bluuebunny/crossref_metadata_2025 huggingface dataset:
13C Solid‐State Cross Polarization/Magic‐Angle‐Spinning Nuclear Magnetic Resonance Spectra of Natural and Synthetic Melanins
Authors: AIME SILVIO , CRIPPA PIER RAIMONDO
Published: July 2006

The availability of NMR spectrometers operating in cross polarization/magic angle spinning (CP‐MAS) has provided a powerful tool for the structural elucidation of insoluble materials. In this 13C NMR study of eumelanins we report the first direct evidence of the presence of different chemical functionalities in synthetic and natural eumelanins. These spectra contain useful information for the characterization of melanins from different sources.
Biomedical Applications of Synthetic Melanotropins
Authors: HADLEY MAC E. , DAWSON BRENDA V.
Published: July 2006

Alpha‐melanotropin (alpha‐melanocyte stimulating hormone, alpha‐MSH) is a hormone produced by the pituitary gland of most vertebrate animals. This melanotropic peptide, Ac‐Ser‐Tyr‐Ser‐Met‐Glu‐His‐Phe‐Arg‐Trp‐Gly‐Lys‐Pro‐Val‐NH2, regulates melanin pigmentation of the skin of some mammals. Although MSH may be absent from the human pituitary gland, this peptide can stimulate pigment formation in human skin. We have synthesized several analogues of alpha‐MSH, which are superpotent, prolonged‐acting, and resistant to inactivation by serum enzymes. One such analogue, [NLe4, D‐Phe7]alpha‐MSH, has proven particularly useful in a number of physiological studies. In addition, some [Nle4, D‐Phe7]‐substituted fragment analogues of MSH are even more active than the native hormone, alpha‐MSH. For example, these analogues are 100–1,000 times more active than alpha‐MSH in stimulating S‐91 mouse melanoma tyrosinase activity in vitro. We have successfully labeled one such peptide to high specific activity; this melanotropin, [3H]‐Ac‐[Nle4, D‐Phe7]alpha‐MSH4–11NH2, has been shown by others to bind to B16 melanoma cells. We have also conjugated several ligands (fluorescein and biotin) to [Nle4, D‐Phe7]alpha‐MSH. These melanotropin conjugates might prove useful for melanotropin receptor studies and for the clinical localization of metastatic melanoma. We have demonstrated that [Nle4, D‐Phe4]alpha‐MSH can be topically applied and transdermally delivered across the skin of mice and humans in vitro, as determined by bioassay and RIA. Initial toxicologic studies indicate that the analogue is nontoxic to mice and is not mutagenic. Studies are underway to determine whether this analogue may prove useful as a “tanning hormone” for increasing the pigmentation of light‐skinned individuals or possibly even for treating people with certain hypopigmentary disorders.
Analysis of Mammalian Pigmentation at the Molecular Level
Authors: HEARING VINCENT J. , JIMÉNEZ MERCEDES
Published: July 2006

There has been great interest lately in the cloning of pigment‐related genes; several laboratories have succeeded in isolating melanocyte‐specific genes which have many of the characteristics expected for tyrosinase. In this paper, we review the selection criteria, the physical properties, and the functional characteristics of several of these gene products. Two of the clones map to the brown (b) and albino (c) loci, genes that are involved in the regulation of the quantity and quality of melanin production. The functional characteristics of these gene products are not easily reconciled with existing schemes of melanogenesis, and a reevaluation of our concepts of melanogenic regulation may be necessary. The altered expression of these gene products in normal and in transformed melanocytes, and the alternative mRNA processing that occurs in those cells, makes this system an appropriate and interesting one for studies of normal metabolic regulation of gene expression, as well as altered gene expression by neoplastic cells.
Differential Radiosensitivity in Cultured B‐16 Melanoma Cells Following Interrupted Melanogenesis Induced by Glucosamine
Authors: MILEO ANNA MARIA , MATTEI ELISABETTA , FANUELE MONICA , DELPINO ANDREA , FERRINI UMBERTO
Published: July 2006

The relationship between cell pigmentation and radiosensitivity was investigated in a cell model in which melanogenesis was suppressed by a glycosylation inhibitor. It was found that X‐irradiation of melanotic B‐16 melanoma cells and their amelanotic counterparts, obtained by glucosamine treatment, showed an inverse correlation between radiosensitivity and melanin contents. Since melanogenesis interruption by glucosamine does not affect the DNA repair capacity of nonpigmented cells, it is likely that intracellular melanins play a role in the relative resistance of pigmented cells to X‐irradiation.
RBEs of Thermal Neutron Capture Therapy and 10B(n,α)7 Li Reaction on Melanoma‐Bearing Hamsters
Authors: HIRATSUKA JUNICHI , KONO MICHIO , MISHIMA YUTAKA
Published: July 2006

Using Greene's melanoma transplanted into Syrian (golden) hamsters, we determined the relative biological effectiveness (RBE) of thermal neutron capture therapy (TNCT) using 10B‐paraboronophenylalanine (10B‐BPA) in comparison with a 9‐MeV electron beam. We also obtained the RBE of the 10B(n,α)7Li reaction by calculation based on summed dose data from TNCT. Throughout this study, the Kyoto University Research Reactor was used as the source for thermal neutrons; the reactor was specially altered to attain a low contamination level both for gamma‐rays and fast neutrons. 10B‐BPA was administered 8 hours before thermal neutron irradiation to the hamsters with melanoma. The tumor was then irradiated at 5 MW for 90 minutes. The absorbed dose from this TNCT was calculated by the method of Fairchild and Goodman (Phys. Med. Biol. 1966; 2:15–30). The RBEs of the TNCT and the 10B(n,α)7Li reaction obtained by the tumor growth delay time (TGDT) method were 2.22 and 2.51, respectively, at 10.5 days of TGDT. These RBE values varied with TGDT and the absorbed dose. The RBE value of TNCT had a peak at 7.0 days of TGDT; that of the 10B(n,α)7Li reaction was higher at a low absorbed dose level and lower at a high absorbed dose level.
Electron Spin Resonance of Eumelanin From Hair: Photoinduced Radicals in Solid Matrix
Authors: BIBANG RENÉ , ARNAUD RENÉ , LEMAIRE JACQUES , DEFLANDRE ANDRÉ , LANG GÉRARD
Published: July 2006

