Arterial constrictor response in a diving mammal

Angiograms were obtained in the harbor seal, Phoca vitulina, in air and during diving. During diving there is arterial constriction of the vascular beds of muscle, skin, kidney, liver, spleen, and presumably of all vascular beds except those perfusing the brain and heart. There is sudden constriction and narrowing of muscular arteries close to their origin from the aorta. Constriction of small arterial branches is so intense that blood flow is essentially lost in all involved organs.     

Pulmonary blood flow regulation in an aquatic snake

Regulation of pulmonary blood flow was studied during voluntary diving in the aquatic file snake, Acrochordus granulatus. Measurements of pressure and blood flow in pulmonary and systemic vessels indicate that blood flow completely bypasses the lung for significant periods during prolonged and quiescent submergence (greater than 30 minutes). When the lung is ventilated, pulmonary blood flow increases to 36 milliliters per minute per kilogram of body mass (measured in the anterior pulmonary artery), and the cardiac output largely bypasses the systemic circulation. These reciprocating patterns of preferential blood flow reflect inverse relations between flow and vascular resistance, with the result that systemic and pulmonary arterial pressures remain virtually constant throughout repetitive dive cycles. Neuropharmacological studies of freely diving snakes and isolated, perfused lung preparations show that pulmonary blood flow is regulated by an interplay of adrenergic vasodilatation and cholinergic vasoconstriction within the densely innervated lung vasculature. The patterns of blood circulation shown by diving Acrochordus reflect an unusual lability of intracardiac shunts.     

Angiotensin. II. Important role in the maintenance of arterial blood pressure

An angiotensin II antagonist, [1-sarcosine, 8-alanine]-angiotensin II, was given intravenously to anesthetized dogs with thoracic caval constriction and ascites to investigate the role of angiotensin II in the control of arterial pressure. The antagonist produced a striking fall in arterial pressure and in aldosterone secretion and an accompanying increase in plasma renin activity. In a control experiment, normal anesthetized dogs were given the angiotensin analog, but it failed to reduce arterial pressure or to influence plasma renin activity. In conscious dogs with caval constriction, the antagonist produced essentially the same drop in arterial pressure as observed in anesthetized animals. These results suggest an important role for angiotensin II in the maintenance of arterial pressure by its action on specific receptor sites in arteriolar smooth muscle and in the adrenal cortex.     

龙虱的营养、生物学特性及其养殖前景

龙虱是一种珍贵的野生药食两用水生昆虫,具有良好的食用和药用价值,龙虱有独特的营养、生物特性,发展淡水养殖是开发庭院经济,低投入、高产出、增产增效的农业新途径。     

潜水旅游对珊瑚礁生态系统影响研究的进展

早期潜水活动曾被认为是一种经济价值高且对珊瑚礁影响较小的生态旅游项目,但随着潜水旅游逐渐盛行,诸多研究结果表明,全世界潜水区的珊瑚礁均出现了不同程度的退化,一些热门潜水旅游区每年接纳的游客数量甚至远超出珊瑚礁的生态承受极限.笔者对与珊瑚礁生态系统与潜水旅游承载能力相关的研究结果进行了统计分析,总结了潜水活动影响珊瑚礁的...     

Sink or swim: strategies for cost-efficient diving by marine mammals

Locomotor activity by diving marine mammals is accomplished while breath-holding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonged gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged.     

农用潜水泵内部流场的三维湍流数值模拟

针对同一叶轮配不同导流器,通过试验分析,探索提高潜水泵效率的途径。以250QJ125型潜水泵配两种导流器为例,通过CFD数值计算,预测出潜水泵的性能,将解析法求得的潜水泵最佳工况点与模拟试验结果进行了比较,其结果较为吻合。经对两种导流器内部的速度场和压力场分析,提出了增加导流器长度、增大导叶片进口冲角和壁角等方法可提高潜水泵的效率。     

农业用潜水电泵应用前景探讨

论述了潜水电泵结构组成,通过对国内外大小口径潜水电泵发展情况进行比较,探讨了其在农业灌溉的主要作用,结合目前农村所需灌溉的实际情况,对不同类型潜水电泵的应用前景进行了论述。     

Leukotriene C4 transport by the choroid plexus in vitro

Nanomolar concentrations of peptidoleukotrienes evoke sustained cerebral edema and arterial constriction. Peptidoleukotrienes are thus considered to play an important role in eliciting cerebral edema after cerebral ischemia and vasospasm after subarachnoid hemorrhage. It was hypothesized that the choroid plexus, the locus of the blood-cerebrospinal fluid barrier, might minimize the vasoactivity of locally generated or systemically derived leukotrienes by transporting leukotrienes from cerebrospinal fluid into the blood. Consistent with this hypothesis, leukotriene C4 in vitro was transported into and released from isolated rabbit choroid plexus by a system that was specific, energy-dependent, probenecid-sensitive, and depressed by cold temperatures. The accumulation of leukotriene C4 in the choroid plexus was not dependent on tissue binding or metabolism of leukotriene C4.     

