The effect of exposure of acetylcholinesterase to 2,450-MHz microwave radiation

The effect of 2,450-MHz pulsed microwave radiation on the enzyme activity of membrane-free acetylcholinesterase was studied while the enzyme was in the microwave field. We found no significant effect of microwave radiation on enzyme activity using a wide variety of power densities, pulse widths, repetition rates, and duty cycles. This suggests that simple, direct modification by microwave energy of acetylcholinesterase structure and enzymic activity is not related to microwave alteration of acetylcholinesterase central nervous system levels.     

The action of gamma irradiation on terrilytin immobilized on cellulose-fiber materials

The effect of gamma-radiation on terrilytin, a proteolytic enzyme immobilized on modified and nonmodified cellulose materials was studied by EPR. Dialdehyde cellulose and graft copolymer of cellulose and polyacrylic acid were used as the modified cellulose materials. Dependence of the native and immobilized terrilytin activity and the content of free radicals in the irradiated samples on the irradiation dose was observed. It was shown that immobilization of the enzyme led to increasing of its stability to the effect of the ionizing radiation. This was due to transfer of the free valency from terrilytin to the carrying polymer which prevented radiation and chemical destruction of the enzyme. The proteolytic activity of native terrilytin subjected to gamma-irradiation markedly decreased because of intramolecular and intermolecular interactions during reactions of the terrilytin free radicals, since in this case there was no polymer as an acceptor of the enzyme free valency.     

Detection of microwave radiation of cytochrome CYP102 A1 solution during the enzyme reaction

Microwave radiation at 3.4–4.2 GHz frequency of the cytochrome P450 CYP102 A1 (BM3) solution was registered during the lauric acid hydroxylation reaction. The microwave radiation generation was shown to occur following the addition of electron donor NADPH to a system containing an enzyme and a substrate. The radiation occurs for the enzyme solutions with enzyme concentrations of 10^?8 and 10^?9 М. The microwave radiation effect elicited by the aqueous enzyme solution was observed for the first time. The results obtained can be used to elaborate a new approach to enzyme systems research, including studying of the mechanism of interaction of a functioning enzyme system with microenvironment.     

The effect of ionizing radiation on the regulation of the Na,K-ATPase activity of the kidney by univalent cations

The effect of ionizing radiation of 0.206 C/kg on the kinetics of activation of rat kidney Na,K-ATPase preparation by Na and K ions was studied as an index of possible qualitative and quantitative changes in the properties of the enzyme. Ionizing radiation was shown not only to increase the enzyme activity but also to change the optimal rate of ATP hydrolysis by Na,K-ATPase and to induce some differences in the shape of the curve for Na,K-ATPase dependence upon Na-sodium//potassium ion ratio in the incubation medium.     

Influence of 2.45 GHz microwave radiation on enzyme activity

Summary The in vitro activity of acetylcholinesterase and creatine phosphokinase was determined during in vitro exposure to 2.45 GHz microwave radiation. The enzyme activities were examined during exposure to microwave radiation at specific absorption rates (SAR) of 1, 10, 50, and 100 mW/g. These specific absorption rates had no effect on the activity of either enzyme when the temperature of the control and exposed samples were similar. These data demonstrate that the activity of these two enzymes is not affected by microwave radiation at the SARs and frequency employed in this study.     

Immobilization of enzymes masks their active site

We studied the effect of immobilizing cellulase to carboxycellulose sodium by radiation polymerization on the masking of the active site of the enzyme. Masking of the enzyme during the preparation of immobilized enzyme was assayed at tow temperature. The activity of immobilized enzyme was retained during repeated batch reactions, indicating that the enzyme was firmly trapped in the polymer matrix. Various compounds (designated monomers) were used to dissolve the carboxymethylcellulose; enzyme activity was affected by the nature of the monomer, by the monomer concentration, and by the solubility of the substrate in monomer.     

Enhanced Activity of Deoxycytidine Kinase After Pulsed Low Dose Rate and Single Dose Gamma Irradiation

In both pulsed low dose rate (LDR) and single high dose radiation schedules, gemcitabine pretreatment sensitizes tumor cells to radiation. These radiosensitizing effects could be the result of decreased DNA repair. In this study, the effect of irradiation on the deoxycytidine kinase (dCK) needed for DNA repair was investigated. The activity of dCK, a deoxynucleoside analogue-activating enzyme was increased upon irradiation in both schedules. No change in dCK protein expression was observed that indicates a post-translational regulation. The benefit of this increased activity induced by irradiation should be further investigated in combination with deoxynucleoside analogues activated by this enzyme.     

