Pigmentation in Anuran Testes: Anatomical Pattern and Variation

In amphibians, pigmented cells are present in several organs, composing an extracutaneous pigmentary system. Seventeen species from two families were studied to develop a protocol for pigmentary classification. The amount and distribution of these cells are variable, allowing the establishment of anatomical patterns for visceral pigmentation in anuran testes. Anat Rec 2009. © 2008 Wiley‐Liss, Inc.     

Visceral Pigmentation in Three Species of the Genus Scinax (Anura: Hylidae): Distinct Morphological Pattern

Amphibians share with other ectothermic vertebrates an extracutaneous pigmentary system consisting of melanin‐containing cells in various organs and tissues. We describe the interspecific variation in the visceral pigmentation in three anuran species (Scinax similis, S. fuscovarius, and S. fuscomarginatus). We analyzed the visceral pigmentation of 15 adult males from each species during the reproductive period. The individuals were weighed and measured, and the pigmented visceral cells were classified and documented in stereomicroscope. The shape and amount of pigment cells differed among organs and also among species. Significant differences were detected in the cardiorespiratory system, digestory system, urogenital system, and lumbosacral peritoneum. In the urogenital system, the main difference was observed in the testes, in which only S. fuscomarginatus had varying degrees of pigmentation. Anat Rec, 2012. © 2011 Wiley Periodicals, Inc.     

Ultrastructural evidence of cell communication between epithelial dark cells and melanocytes in vestibular organs of the human inner ear

Background: The possibility of interaction between epithelial dark cells and melanocytes in the mammalian inner ear has been pointed out because of their morphological and biochemical characteristics, although very few studies have dealt directly with communication between these two types of cells. We investigated the dark cell area of human vestibular organs in order to clarify the ultrastructual evidence for cell interaction between epithelial dark cells and melanocytes. Methods: All of the material was obtained from vestibular schwannoma operations. Paraffin sections were stained with hematoxylin and eosin (H&E) and by the Fontana-Masson technique. Other paraffin sections were also stained immunohistochemically for S-100 protein. Glutaraldehyde fixed specimens were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results: Light microscopy revealed melanin pigment granules in the cytoplasm of epithelial dark cells. Melanocytes in the subepithelial layer stained positively for S-100 protein. The presence of intraepithelial melanocytes was confirmed by the presence of cell profiles with a large number of melanin pigment granules and S-100 protein in the cytoplasm. SEM showed that the dark cells had a pentagonal surface with microvilli on the apical surface edge. They had complicated structures at the basal portion of their cytoplasm. Melanocytes extending cytoplasmic processes to adjacent areas were observed under the dark cells. TEM showed that the dark cells were tightly linked by junctional complexes in the upper lateral portion of their cytoplasmic membrane and interdigitated by lateral infoldings. Compound melanosomes (phagosomes or secondary lysosomes) found in the cytoplasm of the dark cells contained poorly pigmented melanosomes with a periodic internal structure. Gap junctions were clearly showed between adjacent melanocytes in the subepithelial layer. Conclusions: The characteristic substructures of dark cells and melanocytes suggested the presence of intimate cell interaction between these two types of cells in the vestibular organs of the human inner ear, although it is not clear at this stage whether such cell interaction is specific only for patients with vestibular schwannoma. Dark cells and melanocytes form a cell community that serves to maintain homeostasis in vestibular organs through communication in which cell information obtained by both dark cells and melanocytes serves to facilitate the system. © 1995 Wiley-Liss, Inc.     

Pigmented myomatous neurocristoma of the uterus

A tumor of the myometrium composed of pigmented and nonpigmented melanocytes in a matrix of altered smooth-muscle cells is reported. Electron microscopy and immunohistochemical studies were used to identify the cellular constituents. The neurocristic components were arranged in patterns comparable with those in cellular blue nevus of the skin. Problems relating to histogenesis and to taxonomy are addressed using neurocristic dysplasias of the skin as models. It is believed that melanin production should not be the only criterion used to classify pigmented neurocristic dysplasias arising in extracutaneous mesenchyme. The designation pigmented myomatous neurocristoma is proposed as a suitable alternative to cellular blue nevus To our knowledge, no similar lesion has been reported previously.     

