bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment of intermediate and advanced stage Hodgkin's disease with modified baseline BEACOPP regimen: a Hellenic Co‐operative Oncology Group Study
Authors: Economopoulos T. , Fountzilas G. , Dimopoulos M. A. , Papageorgiou S. , Xiros N. , Kalantzis D. , Dervenoulas J. , Raptis S.
Published: September 2003

Abstract: The purpose of this prospective phase II trial was to investigate the safety and efficacy of a modified baseline BEACOPP (bleomycin, etoposide, adriamycin, cyclophosphamide, vincristine, procarbazine, and prednisone) regimen in the treatment of intermediate and advanced stage Hodgkin's disease (HD). From October 1997 to November 2001, 51 consecutive, previously untreated patients with stage IIA (bulky), IIB, III, and IV disease were treated with a modified baseline BEACOPP regimen with the etoposide administered i.v. on day 1 and orally at a dose of 100 mg/m2, on days 2 and 3. Each patient was scheduled to receive eight courses of BEACOPP with consolidation radiotherapy to bulky (≥5 cm) or residual disease. There were 25 males and 26 females with a median age of 32 yr (16–65 yr); 80.3% of the patients had nodular sclerosis HD, 41% had bulky disease (≥5 cm), 10 were in stage IIA (bulky ≥10 cm), 15 in stage IIB, 19 in stage III, and seven in stage IV. Thirty‐seven patients (72.5%) achieved a complete response and 17.6% partial response. No significant difference in overall response rate was observed between patients with: (i) 0–2 vs. ≥3 negative prognostic factors, (ii) in stage II vs. stages III/IV, LDH level, and bulky disease. With a median follow up period of 39.5 months, actuarial 3‐yr survival rate is 82% and time to progression rate 72.5%. Treatment with this combination was well tolerated. Grades 3 and 4 leukopenia and neutropenia occured in 26% and 28% of the patients, respectively, whereas in 16.3% of the patients infection was observed. Support with granulocyte colony‐stimulating factor was given to 59% of the patients. No case of secondary MDS/leukemia has been observed. The results of the present study demonstrate that the modified baseline BEACOPP regimen with radiotherapy used in our patients was well tolerated and effective therapy for intermediate and advanced stage HD. Further follow up time is required to evaluate long‐term toxicity.
Isolation and Developmental Expression of Tyrosinase Family Genes in Xenopus laevis
Authors: Kumasaka Mayuko , Sato Shigeru , Yajima Ichiro , Yamamoto Hiroaki
Published: September 2003

The tyrosinase family of genes in vertebrates consists of three related members encoding melanogenic enzymes, tyrosinase (Tyr), tyrosinase‐related protein‐1 (TRP‐1, Tyrp1) and tyrosinase‐related protein‐2 (Dct, TRP‐2, Tyrp2). These proteins catalyze melanin production in pigment cells and play important roles in determining vertebrate coloration. This is the first report examining melanogenic gene expression in pigment cells during embryonic development of amphibians. Xenopus provides a useful experimental system for analyzing molecular mechanisms of pigment cells. However, in this animal little information is available not only about the developmental expression but also about the isolation of pigmentation genes. In this study, we isolated homologues of Tyr, Tyrp1 and Dct in Xenopus laevis (XlTyr, XlTyrp1, and XlDct). We studied their expression during development using in situ hybridization and found that all of them are expressed in neural crest‐derived melanophores, most of which migrate through the medial pathway, and in the developing diencephalon‐derived retinal pigment epithelium (RPE). Further, XlDct was expressed earlier than XlTyr and XlTyrp1, which suggests that XlDct is the most suitable marker gene for melanin‐producing cells among them. XlDct expression was detected in migratory melanoblasts and in the unpigmented RPE. In addition, the expression of XlDct was detected in the pineal organ. The sum of these studies suggests that expression of the tyrosinase family of genes is conserved in pigment cells of amphibians and that using XlDct as a marker gene for pigment cells will allow further study of the developmental mechanisms of pigment cell differentiation using Xenopus.
Ca2+‐Inactivated K+ Current is Modulated by Endothelin‐1 in B‐16 Murine Melanoma Cells
Authors: Ma Lai‐Ji , Liu Lin‐Yun , Jiao Song , Wei Shao‐Ming , Mei Yan‐Ai
Published: September 2003

It is well established that endothelin‐1 (ET‐1) plays a role in differentiation and proliferation in a variety of cells such as fibroblasts and human melanoma cells via a receptor‐mediated mechanism. However, whether ET‐1 modulates ion channel activity in these cell types is still unknown. In this report, we recorded the voltage‐dependent outward K+ current in cultured B16 melanoma cells using the patch‐clamp technique. Biophysical and pharmacological properties of the K+ current, and the effect of ET‐1 on the K+ current were investigated. When cells were loaded with a Ca2+‐chelating agent (EGTA or BAPTA), the K+ current amplitude gradually increased with time after establishment of the whole cell configuration. Replacement of Ca2+ with Co2+ in the extracellular medium caused no significant modulation of the K+ current amplitude. Addition of BaCl2 or quinidine to the extracellular solution reduced the K+ current amplitude, whereas the K+ current was insensitive to tetraethylammonium. ET‐1 (10 nM) reversibly decreased the K+ current amplitude and accelerated the decay of the K+ current. The ET‐1‐induced inhibitory effect displayed no desensitization following repeated ET‐1 application. Pretreatment with pertussis toxin (PTX) or perfusion of cells with the protein kinase C (PKC) inhibitor H‐7 abolished the inhibitory effect of ET‐1 on the K+ current. We conclude that the outward K+ current recorded in murine B‐16 melanoma cells represents a Ca2+‐inactivated K+ current, and that the inhibitory effect of ET‐1 on the K+ current may reveal a novel mechanism to control the differentiation and proliferation of melanoma cells.
Mouse Models for Four Types of Waardenburg Syndrome
Authors: Tachibana Masayoshi , Kobayashi Yasuhito , Matsushima Yoshibumi
Published: September 2003

