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目的由于卒中风险随着狭窄严重程度的增加而升高,因此认为颈内动脉(ICA)接近闭塞患者的卒中风险很高。在现有的随机试验中,还没有专门针对这种情况进行探讨,因此其处理尚存在争汶。方法:对相关文献进行系统评价。结果:对ICA接近闭塞患者的处理还存在争议:一些学者支持进行干预,而另一些学者则认为存在风险或没有益处而反对进行干预。在ICA接近闭塞的有症状患者中进行一项比较外科治疗与最佳内科治疗的多中心前瞻性随机试验似乎非常困难,因为这类研究需要大量的患者。尽管如此,基于目前的证据,似乎很难拒绝手术治疗。结论:由于目前对ICA接近闭塞患者的最佳处理方案仍存在着争议,因此需要前瞻性观察性研究以证实其在有症状和无症状人群中的患病率以及相关的卒中风险。基于目前的证据,大多数医疗中心选择手术治疗,但它相对干内科治疗的特粱尚右待证章. 相似文献
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Rupture of the distal biceps tendon: evaluation with MR imaging 总被引:2,自引:0,他引:2
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Previous studies on the metabolism of capsaicinoids, natural products isolated from chili peppers, demonstrated the production of unique macrocyclic, alkyl dehydrogenated, omega-, and omega-1-hydroxylated products. This study investigated the structural and enzymatic parameters that direct selective alkyl dehydrogenation and hydroxylation of capsaicinoids, using a variety of structurally related capsaicinoid analogs and cytochrome P450 (P450) enzymes. CYP2C9 preferentially catalyzed alkyl dehydrogenation, whereas CYP2E1 and 3A4 catalyzed omega- and omega-1-hydroxylation, respectively. Analysis of incubations containing various P450s and structural variants of capsaicin by liquid chromatography-tandem mass spectrometry demonstrated similarities in the rate of capsaicinoid metabolism, but marked differences in the metabolite profiles. Production of macrocyclic and omega-1-hydroxylated metabolites from the various capsaicinoids was dependent on the structure of the alkyl terminus and P450 enzyme. A tertiary carbon at the omega-1 position, coupled to an adjacent unsaturated bond at the omega-2,3 position, enhanced the formation of the macrocyclic and dehydrogenated metabolites and were requisite structural features for omega-1-hydroxylated product formation. Conversely, substrates lacking these structural features were efficiently oxidized to the omega-hydroxylated metabolite. These data were consistent with our hypothesis that metabolism of the alkyl portion of capsaicinoids was governed, in part, by the stability and propensity to form an intermediate radical and a carbocation, and a direct interaction between the alkyl terminus and the heme of many P450 enzymes. These results provided valuable insights into potential mechanisms by which P450s metabolize capsaicinoids and highlight critical chemical features that may also govern the metabolism of structurally related compounds including fatty acids, monoter-penes, and isoprenoids. 相似文献
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Heparan sulfate (HS) is an unbranched chain of repetitive disaccharides, which specifically binds ligands when attached to the cell surface or secreted extracellularly. HS chains contain sulfated domains termed the HS fine structure, which gives HS specific binding affinities for extracellular ligands. HS 3-O-sulfotransferases (3-OST) catalyze the transfer of sulfate groups to the 3-O position of glucosamine residues of HS, a rare, but essential HS chain modification required for HS fine structure. We report here the first characterization and developmental expression analysis of the 3-OST gene family in a vertebrate. There are eight 3-OST genes in zebrafish: seven genes with homology to known 3-OST genes in mouse and human, as well as a novel, 3-OST-7. A phylogenetic comparison of human, mouse, and zebrafish indicates the 3-OST family can be subdivided into two distinct subgroups. We examined the mRNA expression patterns in several tissues/organs throughout early zebrafish development, including early cleavage stages, somites, brain, internal body organ primordial, and pectoral fin development. The 3-OST gene family has both specifically expressed and ubiquitously expressed genes, suggesting in vivo functional differences exist between members of this family. 相似文献
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Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability 总被引:1,自引:15,他引:1
La Spada AR; Peterson KR; Meadows SA; McClain ME; Jeng G; Chmelar RS; Haugen HA; Chen K; Singer MJ; Moore D; Trask BJ; Fischbeck KH; Clegg CH; McKnight GS 《Human molecular genetics》1998,7(6):959-967
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG
repeat expansion in the first exon of the androgen receptor (AR) gene.
Disease-associated alleles (37-66 CAGs) change in length when transmitted
from parents to offspring, with a significantly greater tendency to shift
size when inherited paternally. As transgenic mice carrying human AR cDNAs
with 45 and 66 CAG repeats do not display repeat instability, we attempted
to model trinucleotide repeat instability by generating transgenic mice
with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions
in their genomic context. Studies of independent lines of AR YAC transgenic
mice with CAG 45 alleles reveal intergenerational instability at an overall
rate of approximately 10%. We also find that the 45 CAG repeat tracts are
significantly more unstable with maternal transmission and as the
transmitting mother ages. Of all the CAG/CTG repeat transgenic mice
produced to date the AR YAC CAG 45 mice are unstable with the smallest
trinucleotide repeat mutations, suggesting that the length threshold for
repeat instability in the mouse may be lowered by including the appropriate
flanking human DNA sequences. By sequence-tagged site content analysis and
long range mapping we determined that one unstable transgenic line has
integrated an approximately 70 kb segment of the AR locus due to
fragmentation of the AR YAC. Identification of the cis - acting elements
that permit CAG tract instability and the trans -acting factors that
modulate repeat instability in the AR YAC CAG 45 mice may provide insights
into the molecular basis of trinucleotide repeat instability in humans.
相似文献
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D F Hoft K S Kim K Otsu D R Moser W J Yost J H Blumin J E Donelson L V Kirchhoff 《Infection and immunity》1989,57(7):1959-1967
We screened a Trypanosoma cruzi cDNA expression library with human and rabbit anti-T. cruzi sera and identified cDNA clones that encode polypeptides containing tandemly arranged repeats which are 6 to 34 amino acids in length. The peptide repeats encoded by these cDNAs varied markedly in sequence, copy number, and location relative to the polyadenylation site of the mRNAs from which they were derived. The repeats were specific for T. cruzi, but in each case the sizes of the corresponding mRNAs and the total number of repeat copies encoded varied considerably among different isolates of the parasite. Expression of the peptide repeats was not stage specific. One of the peptide repeats occurred in a protein with an Mr of greater than 200,000 and one was in a protein of Mr 75,000 to 105,000. The frequent occurrence and diversity of these peptide repeats suggested that they may play a role in the ability of the parasite to evade immune destruction in its invertebrate and mammalian hosts, but the primary roles of these macromolecules may be unrelated to the host-parasite relationship. 相似文献