不同疾病状态下新生儿脑组织氧合变化的对照研究

目的采用近红外光谱测定技术(NIRS)检测新生儿脑组织氧饱和度（rSO2）,探讨不同疾病状态下新生儿脑rSO2的变化规律,为临床应用提供依据。方法2007年4月至2008年10月以无特殊疾病的223名足月儿作为正常组足月儿亚组,于生后3 d内测定脑rSO2;以196例患有可能影响脑氧合疾病的新生儿作为疾病组,在疾病急性期测定脑rSO2。疾病组分为呼吸系统疾病亚组（97例）,分析脑rSO2与PaO2 的关系;循环系统疾病亚组（44例）,分析脑rSO2与心率的关系;脑损伤亚组（55例）,分析脑rSO2与脑血流的关系。结果①疾病组脑rSO2为（56±6）％,显著低于正常组足月儿亚组(P<0.05)。②轻度与重度呼吸系统疾病亚组脑rSO2分别为（60±3）％和（54±6）％,轻度和重度循环系统疾病亚组脑rSO2分别为（59±3）％和（53±6）％,轻度和重度脑损伤亚组脑rSO2分别为（59±3）％和（54±4）％。3个疾病亚组中轻度与重度间脑rSO2差异均有统计学意义(P<0.01)。③呼吸系统疾病亚组脑rSO2与PaO2呈三次方程曲线(y=-62.93+4.75x-0.059x2+0.00024x3)。PaO2≥60 mmHg时,脑rSO2约为62%,脑氧合正常;PaO2<50 mmHg时,脑rSO2<57%,脑组织缺氧。循环系统疾病亚组脑rSO2与心率呈二次方程曲线（y=1.11+0.8241x-0.0027x2）。心率在105~200·min-1时,脑rSO2>58%,脑氧合正常;心率低于105·min-1或高于200·min-1时,脑rSO2<58%,脑组织缺氧。脑损伤亚组脑rSO2<58%时,大脑前动脉血流平均速度代偿性增高,阻力指数偏低,脑损伤较重。结论严重疾病状态下可同时伴有脑组织缺氧。脑rSO2的变化与PaO2、心率及脑血流的变化密切相关。NIRS技术为临床提供了一种可靠的、有价值的脑氧合检测方法,有助于临床直观量化地发现脑组织的缺氧。     

脑源性神经营养因子对新生大鼠缺氧缺血性脑损伤后脑内脂质过氧化物、乳酸水平的影响

目的 探讨脑源性神经营养因子（BDNF）对新生大鼠缺氧缺血性脑损伤后脑内脂质过氧化物（MDA）、乳酸（LA）水平的影响。方法 7d龄大鼠一侧结扎颈总动脉联合代氧吸入形成缺氧缺血性脑损伤,伤后立即向脑室注射BDNF 0.5μg,2h、24h后分别观察其对不同脑区MDA、LA水平的影响。结果 新生大鼠缺氧缺血性脑损伤后不同时间皮层、海马MDA、LA水平均显著升高。给予BDNF后,皮层、海马MDA水平的升高在给药2h和（或）24h部分逆转;给药后24h左右侧海马LA水平的升高也被部分逆转。结论 BDNF具有清除氧自由基作用,使脂质过氧化反应减弱;并在一定程度上改善脑组织的能量代谢状况,有利于脑损伤的恢复。     

