Monitoring and estimating concentrations of polychlorinated biphenyls, dioxins, and furans in cattle milk and soils of Rhine-Delta floodplains

Neuregulins have become the focus of intense research due to their putative roles in the etiology of certain cancers and to their evolving roles in PNS and CNS development. Evidence has been presented that neuregulins are present in neuronal cells where they act as mediators of neuron-glial signaling. Consistent with this view, we now report that there is a dramatic differential response of Schwann cells to the two major isoforms of neu differentiation factor (NDF alpha and NDF beta). NDF beta is a potent mitogen, whereas NDF alpha is nonmitogenic for Schwann cells. In addition, we report that Schwann cells contain endogenous NDF as well as the mRNA for both isoforms of NDF. Evidence is also presented that several isoforms of NDF are released from cultured Schwann cells. Our data suggest that in addition to functioning as a neuron-glial mediator, endogenous neuregulins may function in an autocrine/paracrine loop or in a juxtacrine- (cell-to-cell) mediated signal between individual Schwann cells or between Schwann cells and neurons.     

Chloroquine-induced venodilation in human hand veins

OBJECTIVE: Hypotension induced by parenteral administration of chloroquine is a common and serious adverse effect of this drug. Our aim was to investigate whether chloroquine produces venodilation in vivo and to explore the underlying mechanisms. METHODS: Vascular effects of chloroquine were studied in healthy volunteers with use of the dorsal hand vein technique at the Geriatric Research Education and Clinical Center, Veterans Affairs Palo Alto Health Care System. We studied 22 healthy volunteers (19 men and three women). Venous responsiveness was determined with the dorsal hand vein technique, which measures the diameter of the vein. RESULTS: Chloroquine was found to produce a dose-dependent relaxation of hand veins preconstricted with the alpha 1-receptor selective agonist phenylephrine. The venodilatory response to chloroquine ranged from 15% +/- 19% at an infusion rate of 0.75 microgram/min to 61% +/- 24% at 48 microgram/min. Venodilation was attenuated by the nitric-oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) so that the dose of chloroquine required to produce 20% venodilation was increased from 3.7 micrograms/min to 15 micrograms/min (p < 0.01). In the presence of a combination of histamine receptor antagonists, there was also a diminution of the vasodilatory response to chloroquine from 72% +/- 5% to 44% +/- 5% at the infusion rate of 96 micrograms/min. The response was further reduced to 33% +/- 7% by the coinfusion of H1-/H2-receptor antagonists with L-NMMA. CONCLUSION: Chloroquine produces venodilation at infusion rates that achieve local concentrations likely similar to those observed systemically after clinically relevant intravenous doses. The date also suggest a role for nitric oxide and histamine release in mediating this response.     

CYP2D6 allelic frequencies in young-onset Parkinson's disease

Parkinson's disease (PD) is thought to develop as a result of interactions between genetic susceptibility factors and environmental exposures. One candidate gene is CYP2D6, which codes for the debrisoquine 4-hydroxylase cytochrome P450. Impairment of debrisoquine 4-hydroxylase activity has been associated with an increased risk of PD in patients with younger age at disease onset. Genotyping studies in patients with an older age at onset have reported modest increases in risk associated with the CYP2D6 B and A alleles; however, the risk for young-onset PD has not been adequately evaluated. We designed a case-control study to investigate the role of nonfunctional CYP2D6 allelic risk factors for young-onset PD in a sizable patient population and compared the distributions of CYP2D6 genotypes between young-onset ( < or = 51 years) PD patients (n = 108) and controls (n = 236). In contrast with the results from genotyping studies conducted among patients with an older age at onset, there were no significant differences in CYP2D6 allelic frequencies between young-onset PD cases and controls. The frequency of the B allele was slightly lower in the young-onset PD cases than in the controls (0.14 versus 0.20) (X2 = 2.66, p = 0.10). The presence of one or more B alleles was not associated with an increased risk of young-onset PD (odds ratio 0.58; 95% CI 0.33 to 1.00), nor was the presence of one or more nonfunctional alleles (i.e., A, B, D, and D2) (odds ratio 0.68; 95% CI 0.41 to 1.13). This study suggests that the young-onset PD population may differ from the older-onset population with respect to risk factors.     

Tissue boundary refinement in magnetic resonance images using contour-based scale space matching

An algorithm for computationally focusing the tissue boundaries detected from magnetic resonance images is presented. The proposed approach is a novel, whole-contour-based technique for tracing edges selected at a coarse scale into successively finer scales to recover the needed precision. The tracing algorithm builds consensus through a fast pixel voting scheme. Also presented is a rigorous method for determining the appropriate itinerary when traversing scale space, beginning from the premise of a maximum pixel migration per unit change in scale parameter. This leads to an efficient method of processing images so as to maximize accuracy and minimize noise. Although the LoG (Laplacian of Gaussian) is used for many of the experiments, results using a novel edge detector which is mathematically superior to and faster to compute than the LoG and for which fewer steps are required to traverse the same effective span in scale space are presented. Experimental results on real data are presented, and other potential applications are discussed.     

