Metagenomic insights into comparative study of nitrogen metabolic potential and microbial community between primitive and urban river sediments.

As a result of anthropogenic pollution, the nitrogen nutrients load in urban rivers has increased, potentially raising the risk of river eutrophication. Here, we studied how anthropogenic impacts alter nitrogen metabolism in river sediments by comparing the metagenomic function of microbial communities between relatively primitive and human-disturbed sediments. The contents of organic matter (OM), total nitrogen (TN), NO3--N and NO2--N were higher in primitive site than in polluted sites, which might be due to vegetation density, sediment type, hydrology, etc. Whereas, NH4+-N content was higher in midstream and downstream, indicating that nitrogen loading increased in the anthropogenic regions and subsequently leading higher NH4+-N. Hierarchical cluster analyses revealed significant changes in the community structure and functional potential between the primitive and human-affected sites. Metagenomic analysis demonstrated that Demequina, Streptomyces, Rubrobacter and Dechloromonas were the predominant denitrifiers. Ardenticatena and Dechloromonas species were the most important contributors to dissimilatory nitrate reduction. Furthermore, anthropogenic pollution significantly increased their abundance, and resulting in a decrease in NO3-, NO2--N and an increase in NH4+-N contents. Additionally, the SOX metabolism of Dechloromonas and Sulfuritalea may involve in the sulfur-dependent autotrophic denitrification process by coupling the conversion of thiosulfate to sulfate with the reduction of NO3--N to N2. From pristine to anthropogenic pollution sediments, the major nitrifying bacteria harboring Hao transitioned from Nitrospira to Nitrosomonas. This study sheds light on the consequences of anthropogenic activities on nitrogen metabolism in river sediments, allowing for better management of nitrogen pollution and eutrophication in river.

Biofilm characteristics and transcriptomic profiling of Acinetobacter johnsonii defines signatures for planktonic and biofilm cells.

Most bacteria in the natural environment have a biofilm mode of life, which is intrinsically tolerant to antibiotics. While until now, the knowledge of biofilm formation by Acinetobacter johnsonii is not well understood. In this study, the characteristics and the effect of a sub-inhibitory concentration of antibiotic on A. johnsonii biofilm and planktonic cells were determined. We discovered a positive relationship between biofilm formation and tetracycline resistance, and biofilms rapidly evolve resistance to tetracycline they are treated with. Persister cells commonly exist in both planktonic and biofilm cells, with a higher frequency in the latter. Further transcriptomic analysis speculates that the overexpression of multidrug resistance genes and stress genes were mainly answered to sub lethal concentration of tetracycline in planktonic cells, and the lower metabolic levels after biofilm formation result in high resistance level of biofilm cells to tetracycline. Altogether, these data suggest that A. johnsonii can adjust its phenotype when grown as biofilm and change its metabolism under antibiotic stress, and provide implications for subsequent biofilm control.

Metagenomic assembly and binning analyses the prevalence and spread of antibiotic resistome in water and fish gut microbiomes along an environmental gradient.

The pristine river and urban river show an environmental gradient caused by anthropogenic impacts such as wastewater treatment plants and domestic wastewater discharges. Here, metagenomic and binning analyses unveiled antibiotic resistance genes (ARGs) profiles, their co-occurrence with metal resistance genes (MRGs) and mobile genetic elements (MGEs), and their host bacteria in water and Hemiculter leucisculus samples of the river. Results showed that the decrease of ARG abundances from pristine to anthropogenic regions was attributed to the reduction of the relative abundance of multidrug resistance genes in water microbiomes along the environmental gradient. Whereas anthropogenic impact contributed to the enrichment of ARGs in fish gut microbiomes. From pristine to anthropogenic water samples, the dominant host bacteria shifted from Pseudomonas to Actinobacteria. Potential pathogens Vibrio parahaemolyticus, Enterobacter kobei, Aeromonas veronii and Microcystis aeruginosa_C with multiple ARGs were retrieved from fish gut microbes in lower reach of Ba River. The increasing trends in the proportion of the contigs carrying ARGs (ARCs) concomitant with plasmids along environmental gradient indicated that plasmids act as efficient mobility vehicles to enhance the spread of ARGs under anthropogenic pressures. Moreover, the higher co-occurrence of ARGs and MRGs on plasmids revealed that anthropogenic impacts accelerated the co-transfer potential of ARGs and MRGs and the enrichment of ARGs. Partial least squares path modeling revealed anthropogenic contamination could shape fish gut antibiotic resistome mainly via affecting ARG host bacteria in water microbiomes, following by ARGs co-occurrence with MGEs and MRGs in gut microbiomes. This study enhanced our understanding of the mechanism of the anthropogenic activities on the transmission of antibiotic resistome in river ecosystem and emphasized the risk of ARGs and pathogens transferring from an aquatic environment to fish guts.