碱性成纤维细胞生长因子对新生鼠缺氧缺血性脑损伤的保护作用

目的研究碱性成纤维细胞生长因子（bFGF）对新生鼠缺氧缺血性脑损伤（HIBD）的保护作用。方法7日龄新生Wistar大鼠96只,制备HIBD模型,随机分为生理盐水对照组和bFGF治疗组;另取48只为假手术组。通过免疫组化方法检测三组大鼠（每组40只）不同时点（术后第4、7、10、17、24天）海马CA1区巢蛋白（Nestin）、生长相关蛋白（GAP-43）的表达。各组余8只大鼠于生后30d开始进行Morris水迷宫测试,观察其学习记忆功能。结果（1）Nestin表达：对照组术后第4、7、10、17、24天Nestin阳性细胞数（9．51±1．45、11．35±1．87、17．124-2．13、11．17±1．11、2．92±1．02）较假手术组（6．17±1．85、4．92±1．88、3．75±1．22、3．08±1．20、2．83±1．12）增加,治疗组各时点Nestin阳性细胞数（14．83±1．75、19．17±1．69、24．50±1．45、28．33±1．67、16．17±1．69）增加较对照组更明显,三组各时点比较差异有统计学意义（P〈0．01）。（2）GAP-43表达：三组新生鼠GAP-43表达均于术后第10天达高峰,积分光密度值对照组术后第4、7、10、17、24天（9．35±1．10、12．94±1．01、14．29±1．21、13．28±1．26、6．51±0．99）较假手术组（7．88±1．27、11．75±1．30、13．06±1．54、11．79±1．18、4．66±0．91）均升高,治疗组（10．63±1．02、13．98±0．79、15．11±0．89、14．60±1．28、7．40±1．08）升高更明显,三组各时点比较差异有统计学意义（P〈0．01）。（3）对照组逃避潜伏期（51．75±11．27s）较治疗组（40．32±11．48s）和假手术组（36．58±10．83s）明显延长（P〈0．05）;对照组拆除平台后跨越平台的次数（2．34±2．42次）较治疗组（5．08±3．86次）和假手术组（7．03±3．62次）明显减少（P〈0．05）;治疗组与假手术组比较,差异无统计学意义（P〉0．05）。结论（1）新生鼠HIBD后海马CA1区Nestin、GAP-43的表达增加,可能与脑损伤后神经再生和轴突重塑有关;（2）bFGF可明显改善大鼠HIBD后的学习记忆能力;（3）外源性bFGF可增强新生鼠脑缺氧缺血后损伤区Nestin、GAP-43的表达,在神经细胞损伤的修复中发挥一定的保护作用。     

神经营养素3及神经干细胞联合移植治疗实验性大鼠缺氧缺血性脑损伤

目的研究神经营养素3（NT-3）及神经干细胞联合移植对缺氧缺血性脑损伤（HIBD）大鼠神经功能恢复及神经干细胞分化为神经元的比例的影响,并探讨其可能机制。方法取新出生的24h内的wistar大鼠,从海马中分离神经细胞,进行培养、鉴定。用出生7d的wistar新生大鼠制作缺氧缺血性脑损伤的动物模型,模型成功后7d进行移植。将实验大鼠随机分为5组：正常组、模型组、假移植组、神经干细胞移植组、NT-3及神经干细胞联合移植组（简称联合移植组）,每组12只。移植部位为损伤同侧侧脑室。移植后4周进行功能实验,取脑组织进行免疫组化及免疫荧光检查。结果从新生鼠海马中成功培养出神经干细胞,培养条件下呈悬浮状态生长,形成神经球,绝大多数的细胞表达神经干细胞的标志物神经巢蛋白（nestin）。说明培养的细胞大部分为神经干细胞,细胞纯度达90％以上。Y迷宫实验结果：神经干细胞移植组平均（163±11．6）次学会,记忆的平均正确率为（50±13．3）％;神经干细胞（NSC）＋NT-3联合移植组平均（117．27±11．04）次学会,记忆的正确率平均（63±11．2）％。握持牵引实验结果：神经干细胞移植组平均（30．1±11．8）s,右下肢能放置的占40％;NSC＋NT-3联合移植组平均（40．64±10．6）s,右下肢能放置的占72．73％。斜坡实验结果：神经干细胞移植组平均（20．3±8．25）;NSC＋NT-3联合移植组平均（12．9±5．15）s。说明接受NT-3及神经干细胞移植组大鼠的学习能力、记忆能力及肢体功能与单纯神经干细胞移植组相比有明显提高,差异具有统计学意义（P〈0．05）。其神经干细胞分化成神经元的比例（50％）与单纯神经干细胞移植组（30％）比有明显增多。结论NT-3与神经干细胞联合移植能提高缺氧缺血性脑损伤大鼠的学习、记忆能力和肢体功能,并能提高神经干细胞向神经元转化的比率,NT-3和神经干细胞联合移植较单独神经干细胞移植对缺氧缺血性脑损伤有更好的治疗效果。     

