血清sTM、PCT、CRP/PAB比值与脓毒症患者APACHEⅡ评分、SOFA评分的相关性及其联合检测对预后的预测价值

摘要 目的：探讨血清可溶性血栓调节蛋白（sTM）、降钙素原（PCT）、C-反应蛋白与前白蛋白（CRP/PAB）比值与脓毒症患者急性生理和慢性健康评估Ⅱ（APACHEⅡ）评分、序贯器官衰竭评估（SOFA）评分的相关性及其联合检测对预后的预测价值。方法：选取2020年3月～2020年12月我院重症医学科收治的97例脓毒症患者,根据Sepsis-3.0诊断标准分为普通脓毒症组44例、脓毒性休克组53例,根据入院后30 d内预后情况分为死亡组35例和存活组62例。收集患者基线资料和APACHEⅡ评分、SOFA评分,并检测血清sTM、PCT、CRP/PAB比值。采用Spearman相关性分析脓毒症患者血清sTM、PCT、CRP/PAB比值与APACHEⅡ评分、SOFA评分的相关性,多因素Logistic回归分析脓毒症患者预后不良的影响因素,受试者工作特征（ROC）曲线分析血清sTM、PCT、CRP/PAB比值对脓毒症患者预后不良的预测价值。结果：脓毒性休克组血清sTM、PCT、CRP/PAB比值和APACHEⅡ评分、SOFA评分高于普通脓毒症组（P均＜0.05）。Spearman相关性分析显示,脓毒症患者血清sTM、PCT、CRP/PAB比值与APACHEⅡ评分、SOFA评分呈正相关（P＜0.05）。多因素Logistic回归分析显示,收缩压升高为脓毒症患者预后不良的独立保护因素（P＜0.05）,脓毒性休克、合并器官损伤≥3个、机械通气时间延长、APACHEⅡ评分增加、SOFA评分增加、sTM升高、PCT升高、CRP/PAB比值升高为独立危险因素（P均＜0.05）。ROC曲线分析显示,血清sTM、PCT、CRP/PAB比值联合预测脓毒症患者预后不良的曲线下面积大于各指标单独预测。结论：脓毒症患者血清sTM、PCT、CRP/PAB比值升高与APACHEⅡ评分、SOFA评分增加密切相关,血清sTM、PCT、CRP/PAB比值联合检测对脓毒症患者预后不良的预测价值较高。     

脓毒症患者血清H2S、GDF-15、PTX-3水平与凝血功能、炎症指标及病情评分的相关性分析

摘要 目的：探讨脓毒症患者血清硫化氢（H₂S）、生长分化因子-15（GDF-15）、穿透素-3（PTX-3）水平与其凝血功能、炎症指标及病情评分的相关性。方法：随机选取我院2018年2月～2020年2月收治的脓毒症患者52例作为脓毒症组,另选取我院同期收治的脓毒症休克患者46例作为休克组以及同期于我院进行体检的健康者50例作为对照组。检测三组血清H₂S、GDF-15、PTX-3水平以及凝血功能、炎症指标,其中凝血功能指标包括血小板计数（PLT）、部分凝血活酶时间（APTT）、凝血酶原时间（PT）、纤维蛋白原（FIB）。炎症指标包括降钙素原（PCT）、C反应蛋白（CRP）。采用急性生理学和慢性健康状况评分系统Ⅱ（APACHEⅡ）、快速序贯器官功能（qSOFA）评分对脓毒症组、休克组患者病情进行评分。分析血清H2S、GDF-15、PTX-3与患者凝血功能、炎症指标及病情评分的相关性。结果：脓毒症组、休克组的血清H₂S、PLT均低于对照组,且休克组低于脓毒症组（P＜0.05）。脓毒症组、休克组的血清GDF-15、PTX-3、APTT、PT、FIB、PCT、CRP均高于对照组,且休克组高于脓毒症组（P＜0.05）。脓毒症组APACHEⅡ、qSOFA评分均显著低于休克组（P＜0.05）。血清H2S与PLT呈正相关（P＜0.05）,与APTT、PT、FIB、PCT、CRP、APACHEⅡ评分、qSOFA评分呈负相关（P＜0.05）。血清GDF-15、PTX-3与PLT呈负相关（P＜0.05）,与APTT、PT、FIB、PCT、CRP、APACHEⅡ评分、qSOFA评分呈正相关（P＜0.05）。结论：脓毒症患者的血清H₂S明显下降,而血清GDF-15、PTX-3增高,三者与凝血功能、炎症以及病情评分均存在密切关联,这可能是影响脓毒症进展的重要原因之一。     

