PARATI – a dynamic model for radiological assessments in urban areas

The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide ¹³⁷Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated surfaces to these rates after dry or wet deposition are discussed. Received: 12 April 1996 / Accepted in revised form: 30 August 1996     

Ubiquinol prevents alpha-tocopherol consumption during liposome peroxidation

In this study we investigated whether alpha-tocopherol can be spared by ubiquinol-3 during autoxidation of multilamellar liposome. A lipophilic azocompound, 2,2'-azobis-(2,4-dimethyl-valeronitrile), was chosen to initiate liposome autoxidation. The effect of either alpha-tocopherol, ubiquinol-3, or a mixture of them was compared. Rates of conjugated diene formation and concomitant disappearance of the two antioxidants was measured. Since the inhibition rate constant for the scavenging of peroxyl radical for alpha-tocopherol was higher than that for quinol-3, it was concluded that alpha-tocopherol is regenerated by ubiquinol-3.     

Genetic structure of a wide-spectrum chicken gene pool

The genetic structure of 65 chicken populations was studied using 29 simple sequence repeat loci. Six main clusters which corresponded to geographical origins and histories were identified: Brown Egg Layers; predominantly Broilers; native Chinese breeds or breeds with recent Asian origin; predominantly breeds of European derivation; a small cluster containing populations with no common history and populations that had breeding history with White Leghorn. Another group of populations that shared their genome with several clusters was defined as 'Multi-clusters'. Gallus gallus gallus (Multi-clusters), one of the subspecies of the Red Jungle Fowl, which was previously suggested to be one of the ancestors of the domesticated chicken, has almost no shared loci with European and White Egg layer populations. In a further sub-clustering of the populations, discrimination between all the 65 populations was possible, and relationships between each were suggested. The genetic variation between populations was found to account for about 34% of the total genetic variation, 11% of the variation being between clusters and 23% being between populations within clusters. The suggested clusters may assist in future studies of genetic aspects of the chicken gene pool.     

Right lower lobe oedema as a rare sign of left heart failure

Two cases of right lower lobe oedema are presented as a supposedly very rare sign of left heart failure after myocardial infarction in the presence of acute mitral regurgitation. Causes of unilateral oedema and its clinical relevance in the diagnostic and therapeutic perspectives are discussed, and a review of the literature on this topic is presented.     

Conserved water-mediated H-bonding dynamics of catalytic Asn 175 in plant thiol protease

The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the 11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220 and W222 in the template 1PPN structure) were observed to form H-bonds with the O_b atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad.     

Association of folate molecules as determined by proton NMR: implications on enzyme binding

The self-association in aqueous solution of folic acid (FA), 7,8-dihydrofolic acid (DHFA) and 5,6,7,8-tetrahydrofolic acid (THFA) has been studied by the use of proton magnetic resonance (1H NMR) spectroscopy. At concentrations below 10 mM, all three folates exist in (monomer)2 in equilibrium dimer equilibria with association constants (Ka) equal to 400, 66 and 14 M-1 for FA, DHFA and THFA respectively. These values decreased markedly to 157, 18 and 3 M-1, for FA, DHFA and THFA respectively, in the presence of 0.8 M KCl. The high extent of dimerization of FA is believed to impede the interaction with the active site of dihydrofolate reductase (DHFR) rendering it a poor substrate. In contrast, the DHFA with a much lower Ka is a better substrate. Conditions that lower the Ka of both FA and DHFA, (i.e., 0.8M KCl) turn them into better substrates. Based on the findings of the present study, it is also predicted that dihydro MTX may be a better inhibitor of DHFR than MTX.     

Long-term memory modules

One particular kind of structure offers possible explanations, for long-term memory, efficient consolidation of stored information from the environment, clustering of data strings and multimodal functioning. It is a possible model for pieces of neural structure and its use offers a uniform method for both studying and constructing an extensive class of mechanisms.