KBr matrices appear to be convenient media to reveal the radicals formed on light exposure of eumelanin dispersions. The ESR signal of eumelanin dispersed at low concentration in KBr pellets is analyzed during and after irradiation at various wavelengths. Different types of radicals are observed. R′1 and R1‐types of radicals are assigned, respectively, to neutral and deprotonated intrinsic phenoxy radicals of eumelanin. R′1 can be oxidized by oxygen as opposite to R1. R2‐ and R′2‐types are formed in the indolic site. Water favours the conversion of R2, unreactive with oxygen, into R′2 which can be oxidized. R′1 and R2 result of an electron photoejection, respectively, from the phenolic and the indolic site. The R3‐type radicals are associated with the band‐to‐band excitation of eumelanin considered as a semiorganized solid.
Dermal and Epidermal Chromatophores of the Antarctic Teleost Trematomus bernacchii
Authors: OBIKA MASATAKA , MEYER‐ROCHOW VICTOR B.
Published: July 2006

The physiological response and ultrastructure of the pigment cells of Trematomus bernacchii, an Antarctic teleost that lives under the sea ice north of the Ross Ice Shelf, were studied. In the integument, two types of epidermal chromatophores, melanophores and xanthophores, were found; in the dermis, typically three types of chromatophores—melanophores, xanthophores, and iridophores—were observed. The occurrence of epidermal xanthophore is reported for the first time in fish. Dermal melanophores and xanthophores have well‐developed arrays of cytoplasmic microtubules. They responded rapidly to epinephrine and teleost melanin‐concentrating hormone (MCH) with pigment aggregation and to theophylline with pigment dispersion. Total darkness elicited pigment aggregation in the majority of dermal xanthophores of isolated scales, whereas melanophores remained dispersed under both light and dark conditions. Pigment organelles of epidermal and dermal xanthophores that translocate during the pigmentary responses are carotenoid droplets of relatively large size. Dermal iridophores containing large reflecting platelets appeared to be immobile.
ATP‐Induced Protyrosinase Synthesis and Carboxyl‐Terminal Processing in Neurospora crassa
Authors: KUPPER URS , NIEDERMANN DENISE M. , SCHILLING BORIS C. , LERCH KONRAD
Published: July 2006

The effects of 3′‐5’cyclic AMP and ATP upon tyrosinase induction in Neurospora crassa were examined. Northern analysis of total cellular RNA revealed rapid de novo synthesis of protyrosinase after addition of these substances to stationary‐phase mycelia. The maturation of protyrosinase in crude extracts of mycelia was followed by Western analysis. Polyclonal rabbit antiserum directed against the denatured carboxyl‐terminal extension of protyrosinase does recognize the proform and several intermediate forms of different molecular weight but not mature tyrosinase. Disruption of ATP‐induced mycelia in sodium phosphate buffer (pH 6.0) demonstrate processing at the carboxyl‐terminal end of protyrosinase. The activity assays revealed that protyrosinase is an inactive precursor and that at least two active forms of slightly different molecular weight are present in crude extracts. Maturation of protyrosinase thus involves specific and sequential proteolytic cleavage at the carboxyl‐terminus. These results suggest the presence of a tyrosinase activator in Neurospora crassa mycelia, which is kept apart from protyrosinase in the intact mycelium.
Complete Sequence and Expression of a cDNA Encoding a Chicken 115‐kDa Melanosomal Matrix Protein
Authors: MOCHII MAKOTO , AGATA KIYOKAZU , EGUCHI GORO
Published: July 2006

A full‐length cDNA clone encoding a 115‐kDa melanosomal matrix protein (MMP115) was isolated from a cDNA library constructed from poly(A)+ RNA of the chicken pigmented epithelial cells. Sequence analysis showed that the cDNA encoded a polypeptide of 762 amino acids, including a hydrophobic signal peptide. There are no membrane‐spanning regions, but there are five N‐linked glycosylation signals. A cysteine‐ and histidine‐rich domain is present near the C‐terminus. A sequence of 24 amino acids is repeated three times in the polypeptide. A database search for homologies yielded no sequence similarities in other proteins. A plasmid containing the full‐length cDNA was transferred into mouse cell lines by transfection. The transfected cells produced a protein that had the same size, 115 kDa, as the mature MMP115. When B16 mouse melanoma cells were transfected, the chicken MMP115 was expressed in the melanosomes. The presence of a specific sorting signal was suggested for localization of melanosomal proteins. Southern blot analysis has revealed that the homologues of the chicken MMP115 gene are found in many vertebrate genomes.
The Effect of Oxygen on Melanin Precursors Released from Retinal Pigment Epithelial Cells In Vitro
Authors: AKEO KIYOSHI , UENO NORIO , DOREY C. KATHLEEN
Published: July 2006

