The differential effects of 200, 591, and 2,450 MHz radiation on rat brain energy metabolism

Three key compounds in brain energy metabolism have been measured during and after exposure to continuous wave radiofrequency radiation at 200, 591, and 2,450 MHz. Frequency-dependent changes have been found for all three compounds. Changes in NADH fluorescence have been measured on the surface of a surgically uncovered rat brain during exposure. At 200 and 591 MHz, NADH fluorescence increased in a dose-dependent manner between approximately 1 and 10 mW/cm2, then became constant at higher exposures. There was no effect at 2,450 MHz. Levels of ATP and CP were measured in whole brain after exposure. The ATP levels were decreased at 200 and 591 MHz but not at 2,450 MHz. The CP levels decreased only at 591 MHz. The effect of duration of exposure (up to 5 min) was investigated for all compounds at 200 MHz and 2,450 MHz, and exposures to 20 minutes were examined at 591 MHz. Temperature in the rat brain was essentially constant for all exposures. A general mechanism for inhibition of the mitochondrial electron transport chain and the CP-kinase reaction pathway by radiofrequency radiation has been proposed.     

Submillisecond folding of the peripheral subunit-binding domain.

Folding and unfolding rates have been measured for the peripheral subunit-binding domain, a small three-helix protein. The protein folds very fast, with rates too rapid to be measured using traditional stopped-flow techniques. Folding and unfolding rates were measured as a function of temperature using dynamic NMR lineshape analysis. At the lowest temperature at which there is sufficient broadening to measure rates, 41 degrees C, the folding rate is 16,050 s(-1). Thus, the halftime required for folding is 43 micros. At the same temperature, the unfolding rate is 2800 s(-1). Identical rates were measured using resolved resonances from Val16 in the loop and Val21 at the end of the 310-helix. Folding rates have been correlated with protein topology, and this correlation is consistent with the rapid folding of the peripheral subunit-binding domain. The results presented here show that the peripheral subunit-binding domain is the third fastest folding protein for which rates have been estimated. The folding rate is the fastest that has been directly measured and provides further support for the importance of chain topology as a major determinant of folding rates.     

The effect of hyperthermia on transmembrane potential in Chinese hamster ovary cells in vitro

The effect of elevated temperature on transmembrane potential was studied in Chinese hamster ovary cells in vitro using tetraphenylphosphonium cation (TPP+) and 3,3'-dipentyloxacarbocyanine [Di-O-C5(3)], two unrelated lipophilic cation probes that equilibrate across the plasma membrane according to the transmembrane potential. Uptake of TPP+ was measured using a tritium-labeled probe and the uptake of the fluorescent probe Di-O-C5(3) was measured by flow cytometry. The Nernst equation was used to calculate transmembrane potential. The absolute values obtained for transmembrane potential at 37 degrees C using the two probes were different, but qualitatively similar results were obtained using either probe in the hyperthermia studies. Transmembrane potential measured at 43 and 45 degrees C was at least 20% higher than that measured at 37 degrees C, and the difference was statistically significant (P = 0.025 and P less than 0.01, respectively). The hyperpolarization induced by exposure to 45 degrees C persisted temporarily after cells had been returned to 37 degrees C. The hyperpolarization at 37 degrees C associated with a previous exposure to hyperthermia was maximal after cells had been held at 45 degrees C for 2.0 min, and fell to normal levels after 15.0 min at 37 degrees C.     

Photoelectric effects of deoxyribonucleic acid

Studies have been made of the d.c. semiconductive behavior of fibers and solid gels of DNA. The semiconductive behavior under high vacuum is similar in solid gels of DNA and stretched fibers of DNA measured along and across the fiber axis. Photoelectric effects have been studied, and an action spectrum is reported which agrees with the absorption spectrum of DNA. No photoelectric effects are observed at wavelengths corresponding to the thermal energy gap. The temperature dependence of the photocurrent has been determined, and the effects of air, oxygen, and nitrogen at different pressures on the photocurrent have been measured.     

Alkylation of nucleic acids by DNA-targeted 4-anilinoquinolinium aniline mustards: kinetic studies

The rate of constant for hydrolysis of a series of 4-substituted aniline mustards Ar-X-pC6H4-N(CH2CH2Cl)2, where Ar is 4-anilinoquinolinium and X = O, CH2, CONH and CO, have been measured in water and 0.02 M imidazole buffer at 37 degrees C and in 50% aqueous acetone at 66 degrees C. The equilibrium binding constants of the compounds and their hydrolysis products to nucleic acids of differing base composition have been determined at varying ionic strengths, and the results are consistent with the compounds binding as expected in the DNA minor groove. The alkylating reactivity of the mustards towards these nucleic acids has been measured in water at 37 degrees C and in 0.01 M HEPES buffer over a range of temperatures from 25 degrees C to 60 degrees C. Evaluation of the thermodynamic parameters for these kinetic and equilibrium studies suggests that the interaction with nucleic acids is via an internal SN2 mechanism involving an aziridinium ion.     

