Relative changes of cerebral arterial and venous blood volumes during increased cerebral blood flow: implications for BOLD fMRI.

Measurement of cerebral arterial and venous blood volumes during increased cerebral blood flow can provide important information regarding hemodynamic regulation under normal, pathological, and neuronally active conditions. In particular, the change in venous blood volume induced by neural activity is one critical component of the blood oxygenation level-dependent (BOLD) signal because BOLD contrast is dependent only on venous blood, not arterial blood. Thus, relative venous and arterial blood volume (rCBV) and cerebral blood flow (rCBF) in alpha-chlorolase-anesthetized rats under hypercapnia were measured by novel diffusion-weighted (19)F NMR following an i.v. administration of intravascular tracer, perfluorocarbons, and continuous arterial spin labeling methods, respectively. The relationship between rCBF and total rCBV during hypercapnia was rCBV(total) = rCBF(0.40), which is consistent with previous PET measurement in monkeys. This relationship can be linearized in a CBF range of 50-130 ml/100 g/min as DeltarCBV(total)/ DeltarCBF = 0.31 where DeltarCBV and DeltarCBF represent rCBV and rCBF changes. The average arterial volume fraction was 0.25 at a basal condition with CBF of approximately 60 ml/100 g/min and increased up to 0.4 during hypercapnia. The change in venous rCBV was 2-fold smaller than that of total rCBV (DeltarCBV(vein)/DeltarCBF = 0.15), while the arterial rCBV change was 2.5 times larger than that of total rCBV (DeltarCBV(artery)/DeltarCBF = 0.79). These NMR results were confirmed by vessel diameter measurements with in vivo videomicroscopy. The absolute venous blood volume change contributes up to 36% of the total blood volume change during hypercapnia. Our findings provide a quantitative physiological model of BOLD contrast.     

Physiologic tomography: A new means for the non-invasive measurement of myocardial metabolism,blood flow and function

Although radionuclide procedures for the non-invasive study of ventricular function and relative myocardial perfusion were developed only recently, their value for the diagnosis and management of cardiovascular disease has been readily recognized by many clinicians. These procedures are now part of the routine diagnosic work-up of cardiac patients in many institutions throughout the world. However, these conventional techniques are limited in two ways: The radiopharmaceuticals employed with these procedures are either largely unphysiologic or there is a limited understanding of their kinetics and mechanisms of uptake.More importantly, traditional Anger type scintillation cameras compress or superimpose three-dimensional information into two-dimensional images and thus limit detailed perception of internal structures. Further, sensitivity and resolution of scintillation cameras decreases from the surface to the internal portions of the body. Lastly, gamma photons are attenuated to varying degrees by body tissues prior to reaching the scintillation camera. Because of superimposition of three-dimensional information, depthdependent resolution and varying degrees of photon attenuation, scintigrams obtained with conventional scintillation cameras provide only a qualitative indication of the distribution of radioindicators in organs. These images do not provide a capability for determining the local tissue concentration of a given radioindicator. Regarding conventional cardiovascular procedures, quantification of myocardial blood flow or ventricular volumes from count measurements alone is very limited.     

Effects of MDMA on blood glucose levels and brain glucose metabolism

Purpose This study was designed to assess changes in glucose metabolism in rats administered single or repeated doses of MDMA. Methods Two different experiments were performed: (1) A single-dose study with four groups receiving 20 mg/kg, 40 mg/kg, saline or heat, and (2) a repeated-dose study with two groups receiving three doses, at intervals of 2 h, of 5 mg/kg or saline. Rats were imaged using a dedicated small-animal PET scanner 1 h after single-dose administration or 7 days after repeated doses. Glucose metabolism was measured in 12 cerebral regions of interest. Rectal temperature and blood glucose were monitored. Results Peak body temperature was reached 1 h after MDMA administration. Blood glucose levels decreased significantly after MDMA administration. In the single-dose experiment, brain glucose metabolism showed hyperactivation in cerebellum and hypo-activation in the hippocampus, amygdala and auditory cortex. In the repeated-dose experiment, brain glucose metabolism did not show any significant change at day 7. Conclusion These results are the first to indicate that MDMA has the potential to produce significant hypoglycaemia. In addition, they show that MDMA alters glucose metabolism in components of the motor, limbic and somatosensory systems acutely but not on a long-term basis.     

Use of carbon 11-acetate for the measurement of myocardial oxygen consumption

J Nucl Cardiol 2000;7:282–5.     

