Intramammary challenge with Escherichia coli following immunization with a curli-producing Escherichia coli

Holstein and Jersey cattle were immunized with a curli-producing strain of Escherichia coli (pCRL65/A012) or a noncurli-producing strain (pUC18/HB101) to determine differences in resistance to establishment of experimental intramammary infection. Cows (n = 6 per group) were immunized at 14 d prior to drying off, 7 d of involution, and at calving with 3 x 10(10) E. coli in Freund's Incomplete Adjuvant. At 30 d of lactation, one mammary quarter of each cow was infused with a wild strain of E. coli (727). Escherichia coli 727 was isolated from a naturally occurring intramammary infection and produced curli. All challenged quarters became infected, and all cows developed acute clinical mastitis. Geometric mean duration of intramammary infections was 6 d for both immunization groups. All infections were spontaneously eliminated within 10 d. No differences occurred between immunization groups in blood selenium and glutathione peroxidase activity, plasma selenium, number of E. coli 727 isolated from secretion after challenge, rectal temperature and SCC response, clinical status of mammary quarters, or DMI. Reduction in milk production after challenge was greater for cows immunized with E. coli pCRL65/A012. Immunization of dairy cattle with a curli-producing strain of E. coli did not protect against experimental intramammary challenge during lactation.     

Characterization of thermoelectric elements and devices by impedance spectroscopy

This article describes a new measurement technique that utilizes impedance spectroscopy for the characterization of thermoelectric materials and devices. Two circuit models were developed and used to help explain the impedance spectroscopy data using transmission line theory and a coupled electrothermal model. Two testing configurations have been investigated including one based on a sinusoidal source (ac lock-in technique) and one based on a pulsed wave source. Methods for reducing the measurement times for this technique are discussed. In addition, the influence of radiation losses on this measurement technique has also been analyzed to further understand the limitations of this technique at higher temperatures.     

Bipolar spectrum–substance use co-occurrence: Behavioral approach system (BAS) sensitivity and impulsiveness as shared personality vulnerabilities.

Bipolar disorders and substance use disorders (SUDs) show high co-occurrence. One explanation for this co-occurrence may be common personality vulnerabilities involved in both. The authors tested whether high behavioral approach system (BAS) sensitivity and impulsiveness are shared personality vulnerabilities in bipolar spectrum disorders and substance use problems and their co-occurrence in a longitudinal study of 132 individuals on the bipolar spectrum and 153 control participants. At Time 1, participants completed the Behavioral Inhibition System/BAS Scales and the Impulsive Nonconformity Scale. Substance use problems were assessed via the Michigan Alcoholism Screening Test and the Drug Abuse Screening Test at 4-month intervals for 1 year. Participants with bipolar disorder had higher rates of lifetime SUDs and substance use problems during the follow-up, relative to control participants. In line with hypotheses, higher BAS sensitivity and impulsiveness predicted bipolar status and increased substance use problems prospectively. BAS total, BAS Fun Seeking, and impulsiveness mediated the association between bipolar spectrum status and prospective substance use problems, with impulsiveness as the most important mediator. High BAS sensitivity and impulsiveness may represent shared personality vulnerabilities for both disorders and may partially account for their co-occurrence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ischemic preconditioning attenuates postischemic coronary artery endothelial dysfunction in a model of minimally invasive direct coronary artery bypass grafting

