右美托咪定通过抑制线粒体凋亡水平缓解大鼠脑缺血后记忆障碍的实验研究

摘要 目的：探右美托咪定缓解缺血性脑损伤记忆障碍大鼠记忆功能的作用机制。方法：选择雄性SD大鼠36只,随机分为三组,分别为：假手术组（12只）、缺血性脑损伤模型组（12只）、右美托咪定组（12只）,除假手术组外其余动物均采用双侧颈动脉结扎术建立慢性脑缺血模型。假手术组和模型组给予生理盐水静注,右美托咪定组给予右美托咪定0.5 μg /kg,静注,均在15 min内滴完。比较大鼠给药前和给药后4 w的记忆情况以及线粒体凋亡因子Bcl-2、Cleaved Caspase-3、Caspase-9的表达水平。结果：（1）与假手术组相比,模型组和右美托咪定组大鼠逃逸潜伏期明显增高（P＜0.05）,右美托咪定组逃逸潜伏期与模型组相比有显著降低（P＜0.05）;与假手术组相比,模型组和右美托咪定组大鼠游泳路程明显延长（P＜0.05）,右美托咪定组游泳路程与模型组相比有显著降低（P＜0.05）;（2）与假手术组相比,模型组和右美托咪定组大鼠海马区部分凋亡因子Bcl-2,Cleaved Caspase-9,Cleaved Caspase-3的蛋白表达均有明显提升（P＜0.05）;与模型组相比,右美托咪定组在给药4 w后上述蛋白的表达有明显降低（P＜0.05）。结论：右美托咪定对脑缺血记忆障碍大鼠的记忆功能有显著改善作用,其作用机制可能与抑制线粒体凋亡水平有关,具体信号通路还有待进一步探索。     

不同剂量右美托咪定联合丙泊酚全凭静脉麻醉对食管癌根治术患者炎症因子、氧化应激和术后谵妄的影响

摘要 目的：探讨不同剂量右美托咪定联合丙泊酚全凭静脉麻醉对食管癌根治术患者炎症因子、氧化应激和术后谵妄的影响。方法：选择南京医科大学附属宿迁第一人民医院2019年1月~2021年12月期间120例择期行食管癌根治术的患者。按照随机数字表法将患者分为对照组（41例,丙泊酚全凭静脉麻醉）、低剂量组（40例,对照组基础上联合0.50 μg/kg右美托咪定麻醉）、高剂量组（39例,对照组基础上联合1.00 μg/kg右美托咪定麻醉）。对比三组神经损伤指标、炎症因子、氧化应激相关指标,同时记录三组不良反应发生率和术后谵妄发生率。结果：高剂量组、低剂量组T2~T4时间点S100β蛋白、神经元特异性烯醇化酶（NSE）低于对照组,且高剂量组低于低剂量组（P<0.05）。高剂量组、低剂量组T2~T4时间点肿瘤坏死因子-α（TNF-α）、C反应蛋白（CRP）、白介素-6（IL-6）、白介素-1β（IL-1β）低于对照组,且高剂量组低于低剂量组（P<0.05）。高剂量组、低剂量组T2~T4时间点超氧化物歧化酶（SOD）、谷胱甘肽过氧化物酶（GSH-Px）高于对照组,且高剂量组高于低剂量组（P<0.05）。高剂量组、低剂量组T2~T4时间点丙二醛（MDA）低于对照组,且高剂量组低于低剂量组（P<0.05）。三组麻醉期间不良反应发生率对比无差异（P>0.05）。高剂量组的术后谵妄发生率低于低剂量组、对照组（P<0.05）。结论：1.00 μg/kg剂量的右美托咪定联合丙泊酚全凭静脉麻醉用于食管癌根治术患者麻醉效果较好,可降低术后谵妄发生率,有效控制氧化应激和炎症因子水平。     

