A dark spot was found to appear in each blastomere of the vegetal surface of blastulae of Rana rugosa, Hyla arborea. The spot divided into two before division of the blastomere, so that one new spot was allotted to each daughter cell. These dark spots were formed at early blastula stage, and persisted until the end of yolk plug stage. Cytological observations showed that each dark spot correspo...

Ultrastructures of circulating hemocytes were studied in 9 botryllid ascidians. The hemocytes are classified into five types: hemoblasts, phagocytes, granulocytes, morula cells, and pigment cells. These five types are always found in the 9 species. They should represent the major hemocyte types of the circulating cells in the blood. Hemoblasts are small hemocytes having a high nucleus/cytoplasm...

The fish melanophore has been considered the exemplar of microtubule-based organelle transport. In this system, a radial array of uniformly polarized microtubules [1] provides a framework on which dynein-related and kinesin-related motors drive pigment granules toward the minus or plus ends, respectively [2-4]. Stimulation of minus-end motors accounts satisfactorily for aggregation of granules ...

The dermal melanocyte system of the Syrian hamster is particularly responsive to the melanogenetic and tumor-inducing effects of 7,12-dimethylbenz(a)anthracene (DMBA). The melanocytes of the hair follicles appear to be susceptible to the melanogenetic effect of DMBA but not to its tumor-inducing effect. The epidermal melanocytes are non-pigmented and are unresponsive to both melanogenetic and c...

An examination of the topographic distribution of lipofuscin pigment granules with the light and electron microscope revealed either smaller and randomly "dispersed" or larger and more complex "clustered" pigment configurations in the cytoplasm of neurons in the dorsal ganglia and ventral spinal cord of 24-month old male mice. Qualitative comparisons revealed no major differences in shape, size...

When a fish or a reptile changes color, it is because of the movement of tiny pigment granules in specialized skin cells called melanophores. These cells have hundreds of membrane-bound pigment granules, or melanosomes, which can be aggregated at the center of the cell or dispersed throughout the cytoplasm. When the melanosomes are aggregated the animal appears lighter, and as they disperse the...

Horky D.: Submicroscopic Structure of the Human Joint Cartilage and Synovial Membrane in Ochronosis. Acta vet. Bmo,.50, 1981: 131-156. Using a transmission electron .lInd Sc8nning electron microscope the joint cartilage and synovial membrane were studied in 5 persons of the age from 30 to 55 years. In its majority the superficial cartilage layer is absent due to arthritic changes caused by the ...

The Holocentrus erythrophore, a red pigment cell, represents a model system for the study of organized intracellular transport. We have investigated the possibility that microtubules and actin are integral components of the pigment translocating motil ity machine. By creating cells that have total or partial loss of the microtubule framework we have demonstrated that the presence of microtubule...

Drug discovery in skin pharmacotherapy is an enormous, continually expanding field. Researchers are developing novel and sensitive pharmaceutical products and drugs that target specific receptors to elicit concerted and appropriate responses. The pigment-bearing cells called melanophores have a significant contribution to make in this field. Melanophores, which contain the dark brown or black p...

The presence of pigment has been demonstrated in different nervous structures such as those of retina, substantia nigra, and locus coeruleus. These pigments have also been described in the pineal gland of different mammal species. Histochemical and ultrastructural studies of the pineal gland of female viscacha (Lagostomus maximus maximus) were performed to analyze the presence of pigmented cell...