communication facilities. Multiple regression analysis of data aggregated at the state level demonstrates that conditions conducive to fertility decline include high adult female literacy and low infant mortality as indicators of social development, and high contraceptive use and, to a lesser extent, high female age at marriage as proximate determinants of fertility. There are reasons to believe that India's national family planning program contributed to the decline in fertility observed since the 1960s. The pace of fertility decline in the future will depend upon the pace of infant mortality decline, enhancement in female education, and improvements in family planning programs.

Birth Rate↗
PubMedDate not supplied

Effects of PKC zeta on early genome transcription activation in mouse 1-cell stage fertilized eggs.

Effects of PKC zeta on the activation of embryonic transcription in 1-cell stage fertilized mouse eggs were explored. The effects of PKC antagonist calphostin C and PKC zeta specific inhibitor on the activation of embryonic early transcription were observed by Western blotting and cell immunofluorescence. PKC activity increased gradually from G1 phase to late G2 phase in mouse 1-cell stage fertilized eggs, and reached a maximum in G2 stage. Calphostin C inhibited PKC activity by about 47% in 1-cell stage fertilized eggs. Calphostin C inhibited early transcription in 1-cell stage fertilized eggs (p < 0.01). PKC zeta-Thr410 in G2 were about 27% and 110% higher than those in G1 phase of 1-cell stage fertilized eggs and MII oocytes, respectively. PKC zeta specific inhibitor can also inhibit early transcription in 1-cell stage fertilized eggs (p < 0.05). The results suggest that PKC zeta participates in early transcription activation in mouse 1-cell stage fertilized eggs.

Animals↗
PubMed2004

Fertility after testicular cancer treatments: results of a large multicenter study.

BACKGROUND: Patients with testicular cancer have an excellent survival rate, and fertility is one of the main concerns of survivors. The authors investigated fertility status after treatment for testis cancer in long-term survivors. METHODS: Four hundred fifty-one consecutive patients with testicular cancer (1979-1999) from health facilities in the French Midi-Pyrenees region were enrolled. Testis tumors were classified according to the Royal Marsden Hospital Classification. Fertility status was assessed by means of a mailed, standardized questionnaire focused on reproductive events that occurred before and after treatment. Of 451 patients with germ-cell tumors, information concerning fertility was obtained in 446 patients (98.9%). The follow-up was at least 3 years. RESULTS: Before they were diagnosed with testicular cancer, 91.2% of patients who had tried to get their partners pregnant had succeeded, compared with 67.1% of patients after treatment. Radiotherapy had a much more deleterious effect on fertility compared with chemotherapy alone. Furthermore, cumulative conception rates (log-rank test) for patients who received radiotherapy were significantly lower compared with the rates for patients who received chemotherapy. CONCLUSIONS: The outcome of this study, which included the largest series reported to date, showed that fertility in patients with testicular cancer decreased by 30% after treatments and that radiotherapy seemed to have the most deleterious effect on fertility.

Adolescent↗
PubMed1980

Glycerol permeabilities of fertilized and infertilized mouse ova.

The coefficients of permeability to glycerol, Pglyc, and their temperature-dependence were determined from volume changes of fertilized and unfertilized mouse ova under hyperosmotic conditions. Fertilization caused a significant increase in the value of Pglyc. Unfertilized ova exhibited Pglyc values of 1 X 10(-5), 2 X 10(-6), and 5 X 10(-7) cm/min at approximately 20 degrees C, and approximately 12 degrees C, and approximately 3 degrees C, respectively. Fertilized ova exhibited Pglyc values of 3.4 X 10(-5), 1.3 X 10(-5), and 4.7 X 10(-6) cm/min at apoproximately 20 degrees C, 12 degrees C, and approximately 3 degrees C, respectively. The activation energy of glycerol permeation into fertilized and unfertilized ova was calculated to be 18.7 and 28.4 kcal/mol, respectively. Fertilization caused a rather dramatic increase in glycerol permeability, the major extent of which occurred within about 3 hours after fertilization. Pglyc was also measured at approximately 20 degrees C by isotope uptake. Glycerol uptake calculated indirectly from the volume changes of the ova agreed well with that measured directly by labeled glycerol uptake. It was also found that the zona pellucida fertilized and unfertilized ova did not detectably impede the permeation by glycerol.

Animals↗
PubMed1992

The sperm entry site during fertilization of the zebrafish egg: localization of actin.

The sperm entry site (SES) of zebrafish (Brachydanio rerio) eggs was studied before and during fertilization by fluorescence, scanning, and transmission electron microscopy. Rhodamine phalloidin (RhPh), used to detect polymerized filamentous actin, was localized to microvilli of the SES and to cytoplasm subjacent to the plasma membrane in the unfertilized egg. The distribution of RhPh staining at the SES correlated with the ultrastructural localization of a submembranous electrondense layer of cortical cytoplasm approximately 500 nm thick and containing 5- to 6-nm filaments. Actin, therefore, was organized at the SES as a tightly knit meshwork of filaments prior to fertilization. Contact between the fertilizing sperm and the filamentous actin network was observed by 15-20 sec postinsemination or just before the onset of fertilization cone formation. Growing fertilization cones of either artificially activated or inseminated eggs exhibited intense RhPh staining and substantial increase in thickness of the actin meshwork. Collectively, TEM and RhPh fluorescence images of inseminated eggs demonstrated that the submembranous actin became rearranged in fertilization cones to form a thickened meshwork around the sperm nucleus during incorporation. The results reported here suggest that activation of the egg triggers a dramatic polymerization of actin beneath the plasma membrane of the fertilization cone. Furthermore, the actin involved in sperm incorporation is sensitive to the action of cytochalasins.

