棕色棉细胞质雄性不育花药的细胞学观察

对棕色棉细胞质雄性不育系和保持系的小孢子发生进行了细胞学观察. 结果表明,棕色棉不育系小孢子发生败育的时期是在造孢细胞增殖至小孢子母细胞进行减数分裂的整个过程中. 造孢细胞和小孢子母细胞退化导致雄性不育的主要细胞形态学特征是:造孢细胞核仁增大、细胞质液泡化和细胞形状畸形,还有因核仁物质弥散而使整个细胞染色较深;小孢子母细胞核仁穿壁普遍、多核仁、染色体行为异常、细胞互相粘连成巨型团块和液泡化,彩色棉细胞质雄性不育花药内的造孢细胞和小孢子母细胞的败育与绒毡层的过早退化密切相关.     

Lateral hopping of molecules induced by excitation of internal vibration mode

We demonstrate electron-stimulated migration for carbon monoxide (CO) molecules adsorbed on the Pd(110) surface, which is initiated by the excitation of a high-frequency (HF) vibrational mode (C-O stretching mode) with inelastic tunneling electrons from the tip of scanning tunneling microscopy. The hopping phenomenon, however, cannot be detected for CO/Cu(110), even though the hopping barrier is lower than in the CO/Pd(110) case. A theoretical model, which is based on the anharmonic coupling between low-frequency modes (the hindered-translational mode related to the lateral hopping) and the HF mode combined with electron-hole pair excitation, can explain why the hopping of CO is observed on Pd(110) but not on Cu(110).     

Conversion of ectoderm to mesoderm by cytoplasmic extrusion in leech embryos

The role of cytoplasmic domains in the determination of the fates of ectodermal and mesodermal cells has been investigated in leech embryos. When yolk-deficient cytoplasm (teloplasm) was extruded from the animal pole of the zygote, the ectodermal precursor blastomere was converted to a mesodermal fate. This change of fate can be prevented by replacement of the extruded animal teloplasm with teloplasm from the vegetal pole. The fate of the mesodermal precursor blastomere was unaffected by teloplasm extrusion or rearrangement. These results demonstrate that ectodermal and mesodermal determination offate involves a binary decision dependent on the position of teloplasm along the animal-vegetal axis.     

Disrupted timing of discontinuous but not continuous movements by cerebellar lesions

Patients with cerebellar damage are known to exhibit deficits in the temporal control of movements. We report that these deficits are restricted to discontinuous movements. Cerebellar patients exhibited no deficit in temporal variability when producing continuous, rhythmic movements. We hypothesize that the temporal properties of continuous movements are emergent and reflect the operation of other control parameters not associated with the cerebellum. In contrast, discontinuous movements require an explicit representation of the temporal goal, a function of the cerebellum. The requirement for explicit temporal representation provides a parsimonious account of cerebellar involvement in a range of tasks.     

Prenatal cerebral development: effect of restricted diet, reversal by growth hormone

Caloric restriction of rats from day 10 to day 20 of pregnancy results in significant decreases in body weight, placental weight, cerebral weight, cerebral DNA, and cerebral protein of the offspring at birth. These decreases did not usually occur if mothers on the restricted diet were treated concomitantly with bovine growth hormone. If growth hormone did not cross the placenta, then, it is postulated, at least one effect of growth hormone was the mobilization of maternal nutrient reserves.     

基于转录组测序对紫花苜蓿细胞质雄性不育系相关代谢通路的鉴定

【目的】研究紫花苜蓿(Medicago sative L.)细胞质雄性不育(CMS)的机理,为紫花苜蓿利用不育系的育种工作提供理论基础。【方法】本研究以紫花苜蓿细胞质雄性不育系MSGN1A及其保持系MSGN1B为材料,进行转录组测序(RNA-Seq)以及基因功能注释,筛选与不育系机理相关的差异表达基因及代谢通路。【结果】Illumina测序共得到紫花苜蓿95 679条功能基因,经过差异表达分析筛选出187个显著差异表达的基因(DEGs),其中包括18个上调基因,169个下调基因。采用GO、KEGG、COG注释库分别对187个DEGs进行功能注释,其主要涉及催化活性、代谢活动、信号传导机制、合成、膜功能、碳水化合物运输和代谢、能量代谢等相关通路。【结论】筛选出与紫花苜蓿细胞质雄性不育性相关的代谢通路,初步探讨了紫花苜蓿细胞质雄性不育系的分子机理。     

Identifying kinetic barriers to mechanical unfolding of the T. thermophila ribozyme

Mechanical unfolding trajectories for single molecules of the Tetrahymena thermophila ribozyme display eight intermediates corresponding to discrete kinetic barriers that oppose mechanical unfolding with lifetimes of seconds and rupture forces between 10 and 30 piconewtons. Barriers are magnesium dependent and correspond to known intra- and interdomain interactions. Several barrier structures are "brittle," breakage requiring high forces but small (1 to 3 nanometers) deformations. Barrier crossing is stochastic, leading to variable unfolding paths. The response of complex RNA structures to locally applied mechanical forces may be analogous to the responses of RNA during translation, messenger RNA export from the nucleus, and viral replication.     