Waardenburg syndrome (WS) is an auditory‐pigmentary syndrome caused by a deficiency of melanocytes and other neural crest‐derived cells. Depending on a variety of symptoms associated with the auditory‐pigmentary symptoms, WS is classified into four types: WS type 1 (WS1), WS2, WS3, and WS4. Six genes contributing to this syndrome –PAX3, SOX10, MITF, SLUG, EDN3 and EDNRB– have been cloned so far, all of them necessary for normal development of melanocytes. Mutant mice with coat color anomalies were helpful in identifying these genes, although the phenotypes of these mice did not necessarily perfectly match those of the four types of WS. Here we describe mice with mutations of murine homologs of WS genes and verify their suitability as models for WS with special interest in the cochlear disorder. The mice include splotch (Sp), microphthalmia (mi), Slugh−/−, WS4, JF1, lethal‐spotting (ls), and Dominant megacolon (Dom). The influence of genetic background on the phenotypes of mice mutated in homologs of WS genes is also addressed. Finally, possible interactions among the six WS gene products are discussed.
Genistein Enhances the Cisplatin‐Induced Inhibition of Cell Growth and Apoptosis in Human Malignant Melanoma Cells
Authors: Tamura Shingo , Bito Toshinori , Ichihashi Masamitsu , Ueda Masato
Published: September 2003

Genistein, a naturally occurring isoflavone found chiefly in soybeans, has been reported to be a potent antitumor agent. Genistein is presumed to exert multiple effects related to the inhibition of cancer growth. Metastatic melanoma is a chemotherapy‐refractory neoplasm. The present study was designed to explore the possible activity of genistein to inhibit the aberrant proliferation and to induce apoptosis of human malignant melanoma cells in cooperation with cisplatin treatment. Five human melanoma cell lines were utilized for these experiments. Genistein at physiologic concentrations (20 μM) did not induce apoptosis by itself but did enhance cisplatin‐induced apoptosis in all five human melanoma cell lines tested. The enhanced susceptibility among the cell lines was diverse. Changes in the expression of two anti‐apoptotic proteins, bcl‐2 and bcl‐xL, and one pro‐apoptotic protein, apoptotic protease activating factor‐1 (Apaf‐1), were examined. Genistein alone or cisplatin alone generally did not alter bcl‐2 expression or bcl‐xL expression, but slightly increased Apaf‐1 in some cell lines. The combined treatment with genistein and cisplatin significantly reduced bcl‐2 and bcl‐xL protein and increased Apaf‐1 protein expression. These data suggest that genistein therapy may enhance the chemosensitivity of melanoma patients.
Melanogenesis and Melanoma
Authors: Riley Patrick A.
Published: September 2003

Melanins are the principal surface pigments in vertebrates and, in humans, play a major role in photoprotection. Although the product (melanin) has a mainly protective function in the skin, the process of melanogenesis represents a potential cellular hazard and is confined to special membrane‐limited organelles (melanosomes) in a set of specialized dendritic cells (melanocytes) which synthesize the pigment and transfer it to recipient cells. Malignant melanocytes tend to exhibit up‐regulated melanogenesis and defective melanosomes. These features suggest ways in which anti‐melanoma therapy may be specifically targeted. Two general chemotherapeutic modalities are considered:  1 The ‘Achilles heel’ approach in which the generation of reactive quinones capable of leaking into the cytosolic compartment and causing structural and functional derangement is encouraged by the use of analogue substrates.  2 The ‘Trojan horse’ approach, in which a cytotoxic agent is selectively released by a tyrosinase‐dependent mechanism.
Quantitative Analysis of Eumelanin and Pheomelanin in Humans, Mice, and Other Animals: a Comparative Review
Authors: Ito Shosuke , Wakamatsu Kazumasa
Published: September 2003

The color of hair, skin, and eyes in animals mainly depends on the quantity, quality, and distribution of the pigment melanin, which occurs in two types: black to brown eumelanin and yellow to reddish pheomelanin. Microanalytical methods to quantify the amounts of eumelanin and pheomelanin in biological materials were developed in 1985. The methods are based on the chemical degradation of eumelanin to pyrrole‐2,3,5‐tricarboxylic acid and of pheomelanin to aminohydroxyphenylalanine isomers, which can be analyzed and quantitated by high performance liquid chromatography. This review summarizes and compares eumelanin and pheomelanin contents in various pigmented tissues obtained from humans, mice, and other animals. These methods have become valuable tools to study the functions of melanin, the control of melanogenesis, and the actions and interactions of pigmentation genes. The methods have also found applications in many clinical studies. High levels of pheomelanin are found only in yellow to red hairs of mammals and in red feathers of birds. It remains an intriguing question why lower vertebrates such as fishes do not synthesize pheomelanin. Detectable levels of pheomelanin are detected in human skin regardless of race, color, and skin type. However, eumelanin is always the major constituent of epidermal melanin, and the skin color appears to be determined by the quantity of melanin produced but not by the quality.
Rate Limiting Factors in Melanocortin 1 Receptor Signalling Throughthe cAMP Pathway
Authors: MÁs JesÚs SÁnchez , Gerritsen Ineke , Hahmann Christa , JimÉnez‐Cervantes Celia , García‐BorrÓn JosÉ Carlos
Published: September 2003