低体积分数氧预处理对缺氧缺血性脑损伤新生大鼠海马区脑红蛋白变化的影响

目的观察低体积分数氧（低氧）预处理对缺氧缺血性脑损伤（HIBD）新生大鼠脑红蛋白（NGB）变化的影响，探讨低氧预处理与NGB的关系。方法随机将出生7d Wistar大鼠110只分为3组：假手术组（n=10）、HIBD组（n=50）、低氧预处理后HIBD组（n=50），HIBD组和低氧预处理后HIBD组在模型建立后1、5、15、30和60min各个时间点再分为5个亚组。采用双侧颈总动脉结扎的方法建立HIBD模型，应用反转录-聚合酶链反应（RT-PCR）和免疫组织化学方法检测在低氧预处理干预下脑缺氧缺血后NGB mRNA及蛋白质在不同时间的表达量。结果RT-PCR半定量分析：HIBD组NGB mRNA在1、5min时相对表达量均显著高于假手术组（Pa〈0．05）；15、30和60min表达下降，与假手术组比较无统计学意义（Pa〉0．05）。与HIBD组比较，低氧预处理后HIBD组1、5min NGB mRNA相对表达量增加，15、30和60min下降，但差异均无统计学意义（Pa〉0.05）。免疫组织化学结果显示低氧预处理后HIBD组海马区域NGB在1、5、15、30和60min平均吸光度（195．0&#177;11．26，202．41&#177;12．20，182．60&#177;15．72，178．22&#177;14．37，164．86&#177;28．99）与HIBD组（195．59&#177;11．59，201．40&#177;13．61，178．09&#177;18．92，173．75&#177;14．30，163．45&#177;18．66）比较无统计学意义（Pa〉0．05）。结论低氧预处理对新生大鼠的脑保护作用可能与NGB的变化关系不大。     

未成熟大鼠缺氧缺血性脑白质损伤中F-actin及RhoA变化

目的研究丝状肌动蛋白（filament actin,F-actin）和RhoA在未成熟大鼠缺氧缺血（hypoxic-ischemia,HI）性脑白质损伤（white matter damage,WMD）中的变化,探讨两者作用及可能存在的关系。方法2日龄SD大鼠（n=184只）随机分为14组：7个时段WMD组（HI后12、24、48、72h,7、14、28d）和7个相应时段对照组。采用Back方法制作WMD动物模型。HE染色观察脑组织病理学变化,电镜观察超微结构改变。采用荧光免疫组织化学方法（n=80只）和实时荧光定量PCR（n=80只）分别观察HI后12、24、48、72h,7d脑组织中F—actin和RhoA的变化。结果（1）光镜和透射电镜检查脑组织,符合WMD的病理及超微结构也改变。（2）WMD组胞膜荧光染色不连续细胞百分比与对照组相比明显增高（P〈0．05）,WMD组分别为0．32±0．04,0．43±0．04,0．56±0．03,0．65±0．04,0．87±0．03;对照组为0．02±0．01,0．02±0．01,0．01±0．01,0．02±0．01,0．02±0．01。（3）WMD组RhoAmRNA表达在HI后12、24、48、72h均明显高于对照组（P〈0．05）,WMD组分别为1．205,2．415,4．830,1．500;对照组为0．300,0．375,0．375,0．530。HI后7dWMD组RhoAmRNA表达接近对照组（P〉0．05）。结论（1）2日龄未成熟大鼠WMD模型建立成功。（2）HI后,F-actin在细胞内分布发生变化：细胞膜上分布减少,胞浆中分布增高,该变化可能与神经细胞生长锥的塌陷和回缩有关。（3）WMD中RhoA可能在一定程度上参与了F-actin分布表达的变化,但并不是影响F-actin的惟一因素。     

氧化应激在新生大鼠常压高体积分数氧致脑损伤发生中的作用

目的探讨氧化应激在7日龄新生大鼠高体积分数氧（高氧）性脑损伤发生中的作用。方法体质量12～18g的7日龄SD大鼠42只，随机分为空气组和高氧组。高氧组与其乳母一起置于氧箱中，调节氧流量（3L／min），使箱内氧体积分数维持（800&#177;50）mL／L，用数字式测氧仪进行监测。空气组置于同一室内空气中，氧体积分数为210mL／L，饲养条件与高氧组相同。高氧／空气开始暴露30min后，各取3只大鼠，麻醉后采血，行动脉血气分析。高氧／空气暴露12h后2组大鼠各处死8只，化学比色法检测其脑组织还原型谷胱甘肽（GSH）、氧化型谷胱甘肽（GSSG）、GSSG／GSH、超氧化物歧化酶（SOD）、丙二醛（MDA）水平。高氧／空气暴露12h后2组各处死10只大鼠，取其脑组织常规脱水、包埋、切片（经海马），脱氧核糖核苷酸末端转移酶介导的原位缺口末端标记法观察脑组织细胞凋亡指数。结果空气组平均动脉血氧分压[pa（O2）]为（87．0&#177;2．71）mmHg（1mmHg=0．133kPa），高氧组为（219．0&#177;10．7）mmHg，高氧组明显高于空气组[（87．0&#177;2．71）mmHg]（P〈0．05）。高氧组暴露12h脑细胞凋亡指数[（39．20&#177;7．59）％]较空气组[（4．50&#177;1．87）％]显著增加（P〈0．01）。高氧暴露12h组GSH[（0．994&#177;0．230）μmol／g]较空气组[（1．210&#177;0．210）μmoL／g]明显下降（P〈0．05），高氧组暴露12h SOD[（124．60&#177;4．14）&#215;10^3 U／g]也较空气组[（145．0&#177;6．62）&#215;10^3 U／g]明显下降（P〈0．01）；高氧组GSSG[（0．0283&#177;0．0043）μmol／g]、GSSG／GSH（0．0296&#177;0．0045）、MDA[（5．21&#177;0．41）μmol／g]均较空气组[（0．0212&#177;0．0029）μmol／g，0．0181&#177;0．0031，（4．85&#177;0．25）μmol／g]显著升高（Pa〈0．05）。结论常压高氧可引起新生大鼠脑细胞的凋亡及氧化应激，氧化应激与高氧性脑损伤密切相关。     

