N-Methyl-D-Aspartate receptors in acquisition of the short-term memory in the honeybeeApis mellifera

Role of NMDA receptors in the process of associative learning has been studied in the honeybeeApis mellifera L. in behavior experiments, using method of conditional reflexes. To determine pharmacological profile of NMDA receptors, effects of Mg²⁺ ions, NMDA, glycine (Gly), antagonist of the glycine site 5,7-dichlorokynurenic acid (DCK), competitive antagonists of NMDA receptors: D,L-2-aminophosphovalerate (APV), L-2-aminophosphobutyrate (APB), and D-glutamyl-aminomethylphosphonic acid (GAMP) as well of antagonists of NMDA receptor ion channels MK-801 and ketamine (Ket) were studied on acquisition of alimentary conditional reflex and its retention in memory. NMDA increased capacity for learning by stimulating shortterm memory. The NMDA receptor co-agonist Gly activated this NMDA effect. DCK eliminated the NMDA and Gly stimulatoty effects. All tested antagonists at millimolar concentrations inhibited associative function. The data obtained confirm our hypothesis about participation of NMDA receptors in processes of formation of short-term memory in the honeybeeApis mellifera and suggest that functional characteristics of the NMDA receptors involved in the process of associative learning in the honeybee resemble those in mammals.     

Structural features of the brains of rats selected for their thresholds of neuromuscular excitability

As a result of selection of rats possessing a high threshold of neuro-muscular exitability in comparison with rats possessing a low threshold of neuro-muscular exitability, certain changes take place in the structures that are connected with the learning process: the visual cortex is wider, volumes of the pyramidal cells in the fields CA1 and CA3 of the hippocampus are increased, density of the glial elements in the fornix is essentially increased and that of neurons in the septal nucleus is decreased.     

Increased affinity of liposomes derived from total spleen and liver lipids to spleen cells

The interaction of liposomes derived from total lipids of mouse spleen and liver with mouse spleen cells was studied. It was shown that the binding of these liposomes is much higher than the binding of liposomes obtained from a model lipid mixture--phosphatidylcholine--phosphatidylethanolamine--cholesterol (2:1:1). Adherent and nonadherent spleen cells were found to have affinity for liposomes derived from total lipids of spleen or liver. Removal of gangliosides and protein contaminants from the liposomes derived from total spleen lipids caused an increased binding of liposomes to spleen cells. Multilamellar liposomes bound more effectively to ultrasonicated vesicles having a homologous lipid composition than the liposomes with a different lipid composition. The increased affinity of liposomes derived from total lipids of spleen or liver for spleen cells may account for the identical fluidity of the lipid bilayer of liposomes and plasma membranes of spleen cells.     

Changes in the Activity of the Maturation-Promoting Factor Are Correlated with Those of a Major Cyclic AMP and Calcium-Independent Protein Kinase During the First Mitotic Cell Cycles in the Early Starfish Embryo

Many studies suggest that MPF activation depends on protein phosphorylation or that MPF is itself a protein kinase. In the present report, cyclic variations of MPF activity have been correlated in vivo with changes in the extent of protein phosphorylation or in vitro with changes of a major protein kinase during the first cell cycles of fertilized starfish eggs. This cycling protein kinase neither requires cAMP nor Ca²⁺. Neither colchicine nor aphidicoline, which inhibits cleavage and chromosome replication respectively, was found to suppress the synchronous and cyclic variations of both MPF and protein kinase activities. Protein synthesis was found to be required for both MPF and protein kinase activities to reappear after their simultaneous drop at the time of mitotic or meiotic cleavages. Production of either MPF or protein kinase activities is not the immediate result of protein synthesis since there is a delay at each cell cycle between the time when protein synthesis is required and the time when both MPF and protein kinase activities are produced. This suggests that both MPF and protein kinase activities might involve some post-translational modification of a precursor protein synthesized during the preceeding cell cycle.     

Cardio- and hemodynamics of dogs during the development of postischemic shock reaction

Experiments on dogs have shown that tension of peripheral capacitive vessels decreased and development of the blood deposition reaction in the venous part of the vascular bed occurred immediately after beginning of long-ischemized tissue perfusion. This leads to limitation of venous blood return to the heart, decrease of the cardiac output and development of the system hypotension. Lowering in the perfusion coronary pressure induced limitation of the coronary blood flow and inhibition of the myocardial contractility. Indicated constriction of resistive vessels and dilatation of the capacitive ones may be due to an increase of the prostacyclin and thromboxane A2 blood levels. Described disturbances achieved their maximum 3 hours later and were accompanied by arterial hypoxemia, metabolic acidosis and hypercapnia.     

Structure and properties of lipoteichoic acid of group A Streptococcus type M 29

Lipoteichoic acid (LTA) of group A streptococci, type M 29 was studied. Chemical and 13C NMR spectroscopic analysis showed that the polymer contained poly(glycerophosphate) chain consisting of 12-14 glycerophosphate elements united by the 1----3 type phosphodiether bond and diglucosylglyceride. Oleic, stearic, palmitic and palmitoleic fatty acids predominated in the polymer composition. The content of the fatty acids amounted approximately to 2 per cent of LTA dry weight. The poly(glycerophosphate) chain contained 6-7 ether linked alanyl moieties. The results of the LTA biological study were analyzed in comparison to the data on a previous study of antitumor and cardiotoxic properties of teichoic acid from Streptomyces levoris K-3053 which is structurally close to the LTA hydrophilic moiety. It was assumed that the molecule negative charge had an effect on the cardiotoxic and antitumor activity.     

The protoplasts of Acremonium chrysogenum. Biochemical and morphological studies

A procedure for preparing stable A. chrysogenum protoplasts capable of 60 per cent regeneration was developed. Two morphogenetic types of the regeneration were detected. The variants isolated after the protoplast regeneration were characterized by wide ranges of morphological variation. Capacity for the antibiotic production varied from 60 to 160 per cent of the activity of the starting strain. A procedure for isolating functionally active mitochondria from protoplasts of A. chrysogenum was also developed. Their main bioenergetic parameters were studied. In the respiratory chain of the A. chrysogenum mitochondria there were detected three conjugation sites of oxidative phosphorylation.