Two-stage error detection to improve electron microscopy image mosaicking.

Large-scale electron microscopy (EM) has enabled the reconstruction of brain connectomes at the synaptic level by serially scanning over massive areas of sample sections. The acquired big EM data sets raise the great challenge of image mosaicking at high accuracy. Currently, it simply follows the conventional algorithms designed for natural images, which are usually composed of only a few tiles, using a single type of keypoint feature that would sacrifice speed for stronger performance. Even so, in the process of stitching hundreds of thousands of tiles for large EM data, errors are still inevitable and diverse. Moreover, there has not yet been an appropriate metric to quantitatively evaluate the stitching of biomedical EM images. Here we propose a two-stage error detection method to improve the EM image mosaicking. It firstly uses point-based error detection in combination with a hybrid feature framework to expedite the stitching computation while maintaining high accuracy. Following is the second detection of unresolved errors with a newly designed metric of EM stitched image quality assessment (EMSIQA). The novel detection-based mosaicking pipeline is tested on large EM data sets and proven to be more effective and as accurate when compared with existing methods.

A point-of-care detection platform for Escherichia coli O157:H7 by integration of smartphone and the structural colour of photonic microsphere.

A smartphone-based sensitive, rapid, label-free and high-throughput detection platform for Escherichia coli O157:H7 was established. The specific recognition capability of this platform was dependent of the aptamer modified on the silica photonic microsphere (SPM), whose structural colour was utilized for the quantification of the target bacterium. Gold nanoparticles and silver staining technique were employed to improve the sensitivity of the detection platform. Such smartphone-based detection platform gave a wide linear detection range of 102 âˆ¼ 108 CFU/mL with a low limit of detection (LOD) of 68 CFU/mL and high specificity for Escherichia coli O157:H7. Moreover, the recovery rates of the detection method were measured in the range of 99 âˆ¼ 108% in the milk, pork and purified water samples. Furthermore, the developed detection platform did not require complex sample pretreatment and could be easily manipulated, displaying great application potential in the fields of food safety, environmental monitoring and disease diagnosis.

Identification of potential pathogenic genes for severe aplastic anemia by whole-exome sequencing.

BACKGROUND: Severe aplastic anemia (SAA) is a syndrome of severe bone marrow failure due to hyperfunction of CD8+ T cells. While, the genetic background of SAA is still unknown. In this study, we tried to explore the possible genetic variants in CD8+ T cells of SAA patients. METHODS: We performed whole-exome sequencing (WES) in CD8+ T cells of 4 SAA patients and 7 normal controls. The mutations that existed in SAA but not in NCs were identified as candidate genes. Then, we compared them with genes in the enriched KEGG pathway of differently expressed genes (DEGs) from previous RNA-seq. After analyzing the types of mutations, we identified possible pathogenic genes and validated them by RT-PCR. Finally, we compared them with the autoimmune disease-related genes in DisGeNET database to select the most possible pathogenic genes. RESULTS: We found 95 candidate mutant genes in which, 4 possible pathogenic genes were identified: PRSS1, KCNJ18, PRSS2, and DGKK. RT-PCR results showed that compared with NCs, PRSS1 and KCNJ18 mRNA expression was significantly increased in SAA patients (p < 0.05), PRSS2 was also increased in SAA patients but without statistical difference, and DGKK gene could not be detected by RT-PCR in SAA patients. In addition, PRSS1 was associated with autoimmune diseases from the DisGeNET database. CONCLUSION: The mutations of PRSS1, KCNJ18, PRSS2, and DGKK, especially PRSS1 in CD8+T cells, may be involved in the immune pathogenesis of SAA.

Positioning Performance of a Sub-Arc-Second Micro-Drive Rotary System.

