scholarly journals Elucidating the role of nanostructured pigment granules in the dynamic coloration of cephalopods

2019 ◽  
Author(s):  
Thomas L. Williams
Keyword(s):  
Pigment Granules

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.

Cytoplasmic hybrids, by fusing fish erythrophores and normal rat kidney cells

1991 ◽  
Vol 49 ◽  
pp. 266-267
Author(s):  
K.R. Porter ◽  
K.L. Anderson
Keyword(s):  
Rat Kidney ◽  
Structural Features ◽  
Cell Type ◽  
Pigment Granules ◽  
Normal Rat ◽  
Cytoplasmic Hybrids ◽  
Pigment Aggregation ◽  
General Architecture

When cultured together in the presence of PEG, these cells fuse (M1,M3) and survive in vitro for several days. This offers an opportunity to explore the capacity of one cell type (highly organized structurally) to impose it's structural features on a relatively unorganized cell type (NRK). Also, with two cells differing in several respects, one can ask questions regarding a role of the cell center in the control of pigment aggregation and dispersion, as well as the capacity of one cell type to assemble pigment granules in the cytplasm of another.First, in observations on general architecture .the hybrids have numerous microtubules (M3), but not the organized array of thousands observed in the erythrophores (M2). Furthermore, the microtubules in the hybrid are randomly oriented essentially as they are in the NRK cell (M4). There is a tendency observed in the hybrids for the pigment granules to concentrate among the microtubules and the cistemae of the ER (M3). Thus far, however, we have not succeeded consistently with epinephrine to induce aggregation, or with caffeine, dispersion.

scholarly journals THE ROLE OF MICROTUBULES IN THE MOVEMENT OF PIGMENT GRANULES IN TELEOST MELANOPHORES

1974 ◽  
Vol 61 (3) ◽  
pp. 757-779 ◽  
Author(s):  
Douglas B. Murphy ◽  
Lewis G. Tilney
Keyword(s):  
Endoplasmic Reticulum ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
Nearest Neighbor ◽  
Cytoplasmic Matrix ◽  
Pigment Granules ◽  
Fixed Array ◽  
Nearest Neighbor Distances ◽  
Rule Out

When microtubules in teleost melanophores are disrupted with antimitotic agents, colchicine, high hydrostatic pressure, low temperature, and vinblastine, the alignment and movement of the pigment granules in these cells disappear; during recovery, the return of alignment and movement corresponds in both time and space with the repolymerization of microtubules. Furthermore, analysis of nearest neighbor distances in untreated melanophores reveals that pigment granules are closely associated with microtubules. Other structures such as microfilaments, the endoplasmic reticulum, and the cytoplasmic matrix do not appear to be involved. Thus we conclude that microtubules determine the alignment and are essential for the selective movements of the pigment granules in these cells. Investigations of the mechanism of movement show that microtubules are required for both centrifugal and centripetal migrations and that they do not change in number or location during redistribution of pigment. Our results further indicate that microtubules in melanophores behave as semistable organelles as determined by investigation with colchicine and hydrostatic pressure. These observations and others rule out a push-pull mechanism based on the polymerization and depolymerization of microtubules or one which distinguishes two operationally different sets of microtubules. We propose instead that particles move by sliding along a fixed array of microtubules.

scholarly journals Calcium regulation of pigment transport in vitro.

1988 ◽  
Vol 106 (1) ◽  
pp. 111-125 ◽  
Author(s):  
M A McNiven ◽  
J B Ward
Keyword(s):  
Plasma Membranes ◽  
Calcium Regulation ◽  
Organelle Transport ◽  
Cellular Motility ◽  
Intracellular Organelle ◽  
Pigment Granules ◽  
Calmodulin Inhibitors

Calcium has been implicated in the regulation of many cellular motility events. In this study we have examined the role of different Ca2+ concentrations on the in vitro transport of pigment within cultured chromatophores. Cells treated with Brij detergent for 1-2 min were stripped of their plasma membranes, leaving their cytoskeleton and associated pigment granules exposed to the external milieu. We found that retrograde pigment transport (aggregation) is induced upon addition of 1 mM MgATP2- with 10(-7) M free Ca2+, while an orthograde transport (redispersal) of pigment results from lowering the concentration of free Ca2+ to 10(-8) M while maintaining 1 mM MgATP2-. These Ca2+-regulated movements are ATP dependent but are apparently independent of cAMP and insensitive to calmodulin inhibitors. The observations reported here provide novel evidence that the concentration of free Ca2+ acts to regulate the direction of intracellular organelle transport.

