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DIALNET OAI Articles (621,894 recursos)
Dialnet (Difusión de Alertas en la Red) es una plataforma de recursos y servicios documentales, cuyo objetivo fundamental se centra en mejorar la visibilidad y el acceso a la literatura científica hispana a través de Internet.

Ciencias biológicas

Mostrando recursos 1 - 20 de 18,380

1. La dansa de les cèl·lules - Hermelo Akhtar, Ismaïl
Un punt. Una circumferència quasi perfecte al mig del no res. Una coordenada com a referència en un sistema de tres dimensions. Una esfera, i no una qualsevol... l’esfera Primordial. Sota una llum suau, la nostra esfera es revela translúcida i observem que esta plena d’una substancia molt semblant a un gel. Si seguim escodrinyant pacientment, veurem que aquest “gel” esta ple de components immersos en una activitat frenètica. De sobte, un calfred fa que la esfera es contragui en el seu interior i aparegui un línia que sembla el seu propi radi, que lentament segueix creixent fins a formar...

2. Metabolits, petits oblidats - Sabater Barragan, Albert
Durant molts anys, el món científic va estar obsessionat amb les proteïnes. Es volia saber quants tipus diferents hi havia, quina era la seva funció, com estaven formades, a on es podien trobar o la seva rellevància en els organismes vius. Estaven considerades en una estima tan elevada que es va valorar la possibilitat que les proteïnes fossin les responsables de contenir les instruccions necessàries per possibilitar la vida. Una de les raons que recolzava la idea es devia a una major complexitat a les seves estructures i major varietat de formes.  Els canvis d’expressió de proteïnes i gens en...

3. El món dels líquens: naturalesa i utilització d'uns organismes únics - Izquierdo López, Alejandro
Els trobem a les escorces dels arbres, recobrint superfícies rocoses o fins i tot en les estructures creades per la mà de l'home. Habiten múltiples ambients: des de boscos fins al cims de les muntanyes. D'ells se'n poden extreure tant tints com productes farmacèutics i la seva història evolutiva és clarament sorprenent. Els líquens, generalment petits (almenys a la Península Ibèrica), passen desapercebuts per a la majoria de nosaltres i, malauradament, poques vegades són focus de l'atenció mediàtica. Malgrat això, ens trobem amb un conjunt d'organismes únic dintre de l'arbre de la vida que no només són interessants des del...

4. Si no ho veus, no ho creus? Una petita història de virus - Jácome Sanz, Daphne
Refredats, influença, herpes, meningitis, encefalitis, poliomielitis, pneumònia, hepatitis, sida, èbola, algunes berrugues i alguns càncers. Què tenen en comú totes aquestes malalties? Doncs que estan originades per virus infecciosos. De fet, s’estima que més del 90% de les malalties humanes poden estar originades per ells. Els virus són conspicus, cosmopolites, universals i molt molt abundants. Cada dia hi estem exposats. No són raons més que suficients per tal de voler-ne saber una mica més, d’ells?

5. Reovirus FAST proteins: virus-encoded cellular fusogens - Ciechonska, Marta; Duncan, Roy
Reovirus fusion-associated small transmembrane (FAST) proteins are the only known nonenveloped virus fusogens and are dedicated to inducing cell-to-cell, not virus–cell, membrane fusion. Numerous structural and functional attributes distinguish this novel family of viral fusogens from all enveloped virus membrane fusion proteins. Both families of viral fusogens play key roles in virus dissemination and pathogenicity, but employ different mechanisms to mediate membrane apposition and merger. However, convergence of these distinct families of viral membrane fusion proteins on common pathways needed for pore expansion and syncytium formation suggests syncytiogenesis represents a cellular response to the presence of cell–cell fusion pores. Together,...

6. Candida albicans hyphal initiation and elongation - Lu, Yang; Su--, Chang; Liu, Haoping
The fungus Candida albicans is a benign member of the mucosal microbiota, but can cause mucosal infections and life-threatening disseminated invasive infections in susceptible individuals. The ability to switch between yeast, pseudohyphal, and hyphal growth forms (polymorphism) is one of the most investigated virulence attributes of C. albicans. Recent studies suggest that hyphal development in C. albicans requires two temporally linked regulations for initiation and maintenance of the hyphal transcriptional program. Hyphal initiation requires a rapid but temporary disappearance of the Nrg1 transcriptional repressor of hyphal morphogenesis. Hyphal maintenance requires active sensing of the surrounding environment, leading to exclusion of...