The melanotropic actions of α‐melanocyte‐stimulating hormone (α‐MSH) and other melanocortins are mediated by activation of the melanocortin 1 receptor (MC1R). This G protein‐coupled receptor is positively coupled to Gs and triggers the cyclic adenosine mono‐phosphate (cAMP) pathway. Mutations of the MC1R gene are associated with skin type and pigmentation phenotypes, and with increased risk of skin cancers. Genetic studies have demonstrated an heterozygote carrier effect for these associations, suggesting the importance of variant allele dosage. This could be accounted for, at least partially, if the number of MC1R molecules, rather than the Gs protein or the effector enzyme, adenylyl cyclase, is limiting for the activation of the signalling pathway. However, the nature of the limiting factor(s) in MC1R signalling has not been investigated. We addressed this question by comparing the cAMP output of clones of human melanoma cell lines enriched in MC1R by stable transfection. We also analysed heterologous cell systems widely used for functional studies of MC1R. We show that cAMP production in clones of Chinese hamster ovary cells stably expressing the MC1R is a linear function of receptor number up to high, supraphysiological levels of approximately 50 000 α‐MSH binding sites per cell. Enrichment of human melanoma cell lines with MC1R also results in increased cAMP levels, with a small leftward shift of the agonist dose–response curves. Therefore, at physiological expression levels second‐messenger generation is dependent on receptor density. Within melanoma cells and also likely in normal melanocytes, MC1R appears the limiting factor controlling the output of the cAMP signalling pathway.
Enigmas of Pterorhodin, a Red Melanosomal Pigment of Tree Frogs
Authors: Bagnara Joseph T.
Published: September 2003

Melanosomes observed in dermal melanophores of adult leaf frogs contain a unique wine red pigment identified as pterorhodin, a pteridine dimer never before found in any vertebrate. This type of melanosome, almost twice as large as the typical eumelanin melanosome, contains a small electron dense core of eumelanin surrounded by a concentric fibrous mass of pterorhodin. Dermal melanophores of larval leaf frogs contain small eumelanin melanosomes that transform at metamorphosis through the gradual accumulation of pterorhodin on the eumelanin surface to form the compound melanosomes of adults. This process may be mediated by thyroxine. No explanation for the unique presence of pterorhodin in leaf frogs has yet surfaced. A variety of tree frog species from Australia and Papua New Guinea also possess pterorhodin and the large melanosome suggesting that tree frogs from the New World and those from Australia are closely related and may have been separated during continental drift. Several of the unsolved problems posed by the emergence of pterorhodin in a unique melanosome are discussed.
The Relationship Between Constitutive Pigmentation and Sensitivity to Ultraviolet Radiation Induced Erythema is Dose–Dependent
Authors: Ha Thomas , Javedan Houman , Waterston Karen , Naysmith Lisa , Rees Jonathan L.
Published: September 2003

The relationship between skin colour and experimental exposure to ultraviolet radiation (UVR) B, with response measured as erythema was studied. Two reflectance methods were used to measure skin colour – tristimulus colorimetry using a Minolta instrument (summarized as the α characteristic angle) and the melanin index based on the Diastron reflectance instrument. As expected both measures are highly correlated (0.91). A dose–dependent relationship between skin colour measured as the α characteristic angle and UVR was established, with the gradient increasing from 0.99 at 119 mJ to 2.7 at 300 mJ, with the relevant standard errors being 0.39 and 0.47, respectively. Similarly, for the melanin index (where the scale goes in the opposite direction) the gradient differs between −0.49 for 119 mJ and −0.91 for 300 mJ, with the standard errors being 0.14 and 0.17 respectively. The proportion of variation explained is also greater at higher UVR challenge doses. Studies relating UVR sensitivity and pigmentation need to take account of the dose of UVR administered.
Localization of Sepiapterin Reductase in Pigment Cells of Oryzias latipes
Authors: Negishi Sumiko , Fujimoto Kengo , Katoh Setsuko
Published: September 2003

Body colors of poikilothermal vertebrates are derived from three distinct types of pigment cells, melanophores, erythro/xanthophores and irido/leucophores. It is well known that melanin in melanophores is synthesized by tyrosinase within a specific organelle termed the melanosome. Although sepiapterin reductase (SPR) is an important enzyme involved in metabolizing biopterin and sepiapterin (a conspicuous pteridine as a coloring pigment in xanthophores) the distribution of SPR has not been shown in pigment cells. An antibody raised in rabbits against rat SPR was used to demonstrate the presence of SPR in pigment cells of Oryzias latipes. This study, which used immunohistochemistry with fluorescence or peroxidase/diaminobenzidine as markers, revealed that SPR could be detected readily in xanthophores, but only faintly in melanophores. These results suggest that sepiapterin is metabolized within xanthophores. Moreover, these experiments show that a protein sharing immunological cross‐reactivity with rat SPR is located in teleost O. latipes xanthophores, which is significant considering the relationship of pteridine metabolism between poikilothermal vertebrates and mammals. Further progress in investigations of the roles of pteridines in vertebrates will be promoted by using these fish which can be bred in mass rather easily in the laboratory.
Melanogenesis in the Ink Gland of Sepia officinalis
Authors: Palumbo Anna
Published: September 2003

