Modular catalytic activity of nonribosomal peptide synthetases depends on the dynamic interaction between adenylation and condensation domains

Nonribosomal peptide synthetases (NRPSs) are large multidomain enzymes for the synthesis of a variety of bioactive peptides in a modular and pipelined fashion. Here, we investigated how the condensation (C) domain and the adenylation (A) domain cooperate with each other for the efficient catalytic activity in microcystin NRPS modules. We solved two crystal structures of the microcystin NRPS modules, representing two different conformations in the NRPS catalytic cycle. Our data reveal that the dynamic interaction between the C and the A domains in these modules is mediated by the conserved "RXGR" motif, and this interaction is important for the adenylation activity. Furthermore, the "RXGR" motif-mediated dynamic interaction and its functional regulation are prevalent in different NRPSs modules possessing both the A and the C domains. This study provides new insights into the catalytic mechanism of NRPSs and their engineering strategy for synthetic peptides with different structures and properties.

[The cases of tracing the source of patients infected with Omicron variant of SARS-CoV-2 based on wastewater-based epidemiology in Shenzhen]

Wastewater-based epidemiology (WBE) is an emerging discipline, which has been applied to drug abuse tracking and infectious disease pathogen surveillance. During the COVID-19 epidemic, WBE has been applied to monitor the epidemic trend and SARS-CoV-2 variants etc. In order to detect hidden COVID-19 cases and prevent transmission in the community, wastewater surveillance system for monitoring SARS-CoV-2 RNA was developed in Shenzhen. The sewage sampling sites were set up in key places such as the port areas, urban villages and residential communities of Futian, Nanshan, Luohu and Yantian districts. From July 26 to November 30, 2022, a total of 369 sewage sampling sites were set up, covering 1.93 million people. Continuous sampling was carried out for 3 hours in the peak period of water use every day. Sewage virus enrichment and SARS-CoV-2 nucleic acid detection were carried out by polyethylene glycol precipitation method and RT-qPCR, and a positive water sample disposal process was molded. This article aims to introduce the case of source tracing of COVID-19 infected patients based on urban sewage in Shenzhen. The sewage monitoring of Honghu water treatment plant in Luohu District played an early warning role, and the source of infection was traced. In the disposal of positive water samples in Futian South Road, Futian District, the important experience of monitoring point layout was obtained. In the sewage monitoring of Nanshan village, Nanshan District, the existence of occult infection was revealed. Sharing the experience of tracing the source of COVID-19 patients to avoid the spread of COVID-19 in the community based on wastewater surveillance of SARS-CoV-2 RNA in Shenzhen, and summarizing the advantages and application prospects of sewage surveillance can provide new ideas for monitoring emerging or re-emerging pathogens that are known to exhibit gastrointestinal excretion in the future.

A c-di-GMP binding effector controls cell size in a cyanobacterium

Cyclic-di-GMP (c-di-GMP) is a ubiquitous bacterial signaling molecule. It is also a critical player in the regulation of cell size and cell behaviors such as cell aggregation and phototaxis in cyanobacteria, which constitute an important group of prokaryotes for their roles in the ecology and evolution of the Earth. However, c-di-GMP receptors have never been revealed in cyanobacteria. Here, we report the identification of a c-di-GMP receptor, CdgR, from the filamentous cyanobacterium Anabaena PCC 7120. Crystal structural analysis and genetic studies demonstrate that CdgR binds c-di-GMP at the dimer interface and this binding is required for the control of cell size in a c-di-GMP-dependent manner. Different functions of CdgR, in ligand binding and signal transmission, could be separated genetically, allowing us to dissect its molecular signaling functions. The presence of the apo-form of CdgR triggers cell size reduction, consistent with the similar effects observed with a decrease of c-di-GMP levels in cells. Furthermore, we found that CdgR exerts its function by interacting with a global transcription factor DevH, and this interaction was inhibited by c-di-GMP. The lethal effect triggered by conditional depletion of DevH or by the production of several point-mutant proteins of CdgR in cells indicates that this signaling pathway plays critical functions in Anabaena. Our studies revealed a mechanism of c-di-GMP signaling in the control of cell size, an important and complex trait for bacteria. CdgR is highly conserved in cyanobacteria, which will greatly expand our understanding of the roles of c-di-GMP signaling in these organisms.