Phenotype profiles and adaptive preference of Acinetobacter johnsonii isolated from Ba River with different environmental backgrounds.

Acinetobacter johnsonii is a potentially opportunistic pathogen widely distributed in nosocomial and natural environments, but little attention has been paid to this bacillus. Here A. johnsonii strains from Ba River with different pollution levels were isolated. In this study, we found that the increasing anthropogenic contaminants accounted for the emergence of multidrug-resistant (MDR) A. johnsonii strains. Correlation analysis results showed that the resistance phenotype of strains could be generated by co-selection of heavy metals or non-corresponding antibiotics. The whole genome sequence analysis showed that the relative heavy pollution of water selects strains containing more survival-relevant genes. We found that only some genes like blaOXA-24 were responsible for its corresponding resistance profile. Additionally, the tolerance profiles toward heavy metals also attribute to the expression of efflux pumps rather than corresponding resistance genes. In summary, our finding revealed that the resistance profiles of A. johnsonii could be generated by cross or co-selection of anthropogenic contaminants and mediated by efflux pumps instead of corresponding resistance determinants. Our study also has deep-sight into the adaptive preference of bacteria in natural environments, and contributes to surveillance studies and MDR- A. johnsonii monitoring worldwide.

Characterization of tetracycline effects on microbial community, antibiotic resistance genes and antibiotic resistance of Aeromonas spp. in gut of goldfish Carassius auratus Linnaeus.

The gut of aquatic animals was a significant niche for dissemination of antibiotic resistance genes (ARGs) and direct response of living conditions. In this study, the gut microbiota of goldfish Carassius auratus Linnaeus was sampled at 7 days and 21 days after treatment with tetracycline at 0.285 and 2.85 µg L-1 to investigate the influences on the microbial structure and antibiotic resistance. The proportion of tetracycline resistance bacteria was 1.02% in the control group, while increased to 23.00%, 38.43%, 62.05% in groups of high concentration for 7 days (H7), low concentration for 21 days (L21) and high concentration for 21 days (H21), respectively. Compared to the control group, the diversity of isolated Aeromonas spp. was decreased in the treatment groups and the minimal inhibitory concentration (MIC) of resistant isolates was enhanced from 32 to 256 µg mL-1 with the treatment of tetracycline in time- and dose-dependent manners. Furthermore, the abundance of most genes was increased in treatment groups and efflux genes mainly responded to the stress of tetracycline with an average level of 1.0 × 10-2. After treatment with tetracycline, the predominant species were changed both at phylum and genus levels. The present study explored the impact of tetracycline on gut microbiota of goldfish at environmentally realistic concentrations for the first time and our findings will provide a reference for characterizing the microbiome of fish in the natural environment.

Diffusion tensor imaging of microstructural alterations in the trigeminal nerve due to neurovascular contact/compression.