Study of anisotropy in nuclear magnetic resonance relaxation times of water protons in skeletal muscle.

The anisotropy of the spin-lattice relaxation time (T1) and the spin-spin relaxation times (T2) of water protons in skeletal muscle tissue have been studied by the spin-echo technique. Both T1 and T2 have been measured for the water protons of the tibialis anterior muscle of mature male rats for theta = 0, 55, and 90 degrees, where theta is the orientation of the muscle fiber with respect to the static field. The anisotropy in T1 and T2 has been measured at temperatures of 28, -5 and -10 degrees C. No significant anisotropy was observed in the T1 of the tissue water, while an average anisotropy of approximately 5% was observed in T2 at room temperature. The average anisotropy of T2 at -5 and -10 degrees C was found to be approximately 2 and 1.3%, respectively.     

人眼的阈上调制传递函数

视觉系统的阈上调制传递函数与阈值对比敏感度函数具有明显的区别.但由于阈上测试方法复杂,因而迄今为止阈上调制传递函数的测试数据比阈值对比敏感度函数要少得多.我们应用传统的极限调节法和对比度比配法分别测试了人眼的阈值对比敏感度函数和三种对比度级别的阈上调制传递函数.测试结果表明,一个以DOG(Difference of two Gaussians)函数为基础的函数是一种合理的模型,可由现有阈值对比敏感度函数预测不同对比度和象场亮度级别下的人眼阈上调制传递函激.这个模型也可做为一种有效的人眼生理光学经验公式,用于目视光电成象系统的设计和象质评价.     

Heats of dilution of polyacrylic acid at various degrees of ionization

The heats of dilution of polyacrylic acid at four constant degrees of ionization (α = 0, 0.25, 0.50, and 1.00) have been measured in the concentration range 0.6–0.002 monomolal. The heat of dilution for pure acid (α = 0) is positive in the investigated concentration range, whereas it is negative for partially neutralized acid (α = 0.25 and 0.50). For completely neutralized add, for sodium polyacrylate (α = 1), the measured heat effects are exothermic at concentrations above about 0.05 monomolal. while below 0.05 M they become endothermic. The experimental results have been evaluated with the help of a previously developed theoretical treatment based on the cell model.     

Determination of the chlorine kinetic isotope effect on the 4-chlorobenzoyl-CoA dehalogenase-catalyzed nucleophilic aromatic substitution

The chlorine kinetic isotope effect (KIE) on the dehalogenation of 4-chlorobenzoyl-CoA catalyzed by 4-chlorobenzoyl-CoA dehalogenase has been measured at room temperature and optimal pH. The measured value of (37)k = 1.0090 +/- 0.0006 is larger than the KIEs recently measured for haloalkane and fluoroacetate dehalogenase. This indicates that the transition state for dissociation of chloride ion from the Meisenheimer intermediate is sensitive to the chlorine isotopic substitution. Simple modeling suggests that this sensitivity originates in the high isotopic sensitivity of the C-Cl bond bending modes.     

Bimetallic ferrocenyl derivatives: Molecular second order hyperpolarizabilities and second harmonic generation

The ground and excited states dipole moments and the second order hyperpolarizabilities of a series of oxazolinyl-ferrocenyl derivatives have been measured. After complexation of the oxazoline group with a second metal ion, the new bimetallic complexes show an increased hyperpolarizability, as determined by the EFISHG technique. A copolymer of the same bimetallic complex with methyl methacrylate has been synthesized, and the second order susceptibility has been measured by second harmonic generation at 1.06µm.     

Surface potential effects on metal ion binding to phosphatidylcholine membranes 31P NMR study of lanthanide and calcium ion binding to egg-yolk lecithin vesicles

31P NMR of phosphatidylcholine (lecithin) from egg-yolk in sonicated vesicles has been measured in the presence of various ions. Addition of Ln3+ or Ca2+ shifted the 31P resonance of the phosphate groups of the outer surface of the vesicles. These shifts were measured at varied lanthanide or Ca2+ concentration at different ionic strengths obtained by addition of NaCl. The shifts induced by Tb3+ and Ca2+ have been analyzed using the theory of the diffuse double layer. Corrections were introduced for the effect of the ionic strength on the activities of the ions. The binding efficiency is shown to be controlled by the electrostatic potential produced by the bound cations at the membrane surface. This potential is slightly modified due to weak chloride binding. Binding constants have been derived.     

