Type I IFN-induced expression of dsRNA-activated protein kinase (PKR) during viral infection is a well-established antiviral mechanism. However, little is known about the expression of PKR in the context of p53 and about PKR involvement in p53-mediated tumor suppression. Here, we report that PKR is a p53 target gene and plays an important role in the tumor-suppressor function of p53. Activation of p53 by genotoxic stress induces a significant level of PKR expression by acting on the newly identified cis-acting element (ISRE), which is separated from the IFN-stimulated responsive element on the PKR promoter, resulting in translational inhibition and cell apoptosis. The genotoxin-mediated inhibition of translation is associated with the p53/PKR/elF2a (eukaryotic initiation factor-2␣) pathway. To some extent, p53 activation induced by DNA damage facilitates cell apoptosis by activating PKR. PKR-knockdown human colon cancer cells grew rapidly in nude mice and proved resistant to anti-cancer drugs. These data indicate that p53-mediated tumor suppression can be attributed at least in part to the biological functions of PKR induced by p53 in genotoxic conditions. p53 tumor suppression ͉ p53RE ͉ translation inhibition and apoptosis

Sustained ER stress leads to apoptosis. However, the exact mechanism still remains to be elucidated. Here, we demonstrate that the double strand RNA-dependent protein kinase (PKR) is involved in the ER stress-mediated signaling pathway. ER stress rapidly activated PKR, inducing the phosphorylation of eIF2a, followed by the activation of the ATF4/CHOP pathway. ER-stress-mediated eIF2a/ATF4/CHOP signaling and associated cell death was markedly reduced by PKR knockdown. We also found that PKR activation was mediated by PACT, the expression of which was elevated by ER-stress. These results indicate that the ER-stress-mediated eIF2a/ATF4/CHOP/cell death pathway is, to some degree, dependent on PACT-mediated PKR activation apart from the PERK pathway.

ipids are an essential component in the pathogenesis of atherosclerosis. As atherosclerosis advances, lipids play an important role in determining plaque vulnerability. [1][2][3] Vulnerable plaques are characterized by distinct morphological features: thin fibrous caps and enlarged lipid cores. 4 -6 The latter is composed of free and modified cholesterols, phospholipids, triacylglycerol, and fatty acids. 7 Cholesterols, which comprise the main component of these lipid cores, can exist in a soft gruel-like phase and in various crystallized forms such as plates, needles, and sometimes helices. 8,9 Recently, Virmani et al 6 reported that ruptured plaques contain greater amounts of cholesterol clefts or crystals in their necrotic cores than stable plaques, potentially indicating that these cholesterol clefts and crystals may be partly responsible for plaque vulnerability. However, little is known about the role of lipid crystals in the pathogenesis of atherosclerosis and plaque vulnerability, most likely because of the lack of currently available non-tissue-destructive imaging techniques and ex vivo chemical profiling tools.Nonlinear spectroscopic imaging modalities have the potential to visualize cellular organelles and tissue architecture with molecular specificity. Coherent anti-Stokes Raman scattering (CARS) microcopy has recently emerged as the most viable means for 3D chemical imaging of tissues. 10 -12 It works by probing intrinsic molecular vibrations, which obviates the need to label target molecules and fix specimens. 13 Original received September 8, 2009; revision received March 2, 2010; accepted March 9, 2010 CARS microscopy has been used in a full-scale biological study of lipid metabolism in a living organism after direct evidence of the undesirable bias associated with fluorescence labeling techniques was demonstrated. 14 Recently, a videorate CARS microscopy system has been developed for imaging skin tissue in vivo. 15,16 Because of the nonlinear nature of the CARS process, rapid scanning of the tight focal spot over the specimen permitted real-time acquisition of vibrational contrast images with 3D submicron resolution, 14 which is not possible with conventional Raman microscopes. CARS microscopy is particularly ideal for selective imaging of lipids because of the abundance of carbon-hydrogen (CH) bonds that exist in lipids as compared to the surrounding tissues. Lipids exhibit strong and distinct vibrational signatures in CARS spectra from 2700 to 3100 cm Ϫ1 . 15,16 Because of these unique characteristics, CARS microscopy is a suitable tool for atherosclerosis which is one of lipid-related diseases. Le et al applied CARS to image lipid-laden cells in atheroma, 17 and the morphological components of arterial walls were imaged as well 18 by integrating other nonlinear optics such as second harmonic generation and 2-photon auto-fluorescence (TPAF) into CARS. However, detailed chemical analysis of lipid composition beyond mere vibrational histology is still limited in the currently available CAR...

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Fast signal processing and real-time displays are essential for practical imaging modality in various fields of applications. However, the imaging speed in optical-resolution photoacoustic microscopy (OR-PAM), in particular, depends on factors such as the pulse repetition rate of the laser, scanning method, field of view (FOV), and signal processing time. In the past, efforts to increase acquisition speed either focused on developing new scanning methods or using lasers with higher pulse repetition rates. However, high-speed signal processing is also important for real-time volumetric display in OR-PAM. In this study, we carried out parallel signal processing using a graphics processing unit (GPU) to enable fast signal processing and wide-field real-time displays in laser-scanning OR-PAM. The average total GPU processing time for a B-mode PAM image was approximately 1.35 ms at a display speed of 480 fps when the data samples were acquired with 736 (axial) × 500 (lateral) points/B-mode-frame at a pulse repetition rate of 300 kHz. In addition, we successfully displayed maximum amplitude projection images of a mouse's ear as volumetric images with an FOV of 3 mm × 3 mm (500 × 500 pixels) at 1.02 s, corresponding to 0.98 fps.

No abstract

We present a new family of fluorescent probes which can image ALDH activity in cells.

The ineidenee ofacute mastoiditis has declin ed dramatieally during the postantibiotie era. Even so, antibioticresistant or unu sual path ogens can still eause this disease entity. At ou r hospital, we docum ented an increa se in antibiotic-r esistant and atypi eal pathogens such as Aetinomyce s spp. and Mycobacterium tuberc ulosis. In this pap er, we diseuss the optimal dia gno sis and treatm ent strategy for aeute mastoiditis, and we deserib e our retrospeetive revi ew of 13 patients with mastoiditis who were treated at our hospital from 1988 throu gh 1998. Eight of these pati ents reeo vered f ollowing treatmeilt with intravenous antibiotics, with or without myrin gotomy, andfive who had complications of diseas e were managed surgieally. Among these five , one de velop ed chronic otitis media and one deve loped eholesteatoma 3 years later. For patients with ac ute mastoiditis, we eniphasize the need to be aware of any unusua l pathogens tha t do not respand to emp iric atu ibiotic therapy.