SummaryThe biological effect of visible light of low energy density was investigated in this study. The effects of diffuse (DL) and linearly polarized (LPL) light were compared on models in vitro and in vivo.Experiments in vitro were performed on human lymphocytes to study their blast-transformation and rosette-formation abilities. Both DL and LPL increased the number of blast-transformed cells even in a lymphocyte culture without PHA, and reduced rosette-formation of T lymphocytes. LPL had a more pronounced effect.In vivo exposure to DL and LPL of the spleens of tumour-bearing mice caused the appearance of factor(s) in their serum, inhibiting the incorporation in vitro of [^H]-thymidine into the tumour cells obtained from non-exposed animals. In the other series of experiments serum samples were taken from tumorous animals after the exposure of their spleens to LPL. Following the daily administration of these sera to another group of non-exposed tumorous mice a decreasing tendency of the mitotic kinetics of ascites tumour was observed.The application of visible (preferably linearly polarized) light for the stimulation of human immune competent cells, and clinical trials with extracorporeal irradiation of blood for the promotion of natural defences of an immune-repressed organism are suggested.

The aim of this review was to discuss the effects of heat stress on antioxidant status and performance in poultry. Based on the recent literature data, the following conclusions can be drawn: (1) Heat stress can cause harmful effects in birds (e.g. increased ROS (Reactive Oxygen Spices) production and lipid peroxidation, decreased vitamin concentrations, changed enzyme activity) and consequently in production parameters (e.g. feed intake, body weight and feed conversion ratio). (2) Diets containing high Vitamin A (9000-15 000 IU/kg diet), E (150-500 mg/ kg diet), C (150-500 mg/kg diet) and Zn (30/60 mg/kg diet) and Se (0.1-1 mg/kg diet) can decrease the amounts of free radicals, support enzyme activity and prevent lipid peroxidation in poultry.(3) Application of antioxidant vitamins and micro minerals in poultry nutrition is more effective in combination than separately. ARTICLE HISTORY

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