Fertility determinants in the oil region of Mexico

This study analyzes fertility determinants in the oil region of Mexico, consisting of the states of Veracruz, Tabasco, and Campeche. Data are from the 1980 Mexican census and the unit of analysis is the municipio. The regression models, in which the dependent variables of children ever born and child-woman ratio are examined, reveal religious variables to be most significant, with greater fertility for non-Catholics and persons with no religion than for Catholics. Also of great importance are economic variables. Literacy and urbanization, both "classical" Mexican fertility variables, reduce fertility. There are major differences among three urban/rural and three indigenous language subsamples. Results are discussed vis-a-vis demographic theories and prior research.     

Fertility and pacification among the mekranoti of Central Brazil

Demographers and anthropologists have recently turned their attention to the fertility increases that seem to have occurred with the “demographic transition.” This study examines various explanations for historical changes infertility among the Mekranoti-Kayapo Indians of Central Brazil. Data from pregnancy histories and genealogies suggest that changes in health status, use of contraceptives, lactation periods, and post-partum sexual abstinence are not as important in accounting for Mekranoti fertility as is warfare. Because of high male mortality from war, many Mekranoti women spent a large portion of their reproductive years without a husband, and their fertility was significantly lower as a result. This finding may have implications for demographic changes elsewhere and in other periods of human evolution.     

Fertility assessment: new methods and implications for endangered species

Practical and reliable methods for assessing reproductive status are essential for any work designed to enhance fertility in captive endangered species. This paper described recent advances in the development and application of such methods and their implications for the management of captive breeding. Since non-invasive procedures are necessary when working with animals that are easily stressed, urinary hormone analysis provides the most feasible approach to long term studies on most endangered species. Simplified hormone assay methods have been developed and applied to the detection of ovulation and pregnancy in a variety of animals, including primates, the Giant Panda and ungulates. The possibility now exists for extending the application of these methods to studies in the field. Finally, the ability to monitor reproductive status in endangered animals provides the basis for future attempts to accelerate captive breeding by artificial means.     

Fertility evaluation of frozen/thawed semen

In vitro semen analyses have been used for more than half a century to estimate the fertilizing potential of a semen sample. Unfortunately, none of the assays developed provide results that consistently correlate well with fertility. The reasons for this lack of consistency, due in part to the complexity of the spermatozoon itself, the collection of fertility data, and factors beyond control of the semen analyses themselves, are discussed. Different spermatozoal attributes that are necessary for a spermatozoon to fertilize an oocyte are presented and assays used to evaluate each attribute described. Although laboratory assay results do not correlate well with semen fertility, the importance of conducting laboratory assays on every semen sample used for artificial insemination or to attempt to determine causes for infertility, is discussed.     

Fertility levels and trends in Arsi and Shoa regions of Central Ethiopia

Levels and trends of fertility in the Arsi and Shoa regions of Central Ethiopia are examined, using data from the 1986 Population, Health and Nutrition baseline survey of the Ministry of Health of Ethiopia. The population has high fertility. Total fertility of six children per woman in the late 1960s increased to eight children per woman in the early 1980s, then declined to seven children per woman in the mid-1980s. Urban fertility declined by a substantial amount during the 15 years before the survey while rural fertility increased during the same period. The implications of high fertility are considered.     

与衰老相关的母源性生育力下降

老龄妇女与雌性动物生育力下降和丧失的原因包括卵母细胞库减少以及卵巢、输卵管和子宫的结构和功能障碍,但由减数分裂错误引起的卵母细胞质量下降是与衰老相关的母源性生育力下降的主要原因之一。卵母细胞的减数分裂错误主要表现为非整倍性和染色单体提前分离。本文主要综述了影响母源性生育力的各种因素、老龄动物卵母细胞减数分裂错误的原因、纺锤体和染色体改变的机制以及小鼠作为研究妇女年龄与生育力相互关系的动物模型等问题。     

Fertility Desires among Men and Women Living with HIV/AIDS in Nairobi Slums: A Mixed Methods Study

Objectives

Fertility desires require new understanding in a context of expanding access to antiretroviral therapy for people living with HIV/AIDS in Sub-Saharan Africa. This paper studies the fertility desires and their rationales, of slum-dwelling Kenyan men and women living with HIV/AIDS who know their serostatus, but have different antiretroviral therapy treatment statuses. It addresses two research questions: How do people living with HIV/AIDS consider their future fertility? What factors contribute to an explanation of fertility desires among people living with HIV/AIDS.

