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The growth of three plague phages from Qinghai Plateau in two Yersinia pestis strains(plague vaccine strains EV76 and 614F)and four non-Yersinia pestis strains(Yersinia pseudotuberculosis PTB3,PTB5,Escherichia coli V517,and Yersinia enterocolitica 52302-2)were detected through a micromethod based on the OmniLogTM microbial identification system and by the drop method,to provide a scientific basis for future ecological studies and classification based on the host range.For plague vaccine strains EV76 and 614F,successful phage infection and subsequent phage growth were observed in the host bacte-rium.Diminished bacterial growth and respiration and a concomitant decrease in color were observed with the OmniLogTM mi-crobial identification system at 33 ℃ for 48 h.Yersinia pseudotuberculosis PTB5 was sensitive to Yersinia pestis phage 476,but Yersinia pseudotuberculosis PST5 was insensitive to phage 087 and 072204.Three strains of non-Yersinia pestis(Yersinia pseudotuberculosis PTB3,Escherichia coli V517,and Yersinia enterocolitica 52302-2)were insensitive to Yersinia pestis pha-ges 087,072204,and 476 showed similar growth curves.The growth of phages 476 and 087,as determined with the drop method,in two Yersinia pestis strains(plague vaccine strains EV76 and 614F)and four non-Yersinia pestis strains(Yersinia pseudotuberculosis PTB3,Escherichia coli V517,and Yersin-ia enterocolitica 52302-2)showed the same results at 37 ℃,on the basis of comparisons with the OmniLogTM microbial i-dentification system;in contrast,phages 072204 did not show plaques on solid medium at 37 ℃ with plague vaccine strains EV76 and 614F.Determination based on the OmniLogTM detection system can be used as an alternative to the traditional determination of the host range,thus providing favorable application val-ue for determining the interaction between the phage and host bacteria.
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Honokiol is the dominant biphenolic compound isolated from the Magnolia tree, and has long been considered as the active constituent of the traditional Chinese herb, 'Houpo', which is widely used to treat symptoms due to 'stagnation of qi'. Pharmacological studies have shown that honokiol possesses a wide range of bioactivities without obvious toxicity. Honokiol protects the liver, kidneys, nervous system, and cardiovascular system through reducing oxidative stress and relieving inflammation. Moreover, honokiol shows anti-diabetic property through enhancing insulin sensitivity, and anti-obese property through promoting browning of adipocytes. In vivo and in vitro studies indicated that honokiol functions as an anti-cancer agent through multiple mechanisms: inhibiting angiogenesis, promoting cell apoptosis, and regulating cell cycle. A variety of therapeutic effects of honokiol may be associated with its physiochemical properties, which make honokiol readily cross the blood brain barrier and the blood-cerebrospinal fluid barrier, with high bioavailability. In the future, more clinical researches on honokiol are needed to fully authenticate its therapeutic values.
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Humanos , Apoptosis , Compuestos de Bifenilo/farmacología , Medicamentos Herbarios Chinos/farmacología , Lignanos/farmacología , MagnoliaRESUMEN
Objective@#To investigate reciprocal regulation between Fur and two RyhB homologs in @*Methods@#Regulatory relationships were assessed by a combination of colony morphology assay, primer extension, electrophoretic mobility shift assay and DNase I footprinting.@*Results@#Fur bound to the promoter-proximal DNA regions of @*Conclusion@#Fur and the two RyhB homologs exert negative reciprocal regulation, and RyhB homologs have a positive regulatory effect on biofilm formation in
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Proteínas Bacterianas/metabolismo , Biopelículas , Regulación Bacteriana de la Expresión Génica/fisiología , Yersinia pestis/fisiologíaRESUMEN
OBJECTIVE@#To observe the effect on supplementary analgesia after total knee arthroplasty (TKA) treated with electroacupunture, and explore it's mechanism.@*METHODS@#A total of 40 patients with severe knee osteoarthritis were randomized into an observation group and a control group, 20 cases in each one. During the operation, patients were given epidural anesthesia in the two groups, conventional patient controlled epidural analgesia and oral celecoxib were applied after the operation. In the observation group, electroacupunture was used at Liangqiu (ST 34), Xuehai (SP 10), Yinlingquan (SP 9), Zusanli (ST 36), Fenglong (ST 40) and Qiuxu (GB 40) on the operation side from the 1st to 7th day after the operation to support analgesia, 30 min for each time, once a day. The visual analogue scale (VAS) was used to record postoperative pain of resting state and active state. The levels of serum prostaglandin E and β-endorphin were measured on the 1st and 7th day after surgery in the two groups.@*RESULTS@#In the observation group, the VAS scores of resting state and active state were superior to the control group on the 3rd, 5th and 7th day after the operaton (all <0.05); after the treatment, the level of serum β-endorphin was increased and the level of serum prostaglandin E was reduced in the two groups (all <0.05), and the change of the observation group was larger than that of the control group (both <0.05).@*CONCLUSION@#Electroacupunture has the effect of supplementary analgesia for patients after TKA, the mechanism may be related to promote the synthesis of β-endorphin and inhibit the synthesis of prostaglandin E.
