Metformin Attenuates the Inflammatory Response via the Regulation of Synovial M1 Macrophage in Osteoarthritis.

Osteoarthritis (OA), the most common chronic inflammatory joint disease, is characterized by progressive cartilage degeneration, subchondral bone sclerosis, synovitis, and osteophyte formation. Metformin, a hypoglycemic agent used in the treatment of type 2 diabetes, has been evidenced to have anti-inflammatory properties to treat OA. It hampers the M1 polarization of synovial sublining macrophages, which promotes synovitis and exacerbates OA, thus lessening cartilage loss. In this study, metformin prevented the pro-inflammatory cytokines secreted by M1 macrophages, suppressed the inflammatory response of chondrocytes cultured with conditional medium (CM) from M1 macrophages, and mitigated the migration of M1 macrophages induced by interleukin-1ß (IL-1ß)-treated chondrocytes in vitro. In the meantime, metformin reduced the invasion of M1 macrophages in synovial regions brought about by the destabilization of medial meniscus (DMM) surgery in mice, and alleviated cartilage degeneration. Mechanistically, metformin regulated PI3K/AKT and downstream pathways in M1 macrophages. Overall, we demonstrated the therapeutic potential of metformin targeting synovial M1 macrophages in OA.

A multi-faceted, location-specific assessment of land degradation threats to peri-urban agriculture at a traditional grain base in northeastern China.

Urbanization-induced cultivated land degradation can hamper the ability of peri-urban agriculture (PUA) to deliver clean food and agroecosystem services. Detailed geo-information about which cultivated lands are being influenced by urbanization will be important to designing future measures for the conservation of PUA. This information will be especially relevant for traditional grain bases because PUA is often underappreciated in these regions. For this reason, we performed a multi-faceted and location-specific assessment, including soil pollution, soil fertility, basic tillage conditions and land fragmentation, of cultivated land in a rural-urban transition zone outside of a city in northeast China. We also illustrated the combined risks in different urbanized environments via GIS-based two-step spatial clustering. The results indicated that, in general, cultivated lands were more polluted and fragmented, as well as less fertile and tillable, the closer they were to the urban area. Most of the affected cultivated lands were located within 8 km of the urban periphery. Furthermore, certain urban environments exposed the surrounding cultivated lands to specific degradation in relation to different combined risks. PUA in long-standing industrial areas mainly faced risks of polluted agricultural production, underutilization and impaired landscape ecological security (LES), whereas cultivated lands close to a recently developed residential area were characterized by risks of supplying service disruption, unsustainable agricultural production, underutilization and impaired LES. The present study highlighted that PUA associated with traditional grain bases must be preserved to enhance urban sustainability and resilience, and suggests that measures which can adapt to multi-faceted local degradation issues will be the most effective protection for peri-urban areas. Furthermore, the results also suggest that multi-functional and profitable agriculture will contribute to breaking the vicious circle of land degradation in peri-urban cultivated areas of traditional grain bases.

miR-148b-3p functions as a tumor suppressor in GISTs by directly targeting KIT.

BACKGROUND: Gain-of-function mutations and overexpression of KIT are characteristic features of gastrointestinal stromal tumor (GIST). Dysregulation in miRNA expression may lead to KIT overexpression and tumorigenesis. METHODS: miRNA microarray analysis and real-time PCR were used to determine the miRNA expression profiles in a cohort of 69 clinical samples including 50 CD117IHC+/KITmutation GISTs and 19 CD117IHC-/wild-type GISTs. GO enrichment and KEGG pathway analyses were performed to reveal the predicted targets of the dysregulated miRNAs. Of the dysregulated miRNAs whose expression was inversely correlated with that of KIT miRNAs were predicted by bioinformatics analysis and confirmed by luciferase reporter assay. Cell counting kit-8 (CCK-8) and flow cytometry were used to measure the cell proliferation, cycle arrest and apoptosis. Wound healing and transwell assays were used to evaluate migration and invasion. A xenograft BALB/c nude mouse model was applied to investigate the tumorigenesis in vivo. Western blot and qRT-PCR were used to investigate the protein and mRNA levels of KIT and its downstream effectors including ERK, AKT and STAT3. RESULTS: Of the six miRNAs whose expression was inversely correlated with that of KIT, we found that miR-148b-3p was significantly downregulated in the CD117IHC+/KITmutation GIST cohort. This miRNA was subsequently found to inhibit proliferation, migration and invasion of GIST882 cells. Mechanistically, miR-148b-3p was shown to regulate KIT expression through directly binding to the 3'-UTR of the KIT mRNA. Restoration of miR-148b-3p expression in GIST882 cells led to reduced expression of KIT and the downstream effectors proteins ERK, AKT and STAT3. However, overexpression of KIT reversed the inhibitory effect of miR-148b-3p on cell proliferation, migration and invasion. Furthermore, we found that reduced miR-148b-3p expression correlated with poor overall survival (OS) and disease-free survival (DFS) in GIST patients. CONCLUSION: miR-148b-3p functions as an important regulator of KIT expression and a potential prognostic biomarker for GISTs.

