Weissella koreensis and Pediococcus pentosaceus bacterial ghosts induce inflammatory responses as immunostimulants.

In this study, bacterial ghosts (BGs) were generated from Weissella koreensis LKS42 (WKorGs) and Pediococcus pentosacues KA94 (PPGs) by chemically inducing lysis using substances such as hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), acetic acid (CH3COOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate (Na2CO3), n-butanol, and C6H8O7. HCl-induced WKorGs and PPGs exhibited complete removal of DNA and displayed transverse membrane dissolution tunnel structures under scanning electron microscopy (SEM). Cell viability assays showed high viability of RAW 264.7 cells exposed to HCl-induced WKorGs and PPGs. Additionally, treatment with HCl-induced WKorGs and PPGs elevated mRNA levels of pro-inflammatory cytokines (IL-1ß, IL-6, TNF-α, iNOS) and the anti-inflammatory cytokine IL-10 in RAW 264.7 cells. These findings suggest that HCl-induced WKorGs and PPGs have the potential to be used as inactivated bacterial immunostimulants, highlighting their promising applications in immunization and immunotherapy.

Response of vesicle shapes to dense inner active matter.

We consider experimentally the Takatori-Sahu model of vesicle shape fluctuations induced by enclosed active matter, a model till present tested only in the absence of collective motion because few enclosed bacteria were used to generate the desired active motion (S. C. Takatori and A. Sahu, Phys. Rev. Lett., 2020, 124, 158102). Using deformable giant unilamellar vesicles (GUVs) and phase contrast microscopy, we extract the mode-dependence of GUV shape fluctuations when hundreds of E. coli bacteria are contained within each GUV. In the microscope focal plane, patterns of collective bacteria flow include vortex flow, dipolar flow, and chaotic motion, all of which influence the GUV shapes. The Takatori-Sahu model generalizes well to this situation if one considers the moving element to be the experimentally-determined size of the collecively-moving flock.

Effective Model Update for Adaptive Classification of Text Streams in a Distributed Learning Environment.

In this study, we propose dynamic model update methods for the adaptive classification model of text streams in a distributed learning environment. In particular, we present two model update strategies: (1) the entire model update and (2) the partial model update. The former aims to maximize the model accuracy by periodically rebuilding the model based on the accumulated datasets including recent datasets. Its learning time incrementally increases as the datasets increase, but we alleviate the learning overhead by the distributed learning of the model. The latter fine-tunes the model only with a limited number of recent datasets, noting that the data streams are dependent on a recent event. Therefore, it accelerates the learning speed while maintaining a certain level of accuracy. To verify the proposed update strategies, we extensively apply them to not only fully trainable language models based on CNN, RNN, and Bi-LSTM, but also a pre-trained embedding model based on BERT. Through extensive experiments using two real tweet streaming datasets, we show that the entire model update improves the classification accuracy of the pre-trained offline model; the partial model update also improves it, which shows comparable accuracy with the entire model update, while significantly increasing the learning speed. We also validate the scalability of the proposed distributed learning architecture by showing that the model learning and inference time decrease as the number of worker nodes increases.

Apparatus to Measure Subnanometer Fluctuation of Giant Unilamellar Vesicle Membranes.

The design, calibration, and performance of an apparatus are described to study the nanometer-scale thermal or driven fluctuations of free-standing vesicle membranes using a design resembling the position detection system of optical tweezers except for the laser power lower by orders of magnitude to avoid trapping. Over four decades of frequency, 1-10,000 Hz, it reports membrane fluctuation amplitudes 0.01-100 nm by measuring scattering of a laser beam as it passes membranes (∼1 µm cross-section) suspended in the aqueous medium. The low-power laser beam, <100 µW, is sharply focused on the edge of a giant unilamellar vesicle, and fluctuations of position are measured using a position-sensitive photodetector. The central result of this approach is the capability to reach small fluctuations otherwise inaccessible using other techniques. The typical obtained data are fit to the standard Helfrich mechanical model. The applications and limitations of the device are discussed, as well as other potential uses to which the apparatus may be applied by rational extension of the approach presented.

A hybrid and scalable error correction algorithm for indel and substitution errors of long reads.

