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861.
Mitsue Haraguchi Mario Motidome Massayoshi Yoshida Otro R. Gottlieb 《Phytochemistry》1983,22(2):561-563
The trunk bark of Ocotea catharinensis yielded, besides the known bicyclo(3.2.1)octanoid neolignans canellin-C and 5′-methoxycanellin-C, two epimers rel-(1R,4S and 4R,5S,6R,7S,8R)-1-allyl-4,8-dihydroxy-3,5-dimethoxy-7-methyl-6-piperonyl-bicyclo(3.2.1)oct-2-enes and rel-(1R,5S,6R,7S,8R)-1-allyl-3,8-dihydroxy-5-methoxy-7-methyl-6-piperonyl-4-oxobicyclo(3.2.1)oct-2-ene. The hydrobenzofuranoid neolignans are represented by the equally novel (2S,3S,5R)-5-allyl-5,7-dimethoxy-3-methyl-2-piperonyl-2,3,5,6-tetrahydro-6-oxobenzofuran and (2R,3S,3aS)-3a-allyl-5,7-dimethoxy-3-methyl-2-piperonyl-2,3,3a,6-tetrahydro-6-oxobenzofuran. 相似文献
862.
Standardization of Radiorenography in Dehydrated and Rehydrated Primates Under Laboratory Conditions
Irene C. Dormehl D.J. Jacobs Maryke du Plessis J.J. van der Watt D.J. du Plessis M. Bornmann 《Journal of medical primatology》1983,12(2):68-76
Radiorenography with 99mTo-labelled diethylenctriaminepcntacetic acid ([99mTc]-DTPA) was performed on chacma baboons (Papio ursinus) and vervet monkeys (Cereopithecus pygerythus) to establish the effects of various states of hydration on the data obtained from the DTPA-renogram. The renogram parameters, which can be related to certain aspects of kidney function, varied significantly with the degree of hydration. It is therefore imperative for clinically directed animal research projects on the urinary system to standardise the experimental procedure for radiorenography. A dehydration of 6 h followed by an hour IU rehydration period using 200 ml of a 0.9% NaCI solution on baboons under thiopentone sodium anaesthetic, was found to be the most suitable procedure for radiorenographic investigations in this primate model. 相似文献
863.
864.
Hydrolysis of sphingomyelin and 2-N-(hexade-canoyl)-amino-4-nitrophenyl-phosphorylcholine (HDA-PC), a synthetic analogue of sphingomyelin, by acid and Mg-dependent neutral sphingomyelinases was tested with a homogenate of normal human brain cortex. Results demonstrated quite different substrate specificities for these enzymes. Acid sphingomyelinase, which is neither activated by MgCl2 nor inhibited by EDTA, hydrolyzed both substrates (the hydrolysis ratio of HDA-PC to sphingomyelin is ?2). In contrast, Mg-dependent neutral sphingomyelinase, which is inhibited by EDTA and reactivated by MgCl2, hydrolyzed only sphingomyelin (the hydrolysis ratio of HDA-PC to sphingomyelin is ?0-0.05). This synthetic substrate seems to be useful for selective determination of acid sphingomyelinase and for avoiding interference of Mg-dependent neutral sphingomyelinase. 相似文献
865.
Perry Barrett Peter-M. Kloetzel John Sommerville 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(4)
During early oogenesis in amphibia, most of the 5 S RNA and tRNA is stored in a ribonucleoprotein particle that sediments at 42 S. In Xenopus laevis the 42 S particle contains two major proteins: of Mr 48 000 (P48) and 43 000 (P43). It is shown that heterogeneity in composition of the 42 S particle reflects a changing situation whereby initially, both 5 S RNA and tRNA are complexed with P48 (1 molecule 5 S RNA: 1 molecule P48; 2 or 3 molecules tRNA: 1 molecule P48), but later, tRNA becomes increasingly associated with P43 (in a 1:1 ratio) although 5 S RNA remains complexed with a cleavage product of P48. These changes relate to the eventual utilization of the excess 5 S RNA and tRNA in ribosome assembly and protein synthesis. 相似文献
866.
Ichiro Oohara Akira Suyama Akiyoshi Wada 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,741(3)
Poly(l-glutamic acid) has been reported to mediate in vitro nucleosome assembly (Stein, A., Whitlock, J.P., Jr. and Bina, M. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 5000–5004). To study the reaction mechanism, we have reconstituted nucleosome core particles from chicken erythrocyte core DNA and core histones in the presence of poly(l-glutamic acid) and analyzed the assembly products by polyacrylamide gel electrophoresis. Poly(l-glutamic acid), which binds and forms a large complex with core histones, is replaced with core DNA in the reconstitution process. When histone-poly(l-glutamic acid) complex and core DNA are mixed with a histone:DNA ratio of 1.0, the yield of core particles increases by prolonged reconstitution time. Two phases with a distinct time range appear in the process. In the fast phase within 30 min, 60% of the DNA is involved in products containing histones: reconstituted core particles, a larger nucleoprotein complex and aggregation. In the second phase, the remaining DNA and the DNA in the aggregation decrease, and the core particles increase slowly. The yield of core particles is approx. 60% after 24 h. The slow phase is not observed by reconstitution with a histone:DNA ratio of 2.0 in the initial mixture. The reaction scheme of the assembly process derived from these data is given. Based on the in vitro reaction scheme, the possible role of in vivo ‘nucleosome assembly factors’ is also discussed. 相似文献
867.