Head and neck angiography at 70 kVp with a third-generation dual-source CT system in patients: comparison with 100 kVp.

PURPOSE: This study was conducted in order to evaluate the image quality of 70 kVp and 25 mL contrast medium (CM) volume for head and neck computed tomographic angiography (CTA) and assess the diagnostic accuracy for arterial stenosis. METHODS: Fifty patients were prospectively divided into two groups randomly: group A (n = 25), 70 kVp with 25 mL CM, and group B (n = 25), 100 kVp with 40 mL CM. CT attenuation values, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of the shoulder, neck, and cerebral arteries were measured for objective image quality. Subjective image quality of the shoulder and cerebral arteries was also evaluated. For patients undergoing digital subtracted angiography (DSA), diagnostic accuracy of CTA was assessed with DSA as reference standard. RESULTS: The SNRs of the shoulder, neck, and cerebral arteries in group A were higher than those in group B (P < 0.05). The CNRs of the shoulder and neck arteries in group A were higher than those in group B (P < 0.05). There was no significant difference in subjective image quality of arteries between group A and group B (P > 0.05). The accuracy was noted as 94.0% (156/166) in group A and 97.1% (134/138) in group B for ≥ 50% stenosis. The accuracy of intracranial arterial stenosis was lower than that of extracranial arterial stenosis in group A. The radiation dose of group A was significantly decreased by 56% than that of group B. CONCLUSION: Head and neck CTA at 70 kVp using 25 mL CM can obtain diagnostic image quality with lower radiation dose while maintaining high accuracy in detecting the arterial stenosis compared with the 100-kVp and 40-mL CM.

Third-generation Dual-source CT for Head and Neck CT Angiography with 70 kV Tube Voltage and 20-25 ml Contrast Medium in Patients With Body Weight Lower than 75 kg.

Objective To investigate the image quality of head and neck CT angiography (CTA)using the third-generation dual-source CT combined with 70 kV tube voltage and 20-25 ml contrast medium (CM),and evaluate the effects of venous artifacts arising from the CM on the ipsilateral side of injection. Methods Totally 40 consecutive patients with suspected vascular diseases and body weight lower than 75 kg prospectively underwent head and neck CTA examination using the third-generation dual-source CT. CTA was performed with a third-generation dual-source CT system. Patients were randomly divived into 70 kV group (n=20)and 100 kV group (n=20). The 70 kV group used 20-25 ml CM and advanced modeled iterative reconstruction technique,and the 100 kV group used 40 ml CM and filtered back projection. Venous artifacts and CM residues were evaluated by a 3-point scale (1=excellent,3=poor),respectively. Results The effective dose of 70 kV group decreased 58% compared to 100 kV group (t=-18.14,P<0.001).In the 70 kV group,16 patients (80.0%)presented with venous artifacts and six of them (37.5%,6/16)affected the adjacent arteries. In the 100 kV group,19 patients (95.0%)presented with venous artifacts,and seven of them (36.8%,7/19)affected the adjacent arteries (Z=-0.878,P=0.380). In the 70 kV group,13 patients (65.0%)presented with obvious CM residues and two of them (15.3%,2/13)prolonged into the superior vena cava (SVC). In the 100 kV group,19 patients(95.0%)presented with obvious CM residues,and thirteen of them(68.4%,13/19)prolonged into the SVC (Z=-3.654,P<0.001). Conclusion Compared with the 100 kV,the third-generation dual-source CT for head and neck CTA,combined with 70 kV and 20-25 ml CM,can remarkably decrease the radiation dose,along with reduced CM residues and comparable venous artifacts.

