The initiation of excitation and light-adaptation in Limulus ventral photoreceptors

Lisman, John; Strong, Judith A.

doi:10.1016/0042-6989(79)90060-9

Cited by 21 publications

(31 citation statements)

References 37 publications

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“…Similar calibrations were carried out for phenol red. The effective extinction coefficients for both the protonated and unprotonated forms of phenol red for the 480(10) nm filter were taken to be 11 000 m −1 cm −1 , the value at the isosbestic wavelength of 480 nm (Lisman & Strong, 1979). As for the 520(10) nm filter in the TMX calibrations, the 480(10) nm filter served as the reference for the other filters.…”

Section: Methodsmentioning

confidence: 99%

Role of calsequestrin evaluated from changes in free and total calcium concentrations in the sarcoplasmic reticulum of frog cut skeletal muscle fibres

Pape

Fénelon

Lamboley

et al. 2007

The Journal of Physiology

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Calsequestrin is a large-capacity Ca-binding protein located in the terminal cisternae of sarcoplasmic reticulum (SR) suggesting a role as a buffer of the concentration of free Ca in the SR ( Calsequestrin is a high-capacity Ca binding protein located in the terminal cisternae of the sarcoplasmic reticulum (SR) of skeletal muscle (MacLennan & Wong, 1971). One function proposed for calsequestrin is that it rapidly buffers [Ca 2+ ] in the sarcoplasmic reticulum (denoted [Ca 2+ ] SR ). In this way, local depletion of Ca 2+ would be avoided and the driving force for Ca 2+ release maintained. In support of this idea, the in vitro kinetics of the Ca-calsequestrin binding reaction appear to be fast ('rates of calcium association and dissociation are faster than 1 ms −1 ; Prieto et al. 1994) indicating that they would not be rate limiting for physiological SR Ca 2+ release. Therefore, unless its kinetic properties change significantly in intact muscle, calsequestrin should essentially be in instantaneous equilibrium with [Ca 2+ ] SR during physiological stimulation. The ability of calsequestrin to act as a local buffer should then depend on the amount of calsequestrin, its steady-state binding curve with Ca, and the location on this curve determined by [Ca 2+ ] SR . Essentially all of the information on calsequestrin's binding properties thus far has come from studies with purified calsequestrin or with disrupted preparations, principally terminal cisternae vesicles. The main aim of this article is to evaluate these properties under more physiological conditions during depolarization-induced Ca 2+ release.The main experiments in this article involved measurements of two optical signals in response to voltage-clamp stimulation, one signal approximately proportional to total SR Ca content and the other driven by changes in [Ca 2+ ] SR . The concentration of total SR Ca content (denoted [Ca T ] SR ) were obtained from absorbance measurements of phenol red (the first optical signal) with the EGTA-phenol red method . [Ca 2+ ] SR was monitored with the absorbance indicator-dye tetramethylmurexide (TMX, the second optical signal), an application suggested by the results of Maylie et al. (1987). They described TMX-related absorbance changes ( A TMX ) from cut muscle fibres equilibrated with a low concentration of EGTA (0.1 mm) in response to action-potential stimulation. The A TMX signal had two components, an early transient component consistent with an increase in [Ca 2+ ] in the myoplasm followed by a rapid decrease to a somewhat maintained signal of opposite sign to the initial transient component. They proposed that the maintained signal was due to a decrease in [Ca 2+ ] SR . In a subsequent study, measurements were carried out using modified Ca 2+ indicators which were essentially TMX or a similar dye, murexide, with two charged groups added to prevent their entry into the SR (Hirota et al. 1989). As predicted, the action-potential-generated, dye-related A signals showed a rapid transient component that ...

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Section: Methodsmentioning

confidence: 99%

Role of calsequestrin evaluated from changes in free and total calcium concentrations in the sarcoplasmic reticulum of frog cut skeletal muscle fibres

Pape

Fénelon

Lamboley

et al. 2007

The Journal of Physiology

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“…The intracellular pH value measured with microelectrodes or the indicator-dye phenol red is about 7-0 in Limulus ventral photoreceptor (Levy & Coles, 1977;Lisman & Strong, 1979). Strong illumination causes a small increase in the intracellular proton concentration (the decrease of the pH value is between o -1 and 0-4; Brown et al 1977).…”

Section: Ion Concentrationsmentioning

confidence: 99%

“…Both the excitation and the adaptation are initiated by the absorption of light by rhodopsin molecules (Strong & Lisman, 1978;Lisman & Strong, 1979;Payne, 1986) and thus occur in the R-lobe of the cell (Payne & Fein, 1983). It could be assumed that the reduced number of the single photon responses elicited by lightadaptation is due to a reduction in the quantum-efficiency.…”

Section: Multiple Functions Of Calcium Ionsmentioning

confidence: 99%

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Nagy

1991

Quart. Rev. Biophys.

