bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Marangoni‐induced flow on the rate of refractory dissolution in molten slags
Authors: Fagerlund Kim , Sun Shouyi , Jahanshahi Sharif
Published: March 2003

Dissolution rate of silica rods in iron‐saturated silicate slags containing 15–30% SiO2 was measured using the rotating cylinder technique at 1300°C, under a controlled atmosphere of deoxidized Ar‐gas. These measurements were aimed at quantifying the magnitude of Marangoni‐induced flow near the slag–refractory region. The Marangoni effect was found to be significant under stagnant conditions, but gradually became dominated by bulk flow when the linear velocity of the flowing melt was increased, and reached values in the range of 0.09–0.16 m/s. This implies that, in highly agitated vessels, the Marangoni effect is unlikely to play a dominant role in refractory wear at the slag line. Also, the silica dissolution rate and mass transfer coefficient were examined, and it was found that with increasing silica content of the slag, the dissolution rate and mass transfer coefficient decreased. Furthermore, the relationship between Marangoni number and Reynolds number was calculated, and boundary flow conditions determined using the experimental critical velocity.
Activity measurement of silicate slags equilibrated with molten silicon alloys
Authors: Morita Kazuki , Kume Kousuke , Sano Nobuo
Published: March 2003

The activities of components in the CaO‐SiO2‐AlO1.5‐MgO slags were directly measured by equilibrating the slags with silicon‐based alloys on the basis of a new integration method derived from the Gibbs–Duhem relation. For the CaO‐SiO2, CaO‐SiO2‐AlO1.5 and CaO‐SiO2‐MgO slags, the activity of SiO2 was obtained from the distribution of each element between slag and metal using each thermodynamic property in molten silicon alloys, and the activities of other components in the slags were subsequently derived at 1823 or 1873 K. For the CaO‐SiO2‐AlO1.5‐MgO slags, the activities of components other than SiO2 on the 10 mass% MgO plane were obtained at 1873 K by using the activity of SiO2 available in the literature. Therefore, it has been confirmed that the activities of components other than SiO2 in multicomponent silicate slag systems can be determined by this technique as long as the activity data of at least one component in the system are available.
Germ cell parasitism as an ecological and evolutionary puzzle: hitchhiking with positively selected genotypes
Authors: Rinkevich Baruch
Published: March 2003

The phenomenon of intraspecific germ cell parasitism may reveal a theoretical puzzle to the concept of Darwinian selection. In natural chimeras of the colonial protochordate Botryllus schlosseri, parasitic germ lines hitchhike with positively selected allogeneic soma, passing throughout successive generations without being visible to natural selection forces. This may cause the possible development of super‐parasitic entities, specialized in allogeneic invasion and germ cell parasitism. Three evolutionary selected mechanisms (diversification of fusibility allele repertoire, the establishment of multichimeric entities, induction of programmed life spans) reduce opportunities for parasitic forms to hitchhike to a high frequency with selected genotypes, and may shape, on the other hand, more benign germ cell parasitic forms that share overlapping future expectations with their hosts. These benign forms are expected to contribute cells for somatic functions, forming entities with fitness that depends on joint genomic fitness of the partners. Population‐level feedback thus may stabilize chimeric entities, shaping the evolution of chimerism.
Effects of time‐dependent competition for oviposition sites on clutch sizes and offspring sex ratios in a fig wasp
Authors: Kinoshita Motoaki , Kasuya Eiiti , Yahara Tetsukazu
Published: March 2003

Fig wasps have been known as one of the best‐documented examples of female‐biased sex ratio predicted from the local mate competition (LMC) theory. However, observed sex ratios appear more female‐biased than predicted. Before a close match between theory and observation can be claimed, the number and sex ratio of offspring left by each foundress in a multi‐foundress syconium need to be determined. We examined the clutch size and sex ratio of individual females of the pollinator fig wasp Blastophaga nipponica (Agaonidae) in experiments using a pair of fertile and sterile females in which sequence and time interval of entering syconia were manipulated. To determine the number and sex ratio of offspring left by each foundress in a multi‐foundress syconium, we prepared sterilized females that could oviposit ordinarily but whose offspring could not develop at all, by irradiating the females with 60Co gamma rays. Female fig wasps contributed different numbers and sex ratios of offspring to the total brood within a syconium, due to different entry times among them. The variation in clutch sizes with different entry times appeared to be caused by competition for oviposition sites, and sex ratios to be adjusted according to the clutch size.
Effects of site and fruit size on the composition of avian frugivore assemblages in a fragmented Afrotropical forest
Authors: Githiru M. , Lens L. , Bennur L. A. , Ogol C. P. K. O.
Published: March 2003

Factors influencing the interaction between fruiting trees and their frugivorous seed dispersers in fragmented Afrotropical landscapes are poorly known. With the use of Mantel statistics we analysed assemblages of frugivorous birds on 58 individual trees belonging to 11 species growing in seven Kenyan cloud forest fragments. Overall, frugivores showed little specialization on particular trees. Fruit size explained a substantial amount of the variation in frugivore assemblages among different tree species at the same site. In addition, frugivore assemblages on conspecific trees were significantly more similar when the trees occurred at the same site. This location effect was attributable to the different sites and forest fragments (of different sizes and disturbance levels) varying in the densities and composition of their avian frugivores, vegetation composition and tree fruiting phenologies. It was consolidated further by the low mobility of most of these avian frugivores, particularly their reluctance to cross between forest fragments. Habitat disturbance and fragmentation may therefore have affected fruit selection, with implications for both seed dispersal and regeneration.
Fitness consequences of the timing of metamorphosis in a freshwater crustacean
Authors: Twombly Saran , Tisch Nancy
Published: March 2003

