Construction and functional verification of size-reduced plasmids based on TMP resistance gene dfrB10.

IMPORTANCE: Plasmid size is one of the factors affecting transfection efficacy in most of the molecular genetic research studies. One effective approach for reducing plasmid size is to replace relatively large, conventional antibiotic resistance genes with the short-size dfrB10 gene. The successful construct of a series of dfrB10-based tool plasmids and their functional validation, via comparison with original plasmids, suggest that dfrB10 is a potent drug resistance selection marker. The antibiotic trimethoprim offers convenient usage comparable to that of ampicillin or kanamycin. Additionally, fluorescence analysis has demonstrated the compatibility of TMP with protein expression in various host cells. Based on these findings, TMP-dfrB10 could be an alternative choice for future use in molecular genetic research studies that require miniature plasmids to achieve optimal results.

Active control of terahertz waves based on hybrid VO2 periodic corrugated waveguides.

We describe a method for the active control of terahertz (THz) waves using hybrid vanadium dioxide (VO2) periodic corrugated waveguide. Unlike liquid crystals, graphene and semiconductors and other active materials, VO2 exhibits a unique insulator-metal transition characteristic by the electric fields, optical, and thermal pumps, resulting in five orders of magnitude changes in its conductivity. Our waveguide consists of two gold coated plates with the VO2-embedded periodic grooves, which are placed in parallel with the grooves face to face. Simulations show that this waveguide can realize mode switching by changing the conductivity of the embedded VO2 pads, whose mechanism is attributed to the local resonance induced by defect mode. Such a VO2-embedded hybrid THz waveguide is favorable in practical applications such as THz modulators, sensors and optical switches, and provides an innovative technique for manipulating THz waves.

The Comparison of PCR Kits for the Detection of Erythrocytic Parasites on Filter Paper.

Dried blood spot (DBS) based PCR was considered an inexpensive and feasible method for detecting pathogens in the blood. The DBS carrier filter paper and PCR kits are crucial for accurate diagnosis. We evaluated 4 types of filter papers and 20 PCR kits for DBS samples. The PCR detecting Plasmodium results showed that the minimum detection limit of the 4 filter papers was 1 × 102 parasites/µL, and the positive rates of 20 PCR kits ranged from 0% to 100%. PCR results were satisfactory for detecting Plasmodium falciparum (P. falciparum) and Plasmodium. vivax (P. vivax) in archived DBS samples and Babesia gibsoni (B. gibsoni) in fresh pet DBS samples. Our results provided a useful reference for the detection of blood pathogens with DBS samples and direct PCR, especially for screening the cost-efficacy combination of filter paper and PCR kit in resource-limited areas.

Plasmodium infection suppresses colon cancer growth by inhibiting proliferation and promoting apoptosis associated with disrupting mitochondrial biogenesis and mitophagy in mice.

BACKGROUND: Colon cancer is a common gastrointestinal tumor with a poor prognosis, and thus new therapeutic strategies are urgently needed. The antitumor effect of Plasmodium infection has been reported in some murine models, but it is not clear whether it has an anti-colon cancer effect. In this study, we investigated the anti-colon cancer effect of Plasmodium infection and its related mechanisms using a mouse model of colon cancer. METHODS: An experimental model was established by intraperitoneal injection of Plasmodium yoelii 17XNL-infected erythrocytes into mice with colon cancer. The size of tumors was observed dynamically in mice, and the expression of Ki67 detected by immunohistochemistry was used to analyze tumor cell proliferation. Apoptosis was assessed by terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, and the expression of apoptosis-related proteins including Bax, Bcl-2, caspase-9, and cleaved caspase-3 was detected by western blot and immunohistochemistry, respectively. Transmission electron microscopy (TEM) was used to observe the ultrastructural change in colon cancer cells, and the expression of mitochondrial biogenesis correlative central protein, PGC-1α, and mitophagy relevant crucial proteins, PINK1/Parkin, were detected by western blot. RESULTS: We found that Plasmodium infection reduced the weight and size of tumors and decreased the expression of Ki67 in colon cancer-bearing mice. Furthermore, Plasmodium infection promoted mitochondria-mediated apoptosis in colon cancer cells, as evidenced by the increased proportion of TUNEL-positive cells, the upregulated expression of Bax, caspase-9, and cleaved caspase-3 proteins, and the downregulated expression of Bcl-2 protein. In colon cancer cells, we found destroyed cell nuclei, swollen mitochondria, missing cristae, and a decreased number of autolysosomes. In addition, Plasmodium infection disturbed mitochondrial biogenesis and mitophagy through the reduced expression of PGC-1α, PINK1, and Parkin proteins in colon cancer cells. CONCLUSIONS: Plasmodium infection can play an anti-colon cancer role in mice by inhibiting proliferation and promoting mitochondria-mediated apoptosis in colon cancer cells, which may relate to mitochondrial biogenesis and mitophagy.

