Gene structures and properties of enzymes of the plasmid-encoded nicotine catabolism of Arthrobacter nicotinovorans

Arthrobacter nicotinovorans is a Gram-positive aerobic soil bacterium able to grow on nicotine as its sole source of carbon and nitrogen. The initial steps of nicotine catabolism are catalyzed by nicotine dehydrogenase, the l- and d-specific 6-hydroxynicotine oxidases, and ketone dehydrogenase. The genes encoding these enzymes reside on a 160 kb plasmid, pAO1. The cccDNA of this plasmid was isolated in high purity and reasonable yield. It served as template material for the construction of a lambda-phage DNA library of the plasmid. The genes coding for 6-hydroxy-l-nicotine oxidase and for the subunits of the heterotrimeric ketone dehydrogenase were identified, subcloned and sequenced. The 6-hlno gene was identified as a 1278 bp open reading frame; its regulatory elements were also recognized. The derived primary structure of the monomer of apo-6-hydroxy-l-nicotine oxidase (46,264.5 Da) agrees with the data obtained by partial amino acid sequencing. 6-Hydroxy-l-nicotine oxidase and 6-hydroxy-d-nicotine oxidase were expressed in Escherichia coli and obtained in a state of high purity and crystallized. Ketone dehydrogenase (KDH) was found to be a heterotrimer with subunits of molecular mass 89,021.71, 26,778.65 and 17,638.88. The genes of KDH-A and KDH-B are juxtaposed; the A of the stop codon of KDH-A is used in the start codon of KDH-B, eliciting a frame shift. KDH-C is separated from KDH-A by 281 bp.     

Elastic limit and microplastic response of hardened steels

Tempered martensite-retained austenite microstructures were produced by direct quenching a series of 41XX medium carbon steels, direct quenching and reheating a series of five 0.8C-Cr- Ni-Mo steels and intercritically austenitizing at various temperatures, and quenching a SAE 52100 steel. All specimens were tempered either at 150 °C or at 200 °C. Specimens were subjected to compression and tension testing in the microstrain regime to determine the elastic limits and microplastic response of the microstructures. The retained austenite and matrix carbon content of the intercritically austenized specimens were measured by X-ray diffraction and Mossbauer spectroscopy. The elastic limit of the microstructures decreases with increasing amounts of retained austenite. Refining of the austenite distribution increases the elastic limit. Low elastic limits are mainly due to low flow stresses in the austenite and not internal stresses. The elastic limit correlates with the largest austenite free-mean path by a Hall-Petch type equation. The elastic limit increases with decreasing intercritical austenitizing temperature in the SAE 52100 due to (1) a lower carbon content in the matrix reducing the retained austenite levels and (2) retained carbides that refine grain size and, therefore, the austenite distribution in quenched specimens. The microplastic response of stable austenite-martensite composites may be modeled by a rule of mixtures. In the microplastic region, the strain is accommodated by successively smaller austenite regions until the flow strength matches that of the martensite. Reheating and quenching refines the microstructure and renders the austenite unstable in the microplastic regime, causing transformation of the austenite to martensite by a strain-induced mechanism. The transformation of austenite to martensite occurs by a stress-assisted mechanism in medium carbon steels. The low elastic limits in medium carbon steels were due to the inability of the strain from the stress-assisted transformation of austenite to martensite to balance the plastic strain accumulated in the austenite.     

Effects of pitch and speech rate on personal attributions.

In 3 experiments, 61 undergraduates listened to recordings of male speakers answering 2 interview questions and rated the speakers on a variety of semantic differential scales. The recordings had been altered so that the pitch of the speakers' voices was raised or lowered by 20% or left at its normal level, and speech rate was expanded or compressed by 30% or left at its normal rate. The results provide clear evidence that listeners use these acoustic properties in making personal attributions to speakers. Speakers with high-pitched voices were judged less truthful, less emphatic, less "potent" (smaller, thinner, faster), and more nervous. Slow-talking speakers were judged less truthful, less fluent, and less persuasive and were seen as more "passive" (slower, colder, passive, weaker) but more "potent." However, the effects of the acoustic manipulations on personal attributions also depended on the particular question that elicited the response. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Richard Christie (1918–1992): Obituary.

Memorializes Richard Christie, a researcher on the relationship of personality and political ideology and a pioneer in the application of experimental methodology to the study of personality. A psychology professor at Columbia University for 33 yrs, his research foci included the Machiavellian personality and the authoritarian personality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lamellar lipoproteins uniquely contribute to hyperlipidemia in mice doubly deficient in apolipoprotein E and hepatic lipase