BACKGROUND: Several recent studies have focused on microstructural changes in the trigeminal nerve in trigeminal neuralgia using diffusion tensor imaging (DTI). However, alterations after microvascular decompression (MVD) have rarely been investigated. Furthermore, the trigeminal nerve of asymptomatic individuals also presenting with neurovascular contact/compression (NVC) has not yet been studied. METHODS: Thirty-four patients suffering from trigeminal neuralgia and 34 healthy age-matched controls, who were identified as having unilateral NVC signs, underwent both DTI and high-resolution magnetic resonance imaging (MRI) for comparison. All trigeminal neuralgia patients underwent a post-surgical MRI scan after 7 days and a follow-up MRI scan within 6-8 months after surgery. The apparent diffusion coefficients (ADCs) and fractional anisotropy (FA) values were measured from coronal images in which the nerves from the root exit point to the distal segment were clearly shown. RESULTS: In 34 trigeminal neuralgia patients, the absolute FA value was significantly lower on the affected side (mean FA, 0.34 ± 0.03) than on the unaffected side (mean FA, 0.37 ± 0.05, p < 0.001). The FA ratio was also significantly different between the trigeminal neuralgia group (RsFA, 0.92 ± 0.06) and the control group (RsFA, 0.99 ± 0.09) (p = 0.001). The absolute ADC value between the two sides in patients and the ratios of ADC between the trigeminal neuralgia and control groups did not show any significant differences (p = 0.21 and 0.29, respectively). However, in 34 healthy subjects presenting with signs of NVC, neither the FA value nor the ADC showed a difference between sides (p > 0.05). The FA ratio of patients showed a significant increase on two follow-up MRI scans compared to the preoperative FA (p = 0.02 and 0.002, respectively), while the ADC ratio showed a significant decrease at 6 months after MVD (p = 0.004). CONCLUSION: This study of trigeminal neuralgia due to NVC found that DTI indexes could reflect alterations in the affected trigeminal nerve. Furthermore, a reversible change after MVD surgery could be potentially valuable for monitoring the change in white matter of the trigeminal nerve.

Bisphenol A induced abnormal DNA methylation of ovarian steroidogenic genes in rare minnow Gobiocypris rarus.

Bisphenol A (BPA), an ubiquitous environmental endocrine disruptor chemical, disturbs the mRNA expressions of steroidogenic genes and subsequently steroid hormone synthesis in mammals and aquatic species. However, the underlying regulation mechanisms are barely understood, especially in fish. To explore the regulation mechanism, we exposed female rare minnow Gobiocypris rarus (G. rarus) to BPA at a nominal concentration of 15 µg/L for 7 and 14 days in the present study. Results showed significant increase of gonad somatic index (GSI) and serum estradiol (E2) levels in response to BPA at day 14. The 7-day BPA exposure notably repressed the expression of two ovarian steroidogenic genes (star and hsd11b2) and suppressed their capacity of estrogen response elements (ERE) to recruit estrogen receptor (ER), while the 14-day BPA treatment remarkably induced transcript of hsd3b and enhanced the capacity of ERE to recruitment ER in ovaries. Furthermore, the 7-day BPA exposure caused DNA hypermethylation of star (CpGs: -742 bp and -719 bp) and hsd11b2 (CpG: -1788 bp). However, 14-day BPA exposure resulted in DNA hypomethylation of hsd3b (CpG: -181 bp). Correlation analysis revealed that the DNA methylation levels at specific CpGs in star, hsd3b and hsd11b2 were significantly correlated to their mRNA levels and ER-EREs interactions. These findings suggest that the disturbed steroidogenesis and the transcripts of ovarian steroidogenic genes might attribute to the altered DNA methylation status of these ovarian steroidogenic genes in response to BPA.

Bisphenol A regulates rare minnow testicular vitellogenin expression via reducing its promoter Er recruitment.

Vitellogenins (Vtgs) are major precursor of the egg-yolk proteins. They are synthesized in liver of adult female ovipara, but normally silent in males. For their sensitive response to estrogen, Vtgs are usually used as biomarkers for environmental estrogenic compounds. In the present study, three vtg subtypes (vtg1, vtg2 and vtg3) were proved to present in the testis of rare minnow Gobiocypris rarus for the first time. Immunohistochemistry result showed that Vtg proteins mainly deposit in spermatogonium and spermatocytes. Following 225µg/L bisphenol A (BPA) exposure 1, 3 and 9 weeks, testicular vtg mRNAs were mostly significantly decreased. The further chromatin immunoprecipitation showed that BPA could decrease estrogen receptor (Er) recruitment in vtg promoter, which possibly reduced Er's transcription activation effect on vtgs. However, different from the continuously decreased vtg mRNA levels, testicular Vtg protein levels were recovered at week 9. Considering the induced hepatic Vtg expression, testicular Vtgs may be replenished by the induced hepatic Vtgs under BPA exposure.

