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21.
Origin of the Thymidine Kinase Induced by Polyoma Virus in Productively Infected Cells 总被引:13,自引:4,他引:9
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Cells of the 3T3 mouse line efficiently supported the multiplication of polyoma virus, and the infectious process was accompanied by a marked increase in thymidine kinase (TK) activity. Two lines of 5-bromodeoxyuridine-resistant 3T3 cells have been isolated. As expected, these cells incorporated practically no exogenous thymidine into their deoxyribonucleic acid (DNA) and contained negligible TK activity. Like the parental 3T3 cells, TK(-) lines were susceptible to productive infection by polyoma virus, but infection did not lead to an increase in TK activity. Since kinase activity did appear after infection with another virus (vaccinia) known to contain the gene(s) for that enzyme, it is concluded that TK is not one of the gene products of polyoma virus. As induction of cellular DNA synthesis by polyoma virus occurs normally when the TK(-) cells are infected in the stationary phase, TK cannot play a role in the determination of this phenomenon. 相似文献
22.
Giovanna P. Marziani Longo Marcella Bracale Gianfranca Rossi Claudio P. Longo 《Plant molecular biology》1990,14(4):569-573
Cotyledons were excised from imbibed watermelon seeds, grown for 4 days in darkness on water or 10 M benzyladenine (BA) and then tested for the presence of the light-harvesting chlorophyll a/b protein (LHCP) and its mRNA. LHCP was assayed immunologically by western blotting of SDS gels: the protein was present in plastids, but it was not recovered with the thylakoid fraction. Antibodies directed against LHCP precipitated a 32 kDa polypeptide from translation products of poly(A) RNA of cotyledons only if these had been grown on BA. Taken together the data suggest that in absence of light cytokinins are necessary for the maintenance of a detectable level of LHCP-mRNA as well as for synthesis of the protein. 相似文献
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24.
In this article, a neural model for generating and learning a rapid ballistic movement sequence in two-dimensional (2D) space
is presented and evaluated in the light of some considerations about handwriting generation. The model is based on a central
nucleus (called a planning space) consisting of a fully connected grid of leaky integrators simulating neurons, and reading
an input vector Ξ (t) which represents the external movement of the end effector. The movement sequencing results in a succession of motor strokes
whose instantiation is controlled by the global activation of the planning space as defined by a competitive interaction between
the neurons of the grid. Constraints such as spatial accuracy and movement time are exploited for the correct synchronization
of the impulse commands. These commands are then fed into a neuromuscular synergy whose output is governed by a delta lognormal
equation. Each movement sequence is memorized originally as a symbolic engram representing the sequence of the principal reference
points of the 2D movement. These points, called virtual targets, correspond to the targets of each single rapid motor stroke
composing the movement sequence. The task during the learning phase is to detect the engram corresponding to a new observed
movement; the process is controlled by the dynamics of the neural grid.
Received: 16 March 1995/Accepted in revised form: 25 July 1995 相似文献
25.
26.
Identification of a gene that complements an Arabidopsis mutant deficient in chloroplast omega 6 desaturase activity. 总被引:3,自引:1,他引:2
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Membrane lipids of the fad6 (formerly fadC) mutant of Arabidopsis, which is deficient in chloroplast omega 6 desaturase activity, have increased levels of monounsaturated fatty acids and are deficient in trienoic fatty acids. A putative fad6 cDNA clone was isolated by probing a cDNA library with a degenerate oligonucleotide based on a conserved region within known omega 3 desaturase genes. Expression of the cDNA in transgenic plants of a fad6 mutant restored normal levels of all fatty acids. When used as a hybridization probe, the cDNA identified a restriction fragment-length polymorphism that co-segregated with the fad6 mutation. Thus, on the basis of a genetic complementation test and genetic map position, the fad6 gene is encoded by the cDNA. The cDNA encoded a 418-amino acid polypeptide of 47,727 D that displayed a high degree of sequence similarity to a delta 12 desaturase from the cyanobacterium Synechocystis. The fad6 gene exhibited less sequence homology to any known higher plant desaturase, including an endoplasmic reticulum-localized omega 6 desaturase corresponding to the Arabidopsis fad2 gene. 相似文献
27.