不同剂量右美托咪定联合舒芬太尼对老年全髋关节置换术患者血流动力学、脑保护效应和 T淋巴细胞亚群的影响

摘要 目的：观察不同剂量右美托咪定联合舒芬太尼对老年全髋关节置换术（THA）患者血流动力学、脑保护效应和 T淋巴细胞亚群的影响。方法：选择2017年3月到2021年8月期间来我院接受治疗的老年THA患者90例。将患者根据随机数字表法分为低剂量组、中剂量组和高剂量组,例数分别为30例。麻醉诱导前,低剂量组（0.25 μg/kg）、中剂量组（0.50 μg/kg）和高剂量组（1.00 μg/kg）静脉输注右美托咪定,输注 10 min。观察三组血流动力学、脑保护效应指标、T淋巴细胞亚群指标、不良反应发生情况及镇痛情况。结果：中剂量组气管插管即刻（T1）~手术结束时（T3）时间点心率（HR）、平均动脉压（MAP）高于低剂量组和高剂量组（P<0.05）。高剂量组及中剂量组的术后2 h、术后 6 h、术后12 h、术后24 h疼痛视觉模拟评分法 (VAS )评分均低于低剂量组(P<0.05),且高剂量组低于中剂量组( P<0.05 )。高剂量组、中剂量组术后3 d血清S100β蛋白、神经元特异性烯醇化酶（NSE）低于低剂量组,且高剂量组低于中剂量组（P<0.05）。高剂量组、中剂量组术后3 d的脑氧摄取率（CERO₂）高于低剂量组,且高剂量组高于中剂量组（P<0.05）。高剂量组、中剂量组术后3 d CD3⁺、CD4⁺、CD4⁺/ CD8⁺高于低剂量组（P<0.05）。高剂量组、中剂量组术后3 d CD3⁺、CD4⁺、CD4⁺/ CD8⁺对比差异无统计学意义（P>0.05）。高剂量组的不良反应发生率比低剂量组和中剂量组的更高（P<0.05）。结论：右美托咪定联合舒芬太尼应用于老年THA患者,可获得较好的镇痛效果,且右美托咪定具有剂量差异,0.50 μg/kg及 1.00 μg/kg可获得相当的免疫功能恢复程度,0.50 μg/kg的患者血流动力学更稳定,而1.00 μg/kg的患者脑保护效应更好,但不良反应高,综合考虑,认为0.50 μg/kg右美托咪定相对更为安全。     

右美托咪定对脑缺血/再灌注大鼠海马兴奋性氨基酸含量及NMDA受体亚单位NR1表达的影响

目的：观察右美托咪定预处理对全脑缺血/再灌注大鼠海马细胞外谷氨酸（Glu）、天门冬氨酸（Asp）含量及N-甲基-D-天冬氨酸（NMDA）受体1（NR1）表达的影响,探讨右美托咪定脑保护作用及其神经递质机制。方法：雄性Wistar大鼠54只,随机分为3组（n=18）：假手术组、脑缺血/再灌注组和右美托咪定预处理组。用四血管闭塞法建立大鼠全脑缺血模型。收集清醒、缺血15 min及再灌注0~1 h微透析标本。于全脑缺血15 min再灌注1 h后,迅速断头取脑,采用免疫组化法和蛋白免疫印迹法检测海马NMDA受体NR1亚单位的表达情况。结果：与脑缺血/再灌注组相应时点比较,右美托咪定预处理组大鼠海马微透析液中Glu、Asp含量明显降低（P<0.05, 0.01）;免疫组化和Western-blot法检测显示右美托咪定预处理组大鼠海马组织NMDA受体亚单位NR1表达明显受抑制（P<0.05, 0.01）。结论：右美托咪定预处理不仅减少脑缺血/再灌注时兴奋性氨基酸释放,还能抑制NMDA受体亚单位NR1的高表达而产生脑保护作用。     

不同剂量右美托咪定静脉维持对重型颅脑损伤患者术后生命体征、免疫功能和血清神经细胞因子的影响

摘要 目的：观察不同剂量右美托咪定静脉维持在重型颅脑损伤患者中的应用价值。方法：选取2018年9月~2020年9月期间江苏大学附属宜兴市人民医院麻醉与重症医学科接收的重型颅脑损伤患者96例,根据随机数字表法分为三组：A组（右美托咪定剂量为0.3μg/kg?h）、B组（右美托咪定剂量为0.5 μg/kg?h）和C组（右美托咪定剂量为0.7 μg/kg?h）,各32例。观察三组患者不同时间点的生命体征、免疫功能、镇静镇痛情况、血清神经细胞因子,记录三组不良反应发生情况。结果：B组、C组术后24 h、术后72 h的心率（HR）、呼吸频率（RR）、平均动脉压（MAP）低于A组（P<0.05）。B组、C组术后24 h、术后72 h的Ramsay镇静评分、视觉模拟评分法（VAS）评分低于A组（P<0.05）。B组、C组术后24 h、术后72 h的CD3⁺、CD4⁺/CD8⁺高于A组（P<0.05）。B组、C组术后24 h、术后72 h的神经元特异性烯醇化酶（NSE）、中枢神经特异性蛋白（S100β）低于A组（P<0.05）。C组的不良反应总发生率高于A组、B组（P<0.05）。结论：重型颅脑损伤患者术中给予右美托咪定剂量为0.5 μg/kg?h、0.7 μg/kg?h维持,可有效维持患者生命体征平稳,促进患者免疫功能和血清神经细胞因子水平改善,但0.7 μg/kg?h剂量的右美托咪定使用后不良反应发生率相对更高。     