The complete mitochondrial genome of major malaria vector Anopheles anthropophagus (Diptera: Culicidae) in China.

Anopheles anthropophagus (Xu and Feng 1975) is the major vector of malaria in Eastern and Southern China. The species An. anthropophagus is considered a synonym of An. lesteri (Baisas & Hu, 1936), although they differ in several key biological characteristics. Here, we report the complete mitochondrial genome of An. anthropophagus for the first time. The mitogenome of An. anthropophagus is a typical circular, double-stranded molecule with a total length of 15,413 base pairs, and contains 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and an AT-rich control region. A phylogenetic analysis of the complete mitogenomes of 16 species of Anopheles (Culicidae) revealed that An. anthropophagus is closely related to An. sinensis (Wiedemann 1828), in the family Culicidae. The An. anthropophagus mitogenome provides new data for further taxonomic and phylogenetic studies of the genus Anopheles.

Dimeric artesunate-choline conjugate micelles coated with hyaluronic acid as a stable, safe and potent alternative anti-malarial injection of artesunate.

Artesunate (ARS) is the only artemisinin-based intravenous drug approved for treatment of malaria in the clinic. ARS is rapidly metabolized in vivo to short lived (∼30-45 min) but fast acting, dihydroartemisinin (DHA). The short half-life of DHA necessitates multiple dose administration to circumvent the risk of recrudescence and development of artemisinin resistance. In this work, we report a stable, safe and potent alternative artemisinin-based injectable nanocomplex consisting of dimeric artesunate-choline conjugate (dACC) micelles coated with hyaluronic acid (HA). Firstly, dACC was synthesized by one-step esterification of two artesunate molecules with 3-(dimethylamino)-1,2-propanediol followed by quaternization. After that, dACC was self-assembled into cationic nanomicelles and further coated with anionic small molecular weight HA. The HA-coated dACC nanocomplex (dACC/HA nanocomplex) has a narrow size distribution of about 30 nm. Hemolytic toxicity and cytotoxicity studies revealed a favorable bio-safety profile. Finally, in vitro and in vivo studies showed the dACC/HA nanocomplex possess superior safety and antimalarial efficacy compared to ARS. Taken together, the dACC/HA nanocomplex is a promising injectable alternative to the traditional clinically used artesunate.

Underwater image sharpening based on structure restoration and texture enhancement.

Light can be absorbed and scattered when traveling through water, which results in underwater optical images suffering from blurring and color distortion. To improve the visual quality of underwater optical images, we propose a novel, to the best of our knowledge, image sharpening method. We utilize the relative total variation model to decompose images into structure and texture layers in a novel manner. On those two layers, the red-blue dark channel prior (RBDCP) and detail lifting algorithms are proposed, respectively. The RBDCP model calculates background light based on brightness, gradient discrimination, and hue judgment, which then generates transmission maps using red-blue channel attenuation characteristics. The linear combination of the Gaussian kernel and binary mask is employed in the proposed detail lifting algorithm. Furthermore, we combine the layers of restoration structure and enhancement texture for image sharpening, inspired by the concept of fusion. Our methodology has rich texture information and is effective in color correction and atomization removal through RBDCP. Extensive experimental results indicate that the proposed method effectively balances image hue, saturation, and clarity.

