Determination of oxygen consumption in water by continuous flow injection analysis using potassium permanganate / 预防医学

Objective@#To establish a continuous flow injection analysis with potassium permanganate for determination of oxygen consumption in water.@*Methods@#The water samples and acid potassium permanganate working solutions were mixed using the continuous flow bubble spacing, and subjected to online heating reaction at 97 ℃. The peak height of the electrical signal of potassium permanganate was measured at the maximum absorption wavelength of 520 nm, and the standard substance, sulfuric acid concentration and potassium permanganate concentration were optimized according to the peak height of the electrical signal. The standard curve was plotted to measure the limit of detection, the limit of quantification, and spiked recovery rate of the method. The CODMn concentration was determined in 40 drinking water samples using acid potassium permanganate titration and continuous flow injection analysis using potassium permanganate, and the determination results of the two methods were compared with paired t-test.@*Results@#Glucose was selected as the standard substance, and the mixture of 17.5% sulfuric acid and 3.2 mmol/L potassium permanganate was selected as the working solution. CODMn had a good linear relationship at concentrations of 0 to 6.00 mg/L, with a correlation coefficient of 0.999 and higher, a detection limit of 0.013 mg/L and a quantitation limit of 0.043 mg/L, respectively. The spiked recovery rates were 90.00% to 105.00% in 40 drinking water samples, with relative standard deviations of 0.12% to 1.36%. The determination results of two permanganate index standard substances were all within the range of standard values. The relative errors of CODMn concentration were 1.55% to 9.26% between the continuous flow injection analysis using potassium permanganate and acid potassium permanganate titration, and there was no significant difference (t=2.023, P=0.185). @*Conclusion@#The established continuous flow injection analysis with potassium permanganate is feasible for batch determination of oxygen consumption in water.

Butorphanol reduces the neuronal inflammatory response and apoptosis via inhibition of p38/JNK/ATF2/p53 signaling.

Neuronal cell apoptosis is a complex pathophysiological change that occurs following spinal cord injury (SCI) and affects self-repair. Therefore, preventing neuronal cell apoptosis can promote the recovery of nerve function. The present study aimed to investigate the effects of butorphanol on neuronal inflammatory response and apoptosis. The effects of butorphanol on cell viability and pathway-related protein expression were first assessed using the CCK8 and western blot assays, respectively. Lipopolysaccharide (LPS) was used to establish models. The influences of additional anisomycin, an agonist of MAPK pathway, on cell viability, pathway-related protein expression and lactate dehydrogenase level were determined using the CCK8 assay, western blotting and assay kits, respectively. In addition, the roles of butorphanol and anisomycin in inflammatory factor levels and cell apoptosis were determined using reverse transcription-quantitative PCR, TUNEL and western blot assays. Butorphanol was found to protect PC12 cells from the action of LPS on viability and effectively upregulated the p38/JNK/activation of transcription factor 2 (ATF2)/p53 protein expression levels. In addition, anisomycin could break the protective role of butorphanol in cell viability and the inhibitory roles in inflammatory response and apoptosis. To sum up, butorphanol reduces neuronal inflammatory response and apoptosis via inhibiting p38/JNK/ATF2/p53 signaling. The present findings may provide a new direction for the treatment for SCI.

MEF2D Participates in Microglia-Mediated Neuroprotection in Cerebral Ischemia-Reperfusion Rats.