万荣县冬小麦产量与气象条件的关系研究

以直线滑动平均法为主要方法,从1951—2011年万荣县冬小麦产量中分离出气象产量和趋势产量,趋势产量表明,20世纪70年代末到90年代增长迅速,但进入21世纪后产量徘徊不前。分析了气象产量与1957—2011年的平均气温、降水量和日照时数的月资料和旬资料的线性相关性,并结合1981—2011年的冬小麦发育期平均值,找出相关性明显的关键气象要素,利用逐步线性回归法建立气象产量预报方程。结果表明,影响产量的主要因素有上年9—11月、2月中下旬和上年11月上旬的降水量和上年11月下旬的日照时数。并对2012年产量进行了预报。这些可为精确估产,合理安排灌溉、小麦生育期评价以及人工增雨服务小麦生产提供可靠技术依据,特别是抓住关键期进行人工增雨将会取得明显的社会效益和经济效益。     

BRADYKININ: VASCULAR RELAXANT, CARDIAC STIMULANT

Bradykinin infusion causes an increase in cardiac output in rats whether the autonomic nervous system is blocked or not. After autonomic blockade, bradykinin causes a lesser decrease in the total peripheral resistance but a greater increase in cardiac output, resulting in an elevation of arterial pressure. The increase in cardiac output is caused by a small increase in heart rate and a substantial increase in stroke volume. The fact that these increases are observed after autonomic blockade suggests that bradykinin increases cardiac output by direct stimulation of the heart.     

赛拉唑—戊巴比妥麻醉与育亨宾对其拮抗作用

5只犬在肌注赛拉唑1mg/kg 10分钟后静脉注射戊巴比妥8mg/kg 可引起良好的外科麻醉,其麻醉、足反射消失和从恢复知觉到可走动的时间分别为82,64和33分钟。在麻醉过程中,血压略有上升,心率减慢和呼吸明显抑制。在另一次相同的实验中,在给予戊巴比妥30分钟后静注育亨宾0.2mg/kg,不仅可中止或明显缩短麻醉、足反射消失和可走动的时间,而且也可阻断赛拉唑引起的心率减慢和赛拉唑-戊巴比妥所致的呼吸抑制,恢复也十分平静。赛拉唑-戊巴比妥配合麻醉对犬是有效和安全的麻醉方法。育亨宾是一种有效的拮抗剂。     

基于纤维角预测的针叶材抗压弹性模量建模方法

目的针叶材的管胞不仅具有输导养分的作用，而且具有较强的支撑能力，其管胞分布状态影响着木材力学特性。探究管胞分布状态与木材力学特征的内部关系对实现木材抗压弹性模量的预测有重要意义。方法本研究从针叶材管胞效应入手，设计了一套集光源发射、光斑采集与分析、木材遍历为一体的纤维角检测平台，构建了木材纤维角分布与其抗压弹性模量的数值关系模型。首先，利用最小二乘法拟合投射在木材表面激光光斑的椭圆轮廓，完成纤维角测量；然后，通过分析纤维角测量误差，选用系数为20的均值滤波方法以提高纤维角测量精度；通过对木材遍历采样，完成纤维角分布的采集；最后，以木材两个面上纤维角分布的均值、潜入系数与标准差为输入，以试样的抗压弹性模量为输出，构建了6输入1输出的4层神经网络，完成抗压弹性模量的预测。按照GB/T 15777—1995《木材顺纹抗压弹性模量测定方法》加工了落叶松试样100个，应用检测平台采集了相应试件的纤维角分布后，采用力学试验机得到对应力学真值，按照3:1的比例划分训练样本与测试样本。结果平均滤波次数选取20时，该设备纤维角采集测量误差达到0.65°以下；分别构建了以双面纤维角分布特征、单面纤维角分布特征以及双面纤维角分布特征均值为输入，抗压弹性模量为输出的网络预测模型。实验比较发现:以双面纤维角分布特征为变量的网络模型预测精度上优于其他两组，此时网络预测的抗压弹性模量准确率达到90.80%。结论应用纤维角分布特征可以实现针叶材抗压弹性模量的有效预测。最小二乘拟合与均值滤波法的结合可以有效、准确地表达纤维角的特征信息。纤维角的均值、潜入系数与标准差可以有效描述纤维角的分布特征。在构建木材抗压弹性模量时，木材双面的纤维角分布特征对其抗压弹性模量预测精度最高。      

Adaptation of cardiac output to peripheral runoff studied in intact dogs

A pump with sinusoidal piston movement was connected to the abdominal aorta of intact anesthetized dogs, causing slow oscillations of arterial blood pressure. Evidence was found for the existence of a mechanism which enables the heart to adjust its output immediately to changes of peripheral outflow.     

