Sijunzi decoction enhances sensitivity of colon cancer cells to NK cell destruction by modulating P53 expression.

ETHNOPHARMACOLOGICAL RELEVANCE: Sijunzi Decoction (SJZD), a traditional Chinese herbal remedy, is frequently employed in the treatment of various cancers, including colon cancer. Previous research suggests that SJZD plays a pivotal role in modulating the immune system and enhancing immunity against tumors. However, the precise role of SJZD in combating colon cancer and its potential molecular functions in regulating natural killer cells remain elusive. AIMS OF THE STUDY: To elucidate the potential mechanism underlying the anticolon cancer effects of SJZD in synergy with natural killer (NK) cells through both in vivo and in vitro experiments. MATERIALS AND METHODS: In vivo experiments: A subcutaneous tumor mouse model of colon cancer and in vivo NK cell depletion experiments were conducted to observe the anticolon cancer effects of SJZD. Flow cytometry assessed immune cell depletion in mouse spleens, while immunohistochemical (IHC) staining detected the expression of apoptotic genes in tumor tissues. In vitro experiments: The mechanism by which SJZD regulates the sensitization of colon cancer cells to NK cells was investigated using real-time polymerase chain reaction (RT-PCR), western blotting (WB), and co-culture experiments with NK cells. RESULTS: Sijunzi Decoction (SJZD) significantly impeded tumor growth in mice; however, NK cell depletion markedly attenuated the tumor-suppressive effect of SJZD. Immunohistochemical (IHC) results indicated that SJZD increased the expression of P53, death receptor 4 (DR4), and death receptor 5 (DR5) in tumor tissues. In vitro experiments, 24 h SJZD-pretreated colon cancer cells showed a substantial elevation in P53, DR4, and DR5 levels, and the activity of colon cancer cells significantly diminished after co-culture with NK cells. These effects of SJZD were reversed with the addition of the P53 inhibitor pifithrin-α (PFT-α), resulting in reduced inhibition of colon cancer cells by NK cells. CONCLUSION: SJZD enhances the levels of DR4 and DR5 through the modulation of P53 expression, consequently increasing the sensitivity of colon cancer cells to NK cell-mediated killing. These findings provide a theoretical foundation for the clinical application of SJZD in patients with colon cancer. In this study, we first investigated the effect of SJZD on subcutaneous tumor growth in mice with colon cancer using in vivo assays and assessed the impact of NK cells on the anticolon cancer effect of SJZD in vivo through NK cell depletion. In vitro experiments were conducted to explore the potential mechanism of action of SJZD in NK cell-mediated anticolon cancer effects.

Machine learning-mediated identification of ferroptosis-related genes in osteonecrosis of the femoral head.

Osteonecrosis of the femoral head (ONFH) is a condition caused by a disruption or damage to the femoral head's blood supply, which causes the death of bone cells and bone marrow components and prevents future regeneration. Ferroptosis, a type of controlled cell death, is caused by iron-dependent lipid peroxidation. Here, we identified ferroptosis-related genes and infiltrating immune cells involved in ONFH and predicted the underlying molecular mechanisms. The GSE123568 dataset was subjected to differential expression analysis to identify genes related to ferroptosis. Subsequently, GO and KEGG pathway enrichment analyses, as well as protein-protein interaction (PPI) network analysis, were conducted. Hub genes involved in ferroptosis were identified using machine learning and other techniques. Additionally, immune infiltration analysis and lncRNA-miRNA-mRNA network prediction analysis were performed. Finally, we determined whether ferroptosis occurred by measuring iron content. The hub genes were validated by ROC curve analysis and qRT-PCR. Four ferroptosis-related hub genes (MAPK3, PTGS2, STK11, and SLC2A1) were identified. Additionally, immune infiltration analysis revealed a strong correlation among ONFH, hub genes, and various immune cells. Finally, we predicted the network relationship between differentially expressed lncRNAs and hub genes in the lncRNA-miRNA-mRNA network. MAPK3, PTGS2, STK11, and SLC2A1 have been identified as potential ferroptosis-related biomarkers and drug targets for the diagnosis and prognosis of ONFH, while some immune cells, as well as the interaction between lncRNA, miRNA, and mRNA, have also been identified as potential pathogenesis markers and therapeutic targets.