Metamorphosis is a common life‐cycle transition in organisms as diverse as amphibians, insects, fishes and crustaceans, and the timing of this transition often affects an individual's fitness. Here, we measured age and size at metamorphosis in laboratory‐reared individuals of the freshwater copepod, Diaptomus leptopus, and then followed individuals over their entire life cycle to assess the fitness consequences of variation in age and size at metamorphosis. In 3 separate experiments, individuals were raised in different food conditions: low food (0.2 μg C/ml) switched to high food (0.7 μg C/ml), or high food switched to low food, at several different larval and juvenile stages. Control individuals were reared on high or low food concentrations over their entire life cycles. For each individual, we measured age and size at metamorphosis and age and size at maturity; for females, we also measured total lifetime egg production, longevity, and calculated a composite fitness measure, λ. Statistical analyses showed no significant effects of age or size at metamorphosis on these same traits measured at maturity, or on the fitness components we estimated. The first individuals to mature had the highest total egg production and individual fitness; differences in body size at maturation explained none of the variation observed in fitness components. Our results show that metamorphosis was uncoupled from maturity and from fitness components by growth and development achieved during the juvenile phase of the life cycle, and support the conclusion that fitness consequences of metamorphosis depend fundamentally on the organization of an organism's life cycle. They also suggest that body size plays a different life‐history role in these organisms than is recognized in most poikilotherms, and suggest the hypothesis, based on laboratory experiments, that selection may act primarily on juvenile developmental rates in field populations.
Correlated evolution of fruit and leaf size in bird‐dispersed plants: species‐level variance in fruit traits explained a bit further?
Authors: Herrera Carlos M.
Published: March 2003

The astounding morphological diversity exhibited by the fruits of vertebrate‐dispersed plants has been traditionally interpreted as the adaptive outcome of divergent selective pressures exerted on plants by the broad array of frugivorous animals involved in seed dispersal. Although the selective capacity of frugivores provides support to this interpretation, recent studies have challenged it by documenting a strong phylogenetic component associated to interspecific variation in most fruit characteristics. Size‐related fruit traits provide a conspicuous exception to this pattern, because they exhibit considerable variation at the between‐species level which is largely independent of phylogeny and is correlated with consumption by differently‐sized dispersal agents. Substantial species‐level variance in size‐related traits may reflect genuine disperser‐driven diversification, but may also be partly influenced by correlated evolution of fruit size with the size of other plant structures. This latter possibility is tested here for bird‐dispersed plants of the Iberian Peninsula using phylogenetically independent contrasts. Results demonstrate the existence of correlated evolution of fruit and leaf size at the species level. As all the plant taxa considered have their fruits eaten, and seeds dispersed, by the same relatively reduced set of frugivorous bird species, results suggest that a significant fraction of the variation in fruit size represented in the species sample may be explained as an indirect consequence of variation in leaf size, rather than being associated with adaptive divergence related to seed dispersal agents.
Seagull influence on soil properties, chenopod shrub distribution, and leaf nutrient status in semi‐arid Mediterranean islands
Authors: García Luis V. , Marañón Teodoro , Ojeda Fernando , Clemente Luis , Redondo Ramón
Published: March 2003

Concentration of seagulls in the Chafarinas Islands (three semi‐arid North African islets) induces profound changes in soil properties including eutrophication, salinization, acidification and nutrient imbalances. Soils of heavily seabird‐affected sites have significantly higher soluble K and NO3 levels (>20‐fold), Zn and Fe availability (>5‐fold), water‐retention capacity (>40% increase) and 15N enrichment, compared with control sites. These seabird‐induced soil changes are paralleled by (i) different patterns of abundance of the two main chenopod shrubs: Suaeda vera abundance is higher (>30‐fold) in seabird‐affected sites while Salsola oppositifolia largely dominates in low‐affected areas. No differences were found for Atriplex halimus. The abundance of the first two species may be largely explained by changes in soil soluble K‐to‐available Ca ratio whose value depends of the interaction between seabird products and soil constituents; (ii) significant increases in leaf N, P and Zn levels, and in all K ratios, paralelled by a decrease in Ca, in Salsola; but only by increased K/Na and P/Ca ratios in Suaeda leaves. These changes were significantly correlated to changes in species abundances; (iii) an increase of δ15N, paralleled by a decrease in δ13C values, in Salsola leaves but not in Suaeda. Conjoint analysis of the seabird‐related changes in soil properties, species abundance, leaf composition and differential response to the seabird‐induced fertilization/severity gradient of the two main chenopod shrub species, has led us to propose an explanatory hypothesis of seagull‐soil‐shrub relationships. According to this, the seagull‐induced soil changes, mediated by processes of (in)tolerance‐facilitation, play a main role in determining the abundance and the leaf nutrient status of the studied chenopod shrubs, which have contrasting physiological adaptations.
Population history and life history influence the migration rate of female Glanville fritillary butterflies
Authors: Hanski Ilkka , Breuker Casper J. , Schöps Katrin , Setchfield Rosemary , Nieminen Marko
Published: March 2003

