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1.
D J Méwissen J H Rust J Rust 《Comptes rendus des séances de la Société de biologie et de ses filiales》1987,181(4):439-444
A total of 2,377 C 57 Bl/6M mice were assigned to control groups and experimental groups exposed to tritiated water administered as a pulse injection or in drinking water, at a dose of 1.0 microCi per injection or per ml of drinking water. Weanlings were observed for the duration of life span. Data analysis was based on two coefficient estimates (1) individual carcinogenic induction coefficient and (2) specific tumorigenic induction coefficient. The carcinogenic potency of tritium was found to be dual in nature in enhancing the absolute induction of lymphocytic lymphomas in both sexes as well as their relative induction in competition with reticulo-endothelial tumors of other types. 相似文献
2.
Inhibition of methanogenesis in ruminal cultures was attempted by hindering thiamine availability through its degradation
by ‘polyphenols’ and competition for active sites on enzymes and transporters using thiamine structural analogs. Effects on
fermentation were small and not consistently reversed by adding thiamine. Lack of major effects of the compounds evaluated
could be due to intracellular synthesis of thiamine covering most requirements. 相似文献
3.
Sedimentation in fluvial and lacustrine environments 总被引:1,自引:1,他引:0
Sedimentation in rivers is dominated by a complex set of physical processes, associated with the unidirectional flow of water.
Variations in these processes give rise to different fluvial channel types, whose character can commonly be recognised in
the ancient record. Chemical and biological processes are comparatively unimportant in fluvial sedimentation.
In contrast, physical, chemical or biological processes can each dominate sedimentation in lakes. Physical (clastic) deposition
dominates in high-latitude and mountain lakes (in which chemical and biological activity are low), and in lakes with high
relief of the drainage basin and lake floor. Its variety reflects a range of processes influenced by river inflow, wave and
current action, thermal and density effects.
Economic benefits from the study of lake and river sedimentation include both resource and environmental aspects. An example
is given of a mercury pollution study in a fluvial ecosystem. It shows that return to background levels can take place within
a relatively short interval after cessation of pollutant input. 相似文献
4.
5.
Homozygous lymphoblastoid cell lines representing various Dw subtypes of DR2 were examined for polymorphism at the DQ
locus by molecular and cellular techniques. The subtypes studied included Dw2, Dw12, and a group heterogenous by cellular typing that we shall refer to as non-Dw2/non-Dw12. Restriction fragment length polymorphism analysis of cell lines representing these subtypes revealed DQ
-specific patterns consistent with cellular typing. Two-dimensional gel electrophoresis of DQ molecules from representative cell lines revealed a structural polymorphism of DQ
among the three subtypes. The DQ
chain migrated to a position that was unique to each subtype and was consistent among various representative cell lines of each subtype. Nucleotide sequence analysis of cDNA clones of DQ
from Dw2, Dw12, and non-Dw2/non-Dw12 lines confirmed that the variability resided at the genetic level. Variability was found in the form of numerous scattered nucleotide substitutions throughout the first domain of these alleles. The DQ
gene of the non-Dw2/non-Dw12 cell line AZH was further found to be almost identical with the DQ
gene of a DR1 line (Bell et al. 1985b), implicating a common evolutionary origin of these alleles. The only difference between these two sequences was due to an apparent gene conversion event at amino acid 57. T-cell cloning experiments resulted in the derivation of Epstein-Barr virus-specific, DQw1-restricted clones that proliferated against only those cell lines that exhibited the DQ
gene common to AZH and the DR1 cell line. Thus, the polymorphism among DQ
alleles within DR2 results in subtype-specific restriction. 相似文献
6.
7.
Infection of cat flea, Ctenocephalides felis, larvae by the entomophilic nematode Neoaplectana carpocapsae was accomplished in the laboratory. The Breton strain of N. carpocapsae provided higher larval mortality at lower dosages than did the DD-136 strain. Adult nematodes were evident in the insect hemocoel after 48 h; however, no infective third-stage larvae were produced. Larval flea infection increased with an increase in the moisture content of sand from 2% to 7% and of sandy clay from 7% to 12%. Larval flea infection was also obtained on turf containing dauer larvae. Nematode penetration of cocoons with invasion of prepupal and pupal fleas was apparent. 相似文献
8.
D J Mewissen A S Ugarte J H Rust 《Comptes rendus des séances de la Société de biologie et de ses filiales》1984,178(2):230-235
An heritable multiple intestinal adenocarcinoma was observed in the offspring of an outcross between a male (or female) parent originating from our C57 Black/6M strain and his female (or male) mating counterpart originating from an experimental subline of the same strain, propagated following multigeneration exposure of the male parent to low level tritium, as drinking water (10 microCi/ml) for 35 days prior to mating. 相似文献
9.
Screening assay for promigratory/antimigratory compounds 总被引:4,自引:0,他引:4
Large-scale screening strategies aimed at finding anticancer drugs traditionally focus on identifying cytotoxic compounds that attack actively dividing cells. Because progression to malignancy involves acquisition of an aggressively invasive phenotype in addition to hyperproliferation, simple and effective screening strategies for finding compounds that target the invasive aspects of cancer progression may prove valuable for identifying alternative and preventative cancer therapies. Here, we describe a fluorescence-based automated assay for identifying antimigratory compounds, with the ability to discern cytotoxic from noncytotoxic modes of action. With this assay, we analyzed the effects of two drugs on tumorigenic (MDA-MB-435) and nontumorigenic (MCF-10A) human breast cell lines. We chose to compare carboxyamidotriazole (CAI), an experimental compound shown to inhibit migration of various cell types, with tamoxifen, a common preventative and therapeutic anticancer compound. Our assay demonstrated that both these compounds inhibit migration at sublethal concentrations. Furthermore, CAI was more effective than tamoxifen at inhibiting chemotactic and haptotactic migration of both cell lines at all concentrations tested. 相似文献
10.
S-nitrosoglutathione reductase affords protection against pathogens in Arabidopsis, both locally and systemically 下载免费PDF全文
Nitric oxide and S-nitrosothiols (SNOs) are widespread signaling molecules that regulate immunity in animals and plants. Levels of SNOs in vivo are controlled by nitric oxide synthesis (which in plants is achieved by different routes) and by S-nitrosoglutathione turnover, which is mainly performed by the S-nitrosoglutathione reductase (GSNOR). GSNOR is encoded by a single-copy gene in Arabidopsis (Arabidopsis thaliana; Martínez et al., 1996; Sakamoto et al., 2002). We report here that transgenic plants with decreased amounts of GSNOR (using antisense strategy) show enhanced basal resistance against Peronospora parasitica Noco2 (oomycete), which correlates with higher levels of intracellular SNOs and constitutive activation of the pathogenesis-related gene, PR-1. Moreover, systemic acquired resistance is impaired in plants overexpressing GSNOR and enhanced in the antisense plants, and this correlates with changes in the SNO content both in local and systemic leaves. We also show that GSNOR is localized in the phloem and, thus, could regulate systemic acquired resistance signal transport through the vascular system. Our data corroborate the data from other authors that GSNOR controls SNO in vivo levels, and shows that SNO content positively influences plant basal resistance and resistance-gene-mediated resistance as well. These data highlight GSNOR as an important and widely utilized component of resistance protein signaling networks conserved in animals and plants. 相似文献