Indirect Measurement of Intracellular Conductivity

The apparent resistance of a fluid-filled micropipette depends upon the conductivity of the fluid in which its tip-is immersed. When the electrode is involved in the determination of the impedance of cell membranes, then the intracellular conductivity must be known. Techniques used in large cells require extrusion of intracellular fluid or the simultaneous insertion of two or more electrodes in a single cell, and are not feasible for small cardiac cells. We present an indirect method in which. two unlike electrodes are inserted individually into distinct cells of a given type. The difference in measured resistances is independent of the membrane impedance, and can be calibrated by immersion in a sequence of fluids of known conductivities.     

Young children's knowledge about the apparent-real and pretend-real distinctions.

Three experimental tests were made of the hypothesis that understanding of the pretend–real distinction develops earlier than understanding of the theoretically related apparent–real distinction. As predicted, 3-yr-old children consistently performed better on pretend–real tasks than on apparent–real tasks, even when the two tasks were identical except for the distinction tested. Speculations were made about why understanding of the two distinctions might develop in that particular sequence and about how they might be related developmentally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"I keep that hush-hush": Male survivors of sexual abuse and the challenges of disclosure.

Disclosure is a prominent variable in child sexual abuse research, but little research has examined male disclosure experiences. Sixteen male survivors of childhood sexual abuse were interviewed regarding experiences of disclosure. Analytic techniques included a grounded theory approach to coding and the use of conceptually clustered matrices. Participants described distinct personal (e.g., lack of cognitive awareness, intentional avoidance, emotional readiness, and shame), relational (e.g., fears about negative repercussions, isolation), and sociocultural (e.g., lack of acceptance for men to experience or acknowledge victimization) reasons for their struggles with disclosure. These results highlight that barriers to disclosure exist in multiple domains of experience and are encountered across the lifespan. Implications for future research and clinical interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Manufacture of a mechanical test rig to simulate the movements of forces within the shoulder

The shoulder complex, also known as the glenohumeral joint is the most manoeuvrable and one of the most well used joints of the human body. Over time problems can occur with the glenohumeral joint and surrounding muscles, cartilage, tendons and ligaments caused by ageing or by over stressing the shoulder complex. This work examines the design of a new innovative glenohumeral test rig. The test rig was required to imitate the movement of the humerus in the human body and replicate all the ranges of motion, which it can move in when combined with the relevant bones, muscles, ligaments and tendons in the shoulder complex. A variable force also had to be applied to the glenoid in all ranges of motion. Research had to be undertaken in the ranges of motion of the shoulder complex and the forces acting on the glenoid. Concept designs were initially created to mimic specific ranges of motion; adduction, flexion, internal (medial) and external (lateral) rotation for example. The concepts were evolved and combined to develop a test rig that would replicate any axial movement of the shoulder. Research determined the most appropriate manufacturing processes and materials so that the test rig could be manufactured in the material laboratories.     

Multiplexed magnetic microsphere immunoassays for detection of pathogens in foods

Foodstuffs have traditionally been challenging matrices for conducting immunoassays. Proteins, carbohydrates, and other macromolecules present in food matrices may interfere with both immunoassays and PCR-based tests, and removal of particulate matter may also prove challenging prior to analyses. This has been found true when testing for bacterial contamination of foods using the standard polystyrene microspheres utilized with Luminex flow cytometers. Luminex MagPlex microspheres are encoded with the same dyes as standard xMAP microspheres, but have superparamagnetic properties to aid in preparation of samples in complex matrices. In this work, we present results demonstrating use of MagPlex for sample preparation and identification of bacteria and a toxin spiked into a variety of food samples. Fluorescence-coded MagPlex microsphere sets coated with antibodies for Salmonella, Campylobacter, Escherichia coli, Listeria, and staphylococcal enterotoxin B (SEB) were used to capture these bacteria and toxin from spiked foodstuffs and then evaluated by the Luminex system in a multiplex format; spiked foods included apple juice, green pepper, tomato, ground beef, alfalfa sprouts, milk, lettuce, spinach, and chicken washes. Although MagPlex microspheres facilitated recovery of the microspheres and targets from the complex matrices, assay sensitivity was sometimes inhibited by up to one to three orders of magnitude; for example the detection limits E. coli spiked into apple juice or milk increased 100-fold, from 1000 to 100,000 cfu/mL. Thus, while the magnetic and fluorescent properties of the Luminex MagPlex microspheres allow for rapid, multiplexed testing for bacterial contamination in typically problematic food matrices, our data demonstrate that achieving desired limits of detection is still a challenge.     