Methods

A mixed methods study (survey [n = 513] and in-depth interviews [n = 41]) with adults living with HIV/AIDS living in Nairobi slums was conducted in 2010. Regression analyses assess independent relationships between fertility desires and socio-demographic factors. Analyses of in-depth interviews are used to interpret the statistical analyses of fertility desires.

Results

Our analyses show that fertility desires are complex and ambivalent, reflecting tensions between familial and societal pressures to have children versus pressures for HIV (re-)infection prevention. More than a third (34%) of men and women living with HIV expressed future fertility desires; however, this is significantly lower than in the general population. Factors independently associated with desiring a child among people living with HIV/AIDS were age, sex, number of surviving children, social support and household wealth of the respondent.

Discussion

Increasing access to ART is changing the context of future childbearing for people living with HIV/AIDS. Prevailing values mean that, for many people living with HIV/AIDS, having children is seen as necessary for a “normal” and healthy adult life. However, the social rewards of childbearing conflict with moral imperatives of HIV prevention, presenting dilemmas about the “proper” reproductive behaviour of people living with HIV/AIDS. The health policy and service delivery implications of these findings are explored.     

Rapid fertility decline in Iran: analysis of intermediate variables

The remarkable decline in fertility in Iran, which saw the total fertility rate fall from 7 children per woman in 1986 to 2 in 2000, has received only limited analysis in the demographic literature. Using the 2000 Iran Demographic and Health Survey and Bongaarts' age-specific fertility model, this paper examines the role of the major proximate determinants of fertility in bringing about the rapid decrease in fertility in Iran. The analysis indicates that contraception had the largest effect on fertility, accounting for 61% of the reduction in fertility from its theoretical maximum. The fertility-inhibiting effect of marriage patterns accounted for an additional 31% reduction, and was most important among the young. Further analysis of contraceptive behaviour suggests that the current period fertility rate of 2.0 children per woman is an outcome of a synchronization of delaying and spacing of births among younger women with stopping of childbearing among women in the middle and late reproductive ages. The policy implications of the results are discussed.     

植物细胞质雄性不育及其育性恢复的分子生物学研究进展

植物细胞质雄性不育（CMS）和恢复系统在作物杂交种子生产中具有重要的意义。综述了目前已发现的与植物CMS相关的线粒体DNA位点,育性恢复基因对CMS相关DNA位点表达的影响,育性恢复基因的分子标记定位、克隆,及育性恢复分子机理等方面的研究进展,并讨论了恢复基因在植物分子育种上的应用。     

Promiscuity and Fertility: Comments on Greenfield's "The Bruce Effect and malinowski's hypothesis on Mating and Fertility"

Recently, Greenfield has invoked the "Bruce effect' (pregnancy block caused by odors from a strange male) in mice and studies on antisperm antibodies in the serum of prostitutes as support for the hypothesis that promiscuity reduces the fertility of women. This paper disagrees with Greenfield's interpretation and explains why it is invalid to extrapolate such findings in mice to the human condition. Reference is made to studies of human populations that indicate veneral disease may be an important factor in any observed negative correlation between promiscuity and fertility in adults. The phenomenon of adolescent sterility seems likely to be determined mainly by adolescent endocrine imbalance and by immaturity of the female reproductive tract. [population, fertility, promiscuity, sexual relations, adolescent sterility]     

