[Nitrogen compounds and their role in the contamination of the environment]. / Zwiazki azotu i ich udzial w skazeniu srodowiska.

Nitrogen compounds occur in excess in the air, water, soil and food, which unfavourably affects human's health, causing a number of diseases. Toxic effect of nitrates and nitrites ought to be mentioned here in the first place. Nitrates and nitrites cause intoxications, specially of infants and of children, manifesting themselves by methemoglobinemia, anaemia and decreased content of vitamin A in the liver. Besides, nitrates and nitrites participate in the formation of strong nitrogen carcinogenic compounds, which may lead to stomach cancer. Due to big harmfulness of nitrogen compounds one should strive after lowering, minimizing their presence in the environment.

The influence of selenium on the reproduction of rats.

Selenium is a vestigial element indispensable for man and animal, having adverse effects when in bigger quantities. Among the diseases resulting from selenium deficiency in animals the most important are nutritional muscular dystrophy, exudative disthesis (most common in poultry), and nutritional hepatic dystrophy. In the man chronic intoxication occurs most of all, which is observed in selenium bearing regions. Taking into consideration geographic distribution on some of the diseases beneficial influence of selenium is observed in cardiac and vascular diseases, and hypertension. The correlation between selenium deficiency and mortality caused by neoplasm is also notable. It is unquestionable that selenium inhibits the activity of enzymes, especially those containing sulfohydryl groups. The stabilization of lysosomal membranes leads to the presumption that selenium prevents peroxidation processes in tissues and cell membranes. The influence of selenium on reproduction is also worth noticing. Its supply turns out to be effective in cases of infertility of sheep, and partly in rats, pigs, and poultry. The embryo dies in pigs fed on fodder poor in selenium and vitamin E. The degeneration of the ovaries and placenta accretion occur in cows in cases of selenium deficiency. The excess of selenium can affect negatively the reproductive system. The element is thought to be a teratogenic agent. Since it permeates through the placenta and lactic gland easily, the symptoms of selenosis appear in new-born animals; many of them have developmental anomalies occurring at the same time. In birds the decrease in laying eggs and their incubation occur in case of selenium deficiency.