Transmission electron microscopy and scanning force microscopy of poly r(A-U) and poly r(A-U)-ethidium bromide

Transmission electron microscopy and scanning force microscopy of negative-stained, carbon-coated replica and mica-adsorbed preparations of 200 μM poly r(A-U) and 50 μM ethidium bromide/200 μM poly r(A-U) have been employed to evaluate ethidium-induced changes in poly r(A-U) topology. Poly r(A-U) alone exhibits elongated conformations 85–115 nm in length that possess a number of hairpin loops as well as single-stranded domains. While the double-stranded domains are found predominately at the base of the hairpin loops (diameter = 5–30 nm), other rod-like (presumably double-stranded) regions ranging from 25–80 nm in length are present in other portions of the poly r(A-U). In contrast with the poly r(A-U) alone, the EB/poly r(A-U) combination appears as a heterogeneous population of condensed structures whose lengths and widths vary from 12–88 nm and 15–45 nm, respectively. These conformational changes are due to a number of factors, including the displacement of ordered water surrounding the poly r(A-U) and charge shielding of the phosphate groups of the poly r(A-U) upon the binding of the ethidium.     

The effect of intolerance of ambiguity upon product perceptions.

32 male undergraduates, with high and low scores on S. Budner's (see record 1964-08477-001) measure of intolerance of ambiguity, judged the newness of products varying systematically in atypicality and reported their willingness to buy them. The more intolerant Ss perceived the atypical products as newer than did tolerant Ss. Perceived product newness tended to be positively related to willingness to buy among tolerant Ss, but negatively related among intolerant ones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On Hilgard's "pain puzzle."

With regard to E. Hilgard's (see record 1969-09295-001) pain puzzle, a laboratory study attempted to mimic pain's clinical characteristics. The mean pain threshold of 9 Ss was lower when the experimenter had control than when the S had control of the pain source. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DNA and RNA polymerase/DNA complex imaged by scanning force microscopy: Influence of molecular-scale friction

Reproducible images of DNA and the interaction of RNA polymerase with supercoiled DNA on mica have been obtained by scanning force microscopy (SFM) in air. This technique allowed visualization of the assembly of distinct nucleoprotein complexes at specific sites which initiate DNA replication. Transmission electron microscopic controls were performed on the carbon-coated replica of the same specimens previously scanned by scanning force microscope. Image contrast formation has been investigated and lateral friction forces have been qualitatively characterized with SFM on DNA-covered samples.     

Electrodeless dielectrophoresis for micro total analysis systems

Several examples where a sample-to-answer, lab-on-a-chip chemical analysis system may benefit from EDEP technology in upstream sample preparation (cell sorting, cell lysing, DNA concentration, and purification) and in a back-end detection platform for hybridization and sensitivity enhancement were presented. The simplicity of the device and the lack of metallic electrodes at the trap, which cause electrochemical reactions involving gas evolution, made possible the investigation of the response of biological objects in a wide range of frequencies, especially the low-frequency regime. Above all, EDEP may be seamlessly integrated with the metallic DEP layout, this increasing the flexibility in custom-tailored chip design.     

Further suggestions on the improvement of the undergraduate psychology laboratory.

Comments that the use of classic experiments, as discussed by C. R. Regula (see record 1972-25869-001), leads to several counterproductive effects in the undergraduate psychology laboratory, including the tailoring of hypotheses to meet results. The author recommends using undergraduate lab experiments that have never been reported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Emerging Role of Decellularized Plant-Based Scaffolds as a New Biomaterial