Absolute cerebral blood flow quantification with pulsed arterial spin labeling during hyperoxia corrected with the simultaneous measurement of the longitudinal relaxation time of arterial blood

Quantitative arterial spin labeling (ASL) estimates of cerebral blood flow (CBF) during oxygen inhalation are important in several contexts, including functional experiments calibrated with hyperoxia and studies investigating the effect of hyperoxia on regional CBF. However, ASL measurements of CBF during hyperoxia are confounded by the reduction in the longitudinal relaxation time of arterial blood (T(1a) ) from paramagnetic molecular oxygen dissolved in blood plasma. The aim of this study is to accurately quantify the effect of arbitrary levels of hyperoxia on T(1a) and correct ASL measurements of CBF during hyperoxia on a per-subject basis. To mitigate artifacts, including the inflow of fresh spins, partial voluming, pulsatility, and motion, a pulsed ASL approach was implemented for in vivo measurements of T(1a) in the rat brain at 3 Tesla. After accounting for the effect of deoxyhemoglobin dilution, the relaxivity of oxygen on blood was found to closely match phantom measurements. The results of this study suggest that the measured ASL signal changes are dominated by reductions in T(1a) for brief hyperoxic inhalation epochs, while the physiologic effects of oxygen on the vasculature account for most of the measured reduction in CBF for longer hyperoxic exposures.     

Comparison of arterial and venous blood lactate kinetics after short exercise

Seventeen healthy male volunteers participated in this study designed to compare arterial with both arterialized venous and venous lactate kinetics after short exercise. Blood samples drawn before, during, and after bicycle exercise were analyzed continuously for lactate. A mathematical function incorporating two exponential terms was fitted to the arterial, arterialized venous, and venous lactate recovery curves, and the parameters of the mathematical function were compared using a linear regression. All parameters measured on or fitted to the arterialized venous curves correlated well with the respective arterial data (correlation coefficient R = 0.82 to 0.99, P less than 0.001). Among the parameters obtained from the fit to the venous curves, only those describing lactate removal correlated closely with the arterial results. It is concluded that for lactate kinetic studies during recovery following short-term muscular exercise, the information obtained from arterialized venous blood is comparable to arterial blood, whereas the use of venous blood, from the sampling site in this study, appears suitable for determining only the parameters for lactate disappearance. These conclusions are illustrated by the comparison between arterial, arterialized venous, and venous parameters as a function of the work rate of the previously performed exercise.     

急性心肌梗死患者糖代谢状况分析

目的探讨急性心肌梗死患者的糖代谢状况。方法连续选择自2010年10月～2011年9月在我院住院的235例急性心肌梗死患者为研究对象,无明确糖尿病史的患者在出院前均常规行口服葡萄糖耐量（OGTT）试验,以明确糖代谢状况。结果急性心肌梗死患者中糖尿病患病率为44.7%,糖调节受损患病率为25.1%,总的糖代谢异常患病率为69.8%。除去既往有糖尿病史的患者,新诊断的糖尿病和糖调节受损患病率分别为24.9%和34.1%。结论急性心肌梗死患者中大多数存在糖代谢异常,行OGTT可及早发现糖代谢异常患者。     

高血糖对脑葡萄糖代谢的影响研究

目的：通过比较不同血糖水平人群脑PET图像,分析高血糖对脑葡萄糖代谢的影响。方法回顾性地分析行全身PET/CT检查发现的血糖增高者236例,按照有无糖尿病史分为两组：高血糖无糖尿病组131例和高血糖有糖尿病组105例;并以血糖增高者的平均年龄＆#177;5岁为范围选择血糖正常对照组292例。测量所有受检者的身高、体重,计算体重指数。用Scenium软件进行图像归一化并勾画脑区,得到3组人群各脑区的SUV平均值（SUVmean）后进行分析。结果高血糖无糖尿病组与高血糖有糖尿病组的体重指数差异无统计学意义（t=0.464,P〈0.05）,但均高于正常对照组（t=4.742和3.244,P均〈0.05）;比较3组的各脑区代谢发现,距状裂及周围皮层的代谢水平最高,而内侧颞叶、小脑的代谢水平较低;随着3组间血糖水平的升高,不同脑区SUVmean逐步降低,即：正常对照组〉高血糖无糖尿病组〉高血糖有糖尿病组。结论高血糖能降低大脑的葡萄糖代谢水平,有助于临床理解糖尿病脑病的发病机制。     

Noninvasive measurement of arterial cerebral blood volume using Look-Locker EPI and arterial spin labeling.