Among the various melanin‐producing systems, the ink gland of the cuttlefish (Sepia officinalis) has traditionally been regarded as a most convenient model system for the studies of melanogenesis. The ink gland is a highly specialized organ with immature cells in the inner portion, from where the cells gradually mature, migrate towards the outer portion of the gland and become competent to produce melanin giving rise to particulate melanosomes. When cell maturation is complete, melanin is secreted into the lumen of the gland, accumulated into the ink sac and ejected on demand. Biochemical studies carried out over the past two decades have shown that the ink gland contains a variety of melanogenic enzymes, including tyrosinase, a peculiar dopachrome rearranging enzyme (which catalyses the rearrangement of dopachrome to 5,6‐dihydroxyindole) and a peroxidase (presumably involved in the later stages of melanin biosynthesis). These enzymes are functionally interactive in close subcellular compartments of ink gland cells and appear to act in a concerted fashion during the process of melanogenesis in the mature portion of the gland. More recent studies have revealed that ink production and ejection are affected and modulated by the N‐methyl‐d‐aspartate (NMDA)–nitric oxide (NO)–cyclic GMP (cGMP) signalling pathway. Glutamate NMDA receptor and NO synthase, the enzyme responsible for the synthesis of NO, have been detected by biochemical and immunohistochemical techniques in immature ink gland cells. Stimulation of NMDA receptors caused a marked elevation of cGMP levels, activation of tyrosinase and increased melanin synthesis in the mature portion of the gland, via the NO–guanylyl cyclase interaction. This signalling is also present in different regions of the nervous system in Sepia and in certain neural pathways controlling contraction of the ink sac sphincters and wall muscle in the ejection mechanism. Overall, these and other findings allowed elaboration of an improved model of melanin formation in Sepia, which underscores the complex interplay of melanogenic enzymes and regulatory factors, highlighting both the similarities and the differences with melanogenesis in mammals.
Effect of Cyclosporin A on Melanogenesis in Cultured Human Melanocytes
Authors: Lee Ji Yeoun , Kang Won Hyoung
Published: September 2003

Cyclosporin A (CsA) is a widely used immunosuppressant. Reports on the effect of CsA on hyperpigmentation in patients appear inconsistent, and the effect of CsA on skin pigment cells (melanocytes) in vitro is unknown. We examined the effect of CsA on human melanocyte proliferation and melanogenesis in vitro. Melanocyte proliferation was dose‐dependently inhibited by 0.1–10 μM CsA, with no effect on cell viability. Melanocytes incubated with 10 μM CsA for 6 days showed decreased pigmentation and tyrosinase activity. Western blot analysis using an anti‐tyrosinase antibody revealed that CsA (0.1–10 μM) decreased tyrosinase protein levels in a dose‐dependent manner. Northern blot analysis showed similar effects on tyrosinase mRNA levels. These effects of CsA on melanogenesis in vitro are not consistent with suggestions that systemic CsA therapy causes patient skin hyperpigmentation.
Rate Constants for the First Two Chemical Steps of Eumelanogenesis
Authors: Land E. J. , Ito S. , Wakamatsu K. , Riley P. A.
Published: September 2003

The kinetics of the initial cyclization and redox exchange reactions involved in the eumelanogenic pathway have been studied previously but because of the difficulty of detecting the intermediate cyclodopa by optical means (because its absorbance is in the same range as dopa which is present in excess in the experimental system) no accurate value for the redox exchange reaction has so far been obtained and there is no available analytical methodology that can be applied to the successive first‐ and second‐order reactions involved. We have synthesized cyclodopa and examined the kinetics of the formation of dopachrome following the pulse radiolytic generation of dopaquinone in its presence. From this direct measurement we determined that the rate constant of the reaction between cyclodopa and dopaquinone is 5.3 × 106/M/s. Employing this value in a computational model of the combined cyclization and redox exchange reactions we calculate that the observed kinetics of dopaquinone decay and dopachrome formation are compatible with a cyclization rate constant of 3.8/s.
Down‐Regulation of Melanin Synthesis by a Biphenyl Derivative and Its Mechanism
Authors: Nakamura Kyoko , Yoshida Masaki , Uchiwa Hideyo , Kawa Yoko , Mizoguchi Masako
Published: September 2003

Down‐regulation of melanin synthesis is required for recovery of pigmentary disorders and it is known that direct inhibitors of tyrosinase, the key enzyme in melanin synthesis, such as hydroquinone with a phenol structure, suppress melanin synthesis. We screened several phenolic derivatives using B16 melanoma cells and found that a biphenyl derivative, 2,2′‐dihydroxy‐5,5′‐dipropyl‐biphenyl (DDB), down‐regulated melanin synthesis effectively. Although DDB has a phenol structure, it did not inhibit tyrosinase in vitro, thus we examined its mechanism in detail. Western blotting revealed that the amount of tyrosinase was decreased by DDB, and pulse‐chase labeling and immunoprecipitation analysis showed a decrease of mature tyrosinase and acceleration of tyrosinase degradation in its presence. These results suggest that DDB down‐regulates melanin synthesis by inhibiting the maturation of tyrosinase, leading to acceleration of tyrosinase degradation.
1,4‐Benzothiazines as Key Intermediates in the Biosynthesis of Red Hair Pigment Pheomelanins
Authors: Donato Paola Di , Napolitano Alessandra
Published: September 2003

