Reversal of chloroquine resistance in Plasmodium falciparum by verapamil

The parasite Plasmodium falciparum, like neoplastic cells, develops resistance to multiple structurally unrelated drugs. If the mechanisms by which P. falciparum and neoplastic cells become resistant are similar, then it may be possible to reverse the resistance in the two types of cells by the same pharmacological agents. Verapamil, a calcium channel blocker, completely reversed chloroquine resistance in two chloroquine-resistant P. falciparum clones from Southeast Asia and Brazil. Verapamil reversed chloroquine resistance at the same concentration (1 X 10(-6)M) as that at which it reversed resistance in multidrug-resistant cultured neoplastic cells. This same concentration of verapamil had no effect on chloroquine-sensitive parasites. Hence, chloroquine resistance in P. falciparum may fit the criteria for the multidrug-resistant phenotype.     

Laser manipulation of atoms and particles

A variety of powerful techniques to control the position and velocity of neutral particles has been developed. As examples of this new ability, lasers have been used to construct a variety of traps, to cool atoms to temperatures below 3 x 10(-6) kelvin, and to create atomic fountains that may give us a hundredfold increase in the accuracy of atomic clocks. Bacteria can be held with laser traps while they are being viewed in an optical microscope, and organelles within a cell can be manipulated without puncturing the cell wall. Single molecules of DNA can now be stretched out and pinned down in a water solution with optical traps. These new capabilities may soon be applied to a wide variety of scientific questions as diverse as precision measurements of fundamental symmetries in physics and the study of biochemistry on a single molecule basis.     

桑树杂交组合花叶病发生情况的调查研究

2005～2009年对广西蚕业科学研究院下属3个品种试验圃的桑树杂交组合进行连续5年的花叶病田间发病规律调查,结果表明：不同桑树杂交组合对花叶病的抗性有差异,其中以A2×9512、桂桑优62-B、C2×K1、A51×G3、A2×G30、A2×93133、A2×伦109、A2×94168、A2×9102等杂交组合的抗性较好;而同一杂交组合群体不同年份花叶病发病情况也有差异,随着树龄的增加,桑树杂交组合的发病率和病情指数呈逐年上升趋势。可见,桑树杂交组合对花叶病的抗性是遗传因素与环境因素共同作用的结果。因此,通过选育抗花叶病品种（或组合）、合理的人为干预能够有效地防治桑树花叶病。     

Generalized potential of adult neural stem cells

The differentiation potential of stem cells in tissues of the adult has been thought to be limited to cell lineages present in the organ from which they were derived, but there is evidence that some stem cells may have a broader differentiation repertoire. We show here that neural stem cells from the adult mouse brain can contribute to the formation of chimeric chick and mouse embryos and give rise to cells of all germ layers. This demonstrates that an adult neural stem cell has a very broad developmental capacity and may potentially be used to generate a variety of cell types for transplantation in different diseases.     

Atomic-resolution microscopy in water

The scanning tunneling microscope is revolutionizing the study of surfaces. In ultra-high vacuum it is capable not only of imaging individual atoms but also of determining energy states on an atom-by-atom basis. It is now possible to operate this instrument in water. Aqueous optical microscopy is confined to a lateral resolution limit of about 2000 angstroms, and aqueous x-ray microscopy has yielded a lateral resolution of 75 angstroms. With a scanning tunneling microscope, an image of a graphite surface immersed in deionized water was obtained with features less than 3 angstroms apart clearly resolved. Further, an image measured in saline solution demonstrated that the instrument can be operated under conditions useful for many biological samples.     

Scanning electron microscopes: is high resolution possible?

Experiments with this scanning microscope have produced extremely encouraging results so that we feel Confident in predicting high resolution and high contrast after some obvious modifications are made in the system, such as providing a good objective lens. Experience with conventional lenses indicates that the instrument behaves in a predictable manner and there is no reason to doubt that the resolution can be as good as that of a conventional microscope. The use of quadrupole lenses will depend on calculations now being performed. There is cause for optimism; high resolution may also be possible with this kind of lens. Experience with field emission shows that the technology is not difficult and that there is more than enough current available for any conceivable use. Energy-loss measurements have been made on a variety of materials. It is attractive to consider the possibility of chemical analysis of selected areas of a specimen. We believe that a very crude form of analysis may indeed be possible. The principal advantage of the use of energy-loss techniques, however, may be in the availability of another contrast mechanism. The ability to "see" small details may be considerably enhanced. Finally, we are experimenting with the possibility of using transmitted electrons of different energy losses to produce different colors on a color television display. This should add an extra element to the picture contrast which may be of some value.     

