Invasion of hereditary ovalocytes by Plasmodium falciparum in vitro and its relation to intracellular ATP concentration

Hereditary ovalocytes (stomatocytic ovalocytes), when examined within 1-2 days from the time that the blood sample is drawn, are invaded by Plasmodium falciparum in culture to the extent of at least 55% of normal control cells. The ovalocytes have extremely rigid membranes, characterised by a shear elastic modulus some 3-4 times greater than that of normal cells. The extent of invasion falls off very much more rapidly than that into normal cells on storage, and we surmise that this is the reason for earlier reports of resistance of ovalocytes to malarial invasion in vitro. The initial loss of susceptibility to invasion with time is not accompanied by any change in membrane rigidity, but is primarily a consequence of a rapid decline in intracellular ATP concentration: this falls to below the threshold level required for invasion (approx. 0.1 mM) over a period in which the ATP in normal cells remains almost constant. Incubation in a metabolic regenerating medium leads to a rise in the intracellular ATP concentration and invasion by P. falciparum is recovered, though to a much lower extent than in normal cells. The resistance of ovalocytes to invasion becomes irreversible, due possibly to degradative processes in the membrane, on further storage. The developing parasites in ovalocytes have a reduced number of merozoites and show distinct morphological abnormalities.     

Melatonin-Based Therapeutics for Neuroprotection in Stroke

The present review paper supports the approach to deliver melatonin and to target melatonin receptors for neuroprotection in stroke. We discuss laboratory evidence demonstrating neuroprotective effects of exogenous melatonin treatment and transplantation of melatonin-secreting cells in stroke. In addition, we describe a novel mechanism of action underlying the therapeutic benefits of stem cell therapy in stroke, implicating the role of melatonin receptors. As we envision the clinical entry of melatonin-based therapeutics, we discuss translational experiments that warrant consideration to reveal an optimal melatonin treatment strategy that is safe and effective for human application.     

Image-guided endoscopic surgery: results of accuracy and performance in a multicenter clinical study using an electromagnetic tracking system

Image-guided surgery has recently been described in the literature as a useful technology for improved functional endoscopic sinus surgery localization. Image-guided surgery yields accurate knowledge of the surgical field boundaries, allowing safer and more thorough sinus surgery. We have previously reviewed our initial experience with The InstaTrak System. This article presents a multicenter clinical study (n=55) that assesses the system's capability for localizing structures in critical surgical sites. The purpose of this paper is to present quantitative data on accuracy and performance. We describe several new advances including an automated registration technique that eliminates the redundant computed tomography scan, compensation for head movement, and the ability to use interchangeable instruments.     

Proton Spin–Spin Relaxation Study of the Effect of Temperature on White Cement Hydration

The chemical and microstructural changes within a white cement paste were characterized in situ using proton nuclear magnetic resonance spin–spin relaxation at 30 MHz, and X-ray diffraction. Paste samples with a water-to-cement ratio of 0.42 were cured at constant temperatures of 2°, 20°, 60°, and 100°C. Proton nuclear magnetic resonance spin–spin relaxation allows tracking the evolution of the mixing water into the solid fractions of calcium silicate hydrate, calcium hydroxide, and monosulfate, and the liquid phases: the calcium silicate hydrate interlayer water, gel pore water, and capillary pore water. It is shown that the hydration process is markedly accelerated with increasing hydration temperature, and that proton nuclear magnetic resonance relaxation measurements can quantitatively determine the proportions of water phases, their magnetic resonance characteristics, as well as the setting times of the cement during the hydration process.     

CONSTRUCTION OF AN ANALYTICAL MODEL OF PAPER DRYING

A theoretical model developed is presented to simulate the paper drying process on a production paper machine. The paper sheet is represented as a matrix of pulpfibres which contains free and bound water, water vapour and air. The model is heavily dependent upon a wide range of physical data including pore size distribution, permeability sorptive characteristics, thermal conductivity, specific heat capacity, density, diffusion coefficients and shrinkage characteristics as well as heat and mass transfer behaviour at the interfaces. Theoretical relationships to describe these parameters in terms of the physical pore structure are developed and compared with published data. The model was compared against actual measurements on the Australian Newsprint Mills Boyer PM3 newsprint machine. The comparison with actual machine moisture content values showed the model prediction of moisture change during drying to cylinder No. 38 on PM3 to be 2% less than actual and 0.1% more than actual by the exit from the drying cylinder. In terms of predicting thermal energy consumption of the paper machine a 91% correlation was obtained.     

Extended time on academic assignments: Does increased time lead to improved performance for children with attention-deficit/hyperactivity disorder?

Researchers examined the impact of an extended time accommodation on appropriate classroom behavior and rate of work completion for 33 children with attention-deficit/hyperactivity disorder (ADHD). Participants received standard (30 min) or extended (45 min) time to complete seatwork in a within-subject, crossover design study. Appropriate behavior (i.e., rule-following behavior) and rate of problems completed accurately per minute were compared across conditions. Children completed significantly more problems correctly per minute when given standard time compared with extended time; however, no difference in appropriate behavior was found between the two conditions. Appropriate behavior over time was examined by segmenting each condition into time intervals. Analyses indicated that children's appropriate behavior significantly decreased over time in both conditions. The implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimizing the Hot Isostatic Pressing Process

A genetic algorithm (GA) is used to optimize the hot isostatic pressing (HIPing) process for beryllium powder. The GA evaluates a HIPing model with different processing schedules in an effort to minimize temperature, pressure, processing time, ramp rates, grain growth, and distance to target relative density. It is shown that this is a constrained, multiobjective, noisy, optimization problem to which the GA is able to evolve a large number of viable solutions. However, for the GA to work in such a large multidimensional search space, it is suggested that the constraints be treated as objectives and then penalize the Pareto ranking for each constraint violated. This approach is necessary because a large-dimensional objective space naturally results in most members being Pareto rank 1.     

Molecular analysis of the PDS gene in Pendred syndrome

Pendred syndrome is an autosomal recessive disorder characterized by the association between sensorineural hearing loss and thyroid swelling or goitre and is likely to be the most common form of syndromic deafness. Within the thyroid gland of affected individuals, iodide is incompletely organified with variable effects upon thyroid hormone biosynthesis, whilst the molecular basis of the hearing loss is unknown. The PDS gene has been identified by positional cloning of chromosome 7q31, within the Pendred syndrome critical linkage interval and encodes for a putative ion transporter called pendrin. We have investigated a cohort of 56 kindreds, all with features suggestive of a diagnosis of Pendred syndrome. Molecular analysis of the PDS gene identified 47 of the 60 (78%) mutant alleles in 31 families (includes three homozygous consanguineous kindreds and one extended family segregating three mutant alleles). Moreover, four recurrent mutations accounted for 35 (74%) of PDS disease chromosomes detected and haplotype analysis would favour common founders rather than mutational hotspots within the PDS gene. Whilst these findings demonstrate molecular heterogeneity for PDS mutations associated with Pendred syndrome, this study would support the use of molecular analysis of the PDS gene in the assessment of families with congenital hearing loss.