The autoxidation of dopa to melanin in culture media causes toxicity to retinal pigment epithelial (RPE) cells and endothelial cells. The damage is specific to cell type and to the ambient oxygen concentration. To determine whether RPE cells influence the oxidation of dopa to media, we compared light absorbing dopa derivatives in the media exposed to cells with those found in the media incubated without cells. Dopa was extensively oxidized in the presence of RPE cells, and more light absorbing substances were generated with higher dopa and oxygen concentrations. However, an increase in ambient oxygen concentration decreased the quantity of several dopa derivatives which had been formed. The data provided evidence that RPE modulated dopa metabolism. Quinolic derivatives produced from a tyrosinase reaction and dopa‐melanin formation moved the peak absorbance wavelength of dopa into the visible range. The spectrum between the dopa‐derived compounds in the media has an absorbance at 240–275 nm and a maximum around 300 nm wth a shoulder near 375 nm. Gaussian analysis (peak separation) resolved these spectra into five components: a sharp band at 248 nm, a band at 295 nm, a large band at 359 nm, and two broad bands at 459 and 585 nm.
Vitiligo in Two Water Buffaloes: Histological, Histochemical, and Ultrastructural Investigations
Authors: CERUNDOLO R. , DE CAPRARIIS D. , ESPOSITO L. , MAIOLINO P. , RESTUCCI B. , ROPERTO F.
Published: July 2006

Vitiligo, a skin disease, characterized by the spontaneous loss of melanin, has been described in several animals as well as in humans. Most of the reports of large domestic animals have dealt with clinical investigations without morphological data. In this report, the histological and ultrastructural characteristics of two cases of vitiligo in water buffaloes (Bubalus bubalis) are presented. Interestingly, many of the ultrastructural observations for vitiliginous buffaloes resemble those previously described for other species, e.g., humans, mouse, and chicken. These data suggest that one or more forms of human vitiligo may have a similar etiopathogenesis to that of the buffalo. Therefore, it is proposed that vitiliginous buffalo may prove to be a useful animal model for the human disease.
An Ultrastructural Study of Melanocytes and Melanosomes in the Skin and Hair Bulbs of Rufous Albinos
Authors: KIDSON S.H. , RICHARDS P.D.G. , RAWOOT F. , KROMBERG J.G.R.
Published: July 2006

We have examined hair bulb and skin melanocytes of rufous albinos from Southern Africa to further characterize this form of albinism. In the skin melanocytes we find both eumelanosomes and pheomelanosomes at various stages of melanization and, in addition, there appeared to be many aberrant incompletely melanized melanosomes. On average, rufous melanosomes are 30% smaller than normal black skin melanosomes. In the keratinocytes, the melanosomes are packaged into distinct aggregations, whereas in normal black skin, they occur singly. We suggest that the reddish skin color of these albinos is a consequence of an increase in the pheomelanin synthesis resulting in a raised pheomelanin/eumelanin ratio and that the aggregation of melanosomes results in a skin color slightly lighter than normal. In hair bulb melanocytes, only eumelanosomes were seen and these were mostly incompletely melanized. These findings correlate with our visual observations that the hair color of Southern African albinos is very pale (light brown or ginger). Based on our observations, we speculate on the possible cause of rufous albinism.
From the Crest to the Periphery: Control of Pigment Cell Migration and Lineage Segregation
Authors: ERICKSON CAROL A.
Published: July 2006

Pigment cells are one of many cell types derived from the neural crest. This review focuses on the mechanisms that control the timing and pathways of migration of pigment cells into the epidermis and determinants that control the differentiation of pigment cells. Several factors may control the timing and pattern of pigment cell migration in the dorsolateral space including the loss of inhibitory molecules in the pathway, the appearance of chemotactic molecules emanating from the dispersing dermatome, and the differentiation of pigment cells, which may be the only neural crest derivative capable of utilizing the substratum found in the dorsolateral path

Control of pigment cell differentiation remains controversial. A working model presented in this review suggests that multipotent neural crest cells that disperse ventrally upon separation from the neural tube preserve neurogenic ability and lose melanogenic ability, whereas those cells that are arrested at the entrance to the dorsolateral path lose neurogenic ability so that the population becomes primarily melanogenic. During the time that the latter population is arrested in migration it is speculated that the neural crest cells are exposed to an environment comprised of specific extracellular matrix molecules and/or growth factors that enhance pigment cell differentiation.
Antimelanoma Activity of Chloroquine, an Antimalarial Agent With High Affinity for Melanin
Authors: INOUE SHIGEKI , HASEGAWA KATSUTOSHI , ITO SHOSUKE , WAKAMATSU KAZUMASA , FUJITA KEISUKE
Published: July 2006

The antimalarial agent chloroquine is known for high affinity for melanin. This 4‐aminoquinoline derivative was examined for anti‐melanoma activity and uptake into melanoma cells. Chloroquine inhibited growth of cultured melanoma cells; the effect was much greater to a moderately pigmented cell line HMV‐II than to a nonpigmented HMV‐I. Treatment with chloroquine at a dose of 62 mg/kg i.p. for 12 days prolonged by 71% the life span of mice bearing B16 melanoma, while 24‐day treatment at 31 mg/kg resulted in a 81% increase in life span. HMV‐II cells showed a two‐fold increase in up‐take of chloroquine as compared with HMV‐I cells. Chloroquine, 24 hr after administration to mice implanted s.c. with B16 melanoma, was selectively accumulated in the pigmented tissues, melanoma and eyes. Other nonpigmented tissues such as the liver, lung, and kidney showed rapid uptake (within 1 hr) and release. These results suggest that chloroquine is toxic to pigmented melanoma cells, the process being partly mediated by binding to melanin
Calcium Plays a Complex Role in the Regulation of Melanogenesis in Murine B16 Melanoma Cells
Authors: BUFFEY JAYNE A. , EDGECOMBE MANDY , NEIL SHEILA MAC
Published: July 2006

To learn more of the role of calcium in the regulation of melanogenesis, we have used direct manipulation of medium calcium and pharmacological modulation of intracellular calcium to examine the consequences on unstimulated and cyclic AMP elevated tyrosinase activity and melanin synthesis and distribution in B16 melanoma cells.