This study examines the causes of emigration from small fragments of suitable habitat in a species that has a distinct metapopulation structure, frequent turnover of local populations, and substantial migration among local populations and currently unoccupied habitat fragments. We conducted a field experiment in which 727 individuals of the Glanville fritillary butterfly (Melitaea cinxia) originating from four regions were marked and released simultaneously in a natural environment. In three of the four source regions, larvae for the experiment were collected from dozens of small local populations, some of which had been established in the previous summer (new populations), whereas the remaining populations were older. In two of the source regions, female butterflies prefer a host plant (Veronica spicata) that is not present in the release area, where there is onlyPlantago lanceolata, the preferred host plant of females from the other two source regions. We found that migration rate of males was unrelated to any of the factors studied in this experiment. In contrast, two factors influenced the migration rate of females. First,Veronica‐preferring females had higher emigration rate thanPlantago‐preferring females from thePlantago‐containing release patches, demonstrating that the individual perception of habitat quality significantly influences the migration rate of females. Second, females from newly‐established populations were more dispersive than females from older populations, supporting the notion that metapopulation processes (recurrent colonizations) select for increased migration. The observed migration rate was not correlated with any body size measurements, and thus the observed differences in migration rate were apparently caused by differences in the behaviour of female butterflies rather than in their flight capacity.
Escape from pupal predation as a potential cause of outbreaks of the winter moth, Operophtera brumata
Authors: Raymond B. , Vanbergen A. , Watt A. , Hartley S. E. , Cory J. S. , Hails R. S.
Published: March 2003

The winter moth, Operophtera brumata, shows varying population dynamics in different host plant habitats. Populations in Sitka spruce, Picea sitchensis, plantations and in Scottish moorlands have a tendency to outbreak that is not shown by winter moth in lowland oak woods. Since pupal predators have previously been identified as being important for the regulation of winter moth in a lowland oak wood it was hypothesized that invertebrate pupal predators were failing to control winter moth in outbreak populations. This hypothesis was tested by comparing the abundance of invertebrate predators and patterns of spatially density dependent pupal predation across habitats. Several results supported this hypothesis. Carabid predators of winter moth were one or two orders of magnitude more abundant in oak woods than in moorland or spruce habitats. Staphylinid predators were also more abundant in high winter moth density oak woods than in any other habitat. Beetle predation of tagged cocoons in the field was inversely density dependent in Highland moors in experiments in 1999 and 2000, and in Sitka spruce in 1999. However, in opposition to our hypothesis, pupal predation was also inversely density dependent in oak woods in 2000, although this result may be explained by the low range of winter moth densities in the field that year. These results are discussed in relation to the role of natural enemies in regulating winter moth populations and the differences in life‐history of the beetle predators in different habitats.
Examining the effects of species richness on community stability: an assembly model approach
Authors: Wilmers Christopher C. , Sinha Sitabhra , Brede Markus
Published: March 2003

We build dynamic models of community assembly by starting with one species in our model ecosystem and adding colonists. We find that the number of species present first increases, then fluctuates about some level. We ask: how large are these fluctuations and how can we characterize them statistically? As in Robert May's work, communities with weaker interspecific interactions permit a greater number of species to coexist on average. We find that as this average increases, however, the relative variation in the number of species and return times to mean community levels decreases. In addition, the relative frequency of large extinction events to small extinction events decreases as mean community size increases. While the model reproduces several of May's results, it also provides theoretical support for Charles Elton's idea that diverse communities such as those found in the tropics should be less variable than depauperate communities such as those found in arctic or agricultural settings.
Hepatitis C virus‐associated oral lichen planus: no influence from hepatitis G virus co‐infection
Authors: Lodi Giovanni , Carrozzo Marco , Harris Katherine , Piattelli Adriano , Teo Chong G. , Gandolfo Sergio , Scully Crispian , Porter Stephen R.
Published: March 2003

Abstract: There is a variable geographic distribution in the prevalence of hepatitis C virus (HCV)‐related oral lichen planus (OLP), which appears unrelated to either HCV genotype or HCV epidemiology. The present study investigated whether hepatitis G virus (HGV) co‐infection may be a feature of patients with HCV‐related OLP, which might explain these phenomena. HGV co‐infection was detected in 6 of 39 Italian patients with HCV‐related OLP, but the presence of HGV did not influence the clinical presentation of OLP. It is concluded that HGV co‐infection is unlikely to influence the clinical detection of HCV‐related OLP.
Lip cancer in Northern Finland: changing incidence and clinical characteristics
Authors: Alho Olli‐Pekka , Keränen Marja‐Riitta , Kantola Saara , Riihimäki Seija , Jokinen Kalevi , Alho Pentti , Nuutinen Juhani
Published: March 2003

Abstract: A population‐based survey was conducted in 35 municipalities in Northern Finland to assess the incidence of lip cancer as well as the patient and tumour characteristics in cases diagnosed between 1983 and 1997. A total of 96 new patients emerged. The age‐standardised incidence (per 100,000 years) of lip cancer in men decreased from 4.8 in 1983–1987 to 1.4 in 1993–1997. The incidences in women were 0.30 to 0.36, respectively. The median age of the patients increased from 66 to 73 years through the years. Overall, 90% of the patients had at least one of the known risk factors, namely rural domicile, outdoor occupation or smoking. The median duration of symptoms also remained the same, as did the median size and location of the tumour at diagnosis. In contrast, spread to regional lymph nodes became rare during the period.
Gene expression of differentiation‐specific keratins (K4, K13, K1 and K10) in oral non‐dysplastic keratoses and lichen planus
Authors: Bloor Balvinder K. , Seddon Sophie V. , Morgan Peter R.
Published: March 2003

