bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of TRPs From Murine and Human Malignant Melanocytes
Authors: MARTINEZ‐ESPARZA MARIA , JIMÉNEZ‐CERVANTES CELIA , GARCÍA‐BORRÓN JOSÉ C. , LOZANO JOSÉ A. , MARMOL VERONIQUE DEL , GHANEM GHANEM , SOLANO FRANCISCO
Published: July 2006

Most of our knowledge of the mammalian tyrosinase related protein (TRP) activities is derived from studies using murine melanoma models, such as B16 or Cloudman S‐91 melanocytes. Owing to the high degree of homology between the murine and human enzymes, it has been assumed that their kinetic behavior could be similar. However, the protein sequences at the metal binding sites of the murine and human enzymes show some differences of possible functional relevance. These differences are more significant in the metal‐A site than in the metal‐B site. By using three human melanoma cell lines (HBL, SCL, and BEU), we have studied the catalytic abilities of the human melanogenic enzymes in comparison to those obtained for the counterpart murine enzymes isolated from B16 melanoma. We have found that TRP2 extracted from all cell lines show dopachrome tautomerase activity, although the activity levels in human malignant melanocytes are much lower than in mouse cells. Reconstitution experiments of the human enzyme indicate that TRP2 has Zn at its metal binding‐sites. Although mouse tyrosinase does not show DHICA oxidase activity, and this step of the melanogenesis pathway is specifically catalyzed by mouse TRP1, the human enzyme seems to recognize carboxylated indoles. Thus, human tyrosinase could display some residual DHICA oxidase activity, and the function of human TRP1 could differ from that of the murine protein. Attempts to clarify the nature of the metal cofactor in TRP1 were unsuccessful. The enzyme contains mostly Fe and Cu, but the reconstitution of the enzymatic activity from the apoprotein with these ions was not possible.
Characterisation of ACTH Peptides in Human Skin and Their Activation of the Melanocortin‐1 Receptor
Authors: WAKAMATSU KAZUMASA , GRAHAM ALISON , COOK DAVID , THODY ANTHONY J.
Published: July 2006

α‐Melanocyte‐stimulating hormone (α‐MSH) is a proopiomelanocortin (POMC)‐derived peptide, which is produced in the pituitary and at other sites including the skin. It has numerous effects and in the skin has a pigmentary action through the activation of the melanocortin‐1 (MC‐1) receptor, which is expressed by melanocytes. Recent evidence suggests that the related POMC peptides such as adrenocorticotrophin (ACTH), which is the precursor of α‐MSH, is also an agonist at the MC‐1 receptor. By using immunocytochemistry, we confirmed the presence of α‐MSH in human skin where staining was evident in keratinocytes and especially strong in melanocytes and possibly Langerhans cells. ACTH was also present and tended to show the strongest reaction in differentiated keratinocytes. Immunostaining was also observed for the prohormone convertases, PC1 and PC2, which are involved in the formation of ACTH and its cleavage to α‐MSH, respectively. The amounts of immunoreactive ACTH exceeded those of α‐MSH. Using HPLC we identified for the first time the presence of ACTH1‐39, ACTH1‐17, ACTH1‐10, acetylated ACTH1‐10, α‐MSH, and desacetyl α‐MSH in epidermis and in cultured keratinocytes. The ability of these peptides to activate the human MC‐1 receptor was examined in HEK 293 cells that had been transfected with the receptor. All peptides increased adenylate cyclase in these cells with the following order of potency: ACTH1‐17 > α‐MSH > ACTH1‐39 > desacetyl α‐MSH > acetylated ACTH1‐10 > ACTH1‐10. ACTH1‐17 also increased the dendricity and melanin content of cultured human melanocytes indicating that the peptide was able to activate MC‐1 receptors when present in their normal location. However, as found with α‐MSH, not all cultures were responsive and, as we have previously suggested, we suspect that this was the result of changes at the MC‐1 receptor. Nevertheless, it would appear that ACTH peptides can serve as natural ligands of the MC‐1 receptor on human melanocytes and their presence in the skin suggests that, together with α‐MSH, they may have a role in the regulation of human melanocytes.
Albinism Due to Transposable Element Insertion in Fish
Authors: KOGA AKIHIKO , HORI HIROSHI
Published: July 2006

The i locus of the medaka fish, Oryzias latipes, is responsible for tyrosinase expression, and several mutant alleles have been identified. The genotype i1/i1 exhibits a complete albino phenotype, having pale orange‐red skin and red eyes. This mutant lacks in vivo tyrosinase activity. The genotype i4/i4, on the other hand, shows a quasi‐albino phenotype with skin as bright as that of i1/i1 but with red‐wine‐colored eyes. At the light microscope level, reduced pigmentation is observed both in the skin and eyes of this mutant. The tyrosinase genes for the i1 and the i4 alleles were cloned and sequenced, and compared with that of the wild‐type tyrosinase gene. The i1 allele was found to contain a 1.9‐kb transposable element in the 1st exon, and the i4 allele was found to contain a 4.7‐kb transposable element in the 5th exon. Both i1 and i4 are alleles that were found in a commercial breeding population. The insertion of a transposable element thus appears to constitute a natural cause of mutations that cause albinism in this organism.
Pigmented Human Skin Equivalent: New Method of Reconstitution by Grafting an Epithelial Sheet Onto a Non‐Contractile Dermal Equivalent
Authors: NAKAZAWA KEIKO , NAKAZAWA HISAYOSHI , SAHUC FLORENT , LEPAVEC ANNIE , COLLOMBEL CHRISTIAN , DAMOUR ODILE
Published: July 2006

