Characteristics and phylogenetic analysis of the complete mitochondrial genome of Glyptothorax pallozonus (Siluriformes, Sisoridae)

Glyptothorax pallozonus Lin, 1934 is a small benthic fish belonging to the Sisoridae family that is distributed in the Dongjiang and Rongjiang Rivers of China. In the present study, we sequenced and characterized the complete mitochondrial genome of G. pallozonus for the first time. The complete mitogenome of G. pallozonus is 16,542 bp in length and includes 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), two ribosomal RNA (rRNAs), and a control region (CR). The mitogenome architecture was identical to that of other teleosts. Maximum likelihood (ML) phylogenetic analysis strongly supported the monophyly of Glyptothorax, which contains two clades. These results advance our understanding of the molecular phylogeny of the genus Glyptothorax.

Assessing the construction of a Healthy City in China: a conceptual framework and evaluation index system

OBJECTIVES

COVID-19 has brought challenges to the health of all mankind. It is particularly important to promote the construction of a 'Healthy China' and build a 'healthy community'. The aims of this study were to construct a reasonable conceptual framework for the Healthy City concept and to assess Healthy City construction in China.

STUDY DESIGN

This study combined qualitative and quantitative research.

METHODS

This study proposes the concept model of 'nature-human body-Healthy City' and accordingly constructs an evaluation index system for the construction of a Healthy City that integrates five dimensions, namely, the medical level, economic basis, cultural development, social services, and ecological environment to explore the spatial and temporal heterogeneity of Healthy City construction in China. Finally, the influencing factors of Healthy City construction patterns are explored using GeoDetector.

RESULTS

(1) The pace of Healthy City construction is generally on the rise; (2) the construction of Healthy Cities exhibits significant global spatial autocorrelation and gradually increasing agglomeration. The spatial distribution of cold hotspot areas was relatively stable; (3) medical and health progress is an important factor; the level of economic development is the leading support; the endowment of resources and environment is the basic condition; public service support provides important support; and scientific and technological innovation capabilities provide technical support for the construction of a Healthy City.

CONCLUSIONS

The spatial heterogeneity of Healthy City construction in China is evident, and the state of spatial distribution is relatively stable. The spatial pattern of Healthy City construction is shaped by a combination of factors. Our research will provide a scientific basis for promoting the construction of Healthy Cities and helping to implement the Health China Strategy.

Efficient visible-light-driven S-scheme AgVO3/Ag2S heterojunction photocatalyst for boosting degradation of organic pollutants

The traditional semiconductor photocatalysts for solving the related environmental aggravation are often challenged by the recombination of photogenerated carriers. Designing an S-scheme heterojunction photocatalyst is one of the keys to tackling its practical application problems. This paper reports an S-scheme AgVO₃/Ag₂S heterojunction photocatalyst constructed via a straightforward hydrothermal approach that exhibits outstanding photocatalytic degradation performances to the organic dye Rhodamine B (RhB) and antibiotic Tetracycline hydrochloride (TC-HCl) driven by visible light. The results show that AgVO₃/Ag₂S heterojunction with a molar ratio of 6:1 (V6S) possesses the highest photocatalytic performances, 99% of RhB can be almost degraded by 0.1 g/L V6S within 25 min light illumination, and about 72% of TC-HCl can be photodegraded with the act of 0.3 g/L V6S under 120 min light irradiation. Meanwhile, the AgVO₃/Ag₂S system exhibits superior stability and maintains high photocatalytic activity after 5 repeated tests. Moreover, the EPR measurement and radical capture test identify that superoxide radicals and hydroxyl radicals mainly contribute to the photodegradation process. The present work demonstrates that constructing an S-scheme heterojunction can effectively inhibit the recombination of carriers, providing insights into the fabrication of applied photocatalysts for practical wastewater purification treatment.

Influence of Al Addition on the Microstructure and Mechanical Properties of Mg-Zn-Sn-Mn-Ca Alloys

The effects of Al addition on the microstructure and mechanical properties of Mg-Zn-Sn-Mn-Ca alloys are studied in this paper. It was found that the Mg-6Sn-4Zn-1Mn-0.2Ca-xAl (ZTM641-0.2Ca-xAl, x = 0, 0.5, 1, 2 wt.%; hereafter, all compositions are in weight percent unless stated otherwise) alloys have α-Mg, Mg₂Sn, Mg₇Zn₃, MgZn, α-Mn, CaMgSn, AlMn, Mg₃₂(Al,Zn)₄₉ phases. The grain is also refined when the Al element is added, and the angular-block AlMn phases are formed in the alloys. For the ZTM641-0.2Ca-xAl alloy, the higher Al content is beneficial to elongation, and the double-aged ZTM641-0.2Ca-2Al alloy has the highest elongation, which is 13.2%. The higher Al content enhances the high-temperature strength for the as-extruded ZTM641-0.2Ca alloy; overall, the as-extruded ZTM641-0.2Ca-2Al alloy has the best performance; that is, the tensile strength and yield strength of the ZTM641-0.2Ca-2Al alloy are 159 MPa and 132 MPa at 150 °C, and 103 MPa and 90 MPa at 200 °C, respectively.

Microstructure and Mechanical Properties of As-Aged Mg-Zn-Sn-Mn-Al Alloys

The microstructure and mechanical properties of as-aged Mg-6Zn-4Sn-1Mn-xAl (ZTM641-xAl, x = 0, 0.2, 0.5, 1, 2, 3 and 4 wt.%) alloys are studied in this paper. In terms of microstructure, the results reveal that the addition of Al mainly leads to the formation of the Al₈Mn₅, Al₁₁Mn₄, Al₂Mg₅Zn₂ and Mg₃₂(Al,Zn)₄₉ phases. With increases in the addition of Al, the average grain size first decreases and then increases, while the undissolved phases increase. The average grain size of the ZTM641-0.5Al alloy is the smallest, and the single-aged and double-aged grain size is 14 μm and 12 μm, respectively. As for mechanical properties, with increases in the Al element, the strength decreases, and the elongation first increases and then decreases. The double-aged ZTM641-0.2Al alloy exhibits favorable mechanical properties at room temperature, and the UTS, YS and elongation are 384 MPa, 360 MPa and 9%, respectively. Further, the double-aged ZTM641-0.2Al alloy exhibits the comprehensive mechanical properties at 150 °C, that is, the UTS, YS and elongation are 212 MPa, 196 MPa and 29%, respectively, which is about 45% higher than that of the elongation of ZTM641. The ZTM641-xAl alloys exhibits mixed fracture at room temperature, and, with increases in the addition of Al, the fracture mechanisms of alloys are mixed fracture, ductile fracture and mixed fracture at 200 °C.

