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Background Purpose Methods Results Conclusions In ovo MR presents a promising and viable alternative to traditional in vivo small animal experiments. Sodium MRI complements proton MRI by providing potential access to tissue cellular metabolism. Despite its abundance, sodium MRI is challenged by lower MR sensitivity and faster relaxation times compared to proton MRI. Ensuring a high signal‐to‐noise ratio and effective B0 shimming is essential. Double‐tuned coils combining 23Na and 1H are frequently employed to achieve structural imaging and efficient shim adjustment.This study introduces a novel, highly optimized, double‐tuned coil design, specifically for MR scans of chick embryos.A tapered‐spiral, double‐tuned coil was designed and constructed following careful consideration of design parameters. The performance of the coil was rigorously assessed through bench tests, and final validation was conducted on a 7 T MRI scanner using a chick embryo.Bench tests demonstrated that the return losses for both 1H and 23Na coils were better than − 30 dB, and isolation factors were better than − 21 dB, indicating that the double‐tuned coil was well‐set, with negligible coupling between channels. MR images of chick embryos, obtained using the coil, validated the feasibility of utilizing the design concept for in ovo applications.The innovative design of the proposed double‐tuned coil, characterized by its unique arrangement, offers improved performance. This design has the potential to significantly enhance the quality of in ovo 1H and 23Na measurements. [ABSTRACT FROM AUTHOR]

Phosphorylation of the actin-related protein 2 (Arp2) subunit of the Arp2/3 complex on evolutionarily conserved threonine and tyrosine residues was recently identified and shown to be necessary for nucleating activity of the Arp2/3 complex and membrane protrusion of Drosophila cells. Here we use the Dictyostelium diploid system to replace the essential Arp2 protein with mutants that cannot be phosphorylated at Thr-235/6 and Tyr-200. We found that aggregation of the resulting mutant cells after starvation was substantially slowed with delayed early developmental gene expression and that chemotaxis toward a cAMP gradient was defective with loss of polarity and attenuated F-actin assembly. Chemotaxis toward cAMP was also diminished with reduced cell speed and directionality and shorter pseudopod lifetime when Arp2 phosphorylation mutant cells were allowed to develop longer to a responsive state similar to that of wild-type cells. However, clathrin-mediated endocytosis and chemotaxis under agar to folate in vegetative cells were only subtly affected in Arp2 phosphorylation mutants. Thus, phosphorylation of threonine and tyrosine is important for a subset of the functions of the Arp2/3 complex, in particular an unexpected major role in regulating development.

Increased intracellular pH is an evolutionarily conserved signal necessary for directed cell migration. We reported previously that in Dictyostelium cells lacking H(+) efflux by a Na(+)-H(+) exchanger (NHE; Ddnhe1(-)), chemotaxis is impaired and the assembly of filamentous actin (F-actin) is attenuated. We now describe a modifier screen that reveals the C-terminal fragment of actin-interacting protein 1 (Aip1) enhances the chemotaxis defect of Ddnhe1(-) cells but has no effect in wild-type Ax2 cells. However, expression of full-length Aip1 mostly suppresses chemotaxis defects of Ddnhe1(-) cells and restores F-actin assembly. Aip1 functions to promote cofilin-dependent actin remodeling, and we found that although full-length Aip1 binds cofilin and F-actin, the C-terminal fragment binds cofilin but not F-actin. Because pH-dependent cofilin activity is attenuated in mammalian cells lacking H(+) efflux by NHE1, our current data suggest that full-length Aip1 facilitates F-actin assembly when cofilin activity is limited. We predict the C-terminus of Aip1 enhances defective chemotaxis of Ddnhe1(-) cells by sequestering the limited amount of active cofilin without promoting F-actin assembly. Our findings indicate a cooperative role of Aip1 and cofilin in pH-dependent cell migration, and they suggest defective chemotaxis in Ddnhe1(-) cells is determined primarily by loss of cofilin-dependent actin dynamics.

Parallel transmission (pTX) techniques are required to tackle a number of challenges, e.g., the inhomogeneous distribution of the transmit field and elevated specific absorption rate (SAR), in ultra-high field (UHF) MR imaging. Additionally, they offer multiple degrees of freedom to create temporally- and spatially-tailored transverse magnetization. Given the increasing availability of MRI systems at 7 T and above, it is anticipated that interest in pTX applications will grow accordingly. One of the key components in MR systems capable of pTX is the design of the transmit array, as this has a major impact on performance in terms of power requirements, SAR and RF pulse design. While several reviews on pTX pulse design and the clinical applicability of UHF exist, there is currently no systematic review of pTX transmit/transceiver coils and their associated performance. In this article, we analyze transmit array concepts to determine the strengths and weaknesses of different types of design. We systematically review the different types of individual antennas employed for UHF, their combination into pTX arrays, and methods to decouple the individual elements. We also reiterate figures-of-merit (FoMs) frequently employed to describe the performance of pTX arrays and summarize published array designs in terms of these FoMs. [ABSTRACT FROM AUTHOR]

Simultaneously operating MR-PET systems have the potential to provide synergetic multi-parametric information, and, as such, interest surrounding their use and development is increasing. However, despite the potential advantages offered by fully combined MR-PET systems, implementing this hybrid integration is technically laborious, and any factors degrading the quality of either modality must be circumvented to ensure optimal performance. In order to attain the best possible quality from both systems, most full MR-PET integrations tend to place the shielded PET system inside the MRI system, close to the target volume of the subject. The radiofrequency (RF) coil used in MRI systems is a key factor in determining the quality of the MR images, and, in simultaneous acquisition, it is generally positioned inside the PET system and PET imaging region, potentially resulting in attenuation and artefacts in the PET images. Therefore, when designing hybrid MR-PET systems, it is imperative that consideration be given to the RF coils inside the PET system. In this review, we present current state-of-the-art RF coil designs used for hybrid MR-PET experiments and discuss various design strategies for constructing PET transparent RF coils. [ABSTRACT FROM AUTHOR]

