Cytoskeleton of retinular cells from the stomatopod, Gonodactylus oerstedii: possible roles in pigment granule migration

1993 ◽  
Vol 274 (2) ◽  
pp. 315-328 ◽  
Author(s):  
Christina A. King ◽  
Thomas W. Cronin
Keyword(s):  
Pigment Granule ◽  
Retinular Cells ◽  
Pigment Granule Migration

Pigment granule migration in crustacean photoreceptors requires calcium

1996 ◽  
Vol 13 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Christina King-Smith ◽  
Thomas W. Cronin
Keyword(s):  
Pigment Granule ◽  
Size And Shape ◽  
Pigment Granules ◽  
Gradual Loss ◽  
Light Stimuli ◽  
Pigment Granule Migration ◽  
Normal Calcium

AbstractWe have investigated the role of calcium in the regulation of pigment granule migration in photoreceptors of the semi-terrestrial crab, Sesarma cinereum. Isolated crab eyes (eyecup plus eyestalk) were maintained in crustacean Ringer either prepared normally or calcium-free plus 50 mM EGTA. Pigment granule movement was indirectly observed by monitoring reflectance from the eye during light stimuli using intracellular optical physiological techniques. Electroretinograms (ERGs) were also measured during light stimuli. EGTA treatment caused gradual loss of centripetal migration of pigment granules (normally leading to pupillary closure), and photoreceptors eventually became locked in the open-pupil, dark-adapted state despite repeated stimuli. In contrast, ERG responses continued throughout EGTA treatment, although the size and shape ofthe response was altered. Normal ERG responses and pigment granule movements returned after replacing EGTA-Ringer with normal-calcium medium. These results suggest that centripetal migration of pigment granules in crustacean photoreceptors requires calcium.

scholarly journals Light-induced pigment granule migration in the retinular cells of Drosophila melanogaster. Comparison of wild type with ERG-defective mutants.

1981 ◽  
Vol 77 (2) ◽  
pp. 155-175 ◽  
Author(s):  
M V Lo ◽  
W L Pak
Keyword(s):  
Drosophila Melanogaster ◽  
Transient Receptor Potential ◽  
Light Stimulus ◽  
Strong Support ◽  
Pigment Granule ◽  
Receptor Potential ◽  
Temperature Sensitive ◽  
Experimental Conditions ◽  
Trp Mutant ◽  
Pigment Granule Migration

The dependence of pigment granule migration (PGM) upon the receptor potential was examined using several strains of electroretinogram (ERG)-defective mutants of Drosophila melanogaster. The mutants that have a defective lamina component but a normal receptor component of the ERG (no on-transient A [nonA] and tan) exhibited normal pigment granule migration. The mutants that have very small or no receptor potentials (certain no receptor potential A [norpA] alleles), on the other hand, exhibited no PGM. In the case of the temperature-sensitive norpA mutant, norpAH52, normal PGM was present at 17 degrees but not at 32 degrees C or above, corresponding to its electrophysiological phenotype. In the transient receptor potential (trp) mutant, whose receptor potential decays to the baseline within a few seconds during a sustained light stimulus, the pigment granules initially moved close to the rhabdomere when light was turned on but moved away after about 5 s during a sustained light stimulus. All these results lend strong support to the notion that PGM is initiated by a light-evoked depolarization of the receptor membrane, i.e., the receptor potential. However, under certain experimental conditions, the receptor potentials failed to induce PGM in the trp mutant. The depolarization of the receptor, thus, appears to be closely associated with PGM but is not a sufficient condition for PGM.

Calcium-independent regulation of pigment granule aggregation and dispersion in teleost retinal pigment epithelial cells

1996 ◽  
Vol 109 (1) ◽  
pp. 33-43
Author(s):  
C. King-Smith ◽  
P. Chen ◽  
D. Garcia ◽  
H. Rey ◽  
B. Burnside
Keyword(s):  
Intracellular Calcium ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Pigment Granule ◽  
Retinal Pigment Epithelial Cells ◽  
Rod Photoreceptor ◽  
Rpe Cells ◽  
Pigment Granules ◽  
Pigment Granule Migration

