Evaluation Of Chronic Toxicity Research Articles

A bioassay of toxicity using protozoa in the study of aquatic environment pollution and its prevention

Protozoa are of particular importance in nature playing an active role in water purification. Since they are increasingly used as toxicological models in medicine and pharmacology, it is suggested that protozoa could be employed advantageously in the field of water pollution. Methods are described in this paper for short-term (acute) and long-term (chronic) toxicity evaluation in order to determine the degree of toxicity of various water-borne contaminants and to establish the tolerance to these agents. The technique consists in exposure of cultures of Paramecium caudatum Ehr. in serial dilution tests for short and extended time intervals. Results may be rapidly obtained within a few hours in the acute and within 2 weeks in the chronic tests.

Toxicology of hexamethylphosphoric triamide in rats and rabbits

Hexamethylphosphoric triamide (HEMPA), an insect chemosterilant, was tested for acute and chronic toxicity in rats and rabbits. In rabbits, the estimated dermal LD50 was 2600 mg/kg. Clinical signs of systemic toxicity preceding death included alterations of nervous, gastrointestinal, and respiratory systems. Repeated application of HEMPA at 100 or 500 mg/kg to the skin of rabbits caused dose-related weight loss, altered gastrointestinal function and produced apparent nervous system dysfunction. Administration of HEMPA to rats at 50 (oral toxicity study) and 10 (reproductive study) mg/kg resulted in exacerbation of the chronic murine pneumonia complex when compared to lower-dosed and control animals. Morphologic differences in the oral toxicity study included imbibition of minimal amounts of proteinaceous material into renal tubular epithelium and increased splenic extramedullary hematopoietic activity in animals given 50 mg/kg when compared to control, 2 mg/kg and 10 mg/kg treated rats. No other compound-related pathologic or morphologic change was present in other tissues examined including the reproductive organs. No teratologic or unequivocal change that could be attributed directly to the compound was observed in the fertility, gestation, live birth, or lactation indices following administration of HEMPA at 2 or 10 mg/kg/day for a total of 169 days during which time the first (F1A) of 3 filial sets of pups were produced. Also, the reproductive activity and function of the offspring were normal.