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1.
2.
Kazimierz S. Kasprzak Michael P. Waalkes Lionel A. Poirier 《Biological trace element research》1987,13(1):253-273
Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel
and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed
several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary
adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous
sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation.
Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of
this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances
in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit
nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent
influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but
not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention
of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found
to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium
binding to DNA in vitro. 相似文献
3.
Lionel Sibold Dominique Pariot Lakshmi Bhatnagar Marc Henriquet Jean-Paul Aubert 《Molecular & general genetics : MGG》1985,200(1):40-46
Summary Using the Southern hybridization technique, homologies were examined between restricted DNA of four methanogenic bacteria (Methanobacterium ivanovi, Methanobacterium thermoautotrophicum, Methanococcus voltae, Methanosarcina barkeri) and the nif (nitrogen fixation) genes of Klebsiella pneumoniae and Anabaena strain 7120. With K. pneumoniae probes, no hybridization was observed with nifA, nifNE, and nifJ but positive results were obtained with the nifHDK genes coding for nitrogenase. Homology was detected, in the four strains, with K. pneumoniae and Anabaena nifH probes. In M. voltae and M. ivanovi, the homology found with nifH was estimated to be about 70% and a weaker hybridization was observed also with nifD and nifK. In M. voltae, the sequence homologous to nifH was found on a 3.0 kbp HindIII fragment and sequences homologous to nifD and nifK on a 3.8 kbp HindIII fragment. The 3.0 kbp fragment was cloned and the region homologous to nifH was localized more precisely. When this fragment was used as a probe against other DNAs, it behaved as a K. pneumoniae and Anabaena nifH probe. The results suggest that the structural genes for nitrogenase may be present in archaebacteria and raise interesting questions regarding their evolution. 相似文献
4.
Structural Aspects of Saltatory Particle Movement 总被引:8,自引:0,他引:8
Lionel I. Rebhun 《The Journal of general physiology》1967,50(6):223-239
A variety of cells possess particles which show movements statistically different from Brownian movements. They are characterized by discontinuous jumps of 2–30 µ at velocities of 0.5–5 µ/sec or more. A detailed analysis of these saltatory, jumplike movements makes it most likely that they are caused by transmission of force to the particles by a fiber system in the cell outside of the particle itself. Work with isolated droplets of cytoplasm from algae demonstrates a set of fibers involved in both cytoplasmic streaming and saltatory motion, suggesting that both phenomena are related to the same force-generating set of fibers. Analysis of a variety of systems in which streaming and/or saltatory movement occurs reveals two types of fiber systems spatially correlated with the movement, microtubules and 50 A microfilaments. The fibers in Nitella (alga) are of the microfilament type. In other systems (melanocyte processes, mitotic apparatus, nerve axons) microtubules occur. A suggestion is made, based on work on cilia, that a microtubule-microfilament complex may be present in those cases in which only microtubules appear to be present, with the microfilament closely associated with or buried in the microtubule wall. If so, then microfilaments, structurally similar to smooth muscle filaments, may be a force-generating element in a very wide variety of saltatory and streaming phenomena. 相似文献
5.
6.
The mechanisms of chain selection and assembly of type IX collagen, a heterotrimer 1(IX)2(IX)3(IX), must differ from that of fibrillar collagens since it lacks the characteristic C-propeptide of these latter molecules. We have tested the hypothesis that the information required for this process is contained within the C-terminal triple helical disulfide-bonded region (LMW). The reassociations of the purified LMW fragments of pepsinized bovine type IX collagen were followed by the formation of disulfide-bonded multimers. Our data demonstrate that only three triple helical assemblies form readily, (1)3, (2)3, and 123. The information required for chain selection and assembly is thus, at least in part, contained in the studied fragments. Molecular stoichiometries different from the classical heterotrimer may thus also form under certain conditions. 相似文献
7.
Thelma Panaïotis Marcel Babin Tristan Biard François Carlotti Laurent Coppola Lionel Guidi Helena Hauss Lee Karp-Boss Rainer Kiko Fabien Lombard Andrew M. P. McDonnell Marc Picheral Andreas Rogge Anya M. Waite Lars Stemmann Jean-Olivier Irisson 《Global Ecology and Biogeography》2023,32(11):1991-2005
Aim
The distribution of mesoplankton communities has been poorly studied at global scale, especially from in situ instruments. This study aims to (1) describe the global distribution of mesoplankton communities in relation to their environment and (2) assess the ability of various environmental-based ocean regionalizations to explain the distribution of these communities.Location
Global ocean, 0–500 m depth.Time Period
2008–2019.Major Taxa Studied
Twenty-eight groups of large mesoplanktonic and macroplanktonic organisms, covering Metazoa, Rhizaria and Cyanobacteria.Methods
From a global data set of 2500 vertical profiles making use of the Underwater Vision Profiler 5 (UVP5), an in situ imaging instrument, we studied the global distribution of large (>600 μm) mesoplanktonic organisms. Among the 6.8 million imaged objects, 330,000 were large zooplanktonic organisms and phytoplankton colonies, the rest consisting of marine snow particles. Multivariate ordination (PCA) and clustering were used to describe patterns in community composition, while comparison with existing regionalizations was performed with regression methods (RDA).Results
Within the observed size range, epipelagic plankton communities were Trichodesmium-enriched in the intertropical Atlantic, Copepoda-enriched at high latitudes and in upwelling areas, and Rhizaria-enriched in oligotrophic areas. In the mesopelagic layer, Copepoda-enriched communities were also found at high latitudes and in the Atlantic Ocean, while Rhizaria-enriched communities prevailed in the Peruvian upwelling system and a few mixed communities were found elsewhere. The comparison between the distribution of these communities and a set of existing regionalizations of the ocean suggested that the structure of plankton communities described above is mostly driven by basin-level environmental conditions.Main Conclusions
In both layers, three types of plankton communities emerged and seemed to be mostly driven by regional environmental conditions. This work sheds light on the role not only of metazoans, but also of unexpected large protists and cyanobacteria in structuring large mesoplankton communities. 相似文献8.
M. Lionel Bender 《American anthropologist》1984,86(2):496-496
Book reviewed in this article:
Archeology: Archaeology as Human Ecology . Karl W. Butzer
Archeology: Environmental Archaeology . Myra Shackley 相似文献
Archeology: Archaeology as Human Ecology . Karl W. Butzer
Archeology: Environmental Archaeology . Myra Shackley 相似文献
9.
10.
André Dupont Lionel Cusan Marie Garon Gabriel Alvarado-Urbina Fernand Labrie 《Life sciences》1977,21(7):907-914
Thirty sec after the intrajugular injection of [3H] methionine-enkephalin (met-enkephalin) in the rat, the radioactivity was already distributed in an apparent volume of 53 ml and the metabolic clearance rate calculated from the characteristics of the plasma disappearance curve was 10 ml/min. As shown by partition chromatography plasma extracts obtained 15 sec after injection of [3H] met-enkephalin, only 5% of the total radioactivity migrated as the intact pentapeptide, while no detectable intact pentapeptide remained 2 min after injection, thus indicating a half-life of [3H] met-enkephalin of the order of 2 to 4 sec. Incubation of rat cerebral tissue with [3H] met-enkephalin indicates that the first step in the breakdown of met-enkephalin in both plasma and brain tissue is cleavage of the Tyr-Gly amide bond. These data offer an explanation for the low activity of met-enkephalin after intraventricular or intravenous administration. 相似文献