不同海拔地区种植的水稻地上部干物质的生产和分配

根据1983—1985年“高原水稻高产栽培的生理生态规律研究”中低热的元江(海拔400米左右)、温凉的昆明(约1900米)和冷凉的丽江(约2400米)的资料,以六个处理、十八个小区、三年总平均值,比较了不同海拔地区种植的水稻中地上部干物质生产和分配的总趋势。主要结果如下: 1.全生育期总的干物质生产量以温凉地区最高,低热地区居中,冷凉地区最低。 2.抽穗前干物质生产速率和齐穗期干物重占黄熟期干物重的比例随海拔降低而增加;抽穗期至黄熟期干物质生产速率,以温凉地区最高,低热地区居中,冷凉地区最低,但低热地区低于前期,高海拔地区高于前期,不过冷凉的丽江增加的更多。 3.抽穗前(旗叶完全展开后)叶干重占当时植株总干重的比例,随海拔升高而降低。 4.抽穗期至黄熟期的次库(茎 叶鞘)干重的改变,不同海拔地区种植的水稻表现不同:低热地区减重,温凉地区稍增,冷凉地区明显增加。 5.与高海拔地区种植的水稻相比,在黄熟期低海拔地区的有较高的穗重/总重和穗增重/总增重的比例。另外低海拔地区的穗增重超过总增重。结实率和谷/草比例均随海拔增高而减低。     

The influence of diet on the growth of Stenonema vicarium (Walker) (Ephemeroptera: Heptageniidae)

Laboratory studies compared the growth rate of Stenonema vicarium (Walker) nymphs on diets of detritus and natural stream periphyton. In three consecutive runs of the experiment, growth rates were consistently higher on periphyton (mean growth rate = 2.1% wet wt. d⁻¹) than detritus (mean = 1.8% wet wt. d⁻¹). The starting date of each run also significantly influenced growth rates. In each treatment growth rates generally decreased over the course of the 3 runs, and ca. one-half of the nymphs in the last run did not molt or grow. It appeared that growth of S. vicarium may be partially controlled by seasonal factors.     

NAD-linked aldehyde dehydrogenase for aerobic utilization of L-fucose and L-rhamnose by Escherichia coli.

Mutant analysis revealed that complete utilization of L-fucose and L-rhamnose by Escherichia coli requires the activity of a common NAD-linked aldehyde dehydrogenase which converts L-lactaldehyde to L-lactate. Mutations affecting this activity mapped to the ald locus at min 31, well apart from the fuc genes (min 60) encoding the trunk pathway for L-fucose dissimilation (as well as L-1,2-propanediol oxidoreductase) and the rha genes (min 88) encoding the trunk pathway for L-rhamnose dissimilation. Mutants that grow on L-1,2-propanediol as a carbon and energy source also depend on the ald gene product for the conversion of L-lactaldehyde to L-lactate.     

Characterization of the Erwinia carotovora pelB gene and its product pectate lyase.

The pelB gene encodes pectate lyase B, one of three pectate lyases identified in Erwinia carotovora EC. Pectate lyase B was purified from Escherichia coli containing the pelB gene on a recombinant plasmid. The activity of the protein was optimal at a pH of 8.3. The amino acid composition, N-terminal amino acid sequence, and C-terminal peptide sequence were determined and compared with the polypeptide sequence deduced from the DNA sequence of pelB. Purified pectate lyase B started at amino acid 23 of the predicted sequence, suggesting that a 22-amino-acid leader peptide had been removed. Pectate lyase B of E. carotovora EC and pectate lyase B of E. chrysanthemi EC16 contain 352 and 353 amino acids, respectively (N. T. Keen, S. Tanaki, W. Belser, D. Dahlbeck, and B. Staskawicz, J. Bacteriol. 168:595-606, 1986). The two proteins are 72% homologous on the basis of DNA sequence data, and 75% of the amino acids are identical.     

Protein damage and degradation by oxygen radicals. IV. Degradation of denatured protein

