Spiramycin (SP) belongs to the 16-member macrolide antibiotics. It contains three components,namely SP I, SP II and SP III, which differ structurally in the acylation moieties on the C3 of the lactone. The SP I component contains a hydroxyl group at C3. SP II, and SP III are formed by further acetylation or propionylation of the C3 of SP I, by the same 3-O-acyltransferase (3-O-AT) . The study focused on simplifying spiramycin components. Theoretically, disruption/deletion of the 3-O-AT gene will reduce/stop the acylation of SP I to SP II and SP III. In this study, degenerated primers were designed according to the conserved regions of 3-O-acyltransferase, MdmB and AcyA in the medicamycin and carbomycin producers of S. mycarofaciens and S. thermotolerans, respectively, and an 878bp DNA fragment was amplified from the spiramycin-producer of S. spiramyceticus F21. Blast analysis of the 878bp DNA fragment suggested that it encoded the 3-O-acyltransferase (3-0-AT, sspA) gene for spiramycin biosynthesis. The flanking regions of this 878bp DNA fragment were then amplified by single-oligonucleotide-nested PCR, and a total of 4.3 kb DNA was obtained (3457nt among the 4.3kb fragment was sequenced, and deposited in GenBank DQ642742),covering the whole putative 3-O-acyltransferase gene, sspA. The sspA was then deleted from the S. spiramyceticus F21 genome by double cross-over homologous recombination, mediated by temperature-sensitive plasmid pKC1139. A comparison was done of the components of spiramycins produced by the sspA-deleted mutant strain with that of the parent strain by HPLC analysis, which showed that sspA-deleted mutant produced SP I (72%), SP II (18%), and SP III (9.6%), whereas parent strain produced SP I (7.8%), SP II (67%), and SP III (25%), respectively, demonstrating the role of ssp A in the acylation of SP I into SP II and SP III. The ssp A-deleted mutant strain obtained in this study may be used for the production of SP I, or may serve as a good starter for the construction of spiramycin derivatives.
Acyltransferases ; genetics ; Aminoglycosides ; biosynthesis ; Gene Deletion ; Genes, Bacterial ; genetics ; Genetic Engineering ; methods ; Streptomyces ; enzymology ; genetics

Microbial secondary metabolites are one of the major sources of anti-bacterial, anti-fungal, antitumor, anti-virus and immunosuppressive agents for clinical use. Present challenges in microbial pharmaceutical development are the discovery of novel secondary metabolites with significant biological activities, improving the fermentation titers of industrial microbial strains, and production of natural product drugs by re-establishing their biosynthetic pathways in suitable microbial hosts. Synthetic biology, which is developed from systematic biology and metabolic engineering, provides a significant driving force for microbial pharmaceutical development. The review describes the major applications of synthetic biology in novel microbial secondary metabolite discovery, improved production of known secondary metabolites and the production of some natural drugs in genetically modified or reconstructed model microorganisms.
Bacteria ; metabolism ; Biological Products ; metabolism ; Drug Discovery ; Fermentation ; Fungi ; metabolism ; Gene Transfer Techniques ; Metabolic Engineering ; Synthetic Biology

Chuangxinmycin (CM) from Actinoplanes tsinanensis was an antibiotic discovered by Chinese scientists about 40 years ago. It contains a new heterocyclic system of indole fused with dihydrothiopyran, whose biosynthetic mechanism remains unclear. CM is used as an oral medicine in the treatment of bacterial infections in China. The simple structure makes CM as an attractive candidate of structure modification for improvement of antibacterial activity. Recently, we analyzed the secondary metabolites of Actinoplanes tsinanensis CPCC 200056, a CM producing strain, as a natural CM analogue. We discovered the first natural CM analogue 3-demethylchuangxinmycin (DCM) as a new natural product. Compared to CM, DCM exhibited a much weaker activity in the inhibition of the bacterial strains tested. The finding provides valuable information for the structure-activity relationship in the biosynthesis of CM.
Anti-Bacterial Agents ; chemistry ; isolation & purification ; China ; Indoles ; chemistry ; isolation & purification ; Micromonosporaceae ; chemistry ; Structure-Activity Relationship

