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1.
本文利用激光散斑屈光测试系统详细探讨了夜近视(night myopia)的产生机制。夜近视在环境亮度降低到产生暗视觉时出现,并随亮度继续降低而增大,平均值为1.35D。实验证明眼睛球差和色差不是造成夜近视的主要因素。夜近视数值在暗适应过程中呈增大的趋势。在暗视觉时,由于视野中缺少适宜的刺激,眼睛处于暗焦(dark focus)休止状态,这是造成夜近视的主要原因。 相似文献
2.
Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin 总被引:2,自引:0,他引:2 下载免费PDF全文
RK Draper D Chin D Eurey-Owens IE Scheffler MI Simon 《The Journal of cell biology》1979,83(1):116-125
We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells. 相似文献
3.
本文用脑室灌注和Fura2测定细胞内游离钙技术观察了地塞米松(dexamethasone,DEX)对家兔乙二醇双(2氨基乙醚)四乙酸性发热效应和下丘脑细胞内游离钙浓度([Ca2+]i)的影响,借此深入探讨地塞米松解热作用的中枢机制。结果发现:脑室灌注乙二醇双(2氨基乙醚)四乙酸(06nmol)引起家兔结肠温度明显升高,静脉注射地塞米松(5mg/kg)显著抑制家兔乙二醇双(2氨基乙醚)四乙酸性发热,地塞米松(60~120μmol/L)并不影响下丘脑细胞内[Ca2+]i,而事先脑室灌注抑制基因转录的放线菌素D(3nmol)则完全取消了地塞米松对乙二醇双(2氨基乙醚)四乙酸性发热的解热作用。这些结果提示:地塞米松显著抑制家兔乙二醇双(2氨基乙醚)四乙酸性发热,其机制与地塞米松激活脑内某些基因的表达有关,而与下丘脑神经细胞跨膜钙离子流无关。 相似文献
4.
IE Hughes 《BioEssays : news and reviews in molecular, cellular and developmental biology》1999,21(11):980-981
Instant Pharmacology (1999). Saeb-Parsy K, Assomull RG, Kahn FZ, Saeb-Parsy K, and Kelly E. John Wiley and Sons 349 pp. £19.99 pbk; ISBN 0471976393 © 1999 John Wiley & Sons, Inc. 相似文献
5.
Ng SH Artieri CG Bosdet IE Chiu R Danzmann RG Davidson WS Ferguson MM Fjell CD Hoyheim B Jones SJ de Jong PJ Koop BF Krzywinski MI Lubieniecki K Marra MA Mitchell LA Mathewson C Osoegawa K Parisotto SE Phillips RB Rise ML von Schalburg KR Schein JE Shin H Siddiqui A Thorsen J Wye N Yang G Zhu B 《Genomics》2005,86(4):396-404
A physical map of the Atlantic salmon (Salmo salar) genome was generated based on HindIII fingerprints of a publicly available BAC (bacterial artificial chromosome) library constructed from DNA isolated from a Norwegian male. Approximately 11.5 haploid genome equivalents (185,938 clones) were successfully fingerprinted. Contigs were first assembled via FPC using high-stringency (1e-16), and then end-to-end joins yielded 4354 contigs and 37,285 singletons. The accuracy of the contig assembly was verified by hybridization and PCR analysis using genetic markers. A subset of the BACs in the library contained few or no HindIII recognition sites in their insert DNA. BglI digestion fragment patterns of these BACs allowed us to identify three classes: (1) BACs containing histone genes, (2) BACs containing rDNA-repeating units, and (3) those that do not have BglI recognition sites. End-sequence analysis of selected BACs representing these three classes confirmed the identification of the first two classes and suggested that the third class contained highly repetitive DNA corresponding to tRNAs and related sequences. 相似文献
6.
Danke J Miyake T Powers T Schein J Shin H Bosdet I Erdmann M Caldwell R Amemiya CT 《Journal of experimental zoology. Part A, Comparative experimental biology》2004,301(3):228-234
We have generated a BAC library from the Indonesian coelacanth, Latimeria menadoensis. This library was generated using genomic DNA of nuclei isolated from heart tissue, and has an average insert size of 171 kb. There are a total of 288 384-well microtiter dishes in the library (110,592 clones) and its genomic representation is estimated to encompass > or = 7X coverage based on the amount of DNA presumably cloned in the library as well as via hybridization with probes to a small set of single copy genes. This genomic resource has been made available to the public and should prove useful to the scientific community for many applications, including comparative genomics, molecular evolution and conservation genetics. 相似文献
7.