We have established a new protocol for reconstituting a pigmented human skin equivalent (PSE) and have evaluated its functional responses to environmental stimulus, UVB. The PSE is reconstituted by grafting an epithelial sheet consisting of keratinocytes and melanocytes onto a porous non‐contractile dermal equivalent populated with mitotically and metabolically active fibroblasts. i) The PSE has a multilayered, well‐differentiated epidermis with cuboidal basal cells and highly organised dermis with newly synthesised extracellular matrix components. ii) Ki67‐positive proliferating keratinocytes (18.1 ± 7.4%) were detected on the basal layer of the epidermis. iii) Melanocytes located exclusively within the basal layer were detected by monoclonal antibody against tyrosinase‐related protein (TRP‐1). iv) After exposure to UVB (100 mJ/cm2 per day) for 7 consecutive days, the intensity of TRP‐1 staining was increased in the PSE, showing their functional state, whereas the number of melanocytes was not changed.

This non‐contractile and functioning new PSE is potentially useful as a model for studying the role of melanocyte‐keratinocyte‐fibroblast interactions in photoprotection of the skin in more complex cutaneous microenvironment than monolayer culture, and for developing in vitro disease models and therapeutic protocols with genetically altered cells both in epidermis and dermis.
The Effect of 3‐Aminobenzamide on Thymidine Incorporation in Ultra‐Violet Irradiated Chick Pigment Epithelium Cells
Authors: BAICH ANNETTE , WANDA PAUL E. , MITCHELL MICHAEL D.
Published: July 2006

The addition of 3‐aminobenzamide (3‐AB) to cultures of chick embryo pigmented epithelium rescues these cells after high doses of ultraviolet treatment. The addition of 3‐AB prevents cells from losing pre‐formed protein and DNA and stimulates thymidine incorporation by the cells after ultraviolet irradiation. Since 3‐AB is an inhibitor of poly (ADP) ribosylation, these observations support the conclusion that death of these cells after ultra‐violet irradiation depends upon poly (ADP) ribosylation and may be an apoptotic response.
Cellular Plasticity Among Axolotl Neural Crest‐Derived Pigment Cell Lineages
Authors: THIBAUDEAU G. , HOLDER S.
Published: July 2006

Many of the factors and mechanisms guiding the migration/differentiation of neural crest cells that give rise to a number of distinguishable cell types, including all dermal and epidermal pigment cells, remain unknown. The axolotl possesses three pigment cell types that differentiate according to specific developmentally programmed sequences and contribute to pigment pattern in the adult. A single lineage of the crest that becomes restricted to one of three pigment cell types gives us the opportunity to examine the existence of a neural crest stem cell population and the potential for transdifferentiation events. Interpretations of experiments involving drug‐treated and mutant axolotls implicate cellular plasticity leading to observed phenotypes. We present results from recent in vitro studies designed to identify parameters influencing differentiation events of individual neural crest‐derived pigment cell lineages. We demonstrate that the differentiation of xanthophores is enhanced, while that of the melanophores are inhibited in guanosine‐supplemented neural crest cell cultures. Data suggest that the increase in one pigment cell population is at the expense of another, indicative of cellular plasticity. Videomicroscopy used in this study agrees with an abundance of correlative evidence supporting the hypothesis of transdifferentiation events among neural crest‐derived pigment cell populations. The embryonic neural crest‐derived pigment cell system is an ideal model to study differentiation of multipotential stem cells that play critical roles in patterning.
Tyrosinase Kinetics: Failure of Acceleration in Oxidation of Ring‐Blocked Monohydric Phenol Substrate
Authors: NAISH‐BYFIELD S. , RILEY P. A.
Published: July 2006

When 2, 5, 6‐trimethyl‐4‐hydroxyanisole is used as substrate for mushroom tyrosinase the oxidation rate is slow and the kinetics do not exhibit an initial acceleration (lag period), in contrast to the kinetics of oxidation of the parent compound, 4‐hydroxyanisole. This finding is interpreted as evidence that the acceleration of oxidation of 4‐hydroxyanisole is indirectly contingent on a reductive nucleophile addition to the orthoquinone product of the monohydric phenol, which is prevented by ring methylation. Such a view is consistent with the proposal that the lag‐phase characteristic of the kinetics of monohydric phenol oxidation by tyrosinase is due to the activation of previously inactive enzyme by electron donation from an orthodiphenol substrate formed from the orthoquinone oxidation product.
Chemical Degradation of Melanins: Application to Identification of Dopamine‐melanin
Authors: ITO SHOSUKE , WAKAMATSU KAZUMASA
Published: July 2006