OBJECTIVE: Unmodified reperfusion without cardioplegia in minimally invasive direct coronary artery bypass grafting procedures causes endothelial dysfunction that may predispose to polymorphonuclear neutrophil-mediated myocardial injury. This study tested the hypothesis that ischemic preconditioning in a minimally invasive direct coronary artery bypass grafting model attenuates postischemic endothelial dysfunction in coronary vessels. METHODS: In anesthetized dogs, the left anterior descending coronary artery was occluded for 30 minutes and reperfused for 3 hours without ischemic preconditioning (no-ischemic preconditioning; n = 7); in 7 dogs, the left anterior descending occlusion was preceded by 5 minutes occlusion followed by 5 minutes of reperfusion. Relaxation responses to stimulators of nitric oxide synthase were used to evaluate endothelial function in arteries from the ischemic-reperfused (left anterior descending) and nonischemic (left circumflex coronary artery) zones. RESULTS: Stimulated endothelial-dependent relaxation of epicardial left anterior descending artery to incremental concentrations of acetylcholine in the no-ischemic preconditioning animals was shifted to the right, and maximal relaxation was attenuated compared with the nonischemic left circumflex coronary artery (117% +/- 4% vs 138% +/- 5%). In contrast, acetylcholine-induced maximal relaxation was comparable in the left anterior descending artery versus left circumflex coronary artery in the ischemic preconditioning group (130% +/- 6% vs 135% +/- 5%). In 150- to 200- microm left anterior descending microvessels, 50% relaxation occurred with a lower concentration (log[M]) of acetylcholine in ischemic preconditioning versus no-ischemic preconditioning (-8.0 +/- 0.4 vs -7.0 +/- 0.1) with no group differences in smooth muscle relaxation to sodium nitroprusside, suggesting endothelial-specific damage. Adherence of fluorescent labeled polymorphonuclear neutrophils to epicardial coronary artery endothelium, used as an index of basal (unstimulated) anti-polymorphonuclear neutrophil function, was significantly attenuated by ischemic preconditioning versus no-ischemic preconditioning (293 +/- 25 polymorphonuclear neutrophils/mm2 vs 528 +/- 29 polymorphonuclear neutrophils/mm2). CONCLUSION: In this minimally invasive direct coronary artery bypass grafting model, both agonist-stimulated and basal postischemic endothelial dysfunction were attenuated by ischemic preconditioning.     

The phenotype of mutations of G2655 in the sarcin/ricin domain of 23 S ribosomal RNA

The sarcin/ricin domain (SRD) in Escherichia coli 23 S rRNA forms a part of the site for the association of the elongation factors with the ribosome and hence is critical for the binding of aminoacyl-tRNA and for translocation. The domain is also the site of action of the eponymous toxins which catalyze covalent modification of single nucleotides that inactivate the ribosome. The conformation of the conserved guanosine at position 2655 is an especially prominent feature of the structure of the SRD: the nucleotide is bulged out of a helix and forms a base-triple with A2665 and U2656. G2655 in 23 S rRNA is protected from chemical modification when the elongation factors, EF-Tu and EF-G, are bound to ribosomes and the analog of G2655 in oligoribonucleotides is critical for recognition by the toxin sarcin and by EF-G. The contribution of G2655 to the function of the ribosome has been evaluated by constructing mutations in the nucleotide and determining the phenotype. Constitutive expression of a plasmid-encoded rrnB operon with a deletion of, or transversions in, G2655 is lethal to E. coli cells, whereas a defect in the growth of cells with a G2655A transition is observed only in competition with wild-type cells. The sedimentation profiles of ribosomes with mutations in G2655 are altered; most markedly by deletion or transversion of the nucleotide, less severely by transition to adenosine. Mutations of G2655 confer resistance to sarcin on ribosomes. Ribosomes with G2655Delta, G2655C, or G2655U mutations in 23 S rRNA are not active in protein synthesis, whereas those with the G2655A transition mutation suffer decreased activity.     

Statistical Analysis of a Round-Robin Measurement Survey of Two Candidate Materials for a Seebeck Coefficient Standard Reference Material

In an effort to develop a Standard Reference Material (SRM™) for Seebeck coefficient, we have conducted a round-robin measurement survey of two candidate materials—undoped Bi₂Te₃ and Constantan (55 % Cu and 45 % Ni alloy). Measurements were performed in two rounds by twelve laboratories involved in active thermoelectric research using a number of different commercial and custom-built measurement systems and techniques. In this paper we report the detailed statistical analyses on the interlaboratory measurement results and the statistical methodology for analysis of irregularly sampled measurement curves in the interlaboratory study setting. Based on these results, we have selected Bi₂Te₃ as the prototype standard material. Once available, this SRM will be useful for future interlaboratory data comparison and instrument calibrations.     

