人尾加压素Ⅱ对大鼠脑微循环的影响

目的:探讨尾加压素Ⅱ(UII)对于大鼠软脑膜微循环的影响.方法:健康成年SD大鼠随机分为对照组、生理盐水(NS)、UII(10-7mol/L)、去甲肾上腺素(NA,10-6mol/L)、UII(10-7mol/L) NA(10-6mol/L)等五组,采用活体微循环观测技术观察大鼠软脑膜微血管内径、血流速度等微循环参数,采用激光多普勒血流量仪测定软脑膜血流量的变化.结果:正常对照组软脑膜细动脉和细静脉血管内径分别为(35.4±3.6)μm和(40.6±8.5)μm,UII组于滴加UII(10-7mol/L)后即刻细动脉和细静脉出现收缩,1 min时细动脉和细静脉收缩达到高峰,血管内径分别为(25.6±3.4)μm和(23.4±3.3)μm (与正常对照组比较,P均<0.05);细动、静脉内血流速度无明显变化(与正常对照组比较P均>0.05);软脑膜血流量于滴加UII(10-7mol/L)后1 min开始升高,5 min达到高峰(3.5±0.4 )PU 值,正常对照组(2.3±0.6)PU值(P<0.05).结论:UII可以使大鼠软脑膜微血管收缩,血流量增加.     

心房钠尿因子对麻醉家兔局部血流的影响

在42只麻醉家兔,观察了静脉注射心房肽Ⅱ(AtriopeptinⅡ,APⅡ)对局部血流量以及动脉内注射 AP Ⅱ 对局部血管阻力的影响。结果如下:(1)静脉注射 APⅡ(30μg/kg)5min后,平均动脉压(MAP)降低11.0±1.5mmHg(n=8,M±SE,下同),与溶剂对照组相比有明显差异(P相似文献   

同步遥测分析大鼠棕色脂肪产热与体温昼夜节律变化的时间关系

目的：同步遥测棕色脂肪组织（BAT）产热与体核温度昼夜律变化的时间曲线,分析二者昼夜节律变化的时间关系。方法：实验用成年雄性SD大鼠,在22℃环境温度下,明暗时间各12h,昼光时间为06：00h-18：00h,同步无线遥测体核温度（TC）、BAT温度（T队T）、腋窝温度（Tax）和动物活动的昼夜节律变化。结果：①在昼光中,TBAT较TC低0．67％,而在暗光中二者则相似。大鼠从昼光进入暗光时,TBAT升高的速率较TC升高速率快,开始上升的时间较TC提前8min;而从暗光进入昼光时,TBAT开始下降的时间则较TC提前4min。②Tax的昼夜节律幅度与TC相似,但无论动物在明光期或暗光期中,Tax均低于同步测量的TC。③从昼光期转入暗光期时,动物的行为活动出现增加反应先于TBAT和TC开始上升的时间。结论：实验结果证明,在暗光期中大鼠TC升高与BAT产热增加有关,说明BAT昼夜节律性产热的变化在维持体温昼夜生理节律中有重要的作用。     

急性低氧对大鼠微血管反应性及抗氧化酶的影响

目的：探讨不同急性低氧条件下对肠系膜微动脉血管反应性和抗氧化酶的影响。方法：实验采用给予大鼠吸入含氧量为12．5％和8．5％的氮氧混合气体,观察急性低氧后肠系膜微动脉血管口径、血流速度和血中谷光甘肽过氧化物酶（GSH—PX）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性和活性氧（ROS）含量的变化。结果：肠系膜微动脉血管口径随急性低氧时间延长而逐渐增大,而血液流速却减慢（P〈0．01,P〈0．05）;SOD、CAT和GSH—PX活力明显下降,ROS含量增加（P〈0.01,P〈0．05）。结论：急性低氧可使肠系膜微动脉管径变大和血液流速减慢;同时体内抗氧化酶活性减弱,这可能与自由基产生增加有关。     

