Hugoniot equation of state of rock materials under shock compression.

Two sets of shock compression tests (i.e. conventional and reverse impact) were conducted to determine the shock response of two rock materials using a plate impact facility. Embedded manganin stress gauges were used for the measurements of longitudinal stress and shock velocity. Photon Doppler velocimetry was used to capture the free surface velocity of the target. Experimental data were obtained on a fine-grained marble and a coarse-grained gabbro over a shock pressure range of approximately 1.5-12 GPa. Gabbro exhibited a linear Hugoniot equation of state (EOS) in the pressure-particle velocity (P-up) plane, while for marble a nonlinear response was observed. The EOS relations between shock velocity (US) and particle velocity (up) are linearly fitted as US = 2.62 + 3.319up and US = 5.4 85 + 1.038up for marble and gabbro, respectively.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

Signaling by glutamate dehydrogenase in response to pesticide treatment and nitrogen fertilization of peanut (Arachis hypogaea L.).

The responses of glutamate dehydrogenase (GDH) to NH(4)(+) and herbicides offer a new approach for probing the effects of NH(4)(+)-pesticide interactions at the whole-plant level. Although pesticides and fertilizers have greatly enhanced food production, their combined biochemical effects are not known in detail. Peanut plants were treated with different rates of Basagran (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), Bravo 720 (tetrachloroiso-phthalonitrile), and Sevin XLR Plus (1-naphthyl N-methylcarbamate), with and without 25 mM NH(4)Cl fertilization. Isoelectric focusing, followed by native 7.5% polyacrylamide gel electrophoresis (PAGE) fractionated the peanut seed GDH fully to its isoenzyme population patterns. The pesticide treatments induced positive skewing of the GDH isoenzymes, but NH(4)Cl-pesticide cotreatments induced a negatively skewed distribution. Basagran, Sevin, and Bravo increased the amination activities of GDH from 30.0 +/- 2.8 units in the control assay to 479.0 +/- 20.7, 63.0 +/- 5.8, and 35.2 +/- 2.2 units, respectively, therefore indicating a direct GDH-pesticide interaction. Neither the NH(4)(+) nor the pesticides increased the peanut seed protein yields above the threshold of 3.8 +/- 0.7 g per pot. But in the GDH combination of the signals from a pesticide and NH(4)(+), at least 70% of the pesticide signal was overridden by NH(4)(+) with concomitant increases in peanut seed protein yields to 7.0 +/- 1.8 g per pot. Basagran, Sevin, and Bravo possess different pesticidal properties, but their effects on GDH activity were related in the decreasing order of their nucleophilicity, viz. Basagran > Sevin > Bravo.

Pesticide inactivation of peanut glutamate dehydrogenase: biochemical basis of the enzyme's isomerization.

Glutamate dehydrogenase (GDH) isomerizes in response to pesticides and environmental chemicals, but the biochemical basis of the isomerization is not known. Clearer understanding of the isomerization would permit expansion of its utility in the diagnosis of the responses of plant tissues to challenged environments. Peanut plants were treated with different rates of Basagran (3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide), Bravo 720 (tetrachloroiso-phthalonitrile), and Sevin XLR Plus (1-naphthyl N-methylcarbamate). Free solution isoelectric focusing, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) fractionated the peanut seed GDH to its constituent subunits and degradation polypeptides. After western transfer to nitrocellulose membrane, the GDH subunits and degradation polypeptides were immunodetected with anti-GDH. The pesticide treatments did not induce increased proteolytic activity, but induced about 50% degradation of the GDH, whereas the GDH of the control peanut suffered only about 25% degradation, thus showing that the degradation rate was about double the rate of de novo synthesis in the pesticide treatments. The heavy displacement of the GDH subunit equilibrium toward degradation explains the biochemical basis of the isomerization reaction.

Colicin V38 and microcin C38 produced by Escherichia coli strain 38.

Escherichia coli strain 38, an isolate from turkeys, has been previously shown to produce one or more broad-spectrum bacteriocins against other related enteric bacteria. Using a collection of E. coli strains that synthesized well-characterized colicins or microcins, along with a set of colicin/microcin-insensitive mutants, we were able to classify the bacteriocins produced by strain 38. We determined that strain 38 produced a microcin (microcin C38) and a colicin (colicin V38) and that the amount of microcin C38 depended on the type of media on which it was grown. Escherichia coli strain 38 was found to have cross-immunity with the microcin C7-producing strain MC4100 and with the colicin V-producing strain 4674. OmpF mutant cells were found to be insensitive to microcin C38, whereas colicin V38 was not active on cells that had a cir mutation. Both microcin C38 and colicin V38 were inactivated by proteases. Microcin C38 was stable at extremes of pH (pH 1.5 and pH 13) and heat (10 min at 98 C) conditions, whereas colicin V38 was not. In addition, microcin C38 was found to be active against a broader spectrum of gram-negative bacteria than was colicin V38.

Favoured carbonyl binding regions around the QA and Q B sites of Rps. viridis.

