Comparison of 3D Bone Position Estimation Using QR Code and Metal Bead Markers.

To improve the accuracy of a 3D bone position estimation system that displays 3D images in response to changes in the position of fluoroscopic images, modified markers using quick response (QR) codes were developed. The aims of this study were to assess the accuracy of the estimated bone position on 3D images with reference to QR code markers on fluoroscopic images and to compare its accuracy with metal bead markers. Bone positions were estimated from reference points on a fluoroscopic image compared with those on a 3D image. The positional relationships of QR code and metal bead markers on the fluoroscopic image were compared with those on the 3D image in order to establish whether a 3D image may be drawn by tracking positional changes in radius models. Differences were investigated by comparing the distance between markers on the fluoroscopic image and that on the 3D image, which was projected on the monitor. The error ratio, which was defined as the difference in the measurement between the fluoroscopic and 3D images divided by the fluoroscopic measurement, was compared between QR code and metal bead markers. Error ratios for the QR code markers were 5.0 ± 2.0%, 6.4 ± 7.6%, and 1.0 ± 0.8% in the anterior-posterior view, ulnar side lateral view, and posterior-anterior view, respectively. Error ratios for the metal bead markers were 1.3 ± 1.7%, 13.8 ± 14.5%, and 4.7 ± 5.7% in the anterior-posterior view, ulnar side lateral view, and posterior-anterior view, respectively. The error ratio for the metal bead markers was smaller in the initial position (p < 0.01). However, the error ratios for the QR code markers were smaller in the lateral position and the posterior-anterior position (p < 0.05). In QR code marker tracking, tracking was successful even with discontinuous images. The accuracy of a 3D bone position estimation was increased by using the QR code marker system. QR code marker tracking facilitates real-time comparisons of dynamic changes in preoperative 3D and intraoperative fluoroscopic images.

An Experimental Study of a 3D Bone Position Estimation System Based on Fluoroscopic Images.

To compare a 3D preoperative planning image and fluoroscopic image, a 3D bone position estimation system that displays 3D images in response to changes in the position of fluoroscopic images was developed. The objective of the present study was to evaluate the accuracy of the estimated position of 3D bone images with reference to fluoroscopic images. Bone positions were estimated from reference points on a fluoroscopic image compared with those on a 3D image. The four reference markers positional relationships on the fluoroscopic image were compared with those on the 3D image to evaluate whether a 3D image may be drawn by tracking positional changes in the radius model. Intra-class correlations coefficients for reference marker distances between the fluoroscopic image and 3D image were 0.98-0.99. Average differences between measured values on the fluoroscopic image and 3D bone image for each marker corresponding to the direction of the bone model were 1.1 ± 0.7 mm, 2.4 ± 1.8 mm, 1.4 ± 0.8 mm, and 2.0 ± 1.6 mm in the anterior-posterior view, ulnar side lateral view, posterior-anterior view, and radial side lateral view, respectively. Marker positions were more accurate in the anterior-posterior and posterior-anterior views than in the radial and ulnar side lateral views. This system helps in real-time comparison of dynamic changes in preoperative 3D and intraoperative fluoroscopy images.

Conformational equilibrium shift underlies altered K+ channel gating as revealed by NMR.

The potassium ion (K+) channel plays a fundamental role in controlling K+ permeation across the cell membrane and regulating cellular excitabilities. Mutations in the transmembrane pore reportedly affect the gating transitions of K+ channels, and are associated with the onset of neural disorders. However, due to the lack of structural and dynamic insights into the functions of K+ channels, the structural mechanism by which these mutations cause K+ channel dysfunctions remains elusive. Here, we used nuclear magnetic resonance spectroscopy to investigate the structural mechanism underlying the decreased K+-permeation caused by disease-related mutations, using the prokaryotic K+ channel KcsA. We demonstrated that the conformational equilibrium in the transmembrane region is shifted toward the non-conductive state with the closed intracellular K+-gate in the disease-related mutant. We also demonstrated that this equilibrium shift is attributable to the additional steric contacts in the open-conductive structure, which are evoked by the increased side-chain bulkiness of the residues lining the transmembrane helix. Our results suggest that the alteration in the conformational equilibrium of the intracellular K+-gate is one of the fundamental mechanisms underlying the dysfunctions of K+ channels caused by disease-related mutations.

Light intensity influences feeding and fecundity of Tetranychus urticae (Acari: Tetranychidae) through the responses of host Cucumis sativus leaves.

We investigated feeding and fecundity of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), on leaves of cucumber (Cucumis sativus) seedlings that had been acclimatized to different light intensities. Based on these data, we analyzed the relationships between mite performance (feeding and fecundity) and leaf properties. The cucumber seedlings were grown in controlled-environment chambers under different light intensities at a photosynthetic photon flux density of 50, 100, 150, 300, or 450 µmol m- 2 s- 1 until the first true leaves had expanded. Adult females were released on the adaxial surfaces of excised leaf samples from the seedlings of each treatment group and held under standardized light intensity (200 µmol m- 2 s- 1). Fecundity and leaf damage area increased and decreased, respectively, as the acclimatization light intensity increased, indicating indirect effects of light intensity on feeding and fecundity through changes in the host leaf properties. Leaf mass per area (LMA) and photosynthetic capacity, which increased as the acclimatization light intensity increased, was positively related to the fecundity, but was negatively related to the leaf damage area. The higher LMA and photosynthetic capacity results in an increased amount of mesophyll per unit leaf area. This would allow the mites to feed efficiently from a limited area, which may explain the increased fecundity on these leaves.

Structural mechanism underlying G protein family-specific regulation of G protein-gated inwardly rectifying potassium channel.

G protein-gated inwardly rectifying potassium channel (GIRK) plays a key role in regulating neurotransmission. GIRK is opened by the direct binding of the G protein ßγ subunit (Gßγ), which is released from the heterotrimeric G protein (Gαßγ) upon the activation of G protein-coupled receptors (GPCRs). GIRK contributes to precise cellular responses by specifically and efficiently responding to the Gi/o-coupled GPCRs. However, the detailed mechanisms underlying this family-specific and efficient activation are largely unknown. Here, we investigate the structural mechanism underlying the Gi/o family-specific activation of GIRK, by combining cell-based BRET experiments and NMR analyses in a reconstituted membrane environment. We show that the interaction formed by the αA helix of Gαi/o mediates the formation of the Gαi/oßγ-GIRK complex, which is responsible for the family-specific activation of GIRK. We also present a model structure of the Gαi/oßγ-GIRK complex, which provides the molecular basis underlying the specific and efficient regulation of GIRK.