The decellularization of plant-based biomaterials to generate tissue-engineered substitutes or in vitro cellular models has significantly increased in recent years. These vegetal tissues can be sourced from plant leaves and stems or fruits and vegetables, making them a low-cost, accessible, and sustainable resource from which to generate three-dimensional scaffolds. Each construct is distinct, representing a wide range of architectural and mechanical properties as well as innate vasculature networks. Based on the rapid rise in interest, this review aims to detail the current state of the art and presents the future challenges and perspectives of these unique biomaterials. First, we consider the different existing decellularization techniques, including chemical, detergent-free, enzymatic, and supercritical fluid approaches that are used to generate such scaffolds and examine how these protocols can be selected based on plant cellularity. We next examine strategies for cell seeding onto the plant-derived constructs and the importance of the different functionalization methods used to assist in cell adhesion and promote cell viability. Finally, we discuss how their structural features, such as inherent vasculature, porosity, morphology, and mechanical properties (i.e., stiffness, elasticity, etc.) position plant-based scaffolds as a unique biomaterial and drive their use for specific downstream applications. The main challenges in the field are presented throughout the discussion, and future directions are proposed to help improve the development and use of vegetal constructs in biomedical research.     

Thermal management of BioMEMS: temperature control for ceramic-based PCR and DNA detection devices

Integrated microfluidic devices for amplification and detection of biological samples that employ closed-loop temperature monitoring and control have been demonstrated within a multilayer low temperature co-fired ceramics (LTCC) platform. Devices designed within this platform demonstrate a high level of integration including integrated microfluidic channels, thick-film screen-printed Ag-Pd heaters, surface mounted temperature sensors, and air-gaps for thermal isolation. In addition, thermal-fluidic finite element models have been developed using CFDRC ACE+ software which allows for optimization of such parameters as heater input power, fluid flow rate, sensor placement, and air-gap size and placement. Two examples of devices that make use of these concepts are provided. The first is a continuous flow polymerase chain reaction (PCR) device that requires three thermally isolated zones of 94/spl deg/C, 65/spl deg/C, and 72/spl deg/C, and the second is an electronic DNA detection chip which requires hybridization at 35/spl deg/C. Both devices contain integrated heaters and surface mount silicon transistors which function as temperature sensors. Closed loop feedback control is provided by an external PI controller that monitors the temperature dependant I-V relationship of the sensor and adjusts heater power accordingly. Experimental data confirms that better than /spl plusmn/0.5/spl deg/C can be maintained for these devices irrespective of changing ambient conditions. In addition, good matching with model predictions has been achieved, thus providing a powerful design tool for thermal-fluidic microsystems.     

Lateralized presentation and hemispheric integration.

Argues that, in the intact brain, behavior is the result of the integrated functioning of both hemispheres, even if input is lateralized. The fact that left-hemisphere presentation results in faster or more efficient processing than right-hemisphere presentation will be interpreted differently depending on performance with central presentation. In a limited review of 34 articles involving lateralized presentation of visual material, only 9 included a central presentation condition as a control condition. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimization of a Microfluidic Mixing Process for Gene Expression-Based Bio-dosimetry

In recent decades advances in radiation imaging and radiation therapy have led to a dramatic increase in the number of people exposed to radiation. Consequently, there is a clear need for personalized biodosimetry diagnostics in order to monitor the dose of radiation received and adapt it to each patient depending on their sensitivity to radiation exposure (Hall E.J. and Brenner D. J., 2008). Similarly, after a large-scale radiological event such as a dirty bomb attack, there will be a major need to assess, within a few days the radiation doses received by tens of thousands of individuals. Current high throughput devices can handle only a few hundred individuals per day. Hence there is a great need for a very fast self-contained non-invasive biodosimetric device based on a rapid blood test.This paper presents a case study where regression methods and designed experiments are used to arrive at the optimal settings for various factors that impact the kinetics in a biodosimetric device. We use ridge regression to initially identify a set of potentially important variables in the mixing process which is one of the critical sub systems of the device. This was followed by a series of designed experiments to arrive at the optimal setting of the significant microfluidic cartridge and piezoelectric disk (PZT) (D. Sadler, F. Zenhausern, U.S. Patent 6,986,601; Lee, S. Y., Ko, B., Yang, W., 2005) related factors. This statistical approach has been utilized to study the microfluidic mixing to mix water and dye mixtures of 70 μl volume. The outcome of the statistical design, experimentation and analysis was then exploited for optimizing the design, fabrication and assembly of the microfluidic devices. As a result of the experiments that were performed, the system was fine tuned and the mixing time was reduced from 5.5 minutes to 2 minutes.