This research was supported by National Heart, Lung, and Blood Institute Grant HL-093113.

1.振荡下体负压（OLBNP） <ol><li>设备安装<ol><li>心电图导联II（ECG）:粘贴三个（或更多）的电极对被检者的躯干对心脏速率的整个研究过程中监测。 </li><li>氯丁橡胶裙:使用定制的氯丁橡胶裙密封的主题为下体负压室至髂嵴。把它围绕受验者的胸部它们被放置在仰卧罐之前，确保ECG信号仍然是足够的。确保它是温暖的，但不是那么严格，限制呼吸。 </li><li>下体负压室:有在床上的主题仰卧和操纵下体负压室它们的下面。如果下体负压室具有可调节车座（以尽量减少运动伪影没有抵消吸力的作用），确保在它的主题是坐在舒适。使用定制的有机玻璃隔板下调至主体的WAIST尺寸，以帮助密封所述腔室。密封围绕下体负压室用胶带氯丁橡胶裙子。 </li><li>下体负压腔压力:在下体负压腔连接到标准的压力传感器。校准压力传感器，以毫米汞柱。 </li><li>重复循环定时器附机械阀:将内置机械阀和重复循环定时器的下体负压室的习俗。 注:连接到两台电机控制的机械阀A延时继电器用负压和环境压力之间交替。延时继电器交替电压施加到电动机以固定的时间间隔来打开和关闭的腔室和真空之间的阀。这将创建一个下体负压腔的压力波形大致是方波的形状。调节循环时间为所需OLBNP频率。 </li><li>变变压器及真空:将一个标准的家用真空吸尘器的机械阀。堵塞真空成可变变压器，其允许电压施加到真空被控制。打开真空吸尘器，并调整可变变压器，直到目标下体负压压力（ 例如，30毫米汞柱）的实现。 </li><li>动脉血压:附加的非侵入性的光体积描记动脉压箍（ 例如 ，Portapres，Finapres）至一只手的手指（多个）。通过从相对的臂肱动脉比较压力示波压力保证测量精度。 </li><li> 2 MHz的经颅多普勒超声探头及固定装置<ol><li>使用2 MHz的脉冲多普勒探头受超声波大脑中动脉M1段在寺庙（ 即颞部窗口）。 </li><li>改变探测角，声波作用深度（〜55 MM），增益和发射功率，以最大化信号的光谱强度。 </li><li>使用固定装置有没有回来（ 即不是一个头带），使运动伪影不引入信号作为志愿者招解决多普勒探头到位s的负压力振荡。 注意:脑血流量可单侧或双侧来衡量，但在脑自动调节无差别预计半球之间，除非像中风或脑外伤局部损伤是目前20 </li></ol></li><li>过期的CO 2:使用附连到红外的CO 2分析仪鼻插管以监测过期的CO 2，并指示受试者对呼吸仅通过他们的鼻子。鉴于深远的影响动脉血二氧化碳对脑血流，21显示器CO 2遍布每一个研究。 </li></ol></li><li>数据采集<ol><li>设置模拟到动脉压，脑血流量，下体负压腔压力的数字转换，并且过期的CO 2，以获得至少为每信道50赫兹。收购心电图在1 kHz。 注意:虽然随后的分析处理低得多的频率信息（≤0.07赫兹）时，它是Critical监视的信号的质量的研究过程中被获得的。为50赫兹的采样速率将允许血压和脑血流量为伪像的检测的准确的可视化。 </li></ol></li><li>振荡下体负压协议<ol><li>打开真空并确保油箱压力稳定在-30毫米汞柱。 </li><li>设置重复周期定时器33秒，0.03赫兹OLBNP。 </li><li>调整多普勒探头（S），以确保最佳的信号。 </li><li>采集数据至少15个周期（500秒0.03赫兹），以确保有足够的信心PPR估计。如果时间允许，收集比这更多的数据，因为它会进一步提高信噪比。 </li><li>通过改变重复周期计时器的持续时间重复0.03赫兹，0.08赫兹之间的任何频率的上述步骤。 注:适用于以频率，但随机地改变主体之间的起始频率。 </li></ol></li></ol> 2.投影寻踪回归（PPR） <ol><li>数据预处理<ol><li>抽取和低通滤波<ol><li>打开Matlab的。键入命令"数据=重采样（数据，1，SR / 5）"（其中SR是原始采样率）的动脉压和脑血流量抽取5赫兹。 注意:任选地，低通滤波器（19 阶切比雪夫型II）与0.4 Hz的截止。过滤是多余的，因为后续的处理，而造成平均波形不依赖于峰值检测有时嘈杂的动脉压及脑血流信号。 </li></ol></li><li>神器去除<ol><li>使用原非抽取波形为指导，消除信号中的任何部分与文物和线性插值。如果这些部分占所述记录期间的10％以上，完全弃去记录。 注意:在这一点上，该波形被适当地处理为传统线性方法，例如传递函数的分析。</li></ol></li><li>带通滤波<ol><li>在Matlab中，键入:[B，A] = cheby1（1,1，[F - 0.005 F + 0.005] /（SRD / 2））的数据= filtfilt（B，A，detrend（数据，"线性"），以波段-pass过滤压力和流量在±0.005赫兹频带（第1次阶切比雪夫I型与通带波纹的1分贝）围绕OLBNP的频率（ 图2），其中F是主导OLBNP频率，SRD是抽取采样率（5赫兹后步骤2.1.1）和"数据"是抽取信号（动脉压或流）。 注意:这最小化潜在的干扰，并增加了信号 - 噪声比在后续的PPR分析。虽然占主导地位的动脉压力波动发生在下体负压的振荡频率，随机噪声中的信号会干扰压力 - 流量关系的推导。结果，而不带通滤波将是定性相似，但百分之方差Ëxplained（ 即，R 2）会较低。19 </li></ol></li></ol></li><li>投影寻踪回归估计 注意:使用内置函数"PPR"R中语言和环境统计计算，和/或经由其它的平台定制编写的函数，产生一个单一的脊功能（M = 1）的动脉压脑流关系。 <ol><li>在Matlab，输入命令"CVLabPPR（压力，流量）"。进入研究ID为XXXYYY，其中XXX为3个字母的代码，研究和YYY是主题ID三个数字字符。请在下面的格式研究日期:YYYY-MM-DD。输入数字测量＃（ 例如，"1"为第1天）。 </li><li>进入APM（进入FP供finapress或AL艺术行）。进入船（MCA，ACA或PCA）。输入"Y"或"N"来​​查询"你有正确的MCA测量？"输入"Y＆＃8221;或"n"来查询"你已离开马华测量？" 注意: <img alt="式（1）" fo:content-width="3in" src="/files/ftp_upload/51082/51082eq1.jpg" width="300" /> 对于每个输入（X 吨 -动脉血压）和输出（Y 吨 -脑血流）线性自回归传递函数（等式1 -括号内的术语）通过非参数的核函数（K m的传递;被称为"脊功能&#39;），其通过最小化均确定方误差。投影寻踪回归可以包括多个脊功能（ 即M&gt; 1）。然而，虽然它会降低平均平方误差，可能掩盖的脊功能的解释，由于它们之间的潜在相互作用。因为其主要目的是要获得动脉压和脑血流量该CA的关系的n为生理学上解释，PPR应当限于仅一个脊功能（M = 1）。 </li><li>分段线性参数。参数脊函数作为用于随后的统计分析（ 图3）的分段线性函数。对于MATLAB，使用布鲁诺陈德良的自由结点样条逼近。输入命令"BSFK（X，Y，K，nknots）"，其中k = 2的线性拟合和nknots = 3为三个区域。 注意:此标识的那些点处的动脉压脑流动关系的变化，以及范围，其中所述关系是近似线性的图3示出了结果的示意图。每个区域内的压力-流量关系的增益（ 即 ，线性斜率）提供脑自动调节的该地区内的效力的量度。较低的增益表明更有效的反调控的压力波动而高收益表示更被动FL流响应压力变化。 </li></ol></li></ol>

