Capitalizing on multi-element interactions through balanced nutrition — A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.

     

大鼠发育过程中肝、肺r-GT酶活性和定位

用生物化学和组织化学方法研究正常发育中大鼠肝、肺r-GT活性和定位。结果表明:肝r-GT活性自胚龄17天开始升高,21天达高峰,出生第一天明显降低,第六天降至接近成年低水平。在胚胎期肝r-GT主要位于肝细胞内,出生后则主要位于胆小管。该结果提示胚胎期肝r-GT主要参与肝细胞膜上氨基酸的转运。出生后可能主要参与解毒功能,大鼠肺r-GT活性随发育逐步升高,主要分布于肺支气管上皮细胞。提示肺r-GT可能参与解毒功能。     

Platelet-collagen interaction. Inhibition by a monoclonal antibody raised against collagen receptor

Monoclonal antibodies to the purified platelet type I collagen receptor were produced to study platelet receptor function. The antibody specifically reacted with the platelet receptor in immunoblot experiments. The IgG purified from the monoclonal antibodies and isolated Fab' fragments inhibited the binding of radiolabeled alpha 1(I) chain to washed platelets competitively. Soluble and fibrillar type I collagen-induced platelet aggregations were inhibited by purified IgG suggesting that soluble and fibrillar collagens shared a common receptor. The adhesion of platelets to an artificial collagen matrix was also inhibited by the monoclonal antibody. However, adenosine diphosphate-induced platelet aggregation was not inhibited by the same amount of IgG that inhibited collagen-induced platelet aggregation. The results suggest that collagen-induced platelet aggregation is mediated through the interaction of collagen with the platelet receptor.     

鄂中一些被子植物硅化木研究

本文研究了我国首次在长江北岸,湖北省新洲县发现的新生代晚第三纪大戟科、豆科和樟科的被子植物硅化木。这些硅化木的发现和鉴定,反映了该地区当时较为炎热潮湿的气候环境,并为长江流域新生代的地质、古气候、古地理、古生物群演变等方面的研究,提供了论据。     

季节、环境温度与黄鼠冬眠的关系

观察了达乌尔黄鼠在实验室内冬眠的一般情况。常温黄鼠的体温有着规律性的年周期,与环境温度的年周期变动不完全呈依从关系。出眠初期(4月下旬),动物体温高而稳定。4月至6月常温黄鼠的平均体温(皮温)为35.6℃,波动菹围32—37.5℃。随着体重达到顶峰,体温逐渐降低。8月份部分黄鼠出现低于32℃的低常体温,表明部分黄鼠自8月盛夏开始冬眠。但就整个种群而言,北京地区实验室内黄鼠冬眠季自9月下半月开始。3月底止,共6.5个月。秋季室温下降,动物入眠趋势增长。浅低体温(31.9—15℃)的比数逐渐升高。9月至12月,低体温(低于31.9℃)的百分比从47％增至84.8％,反映了动物从浅冬眠向深冬眠过渡。1月至2月份,低体温占85％以上,深低体温(低于15℃)占绝对优势。标志着动物种群的深眠月份。秋季动物从常温期向冬眠期转化的界线是不清的,而春季从冬眠期向常温相转化的界限却比较明显。     

记辽宁东部新鳞齿鱼属一新种

本文记述了产自辽宁东部红庙子盆地下桦皮甸子组的新鳞齿鱼属—新种——Neolepidotes liaodongensis sp. nov..根据新材料,将 Neolepidotes 与 Lepidotes 等属作了补充比较,增订了新鳞齿鱼属的特征.     

E.p.r.-spectroscopic studies on the molybdenum-iron site of nitrogenase from Clostridium pasteurianum.

The e.p.r. spectroscopy of the nitrogenase molybdenum-iron protein from Clostridium pasteurianum was re-investigated. The sharpness of the delta Ms = +/- 3 g'z peak from the +/- 3/2 Kramer's doublet enables the observation and quantification of incompletely resolved hyperfine splittings from the stable magnetic nuclei 95Mo and 57Fe in samples enriched in these isotopes. No couplings to 1H or 17O could be discerned by examination of spectra from samples exchanged into 2H2O and H2(17)O respectively. Simulation of the spectrum from 95Mo-enriched samples yields a hyperfine coupling of 2.9 MHz, and indicates that the earlier electron-nuclear-double-resonance-derived estimate of 8.1 +/- 0.2 MHz is substantially in error.     

