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The applicability of male plasma vitellogenin as an indicator of reproductive dysfunction in estrogen-treated cunner was investigated. Results suggest that male plasma vitellogenin is not a reliable indicator of reproductive impairment.
Environmental pollutants are suspected of causing observed adverse effects on development and reproduction in fish and wildlife. Evidence from the laboratory and field suggests that low levels of synthetic or natural chemicals that modulate or disrupt endocrine processes may be responsible. The aquatic environment is a sink for most all potential endocrine disrupting chemicals (EDCs). From egg fertilization to spawning, fish may be exposed to complex mixtures of steroidogenic chemicals that can interfere with the important activational and organizational processes of their endogenous hormones. One consequence of exposure to EDCs may be disruption of the normal mechanisms of sexual development and differentiation, processes that are highly hormone dependent, with subsequent adverse effects on reproduction. My experiments address the hypothesis that exposure to EDCs during early ontogeny affects sexual development and differentiation in fish manifest at maturation. The dr-R strain of medaka was used as the test organism because of qualities that make it a good laboratory animal model and because it possesses a sex-linked gene for body color allowing visual determination of genetic sex from hatch. Medaka were exposed in ovo by nano-injection to five chemical compounds known or suspected to be hormone mimics or disruptors. Details of the effects resulting from exposure to the synthetic sex steroids ethinyl estradiol (EE 2) and methyl testosterone (MT) provided a reference and established a model for predicting effects of in ovo exposure to chemicals which mimic estrogens and androgens. Effects on medaka exposed to the EDCs, o, p ' -DDE and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and three mixtures of polychlorinated naphthalenes (PCN), which have not been tested for their endocrine disrupting potential, were also investigated. In ovo exposure to 0.5 and 2.5 ng EE 2 /embryo or 0.8 and 8.0 ng MT/embryo affected sexual differentiation by causing sex reversal in males and females, respectively. Sexual development of male and female gonads was also affected at these doses. Most notably, all doses of MT resulted in precocious maturation of male and female medaka. Effects on sexual differentiation of the gonads were not as apparent for o, p ' -DDE, TCDD, and the PCNs as were effects on sexual development. Observed effects of these chemicals included one or more abnormalities: histopathological lesions (e.g., atresia), reduced gonad size, and changes in primary germ cell numbers along with volume of primordial gonads. Results for these chemicals together with other's field and laboratory observations provide further evidence that environmental EDCs may be adversely affecting reproduction and development of wild fishes. These results also support the utility of laboratory studies with the dr-R medaka model within the framework of a weight-of-evidence approach to establish a cause-and-effect relationship between environmental exposure to EDCs and reproductive impairment at the individual and population levels.
Endocrine Disrupting Chemicals (EDCs) have been shown to produce changes in the endocrine system of organisms, leading to increases in cancers and abnormalities in reproductive structure and function. This book presents research on the endocrine-disrupting effects of sewage and industrial effluents, covering the sources, fate, and transport of EDCs
Some investigators have hypothesized that estrogens and other hormonally active agents found in the environment might be involved in breast cancer increases and sperm count declines in humans as well as deformities and reproductive problems seen in wildlife. This book looks in detail at the science behind the ominous prospect of "estrogen mimics" threatening health and well-being, from the level of ecosystems and populations to individual people and animals. The committee identifies research needs and offers specific recommendations to decision-makers. This authoritative volume: Critically evaluates the literature on hormonally active agents in the environment and identifies known and suspected toxicologic mechanisms and effects of fish, wildlife, and humans. Examines whether and how exposure to hormonally active agents occursâ€"in diet, in pharmaceuticals, from industrial releases into the environmentâ€"and why the debate centers on estrogens. Identifies significant uncertainties, limitations of knowledge, and weaknesses in the scientific literature. The book presents a wealth of information and investigates a wide range of examples across the spectrum of life that might be related to these agents.
Physiology of the Cladocera, Second Edition, is a much-needed summary of foundational information on these increasingly important model organisms. This unique and valuable review is based on the world’s literature, including Russian research not previously widely available, and offers systematically arranged data on the physiology of Cladocera, assisting with explanation of their life and distribution. It features the addition of new sections and a vast amount of new information, such as the latest data on feeding, nutrition, pathological physiology, chemical composition, neurosecretion, and behavior, as well as hormonal regulation, antioxidants, and the biochemical background of effects of natural and anthropogenic factors. Additional expertly updated contributions in genetics and cytology, and a new chapter in embryology, round out the physiological chapters, and provide comprehensive insight into the state of knowledge of Cladocera and their underlying mechanisms. Cladocera crustaceans have become globally studied for many purposes, including genetic, molecular, ecological, environmental, water quality, systematics, and evolutionary biology research. Since the genome of Daphnia was sequenced and published, that system has gained much wider exposure, also leading to a rapidly growing awareness of the importance of understanding physiological processes as they relate to evolutionary and ecological genomics as well as ecogenomic toxicology. However, the physiological background on Cladocera has been fragmentary (including on the other 700 known species besides Daphnia), despite the extensive literature on species identification and morphology. This work addresses this issue by collecting and synthesizing from the literature the state of knowledge of cladoceran physiology, including discussion on both adequately and inadequately investigated fields, and thus directions of future research. Summarizes fundamental information obtained in recent years, including on steroids, antioxidants, hormones, nanoparticles, and impact of wastewater of pharmaceutical industries Provides the foundational information needed for scientists and practitioners from a variety of fields, including conservation and evolutionary biology, genomics, ecology, ecotoxicology, comparative physiology, limnology, zoology–carcinology, and water quality assessment Features coverage of both Daphniids and representatives of other families, with attention drawn to little-studied aspects of their physiology, especially of those living in the litt oral zone Includes guidance to the literature on cladoceran physiology in four languages Discusses advantages and shortcomings of Cladocera as experimental animals and indicators of water quality