Blue nevus of the uterine cervix: description of a case and review of the literature

Blue nevus is a pigmented lesion of dermal melanocytes; the extracutaneous locations are uncommon. We report a case of a blue nevus of the uterine cervix in a 53 years old woman, with histochemical and immunohistochemical investigations.     

Changes of melanosome morphology associated with the differentiation of epidermal melanocytes in slaty mice

The slaty (Dct^slt) mutation is known to reduce the activity of dopachrome tautomerase, which converts dopachrome to 5,6‐dihydroxyindole‐2‐carboxylic acid in the pathway of eumelanin synthesis and to inhibit melanosome maturation in melanocytes. However, it is not known whether the inhibition of melanosome maturation in slaty melanocytes is developmentally regulated. To address this point, changes in the morphology and maturation of melanosomes in cultured epidermal melanocytes derived from newborn mice of wild‐type (black) and slaty mutant were surveyed under the electron microscope. In black melanocytes (Dct⁺), almost all melanosomes were elliptical stage IV melanosomes. However, in slaty melanocytes, numerous spherical stage III melanosomes with globular depositions of pigment in addition to elliptical stage III melanosomes with intraluminal fibrils were observed. Mixed‐type melanosomes containing both globular deposition and intraluminal fibrils of pigment were also observed. In slaty melanocytes, spherical and mixed‐type melanosomes were gradually decreased after birth, whereas elliptical melanosomes were gradually increased. Stage IV melanosomes were very few in slaty melanocytes, and the number did not increase after birth. These results suggest that the slaty mutation blocks the melanosome maturation at stage III and affects the melanosome morphology (elliptical or spherical) in a developmental stage‐specific manner. Anat Rec, 2007. © 2007 Wiley‐Liss, Inc.     

Pigmented mucoepidermoid carcinoma of the oral cavity: a case report

Melanocytes are normally present in the oral mucosa, but unlike the skin, melanocytic colonization and pigmentation of nonmelanocytic tumors rarely occur. A case of pigmented mucoepidermoid carcinoma (MEC) in a 36-year-old woman is reported. On H&E-stained sections, brownish granules were seen in intermediate and epidermoid neoplastic elements and in elongated or dendritic cells showing histologic and immunohistochemical features of melanocytes. Ultrastructurally numerous epithelial cells contained large aggregates of melanin granules, a feature suggestive of phagocytosis. In addition small individual melanin granules were observed at the external border of the epithelial cell membrane. These features suggest that melanocytes colonized the MEC and that neoplastic cells may phagocytose the granules, similarly to what occurs with epidermal melanocytes. The phenomenon of melanocyte colonization of nonmelanocytic tumors should be taken into consideration in dealing with pigmented lesions of the oral cavity.     

Pigmentary mosaicism of the hyperpigmented type in two half‐brothers

Pigmentary mosaicism is a heterogeneous cutaneous phenotype that is often associated with extracutaneous anomalies. It is widely accepted that these phenotypes arise de novo as a result of a postzygotic mutation, leading to a mosaic status of the embryo. In the vast majority of cases, the occurrence of pigmentary mosaicism is sporadic. We report two paternal half‐brothers affected with pigmentary mosaicism of the hyperpigmented type. The hyperpigmentation in both patients is distributed along the lines of Blaschko. In addition, mental retardation, facial asymmetry, short stature, scoliosis, and short fingers with clinodactyly of the 5th digit were noted in one of them. Chromosome analysis in this 15‐year‐old patient demonstrated a mosaic 46,XY,dup(3)(p21.3;pter)/46,XY with 12% aberrant cells in lymphocytes and 2% in skin fibroblasts derived from a hyperpigmented area. His nine‐year‐old half‐brother had similar systematized hyperpigmented skin lesions, macrocephaly, facial asymmetry, and clinodactyly of the 5th digit. Chromosome analysis of peripheral lymphocytes showed a normal karyotype 46,XY. A skin biopsy could not be obtained. So far, some familial cases of hypopigmentation along the lines of Blaschko have been reported, but familial occurrence of the hyperpigmented type of pigmentary mosaicism appears to be extremely unusual. It is difficult to establish a causal relationship with the chromosomal mosaicism as observed in patient 1. Paradominant transmission seems unlikely because this would likewise imply that the chromosomal mosaicism is an incidental finding. © 2002 Wiley‐Liss, Inc.     