Fertility Preservation Options for Men and Women With Cancer

Approximately 0.2% of Americans aged 20 to 39 years are childhood cancer survivors. Advances in cancer detection and therapy have greatly improved survival rates for young cancer patients; however, treatment of childhood cancers can adversely impact reproductive function. Many cancer patients report a strong desire to be informed of existing options for fertility preservation and future reproduction prior to initiation of gonadotoxic cancer therapies, including surgery, chemotherapy, and radiotherapy. This article discusses, in detail, the effects of cancer treatment on fertility in men and women, and outlines both current and experimental methods of fertility preservation among cancer patients.Key words: Fertility preservation, Childhood cancer, Sperm cryopreservation, Testicular tissue cryopreservation, Spermatogonial stem cell cryopreservation, Embryo cryopreservation, Oocyte cryopreservation, Ovarian tissue cryopreservationIn 2014, an estimated 15,780 new cancer cases were diagnosed among children and adolescents younger than age 20 years, resulting in 1960 deaths. In addition, 1 in 285 children will be diagnosed with cancer before age 20, and approximately 0.2% of Americans aged 20 to 39 years are childhood cancer survivors.¹ Advances in cancer detection and therapy have greatly improved survival rates for young cancer patients; however, treatment of childhood cancers can adversely impact reproductive function (eg, men who survive childhood cancer are half as likely as their siblings to father a child).² Many cancer patients report a strong desire to be informed of existing options for fertility preservation and future reproduction.³ Therefore, the American Society of Clinical Oncology and the American Society for Reproductive Medicine recommend that consideration of fertility preservation be included prior to initiation of gonadotoxic cancer therapies, including surgery, chemotherapy, and radiotherapy.^4–6Infertility as a result of cancer treatment can be psycho logically upsetting for many patients,^3,7,8 and data suggest that those who pursued fertility preservation usually cope better with their cancer treatment.⁹ Infertile cancer survivors have an option to become parents through adoption or gamete donation, but most declare a preference for having a biological child.^3,10 Schover and colleagues³ found that 51% of newly diagnosed young male cancer patients reported a desire to have children in the future, and this rate increased to 77% for those who did not have children at the time of diagnosis. The desire to become a biological parent persists in male cancer survivors, as 70% reported wanting to father a child after chemotherapy treatment.⁹ A history of cancer treatment may be perceived by some to pose an increased risk to the health of future offspring; however, several studies have shown that male cancer survivors have not demonstrated an increased risk for having a child with birth defects or cancer.^11,12 Recently, a retrospective cohort study conducted in the United States showed no increased risk of malformations or premature birth in the offspring of male cancer survivors.¹³The optimal time for consideration of fertility preservation is before the initiation of any oncologic therapy that can affect gametogenesis; thus, it is critical that fertility preservation is discussed with all patients at the time of diagnosis and before treatment starts. Practitioners who provide care for cancer patients should be aware of the relationship between cancer treatment and infertility. Moreover, they need to be able to appropriately refer patients to a reproductive medicine specialist in a timely fashion for further counseling and fertility preservation. Although fertility concerns are paramount to young adults with cancer, many oncologists still do not routinely address these concerns.^3,14 In a survey of 200 young male cancer survivors who were primarily treated at a comprehensive cancer center, only 51% recalled being offered sperm cryopreservation prior to their cancer treatment.³ Further, it is important to recognize the psychologic stressors associated with a new cancer diagnosis and associated late effects of cancer treatment, such as infertility or early menopause. Findings from several studies support the importance of counseling patients regarding their risk for fertility issues and educating providers regarding the potential fertility preservation options that are available. For example, Babb and colleagues¹⁵ found that, at many institutions, this counseling is already taking place and there is a high rate of discussion with newly diagnosed patients regarding infertility.     