In unstimulated cells, calcium is clearly inhibitory to tyrosinase activity. However, in cells stimulated with cAMP‐elevating agents the requirement for extracellular calcium was changed such that cells required a minimum of 0.4–0.6 mmol medium calcium for maximum tyrosinase response to these agents.

Paradoxically, pharmacologically increasing intracellular calcium in cAMP‐stimulated cells with ionophore inhibited tyrosinase activity, and the calcium‐lowering agent TMB8 and the calcium channel blocker verapamil both stimulated tyrosinase activity.

When melanin synthesis was measured in cAMP‐stimulated cells, TMB8 was found to significantly increase the sensitivity and the maximum melanogenic response to α‐MSH, suggesting the presence of at least one level of endogenous calcium inhibitory control operative in these cells. In addition, TMB8 changed the distribution of melanin between the cell and the medium such that, in the presence of α‐MSH and TMB8, significantly more melanin was secreted into the medium.

These data suggest that calcium is required for several steps in melanogenesis, having an apparently inhibitory effect on pre‐tyrosinase activity in unstimulated cells, but also showing evidence of a positive role in cyclic AMP‐stimulated tyrosinase activity, as well as a further possible inhibitory role in melanin movement or secretion.
Modulation of Normal Human Melanocyte Dendricity by Growth‐Promoting Agents
Authors: NAKAZAWA KEIKO , DAMOUR ODILE , COLLOMBEL CHRISTIAN
Published: July 2006

Dendrite formation and extension, which comprise a characteristic morphology of human normal melanocytes in the skin, represent one of the functional activities of melanocytes, the ability to transfer melanosomes into neighboring keratinocytes. However, the morphology of the melanocyte in vitro is usually quite different from that observed in vivo. it is probably due to the hyperproliferative condition of the melanocytes in culture. No studies have ever compared the effects of a single factor on both dendricity and proliferation at the same time. Therefore, we have compared the effects of six growth‐promoting agents commonly used for melanocyte cultures on dendrite formation and proliferation.

The addition of agents that increase the intracellular levels of cyclic adenosine monophosphate (cAMP)—dibutyryl cyclic adenosine monophosphate (db cAMP; 1 mM) or isobutylmethyl xanthine (IBMX; 0.1 mM)—had a strong effect on dendrite formation and a negative effect on proliferation. This was especially true with db cAMP. In the presence of 2% or 5% of heat‐inactivated fetal bovine serum (FBS), dendrite formation was significantly increased as was proliferation. The number of dendrites was decreased in the culture with 12‐o‐tetradecanoylphorbol‐13‐acetate (TPA), but cell growth was slightly increased. With human recombinant basic fibroblast growth factor (bFGF) (0.5, 1.0 ng/ml) in the presence of bovine pituitary extract (BPE) (60 μg/ml), cell growth was increased. With 2 ng/ml of bFGF, however, a strong inhibitory effect on proliferation was observed. However, dendrite formation was constant at all concentrations of bFGF tested (0.5, 1.0 or 2.0 ng/ml) with BPE (30 or 60 μg/ml).

In this study, we have demonstrated that dendrite formation was suppressed by the reagents that stimulate melanocyte proliferation, and vice versa, with the only exception being heat‐inactivated FBS. Both dendrite formation and proliferation were induced by the heat‐inactivated FBS. This approach is crucial to the development of an adequate culture system for proliferation and/or dendrite formation of normal human melanocytes. It is necessary to keep these aspects in mind as we further investigate the biology of melanocytes, especially the cell‐to‐cell interactions between melanocytes and keratinocytes, involved in melanogenesis and melanin pigmentation in vivo. This study also provides practical and important information for a future reconstitutive skin system composed of melanocytes, keratinocytes, and fibroblasts in a single culture medium.
Interactions of Melanocytes and Melanoma Cells With the Microenvironment
Authors: HERLYN MEENHARD , SHIH IE‐MING
Published: July 2006

Normal or malignant melanocytes interact with the microenvironment through the release of soluble factors from cells and through direct cell‐cell contact. Melanoma cells produce a large number of different growth factors and cytokines that affect angiogenesis, stroma formation, motility, and the inflammatory and immune response. Most of the angiogenic growth factors produced by melanoma cells are also mitogenic for fibroblasts. The mechanisms and the receptors involved in direct cell‐cell contacts of melanocytes and melanoma cells are largely unknown, but the regulatory role of keratinocytes for melanocytic cells appears at several levels. Keratinocytes induce a dendritic morphology in melanocytes, and control proliferation to maintain a constant keratinocyte/melanocyte ratio during exponential growth. Expression of cell surface adhesion receptors is controlled by keratinocytes on melanocytes and nevus cells but not on advanced melanoma cells. These studies underline the complex interactions between skin cells. The escape of melanocytes from the control by keratinocytes may be a hallmark of nevus cells, and the constitutive production of various growth factors and cytokines appears to represent a major characteristic of melanoma cells.
Molecular and Biological Control of Melanogenesis Through Tyrosinase Genes and Intrinsic and Extrinsic Regulatory Factors
Authors: MISHIMA YUTAKA
Published: July 2006

Non‐premelanosomal melanogenic compartments and their melanogenesis‐controlling functions have been further elucidated. In addition to enzymatic and nonenzymatic controlling factors, we have also been exploring the role of melanogenesis‐related genes. Naturally occurring intrinsic melanogenic inhibitors, MW <6,000(α), 6,000‐30,000(β), and >30,000(γ), having different modes of action, have been identified within melanoma cells. One of the α‐type melanogenic inhibitors of isolated tyrosinase(Ty) nonsuppressive types, later identified as lactic acid, induces depigmentation of cultured B‐16 cells by the reduction in Ty activity level due to the inhibition of its mRNA expression.