小剂量糖皮质激素联合持续性血液净化治疗儿童严重脓毒症的效果及安全性研究

摘要 目的：分析小剂量糖皮质激素联合持续性血液净化治疗儿童严重脓毒症的效果及安全性。方法：选择自2021年1月至2023年1月接诊的102例儿童严重脓毒症患儿作为研究对象,随机分为对照组和观察组,各51例;对照组予以经典治疗方案,观察组在对照组的基础上,予以小剂量糖皮质激素联合持续性血液净化治疗;记录两组治疗后各项信息,比较两组治疗前后外周血乳酸、中心静脉血氧饱和度（ScvO₂）、血清炎症指标、PCIS评分、APACHE Ⅱ评分,观察主要并发症发生情况。结果：与对照组相比,观察组机械通气、低血压持续及入住ICU等时间较短,7 d内停升压药率较高（P＜0.05）;两组28 d病死率比较无差异（P＞0.05）;观察组治疗后乳酸、降钙素原（PCT）、肿瘤坏死因子-α（TNF-α）、白介素-6（IL-6）水平均较对照组低,ScvO₂水平较对照组高（P＜0.05）;观察组治疗后PCIS评分较对照组高,APACHE Ⅱ评分较对照组低（P＜0.05）;观察组主要并发症发生率低于对照组（P＜0.05）。结论：小剂量糖皮质激素联合持续性血液净化治疗有利于儿童严重脓毒症患儿病情转归,减少主要并发症发生,可能与阻断炎症反应有关,值得进一步研究应用。     

脓毒症合并急性肾损伤患者尿液NGAL水平与肾动脉阻力指数、APACHEⅡ评分及28 d病死率的关系

摘要 目的：研究脓毒症合并急性肾损伤（AKI）患者尿液中性粒细胞明胶酶相关脂质运载蛋白（NGAL）水平与肾动脉阻力指数（RRI）、急性生理学与慢性健康状况评分系统Ⅱ（APACHEⅡ）评分及28 d病死率的关系。方法：选取2017年2月～2019年12月期间我院收治的脓毒症患者251例纳入研究,将其按照是否发生AKI分为AKI组116例和非AKI组135例。检测并比较两组尿液NGAL水平、RRI、APACHEⅡ评分。采用Pearson相关性分析尿液NGAL水平与RRI、APACHEⅡ评分的关系。此外,将AKI组患者按照随访28d时是否死亡分为死亡组32例和存活组84例,比较两组尿液NGAL水平、基线资料、序贯性器官功能衰竭（SOFA）评分以及实验室指标,通过多因素Logistic回归分析脓毒症合并AKI患者28 d死亡率与相关因素的关系。结果：AKI组尿液NGAL水平、RRI、APACHEⅡ评分均明显高于非AKI组（均P＜0.05）。经Pearson相关性分析表明：尿液NGAL水平与RRI、APACHEⅡ评分均呈正相关（均P＜0.05）。死亡组AKI分期2～3期人数占比高于存活组,且SOFA评分、APACHEⅡ评分以及尿液NGAL、尿肾损伤分子-1（Kim-1）水平均高于存活组,而尿胱抑素C（CysC）水平低于存活组（均P＜0.05）。经多因素Logistic回归分析发现：AKI分期2～3期、SOFA评分、APACHEⅡ评分、尿液NGAL以及尿Kim-1均是脓毒症合并AKI患者28 d死亡的危险因素,而尿CysC为其保护因素（均P＜0.05）。结论：尿液NGAL在脓毒症合并AKI患者中明显高表达,且和RRI、APACHEⅡ评分及28 d病死率密切相关。     

