Components of woody-tissue respiration in young Abies amabilis (Dougl.) Forbes trees

Summary Woody-tissue respiration was measured on five different dates at three to five locations on each of 12 30-year-old Abies amabilis trees. On any given date, temperature-corrected respiration per unit surface area varied 10 to 40-fold between sampling locations. In stems, the two major components of respiration were growth respiration and sapwood maintenance respiration, which were of roughly equal importance during the growing season. There was no evidence of significant cambial maintenance respiration, suggesting that a stand with high bole surface area would not automatically have high respiration. Respiration in branches was much greater than in boles of comparable volume and growth rates, and was significantly correlated with branch height. Branch respiration may include an another significant component in addition to the two seen in bole respiration, possibly associated with carbohydrate mobilization and transport or with CO₂ efflux from the transpiration stream.     

Dependency of growth yield,maintenance and K s-values on the dissolved oxygen concentration in continuous cultures of Azotobacter vinelandii

Azotobacter vinelandii was grown diazotrophically in sucrose-limited chemostat cultures at either 12, 48, 108, 144 or 192 M dissolved oxygen. Steady state protein levels and growth yield coefficients (Y) on sucrose increased with increasing dilution rate (D). Specific rate of sucrose consumption (q) increased in direct proportion to D. Maintenance coefficients (m) extrapolated from plots of q versus D, as well as from plots of 1/Y versus 1/D exhibited a nonlinear relationship to the dissolved oxygen concentration. Constant maximal theoretical growth yield coefficients (Y ^G) of 77.7 g cells per mol of sucrose consumed were extrapolated irrespective of differences in ambient oxygen concentration. For comparison, glucose-, as well as acetate-limited cultures were grown at 108 M oxygen. Fairly identical m- and Y ^G-values, when based on mol of substrate-carbon with glucose and sucrose grown cells, indicated that both substrates were used with the same efficiency. However, acetate-limited cultures showed significantly lower m- and, at comparable, D, higher Y-values than cultures limited by either sucrose or glucose. Substrate concentrations (K _s) required for half-maximal growth rates on sucrose were not constant, they increased when the ambient oxygen concentration was raised and, at a given oxygen concentration, when D was decreased. Since biomass levels varied in linear proportion to K _s these results are interpreted in terms of variable substrate uptake activity of the culture.Abbreviations D dilution rate - K _s substrate concentration required for half maximal growth rate - m maintenance coefficient - q specific rate of substrate consumption - Y growth yield coefficient - Y ^G maximum theoretical growth yield coefficient     

The complete nucleotide sequence of the colicinogenic plasmid ColA. High extent of homology with ColE1

Summary The complete nucleotide sequence of the colicinogenic plasmid ColA has been determined. The plasmid DNA consists of 6720 bp (molecular weight 4.48×10⁶). Fifteen putative biological functions have been identified using the functional map previously determined. These include 11 genes and 3 DNA sites. Nine genes encode proteins of which 3 have been fully characterized. The replication region of ColA coding for RNAI and RNAII is highly homologous to that of ColE1 andClo DF13. The same holds true for the site-specific recombination region containing palindromic symmetry and involved in stable maintenance of the plasmids. A high percentage of homology has been detected for putative mobility proteins encoded by ColA and ColE1. The exclusion proteins are also highly homologous.     

Photosynthesis and respiration in Alocasia macrorrhiza following transfers to high and low light

Summary Photosynthetic capacities and respiration rates of Alocasia macrorrhiza leaves were measured for 4 weeks following reciprocal transfers between high (20% of full sun) and low (1% of full sun) light environments. Photosynthetic capacities and respiration rates of mature, high-light leaves were 1.7 and 4.5 times those of low-light leaves, respectively. Following transfer, respiration rates adjusted within 1 week to those characteristic of plants grown in the new environment. By contrast, photosynthetic capacities either did not adjust or changed only slowly following transfer. Most of the difference in respiration between high- and low-light leaves was related to the carbohydrate status as determined by the daily PFD and little was directly related to the maintenance costs of the photosynthetic apparatus. Leaf construction cost was directly proportional to maximum photosynthetic capacity. Consequently, although daily carbon gain per unit leaf area was the same for low-light and high to low-light transferred plants within a week after transfer, the carbon return per unit of carbon investment in the leaves remained lower in the high to low transfer plants throughout the 4 week measurement period. Conversely, in high-light, the low leaf construction cost of the low to high-light transferred plants resulted in carbon gain per unit investment just as high as that of the high-light plants.     

