[Radio Frequency Electromagnetic Field Effect on the State of Na+/Ca2+ Exchange in the Isolated Rat Heart].

It has been shown that a single exposure to 171 MHz electromagnetic field with 180 V/m electric field strength and 0.04 mW/kg specific absorption rate significantly alters the Na+/Ca2+ exchange in the isolated rat heart. It is assumed that enhancement of the Na+/Ca2+ exchange towards removing Ca2+ from the cardiomyocytes electromagnetic field exposure is a result of Ca2+ extraction from the sarcoplasmic reticulum and the increase of its intracellular level.

[The strategy of the "useful sun" improves physical endurance and structural adaptation in the myocardium].

The action of solar light transformed by special screens has been studied on CD-1 male mice. In the active control group, mice were irradiated through screens absorbing the UV-component. In the experimental group, screens transforming the UV-component into the orange-red light were used. In the active control, changes in the swimming activity, as compared to the same parameter before irradiation, were manifested much less than in animals of the experimental group. A morphological analysis showed changes in the structure of all cardiomyocyte organelles studied: the relative area of mitochondria in the experimental mice increased by more than 20% compared to intact animals (p < 0.05). A significant increase in the area of the sarcoplasmic reticulum, by 23.4% (p < 0.05), and in the volume of the myofibrillar apparatus, by 19.4% (p < 0.05), was detected. The results of our experiment show that the irradiation with using an additional orange-red component improves the physical endurance 1.5 times and initiates morphogenetic processes in cardiac muscle cells.

[Effects of 50 Hz sinusoidal magnetic field on Ca2+ release channel ryanodine receptor of sarcoplasmic reticulum vesicles].

OBJECTIVE: To investigate the effects of sinusoidal magnetic field on isolated sarcoplasmic reticulum (SR) calcium release channel (RyR1) function. METHODS: With the Ca2+ dynamic spectrum and isotope labeled methods, the Ca2+ release and [(3)H]-Ryanodine binding, the initial rates of NADH oxidation and the production of superoxide of SR exposed to 50 Hz sinusoidal magnetic field (MF) were investigated respectively. RESULTS: 0.4 mT, 50 Hz sinusoidal MF exposure for 30 min increased SR Ca2+ release initial rate about 35% from (10.82 +/- 0.89) pmol.mg(-1) pro.s(-1) to (14.69 +/- 1.21) pmol.mg(-1) pro.s(-1); and the [(3)H]-Ryanodine binding by about 15% from (2.13 +/- 0.05) pmol/mg pro to (2.45 +/- 0.07) pmol/mg pro, which regulated by 1 mmol/L NADH with 1 mmol/L NAD+. Meanwhile MF upregulated the rate of NADH oxidation by about 22% from (0.88 +/- 0.11) x 10(-4) FI/s to (1.07 +/- 0.13) x 10(-4) FI/s and upregulated the production of superoxide by about 32% from (0.99 +/- 0.09) x 10(-5) FI/s to (1.31 +/- 0.06) x 10(-5) FI/s. CONCLUSION: 0.4 mT sinusoidal MF increases the activity of RyR1 within the low redox potential environment, and promotes NADH oxidase activity and superoxide production.

Gamma-radiation induces apoptosis via sarcoplasmatic reticulum in guinea pig ileum smooth muscle cells.

We investigated the effects of gamma-radiation on cells isolated from the longitudinal smooth muscle layer of the guinea pig ileum, a relatively radioresistant tissue. Single doses (up to 50 Gy) reduced the amount of sarcoplasmatic reticulum and condensed the myofibrils, as shown by electron microscopy 3 days post-irradiation. After that, contractility of smooth muscle strips was reduced. Ca(2+) handling was altered after irradiation, as shown in fura-2 loaded cells, with elevated basal intracellular Ca(2+), reduced amount of intrareticular Ca(2+), and reduced capacitive Ca(2+) entry. Radiation also induced apoptosis, judged from flow cytometry of cells loaded with proprium iodide. Electron microscopy showed that radiation caused condensation of chromatin in dense masses around the nuclear envelope, the presence of apoptotic bodies, fragmentation of the nucleus, detachment of cells from their neighbors, and reductions in cell volume. Radiation also caused activation of caspase 12. Apoptosis was reduced by the administration of the caspase inhibitor Z-Val-Ala-Asp-fluoromethyl-ketone methyl ester (Z-VAD-FMK) during the 3 day period after irradiation, and by the chelator of intracellular Ca(2+), 1,2-bis(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), from 1 h before until 2 h after irradiation. BAPTA also reduced the effects of radiation on contractility, basal intracellular Ca(2+), amount of intrareticular Ca(2+), capacitative Ca(2+) entry, and apoptosis. In conclusion, the effects of gamma radiation on contractility, Ca(2+) handling, and apoptosis appear due to a toxic action of intracellular Ca(2+). Ca(2+)-induced damage to the sarcoplasmatic reticulum seems a key event in impaired Ca(2+) handling and apoptosis induced by gamma-radiation.