BACKGROUND: Long-read sequencing has shown the promises to overcome the short length limitations of second-generation sequencing by providing more complete assembly. However, the computation of the long sequencing reads is challenged by their higher error rates (e.g., 13% vs. 1%) and higher cost ($0.3 vs. $0.03 per Mbp) compared to the short reads. METHODS: In this paper, we present a new hybrid error correction tool, called ParLECH (Parallel Long-read Error Correction using Hybrid methodology). The error correction algorithm of ParLECH is distributed in nature and efficiently utilizes the k-mer coverage information of high throughput Illumina short-read sequences to rectify the PacBio long-read sequences.ParLECH first constructs a de Bruijn graph from the short reads, and then replaces the indel error regions of the long reads with their corresponding widest path (or maximum min-coverage path) in the short read-based de Bruijn graph. ParLECH then utilizes the k-mer coverage information of the short reads to divide each long read into a sequence of low and high coverage regions, followed by a majority voting to rectify each substituted error base. RESULTS: ParLECH outperforms latest state-of-the-art hybrid error correction methods on real PacBio datasets. Our experimental evaluation results demonstrate that ParLECH can correct large-scale real-world datasets in an accurate and scalable manner. ParLECH can correct the indel errors of human genome PacBio long reads (312 GB) with Illumina short reads (452 GB) in less than 29 h using 128 compute nodes. ParLECH can align more than 92% bases of an E. coli PacBio dataset with the reference genome, proving its accuracy. CONCLUSION: ParLECH can scale to over terabytes of sequencing data using hundreds of computing nodes. The proposed hybrid error correction methodology is novel and rectifies both indel and substitution errors present in the original long reads or newly introduced by the short reads.

Characterization of Chemically-Induced Bacterial Ghosts (BGs) Using Sodium Hydroxide-Induced Vibrio parahaemolyticus Ghosts (VPGs).

Acellular bacterial ghosts (BGs) are empty non-living bacterial cell envelopes, commonly generated by controlled expression of the cloned lysis gene E of bacteriophage PhiX174. In this study, Vibrio parahaemolyticus ghosts (VPGs) were generated by chemically-induced lysis and the method is based on minimum inhibitory concentration (MIC) of sodium hydroxide (NaOH), acetic acid, boric acid, citric acid, maleic acid, hydrochloric acid, and sulfuric acid. The MIC values of the respective chemicals were 3.125, 6.25, <50.0, 25.0, 6.25, 1.56, and 0.781 mg/mL. Except for boric acid, the lysis efficiency reached more than 99.99% at 5 min after treatment of all chemicals. Among those chemicals, NaOH-induced VPGs appeared completely DNA-free, which was confirmed by quantitative real-time PCR. Besides, lipopolysaccharides (LPS) extracted from the NaOH-induced VPGs showed no distinctive band on SDS-PAGE gel after silver staining. On the other hand, LPS extracted from wild-type bacterial cells, as well as the organic acids-induced VPGs showed triple major bands and LPS extracted from the inorganic acids-induced VPGs showed double bands. It suggests that some surface structures in LPS of the NaOH-induced VPGs may be lost, weakened, or modified by the MIC of NaOH. Nevertheless, Limulus amoebocyte lysate assay revealed that there is no significant difference in endotoxic activity between the NaOH-induced VPGs and wild-type bacterial cells. Macrophages exposed to the NaOH-induced VPGs at 0.5 × 106 CFU/mL showed cell viability of 97.9%, however, the MIC of NaOH did not reduce the cytotoxic effect of wild-type bacterial cells. Like Escherichia coli LPS, the NaOH-induced VPGs are an excellent activator of pro-inflammatory cytokines (IL-1ß and iNOS), anti-inflammatory cytokine (IL-10), and dual activities (IL-6) in the stimulated macrophage cells. On the other hand, the induction of TNF-α mRNA was remarkable in the macrophages exposed with wild-type cells. Scanning electron microscopy showed the formation of trans-membrane lysis tunnel structures in the NaOH-induced VPGs. SDS-PAGE and agarose gel electrophoresis also confirmed that cytoplasmic proteins and genomic DNA released from the VPGs to culture medium through the lysis tunnel structures. Taken together, all these data indicate that the NaOH-induced VPGs show the potency of a safe, economical, and effective inactivated bacterial vaccine candidate.