The transfection of Ty cDNA, rather than nuclear DNA‐binding master regulatory gene, can induce, within both Ty‐deficient amelanotic melanoma cells and also within fibroblasts, melanin polymer formation. This multisequential step occurs not only by the induction of Ty synthesis but also by the induction of other regulatory proteins and factors such as dopachrome tautomerase, DHICA‐oxidase, catalase, Ty‐glycosylation in GERL, and Ty‐transfer by coated vesicles to newly assigned melanogenic vacuoles in which not only eumelanin but also rather pronounced concomitant pheomelanin formation is seen.

Investigation of melanin‐producing vacuoles in transfected fibroblasts and reexamination of premelanosomes in pigment cells has revealed the following: 1) Melanosomes possess phagocytic ability; 2) melanosomes receive tyrosinase and hydrolases via coated vesicles from GERL; 3) melanosomes possess lysosome‐associated membrane protein 1 (LAMP‐1); 4) amelanotic melanoma contains lysosome‐like vacuoles with myelin figures that acquire typical premelanosome structure after Ty‐cDNA transfection. Thus it is proposed that melanosomes are specialized lysosomes in pigment cells.

Coated vesicles synthesize melanin monomers such as DHICA and some DHI, and have a monomer‐stabilizing system. Thus they can transport them in intact form with Ty to premelanosomes, which subsequently polymerize these monomers by the action of DHICA‐oxidase and T3‐Ty.

Selective eradication and diagnosis of malignant melanoma using our 10B‐dopa analogue has been successfully performed in human melanoma patients using combined thermal neutron irradiation for the former and positron emission CT for the latter.
Analysis of the UV‐Induced Melanogenesis and Growth Arrest of Human Melanocytes
Authors: ABDEL‐MALEK ZALFA , SWOPE VIKI , SMALARA DOUGLAS , BABCOCK GEORGE , DAWES SUSAN , NORDLUND JAMES
Published: July 2006

Cultured human melanocytes derived from different skin types responded to frequent treatment with ultraviolet (UV) light with increased melanin synthesis, decreased proliferation, and morphologic signs of aging. These effects were augmented by increased frequency of irradiation with 15.5 mJ/cm2 UV light. Stimulation of melanogenesis by UV light involved an increase in tyrosinase activity, without any change in the amounts of either tyrosinase or tyrosinase‐related protein (TRP)‐1, and a decrease in the amount of TRP‐2, as determined by Western blot analysis. These results are different from the mechanisms by which other melanogenic agents, such as cholera toxin and isobutyl methylxanthine, stimulated melanogenesis, whereby the amounts of tyrosinase, TRP‐1 and TRP‐2 were increased. The decrease in the amount of TRP‐2 might be significant in that it might alter the properties of the newly synthesized melanin. The UV irradiation protocol that was followed blocked melanocytes in G2‐M phase of the cell cycle without compromising cellular viability. Following three rounds of UV irradiation, melanocytes could recover from the growth arrest and resume proliferation. Treatment with 0.1 μM α‐melanocyte stimulating hormone (α‐MSH) postirradiation enhanced the melanogenic effect of UV light and stimulated the melanocytes to proliferate. The effects of α‐MSH on the UV induced responses and their implications on photocarcinogenesis are being further investigated. Analyzing the mechanisms by which UV light exposure affects normal melanocytes might lead to a better understanding of how these cells undergo malignant transformation, and why individuals with different skin types differ in their susceptibility to skin cancers.
Cytoskeleton and PCH‐Induced Pigment Aggregation in Macrobrachium potiuna Erythrophores
Authors: TUMA MARIA CAROLINA B. , JOSEFSSON LARS , DEL CASTRUCCI ANA MARIA
Published: July 2006

Herein we report the effects of microtubule‐ and actin‐like filament disrupting drugs, as well as the microtubule stabilizer taxol, on PCH‐induced pigment granule aggregation within erythrophores of the freshwater crustacean Macrobrachium potiuna. Dose‐response curves (DRCs) to the pigment‐concentrating hormone PCH were determined under control and experimental conditions to evaluate the effects elicited by the cytoskeleton‐affecting drugs. Colchicine, at temperatures 22°C and 4°C, and vinblastine significantly inhibited the aggregating response to PCH and affected the dynamics of the process, as shown by the change in the slope of the regression curve calculated from the DRCs. Lumicolchicine, a colchicine analogue with no affinity for tubulin, also inhibited pigment migration, though no change in the slope of the regression curve was observed. The inhibitory effects of lumicolchicine demonstrate that changes in sites other than cytoskeleton, such as membrane permeability, may also cause a decrease in the PCH‐induced aggregating responses and that the colchicine effects may result from its action on cellular sites additional to the cytoskeleton. Taxol, a microtubule stabilizer, did not affect the DRC to PCH, and DMSO improved the PCH‐evoked responses, pointing out to the maintenance of tubulin in the polymerized state as the appropriate condition for aggregation. Cytochalasin B, an actin‐like filament disrupter, diminished the aggregating responses to the hormone, with no change in the slope of the regression curve, indicating that these elements take part in the process and that cytosolic calcium rise, sol/gel transformations and endoplasmic reticulum motility may well play an important role in granule migration. It is suggested that microtubules are steadily polymerized as a requirement for pigment aggregation and that the process is biphasic, the initial phase being dependent on the microtubule integrity.
The Interaction of Agouti Signal Protein and Melanocyte Stimulating Hormone to Regulate Melanin Formation in Mammals
Authors: FURUMURA MINAO , SAKAI CHIE , ABDEL‐MALEK ZALFA , BARSH GREGORY S. , HEARING VINCENT J.
Published: July 2006

