bluuebunny/crossref_metadata_2025 huggingface dataset:
Reindeer grazing and soil microbial processes in two suboceanic and two subcontinental tundra heaths
Authors: Stark Sari , Strömmer Rauni , Tuomi Juha
Published: March 2003

In oceanic, nutrient‐rich Fennoscandian arctic‐alpine tundra heaths, grazing by reindeer has been found to increase herbs and graminoids in relation to dwarf shrubs. In continental lichen heaths in the inland with nutrient‐poor conditions, however, slowly decomposable dwarf shrubs are favoured by grazing. According to a hypothesis, by favouring easily decomposing plants in nutrient‐rich conditions and slowly decomposing plants in nutrient‐poor conditions, herbivory enhances soil nutrient cycling in nutrient‐rich and retards it in nutrient‐poor areas. We tested this hypothesis by comparing the impact of reindeer grazing on soil C and N mineralization between two oceanic and two continental arctic‐alpine tundra heaths.  Although soil respiration and microbial metabolic activity were enhanced by grazing in the suboceanic but not in the subcontinental tundra heaths, gross N mineralization rates were higher in the grazed areas in soils from all study sites, indicating that reindeer grazing leads to increased rates of nutrient cycling in both nutrient‐poor and nutrient‐rich tundra heaths. Thus, in the subcontinental tundra heaths, the increase in soil N concentrations due to mammalian waste products enhances N mineralization rates, even though the organic C quality is not improved by reindeer grazing. There was some site‐specific variation in the strength of the reindeer effects on various microbial processes and soil properties, which can be related to spatial variation in grazing intensity and timing, as these factors in turn affect the nutrient sink strength of the vegetation.
Indirect interactions in a microcosm‐assembled cladoceran community: implications for apparent competition
Authors: Martínez Ginger , Medel Rodrigo
Published: March 2003

Apparent competition occurs when species that otherwise may not directly interact still exhibit negative indirect effects on one another because they share a food‐limited predator (enemy). Even though this type of indirect interaction has received significant theoretical and empirical attention, alternative mechanisms producing similar results have not been considered in the literature. In this paper we document the results of a series of microcosm experiments aimed to evaluate the importance of the generalist consumer Daphnia ambigua upon the relative abundance of the more specialized Moina micrura and Ceriodaphnia dubia (Cladocera). We compared the population parameters of M. micrura and C. dubia when alone, in coexistence, and in the presence and absence of D. ambigua. While M. micrura and C. dubia did not show evidence for interspecific competition, the addition of D. ambigua promoted a reduction in the maximal population density of M. micrura, causing a pattern of indirect competition with C. dubia that resembles predator‐mediated apparent competition. This result suggests that non‐predatory interactions need to be considered as a potential source of apparent interactions in natural communities.
The role of indirect interactions in structuring tropical insect communities
Authors: Morris Rebecca J. , Lewis Owen T.
Published: March 2003

Apparent competition is a form of indirect interaction among species that can potentially structure biological communities. In insect communities, parasitoid‐mediated apparent competition has been proposed as a particularly important structuring force. We argue that short‐term apparent competition may be less important in structuring insect communities in tropical regions, compared with temperate regions. This prediction arises because, compared with temperate insects, tropical insects that share natural enemies are more likely to be isolated in both space and time.
Risk‐averse inflorescence departure in hummingbirds and bumble bees: could plants benefit from variable nectar volumes?
Authors: Biernaskie Jay M. , Cartar Ralph V. , Hurly T. Andrew
Published: March 2003

Most hermaphroditic, many‐flowered plants should suffer reduced fitness from within‐plant selfing (geitonogamy). Large inflorescences are most attractive to pollinators, but also promote many flower visits during a single plant visit, which may increase selfing and decrease pollen export. A plant might avoid the negative consequences of attractiveness through modification of the floral display to promote fewer flower visits, while retaining attractiveness. This report shows that increasing only the variance in nectar volume per flower results in fewer flower visits per inflorescence by wild hummingbirds (Selasphorus rufus) and captive bumble bees (Bombus flavifrons) foraging on artificial inflorescences. Inflorescences were either constant (all flowers contained the same nectar volume) or variable (half the flowers were empty, the other half contained twice as much nectar as in the constant flowers). Both types of inflorescence were simultaneously available to foragers. Risk‐averse foraging behaviour was expressed as a patch departure preference: birds and bees visited fewer flowers on variable inflorescences, and this preference was expressed when resource variability could be determined only by concurrent sampling. When variance treatments were clearly labelled with colour and offered to hummingbirds, the departure effect was maintained; however, when preference was measured by inflorescence choice, birds did not consistently prefer to visit constant inflorescences. The reduced visitation lengths on variable inflorescences by both birds and bees documented in this study imply that variance in nectar production rates within inflorescences may represent an adaptive trait to avoid the costs of geitonogamy.
Paradoxical host shift by Depressaria pastinacella in North America: is enemy‐free space involved?
Authors: Zangerl A. R. , Huang T. , McGovern J. L. , Berenbaum M. R.
Published: March 2003

