Palladium/Norbornene Cooperative Catalysis Bifunctionalization: Acylation/Cyanation of Aryl Iodides by Cleaving C-CN Bond of Aryl Acyl Nitrile.

A palladium/norbornene catalyzed two-component coupling process involving acylation/cyanation of aryl iodides is reported. In this work, aryl acyl nitrile compounds are cleverly selected to provide both nitrile and acyl sources by palladium-catalyzed cleavage of the C-CN bond as both an electrophilic reagent and a termination reagent. This is the first example of C-CN bond cleavage bifunctionalization of aryl iodides. After a series of important NBE derivatives are screened, the products resulting from the bifunctionalization of aryl iodides are smoothly obtained. This strategy has a wide range of substrates and good functional group compatibility. Moreover, this synthetic protocol demonstrated a good application for the synthesis of diverse O,N,C-substituted isoindolinones.

Andrographolide anti-proliferation and metastasis of hepatocellular carcinoma through LncRNA MIR22HG regulation.

Hepatocellular carcinoma (HCC) treatment is a major challenge. Although andrographolide (Andro) has an anti-proliferation effect on HCC, its underlying mechanism is not yet elucidated, and whether Andro can inhibit HCC metastasis has not been reported. The present study aimed to clarify whether Andro inhibits SK-Hep-1 cell proliferation and HCC metastasis, and the mechanisms. The results showed that Andro significantly reduced the survival of HCC cells and tumor weight and volume in tumor-bearing nude mice. Andro also triggered apoptosis of HCC cells and upregulated MIR22HG, Cleaved Caspase 9/7/3 expression levels, and downregulated BCL-2 mRNA, BCL-2 expression levels. Knockdown of MIR22HG or overexpression of HuR attenuated the effects of Andro on the signal transduction of mitochondrial apoptotic pathway and proliferation ability in HCC cells. Moreover, Andro significantly reduced the invasive ability of the cells and the level of HCC cell lung metastasis, upregulated miR-22-3p expression level and downregulated HMGB1 and MMP-9 expression levels. MIR22HG or miR-22-3p knockdown attenuated the effects of Andro on the signaling of HMGB1/MMP-9 pathway and invasive ability in HCC cells, while the overexpression of HMGB1 attenuated the inhibitory effects of Andro on the MMP-9 expression level and invasive ability in HCC cells. Thus, the regulation of MIR22HG-HuR/BCL-2 and MIR22HG/HMGB1 signaling pathways is involved in the anti-HCC proliferation and metastasis effects of Andro. This study provided a new pharmacological basis for Andro in HCC treatment and, for the first time, identified a natural product molecule capable of positively regulating MIR22HG, which has a robust biological function.

TUG1 protects against ferroptosis of hepatic stellate cells by upregulating PDK4-mediated glycolysis.

The induction of ferroptosis in hepatic stellate cells (HSCs) has shown promise in reversing liver fibrosis. And ferroptosis has been confirmed to be associated with glycolysis. The objective of this study is to determine whether ferroptosis inhibition in HSCs, induced by elevation of recombinant pyruvate dehydrogenase kinase isozyme 4 (PDK4)-mediated glycolysis, could mediate the pathogenesis of liver fibrosis. Liver fibrosis was induced using CCl4, the level of which was assessed through histochemical staining. Lentivirus was used to modulate the expression of specific genes. And underlying mechanisms were explored using primary HSCs extracted from normal mice. The results confirmed that Taurine up-regulated gene 1 (TUG1) expression was upregulated in liver fibrotic tissues and HSCs, showing a positive correlation with fibrosis. In addition, TUG1 attenuated ferroptosis in HSCs by promoting PDK4-mediated glycolysis, thereby promoting the progression of liver fibrosis. Moreover, TUG1 was observed to impact HSCs activation, exacerbating liver fibrosis to some extent. In conclusion, our study revealed that TUG1 expression was elevated in mouse models of liver fibrosis and activated HSCs, which inhibited ferroptosis in HSCs through PDK4-mediated glycolysis. This finding may open up a new therapeutic strategy for liver fibrosis.

