The action of the venom of the spider Eresus niger on the neuromuscular synapses of the frog

The effect of Eresus niger spider venom on frog neuromuscular preparations has been studied using the intracellular microelectrodes. The spider venom has been found to block both spontaneous and elicited transmitter release and possesses the phospholipase activity. It has been suggested that the venom blocking synaptic transmission results from its phospholipase activity by analogy with the action of snake presynaptic neurotoxins.     

Tissue respiration of rat internal organs and skin during prolonged exposure to high ambient temperature]

Oxygen consumption by tissues of various organs was studied in acute experiments on albino rats in Warburg apparatus at a temperature of 37 degrees C. High environmental temperature proved to decrease the tissue gas exchange level. Participation of different organs in the reduction of total metabolic level varied and depended on the number of actions of the thermal factor. A more active inclusion of the majority of the organs into the adaptive reactions of the organism to the high temperature occurred during the third week.     

Purification and properties of two endonucleases specific for apurinic/apyrimidinic sites in DNA from Saccharomyces cerevisiae

Two distinct endonucleases from Saccharomyces cerevisiae, specific for apurinic/apyrimidinic sites (AP-endonucleases A and B), have been extensively purified and characterized. Both are free from unspecific and ultraviolet-specific endonucleases and exonucleases. The two enzymes are monomeric proteins of around 24000 daltons. Both are sensitive to ionic strength and most active in the presence of 150 and 100 mM NaCl for AP-endonucleases A and B, respectively. They are not absolutely dependent on divalent cations, since they are insensitive to EDTA, although AP-endonuclease A is activated by Ca2+ or Mg2+ and AP-endonuclease B by Mg2+ only. ATP inhibits the enzymes. AP-endonuclease A reacts optimally between pH 6 and 8, and AP-endonucleases B at pH 8. AP-endonuclease A is more stable at 60 degree C (half-life of 17 min) than B (half-life of 4 min). AP-endonuclease A is insensitive to N-ethylmaleimide or rho-chloromercuribenzoate. AP-endonuclease B is also insensitive to N-ethylmaleimide, but rho-chloromercuribenzoate inhibits its activity.     

Structural organization of [met]enkephalin and endorphin molecules. II. Theoretical conformation analysis of alpha-, gamma- and delta-endorphins]

Conformational energy calculations were carried out for neuropeptides alpha-, gamma- and delta-endorphins, which are 1-16, 1-17 and 1-19 fragments respectively, of beta-endorphin. The proposed computational scheme yielded all possible low-energy conformational sets for these hormones. Specific features of spatial organization of each compound and similarities of their structures are discussed.     

Approach to studying the structure-activity relationship of native peptides. II. Structural organization of alpha- and beta-neoendorphins]

By means of a semi-empirical method, an a priori conformational analysis of alpha- and beta-neo-endorphins was carried out. Calculations yielded the values of all dihedral angles of the backbone and side chains of the peptide's various forms as well as intra- and inter-residue interaction energies.     

Structural organization of [Met]enkephalin and endorphin molecules. I. Theoretical conformation analysis of [Met]enkephalin

Using a semi-empirical method, an a priori conformational analysis of the [Met]-enkephalin molecule was carried out. Calculations yielded the values of all dihedral angles of the backbone and side chains of the peptide's forms as well as intra- and inter-residue interaction energies.     

Theoretical conformational analysis of brain peptides. beta-Melanocyte-stimulating hormone

Using a semi-empirical method, an a priori conformational analysis of the octadecapeptide beta-melanocyte-stimulating hormone (beta-MSH) was carried out. The spatial structure of beta-MSH can be described by eight low-energy conformations, yielded by combinations of the most stable states of the respective free fragments. Calculations produced the values of all dihedral angles of the backbones and side chains of these forms as well as intra- and inter-residue interaction energies.