Application of Third-generation Dual-source CT for Ultra-high Resolution Temporal Bone Imaging Using Automated Tube Voltage Adaptation in Children with Hearing Impairment.

Objective To evaluate the radiation dose and image quality of the third-generation dual-source CT using automated tube voltage adaptation (CARE kV) in temporal bone scanning in pediatric patients with hearing impairment. Methods Totally 27 children with hearing impairment less than 18 years old were randomly divided into two groups:Group A (n=14),examined with CARE kV (reference with 100 kV and 214 mA)and sinogram-affirmed iterative reconstruction;and Group B (n=13),examined with CARE kV (reference with 100 kV and 171 mA)and advanced modeled iterative reconstruction. The scan range was from eyebrow to the end of the mastoid process. CT values and image noise were measured.The signal to noise ratio (SNR)was calculated. Subjective image quality was assessed by two radiologists and later in a consensus reading. Results There was no significant difference in CT value,image noise,and SNR between these two groups (all P>0.05). Also,the subjective scores of the 10 anatomical structures showed no significant difference (all P>0.05). The CT dose index volume and dose-length product were (11.62+1.92)mGy and (106.92+37.48)mGy·cm,respectively,in group B and (21.28+2.19)mGy (t=12.15,P<0.001)and (229.65+56.26)mGy·cm (t=6.62,P<0.001)in group A,decreased by 45% and 53%. Conclusion Compared with the second-generation dual-source CT,the third-generation dual-source CT for the scanning of temporal bone with CARE kV can ensure image quality and reduce radiation dose.

Statistical approach for the retrieval of phytoplankton community structures from in situ fluorescence measurements.

Knowledge of phytoplankton community structures is important to the understanding of various marine biogeochemical processes and ecosystem. Fluorescence excitation spectra (F(λ)) provide great potential for studying phytoplankton communities because their spectral variability depends on changes in the pigment compositions related to distinct phytoplankton groups. Commercial spectrofluorometers have been developed to analyze phytoplankton communities by measuring the field F(λ), but estimations using the default methods are not always accurate because of their strong dependence on norm spectra, which are obtained by culturing pure algae of a given group and are assumed to be constant. In this study, we proposed a novel approach for estimating the chlorophyll a (Chl a) fractions of brown algae, cyanobacteria, green algae and cryptophytes based on a data set collected in the East China Sea (ECS) and the Tsushima Strait (TS), with concurrent measurements of in vivo F(λ) and phytoplankton communities derived from pigments analysis. The new approach blends various statistical features by computing the band ratios and continuum-removed spectra of F(λ) without requiring a priori knowledge of the norm spectra. The model evaluations indicate that our approach yields good estimations of the Chl a fractions, with root-mean-square errors of 0.117, 0.078, 0.072 and 0.060 for brown algae, cyanobacteria, green algae and cryptophytes, respectively. The statistical analysis shows that the models are generally robust to uncertainty in F(λ). We recommend using a site-specific model for more accurate estimations. To develop a site-specific model in the ECS and TS, approximately 26 samples are sufficient for using our approach, but this conclusion needs to be validated in additional regions. Overall, our approach provides a useful technical basis for estimating phytoplankton communities from measurements of F(λ).

Remote estimation of phytoplankton size fractions using the spectral shape of light absorption.

