Diatoms in the plankton and sediments of two lakes of different trophic type

Species composition, quantity and distribution of diatoms in both the plankton and the surface sediments (0–30 cm) of mesotrophic Lake Krasnoye and eutrophic Lake Vishnevskoye (Karelian Isthmus) were studied. In the mesotrophic lake the composition of dominant diatoms (mainly Melosira) corresponded to those in the plankton. The Araphidineae/Centrales (A/C) ratio was 0.2–0.3%, increasing in the upper layers to 7%. Alkaliphilous and alkalibiontic forms constituted 60% of the total. In the eutrophic lake diatoms with thin valves (mainly Synedra) predominated in the plankton but their quantity in the sediments was insignificant in comparison with other plankton. Nevertheless, the A/C ratio was much higher, 17–35%. Alkaliphilous and alkalibiontic forms accounted for 78–90% of the total number of valves. In both lakes the highest number of diatom valves was registered in the upper layer of the sediments. From the ratio of the total number of diatoms in the upper 5 cm layer to their annual flux to the sediment from the plankton the approximate sediment accumulation rate was calculated to be 1.9 mm a^?1 for the mesotrophic lake and 2.5 mm a^?1 for the eutrophic one.     

Eukaryotic elongation factor 2 loses its non-specific affinity for RNA and leaves polyribosomes as a result of ADP-ribosylation

ADP-ribosylation of rabbit reticulocyte elongation factor 2 (EF-2) catalyzed by the A fragment of diphtheria toxin leads to a loss of its non-specific affinity for RNA. The removal of the ADP-ribose residue from EF-2 in the reverse reaction with nicotinamide restores its affinity for RNA. ADP-ribosylation of EF-2 is accompanied by its dissociation from the complexes with mono- and polyribosomes detected in the rabbit reticulocyte lysate at low ionic strength. The loss of the non-specific affinity of EF-2 for RNA as a result of ADP-ribosylation and, as a consequence, its decompartmentation from polyribosomes is assumed to be a reason for the diphtheria toxin-induced inactivation of the factor in eukaryotic cells.     

The migratory activity of HIV-infected people in the northwestern region and the routes of the possible spread of the infection]

The epidemic situation in HIV infection in the northwestern region of this country has been analyzed. The ways of the spread of HIV infection among the infected persons, residents of the St. Petersburg region, Kaliningrad, Novgorod and Murmansk, have been studied. The infection is transmitted mainly through sexual contacts, both homosexual and heterosexual. High migration activity of HIV-infected persons, homo- and heterosexuals, has been established, and a great number of unknown (casual) sexual contacts among them was noted. The results of these observations may be useful in the prognostication of the epidemic situation in HIV infection not only in the northwestern region, but also beyond its boundaries, and later in the optimization of screening.     

Experimental study of the immunosuppressive properties of vitamin D

The experiments on CBA mice and guinea-pigs have shown that oral vitamin D administration suppressed natural killer activity, decreased the number of T lymphocytes in the peripheral blood and prolonged allograft survival.     

Effects of passive administration of serotonin and catecholamine antibodies on alcohol consumption of C57Bl/6 mice in experimental alcoholism]

The experiments on C57Bl/6 mice with natural ethanol motivation have shown that passive injection of anti-noradrenaline and particularly antiserotonin antibodies reduces several times alcohol consumption by animals. On the contrary the injection of anti-dopamine antibodies to affect voluntary alcohol consumption by mice have been found.     

Movement as a signal during classical conditioning

Analysis of the available data and that of the author disclosed the peculiarities of motor reaction when used as a conditioned stimulus. The author's data showed that if signal value is attributed to a motor reaction (passive movement or movement evoked by the direct stimulation of the motor cortex), the changes of excitability in the motor cortex representation of the dog's leg depend on the biological sign of the reinforcing stimulus during classic conditioning. They also remained the same during instrumental conditioning and were opposite in sign, showed increased excitability in the food situation, and decreased excitability in the defense situation. Using the movement as a conditional stimulus, we managed to uncover the commonality between classic and instrumental conditioning. This enabled us to answer questions, discussed by Pavlov and Guthrie, which, it seems to us, had not been convincingly answered during their time.