Performances of a protector against scattered radiation during intraoperative use of a C-arm fluoroscope.

The scattered radiation protector for mobile x-ray systems, Creative Valuable Protector-2, has been recently developed. However, there have been no studies investigating the effects of this device. We aim to investigate the effects of the scattered radiation protector on the equivalent doses from scattered radiation delivered to radiosensitive organs while simulating spine surgery using a C-arm fluoroscope. Chest and rando phantoms were used to simulate a patient and a surgeon in this study. The equivalent dose from scattered radiation to radiosensitive organs was measured in four different situations according to the use of the scattered radiation protector and the C-arm configuration. To compare the quality of the images with and without the scattered radiation protector, an acryl step phantom with five steps was used, and the contrast resolution of each step was calculated. The equivalent dose from the scattered radiation to the surgeon's eye, thyroid, and gonad decreased significantly by using the scattered radiation protector for both the Posteroanterior (PA) (p < 0.001) and Anteroposterior (AP) (p < 0.001) C-arm configurations. The installation of the scattered radiation protector also reduced the direct radiation dose to the chest phantom. A scattered map showed that scattered radiation doses decreased by approximately 50% for the PA configuration and 75% for the AP configuration by using the scattered radiation protector. Before and after installation of the scattered radiation protector, the contrast resolution of each adjacent step area was 0.025-0.404 and 0.216-0.421. The scattered radiation protector was effective in reducing not only the equivalent dose from scattered radiation to the surgeon's radiosensitive organs, but also the direct radiation dose to the patient. This was all achieved without decreasing the quality of the C-arm fluoroscopic images.

Characterization of Saccharomyces cerevisiae promoters for heterologous gene expression in Kluyveromyces marxianus.

Kluyveromyces marxianus is now considered one of the best choices of option for industrial applications of yeast because the strain is able to grow at high temperature, utilizes various carbon sources, and grows fast. However, the use of K. marxianus as a host for industrial applications is still limited. This limitation is largely due to a lack of knowledge on the characteristics of the promoters since the time and amount of protein expression is strongly dependent on the promoter employed. In this study, four well-known constitutive promoters (P(CYC), P(TEF), P(GPD), and P(ADH)) of Saccharomyces cerevisiae were characterized in K. marxianus in terms of protein expression level and their stochastic behavior. After constructing five URA3-auxotrophic K. marxianus strains and a plasmid vector, four cassettes each comprising one of the promoters--the gene for the green fluorescence protein (GFP)--CYC1 terminator (T(CYC)) were inserted into the vector. GFP expression under the control of each one of the promoters was analyzed by reverse transcription PCR, fluorescence microscopy, and flow cytometer. Using these combined methods, the promoter strength was determined to be in the order of P(GPD) > P(ADH) ∼ P(TEF) >> P(CYC). All promoters except for the P(CYC) exhibited three distinctive populations, including non-expressing cells, weakly expressing cells, and strongly expressing cells. The relative ratios between populations were strongly dependent on the promoter and culture time. Forward scattering was independent of GFP fluorescence intensity, indicating that the different fluorescence intensities were not just due to different cell sizes derived from budding. It also excluded the possibility that the non-expressing cells resulted from plasmid loss because plasmid stability was maintained at almost 100 % over the culture time. The same cassettes, cloned into a single copy plasmid pRS416 and transformed into S. cerevisiae, showed only one population. When the cassettes were integrated into the chromosome, the stochastic behavior was markedly reduced. These combined results imply that the gene expression stochasticity should be overcome in order to use this strain for delicate metabolic engineering, which would require the co-expression of several genes.

The progesterone receptor as a transcription factor regulates phospholipase D1 expression through independent activation of protein kinase A and Ras during 8-Br-cAMP-induced decidualization in human endometrial stromal cells.