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Humanos , Analgesia Controlada por el Paciente , Artroplastia de Reemplazo de Rodilla , Manejo del Dolor , Dolor Postoperatorio , Prostaglandinas , betaendorfinaRESUMEN
BACKGROUND: Human neuronal calcium sensor-1 (NCS-1) protein with a high charge is extremely sensitive to solution temperature, but whether the change of ion concentration in the solution can change the protein structure and affect the physiological function has not been reported. OBJECTIVE: To investigate the molecular mechanism of variations of sodium chloride concentration altering conformational dynamics of human NCS-1. METHODS: Through molecular dynamics simulation, the first two minimum energy models (PDB id: 2LCP) were utilized as the starting states of each independent molecular dynamics simulation of the human NCS-1 protein. After energy minimization, two different initial structures were used to conduct three independent 500 ns molecular dynamics simulations with explicit solvent for human NCS-1 protein at 0.1, 0.3 and 1 mol/L sodium chloride concentration. RESULTS AND CONCLUSION: The slightly high concentration of sodium chloride increased the flexibility of loop L2, simultaneously expanded the global and local structure of NCS-1 protein. Increase in sodium chloride concentration induced loop L3 to adopt a collapsed state and reduced the connectivity between the starting and ending residues of loop L3. N-domain and C-domain interdomain correlation was weakened and the intradomain coupling strengthened. Formation number and the probability of the salt bridges were reduced dramatically, especially at 0.3 mol/L sodium chloride. These findings manifest that human NCS-1 protein is sensitive to the small variation of sodium chloride concentration, which may alter the key factors on protein conformation. Our study may provide the theoretical reference at the atomic structural insights for probing the conformational variations of human NCS-1 protein at the different aqueous solutions.
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Objective To investigate the clinical efficacy and effects of Tongmai Powder external application on serum inflammatory cytokines levels in patients with chemotherapeutic phlebitis. Methods Totally 60 patients with chemotherapeutic phlebitis were randomly divided into observation group and control group by order of inclusion, with 30 cases in each group. The observation group was treated with Tongmai Powder. The Tongmai Powder was evenly applied to the gauze. The thickness was 0.5–1 cm. The area was slightly larger than the lesion. The gauze was applied externally to the lesion and fixed with tape. The control group was given magnesium sulfate, twice a day for not less than 2 hours. 3 d was one treatment course for both groups, for successive three courses. Clinical efficacy and VAS of both groups were observed. The levels of TNF-α, IL-4, IL-8 and IL-10 before and after treatment in the two groups were compared. Results The total effective rate was 96.67% (29/30) in the observation group and 83.33% (25/30) in the control group. The observation group was significantly better than the control group (P=0.007). Compared with before treatment, the VAS of the two groups were significantly lower. The serum levels of TNF-α and IL-8 in the observation group decreased significantly, and the levels of IL-4 and IL-10 increased significantly (P<0.05). After treatment, the VAS was lower in the observation group than in the control group (P<0.05), the levels of TNF-α and IL-8 were lower in the observation group (P<0.05) and the IL-4 and IL-10 levels were higher than the control group (P<0.05). Conclusion Tongmai Powder external application can effectively treat chemotherapeutic phlebitis, which mechanism may be related to regulating the balance of inflammatory cytokines.