Study on Bone-like Microstructure Design of Carbon Nanofibers/Polyurethane Composites with Excellent Impact Resistance

It is a challenge to develop cost-effective strategy and design specific microstructures for fabricating polymer-based impact-resistance materials. Human shin bones require impact resistance and energy absorption mechanisms in the case of rapid movement. The shin bones are exciting biological materials that contain concentric circle structures called Haversian structures, which are made up of nanofibrils and collagen. The "soft and hard" structures are beneficial for dynamic impact resistance. Inspired by the excellent impact resistance of human shin bones, we prepared a sort of polyurethane elastomers (PUE) composites incorporated with rigid carbon nanofibers (CNFs) modified by elastic mussel adhesion proteins. CNFs and mussel adhesion proteins formed bone-like microstructures, where the rigid CNFs are served as the bone fibrils, and the flexible mussel adhesion proteins are regarded as collagen. The special structures, which are combined of hard and soft, have a positive dispersion and compatibility in PUE matrix, which can prevent cracks propagation by bridging effect or inducing the crack deflection. These PUE composites showed up to 112.26% higher impact absorbed energy and 198.43% greater dynamic impact strength when compared with the neat PUE. These findings have great implications for the design of composite parts for aerospace, army vehicles, and human protection.

Study on Mechanical Properties and High-Speed Impact Resistance of Carbon Nanofibers/Polyurethane Composites Modified by Polydopamine

Polyurethane elastomers (PUE), with superior mechanical properties and excellent corrosion resistance, are applied widely to the protective capability of structures under low-speed impact. However, they are prone to instantaneous phase transition, irreversible deformation and rupture even arising from holes under high-speed impact. In this paper, mussel adhesion proteins were applied to modify carbon nanofibers (CNFs) in a non-covalent way, and creatively mixed with PUE. This can improve the dispersity and interfacial compatibility of nanofillers in the PUE matrix. In addition, the homogeneous dispersion of modified nanofillers can serve as "reinforcing steel bars". The nanofillers and PUE matrix can form "mud and brick" structures, which show superb mechanical properties and impact resistance. Specifically, the reinforcement of 1.0 wt.% modified fillers in PUE is 103.51%, 95.12% and 119.85% higher than the neat PUE in compression modulus, storage modulus and energy absorption capability, respectively. The results have great implications in the design of composite parts for aerospace and army vehicles under extreme circumstances.

Preparation of poly(ionic liquid)/multi-walled carbon nanotube fillers using divinylbenzene as a linker to enhance the impact resistance of polyurethane elastomers

The brittle fracture of polyurethane elastomer (PUE) under high-speed impact limits its application in high-speed impact protection. Here, based on the principle of free radical polymerization and π-π conjugation, composite nanoparticles (C-MWCNTs) are prepared by copolymerization of epoxy group ionic liquid (GVIMBr) and divinylbenzene (DVB) on MWCNTs using DVB as a linker. C-MWCNTs participate in the curing process of PUE through epoxy groups to form in situ crosslinked C-MWCNTs/PUE, which improves the energy absorption and high-speed impact properties of PUE. Compared with neat PUE, the maximum compressive strength and energy absorbed by C-MWCNTs/PUE are increased by 46.3% and 23.6%, respectively. By observing the microsurface and fracture morphology of C-MWCNTs/PUE, the relationship between macroscopic mechanical properties and microstructure is constructed. The improvement of the mechanical properties of the C-MWCNTs/PUE is attributed to the interfacial interaction and homogeneous dispersion of the C-MWCNTs in the PUE matrix. These microscopic effects are caused by the good compatibility between GVIMBr and PUE matrix and the synergistic enhancement between GVIMBr and MWCNTs.

In Situ Grafted Composite Nanoparticles-Reinforced Polyurethane Elastomer Composites with Excellent Continuous Anti-Impact Performance

Polyurethane elastomer (PUE) has attracted much attention in impact energy absorption due to its impressive toughness and easy processability. However, the lack of continuous impact resistance limits its wider application. Here, an amino-siloxane (APTES) grafted WS₂-coated MWCNTs (A-WS₂@MWCNTs) filler was synthesized, and A-WS₂@MWCNTs/PUE was prepared by using the filler. Mechanical tests and impact damage characterization of pure PUE and composite PUE were carried out systematically. Compared with pure PUE, the static compressive strength and dynamic yield stress of A-WS₂@MWCNTs/PUE are increased by 144.2% and 331.7%, respectively. A-WS₂@MWCNTs/PUE remains intact after 10 consecutive impacts, while the pure PUE appears serious damage after only a one-time impact. The improvement of mechanical properties of A-WS₂@MWCNTs/PUE lies in the interfacial interaction and synergy of composite fillers. Microscopic morphology observation and damage analysis show that the composite nanofiller has suitable interfacial compatibility with the PUE matrix and can inhibit crack growth and expansion. Therefore, this experiment provides an experimental and theoretical basis for the preparation of PUE with excellent impact resistance, which will help PUE to be more widely used in the protection field.

Effects of Modified Al2O3-Decorated Ionic Liquid on the Mechanical Properties and Impact Resistance of a Polyurethane Elastomer

In this work, a new composite material with excellent dynamic impact resistance and outstanding quasi-static mechanical properties was synthesized. The composite material is composed of a polyurethane elastomer and a novel nano-polymer. The nano-polymer was composed of silane coupling agent-modified alumina microspheres and functionalized ionic liquids by double bond polymerization. The universal testing machine and split Hopkinson pressure bar were used to characterize the compression behavior, strength and energy absorption of the composite materials under static and dynamic conditions. Additionally, the comprehensive mechanical properties of polyurethane elastomer with different nano-polymer loadings (0.5–2.5 wt.%) were studied. The results show that whether it was static compression or dynamic impact, the polyurethane elastomer with 1% nano-polymer had the best performance. For the composite material with the best properties, its compressive yield strength under the static compression was about 61.13% higher than that of the pure polyurethane elastomer, and its energy absorption of dynamic impacts was also increased by about 15.53%. Moreover, the shape memory effect was very good (shape recovery is approximately 95%), and the microscopic damage degree was relatively small. This shows that the composite material with the best properties can withstand high compression loads and high-speed impacts. The developed composite material is a promising one for materials science and engineering, especially for protection against compression and impacts.