Remnants of triglyceride-rich lipoproteins containing apolipoprotein (apo) B-48 accumulate in apo E-deficient mice, causing pronounced hypercholesterolemia. Mice doubly deficient in apo E and hepatic lipase have more pronounced hypercholesterolemia, even though remnants do not accumulate appreciably in mice deficient in hepatic lipase alone. Here we show that the doubly deficient mice manifest a unique lamellar hyperlipoproteinemia, characterized by vesicular particles 600 A-1,300 A in diameter. As seen by negative-staining electron microscopy, these lipoproteins also contain an electron-lucent region adjacent to the vesicle wall, similar to the core of typical lipoproteins. Correlative chemical analysis indicates that the vesicle wall is composed of a 1:1 molar mixture of cholesterol and phospholipids, whereas the electron-lucent region appears to be composed of cholesteryl esters (about 12% of the particle mass). Like the spherical lipoproteins of doubly deficient mice, the vesicular particles contain apo B-48, but they are particularly rich in apo A-IV. We propose that cholesteryl esters are removed from spherical lipoproteins of these mice by scavenger receptor B1, leaving behind polar lipid-rich particles that fuse to form vesicular lipoproteins. Hepatic lipase may prevent such vesicular lipoproteins from accumulating in apo E-deficient mice by hydrolyzing phosphatidyl choline as scavenger receptor B1 removes the cholesteryl esters and by gradual endocytosis of lipoproteins bound to hepatic lipase on the surface of hepatocytes.     

Void formation during tensile testing of dual phase steels

The effects of martensite volume fraction (MVF) and strain state on necking behavior, post-uniform elongation, and the nucleation and growth of voids in thin sheet dual phase steel, strained in tension, were investigated. Steel containing, in weight percent, 0.08C, 1.45Mn, and 0.21Si, was cold rolled 50 pct and intercritically annealed to produce dual phase microstructures. The effects of MVF were evaluated with a series of constant geometry tensile samples with martensite volume fractions between 5 and 40 pct. The effects of strain state within the neck were evaluated with a series of constant thickness samples with 20 pct MVF and with width variations between 3 and 25 mm. A transition from diffuse to localized necking, as well as a decrease in post-uniform elongation, occurred with both an increase in MVF and sample width. Metallographic analysis of deformed samples revealed that the void nucleation occurs primarily at martensite particles by three distinct mechanisms. The void size and density in the necked region increased toward the fracture surface in all samples and the void density was significantly higher for the samples which exhibited localized necking. However, independent of neck geometry, voids were nucleated uniformly throughout the samples, and were associated with the martensite. The difference in void size and density between the samples with different necking behavior indicates that void growth is a consequence of the strain gradient while the shape of the voids depends on both the strain state and strain gradient. The implications of the void structure analysis are interpreted based on the dual phase microstructure. Formerly Graduate Research Assistant, Colorado School of Mines.     

Intercritically annealed and isothermally transformed 0.15 Pct C steels containing 1.2 Pct Si-1.5 Pct Mn and 4 Pct Ni: Part I. transformation,microstructure, and room-temperature mechanical properties

Steels containing 0.15 pct C and 1.2 pct Si-1.5 pct Mn or 4 pct Ni were intercritically annealed and isothermally transformed between 300 °C and 500 °C for 1 to 60 minutes. The specimens were subjected to tensile testing at room temperature, and the microstructures were evaluated by light microscopy, scanning and transmission electron microscopy (SEM and TEM, respectively), and X-ray diffraction (XRD). The microstructures consist of dispersed regions of bainite, martensite, and austenite in a matrix of ferrite, and a maximum of 11.6 pct austenite is retained after isothermal holding at 450 °C in the Si-Mn steel. In specimens where austenite transforms to martensite during quenching after isothermal holding, the stress-strain curves show continuous yielding, high ultimate tensile strength (UTS), and relatively low ductility. In specimens where higher volume fractions of austenite transform to bainite during isothermal holding, the stress-strain curves show discontinuous yielding, low UTS, and high ductility.     

Refolding and reassociation of glycerol dehydrogenase from Bacillus stearothermophilus in the absence and presence of GroEL

The refolding of the tetrameric, metalloenzyme glycerol dehydrogenase (GDH) from Bacillus stearothermophilus has been investigated using stopped-flow fluorescence and circular dichroism spectroscopy. The effects of metal ions on the refolding of the native enzyme and the refolding of a monomeric mutant ([A208]GDH) have also been studied. The refolding process of the wild-type enzyme is at least biphasic; 70% of the respective signal changes occur in the first 2 ms followed by a slower process with a half-life of 3 s. The presence of the metal ion does not affect the slowest biphasic refolding rate, which is virtually the same for all three versions of the enzyme. The presence of GroEL slows down the first phase of refolding. The reassociation of subunits was examined by measuring the regain in catalytic activity and the enhancement in the fluorescence emission from NADH on binding to the oligomeric form of the enzyme. The rate and extent of reassociation is dependent on enzyme concentration and the extent of reactivation is dependent on the presence of the metal ion. The reassociation process was more efficient in the presence of NADH particularly for the metal-depleted enzyme (apo-GDH). The presence of GroEL or GroEL plus ATP leads to a higher yield of reassociation and therefore catalytically active enzyme. The additional presence of Mg-ATP does not affect the extent of reassociation, but has a small positive effect on the rate of reassociation. These data suggest that GDH is bound weakly to GroEL and that GroES is not required for release of the protein.     

In vivo formation of prostaglandin E1 and prostaglandin E2 in atopic dermatitis

The authors present the young man case who had undergone 6 months long antibiotic therapy first, than has been operated because of growing nose obstruction with bloody pus secretion. Diagnostic difficulties were responsible for diagnosis and undertaking treatment. Fulminant course of disease resulted in death of patient in the course of immunosupression therapy.