气囊面罩联合气管插管通气救治对急诊心肺复苏患者动脉血气指标及预后的影响

摘要 目的：观察气囊面罩联合气管插管通气救治对急诊心肺复苏患者动脉血气指标及预后的影响。方法：选取中国人民解放军联勤保障部队第九四〇医院2020年4月-2022年10月期间收治的急诊心肺复苏患者86例作为研究对象。根据通气方式的不同将患者分为A组（n=41,常规气管插管通气救治）和B组（n=45,气囊面罩联合气管插管通气救治）。对比两组临床指征、急性生理与慢性健康评分（APACHEⅡ）、血气指标[二氧化碳分压（PCO2）、实际碳酸氢根（AB）、氧分压（PO₂）、二氧化碳总量（TCO₂）]、复苏成功率、格拉斯哥昏迷评分（GCS）、6个月存活率。结果：与A组相比,B组的自主呼吸恢复时间、心跳恢复时间、气道开放时间、意识恢复时间更短（P<0.05）。治疗后B组AB、TCO₂、PCO₂低于A组,PO₂高于A组（P<0.05）。治疗后B组APACHEⅡ评分低于A组,GCS高于A组（P<0.05）。B组的复苏成功率、6个月存活率高于A组（P<0.05）。结论：急诊心肺复苏患者使用气囊面罩联合气管插管通气救治,患者的临床指征、动脉血气指标均得到显著改善,且预后良好。     

AIMS65评分联合血清GAS、PGE2、BAR对急性非静脉曲张性上消化道出血患者预后的评估价值

摘要 目的：探讨AIMS65评分联合血清胃泌素（GAS）、前列腺素E₂（PGE₂）、血尿素氮/白蛋白比值（BAR）对急性非静脉曲张性上消化道出血（ANVUGIB）患者内镜下止血治疗后预后的评估价值。方法：选取2020年5月～2022年5月北京市和平里医院消化内科收治的108例的ANVUGIB患者,根据患者住院28 d内的预后分为预后不良组和预后良好组。收集患者临床资料,检测血清GAS、PGE₂水平和计算AIMS65评分、BAR。采用单因素和多因素Logistic回归分析ANVUGIB患者内镜下止血治疗后预后不良的影响因素,受试者工作特征（ROC）曲线分析AIMS65评分、GAS、PGE₂和BAR对ANVUGIB患者内镜下止血治疗后预后不良的评估价值。结果：108例ANVUGIB患者预后不良发生率为37.96％（41/108）。单因素分析显示,预后不良组年龄大于预后良好组,心率、休克指数、AIMS65评分、GAS、BAR高于预后良好组,PGE₂水平低于预后良好组（P均＜0.05）。多因素Logistic回归分析显示,年龄增加和休克指数、AIMS65评分、GAS、BAR升高为ANVUGIB患者内镜下止血治疗后预后不良的独立危险因素,PGE₂升高为其独立保护因素（P均＜0.05）。ROC曲线分析显示,AIMS65评分联合GAS、PGE₂和BAR评估ANVUGIB患者内镜下止血治疗后预后不良的曲线下面积大于AIMS65评分、GAS、PGE₂和BAR单独评估。结论：预后不良的ANVUGIB患者AIMS65评分、GAS、BAR均高于预后良好的患者,AIMS65评分联合GAS、PGE₂和BAR评估ANVUGIB患者内镜下止血治疗后预后的价值较高。     