Decidualization is a biological and morphological process occurring in hES (human endometrial stromal) cells. Previously, we reported that PLD1 (phospholipase D1) plays an important role in cAMP-induced decidualization of hES cells. In the present study, we focused on how PLD1 expression is up-regulated during decidualization. Treatment with PKA (protein kinase A) inhibitors (Rp-cAMP or H89) or a Ras inhibitor (manumycin) partially inhibited PLD1 expression and decidua formation in response to cAMP treatment. Interestingly, dual inhibition of PKA and Ras completely inhibited PLD1 expression and cAMP-induced decidualization. These results suggest that PLD1 expression during decidualization is controlled additively by PKA and Ras. The use of inhibitors showed that extracellular-signal-regulated kinase, a downstream effector of Ras, was required for PLD activation and the morphological changes during decidualization, but not for the increase in PLD1 protein. Next, to investigate the regulator of the PLD1 gene at the transcriptional level, a promoter assay using deletion mutants of the PLD1 promoter was performed; the result indicated that PR (progesterone receptor) was a possible regulator of the PLD1 gene. In addition, chromatin immunoprecipitation assays on the PLD1 promoter identified PR as a transcription factor for PLD1 expression during 8-Br-cAMP-induced decidualization. Taken together, our findings demonstrate that PKA and Ras are novel regulators of PLD1 expression and also identify PR as a transcription factor for PLD1 expression during the decidualization of hES cells.

Feasibility study of a plasma display-like radiation detector for X-ray imaging.

In this study we have investigated a 2-dimensional gas type detector based on plasma display technology as a candidate for the flat-panel radiation detector. By using the Garfield code, the dependence of X-ray absorption and multiplication on gas composition, cell gap and electric field were examined. Considering the simulation results, three prototype detectors were designed and fabricated. The performance of these detectors was evaluated by measuring the collected charge density, dark current density and sensitivity. The collected charge had the highest value at a condition when Xe 100% and 2.8 mm gap was 108.8 nC/cm² at 1000 V. The dark current of the same detector was varied from 0.0095 to 0.10 nA/cm² and about a fourth of the dark current density of a-Se based detector was at the bias range of 100-1000 V. The sensitivity of Xe 100% and 2.8 mm detector was 0.20 nC/mR·cm² at 0.36 V/um. It is about a tenth lower than that of a-Se based detector at 10 V/um.

A comparative experimental study of distributed storage engines for big spatial data processing using GeoSpark.

With increasing numbers of GPS-equipped mobile devices, we are witnessing a deluge of spatial information that needs to be effectively and efficiently managed. Even though there are several distributed spatial data processing systems such as GeoSpark (Apache Sedona), the effects of underlying storage engines have not been well studied for spatial data processing. In this paper, we evaluate the performance of various distributed storage engines for processing large-scale spatial data using GeoSpark, a state-of-the-art distributed spatial data processing system running on top of Apache Spark. For our performance evaluation, we choose three distributed storage engines having different characteristics: (1) HDFS, (2) MongoDB, and (3) Amazon S3. To conduct our experimental study on a real cloud computing environment, we utilize Amazon EMR instances (up to 6 instances) for distributed spatial data processing. For the evaluation of big spatial data processing, we generate data sets considering four kinds of various data distributions and various data sizes up to one billion point records (38.5GB raw size). Through the extensive experiments, we measure the processing time of storage engines with the following variations: (1) sharding strategies in MongoDB, (2) caching effects, (3) data distributions, (4) data set sizes, (5) the number of running executors and storage nodes, and (6) the selectivity of queries. The major points observed from the experiments are summarized as follows. (1) The overall performance of MongoDB-based GeoSpark is degraded compared to HDFS- and S3-based GeoSpark in our experimental settings. (2) The performance of MongoDB-based GeoSpark is relatively improved in large-scale data sets compared to the others. (3) HDFS- and S3-based GeoSpark are more scalable to running executors and storage nodes compared to MongoDB-based GeoSpark. (4) The sharding strategy based on the spatial proximity significantly improves the performance of MongoDB-based GeoSpark. (5) S3- and HDFS-based GeoSpark show similar performances in all the environmental settings. (6) Caching in distributed environments improves the overall performance of spatial data processing. These results can be usefully utilized in decision-making of choosing the most adequate storage engine for big spatial data processing in a target distributed environment.

A bacteria-based carbon sequestration and waste recycling system.