[Effects of power frequency magnetic field on Ca2+ transport of skeletal muscle sarcoplasmic reticulum vesicles].

OBJECTIVE: To investigate the effects of power frequency magnetic field on the Ca2+ transport dynamics of isolated sarcoplasmic reticulum vesicles. METHODS: The assays of Ca2+ uptake time course and the Ca2+-ATPase activity of sarcoplasmic reticulum vesicles were investigated by using dynamic mode of spectrometry with a Ca2+ dye; Ca2+ release channel activation was examined by 3H-ryanodine binding and Ca2+ release assays; membrane fluidity of sarcoplasmic reticulum vesicles was examined by fluorescence polarization, without or with exposure to the vesicles at a 0.4 mT, 50 Hz sinusoidal magnetic field. RESULTS: 0.4 mT, 50 Hz sinusoidal magnetic field exposure caused about a 16% decline of the initial Ca2+ uptake rate from a (29.18 +/- 3.90) pmol.mg(-1).s(-1) to a (24.60 +/- 3.81) pmol.mg(-1).s(-1) and a 26% decline of the Ca2+-ATPase activity from (0.93 +/- 0.05) micromol.mg(-1).min(-1) to (0.69 +/- 0.07) micromol.mg(-1).min(-1) of sarcoplasmic reticulum vesicles, whereas caused a 15% increase of the initial Ca2+ release rate from (4.83 +/- 0.82) pmol.mg(-1).s(-1) to (5.65 +/- 0.43) pmol.mg(-1).s(-1) and a 5% increase in 3H-ryanodine binding to the receptor from (1.10 +/- 0.12) pmol/mg to (1.16 +/- 0.13) pmol/mg, respectively. CONCLUSION: The decline of Ca2+-ATPase activity and the increase of Ca2+ release channel activity should result in a down-regulation of Ca2+ dynamic uptake and an up-regulation of Ca2+ release induced by exposing the sarcoplasmic reticulum to a 0.4 mT, 50 Hz power frequency magnetic field.

A photoactivable probe for calcium binding proteins.

Ca2+ as a signaling molecule carries information pivotal to cell life and death via its reversible interaction with a specific site in a protein. Although numerous Ca2+-dependent activities are known, the proteins responsible for some of these activities remain unidentified. We synthesized and characterized a photoreactive reagent, azido ruthenium (AzRu), which interacts specifically with Ca2+ binding proteins and strongly inhibits their Ca2+-dependent activities, regardless of their catalytic mechanisms or functional state as purified proteins, embedded in the membrane or in intact cells. As expected from a Ca2+ binding protein-specific reagent, AzRu had no effect on Ca2+-independent and Mg2+-dependent activities. Az103Ru covalently bound, and specifically labeled, known Ca2+ binding proteins. AzRu is a photoreactive reagent that provides an approach for identification of Ca2+ binding proteins, characterization of their binding sites, and exploration of new Ca2+-dependent processes.

[Hormonal regulation of the function of the myocyte intracellular membranes under radiation influence]. / Gormonal'naia reguliatsiia funktsii vnutrennikh membran miotsitov pri deistvii radiatsii.

It was shown that the experimental hypofunction of thyroid, induced by thyroidectomy and strong gamma-irradiation with a dose of 1 Gy lead to disturbance of function and structure of membranes of sarcoplasmic reticulum of myocites in rats. Introduction in vivo of L-thyroxine rose functional capacity of membranes with insignificaut changes in their lipid bilayer.

Time-resolved charge movements in the sarcoplasmatic reticulum Ca-ATPase.