AECOPD合并Ⅱ型呼吸衰竭患者发生营养风险的影响因素分析及其预测模型构建

摘要 目的：探讨慢性阻塞性肺疾病急性加重期（AECOPD）合并Ⅱ型呼吸衰竭患者发生营养风险的影响因素,并构建预测模型。方法：回顾性选择2021年1月至2022年12月内蒙古自治区人民医院收治的AECOPD合并Ⅱ型呼吸衰竭患者177例,根据营养风险筛查2002（NRS2002）评分将患者分为营养风险组（122例）和无营养风险组（55例）。单因素和多因素Logistic回归分析AECOPD合并Ⅱ型呼吸衰竭患者营养风险的影响因素,并根据回归模型构建预测模型。受试者工作特征（ROC）曲线验证预测模型的预测效能。结果：单因素分析显示营养风险组年龄大于无营养风险组（P＜0.05）,COPD病程长于无营养风险组（P＜0.05）,慢性胃病,急性加重次数≥3次/年,改良版英国医学研究委员会呼吸困难问卷（mMRC）评分3-4级比例高于无营养风险组（P＜0.05）,第1秒用力呼气容积（FEV₁）、FEV₁/用力肺活量（FVC）,体质量指数（BMI）,白蛋白、前白蛋白,握力,氧分压（PO2）低于无营养风险组（P＜0.05）,中性粒细胞计数/淋巴细胞计数比值（NLR）,慢性阻塞性肺疾病评估测试问卷（CAT）评分,急性生理学与慢性健康状况评分系统Ⅱ（APACHE Ⅱ）评分高于无营养风险组（P＜0.05）。多因素Logistic回归分析结果显示高年龄、高mMRC评分、合并慢性胃病、高NLR是AECOPD合并Ⅱ型呼吸衰竭患者发生营养风险的危险因素（P＜0.05）,高FEV₁/FVC是保护因素（P＜0.05）。基于回归模型预测AECOPD合并Ⅱ型呼吸衰竭患者营养风险的曲线下面积为0.820,灵敏度、特异度分别为81.97%、83.64%,Hosmer-Lemeshow检验P＞0.05,模型拟合效果良好。结论：高龄、高mMRC评分、合并慢性胃病、高NLR是AECOPD合并Ⅱ型呼吸衰竭患者发生营养风险的危险因素,高FEV₁/FVC是保护因素。基于回归模型预测AECOPD合并Ⅱ型呼吸衰竭患者发生营养风险具有较高的价值。     

臂丛神经阻滞复合静脉全麻进行锁骨骨折手术对患者疼痛阈值和术后谵妄的影响

摘要 目的：探讨臂丛神经阻滞复合静脉全麻进行锁骨骨折手术对患者疼痛阈值和术后谵妄的影响。方法：选取本院2018年4月-2021年5月收治的100例锁骨骨折患者作为研究对象,随机将其分为观察组（n=50）和对照组（n=50）。观察组采用臂丛神经阻滞复合静脉全麻进行手术,对照组单独采用静脉全麻进行手术,对比两组患者手术时间、住院时间以及唤醒时间;不同时间生命体征;麻醉效果和术后疼痛阈值;术后谵妄发生率、谵妄持续时间以及每天睡眠时间。结果：观察组患者的术后住院时长以及唤醒时间明显低于对照组（P＜0.05）。观察组T₁到T₄时间血氧饱和度（SPO₂）、收缩压（SBP）、舒张压（DBP）、平均动脉压（MAP）、心率（HR）无明显波动,对照组T₁到T₄时间上述指标波动明显,且两组患者T₂、T₃时间SPO₂、SBP、DBP、MAP、HR对比差异显著（P＜0.05）;观察组患者的COR、NE在T₂、T3明显下降,而对照组的COR在T₂、T₃呈上升趋势（P＜0.05）。观察组运动神经阻滞时间以及感觉神经阻滞时间明显高于对照组（P＜0.05）,术后2 h、12 h、24 h疼痛阈值明显低于对照组（P＜0.05）。观察组术后谵妄发生率和谵妄持续时间明显低于对照组（P＜0.05）。结论：对锁骨骨折手术患者进行臂丛神经阻滞复合静脉全麻,有效降低患者手术时间、住院时间以及唤醒时间,同时稳定患者生命体征,提升麻醉效果,降低术后疼痛阈,并且谵妄发生率、谵妄持续时间以及每天睡眠时间相对较低。     