不同压力二氧化碳气腹对兔血液流变学和微循环的影响

目的：研究不同压力二氧化碳气腹对兔血液流变学和微循环的影响。方法：18只雌性健康实验兔按气腹压力随机均分为三组：气腹压0mmHg组（Ⅰ组）、气腹压10mmHg组（Ⅱ组）和气腹压15mmHg组（Ⅲ组）。每组兔均在不同的压力下接受气腹1h。在二氧化碳气腹前5min（T0）、气腹后30min（T1）、气腹后60min（T2）测定血液流变学指标。监测心率（HR）、平均动脉压（MAP）、耳廓微循环的血流量和血流速率并记录在相应时点的上述参数值。结果：气腹后30min、60min,Ⅱ组与Ⅰ组比较,HR、MAP、全血粘度、红细胞刚性指数和聚集指数显著增加（P〈0.05）,红细胞变形指数、耳廓微循环的血流量和血流速率显著下降（P〈0.05）,Ⅲ组与Ⅰ组比较,各参数变化更为显著（P〈0.01）。血浆粘度和红细胞压积气腹前后无明显变化。结论：二氧化碳气腹后血液流变性减弱;虽然HR、MAP增加,但微循环的血流量和血流速率下降。     

头顶一颗珠对烧伤大鼠微血管反应性及抗氧化酶的影响

目的：探讨头顶一颗珠对烧伤大鼠微血管反应性及抗氧化酶的影响。方法：采用大鼠烧伤模型,分为对照组、烧伤组和头顶一颗珠治疗组（n=10）,在烧伤组和头顶一颗珠治疗组背部皮肤造成大鼠体表面积（BSA）20％深Ⅱ度烧伤模型,头顶一颗珠治疗组大鼠给予头顶一颗珠治疗。观察大鼠烧伤后肠系膜微动脉血管口径、血流速度和血中谷胱甘肽过氧化物酶（GSH-Px）、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性和活性氧簇（ROS）含量的变化。结果：头顶一颗珠能使烧伤后肠系膜微动脉血管口径增大,血液流速增快,SOD、CAT和GSH-Px活力明显增强,ROS含量降低。结论：头顶一颗珠可明显改善烧伤大鼠肠系膜微循环。增强抗氧化能力。     

肝素钠对肢体缺血/再灌注损伤大鼠肠系膜微循环的保护作用

目的:通过观察肝素钠对肢体缺血/再灌注(LI/R)过程中肠系膜微循环的动态变化和血液流变性的影响,探讨肝素减轻LI/R损伤的可能机制,为LI/R损伤的防治提供理论依据。方法:实验采用本室常规方法复制大鼠LI/R模型,正常雄性Wistar大鼠20只,随机分为2组(n=10):肝素组(H组)和单纯缺血/再灌注组(I/R组),两组动物均于再灌注损伤后2h时动态观察肠系膜微血管管径、血流速度、白细胞黏附、白微栓及微血管壁的完整性(管周出血)等情况,同时测定各组动物血液流变学指标和血清中P-选择素和细胞间粘附分子1(ICAM-1)的值。结果:肠系膜微动、静脉管径扩张,血流速度减慢,微血管中大量白细胞贴壁、粘附,白微栓形成增多,与I/R组比较,H组大鼠肠系膜微动脉血流速度(AFV)和微静脉血流速度(VFV)显著下降(P0.01);血浆黏度(ηp)、全血低切还原黏度(Lηre)、全血高切还原黏度(Hηre)、红细胞压积(Hct)、红细胞聚集指数(EAI)、血沉方程K值(ESRK)、红细胞刚性指数(TK)均显著下降(P0.01);红细胞变形指数(EDI)显著升高(P0.01);血清中P-选择素、ICAM-1水平均显著下降(P0.01)。结论:肝素可能通过降低血清中P-选择素和ICAM-1的水平而改善肢体缺血/再灌注损伤大鼠的全身微循环状态。     

缺氧对右心室最大心肌血流量的影响

为了探讨缺氧对冠状血管贮备力的影响,我们观察了缺氧时大鼠血流动力学及右心室最大心肌血流量的变化。结果表明,急性缺氧引起ＰａＯ２、心输出量及氧运送量降低,但右心室心肌血流量增加,右心室最大与安静血流量比值降低。慢性缺氧时ＰａＯ２降低,血球比积和右心室重量指数增加,氧运送量和右心室血流量正常,但最大血流量降低,小动脉增厚、外膜胶元增加。以上结果提示,慢性缺氧对冠状血管贮备减少可能是小动脉壁增厚、外膜胶元增加和血液粘滞性增加及右心室肥大的结果。     