Survey of residential 50 Hz EMF exposure from transformer stations

In Hungary it is typical that 10/04 kV transformer stations are being installed in multistory residential and office buildings. Magnetic fields (MFs) up to several tens of microT have been measured in apartments close to transformers. The aim of the present study was to provide systematic assessment of MF exposure of residents living above transformer stations. Out of 41 addresses provided by the electricity supplier, current load of 21 transformers and MF in 21 apartments was measured. Spot MFs at 1 m height and time weighted average 24 h MF exposure at bed height was measured. All-day personal MF exposure was measured at waist and HOME exposure was calculated. BED exposure was measured at bed height. Participants kept a time-activity diary. The time-weighted average 24 h MF exposure (3.03 microT) exceeded the usual residential exposure (<0.2 microT). The mean HOME and BED personal exposure above transformers was 0.825 and 1.033 microT, respectively. Our study provides exposure assessment of a cohort with a wider exposure range, compared to power-line epidemiological studies.     

On the movement and distribution of calcium in white cabbage in dependence of the water status

Summary The uptake and distribution of Ca in white cabbage have been measured under controlled climatic conditions. The uptake of Ca has been determined by continuous -intensity measurements of⁴⁵Ca simultaneously at an outer transpiring leaf and at an inner head leaf. In the outer leaves the Ca content increased during the day in dependence of the transpiration amplitude. With-in the inner head leaves Ca was transported mainly during the night when the head mass additionally measured by -absorption increased due to the increasing plant water potential. At the end of the experiment the stable and active Ca concentration has been measured. re]19760823     

Effect of morphine analogues on the conformational state of polyriboadenylic acid in solution: An NMR study

The interaction of morphine analogues with polyadenylic acid in aqueous solution at pH 7 has been investigated. The NMR spectra measured at several temperatures were shown to give evidence of a lowering, of the transition temperature from the helix to the random-coil structure. The measured chemical shifts and relaxation times were interpreted in terms of an ionic interaction between the ⁺N-CH₃ group of the drug and the phosphate residue of the polynucleotide.     

Fluorescence emission spectra of photosystem I, photosystem II and the light-harvesting chlorophyll a/b complex of higher plants

Fluorescence emission spectra excited at 514 and 633 nm were measured at -196 degrees C on dark-grown bean leaves which had been partially greened by a repetitive series of brief xenon flashes. Excitation at 514 nm resulted in a greater relative enrichment of the 730 nm emission band of Photosystem I than was obtained with 633 nm excitation. The difference spectrum between the 514 nm excited fluorescence and the 633 nm excited fluorescence was taken to be representative of a pure Photosystem I emission spectrum at -196 degrees C. It was estimated from an extrapolation of low temperature emission spectra taken from a series of flashed leaves of different chlorophyll content that the emission from Photosystem II at 730 nm was 12% of the peak emission at 694 nm. Using this estimate, the pure Photosystem I emission spectrum was subtracted from the measured emission spectrum of a flashed leaf to give an emission spectrum representative of pure Photosystem II fluorescence at -196 degrees C. Emission spectra were also measured on flashed leaves which had been illuminated for several hours in continuous light. Appreciable amounts of the light-harvesting chlorophyll a/b protein, which has a low temperature fluorescence emission maximum at 682 nm, accumulate during greening in continuous light. The emission spectra of Photosystem I and Photosystem II were subtracted from the measured emission spectrum of such a leaf to obtain the emission spectrum of the light-harvesting chlorophyll a/b protein at -196 degrees C.     

Mössbauer spectroscopic studies of hemoglobin and its isolated subunits.

Samples of 90% enriched 57Fe hemoglobin and its isolated subunits have been prepared. M?ssbauer spectroscopic measurements have been made on three such samples. Sample one contained contributions of oxyhemoglobin, deoxyhemoglobin, and carbonmonoxyhemoglobin. This sample was studied from a temperature of 90 K down to 230 mK. Measurements were also made at 4.2 K using a small applied magnetic field of 1.0 T. In general, the measured quadrupole splittings and isomer shifts for each component agreed with previous measurements on single component samples in the literature, and thus demonstrated that chemically enriched hemoglobin has not been altered. The second and third samples were isolated alpha and beta subunits, respectively. We have found measurable M?ssbauer spectral differences between the HbO2 sites in the alpha subunit sample and the beta subunit sample. The measured M?ssbauer spectral areas indicate that the iron ion has the largest mean-square displacement at the deoxy Hb sites as compared to that at the oxy- and carbonmonoxy Hb sites. The mean-square displacement at the HbO2 sites is the smallest.     