Effect of Rapid Cold Stamping on the Evolution of Long Strip-Shaped Nanoprecipitation in Al-Cu-Mg Alloy

High-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS), and hardness testing are used to investigate the evolution of the long strip-shaped S' phase of spray-formed fine-grained Al-Cu-Mg alloy during rapid cold stamping deformation. The elongated S' phase of the extruded Al-Cu-Mg alloy is subjected to twisting, brittle fracturing, redissolution, and necking during rapid cold stamping deformation. As a result, the morphology, size, distribution, and orientation relationship with the matrix of the long strip-shaped S' phase changed significantly. The regularly distributed long strip-shaped nanoscale precipitates evolved into irregularly distributed short rod-shaped S' phases and diffusely distributed granular reprecipitates. The twist and brittle fracture of the long strip-shaped S' phase significantly increased the contact surface between the precipitated phase and the aluminum matrix, improved the interfacial distortion energy of the precipitated phase and the aluminum matrix, and promoted the redissolution of the S' phase. The supersaturation state is reached, thus resulting in reprecipitation, which then lowered the matrix free energy. The hardness of the extruded Al-Cu-Mg alloy increased from 54.2 HB to 128.1 HB during the rapid cold stamping process.

[Research on feasibility of in vitro inflammatory wound microenvironment simulated by using inflammatory wound tissue homogenate of mice]

Objective: To investigate the feasibility of in vitro inflammatory wound microenvironment simulated by using inflammatory wound tissue homogenate of mice. Methods: (1) Ten eight-week-old C57BL/6 male mice were collected and full-thickness skin tissue with diameter of 1.0 cm on both sides of the midline of the back was taken with a perforator to make the normal skin tissue homogenate supernatant. At 48 h after the full-thickness skin defect wound was established, the wound tissue within 2 mm from the wound edge was taken to make inflammatory wound tissue homogenate supernatant. Two kinds of tissue homogenate supernatant were taken to adjust the total protein concentration to 1 mg/mL, and the tumor necrosis factor α (TNF-α) content was detected by enzyme-linked immunosorbent assay. The number of sample was 6. (2) The primary passage of human umbilical cord mesenchymal stem cells (hUCMSCs) were collected and cultured to the 3rd passage with the normal exosomes being extracted from the hUCMSCs after cultured for 48 h. Another batch of hUCMSCs in the 3rd passage was collected and stimulated with inflammatory wound tissue homogenate supernatant of 30, 50, and 100 μg/mL total protein and normal skin tissue homogenate supernatant of 30, 50, and 100 μg/mL total protein, respectively. After cultured for 48 h, the exosomes stimulated with normal protein of 30, 50, and 100 μg/mL and exosomes stimulated with inflammatory protein of 30, 50, and 100 μg/mL were extracted. Normal exosomes, exosomes stimulated with 30 μg/mL normal protein, and exosomes stimulated with 30 μg/mL inflammatory protein were collected, the morphology was observed by transmission electron microscope, the particle size was detected by nanoparticle tracking analyzer, and the expressions of CD9 and CD63 were detected by Western blotting. (3) Twenty one-day-old C57BL/6 mice were taken to isolate the primary passage of fibroblasts (Fbs) and the 3rd passage of Fbs, whose morphology was observed under the inverted phase contrast microscope. The Fbs of 3rd passage were collected to observe the expression of vimentin by cell crawling method combined with immunofluorescence method at culture hour (CH) 2. (4) The Fbs of 3rd passage were divided into control group, normal exosome group, 30, 50, 100 μg/mL normal protein stimulating exosome group, and 30, 50, 100 μg/mL inflammatory protein stimulating exosome group according to the random number table, with 4 wells in each group. Cells in control group received no treatment, and cells in the other 7 groups were respectively added with normal exosomes, exosomes stimulated with normal protein of 30, 50, and 100 μg/mL, and exosomes stimulated with inflammatory protein of 30, 50, and 100 μg/mL prepared in experiment (2). The final mass concentration of exosomes was adjusted to 10 μg/mL. The cell viability was detected by cell count kit 8 at CH 48. (5) Two batches of Fbs in the 3rd passage were divided and treated as those in experiment (4), with 4 wells in each group, and the final mass concentration of exosomes was adjusted to 1 and 10 μg/mL, respectively. The cell mobility was detected by cell scratch test at CH 6, 12, and 24. (6) Two batches of the Fbs of 3rd passage were collected, divided, and treated as those in experiment (4) except with no control group, with 3 wells in each group, and the final mass concentration of exosomes was respectively adjusted to 1 and 10 μg/mL. The mRNA expression levels of transforming growth factor β(1) (TGF-β(1)), TGF-β(3), and α smooth muscle actin (α-SMA) were detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction at CH 48. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and Bonferroni method. Results: (1) The content of TNF-α in inflammatory wound tissue homogenate supernatant of mice was (116±3) pg/mL, significantly higher than (97±5) pg/mL in normal skin tissue homogenate supernatant at post injury hour 48 (t=3.306, P<0.05). (2) Normal exosomes, exosomes stimulated with 30 μg/mL normal protein, and exosomes stimulated with 30 μg/mL inflammatory protein of hUCMSCs showed the typical saucer-like shape. The particle sizes of the three exosomes of hUCMSCs were 30-150 nm, which were all within the normal particle size range of exosome. Three exosomes of hUCMSCs positively expressed CD9 and CD63. (3) The primary passage of cells were clearly defined and showed protruding spindle shape, irregular polygon shape, or slender strip shape. The morphology of the 3rd and the primary passage of cells is similar. At CH 2, vimentin in cells was positively expressed, and the cells were identified as Fbs. (4) At CH 48, the cell viability was (137.4±2.8)% in 30 μg/mL inflammatory protein stimulating exosome group, obviously higher than 100%, (107.5±2.4)%, (113.3±3.2)%, (104.0±2.0)%, and (101.9±1.5)% in control group, normal exosome group, 30 μg/mL normal protein stimulating exosome group, and 50 and 100 μg/mL inflammatory protein stimulating exosome groups, respectively (P<0.01), and cell viability in 30 μg/mL normal protein stimulating exosome group was obviously higher than that in control group, normal exosome group, and 50 and 100 μg/mL normal protein stimulating exosome groups [(103.4±2.2)% and (102.5±1.4)%], respectively (P<0.01). (5) At CH 6, 12, and 24, the mobility rate of cells in 30 μg/mL inflammatory protein stimulating exosome group was significantly higher than that in control group, normal exosome group, 30 μg/mL normal protein stimulating exosome group, and 50 and 100 μg/mL inflammatory protein stimulating exosome groups, respectively, when the final mass concentrations of exosome was 1 μg/mL (P<0.05) . At CH 12, the mobility rate of cells in 30 μg/mL normal protein stimulating exosome group was obviously higher than that in control group, normal exosome group, and 50 and 100 μg/mL normal protein stimulating exosome groups, respectively, when the final mass concentration of exosome was 1 μg/mL (P<0.05). At CH 6, the mobility rate of cells in 30 μg/mL inflammatory protein stimulating exosome group was significantly higher than that in control group and normal exosome group (P<0.05), and the mobility rate of cells in 30 μg/mL normal protein stimulating exosome group was significantly higher than that in 50 and 100 μg/mL normal protein stimulating exosome groups, respectively, when the final mass concentration of exosome was 10 μg/mL (P<0.05). At CH 12 and 24, the mobility rate of cells in 30 μg/mL inflammatory protein stimulating exosome group was significantly higher than that in control group, normal exosome group, and 50 and 100 μg/mL inflammatory protein stimulating exosome groups (P<0.05), and the mobility rate of cells in 30 μg/mL normal protein stimulating exosome group was significantly higher than that in control group, normal exosome group, and 50 and 100 μg/mL normal protein stimulating exosome groups, respectively, when the final mass concentration of exosome was 10 μg/mL (P<0.05). (6) There were no statistically significant differences in mRNA expression levels of TGF-β(1), TGF-β(3), and α-SMA of cells among the 7 groups at CH 48 when the final mass concentration of exosome was 1 μg/mL (F=1.123, 1.537, 1.653, P>0.05). There were no statistically significant differences in mRNA expression levels of TGF-β(1) and α-SMA of cells among the 7 groups at CH 48 when the final mass concentration of exosome was 10 μg/mL (F=1.487, 1.308, P>0.05), and mRNA expression level of TGF-β(3) of cells in 50 μg/mL inflammatory protein stimulating exosome group at CH 48 was significantly higher than that in normal exosome group, 50 μg/mL normal protein stimulating exosome group, and 30 and 100 μg/mL inflammatory protein stimulating exosome groups when the final mass concentration of exosome was 10 μg/mL (P<0.05). Conclusions: The pretreatment with inflammatory wound tissue homogenate supernatant of mice has no significant effect on the total protein of hUCMSCs exosomes. The hUCMSCs exosomes stimulated by low concentration inflammatory wound tissue homogenate supernatant can significantly promote the proliferation and migration ability of Fbs. The content of inflammatory mediators in the wound tissue homogenate supernatant during the inflammatory phase is extremely low, which may be the reason that the anti-inflammation and tissue repair paracrine effects of mesenchymal stem cell cannot be effectively started.