In the macro/micro dual-drive rotary system, the micro-drive system compensates for the position error of the macro-drive system. To realize the sub-arc-second (i.e., level of 1″-0.1″) positioning of the macro/micro dual-drive rotary system, it is necessary to study the positioning performance of the sub-arc-second micro-drive rotary system. In this paper, we designed a sub-arc-second micro-drive rotary system consisting of a PZT (piezoelectric actuator) and a micro rotary mechanism, and used simulation and experimental methods to study the positioning performance of the system. First, the micro-drive rotary system was developed to provide ultra-precise rotary motion. In this system, the PZT has ultrahigh resolution at a level of 0.1 nanometers in linear motion; a micro rotating mechanism was designed according to the composite motion principle of the flexible hinge, which could transform the linear motion of piezoelectric ceramics into rotating motion accurately. Second, the drive performance was analyzed based on the drive performance experiment. Third, kinematics, simulation, and experiments were carried out to analyze the transformation performance of the system. Finally, the positioning performance equation of the system was established based on the two performance equations, and the maximum rotary displacements and positioning error of the system were calculated. The study results showed that the system can provide precision motion at the sub-arc-second and good linearity of motion. This study has a certain reference value in ultra-precision positioning and micromachining for research on rotary motion systems at the sub-arc-second level.

Hydrogenation of CO2 to Methanol Catalyzed by Cp*Co Complexes: Mechanistic Insights and Ligand Design.

A direct hydride transfer mechanism with three cascade cycles for the conversion of carbon dioxide and dihydrogen to methanol (CO2 + 3H2 → CH3OH + H2O) catalyzed by a half-sandwich cobalt complex [Cp*Co(bpy-Me)OH2]2+ (1) is proposed based on density functional theory calculations. The formation of methanediol via hydride transfer from Co to formic acid (4 → TS8,11) is the rate-determining step with a total barrier of 26.0 kcal/mol in free energy. Furthermore, 15 analogues of 1 are constructed by replacing the hydrogen atoms at the two meta and para positions of the bipyridine ligand with different functional groups (1b-1l), the carbon atoms in the bipyridine ligand with nitrogen atoms (1m-1o), and one pyridine ligand with N-heterocyclic carbene (1p). Among all newly proposed complexes, [Cp*Co(2,2'-bipyrazine)OH2]2+ (1n) is the most active one with a total barrier of 19.6 kcal/mol in free energy. Such a low barrier indicates 1n is a promising catalyst for efficient conversion of CO2 and H2 to methanol at room temperature.

Fast esophageal layer segmentation in OCT images of guinea pigs based on sparse Bayesian classification and graph search.

Endoscopic optical coherence tomography (OCT) devices are capable of generating high-resolution images of esophageal structures at high speed. To make the obtained data easy to interpret and reveal the clinical significance, an automatic segmentation algorithm is needed. This work proposes a fast algorithm combining sparse Bayesian learning and graph search (termed as SBGS) to automatically identify six layer boundaries on esophageal OCT images. The SBGS first extracts features, including multi-scale gradients, averages and Gabor wavelet coefficients, to train the sparse Bayesian classifier, which is used to generate probability maps indicating boundary positions. Given these probability maps, the graph search method is employed to create the final continuous smooth boundaries. The segmentation performance of the proposed SBGS algorithm was verified by esophageal OCT images from healthy guinea pigs and the eosinophilic esophagitis (EoE) models. Experiments confirmed that the SBGS method is able to implement robust esophageal segmentation for all the tested cases. In addition, benefiting from the sparse model of SBGS, the segmentation efficiency is significantly improved compared to other widely used techniques.

Carboxymethyl cellulose modified graphene oxide as pH-sensitive drug delivery system.

Nanotechnology has been studied to improve drug delivery and cancer treatment. The aim of this study is to introduce amino groups into graphene oxide (GO) to form aminated fumed graphene (GO-ADH) and combine GO-ADH with carboxymethyl cellulose (CMC) to produce GO-CMC complex as a drug carrier matrix. The anti-cancer drug small molecule doxorubicin hydrochloride (DOX) was bond to GO-CMC by π-π bond interaction and hydrogen bonding to form GO-CMC/DOX drug loading system. Via the FT-IR, transmission electron microscopy (TEM) and Zeta potential analyzer analysis showed that GO-CMC complex was successfully synthesized. Studies have shown that when pH=5.0, the cumulative release rate of drugs can reach 65.2%, which means it has pH-sensitive ability. The cells were treated with MTT method and human cervical cancer cells (Hela cells) and mouse fibroblasts (NIH-3T3 cells). The results showed that GO-CMC had no obvious cytotoxicity and good biocompatibility.