Abstract: Gene expression for the differentiation‐specific keratins (K4, K13, K1 and K10) was analyzed in oral non‐dysplastic keratoses, oral lichen planus (OLP) and lichenoid reactions (LR) by comparative in situ hybridization (ISH) and immunohistochemistry (IHC) to investigate molecular changes in the altered differentiation pattern from non‐ to para‐ or orthokeratinization. At the protein level, K4 and K13 were detected homogeneously in the suprabasal compartment of parakeratotic epithelium but showed reduced expression in orthokeratoses, particularly in the presence of lymphocytes. Corresponding transcripts were restricted to basal and lower prickle cells. Synthesis of K1 and K10 was upregulated and more pronounced in orthokeratotic epithelia. The study showed an alteration in the pattern of differentiation‐specific keratins, although involvement of the lymphocytic infiltrate in OLP and LR resulted in further gene modulation. In both diseases, K1 and K10 showed transcriptional control, proteins having the same distribution as their transcripts. This represented a change from post‐transcriptional regulation in normal buccal epithelium, in which mRNAs for K1 and K10 are more widely expressed than their proteins. Thus, the pattern of keratin gene expression may be altered in response to frictional/smoking stimuli or immune‐mediated mechanisms.
First hints for a correlation between amplification of the Int‐2 gene and infection with human papillomavirus in head and neck squamous cell carcinomas
Authors: Kleist Britta , Poetsch Micaela , Bankau Alexander , Werner Eberhard , Herrmann Falko H. , Lorenz Gerd
Published: March 2003

Abstract: Infection with human papillomavirus (HPV) and alterations in certain genes have frequently been proposed as mechanisms in the pathogenesis of head and neck squamous cell carcinoma (HNSCC). Here, we investigated 47 HNSCC for the presence of HPV and, by fluorescence in situ hybridisation, for amplification of Int‐2 and Hst‐1 in the search for a possible correlation. The highest frequency of HPV infection was found in hypopharyngeal carcinomas, while amplification of Int‐2 or Hst‐1 was distributed more equally among the different localisations. Amplification of Int‐2 was detectable (7 of 9 cases) in 78% of the HPV‐positive carcinomas, whereas no virus infection could be found in the five cases with amplified Hst‐1 only. In spite of the rather low number of infected tumour samples, our results suggest a correlation between HPV infection and amplification of Int‐2.
Peripheral ameloblastoma with potentially malignant features: report of a case with special regard to its keratin profile
Authors: Tajima Yoshifumi , Kuroda‐Kawasaki Mina , Ohno Jun , Yi Jiang , Kusama Kaoru , Tanaka Hiromasa , Fukunaga Shuichi , Shimada Jun , Yamamoto Yoshiro
Published: March 2003

Abstract: A peripheral ameloblastoma with atypical features occurring on the left maxillary alveolar ridge of 40‐year‐old man is described, along with an immunohistochemical profile of its cytokeratin (CK). The lesion apparently originated from the surface gingival epithelium. The tumor nests or strands were highly cellular with a variable degree of squamous differentiation and microcyst formation. Occasional mitotic figures and dystrophic calcification, both of which are not seen in conventional ameloblastomas, were also observed. The tumor infiltrated deep into the alveolar mucosa, including the periodontal ligament, and showed histological and topographical evidence of atypism, resulting in resorption of the underlying alveolar bone. On the CK immunohistochemistry, CK19 was demonstrated in all the types of neoplastic epithelia, including microcyst‐forming cells, densely packed round or spindle cells within the tumor nests, cells with squamous metaplasia, and peripheral tall columnar cells. The CK immunohistochemical findings suggest the lesion’s cell of odontogenic origin; they may reflect an immature phenotypic expression of cell differentiation in the odontogenic epithelia during the tumor growth in the gingival mucosa.
Quantification of oral mucositis due to radiotherapy by determining viability and maturation of epithelial cells
Authors: Stokman M. A. , Spijkervet F. K. L. , Wymenga A. N. M. , Burlage F. R. , Timens W. , Roodenburg J. L. N. , De Vries E. G. E.
Published: March 2003

Background:  An in‐vitro assay has been developed for quantitative assessment of chemotherapy induced oral mucositis. In the present study this method was evaluated for assessment of irradiation mucositis at a cellular level.

Methods:  Ten patients participated in this consecutive study. All patients were treated with conventional fractionated curative postoperative radiotherapy. Prior to, and weekly during, the irradiation course, oral washings were obtained to determine viability of epithelial cells by trypan blue dye exclusion. Maturation of epithelial cells was assessed from smears (Papanicolaou staining). The viability data were compared with the WHO‐score for mucositis.

Results:  Epithelial cell viability increased during the first three weeks of radiation (P = 0.04), and was seen earlier than the subjective mucosal changes with the WHO‐score. Cell maturity shifted from immature and intermediate to mature (P = 0.03).