Enhanced activity of deoxycytidine kinase after pulsed low dose rate and single dose gamma irradiation

In both pulsed low dose rate (LDR) and single high dose radiation schedules, gemcitabine pretreatment sensitizes tumor cells to radiation. These radiosensitizing effects could be the result of decreased DNA repair. In this study, the effect of irradiation on the deoxycytidine kinase (dCK) needed for DNA repair was investigated. The activity of dCK, a deoxynucleoside analogue-activating enzyme was increased upon irradiation in both schedules. No change in dCK protein expression was observed that indicates a post-translational regulation. The benefit of this increased activity induced by irradiation should be further investigated in combination with deoxynucleoside analogues activated by this enzyme.     

光活化杀虫剂α-三噻吩的电子自旋共振分析及其对库蚊保护酶系统活性的影响

以淡色库蚊Culex pipiens pallens为试材,初步进行了典型光活化杀虫剂α-三噻吩（α-T）的电子自旋共振（ESR）分析,并研究其对昆虫保护酶系统的影响。ESR分析表明,近紫外光和药剂α-T均可促进活性氧自由基浓度升高,且两者具有协同关系,近紫外光能显著促进α-T增加自由基的作用,处理3 h时试虫自由基总浓度增加了99.6%。近紫外光和药剂α-T对保护酶系统的影响随酶的种类而有所不同,但在近紫外光存在的条件下,α-T对超氧物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活体活性均有抑制作用,且光照3 h时,抑制作用最强。     

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.     

Postradiation changes in the activity of membrane-bound nerve tissue enzymes

A study was made of the effect of various radiation doses (1.75 to 12.25 Gy) on the enzyme activity of Na,K-ATPase system of the microsomal brain fraction of mongrel and Wistar rats. With a similar method of the fraction isolation different response of the activity of this enzyme was registered. Different radiosensitivity of M9-ATPase is responsible for the direction of changes in the Na,K-ATPase activity of the preparations.     

Post-radiation changes in active transport in he CNS: Mg2+, Ca2+-ATPase

The effect of ionizing radiation of lethal (0.31 C/kg) and superlethal (9.288 C/kg) doses on Mg2+, Ca2+-ATPase activity in plasma membranes of brain cortex and cerebellum has been studied. As is shown, ionizing radiation has an inhibitory effect on the enzyme activity which is most pronounced and irreversible after exposure to superlethal doses.     

Effects of Alkali Halides and Other Inorganic Salts on Radiation Inactivation of Taka-amylase in Aqueous System

Effects of alkali halides on radiation inactivation of Taka-amylase A were investigated in connection with their synergistic action to the radiation inactivation of microorganisms. Effective concentrations of these halides in protection against irradiation inactivation of this enzyme were well corresponded to that observed in the synergistic action to microorganisms. Removal of dissolved oxygen from halide solutions decreased their protective effect. Irradiated alkali halide solutions of relatively higher concentrations exhibited the inactivating action to this enzyme, and various types of addition effects of halogens and halogenoxyacids were observed with or without irradiation. Sodium nitrite showed effective protection even with higher radiation doses, and the heavy metal cations, Cu⁺⁺ and Fe⁺⁺⁺, also gave a protective action in low concentrations. From these observations, the possible interpretation on the mode of protection of alkali halides was attempted.     

RecBC enzyme overproduction affects UV and gamma radiation survival of Deinococcus radiodurans

Deinococcus radiodurans recovering from the effect of acute dose of gamma (gamma) radiation shows a biphasic mechanism of DNA double strands breaks repair that involves an efficient homologous recombination. However, it shows higher sensitivity to near-UV (NUV) than Escherichia coli and lacks RecBC, a DNA strand break (DSB) repair enzyme in some bacteria. Recombinant Deinococcus expressing the recBC genes of E. coli showed nearly three-fold improvements in near-UV tolerance and nearly 2 log cycle reductions in wild type gamma radiation resistance. RecBC over expression effect on radiation response of D. radiodurans was independent of indigenous RecD. Loss of gamma radiation tolerance was attributed to the enhanced rate of in vivo degradation of radiation damaged DNA and delayed kinetics of DSB repair during post-irradiation recovery. RecBC expressing cells of Deinococcus showed wild type response to Far-UV. These results suggest that the overproduction of RecBC competes with the indigenous mechanism of gamma radiation damaged DNA repair while it supports near-UV tolerance in D. radiodurans.     