Origin of mountains on Io by thrust faulting and large-scale mass movements

Voyager stereoimages of Euboea Montes, Io, indicate that this mountain formed when a large crustal block was uplifted 10.5 kilometers and tilted by approximately 6 degrees. Uplift triggered a massive slope failure on the northwest flank, forming one of the largest debris aprons in the solar system. This slope failure probably involved relatively unconsolidated layers totaling approximately 2 kilometers in thickness, overlying a rigid crust (or lithosphere) at least 11 kilometers thick. Mountain formation on Io may involve localized deep-rooted thrust faulting and block rotation, due to compression at depth induced during vertical recycling of Io's crust.     

Cnidocyte mechanoreceptors are tuned to the movements of swimming prey by chemoreceptors

Cnidocytes, the stinging cells of cnidarians, discharge nematocysts in response to physical contact accompanied by the stimulation of specific chemoreceptors. Cnidocytes in fishing tentacles of a sea anemone are now found to discharge nematocysts preferentially into targets vibrating at 30, 55, and 65 to 75 hertz. Moreover, in the presence of submicromolar concentrations of known chemosensitizers, such as N-acetylated sugars and mucin, these optima shift to 5, 15, 30, and 40 hertz, frequencies that correspond to the movements of swimming prey. Hence, chemoreceptors for these substances tune cnidocyte mechanoreceptors to frequencies that match the movements of the prey.     

Lateral giant fibers of cray fish: location of somata by dye injection

Using a new technique for injecting fluorescent dye, we have analyzed the intraganglionic architectutre of the lateral giant interneuron in crayfish. Each lateral giant interneuron comprises a giant axon, an ipsilateral dendritic arborization of fairly constant form, and a contralateral soma. Antidromic axon spikes produce only, small, electronic potentials in the soma; direct depolarization there fails to produce electrically excitable membrane responses and cannot discharge the main axon.     

花椰菜异源细胞质雄性不育转育材料农艺性状的观察

本研究是在对所获几份花椰菜胞质雄性不育转育材料继续进行回交转育工作的基础上，对材料的农艺性状及开花、结实性进行田间观察，进一步对材料进行评估。具有雄性不育特性的材料通过回交转育，克服了不育胞质供体存在的苗期黄化、雌蕊功能障碍、闭蕾、败蕾、柱头外露以及蜜腺外露等缺陷，提高了繁殖力，CMS系BC3代不育株率和不育度均达100％，为胞质雄性不育类型。但存在营养生长偏强，产品成熟期低温紫花等问题，须进一步回交转育和加强选择.     

NFAT binding and regulation of T cell activation by the cytoplasmic scaffolding Homer proteins

T cell receptor (TCR) and costimulatory receptor (CD28) signals cooperate in activating T cells, although understanding of how these pathways are themselves regulated is incomplete. We found that Homer2 and Homer3, members of the Homer family of cytoplasmic scaffolding proteins, are negative regulators of T cell activation. This is achieved through binding of nuclear factor of activated T cells (NFAT) and by competing with calcineurin. Homer-NFAT binding was also antagonized by active serine-threonine kinase AKT, thereby enhancing TCR signaling via calcineurin-dependent dephosphorylation of NFAT. This corresponded with changes in cytokine expression and an increase in effector-memory T cell populations in Homer-deficient mice, which also developed autoimmune-like pathology. These results demonstrate a further means by which costimulatory signals are regulated to control self-reactivity.     

甘蓝型油菜细胞质雄性不育恢复基因的分子标记及定位

以甘蓝型油菜恢复系CP015和不育系77A构建的F2群体为供试材料,运用RAPD,SSR和AFLP 3种标记技术,对甘蓝型油菜恢复基因进行分子标记和图谱定位。在260条RAPD引物、185对SSR引物、58对AFLP引物中,在两亲本间筛选多态性高的RAPD引物121条,SSR引物128对,AFLP引物组合26对,进一步通过BSA法筛选,获得了与甘蓝型油菜恢复基因Rf连锁的1个RAPD标记S1009-750和1个AFLP标记E5M11-150,标记与基因Rf之间的遗传距离分别为4.9cM和8.6cM。     

辐射作用下含修复DNA主链断裂随机动力学理论的研究

在辐射诱发DNA单链与双链断裂问题的研究中,迄今为止的主要理论——靶学说与击中理论,存在缺少修复机制等缺点,而Chadwick的理论仍属半经验性的.本文在Hug与Kellerer基本思想的基础上,发展了一个辐射诱发含修复DNA单、双链断裂的随机动力学理论,建立了随机动力学微分方程组数学模型.     

安全屏障对储油罐区池火灾多米诺效应概率的影响

随着石油储库朝大型化、集约化方向发展,罐区工艺与设备日趋繁杂,一旦发生火灾事故,极易引发多米诺效应,导致灾难性后果.为了降低石油储库事故对周边人员、环境等造成的影响,基于主动、被动、应急与响应措施3种安全屏障的性能,采用事件树与贝叶斯网络方法针对不同安全屏障建模,进而对事故多米诺效应概率进行定量评估.结果表明:多层安全...     

菜薹细胞质雄性不育相关基因orf224的克隆

利用分子标记技术克隆菜薹雄性不育基因,为利用菜薹不育性提供依据.采用间源序列的候选基因法,通过检索NCBI核酸数据库,获得细胞质雄性不育(CMS)相关的基因或开放读码框序列.根据保守区设计1对特异引物.对不育系和保持系的基因组DNA进行PCR扩增.结果表明:特异引物在不育系中扩增出1条675 bp的片段.序列分析表明该片段与Pol型胞质不育orf224基因同源性为100%.CMS特异扩增结果证明试验所用的菜薹其不育类型为胞质Pol型.