Conclusions:  The cell viability assay can be considered an objective method for following the development of irradiation mucositis, and seems to be more sensitive during the first three weeks of irradiation than the WHO‐scoring method.
Clear cell odontogenic carcinoma with ghost cells and inductive dentin formation – report of a case in the mandible
Authors: Ariyoshi Yasunori , Shimahara Masashi , Miyauchi Mutsumi , Nikai Hiromasa
Published: March 2003

An atypical case of clear cell odontogenic carcinoma occurred in the mandible of a 50‐year‐old Japanese man. Microscopically, the tumor mainly consisted of clear, glycogen‐rich epithelial cell nests, aggressively proliferated in the mandible and invading into the surrounding soft tissues. Within the tumor cell nests, clusters of ghost cells were observed in addition to occasional foci of microcystic degeneration. Hyaline, osteoid or dentinoid‐like deposits were also demonstrated adjacent to the tumor cell nests. Dentinal tubules were clearly revealed in some of these structures. Hence, this tumor was regarded as an epithelial neoplasm with odontogenic ectomesenchyme induction.
Narrativik des Detektivromans Zwei Geschehen – zwei Geschichten – ein Text
Authors: Lindemann Uwe
Published: March 2003

In narratologischer Hinsicht gehört der Detektivroman zu den interessantesten Formen epischen Erzählens, da in ihm alle zentralen Techniken narrativer Informationsvermittlung aufgewiesen werden können. So nimmt es kaum Wunder, daß sich seit Ende der siebziger Jahre eine Reihe von wissenschaftlichen Studien mit diesem Problemfeld befaßt haben. Besonders kontrovers wurde die narrative Doppelstruktur des Detektivromans diskutiert: in welchem Verhältnis Aufklärungsgeschichte und Verbrechensgeschichte zueinander stehen. Der folgende Beitrag hat sich zweierlei zum Ziel gesetzt: Zunächst soll eine kritische Bestandsaufnahme der früheren Modelle zur Narrativik des Detektivromans erfolgen. Anschließend wird auf Basis der Erzähltheorie Gérard Genettes ein neues narratologisches Modell für den Detektivroman entwickelt, mit dem sich nicht nur die Unstimmigkeiten in früheren Modellen klären lassen, sondern gleichfalls das dort weitgehend ausgesparte Verhältnis der narratologischen Kategorien Zeit, Perspektive und narrative Ebenen kohärent rekonstruiert werden kann.
Lessons from Kipling and Rao: How to Re‐Appropriate Another Culture
Authors: Almond Ian
Published: March 2003

This brief study will examine Anglo‐Indian Rudyard Kipling and Indo‐Anglian Raja Rao's, attempts to re‐appropriate a foreign culture in terms of their own wills. The novelist Rao's conviction of India's position as the origin of all Western culture, alongside Kipling's own curious tale of a tribe of distant “Englishmen” rediscovered in Northwest Afghanistan, both offer examples of attempts to re‐describe and ultimately re‐locate radically different cultures within the authors' own more familiar vocabularies. How does this cultural re‐appropriation take place, and what happens to the author's parent culture when something as radically ‘other’ as an Afghan tribe or a medieval French heresy is suddenly and unexpectedly re‐incorporated into the ‘family’? The often unsettling consequences of this operation are considered as they manifest themselves in both texts in similar ways, advancing the possibility that cultural‐appropriation affects the appropriator as much as the appropriated.

And so strong is the inclination that is rooted in Mankind to the Love of their Country, that some learned and witty Men … have used great Art and Industry to represent them with such advantage to the World, as though Paradise were but another Name for their native Country.

Bishop Stillingfleet1
Assembly, Target‐Signaling and Intracellular Transport of Tyrosinase Gene Family Proteins in the Initial Stage of Melanosome Biogenesis
Authors: JIMBOW KOWICHI , PARK JONG S. , KATO FUMIHIRO , HIROSAKI KUNINORI , TOYOFUKU KAZUTOMO , HUA CHEN , YAMASHITA TOSHIHARU
Published: March 2003

Assembly, target‐signaling and transport of tyrosinase gene family proteins at the initial stage of melanosome biogenesis are reviewed based on our own discoveries. Melanosome biogenesis involves four stages of maturation with distinct morphological and biochemical characteristics that reflect distinct processes of the biosynthesis of structural and enzymatic proteins, subsequent structural organization and melanin deposition occurring in these particular cellular compartments. The melanosomes share many common biological properties with the lysosomes. The stage I melanosomes appear to be linked to the late endosomes. Most of melanosomal proteins are glycoproteins that should be folded or assembled correctly in the ER through interaction with calnexin, a chaperone associated with melanogenesis. These melanosomal glycoproteins are then accumulated in the trans Golgi network (TGN) and transported to the melanosomal compartment. During the formation of transport vesicles, coat proteins assemble on the cytoplasmic face of TGN to select their cargos by interacting directly or indirectly with melanosomal glycoproteins to be transported. Adapter protein‐3 (AP‐3) is important for intracellular transport of tyrosinase gene family proteins from TGN to melanosomes. Tyrosinase gene family proteins possess a di‐leucine motif in their cytoplasmic tail, to which AP‐3 appears to bind. Thus, the initial cascade of melanosome biogenesis is regulated by several factors including: 1) glycosylation of tyrosinase gene family proteins and their correct folding and assembly within ER and Golgi, and 2) supply of specific signals necessary for intracellular transport of these glycoproteins by vesicles from Golgi to melanosomes.
Spontaneous Redox Reactions of Dopaquinone and the Balance between the Eumelanic and Phaeomelanic Pathways
Authors: LAND E.J. , RILEY P.A.
Published: March 2003