Achieving carbon neutrality requires a variety of technological approaches. In the present study, we confirmed the applicability of a carbon cycle system in several industrial fields using sulphur-oxidising bacteria. This system produces a nitrogen fertiliser, which decreases carbon emissions by recycling H2S and NH3 pollutants discharged into the atmosphere or wastewater. It should be considered in industrial fields as a carbon reduction strategy.

Hydrochloric acid-treated Bacillus subtilis ghosts induce IL-1 beta, IL-6, and TNF-alpha in murine macrophage.

Background: Bacterial ghosts (BGs) are empty cell envelopes commonly generated using Gram-negative bacteria; they represent a potential platform for efficient adjuvant and vaccine delivery systems. However, the efficient production of BGs from bacteria in a short period of time is challenging. Objective: The purpose of this study was to investigate the possibility of producing BGs in the Gram-positive Bacillus subtilis using various chemicals, and the potential application of BGs as a novel immunomodulatory agent. Results: In this study, Bacillus subtilis ghosts (BSGs) were generated, for the first time to the best of our knowledge, using the minimum inhibitory concentration (MIC) of hydrochloric acid (HCl; 6.25 mg/mL), sulfuric acid (H2SO4; 3.125 mg/mL), and nitric acid (HNO3; 6.25 mg/mL). Among the BSGs generated using these chemicals, HCl-induced BSGs were completely DNA-free as confirmed by real-time polymerase chain reaction. Scanning electron microscopy showed the formation of transmembrane lysis tunnel structures in HCl-induced BSGs. Murine macrophages exposed to the HCl-induced BSGs at a concentration of 1 × 105 CFU/mL showed a cell viability of 97.8%. Additionally, HCl-induced BSGs upregulated the expression of pro-inflammatory cytokines including interleukin (IL)-1ß, tumor necrosis factor alpha, and IL-6. Furthermore, we found differences in the protein expression profiles between intact live bacteria and BSGs using two-dimensional electrophoresis coupled with peptide mass fingerprinting/matrix-assisted laser desorption/ionization-time of flight mass spectrometry analysis. Conclusion: These data suggest that the HCl-induced BSGs may be potentially safe and effective candidates for inactivated bacterial vaccines and/or immunostimulants. Supplementary Information: The online version contains supplementary material available at 10.1007/s13273-022-00221-5.

Bacterial persisters tolerate antibiotics by not producing hydroxyl radicals.

In a phenomenon called persistence, small numbers of bacterial cells survive even after exposure to antibiotics. Recently, bactericidal antibiotics have been demonstrated to kill bacteria by increasing the levels of hydroxyl radicals inside cells. In the present study, we report a direct correlation between intracellular hydroxyl radical formation and bacterial persistence. By conducting flow cytometric analysis in a three-dimensional space, we resolved distinct bacterial populations in terms of intracellular hydroxyl radical levels, morphology and viability. We determined that, upon antibiotic treatment, a small sub-population of Escherichia coli survivors do not overproduce hydroxyl radicals and maintain normal morphology, whereas most bacterial cells were killed by accumulating hydroxyl radicals and displayed filamentous morphology. Our results suggest that bacterial persisters can be formed once they have transient defects in mediating reactions involved in the hydroxyl radical formation pathway. Thus, it is highly probable that persisters do not share a common mechanism but each persister cell respond to antibiotics in different ways, while they all commonly show lowered hydroxyl radical formation and enhanced tolerance to antibiotics.

Improved galactose fermentation of Saccharomyces cerevisiae through inverse metabolic engineering.

