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91.
Herbert N. Arst Jr. David Tollervey Mark X. Caddick 《Molecular & general genetics : MGG》1989,215(2):364-367
Summary The areA
r
-18 mutation is a loss-of-function mutation in areA, the positive acting regulatory gene mediating nitrogen metabolite repression in Aspergillus nidulans. It results from a reciprocal translocation which splits the coding region into 5 and 3 moieties. Surprisingly, we have selected rare intracistronic revertants of areA
r
-18. From crosses heterozygous for areA
r
-18 revertant alleles, duplication-deficiency progeny containing two copies of a substantial portion of chromosome IV but lacking part of chromosome III, including the 5 moiety of areA, have been obtained. For all four revertants analysed genetically, growth properties of these duplication-deficiency strains indicate that the reversion events involve the 3 portion of areA and that the 5 portion of areA is unnecessary for the revertant phenotype. This conclusion was directly confirmed for one revertant using Southern blotting. As all four reversion events involve additional chromosomal rearrangements, they probably fuse functional promoters, ribosome binding sites and in frame initiation codons to the 3 portion of the gene. In the course of characterisation of these mutations, new mapping data for a large region of chromosome IV have been generated, and a new reciprocal translocation activating the cryptic regulatory gene areB, whose product can substitute for that of areA, has been identified. 相似文献
92.
Summary The aim of this study was to assess the effects of developmental events, occurring in fish during the first weeks after hatching, on the quantity and quality of the ingested food and on growth. The investigation was carried out with the larvae and juveniles of Rutilus rutilus, the single cyprinid species occurring in an oligotrophic subalpine lake in Tirol, Austria. Comparison between availability of prey in the water and gut contents suggests that the selection of food by the young fish is strongly influenced by developmental processes. For example, the prevalence of indigestible phytoplankton in the gut of young larvae can be taken as a sign of the not yet fully developed sensory and locomotory capacities of the young fish (El-Fiky et al. 1987). Furthermore, quantitative and qualitative changes in the gut contents correlate strongly with changes in the form and relative length of the gut, but reflect only weakly the availability of prey in the water. In the Seefelder See population of R. rutilus the switch from a phytoplankton to a cladoceran dominated diet is accompanied by an increase in relative growth rate by nearly one order of magnitude (Wieser et al. 1988). 相似文献
93.
We report the partial amino acid sequence of chicken intestinal microvillar 110-kDa protein that, as a complex with calmodulin, has previously been shown to exhibit myosin-like ATPase and actin-binding activities. The sequence shows a high degree of similarity to the sequence of a novel vertebrate myosin I-like heavy chain encoded by a cDNA isolated from bovine intestine. This confirms that the bovine and chicken proteins are the first examples of Acanthamoeba myosin I-like proteins from higher eukaryotes. Comparison of available structural and functional data leads us to postulate that the myosin I family of proteins result from the fusion of a conserved myosin headlike motor domain, with variable COOH-terminal domains responsible for binding to specific intracellular structures. 相似文献
94.
The ras oncogene and tumour metastasis: observations on murine cells transfected with activated human c-Ha-ras 总被引:1,自引:0,他引:1
Jeannie S. Wallace Allan J. Hayle Allan J. Syms Margaret Cairney Ben Tutty rew Gazzard Mark F. Evans Kenneth A. Fleming David Tarin 《Differentiation; research in biological diversity》1989,41(3):208-215
Transfection of cells with cloned genes or total genomic DNA offers a means for studying aspects of neoplastic behaviour. We have used this method to examine whether incorporation of the cloned 6.6-kilobase (kb) fragment of DNA containing the mutant c-Ha-ras human oncogene can confer metastatic capability on murine NIH 3T3 cells. Cells co-transfected with the mutated ras gene and the neomycin resistance marker pSV2neo were selected by culture in neomycin. On subcutaneous inoculation into MF 1 nude mice, these cells proved to be tumourigenic with short latent periods (approximately 14 days)--nude mice were used to circumvent immunological rejection of the mouse cells expressing the product of the human oncogene. Transfectants were capable of lung colonisation after intravenous injection, but there was no evidence of spontaneous metastasis at autopsy, or on histological examination of the lungs and other organs, 90 days after inoculation. Incorporation of the transfected oncogene was confirmed by Southern blotting and its expression by dot-blot hybridisation and immunoprecipitation. The results in this experimental system indicate that transfection of a mutated human ras oncogene into non-neoplastic 3T3 cells can confer part of the metastatic phenotype, namely lung colonisation, but is not by itself sufficient to induce spontaneous metastatic behaviour. 相似文献
95.