Eumelanogenesis and phaeomelanogenesis diverge at an early stage in pigment formation, namely at the point where dopaquinone, the initial product of tyrosine oxidation by tyrosinase, undergoes one of two types of reaction: either (1) a reductive endocyclisation in which a Michael addition of the side‐chain amino group takes place; or (2) a reductive addition of cysteine to give cysteinyldopa. In the former case, the product cyclodopa, is known rapidly to undergo a redox exchange reaction with dopaquinone to yield dopachrome, the precursor of the eumelanogenic pathway. In the second instance, cysteinyldopa is regarded as leading to the formation of benzothiazoles, which are characteristic of phaeomelanin. The precursor molecule of the phaeomelanic pathway is cysteinyldopaquinone. We have examined quantitatively the role of dopaquinone in the non‐enzymatic oxidation of 5‐S‐cysteinyldopa using pulse radiolysis and have demonstrated that the redox exchange reaction between dopaquinone and 5‐S‐cysteinyldopa occurs spontaneously with a rate constant of 8.8×105 M−1 sec−1. This study has also enabled an improved estimate of ≤4×107 M−1sec−1 to be obtained for the rate constant of the reaction of dopaquinone with cyclodopa. Calculations utilising these figures and estimates of the rate constants for the other reactions in early melanogenesis, demonstrate that, whilst similar pathways are invoked, the phaeomelanic pathway predominates in the presence of cysteine, irrespective of the availability of dopaquinone and thus independently of the rate of tyrosinase‐catalysed oxidation. This suggests that the balance between the formation of eumelanin and phaeomelanin is regulated principally by the availability of cysteine at the site of melanogenesis.
Herpesvirus Connection in the Expression of Autoimmune Vitiligo in Smyth Line Chickens
Authors: ERF GISELA F. , BERSI TINA K. , WANG XIAOLI , SREEKUMAR G. PILLAI , SMYTH, JR. J. ROBERT
Published: March 2003

The Smyth line (SL) chicken is an animal model for human vitiligo, a common acquired depigmentary disorder affecting about 1–2% of people worldwide. The vitiligo‐like depigmentation in SL chickens typically develops when the birds are between 6 and 14 weeks of age and may affect 70–95% of hatch mates. The development of SL vitiligo is considered to depend on two interacting components, namely an inherent melanocyte defect and an autoimmune reaction to melanocytes. Recently, a role for an environmental factor in the expression of vitiligo was suggested by the observation that only 10% of SL chicks imported from the University of Massachusetts (UM) and reared in isolation at biosecurity level 2 (BSL 2) at the University of Arkansas (UA) exhibited vitiligo. Following further assessment of environmental differences between UA and UM SL chickens, three environmental factors that may have influenced the expression of SL vitiligo were identified. Included were housing condition, status of Mycoplasma synoviae infection, and turkey herpesvirus (HVT) vaccination status. Studies were subsequently conducted at UA and UM to assess the role of these environmental factors in the expression of SL vitiligo. M. synoviae infection was not found necessary for vitiligo expression in SL chickens. However, HVT emerged as a strong candidate for an important environmental factor in SL vitiligo. The connection between HVT and SL vitiligo was confirmed for both BSL 2 and conventional housing. Therefore, the observations reported here suggest a strong causative link between HVT infection and SL vitiligo.
Gene Regulation in Melanoma Progression by the AP‐2 Transcription Factor
Authors: BAR‐ELI MENASHE
Published: March 2003

The molecular changes associated with the transition of melanoma cells from radial growth phase (RGP) to vertical growth phase [(VGP), metastatic phenotype] are not very well defined. We previously demonstrated that expression of the cell‐surface adhesion molecule MCAM/MUC18 correlates directly with the metastatic potential of human melanoma cells. In addition, the progression of human melanoma towards the metastatic phenotype is associated with loss of expression of the tyrosine‐kinase receptor c‐KIT. In this review, I will summarize our recent studies demonstrating that the expression of both genes is regulated by the AP‐2 transcription factor. Moreover, we have observed a loss of AP‐2 expression in metastatic melanoma cells. Re‐expression of AP‐2 in the highly metastatic A375SM cells decreased their tumorigenicity and inhibited their metastatic potential in nude mice. MCAM/MUC18 mRNA and protein expression was significantly down‐regulated while c‐KIT expression was up‐regulated in the AP‐2‐transfected cells. To further investigate the role of AP‐2 in the progression of human melanoma, we attempted to inactivate AP‐2 in primary cutaneous melanoma by using a dominant‐negative AP‐2, or the AP‐2B gene. Expression of AP‐2B in SB‐2 cells augmented their tumorigenicity in nude mice, and upregulated MMP‐2 expression and activity. As AP‐2 also regulates other genes that are involved in the progression of human melanoma such as E‐cadherin, p21/WAF‐1, HER2/neu, Bcl‐2, FAS/APO‐1, IGF‐R‐1, VEGF and the thrombin receptor (PAR‐1), we therefore propose that loss of AP‐2 is a crucial event in the development of malignant melanoma. In addition, the transition of melanoma cells from RGP to VGP is also associated with over‐expression of the transcription factors CREB and ATF‐1. The notion that the balance between AP‐2 and CREB/ATF‐1 expression determines the progression of melanoma cells towards the metastatic phenotype will be discussed.
Development of Pigment Cells in the Brain of Ascidian Tadpole Larvae: Insights into the Origins of Vertebrate Pigment Cells
Authors: Sato Shigeru , Yamamoto Hiroaki
Published: March 2003