Molecular identification of Kiss/GPR54 and function analysis with mRNA expression profiles exposure to 17α-ethinylestradiol in rare minnow Gobiocypris rarus.

17α-ethinylestradiol (EE2) is a widely existed endocrine disrupting chemical in water environment. Kisspeptins act as indispensable regulators through GPR54 in the hypothalamic-pituitary-gonadal (HPG) axis. This study aimed to provide further understanding of the effect of EE2 on HPG axis. Molecular cloning and tissue distribution of kiss genes and GPR54s were performed in Gobiocypris rarus. The mRNA expression profiles of kiss1, kiss2, GPR54s and GnRHs were detected in G. rarus brain and/or gonad following 3- and 6-days EE2 (1, 5, 25 and 125 ng/L) exposure. Results showed that kiss genes and GPR54s were highly expressed in brain and gonad. Both kiss1 and kiss2 were increased in female brain and suppressed in male brain following EE2 exposure. GnRHs were inhibited in a concentration-dependent manner in male brain following 3-days EE2 exposure. In gonad, GPR54b was almost suppressed in all of EE2 concentrations. The present findings suggest that EE2 impacts the genes expression of Kiss/GPR54-GnRH system in G. rarus, thereby probably disturbing the neuroendocrine homeostasis.

Effect of low-dose malathion on the gonadal development of adult rare minnow Gobiocypris rarus.

Malathion is an organophosphorus pesticide that extensively used in agriculture and veterinary practices. To investigate the effects of low dose malathion on rare minnow Gobiocypris rarus gonadal development, we exposed adult rare minnow to environmentally relevant concentration malathion (2 and 20µg/L) for 21 days. Gonadal histology, sex hormone levels and mRNA expressions of steroidogenic genes were investigated. Malathion at both 2 and 20µg/L significantly up-regulated rare minnow testicular weight and promoted the progression of spermatogenesis. Neither ovarian weight nor process of ovary development was markedly changed. In testis, 2µg/L malathion significantly down-regulated testosterone and 11-ketotestosterone levels, and up-regulated mRNA expression of steroidogenic genes. In ovaries, 2 and 20µg/L malathion significantly inhibited estradiol17ß levels and induced testosterone levels, both in concentration dependent manners; mRNA expressions of almost all the detected ovarian steroidogenic genes were up-regulated. The present result suggested that malathion even at low dose could pose a potential threat to adult rare minnow gonadal development.

Global DNA methylation in gonads of adult zebrafish Danio rerio under bisphenol A exposure.

Altered DNA methylation is pervasively associated with changes in gene expression and signal transduction after exposure to a wide range of endocrine disrupting chemicals. As a weak estrogenic chemical, bisphenol A (BPA) has been extensively studied for reproductive toxicity. In order to explore the effects of BPA on epigenetic modification in gonads of zebrafish Danio rerio, we measured the global DNA methylation together with the gene expression of DNA methyltransferase (dnmts), glycine N-methyltransferase (gnmt), and ten-eleven translocation (tets) in gonads of D. rerio under BPA exposure by ELISA and quantitative real-time PCR method, respectively. The global level of DNA methylation was significantly decreased in ovaries after exposed to BPA for 7 days, and testes following 35-day exposure. Moreover, the global level of DNA methylation was also significantly reduced in testes after exposed to 15µg/L BPA for 7 days. Besides the alteration of the global level of DNA methylation, varying degrees of transcriptional changes of dnmts, gnmt and tets were detected in gonads of D. rerio under BPA exposure. The present study suggested that BPA might cause the global DNA demethylation in gonads of zebrafish by regulating the transcriptional changes of the DNA methylation/demethylation-associated genes (dnmts, gnmt, and tets).

Collateral circulation prevents masticatory muscle impairment in rat middle cerebral artery occlusion model.

