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1.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
2.
DM Woolley 《The Journal of cell biology》1977,75(3):851-865
Motile spermatozoa from the golden hamster have been arrested by rapid freezing and then fixed with glutaraldehyde at low temperature after substitution with ethylene glycol. As far as can be judged, the flagellar waveforms thus stabilized are similar to those seen in living sperm; in contrast, fixation in glutaraldehyde, without prior freezing, induces agonal changes in flagellar conformation. The characteristics waveform after freeze substitution contains three bends. Approx. half of these flagella are entirely planar. The rest are three dimensional, with the third bend displaced in a regular way from the plane containing the proximal two bends. From the geometry of these flagella, it is concluded that the plane of action of a given bending cycle undergoes a clockwise twist (from a forward viewpoint) as the cycle is succeeded by new bending cycles. This "twisted plane" undulation is quite different from helical movement. The twisting seems to occur abruptly, between cycles, as if each bending cycle has a preferred plane of action. The mechanism underlying the twisting is uncertain. However, on the basis of the angular displacements between the preferred planes, and the findings from electron microscopy, the following idea is presented as a working hypothesis: that, if the most proximal plane of bending is topographically determined by peripheral doublet 1, then successive distal planes of action are influenced predominantly by doublets 2, 3, etc., in clockwise sequence. The merits and weaknesses of this hypothesis are discussed. 相似文献
3.
细胞粘附分子(CAM)可介导细胞间及细胞与间质之间的相互作用并传导信息,参与机体胚胎发育、免疫调节、炎症反应、组织修复及肿瘤转移等生理和病理过程。细胞间粘附分子1(ICAM1)是主要的CAM分子之一,可表达于活化的细胞,内皮细胞等。人膜是母体与胚胎滋养层直接接触的特殊组织、已发现蜕膜细胞在着床过程中参与了局部免疫耐受的形成,但对着床期ICAM1在蜕膜细胞表达的动态研究鲜见报道。本研究采用免疫荧光、多参数流式细胞术,分别从整体和局部角度、着床过程中外周血淋巴细胞(PBLC)及子宫内膜/蜕膜(EC/DC)细胞ICAM1的不同表达特点进行了动态观察和对比性分析。结果发现,ICAM1在着床期PBLC及EC/DC中的表达均存在明显的动态变化(Tab.1;Figs.1&2)。ICAM1在PBLC中的表达于妊娠第一天(D1)即开始降低,D2降至最低;与此不同,ICAM1在EC/DC中的表达于D2开始降低,D4降至最低,D5开始恢复,但尚未恢复到对照水平。结果表明,ICAM1在蜕膜局部的表达调节方式不同于外周血;ICAM1表达阳性的外周血,淋巴细胞和蜕膜细胞均代表着活化的功能性细胞,这些细胞表面ICAM 相似文献
4.
The ITS sequences of Acropora spp. are the shortest so far identified in
any metazoan and are among the shortest seen in eukaryotes; ITS1 was 70-80
bases, and ITS2 was 100-112 bases. The ITS sequences were also highly
variable, but base composition and secondary structure prediction indicate
that divergent sequence variants are unlikely to be pseudogenes. The
pattern of variation was unusual in several other respects: (1) two
distinct ITS2 types were detected in both A. hyacinthus and A. cytherea,
species known to hybridize in vitro with high success rates, and a putative
intermediate ITS2 form was also detected in A. cytherea; (2) A. valida was
found to contain highly (29%) diverged ITS1 variants; and (3) A.
longicyathus contained two distinct 5.8S rDNA types. These data are
consistent with a reticulate evolutionary history for the genus Acropora.
相似文献
5.
6.
VLJ Whitehall TD Dumenil DM McKeone CE Bond ML Bettington RL Buttenshaw L Bowdler GW Montgomery LF Wockner BA Leggett 《Epigenetics》2014,9(11):1454-1460
The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features. 相似文献
7.
WU YU ZHANG YING WAN DAO GUO LI YAN TANG WEI ZHOU Institute of Immunology PLA The Third Medical University Chongqing China Medical Center General Hospital of Weifang Weifang China 《Cell research》2001,(3)
INTRODUCTIONHepatitis B virus (HBV) infection is the mostcommon viral infection in humans especially inChina and East Asia. At present, the most effi-cient method to control the disease is vaccinationof new-borns. Both blood derived vaccine and re-combinant vaccine are hepatitis B surface alltigen(HBsAg)-based and useful in the prevention of thedisease[1-3]. HBsAg could evoke protective humoralimmune response in vivo, but the immune memoryonly last for 5 years or so[3, 4]. How to des… 相似文献
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