Internal Cylinder Identification Based on Different Transmission of Longitudinal and Shear Ultrasonic Waves.

We have built a Fizeau fiber interferometer to investigate the internal cylindrical defects in an aluminum plate based on laser ultrasonic techniques. The ultrasound is excited in the plate by a Q-switched Nd:YAG laser. When the ultrasonic waves interact with the internal defects, the transmitted amplitudes of longitudinal and shear waves are different. The experimental results show that the difference in transmission amplitudes can be attributed to the high frequency damping of internal cylinders. When the scanning point is close to the internal defect, the longitudinal waves attenuate significantly in the whole defect area, and their amplitude is always smaller than that of shear waves. By comparing the transmitted amplitudes of longitudinal and shear waves at different scanning points, we can achieve a C scan image of the sample to realize the visual inspection of internal defects. Our system exhibits outstanding performance in detecting internal cylinders, which could be used not only in evaluating structure cracks but also in exploring ultrasonic transmission characteristics.

Hybrid structure of PbS QDs and vertically-few-layer MoS2 nanosheets array for broadband photodetector.

A novel three-dimensional (3D) vertically-few-layer MoS2 (V-MoS2) nanosheets- zero-dimensional PbS quantum dots (QDs) hybrid structure based broadband photodetector was fabricated, and its photoelectric performance was investigated in detail. We synthesized the V-MoS2 nanosheets by chemical vapor deposition, using the TiO2 layer as the induced layer, and proposed a possible growth mechanism. The use of the TiO2 induction layer successfully changed the growth direction of MoS2 from parallel to vertical. The prepared V-MoS2 nanosheets have a large specific surface area, abundantly exposed edges and excellent light absorption capacity. The V-MoS2 nanosheets detector was then fabricated and investigated, which exhibits a high sensitivity for 635 nm light, a fast response time and an excellent photoelectric response. The V-MoS2 nanosheets with a height of approximately 1 µm successfully broke the light absorption limit caused by the atomic thickness. Finally, we fabricated the PbS QDs/V-MoS2 nanosheets hybrid detector and demonstrated their potential for high-performance broadband photodetectors. The response wavelength of the hybrid detector extends from the visible band to the near-infrared band. The responsivity of the hybrid detector reaches 1.46 A W-1 under 1450 nm illumination. The combination of 3D MoS2 nanosheets and QDs further improves the performance of MoS2-based photodetector devices. We believe that the proposed zero-dimensional QDs and 3D vertical nanosheets hybrid structure broadband photodetector provides a promising way for the next-generation optoelectronic devices.

Self-catalyst ß-Ga2O3 semiconductor lateral nanowire networks synthesis on the insulating substrate for deep ultraviolet photodetectors.

Monoclinic gallium oxide (ß-Ga2O3) is a super-wide bandgap semiconductor with excellent chemical and thermal stability, which is an ideal candidate for detecting deep ultraviolet (DUV) radiation (100-280 nm). The growth of ß-Ga2O3 is challenging and most methods require Au as the catalyst and a long reacting time (more than 1 hour). In this work, the self-catalyst ß-Ga2O3 lateral nanowire networks were synthesized on an insulating substrate rapidly by a simple low-cost Chemical Vapor Deposition (CVD) method. A thin film of ß-Ga2O3 nanowire networks was synthesized within a reacting time of 15 minutes, which possesses a huge possibility for the rapid growth of ß-Ga2O3 metal oxide nanowires networks and application in the future solar-blind photodetector. MSM (metal-semiconductor-metal) photodetectors based on the ß-Ga2O3 nanowire networks revealed fast response (on-off ratios is about 103), which is attributed to the unique cross-junction barrier-dominated conductance of the nanowire networks. In addition, the self-catalyst ß-Ga2O3 nanowires grown on insulating SiO2 are achieved and could be expected to find important applications in a bottom-up way of fabricating the next generation semiconductor nanoelectronics.