A yeast prion, Mod5, promotes acquired drug resistance and cell survival under environmental stress

Prion conversion from a soluble protein to an aggregated state may be involved in the cellular adaptation of yeast to the environment. However, it remains unclear whether and how cells actively use prion conversion to acquire a fitness advantage in response to environmental stress. We identified Mod5, a yeast transfer RNA isopentenyltransferase lacking glutamine/asparagine-rich domains, as a yeast prion protein and found that its prion conversion in yeast regulated the sterol biosynthetic pathway for acquired cellular resistance against antifungal agents. Furthermore, selective pressure by antifungal drugs on yeast facilitated the de novo appearance of Mod5 prion states for cell survival. Thus, phenotypic changes caused by active prion conversion under environmental selection may contribute to cellular adaptation in living organisms.     

普通小麦(Triticum aestivum)两种不育类型小孢子发生的形态学比较

雄性不百类型的性质如何是小麦杂种优势利用中的关键环节之一,目前国内所利用的小麦雄性不育系多属 T 型,为细胞质雄性不育.从地方品种平度紫秸白不育株所选育的潍型不育系,属核不育.为探索这两类不育系花粉败育的具体状况,以进一步了解其相应的遗传机理,1978年以来我们曾先后对两种不育系小孢子发生和成熟花粉的形态进行了光学显微镜和扫描电镜的观察比较。     

Tumor growth need not be driven by rare cancer stem cells

The cancer stem cell hypothesis postulates that tumor growth is driven by a rare subpopulation of tumor cells. Much of the supporting evidence for this intriguing idea is derived from xenotransplantation experiments in which human leukemia cells are grown in immunocompromised mice. We show that, when lymphomas and leukemias of mouse origin are transplanted into histocompatible mice, a very high frequency (at least 1 in 10) of the tumor cells can seed tumor growth. We suggest that the low frequency of tumor-sustaining cells observed in xenotransplantation studies may reflect the limited ability of human tumor cells to adapt to growth in a foreign (mouse) milieu.     

玉米品种抗感玉米粗缩病毒与过氧化物酶关系的研究

 研究选取对玉米粗缩病毒（MRDV）表现抗病、中感及高感3个不同类型的代表性品种,分析了三叶期、五叶期室内盆栽及抽穗期田间采取的病叶及健康玉米叶片的过氧化物酶（POD）的变化,旨在研究玉米品种抗感病性与过氧化物酶的关系及感染病毒后的诱导抗病性机理。结果表明:玉米三叶期、五叶期及抽穗期,感病品种的POD酶活性大于抗病品种,显示玉米叶片内的POD含量与品种的感病性有相关性。发病后,各品种酶活性均上升,抗病品种上升幅度最大,说明防御酶POD的应激表达与品种的抗病性相关;同工酶研究结果表明:玉米抽穗期,抗病品种健叶具有一条Rf 0.261差异酶带,而感病品种则没有,这一特异蛋白带的组成型表达显示出与品种抗病的相关性,可作为评价品种抗病性的生理生化指标之一。发病后,抗病品种及中感品种又新增一条酶带,Rf为0.471;三叶期及五叶期,抗病品种同样都比感病品种多出现一酶带区,进一步证明了在玉米植株体内存在与抗玉米粗缩病毒相关的POD同工酶,这一结果将为抗病育种提供极有价值的生理生化基础。     

小麦抗白粉菌初侵染过敏性反应的细胞学研究

利用细胞学方法对小麦抗白粉菌初侵染过敏性反应的研究表明，高抗寄主的反应是在病菌入侵栓活动前，由初生芽管或附着胞侵染诱导的主动防卫反应；而在中抗寄主的反应与高感寄主细胞的死亡，则是由坏死的病菌吸器诱导的；且吸器周围的寄主细胞器越少细胞坏死也越早．不论是感病还是抗病寄主细胞死亡时，细胞壁上的过氧化物酶活性均显著增强，说明它可能不是决定抗性的重要因子．     

