Axial localization of luminophores by partial coherence interferometry

We propose a solution for increasing the axial resolution of confocal microscopes. In the experimental set-up described in this paper an interference phenomenon between two counterpropagating beams is used to determine the axial position of a luminophore. The optical path difference between the two waves, which is related to the position of the luminophore, is recovered thanks to a second interferometer by using partial coherence interferometry demodulation technique. The proposed solution can find applications in biology for localizing with nanometric resolution a small number of tagged species

Farmers' participatory integrated management of foliar diseases of groundnut

Late leaf spot (LLS) caused by Phaeoisariopsis personata [(Berk and Curt) v. Arx = Cercosporidium personatum (Berk. & Curt.) Deighton] and rust caused by Puccinia arachidis (Speg.) are the two most destructive fungal foliar diseases of groundnut worldwide. Together, these two diseases can cause more than 50% yield loss in groundnut in many countries. Foliar disease management in groundnut often involves indiscriminate use of chemicals or total reliance on host plant resistance (HPR). On-station experiments on integrated disease management (IDM) at ICRISAT-Patancheru, India, have clearly demonstrated that when moderate levels of HPR are combined with seed treatment and affordable levels of chemical control, expected yields and economic returns are higher than obtained with chemical control of susceptible genotypes. We evaluated the performance of this combination in on-farm farmer-participatory research. The groundnut genotypes were ICGV 89104, ICGV 91114, TMV 2 and a local cultivar. Thirty farmers from Anantapur, Kurnool, and Nalgonda districts in the state of Andhra Pradesh, India, conducted the experiments during the 1995 and 1996 rainy seasons. Local agronomic practices were followed. Experiments were conducted under both high disease pressure [nonintegrated disease management (non-IDM) i.e. natural] and low disease pressure [integrated disease management (IDM), i.e. seed treatment and fungicide, chlorothalonil sprayed once at 60 days after sowing, d.a.s.]. The severities of LLS and rust on test genotypes were significantly lower than on TMV 2 and the local cultivar up to 65 d.a.s. The increase in pod yield over the local cultivar and TMV 2 in IDM plots was 60% in ICGV 89104, and 55% in ICGV 91114. Farmers preferred these two genotypes because of their close phenotypic similarity to the local cultivar. Our studies also suggest that any technology developed for groundnut should offer a clear yield and foliar disease resistance advantage over farmers' current practices

Aflatoxin Contamination of Groundnut: Prospects for a Genetic Solution through Conventional Breeding

Af latoxin contamination of groundnut is a serious problem in most groundnut-producing countries. The aflatoxin-producing fungi, Aspergillus flavus and A. parasiticus, can invade groundnut seed in the field before harvest, during postharvest drying and curing, and in storage. The semi-arid tropical environment is conducive to preharvest contamination when the crop experiences drought before harvest, whereas in wet and humi d areas, postharvest contamination is more prevalent. Af latoxin contamination can be minimized by adopting some cultural, produce-handling, and storage practices. However, these practices have not been widely adopted by small farmers in developing countries which contribute about 60% of the world's groundnut product ion. Cultivars resistant to seed invasion by aflatoxin-producing fungi or to aflatoxin product ion woul d be of great value to farmers in both developed and developing countries. Therefore, breeding for resistance to aflatoxin-producing fungi and/or aflatoxin product ion can play a significant role in preventing aflatoxin contamination in groundnut , consequent economic losses, and health hazards. The alleviation of aflatoxin contamination through genetic manipulation has been at tempted since the mid 1970s. In spite of the significant progress achieved to date, these efforts have not resulted in complete freedom f rom aflatoxin contamination. The current status and future prospects of genetic solutions to the aflatoxin contamination problem are briefly discussed in this paper

Mechanical Strength of 17 134 Model Proteins and Cysteine Slipknots

A new theoretical survey of proteins' resistance to constant speed stretching is performed for a set of 17 134 proteins as described by a structure-based model. The proteins selected have no gaps in their structure determination and consist of no more than 250 amino acids. Our previous studies have dealt with 7510 proteins of no more than 150 amino acids. The proteins are ranked according to the strength of the resistance. Most of the predicted top-strength proteins have not yet been studied experimentally. Architectures and folds which are likely to yield large forces are identified. New types of potent force clamps are discovered. They involve disulphide bridges and, in particular, cysteine slipknots. An effective energy parameter of the model is estimated by comparing the theoretical data on characteristic forces to the corresponding experimental values combined with an extrapolation of the theoretical data to the experimental pulling speeds. These studies provide guidance for future experiments on single molecule manipulation and should lead to selection of proteins for applications. A new class of proteins, involving cystein slipknots, is identified as one that is expected to lead to the strongest force clamps known. This class is characterized through molecular dynamics simulations.Comment: 40 pages, 13 PostScript figure

