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991.
Inequality in mutation rates of the two strands of DNA 总被引:4,自引:0,他引:4
As the mechanisms for replicating the two strands of duplex DNA differ it is, in principle, possible for the mutation rates to differ depending on which strand is being copied. In the absence of selection this would lead to a difference in the measured rate of a particular base substitution, such as T to C, depending on which DNA strand was analysed to determine the rate. Thus a change such as T to C on one DNA strand results from either a direct T-to-C mutation on that strand or an A-to-G mutation on the complementary strand; for the other strand the situation is reversed, and it can be seen that different processes are responsible for the two cases, allowing for asymmetry in substitution rate. We have tested whether such asymmetry indeed occurs by studying equivalent sequences from the beta-globin complexes of six species of primate. Our results reveal an asymmetry in substitution rates consistent with predictions based on strand-inequalities in mutation rates. Our sequence comparisons also allow us to make predictions about the positions of replication origins and the replication error rates of one strand relative to the other. 相似文献
992.
Protein kinases mediate nitric oxide-induced apoptosis in the insect cell line IPLB-LdFB 总被引:2,自引:0,他引:2
The involvement of protein kinases (PKA, PKC and PKB) in nitric oxide (NO)-induced apoptosis with sodium nitroprusside plus
N-acetyl-L-cysteine in the IPLB-LdFB cell line from the insect Lymantria dispar was investigated. The presence of protein kinase-like molecules was demonstrated by western blot analysis. The role of the
kinases in programmed cell death was analysed in cytofluorimetric experiments by incubating the insect cells with H-89 (a
specific inhibitor of PKA), calphostin C (an inhibitor of PKC) or wortmannin (an inhibitor of phosphatidylinositol 3-kinase).
The results show that PKA is correlated with the induction and PKC and PKB with the prevention of NO-induced insect cell death.
Moreover, NO-induced apoptosis involves the release of cytochrome c.
Received 15 March 2002; accepted 25 March 2002 相似文献
993.
RAGE is a multiligand receptor of the immunoglobulin superfamily: implications for homeostasis and chronic disease 总被引:19,自引:0,他引:19
Bucciarelli LG Wendt T Rong L Lalla E Hofmann MA Goova MT Taguchi A Yan SF Yan SD Stern DM Schmidt AM 《Cellular and molecular life sciences : CMLS》2002,59(7):1117-1128
Receptor for AGE (RAGE) is a member of the immunoglobulin superfamily that engages distinct classes of ligands. The biology of RAGE is driven by the settings in which these ligands accumulate, such as diabetes, inflammation, neurodegenerative disorders and tumors. In this review, we discuss the context of each of these classes of ligands, including advance glycation end-products, amyloid beta peptide and the family of beta sheet fibrils, S100/calgranulins and amphoterin. Implications for the role of these ligands interacting with RAGE in homeostasis and disease will be considered. 相似文献
994.
Morphine 6 glucuronide stimulates nitric oxide release in mussel neural tissues: evidence for a morphine 6 glucuronide opiate receptor subtype 总被引:1,自引:0,他引:1
Mantione K Zhu W Rialas C Casares F Cadet P Franklin AL Tonnesen J Stefano GB 《Cellular and molecular life sciences : CMLS》2002,59(3):570-574
We have previously demonstrated that Mytilus edulis pedal ganglia contain opiate alkaloids, i.e., morphine and morphine 6 glucuronide (M6G), as well as mu opiate receptor subtype
fragments exhibiting high sequence similarity to those found in mammals. Now we demonstrate that M6G stimulates pedal ganglia
constitutive nitric oxide (NO) synthase (cNOS)-derived NO release at identical concentrations and to similar peak levels as
morphine. However, the classic opiate antagonist, naloxone, only blocked the ability of morphine to stimulate cNOS-derived
NO release and not that of M6G. CTOP, a mu-specific antagonist, blocked the ability of M6G to induce cNOS-derived NO release
as well as that of morphine, suggesting that a novel mu opiate receptor was present and selective toward M6G. In examining
a receptor displacement analysis, both opiate alkaloids displaced [3H]-dihydromorphine binding to the mu opiate receptor subtype. However, morphine exhibited a twofold higher affinity, again
suggesting that a novel mu opiate receptor may be present.
Received 1 November 2001; received after revision 1 February 2002; accepted 1 February 2002 相似文献
995.
The Ror receptor tyrosine kinase family 总被引:6,自引:0,他引:6
Forrester WC 《Cellular and molecular life sciences : CMLS》2002,59(1):83-96
Receptor tyrosine kinases (RTKs) participate in numerous developmental decisions. Ror RTKs are a family of orphan receptors
that are related to muscle specific kinase (MuSK) and Trk neurotrophin receptors. MuSK assembles acetylcholine receptors at
the neuromuscular junction [1, 2], and Trk receptors function in the developing nervous system (reviewed in [3-5]). Rors have
been identified in nematodes, insects and mammals. Recent studies have begun to shed light on Ror function during development.
