Impairment of the reproductive potential of male fathead minnows by environmentally relevant exposures to 4-nonylphenolf.

The synthetic organic compound 4-nonylphenol (NP) has been detected in many human-impacted surface waters in North America. In this study, we examined the ability of NP to alter reproductive competence in male fathead minnows after a 28 day flow-through exposure in a range of environmentally relevant concentrations bracketing the U.S. Environmental Protection Agency toxicity-based NP chronic exposure criterion of 6.1 microg NP/L. Exposure to NP at and above the EPA chronic exposure criterion resulted in an induction of plasma vitellogenin (VTG) within 14 days. However, 7 days after the cessation of exposure, VTG concentrations had dropped more than 50% and few males expressed VTG above the detection threshold. All of the morphological endpoints, including gonadosomatic index, hepatosomatic index, secondary sexual characters, and histopathology, were unaltered by all NP treatments. However, when NP-exposed male fish were allowed to compete with control males for access to nest sites and females, most treatments altered the reproductive competence of exposed males. At lower NP concentrations, exposed males out-competed control males, possibly by being primed through the estrogenic NP exposure in a fashion similar to priming by pheromones released from female fathead minnows. At higher NP exposure concentrations, this priming effect was negated by the adverse effects of the exposure and control males out-competed treated males. Results of this study indicate the complexity of endocrine disrupting effects and the need for multiple analysis levels to assess the effects of these compounds on aquatic organisms.

Identity development in interracial, Asian/white late adolescents: Must it be so problematic?

The present study examines the extent to which Asian/white late adolescents are an at-risk group whose identity development is significantly different from Asian or white identity development. The centrality of race and ethnicity to Asian/white identity formation is also explored. Fifty-one Asian/white, Asian, and white college students were administered Marcia's Identity Interview (1966), with a section on race, and Mar's Asian Values Scale (1988). Asian/white subjects did not possess significantly different identity statuses than Asians or whites. Asian/white subjects held values similar to Asians on the Asian Values Scale, but rated race as significantly less important in identity formation than did Asian subjects. In some contexts, then, Asian/white subjects may not be as at-risk as previously thought. In the present study, Asian/whites had positively resolved racial issues such that race was no longer a matter of daily contention.

Lesions of experimentally induced Tyzzer's disease in Syrian hamsters, guineapigs, mice and rats.

The relative susceptibilities of C57BL/6NCR and BALB/cANNCR mice, F344/NCR rats, 2/NCR guineapigs and CR:RGH Syrian hamsters to Bacillus piliformis infection were determined by orally inoculating 20 weanling females from each species with suspensions of B. piliformis spores. Animals from each group were sequentially necropsied over 2 week periods to document the lesions produced. No significant gross or microscopic lesions were observed in the BALB mice or the Fischer rats. Gross and microscopic lesions were observed in the livers and intestines of many guineapigs and hamsters killed 3-14 days after inoculation. A large lesion was observed in the left cardiac ventricle of one C57BL mouse 10 days after inoculation. Warthin-Starry silver-stained tissue sections revealed clusters of B. piliformis within the cytoplasm of intestinal epithelial cells, smooth muscle cells, hepatocytes and myocytes bordering foci of necrosis in the intestines, liver and heart.