[The study of the creatine kinase radiation stability in 25Mg-enzyme enrichment experiment].

The radiation inactivation technique was applied to conduct the study on catalytic activity changes of creatine kinase species isolated from the Mid-Asian Death Adder venom. Both intact and the 25Mg-enriched enzyme samples were separately tested. Some differences in radiation stability levels were found to be indicating to a shift in conformational condition (a so called "conformational distribution") of the native enzyme that had happen in the presence of the magnetic nuclei excess.

Free radical-induced inactivation of creatine kinase: influence on the octameric and dimeric states of the mitochondrial enzyme (Mib-CK).

Free radicals of X-ray-induced water radiolysis, either directly or indirectly via their reaction products, reduce the activity of both dimeric cytoplasmic muscle-type creatine kinase (MM-CK) and octameric mitochondrial creatine kinase (Mi-CK) to virtually zero. Similarly values of the characteristic D(37)-dose of enzyme inactivation (dose required to reduce enzyme activity to 37%) were found for the two isoenzymes of CK under identical conditions. Octamer stability was not significantly affected within the dose range considered. However, both the dissociation of octamers into dimers by a transition-state analogue complex (TSAC), and the reassociation of the dimers into octamers, showed dose-dependent reduction. Binding of the TSAC to the active centre was found to protect the enzyme against inactivation by free radicals. No protection was observed for the radiation-induced decrease of the endogenous tryptophan fluorescence. The experimental results are in line with the following interpretation: (i) the reduction of Mi(b)-CK dimer association is due to free radical-induced modification of Trp-264, situated at the dimer/dimer interface; (ii) the active-site Trp-223 is not a prime target for free radicals and is not involved in the inactivation of the enzyme; (iii) the inhibition of TSAC-induced dissociation of Mi(b)-CK, like enzyme inactivation, is primarily due to a modification of the active-site Cys-278.

[Biologic effects of the static magnetic field generated by a 0.5 T magnetic resonance tomograph on the enzyme activity of catalase and creatine kinase in the rat]. / Effetti biologici del campo magnetico statico di un tomografo a Risonanza Magnetica da 0,5 T sull'attività enzimatica della catalasi e della creatinchinasi nel ratto.

PURPOSE: We investigated possible alterations in the enzyme activity of catalase and isozyme MB-creatine kinase induced by prolonged exposure of laboratory rodents to a static magnetic field generated by a .5 T Magnetic Resonance unit. MATERIAL AND METHODS: Thirty Wistar albino mice were divided into two groups of 15 mice, one to be exposed to the static magnetic field for 12 hours and the other to be kept in the same environmental conditions as a control group. Immediately after the exposure a peripheral venous blood sample was collected, the cardiac muscle was removed from the mice and the enzyme activity of catalase and MB-creatine kinase were assayed using the spectrophotometric analysis. RESULTS: No statistically significant variation was detected between the enzyme activity of catalase and MB-creatine kinase in the serum and cardiac muscle of the exposed versus the control mice. In the mice exposed to the static magnetic field the enzyme activity of serum and cardiac muscle catalase were respectively .2154 U/L and .0707 U/L after 10 minutes; they were; .2699 U/L and .0946 U/L after 160 minutes. In the control mice the enzyme activity of serum and cardiac muscle catalase were respectively .1941 U/L and .0707 U/L after 10 minutes; they were .2061 U/L and .1068 U/L after 160 minutes. The enzyme activity of MB-creatine kinase in mice was measured in the exposed (80.8 U/L) versus the control (79.6 U/L) group: the difference does not exceed standard deviation. DISCUSSION AND CONCLUSION: Our results seem to exclude any alteration in the activity of catalase and MB-CK after 12 hours' exposure to the static magnetic field. However some homeostatic mechanisms peculiar to pluricellular organisms might act in vivo to adapt to the effects of the static magnetic field during exposure.

[The creatine kinase activity of chick myoblasts and neuroblasts in primary culture after intensive laser irradiation]. / Kreatinkinaznaia aktivnost' kurinykh mioblastov i neiroblastov v pervichnoi kul'ture posle intensivnogo lazernogo oblucheniia.

The influence of green-yellow light of copper laser (mean power of impulse-periodic emanation 3 W, working density of power in experiment is 200 mW/cm2) on biochemical indices of chick embryo myoblasts and neuroblasts in primary culture was studied. The content of water extracted protein was found to increase progressively, the total and specific activities of creatine kinase elevated considerably in both the cell cultures under irradiation with the total doses equal to 3 and 15 J. However, with dose of 30 J these parameters corresponded to the level characteristic of nonirradiated cultures. Mechanisms of stimulating action of highly intensive laser emanation on cell functions are discussed.