In vertebrates, melanins produced in specialized pigment cells are required for visual acuity, camouflage, sexual display and protection from ultra violet (UV) radiation. There are three pigment cell types that are classified based on their distinct embryonic origins. Retinal pigment epithelium (RPE) cells originate from the outer layer of the optic cup. Pigment cells of the pineal organ are formed from the developing diencephalon. Melanocytes are derived from the neural crest unique to vertebrate embryos. Some of these pigment cells also play roles that are independent of the activity of tyrosinase, the key melanogenesis enzyme, or melanin: production of substrate(s) for catecholamine synthesis, maintenance of endolymph composition in the cochlea, maintenance of photoreceptor cells in the retina and retinoid metabolism essential for the visual cycle. To deduce the evolutionary origins of vertebrate pigment cells and a possible archetypal genetic circuitry, which may have been modified and utilized to generate multiple pigment cell types, comparison of developmental mechanisms of pigment cells between vertebrates and closely related invertebrate ascidians are proposed to provide useful information. The tadpole‐type larva of ascidians possesses two melanin‐containing pigment cells, termed the otolith and ocellus pigment cells, in the brain that are believed to be required for photo‐ and geotactic responses during swimming. In this review, current knowledge on the development of the two ascidian pigment cells is summarized, i.e. complete cell lineage, structure and expression of genes encoding two melanogenesis enzymes, and molecular developmental mechanisms involving BMP‐CHORDIN antagonism, and possible evolutionary relationships between ascidian and vertebrate pigment cells are discussed.
Actin‐dependent, Retrograde Motility of Surface‐attached Beads and Aggregating Pigment Granules in Dissociated Teleost Retinal Pigment Epithelial Cells
Authors: Basciano Paul A. , King‐Smith Christina
Published: March 2003

Teleost retinal pigment epithelial (RPE) cells contain pigment granules within apical projections which undergo actin‐dependent, bi‐directional motility. Dissociated RPE cells in culture attach to the substrate and extend apical projections in a radial array from the central cell body. Pigment granules within projections can be triggered to aggregate or disperse by the presence or absence of 1 mM cAMP. Aminated, fluorescent latex beads attached to the dorsal surface of apical projections and moved in the retrograde direction, towards the cell body. Bead rates on RPE cells with aggregating or fully aggregated pigment granules were 2.2 ± 0.5 and 2.6 ± 0.2 μm/min (mean ± SEM), respectively, similar to rates of aggregating (retrograde) pigment granule movement (2.0 ± 0.4 μm/min). Bead rates were slightly slower on cells with fully dispersed or dispersing pigment granules (1.5 ± 0.1 and 1.5 ± 0.4 μm/min). Movements of surface‐attached beads and aggregating pigment granules were closely correlated in the distal portions of apical projections, but were more independent of each other in proximal regions of the projections. The actin disrupting drug, cytochalasin D (CD), reversibly halted retrograde bead movements, suggesting that motility of surface‐attached particles is actin‐dependent. In contrast, the microtubule depolymerizing drug, nocodazole, had no effect on retrograde bead motility. The similar characteristics and actin‐dependence of retrograde bead movements and aggregating pigment granules suggest a correlation between these two processes.
The Usefulness of 4‐Amino‐3‐hydroxyphenylalanine as a Specific Marker of Pheomelanin
Authors: Wakamatsu Kazumasa , Ito Shosuke , Rees Jonathan L.
Published: March 2003

Reductive hydrolysis of pheomelanin with hydriodic acid (HI) gives two aminohydroxyphenylalanine isomers, 4‐amino‐3‐hydroxyphenylalanine (`specific AHP') and 3‐amino‐4‐hydroxyphenylalanine (3‐aminotyrosine, AT), which derive from the oxidative polymerization of 5‐S‐cysteinyldopa, and 2‐S‐cysteinyldopa, respectively. Since we first introduced this analytical method, the combined amount of AHP and AT (`total AHP') has been extensively used as a marker of pheomelanin. However, one problem with using total AHP as a marker is that background levels originate from precursors other than pheomelanin. Considerable and variable amounts of background AT are produced from other sources, most likely nitrotyrosine residues in proteins. In order to overcome this problem, we developed HPLC conditions which enable the direct injection of the HI reduction products into the HPLC system allowing good separation of AHP and AT. In this way we could study the importance of both degradation products separately and their specificity as markers for pheomelanin. The usefulness of the present method is validated using human hair samples of various colours which were divided into dark, fair or red colours. The combined amount of specific AHP and AT shows an excellent correlation with total AHP, and the amount of specific AHP also correlates with the amount of total AHP. We also examined total AHP and specific AHP values against pyrrole‐2,3,5‐tricarboxylic acid (PTCA) values in the human hair samples. These results show that specific AHP measurement gives a more prominent segregation for the ratio of specific AHP to PTCA among hairs of various colours than the ratio of total AHP to PTCA. Thus, we conclude that `specific AHP' is a more specific marker of pheomelanin than is `total AHP'.
Periodontal ligament cells secrete the factor that inhibits osteoclastic differentiation and function: the factor is osteoprotegerin/osteoclastogenesis inhibitory factor
Authors: Wada Naohisa , Maeda Hidefumi , Tanabe Kazunari , Tsuda Eisuke , Yano Kazuki , Nakamuta Hiroyoshi , Akamine Akifumi
Published: March 2003