<ol>
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L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sympathetic+restraint+of+respiratory+sinus+arrhythmia:+implications+for+vagal-cardiac+tone+assessment+in+humans.">Sympathetic restraint of respiratory sinus arrhythmia: implications for vagal-cardiac tone assessment in humans.</a> Am. J. Physiol. Heart Circ. Physiol. 280, 2804-2814 (2001).</li><li>Aries, M. J., Elting, J. W., De Keyser, J., Kremer, B. P., Vroomen, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebral+autoregulation+in+stroke:+a+review+of+transcranial+Doppler+studies.">Cerebral autoregulation in stroke: a review of transcranial Doppler studies.</a> Stroke. 41, 2697-2704 (2010).</li><li>Rangel-Castilla, L., Gasco, J., Nauta, H. J., Okonkwo, D. O., Robertson, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cerebral+pressure+autoregulation+in+traumatic+brain+injury.">Cerebral pressure autoregulation in traumatic brain injury.</a> Neurosurg. Focus. 25, 7 (2008).</li></ol>

The authors declare that they have no competing financial interests.

精确定义的输入输出关系可以要求输入（在这种情况下，压力）积极跨越足够宽的范围内改变，观察输出响应。然而，自发产生的压力波动幅度非常不一致和小脑自动调节的频率范围内。27，这是在压力和自发流向变化显示具有高相关性周期和极低的相关性周期有关系的原因，并在振荡脑血流量似乎出现，没有明显的动脉压驱动器28 OLBNP 22提供的关键技术，以产生不同的频率和幅度的一致性动脉压力振荡，以评估脑血流响应。虽然可能有其它的方法可能提供类似的探针，这种方法允许在频率和/或幅度依赖关系赌注的严格测试威恩动脉压和脑血流速度。 以前的研究探索电位测量工具为脑自动调节已经使用动脉压和脑血流量（ 例如，传递函数分析）之间的关系的线性模型。压力和流量与无衰减的变化之间的密切的线性关系，观察时的压力振荡是比较快的， 即 &gt;〜10秒。然而，慢振荡（&gt;〜20秒），产生压力之间的关系和流量的逐渐变小线性相关。8,24如果关系不是高度线性相关（低R 2，低交叉谱相干性）可以没有任何信心的线性措施，如传递函数的增益和相位的精度。线性关系的缺乏指示重要的非线性是脑自动调节的特征的存在。事实上，就其本质而言，autoregulati对不适合通过线性方法表征;线性方法可以指示存在自动调节的或不存在，但不能描述其特性和它的有效性。 有迹象表明，比得上在它们的简单的线性方法，但是，可以评估输入（压力）和输出（流动）变量之间的非线性关系的方法。投影寻踪回归是一个简单的非参数，非理论，多元回归方法29,30并不断定一个先验的模型或承担线性输入输出关系。这些都是明显的优势特征是不完全了解一个系统。但是，应该指出的是，使用一个以上的脊功能将增加百分之方差解释，但在模糊特性的关系的生理解释为代价的。因此，建议投影寻踪回归仅限于一脊福nction。尽管如此，与单个脊功能概述在PPR方法可以解释在动脉压和脑血流量之间的关系的方差的显著部和显示特性的非线性关系是不同个体一致。 限制和可能的修改 振荡下体负压需要具体和突兀的设备和程序等不适合临床基础的评估。这可能是静止的足够的长度的记录可以用于脑自动调节的PPR分析提供足够的数据。然而，以往的工作表明，静止数据投影寻踪回归的性能比为0.03赫兹OLBNP数据分析显著恶化。虽然量化在休息期间0.03赫兹OLBNP压力流量的关系是相关的，19的适度通信只是表明，压力流量relationsh估计在休息IPS可能无法可靠地反映这些从0.03赫兹OLBNP而得。一种解决方案可以是生成通过缓慢，深eucapnic呼吸或反复蹲机架机动自动调节的频率范围内保持一致，以及较大的振幅的压力变动。这些方法已被证明产生可靠的大的压力波动，其可以提供跨越一个足够宽的范围内变化时，观察脑血流反应。31,32 虽然平均来说，投影寻踪回归可以解释显著量动脉压和脑流量波动之间的关系，解释差异可能是低在少数情况下（6〜19％）。低性能可以得出，例如，从呼吸型态如果频率和潮气量没有控制。然而，每一个生理测试有一些异常的观察，并且该方法也不例外。在1〜20观察测量差不应该吨削弱该方法的潜在效用。 未来的应用/结论 特性压力-流量关系可以改变在某些病理生理条件，如中风33和外伤性脑损伤。34如果准确关系可以在临床上获得，脑自动调节的投影寻踪回归可以具有更广泛的应用，并作为一种有用评估工具，其中OLBNP不可用。这可能是简单的动作（ 如深呼吸，大腿袖口，坐姿到站姿）和/或持续时间较长的休息录音，可能会导致可起诉派生脑自动调节媲美OLBNP数据压力-流的关系。尽管如此，基于实验室的测定不同的监管制度和他们的自身调节的非线性贡献可以提供独特的见解脑血管的控制，并允许直径灵知病理生理改变的脑自动调节（ 例如 ，脑外伤后）的。

通过该过程脑灌注保持恒定在宽范围内被称为"脑自动调节。"脑潮流响应1的原始观测系统的压力的支承反调节针对变化的动脉压力是非常重要的日常规脑灌注。虽然自动调节的表征是根据持续，控制低渗和高血压的研究，2,3-人们认识到，在耐压力引起的变化是"的振荡过程&#39;3包围的变化从10到90秒。4此外，内过去二十年间，对一个节拍逐拍基础5表明脑流量被调节在周期短短短心脏跳动。-6,7-脑血流速度的测量，这些节拍逐拍的数据表明，有效流缓冲对压力变化发生在因此时段短至〜15秒，它逐渐变得更大在更长的时间段。 如图8所示 ，作为高通滤波器的压力和流量的功能之间的关系，其中7,9-12血压较慢变化被有效地减弱和更快的振荡传递通过相对不受影响。 在表征频率脑自动调节的依存性的主要困难是在围绕感兴趣的频率动脉压缺乏突出自发波动（低于〜0.07赫兹或约15秒）。没有足够大的压力振荡，不能准确地量化脑血流量的响应。我们的实验室已通过使用被称为振荡下体负压（OLBNP）的技术处理该约束。这产生尾静脉血液量的变化成比例的在罐内的负压水平，由于降低了静脉压差。当负PRESSU重新被应用在设定的时间间隔，在中央静脉回流导致血压波动在OLBNP的频率振荡。这种方法已用于在不同的实验室数项研究。8,14-17这产生尾静脉血液量的变化成比例的在罐内的负压水平，由于减少静脉压差。当负压施加在设定的时间间隔，在中央静脉回流振荡导致动脉压力波动在OLBNP的频率。这种方法已用于在不同的实验室数项研究。8,15-18 即使能够产生围绕感兴趣的频率，血压波动显着的方法，还有一个复杂的因素:有非线性的脑自动调节显著的证据，特别是在最低频率8况且，没有强有力的理论指导。以存在于脑自动调节非线性的性质。因此，我们使用一个理论无关，在我们的分析中被称为投影寻踪回归（PPR）驱动数据的方法。19 PPR是一个非参数的方法中固有的系统没有任何先验假设为这些非线性性质的非线性关系进行表征。这是捕捉系统，其生理机能尚未被明确的非线性模型定义了一个决定性的优势。 PPR揭示的特征的非线性脑自动调节的类似于"经典自动调节曲线"首先通过拉森在1959年描述（ 图1）。2,19即，脑血流量保持在一定范围内的压力的动脉内相对恒定的，但被动跟踪以线性方式在该范围之外。这种形状变得更加明显，血压波动变得更慢。因此，线性分析不足以充分interrogaTE脑自动调节和依赖线性技术可能错过重要的信息。 在这篇文章中，我们详细介绍的方法来两个数据采集（实验室用OLBNP）和分析（PPR），我们使用在健康和疾病表征脑自动调节。

