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排序方式: 共有129条查询结果,搜索用时 15 毫秒
1.
The ATP-binding-cassette transmembrane transporters (ABC transporters)
known from vertebrates belong to four major subfamilies: (1) the P-
glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance
regulators (CFTR); (3) the Tap proteins encoded with the major
histocompatibility complex of mammals; and (4) the peroxisomal membrane
proteins. Both Pgp and CFTR have a structure suggesting a past internal
gene duplication; a phylogenetic analysis indicated that these duplications
occurred independently, while an independent tandem gene duplication
occurred in the case of the Tap family. Both the Pgp and Tap proteins show
evidence of relationship to bacterial ABC transporters lacking internal
duplication, and both are significantly more closely related to the HlyB
and MsbA families of transporters from purple bacteria than they are to ABC
transporters from nonpurple bacteria. The simplest hypothesis to explain
this observation is that eukaryotic Pgp and Tap genes are descended from a
mitochondrial gene or genes that were subsequently translocated to the
nuclear genome. The Pgp genes of eukaryotes are characterized by a
remarkable degree of convergent evolution between the ATP-binding cassettes
of their N- terminal and C-terminal halves, whereas no such convergence is
seen between the two halves of CFTR genes or between the duplicated Tap
genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain
not found in other ABC transporters apart from CFTR, showed high levels of
both synonymous and nonsynonymous difference in comparisons among different
mammalian species, suggesting that this region is a mutational hot spot.
相似文献
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3.
X Xiao G Hintermann AL Demanin J Piret 《Journal of industrial microbiology & biotechnology》1996,16(4):261-262
Streptomyces glaucescens is shown to possess -lactamase activity which is inhibitable by clavulanate. This is important in regard to its use as a cloning host for enzymes of \-lactam biosynthesis. 相似文献
4.
ERIC S. BONO PATRICK SMOLINSKI AL CASAGRANDA JUNDE XU 《Computer methods in biomechanics and biomedical engineering》2013,16(2):125-131
The Shear-slip Mesh Update Method (SSMUM) is being used in flow simulations involving large but regular displacements of one or more boundaries of the computational domain. We follow up the earlier discussion of the method with notes on practical implementation aspects. In order to establish a benchmark problem for this class of flow problems, we define and report results from a two-dimensional viscous flow around a rotating stirrer in a square chamber. The application potential of the method is demonstrated in the context of biomedical design problem, as we perform an analysis of blood flow in a centrifugal left ventricular assist device, or blood pump, which involves a rotating impeller in a non-axisymmetric housing. 相似文献
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Joseph Khoory Jessica Estanislau Abdallah Elkhal Asmae Lazaar Mark I. Melhorn Abigail Brodsky Ben Illigens Itaru Hamachi Yasutaka Kurishita Alexander R. Ivanov Sergey Shevkoplyas Nathan I. Shapiro Ionita C. Ghiran 《PloS one》2016,11(1)
Acute, inflammatory conditions associated with dysregulated complement activation are characterized by significant increases in blood concentration of reactive oxygen species (ROS) and ATP. The mechanisms by which these molecules arise are not fully understood. In this study, using luminometric- and fluorescence-based methods, we show that ligation of glycophorin A (GPA) on human red blood cells (RBCs) results in a 2.1-fold, NADPH-oxidase-dependent increase in intracellular ROS that, in turn, trigger multiple downstream cascades leading to caspase-3 activation, ATP release, and increased band 3 phosphorylation. Functionally, using 2D microchannels to assess membrane deformability, GPS-ligated RBCs travel 33% slower than control RBCs, and lipid mobility was hindered by 10% using fluorescence recovery after photobleaching (FRAP). These outcomes were preventable by pretreating RBCs with cell-permeable ROS scavenger glutathione monoethyl ester (GSH-ME). Our results obtained in vitro using anti-GPA antibodies were validated using complement-altered RBCs isolated from control and septic patients. Our results suggest that during inflammatory conditions, circulating RBCs significantly contribute to capillary flow dysfunctions, and constitute an important but overlooked source of intravascular ROS and ATP, both critical mediators responsible for endothelial cell activation, microcirculation impairment, platelet activation, as well as long-term dysregulated adaptive and innate immune responses. 相似文献
7.