Surface construction from planar contours

Many applications of computer graphics involve the display of a three-dimensional solid reconstructed from a sequence of two-dimensional planar contours. Surface construction algorithms accomplish this by mapping individual pairs of contours, forming triangular surface patches, that approximate the original three-dimensional solid. In this paper, we present an expanded algorithm that not only handles the mappings of multiple contours per plane and partial contour mappings, but also allows human interaction to resolve mapping problems. We include a discussion of our algorithm's limitations and the proposed solutions to those limitations.     

Moral judgment, personality, and attitudes toward authority.

Two studies investigating attitudes toward authority using the Survey of Ethical Attitudes (SEA) clarify the dynamics of conformity. The SEA and a semantic differential were administered to 369 college students, who rated the concepts mother, father, police, and government on 10 evaluative adjective pairs. Ss endorsing the "ethics of social responsibility" held more favorable attitudes toward authority than did those endorsing the "ethics of personal conscience." This result was replicated in the 2nd study. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of in vitro and in vivo mutations in non-conserved nucleotides in the ribosomal RNA recognition domain for the ribotoxins ricin and sarcin and the translation elongation factors

The sarcin/ricin domain in 23 S/28 S rRNA is crucial for ribosome function, since it constitutes at least part of the binding site for the elongation factors and hence is essential for binding aminoacyl-tRNA and for translocation. The domain is also the site of action of ricin and sarcin and analysis of the effect of mutations in the RNA on recognition by the cytotoxins has helped to define the structure and to understand the function of the region. We have constructed deletions, separately, of pairs of non-conserved, juxtaposed but non-hydrogen-bonded nucleotides that correspond to C4317 and C4331, and to U4316 and C4332, in an oligoribonucleotide that mimics the sarcin/ricin domain in rat 28 S rRNA. The deletions had no effect on the depurination of A4324 by ricin nor on the cleavage of the phosphodiester bond on the 3' side of G4325 by sarcin. However, simultaneous deletion of the four nucleotides decreased cleavage by sarcin but did not affect depurination by ricin. Removal of the non-canonical A4318.A4330 pair abolished recognition by both toxins. Deletion from oligoribonucleotides, that reproduce the sarcin/ricin domain of Escherichia coli 23 S rRNA, of U2653 and C2667 (equivalent to U4316, C4317 and C4331, C4332 in 28 S rRNA), or substitution of guanosine for U2653 (designed to form a Watson-Crick G2653.C2667 pair), reduced cleavage by sarcin whereas depurination by ricin was slightly increased. An increase in the stability of the mutant oligoribonucleotides may be the basis of the impairment in sarcin action. The tm for the wild-type RNA is 60 degreesC; for the double-deletion mutant U2653Delta/C2667Delta it is 65 degreesC; and for the U2653G transversion it is 69 degreesC. Expression of a mutant 23 S rRNA gene lacking U2653 and C2667 is lethal and a U2653G transversion mutation impairs growth. The mutant ribosomes are less active in protein synthesis than the wild-type and ribosomes with the U2653G mutation are resistant to sarcin. The binding of EF-G to oligoribonucleotides with a U2653/C2667 double deletion is reduced and an effect on the affinity of the factor for the sarcin/ricin domain may account in part for the decrease in ribosome efficiency. The results stress the potential importance in rRNA structure and function of non-conserved nucleotides, and suggest that the sarcin/ricin domain in ribosomes requires a region of structural flexibility for optimal efficiency.     

Investigation of the relationships between die build up and die swell

Die build up (DBU) is a common problem encountered during extrusion of polymers where material accumulates around the die exit and may cause defects in the surface of the product. This study was initiated to better understand the fundamental relationships between DBU and die swell. The study was conducted on a strand die extrusion system using an ethylene‐octene polyolefin elastomer resin. This study demonstrated that die swell is not a root cause of DBU. It was shown that at constant shear rate, increasing the die L/D ratio results in an increase in DBU, while die swell decreases. The important variables influencing DBU for the resin used in this study were: the shear rate or shear stress in capillary portion of the die, the nominal residence time that the resin is exposed to the high shear stress in the die capillary, and the concentration of oligomers present in the resin or generated during processing. These data support the conclusion that DBU is due to the shear‐induced migration of oligomeric species in the polymer to the die surface. Higher shear rates and stresses in the die promote this migration and result in a higher concentration of oligomeric species near the die wall. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers