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R E Boissy

Publications and source records attributed to R E Boissy.

At least 73 records · Page 4Linked to original sources
PubMed1989

Separation of pigmented and albino melanocytes and the concomitant evaluation of endogenous peroxide content using flow cytometry.

Flow cytometry (FCM) has been used extensively to analyze various biological properties of the cell. In this report, we describe a method by which FCM was used to determine the light scattering profile of a mixed population of pigmented and non-pigmented melanocytes, plus its subsequent use for the sorting and separation of the two cell types. In addition, the relative peroxide content in pigmented and non-pigmented melanocytes was compared by flow cytometry. Cultured avian melanocytes from a pigmented control and from three genetically distinct albino sources were studied. FCM analysis of forward versus side light scatter within a mixed suspension of pigmented and amelanotic melanocytes distinguished two overlapping populations of cells. Sorting of these two populations demonstrated that the population exhibiting much side and minimal forward light scatter was primarily pigmented melanocytes, while conversely the population exhibiting less side and more forward scatter was principally non-pigmented cells. These two melanocyte types also demonstrated differences in levels of endogenous peroxides. The intracellular content of peroxide in the two subpopulations of cells was measured utilizing the nonfluorescent compound, 2',7'-dichlorofluorescein diacetate (DCFH-DA), which within the cell is oxidized by intracellular peroxides to a fluorescent dichlorofluorescein (DCF). Non-pigmented albino melanocytes had the highest quantity of endogenous peroxides, while heavily pigmented cells had considerably less peroxide-related fluorescence. The amount of this DCF fluorescence could be enhanced by increasing concentrations of DCF used in the assay. These flow cytometric methods are useful for isolating and culturing subpopulations of melanocytes expressing various pigment levels and to investigate the relationship between melanin and its precursors with hydrogen and lipid peroxides in melanocytes.

Animals↗
PubMed1988

Alteration of the Cloudman melanoma cell cycle by prostaglandins E1 and E2 determined by using a 5-bromo-2'-deoxyuridine method of DNA analysis.

Prostaglandins (PGs) E1 and E2 stimulate tyrosinase activity and suppress the proliferation of Cloudman S91 melanoma cells by altering their progression through the cell cycle. Prostaglandin E1 and PGE2 have prolonged or residual effects on melanoma cells. Cells treated for 5 or 24 hours with 10 micrograms/ml PGE1 or cells treated for 8 or 24 hours with 10 micrograms/ml PGE2 demonstrated decreased proliferation and increased tyrosinase activity for 48 hours after removal of the PGs. The effects of PGs on the cell cycle were investigated by determining total DNA content in cells stained with propidium iodide (PI) and analyzed by a fluorescence activated cell sorter (FACS). Prostaglandin E1 blocked cells in G2 phase after 5 hours of treatment, corresponding to when inhibition of proliferation was first evident. Similarly, after 9 hours of treatment with PGE2, more cells were in late S, early G2 phase and less in G1 than their control counterparts. Also, melanoma cells were pulse-labeled with 5-bromo-2'-deoxyuridine (BrdUrd) prior to or at the end of PG treatment and then stained with a fluoresceinated monoclonal antibody to BrdUrd, and with PI. This allows one to observe how BrdUrd-labeled S-phase cells cycle with time. Both PGE1 and PGE2 inhibit proliferation by blocking cells in G2 phase of the cell cycle. The PG-induced block in G2 may be required by melanoma cells to synthesize mRNA and proteins that are essential for stimulation of tyrosinase activity. Ultrastructurally, only a subpopulation of the cells treated with PGE1 or PGE2 contained more mature melanosomes than control cells.

Alprostadil↗
PubMed1988

Ocular pathology in the minimally depigmented subline of the vitiliginous Smyth chicken.

