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排序方式: 共有142条查询结果,搜索用时 203 毫秒
91.
Protein structure: a new strategy for sequence analysis 总被引:2,自引:0,他引:2
92.
Various factors are known to regulate cell growth and differentiation, but less is known of agents which affect movement and positioning, particularly in epithelial-mesenchymal interactions. Cultured human embryo fibroblasts release a protein with a relative molecular mass (Mr) of approximately 50,000 (50K) that affects epithelial cells by causing a disruption of junctions, an increase in local motility and a scattering of contiguous sheets of cells. To investigate specificity, a range of cells has been examined for the ability to produce the factor and for sensitivity to its action. Most freshly isolated normal epithelia and epithelia from cell lines of normal tissue, but not epithelia from tumour cell lines or fibroblasts, were sensitive to scatter factor. In contrast, production of the factor, as identified by activity and by chromatography, was restricted to embryonic fibroblasts and certain variants of 3T3 and BHK21 cells and their transformed derivatives. We conclude that the scatter factor is a paracrine effector of epithelial-mesenchymal interaction, which affects the intercellular connections and mobility of normal epithelial cells. The factor might be involved in epithelial migration, such as occurs in embryogenesis or wound healing. 相似文献
93.
Expression of human immune interferon cDNA in E. coli and monkey cells 总被引:118,自引:0,他引:118
P W Gray D W Leung D Pennica E Yelverton R Najarian C C Simonsen R Derynck P J Sherwood D M Wallace S L Berger A D Levinson D V Goeddel 《Nature》1982,295(5849):503-508
94.
Andrés E Askebjer P Bai X Barouch G Barwick SW Bay RC Becker KH Bergström L Bertrand D Bierenbaum D Biron A Booth J Botner O Bouchta A Boyce MM Carius S Chen A Chirkin D Conrad J Cooley J Costa CG Cowen DF Dailing J Dalberg E DeYoung T Desiati P Dewulf JP Doksus P Edsjö J Ekström P Erlandsson B Feser T Gaug M Goldschmidt A Goobar A Gray L Haase H Hallgren A Halzen F Hanson K Hardtke R He YD Hellwig M Heukenkamp H Hill GC Hulth PO Hundertmark S Jacobsen J Kandhadai V Karle A Kim J Koci B Köpke L 《Nature》2001,410(6827):441-443
Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations. 相似文献
95.
Nucleotide sequence of epidermal growth factor cDNA predicts a 128,000-molecular weight protein precursor 总被引:5,自引:0,他引:5
Epidermal growth factor (EGF) has a profound effect on the differentiation of specific cells in vivo, and has been shown to be a potent mitogenic factor for a variety of cultured cells, of both ectodermal and mesodermal origin (see ref. 1 for review). This 53-amino acid polypeptide of known sequence contains six cysteine residues, which are thought to form three intrachain disulphide bonds. Urogastrone, a polypeptide bearing anti-gastric secretory activity isolated from human urine, which is presumably synthesized in submandibular and Brunner's glands, shares extensive sequence homology (70%) with EGF and may represent the human EGF equivalent. Here we present the sequence of a mouse EGF cDNA clone, which suggests that EGF is synthesized as a large protein precursor of 1,168 amino acids. Our data indicate that the discrepancy between EGF levels in male and female mouse submaxillary glands (MSGs) is due to different EGF mRNA levels in these tissues, and suggest that precursor EGF processing may differ from that described previously for other polypeptide hormones. 相似文献
96.
Structure of the human immune interferon gene 总被引:62,自引:0,他引:62
Sequence determination of cloned cDNAs and genes of the three classes of interferon (IFN-alpha, -beta and -gamma) has revealed more than a dozen members of the human IFN-alpha gene family and a single gene for IFN-beta. These genes are found on chromosome 9 and contain no introns. We recently reported that the 146-amino acid sequence of mature IFN-gamma deduced from the nucleotide sequence of a cloned cDNA was quite unrelated to those of the other IFNs, and that the gene for IFN-gamma contains at least one intron. We now describe the isolation, characterization and DNA sequence of the human IFN-gamma gene. It contains three introns, a repetitive DNA element, and is not highly polymorphic. All our evidence to date and the present data suggest that this is the only gene for IFN-gamma and that the resolution of IFN-gamma into two components is probably the result of post-translational processing of the protein. 相似文献
97.
98.
This paper is the second part of an investigation into Babylonian non-mathematical astronomical texts and the relationships
between Babylonian observational and predicted astronomical data. Part I (Gray and Steele 2008) showed that the predictions
found in the Almanacs and Normal Star Almanacs were almost certainly made by applying Goal-Year periods to observations recorded
in the Goal-Year Texts. The paper showed that the differences in dates of records between the Goal-Year Texts and the Almanacs
or Normal Star Almanacs were consistent with the date corrections of a few days which, according to theoretical calculations,
should be added to allow for the inexactness of Goal-Year periods. The current paper follows on from our earlier study to
consider the effect of the Babylonian calendar on Goal-Year methods of prediction. Due to the fact that the Babylonian calendar
year can contain either 12 or 13 months, a Goal-Year period can occasionally be month longer or shorter than usual. This suggests
that there should in theory be certain points in the Metonic intercalation cycle where a predicted event occurs one Babylonian
month earlier or later than the corresponding event a Goal-Year period later. By comparing dates of lunar and planetary records
in the Astronomical Diaries, Goal-Year Texts, Almanacs and Normal Star Almanacs, we show that these month differences between
the observational records and the predictions occur in the expected years. This lends further support to the theory that the
Almanacs’ and Normal Star Almanacs’ predictions originated from records in the Goal-Year Texts, and clarifies how the Goal-Year
periods were used in practice. 相似文献
99.
Two classes of molecules often released after the interaction of T lymphocytes, macrophages and antigen are B-cell maturation factors (BMF)1-3 and immune (gamma) interferon (IFN-gamma)4-7. BMFs directly induce the maturation of resting B lymphocytes to the state of active immunoglobulin secretion, while IFN-gamma is defined by the reduction of viral infectivity in vitro. However, interferons have been shown to have a variety of effects and they have also been reported both to increase and decrease B-cell differentiation in intact animals and complex cellular mixtures in vitro. Here we show that murine IFN-gamma produced by recombinant DNA technology shows similar biological effects to BMFs from two other sources. All three preparations induce immunoglobulin secretion by both normal resting murine splenic B cells and the comparable B-cell tumour line WEHI-279.1 (refs 1, 3). IFN-gamma and the other two BMFs are not identical, however, as anti-IFN-gamma antibodies block the effects on B cells of IFN-gamma, but not those of the other two lymphokines. IFN-gamma may be one of several molecules with a direct role in driving the maturation of resting B cells to active immunoglobulin secretion. 相似文献
100.