Identification of basement membrane-related biomarkers associated with the diagnosis of osteoarthritis based on machine learning.

BACKGROUND: Osteoarthritis is a very common clinical disease in middle-aged and elderly individuals, and with the advent of ageing, the incidence of this disease is gradually increasing. There are few studies on the role of basement membrane (BM)-related genes in OA. METHOD: We used bioinformatics and machine learning methods to identify important genes related to BMs in OA patients and performed immune infiltration analysis, lncRNA‒miRNA-mRNA network prediction, ROC analysis, and qRT‒PCR. RESULT: Based on the results of machine learning, we determined that LAMA2 and NID2 were the key diagnostic genes of OA, which were confirmed by ROC and qRT‒PCR analyses. Immune analysis showed that LAMA2 and NID2 were closely related to resting memory CD4 T cells, mast cells and plasma cells. Two lncRNAs, XIST and TTTY15, were simultaneously identified, and lncRNA‒miRNA‒mRNA network prediction was performed. CONCLUSION: LAMA2 and NID2 are important potential targets for the diagnosis and treatment of OA.

SY-Net: A Rice Seed Instance Segmentation Method Based on a Six-Layer Feature Fusion Network and a Parallel Prediction Head Structure.

During the rice quality testing process, the precise segmentation and extraction of grain pixels is a key technique for accurately determining the quality of each seed. Due to the similar physical characteristics, small particles and dense distributions of rice seeds, properly analysing rice is a difficult problem in the field of target segmentation. In this paper, a network called SY-net, which consists of a feature extractor module, a feature pyramid fusion module, a prediction head module and a prototype mask generation module, is proposed for rice seed instance segmentation. In the feature extraction module, a transformer backbone is used to improve the ability of the network to learn rice seed features; in the pyramid fusion module and the prediction head module, a six-layer feature fusion network and a parallel prediction head structure are employed to enhance the utilization of feature information; and in the prototype mask generation module, a large feature map is used to generate high-quality masks. Training and testing were performed on two public datasets and one private rice seed dataset. The results showed that SY-net achieved a mean average precision (mAP) of 90.71% for the private rice seed dataset and an average precision (AP) of 16.5% with small targets in COCO2017. The network improved the efficiency of rice seed segmentation and showed excellent application prospects in performing rice seed quality testing.

STC-YOLO: Small Object Detection Network for Traffic Signs in Complex Environments.

The detection of traffic signs is easily affected by changes in the weather, partial occlusion, and light intensity, which increases the number of potential safety hazards in practical applications of autonomous driving. To address this issue, a new traffic sign dataset, namely the enhanced Tsinghua-Tencent 100K (TT100K) dataset, was constructed, which includes the number of difficult samples generated using various data augmentation strategies such as fog, snow, noise, occlusion, and blur. Meanwhile, a small traffic sign detection network for complex environments based on the framework of YOLOv5 (STC-YOLO) was constructed to be suitable for complex scenes. In this network, the down-sampling multiple was adjusted, and a small object detection layer was adopted to obtain and transmit richer and more discriminative small object features. Then, a feature extraction module combining a convolutional neural network (CNN) and multi-head attention was designed to break the limitations of ordinary convolution extraction to obtain a larger receptive field. Finally, the normalized Gaussian Wasserstein distance (NWD) metric was introduced to make up for the sensitivity of the intersection over union (IoU) loss to the location deviation of tiny objects in the regression loss function. A more accurate size of the anchor boxes for small objects was achieved using the K-means++ clustering algorithm. Experiments on 45 types of sign detection results on the enhanced TT100K dataset showed that the STC-YOLO algorithm outperformed YOLOv5 by 9.3% in the mean average precision (mAP), and the performance of STC-YOLO was comparable with that of the state-of-the-art methods on the public TT100K dataset and CSUST Chinese Traffic Sign Detection Benchmark (CCTSDB2021) dataset.