Phytoplankton size structure plays an important role in ocean biogeochemical processes. The light absorption spectra of phytoplankton provide a great potential for retrieving phytoplankton size structure because of the strong dependence on the packaging effect caused by phytoplankton cell size and on different pigment compositions related to phytoplankton taxonomy. In this study, we investigated the variability in light absorption spectra of phytoplankton in relation to the size structure. Based on this, a new approach was proposed for estimating phytoplankton size fractions. Our approach use the spectral shape of the normalized phytoplankton absorption coefficient (a(ph)(λ)) through principal component analysis (PCA). Values of a(ph)(λ) were normalized to remove biomass effects, and PCA was conducted to separate the spectral variance of normalized a(ph)(λ) into uncorrelated principal components (PCs). Spectral variations captured by the first four PC modes were used to build relationships with phytoplankton size fractions. The results showed that PCA had powerful ability to capture spectral variations in normalized a(ph)(λ), which were significantly related to phytoplankton size fractions. For both hyperspectral a(ph)(λ) and multiband a(ph)(λ), our approach is applicable. We evaluated our approach using wide in situ data collected from coastal waters and the global ocean, and the results demonstrated a good and robust performance in estimating phytoplankton size fractions in various regions. The model performance was further evaluated by a(ph)(λ) derived from in situ remote sensing reflectance (R(rs)(λ)) with a quasi-analytical algorithm. Using R(rs)(λ) only at six bands, accurate estimations of phytoplankton size fractions were obtained, with R(2) values of 0.85, 0.61, and 0.76, and root mean-square errors of 0.130, 0.126, and 0.112 for micro-, nano-, and picophytoplankton, respectively. Our approach provides practical basis for remote estimation of phytoplankton size structure using a(ph)(λ) derived from satellite observations or rapid field instrument measurements in the future.

Long-term response of interspecific competition among three typical bloom-forming species to changes in phosphorus and temperature.

Phosphorus and temperature play an important role in the succession of diatom-dinoflagellate blooms. However, there is little long-term research on interspecific competition based on phosphorus source and temperature. Here, interspecific competition among Skeletonema costatum, Prorocentrum donghaiense and Karenia mikimotoi was studied using trialgal laboratory co-cultures under different phosphorus and temperature conditions. These results suggest that S. costatum and P. donghaiense alternated as competing dominant species during the experimental period, which coincides with the different phosphorus conditions. However, K. mikimotoi growth was significantly inhibited throughout the experiment. We suggest that this may be due to different algal requirements for phosphorus, optimal growth temperatures, and possible allelopathic effects. This study provides a comprehensive mechanism of interspecific competition between diatom-dinoflagellate in response to phosphorus and temperature and elucidates the seasonal succession of diatom-dinoflagellate from late spring to early summer in the Changjiang River Estuary and the adjacent East China Sea.

Changes in dinoflagellate and diatom blooms in the East China Sea over the last two decades, under different spatial and temporal scale scenarios.

Frequent algal blooms in the nearshore area of the East China Sea (ECS) pose a serious threat to both the marine environment and human health. Climate and environmental changes play an important role in the occurrence of diatoms and dinoflagellates blooms. Using the MODIS-Aqua 1-km satellite observations, the outbreaks of dinoflagellate and diatom blooms in the ECS coast in summer during 2003-2022 were mapped. Our results found that although the bloom frequency of dinoflagellate was consistently higher than diatoms, its bloom intensity showed a slightly decline trend in recent decades. The driving factors analysis showed that river runoff and sediments discharge played different effect on the formation of diatom and dinoflagellate blooms. Besides, our results compared the effect of El Niño and La Niña on bloom occurrences. This study was supposed to provide detailed insights into algal blooms, with important implications for relevant meteorological and climate changes in coastal regions.

Identifying the Local Influencing Factors of Arsenic Concentration in Suburban Soil: A Multiscale Geographically Weighted Regression Approach.

Exploring the local influencing factors and sources of soil arsenic (As) is crucial for reducing As pollution, protecting soil ecology, and ensuring human health. Based on geographically weighted regression (GWR), multiscale GWR (MGWR) considers the different influence ranges of explanatory variables and thus adopts an adaptative bandwidth. It is an effective model in many fields but has not been used in exploring local influencing factors and sources of As. Therefore, using 200 samples collected from the northeastern black soil zone of China, this study examined the effectiveness of MGWR, revealed the spatial non-stationary relationship between As and environmental variables, and determined the local impact factors and pollution sources of As. The results showed that 49% of the samples had arsenic content exceeding the background value, and these samples were mainly distributed in the central and southern parts of the region. MGWR outperformed GWR with the adaptative bandwidth, with a lower Moran's I of residuals and a higher R2 (0.559). The MGWR model revealed the spatially heterogeneous relationship between As and explanatory variables. Specifically, the road density and total nitrogen, clay, and silt contents were the primary or secondary influencing factors at most points. The distance from an industrial enterprise was the secondary influencing factor at only a few points. The main pollution sources of As were thus inferred as traffic and fertilizer, and industrial emissions were also included in the southern region. These findings highlight the importance of considering adaptative bandwidths for independent variables and demonstrate the effectiveness of MGWR in exploring local sources of soil pollutants.

