Streptomycetes are Gram-positive bacteria of Actinomycetales. These organisms can produce many economically important secondary metabolites. With the development of molecular biology, gene sequencing technology and synthetic biology, people gained a better understanding of the Streptomyces family. The means to transform genome on the molecular level is also increasing. By simplifying the Streptomyces genome rationally and efficiently, it will improve the yield and quality of the metabolites as well as reduce the consumption of the substrates. Markerless knockout is an important way to carry out genetic modification. Here we describe novel genome modification techniques developed for Streptomyces in recent years with focus on the markerless knockout technologies.
Chromosomes, Bacterial ; genetics ; Gene Knockout Techniques ; methods ; Genes, Bacterial ; genetics ; Streptomyces ; genetics

Objective To assess the toxicity risks of diphenylchlorarsine (DA) to environments, human beings and livestock. Methods Totally 120 mice were randomly divided into 6 groups and given DA by gastric gavage at the doses of 32, 30, 28, 26, 24, 22 mg/kg respectively for LD_(50) of DA in mice. The toxicity of DA in rat skin were evaluated by smearing 50 ?l DA at the concentrations of 140, 70, 35, 17.5, and 8.8 mg/ml to an area of 4 cm2, and that of eyes exposure was carried out by dropping 10 ?l DA of 140.7, 70, 7, 0.7 mg/ml in rat eyes. The counterpart skin area and eyes served as control. Results LD_(50) of DA in mice was 28.07 mg/kg, the estimated doses for no-observed-adverse-effect levels (NOELs) were 8.8 mg/ml (0.44 mg) to the skin and 0.7 mg/ml (0.014 mg) to the eyes respectively. Conclusion DA can induce the injuries on the liver, kidneys, esophagus and stomach. High concentration of DA can cause inflammation of the skin and lens opacification, even blind.

Objective To investigate the value of three-dimensional speckle tracking imaging(3D-STI) in assessment of left ventricular regional systolic function in acute myocardial infarction model of dogs.Methods Left anterior descending (LAD) coronary artery was ligated in 24 adult beagle dogs.Longitudinal strain(LS) of every left ventricular segment before ligation and 180 min after ligation,and the time for acquisition and analysis were obtained using two-dimensional speckle tracking imaging (2D-STI) and 3D-STI.After the experiment,left ventricular myocardium were determined by TTC staining and divided into two groups:infarcted myocardial segments and non-infarcted myocardial segments.Results Experimental model of acute myocardial infarction was established successfully in 20 dogs.After ligation,both LS of 2D-STI and 3D-STI in infarcted myocardial segments were significantly lower (P ＜ 0.01).The time for acquisition and analysis of the images by 3D-STI were significantly shorter than that by 2D-STI (P ＜0.01).The area under the ROC curve of 3D-STI was larger than that of 2D-STI.A cut-off value of-12.56％ for LS of the 3D-STI had 77.9％ sensitivity and 88.2％ specificity in predicting acute myocardial infarction.Conclusions 3D-STI is a convenient,accurate method for evaluating left ventricular regional systolic function.

ObjectiveTo evaluate the effect and safety of different thrombolytic therapies for acute cerebral infarction due to occlusion of middle cerebral artery(MCA).MethodsOne hundred and thirty-two cases of acute cerebral infarction in territory of MCA were randomly divided into 3 groups,all of which were treated with alteplase.Group A (48 cases) was treated by intra-venous therapy with alteplase,group B (43 cases) was treated by infusing alteplase at the site of the internal carotid artery,and group C(41 cases) was treated by infusing alteplase into the thrombus.The improvement of neurological function,complications and mortality rate were recorded and statistically compared,with analysis of variance for counting data of normal distribution,x2 test for quantitative data,and the mean difference was significant at the 0.05level.ResultsThe effective rates of group A,B and C at 2 h,24 h,2 w were 18.8％ (9/48),39.6％ ( 19/48),45.8％ (22/48) ;39.5％ (17/43),53.5％ (23/43),58.1％ (25/43) ;78.0％ (32/41),85.4％ (35/41 ),87.8％ (36/41)respectively.The effective rate of group C was obviously better than group A( x2 =12.809,9.979,9.289,P ＜ 0.01 ) and B (x2 =31.295,19.425,17.161,P ＜ 0.01 ) with statistical significance.The effective rate of group B was better than group A at 2 h after thrombolytic therapy with statistical significance (x2 =4.801,P ＜ 0.05 ).The effective rate of group A and B did not have significant difference at 24 h,2 w after therapy ( x2 =1.765,1.375,P ＞ 0.05 ).The hemorrhage rates of group A,B and C were 14.6％ (7/48),14.0％ (6/43),7.3％ (3/41 ),the mortality rates of group A,B and C were 6.2％ (3/48),4.6％ (2/43),2.4％ (1/41),and there was no significant difference among the 3 groups ( x2 =1.328,0.786,P ＞ 0.05 ).ConclusionIt is suggested that the thrombus-imbeded thrombolytic therapy is a better way in treating acute cerebral infraction due to occlusion of MCA for its rapid and better therapeutic effect.