Woody-tissue respiration for Simarouba amara and Minquartia guianensis,two tropical wet forest trees with different growth habits

We measured CO₂ efflux from stems of two tropical wet forest trees, both found in the canopy, but with very different growth habits. The species were Simarouba amara, a fast-growing species associated with gaps in old-growth forest and abundant in secondary forest, and Minquartia guianensis, a slow-growing species tolerant of low-light conditions in old-growth forest. Per unit of bole surface, CO₂ efflux averaged 1.24 mol m^–2 s^–1 for Simarouba and 0.83 mol m^–2s^–1 for Minquartia. CO₂ efflux was highly correlated with annual wood production (r ²=0.65), but only weakly correlated with stem diameter (r ²=0.22). We also partitioned the CO₂ efflux into the functional components of construction and maintenance respiration. Construction respiration was estimated from annual stem dry matter production and maintenance respiration by subtracting construction respiration from the instantaneous CO₂ flux. Estimated maintenance respiration was linearly related to sapwood volume (39.6 mol m^–3s^–1 at 24.6° C, r ²=0.58), with no difference in the rate for the two species. Maintenance respiration per unit of sapwood volume for these tropical wet forest trees was roughly twice that of temperate conifers. A model combining construction and maintenance respiration estimated CO₂ very well for these species (r ²=0.85). For our sample, maintenance respiration was 54% of the total CO₂ efflux for Simarouba and 82% for Minquartia. For our sample, sapwood volume averaged 23% of stem volume when weighted by tree size, or 40% with no size weighting. Using these fractions, and a published estimate of aboveground dry-matter production, we estimate the annual cost of woody tissue respiration for primary forest at La Selva to be 220 or 350 g C m^–2 year^–1, depending on the assumed sapwood volume. These costs are estimated to be less than 13% of the gross production for the forest.     

23个实验小鼠和大鼠近交系的保种研究

从1985年开始,陆续从国外实验动物著名机构引进常用近交系小鼠共23个品系(亚系和亚群)。在多年来保种繁殖过程中,根据修饰平行线系统选择留种动物,同时对动物进行全兄妹近亲交配繁殖,保持完整的谱系记录,控制饲养环境条件,成功地保持了绝大多数品系。同时对多数品系的繁殖性能和体重增长进行了观察,为这些品系的实验应用提供基本参数。     