Choroidal melanocytes and the retinal pigmented epithelium (RPE) were studied morphologically and histochemically in the Smyth chicken, an avian model for human vitiligo. The sequence of cytological events occurring in the ocular tissue of minimally depigmented Smyth birds was determined. Abnormalities of melanocytes and the associated inflammation was least severe in peripheral areas of the choroid and most pronounced in the back of the eye at the base of the optic nerve head. In the peripheral choroid, morphologically normal melanocytes and an occasional mononuclear leukocyte were observed. However, some of these morphologically normal melanocytes histochemically demonstrated atypical tyrosinase activity at the trans area of the Golgi apparatus. Toward the back of the eye, the melanocytes first appeared swollen and had retracting dendrites. Ultrastructurally these melanocytes demonstrated an increase in extramelanosomal cytoplasm. Later, melanocytes became spherical and had membrane bound, autophagosome-like compartments of pigment granules. As the melanocyte injury progressed, macrophages invaded the tissue and phagocytized melanocytic dendrites. These were followed by numerous plasma cells. Eventually, the back of the eye contained no pigment and was infiltrated with numerous mononuclear inflammatory cells. The retinal pigment epithelium also demonstrated a gradient in the degree of destruction, related to its topography. These cytological features consisted of the retraction of apical RPE processes, the disappearance of the basal plasma membrane infoldings, and the replacement of Bruch's membrane by collagen-like fibrils. These results demonstrate that the uveitis which develops in vitiligo appears to be a consequence of an inherent choroidal melanocyte defect.

Animals↗
PubMed1988

Animal models of an acquired pigmentary disorder--vitiligo.

Vitiligo appears to be a complex disorder that involves a melanocyte dysfunction and/or an autoimmune response. Further investigations of the animal models described in this report, and the less well-studied models that exist, is needed to clarify the mechanisms of this disorder. Three additional animal lines which appear potentially to be excellent animal models for vitiligo are: the Barred Plymouth Rock chicken which exhibits periodic degenerating melanocytes presumably due to a cytotoxic agent (Bowers et al, 1986), the White Leghorn chicken which exhibits preprogrammed melanocyte autophagocytosis (Jimbow et al, 1974), and the Duroc pig which exhibits spontaneous tumor regression and depigmentation (Hordinsky, personal communication). These numerous animal studies must be undertaken with the understanding that the specific etiologies and characteristics differ among these animal models and that each model represents only a facet of the complex condition, vitiligo. To unravel the complexity of this syndrome, the insightful correlation of the results of many investigators working with multiple model systems is required.

Animals↗
PubMed1988

The melanocyte. Its structure, function, and subpopulations in skin, eyes, and hair.

I would like to stress that there seem to be three subpopulations of neural crest-derived melanocytes in the body that can be functionally and morphologically distinguished: the cutaneous melanocytes, which continuously synthesize small melanosomes to be transferred to keratinocytes; the uveal melanocytes, which synthesize larger melanosomes for only a short while to be retained by this melanogenically dormant cell; and the hair melanocyte, which intermittently produces melanin either in a cyclic manner or as a periodic supply from a stem population. These three types of melanocytes synthesize melanin granules by an identical bipartite system. However, the control mechanism regulating the specific differentiation and postmelanin synthesis function of these cell types needs to be addressed in future research.

Hair↗
PubMed1987

Tyrosinase and acid phosphatase activities in melanocytes from avian albinos.

Two forms of cutaneous albinism in the chicken were investigated for the presence and distribution of tyrosinase and acid phosphatase in melanocytes in situ and in culture. In sex-linked recessive tyrosinase-positive albinism, sal, melanocytes in regenerating feathers and neural tube-derived cultures contained morphologically normal and abnormal premelanosomes. Tyrosinase was localized primarily to the abnormal premelanosomes and probably not to the normal ones. The cells possessed, in addition, vacuoles with membranous inclusions, located in the dendrites, and capped by dopa-positive vesicles (capping vesicles). Acid phosphatase colocalized with tyrosinase in the abnormal premelanosomes and capping vesicles. Tyrosinase activity in extracts of cultured sal melanocytes equalled that of e+ control melanocytes. A tyrosinase antiserum, raised against hamster tyrosinase (Pomerantz), precipitated 2 proteins, 68 kD and 82 kD, which had a precursor-product relationship. The amount of immunoprecipitate was the same in sal and control extracts, but in sal extracts the lower-molecular-weight protein was twice as abundant as the higher-molecular-weight protein. Melanocytes in regenerating feathers from an autosomal recessive, tyrosinase-negative albino, ca, also contained morphologically normal and abnormal premelanosomes. In culture, ca melanocytes had no formal premelanosomes but only dopa-negative multivesicular bodies with wispy filamentous material. Tyrosinase activity and immunoprecipitable tyrosinase were absent. These results suggest that: the tyrosinase-positive albino, sal, has an aberration in both its tyrosinase and acid phosphatase profiles and the tyrosinase-negative albino, ca, lacks functionally and antigenically normal tyrosinase.

Acid Phosphatase↗
PubMed1987

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.