莆田黑鸭体型性状的主成分分析*

 应用主成分分析法对莆田黑鸭的11个体型性状进行统计分析,将众多的性状综合成几个主成分,旨在为莆田黑鸭体型性状的选育提供方向和重点。试验结果表明：不同体型性状之间呈现不同程度的相关,公鸭以体重与胸深的相关性最高,母鸭则以体重与半潜水长的相关性最高。公鸭的11个体型性状可简化为2个主成分（累计贡献率占信息总量的86.01%）,可从这2个主成分中选取体重、嘴长、半潜水长、胸宽和骨盆宽为代表性的性状指标。母鸭的11个体型性状可简化为4个主成分（累计贡献率占信息总量的88.83%）,可从这4个主成分中选取体重、半潜水长、胸宽、体斜长和胫长为代表性的性状指标。     

老年心房颤动患者发生缺血性脑卒中危险因素的研究

目的:了解老年心房颤动(A f)患者发生缺血性脑卒中的危险因素。方法:采用病例对照研究对372例老年慢性A f患者的临床资料,比较发生与不发生缺血性脑卒患者的病因、心室率、年龄、性别、心衰、并发高血压病、糖尿病、心房扩大与心脏瓣膜钙化的差异。结果:A f患者中,发生与不发生缺血性脑卒患者的病因、心室率、并发高血压病、糖尿病、心房扩大、心脏瓣膜钙化的发生情况差异有非常显著性(P均<0.01),但性别、年龄、心衰、A f类型的发生情况差异均无显著性(P均>0.05)。结论:心脏瓣膜病、心室率过缓、高血压病与糖尿病是A f并缺血性脑卒中的高危因素,老年人A f并发上术疾病者容易出现缺血性脑卒中,应予临床干预。     

埋藏式心脏起搏器术后起搏阈值的动态变化

目的:观察埋藏式心脏起搏器术后电极成熟期前后起搏阈值的变化规律。方法:对30例接受埋藏式心脏起搏治疗的患者分别于术中、术后1周、2周、1个月、2个月、3个月、6个月测定起搏阈值。结果:16例应用Medtronic CAPSURESP系列(激素洗提)心房电极的患者心房起搏阈值术后升高,本后1周达峰值,后逐渐降低,术后2个月开始趋于稳定,除术后6个月外,其余各时间点与术中比较差异均有非常显著性(P<0.01);24例应用MCSP系列心室电极的患者心室起搏阚值术后均明显高于术中(P<0.01);9例应用BIOTRONIK SYNOX SX系列(高阻抗非激素洗提)电极的患者心房、心室平均起搏阈值具有与MCSP系列起搏电极类似的术后演变趋势.其急性期起搏阈值呈明显峰化现象,且具有较高的慢性期阚值,与40条MCSP系列电极比较,两者急、慢性期起搏阈值差异均有非常显著性(P<0.01)。结论:埋藏式心脏起搏器术后6个月内,起搏阈值明显升高;激素洗提电极能明显降低急性期和慢性期阚值。     

Attitudes,beliefs, and prevalence of dumpster diving as a means to obtain food by Midwestern,low-income,urban dwellers

Dumpster diving is a term generally used for obtaining items, in this case food for consumption, from dumpsters. This study evaluates the prevalence of dumpster diving in two low-income urban communities in Minneapolis, Minnesota. Additionally, attitudes and beliefs of adults who engage in this behavior are reported. Surveys (n=396) were used to collect data including individual dumpster diving behavior, food security, health, and demographic data. Nearly one-fifth of those surveyed had used dumpster diving as a means to obtain food. Focus groups (n=17) were conducted to further evaluate dumpster divers attitudes and beliefs about dumpster diving, use of food assistance programs including benefits and barriers, and other strategies used to obtain food such as stealing. Focus group participants were primarily homeless and most were high school educated. Ways to improve delivery of food assistance are suggested. In conclusion, more research on the use of dumpsters as a source of food is needed. Utilizing more of the 96 billion pounds of food wasted each year in the US through food recovery and donation programs could help to provide socially acceptable means for low-income urban dwellers to obtain food.     

浅埋条件下地下水对人工草地SPAC系统影响初探

在地下水埋深较浅的地区,潜水参与和影响了SPAC系统的水分、生物、化学等过程.试验结果表明,潜水对土壤-植物-大气连续体的水分过程和生物过程都有影响.潜水通过控制土壤水分进而影响土壤水势、莒蓿叶水势,从而影响苜蓿的生育过程,最终影响苜蓿的产量.结果显示:对于紫花苜蓿,在没有灌溉的条件下,其根区土壤水分、土水势、叶水势和叶面积指数、株高等生理指标与充分灌溉的差异不显著.研究成果对于深入分析SPAC系统水分运移规律和充分利用地下水、制定合理的节水灌溉方案以及通过控制地下水对农作物生长进行调控等有着一定的理论价值和生产意义.     

Triggering a cell shape change by exploiting preexisting actomyosin contractions

Apical constriction changes cell shapes, driving critical morphogenetic events, including gastrulation in diverse organisms and neural tube closure in vertebrates. Apical constriction is thought to be triggered by contraction of apical actomyosin networks. We found that apical actomyosin contractions began before cell shape changes in both Caenorhabitis elegans and Drosophila. In C. elegans, actomyosin networks were initially dynamic, contracting and generating cortical tension without substantial shrinking of apical surfaces. Apical cell-cell contact zones and actomyosin only later moved increasingly in concert, with no detectable change in actomyosin dynamics or cortical tension. Thus, apical constriction appears to be triggered not by a change in cortical tension, but by dynamic linking of apical cell-cell contact zones to an already contractile apical cortex.