Electrical coupling of neuro-ommatidial photoreceptor cells in the blowfly

A new method of microstimulation of the blowfly eye using corneal neutralization was applied to the 6 peripheral photoreceptor cells (R1-R6) connected to one neuro-ommatidium (and thus looking into the same direction), whilst the receptor potential of a dark-adapted photoreceptor cell was recorded by means of an intracellular microelectrode. Stimulation of the photoreceptor cells not impaled elicited responses in the recorded cell of about 20% of the response elicited when stimulating the recorded cell. This is probably caused by gap junctions recently found between the axon terminals of these cells. Stimulation of all 6 cells together yielded responses that were larger and longer than those obtained with stimulation of just the recorded cell, and intensity-response curves that deviated more strongly from linearity. Evidence is presented that the resistance of the axon terminal of the photoreceptor cells quickly drops in response to a light flash, depending on the light intensity. Incorporating the cable properties of the cell body and the axon, the resistance of the gap junctions, and the (adapting) terminal resistance, a theoretical model is presented that explains the measurements well. Finally, it is argued that the gap junctions between the photoreceptor cells may effectively uncouple the synaptic responses of the cells by counteracting the influence of field potentials.

Angular sensitivity of blowfly photoreceptors: intracellular measurements and wave-optical predictions

The angular sensitivity of blowfly photoreceptors was measured in detail at wavelengths λ = 355, 494 and 588 nm. The measured curves often showed numerous sidebands, indicating the importance of diffraction by the facet lens. The shape of the angular sensitivity profile is dependent on wavelength. The main peak of the angular sensitivities at the shorter wavelengths was flattened. This phenomenon as well as the overall shape of the main peak can be quantitatively described by a wave-optical theory using realistic values for the optical parameters of the lens-photoreceptor system. At a constant response level of 6 mV (almost dark adapted), the visual acuity of the peripheral cells R1-6 is at longer wavelengths mainly diffraction limited, while at shorter wavelengths the visual acuity is limited by the waveguide properties of the rhabdomere. Closure of the pupil narrows the angular sensitivity profile at the shorter wavelengths. This effect can be fully described by assuming that the intracellular pupil progressively absorbs light from the higher order modes. In light-adapted cells R1-6 the visual acuity is mainly diffraction limited at all wavelengths.

Trends in Occupational Exposure to Styrene in the European Glass Fibre-Reinforced Plastics Industry

Aim: This study presents temporal trends of styrene exposure for workers in the European glass fibre-reinforced plastics (GRP) industry during the period 1966–2002

Measurement of the electrotonic length constant in cultured muscle fibres

The measurement of passive electrical membrane properties in cultured muscle cells is complicated by the fact that the electrotonic length in these cells often exceeds their actual length, leading to serious deviations from the simple infinite cable behaviour. By using very short current pulses for these measurements and integrating the responses, the cells can be made to behave as infinite cables

Human volunteer study with PGME: Eye irritation during vapour exposure

The objective of this study was to establish the possible occurrence of eye irritation and subjective symptoms in human volunteers exposed to propylene glycol monomethyl ether (PGME) vapour at concentrations of 0, 100 and 150 ppm. Testing was conducted in 12 healthy male volunteers using a repeated measures design. Each subject was exposed for 2.5 h to each of the three exposure conditions that were spaced 7 days apart. The exposure sequences were counterbalanced and the exposure to the test substance and the effect measurements were conducted in a double-blind fashion. During all exposure sessions, 20 ppm diethyl ether was used as a 'masking agent' for vapour exposure. Measurements of pre- and post exposure eye redness, corneal thickness, tear film break-up time, conjunctival epithelial damage, blinking frequency, and subjective ratings on discomfort were used to evaluate the possible irritating effects of PGME. The results indicated no significant treatment effects for any of the objective parameters. Results of the subjective ratings indicated very slight effects on the eyes in the 150 ppm PGME condition only. No significant effects of treatment were found for the remaining questions concerning the perceived intensity of the smell in the room, the (un)pleasantness of the smell, the perceived effects on the skin, effects on the throat, shivering, muscle aching, and intestinal cramps. In conclusion, the results of the present study indicated minimal subjective eye effects at 150 ppm only, and no impact on the objective measures of eye irritation at either of the two exposure levels. It was concluded that the no adverse effect concentration for eye irritation due to PGME vapour was at least 150 ppm. © 2003 Elsevier Science Ireland Ltd. All rights reserved

Lead exposure during demolition of a steel structure coated with lead-based paints. II. Reversible changes in the conduction velocity of the motor nerves in transiently exposed workers.

In a group of workers exposed to high levels of lead during five months nerve conduction velocity parameters were evaluated at the termination of exposure, and also three and fifteen months later. At the termination of exposure the mean blood lead level was 4.0 ??mol/l, and motor conduction velocities in the median and the ulnar nerves were slower and the distal latencies in the median nerve were longer compared to the values measured 15 months later. Sensory conduction velocities, measured distally in the same nerves, were not depressed compared to the values measured three or fifteen months later. It was tentatively concluded that the effect of lead on the conduction velocity of the motor nerves has an initial reversible phase, dependent on the duration of exposure. Chemicals/CAS: lead, 7439-92-1; Air Pollutants, Occupational; Lead, 7439-92-1 This work is licensed under a Creative Commons Attribution 4.0 International License

Sensitivity of several cell systems to acrylamide

Chick spinal ganglia, chick muscle cells combined with mouse spinal cord explants, C1300 neuroblastoma cells, Chinese hamster ovary cells and newborn rat cerebral cells were exposed to various concentrations of acrylamide in culture. Four morphological and 1 electrophysiological parameter were applied in order to score toxic effects. It appeared that the neurite formation of rat cerebral neurons was the most sensitive criterion showing an effect at 10-7 M acrylamide. Chemicals/CAS: acrylamide, 79-06-1; Acrylamide