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Perchlorate is a known environmental contaminant, largely due to widespread military use as a propellant. Perchlorate acts pharmacologically as a competitive inhibitor of thyroidal iodide uptake in mammals, but the impacts of perchlorate contamination in aquatic ecosystems and, in particular, the effects on fish are unclear. Our studies aimed to investigate the effects of concentrations of ammonium perchlorate that can occur in the environment (1, 10, and 100 mg/L) on the development of fathead minnows, Pimephales promelas. For these studies, exposures started with embryos of < 24-hr postfertilization and were terminated after 28 days. Serial sectioning of thyroid follicles showed thyroid hyperplasia with increased follicular epithelial cell height and reduced colloid in all groups of fish that had been exposed to perchlorate for 28 days, compared with control fish. Whole-body thyroxine (T4) content (a measure of total circulating T4) in fish exposed to 100 mg/L perchlorate was elevated compared with the T4 content of control fish, but 3,5,3′-triiodothyronine (T3) content was not significantly affected in any exposure group. Despite the apparent regulation of T3, after 28 days of exposure to ammonium perchlorate, fish exposed to the two higher levels (10 and 100 mg/L) were developmentally retarded, with a lack of scales and poor pigmentation, and significantly lower wet weight and standard length than were control fish. Our study indicates that environmental levels of ammonium perchlorate affect thyroid function in fish and that in the early life stages these effects may be associated with developmental retardation.

Two maternally derived chromosome sets and both maternal histocompatibility antigen haplotypes were identified in the tissues of a malformed triploid acardiac twin that developed within the same chorion as its normal twin. These findings indicate that the twins arose as a result of independent fertilizations, by two different spermatozoa, of a normal haploid ovum and its diploid first-meiotic-division polar body.

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We have used 9 conventional RFLPs and 6 dinucleotide repeat polymorphisms on chromosome 21q to demonstrate that 17 of 19 cases of rea(21q21q) were consistent with isochromosomes i(21q) with the remaining 2 being true Robertsonian translocations. Eight of the 17 isochromosomes were of maternal origin and 9 cases were paternally derived. The 2 Robertsonian translocations were both maternally derived. Of the 17 isochromosomes, 7 were dicentric [idic(21q)] and 10 were monocentric [i(21q)]. Both rob(21q21q) were monocentric. Our findings agree with those made in 17 previously published cases of rea(21q21q). The parental origins of the i(21q) were equally divided between maternal (n = 17) and paternal (n = 15) origins. All 4 true rob(21q21q) reported to date are of maternal origin. Collectively, it appears that most homologous rearrangements of chromosome 21 are isochromosomes and only a small proportion are consistent with true Robertsonian translocations.

Recent measurements of plasma arginine vasotocin (AVT) in teleost fish suggest circulating concentrations of 10(-10)-10(-12)M. Previous studies of the renal actions of AVT in vivo suggest both diuretic and antidiuretic effects, but at unknown circulating concentrations. We have investigated the renal actions of 10(-9) and 10(-11) M AVT in vitro using an in situ perfused kidney preparation of rainbow trout (oncorhynchus mykiss). AVT increased vascular resistance (56%), reduced perfusate flow (P < 0.001), and increased interrenal aortic pressure (P < 0.001). AVT resulted in dose-dependent decreases in urine flow rates, glomerular filtration rates, and tubular transport maxima for glucose. AVT at 10(-11) M reduced relative free water clearances (P < 0.01), but urine/plasma inulin ratios were unchanged, whereas 10(-9)M AVT reduced urine/plasma inulin ratios (P < 0.01) and increased relative free water clearances (P < 0.05). The filtering population of glomeruli was reduced by both 10(-11) and 10(-9)M AVT to approximately one-third of the glomeruli, and a similar population of arterially perfused but nonfiltering glomeruli emerged. These results demonstrate that physiological concentrations of AVT have potent glomerular antidiuretic action in the trout, reducing the number of functional glomeruli, and imply reduced individual nephron filtration rates.

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