[Analysis on the situation of being supported by the national natural science foundation of China in the field of occupational diseases from 2010 to 2019]

Objective: To understand the situation supported by the National Natural Science Foundation in the field of occupational diseases (H2402) in China, so as to provide a reference basis for the application and research of scientific researchers in the field of occupational diseases in China. Methods: The information system of scientific and technological achievements was used to search the financial support of the National Natural Science Foundation of China (NSFC) in the field of occupational diseases from 2010 to 2019. Results: From 2010 to 2019, a total of 55 projects were funded under the Occupational Disease code (H2402) , with a total funding of 22.33 million yuan, of which 30 were supported by the Youth Science Foundation, 20 by the Youth Science Foundation and 5 by the Regional Science Foundation. Thirty five items of the research projects focused on pneumoconiosis and other respiratory diseases which accounted for 63.64 per cent. Forty one items of scientific research projects are supported by domestic institutions of higher learning which accounted for 74.55 per cent. Conclusion: The research support of the National Natural Science Foundation of China to the field of occupational diseases (H2402) has increased steadily, but the support of different research directions and supporting units is not balanced. It is suggested that departments concerned strengthen guidance and support for the applicants in less developed areas and weak research directions of the projects in the National Natural Science Foundation.

MiR-204 inhibits inflammation and cell apoptosis in retinopathy rats with diabetic retinopathy by regulating Bcl-2 and SIRT1 expressions

OBJECTIVE

To explore the influences of micro ribonucleic acid (miR)-204 on the rats with diabetic retinopathy by regulating the expressions of B-cell lymphoma 2 (Bcl-2) and sirtuin 1 (SIRT1).

MATERIALS AND METHODS

A total of 36 Sprague-Dawley rats were randomly assigned into normal group (n=12), model group (n=12), and miR-204 mimics group (n=12). No treatment was performed in the normal group, the diabetic retinopathy model was established in model group, and miR-204 mimics were administered for intervention after modeling in the inhibitor group. After 7 d, materials were sampled for detection. The expressions of Bcl-2 and SIRT1 were detected via immunohistochemistry, and their relative protein expression levels were determined via Western blotting (WB). Quantitative Polymerase Chain Reaction (qPCR) was performed to detect the expression of miR-204, and the content of inflammatory factors interleukin (IL)-6, IL-18, and tumor necrosis factor-α (TNF-α) was measured using enzyme-linked immunosorbent assay (ELISA). Finally, cell apoptosis was evaluated via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL).

RESULTS

Immunohistochemistry results showed that the positive expression levels of Bcl-2 and SIRT1 were substantially lower in the model and miR-204 mimics groups than those in the normal group (p<0.05), and their positive expression levels in miR-204 mimics group were notably higher than those in model group (p<0.05). According to Western blot (WB) results, the relative protein expression levels of Bcl-2 and SIRT1 markedly declined in the other two groups compared with those in the normal group (p<0.05), while miR-204 mimics group exhibited remarkably higher relative protein expression levels of Bcl-2 and SIRT1 than the model group (p<0.05). The results of qPCR revealed that the relative expression level of miR-204 was markedly lowered in model and miR-204 mimics groups compared with that in the normal group (p<0.05), and its relative expression level in miR-204 mimics group was remarkably higher than that in the model group. It was found through enzyme-linked immunosorbent assay (ELISA) that compared with normal group, the other two groups had substantially increased content of IL-6, IL-18, and TNF-α (p<0.05), and the content of IL-6, IL-18, and TNF-α in miR-204 mimics group was markedly lower than that in the model group (p<0.05). According to TUNEL results, the apoptosis rate of cells rose substantially in the other two groups compared with that in the normal group (p<0.05), while was notably lower in the miR-204 mimics group than that in the model group (p<0.05).

