David W. Johnson

Bio: David W. Johnson is an academic researcher from University of Queensland. The author has contributed to research in topics: Peritoneal dialysis & Kidney disease. The author has an hindex of 160, co-authored 2714 publications receiving 140778 citations. Previous affiliations of David W. Johnson include Minnesota Department of Transportation & Open University.

Accumulation of pristanic acid (2, 6, 10, 14 tetramethylpentadecanoic acid) in the plasma of patients with generalised peroxisomal dysfunction

Abstract: The plasma of some patients with biochemical evidence of a generalised peroxisomal dysfunction (GPD) show greatly increased levels of phytanic acid as well as its α-oxidation product, pristanic acid (2, 6, 10, 14-tetramethylpentadecanoic acid). Increased amounts of 14- and 16- carbon branched chain fatty acids are also found in some of these patients. As pristanic acid is present in normal or near-normal amounts in classical Refsum disease and rhizomelic chondrodysplasia, two disorders characterised by deficiencies in phytanic acid oxidation, we speculate that its accumulation is not secondary to a defect in the α-oxidation of phytanic acid, but is indicative of a block in the peroxisomal β-oxidation of pristanic acid. The finding of phytanic acid, as well as a number of its metabolites in patients with inherited defects in peroxisomal biogenesis indicates that a number of the steps in phytanic acid degradation may be confined to peroxisomes.

Occurrence of unusual molecular species of sphingomyelin containing 28-34-carbon polyenoic fatty acids in ram spermatozoa.

Abstract: The high levels of very long chain fatty acids found in ram spermatozoa are located almost exclusively in one of two separable species of sphingomyelin. Mass spectral analysis, including fast atom bombardment of the purified sphingomyelin, has shown the fatty acids to have a carbon chain length of between 28 and 34, with between four and six double bonds, and to belong predominantly to the n-3 series.

The occurrence of polyenoic very long chain fatty acids with greater than 32 carbon atoms in molecular species of phosphatidylcholine in normal and peroxisome-deficient (Zellweger's syndrome) brain.

Abstract: The n-6 tetra- and pentaenoic fatty acids with carbon chain lengths greater than 32 found in normal brain are located predominantly in a separable species of phosphatidylcholine A similar phospholipid is found in increased amounts in the brain of peroxisome-deficient (Zellweger's syndrome) patients, but the fatty acid composition differs in that penta- and hexaenoic derivatives predominate Our data strongly suggest that the polyenoic very long chain fatty acids are confined to the sn-1 position of the glycerol moiety, while the sn-2 position is enriched in saturated, monounsaturated and polyunsaturated fatty acids with less than 24 carbon atoms It is postulated that these unusual molecular species of phosphatidylcholine may play some, as yet undefined, role in brain physiology

Determination of the composition of Ultra-thin Ni-Si films on Si: constrained modeling of electron probe microanalysis and x-ray reflectivity data

Abstract: The homogeneous bulk assumption used in traditional electron probe microanalysis (EPMA) can be applied for thin-layered systems with individual layers as thick as 50 nm provided the penetration depth of the lowest accelerating voltage exceeds the total film thickness. Analysis of an NIST Ni-Cr thin film standard on Si using the homogeneous model yielded certified compositions and application of the same model to ultra-thin Ni-Si layers on GaAs yielded their expected compositions. In cases where the same element is present in multiple layers or in the substrate as well as the film, the homogeneous assumption in EPMA alone is not sufficient to determine composition. By combining x-ray reflectivity (XRR) thickness and critical angle data and using an iterative approach, quantitative compositional data in EPMA can be achieved. This technique was utilized to determine the composition of Ni-Si ultra-thin films grown on silicon. The Ni-Si composition determined using this multi-instrumental technique matched that of Ni-Si films simultaneously deposited on GaAs. Copyright © 2008 John Wiley & Sons, Ltd.

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The social identity theory of intergroup behavior

Abstract: This chapter presents an outline of a theory of intergroup conflict and some preliminary data relating to the theory. Much of the work on the social psychology of intergroup relations has focused on patterns of individual prejudices and discrimination and on the motivational sequences of interpersonal interaction. The intensity of explicit intergroup conflicts of interests is closely related in human cultures to the degree of opprobrium attached to the notion of "renegade" or "traitor." The basic and highly reliable finding is that the trivial, ad hoc intergroup categorization leads to in-group favoritism and discrimination against the out-group. Many orthodox definitions of "social groups" are unduly restrictive when applied to the context of intergroup relations. The equation of social competition and intergroup conflict rests on the assumptions concerning an "ideal type" of social stratification in which the salient dimensions of intergroup differentiation are those involving scarce resources.