Influence of CW microwave radiation on in vitro release of enzymes from retinol- treated hepatic lysosomes

Hepatic lysosomes were exposed in vitro to microwave radiation (2450 MHz) either prior to or simultaneously with treatment with retinol (vitamin A), and the release of the lysosomal enzymes, beta-glucuronidase, acid phosphatase, and cathepsin D, determined. A 60-min microwave exposure (10 or 100 mW/g) of retinol-treated lysosomes had no effect on the amount of release of beta-glucuronidase, cathepsin D, or acid phosphatase. In addition, 10 and 100 mW/g irradiation of lysosome fractions for 40 min prior to a 20-min retinol and microwave treatment, had no influence on the release of these enzymes. Finally, the effect of microwave radiation on the loss of latency of acid phosphatase and beta-glucuronidase from retinol-treated lysosomes was determined. Microwave radiation had no influence on the rate of appearance of these enzymes in the suspending medium. The results indicate that microwave radiation had no effect on the retinol-induced lysosomal enzyme release.     

A Threshold Dose of Heavy Ion Radiation that Decreases the Oxidative Enzyme Activity of Spinal Motoneurons in Rats

The effect of heavy ion radiation exposure of the spinal cord on the properties of the motoneurons innervating the slow soleus and fast plantaris muscles was investigated. A 15-, 20-, 40-, 50-, or 70-Gy dose of carbon ions (5 Gy/min) was applied to the 2nd to the 6th lumbar segments of the spinal cord in rats. After a 1-month recovery period, the number and cell body size of the irradiated motoneurons innervating the soleus and plantaris muscles did not differ from that of the non-irradiated controls, irrespective of the dose received. However, the oxidative enzyme activity of these motoneurons was decreased by heavy ion radiation at doses of 40, 50, and 70 Gy compared to that of the non-irradiated controls. This decrease in oxidative enzyme activity levels in the motoneurons returned to that of the non-irradiated controls after a 6-month recovery period. We conclude that heavy ion radiation at doses of 40–70 Gy reversibly decreases the oxidative enzyme activity of motoneurons in the spinal cord of rats.     

Catalytic properties of testicular hyaluronidase after gamma-irradiation

The effect of gamma-irradiation on ovine testicular hyaluronidase was studied in aqueous solution. Following irradiation, hyaluronidase is inhibited, and the kinetics of inhibition follow a pattern in which Km and Vmax decline as radiation dose is increased. It was indicated that the binding affinity of the residual activity of hyaluronidase with substrate is enhanced and depends upon radiation damage. Effects of various agents such as pH, salts, PCMB and glutathione on irradiated hyaluronidase have been compared with non-irradiated enzyme. The irradiated hyaluronidase was more sensitive to inhibition by CuSO4 than the non-irradiated enzyme. The residual activity after irradiation is less refractory to FeCl3 inhibition and less sensitive to NaCl stimulation compared to non-irradiated hyaluronidase. pH response curves of ovine testicular hyaluronidase show two maxima which become more evident after irradiation.     

Differential radiation effect in tumor and normal tissue after treatment with ramipril, an angiotensin-converting enzyme inhibitor

The angiotensin-converting enzyme inhibitor, ramipril, has been shown to mitigate radiation injury in normal tissues. Using A549 cell xenografts grown in athymic mice, we measured the effect of ramipril on radiation damage to tumors. Ramipril did not alter tumor response to radiation despite different times of drug administration with respect to radiation delivery (drug started 2 weeks before or immediately after irradiation). In contrast, using the same dose, ramipril reduced normal tissue radiation injury (30 Gy x 2 or 6 Gy x 10) as assessed by a semi-quantitative scale of skin damage and relative leg contraction. The results indicate that ramipril could offer therapeutic gain due to its different effect on normal tissues and tumors.