Prostaglandin H synthase: protein synthesis-independent regulation in bovine aortic endothelial cells

The objective ofthe present study was to examine whether prostaglandin H synthase(PGHS) can be regulated by pathways independent of de novo synthesis ofPGHS. Incubation of bovine aortic endothelial cells (BAEC) for as shortas 5 min with NaF (40 mM) resulted in a 60% increase in PGHS activity.PGHS activity induced by NaF was unaffected by either 10 µMcycloheximide or 1 µM actinomycin D. Aspirin (25 µM) completelyinhibited resting PGHS activity, and NaF did not induce furtherstimulation. NS-398 (500 nM), a specific PGHS-2 inhibitor, wasineffective. Basic fibroblast growth factor (bFGF) induced asignificant increase in PGHS activity within 30 min and was insensitiveto cycloheximide. The levels of PGHS-1 and PGHS-2 proteins, as measuredby Western blots, were not affected by NaF or bFGF. The tyrosine kinaseinhibitor genistein attenuated PGHS activity that was induced by NaFand bFGF, whereas the tyrosine phosphatase inhibitor, sodiumorthovanadate, augmented these responses. The G protein activators5'-guanylyl imidodiphosphate and guanosine5'-O-(3-thiotriphosphate) inhibited both resting andNaF-induced PGHS activities. These results suggest that, in BAEC,PGHS-1 activity can be regulated by tyrosine kinase and/or Gproteins, independently of de novo protein synthesis.

     

Lysophospholipase activity in rabbit skeletal muscle

Skeletal muscle contains appreciable lysophospholipase activity which is differentiated by muscle type with red muscle subcellular fractions having greater activity than the corresponding white ones.     

Stimulation of ATP synthesis in Halobacterium halobium R1 by light-induced or artifically created proton electrochemical potential gradients across the cell membrane.

The relationship between proton movement and phosphorylation in Halo-bacterium halobium R1 has been investigated under anaerobic conditions. The light-induced changes in the bacteriorhodopsin are accompanied by proton movements across the membrane which result in pH changes in the suspending medium. The initial alkaline shift is shown to be closely paralleled by (and hence correlated with) ATP synthesis. Acidification of the medium in the presence of valinomycin, under conditions of low external potassium, brings about ATP synthesis in the dark.     

A reproducible scoring system for quantification of histologic lesions of inflammatory disease in mouse gastric epithelium

Comparison of experimental groups by microscopic examination is a common and useful method for evaluating animal models of disease. Quantification of lesions is challenging, however, and differences in scoring systems hinder comparison of results from different laboratories. The purpose of this study was to validate a simple and reproducible scoring system for Helicobacter pylori-associated gastric disease in mice. The system is based on quantification of the percentage of microscopic fields in which lesions are present, rather than on subjective estimates of lesion severity. Linear regression analyses revealed good agreement between investigators in scoring of all 3 histologic criteria examined. The range of correlation coefficients between individual readers' scores and mean scores for the 3 histologic criteria examined were: neutrophilic inflammation, 0.845 to 0.935; gastritis sufficient to displace glands, 0.919 to 0.943; and epithelial metaplasia, 0.650 to 0.799. Comparison of scores in different experimental groups by analysis of variance and Fisher least significant difference tests revealed significant differences between infected and uninfected groups and between immunodeficient and immunocompetent groups. We propose that this system may be useful in standardizing the morphologic evaluation of rodent models of H. pylori and that a similar system could be devised for evaluation of other animal models of enteric disease.     

Demographic structure and pathogen dynamics on the network of livestock movements in Great Britain

Using a novel interpretation of dynamic networks, we analyse the network of livestock movements in Great Britain in order to determine the risk of a large epidemic of foot-and-mouth disease (FMD). This network is exceptionally well characterized, as there are legal requirements that the date, source, destination and number of animals be recorded and held on central databases. We identify a percolation threshold in the structure of the livestock network, indicating that, while there is little possibility of a national epidemic of FMD in winter when the catastrophic 2001 epidemic began, there remains a risk in late summer or early autumn. These predictions are corroborated by a non-parametric simulation in which the movements of livestock in 2003 and 2004 are replayed as they occurred. Despite the risk, we show that the network displays small-world properties which can be exploited to target surveillance and control and drastically reduce this risk.     

A Motif-Based Approach to Network Epidemics

Networks have become an indispensable tool in modelling infectious diseases, with the structure of epidemiologically relevant contacts known to affect both the dynamics of the infection process and the efficacy of intervention strategies. One of the key reasons for this is the presence of clustering in contact networks, which is typically analysed in terms of prevalence of triangles in the network. We present a more general approach, based on the prevalence of different four-motifs, in the context of ODE approximations to network dynamics. This is shown to outperform existing models for a range of small world networks.     

Rapid induction of distinct stress responses after the release of singlet oxygen in Arabidopsis

The conditional fluorescent (flu) mutant of Arabidopsis accumulates the photosensitizer protochlorophyllide in the dark. After a dark-to-light shift, the generation of singlet oxygen, a nonradical reactive oxygen species, starts within the first minute of illumination and was shown to be confined to plastids. Immediately after the shift, plants stopped growing and developed necrotic lesions. These early stress responses of the flu mutant do not seem to result merely from physicochemical damage. Peroxidation of chloroplast membrane lipids in these plants started rapidly and led to the transient and selective accumulation of a stereospecific and regiospecific isomer of hydroxyoctadecatrieonic acid, free (13S)-HOTE, that could be attributed almost exclusively to the enzymatic oxidation of linolenic acid. Within the first 15 min of reillumination, distinct sets of genes were activated that were different from those induced by superoxide/hydrogen peroxide. Collectively, these results demonstrate that singlet oxygen does not act primarily as a toxin but rather as a signal that activates several stress-response pathways. Its biological activity in Arabidopsis exhibits a high degree of specificity that seems to be derived from the chemical identity of this reactive oxygen species and/or the intracellular location at which it is generated.     

ADP-dependent phosphorylation regulates RNA-binding in vitro: implications in light-modulated translation.

Light-regulated translation of chloroplastic mRNAs in the green alga Chlamydomonas reinhardtii requires nuclear encoded factors that interact with the 5'-untranslated region (5'-UTR) of specific mRNAs to enhance their translation. We have previously identified and characterized a set of proteins that bind specifically to the 5'-UTR of the chloroplastic psbA mRNA. Accumulation of these proteins is similar in dark- and light-grown cells, whereas their binding activity is enhanced during growth in the light. We have identified a serine/threonine protein phosphotransferase, associated with the psbA mRNA-binding complex, that utilizes the beta-phosphate of ADP to phosphorylate and inactivate psbA mRNA-binding in vitro. The inactivation of mRNA-binding in vitro is initiated at high ADP levels, levels that are attained in vivo only in dark-grown chloroplasts. These data suggest that the translation of psbA mRNA is attenuated by phosphorylation of the mRNA-binding protein complex in response to a rise in the stromal concentration of ADP upon transfer of cells to dark.