Following the discovery of cysteinyldopas as the early intermediates in the biogenesis of pheomelanins, the typical red hair pigments, the reactivity of the biosynthetic precursors under biomimetic conditions was extensively investigated. As a result, the early stages of pheomelanogenesis were envisaged as involving oxidative cyclization of cysteinyldopas, mainly the 5‐S‐isomer, to 1,4‐benzothiazine (BTZ) intermediates which undergo oxidative polymerization leading eventually to the pigments. In the last decade, several aspects of the chemistry and biosynthesis of pheomelanins were re‐examined. In particular, (i) transient BTZ intermediates were identified by pulse radiolytic techniques and NMR analysis; (ii) the effect of reaction conditions and additives on the rearrangement vs. redox exchange reaction paths of such intermediates were investigated in detail; (iii) the mechanism of the oxidative polymerization of BTZs was characterized by the first isolation of oligomer species, and (iv) the pigment eventually resulting from oxidation of 5‐S‐cysteinyldopa (CD) was directly analyzed by spectroscopic and chemical methodologies in comparison with pheomelanins isolated from human hair. These advances led eventually to an integrated picture of the biogenetic route highlighting the intervention of various chemical and enzymatic factors which affect the kinetics of the different steps and the nature of the key benzothiazine precursors. A likely biogenetic route was also postulated for the Δ2,2′‐bi(2H‐1,4‐benzothiazine) pigments, termed trichochromes, whose origin had remained an open issue since their first isolation from red human hair and avian feathers. Finally, a more detailed description of the structure of pheomelanin pigments in terms of the monomer units, their mode of linking, and postsynthetic modifications was gained.
HPLC Analysis of Pheomelanin Degradation Products in Human Urine
Authors: Takasaki Akihiko , Nezirević Dženeta , Årstrand Kerstin , Wakamatsu Kazumasa , Ito Shosuke , Kågedal Bertil
Published: September 2003

A sensitive and specific high performance liquid chromatography (HPLC) method was developed to quantify 4‐amino‐3‐hydroxyphenylalanine (4‐AHP) and 3‐amino‐4‐hydroxyphenylalanine (3‐AHP) in urine. In degradation studies of melanin pigment, 4‐AHP and 3‐AHP are derived from benzothiazine units of pheomelanin and pheomelanin‐related metabolites such as trichochromes. 5‐S‐Cysteinyldopa‐derived benzothiazine products give 4‐AHP while 2‐S‐cysteinyldopa‐derived benzothiazine products give 3‐AHP. 3‐AHP is also derived from nitrotyrosine formed by nitration of tyrosine with reactive nitrogen species. For this reason, the influence of this biological process on the amount of 3‐AHP found in biological material have been investigated. The method is based on hydriodic acid hydrolysis of the melanin polymer and reversed‐phase HPLC with electrochemical detection of the degradation products 4‐AHP and 3‐AHP. The mobile phase consists of 25 mM ammonium acetate and sodium octanesulfonate as an ion‐pairing reagent. The 4‐AHP and 3‐AHP peaks were well separated and the detector response was linear within the range 0–2 ng injected for both compounds. With the developed chromatographic system, 4‐AHP and 3‐AHP showed good separation in the biological samples. There was a strong correlation between 4‐AHP and 3‐AHP in the urine of 50 malignant melanoma patients and two healthy subjects (R0.977). The two compounds were also strongly correlated with 5‐S‐cysteinyldopa in urine, the correlation coefficients being 0.862 and 0.907, respectively. The method described is sensitive enough for analysis of pheomelanin in urine and in several other biological samples. The results indicate that 3‐AHP in urine is not influenced by excreted 3‐nitrotyrosine and the data indicate that pheomelanins are excreted in the urine of melanoma patients.
Alterations of Mitochondria in Peripheral Blood Mononuclear Cells of Vitiligo Patients
Authors: Dell'Anna Maria Lucia , Urbanelli Sandra , Mastrofrancesco Arianna , Camera Emanuela , Iacovelli Paolo , Leone Giovanni , Manini Paola , D'ischia Marco , Picardo Mauro
Published: September 2003

The possible role for a defective mitochondrial functionality in the pathogenesis of vitiligo was investigated by measuring intracellular levels of reactive oxygen species and of antioxidants, the activity of Krebs cycle enzymes, as well as the effects of inhibitors of the electron transport chain, in peripheral blood mononuclear cells from patients with active or stable disease vs. normal subjects. Plasma glyoxal levels were also determined in the same groups of subjects as an index of systemic oxidative stress. In patients with vitiligo in active phase, we observed an increased intracellular production of reactive oxygen species with a consequent imbalance of the prooxidant/antioxidant equilibrium, whereas plasma did not show apparent alterations in glyoxal levels, ruling out a systemic oxidative stress. In patients with stable disease, the balance between pro‐oxidants and anti‐oxidants seems to be maintained. Moreover, a marked increase in the expression of mitochondrial malate dehydrogenase activity and a specific sensitivity to electron transport chain complex I inhibitor were observed. Overall, these data provide further evidence for an altered mitochondrial functionality in vitiligo patients.
Cutaneous Photobiology. The Melanocyte vs. the Sun: Who Will Win the Final Round?
Authors: Kadekaro Ana Luisa , Kavanagh Renny J. , Wakamatsu Kazumasa , Ito Shosuke , Pipitone Michelle A. , Abdel‐Malek Zalfa A.
Published: September 2003

