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Diverse Composition (diverse + composition)

Distribution by Scientific Domains
Medical Sciences75%

Selected Abstracts

Remodeling of extracellular matrix and epileptogenesis

EPILEPSIA, Issue 2010
Alexander Dityatev
Summary Extracellular matrix (ECM) in the brain is composed of molecules synthesized and secreted by neurons and glial cells, which form stable aggregates of diverse composition in the extracellular space. In the mature brain, ECM undergoes a slow turnover and restrains structural plasticity while supporting multiple physiologic processes, including perisomatic ,-aminobutyric acid (GABA)ergic inhibition, synaptic plasticity, and homeostatic regulations. Seizures lead to striking remodeling of ECM, which may be essentially engaged in different aspects of epileptogenesis. This view is supported by human genetic studies linking ECM molecules and epilepsy, by data showing altered epileptogenesis in mice deficient in ECM molecules, and by evidence that ECM may shape seizure-induced sprouting of mossy fibers, granule cell dispersion, and astrogliosis. Therefore, restraining seizure-induced remodeling of ECM or suppressing the signaling triggered by the remodeled ECM might provide effective therapeutic strategies to antagonize the progression of epileptogenesis. [source]

The sarcomatous guise of cervical ectopic hamartomatous thymoma,

HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 8 2002
Jeff Marschall MD
Abstract Background Ectopic hamartomatous thymoma is a rare benign neoplasm occurring in the deep soft tissues adjacent to the sternoclavicular joint. Although clinical presentation and diagnostic imaging can be consistent with a malignant lesion such as a sarcoma, recognition of pathologic features can readily exclude such a diagnosis. However, this remains a challenge caused by their unusual histologic features and diverse composition. Recognition of this tumor is, however, important, because it follows a benign clinical course, and conservative surgical excision is the therapy of choice. Methods A literature review of all reports of ectopic hamartomatous thymoma was undertaken and compared with our indexed case. Results From this review, we identified 26 previous reports. Most patients were men, with a 4.5:1 predominance. There was a wide range of ages at presentation, from 26 to 79 years. All tumors were located in the lower neck, with the exception of one arising presternally. Treatment predominantly consisted of tumor resection, with no reported recurrences on follow-up. Conclusions We conclude that ectopic hamartomatous thymoma is an extremely rare neoplasm usually presenting in the lower neck. Correct identification of this tumor is important, because it follows a benign course, and surgical excision is adequate therapy. © 2002 Wiley Periodicals, Inc. Head Neck 24: 800,804, 2002 [source]

Pollution status of a tropical forest river using aquatic insects as indicators

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2010
Tunde Ohiokhioya Thadeus Imoobe
Abstract Aquatic insects inhabiting Okhuo River, in a tropical forest near Benin City, Southern Nigerian, were studied between January and December 2006 to determine the taxa composition, diversity, EPT index, relative proportions of the various groups and hence the pollution level of the waterbody. Three stations were selected and sampled monthly using the kick sampling technique. A total of 3235 individual aquatic insects belonging to 24 taxa distributed among 23 genera in six orders were collected. The insect orders occurred in the following order of dominance: Ephemeroptera > Odonata > Coleoptera > Diptera > Plecoptera > Tricoptera. Based on the diverse composition of the community dominated by organisms intolerant of organic enrichment, and the high diversity and EPT index, water quality in Okhuo River is not significantly degraded. Community composition varies seasonally, with a trend toward a declining proportion during the rainy season and increasing proportions during the dry season. Aquatic insect composition in Okhuo River compares favourably with those in similar, relatively undisturbed forest streams and rivers in Nigeria, but the diversity and proportional distribution of taxa vary considerably between streams. Résumé Les insectes aquatiques qui vivent dans la rivière Okhuo près de la ville de Benin, au sud du Nigeria, ont étéétudiés entre janvier et décembre 2006 afin de déterminer la composition des taxons, leur diversité, l'indice EPT, les proportions relatives des différents groupes et, de là, le taux de pollution de la rivière. On a sélectionné trois stations qui ont étééchantillonnées chaque mois en utilisant la technique d'échantillonnage par coups de pied. On a collecté un total de 3 235 insectes aquatiques appartenant à 24 taxons répartis entre 23 genres de six ordres. Les ordres des insectes se plaçaient dans l'ordre de dominance suivant : Ephéméroptères > Odonates > Coléoptères > Diptères > Plécoptères > Trichoptères. Si l'on se base sur la composition diversifiée de la communauté où dominent des organismes intolérants aux enrichissements organiques, et sur la grande diversité et l'indice EPT, on peut dire que la qualité de l'eau de la rivière Okhuo n'est pas significativement dégradée. La composition de la communauté varie avec les saisons, avec une tendance à la diminution au cours de la saison des pluies et à une augmentation au cours de la saison sèche. La composition des insectes aquatiques de la rivière Okhuo se compare avantageusement avec celles des cours d'eau semblables des forêts intactes du Nigeria, mais la diversité et la distribution proportionnelle des différents taxons varient considérablement entre les cours d'eau. [source]

Dental plaque: biological significance of a biofilm and community life-style

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2005
P. D. Marsh
Abstract Background: Most microorganisms in nature attach to surfaces and form matrix-embedded biofilms. Biofilms are highly structured and spatially organized, and are often composed of consortia of interacting microorganisms, termed microbial communities, the properties of which are more than the sum of the component species. Microbial gene expression alters markedly in biofilms; organisms communicate by gene transfer and by secretion of diffusible signalling molecules. Cells in biofilms are less susceptible to antimicrobial agents. Aim and Materials & Methods: To comprehensively review the literature to determine whether dental plaque displays properties consistent with those of a typical biofilm and microbial community. Results: Novel microscopic and molecular techniques have demonstrated that plaque has a structured architecture with an extracellular matrix, and a diverse composition (around 50% of cells are unculturable). The constituent species communicate by gene transfer, by secreted peptides (Gram-positive bacteria) and autoinducer-2 (Gram-positive and Gram-negative bacteria). These organisms are functionally organized for increased metabolic efficiency, greater resistance to stress and for enhanced virulence. Plaque formation has direct and indirect effects on gene expression. Conclusion: Dental plaque displays properties that are typical of biofilms and microbial communities in general, a clinical consequence of which is a reduced susceptibility to antimicrobial agents as well as pathogenic synergism. [source]