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排序方式: 共有322条查询结果,搜索用时 15 毫秒
1.
I Barrai R Barale C Scapoli P Ambrosino M Beretta C Sbrana R Micheletti N Loprieno 《Mutation research》1992,267(2):173-182
The statistical methods for the analysis of mutagenicity and carcinogenicity underwent considerable theoretical-practical development following the need for assessing the mutagenic and carcinogenic potential of substances. Antimutagenicity is investigated through the analysis of respondents in dose-response assays, when two different molecules are administered separately and as a mixture to a respondent system. When the number of respondent units is high, and doses are orthogonal, it is possible to apply simple models such as analysis of variance. This is not always possible or common, and alternative approaches have been developed, based on multiple regression and on tables of proportions. In this work, some of the most frequently used methods for the assessment of joint responses are reviewed, particularly those based on multiple regression, such as the method of Shaeffer et al. and the method of Hass et al. In order to illustrate these methods, joint responses of perylene and cyclopentapyrene, of N-acetylcysteine and dinitropyrene, and of N-acetylcysteine and extracts from diesel exhausts were analyzed. An antagonistic effect of perylene on the action of CPP was detected by the algorithm of Shaeffer et al. The effect is not multiplicative, i.e., it is not proportional to the product of doses. The antimutagenic effect of N-acetylcysteine on dinitropyrene is multiplicative, as detected by the method of Hass et al. The latter reveals that the inhibition by N-acetylcysteine on the mutagenic effect of extracts from diesel exhausts is also multiplicative. 相似文献
2.
In this paper we consider the stability property of single-species patches connected by diffusion with a within-patch dynamics
of Volterra type and with continuous time delays. We prove that this system can only have two kinds of equilibria: the positive
and the trivial one. By the assumption that the delay kernels are convex combinations of suitable non-negative and normalized
functions, the linear chain trick gives an expanded system of O.D.E. with the same stability properties as the original integro-differential
system. Homotopy function techniques provide sufficient conditions for the existence of the positive equilibrium and for its
global stability. We also prove the local stability of any positive equilibrium and the local instability both of positive
and trivial equilibria. The biological meanings of the results obtained are compared with known results from the literature.
This work was performed under the auspices of G.N.F.M., C.N.R. (Italy) and within the activity of the Evolution Equations
and Applications group, M.P.I. (Italy).
I thank the Department of Applied Mathematics, Shizuoka University, Japan, which enabled me to visit Urbino. 相似文献
3.
We study a system of two integrodifierential equations which models the evolution of a biotic species feeding on an abiotic resource. We also consider nutrient recycling with time delay. By Hopf bifurcation theory we prove the existence of stable oscillations for a range of values of the input of nutrients.Work performed within the activity of the research group Evolution Equations and Physico-Mathematical Applications, M.P.I. (Italy), and under the auspices of G.N.F.M., C.N.R. (Italy) 相似文献
4.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
5.
Polsinelli, M. (University of Pavia, Pavia, Italy), and Maria Beretta. Genetic recombination in crosses between Streptomyces aureofaciens and Streptomyces rimosus. J. Bacteriol. 91:63-68. 1966.-Biochemical mutants were obtained from Streptomyces rimosus and S. aureofaciens by ultraviolet irradiation. Crosses were performed between auxotrophic strains of S. rimosus and S. aureofaciens with positive results. Data are reported which indicate that the interaction observed in some crosses is due to gene recombination. 相似文献
6.