Melanocytes produce two chemically distinct types of melanin pigments, eumelanins and pheomelanins. These pigments can be quantitatively analyzed by acidic KMnO4 oxidation or reductive hydrolysis with hydriodic acid (HI) to form pyrrole‐2,3,5‐tricarboxylic acid (PTCA) or aminohydroxyphenylalanine (AHP), respectively. Dark brown melanin‐like pigments are also widespread in nature, for example, in the substantia nigra of humans and primates (neuromelanin), in butterfly wings and in the fungus Cryptococcus neoformans. To characterize such diverse types of melanins, we have improved the alkaline H2O2 oxidation method of Napolitano et al. (Tetrahedron, 51: 5913–5920, 1995) and re‐examined the HI hydrolysis method of Wakamatsu et al. (Neurosci. Lett., 131: 57–60, 1991). The results obtained with H2O2 oxidation show that 1) pyrrole‐2,3‐dicarboxylic acid (PDCA), a specific marker of 5,6‐dihydroxyindole units in melanins, is produced in yields ten times higher than by acidic KMnO4 oxidation, and 2) PTCA is artificially produced from pheomelanins. The results with HI hydrolysis show that dopamine‐melanin produces a 1:1 mixture of 3‐amino and 4‐amino isomers of aminohydroxyphenylethylamine, while the isomer ratio is about 0.2 in melanins prepared from dopamine and cysteine. These results indicate that alkaline H2O2 oxidation is useful in characterizing synthetic and natural eumelanins and that reductive hydrolysis with HI can be applied to analyzing oxidation products of dopamine such as neuromelanin.
Melanoma × Macrophage Fusion Hybrids Acquire Increased Melanogenesis and Metastatic Potential: Altered N‐Glycosylation as an Underlying Mechanism
Authors: SODI S.A. , CHAKRABORTY A.K. , PLATT J.T. , KOLESNIKOVA N. , ROSEMBLAT S. , KEH‐YEN A. , BOLOGNIA J.L. , RACHKOVSKY M.L. , ORLOW S. J. , PAWELEK J.M.
Published: July 2006

We recently reported that a majority of hybrids generated in vitro between weakly metastatic mouse Cloudman S91 melanoma cells and human or mouse macrophages showed enhanced metastatic potential. With few exceptions, hybrids with enhanced metastatic potential also had elevated basal melanin content and increased responsiveness to MSH compared to parental cells. Here we investigated the hybrid melanotic phenotype in more detail, comparing the pigmentary systems of hybrids and parental Cloudman S91 cells by several techniques. Cells were studied by electron microscopy, cell lysates were analyzed for tyrosinase (E.C.1.14.18.1) activity, and melanosomal proteins were analyzed by gel electrophoresis and immunoblotting. Melanosomes in parental Cloudman melanoma cells were few in number and relatively amorphous, whereas those in the hybrids were numerous and heavily pigmented, containing highly organized lattice structures. Both basal and MSH‐inducible tyrosinase activities were elevated several fold in hybrids compared to parental cells. Tyrosinase, TRP‐2, and LAMP‐1 from hybrids migrated more slowly on gels compared to the same proteins from parental melanoma cells, consistent with increased glycosylation. Migration of LAMP‐1 from hybrids was similar to that from peritoneal macrophages, which also appeared to be more heavily glycosylated than LAMP‐1 from Cloudman cells. By using 3H‐glucosamine as a marker of N‐glycosylation, its incorporation into tyrosinase and LAMP‐1 was found to be elevated in hybrids, suppressed by N‐glycosylation inhibitors, and stimulated by MSH to a greater degree in hybrids compared to parental cells. These results indicate N‐glycosylation as an important regulatory pathway for MSH‐induced melanogenesis and further suggest that altered N‐linked glycosylation may be an underlying mechanism for regulation of both melanogenesis and metastasis in macrophage x melanoma hybrids.
Agouti‐Related Maturation and Tissue Distribution of oc‐Melanocyte Stimulating Hormone in Wild‐Type (AwJ/AwJ) and Mutant (Ay/a, a/a) Mice
Authors: MONROE DAVID G. , WIPE LOREN P. , DIGGINS MAUREEN R. , MATTHEES DUANE P. , GRANHOLM NELS H.
Published: July 2006

Because of ectopic overproduction of agouti protein, yellow alleles (Ay and Avy) of the murine agouti gene may secondarily modulate the synthesis, maturation (i.e., acetylation), and/or tissue deployment of α‐Melanocyte Stimulating Hormone (MSH). We used HPLC to test the hypothesis that Ay/a mice exhibit altered concentrations of desacetyl‐, monoacetyl‐, and diacetyl‐α‐MSH in pituitaries, sera, and telogen hair bulbs when compared to black (a/a) mice. We also used RIA to measure total MSH in those same tissues of Ay/a, a/a, and white‐bellied agouti (AwJ/AwJ) mice (Strain C57BL/6J). We found no evidence that Ay/a mice possessed an imbalance of des‐, mono‐, and diacetylated α‐MSH species. However, radioimmunoassay (RIA) analyses of total MSH suggest that wild‐type agouti mice (AwJ/AwJ) exhibited significantly decreased (P < 0.05) tissue levels of total α‐MSH in pituitaries, sera, and regenerating hair bulbs when compared to those of mutant Ay/a and a/a mice.
Changes in Lipid Peroxide Level in Retinal Pigment Epithelial Cells In Vitro Upon Addition of Linoleic Acids or Linoleic Acid Hydroperoxides Under Varying Concentrations of Oxygen
Authors: AKEO KIYOSHI , HIRAMITSU ADAHISA
Published: July 2006

We previously observed the presence of autofluorescent lipofuscin or its like in retinal pigment epithelial (RPE) cells, which were incubated with linoleic acid hydroperoxides (LHP). We studied the effect of oxygen on the level of lipid peroxides in RPE cells in the presence of linoleic acids (LA) or LHP. The level of lipid peroxides in these cells was determined by use of the thiobarbituric acid‐reactive substance (TBARS), which responded to oxygen concentrations qualitatively, and a linear regression analysis. Multiple linear regression analysis disclosed that treatment with LA for 24 hr resulted in detectable increase in the level of TBARS in the cells, whereas treatment with LA or LHP for 48 hr caused detectable decrease. Stepwise linear regression analysis showed that the level of TBARS decreased in an oxygen‐tension dependent manner in the cells incubated with LA for 48 hr. Thus, it was shown that short‐term incubation with LA increased the level of TBARS in the cells and that LA decreased its level in an oxygen‐tension dependent manner. For these results, the postulation was made that the prolonged auto‐oxidation of LA caused production of lipofuscin‐like materials, a complex of lipid peroxides and proteins that were insoluble in SDS and acetic acid solution.
Cysteine Transport in Melanosomes from Murine Melanocytes
Authors: POTTERF S. BRIAN , VIRADOR VICTORIA , WAKAMATSU KAZUMASA , FURUMURA MINAO , SANTIS CHIE , ITO SHOSUKE , HEARING VINCENT J.
Published: July 2006

