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排序方式: 共有233条查询结果,搜索用时 11 毫秒
1.
Reinnervation of experimental superficial wounds in rats 总被引:1,自引:0,他引:1
Sensory reinnervation of a superficial skin wound in the rat was studied by labeling sensory axons with anterogradely transported wheat germ agglutinin-horseradish peroxidase. Reinnervation starts after 3 days from the edge of the wound as well as from beneath the wound. About 2 weeks after the production of the wound, some hyperinnervation appears to be present, but after a few additional weeks, the innervation pattern is essentially normal. The results indicate that structural recovery of sensory axons is rapid and probably complete when skin wounds heal with no or minimal scar formation. 相似文献
2.
L Selleri J H Eubanks M Giovannini G G Hermanson A Romo M Djabali S Maurer D L McElligott M W Smith G A Evans 《Genomics》1992,14(2):536-541
"Chimeric" yeast artificial chromosomes (YACs) are clones containing two or more noncontiguous segments of DNA and represent the most common artifact found in total genomic YAC libraries currently used for large-scale genome mapping. These YACs create spurious mapping information that complicates the construction of YAC contigs and leads to erroneous maps during chromosome walks. The presence of these artifactual clones necessitates laborious and time-consuming characterization of each isolated YAC clone, either by comparison of the physical map of the YAC with the corresponding source genomic DNA, or by demonstrating discrepant chromosomal origins for the two ends of the YAC by hybridization or polymerase chain reaction (PCR). Here, we describe a rapid and sensitive method for the assessment of YAC colinearity by fluorescence in situ suppression hybridization (FISSH) by utilizing fluorescein-12-dUTP for labeling YAC clones. We have analyzed 51 YACs and found that 43% (22 out of 51) are chimeric and significantly larger (302 kb) than colinear ones (228 kb). One of the 51 YAC clones (2%) examined contains portions of three chromosomes and 2 (4%) seem to map to a chromosome different than that of the identifying STS. FISSH analysis offers a straightforward visualization of the entire YAC insert on the chromosomes and can be used to examine many YACs simultaneously in few days. 相似文献
3.
Methods for computing the standard errors of branching points in an evolutionary tree and their application to molecular data from humans and apes 总被引:23,自引:2,他引:21
Statistical methods for computing the standard errors of the branching
points of an evolutionary tree are developed. These methods are for the
unweighted pair-group method-determined (UPGMA) trees reconstructed from
molecular data such as amino acid sequences, nucleotide sequences,
restriction-sites data, and electrophoretic distances. They were applied to
data for the human, chimpanzee, gorilla, orangutan, and gibbon species.
Among the four different sets of data used, DNA sequences for an
895-nucleotide segment of mitochondrial DNA (Brown et al. 1982) gave the
most reliable tree, whereas electrophoretic data (Bruce and Ayala 1979)
gave the least reliable one. The DNA sequence data suggested that the
chimpanzee is the closest and that the gorilla is the next closest to the
human species. The orangutan and gibbon are more distantly related to man
than is the gorilla. This topology of the tree is in agreement with that
for the tree obtained from chromosomal studies and DNA-hybridization
experiments. However, the difference between the branching point for the
human and the chimpanzee species and that for the gorilla species and the
human-chimpanzee group is not statistically significant. In addition to
this analysis, various factors that affect the accuracy of an estimated
tree are discussed.
相似文献
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6.
A highly conserved nuclear gene for low-level phylogenetics: elongation factor-1 alpha recovers morphology-based tree for heliothine moths 总被引:8,自引:2,他引:6
Cho S; Mitchell A; Regier JC; Mitter C; Poole RW; Friedlander TP; Zhao S 《Molecular biology and evolution》1995,12(4):650-656
Molecular systematists need increased access to nuclear genes. Highly
conserved, low copy number protein-encoding nuclear genes have attractive
features for phylogenetic inference but have heretofore been applied mostly
to very ancient divergences. By virtue of their synonymous substitutions,
such genes should contain a wealth of information about lower-level
taxonomic relationships as well, with the advantage that amino acid
conservatism makes both alignment and primer definition straightforward. We
tested this postulate for the elongation factor-1 alpha (EF-1 alpha) gene
in the noctuid moth subfamily Heliothinae, which has probably diversified
since the middle Tertiary. We sequenced 1,240 bp in 18 taxa representing
heliothine groupings strongly supported by previous morphological and
allozyme studies. The single most parsimonious gene tree and the
neighbor-joining tree for all nucleotides show almost complete concordance
with the morphological tree. Homoplasy and pairwise divergence levels are
low, transition/transversion ratios are high, and phylogenetic information
is spread evenly across gene regions. The EF-1 alpha gene and presumably
other highly conserved genes hold much promise for phylogenetics of
Tertiary age eukaryote groups.
相似文献
7.
