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61.
Edward W. Khandjian Consuelo Salomon Nicole Lonard Sandra Tremblay Hans Türler 《Experimental cell research》1992,202(2):464-470
To study alterations in cellular gene expression in mouse kidney cell cultures infected with simian virus 40 (SV40) or polyomavirus, we performed a differential screening of a mouse kidney cDNA library with probes prepared from mRNAs of virus-infected and mock-infected cells. We isolated and characterized cDNA recombinant pKT13 which detected increased mRNA levels in infected cells. Sequence analysis of pKT13 revealed close to 100% homology with the 3'-end of mouse fibronectin (FN) mRNA. Since primary cultures of baby mouse kidney cells have been extensively characterized in our laboratories, we studied FN gene expression at different stages of uninfected and virus-infected cultures. High levels of FN and of its mRNA were found in the kidneys of suckling mice, while in primary cultures of proliferating epithelial kidney cells the expression of FN was very low until the cultures became confluent. Thereafter FN increased and reached high levels in cells which were irreversibly arrested in phase Go and which had apparently exhausted their finite division potential. Infection of confluent cultures with polyomavirus or SV40 resulted in a further stimulation of FN gene expression. However, during abortive infection with SV40, FN mRNA and FN levels decreased with emergence of transformed cells and were low in an established SV40-transformed mouse kidney cell line. These changes in FN gene expression suggest that high levels of FN might be indicative in vivo for terminal differentiation and in vitro for cellular senescence. 相似文献
62.
Drosophila embryonic cells were exposed to a number of metal ions that have been previously reported to act as teratogens in mammalian systems, including some known to induce heat shock (stress) proteins in a variety of model systems. This study examined the effects of these ions both on differentiation of muscles and neurons and on the induction of heat shock proteins. Metals such as arsenate, cadmium, and mercury all inhibited neuron and/or muscle differentiation in Drosophila embryonic cultures, while they also induced the entire set of heat shock proteins. Two metal ions, nickel and zinc, were shown to induce only the 22-and 23-K proteins, a pattern similar to that seen in “classical” teratogens reported previously. None of the metals tested induced only the 26-and 27-K proteins. These results suggest that there exist different regulatory mechanisms responsible for the heat shock response. 相似文献
63.
Nicole Lair 《Hydrobiologia》1990,194(1):1-12
Saline playa lakes represent major geomorphic and hydrologic components of internal drainage basins in the arid to semiarid interior of Australia. These lakes mark the outcrop areas of regional shallow groundwater; thus, they are effective hydro-chemical sinks for elemental concentration and authigenic formation of carbonate, evaporite, and silica/silicate minerals.Field observations and petrochemical characterization of playa sediments from drainage basins in Western and Central Australia indicate that localized discharge of groundwater, from shallow aquifers in calcrete deposits, plays a fundamental role in geochemical evolution of playa-lake marginal facies. The available data indicates also that although evaporative concentration and salt recycling are major controls on geochemistry of the playas, yet a simple evaporative concentration model does not provide a complete explanation for brine evolution and particularly the geochemical process-product relationships observed in the individual playa lakes. The distribution of the chemical facies in the playas, in relation to geomorphic setting of the internal drainage basins, reflects a significant impact of variation in groundwater discharge pattern on the geochemical evolution of the playa lakes. Accordingly, the development of chemical facies in individual playas have progressed through repeated episodes of evaporative concentration, groundwater-level fluctuations and ion-exchange processes. 相似文献
64.
65.
Ganglioside distribution was studied in peripheral nerves of normal controls and those of Trembler mutant mouse with defect in Schwann cell differentiation and myelination. Neuraminic acid content was considerably decreased in the mutant. Ganglioside distribution as evaluated by densitometry of resorcinol positive spots on thin-layer chromatography revealed a major peak for GDla in normal controls. In the mutant, the relative proportion was modified with qualitative modifications in the GDla area and a tremendous increase in GM3 content. The relation with the intense Schwann cell proliferation observed in the mutant is discussed. 相似文献
66.
A simple procedure to label individual tRNA species in a total tRNA preparation has been developed. The principle of the method is as follows: total crude tRNA (from E. coli) is incubated in the presence of a crude aminoacyl-tRNA synthetase preparation, containing most aminoacyl-tRNA synthetases and only one specific amino acid corresponding to the tRNA species which is intended to be labelled. This achieves the purpose of charging the desired tRNA species thereby protecting its 3'OH-terminus; obviously all the other tRNA species will have a free 3'OH group. Periodate oxidation, followed by beta-elimination, destroys any free 3'OH. After deacylation of the specific aminoacylated tRNA at pH 8.8 the only free 3'OH group will be the one of the desired tRNA species. High specific activity (32P)-pCp is ligated to this 3'OH by means of T4-RNA ligase. Two-dimensional polyacrylamide gel electrophoresis (2D-PGE) and sequence analysis of the isolated tRNA show that the method is very specific. Individually labelled tRNA species can be used as probes for cloning tRNA genes. 相似文献
67.
