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661.
Batchwise purification of liver ribosomes and polysomes on hydroxyl-apatite is a rapid procedure to remove glycogen, hemoglobin, ribonuclease and other contaminants from ribosomal preparations. Ribosomes and polysomes are adsorbed to hydroxylapatite in a Büchner filter funnel and the contaminants are eluted from the hydroxylapatite with 0.15 M KH2PO4. The ribosomes and polysomes are then eluted with 0.3–0.4 M KH2PO4 and concentrated by centrifugation. The resolution of the polysome profiles was greatly improved following purification. The purified ribosomes could be dissociated into subunits at 0.3 M KCl, and showed no loss of activity in poly-U directed phenylalanine synthesis. 相似文献
662.
H. Lorberboum D. Weinstein H. Galski N. de Groot S. Segal J. Ilan R. Folman A. A. Hochberg 《Molecular biology reports》1982,8(2):103-110
The in vitro synthesis of RNA in the human placental tissue, incubated in organ culture, was investigated. We followed the synthesis of the poly A(-) and poly A(+) RNA fractions, and investigated the distribution of the newly synthesized RNA among the subcellular fractions isolated from first and third trimester placentas.The poly A(-) RNA was the major fraction of the RNA synthesized in vitro. The incorporation of [3H]uridine into the poly A(+) RNA fraction was very low.As protein synthesis occurred during the entire incubation period, we suggest the presence of a pool of mRNA molecules in the form of mRNP particles. 相似文献
663.
cytokinin-induced amylolytic activity in bean cotyledons: Identification of the regulated enzyme 总被引:1,自引:0,他引:1
Separation of an extract of cotyledons of Phaseolus vulgarison a column of Sephadex G-200 revealed three amylolytic fractions.The slower migrating fraction hydrolyzed/ß-Limit dextrinazure and was inhibited by EDTA. The activity of this fractionwas enhanced by the embryo axis and this effect could be fullyreplaced by kinetin or benzyladenine. These results suggestthat the bean embryo axis exerts a promotive influence on theactivity of a-amylase in the cotyledons and that this effectis mediated by cytokinins. The other two amylolytic fractions did not show a-amylase activity.No effect of the embryo axis or of cytokinins on their activitycould be noted.
1Present address: The Thimann Laboratories, University of California,Santa Cruz, California, U.S.A. (Received June 27, 1979; ) 相似文献
664.
R. Folman J. Ilan J. Shiklosh N. De Groot S. Segal A. A. Hochberg 《Molecular biology reports》1979,5(3):175-179
Placental tissue slices from first trimester placentas synthesize and secrete proteins labeled by radioactive glucosamine are preferentially secreted as compared to proteins in general. One of the proteins synthesized and secreted is hCG. Processing and secretion of proteins, including hCG, by the tissue slices need a two-hour period. Both secretion and glycosylation of the protein can take place independently of protein synthesis. A method was developed for the specific determination of newly synthesized radioactive hCG in placental tissue.Department of Reproductive Biology, Case Western Reserve University, Cleveland, Ohio, USA 相似文献
665.
Ilan Eshel 《Journal of mathematical biology》1996,34(5-6):485-510
Eighteen different terms, currently employed to define various concepts of evolutionary stability in population dynamics
are mentioned in this paper. Most of these terms are used in different connotations and even different meanings by different
authors. On the other hand, different terms are often employed by different authors to define quite the same concept. Twenty-five
years ago there was only one, well-defined, concept of stability, universally recognized in the field. In this paper I will
try to relate the recent confusion, concerning concepts of population stability, with a more serious, though not that well-recognized,
confusion in the modern analytic approach to population dynamics and quantitative evolution. Concepts of population stability
will be examined in relation to each other on the one hand and, on the other hand, in relation to two dichotomies regarding
the dynamic processes to which they correspond: Short-term versus long-term processes and processes concerning phenotypic
changes versus process concerning genotypic changes. A hopefully more consistent use of the current terminology is suggested.
Received 15 August 1993; received in revised form 15 September 1994 相似文献
666.
The fungusTrichoderma harzianum which parasitizes its hostRhizoctonia solani (AG 1–6) was observed under a light microscope and the interaction sites photomicrographed with infrared film. Bright regions indicating infrared irradiation were observed at the interaction sites, apparently due to the high parasitic activity occurring there. The possible use of infrared photomicrography in cell-cell interactions is discussed. 相似文献
667.
The hypothesis that the regulative action of the barley embryoon amylase synthesis in the aleurone layer is partially exertedby a mechanism of osmotic regulation was tested. When embryo growth was retarded by a drought treatment no concomitantrepression of amylase production could be detected. Inhibitionof growth by a cold treatment was not accompanied by an elevationof osmotic pressure or by a depression of the amylase levelin the endosperm. Osmotic concentration of de-embryonated seedswas lower than that of the endosperm of intact seedlings. We concluded that the results do not support the tested hypothesis. (Received June 4, 1973; ) 相似文献