Animals↗
PubMed1986

Delayed-amelanotic (DAM or Smyth) chicken: melanocyte dysfunction in vivo and in vitro.

Chickens of the autoimmune delayed-amelanotic (DAM or Smyth) line develop postnatal feather amelanosis and severe visual defects, both of which are presumed to be due to a dysfunction of melanocytes and a subsequent autoimmune response that eliminates pigment cells. In this report we elucidate further the melanocytic defect. We present a morphologic analysis of the mildly affected erratic (eDAM) group of Smyth chicken whose partial depigmentation and lack of visual impairment resemble human vitiligo more so than do the complete amelanosis and blindness in the classical Smyth line. Histologically, the sequential events leading to amelanosis in the young Smyth chicken occur simultaneously in the feathers of adult eDAM Smyth chickens, and the infiltration of the feather pulp with mononuclear leukocytes correlates with the extent of local pigmentary abnormality. Cytochemical localizations of dopa-oxidase and acid-phosphatase activities in eDAM feather melanocytes suggest that melanogenesis and autophagocytosis of melanosomes occur in tandem and that the rates of both are higher in these cells than in melanocytes of normally pigmented control chickens. Assays for tyrosinase activity in feather follicles indicate a hypermelanization in eDAM feathers and in the pigmented feathers of young Smyth chicks prior to the onset of depigmentation. Finally, we report on the establishment of pure, proliferative cultures of neural crest-derived melanocytes from control and Smyth chicken embryos. The degenerative events in Smyth chicken melanocyte cultures mimic in part those of the cells in vivo and are therefore indicative of a genetic defect that is independent of the immune system.

Animals↗
PubMed1986

A mouse model for vitiligo.

As the result of a long search for a depigmenting mouse that could serve as a model for the study of vitiligo, we have located a strain that arose from the C57BL/6J. Its provisional genetic designation is C57BL/6J Ler-vit/vit. This vitiligo mouse has congenital dorsal and ventral white spots (piebaldism) as well as progressive replacement of pigmented hairs by white hairs with each spontaneous molt or after plucking. The lack of pigment is due to the absence of melanocytes from the amelanotic hair follicles and epidermis. As in human beings and the Smyth chicken model, there is also diminution of ocular pigment. Reciprocal skin transplants between C57BL/6J and vitiligo mice, and transplants into nude mice, suggest a programmed pigment cell death in the vitiligo mice. Like human beings with vitiligo, maximally depigmented vitiligo mice have a decreased contact sensitivity response in comparison to age-matched C57BL/6J controls. The resistance to injected B16 melanomas is lowered. Vitiligo mice show no signs of premature aging. Already at this early stage in the study of this new animal model, there are findings that open a range of new approaches to the study and treatment of patients with vitiligo and melanomas.

Animals↗
PubMed1985

Establishment of proliferative, pure cultures of pigmented chicken melanocytes from neural tubes.

In order to obtain pure cultures of chicken melanocytes, neural tubes were excised from 22-somite stage embryos and placed in culture dishes to allow melanoblasts to migrate out and proliferate. The growth of contaminating cells was inhibited by maintaining the primary cultures in low-calcium and low-magnesium medium supplemented with 32 nM 12-O-tetradecanoylphorbol-13-acetate (TPA). Subsequently the pure cultures of melanocytes were maintained in Ham's F-10 medium supplemented with TPA. The population doubling time was approximately 12 h. The cell density at confluency in medium containing 32 nM TPA, 80 nM TPA, or 32 nM TPA plus 1 nM cholera toxin was 3.4, 5.6, or 8.3 X 10(4) cells/cm2, respectively. The melanocytes were highly pigmented and had tyrosinase activities ranging from 0.7-5.0 mU/mg protein.

Animals↗
PubMed1984

Persistence of abnormal melanocytes in immunosuppressed chickens of the autoimmune "DAM" line.

The delayed amelanotic (DAM) line of chickens (Gallus gallus) is characterized by the postnatal elimination of melanocytes from regenerating feathers and from the choroid. The process of elimination is accompanied by a massive infiltration of mononuclear leukocytes (MNL) into the supporting connective tissues. When surgically bursectomized at day of hatching, chickens from this lineage develop significantly less amelanosis of the feathers. We report here a histological analysis of regenerating feathers and choroids from bursectomized birds that maintained their plumage pigmentation. In the feathers we observed the presence of morphologically abnormal melanocytes in the absence of MNL infiltration. Choroids also contained abnormal melanocytes without MNL infiltration; however, we observed a few cases of amelanotic choroids with a few MNL. These findings indicate that melanocytes of pigmented birds are morphologically abnormal even in the absence of a bursa and in the absence of leukocytic infiltrates into regenerating feathers and possibly into the choroids. We conclude from these findings that the amelanosis in unbursectomized DAM birds is due to the response of the immune system to an abnormality in the melanocytes which, by itself, does not lead to depigmentation.

