Steady-State Spatial Patterns in a Cell-Chemotaxis Model

We investigate a simple cell-chemotaxis model for the generationof spatial patterns in cell aggregations. For simple boundary-valueproblems, we analyse the local and global bifurcation of spatiallyheterogeneous patterns away from the uniform equilibria as thetotal number of cells is varied. We also discuss the existenceof periodic spatially structured solutions for the cells andchemoattractant in the infinite domain.     

ADH and ALDH genotype profiles in Caucasians with alcohol-related problems and controls

Eighty-two Caucasian patients receiving treatment for alcohol-related problems and eighty four controls were DNA typed for variants in the alcohol dehydrogenase (ADH₂ and ADH₃) and mitochondrial aldehyde dehydrogenase (ALDHJ gene loci. No association was observed between individual, or combined gene frequencies and the presence of alcohol-related problems.     

Corrosion of Pacemaker Electrodes

As improvements in pacemaker components and design increase pacemaker life, problems with other components may emerge such as corrosion of the electrodes. Explanted electrodes were examined under a scanning electron microscope and the degree of corrosion was graded and correlated with the reasons for expiantation, the status of the explanted pacemaker, and the duration of the implant. Fifty-six explanted electrodes were removed for loss of capture or sensing, pacemaker extrusion, broken wires, or after death. A numerical grading system was used to qualitate the degree of corrosion. The pacemaker itself was retrieved in 50 cases, permitting evaluation of the entire pacing system. The dc component of the pacemaker output was measured. Without She aid of magnification most electrodes appeared shiny and smooth. With one exception all corrosion was microscopic. Significant corrosion was seen on all pacemaker electrodes that had been connected to pacemakers with dc offset currents greater than 5 microamperes. All except the "youngest" explanted electrode showed some degree of corrosion. The data suggest that corrosion was directly related to the duration of implantation. With the possible exception of one case, no consistent adverse clinical effects were observed, even when electrodes were heavily corroded. Whether or not corrosion eventually will progress to the point that clinical problems become manifest cannot be predicted at this time.     

An Investigation into the Value of Cholinesterase Estimations of Workers in a Plant Manufacturing Tri-aryl Phosphate Plasticizers

An investigation was carried out in a chemical plant to determinethe value of cholinesterase estimations in those working withtri-aryl phosphates. A series of 124 personnel was subjectedto blood examinations and a statistical analysis was carriedout. The investigation demonstrated that plasma cholinesteraseestimations in workers exposed to tri-aryl phosphate compoundscannot be used as a sensitive barometer of organic phosphateabsorption, so that routine regular estimations serve no usefulpurpose. Its value is chiefly as a screening method at the pre-employmentmedical examination to exclude personnel at risk and to serveas a baseline in the event of massive exposure, or in the elucidationof the diagnosis if disease of the central nervous system develops,which may simulate tri-aryl phosphate poisoning. Safety guidelinesare recommended, as adopted on this plant. Requests for reprints should be addressed to: Dr A. A. Morgan, 37 Holcombe Road, Ilford, Essex IG1 4XF.     

The effects of bromocriptine on pre-synaptic and post-synaptic α-adrenoceptors in the mouse vas deferens

Noradrenaline (NA) and dopamine (DA) contracted the mouse vas deferens and reduced the responses to low frequency nerve stimulation (0·1 Hz). The relative potencies of antagonists suggested that these effects were due to stimulation of post-synaptic and pre-synaptic α-adrenoceptors respectively. Bromocriptine produced a non-competitive antagonism of contractile responses to NA (pD 2 ′ = 7·6) and DA (pD 2 ′ = 8·0) but had no effect on responses to carbachol. Bromocriptine also reduced single twitch responses of the vas to low frequency field stimulation (0·1 Hz), but did not affect stimulation at higher frequencies (1·20Hz). Yohimbine selectively and rapidly reversed the inhibiting effects of bromocriptine on single twitches, although they could not easily be reversed by washing. Bromocriptine produced a yohimbine-reversible reduction in the stimulated overflow of tritium from vasa previously loaded with ³H-NA. Thus the mouse vas deferens does not appear to contain specific DA receptors and the results suggest that bromocriptine acts as a pre-synaptic α-adrenoceptor agonist and post-synaptic α-adrenoceptor antagonist in this tissue.     

THE PREFERRED CONFORMATIONS OF PROTECTED HOMODI-TO HOMOHEPTAMETHIONINE PEPTIDES A 1H N.M.R. Study in Deuterochloroform Medium

Detailed analyses of the conformations of the homo-oligopeptide series, Boc-(L-Met)_n-OMe n = 2–7, in deuterochloroform have been carried out with proton n.m.r. and IR spectroscopy. Well-resolved high field n.m.r. spectra with assignments for the NH and α-CH resonances of these homo-methionine peptides are presented. Extensive n.m.r. concentration-dependent chemical shift studies are combined with IR results to delineate the involvement of the various methionine NH protons in intra- and/or intermolecular hydrogen bonding. N.m.r. chemical shift dependencies with temperature and solvent, DMSO-d₆, are used to explore the strength of the hydrogen bonds for the various oligopeptides. At low concentrations, where peptide aggregation is absent, the dipeptide is found to be disordered. The tetra- to heptapeptides possess intramolecular hydrogen bonded seven-membered rings at internal residues. The number of internal rings and the oligopeptide self-association increase with increasing peptide chainlength. At intermediate concentrations associations of peptide molecules with folded structures occur with initial association at the C-terminal region. At high concentrations, “in-register” associated extended β structures are formed.     

HYPERPYREXIA OF UNCERTAIN ORIGIN

Hyperpyrexia occurring in a 27-year-old woman undergoing eyesurgery is described. The cause, although open to doubt, appearedto be a thyroid storm.