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			<td height="22" style="height:22px;width:216px;">Device</td>
			<td style="width:185px;">Company</td>
			<td style="width:119px;">Product</td>
			<td style="width:167px;">Comments</td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Transcranial Doppler Ultrasound</td>
			<td style="width:185px;">Compumedics DWL</td>
			<td style="width:119px;">Multi-Dop X digital</td>
			<td style="width:167px;">&#160;2 MHz probe</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">ECG and Brachial BP</td>
			<td style="width:185px;">GE</td>
			<td style="width:119px;">Dash 2000</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">LBNP Tank</td>
			<td style="width:185px;">U. of Iowa Bioengineering</td>
			<td style="width:119px;"></td>
			<td>Custom Built</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Mechanical Valve</td>
			<td style="width:185px;">U. of Iowa Bioengineering</td>
			<td style="width:119px;"></td>
			<td>Custom Built</td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Repeat Cycle Timer</td>
			<td style="width:185px;">Macromatics</td>
			<td style="width:119px;">TR-50826-07</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:216px;">Pressure Transducer</td>
			<td style="width:185px;">Gould</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="43">
			<td height="43" style="height:43px;width:216px;">Photoplethysmographic finger pressure monitor</td>
			<td style="width:185px;">Finapres Medical Systems</td>
			<td style="width:119px;">Finometer PRO</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">CO2 gas analyzer</td>
			<td style="width:185px;">VacuMed</td>
			<td style="width:119px;">#17515 CO2 Analyzer, Gold Edition</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="64">
			<td height="64" style="height:64px;width:216px;">Data acquisition system</td>
			<td style="width:185px;">AD Instruments</td>
			<td style="width:119px;">Data Acquisition Systems - PowerLab</td>
			<td style="width:167px;"></td>
		</tr>
	</tbody>
</table>

assessing cerebral autoregulation via oscillatory lower body negative pressure and projection pursuit regression

由脑灌注保持恒定在宽范围的系统性压力的过程被称为"脑自动调节"。流对压力变化的有效阻尼发生在周期短至〜15秒，并逐渐变得更大在更长的时间段。因此，在血压较慢变化被有效地减弱和更快的变化或波动通过向脑血流相对不受影响。在表征频率脑自动调节的依存性的主要困难是在围绕感兴趣的频率动脉压缺乏突出自发波动（低于〜0.07赫兹或约15秒）。振荡下体负压（OLBNP）可被用于产生在中央静脉回流振荡导致在动脉压力波动在OLBNP的频率。此外，投影寻踪回归（PPR）提供了一个非参数方法characterizË系统固有的非线性关系，没有一个先验的假设，并显示性能非线性脑自动调节。 OLBNP产生动脉压力较大波动的负面压力振荡的频率变慢;然而，在脑血流的波动逐渐变得更低。因此，在PPR示出以0.05赫兹OLBNP频率和低于（20秒周期）的日益突出自身调节区域。这种方法也允许基于实验室的测定压力与脑流量之间的特性的非线性关系，并且可以提供独特的见解，以综合性脑控制以及生理改变的目标底层证券受损脑自动调节（ 例如 ，创伤性脑损伤，中风后等 ）。

