Effect of sinusoidal 50 Hz magnetic field on the testosterone production of mouse primary Leydig cell culture.

This study evaluated the effect of sinusoidal 50 Hz magnetic field on the basal and human chorionic gonadotropin (hCG)-stimulated testosterone (T) production of 48-h mouse Leydig cell culture. The luteinizing hormone (LH) analog hCG was used to check the T response of the controls and to evaluate the possible effect of the applied magnetic field on the steroidogenic capacity of the exposed cells. Leydig cells were obtained from the testes of 35- to 45-g CFLP mice and isolated by mechanical dissociation without enzyme treatment. The cell cultures were exposed to sinusoidal 50 Hz 100 microT (root mean square) AC magnetic field during the entire time of a 48-h incubation. Testosterone content of the culture media was measured by radioimmunoassay. In cultures exposed to the magnetic field, a marked increase of basal T production was found (P < .05), compared with the unexposed controls, whereas no significant difference was seen between the exposed or unexposed cultures in the presence of maximally stimulating concentration of hCG. These findings demonstrate that sinusoidal 50 Hz 100 microT magnetic fields are able to stimulate the basal T production of primary mouse Leydig cell culture, leaving the steroidogenic responsiveness to hCG unaltered.

Urinary 6-sulphatoxymelatonin excretion is increased in rats after 24 hours of exposure to vertical 50 Hz, 100 microT magnetic field.

The effect of exposure to a 50 Hz, vertical magnetic field on the excretion of urinary 6-sulphatoxymelatonin (aMT6s) of rats was studied in a self-controlled experiment. Ten male Wistar rats were kept under 9:15 h light: dark conditions in metabolic cages. The rats were exposed to 1.0 or 100 microT flux density for 24 h. The excretion of aMT6s, which is the primary metabolite of melatonin in the urine, did not show a statistically significant decrease, as measured by 125I radioimmunoassay, during or after magnetic field exposure of rats to either flux density. At 100 microT flux density, the increase of aMT6s excretion on the day after exposure was statistically significant (P < .02), compared with the value under exposure, but was not significant compared with the baseline values before exposure.

Effect on the immune system of mice exposed chronically to 50 Hz amplitude-modulated 2.45 GHz microwaves.

The effect of continuous (CW; 2.45 GHz carrier frequency) or amplitude-modulated (AM; 50 Hz square wave) microwave radiation on the immune response was tested. CW exposures (6 days, 3 h/day) induced elevations of the number of antibody-producing cells in the spleen of male Balb/c mice (+37%). AM microwave exposure induced elevation of the spleen index (+15%) and antibody-producing cell number (+55%) in the spleen of male mice. No changes were observed in female mice. It is concluded that both types of exposure conditions induced moderate elevation of antibody production only in male mice.

Effect of continuous-wave and amplitude-modulated 2.45 GHz microwave radiation on the liver and brain aminoacyl-transfer RNA synthetases of in utero exposed mice.

Investigations have been carried out concerning the effects of microwave (MW) exposure on the aminoacyl-transfer ribonucleic acid (tRNA) synthetase of the progeny of females that were exposed during their entire period of gestation (19 days). The changes caused by continuous-wave (CW) and amplitude-modulated (AM) MW radiation have been compared. CFLP mice were exposed to MW radiation for 100 min each day in an anechoic room. The MW frequency was 2.45 GHz, and the amplitude modulation had a 50 Hz rectangular waveform (on/off ratio, 50/50%). The average power density exposure was 3 mW/cm2, and the whole body specific absorption rate (SAR) was 4.23 +/- 0.63 W/kg. The weight and mortality of the progeny were followed until postnatal day 24. Aminoacyl-tRNA synthetase enzymes and tRNA from the brains and livers of the offspring (461 exposed, 487 control) were isolated. The aminoacyl-tRNA synthetase activities were determined. The postnatal increase of body weight and organ weight was not influenced by the prenatal MW radiation. The activity of enzyme isolated from the brain showed a significant decrease after CW MW exposure, but the changes were not significant after 50 Hz AM MW exposure. The activity of the enzyme isolated from liver increased under CW and 50 Hz modulated MW.

Sinusoidal 50 Hz, 500 microT magnetic field has no acute effect on urinary 6-sulphatoxymelatonin in Wistar rats.

The effect of a 50 Hz, vertical magnetic field on the excretion of urinary 6-sulphatoxymelatonin (aMT6s) of male and female Wistar rats was studied in a self-controlled experiment. Twenty rats were kept in metabolic cages under 9:15 h light:dark conditions. The urine of the animals was collected twice per day for 5 consecutive days. The concentration of aMT6s in the rat urine was measured by 125I radioimmunoassay. The rats were exposed to 5 and 500 microT flux density for 24 h. The excretion of urinary aMT6s did not show significant changes during or after magnetic field exposure.