不同剂量右美托咪定辅助脑梗死介入术治疗患者效果及对血流动力学及疼痛水平的影响

摘要 目的：分析不同剂量右美托咪定辅助脑梗死介入术治疗患者效果及对血流动力学及疼痛水平的影响。方法：选取2019年6月～2022年12月在本院行介入手术的90例脑梗死患者进行研究,将术中辅助应用生理盐水的30例患者纳入对照组,将辅助应用0.2 μg?kg^-1右美托咪定的30例患者纳入低剂量组,应用0.6 μg?kg^-1右美托咪定的30例患者纳入高剂量组。记录三组患者的呼吸恢复时间、定向力恢复时间、拔管时间及不良反应发生率,并在入室时（T0）、手术开始30 min（T1）、术毕（T3）和术后12 h（T4）检测三组患者的血流动力学[平均动脉压（MAP）、舒张压（DBP）、收缩压（SBP）、心率（HR）]和疼痛因子[血清P物质（SP）、5-羟色胺（5-HT）]水平。结果：三组呼吸恢复时间、定向力恢复时间、拔管时间比较,差异无统计学意义（P＞0.05）。与对照组比较,低剂量组和高剂量组T1、T2时间段的MAP、HR、SBP、DBP水平较低;与低剂量组比较,高剂量组T1、T2时间段的MAP、HR、SBP、DBP水平较低（P＜0.05）。与对照组比较,低剂量组和高剂量组T1、T2、T3时间段的SP、5-HT水平较低;与低剂量组比较,高剂量组T1、T2、T3时间段的SP、5-HT水平较低（P＜0.05）。三组不良反应发生率比较,差异无统计学意义（P＞0.05）。结论：高、低剂量右美托咪定均能帮助脑梗死介入治疗患者稳定血流动力学,还能减轻其疼痛感,而高剂量右美托咪定效果更为明显。     

不同剂量羟考酮复合右美托咪定麻醉对肺癌根治术患者自控静脉镇痛效应及免疫应答的影响

摘要 目的：观察不同剂量羟考酮复合右美托咪定麻醉在肺癌根治术患者中的临床应用效果。方法：采用随机数字表法,将2017年3月~2020年12月期间在我院行肺癌根治术的肺癌患者（n=140）分为A组（1.0 mg/kg羟考酮）、B组（2.5 μg/kg右美托咪定、1.0 mg/kg羟考酮）、C组（2.5 μg/kg右美托咪定、0.75 mg/kg羟考酮）、D组（2.5 μg/kg右美托咪定、0.5 mg/kg羟考酮）,各为35例。观察四组患者的血流动力学、免疫应答、镇痛效应满意度及不良反应发生率。结果：C组、D组术后2 h（T1）~术后6 h（T2）时间点心率（HR）、平均动脉压（MAP）小于A组、B组（P<0.05）。而A组、B组之间和C组、D组之间的T1、T2时间点HR、MAP组间对比差异不显著（P>0.05）。A组、D组的镇痛效应满意度小于C组和B组（P<0.05）。而A组、D组之间和C组、B组之间的镇痛效应满意度组间对比无差异（P>0.05）。C组、D组CD3⁺、CD4⁺、CD4⁺/CD8⁺高于A组、B组;CD8⁺则低于A组、B组（P<0.05）。而C组、D组之间、A组、B组之间的CD3⁺、CD4⁺、CD8⁺、CD4⁺/CD8⁺组间对比差异不显著（P>0.05）。C组的不良反应发生率小于A组、B组、D组（P<0.05）。结论：羟考酮复合右美托咪定麻醉用于肺癌根治术患者,以0.75 mg/kg羟考酮+2.5 μg/kg右美托咪定的效果最好,可获得较好的镇痛效应满意度,稳定血流动力学,减轻免疫抑制,安全可靠。     