从10毫米汞柱22 OLBNP振幅高达120毫米汞柱17已被用于增加动脉压的波动，但在30毫米汞柱OLBNP足以23,24和不超出cerebrovasculature的调控能力。17 OLBNP结果这种水平在血液中的压力振荡是是约15-20毫米汞柱的大小在0.03赫兹，这是不大于从就座要站立时发生的血压变化更大。25有一些限制，以在其内OLBNP可以产生动脉压力的变动范围内。自动调节器仅在〜0.07赫兹和较慢，因此上限是不是一个问题。然而，在产生的低频振荡低于0.03赫兹的困难是，对心血管系统的反调节对下体负压引起动脉压的变化的周期结束之前。 如图4所示，在0.025赫兹OLBNP我们实际看到的最大峰值血压波动在0.05赫兹。而脑自动调节器的频率响应的特点可以从0.03 Hz至0.08赫兹以限定的时间尺度内其自身调节是活动的，23,24 0.03赫兹和0.08赫兹OLBNP足够，因为它们代表了一系列自动调节功能的（ 即 ，一个宣判自动调节区域无法比拟的还是温和的）。 OLBNP产生于动脉压较大的波动作为负压力振动的频率变得更慢。 图5示出了动脉压力和随之而来的脑血流量的波动与OLBNP 0.08赫兹（12.5秒的周期）至0.03赫兹（33秒周期）。在较高的频率，脑血流量波动在音乐会与动脉压。该PPR说明了这一点;有在0.08赫兹，0.07赫兹（14秒周期），和0.0的较高频率动脉压和脑血流量之间的比例关系的线性6赫兹（16.6秒周期）。在OLBNP慢的频率，虽然动脉压力变动变大，在脑血流的波动逐渐更有效地衰减。因此，在PPR示出了在从0.05赫兹（20秒周期）OLBNP频率日益更加突出自动调节区域，以0.04赫兹（25秒周期），到0.03赫兹。在示出的例子中，在0.03赫兹，在PPR曲线清楚地类似于由拉森（ 图1）中描述的"经典自动调节曲线"。我们以前曾表明这一观察，不能简单地通过增加动脉压力变动幅度解释为振荡频率变得更慢。我们在OLBNP（因此，不同的压力波动的幅度）。19的不同大小已预先施加的PPR将数据从48个人尽管我们没有明确地探索之间自动调节范围和压力波动的大小的电势关系，我们再停泊在自动调节范围的变化仅为〜6％。因此，我们的现有结果清楚地表明，在PPR曲线与频率的变化不能完全由在压力波动的大小的变化进行说明。在同一研究中，我们评估自身调节的PPR特征是否可以通过单独的会话可重复性。这一分析表明，自动调节范围的期间0.03赫兹OLBNP斜率没有改变（Lin的一致性= 0.96，P &lt;0.001），从而使非线性压力-流量关系是在整个研究日相一致。 虽然脑血管床是由交感神经纤维以及支配，他们的自身调节作用还没有被广泛接受。26因此，我们的一些前期工作的探讨脑血管自动调节交感神经系统的潜在作用。24，我们找到了一个明确的角色交感神经系统在调节脑流，但我们瓦特ERE无法描述的关系具有去除交感神经的影响如何改变由于线性方法表征自动调节的局限性。 图6显示了之前（基线）从PPR应用程序数据的结果，并在0.05 Hz的交感神经阻滞后。整体曲线明显变得更加线性。此外，为0.03赫兹数据，其中自动调节是最明显的PPR分析表明，该自动调节区域的范围保持不变，但在该区域的增加斜率，反映不太有效的自动调节（ 图7）。 <img alt="图1" src="/files/ftp_upload/51082/51082fig1highres.jpg" /> 图1."经典"自动调节曲线来源于静态的增加之间的关系，减少压力和稳态脑血流量。不变的流动沙漠的区域皮特改变压力（ 即 ，斜率= 0）是由区域界定，其中增加和减少压力导致比例脑血流量的变化。 <img alt="图2" src="/files/ftp_upload/51082/51082fig2highres.jpg" /> 图2.执行PPR分析必要的预处理。信号首先被抽取为5赫兹，然后带通在OLBNP的频率滤波（±0.005赫兹）。 <img alt="图3" src="/files/ftp_upload/51082/51082fig3highres.jpg" /> 图中0.03赫兹OLBNP来源于动脉压及脑血流的PPR分析脑自动调节曲线的参数3。 <img alt="图4" src="/files/ftp_upload/51082/51082fig4highres.jpg" /> <str翁&gt;图4 的功率谱示出了在动脉压力波动的幅度时OLBNP频率低于0.03赫兹（33秒周期）。请注意，有在0.025 2大峰中的动脉压谱功率和0.05赫兹（40和20秒周期），但是只有在0.025赫兹在下体负压频谱功率的单峰。此外，在压力的最大波动是在0.05赫兹，并会混淆的脑血流量的反应的解释。 <img alt="图5" src="/files/ftp_upload/51082/51082fig5highres.jpg" /> 图的OLBNP的效果从0.08到0.03赫兹的动脉压和脑血流量5.实施例。动脉压力变动变得较慢OLBNP较大而脑血流的波动变得更小。此自动调节功能由在底部面板中所示的PPR分析的结果进行说明。牛逼脑血流量，他自动调节区域逐渐变得更加明显较慢OLBNP。 <img alt="图6" src="/files/ftp_upload/51082/51082fig6highres.jpg" /> 图6.个人，平均从0.05科目赫兹OLBNP数据PPR自动调节曲线之前（基线）和交感神经阻滞后，需要注意的是狭窄的自动调节区域的交感神经阻滞后的损失。 <img alt="图7" src="/files/ftp_upload/51082/51082fig7highres.jpg" /> 图7.平均0.03赫兹OLBNP数据PPR参数之前和交感神经阻滞后，交感神经阻断了大脑自身调节曲线上的一个显着的效果自动调节的范围内，显着增加了坡（ 即更多的比例脑流量与压力变化的变化）。

Watch this Scientific Journal Video about Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression at JoVE.com

Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression

Cerebral perfusion is maintained across a range of pressures via cerebral autoregulation. However, characterizing autoregulation requires prominent pressure fluctuations at regulated frequencies. The described protocol will show how oscillatory lower body negative pressure can generate pressure fluctuations to provide data for projection pursuit regression for quantification of the autoregulatory curve.

通过振荡下体负压和投影寻踪回归评估脑自动调节

The process by which cerebral perfusion is maintained constant over a wide range of systemic pressures is known as &#8220;cerebral autoregulation.&#8221; ...

assessing-cerebral-autoregulation-via-oscillatory-lower-body-negative

Research

JoVE Journal

Biology

12.3K 次观看.  Harvard Medical School. Cerebral perfusion is maintained across a range of pressures via cerebral autoregulation. However, characterizing autoregulation requires prominent pressure fluctuations at regulated frequencies. The described protocol will show how oscillatory lower body negative pressure can generate pressure fluctuations to provide data for projection pursuit regression for quantification of the autoregulatory curve.

视频: Assessing Cerebral Autoregulation via Oscillatory Lower Body Negative Pressure and Projection Pursuit Regression

Pressure-polishing Pipettes for Improved Patch-clamp Recording

Pressure-polishing is a method for shaping glass pipettes for patch-clamp recording. We first developed this method for fabricating pipettes suitable for recording from small (&lt;3 m) neuronal cell bodies. The basic principal is similar to glass-blowing and combines air pressure and heat to modify the shape of patch pipettes prepared by a conventional micropipette puller. It can be applied to so-called soft (soda lime) and hard (borosilicate) glasses. Generally speaking, pressure polishing can reduce pipette resistance by 25% without decreasing the diameter of the tip opening (Goodman and Lockery, 2000). It can be applied to virtually any type of glass and requires only the addition of a high-pressure valve and fitting to a microforge. This technique is essential for recording from ultrasmall cells (&lt;5 m) and can also improve single-channel recording by minimizing pipette resistance. The blunt shape is also useful for perforated-patch clamp recording since this tip shape results in a larger membrane bleb available for perforation.

This is a guide to modifying the shape of glass micropipettes. Specifically, by using heat and air pressure the taper is widened without increasing the tip opening, leading to lower pipette resistance. This is critical to obtain low noise recordings of small cells but is useful in many applications.

改进的膜片钳记录的压力抛光移液器

Pressure-polishing is a method for shaping glass pipettes for patch-clamp recording.  We first developed this method for fabricating pipettes suitable for ...