Herbivorous insects often preferentially oviposit and develop on hostplants that support suboptimal growth relative to alternative hostplants available in the same habitat. In some cases, this preference results from reduced predation risk on the nutritionally suboptimal hostplant. Thus, the availability of enemy‐free space has been postulated to affect hostplant choice for herbivorous insects. In the midwestern United States, populations of the parsnip webworm, Depressaria pastinacella Duponchel, introduced from Europe over 150 years ago, feed not only on wild parsnip, Pastinaca sativa L., one of its hosts in Europe, but also on cow parsnip, Heracleum lanatum Michx., a native North American plant. Survival of larvae in the laboratory on fruits of H. lanatum, however, is lower than on fruits of P. sativa, suggesting nutritional or chemical unsuitability. In view of the persistent use of this novel hostplant, we compared susceptibility to predation on these two hostplants in the field. Over a four‐year period, contrary to expectations, webworms pupating in cow parsnip stems consistently experienced intense predation, whereas pupae in parsnip stems escaped predation. The pattern persisted when stems of both hostplants containing pupae were placed in pots at a single location. The predator appears to be avian, as only exclosures that prevented access by both birds and mice eliminated predation, whereas exclosures preventing access by mice alone did not reduce predation. The apparent existence of enemy‐free space in wild parsnip may be due to differences in stem characteristics; parsnip stems contain significantly greater amounts of the highly photoactive furanocoumarin xanthotoxin and are also significantly tougher compared to stems of cow parsnip. The persistent use of cow parsnips by parsnip webworms in the face of high levels of predation and without clear benefits in terms of growth and development suggests that webworms may have lost genetic variation for host discrimination as a consequence of introduction.
Predation risk and habitat selection of Australian house mice , Mus domesticus, during an incipient plague: desperate behaviour due to food depletion
Authors: Ylönen Hannu , Jacob Jens , Davies Micah J. , Singleton Grant R.
Published: March 2003

We studied habitat selection and foraging behaviour of the house mouse (Mus domesticus) related to increasing mouse densities and depleting food resources over the breeding season. The study was conducted during the increase phase of an incipient outbreak of mice in a grain‐growing area of southeastern Australia. A 3‐year rotation created a mosaic of large paddocks of grain crop, pasture, and fallow. The narrow fence lines between paddocks provide an important stable habitat for the mice. We monitored population densities with live‐trapping and habitat preference by measuring giving‐up densities (GUD) using artificial food patches. Food patches were established in crop fields, fence lines, and pasture. Avian predation risk was assessed by daily counts of raptors. Before harvest most mice were found in the crop fields. Fewer mice were found along the fence lines and no mice were found in the pasture. After harvest, the number of mice increased along the fence line and in the pasture. Mice started to exploit pasture but only a few trays were visited. As the population densities of mice increased, they inhabited all habitats. Feeding activity in the pasture remained low due to high predation risk. Along fence lines feeding activity increased and mice exploited open and covered patches similarly. We conclude that during high densities mice experience a strong trade‐off between food and safety. Vegetation along fence lines offered cover but little food. However, soon after harvest this habitat was favoured by mice. Pasture offered little food and was an extremely risky habitat because of the lack of cover. We suggest that during high densities of mice, habitat use became more opportunistic. Mice took greater risks in all habitats and within each habitat at the microhabitat level. The “Stalingrad effect” is a good descriptor of foraging decisions of mice during the progression of an incipient plague in the cereal‐growing regions of southeastern Australia.
Cyclin D1 expression in oral squamous cell carcinomas: clinicopathological relevance and correlation with p53 expression
Authors: Lam King Y. , Ng Irene O. L. , Yuen Anthony P. W. , Kwong Dora L. W. , Wei William
Published: March 2003

Abstract: The aim of the present study is to study the relationship between cyclin D1 and the clinicopathological features of oral squamous cell carcinomas. The cyclin D1 and p53 expression in oral squamous cell carcinomas from 56 patients (45 men, 11 women) was studied by immunohistochemistry using monoclonal antibodies. The correlation between cyclin D1 and the clinicopathological features of the oral cancers was evaluated. Cyclin D1 expression was found in 63% of oral squamous cell carcinomas; it was often weak but was more frequently positive in high‐grade lesions (P=0.019). The expression was positively correlated with p53 expression (P=0.06). Radiation therapy did not alter the expression of either cyclin D1 or p53 proteins. Expression of these proteins was not related to the age, gender or survival of the patients, or to stages of the tumors. The cyclin D1 expression was more frequently seen in patients with squamous cell carcinomas of oropharynx, palate, floor of mouth and gingiva. To conclude, cyclin D1 was frequently expressed in oral squamous cell carcinomas. This expression was related to the grade of the tumors and was not similar in various regions in the oral cavity, which may indicate the different tumor biology of cancers from these regions.
Erosive oral lichen planus and salivary cortisol
Authors: Rödström Per‐Olof , Jontell Mats , Hakeberg Magnus , Berggren Ulf , Lindstedt Göran
Published: March 2003

Abstract: Patients with oral lichen planus (OLP) often relate the onset and aggravation of oral symptoms to increased levels of stress. Under normal conditions, stress induces increased cortisol secretion that counteracts inflammatory reactions. The objective of the present study was to assess whether patients with OLP have an impaired capacity to elevate their cortisol concentrations as a response to stress. Saliva samples were collected for cortisol analysis from 10 OLP patients once every 15 min during a 2‐h test period. In order to induce stress during a part of this test period, the patients were confronted with a computerised device specifically developed for the induction of transient stress. A visual analogue scale (VAS) and a mood adjective check list (MACL) were used to estimate the degree of permanent stress. A control group of patients was matched for age and sex. The OLP patients did not present with different stress scores when a psychometric test (MACL) was used. No statistically significant correlation between cortisol concentration and stress level was observed. Thus, no support for an impaired capacity of OLP patients to suppress an immune response through cortisol induction in conjunction with experimental stress was revealed.
Elemental sulphur and alkali elutable melanin detected in oral melanosis and malignant melanoma by energy‐filtering transmission electron microscopy
Authors: Nagai Noriyuki , Lee You‐Jin , Nagaoka Noriyuki , Gunduz Mehmet , Nakano Keisuke , Nojima Tetsundo , Tsujigiwa Hidetsugu , Gunduz Esra , Siar Chong Huat , Nagatsuka Hitoshi
Published: March 2003

