An in vivo model for assessing effects of drugs and toxicants on immunocompetence

A Pathology Review of the Lower Gastrointestinal Tract in Relation to Ulcerative Colitis in Rats and Cynomolgus Macaques Treated With Ammonium Perfluorooctanoate

Among many short-term, subchronic, and chronic toxicology studies with ammonium perfluorooctanoate (PFOA), the gastrointestinal tract has not been identified as a target organ for PFOA-related toxicity in laboratory animals where the corresponding serum PFOA concentrations typically approach several orders of magnitude higher than the general human population. These lack of gastrointestinal tract-related findings were in direct contrast to an epidemiological observation where a positive trend was observed for ulcerative colitis, an idiopathic chronic inflammatory condition of the gut, in a Mid-Ohio River community whose drinking water contained higher levels of PFOA. This study was conducted to perform a histological reevaluation of large intestine sections in laboratory animals from 2 long-term toxicological studies: one was with Sprague Dawley rats that received ammonium PFOA in their diet for 2 years and the other one was with cynomolgus macaques that received daily capsules of ammonium PFOA for 6 months. In both studies, there was a lack of histological evidence of treatment-related inflammatory lesions that was suggestive of the occurrence of ulcerative colitis in these laboratory animals even under the most rigorous treatment schedules. These findings do not offer support for the biological plausibility of the epidemiological associations reported.

Immunotoxicological Evaluation: An Overview

Many new drug candidates being developed within the pharmaceutical industry possess immunological activity, which may eventually necessitate an evaluation of potential toxicity to the immune system. At present, no consensus exists on which immunotoxicological procedures are most suitable for incorporation into the routine toxicology studies. This paper describes a few immunological test procedures that seem feasible for extrapolating to man, since similar approaches are now used clinically to evaluate immune reactivity. At present, data demonstrating the efficacy of immunotoxicological assays have been limited to humans exposed to environmental contaminants.

The immunomodulatory effects of two plant growth regulators, cycloheximide and maleic hydrazide, in white mice

The immunomodulatory effects of two plant regulators, cycloheximide and maleic hydrazide, were investigated by injecting the compounds twice weekly for 4 weeks in female Swiss Webster white mice. The animals were antigenically challenged with sheep red blood cells on day 24 of the study. Although humoral immunity was the primary system examined, analysis included all of the following parameters: spleen plaque forming cells (PFC's), lymphocyte viability, spleen lymphocyte counts, hemolysin titers, total plasma proteins, total white blood cells counts, hematocrit, total body weight, and liver, thymus and spleen weights. Cyclophosphamide and physiological saline were used as the respective positive and negative control substances. The dosing was as follows: cyclophosphamide at 50 mg/kg/injection, cycloheximide at 12.5, 25 and 50 mg/kg/injection and maleic hydrazide at 125 and 250 mg/kg/injection. Cycloheximide significantly (P less than .05) reduced, in a dose-dependent fashion, the thymus wt/gram of body weight, the number of PFC's/gram of spleen, total lymphocytes/gram of spleen, PFC's per 10(6) viable spleen lymphocytes and the hemolysin antibody titer levels. Maleic hydrazide significantly reduced thymus weights and moderately lowered the ratio of PFC's per 10(6) viable spleen lymphocytes. Maleic hydrazide significantly elevated total lymphocytes per gram of spleen and the hemolysin titer (up to 133% over saline control values). There was an elevation in the number of PFC's per gm of spleen by maleic hydrazide and the overall effects were dose related. Cycloheximide, a known inhibitor of protein synthesis, was distinctly the most suppressive of the two plant growth regulators. Both agents are widely utilized on agricultural products and the results suggest the need for care in their application and residue removal. Used properly, the plant growth regulators may pose little or no human health hazard, but this report documents a new biological activity for these agents.