7. Discovering new indicators of fecal pollution - McLellan, Sandra L.; Eren, A. Murat
Fecal pollution indicators are essential to identify and remediate contamination sources and protect public health. Historically, easily cultured facultative anaerobes such as fecal coliforms, Escherichia coli, or enterococci have been used but these indicators generally provide no information as to their source. More recently, molecular methods have targeted fecal anaerobes, which are much more abundant in humans and other mammals, and some strains appear to be associated with particular host sources. Next-generation sequencing and microbiome studies have created an unprecedented inventory of microbial communities associated with fecal sources, allowing reexamination of which taxonomic groups are best suited as informative indicators....

8. Carbapenemase-producing Klebsiella pneumoniae: molecular and genetic decoding - Chen, Liang; Mathema, Barun; Chavda, Kalyan D.; DeLeo, Frank R.; Bonomo, R. A.; Kreiswirth, B.N.
Klebsiella pneumoniae carbapenemases (KPCs) were first identified in 1996 in the USA. Since then, regional outbreaks of KPC-producing K. pneumoniae (KPC-Kp) have occurred in the USA, and have spread internationally. Dissemination of blaKPC involves both horizontal transfer of blaKPC genes and plasmids, and clonal spread. Of epidemiological significance, the international spread of KPC-producing K. pneumoniae is primarily associated with a single multilocus sequence type (ST), ST258, and its related variants. However, the molecular factors contributing to the success of ST258 largely remain unclear. In this review, we discuss the recent progresses in understanding KPC-producing K. pneumoniae that are contributing to...

9. What role does the quorum-sensing accessory gene regulator system play during Staphylococcus aureus bacteremia? - Painter, Kimberley L.; Krishna, Aishwarya; Wigneshweraraj, Sivaramesh; Edwards, A. M.
Staphylococcus aureus is a major cause of bacteremia, which frequently results in serious secondary infections such as infective endocarditis, osteomyelitis, and septic arthritis. The ability of S. aureus to cause such a wide range of infections has been ascribed to its huge armoury of different virulence factors, many of which are under the control of the quorum-sensing accessory gene regulator (Agr) system. However, a significant fraction of S. aureus bacteremia cases are caused by agr-defective isolates, calling into question the role of Agr in invasive staphylococcal infections. This review draws on recent work to define the role of Agr during...

10. Variability of the transporter gene complement in ammonia-oxidizing archaea - Offre, Pierre; Kerou, Melina; Schleper, Christa; Spang, Anja
Ammonia-oxidizing archaea (AOA) are a widespread and abundant component of microbial communities in many different ecosystems. The extent of physiological differences between individual AOA is, however, unknown. Here, we compare the transporter gene complements of six AOA, from four different environments and two major clades, to assess their potential for substrate uptake and efflux. Each of the corresponding AOA genomes encode a unique set of transporters and although the composition of AOA transporter complements follows a phylogenetic pattern, few transporter families are conserved in all investigated genomes. A comparison of ammonia transporters encoded by archaeal and bacterial ammonia oxidizers highlights...

11. The end of Nef's tether - Serra-Moreno, Ruth
Tetherin represents an important barrier for successful cross-species transmissions of primate lentiviruses. HIV-1 overcame this obstacle by using Vpu as a countermeasure. However, Kluge and collaborators now show that HIV-1 group O uses Nef to antagonize tetherin, and that this activity may have contributed to its spread in West-Central Africa.

12. Can chatter between microbes prevent cholera? - Thompson, Jessica A.; Almeida Oliveira, Rita; Xavier, Karina B.
Tackling the global rise in antibiotic resistance requires new therapies against infectious microbes. A recent microbiome study identified commensal gut bacteria that reduce colonisation by the cholera pathogen, Vibrio cholerae. This antagonistic interaction might be mediated by quorum sensing, suggesting that these natural microbe–microbe interactions can help prevent infectious disease.

13. Changing academic culture to improve undergraduate STEM education - Suchman, Erica L.
Improving undergraduate science, technology, engineering, and math (STEM) education requires faculty with the skills, resources, and time to create active learning environments that foster student engagement. Current faculty hiring, promotion, and tenure practices at many universities do not measure, reward, nor encourage faculty pursuit of these skills. A cultural change is needed to foster improvement.