Background:  The morphology and contents of melanosomes are important features for differentiating melanocyte‐derived melanotic lesions such as melanosis and malignant melanoma.

Methods:  In this study, we attempted to elucidate the structure of melanin and sulphur content in oral melanosis and malignant melanomas by ultrastructural analysis.

Results:  In oral melanosis, the essential pathological findings were overproduction of eumelanin and discharge of melanin into keratinocytes. In malignant melanoma in situ, pleomorphic and ellipsoid abnormal melanosomes with an increase in sulphur content and alkali elution rate were detected. In invasive malignant melanoma, the irregular ellipsoid and spheroid melanosomes existing either as discrete bodies or compound melanosomes with furtherly increased sulphur content and alkali elution were detected.

Conclusions:  Our findings suggest that abnormal melanosome morphology and high sulphur content are predictive markers for assessment of early or precancerous melanotic lesions and malignant melanoma.
Immunohistochemical analysis of inducible nitric oxide synthase (iNOS) and heat shock proteins (HSPs) in ameloblastomas
Authors: Kumamoto Hiroyuki , Suzuki Takahiro , Ooya Kiyoshi
Published: March 2003

Background:  To clarify the possible role of nitric oxide (NO) and stress proteins in oncogenesis and cytodifferentiation of odontogenic epithelium. Inducible NO synthase (iNOS) and heat shock proteins (HSPs) were analyzed in ameloblastomas as well as in tooth germs.

Methods:  Specimens of seven tooth germs, 36 benign ameloblastomas and five malignant ameloblastomas were examined by immunohistochemistry using antibodies against iNOS and 27‐, 60‐ and 70‐kDa HSPs (HSP27, HSP60 and HSP70).

Results:  Immunoreactivity for iNOS was detected in normal and neoplastic odontogenic epithelial cells and was higher in malignant ameloblastomas than in tooth germs and benign ameloblastomas. HSP27 was expressed constitutively in all odontogenic epithelial cells in tooth germs and benign and malignant ameloblastomas. Expression of HSP60 and HSP70 was detected in normal and neoplastic odontogenic epithelial cells and was prominent in cells neighboring the basement membrane. HSP60 reactivity showed no apparent difference between normal and neoplastic odontogenic epithelium, whereas HSP70 expression was slightly higher in benign and malignant ameloblastomas than in tooth germs.

Conclusions:  Activation of iNOS might be associated with malignant potential of epithelial odontogenic tumors. Elevated expression of HSP70 is considered to be involved in neoplastic transformation of odontogenic epithelial cells.
HER2/neu expression in adenoid cystic carcinoma of salivary gland origin: an immunohistochemical study
Authors: Dori Shai , Vered Marilena , David Raphael , Buchner Amos
Published: March 2003

Background:  Adenoid cystic carcinoma (ACC) is a malignant tumor of salivary gland origin, which is characterized by a high rate of local recurrence and distant hematogenous metastasis. Despite aggressive surgical treatment and radiotherapy, the patient's long‐term prognosis is dismal. Prompted by recent studies on the amplification of the oncogene HER2/neu in salivary gland tumors, we analyzed the immunohistochemical overexpression of HER2/neu in salivary glands ACC. If the tumor exhibits overexpression of HER2/neu, then treating it with the anti‐HER2/neu therapeutic agent, Herceptin (Trastuzumab, Genentech, CA), could be considered.

Methods:  The study comprised of 32 samples of formalin‐fixed, paraffin‐embedded specimens. All laboratory procedures and scoring criteria were performed according to currently approved FDA methods.

Results:  HER2/neu overexpression was found in only five (16%) cases. Four cases (13%) scored 1+ and one case (3%) scored 2+.

Conclusions:  The low prevalence of HER2/neu overexpression in ACC limits the clinical utility of Herceptin therapy for salivary gland ACC.
A case of multiple AOT‐like jawbone lesions in a young patient – a new odontogenic entity?
Authors: Larsson Å. , Swartz K. , Heikinheimo K.
Published: March 2003

We assessed the immunohistochemical profile of an unusual case of multiple similarly looking tumors in the jawbone of a young patient. Histologically, the tumors exhibited features of adenomatoid odontogenic tumor (AOT) and adenomatoid dentinoma but showed no resemblance to any other defined odontogenic tumor entities. They expressed high amounts of cytokeratin (CK) 8 and 14 together with some Vimentin. A small rim of peripheral cells showed CK 5, 17, and 19 reactivity. Also, these lesions expressed some bcl‐2 as well as p53 and Ki67. Histologically and immunohistochemically, the unusual multiple lesions differed in details from a simultaneously examined group of 24 classical AOT cases, suggesting that they may represent a hitherto less well‐defined odontogenic tumor entity.
Cell death regulation in oral squamous cell carcinoma: methodological considerations and clinical significance
Authors: Loro L. L. , Vintermyr O. K. , Johannessen A. C.
Published: March 2003

