Development of date acquisition system for the human OpenPET

NIRS Workshop on PET Imaging Physics and Applications PIPA201

Improvement of crystal identification performance for a four-layer DOI detector composed of crystals segmented by laser processing

We have developed a four-layer depth of interaction (DOI) detector with single-side photon readout, in which segmented crystals with the patterned reflector insertion are separately identified by the Anger-type calculation. Optical conditions between segmented crystals, where there is no reflector, affect crystal identification ability. Our objective of this work was to improve crystal identification performance of the four-layer DOI detector that uses crystals segmented with a recently developed laser processing technique to include laser processed boundaries (LPBs). The detector consisted of View the MathML source2×2×4mm3 LYSO crystals and a 4×44×4 array multianode photomultiplier tube (PMT) with 4.5 mm anode pitch. The 2D position map of the detector was calculated by the Anger calculation method. At first, influence of optical condition on crystal identification was evaluated for a one-layer detector consisting of a 2×22×2 crystal array with three different optical conditions between the crystals: crystals stuck together using room temperature vulcanized (RTV) rubber, crystals with air coupling and segmented crystals with LPBs. The crystal array with LPBs gave the shortest distance between crystal responses in the 2D position map compared with the crystal array coupled with RTV rubber or air due to the great amount of cross-talk between segmented crystals with LPBs. These results were used to find optical conditions offering the optimum distance between crystal responses in the 2D position map for the four-layer DOI detector. Crystal identification performance for the four-layer DOI detector consisting of an 8×88×8 array of crystals segmented with LPBs was examined and it was not acceptable for the crystals in the first layer. The crystal identification was improved for the first layer by changing the optical conditions between all 2×22×2 crystal arrays of the first layer to RTV coupling. More improvement was observed by combining different optical conditions between all crystals of the first layer and some crystals of the second and the third layers of the segmented array

NK Cells Can Preferentially Target Prostate Cancer Stem-like Cells via the TRAIL/DR5 Signaling Pathway

Background: The occurrence of androgen-dependent prostate cancer mainly depends on prostate cancer stem cells. To reduce the risk of androgen-dependent prostate cancer, the direct elimination of prostate cancer stem cells is important, but an elimination strategy has not yet been established. A previous study showed that natural killer (NK) cells can preferentially target cancer stem cells in several solid tumors except prostate cancer. In this context, this study was undertaken to investigate if NK cells can selectively attack androgen-dependent prostate cancer stem cells. Methods: Prostate cancer stem-like cells were separated from an androgen-dependent prostate cancer cell line (LNCaP) using a three-dimensional culture system. LNCaP stem-like cells or LNCaP cells were co-cultured with human NK cells (KHYG-1) for 24–72 h, and cell viability was determined using the WST-8 method. The expression of each protein in the cell membrane was evaluated through FACS analysis, and mRNA levels were determined using real-time PCR. Results: KHYG-1 cells had more potent cytotoxicity against LNCaP stem-like cells than LNCaP cells, and the potency of the cytotoxicity was strongly related to the TRAIL/DR5 cell death pathway. Conclusion: NK cells can preferentially target prostate cancer stem-like cells via the TRAIL/DR5 pathway

The asparagine 533 residue in the outer pore loop region of the mouse PKD2L1 channel is essential for its voltage-dependent inactivation

Voltage-dependent inactivation of ion channels contributes to the regulation of the membrane potential of excitable cells. Mouse polycystic kidney disease 2-like 1 (PKD2L1) forms voltage-dependent nonselective cation channels, which are activated but subsequently inactivated in response to membrane depolarization. Here, we found that the mutation of an asparagine 533 residue (N533Q) in the outer pore loop region of PKD2L1 caused a marked increase in outward currents induced by depolarization. In addition, the tail current analysis demonstrated that the N533Q mutants are activated during depolarization but the subsequent inactivation does not occur. Interestingly, the N533Q mutants lacked the channel activation triggered by the removal of stimuli such as extracellular alkalization and heating. Our findings suggest that the N533 residue in the outer pore loop region of PKD2L1 has a key role in the voltage-dependent channel inactivation.status: publishe