Wave packet interactions in a thin aluminum plate partially immersed in water.

When investigating the wave propagation and mode conversions in a thin aluminum plate partially immersed in water, a kind of wave packet interaction was observed. It was found that the transmitted ultrasonic signal consists of different wave packets, which contain essential information of different wave types. When the incident angle is very small, the signals can be identified as the major wave packet followed by its tail. The major packet includes the information of the incident wave while the tail is related to the mode conversion and propagation in the plate. When the incident angle increased, the major packet was literally engulfed by its tail, indicating that the directly transmitted incident ultrasound disappeared and more energy was coupled into the plate. The interactions between different wave packets found here reveal the excitation and propagation mechanisms of Lamb waves in plates, which would benefit applications in ultrasonic imaging, signal recognition, underwater acoustic communication, and so on.

The use of facemasks may not lead to an increase in hand-face contact.

Advocacy of the use of facemasks by the public as a measure against the spread of COVID-19 is controversial, with some healthcare professionals arguing that the use of a face mask may increase the rate at which people touch their faces, due to readjusting the mask. We assessed the facial touching behaviour of bus passengers in China before and after the outbreak of COVID-19 and found that wearing a face mask does not increase the number of hand-face contacts and is likely, therefore, to have a positive beneficial effect on suppressing the spread of COVID-19 within populations when used in conjunction with social distancing measures.

Esophageal Scab Mimicking a Parasite: A Case Report.

BACKGROUND Parasitic helminths in the esophagus are rare. Here, we report a case of esophageal scab mimicking a parasite. CASE REPORT A 65-year-old man was admitted to our hospital because after choking on food. Gastroscopy showed 2 foreign bodies adherent to the esophagus wall 28 and 34 cm from the incisor, which appeared to be a fluke. Two fluke-like foreign bodies (1.5 and 1.8 cm in length) were removed from the esophageal ulcer with forceps. After fixation with alcohol, the suspected fluke-like foreign bodies were noted to be brown and woody. Under a light microscope, the structure of the foreign body was not apparent, and no typical flatworm tegument structure was demonstrated on pathologic sections, but it had a blood clot-like structure. Administration of albendazole did not expel any helminths. A stool examination showed no eggs of the putative flukes. The genomic DNA of the suspected flukes was extracted and a 700 bp fragment was amplified by universal barcoding primers. The sequencing showed that the homology with human cytochrome c oxidase subunit I gene was 98.8%. CONCLUSIONS The scab formed by the esophageal ulcer was identified based on clinical manifestations, anti-helminth and stool examinations, parasite morphology, and molecular biology. Our experience with this case suggests that the universal barcoding technique can be used for identification of foreign bodies suspected to be parasites.

Actin-related protein Arp4 regulates euchromatic gene expression and development through H2A.Z deposition in blood-stage Plasmodium falciparum.

