A natural inhibitor of diapophytoene desaturase attenuates methicillin-resistant Staphylococcus aureus (MRSA) pathogenicity and overcomes drug-resistance.

BACKGROUND AND PURPOSE: At present, the inhibition of staphyloxanthin biosynthesis has emerged as a prominent strategy in combating methicillin-resistant Staphylococcus aureus (MRSA) infection. Nonetheless, there remains a limited understanding regarding the bio-structural characteristics of staphyloxanthin biosynthetic enzymes, as well as the molecular mechanisms underlying the interaction between inhibitors and proteins. Furthermore, the functional scope of these inhibitors is relatively narrow. EXPERIMENTAL APPROACH: In this study, we address these limitations by harnessing the power of deep learning techniques to construct the 3D structure of diapophytoene desaturase (CrtN). We perform efficient virtual screening and unveil alnustone as a potent inhibitor of CrtN. Further investigations employing molecular modelling, site-directed mutagenesis and biolayer interferometry (BLI) confirmed that alnustone binds to the catalytic active site of CrtN. Transcriptomic analysis reveals that alnustone significantly down-regulates genes associated with staphyloxanthin, histidine and peptidoglycan biosynthesis. KEY RESULTS: Under the effects of alnustone, MRSA strains exhibit enhanced sensitivity to various antibiotics and the host immune system, accompanied by increased cell membrane permeability. In a mouse model of systemic MRSA infection, the combination of alnustone and antibiotics exhibited a significant therapeutic effect, leading to reduced bacterial colony counts and attenuated pathological damage. CONCLUSION AND IMPLICATIONS: Alnustone, as a natural inhibitor targeting CrtN, exhibits outstanding antibacterial properties that are single-targeted yet multifunctional. This finding provides a novel strategy and theoretical basis for the development of drugs targeting staphyloxanthin producing bacteria.

Real-time detection of isoprene marker gas based on micro-integrated chromatography system with GOQDs-modifiedµGC column and metal oxide gas detector.

Isoprene is a typical physiological marker that can be used to screen for chronic liver disease. This work developed a portable micro-integrated chromatography analysis system based on micro-electromechanical system technology, nanomaterials technology and embedded microcontroller technology. The system integrated components such as graphene oxide quantum dots modified semi-packed microcolumn, In2O3nanoflower (NF) gas-sensitive detector and 3D printed miniature solenoid valve group. The effectiveness of the separation effect of the micro-integrated system was verified by gas mixture test; the laws of the influence of carrier gas pressure and column temperature on the chromatographic separation performance, respectively, were investigated, and the working conditions (column temperature 90 °C and carrier gas pressure 7.5 kPa) for system testing were determined. The percentages of relative standard deviation of the peak areas and retention times obtained for the separated gases were in the range of 0.95%-6.06%, indicating the good reproducibility of the system. Meanwhile, the microintegrated system could detect isoprene down to 50 ppb at small injection volume (1 ml). The system response increased with increasing isoprene concentration and was linearly correlated with isoprene concentration (R2= 0.986), indicating that the system was expected to be used for trace detection of isoprene, a marker gas for liver disease, in the future.

A Novel Manifold Dual-Microchannel Flow Field Structure with High-Performance Heat Dissipation.

With the development of miniaturization and integration of electronic devices, the conventional manifold microchannels (MMCs) structure has been unable to meet the heat dissipation requirements caused by the rapid growth of internal heat flux. There is an urgent need to design a new heat dissipation structure with higher heat dissipation capacity to ensure the working stability and life of electronic devices. In this paper, we designed a novel manifold dual-microchannel (MDMC) cooling system that embedded the microchannel structure into the manifold microchannel structure. The MDMC not only has good heat dissipation performance that can meet the development needs of electronic equipment to miniaturization and integration, but also has a compact structure that does not increase the overall thickness and volume compared with MMC. The high temperature uniformity and heat transfer performance of MDMC are significantly improved compared to MMC. The Tmax is reduced by 13.6% and 17.5% at the heat flux density of 300 W/cm2 and 700 W/cm2, respectively. In addition, the influence of the inlet-2 velocity and the total microchannels number on the heat transfer performance of the MDMC structure are numerically investigated. The results show that the decrease rate of Tmax and ΔT is about 6.69% and 16% with the increase of inlet-2 velocity from 1.2 m/s to 2.4 m/s and microchannels number from 10 to 48, respectively. At the same time, the best temperature uniformity is obtained when the number of microchannels is 16.