Development of a dual-ended readout detector with segmented crystal bars made using subsurface laser engraving technique

Depth of interaction (DOI) information is indispensable to improve sensitivity and spatial resolution of positron emission tomography (PET) systems especially for small field-of-view PET such as small animal PET and human brain PET. We have already developed a series of X’tal cube detectors for isotropic spatial resolution and we obtained the best isotropic resolution of 0.77 mm for the detectors with six-sided readout. However, it is still challenging to apply the detector for PET systems due to the high costs of six-sided readout electronics and carrying out segmentation of a monolithic cubic scintillator using the three-dimensional (3D) subsurface laser engraving (SSLE) technique. In this work, we proposed a more practical X’tal cube with the two-sided readout detector, which was made of crystal bars segmented by the one-dimensional (1D) SSLE technique. We developed two types of prototype detectors with a 3 mm cubic segment and a 1.5 mm cubic segment by using 3×3×20 mm3 and 1.5×1.5×20 mm3 crystal bars segmented into 7 and 13 DOI segments, respectively, using the 1D SSLE technique. First, performance of the detector composed of one crystal bar with different DOI segments and readout at both ends of two thorough silicon via (TSV) multi-pixel photon counters (MPPCs) were evaluated in order to demonstrate capability of the segmented crystal bars as a DOI detector. Then, performance evaluation was carried out for a 4×4 crystal array of 3×3×20 mm3 with 7 DOI segments and an 8×8 crystal array of 1.5×1.5×20 mm3 with 13 DOI segments. Each readout included a 4×4 channel of the 3×3 mm2 active area TSV MPPCs. The 3D position maps of the detectors were obtained by the Anger type calculation. All the segments in the 4×4 array were identified very clearly when there was air between the crystal bars as each crystal bar was coupled to one channel of the MPPCs; however, it was necessary to optimize optical conditions between crystal bars for the 8×8 array because of light sharing between crystal bars coupled to one channel of the MPPCs. The optimization was performed for the 8×8 array by inserting reflectors fully or partially between the crystal bars and the best crystal identification performance was obtained with the partial reflectors between the crystal bars. The mean energy resolutions at the 511 keV photo peak for the 4×4 array with air between the crystal bars and for the 8×8 array with partial reflectors between the crystal bars were 10.1% ± 0.3% and 10.8% ± 0.8%, respectively. Timing resolution of 783 ± 36 ps and 1.14 ± 0.22 ns were obtained for the detectors composed of the 4×4 array and the 8×8 array with partial reflectors, respectively. Practical X’tal cubes with 3 mm and 1.5 mm DOI resolutions and two-sided readout were developed

Size-driven parr-smolt transformation in masu salmon (Oncorhynchus masou)

Abstract Anadromous salmonids exhibit partial migration, where some individuals within a population migrate down to the ocean through complex interactions between body size and photoperiod. This study aimed to integrate the ontogenetic and seasonal patterns of smoltification, a series of changes for future marine life, in a strain of masu salmon (Oncorhynchus masou). Spring smoltification, as evidenced by the activation of gill Na+,K+-ATPase (NKA), was induced during winter under an advanced photoperiod. In addition, juveniles showed an additional peak in gill NKA activity in August regardless of the photoperiod. When juvenile masu salmon were subjected to feeding manipulations during the first spring/summer, only fish exceeding a fork length of 12 cm exhibited an increased gill NKA activity. We tested whether size-driven smoltification required a long-day period by exposing juveniles to a constant short-day length (9-h light and 15-h dark) from January to November. Juveniles under short-day conditions exceeded 12 cm in June but showed no signs of smoltification. Thus, masu salmon undergo photoperiod-limited, size-driven smoltification during the first summer and size-limited, photoperiod-driven smoltification the following spring. The findings of the present study provide a framework for further elucidation of the physiological mechanisms underlying partial migration in salmonids