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排序方式: 共有105条查询结果,搜索用时 15 毫秒
71.
72.
Joeri Borstlap Mai X. Luong Heather M. Rooke B. Aran A. Damaschun A. Elstner Kelly P. Smith Gary S. Stein Anna Veiga 《In vitro cellular & developmental biology. Animal》2010,46(3-4):242-246
Rapid advances in stem cell research have led to the derivation of hundreds of human embryonic stem (hES) cell lines in centers throughout the world, as well as the development of new technologies for producing pluripotent stem cells. These cell lines have unique characteristics and were derived using a variety of ethical guidelines. Stem cell registries have been developed in order to collect, organize, and disseminate cell line-specific information. In this review, we describe the current state of the field by providing an overview of the unique qualities and mandates of the three major stem cell registries: the European hES Cell Registry, the Registry of hES Cell Line Provenance developed by the International Society for Stem Cell Research, and the International Stem Cell Registry of hES and induced pluripotent stem cell lines established at the University of Massachusetts Medical School. While each registry has its own unique mandate and features, there is some overlap in the goals and information provided. This review discusses the challenges and prospects for an integrated approach in which all three registries effectively collaborate to minimize duplication and facilitate information exchange within the stem cell community. 相似文献
73.
Background
The fish, Erythrinus erythrinus, shows an interpopulation diversity, with four karyomorphs differing by chromosomal number, chromosomal morphology and heteromorphic sex chromosomes. Karyomorph A has a diploid number of 2n = 54 and does not have differentiated sex chromosomes. Karyomorph D has 2n = 52 chromosomes in females and 2n = 51 in males, and it is most likely derived from karyomorph A by the differentiation of a multiple X1X2Y sex chromosome system. In this study, we analyzed karyomorphs A and D by means of cytogenetic approaches to evaluate their evolutionary relationship. 相似文献74.
RENAN MILAGRES LAGE NOVAES JOSÉ PIRES DE LEMOS FILHO RENATA ACÁCIO RIBEIRO MARIA BERNADETE LOVATO 《Molecular ecology》2010,19(5):985-998
Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS‐trnG and trnL‐trnL‐trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long‐branched star‐like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central‐north Minas Gerais (between 15°–18° S and 42°–46° W), should be given the highest priority for conservation. 相似文献
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76.
77.
Jennie Ursum Wouter H Bos Nancy van Dillen Ben AC Dijkmans Dirkjan van Schaardenburg 《Arthritis research & therapy》2010,12(1):R8
Introduction
To investigate whether baseline levels of anti-citrullinated protein antibody (ACPA) or IgM rheumatoid factor (IgM-RF) and changes in the year thereafter are associated with disease activity, functional and radiographic outcome in early arthritis patients, and provide additional information over baseline autoantibody status. 相似文献78.
This report describes a lysozyme expressed at high levels in the stomach of
the hoatzin, the only known foregut-fermenting bird. Evolutionary
comparison places it among the calcium-binding lysozymes rather than among
the conventional types. Conventional lysozymes were recruited as digestive
enzymes twice in the evolution of mammalian foregut fermenters, and these
independently recruited lysozymes share convergent structural changes
attributed to selective pressures in the stomach. Biochemical convergence
and parallel amino acid replacements are observed in the hoatzin stomach
lysozyme even though it has a different genetic origin from the mammalian
examples and has undergone more than 300 million years of independent
evolution.
相似文献
79.
Overbeek MJ Boonstra A Voskuyl AE Vonk MC Vonk-Noordegraaf A van Berkel MP Mooi WJ Dijkmans BA Hondema LS Smit EF Grünberg K 《Arthritis research & therapy》2011,13(2):R61-13
Introduction
Systemic sclerosis (SSc) complicated by pulmonary arterial hypertension (PAH) carries a poor prognosis, despite pulmonary vascular dilating therapy. Platelet-derived growth factor receptor-β (PDGFR-β) and epidermal growth factor receptor (EGFR) are potential therapeutic targets for PAH because of their proliferative effects on vessel remodelling. To explore their role in SScPAH, we compared PDGFR- and EGFR-mmunoreactivity in lung tissue specimens from SScPAH. We compared staining patterns with idiopathic PAH (IPAH) and pulmonary veno-occlusive disease (PVOD), as SScPAH vasculopathy differs from IPAH and sometimes displays features of PVOD. Immunoreactivity patterns of phosphorylated PDGFR-β (pPDGFR-β) and the ligand PDGF-B were evaluated to provide more insight into the patterns of PDGFR-b activation.Methods
Lung tissue specimens from five SScPAH, nine IPAH, six PVOD patients and five controls were examined. Immunoreactivity was scored for presence, distribution and intensity.Results
All SScPAH and three of nine IPAH cases (P = 0.03) showed PDGFR-β-immunoreactivity in small vessels (arterioles/venules); of five SScPAH vs. two of nine IPAH cases (P = 0.02) showed venous immunoreactivity. In small vessels, intensity was stronger in SScPAH vs. IPAH. No differences were found between SScPAH and PVOD. One of five normal controls demonstrated focally mild immunoreactivity. There were no differences in PDGF-ligand and pPDGFR-b-immunoreactivity between patient groups; however, pPDGFR-b-immunoreactivity tended to be more prevalent in SScPAH small vasculature compared to IPAH. Vascular EGFR-immunoreactivity was limited to arterial and arteriolar walls, without differences between groups. No immunoreactivity was observed in vasculature of normals.Conclusions
PDGFR-β-immunoreactivity in SScPAH is more common and intense in small- and post-capillary vessels than in IPAH and does not differ from PVOD, fitting in with histomorphological distribution of vasculopathy. PDGFR-β immunoreactivity pattern is not paralleled by pPDGFR-β or PDGF-B patterns. PDGFR-β- and EGFR-immunoreactivity of pulmonary vessels distinguishes PAH patients from controls. 相似文献80.
Transport of amino acids across the plasma membranes of various cell types is a key process in controlling the nitrogen balance of leaves. We studied the transport of the neutral amino acid L-valine into plasma membrane vesicles obtained by aqueous polymer two-phase partitioning of a microsomal fraction isolated from leaves of the wild-type and the Val(r)-2 mutant of tobacco (Nicotiana tabacum L.). Initial influxes were determined after the imposition of a pH-gradient (DeltapH, inside alkaline) and/or an electrical gradient (Deltapsi, inside negative) across the vesicle membrane. The initial magnitudes of the imposed gradients were DeltapH=2 and Deltapsi=-68 mV. In vesicles from the wild-type, the DeltapH-dependent valine influx could be analysed into a high-affinity (Km approximately 20 microM) and a low-affinity (Km approximately 3 mM) component. The influx of valine by the low-affinity system was stimulated about twofold, and that by the high-affinity system more than sixfold by the imposition of Deltapsi. This strong stimulation of the high-affinity system may indicate that it transports 2H+/amino acid. In the Val(r)-2 mutant the high-affinity component appeared to be completely absent. 相似文献