Multi‐Stimuli Responsive Hydrogel Cilia

Large arrays of high aspect ratio, artificial hydrogel based cilia that can respond to multiple stimuli are produced by means of micro‐fabrication techniques. The cilia operate in aqueous solutions and are sensitive to pH, electric and/or magnetic fields. The biomimetic system combines both sensing and motility. Detection of changes in environment, such as a decrease in pH, triggers a collective response, to an external time‐dependent magnetic field.     

Chromosomal mutations induced by triplex-forming oligonucleotides in mammalian cells

Specific recognition of a region of duplex DNA by triplex-forming oligonucleotides (TFOs) provides an attractive strategy for genetic manipulation. Based on this, we have investigated the ability of the triplex-directed approach to induce mutations at a chromosomal locus in living cells. A mouse fibroblast cell line was constructed containing multiple chromosomal copies of the lambdasupFG1 vector carrying the supFG1 mutation-reporter gene. Cells were treated with specific (psoAG30) or control (psoSCR30) psoralen-conjugated TFOs in the presence and absence of UVA irradiation. The results demonstrated a 6- to 10-fold induction of supFG1 mutations in the psoAG30-treated cells as compared with psoSCR30-treated or untreated control cells. Interestingly, UVA irradiation had no effect onthe mutation frequencies induced by the psoralen-conjugated TFOs, suggesting a triplex-mediated but photoproduct-independent process of mutagenesis. Sequencing data were consistent with this finding since the expected T.A-->A.T transversions at the predicted psoralen crosslinking site were not detected. However, insertions and deletions were detected within the triplex binding site, indicating a TFO-specific induction of mutagenesis. This result demonstrates the ability of triplex-forming oligonucleotides to influence mutation frequencies at a specific site in a mammalian chromosome.     

In my opinion!

Briefly discusses articles appearing in this issue of the International Journal of Play Therapy. The first two articles are case studies on two specific interventions using play therapy. The final article by Bratton and Ray is a review of a number of studies of outcome research on play therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Instrumental response persistence following induction of hippocampal theta frequency during fixed-ratio responding in rats.

Four groups of 6 male albino rats (24 Ss) were used to investigate the relationship between hippocampal theta and instrumental response persistence. All Ss were first trained on a discrete-trial FR-10 schedule of reinforcement. In Phase 2, hippocampal theta was induced via electrical stimulation of medial septal pacemaker cells through implanted electrodes at the beginning of 50% of the 8 daily FR-10 trials for experimental Ss, while stimulated-control Ss received 200-Hz medial septal stimulation which does not induce theta. The 2 remaining control groups continued as in the training phase. In Phase 3, FR-10 responding was extinguished in all Ss. Induction of hippocampal theta depressed responding and led to greater resistance to extinction in the experimental group compared with the other groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Images of absolute retardance L.Δn, using the rotating polariser method

Modulation techniques for measuring changes in optical birefringence, such as the rotating-polariser method (Wood & Glazer, 1980, J. Appl. Crystallogr . 13, 217), allow one to determine |sin δ|, δ = 2π L Δ n /λ, Δ n = double refraction, L  = light path and λ = wavelength. However, they generally suffer from not providing absolute values of the optical retardance or are limited to relatively low retardance values. In addition, knowledge of the absolute phase is required when establishing the correct values of optical orientation information. In this paper, it is shown how the phase δ, and thus optical retardance, can be extracted from combining measurements of |sin δ| at different wavelengths. The new approach works on each single point of a 2-D picture without the need to correlate with neighbouring points. There is virtually no limit to the retardance, and the computational efforts are small compared with other methods (e.g. Ajovalasit et al. 1998, J. Strain Analysis 33 , 75). When used with imaging techniques, such as the rotating polariser method of Glazer, Lewis & Kaminsky 1996 ( Proc. R. Soc. London Series A452 , 2751) this process has the potential to identify automatically optically anisotropic substances under the microscope. The algorithm derived in this paper is valid not only for birefringence studies, but can be applied to all studies of interfering light waves.     

From the editor.

This issue of the Journal illustrates the growth in the research base supporting play therapy. The variety of methodologies and the rigor of the research are impressive. The multicultural nature of some of the articles speaks highly of our recognition that is essential to be inclusive in play therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive optics implementation with a Fourier reconstructor

Adaptive optics takes its servo feedback error cue from a wavefront sensor. The common Hartmann-Shack spot grid that represents the wavefront slopes is usually analyzed by finding the spot centroids. In a novel application, we used the Fourier decomposition of a spot pattern to find deviations from grid regularity. This decomposition was performed either in the Fourier domain or in the image domain, as a demodulation of the grid of spots. We analyzed the system, built a control loop for it, and tested it thoroughly. This allowed us to close the loop on wavefront errors caused by turbulence in the optical system.     

Developmental Exposure to Low Concentrations of Methylmercury Causes Increase in Anxiety-Related Behaviour and Locomotor Impairments in Zebrafish

Methylmercury (MeHg) is a ubiquitous pollutant shown to cause developmental neurotoxicity, even at low levels. However, there is still a large gap in our understanding of the mechanisms linking early-life exposure to life-long behavioural impairments. Our aim was to characterise the short- and long-term effects of developmental exposure to low doses of MeHg on anxiety-related behaviours in zebrafish, and to test the involvement of neurological pathways related to stress-response. Zebrafish embryos were exposed to sub-acute doses of MeHg (0, 5, 10, 15, 30 nM) throughout embryo-development, and tested for anxiety-related behaviours and locomotor activity at larval (light/dark locomotor activity) and adult (novel tank and tap assays) life-stages. Exposure to all doses of MeHg caused increased anxiety-related responses; heightened response to the transition from light to dark in larvae, and a stronger dive response in adults. In addition, impairment in locomotor activity was observed in the higher doses in both larvae and adults. Finally, the expressions of several neural stress-response genes from the HPI-axis and dopaminergic system were found to be disrupted in both life-stages. Our results provide important insights into dose-dependent differences in exposure outcomes, the development of delayed effects over the life-time of exposed individuals and the potential mechanisms underlying these effects.     

Properties of electrically responsive hydrogels as a potential dynamic tool for biomedical applications

Hydrogels with electric responsive properties are gaining research focus due to increasing demand for miniaturized devices that can be precisely controlled using an external stimulus. Such systems are well suited due to their ability to expand and contract when in contact with different types of fluid. This study reports on the synthesis of a “smart” electroresponsive network, using a neutral, “non‐smart,” biocompatible hydrogel forming building block, Pluronic F127 (PF127), as a starting molecule. The PEO–PPO–PEO copolymer was modified with telechelic methacrylic end functionalities to form a triblock linear prepolymer with crosslinkable end groups (crosslinker). This bifunctional prepolymer, PF127 bismethacrylate (PF127BMA), was copolymerized covalently with anionic methacrylic acid sodium salt groups into a nonsoluble 3D hydrogel network in the presence of redox initiators. The polyelectrolyte domains in the pluronic hydrogel afforded controllable swelling capabilities with volumetric expansion exceeding 8500% in deionized water or 1400% in Krebs solution. The hydrogels were further assessed for their mechanical and electroactive response as a function of increasing acid salt content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41195.