A stochastic version of the brass PF ratio adjustment of age-specific fertility schedules

Estimates of age-specific fertility rates based on survey data are known to suffer down-bias associated with incomplete reporting. Previously, William Brass (1964, 1965, 1968) proposed a series of adjustments of such data to reflect more appropriate levels of fertility through comparison with data on children-ever-born by age, a measure of cohort-specific cumulative fertility. His now widely-used Parity/Fertility or PF ratio method makes a number of strong assumptions, which have been the focus of an extended discussion in the literature on indirect estimation. However, while it is clear that the measures used in making adjusted age-specific fertility estimates with this method are captured with statistical uncertainty, little discussion of the nature of this uncertainty around PF-ratio based estimates of fertility has been entertained in the literature. Since both age-specific risk of childbearing and cumulative parity (children ever born) are measured with statistical uncertainty, an unknown credibility interval must surround every PF ratio-based estimate. Using the standard approach, this is unknown, limiting the ability to make statistical comparisons of fertility between groups or to understand stochasticity in population dynamics. This paper makes use of approaches applied to similar problems in engineering, the natural sciences, and decision analysis--often discussed under the title of uncertainty analysis or stochastic modeling--to characterize this uncertainty and to present a new method for making PF ratio-based fertility estimates with 95 percent uncertainty intervals. The implications for demographic analysis, between-group comparisons of fertility, and the field of statistical demography are explored.     

Molecular Control of Male Reproductive Development and Pollen Fertility in Rice

Anther development and male fertility are essential biological processes for flowering plants and are important for crop seed production. Genetic manipulation of male fertility/sterility is critical for crop hybrid breeding. Rice (Oryza sativa L.) male sterility phenotypes, including genic male sterility, hybrid male sterility, and cytoplasmic male sterility, are generally caused by mutations of fertility‐related genes, by incompatible interactions between divergent allelic or non‐allelic genes, or by genetic incompatibilities between cytoplasmic and nuclear genomes. Here, we review the recent advances in the molecular basis of anther development and male fertility‐sterility conversion in specific genetic backgrounds, and the interactions with certain environmental factors. The highlighted findings in this review have significant implications in both basic studies and rice genetic improvement. [ Yao‐Guang Liu (Corresponding author)]     

Fertility in Pakistan during the 1970s

Evidence of trends in fertility and related variables in Pakistan during the 1970s is analyzed using data from 2 comparable surveys: the 1975 Pakistan Fertility Survey (PFS) and the 1979-80 Population, Labor Force and Migration Survey (PLM). Both suggest that fertility was fairly constant, with a total fertility rate around 7.0 until the 5-year period preceding the surveys (1970-74 and 1975-79, respectively), during which it declined abruptly. The apparent date of the decline is thus conflicting. The evidence of recent decline in each survey is likely to be spurious, the result of systematic distortions in the reporting of dates. The present research finds evidence that fertility as measured by age-specific and marital age-specific rates did not change in Pakistan during the 1970s, except for a decline in age group 15-19 as a result of delayed marriage. An analysis of levels and trends in selected components of fertility indicates that all subgroups, except literate women, show a rise in the average age at marriage of the order of 1/2 a year or so. Differentials between subgroups are in the expected direction, with literate women marrying later than illiterate ones and women in urban areas marrying later than those in rural areas. There is no notable change in the % of children being breastfed; however, the average duration of breastfeeding shows a non-trivial decline in all subgroups. Nonetheless prolonged breastfeeding is still the general practice. Current use of contraception at the time of the 2 surveys actually declined by 1980, while knowledge, reported ever-use, and fertility preferences all moved in a pronatalist direction. The lessons of this study are primarily methodological. In particular, the analysis of fertility change in the future in Pakistan will require either more reliable reporting of birth histories, or the continued piecing together of 2 or more surveys.     