The synthesis of pheomelanin requires the incorporation of thiol‐containing compound(s) during the process of mammalian melanogenesis. Since melanins are produced only in specialized, membrane‐bound organelles, known as melanosomes, such thiol donor(s) must cross the membrane barrier from the cytosol to the melanosome interior. Cysteine and/or glutathione (GSH) were proposed as suitable thiol donors, although uptake of these compounds into melanosomes was not previously characterized. In this study, we show that cysteine is transported, in a temperature‐ and concentration‐dependent manner, across membranes of melanosomes derived from murine melanocytes. Additional proof that cysteine uptake results from a carrier‐mediated process and is not due to simple diffusion or to a membrane channel, was obtained in counter‐transport experiments, in which melanosomes preloaded with cysteine methyl ester took up significantly more [35S]cysteine than did unloaded controls. In contrast, we were unable to detect any significant uptake of [35S]GSH over a wide concentration range, in the presence or in the absence of reducing agent. This study is the first demonstration of melanosomal membrane transport of cysteine, and it strongly suggests that free cysteine is the thiol source utilized for pheomelanin synthesis in mammalian melanocytes.
Hepatocyte Growth Factor/Scatter Factor‐MET Signaling in Neural Crest‐Derived Melanocyte Development
Authors: KOS LIBIA , ARONZON ANNA , TAKAYAMA HISASHI , MAINA FLAVIO , PONZETTO CAROLA , MERLBVO GLENN , PAVAN1 WILLIAM
Published: July 2006

The mechanisms governing development of neural crest‐derived melanocytes, and how alterations in these pathways lead to hypopigmen‐tation disorders, are not completely understood. Hepatocyte growth factor/scatter factor (HGF/SF) signaling through the tyrosine‐kinase receptor, MET, is capable of promoting the proliferation, increasing the motility, and maintaining high tyrosinase activity and melanin synthesis of melanocytes in vitro. In addition, transgenic mice that ubiquitously overexpress HGF/SF demonstrate hyperpigmentation in the skin and leptomenigenes and develop melanomas. To investigate whether HGF/ SF‐MET signaling is involved in the development of neural crest‐derived melanocytes, transgenic embryos, ubiquitously overexpressing HGF/SF, were analyzed. In HGF/SF transgenic embryos, the distribution of melanoblasts along the characteristic migratory pathway was not affected. However, additional ectopically localized melanoblasts were also observed in the dorsal root ganglia and neural tube, as early as 11.5 days post coitus (p.c.). We utilized an in vitro neural crest culture assay to further explore the role of HGF/SF‐MET signaling in neural crest development. HGF/SF added to neural crest cultures increased melanoblast number, permitted differentiation into pigmented melanocytes, promoted melanoblast survival, and could replace mast‐cell growth factor/Steel factor (MGF) in explant cultures. To examine whether HGF/SF‐MET signaling is required for the proper development of melanocytes, embryos with a targeted Met null mutation (Met–/–) were analysed. In Met–/– embryos, melanoblast number and location were not overtly affected up to 14 days p.c. These results demonstrate that HGF/SF‐MET signaling influences, but is not required for, the initial development of neural crest‐derived melanocytes in vivo and in vitro.
Bicyclic Monoterpene Diols Induce Differentiation of S91 Melanoma and PC 12 Pheochromocytoma Cells by a Cyclic Guanosine‐Monophosphate‐Dependent Pathway
Authors: BROWN DAVID A. , LESIAK KRYSTYNA , REN WU‐YUN , STRZELECKI KAREN L. , KHORLIN ALEXANDER A.
Published: July 2006

Previously, we showed that 5‐norbornene‐2,2‐dimethanol (5‐NBene‐2,2‐DM) is an effective inducer of melanogenesis in cultured cells and guineapig skin [Brown et al. (1998) J. Invest. Dermatol., 110:428‐437]. This study shows that 2,3‐cis/exo‐pinanediol (2,3‐cs/ex‐PinD) is a more effective inducer of melanogenesis than 5‐NBene‐2,2‐DM in S91 mouse melanoma cells. Furthermore, 2,3‐cs/ex‐PinD appears to penetrate guinea‐pig skin better than 5‐NBene‐2,2‐DM and to induce higher levels of pigmentation. Both 5‐NBene‐2,2‐DM and 2,3‐cs/ex‐PinD induce synthesis of nitric oxide (NO) in S91 cells, and the melanogenic activity of both compounds is reduced by inhibitors of the NO/cyclic guanosine monophosphate (cGMP)/protein kinase(PK) G signaling pathway, but not by inhibitors of the PKC or PKA pathways. Thus, these bicyclic monoterpene diols appear to induce melanogenesis by the same pathway in S91 cells as that shown previously for ultraviolet radiation in melanocytes (Romero‐Graillet et al. (1996) J. Biol. Chem., 271:28052‐28056). These compounds also induce NO synthesis, neurite outgrowth, and tyrosine hydroxylase activity in PC 12 pheochromocytoma cells. Neurite outgrowth in PC 12 cells is blocked by the guanylate cyclase inhibitor, LY83583 (6‐anilino‐2,8‐quinolinequinone), indicating that, similar to S91 cells, the induction of morphological differentiation of PC12 cells by bicyclic monoterpene diols is regulated by a cGMP‐dependent pathway.
The Emergence of Pigment Cell Biology: A Personal View
Authors: BAGNARA JOSEPH T.
Published: July 2006