Important regulatory controls of melanogenesis that operate at the subcellular level to modulate the structural and/or the functional nature of the melanins and melanin granules produced in melanocytes are reviewed. Melanocyte stimulating hormone and agouti signal protein have antagonistic roles and possibly opposing mechanisms of action in the melanocyte. In the mouse, melanocyte stimulating hormone promotes melanogenic enzyme function and elicits increases in the amount of eumelanins produced, while agouti signal protein reduces total melanin production and elicits the synthesis of pheomelanin rather than eumelanin. We are now beginning to understand the complex controls involved in regulating this switch at the molecular and biochemical levels. The quality and quantity of melanins produced by melanocytes have important physiological consequences for melanocyte function and undoubtedly play important roles in the various functions of the melanins per se, including hair and skin coloration and photoprotection.
K‐Casein Suppresses Melanogenesis in Cultured Pigment Cells
Authors: NAKAJIMA MITSUNARI , SHINODA ICHIZO , JIMA YOSHIKO SAME , MIYAUCHI HIROFUMI , FUKUWATARI YASUO , HAYASAWA HIROTOSHI
Published: July 2006

The effects of bovine milk proteins on melanogenesis in B16 cells were examined. Both whey protein isolate and casein exhibited depigmenting properties. Among the major protein components of milk—including β‐lactoglobulin, α‐lactalbumin, α‐, β‐, and k‐casein—only K‐casein exhibited the depigmenting effect. However, the carboxyl terminal peptide of K‐casein, glycomacropeptide, did not show this activity. Also, K‐casein promoted the proliferation of the cells and inhibited the activity of tyrosinase in the cells. These results indicate that K‐casein acts as a melanogenesis‐suppressing modulator.
Stereological Studies of the Effects of α‐MSH and cAMP on Melanosomes in Melanoma Cells
Authors: FANG DONG , DOCKERY PETER , WEATHERHEAD BRIAN
Published: July 2006

The effects of α‐MSH and cAMP on melanosomes in Cloudman S91 melanoma cells were investigated by modern stereological techniques. Cells were cultured for 4 days in medium containing α‐MSH or cAMP harvested at 24 hour intervals; some were frozen for melanin assay and the reminder embedded in Epon for light and electron microscopy. Cellular and melanosomal parameters were estimated by new stereological probes. We found that both stimulators induced increases in nuclear volume, cell volume, and the volume fractions and volumes of premelanosomes (VVpm,cell’Vpm) and mature melanosomes (VVmm,cell’Vmm) and the number of mature melanosomes (Nmm). Both stimulators also caused declines in the volume of individual mature melanosomes (Vimm) the melanin content per mature melanosome unit volume and the melanin content per individual mature melanosome. The increases in the volume of individual premelanosomes and the number of premelanosomes were only induced by cAME The effect cAMP on some parameters occurred 24 hours prior to α‐MSH and was more marked. The response of premelanosomes to the stimulators was more sensitive than mature melanosomes. These results suggest that both stimulators enchanced melanogenesis by increasing the VVpm,cell’VVmm,cell’Vpm, Vmm and Nmm. The melanogenic level did not depend on the Vimm and melanin concentration in melanosomes. The maturation of premelanosomes was involved in melanogenesis induced by both stimulators, but, de novo synthesis and enlargement of premelanosomes were only stimulated by cAME It imply that exogenous cAMP may affect melanosomes, and hence melanogenesis in quantitatively or qualitatively different ways to α‐MSH.
Formation of the Dermal Chromatophore Unit (DCU) in the Tree Frog Hyla Arborea
Authors: YASUTOMI MASUMI , YAMADA SHINPEI
Published: July 2006

In the tadpole of the tree frog Hyla arborea, the color of the dorsal skin was dark brown. Dermal melanophores, xanthophores, and iridophores were scattered randomly under the subepidermal collagen layer (SCL). After metamorphosis, the dorsal color of the animal changed to green and the animal acquired the ability of dramatic color change, demonstrating that the dermal chromatophore unit (DCU) was formed at metamorphosis. Fibroblasts invaded the SCL and divided it into two parts: the stratum spongiosum (SS) and the stratum compactum (SC). The activity of collagenase increased at metamorphosis. The fibroblasts appeared to dissolve the collagen matrix as they invaded the SCL. Then, three types of chromatophores migrated through the SCL and the DCU was formed in the SS. The mechanism how the three types of chromatophores were organized into a DCU is uncertain, but different migration rates of the three chromatophore types may be a factor that determines the position of the chromatophores in the DCU.

Almost an equal number of each chromatophore type is necessary to form the DCUs. However, the number of dermal melanophores in the tadpoles was less than the number of xanthophores and iridophores. It was suggested that epidermal melanophores migrated to the dermis at metamorphosis and developed into dermal melanophores. This change may account for smaller number of dermal melanophores available to form the DCUs.
Microphthalmia‐Associated Transcription Factor (MITF) Locus Lacks Linkage To Human Vitiligo Or Osteopetrosis: An Evaluation
Authors: TRIPATHI RAM K. , FLANDERS DEAN J. , YOUNG TERRI L. , OETTING WILLIAM S. , RAMAIAH ABBURI , KING RICHARD A. , BOISSY RAYMOND E. , NORDLUND JAMES J.
Published: July 2006