Proteolytic degradation of oxidatively damaged [3H] bovine serum albumin [( 3H]BSA) was studied during incubation with cell-free erythrocyte extracts and a wide variety (14) of purified proteases. [3H]BSA was pretreated by exposure (60Co radiation) to the hydroxyl radical (.OH), the superoxide anion radical (O2-), or the combination of .OH + O2- + oxygen. Treated (and untreated) samples were dialyzed and then incubated with erythrocyte extract or proteases for measurements of proteolytic susceptibility (release of acid-soluble counts). Both .OH and .OH + O2- + caused severalfold increases in proteolytic susceptibility (with extract and proteases), but O2- alone had no effect. Proteolytic susceptibility reached a maximum at 15 nmol of .OH/nmol of BSA and declined thereafter. In contrast, proteolytic susceptibility was still increasing at an .OH + O2-/BSA molar ratio of 100 (50% .OH + 50% O2-). Degradation in erythrocyte extracts was conducted by a novel ATP- and Ca2+-independent pathway, with maximal activity at pH 7.8. Inhibitor profiles indicate that this pathway may involve metalloproteases and serine proteases. Comparisons of proteolytic susceptibility with multiple modifications to BSA primary, secondary, and tertiary structure revealed a high correlation (r = 0.98) with denaturation/increased hydrophobicity by low concentrations of .OH. Covalent aggregation reactions (BSA cross-linking) may explain the declining proteolytic susceptibility observed at .OH/BSA molar ratios greater than 20. Protein denaturation may also have caused the increased proteolytic susceptibility induced by .OH + O2- + O2, but no simple correlation could be obtained. Results with .OH + O2- + O2 appear to have been complicated by direct BSA fragmentation reactions involving (.OH-induced) protein radicals and oxygen. These data indicate a direct and quantitative relationship between protein damage by oxygen radicals and increased proteolytic susceptibility. Oxidative denaturation may exemplify a simple, yet effective inherent mechanism for intracellular proteolysis.     

The primary structure of rat ribosomal protein L7. The presence near the amino terminus of L7 of five tandem repeats of a sequence of 12 amino acids

The covalent structure of rat ribosomal protein L7 was determined in part from the sequence of nucleotides in a recombinant cDNA and in part from the sequence of amino acids in portions of the protein. The complementary analyses supplemented and confirmed each other. Ribosomal protein L7 contains 258 amino acids and has a molecular weight of 30,040. The protein has an unusual and striking structural feature near the NH2 terminus: five tandem repeats of a sequence of 12 residues. Rat L7 appears to be related to ribosomal protein L7 from the moderate halophile Vibrio costicola and perhaps to L30 from Bacillus stearothermophilus, to L7 from the moderate halophile NRCC 41227, and to L22 from Nicotinia tobaccum chloroplast. In addition, there is a sequence of 24 amino acids in rat protein L7 that may be related to segments of the same number of residues in Escherichia coli ribosomal proteins S10, S15, L9, and L22.     

Regulation of β-1,4-Endoglucanase Synthesis in Thermomonospora fusca

In Thermomonospora fusca YX, endocellulase synthesis varies over a 100-fold range depending on the carbon source used. This study shows that the variation is caused by two regulatory mechanisms: an induction mechanism that increases the rate of endocellulase synthesis about 20-fold and a growth rate-dependent repression mechanism that changes the rate of synthesis over a 6-fold range in both induced and noninduced cells. In T. fusca, endocellulase synthesis can be induced by cellulose, cellobiose, or cellodextrin. Cellulase is involved in inducer generation from cellulose. Growth rate-dependent repression can be reversed by limiting cultures for carbon, nitrogen, or, to a lesser extent, phosphorus. Further evidence for two separate regulatory mechanisms is provided by the isolation of mutants (CC-1 and CC-2) whose endocellulases are synthesized constitutively but are still sensitive to growth rate-dependent repression. These conclusions about total endocellulase synthesis were extended to the individual endocellulases by showing that three T. fusca endocellulases are coordinately regulated.     

Freeze-Thawing of Aquaspirillum magnetotacticum Cells Selectively Releases Periplasmic Proteins

Cells of the gram-negative bacterium Aquaspirillum magnetotacticum, when suspended in buffer and freeze-thawed, produced pinkish orange supernatant fluid. The fluid contained ≤2.0% of total extractable outer membrane component 2-keto-3-deoxyoctonate or of the cytoplasmic membrane marker succinic dehydrogenase. Electrophoretic banding patterns and difference spectra of proteins and hemoproteins released by freeze-thawing cells were distinct from those of membrane-associated substances and similar to those of periplasmic substances obtained by applying conventional fractionation methods to this organism.     

Specific interaction of vinculin with alpha-actinin

Vinculin and alpha-actinin are cytoskeletal proteins present at focal contacts of the ventral surface of cultured fibroblasts. We labelled alpha-actinin with an acceptor fluorophore and vinculin with a donor. A mixture of vinculin and alpha-actinin showed a 28% quench, due to energy transfer, suggesting an interaction. Quench of vinculin was dependent on the concentration of alpha-actinin; Scatchard analysis gives a dissociation constant in the microM range. Quench was inhibited by excess unlabelled alpha-actinin, and by reaction of the acceptor protein with p-chloromercuribenzoate. We found that vinculin had a slightly greater elution volume in a gel filtration column equilibrated with alpha-actinin, indicating a higher effective Stokes radius due to the interaction of the two proteins.