Solar ultraviolet radiation (UV) is a major environmental factor that dramatically alters the homeostasis of the skin as an organ by affecting the survival, proliferation and differentiation of various cutaneous cell types. The effects of UV on the skin include direct damage to DNA, apoptosis, growth arrest, and stimulation of melanogenesis. Long‐term effects of UV include photoaging and photocarcinogenesis. Epidermal melanocytes synthesize two main types of melanin: eumelanin and pheomelanin. Melanin, particularly eumelanin, represents the major photoprotective mechanism in the skin. Melanin limits the extent of UV penetration through the epidermal layers, and scavenges reactive oxygen radicals that may lead to oxidative DNA damage. The extent of UV‐induced DNA damage and the incidence of skin cancer are inversely correlated with total melanin content of the skin. Given the importance of the melanocyte in guarding against the adverse effects of UV and the fact that the melanocyte has a low self‐renewal capacity, it is critical to maintain its survival and genomic integrity in order to prevent malignant transformation to melanoma, the most fatal form of skin cancer. Melanocyte transformation to melanoma involves the activation of certain oncogenes and the inactivation of specific tumor suppressor genes. This review summarizes the current state of knowledge about the role of melanin and the melanocyte in photoprotection, the responses of melanocytes to UV, the signaling pathways that mediate the biological effects of UV on melanocytes, and the most common genetic alterations that lead to melanoma.
A genomic overview of pyridoxal‐phosphate‐dependent enzymes
Authors: Percudani Riccardo , Peracchi Alessio
Published: September 2003

Enzymes that use the cofactor pyridoxal phosphate (PLP) constitute a ubiquitous class of biocatalysts. Here, we analyse their variety and genomic distribution as an example of the current opportunities and challenges for the study of protein families. In many free‐living prokaryotes, almost 1.5% of all genes code for PLP‐dependent enzymes, but in higher eukaryotes the percentage is substantially lower, consistent with these catalysts being involved mainly in basic metabolism. Assigning the function of PLP‐dependent enzymes simply on the basis of sequence criteria is not straightforward because, as a consequence of their common mechanistic features, these enzymes have intricate evolutionary relationships. Thus, many genes for PLP‐dependent enzymes remain functionally unclassified, and several of them might encode undescribed catalytic activities. In addition, PLP‐dependent enzymes often show catalytic promiscuity (that is, a single enzyme catalyses different reactions), implying that an organism can have more PLP‐dependent activities than it has genes for PLP‐dependent enzymes. This observation presumably applies to many other classes of protein‐encoding genes.
Myotome meanderings
Authors: Hollway Georgina E , Currie Peter D
Published: September 2003

The formation of muscles within the vertebrate embryo is a tightly orchestrated and complex undertaking. Beyond the initial specification of cells to become muscle are several complex cellular movements and migrations, which lead to the positioning of muscle precursors at specific locations within the embryo. The consequent differentiation, elongation and striation of these cells results in the formation of individual muscles. Investigation of the in vivo morphogenesis of individual vertebrate muscle cells has only recently begun, and is being approached through the use of sophisticated cell labelling and lineage analysis techniques. However, a consensus about the mechanisms involved has yet to be achieved. This review outlines vertebrate embryonic muscle formation in chick, fish and mice, focusing on the embryonic myotome, which generates both the axial musculature and the appendicular muscle of the fins and limbs. We highlight the points of consensus about, and the complexity of, this developmental system, and propose an evolutionary context for the basis of these understandings.
Condensed chromatin domains in the mammalian nucleus are accessible to large macromolecules
Authors: Verschure Pernette J , van der Kraan Ineke , Manders Erik M M , Hoogstraten Deborah , Houtsmuller Adriaan B , van Driel Roel
Published: August 2003

Most chromatin in interphase nuclei is part of condensed chromatin domains. Previous work has indicated that transcription takes place predominantly at the surface of chromatin domains, that is, in the perichromatin region. It is possible that genes inside chromatin domains are silenced due to inaccessibility to macromolecular components of the transcription machinery. We have tested the accessibility of chromatin domains in nuclei of living cells with proteins and dextrans of different molecular sizes. Our results show that chromatin domains are readily accessible to large macromolecules, including proteins with a molecular weight of several hundred kilodaltons. Therefore, the silencing of genes that are incorporated into such domains is not due to the physical inaccessibility of condensed chromatin domains to transcription factors.
Crystal structure of the PsbQ protein of photosystem II from higher plants
Authors: Calderone Vito , Trabucco Michela , Vujičić Andreja , Battistutta Roberto , Giacometti Giorgio Mario , Andreucci Flora , Barbato Roberto , Zanotti Giuseppe
Published: September 2003