This is a semi‐autobiographical coverage of my research career in pigment cell biology presented in the context of the emergence and growth of the discipline. This anecdotal presentation tells about some historical personages in the field. My undergraduate studies at the University of Rochester are related to my graduate work at the University of Iowa. I tell how my dissertation research was derived from a marriage between my interests in experimental embryology and the new field of comparative endocrinology. My early years of research at Iowa and as a young faculty member in Zoology at the University of Arizona were much concerned with the evolution of our knowledge of the chemistry and biology of melanocyte‐stimulating hormone (MSH), especially concerning the pigment cells of lower vertebrates. Our developmental, structural, functional, and biochemical characterization of vertebrate chromatophores is described, as is our elucidation of the dermal chromatophore unit. The direct effects of light on changes in pigmentation are considered in descriptions of both the tail‐darkening reaction and the role of the pineal gland in melanophore control. Emphasis is placed on the developmental biology of pigmentation, especially on the concept that all pigment cells are derived in common from a stem cell of neural‐crest origin, whose expression is influenced by factors, such as melanization‐inhibiting factor (MIF), localized in specific areas of the skin to thus produce specific pigmentation patterns. This research is considered in light of what is known about the agouti locus and MSH in the expression of mammalian pigmentation patterns. Part of my work has included ecological considerations, and some of this is touched upon. My role as founder of the journal‘Pigment Cell Research', is presented briefly, as is my involvement in the XIHth International Pigment Cell Conference and in the establishment of both the International Pigment Cell Society and the International Federation of Pigment Cell Societies. Finally, I comment on the future of research in pigmentation.
An Ex Vivo Study of Congenital Pigmented Nevi in Epidermal Reconstructs
Authors: BESSOU‐TOUYA SANDRINE , MORICHON FABIENNE , SURLÈVE‐BAZEILLE JEAN‐ETIENNE , BIOULAC‐SAGE PAULETTE , PAIN CATHERINE , TAÏEB ALAIN
Published: July 2006

In order to study morphologic and functional characteristics of pigment cells in congenital pigmented nevi, autologous or heterologous reconstructs have been made using normal keratinocytes and nevus cells from the dermal‐epidermal junction or from the dermis. All these cells, keratinocytes and nevus cells, were used as cell suspensions immediately after dissociation from the tissues or after subsequent brief cultivation in a serum‐free medium. Reconstructed epidermis were cultured for 15 days at the air‐liquid interface with or without ultraviolet (UV) B exposure. The reconstructs were examined macroscopically (formation of hyperpigmented macules), histologically (pigment cell nesting) and ultrastructurally (pigment structure and transfer).

Typical nesting of nevus cells was observed in the dermal‐epidermal junction or in the superficial dermis associated with macroscopically detectable small pigmented macules. UVB exposure induced an upward migration of nevus cells in the suprabasal layers of the epidermis.

This tissue model can be considered as an excellent system for the ex vivo reproduction of pigmented nevi and as an assay of the sensitivity of nevus cells towards UVB irradiation.
The Patchwork Mouse Phenotype: Implication for Melanocyte Replacement in the Hair Follicle
Authors: AUBIN‐HOUZELSTEIN GENEVIEVE , PANTHIER JEAN‐JACQUES
Published: July 2006

Mice homozygous for the recessive patchwork (pwk) mutation are characterized by a variegated pigment pattern with a mixture of unpigmented and normally pigmented hairs. The pigmented hair bulbs contain functional melanocytes. By contrast, the unpigmented hair bulbs contain no melanocytes. This lack results from the death of melanoblasts in the hair follicle at the end of embryogenesis. Here, we report that melanoblasts and melanocytes are found in the epidermis of pwk/pwk mice. Furthermore, these epidermal pigment cells are able to colonize new hair follicles after skin wounding. Despite the presence of epidermal pigment cells with a colonization potential, a follicle that had produced an unpigmented hair produces a new unpigmented hair during the successive hair growth cycles. This hair color continuity is also true for the pigmented hair follicles. Thus, in normal conditions, the hair acts as an independent functional unit as regards its pigment cells population.
Sound Needs Sound Melanocytes to Be Heard
Authors: TACHIBANA MASAYOSHI
Published: July 2006

Intermediate cells in the stria vascularis of the mammalian cochlea are melanocytes, which contain melanin pigments and are capable of synthesizing melanin. These melanocytes are required for normal development of the cochlea, as evidenced by studies of mutant mice with congenital melanocyte anomalies. Melanocytes are also needed for developed cochleae to function normally, as evidenced by studies of mutant mice with late‐onset melanocyte anomaly and humans with acquired melanocyte anomaly. Melanin, per se, does not seem to be essential for normal hearing function, but it may protect against traumata to the cochlea, e.g., noise and ototoxic aminoglycosides. Recent electrophysiological studies have revealed that strial intermediate cells are provided with specific ionic channels, such as inwardly rectifying K+ channels (Kir4.1) and voltage‐dependent outwardly rectifying K+ channels. These channels may play central roles in strial function and thus in normal hearing.
Transgenic Mouse Models for Tumors of Melanocytes and Retinal Pigment Epithelium
Authors: BEERMANN FRIEDRICH , HUNZIKER AGNÈS , FOLETTI ALESSANDRO
Published: July 2006

