In vitro exposure parameters with linearly and circularly polarized ELF magnetic fields.

A comparison is made of induced current densities, electric fields, and rates of energy deposition during in vitro studies with linearly and circularly polarized, extremely low frequency magnetic fields for a cylindrical volume of culture medium.     

Time coding in the midbrain of mormyrid electric fish. I. Physiology and anatomy of cells in the nucleus exterolateralis pars anterior

In mormyrid electric fish, species-specific electric organ discharge waveforms are thought to be analyzed by the Knollenorgan electroreceptor subsystem. The midbrain anterior and posterior exterolateral nuclei (ELa and ELp) are thought to be the sites of this analysis. This paper is an electrophysiological study of the properties of the neurons in ELa. We recorded intracellularly from three classes of cells within ELa: the afferent axons from the nucleus of the electrosensory lateral line lobe (NELL), the large interstitial cells of ELa and an unidentified cell type. The large cells and the NELL axons were identified by intracellular injection of biocytin and are physiologically similar. Cells in ELa responded to square pulse stimuli with one or more time-locked action potentials with 2.8–3.0 ms latency. Both large cells and NELL axons arborized extensively in ELa and contacted numerous small cells. Based on the pattern of arborizations, we constructed a counter- current flow model of temporal coding by the small cells of ELa. We postulate that individual small cells are not selectively tuned for specific stimulus durations, but rather, the firing patterns of groups of small cells must be analyzed by neurons further up in the sensory hierarchy to determine the stimulus duration. Accepted: 25 June 1997     

A family of versatile centromeric vectors designed for use in the sectoring-shuffle mutagenesis assay in Saccharomyces cerevisiae

A simple assay called the sectoring shuffle was developed to monitor the mutational state of essential genes cloned into yeast centromeric plasmids. The essence of this assay is the creation of a conditional phenotype, colony color sectoring, for an essential gene in the absence of conditional thermosensitive or cold-sensitive alleles of that gene. This allows the quick determination of the mutational state of a cloned essential gene by observing its effect on the sectoring phenotype of the tester strain. During the course of this work we developed a family of 20 Escherichia coli-yeast shuttle vectors, pUN plasmids, containing ARS1 CEN4 and a variety of selectable markers as well as the SUP11 gene which can act as a color marker in the proper background. These vectors are compact and have been very useful for the sectoring-shuffle assay and for gene analysis in general. This paper decribes these vectors, the sectoring shuffle and several applications of sectoring phenotypes.     

Influence of Potential Difference and Current on the Electrotaxis of Caenorhaditis elegans

C. elegans responds directionally to a DC current. The response may be to the anode or cathode, depending on the current, potential difference, and ion concentration of KC1, Tracks of the responding nematodes show that electrotaxes are genuine orientation phenomena. The directional movement is not due to the passive movement of nematodes or to the influence of currents on the muscular physiology; electrotaxes are mediated sensorily. Details of the response are described.     

The electric image in weakly electric fish: I. A data-based model of waveform generation inGymnotus carapo

Understanding how electrosensory images are generated and perceived in actively electrolocating fish requires the study of the characteristics of fish bodies as electric sources. This paper presents a model ofGymnotus carapo based on measurements of the electromotive force generated by the electric organ and the impedance of the passive tissues. A good agreement between simulated and experimentally recorded transcutaneous currents was obtained. Passive structures participate in the transformation of the electromotive force pattern into transcutaneous current profiles. These spatial filtering properties of the fish's body were investigated using the model. The shape of the transcutaneous current profiles depends on tissue resistance and on the geometry and size of the fish. Skin impedance was mainly resistive. The effect of skin resistance on the spatial filtering properties of the fish's body was theoretically analyzed.The model results show that generators in the abdominal and central regions produce most of the currents through the head. This suggests that the electric organ discharge (EOD), generated in the abdominal and central regions is critical for active electrolocation. In addition, the well-synchronized EOD components generated all along the fish produce large potentials in the far field. These components are probably involved in long-distance electrocommunication.Preliminary results of this work were published as a symposium abstract.     

Impact of surface electric properties of carbon-based thin films on platelets activation for nano-medical and nano-sensing applications

Electric surface properties of biomaterials, playing key role to various biointerfacial interactions, were related to hemocompatibility and biosensing phenomena. In this study, the examination of surface electric properties of amorphous hydrogenated carbon thin films (a-C:H) was carried out by means of electrostatic force microscope (EFM) and observation of differences in spatial charge distribution on the surface of the examined films during platelets adhesion was made. The thrombogenic potential of a-C:H thin films developed by magnetron sputtering with ~42% sp³ content and hydrogen partial pressure during deposition was evaluated, by in situ observation with atomic force microscope (AFM) of platelets’ activation and their subsequent adhesion. Platelet-rich plasma drawn from healthy donors was used and semi-contact mode of AFM was applied. Platelets behavior and their correlation with the electric surface properties of the examined a-C:H films by EFM was made for hemocompatibility enhancement and sensing platelets that are less electrical negatively charged and with higher tendency to aggregate and form thrombus. The results are discussed in view of the effect of different deposition conditions of hydrogenated carbon films on their structural and morphological characteristics, surface roughness and electrical properties attributing to different hemocompatibility and sensing aspects.     

Detection of 60-hertz vertical electric fields by rats

Rats were trained to press levers to indicate the presence or absence of 60-Hz vertical electric fields at intensities from 0 to 27 kV/m (rms). The probability of detecting the field increased as the strength of the field increased. The shape of the detection curve (psychometric function) for most subjects (Ss) was similar whether the discriminative stimulus was the electric field or a tone. Two protocols were used to estimate the minimum field intensity necessary to detect the field (Reiz Limen, RL). The RL was estimated to be 13.3 kV/m (rms) when using one protocol (the staircase method) and 7.9 kV/m (rms) when using another protocol (the method of constant stimuli).     

Effects of electric field exposure on some indices of CNS arousal in the mouse

Mice given ELF electric field exposures of 50-400 Vm-1 at frequencies of 15, 30, and 50 Hz failed to display any significant changes in barbiturate sleeping time or exploratory activity.     

What are non-thermal electric biological effects?

A discussion of the general implication of the existance of non-thermal biological effects of electromagnetic fields is presented.