Simultaneous response of brain electrical activity (EEG) and cerebral circulation (REG) to microwave exposure in rats.

The correlations between physiological modalities in microwave field-activated systemic or localized regulatory mechanisms with changes in the central nervous system (CNS) seem not to be identical. These problems are important because of the increased number of radiating appliances, e.g. portable radios and mobile telephones. In two series of experiments on anaesthetized rats (N = 40) (i) before and after 10 min, whole body exposures to 2.45 GHz CW microwaves, and (ii) during 30 min exposures to 4 GHz amplitude modulated (AM, 16 Hz) microwaves, the effects on the CNS were observed simultaneously with those on the cardiovascular system by quantitative polygraphic measurement. In acute experiments on rats, electroencephalograms (EEG), rheoencephalograms (REG) as an index of cerebral blood flow (CBF), brain tissue DC impedance and temperature and ECG were recorded simultaneously. The total power of EEG spectra increased after whole body 30 mW/cm2 2.45 GHz CW exposure for 10 min. No changes occurred at 10 mW/cm2. The CBF increased after 10 mW/cm2 exposure. The power of EEG delta (0.5-4 Hz) waves was increased by thermal level of brain localized 4 GHz CW exposure at 42 mW/g specific absorption rate (SAR) simultaneously with the REG amplitude as an index of cerebral blood flow. Amplitude modulation at 16 Hz and 8.4 mW/g SAR was associated with increased power of EEG beta (14.5-30 Hz) waves but changes in the CBF were not observed. CW radiation at 8.4 mW/g increased the cerebral blood flow, but did not change EEG spectra.

Effects of modulated and continuous microwave irradiation on the morphology and cell surface negative charge of 3T3 fibroblasts.

Mouse embryo 3T3 cells were irradiated with 2450 MHz continuous and low frequency (16 Hz) square modulated waves of absorbed energy ranging from 0.0024 to 2.4 mW/g. The low frequency modulated microwave irradiation yielded more morphological cell changes than did the continuous microwave fields of the same intensity. The amount of free negative charges (cationized ferritin binding) on cell surfaces decreased following irradiation by modulated waves but remained unchanged under the effect of a continuous field of the same dose. Modulated waves of 0.024 mW/g dose increased the ruffling activity of the cells, and caused ultrastructural alteration in the cytoplasm. Similar effects were experienced by continuous waves at higher (0.24 and 2.4 mW/g) doses.

The effect of 2.45 GHz microwave irradiation on human peripheral lymphocytes.

The effect of 2.45 GHz frequency and 10 mW/cm2 power density microwave irradiation on the in vitro cultured human peripheral lymphocytes blast transformation was examined. In the number of the blast cells we did not find significant difference at cultures irradiated for 1 x 5 hours and 3 x 1 hours as compared to the controls. The number of the blast cells was found to increase when Phytohemagglutinin-stimulated lymphocyte cultures were exposed to repeated irradiation for 6 days (1 hour a day). The microwave irradiation did not influence the degree of the spontaneous blast transformation in any groups.

Decreased cytosolic free calcium concentration of aged human lymphocytes in resting state.

Cytosolic free calcium concentration was measured in lymphocytes from individuals over the age of 80, using quin2 and fura-2 calcium indicators. The average intracellular free calcium concentration of the samples was 62 nM, which value is roughly half the adult (age between 35 and 55) level (116 nM). It is supposed that the decline in immune function of aged individuals is connected to the decrease in free calcium concentration in their lymphocytes. We also discuss the consequences and the adaptive character of this decrease.

Difference in radiosensitivity of valyl-tRNA synthetases isolated from chick embryo liver and brain.

The sensitivity in vitro against gamma-radiation of valyl-tRNA synthetase (VRS) from chick embryo brain proved to be higher than that of liver VRS. In order to study this phenomenon properties of VRS isolated from both organs were compared. Both enzymes have the same molecular weight (Mr = 110 000) determined by equilibrium sedimentation and by gel filtration. Electrophoresis on polyacrylamide gel in the presence of sodium dodecyl sulphate showed no evidence for subunit structure. The optimal reaction conditions in valyl-tRNA formation were found to be the same, except the pH values. Km values of the reactions were also similar. Both enzymes reacted with the tRNAs isolated from the other organ. The stability during storage of the liver VRS was higher than that of the brain VRS. In the brain VRS molecule one buried and eleven free SH groups could be detected and divided into three classes with different reactivities. In 1 mol of liver VRS one buried and nine free thiol groups were determined and these could be divided only into two classes. These observations suggest the existence of two VRS isoenzymes with different radiosensitivities: the more sensitive occurs mainly in brain and the less sensitive mainly in the liver of chick embryo.

Study of nucleic acid metabolism in two astronauts.