[Analysis of the risk factors for poor prognosis and recurrence in patients with anti-NMDAR encephalitis]

To investigate the risk factors of poor prognosis and recurrence in patients with anti-NMDAR encephalitis. A single center, observational cohort study was used to retrospectively analyze 44 patients with anti NMDAR encephalitis hospitalized in the Department of Neurology of Beijing Tong Ren Hospital from January 2014 to October 2020. The results showed that the interval from onset to immunotherapy in the poor prognosis group was significantly longer than that in the good prognosis group (t=2.045,P=0.047), and the course of disease in the poor prognosis group was significantly longer than that in the good prognosis group (t=4.127,P=0.000 2). The number of patients with clinical manifestations of dyskinesia was significantly increased (Fisher exact test: P=0.014). The patients with abnormal brain MRI in the poor prognosis group were significantly more than those in the good prognosis group (Fisher exact test: P=0.017), and the patients with slow wave>50% in the poor prognosis group were significantly more than those with slow wave <50% (Fisher exact test: P<0.001). Patients with the first onset of immunotherapy time <3 months, long course of disease, high intracranial pressure, and high cerebrospinal fluid protein are prone to relapse. Bivariate logistic regression analysis showed that patients with dyskinesia, abnormal brain MRI, and slow wave EEG more than 50% were risk factors for poor prognosis (OR values were 4.687, 4.978, and 24.500, respectively; P values were 0.018, 0.016, and 0.000, respectively). The time of first-line immunotherapy for the first onset<3 months was the risk factor for recurrence (OR 17.231, P=0.010). In conclusion, dyskinesia, abnormal brain MRI and slow wave of EEG more than 50% may be the risk factors for poor prognosis of patients. The duration of immunotherapy less than 3 months after the first onset might be the risk factor for recurrence.

[Exploration and practice of artificial intelligence assisted primary vision health management]

It has attracted much attention worldwide that the application of artificial intelligence (AI) in primary screening and clinical diagnosis and treatment of eye diseases. In recent years, this technology has also been widely used in various grass-roots eye disease management, effectively improving the current situation of weak eye disease diagnosis ability and shortage of human resources in primary medical institutions. At present, there is no reference standard or guideline for the management mode, implementation content and management method of vision health management based on this technology, which are in urgent need of standardization. The article described the work mode exploration of AI-assisted grass-roots visual health management in Shanghai and shared practical experience. The aim is to provide reference for other provinces in China to carry out relevant work.

[Study on the correlation between subgroup of blood lipid with degree of coronary artery stenosis in patients with coronary atherosclerotic heart disease]

Objective: To study the correlation between low-density lipoprotein particles (LDL-P) with other lipoprotein indexes. To explore the correlation between LDL-P and its subgroup particles(LDL1-P-LDL6-P) with the degree of coronary artery stenosis in patients with coronary atherosclerotic heart disease(CHD) combining with the result of coronary arteriography. To explore the value of lipoprotein subgroup granules in preventing the severity of coronary artery stenosis in CHD patients. Methods: Cross-sectional study. A total of 259 patients without lipid-lowering drugs for coronary angiography in the department of cardiology of TEDA International Cardiovascular Hospital during 3 months from August 2019 to December 2019 were collected, and 52 healthy subjects were recruited during the same period. The level of high sensitivity C-reactive protein (hs-CRP) and other biochemical indexes were detected by automatic biochemical analyzer. The level of LDL-P and other biochemical indexes were detected by nuclear magnetic resonance spectroscopy(NMRS). The relation between various biomarkers levels with coronary artery stenosis degree was analyzed. Analysis of variance and nonparametric tests were used to compare the differences of indexes among each group. Pearson correlation analysis was used to determine the correlation among the measured indexes. Logistic regression was used for multi-factor analysis, ROC curve was used to evaluate the diagnostic value of related indexes. Results: LDL-P was highly correlated with low-density lipoprotein cholesterol (LDL-C),apolipoprotein B (ApoB) and total cholesterol (TC) (r= 0.927, P<0.001; r=0.921, P<0.001; r=0.844, P<0.001). LDL-P, LDL4-P, LDL5-P and LDL6-P in patients with severe coronary stenosis were higher than those in patients with mild coronary stenosis(U=4 172.000, Z=4.256, P<0.001; t=2.573, P=0.011; U=3 995.000, Z=4.621, P<0.001;t=5.223, P<0.001), LDL-P and LDL6-P were higher than those of patients with moderate coronary stenosis (U=1 159.000, Z=2.294, P=0.022; t=2.075, P=0.041). High levels of hs-CRP, LDL5-P and LDL6-P were risk factors for the degree of coronary stenosis(OR=1.095, P=0.036;OR=1.015, P=0.046;OR=1.012, P=0.039). ROC analysis showed that the AUC of LDL-P, LDL5-P and LDL6-P on coronary stenosis was 0.67, 0.68 and 0.69, respectively. Hs-CRP combined with LDL5-P and LDL6-P had the greatest effect on the degree of coronary stenosis (AUC= 0.70). Conclusions: LDL-P is highly correlated with LDL-C. The levels of LDL-P and LDL6-P were significantly higher in patients with severe stenosis than in patients with mild and moderate stenosis. hs-CRP, LDL5-P and LDL6-P can be used as new risk factors for the degree of coronary stenosis and may be further used as risk predictors. The combined detection of hs-CRP, LDL5-P and LDL6-P is helpful for the diagnosis of the severity of coronary stenosis, and may further become risk predictors.