Bridging the incompatibility gap in dual asymmetric catalysis over a thermoresponsive hydrogel-supported catalyst.

The integration of dual asymmetric catalysis is highly beneficial for the synthesis of organic molecules with multiple stereocenters. However, two major issues that need to be addressed are the intrinsic deactivation of dual-species and the extrinsic conflict of reaction conditions. To overcome these concerns, we have utilized the compartmental and thermoresponsive properties of poly(N-isopropylacrylamide) (PNIPAM) to develop a cross-linked PNIPAM-hydrogel-supported bifunctional catalyst. This catalyst is designed with Rh(diene) species situated on the outer surface and Ru(diamine) species positioned within the interior of the hydrogel. The compartmental function of PNIPAM in the middle overcomes intrinsic mutual deactivations between the dual-species. The thermoresponsive nature of PNIPAM allows for precise control of catalytic pathways in resolving external conflicts by controlling the reaction switching between an Rh-catalyzed enantioselective 1,4-addition at 50°C and a Ru-catalyzed asymmetric transfer hydrogenation (ATH) at 25°C. As we envisioned, this sequential 1,4-addition/reduction dual enantioselective cascade reaction achieves a transformation from incompatibility to compatibility, resulting in direct access to γ-substituted cyclic alcohols with dual stereocenters in high yields and enantio/diastereoselectivities. Mechanistic investigation reveals a reversible temperature transition between 50°C and 25°C, ensuring a cascade process comprising a 1,4-addition followed by the ATH process.

[Spatial Diffusion Mechanism Underlying Peri-urban Cropland Heavy Metal Contamination in the Black Soil Region].

The spatial diffusion mechanism underlying cropland heavy metal contamination in a complex peri-urban environment provides a crucial basis for controlling soil contamination from the source and also for ensuring the quality of black soil croplands. However, previous studies have struggled to locate the contamination sources or trace their diffusion trajectories in space. In this regard, representative peri-urban croplands in the black soil region were selected as a case, and soil As, Pb, Hg, and Cd were deemed as the main research objects. Moreover, an affinity propagation algorithm and spatial autocorrelation regression were adopted to measure the contamination patterns and identify the major determinants, in an attempt to reveal how heavy metals are diffused in the peri-urban cultivated area. The results indicated that ① the average concentrations of soil As and Cd were 39.35 mg·kg-1 and 0.183 mg·kg-1, respectively, which exhibited heavier accumulation in the study area. The Nemerow index indicated that there were 52.38% of croplands indicating slight contamination. ② The affinity propagation algorithm identified three potential sources with a similar impact extent for As, which were situated in the typical cultivated area. Both of the two identified potential sources for Pb were situated in close proximity to Fanjiatun Town. The diffusion patterns for Hg and Cd were complex, particularly for the latter, of which the potential sources were scattered in multiple places. ③ The spatial lag model indicated that the distributions of As and Cd were mainly controlled by the intensive agriculture in peri-urban areas, among which As was related to the application of herbicide and Cd was related to the distribution of protected agriculture. Pb was mainly influenced by urbanization and industrialization, whereas Hg was found to be associated with the migration conditions of the soil. However, the regulating function provided by either croplands or their nearby environment did not play an important role in determining the diffusion patterns of heavy metals. The present study enriches the theory and methods for the spatial analysis of cropland heavy metal contamination and is significant for controlling contamination from the source in peri-urban croplands in the black soil region.

Iodine Molecules within Triethylenediamine-Based Metal-Organic Frameworks for Hydrolysis/Alkylation Tandem Reactions.