Cutaneous and ocular melanomas are due to malignant transformation of neural crest‐derived melanocytes. The rising incidence of this tumor in humans has stimulated experiments to devise suitable mouse models. In the past years, transgenic mouse lines have been generated using different oncogenes ‐ Ha‐ras, SV40 T antigen (Tag), ret ‐ which develop benign lesions of melanocytes, melanoma, and/or eye tumors. Pigment cell tumors in humans, although rather rare, can also develop from the retinal pigment epithelium (RPE), a cell layer of neuroectodermal origin. We, therefore, established transgenic models for this ocular tumor. Regulated by the promoter of tyrosinase‐related protein‐1 (TRP‐1), two oncogenes, ret and SV40 Tag, were targeted to the developing RPE in transgenic mice. The TRP‐1/ret transgenic mice displayed microphthalmia and benign tumors of the RPE. Expression of SV40 T antigen (TRP‐1/Tag) led to malignant tumors, which were invasive and metastasized to inguinal lymph node and spleen.
Molecular Mechanisms of Pigment Transport in Melanophores
Authors: TUMA M. CAROLINA , GELFAND VLADIMIR I.
Published: July 2006

We present an overview of the research on intracellular transport in pigment cells, with emphasis on the most recent discoveries. Pigment cells of lower vertebrates have been traditionally used as a model for studies of intracellular transport mechanisms, because these cells transport pigment organelles to the center or to the periphery of the cell in a highly co‐ordinated fashion. It is now well established that both aggregation and dispersion of pigment in melanophores require two elements of the cytoskeleton: microtubules and actin filaments. Melanosomes are moved along these cytoskeletal tracks by motor proteins. Recent studies have identified the motors responsible for pigment dispersion and aggregation in melanophores. We propose a model for the possible roles of the two cytoskeletal transport systems and how they might interact. We also discuss the putative mechanisms of regulation of pigment transport, especially phosphorylation. Last, we suggest areas of research that will receive attention in the future in order to elucidate the mechanisms of organelle transport.
Age Associated Variations in RNA Biosynthesis by Cells of the Periodontal Ligament: An Autoradiographic Study1
Authors: Singh I. J. , Tonna E. A.
Published: July 2006

The utilization of 3H‐uridine (3H‐U) was used to assess age related changes in RNA biosynthesis by connective tissue cells of the periodontal ligament. One hundred forty‐four BNL mice from 5 to 78 weeks old were injected with 5μ Ci/gm body weight of 3H‐U and killed from 15 min to 30 days later. Autoradiographs were prepared from 5μm thick, decalcified, sagittal sections of the maxillae. Labeled periodontal connective tissue cells were grain‐counted (1) below epithelial attachment, (2) below crevicular epithelium, (3) above alveolar crest, and (4) at the alveolar crest. 3H‐U incorporation was apparent at all time periods (15 min to 30 days). Nuclear labeling achieved peak values 1–4 hours after 3H‐U injection. Cytoplasmic values were maximum at 1–2 days. Nuclear and cytoplasmic counts were similar at 8–16 hours. From 5 to 52 weeks of age, peak values were progressively reduced, curves were broadened and shifted towards later time periods. This age decline in the rate and magnitude of incorporation of 3H‐U reflects changes in the cellular needs for RNA and protein synthesis necessary for matrix production and cellular maintenance. Some age changes were seen at 26 weeks of age. In the oldest animals (78 weeks), there appeared to be an arrest in the age‐decline in 3H‐U utilization. This was probably associated with the inflammatory changes reported in the periodontal ligament of old animals.
Periodontal Disease and Aging
Authors: Anderson D. L.
Published: July 2006

Periodontitis is a chronic disease of humans and animals which becomes more prevalent and severe with increasing age. The prevalent interpretation of the strong correlation between periodontal disease and age is that age merely occurs simultaneously during the extended time that irreversible loss of tooth support results from the accumulative effects of plaque and calculus. In both animals and humans, changes in the periodontium occur with age and are similar to those seen in the same type of tissues elsewhere in the body. To date, it is not clear to what extent these aging changes affect the response of the periodontium to local irritants. At all ages, periodontitis is more severe in mouths with abundant debris and calculus. However, even when these accumulations are minimal, periodontitis becomes more severe with age. Yet, not all elderly, and especially not all teeth in the elderly, suffer from destructive periodontal disease. The periodontium of old animals and humans retains the ability to respond adequately to changes in occlusal forces and to wounding, but the response is delayed in onset and duration. As well, the elderly are likely to suffer from other chronic diseases which may affect the periodontium and its therapy.
Age‐ and Strain‐Associated Dysplasia of Mouse Maxillary Incisor Teeth1
Authors: Cohen Bennett J. , Chrisp Clarence E. , McClatchey Kenneth D. , Anver Miriam R.
Published: July 2006

The occurrence of longitudinal grooves and other dysplastic changes in mouse maxillary incisor teeth was shown to be age‐ and strain‐associated. The dysplasia appears analogous in some respects to human dens invaginatus. Twelve strains of inbred or F1 hybrid mice (282 males, 73 females) were examined at 6, 12, 18, 24, and 30 months of age. Lesions occurred in low prevalence (4–9% of the mice examined) in DBA/2, B10. 129 and Swiss Webster mice, in moderate prevalence (26–48%) in B6D2F1, C57BL/6, CBA/CA, B6C3F1, and A/JN mice, and in high prevalence (58–70%) in HO B/C (nude), CBA/HT6, CBF1 and BALB/c mice. No six month old mice of any strain and only a few 12 month old animals from the high prevalence strains were affected. The prevalence of lesions increased rapidly with age in moderate and high prevalence strains starting at 18 months. The origin of the dysplasia appears to be an age‐ and strain‐associated change in the odontogenic epithelium comprising the enamel organ. We do not yet understand the factors promoting these changes.
Elastoid Changes in the Gingiva of Aged Humans
Authors: Bernick Sol , Paule W.J.
Published: July 2006

