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1.
The morphology of dissociated single cerebellar Purkinje cells obtained from wild-type P1 CD1 mice was assessed in the absence
and in the presence of glia. A dedicated noninvasive technique based on optical microscopy was developed. Image processing
algorithms were implemented to extract metrical features characterizing cell structure and dendritic arborization. The morphological
features were analyzed in order to identify quantitative differences in Purkinje cell morphology due to interactions with
astrocytes. 相似文献
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Expression sites of genes encoding (13,14)--glucan 4-glucanohydrolase (EC 3.2.1.73) have been mapped in germinated barley grains (Hordeum vulgare L.) by hybridization histochemistry. A32P-labelled cDNA (copy DNA) probe was hybridized to cryosections of intact barley grains to localize complementary mRNAs. No mRNA encoding (13,14)--glucanase is detected in ungerminated grain. Expression of (13,14)--glucanase genes is first detected in the scutellum after 1 d and is confined to the epithelial layer. At this stage, no expression is apparent in the aleurone. After 2 d, levels of (13,14)--glucanase mRNA decrease in the scutellar epithelium but increase in the aleurone. In the aleurone layer, induction of (13,14)--glucanase gene expression, as measured by mRNA accumulation, progresses from the proximal to distal end of the grain as a front moving away from, and parallel to, the face of the scutellum.Abbreviations cDNA
copy DNA
- RNase
ribonuclease 相似文献
5.
A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera 总被引:14,自引:1,他引:13
Levels of mitochondrial DNA (mtDNA) sequence divergence between species
within each of several avian (Anas, Aythya, Dendroica, Melospiza, and
Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were
compared. An analysis of digestion profiles generated by 13-18 restriction
endonucleases indicates little overlap in magnitude of mtDNA divergence for
the avian versus nonavian taxa examined. In 55 interspecific comparisons
among the avian congeners, the fraction of identical fragment lengths (F)
ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these
translate into estimates of nucleotide sequence divergence (p) ranging from
0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F
values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater
than 0.070. The small mtDNA distances among avian congeners are associated
with protein-electrophoretic distances (D values) less than approximately
0.2, while the mtDNA distances among assayed fish and amphibian congeners
are associated with D values usually greater than 0.4. Since the
conservative pattern of protein differentiation previously reported for
many avian versus nonavian taxa now appears to be paralleled by a
conservative pattern of mtDNA divergence, it seems increasingly likely that
many avian species have shared more recent common ancestors than have their
nonavian taxonomic counterparts. However, estimates of avian divergence
times derived from mtDNA- and protein-calibrated clocks cannot readily be
reconciled with some published dates based on limited fossil remains. If
the earlier paleontological interpretations are valid, then protein and
mtDNA evolution must be somewhat decelerated in birds. The empirical and
conceptual issues raised by these findings are highly analogous to those in
the long-standing debate about rates of molecular evolution and times of
separation of ancestral hominids from African apes.
相似文献
6.
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
7.
A Nanci J P Ahluwalia S Zalzal C E Smith 《The journal of histochemistry and cytochemistry》1989,37(11):1619-1633
Biochemical and histochemical studies have shown the presence of various carbohydrates in enamel. Using lectin-gold cytochemistry, we have examined the distribution of glycoconjugates containing N-acetyl-D-galactosamine (GalNAc) and/or N-acetyl-glucosamine (GlcNAc)/N-acetyl-neuraminic acid (NeuNAc) residues in rat incisor ameloblasts and in forming and maturing enamel embedded in Lowicryl K4M, LR Gold, and LR White resins. The enamel proteins that contain these carbohydrate moieties were further characterized by lectin blotting. All three resins allowed, albeit to a variable degree, detection of the binding sites for Helix pomatia agglutinin (HPA) and wheat germ agglutinin (WGA) GalNAc, and GlcNAc/NeuNAc, respectively. In general, Lowicryl K4M permitted more intense reactions with both lectins. Lectin binding was observed over the rough endoplasmic reticulum (weak labeling with WGA), the Golgi apparatus, lysosomes, secretory granules, and the enamel matrix. These compartments were shown by double labeling with WGA and anti-amelogenin antibody, and by previous immunocytochemical studies, to contain enamel proteins. Furthermore, WGA binding was more concentrated at the growth sites of enamel. Lectin blotting showed that several proteins in the amelogenin group were glycosylated and contained the sugars GalNAc and GlcNAc/NeuNAc. Fewer proteins were stained by HPA than by WGA, and the staining pattern suggested that the extracellular proteins recognized by these two lectins are processed differently. The HPA-reactive proteins were lost by or during the early maturation stage, whereas many of the WGA-reactive proteins persisted into the mid maturation stage. The heterogeneous staining of certain protein bands observed with WGA suggests that they contain more than one component. Two distinct glycoproteins containing GlcNAc/NeuNAc also appeared during the maturation stage. These results are consistent with the notion that ameloblasts produce an extracellular matrix composed mainly of glycosylated amelogenins which are differently processed throughout amelogenesis. 相似文献
8.
Anonymous nuclear DNA markers in the American oyster and their implications for the heterozygote deficiency phenomenon in marine bivalves 总被引:4,自引:0,他引:4
A puzzling population-genetic phenomenon widely reported in allozyme
surveys of marine bivalves is the occurrence of heterozygote deficits
relative to Hardy-Weinberg expectations. Possible explanations for this
pattern are categorized with respect to whether the effects should be
confined to protein-level assays or are genomically pervasive and expected
to be registered in both protein- and DNA-level assays. Anonymous nuclear
DNA markers from the American oyster were employed to reexamine the
phenomenon. In assays based on the polymerase chain reaction (PCR), two
DNA-level processes were encountered that can lead to artifactual genotypic
scorings: (a) differential amplification of alleles at a target locus and
(b) amplification from multiple paralogous loci. We describe symptoms of
these complications and prescribe methods that should generally help to
ameliorate them. When artifactual scorings at two anonymous DNA loci in the
American oyster were corrected, Hardy-Weinberg deviations registered in
preliminary population assays decreased to nonsignificant values.
Implications of these findings for the heterozygote-deficit phenomenon in
marine bivalves, and for the general development and use of PCR-based
assays, are discussed.
相似文献
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