Synthesis and antibacterial activity of C6-carbazate ketolides

A novel series of ketolides containing heteroaryl groups that are linked to the erythronolide ring via a C6-carbazate functionality has been successfully synthesized. Careful modulation of the heteroaryl groups, the length and degree of saturation of the C6-carbazate linker, and the substituents present on each of the carbazate nitrogens led to compounds with potent activity against key bacterial respiratory pathogens. The best analogs of this series had in vitro and in vivo (sc dosing) profiles that were comparable to telithromycin.     

Distribution of Metabolites and Enzymes of Nitrogen Metabolism between the Mesophyll and Paraveinal Mesophyll of Non-Nodulated Glycine max

The distribution of amino acids and key enzymes involved innitrogen metabolism was determined in mesophyll cells (MC),mesophyll protoplasts (MP), and paraveinal mesophyll protoplasts(PVMP) isolated from fully expanded trifoliolate leaves of non-nodulatedsoybean. Qualitative and quantitative differences were foundin the distribution of amino acids, with MP containing the highestconcentrations. Activity of nitrate reductase, glycolate oxidase,glutamine synthetase and glutamate dehydrogenase was measuredin both tissue types and differences in activities between thetissue types were seen. PVMP had high glutamate dehydrogenaseactivity when compared to MP. Activities of glycolate oxidaseand glutamine synthetase were much higher in MP on a protoplastbasis while nitrate reductase activity was similar between thetwo protoplast types. These results, on the distribution ofmetabolites and associated enzymes, are discussed as to theirpossible significance to nitrogen metabolism in the soybeanleaf. Key words: Amino acids, glutamate dehydrogenase, Glycine max, nitrate reductase, nitrogen metabolism, paraveinal mesophyll, protoplasts     

The physiological basis of increased biomass partitioning to roots upon nitrogen deprivation in young clonal tea (Camellia sinensis (L.) O. Kuntz)

Deprivation of nitrogen (N) increases assimilate partitioning towards roots at the expense of that to shoots. This study was done to determine the physiological basis of increased root growth of tea (sCammellia sinensis L.) under N shortage. Nine-month-old clonal tea (clone TRI2025) was grown in quartz sand under naturally lit glasshouse conditions. Three levels of N (0, 3.75 and 7.5 mM N) were incorporated in to the nutrient solution and applied daily. Plant growth, photosynthesis, root respiration and plant N contents were measured at 10-day intervals over a 45-day period. Root dry weight showed a sharp increase during the first 15 days after the plants were transferred to 0 mM N, whereas no such increase was shown in plants transferred to 7.5 mM N. In contrast, shoot dry weight increased at 7.5 mM N and was significantly greater than at 0 mM N, where no increase was observed. Due to the above changes, root weight ratio increased and leaf weight ratio decreased during the first 15 days of N deprivation. Leaf photosynthetic rates did not vary between N levels during the initial 15-day period. Thereafter, photosynthetic rates were greater at 7.5 mM and 3.75 mM N than at 0 mM N. Root respiration rate decreased at 0 mM N, whereas it increased at 3.75 and 7.5 mM N, probably because of the greater respiratory cost for nitrate uptake. Root respiratory costs associated with maintenance (R _m) and nitrate uptake (R _u) were calculated to investigate whether the sharp increase of root growth observed upon nitrogen deprivation was solely due to the reduced respiratory costs for nitrate uptake. The estimated values for R _m and R _u were 3.241 × 10^–4 mol CO₂ g^–1 (root dry matter) s^–1 and 0.64 mol CO₂ (mol N)^–1, respectively. Calculations showed that decreased respiratory costs for nitrate uptake could not solely account for the significant increase of root biomass upon N deprivation. Therefore, it is concluded that a significant shift in assimilate partitioning towards roots occurs immediately following N deprivation in tea.     

电刺激大鼠延髓头端腹外侧区对交感节前神经元单位放电的影响

本实验用氨基甲酸乙酯麻醉和箭毒化的雄性大鼠,细胞外记录脊髓胸2节段的交感节前神经元(SPN)单位放电,电刺激同侧颈交感干,逆向激活 SPN,以确定所记录的神经元为交感节前神经元。共分析了80个 SPN 单位放电,其中有自发活动和无自发活动的单位各40个。SPN 轴突传导速度为0.59—3.75m/s。实验观察到电刺激同侧延髓头端腹外侧区(Rostralventrolateral medulla:RVL)可兴奋多数有自发活动的 SPN(19/25),并可使少数静止SPN 产生诱发反应(4/23),潜伏期为6—115ms。电刺激对侧 RVL 结果类似:多数自发活动的 SPN(6/9)呈兴奋反应,及少数静止 SPN(3/17)产生诱发反应,潜伏期为11—105ms。表明 RVL 对双侧 SPN 有兴奋性影响。     

Structural attributes of the hypogeous holoparasite Hydnora triceps Drege & Meyer (Hydnoraceae)

The morphology of the hypogeous root holoparasite Hydnora triceps is highly reduced, and as with many holoparasites, the vegetative body is difficult to interpret. The vegetative body of H. triceps has been historically considered a "pilot root" studded with lateral appendages known as "haustorial roots." We found the vegetative body of H. triceps to consist of a rhizome with a thickened root-cap-like structure that covered a vegetative shoot apical meristem. From the apical meristem, procambial strands originated and developed into endarch collateral vascular bundles arranged radially around a pith without an interfascicular cambium. Xylem vessels had scalariform pitting and simple perforation plates. A continuous periderm without root hairs was observed. Increase in girth was attributed to cork and fascicular cambia. "Haustorial roots" or bumps on the surface of the vegetative body were exogenous, contained meristems and were the origins of vegetative branching, budding, and haustoria. The haustoria of H. triceps were cylindrical and penetrated the host root stele. Phloem and xylem elements were observed within the endophyte, and direct xylem to host-xylem contacts were observed. The arrangement of vascular tissues and xylem anatomy of H. triceps are likely plesiomorphic features in light of Hydnoraceae's placement in the Piperales.     