The rat suture middle cerebral artery occlusion (MCAO) is a frequently used animal model for investigating the mechanisms of ischemic brain injury. During suture MCAO, transection of the external carotid artery (ECA) potentially restrains blood flow and impairs masticatory muscle and other ECA-supported territories, consequently influencing post-operation animal survival. This study was aimed at investigating the effect of ECA transection on the hemodynamic alterations using a novel synchrotron radiation (SR) angiography technique and magnetic resonance imaging in live animals. Fifteen male adult Sprague-Dawley rats were used in this study. Animals underwent MCAO, in which the ECA was transected. SR angiography was performed before and after MCAO. Rats then underwent magnetic resonance imaging (MRI) to detect the tissue lesion both intra- and extra-cranially. Animals with SR angiography without other manipulations were used as control. High-resolution cerebrovascular morphology was analyzed using a novel technique of SR angiography. The masticatory muscle lesion was further examined by hematoxylin and eosin staining. MRI and histological results showed that there was no masticatory muscle lesion at 1, 7 and 28 days following MCAO with ECA transection. In normal condition, the ECA and its branch external maxillary artery were clearly detected. Following ECA transection, the external maxillary artery was still observed and the blood supply appeared from the anastomotic branch from the pterygopalatine artery. SR angiography further revealed the inter-relationship of hemisphere extra- and intra-cranial vasculature in the rat following MCAO. Transection of the ECA did not impair masticatory muscles in rat suture MCAO. Interrupted blood flow could be compensated by the collateral circulation from the pterygopalatine artery.

Spatial distribution and modelling of 239+240Pu in the sediments and seawater columns of the South China Sea and Indian Ocean.

In order to investigate the 239+240Pu potential influence in the ocean, and develop a new method for rapidly monitoring radioactive pollution, the 239+240Pu spatial distribution in the South China Sea (SCS) and the Indian Ocean (IND) sediments is analyzed by SF-ICP-MS (ELEMENT 2). The inventory-weighted mean activities of 239+240Pu were 0.413 ± 0.333 mBq/g, 0.128 ± 0.044 mBq/g, and 0.483 ± 0.606 mBq/g in the sediments of the SCS, eastern IND, and Arabian Sea, respectively. The 239+240Pu activity spatial distribution in the SCS sediments was influenced by the current, the vertical distribution of Pu in seawater, and the transport of particulate matter. The 239+240Pu activity spatial distribution in the IND sediments could be impacted by Antarctic Intermediate Water. The average of 240Pu/239Pu atomic ratios were 0.258 ± 0.034, 0.219 ± 0.031, and 0.212 ± 0.028 in the sediments of the SCS, eastern IND, and Arabian Sea, respectively. The 240Pu/239Pu atomic ratios in the SCS and IND indicate that Pu from the Pacific Proving Ground (PPG) is transported to the IND via the SCS internal current and transverse ocean currents within Indonesia. In addition, a seawater advection-dispersion equation (S-ADE) model is established based on the actual physical processes of radionuclides in the seawater column and well fitting results were obtained (R2 = 0.49 to 0.99). The 239+240Pu data and the geographic information from the sample site were used to correct the Pu distribution in the seawater. The calculated 239+240Pu mean concentrations in the surface seawater were 2.465 mBq/m3 and 2.205 mBq/m3 for the SCS and the eastern IND seawater, respectively, and the result is consistent with the previous measurements. Then, the 239+240Pu stored in the study area of SCS and eastern IND was estimated to be approximately 1.0-1.4% of the global ocean based on the model. This study provides a useful model for guiding and designing future monitoring of pollution by anthropogenic Pu and other isotopes.

Migration mechanisms of 90Sr and 137Cs on terraces.

In order to investigate the impact of environmental conditions on the distribution and migration of 90Sr in the Longji terrace environment, the activity concentrations of 90Sr and 137Cs were determined. The activity concentration ranges of 90Sr and 137Cs in surface soil were 0.15-1.04 Bq/kg and 2.16-6.94 Bq/kg, respectively. These results showed that there was a similar trend between the activity concentration of 90Sr and 137Cs in the surface soil along the runoff path and their activity concentration were influenced by the slope of the terraced terrain. On the other hand, the activity ranges of 90Sr and 137Cs in soil cores were 0.01-2.74 Bq/kg and 0.43-7.19 Bq/kg, respectively. These results indicate that the migration mechanism of 90Sr is different from that of 137Cs. As compared with 137Cs, 90Sr is significantly influenced by the moisture content. In addition, high span of 137Cs/90Sr activity ratios were found in this study, which were attributed to the characteristics of cultivated land and frequent artificial disturbances that intensified the migration of 90Sr.

