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排序方式: 共有201条查询结果,搜索用时 190 毫秒
101.
102.
103.
Solanaceae is a family with nearly 2400 species of cosmopolitan distribution. Vassobia breviflora is the only species of the genus present in Argentina. The goal of this work was to review and characterize the anatomy of the flower and fruit of V. breviflora from samples collected in populations of Yungas in the argentine Northwest. Conventional anatomical techniques were applied. The results showed that most flower, fruit and seed structures did not differ from those previously reported regarding the structural organization described for other species of the Solanaceae family. However, for the first time, we described the androecium, fruit, seed, floral and fruit pedicels, five types of tricomes and five types of stomata in the perianth. We found some differences in the shape of the transmission tissue and in the type of ovule with respect to that previously reported. Also, we located the parenchyma and the epidermic secretory cells of the nectary. In the context of the family Solanaceae, we discussed the function and diagnostic value of the described structures. 相似文献
104.
ERCC1/XPF limits L1 retrotransposition 总被引:1,自引:0,他引:1
Retrotransposons are currently active in the human and mouse genomes contributing to novel disease mutations and genomic variation via de novo insertions. However, little is known about the interactions of non-long terminal repeat (non-LTR) retrotransposons with the host DNA repair machinery. Based on the model of retrotransposition for the human and mouse LINE-1 element, one likely intermediate is an extension of cDNA that is heterologous to the genomic target, a flap intermediate. To determine whether a human flap endonuclease could recognize and process this potential intermediate, the genetic requirement for the ERCC1/XPF heterodimer during LINE-1 retrotransposition was characterized. Reduction of XPF in human cells increased retrotransposition whereas complementation of ERCC1-deficiency in hamster cells reduced retrotransposition. These results demonstrate for the first time that DNA repair enzymes act to limit non-LTR retrotransposition and may provide insight into the genetic instability phenotypes of ercc1 and xpf individuals. 相似文献
105.
Rainer Voisard Eva Kucharczyk Ute Deininger Regine Baur Vinzenz Hombach 《BMC cardiovascular disorders》2002,2(1):2-10
Background
Strictly intravascular approaches for the treatment of postangioplasty restenosis are effective in the intima and the inner parts of the media but may be insufficient to control redundant pathways in the more outer parts of the media and the adventitia. An inverse situation may occur subsequently to a strictly extravascular approach, like the recently suggested pericardial approach in pigs. We hypothesized that simultaneous intra/extravascular administration of anti-restenotic agents inhibits restenosis by blocking all stimulatory pathways in the entire arterial wall. 相似文献106.
Cristina M. Justice Zhining Den Son V. Nguyen Mark Stoneking Prescott L. Deininger Mark A. Batzer Bronya J.B. Keats 《Journal of molecular evolution》2001,52(3):232-238
Friedreich ataxia is an autosomal recessive neurodegenerative disorder associated with a GAA repeat expansion in the first
intron of the gene (FRDA) encoding a novel, highly conserved, 210 amino acid protein known as frataxin. Normal variation in
repeat size was determined by analysis of more than 600 DNA samples from seven human populations. This analysis showed that
the most frequent allele had nine GAA repeats, and no alleles with fewer than five GAA repeats were found. The European and
Syrian populations had the highest percentage of alleles with 10 or more GAA repeats, while the Papua New Guinea population
did not have any alleles carrying more than 10 GAA repeats. The distributions of repeat sizes in the European, Syrian, and
African American populations were significantly different from those in the Asian and Papua New Guinea populations (p < 0.001). The GAA repeat size was also determined in five nonhuman primates. Samples from 10 chimpanzees, 3 orangutans, 1
gorilla, 1 rhesus macaque, 1 mangabey, and 1 tamarin were analyzed. Among those primates belonging to the Pongidae family,
the chimpanzees were found to carry three or four GAA repeats, the orangutans had four or five GAA repeats, and the gorilla
carried three GAA repeats. In primates belonging to the Cercopithecidae family, three GAA repeats were found in the mangabey
and two in the rhesus macaque. However, an AluY subfamily member inserted in the poly(A) tract preceding the GAA repeat region in the rhesus macaque, making the amplified
sequence approximately 300 bp longer. The GAA repeat was also found in the tamarin, suggesting that it arose at least 40 million
years ago and remained relatively small throughout the majority of primate evolution, with a punctuated expansion in the human
genome.
Received: 18 August 2000 / Accepted: 10 November 2000 相似文献
107.