Chronic enteritis can produce an excess of reactive oxygen species resulting in cellular damage. Stanniocalcin-1(STC-1) reportedly possesses anti-oxidative activity, the aim of this study was to define more clearly the direct contribution of STC-1 to anti-oxidative stress in cattle. In this study, primary intestinal epithelial cells (IECs) were exposed to hydrogen peroxide (H2O2) for different time intervals to mimic chronic enteritis-induced cellular damage. Prior to treatment with 200 microM H2O2, the cells were transfected with a recombinant plasmid for 48 h to over-express STC-1. Acridine orange/ethidium bromide (AO/EB) double staining and trypan blue exclusion assays were then performed to measure cell viability and apoptosis of the cells, respectively. The expression of STC-1 and apoptosis-related proteins in the cells was monitored by real-time PCR and Western blotting. The results indicated that both STC-1 mRNA and protein expression levels positively correlated with the duration of H2O2 treatment. H2O2 damaged the bovine IECs in a time-dependent manner, and this effect was attenuated by STC-1 over-expression. Furthermore, over-expression of STC-1 up-regulated Bcl-2 protein expression and slightly down-regulated caspase-3 production in the damaged cells. Findings from this study suggested that STC-1 plays a protective role in intestinal cells through an antioxidant mechanism.
Animals ; Animals, Newborn ; Blotting, Western/veterinary ; Caspase 3/*genetics/metabolism ; Cattle ; Cattle Diseases/etiology/*genetics/metabolism ; Duodenum/metabolism ; Enteritis/etiology/genetics/metabolism/*veterinary ; Epithelial Cells/metabolism ; *Gene Expression Regulation ; Glycoproteins/*genetics/metabolism ; Hydrogen Peroxide/pharmacology ; Male ; Proto-Oncogene Proteins c-bcl-2/*genetics/metabolism ; RNA, Messenger/genetics/metabolism ; Real-Time Polymerase Chain Reaction/veterinary

Objective To investigate the pharmacokinetics of floxuridine (FUDR) when administered postoperatively via the celiac axis in experimental animals. Methods Ten healthy prepubertal pigs underwent first radical gastrectomy, then were randomly divided into two groups (each n=5): the one group in which the drug was given via the celiac artery (CAI). and the other in which the drug was administered systemically through a vein (SC). High performance liquid chromatography (HPLC) was applied to determine the concentration of FUDR in the peripheral blood, tissues surrounding the gastric anastomosis, stomach-neighboring organs and tissues as well as in the related lymph nodes. Results The AUC0-49 and Cmax of FUDR in the tissues neigboring the gastric anastomosis in the liver, pancreas colic mesentery and the Cmax of FUDR in the lymph nodes along the celiac artery and the middle colic vessels, were significantly higher in the CAI group compared with the SC group. There were no significant difference in terms of the Cmax of FUDR in the heart and kidney between the 2 groups. Conclusions A higher concentration of FUDR in the tissues surrounding the gastric anastomosis and in the other neighboring organs and tissues can be achieved in the CAl group, indicating that a better outcome in the treatment and prevention of metastases and recurrence can be obtained through the use of CAI than the SC and without additional toxic reaction.

Objective To delimit the natural infectious focus, including the distribution of wildlife,species, ecology of intermediate hosts and final host of Angiostrongylus cantonensis, as well as the routes of transmission and epidemiological characteristics and wildlife of human Angiostrongylus cantonensis, based on human diverging cases identified in Shenzhen, southern area of China. Methods Data including rate of infection and density of Angiostrongylus cantonensis among different hosts in 12 different areas in Shenzhen was collected, using microscope to inspect homogenate liquids of snails. Wild mice were captured with mouse cage to examine the adult Angiostrongylus cantonensis. Using larva isolated from wild-snails-infected rats to observe the life cycle of Angiostrongylus cantonensis. Results Wild life of Angiostrongylus cantonensis existed in the southwest part of Shenzhen with its majority intermediate hosts as Achatina fulica. The overall rate of infection was 31% in wildlife and final host was found to be Rattus andersoni, Achatina fulica which were extensively distributed in the shrub region of Shenzhen because of suitable climate,humidity and vegetation for generating the life cycle of Achatina fulica. Human infected Angiostrongylus cantonensis was mainly due to eating raw snails or vegetables contaminated by larva of Angiostrongylus cantonensis.The peak of infection was seen from April to November in Shenzhen area.Conclusion Wildlife of Angiostrongylus cantonensis existed in the southwest part of Shenzhen with major wildlife reservoir including fresh water snail and wild mouse. The existence of natural focus Angiostrongylus cantonensis was now recognized as an important source of human angiostrongliasis in Shenzhen area.