长程服用苯巴比妥、氯硝安定、丙戊酸和托吡酯对未成熟脑发育影响的实验研究

目的探讨治疗血浓度下常用抗癫痫药（AEDs）对未成熟脑损伤的可能性。方法160只健康sD大鼠,幼鼠与成年鼠各80只。以AEDs血浓度达到临床治疗稳态血浓度为实验剂量,设立健康7日龄幼鼠及2月龄成年SD大鼠氯硝安定（CZP）、苯巴比妥（PB）、丙戊酸钠（VPA）、托吡酯（TPM）给药组及正常对照组。每一给药组又分为2周短程及5周长程给药组,每组8只。停药当天称取体重及脑重,尼氏染色及电镜观察脑组织病理改变,ELISA法测定血清神经元特异性烯醇化酶（NSE）含量,免疫组化检测Bcl-2、Bax蛋白表达,原位末端标记法（TUNEL）检测凋亡细胞。结果（1）短程PB给药幼鼠血清NSE浓度[（8．84±2．10）nmol／L]较正常对照[（6．27±1．27）nmol／L]高,差异有统计学意义（P〈0．01）;（2）长程CZP及PB组幼鼠脑重较对照明显减轻,额叶皮层神经细胞减少,神经元超微结构明显异常,血清NSE浓度[分别为（8．15±1．67）nmol／L及（8．07±1．27）nmol／L]较对照[（6．02±1．20）nmol／L]高,差异有统计学意义（P〈0．01）,Bax蛋白表达强于正常对照组（P〈0．01）,TUNEL染色阳性细胞较对照组多。结论治疗血浓度下4种AEDs中,PB、CZP可引起发育中脑组织明显而持久的组织学损伤及神经元坏死与过度凋亡。     

孕酮对缺氧缺血性脑病新生大鼠皮层和海马神经元凋亡及一氧化氮水平的影响

目的探讨孕酮对HIE新生大鼠皮层和海马组织神经元凋亡率及一氧化氮（NO）水平的影响。方法7日龄新生Wistar大鼠30只随机分为3组：假手术组、缺氧缺血（HI）组和药物预防组。HI组和药物预防组动物先行左侧颈总动脉结扎术,置37℃恒温的密闭容器中,以1.5L/min的速度吸入80mL/L氧气和920mL/L氮气混合气体2.5h,建立HIE动物模型。假手术组仅分离左侧颈总动脉,不结扎,亦不做缺氧处理。药物预防组大鼠于建立模型前30min按8mg/kg腹腔注射0.5g/L孕酮溶液,假手术组和HI组注射同等量的9g/L盐水,24h后处死动物,采用流式细胞仪检测其皮层和海马神经元凋亡情况,硝酸还原酶法检测其NO水平的变化。结果HI组大鼠皮层和海马组织神经元凋亡率分别为（10.09&#177;0.36）%、（12.32&#177;0.28）%,明显高于假手术组[（2.49&#177;0.23）%、（2.58&#177;0.26）%]（Pa〈0.01）,药物预防组大鼠皮层和海马组织神经元凋亡率为（3.47&#177;0.32）%、（4.56&#177;0.30）%,明显低于HI组（Pa〈0.05）。HI组大鼠皮层和海马组织NO水平分别为（51.36&#177;9.71）μmol/L、（52.34&#177;4.26）μmol/L,明显高于假手术组水平[（18.16&#177;6.24）μmol/L、（19.28&#177;3.58）μmol/L）]（Pa〈0.01）,药物预防组大鼠皮层和海马组织NO水平为（33.47&#177;8.02）μmol/L、（32.57&#177;4.27）μmol/L,明显低于HI组（Pa〈0.05）。结论孕酮通过降低新生大鼠HI时皮层和海马组织神经元凋亡率和NO水平,拮抗神经元凋亡发挥对缺氧缺血性脑损伤的保护作用。     