Animals↗
PubMed1983

Progressive cytologic changes during the development of delayed feather amelanosis and associated choroidal defects in the DAM chicken line. A vitiligo model.

Newly hatched Gallus domesticus chicks of the delayed amelanotic (DAM) line have phenotypically normal down pigmentation. Functioning pigment cells are present in the down plumage, choroid, and retinal pigment epithelium. However, histologic and ultrastructural studies reveal that after hatching regenerating feather melanocytes synthesize melanosomes with abnormal, irregularly shaped surfaces and pigmented extensions. Eventually retraction of melanocytic dendrites and clumping of pigment occurs concomitantly with intracellular compartmentalization of the abnormal melanosomes. Melanocyte degeneration is accompanied by the appearance of mononuclear leukocytes (MNLs) in the pulp of the regenerating feathers. Concurrently, melanocytes cease to migrate into the regenerating feather epithelium, and the result is amelanosis. Changes in choroidal melanocytes are first evident as swelling of cell bodies and associated dendrites. Ultrastructurally, the choroidal melanocytes demonstrate increased cytoplasmic material, melanosomal irregularities, retraction of dendrites, melanosome compartmentalization, and eventual necrosis. Concurrently, MNLs arrive and remove the pigment from the choroid. The authors conclude that a basic melanocyte defect precedes the arrival of immunocytes in the delayed cutaneous and choroidal amelanosis in the genetic DAM vitiligo model of the chicken.

Animals↗
PubMed1982

Humoral immune response and expression of spontaneous postnatal amelanosis in DAM line chickens.

The delayed amelanotic (DAM) chicken line has been developed as a model of human vitiligo. Vitiligo in humans and chickens is characterized symptomatically by spontaneous loss of integumentary pigmentation and is often associated with uveitis. In humans, vitiligo is also associated with increased frequencies of several autoantibodies, suggesting a state of immune hyperreactivity. An adult DAM chicken population was tested for levels of circulating antibody after challenge with sheep red blood cells or Brucella abortus. There was a significantly higher mean titer level to both antigens in the amelanotic birds than in normally pigmented birds. The severity of feather amelanosis and visual defects was associated with increased antibody levels. This suggests that amelanosis and blindness in DAM chickens may be associated with elevated antibody responses to foreign antigens and perhaps with a generalized state of hyperimmunity.

Animals↗
PubMed1981

Retinal dystrophy associated with a postnatal amelanosis in the chicken.

Melanin pigmentation changes were studied in a mutant (delayed amelanotic) line of chickens characterized by a postnatal, spontaneous cutaneous amelanosis and a high incidence of blindness. Cutaneous pigment loss was accompanied by destruction of the choroidal melanocytes throughout the orbit. The presence of blindness appeared to be correlated with the histopathologic finding of severe degenerative changes in the pigment epithelium and neural retina first seen near the base of the pecten and progressing radially in irregular patterns.

Animals↗
PubMedDate not supplied

Effects of commonly used mitogens on the cytotoxicity of 4-tertiary butylphenol to human melanocytes.

In the search for environmental compounds responsible for contact or occupational vitiligo, it was found that the most potent was 4-tertiary butylphenol (4-TBP). Exposure to 4-TBP is widespread both in industry and in consumer items including synthetic leather, plastic, glues, and germicidal phenolic detergents. How 4-TBP causes depigmentation and the death of melanocytes is currently unclear. Growth mitogens for human melanocytes include alpha-melanocyte stimulating hormone (alpha-MSH), basic fibroblast growth factor (bFGF) and 12-o-tetradecanoylphorbol-13-acetate (TPA). The former two mitogens are physiological growth factors for melanocytes. We have studied the effects of these mitogens on the cytotoxicity of 4-TBP in human melanocytes. Our results demonstrated that deprivation of alpha-MSH or bFGF from melanocyte cultures resulted in reduced cytotoxicity to 4-TBP. Similar results were obtained upon treatment of melanocytes with an inhibitor of cAMP-dependent protein kinase A (PKA), that is known to be activated by alpha-MSH, or with an inhibitor of the tyrosine kinase bFGF receptor. In contrast, removal of fetal bovine serum or TPA from the culture medium did not influence the susceptibility of melanocytes to 4-TBP. These results suggest that activation of the cAMP and tyrosine kinase signaling pathways, both of which are involved in the mitogenic response of melanocytes, increase the susceptibility of these cells to the cytotoxic effects of 4-TBP.