Genetic convergence during serial in vitro passage of a polyclonal squamous cell carcinoma

A cell line was established from an in situ squamous cell carcinoma of the skin (Bowen's disease), and its in vitro karyotypic evolution was cytogenetically analyzed. Initially, considerable genetic heterogeneity was evident. Nine cytogenetically abnormal clones, eight of which were apparently unrelated, were found among the 83 metaphases analyzed from the primary culture and the first passage. With increasing time in culture this complexity was reduced, so that a single clone dominated passages 7-11. The clone that emerged from this genetic convergence had a t(12;17)(p13;q21) as the sole abnormality. Our findings indicate that the cytogenetic multiclonality that has been repeatedly detected in short-term cultures of squamous cell carcinomas is not caused by the in vitro conditions. Instead, the principles of Darwinian selection apply: the altered, but stable, selection pressure facing a newly established and initially multiclonal cell line will lead to a reduction of genetic heterogeneity until the one clone that now has the proliferative advantage outgrows the other subpopulations.     

How does l-glutamate transport relate to selection of mixed nitrogen sources in Rhizobium leguminosarum biovar trifolii MNF1000 and cowpea Rhizobium MNF2030?

When growing on a mixture of ammonia and l-glutamate as nitrogen sources, Rhizobium leguminosarum biovar trifolii MNF1000 utilizes ammonia exclusively, while cowpea Rhizobium MNF2030 utilizes both compounds at similar rates. l-Glutamate transport in both strain MNF1000 and MNF2030 is active, giving rise to a 60-fold concentration gradient across the membrane of cells of strain MNF2030. Both strains produce two kinetically distinguishable glutamate transport systems under all conditions of growth — a high affinity system with an apparent K _m of 0.06–0.17 M but of relatively low V _max, and a low affinity system with a K _m of 1.2–6.7\ M, but of higher overall capacity. l-Glutamate transport activity in cells of MNF2030 was relatively insensitive to the presence of ammonia in the growth medium. By contrast, ammonia in the growth medium resulted in low activities of glutamate transport in cells of MNF1000 which were provided with a carbon source, offering one explanation for the failure of this strain to use glutamate in the presence of ammonia. However, in cells of MNF1000 growing on glutamate as sole source of carbon and nitrogen, the glutamate transport system is synthesized, even in the presence of accumulated or added ammonia. This suggests that the regulation of the glutamate permease also depends on availability of carbon source.Abbreviations CCCP carbonyl cyanide m-chlorophenyl hydrazone - HEPES N-hydroxyethylpiperazine-N-2-ethanesulphonic acid     

4-aminobutyrate is not available to bacteroids of cowpea Rhizobium MNF2030 in snake bean nodules

Laboratory cultures of cowpea Rhizobium MNF2030 grew on 4-aminobutyrate (GABA) as sole source of carbon and nitrogen. GABA transport was active since it was inhibited by carbonyl cyanide mchlorophenyl hydrazone and 2,4-dinitrophenol and cells developed a 400-fold concentration gradient across the cell membrane. Arsenite treatment of GABA-grown cells revealed stoichiometric conversion of GABA to pyruvate, indicating that 2-oxoglutarate is not an intermediate in GABA catabolism. GABA catabolism by cells of strain MNF2030 grown on GABA appreared to involve GABA transaminase, succinic semialdehyde dehydrogenase and malic enzyme; the first two enzymes were specifically induced by growth on GABA. The deamination process and removal of NH₃ in cells catabolizing GABA involved GABA: 2-oxoglutarate transaminase; glutamate: oxaloacetate aminotransferase; asparate: pyruvate aminotransferase and alanine dehydrogenase.Isolated snakebean bacteroids of strain MNF2030 transported only small amounts of GABA and had uninduced levels of GABA catabolic enzymes, even though the nodules contained significant levels of GABA. The data suggest that GABA is not available to snakebean nodule bacteroids, presumably because of a control imposed by the peribacteroid membrane.Abbreviations CCCP Carbonyl cyanide m-chlorophenyl hydrazone - HEPES N-hydroxyethylpiperazine-N-2-ethanesulphonic acid - DTT dithiothreitol - SSAD succinic semialdehyde dehydrogenase - GABAT 4-aminobutyrate transaminase - GABA 4-aminobutyrate