The mechanical and electrical properties of ZrO2-Naβ″-Al2O3 composites

ZrO₂-Na-Al₂O₃ composites were prepared by a conventional method using two different powder routes and different milling liquids. The retained tetragonal-phase ZrO₂ was 85 to 90% for composites with 2.4 to 15 vol% ZrO₂. The fracture toughness (K _lc) and strength increased with increasing ZrO₂ content. At 20 vol % ZrO₂,K _lc and bend strength were 4.35 M Pa m^1/2 and 390 MPa, respectively. Stress-induced transformation toughening is the predominant toughening mechanism. Dispersion toughening also contributes to the increase ofK _lc. Surface strengthening was found to be an effective strengthening method for low ZrO₂ levels. The critical tetragonal ZrO₂ grain size was found to increase from 0.86 to 1.02gmm as the ZrO₂ content increased from 2.5 to 15 vol %. A detailed study of the ionic conductivity of the 15 vol % ZrO₂ dispersed sample was conducted by an a.c. technique between –124° C and 300° C. The bulk and total conductivities were calculated via complex-plane analysis. The total (grain and grain-boundary) ionic specific resistivity was 9 cm at 300° C. The activation enthalpies of the bulk and total conductivity processes were 0.30 and 0.32 eV, respectively.     

“Dicranin” in the Membrane Phospholipids of a Dicranaceae and Pottiaceae Moss Member of the Eastern Himalayan Biodiversity Hotspot

The phospholipids of two moss samples Oreoweisia laxifolia (Hookf.) Kindb. (family‐Dicranaceae Schimp.) and Leptodontium viticulosoides (P. Beauv.) Wijk & Margad (family‐Pottiaceae Schimp.) of the Eastern Himalayan Biodiversity Hotspot were investigated to find out any peculiarity in their fatty acid profiles. Detailed analysis of phospholipid classes and the respective fatty acids was performed using high‐performance thin‐layer chromatography and gas chromatography‐mass spectrometry. An array of different saturated and unsaturated fatty acids were detected in both the samples. Although it has been proposed previously that acetylenic fatty acids are associated only with triacylglycerol of storage lipids, the most striking observation of the present investigation is the abundance of an acetylenic fatty acid, octadeca‐6‐yn‐9,12,15‐trienoic acid (18:4a), or Dicranin, in the phospholipids of both the mosses. The position of the triple bond in the hydrocarbon chain of the fatty acids was confirmed by dimethyloxazoline derivatization of fatty acids and their characteristic mass fragmentation pattern. The occurrence of Dicranin in phospholipids and in the Pottiaceae family is reported for the first time, with substantial explanations of the observed results. This may raise the issue of rethinking “Dicranin” as a chemotaxonomic marker of Dicranaceae.     

Influence of microstructure on the premature failure of a second-intermediate sendzimir mill drive roll

Although a precise understanding of roll failure genesis is complex, the microstructure of a broken roll can often unravel intrinsic deficiencies in material quality responsible for its failure. This is especially relevant in circumstances when, even under a similar mill-operating environment, the failure involves a particular roll or a specific batch of rolls. This paper provides a microstructural insight into the cause of premature breakage of a second-intermediate Sendzimir mill drive roll used at a stainless steel sheet rolling plant under the Steel Authority of India Limited. Microstructural issues influencing roll quality, such as characteristics of carbides, tempered martensite, retained austenite, etc., have been extensively studied through optical and scanning electron microscopy, electron-probe microanalysis, image analysis, and x-ray diffractometry. These are discussed to elucidate specific microstructural inadequacies that accentuated the failure. The study reveals that even though retained austenite content is low (6.29 vol%) and martensite is non-acicular, the roll breakage is a consequence of intergranular cracking caused by improper carbide morphology and distribution.     

Using directed hypergraphs to verify rule-based expert systems

Rule-based representation techniques have become popular for storage and manipulation of domain knowledge in expert systems. It is important that systems using such a representation are verified for accuracy before implementation. In recent years, graphical techniques have been found to provide a good framework for the detection of errors that may appear in a rule base. The authors present a graphical representation scheme that: 1) captures complex dependencies across clauses in a rule base in a compact yet intuitively clear manner and 2) is easily automated to detect structural errors in a rigorous fashion. Their technique uses a directed hypergraph to accurately detect the different types of structural errors that appear in a rule base. The technique allows rules to be represented in a manner that clearly identifies complex dependencies across compound clauses. Subsequently, the verification procedure can detect errors in an accurate fashion by using simple operations on the adjacency matrix of the directed hypergraph. The technique is shown to have a computational complexity that is comparable to that of other graphical techniques. The graphical representation coupled with the associated matrix operations illustrate how directed hypergraphs are a very appropriate representation technique for the verification task