Oxidation of low density lipoprotein by iron or copper at acidic pH

Oxidized low density lipoprotein (LDL) may play a significant role in atherosclerosis. We have investigated the effect of pH on the oxidation of LDL by iron or copper. When LDL was oxidized by iron in the presence of cysteine in either Hanks' balanced salt solution (HBSS) or Ham's F-10 medium, an acidic pH greatly decreased the lag period and increased the rate of formation of hydroperoxides and thiobarbituric acid-reactive substances (TBARS), and increased its uptake by macrophages. There was a dose-dependent increase of LDL oxidation at acidic pH in the presence of increasing concentrations of cysteine. When LDL was oxidized by copper in HBSS, an acidic pH increased the lag phase before the rapid formation of conjugated dienes, hydroperoxides, and TBARS, but increased its uptake by macrophages. Similar results were obtained using Ham's F-10 medium. Cysteine (100 microM) inhibited the modification of LDL by copper in HBSS at both pH 7.4 and 5.5 As atherosclerotic lesions may be acidic, these observations may help to explain why LDL oxidation occurs locally at these sites.     

Maintaining Case-Based Reasoners: Dimensions and Directions

Experience with the growing number of large-scale and long-term case-based reasoning (CBR) applications has led to increasing recognition of the importance of maintaining existing CBR systems. Recent research has focused on case-base maintenance (CBM), addressing such issues as maintaining consistency, preserving competence, and controlling case-base growth. A set of dimensions for case-base maintenance, proposed by Leake and Wilson, provides a framework for understanding and expanding CBM research. However, it also has been recognized that other knowledge containers can be equally important maintenance targets. Multiple researchers have addressed pieces of this more general maintenance problem, considering such issues as how to refine similarity criteria and adaptation knowledge. As with case-base maintenance, a framework of dimensions for characterizing more general maintenance activity, within and across knowledge containers, is desirable to unify and understand the state of the art, as well as to suggest new avenues of exploration by identifying points along the dimensions that have not yet been studied. This article presents such a framework by (1) refining and updating the earlier framework of dimensions for case-base maintenance, (2) applying the refined dimensions to the entire range of knowledge containers, and (3) extending the theory to include coordinated cross-container maintenance. The result is a framework for understanding the general problem of case-based reasoner maintenance (CBRM). Taking the new framework as a starting point, the article explores key issues for future CBRM research.     

Inter‐city travel: some planning implications

The first part of the paper is concerned with the development and calibration of a suitable mathematical model for determining the choice of travel mode between rail and air on four inter‐city routes in the U.K. Using the results obtained from the developed model, the second part of the paper is devoted to discussing some of the more important planning implications which have been highlighted. In particular, access/egress to the termini, the importance of travel time for both work and nonwork travellers, and car parking implications, are stressed.     

AMPH-IMA97: a hypercard program to determine the name of an amphibole from electron microprobe and wet chemical analyses

In 1997, the International Mineralogical Association (IMA) revised the amphibole naming scheme making it necessary to amend the previous EMP-AMPH Macintosh program to the new rules. The AMPH-IMA97 program allows single input or automatic input of as many amphibole analyses as are available following a set input format. There are three options for calculation scheme of amphibole analysis: (1) complete chemical analyses can be calculated to 24(O, OH, F, Cl); (2) analyses with determined FeO and Fe₂O₃ but without H₂O can be calculated to 23(O) and (3) electron microprobe analyses with only total Fe determined and without H₂O can be calculated to 23(O) with IMA97-recommended normalization for Fe³⁺ and Fe²⁺ values. To test the program, over 500 analyses were calculated using the three options. The first comprehensive test of the third option successfully estimated Fe²⁺ (R²=0.88), but became less successful for Fe³⁺ (R²=0.42) estimation. Problems in the normalization of Mn³⁺- and Mn²⁺-bearing amphiboles and in the IMA97 sodic amphibole classification procedure emerged for Mn-rich amphiboles. This necessitated the proposal and implementation with the program of a simplified sodic amphibole classification scheme. A new coloured amphibole classification chart accompanies the program.     

Racial and ethnic disparities in the use of cardiovascular procedures: associations with type of health insurance

This is the first report showing VIP fibers in the optic chiasm and the optic nerves of intact rats. These fibers form a fan-shaped dorso-medial bundle in the optic nerves. After colchicine injection into the vitreous body VIP fibers could be followed farther in the optic nerve toward the eye when compared to intact rats. After removal of eyes (enucleation) the VIP fiber-bundle became more prominent and VIP immunoreactive perikarya appeared in the supraoptic and para ventricular nuclei. When five-nine months after the enucleation Phaseolus vulgaris leucoagglutinin was administered to the paraventricular or supraoptic area, the anterogradely transported tracer was demonstrated in the optic nerve. These observations suggest the existence of a hypothalamic projection to the eye, which is, at least in part, VIP immunoreactive.     

Cloning of zebrafish neurofilament cDNAs for plasticin and gefiltin: increased mRNA expression in ganglion cells after optic nerve injury

During retinal growth and optic axon regeneration, the differential expression of the neuronal intermediate filament proteins, plasticin and gefiltin, in the goldfish visual pathway suggests that these proteins support programmed axonal growth. To investigate plasticin and gefiltin during axonogenesis, we turned to the zebrafish, a system that is more amenable to mutational analysis. As a first step, we demonstrated that the intermediate filament compositions of goldfish and zebrafish are similar. In addition, the cDNAs for zebrafish plasticin and gefiltin were cloned and characterized. Using in situ hybridization in retina, we show increased mRNA levels for these proteins following optic nerve crush. Zebrafish plasticin and gefiltin peak and return to baseline levels of expression more rapidly than in goldfish. Furthermore, in the unoperated eye of experimental fish, there was a moderate increase in the levels of plasticin and gefiltin mRNA, suggesting that soluble factors influence the expression of these proteins. The successive expression of plasticin and gefiltin suggests that these neuronal intermediate filament proteins are integral components of axonogenesis. The cloning and characterization of cDNAs for plasticin and gefiltin permit mutational analyses of these proteins during zebrafish axonogenesis.     

Microchemical Characterization of Alluvial Gold Grains as an Exploration Tool

There is considerable variation in the composition of native gold and the nature of minerals co-existing with it, and this reflects differences in the geological environment and chemistry of ore-forming processes. In areas where gold-bearing mineralization is subject to active fluvial erosion, especially in temperate climatic regimes, any discrete grains of native gold pass into alluvial sediment with little modification. The chemical characteristics of alluvial grains and the nature of preserved mineral inclusions provide a signature which points back to the type of source mineralization. This signature may be established using electron probe microanalysis and scanning electron microscopy and can be interpreted to provide information about the original bedrock mineralization. Identification of the type of source mineralization using the technique at an early stage in regional exploration can help focus attention on targets with the most potential economic importance.     

Hollow waveguides with low intrinsic photoluminescence fabricated with Ta(2)O(5) and SiO(2) films

A type of integrated hollow core waveguide with low intrinsic photoluminescence fabricated with Ta(2)O(5) and SiO(2) films is demonstrated. Hollow core waveguides made with a combination of plasma-enhanced chemical vapor deposition SiO(2) and sputtered Ta(2)O(5) provide a nearly optimal structure for optofluidic biofluorescence measurements with low optical loss, high fabrication yield, and low background photoluminescence. Compared to earlier structures made using Si(3)N(4), the photoluminescence background of Ta(2)O(5) based hollow core waveguides is decreased by a factor of 10 and the signal-to-noise ratio for fluorescent nanobead detection is improved by a factor of 12.