温度升高对高光强环境下蛋白核小球藻(Chlolorella pyrenoidosa)光能利用和生长的阻抑效应

以蛋白核小球藻（Cholorella pyrenoidosa）为实验材料,研究了温度变化对不同光照水平下蛋白核小球藻的光能利用和生长的影响,以明确光照强度对微藻的光能利用和生长的影响是否因温度不同而发生变化。实验中共设置了3个光照强度水平（50,150,300μmol·m^-2s^-1）和2个温度水平（15℃,25℃）。实验结果表明,不同光照水平下小球藻叶绿素荧光的非光化学淬灭（NPQ）大小与温度有关,光照强度为150,300μmol·m^-2s^-1时,温度升高使小球藻叶绿素荧光NPQ提高,并且光照强度越高小球藻叶绿素荧光NPQ增大越多,50μmol·m^-2s^-1光照强度下温度升高对叶绿素荧光NPQ没有影响。实验发现,25℃培养温度下小球藻的光合电子传递速率（ETR）随光照强度增高而上升的速率要低于15℃时小球藻ETR上升的速率;随着光照强度增高,温度升高使小球藻ETR降低程度增大。实验结果还表明,15℃时小球藻培养液叶绿素a浓度随光照强度升高而增高,300μmol·m^-2s^-1培养光强下具有最高的叶绿素a浓度。但在25℃时,光照强度升高叶绿素a浓度并不一定增高,300μmol·m^-2s^-1光照强度下的叶绿素a浓度比150μmol·m^-2s^-1光照强度下要低。本研究表明,温度升高增大了高光照水平下蛋白核小球藻对光能的热耗散,使光照增强对小球藻生长的促进作用减弱。由于温度升高对小球藻光能利用和生长的阻抑作用,小球藻生长的适宜光照水平因温度升高而降低。     

狗急性心肌缺血早期冠脉侧支血流量与血液流变学变化的关系

本实验在14只麻醉开胸狗身上观察了急性心肌缺血早期冠脉侧支血流量与血液流变学变化的关系。动物均分为两组:Ⅰ组,在不控制血压的情况下,观察心肌缺血早期单位压力差下冠脉侧支血管流量(CVC)的变化;Ⅱ组,在保持主动脉血压不变的条件下,根据 Wyatt 等公式计算流经缺血区末梢血管的有效侧支血流量(ECF)。实验结果表明,阻断冠脉血流30min时,低切变率下全血比粘度已明显增高,随后继续增加,60min 时Ⅰ、Ⅱ两组分别较对照值增高19.0%和11.4%(均为P<0.01)。血液粘度增高时,CVC 仅轻度降低(p>0.05),但 ECF却随着血液粘度的增高而逐渐明显降低,缺血60min 时较对照值降低12.1±2.6%(P<0.01)。血液粘度变化与 ECF 变化之间呈明显负相关(r=-0.796,p<002)。上述结果提示,心肌缺血早期血液流变学的异常变化虽然对冠脉侧支血管的血流阻力影响较小,但却使流经缺血区末梢血管的有效侧支血流量明显减少而加重心肌缺血。     

Effect of hot-water treatments in vitro on conidial germination and mycelial growth of grapevine trunk pathogens

In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, Cn. macrodidymum and eight species of the genus Phaeoacremonium to hot-water treatments (HWTs) in vitro was evaluated. Conidial suspensions and plugs of agar with mycelia were placed in Eppendorf vials and incubated for 30, 45 or 60 min in a hot-water bath at 41, 42, 43, 44, 45, 46, 47, 48 or 49°C for Cylindrocarpon spp. and at 49, 50, 51, 52, 53, 54 or 55°C for Ca. luteo-olivacea and Phaeoacremonium spp. In general, conidial germination and the colony growth rate of all pathogens decreased with increased temperature and time combinations. Cylindrocarpon spp. were more sensitive than Ca. luteo-olivacea and Phaeoacremonium spp. to HWT temperatures. Conidial germination of Ca. luteo-olivacea was inhibited by treatments above 51°C–30 min, while treatments up to 54°C–60 min were necessary to inhibit the mycelial growth. For Cylindrocarpon spp., conidial germination was inhibited by treatments above 45°C–45 min, while treatments above 48°C–45 min were necessary to inhibit the mycelial growth. Regarding Phaeoacremonium spp., treatments up to 54°C–60 min were necessary to completely inhibit both conidial germination and mycelial growth. These results suggest that current HWT protocols at 50°C for 30 min may be sufficient to control Cylindrocarpon spp. However, it would be necessary to develop HWT using higher temperatures to reduce the incidence of Ca. luteo-olivacea and Phaeoacremonium spp. infections.     