[Biomechanical study of anterior occipital condyle screw plate system]

Objective: To analyze the feasibility of anterior occipitocervical fusion biomechanical characteristic of craniovertebral reconstruction by anterior occipital condyle screw plate system. Methods: Six cervical vertebra specimens including 4 males and 2 females were enrolled, whose mean age of death was (49.3±7.5) years. The normal models were established by soft tissue dissection, and the instability models were established by destroy bone and ligament structure including, anterior arch of the atlas, part of the lateral mass of the atlas, the odontoid process, the odontoid apical ligament, the pterygoid ligament, the transverse ligament of the atlas the joint capsule. The clivus screw fixation models were established by anterior clivus screw fixation, and then those models were performed by anterior occipital condyle screw fixation. All four groups were loaded with a 1.5 N·m continuous pure force in flexion-extension, lateral bending, and axial rotation. Then measured the range of motion of specimen C₀-C₁ and C₀-C₂. And the pull-out force test was conducted to compare the effects of unicortical and bicortical fixation on the pull-out force of screws. Results: In the C₀-C₁ segment, the range of motion in flexion-extension (forward and posterior), lateral bending and axial rotation in the clivus group was 6.46°±0.85°, 5.14°±0.76°, 2.73°±0.36°, 1.12°±0.41°, respectively; and it was 5.92°±0.90°, 4.16°±1.06°, 2.86°±0.50°, 1.05°±0.27°, respectively in the occipital condyle group. As for C₀-C₂ segment, the range of motion in the clivus group was 9.55°±1.99°, 10.46°±2.03°, 6.90°±1.29°, 13.51°±1.37°, respectively; and it was 8.14°±1.38°, 9.53°±1.55°, 4.75°±1.06°, 7.90°±1.68°, respectively, in the occipital condyle group. The ranges of motion in the occipital condyle group were significantly lower than clivus group (all P<0.05). The maximum pull out force by bicortical fixation was significantly better than unicortical fixation ((439±33) N vs (408±28) N, P<0.05). Conclusion: The anterior occipital condyle screw plate system provides better stability especially in anti-bending and anti-rotation than the anterior clival screw fixation.

[Digital and anatomical study of posterior atlantooccipital joint-occipital condyle-clivus screw technique]