In the last three decades, more work has been done on apoptosis and its role in the pathogenesis of many diseases including cancer. In almost all instances of cancer, dysregulation of cell death (apoptosis) and cell proliferation have been found to play a major role in tumourigenesis. A lot of progress has been made on understanding the molecular basis of apoptosis and its regulatory mechanisms. This review focuses on current knowledge on the regulation of apoptosis in oral squamous cell carcinoma, current methodologies and methodological consideration in estimation of cell death in tissue sections and the clinical significance of apoptosis related molecules in progression of oral squamous cell carcinoma.
Sorting and Targeting of Melanosomal Membrane Proteins: Signals, Pathways, and Mechanisms
Authors: SETALURI VIJAYASARADHI
Published: March 2003

Newly synthesized melanosomal proteins, like many other cellular proteins, traverse through a series of intracellular compartments en route to melanosomes. Entry and exit of proteins through these compartments is orchestrated by cellular sorting machinery that recognize specific sorting signals. Melanosomal membrane proteins begin their intracellular journey upon co‐translational importation into the endoplasmic reticulum (ER). The biosynthetic output of tyrosinase, the key melanogenic enzyme, appears to be regulated by quality‐control events at the ER, the ‘port of entry’ to the secretory pathway. Following maturation in the ER and through the Golgi, the sorting of these proteins in the trans‐Golgi network for intracellular retention and transport along endosome/lysosome pathway requires cytoplasmically exposed signals. A di‐leucine motif, present in the cytoplasmic tails of most melanosomal proteins, and its interaction with adaptor protein (AP) complexes, specifically AP‐3, are critical for these events. Defects in sorting signals and the cytosolic components that interact with these signals result in a number of murine coat color phenotypes and cause human pigmentary disorders. Thus, missense or frame‐shift mutations that produce truncated tyrosinase lacking the melanosomal sorting signal(s) appear to be responsible for murine platinum coat color phenotypes and a proportion of human oculocutaneous albinism‐1; mutations in AP‐3 appear to be responsible for the mocha phenotype in mice and Hermansky–Pudlak‐like syndrome in man. Additional signals and sorting steps downstream of AP‐3 appear to be required for endosomal sorting and targeting proteins to melanosomes. Signals and mechanisms that sequester melanosomal proteins from endosomes/lysosomes are not understood. Potential candidates that mediate such processes include proteins encoded by lyst and pallid genes. The common occurrence of abnormalities in melanosomes in many storage‐pool disorders suggests that melanocytes utilize signals, pathways, and mechanisms shared by other proteins and cell types to assemble a number of specialized proteins and produce unique cell‐type‐specific organelles.
The Use of Expression Profiling to Study Pigment Cell Biology and Dysfunction
Authors: LOFTUS STACIE K. , PAVAN WILLIAM J.
Published: March 2003

Regulation of gene expression is a fundamental process by which cells respond to both intracellular and extracellular signals. For a pigment cell, alterations in gene expression regulate the processes of cell migration, lineage restriction, differentiation, type of pigment produced, and progression from a normal pigment cell to that of melanoma. To date, the identification of genes involved in normal pigment cell development has been accomplished by the cloning of individual mutant alleles, a single gene at a time. Current advances in technology have now made it possible to use expression profile analysis to investigate, on a genomic scale, the process of pigment cell development and function. This review compares and contrasts the methods of subtractive suppressive polymerase chain reaction (PCR) and differential display with that of cDNA microarray analysis.
Identification of a Distal Enhancer for the Melanocyte‐Specific Promoter of the MITF Gene
Authors: Watanabe Ken‐ichi , Takeda Kazuhisa , Yasumoto Ken‐ichi , Udono Tetsuo , Saito Hideo , Ikeda Katsuhisa , Takasaka Tomonori , Takahashi Kazuhiro , Kobayashi Toshimitsu , Tachibana Masayoshi , Shibahara Shigeki
Published: March 2003

Waardenburg syndrome (WS) is characterized by deafness and hypopigmentation because of the lack of melanocytes in the inner ear and skin. WS type 2 is associated with mutations in the gene encoding microphthalmia‐associated transcription factor (MITF) that is required for melanocyte differentiation. MITF consists of multiple isoforms with different N‐termini, one of which is exclusively expressed in melanocytes, named MITF‐M. Its N‐terminus is encoded by exon 1M that is under the regulation of the melanocyte‐specific (M) promoter. Here we identify a distal regulatory region of 298 bp, located 14.5 kb upstream from exon 1M, which enhances the M promoter activity in cultured melanoma cells. This enhancer activity depends on the proximal M promoter region (−120 to −46). The MITF‐M distal enhancer (MDE), thus identified, contains the binding sites for SOX10, a transcription factor responsible for another type of WS, known as Waardenburg–Hirschsprung syndrome. Characterization of MDE has suggested SOX10 as one of factors that are involved in the function of MDE. A putative MDE counterpart is located 12 kb upstream from mouse exon 1M and its role is discussed in relevance to the pathogenesis of red‐eyed white Mitf mi–rw mice that exhibit small red eyes and white coat. Moreover, by in situ hybridization analysis, we suggest that Sox10 and Mitf‐M (mRNA) are expressed in melanoblasts migrating toward the otic vesicle (prospective inner ear) of mouse embryos but are separately expressed in different cell types of the newborn cochlea. Thus, SOX10 regulates transcription from the M promoter in a developmental stage‐specific manner.
γ ‐Glutamyl Transpeptidase and its Role in Melanogenesis: Redox Reactions and Regulation of Tyrosinase
Authors: Chaubal Vaishali A. , Nair Sujit S. , Ito Shosuke , Wakamatsu Kazumasa , Mojamdar Manoj V.
Published: March 2003