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<p><b>OBJECTIVE</b>This study aimed at investigating whether notoginsenoside R1 (R1), a unique saponin found in Panax notoginseng could promote angiogenic activity on human umbilical vein endothelial cells (HUVECs) and elucidate their potential molecular mechanisms. In addition, vascular restorative activities of R1 was assessed in a chemically-induced blood vessel loss model in zebrafish.</p><p><b>METHODS</b>The in vitro angiogenic effect of R1 was compared with other previously reported angiogenic saponins Rg1 and Re. The HUVECs proliferation in the presence of R1 was determined by cell proliferation kit II (XTT) assay. R1, Rg1 and Re-induced HUVECs invasion across polycarbonate membrane was stained with Hoechst-33342 and quantified microscopically. Tube formation assay using matrigelcoated wells was performed to evaluate the pro-angiogenic actions of R1. In order to understand the mechanism underlying the pro-angiogenic effect, various pathway inhibitors such as SU5416, wortmannin (wort) or L-Nω-nitro- L-arginine methyl ester hydrochloride (L-NAME), SH-6 were used to probe the possible involvement of signaling pathway in the R1 mediated HUVECs proliferation. In in vivo assays, zebrafish embryos at 21 hpf were pre-treated with vascular endothelial growth factor (VEGF) receptor kinase inhibitor II (VRI) for 3 h only and subsequently post-treated with R1 for 48 h, respectively. The intersegmental vessels (ISVs) in zebrafish were assessed for the restorative effect of R1 on defective blood vessels.</p><p><b>RESULTS</b>R1 could stimulate the proliferation of HUVECs. In the chemoinvasion assay, R1 significantly increased the number of cross-membrane HUVECs. In addition, R1 markedly enhanced the tube formation ability of HUVECs. The proliferative effects of these saponins on HUVECs were effectively blocked by the addition of SU5416 (a VEGF-KDR/Flk-1 inhibitor). Similarly, pre-treatment with wort [a phosphatidylinositol 3-kinase (PI3K)-kinase inhibitor], L-NAME [an endothelial nitric oxide synthase (eNOS) inhibitor] or SH-6 (an Akt pathway inhibitor) significantly abrogated the R1 induced proliferation of HUVECs. In chemicallyinduced blood vessel loss model in zebrafish, R1 significantly rescue the damaged ISVs.</p><p><b>CONCLUSION</b>R1, similar to Rg1 and Re, had been showed pro-angiogenic action, possibly via the activation of the VEGF-KDR/Flk-1 and PI3K-Akt-eNOS signaling pathways. Our findings also shed light on intriguing pro-angiogenic effect of R1 under deficient angiogenesis condition in a pharmacologic-induced blood vessels loss model in zebrafish. The present study in vivo and in vitro provided scientific evidence to explain the ethnomedical use of Panax notoginseng in the treatment of cardiovascular diseases, traumatic injuries and wound healing.</p>
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Animales , Humanos , Vasos Sanguíneos , Patología , Movimiento Celular , Proliferación Celular , Colágeno , Farmacología , Modelos Animales de Enfermedad , Combinación de Medicamentos , Ginsenósidos , Química , Farmacología , Células Endoteliales de la Vena Umbilical Humana , Biología Celular , Fisiología , Laminina , Farmacología , Neovascularización Fisiológica , Fosfatidilinositol 3-Quinasas , Metabolismo , Inhibidores de Proteínas Quinasas , Farmacología , Proteoglicanos , Farmacología , Proteínas Proto-Oncogénicas c-akt , Metabolismo , Receptor 2 de Factores de Crecimiento Endotelial Vascular , Metabolismo , Pez CebraRESUMEN
The present study investigated the chemical constituents of the roots and rhizomes of Panax notoginseng. Compounds were isolated by various column chromatographic methods, and their structures were elucidated by the extensive analysis of spectroscopic data and chemical evidences. A novel 12, 23-epoxy dammarane-type saponin, named epoxynotoginsenoside A (1), together with four known compounds (2-5), was isolated and characterized.
