The molecular mechanisms that evolution has been employing to adapt to environmental temperatures are poorly understood. To gain some further insight into this subject we solved the crystal structure of triosephosphate isomerase (TIM) from the hyperthermophilic bacterium Thermotoga maritima (TmTIM). The enzyme is a tetramer, assembled as a dimer of dimers, suggesting that the tetrameric wild-type phosphoglycerate kinase PGK-TIM fusion protein consists of a core of two TIM dimers covalently linked to 4 PGK units. The crystal structure of TmTIM represents the most thermostable TIM presently known in its 3D-structure. It adds to a series of nine known TIM structures from a wide variety of organisms, spanning the range from psychrophiles to hyperthermo-philes. Several properties believed to be involved in the adaptation to different temperatures were calculated and compared for all ten structures. No sequence preferences, correlated with thermal stability , were apparent from the amino acid composition or from the analysis of the loops and secondary structure elements of the ten TIMs. A common feature for both psychrophilic and T. maritima TIM is the large number of salt bridges compared with the number found in mesophilic TIMs. In the two ther-mophilic TIMs, the highest amount of accessible hydrophobic surface is buried during the folding and assembly process. Proteins 1999;37:441-453. 1999 Wiley-Liss, Inc.

This study presents the epidemiological and mycological aspects of 299 patients with nail lesions who were referred to three diagnostic laboratories in the city of Cali. The diagnosis of mycoses was established through visualization of mycotic structures in a direct microscopic examination of skin scrapings and by isolation. Onychomycosis was found in 183 cases (61.2%), of which 141 were in toenails (44 in males and 97 in females), 38 in fingernails (9 males and 29 females), and 4 cases in toenails and fingernails simultaneously (all females). No statistically significant relation was found between sex and onychomycosis. Yeasts accounted for 40.7% of the mycoses, dermatophytes for 38%, nondermatophyte molds for 14% and the etiology was mixed in the remaining cases (7.3%). Candida albicans was the most commonly isolated yeast species; the most common dermatophyte was Trichophyton rubrum and Fusarium spp. and Scytalidium dimidiatum were the most common nondermatophytic molds. Them common fungi found in fingernails were yeasts; in toenails dermatophytes were more prevalent (chi2 with Yates' correction = 19.75, P= 0.000088). Yeasts were observed more frequently in females while dermatophytes were more common in males. The difference between these two etiologic groups was statistically significant (chi2 with Yates' correction = 7.43, P = 0.0064); no relation was observed according to age.

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Este artículo se basa en una investigación etnográfica en curso con cooperativas de vendedores ambulantes que integran la Confederación de los Trabajadores de la Economía Popular (CTEP), una organización gremial formada recientemente en Argentina con el objetivo de representar a los trabajadores de la “economía popular”. Esta investigación busca contribuir al estudio de las formas en que los denominados “sectores populares” desarrollan prácticas creativas para atender a la producción y reproducción de la vida desde experiencias variadas de precariedad. En este trabajo se analiza cómo esta experiencia de precariedad habilitó un proceso de construcción colectiva que vincula un pasado vivo anclado en la experiencia subjetiva con un futuro que proyecta esta experiencia en términos políticos bajo la forma de organización gremial. Se sostiene que este proceso de construcción colectiva pone en tensión fronteras clásicas entre trabajo formal/informal, asalariado/no salarial, movimiento obrero/movimientos sociales, en la medida en que el trabajo asalariado opera como un horizonte desde el cual se proyectan subjetividades menos como materia a transformar y más como fundamento para la producción de derechos colectivos.

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Phosphorus (P) and other chemical elements have been used to identify residential middens at archaeological sites. This study discusses the relationship of soil chemical elements and middens at Group Chispa, a Late Classic residential complex at a commoner village in the Maya lowlands. The complex was extensively excavated and soil sampled. Ceramic sherd densities, which serve as a proxy for artifact densities, correlate only partially with phosphorus and other chemical elements. One of the three middens in Group Chispa coincides with the highest concentration of P while the two others—including the most extensive one—have medium to low P levels. A spectrum of human activities that include the preparation of pigments explains the nontraditional distribution of chemical elements. High P levels remain useful to detect middens but they provide an incomplete picture and need to be contextualized by comprehensive archaeological data.

Leishmania parasites are sensitive to peptides with antimicrobial and ion-channel inhibitory activity. Because scorpion venoms are rich sources of such peptides, the leishmanicidal effect of Tityus discrepans venom was investigated. A negative correlation between cell growth and venom concentration was observed for venom-treated cultures of Leishmania (L.) mexicana mexicana promastigotes; 50% growth inhibition was obtained at 0.4 microg/ml. Light microscopy showed rounded, highly vacuolated L. (L.) m. mexicana cells with impaired flagellar motion after 15 min of incubation at 35 microg/ml. Ultrastructural studies confirmed an intense cytoplasm vacuolation and also enlargement of the flagellar pocket. Survival rates for New World Leishmania promastigotes (75% venom effective concentration, microg/ml) obtained after acute (1 h) venom toxicity tests were: L. (L.) m. mexicana (2.3), Leishmania (V.) braziliensis (11.3), and Leishmania (L.) chagasi (56.2). Heat (90 degrees C) treatment of venom and fraction TdII abolished most of their leishmanicidal effect. Acute toxicity assays performed with Sephadex G-50 fractions indicated that leishmanicidal activity is associated with the venom lowest molecular mass components (2.8-7.4 kDa), as determined by MALDI-TOF mass spectrometry.

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