新生儿局部脑组织氧检测的多中心研究

目的 探讨近红外光谱测定技术(near-infrared spectroscopy,NIRS)检测新生儿局部脑组织氧饱和度(Regional oxygen saturation,rSO2)对评估脑氧合状态的价值,建立新生儿脑rSO2的测定值,为临床应用提供依据.方法 采用NIRS技术对无特殊疾病的223例足月儿和95例早产儿分别在生后第1天、第2天及第3天进行脑rSO2测定,选取102例患有影响脑氧合疾病的新生儿,对照两组间脑rSO2数值差异.同步分析脑rSO2与脉搏氧饱和度(pulse oxygen saturation,SpO2)及动脉血氧饱和度(arterial oxygen saturation,SaO2)间的关系.结果 (1)正常足月新生儿脑rSO2测定值为(62±2)%,以低于两个标准差作为脑rSO2测定值异常,可以认为低于58%提示为脑组织缺氧.疾病状态新生儿脑rSO2范围(55±7)%,与无特殊疾病新生儿组差异有统计学意义(P<0.05).(2)脑rSO2与经皮SpO2及SaO2呈正相关,直线相关系数r分别为0.74和0.71.(3)特殊的疾病状态下,脑rSO2与SpO2可出现不同步的变化趋势,表现为:①spO2尚正常,而脑rSO2已降低.体现在18例严重的颅脑疾病及血红蛋白较低的病例.②一些危重病儿病情恢复过程中,脑rSO2的恢复滞后于SpO2在6例多脏器功能衰竭患儿尤为突出.③在3例重度缺氧缺血性脑损伤(HIE)急性期,脑rSO2有异常增高现象.结论 正常足月新生儿脑rSO2测定值为(62±2)%,低于58%提示脑组织缺氧.NIRS技术客观反映了脑组织的氧合变化,可为临床应用提供依据.     

Impact of norepinephrine and fluid on cerebral oxygenation in experimental hemorrhagic shock

Few data exist regarding resuscitation of hypovolemic shock in infants, and alternative strategies such as vasopressor therapy merit further evaluation. However, the effects of norepinephrine on cerebral perfusion and oxygenation during hemorrhagic shock in the pediatric population are still unclear. Eight anesthetized piglets were subjected to hypotension by blood withdrawal of 25 mL/kg. Norepinephrine was titrated to achieve baseline mean arterial blood pressure (MAP), and cerebral oxygenation was determined by brain tissue Po2 (Ptio2) and near-infrared spectroscopy-derived tissue oxygen index (TOI). Then, norepinephrine was stopped, MAP was allowed to decrease again below 30 mm Hg, and shed blood was retransfused. During hemorrhage, TOI dropped from 69+/-3 to 59+/-3%, and Ptio2 from 29+/-6 to 13+/-1 mm Hg (mean+/-SEM; p<0.001). Following norepinephrine, cerebral perfusion pressure (CPP) could be restored immediately, whereas TOI and Ptio2 did not increase significantly. In contrast, following retransfusion, TOI and Ptio2 increased to 68+/-3% and 27+/-7 mm Hg reaching baseline values, respectively. In conclusion, while norepinephrine increased CPP immediately, cerebral oxygenation as reflected by TOI and Ptio2 could not be improved by norepinephrine, but only by retransfusion.     

Effect of therapeutic dose of indomethacin on the cerebral circulation of newborn pigs

The effects of treatment with 0.2 mg/kg of indomethacin on the cerebral blood flow and cerebral oxygen consumption of hypotensive, unanesthetized, newborn pigs were investigated. Hypotension was induced by hemorrhage (30 ml/kg) which reduced mean arterial pressure from 60 to 34 mm Hg. The decline in cerebral vascular resistance that occurred with hemorrhage allowed blood flow to all brain regions and cerebral oxygen consumption to continue unchanged. Treatment with 0.2 mg of indomethacin decreased plasma 6-keto-prostaglandin F1 alpha markedly and caused a modest increase in cerebral vascular resistance from 0.75 +/- 0.07 to 0.85 +/- 0.02 mm Hg X 100 g X min/ml at 40 min posttreatment. As a result, blood flow throughout the brain fell about 20%. Similarly, cerebral oxygen consumption declined from 2.88 +/- 0.13 to 2.03 +/- 0.21 ml O2/100 g X min following treatment of hypotensive piglets with 0.2 mg/kg of indomethacin. However, all piglets were conscious 40 min after treatment. We conclude that, although 0.2 mg/kg of indomethacin affects cerebral hemodynamics of hypotensive piglets, the effects are very modest in comparison to large increases in cerebral vascular resistance, decreases in cerebral blood flow and oxygen consumption, and coma that follow treatment of hypotensive piglets with 5 mg/kg of indomethacin.     