CONCLUSIONS

MiR-204 up-regulates Bcl-2 and SIRT1 expressions to inhibit the inflammation and cell apoptosis in rats with diabetic retinopathy.

CRISPR-dCas9-mediated knockdown of prtR, an essential gene in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a widely distributed non-fermentative Gram-negative opportunistic pathogen that is often responsible for nosocomial infections. Gene interference is a potentially valuable tool for investigating essential genes in P. aeruginosa. To establish a gene interference platform in P. aeruginosa, CRISPR system was used with an inactive Cas9 protein. The CRISPR-dCas9 system was cloned into pHERD20T, a shuttle vector with arabinose inducible promoter, and was further modified to target a regulatory gene prtR that is essential for the viability of P. aeruginosa. Cells expressing the prtR-targeting CRISPR interference (CRISPRi) showed growth defect in an arabinose dose-dependent manner. A high-throughput RNA sequencing analysis of bacterial cells with or without the CRISPRi-mediated prtR inhibition indicated that prtRis a global regulator affecting multiple biological processes. In conclusion, the CRISPR-dCas9-based gene knockdown system has been successfully implemented in P. aeruginosa and demonstrated to be an effective tool in the investigation of essential or difficult-to-inactivate genes in this species.

Effect of Y Addition on the Microstructure and Mechanical Properties of ZM31 Alloy

Effects of different Y contents (0, 0.3, 0.7, 1.5, 3, 5 and 10 wt.%) on the microstructure, thermal stability and mechanical properties of Mg-3Zn-1Mn (ZM31) alloys were systematically studied. The existence form and action mechanism of Y in the experimental alloys were investigated. The results revealed that with the change of Y content, the main phases of the ZM31-xY alloys changed from Mg₇Zn₃ phase, I-phase, I + W-phase, W-phase, W + LPSO phase to LPSO phase. When Y content was low (≤1.5%), hot extrusion could break up the residual phases after homogenization to form dispersed fine rare-earth phase particles, and fine second phases would also precipitate in the grain, which could inhibit the grain growth. When Y content was high (≥3%), the experimental alloys were only suitable for high-temperature extrusion due to the formation of the high heat stable rare-earth LPSO phase. In addition, Y could evidently enhance the mechanical properties of the as-extruded ZM31 alloy, of which the ZM31-10Y alloy had the best mechanical properties, that is, the tensile and yield strengths are 403 MPa and 342 MPa. The high strengths of the alloys were mainly determined by fine grain strengthening, rare-earth phase strengthening and dispersion strengthening of fine α-Mn particles.

[The basic characteristics and medical status of pneumoconiosis patients under different investigation methods]

Objective: To analyze the characteristics of pneumoconiosis patients and the basic status of medical treatment. Methods: Research objects were chosen by stratified sampling method and typical survey method from existing pneumoconiosis patients in China. The survey was carried out from March 2017 to January 2018 in nine provinces including provinces from east, medium and western region in China. Source of pneumoconiosis cases were inpatient cases, outpatient or physical-examined cases and household-investigation cases. The survey mainly included demographic and sociological characteristics, economic status, occupational history and dust exposure history, disease status, work-related injury insurance and social security status and related indicators of pneumoconiosis treatment. Results: Investigated 1037 pneumoconiosis cases which included 186 (19.9%) household-investigation cases, 212 (20.4%) outpatient or physical-examined cases and 639 (61.7%) inpatient cases. Demographic and sociological characteristics, individual monthly income, economic source, occupational history and work-related injury insurance were statistically significant among different source of pneumoconiosis patients (P<0.05) . Among all of the household-investigation cases, there were 74 cases (40.2%) had no income, 117 cases (62.9%) used to work in private enterprises, 36 cases (19.4%) had work-related injuries insurance, 95 cases (51.1%) were at three phase of pneumoconiosis, 108 cases (59.0%) haven't had any drugs for pneumoconiosis. 65 cases (39.4%) haven't went to the clinic, 53 cases (28.5%) hadn't seek medical advice although they needed medical treatment very much. Among all of the outpatient or physical-examined cases, there were 95 cases (46.1%) had no income, 36 cases (17.0%) had work-related injuries Insurance, 139 cases (65.6%) went to the clinic for treatment of pneumoconiosis, 81 cases (38.2%) went to the clinic for more than ten times. Among all the inpatient cases, 310 cases' (49.3%) personal monthly income was above 2000 yuan, 352 cases (55.1%) had work-related injuries Insurance, 588 cases (92.2%) were taking drugs for treatment of pneumoconiosis, 153 canses (24.2%) had hospitalization for than ten times. Conclusion: Household-investigation cases have lower economic conditions, lower rates of Insurance coverage for work-related injuries, severer pneumoconiosis and higher clinical service utilization. Clinical or physical-examined cases have lower economic conditions, lower rates of Insurance coverage for work-related injuries and higher clinical service utilization. Hospitalized cases have better economic conditions, higher rates of insurance coverage for work-related injuries and higher hospitalization service utilization.

A paper-based colorimetric microfluidic sensor fabricated by a novel spray painting prototyping process for iron analysis

A novel, simple, and low-cost spray painting technique has been developed for the fabrication of microfluidic paper-based devices. The devices that we developed utilize aerosol spray paint to build hydrophobic barriers and employ a hole puncher to obtain paper-based patterned layers and paper dots without using any specialized instruments (e.g., without a laser cutter). The entire manufacturing process is extremely simple, inexpensive, and rapid, which means that it can be applied broadly. Furthermore, the application of the device to iron detection was demonstrated. A linear relationship between the colour value and the iron concentration was observed from 0 to 0.02 g/L. The developed microfluidic paper-based device for iron detection exhibited a low detection limit (0.00090 g/L), good selectivity, and acceptable recovery.

Abstract P1-08-23: Not presented

This abstract was not presented at the conference.

Citation Format: Zang Y-S, Qi F, Qin W-X. Not presented [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-23.

Flake-like InVO4 modified TiO2 nanofibers with longer carrier lifetimes for visible-light photocatalysts

TiO₂/InVO₄ nanofibers have been designed and fabricated successfully by one-pot electrospinning process, which display longer carrier lifetime (22 ns) and enhanced visible-light photocatalytic activity.