Dependence of the Post-Illumination Burst of CO2 on Temperature, Light, CO2, and O2 Concentration in Wheat (Triticum aestivum)

The effect of environmental factors on the post-illumination burst of CO₂ (PIB) and O₂ inhibition of apparent photosynthesis (APS) in wheat (Triticum aestivum L.) was studied in an open gas exchange system utilizing the mathematics of non-steady-state systems. Two components of inhibition by O₂ are suggested: one is caused by photorespiration as measured from the maximum rate of the PIB, and the second is direct inhibition as taken as APS_2%O2— (APS_x%O2+ PIB_x%O2) where X is the oxygen concentration. A primary PIB which occurred from 16–28 s after the darkening of the foliage was attributed to photorespiration. No primary PIB was observed at 2% O₂. At a CO₂ concentration of 100 μ/1 in the atmosphere (about 2.5 μM based on leaf intercellular concentration) and at 30°C and 145 nE/cm² nE/cm²·s, APS decreased curve-linearly with increasing O₂ and reached an O₂ compensation point of 560 μM (48% by volume), above which there was a net loss of CO₂ in the light. The PIB increased with increasing O₂ and became saturated at about 500 μM O₂ but decreased above 900 μM O₂. Direct inhibition of photosynthesis by O₂ increased with increasing O₂ concentration. Decreasing CO₂ concentration had an effect on the magnitude of the PIB similar to that of increasing O₂. At 30°C and 21% O₂, the PIB increased with decreasing CO₂ down to the CO₂ compensation point (I) of 1.4 μM (47 μM/l). Below Γ, both PIB and CO₂ evolution into the air in the light (at 21% O₂) increased and then decreased at CO₂ below 0.8 μM. The ratio of the PIB to APS_{2% o} O₂ increased linearly with increasing O₂/CO₂ ratio where O₂ was held constant at 21% and CO₂ was varied from 1.4 to 8.5 μM, while direct inhibition of photosynthesis expressed as a proportion of APS_2%O2 remained constant over this range. At low CO₂ concentration photorespiration as estimated by the PIB is the major part of O₂ photosynthesis, while at atmospheric CO₂ levels, direct inhibition is the major component. The PIB and APS at 2% and 21% O₂ increased hyperbolically with increasing irradiance and all became light-saturated at about 65 nE/cm₂ s. The percentage total O₂ inhibition of photosynthesis remained constant with increasing irradiance as did the relative contribution of direct O₂ inhibition or photorespiration (PIB) to total O₂ inhibition. The PIB and APS at 21% O₂ had similar temperature optima of 30°C when experimental conditions were adjusted to provide a constant internal O₂/CO₂ solubility ratio at varying temperatures. However, with a constant external CO₂ concentration, the temperature optimum for the PIB shifted upward to 35°C while that for APS at 21% O₂ remained at 30°C, which may be due to an increased O₂/CO₂ concentration in the leaf with increasing temperature.     

低钾胁迫对不同基因型水稻苗期根系生长和内源激素含量的影响

以2个耐低钾基因型水稻N18、N19和2个低钾敏感基因型水稻N27、N28为材料,采用溶液培养试验,研究低钾胁迫对其苗期根系生长和内源激素含量的影响。结果表明,低钾胁迫下,水稻根长、地上部干重和根干重均降低,但N18和N19显著高于N27和N28。低钾胁迫使4个基因型水稻的根冠比增大,而各基因型之间差异不显著。低钾胁迫下,水稻根中IAA、GA₁和ZR含量均减少,ABA含量增加;N18、N19根中IAA、GA₁和ZR含量都高于N27、N28。此外,低钾胁迫使水稻根中IAA/ABA、ZR/ABA、GA₁/ABA值降低,但N18、N19的上述比值高于N27、N28。     

Mineral nutrition of the hyperparasitic mistletoe Viscum articulatum Burm. f. (Viscaceae) in tropical Brunei Darussalam

A plant parasite parasitizing another plant parasite is known as a hyperparasite. Information is scarce regarding the ecophysiology of hyperparasites and their hosts despite their potential to illuminate processes of host–parasite solute flux. Here we present mineral profiles and stable isotopic data for two associations of the hyperparasite Viscum articulatum and its primary mistletoe and tree hosts. Acting as the terminal sink, the hyperparasite had consistently higher contents of all major and minor elements evaluated compared to the primary parasite and the proximal portion of the tree host branch. The primary parasite had lower contents of Cu, Mg, Mn, N, and Z relative to the proximal portion of the tree host branch, suggesting nutritional stress applied by the hyperparasite. Interestingly Fe and Cu showed no consistent pattern between host and primary parasite, while the osmotically active elements P and K increased from tree host, to primary mistletoe, and finally the hyperparasitic mistletoe. The δ¹³C partitioning patterns for hyperparasites, primary parasites, and hosts were non‐linear in contrast to linear patterns reported from the literature for autoparasitic mistletoe associations, demonstrating fundamental differences between nutrition in hyperparasites and autoparasites.