Kelleher CT Chiu R Shin H Bosdet IE Krzywinski MI Fjell CD Wilkin J Yin T DiFazio SP Ali J Asano JK Chan S Cloutier A Girn N Leach S Lee D Mathewson CA Olson T O'connor K Prabhu AL Smailus DE Stott JM Tsai M Wye NH Yang GS Zhuang J Holt RA Putnam NH Vrebalov J Giovannoni JJ Grimwood J Schmutz J Rokhsar D Jones SJ Marra MA Tuskan GA Bohlmann J Ellis BE Ritland K Douglas CJ Schein JE 《The Plant journal : for cell and molecular biology》2007,50(6):1063-1078
As part of a larger project to sequence the Populus genome and generate genomic resources for this emerging model tree, we constructed a physical map of the Populus genome, representing one of the few such maps of an undomesticated, highly heterozygous plant species. The physical map, consisting of 2802 contigs, was constructed from fingerprinted bacterial artificial chromosome (BAC) clones. The map represents approximately 9.4-fold coverage of the Populus genome, which has been estimated from the genome sequence assembly to be 485 ± 10 Mb in size. BAC ends were sequenced to assist long-range assembly of whole-genome shotgun sequence scaffolds and to anchor the physical map to the genome sequence. Simple sequence repeat-based markers were derived from the end sequences and used to initiate integration of the BAC and genetic maps. A total of 2411 physical map contigs, representing 97% of all clones assigned to contigs, were aligned to the sequence assembly (JGI Populus trichocarpa , version 1.0). These alignments represent a total coverage of 384 Mb (79%) of the entire poplar sequence assembly and 295 Mb (96%) of linkage group sequence assemblies. A striking result of the physical map contig alignments to the sequence assembly was the co-localization of multiple contigs across numerous regions of the 19 linkage groups. Targeted sequencing of BAC clones and genetic analysis in a small number of representative regions showed that these co-aligning contigs represent distinct haplotypes in the heterozygous individual sequenced, and revealed the nature of these haplotype sequence differences. 相似文献
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9.
The distribution of the Golgi enzyme beta1, 6-N-
acetylglucosaminyltransferase (core 2 GlcNAc-T for short) has been
investigated in several tissue and cell systems by combining the potentials
of a polyclonal antibody and a novel, sensitive fluorescent enzyme assay.
In normal rat tissues, levels of the protein were found to vary and as a
general trend did not correlate with enzyme activities. Additionally, we
observed tissue-specific core 2 GlcNAc-T forms of various size: 75 kDa
(liver), 70 kDa (spleen), 60 kDA (heart), and 50 kDa (heart and lung).
These forms might arise from differential protein modifications;
alternatively, the smaller form may be a product of proteolytic cleavage,
given the presence of a catalytically inactive 50 kDa species in rat serum.
Chinese hamster ovary (CHO), MDAY-D2, PSA- 5E, and PYS-2 cell lines
consistently displayed a 70 kDa enzyme. When induced to retrodifferentiate
in the presence of butyrate + cholera toxin, CHO cells exhibited a 21-fold
increase in enzyme activity, while protein levels remained constant. A
similar trend was observed in the embryonal endoderm cell lines PSA-5E and
PYS-2, where an approximately 100-fold difference in core 2 GlcNAc-T
activity was found notwithstanding unchanged amounts of the protein and
identical mRNA levels, as evidenced by RT-PCR. In contrast, levels of core
2 GlcNAc-T activity in MDAY-D2 cells correlated well with protein
expression. Taken together, these observations demonstrate that core 2
GlcNAc-T expression may be subjected to multiple mechanisms of regulation
and suggest that in at least some instances (i.e., PSA-5E and PYS-2 cells)
expression may be regulated exclusively via posttranslational mechanism(s)
of control.
相似文献
10.
Snelling WM Chiu R Schein JE Hobbs M Abbey CA Adelson DL Aerts J Bennett GL Bosdet IE Boussaha M Brauning R Caetano AR Costa MM Crawford AM Dalrymple BP Eggen A Everts-van der Wind A Floriot S Gautier M Gill CA Green RD Holt R Jann O Jones SJ Kappes SM Keele JW de Jong PJ Larkin DM Lewin HA McEwan JC McKay S Marra MA Mathewson CA Matukumalli LK Moore SS Murdoch B Nicholas FW Osoegawa K Roy A Salih H Schibler L Schnabel RD Silveri L Skow LC Smith TP Sonstegard TS Taylor JF Tellam R 《Genome biology》2007,8(8):R165