Identification of the signalling molecules involved in mesoderm formation in amphibian embryos still presents problems. None of the original candidates, such as activin, have been definitively ruled out, and the new factors, such as the nodal-related genes, have come on to the scene. Of the original candidates, activin has been definitively shown to act as a morphogen, whereas bone morphogenetic protein (BMP)-4 has emerged as a ventral inducer and an inhibitor of neural differentiation. The effects of BMP-4 are antagonized by chordin, a molecule related to the product of the Drosophila gene short gastrulation. 相似文献
8.
Hjördis Thor Peter Moldéus Rolf Hermanson Johan Högberg Donald J. Reed Sten Orrenius 《Archives of biochemistry and biophysics》1978,188(1):122-129
Hepatocytes freshly isolated from diethylmaleate-treated rats exhibited a markedly decreased concentration of reduced glutathione (GSH) which increased to the level present in hepatocytes from nontreated rats upon incubation in a complete medium. When bromobenzene was present in the medium, however, this increase in GSH concentration upon incubation was reversed and a further decrease occurred that resulted in GSH depletion and cell death. This was prevented by metyrapone, an inhibitor of the cytochrome P-450-linked metabolism of bromobenzene. Bromobenzene metabolism in hepatocytes was accompanied by a fraction of metabolites covalently binding to cellular proteins. The size of this fraction, relative to the amount of total metabolites, was increased in hepatocytes isolated from diethylmaleate-treated rats and in hepatocytes from phenobarbital-treated rats incubated with bromobenzene in the presence of 1,2-epoxy-3,3,3-trichloropropane, an inhibitor of microsomal epoxide hydrase which, however, also acted as a GSH-depleting agent. In addition, the metabolism of bromobenzene by hepatocytes was associated with a marked decrease in various coenzyme levels, including coenzyme A, NAD(H), and NADP(H). Cysteine and cysteamine inhibited the formation of protein-bound metabolites of bromobenzene in microsomes, but did not prevent bromobenzene toxicity in hepatocytes when added at higher concentrations to the incubation medium (containing 0.4 mm cysteine). Methionine, on the other hand, did not cause a significant effect on bromobenzene metabolism in microsomes and prevented toxicity in hepatocytes, presumably by stimulating GSH synthesis and thereby decreasing the amount of reactive metabolites available for interaction with other cellular nucleophiles. It is concluded that, in contrast to hepatocytes with normal levels of GSH, hepatocytes from diethylmaleate-treated rats were sensitive to bromobenzene toxicity under our incubation conditions. In this system, bromobenzene metabolism led to GSH depletion and was associated with a progressive decrease in coenzyme A and nicotinamide nucleotide levels and a moderate increase in the formation of metabolites covalently bound to protein. Methionine was a potent protective agent which probably acted by enhanced GSH synthesis via the formation of cystathionine. 相似文献
9.
Getting the right stuff: controlling neural stem cell state and fate in vivo and in vitro with biomaterials 总被引:1,自引:0,他引:1
Stem cell therapy holds great promises in medical treatment by, e.g., replacing lost cells, re-constitute healthy cell populations and also in the use of stem cells as vehicles for factor and gene delivery. Embryonic stem cells have rightfully attracted a large interest due to their proven capacity of differentiating into any cell type in the embryo in vivo. Tissue-specific stem ceils are however already in use in medical practice, and recently the first systematic medical trials involving human neural stem cell (NSC) therapy have been launched. There are yet many obstacles to overcome and procedures to improve. To ensure progress in the medical use of stem cells increased basic knowledge of the molecular mechanisms that govern stem cell characteristics is necessary. Here we provide a review of the literature on NSCs in various aspects of cell therapy, with the main focus on the potential of using biomaterials to control NSC characteristics, differentiation, and delivery. We summarize results from studies on the characteristics of endogenous and transplanted NSCs in rodent models of neurological and cancer diseases, and highlight recent advancements in polymer compatibility and applicability in regulating NSC state and fate. We suggest that the development of specially designed polymers, such as hydrogels, is a crucial issue to improve the outcome of stem cell therapy in the central nervous system. 相似文献
10.
Sensibility and cutaneous reinnervation in free flaps 总被引:2,自引:0,他引:2
A Hermanson C J Dalsgaard C Arnander U Lindblom 《Plastic and reconstructive surgery》1987,79(3):422-427
Sensibility and sensory reinnervation were investigated in 19 free flaps, predominantly located on the lower extremities, between 2 months and 3 years after flap transfer. All patients showed deep pressure sensibility. In 10 of the patients, primarily those examined late after surgery, a heat pain threshold was obtained at about 50 degrees C. None of the patients had superficial sensibility of any other modality. No neurofilament-positive sensory nerve fibers were observed in the dermis or epidermis. In one patient nerve fibers were detected in the subcutaneous tissue. It is concluded that patients will have deep pressure sensibility of the flap area even early after the operation and that most patients will develop a heat pain sensitivity, probably due to subcutaneous reinnervation. 相似文献