Elastotic changes were demonstrable in the gingivae of both dentulous and edentulous jaws obtained from both male and female humans varying in age from 62–92 years. Sections of gingivae from all the aged individuals exhibited numerable thick fibers that stained positive with iron hematoxylin or orcein. These positive staining fibers were found in the lamina propria radiating into the connective tissue papillae, coursing throughout the zona reticularis, as well as appearing as black amorphous masses. Pretreatment of sections with acid hydrolysis before staining by the two elastic tissue stains led to a loss of stainable fibers for elastin. In contrast the gingivae of a young adult did not contain elastic positive fibers as seen in the aged gingivae. The thick elastotic fibers found in the aged gingivae were argyrophilic in nature when the sections were impregnated with silver nitrate indicating that they were collagenous in nature. It is felt that the elastoid‐like fibers in aging gingiva are another phase in the altering of collagen during the aging process.
Comparative Properties of Deciduous and Permanent (Young and Old) Human Enamel1
Authors: LeGeros Racquel Z. , Piliero Joseph A. , Pentel Leon
Published: July 2006

Some physico‐chemical properties of the enamel of deciduous and permanent (young and old) teeth were investigated and compared using x‐ray diffraction, infrared absorption spectroscopy, scanning electron microscopy and chemical analyses. Results demonstrated the following: all enamel samples gave x‐ray diffraction patterns of only apatite; all enamel samples gave IR absorption spectra of carbonate‐containing apatite; the α‐axis of deciduous enamel apatite was larger than that of permanent (both young and old) enamel apatite (mean values, deciduous = 9.458 ± 0.003A; permanent =9 443 ± 0.003A); apatite crystallite dimensions increased with age especially along the c‐axis; when compared to permanent, deciduous enamel contained slightly more carbonate, magnesium and HPO42‐; the prism (enamel rods) dimensions were slightly smaller, and the extent of acid‐etching was more extensive in deciduous enamel than in permanent enamel. These observations combined with other factors such as the difference in the orientation of and crystal density in prism rods and the difference in conditions of the oral environment between deciduous and permanent enamel may account for the reported observations of a decrease in caries prevalance with age.
Longitudinal Stability and Masticatory Function of Human Dentition1
Authors: Feldman Roy S. , Alman John , Muench Marianne E. , Chauncey Howard H.
Published: July 2006

In view of the need for a multidisciplinary approach to study the effect of aging on the oral cavity, “The Veterans Administration Longitudinal and Cross‐Sectional Study of Oral Health in Healthy Veterans” or the Dental Longitudinal Study (DLS) was initiated in 1968, as an associated research program of the larger “VA Normative Aging Study.”. The current report presents a review of the literature of masticatory performance and relevant experimental data from the DLS on dentition and age‐related changes in performance levels. These data sets demonstrate that in volunteers with natural dentition, there was a slight, but significant, decrease in masticatory performance while dentitions with prostheses showed little change. It appears that when appreciable declines in masticatory function occur, significant alterations also occur in certain perceptual and sensory measures associated with food hedonics and consumption behavior. Generally, these perceptual changes reflect an alteration in taste and texture preferences; phenomena which persist even after appropriate restorative therapy with either removable partial or complete dentures. Information collected in some of our studies suggests that dentate‐impaired persons, with and without a dental prosthesis, may self‐impose certain dietary restrictions which, in time, can compromise their nutritional status and ultimately place them at health risk. These longitudinal results are attempting to provide a comprehensive description of oral phenomena and represent a unique study of the oral aging process.
Oral Health and Treatment Needs of Patients in Two Communal Nursing Homes
Authors: Honkala Eino , Rantala Erkki , Nyyssönen Viljo
Published: July 2006

The aim of this study was to describe the oral status of patients in two communal nursing homes and to assess the need of those patients for dental treatment. The study was based on a sample that included all patients in the nursing homes of two typical Finnish rural communes. Data were collected for the 132 patients who were examined by a dentist in the nursing homes. As background data for the study we used patient records and interviews. Fifty percent of the patients had no teeth. Among the totally edentulous, every second man and every fourth woman either did not have or did not use dentures. Only half of the patients could be classified as eligible for dental treatment. The main treatment need was prosthetic care treatment. The total estimated number of visits needed per patient was 2.4. The total cost of this treatment series was estimated to be 71 US$/patient. Based on this evaluative study, the dental treatment for nursing home patients could easily be organized by using one dental unit for three weeks.
Action of Urea Solutions on Unerupted and Erupted Teeth: An Investigation on Late Maturation of Human Enamel1
Authors: Goldberg M. , Arends J. , Jongebloed W.L. , Schuthof J. , Septier D. , Apap M.
Published: July 2006

Replicas of unerupted and erupted human enamel submitted to protein‐disrupting solutions showed: (1) an inequal distribution of porosities in the subsurface; (2) such porosities were restricted gradually in each enamel subunit (enamel segments limited by two perikymata). First the whole surface was covered by a network, reduced at a later stage to half of the surface and ultimately the porosities were present only in the perikymata. This paper confirms the occurrence of a late maturation at stage where cells are no longer active and details the time‐dependent involution of these porosities.
Dental Status in the Elderly: A Review of the Swedish Literature1
Authors: Nordenram Gunilla , Böhlin Erling
Published: July 2006

1. Elderly persons living in their own homes have over the past 20 years tended to retain an increased number of natural teeth. This tendency is confirmed especially in the ongoing studies by Tor Österberg, nr 12 and 13. These studies indicate a decreasing edentulous part of the 70‐year old cohorts from 1971, 1976 and 1981.