Objective: To investigate the screw placement parameters, feasibility and safety of posterior atlantooccipital joint-occipital condyle-clivus screw technique in Chinese people. Methods: Upper cervical spine CT images of 46 patients, including 24 males and 22 females, were collected with random number table from June 2019 to May 2020 in Ningbo No.6 Hospital. The patients aged 20-55 years, with a mean age of (39±9) years. Total of 92 sides of upper cervical spine models were obtained by Mimics 19.0 digital three-dimensional reconstruction, and screw placement was conducted simulately. The midpoint of transition zone between the posterior arch of atlas and the inferior articular process of lateral mass was selected as the screw entry point. The diameter and length of screws was 3.5 mm and 50 mm, respectively. Detailed morphometric measurements of the 92 atlantooccipital joint-occipital condyle-clivus screws were conducted. The distance between the screw and its surrounding important structures, screw inside and upper tilting angles, the length of screw trajectory in atlas and the length of screw trajectory on occipital side (occipital condyle-clivus) were all measured. Paired t test was performed on the parameters of left and right screw placement to confirm whether there was difference between the two sides. Results: In the 46 cases of upper cervical spine digital three-dimensional models, 92 posterior atlantooccipital joint-occipital condyle-clivus screws were implanted. All the screws were completely fixed in the clivus, without breaking through the upper sphenoid sinus, entering into the canalis spinalis and foramen magnum, and damaging the surrounding structures such as hypoglossal canal. The screw trajectory parameters between the left and right sides were slightly different, but there was no statistical differences between the two sides (P>0.05). The vertical distance between the screw entry point and the upper edge of atlas was (12.6±1.0) mm, the vertical distance between the screw entry point and the lower edge of atlas was (6.5±0.6) mm, the distance between the screw and the medial border of atlas vertebral artery foramen was (6.7±0.6) mm, the distance between the screw entry point and the medial wall of atlas was (6.6±0.7) mm, the distance between the screw outer margin and the hypoglossal canal was (5.5±0.6) mm, screw inside tilting angle was 21.2°±2.5°, screw upper tilting angle was 52.0°±3.4°, the length of screw trajectory in atlas was (12.1±0.9) mm, the length of screw trajectory on occipital side (occipital condyle-clivus) was (37.9±0.9) mm. Conclusion: The posterior atlantooccipital joint-occipital condyle-clivus screw technique can serve as a feasible and safe treatment for instability of the occipitocervical junction, which can be used as a new posterior occipitocervical fusion technique.

Abnormal methylation of spermatozoa induced by benzo(a)pyrene in rats

Epigenetic mutations caused by pollutants are possibly linked to many diseases. Benzo(a)pyrene (BaP) is one of the most representative air pollutants and has aroused wide concern because of its strong carcinogenicity. The reproductive toxicity induced by BaP has been identified, but little is known about the characteristics of the methylation changes induced by BaP. In this study, a methylated DNA immunoprecipitation sequencing method was used to detect the methylation of sperm DNA of rats exposed to BaP. Compared with the respective genes in normal rats, there were 3227 hypomethylated genes and 828 hypermethylated genes after BaP exposure. Gene ontology enrichment analysis reported that differentially methylated genes (DMGs) were enriched in the localization, single-multicellular organism process and plasma membrane. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the DMGs were significantly enriched in the Ras signalling pathway, Rap1 signalling pathway, pancreatic secretion and neuroactive ligand-receptor interaction. DisGeNET disease spectrum analysis showed that DMGs were associated with infertility and certain genetic diseases. Further research needs to be done to explore whether these abnormal methylation are transgenerational.

[The association of lipid profile and bleeding in patients with minor stroke or transient ischemic attack on antiplatelet therapy: subgroup analysis of CHANCE]

Objective: Abnormalities of lipid profile were considered as risk factors of hemorrhage after ischemic stroke. We aimed to determine the relationship between lipid levels and bleeding in minor stroke or transient ischemic attack (TIA) patients receiving antiplatelet therapy. Methods: Serum total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglyceride were tested in a subgroup of 3 044 consecutive patients from Clopidogrel in High-risk patients with Acute Non-disabling Cerebrovascular Events (CHANCE) trial. Patients were randomized to clopidogrel plus aspirin group or single aspirin group. The primary endpoint was any bleeding within 90 days. The secondary endpoint was severe bleeding according to the Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries (GUSTO) definition. Cox proportional hazards models were used to assess the associations of lipid levels and outcomes. Results: A total of 59 (1.9%) bleeding events occurred at 90 days. High-density lipoprotein cholesterol (adjusted HR=2.16; 95%CI 1.17-4.00, P=0.014) and age (adjusted HR=1.04; 95%CI 1.01-1.06, P=0.006) were significantly associated with any bleeding. High-density lipoprotein cholesterol was also associated with severe bleeding (adjusted HR=3.05; 95%CI 1.39-6.68, per 1 mmol/L increase). No correlations between outcomes and levels of total cholesterol, low-density lipoprotein cholesterol and triglyceride were found. There was no interaction of any lipid component level with randomized antiplatelet therapy. Conclusions: Elevated high-density lipoprotein cholesterol is independently associated with any bleeding and severe bleeding in the patients with acute minor stroke or high-risk TIA on antiplatelet therapy.