Human endothelial cell a

Composite materials comprised of the electrically conducting polymer, polypyrrole, with a variety of biologically active molecules, e.g. proteins or polysaccharides, are emerging as a novel class of smart biomaterials. In the present work we have studied the utility of a heparin–polypyrrole composite as a substrate for human umbilical vein endothelial cell (HUVEC) growth. We found that the polymer composites were well suited to support cell attachment and growth; displaying low surface hydrophobicity (water contact angle of approximately 20°) and roughness, Rq of approximately 10–12 nm. Doubling times for HUVEC on heparin–polypyrrole were greater than observed for gelatin-coated tissue culture polystyrene (44 and 36 h, respectively), however, the cells did proliferate to cover the polymer in an even monolayer. The initial mechanism of attachment and subsequent proliferation of HUVEC on heparin–polypyrrole was critically dependent on the presence of the serum adhesion glycoprotein vitronectin. Polymers that were composed of polypyrrole and sodium nitrate were more hydrophobic than heparin–polypyrrole and they did not support HUVEC growth. Given the relative ease with which these polymer composites can be electrochemically synthesized, the diverse range of cellular signal agents, e.g. growth factors, that can be incorporated within them, and the high degree of control that can be achieved in the release–surface exposure of these agents, we suggest that polypyrrole composites could serve a useful role as smart biomaterials in the near future. © 1999 Kluwer Academic Publishers     

Volatile organic compound concentrations and emission rates in new manufactured and site-built houses

Concentrations of 54 volatile organic compounds (VOCs) and ventilation rates were measured in four new manufactured houses over 2-9.5 months following installation and in seven new site-built houses 1-2 months after completion. The houses were in four projects located in hot-humid and mixed-humid climates. They were finished and operational, but unoccupied. Ventilation rates ranged from 0.14-0.78 h-1. Several of the site-built houses had ventilation rates below the ASHRAE recommended value. In both manufactured and site-built houses, the predominant airborne compounds were alpha-pinene, formaldehyde, hexanal, and acetic acid. Formaldehyde concentrations were below or near 50 ppb with a geometric mean value for all houses of 40 ppb. Similarities in the types of VOCs and in VOC concentrations indicated that indoor air quality in the houses was impacted by the same or similar sources. Major identified sources included plywood flooring, latex paint and sheet vinyl flooring. One site-built house was operated at ventilation rates of 0.14 and 0.32 h-1. VOC emission rates calculated at the two conditions agreed within +/- 10% for the most volatile compounds. Generally, the ratios of emission rates at the low and high ventilation rates decreased with decreasing compound volatility. Changes in VOC emission rates in the manufactured houses over 2-9.5 months after installation varied by compound. Only several compounds showed a consistent decrease in emission rate over this period.     

A simple method for assessing that internal doses are below action levels

The accidental or deliberate dispersal of radioactive aerosols into the public environment may require urgent assessments of radiation dose to be made to aid decisions on whether treatment should be implemented, or to reassure the public that doses are acceptably low. However, rapid assessments will be difficult due to lack of information on factors such as the particle size distribution and biokinetic characteristics of the aerosol. A procedure is described that relates the amount of activity of a radionuclide in the body and excreta to time after intake for a specified dose, taking into account the likely variations in aerosol size and differences in the biokinetic behaviour of the same or different chemical forms of the radionuclide. The implementation of the procedure for an intake of caesium-137 and a dose level of 1 mSv is described and the information presented graphically. Figures for other specified dose levels can be produced by simply scaling the data by an appropriate factor. The figures can also be used to assess the most appropriate monitoring procedure and indicate the uncertainty in the assessed dose according to the parameter and parameter values used. This approach is proposed for rapid decisions on public reassurance when potentially large numbers of people are involved. It is not intended as a substitute for individual dose assessment.