Trace elements in animals.

Trace element deficiency and toxicity in animals induces a wide variety of clinical effects although few are sufficiently specific to permit diagnosis without supporting investigation of changes in tissue trace element content or of the activity of metabolic processes influenced by trace element supply. Study of such trace element dependent processes has shown that extensive changes often arise before overt signs of disease appear. Some of these subclinical effects have pathological consequences and thus cannot be ignored when seeking correlations between geochemical anomalies and disease incidence. Many past estimates of the quantitative requirements of animals for the essential trace elements are imprecise. Although recent work is providing clearer definition of requirements, many common dietary components have a marked influence upon the efficiency with which such elements can be utilized from the diet. Recent evidence indicates that such antagonists influence both the absorption and the subsequent fate of essential and toxic elements in body tissues and these processes have to be taken into account when investigating the aetiology of disorders believed to be attributable to anomalies in trace element supply. Their existence is not always detectable if attention is confined to the trace element analysis of body tissues or to the nature of clinical lesions. Provided the complexity of soil-plant-animal relations with respect to trace element supply is fully recognized in the interpretation of data, the geochemical approach to the initial recognition of areas associated with a high risk of anomalies in trace element supply to animals and man has considerable potential value. This is already apparent from investigations upon the incidence of trace element problems in animals. As yet, its validity for similar purposes in man is less fully established.     

Antisense transgenics in animals.

Antisense transgenesis provides a methodology for ablating gene expression in targeted tissues through the use of tissue-specific or controllable promoters. The two major features to be considered in the design of a construct for injection are (1) the target sequence and (2) the promoter to be used. Information is provided to help the investigator make decisions in these regards. The standard methodology of making transgenics is not replicated but some hints as how best to use a transgenic facility are provided. An overview of methods for studying transgene expression and target gene suppression is given. In summary, antisense transgenesis may provide a more readily achievable method for tissue-specific ablation of a gene's function than controllable knockouts provide.     

Survey of aflatoxicosis in farm animals.

Over a 22-month period, 278 submissions of farm animals were made to the North Carolina Diagnostic Laboratory for suspected aflatoxicosis, and 94 cases were confirmed on the basis of finding aflatoxin in the feed and the occurrence of bile ductule proliferation. There was an annual variation in the incidence of aflatoxicosis, as well as a seasonal variation: the peak incidence occurred in the winter, and the minimum incidence occurred during the summer. The annual increase coincided with the corn harvest. All confirmed cases occurred on farms that raised and stored their own corn, and 88% were in swine. The cases were geographically localized in the eastern section of North Carolina (94% of the total cases) where 82% of the swine and 79% of the corn are produced. Mean concentration of aflatoxin in feed samples from the confirmed cases was 3,890 mug/kg, and the mean value for corn used in making the feed was 5,180 mug/kg. Only aflatoxin B1 was found in the samples. These data were interpreted to mean that the incidence and severity of aflatoxicosis is greater than previously suspected, that poor on-farm storage of corn is a primary contributing factor, that aflatoxin formation continues during and after the milling process, and that mycotoxicoses other than aflatoxicosis may cause equal or greater problems.