DNA supercoiling and thermal regulation of unsaturated fatty acid synthesis in Bacillus subtilis 总被引:4,自引:1,他引:3
Roberto Grau Daniela Gardiol Gerardo Claudio Glikin Diego de Mendoza 《Molecular microbiology》1994,11(5):933-941
Bacillus subtilis growing at 37° C synthesizes, almost exclusively, saturated fatty acids. However, when a culture growing at 37°C is transferred to 20°C, the synthesis of unsaturated fatty acids is induced. The addition of the DNA gyrase inhibitor novobiocin specifically prevented the induction of unsaturated fatty acid synthesis at 20° C. Furthermore, it was determined that plasmid DNA isolated from cells growing at 20°C was significantly more negatively supercoiled than the equivalent DNA isolated from cells growing at 37°C. The overall results agree with the hypothesis that an increase in DNA supercoiling associated with a temperature downshift could regulate the unsaturated fatty acids synthesis in B. subtilis. 相似文献
28.
Yves Thériault Thomas C. Pochapsky Claudio Dalvit Mark L. Chiu Stephen G. Sligar Peter E. Wright 《Journal of biomolecular NMR》1994,4(4):491-504
Summary Sequence-specific backbone 1H and 15N resonance assignments have been made for 95% of the amino acids in sperm whale myoglobin, complexed with carbon monoxide (MbCO). Many assignments for side-chain resonances have also been obtained. Assignments were made by analysis of an extensive series of homonuclear 2D spectra, measured with unlabeled protein, and both 2D and 3D 1H-15N-correlated spectra obtained from uniformly 15N-labeled myoglobin. Patterns of medium-range NOE connectivities indicate the presence of eight helices in positions that are very similar to those found in the crystal structures of sperm whale myoglobin. The resonance assignments of MbCO form the basis for determination of the solution structure and for hydrogen-exchange measurements to probe the stability and folding pathways of myoglobin. They will also form a basis for assignment of the spectra of single-site mutants with altered ligand-binding properties. 相似文献
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30.
Maja Wiprächtiger Melanie Haupt Andreas Froemelt Magdalena Klotz Claudio Beretta Dominik Osterwalder Vanessa Burg Stefanie Hellweg 《Journal of Industrial Ecology》2023,27(1):254-271
Industrial ecology (IE) methodologies, such as input/output or material flow analysis and life cycle assessment (LCA), are often used for the environmental evaluation of circular economy strategies. Up to now, an approach that utilizes these methods in a systematic, integrated framework for a holistic assessment of a geographic region's sustainable circular economy potential has been lacking. The approach developed in this study (IE4CE approach) combines IE methodologies to determine the environmental impact mitigation potential of circular economy strategies for a defined geographic region. The approach foresees five steps. First, input/output analysis helps identify sectors with high environmental impacts. Second, a refined analysis is conducted using material flow and LCA. In step 3, circular strategies are used for scenario design and evaluated in step 4. In step 5, the assessment results are compiled and compared across sectors. The approach was applied to a case study of Switzerland, analyzing 8 sectors and more than 30 scenarios in depth. Carbon capture and storage (CCS) from waste incineration, biogas and cement production, food waste prevention in households, hospitality and production, and the increased recycling of plastics had the highest mitigation potential. Most of the scenarios do not influence each other. One exception is the CCS scenarios: waste avoidance scenarios decrease the reduction potential of CCS. A combination of scenarios from different sectors, including their impact on the CCS scenario potential, led to an environmental impact mitigation potential of 11.9 Mt CO2-eq for 2050, which equals 14% of Switzerland's current consumption-based impacts. 相似文献