科研

生物学

Measuring Blood Pressure in Mice using Volume Pressure Recording, a Tail-cuff Method

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. The CODA tail-cuff system uses Volume Pressure Recording (VPR) to measure the blood pressure by determining the tail blood volume. A specially designed differential pressure transducer and an occlusion tail-cuff measure the total blood volume in the tail without the need to obtain the individual pulse signal. Special attention is afforded to the length of the occlusion cuff in order to derive the most accurate blood pressure readings. VPR can easily obtain readings on dark-skinned rodents, such as C57BL6 mice and is MRI compatible. The CODA system provides you with measurements of six (6) different blood pressure parameters; systolic and diastolic blood pressure, heart rate, mean blood pressure, tail blood flow, and tail blood volume. Measurements can be made on either awake or anesthetized mice or rats. The CODA system includes a controller, laptop computer, software, cuffs, animal holders, infrared warming pads, and an infrared thermometer. There are seven different holder sizes for mice as small as 8 grams to rats as large as 900 grams.

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. This tail-cuff system uses Volume Pressure Recording (VPR) to measure the blood pressure by determining the tail blood volume.

使用卷压力记录，一条尾巴袖套法小鼠的血压测量

The CODA 8-Channel High Throughput Non-Invasive Blood Pressure system measures the blood pressure in up to 8 mice or rats simultaneously. The CODA ...

Born Normalization for Fluorescence Optical Projection Tomography for Whole Heart Imaging

Optical projection tomography is a three-dimensional imaging technique that has been recently introduced as an imaging tool primarily in developmental biology and gene expression studies. The technique renders biological sample optically transparent by first dehydrating them and then placing in a mixture of benzyl alcohol and benzyl benzoate in a 2:1 ratio (BABB or Murray s Clear solution). The technique renders biological samples optically transparent by first dehydrating them in graded ethanol solutions then placing them in a mixture of benzyl alcohol and benzyl benzoate in a 2:1 ratio (BABB or Murray s Clear solution) to clear. After the clearing process the scattering contribution in the sample can be greatly reduced and made almost negligible while the absorption contribution cannot be eliminated completely. When trying to reconstruct the fluorescence distribution within the sample under investigation, this contribution affects the reconstructions and leads, inevitably, to image artifacts and quantification errors.. While absorption could be reduced further with a permanence of weeks or months in the clearing media, this will lead to progressive loss of fluorescence and to an unrealistically long sample processing time. This is true when reconstructing both exogenous contrast agents (molecular contrast agents) as well as endogenous contrast (e.g. reconstructions of genetically expressed fluorescent proteins).

We suggest a Born normalized approach for Optical Projection Tomography (BnOPT) that accounts for the absorption properties of imaged samples to obtain accurate and quantitative fluorescence tomographic reconstructions. We use the proposed algorithm to reconstruct the fluorescence molecular probe distribution within small animal organs.

生于正常化荧光整个心脏成像的光学投影层析成像

Optical projection tomography is a three-dimensional imaging technique that has been recently introduced as an imaging tool primarily in developmental ...

Making Gynogenetic Diploid Zebrafish by Early Pressure

Heterozygosity in diploid eukaryotes often makes genetic studies cumbersome. Methods that produce viable homozygous diploid offspring directly from heterozygous females allow F1 mutagenized females to be screened directly for deleterious mutations in an accelerated forward genetic screen. Streisinger et al.1,2 described methods for making gynogenetic (homozygous) diploid zebrafish by activating zebrafish eggs with ultraviolet light-inactivated sperm and preventing either the second meiotic or the first zygotic cell division using physical treatments (heat or pressure) that deploymerize microtubules. The "early pressure" (EP) method blocks the meiosis II, which occurs shortly after fertilization. The EP method produces a high percentage of viable embryos that can develop to fertile adults of either sex. The method generates embryos that are homozygous at all loci except those that were separated from their centromere by recombination during meiosis I. Homozygous mutations are detected in EP clutches at between 50% for centromeric loci and less than 1% for telomeric loci. This method is reproduced verbatim from the Zebrafish Book3.

This is a method for generating gynogenetic diploid zebrafish embryos (embryos whose only genetic contribution comes from the mother) by blocking the second meiotic division immediately after fertilization with ultraviolet light-inactivated sperm. EP embryos are not fully homozygous due to recombination during the first meiotic division, however they are homozygous at all loci that have not been separated from their centromere by recombination.

初压雌核发育二倍体的斑马鱼

Heterozygosity in diploid eukaryotes often makes genetic studies cumbersome. Methods that produce viable homozygous diploid offspring directly from ...

Long-term Culture of Human Breast Cancer Specimens and Their Analysis Using Optical Projection Tomography

Breast cancer is a leading cause of mortality in the Western world. It is well established that the spread of breast cancer, first locally and later distally, is a major factor in patient prognosis. Experimental systems of breast cancer rely on cell lines usually derived from primary tumours or pleural effusions. Two major obstacles hinder this research: (i) some known sub-types of breast cancers (notably poor prognosis luminal B tumours) are not represented within current line collections; (ii) the influence of the tumour microenvironment is not usually taken into account.
We demonstrate a technique to culture primary breast cancer specimens of all sub-types. This is achieved by using three-dimensional (3D) culture system in which small pieces of tumour are embedded in soft rat collagen I cushions. Within 2-3 weeks, the tumour cells spread into the collagen and form various structures similar to those observed in human tumours1. Viable adipocytes, epithelial cells and fibroblasts within the original core were evident on histology. Malignant epithelial cells with squamoid morphology were demonstrated invading into the surrounding collagen. Nuclear pleomorphism was evident within these cells, along with mitotic figures and apoptotic bodies.
We have employed Optical Projection Tomography (OPT), a 3D imaging technology, in order to quantify the extent of tumour spread in culture. We have used OPT to measure the bulk volume of the tumour culture, a parameter routinely measured during the neo-adjuvant treatment of breast cancer patients to assess response to drug therapy. 
Here, we present an opportunity to culture human breast tumours without sub-type bias and quantify the spread of those ex vivo. This method could be used in the future to quantify drug sensitivity in original tumour. This may provide a more predictive model than currently used cell lines.