The time-resolved kinetics of the Ca(2+)-translocating partial reaction of the sarcoplasmatic reticulum Ca-ATPase was investigated by ATP-concentration jump experiments. ATP was released by an ultraviolet light flash from its inactive precursor and charge movements in the membrane domain of the ion pumps were detected by the fluorescent styryl dye 2BITC. Two oppositely directed cation movements were found, which were assigned to Ca(2+) release and H(+) binding. The faster process with a typical time constant of 30 ms reports the rate-limiting process before Ca(2+) release, probably the conformation transition E(1) --> E(2). The following, slow uptake of positive charge had a pH-dependent time constant, which was 1 s at low pH and approximately 3 s at pH > 8. This process is assigned to an electrically silent conformational relaxation of the state P-E(2) preceding H(+) binding. This interpretation is in agreement with the observation that the fast process was independent of the substrate concentrations (i.e., when [Ca(2+)] > 200 nM, and [ATP] > 20 micro M). The slow process was independent of the Ca(2+) concentration. The activation energy of the resolved processes was between 80 kJ/mol and 90 kJ/mol, which is comparable to the activation energy of the enzymatic activity (92 kJ/mol) and these high values point to conformational changes underlying rate-limiting steps of the pump cycle.

Calcium quarks.

Elementary subcellular Ca2+ signals arising from the opening of single ion channels may offer the possibility to examine the stochastic behavior and the microscopic chemical reaction rates of these channel proteins in their natural environment. Such an analysis can yield detailed information about the molecular function that cannot be derived from recordings obtained from an ensemble of channels. In this review, we summarize experimental evidence suggesting that Ca2+ sparks, elementary Ca2+ signaling events of cardiac and skeletal muscle excitation contraction coupling, may be comprised of a number of smaller Ca2+ signaling events, the Ca2+ quarks.

[Effects of gamma-irradiation and thyro-parathyroidectomy on structural-functional state of membranes of sarcoplasmic reticulum of skeletal muscle]. / Vliianie vozdeistviia gamma-izlucheniia i tireoparatireoidéktomii na strukturno-funktsional'noe sostoianie membran sarkoplazmaticheskogo retikuluma skeletnoi myshtsy.

It has been found that the combined effect of the acute gamma-irradiation with 1 Gy dose and thyroparathyroidectomy (TPTE) changes the structure-functional state of SR membranes of rat skeletal muscles conditioned by the disturbance of hormonal regulation of molecular-cellular mechanisms of calcium exchange.

Inverse dose-rate effects at the level of proteins observed in the presence of lipids.

PURPOSE: Radical-chain mechanisms such as lipid peroxidation are known to show an inverse dose-rate effect, i.e. the radiation effect increases with decreasing dose rate at identical doses applied. The present study was intended to investigate whether an inverse dose-rate effect can be transferred from the level of lipids to the level of proteins. METHOD: Functional inactivation or structural modification by 80kV X-rays of two classes of proteins was investigated: membrane proteins with a natural environment of lipids like the Ca-ATPase of the sarcoplasmic reticulum, succinate dehydrogenase and F0F1-ATPase from the inner mitochondrial membrane. The second class comprises the water-soluble proteins cytosolic creatine kinase (MM-CK) and bovine serum albumin (BSA). Their modification by free radicals of water radiolysis was investigated in the absence and presence of lipid vesicles. RESULTS: For all proteins investigated, an inverse dose-rate effect was observed in the presence of lipids. This also holds for the water-soluble proteins MM-CK and BSA. In the latter two cases, the dose-rate effect disappeared either in the absence of (unsaturated) lipids or in the presence of alpha-tocopherol. CONCLUSION: The largely identical results obtained for a variety of different proteins indicate that inverse dose-rate effects are a normal consequence of radiation induced protein damage in the presence of lipids. In view of the high amount of cellular lipids, this should also hold for the situation in vivo, although due to the comparatively high concentration of intracellular antioxidants the dose-rate dependence might be strongly reduced or even virtually abolished.

Effect of global system for mobile communication (GSM) microwave exposure on blood-brain barrier permeability in rat.

We investigated the effects of global system for mobile communication (GSM) microwave exposure on the permeability of the blood-brain barrier using a calibrated microwave exposure system in the 900 MHz band. Rats were restrained in a carousel of circularly arranged plastic tubes and sham-exposed or microwave irradiated for a duration of 4 h at specific brain absorption rates (SAR) ranging from 0.3 to 7.5 W/kg. The extravasation of proteins was assessed either at the end of exposure or 7 days later in three to five coronal brain slices by immunohistochemical staining of serum albumin. As a positive control two rats were subjected to cold injury. In the brains of freely moving control rats (n = 20) only one spot of extravasated serum albumin could be detected in one animal. In the sham-exposed control group (n = 20) three animals exhibited a total of 4 extravasations. In animals irradiated for 4 h at SAR of 0.3, 1.5 and 7.5 W/kg (n = 20 in each group) five out of the ten animals of each group killed at the end of the exposure showed 7, 6 and 14 extravasations, respectively. In the ten animals of each group killed 7 days after exposure, the total number of extravasations was 2, 0 and 1, respectively. The increase in serum albumin extravasations after microwave exposure reached significance only in the group exposed to the highest SAR of 7.5 W/kg but not at the lower intensities. Histological injury was not observed in any of the examined brains. Compared to other pathological conditions with increased blood-brain barrier permeability such as cold injury, the here observed serum albumin extravasations are very modest and, moreover, reversible. Microwave exposure in the frequency and intensity range of mobile telephony is unlikely to produce pathologically significant changes of the blood-brain barrier permeability.