Gradual increase in leg oxygen uptake during repeated submaximal contractions in humans

We examine whether muscle oxygen consumption (VO2) increases gradually during repeated submaximal isometric contractions. Six subjects made two-legged isometric quadriceps contractions at 30% maximal voluntary contraction for 6 s with 4 s of rest between until exhaustion (58 +/- 8 min). Blood samples were taken from the femoral vein and artery, and blood velocity was recorded by ultrasound-Doppler technique in the femoral artery. Blood flow was calculated from velocity and artery diameter values. Leg VO2 increased sixfold within the 1st min of exercise. A further doubling of the VO2 was seen during the remainder of the exercise, reaching 307 +/- 22 ml/min at exhaustion. This latter increase was due to a 54% increase in blood flow and a 34% increase in oxygen extraction. After 20 min of recovery VO2 was still 75% higher than preexercise values. The results show a twofold increase in energy demand of the working muscle during repeated constant-force isometric contractions. The increased energy cost of contraction is probably localized at the cellular level, and it parallels fatigue determined as decreased force-generating capacity.     

根田鼠的活动代谢率

在15～30℃温度范围内, 运用踏车呼吸室以5 m/min, 10 m/min 和15 m/min 的运动速度, 对栖息于青海高原的根田鼠的代谢率、体温、蒸发失水进行了测定, 并计算了每个温度和运动速度时的热传导率。根田鼠的体温在任一速度时, 随环境温度的增加而增加, 当环境温度一定时, 体温随运动强度而升高, 代谢率随运动速度增加而增加。活动产热在低温条件下, 可能是对寒冷产热的替代, 而在比较缓和的温度时, 可能是对冷诱导产热的附加。温度一定时, 蒸发失水随运动速度增加而增加, 热传导也呈相似的变化趋势(15℃除外)。热传导在任一运动速度下, 随环境温度增加而增加。结果表明蒸发散热在高温或活动期间对根田鼠的体温调节有不可替代的作用。     

Sensitivity of Petri disease pathogens to hot-water treatments in vitro

Petri disease pathogens ( Phaeoacremonium spp. and Phaeomoniella chlamydospora ) are able to colonize the vessels in the xylem of grapevine propagating material. Hot-water treatment (HWT) protocols at 50°C for 30 min have been applied in grapevine nurseries to control these pathogens with variable results. The effect of HWT in vitro at higher temperatures on Pa.   chlamydospora , Phaeoacremonium aleophilum and Phaeoacremonium parasiticum isolates was determined by placing conidial suspensions and plugs of agar with mycelia in Eppendorf vials and incubated in hot water at 49, 50, 51, 52, 53 or 54°C for 30, 45 or 60 min. Conidial germination and the colony growth rate decreased with increased temperature and time combinations. Pa.   chlamydospora was more sensitive than Phaeoacremonium spp. to the experimental temperatures for all periods of time. Pa.   chlamydospora tolerated temperatures of 53°C, while Pm.   aleophilum and Pm.   parasiticum tolerated temperatures of 54°C, although the treatments above 51–52°C drastically reduced conidial germination and mycelial growth. These results highlight the need to develop HWT using temperatures above 51°C to reduce the incidence of fungal infections and ensure high-quality propagating material for grapevine growers.     

Insulin at physiological concentrations increases microvascular perfusion in human myocardium

Vascular endothelium regulates vascular tone and tissue perfusion in response to various physiological and pathological stimuli. Insulin and meal feeding increase microvascular perfusion and thus oxygen, nutrient, and hormone delivery to human skeletal muscle. Meal feeding also increases cardiac microvascular perfusion in healthy humans. To examine whether insulin at physiological concentrations increases microvascular perfusion in human myocardium, we studied 13 healthy, overnight-fasted, lean, young human volunteers by using myocardial contrast echocardiography (MCE) and insulin-clamp techniques. We measured cardiac microvascular blood volume (MBV), microvascular flow velocity (MFV), and microvascular blood flow (MBF) at baseline, 60 min, and 120 min after initiating insulin infusion at 1 mU.kg(-1).min(-1). MBF is the product of MBV and MFV and represents microvascular perfusion. Insulin increased myocardial MBV by 23% at 60 min (P < 0.01) and by 41% at 120 min (P = 0.001) without changing MFV. As a result, insulin-mediated myocardial MBF increased significantly at both 60 min (P < 0.01) and 120 min (P < 0.0005). Insulin also significantly increased brachial artery diameter, flow velocity, and total blood flow at 60 and 120 min (P < 0.05 for all). The changes in cardiac MBV correlated positively with quantitative insulin sensitivity check index (QUICKI) and negatively with body mass index but not with the steady-state glucose-infusion rates or the changes in brachial artery parameters. We conclude that insulin, at physiologically relevant concentrations, increases microvascular perfusion in human heart muscle by increasing cardiac MBV in healthy, insulin-sensitive adults. This insulin-mediated cardiac microvascular perfusion may play an important role in normal human myocardial oxygen and substrate physiology.     