Effect of Brominated Epoxy Resins on the Thermal Stability and Flame Retardancy of Long-Glass-Fiber Reinforced Polyamide 6

In this work, the compounds of brominated epoxy resins and antimony trioxide (BER/Sb2O3) additives are analyzed and added into long-glass-fiber reinforced polyamide 6 (PA6/LGF) composites in order to solve the “candle-wick effect” caused by glass fibers. The thermal stability, flammability, and morphology of charred residues of the flame retardant PA6/LGF composites are investigated by thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), and scanning electronic microscopy (SEM). The results show the addition of BER/Sb2O3 provides improvements in flame retardancy by increasing the LOI values, enhancing UL-94 rating, and reducing the heat release rate, total heat release and effective heat of combustion due to the formation of consolidated and thick charred residual structures on the surfaces of the LGF reinforced PA6 composites. When the content of BER/Sb2O3 is increased to 12 wt%, the LOI value and UL-94 rating of BER/PA6/LGF composites reach 24.8 and V-0, respectively. The TGA results exhibit that the decomposition temperature of the PA6/LGF composites decreases with the addition of BER/Sb2O3 additive, resulting in forming some high quality residual char layer. A possible flame retardant mechanism is proposed to illustrate the effect of the gaseous and condensed phases on the flame retardancy of the PA6/LGF composites.

Experimentally simulating quantum walks with self-collimated light

In self-collimated photonic crystal, periodically arranged air holes of sub-wavelength scale provide flattened equi-frequency curves perpendicular to the ΓM direction, which allow light or photons propagating in a quasi-uniform medium without diffraction. Here we for the first time experimentally simulate four-step single-photon discrete time quantum walks with classical light in such a photonic crystal chip fabricated on silicon-on-insulator. Similarities between theoretical expectations and experimental results are higher than 0.98. The functional area is compact and can be extended to construct more complicated linear quantum circuits.

Expression of TRPM8 in diabetic rats and its relationship with visceral pain stimulation

Transient receptor potential cation channel, subfamily M, member 8 (TRPM8) is a nonselective cation channel and a candidate for cold sensation signaling, but the relationship between TRPM8 and diabetes remains unclear. In the present study, we determined the expression levels of TRPM8 messenger RNA (mRNA) and the levels of the TRPM8 protein in the bladder tissue of diabetic rats. We also investigated the correlation between TRPM8 expression and the visceral pain stimulation-related factor, calcitonin gene-related peptide (CGRP) in diabetic rats. The rats were sacrificed 3, 5, 7, and 15 days after streptozotocin injection, and blood was collected from their tail veins to determine the blood glucose levels. Bladder tissue was removed to assess the expression of TRPM8 mRNA by reverse transcription-polymerase chain reaction, and the expression of the TRPM8 protein by western blotting. After administering electrical stimulation (5 V/1 Hz), the expression levels of TRPM8 and CGRP proteins were determined. Our results revealed that the blood glucose level, and TRPM8 mRNA and TRPM8 protein expression levels increased significantly in the diabetic rats. Spinal tissue protein expression levels of both TRPM8 and CGRP also increased significantly following electrical stimulation. This possibly indicates that TRPM8 is closely associated with visceral pain stimulation, and could be an independent prognostic biomarker for diabetes.

Assessment of genetic diversity of cucumber cultivars in China based on simple sequence repeats and fruit traits

The cucumber (Cucumis sativus L.) is an important crop grown worldwide. In this study, the genetic diversity of 42 cucumber cultivars in China was analyzed using 51 pairs of simple sequence repeat (SSR) primers. These primers identified 129 polymorphic loci, 95.6% of which were polymorphic. The mean effective number of alleles, mean Nei's gene diversity, and mean Shannon's information index were 0.36, 0.16, and 0.21, respectively. A cluster analysis demonstrated that the 42 cultivars could be divided into three groups, a result that was largely consistent with those of a principal component analysis (PCA). The PCA indicated that the three groups displayed significant variation in fruit traits. The cultivars of group 1 tended to have longer fruits (>30 cm), longer fruit ends (>4 cm), larger fruit diameters (>5 cm), a sharp strigose fruit spine, and the same fruit end shape. The basal color of the fruit in group 2 was dark green. Group 3 cultivars have no wax or mottling on the fruit surface. Our study demonstrates the value of our SSR primers for assessing genetic diversity in cucumber.

Improved Cuff Technique for Establishing a Mouse-Rat Heterotopic Cardiac Xenotransplantation Model

BACKGROUND

The small animal model of cardiac transplantation is the most common model in organ transplantation studies. The cervical heterotopic transplantation is widely performed because this allows for direct observation of the graft heartbeat and contributes to early prediction of graft rejection.

OBJECTIVE

A mouse-rat cervical heterotopic cardiac xenotransplantation model was modified with respect to the anesthesia method, cardiac graft harvesting method, and perioperative treatment. These improvements ensure the stability and reliability of xenotransplantation models for in vivo studies of immune-mediated graft rejection.

METHODS

After establishing isoflurane inhalation anesthesia, the donors' hearts were harvested. The experimental method involved separate ligation of the left and right superior venae cavae; the other blood vessels were ligated in a cluster. Both the donor and recipient animals were placed on a heating pad intraoperatively to maintain a body temperature of 37-40 °C. The model establishment was divided into 3 stages: practice, stabilization, and stereotyping. The surgical success rate and operation time were recorded. Specimens were harvested at different time points for histopathological examination.

RESULTS

The anesthetic effect of isoflurane was well maintained, and no animals died of adverse anesthetic events. Body temperature was maintained at 37-40 °C which effectively shortened the time to restoration. The modification of the cardiac graft harvesting method is conducive to rebeating of the donor heart. The success rates in the stabilization and stereotyping stages were significantly higher than that in the practice stage (P < .05). The operation time in the stabilization and stereotyping stages were significantly shorter than those in the practice stage (P < .05). Histopathological examination revealed thrombosis formation, interstitial hemorrhage, and inflammatory cell infiltration in the donor hearts.

CONCLUSION

Our findings suggest that the mouse-rat cervical heterotopic cardiac xenotransplantation model is the ideal animal model for studying xenograft rejection.

