Major signaling cascades have been shown to play a role in the regulation of intracellular organelle transport . Aggregation and dispersion of pigment granules in melanophores are regulated by the second messenger cAMP through the protein kinase A (PKA) signaling pathway ; however, the exact mechanisms of this regulation are poorly understood. To study the role of signaling molecules in the reg...

A histochemical study of conjugated and total bilirubin was made on liver biopsies of 150 patients. Three types of cholestasis were defined: type I, characterized by the presence of intracellular pigment granules in the hepatocytes; type II, showing intracellular granules and extracellular thrombi (this group may be subdivided according to the eventual presence of coarse pigment deposits in the...

The origin of giant granules in the retinal pigment epithelium of the beige mouse was investigated with electron microscopy and ultrastructural histochemistry. These granules were found to contain melanin and acid phosphatase. Apparently they arise from fusions of primary lysosomes with melanin granules which are already enlarged from multiple fusions among melanosomes. Therefore, the giant gra...

Studies on the formation of ommochrome pigment granules are very few, despite their generalized occurrence as screening pigments in insect eyes. This is particularly true for ommochrome granules responsible for epidermal coloration. The aims of this study were to characterize the localization of major body pigments in a color changing mimetic spider, Misumena vatia (Thomisidae), and to describe...

OBJECTIVE To determine whether patients with acute posterior vitreous detachment with pigmented vitreous granules or hemorrhage have a higher likelihood of retinal tear compared with those with qualitatively normal vitreous examination findings. METHODS A multicenter cross-sectional study was performed in 3 peripheral ophthalmic clinics. Patients with acute posterior vitreous detachment were ...

1The terminology used in this report is the one adopted by the 5th International Congress of Pigment Cell Biology held at the New York Academy of Sciences in 1961. into the differentiating medullary and cortical cells of the hair. A number of genes affect hair color in mammals by controlling both the synthesis and transfer of pigment. Investigations of the melanocytes of the hair follicle with ...

Ommochromes are end products of the tryptophan metabolism in arthropods. While the anabolism of ommochromes has been well studied, the catabolism is totally unknown. In order to study it, we used the crab-spider Misumena vatia, which is able to change color reversibly in a few days, from yellow to white and back. Ommochromes is the only pigment class responsible for the body coloration in this ...

The production of thermal lesions in the ocular fundus depends, among other factors, upon the spectral quality of the light incident on the cornea, and the energy-density gradient in the fundus. The latter depends, in turn, upon the concentration of pigment within the granules and the space distribution of the granules within a given stratum or layer. The distribution of pigmented granules vari...

Xanthommatin is the primary ommochrome eye pigment in mosquitoes. The terminal step in xanthommatin biosynthesis, involving oxidation of 3-hydroxykynurenine (3HK), can proceed enzymatically by phenoxazinone synthase or by nonenzymatic auto-oxidation of 3HK. The relative contributions of these pathways, however, are unclear. We isolated a novel Culex pipiens mutant (crimson) that could be used t...

We have observed pigmented cytoplasmic granules, with the characteristic staining properties of lipofuscin (ceroid, "wear-and-tear") pigment, in newborn human liver. The pigment is found at the periphery of the lobule in hepatocytes and some bile ductular cells. It is acid-fast, PAS-positive after diastase digestion, slightly argyophilic and sudanophilic, and markedly Schmorl's- and peroxidase ...