Clinical profiles and intraoperative identification of complex glands in stage I lung adenocarcinoma.

OBJECTIVES: This study aimed to investigate the potential of complex glandular patterns (CGP) in lymph node micrometastasis (LNMM) and to determine the clinical beneficiaries in stage I lung adenocarcinoma (LUAD) with CGP. Meanwhile, the feasibility of detecting CGP on frozen section was also evaluated. METHODS: We retrospectively analysed the clinicopathological characteristics of 848 pathologic-stage I LUADs. A logistic regression model and a Cox proportional-hazards model were conducted to define the risk factors for LNMM and survival respectively. Furthermore, 5 pathologists reviewed frozen sections of 100 LUADs independently. RESULTS: The logistic regression model indicated that CGP [odds ratio 3.89, 95% confidence interval (CI) 2.46-6.15; P < 0.001] was an independent predictor of the presence of LNMM. Subgroup analysis revealed that CGP-present/LNMM-positive LUAD had the highest risk of both loco-regional and distant recurrence. Moreover, adequate lymphadenectomy [recurrence-free survival: hazard ratio (HR) 0.61, 95% CI 0.40-0.95; P = 0.028; overall survival: HR 0.64, 95% CI 0.41-0.99; P = 0.043] and adjuvant chemotherapy (recurrence-free survival: HR 0.30, 95% CI 0.18-0.52; P < 0.001; overall survival: HR 0.33, 95% CI 0.19-0.57; P < 0.001) brought survival benefits to CGP-present patients, especially to CGP-present/LNMM-positive subgroup. Across the 5 pathologists, sensitivity ranged from 59 to 68% and specificity ranged from 79 to 83%, with moderate diagnostic agreement and high interobserver agreement for detecting CGP on frozen section. CONCLUSIONS: LNMM was more frequently observed in stage I LUAD with CGP. Adequate lymphadenectomy and adjuvant chemotherapy were associated with improved survival in CGP-present patients, especially in CGP-present/LNMM-positive subgroup. Additionally, it is feasible to identify CGP on frozen section intraoperatively.

Layer-by-layer assembly of procyanidin and collagen promotes mesenchymal stem cell proliferation and osteogenic differentiation in vitro and in vivo.

Collagen, commonly used in tissue engineering, is widespread in various tissues. During bone tissue regeneration, collagen can stimulate the cellular response and determine the fate of cells. In this work, we integrated collagen type II with procyanidin (PC) onto an implant coating by applying a layer-by-layer technique to demonstrate that collagen and PC can participate in the construction of new biomaterials and serve as multifunctional components. The effects of PC/collagen multilayers on the viability of cocultured bone marrow mesenchymal stem cells (BMSCs) were analyzed by cell counting kit-8 analysis and phalloidin staining. The reactive oxygen species level of BMSCs was revealed through immunofluorescent staining and flow cytometry. Osteogenesis-related genes were detected, and in vivo experiment was performed to reveal the effect of newly designed material on the osteogenic differentiation of BMSCs. Our data demonstrated that in BMSCs PC/collagen multilayers accelerated the proliferation and osteogenic differentiation through Wnt/ß-catenin signaling pathway and enhanced bone generation around the implant in the bone defect model of rabbit femurs. In summary, combination of collagen and PC provided a new sight for the research and development of implant materials or coatings in the future.

Engineering a mucin coating to promote osteogenic differentiation of BMSCs in vitro and bone formation in vivo through the Wnt/ß-catenin pathway.