14. Microbial mixing zone dolomitization and karst development within Isla de Mona Dolomite, Isla de Mona, Puerto Rico - Sumrall, Jonathan; Mylroie, John E.; Kambesis, Patricia
Modification of the mixing zone model to include microbial processes that promote dolomitization explains many of the petrographic, isotopic, and outcrop observations found on Isla de Mona. Large flank margin caves at the contact between the Isla de Mona Dolomite and the capping Lirio Limestone formed during prolonged, likely episodic, periods with a stable lens position. These periods would produce a stable halocline. The halocline is hypothesized to be the zone of dolomitization in the microbial mixing zone model. Collection of organics at the density interface of the halocline coupled with sulfate reduction by sulfate-reducing bacteria would establish a geochemical...

15. Dolomitization and burial history of lower triassic carbonate reservoir-rocks in the Persian Gulf (Salman offshore field) - Peyravi, Maryam; Rahimpour Bonab, Hossain; Nader, Fadi H.; Reza Kamali, Mohammad
Shallow marine carbonate sedimentation prevailed during the Early Triassic in the northern part of the Persian Gulf (Kangan Formation; offshore Iran). Associated near surface and (to a lesser extent) burial diagenesis had significant impacts on the evolution of reservoir properties of the Kangan Formation. In some Iranian offshore fields such as Salman, pervasive, early dolomitization of the Kangan carbonate rocks is believed to have played an important role in improving the reservoir characteristics of this unit. Detailed petrographic and geochemical analyses indicate that such dolomitization could be explained by means of the sabkha/seepage-reflux model. Furthermore, three types of dolomites, found...

16. Evaluation of coralline algal diversity from the Serravallian carbonate sediments of Little Andaman Island (Hut Bay), India - Sarkar, Suman; Ghosh, Amit K.
Palaeodiversity of coralline algae has been studied from the Serravallian carbonate sediments outcropping in the Little Andaman Island (Hut Bay). Little Andaman is the southernmost island of the Andaman Group, situated between South Andaman and Car Nicobar. The algae described in the present case study have been recovered from the fossiliferous limestone samples of Hut Bay Limestone Quarry belonging to the Long Formation and examined by means of thin-section microscopic analysis. Shannon�Weaver index has been applied for measuring the degree of algal diversity. A total of nine coralline algal genera, including three geniculate and six non-geniculate algae have been reported...

17. Investigation into rock moisture and salinity regimes: Implications of sandstone weathering in Yungang Grottoes, China - Guo, Fang; Jiang, Guanghui
Yungang Grottoes in north of China are the classical masterpieces of Chinese Buddhists, dating from the Northern Wei Dynasty 1,500 years ago. This rock art is threatened by weathering processes that has been accelerated due to coal mining. The dominant weathering processes occurring on the rock surface are collapse, flaking, and efflorescence. Salt crystal growth plays a major cause of these deteriorations, and it has a close relationship with water movement. The major salt on the rock surface are sulfates, with a primary composition of epsomite, thenardite, and gypsum. In addition, carbonate minerals are found, mostly calcite and nesquehonite. In...

18. Míiase com exposição de calota craniana causada pela associação de Cochliomyia hominivorax (Coquerel, 1858), Cochliomyia macellaria (Fabricius,1775) e Chrysomya albiceps (Wiedemann, 1819), (Diptera: Calliphoridae) em um paciente atendido em Hospital Público, Rio de Janeiro. - Gomes de Almeida Valviesse, Vitor Ribeiro; Pedroso Ferraz, Adriana Cristina; Proença, Barbara; Novaes Werneck, Geovana Rotatori; Magalhães Aguiar Coelho, Valéria

19. Primer registro de Euoniticellus intermedius (Reiche, 1849) y Sulcophanaeus noctis cupricollis (Nevinson, 1891) (Coleoptera: Scarabaeidae) para Honduras. - Rivera Duarte, José Daniel; Schlein, Oliver

20. Tetracha brasiliensis brasiliensis (Kirky, 1818) (Coleoptera: Cicindelidae) as a predator of newly-metamorphosed anurans. - Hiroiuki Oda, Fabrício; Vieira Barbosa, Letícia; Guerra Batista, Vinicius

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