Target sites of polymyxin B ototoxicity

Summary The present study was undertaken to determine the target sites of polymyxin B ototoxicity. This drug, at the concentration of 1 mM, was perfused through the scala tympani of the guinea pig cochlea, and cochlear microphonics and endocochlear potentials were monitored. Both cochlear potentials altered but in an independent manner. These findings indicated that not only the organ of Corti but also another tissue is involved in the ototoxicity produced. The best locus for this is the vascular stria.     

多黏菌素B抗炎作用机制的研究

目的观察多黏菌素B(PMB)和内毒素(LPS)共同处理大鼠肺泡巨噬细胞(PAM)后对核因子-κB(NF-κB)信号通路的变化。方法分离、培养大鼠PAM,分为正常对照组、LPS刺激组及PMB干预组。采用原位杂交(ISN)技术、凝胶电泳迁移率改变(EMSA)及ELISA法,检测刺激后0、15、30、60、120和240min各时相点PAM中IKK-βmRNA及IκB-α的表达、NF-κB的活性和TNF-α的含量。结果LPS刺激组IKK-βmRNA的水平在刺激后15min出现升高,30min达高峰,60min后逐渐下降;IκB-α的水平的变化趋势在各时相点与IKK-βmRNA刚好相反;NF-κB活性的峰值相出现在60min,15min出现升高,120min后逐渐下降;TNF-α的含量峰值相出现在60min,30min出现升高,120~240min后恢复至刺激前水平。PMB干预组NF-κB的活性与TNF-α的含量虽较刺激前和正常对照组升高,但均显著低于LPS刺激组(P<0.01)。IκB-α水平的最低值显著高于LPS刺激组(P<0.01);而IKK-βmRNA的峰值则显著低于LPS刺激组(P<0.01)。结论LPS能诱导PAM中的IKK-β激活、IκB-α降解和NF-κB活化,并促进TNF-α释放。而PMB则能抑制LPS诱导的IKK-β激活、IκB-α降解、NF-κB活化和TNF-α释放。     

Kontaktallergien bei Patienten mit Ekzemen des äußeren Gehörgangs Ergebnisse des Informationsverbundes Dermatologischer Kliniken und der Deutschen Kontaktallergie-Gruppe

Zusammenfassung Hintergrund und Fragestellung. Ziel der Untersuchung war die Analyse der innerhalb des Informationsverbundes Dermatologischer Kliniken (IVDK) und der Deutschen Kontaktallergie-Gruppe (DKG) erfassten Daten von Patienten mit Geh?rgangsekzemen. Patienten/Methodik. In dem Datenpool des IVDK wurden zwischen 1992 und 1997 145 Patienten mit Geh?rgangsekzemen gefunden. Ausgewertet wurden neben den DKG-Testreihen auch die getesteten patienteneigenen Substanzen. Ergebnisse. Bei einem Drittel des untersuchten Patientenkollektivs wurde ein allergisches Kontaktekzem diagnostiziert. Inhaltsstoffe medizinischer Externa nahmen eine führende Rolle als Kontaktallergene ein. Im Vergleich der populationskorrigierten Sensibilisierungsh?ufigkeiten (PAFS) zeigte sich für Neomycinsulfat im Untersuchungskollektiv eine deutlich h?here, für Nickelsulfat dagegen eine deutlich niedrigere PAFS als im Gesamtkollektiv. Dies zeigt, dass auf topographisch engstem Raum unterschiedliche Kontaktallergene von Bedeutung sind. Schlussfolgerungen. W?hrend Nickelsulfat am ?u?eren Ohr ein wesentliches Allergen darstellt, dominieren bei Geh?rgangsekzemen die Inhaltsstoffe medizinischer Externa, insbesondere Neomycinsulfat und, wie die Auswertung der getesteten patienteneigenen Substanzen ergab, m?glicherweise auch Polymyxin B.     