Salidroside ameliorates acetaminophen-induced acute liver injury through the inhibition of endoplasmic reticulum stress-mediated ferroptosis by activating the AMPK/SIRT1 pathway.

Acetaminophen (APAP) overdose has long been considered a major cause of drug-induced liver injury. Ferroptosis is a type of programmed cell death mediated by iron-dependent lipid peroxidation. Endoplasmic reticulum (ER) stress is a systemic response triggered by the accumulation of unfolded or misfolded proteins in the ER. Ferroptosis and ER stress have been proven to contribute to the progression of APAP-induced acute liver injury (ALI). It was reported that salidroside protects against APAP-induced ALI, but the potential mechanism remain unknown. In this study, male C57BL/6 J mice were intraperitoneally (i.p.) injected APAP (500 mg/kg) to induce an ALI model. Salidroside was i.p. injected at a dose of 100 mg/kg 2 h prior to APAP administration. Mice were sacrificed 12 h after APAP injection and the liver and serum of the mice were obtained for histological and biochemistry analysis. AML12 cells were used in in vitro assays. The results indicated that salidroside mitigated glutathione degradation via inhibiting cation transport regulator homolog 1 (CHAC1) to attenuate ferroptosis, and simultaneously suppressing PERK-eIF2α-ATF4 axis-mediated ER stress, thus alleviating APAP-induced ALI. However, PERK activator CCT020312 and overexpression of ATF4 inhibited the protective function of salidroside on CHAC1-mediated ferroptosis. Besides this, activation of the AMPK/SIRT1 signaling pathway by salidroside was demonstrated to have a protective effect against APAP-induced ALI. Interestingly, selective inhibition of SIRT1 ameliorated the protective effects of salidroside on ER stress and ferroptosis. Overall, salidroside plays a significant part in the mitigation of APAP-induced ALI by activating the AMPK/SIRT1 signaling to inhibit ER stress-mediated ferroptosis in the ATF4-CHAC1 axis.

Authentication of Platycladus Orientalis Leaves and Its Five Adulterants by Combination of Morphology and Microscopic Characteristics, TLC, and HPLC Analysis.

BACKGROUND: Platycladus orientalis leaves (POL), as the source of the traditional Chinese medicine (TCM) Platycladi Cacumen, has frequently been found to be misused with five adulterants including Chamaecyparis obtusa leaves (COL), Cupressus funebris leaves (CFL), Juniperus virginiana leaves (JVL), Sabina chinensis leaves (SCL), and Juniperus formosana leaves (JFL). OBJECTIVE: The purpose of this study was to distinguish POL (fresh leaves) from its five adulterants (fresh leaves). METHODS: The micromorphological features in terms of transection and microscopic characteristics of POL and adulterants were captured and compared using the an microscope. Both HPLC and TLC methods for the simultaneous determination of six bioactive flavonoids (myricitrin, isoquercitrin, quercitrin, amentoflavone, afzelin, and hinokiflavone) have been developed. RESULTS: There were significant differences in microscopic features of transverse section and powders. The TLC results suggested that the spots of myricitrin in POL were more obvious than those in the five adulterants. The contents of myricitrin and quercitrin, or the total content of flavonoids in POL, determined by HPLC, were significantly higher than those in the adulterants. CONCLUSION: POL was successfully distinguished from its five adulterants by the comparison of morphology, microscopic characteristics, and chemical profiles. HIGHLIGHTS: This research provides a comprehensive morphology, microscopic identification, TLC, and HPLC analysis for authenticating POL and its five adulterants.

Targeting Hepatic Stellate Cell Death to Reverse Hepatic Fibrosis.

To date, the incidence and mortality of chronic liver diseases such as cirrhosis and hepatocellular carcinoma due to the continued progression of hepatic fibrosis are increasing annually. Unfortunately, although a large number of studies have exhibited that some drugs have great potential for anti-fibrosis in animal and clinical trials, no specific anti-fibrosis drugs have been developed, and there is no better treatment for advanced cirrhosis than liver transplantation. It is a prevailing viewpoint that hepatic stellate cells (HSCs), as the mainstay of extracellular matrix secretion, are of great concern in the development of hepatic fibrosis. Therefore, targeting HSCs becomes extremely important to confront hepatic fibrosis. As previous studies described, inhibition of HSC activation and proliferation, induction of HSC death, and restoration of HSC quiescence are effective in reversing hepatic fibrosis. This review focuses on the current status of research on the treatment of hepatic fibrosis by inducing HSC death and elucidates the HSC death modes in detail and the crosstalk between them.