ATP promotes 45Ca uptake by the microsomal fraction from the longitudinal smooth muscle of guinea-pig ileum and this uptake is stimulated by oxalate. As the microsomal fraction is made up of various subcellular entities, we examined the localization of the Ca2+-transport activity by density gradient centrifugation, taking advantage of the selective effect of digitonin (at low concentration) on the density of plasmalemmal elements. When the 45Ca-uptake activity was measured in the absence of oxalate, its behavior in subfractionation experiments closely paralleled that of the plasmalemmal marker 5′-nucleotidase. In contrast, the additional Ca2+-transport activity elicited by oxalate behaved like NADH-cytochrome reductase, a putative endoplasmic reticulum marker. The endoplasmic reticulum vesicles constituted only a small part of the membranes in the microsomal fraction, which explains that their Ca2+-storage capacity was not detectable in the absence of Ca2+-trapping agent. Low digitonin concentrations selectively increased the Ca2+ permeability of the plasmalemmal vesicles. The two Ca2+-transport activities were further differentiated by their distinct sensitivities to K+, vanadate and calmodulin. In this respect, the oxalte-insensitive and oxalate-stimulated Ca2+-transport systems resembled, respectively, the sarcolemmal and sarcoplasmic reticulum Ca2+ pumps in cardiac and skeletal muscle, in accordance with the subcellular locations established by density gradient centrifugation. 相似文献
68.
The structure of cyanobacterial phycobilisomes: a model 总被引:7,自引:0,他引:7
Donald A. Bryant Gérard Guglielmi Nicole Tandeau de Marsac Anne-Marie Castets Germaine Cohen-Bazire 《Archives of microbiology》1979,123(2):113-127
Phycobilisomes, supramolecular complexes of water-soluble accessory pigments, serve as the major light-harvesting antennae in cyanobacteria and red algae. Regular arrays of these organelles are found on the surface of the thylakoid membranes of these organisms. In the present study, the hemi-discoidal phycobilisomes of several species of cyanobacteria were examined in thin sections of cells and by negative staining after isolation and fixation. Their fundamental structures were found to be the same. Isolated phycobilisomes possessed a triangular core assembled from three stacks of disc-shaped subunits. Each stack contained two discs which were 12 nm in diameter and 6–7 nm thick. Each of these discs was probably subdivided into halves 3–3.5 nm thick. Radiating from each of two sides of the triangular core were three rods 12 nm in diameter. Each rod consisted of stacks of 2 to 6 disc-shaped subunits 6 nm thick. These discs were subdivided into halves 3 nm thick.The average number of discs of 6 nm thickness forming the peripheral rods varied among the strains studied. For certain chromatically adapting strains, the average rod length was dependent upon the wavelength of light to which cells were exposed during growth. Analyses of phycobilisomes by spectroscopic techniques, polyacrylamide gel electrophoresis, and electron microscopy were compared. These analyses suggested that the triangular core was composed of allophycocyanin and that the peripheral rods contained phycocyanin and phycoerythrin (when present). A detailed model of the hemi-discoidal phycobilisome is proposed. This model can account for many aspects of phycobiliprotein assembly and energy transfer.Abbreviations PBS
phycobilisome(s)
- PBP
phycobiliprotein(s)
- AP
allophycocyanin
- PC
phycocyanin
- PE
phycoerythrin
- PEC
phycoerythrocyanin
- AP-B
allophycocyanin B
- C-
cyanobacterial
- R-
rhodophytan
- B-
Bangiophycean
- SDS
sodium dodecyl sulfate
- LPP
Lyngbya-Plectonema-Phormidium group
- Na-KPO4 buffers
NaH2PO4 titrated with a solution of KH2PO4 of equivalent molarity to a given pH 相似文献
69.
Climbing fiber (CF)–-Purkinje cell (PC) relationships were studied electrophysiologically on the cerebellum of 8 to 15 day old rats. Some animals were rendered agranular by x-irradiation from birth; some others were treated with 3-acetyl pyridine 3 days before study to selectively destroy the CF. Unitary extracellular recordings in 8–9 day old normal rats revealed that more than 50μ of the PC units each exhibited either two types of all-or-none climbing fiber responses (CFR) or stepwise graded CFRs. The other PC units only presented one type of all-or-none CFR. These activities were entirely mediated via CF since they persisted at the same age in x-irradiated rats, but were absent in animals treated with 3-acetyl pyridine. Interaction experiments were performed between juxtafastigial and Inferior Olive stimulations on 49 PC units in 8–9 day old normal rats. Collisions between impulses set up in CFs were disclosed in 21 out of the 24 PCs which exhibited only one type of CFR. In the three others and in each of the 25 PCs that displayed two types of all-or-none CFRs, or CFRs graded by steps, no collision was detected. Moreover intracellular recordings of epsp's mediated via CFs in PCs of 8–9 day old normal rats revealed that they frequently fluctuated in stepwise fashion. These results demonstrate that in the immature rat more than 50μ of PCs are each innervated by at least two distinct CFs; later on, the disappearance of the supernumerary synapses between CF and PC leads, as early as day 15, to the one-to-one relationship between CF and PC. 相似文献
70.