Cuttlefish, Sepia officinalis, possess neurally controlled, pigmented chromatophore organs that allow rapid changes in skin patterning and coloration in response to visual cues. This process of adaptive coloration is enabled by the 500% change in chromatophore surface area during actuation. We report two adaptations that help to explain how colour intensity is maintained in a fully expanded chr...

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...

The eyespot of the biflagellate unicellular green alga Chlamydomonas reinhardtii is a complex organelle that facilitates directional responses of the cell to environmental light stimuli. The eyespot, which assembles de novo after every cell division and is associated with the daughter four-membered (D4) microtubule rootlet, comprises an elliptical patch of rhodopsin photoreceptors on the plasma...

The effect of strychnine sulfate and light on pigmentation in the ciliate protozoan Blepharisma undulans has been determined. Upon exposure of cells to strychnine, the pigment granules become loosened from their surrounding membranes. Eventually these membranes break and the granules are simultaneously released from the cell. At the cell surface, a fusion occurs between adjacent membraneless gr...

Retinomotor movements are morphological changes in the outer retina in response to changing light conditions. They can be separated into two components: Migration of pigment granules within the microvilli of the retinal pigment epithelium (RPE) and positional changes in photoreceptor cells. These positional changes optimize exposure of the cone and rod photoreceptors to light. The aim of this s...

leukemia. The cells were examined daily under the electron micro scope between the 5th and 15th day following inoculation. The tumorous tissue was found to contain a single type of cells. The polygonal cells were loosely arranged, without intercellular at taching structures between them. Pseudopodia projecting into the intercellular space and rows of pinocytotic intracellular vesi cles pointed ...

The redistribution of melanin granules within dermal and epidermal melanocytes of the frog is responsible for changes in skin color . Surviving frog skin can be lightened and darkened by many different compounds (I). When the granules are dispersed into the branched processes of individual melanocytes, the skin appears dark . When melanin granules are aggregated in the perikaryon, the melanocyt...

Albino-beige mice were produced in order to combine two experimentally useful characteristics, albinism and lysosomal dysfunction, in the same animal. The retinal pigment epithelium of albino-beige mice formed giant intracellular granules. Exposure of albino-beige mice to white light of 150 foot-candles for 3 to 10 hr induced marked phagocytosis of rod outer segment fragments by the retinal pig...

Melanosomes, the pigment granules that provide tissues with colour and photoprotection, are the cellular site of synthesis, storage and transport of melanin pigments. They are synthesised in mammalian skin melanocytes, in choroidal melanocytes and retinal pigment epithelial (RPE) cells in the eye, and in melanophores (a class of pigment-containing cells) in lower vertebrates. The precise fate a...