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Panax notoginseng , Química , Raíces de Plantas , Química , Rizoma , Química , Saponinas , Química , Triterpenos , QuímicaRESUMEN
Seventeen compounds were isolated from the 95% ethanolic extract of the root of Ficus hirta. Their structures were identified on the basis of physicochemical properties and spectral data analysis. The structures were elucidated as cyclomorusin (1), 3-O-[(6-O-E-sinapoyl)-beta-D-glucopyranosyl]-(1 --> 2)-beta-D-glucopyranoside (2), 3,5,4'-trihydroxy-6,7,3'-trimethoxyflavone (3), quercetin (4), tricin (5), acacetin (6), luteolin (7), apigenin (8), (E) -suberenol (9), meranzin hydrate (10), methyl eugenol (11), 3-methoxy-4-hydroxybenzoic acid (12), p-hydroxybenzoic acid (13), methyl chlorogenate (14), emodin (15), alpha-amyrin acetate (16), and beta-sitosterol emodin (17), respectively. Compounds 1-6, 9-15 were isolated from this plant for the first time.
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Medicamentos Herbarios Chinos , Química , Ficus , Química , Espectrometría de Masas , Estructura MolecularRESUMEN
Objective To evaluate the protective effect of Yersinia pestis capsular antigen F1 and recombinant rV270 on mice after immunization with them.Methods According to body weight,40 female Balb/c mice aged 6 to 8 weeks were randomly divided into four experimental groups(Fl-10 μg + aluminum adjuvant,F1-20 μg + aluminum adjuvant,rV-10 μg + aluminum adjuvant,and rV-20 μg + aluminum adjuvant) and a control group,8 in each group.Mice in experimental groups were immunized with the natural antigen F1 and recombinant antigen rV270 adsorbed to 25% aluminum adjuvant and the control group was immunized with the same amount of aluminum adjuvant.Each mouse was immunized at the hind leg muscle with 100 ml immunizing agent,then a booster immunization was done once on the 21st day after the first immunization.The blood of all mice was collected on the 8th week after the first immunization,serum antibody titers were detected by ELISA and the data of antibody titers were analyzed by t test for comparison between groups.At the same time the mice were injected subcutaneously with 2000-fold LD50 of Yersinia pestis virulent strain 141,after 14 days,the protective effect of immunization was analyzed.Results The control group did not produce antibody.Antibody geometric mean titers (GMT) of the F1-10 mg + aluminum adjuvant and F1-20 mg + aluminum adjuvant groups were 1 ∶ 30443.9,and 1 ∶21527.8,respectively,and compared between the two groups,the difference was not statistically significant (t =1.1282,P > 0.05).The GMTs of the rV-10 μg + aluminum adjuvant and rV-20 μg + aluminum adjuvant groups were 1 ∶ 13957.3 and 1 ∶18100.9,respectively,and compared between the two groups,the difference was not statistically significant(t =0.9408,P > 0.05 ).After subcutaneous injection with Yersinia pestis virulent strain 141,all mice died in the control group but all survived in the experimental group.Conclusion The immune activity of natural antigen F1 and recombinant rV270 is high,which can be used as the main component of subunit vaccine in the plague subunit vaccine study.
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<p><b>OBJECTIVE</b>LcrV is an important component for the development of a subunit vaccine against plague. To reduce immunosuppressive activity of LcrV, a recombinant LcrV variant lacking amino acids 271 to 326 (rV270) was prepared by different methods in this study.</p><p><b>METHODS</b>A new strategy that produced non-tagged or authentic rV270 protein was designed by insertion of rV270-thrombin-hexahistidine fusion gene into the vector pET24a, or by insertion of hexahistidine-enterokinase-rV270 or hexahistitine-factor Xa-rV270 fusion gene into the vector pET32a. After Co(2+) affinity chromatography, a purification strategy was developed by cleavage of His tag on column, following Sephacryl S-200HR column filtration chromatography.</p><p><b>RESULTS</b>Removal of His tag by thrombin, enterokinase and factor Xa displayed a yield of 99.5%, 32.4% and 15.3%, respectively. Following Sephacryl S-200HR column filtration chromatography, above 97% purity of rV270 protein was obtained. Purified rV270 that was adsorbed to 25% (v/v) Al(OH)₃ adjuvant in phosphate-buffered saline (PBS) induced very high titers of antibody to rV270 in BALB/c mice and protected them (100% survival) against subcutaneous challenge with 10⁶ CFU of Y. pestis virulent strain 141.