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51.
A Elbe E Tschachler G Steiner A Binder K Wolff G Stingl 《Journal of immunology (Baltimore, Md. : 1950)》1989,143(8):2431-2438
The adult murine epidermis harbors two separate CD45+ bone marrow (BM)-derived dendritic cell systems, i.e., Ia+, ADPase+, Thy-1-, CD3- Langerhans cells (LC) and Ia-, ADPase-, Thy-1+, CD3+ dendritic epidermal T cells (DETC). To clarify whether the maturation of these cells from their ill-defined precursors is already accomplished before their entry into the epidermis or, alternatively, whether a specific epidermal milieu is required for the expression of their antigenic determinants, we studied the ontogeny of CD45+ epidermal cells (EC). In the fetal life, there exists a considerable number of CD45+, Ia-, ADPase+ dendritic epidermal cells. When cultured, these cells become Ia+ and, in parallel, acquire the potential of stimulating allogeneic T cell proliferation. These results imply that CD45+, Ia-, ADPase+ fetal dendritic epidermal cells are immature LC precursors and suggest that the epidermis plays a decisive role in LC maturation. The day 17 fetal epidermis also contains a small population of CD45+, Thy-1+, ADPase-, CD3- round cells. Over the course of 2 to 3 wk, they are slowly replaced by an ever increasing number of round and, finally, dendritic CD45+, Thy-1+, CD3+ EC. Thus, CD45+, Thy-1+, ADPase-, CD3- fetal EC may either be DETC precursors or, alternatively, may represent a distinctive cell system of unknown maturation potential. According to this latter theory, these cells would be eventually outnumbered by newly immigrating CD45+, Thy-1+, CD3+ T cells--the actual DETC. 相似文献
52.
Helmut Wieczorek Gabriele Wolff 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1989,164(6):825-834
1. | The electrophysiology of the sugar receptor in labellar taste hairs ofDrosophila melanogaster (Diptera) was investigated using 33 monosaccharides, oligosaccharides, glucosides, and amino acids which in calyptrate flies are known to bind to specific receptor sites or which may be assigned to specific receptor sites on the basis of structural criteria. |
2. | The pyranose site ofDrosophila is very similar to the pyranose site of the calyptrate flies: regarding monosaccharides of the pyranose type three adjacent equatorial hydroxyl groups (C-2, C-3, C-4) seem to be important for stimulating effectiveness. On the other hand, it exhibits a more rigid stereospecificity with regard to the substituents at C-1 and C-5. |
3. | A furanose site as in calyptrate flies does not exist inDrosophila. First, D-galactose, phenylalanine and 2,5-anhydro-D-mannitol are not or nearly not stimulatory. Secondly, according to different sugar receptor responses after treatment of the taste hairs with papain, D-fucose binds to another receptor site than D-fructose. Thirdly, the effective conformation of D-fructose is not the furanose, but most probably the pyranose form as can be concluded from experiments with freshly prepared and equilibrium solutions of D-fructose. |
4. | The characteristic differences between the properties of the sugar receptors ofDrosophila and of the calyptrate flies lead to the suggestion that the actual number of types of receptor sites in the various fly species is greater than assumed up till now. The broad specificity of the sugar receptors of flies may therefore result from a mosaic of different types of highly specific receptor sites. |
53.
Analysis of chromosome 22 deletions in neurofibromatosis type 2-related tumors. 总被引:7,自引:0,他引:7
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R K Wolff K A Frazer R K Jackler M J Lanser L H Pitts D R Cox 《American journal of human genetics》1992,51(3):478-485
The neurofibromatosis type 2 (NF2) gene has been hypothesized to be a recessive tumor suppressor, with mutations at the same locus on chromosome 22 that lead to NF2 also leading to sporadic tumors of the types seen in NF2. Flanking markers for this gene have previously been defined as D22S1 centromeric and D22S28 telomeric. Identification of subregions of this interval that are consistently rearranged in the NF2-related tumors would aid in better defining the disease locus. To this end, we have compared tumor and constitutional DNAs, isolated from 39 unrelated patients with sporadic and NF2-associated acoustic neuromas, meningiomas, schwannomas, and ependymomas, at eight polymorphic loci on chromosome 22. Two of the tumors studied revealed loss-of-heterozygosity patterns, which is consistent with the presence of chromosome 22 terminal deletions. By using additional polymorphic markers, the terminal deletion breakpoint found in one of the tumors, an acoustic neuroma from an NF2 patient, was mapped within the previously defined NF2 region. The breakpoint occurred between the haplotyped markers D22S41/D22S46 and D22S56. This finding redefines the proximal flanking marker and localizes the NF2 gene between markers D22S41/D22S46 and D22S28. In addition, we identified a sporadic acoustic neuroma that reveals a loss-of-heterozygosity pattern consistent with mitotic recombination or deletion and reduplication, which are mechanisms not previously seen in studies of these tumors. This finding, while inconsistent with models of tumorigenesis that invoke single deletions and their gene-dosage effects, lends further support to the recessive tumor-suppressor model. 相似文献
54.