Metabolism of glutathione by γ‐glutamyl transpeptidase (γ‐GT) at the level of cell membrane has been shown to generate hydrogen peroxide in many cell types including human melanomas. γ‐GT does not appear to be involved in cysteine uptake for pheomelanin production in melanoma cells and does not contribute significantly to the pheomelanin synthesized in B16 melanoma cells. We have therefore examined the possibility of γ‐GT mediated production of prooxidant reactions and its effect, if any, on pigmentation using B16 melanoma cells. Our results indicate that in B16 melanoma cells, γ‐GT activity leads to the production of hydrogen peroxide. We further show that the nuclear levels of the redox sensitive transcription factor NF‐κB is regulated by H2O2 formed by the action of γ‐GT: stimulation and inhibition of γ‐GT affect the levels of NF‐κB. Tumor necrosis factor α, a hypopigmenting cytokine, known to activate NF‐κB also up‐regulates the γ‐GT messenger RNA and activity. Stimulation of γ‐GT generated prooxidant reactions led to a decrease in tyrosinase activity. We therefore propose that prooxidant reactions mediated by γ‐GT in turn regulate the levels of tyrosinase in pigment cells. Our findings thus introduce a new aspect in the regulation of pigmentation and ascribe a novel role for γ‐GT in pigment cells.
Heterogeneous Susceptibility to Spontaneous and Induced Apoptosis Characterizes Two Related Transplantable Melanomas with Different Biological Properties
Authors: Kozłowska Krystyna , Cichorek Mirosława , Zarzeczna Małgorzata , Brożek Jacek , Witkowski Jacek M.
Published: March 2003

A family of phenotypically and biologically different transplantable hamster melanomas was derived from a single tumor more than 40 yr ago. In this work, we were seeking the differences between the abilities of the cells from two biologically heterogeneous (melanotic and amelanotic) members of this family to undergo spontaneous or camptothecin‐induced apoptosis. We studied these differences by looking at three important features of the apoptotic process, i.e. binding of annexin V, DNA fragmentation and caspase‐3 activity. Of these, annexin binding and DNA fragmentation were more pronounced in the parental, melanotic line while the activity of caspase‐3 was stronger in the amelanotic tumor cells. We concluded that a spontaneous alteration of the original, melanotic melanoma line into an amelanotic one, associated with more aggressive tumor progression, was accompanied by significant decrease in ability to undergo spontaneous and camptothecin‐induced apoptosis, and that apoptosis of these two cell types may not depend on the activity of caspase‐3.
Type I γ‐GT mRNA is Expressed in B16 Melanoma and Levels Correlate with Pigmentation
Authors: Chaubal Vaishali A. , Nair Sujit S. , Mojamdar Manoj V.
Published: March 2003

γ‐Glutamyl transpeptidase (γ‐GT), an ectoenzyme involved mainly in glutathione metabolism, is expressed in B16 melanoma cells. B16 melanoma cells under continuous culture conditions show a phenotypic drift from melanotic to amelanotic and re‐melanotic stages. We have investigated the regulation of γ‐GT in B16 melanoma cells under such different pigmentary conditions. High levels of γ‐GT messenger RNA (mRNA) and activity were detected in pigmented B16 melanoma cells, whereas in amelanotic B16 melanoma cells the levels were very low. Treatment with lactic acid, a known inhibitor of tyrosinase gene expression, also led to the down‐regulation of γ‐GT mRNA and activity. Thus our results indicate that γ‐GT regulation depends on the pigmentation status in pigment cells. We have also assessed the levels of γ‐GT in normal murine melanocytes (melan‐a cells). It was seen that melan‐a cells express very low levels of γ‐GT. As γ‐GT is known to be regulated in a tissue‐specific manner, and is expressed from as many as six promoters giving rise to six different types of mRNAs each having unique 5′ ends, we have further investigated the type of γ‐GT mRNA expressed in B16 melanoma and melan‐a cells. In this study, we have conclusively demonstrated that type I mRNA transcript of γ‐GT is expressed in B16 melanoma and melan‐a cells.
Du Temps Perdu a la Recherche
Authors: Riley Patrick A.
Published: March 2003

An attempt has been made to justify an academic career by outlining the approximate history of the development of ideas and tracing their origins and arborization. Because there are multifarious influences and formative factors involved in their genesis it has proved almost impossible to acknowledge all the important contributors to the patchwork of investigations that are summarized. However, whilst the review is incomplete and necessarily brief, it is hoped that a glimpse of some twentieth century preoccupations with biological science is afforded.
Hypothalamic‐pituitary‐adrenal axis activation by experimental periodontal disease in rats
Authors: Breivik T. , Thrane P. S. , Gjermo P. , Opstad P. K. , Pabst R. , Von Hörsten S.
Published: March 2003

