Presymptomatic detection of prions in blood

Prions are thought to be the proteinaceous infectious agents responsible for transmissible spongiform encephalopathies (TSEs). PrP(Sc), the main component of the infectious agent, is also the only validated surrogate marker for the disease, and its sensitive detection is critical for minimizing the spread of the disease. We detected PrP(Sc) biochemically in the blood of hamsters infected with scrapie during most of the presymptomatic phase of the disease. At early stages of the incubation period, PrP(Sc) detected in blood was likely to be from the peripheral replication of prions, whereas at the symptomatic phase, PrP(Sc) in blood was more likely to have leaked from the brain. The ability to detect prions biochemically in the blood of infected but not clinically sick animals offers a great promise for the noninvasive early diagnosis of TSEs.     

Chronic lymphocytic inflammation specifies the organ tropism of prions

Prions typically accumulate in nervous and lymphoid tissues. Because proinflammatory cytokines and immune cells are required for lymphoid prion replication, we tested whether inflammatory conditions affect prion pathogenesis. We administered prions to mice with five inflammatory diseases of the kidney, pancreas, or liver. In all cases, chronic lymphocytic inflammation enabled prion accumulation in otherwise prion-free organs. Inflammatory foci consistently correlated with lymphotoxin up-regulation and ectopic induction of FDC-M1+ cells expressing the normal cellular prion protein PrPC. By contrast, inflamed organs of mice lacking lymphotoxin-alpha or its receptor did not accumulate the abnormal isoform PrPSc, nor did they display infectivity upon prion inoculation. By expanding the tissue distribution of prions, chronic inflammatory conditions may act as modifiers of natural and iatrogenic prion transmission.     

Developing neuromuscular junctions: first signs of chemical transmission during formation in tissue culture

Electrophysiological study of rat neuromuscular junctions in the early stage of formation in tissue culture showed that chemical transmission begins with discrete, localized release of transmitter about the time when nerve-muscle contacts are first visible with light microscopy. Noncontractile myotubes with as few as three nuclei showed evidence of junctional transmission.     

Infectious prions in the saliva and blood of deer with chronic wasting disease

A critical concern in the transmission of prion diseases, including chronic wasting disease (CWD) of cervids, is the potential presence of prions in body fluids. To address this issue directly, we exposed cohorts of CWD-na?ve deer to saliva, blood, or urine and feces from CWD-positive deer. We found infectious prions capable of transmitting CWD in saliva (by the oral route) and in blood (by transfusion). The results help to explain the facile transmission of CWD among cervids and prompt caution concerning contact with body fluids in prion infections.     

Epigenetics in the extreme: prions and the inheritance of environmentally acquired traits

Prions are an unusual form of epigenetics: Their stable inheritance and complex phenotypes come about through protein folding rather than nucleic acid-associated changes. With intimate ties to protein homeostasis and a remarkable sensitivity to stress, prions are a robust mechanism that links environmental extremes with the acquisition and inheritance of new traits.     

Identification of a coordinate regulator of interleukins 4, 13, and 5 by cross-species sequence comparisons

Long-range regulatory elements are difficult to discover experimentally; however, they tend to be conserved among mammals, suggesting that cross-species sequence comparisons should identify them. To search for regulatory sequences, we examined about 1 megabase of orthologous human and mouse sequences for conserved noncoding elements with greater than or equal to 70% identity over at least 100 base pairs. Ninety noncoding sequences meeting these criteria were discovered, and the analysis of 15 of these elements found that about 70% were conserved across mammals. Characterization of the largest element in yeast artificial chromosome transgenic mice revealed it to be a coordinate regulator of three genes, interleukin-4, interleukin-13, and interleukin-5, spread over 120 kilobases.     

High-speed lightwave transmission in optical fibers

There has been considerable progress in the telecommunications technology based on the transmission of lightwaves through optical fibers. Systems experiments in the 1.55-micrometer band have now demonstrated the capability of transmitting at rates as high as 2 gigabits per second over fiber lengths exceeding 100 kilometers, without the use of repeaters to boost the signal. Elements of this progress are advances in the fabrication of low-loss single-mode fibers, in the spectral control of semiconductor junction lasers assuring single-frequency operation, and in high-speed detectors and receivers.     