Preparation and characterization of aminoethyl hydroxypropyl starch modified with collagen peptide.

The preparation of aminoethyl hydroxypropyl starch collagen peptide (AEHPS-COP) was via an enzyme-catalyzed reaction between amino groups in aminoethyl hydroxypropyl starch (AEHPS) and γ-carboxamide groups in collagen peptide (COP) by using microbial transglutaminase (MTGase) as biocatalyst. As an intermediate reactant, AEHPS was synthesized from hydroxypropyl starch (HPS) and 2-chloroethylamine hydrochloride (CEH). The chemical structures of HPS, AEHPS and AEHPS-COP were characterized by Fourier transform infrared spectroscopy (FT-IR) and 13C nuclear magnetic resonance (13C NMR). The reaction conditions that influenced the degree of substitution (DS) of AEHPS-COP were optimized, which included the reaction temperature, the reaction time, the mass ratio of collagen peptide to aminoethyl hydroxypropyl starch and the pH value. In addition, in vitro antioxidant activities of AEHPS-COP were evaluated through the scavenging activity of hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. Furthermore, the methylthiazol tetrazolium (MTT) assay was applied to investigate the cell viability of AEHPS-COP. The results indicated that the AEHPS-COP exhibited better cell viability to L929 mouse fibroblast cells. Therefore, the AEHPS-COP showed a promising potential application in cosmetic, biomedical and pharmaceutical fields.

Enzymatic synthesis of N-succinyl chitosan-collagen peptide copolymer and its characterization.

Collagen peptide (COP) grafted N-succinyl chitosan (NSC) was prepared by using microbial transglutaminase (MTGase) as biocatalyst. The catalyzed reaction displayed high efficiency, high selectivity, mild reaction condition and environmental friendliness. The degree of substitution (DS) of N-succinyl chitosan-collagen peptide (NSC-COP)depended on the reaction time, the reaction temperature, the mass ratio of COP to NSC and the mass ratio of MTGase to NSC. NSC-COP showed excellent moisture absorption and retention properties. Antioxidant activities of varying DS and concentration of NSC-COP were evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl. Methylthiazol tetrazolium (MTT) assay exhibited that at a suitable concentration NSC-COP with different DS value could promote L929 mouse fibroblasts effectively. The animal experiment indicated that the wound covered with NSC-COP were completely filled with new epithelium within 2 weeks without any significant adverse side reactions. Therefore, the results may contribute to finding the application of NSC-COP in pharmaceutical and biomedical fields.

Hydrogenation of Carbon Dioxide to Methanol Catalyzed by Iron, Cobalt, and Manganese Cyclopentadienone Complexes: Mechanistic Insights and Computational Design.

Density functional theory study of the hydrogenation of carbon dioxide to methanol catalyzed by iron, cobalt, and manganese cyclopentadienone complexes reveals a self-promoted mechanism, which features a methanol- or water-molecule-assisted proton transfer for the cleavage of H2 . The total free energy barrier of the formation of methanol from CO2 and H2 catalyzed by Knölker's iron cyclopentadienone complex, [2,5-(SiMe3 )2 -3,4-(CH2 )4 (η5 -C4 COH)]Fe(CO)2 H, is 26.0 kcal mol-1 in the methanol solvent. We also evaluated the catalytic activities of 8 other experimentally reported iron cyclopentadienone complexes and 37 iron, cobalt, and manganese cyclopentadienone complexes proposed in this study. In general, iron and manganese complexes have relatively higher catalytic activities. Among all calculated complexes, [2,5-(SiMe3 )2 -3,4-CH3 CHSCH2 (η5 -C4 COH)]Fe(CO)2 H (1Fe-Casey-S-CH3 ) is the most active one with a total free energy barrier of 25.1 kcal mol-1 in the methanol solvent. Such a low barrier indicates that 1Fe-Casey-S-CH3 is a very promising low-cost and high efficiency catalyst for the conversion of CO2 and H2 to methanol under mild conditions.