SAR measurement due to mobile phone exposure in a simulated biological media

The specific absorption rate (SAR) measurements are carried out for compliance testing of personal 3G Mobile phone. The accuracy of this experimental setup has been checked by comparing the SAR in 10 gm of simulated tissue and an arbitrary shaped box. This has been carried out using a 3G mobile Phone at 1718.5 MHz, in a medium simulating brain and muscle phantom. The SAR measurement system consists of a stepper motor to move a monopole E-field probe in two dimensions inside an arbitrary shaped box. The phantom is filled with appropriate frequency-specific fluids with measured electrical properties (dielectric constant and conductivity). That is close to the average for gray and white matters of the brain at the frequencies of interest (1718.5 MHz). Induced fields are measured using a specially designed monopole probe in its close vicinity. The probe is immersed in the phantom material. The measured data for induced fields are used to compute SAR values at various locations with respect to the mobile phone location. It is concluded that these SAR values are position dependent and well below the safety criteria prescribed for human exposure.     

The cost of herbicide resistance measured by a competition experiment

Summary The cost of resistance has been measured by a competition experiment over a range of densities, in the absence of herbicide treatment, on two nearly isogenic lines of Foxtail millet, differing in a chloroplastic resistance to herbicide. Three characters have been measured: shoot height, shoot weight, and seed production. Sensitive individuals were better competitors despite a larger decrease in production under within-biotype competition. The cost of resistance was density dependent and increased with density. The cost was higher when measured on seed production and reached 65% at the higher density for resistant individuals. This is compatible with the low frequency or the absence of that gene in natural populations. This work illustrates that the cost is easiest to observe when high levels of constraints are used.     

Rates of various reactions catalyzed by ATP synthase as related to the mechanism of ATP synthesis.

The forward and reverse rates of the overall reaction catalyzed by the ATP synthase in intact rat heart mitochondria, as measured with 32P, were compared with the rates of two partial steps, as measured with 18O. Such rates have been measured previously, but their relationship to one another has not been determined, nor have the partial reactions been measured in intact mitochondria. The partial steps measured were the rate of medium Pi formation from bound ATP (in state 4 this also equals the rate of medium Pi into bound ATP) and the rate of formation of bound ATP from bound Pi within the catalytic site. The rates of both partial reactions can be measured by 31P NMR analysis of the 18O distribution in Pi and ATP released from the enzyme during incubation of intact mitochondria with highly labeled [18O]Pi. Data were obtained in state 3 and 4 conditions with variation in substrate concentrations, temperature, and mitochondrial membrane electrical potential gradient (delta psi m). Although neither binding nor release of ATP is necessary for phosphate/H2O exchange, in state 4 the rate of incorporation of at least one water oxygen atom into phosphate is approximately twice the rate of the overall reaction rate under a variety of conditions. This can be explained if the release of Pi or ATP at one catalytic site does not occur, unless ATP or Pi is bound at another catalytic site. Such coupling provides strong support for the previously proposed alternating site mechanism. In state 3 slow reversal of ATP synthesis occurs within the mitochondrial matrix and can be detected as incorporation of water oxygen atoms into medium Pi even though medium [32P]ATP does not give rise to 32Pi in state 3. These data can be explained by lack of translocation of ATP from the medium to the mitochondrial matrix. The rate of bound ATP formation from bound Pi at catalytic sites was over twice the rate of the overall reaction in both states 4 and 3. The rate of reaction at the catalytic site is considerably less sensitive to the decrease in membrane potential and the concentration of medium ADP than is the rate of medium ATP formation. This supports the view that the active catalytic site is occluded and proceeds at a rapid rate which is relatively independent of delta psi m and of media substrates.     

SAR measurement due to mobile phone exposure in a simulated biological media

The specific absorption rate (SAR) measurements are carried out for compliance testing of personal 3G Mobile phone. The accuracy of this experimental setup has been checked by comparing the SAR in 10?gm of simulated tissue and an arbitrary shaped box. This has been carried out using a 3G mobile Phone at 1718.5?MHz, in a medium simulating brain and muscle phantom. The SAR measurement system consists of a stepper motor to move a monopole E-field probe in two dimensions inside an arbitrary shaped box. The phantom is filled with appropriate frequency-specific fluids with measured electrical properties (dielectric constant and conductivity). That is close to the average for gray and white matters of the brain at the frequencies of interest (1718.5?MHz). Induced fields are measured using a specially designed monopole probe in its close vicinity. The probe is immersed in the phantom material. The measured data for induced fields are used to compute SAR values at various locations with respect to the mobile phone location. It is concluded that these SAR values are position dependent and well below the safety criteria prescribed for human exposure.