不同病情急性呼吸窘迫综合征患者血清铁蛋白、血管生成素样蛋白4、降钙素原与白蛋白比值的变化及对预后的评估价值

摘要 目的：探讨不同病情急性呼吸窘迫综合征（ARDS）患者血清铁蛋白、血管生成素样蛋白4（ANGPTL4）、降钙素原与白蛋白比值（PAR）的变化及对预后的评估价值。方法：选取2019年3月至2022年6月四川大学华西第四医院重症医学科收治的109例ARDS患者,根据氧合指数（PaO₂/FiO₂）将患者分为轻度组（200 mmHg＜PaO₂/FiO₂≤300 mmHg,38例）、中度组（100 mmHg＜PaO₂/FiO₂≤200 mmHg,42例）、重度组（≤100 mmHg,29例）。检测所有ARDS患者血清铁蛋白、ANGPTL4水平及PAR,根据患者入院后28 d内生存状况将其分为存活组（69例）、死亡组（40例）。多因素Logistic回归分析ARDS患者入院后28 d内死亡的危险因素。受试者工作特征（ROC）曲线分析血清铁蛋白、ANGPTL4、PAR评估ARDS患者预后的预测价值。结果：重度组血清铁蛋白、ANGPTL4、降钙素原及PAR高于中度组和轻度组（P＜0.05）,血清白蛋白水平低于中度组和轻度组（P＜0.05）。死亡组血清铁蛋白、ANGPTL4、降钙素原及PAR高于存活组（P＜0.05）,血清白蛋白水平低于存活组（P＜0.05）。高SOFA评分、高PAR及血清铁蛋白、ANGPTL4水平升高是 ARDS患者入院28 d内死亡的危险因素（P＜0.05）。联合血清铁蛋白、ANGPTL4、PAR三项指标预测ARDS患者预后的曲线下面积为0.867,高于单独指标预测的0.775、0.727、0.776。结论：ARDS患者血清铁蛋白、ANGPTL4水平及PAR增高与病情加重以及预后不良有关,联合检测三项指标在ARDS患者预后评估中具有较高价值。     

脓毒症患者发生凝血功能紊乱的临床特征及预后影响因素分析

摘要 目的：探究脓毒症患者发生凝血功能紊乱的临床特征及预后影响因素。方法：选择2019年9月~2023年1月本院收治的80例脓毒症患者为本次研究对象,对所有患者开展凝血功能检验,并依据检验结果,将患者分为凝血功能异常组（n=60）及正常组（n=20）,分析凝血功能障碍异常及正常患者临床特征、凝血功能障碍异常及正常患者病情严重程度,并依据脓毒症患者预后,将其分为存活组（n=64）及死亡组（n=16）脓毒症患者预后的单因素与多因素Logistic回归分析。结果：凝血功能正常组及异常组平均动脉压、体温、白细胞计数（WBC）、纤维蛋白原（FIB）、凝血酶时间（TT）指标水平无较大差异（P＞0.05）,与凝血功能正常组比较,凝血功能异常组患者呼吸、脉率、降钙素原（PCT）、C反应蛋白（CRP）指标水平相对较高,部分凝血活酶时间（APTT）、凝血酶原时间（PT）指标水平相对较长,PLT指标水平相对较高（P＜0.05）;与凝血功能正常的脓毒症患者相比较,凝血功能异常患者急性肾损伤（AKI）及急性呼吸窘迫综合征（ARDS）发生率、急性生理与慢性健康评分（APACHE Ⅱ）及急性生理功能评分（SOFA）评分更高,住ICU时间均相对较长（P＜0.05）,机械通气及住院时间比较（P＞0.05）;脓毒症患者预后影响因素分析中,结果显示,年龄、体质量指数（BMI）、性别、糖尿病史、高血压病史均未对脓毒症患者预后产生较大影响（P＞0.05）,PT、PCT、APTT、CRP、SOFA评分及APACHE Ⅱ评分对脓毒症预后产生严重影响,死亡组患者各指标水平均高于存活组（P＜0.05）;将影响脓毒症患者预后的单因素予以赋值,纳入Logistic回归分析,以PCT、PT、APTT、CRP、SOFA、APACHE Ⅱ 评分为自变量,结果显示,PCT、PT、CRP、SOFA、APACHE Ⅱ 评分是影响脓毒症患者预后的独立危险因素（P＜0.05）。结论：脓毒症患者发生凝血功能紊乱会对临床相关指标产生影响,从而增加疾病严重程度,依据脓毒症患者预后,研究结果显示,PT、PCT、CRP、SOFA及APACHE Ⅱ评分均会对脓毒症患者预后产生不良影响,检验上述指标水平,可为临床评估脓毒症预后提供一定参考价值。     