右美托咪定联合不同剂量咪达唑仑对非小细胞肺癌手术患者血流动力学和炎症介质、认知功能的影响

摘要 目的：探讨右美托咪定联合不同剂量咪达唑仑对非小细胞肺癌（NSCLC）手术患者血流动力学和术后炎症介质、认知功能的影响。方法：纳入2019年1月-2021年2月期间来郑州大学第一附属医院接受手术治疗的NSCLC患者（n=120）,按照麻醉方案的不同分为低剂量组（n=60）和高剂量组（n=60）,两组均予以右美托咪定,在此基础上,低剂量组予以0.05 mg/kg咪达唑仑,高剂量组予以0.10 mg/kg咪达唑仑。对比两组患者的血流动力学、炎症介质、认知功能、苏醒质量和不良反应发生率。结果：两组麻醉诱导后10 min（T1）~拔管后5 min（T3）时间点心率（HR）、平均动脉压（MAP）升高后下降,且拔管即刻（T2）、T3时间点高剂量组低于低剂量组（P<0.05）。高剂量组的苏醒后疼痛视觉模拟评分（VAS）评分低于低剂量组,睁眼时间、拔管时间、麻醉恢复室（PACU）停留时间均短于低剂量组（P<0.05）。两组术前、术后3 d、术后7 d白介素-1（IL-1）、C反应蛋白（CRP）、肿瘤坏死因子-α（TNF-α）升高后下降,且术后3 d、术后7 d高剂量组低于低剂量组（P<0.05）。两组术后1 d、术后3 d、术后7 d简易精神状态量表（MMSE）评分组间对比未见统计学差异（P>0.05）。两组不良反应发生率组间对比无统计学差异（P>0.05）。结论：与0.05 mg/kg咪达唑仑相比,右美托咪联合0.10 mg/kg咪达唑仑定用于NSCLC手术患者,维持血流动力学稳定、提高苏醒质量、减轻炎症应激的效果更为显著,且不增加认知功能损害和不良反应发生率。     

右美托咪定神经保护作用的自噬机制研究

摘要 目的：探讨右美托咪定发挥神经保护作用的细胞自噬和线粒体自噬机制。方法：通过对SH-SY5Y细胞进行氧糖剥夺再灌注模拟全脑的缺血再灌注损伤,将细胞随机分为7组：（1）C组：对照组;（2）OGD/R组：氧糖剥夺再灌注损伤组;（3）DEX组：右美托咪定组;（4）3MA组：3-甲基腺嘌呤组;（5）D+3MA组;（6）RAPA组：雷帕霉素组;（7）D+RAPA组。结果：与OGD/R组相比,DEX组、3MA组、D+3MA组的细胞活性、电镜下完整线粒体的数量、自噬体数量明显好于OGD/R组（P<0.05）;RAPA组与OGD/R组相比上述指标无明显差异（P>0.05）;而RAPA中加入右美托咪定以后,可以部分逆转RAPA的作用,细胞活性增加,完整线粒体数量增加,自噬体数量减少（P<0.05）。免疫印迹结果显示,与OGD/R组相比,DEX组、3MA组、D+3MA组LC3II/LC3I、Beclin 1表达减少,BCL-2、P62、TOM20的表达增加,RAPA组各种自噬蛋白的表达与OGD/R组相比没有统计学意义,当应用右美托咪定之后逆转了各种蛋白的表达（P<0.05）。结论：右美托咪定通过减少过度的细胞自噬和线粒体自噬发挥神经保护作用。     