2. Elderly persons dependent on institutional care are edentulous in as high degree today as 20 years ago. According to this criterion, therefore, their dental health has not improved.

3. Dentures worn by elderly persons frequently are defective in fit and function. For the general wellbeing and health in later life, mastication of a well‐balanced diet and lack of discomfort from denture‐bearing mucosal surfaces are important. Information in this respect and measures to improve masticating function are greatly needed among persons in the higher age groups, whether living at home or in institutional care.

4. Caries activity is increasing among elderly persons.

5. Periodontitis (loosening of the teeth) is very frequently found in elderly persons.

6. Oral hygiene requires improvement.

7. Among the elderly, living in their own homes or in institutions, the need for odontologic care is objectively great, but the demands currently made are remarkably low.

8. Of the aged in institutional care, about 75 per cent are suitable for measures of oral care.

A change in dental health seems to be slowly taking place among the elderly, in that increasing numbers keep more of their own teeth longer in life. The demands made by the high age groups on the odontologic services, though increasing, are still very low relative to the objective and consequently great accumulated needs. This contrast is especially pronounced among geriatric patients in institutions.

An aggressive, searching approach to both restorative and preventive oral care in the higher age groups is of pressing importance if optimum conditions for eating and chewing late in life are to be achieved. For timely counteraction of the tendency to a more passive attitude t o dental care that commonly accompanies rising age, information on these matters should be energetically disseminated among persons due for retirement or new‐l y retired.
The Condition of the Oral Mucosa at Age 70: A Population Study1
Authors: ÖSterberg Tor , ÖHman Alf , Heyden Guy , Svanborg Alvar
Published: July 2006

At oral examinations of 70‐year old men (186) and women (199) in Göteborg (H‐70‐study) it was concluded that the degrees of dental invalidity and the frequencies of oral red, white and hyperplastic lesions were high in spite of the rather good physical conditions of the elderly. Variations in the general health of the subjects and their drug utilizations seemed to participate in the regulation of the threshold levels of the oral tissues against external irritations. A high percentage of the oral lesions were related to local factors, such as dental state, removable dentures, tobacco habits and factors affiliated with secretion of saliva. Insufficient functions of the dentures were found to induce hyperplastic changes even if the dentures had been worn for only a short period of time. Smoking was statistically demonstrated to be a significant contributing factor to tooth losses as well as to the induction of oral white lesions. The supervising responsibilities of the dentists are discussed on the basis of the clinical and statistical findings in this investigation.
The Clinical Identification of Root Caries
Authors: Katz Ralph V.
Published: July 2006

This paper discusses a variety of considerations associated with the clinical identification of root caries. While focusing upon this clinical identification process from the perspective of the clinical researcher, the differing diagnostic needs between the clinical researcher and the dental practitioner are frequently addressed. The topic of the identification of untreated root caries lesions includes a presentation of both existing definitions and a proposed set of diagnostic criteria. The presentation of the topic on the identification of arrested and treated root caries lesions emphasizes the diagnostic challenge that will occur due to the newly introduced chemotherapeutic treatments that have been proposed for the control of root caries. The influence of varying examination conditions, techniques and instruments on the reliability and validity of the clinical identification of root caries are also considered. Finally, a preliminary set of clinical research diagnostic conventions, which would both aid the researcher in “grey zone decisions” and enhance comparability of findings across studies, are proposed.
Demineralization and Remineralization of Root Surface Caries
Authors: Mellberg J.R.
Published: July 2006

Although enamel, cementum and dentin all develop carious lesions in roughly the same manner there are significant differences between enamel and the other two tissues. While early enamel lesions are white, root surface lesions in cementum or dentin are light brown or yellow. The color probably arises from extrinsic stain materials, and it is possible that very early, actively forming lesions are colorless. Cementum and dentin often acquire a hypermineralized surface when first exposed to the oral environment. When caries begins to form, this layer can enlarge or disappear. Therefore, it is possible to have lesions with hypermineralized surface layers, hypomineralized surface layers, or no surface layer. Hypermineralization can also occur deeply within a lesion, probably as a result of remineralization. When this occurs the lumen of the tubules fill with mineral and the crystals within the lesion body become larger. Fluoride is readily taken up by carious root tissues and contributes to remineralization. Remineralization of artificial root surfaces after treatment with monofluorophosphate has been shown. In these lesions much of the newly acquired mineral was found near the surface but some was also found in the lesion body.
Restoration of Carious Lesions of the Root1
Authors: Billings Ronald J.
Published: July 2006

This paper summarizes and evaluates the indications and limitations of various dental materials and techniques for the treatment and restoration of root surface dental caries. Development of a severity index for classifying and sorting lesions is described. Historical materials such as silver amalgam and gold foil are briefly discussed as are contemporary materials such as composite resins and dentin bonding primers. Emphasis is placed on materials and techniques requiring minimal invasion or preparation of the root surface. Eradication of root lesions by recontouring and smoothing the root surface is discussed at length. A new dental material, glass ionomer cement, which contains fluoride and forms a physicochemical bond with enamel and dentin. and requires no preparation of the root surface other than lesion debridement, is described in detail. Guidelines for managing arrested lesions are offered. In addition, the importance of topical fluoride in the treatment and management of root caries is discussed. Lastly, some suggestions are offered for future directions of research in this area.