Acta biochimica et biophysica; Academiae Scientiarum Hungaricae最新文献

We describe here simple methods to introduce spacer arms with amino functional group into polysaccharides. (Formula: see text) The technique includes the following steps: Compounds comprising epoxide group(s) are introduced into polymer supports to form the spacers. Then, reactive groups on the other side of the introduced spacers are reacted with ammonia. Since spacers are attached via ether linkage to the supports, the escape of ligands from specific sorbents can be prevented. Moreover, no charged groups arise on the carrier during the activation procedure, thus decreasing the nonspecific protein retention.

Experiments were performed on six volunteers, in order to investigate the effect of the activity of the m. biceps branchii on the median and ulnar nerves. The reflex of the m. biceps brachii was evoked by a sudden stretch and the EMG responses of the m. biceps brachii, m. abductor dig. V. and thenar muscles were recorded. Hand muscles produced early EMG potentials, the latency between them, as well as the onset of the electrical response recorded from the m. biceps brachii, being about the same as the conduction time of nerve excitation from biceps to the hand muscles. The possible mechanisms of the origin of the early EMG activity recorded from the hand muscles are discussed.

Partially fragmented 12-21S rat liver messenger ribonucleoprotein (mRNP), labelled either with [3H]-orotic acid or [3H]-adenine was treated with 5 (micrograms/ml or 0.1 microgram/ml pancreatic ribonuclease (EC 3.1.27.5) and the resistant fragments were separated by sucrose gradient centrifugation. Two types of fragments were obtained. Digestion of mRNP with ribonuclease at a concentration of 5 micrograms/ml resulted in 9S poly(A)-protein particles of mRNP as evidenced by their characteristic sedimentation, electrophoretic mobility of the RNA moiety and protein composition. In contrast, ribonuclease at a concentration of 0.1 microgram/ml produced 2-5S pyrimidine labelled fragments carrying polynucleotide sequences consisting of approximately 16-50 residues. Two polypeptides of rat liver mRNP with molecular weights of 38 000 (P38) and 44 000 (P44) were found to be attached to these sequences. The data demonstrate that RNA sequences other than poly(A) interact with protein in mRNP. Electron microscopic studies revealed that the liberation of mRNP from the polysomes by EDTA changes its surface properties since EDTA releases the mRNP mainly in the form of globular particles. However, a small proportion of the mRNP remains in fibril-like form. Among the fibrils several blobs could be seen which were probably the proteins attached to the mRNA. From the available data a model for the structure of an "average" mRNP molecule is proposed.

In view of the very high correlation coefficient between actual redox state potential level in the biophase and spike activity--triggered by acetylcholine and influenced by cAMP--in skeletal muscles it seems rather reasonable the conclusion that the redox state potential level influences the cooperative effects not only in the case of acetylcholine but, directly, also the actions of cAMP, since the type of the regulatory influence of actual redox state potential level is non-additive in some cases, though additive in others.

The mechanism of action on RNA synthesis of anticancer dibromo-dulcitol (DBD, NSC-104800) and dianhydro-dulcitol (DAD, or elsewhere dianhydrogalactitol, DAG, NSC-132313) was investigated. Rats, bearing Yoshida or Novikoff hepatoma ascites tumor cells sensitive to these drugs were treated with doses equivalent to half the LD50 value. Nucleolar RNA (noRNA) and nuclear RNA (nRNA) were pulse labelled with 3H-uridine, isolated and fractionated on sucrose density gradient. After 18 h treatment with either drug and after 3 h with DAD noRNA synthesis increased and the rate of ribosomal RNA (rRNA) precursor processing was enhanced. Investigation of low-molecular weight nRNAs (LMW nRNAs) (separated by polyacrylamide gel electrophoresis) showed increased synthesis and/or accumulation of RNA species (5S RNA, uridylic acid rich RNAs) related to rRNA synthesis. The tritium labelled drugs were bound to distinct fractions of nRNA, separated by sucrose density gradient ultracentrifugation, both in vivo and in vitro. This fact may be explained by the formation of intra-, or intermolecular crosslinking of pre-messenger RNA. The enhanced RNA synthesis might be interpreted as an alteration in the functions of nuclear proteins, involved in the regulation of gene transcription and processing of RNA precursors.

Ca2+-sensitive K+ transport ("Gárdos-effect") was investigated in inside-out red cell membrane vesicles (IOVs) by measuring the effect of Ca2+ and other agents on the 86Rb+ (K+-analogue) influx. 50 micro M-5 mM Ca2+ stimulated the 86Rb+ influx as compared to the effect of 1 mM EDTA. Mg2+ and chlorpromazine inhibited the effect of Ca2+, oligomycin and quinine were without effect. The permeability increase of K+, elicited by Ca2+ in IOVs, corresponded to that of intact cells. The effect of Ca2+ was not specific to K+ with respect to Na+. The Ca2+-sensitive K+ channels saturated about 5-10 mM KCl in the medium. The results indicate that IOVs the Ca2+-sensitive K+ transport has altered characteristics as compared to that of intact cells and resealed ghosts. However, in contrast to the suggestion of other investigators, it was found that some features of this phenomenon are still preserved in IOVs.