Irradiation with ultraviolet light in the presence of vanadate increases Ca2+ permeability of the sarcoplasmic reticulum membrane via Ca(2+)-ATPase.

The sarcoplasmic reticulum (SR) of rabbit skeletal muscle was irradiated with ultraviolet light (UV) in the presence of vanadate plus 2 mM EGTA, 10 mM MgCl2, 20% DMSO, and 50 mM PIPES (pH 6.5) at room temperature. In the presence of 100 microM vanadate, the Ca(2+)-uptake activity of SR rapidly decreased and was almost lost in 20 min. The activity was inhibited as a function of vanadate concentration with an apparent Ki of about 20 microM. On the other hand, Ca(2+)-dependent ATP hydrolytic activity as well as phosphoenzyme (EP) formation activity decreased very slowly, and more than 50% of these activities remained 20 min after initiation of the vanadate-UV treatment. Half inhibition of these activities required about 100 microM vanadate. The loss of the relationship between Ca(2+)-uptake and ATPase reaction was found to be mainly caused by an increase in the Ca2+ permeability of the SR membrane, which was raised by increasing the vanadate concentration or UV irradiation time in a manner similar to that observed for the Ca2+ uptake. No rise in Ca2+ permeability occurred in liposomes reconstituted from SR lipid when they were irradiated with UV in the presence of 100 microM vanadate. When the vanadate-UV-treated SR was allowed to react with fluoral-P (4-amino-3-penten-2-one), an indicator of aldehyde, and the membrane proteins were separated by HPLC in the presence of SDS, the fluorescent probe was found to be closely associated with the Ca(2+)-ATPase fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Catalysis of an ATP analogue untethered and tethered to lysine 492 of sarcoplasmic reticulum Ca(2+)-ATPase.

2',3'-O-(2,4,6-trinitrophenyl)-8-azido-AMP (TNP-8N3-AMP) and -ATP photolabel Lys-492 at the active site of the Ca(2+)-ATPase of sarcoplasmic reticulum (McIntosh, D. B., Woolley, D. G., and Berman, M. C. (1992) J. Biol. Chem. 267, 5301-5309). We now find that the hydrolysis of the gamma-phosphate of both TNP-8N3-ATP and the TNP-nucleotide tethered to Lys-492 is stimulated by Ca2+ (kcat = 0.02 s-1, Km = 1.6 microM; k(obs) = 0.08 s-1, respectively, pH 6.0) and exhibits acidic pH optima with shifted pH dependences (pKa = 5.7 and 7.0, respectively). TNP-8N3-ATP supports Ca2+ transport with a coupling stoichiometry of 2:1 in the pH range 5.0-7.5. Hydrolysis of the tethered substrate is largely uncoupled from transport; a small, substoichiometric amount of transport is observable at acidic pH. Ca(2+)-dependent phosphorylation of the ATPase with TNP-8N3-ATP is demonstrable under select conditions but with the tethered substrate is too low to be measured with confidence. Neither ADP nor ATP has any effect on the Ca(2+)-dependent catalysis of the tethered nucleotide. Tethering does not appear to affect formation of phosphoenzyme as shown by P(i)-dependent superfluorescence of the tethered nucleotide. The results indicate that Lys-492 is located at the catalytic site within approximately 14 A of Asp-351, which is phosphorylated, and Lys-492 and the adenyl moiety of the nucleotide are closely associated during phosphorylation. Evidently, Lys-492 is not essential for catalysis of phosphoryl transfer, but its movement, specifically separation from the nucleotide, may be critical for coupling with the transport sites.

[Effect of staphylococcal peptidoglycan on the activity of Ca2+-ATP-ase from the sarcoplasmic reticulum in the early stages of ionizing radiation effect]. / Vplyv stafilokokovoho peptydohlikany na aktyvnist' Ca2+-ATP-azi sarkoplazmatychnoho retykulumu hnoho rannikh etapakh promenevoï diï.

