Gisela Moellmann

Cytochalasin B: Effects on Microfilaments and Movement of Melanin Granules within Melanocytes

The intracellular translocation of melanin granules within both epidermal and dermal melanocytes of Rana pipiens is influenced by cytochalasin B. Cytochalasin B prevents dispersion of pigment granules by melanocytestimulating hormone (MSH) and causes centripetal movement of pigment granules that have been dispersed by MSH. Microfilaments are abundant in the dendritic processes of epidermal melanocytes in which pigment granules have been dispersed by MSH. Microfilaments are dramatically reduced in number in the processes of melanocytes that have been lightened by cytochalasin B. These observations suggest that microfilaments mediate dispersion of pigment granules.

Pigment cell transplantation for treatment of vitiligo: A progress report

BACKGROUND Because available treatments for vitiligo generally provide unsatisfactory results, the search for viable therapeutic alternatives continues. OBJECTIVE Our purpose was to evaluate several transplantation procedures with cultured autologous melanocytes for their practicality in treating patients with vitiligo. METHODS Twenty-seven patients with stable or active vitiligo were treated after superficial dermabrasion with application of suspensions of autologous cultured melanocytes, melanocyte-keratinocyte mixtures, or epidermal sheets established in vitro. RESULTS Regardless of disease activity, use of each method resulted in repigmentation to a similar degree and without scarring in all patients. Melanocyte suspensions offer several advantages: They are easily prepared, can be applied in a controlled manner, permit coverage of large areas, and produce a homogeneous skin color that affords the best cosmetic restoration. The ultrastructure of transplant sites resembled that of uninvolved skin, with one exception: the melanocytes were located slightly higher than in uninvolved skin. CONCLUSION Application of cultured autologous melanocytes to lightly abraded skin is an advantageous addition to the treatments available for patients with vitiligo.

Normal murine melanocytes in culture

SummaryA major obstacle to applying the techniques of molecular biology to the genetics and cell biology of pigmentation has been our inability to grow normal murine melanocytes in culture. We report here the establishment and characterization of continuously proliferating cultures of cutaneous pigment cells from seven strains of mice. Melanocytes were grown from the dermis of newborn mice in medium containing 12-0-tetradecanoyl-13-phorbol-acetate; a substance, such as melanotropin, that raises intracellular levels of cyclic AMP; and an extract made from human placenta.

Supermelanotic hybrids derived from mouse melanomas and normal mouse cells

Hybrids formed between HPRT− Cloudman mouse melanoma and normal cells were isolated. The parental origin of the hybrids was verified by isozyme and karyotype analyses. These hybrid cells differed in two major characteristics from hybrids of melanoma and established fibroblastic cells. (1) They grew as tumors when injected into mice, and (2) they expressed differentiated melanocytic functions. At least one of the differentiated functions was overexpressed. The specific activity of tyrosinase was 3–20 times higher in the hybrid cells than in the parental mouse melanoma. The overexpression of tyrosinase in these hybrid cells has been stable for more than a year, has been transmitted to subclones of the original hybrid cell lines, and has been expressed in tumors that grew after injections of hybrid cells into animals.

Pigmentation and tumorigenicity of reconstituted, cybrid and hybrid mouse cells☆

Abstract Cybrid, reconstituted and hybrid cells were formed by fusing cytoplasts with whole cells, cytoplasts with nucleoplasts, or whole cells with whole cells, respectively. The cells or cellular fragments were derived from murine melanomas expressing melanocytic functions and from tumorigenic or non-tumorigenic fibroblasts. The cybrids and reconstituted cells resembled the nuclear donor parent in the expression of melanocytic activity and tumorigenicity. The hybrid cells resembled the fibroblastic parent when comparable numbers of chromosomes were present from each parent. A ratio of 1.5:1 in favor of the melanoma genome resulted in hybrids of either phenotype. The expression and extinction of melanocytic functions and the expression and suppression of tumorigenicity were transmitted only through the nucleus. The stable expression of A-type viral particles, on the other hand, may have been inherited also by cytoplasmic transfer.

Synthesis of a hormonally active conjugate of α-MSH, ferritin, and fluorescein

A conjugate composed of α-MSH, ferritin, and fluorescein has been synthesized. The conjugate is biologically active: It is one-tenth as active as free α-MSH in darkening frog skin and one-third as active as free α-MSH in stimulating tyrosinase activity in cultivated Cloudman melanoma cells. Binding of the conjugate to cultivated Cloudman melanoma cells was specific; binding was inhibited by at least 80% with either 5 × 10−5m α- or β-MSH. An average affinity constant of 1.3 × 109 liters/mol with approximately 1 to 4 × 104 sites/cell was calculated. The half-life of the conjugate-receptor complex is 58 min. The binding of the conjugate to cultivated Cloudman melanoma cells can be visualized by fluorescence microscopy. A patchy, perinuclear distribution of the conjugate, similar to that of FITC-β-MSH, was observed. Electron microscopic examination revealed the conjugate to be at the cell surface.

The mechanism of frog skin lightening by acetylcholine

Abstract Darkening of frog skin by melanocyte-stimulating hormone (MSH) is accompanied by an increase in adenosine-3′,5′-cyclic monophosphate (cyclic AMP). Among agents that lighten frog skin, norepinephrine and melatonin have been shown to diminish the MSH-induced increase in cyclic AMP. To characterize the mode of action of acetylcholine (AcCh) as a lightening agent of frog skin melanocytes, AcCh-responsive skins of Rana pipiens were darkened in vitro with MSH, lightened with AcCh in MSH solution, rinsed in MSH and then exposed to one of the following: dibutyryl cyclic AMP (DBcAMP); 5′-AMP, ATP, theophylline, or caffeine. As a permutation, theophylline was added before or directly after MSH. The lightening of frog skin by AcCh was reversed by all agents except 5′-AMP and was prevented by theophylline. In other experiments AcCh was added to skins darkened with MSH, theophylline, DBcAMP, ATP, epinephrine, or isoproterenol. AcCh reversed only the darkening induced by MSH. We suggest that in melanocytes of AcCh-responsive frog skin, AcCh may bind to the MSH receptor, thereby preventing the MSH-induced increase in cyclic AMP.