Thermal Induced Interface Mechanical Response Analysis of SMT Lead-Free Solder Joint and Its Adaptive Optimization.

Surface mount technology (SMT) plays an important role in integrated circuits, but due to thermal stress alternation caused by temperature cycling, it tends to have thermo-mechanical reliability problems. At the same time, considering the environmental and health problems of lead (Pb)-based solders, the electronics industry has turned to lead-free solders, such as ternary alloy Sn-3Ag-0.5Cu (SAC305). As lead-free solders exhibit visco-plastic mechanical properties significantly affected by temperature, their thermo-mechanical reliability has received considerable attention. In this study, the interface delamination of an SMT solder joint using a SAC305 alloy under temperature cycling has been analyzed by the nonlinear finite element method. The results indicate that the highest contact pressure at the four corners of the termination/solder horizontal interface means that delamination is most likely to occur, followed by the y-direction side region of the solder/land interface and the top arc region of the termination/solder vertical interface. It should be noted that in order to keep the shape of the solder joint in the finite element model consistent with the actual situation after the reflow process, a minimum energy-based morphology evolution method has been incorporated into the established finite element model. Eventually, an Improved Efficient Global Optimization (IEGO) method was used to optimize the geometry of the SMT solder joint in order to reduce the contact pressure at critical points and critical regions. The optimization result shows that the contact pressure at the critical points and at the critical regions decreases significantly, which also means that the probability of thermal-induced delamination decreases.

Magnetic mesoporous carbon material based electrochemical sensor for rapid detection of penicillin sodium in milk.

In recent years, to increase growth rate and prevent infectious diseases, an excessive use of antibiotics in livestock breeding processes has resulted in the presence of antibiotic residues in animal foods. In this experiment, a new kind of electrochemical sensor is prepared based on magnetic mesoporous hollow carbon microspheres (MHM) as a penicillinase (Pen X) adsorption carrier to rapidly detect penicillin sodium (Pen G), named Pen X/MHM/MGCE. The MHM-adsorbed penicillinase can be separated from the solution by magnetic attraction and fixed on a magnetic glassy carbon electrode by physical adsorption, which is easy to operate and avoids the interference of a crosslinking agent at the active site of the enzyme. A differential pulse voltammetry (DPV) method is used to immerse the working electrode in test samples containing different concentrations of penicillin sodium solution with 0.5 mg/mL oxidized hematoxylin. According to the quantitative relationship between the current value and the concentration of penicillin sodium, the concentration of penicillin sodium in the tested samples can be determined. The detection range of the sensor is 10-8 to 10-2 mg/mL, the linear relationship is good (R2 = 0.9983), and the detection limit (LOD) is 2.655 × 10-7 mg/mL (S/N = 3). The detection of penicillin sodium in milk using a standard addition method shows good recovery. Furthermore, the proposed method has the advantages of a wide detection range, good enzyme immobilization capacity, good precision and stability, convenient cleaning, and recycling of solid materials. Thus, it can successfully achieve rapid detection in milk samples. PRACTICAL APPLICATION: The sensor provides a low detection limit and high recovery rate of electrode material; therefore, the sensor can realize the rapid and quantitative detection of penicillin sodium in milk.

Experimental investigation of the strong stability, antibacterial and anti-inflammatory effect and high bioabsorbability of a perilla oil or linseed oil nanoemulsion system.

Perilla oil (PO) and linseed oil (LO) are very rich in nutrients and have great potential market value. Using the Cremophor RH40-Span80 preparation system to make a perilla oil nanoemulsion (PON) or linseed oil nanoemulsion (LON) can improve the bioavailability and stability of these oils. The effect of different reaction conditions on the stability of the emulsion was investigated. The results showed that the PON and LON have good stability at pH ≥ 7, different storage temperatures (4 °C, 25 °C, 37 °C and 55 °C) and different NaCl concentrations (0, 2, 4, 6, 8 M). Meanwhile, it was found that the content of the lipid peroxidation product malondialdehyde (MDA) in the nanoemulsion did not change significantly over 7 days, further demonstrating the stability of the nanoemulsion. Through anti-inflammatory and antibacterial tests, it was found that the PON and LON have an effective inhibitory effect on inflammation; moreover, the PON inhibits the growth of Escherichia coli, Salmonella enteritidis and Pseudomonas tolaasii, and the LON has an inhibitory effect on Staphylococcus aureus and Pseudomonas tolaasii (inhibition zone > 10 mm). In addition, we found that there were no pathological differences in the heart, liver, spleen and kidney of Kunming mice between the PO and PON groups and the LO and LON groups. Furthermore, after intraperitoneal injection of P 407 into mice, the comparison between PON and PO and between LON and LO showed that the blood lipid levels of the mice in the PON and LON treatment groups increased, indicating that the absorption capacity of the small intestine of the mice for the PON and LON was enhanced. Therefore, the preparation of the PON and LON has good development prospects and opens up opportunities in the development of the food industry.