Organisms respond to inflammatory conditions by mounting a co‐ordinated complex series of adaptive responses involving the immune, nervous and endocrine systems that are aimed at restoring the homeostatic balance. We have recently shown in a rat model that inappropriate hypothalamic‐pituitary‐adrenal (HPA) axis regulation and a subsequent inability to mount a suitable glucocorticoid response to gingival inflammation may influence susceptibility to periodontal disease. This study was designed to investigate whether ligature‐ and bacterial lipopolysaccharide (LPS)‐induced inflammation in the gingival connective tissues may activate this physiological axis, and to further explore the significance of HPA regulation in periodontal disease. Experimental periodontal disease was induced in major histocompability complex (MHC)‐identical but HPA low (LEW) and high (F344) responding rat strains. We tested (1) whether ongoing periodontal disease activates the HPA axis as measured by corticosterone levels, and (2) whether genetic differences in HPA regulation modulate periodontal disease progression. In the F344 strain, the periodontal tissue destruction was more severe. This observation was associated with a significant increase of corticosterone levels in F344 rats only. Addition of LPS at the gingival inflammatory site led to a further increase of corticosterone levels and disease severity in F344 rats. These findings illustrate a positive feedback loop between the HPA axis and periodontal disease: the disease activates the HPA axis, and a genetically determined high HPA responsitivity further increases disease susceptibility.
Detection of putative periodontal pathogens in non‐insulin‐dependent diabetes mellitus and non‐diabetes mellitus by polymerase chain reaction
Authors: Yuan Kuo , Chang Chih‐jen , Hsu Ping‐chi , Sun H. Sunny , Tseng Chuen‐chyi , Wang Jen‐ren
Published: March 2003

It has been assumed that there is a relationship between periodontal diseases and diabetes mellitus, however the putative periodontal microorganisms in non‐diabetes mellitus (non‐DM) individuals and non‐insulin‐dependent diabetes mellitus (NIDDM) patients have not been well studied. In this study, the detection rates of 5 putative periodontal pathogens: Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eikenella corrodens, Treponema denticola, and Candida albicans by polymerase chain reaction (PCR) between NIDDM and non‐DM adults were compared. A total of 246 adults were randomly recruited and periodontal parameters including: plaque index (PlI), gingival index (GI), probing depth (PD) and attachment level (AL) were recorded. Subgingival plaque samples were collected by sterile curettes from the most diseased and healthy sites based on PD and AL. The differences in periodontal parameters and microbiological data in healthy and diseased sites between non‐DM and NIDDM patients were compared by chi‐square analysis. The results showed no significant differences in age, gender, GI, PlI, PD, and prevalence of the 5 microorganisms between the NIDDM and the non‐diabetic groups. However, except for A. actinomycetemcomitans, the prevalence of the periodontal microorganisms tested was significantly higher (p<0.01) in diseased sites than in the healthy sites in both groups. The PlI, GI, PD and AL were significantly higher in T. denticola positive sites than in negative sites. The results suggested that P. gingivalis, T. denticola, E. corrodens and C. albicans may play important roles in the periodontitis of both NIDDM and non‐DM individuals, however the etiology of periodontitis in both groups may not be different from each other.
Regulation of matrix metalloproteinase production by cytokines, pharmacological agents and periodontal pathogens in human periodontal ligament fibroblast cultures
Authors: Chang Yu‐Chao , Yang Shun‐Fa , Lai Chung‐Chih , Liu Jer‐Yuh , Hsieh Yih‐Shou
Published: March 2003

Matrix metalloproteinases (MMPs), produced by both infiltrating and resident cells of the periodontium, play a role in physiologic and pathologic events. It is recognized that an imbalance between activated MMPs and their endogenous inhibitors leads to pathologic breakdown of the extracellular matrix during periodontitis. To date, little is known about the regulation of MMP synthesis and secretion in human periodontal ligament fibroblasts (PDLFs). The purpose of this study was to examine the effects of cytokines, pharmacological agents (protein synthesis inhibitor and protein kinase C inhibitors) and predominant periodontal pathogens (Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis) on MMP production in human PDLFs using gelatin zymography. The gelatin zymograms revealed that the main gelatinase secreted by human PDLFs migrated at 72 kDa and represents MMP‐2. Minor gelatinolytic bands were also observed at 92 kDa regions that correspond to MMP‐9. We found that A. actinomycetemcomitans, P. gingivalis and IL‐1α can elevate MMP‐2 secretion in human PDLFs. These results indicate that periodontal pathogens and inflammatory cytokines play an important role in tissue destruction and disintegration of extracellular matrix in periodontal diseases. Thus, activation of MMPs may be one of the distinct host degradative pathways in the pathogenesis of periodontitis. In addition, H7, staurosporine, cycloheximide and TGF‐β could suppress MMP‐2 production. Agents that target protein synthesis or the protein kinase C pathway in human PDLFs inhibit MMP‐2 production, and such inhibition may contribute to the pathogenesis of periodontal inflammation. Taken together, these findings suggest a possible new therapeutic approach, involving the use of drugs that modify host‐response mechanisms to suppress or inhibit MMP‐mediated tissue destruction.
Relationship between fibrinolytic activity and gingival inflammatory reaction in young individuals
Authors: Olofsson A. , Lindberg P. , Lanke J. , Matsson L. , Kinnby B.
Published: March 2003