Associations of Indoor Environmental Quality Parameters with Students' Perceptions in Undergraduate Dormitories: A Field Study in Beijing during a Transition Season.

A healthy and comfortable dormitory environment is crucial to the quality of students' daily lives. In this field study, the indoor environmental quality (IEQ) parameters of undergraduate dormitories in Beijing were measured, while questionnaire surveys were conducted to evaluate the corresponding subjective perceptions of students. Integrated environmental monitoring kits were used to collect temperature, relative humidity, CO2, PM2.5, PM10, TVOC, formaldehyde, and noise data in the investigated dormitories, during the transition season from winter to spring. Questionnaires and scales were distributed to obtain the students' subjective perceptions of and satisfaction with the IEQ, and their health and well-being status. The measured IEQ data showed that the thermal environment tended to be warm and dry during the heating period. The CO2 concentrations seriously exceeded standard levels due to insufficient indoor natural ventilation. Noise exposure could sometimes interfere with students' rest. The students' overall satisfaction with the dormitory environment was low, especially in terms of air quality and acoustic environment. The unsatisfactory IEQ factors have led to several health symptoms, poor sleep quality, and slightly lower well-being. Correlations were found between the IEQ parameters and the corresponding subjective perceptions and satisfaction levels. It was speculated that students' satisfaction and well-being could be effectively improved by appropriately adjusting the corresponding IEQ parameters.

Underdevelopment of gut microbiota in failure to thrive infants of up to 12 months of age.

Laboratory and clinical studies have revealed the importance of gut microbiota in children with severe pediatric pathological conditions such as severe acute malnutrition (SAM); however, under relatively milder conditions such as, failure to thrive (FTT), the role of the gut microbiota remains poorly characterized. Here, we analyzed stool samples from 54 subjects with a clinical diagnosis of failure to thrive (FTT), 49 preterm subjects with corrected normal growth (NFTT-pre), and 49 healthy subjects (NFTT) between 3-12 months of age using 16S rRNA gene sequencing. We observed that the clinical condition of FTT, age, head circumference, intrauterine growth restriction (IUGR), and feeding methods significantly affected gut microbiota. The microbiota age of subjects was significantly correlated with their anthropomorphic features, and the FTT subjects exhibited underdeveloped gut microbiota characterized by a significantly decreased microbiota-for-age Z-score (MAZ). The FTT and NFTT-pre groups exhibited an obvious disrupted developmental trajectory of gut microbiota across age, and the development of their alpha diversities and the observed OTU and Shannon indices were inadequate, particularly in subjects with FTT. Moreover, sequential colonization and enrichment of bacteria such as Bacteroides, Bifidobacterium, Streptococcus and most age-discriminatory bacterial taxa and their microbial functions were disorganized in FTT compared to that in NFTT. Our results revealed an underdevelopment of the gut microbiota in infants with failure to thrive that possesses potential clinical and practical importance.

Metabolic control of progenitor cell propagation during Drosophila tracheal remodeling.

Adult progenitor cells in the trachea of Drosophila larvae are activated and migrate out of niches when metamorphosis induces tracheal remodeling. Here we show that in response to metabolic deficiency in decaying tracheal branches, signaling by the insulin pathway controls the progenitor cells by regulating Yorkie (Yki)-dependent proliferation and migration. Yki, a transcription coactivator that is regulated by Hippo signaling, promotes transcriptional activation of cell cycle regulators and components of the extracellular matrix in tracheal progenitor cells. These findings reveal that regulation of Yki signaling by the insulin pathway governs proliferation and migration of tracheal progenitor cells, thereby identifying the regulatory mechanism by which metabolic depression drives progenitor cell activation and cell division that underlies tracheal remodeling.