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Limulus ventral nerve photoreceptor, a classical preparation for the study the phototransduction in invertebrate eyes, seems to have a very complex mechanism to transform light energy into a physiological signal. Although the main function of the photoreceptor is to change the membrane conductance according to the illumination, the cell has voltage-activated conductances as well. The voltage-gated conductances are matched to the light-activated ones in the sense that they make the function of the cell more efficient. The complex mechanism of phototransduction and the presence of four different voltage-gated conductance in Limulus ventral nerve photoreceptors indicate that these cells are far less differentiated than the photoreceptor cells of vertebrates. Indications accumulated in recent years support the view that the ventral photoreceptor of Limulus has different light-activated macroscopic current components, ion channels and terminal transmitters. After conclusions from macroscopic current measurements (Payne, 1986; Payne et al. 1986 a, b), direct evidence was presented by single-channel (Nagy & Stieve, 1990 a, b; Nagy, 1990 a, b) and macroscopic current measurements (Deckert et al. 1991 a, b) for three different light-activated conductances. It has been shown that two of these conductances are stimulated by two different excitation mechanisms. The two mechanisms, having different kinetics, release probably two different transmitters. One of them might be the cGMP (Johnson et al. 1986), the other one the calcium ion (Payne et al. 1986 a, b). However, the biochemical processes which link the rhodopsin molecules and the ion channels are not known. The unknown chemical details of the phototransduction result in a delay for the mathematical description of the biophysical mechanisms. More biochemical details are known about the adaptation mechanism. It was found that inositol 1,4,5-trisphosphate is a messenger for the release of calcium ions from the intracellular stores and that calcium ions are the messengers for adaptation (Payne et al. 1986 b; Payne & Fein, 1987). Concerning the mechanism of calcium release, it was revealed that a negative feedback acts on the enzyme cascade to regulate the internal calcium level and to protect the stores against complete emptying (Payne et al. 1988, 1990). Calcium ions also play an important role in the excitation mechanism. (a) In [Ca2+]i-depleted cells the light-induced current was increased after intracellular Ca2+ injection, suggesting that calcium is necessary for the transduction mechanism (Bolsover & Brown, 1985).(ABSTRACT TRUNCATED AT 400 WORDS)

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“…As discussed above, large injections sometimes in themselves lead to desensitization and slower kinetics of the light response of ventral photoreceptors. Secondly, the kinetics of the receptor response itself depend upon [Ca2+]i; when [Ca2+]i is raised, the time scale of the light response becomes faster ; conversely, when [Ca2+]i is lowered, the time scale of the response becomes slower (Lisman & Brown, 1974;Srebro & Behbehani, 1975). Therefore, if 318 ARSENAZO III DETECTS CHANGES OF [Ca2+]i intracellular arsenazo III tended to buffer a light-induced increase of [Ca2+]i, the light response itself would be slower; this might account in part for the slower light-induced rise of [Ca2+]1 indicated by the dye.…”

Section: Ionic Basis Of Rapid Changes Of 660mentioning

confidence: 99%

Detection of light‐induced changes of intracellular ionized calcium concentration in Limulus ventral photoreceptors using arsenazo III

Brown

Pinto

1977

The Journal of Physiology

145

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SUMMARY1. The metallochromic indicator dye, arsenazo III, was injected intracellularly into Limnulus ventral photoreceptor cells to concentrations greater than 1 mm.2. The absorption spectrum (450-750 nm) of the dye in single darkadapted cells was measured by a scanning microspectrophotometer. When a cell was light-adapted, the absorption of the dye changed; the difference spectrum had two maxima at about 610 and 660 nm, a broad minimum at about 540 nm and an isosbestic point at about 585 nm.3. When intracellular calcium concentration was raised in dark-adapted cells previously injected with arsenazo III, the difference spectrum had two maxima at about 610 and 660 nm, a broad-minimum at about 530 nm and an isosbestic point at about 5L5 nm. The injection of Mg2+ into darkadapted cells previously injected with the dye induced a difference spectrum that had a single maximum at about 620 nm. Also, decreasing the intracellular pH of cells previously injected with the dye induced a difference spectrum that had a minimum at about 620 nm. The evidence suggests that there is a rise of intracellular ionized calcium when a Limulus ventral photoreceptor is light-adapted.

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The initiation of excitation and light-adaptation in Limulus ventral photoreceptors

Cited by 21 publications

References 37 publications

Role of calsequestrin evaluated from changes in free and total calcium concentrations in the sarcoplasmic reticulum of frog cut skeletal muscle fibres

Role of calsequestrin evaluated from changes in free and total calcium concentrations in the sarcoplasmic reticulum of frog cut skeletal muscle fibres

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Detection of light‐induced changes of intracellular ionized calcium concentration in Limulus ventral photoreceptors using arsenazo III

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