燕麦-绿豆间作效应及氮素转移特性

为探究燕麦(Avena sativa)-绿豆(Phaseolus radiatus)间作效应及氮素转移特性, 在不施氮肥的大田试验条件下, 设置3种种植模式(燕麦单作、绿豆单作和燕麦-绿豆间作), 采用传统挖根法和¹⁵N同位素标记法进行研究。结果表明, 间作系统中燕麦侵袭力强于绿豆, 绿豆生长受到抑制。整个生育期, 间作燕麦地上部干物质积累量比单作增加14.9%-33.1%, 2年成熟期间作燕麦的氮素积累量比单作分别提高53.1%和44.8%; 间作减少了开花结荚期绿豆氮素积累量和根瘤重量, 降低了绿豆的固氮效率, 绿豆的固氮效率2年平均降低23.7%, 生物固氮量平均减少11.66%。间作绿豆向燕麦的氮素转移率2年平均值达31.7%, 氮素转移量为212.16 kg∙hm^-2。燕麦-绿豆间作降低了开花结荚期绿豆的根瘤固氮酶活性和固氮效率, 但绿豆体内氮素转移增加了燕麦对氮素的吸收利用, 实现了地上部与地下部生长的相互调节和促进, 优化了农田生态系统的氮素管理。     

真核生物DNA复制起始调控

复制起始调控是真核生物复制调控机制的重要环节,也是细胞生长调控的核心问题．对SV40病毒和酵母体系的研究为阐明真核生物的复制起始机制及其与细胞周期的关系提供了线索．目前,与DNA复制起始有关的多种蛋白质因子（如核蛋白P₁,DNA单链结合蛋白,DNA聚合酶α,增殖细胞核抗原等）的作用机理逐渐明朗,周期依赖的调控特点得到了证实文章着重介绍了DNA复制起始在细胞周期中的两个调控点及各种周期蛋白在该点的作用,文中还涉及复制起始异常与肿瘤发生的关系.     

Large-scale physical mapping within the region 22q12.3-13.1 in meningioma

The lack of physical mapping data strongly restricts the analysis of the meningioma chromosomal region that was assigned to the bands 22q12.3-qter. Recently, we reported a new marker D22S16 for chromosome 22 that was assigned to the region 22q13-qter by in situ hybridization. Utilizing somatic cell hybrids we now sublocalized the marker D22S16 within the band region 22q12-13.1, thus placing it in the vicinity of the gene for the platelet derived growth factor (PDGFB). A physical map was established for the regions surrounding the PDGFB gene and the D22S16 marker. By means of pulsed-field gel electrophoresis (PFGE) D22S16 and PDGFB were found to be physically linked within 900 kb. We also identified two CpG clusters bordering the PDGFB gene. For the enzyme NotI, a variation of the PDGFB restriction pattern was found between different individuals. PFGE analysis of the two loci (PDFGB and D22S16) failed to identify major rearrangements in meningioma.     

Quantitative studies on the arrangement of human metaphase chromosomes

Summary The spatial relationships between the homologous pairs of chromosomes in the normal human colcemid-treated metaphase plate were tested by two different mathematical approaches: (a) determination of the distances between the centromeres of the homologous chromosomes compared to the mean distance of all centromeres of the mitosis in question; (b) measuring the distances of the different chromosomes from the center of the mitosis.The following results were obtained: (1) The arrangement of human metaphase chromosomes does not follow a normal distribution; the distribution is narrower and taller, probably due to an impairment of free chromosome spreading by the cell membrane. We believe that only in membraneless mitotic cells should the chromosome-spread correspond to a normal distribution under the same preparation conditions. (2) There is a positive correlation between decreasing chromosome size and decreasing mean distance between homologous chromosomes. (3) A close positive correlation exists between increasing chromosome size and increasing distance to the barycenter of the mitosis. (4) There is also a close positive correlation between the distance of homologous chromosome pairs and their distance from the center of the mitosis, i.e., with increasing distance from the center of the mitosis, the distance between the homologous partners increases. (5) The following statistically significant deviations from these rules could be established: (a) The large acrocentric chromosomes are closer associated, as one would expect from their size, probably due to their participation in the nucleolus organization; (b) in the female cell one of the two X chromosomes has an extremely peripheral localization; the X chromosomes are furthest apart of all pairs of homologous chromosomes; (c) the chromosome pairs 6 and 8 are relatively close together in spite of their peripheral position, suggesting a truc close association of the homologus partners; (d) the chromosome pair 18 has a more peripheral position than expected, and a relatively large mean distance between the homologous partners; (e) the chromosome pair 1 has a much more central position and a closer association than is expected from its size.     

