Search PubMed⌕ Search

Biomedical subjects

V J Wulff

Publications and source records attributed to V J Wulff.

25 records · Page 2Linked to original sources
PubMed1965

Light-initiated responses of retinula and eccentric cells in the Limulus lateral eye.

The relationship between retinula and eccentric cells in the lateral eye of Limulus polyphemus was studied using a double electrode technique which permitted simultaneous recording of light-initiated responses in two sense cells and the labeling of the cells for subsequent histological examination and identification. The following results were obtained: (a) light-initiated slow responses with and without superimposed spike potentials were recorded from retinula cells and from eccentric cells (only one eccentric cell yielded responses without superimposed spike potentials); (b) spike potentials recorded in different cells within the same ommatidium were always synchronous; (c) a complete absence of spike potentials was observed in two experiments in which no eccentric cells could be found in the ommatidia containing the labeled retinula cells; (d) the greatest differences in the characteristics of responses recorded simultaneously occurred in those recorded from retinula-eccentric combinations. The results indicate that there is only one source of spike potential activity within an ommatidium (presumably the eccentric cell) and that the light-initiated response of retinula cells may be independent of the eccentric cell response. The suggestion is advanced that the response of the retinula cell may "trigger" the eccentric cell response.

Animals↗
PubMedDate not supplied

A study of light-initiated currents in Limulus lateral eye retinular cells.

Light-initiated currents in Limulus lateral eye retinular cells were studied using the voltage clamp technique. To assess the validity of such current measurements, the isopotentiality of retinular cells was determined on triply impaled cells and the effect of voltage clamping one retinular cell on adjacent retinular cells and on the eccentric cell in the same ommatidium was determined. The results of the experiments are: (1) retinular cells are isopotential at loci 100 micron apart; (2) appreciable steady state current during the clamping episodes leaks into neighboring retinular cells and the eccentric cell; (3) light-initiated currents exhibit two components; (4) there is a dynamic change in the resistance of the photoreceptor membrane during development of the receptor potential; (5) suppression of the rising phase (C1) of the receptor potential does not affect subsequent voltage changes; (6) suppression of the sodium influx which normally produces C1 has only minor effects on subsequent voltage changes; (7) reduced [KC1]out increases and increased [CK1]out decreases the reversal potential of light-initiated currents; and (8) reduced [NaC1]out reduces the magnitude and the reversal potential of light-initiated currents.

Animals↗
PubMedDate not supplied

The latent period of the Limulus lateral eye receptor potential: action of chlorobutanol.

Excised lateral eye retinular cells of Limulus polyphemus exposed to chlorobutanol were examined using microelectrode techniques. The effects observed were: (1) a marked shortening of the receptor potential latent period; (2) a decrease in the effective input resistance of retinular cells to hyperpolariziog currents; and (3) a reduction in magnitude of retinular cell receptor and membrane potential. The magnitude of the changes were concentration dependent and reversible and were only produced by chlorobutanol and closely related compounds. Chlorobutanol does not alter the sodium permeability of the receptor cell membrane but it may increase the rate of the process or processes occurring during the latent period of the receptor potential.

Animals↗
PubMedDate not supplied

Effect of chlorobutanol on Limulus ventral photoreceptor latency: a model of a two component latent period.

Chlorobutanol (1,1,1-trichlor-2-methyl-2-propanol) decreases the duration of the latent period of Limulus ventral eye receptor potentials. This effect is both concentration and intensity dependent. Between 0.05 and 1 mM chlorobutanol in sea water the extent of latency shortening effect of chlorobutanol linear function of the logarithm of the chlorobutanol concentration. The latency shortening effect of chlorobutanol diminishes with decreasing intensity of stimulation and virtually disappears at intensities just exceeding threshold. These results are explained by postulating that the latent period is composed of two processes only one of which is sensitive to chlorobutanol and, further, that the duration of the chlorobutanol-sensitive process is not appreciably affected by the stimulating intensity. This model of a two component latent period may be tested experimentally. In several experiments prolonged exposure of ventral photoreceptor cells to chlorobutanol coupled with a short exposure to calcium deficient sea water produced a collapse of the receptor potential followed by a slow recovery after returning to perfusion with normal sea water. During the recovery a slow, low amplitude positive wave exists which has been tentatively called a prepotential.

Animals↗
PubMedDate not supplied

Partial voltage clamping of Limulus ventral photoreceptor potentials: evidence of programmed conductance changes.

Light-initiated currents elicited by brief light stimuli from Limulus ventral photoreceptors bathed in normal sea water generally exhibit a smooth contour, although the unclamped receptor potential elicited by an identical light stimulus usually exhibits distinct C1 and C2 components. However, light-initiated currents obtained from cells exposed to chlorobutanol often exhibit two components. Data from such experiments indicate that peak C2 current is more strongly voltage dependent than peak C1 current, as in Limulus lateral eye retinular cells. The results of partial voltage clamp experiments with ventral photoreceptors in which the clamping episode terminated at different times during the receptor potential reveal relatively minor perturbations of the rebound receptor potential when compared with the unclamped control response. These findings suggest that the temporal pattern of the membrane conductance changes which underlie the receptor potential is determined prior to the occurrence of the receptor potential. It is likely that the program for these conductance changes is developed during the latent period of the receptor potential.

Animals↗
PubMedDate not supplied

Interaction of light and chlorobutanol on Limulus ventral photoreceptor potential latency.

Exposure of Limulus ventral photoreceptors to light or to chlorobutanol produces a shortening of the latent period of the receptor potential. The latency shortening effect of chlorobutanol (0.5 mM) is maximal in dark adapted photoreceptors and decreases progressively as the level of light adaptation increases. At the highest usable levels of light adaptation, the latencies of receptor potentials from cells exposed only to sea water containing chlorobutanol were virtually identical. This confluence of the latent periods suggests that light and chlorobutanol may affect the same component of the latent period.

Animals↗