Assessment of the depositional characteristics of the Yellow River estuary from 1960s by 239+240Pu and 137Cs.

The spatial and vertical distribution of 239+240Pu and 137Cs in the sediments of the Yellow River Delta was studied to evaluate the deposition dynamics in the Yellow River estuary from 1960s. The activity of 239+240Pu and 137Cs in sediment core ranged from 0.001 to 0.212 Bq/kg and 0.52-2.53 Bq/kg, respectively. A maximum accumulation peak and two secondary accumulation peaks appeared in the sediment core YR2. The average deposition rate of 8.3 cm/y for the Yellow River estuary from 1964 to 1976 was obtained. The proportion of Pu from the Yellow River net input and direct deposition to the total inventory of Pu in the estuary was assessed, with a total inventory of Pu in the abandoned estuary of 7.4 × 1010 Bq and a net input of 2.2 × 1010 Bq from the Yellow River. Pu deposited in the estuary only accounts for 18 % of the total Pu transported by the Yellow River, and most of the Pu is injected into the Bohai Sea with the Yellow River.

Species distribution modeling combined with environmental DNA analysis to explore distribution of invasive alien mosquitofish (Gambusia affinis) in China.

China has become one of the most serious countries suffering from biological invasions in the world. In the context of global climate change, invasive alien species (IAS) are likely to invade a wider area, posing greater ecological and economic threats in China. Western mosquitofish (Gambusia affinis), which is known as one of the 100 most invasive alien species, has distributed widely in southern China and is gradually spreading to the north, causing serious ecological damage and economic losses. However, its distribution in China is still unclear. Hence, there is an urgent need for a more convenient way to detect and monitor the distribution of G. affinis to put forward specific management. Therefore, we detected the distribution of G. affinis in China under current and future climate change by combing Maxent modeling prediction and eDNA verification, which is a more time-saving and reliable method to estimate the distribution of species. The Maxent modeling showed that G. affinis has a broad habitat suitability in China (especially in southern China) and would continue to spread in the future with ongoing climate change. However, eDNA monitoring showed that occurrences can already be detected in regions that Maxent still categorized as unsuitable. Besides temperature, precipitation and human influence were the most important environmental factors affecting the distribution of G. affinis in China. In addition, by environmental DNA analysis, we verified the presence of G. affinis predicted by Maxent in the Qinling Mountains where the presence of G. affinis had not been previously recorded.

Spatial distribution, source identification, and transportation paths of plutonium in the Beibu Gulf, South China Sea.

To investigate the spatial distribution and source of plutonium isotopes in the Beibu Gulf, surface sediments were collected and analyzed using sector field inductively coupled plasma mass spectrometry (SF-ICP-MS). The activities of 239+240Pu in surface sediments ranged from 0.012 to 0.451 mBq/g (mean: 0.171 ± 0.138 mBq/g, n = 36), indicating a decreasing trend in a counterclockwise direction from the southern bay mouth. The counterclockwise decreasing trend in the south of the bay mouth is similar to the current in the Beibu Gulf. The 240Pu/239Pu atom ratios in surface sediments ranged from 0.156 to 0.283 (mean: 0.236 ± 0.031, n = 36), slightly higher than that of the global fallout value of 0.18. This suggests that the Pu in the Beibu Gulf was a combination of global fallout and Pacific Proving Ground (PPG). The average contribution of the plutonium (Pu) derived from the PPG in the sediment was estimated to be 52 % ± 24 %.

Nonsteroidal anti-inflammatory drug diclofenac accelerates the emergence of antibiotic resistance via mutagenesis.