Actin Cytoskeleton↗
PubMed1999

Seasonal patterns of singing in the willow warbler: evidence against the fertility announcement hypothesis.

Males of many bird species use a variety of behaviour patterns that reduce their chances of being cuckolded. The 'fertility announcement' hypothesis (Møller 1991, American Naturalist, 138, 994-1014) proposes that song might be one such paternity guard. According to this hypothesis, paired males would announce their female's fertile status by singing. This has been interpreted as an honest signalling, evolutionarily stable strategy. Contrary to the predictions of this hypothesis, male willow warblers, Phylloscopus trochilus, sang very little when females were fertile. Intrusions by other males in the fertile period were not less common when males sang at higher rates. Mate guarding and singing are best interpreted as two conflicting behaviours during this period, the former being directed to the fertile female and the latter to attracting a second female, or an extrapair female. A survey of recent studies suggests that, in most passerine species studied, males do not sing during the fertile period of their females. The different conclusions of Møller (1991) are probably due to his use of population-wide estimates of the timing of singing behaviour and egg laying. Breeding asynchronies within populations would be responsible for the apparent matching between the peaks of singing activity and fertility. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1993

Involvement of the plasminogen activator/plasmin proteolytic cascade in fertilization.

At the time of fertilization both murine gametes express plasminogen-dependent proteolytic activity: unfertilized eggs secrete tissue-type plasminogen activator and ejaculated spermatozoa have urokinase-type plasminogen activator bound to their surface. We now report that plasminogen is present in the fertilization environment and that both spermatozoa and eggs are able to specifically bind plasminogen. Furthermore, in vitro fertilization of mouse eggs is inhibited by antibodies which inhibit the catalytic activity of plasmin. Finally, with two different in vitro fertilization protocols, the addition of plasminogen to the fertilization medium increases the yield of fertilized eggs. These results provide evidence for a role of the plasminogen activator/plasmin proteolytic cascade in mammalian fertilization.

Animals↗
PubMed2002

Considerations of correlated fertility between genders on genetic diversity: the Pinus densiflora seed orchard as a model.

The correlation between 99 clone female and male fertilities in a first generation seed orchard of Pinus densiflora was studied over 6 years. The effective number of the parent ( N(p)) and the variance effective population number [ N(e)((v))] were used to assess the impact of total (Psi(T)), female (psi(f)) and male (psi(m)) fertility variation. A theoretical framework was developed to account for female and male fertility correlations as well as the impact of possible pollen contamination. Total fertility variation was described by the sibling coefficient (Psi(T): the probability that two genes randomly chosen from the gamete gene pool originate from the same parent), which was further subdivided into psi(f) and psi(m). These parameters were compared under various conditions including the total seed harvest, imposing on equal seed harvest among the orchard's clones and two contamination scenarios ( M = 0 and 20%). Fertility variations among females, males and clones were observed within and among years. Sibling coefficients (Psi(T)) were lower, but the effective number of parent ( N(p)) and variance effective population number ( N(e)((v))) were higher in years with moderate female and good male strobilus production. N(p) for female and male reproductive outputs varied from 49 to 82 and from 57 to 93, respectively. N(p) was higher for males than females. When the crop of the 6 years was pooled, N(p) for female, male and the clone were 73, 87 and 85, respectively. The impact of female-male fertility correlation for conditions with no-, positive- and negative-correlations were assessed and their impact on Psi(T), N(p) and N(e)((v)) was also evaluated. It was demonstrated that the practice of equal seed harvesting from every clone, or the mixing of seeds from several years, would substantially improve the genetic diversity and the genetic representation of the seed orchard population when a positive correlation between gender fertilities was observed. The relevance of these results to supplemental-mass-pollination was discussed under two cases where equal- and un-equal amounts of pollen from clones were included in the pollen mixes.

Journal Article↗
PubMed2003

Identification of AFLP markers linked to fertility restorer genes for tournefortii cytoplasmic male-sterility system in Brassica napus.

The tournefortii cytoplasmic male-sterility system is being used as a method of pollination control to develop hybrids in Brassica napus. Genetic analyses have indicated that two dominant genes, one major ( Rft1) and another minor ( Rft2), were required to achieve complete fertility restoration. Though the major gene ( Rft1) can cause complete fertility restoration on its own, its expression was significantly enhanced in the presence of the minor gene ( Rft2). In the absence of Rft1, Rft2 caused only partial fertility restoration. We used a pair of near-isogenic lines (NILs), differing for the presence/absence of Rf genes, to identify AFLP markers linked to fertility restorer genes. A total of 64 EcoRI/ MseI primer combinations were surveyed which produced 3,225 bands, of which 19 (0.006%) were polymorphic between parental NILs. Primer combinations which led to the identification of polymorphic bands present in fertile parental NILs were used for assaying a mapping population of 70 F(2) plants for determining the segregation pattern of markers. Initial screening resulted in the identification of five AFLP markers. The recombination analyses of these AFLP markers revealed that at least two (EACC/MCTT(105), EAAG/MCTC(80)) were present in the same linkage group along with the Rf loci. Marker EACC/MCTT(105) was separated from the major gene ( Rft1) by a distance of 18.1 cM, while it was 33.2 cM away from the minor fertility restorer gene ( Rft2). Another marker EAAG/MCTC(80) was also located adjacent to Rft1 at a distance of 18.1 cM, but on other side. Identification of flanking markers (EACC/MCTT(105), EAAG/MCTC(80)) for the major fertility restorer gene ( Rft1) provides a crucial component for marker-assisted selection and map-based cloning of the restorer genes, and can hence be used to construct elite restorer genotypes.

Brassica↗