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排序方式: 共有987条查询结果,搜索用时 31 毫秒
981.
Tamara Sternlieb Alejandra C. Schoijet Patricio D. Genta Salom C. Vilchez Larrea Guillermo D. Alonso 《PLoS neglected tropical diseases》2021,15(5)
Trypanosoma cruzi, the etiological agent of Chagas disease, has a digenetic life cycle. In its passage from the insect vector to the mammalian host, and vice versa, it must be prepared to cope with abrupt changes in environmental conditions, such as carbon source, pH, temperature and osmolarity, in order to survive. Sensing and signaling pathways that allow the parasite to adapt, have unique characteristics with respect to their hosts and other free-living organisms. Many of the canonical proteins involved in these transduction pathways have not yet been found in the genomes of these parasites because they present divergences either at the functional, structural and/or protein sequence level. All of this makes these pathways promising targets for therapeutic drugs. The AMP-activated protein kinase (AMPK) is a serine/threonine kinase activated by environmental stresses such as osmotic stress, hypoxia, ischaemia and exercise that results in reduction of ATP and increase of AMP levels. Thus, AMPK is regarded as a fuel gauge, functioning both as a nutrient and an energy sensor, to maintain energy homeostasis and, eventually, to protect cells from death by nutrient starvation. In the present study we report the characterization of AMPK complexes for the first time in T. cruzi and propose the function of TcAMPK as a novel regulator of nutritional stress in epimastigote forms. We show that there is phosphotransferase activity specific for SAMS peptide in epimastigotes extracts, which is inhibited by Compound C and is modulated by carbon source availability. In addition, TcAMPKα2 subunit has an unprecedented functional substitution (Ser x Thr) at the activation loop and its overexpression in epimastigotes led to higher autophagic activity during prolonged nutritional stress. Moreover, the over-expression of the catalytic subunits resulted in antagonistic phenotypes associated with proliferation. Together, these results point to a role of TcAMPK in autophagy and nutrient sensing, key processes for the survival of trypanosomatids and for its life cycle progression. 相似文献
982.
Dose‐response study for the highly aggressive and metastatic primary F3II mammary carcinoma under direct current
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Maraelys M. González Dasha F. Morales Luis E. B. Cabrales Daniel J. Pérez Juan I. Montijano Antonio R. S. Castañeda Victoriano G. S. González Oscar O. Posada Janet A. Martínez Arlem G. Delgado Karina G. Martínez Mayrel L. Mon Kalet L. Monzón Héctor M. C. Ciria Emilia O. Beatón Soraida C. A. Brooks Tamara R. González Manuel V. Jarque Miguel A. Ó. Mateus Jorge L. G. Rodríguez Enaide M. Calzado 《Bioelectromagnetics》2018,39(6):460-475
983.
984.
Cecilia Smith-Ramírez Iván Díaz Patricio Pliscoff Claudio Valdovinos Marco A. Méndez Juan Larraín Horacio Samaniego 《Biodiversity and Conservation》2007,16(9):2627-2648
Knowledge of species richness centers is necessary for the design of conservation areas. In this study, we present a GIS analysis
of two years of field data on animal and plant diversity distributions in evergreen, coastal rain forests of southern Chile
(39°30′–41°25′ S). Despite their high endemism, these forests have remained largely unprotected. Field records were complemented
with data from museum collections and scientific literature. We used selected environmental variables (evapotranspiration,
altitude) and, in some cases, forest types as predictors of species distributions. Our study focused on the distribution of
forest bryophytes, vascular plants, soil invertebrates, amphibians and birds. We generated distributional maps for each taxa
based on their field records in the study area, complemented by natural history information, except in the case of bryophytes
and soil invertebrates. In general, species richness was lower at 600 m elevation or above for all the taxa studied. Species
richness tends to increase in the northern sector of the study area. We observed a greater richness of vascular plants near
rivers and streams, and noted important floristic differences between west and east-facing slopes of the Coastal Range, with
more species in the oriental side. Because species in high altitude forests are not a subset of those found at lower elevations,
we propose that conservation strategies should prioritize the protection of the entire altitudinal gradient of the southern
Coastal Range, especially in the more diverse oriental and northern sectors. 相似文献
985.
We detected that Galaxias maculatus exhibits a pattern where metabolic activity increases after sunrise and peaks between noon and sunset, but this species feeds in the afternoon, until several hours after sunset. Moreover, we showed that G. maculatus is observed in the littoral zone during the day, disappears completely from this zone after sunset and returns at sunrise. Littoral prey species are common in the diet of G. maculatus, but this study showed that pelagic prey is also present during twilight and night hours in smaller individuals (<50 mm), which is related to habitat use. These behavioural rhythms are especially important for G. maculatus, which runs a high predation risk when consuming prey that is widely available outside the littoral zone. This risk is ameliorated under the protection of low light intensity. Thus, G. maculatus is a key species linking lower trophic levels, such as the plankton community, to higher levels of native and exotic piscivores. These displacements of G. maculatus generate an active flow of energy and matter between habitats, with a potentially profound effect on the entire food network and energy dynamics of the lake. 相似文献
986.
987.
B. Fontaine Sophie Nicole Haluk Topaloglu C. Ben Hamida Peter Beighton Frank Spaans Jose M. A. Cantu Salim Bakouri Norma Romero K. Ricker Patricio Barros-Nunez Gérard Ponsot M. Ben Hamida Jean Weissenbach F. Hentati Frank Lehmann-Horn 《Human genetics》1996,98(3):380-385
Schwartz-Jampel syndrome (SJS), or chondrodystrophic myotonia, is a rare autosomal recessive disorder characterized by generalized
myotonia resulting in a particular, recognizable facies and osteoarticular abnormalities. Some of us have recently shown genetic
linkage of SJS to a locus on 1p34–p36.1 in five families. Here, we show by homozygosity mapping and segregation analysis that
eight new families are most likely linked to the SJS locus on chromosome 1, confirming the localization of SJS to chromosome
1p and suggesting genetic homogeneity. Recombination events reduced the SJS locus from a genetic interval of 8 to 3 cM, which
should facilitate the identification of the SJS gene. Low clinical variability was observed between the studied families,
except for osteoarticular abnormalities. Since the severity and the location of osteoarticular abnormalities varied from one
individual to another, even in the same families, other factors than the SJS gene itself, genetic or epigenetic, might contribute
to the phenotype.
Received: 11 February 1996 / Revised: 6 April 1996 相似文献