Evaluation of the use of an integration-type laser-Doppler flowmeter with a temperature-loading instrument for measuring skin blood flow in elderly subjects during cooling load: comparison with younger subjects

An integration-type laser-Doppler flowmeter, equipped with a temperature-load instrument, for measuring skin blood flow (ILD-T), and analytical parameters developed in a previous study were used to compare changes in the skin blood flow in the forehead and cheek in elderly subjects (in their 60s and 70s) with those in younger subjects (in their teens to 50s). Age-related differences in skin blood flow in the forehead and cheek in response to cooling were evaluated in 90 healthy women in their teens to 70s (mean age: 17.2 +/- 0.33 years for teenagers; 24.3 +/- 0.76 years for those aged 20-29 years; 34.8 +/- 1.12 years for those aged 30-39 years; 43.3 +/- 0.78 years for those aged 40-49 years; 53.8 +/- 1.13 years for those aged 50-59 years; 63.5 +/- 0.55 years for those aged 60-69 years; 72.2 +/- 0.70 years for those aged 70-79 years). The measurement was performed continuously for 5 min: for 1 min at a sensor temperature of 30 degrees C, for 2 min after the setting of the sensor temperature had been changed to 10 degrees C, and for 2 min after the temperature setting had been cancelled. The parameters analyzed were (1) skin temperature in a resting state before measurement ( T(rest)), (2) mean skin blood flow in 1 min at a sensor temperature of 30 degrees C ( F(30 degrees C)), (3) minimum skin blood flow at a sensor temperature of 10 degrees C ( F(min)), (4) slope of the blood flow plot during the period from the beginning of cooling at 10 degrees C to F(min) ( S(fall)), (5) time required for the sensor temperature to reach 10 degrees C (Delta t(s)), (6) maximum skin blood flow during the period from the end of cooling to the end of measurement ( F(max)), (7) slope of the blood flow plot during the period from F(min) to F(max) ( S(rise)), (8) rate of decrease of the skin blood flow during cooling: FDR = ( F(min)/ F(30 degrees C))x100, (9) recovery rate of the skin blood flow after the end of cooling: FRR = ( F(max)/ F(30 degrees C))x100. When correlations among the above nine parameters were evaluated by combining all age groups, significant correlations ( P < 0.01) were observed between F(30 degrees C) and F(min), F(30 degrees C) and F(max), F(30 degrees C) and S(fall), F(min) and F(max), and F(max) and S(rise) in the forehead. In the cheek, significant correlations ( P < 0.01) were observed in all these combinations except between F(max) and S(rise). When these analytical parameters were compared among the age groups, F(30 degrees C), T(rest), F(max), and S(rise) decreased significantly ( P < 0.02 for F(30 degrees C) and T(rest), P < 0.01 for F(max) and S(rise)) and S(fall) increased significantly ( P < 0.03) in the forehead with aging. However, no significant change with aging was observed in FDR, Delta t(s), F(min), and FRR. In the cheek, FDR increased significantly ( P < 0.03), and S(rise) decreased significantly ( P < 0.01) with aging. However, no significant change with aging was observed in F(30 degrees C), T(rest), F(max), S(fall), Delta t(s), F(min), and FRR. Thus, the decrease in the skin blood flow during cooling showed no marked quantitative change with age, but, with aging, the rate of this decrease was clearly reduced in the forehead. In the cheek, on the other hand, the skin blood flow decreased markedly with aging, but no clear change was observed in the rate of this decrease. By using ILD-T and examining various parameters obtained, the skin hemodynamics in the forehead and cheek during cooling from 30 degrees C to 10 degrees C could be analyzed, and differences in the hemodynamics between the forehead and cheek and between elderly and younger individuals were clarified. This instrument is expected to be clinically useful.     

