Since the discovery of Bacillus thuringiensi s var. israelensis (Bti) in 1976, extensive literature has proved its eYcacy to control mosquitoes and black Xies, of which many species are known as important vectors of diseases or simply as pests of humans and animals. Since 1978, Bti has been used in many countries on all continents and numerous studies have been made on target mosquitoes and black Xies, as well as nontarget organisms (NTO). This review analyses the results of 75 studies on these organism s covering approximatel y 125 families, 300 genera and 400 species. DiVerent factors such as species, instar, feeding behaviour and environmental parameters (larval density, water temperature, suspended matter etc.) may drastically aVect the eYcacy of the Bti products. This is addressed in detail by reviewing the main factors aVecting mosquitoes as well as black Xies. The results of a wide range of laboratory and Weld experiments using diVerent target and nontarget species, various preparation s and formulations of Bti and diVerent biotic or abiotic factors are present in the literature, making the data diYcult to compare on a common basis. Our analysis shows that, under diVerent application conditions, the eVects of Bti on target and nontarget organism s may be hard to predict. Although Bti has been proclaimed to be relatively highly speciWc, some studies show that some NTO are aVected either by single or repeated Bti treatments. Present use against black Xies seems ecologically acceptable. High frequencies of applicatio n and/or overdosages against mosquitoes may result in some persistence of the toxin crystals and ultimately this may have adverse eVects on the food web. A long-term study (publishe d in 1998) in mosquito habitats has shown that intensive Bti treatments over three years did in fact produce an impact on the food web in wetlands. This raises questions, for the Wrst time, on Bti environmental speciWcity. The importance of this impact is discussed and the alternatives for practical pest control are considered. Some modiWcations of Bti use against mosquitoes, guided by research, is probably the best of these alternatives.
To assess the diagnostic value of ultrasound (US) in clinically suspected acute intestinal intussusception in children, the authors prospectively compared US and enema studies in 83 episodes. None of the cases negative at US proved to be intussusception at enema study (negative predictive value = 100%). The sensitivity of US was 100%, and the specificity was 88%. Most of the sonograms were initially obtained and examined by residents. Several unsuspected abnormalities were also found with US. The authors conclude that a few months of training in US appears to be sufficient for high-accuracy investigation of clinically suspected intussusception, enabling selection of those patients in need of an enema.
The presence of a single centromere on each chromosome that signals formation of a mitotic kinetochore is central to accurate chromosome segregation. The histone H3 variant centromere protein-A (CENP-A) is critical for centromere identity and function; CENP-A chromatin acts as an epigenetic mark to direct both centromere and kinetochore assembly. Interpreting the centromere epigenetic mark ensures propagation of a single centromere per chromosome to maintain ploidy. Thus, understanding the nature of CENP-A chromatin is crucial for all cell divisions. However, there are ongoing debates over the fundamental composition of centromeric chromatin. Here we show that natively assembled human CENP-A nucleosomes are octameric throughout the cell cycle. Using total internal reflection fluorescence (TIRF)-coupled photobleaching-assisted copy-number counting of single nucleosomes obtained from cultured cells, we find that the majority of CENP-A nucleosomes contain CENP-A dimers. In addition, we detect the presence of H2B and H4 in these nucleosomes. Surprisingly, CENP-A associated with the chaperone HJURP can exist as either monomer or dimer, indicating possible assembly intermediates. Thus, our findings indicate that octameric CENP-A nucleosomes mark the centromeric region to ensure proper epigenetic inheritance and kinetochore assembly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.