Mucin, a family of glycoproteins, is widespread in the inner linings of various lumen organs and plays key roles in protecting epithelial cells from invasion by foreign species and communicating with the external environment. Here, we demonstrated that Mucin could be engineered as a promising building block in biomaterials with unexpected multifunctionalities by codepositing with procyanidin (PC, a kind of flavanol polyphenol) through a layer-by-layer technique. The process of generating PC/Mucin multilayers was well characterized and monitored, which was controllable by the assembly conditions. The behaviors of bone marrow mesenchymal stem cells (BMSCs), including proliferation, antioxidant ability, and expression of vinculin, were investigated to reveal the role of PC/Mucin multilayers on the osteogenic differentiation of BMSCs. Our data showed that PC/Mucin multilayers promoted osteogenesis-related genes (Col1, ON, OCN and RUNX2) in BMSCs in vitro and bone generation in vivo by activating the Wnt/ß-catenin pathway. These findings demonstrate that engineering Mucin might be a new route in the future to implant materials or coatings for bone regeneration.

Synergistic passivation and stepped-dimensional perovskite analogs enable high-efficiency near-infrared light-emitting diodes.

Formamidinium lead iodide (FAPbI3) perovskites are promising emitters for near-infrared light-emitting diodes. However, their performance is still limited by defect-assisted nonradiative recombination and band offset-induced carrier aggregation at the interface. Herein, we introduce a couple of cadmium salts with acetate or halide anion into the FAPbI3 perovskite precursors to synergistically passivate the material defects and optimize the device band structure. Particularly, the perovskite analogs, containing zero-dimensional formamidinium cadmium iodide, one-dimensional δ-FAPbI3, two-dimensional FA2FAn-1PbnI3n+1, and three-dimensional α-FAPbI3, can be obtained in one pot and play a pivotal and positive role in energy transfer in the formamidinium iodide-rich lead-based perovskite films. As a result, the near-infrared FAPbI3-based devices deliver a maximum external quantum efficiency of 24.1% together with substantially improved operational stability. Combining our findings on defect passivation and energy transfer, we also achieve near-infrared light communication with device twins of light emitting and unprecedented self-driven detection.

The circular RNA circ-ERBIN promotes growth and metastasis of colorectal cancer by miR-125a-5p and miR-138-5p/4EBP-1 mediated cap-independent HIF-1α translation.

BACKGROUND: Circular RNA (circRNAs) and hypoxia have been found to play the key roles in the pathogenesis and progression of cancer including colorectal cancer (CRC). However, the expressions and functions of the specific circRNAs in regulating hypoxia-involved CRC metastasis, and the circRNAs that are relevant to regulate HIF-1α levels in CRC remain elusive. METHODS: qRT-PCR was used to detect the expression of circRNAs and mRNA in CRC cells and tissues. Fluorescence in situ hybridization (FISH) was used to analyze the location of circ-ERBIN. Function-based experiments were performed using circ-ERBIN overexpression and knockdown cell lines in vitro and in vivo, including CCK8, colony formation, EdU assay, transwell, tumor growth and metastasis models. Mechanistically, luciferase reporter assay, western blots and immunohistochemical stainings were performed. RESULTS: Circ-Erbin was highly expressed in the CRC cells and Circ-Erbin overexpression facilitated the proliferation, migration and metastasis of CRC in vitro and in vivo. Notably, circ-Erbin overexpression significantly promoted angiogenesis by increasing the expression of hypoxia induced factor (HIF-1α) in CRC. Mechanistically, circ-Erbin accelerated a cap-independent protein translation of HIF-1α in CRC cells as the sponges of miR-125a-5p and miR-138-5p, which synergistically targeted eukaryotic translation initiation factor 4E binding protein 1(4EBP-1). CONCLUSIONS: Our findings uncover a key mechanism for circ-Erbin mediated HIF-1α activation by miR-125a-5p-5p/miR-138-5p/4EBP-1 axis and circ-ERBIN is a potential target for CRC treatment.

NSD2 circular RNA promotes metastasis of colorectal cancer by targeting miR-199b-5p-mediated DDR1 and JAG1 signalling.