The Ames test and the SOS-chromotest are widely used bacterial mutagenicity/genotoxicity assays to test potential carcinogens. Though the molecular mechanisms leading to backmutations and to the induction of SOS-repair are in principle known the role of alkylation mechanisms, of different DNA-lesions and of DNA-repair is in parts still unknown. In this study we investigated 14 monofunctional methanesulfonates of widely varying structures for mutagenicity in Salmonella typhimurium strain TA 1535 sensitive for O(6)-guanine alkylation for comparison with strain TA 100 in order to obtain additional information on the role of alkylation mechanisms, formation of the procarcinogenic DNA-lesion O(6)-alkylguanine and the role of DNA-repair in induction of backmutation. The substances were also tested in the SOS-chromotest with Escherichia coli strain PQ 37 and strain PQ 243 lacking alkyl base glycosylases important for base excision repair in order to examine the role of alkylation mechanisms, of base excision repair and the role of O-alkyl and N-alkyl DNA-lesions on the induction of SOS-repair. The secondary methanesulfonates with very high S(N)1-reactivity isopropyl methanesulfonate and 2-butyl methanesulfonate showed highest mutagenicities in both strains. The higher substituted methanesulfonates with very high S(N)1-reactivity had lower mutagenic activities because of reduced half lives due to their high hydrolysis rates. A clear increase in mutagenicities in strain TA 100 was observed for the primary compounds methyl methanesulfonate and allyl methanesulfonate with very high S(N)2-reactivity. The primary compound phenylethyl methanesulfonate has a relatively high mutagenicity in both Salmonella strains which can be explained by an increased S(N)1-reactivity and by low repair of the O(6)-phenylethylguanine. Highest SOSIPs (SOS inducing potency) in strains PQ 37 and PQ 243 were found for methyl methanesulfonate and for the secondary compounds with high S(N)1-reactivity. The ratios in the SOSIPs between strain PQ 243 and PQ 37, indirectly indicative for the role of O- and N-alkylation in the induction of SOS-repair, was high for the primary methanesulfonates and lower for the secondary, indicating that the SOS-repair is, to a certain extent, also induced by other lesions than O(6)-alkylation. The results indicate that O(6)-alkylation is also a predominant lesion for backmutation in strain TA 100 and that in the case of monofunctional alkylating agents high S(N)2-reactivities are required to induce error prone repair mediated backmutations. The O(6)-alkylguanine lesion is also important for induction of SOS-repair in the SOS-chromotest, however, other sites of alkylation which are repaired by the base pair excision repair system can also efficiently contribute to the induction of SOS-repair. 相似文献
108.
Roy-Engel AM Carroll ML Vogel E Garber RK Nguyen SV Salem AH Batzer MA Deininger PL 《Genetics》2001,158(1):279-290
We analyze genetic variation at fused1, a locus that is close to the centromere of the X chromosome-autosome (X/4) fusion in Drosophila americana. In contrast to other X-linked and autosomal genes, for which a lack of population subdivision in D. americana has been observed at the DNA level, we find strong haplotype structure associated with the alternative chromosomal arrangements. There are several derived fixed differences at fused1 (including one amino acid replacement) between two haplotype classes of this locus. From these results, we obtain an estimate of an age of approximately 0.61 million years for the origin of the two haplotypes of the fused1 gene. Haplotypes associated with the X/4 fusion have less DNA sequence variation at fused1 than haplotypes associated with the ancestral chromosome arrangement. The X/4 haplotypes also exhibit clinal variation for the allele frequencies of the three most common amino acid replacement polymorphisms, but not for adjacent silent polymorphisms. These patterns of variation are best explained as a result of selection acting on amino acid substitutions, with geographic variation in selection pressures. 相似文献
109.
Alu elements undergo amplification through retroposition and integration into new locations throughout primate genomes. Over
500,000 Alu elements reside in the human genome, making the identification of newly inserted Alu repeats the genomic equivalent
of finding needles in the haystack. Here, we present two complementary methods for rapid detection of newly integrated Alu
elements. In the first approach we employ computational biology to mine the human genomic DNA sequence databases in order
to identify recently integrated Alu elements. The second method is based on an anchor-PCR technique which we term Allele-Specific
Alu PCR (ASAP). In this approach, Alu elements are selectively amplified from anchored DNA generating a display or 'fingerprint'
of recently integrated Alu elements. Alu insertion polymorphisms are then detected by comparison of the DNA fingerprints generated
from different samples. Here, we explore the utility of these methods by applying them to the identification of members of
the smallest previously identified subfamily of Alu repeats in the human genome termed Ya8. This subfamily of Alu repeats
is composed of about 50 elements within the human genome. Approximately 50% of the Ya8 Alu family members have inserted in
the human genome so recently that they are polymorphic, making them useful markers for the study of human evolution.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
110.
West N Roy-Engel AM Imataka H Sonenberg N Deininger P 《Journal of molecular biology》2002,321(3):423-432
The heterogeneous, short RNAs produced from the high, copy, short mobile elements (SINEs) interact with proteins to form RNA-protein (RNP) complexes. In particular, the BC1 RNA, which is transcribed to high levels specifically in brain and testis from one locus of the ID SINE family, exists as a discrete RNP complex. We expressed a series of altered BC1, and other SINE-related RNAs, in several cell lines and tested for the mobility of the resulting RNP complexes in a native PAGE assay to determine which portions of these SINE RNAs contribute to protein binding. When different SINE RNAs were substituted for the BC1 ID sequence, the resulting RNPs exhibited the same mobility as BC1. This indicates that the protein(s) binding to the ID portion of BC1 is not sequence specific and may be more dependent upon the secondary structure of the RNA. It also suggests that all SINE RNAs may bind a similar set of cellular proteins. Deletion of the A-rich region of BC1 RNA has a marked effect on the mobility of the RNP. Rodent cell lines exhibit a slightly different mobility for this shifted complex when compared to human cell lines, reflecting evolutionary differences in one or more of the protein components. On the basis of mobility change observed in RNP complexes when the A-rich region is removed, we decided to examine poly(A) binding protein (PABP) as a candidate member of the RNP. An antibody against the C terminus of PABP is able to immunoprecipitate BC1 RNA, confirming PABP's presence in the BC1 RNP. Given the ubiquitous role of poly(A) regions in the retrotransposition process, these data suggest that PABP may contribute to the SINE retrotransposition process. 相似文献