Quantitative studies on the arrangment of human metaphase chromosomes

Summary The pattern of association of acrocentric chromosomes was examined in ten and five carriers of a 15/21 and a 13/14 Robertsonian translocation, respectively, and was compared with that of the same numbers of relatives with normal karyotypes. In the carriers of 15/21 translocation, the number of large associations (involving more than two acrocentrics) and the association frequencies for individual acrocentric chromosomes, were significantly higher than in the control group. The mean number of associations of the single homologs of the translocation chromosomes was much higher than that of the other acrocentrics. In the carriers of 13/14 translocations, only the association frequency for chromosome 13 was higher than in the normal relatives. The uninvolved chromosomes homologous to those involved in translocations showed an insignificant increase in associations in comparison with the other acrocentrics. These results suggest that some mechanism within the cells compensates for the effect of missing acrocentrics or of acrocentrics lacking NORs on the number of associations. The possible relations of this phenomenon to the activity of the nucleolus organizing regions are discussed.     

Cytological and cytogenetical studies on brain tumors. V. Preferential loss of sex chromosomes in human meningiomas.

Twelve out of 88 cytogenetically examined meningiomas of female patients showed, in addition to the typical loss of a chromosome 22, a loss of 1 or more chromosomes of group C. Among them 8 tumors had less than 8% cells with Barr-body-like particles, whereas in one tumor 12% and in 3 others over 20% Barr bodies were found, which, based on control studies, were classified as sex-chromatin negative, partly positive, and positive, respectively. In one case the loss of an X chromosome was verified by Giemsa banding. In 6 out of 24 meningiomas of male origin, the chromosomal morphology and association pattern strongly indicated that besides the loss of a chromosome 22, the Y chromosome was also missing. Moreover, the loss of the male sex chromosome could be ascertained in 4 tumors by the conspicuous absence of Y fluorescence in interphase nuclei and in metaphase plates after fluorescence staining. The findings are discussed in connection with the gonosomal loss in other human tumors and in old age.     

Cytological and cytogenetical studies on brain tumors

Summary Twelve out of 88 cytogenetically examined meningiomas of female patients showed, in addition to the typical loss of a chromosome 22, a loss of 1 or more chromosomes of group C. Among them 8 tumors had less than 8% cells with Barr-body-like particles, whereas in one tumor 12% and in 3 others over 20% Barr bodies were found, which, based on control studies, were classified as sex-chromatin negative, partly positive, and positive, respectively. In one case the loss of an X chromosome was verified by Giemsa banding.In 6 out of 24 meningiomas of male origin, the chromosoma. morphology and association pattern strongly indicated that besides the loss of a chromosome 22, the Y chromosome was also missing. Moreover, the loss of the male sex chromosome could be ascertained in 4 tumors by the conspicuous absence of Y fluorescence in interphase nuclei and in metaphase plates after fluorescence staining.The findings are discussed in connection with the gonosomal loss in other human tumors and in old age.

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Zusammenfassung Unter 88 cytogenetisch untersuchten Meningeomen von Frauen wurden 12 Tumoren gefunden, bei denen außer dem für Meningeome typischen Verlust eines Chromosoms 22 auch ein oder mehrere Chromosomen der C-Gruppe verlorengegangen waren. Bei 8 dieser Tumoren konnte in Gewebekulturpräparaten nur in weniger als 8% der untersuchten Zellen Barr-body-ähnliche Kernstrukturen nachgewiesen werden, bei einem Tumor fanden sich 12% und bei 3 über 20% Barr-bodies. Auf Grund von Vergleichsuntersuchungen wurden 8 Tumoren als geschlechtschromatinnegativ, 1 Tumor als teilweise positiv und die übrigen 3 als eindeutig positiv eingestuft. Bei einem Meningeom konnte das Fehlen eines X-Chromosoms direkt mit der Giemsa-Bandentechnik nachgewiesen werden.Bei 6 von 24 Meningeomen männlicher Herkunft konnte auf Grund der Chromosomenmorphologie und des Assoziationsverhaltens sehr wahrscheinlich gemacht werden, daß außer dem Chromosom 22 auch das Y-Chromosom verlorengegangen war. Bei 4 dieser Tumoren konnte eine Fluorescenzfärbung durchgeführt werden, wobei das Fehlen einer Y-Fluorescenz in Interphasezellen und Metaphaseplatten nachweisbar war.Diese Befunde werden im Zusammenhang mit dem Geschlechtschromosomenverlust bei anderen menschlichen Tumoren und im hohen Lebensalter diskutiert.