</p><p><b>CONCLUSION</b>The completely authentic rV270 protein can be prepared by using enterokinase or factor Xa, but they exhibited extremely low cleavage activity to the corresponding recognition site. Thrombin cleavage is an efficient strategy to prepare non-tagged rV270 protein and can be easily operated in a large scale due to its relatively low cost and high cleavage efficacy. The recombinant rV270 can be used as a key component to develop a subunit vaccine of plague.</p>
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Animales , Femenino , Ratones , Secuencia de Aminoácidos , Anticuerpos Antibacterianos , Sangre , Antígenos Bacterianos , Genética , Alergia e Inmunología , Western Blotting , Clonación Molecular , Electroforesis en Gel de Poliacrilamida , Escherichia coli , Genética , Vectores Genéticos , Ratones Endogámicos BALB C , Datos de Secuencia Molecular , Peste , Alergia e Inmunología , Vacuna contra la Peste , Genética , Alergia e Inmunología , Plásmidos , Proteínas Citotóxicas Formadoras de Poros , Genética , Alergia e Inmunología , Ingeniería de Proteínas , Métodos , Proteínas Recombinantes de Fusión , Genética , Alergia e Inmunología , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Análisis de Supervivencia , Vacunas de Subunidad , Genética , Alergia e Inmunología , Yersinia pestis , Alergia e InmunologíaRESUMEN
To study chemical constituents of the leaves of Nauclea officinalis, eight alkaloids were isolated from 95% ethanol extract by various chromatographic methods. The structures were elucidated on the basis of spectroscopic data (IR, UV, ESI-MS, 1D and 2D NMR) and identified as naucleactonin C (1), strictosamide (2), vincosamide (3), pumiloside (4), angustoline (5), angustine (6), 18, 19-dihydroangustine (7) and naucleofficine D (8). Compound 1 is a new indole alkaloid. Compounds 6 and 7 were isolated from this plant for the first time.
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Alcaloides , Química , Camptotecina , Química , Alcaloides Indólicos , Química , Indoles , Química , Estructura Molecular , Hojas de la Planta , Química , Plantas Medicinales , Química , Rubiaceae , Química , Alcaloides de la Vinca , QuímicaRESUMEN
<p><b>OBJECTIVE</b>To evaluate the protective efficacy of plague subunit vaccine, BALB/c mice, guinea pigs and rabbits were used in this study.</p><p><b>METHODS</b>Groups of mice (10 per group), guinea pigs (14 per group) and rabbits (6 per group) were immunized with F1 + rV270 vaccine, EV76 vaccine and alum adjuvant by intramuscular route, respectively. Serum antibody titres of mice, guinea pigs and rabbits were determined by ELISA and the immunized animals were challenged with 10(6) CFU of Y. pestis strain 141 at the 8th week after the primary immunization.</p><p><b>RESULTS</b>The immunized mice, guinea pigs or rabbits with subunit vaccine developed anti-F1 IgG titre of 41 587.3 +/- 2.1, 11 543.7 +/- 2.1 or 522.4 +/- 22.4 and elicited statistical anti-F1 IgG titre difference among them (F = 17.58, P < 0.01). The immunized mice, guinea pigs or rabbits with subunit vaccine had anti-rV270 IgG titre of 15 748.7 +/- 1.6, 12.6 +/- 1.4 or 1648.0 +/- 5.0 and induced statistical anti-rV270 IgG titre difference among them (F value was 16.34, P < 0.01). There was significant anti-F1 IgG titre difference among mice, guinea pigs and rabbits immunized with EV76 vaccine that developed anti-F1 IgG titre of 913.4 +/- 4.5, 937.0 +/- 2.0 or 342.0 +/- 12.0 (F = 23.67, P < 0.01), whereas the immunized mice, guinea pigs and rabbits with EV76 vaccine developed anti-rV270 IgG titre of 12.0 +/- 1.0, 447.0 +/- 10.0, 40.0 +/- 11.0 and there was no anti-rV270 IgG titre difference between them (F = 2.20, P = 0.1314). The immunized mice with subunit vaccine developed significantly higher anti-F1 IgG titres than immunized guinea pigs and rabbits (q value was 30.57 and 19.04, respectively, P < 0.01), and there were no anti-F1 IgG titre differences between the immunized guinea pigs and rabbits (q = 0.04, P = 0.8485). The immunized mice with subunit vaccine developed significantly higher anti-rV270 