The Rhabdomere organization of some nocturnal pisaurid spiders in light and darkness

1978 ◽  
Vol 283 (993) ◽  
pp. 1-23 ◽  
Keyword(s):  
Endoplasmic Reticulum ◽  
Light Adaptation ◽  
Retinal Pigment ◽  
Cell System ◽  
Coated Vesicles ◽  
Golgi Bodies ◽  
Supportive Cell ◽  
Highly Active ◽  
Pigment Granules

The retinae of the posterior eyes of pisaurid spiders in the genus Dolomedes are described.They resemble those of Lycosidae, but the receptors are much larger, and proximal to the strips of tapetum upon which they rest the receptor axons are grossly dilated. Each receptive segment contains two rhabdomeres, and pairs of rhabdomeres belonging to adjacent receptors are contiguous. Prolonged (6 h) illumination at physiological levels causes the rhabdomeres to diminish in volume by loss of membrane which is restored on return to darkness. W hen spiders are kept in darkness for 4-5 d, the rhabdomeres grow by the orderly addition of membrane to the microvilli until they completely fill the receptive segments, and such novel membrane is subsequently disassembled when the retina is illuminated. It is proposed that under normal conditions there is a balance maintained between the growth and destruction of rhabdomere membrane. The paired rhabdomeres are flanked by the processes of supportive cells which exhibit much membrane amplification, and the supportive cell system extends below the tapetum completely to ensheath the swollen receptor axons, which are some 70-80 pm long. In dark-adapted retinae the supportive processes are shrunken; illumination causes them to swell, and the extracellular space between the interdigitations fills with electron-dense material derived from the breakdown of rhabdom ere membrane. The material is passed basally and reintroduced into the receptor axons via an extensive system of endocytotic pleats. The tips of pleats often enclose pigment granules from the supporting system, and identical granules in various states of lysis are found within the axoplasm after exposure to light, thus implying that the pleats burst rather than merely transport material across their membranes. There is evidence that pleats may become detached. Exposure of retinae to infrared radiation also evokes breakdown of rhabdomere membrane, but the extracellular route is not employed. The swollen axons are filled with whorls of rough endoplasmic reticulum, abundant Golgi bodies, and mitochondria. After long periods of darkness, all these systems are depleted, and the space they occupied becomes highly vacuolated. Light adaptation from dim light on a normal diurnal cycle evokes dilation of the cisternae of the endoplasmic reticulum, which pinch off smooth vesicles, and the Golgi bodies become highly active and produce coated vesicles in abundance. The relations between smooth vesicles and microvilli are ambiguous; precedents exist for supposing that smooth vesicles in the inter-rhabdom eral cytoplasm are pinocytotic and have been pinched off from the bases of the microvilli, but in Dolomedes there is some evidence to suggest that they may be identical with those manufactured by the endoplasmic reticulum and are also fusing with rhabdomere membrane. Multivesicular and multilamellar bodies are the product of membrane fragments which have broken off from the rhabdomeres during light adaptation, and of coated vesicles produced by pinocytosis; they are transported within the receptors to the swollen axons where they undergo lysis. It is proposed that in Dolomedes the role of the endoplasmic reticulum is to synthesize materials for the repair of rhabdomere membrane, and that the bulk of precursors to sustain this process is obtained by recycling the products of rhabdom ere breakdown via the supportive cell system. The hypothesis is discussed in terms of current information about invertebrate retinae, and analogous processes which are well established for those of vertebrates. Dolomedes do not move retinal pigment granules to modulate the shielding of their receptors, and it is likely that manipulation of the properties of photoreceptor membrane is the only strategy of adaptation available to them.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor

Role of the allergist in diagnosis and management of patients with uveitis

JAMA ◽  
1966 ◽  
Vol 195 (3) ◽  
pp. 167-172 ◽  
Author(s):  
T. E. Van Metre
Keyword(s):  
Diagnosis And Management

The power of norms to sway fused group members

2018 ◽  
Vol 41 ◽  
Author(s):  
Winnifred R. Louis ◽  
Craig McGarty ◽  
Emma F. Thomas ◽  
Catherine E. Amiot ◽  
Fathali M. Moghaddam
Keyword(s):  
Evolutionary Anthropology ◽  
Normative Systems ◽  
Violent Extremism ◽  
Identity Fusion ◽  
Group Members

AbstractWhitehouse adapts insights from evolutionary anthropology to interpret extreme self-sacrifice through the concept of identity fusion. The model neglects the role of normative systems in shaping behaviors, especially in relation to violent extremism. In peaceful groups, increasing fusion will actually decrease extremism. Groups collectively appraise threats and opportunities, actively debate action options, and rarely choose violence toward self or others.

Elaborating the role of reflection and individual differences in the study of folk-economic beliefs

2018 ◽  
Vol 41 ◽  
Author(s):  
Kevin Arceneaux
Keyword(s):  
Decision Making ◽  
Individual Differences ◽  
Cognitive Processes ◽  
Evolutionary History ◽  
Behavioral Responses ◽  
History Of ◽  
Economic Beliefs

AbstractIntuitions guide decision-making, and looking to the evolutionary history of humans illuminates why some behavioral responses are more intuitive than others. Yet a place remains for cognitive processes to second-guess intuitive responses – that is, to be reflective – and individual differences abound in automatic, intuitive processing as well.

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