Inhibitory and enhancing effects of insertion of central polypurine tract sequence on gene expression with vectors derived from human immunodeficiency virus type 1

Reportedly, in human immunodeficiency virus type 1 (HIV) vectors, insertion of central polypurine tract (cPPT) increased expression of transgenes for a short period. To test this for a stable condition, we constructed a series of vectors carrying a Neo(r) gene as a stable marker driven by a synthetic thymidine kinase (hTK) promoter. Transduction efficiency was increased in about 2-fold and decreased in about 8-fold by insertion of the reported 178bp and our 282bp cPPTs, respectively. PCR analyses revealed that insertion of 282bp cPPT, but not 178bp cPPT, impaired integration, although it did not deteriorate nuclear transport much. Furthermore, we found that insertion of 282bp cPPT between hTK promoter and an upstream LTR sequence reduced reporter gene activity in about 5-fold. This inhibitory effect of 282bp cPPT may partly account for the observed decrease in transduction efficiency. We suggest that actual effect of cPPT insertion should be examined in each HIV vector.     

A preliminary survey of the Chironomidae (Diptera) of Costa Rica,with emphasis on the lotic fauna

Extensive collections of Chironomidae were made in Costa Rica, Central America, during 1986 and 1987. Fifty-five genera and at least 148 species belonging to the subfamilies Podonominae, Tanypodinae, Orthocladiinae and Chironomidae were found. Chironominae and Orthocladiinae predominated. Only one species of Podonominae was collected. Tanypodinae was represented by many genera, but species richness was low.Cricotopus was the most widespread and diverse genus of Orthocladiinae. Among the Chironominae the generaPolypedilum, Pseudochironomus, Tanytarsus andRheotanytarsus showed high species richness. Several species were collected that could not be assigned to genus. A number of range extensions were recorded for taxa found in the Neotropical region for the first time and for Neotropical taxa recorded outside of South America for the first time. The Costa Rican chironomid fauna consists of cosmopolitan, holarctic and neotropical components. There is probably an endemic Central American chironomid fauna at the species level.     

宫内和出生后早期发育环境对成年期糖代谢影响的中枢调控作用机制

目前有大量证据表明早期不良的发育环境对成年期增加代谢性疾病的易感性起着决定性的作用。另外,随着人们对中枢胰岛素抵抗的认识增加,中枢对调控外周葡萄糖稳态起着极其重要的作用,越来越多的研究表明这可能是一种表观遗传学机制。表观遗传学是研究在没有DNA序列变化的情况下,引起基因表达可遗传性的改变。它能特异性地调节相关组织的基因表达,从而诱导物质代谢长期的改变。本文着重探讨早期发育环境对成年期糖代谢影响的中枢调控作用的表观遗传学机制。     

Aqueous humor nitric oxide in patients with central retinal vein occlusion

PurposeIt has been suggested that nitric oxide (NO) has a role in ischemic retinopathies. Since retinal ischemia may develop in retinal vein occlusion, we investigated the presence of nitric oxide in the pathogenesis of central retinal vein occlusion (CRVO).MethodsEighteen consecutive patients with CRVO were included in this study. Aqueous humor specimens were obtained within 21 days of diagnosis. Samples of aqueous humor were also collected from 20 control patients undergoing cataract surgery. For each sample after reduction of nitrate to nitrite with vanadium chloride (VCl₃), we used spectrophotometric method for simultaneous detection of nitrate and nitrite (NO_x).ResultsMean level of aqueous humor NO_x in CRVO and control group was 94.1 ± 23.2 μmol/l and 55.6 ± 11.0 μmol/l, respectively. The difference between two groups was statistically significant (p < 0.0001).ConclusionsOur results may support involvement of nitric oxide in the pathogenesis of CRVO.     

