Coital exanthema in stallions.

Equine coital exanthema can be produced experimentally in stallions by inoculation with an equine herpesvirus (strain 65/61) and be transmitted during coitus with an infected mare. Serological responses to this infection include the production of complement-fixing and serum-neutralizing antibodies which reach maximum levels 14 to 21 days after infection. Complement-fixing antibodies decline rapidly and are usually not detectable by 60 days after infection, whereas serum-neutralizing antibody activity is maintained for at least 1 year. This disparity provides a useful method for the diagnosis of recent infections and estimation of the temporal incidence of infection in groups of mares. It seems likely that clinically normal carrier mares spread the virus on studs where the disease has previously not occurred.     

Relationship between cellular calcium and vitamin E metabolism during protection against cell injury

The extent of chemically induced injury to isolated hepatocytes has been previously shown to depend on the content of alpha-tocopherol in the cells, the levels of which are influenced by the concentration of extracellular calcium. Investigations into the effect of calcium on the alpha-tocopherol content of nonchemically exposed cells demonstrated that incubation of isolated hepatocytes in a calcium-deficient medium decreased cell calcium content to 10% of initial levels, and resulted in the depletion of endogenous alpha-tocopherol. This loss in alpha-tocopherol was not accounted for by alpha-tocopherylquinone formation. After supplementation of the cell incubation medium with alpha-tocopheryl succinate, the decreased cell calcium content was associated with higher levels of cellular alpha-tocopherol than in calcium-adequate cells. This was the result of greater intracellular hydrolysis of the tocopheryl ester in the calcium-depleted cells, and not an effect of extracellular calcium concentration on the uptake of alpha-tocopheryl succinate into the cells or on the extracellular hydrolysis of the ester. Uptake studies indicated a much greater achievable level of alpha-tocopherol in hepatocytes after incubation with alpha-tocopherol than with the alpha-tocopheryl ester. These data provide substantial support for the hypotheses that the content of extracellular calcium per se is not the determinant in toxic injury to hepatocytes, but that cell calcium content affects the intracellular metabolism of alpha-tocopherol and its esters, which may subsequently govern the outcome of a toxic challenge.     

The toxicity of cadmium to different larval instars of the trichopteran larvae Agapetus fuscipes Curtis and the importance of life cycle information to the design of toxicity tests

The acute toxicity of cadmium to three larval instars (1 st, 3rd and 4th) of the cased trichopteran Agapetus fuscipes Curtis was determined for animals both in the cased and uncased state. First instar larvae were significantly more sensitive than 3rd or 4th instars and for all ages cased animals were more resistant than uncased. Sub-lethal toxicity was demonstrated by a reduction in case building activity and aggregation response. The need to consider life cycle information when designing toxicity testy and the importance of incorporating sub-lethal responses into a study are discussed.