Mycobacterial DnaQ is an Alternative Proofreader Ensuring DNA Replication Fidelity.

Remove of mis-incorporated nucleotides ensures replicative fidelity. Although the ε-exonuclease DnaQ is a well-established proofreader in the model organism Escherichia coli, proofreading in mycobacteria relies on the polymerase and histidinol phosphatase (PHP) domain of replicative polymerase despite the presence of an alternative DnaQ homolog. Here, we show that depletion of DnaQ in Mycolicibacterium smegmatis results in increased mutation rate, leading to AT-biased mutagenesis and elevated insertions/deletions in homopolymer tract. We demonstrated that mycobacterial DnaQ binds to the b-clamp and functions synergistically with the PHP domain to correct replication errors. Further, we found that the mycobacterial DnaQ sustains replicative fidelity upon chromosome topological stress. Intriguingly, we showed that a naturally evolved DnaQ variant prevalent in clinical Mycobacterium tuberculosis isolates enables hypermutability and is associated with extensive drug resistance. These results collectively establish that the alternative DnaQ functions in proofreading, and thus reveal that mycobacteria deploy two proofreaders to maintain replicative fidelity.

Synergistic value of fractional flow reserve and low­density non­calcified plaque based on coronary computed tomography angiography for the identification of lesion­specific ischemia.

Increasing evidence has suggested that plaque characteristics are closely associated with ischemia, and coronary computed tomography (CT) angiography-derived fractional flow reserve (FFRCT) based on deep machine learning algorithms has also been used to identify lesion-specific ischemia. Therefore, the aim of the present study was to explore the predictive ability of plaque characteristics in combination with deep learning-based FFRCT for lesion-specific ischemia. To meet this end, invasive FFR was used as a reference standard, with the joint aims of the early prediction of ischemic lesions and guiding clinical treatment. In the present study, the plaque characteristics, including non-calcified plaque (NCP), low-density NCP (LD-NCP), plaque length, total plaque volume (TPV), remodeling index, calcified plaque, fibrous plaque and plaque burden, were obtained using a semi-automated program. The FFRCT values were derived based on a deep machine learning algorithm. On the basis of the data obtained, differences among the values between the atopic ischemia and the non-significant lesions groups were analyzed to further determine the predictive value of independent predictors for atopic ischemia. Of the plaque features, FFRCT, LD-NCP, NCP, TPV and plaque length differed significantly when comparing between the lesion-specific ischemia and no hemodynamic abnormality groups, and LD-NCP and FFRCT were both independent predictors for ischemia. Additionally, FFRCT combined with LD-NCP showed a greater ability at discriminating ischemia compared with FFRCT or LD-NCP alone. Taken together, the findings of the present study suggest that the combination of FFRCT and LD-NCP has a synergistic effect in terms of predicting ischemia, thereby facilitating the identification of specific ischemia in patients with coronary artery disease.

[Values of Apparent Diffusion Coefficient and Fractional Anisotropy in the Diagnosis of Brucella Spondylitis].

Objective To compare the differences in apparent diffusion coefficient (ADC) and fractional anisotropy (FA) between brucella spondylitis (BS) groups at different stages before treatment and the normal control group and to evaluate the change trend of ADC value and FA value at different time points before and after treatment. Methods Totally 53 patients suspected of BS by conventional magnetic resonance imaging (MRI) and later confirmed as BS patients by serological tests were enrolled in this study. These patients underwent conventional MRI and diffusion tensor imaging scans,and the ADC value and FA value were measured. Independent sample t test was used to compare the ADC value and FA value between the BS group and the control group,the ADC value and FA value between the BS group at each stage. Repeated measurement ANOV was used to compare the ADC values and FA values at different time points before and after treatment. Results FA imaging showed that the color code of BS was different from that of the normal control group,and the color code of FA imaging showed increased singal. The ADC values of BS in the acute,subacute,and chronic stages [(1.45±0.02)×10 -3 mm 2/s,(1.35±0.03)×10 -3 mm 2/s,(1.26±0.05)×10 -3 mm 2/s,respectively] were significantly higher than those in the control group [(1.06±0.09) ×10 -3 mm 2/s](t=2.538,P=0.009;t=1.998,P=0.032;t=1.575,P=0.004),and the FA value (0.55±0.02,0.65±0.03,0.71±0.04,respectively) were significantly lower than those of the control group (0.78±0.02) (t=2.440,P=0.012; t=1.847,P=0.041;t=2.102,P=0.003). Repeated measurement analysis showed that there were statistically significant differences in ADC values and FA values at different time points before and after treatment in the acute,subacute,and chronic stages (ADC:F=12.100,P<0.001;F=8.439,P=0.005;F=9.704,P=0.004,respectively;FA:F=7.080,P=0.002;F=6.607;P=0.003;F=8.868,P=0.001,respectively). The ADC values at different time points after treatment were significantly lower than those before treatment or at a previous time point after treatment (F=332.14,P<0.001),and the FA values were significantly higher than those before treatment or at a previous time point after treatment (F=134.26,P<0.001). Conclusions FA color code can intuitively display differences in BS and normal vertebral bodies and show change of color code before and after treatment. Also,the ADC values and FA values can quantitatively reveal differences between BS and normal vertebral body in different time points and quantify BS vertebral lesion changes before and after treatment. In particular,in BS patients who are recovering from treatment,it can quantify microscopic edema. Therefore,diffusion tensor imaging may be useful objective indicator in evaluating the effectiveness of a specific treatment for BS.

