Effect of cropping system on composition of the <Emphasis Type="Italic">Rhizoctonia</Emphasis> populations recovered from canola and lupin in a winter rainfall region of South Africa

Rhizoctonia spp. anastomosis groups (AGs) associated with canola and lupin in the southern and western production areas of the Western Cape province of South Africa were recovered during the 2006 and 2007 growing seasons and identified using sequence analyses of the rDNA internal transcribed spacer regions. The effect of crop rotation systems and tillage practices on the recovery of Rhizoctonia spp. was evaluated at Tygerhoek (southern Cape, Riviersonderend) and Langgewens (western Cape, Moorreesburg) experimental farms. Isolations were conducted from canola planted after barley, medic/clover mixture and wheat, and lupin planted after barley and wheat, with sampling at the seedling, mid-season and seedpod growth stages. In the 2006 study, 93.5% of the Rhizoctonia isolates recovered were binucleate and 6.5% multinucleate; in 2007, 72.8% were binucleate and 27.2% were multinucleate. The most abundant AGs within the population recovered included A, Bo, I and K, among binucleate isolates and 2-1, 2-2 and 11 among multinucleate isolates. Crop rotation sequence, tillage and plant growth stage at sampling all affected the incidence of recovery of Rhizoctonia, but certain effects were site-specific. The binucleate group was more frequently isolated from lupin and the multinucleate group from canola. AG-2-1 was only isolated from canola and AG-11 only from lupin. This study showed that important Rhizoctonia AGs such as AG-2-1, 2-2 and 11 occur in both the southern and the western production areas of the Western Cape province and that crop rotation consistently influences the incidence and composition of the Rhizoctonia community recovered from the cropping system.     

Susceptibility locus for Alzheimer's disease on chromosome 10

The apolipoprotein E (APOE) gene is the only genetic risk factor that has so far been linked to risk for late-onset Alzheimer's disease (LOAD). However, 50 percent of Alzheimer's disease cases do not carry an APOE4 allele, suggesting that other risk factors must exist. We performed a two-stage genome-wide screen in sibling pairs with LOAD to detect other susceptibility loci. Here we report evidence for an Alzheimer's disease locus on chromosome 10. Our stage one multipoint lod score (logarithm of the odds ratio for linkage/no linkage) of 2.48 (266 sibling pairs) increased to 3.83 in stage 2 (429 sibling pairs) close to D10S1225 (79 centimorgans). This locus modifies risk for Alzheimer's disease independent of APOE genotype.     

Rheumatoid factor secretion from human Leu-1+ B cells

A human B cell subpopulation identifiable by the expression of the cell surface antigen Leu-1 (CD5) is responsible for most of the immunoglobulin M rheumatoid factor secreted in vitro after the cells are stimulated with Staphylococcus aureus. The ability of B cells bearing the Leu-1 marker (Leu-1+) to secrete rheumatoid factor is present early in development and extends to adulthood, since Leu-1+ B cells from cord blood and from peripheral blood lymphocytes of both normal adults and patients with certain autoimmune conditions secrete rheumatoid factor in comparable amounts. The neonatal enrichment of Leu-1+ B cells, the presence of Leu-1+ B cells in increased frequencies in patients with autoimmune disease, and the involvement of Leu-1+ B cells in autoantibody secretion suggest both developmental and functional homologies between this human B cell subpopulation and the murine Ly-1 B cell subpopulation.     

The 10 Australian ecosystems most vulnerable to tipping points

We identify the 10 major terrestrial and marine ecosystems in Australia most vulnerable to tipping points, in which modest environmental changes can cause disproportionately large changes in ecosystem properties. To accomplish this we independently surveyed the coauthors of this paper to produce a list of candidate ecosystems, and then refined this list during a 2-day workshop. The list includes (1) elevationally restricted mountain ecosystems, (2) tropical savannas, (3) coastal floodplains and wetlands, (4) coral reefs, (5) drier rainforests, (6) wetlands and floodplains in the Murray-Darling Basin, (7) the Mediterranean ecosystems of southwestern Australia, (8) offshore islands, (9) temperate eucalypt forests, and (10) salt marshes and mangroves. Some of these ecosystems are vulnerable to widespread phase-changes that could fundamentally alter ecosystem properties such as habitat structure, species composition, fire regimes, or carbon storage. Others appear susceptible to major changes across only part of their geographic range, whereas yet others are susceptible to a large-scale decline of key biotic components, such as small mammals or stream-dwelling amphibians. For each ecosystem we consider the intrinsic features and external drivers that render it susceptible to tipping points, and identify subtypes of the ecosystem that we deem to be especially vulnerable.     

Intranuclear localization of mercury in vivo

Purified nuclei isolated from mice challenged with nonlethal levels of mercury chloride (10-(3)M) in drinking water for 4 to 7 weeks (experimental) and from animals given deionized water (control) were fractionated and the subsequent fractions were analyzed for mercury by flameless atomic absorption. Control (active) euchromatin contained 1.75 +/- 0.53 micrograms of mercury per milligram of DNA. There was a 12- to 15-fold enrichment of mercury in the euchromatin fraction of challenged animals. Mercury was not detected in control (inactive) heterochromatin, and only trace levels (parts per billion) appeared in experimental heterochromatin. It seems likely that mercury can be incorporated into chromatin as a metal-protein complex, but the possibility of protein-mercury-DNA or mercury-DNA complexes within euchromatin cannot be excluded.     

Production of feedstock chemicals

Renewable raw materials may be converted by biological means to feedstocks for the chemical industry. Glucose from cornstarch is the current choice as a substrate, although advances may enable the use of less expensive lignocellulosic materals. The production of oxychemicals and their derivatives from renewable resources could amount to about 100 billion pounds annually, or about half of the U.S. production of organic chemicals. Ethanol produced by fermentation is now cost-competitive with industral ethanol produced from fossil fuel. Biological routes to other oxychemicals exist and are expected to be important in the future. Several product recovery methods may be used, but new energy-conserving methods will be needed to make the engineering-biology combinations economical.     

The amyloid hypothesis of Alzheimer's disease: progress and problems on the road to therapeutics

It has been more than 10 years since it was first proposed that the neurodegeneration in Alzheimer's disease (AD) may be caused by deposition of amyloid beta-peptide (Abeta) in plaques in brain tissue. According to the amyloid hypothesis, accumulation of Abeta in the brain is the primary influence driving AD pathogenesis. The rest of the disease process, including formation of neurofibrillary tangles containing tau protein, is proposed to result from an imbalance between Abeta production and Abeta clearance.