Liver metastasis is the main cause of death in patients with colorectal cancer (CRC). Here, we searched for CRC metastasis-associated circular RNA in a mouse model of liver metastasis of CRC by using RNA (transcriptome)-sequencing. We identified a novel and conserved circular RNA, circ-NSD2, functioning as a promoter of CRC metastasis. Circ-NSD2 expression was elevated in CRC tissues and was markedly increased in advanced stages or metastatic tumours of CRC patients. Gain-of-function and loss-of-function experiments demonstrated that circ-NSD2 promoted migration and metastasis of CRC in vitro and in vivo. Mechanistically, circ-NSD2 acted as a sponge for the tumour suppressor miR-199b-5p and activated DDR1 (discoidin domain receptor tyrosine kinase 1) and JAG1 (Jagged 1) genes, which synergistically helped with cell-matrix interaction, migration and metastasis of CRC cells. Taken together, our findings highlight a novel oncogenic function of circ-NSD2 and uncover a key mechanism for the circ-NSD2/miR-199b-5p/DDR1/JAG1 axis in CRC metastasis, which may serve as a prognostic factor and therapeutic target for antimetastatic therapy in CRC patients. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Dicer suppresses cytoskeleton remodeling and tumorigenesis of colorectal epithelium by miR-324-5p mediated suppression of HMGXB3 and WASF-2.

Emerging evidence indicates that microRNAs, a class of small and well-conserved noncoding RNAs, participate in many physiological and pathological processes. RNase III endonuclease DICER is one of the key enzymes for microRNA biogenesis. Here, we found that DICER was downregulated in tumor samples of colorectal cancer (CRC) patients at both mRNA and protein levels. Importantly, intestinal epithelial cell (IEC)-specific deletion of Dicer mice got more tumors after azoxymethane and dextran sulfate sodium (DSS) administration. Interestingly, IEC-specific deletion of Dicer led to severe chronic inflammation and epithelium layer remodeling in mice with or without DSS administration. Microarray analysis of 3 paired Dicer deletion CRC cell lines showed that miR-324-5p was one of the most significantly decreased miRNAs. In the intestinal epithelium of IEC-specific deletion of Dicer mice, miR-324-5p was also found to be markedly reduced. Mechanistically, miR-324-5p directly bound to the 3'untranslated regions (3'UTRs) of HMG-box containing 3 (HMGXB3) and WAS protein family member 2 (WASF-2), two key proteins participated in cell motility and cytoskeleton remodeling, to suppress their expressions. Intraperitoneal injection of miR-324-5p AgomiR (an agonist of miR-324-5p) curtailed chronic inflammation and cytoskeleton remodeling of colorectal epithelium and restored intestinal barrier function in IEC-specific deletion of Dicer mice induced by DSS. Therefore, our study reveals a key role of a DICER/miR-324-5p/HMGXB3/WASF-2 axis in tumorigenesis of CRC by regulation of cytoskeleton remodeling and maintaining integrity of intestinal barriers.

SIRT1 suppresses colorectal cancer metastasis by transcriptional repression of miR-15b-5p.

The class III deacetylase sirtuin 1 (SIRT1), a member of the sirtuin family proteins, plays a key role in many types of cancers including colorectal cancer (CRC). Here we report that SIRT1 suppressed CRC metastasis in vitro and in vivo as a negative regulator for miR-15b-5p transcription. Mechanistically, SIRT1 impaired regulatory effects of activator protein (AP-1) on miR-15b-5p trans-activation through deacetylation of AP-1. Importantly, acyl-CoA oxidase 1 (ACOX1), a key enzyme of the fatty acid oxidation (FAO) pathway, was found as a direct target for miR-15b-5p. SIRT1 expression was positively correlated with ACOX1 expression in CRC cells and in xenografts. Moreover, ACOX1 overexpression attenuated the augmentation of migration and invasion of CRC cells by miR-15b-5p overexpression. In conclusion, our study demonstrated a functional role of the SIRT1/miR-15b-5p/ACOX1 axis in CRC metastasis and suggested a potential target for metastatic CRC therapy.

Adsorption behavior and mechanism of glufosinate onto goethite.

