排序方式: 共有34条查询结果,搜索用时 15 毫秒
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Brian B. Tuch Rebecca R. Laborde Xing Xu Jian Gu Christina B. Chung Cinna K. Monighetti Sarah J. Stanley Kerry D. Olsen Jan L. Kasperbauer Eric J. Moore Adam J. Broomer Ruoying Tan Pius M. Brzoska Matthew W. Muller Asim S. Siddiqui Yan W. Asmann Yongming Sun Scott Kuersten Melissa A. Barker Francisco M. De La Vega David I. Smith 《PloS one》2010,5(2)
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Tuch DS Wisco JJ Khachaturian MH Ekstrom LB Kötter R Vanduffel W 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2005,360(1457):869-879
Diffusion-weighted magnetic resonance imaging holds substantial promise as a technique for non-invasive imaging of white matter (WM) axonal projections. For diffusion imaging to be capable of providing new insight into the connectional neuroanatomy of the human brain, it will be necessary to histologically validate the technique against established tracer methods such as horseradish peroxidase and biocytin histochemistry. The macaque monkey provides an ideal model for histological validation of the diffusion imaging method due to the phylogenetic proximity between humans and macaques, the gyrencephalic structure of the macaque cortex, the large body of knowledge on the neuroanatomic connectivity of the macaque brain and the ability to use comparable magnetic resonance acquisition protocols in both species. Recently, it has been shown that high angular resolution diffusion imaging (HARDI) can resolve multiple axon orientations within an individual imaging voxel in human WM. This capability promises to boost the accuracy of tract reconstructions from diffusion imaging. If the macaque is to serve as a model for histological validation of the diffusion tractography method, it will be necessary to show that HARDI can also resolve intravoxel architecture in macaque WM. The present study therefore sought to test whether the technique can resolve intravoxel structure in macaque WM. Using a HARDI method called q-ball imaging (QBI) it was possible to resolve composite intravoxel architecture in a number of anatomic regions. QBI resolved intravoxel structure in, for example, the dorsolateral convexity, the pontine decussation, the pulvinar and temporal subcortical WM. The paper concludes by reviewing remaining challenges for the diffusion tractography project. 相似文献
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Proliferation of direct repeats near the Oenothera chloroplast DNA origin of replication 总被引:1,自引:0,他引:1
The spacer between the 16S and 23S rRNA genes of the chloroplast DNA has
been implicated as an origin of replication in several species of plants.
In the evening primrose, Oenothera, this site was found to vary greatly in
size, with plastid genomes (plastomes) being readily distinguished. To
determine whether plastome "strength" in transmission could be correlated
with variation at oriB, the 16S rRNA-trnI spacer was sequenced from five
plastomes. The size variation was found to be due to differential
amplification (and deletion) of combinations of sequences belonging to
seven families of direct repeats. From these comparisons, one short series
of direct repeats and one region capable of forming a hairpin structure
were identified as candidates for the factor that could be responsible for
the differences between strong and weak plastome types. Ample sequence
variation allowed phylogenetic inferences to be made about the
relationships among the plastomes. Phylogenetic trees also could be
constructed for most of the families of direct repeats. The amplifications
and deletions of repeats that account for the size variation at oriB are
proposed to have occurred through extensive replication slippage at this
site.
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Assembly of the Candida albicans genome into sixteen supercontigs aligned on the eight chromosomes
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van het Hoog M Rast TJ Martchenko M Grindle S Dignard D Hogues H Cuomo C Berriman M Scherer S Magee BB Whiteway M Chibana H Nantel A Magee PT 《Genome biology》2007,8(4):R52-11
Background
The 10.9× genomic sequence of Candida albicans, the most important human fungal pathogen, was published in 2004. Assembly 19 consisted of 412 supercontigs, of which 266 were a haploid set, since this fungus is diploid and contains an extensive degree of heterozygosity but lacks a complete sexual cycle. However, sequences of specific chromosomes were not determined.Results
Supercontigs from Assembly 19 (183, representing 98.4% of the sequence) were assigned to individual chromosomes purified by pulse-field gel electrophoresis and hybridized to DNA microarrays. Nine Assembly 19 supercontigs were found to contain markers from two different chromosomes. Assembly 21 contains the sequence of each of the eight chromosomes and was determined using a synteny analysis with preliminary versions of the Candida dubliniensis genome assembly, bioinformatics, a sequence tagged site (STS) map of overlapping fosmid clones, and an optical map. The orientation and order of the contigs on each chromosome, repeat regions too large to be covered by a sequence run, such as the ribosomal DNA cluster and the major repeat sequence, and telomere placement were determined using the STS map. Sequence gaps were closed by PCR and sequencing of the products. The overall assembly was compared to an optical map; this identified some misassembled contigs and gave a size estimate for each chromosome.Conclusion
Assembly 21 reveals an ancient chromosome fusion, a number of small internal duplications followed by inversions, and a subtelomeric arrangement, including a new gene family, the TLO genes. Correlations of position with relatedness of gene families imply a novel method of dispersion. The sequence of the individual chromosomes of C. albicans raises interesting biological questions about gene family creation and dispersion, subtelomere organization, and chromosome evolution. 相似文献28.
The use of flow microfluorimetry in the analysis of the phenotype expression of mouse histocompatibility antigens 总被引:1,自引:0,他引:1
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Quantitation of the expression of cell surface antigens has hitherto been limited to analysis by either cytotoxicity tests or radioimmune assays (5, 15). We report here the use of a new methodology to analyze and quantitate the expression of mouse histocompabililty antigens (H-2 locus) in hybrid clones and parental cell types. The binding of fluorescein-tagged antibody is measured on a cell-to-cell basis in large viable cell populations using flow microfluorimetric techniques. These techniques have been used to measure hapten and immunoglobulin binding to lymphocyte populations (8, 9, 14). However, this is the first report in which these techniques have been used to examine the expression of the H-2 locus. The advantage of this approach is twofold: first, a large and statistically significant sample population may be analyzed one cell at a time, thus revealing the fine detail of heterogeneity in the expression of the cell surface markers within a population. Second, as has been demonstrated for analysis of specific components of the immune system, this method does permit fluorescence-activated sorting of cell types according to their different surface populations (8, 9, 14). 相似文献
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Fourteen thioredoxin sequences were used to construct a minimal
phylogenetic tree by using parsimony. The bacterial thioredoxins clustered
into three groups: one containing the photosynthetic purple bacteria,
Escherichia and Corynebacterium; a second containing the photosynthetic
green bacterium, Chlorobium; and a third containing cyanobacteria. These
groupings are similar to those generated from earlier 16s RNA analyses.
Animal thioredoxins formed a fourth group. The two thioredoxins of
chloroplasts (f and m) showed contrasting phylogenetic patterns. As
predicted from prior studies, spinach chloroplast thioredoxin m grouped
with its counterparts from cyanobacteria and eukaryotic algae, but,
unexpectedly, thioredoxin f grouped with the animal thioredoxins. The
results indicate that, during evolution, thioredoxin m of contemporary
photosynthetic eukaryotic cells was derived from a prokaryotic symbiont,
whereas thioredoxin f descended from an ancestral eukaryote common to
plants and animals. The findings illustrate the potential of thioredoxin as
a phylogenetic marker and suggest a relationship between the animal and
f-type thioredoxins.
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