The integration of radionuclide iodine molecules in metal-organic frameworks (MOFs) for organic synthesis is attracting considerable research attention due to their specific catalytic performance. However, understanding the comprehensive catalytic behaviors of different types of molecular iodine encapsulated in MOFs for a sequential organic transformation is a great challenge. To address this issue, we have designed two triethylenediamine-functionalized MOFs assembled from 1,3,5-tricarboxyphenyl-2-(triethylenediaminemethyl)benzene-linker and {Cd(COO)3N} or {Cu4(u3-OH)2(COO)6N} clusters. Both MOFs show good stability and adsorption of I2 in the solution and vapor phases. Catalysts obtained after treatment with ethyl acetate present efficient catalytic activity in hydrolysis/alkylation tandem reactions in water. The mechanistic investigations disclose a sequential catalytic process comprising a "hidden" Brønsted acid catalytic hydrolysis of acetals to aldehydes followed by the I2-bonding Lewis acid catalytic alkylation of aldehydes to 3,3'-disubstituted 1H-indoles.

Cystathionine-γ-lyase attenuates inflammatory response and pain of osteoarthritis.

The chronic articular disease osteoarthritis (OA) is characterized by osteophyte generation, subchondral bone remodeling, and cartilage deterioration. Low levels of H2S catalyzed by cystathionine-γ-lyase (CSE) encoded by Cthhas neuroprotective, cardioprotective, anti-apoptotic, and anti-inflammatory effects thus, Cth is being developed as a potential therapy for the management of the pathogenesis and symptoms of osteoarthritis. Single-cell RNA sequencing (scRNA-seq) and immunohistochemistry of human cartilage revealed that the expression of CTH was decreased in OA patients. We found that Cthoverexpression decrease IL-1ß-induced overactivation of the NF-κB signaling pathway. In vivo, Cthoverexpression relieved pain response and cartilage damage in the anterior cruciate ligament transection (ACLT) rat model. In vitro, CSE alleviated chondrocytes catabolism, inflammation, apoptosis, and senescence, and suppressed the NF-κB pathway. We postulate that CSE has therapeutic effects in suppressing inflammation and degeneration in OA and should be further investigated clinically.

Light-driven redox deracemization of indolines and tetrahydroquinolines using a photocatalyst coupled with chiral phosphoric acid.

The integration of oxidation and enantioselective reduction enables a redox deracemization to directly access enantioenriched products from their corresponding racemates. However, the solution of the kinetically microscopic reversibility of substrates used in this oxidation/reduction unidirectional event is a great challenge. To address this issue, we have developed a light-driven strategy to enable an efficient redox deracemization of cyclamines. The method combines a photocatalyst and a chiral phosphoric acid in a toluene/aqueous cyclodextrin emulsion biphasic co-solvent system to drive the cascade out-of-equilibrium. Systemic optimizations achieve a feasible oxidation/reduction cascade sequence, and mechanistic investigations demonstrate a unidirectional process. This single-operation cascade route, which involves initial photocatalyzed oxidation of achiral cyclamines to cyclimines and subsequent chiral phosphoric acid-catalyzed enantioselective reduction of cyclimines to chiral cyclamines, is suitable for constructing optically pure indolines and tetrahydroquinolines.

Size-fractionated N2 fixation off the Changjiang Estuary during summer.

Recent evidence has shown active N2 fixation in coastal eutrophic waters, yet the rate and controlling factors remain poorly understood, particularly in large estuaries. The Changjiang Estuary (CE) and adjacent shelf are characterized by fresh, nitrogen-replete Changjiang Diluted Water (CDW) and saline, nitrogen-depletion intruded Kuroshio water (Taiwan Warm Current and nearshore Kuroshio Branch Current), where N2 fixation may be contributed by different groups (i.e., Trichodesmium and heterotrophic diazotrophs). Here, for the first time, we provide direct measurement of size-fractionated N2 fixation rates (NFRs) off the CE during summer 2014 using the 15N2 bubble tracer method. The results demonstrated considerable spatial variations (southern > northern; offshore > inshore) in surface and depth-integrated NFRs, averaging 0.83 nmol N L-1 d-1 and 24.3 µmol N m-2 d-1, respectively. The highest bulk NFR (99.9 µmol N m-2 d-1; mostly contributed by >10 µm fraction) occurred in the southeastern East China Sea, where suffered from strong intrusion of the Kuroshio water characterized by low N/P ratio (<10) and abundant Trichodesmium (up to 10.23 × 106 trichomes m-2). However, low NFR (mostly contributed by <10 µm fraction) was detected in the CE controlled by the CDW, where NOx concentration (up to 80 µmol L-1) and N/P ratio (>100) were high and Trichodesmium abundance was low. The >10 µm fraction accounted for 60% of depth-integrated bulk NFR over the CE and adjacent shelf. We speculated that the present NFR of >10 µm fraction was mostly supported by Trichodesmium. Spearman rank correlation indicated that the NFR was significantly positively correlated with Trichodesmium abundance, salinity, temperature and Secchi depth, but was negatively with turbidity, N/P ratio, NOx, and chlorophyll a concentration. Our study suggests that distribution and size structure of N2 fixation off the CE are largely regulated by water mass (intruded Kuroshio water and CDW) movement and associated diazotrophs (particularly Trichodesmium) and nutrient conditions.