右美托咪啶对肺缺血/再灌注诱发小鼠肾脏超微结构改变的影响

目的：评价右美托咪啶对小鼠肺缺血/再灌注诱发肾脏损伤的影响。方法：雄性健康SPF级C57BL/6J小鼠50只,体重20 g~24 g,8~10周龄,采用随机数字表法,将其分为5组（n=10）：假手术组（sham组）、肺缺血/再灌注损伤组（I/R组）、肺缺血/再灌注+生理盐水组（NS组）、右美托咪啶组（Dex组）、右美托咪啶+阿替美唑（Atip）（DA组）。采用小鼠在体左侧肺门夹闭30 min再灌注180 min方法制备肺缺血/再灌注损伤（I/R）模型。Dex组在肺门阻断前30 min腹腔注射右美托咪啶20 μg/kg,NS组为用同Dex组等体积的生理盐水替代Dex,DA组腹腔注射右美托咪啶（20 μg/kg）+阿替美唑（250 μg/kg）,其余处理同I/R组。再灌注结束后静脉取血ELISA法检测血浆中IL-1β和TNF-α浓度;取双肾组织,透射电镜下观察肾组织病理学结果。结果：与对照组相比,其余组血浆IL-1β和TNF-α浓度明显升高,肾组织病理学损伤明显加重;与I/R、NS、DA组相比,Dex组IL-1β和TNF-α浓度明显下降,差异有统计学意义（P<0.05）,且肾组织超微结构损伤有所减轻。结论：右美托咪啶预先给药可减轻小鼠肺缺血/再灌注诱发肾脏损伤,其机制可能与抑制炎性反应有关。     

A/California/7/2009与A/California/4/2009病毒感染力比较

目的甲型H1N1流感病毒A/California/7/2009与A/California/4/2009病毒序列比较同源性在99%以上,本实验旨在比较两株病毒感染BALB/c小鼠研究感染力强弱。方法分别将A/California/7/2009（CA7）与A/California/4/2009（CA4）两株病毒分别连续10倍稀释后,对4~6周龄雌性BALB/c小鼠经乙醚麻醉后进行滴鼻攻毒,每个稀释度接种10只实验小鼠,测定CA7 MLD50为101.24/0.05 mL,检测小鼠感染、致病的多项指标,观察期为14 d。结果相同TCID50的CA7和CA4病毒感染小鼠,CA4感染小鼠后14 d内死亡率为20%,而CA7感染小鼠后8 d内死亡率为100%。CA7 106TCID50感染的小鼠病理表现为重度弥漫性间质性肺炎,CA4 106TCID50感染的小鼠病理表现为中度-重度间质性肺炎。结论在相同条件下,CA7感染力明显强于CA4。     

The COP/DET/FUS proteins-regulators of eukaryotic growth and development

Eleven recessive mutant loci define the class of cop / det / fus mutants of Arabidopsis. The cop / det / fus mutants mimic the phenotype of light-grown seedlings when grown in the dark. At least four cop / det / fus mutants carry mutations in subunits of the COP9 signalosome, a multiprotein complex paralogous to the 'lid' subcomplex of the 26S proteasome. COP1, another COP/DET/FUS protein, is itself not a subunit of the COP9 signalosome. In the dark, COP1 accumulates in the nucleus where it is required for the degradation of the HY5 protein, a positive regulator of photomorphogenesis. In the light, COP1 is excluded from the nucleus and the constitutively nuclear HY5 protein can accumulate. Nuclear accumulation of COP1 and degradation of HY5 are impaired in the cop / det / fus mutants that carry mutations in subunits of the COP9 signalosome. Although the cellular function of the COP/DET/FUS proteins is not yet well understood, taken together the current findings suggest that the COP/DET/FUS proteins repress photomorphogenesis in the dark by mediating specific protein degradation.     

SSeCKS/Gravin/AKAP12 Inhibits Cancer Cell Invasiveness and Chemotaxis by Suppressing a Protein Kinase C- Raf/MEK/ERK Pathway