Randomized trial of volume infusion during resuscitation of asphyxiated neonatal piglets

Despite its use, there is little evidence to support volume infusion (VI) during neonatal cardiopulmonary resuscitation (CPR). This study compares 5% albumin (ALB), normal saline (NS), and no VI (SHAM) on development of pulmonary edema and restoration of mean arterial pressure (MAP) during resuscitation of asphyxiated piglets. Mechanically ventilated swine (n=37, age: 8 +/- 4 d, weight: 2.2 +/- 0.7 kg) were progressively asphyxiated until pH <7.0, Paco2 >100 mm Hg, heart rate (HR) <100 bpm, and MAP <20 mm Hg. After 5 min of ventilatory resuscitation, piglets were randomized blindly to ALB, NS, or SHAM infusion. Animals were recovered for 2 h before euthanasia and lung tissue sampled for wet-to-dry weight ratio (W/D) as a marker of pulmonary edema. SHAM MAP was similar to VI during resuscitation. At 2 h post-resuscitation, MAP of SHAM (48 +/- 13 mm Hg) and ALB (43 +/- 19 mm Hg) was higher than NS (29 +/- 10 mm Hg; p=0.003 and 0.023, respectively). After resuscitation, SHAM piglets had less pulmonary edema (W/D: 5.84 +/- 0.12 versus 5.98 +/- 0.19; p=0.03) and better dynamic compliance (Cd) compared with ALB or NS (Cd: 1.43 +/- 0.69 versus 0.97 +/- 0.37 mL/cm H2O, p=0.018). VI during resuscitation did not improve MAP, and acute recovery of MAP was poorer with NS compared with ALB. VI was associated with increased pulmonary edema. In the absence of hypovolemia, VI during neonatal resuscitation is not beneficial.     

Intrauterine growth restriction ameliorates the effects of gradual hemorrhagic hypotension on regional cerebral blood flow and brain oxygen uptake in newborn piglets

Data are scant regarding the development of cerebrovascular autoregulation in intrauterine growth-restricted (IUGR) newborns. We tested the hypothesis that IUGR improves the ability of neonates to withstand critical periods of gradual hemorrhagic hypotension by optimizing cerebrovascular autoregulation. Studies were conducted on 1-d-old anesthetized piglets divided into groups of normal weight (NW, n = 14, body weight = 1518 +/- 122 g) and IUGR (n = 14, body weight = 829 +/- 50 g) animals. Physiologic parameters, including regional cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO(2)), were similar in NW and IUGR piglets under baseline conditions. Controlled arterial blood loss [hemorrhagic hypotension (HH)] induced a stepwise reduction of the mean arterial blood pressure of 49 +/- 3 mm Hg (mild HH), 39 +/- 3 mm Hg (moderate HH), and 30 +/- 3 mm Hg (severe HH) in seven NW and seven IUGR piglets (p < 0.05). In NW piglets, cortical CBF and CMRO(2) was reduced already at moderate HH (p < 0.05). A similar CMRO(2) reduction occurred during severe HH in NW and IUGR piglets (p < 0.05). In addition, during mild and moderate HH, primarily in IUGR piglets, an increase in regional CBF of brainstem, cerebellum, and thalamus was shown compared with baseline values (p < 0.05). Furthermore, under these conditions, cerebral cortex blood flow was maintained in newborn IUGR animals. In contrast, NW piglets exhibited a significant reduction in CBF (p < 0.05) during moderate HH. Thus, IUGR resulted in an improved ability to withstand critical periods of gradual oxygen deficit as shown by improved cerebrovascular autoregulation during hemorrhagic hypotension.     