Micro-fabricated packed metal gas preconcentrator for enhanced monitoring of ultralow concentration of isoprene.

A novel non-silicon-based micro-preconcentration device, as a pretreatment component in a portable gas chromatography system, was developed for the preconcentration one of the trace volatile organic compounds (VOCs) in the exhaled gases, which is one typical biomarker for the chronic liver disease (CLD). The device was designed as an array of manifold-shaped rectangular metal micro-channels with flat dimensions of 16 mm × 12.6 mm and the internal empty volume is 14.4 µL on the copper substrate. Instead of the non-silicon fabrication process, the traditional laser etching technology (LET) was optimized to etch micro-channels, and vacuum diffusion welding (VDW) was applied to form internal channels. The fabricated chip was filled with Carbopack X adsorbent. In the testing, the metal gas preconcentrator (MGP) was installed in a commercial GC (gas chromatography) and nitrogen was used as carrier gas and desorbed gas. With the MPG, up to 352 of concentration factor can be achieved for 10 ppb isoprene. The developed MGP, which has advantages of high strength, low cost, good thermal conductivities, can potentially be used for non-invasive screening of advanced liver fibrosis by monitoring isoprene concentrations in exhaled breath.

Post-ischemia mdivi-1 treatment protects against ischemia/reperfusion-induced brain injury in a rat model.

When given prior to brain ischemia, mitochondrial division inhibitor-1 (mdivi-1) attenuates the brain damage caused by ischemia. Here, we investigated the potential effects of post-ischemia mdivi-1 treatment (1mg/kg, i.p., administered immediately after 2h of ischemia and prior to reperfusion) using a MCAO rat model. Mdivi-1 treatment decreased infarct volume and improved neurological function. In addition, cytochrome C release was attenuated, and neuronal apoptosis was decreased. The mitochondrial fission protein dynamin-related protein 1 (Drp1) was decreased in the mitochondrial fraction but increased in the cytosolic fraction. Mdivi-1 treatment augmented the increases in the mRNA expression of peroxisome proliferator-activated receptor coactivator-1α, nuclear respiratory factor-1, and mitochondrial transcriptional factor A. In conclusion, when given after ischemia and prior to reperfusion, mdivi-1 can protect against brain damage by inhibiting the mitochondria-mediated apoptosis induced by mitochondrial fission. Post-ischemia mdivi-1 treatment might promote I/R-induced mitochondrial biogenesis.

[Effects of dexmedetomidine combined with fentanyl in patients undergoing anesthesia induction by sevoflurane].

OBJECTIVE: To investigate the effects of dexmedetomidine combined with fentanyl in patients undergoing anesthesia induction by sevoflurane. METHOD: Eighty patients for elective endotracheal intubation under general anesthesia operations were randomly and double-blindly divided into Dex combined with fentanyl group (Group DF) and the fentanyl group (Group F) from April 2011 to September 2011 at the Fourth Affiliated Hospital of Harbin Medical University, and there were 40 cases in each group. The investigation was approved by all the patients and by the Ethics Committee of the hospital. In group DF, each patient was pumped in the 0.5 µg/kg Dex by vein before 10 minutes of anesthesia induction and group F were given the same amount of normal saline, and tidal volume method was used to induce anesthesia of sevoflurane. All the patients were given 2 µg/kg fentanyl and 0.1 mg/kg vecuronium by tracheal intubation and the MAP and HR and adverse reactions were observed before anesthesia induction (T(0)), before endotracheal intubation (T(1)), at the moment of tracheal intubation (T(2)), after 1 minutes of tracheal intubation (T(3)), after 3 minutes of tracheal intubation (T(4)) and after 5 minutes of tracheal intubation (T(5)). RESULT: The loss of eyelash reflex time of group DF is shorter (P < 0.05), adverse reaction is less (P < 0.05) and the number of adding atropine case is higher than that of group F (P < 0.05), the MAP of the two groups after induction of other moments are lower than that of T(0) (P < 0.05); MAP of group F at T(1) is lower than that of T(0), T(2), T(3) and group DF (P < 0.05); T(1) of group DF is lower than that of T(0) (P < 0.05), the HR after induction of group DF is lower than that of T(0) and F group (P < 0.05), and that of T(2) and T(4) are higher than that of T(1) (P < 0.05); HR of group F at T(1) is lower than that of T(2) and T(3) (P < 0.05). CONCLUSION: Dexmedetomidine in combination with fentanyl can inhibit stress response of tracheal intubation of sevoflurane induction efficiently and stabilize hemodynamics.