We have developed a collagen-based in vitro assay which promotes proliferation and invasion from samples of all breast cancer subtypes. Optical Projection Tomography, a three dimensional microscopy technique was utilised to visualise and quantify tumour expansion. This assay may be used to quantify drug response of individual tumour samples.

长期培养的人类乳腺癌标本，并利用光学投影层析成像分析

Breast cancer is a leading cause of mortality in the Western world. It is well established that the spread of breast cancer, first locally and later ...

Collection, Isolation and Enrichment of Naturally Occurring Magnetotactic Bacteria from the Environment

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of Massachusetts (USA). Since then MTB have been discovered in stratified water- and sediment-columns from all over the world2. One feature common to all MTB is that they contain magnetosomes, which are intracellular, membrane-bound magnetic nanocrystals of magnetite (Fe3O4) and/or greigite (Fe3S4) or both3, 4. In the Northern hemisphere, MTB are typically attracted to the south end of a bar magnet, while in the Southern hemisphere they are usually attracted to the north end of a magnet3,5. This property can be exploited when trying to isolate MTB from environmental samples.
One of the most common ways to enrich MTB is to use a clear plastic container to collect sediment and water from a natural source, such as a freshwater pond. In the Northern hemisphere, the south end of a bar magnet is placed against the outside of the container just above the sediment at the sediment-water interface. After some time, the bacteria can be removed from the inside of the container near the magnet with a pipette and then enriched further by using a capillary racetrack6 and a magnet. Once enriched, the bacteria can be placed on a microscope slide using a hanging drop method and observed in a light microscope or deposited onto a copper grid and observed using transmission electron microscopy (TEM).
Using this method, isolated MTB may be studied microscopically to determine characteristics such as swimming behavior, type and number of flagella, cell morphology of the cells, shape of the magnetic crystals, number of magnetosomes, number of magnetosome chains in each cell, composition of the nanomineral crystals, and presence of intracellular vacuoles.

We demonstrate a method to collect magnetotactic bacteria (MTB) that can be applied to natural waters. MTB can be isolated and enriched from sediment samples using a relatively simple setup that takes advantage of the bacteria's natural magnetism. Isolated MTB can then be examined in detail using both light and electron microscopy.

从环境中自然产生的趋磁细菌的采集，分离和富集

Magnetotactic bacteria (MTB) are aquatic microorganisms that were first notably described in 19751 from sediment samples collected in salt marshes of ...

Whole-Body Nanoparticle Aerosol Inhalation Exposures

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle inhalation toxicology studies, the aerosols in a chamber housing the experimental animals must have: 1) a steady concentration maintained at a desired level for the entire exposure period; 2) a homogenous composition free of contaminants; and 3) a stable size distribution with a geometric mean diameter &lt; 200 nm and a geometric standard deviation &sigma;g &lt; 2.5 5. The generation of aerosols containing nanoparticles is quite challenging because nanoparticles easily agglomerate. This is largely due to very strong inter-particle forces and the formation of large fractal structures in tens or hundreds of microns in size 6, which are difficult to be broken up. Several common aerosol generators, including nebulizers, fluidized beds, Venturi aspirators and the Wright dust feed, were tested; however, none were able to produce nanoparticle aerosols which satisfy all criteria 5.
A whole-body nanoparticle aerosol inhalation exposure system was fabricated, validated and utilized for nano-TiO2 inhalation toxicology studies. Critical components: 1) novel nano-TiO2 aerosol generator; 2) 0.5 m3 whole-body inhalation exposure chamber; and 3) monitor and control system. Nano-TiO2 aerosols generated from bulk dry nano-TiO2 powders (primary diameter of 21 nm, bulk density of 3.8 g/cm3) were delivered into the exposure chamber at a flow rate of 90 LPM (10.8 air changes/hr). Particle size distribution and mass concentration profiles were measured continuously with a scanning mobility particle sizer (SMPS), and an electric low pressure impactor (ELPI). The aerosol mass concentration (C) was verified gravimetrically (mg/m3). The mass (M) of the collected particles was determined as M = (Mpost-Mpre), where Mpre and Mpost are masses of the filter before and after sampling (mg). The mass concentration was calculated as C = M/(Q*t), where Q is sampling flowrate (m3/min), and t is the sampling time (minute). The chamber pressure, temperature, relative humidity (RH), O2 and CO2 concentrations were monitored and controlled continuously. Nano-TiO2 aerosols collected on Nuclepore filters were analyzed with a scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis.
In summary, we report that the nano-particle aerosols generated and delivered to our exposure chamber have: 1) steady mass concentration; 2) homogenous composition free of contaminants; 3) stable particle size distributions with a count-median aerodynamic diameter of 157 nm during aerosol generation. This system reliably and repeatedly creates test atmospheres that simulate occupational, environmental or domestic ENM aerosol exposures.