This paper describes a method of noninvasively measuring regional arterial cerebral blood volume fractions (CBV(a)) in vivo using the combination of Look-Locker echo-planar imaging (LL-EPI) with arterial spin labeling (ASL). Using this technique the arterial inflow curve is rapidly sampled and the regional CBV(a) is measured, while tissue perfusion signals are suppressed. Two methods of spin labeling (LL-EPI flow-sensitive alternating inversion recovery (LL-EPI-FAIR) and LL-EPI signal targeting using alternating radiofrequency (LL-EPI-STAR)) are assessed and their advantages discussed. The application of vascular crushing to LL-EPI-FAIR is described and used to validate the insensitivity of the sequence to the perfusion difference signal. LL-EPI-STAR is used to assess changes in CBV(a) in response to a finger-tapping task. LL-EPI-STAR signal difference curves are shown to have a shortened vascular transit delay and increased peak signal change on activation. A 33 +/- 14% increase in CBV(a) on activation is found. CBV(a) is measured with a 6-s temporal resolution and the temporal response is compared with the BOLD signal change. CBV(a) is shown to increase more rapidly and return to baseline significantly faster than the BOLD signal change, which supports the suggestion that a change in CBV(a) is an input to the BOLD response.     

Use of digitized functional angiography to evaluate arterial blood flow

Digital angiography (DA), being a computer-based imaging system, allows for manipulation of the image data. One potential use derived from data manipulation is the production of functional images or images that reflect a physiologic parameter in addition to anatomic information. A discussion is presented of the background work employed to derive blood flow measurements using DA images, including the theoretical and practical limitations of the methodology. While absolute blood flow is hard to determine by any noninvasive and many invasive methods, flow velocity and relative blood flow in large vessels is obtainable with small vlumes of intraarterial contrast injection using the basic principles of indicator dilution techniques and evaluation of the time versus density relationships of contrast bolus. An appraisal of the functional imaging method is provided, including its drawbacks and the potential areas of application.     

三种止血带动脉止血对犬束扎肢体静脉血气的影响

Objective To observe changes of venous blood gas when applying tourniquets to arterial bleeding dog models and compare the injury of the bundled tissues caused by three different tourniquets. Methods A total of 18 dogs were randomly divided to three groups and made into femoral artery bleeding model of the hind limbs. Then, rubber tubing, half-hitch tourniquet and multi-function pressure-control bandage (hemostatic bandage group) were employed respectively for femoral artery hemostasis in three groups. The pressure produced by the bandage and femoral vein blood gas indices were measured at 0.5, 1, 3 and 6 hours respectively after tourniquet application. Results The pressure produced by the hemostatic bandage group was 0.74 kg, which was obviously lower than 1.46 kg in the rubber tubing group and 2.09 kg in the half-hitch tourniquet group ( P ＜ 0.05 ). At one hour after hemostasis, PvO2 was (36.45 ± 10.45 )mm Hg in the hemostatic bandage group and (28.73 ± 9.07 )mm Hg in the rubber tubing group, which was significantly higher than (21.87 ±4.30) mm Hg in the half-hitch tourniquet group ( P ＜ 0.05 ). At 3 and 6 hours after hemostasis, PvCO2 was (50.67 ± 9.31 ) mm Hg and (60.02 ± 10.85)mm Hg respectively in the hemostatic bandage group, while (16.85 ± 16.51 )mm Hg and ( 60.02 ± 10.85) mm Hg respectively in the rubber tubing group, which were lower than that in the half-hitch tourniquet group ( P ＜ 0.05 or 0.01 ) . Conclusion Compared with rubber tubing and Halfhitch tourniquet, the hemostatic bandage can efficiently stop bleeding under slight pressure, with the least injury to the bundled tissues.     

三种止血带动脉止血对犬束扎肢体静脉血气的影响

Objective To observe changes of venous blood gas when applying tourniquets to arterial bleeding dog models and compare the injury of the bundled tissues caused by three different tourniquets. Methods A total of 18 dogs were randomly divided to three groups and made into femoral artery bleeding model of the hind limbs. Then, rubber tubing, half-hitch tourniquet and multi-function pressure-control bandage (hemostatic bandage group) were employed respectively for femoral artery hemostasis in three groups. The pressure produced by the bandage and femoral vein blood gas indices were measured at 0.5, 1, 3 and 6 hours respectively after tourniquet application. Results The pressure produced by the hemostatic bandage group was 0.74 kg, which was obviously lower than 1.46 kg in the rubber tubing group and 2.09 kg in the half-hitch tourniquet group ( P ＜ 0.05 ). At one hour after hemostasis, PvO2 was (36.45 ± 10.45 )mm Hg in the hemostatic bandage group and (28.73 ± 9.07 )mm Hg in the rubber tubing group, which was significantly higher than (21.87 ±4.30) mm Hg in the half-hitch tourniquet group ( P ＜ 0.05 ). At 3 and 6 hours after hemostasis, PvCO2 was (50.67 ± 9.31 ) mm Hg and (60.02 ± 10.85)mm Hg respectively in the hemostatic bandage group, while (16.85 ± 16.51 )mm Hg and ( 60.02 ± 10.85) mm Hg respectively in the rubber tubing group, which were lower than that in the half-hitch tourniquet group ( P ＜ 0.05 or 0.01 ) . Conclusion Compared with rubber tubing and Halfhitch tourniquet, the hemostatic bandage can efficiently stop bleeding under slight pressure, with the least injury to the bundled tissues.     