植物体内信息传递研究概述

许多研究表明 ,植物虽然不象动物那样具有神经系统 ,但也具有信息传递的能力 ,植物可以感知并传递外界环境刺激 ,调节生理活动并作出适应性反应。但植物有别于动物 ,它难以逃避和改变环境 ,因此 ,适应多变的环境是其维持生存的主要出路。近年来 ,人们越来越注意与信号传递有关的植物环境刺激因子的研究 ,这些因子包括光、温、重力、伤害、机械力、病原菌侵袭等。当环境刺激作用位点与效应位点处于植物的不同部位时 ,必然有胞间信号传递信息 ,例如植物具有一种感知土壤水分相应调节其生理状况的能力[13 ,14 ] ;并且可以在叶片水分表现出亏缺…     

Germline transmission of exogenous genes in the chicken

Difficulties associated with in vitro manipulation and culture of the early chicken embryo have restricted generation of transgenic chickens to approaches that use replication-competent retroviruses. The need to produce transgenic chickens in the absence of replicating virus prompted development of a new method of gene transfer into the chicken. Microinjection of the replication-defective reticuloendotheliosis virus (REV) vector ME111 beneath unincubated chicken embryo blastoderms results in infection of germline stem cells. This vector contains genetic information exogenous to the chicken genome, including both the herpes simplex virus type 1 thymidine kinase gene and the Tn5 neomycin phosphotransferase gene. About 8 percent of male birds hatched from injected embryos contained vector DNA in their semen. All four positive males tested passed vector sequences onto their progeny. Analysis of G1 offspring showed that gonads of G0 male birds were mosaic with respect to insertion of vector provirus. Thus, primordial germ cells present in the unincubated chicken embryo blastoderm are susceptible to infection by defective REV vectors.     

Spot-scan imaging in transmission electron microscopy.

The determination of the structure of proteins and other organic materials by transmission electron microscopy is a rapidly developing field. Obtaining high-resolution images of these radiation-sensitive specimens has, until recently, been problematic. The development of spot-scan imaging, in which the electron beam is focused to a spot with a diameter of about 1000 angstroms and moved over the specimen to record the image, has overcome some of the most severe problems, which result from beam-induced motion of the specimen and its image. Elimination of this motion greatly enhances the contrast of high-resolution features of the image and promises a significant increase in the speed with which future structural work can be accomplished.     

Vibration signal transmission in spider orb webs

Vibration transmission from the prey-catching region to the hub of the unloaded orb web of Nuctenea sclopetaria was measured by laser vibrometry. Compared to transverse or lateral vibrations, longitudinal vibration shows less attenuation and contains more directional information. It is transmitted well throughout the entire frequency range measured (1 to 10,000 hertz).     

茶树组织培养研究进展

对茶树组织培养技术在茶树种苗快速繁殖、辅助育种、次生代谢产物生产等方面的应用进行综述,阐述了以茶树根、茎、花、种子等为外植体开展的组织培养的培养基研究,并提出组织培养过程中产生褐化、污染的原因及控制对策。     

Persistence of alkaloids in plant tissue

Under appropriate conditions of preservation, alkaloids can be detected in plant tissues after extended periods of time. A positive test for this class of compounds was given by a sample of plant material estimated to be 1300 years old.     

新型黄病毒在种鹅中垂直传播的研究

[目的]证实新型黄病毒在种鹅中是否存在垂直传播,为控制该病提供可靠的流行病学依据.[方法]采用巢式RT-PCR和病毒分离技术,对患病种鹅病料、不同孵化阶段死胚、出雏蛋壳内部冲洗液、弱雏样品进行黄病毒分离及基因检测.[结果]在患病种鹅、孵化过程中死亡鹅胚尿囊液、出雏蛋壳内壁洗液和雏鹅中均能检测和分离到黄病毒,其中患病种鹅病料的黄病毒阳性率为100.0%,孵化死亡鹅胚黄病毒阳性率为39.6%,出雏蛋壳内部冲洗液黄病毒阳性率为45.0%;1日龄和15日龄弱雏黄病毒阳性率为80.0%.[结论]黄病毒可以通过鹅胚传到下一代,即新型黄病毒在种鹅中存在垂直传播的现象.     

Head capsule transmission of long-wavelength light in the curculionidae

The head capsule of many weevils contains a region that transmits only far-red and near-infrared light. In the alfalfa weevil, Hypera postica, this extraocular cutoff filter evidently works in conjunction with the compound eyes, enabling the insect to use visual cues in locating or recognizing its host plant.     

Suppression of avian influenza transmission in genetically modified chickens

Infection of chickens with avian influenza virus poses a global threat to both poultry production and human health that is not adequately controlled by vaccination or by biosecurity measures. A novel alternative strategy is to develop chickens that are genetically resistant to infection. We generated transgenic chickens expressing a short-hairpin RNA designed to function as a decoy that inhibits and blocks influenza virus polymerase and hence interferes with virus propagation. Susceptibility to primary challenge with highly pathogenic avian influenza virus and onward transmission dynamics were determined. Although the transgenic birds succumbed to the initial experimental challenge, onward transmission to both transgenic and nontransgenic birds was prevented.     

农业系统灰色文献的收集与传递

本文分析了农业系统当前灰色文献收集、传递中存在的问题，并提出了相应的对策。