Pigmented human skin equivalent—as a model of the mechanisms of control of cell-cell and cell-matrix interactions

The melanin pigment system in human skin is extraordinarly well developed and assures the photoprotection of the skin against harmful solar radiation. Specific cell-cell interactions between one melanocytes and keratinocytes play a fundamental role in the regulation of melanogenesis and melanin pigementation, the two key elements of this system, giving rise to the concept of a structural, functional collaborative ‘epidermal melanin unit,’ Early experiments strongly suggested that melanocyte growth and differentiation are regulated by paracrine factors from keratinocytes and other skin cells. In addition, co-culture studies with keratinocytes has shown that the extracellular matrix acts as a local environmental signal for dendrite formation and melanogenesis. Attempts to reconstruct pigmented human skin in vitro have made great progress over the last decade. The behavior of cells in these pigmented human skin equivalents closely resembles that in vivo, and the cells can still respond to appropriate extrinsic regulatory stimuli such as ultraviolet radiation. Keratinocytes and fibroblasts have been shown to be active partners in the regulation of melanocyte distribution, viability and other differentiation functions, presumably by direct contact and the effects of various soluble paracrine factors. By reproducing cell-cell and cell-matrix interactions, these culture systems provide a promising experimental model for investigating regulation of the skin pigmentary system and the role of photoprotection against harmful solar radiation.     

Epitheloidzellige und hyperpigmentierte melanozytäre Tumoren

Spindle cell and epithelioid cell differentiation occur in both benign and malignant hyperpigmented melanocytic lesions. Reed nevus is characterized by compact, sharply circumscribed junctional cellular nests composed of slender hyperpigmented melanocytes shaped like spindle cells. Deep penetrating nevus is characterized by a diffuse dermal proliferation composed of small nests and fascicles of pale ovoid and epithelioid melanocytes. Cellular blue nevi often have a characteristic hourglass or dumbbell shape, with sharply circumscribed elongated nests and fascicles of pale, densely layered ovoid melanocytes and adjacent melanophages. Epithelioid blue nevus is characterized by large epithelioid melanocytes with abundant cytoplasm and melanin often concentrated to some degree in the cell membrane. Animal-type melanoma is a particularly hyperpigmented variant of melanoma in which large melanophages predominate and there are varying proportions of melamin-rich spindle-shaped and large atypical epithelioid melanocytes. Morphologically, pigmented epithelioid melanocytoma combines characteristics of both animal-type melanoma and pigmented epithelioid nevus. Malignant melanoma may occur in conjunction with a preexistent blue nevus. Malignant blue nevus is now regarded as a malignant melanoma mimicking a blue nevus in structure and pattern. It is therefore of paramount importance to view multiple mitoses within a cellular blue nevus-like proliferation as an alarm signal as they are usually indicators of a malignant melanoma.     

