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The clinical and histopathological picture of the pigmented epidermal cyst and the pigmented trichilemmcyst is illustrated by three case-reports. The pigment is melanin, which is located in the epithelium of the cyst-wall, the corneocytes of the lumen and in macrophages in the dermis. The clinical appearance of melanin pigmented cysts is blue due to the Tyndall-phenomenon.
BACKGROUND: This study investigated the anti-oxidant properties, starch composition, pasting behavior, structural properties, textural properties and non-targeted metabolomic profiles of pigmented and non-pigmented rice landraces as potential next-generation functional food ingredients. RESULTS: Pigmented rice demonstrated 1.34 times more anti-oxidant activity as compared to non-pigmented rice. Pigmented landraces showcased superior nutritional and functional attributes, including higher total dietary fiber and starch content. Fourier-transform infrared (FTIR) analysis revealed distinct molecular signatures with enhanced peak transmittance, while X-ray diffraction (XRD) indicated greater crystallinity ranging from 36-44.3% in pigmented rice compared with 30-40% in non-pigmented rice, suggesting improved digestibility and processing versatility. Pigmented rice recorded less amylose content hence tended to possess increased adhesiveness values whereas non-pigmented rice revealed greater amylose content hence was coupled with greater hardness values. Field-emission scanning electron microscopy (FE-SEM) images revealed that pigmented rice had densely packed and polygonal starch granules whereas non-pigmented rice had loosely packed starch granules with intergranular voids. Untargeted gas chromatography-mass spectrometry (GC-MS) profiling identified 84 metabolites, including unique compounds such as 3,3-dimethylbutanol and ethanoic acid, along with shared metabolites such as sucrose and linoleic acid, highlighting notable biochemical diversity. Multivariate statistical analyses using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway mapping further differentiated the metabolomic landscapes, with variable importance in the projection (VIP) scores identifying key bioactive contributors. CONCLUSION: Pigmented rice landraces exhibited significant functional and nutritional advantages, making them promising candidates for functional food development and nutritional improvement programs. These findings support their potential role in advancing sustainable and health-oriented food systems. © 2026 Society of Chemical Industry.
When pigmented and non-pigmented rabbit irides were incubated with various concentrations of 14C-imipramine at equilibrium (120 min), the accumulation of the drug by the pigmented iris was 1.5 times as great as that by the non-pigmented iris. The accumulated drug is lost from both types of irides in a complex fashion. However, even after 120 min of washing, the differences in accumulation remain nearly constant. When accumulation of the drug in the non-pigmented iris was analyzed by discontinuous sucrose density gradient, it was observed that the drug was bound mainly by the low density sucrose fractions where the synaptosomes separate. On the contrary, in the pigmented iris approximately 70% of the drug was found in the melanin-containing fraction. The homogenate from the substantia nigra accumulated 1.5 times more than that from the human brain cortex. The affinity of the drug for bovine iris melanin granules and the synthetic L-dopa melanin was 9.9 X 10(5) M-1 and 3.8 X 10(3) M-1, respectively. On the rabbit iris sphincter muscles, imipramine was evaluated for antimuscarinic effects. The apparent dissociation constants, KB values, for the antagonist in the non-pigmented and pigmented iris were 1.7 X 10(-7) M and 3.8 X 10(-6) M, respectively. The low antimuscarinic activity in the pigmented iris is attributed to the loss of the drug to the pigment. On this basis, relevancy of the drug binding by pigmented tissues to the effects of this tricyclic drug is discussed.
Yellow and white mutants of the strains Nocardia pellegrino SN 5108 R have been isolated. Regarding their morphological and physiological properties, the mutants are identical with the wild type bacteria with the exception of their pigmentation and lipid composition. However, the pigment composition (number, Rf-values and spectra of the pigment components) of the yellow mutant is identical with that of the wild type; as a consequence, the modified pigmentation of the yellow mutant cannot be explained by an altered pigment synthesis. The wild type cells and the mutant SN 5108 G contain three main pigment components designated as I, II and III. Components II and III posses a marked indicator character and show a bathochromic shift in solutions of pH 12 or higher. Components II and III contain functional groups which are able to react with acetic acid yielding acetylated products; after acetylating, no bathochromic shift in alkali occurs. Intact cells of the wild type retain their orange-red pigmentation in buffer solution with a pH-value of 12 or higher. Cells of the yellow mutant, however, change the yellow color immediately after the alkali treatment to orange-red; this new color is identical with that of the wild type and can be changed to yellow by placing the cells into 1 N HCl. Regarding these facts it seems to be very probable that the functional groups of the pigment components II and III are differently bound in the wild type and mutant cells. In the mutant, they are accessible to OH- ions yielding a bathochromic shift while in the wild type cells, OH- ions are unable to provoke this shift. It seems to be also probable that different lipids in the two strains are responsible for the binding of the pigments. So far known, this is the first observation about the occurence of pigment mutants with an altered pigment binding site in the cells.
