Room temperature operation of germanium-silicon single-photon avalanche diode.

The ability to detect single photons has led to the advancement of numerous research fields1-11. Although various types of single-photon detector have been developed12, because of two main factors-that is, (1) the need for operating at cryogenic temperature13,14 and (2) the incompatibility with complementary metal-oxide-semiconductor (CMOS) fabrication processes15,16-so far, to our knowledge, only Si-based single-photon avalanche diode (SPAD)17,18 has gained mainstream success and has been used in consumer electronics. With the growing demand to shift the operation wavelength from near-infrared to short-wavelength infrared (SWIR) for better safety and performance19-21, an alternative solution is required because Si has negligible optical absorption for wavelengths beyond 1 µm. Here we report a CMOS-compatible, high-performing germanium-silicon SPAD operated at room temperature, featuring a noise-equivalent power improvement over the previous Ge-based SPADs22-28 by 2-3.5 orders of magnitude. Key parameters such as dark count rate, single-photon detection probability at 1,310 nm, timing jitter, after-pulsing characteristic time and after-pulsing probability are, respectively, measured as 19 kHz µm-2, 12%, 188 ps, ~90 ns and <1%, with a low breakdown voltage of 10.26 V and a small excess bias of 0.75 V. Three-dimensional point-cloud images are captured with direct time-of-flight technique as proof of concept. This work paves the way towards using single-photon-sensitive SWIR sensors, imagers and photonic integrated circuits in everyday life.

Morphological control of mitochondria as the novel mechanism of Gastrodia elata in attenuating mutant huntingtin-induced protein aggregations.

BACKGROUND: According to Compendium of Materia Medica, Gastrodia elata (GE) Blume as a top grade and frequently prescribed herbal medicine has been used in treating dizziness, headaches, and epilepsy, indicating a neuroprotective effect. Because GE is capable of suppressing a hyperactive liver and thus calming endogenous wind, and because Huntington's disease (HD) can be classified as a phenomenon of disturbed liver wind, it is suggested that GE might be beneficial in treating HD. However, although current studies support GE for the prevention of diverse neurodegenerations such as HD, its detailed mechanisms remain elusive. PURPOSE: To investigate the molecular mechanism of GE in preventing HD by focusing on mitochondrial morphology, which is highly associated with HD etiology and thus proposed as a therapeutic target of neurodegenerations. STUDY DESIGN/METHODS: The overexpression of the mutant huntingtin (mHTT) gene in rat pheochromocytoma (PC12) cells was used as an in vitro cell model of HD. A filter retardation assay was applied to measure protein aggregations during HTT expression. Cotransfection with mitochondrial fusion and fission genes was used to test their relationships with HTT aggregates by monitoring with a confocal laser scanning microscope and filter retardation assay. Western blot analysis was used to estimate protein expression under different drug treatments or cotransfections with other related genes. RESULTS: The overexpression of mutant but not normal HTT genes significantly resulted in protein aggregations in PC12 cells. GE dose-dependently attenuated mHTT-induced protein aggregations and free radical formations. GE significantly reversed mHTT-induced mitochondrial fragmentation and dysregulation of mitochondrial fusion and fission molecules. The overexpression of mitochondrial fusion genes attenuated mHTT-induced protein aggregations. Further, Mdivi-1, a DRP1 fission molecule inhibitor, significantly reversed mHTT-induced protein aggregations and mitochondrial fragmentation. CONCLUSION: GE attenuated mHTT aggregations through the control of mitochondrial fusion and the fission pathway.

3D Imaging of Tapetal Mitochondria Suggests the Importance of Mitochondrial Fission in Pollen Growth.

Mitochondrial fission occurs frequently in plant cells, but its biological significance is poorly understood because mutants specifically impaired in mitochondrial fission do not show obvious defects in vegetative growth. Here, we revealed that the production of viable pollen was reduced in mutants lacking one of the three main proteins involved in mitochondrial fission in Arabidopsis (Arabidopsis thaliana), DYNAMIN-RELATED PROTEIN3A (DRP3A)/Arabidopsis DYNAMIN-LIKE PROTEIN2A, DRP3B, and ELONGATED MITOCHONDRIA1 (ELM1). In drp3b and elm1, young microspores contained an abnormal number of nuclei, and mature pollen had aberrant accumulation of lipids in their coat and an irregular pollen outer wall. Because the formation of the pollen wall and coat is mainly associated with tapetal function, we used 3D imaging to quantify geometric and textural features of cells and mitochondria in the tapetum at different stages, using isolated single tapetal cells in which the in vivo morphology and volume of cells and mitochondria were preserved. Tapetal cells and their mitochondria changed in the volume and morphology at different developmental stages. Defective mitochondrial fission in the elm1 and drp3b mutants caused changes in mitochondrial status, including mitochondrial elongation, abnormal mitochondrial ultrastructure, a decrease in cross-sectional area, and a slight alteration of mitochondrial distribution, as well as a large reduction in mitochondrial density. Our studies suggest that mitochondrial fission is required for proper mitochondrial status in the tapetum and possibly in pollen as well and therefore plays an important role for the production of viable pollen.

Novel Cancer Therapeutics with Allosteric Modulation of the Mitochondrial C-Raf-DAPK Complex by Raf Inhibitor Combination Therapy.