Computational Design of Cobalt Catalysts for Hydrogenation of Carbon Dioxide and Dehydrogenation of Formic Acid.

A series of cobalt complexes with acylmethylpyridinol and aliphatic PNP pincer ligands are proposed based on the active site structure of [Fe]-hydrogenase. Density functional theory calculations indicate that the total free energy barriers of the hydrogenation of CO2 and dehydrogenation of formic acid catalyzed by these Co complexes are as low as 23.1 kcal/mol in water. The acylmethylpyridinol ligand plays a significant role in the cleavage of H2 by forming a strong Co-Hδ-···Hδ+-O dihydrogen bond in a fashion of frustrated Lewis pairs.

A mechanistic study and computational prediction of iron, cobalt and manganese cyclopentadienone complexes for hydrogenation of carbon dioxide.

A series of cobalt and manganese cyclopentadienone complexes are proposed and examined computationally as promising catalysts for hydrogenation of CO2 to formic acid with total free energies as low as 20.0 kcal mol-1 in aqueous solution. Density functional theory study of the newly designed cobalt and manganese complexes and experimentally reported iron cyclopentadienone complexes reveals a stepwise hydride transfer mechanism with a water or a methanol molecule assisted proton transfer for the cleavage of H2 as the rate-determining step.

Sodium alginate conjugated graphene oxide as a new carrier for drug delivery system.

The biomedical applications of graphene-based materials, including drug delivery, have grown rapidly in the past few years. The aim of this present study is to enhance the efficiency and specificity of anticancer drug delivery and realize intelligently controlled release and targeted delivery. Graphene oxide (GO) was first prepared from purified natural graphite according to a modified Hummers' method. Then GO was functionalized with adipic acid dihydrazide to introduce amine groups, and sodium alginate (SA) was covalently conjugated to GO by the formation of amide bonds. The resulting GO-SA conjugate was characterized and used as a carrier to encapsulate the anticancer drug doxorubicin hydrochloride (DOX·HCl) to study in vitro release behavior. The maximum loading capacity of DOX on GO-SA was 1.843mg/mg and the drug release rate under tumor cell microenvironment of pH 5.0 was significantly higher than that under physiological conditions of pH 6.5 and 7.4. Methylthiazol tetrazolium (MTT) assay was applied to evaluate the Hela cells and NIH-3T3 cells cytotoxicity of GO-SA. Results showed that GO-SA had no obvious toxicity and GO-SA/DOX exhibits notable cytotoxicity to Hela cells. Cell uptake studies indicated that GO-SA could specifically transport the DOX into Hela cells over-expressing CD44 receptors and showed enhanced toxicity.

Preparation and characterization of hydroxypropyl chitosan modified with collagen peptide.

Collagen peptide (COP) had been grafted to hydroxypropyl chitosan (HPCS) by using microbial transglutaminase (MTGase) as biocatalyst. HPCS was synthesized from chitosan and propylene oxide under alkali condition. The chemical structures of derivative were characterized by FT-IR and 1H NMR spectroscopy. The process conditions were optimized from the aspects of the reaction time, the reaction temperature, the molar ratio of COP and the mass ratio of MTGase to HPCS. In this study, HPCS-COP could serve not only to reduce the loss of moisture but also to absorb the moisture, and the moisture absorption and moisture retention abilities were closely related to the degree of substitution (DS) values. In addition, with the DS and concentration increase of HPCS-COP, the radical scavenging activity increased in vitro antioxidant activity. Furthermore, the methyl thiazolyl tetrazolium assay (MTT) was applied to evaluate the biocompatibility of HPCS-COP, and the result indicated that HPCS-COP with the DS of 0.34 displayed pronounced cell viability at 50ppm. Therefore, the results suggest that HPCS-COP could be potential wound dressings for clinical applications.

Preparation and characterization of oxidized konjac glucomannan/carboxymethyl chitosan/graphene oxide hydrogel.