The smallest extrinsic polypeptide of the water‐oxidizing complex (PsbQ) was extracted and purified from spinach (Spinacia oleracea) photosystem II (PSII) membranes. It was then crystallized in the presence of Zn2+ and its structure was determined by X‐ray diffraction at 1.95‐Å resolution using the multi‐wavelength anomalous diffraction method, with the zinc as the anomalous scatterer. The crystal structure shows that the core of the protein is a four‐helix bundle, whereas the amino‐terminal portion, which possibly interacts with the photosystem core, is not visible in the crystal. The distribution of positive and negative charges on the protein surface might explain the ability of PsbQ to increase the binding of Cl− and Ca2+ and make them available to PSII.
The MRN complex: coordinating and mediating the response to broken chromosomes
Authors: van den Bosch Michael , Bree Ronan T , Lowndes Noel F
Published: September 2003

The MRE11–RAD50–NBS1 (MRN) protein complex has been linked to many DNA metabolic events that involve DNA double‐stranded breaks (DSBs). In vertebrate cells, all three components are encoded by essential genes, and hypomorphic mutations in any of the human genes can result in genome‐instability syndromes. MRN is one of the first factors to be localized to the DNA lesion, where it might initially have a structural role by tethering together, and therefore stabilizing, broken chromosomes. This suggests that MRN could function as a lesion‐specific sensor. As well as binding to DNA, MRN has other roles in both the processing and assembly of large macromolecular complexes (known as foci) that facilitate efficient DSB responses. Recently, a novel mediator protein, mediator of DNA damage checkpoint protein 1 (MDC1), was shown to co‐immunoprecipitate with the MRN complex and regulate MRE11 foci formation. However, whether the initial recruitment of MRN to DSBs requires MDC1 is unclear. Here, we focus on recent developments in MRN research and propose a model for how DSBs are sensed and the cellular responses to them are mediated.
An exosome‐like complex in Sulfolobus solfataricus
Authors: Evguenieva‐Hackenberg Elena , Walter Pamela , Hochleitner Elisabeth , Lottspeich Friedrich , Klug Gabriele
Published: August 2003

We present the first experimental evidence for the existence of an exosome‐like protein complex in Archaea. In Eukarya, the exosome is essential for many pathways of RNA processing and degradation. Co‐immunoprecipitation with antibodies directed against the previously predicted Sulfolobus solfataricus orthologue of the exosome subunit ribosomal‐RNA‐processing protein 41 (Rrp41) led to the purification of a 250‐kDa protein complex from S. solfataricus. Approximately half of the complex cosediments with ribosomal subunits. It comprises four previously predicted orthologues of the core exosome subunits from yeast (Rrp41, Rrp42, Rrp4 and Csl4 (cep1 synthetic lethality 4; an RNA‐binding protein and exosome subunit)), whereas other predicted subunits were not found. Surprisingly, the archaeal homologue of the bacterial DNA primase DnaG was tightly associated with the complex. This suggests an RNA‐related function for the archaeal DnaG‐like proteins. Comparison of experimental data from different organisms shows that the minimal core of the exosome consists of at least one phosphate‐dependent ribonuclease PH homologue, and of Rrp4 and Csl4. Such a protein complex was probably present in the last common ancestor of Archaea and Eukarya.
Gcn4 occupancy of open reading frame regions results in the recruitment of chromatin‐modifying complexes but not the mediator complex
Authors: Topalidou Irini , Thireos George
Published: September 2003

Eukaryotic transcriptional activators usually recognize short DNA motifs, which are not only located within promoter regions, but also scattered throughout the genome. Assuming that the function of activators at non‐promoter regions is wasteful and perhaps harmful, one can ask whether such binding is somehow prevented or if transcription is blocked at a downstream step. Here, we show that the yeast transcriptional activator Gcn4 is associated in vivo with several non‐promoter euchromatic sites. This association results in the recruitment of the SAGA (Spt3/Ada/Gcn5/acetyltransferase) complex and the consequent activity of the Gcn5 histone acetyltransferase. The functional recruitment of the Swi/Snf nucleosome‐remodelling complex was also evident at sites located in positioned nucleosomes. We show that this assemblage of coactivator complexes is not productive because of the absence of core promoter elements, other than the TATA box, that are required for stable mediator recruitment.
In vivo temperature response functions of parameters required to model RuBP‐limited photosynthesis
Authors: BERNACCHI C. J. , PIMENTEL C. , LONG S. P.
Published: September 2003

The leaf model of C3 photosynthesis of Farquhar, von Caemmerer & Berry (Planta 149, 78–90, 1980) provides the basis for scaling carbon exchange from leaf to canopy and Earth‐System models, and is widely used to project biosphere responses to global change. This scaling requires using the leaf model over a wider temperature range than that for which the model was originally parameterized. The leaf model assumes that photosynthetic CO2 uptake within a leaf is either limited by the rate of ribulose‐1,5‐bisphosphate (RuBP) regeneration or the activity of RuBP carboxylase‐oxygenase (Rubisco). Previously we reported a re‐parameterization of the temperature responses of Rubisco activity that proved robust when applied to a range of species. Herein this is extended to re‐parameterizing the response of RuBP‐limited photosynthesis to temperature. RuBP‐limited photosynthesis is assumed to depend on the whole chain electron transport rate, which is described as a three‐parameter non‐rectangular hyperbolic function of photon flux. Herein these three parameters are determined from simultaneous measurement of chlorophyll fluorescence and CO2 exchange of tobacco leaves, at temperatures from 10 to 40 °C. All varied significantly with temperature and were modified further with variation in growth temperature from 15 to 35 °C. These parameters closely predicted the response of RuBP‐limited photosynthesis to temperature measured in both lemon and poplar and showed a significant improvement over predictions based on earlier parameterizations. We provide the necessary equations for use of the model of Farquhar et al. (1980) with our newly derived temperature functions for predicting both Rubisco‐ and RuBP‐limited photosynthesis.
Carbon use efficiency depends on growth respiration, maintenance respiration, and relative growth rate. A case study with lettuce
Authors: VAN IERSEL M. W.
Published: September 2003