Establishment and Validation of a Peroxisome-related Gene Signature for Prognostic Prediction and Immune Distinction in Hepatocellular Carcinoma.

Background: Hepatocellular carcinoma (HCC) is a highly heterogeneous disease, which makes the prognostic prediction challenging. Abnormal peroxisomes can promote the development of cancers. This study aimed to construct a prognostic model based on peroxisome-related genes and identify its prognostic prediction and immune distinction abilities in HCC. Methods: The prognostic model was constructed based on The Cancer Genome Atlas (TCGA) and The International Cancer Genome Consortium (ICGC). Kaplan-Meier curve, time-dependent receiver operating characteristic curve and Cox analysis were used to evaluate the model. The immune status, tumor microenvironment, drug sensitivity and expression levels of the mRNA and protein between HCC and adjacent non-tumorous tissues were analyzed and compared. Results: A prognostic model of 9 peroxisome-related genes was established and validated. Overall survival was markedly higher in the low-risk group relative to the high-risk group. The risk score was an independent prognostic factor. Tumor-related pathways were enriched in the high-risk group and the HCC patients in high-risk group showed depleted immune status. Furthermore, immune checkpoint-related genes, cell cycle-related genes, and multidrug resistance-related genes were overexpressed in the high-risk group. The expression levels of prognostic genes were negatively related to the anti-tumor drugs sensitivity. In addition, the expression level of each prognostic gene in HCC tissues was higher than that in adjacent non-tumorous tissues in an independent sample cohort and the similar results were found in most cancer types. Conclusion: A signature based on the nine peroxisome-related genes is a promising biomarker of HCC and is beneficial to the realization of individualized treatment.

Glycolysis-Related Gene Signature Can Predict Survival and Immune Status of Hepatocellular Carcinoma.

BACKGROUND: Concise and precise prognostic models are urgently needed due to the intricate genetic variations among hepatocellular carcinoma (HCC) cells. Disorder or change in glycolysis metabolism has been considered one of the "hallmarks" of cancer. However, the prognostic value of glycolysis-related genes in HCC remains elusive. METHODS: A multigene prognostic model was constructed by least absolute shrinkage and selection operator Cox regression analysis in the The Cancer Genome Atlas (TCGA) cohort with 365 HCC patients and validated in the International Cancer Genome Consortium (ICGC) cohort with 231 HCC patients. The Kaplan-Meier methodology and time-dependent receiver operating characteristic curve were employed to confirm its predictive capability. A predictive nomogram was established based on the stepwise multivariate regression model. The differential expression of prognostic genes between HCC tissues and normal tissues was verified by quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry in an independent sample cohort with 30 HCC patients. RESULTS: The glycolysis-related gene signature and the nomogram model exhibited robust validity in predicting prognosis. The risk score was an independent predictor for overall survival (OS). Expression levels of immune checkpoint genes and cell cycle genes were significantly elevated in the high-risk group. The high-risk group presented high levels of immune exclusion. The risk score can distinguish the effect of immunotherapy in the IMvigor210 cohort. The prognostic gene expression showed a significant difference between HCC tissues and adjacent nontumorous tissues in the independent sample cohort. CONCLUSION: The currently established glycolysis-related gene signature can accurately predict prognosis and reflect immune status, which may be a therapeutic alternative.

Comprehensive Analysis Identified Mutation-Gene Signature Impacts the Prognosis Through Immune Function in Hepatocellular Carcinoma.