The adsorption of glufosinate (GLU), a widely used herbicide similar to glyphosate (GLY), onto goethite was investigated as a function of the pH, ionic strength, background cations and anions, heavy metal ions and fulvic acids (FAs) by using batch adsorption experiments. In situ ATR-FTIR spectroscopy and density functional theory (DFT) calculations were carried out to characterize the molecular interactions between GLU and goethite surfaces. The macroscopic results indicated that an increasing pH exerted an adverse effect on GLU adsorption because of the electrostatic repulsion, and the adsorption was not sensitive to ionic strengths or background cation types, indicating that an inner-sphere surface complex was involved. GLU adsorption can be considerably depressed by PO4(3-), SO4(2-), and a high level of FA because of the competitive effect, while being enhanced by Cu(2+) with a maximum adsorption at approximately pH5 because of the metal ion bridging effect. Other examined divalent metal cations (Cd(2+), Zn(2+), and Pb(2+)) showed almost no effect on GLU adsorption, indicating weak interaction between them. ATR-FTIR spectra and the DFT calculations further proved that GLU was bonded to goethite surfaces through the formation of a monodentate mononuclear inner-sphere complex between the phosphinic moiety and surface Fe(III) centers under an acidic condition. The results showed that GLU had a similar adsorption mechanism to that of GLY onto goethite, but with a lower adsorption affinity, possibly exerting higher mobility and risk in soils.

Alleviating versus stimulating effects of bicarbonate on the growth of Vallisneria natans under ammonia stress.

Bicarbonate plays a crucial role in limiting the growth of submersed aquatic macrophytes in eutrophic lakes, and high ammonia is often toxic to macrophytes. In order to evaluate the combined effect of HCO3 (-) and total ammonia (i.e., the total of NH3 and NH4 (+)) on submersed macrophytes Vallisneria natans, the growth and physiological response of V. natans in the presence of HCO3 (-) and ammonia were studied. The results showed that with the increase of ammonia, morphological parameters of V. natans declined. In contrast, increased HCO3 (-) concentration stimulated the growth of V. natans, especially when the NH4 (+)-N/NO3 (-)-N ratio was 1:7. High ammonia concentration induced excess free amino acids (FAA) accumulation and soluble carbohydrates (SC) depletion in plant tissues. However, the elevated HCO3 (-) promoted the synthesis of SC and rendered the decrease of FAA/SC ratio. The results also suggested that HCO3 (-) could partially alleviate the stress of ammonia, as evidenced by the decrease of FAA/SC ratio and the growth enhancement of V. natans when the ammonia concentration was 0.58 mg L(-1). Given the fact that HCO3 (-) is probably the dominant available carbon source in most eutrophic lakes, the ability of V. natans to use HCO3 (-) for SC synthesis may explain the alleviating effect of HCO3 (-) on V. natans under ammonia stress.

Epidermal growth factor receptor gene amplification and protein overexpression in basal-like carcinoma of the breast.

AIMS: Epidermal growth factor receptor (EGFR) is frequently expressed in basal-like breast cancer (BLBC). The aim of this study was to evaluate their correlation as detected by immunohistochemistry (IHC) or fluorescence in-situ hybridization (FISH). METHODS AND RESULTS: IHC for oestrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor (HER) 2, cytokeratin (CK) 5/6 and EGFR, and FISH for EGFR amplification, were performed in 59 cases of BLBC. EGFR IHC results were scored semiquantitatively, and compared with its gene amplification status. ER, PR and HER2 were negative in all cases, whereas 35 and 55 cases were positive for CK5/6 and EGFR. For EGFR IHC, 20, 11, 11 and 17 cases showed a negative, a low, an intermediate or a high staining level, respectively, and seven cases showed gene amplification by FISH, with two, 19, 11 and 20 cases showing balanced monosony, disomy, trisomy, and polysomy respectively. Immunohistochemical expression in gene-amplified tumours was significantly higher than in those without amplification, including balanced polysomy tumours. EGFR immunohistochemical expression also correlated with the EGFR/chromosome 7 ratio. High sensitivity (86%) and negative predictive value (98%) were achieved with high-level immunohistochemical expression as a cut-off to predict gene amplification. CONCLUSIONS: High-level EGFR immunohistochemical expression correlated with and predicted EGFR amplification, and may be used as a screening method to exclude gene amplification.