George H. Jones 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,741(3):333-340
Transfer RNAs have been prepared from control and regenerating rat skeletal muscle. The yield of tRNA is highest during the early stages of the regeneration process (5 and 8 days following the induction of regeneration) and decreases to near control values thereafter. The amino acid acceptor activity (extent of aminoacylation) of tRNA from regenerating muscle was also found to be higher for some amino acids than the activity of control tRNA, and the maximum increase in activity was observed between 5 and 8 days following the initiation of regeneration with a decrease to control levels through 15 and 30 days. The isoacceptor pattern, determined by RPC-5 chromatography, for methionyl-tRNAs from control muscle and 5-day regenerating muscle were essentially indistinguishable, while a minor peak of prolyl-tRNA was observed in the population from 5-, 8- and 15-day regenerates which was apparently absent from the control tRNA. Lysyl-tRNAs from control muscle contain two major isoacceptors while a third isoacceptor is observed in the tRNA preparations from 5-, 8- and 15-day regenerating muscle. The relative amount of this third isoacceptor is highest in the 8-day population and decreases in amount in tRNAs from 15- and 30-day regenerates. Control muscle also contains two major glutamyl-tRNA species while a third isoacceptor can be detected in regenerates. The relative amount of this species increases during the early course of the regeneration process but is present at near control levels by 30 days following Marcaine injection. Cell-free protein synthesis using muscle polyribosomes showed that tRNAs from regenerating muscle were more effective in stimulating [35S]methionine incorporation than tRNAs from control muscle. 相似文献
868.
Erasmus Schneider Barbara Müller Richard Schindler 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,741(1):77-85
Two heat-sensitive (arrested in G1 at 39.5°C) and two cold-sensitive (arrested in G1 at 33°C) clonal cell-cycle mutants that had been isolated from the same clone (K 21), of the murine mastocytoma P-815 cell line, were tested for thymidine kinase (EC 2.7.1.21) activity. After shift of mutant cells to the nonpermissive temperature, thymidine kinase activity decreased, and minimal levels (i.e., less than 3% of those observed for ‘wild-type’ K 21 cells at the respective temperature) were attained within 16 h in heat-sensitive and after 3–4 days in cold-sensitive mutants, which is in good agreement with kinetics of accumulation of heat-sensitive and cold-sensitive cells in G1 phase. After return of arrested mutant cells to the permissive temperature, thymidine kinase of heat-sensitive cells increased rapidly and in parallel with entry of cells into the S phase. In cultures of cold-sensitive cells, however, initiation of DNA synthesis preceded the increase of thymidine kinase activity by approx. one cell-cycle time. Thymidine kinase activities in revertants of the heat-sensitive and cold-sensitive mutants were similar to those of ‘wild-type’ cells. In ‘wild-type’ K 21 cells incubated at 39.5°C, thymidine kinase activity was approx. 30% of that at 33°C. This difference is attributable, at least in part, to a higher rate of inactivation of the enzyme at 39.5°C, as determined in cultures incubated with cycloheximide. The rapid increase of thymidine kinase activity that occurred after shift of K 21 cells and of arrested heat-sensitive mutant cells from 39.5°C to 33°C was inhibited by actinomycin D and cycloheximide. 相似文献
869.
870.
L.H.F. Mullenders A.A. Van Zeeland A.T. Natarajan 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(4):428-435
The distribution of ultraviolet-induced repair patches along DNA loops attached to the nuclear matrix, was investigated by digestion with DNA-degrading enzymes and neutral sucrose gradient centrifugation. When DNA was gradually removed by DNAase 1, pulse label incorporated by ultraviolet-irradiated cells during 10 min in the presence of hydroxyurea or hydroxyurea/arabinosylcytosine showed similar degradation kinetics as prelabelled DNA. No preferential association of pulse label with the nuclear matrix was observed, neither within 30 min nor 13 h after irradiation. When the pulse label was incorporated by replicative synthesis under the same conditions, a preferential association of newly-synthesized DNA with the nuclear matrix was observed. Single-strand specific digestion with nuclease S1 of nuclear lysates from ultraviolet-irradiated cells, pulse labelled in the presence of hydroxyurea/arabinosylcytosine, caused a release of about 70% of the prelabelled DNA and 90% of the pulse-labelled DNA from the rapidly sedimenting material in sucrose gradients. The results suggest no specific involvement of the nuclear matrix in repair synthesis, a random distribution of repair patches along the DNA loops, and simultaneously multiple incision events per DNA loop. 相似文献