OBJECTIVE: Microglial activation is a vital process in the neuroinflammatory response induced by I/R injury. It has been reported that myocyte enhancer factor (MEF)2D expression in activated microglia is associated with microglia-induced inflammatory responses and plays an important role in neuronal survival. This research aimed to investigate the role and mechanism of MEF2D in microglial activation and neuroinflammation in cerebral I/R in vitro and in vivo. METHODS: A cerebral I/R model was established. In vitro, neuronal, or microglial cells were exposed to oxygen-glucose deprivation and reoxygenation to mimic I/R. MEF2D overexpression was induced, and siRNA was administered in vitro and in vivo. Microglial polarization; MEF2D, nuclear transcription factor (NF)-κb, TLR4, and cytokine levels; neuronal injury; mitochondrial function; brain injury and cognitive function were detected in the different groups in vitro and in vivo. RESULTS: We found that oxygen-glucose deprivation increased MEF2D expression in a time-dependent manner in BV2 cells and primary microglia. MEF2D overexpression inhibited microglial activation, the expression of NF-κb and TLR, cytokine levels, and neuronal injury in microglia exposed to oxygen-glucose deprivation and reoxygenation. In the middle cerebral artery occlusion model, microglial activation, the neuroinflammatory response, mitochondrial dysfunction, brain injury, and cognitive function were improved by MEF2D overexpression and aggravated by MEF2D siRNA treatment. CONCLUSION: These results indicate that MEF2D is a necessary molecule for neuroinflammation regulation and neuronal injury in cerebral ischemia.

An artificial photosynthetic model based on a molecular triad of boron dipyrromethene and phthalocyanine.

A boron dipyrromethene (BDP) unit and its monostyryl derivative (MSBDP) were introduced at the axial positions of a silicon(iv) phthalocyanine (SiPc) core. The absorption spectrum of this compound virtually covered the entire visible region (300-700 nm) and could be interpreted as a superposition of the spectra of individual components. The intramolecular photoinduced energy and charge transfer processes of this triad were studied using steady-state and time-resolved spectroscopic methods in polar and nonpolar solvents. Upon BDP-part excitation, a fast and highly efficient excitation energy transfer (EET) occurred resulting in strong quenching of its fluorescence and the formation of the first excited singlet state of SiPc or MSBDP. It was found that both EET and charge transfer (CT) processes competed with each other in the depopulation of the first excited singlet state of the MSBDP moiety. The former strongly superseded CT in nonpolar toluene, whereas the latter was dominant in a polar environment. Direct or indirect (via EET) excitation of the SiPc-part of the triad was followed by CT yielding the charge-separated (CS) species BDP-SiPc(˙-)-MSBDP(˙+). The energy gap between the CS state and the S1-state of the SiPc moiety was found to be only 0.06 eV in toluene, which facilitated the back CT process and resulted in the appearance of thermally activated delayed fluorescence. With increasing solvent polarity, the energy of the CS state reduced resulting in the disappearance of the delayed fluorescence in CHCl3, tetrahydrofuran or N,N-dimethylformamide. The charge recombination rate, k(CR), was very fast in polar DMF (3.3 × 10(10) s(-1)), whereas this process was two-orders of magnitude slower in nonpolar toluene (k(CR) = 4.0 × 10(8) s(-1)).

Photoinduced energy and charge transfer in a p-phenylene-linked dyad of boron dipyrromethene and monostyryl boron dipyrromethene.

Boron dipyrromethenes (BDPs) are excellent building blocks for design of artificial light harvesting and charge separation systems. In the present work, we report the results of photophysical studies of a novel dyad, in which a BDP and a mono-styryl BDP (MSBDP) are covalently linked to each other at the meso-position via a p-phenylene unit. It was found that the photophysical properties of the dyad dissolved in polar as well as nonpolar solvents are strongly affected by two different types of interactions between the BDP and MSBDP parts, namely excitation energy transfer and photoinduced electron transfer. The first process delivers the excitation energy to the first excited singlet state of the MSBDP-part upon excitation of the BDP unit. The direct or indirect (via excitation energy transfer) population of the first excited singlet state of the MSBDP moiety is followed by hole transfer to generate the charge-separated state. In non-polar toluene, the probability of charge separation is low, whereas in polar acetonitrile the charge separation quantum yield is close to unity, resulting in strong quenching of the MSBDP fluorescence.

A boron dipyrromethene-phthalocyanine pentad as an artificial photosynthetic model.

A silicon(IV) phthalocyanine with two axial p-phenylene-linked boron dipyrromethene and monostyryl boron dipyrromethene moieties has been prepared. The resulting pentad absorbs strongly in most of the UV-visible region and serves as an artificial photosynthetic antenna-reaction centre model.