ATP-dependent Ca2+-transporting system in the rat brain during an early period of acute radiation injury

The rate of Mg2+, Ca2+-ATPase reaction and ATP-dependent Ca2+ accumulation in a preparation of plasma membranes from brain synaptosomes increases 60 min following whole-body X-irradiation of rats with a dose of 0.21 C/kg, a calcium sensitivity of both processes being increased. A unidirectional change in their kinetics indicates the early radiosensitivity of Ca2+ transfer systems in the brain synaptosome membranes. There is an increase in the availability of SH-groups of membrane preparation proteins for SH-reagents and in the sensitivity of Mg2+, Ca2+-ATPase reaction and ATP-dependent Ca2+ accumulation to trifluoperazine, a calmodulin inhibitor. Both processes lose their ability to be activated by exogenous calmodulin. It is suggested that at an early stage of radiation affection, a change occurs in the molecular organization of the ATPase-calmodulin membrane complex in plasma membranes of rat brain synaptosomes.     

Morphological restructuring of the cellular elements of the ventral tegmental area in selective damage to the catecholaminergic systems of the brain

Electron microscopical investigation of the ventral tegmental area at various time after administration of a specific neurotoxin 6-hydroxydopamine made it possible not only to reveal catecholamine reactive elements, but also those structural reorganizations in them, that are dependent on the lesion of the catecholaminergic systems, including certain changes in the receptor apparatus. Dark neurons with the change of different organelles preserve for a long time, up to 2.5 months. Reactive and destructive reorganizations of some axons, terminal buttons and postsynaptic poles of the ventral tegmental area are accompanied with certain functional disturbances, observed both experimentally and at a pathological process. The results of the work demonstrate that under conditions of the model experiments there is a possibility to study various stages of pathogenesis of a number of nervous-psychical diseases, connected or accompanied with disorders in certain mediator systems.     

Structural changes in the sarcoplasmic reticulum membrane of skeletal muscles at the early stage of x-ray irradiation]

A single X-ray irradiation of the rabbit hindlimbs in a dose of 0.24 C/kg evokes a decrease in fluorescence of the ANS probe bound with membranes of the sarcoplasmatic reticulum as a result of the decrease of binding sites, binding constant as well as the quantum output of the probe. A decrease in fluorescence of tryptophan residues of Ca-ATPase localized in membranes and attenuation of interaction of its SH-group with dithionitrobenzoic acid has been also observed at early postradiation terms (1 and 24 h). The obtained results evidence for structural rearrangements occurring in membranes of the sarcoplasmic reticulum under the effect of ionizing radiation. Changes in conformation of CA-ATPase molecules contribute much to this process.     

Phospholipase A2 from rat spleen lymphocytes hydrolyzing arachidonoyl-phospholipids]

Phospholipase A2 activity in the postnuclear supernatant of lymphocytes has been studied by measuring 14C arachidonate released from labelled phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC) as exogenous substrates. The pH optimum was 7.5-9.0 for PE and 9.0 for PC. Phospholipase A2 was not detected in the presence of 2 mM EGTA. It was optimal with the millimolar calcium concentrations and higher towards PE. Preincubation of lymphocytes with 0.5 M ionophore A-23187 was followed by 2.4 fold stimulation of the phospholipase activity. A stimulatory effect was observed after preincubation of cells with 10 micrograms/ml of phytohemagglutinin, lipopolysaccharide, concanavalin A; it decreased as: lipopolysaccharide greater than phytohemagglutinin greater than concanavalin A. The results obtained have suggested the possibility of existence of different forms of phospholipase A2 in the spleen lymphocytes and participation of the enzyme in the early signalling events.     

Study of the kinetics of thermoinactivation of lysyl-tRNA-synthetase from the liver of x-irradiated rats

A study was made of the kinetics of thermoinactivation of lysyl-tRNA-synthetase isolated from rat liver at early times of radiation damage development after the effect of a minimum absolutely lethal X-radiation dose (0.21 C/kg). The thermostability of a dimer form of the enzyme was shown to be higher than that of a monomer. It was established that substrates had a stabilizing effect on the enzyme during thermoinactivation. On the basis of the data obtained from the studies in the kinetic properties of the enzyme and the thermoinactivation a conclusion is made that lysyl-tRNA-synthetase is stabilized during subunit aggregation. The thermostability of the enzyme was decreased by irradiation.     

Effect of gaseous hypoxic mixture GHM-10 on the intestinal death of Wistar rats and Na+,K+-ATPase activity of the plasma membrane of the small intestine mucosa after irradiation

It was shown that gas hypoxic mixture containing O2 (10%) and N2 (90%) significantly decreases "intestinal" death of Wistar rats on the 5th day following irradiation and normalizes Na+,K+-ATPase activity of the small intestine mucosa plasma membranes.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

The content of phospholipids and free fatty acids in the sarcoplasmic reticulum membranes in the early stage of an x-ray radiation lesion

One and 24 h following single X-irradiation (0.21 C/kg) of rabbit hind leg the content of free fatty acids and phospholipid lysoforms increased in the sarcoplasmic reticulum (SR) membrane of skeletal muscles. The results obtained are important in estimating the mechanisms of action of ionizing radiation on the structural and functional properties of SR.     

Intraspecific diversity in the fungal speciesChaunopycnis alba: Implications for microbial screening programs

Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics.