Variation in clinical disease and species susceptibility to psittacine beak and feather disease in Zimbabwean lovebirds

While psittacine beak and feather disease has caused 100% mortality in captive flocks of 2 species of native Zimbabwean lovebirds (Agapornis nigrigensis and A. lilianae), other lovebird species in close contact with the sick birds have been only transiently affected or not at all. The clinical course of the disease in affected lovebirds may differ from that reported elsewhere, with recovery in some cases. These differences, along with ultrastructural differences may suggest a different virus or different strain of virus underlying disease in Zimbabwe.     

Ferroxidase kinetics of human liver apoferritin, recombinant H-chain apoferritin, and site-directed mutants

A detailed study of the kinetics of iron(II) oxidation by molecular oxygen in natural and recombinant human apoferritins has been carried out using electrode oximetry to better understand the ferroxidase activity of the protein shell. A comparative study of recombinant L-chain ferritin (rLF), recombinant H-chain ferritin (rHF), and variants has shown that (1) rLF lacks a ferroxidase activity, confirming the results of previous studies; (2) the ferroxidase site of rHF involves Glu-62 and His-65, presumably as Fe2+ ligands, since mutation of these residues abolishes most of the oxidase activity, in agreement with previous studies; and (3) mutation of both the putative ferroxidase and nucleation site ligands in rHF renders the protein totally incapable of catalyzing the oxidation of Fe2+ whereas mutation of nucleation site ligands alone (Glu-61, Glu-64, and Glu-67) decreases the activity only slightly. Analysis of the kinetics of rHF and natural human liver ferritin (HLF) (4% H-chain, 96% L-chain) gave the following apparent parameters at pH 7: Km,O2 = 6 +/- 2 microM, Km,Fe = 80 +/- 10 microM, and kcat = 201 +/- 14 min-1 for rHF and Km,O2 = 60 +/- 12 microM, Km,Fe = 50 +/- 10 microM, and kcat = 31.2 +/- 0.6 min-1 for HLF. Furthermore, Zn2+ was shown to be a noncompetitive inhibitor of Fe2+ oxidation in rHF but a mixed inhibitor in HLF. These different forms of Zn2+ inhibition in the two proteins and the higher activity of HLF than expected, based on its H-chain composition as well as differences in their enzyme kinetic parameters, suggest that H- and L-chains cooperate in modulating the ferroxidase activity of the apoferritin even though the L-subunit lacks a ferroxidase site itself.     

Value‐added use of mushroom ergothioneine as a colour stabilizer in processed fish meats

BACKGROUND: Ergothioneine (ESH), a potent antioxidant, has been found in certain edible mushrooms. Our previous research showed that ESH extracted from the edible mushroom Flammulina velutipes has a positive effect on the colour stability of beef and tuna meat. The purpose of the present study was to compare the efficacy and applicability of ESH extracts prepared from different mushroom species as a colour stabilizer in fish meats. RESULTS: Levels of ESH higher than 2.8 mg mL^?1 were found in extracts prepared from the fruiting bodies of F. velutipes, Lentinula edodes, Pleurotus cornucopiae and Pleurotus eryngii and the processing waste of F. velutipes. When 1 mL of each of the extracts was added to 100 g of minced bigeye tuna and yellowtail meats, the bright‐red colour remained after 5 and 2 days, respectively, of ice storage. The anti‐discoloration efficacy of 1 mL of the extracts prepared from 10 g of the fresh waste portion of F. velutipes was similar to that of its fruiting body or 0.5 g kg^?1 of sodium ascorbate when added to 100 g of minced bigeye tuna meat under ice storage. CONCLUSION: The results of this study clearly showed that ESH prepared from different mushroom species stabilized the colour of fish meats, and the extract from the F. velutipes was the most effective. Copyright © 2010 Society of Chemical Industry     

A single side chain prevents Escherichia coli DNA polymerase I (Klenow fragment) from incorporating ribonucleotides

Although nucleic acid polymerases from different families show striking similarities in structure, they maintain stringent specificity for the sugar structure of the incoming nucleoside triphosphate. The Klenow fragment of E. coli DNA polymerase I selects its natural substrates, deoxynucleotides, over ribonucleotides by several thousand fold. Analysis of mutant Klenow fragment derivatives indicates that discrimination is provided by the Glu-710 side chain which sterically blocks the 2'-OH of an incoming rNTP. A nearby aromatic side chain, at position 762, plays an important role in constraining the nucleotide so that the Glu-710 "steric gate" can be fully effective. Even with the E710A mutation, which is extremely permissive for addition of a single ribonucleotide to a DNA primer, Klenow fragment does not efficiently synthesize pure RNA, indicating that additional barriers prevent the incorporation of successive ribonucleotides.     

Activation of p38 mitogen-activated protein kinase by lipopolysaccharide in human neutrophils requires nitric oxide-dependent cGMP accumulation

This study examined the signal transduction pathway(s) leading to phosphorylation of p38 in human neutrophils stimulated with lipopolysaccharide and formyl peptides. Blockade of the nitric oxide (NO) pathway in neutrophils with the NO synthase inhibitor N-nitro-L-arginine methyl ester or by treatment with the NO scavenger 2-phenyl-tetramethylimidazoline-1-oxyl-3-oxide attenuated phosphorylation of the mitogen-activated protein kinase p38 in response to lipopolysaccharide but not fMet-Leu-Phe. Using the NO releasing agents S-nitroso-N-acetylpenicillamine and sodium nitroprusside it was determined that nitric oxide is sufficient to cause an increase in phosphorylation of p38. Increasing cellular cGMP with phosphodiesterase inhibitors, by stimulation of soluble guanylyl cyclase with YC-1 or with exogenous dibutyryl cGMP resulted in mitogen-activated protein kinase/extracellular signal-regulated kinase kinase 3,6 (MEK3,6) activation and phosphorylation of p38. This phenomenon was specific for MEK3,6, because these agents had no effect on the phosphorylation state of MEK1,2. A role for protein kinase G but not protein kinase A downstream of lipopolysaccharide but not formylmethionylleucylphenylalanine was shown using the specific inhibitors KT5823 and H89, respectively. These data indicate that activation of p38 by fMet-Leu-Phe and lipopolysaccharide involve different mechanisms, and that activation of protein kinase G by NO-dependent stimulation of guanylyl cyclase is necessary and sufficient for phosphorylation of p38 downstream of lipopolysaccharide.     

Post-traumatic seizures: a critical review

Post-traumatic seizures are a well-recognized complication of head injury; however, the issue of seizure risk assessment remains controversial. The authors present a critical review of the literature pertaining to post-traumatic seizures, with particular emphasis on current concepts of definitions, incidence and risk factors. Different methods of risk assessment are reviewed and the possibility of utilizing functional imaging techniques for seizure risk assessment is also explored.     

Cloning and characterization of ERG25, the Saccharomyces cerevisiae gene encoding C-4 sterol methyl oxidase

We have cloned the Saccharomyces cerevisiae C-4 sterol methyl oxidase ERG25 gene. The sterol methyl oxidase performs the first of three enzymic steps required to remove the two C-4 methyl groups leading to cholesterol (animal), ergosterol (fungal), and stigmasterol (plant) biosynthesis. An ergosterol auxotroph, erg25, which fails to demethylate and concomitantly accumulates 4,4-dimethylzy-mosterol, was isolated after mutagenesis. A complementing clone consisting of a 1.35-kb Dra I fragment encoded a 309-amino acid polypeptide (calculated molecular mass, 36.48 kDa). The amino acid sequence shows a C-terminal endoplasmic reticulum retrieval signal KKXX and three histidine-rich clusters found in eukaryotic membrane desaturases and in a bacterial alkane hydroxylase and xylene monooxygenase. The sterol profile of an ERG25 disruptant was consistent with the erg25 allele obtained by mutagenesis.     

Use of tilmicosin in a severe outbreak of respiratory disease in weaned beef calves

In a liability lawsuit an expertise had to answer the question whether a mania in the course of an affective psychosis could have been caused by chronic mercury intoxication resulting from dental amalgam fillings. On the basis of current psychiatric and toxicological knowledge, such an association can be disproved. Mercury intake from amalgam fillings does not lead to toxic concentrations in organs or body fluids. Therefore physicians and dentists should avoid alarming patients and thus causing iatrogenic harm.     

Diffuse neuroendocrine system: structural and functional effects of radiation injury to amine precursor uptake and decarboxylation (APUD) cells

The paper presents a review of the results obtained by the authors on the study of external (gamma) and internal (I-131) radiation effects on the functional morphology and linkage of the diffuse neuroendocrine system (DNES) and amine precursor uptake and decarboxylation (APUD) cells of the stomach and duodenum. The investigations performed enabled us to determine that the morphological changes noted in APUD cells had a dose and time dependency. The present study supports the point of view that the radiation initiates serotonin release from APUD cells, which appears to initiate the mechanism of early postirradiation dysfunctions of the gastrointestinal tract and the subsequent adaptive response of DNES. Analysis of our results, together with a review of the literature, indicates that APUD cells actively participate both in pathogenesis of radiation injury and development of organ and tissue radiosensitivity.     

Spurious associations in unreplicated selected lines

INTRODUCTION: Shocks during the vulnerable period of the cardiac cycle induce ventricular fibrillation (VF) if their strength is above the VF threshold (VFT) and less than the upper limit of vulnerability (ULV). However, the range of shock strengths that constitutes the vulnerable zone and the corresponding range of coupling intervals have not been defined in humans. The ULV has been proposed as a measure of defibrillation because it correlates with the defibrillation threshold (DFT), but the optimal coupling interval for identifying it is unknown. METHODS AND RESULTS: We studied 14 patients at implants of transvenous cardioverter defibrillators. The DFT was defined as the weakest shock that defibrillated after 10 seconds of VF. The ULV was defined as the weakest shock that did not induce VF when given at 0, 20, and 40 msec before the peak of the T wave or 20 msec after the peak in ventricular paced rhythm at a cycle length of 500 msec. The VFT was defined as the weakest shock that induced VF at any of the same four intervals. To identify the upper and lower boundaries of the vulnerable zone, we determined the shock strengths required to induce VF at all four intervals for weak shocks near the VFT and strong shocks near the ULV. The VFT was 72 +/- 42 V, and the ULV was 411 +/- V. In all patients, a shock strength of 200 V exceeded the VFT and was less than the ULV. The coupling interval at the ULV was 19+/- 11 msec shorter than the coupling interval at the VFT (P < 0.001). The vulnerable zone showed a sharp peak at the ULV and a less distinct nadir at the VFT. A 20-msec error in the interval at which the ULV was measured could have resulted in underestimating it by a maximum of 95 +/- 31 V. The weakest shock that did not induce VF was greater for the shortest interval tested than for the longest interval at both the upper boundary (356 +/- 108 V vs 280 +/- 78 V; P < 0.01) and lower boundary (136 +/- 68 msec vs 100 +/- 65 msec; P < 0.05). CONCLUSIONS: The human vulnerable zone is not symmetric with respect to a single coupling interval, but slants from the upper left to lower right. Small differences in the coupling interval at which the ULV is determined or use of the coupling interval at the VFT to determine the ULV may result in significant variations in its measured value. An efficient strategy for inducing VF would begin by delivering a 200-V shock at a coupling interval 10 msec before the peak of the T wave.