BACKGROUND: Malaria caused by Plasmodium spp. is still a major threat to public health globally. The various approaches to developing new antimalarial agents rely on the understanding of the complex regulatory mechanisms of dynamic gene expression in the life-cycle of these malaria parasites. The nuclear members of the evolutionarily conserved actin-related protein nuclear (ARP) superfamily are the major components of nucleosome remodelling complexes. In the human malaria parasite Plasmodium falciparum, bioinformatics analysis has predicted three ARP orthologues: PfArp1, PfArp4 and PfArp6. However, little is known about the biological functions of putative PfArp4. In this study, we aimed to investigate the function and the underlying mechanisms of PfArp4 gene regulation. METHODS: A conditional gene knockdown approach was adopted by incorporating the glucosamine-inducible glmS ribozyme sequence into the 3' UTR of the PfArp4 and PfArp6 genes. The transgenic parasites PfArp4-Ty1-Ribo, PfArp6-Ty1-Ribo and pL6-PfArp4-Ty1::PfArp6-HA were generated by the CRISPR-Cas9 technique. The knockdown effect in the transgenic parasite was measured by growth curve assay and western blot (WB) analysis. The direct interaction between PfArp4 and PfArp6 was validated by co-IFA and co-IP assays. The euchromatic gene expression mediated through H2A.Z (histone H2A variant) deposition and H3K9ac modification at promoters and regulated by PfArp4, was determined by RNA-seq and ChIP-seq. RESULTS: The inducible knockdown of PfArp4 inhibited blood-stage development of P. falciparum. PfArp4 and PfArp6 were colocalized in the nucleus of P. falciparum parasites. PfArp4 gene knockdown altered the global transcriptome. PfArp4 protein colocalized with the histone variant H2A.Z and euchromatic marker H3K9ac in intergenic regions. The inducible downregulation of PfArp4 resulted in the depletion of H2A.Z and lower H3K9ac levels at the upstream regions of eukaryotic genes, thereby repressing the transcriptional abundance of H2A.Z-dependent genes. CONCLUSIONS: Our findings suggest that PfArp4 regulates the cell cycle by controlling H2A.Z deposition and affecting centromere function, contributing to the understanding the complex epigenetic regulation of gene expression and the development of P. falciparum.

Ex vivo susceptibilities of Plasmodium vivax isolates from the China-Myanmar border to antimalarial drugs and association with polymorphisms in Pvmdr1 and Pvcrt-o genes.

BACKGROUND: Vivax malaria is an important public health problem in the Greater Mekong Subregion (GMS), including the China-Myanmar border. Previous studies have found that Plasmodium vivax has decreased sensitivity to antimalarial drugs in some areas of the GMS, but the sensitivity of P. vivax to antimalarial drugs is unclear in the China-Myanmar border. Here, we investigate the drug sensitivity profile and genetic variations for two drug resistance related genes in P. vivax isolates to provide baseline information for future drug studies in the China-Myanmar border. METHODOLOGY/PRINCIPAL FINDINGS: A total of 64 P. vivax clinical isolates collected from the China-Myanmar border area were assessed for ex vivo susceptibility to eight antimalarial drugs by the schizont maturation assay. The medians of IC50 (half-maximum inhibitory concentrations) for chloroquine, mefloquine, pyronaridine, piperaquine, quinine, artesunate, artemether, dihydroartemisinin were 84.2 nM, 34.9 nM, 4.0 nM, 22.3 nM, 41.4 nM, 2.8 nM, 2.1 nM and 2.0 nM, respectively. Twelve P. vivax clinical isolates were found over the cut-off IC50 value (220 nM) for chloroquine resistance. In addition, sequence polymorphisms in pvmdr1 (P. vivax multidrug resistance-1), pvcrt-o (P. vivax chloroquine resistance transporter-o), and difference in pvmdr1 copy number were studied. Sequencing of the pvmdr1 gene in 52 samples identified 12 amino acid substitutions, among which two (G698S and T958M) were fixed, M908L were present in 98.1% of the isolates, while Y976F and F1076L were present in 3.8% and 78.8% of the isolates, respectively. Amplification of the pvmdr1 gene was only detected in 4.8% of the samples. Sequencing of the pvcrt-o in 59 parasite isolates identified a single lysine insertion at position 10 in 32.2% of the isolates. The pvmdr1 M908L substitutions in pvmdr1 in our samples was associated with reduced sensitivity to chloroquine, mefloquine, pyronaridine, piperaquine, quinine, artesunate and dihydroartemisinin. CONCLUSIONS: Our findings depict a drug sensitivity profile and genetic variations of the P. vivax isolates from the China-Myanmar border area, and suggest possible emergence of chloroquine resistant P. vivax isolates in the region, which demands further efforts for resistance monitoring and mechanism studies.