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Supported by the Deutsche Forschungsgemeinschaft (SFB 51 E 12).

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Parts of this work are included in the doctoral thesis (M.D.) of H.S. at the University of Munich, Germany.     

资源型城市土地利用转型及其对生境质量的影响——以乌海市为例

资源型城市前期发展导致了生境丧失或退化,实现高质量转型需要深入理解城市转型与生态环境质量之间的关系,土地利用转型特征及其对生境质量的影响规律研究为此提供依据与支撑。以资源型城市--乌海市为研究区,通过地学信息图谱和InVEST模型探究2005-2018年乌海市土地利用转型特征、生境质量时空变化及土地利用转型对生境质量的影响。结果表明：（1）2005-2018年乌海市土地利用变化趋势发生改变,土地利用转型明显,土地利用变化图谱单元数量逐渐增加78.14%,分布范围逐渐广泛。主要表现为草地与建设用地、采矿用地之间的相互转化,第一阶段（2005-2015年）草地大面积减少,建设用地和采矿用地大面积增加,第二阶段（2015-2018年）趋势相反。（2）乌海市生境质量变化呈现先强退化后弱提升趋势。2005-2015年乌海市18.75%的区域生境质量退化,提升面积较小;2015-2018年生境质量提升面积略大于退化面积。（3）2005-2015年草地向采矿用地、建设用地转化是区域生境质量降低的主要原因,2015-2018年区域生境质量提升的主导因素是采矿用地和建设用地向草地转化。研究结果揭示了资源型城市土地利用转型过程中生境质量的响应规律,可为资源型城市土地利用转型决策提供参考。     

中国森林生态系统林冠层降雨截留特征

森林生态系统作为陆地生态系统的主体,其发达的林冠层通过调节降水量、改变降水强度等深刻影响着流域全过程水文通量及水分输出。以中国广泛开展的典型森林降雨再分配过程的年尺度监测数据为基础,揭示中国不同类型森林生态系统的降雨再分配及林冠层降雨截留特征,阐明森林生态系统林冠层截留特征与降雨、植被要素的关系。结果表明:我国不同森林生态系统年穿透雨量处于141.4-2450.0 mm之间,年穿透雨率为36.3%-92.3%。5种典型森林生态系统多年平均穿透雨量((445.3±252.9)-(1230.6±479.6) mm)占同期多年平均降雨量的(72.6±9.2)%-(77.4±8.9)%。不同森林生态系统年树干茎流量介于0-508.2 mm之间,占同期年降雨量的0-25.8%。5种典型森林生态系统树干茎流量多年平均值((9.8±17.3)-(87.8±81.6) mm)占同期多年平均降雨量的(1.4±1.9)%-(5.4±4.6)%。不同森林生态系统林冠层年降雨截留范围在25.7-812.9 mm之间,占年降雨量的4.2%-55.6%。5种典型森林生态系统多年平均林冠截留量((154.2±81.6)-(392.2±203.5) mm)占同期年平均降雨量的(18.7±7.4)%-(25.9±8.3)%。进一步分析表明,我国森林生态系统穿透雨量、树干茎流量和林冠层截留量随观测区年降雨量的增加而呈显著增大(P<0.05),年穿透雨率、年树干茎流率随年降雨量的增加呈显著线性上升趋势(P<0.05),而年林冠截留率与年降雨量呈显著的负相关关系(P<0.01),降雨量、叶面积指数是深刻影响森林生态系统林冠层降雨截留率等特征的重要因素。整体上,不同类型森林生态系统林冠截留降雨能力存在明显差异,林冠层截留率突出表现为:落叶林大于常绿林、针叶林大于阔叶林。