Embryonic stem cells. Stem cell programs

The availability of human embryonic stem cell lines provides an important tool for scientists to explore the fundamental mechanisms that regulate differentiation into specific cell types. When more is known about the mechanisms that govern these processes, human embryonic stem cells may be clinically useful in generating cell types that have been damaged or depleted by a variety of human diseases. The NIH is actively pursuing a variety of initiatives to promote this developing research field, while continuing and expanding its long-standing investment in adult stem cells and research.     

Enhanced dexamethasone resistance in cystic fibrosis cells: potential use for heterozygote detection and prenatal diagnosis

Cultured skin fibroblasts from patients with cystic fibrosis (CF) are more resistant to dexamethasone toxicity than are normal cells. We now report that, when fibroblasts cultured from obligate CF heterozygotes are exposed to dexamethasone, they have an intermediate survival compared to normal and homozygous CF cells. When dexamethasone survival was tested on cells from four patients undergoing amniocentesis, cells from a woman at risk of producing a child with CF showed significant dexamethasone resistance, similar to that of fibroblasts derived from lnown CF homozygotes; the other amniotic cell specimens showed dexamethasone sensitivity similar to that of normal skin fibroblasts. These data suggest that the dexamethasone resistance previously observed in skin fibroblasts may also be useful in the prenatal diagnosis of CF.     

苏芸金杆菌感染落叶松毛虫的组织病理

为了探讨苏芸金杆菌对鳞翅目昆虫的作用机理，笔者通过光学镜和电镜对苏芸金杆菌感染落叶松毛虫后的组织病理和细胞病理进行了研究，结果为感染初期松毛虫幼虫中肠柱状铁微绒毛受到破坏，继而中肠细胞开始出现空洞，感染４２ｈ后中肠上皮细胞完全从基低膜上脱藩。     

Control of embryonic motoneuron survival in vivo by ciliary neurotrophic factor

During development of the nervous system, neurons in many regions are overproduced by proliferation, after which the excess cells are eliminated by cell death. The survival of only a proportion of neurons during normal development is thought to be regulated by the limited availability of neurotrophic agents. One such putative trophic agent is ciliary neurotrophic factor (CNTF), a polypeptide that promotes the survival of ciliary, sensory, and sympathetic neurons in vitro. In contrast to the results of in vitro studies, however, the daily treatment of chick embryos in vivo with purified human recombinant CNTF failed to rescue any of these cell populations from cell death, whereas CNTF did promote the in vivo survival of spinal motoneurons. Thus, CNTF may not act as a neurotrophic agent in vivo for those embryonic neurons (especially ciliary neurons) on which it acts in vitro. Rather, CNTF may be required for in vivo survival of motoneurons.     