三种止血带动脉止血对犬束扎肢体静脉血气的影响

目的 通过动物实验观察三种止血带在控制犬下肢动脉出血时静脉血气指标的变化,分析并比较不同止血带对束扎侧组织的损伤程度.方法 将18只犬完全随机分为三组,并制作成后肢股动脉出血模型.采用橡皮管止血带、卡式止血带和多功能自控加压止血绷带(简称止血绷带)三种止血带对三组犬进行股动脉止血.分别测量三组犬止血带下压力并在止血后0.5,1,3,6 h检测束扎肢体静脉血气指标.结果 (1)止血绷带组的带下压力为0.74 kg,显著小于橡皮管止血带组(1.46 kg)和卡式止血带组(2.09 kg)(P＜0.05).(2)止血后1 h,止血绷带组静脉血氧分压(PvO2)为(36.45±10.45)mm Hg,橡皮管止血带组为(28.73±9.07)mm Hg,均高于卡式止血带组的(21.87±4.30)mmHg(P＜0.05);止血后3,6 h,止血绷带组二氧化碳分压(PvCO2)分别为(50.67±9.31)mm Hg和(60.02±10.85)mm Hg,橡皮管止血带组分别为(16.85±16.51)mmHg和(60.02±10.85)mm Hg,均低于卡式止血带组(P＜0.05或0.01).结论 止血绷带在较小压力下能有效止住犬的股动脉出血;在三种止血带中,止血绷带对束侧组织的损伤最小.     

Combined measurement of tumor perfusion and glucose metabolism for improved tumor characterization in advanced cervical carcinoma

Strahlentherapie und Onkologie - The aim of this pilot study was (1) to evaluate the combination of [18F]fluorodeoxyglucose (FDG) and [15O]water for detection of flow–metabolism mismatch in...     

Use of transgenic models to understand effects of exercise on glucose metabolism

This review will focus on the achievements obtained using transgenic animals in our understanding of exercise-induced insulin sensitivity as well as the regulation of glycogen storage in skeletal muscle, including the effects of acute exercise and insulin on the major determinants: glycogen synthesis and glucose uptake.     

Validity of predicting mean arterial blood pressure during exercise

PURPOSE: Mean arterial blood pressure (mean arterial pressure (MAP)) at rest is conventionally estimated as the product of the diastolic pressure plus one-third of the pulse pressure. Since pulse wave forms and the duration of diastole change during exercise, one might question the validity of this prediction equation for the exercise state. Our purpose was to test this by directly measuring blood pressure over a wide range of exercise intensities. METHODS: Pressure was recorded by arterial catheterization in 29 subjects performing progressive exercise and/or constant-load exercise at different intensities. Actual MAP was measured by integrating the area under the pulse curve and compared it with the value which was predicted from systolic and diastolic measures over heart rates ranging from 100 to 200 beats x min(-1). RESULTS: Predicted values were quite close to actual MAP, and the accuracy of the prediction equation changed minimally with increased exercise intensity. CONCLUSION: This method provides a valid estimation of MAP during exercise.     

火绒草对2型糖尿病大鼠糖脂代谢的影响

目的 观察火绒草对2型糖尿病大鼠血糖、血脂代谢的影响。方法采用高糖高脂饮食诱导联合链脲佐菌素（STZ）腹腔注射建立2型糖尿病大鼠模型,将Wistar大鼠随机分为正常组,糖尿病模型组,火绒草低剂量组（10g/kg）,火绒草高剂量组（20g/kg）,西格列汀组（10mg/kg）,连续给药4周后分别检测各组大鼠的体重、空腹血糖、空腹胰岛素、甘油三酯和胆固醇,并行葡萄糖耐量试验。结果与糖尿病模型组大鼠相比,火绒草高剂量组糖尿病空腹血糖、甘油三酯、胆固醇水平、葡萄糖耐量曲线下面积显著降低,胰岛素水平显著升高,且效果优于火绒草低剂量组和西格列汀组。结论火绒草可显著降低2型糖尿病大鼠的血糖水平,改善血脂紊乱。