A loss-of-function RNA interference screen for molecular targets in cancer

The pursuit of novel therapeutic agents in cancer relies on the identification and validation of molecular targets. Hallmarks of cancer include self-sufficiency in growth signals and evasion from apoptosis; genes that regulate these processes may be optimal for therapeutic attack. Here we describe a loss-of-function screen for genes required for the proliferation and survival of cancer cells using an RNA interference library. We used a doxycycline-inducible retroviral vector for the expression of small hairpin RNAs (shRNAs) to construct a library targeting 2,500 human genes. We used retroviral pools from this library to infect cell lines representing two distinct molecular subgroups of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like DLBCL and germinal centre B-cell-like DLBCL. Each vector was engineered to contain a unique 60-base-pair 'bar code', allowing the abundance of an individual shRNA vector within a population of transduced cells to be measured using microarrays of the bar-code sequences. We observed that a subset of shRNA vectors was depleted from the transduced cells after three weeks in culture only if shRNA expression was induced. In activated B-cell-like DLBCL cells, but not germinal centre B-cell-like DLBCL cells, shRNAs targeting the NF-kappaB pathway were depleted, in keeping with the essential role of this pathway in the survival of activated B-cell-like DLBCL. This screen uncovered CARD11 as a key upstream signalling component responsible for the constitutive IkappaB kinase activity in activated B-cell-like DLBCL. The methodology that we describe can be used to establish a functional taxonomy of cancer and help reveal new classes of therapeutic targets distinct from known oncogenes.     

Distribution and postbreeding environmental relationships of northern leopard frogs ( Rana [ Lithobates ] pipiens ) in Washington

Northern leopard frogs ( Rana [ Lithobates ] pipiens ) are considered sensitive, threatened, or endangered in all western states and western Canadian provinces. Historically present in eastern Washington in 6 major river drainages, leopard frogs are now only known to occur at 2 localized areas in the Crab Creek drainage in Grant County. During the summers of 2002–2005, we surveyed both areas to document extent of leopard frog distributions and to describe habitat and vertebrate community characteristics associated with leopard frog site occupancy. At Gloyd Seeps, 2 juvenile leopard frogs were observed in a total of 8.2 person-days of searching along a 5-km stream reach. At Potholes Reservoir, we surveyed 243 wetland sites in 7 management units known to have been occupied by leopard frogs during the 1980s. We confirmed leopard frog presence at only 87 sites (36%) in 4 management units. Site occupancy models for individual ponds indicated that, compared to unoccupied sites, occupied sites had slightly greater pond depths, less tall emergent vegetation, more herbaceous vegetative cover, and fewer neighboring ponds containing nonnative predatory fish. Models developed at the 1-km 2 scale indicated that occupied areas had greater average midsummer pond depths, fewer ponds occupied by bullfrogs ( Rana [ Lithobates ] catesbeiana ) and carp ( Cyprinus carpio ), and more herbaceous vegetation surrounding ponds. The Gloyd Seeps population now appears defunct, and the Potholes Reservoir population is in sharp decline. Unless management actions are taken to reduce nonnative fish and bullfrogs and to enhance wetland vegetation, leopard frogs may soon be extirpated from both sites and possibly, therefore, from Washington.     

Managing a complex exotic vegetation program in Yellowstone National Park

The number of documented exotic plants in Yellowstone National Park has increased from 85 known in 1986 to over 185 today. Exotic plants are substantially impacting the parks natural and cultural resources and are a high management priority. We have adopted an integrated weed management approach with regard to exotic vegetation, emphasizing prevention, education, early detection and eradication, control, and, to a lesser degree, monitoring. The program involves over 140 staff with program expenditures averaging approximately $190,000 annually. Prevention actions include requiring approved gravel on construction projects; banning hay in the backcountry and allowing transport of only certified weed-seed-free hay through Yellowstone; requiring construction equipment to be pressurecleaned prior to entering the park; and native species revegetation after road, housing, and other construction projects have disturbed ground. Over 4500 acres, primarily along roadsides and in developed areas, are surveyed annually in early detection efforts with emphasis placed on eradicating small, new infestations of highly invasive species such as sulfur cinquefoil ( Potentilla recta L.) and leafy spurge ( Euphorbia esula L.). Control efforts focus on about 30 priority species, such as spotted knapweed ( Centaurea maculosa Lam.), oxeye daisy ( Chrysanthemum leucanthemum L.), and hoary cress ( Cardaria draba [L.] Desv.) using chemical, mechanical, and cultural techniques. A total of 2027 acres were treated during 1998, whereas control efforts for 12 species occurred on 2596 acres during the previous 3-year period, 1995-1997. Strong and expanding partnerships with other federal, state, and local agencies and private companies contribute to management efforts within the park. Future program goals emphasize increases in base funding to ensure continued weed management efforts as well as expanding survey, monitoring, and reclamation efforts. Ultimately, a more rigorous assessment of program effectiveness is desired.     

氧化钒簿膜电极在锂充电电池中的应用(英文)

鉴于氧化钒是应用于锂充电电池的最有希望的电极材料之一，采用等离子体增强化学气相沉积法（ＰＥＣＶＤ）和激光溅射沉积法（ＰＬＤ），制备了不同的氧化钒薄膜，并研究了它们的电化学性质。这些薄膜具备较高的充放电容量和优良的充放电稳定性。晶体和非晶体的Ｖ２Ｏ５薄膜都可以用ＰＬＤ方法在２００℃和不同的气氛下制备。这些薄膜的充电容量可达３８０ｍＡ·ｈ／ｇ。所制备的最稳定的薄膜是用ＰＥＣＶＤ方法得到的。这些薄膜的Ｏ／Ｖ比很接近Ｖ６Ｏ１３（厚度约为０．５ｕｍ）。它们的放电容量可达４０８ｍＡ．ｈ／ｇ或１２６５ｍＡｈ／ｃｍ３，其能量密度可达９６０．３Ｗ．ｈ／ｋｇ。即使经过４４００次的充放电后，这些薄膜的放电容量仍基本不变。因此，ＰＥＣＶＤ方法及其用它所制备的氧化钒薄膜将是锂充电电池工业很有希望的一种选择。