Blood flow velocity estimation from x-ray densitometric data: an efficient numerical scheme for the inverse advection problem

In previously published studies, blood flow velocity from x-ray biplane angiography was measured by solving an inverse advection problem, relating velocity to bolus densities summed across sections. Both spatial and temporal velocity variations were recovered through a computationally expensive parameter estimation algorithm. Here we prove the existence and uniqueness of the solution on three sub-domains of the plane defined by the axial position along the vessel and the time of the angiographic sequence. A fast direct scheme was designed in conjunction with a regularization step stemming from the volume flow conservation law applied on consecutive segments. Its accuracy and immunity towards noise were tested on both simulated and real densitometric data. The relative error between the estimated and expected velocities was less than 5% for more than 90% of the points of the spatiotemporal plane with simulated densities normalized to 1.0 and a Gaussian additive noise of standard deviation 0.01. For densities reconstructed from a biplane angiographic sequence, increase in velocity is used as a functional index for the stenosis ratio and to characterize the sharing of flow at bifurcation.

[The coherence analysis between neuronal discharge in the rostral ventrolateral medulla and the cardiovascular activity in rats]

To analyze the coherence between neuronal discharges (ND) in the rostral ventrolateral medulla (RVLM) and the cardiovascular activity, we observed the neuronal discharge in RVLM responding to electric stimulation of the defense area of the mid-brain. Fast Fourier transform (FFT) was performed to analyze the coherence between the signals of ND and blood pressure to determine if the ND were cardiac rhythmic. The coherence between ND variability (NDV) and heart rate variability (HRV) was also analyzed. The results showed: (1) majority of the neurons (67%) were excited responding to electric stimulation in the defense area of the mid-brain; (2) the electric activity of about 70% of the neurons were substantially inhibited by administration of phenylephrine; (3) 64% of the neurons were actively synchronous with cardiac cycle; and (4) significant coherence between NDV and HRV in HF component was shown in a half of the neurons (50%). The coherence analysis thus provides a new tool to investigate the regulation of the autonomic nervous system.

Convergence of midbrain, visceral and somatic inputs onto neurons in the nucleus paragigantocellularis lateralis in rats

Extracellular recordings were made in nucleus paragigantocellularis lateralis (PGL) of the rat in response to stimulation of the dorsal periaqueductoral gray matter (dPAG), ventrolateral periaqueductuctoral gray matter (vPAG), deep peroneal nerve (DPN), median nerve (MN) and great splanchnic nerve (GSPL). Stimulation of dPAG or MN evoked mainly excitatory responses while the responses to stimulation of vPAG were inhibitory. However, stimulation of GSPL or DPN produced both inhibitory and excitatory responses. These neurons were not only responsive to one stimulation site, but were likely responsive to any other stimulation sites. Eighty-nine percent of cells tested (73/82) received convergent inputs from two or more sites. Sixty percent (21/35) of the neurons were identified as cardiovascular units based on their barosensitivity and slow conduction velocities of the descending axons projecting into the spinal cord. This result provided new evidence for the integrative function of neurons in PGL under some circumstances.

GABA(A) receptors in the rostral ventrolateral medulla mediate the depressor response induced by stimulation of the greater splanchnic nerve afferent fibres in rats

Experiments have been carried out to investigate the chemical substrate in the rostral ventrolateral medulla (RVLM) underlying the depressor responses induced by activation of the greater splanchnic nerve (GSPL) afferent fibres of the rat. In anaesthetised rats with urethane and alpha-chloralose, microinjection of bicuculline, a GABA(A) receptor antagonist, into the RVLM, attenuated largely the depressor responses elicited by electrical stimulation of the GSPL afferent fibres, while strychnine or saline had no effect. In 18 RVLM neurons (including seven identified cardiovascular neurons), iontophoresis of bicuculline also significantly blocked the inhibition evoked by stimulation of the GSPL afferent inputs. We suggest that the depressor responses induced by stimulation of the GSPL afferent fibres involve a GABA(A)-receptor-mediated mechanism in the RVLM in rats.