A whole-body nanoparticle aerosol inhalation exposure facility was constructed for nano-sized titanium dioxide (TiO2) inhalation toxicology studies. This system provides nano-TiO2 aerosol test atmospheres that have: 1) a steady mass concentration; 2) a homogenous composition free of contaminants; and 3) a stable particle size distribution during aerosol generation.

全身纳米气溶胶吸入暴露

Inhalation is the most likely exposure route for individuals working with aerosolizable engineered nano-materials (ENM). To properly perform nanoparticle ...

Assessing Murine Resistance Artery Function Using Pressure Myography

Pressure myograph systems are exquisitely useful in the functional assessment of small arteries, pressurized to a suitable transmural pressure. The near physiological condition achieved in pressure myography permits in-depth characterization of intrinsic responses to pharmacological and physiological stimuli, which can be extrapolated to the in vivo behavior of the vascular bed. Pressure myograph has several advantages over conventional wire myographs. For example, smaller resistance vessels can be studied at tightly controlled and physiologically relevant intraluminal pressures. Here, we study the ability of 3rd order mesenteric arteries (3-4 mm long), preconstricted with phenylephrine, to vaso-relax in response to acetylcholine. Mesenteric arteries are mounted on two cannulas connected to a pressurized and sealed system that is maintained at constant pressure of 60 mmHg. The lumen and outer diameter of the vessel are continuously recorded using a video camera, allowing real time quantification of the vasoconstriction and vasorelaxation in response to phenylephrine and acetylcholine, respectively.
	To demonstrate the applicability of pressure myography to study the etiology of cardiovascular disease, we assessed endothelium-dependent vascular function in a murine model of systemic hypertension. Mice deficient in the &alpha;1 subunit of soluble guanylate cyclase (sGC&alpha;1-/-) are hypertensive when on a 129S6 (S6) background (sGC&alpha;1-/-S6) but not when on a C57BL/6 (B6) background (sGC&alpha;1-/-B6). Using pressure myography, we demonstrate that sGC&alpha;1-deficiency results in impaired endothelium-dependent vasorelaxation. The vascular dysfunction is more pronounced in sGC&alpha;1-/-S6 than in sGC&alpha;1-/-B6 mice, likely contributing to the higher blood pressure in sGC&alpha;1-/-S6 than in sGC&alpha;1-/-B6 mice. 
	Pressure myography is a relatively simple, but sensitive and mechanistically useful technique that can be used to assess the effect of various stimuli on vascular contraction and relaxation, thereby augmenting our insight into the mechanisms underlying cardiovascular disease.

In pressure myography, an intact small segment of a vessel is mounted onto two small cannulas and pressurized to a suitable luminal pressure. Here, we describe the method to measure vasorelaxation response of the mouse 3rd order mesenteric arteries in c57 and sGC&alpha;1-/- mice using pressure myography.

评估抗小鼠动脉功能使用压力Myography

Pressure myograph systems are  exquisitely useful in the functional assessment of small arteries, pressurized  to a suitable transmural pressure. The  ...

Measuring Respiratory Function in Mice Using Unrestrained Whole-body Plethysmography

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative assessment of lung function in rodent models is an important tool in the development of future therapies. Commonly used techniques for assessing respiratory function including invasive plethysmography and forced oscillation. While these techniques provide valuable information, data collection can be fraught with artefacts and experimental variability due to the need for anesthesia and/or invasive instrumentation of the animal. In contrast, unrestrained whole-body plethysmography (UWBP) offers a precise, non-invasive, quantitative way by which to analyze respiratory parameters. This technique avoids the use of anesthesia and restraints, which is common to traditional plethysmography techniques. This video will demonstrate the UWBP procedure including the equipment set up, calibration and lung function recording. It will explain how to analyze the collected data, as well as identify experimental outliers and artefacts that results from animal movement. The respiratory parameters obtained using this technique include tidal volume, minute volume, inspiratory duty cycle, inspiratory flow rate and the ratio of inspiration time to expiration time. UWBP does not rely on specialized skills and is inexpensive to perform. A key feature of UWBP, and most appealing to potential users, is the ability to perform repeated measures of lung function on the same animal.

The assessment of respiratory physiology has traditionally relied upon techniques, which require restraint or sedation of the animal. Unrestrained whole-body plethysmography, however, provides precise, non-invasive, quantitative analysis of respiratory physiology in animal models. In addition, the technique allows repeated respiratory assessment of mice allowing for longitudinal studies.

用奔放的整体体积描记测量呼吸功能的影响

Respiratory dysfunction is one of the leading causes of morbidity and mortality in the world and the rates of mortality continue to rise. Quantitative ...

Measuring Pressure Volume Loops in the Mouse

Understanding the causes and progression of heart disease presents a significant challenge to the biomedical community. The genetic flexibility of the mouse provides great potential to explore cardiac function at the molecular level. The mouse&#39;s small size does present some challenges in regards to performing detailed cardiac phenotyping. Miniaturization and other advancements in technology have made many methods of cardiac assessment possible in the mouse. Of these, the simultaneous collection of pressure and volume data provides a detailed picture of cardiac function that is not available through any other modality. Here a detailed procedure for the collection of pressure-volume loop data is described. Included is a discussion of the principles underlying the measurements and the potential sources of error. Anesthetic management and surgical approaches are discussed in great detail as they are both critical to obtaining high quality hemodynamic measurements. The principles of hemodynamic protocol development and relevant aspects of data analysis are also addressed.

This manuscript describes a detailed protocol for the collection of pressure-volume data from the mouse.

测量压力容量环中的鼠标

Understanding the causes and progression of heart disease presents a significant challenge to the biomedical community. The genetic flexibility of the ...