[The stimulation of the creatine kinase activity of tissue cultures with high-energy laser radiation]. / Stimuliatsiia kreatinkinaznoi aktivnosti tkanevykh kul'tur vysokoénergeticheskim lazernym izlucheniem.

Effects of copper laser stimulating doses on biochemical parameters of competent chicken embryo myoblast and neuroblast cultures were studied. It was shown that in both systems biostimulation was characterized by an increase of water-extractable protein level and a considerable rise of total and specific creatine kinase activity. The authors believe that cases of protein drop during myoblast culture exposure to chemical agents described in literature were caused by these agents overdosage and that this drop may be considered as a manifestation of a peculiar biochemical shock induced by overdosage. They suggest to follow up the time course of water-extractable protein levels in the cultures to differentiate between trophic and injurious loading.

[Light sensitivity of creatine kinase in control sera]. / Lichtempfindlichkeit der Kreatinkinase in Kontrollseren.

The light sensitivity of creatine kinase in different control sera was investigated. Control sera were dispensed into reaction vessels, then exposed for 4 h at 25 degrees C to a light source equivalent in intensity to normal laboratory illumination. In 12 out of 22 control sera, the catalytic concentration of the creatine kinase fell by 25-63%. Under the same conditions, in patient sera, creatine kinase is stable. In the "light sensitive" control sera, the instability of the enzyme increased with the intensity of illumination. When exposed to sunlight creatine kinase was unstable in all the investigated control and patient sera. The addition of mercaptoethanol stabilized the creatine kinase in "light sensitive" control sera. The reason for the different light sensitivity of different control sera is not known.

[Effect of combined irradiation and hyperthermia on the creatine kinase activity of rat tissues]. / Deistvie sochetannogo oblucheniia i gipertermii na kreatinkinaznuiu aktivnost' tkanei krys.

Effects of heating (36 degrees, relative air humidity 80-90%, 4 hours) and joint beta (85Kr)-X-ray-irradiation of rats, given separately and simultaneously, in doses 2.5 krad+ + 25 r, 2.5 krad + 50 r, 3.05 krad + 100 r, 4.45 krad + 250 r, 7.4 krad + 400 r on creatine kinase activity in brain and liver were investigated 5, 12, 19 and 26 days after the exposure. It was discovered that the state of thermal stress reduced radiosensitiveness of enzymatic activity in brain and burdened the consequences of irradiation when tested by the liver activity.

Photolabeling reagent for thiol enzymes. Studies on rabbit muscle creatine kinase.

A mixed disulfide reagent for photolabeling is described which reacts stoichiometrically with a cysteine sulfhydryl group of rabbit muscle creatine kinase to form a new mixed disulfide between enzyme and 2-thiobenzyl[14C]diazoacetate. When irradiated at 254 nm for 5 s in a photoreactor, the enzyme-bound diazo group is destroyed, presumably via a carbene intermediate. After photolysis, the enzyme can only be 69+/-2% reactivated by dithiothreitol, and only 67+/-1% of the radiolabel can then be removed from the protein by dialysis in the presence of dithiothreitol. Less than 3% of this permanent labeling occurs if photolysis is carried out in 6 N guanidine hydrochloride, which shows that the native enzyme structure is required for photolabeling. Identification of the tagged products after acid hydrolysis indicates that 30% of the carbene produced on photolysis reacts with the hydroxyl groups of threonine andserine with O-[14C]carboxymethylthreonine as the major product. Photochemical Wolff rearrangement is estimated to occur to less than 30%, and no S-carboxymethylcysteine was detected. The reagent employed and its isomers are proposed as bifunctional photolabeling probes to "scan" the amino acid residues near the active sites of thiol enzymes.

Radiation-induced enzyme efflux from rat heart: sedentary animals.

Serum levels of lactate dehydrogenase, creatine kinase, and glutamate oxaloacetate transaminase show initial elevations within 12 hr of exposure to 2,000 rads of gamma-radiation to the thoracic region of rats. Significant decreases in heart muscle homogenate levels of these enzymes parallel initial elevations in the serum and may suggest that enhanced leakage of enzymes is a consequence of radiation injury to heart muscle. Insignificant alterations in mitochondrial glutamate oxaloacetate transaminase levels after exposure indicate that in vivo injury to the mitochondria from therapeutic levels of gamma-radiation is questionable. The results support the contention that ionizing radiation instigates alterations in the dynamic permeability of membranes, allowing leakage of biologically active material out of the injured cell.