Background: Hepatocellular carcinoma (HCC) is a life-threatening and refractory malignancy with poor outcome. Genetic mutations are the hallmark of cancer. Thus far, there is no comprehensive prognostic model constructed by mutation-gene transcriptome in HCC. The prognostic value of mutation-gene signature in HCC remains elusive. Methods: RNA expression profiles and the corresponding clinical information were recruited from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases. The least absolute shrinkage and selection operator (LASSO) Cox regression analysis was employed to establish gene signature. Kaplan-Meier curve and time-dependent receiver operating characteristic curve were implemented to evaluate the prognostic value. The Wilcoxon test was performed to analyze the expression of immune checkpoint genes, cell cycle genes, and tumor drug resistance genes in different risk groups. Finally, quantitative real-time PCR (qRT-RCR) and immunohistochemistry (IHC) were performed to validate the mRNA and protein expression between HCC and adjacent nontumorous tissues in an independent cohort. Results: A prognostic model consisting of five mutated genes was established by LASSO Cox regression analysis. The prognostic model classified patients into high- and low-risk groups. Compared with the low-risk group, patients in the high-risk group had significantly worse survival results. The prognostic model can accurately predict the overall survival of HCC patients and predict overall survival more accurately when combined with stage. Furthermore, the immune checkpoint genes, cell cycle genes, and tumor drug resistance genes were higher expressed in the high-risk group compared in the low-risk group. In addition, the expression level of prognostic signature genes was validated in an independent sample cohort, which was consistent with RNA sequencing expression in the TCGA database. Conclusion: The prediction model of HCC constructed using mutation-related genes is of great significance for clinical decision making and the personalized treatment of patients with HCC.

Characterization of the Roles of SGT1/RAR1, EDS1/NDR1, NPR1, and NRC/ADR1/NRG1 in Sw-5b-Mediated Resistance to Tomato Spotted Wilt Virus.

The tomato Sw-5b gene confers resistance to tomato spotted wilt virus (TSWV) and encodes a nucleotide-binding leucine-rich repeat (NLR) protein with an N-terminal Solanaceae-specific domain (SD). Although our understanding of how Sw-5b recognizes the viral NSm elicitor has increased significantly, the process by which Sw-5b activates downstream defense signaling remains to be elucidated. In this study, we used a tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) system to investigate the roles of the SGT1/RAR1, EDS1/NDR1, NPR1, and NRC/ADR1/NRG1 genes in the Sw-5b-mediated signaling pathway. We found that chaperone SGT1 was required for Sw-5b function, but co-chaperone RAR1 was not. Sw-5b-mediated immune signaling was independent of both EDS1 and NDR1. Silencing NPR1, which is a central component in SA signaling, did not result in TSWV systemic infection in Sw-5b-transgenic N. benthamiana plants. Helper NLR NRCs (NLRs required for cell death) were required for Sw-5b-mediated systemic resistance to TSWV infection. Suppression of NRC2/3/4 compromised the Sw-5b resistance. However, the helper NLRs ADR1 and NRG1 may not participate in the Sw-5b signaling pathway. Silencing ADR1, NRG1, or both genes did not affect Sw-5b-mediated resistance to TSWV. Our findings provide new insight into the requirement for conserved key components in Sw-5b-mediated signaling pathways.

The phycobilisome core-membrane linkers from Synechocystis sp. PCC 6803 and red-algae assemble in the same topology.

The phycobilisomes (PBSs) of cyanobacteria and red-algae are unique megadaltons light-harvesting protein-pigment complexes that utilize bilin derivatives for light absorption and energy transfer. Recently, the high-resolution molecular structures of red-algal PBSs revealed how the multi-domain core-membrane linker (LCM ) specifically organizes the allophycocyanin subunits in the PBS's core. But, the topology of LCM in these structures was different than that suggested for cyanobacterial PBSs based on lower-resolution structures. Particularly, the model for cyanobacteria assumed that the Arm2 domain of LCM connects the two basal allophycocyanin cylinders, whereas the red-algal PBS structures revealed that Arm2 is partly buried in the core of one basal cylinder and connects it to the top cylinder. Here, we show by biochemical analysis of mutations in the apcE gene that encodes LCM , that the cyanobacterial and red-algal LCM topologies are actually the same. We found that removing the top cylinder linker domain in LCM splits the PBS core longitudinally into two separate basal cylinders. Deleting either all or part of the helix-loop-helix domain at the N-terminal end of Arm2, disassembled the basal cylinders and resulted in degradation of the part containing the terminal emitter, ApcD. Deleting the following 30 amino-acids loop severely affected the assembly of the basal cylinders, but further deletion of the amino-acids at the C-terminal half of Arm2 had only minor effects on this assembly. Altogether, the biochemical data are consistent with the red-algal LCM topology, suggesting that the PBS cores in cyanobacteria and red-algae assemble in the same way.

