The characteristics of exploratory behavior in Wistar rats in a permanent inhomogeneous magnetic field

The influence of weak perturbations (up to 300 microT) in the natural magnetic field (MF) (induced by the introduction of three constant magnets) on the problem task solving in complex maze was studied in two groups of Wistar rats. Under the action of inhomogeneous magnetic field there were no spontaneous change of the orienting for the explorative activity independently of the individual in the presence of the organization of goal-directed behaviour. Instead of the expected explorative activity, the stable and deep locomotor depression developed after orienting in a new environment. Such a phenomenon was manifested only against the background of informational loading. Nevertheless, under these conditions a short external stimulations resulted in even faster rat learning than in the control animals. It is suggested that the MF characteristics play a crucial role in the transformation of the orienting (unconditioned activity) into the explorative (cognitive) activity.     

Structure and function of hepatocyte lysosomes and peroxisomes of rachitic rats

The submicroscopic organization and activity of acid phosphatase and catalase in lysosomes and peroxisomes of the rat hepatocytes were studied with experimental rachitis. It is determined that total and free activity of acid phosphatase in the liver tissue and certain lysosomes with rachitis increases whereas the catalase activity in the tissue and certain peroxisomes decreases. Permeability of the lysosome and peroxisome membranes rises for enzymes and cations. The process of peroxisome differentiation with rachitis is disturbed: there appear peroxisomes containing the marginal plates, that is not peculiar to the redont peroxisomes.     

Decreased oral colonization of Streptococcus mutans during aging of Sprague-Dawley rats

The colonization by streptomycin-resistant Streptococcus mutans strains of the teeth of conventional and ex-germfree Sprague-Dawley rats of various ages fed either a high-sucrose or a high-glucose diet was studied. Bacterial colonization occurred with increasingly greater difficulty as the rats became older. This was observed in studies of the implantation of the test organism after oral inoculation with different cell numbers as well as its transmission between infected and uninfected rats. With rat fed sucrose diet, the effect of age could not be demonstrated until they were age 3 months or older; the results from rats fed a glucose diet suggest that changes may already have occurred early after weaning. Changes in susceptibility to colonization during aging manifested themselves as a decrease in the proportions of rats which became infected as well as lower population levels in infected rats. The possible mechanism(s) involved as well as the possible significance of the findings was discussed.