Effect of sympathetic nerve stimulation on cerebral blood flow in newborn piglets

The purpose of this study was to determine the effect of sympathetic nerve stimulation on regional cerebral blood flow during the first 3 wk of postnatal development in piglets. Forty-one piglets ranging in age from 2 to 24 days were studied while anesthetized with 30% N2O, paralyzed and mechanically ventilated (PaCO2 = 35-40 mm Hg). Regional cerebral blood flow was measured with tracer microspheres (15 +/- micron) during electrical stimulation (15 Hz, 15 V, 3 ms) of the right cervical sympathetic trunk. Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum (gray and white matter) (-15 +/- 2%), hippocampus (-9 +/- 2%), choroid plexus (-50 +/- 5%), and masseter muscle (-93 +/- 2%) compared to the contralateral side where blood flow to these regions was 74 +/- 4, 45 +/- 2, 258 +/- 26, and 24 +/- 4 ml/min/100 g, respectively (mean +/- SEM; p less than or equal to 0.05). The magnitude of the reduction in cerebral blood flow was not dependent on postnatal age as no significant differences were noted when the piglets were grouped according to age. Hypercapnia (PaCO2 = 64 +/- 5 mm Hg) increased blood flow 2- to 4-fold above control in all brain regions except the choroid plexus. The effect of sympathetic nerve stimulation was augmented during hypercapnia where blood flow to the ipsilateral cerebrum, hippocampus, and caudate nucleus was decreased by -34 +/- 4, -23 +/- 5, and -16 +/- 3%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of moderate hypocapnic ventilation on nuclear DNA fragmentation and energy metabolism in the cerebral cortex of newborn piglets

Previous studies have shown that severe hypocapnic ventilation [arterial carbon dioxide partial pressure (PaCO(2)) 7-10 mm Hg] in newborn animals results in decreased cerebral blood flow and decreased tissue oxidative metabolism. The present study tests the hypothesis that moderate hypocapnic ventilation (PaCO(2) 20 mm Hg) will result in decreased cerebral oxidative metabolism and nuclear DNA fragmentation in the cerebral cortex of normoxemic newborn piglets. Studies were performed in 10 anesthetized newborn piglets. The animals were ventilated for 1 h to achieve a PaCO(2) of 20 mm Hg in the hypocapnic (H) group (n = 5) and a PaCO(2) of 40 mm Hg in the normocapnic, control (C) group (n = 5). Tissue oxidative metabolism, reflecting tissue oxygenation, was documented biochemically by measuring tissue ATP and phosphocreatine (PCr) levels. Cerebral cortical nuclei were purified, nuclear DNA was isolated, and DNA content was determined. DNA samples were separated, stained, and compared with a standard DNA ladder. Tissue PCr levels were significantly lower in the H group than the C group (2.32 +/- 0.66 versus 3.73 +/- 0.32 micromol/g brain, p < 0.05), but ATP levels were preserved. Unlike C samples, H samples displayed a smear pattern of small molecular weight fragments between 100 and 12,000 bp. The density of DNA fragments was eight times higher in the H group than the C group, and DNA fragmentation varied inversely with levels of PCr (r = 0.93). These data demonstrate that moderate hypocapnia of 1 h duration results in decreased oxidative metabolism that is associated with DNA fragmentation in the cerebral cortex of newborn piglets. We speculate that hypocapnia-induced hypoxia results in increased intranuclear Ca(2+) flux, which causes protease and endonuclease activation, DNA fragmentation, and periventricular leukomalacia in newborn infants.     

Internal jugular venous oxygen saturation does not reflect sagittal sinus oxygen saturation in piglets

Can blood samples from the internal jugular vein (IJ) be used reliably in place of sagittal sinus (SS) samples in the calculation of cerebral oxygen extraction? To test this question we compared the O2 saturation (Sat) of blood samples drawn from SS, IJ vein, and pulmonary artery (MV) during hypercarbia, eucarbia and hypocarbia in 7 paralyzed, ventilated piglets. Cerebral blood flow was assessed by measuring unilateral internal carotic artery blood flow (ICABF), determined by an electromagnetic flow probe placed around the common carotid artery after ligation of the external carotid artery. During hypocarbia, eucarbia and hypercarbia SatSS (37.3 +/- 9.3, 48.9 +/- 10.2, 70.8 +/- 11.8%, respectively) was significantly different from SatIJ (54.8 +/- 8.9, 54.5 +/- 9.0, 62.0 +/- 15.1%) and SatMV (55.9 +/- 5.5, 58.7 +/- 5.3, 53.5 +/- 11.2%). The mean slope of the SatSS vs. PaCO2 regression lines was +0.583 +/- 0.303%/mm Hg, significantly greater than the mean slope of the regression lines for SatIJ vs. PaCO2 (+0.087 +/- 0.310%/mm Hg) or SatMV vs. PaCO2 (-0.112 +/- 0.230%/mm Hg). The relationship of ICABF vs. PaCO2 (mean slope = 0.444 +/- 0.294 ml/min/mm Hg) was statistically significant, while the relationship of cardiac output (determined by an electromagnetic flow probe placed around the pulmonary artery) vs. PaCO2 (mean slope = 0.470 +/- 1.617 ml/min/mm Hg) was not. We conclude that blood samples from the IJ do not reliably reflect cerebral venous blood and cannot be substituted for SS samples in piglets. It is most probable that the substitution of IJ for SS blood is not valid in piglets because the IJ receives venous effluent from noncerebral tissue.     