Radical treatment of severe open fractures of extremities by orthoplastic surgery: a 10-year retrospective study.

OBJECTIVE: This study aimed to retrospectively analyze clinical data of a series of patients with severe open fractures of extremities (Gustilo IIIb or IIIc), who achieved a satisfactory outcome through radical orthoplastic surgery, so as to provide a reference for determining the treatment of severe open fractures of extremities. METHODS: The clinical data of 41 consecutive patients with severe open fracture (Gustilo IIIb or IIIc) of the limb, who underwent successful surgical debridement, fixation, and soft tissue reconstruction in one stage between January 2008 and January 2019, were retrospectively reviewed. Postoperative indicators, including infection rate and union time, were acquired by a regular follow-up and analyzed. RESULTS: The mean (±SD) age of the patients was 38 ± 16 years. A total of 90 open fractures and severe soft tissue damages were analyzed. The soft tissue cover was achieved within 72 h. The overall rate of infection was 14.6% (6/41). Sex and the Mangled Extremity Severity Score were associated with infection. The median union time of 40 patients (one amputation) was 32 weeks. CONCLUSION: The overall rate of infection exhibited a lower tendency in this study compared with previous studies on high-grade open fractures following a two-stage orthopedic approach. The consequence of infection rate and union time was similar to that in previous studies. These results indicated that the single-stage radical orthoplastic treatment was an effective and reliable option for reconstructing severe open fractures.

A novel focal adhesion related gene signature for prognostic prediction in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a highly heterogeneous disease. Reduced expression of focal adhesion is considered as an important prerequisite for tumor cell invasion and metastasis. However, the prognostic value of focal adhesion related genes in HCC remains to be further determined. In this study, RNA expression profiles were downloaded from public databases. A five focal adhesion related gene signature model was established by the least absolute shrinkage and selection operator Cox regression analysis, which categorized patients into high- and low-risk groups. Multivariate Cox regression analysis showed that the risk score was an independent predictor for overall survival. Single-sample gene set enrichment analysis revealed that immune status was different between the two risk groups, and tumor-related pathways were enriched in high-risk group. The risk score was significantly associated with tumor grade, tumor stage, immune scores, and immune infiltrate types. Pearson correlation showed that the expression level of prognostic genes was associated with anti-tumor drug sensitivity. Besides, the mRNA and protein expression of prognostic genes was significantly different between HCC tissues and adjacent non-tumorous tissues in our separate cohort. Taken together, a novel focal adhesion related gene signature can be used for prognostic prediction in HCC, which may be a therapeutic alternative.

An Inflammatory Response-Related Gene Signature Can Impact the Immune Status and Predict the Prognosis of Hepatocellular Carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is a highly heterogeneous disease, which makes the prognostic prediction challenging. As part of the active cross-talk between the tumor and the host, inflammatory response in the tumor or its microenvironment could affect prognosis. However, the prognostic value of inflammatory response-related genes in HCC remains to be further elucidated. METHODS: In this study, the mRNA expression profiles and corresponding clinical data of HCC patients were downloaded from the public database. The least absolute shrinkage and selection operator Cox analysis was utilized to construct a multigene prognostic signature in the TCGA cohort. HCC patients from the ICGC cohort were used for validation. Kaplan Meier analysis was used to compare the overall survival (OS) between high- and low-risk groups. Univariate and multivariate Cox analyses were applied to determine the independent predictors for OS. Single-sample gene set enrichment analysis was utilized to calculate the immune cell infiltration score and immune related pathway activity. Gene set enrichment analysis was implemented to conduct GO terms and KEGG pathways. The qRT-PCR and immunohistochemistry were utilized to perform the mRNA and protein expression of prognostic genes between HCC tissues and normal liver tissues respectively. RESULTS: An inflammatory response-related gene signature model was constructed by LASSO Cox regression analysis. Compared with the low-risk group, patients in the high-risk group showed significantly reduced OS. Receiver operating characteristic curve analysis confirmed the predictive capacity of the prognostic gene signature. Multivariate Cox analysis revealed that the risk score was an independent predictor for OS. Functional analysis indicated that immune status was definitely different between two risk groups, and cancer-related pathways were enriched in high-risk group. The risk score was significantly correlated with tumor grade, tumor stage and immune infiltrate types. The expression levels of prognostic genes were significantly correlated with sensitivity of cancer cells to anti-tumor drugs. Furthermore, the expression of prognostic genes showed significant difference between HCC tissues and adjacent non-tumorous tissues in the separate sample cohort. CONCLUSION: A novel signature constructed with eight inflammatory response-related genes can be used for prognostic prediction and impact the immune status in HCC. Moreover, inhibition of these genes may be a therapeutic alternative.

