Effect of stretch on the contractile response of isolated portal vein smooth muscle

The character of spontaneous activity of the isolated preparation was shown to be affected only by the first stretching stimulus which was due to release of the intracellular Ca. Active contractile responses to stretching at the peak of the contracture due to perfusion of the preparations with the Krebs sodiumless solution, are directly correlated with the speed of the stretching. Stretching of the preparations in calciumless solution elicited no active response.     

ATP-Dependent human erythrocyte glutathione-conjugate transporter. I. Purification, photoaffinity labeling, and kinetic characteristics of ATPase activity

Dinitrophenyl S-glutathione (DNP-SG) ATPase is a 38 kDa membrane protein expressed in erythrocytes and other tissues. Although stimulation of ATP hydrolysis catalyzed by DNP-SG ATPase has been demonstrated in the presence of several structurally unrelated amphiphilic ions, structural and functional properties of this protein have not been well-defined. In the present study, we have developed an improved protocol for the purification of DNP-SG ATPase and investigated its kinetic and substrate-binding properties. The purification procedure was based on highly specific elution of the 38 kDa protein from DNP-SG affinity resin in the presence of ATP. The protein could not be eluted using either ADP or adenosine-5'-[beta,gamma-methylene]triphosphate (methylene-ATP), a nonhydrolyzable analogue of ATP. Doxorubicin (DOX), a weakly basic anthracycline chemotherapy agent, was found to be the preferred activator for stimulation of ATP hydrolysis by the enzyme. ATP binding to the enzyme was demonstrated using 8-azido-ATP photoaffinity labeling and binding of trinitrophenyl (TNP)-ATP, a fluorescent analogue of ATP. The photoaffinity labeling of DNP-SG ATPase (38 kDa) was saturable with respect to 8-azido ATP (Kd = 2 microM), indicating that the enzyme was capable of specific and saturable binding to ATP. DNP-SG binding was evident from the purification procedure itself and was also demonstrable by quenching of tryptophan fluorescence. Results of quenching of tryptophan fluorescence as well as radioactive isotope-binding studies indicated that DOX was bound to the purified protein as well.     

The secondary structure of amides of adenylic acid containing D- and L-aromatic amino acids

Adenylyl-(5'leads to N)-amino acids containing as amino components, methyl esters of D-, L- and DL-phenylalanine, D-, L- and DL-tyrosine, and D-, L- and DL-tryptophan have been investigated by proton magnetic resonance (PMR) spectroscopy and circular dichroism (CD). The temperature and pD dependences of proton chemical shifts of these compounds have been studied. These data, together with the magnitudes of the upfield chemical shifts of the PMR signals of adenine and aromatic amino acids residues in adenylyl-(5'leads to N)-amino acids, have enabled us to construct conformational models of these compounds. The proposed conformation has been substantiated by the CD results. It is shown that in adenylyl-(5'leads to N)-amino acids the planes of adenine and amino acid aromatic moieties are roughly parallel. The aromatic rings of phenylalanine and tyrosine are localized approximately above the centre of adenine. In adenylyl-(5'leads to N)-D, -(L)-tryptophan, the six-membered rings of the indole overlaps the five-membraned ring of adenine indole partially overlaps the six-membered ring of adenine. A difference in the non-covalent interactions of D- and L-amino acids with nucleotides has been revealed. The mutual localization of the aromatic systems of AMP and the amino acids and also the positions of -OCH3 group with respect to the centre of the amino acid aromatic moiety differs in the series of the studied nucleotide derivatives of D- and L-amino acids.     

Blast-transformation reaction in patients with bone tumors

The authors have studied phytohemagglutinin stimulation of DNA synthesis in leucocytes cultures of the peripheral blood in patients with some malignant osteoplasms and benign tumors, and the influence of plasma factors on this process, as well. In most cases, lymphocytes of patients with malignant tumors were shown to have a considerably decreased, as compared with the control, level of blasttransformation. No such difference was found for leucocytes cultures of patients with benign tumors.     

Lokhvitski? SV

Examination of electrocardiograms of pilots with normal and 10% excessive weight in a moderately hypoxic atmosphere showed that changes in the pulse rate, T voltage, systolic index were less expressed in obese subjects than in normal pilots. This can be attributed to the fact that obese subjects had reduced metabolism, minute oxygen consumption and compensatory capabilities of the cardiovascular system.     

Cyclic changes in platelet dynamics and the pathogenesis and prophylaxis of migraine

Continuous linear gradients improve electrophoretic separations in polyacrylamide. They are obtained by overlayering equal volumes of two monomer solutions with different acrylamide concentrations, namely 180-260 and 23-50 g/l, in the usual gel tubes. The tubes are tilted 3-10 degrees to the horizontal, and rotated around their longitudinal axis until the parts of both solutions in contact are mixed homogeneously. Subsequent polymerization takes place in the vertical position. The more concentrated lower solution contains 4-nitrophenol, so that the final polymer concentration at any point of the gel can be measured densitometrically. The construction and handling of the rotation device are simple and yield highly reproducible results. This versatile method was evaluated for the separation of proteins, lipoproteins, and enzymes in human serum and yields 27-30 protein fractions by additional use of a pH-gradient.