Fertility estimation: a review of past experience and future prospects

Fertility has many components and stages which require that males and females be functionally capable of carrying out all critical stages if each generational reproductive cycle is to be completed. To accomplish this, the male must produce and ejaculate normal fertile sperm. The female must produce, store and ovulate normal fertilizable oocytes. Furthermore, the female must provide a reproductive system compatible with sperm transport, capacitation, and fertilization of the oocytes, embryo and fetal development, and finally birth of healthy young. Reproductive success or failure at several of these points can be estimated quantitatively on a population basis, and in a few situations on an individual basis. It is important that fertility estimates be determined accurately and with precision to be most useful to researchers and managers of animal enterprises. Many studies have underestimated the biological relationship of fertility to other traits because the estimates lacked precision. Many in vitro manipulations of sperm in artificial insemination, of gametes in various assisted reproductive technologies, and of embryos in embryo transfer are utilized in animal breeding programs. Accurate estimation of reproductive efficiency of these in vitro procedures also is important. Conditions surrounding different sets of fertility estimates almost certainly will be different. These conditions should be described as precisely as possible, and appropriate controls included in all experiments. When possible, experiments should be replicated over time and place to determine the repeatability of the various criteria used to estimate fertility and reproductive efficiency. Advances in genomic information and molecular biology should facilitate characterizing more fully inherent potential fertility of animals at birth. In vitro tests will improve, and automated techniques will facilitate making multiple determinations possible on a large scale. Reliability of fertility estimates will increase, with the potential for enhanced animal reproductive performance through more accurate selection, genetic engineering, and enlightened animal care. Simultaneously, it is important to recognize that prediction of future fertility is more hazardous than estimating fertility, as a completely new set of circumstances may occur which are not predictable. Because fertility estimation may be applied under a myriad of conditions, principles and factors affecting fertility will be emphasized in this review as being more useful than a compilation of numerical examples.     

Fertility preservation and preimplantation genetic assessment for women with breast cancer

Breast cancer is the most common cancer diagnosed among reproductive aged women, and its treatment can compromise future fertility. Options for fertility preservation include oocyte or embryo cryopreservation after ovarian stimulation (OS), which are the most established choices and are applicable for adult women with cancer. Ovarian tissue freezing may also be appropriate, as it offers potentially the least delay. The recognisation of the role of BRCA1 and BRCA2 mutations in some women has led to the involvement of preimplantation genetic diagnosis (PGD), recently renamed preimplantation genetic testing for monogenic disorder (PGT-M), whereby embryos are created by IVF and cell(s) are removed and genetically analyzed for specific disease-related mutations. PGT-M offers a valid option for women wishing to avoid transmission of the predisposition for hereditary breast cancer to their offspring. The aim of this paper is to provide an overview of the factors that influence fertility preservation in newly diagnosed breast cancer patients, and to illustrate the option of PGT-M to enable conception of an unaffected child.     

Fertility Advertisement in Birds: a Means of Inciting Male-male Competition?

Certain loud calls made by female red junglefowl and Lapland longspurs are given most frequently immediately after egg laying, when a copulation should have the highest probability of fertilizing the next egg to be laid. In these species there is considerable male-male interaction for access to fertilizable females, and males are attracted to or follow females making these calls. Based on our interpretation of these calls, we develop a general hypothesis to predict the pattern of occurrence of fertility advertisement both within and among bird species. We hypothesize that certain loud calls given by female birds before and during the egg-laying period are designed to advertise fertility and thereby incite male-male competition. This hypothesis predicts that calls advertising female fertility should most often occur soon after an egg is laid (i.e. during the period of highest fertility) but may also occur at any time during the female's fertilizable period. Such calls are unlikely to be given by females in strictly monogamous species (especially those with long-term pair bonds) because in these species each female usually mates with only a single male and extra-pair copulations are avoided. Although reports of loud female calls associated with copulation are rare in the literature, the 18 examples we found (including junglefowl and longspurs) were predominantly (15/18) in species adopting mating systems other than strict monogamy, and these calls were most commonly and disproportionately reported in multi-male mating systems. This form of “estrus” in birds may be widespread because few species appear to be strictly monogamous, but it will be difficult to study because the period of high fertility for female birds is so short.     