Although Saccharomyces cerevisiae is capable of fermenting galactose into ethanol, ethanol yield and productivity from galactose are significantly lower than those from glucose. An inverse metabolic engineering approach was undertaken to improve ethanol yield and productivity from galactose in S. cerevisiae. A genome-wide perturbation library was introduced into S. cerevisiae, and then fast galactose-fermenting transformants were screened using three different enrichment methods. The characterization of genetic perturbations in the isolated transformants revealed three target genes whose overexpression elicited enhanced galactose utilization. One confirmatory (SEC53 coding for phosphomannomutase) and two novel targets (SNR84 coding for a small nuclear RNA and a truncated form of TUP1 coding for a general repressor of transcription) were identified as overexpression targets that potentially improve galactose fermentation. Beneficial effects of overexpression of SEC53 may be similar to the mechanisms exerted by overexpression of PGM2 coding for phosphoglucomutase. While the mechanism is largely unknown, overexpression of SNR84, improved both growth and ethanol production from galactose. The most remarkable improvement of galactose fermentation was achieved by overexpression of the truncated TUP1 (tTUP1) gene, resulting in unrivalled galactose fermentation capability, that is 250% higher in both galactose consumption rate and ethanol productivity compared to the control strain. Moreover, the overexpression of tTUP1 significantly shortened lag periods that occurs when substrate is changed from glucose to galactose. Based on these results we proposed a hypothesis that the mutant Tup1 without C-terminal repression domain might bring in earlier and higher expression of GAL genes through partial alleviation of glucose repression. mRNA levels of GAL genes (GAL1, GAL4, and GAL80) indeed increased upon overexpression of tTUP. The results presented in this study illustrate that alteration of global regulatory networks through overexpression of the identified targets (SNR84 and tTUP1) is as effective as overexpression of a rate limiting metabolic gene (PGM2) in the galactose assimilation pathway for efficient galactose fermentation in S. cerevisiae. In addition, these results will be industrially useful in the biofuels area as galactose is one of the abundant sugars in marine plant biomass such as red seaweed as well as cheese whey and molasses.

The perspectives of users and developers in designing and developing O-arm imaging system.

A questionnaire survey was performed to investigate the different knowledge of radiation exposure, awareness and expectation for O-arm imaging system between the users (orthopaedic surgeons) and the developers (engineers). A total of 93 orthopaedic surgeons and 19 engineers participated and answered the questionnaire consisting of 18 items designed for this study. The items were focused on knowlege, awareness, and expectation. Orthopaedic surgeons had higher scores for items of knowledge domains regarding radiation exposure than the engineers while the engineers were more sensitive to radiation hazards and adopted higher levels of radiation protection than orthopaedic surgeons in the awareness domain. Most engineers and orthopaedic surgeons answered that the requirements of diagnostic and intraoperative imaging systems differ. Image resolution, a low radiation exposure, and the time required for image acquisition was the top three requirements of O-arm selected by engineers. On the other hand, the top three requirements according to orthopaedic surgeons were; image resolution, expediency, and spatial occupancy. User requirements need to be reflected in developing O-arm along with basic requirements such as image resolution and low radiation exposure.

Restoration of growth phenotypes of Escherichia coli DH5alpha in minimal media through reversal of a point mutation in purB.

A point mutation (E115K) resulting in slower growth of Escherichia coli DH5alpha and XL1-Blue in minimal media was identified in the purB gene, coding for adenylosuccinate lyase (ASL), through complementation with an E. coli K-12 genomic library and serial subcultures. Chromosomal modification reversing the mutation to the wild type restored growth phenotypes in minimal media.

Shielding effect of radiation dose reduction fiber during the use of C-arm fluoroscopy: a phantom study.

This study evaluated the shielding effect of a newly developed dose-reduction fiber (DRF) made from barium sulfate, in terms of radiation doses delivered to patients' radiosensitive organs and operator during C-arm fluoroscopy and its impact on the quality of images. A C-arm fluoroscopy unit was placed beside a whole-body phantom. Radiophotoluminescent glass dosimeters were attached to the back and front of the whole-body phantom at 20 cm intervals. Radiation doses were measured without DRF and with it applied to the back (position 1), front (position 2) or both sides (position 3) of the phantom. To investigate the impact of DRF on the quality of fluoroscopic images, step-wedge and modulation transfer function phantoms were used. The absorbed radiation doses to the back of the phantom significantly decreased by 25.3-88.8% after applying DRF to positions 1 and 3. The absorbed radiation doses to the front of the phantom significantly decreased by 55.3-93.6% after applying DRF to positions 2 and 3. The contrast resolution values for each adjacent step area fell in the range 0.0119-0.0209, 0.0128-0.0271, 0.0135-0.0339 and 0.0152-0.0339 without and with DRF applied to positions 1, 2 and 3, respectively. The investigated DRF effectively reduces absorbed radiation doses to patients and operators without decreasing the quality of C-arm fluoroscopic images. Therefore, routine clinical use of the DRF is recommended during the use of C-arm fluoroscopy.