Antimalarial Eudesmane Sesquiterpenoids from Dobinea delavayi.

Eleven new angeloylated eudesmane sesquiterpenoids, dobinins D-N (2, 3, 5, 6, 8, 9, and 11-15), and four known compounds (1, 4, 7, and 10) were isolated from the roots of Dobinea delavayi. A new oxidation product (8a) was also obtained from dobinin H (8). Their structures were elucidated by spectroscopic data and single-crystal X-ray diffraction analyses. Dobinins K-N (12-15) are the first examples of rearrangement noreudesmane analogue sesquiterpenoids with a unique 6/5-fused carbon skeleton. A putative biosynthetic pathway of compounds 12-15 is proposed. Compound 12 exhibited significant antimalarial activity superior to artemisinin with the inhibition ratio of 59.1%, and compounds 3, 5, and 15 exhibited moderate antimalarial activities against Plasmodium yoelii BY265RFP with inhibition ratios ranging from 14.5% to 18.5% at a dose of 30 mg/kg/day. In addition, the apoptosis of P. yoelii BY265RFP by the depolarization of mitochondrial membrane potential with striking ROS production, after parasitized erythrocyte lysis mediated by cytokines IL-12 and IFN-γ, may be a possible mechanism of antimalarial action of compound 12 against P. yoelii BY265RFP.

A New Antimalarial Noreudesmane Sesquiterpenoid from Dobinea delavayi.

One previously undescribed angeloylated noreudesmane sesquiterpenoid, dobinin O (1), along with four known eudesmane sesquiterpenoids (2-5) were isolated from the peeled roots of Dobinea delavayi. Their structures were elucidated by extensive spectroscopic data analyses. In addition, compound 1 exhibited moderate antimalarial activity against Plasmodium yoelii BY265RFP with the inhibition ratio of 17.8 ± 13.3% at the dose of 30 mg/kg/day.

[Diffusion Tensor Imaging in Early Diagnosis and Prognostic Prediction of Intervertebral Disc Change in Patients with Brucella Spondylitis].

Objective To explore the value of fractional anisotropy(FA) and apparent diffusion coefficient(ADC) in the early diagnosis of intervertebral disc change in patients with Brucella spondylitis(BS) and in the assessment of BS disc changes after treatment and to further investigate the imaging features of BS in its acute,subacute,and chronic stages. Methods Totally 60 serologically or pathologically confirmed BS patients who were treated in the First Hospital Affiliated to Hebei North University(n=20) or ZhangJiakou Infectious Diseases Hospital(n=40) were enrolled. BS patients were scanned by CT,magnetic resonance imaging,and diffusion tensor imaging,and the FA and ADC values of the disc were measured using the DTI Fiber Trak package. The FA and ADC values were compared in each period and after treatment. Results The ADC value significantly increased and the FA value significantly decreased in different stages(P<0.01). Six months after treatment,the ADC value was significantly lower than the pre-treatment,and the FA value was significantly increased(P<0.01). The ADC value 12 months after treatment for patients in acute or subacute stage and the FA value 12 months after treatment for patients in all stages were significantly different from those in the 6th month after treatment(P<0.01),and the only exception was that the ADC value in the chronic stage was not significantly different between 12th and 6th month after treatment(P=0.089).Conclusion FA and ADC values are more sensitive than conventional MRI sequences in the diagnosis of BS intervertebral disc change and therefore can be used for the early diagnosis and prognostic prediction.