SSeCKS/Gravin/AKAP12 (“SSeCKS”) encodes a cytoskeletal protein that regulates G₁ → S progression by scaffolding cyclins, protein kinase C (PKC) and PKA. SSeCKS is down-regulated in many tumor types including prostate, and when re-expressed in MAT-LyLu (MLL) prostate cancer cells, SSeCKS selectively inhibits metastasis by suppressing neovascularization at distal sites, correlating with its ability to down-regulate proangiogenic genes including Vegfa. However, the forced re-expression of VEGF only rescues partial lung metastasis formation. Here, we show that SSeCKS potently inhibits chemotaxis and Matrigel invasion, motility parameters contributing to metastasis formation. SSeCKS suppressed serum-induced activation of the Raf/MEK/ERK pathway, resulting in down-regulation of matrix metalloproteinase-2 expression. In contrast, SSeCKS had no effect on serum-induced phosphorylation of the Src substrate, Shc, in agreement with our previous data that SSeCKS does not inhibit Src kinase activity in cells. Invasiveness and chemotaxis could be restored by the forced expression of constitutively active MEK1, MEK2, ERK1, or PKCα. SSeCKS suppressed phorbol ester-induced ERK1/2 activity only if it encoded its PKC binding domain (amino acids 553–900), suggesting that SSeCKS attenuates ERK activation through a direct scaffolding of conventional and/or novel PKC isozymes. Finally, control of MLL invasiveness by SSeCKS is influenced by the actin cytoskeleton: the ability of SSeCKS to inhibit podosome formation is unaffected by cytochalasin D or jasplakinolide, whereas its ability to inhibit MEK1/2 and ERK1/2 activation is nullified by jasplakinolide. Our findings suggest that SSeCKS suppresses metastatic motility by disengaging activated Src and then inhibiting the PKC-Raf/MEK/ERK pathways controlling matrix metalloproteinase-2 expression and podosome formation.     

A/California/07/2009亚型猪流感冷适应减毒疫苗株的拯救及免疫效果评价

应用反向遗传学技术,选择冷适应、温度敏感、减毒的A/Ann Arbor/6/60 ca (H2N2)型流感病毒的6个内部基因为骨架,与A/California/07/2009株流感病毒2个抗原基因HA、NA分别克隆到polⅠ-polⅡ转录表达载体pAD3000中,构建8个转录表达载体重组质粒,共转染Vero细胞,获得重配A/California/07/2009ca株流感病毒．重配病毒的TCID₅₀为7.5,病毒传4代后其血凝素(HA)滴度稳定在1∶256,半数感染剂量EID₅₀为8,鸡胚传20代,经RT-PCR鉴定未发现重组病毒基因突变,电镜观察重配病毒符合流感病毒的主要特征;蔗糖纯化的病毒经肌肉注射(灭活)及滴鼻(减毒活病毒)两种途径免疫BALB/c小鼠,结果显示：滴鼻免疫和肌肉注射都可以产生较高效价的血凝抑制(HI)抗体,肌肉注射组产生的HI抗体略高(P = 0.044),但肌肉注射组检测不到高效价IgA抗体;滴鼻免疫组鼻冲洗液中可以检测到高效价的IgA抗体,同型病毒感染后,IL-1β、TNFα、IFN-α等前炎因子分泌较早,且高于肌肉注射组(P < 0.05),可见,喷鼻减毒疫苗比灭活全病毒疫苗能更好地激发黏膜免疫反应．通过对小鼠各个器官病毒载量的检测发现,4天后鼻腔、气管、脑、肺、脾脏没有病毒存在,证明减毒活疫苗株在小鼠上是安全的．以上数据可以初步断定,重组病毒有作疫苗候选株的可能,而且喷鼻疫苗具有降低免疫剂量、同时激活体内体液免疫和细胞免疫的功能．     

Structural variability of BM-40/SPARC/osteonectin glycosylation: implications for collagen affinity

We performed a detailed investigation of N-glycan structures on BM-40 purified from different sources including human bone, human platelets, mouse Engelbreth-Holm-Swarm (EHS) tumor, and human BM-40 recombinantly expressed in 293 and osteosarcoma cells. These preparations were digested with endoglycosidases and N-glycans were further characterized by sequential exoglycosidase digestion and high-performance liquid chromatography (HPLC) analyses. Bone BM-40 carries high-mannose structures as well as biantennary complex type N-glycans, whereas the protein from platelets and 293 cells has exclusively bi- and triantennary complex type structures. BM-40 derived from the EHS tumor carries biantennary complex type and additional hybrid structures. Using the osteosarcoma-derived MHH-ES1 cell line we successfully expressed a recombinant BM-40 that bears at least in part the bone-specific high-mannose N-glycosylation in addition to complex type and hybrid structures. Using chromatography on Concanavalin-A Sepharose, we further purified a fraction enriched in high-mannose structures. This array of differentially glycosylated BM-40 proteins was assayed by surface plasmon resonance measurements to investigate the binding to collagen I. BM-40 carrying high-mannose structures binds collagen I with higher affinity, suggesting that differentially glycosylated forms may have different functional roles in vivo.     