Normal distribution of melanocytes in the mouse heart

We report the consistent distribution of a population of pigmented trp-1-positive cells in several important septal and valvular structures of the normal mouse (C57BL/6) heart. The pigmented cell population was first apparent by E16.5 p.c. in the right atrial wall and extended into the atrium along the interatrial septum. By E17.5, these cells were found along the apical membranous interventricular septum near or below the surface of the endocardium. The most striking distribution of dark pigmented cells was found in the tricuspid and mitral valvular leaflets and chordae tendineae. The normal distribution of pigmented cells in the valvuloseptal apparatus of C57BL/6 adult heart suggests that a premelanocytic lineage may participate in the earlier morphogenesis of the valve leaflets and chordae tendineae. The origin of the premelanocyte lineage is currently unknown. The most likely candidate populations include the neural crest and the epicardially derived cells. The only cell type in the heart previously shown to form melanocytes is the neural crest. The presence of neural crest cells, but not melanocytes, in some of the regions we describe has been reported by others. However, previous reports have not shown a contribution of melanocytes or neural crest derivatives to the atrioventricular valve leaflets or chordae tendineae in mouse hearts. If these cells are of neural crest origin, it would suggest a possibly greater contribution and persistence of neural crest cells to the valvuloseptal apparatus than has been previously understood.     

Morphology of melanocytes in hair bulbs and eyes of vitiligo mice.

The vitiligo mouse C57BL/6J Ler-vit/vit is a new, murine model for vitiligo in humans. It was studied with respect to morphology and fine structure of melanocytes in hair and eyes before and during depigmentation. The coat of vitiligo mice lightens progressively with age because of an increase in the ratio of white to pigmented hairs with each molt. The bulbs of white hairs are devoid of pigment, and they lack melanocytes. In other respects the epithelium is morphologically normal as determined by light and electron microscopy. The bulbs of pigmented hairs are histologically normal. By electron microscopy, however, some of the melanocytes are shown to have undergone degenerative changes. In addition, disruption of the basement membrane underlying the melanocytes and herniation of melanocytes into dermal papillae were observed at various stages of hair growth. Papillary melanophages are prominent in pigmented as well as in white hair bulbs. Newborn vitiligo mice have no uveal pigment. Pigment appears in the iris and ciliary body by Day 4 and in the choroid by Week 3. On Day 4, along with pigmentation, conspicuous spherical amelanotic cells appear over the anterior border of the iris. These cells become numerous in the ensuing weeks and gradually acquire large melanophagosomes. They occur also in the stroma of the iris and the ciliary body, associated with necrotic melanocytes. The spherical cells are identical to the clump cells of Koganei and are far more numerous in vitiligo mice than in controls. Macroscopically, no progressive decrease in iridial pigment is apparent for the life of the vitiligo mouse. In the choroid, an amelanotic patch surrounds the optic nerve. In the pigmented areas, melanocytes show compartmentalization of melanosomes and degeneration. The retinal pigment epithelium generally appeared continuous. In older animals some epithelial cells contained large fat bodies or were devoid of melanin.     

Ultrastructure of melanocytes in the dark cell area of human vestibular organs: Functional implications of gap junctions,isolated cilia,and annulate lamellae

Background: It is known that melanocytes exist in almost all parts of the inner ear, such as the cochlear duct, stria vascularis, Reissner's membrane, modiolus, vestibular organs in the region surrounding the cristae and maculae, semicircular canals, and pars rugosa of the endolymphatic sac. But there have been few studies using human materials, because of the difficulty of obtaining materials. We attempted to investigate the detailed ultrastructure of melanocytes in the vestibular organs of human inner ear. Methods: Eight surgical specimens obtained from patients with vestibular schwannoma were studied by light microscopy and electron microscopy. Results: Melanocytes were found in the subepithelial layer of the dark cell area. Melanocytes had round or spindle-shaped nuclei and clear cytoplasm with brown pigment granules. Besides melanocytes, there were melanophages, fibroblasts, and small blood vessels. Through electron microscopy we found melanocytes with round-shaped melanosomes in various stages of pigmentation, well-developed Golgi apparatus and endoplasmic reticulum in the cytoplasm, and many cytoplasmic processes. Gap junctions were occasionally found between the cytoplasmic processes. And there were pinocytotic vesicles just under the limiting membrane of melanocytes, and intermediate filaments were abundant in the cytoplasm. Isolated cilia of melanocytes, annulate lamellae, and fusiform banded structures in the connective tissue area around melanocytes were found. Conclusions: Melanocytes in human vestibular organs actively synthesize melanosomes. Frequent findings of isoalted cilia and fusiform banded structures and the incidental existence of annulate lamellae may be an indicator of this metabolically activated state of melanocytes. Moreover, monitoring environmental changes by isolated cilia, melanocytes in the human inner ear could act not only as one cell but also as a group to achieve their physiological functions by means of information transmission through gap junctions. © 1994 Wiley-Liss, Inc.     