New records of benthic marine algae and Cyanobacteria for Costa Rica,and a comparison with other Central American countries

We present the results of an intensive sampling program carried out from 2000 to 2007 along both coasts of Costa Rica, Central America. The presence of 44 species of benthic marine algae is reported for the first time for Costa Rica. Most of the new records are Rhodophyta (27 spp.), followed by Chlorophyta (15 spp.), and Heterokontophyta, Phaeophycea (2 spp.). Overall, the currently known marine flora of Costa Rica is comprised of 446 benthic marine algae and 24 Cyanobacteria. This species number is an under estimation, and will increase when species of benthic marine algae from taxonomic groups where only limited information is available (e.g., microfilamentous benthic marine algae, Cyanobacteria) are included. The Caribbean coast harbors considerably more benthic marine algae (318 spp.) than the Pacific coast (190 spp.); such a trend has been observed in all neighboring countries. Compared to other Central American countries, Costa Rica has the highest number of reported benthic marine algae; however, Panama may have a similarly high diversity after unpublished results from a Rhodophyta survey (Wysor, unpublished) are included. Sixty-two species have been found along both the Pacific and Caribbean coasts of Costa Rica; we discuss this result in relation to the emergence of the Central American Isthmus.     

Predicting the activity phase of a follower neuron with A-current in an inhibitory network

The transient potassium A-current is present in most neurons and plays an important role in determining the timing of action potentials. We examine the role of the A-current in the activity phase of a follower neuron in a rhythmic feed-forward inhibitory network with a reduced three-variable model and conduct experiments to verify the usefulness of our model. Using geometric analysis of dynamical systems, we explore the factors that determine the onset of activity in a follower neuron following release from inhibition. We first analyze the behavior of the follower neuron in a single cycle and find that the phase plane structure of the model can be used to predict the potential behaviors of the follower neuron following release from inhibition. We show that, depending on the relative scales of the inactivation time constant of the A-current and the time constant of the recovery variable, the follower neuron may or may not reach its active state following inhibition. Our simple model is used to derive a recursive set of equations to predict the contribution of the A-current parameters in determining the activity phase of a follower neuron as a function of the duration and frequency of the inhibitory input it receives. These equations can be used to demonstrate the dependence of activity phase on the period and duty cycle of the periodic inhibition, as seen by comparing the predictions of the model with the activity of the pyloric constrictor (PY) neurons in the crustacean pyloric network.     

Temperature-Mediated Interaction of Tetanus Toxin with Cerebral Neuron Cultures: Characterization of a Neuraminidase-Insensitive Toxin-Receptor Complex

Abstract: Energy-dependent internalization of ¹²⁵I-labeled tetanus toxin into cultured neural cells is shown to follow an energy-independent binding process. A three-step model, involving receptor-mediated binding followed by sequestration and internalization is proposed. In the first step, binding of toxin is enhanced in appearance under low ionic strength medium, at 0–4°C; it is suppressed, however, with increasing incubation temperature under physiological salt concentrations. Cell-bound toxin is displaced by approximately 35.5% when high-salt medium (physiological concentrations) is added to cells at 0–4°C; the effect is further amplified at 37°C. Addition of disialoganglioside G_D1b (1–5 μg/ml) also lowers the amount of cell-associated toxin. The fraction of ¹²⁵I-labeled toxin retained by the cells after exposure to high-salt medium at 0–4°C or after addition of G_D1b is operationally defined as sequestered toxin. This second step, characterized by a stable association of the toxin with the neural cells, is affected by both physiological salt and by 37°C conditions. Lastly, an energy-dependent phenomenon of firm association of tetanus toxin with neural cells, compatible with internalization, is described. The toxin residing in this fraction is bioactive and cannot be removed by salts, gangliosides, or by treatment with protease or neuraminidase. Binding, sequestration, and internalization are mutually dependent, as they are all blocked by pretreatment of cells with neuraminidase and by an enhanced energy-independent sequestration event, which results in enhanced tetanus toxin internalization by an energy-dependent process.     

A fragment of substance P with specific central activity: SP(1-7)

Amino-terminal fragments of substance P (SP), SP(1-7) and SP(1-8), were found to produce naloxone-reversible antinociception in the mouse similar to that produced by SP. Similar to SP, these peptides produce antinociception only within a narrow dose range. They have no activity on smooth muscle or blood pressure. These results suggest that contrary to peripheral effects of SP, which are mediated by receptors which recognize the carboxy-terminal part of the SP molecule, certain central actions of SP are mediated by receptors which recognize the amino-terminal part of the SP molecule. SP may be metabolized to this active fragment prior to its action at these receptors.