Overuse of antimicrobial agents are generally considered to be a key factor in the occurrence of antibiotic resistance bacteria (ARB). Nevertheless, it is unclear whether ARB can be induced by non-antibiotic chemicals such as nonsteroidal anti-inflammatory drug (NSAID). Thus, the objective of this study is to investigate whether NSAID diclofenac (DCF) promote the emergence of antibiotic resistance in Escherichia coli K12 MG1655. Our results suggested that DCF induced the occurrence of ARB which showed hereditary stability of resistance. Meanwhile, gene variation was identified on chromosome of the ARB, and DCF can cause bacterial oxidative stress and SOS response. Subsequently, transcriptional levels of antioxidant (soxS, sodA, sodC, gor, katG, ahpF) and SOS (recA, lexA, uvrA, uvrB, ruvA, ruvB, dinB, umuC, polB) system-related genes were enhanced. However, the expression of related genes cannot be increased in high-dosage treatment compared with low-dosage samples because of cytotoxicity and cellular damage. Simultaneously, high-dosage DCF decreased the mutation frequency but enhanced the resistance of mutants. Our findings expand our knowledge of the promoting effect on the emergence of ARB caused by DCF. More attention and regulations should be given to these potential ecological and health risks for widespread DCF.

Radioactivity research in mosses from typical Karst Regions in Leye Tiankeng, Southern China.

Radionuclides in environmental ecosystems have ecotoxicity and health impact on human and environment, so radioactive contamination has always been one of the global concerns. This study mainly focused on the radioactivity of mosses collected from the Leye Tiankeng Group in Guangxi. The activities of 239+240Pu measured by SF-ICP-MS and 137Cs measured by HPGe in moss and soil samples are as follows: 0-2.29 Bq/kg in mosses and 1.5-11.9 Bq/kg in soils for 137Cs, and 0.025-0.25Bq/kg in mosses and 0.07-0.51Bq/kg in soils for 239+240Pu. The range of 240Pu/239Pu atom ratios (0.201 in mosses and 0.184 in soils) and 239+240Pu/137Cs activity ratios (0.128 in mosses and 0.044 in soils) indicated that the 137Cs and 239+240Pu in study area were mainly contributed by global fallout. 137Cs and 239+240Pu showed similar distribution in soils. However, their behaviors in mosses were quite different due to the differences in the growth environment of mosses. The transfer factors of 137Cs and 239+240Pu from soil to moss varied in different growth stages and specific environments. A weak positive correlation among 137Cs, 239+240Pu in mosses and soil-derived radionuclides suggested that resettlement was predominant here. The negative correlation between 7Be, 210Pb and soil-derived radionuclides indicated that 7Be and 210Pb came from atmospheric components, while the weak correlation between them suggested that their specific sources were different. The Cu and Ni were moderately enriched in mosses here due to the use of agricultural fertilizers, At the same time, Zn was at a high level in the Lilang area, where transportation was more developed.

Effect of suture properties on stability of middle cerebral artery occlusion evaluated by synchrotron radiation angiography.

BACKGROUND AND PURPOSE: The intraluminal suture technique for producing middle cerebral artery occlusion in rodents is the most commonly used method for modeling focal cerebral ischemia associated with clinical ischemic stroke. Synchrotron radiation angiography may provide a novel solution to directly monitor the success of middle cerebral artery occlusion. METHODS: Twenty adult Sprague-Dawley rats for middle cerebral artery occlusion models were prepared randomly with different suture head silicone coating. In vivo imaging was performed at beam line BL13W1, Shanghai Synchrotron Radiation Facility, Shanghai, China. RESULTS: Silicone-coated suture was superior to uncoated suture for producing consistent brain infarction. Additionally, silicone coating length was an important variable controlling the extent of the ischemic lesion: infarcts affected predominantly the caudate-putamen with large variability (<2 mm), both the cortex and caudate-putamen (2-3.3 mm), and most of the hemisphere, including the hypothalamus (>3.3 mm). CONCLUSIONS: Synchrotron radiation angiography provides a useful tool to observe hemodynamic changes after middle cerebral artery occlusion, and the physical properties of suture are critical to the success of the middle cerebral artery occlusion model.