A surface plasmon resonance imaging system combined with a multielement electrode array is described. An optical system with shaping optics is used to direct a wedge of light onto a gold-coated sample. The reflected light is detected in the form of an angle-spread image of the surface, with one direction denoting a variable incident angle and the other showing a span of locations along one lateral direction of the sample surface. At the proper incident angle, the angle-spread image shows the complete surface plasmon resonance curve over a span of locations on the surface. This imaging system is combined with a sample configuration consisting of a series of gold microelectrode bands, each with independent electrochemical control. In solution, this system can be used to perform high-throughput and dynamic electrochemical experiments. Simultaneous measurement of electrochemical and surface plasmon resonance can be quantitatively performed on each of the electrode surfaces either by holding each electrode at a different potential value or by scanning the applied potential. The sensitivity of this configuration is demonstrated by monitoring oxide formation and removal at a gold electrode in an aqueous electrolyte. A second example, with the use of a thin poly(aniline) coating, illustrates the ability to monitor film changes, including thickness, dielectric properties, and associated electrochemically induced polymer oxidation/ reduction on multiple electrodes. This represents a simple and compact method for combining the sensitivity of surface plasmon resonance into an array-based, high-throughput electrochemical system. 10.1021/ac100784c

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.03.038 Byline: Chang-Hoon Choi, Beom-Jun Kim, Sun-Young Jeong, Chang-Hun Lee, Ji-Sun Kim, Seong-Jun Park, Hyung-Soon Yim, Sa-Ouk Kang Keywords: Glutaredoxin; Glutathione reductase; Glutathione; Culmination; Cell fate; Dictyostelium discoideum Abstract: Glutaredoxins have been known to be glutathione-dependent oxidoreductases that participate in the redox regulation of various cellular processes. To understand the role of glutaredoxins in the development, we examined glutaredoxin 1 (Grx1) of Dictyostelium discoideum. Its mRNA was highly accumulated at the mound and the culmination stages. When Grx1-overexpressing cells were developed, their culmination was delayed, and the expression of marker genes for prespore and spore decreased. Interestingly, they had about 1.5-fold higher amount of reduced glutathione (GSH) compared with parental cells and their prolonged migration was repressed by the oxidant such as hydrogen peroxide. To confirm the effect of GSH on the culmination, glutathione reductase (Gsr) was overexpressed or underexpressed. Similar to Grx1-overexpressing cells, Gsr-overexpressing cells contained about 1.5-fold higher amount of GSH and exhibited the delayed culmination. In contrast, the knockdown mutant of Gsr had nearly 50% lower amount of GSH and showed accelerated culmination. Taken together, these data suggest that the culmination of Dictyostelium is controlled by GSH. In addition, the cells having higher GSH levels showed a prestalk tendency in the chimeric slugs with parental cells, indicating that the difference in the amount of GSH may affect the determination of cell fate. Author Affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea Article History: Received 19 November 2005; Revised 4 March 2006; Accepted 28 March 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.05.034 Byline: Beom-Jun Kim, Chang-Hoon Choi, Chang-Hun Lee, Sun-Young Jeong, Ji-Sun Kim, Bo-Yeon Kim, Hyung-Soon Yim, Sa-Ouk Kang Keywords: Glutathione; [gamma]-Glutamylcysteine synthetase; Cell fate; Dictyostelium discoideum Abstract: Glutathione (GSH) is the most abundant non-protein thiol in eukaryotic cells and acts as reducing equivalent in many cellular processes. We investigated the role of glutathione in Dictyostelium development by disruption of [gamma]-glutamylcysteine synthetase (GCS), an essential enzyme in glutathione biosynthesis. GCS-null strain showed glutathione auxotrophy and could not grow in medium containing other thiol compounds. The developmental progress of GCS-null strain was determined by GSH concentration contained in preincubated media before development. GCS-null strain preincubated with 0.2 mM GSH was arrested at mound stage or formed bent stalk-like structure during development. GCS-null strain preincubated with more than 0.5 mM GSH formed fruiting body with spores, but spore viability was significantly reduced. In GCS-null strain precultured with 0.2 mM GSH, prestalk-specific gene expression was delayed, while prespore-specific gene and spore-specific gene expressions were not detected. In addition, GCS-null strain precultured with 0.2 mM GSH showed prestalk tendency and extended G1 phase of cell cycle. Since G1 phase cells at starvation differentiate into prestalk cells, developmental defect of GCS-null strain precultured with 0.2 mM GSH may result from altered cell cycle. These results suggest that glutathione itself is essential for growth and differentiation to prespore in Dictyostelium. Author Affiliation: Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea Article History: Received 30 November 2004; Revised 30 March 2005; Accepted 25 May 2005

Non-uniform and steep dopant profiles in poly-gate result in built-in electric field effects and potential drops in the gate region. To overcome the problems, high doped gates with less dopant gradient in the poly-gate can be the most appropriate solution.

Three different methods for calculating physical resistances in an MOS device are examined. The physical resistances obtained from simulated devices are compared with the extracted resistances from the shift-and-ratio method.

Complementary metal-oxide semiconductor (CMOS) circuit robustness in the presence of gate tunneling is examined. Circuit simulation is employed, together with a macro-circuit model of gate-tunneling current and analytic estimates of effects.

A unified mobility inversion and accumulation layer model was used to demonstrate accurate external resistance extraction for shallow source/drain extension MOSFETs.