Poly-Pred中多粘菌素B的含量测定及干扰因素考察

建立了Ｐｏｌｙ－Ｐｒｅｄ中多粘菌素Ｂ二剂量测定法,同时对复方制剂中新霉素对多粘菌素Ｂ含量测定的干扰作用进行了考察。用支气管炎博德特氏菌,ＵＳＰＩ号培养基,在４～２５ｕ／ｍｌ范围内线性关系良好,ｒ＝０．９９９３。当对照液与供试液含有相当量的新霉素时,即可减少新霉素对多粘菌素Ｂ含量测定的干扰     

多粘菌素B对小白鼠右心室肌动作电位的影响

The effects of polymyxin B (PXB) on action potential of the mice right ventricular myocardial cell were studied by means of intracellular capillary glass electrode. The action potential amplitude (APA) and maximal depolarization rate of phase O (V_max) of action potential were lowered after administering PXB for 5 min. APA was lowered from 104.0±4.2 mV to 100.7±5.1mV, decreasing 3.2% (P<0.01); V_max was lowered from 691.5±114.1 v/s to 515.15±71.5 v/s, decreasing 25.5% (P<0.001). Practically, the resting potential remained unchanged. With the continued administration of PXB, the functional refractory period was significantly prolonged. APA₉₀ was temporarily shortened and then prolonged. The results suggest that PXB inactivate or block the fast sodium channel in myocardial cell membrane, which may relate to the antiarrhythmic effect in animal experiment.     

大鼠脑出血蛋白激酶C与细胞凋亡关系的实验研究

目的：研究大鼠脑出血后血肿周围蛋白激酶C（Protein kinase C,PKC）及神经细胞凋亡的表达及其多黏菌素B（polymyxin B PMB）对上述表达的影响。方法：将100只SD大鼠随机分为四组：假手术组、脑出血组、小剂量多黏菌素B干预组（0.4mg/kg.d）、大剂量多黏菌素B干预组（0.8mg/kg.d）,立体定位仪定位注射自体不凝血制造大鼠脑出血模型,分别为术后6h、12h、24h、72h、120h处死,免疫组织化学法检测血肿周围区PKC、TUNEL阳性细胞（凋亡细胞）数的表达、TNF-α（肿瘤坏死因子-α）含量、NO（一氧化氮）含量以及大小剂量PMB对其干预后的影响。结果：假手术组PKC少量表达,偶见凋亡细胞;脑出血组自6h起PKC、凋亡细胞及TNF-α、NO含量大量增加,72h达高峰,PKC在120h基本降至假手术组,但凋亡细胞TNF-α、NO含量仍处于较高水平,与假手术组比较差异有统计学意义（P〈0.01）;大小剂量多黏菌素B干预组均有明显抑制PKC、凋亡细胞、TNF-α含量的表达,有统计学意义（P〈0.01）;但PMB剂量的大小无明显差异性（P〉0.05）。结论：脑出血后血肿周围存在大量PKC表达上调、神经细胞凋亡、TNF-α、NO含量增加,PMB能够明显抑制PKC激活,TNF-α、NO释放,减少血肿周围细胞凋亡,起到神经元保护作用。     

TNFRp55 modulates IL-6 and nitric oxide responses following Yersinia lipopolysaccharide stimulation in peritoneal macrophages