The fibrinolytic system (the plasminogen activating system) is involved in several physiological and pathological processes. Through the transformation of plasminogen to the aggressive broad spectrum protease plasmin, potent enzymatic activity is released. Plasmin acts directly on connective tissue components, and indirectly by activating proforms of the metalloproteinases. The destructive potential of the fibrinolytic system may thus be of importance for the initiation and progression of periodontal diseases. Earlier studies have shown high concentrations of the plasminogen activator t–PA and its inhibitor PAI−2 in gingival crevicular fluid (GCF) as well as enhanced concentrations in areas of gingival inflammation. The aim of this study was to investigate a possible relationship between the gingival inflammatory reactivity and the fibrinolytic activity in gingival crevicular fluid. Thirty‐one young individuals took part in the study. Gingival Index scores and Plaque Index scores were assessed and used to formulate a score expressing an individuals' inflammatory response to microbial plaque levels (Relative G/P score). The fibrinolytic activity of GCF was assessed with a fibrin gel lysis assay, and the levels of t–PA and PAI−2 were assayed with ELISAs. All samples showed fibrinolytic activity. A positive correlation between the fibrinolytic activity and Relative G/P score was found. Thus, in individuals with an enhanced reactivity to dental plaque, a higher plasminogen activating activity in GCF was seen. This indicates a higher potential for tissue proteolysis in these individuals, possibly facilitating spread and deeper involvement of the lesions.
Influence of interleukin‐1 gene polymorphism on periodontal regeneration in intrabony defects
Authors: Christgau M. , Aslanidis C. , Felden A. , Hiller K. A. , Schmitz G. , Schmalz G.
Published: March 2003

The aim of this controlled retrospective study was to evaluate the influence of an IL‐1 gene polymorphism on the clinical and radiographic healing outcomes of GTR therapy. The study included 47 adult periodontitis patients with 94 deep intrabony defects treated by GTR using different membrane materials. The following clinical parameters were recorded at baseline and 12 months after surgery: papillary bleeding index (PBI), gingival recession (REC), probing pocket depth (PPD), clinical attachment level (CAL), and the vertical relative attachment gain (V‐rAG). Bone changes in the defect regions due to GTR therapy were quantitatively evaluated using digital subtraction radiography (DSR). Polymorphisms of the IL‐1A gene at position − 889 and of the IL‐1B gene at position + 3953 were analyzed by PCR. Statistical analysis was performed using the Mann–Whitney‐U and the Wilcoxon‐Signed‐Rank tests (α = 0.05). The study comprised 19 IL‐1 genotype positive (IL‐1 +) patients and 28 IL‐1 genotype negative (IL‐1 –) patients. Twelve months after GTR therapy, both patient groups revealed statistically significant PPD reductions and CAL gain [median (25/75% percentiles)]: ΔPPD [IL‐1 + : 4.0 (2.5/5.0) mm; IL‐1‐: 3.8 (3.0/4.9) mm], ΔCAL [IL‐1 + : 3.5 (3.0/4.8) mm; IL‐1 –: 3.0 (1, 2/4, 5) mm]. V‐rAG amounted to 60.0 (47.7/78.6)% in IL‐1 + patients and 53.1 (43.4/81.9)% in IL‐1 – patients. Both patient groups showed significant bone density gain in 40% (IL‐1 +) and 43.6% (IL‐1 –) of the initial defect area due to GTR. Neither the clinical nor the radiographic healing parameters revealed any statistically significant differences in the GTR healing outcome between IL‐1 + and IL‐1 – patients. In conclusion, these 12‐month findings indicate that the IL‐1 gene polymorphism has no influence on the clinical and radiographic regeneration results following GTR therapy.
Basic fibroblast growth factor induces the expression of matrix metalloproteinase‐3 in human periodontal ligament cells through the MEK2 mitogen‐activated protein kinase pathway
Authors: Shimazu Atsushi , Morishita Masayuki
Published: March 2003

Basic fibroblast growth factor (bFGF, FGF‐2) is one of the potent mitogens for periodontal ligament (PDL) cells. However, the role of bFGF on the matrix metalloproteinase‐3 (MMP‐3) expression in PDL cells is unknown. In this study, the effect of bFGF on MMP‐3 expression in PDL cells and the mechanism of this process were examined. Human PDL cells were exposed to bFGF at various concentrations (0.01–10 ng/ml) in monolayer cultures. bFGF increased [3H]thymidine incorporation and suppressed proteoglycan synthesis concentration‐dependently. However, similar concentration ranges of bFGF increased the release of the cell‐associated proteoglycans into the medium. Furthermore, bFGF increased MMP‐3 mRNA levels concentration‐dependently as examined by reverse transcription‐polymerase chain reaction (RT‐PCR). Induction of MMP‐3 after the stimulation with bFGF was observed as early as 12 h with maximal at 24 h. Thereafter, the MMP‐3 mRNA level gradually decreased until 72 h. Cycloheximide blocked the induction of MMP‐3 by bFGF, indicating the requirement of de novo protein synthesis for this stimulation. Furthermore, MMP‐3 expression induced by bFGF was abrogated by U0126, a specific inhibitor of MEK1/2 and ERK1/2 in mitogen‐activated protein (MAP) kinase pathway, not by PD98059, a specific inhibitor of MEK1. In addition, bFGF up‐regulated the phosphorylated ERK1/2 in 5 min with the maximal at 20 min as examined by Western blotting, and U0126 inhibited the ERK1/2 phosphorylation induced by bFGF. These findings suggest that bFGF induces MMP‐3 expression in PDL cells through the activation of the MEK2 in MAP kinase pathway. bFGF stimulation on MMP‐3 synthesis may be involved in the control of the cell‐associated proteoglycans in PDL cells during periodontal regeneration and degradation.
Prenatal Phencyclidine Induces Heightened Neurodegeneration in Rats in some Brain Regions, Especially during 2nd Trimester, but Possible Anti‐Apoptotic Effects in Others
Authors: Jebelli Azadeh Kokabi , Doan Ngan , Ellison Gaylord
Published: March 2003

