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11.
Skeletal muscle growth, muscle nucleic acids and muscle protein synthesis capacity, were measured to evaluate the protein requirement of adult rats. Wistar rats were fed on diets containing 4%, 10% or 20% casein + D,L-methionine. All diets were provided for 21 days beginning at 90 days of age. Body weight, food efficiency and net weight change increased as the casein content of the diet increased. Muscle DNA, RNA and RNA/protein were lost, but protein and protein/DNA increased on the 4% and 20% protein diet. This fact involves an aplasia phenomenon although the hypertrophic growth is maintained. Alterations of the insulin and GH plasma levels were observed. These findings indicate that for adult rats the 4% and 20% protein diets are not adequate for the period of adult maintenance. 相似文献
12.
Creatine kinase activity and its isoenzymatic profile in rat intestinal mucose during normal development have been studied. Creatine kinase enzymatic activity increased stepwise during fetal development and the first week of life. An isoenzymatic pattern of exclusively CK-BB types occurred in all segments of the digestive tract during the early fetal stage. The isoenzyme profile of creatine kinase in the esophagic tissue with advancing maturation of the fetus shifted in the same way as in adults, with preferential concentration of CK-MM. However, CK-BB continued to be the main isoenzyme in the rest of the digestive tract. Our results show that rats are particularly suitable for experimental studies of intestinal creatine kinase isoenzymes. 相似文献
13.
We calculated the potential H(2) and formate diffusion between microbes and found that at H(2) concentrations commonly found in nature, H(2) could not diffuse rapidly enough to dispersed methanogenic cells to account for the rate of methane synthesis but formate could. Our calculations were based on individual organisms dispersed in the medium, as supported by microscopic observations of butyrate-degrading cocultures. We isolated an axenic culture of Syntrophomonas wolfei and cultivated it on butyrate in syntrophic coculture with Methanobacterium formicicum; during growth the H(2) concentration was 63 nM (10.6 Pa). S. wolfei contained formate dehydrogenase activity (as does M. formicicum), which would allow interspecies formate transfer in that coculture. Thus, interspecies formate transfer may be the predominant mechanism of syntrophy. Our diffusion calculations also indicated that H(2) concentration at the cell surface of H(2)-consuming organisms was low but increased to approximately the bulk-fluid concentration at a distance of about 10 mum from the surface. Thus, routine estimation of kinetic parameters would greatly overestimate the K(m) for H(2) or formate. 相似文献
14.
Effect of maltose on the response of potato anthers in culture 总被引:1,自引:0,他引:1
Anthers of the Solanum tuberosum genotype H3703 were cultured on medium containing equimolar concentrations of sucrose or maltose. It was found that significantly more pollen embryos became plants after culture on maltose and hence the yield of plants per 100 anthers cultured increased significantly. Mechanisms by which carbohydrate source may influence response to anther culture are discussed. 相似文献
15.
Diffusion of the Interspecies Electron Carriers H2 and Formate in Methanogenic Ecosystems and Its Implications in the Measurement of Km for H2 or Formate Uptake 总被引:1,自引:0,他引:1
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We calculated the potential H2 and formate diffusion between microbes and found that at H2 concentrations commonly found in nature, H2 could not diffuse rapidly enough to dispersed methanogenic cells to account for the rate of methane synthesis but formate could. Our calculations were based on individual organisms dispersed in the medium, as supported by microscopic observations of butyrate-degrading cocultures. We isolated an axenic culture of Syntrophomonas wolfei and cultivated it on butyrate in syntrophic coculture with Methanobacterium formicicum; during growth the H2 concentration was 63 nM (10.6 Pa). S. wolfei contained formate dehydrogenase activity (as does M. formicicum), which would allow interspecies formate transfer in that coculture. Thus, interspecies formate transfer may be the predominant mechanism of syntrophy. Our diffusion calculations also indicated that H2 concentration at the cell surface of H2-consuming organisms was low but increased to approximately the bulk-fluid concentration at a distance of about 10 μm from the surface. Thus, routine estimation of kinetic parameters would greatly overestimate the Km for H2 or formate. 相似文献
16.
Disulfide and secondary structures of recombinant human granulocyte colony stimulating factor 总被引:4,自引:0,他引:4
Molecular characteristics and secondary structures of recombinant methionyl human granulocyte colony stimulating factor produced by genetically engineered Escherichia coli are described. Limited radiolabeling of the protein with tritiated iodoacetate and determination of the labeled residue revealed that this recombinant protein contains only one free cysteine at position 17 which is not essential for activity. The free cysteine is inaccessible to modification unless the molecule is unfolded under denaturing conditions. The molecule forms two disulfide bridges which were assigned as Cys(36)-Cys(42) and Cys(64)-Cys(74) based on the results of isolation and characterization of disulfide-containing peptides obtained from a subtilisin digest of the intact protein. CD analyses and secondary structure prediction suggest that the molecule is abundant in alpha-helical structures. 相似文献
17.
Disulfide structures of human interleukin-6 are similar to those of human granulocyte colony stimulating factor 总被引:2,自引:0,他引:2
C L Clogston T C Boone B C Crandall E A Mendiaz H S Lu 《Archives of biochemistry and biophysics》1989,272(1):144-151
The amino acid sequences of human interleukin-6 and granulocyte colony stimulating factor are approximately 30% homologous in the N-terminal region. The relative positions of four half-cystines in human interleukin-6 (IL-6) match four of the five in human granulocyte colony stimulating factor. Labeling experiments of recombinant interleukin-6 with tritiated iodoacetate confirmed that the molecule forms two intramolecular disulfide bonds and contains no detectable level of free sulfhydryls. By isolation and characterization of tryptic and subtilytic peptides obtained from different proteolytic digestions, the disulfide bonds of the IL-6 molecule were assigned to Cys44-Cys50 and Cys73-Cys83. The two disulfide bridges form two small loops which are separated by 22 amino acids. These structures are similar to those of recombinant granulocyte colony stimulating factor. 相似文献
18.
Variable conservation of nucleolus organizer regions during karyotypic evolution in Microtidae 总被引:1,自引:0,他引:1
The location of the nucleolus organizer regions (NORs) was studied in four species of Microtidae (Microtus nivalis, M. cabrerae, M. arvalis, and Arvicola sapidus). The comparative study of these locations shows that some NORs have been conserved despite the chromosome rearrangements that have occurred through karyotypic evolution, while others have been lost. In addition, there are many chromosomes in which NORs seem to have appeared or been lost without apparent relation to the chromosome rearrangements. Some hypotheses regarding these facts are discussed in the text. 相似文献
19.
20.
The photosynthetic behaviour ofDunaliella viridis has been studied under a combination of three variables: irradiance (0–900 mol m–2 s–1), temperature (15, 23, 31, 38, 42 °C) and nitrogen concentration (0.05, 0.5, 1.5, 5, 10 mM NO
3
-
) at a salinity of 2 M NaCl.The highest rates of photosynthesis have been found at 31 °C and a nitrate concentration of 10 mM. There exists a synergistic effect between temperature and nitrogen availability on the photosynthesis ofD. viridis; under nitrogen deficiency oxygen evolution is low, even null at high temperature. The interaction between these two variables of control occurs in a multiplicative way. There is also a general increase in photosynthetic pigments following the increase in nitrogen concentration in the culture medium. The normalization of net photosynthesis data in relation to chlorophylla shows that nitrogen concentration makes an indirect control of the photosynthetic rate ofD. viridis through the variation of pigment concentration. 相似文献