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Biomedical subjects

K H Mild

Publications and source records attributed to K H Mild.

18 recordsLinked to original sources
PubMed1992

The stimulatory effect of magnetic fields on regeneration of the rat sciatic nerve is frequency dependent.

The effects of exposure to sinusoidal magnetic fields on regeneration of the rat sciatic nerve were studied. Regeneration distances were measured after a crush lesion. The rats were exposed to a 0.1-mT magnetic field of various frequencies (50-2000 Hz) inside a pair of Helmholtz coils for various periods of time. Regeneration was measured by the pinch test or by immunocytochemical staining for neurofilaments 3, 4, or 6 days after the lesioning. Frequencies of 250, 500, and 1000 Hz significantly increased the regeneration distance. Higher (2000 Hz) and lower (50 Hz) frequencies had no effect. Maximal stimulation was obtained at 1000 Hz. At this frequency the rate of regeneration was increased by 24%. The results suggest that a broad frequency window exists within which the regeneration processes are sensitive to perturbation by magnetic fields and/or currents induced in the animal.

Animals↗
PubMed1989

Microwave effects on the central nervous system--a study of radar mechanics.

Seventeen radar mechanics and engineers and 12 unexposed referents were examined, using extensive neurological, psychometric and neuropsychiatric techniques to determine whether there were any indications of central nervous system effects of microwave exposure. Pathological neurological findings were not more common in the exposed group than among the referents. In addition, the psychometric tests and the psychiatric rating scales did not reveal any statistically significant adverse effects of microwave exposure. The frequency of the occurrence of an increased protein band with an isoelectric point of 4.5 in the cerebrospinal fluid was higher among the men exposed to microwaves than among the referents. The nature and clinical significance of this or these proteins are still unclear. The time derivative of the magnetic flux density close to some of the transmitter units was surprisingly high (up to 350 T s-1).

Central Nervous System↗
PubMed1988

Chromosomal effects in lymphocytes of 400 kV-substation workers.

In a previous study we found an increased rate of chromosomal aberrations in substation workers. To follow up this finding we in this study present data from 38 employees of electric power companies; 19 of the subjects worked with the repair and maintenance of circuit breakers and disconnectors in 400 kV-substations. The other 19 served as controls and were only exposed to normal environmental electromagnetic fields. Coded blood samples were sent to a laboratory for determination of the rate of chromosomal aberrations (CA), sister chromatid exchanges (SCE), and cells with micronuclei (MN). Compared to the control group the exposed men displayed a statistically significant increase in CA and cells with MN. No increase was found in the frequency of SCE. Since "in vitro" studies of lymphocytes exposed to transient electric currents (spark discharges) produced similar results the increase in chromosomal damage in substation workers may be associated with exposure to transient electric currents during work.

Adult↗
PubMed1985

Radiofrequency electromagnetic leakage fields from plastic welding machines. Measurements and reducing measures.

Operators of unshielded plastic welding machines are often exposed to radiofrequency (RF) electromagnetic leakage fields that substantially exceed all present occupational standards. Measurements show that the Swedish ceiling values (SE = SH = 250 W/m2) in many cases are exceeded at distances up to 1 meter from the electrode. To reduce the stray fields to an acceptable level at the location of the operator, RF field suppression devices should be fitted to the machine. We have studied the strength and the extent of the RF leakage field under various operating conditions and also investigated different methods for reducing the leakage field. The following measurements have been performed: E- and H-field strengths as a function of distance from the electrode, and as a function of load/tuning; the time dependence of [E]2 for various combinations of tuning and welding times producing a welding seam with the same strength; isopower density curves for SE and SH = 250 W/m2 with different types of RF emission control devices fitted to the machine; the RF voltage between the electrode and the welding table and the RF voltage on the machine casing. By decreasing the RF power and increasing the welding time the field strengths at the location of the operator can be reduced to levels below the ceiling values. The RF voltage between the electrode and the welding table ranged from 800 V up to 2100 V for the different plastic material that was welded. The RF voltage on certain parts on the chassis could be as high as 200 V. In order to reduce these voltages and the stray fields the machine should be equipped with a "large capacitive shield" in cases where this is possible.

Electrodes↗
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↗
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↗