In most species, Rors are expressed in many tissue types during development. Analyses of mutants that are defective in the
single nematode Ror demonstrate a role in cell migration and in orienting cell polarity. Mice lacking one of the two Ror gene
products display defects in bone and heart formation. Similarly, two different human bone development disorders, dominant
brachydactyly B and recessive Robinow syndrome, result from mutations in one of the human Ror genes.
Received 17 April 2001; received after revision 2 July 2001; accepted 4 July 2001 相似文献
996.
Microbial cycling of volatile organic sulfur compounds 总被引:7,自引:0,他引:7
Lomans BP van der Drift C Pol A Op den Camp HJ 《Cellular and molecular life sciences : CMLS》2002,59(4):575-588
Microbial cycling of volatile organic sulfur compounds (VOSCs), especially dimethyl sulfide (DMS) and methanethiol (MT), is intensively studied because these compounds play an important role in the processes of global warming, acid precipitation, and the global sulfur cycle. VOSC concentrations in freshwater sediments are low due to the balance between the formation and degradation of these compounds. These reactions occur for the greater part at the oxic/anoxic interphase of sediment and water column. In contrast to marine ecosystems, where dimethylsulfoniopropionate is the main precursor of MT and DMS, in freshwater ecosystems, VOSCs are formed mainly by methylation of sulfide and to a lesser extent from the degradation of S-containing amino acids. One of the major routes for DMS and MT formation through sulfide methylation is anaerobic O-demethylation of methoxylated aromatic compounds. Inhibition studies have revealed that the major part of the endogenously produced MT and DMS is degraded anaerobically by methanogens. The major bacterial groups involved in formation and consumption of VOSCs are described. 相似文献
997.
HIV-1 superinfection despite broad CD8+ T-cell responses containing replication of the primary virus 总被引:21,自引:0,他引:21
Altfeld M Allen TM Yu XG Johnston MN Agrawal D Korber BT Montefiori DC O'Connor DH Davis BT Lee PK Maier EL Harlow J Goulder PJ Brander C Rosenberg ES Walker BD 《Nature》2002,420(6914):434-439
Early treatment of acute HIV-1 infection followed by treatment interruptions has shown promise for enhancing immune control of infection. A subsequent loss of control, however, allows the correlates of protective immunity to be assessed. Here we show that sudden breakthrough of plasma viraemia occurred after prolonged immune containment in an individual infected with HIV-1 at a time when 25 distinct CD8+ T-cell epitopes in the viral proteins Gag, RT, Integrase, Env, Nef, Vpr, Vif and Rev were being targeted. Sequencing of the virus in plasma and cells showed that superinfection with a second clade-B virus was coincident with the loss of immune control. This sudden increase in viraemia was associated with a decline in half of the CD8+ T-cell responses. The declining CD8+ T-cell responses were coupled with sequence changes relative to the initial virus that resulted in impaired recognition. Our data show that HIV-1 superinfection can occur in the setting of a strong and broadly directed virus-specific CD8+ T-cell response. The lack of cross-protective immunity for closely related HIV-1 strains, despite persistent recognition of multiple CD8 epitopes, has important implications for public health and vaccine development. 相似文献
998.
999.
Wabnitz H Bittner L de Castro AR Döhrmann R Gürtler P Laarmann T Laasch W Schulz J Swiderski A von Haeften K Möller T Faatz B Fateev A Feldhaus J Gerth C Hahn U Saldin E Schneidmiller E Sytchev K Tiedtke K Treusch R Yurkov M 《Nature》2002,420(6915):482-485
Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion. 相似文献
1000.
Numerous potentially functional but non-genic conserved sequences on human chromosome 21 总被引:28,自引:0,他引:28
Dermitzakis ET Reymond A Lyle R Scamuffa N Ucla C Deutsch S Stevenson BJ Flegel V Bucher P Jongeneel CV Antonarakis SE 《Nature》2002,420(6915):578-582
The use of comparative genomics to infer genome function relies on the understanding of how different components of the genome change over evolutionary time. The aim of such comparative analysis is to identify conserved, functionally transcribed sequences such as protein-coding genes and non-coding RNA genes, and other functional sequences such as regulatory regions, as well as other genomic features. Here, we have compared the entire human chromosome 21 with syntenic regions of the mouse genome, and have identified a large number of conserved blocks of unknown function. Although previous studies have made similar observations, it is unknown whether these conserved sequences are genes or not. Here we present an extensive experimental and computational analysis of human chromosome 21 in an effort to assign function to sequences conserved between human chromosome 21 (ref. 8) and the syntenic mouse regions. Our data support the presence of a large number of potentially functional non-genic sequences, probably regulatory and structural. The integration of the properties of the conserved components of human chromosome 21 to the rapidly accumulating functional data for this chromosome will improve considerably our understanding of the role of sequence conservation in mammalian genomes. 相似文献