A single cDNA encodes two isoforms of stathmin, a developmentally regulated neuron-enriched phosphoprotein 总被引:6,自引:0,他引:6
V Doye F Soubrier G Bauw M C Boutterin L Beretta J Koppel J Vandekerckhove A Sobel 《The Journal of biological chemistry》1989,264(21):12134-12137
Stathmin, a 19-kDa neuron-enriched soluble phosphoprotein, has been recently proposed as an ubiquitous intracellular relay for the diverse extracellular signals regulating cell proliferation, differentiation, and functions through various second messenger pathways (Sobel, A., Boutterin, M.C., Beretta, L., Chneiweiss, H., Doye, V., and peyro-Saint-Paul, H. (1989) J. Biol. Chem. 264, 3765-3772). Internal sequences of the protein from rat brain were determined after purification by two-dimensional polyacrylamide gel electrophoresis, electrotransfer onto Immobilon, and in situ proteolysis. Oligonucleotide mixtures based on these sequences were used to clone a cDNA for stathmin from a rat PC12 cell lambda gt 10 library. The deduced amino acid sequence reveals partial homologies with the coiled coil structural regions of several intracellular matrix phosphoproteins. Using this cDNA as a probe, we show that the expression of stathmin mRNA parallels that of the protein during brain ontogenesis, reaching a maximum at the neonatal stage. In vitro translation of the derived cRNA yielded all the known molecular forms of stathmin, namely its alpha and beta isoforms in their unphosphorylated and phosphorylated states. Thus, a single cDNA codes for both biologically relevant isoforms of the protein, indicating that they differ by co- or post-translational modifications. 相似文献
7.
D. Sanglard I. Beretta M. Wagner O. K ppeli A. Fiechter 《Biocatalysis and Biotransformation》1990,4(1):19-28
The genes for the alkane-inducible monooxygenase system of the yeast Candida tropicalis, namely a cytochrome P450alk (P450alk) and a NADPH cytochrome P450 oxidoreductase (NCPR) gene, were transferred in Saccharomyces cerevisiae. The P450alk gene was expressed in this host with the help of the yeast alcohol dehydrogenase I (ADHI) promoter and terminator, whereas the NCPR gene could be expressed with its own structural elements. The presence of P450alk in S. cerevisiae microsomal fractions resulted in a new acquired lauric acid terminal hydroxylation activity. Moreover, the same activity, coupled with the appearance of 12-hydroxylauric acid derivatives, could be obtained by the addition of lauric acid to intact cells expressing P450alk. The coordinate expression of the P450alk and NCPR genes in S. cerevisiae elevated the turnover rate of the P450alk monooxygenase activity about 2-fold. 相似文献
8.
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
9.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
10.
Molecular phylogeny and divergence times of drosophilid species 总被引:32,自引:15,他引:17
The phylogenetic relationships and divergence times of 39 drosophilid
species were studied by using the coding region of the Adh gene. Four
genera--Scaptodrosophila, Zaprionus, Drosophila, and Scaptomyza (from
Hawaii)--and three Drosophila subgenera--Drosophila, Engiscaptomyza, and
Sophophora--were included. After conducting statistical analyses of the
nucleotide sequences of the Adh, Adhr (Adh-related gene), and nuclear rRNA
genes and a 905-bp segment of mitochondrial DNA, we used Scaptodrosophila
as the outgroup. The phylogenetic tree obtained showed that the first major
division of drosophilid species occurs between subgenus Sophophora (genus
Drosophila) and the group including subgenera Drosophila and Engiscaptomyza
plus the genera Zaprionus and Scaptomyza. Subgenus Sophophora is then
divided into D. willistoni and the clade of D. obscura and D. melanogaster
species groups. In the other major drosophilid group, Zaprionus first
separates from the other species, and then D. immigrans leaves the
remaining group of species. This remaining group then splits into the D.
repleta group and the Hawaiian drosophilid cluster (Hawaiian Drosophila,
Engiscaptomyza, and Scaptomyza). Engiscaptomyza and Scaptomyza are tightly
clustered. Each of the D. repleta, D. obscura, and D. melanogaster groups
is monophyletic. The splitting of subgenera Drosophila and Sophophora
apparently occurred about 40 Mya, whereas the D. repleta group and the
Hawaiian drosophilid cluster separated about 32 Mya. By contrast, the
splitting of Engiscaptomyza and Scaptomyza occurred only about 11 Mya,
suggesting that Scaptomyza experienced a rapid morphological evolution. The
D. obscura and D. melanogaster groups apparently diverged about 25 Mya.
Many of the D. repleta group species studied here have two functional Adh
genes (Adh-1 and Adh-2), and these duplicated genes can be explained by two
duplication events.
相似文献