Wavelength discrimination (WLD) TOF-PET detector with DOI information.

Depth-of-interaction (DOI) encoding can contribute to improving spatial resolution uniformity and sensitivity in positron-emission-tomography (PET) scanners. In addition, time-of-flight (TOF) PET scanners with DOI encoding have received considerable interest because of their potential for improving the spatial resolution, sensitivity, and image quality of the overall system. In this study, a new DOI detector configuration utilizing scintillators' emission wavelength is proposed, and experimental results on the energy, timing, and DOI performance of the detector are provided. The DOI information from the proposed phoswich-type detector can be acquired at the detector level without complex signal processing by utilizing a single optical filter with customized optical properties. For this, we used either a short pass filter (SPF) or a long pass filter (LPF) that allows light photons of a specific wavelength to pass. The two-layered phoswich detector was configured with two scintillators with different photon-emission spectra. In this study, we used Ce:GAGG (3 mm × 3 mm × 10 mm) and LYSO:Ce (3 mm × 3 mm × 10 mm) as the top and bottom layer scintillators, respectively. A digital silicon photomultiplier (dSiPM) was used as the photosensor and for data acquisition. The phoswich detector was placed in the center of two dSiPM pixels, where one of the dSiPM pixels was covered with the optical filter, and the light guide was placed on the other pixel. The detector was tested for energy, timing, and DOI encoding performance. When an SPF was used, the energy resolutions of 16.2% and 11.8% were achieved for the Ce:GAGG (top layer) and LYSO:Ce (bottom layer) respectively without correcting for saturation effect. With a small (3 mm × 3 mm × 5 mm) LYSO crystal as the reference detector, CRTs (coincidence-resolving times) of 338 ps and 244 ps were recorded for the top and bottom layers respectively. The detector configuration also provides an excellent DOI-separation figure-of-merit (FoM) value of 1.9. In the case of LPF, the energy resolutions of 12.0% and 12.9% were achieved for the Ce:GAGG (top layer) and LYSO:Ce (bottom layer), respectively. CRTs (coincidence resolving times) of 314 ps and 263 ps were recorded for the top and bottom layers, respectively. The DOI-separation FoM value of 1.5 was achieved in this setup. Results show that the proposed method can provide excellent discrete DOI positioning accuracy without compromising the timing performance of the detector.

Overexpression of phospholipase D suppresses taxotere-induced cell death in stomach cancer cells.

Phospholipase D (PLD) catalyzes the hydrolysis of phosphatidylcholine to generate phosphatidic acid (PA) and choline. There are at least two PLD isozymes, PLD1 and PLD2. Genetic and pharmacological approaches implicate both PLD isozymes in a diverse range of cellular processes, including receptor signaling, membrane transport control, and actin cytoskeleton reorganization. Several recent studies reported that PLD has a role in signaling pathways that oppose apoptosis and promote cell survival in cancer. In this study, we examined the role of PLD in taxotere-induced apoptosis in stomach cell lines; normal stomach (NSC) and stomach cancer cells (SNU 484). Taxotere treatment resulted in increase of PLD activity. To confirm the role of PLD in taxotere-induced apoptosis, PLDs were transfected into SNU 484 cells. Overexpression of PLD isozymes resulted in inhibition of taxotere-induced apoptotic cell death, evidenced by decreased degradation of chromosomal DNA, and increased cell viability. Concurrently, Bcl-2 expression was upregulated, and taxotere-induced activation of procaspase 3 was inhibited after PLD's transfection. However, when PLD was selectively inhibited by specific siRNA-PLD1 or -PLD2, taxotere-induced apoptosis was exacerbated in SNU 484 cells. On top of this, PA -- the product of PLDs, also resulted in upregulation of Bcl-2 in SNU 484. Although PA-induced Bcl-2 expression was blocked by mepacrine, an inhibitor of phospholipase A(2) (PLA(2)), increased Bcl-2 expression by PA was not abrogated by propranolol, an inhibitor of PA phospholyhydrolase (PAP). Taken together, PLD1 and PLD2 are closely related with Bcl-2 expression together with PLA(2), but not with PAP, during taxotere-induced apoptosis in SNU 484 cells.