IL-33 Receptor (ST2) Signalling is Important for Regulation of Th2-Mediated Airway Inflammation in a Murine Model of Acute Respiratory Syncytial Virus Infection

T1/ST2, an orphan receptor with homology with the interleukin (IL)-1 receptor family, is the ligand-binding component of the receptor for the cytokine IL-33, a newly identified cytokine known to amplify the Th2 cell-dominant immune responses. The function of IL-33/ST2 signalling during respiratory syncytial virus (RSV) infection is not fully known. In this study, following intranasal infection with RSV, BALB/c mice showed a marked increase in the production of IL-33, with an elevated expression of ST2 mRNA as well as a massive infiltration of CD45(+) ST2(+) cells in the lungs, suggesting that during the early phase of RSV infection, IL-33 target cells which express ST2 on cell surface, may play a critical role for the development of RSV-induced airway inflammation. Indeed, blocking ST2 signalling using anti-ST2 monoclonal antibody diminished not only RSV-induced eosinophil recruitment, but also the amounts of Th2-associated cytokines, particularly IL-13, and Th17-type cytokine IL-17A in the lungs of infected mice. However, anti-ST2 antibody treatment did not affect the production of Th1-type cytokine IFN-γ as well as pulmonary viral growth and clearance. These results indicate that IL-33/ST2 signalling is involved in RSV-induced, Th2-associated airway inflammation but not protective immunity.

Effect of gestational weight gain as well as rehabilitation training on postnatal pelvic muscle strength

OBJECTIVE

The current study explored the impact of gestational weight gain on postnatal pelvic muscle strength and the effect of low-frequency electrical stimulation combined with biofeedback training on strength recovery.

MATERIALS AND METHODS

A total of 126 mothers six to eight weeks after term delivery were recruited at Peking University Shenzhen Hospital from August 2010 to July 2011. According to gestational weight gain, they were divided into two groups: the < 15 kg (A) and > or = 15 kg (B) groups. Pelvic floor muscle fibre strength was determined. Target low-frequency electrical stimulation combined with biofeedback training was conducted. After training, pelvic floor muscle fiber strength was determined again for effect evaluation.

RESULTS

Before training, types I and II pelvic floor muscle fiber strength of group B was noticeably lower than that of group A (p < 0.05). After rehabilitation, the pelvic floor muscle strength of both groups significantly increased (p < 0.05). However, types I and II pelvic floor muscle fiber strength of group B was still significantly lower than that of group A (p < 0.05).

CONCLUSION

Gestational weight gain negatively influences pelvic floor muscles. Low-frequency electrical stimulation combined with biofeedback training improves postnatal pelvic floor muscle fiber strength. A less gestational weight increase indicates faster postnatal pelvic muscle strength recovery and a better rehabilitative effect.

Abstract OT1-1-04: HER2 status of circulating tumor cells in HER2-positive metastatic breast cancer patients: A valuable biomarker in anti-HER2 therapy

Background: In the earlier study which we have conducted, we observed that: among the patients who were histologically positive for HER2 and received anti-HER2 therapy, only those with HER2-positive circulating tumor cells (CTCs) have benefited. We also demonstrated that CTC enumeration with a modified cut-off is a valuable prognostic tool for HER2-positive MBC patients, and formulated the criterion for evaluating CTCs HER2 status. Although the number of cases was not adequate enough so as to make the persuasion of the statistical analysis limited, it was still a valuable innovative study worthy of further exploring.

Purpose: we conducted a prospective study in order to find out whether HER2 expression in circulating tumor cells (CTCs) influenced anti-HER2 therapy in those HER2-positive metastatic breast cancer (MBC) patients.

Trial design

Patients: All the patients randomly enrolled in the trial were diagnosed with metastatic breast cancer, and the metastasis of all eligible subjects can be measured or evaluated, the Eastern Cooperative Oncology Group (ECOG) performance status score is 0 to 3. Each patient had a pathology report confirmed that this was a HER2-positve patient by the means of an immunohistochemistry (IHC) score or a fluorescent in situ hybridization (FISH) ratio, the researcher was also informed of the histological type, nodal status, estrogen receptor (ER), progesterone receptor (PgR) statuses. All of the patients would receive a new line or a new cycle of systematic therapy which must include the anti-HER2 therapy. The blood sample (10 ml) was drawn with an interval of &lt;7days before the initiating of the new treatment. All the therapeutic regimens were made without knowing the CTC results and according to the National Comprehensive Cancer Network (NCCN) clinical practice guidelines (Breast Cancer V.2.2010). Disease status was evaluated by Response Evaluation Criteria in Solid Tumors (RECIST).

Detection method: CTC isolation, enumeration and characterization were performed by using the CellSearch technology. HER2 expression intensity in CTC was given a score of 0, 1+, 2+, or 3+, according to the trial we have conducted previously, the CTC HER2 positive criterion was defined as &gt;30% of CTCs over-expressing HER2 (3+).

Statistical method: PFS was measured as the time between the baseline CTC assessment and the documentation of disease progression or death. Patients who were alive without progression at the time of analysis, PFS was calculated by the most recent follow-up evaluations. Kaplan-Meier survival curves were generated based on the

CTC levels at baseline and the HER2 status of CTC, the curves were compared using the log-rank test.

Present accrual and target accrual: 174 eligible patients were enrolled during September 2010 to April 2013, 76 patients were detected with CTC31, 50 patients received a new line or a new cycle of anti-HER2 therapy within 7days. Among the 50 patients, 40 patients received Trastuzumab and others received Lapatinib. With the ongoing of the trial, we’ll continue following up with PFS and other data of the patients.

Types of anti-HER2 therapyAnti-HER2 therapyNTrastuzumab40Lapatinib10Total50

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT1-1-04.

[Circular dichroism chromatography of secondary structures of anti-HBV IgY in eggs from hens immunized with recombinant yeast HBV vaccine]

OBJECTIVE

To study the generation and structure of anti-HBV IgY in eggs from hens immunized with recombinant yeast HBV vaccine.

METHODS

From the hens immunized three times with the recombinant yeast HBV vaccine, the eggs were collected to extract anti-HBV IgY. After purified, the anti- HBV IgY was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and reverse phase high-performance liquid chromatography (RP-HPLC), and its secondary structure was examined by circular dichroism (CD) chromatography.

RESULTS

The relative molecular mass (Mr;) of anti-HBV IgY expressed by the recombinant yeast HBV vaccine on hens was 178 000. CD chromatography showed that the α-helix, β-fold, β-turn and random coil of anti-HBV IgY had 38, 0, 44 and 17 amino acids, respectively.

