Reproductive changes

Rats and mice both exhibited endocrine and other reproductive changes when exposed to nonlethal doses of PBBs via diet (1000 ppm) or gavage (50 ppm). Toxic doses were embryolethal and in one case teratogenic (rat, single dose 2400 mg/kg). 

Reproductive Change in sex ratio of children Human <1 year 119 174 Mocarelli et al. 1996... 

A rainbow of synthetic colours appeared. Chemists had cracked the chemical structure of colour. Synthetic alizarin allowed thousands of new colours to be produced. Even the legendary Tyrian purple squeezed from the juice of molluscs was duplicated in German laboratories. Nature gave birth to a parallel world, a second nature - artificial colours, then later textiles, substances, any manner of materials. For Engels, the extraction of alizarin and its synthetic reproduction changed everything ... 

Kuhn, H. J., 1976, Antoibitaldriise und TrSnennasengang vonNeotraguspygmaeus, Z. Sdugetier. 41 369-380. Lillie, R. D., 1961, Histopathogenic Technic and Practical Histochemistry. Blakiston Co., New York, pp. 120. Lincoln, G. A., 1971, The seasonal reproductive changes in the red deer stag (Cervus elaphus), J. Zool, Bond. 163 105-123. 

It is often desired to substitute directiy a more readily available fuel for the gas for which a premixed burner or torch and its associated feed system were designed. Satisfactory behavior with respect to dashback, blowoff, and heating capabiHty, or the local enthalpy dux to the work, generally requires reproduction as neady as possible of the maximum temperature and velocity of the burned gas, and of the shape or height of the dame cone. Often this must be done precisely, and with no changes in orifices or adjustments in the feed system. 

To improve the rheological properties and extend the very short working time, a simple polyester is kicluded as thinner. Mixing is easy, and dimensional change ki ak is less than 0.1% over several hours. Elastic recovery and reproduction of detail are exceUent. The elastomeric cycHc imine impression materials have a higher modulus of elasticity than the condensation siHcone or polysulfide mbbers, and are more difficult to remove from the mouth. The materials have relatively low tear strength and an equUibrium water sorption of 14% thus, polyether impression materials tear readily. Because of thek poor dimensional stabUity ki water, they should be stored ki a dry environment. 

A major difficulty which has been encountered with these definitions (identified as a particular problem by EDSTAC) is the definition of the term adverse . For a chemical to be judged an ED, it is important to show that the response seen has an adverse effect on the health or reproductive capacity of affected organisms or populations and is not just a change which falls within the normal range of physiological variation. 

The impact of chemical pollution on the reproductive success and population sizes of wildlife species is often difficult to assess. In many cases, environmental factors such as habitat restriction, stress due to human intrusion and changes in natural food supplies owing to hunting, fishing and restocking policies may have a significant, even predominant, effect on population size. This makes it difficult to determine to what extent, if any, environmental endocrine disrupters may be contributing to observed effects on reproduction or population size in wildlife species. 

In addition to reproductive effects, fish exposed to endocrine disrupters may have a decreased response to stress or decreased growth and metabolism which can affect their ability to survive, or to defend themselves against predators. All of these factors can affect the ability of the species to survive and to reproduce itself in sufficient numbers to maintain the stocks on which our commercial and sport fisheries are based. Not all fish species will be equally susceptible to the effects of endocrine disrupters. Selective sensitivity to such effects, especially those affecting reproduction, may well lead to major changes in the flora and fauna of some of our major aquatic ecosystems as the balance between fish, mammals, invertebrates and plants, and between predators and prey, is destabilised... 

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