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排序方式: 共有508条查询结果,搜索用时 31 毫秒
41.
Four populations of Saponaria bellidifolia situated at the species’ northern range periphery (Apuseni Mountains, southeastern Carpathians) were monitored over a period
of 5 years. They were chosen to represent different habitat types (rocky, fixed screes, open screes and grassy), disturbance
regime (fire), and population sizes (categorized as large and small). The reproductive effort was quantified, and matrix models
were used to describe the population dynamics and to assess population viability. Saponaria bellidifolia had very stable population dynamics in the harsh and stable abiotic conditions of the outcrops where populations occur. Habitat
conditions exerted a notable influence on the species’ population reproductive performance, growth rate, and vital rates,
whereas population size and climate did not have a clear-cut effect on the dynamics of the species. Saponaria bellidifolia maintains viable populations in the southeastern Carpathians, at its northern range periphery. 相似文献
42.
Murphy DA Diaz B Bromann PA Tsai JH Kawakami Y Maurer J Stewart RA Izpisúa-Belmonte JC Courtneidge SA 《PloS one》2011,6(7):e22499
In the adult organism, cell migration is required for physiological processes such as angiogenesis and immune surveillance, as well as pathological events such as tumor metastasis. The adaptor protein and Src substrate Tks5 is necessary for cancer cell migration through extracellular matrix in vitro and tumorigenicity in vivo. However, a role for Tks5 during embryonic development, where cell migration is essential, has not been examined. We used morpholinos to reduce Tks5 expression in zebrafish embryos, and observed developmental defects, most prominently in neural crest-derived tissues such as craniofacial structures and pigmentation. The Tks5 morphant phenotype was rescued by expression of mammalian Tks5, but not by a variant of Tks5 in which the Src phosphorylation sites have been mutated. We further evaluated the role of Tks5 in neural crest cells and neural crest-derived tissues and found that loss of Tks5 impaired their ventral migration. Inhibition of Src family kinases also led to abnormal ventral patterning of neural crest cells and their derivatives. We confirmed that these effects were likely to be cell autonomous by shRNA-mediated knockdown of Tks5 in a murine neural crest stem cell line. Tks5 was required for neural crest cell migration in vitro, and both Src and Tks5 were required for the formation of actin-rich structures with similarity to podosomes. Additionally, we observed that neural crest cells formed Src-Tks5-dependent cell protrusions in 3-D culture conditions and in vivo. These results reveal an important and novel role for the Src-Tks5 pathway in neural crest cell migration during embryonic development. Furthermore, our data suggests that this pathway regulates neural crest cell migration through the generation of actin-rich pro-migratory structures, implying that similar mechanisms are used to control cell migration during embryogenesis and cancer metastasis. 相似文献
43.
Henry Rivera Begoña Merinero Mercedes Martinez-Pardo Ignacio Arroyo Pedro Ruiz-Sala Belen Bornstein Clara Serra-Suhe Esther Gallardo Ramon Marti Maria J. Moran Cristina Ugalde Luis A. Perez-Jurado Antoni L. Andreu Rafael Garesse Magdalena Ugarte Joaquin Arenas Miguel A. Martin 《Mitochondrion》2010,10(4):362-368
The aim of this study was to identify the causative genetic lesion in two apparently unrelated newborns having lethal lactic acidosis, multi-organ failure and congenital malformations including interrupted aortic arch, who exhibited mild methylmalonic aciduria, combined mitochondrial respiratory chain deficiency, and marked muscle mitochondrial DNA depletion. A novel mutation in the SUCLG1 gene was identified. Phenotype severity in Succinate-CoA ligase dysfunction appears to be more correlated to the muscle mtDNA content than to the tissue distribution of the heterodimer subunits. Prominent impairment of mitochondrial respiratory chain may result in deep ravages in developmental tissues leading to multiple organ failure and malformations. 相似文献
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46.
Sot B von Germar F Mäntele W Valpuesta JM Taneva SG Muga A 《Protein science : a publication of the Protein Society》2005,14(9):2267-2274
The biological activity of the double-ring chaperonin GroEL is regulated by complex allosteric interactions, which include positive intra-ring and negative inter-ring cooperativity. To further characterize inter-ring communication, the nucleotide-induced absorbance changes in the vibrational spectrum of the chaperonin GroEL, of two single-point mutants suppressing one inter-ring ionic contact (E461K and E434K) and of a single-ring version of this protein, were investigated by time-resolved infrared difference spectroscopy. Interaction of the nucleotide with the proteins was triggered by its photochemical release from a biologically inactive caged precursor [P3-1-(2-nitro) phenylethyl nucleotide]. The results indicate that (1) ATP binding to the protein induces a conformational change that affects concomitantly both intra-ring and inter-ring communication, and (2) the experimental absorbance changes are sensitive to the double-ring structure of the protein. The characterization of the single-point, inter-ring mutants demonstrates that ionic interactions at both contact sites are involved in the transmission of the allosteric signal. However, both mutations have different effects on the inter-ring interface. While that of E461K still retains ionic contacts sensitive to ATP binding, E434K shows spectroscopic features similar to those of the single-ring version of the protein, therefore suggesting that electrostatic interactions at these contact sites contribute differently to the stability of the inter-ring interface. 相似文献
47.
The G6b gene, located in the human Major Histocompatibility Complex, encodes a receptor of the immunoglobulin (Ig) superfamily. In this study, we show using a variety of techniques that the extracellular domain of the G6b protein, containing a single Ig-like domain, binds to heparin with high affinity. In an ELISA assay, this binding was displaceable with soluble heparin with an IC50 value of approximately 0.5 microg/ml. Other sulfated glycans showed weaker or no competition. The observed interaction between G6b and heparin is strongly salt dependent suggesting a mainly electrostatic interaction. Heparin might modulate the interaction of G6b with its as yet unidentified protein ligand. 相似文献
48.
Cobo AM Sáenz A Poza JJ Urtasun M Indakoetxea B Urtizberea JA López de Munain A Calafell F 《Human biology; an international record of research》2004,76(5):731-741
Limb-girdle muscular dystrophy type 2A (LGMD2A) is caused by any of over 150 mutations in the calpain-3 (CAPN3) gene. Of those, 2362AG --> TCATCT is particularly prevalent in Basque patients, and this mutation was hypothesized to have arisen in the Basque Country. To explore the natural history of this mutation, we genotyped 65 Basque and non-Basque patients with LGMD2A who carry the 2362AG --> TCATCT mutation for four microsatellites within or flanking the gene. A particular haplotype was found in three-fourths of the patients and was assumed to be ancestral. From the average number of recombinations and mutations accumulated from this ancestral haplotype, the age of the 2362AG ----> TCATCT mutation was estimated to be 50 generations (i.e., 1,250 years), which is more recent than the Paleolithic Basque heritage. The subsequent spread of the 2362AG --> TCATCT mutation can be related to gene flow out of the Basque Country, even across a cultural border. 相似文献
49.