Nitrogen cycle: what governs nitrogen loss from forest soils?

Nitrogen is lost as dissolved organic compounds in stream waters from unpolluted South American forests, but it is lost mainly as inorganic nitrate in streams flowing from North American forests that suffer nitrogen deposition from the atmosphere. From this it has been inferred that the standard thinking about how nature deals with nitrogen in soils and waters needs to be re-evaluated and that the conventional wisdom of how nitrogen is absorbed and released by plants must be wrong. We disagree, however, on the grounds that there are other, more likely interpretations of the new results.     

Subtractive proteomic mapping of the endothelial surface in lung and solid tumours for tissue-specific therapy

The molecular complexity of tissues and the inaccessibility of most cells within a tissue limit the discovery of key targets for tissue-specific delivery of therapeutic and imaging agents in vivo. Here, we describe a hypothesis-driven, systems biology approach to identifying a small subset of proteins induced at the tissue-blood interface that are inherently accessible to antibodies injected intravenously. We use subcellular fractionation, subtractive proteomics and bioinformatics to identify endothelial cell surface proteins exhibiting restricted tissue distribution and apparent tissue modulation. Expression profiling and gamma-scintigraphic imaging with antibodies establishes two of these proteins, aminopeptidase-P and annexin A1, as selective in vivo targets for antibodies in lungs and solid tumours, respectively. Radio-immunotherapy to annexin A1 destroys tumours and increases animal survival. This analytical strategy can map tissue- and disease-specific expression of endothelial cell surface proteins to uncover novel accessible targets useful for imaging and therapy.     

Dominant influence of HLA-B in mediating the potential co-evolution of HIV and HLA

The extreme polymorphism in the human leukocyte antigen (HLA) class I region of the human genome is suggested to provide an advantage in pathogen defence mediated by CD8+ T cells. HLA class I molecules present pathogen-derived peptides on the surface of infected cells for recognition by CD8+ T cells. However, the relative contributions of HLA-A and -B alleles have not been evaluated. We performed a comprehensive analysis of the class I restricted CD8+ T-cell responses against human immunodeficiency virus (HIV-1), immune control of which is dependent upon virus-specific CD8+ T-cell activity. In 375 HIV-1-infected study subjects from southern Africa, a significantly greater number of CD8+ T-cell responses are HLA-B-restricted, compared to HLA-A (2.5-fold; P = 0.0033). Here we show that variation in viral set-point, in absolute CD4 count and, by inference, in rate of disease progression in the cohort, is strongly associated with particular HLA-B but not HLA-A allele expression (P < 0.0001 and P = 0.91, respectively). Moreover, substantially greater selection pressure is imposed on HIV-1 by HLA-B alleles than by HLA-A (4.4-fold, P = 0.0003). These data indicate that the principal focus of HIV-specific activity is at the HLA-B locus. Furthermore, HLA-B gene frequencies in the population are those likely to be most influenced by HIV disease, consistent with the observation that B alleles evolve more rapidly than A alleles. The dominant involvement of HLA-B in influencing HIV disease outcome is of specific relevance to the direction of HIV research and to vaccine design.     

Transformation: a tool for studying fungal pathogens of plants

Plant diseases caused by plant pathogenic fungi continuously threaten the sustainability of global crop production. An effective way to study the disease-causing mechanisms of these organisms is to disrupt their genes, in both a targeted and random manner, so as to isolate mutants exhibiting altered virulence. Although a number of techniques have been employed for such an analysis, those based on transformation are by far the most commonly used. In filamentous fungi, the introduction of DNA by transformation typically results in either the heterologous (illegitimate) integration or the homologous integration of the transforming DNA into the target genome. Homologous integration permits a targeted gene disruption by replacing the wild-type allele on the genome with a mutant allele on transforming DNA. This process has been widely used to determine the role of newly isolated fungal genes in pathogenicity. The heterologous integration of transforming DNA causes a random process of gene disruption (insertional mutagenesis) and has led to the isolation of many fungal mutants defective in pathogenicity. A big advantage of insertional mutagenesis over the more traditional chemical or radiation mutagenesis procedures is that the mutated gene is tagged by transforming DNA and can subsequently be cloned using the transforming DNA. The application of various transformation-based techniques for fungal gene manipulation and how they have increased our understanding and appreciation of some of the most serious plant pathogenic fungi are discussed. Received 9 May 2001; received after revision 2 July 2001; accepted 3 July 2001     

Cloned pigs produced by nuclear transfer from adult somatic cells

Since the first report of live mammals produced by nuclear transfer from a cultured differentiated cell population in 1995 (ref. 1), successful development has been obtained in sheep, cattle, mice and goats using a variety of somatic cell types as nuclear donors. The methodology used for embryo reconstruction in each of these species is essentially similar: diploid donor nuclei have been transplanted into enucleated MII oocytes that are activated on, or after transfer. In sheep and goat pre-activated oocytes have also proved successful as cytoplast recipients. The reconstructed embryos are then cultured and selected embryos transferred to surrogate recipients for development to term. In pigs, nuclear transfer has been significantly less successful; a single piglet was reported after transfer of a blastomere nucleus from a four-cell embryo to an enucleated oocyte; however, no live offspring were obtained in studies using somatic cells such as diploid or mitotic fetal fibroblasts as nuclear donors. The development of embryos reconstructed by nuclear transfer is dependent upon a range of factors. Here we investigate some of these factors and report the successful production of cloned piglets from a cultured adult somatic cell population using a new nuclear transfer procedure.     

Forecasting Hourly Peak Call Volume for a Rural Electric Cooperative Call Center

This research forecasts peak call volume of a centralized after‐hours call center for rural electric cooperatives to help the call center determine staffing levels. A Gaussian copula is used to capture the dependence among non‐normal distributions. Using a centralized call center reduces costs by approximately 75% compared to having individual call centers at each cooperative. Adding cooperatives to the centralized call center is projected to further decrease costs per member. An out‐of‐sample forecasting exercise after the call center expanded validated the model's forecast that additional cooperatives could be added without a proportional increase in the peak number of calls. Copyright © 2011 John Wiley & Sons, Ltd.     

奇异的农作物

大家还记得芹菜事件的教训么？80年代中期，美国的芹菜培植者曾推崇过一种他们认为非常好的新品种，不仅抗虫性强，而且可以使产量显著提高。但是有一个小问题，触弄过此芹菜梗的人不久就开始为发生严重皮疹而抱怨。皮肤病学家发现，这种芹菜会不断分泌出扫若仑（psoralen），一种在阳光下会变成刺激物和诱变物的天然化学物质。实际上，人们全都搞错了，许多生物技术业内人士和政府食品管理机构官员（尤其是美国）如是说。到“基因食品”上了人们餐桌的时候，它并非只是同传统食物一样没有危险，而且在某些方面其实还更安全，因为有管理部门…