The Variation of Heavy Metals Bioavailability in Sediments of Liujiang River Basin, SW China Associated to Their Speciations and Environmental Fluctuations, a Field Study in Typical Karstic River.

The bioavailability of heavy metals (HMs) in sediments is closely related to the security of the aquatic environment, but their impacts are poorly researched, particularly in karstic rivers. Therefore, Liujiang River Basin was taken as an example in this study. Seven HMs were analyzed to determine the bioavailability and speciations of HMs in sediments. Moreover, the impacts of environmental factors on HMs were identified. The obtained results suggested that HMs in the sediments are all within their permissible exposure limit (PEL), but Cd and Zn are significantly higher than the soil baseline. Most HMs were found to be in a residual fraction, while their exchangeable fraction was found to be in an extremely low ratio. HMs in bioavailable parts are significantly higher than in the exchangeable and carbonate-bound phases but lower than in the non-residual phase, which demonstrated that HM bioavailability is not confined to the exchangeable and carbonate-bound phases. The correlation coefficients commonly decreased with decreasing speciation ratios, which suggested that the overall bioavailability of metals should be determined by speciation ratios instead of speciations themselves. Noteworthily, most HMs in the residual form were found to be significantly correlated with their overall bioavailability, which highlighted the potential bioavailability of residual form. The non-correlations between pH, electrical conductivity (EC), total dissolved solids (TDS), and HM bioavailability suggested that HMs in the carbonate-bound phase are stable and unsusceptible to environmental variations, while the significant correlations between redox potential (Eh), turbidity, organic matter (OM), main grain size (Mz), and HM bioavailability suggested that HMs in the reducible and oxidizable forms are susceptible to environmental fluctuations. Therefore, the variation of HM bioavailability in karstic rivers is largely regulated by their reducible and oxidizable forms instead of their carbonate-bound form.

Effects of heavy metals speciations in sediments on their bioaccumulation in wild fish in rivers in Liuzhou-A typical karst catchment in southwest China.

Although fish are widely confirmed to be susceptible to heavy metals (HMs) contamination in sediments, this bioconversion haven't been detailed. This is especially the case in karst areas, where HMs are less stably retained in the sediments and are more bioavailable. Therefore, we surveyed representative karst rivers in Liuzhou, China, in order to study the relationship between the speciations of seven HMs in the sediments with their bioaccumulation in wild fish. The results showed that the HMs in sediments are all below their permissible exposure limit (PEL), but Cd and Zn are significantly higher than soil basline. Most HMs are in residual fraction, while their exchangeable fractions are present in extremely low proportions. The concentration of Zn, Cr and Cd in some fish are above their maximum recommended limit (MRL). The concentrations of most of the HMs in the fish are significantly correlated with the levels in the sediments and given the higher correlation coefficients for their carbonate-bound phase, this phase can be seen to play a critical role in HMs bioconversion. However, the presence of this phase in low proportions enables other phases, especially oxidizable form, to play a greater role in HMs bioaccumulation. Apart from Do, HMs in the fish samples are significantly correlated with multiple environmental factors, demonstrating environmental fluctuations can manipulate HMs bioconversion from sediments; however, their significance depend heavily on the proportion of particular species. HMs in reducible and oxidizable fraction are more important in regulating, rather than promoting, their bioconversion during environmental fluctuations. Fluctuations in EC, TDS and pH can increase the impacts of HMs in carbonate-bound fraction on their bioconversion. Given the higher background values of EC and TDS and lower pH values during the monsoon period, careful attention should be paid to the increased bioconversion of HMs in karst rivers during this season.