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Biomedical subjects

K H Mild

Publications and source records attributed to K H Mild.

At least 55 records · Page 3Linked to original sources
PubMed1985

Effects of protracted exposure to low intensity radio frequency fields on CHO cells in culture.

This study was performed in order to investigate the biological effects of chronic exposure to low intensity radio frequency fields. By using CHO cells in culture, it was possible to extend exposure to several cell generations. The RF field consisted of a 27 MHz magnetic field (6 A/m), which produces a specific absorption rate of 1 W/kg. Exposure was continued for two to five days. The cells were then studied with respect to certain cell biological parameters: vital staining, plating efficiency, growth rate, volume and physical properties of the intracellular water, as measured by NMR. Scanning electron microscopy studies were also performed. A significant difference between exposed and control cells was found only with respect to intracellular water. A 10% decrease in line width which may indicate a corresponding increase in the spin-spin relaxation time was noted after exposure. A change in the colony forming pattern was also observed in thin cultures after two days of exposure.

Animals↗
PubMed1984

Clastogenic effects in human lymphocytes of power frequency electric fields: in vivo and in vitro studies.

In vivo and in vitro studies of the clastogenic effects of power frequency electric fields and transient electric currents have been performed. For the in vivo investigation peripheral lymphocytes from twenty switchyard workers were screened for chromosome anomalies. The rates of chromatid and chromosome breaks were found to be significantly increased compared to the rates in 17 controls. Exposure of human peripheral lymphocytes, in vitro, to a 50-Hz current with 1 mA/cm2 current density did not induce any chromosome damage. Exposure to ten 3 mus-long spark discharge pulses with a peak field strength in the samples of 3.5 kV/cm, however, resulted in chromosome breaks at a frequency similar to that induced in lymphocytes in vitro by ionizing radiation at 0.75 Gy. The biological significance of chromosomal damage induced in somatic cells is discussed.

Adult↗
PubMed1982

Output of skeletal muscle contractions. a study of isokinetic plantar flexion in athletes.

Maximum torques, total work and mean power of isokinetic plantar flexions were measured with simultaneous registrations. The integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. The method applied offers possibilities for adequate description of dynamic muscular work which in the case of plantar flexion in trained man declines as a negative exponential function of angular motion velocity. The decline is parallel to that of maximum torques. The summed triceps surae iEMG was inversely proportional to the velocity and direct proportional to time suggesting that structural rather than neural factors determine the relationships between velocity of angular motion and maximum torque/total work of single Mmaneuvers. Moreover, the fact that maximum mean power as well as maximum electrical efficiency were reached at the functional velocity of toe-off during gait suggests an influence of pragmatic demands on plantar flexion mechanical output.

Adult↗
PubMed1982

Cell physiological effects of radiofrequency electromagnetic fields.

Ovarian and body cavity eggs from R. temporaria were exposed to radiofrequency (rf) electromagnetic fields in the frequency range 10-27 MHz with specific absorption rates (SAR) up to 800 W/kg. The effect of the exposure was investigated by measurement of the water-related cell physiological parameters, isotopic and osmotic water membrane permeability and density of the egg cells. Only the osmotic water permeability, Pf, of ovarian eggs was significantly altered. A decrease of about 30% was seen for SARs of 50 W/kg and exposure times up to 2 h. Tests ruled out that the effect was due to temperature increase during the exposure. The observed decrease of Pf was most likely due to cloudy swelling of the egg cytoplasm resulting from the rf irradiation.

Animals↗
PubMed1981

Radiofrequency electromagnetic fields in Swedish radio stations and tall FM/TV towers.

Radiofrequency electric and magnetic fields have been measured around 11 large broadcast stations and tall FM/TV towers in Sweden. The results show that operating personnel may be exposed to fields exceeding by several times the present standard for occupational exposure to RF radiation. Maintenance personnel are especially vulnerable to exposure when climbing energized towers. The present study indicates that the transmitters should be switched off during the performance of certain tasks on the tower. Safe passage of maintenance personnel near energized antennas of certain types is impossible without a drastic reduction of the transmitted power. In the stations, the RF leakage radiation was generally low, but when work was done with the cabinet doors of the transmitter open, high strengths were found in the vicinity of the transmitter even though it was switched off. It was found that the transmitter acted as a tuned receiver of energy from the other transmitters.

Electromagnetic Fields↗
PubMed1981

Some factors of significance for respiratory gas exchange in muscle tissue. A mathematical analysis of a capillary model.

Morphological dimensions of the Krogh cylinder capillary model were calculated by mathematical simulation of respiratory gas exchange and blood flow in muscle tissue, using experimentally determined values for oxygen consumption (n'O2), blood flow (Q'), a-V O2 difference (a-v O2D) and pressure difference over the capillary (delta P), for resting and exercise conditions up to maximum performance. In the resting state a capillary radius, r1, of 3.5 (3-5) microgram a capillary density (CD) of 35 (30-90) capillaries/mm2 and a capillary length (L) of 900 (400-1000) microgram can satisfy experimentally determined values of the physiological variables. During muscular activity a maintained r1 and L with an increased CD allows higher n'O2. An increase in capillaries to about 600/mm2 can allow an n'O2 uptake 30 times the resting value (maximum performance). This increase cannot be achieved by an increase only in the r1. A shift to the right in the O2Hb dissociation curve during exercise has only a small effect on the O2 delivering capacity of the model, as has an increase in the diffusion constant for O2 in tissue. It is remarkable how limited a range of morphological dimensions, particularly of r1, is compatible with the known range of values for n'O2, O', a-v O2D and delta P, at rest and particularly during maximum performance of the muscle.

Capillary Permeability↗
PubMed1979

High density cell water in amphibian eggs?

The exchange of isotopic water, 2H2O and H2(18)O has been studied in amphibian eggs. The experiments were carried out with ovarian and body cavity eggs of Rana temporaria and unfertilized eggs of Ambystoma mexicanum. The cytoplasmic diffusion coefficient for H2(18)O was found to be 4.6 x 10(-6) cm2/s, somewhat higher than that for 2H2O, 3.4 x 10(-6) cm2/s. The total change in reduced weight, delta RW, during the isotope experiments was compared with the total amount of water in the egg cell, m. The ratio delta RW/m was significantly higher than would be expected from calculations using ordinary water density values. The results are discussed in terms of different phases of structured cell water.

Ambystoma↗