Vanadium dioxide-assisted broadband tunable terahertz metamaterial absorber.

Tunable terahertz (THz) functional devices have exhibited superior performances due to the use of active materials, such as liquid crystals, graphene, and semiconductors. However, the tunable range of constitutive parameters of materials is still limited, which leads to the low modulation depth of THz devices. Here, we demonstrate a broadband tunable THz absorber based on hybrid vanadium dioxide (VO2) metamaterials. Unlike other phase change materials, VO2 exhibits an insulator-to-metal transition characteristic and the conductivity can be increased by 4-5 orders of magnitude under external stimulus including electric fields, optical, and thermal pumps. Based on the unique transition character of VO2, the maximum tunable range of the proposed absorber can be realized from 5% to 100% by an external thermal excitation. Meanwhile, an absorption greater than 80% in a continuous range with a bandwidth about 2.0 THz can be obtained when VO2 is in its metal phase at high temperature. Furthermore, the absorber is insensitive to the incident angle up to 50° and such a broadband THz absorber can be used in applications including imaging, modulating, cloaking, and so on.

Acoustic extraordinary transmission manipulation based on proximity effects of heterojunctions.

Heterojunctions between two crystalline semiconductor layers or regions can always lead to engineering the electronic energy bands in various devices, including transistors, solar cells, lasers, and organic electronic devices. The performance of these heterojunction devices depends crucially on the band alignments and their bending at the interfaces, which have been investigated for years according to Anderson's rule, Schottky-Mott rule, Lindhard theory, quantum capacitance, and so on. Here, we demonstrate that by engineering two different acoustic waveguides with forbidden bands, one can achieve an acoustic heterojunction with an extraordinary transmission peak arising in the middle of the former gaps. We experimentally reveal that such a transmission is spatially dependent and disappears for a special junction structure. The junction proximity effect has been realized by manipulating the acoustic impedance ratios, which have been proven to be related to the geometrical (Zak) phases of the bulk bands. Acoustic heterojunctions bring the concepts of quantum physics into the classical waves and the macroscopic scale, opening up the investigations of phononic, photonic, and microwave innovation devices.

Synthesis of ternary oxide Zn2GeO4 nanowire networks and their deep ultraviolet detection properties.

Ternary oxide Zn2GeO4 with a wide bandgap of 4.84 eV, as a candidate for fourth generation semiconductors, has attracted a great deal of attention for deep ultraviolet (DUV) photodetector applications, because it is expected to be blind to the UV-A/B band (290-400 nm) and only responsive to the UV-C band (200-290 nm). Here, we report on the synthesis of Zn2GeO4 nanowire (NW) networks by lower pressure chemical vapor deposition and investigate their corresponding DUV detection properties. We find that pure Zn2GeO4 NWs could be obtained at a growth pressure of 1 kPa. The DUV detection tests reveal that growth pressure exerts a significant effect on DUV detection performance. The Zn2GeO4 NW networks produced under 1 kPa show an excellent solar-blind photoresponsivity with fast rise and decay times (t rise ≈ 0.17 s and t decay ≈ 0.14 s).

Self-adaptive terahertz spectroscopy from atmospheric vapor based on Hilbert-Huang transform.

Absorption lines of atmospheric vapor commonly appear in terahertz (THz) spectra measured in a humid air environment. However, these effects are generally undesirable because they may mask critical spectroscopic information. Here, a self-adaptive method is demonstrated for effectively identifying and eliminating atmospheric vapor noise from THz spectra of an all-fiber THz system with the Hilbert-Huang transform. The THz signal was decomposed into eight components in different time scales called the intrinsic mode functions and the interference of atmospheric vapor was accurately isolated. A series of experiments confirmed the effectiveness and strong self-adaptiveness of the proposed system in vapor noise elimination.