白粉病菌胁迫下甜瓜叶片中Ca2+的细胞化学定位及外源Ca2+对POD、CAT和SOD同功酶的影响

【目的】对接种白粉病菌前后的甜瓜叶片中Ca2+ 进行细胞定位分析,并探讨外源Ca2+ 对白粉病菌胁迫下3种同工酶的影响,为研究甜瓜在白粉病胁迫下的信号转导及抗病机制奠定基础。【方法】通过电镜和细胞化学技术对抗病性不同的甜瓜幼叶在白粉病菌胁迫下的Ca2+ 进行超微细胞化学定位研究,采用Hoagland营养液栽培法,对不同外源Ca2+作用并接种白粉病菌的甜瓜叶片的POD、CAT和SOD同工酶进行分析。【结果】接种白粉病菌2 d时,Ca2+在抗病品种和感病品种叶肉细胞胞质内聚集;液泡和细胞间隙内Ca2+水平急剧下降;接种白粉病菌6 d后,抗病品种‘MR-1’胞质内Ca2+水平又逐渐恢复至接种前的状态,Ca2+主要分布在液泡和细胞间隙,而感病品种‘JS’叶肉细胞内Ca2+在细胞基质中分布集中并聚集成大的沉淀颗粒,细胞结构逐渐破坏,直至死亡,在液泡和细胞间隙未发生Ca2+恢复现象。外源Ca2+对3种同工酶谱的作用结果为：与对照相比,营养液增施6 mmol•L-1 CaCl2可明显缓解白粉菌对甜瓜的伤害,其POD、CAT和SOD同工酶活性高于对照水平;营养液增施75 mmol•L-1 的LaCl3 显著抑制了甜瓜幼叶POD、CAT和SOD同工酶的活性。【结论】白粉病菌胁迫下,抗病性不同的甜瓜叶片中Ca2+的时空定位分布有差异：抗病品种中Ca2+由胞内钙库（即液泡）释放入细胞基质,之后又被泵回液泡,而感病品种中Ca2+仅发生从液泡向胞质释放的过程;外源Ca2+可能增加了Ca2+向甜瓜叶片内的运输,促进白粉病胁迫信号向植株体内的传递,提高甜瓜叶片保护酶的表达量及其活性氧清除水平,从而延缓白粉病胁迫对甜瓜叶片的伤害。     

水稻品种对稻白叶枯病不同菌系的抗性研究

1980～1983年,对5000多份水稻品种资源中经稻白叶枯病单菌株抗性测定后筛选出的208个水稻品种,用我国现行一套鉴别品种上分群的四个菌系的代表菌株,采用人工剪叶接种法对其进行了多菌株的抗性谱测定。根据品种与菌株相互关系的抗性性质,将这些品种分为四种抗性类型,即非分化性的抗或高抗品种、强分化性的高抗品种、分化性的中抗或中感品种,以及弱分化性的感病品种类型。另外还对各抗性类型的一些代表性品种,做了苗期抗性的人工接种测定以及自然病区诱发鉴定。这些研究结果表示,本研究筛选出的59个非分化性的抗或高抗品种可用作我省稻白叶枯病的抗病育种或杂交组合的抗源材料,农艺性状兼优的可直接用于生产。     

不同品质籼稻胚乳糊化前后微结构差异的研究

 利用扫描电镜观察品质差异较大的 4个籼稻品种稻米糊化前后的微结构 ,发现同等条件下不同部位的糊化明显不同。背部糊化最好 ,细胞完全崩解为絮状或小块状的蓬松物质 ;腹部糊化次之 ,呈较大块状或细胞结构刚被破坏 ,有的细胞轮廓仍可见 ;中部糊化最差 ,多为完整胚乳细胞。不同品种糊化后差异明显 ,米质好的品种其背、中、腹部的糊化比米质差的品种的相应部位好 ,米质较差品种的中部明显凹陷 ,而较优品种的断面较平 ,该现象同样表现在早、晚稻的对比上。品种间背部糊化的差异小于中、腹部 ,品种内米质较优的稻米背、腹、中部的差异比米质差的小。米质较好的品种的胚乳横断面可见较多断裂的细胞 ,而米质较差的品种几乎见不到断裂的细胞 ,其数目与米质优劣有一定的正相关。米质优劣与糊化时的吸水率和延长率正相关 ,吸水率和延长率高则糊化较好     

Ⅰ-69杨和大官杨对光肩星天牛抗性的研究

以抗虫品种69杨和感虫品种大官杨为例,从形态解剖构造及某些化学成分分析探讨其与植物抗虫性的关系.提出69杨树皮中石细胞所占比例大,木纤维壁厚、排列紧密且树皮中的营养成分含量比大官杨低等诸因素是造成其对光肩星天牛抗性的主要原因.     

Differentiation of embryonic stem cell lines generated from adult somatic cells by nuclear transfer

Embryonic stem (ES) cells are fully pluripotent in that they can differentiate into all cell types, including gametes. We have derived 35 ES cell lines via nuclear transfer (ntES cell lines) from adult mouse somatic cells of inbred, hybrid, and mutant strains. ntES cells contributed to an extensive variety of cell types, including dopaminergic and serotonergic neurons in vitro and germ cells in vivo. Cloning by transfer of ntES cell nuclei could result in normal development of fertile adults. These studies demonstrate the full pluripotency of ntES cells.