IgG titres than immunized guinea pigs and rabbits (q value was 27.10 and 19.49, respectively, P < 0.01), and there were no anti-rV270 IgG titre differences between the immunized guinea pigs and rabbits with the subunit vaccine (q = 0.25, P = 0.6187). The immunized mice with EV76 elicited higher anti-F1 IgG titres than immunized guinea pigs and rabbits (q value was 40.67 and 29.10, respectively, P < 0.01), whereas there was no difference of F1 IgG titer between immunized guinea pigs and rabbits (q = 0.06, P = 0.8098). The immunized mice, guinea pigs and rabbits with subunit vaccine provided 100% (10/10), 86% (12/14) and 100% (5/5) protection against 10(6) CFU Y. pestis of challenge, respectively. The immunized mice, guinea pigs and rabbits with EV76 vaccine gave 100% (6/6), 93% (13/14) and 100% (6/6) protection against 10(6) CFU Y. pestis of challenge respectively.</p><p><b>CONCLUSION</b>BALB/c mice is the best small animal model for valuation of protective efficacy of plague subunit vaccine. The guinea pigs showed a high individual variation for this purpose. The rabbits can be used as an alternative model for evaluating plague subunit vaccine.</p>
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Animales , Femenino , Ratones , Conejos , Anticuerpos Antibacterianos , Sangre , Relación Dosis-Respuesta Inmunológica , Cobayas , Inmunización , Inmunoglobulina G , Sangre , Ratones Endogámicos BALB C , Modelos Animales , Peste , Vacuna contra la Peste , Alergia e Inmunología , Vacunas de Subunidad , Alergia e InmunologíaRESUMEN
Objective Throush identify biochemical characteristics and virulence factors of 2 strains suspected Yersinia pestis(Y.pestis)isolated from the dead Marmota himalayana(M.himalayana)to confirm the nature epidemic focus in Dege County,Sichuan Province.Methods Y.pestis was analyzed by specific staining and shape,culturing characteristics,splitting-test by bacteriophage,test of biochemical characteristics and glycolysis ability,virulence factors,virulence,nutritional requirement,plasmid,genetic test and genetic type. Results The tested strains were Gram staining bacilus.The main biochemical characteristics were Arabinose(+)、 Rhamnose(-),Maltose(+),Melibiose(-),Glycerol(+),Denitrification(+).The virulence factors with FI+.VW+, Pgm+,Pst I+;and with the common 6.0×106,45.0×106,65.0×106 plasmids,also with the virulence-relative plasmid gene.Both their absolutely lethal dose(LD100)in mice were 50 bacteria.The nutritional requirement appeared which were depended on Phenylalanine and Methionine.With the Genomovar 5 genotype characteristics of M.himalayana plague foci of Qinghai-Tibet plateau.The difference between tested strains and Yersinia pseudotubercuosis on the 3 different culture medium was obvious.The tested strains had a Y.pestis' specific 3a fragment,Pst I and FI-Ag,at 22 ℃,the strains could be split by bacteriophage completely.Conclusions According to the diagnostic criteria of plague in China,the 2 suspected strains isolated from Dege County,Sichuan Province ale confirmed as Y.pestis.both with powerful virulenceand with the characteristics of the Y.pestis of M.himahtyana in Qinghai-Tibet plateau plague natural focus.
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Objective To study the features of Yersinia pestis(Y.pestis)in areas along Qinghai-Tibet Railroad in Qinghai Province.Methods To identify the biologic types and the molecular biological feathers of Y.pestis isolated from areas along Qinghai-Tibet Railroad in Qinghai from 2001-2006.Results All the tested Y.pestis was biologically of classical type and ecologically of Qinghai-Tibet plateau type.The Y.pestis had high virulence.The Y.pestis of 65×106 plasmids was distributed in the Tanggula area,the Y.pestis of 52×106plasmids,in Tianjun and Delingha areas.The Y.pestis srains carried 52 × 106 plasmids.except the two containing 65 X 106 plasmids in Wulan County.The genetic type of Y.pestis in Tanggula was type 5 and that in Zongwulong of Delingha,Saishike,Keke,Tongpu of Wulan was type 8 except 2 strains of Y.pestis isolated from woodchuck and the patients in Dananwan of Tongpu,Wulan County were type 15.Conclusion The Y.pestis in the area along Qinghai-Tibet Railroad in Qinghai belongs to Qinghai-Tibet plateau type with high virulence.