While cytokines are major regulators of macrophage activation following host-pathogen interactions, they also act to limit inflammation to avoid tissue damage. In previous studies we reported the development of progressive Yersinia enterocolitica-induced reactive arthritis (ReA) in mice lacking the tumor necrosis factor receptor p55 (TNFRp55). In this work, we analyzed the response of TNFRp55^−/− macrophages to Y. enterocolitica antigens. We found higher concentration of nitric oxide (NO) in TNFRp55^−/− compared to wild-type macrophages in response to heat-killed Yersinia (HKY) and Yersinia outer membranes (OM). Moreover, Toll-like receptor (TLR)4 expression was increased in OM-stimulated TNFRp55^−/− versus wild-type (WT) macrophages. Accordingly, NO production was inhibited in TLR4-deficient macrophages following stimulation with OM, suggesting that LPS may function as a major OM component implicated in these responses. Thus, augmented NO production together with enhanced expression of inducible nitric oxide synthase (iNOS) and higher IL-6 production, may provide a pro-inflammatory setting in Yersinia LPS-stimulated TNFRp55^−/− macrophages. Augmented synthesis of NO and IL-6 was prevented by treatment with Polymyxin B, or by exposure to a specific NF-κB p65 oligonucleotide antisense, indicating the involvement of TLR4-mediated NF-κB activation in the unleashed pro-inflammatory response triggered by TNFRp55 deficiency. Thus, TNFRp55 modulates macrophage functions in response to Yersinia LPS stimulation through mechanisms involving NO, IL-6 and NF-κB pathways, suggesting an essential regulatory role of TNF via TNFRp55 signaling.     

Tn5AraOut mutagenesis for the identification of Yersinia pestis genes involved in resistance towards cationic antimicrobial peptides

Bacterial pathogens display a variety of protection mechanisms against the inhibitory and lethal effects of host cationic antimicrobial peptides (CAMPs). To identify Yersinia pestis genes involved in CAMP resistance, libraries of DSY101 (KIM6 caf1 pla psa) minitransposon Tn5AraOut mutants were selected at 37 °C for resistance to the model CAMPs polymyxin B or protamine. This approach targeted genes that needed to be repressed (null mutations) or induced (upstream P_BAD insertions) for the detection of CAMP resistance, and predictably for improved pathogen fitness in mammalian hosts. Ten mutants demonstrated increased resistance to polymyxin B or protamine, with the mapped mutations pointing towards genes suspected to participate in modifying membrane components, genes encoding transport proteins or enzymes, or the regulator of a ferrous iron uptake system (feoC). Not all the mutants were resistant to both CAMPs used for selection. None of the polymyxin B- and only some protamine-resistant mutants, including the feoC mutant, showed increased resistance to rat bronchoalveolar lavage fluid (rBALF) known to contain cathelicidin and β-defensin 1. Thus, findings on bacterial resistance to polymyxin B or protamine don’t always apply to CAMPs of the mammalian innate immune system, such as the ones in rBALF.     

耐碳青霉烯肺炎克雷伯菌对多黏菌素B体外敏感性检测方法的差异性研究

摘要：目的 了解不同检测方法在耐碳青霉烯肺炎克雷伯菌(carbapenem-resistant Klebsiella pneumoniae, CRKP)对多黏菌素 B体外药敏检测中的差异,为临床治疗和实验室检测提供依据。方法 选择2018-2020年宁波地区临床分离的CRKP 147株,分 别采用肉汤稀释法、E-test纸片法、仪器法(N335药敏卡)和纸片法检测其体外对多黏菌素B的敏感性,分析4种药敏检测方法所 存在的差异。结果 微量肉汤稀释法、E-test法和仪器检测CRCP对多黏菌素B MIC50分别为1、1和0.5μg/mL,MIC90分别为1、 1和0.5,累积敏感率分别为97.3%、99.3%和98%,具有较高一致性和敏感性;仪器法检测CRKP对多黏菌素B的平均MIC值为 (0.82±0.16)μg/mL,明显低于标准方法的(1.39±0.27)μg/mL,差异有统计学意义(P＜0.01);E-test法和仪器法的基本一致率(EA) 为92.5%和94.6%,标准符合(CA)分别为97.3%和98.6%,严重错误(VME)分别为2.7%和1.4%;重大错误(ME)和小错误(mE)均为 0;纸片法KB值与肉汤稀释法MIC值之间方差分析P＞0.05,故提示KB值与MIC值不具有线性关系。结论 4种方法检测CRKP 对多黏菌素B体外具有较高敏感性;仪器法和E-test法对于多黏菌素B的敏感性检测与微量肉汤稀释法高度一致,但其中仪器法 N335药敏卡检测MIC有所降低,建议标准方法复核。