The microphthalmia‐associated transcription factor (MITF) locus has been mapped to human chromosome 3p12‐p14.1, and encodes a basic helix‐loop‐helix zipper (bHLH‐ZIP) protein homologous to a number of transcription factors. Numerous mutations at the mouse microphthalmia (mi) locus have been described, and all have reduced or absent pigmentation of the eyes, ears, and/or pelage, with some genotypes exhibiting small or absent eyes and osteopetrosis. The mivit/vit mutation at the mouse mi locus produces a postnatal depigmentation that resembles human vitiligo. The mice homozygous for this mi allele show a progressive loss of cutaneous, hair and ocular pigmentation with age. Vitiligo, an acquired depigmentary disorder, is characterized by patchy depigmentation of skin that generally begins around puberty and tends to become more progressive over time. There is suggestive evidence that human vitiligo may be inherited; however, the mode of inheritance is still debated and the pathogenesis is not clearly delineated. The human disorder osteopetrosis is characterized by a generalized net accumulation of skeletal mass and results from reduced osteoclast function in the bone. This is an inherited disorder and has been associated with mi in a mutant mouse. Therefore, the possible involvement of the MITF locus in the pathogenesis of either familial vitiligo or osteopetrosis was investigated. Linkage analysis was performed using microsatellite polymorphic markers D3S2465, D3S1261, and D3S1766 on genomic DNA from 26 families with vitiligo/osteopetrosis. D3S1261 is physically located at or near the MITF locus, while D3S2465 and D3S1766 are flanking the locus at about 17.5 cM genetic distance each side. Evidence from LOD score analysis surprisingly indicated that none of the families with vitiligo or osteopetrosis are linked to these short tandem repeat polymorphisms (STRPs). Thus, the human homolog (MITF) of the mouse mi gene, a good candidate gene at the phenotypic level, may not be involved in the pathogenesis of familial human vitiligo or osteopetrosis.
Ultimate Fate of Rod Outer Segments in the Retinal Pigment Epithelium
Authors: THUMANN GABRIELE , BARTZ‐SCHMIDT KARL ULRICH , KOCIOK NORBERT , HEIMANN KLAUS , SCHRAEMEYER ULRICH
Published: July 2006

To investigate the degradation pathway of rod outer segments (ROS) in vivo, we injected gold‐labeled ROS into the subretinal space of rabbits using a pars plana approach. Histology and electron microscopy performed on the specimens 72 hr after ROS injection revealed that the retina over the injection site was reattached, the retinal pigment epithelial (RPE) cells were intact, and gold granules were localized inside melanin granules and melanosomes. These results indicate that, in RPE, in vivo degradation of ROS is associated with melanosomes.
Hypophysial and Meningeal Melanocytes in the Zucker Rat
Authors: FETISSOV SERGUEI O. , BARCZA MAUREEN A. , MEGUID MICHAEL M. , OLER ALBERT
Published: July 2006

Melanocytes have not been described in the pituitary of mammals or in the meninges of the rat. In this paper, we report the presence of the cluster of melanocytes in the intermediate lobe of the pituitary and around the median eminence of the hypothalamus forming an ‘infundibulo‐hypophysial circle’, and also describe the characteristics of meningeal melanocytes in Zucker rats. In the leptomeninges, numerous melanocytes were found on the ventrolateral surface of cerebral hemisphere in the area of the middle cerebral artery. Pigment granules were also observed in the surrounding tissue outside the melanocytes as well as incorporated in the cytoplasm of neural and epithelial cells. Electron microscopy revealed that melanosomes in hypophysial and meningeal melanocytes were in different (II‐IV) stages of maturity. In the leptomeninges of Zucker rats, HMB‐45 immunoreactivity was found in round non‐melanosome‐containing cells, while no HMB‐45 reaction was found in the leptomeninges of the albino rat. We conclude that both obese and lean Zucker rats possess functionally active melanocytes in the meninges and the pituitary and transfer pigment granules to neighboring cells. The distributions of melanocytes in proximity to blood vessels in the leptomeninges and in the ‘infundibulo‐hypophysial circle’ suggest an endocrine secretory function.
An alternative method for splinting of traumatized teeth: case reports
Authors: Yildirim Öz Gülsün , Ataoğlu Hanife , Kir Nihal , Karaman Ali İhya
Published: July 2006

Abstract –  Injuries to the dentoalveolar complex are fairly common and can be caused by a number of reasons. There are many techniques for repositioning and stabilizing traumatically luxated or avulsed teeth. Many of the splinting techniques previously advocated were time‐consuming. Not only were the splints difficult to fabricate and difficult to remove, they also contributed to injury of the soft and hard supporting tissues. Ribbond (Ribbond Inc., Seattle, Wash) is basically a reinforced ribbon which is made from ultrahigh molecular weight polyethylene fiber having an ultrahigh modulus. It is used in dentistry for various purposes. The use of Ribbond appears to be an adequate and easy method for stabilization and fixation. It can be used in the treatment of dental injuries. In this article the use of Ribbond for the treatment of dentoalveolar injuries is described.
Effects of repeated morphine on locomotion, place preference and dopamine in heterozygous glial cell line‐derived neurotrophic factor knockout mice
Authors: Airavaara M. , Tuomainen H. , Piepponen T. P. , Saarma M. , Ahtee L.
Published: July 2006