HENRY SILVERMAN BABIKER AHMED SAMAR AJEILET SUMAIA AL‐FADIL SUHAIL AL‐AMAD HADIR EL‐DESSOUKY IBRAHIM EL‐GENDY MOHAMED EL‐GUINDI MUSTAFA EL‐NIMEIRI RANA MUZAFFAR AZZA SALEH 《Developing world bioethics》2010,10(2):70-77
To help ensure the ethical conduct of research, many have recommended educational efforts in research ethics to investigators and members of research ethics committees (RECs). One type of education activity involves multi‐day workshops in research ethics. To be effective, such workshops should contain the appropriate content and teaching techniques geared towards the learning styles of the targeted audiences. To ensure consistency in content and quality, we describe the development of a curriculum guide, core competencies and associated learning objectives and activities to help educators organize research ethics workshops in their respective institutions. The curriculum guide is divided into modular units to enable planners to develop workshops of different lengths and choose content materials that match the needs, abilities, and prior experiences of the target audiences. The content material in the curriculum guide is relevant for audiences in the Middle East, because individuals from the Middle East who participated in a Certificate Program in research ethics selected and developed the training materials (e.g., articles, powerpoint slides, case studies, protocols). Also, many of the activities incorporate active‐learning methods, consisting of group work activities analyzing case studies and reviewing protocols. The development of such a workshop training curriculum guide represents a sustainable educational resource to enhance research ethics capacity in the Middle East. 相似文献
8.
VCAM-1 is a member of the Ig superfamily of receptors the expression of which is up-regulated on human airway smooth muscle (ASM) cells following stimulation with inflammatory mediators. The function of these receptors in adhesion is well known, but there is growing recognition that they also possess "outside-in" signaling functions, such as cytoskeletal reorganization, calcium mobilization, and cytokine release. The present study examined the activation of extracellular signal-regulated kinase and phosphatidylinositol 3-kinase (PI3K) in ASM cells following VCAM-1 engagement. VCAM-1 ligation activated extracellular signal-regulated kinase 2 and resulted in increased expression of cyclin D1, yet there was neither p27(kip1) degradation nor an increase in smooth muscle cell DNA synthesis. VCAM-1 ligation, however, augmented the proliferative response to submitogenic concentrations of epidermal growth factor. VCAM-1 engagement also stimulated a rapid increase in PI3K activity. This was associated with phosphorylation of the adapter protein p120(Cbl) and an increase in Cbl-associated PI3K activity. These studies suggest that VCAM-1 is linked to multiple signaling pathways in human ASM cells and may function to augment growth factor-induced responses. 相似文献
9.
Kazi AS Lotfi S Goncharova EA Tliba O Amrani Y Krymskaya VP Lazaar AL 《American journal of physiology. Lung cellular and molecular physiology》2004,286(3):L539-L545
In severe asthma, cytokines and growth factors contribute to the proliferation of smooth muscle cells and blood vessels, and to the increased extracellular matrix deposition that constitutes the process of airway remodeling. Vascular endothelial growth factor (VEGF), which regulates vascular permeability and angiogenesis, also modulates the function of nonendothelial cell types. In this study, we demonstrate that VEGF induces fibronectin secretion by human airway smooth muscle (ASM) cells. In addition, stimulation of ASM with VEGF activates ERK, but not p38MAPK, and fibronectin secretion is ERK dependent. Both ERK activation and fibronectin secretion appear to be mediated through the VEGF receptor flt-1, as evidenced by the effects of the flt-1-specific ligand placenta growth factor. Finally, we demonstrate that ASM cells constitutively secrete VEGF, which is increased in response to PDGF, transforming growth factor-beta, IL-1beta, and PGE(2). We conclude that ASM-derived VEGF, through modulation of the extracellular matrix, may play an important role in airway remodeling seen in asthma. 相似文献
10.
Phylogenetic tests of the hypothesis of block duplication of homologous genes on human chromosomes 6, 9, and 1 总被引:8,自引:1,他引:7
There are 10 gene families that have members on both human chromosome 6
(6p21.3, the location of the human major histocompatibility complex [MHC])
and human chromosome 9 (mostly 9q33-34). Six of these families also have
members on mouse chromosome 17 (the mouse MHC chromosome) and mouse
chromosome 2. In addition, four of these families have members on human
chromosome 1 (1q21-25 and 1p13), and two of these have members on mouse
chromosome 1. One hypothesis to explain these patterns is that members of
the 10 gene families of human chromosomes 6 and 9 were duplicated
simultaneously as a result of polyploidization or duplication of a
chromosome segment ("block duplication"). A subsequent block duplication
has been proposed to account for the presence of representatives of four of
these families on human chromosome 1. Phylogenetic analyses of the 9 gene
families for which data were available decisively rejected the hypothesis
of block duplication as an overall explanation of these patterns. Three to
five of the genes on human chromosomes 6 and 9 probably duplicated
simultaneously early in vertebrate history, prior to the divergence of
jawed and jawless vertebrates, and shortly after that, all four of the
genes on chromosomes 1 and 9 probably duplicated as a block. However, the
other genes duplicated at different times scattered over at least 1.6
billion years. Since the occurrence of these clusters of related genes
cannot be explained by block duplication, one alternative explanation is
that they cluster together because of shared functional characteristics
relating to expression patterns.
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