High detection efficiency silicon single-photon detector with a monolithic integrated circuit of active quenching and active reset.

Silicon single-photon detectors (SPDs) are key devices for detecting single photons in the visible wavelength range. Photon detection efficiency (PDE) is one of the most important parameters of silicon SPDs, and increasing PDE is highly required for many applications. Here, we present a practical approach to increase the PDE of silicon SPDs with a monolithic integrated circuit of active quenching and active reset (AQAR). The AQAR integrated circuit is specifically designed for thick silicon single-photon avalanche diodes (SPADs) with high breakdown voltage (250 V-450 V) and then fabricated via the process of high-voltage 0.35-µm bipolar-CMOS-DMOS. The AQAR integrated circuit implements the maximum transition voltage of ∼68 V with 30 ns quenching time and 10 ns reset time, which can easily boost PDE to the upper limit by regulating the excess bias up to a high enough level. By using the AQAR integrated circuit, we design and characterize two SPDs with the SPADs disassembled from commercial products of single-photon counting modules (SPCMs). Compared with the original SPCMs, the PDE values are increased from 68.3% to 73.7% and 69.5% to 75.1% at 785 nm, respectively, with moderate increases in dark count rate and afterpulse probability. Our approach can effectively improve the performance of the practical applications requiring silicon SPDs.

OsDCL3b affects grain yield and quality in rice.

KEY MESSAGE: We reported that knockdown of OsDCL3b decreased grain yield but increased grain quality in rice, which is helpful for molecular breeding in crops. Multiple DICER-LIKE (DCL) genes usually exist and show diverse biochemical and phenotypic functions in land plants. In rice, the biochemical function of OsDCL3b is known to process 24-nucleotide panicle phased small RNAs, however, its phenotypic functions are unclear. Here we reported that knockdown of OsDCL3b led to reduced pollen fertility, seed setting rate, and decreased grain yield but increased grain quality in rice. To reveal the molecular mechanism of the above phenomena, extracted RNAs from rice panicles of the wild type (WT) and OsDCL3b-RNAi line S6-1 were analyzed by deep sequencing. It showed that knockdown of OsDCL3b affected the biogenesis of both 21- and 24-nucleotide small RNAs including miRNAs and phased small RNAs. Using RNA-seq, 644 up- and 530 down-regulated mRNA genes were identified in panicles of line S6-1, and 550 and 273 differentially spliced genes with various alternative splicing (AS) events were observed in panicles of line S6-1 and WT, respectively, suggesting that OsDCL3b involved in influencing the transcript levels of mRNA genes and the AS events in rice panicles. Thus, our results show that knockdown of OsDCL3b will affect the biogenesis of small RNAs, which is involved in regulating the transcription of mRNA genes, and consequently influence the grain yield and quality in rice.

Hypoxia-inducible factor-1α and Wnt/ß-catenin signaling pathways promote the invasion of hypoxic gastric cancer cells.

The present study aimed to examine the association between hypoxia-inducible factor (HIF)-1α and the Wnt/ß-catenin signaling pathway in a hypoxic environment. The study also aimed to explore the possible mechanisms underlying the invasion of hypoxic gastric cancer cells in vitro and in vivo. The pcDNA™ 6.2­GW/EmGFP­miR­ß­catenin plasmid was transfected into SGC­7901 gastric cancer cells, resulting in cells with stable suppression of ß­catenin expression. The biological characteristics of the control, liposome, negative control, ß­catenin knockdown, hypoxia and hypoxia ß­catenin knockdown groups were tested using an invasion assay. The differences in the invasive capacity of the control, negative control and liposome groups were not statistically significant. However, the hypoxia group demonstrated a significantly enhanced invasive capacity, as compared with that in the control group (P<0.05). In the hypoxia ß­catenin knockdown group, reduced cell penetration and diminished invasive behavior was observed (P<0.05). In the hypoxia and double (chemical + physical) hypoxia groups, HIF­1α, ß­catenin, urokinase­type plasminogen activator (uPA) and matrix metalloproteinase (MMP­7) protein and mRNA expression levels were elevated. In response to knockdown of ß­catenin expression, HIF­1α, ß­catenin, uPA and MMP­7 protein as well as mRNA expression levels were significantly reduced in the hypoxia ß­catenin knockdown and the double hypoxia ß­catenin knockdown groups. In an in vivo experiment, the growth rate of xenograft tumors of hypoxic and control cells was high alongside increased HIF­1α, ß­catenin, uPA and MMP­7 levels according to western blot and immunohistochemical analyses, while growth and protein levels of tumors from hypoxic ß­catenin knockdown cells were significantly lower and those of ß­catenin knockdown cells were lowest. In conclusion, these results suggested that HIF­1α activation was able to regulate the Wnt/ß­catenin pathway, and that HIF­1α may be controlled by the Wnt/ß­catenin pathway. A potential mechanism underlying SGC­7901 tumorigenicity is the activation of the Wnt/ß­catenin signaling pathway, which activates uPA and MMP­7 expression and contributes to the enhanced invasion of hypoxic cancer cells.

Expression pattern and tissue localization of the class B scavenger receptor BmSCRBQ4 in Bombyx mori.

Class B scavenger receptors (SR-Bs) are cell surface glycoproteins involved in various physiological processes in vivo, including the transport and metabolism of lipids, binding and phagocytosis of xenobiotics, and signaling. But little information is available about silkworm SR-Bs; it is necessary to study these SR-Bs for revealing their function. In this study, we cloned the full-length coding sequence of BmSCRBQ4, a SR-B gene from the silkworm Bombyx mori L. We found that the BmSCRBQ4 gene consists of nine exons and eight introns, with an open reading frame of 1371 bp encoding 456 amino acids. Gene expression studies determined that BmSCRBQ4 messenger RNA (mRNA) was expressed in unfertilized eggs, during embryonic development and throughout the majority of the larval period. Expression of mRNA was detected in the mid gut, middle silk gland, posterior silk gland, head, integumentum, fat body, testes and the ovaries of the larval B. mori Dazao strain, as well as in the silkworm cell lines BmN and BmE. Protein expression studies found BmSCRBQ4 protein was expressed only in the testes, fat body and middle silk gland of larvae, as well as in the silkworm cell lines BmN and BmE. The BmSCRBQ4 protein showed variability in banding patterns in different tissues and cells when analyzed by Western blotting. Immunohistochemical staining showed that the BmSCRBQ4 protein localizes to the constitutive membranes or cellular membranes of these tissues. These results indicated that BmSCRBQ4 gene may play some physiologically relevant roles at the cell surface in each tissue.