Polysaccharide hydrogels have been widely used as biomaterials in biomedical field. In this article, composite hydrogels were prepared through the Schiff-base reaction between the aldehyde of oxidized konjac glucomannan (OKGM) and the amino of carboxymethyl chitosan (CMCS). Meanwhile, different amount of graphene oxide (GO) was added as nano-additive. The hydrogels have been characterized by various methods including Fourier transform infrared spectroscopy (FT-IR) and Surface morphology (SEM). Through the observation of SEM, the hydrogels' scaffolds present a homogeneous interconnected pore structure after lyophilizing. In addition, the influence of different GO content on properties including gelation time, swelling ability, water evaporation rate and mechanical properties was investigated. The results indicate that the hydrogels have short gelation time, appropriate swelling ability and water evaporation rate. Especially, the compressive strength and modulus increase 144% and 296% respectively as the GO content increase from 0 to 5mg/ml. Moreover, MTT assay was applied to evaluate the biocompatibility of hydrogels. The result indicate that hydrogels with GO show better biocompatibility. Therefore, due to the appropriate water absorption capacity, the similar compressive modulus with soft tissue and excellent biocompatibility, the composite hydrogels have potential application in wound dressings.

Ratcheting behavior of articular cartilage under cyclic unconfined compression.

The ratcheting deformation of articular cartilage can produce due to the repeated accumulations of compressive strain in cartilage. The aim of this study was to investigate the ratcheting behavior of articular cartilage under cyclic compression. A series of uniaxial cyclic compression tests were conducted for online soaked and unsoaked cartilage samples and the effects of stress variation and stress rate on ratcheting behavior of cartilage were investigated. It is found that the ratcheting strains of online soaked and unsoaked cartilage samples increase rapidly at initial stage and then show the slower increase with cyclic compression going on. On the contrary, the ratcheting strain rate decreases quickly at first and then exhibits a relatively stable and small value. Both the ratcheting strain and ratcheting strain rate increase with stress variation increasing or with stress rate decreasing. Simultaneously, the optimized digital image correlation (DIC) technique was applied to study the ratcheting behavior and Young's modulus of different layers for cartilage under cyclic compression. It is found that the ratcheting behavior of cartilage is dependent on its depth. The ratcheting strain and its rate decrease through the depth of cartilage from surface to deep, whereas the Young's modulus increases.

Up-Regulation of miR-204 Enhances Anoikis Sensitivity in Epithelial Ovarian Cancer Cell Line Via Brain-Derived Neurotrophic Factor Pathway In Vitro.

OBJECTIVE: Genomic loci encoding miR-204, which was predicted to target brain-derived neurotrophic factor (BDNF), were frequently lost in multiple cancer, including epithelial ovarian cancer (EOC). In this study, we aimed to find out the influence of miR-204 expression level on EOC cell anoikis sensitivity and to explore possible mechanisms of this process. METHODS: First, we screened EOC cells, which maintain anoikis resistance forming an anoikis pattern. miR-204 expression level and apoptosis were measured, respectively, by quantitative reverse transcriptase polymerase chain reaction and Annexin-V-R-PE/7-amino-actinomycin assay. Then we restored the expression level of miR-204 by transfection with pre-miR-204. miR-204 expression level and apoptosis were measured as before; cell invasion and migration ability were detected by transwell invasion assay and wound-healing assay. The messenger RNA level of BDNF was also detected by quantitative reverse transcriptase polymerase chain reaction; Western blot analysis was performed to assess pAKT expression. RESULTS: Expression of miR-204 is significantly down-regulated in an anoikis pattern. Restored expression level of miR-204 enables cells to acquire more sensitivity to anoikis and decrease invasive and metastatic behavior, and also results in BDNF down-expression and inhibits activation of mitochondria-dependent pathway through the PI3K/AKT signaling pathway leading to cancer cell anoikis in EOC cells. CONCLUSIONS: miR-204 up-regulation may be linked directly to the sensitivity of EOC cell anoikis by contributing to BDNF down-regulation. Our findings provide a novel mechanism for manipulating miR-204 levels therapeutically to restore anoikis sensitivity.