Animals↗
PubMedDate not supplied

The vit gene maps to the mi (microphthalmia) locus of the laboratory mouse.

The murine model for human vitiligo (the vit/vit mouse) develops progressive depigmentation of the pelage, skin, and eyes. The vit gene is inherited as an autosomal recessive. We have used classical breeding and isozyme marker analysis to map this vit gene that produces a vitiligo-like condition in the mouse. Crossbreeding the C57BL/6J-vit/vit mice with C57BL/6J mice carrying the Miwh and/or miws alleles at the microphthalmia locus resulted in mutant phenotypes, demonstrating absence of complementation. When vit is heterozygous with the Miwh allele, a "blotched" pigment pattern results. When it is heterozygous with the miws allele, a novel expression of the vitiliginous phenotype results. Further mating analysis of these crossbred populations demonstrates allelic inheritance between vit and the alleles at the microphthalmia locus. Other breeding studies using alleles at the agouti, belted, brown, dominant spotting, extension, mahogany, patch, and piebald loci did not demonstrate pigmentation explainable by allelic inheritance with the vit gene. Also, vit was tested for linkage with isozyme markers located on chromosomes 1, 4, 5, 7, 9, and 11, and results were negative. Therefore, the vit (vitiligo) gene of the laboratory mouse has been mapped to the mi (microphthalmia) locus on chromosome 6. The gene properly should be designated as mivit.

Alleles↗
PubMedDate not supplied

Molecular basis of congenital hypopigmentary disorders in humans: a review.

Many specific gene products are sequentially made and utilized by the melanocyte as it emigrates from its embryonic origin, migrates into specific target sites, synthesizes melanin(s) within a specialized organelle, transfers pigment granules to neighboring cells, and responds to various exogenous cues. A mutation in many of the respective encoding genes can disrupt this process of melanogenesis and can result in hypopigmentary disorders. Following are examples highlighting this scenario. A subset of neural crest derived cells emigrate from the dorsal surface of the neural tube, become committed to the melanoblast lineage, and are targeted along the dorsal lateral pathway. The specific transcription factors PAX3 and MITF (microphthalmia transcription factor) appear to play a regulatory role in early embryonic development of the pigment system and in associated diseases (the Waardenburg syndromes). During the subsequent development and commitment of the melanoblast, concomitant expression of the receptors for fibroblasts growth factor (FGFR2), endothelin-B (EDNRB), and steel factor (cKIT) also appears essential for the continued survival of migrating melanoblasts. Lack or dysfunction of these receptors result in Apert syndrome, Hirschsprung syndrome and piebaldism, respectively. Once the melanocyte resides in its target tissue, a plethora of melanocyte specific enzymes and structural proteins are coordinately expressed to form the melanosome and to convert tyrosine to melanin within it. Mutations in the genes encoding these proteins results in a family of congenital hypopigmentary diseases called oculocutaneous albinism (OCA). The tyrosinase gene family of proteins (tyrosinase, TRP1, and TRP2) regulate the type of eumelanin synthesized and mutations affecting them result in OCA1, OCA3, and slaty (in the murine system), respectively. The P protein, with 12 transmembrane domains localized to the melanosome, has no assigned function as of yet but is responsible for OCA2 when dysfunctional. There are other genetically based syndromes, phenotypically resembling albinism, in which the synthesis of pigmented melanosomes, as well as specialized organelles of other cell types, is compromised. The Hermansky-Pudlak syndrome (HPS) and the Chediak-Higashi syndrome (CHS) are two such disorders. Eventually, the functional melanocyte must be maintained in the tissue throughout life. In some cases it is lost either normally or prematurely. White hair results in the absence of melanocytes repopulating the germinative hair follicle during subsequent anagen stages. Vitiligo, in contrast, results from the destruction and removal of the melanocyte in the epidermis and mucous membranes.

Acrocephalosyndactylia↗