In this study, we found that when Pseudomonas mendocina NK-01 accumulated intracellular carbon reserve, medium chain length poly (3-hydroxyalkanoates), it also synthesized extracellular saccharides, alginate oligosaccharides. The high carbon nitrogen ratio of culture medium facilitated alginate oligosaccharides production. We analyzed the structure of alginate oligosaccharide by Ultraviolet-Visible Spectrophotometry, Fourier Transform Infrared Spectroscopy, 1H and 13C of Nuclear Magnetic Resonance, and found that it was compounded in line from beta-D-mannuronic acids and alpha-L-gluronic acids via beta-(1-->4)/ alpha-(1-->4) bonds, which acetylated partly on the 2- and/or 3-hydroxy. In addition, we determined the weight-average molecular weight of alginate oligosaccharides by gel permeation chromatography to be 2054.
Alginates ; chemistry ; Glucuronic Acid ; biosynthesis ; chemistry ; genetics ; Hexuronic Acids ; chemistry ; Molecular Weight ; Oligosaccharides ; biosynthesis ; chemistry ; genetics ; Pseudomonas mendocina ; metabolism

Objective:To explore surgical treatment for persistent pupillary membrane (PPM) and its effect.Methods:The medical records and postoperative follow-up data for 12 consecutive patients (16 eyes),who were submitted to PPM resection in Xiangya Hospital,Central South University from March 2011 to August 2016,were retrospectively reviewed.Results:Among 12 consecutive patients (16 eyes),8 patients (12 eyes) with PPM and clear lens were submitted to simply PPM resection,and 4 patients (4 eyes) with PPM and cataract were submitted to PPM resection combined with cataract surgery.In the patients who received the combined operation,phacoaspiration with or without intraocular lens implantation was performed in 3 eyes or in 1 eye.In the early stage after surgery,1 eye was complicated with a transient high intraocular pressure.In the patients who were submitted to PPM resection,the final follow-up visual acuity in 7 patients (11 eyes) were improved except 1 patient (1 eye).After the PPM resection combined with cataract surgery,the follow-up visual acuity was improved in 2 patients (2 eyes) but not in the other 2 patients (2 eyes).Conclusion:The surgical treatment is effect on congenital pupil residual membrane.Serious membrane pupil residual membrane should be surgically treated at early stage,and amblyopia treatment after the surgery is important.