Nitration of Bax and Bcl-2 proteins during hypoxia in cerebral cortex of newborn piglets and the effect of nitric oxide synthase inhibition.

Previous studies have shown that cerebral tissue hypoxia results in increased expression of Bax protein, thereby altering the ratio of Bax to Bcl-2 or formation of Bax/Bcl-2 heterodimer. Hypoxia also induces the generation of nitric oxide free radicals in the cerebral cortex of newborn animals. The present study tests the hypothesis that tissue hypoxia will result in nitration of Bax and Bcl-2 proteins in the neuronal nuclei of newborn piglets. Studies were performed in 22 piglets, 3-5 days old, divided into normoxic (n = 7), hypoxic (n = 9) and hypoxic + NNLA (n = 6) groups. Hypoxia was induced by decreasing the FiO(2) (5-7%) for 60 min and cerebral hypoxia documented by determining tissue ATP and phosphocreatine (PCr) levels. The density of protein bands was expressed as absorbance (OD x mm(2)). PCr levels were 3.03 +/- 0.85 micromol/g brain in the normoxic group and 0.88 +/- 0.32 micromol/g brain in the hypoxic group (p < 0.001 vs. normoxia) and 0.55 +/- 0.13 (p < 0.001 vs. normoxia) in the NNLA-treated hypoxic group. There was increased nitration of Bax protein in hypoxic neuronal nuclei as compared to normoxic and NNLA-treated-hypoxic group nuclei: 211.61 +/- 25.93 versus 124.8 +/- 14.88 and 133.86 +/- 7.42 OD x mm(2), respectively (p < 0.001 vs. normoxia). Nitration of Bcl-2 was not altered significantly in either group. We conclude that there is increased nitric oxide-mediated nitration of Bax in cortical neuronal nuclei during hypoxia and that this increase correlates inversely with the decrease in tissue energy levels. We speculate that, during hypoxia, nitration of Bax and Bcl-2 proteins may regulate heterodimer formation and activation of programmed cell death mechanisms.     

早期高压氧治疗对缺氧缺血性脑损伤新生大鼠的远期保护作用

目的：高压氧(hyperbaricoxygen,HBO)在缺氧缺血性脑损伤(hypoxic-ischemicbraindamage,HIBD)中的应用及疗效仍存在争议。至目前为止,HBO在新生动物HIBD中的实验研究不多,这些实验注重近期病理和生化结果的评价,缺乏远期功能评价指标。该实验评价早期HBO治疗对HIBD新生大鼠远期脑病理和行为的影响。方法：7日龄大鼠随机分为对照组(n=18)、HIBD组(n=17)和HBO组(n=17,HIBD后0.5~1h开始2个绝对大气压HBO治疗,稳压30min/次,每日1次,共2d),以大鼠37~41日龄的学习记忆功能(Morris水迷宫实验)和42日龄的脑形态组织学(脑重量、海马CA1区存活神经元数、AchE纤维面积和NOS神经元数)来判断干预效果。结果：HIBD组学习记忆功能严重不良伴有脑形态组织学的明显缺损,与对照组比较水迷宫实验的平均逃逸潜伏期(EL)延长(56.35±22.37svs23.07±16.28s);搜索时间和搜索距离缩短(29.29±6.06svs51.21±4.59s)和(548±92cmvs989±101cm),左脑重量减轻(0.601±0.59gvs0.984±0.18g);CA1区存活神经元数减少(100±27个/mmvs183±8个/mm);AchE纤维面积减少(18.50±2.24)%vs(27.50±2.18)%,NOS神经元数减少(19.25±4.33个/mm2vs33.75±5.57个/mm2)以上两组比较均P<0.05。HBO组学习记忆功能不良改善,脑形态组织学缺损减轻,与对照组比较差异有显著性,EL为39.17±21.20s;搜索时间为36.84±4.36s;搜索距离686±76cm;脑重量0.768±0.85g;存活神经元数133±25个/mm;AchE纤维面积(21.94±2.73)%(均P<0.05)。结论：早期HBO治疗在一定程度上改善了HIBD所引起的学习记忆功能不良并减轻了HIBD所导致的远期脑形态组织学缺损。