Integrated biological-chemical control of Botrytis gray mould of chickpea

During 1994-96, Trichoderma viride and vinclozolin were used for the integrated control of B. cinerea on chickpeas in Pantnagar, Uttar Pradesh, India

Downy Mildew of Sorghum. Information Bulletin no. 51

Downy mildew of sorghum (Peronosclerospora sorghi) is one of the most important diseases of sorghum and maize. It is distributed widely in Africa, Asia, and the Americas, where serious epidemics occur. Systemic infection causes complete or partial sterility of the panicle, resulting in yield loss roughly proportional to the disease incidence. The seriousness of the problem has resulted in significant investment to increase knowledge of the pathogen and to investigate various disease control measures. Several alternatives for the control of sorghum downy mildew are now available including cultural and chemical control, and the deployment of resistant varieties. The current state of knowledge of the pathogen's biology, epidemiology, variability, and control are described in this bulletin, together with practical aspects of disease management

Direct Observation of Single Amyloid-β(1-40) Oligomers on Live Cells: Binding and Growth at Physiological Concentrations

Understanding how amyloid-β peptide interacts with living cells on a molecular level is critical to development of targeted treatments for Alzheimer's disease. Evidence that oligomeric Aβ interacts with neuronal cell membranes has been provided, but the mechanism by which membrane binding occurs and the exact stoichiometry of the neurotoxic aggregates remain elusive. Physiologically relevant experimentation is hindered by the high Aβ concentrations required for most biochemical analyses, the metastable nature of Aβ aggregates, and the complex variety of Aβ species present under physiological conditions. Here we use single molecule microscopy to overcome these challenges, presenting direct optical evidence that small Aβ(1-40) oligomers bind to living neuroblastoma cells at physiological Aβ concentrations. Single particle fluorescence intensity measurements indicate that cell-bound Aβ species range in size from monomers to hexamers and greater, with the majority of bound oligomers falling in the dimer-to-tetramer range. Furthermore, while low-molecular weight oligomeric species do form in solution, the membrane-bound oligomer size distribution is shifted towards larger aggregates, indicating either that bound Aβ oligomers can rapidly increase in size or that these oligomers cluster at specific sites on the membrane. Calcium indicator studies demonstrate that small oligomer binding at physiological concentrations induces only mild, sporadic calcium leakage. These findings support the hypothesis that small oligomers are the primary Aβ species that interact with neurons at physiological concentrations

Burden of paediatric Rotavirus Gastroenteritis (RVGE) and potential benefits of a universal Rotavirus vaccination programme with a pentavalent vaccine in Spain

<p>Abstract</p> <p>Background</p> <p>Rotavirus is the most common cause of gastroenteritis in young children worldwide. The aim of the study was to assess the health outcomes and the economic impact of a universal rotavirus vaccination programme with RotaTeq, the pentavalent rotavirus vaccine, versus no vaccination programme in Spain.</p> <p>Methods</p> <p>A birth cohort was followed up to the age of 5 using a cohort model. Epidemiological parameters were taken from the REVEAL study (a prospective epidemiological study conducted in Spain, 2004-2005) and from the literature. Direct and indirect costs were assessed from the national healthcare payer and societal perspectives by combining health care resource utilisation collected in REVEAL study and unit costs from official sources. RotaTeq per protocol efficacy data was taken from a large worldwide rotavirus clinical trial (70,000 children). Health outcomes included home care cases, General Practioner (GP)/Paediatrician, emergency department visits, hospitalisations and nosocomial infections.</p> <p>Results</p> <p>The model estimates that the introduction of a universal rotavirus vaccination programme with RotaTeq (90% coverage rate) would reduce the rotavirus gastroenteritis (RVGE) burden by 75% in Spain; 53,692 home care cases, 35,187 GP/Paediatrician visits, 34,287 emergency department visits, 10,987 hospitalisations and 2,053 nosocomial infections would be avoided. The introduction of RotaTeq would avoid about 76% of RVGE-related costs from both perspectives: €22 million from the national health system perspective and €38 million from the societal perspective.</p> <p>Conclusions</p> <p>A rotavirus vaccination programme with RotaTeq would reduce significantly the important medical and economic burden of RVGE in Spain.</p