CONCLUSION

The anti-HBV IgY can be expressed in eggs from hens immunized with recombinant yeast HBV vaccine. The α-helix and β-turn are major secondary structures of anti-HBV IgY.

A synthetic oxygen carrier in fibrin matrices promotes sciatic nerve regeneration in rats

Tissue-engineering nerve conduits have been studied for a long time in bridging large nerve defects. However, the low oxygen availability within the nerve conduits, which results in death of migratory Schwann cells (SC) or loss of the newly formed tissue's function, is still an obstacle for axonal regeneration. Thus, it was hypothesized that an oxygen-enriched conduit would enhance axonal regeneration and functional recovery in vivo. To address this issue, perfluorotributylamine (PFTBA) enriched fibrin hydrogel was prepared and injected into collagen-chitosan conduits. The conduit containing PFTBA-enriched fibrin hydrogel was then used to bridge a 12-mm sciatic nerve defect in rats. The control rats were bridged with collagen-chitosan conduits filled with fibrin matrices without PFTBA. It was found that axonal regeneration and functional recovery in the combined PFTBA group were significantly higher than those in the control group without PFTBA. Further investigations showed that the mRNA and protein levels of S-100, brain-derived neurotrophic factor and nerve growth factor were enhanced by PFTBA at 1 and 3weeks after surgery. However, the mRNA and protein levels of vascular endothelial growth factor were in a similar range between the combined PFTBA group and the control group without PFTBA. In addition, immunohistochemical results showed that the morphological appearances of regenerated nerve and survival of SC were enhanced by PFTBA at 4 and 12weeks after surgery. In conclusion, PFTBA-enriched nerve conduit is capable of enhancing axonal regeneration, which provides a new avenue for achieving better functional recovery in the treatment of nerve defect.

A new apparatus for study of pressure-dependent laminar premixed flames with vacuum ultraviolet photoionization mass spectrometry

We report a home-made combustion apparatus for study of pressure-dependent laminar premixed flames with tunable vacuum ultraviolet photoionization mass spectrometry. The instrument consists of a flame chamber, a photoionization chamber with a single-stage sampling system, an ion transfer/storage system, and an orthogonal-acceleration reflectron time-of-flight mass spectrometer. Preliminary results of fuel-rich C(2)H(4)/O(2)/Ar flames at pressures of 30, 150, and 760 Torr have been obtained with this instrument. Compared to previous instruments [T. A. Cool, A. McIlroy, F. Qi, P. R. Westmoreland, L. Poisson, D. S. Peterka, and M. Ahmed, Rev. Sci. Instrum. 76, 094102 (2005); F. Qi, R. Yang, B. Yang, C. Q. Huang, L. X. Wei, J. Wang, L. S. Sheng, and Y. W. Zhang, Rev. Sci. Instrum. 77, 084101 (2006)], performances of the new apparatus have higher mass resolution (~3500 at m/z = 40), better detection limit (<1 ppm), and broader dynamic range (better than 5 order of magnitude).

The mutacins of Streptococcus mutans: regulation and ecology

Streptococcus mutans is generally recognized as a causative agent of human dental caries. The production of mutacins (bacteriocins) by S. mutans is considered to be an important factor in the colonization and establishment of S. mutans in the dental biofilm. Two types of mutacins have been characterized: the lantibiotics and the non-lantibiotics. The lantibiotics generally have a wider spectrum of activity than the non-lantibiotics, which make them attractive targets for development into new antimicrobial modalities. The non-lantibiotics are much more prevalent among strains of S. mutans and play a significant role in both community-level and population-level interactions in the dental biofilm. These interactions are directly mediated through the ComCDE two-component system and the newly characterized LytTR Regulation Systems HdrRM and BrsRM. These systems coordinate natural competence development and mutacin production as a means to acquire transforming DNA either by killing closely related streptococcal species in the vicinity of S. mutans, or through an altruistic suicide mechanism among a subpopulation of competent cells within the S. mutans community. As more S. mutans strains are sequenced, it is anticipated that additional mutacins with novel functions will be discovered, which may yield further insights into the ecological role of mutacins within the oral biofilm.

Community and gene composition of a human dental plaque microbiota obtained by metagenomic sequencing

Human dental plaque is a complex microbial community containing an estimated 700 to 19,000 species/phylotypes. Despite numerous studies analysing species richness in healthy and diseased human subjects, the true genomic composition of the human dental plaque microbiota remains unknown. Here we report a metagenomic analysis of a healthy human plaque sample using a combination of second-generation sequencing platforms. A total of 860 million base pairs of non-human sequences were generated. Various analysis tools revealed the presence of 12 well-characterized phyla, members of the TM-7 and BRC1 clade, and sequences that could not be classified. Both pathogens and opportunistic pathogens were identified, supporting the ecological plaque hypothesis for oral diseases. Mapping the metagenomic reads to sequenced reference genomes demonstrated that 4% of the reads could be assigned to the sequenced species. Preliminary annotation identified genes belonging to all known functional categories. Interestingly, although 73% of the total assembled contig sequences were predicted to code for proteins, only 51% of them could be assigned a functional role. Furthermore, ~2.8% of the total predicted genes coded for proteins involved in resistance to antibiotics and toxic compounds, suggesting that the oral cavity is an important reservoir for antimicrobial resistance.

Examination of the hdrRM regulon yields insight into the competence system of Streptococcus mutans

Previous studies have identified the hdrRM operon as a novel regulatory system induced by conditions of high cell density. Little is known about the genes under the control of this system, but a variety of important phenotypes are associated with either hdrR overexpression or mutation of hdrM. To characterize the regulatory function of the HdrRM system in Streptococcus mutans we used a microarray approach to compare the transcriptional profiles of an hdrR overexpression strain with an hdrM mutant. Both strains exhibited almost identical profiles, which included all of the known late competence genes as well as a variety of competence-induced bacteriocins. Through a combination of real-time reverse transcription-polymerase chain reaction (PCR), reporter gene analysis and random amplification of complementary DNA ends PCR, we confirmed the role of comX as a central intermediate regulator of numerous genes in the hdrRM regulon. Through these studies, we also identified novel comX-regulated genes required for natural competence. Taken together, our results suggest that the primary function of the HdrRM system is to regulate the late competence genes together with various bacteriocins. This occurs independently of the ComCDE system, even though both systems regulate nearly identical genes. This suggests that S. mutans has multiple parallel input sensory systems that control the same output response: the induction of natural competence and concurrent production of bacteriocins.