The periodontal ligament, a highly specialized connective tissue situated between the tooth and the alveolar bone of the tooth socket, has been thought to influence the remodeling of the alveolar bone. The effects of two human periodontal ligament fibroblastic cell populations (HPLFs) on osteoclast‐like cell (OCL) formation and the function of authentic osteoclasts were examined. The addition of the conditioned media (CM) from both HPLF cultures (HPLF‐CMs) to mouse bone marrow culture inhibited OCL formation in spite of the presence of 10−8 m 1α, 25 dihydroxyvitamin D3(1α,25(OH)2D3). This inhibitory effect was most remarkable when both CMs were added during day 6 to day 9 following bone marrow culture, just at the late stage of OCL differentiation. HPLF‐CMs also induced a significant decrease in the pit area and the pit number formed by authentic osteoclasts on ivory slices. The administration of neutralizing monoclonal antibody (OI‐1) against human osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF) with HPLF‐CMs to mouse bone marrow culture almost completely blocked the inhibitory effect of these CMs on OCL formation. Immunofluorescent examination of HPLF with OI‐1 revealed intense positive reactivity in the cytoplasm. Western blot analysis of HPLF‐CM using anti‐human OPG/OCIF polyclonal antibody resulted in the detection of bands of 60 kDa and 120 kDa which were consistent with those of OPG/OCIF. These results suggest that HPLF cells produce and secrete OPG/OCIF, and that this factor from HPLF prevents the differentiation of the late preosteoclast and the function of the mature osteoclasts.
Effect of lipopolysaccharide from periodontal pathogens on the production of tissue plasminogen activator and plasminogen activator inhibitor 2 by human gingival fibroblasts
Authors: Xiao Yin , Bunn Clive L. , Bartold P. Mark
Published: March 2003

Both tissue plasminogen activator (t‐PA) and plasminogen activator inhibitor 2 (PAI‐2) are important proteolysis factors present in inflamed human periodontal tissues. The aim of the present study was to investigate the effect of lipopolysaccharide (LPS) on the synthesis of t‐PA and PAI‐2 by human gingival fibroblasts (HGF). LPS from different periodontal pathogens including Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum were extracted by the hot phenol water method. The levels of t‐PA and PAI‐2 secreted into the cell culture media were measured by enzyme‐linked immunosorbent assays (ELISA). The mRNA for t‐PA and PAI‐2 were measured by RT‐PCR. The results showed t‐PA synthesis was increased in response to all types of LPS studied and PAI‐2 level was increased by LPS from A. actinomycetemcomitans and F. nucleatum, but not P. gingivalis. When comparing the effects of LPS from non‐periodontal bacteria (Escherichia coli and Salmonella enteritidis) with the LPS from periodontal pathogens, we found that the ratio of t‐PA to PAI‐2 was greater following exposure of the cells to LPS from periodontal pathogens. The highest ratio of t‐PA to PAI‐2 was found in those cells exposed to LPS from P. gingivalis. These results indicate that LPS derived from periodontal pathogens may cause unbalanced regulation of plasminogen activator and plasminogen activator inhibitor by HGF and such an effect may, in part, contribute to the destruction of periodontal connective tissue through dysregulated pericellular proteolysis.
Involvement of cyclooxygenase‐2 in serum‐induced prostaglandin production by human oral gingival epithelial cells
Authors: Noguchi Kazuyuki , Shitashige Miki , Endo Hirahito , Kondo Hirofumi , Yotsumoto Yukiharu , Izumi Yuichi , Nitta Hiroshi , Ishikawa Isao
Published: March 2003

The purpose of the present study was to investigate the involvement of cyclooxygenase‐1 (COX‐1) and cyclooxygenase‐2 (COX‐2) in prostaglandin (PG) production by human oral gingival epithelial (OGE) cells stimulated with proinflammatory cytokines including interleukin(IL)‐1α, IL‐1β and tumor necrosis factor α(TNFα), and serum. Fetal bovine serum (FBS)‐stimulated OGE cells produced significant levels of PGE2, whereas IL‐1α, IL‐1β and TNFα could not induce significant PGE2 production. FBS induced PGE2 production in a dose‐ and time‐dependent manner. NS‐398, a selective COX‐2 inhibitor, inhibited PGE2 production by FBS‐stimulated cells as completely as indomethacin, a non‐selective COX‐1/COX‐2 inhibitor. Expression of COX‐2 protein in FBS‐stimulated cells was increased, compared with that in unstimulated cells, whereas COX‐1 protein expression was similar both in unstimulated and in FBS‐stimulated cells. COX‐2 mRNA was detected in FBS‐stimulated cells, but not in unstimulated cells. We suggest that COX‐2 is responsible for PG production by human OGE cells stimulated with serum and that OGE cells may be involved in PG production in periodontal lesions. Selective COX‐2 inhibitors, which have the advantage of reduced gastric toxicity, may provide a useful approach to treatment of periodontal disease.
Changes in Markers of Oxidative Stress and Membrane Properties in Synaptosomes from Rats Exposed Prenatally to Toluene
Authors: Edelfors Sven , Hass Ulla , Hougaard Karin S.
Published: March 2003

Abstract: The present study was undertaken in order to investigate if toluene induced oxidative stress in brains from rats exposed prenatally to 1800 ppm toluene 6 hr/day at days 7–20 during the pregnancy. 35–42 days after birth the rats were killed and synaptosomal fractions were prepared for the experiments. Synaptosomes from rats exposed prenatally to toluene exhibited an increased level of oxidative stress when incubated with toluene in vitro compared to synaptosomes from unexposed offspring. Also the cell membrane was affected, as the calcium leakage was more increased from exposed synaptosomes than from unexposed. The membrane fluidity increased significantly when synaptosomes were incubated with toluene for 10 min. in vitro but the change in fluidity was identical in both groups of offspring. The results indicate that prenatal exposure to toluene induces long‐lasting changes in oxidative status and membrane function.