Abstract: Phencyclidine administered to the developing rat brain at high doses for a few hours during late foetal life induces apoptotic neurodegeneration in several brain regions. We sought to investigate whether prolonged, low level foetal exposure to phencyclidine during different gestational periods (2nd trimester versus 3rd trimester) would have different effects on several brain regions showing neurodegeneration as assessed using silver stains. Pregnant rats were treated with phencyclidine (5.45 mg/day) continuously for 5 days via minipumps, and the pups were either perfused immediately after birth and silver‐stained for degeneration, or allowed to mature and then tested for behavioural deficits. In the newborn pups, there was a substantial increase in the number of agrophilic cells in entorhinal cortex and subiculum; this effect was greater when the drug was given during 2nd trimester. However, in the ventromedial nucleus of the hypothalamus, both the 2nd and 3rd trimester phencyclidine pups had significantly fewer degenerating cells than the controls. Behavioural tests of rotorod and open field performance in the pups allowed to mature indicated decreased motor coordination and hyperactivity in the 3rd trimester phencyclidine pups, but minimal alterations in the 2nd trimester pups. Thus, prenatal exposure to phencyclidine can have either neurodegenerative or antiapototic effects depending upon brain region, and there is a discrepancy between persisting behavioural deficits and amount of cell loss for time of maximal prenatal effect of the drug.
Functional Impairment of Renal Organic Cation Transport in Experimental Diabetes
Authors: Grover Brett , Auberger Christopher , Sarangarajan Rangaprasad , Cacini William
Published: March 2003

Abstract: This study was designed to determine the effect of diabetes on the function of the renal organic cation transport system that mediates the excretion of a wide variety of toxicants and drugs. The experiments compared the ability of renal cortex slices from streptozotocin‐induced diabetic and non‐diabetic rats to accumulate the model cation, 14C‐tetraethylammonium under controlled conditions. Initial experiments demonstrated a progressive decline in tetraethylammonium accumulation with increasing duration of diabetes. The maximal decrease was observed at 21 days after streptozotocin injection. Time‐dependent incubations revealed that tetraethylammonium uptake from both diabetic and non‐diabetic rats followed a curvilinear pattern expected of an active process. However, at steady state the diabetic‐derived slices accumulated a significant 38% less tetraethylammonium versus slices from non‐diabetics. Concentration‐dependent incubations of tetraethylammonium (0.01–10 mM, 60 min.) demonstrated saturable transport in both diabetic and non‐diabetic slices with a significantly decreased capacity of diabetic‐derived slices to accumulate tetraethylammonium. Cellular respiration rates in the two groups were not different. Insulin treatment of the diabetic rats prevented the transport decline. While the causative factor of the transport impairment in diabetes is unresolved, this study documents an aspect of diabetic nephropathy that has not been previously reported but which may have important implications for renal excretion of cationic drugs and toxicants. The results also provide a mechanism for the well‐documented “protection phenomenon” by which the kidneys of diabetic rats are resistant to nephrotoxicity induced by the chemotherapeutic agent cisplatin.
δ‐Aminolevulinate Dehydratase Inhibition by Phenyl Selenoacetylene: Effect of Reaction with Hydrogen Peroxide
Authors: Bolzan Rodrigo Cordeiro , Folmer Vanderlei , Farina Marcelo , Zeni Gilson , Nogueira Cristina Wayne , Rocha João Batista Teixeira , Emanuelli Tatiana
Published: March 2003

Abstract: The effect of phenyl selenoacetylene and its selenoxide on δ‐aminolevulinate dehydratase from liver of adult rats (mammalian source) and from cucumber leaves (plant source) was investigated. In vivo, selenides can be oxidized to selenoxides by flavin‐containing monooxygenases and selenoxides can regenerate selenides by thiol oxidation. The compound phenyl selenoacetylene was converted to selenoxides by reaction with hydrogen peroxide. Phenyl selenoacetylene inhibited mammalian and plant δ‐aminolevulinate dehydratase with an IC50 about 250 μM and >400 μM, respectively. Its selenoxide inhibited the enzyme more strongly, with IC50 values of 45 μM and 100 μM for the mammalian and plant source, respectively. The selenoxide inhibitory action was antagonized by dithiothreitol suggesting the involvement of –SH groups. Moreover, δ‐aminolevulinate dehydratase from a plant source was inhibited by the selenoxide, suggesting a possible involvement of –SH groups located at a site distinct from the region implicated in Zn2+ binding in mammalian δ‐aminolevulinate dehydratase. The results of the present study suggest that (i) δ‐aminolevulinate dehydratase is a potential molecular target for phenyl selenoacetylene, due to the oxidation of enzyme sulfhydryl groups, and that (ii) the monooxygenation of this selenocompound, which in vivo could be possibly mediated by flavin‐containing monooxigenases, increases its inhibitory effect.