AB-type lectin (toxin/agglutinin) from mistletoe: differences in affinity of the two galactoside-binding Trp/Tyr-sites and regulation of their functionality by monomer/dimer equilibrium

Viscumin of mistletoe (Viscum album L.) has a concentration-dependent activity profile unique to plant AB-toxins. It starts with lectin-dependent mitogenicity and then covers toxicity and cell agglutination, associated with shifts in the monomer/dimer equilibrium. Each lectin subunit harbors two sections for ligand contact. In the dimer, the B-chain sites in subdomain 2 gamma (designated as the Tyr-sites) appear fully accessible, whereas Trp-sites in subdomain 1 alpha are close to the dimer interface. It is unclear whether both types of sites operate similarly in binding glycoligands in solution. By systematically covering a broad range of lactose/lectin ratio in isothermal titration calorimetry, we obtained evidence for two sites showing dissimilar binding affinity. Intriguingly, the site with higher affinity was only partially occupied. To assign the observed properties to the Trp/Tyr-sites, we next performed chemically induced dynamic nuclear polarization measurements of Trp and Tyr accessibility. A Tyr signal, but not distinct Trp peaks, was recorded when testing the dimer. Lactose-quenchable Trp peaks became visible on the destabilization of the dimer by citraconylation, intimating Trp involvement in ligand contact in the monomer. Fittingly, Tyr acetylation but not mild Trp oxidation reduced the dimer hemagglutination activity and the extent of binding to asialofetuin-Sepharose 4B. Altogether, the results attribute lectin activity in the dimer primarily to Tyr-sites. Full access to Trp-sites is gained on dimer dissociation. Thus, the monomer/dimer equilibrium of viscumin regulates the operativity of these sites. Their structural divergence affords the possibility for differences in ligand selection when comparing monomers (Tyr- and Trp-sites) with dimers (primarily Tyr-sites).     

不同NH4+/NO3-比例的氮素营养对棉花氮素代谢的影响

The influence of different NH₄⁺/NO₃^- ratios on nitrogen metabolism of cotton was studied under controlled hydroponics.The results showed that compared with single nitrate nutrition,solutions with 25/75,50/50,75/25 and 100/0 of NH₄⁺/NO₃^- significantly increased the soluble protein accumulation in leaves and roots of cotton,and the maximum content of soluble protein in leaves and roots appeared respectively in the solution with 50/50 and 75/25 of NH₄⁺/NO₃^-.The soluble protein content in roots was increased with the increase of NH₄⁺ percentage,but was slightly less in the solution of 100/0 than 75/25,which was probably related to the excess NH₄⁺ limiting boot metabolism.With the increase of NH₄⁺ percentage,the nitrate content in petiole and the nitrate reductase activity in functional blade declined,but ammoniac nitrogen content increased in every organ of cotton.These results showed that foreign nitrogen affected the nitrogen metabolism of cotton in a different way,and the nitrogen absorption by cotton was probably related to different forms of foreign nitrogen.     

Biological monitoring of bisphenol A with HLPC/FLD and LC/MS/MS assays

Biological monitoring is a necessary process for risk assessment of endocrine disrupting chemicals (EDCs), particularly, bisphenol A (BPA), in breast milk, because its human risks are not clear yet, and infants, who feed on breast milk, are highly susceptible for EDCs. Concerning biological monitoring of BPA, the HPLC/FLD has been widely used before the LC/MS/MS. However, there was no report, which simultaneously evaluated the two methods in real analyses. Therefore, we analyzed BPA with LC/MS/MS and HPLC/FLD in human breast milk and conducted comparison of two methods in analyzed BPA levels. After establishing optimal condition, e.g. linearity, recovery, reproducibility and free BPA system, we analyzed BPA levels in human breast milk samples (N = 100). The LOQs were similar in the two methods, i.e. 1.8 and 1.3 ng/mL for the HPLC/FLD and LC/MS/MS assays, respectively. There were strong associations between total BPA levels with the two methods (R² = 0.40, p < 0.01), however, only 11% of them were analyzed as similar levels with 15% CVs. In addition, the detection range of BPA was broader in the HPLC method than the LC/MS/MS method. However, the BPA levels in the HPLC/FLD analysis were lower than those in the LC/MS/MS analysis (p < 0.01). Thus, the differences in BPA levels between the two methods may come from mainly over-estimation with the LC/MS/MS method in low BPA samples and some of poor resolution with the HPLC/FLD in high BPA samples.