In the eyes of teleosts and amphibians, melanin pigment granules of the retinal pigment epithelium (RPE) migrate in response to changes in light conditions. In the light, pigment granules disperse into the cells' long apical projections, thereby shielding the rod photoreceptor outer segments and reducing their extent of bleach. In darkness, pigment granules aggregate towards the base of the RPE cells. In vitro, RPE pigment granule aggregation can be induced by application of nonderivatized cAMP, and pigment granule dispersion can be induced by cAMP washout. In previous studies based on RPE-retina co-cultures, extracellular calcium was found to influence pigment granule migration. To examine the role of calcium in regulation of RPE pigment granule migration in the absence of retinal influences, we have used isolated RPE sheets and dissociated, cultured RPE cells. Under these conditions depletion of extracellular or intracellular calcium ([Ca2+]o, [Ca2+]i) had no effect on RPE pigment granule aggregation or dispersion. Using the intracellular calcium dye fura-2 and a new dye, fura-pe3, to monitor calcium dynamics in isolated RPE cells, we found that [Ca2+]i did not change from basal levels when pigment granule aggregation was triggered by cAMP, or dispersion was triggered by cAMP washout. Also, no change in [Ca2+]i was detected when dispersion was triggered by cAMP washout in the presence of 10 microM dopamine, a treatment previously shown to enhance dispersion. In addition, elevation of [Ca2+]i by addition of ionomycin neither triggered pigment movements, nor interfered with pigment granule motility elicited by cAMP addition or washout. Since other studies have indicated that actin plays a role in both pigment granule dispersion and aggregation in RPE, our findings suggest that RPE pigment granule migration depends on an actin-based motility system that is not directly regulated by calcium.

Distribution of tubulin, kinesin, and dynein in light- and dark-adapted octopus retinas

2000 ◽  
Vol 17 (1) ◽  
pp. 127-138 ◽  
Author(s):  
JUANA M. MARTINEZ ◽  
HASSAN ELFARISSI ◽  
BEGONA De VELASCO ◽  
GINA H. OCHOA ◽  
ARIA M. MILLER ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Motor Proteins ◽  
Pigment Granule ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Microtubule Cytoskeleton ◽  
Transport Pathways ◽  
Transport Vesicles ◽  
Pigment Granule Migration ◽  
Cytoskeletal Rearrangements

Cephalopod retinas exhibit several responses to light and dark adaptation, including rhabdom size changes, photopigment movements, and pigment granule migration. Light- and dark-directed rearrangements of microfilament and microtubule cytoskeletal transport pathways could drive these changes. Recently, we localized actin-binding proteins in light-/dark-adapted octopus rhabdoms and suggested that actin cytoskeletal rearrangements bring about the formation and degradation of rhabdomere microvilli subsets. To determine if the microtubule cytoskeleton and associated motor proteins control the other light/dark changes, we used immunoblotting and immunocytochemical procedures to map the distribution of tubulin, kinesin, and dynein in dorsal and ventral halves of light- and dark-adapted octopus retinas. Immunoblots detected α- and β-tubulin, dynein intermediate chain, and kinesin heavy chain in extracts of whole retinas. Epifluorescence and confocal microscopy showed that the tubulin proteins were distributed throughout the retina with more immunoreactivity in retinas exposed to light. Kinesin localization was heavy in the pigment layer of light- and dark-adapted ventral retinas but was less prominent in the dorsal region. Dynein distribution also varied in dorsal and ventral retinas with more immunoreactivity in light- and dark-adapted ventral retinas and confocal microscopy emphasized the granular nature of this labeling. We suggest that light may regulate the distribution of microtubule cytoskeletal proteins in the octopus retina and that position, dorsal versus ventral, also influences the distribution of motor proteins. The microtubule cytoskeleton is most likely involved in pigment granule migration in the light and dark and with the movement of transport vesicles from the photoreceptor inner segments to the rhabdoms.

Ultrastructure of melanocyte-keratinocyte interactions and pigment transfer in vitro

1978 ◽  
Vol 36 (2) ◽  
pp. 650-651
Author(s):  
Raul I. Garcia ◽  
Evelyn A. Flynn ◽  
George Szabo
Keyword(s):  
Direct Injection ◽  
Skin Pigmentation ◽  
Freeze Fracture ◽  
Pigment Granule ◽  
Time Lapse ◽  
Ultrastructural Level ◽  
Lanthanum Tracer ◽  
A Cell

Skin pigmentation in mammals involves the interaction of epidermal melanocytes and keratinocytes in the structural and functional unit known as the Epidermal Melanin Unit. Melanocytes(M) synthesize melanin within specialized membrane-bound organelles, the melanosome or pigment granule. These are subsequently transferred by way of M dendrites to keratinocytes(K) by a mechanism still to be clearly defined. Three different, though not necessarily mutually exclusive, mechanisms of melanosome transfer have been proposed: cytophagocytosis by K of M dendrite tips containing melanosomes, direct injection of melanosomes into the K cytoplasm through a cell-to-cell pore or communicating channel formed by localized fusion of M and K cell membranes, release of melanosomes into the extracellular space(ECS) by exocytosis followed by K uptake using conventional phagocytosis. Variability in methods of transfer has been noted both in vivo and in vitro and there is evidence in support of each transfer mechanism. We Have previously studied M-K interactions in vitro using time-lapse cinemicrography and in vivo at the ultrastructural level using lanthanum tracer and freeze-fracture.

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