F. Mark U. Becker J. N. Herak D. Schulte-Frohlinde 《Radiation and environmental biophysics》1989,28(2):81-99
Summary Two expressions are given for the survival dose of DNA exposed to high-energy radiation in aqueous solution in the presence of a scavenger. They are derived from a model where a diffusion controlled reaction of OH radicals occurs on the surface of the DNA macromolecules in competition with scavenging in the bulk of the solution. The DNA molecules are approximated either by spheres or by cylinders. The model based on molecules of spherical shape corresponds closely to that developed by van Rijn et al. [20]. Expressions obtained from the cylindrical model are used to account for the dependence on the scavenger concentration of some experimentally measured quantities, namely the survival dose and theG value for single-strand breaks upon Co -irradiation ofX 174 DNA and polyadenylic acid, respectively.In memoriam Prof. Dr. O.E. Polansky 相似文献
96.
97.
G Risse U Stochaj K Els?sser J Dieckhoff H G Mannherz K von der Mark 《Biochimica et biophysica acta》1989,994(3):258-263
The 68 kDa laminin-binding protein purified from chicken skeletal muscle and the ectoenzyme 5'-nucleotidase from chicken gizzard are both able to interact with laminin. They were both shown to possess a nearly identical amino acid composition. The 79 kDa glycosylated form of 5'-nucleotidase can be transformed into an enzymatically active form by treatment with endoglycosidase F (Endo F). Deglycosylated (Endo F-treated) 5'-nucleotidase exhibits an apparent molecular mass of 68 kDa. Using immunological and finger-printing techniques, both proteins were analysed to determine their structural relatedness. The results obtained indicate that both proteins are not identical but may posses a few common peptides of yet unknown sequence and length. 相似文献
98.
Monique Aumailley Karlheinz Mann Helga von der Mark Rupert Timpl 《Experimental cell research》1989,181(2)
Twelve of sixteen different cell types including fibroblasts and tumor cells were able to attach and spread on substrates of pepsin-solubilized or intact collagen VI, and on its triple helical domain. Attachment and spreading were independent of soluble mediator proteins (fibronectin, laminin) and collagen VI was distinct from collagens I, IV and V in the cells with which it interacted. Many of the same cells bound and spread on substrates prepared from unfolded α2(VI) and α3(VI) chains but not on the α1(VI) chain. The interactions with the chains were inhibited by low concentrations (10–100 μM) of synthetic RGDS and RGDT but not RGES peptides while the binding of cells to pepsin-solubilized collagen VI was more than 20-fold less sensitive to these peptides. The data incidate that cells have the ability to bind to collagen VI in a specific manner suggesting a similar function for collagen VI in situ. 相似文献
99.
Andrew Clarke J. Cynan Ellis-Evans Mark W. Sanders Lesley J. Holmes 《Hydrobiologia》1989,172(1):183-191
The copepod Pseudoboeckella poppei (Daday) (Calanoida, Centropagidae) was sampled from Sombre and Heywood Lakes on Signy Island, Antarctica (60° S, 45° W) between January 1984 and March 1985. Sombre Lake is clear and oligotrophic with little phytoplankton and a bottom sediment low in organic content. By contrast Heywood Lake is turbid and mesotrophic; a substantial phytoplankton develops in summer and the bottom sediments are comparatively rich in organics. Both lakes freeze over for much of the year, forcing the copepods to adopt a benthic feeding strategy over winter. Adult Pseudoboeckella feed on phytoplankton when this is available, but also on detritus, diatoms and short algal filaments stirred up from the sediment. In Heywood Lake, male copepods show a smooth seasonal trend in lipid content with lipid being synthesised in early summer and utilised in late summer and winter. The summer increase in lipid content is associated with an increase in dry weight. Female lipid contents show evidence of two peaks of egg production. In Sombre Lake both male and female copepods increase in size during summer and show a wider range of lipid contents than in Heywood Lake; it is likely that this is due to the poorer winter feeding conditions which necessitate the synthesis of a much larger store of reserves during the summer. In contrast to marine calanoid copepods, lipid stores are exclusively triacylglycerol with no trace of wax ester. 相似文献
100.
Vesna A. Eterović Lian Li Andrew Palma Mark G. McNamee 《Cellular and molecular neurobiology》1990,10(3):423-433
1. Nicotinic acetylcholine receptors (nAChR)4 from BC3H1 cells (which express a skeletal muscle-type receptor) and from Torpedo californica electric organ were expressed in Xenopus laevis oocytes and studied with a voltage-clamp technique. 2. We found that bath application of ATP in the micromolar to millimolar range increased the ACh-elicited current in both muscle and electrocyte receptors. The effect of ATP increased with successive applications. This "use-dependent" increase in potentiation was Ca2+ dependent, while the potentiation itself was not. 3. Four other nucleotides were tested on muscle nAChR: ADP, AMP, adenosine, and GTP. Of these, only ADP was a potentiator, but its effect was not use dependent. Neither ATP nor ADP affected the resting potential of the oocyte membrane. 4. ADP potentiated the response to suberyldicholine and nicotine, as well as ACh. 5. Finally, ADP reversed the phencyclidine-induced block of ACh currents in oocytes expressing muscle nAChR. 相似文献