不同血液净化方法对维持性血液透析尿毒症动脉粥样硬化患者血清microRNA-144和microRNA-155水平的影响及其临床意义

摘要 目的：探讨不同血液净化方法对维持性血液透析（MHD）尿毒症动脉粥样硬化患者血清microRNA-144和microRNA-155水平的影响及其临床意义。方法：选取2019年6月~2020年6月川北医学院附属医院收治的98例MHD尿毒症动脉粥样硬化患者为研究组,另选取98例同期本院体检健康的志愿者为健康对照组,比较两组血清microRNA-144和microRNA-155、血清炎症因子[白细胞介素-6（IL-6）、单核细胞趋化蛋白-1（MCP-1）、超敏C反应蛋白（hs-CRP）]水平。采用Pearson分析法分析血清microRNA-144、microRNA-155水平与MHD尿毒症动脉粥样硬化患者内膜中层厚度（IMT）值、斑块面积及血清炎症因子的相关性。采用多因素Logistic回归分析MHD尿毒症动脉粥样硬化患者IMT增厚的影响因素。将研究组按随机数字表法分为血液透析滤过组和血液灌流组,各49例。血液透析滤过组给予血液透析滤过联合血液透析治疗,血液灌流组给予血液灌流联合血液透析治疗。比较两组血清microRNA-144和microRNA-155、血清炎症因子水平、IMT值和斑块面积。结果：研究组血清microRNA-144、microRNA-155、IL-6、MCP-1、hs-CRP水平明显高于健康对照组（P<0.05）;Pearson相关性结果显示,血清microRNA-144、microRNA-155均与MHD尿毒症动脉粥样硬化患者IMT值、斑块面积及IL-6、MCP-1、hs-CRP均呈正相关（P<0.05）;多因素Logistic回归分析结果显示,血清microRNA-144、microRNA-155、IL-6、MCP-1、hs-CRP水平均是导致MHD尿毒症动脉粥样硬化患者IMT增厚的危险因素（P<0.05）。治疗后,血液灌流组血清microRNA-144和microRNA-155水平均明显低于血液透析滤过组（P<0.05）,IL-6、MCP-1、hs-CRP水平均明显低于血液透析滤过组（P<0.05）,IMT值和斑块面积均明显低于血液透析滤过组（P<0.05）。结论：血清microRNA-144、microRNA-155水平与IMT值、斑块面积及IL-6、MCP-1、hs-CRP水平呈正相关,均是MHD尿毒症动脉粥样硬化患者IMT增厚的危险因素。血液灌流联合血液透析治疗可减轻机体炎症反应,延缓动脉粥样硬化进程,可能与下调患者血清microRNA-144、microRNA-155水平有关。     

A method for the determination of confidence limits for the P/2e − ratio for chosen values of Y ATP max from the results of continuous culture experiments

A model is described, which allows the determination of 95% confidence limits for the maintenance coefficient and the efficiency of oxidative phosphorylation for chosen values of the growth yield for ATP corrected for energy maintenance (Y _ATP ^max ). As experimental data the specific rates of substrate consumption, product formation and oxygen uptake in chemostat cultures at various growth rates are used.     

Energy conservation during nitrate respiration in Paracoccus denitrificans

P/2e ratios were calculated from anaerobic chemostat cultures of Paracoccus denitrificans with nitrogenous oxides as electron acceptor. P/2e ratios were calculated, using the Y _ATP ^max values determined for aerobic cultures. When succinate was the carbon and energy source the average P/2e values of the sulphate-and succinate-limited cultures with nitrate as electron acceptor were 0.5 and 0.7, respectively, and of the nitrite-limited culture 0.9. With gluconate as carbon and energy source the average P/2e values of the gluconate-limited with nitrate as electron acceptor and nitrate limited cultures were 0.9 and 1.1, respectively.H⁺/O ratios measured in cells obtained from sulphate-, succinate, nitrite-, gluconate-and nitratelimited cultures yielded respective average values of 3.4, 4.5, 3.5, 4.8 and 6.2 for endogenous substrates. From our data we conclude that sulphate-and nitritelimitation causes the loss of site I phosphorylation. Nitrite has no influence on the maximum growth yield on ATP. We propose that metabolism in heterotrophically grown cells of Paracoccus dentrificans is regulated on the level of phosphorylation in the site I region of the electron transport chain.     

Maintenance energy demand affects biomass synthesis but not cellulase production by a mesophilicClostridium

Summary Secretion of cellulolytic activity by the mesophilClostridium strain C7 was studied while the bacterium underwent progressive carbon/energy starvation and the ensuing continuous decline in growth rate. In the slowest range of growth rates studied the organism was in full response to the global regulation imposed by guanosine 5, 3-bispyrophosphate (ppGpp). The exoenzymes of the cellulase complex were produced at the same volumetric rate whether or not the response was active. However, the volumetric rate of biomass synthesis was reduced 45% or more by the response. Energy necessary to maintain the ppGpp-regulated state (i.e., maintenance energy) was, therefore, diverted from energy going to synthesis of biomass but not from that going to exoenzyme synthesis, making the yield of cellulase activity per mole of carbon-energy substrate independent of growth rate and the exoenzyme complex produced from the substrate with equal efficiency at all growth rates. The primary consideration in improving exoenzyme productivity by bacteria with this type of energy distribution between secretion, growth, and maintenance is simply increasing yield per mole of carbon-energy substrate, with growth rate effects on yield a secondary and minimum concern.