The presence of stage II melanosomes (premelanosomes) in neoplasms other than melanomas

Aside from melanomas, other nonmelanocytic pigmented tumors synthesize melanin or contain benign passenger melanocytes. While Stage IV melanosomes (mature melanosomes) occur in neoplasms which synthesize melanin as well as in those with benign companion melanocytes, Stage II melanosomes (premelanosomes), which are found in melanocytes and cells of pigmented nonmelanocytic tumors of neural crest origin, are considered the morphologic hallmark of in vivo melanin synthesis. To test this widely held concept, we studied the ultrastructure of representative malignant melanomas and other pigmented tumors (pigmented variants of the nevocellular nevus, squamous cell carcinoma, schwannoma, basal cell carcinoma, and seborrheic keratosis). Discrete intracytoplasmic Stage II melanosomes were noted in neoplastic cells of tumors of neural crest origin (melanoma, schwannoma, and nevocellular nevus), which are widely believed to synthesize melanin. In addition, they were also detected in neoplastic epithelial cells of a squamous cell carcinoma, basal cell carcinoma, and seborrheic keratosis. In these epithelial tumors, a spectrum of melanosomes from Stage II through Stage IV were presumably acquired from nonneoplastic companion melanocytes, which were an integral part of the tumor. Because squamous epithelium has not been shown to synthesize melanin, this study suggests that the finding of intracytoplasmic Stage II melanosomes does not necessarily imply melanin synthesis. When accompanied by melanocytes, epithelial and perhaps other tumors may contain ingested Stage II melanosomes.     

Morphologic features of melanocytes, pigmented keratinocytes, and melanophages by in vivo confocal scanning laser microscopy.

Confocal scanning laser microscopy (CSLM) represents a novel imaging technique for in vivo microscopic analysis of skin lesions at a level of resolution that allows morphologic analysis of microanatomic structures. We investigated the feasibility of recognizing the cellular constituents of pigmented skin lesions, such as pigmented keratinocytes, melanocytes, and melanophages, by CSLM. Fifteen pigmented lesions (five pigmented seborrheic keratoses, and 10 compound melanocytic nevi) from 15 patients were studied, as well as normal skin. After the clinical lesions were imaged by CSLM, they were biopsied or excised for examination by conventional histology for comparison of the morphologic features. In images obtained by CSLM, pigmented keratinocytes were seen as polygonal cohesive cells with variably bright granular cytoplasm. Melanocytes appeared as bright round, oval, fusiform, or dendritic cells. The architectural growth pattern of melanocytes could be analyzed. Melanocytes were identified by their nested growth pattern as aggregates of bright round to oval structures at the dermoepidermal junction or in the superficial dermis. Melanocytes were also recognizable as single cells along the dermoepidermal junction, usually separated from each other by a variable number of keratinocytes. Melanophages appeared as large bright plump cells with ill-defined cytoplasmic borders, usually located around or near vessels of the superficial dermis. Our results demonstrate that the cellular constituents of pigmented lesions can be recognized by CSLM. This technique sets a new paradigm for noninvasive quasihistologic examination of pigmented lesions in vivo and merits further evaluation for diagnostic use.     