Mitochondria are the powerhouses of cells. Mitochondrial C-Raf is a potential cancer therapeutic target, as it regulates mitochondrial function and is localized to the mitochondria by its N-terminal domain. However, Raf inhibitor monotherapy can induce S338 phosphorylation of C-Raf (pC-Raf(S338)) and impede therapy. This study identified the interaction of C-Raf with S308 phosphorylated DAPK (pDAPK(S308)), which together became colocalized in the mitochondria to facilitate mitochondrial remodeling. Combined use of the Raf inhibitors sorafenib and GW5074 had synergistic anticancer effects in vitro and in vivo, but targeted mitochondrial function, rather than the canonical Raf signaling pathway. C-Raf depletion in knockout MEF(C-Raf-/-) or siRNA knockdown ACHN renal cancer cells abrogated the cytotoxicity of combination therapy. Crystal structure simulation showed that GW5074 bound to C-Raf and induced a C-Raf conformational change that enhanced sorafenib-binding affinity. In the presence of pDAPK(S308), this drug-target interaction compromised the mitochondrial targeting effect of the N-terminal domain of C-Raf, which induced two-hit damages to cancer cells. First, combination therapy facilitated pC-Raf(S338) and pDAPK(S308) translocation from mitochondria to cytoplasm, leading to mitochondrial dysfunction and reactive oxygen species (ROS) generation. Second, ROS facilitated PP2A-mediated dephosphorylation of pDAPK(S308) to DAPK. PP2A then dissociated from the C-Raf-DAPK complex and induced profound cancer cell death. Increased pDAPK(S308) modification was also observed in renal cancer tissues, which correlated with poor disease-free survival and poor overall survival in renal cancer patients. Besides mediating the anticancer effect, pDAPK(S308) may serve as a predictive biomarker for Raf inhibitors combination therapy, suggesting an ideal preclinical model that is worthy of clinical translation.

Impacts of autophagy-inducing ingredient of areca nut on tumor cells.

Areca nut (AN) is a popular carcinogen used by about 0.6-1.2 billion people worldwide. Although AN contains apoptosis-inducing ingredients, we previously demonstrated that both AN extract (ANE) and its 30-100 kDa fraction (ANE 30-100K) predominantly induce autophagic cell death in both normal and malignant cells. In this study, we further explored the action mechanism of ANE 30-100K-induced autophagy (AIA) in Jurkat T lymphocytes and carcinoma cell lines including OECM-1 (mouth), CE81T/VGH (esophagus), SCC25 (tongue), and SCC-15 (tongue). The results showed that chemical- and small hairpin RNA (shRNA)-mediated inhibition of AMP-activated protein kinase (AMPK) resulted in the attenuation of AIA in Jurkat T but not in OECM-1 cells. Knockdown of Atg5 and Beclin 1 expressions ameliorated AIA in OECM-1/CE81T/VGH/Jurkat T and OECM-1/SCC25/SCC-15, respectively. Furthermore, ANE 30-100K could activate caspase-3 after inhibition of Beclin 1 expression in OECM-1/SCC25/SCC15 cells. Meanwhile, AMPK was demonstrated to be the upstream activator of the extracellular-regulated kinase (ERK) in Jurkat T cells, and inhibition of MEK attenuated AIA in Jurkat T/OECM-1/CE81T/VGH cells. Finally, we also found that multiple myeloma RPMI8226, lymphoma U937, and SCC15 cells survived from long-term non-cytotoxic ANE 30-100K treatment exhibited stronger resistance against serum deprivation through upregulated autophagy. Collectively, our studies indicate that Beclin-1 and Atg5 but not AMPK are commonly required for AIA, and MEK/ERK pathway is involved in AIA. Meanwhile, it is also suggested that long-term AN usage might increase the resistance of survived tumor cells against serum-limited conditions.

A healthcare integration system for disease assessment and safety monitoring of dementia patients.

Elderly dementia patients often get lost due to lack of a sense of direction. This may put them at risk and cause their families much worry. The goal of this study is to use information technology to enhance the professional judgment of caregivers, strengthen internal safety monitoring at care organizations, and improve the quality of care for dementia patients. An eXtensible-Markup-Language-based dementia assessment system combining program code and assessment content is used to provide caregivers with better flexibility and real-time response ability. Beyond establishing long-term case files, the system can also perform data consistency analysis, strengthen caregivers' continuing education, improve caregivers' case judgment skills, and reduce the incidence of accidents due to neglect. This study also applies radio frequency identification (RFID) technology to the development of an indoor and outdoor active safety monitoring mechanism. The system can automatically remind caregivers whenever an elderly person approaches a dangerous area or strays too far. Apart from the use of different size tags, the realization of the system also employs the tame transformation signatures (TTS) algorithm to encrypt tag IDs and protect personal privacy. Clinical testing of the system showed that the indoor RFID reader has a response time of 0.5 s when sensing 40 tags, while the outdoor reader has a sensing time of approximately 5 s due to the need to save power. In the latter case, the system can ensure that elderly patients stay less than 15 m away from their caregivers. Patients were relatively willing to wear light tags. We also found that irritable patients with strong mobility were less compliant and often removed their own tags. Caregivers must provide active care and adopt various safety measures to protect the type of patients.