Glial cell line‐derived neurotrophic factor (GDNF) has been shown to be involved in the maintenance of striatal dopaminergic neurons. Neurotrophic factors are crucial for the plasticity of central nervous system and may be involved in long‐term responses to drug exposure. To study the effects of reduced GDNF on dopaminergic behaviour related to addiction, we compared the effects of morphine on locomotor activity, conditioned place preference (CPP) and extracellular accumbal dopamine in heterozygous GDNF knockout mice (GDNF+/−) with those in their wild‐type (Wt) littermates. When morphine 30 mg/kg was administered daily for 4 days, tolerance developed towards its locomotor stimulatory action only in the GDNF+/− mice. A morphine 5 mg/kg challenge dose stimulated locomotor activity only in the GDNF+/− mice withdrawn for 96 h from repeated morphine treatment, whereas clear and similar sensitization of the locomotor response was seen after a 10 mg/kg challenge dose in mice of both genotypes. Morphine‐induced CPP developed initially similarly in Wt and GDNF+/− mice, but it lasted longer in the Wt mice. The small challenge dose of morphine increased accumbal dopamine output slightly more in the GDNF+/− mice than in the Wt mice, but doubling the challenge dose caused a dose‐dependent response only in the Wt mice. In addition, repeated morphine treatment counteracted the increase in the accumbal extracellular dopamine concentration we previously found in drug‐naive GDNF+/− mice. Thus, reduced endogenous GDNF level alters the dopaminergic behavioural effects to repeatedly administered morphine, emphasizing the involvement of GDNF in the neuroplastic changes related to long‐term effects of drugs of abuse.
Analysis of two P‐element enhancer‐trap insertion lines that show expression in the giant fibre neuron of Drosophila melanogaster
Authors: Allen M. J. , Drummond J. A. , Sweetman D. J. , Moffat K. G.
Published: July 2006

The giant fibre system (GFS) of Drosophila is a simple neural circuit that mediates escape responses in adult flies. Here we report the initial characterization of two genes that are preferentially expressed in the GFS. Two P‐element insertion lines, carrying the GAL4 transcriptional activator, were identified that exhibited pronounced expression in elements of the GFS and relatively low levels elsewhere within the adult central nervous system. Genomic DNA flanking the P‐element insertion site was recovered from each of these lines, sequenced, and nearby transcripts identified and confirmed to exhibit GFS expression by in situ hybridization. This analysis revealed that these P‐elements were in previously characterized genes. Line P[GAL4]‐A307 has an insert in the gene short stop for which we have identified a novel transcript, while line P[GAL4]‐141 has an insert in the transcription factor ken and barbie. Here we show that ken and barbie mutants have defects in escape behaviour, behavioural responses to visual stimuli and synaptic functions in the GFS. We have therefore revealed a neural role for a transcription factor that previously had no implicated neural function.
Immunity, Age and Loss of Immunohomeostasis1
Authors: Peterson William J.
Published: July 2006

An interpretative discussion on the cellular basis of the association between immunosenescence and loss of immunologic homeostasis was developed from results of studies performed to resolve the issues (a) of whether cells in certain stages of differentiation are more vulnerable to aging than those in other stages and (b) whether the regulatory cells participating in modulating immune responses are prime targets of aging. Young and old mice were exposed to (1) 6‐thioguanine (6‐TG) to study the activity of their mitotically active and inactive cells and (2) 500R of irradiation to study regeneration of their immune cells. Many alterations were detected in old mice including the existence of a relatively large pool of mitotically inactive pluripotent stem cells in the bone marrow, heightened stem cell regenerative activity, and altered patterns of immunologic regeneration. These kinetic abnormalities reflect age‐related changes in stem cells and their progenies, and in the lymphohematopoietic stromal cells.
Gingival and Periodontal Parameters in a Population of Healthy Adults, 22–90 Years of Age1
Authors: Ship Jonathan A. , Wolff Andy
Published: July 2006

There are little data concerning the periodontal status of aging individuals free of systemic disease and medication utilization. In the present study 55 healthy male and female, non‐medicated adults between the ages of 22 and 90 were evaluated by comparing gingival and periodontal parameters. The results indicate greater proportions of sites with dental plaque, calculus, gingival bleeding and recession, and attachment loss in the oldest age group. The progression of these changes from young to middle to old age was not uniform. Attachment loss showed the most significant age‐related changes. Results from this small, cross‐sectional study of healthy individuals are generally comparable to findings reported from the NIDR 1985 National Survey of Oral Health in U.S. Adults.
Comparison of the effect of the linseed extract Salinum® and a methyl cellulose preparation on the symptoms of dry mouth
Authors: Andersson Gunilla , Johansson Gunvor , Attström Rolf , Edwardsson Stig , Glantz Per‐Olof , Larsson Kåre
Published: July 2006

The effect of a linseed extract Salinum® and a sodium carboxymethyl cellulose preparation called MAS‐84 was compared with regard to its effect on the symptoms of dry mouth. Twenty patients with xerostomia, who had been treated for cancer in the head and neck by radiation were recruited from the clinic for maxillofacial surgery, Malmö University Hospital. Following radiation treatment the salivation was severely reduced. The symptoms of a general feeling of a dry mouth, difficulties in chewing and swallowing, taste disturbances, problems with speech and mouth burning were registered on a subjective verbal rating scale. In addition plaque index and gingival bleeding index were determined. The study design was crossover and performed single blind. The experimental period was 7 weeks. The patients were randomly divided into 2 groups, One group used Salinum® and the other MAS‐84 for 3 weeks. The fourth week was a wash out period and for the next three weeks the patients shifted preparation. Each of the preparations was used ad libitium. Registrations of the various parameters were undertaken on days 0, 7 and 21 of the respective period. At the initial examination all patients reported considerable disturbances from mouth‐dryness. These symptoms were reduced in 15 patients during the Salinum® period and in 9 during the MAS‐84 period. The relief was significantly more pronounced during the use of Salinum® compared to that during the use of the methyl cellulose preparation. On day 21 plaque and gingival bleeding were significantly reduced during the Salinum® period but not during the MAS‐84 period. The results of the present study confirm those of a previous pilot study and indicate that the linseed mucilage significantly reduced the symptoms of dry mouth. This effect increased with increasing time of saliva substitute use. The linseed mucilage Salinum® appeared to be a suitable saliva replacement in mouth dry patients.