Vertical variation of bacterial production and potential role in oxygen loss in the southern Bay of Bengal.

Marine environments wherein long-term microbial oxygen consumption exceeds oxygen replenishment can be associated with oxygen minimum zones (OMZ). The Bay of Bengal OMZ (BOB-OMZ) is one of the most intense OMZs globally. To assess the contribution of bacterial oxygen consumption to oxygen loss in BOB-OMZ, we measured bacterial production (BP), temperature, salinity, and dissolved oxygen (DO) in the whole water column. We then compared the estimated bacterial oxygen demand (BOD) with diapycnal oxygen supply (DOS) at depths of 50-200 m in the southern BOB in January 2020. The average BP was 3.53 ± 3.15 µmol C m-3 h-1 in the upper 200 m of four stations, which was lower than those reported in other tropical waters. The vertical distribution of BP differed between the open ocean and nearshore areas. In the open ocean, temperature and DO were the most important predictors for BP in the whole water column. In the nearshore areas, when DO increased sharply from the suboxic state, extremely high BP occurred at 200 m. The average estimated BOD/DOS could reach up to 153% at depths of 50-200 m, indicating advection and anticyclonic eddies probably are important DO replenishment pathways in the BOB.

Synthesis and characterization of UPPE-PLGA-rhBMP2 scaffolds for bone regeneration.

A novel unsaturated polyphosphoester (UPPE) was devised in our previous research, which is a kind of promising scaffold for improving bone regeneration. However, the polymerization process of UPPE scaffolds was unfavorable, which may adversely affect the bioactivity of osteoinductive molecules added if necessary, such as recombinant human bone morphogenetic protein-2 (rhBMP2). The purpose of this study was to build a kind of optimal scaffold named UPPE-PLGA-rhBMP2 (UPB) and to investigate the bioactivity of rhBMP2 in this scaffold. Furthermore, the cytotoxicity and biocompatibility of UPB scaffold was assessed in vitro. A W1/O/W2 method was used to fabricate PLGA-rhBMP2 microspheres, and then the microspheres were added to UPPE for synthesizing UPB scaffold. The morphological characters of PLGA-rhBMP2 microspheres and UPB scaffolds were observed under the scanning electron microscopy and laser scanning confocal microscopy. The cumulative release of UPB scaffolds was detected by using ELISA. The cytotoxicity and biocompatibility of UPB scaffolds were evaluated through examining the adsorption and apoptosis of bone marrow stromal cells (bMSCs) seeded on the surface of UPB scaffolds. The bioactivity of rhBMP2 in UPB scaffolds was assessed through measuring the alkaline phosphates (ALP) activity in bMSCs seeded. The results showed that UPB scaffolds sequentially exhibited burst and sustained release of rhBMP2. The cytotoxicity was greatly reduced when the scaffolds were immersed in buffer solution for 2 h. bMSCs attached and grew on the surface of soaked UPB scaffolds, exerting well biocompatibility. The ALP activity of bMSCs seeded was significantly enhanced, indicating that the bioactivity of rhBMP2 remained and still took effect after the unfavorable polymerization process of scaffolds. It was concluded that UPB scaffolds have low cytotoxicity, good biocompatibility and preserve bioactivity of rhBMP2. UPB scaffolds are promising in improving bone regeneration.