During the last years data have evidenced that alteration in nucleic acid metabolism, expecially increased urinary excretion of modified nucleosides reflects physiological changes in living organism. In relation with the Soyuz-36-Salyut-6-Soyuz-35 mission in 1980 urinary nucleoside excretion of two astronauts /B.F., V.K./ were traced. Individual daily urine samples were collected for 4 days before starting and 6 days after landing and were analysed with improved analytical procedures /affinity chromatography, high Performance liquid chromatography/. Levels of 1-methylinosine, 1-methylguanosine and N,2,2-dimethylguanosine in urine were determined. Thus recorded changes differ considerably at two astronauts. One of the /V.K./ excreted nucleosides normally, another /B.F./ showed increase to 200-400 % levels excretion of above nucleosides on the second day after landing. The peak values disappeared on the 3-6 days after. To interpret this phenomenon extreme factors of space-flight /weightlessness, stress, radiations, etc./ have to be taken into consideration. However, we attach importance to training of astronauts. During the last decade data have evidenced that alterations in the metabolism of nucleic acids especial increased urinary excretion of modified nucleosides reflects physiological and in some cases pathological changes in living organism. In relation with the Soyuz-36-Salyut-6-Soyuz 35 mission urinary excretion of certain modified nucleosides of two astronauts /B.F. and V.K./ were measured. The aim of the measurements was: how the metabolism of transfer ribonucleic acids /tRNAs/ referring to cosmic flight, how it is reflected in urinary excretions of modified nucleosides. For these purposes we studied the excretion of methylguanosine, dimethylguanosine and methylinosine. These nucleosides are the normal minor components of tRNA.

Effect of 60Co gamma radiation on the valyl-tRNA synthetase isolated from chick embryo brain.

The effect of 60Co gamma irradiation on the activity of valyl-tRNA synthetase isolated from chick embryo brain was studied. The enzyme activity exponentially decreased in the dose range 10--200 krad. The first step of the enzyme action, i.e. the amino acid activation, was found to be less sensitive to irradiation than the whole reaction, the formation of valyl-tRNA, 2-Mercapto ethanol and/or glycerol had a significant radioprotective effect. The lesion caused by radiation in the enzyme was also influenced by its concentration during exposure (dilution effect). According to gel-electrophoretic experiments, no chain rupture occurred in the enzyme molecule. Not even a change in Km was observed; however, the maximum velocity of the reaction was found to decrease with increasing radiation dose.

Studies on valyl-tRNA synthetase obtained from chick embryo brain. Purification and properties.

Valyl-tRNA synthetase (L-valine tRNA ligase (AMP) E. C. 6.1 . 1.9) from chick embryo brain was isolated by two chromatographic steps from the cytosol fraction of brain homogenates. The protein was found to be more than 90 per cent homogeneous on the basis of polyacrylamide gel electrophoresis. It had a molecular weight of 110,000 daltons determined by both high speed equilibrium centrifugation and gel filtration. No evidence was found for a subunit structure. The optimum reaction conditions as well as the kinetic constants for ATP, valine and tRNA were determined. Enzyme stability during storage as a function of temperature and in the presence and absence of polyhydric alcohols is described. Polyhydric alcohols were found to protect the enzyme from inactivation.

Study of the biochemical indicators of chronic irradiation in rats.

Daily urinary excretion of pseudouridine, creatinine and creatine of chronically irradiated Wistar rats was estimated. The irradiation conditions were: 60Co gamma source, dose-rate 10 rad/day, total dose 200, 400 and 600 rad. Control groups were kept under similar conditions. Urine samples were taken three times after the end of the irradiation period. It was found that: (1) pseudouridine excretion seems more suitable for indicating radiation injury than the creatine/creatinine ratio in chronic irradiation in rats; (ii) there are significant changes in dose dependence of pseudouridine excretion in the post-irradiation period; (iii) a new method for pseudouridine estimation gives closely similar data to those of earlier investigations.

Increased synthesis of nuclear RNA in regenerating rat liver after gamma-irradiation.

Nine hours after partial hepatectomy rats were whole-body, 60Co-gamma-irradiated with exposures of 50, 100, 200, 500, 1000 and 2000 R, respectively. RNA was prepared from isolated nuclei of rat liver 12 hours after partial hepatectomy. Animals were injected with 14C-orotic acid 20 minutes before killing. The isolated labelled nuclear RNA was fractionated by sucrose density gradient centrifugation. The specific radioactivity of RNA was correlated with that of the specific radioactivity of nucleotide pool of the liver homogenates. RNA synthesis was found to increase after each dose applied as compared to the rate of RNA synthesis in 12 hours regenerating liver. The increment depended on the dose delivered: 10% at 50 R, 50% at 500 R and 30% at 2000 R. Nuclear RNA synthesis also increased in the liver of non-hepatectomized rats 3 hours after 500 R gamma-irradiation, but the increment was only 20-30% above the non-hepatectomized and unirradiated control.