The factors governing quinone protein binding in the photosynthetic bacterium Rps. viridis are investigated via use of empirical intermolecular energy calculations using the GRID method (PJ Goodford (1985) J Med Chem 28: 849-854). A probe atom corresponding to a carbonyl oxygen atom is used to investigate regions exhibiting preference for carbonyl binding in the QA and QB sites of Rps. viridis. Two distinct regions at the top and bottom of the sites are revealed to be most favourable for carbonyl binding. Overlay of the crystallographically determined positions for the quinone carbonyl groups shows that they lie within the regions predicted theoretically. The method is also shown to be able to give qualitative insight into the affect of amino acid mutations of quinone binding.

Characterization of detergent-soluble proteins of Corynebacterium pseudotuberculosis.

Whole cells and culture supernatant of isolates of Corynebacterium pseudotuberculosis were studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting (immunoblotting). SDS-PAGE analysis of detergent-solubilized whole cells revealed more than 20 bands in silver-stained gels. However, the SDS-soluble proteins that are present in all the isolates of the bacterium can be separated into four groups, as follows, (i) high molecular mass proteins that are greater than 119 kDa, (ii) a set of three proteins with molecular mass of 84, 64 and 58 kDa, (iii) a doublet consisting of proteins of molecular mass 33 to 30 kDa, and (iv) low molecular mass proteins of 25 to 20 kDa. SDS-PAGE analysis of ammonium sulphate concentrated culture supernatant demonstrated more than seven bands in silver-stained gels ranging in molecular mass from 64-14 kDa. Sera from goats with C. pseudotuberculosis-induced disease were used to probe immunoblots of electrophoresed SDS-soluble proteins. Ten or more SDS-soluble proteins from whole cells, ranging in molecular mass from 119-20 kDa were recognized by antibodies in sera of naturally infected goats. These sera also recognized up to five molecules ranging from 64-30 kDa, on immunoblots of ammonium sulfate concentrated culture supernatant.

Toxicological evaluation of aflatoxin and cyclopiazonic acid in broiler chickens.

The individual and combined effects of aflatoxin (AF) and cyclopiazonic acid (CPA) were evaluated in day-old Petersen x Hubbard broiler chickens to 3 wk of age. Treatments were arranged in a 2 x 2 factorial with levels of 0 and 3.5 mg AF/kg of feed, and 0 and 50 mg CPA/kg of feed. Production performance, serum biochemistry, and gross pathological observations were evaluated. Body weight gain was significantly (P less than .05) reduced by AF, CPA, and the AF-CPA combination at the end of 3 wk. Aflatoxin significantly increased the relative weight of the kidney and serum concentration of blood urea nitrogen and decreased serum concentrations of protein, albumin, cholesterol, phosphorus, and the activity of lactate dehydrogenase. The toxicity of CPA was expressed through increased relative weights of the liver, kidney, and proventriculus, increased levels of uric acid and cholesterol, and decreased serum phosphorus. The activity of AF-CPA combination was characterized by increased relative weight of the liver, kidney, pancreas, and proventriculus, decreased concentrations of serum albumin and phosphorus, increased concentrations of serum glutamic oxalacetic transaminase and blood urea nitrogen, and decreases in the relative weight of the bursa of Fabricius. Post-mortem examination revealed that the chickens fed CPA and the AF-CPA combination had thickened mucosa and dilated proventricular lumens, hard fibrotic spleen, and atrophy of the gizzard. The data from the present study demonstrate that both AF and CPA alone and the AF-CPA combination can limit broiler performance and adversely affect broiler health. In most cases the effects of AF and CPA were additive.

Comparison of pregnancy rates following in vitro fertilization-embryo transfer between the donors and the recipients in a donor oocyte program.

Our in vitro fertilization (IVF) program provides a unique opportunity to evaluate influences of hormonal milieu on pregnancy outcome, by using a shared pool of oocytes obtained by donors (in exchange for financial assistance). The study presented herein evaluated 38 retrieval cycles (28 oocyte donors/22 recipients). No difference in mean number of embryos transferred was seen (2.7 in the donors vs 2.8 in the recipients). However, a statistically significant difference was seen in the pregnancy rates per retrieval (10.5% donors vs 29% recipients) and per transfer (4/35, 11.1%, vs 11/34, 32.3%). Abortion rates were similar (25% donor, 27.2% recipients). These data suggest that other reports of higher pregnancy rates from donor oocyte programs may not be due exclusively to better-quality oocytes. Possibly a negative effect of hyperstimulation or adverse endometrial environment of the donor (possible chronic endometritis) may explain these data.

Urine mutagenicity as an indicator of exposure to dietary mutagens formed during cooking of foods.

Studies were undertaken with individuals fed fried bacon meals to determine whether fruit or vegetables, ingested along with bacon, modified uptake and subsequent excretion of bacon mutagen(s). Urinary mutagenic activity was significant in those who had consumed bacon or mixed bacon/vegetable or bacon/fruit meals within the previous 2 to 3 hr period. Although urine activity varied by a factor of 4 among 15 subjects who consumed different meals, there was no evidence from this investigation that fruit or vegetables contributed to the inherent variability in total urinary mutagenic activity. However, some differences in excretion kinetics may be attributable to vegetable or fruit supplements in mixed meals.