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Biomedical subjects

B Greenebaum

Publications and source records attributed to B Greenebaum.

9 recordsLinked to original sources
PubMed1991

An increase in the negative surface charge of U937 cells exposed to a pulsed magnetic field.

Pulsed magnetic fields have been used to enhance healing of bone fractures and purportedly of lesions in soft tissue. However, their mechanism of action is poorly understood. We report changes in the plasma membrane of a nonadherent mammalian cell line, U937, which was exposed to a 25-pps magnetic field for 48 hours. Aqueous polymer two-phase partition studies showed that magnetic-field-exposed cells exhibited an increased negative surface charge but membrane hydrophobicity was not significantly altered. The observed increase in membrane electronegativity of exposed cells did not reflect a significant change in growth rate.

Cell Line↗
PubMed1988

Low frequency electric and magnetic fields have different effects on the cell surface.

There is a considerable controversy over the nature of weak electromagnetic-field effects in living organisms. Part of the controversy can be traced to a lack of understanding of whether electric or magnetic fields are involved in producing bioeffects. We find that both 60 Hz electric and magnetic fields alter the cell surface of Physarum polycephalum. Exposure to electric fields increases the negative charge on the cell surface while magnetic-field exposure decreases the hydrophobic character of the surface. These effects appear to be additive and independent of the waveform of the applied fields.

Cell Membrane↗
PubMed1986

Pulsed magnetic fields alter the cell surface.

Pulsed magnetic fields (PMFS) are routinely used in the medical community to facilitate bone repair in clinical cases of non-union or pseudarthoses [(1984) Orth. Clin. No. Am. 15, 61-87]. Although this therapeutic regimen appears to be reasonably effective, the mechanism of action between specific PMFs and the target tissue remains unknown. Adding urgency to the need to understand the mechanism are a wide number of reports that have appeared which demonstrate that PMFs similar to those in clinical use can alter many basic physiological functions. We report that a 24 h exposure to PMFs alters the cell surface of Physarum polycephalum amoebae. Further, using the technique of aqueous two-phase partitioning, we present evidence for individual magnetic and electric field, cell surface effects.

Cell Membrane↗
PubMed1986

Intracellular recording during magnetic field application to monitor neurotransmitter release events: methods and preliminary results.

A method for simultaneous magnetic field application and intracellular recording is presented. A little used method for magnetic field application was exploited; the field generator consisted of a flat copper sheet through which current was passed to generate a magnetic field. The resultant magnetic field was relatively homogeneous, exhibiting a variation of +/- 5%. This compact, current-sheet field generator was mounted on the condensor of a microscope. The current induced in the intracellular electrode was reduced by injecting current equal and opposite to the induced current into the microelectrode. This step reduces the possibility of cellular effects and voltage artifacts due to the induced electrode current. The technique was used to conduct preliminary studies on the effects of extremely low frequency (ELF) linearly and circularly polarized magnetic fields (1.0 Gauss, 60 and 70 Hz) on miniature end plate potential (mepp) frequency (frequency of neurotransmitter release events) of rat flexor digitorum brevis muscle. The same synapse was utilized for both the sham-exposed control and the exposed experimental halves of an experiment. After 10 min of exposure to a 60-Hz linear field, mepp frequency was significantly increased by 12%, but exposure to a 60-Hz circular field did not significantly alter mepp frequency. Exposure to a 70-Hz linear field did not significantly change mepp frequency, but application of a 70-Hz circular field appears to decrease mepp frequency by 4%. These results indicate that both types of magnetic fields can alter mepp frequency, depending upon the frequency and configuration of the field.

Animals↗
PubMed1986

Effects of sinusoidal 60-Hz electric and magnetic fields on ATP and oxygen levels in the slime mold, Physarum polycephalum.

We have previously reported that exposing the vegetative plasmodia stage of Physarum polycephalum to either individual or simultaneously applied electric and magnetic fields (45-75 Hz, 0.14-2.0 G, and 0.035-0.7 V/m) lengthens their mitotic cycle, depresses their rate of reversible shuttle streaming, and lowers their respiration rate. In this article we report the effects of simultaneously applied electromagnetic fields (60 Hz, 1.0 G, 1.0 V/m), electric fields only (60 Hz, 1.0 V/m), magnetic fields only (60 Hz, 1.0 G) on the haploid amoeba of Physarum exposed for 120-180 days. Statistically significant depressions (about 8-11%) in ATP levels were observed with all field conditions; however, respiration was significantly decreased only when amoebae were subjected to either combined fields or electric fields alone. Magnetic fields alone failed to induce a significant decrease in respiration.

Adenosine Triphosphate↗
PubMed1985

Low-voltage ELF electric field measurements in ionic media.

Low-voltage electric fields were measured in conductive tissue culture media using three techniques: voltage slope, current density-conductivity, and dipole methods. All three methods tested yielded comparable results. However, all three techniques have associated errors. These errors fall into three major categories: those associated with the measurement equipment, those associated with electrodes, and errors in cross-sectional area measurements. Each source of error is discussed so that all can be taken into account during construction and/or testing of exposure equipment.

Culture Media↗