Disruption of the Reproductive Axis in Freshwater Fish, Catla catla, After Bisphenol-A Exposure.

Environmental estrogens such as bisphenol-A (BPA) cause reproductive disorders in many vertebrate species, especially fish. BPA is used extensively in the manufacture of plastic and plastic products, epoxy resins, and dental sealants. The presence of BPA in sewage and surface water raises a potential threat to aquatic populations. In the present study, we investigated the effects of BPA on ovarian histology and transcription of key genes involved in reproduction. Adult female Catla catla were exposed to graded concentrations of BPA (10, 100, 1000 µg/l) for 14 days. Ovary histology and expression of steroidogenic acute regulatory protein (star), ovary aromatase (cyp19a), follicle-stimulating hormone receptor (fshr), and luteinizing hormone receptor (lhr) were evaluated in ovary of female fish after 14 days. Fish ovaries from the control and 10 µg/l BPA exposed groups included primary oocytes (POCs), while fish exposed to higher concentrations of BPA (100 and 1000 µg/l) contained tertiary and mature oocytes with increased numbers of atretic follicles. Significant increases in mRNA transcripts of star were observed in fish exposed to 100 and 1000 µg/l BPA. A 15-fold increase in the expression of ovary aromatase (cyp19a) was detected in fish exposed to 100 µg/l BPA. fshr increased in a dose-dependent manner. Increases in the expression of lhr, although not statistically significant, were observed in fish exposed to 100 and 1000 µg/l BPA when compared to control. The results of the present study indicate that BPA causes alterations in the expression patterns of genes involved in the reproductive pathway, which may lead to negative effects on the reproductive system in female fish.

Fluoride Exposure, Follicle Stimulating Hormone Receptor Gene Polymorphism and Hypothalamus-pituitary-ovarian Axis Hormones in Chinese Women.

The effects of fluoride exposure on the functions of reproductive and endocrine systems have attracted widespread attention in academic circle nowadays. However, it is unclear whether the gene-environment interaction may modify the secretion and activity of hypothalamus-pituitary- ovarian (HPO) axis hormones. Thus, the aim of this study was to explore the influence of fluoride exposure and follicle stimulating hormone receptor (FSHR) gene polymorphism on reproductive hormones in Chinese women. A cross sectional study was conducted in seven villages of Henan Province, China during 2010-2011. A total of 679 women aged 18-48 years were recruited through cluster sampling and divided into three groups, i.e. endemic fluorosis group (EFG), defluoridation project group (DFPG), and control group (CG) based on the local fluoride concentration in drinking water. The serum levels of gonadotropin releasing hormone (GnRH), follicle stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were determined respectively and the FSHR polymorphism was detected by real time PCR assay. The results provided the preliminary evidence indicating the gene-environment interaction on HPO axis hormones in women.

Selected enquiries into the causation of premature ovarian failure.

In most species, reproductive senescence can be explained in the same general terms as physiological senescence. In fact, in some species rapid physiological senescence occurs on the completion of reproduction. The programme in women is unusual in that ovarian function comes to a relatively abrupt halt at 45-50 years of age, when the impact of somatic senescence on most other functions is minimal. Early reproductive senescence has been reported in other species (chimpanzees, macaques and toothed whales) but it is more attenuated and less abrupt. The proximate cause of physiological menopause seems to be oocyte depletion, but less obvious neuroendocrine changes precede or result from the gradual loss of oocytes. This is not surprising as many age-specific processes are controlled by hormones. Hormones provide a way for an animal to co-ordinate the ageing of different tissues. The failure to comprehend completely the reasons for the biological uniqueness of women makes the study of the more extreme examples of premature ovarian failure an important exercise. The premature loss of ovarian function in certain eukaryotic women highlights the role of those special maintenance and repair systems that must be functional in the selection process for healthy germ cells. The purpose of this article is to indicate selected areas of clinical and basic investigation that may provide clues to the mechanisms of untimely ageing of the human ovary. Studies of those human extremes with premature loss, or extended ovarian function, may provide critical insights into the unique discordance between somatic and reproductive senescence that is characteristic of normal women.