Generation of defective interfering particles of Semliki Forest virus in a clone of Aedes albopictus (mosquito) cells.

Serial undiluted passage of Semliki Forest virus in a clone of Aedes albopictus cells resulted in a marked decrease in infectious virus yields due to the generation and accumulation of defective interfering particles. Virus from the third passage had a high particle/infectivity ratio and interfered specifically with homologous but not heterologous standard virus replication. Two RNA species of molecular weights 0.78 X 10(6) and 0.61 X 10(6) were the major RNA components of purified passage 4 virus. These RNA species were also the predominant virus RNA species detected in cells infected with passage 3 virus. Synthesis of standard virus RNA and virus-specified protein was much reduced in passage 3 virus-infected cells. Interference with standard virus replication and the synthesis of large amounts of defective interfering RNA were also observed in chicken embryo cells infected with passage 3 virus from mosquito cells.     

Paraquat Poisoning—Lung Transplantation

A 15-year-old boy ingested a mouthful of paraquat and developed severe respiratory distress. Treatment included the transplantation of one lung, but subsequently changes developed in the graft which are thought to have been due to paraquat, and the patient died two weeks after the operationThe dangers of keeping poisonous substances in incorrectly labelled bottles has once again been demonstrated, while the pattern of paraquat poisoning, especially the development of proliferative alveolitis and terminal bronchiolitis, is confirmed.Immediate forced diuresis followed by haemodialysis is necessary to remove paraquat, thereby perhaps avoiding initiation of the changes in the lungs. The technical feasibility of human lung transplantation has again been demonstrated. It has also been shown that infection does not necessarily pose an insuperable problem, at any rate if, as in the case described, there was no preoperative pulmonary infection in either recipient or donor.     

Hydrolysis of dehydroepiandrosterone sulphate by human placental steroid 3β-sulphatase in [18O]water

1. Dehydroepiandrosterone sulphate was hydrolysed by human placental steroid 3beta-sulphatase in H(2) (18)O. Equimolar amounts of dehydroepiandrosterone and sodium sulphate were similarly incubated as controls. After incubation, unconjugated steroid was extracted with ether and sulphate precipitated as barium sulphate. Both were analysed for (18)O-content by mass spectroscopy, the sulphate as carbon dioxide after initial pyrolysis with graphite. 2. In duplicate experiments, amounts of (18)O equivalent to 67% and 72% respectively of the theoretical content calculated for rupture of the O-S bond were present in the sulphate. As the enzyme preparation used was a microsomal preparation containing unenriched endogenous sulphate and phosphate, and as no incorporation of isotope was found in the steroid, it is concluded that the placental enzyme effects hydrolysis by rupture of the O-S bond.     

The Extrusion of Sodium Ions from Presynaptic Nerve Endings of Rat Cerebral Cortex

(Na⁺-K⁺) ATPase is present in synaptosomal preparations and it is assumed to represent the sodium-potassium pump. 10 μm -noradrenaline activates (Na⁺-K⁺) ATPase approximately 100%, but 50 μm -noradrenaline does not stimulate the rate of ²²Na extrusion from synaptosomes. The results suggest that it is unlikely that the noradrenaline stimulation of (Na⁺-K⁺) ATPase is part of a feedback mechanism whereby released noradrenaline can influence the activity of the presynaptic sodium pump.     

Functional response,numerical response,and stability in arthropod predator-prey ecosystems involving age structure

Summary A general model of arthropod predator-prey systems incorporating age structure in the predator is employed to study the role of functional and numerical responses on stability and the paradox of enrichment. The destabilizing effect of age structure leads to both qualitatively and quantitatively new results for an environment which has an infinite prey carrying capacity, including a lower bound to prey density for a stable equilibrium, a feature not present in models without age structure. When applied to an environment with finite prey carrying capacity, the effect of age structure is to reinforce the arguments implicit to the paradox of enrichment originally developed for traditional models lacking age structure.     

Development and validation of an atlas-based finite element brain model

Traumatic brain injury is a leading cause of disability and injury-related death. To enhance our ability to prevent such injuries, brain response can be studied using validated finite element (FE) models. In the current study, a high-resolution, anatomically accurate FE model was developed from the International Consortium for Brain Mapping brain atlas. Due to wide variation in published brain material parameters, optimal brain properties were identified using a technique called Latin hypercube sampling, which optimized material properties against three experimental cadaver tests to achieve ideal biomechanics. Additionally, falx pretension and thickness were varied in a lateral impact variation. The atlas-based brain model (ABM) was subjected to the boundary conditions from three high-rate experimental cadaver tests with different material parameter combinations. Local displacements, determined experimentally using neutral density targets, were compared to displacements predicted by the ABM at the same locations. Error between the observed and predicted displacements was quantified using CORrelation and Analysis (CORA), an objective signal rating method that evaluates the correlation of two curves. An average CORA score was computed for each variation and maximized to identify the optimal combination of parameters. The strongest relationships between CORA and material parameters were observed for the shear parameters. Using properties obtained through the described multiobjective optimization, the ABM was validated in three impact configurations and shows good agreement with experimental data. The final model developed in this study consists of optimized brain material properties and was validated in three cadaver impacts against local brain displacement data.     

Cloning, overexpression, and characterization of peroxiredoxin and NADH peroxiredoxin reductase from Thermus aquaticus

The genes for peroxiredoxin (Prx) and NADH:peroxiredoxin oxidoreductase (PrxR) have been cloned from the thermophilic bacterium Thermus aquaticus. prx is located upstream from prxR, the two genes being separated by 13 bases. The amino acid sequences show that Prx is related to two-cysteine peroxiredoxins from a range of organisms and that PrxR resembles NADH-dependent flavoenzymes that catalyze the reduction of peroxiredoxins in mesophilic bacteria. The sequence of PrxR also resembles those of thioredoxin reductases (TrxR) from thermophiles but with an N-terminal extension of about 200 residues. PrxR has motifs for two redox-active disulfides, one in the FAD-binding site, as occurs in TrxR, and the other in the N-terminal extension. The molecular masses of the monomers of Prx and PrxR are 21.0 and 54.9 kDa, respectively; both enzymes exist as multimers. The recombinant flavoenzyme requires 3 mol equivalents of dithionite for full reduction, as is consistent with 1 FAD and 2 disulfides per monomer. PrxR and Prx together catalyze the anaerobic reduction of hydrogen peroxide. The activity of Prx is much less than has been observed with homologous proteins. Prx appears to be inactivated by cumene hydroperoxide. PrxR itself has low peroxidase activity.