Fertility,sex determination,and the X chromosome

Because of its function, the X chromosome has a special status in mammalian genomes, with the specific occurrence of genes that influence both female and male fertility. Long ago, the XO karyotype (Turner syndrome) was associated with infertility, proving the correlation between normal X chromosome dosage and normal female fertility. Nevertheless, the search for specific X-borne fertility genes was not completely successful and suggested, instead, that female X-linked fertility, for example, depends upon groups of X-linked genes. Conversely, X-linked hyperfertility has been observed in sheep, where a mutation in BMP15 leads to a hyperfertile phenotype, but only in the heterozygous state. Many male fertility genes map to the X chromosome, consistent with a genetic model developed in the early 1990s. Ironically, NR0B1 (formerly DAX1), once presented as the paradigm of genes responsible for ovarian development and function, is probably one of these male fertility factors and is active in the maintenance of spermatogenesis. Indeed, duplications of this gene on the human X chromosome lead to XY sex reversal, as NR0B1 is able to counterbalance the effect in humans. Nevertheless, invalidation experiments in mice demonstrate the effect of this factor on male germ-cell production.     

Bayesian Inference of Baseline Fertility and Treatment Effects via a Crop Yield-Fertility Model

To effectively manage soil fertility, knowledge is needed of how a crop uses nutrients from fertilizer applied to the soil. Soil quality is a combination of biological, chemical and physical properties and is hard to assess directly because of collective and multiple functional effects. In this paper, we focus on the application of these concepts to agriculture. We define the baseline fertility of soil as the level of fertility that a crop can acquire for growth from the soil. With this strict definition, we propose a new crop yield-fertility model that enables quantification of the process of improving baseline fertility and the effects of treatments solely from the time series of crop yields. The model was modified from Michaelis-Menten kinetics and measured the additional effects of the treatments given the baseline fertility. Using more than 30 years of experimental data, we used the Bayesian framework to estimate the improvements in baseline fertility and the effects of fertilizer and farmyard manure (FYM) on maize (Zea mays), barley (Hordeum vulgare), and soybean (Glycine max) yields. Fertilizer contributed the most to the barley yield and FYM contributed the most to the soybean yield among the three crops. The baseline fertility of the subsurface soil was very low for maize and barley prior to fertilization. In contrast, the baseline fertility in this soil approximated half-saturated fertility for the soybean crop. The long-term soil fertility was increased by adding FYM, but the effect of FYM addition was reduced by the addition of fertilizer. Our results provide evidence that long-term soil fertility under continuous farming was maintained, or increased, by the application of natural nutrients compared with the application of synthetic fertilizer.     

Fertility of Deep Frozen Boar Spermatozoa

In the present investigation the results of two insemination trials with deep frozen boar spermatozoa are presented. The aim of the trials was to study the effect of different thawing diluents and to compare the fertility of deep frozen spermatozoa from four boars. The trials utilized a total of 139 gilts. The thawing diluents used were boar seminal plasma, protein free seminal plasma, the thawing diluent OLEP and isotonic glucose solution. The composition of OLEP was based on physical and biochemical analyses of boar seminal plasma. The electrolyte levels, pH and osmotic pressure of OLEP are similar to those of boar seminal plasma. From the results it is evident that thawing in boar seminal plasma, protein free seminal plasma and OLEP yielded equal results. Thawing in isotonic glucose solution yielded significantly poorer results concerning percentage of fertilized ova 24–48 hrs. after insemination and almost significantly poorer fertility results four weeks after insemination. The possible effects of the thawing diluents are discussed. With the freezing procedure applied, electrolyte levels, pH and osmotic pressure seem to be factors of importance for the survival of the frozen and thawed spermatozoa and for the maintenance of their fertilizing capacity. Almost significant differences were found in fertility of spermatozoa from different boars. These differences were reflected in pregnancy rates as well as ratio of foetuses to c. 1. in pregnant gilts. The differences were found to be independent of thawing diluent. The variation seems to be caused by differences in resistance of the spermatozoa to the freezing and thawing procedure. The need for laboratory methods for selection of boars with spermatozoa of good freezability is stressed.