树干自然温度梯度变化对热扩散法测算树干液流速率的影响

为了揭示树干自然温度梯度的变化规律及其对树干液流速率测算结果的影响,于2007年5月至10月利用改进的SF-L型热扩散式树液流测定装置,对北京低山区生长的油松和侧柏的树干自然温度梯度、加热温差和气象、土壤水分因子进行了连日同步监测。结果表明:(1)树干自然温度梯度对加热针温差的影响,侧柏大于油松。(2)树干自然温度梯度对液流速率计算结果的影响具有显著的统计意义(P0.01),平均误差大于30%,误差峰值出现在太阳高度角较小的时候。(3)影响树干自然温度梯度最重要的环境因子是光照强度,其次是空气温度。上述结果说明,树干自然温度梯度对热扩散法测定的液流速率的影响不可忽视,研究树木耗水机制时应予以充分考虑。光照强度和空气温度是影响树干自然温度梯度最重要的两个因子,但其影响机制仍需进一步研究。     

Effect of histamine and cimetidine on retinal and choroidal blood flow in humans

Intravenous administration of histamine causes an increase in choroidal blood flow and retinal vessel diameter in healthy subjects. The mechanism underlying this effect remains to be elucidated. In the present study, we hypothesized that H2 receptor blockade alters hemodynamic effects of histamine in the choroid and retina. Eighteen healthy male nonsmoking volunteers were included in this randomized, double-masked, placebo-controlled two-way crossover study. Histamine (0.32 microg.kg(-1).min(-1) over 30 min) was infused intravenously in the absence (NaCl as placebo) or presence of the H2 blocker cimetidine (2.3 mg/min over 50 min). Ocular hemodynamic parameters, blood pressure, and intraocular pressure were measured before drug administration, after infusion of cimetidine or placebo, and after coinfusion of histamine. Subfoveal choroidal blood flow and fundus pulsation amplitude were measured with laser-Doppler flowmetry and laser interferometry, respectively. Retinal arterial and venous diameters were measured with a retinal vessel analyzer. Retinal blood velocity was assessed with bidirectional laser-Doppler velocimetry. Histamine increased subfoveal choroidal blood flow (+14 +/- 15%, P < 0.001), fundus pulsation amplitude (+11 +/- 5%, P < 0.001), retinal venous diameter (+3.0 +/- 3.6%, P = 0.002), and retinal arterial diameter (+2.8 +/- 4.2%, P < 0.01) but did not change retinal blood velocity. The H2 antagonist cimetidine had no significant effect on ocular hemodynamic parameters. In addition, cimetidine did not modify effects of histamine on choroidal blood flow, fundus pulsation amplitude, retinal venous diameter, and retinal arterial diameter compared with placebo. The present data confirm that histamine increases choroidal blood flow and retinal vessel diameters in healthy subjects. This ocular vasodilator effect of histamine is, however, not altered by administration of an H2 blocker. Whether the increase in blood flow is mediated via H1 receptors or other hitherto unidentified mechanisms remains to be elucidated.     

水溶性红曲中MonacolinK的稳定性

对红曲中Monacolin K（MK）在水溶液中的稳定性进行研究,考察不同加热温度、时间、pH、盐、维生素C（VC）、氨基酸、蔗糖质量浓度、光照和存放时间对其稳定性的影响。结果表明：100℃保温30min,水溶液中Monacolin K的浓度比20℃保温相同时间仅下降了4．6％。热处理、长时间光照对水溶液中Monacolin K有轻微的破坏作用：pH〈5．0,盐、VC、氨基酸的添加可降低水溶液Monacolin K溶解度。pH〈4．0可使酸型Monacolin K转化为内酯型。在Monacolin K水溶液中添加30g/L蔗糖可使水溶液中Monacolin K饱和质量浓度增至632．9mg／L。     

Volume flow estimation in the precapillary mesenteric microvasculature in vivo and the principle of constant pressure gradient

Volume flow was estimated from axial erythrocyte velocity measurements in 30 mesenteric microvessels of 6 rabbits and was compared to Murray's law predictions. The diameters of capillaries and precapillary arterioles ranged between 5.6 and 12 microm. The significant pulsating flow component existing in these microvessels was taken into account by measuring instantaneous axial blood velocity throughout the course of a cardiac cycle and then averaging over the period. In addition, the effect of the velocity profile variation with diameter was taken into account, for the first time, by using a profile factor function. According to Murray's law, the relation between blood volume flow and diameter is governed by a 'cube' law. Curve fitting to volume flow and diameter data pairs for rabbits, showed a dependence of volume flow on diameter raised to the 4th power (with a correlation coefficient equal to 0.97). The above result supports the hypothesis that, in the precapillary part of microvasculature, the principle of constant longitudinal pressure gradient rather than the principle of minimum work may be valid.