To study the change of the dominant eye in the age-related cataract patients before and after surgery, to analyze the correlation between the orientation of the dominant eye and the visual quality, and to observe whether the patients with the change in dominant eye were converted to dizziness.
 Methods: A total of 44 patients, with age-related cataract between 60 and 80 years old were enrolled. Group A: the non-dominant (secondary) eye served as the surgical eye (n=35); Group B: the dominant eye served as the surgical eye (n=9); Group C: the operation was performed on the contralateral eye after a month (n=28). Measurement of the dominant eye was performed before operation, 1 week after operation and 1 month after the operation. The changes in the uncorrected distance visual acuity (UCDVA), contrast sensitivity (CS), best corrected visual acuity (BCVA) and spherical equivalent (SE) between the dominant and non-dominant eye were compared.
 Results: The UCDVA, CS, BCVA and SE were significantly improved at 1 day after the operation. There was significant difference between the 2 groups (P<0.05). Preoperative: in group A, the UCDVA, CS, BCVA of ocular dominance were better than the non-dominant eye with significant difference (P<0.05), while there was no significant difference between the SE (P>0.05); in group B, the UCDVA, CS, BCVA in the dominant eye were better than the non-dominant eye's, but the difference was not statistically significant (P>0.05). After operation: the UCDVA, CS and BCVA in the dominant eye in group A and group B were higher than those of the non-dominant eye with statistical difference (P<0.05), but there was no statistical difference between SE (P>0.05). The dominant eye's transformation occurred in group A when the non-dominant eye's postoperative visual quality improved over the leading eye. The transformation rate was 60% in 1 week, and the conversion rate was 80% in 1 month. In group C, the dominant eye reduction rate was 100%, and the visual quality was not significant difference between the two eyes (P>0.05). After the operation, the patients with the dominant eye's transformation felt discomfort, which could be relieved within 1 week.
 Conclusion: The location of the dominant eye was correlated with uncorrected visual acuity, contrast sensitivity, and the best corrected visual acuity. The dominant eye's transformation occurred when the non-dominant eye's postoperative visual quality improved over the leading eye after the surgery. If the contralateral eye's surgery was performed in a short term, the dominant eye can be returned to the initial state.
Aged ; Aged, 80 and over ; Cataract ; therapy ; Cataract Extraction ; Humans ; Middle Aged ; Phacoemulsification ; Treatment Outcome ; Visual Acuity

OBJECTIVETo investigate the effects of maxillary protraction combined with repetitive rapid palatal expansions and constrictions (RPE/C) vs. rapid palatal expansion (RPE) alone using cone-beam computed tomography (CBCT).

METHODSTwenty four subjects with maxillary retrusion were recruited and block randomized into either the control group (n = 12) or the RPE/C (n = 12) group.

CONTROL GROUPfacemask protraction after RPE. RPE/C group: facemask protraction after RPE/C. 3D reconstruction, landmarks identifying, superimposition and cephalometric analysis were performed to compare the pre-treatment and post- treatment CBCT images.

RESULTSOne subject in the RPE/C group was lost to follow up during the treatment. Maxilla moved forward [(2.5±1.0) mm] after maxillary protraction with RPE/C, which was significantly greater than that in the control group [(1.6±0.8) mm] (P < 0.05). The distance of basion to subspinale (Ba-A) increased [(3.1±1.0) mm] in the RPE/C group, which was significantly greater than that in the control group [(2.2 ± 0.9) mm] (P < 0.05). The amount of forward movement of upper first molars was significantly greater in the RPE/C group (P < 0.05).

CONCLUSIONSMaxillary protraction with RPE/C might positively affect the forward movement of maxilla compared with the RPE alone protocol with the early treatment of maxillary retrusion patients.

Cephalometry ; Cone-Beam Computed Tomography ; Constriction ; Extraoral Traction Appliances ; Humans ; Malocclusion, Angle Class III ; therapy ; Maxilla ; Molar ; Palatal Expansion Technique

Objective:To evaluate the effect of the improved team-based learning (TBL) teaching method in the undergraduate probation course of ophthalmology based on the goal of cultivating excellent doctors.Methods:The undergraduates of clinical medicine were randomly divided into experimental group and control group. The control group ( n=50) was given conventional ophthalmology probation teaching, while the experimental group ( n=50) was given ophthalmology probation teaching of improved TBL teaching method. The theoretical examination performance and skill assessment results of students in the two groups were compared, and the subjective evaluation of the students on the teaching was also compared. SPSS 23.0 was used to conduct t-test and Wilcoxon's rank sum test. Results:The theoretical examination performance of experimental group (29.68±4.52) was better than that of control group (27.84±4.33), with significant differences ( P<0.05); the skill assessment results of experimental group (32.88±5.05) were also better than those of the control group (30.88±6.99), with significant differences ( P<0.05); the subjective evaluation of teaching effect in each item of experimental group was better than that of control group ( P<0.05). Conclusion:The improved TBL teaching method can not only improve students' theoretical knowledge and experimental skills, but also improve students' self-study and teamwork ability, which will provide a feasible educational reform plan for achieving the goal of cultivating excellent doctors.