Human Prostate DU145 Carcinoma Cells Implanted in Nude Mice Remove the Peritoneal Mesothelium to Invade and Grow as Carcinomas

Implanted human, androgen‐independent prostatic carcinoma cells (DU145) into athymic (NCr nu/nu) mice produce diverse tumors on the peritoneal surfaces of many organs. Light and ultrastructural observations show that the mesothelial covering these surfaces are typically microvilli‐coated, squamous cells or secretory cuboidal cells. The peritoneal regions colonized by tumors lack mesothelial cells and are covered by actively replicating carcinoma cells that grow as poorly differentiated cell clusters made of cell aggregates to somewhat compact spheroids covered with pleiomorphic microvilli and containing an undifferentiated vascular supply. These xenografts clusters invade the diaphragm and develop into tumors with both a basal solid aspect and an upper region of cribriform morphology. Furthermore, each tumor contains two cell types: (1) a poorly differentiated clear cell type, which grows into intraperitoneal tumors and (2) a large, basophilic cell type, which invades the peritoneal stroma of organs, including of the diaphragm. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.     

Enteroantigen (eAg)‐binding B lymphocytes in the mouse – phenotype,distribution, function and eAg‐specific antibody secretion

Studies reporting beneficial effects of B lymphocytes in autoimmune diseases have been accumulating and a regulatory role for certain B cell subsets is hence getting more and more recognition. Recently, B cells were shown to exhibit a regulatory effect in a T cell transfer model of colitis. Here, B cells exposed to enteroantigen (eAg) ex vivo abrogated the colitogenic effect if co‐transplanted with Treg‐depleted (CD4+CD25?) T cells into severe combined immune deficiency (SCID) mice. These data may imply a role for B cells that bind eAg (eAg+ B cells) in the immunopathology of colitis. Here, we report the detection of a subset of eAg+ B cells, including both B2 and B1 lineages, and show that these cells are present in all peripheral lymphoid organs of the mouse including the peritoneal cavity. eAg+ B cells are far more efficient as eAg‐presenting cells than unfractionated splenocytes or eAg? B cells in causing proliferation of eAg‐specific T cells. In comparison with eAg? B cells, eAg+ B cells secrete a significant amount of IL‐10 in vitro, suggesting an anti‐inflammatory potential. Compared with wild‐type B cells, B cell receptor (BCR) transgenic, hen egg lysozyme‐specific B cells show inferior eAg binding and T cell stimulatory activity suggesting involvement of the BCR in eAg binding and processing. After activation of CD19⁺ B cells by eAg and hybridization with hypoxanthine‐aminopterin‐thymidine (HAT) sensitive ×63 lymphoma cells followed by cloning at limiting dilution conditions, around 10% of the hybridoma cells secrete eAg‐specific antibodies.     

High expression of Mcl‐1L via the MEK‐ERK‐phospho‐STAT3 (Ser727) pathway protects melanocytes and melanoma from UVB‐induced apoptosis

Ultraviolet (UV) B is a major factor in melanomagenesis. This fact is linked to the resistance of melanocytes to UVB‐induced apoptosis. In this study, we characterized the involvement of Mcl‐1L in the regulation of UVB‐induced apoptosis in melanocytes and in melanoma cells. In melanocytes, apoptosis was not evident at 24 h after UVB irradiation. The Mcl‐1L expression increased after UVB irradiation, and the high Mcl‐1L expression continued for at least 24 h. This UVB‐dependent increase in Mcl‐1L was mediated by the MEK‐ERK‐pS‐STAT3 (STAT3 phosphorylated at Ser727) pathway. The Ser727 phosphorylation facilitated nuclear localization of STAT3. In melanoma cells, the expression levels of Mcl‐1L varied depending on the cell line. WM39 melanoma cells expressed high levels of Mcl‐1L via the MEK‐ERK‐pS‐STAT3 pathway and were resistant to UVB‐induced apoptosis without up‐regulation of Mcl‐1L. In melanocytes and in WM39 cells, transfection with Mcl‐1 siRNA promoted UVB‐induced apoptosis. Immunohistochemical studies showed that melanoma cells in in situ lesions expressed high amounts of Mcl‐1L. These results indicate that the high expression of Mcl‐1L mediated by the MEK‐ERK‐pS‐STAT3 pathway protects melanocytes and melanoma cells from UVB‐induced apoptosis.