The effects of propofol on hippocampal caspase-3 and Bcl-2 expression following forebrain ischemia-reperfusion in rats.

Transient cerebral ischemia may result in neuronal apoptosis. During this process, several apoptosis-regulatory genes are induced in apoptotic cells. Among these genes, cysteinyl aspartate-specific protease-3 (caspase-3) and B-cell leukemia-2 (Bcl-2) are the most effective apoptotic regulators because they play a decisive role in the occurrence of apoptosis. Research has shown that propofol, which is an intravenous anesthetic agent, exhibits neuroprotective effects against cerebral ischemia-reperfusion injury, although the neuroprotective mechanism is still unclear. In this study, we examined the effects of propofol in rats after forebrain ischemia-reperfusion. We assessed the expression of hippocampal caspase-3, which acts as an apoptotic activator, and Bcl-2, which acts as an apoptotic suppressor. Forebrain ischemia was induced in hypotensive rats by clamping the bilateral common carotid arteries for 10 min. Propofol was administered via a lateral cerebral ventricle injection using a microsyringe after the induction of ischemia. Neuronal damage was determined by histological examination of brain sections at the level of the dorsal hippocampus. Caspase-3 and Bcl-2 expression in the hippocampus were detected using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. We also used an immunohistochemical method after ischemia-reperfusion. In the hippocampus, caspase-3 and Bcl-2 mRNA were dramatically increased at 24h after forebrain ischemia. Following 6-24h of reperfusion, forebrain ischemia for 10 min induced a gradual increase in the expression of caspase-3 and Bcl-2 protein in the rat hippocampus, which peaked at 24h. In the propofol (1.0mg/kg) intervention group, the hippocampal expression of caspase-3 mRNA decreased significantly in rats 24h after ischemia; Bcl-2 mRNA was increased at the same time point. During the 24-h reperfusion period and after treatment with propofol, the level of caspase-3 protein expression was low, while the level of Bcl-2 was high. Thus, our results suggest that the neuroprotective effects of propofol against neuronal apoptosis may be mediated by the inhibition of caspase-3 expression and an increase in Bcl-2 expression.

Pharmacokinetics and biodegradation mechanisms of a versatile carboxymethyl derivative of chitosan in rats: in vivo and in vitro evaluation.

Carboxymethyl chitosan (CM-chitosan), which is a water-soluble derivative of chitosan, has attracted much attention as a new biomedical material. The safety study of this material was persuasive for its potential application. The present study was conducted to assess the tissue distribution, pharmacokinetics, biodegradation mechanism, and excretion of CM-chitosan in rats. After the rats were intraperitoneally injected at the dose of 50 mg/kg, the fluorescein isothiocyanate (FITC)-labeled CM-chitosan was absorbed rapidly and distributed to different organs, including liver, spleen, and kidney. The highest level of CM-chitosan was found in liver. It was at the level of 1.6 +/- 0.6 mg/liver and made up approximately 10-22% of the total injected FTC-CM-chitosan. Urinary excretion was the predominant way of excretion of FITC-labeled CM-chitosan, and 85% of the dose was excreted in urine over the period of 11 days. The molecular weights of body distributed FTC-CM-chitosan and urinary excreted FTC-CM-chitosan were analyzed by gel chromatography. The results indicated that the FTC-CM-chitosan was degraded in abdominal dropsy. The absorbed CM-chitosan forms were found with a relatively high molecular weight (approximately 300 kDa), whereas the molecular weight of the urinary excreted FTC-CM-chitosan was less than 45 kDa. In vitro research revealed that the CM-Chi was also degradable in plasma and homogenate of liver. The CM-chitosan with a molecular weight of approximately 800k was thoroughly degraded to a small molecule after it was incubated in homogenate of liver at 37 degrees C for 24 h. The results suggested that the liver plays a central role in biodegradation of CM-chitosan. The excellent biodegradability of CM-chitosan could potentially contribute to the clinical applications. The results also provide important clues for further modification of CM-chitosan as the postsurgical and other biomedical materials.