Zeitschrift fur Naturforschung. Section C, Biosciences最新文献

The method presented here enables the isolation of three monofunctional adducts. These are: platination of cytosine, adenine and guanosine. The three detected bifunctional complexes were: guanine N7 to N7, adenine N7 to N7 and adenine N7 to N1. A mixed bifunctional complex of guanine and adenosine and the product of polymerization of three adenines and two moieties of cis DDP were also detected. In the peak eluted separately from the guanine standard, no Pt was detected. The sample eluted in this peak had UV spectrum different from the standard and may represent the degraded product of guanine and polymerized Pt.

Antibody against viral gp71 is effective therapeutically for high leukemic AKR mice if injected immediately after birth. No corresponding effect could be observed after inoculation later in life when the endogenous virus burden is already high. However, if antibody treatment was supplemented by the injection of p15(E) antibody, a therapeutic effect was observed even in older mice first treated at an age of 21/2 months. Those mice produced antibodies against viral surface proteins and appeared to be able to survive longer than control mice. Thus p15(E) antibody might be able to overcome retroviral associated immuno-deficiency. This therapy may have implications for the treatment of the apparently retroviral induced acquired immunodeficiency syndrome (AIDS) of man.

Under adequate experimental conditions calmodulin antagonists like compound 48/80 do not dissociate calcium uptake from the calcium-dependent ATP hydrolysis of skeletal muscle sarcoplasmic reticulum membranes but simultaneously inhibit both processes. Apart from the agent's pump inhibiting effect, they interact with the caffeine sensitive calcium channel in the sarcoplasmic reticulum causing a rapid transient calcium release.

Vascular smooth muscle cells from rabbit arteries were grown in tissue culture and stimulated by DC impulses (1 mA, 1 V, 10 Hz, 1 ms/imp). Scanning microscopic examination disclosed that in stimulated cultures the cell surface was enlarged by numerous microvilli. This was interpreted as being indicative of an increase in cell activity. Cellular metabolism was characterized by analyzing the incubation medium for glucose, glutamate/glutamine, and lactate. When compared to unstimulated controls, stimulation caused an increase in the uptake of glucose and glutamine as well as an increased lactate production. The enhancing effect on metabolism was prevented when the "calcium antagonist" verapamil was present (5 X 10(-6) M). Although the exact mechanism by which DC stimulation influences the cells remains obscure, this finding indicates an important mediating role of Ca2+ ions.

The conductivity of human erythrocyte cells dispersed in various uni-univalent electrolyte solutions (NaCl, KCl, LiCl, CsCl; 0.15 M) have been measured in the frequency range from 10 KHz to 100 MHz at five temperatures between 5 and 45 degrees C. The results were analyzed in the light of the theory of conductivity polarization of a suspension of ellipsoidal particles-covered with two confocal shells. Differences in the electrical parameters of the membrane between normal and homozygous beta-thalassemic cells have been evidentiated.

Phosphatidylserine (PS), phosphatidylinositol (PIN) or phosphatidylglycerol (PGL) incubated with synaptosomal plasma membranes (SPM) of dog brain, stimulated adenylate cyclase. The enzyme activity showed a dramatic increase at around 1.6 mumol PS/mg protein, while use of higher concentrations led to inhibition of the activity with respect to the maximal percentage of stimulation. Moreover, PS stimulated the dopamine-sensitive adenylate cyclase. Solubilization of SPM by the detergent Lubrol-PX did not affect the enzyme activation induced by dopamine. The solubilization, also, showed that the enzyme activity does not change at any PS, PIN or PGL concentration used. These results indicate that acidic phospholipids do not directly act on adenylate cyclase, but indirectly, affecting the membrane fluidity probably. Such modifications of interactions through lipid-protein(s) of adenylate cyclase may have implications to physiological responses to hormones or/and neurotransmitters in the central nervous system.

The haemolytic activity of 5-n-alk(en)ylresorcinols is temperature dependent and correlated to their transition temperatures. The values of the parameters describing the 5-n-alk(en)ylresorcinol-induced red blood cell lysis indicate strong affinity of the compounds to the membrane and their high lytic capacity. The affinity of the compounds for the membrane decrease with the increasing quantity of the molecules incorporated into the erythrocyte membrane and is much higher for saturated resorcinols than unsaturated ones. The amount of 5-n-alk(en)ylresorcinol molecules bound to the membrane at a hundred percent lysis is about eighty times and eleven times (for alkyl and alkenyl derivatives respectively) higher than at zero percent lysis. Estimated free energy of erythrocyte lysis was similar for alkyl and alkenyl derivatives of resorcinol provided the preparation of the resorcinolic suspensions above their transition temperatures.

The effects of the administration of a single oral dose of vitamin D3 to rachitic chicks on the in vivo incorporation of [3H]leucine to proteins of skeletal muscle subcellular fractions was studied. A significant stimulation (50%) of labelling of mitochondrial proteins could be seen. The sterol affected the labelling of sarcoplasmic reticulum (20%) and contractile proteins (10%) to a lesser extent. These results confirm previous observations which implicate vitamin D3 in the synthesis of mitochondrial proteins.

The beta 2-dimer of tryptophan synthase from Escherichia coli exhibits weak binding of 8-anilinonaphthalene-1-sulfonic acid (ANS). Titrating the dye at 0.2 mM concentration with the apo-beta 2-dimer at atmospheric pressure causes increased fluorescence emission at 480 nm (lambda exc = 380 nm), corresponding to unspecific binding of the ligand to hydrophobic residues. Increasing hydrostatic pressure affects ANS binding. Up to 700 bar, a sigmoidal increase of ANS fluorescence reflects an increase in hydrophobic surface area, probably caused by subunit dissociation. At approximately 1 kbar, a maximum is reached; beyond this value, pressure competes with ligand binding causing fluorescence emission to be decreased again. Pressure release leads to a drastic fluorescence enhancement, ascribed to ANS binding to the partially and reversibly denatured enzyme. Plotting the total fluorescence enhancement vs. pressure yields a profile which parallels the pressure dependent dimer in equilibrium monomer transition monitored by subunit hybridization (T. Seifert, P. Bartholmes, and R. Jaenicke, Biochemistry, in press).

A new procedure for the isolation of highly purified acylamino acid amidohydrolase from hog kidney is described which allows the preparation of the enzyme with a recovery of about 45%, a 200 fold purification and a spec. activity of 350-500 U. The essential Zn2+ of the enzyme was exchanged for Co2+, Ni2+, Mn2+ and Cd2+, and the kinetic parameters KM, kcat and kcat/KM of the different enzyme species for a series of acetyl-L-amino acids were determined.