A yellow autofluorescent pigment, generally thought to be indicative of membrane autoxidation, was found to accumulate in the retinal pigment epithelium (RPE) of rats maintained for 32 weeks on diets producing physiological antioxidant deficiency. The largest build-up of fluorescent pigment occurred in rats fed a diet high in polyunsaturated fatty acids (PUFAs) and deficient in alpha-tocopherol (vitamin E), selenium, sulfur-containing amino acids, and chromium. These latter four nutrients have all been implicated in maintaining the antioxidant status of tissues, whereas PUFAs are pro-oxidants. Dietary supplementation with methionine and chromium significantly reduced the amount of fluorescent pigment accumulated in the RPE. Supplementation with all four nutrients further reduced the amount of fluorescent pigment to a very low level. Rats maintained on a normal laboratory diet, relatively low in PUFAs and presumably adequate in other nutrients, accumulated relatively small amounts of fluorescent pigment in the RPE. Of all tissues in the retina and choroid, the autofluorescent pigment was found to be almost entirely restricted to the RPE. The autofluorescence produced in the RPE by antioxidant deficiency was more concentrated than that produced in the testes, kidney, intestine, and heart. This suggests that the RPE is particularly sensitive to physiological antioxidant deficiencies. The increased fluorescent pigment build-up in the RPE of antioxidant-deficient rats appears to correlate with a decreased RPE melanin content. Similar changes in pigmentation have been reported to occur in human RPE with age and in dominantly inherited retinitis pigmentosa. Thus, with respect to its effect on RPE pigmentation, antioxidant deficiency appears to mimic aging and possibly some aspects of one type of retinitis pigmentosa.
Mixed cultures of melanocytes (M) and keratinocytes (K) are easily obtained from pigmented guinea pig ear skin. They are suitable for the study of pigment transfer from M to K. However, quantitation is difficult because many K are already loaded with pigment prior to cultivation. A technique is presented in which pigment-producing M are co-cultured with K of albino origin. Pigmented guinea pig ear skin is split with trypsin and basal cells including M are harvested. The cell suspension is treated with sodium citrate which prevents the attachment of K (but not of M) to the culture substrate. Ninety per cent pure M cultures are obtained. Five to seven days later, another basal cell suspension is prepared, this time from albino ear skin. This second suspension is seeded on top of the pigment-forming culture of M. The number of contacts between albino K and pigment-forming M increases as a direct function of time. Contrarily, the number of K which become pigmented increases until the fifth day of co-culture and decreases thereafter.
Black to brown amorphous to microcrystalline granules are encountered in histologic sections prepared from tissues fixed in formalin having a low pH. This pigment is produced by acid acting upon hemoglobin and is known as formalin pigment or acid hematin. A similar pigment is also observed in sites of bleeding ulcers in areas of acid production such as the stomach. These pigments exhibit many physical and histochemical properties similiar to pigments produced by some animal parasites as in malaria, schistosoma and pulmonary mites. These parasites disintegrate erythrocytes in an unknown manner, and liberate an acid hematin-like pigment which is phagocytized by the reticuloendothelial system. Since formalin pigment can be considered as an artifact, confusion with other pigments can be avoided by the use of neutral buffered formalin for the fixation of tissues.
Changes in the activity of intracellular and extracellular nuclease of pigment and pigment-free strains of Serratia marcescens were studied. The activity of intra- and extracellular nuclease of the pigment-free strain was higher than that of the pigment strain at all growth stages of the microorganism. The activity of intracellular nuclease in the lag-phase was higher than in the phase of exponential growth of both strains. Prior to cell division the enzyme activity declined in both strains. At the beginning of the stationary phase the activity of intracellular nuclease was relatively stable in both strains. By the end of the stationary phase the activity of intracellular nuclease of the pigment-free strain increased 4--6 fold and that of the pigment strain remained unchanged. Simultaneously the activity of extracellular nuclease of the pigment-free strain increased and that of the pigment strain grew but slightly.
Small fragments of the retinal pigmented epithelium from White Leghorn, Rhode Island Red chick embryos, and from Quail, Starling and Red Partridge embryos, were grafted into the wing bud of White Leghorn chick embryos. Retinal pigmented epithelium of White Leghorn chick embryos did not give rise to pigmentation of feather primordia in the hosts. In contrast, 60% of grafts from Rhode Island Red, Quail, Starling and Red Partridge, gave rise to feather primordia whose pigmentation was identical to that of the donors. Pigmentation depends on the fact that some graft retinal melanocytes diffuse in the wing bud of the host and reach the feather primordia. This was shown by the Feulgen technique in embryos grafted with Quail retinal pigmented epithelium, taking advantage of the fact that Quail cells possess DNA rich nucleoli. The local factors which allow the migration of the melanocytes are probably inactive on the retinal melanocytes of the White Leghorn chick embryos, whose genotype does not contain the "feather pigmentation" character.