[Jointed estrogenic activities of bisphenol A and three of its analogs].

The combined effect of environmental endocrine disruptors (EEDs) is one of the hottest topics. The estrogenic activities of BPA, BPAF, BPAP, BPF were tested based on recombinant gene yeast assay. Six mixtures were designed based on the result of the test,each of which had an equitoxic ratio ray (EC10 or EC50). The EC50 values are 6.81 x 10(-6) mol x L(-1), 7.44 x 10(-7) mol x L(-1), 1.43 x 10(-5) mol x L(-1), 7.52 x 10(-6) mol x L(-1) for BPA, BPAF, BPAP and BPF respectively,which reveals that the estrogenic activities order among the four bisphenols was BPAF> BPA> BPF> BPAP. The experiment shows that when BPA mixes with BPAF, BPAP and BPF in different ratios individually, different combination effects are produced. It reveals that the combined ratios of the components may affect the combined effect. The dose addition model and the independent action model are used to identify the combined effect. They are testified to be more intuitionistic and more comprehensive than other joint effect indices.

Aqueous oxytetracycline degradation and the toxicity change of degradation compounds in photoirradiation process.

The extensive use of antibiotics has been a worldwide environmental issue. In this study the fate of oxytetracycline (OTC), under photoirradiation, was investigated. The results showed that OTC photolysis followed first order model kinetics. Direct photolysis rate was found to be dependent on the initial OTC concentration, with k value ranging from 0.0075 to 0.0141 min(-1), in the OTC concentration from 40 to 10 mg/L. OTC photolysis was highly pH-dependent and strongly enhanced at a high pH value, with a k value of 0.0629 min(-1) at pH 9. Enhanced OTC photolysis has also been observed in the presence of nitrate and low concentration of dissolved organic matter. Upon irradiation for 240 min, only 13.5% reduction of TOC occured in spite of a rapid consumption of 90% of OTC. The byproducts from OTC photolysis have been analyzed using high-performance liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS), and the degradation pathway of OTC in the photo process was proposed. By employing luminescent bacterium to assess the adversity of the degradation compounds, an increased effect of toxicity occured in spite of the great consumption of OTC in the photoirradiation process. After irradiation for 240 min, the inhibition rate was 47%, significantly higher than the initial rate of 21% (p < 0.05), revealing a potentially higher adversity risk on the microorganism upon OTC photolysis.

Aqueous photolysis of tetracycline and toxicity of photolytic products to luminescent bacteria.

The extensive utilization of antibiotics in the pharmaceutical therapies and agricultural husbandry has led to the worldwide pollution in environments. In this study the photolysis behaviors of tetracycline (TC) and toxicity of its degradation products were investigated. The results showed that TC photolysis followed first-order kinetics. The photolysis rate was found to be dependent on the initial TC concentration and increasing TC concentration from 10 to 40mgl(-1) led to the decrease of the photolysis rate constant from 0.0045min(-1) to 0.0014min(-1). TC photolysis was highly pH-dependent and strongly enhanced at high pH value. Markedly elevated TC photolysis was also observed in the presence of nitrate and dissolved organic matter. Upon irradiation for 300min, only 15% reduction of total organic carbon (TOC) occurred in spite of quick conversion of 73% of TC, suggesting that a majority of TC transformed into intermediate products without complete mineralization. The intermediate products from TC photolysis were analyzed using high-performance liquid chromatography-electrospray ionisation-mass spectrometry (HPLC-ESI-MS) and the main photolysis products of TC were proposed. The toxicity of the photolysis compounds was evaluated using luminescent bacterium, and the results revealed that the toxicity increased with irradiation, indicative of a higher adversity risk of the degradation products of TC on bacteria upon photolysis.