It is established that peptidoglycan of Staphylococcus aureus possess superficial activity and can render influence on the functional activity of biomembranes. It tends to increase Ca(2+)-ATP-ase activity in the sarcoplasmic reticulum membranes, but no changes have been observed in case of the enzyme solubilization. The effect of peptidoglycan was more expressed, if it was used in the early period of acute radiation injury (1 and 24 h) in a dose of 0.21 Cl/kg for samples with irradiation-induced decrease of Ca(2+)-ATP-ase activity.

[Effects of irradiation on fatty acid structure of membrane lipids of the sarcoplasmic reticulum]. / Deistvie rentgenovskogo izlucheniia na zhirno-kislotnyi sostav lipidov membran sarkoplazmaticheskogo retikuluma.

It has been shown that single local X-irradiation (0.21 C/kg) of the rabbit hind limb in the early period of acute radiation injury (1 and 14 h) causes a decrease in saturation of sarcoplasmic reticulum membrane lipids. It is mainly connected with a decreased saturation of the total fraction of phosphatidyl serine, phosphatidyl inositol and phosphatidyl choline. The above changes can increase permeability of the sarcoplasmic reticulum membranes for Ca(2+)-ion after X-irradiation.

[Accumulation of calcium ions in myocardial sarcoplasmic reticulum of restrained rats exposed to the pulsed electromagnetic field]. / Akkumuliatsiia ionov kaltsiia sarkoplazmaticheskim retikulumom serdechnoi myshtsy krys v usloviiakh ogranichennoi podvizhnosti i pri vozdeistvii impulsnym elektromagnitnym polem.

Alteration in the velocity of Ca++ accumulation was investigated in myocardial homogenates from restrained rats which were chronically (1 and 2 months) exposed to the impulse electromagnetic field with frequency 1 Hz and magnetic induction 6-24 mT. The fall of the studied variable by 33% was observed in a month while restoration of the velocity of Ca++ transport was shown after two months of exposure. The results are discussed in terms of the organism adaptation to physico-chemical and physiological impacts.

Photooxidation of skeletal muscle sarcoplasmic reticulum induces rapid calcium release.

The photooxidizing xanthene dye rose bengal is shown to induce rapid Ca2+ release from skeletal muscle sarcoplasmic reticulum (SR) vesicles. In the presence of light, nanomolar concentrations of rose bengal increase the Ca2+ permeability of the SR and stimulate the production of singlet oxygen (1O2). In the absence of light, no 1O2 production is measured. Under these conditions, higher concentrations of rose bengal (micromolar) are required to stimulate Ca2+ release. Furthermore, removal of oxygen from the release medium results in marked inhibition of the light-dependent reaction rate. Rose bengal-induced Ca2+ release is relatively insensitive to Mg2+. At nanomolar concentrations, rose bengal inhibits [3H]ryanodine binding to its receptor. beta,gamma-Methyleneadenosine 5'-triphosphate, a nonhydrolyzable analog of ATP, inhibits rose bengal-induced Ca2+ release and prevents rose bengal inhibition of [3H]ryanodine binding. Ethoxyformic anhydride, a histidine modifying reagent, at millimolar concentrations induces Ca2+ release from SR vesicles in a manner similar to that of rose bengal. The molecular mechanism underlying rose bengal modification of the Ca2+ release system of the SR appears to involve a modification of a histidyl residue associated with the Ca2+ release protein from SR. The light-dependent reaction appears to be mediated by singlet oxygen.

[Structural changes in the sarcoplasmic reticulum membrane of skeletal muscles at the early stage of x-ray irradiation]. / Strukturnye izmeneniia membran sarkoplazmaticheskogo retikuluma skeletnykh myshts na rannem étape rentgenovskogo oblucheniia.

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.

[Action of millimeter-range electromagnetic radiation on the Ca pump of sarcoplasmic reticulum]. / Vozdeistvie EMI millimetrovogo diapazona na Ca-nasos sarkoplazmaticheskogo retikuluma myshts.

The influence of microwave radiation (61 GHz) on Ca(2+) pump of sarcoplasmic reticulum in rat muscle homogenates has been investigated. The microwave field with the surface density power stream of about 4 mW/cm2 has been shown to increase the rate of Ca2+ uptake by the sarcoplasmic reticulum in heart and skeletal muscle homogenate of rats.