Histochemical studies were made of pigmented cutaneous lesions from three cases of lepromatous leprosy treated with B663 to determine the nature and histogenesis of the brown pigmentation which develops as a side effect of the drug. One case of DDS-treated leprosy and four cases of untreated leprosy were also investigated histochemically as controls. The brown pigmentation of the skin is due to deposition of a ceroid-like substance in the macrophages, which is a yellowish-brown, acid-fast lipid pigment. It is insoluble in fat solvents and accepts lipid dyes even after lipid extraction by fat solvents. The macrophages in the B663-treated leprosy contain more neutral fat and less phospholipid than the untreated lepromatous leprosy tissues. Ceroid in the macrophages probably originated from unsaturated fatty acids of the leprosy bacilli through oxidation or their binding with the drug. Crystals of the drug were not found in the macrophages in this series, even on the tissues embedded in carbowax or frozen sections.
Besides carotenoids a complex of flexirubin-type pigments was isolated from the gliding bacterium Cytophaga johnsonae Cy jl and separated into 6 components, which partly containe chlorine. In spite of the fact that these components still consist of pigment mixtures, the gross structures of 18 new flexirubin-type pigments could be deduced by spectroscopic and chemical investigations. The results open insights into biosynthesis and structural variety of the flexirubins, the novel non-isoprenoid pigments recently found in Flexibacter elegans.
The iris anlage of 2-10 and 15 days old chicken embryos were studied histochemically, and by both light and electron microscopy. Light microscopic serial sections showed that pigmentation began at the outer layer of the posterior eye pole and progressed from there forwards to the optic cup margin. The entire outer layer of the optic cup as well as the pupillary margin were completely pigmented by the 4th day of incubation. By the 10th day the posterior iris epithelium was totally pigmented. Electron microscopical studies showed that the first premelanosomes appeared at about the 3rd day of incubation in the anterior iris anlage with the exception of the pupillary margin. It could be shown that melanogenesis progressed through the following steps: premelanosomes, followed by tyrosinase activity in a Golgi-associated system of smooth endoplasmic reticulum (GERL) and small vesicles and finally differentiation of the melanosomes. The possible origin of the premelanosomes and the formation of melanin are discussed.
Visual pigment regeneration in the frog requires apposition between the retina and retinal pigment epithelium. However, regeneration occurs nearly as well with the retina upside down (i.e. with the inner limiting membrane facing the pigment epithelium) as right side up.
The normal ultrastructure of the sheep pigment epithelial cells is described as a basis for the interpretation of toxic (sodium iodate) effects on these cells dealt with in two following papers. The morphological features of the different cell membranes and cell organelles, particularly the phagosomes and the lipid droplets, are discussed in relation to renewal of the photoreceptor outer segment, pigment epithelial and retinal metabolism, barrier mechanisms and electrical properties.
A morphological, caryological and biochemical study of two established cell lines of human malignant melanocytes derived from the same original tumour, when compared with heterotransplantation results in nude Mice, showed that "non-pigmented" cells are more tumorigenic than pigmented cells. Differentiation and tumorigenicity, although concomitant, here seem to be two independent phenomena.
The hypothesis that only melanosomal catecholic amino acids contribute to melanin formation was tested by studying adult bovine eyes in which pigment synthesis is considered to be low or absent. Dopa and 5-S-cysteinyldopa were investigated in different cell fractions of the choroid and retinal pigment epithelium of cattle. Most of the dopa and 5-S-cysteinyldopa was found in the cytoplasm and very little in the large granule fraction. The presence of cysteinyldopa in the adult eye is evidence of tyrosinase activity, but the catechol amino acids in the cytoplasm probably do not give rise to melanin formation. It is assumed that they instead are excreted from the cells.
The pigment content of a B800-850 light-harvesting pigment-protein complex isolated from three different stains of Rhodopseudomonas sphaeroides has been determined. In each case the ratio of carotenoid to bacteriochlorophyll present is very nearly 1 : 3 an no specificity with regard to carotenoid type was observed. The fourth derivative of the infra-red absorption bands of the complex was determined and it is concluded that the minimal functional unit of B800-850 complex consists of 1 carotenoid molecule and three bacteriochlorophyll molecules. The data presented here, together with the previous study of Austin, (Austin, L.A. (1976) Ph.D. Thesis, University of California at Berkeley, Lawrence Berkeley Laboratory Report No. LBL 5512) suggest that the 800 nm absorption band represents one of these bacteriochlorophyll molecules while the remaining two bacteriochlorophylls are responsible for the 850 nm band. The absorption spectra and circular dichroism spectra of the complexes suggests that their structure has not been greatly altered during the purification.
Phagocytic activity of histiotypical and organotypical retinal pigment epithelial cells was studied by SEM and EM. After a latent period polystyrene microspheres of different diameter were captured by newly formed microvilli. No mechanism of discrimination according to the size of microspheres was observed. After engulfment, microvilli of histiotypical cells decreased in length and finally disappeared. Lysosomes increased in number when compared to unstimulated cells and fused with many latex-containing phagosomes. Colchicine, when added at 5 X 10(-5) M to the medium, inhibits phagosome-lysome interaction, thus confirming in vivo observations.