Carbon use efficiency (CUE, the ratio between the amount of carbon incorporated into dry matter to the amount of carbon fixed in gross photosynthesis) is an important parameter in estimating growth rate from photosynthesis data or models. It previously has been found to be relatively constant among species and under different environmental conditions. Here it is shown thatCUEcan be expressed as a function of the relative growth rate (rGR) and the growth (gr) and maintenance respiration coefficients (mr): 1/CUE = 1 + gr + mr/rGR. Net daily carbon gain (Cdg),rGR, andCUEwere estimated from whole‐plant gas exchange measurements on lettuce (Lactuca sativaL.) ranging from 24 to 66 d old. Carbon use efficiency decreased from 0.6 to 0.2 with increasing dry mass, but there was no correlation betweenCUEandCdg. The decrease inCUEwith increasing dry mass was correlated with a simultaneous decrease inrGR. From the above equation,grandmrwere estimated to be 0.48 mol mol−1and 0.039 g glucose g–1 dry matter d−1, respectively. Based on thegrestimate, the theoretical upper limit forCUEof these plants was 0.68. The importance of maintenance respiration in the carbon balance of the plants increased with increasing plant size. Maintenance accounted for 25% of total respiration in small plants and 90% in large plants.
Expansion dynamics, metabolite composition and substance transfer of the primary root growth zone ofZea maysL. grown in different external nutrient availabilities
Authors: WALTER A. , FEIL R. , SCHURR U.
Published: September 2003

A combined analysis of growth and metabolite composition was performed in primary roots ofZea maysL. (Var. Alexander). The seedlings were hydroponically cultivated either in pure water or in complete nutrient solution. The overall root growth performance was similar in both treatments. Yet, digital image sequence processing methods resolved, that growth distribution and oscillatory movements within the growth zone depended strongly on external nutrient availability. Metabolite concentration profiles were similar in both treatments for most investigated metabolites, indicating a thorough mobilization of nutrient resources from the seed, but concentrations of glutamine, glutamic acid, NO3–, NH4+, malate and citrate showed pronounced differences between treatments. No diurnal variations in metabolite concentrations were found. Deposition rate profiles were in general more similar to relative elemental growth rate profiles than concentration profiles and were not affected by the treatment. Major ions were deposited maximally in front of the centre of growth activity, while greatest hexose deposition was found behind that. Relative to their abundance in the root growth zone, net rates of transfer from mature tissue were highest for sucrose, glutamic acid and aspartic acid, whereas glucose, fructose and most amino acids inversely showed high net rates of transfer out of the root growth zone, indicating a high catabolic rate for those substances there. NO3–, but not other nutrients, was transferred to a great extent from the root growth zone to the mature tissue in nutrient solution. Overall, the results show, that a careful analysis of growth dynamics allows quantifying and interpreting a number of important flux parameters in the growing organ and that the performance of the primary root does not depend strongly on external nutrient availability.
Transport and metabolism of free cyanide and iron cyanide complexes by willow
Authors: EBBS S. , BUSHEY J. , POSTON S. , KOSMA D. , SAMIOTAKIS M. , DZOMBAK D.
Published: September 2003

Cyanide compounds are contaminants of growing importance that could be remediated biologically via phytoremediation, provided the plants possess suitable mechanisms for managing these pollutants without toxicity. The transport and metabolism of two cyanide compounds, potassium cyanide and potassium ferrocyanide, by willow (Salix eriocephala L. var. Michaux) were compared using a hydroponic system that preserved cyanide speciation and solubility. The cyanide compounds were labelled with 15N to quantify transport while a novel tissue extraction procedure was used to relate tissue 15N to cyanide content and speciation. These analyses revealed that although little free cyanide was detected in the aerial tissues of plants exposed to either of these two cyanide compounds, significant enrichments in 15N were observed, suggesting transport and subsequent metabolism of free cyanide as well as ferrocyanide. The results for ferrocyanide are of interest because this molecule is resistant to microbial degradation and if oxidized to ferricyanide is purportedly membrane impermeable. Nevertheless, these results and mass balance calculations for tissue 15N and solution cyanide confirming 100% recovery for the added ferrocyanide are suggestive of ferrocyanide uptake and metabolism. This study provides new information describing the biological transport and metabolism of these two cyanide compounds in plants. Moreover, the data also suggest that phytoremediation of cyanide may be possible and ecologically safe due to the lack of cyanide bioaccumulation in aerial tissues.
A systematic review of the effects of interprofessional education on staff involved in the care of adults with mental health problems
Authors: Reeves S.
Published: September 2003

Interprofessional education (IPE) is commonly advocated in policy documentation as a means of enhancing collaboration between heath and social care staff. However, little is known about the effects of this type of education. This paper reports findings from a systematic review which was commissioned to search and begin assessing the quality of the published evidence relating to the effects of IPE on staff involved in the care of adults with mental health problems. Results from this study indicate that there is a current lack of rigorous evidence into the effects of IPE in this field. Conclusions from this work are made in connection to mental health policy and recommendations are offered for strengthening the evaluation of IPE.