Objective To assess the safety, immunogenicity and efficacy of group A and C meningococcal polysaccharide vaccine (A/C MPV) in response to an outbreak of group C meningococcal disease. Methods A vaccination campaign with A/C MPV was prompted 6 weeks after the use of group A MPV in Laibin city, Guangxi, where an outbreak of group C meningococcal meningitis occurred in 2002.Vaccinees were observed for local and systemic reactions after the vaccination and followed up for the meningococcal disease for 5 years. Blood samples were collected from 71 people in the epidemic and 43 in the non-epidemic areas before and 1 month after the vaccination and examined by ELISA to detect IgG antibodies to group A and C polysaccharides. Results The vaccination coverage was 97%. No significant adverse reactions were observed. The positive rates of group C antibodies after vaccination was between 97.67% and 100% among the populations in the epidemic and non-epidemic areas, as well as among those negative and positive for group C antibodies prior to the vaccination.The geometric mean anti-C concentrations ranged 30.81 μg/ml to 37.44 μg/ml, showing no significant difference between groups. The incidence rate of meningococcal disease in students with timely immunization (218.58/100 000) dropped by 69.02% , when compared to that in those with delayed immunization (705.72/100 000). No clinical cases were identified during the follow-up period of 15 760 person-years. Conclusion The vaccination campaign with the Chinese group A/C MPV seemed successful in controlling the group C meningococcal outbreak.The vaccine was shown to be safe even administered after the group A vaccine only 6 weeks apart. It could induce high levels of antibodies in vulnerable population and significantly increase antibody levels in seropositive individuals, thus providing a protection of at least 5 years.

Endodontic diseases are a kind of chronic infectious oral disease.Common endodontic treatment concepts are based on the removal of inflamed or necrotic pulp tissue and the replacement by gutta-percha.However,it is very essential for endodontic treatment to debride the root canal system and prevent the root canal system from bacterial reinfection after root canal therapy(RCT).Recent research,encompassing bacterial etiology and advanced imaging techniques,contributes to our understanding of the root canal system's anatomy intricacies and the technique sensitivity of RCT.Success in RCT hinges on factors like patients,infection severity,root canal anatomy,and treatment techniques.Therefore,improving disease management is a key issue to combat endodontic diseases and cure periapical lesions.The clinical difficulty assessment system of RCT is established based on patient conditions,tooth conditions,root canal configuration,and root canal needing retreatment,and emphasizes pre-treatment risk assessment for optimal outcomes.The findings suggest that the presence of risk factors may correlate with the challenge of achieving the high standard required for RCT.These insights contribute not only to improve education but also aid practitioners in treatment planning and referral decision-making within the field of endodontics.

OBJECTIVE: To study and analyze the clinical effect of the self-developed new adjustable weight-bearing rehabilitation brace in the rehabilitation of the femoral intertrochanteric fracture after the operation of PFNA. METHODS: From July 2015 to June 2017, 62 patients with typeⅡ (Evans-Jensen classification) intertrochanteric fracture of femur were treated with PFNA internal fixation. There were 11 males and 19 females in the routine rehabilitation group, with an average age of (70.73± 6.09) years;17 males and 15 females in the brace rehabilitation group, with an average age of (71.25±6.60) years. Among them, the patients in the routine rehabilitation group recovered according to the routine method, and the patients in the support rehabilitation group used the self-developed new adjustable weight-bearing rehabilitation support of lower limbs to assist the early rehabilitation. The pain intensity(VAS score), weight-bearing of affected limb, clinical healing time of fracture, Harris score and complications were recorded and analyzed. RESULTS: Nine patients lost their visit half a year later, the other 53 patients were followed up for 9 to 18 months. The VAS score at 1, 3, 6 months after operation of brace rehabilitation group was lower than that of routine rehabilitation group(<0.05). The weight bearing of the limbs in the rehabilitation group was significantly higher than that in the conventional rehabilitation group(<0.05), but the clinical healing time of fracture in the brace rehabilitation group was shorter than that in the routine rehabilitation group(<0.05). In addition, the Harris score of the postoperativebrace rehabilitation group was better than that of the conventional rehabilitation group(<0.05). The incidence of complications was lower than that of the conventional rehabilitation group(=0.048). CONCLUSION In the rehabilitation of Evans Jensen typeⅡintertrochanteric fracture after PFNA internal fixation, the new self-developed adjustable weight-bearing rehabilitation brace can significantly relieve postoperative pain, regulate and moderately increase the stress stimulation at the fracture end, so as to promote fracture healing, accelerate the recovery of hip joint function, reduce the incidence of complications, and its clinical effect is safe and reliable.
Aged ; Bone Nails ; Braces ; Female ; Fracture Fixation, Intramedullary ; Hip Fractures ; Humans ; Lower Extremity ; Male ; Middle Aged ; Retrospective Studies ; Treatment Outcome ; Weight-Bearing

This paper describes a bioassay method for the determination of ansamitocin titers. A fungal strain sensitive to ansamitocin was classified to the genus Trichoderma based on phylogenetic analysis of its ITS sequence, and designated as Trichoderma CPCC 400749. PDA plates of Trichoderma CPCC 400749 were prepared to assay ansamitocin titers of Actinosynnema pretiosum ATCC 31565. The titers were consistent with those determined by HPLC. The bioassay method may have the potential use in high-throughput screening for Actinosynnema pretiosum mutants with improved ansamitocin titers.