Characterization of Robertsonian translocations by using fluorescence in situ hybridization.
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Fluorescence in situ hybridization with five biotin-labeled probes (three alphoid probes, a probe specific for beta-satellite sequences in all acrocentric chromosomes, and an rDNA probe) was used to characterize 30 different Robertsonian translocations, including three t(13;13); one t(15;15), four t(21;21), three t(13;14), two t(13;15), two (13;21), two t(13;22), one t(14;15), eight t(14;21), two t(14;22), and two t(21;22). Of 8 de novo homologous translocations, only one t(13;13) chromosome was interpreted as dicentric, while 19 of 22 nonhomologous Robertsonian translocations were dicentric. The three monocentric nonhomologous translocations included both of the t(13;21) and one t(21;22). Two of 26 translocations studied using the beta-satellite probe showed a positive signal, while rDNA was undetectable in 10 cases studied. These results indicate that most homologous Robertsonian translocations appear monocentric, while the bulk of nonhomologous translocations show two alphoid signals. A majority of the breakpoints localized using this analysis seem to be distal to the centromere and just proximal to the beta-satellite and nuclear-organizing regions. 相似文献
55.
Discrete domains of human U6 snRNA required for the assembly of U4/U6 snRNP and splicing complexes. 总被引:17,自引:5,他引:12
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U6 snRNA sequences required for assembly of U4/U6 snRNP and splicing complexes were determined by in vitro reconstitution of snRNPs. Both mutagenesis and chemical modification/interference assays identify a U6 snRNA domain required for U4/U6 snRNP formation. The results support the existence of a U4/U6 snRNA interaction domain previously proposed on the basis of phylogenetic evidence. In addition, two short U6 snRNA regions flanking the U4/U6 interaction domain are essential to assemble the U4/U6 snRNP into splicing complexes. These two regions may represent binding sites for splicing factors or may facilitate the formation of an alternative U6 snRNA secondary structure during spliceosome assembly. 相似文献
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59.
The mouse lethal nonagouti (a(x)) mutation deletes the S-adenosylhomocysteine hydrolase (Ahcy) gene. 总被引:2,自引:0,他引:2
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M W Miller D M Duhl B M Winkes F Arredondo-Vega P J Saxon G L Wolff C J Epstein M S Hershfield G S Barsh 《The EMBO journal》1994,13(8):1806-1816
The lethal nonagouti (a(x)) mutation is a hypomorphic allele of the agouti coat color locus which, when homozygous, also leads to embryonic death around the time of implantation. To understand the molecular basis of these phenotypes, we identified and cloned a deletion breakpoint junction present in the ax chromosome. Long range restriction mapping demonstrated a simple deletion of approximately 100 kb, which does not affect agouti coding sequences, but begins only 4 kb 3' of the last exon, and thus may affect coat color by removing an agouti 3' enhancer. The Ahcy gene, which codes for the enzyme S-adenosylhomocysteine hydrolase (SAHase), is contained within a 20 kb region within the a(x) deletion. SAHase RNA and protein were detectable in early blastocysts and in embryonic stem cells, respectively, and analysis of embryos derived from an a(x)/a x a(x)/a embryo intercross indicated that a(x)/a embryos die between the late blastocyst and early implantation stages. Treatment of cultured embryos with an SAHase inhibitor, 3-deazaaristeromycin, or with metabolites that can result in elevated levels of cellular SAH, resulted in an inhibition of inner cell mass development, suggesting that loss of SAHase activity in a(x)/a(x) embryos is sufficient to explain their death around the time of implantation. 相似文献
60.
Analysis of centromeric activity in Robertsonian translocations: implications for a functional acrocentric hierarchy 总被引:2,自引:0,他引:2
Approximately 90% of human Robertsonian translocations occur between nonhomologous acrocentric chromosomes, producing dicentric elements which are stable in meiosis and mitosis, implying that one centromere is functionally inactivated or suppressed. To determine if this suppression is random, centromeric activity in 48 human dicentric Robertsonian translocations was assigned by assessment of the primary constrictions using dual color fluorescence in situ hybridzation (FISH). Preferential activity/constriction of one centromere was observed in all except three different rearrangements. The activity is meiotically stable since intrafamilial consistency of a preferentially active centromere existed in members of six families. These results support evidence for nonrandom centromeric activity in humans and, more importantly, suggest a functional hierarchy in Robertsonian translocations with the chromosome 14 centromere most often active and the chromosome 15 centromere least often active. 相似文献