Clinical Hemorheology and Microcirculation - Volume 34, issue 1-2

Authors: Sun, Bao-Liang | Xia, Zuo-Li | Wang, Jing-Ru | Yuan, Hui | Li, Wen-Xia | Chen, Yu-She | Yang, Ming-Feng | Zhang, Su-Ming

Article Type: Research Article

Abstract: The study was designed to observe the influence of blockade of cerebral lymphatic drainage on the regional cerebral blood flow (rCBF) and brain edema after experimental subarachnoid hemorrhage (SAH). Wistar rats were divided into non-SAH, SAH, and SAH plus cervical lymphatic blockade (SAH+CLB) groups. Autologous arterial hemolysate was injected into rat's cisterna magna to induce SAH. The rCBF was recorded continuously by a laser Doppler flowmeter. Intracranial pressure (ICP) was also monitored. After 24 hours and 72 hours of SAH, the rats were sacrificed and the brain was harvested for water content detection. It was found that there was no …obvious change of rCBF and brain water content during the experiment in non-SAH group. An immediate and persistent drop in rCBF was found in SAH group. The drop in rCBF was more obvious in SAH+CLB group. CLB also worsened the SAH-induced increase in ICP. The brain water content 24 hours and 72 hours after induction of SAH in SAH group increased significantly. CLB led to a further increase of brain water content. In conclusion, blockade of cerebral lymphatic drainage pathway deteriorates the secondary cerebral ischemia and brain edema after SAH. Show more

Keywords: Cerebral lymphatic drainage, subarachnoid hemorrhage, cerebral blood flow, brain edema

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 227-232, 2006

Authors: Seki, Junji | Satomura, Yasuhiko | Ooi, Yasuhiro | Yanagida, Toshio | Seiyama, Akitoshi

Article Type: Research Article

Abstract: In order to analyze cerebral hemodynamics and its change following neural activation, the cross-sectional profiles of blood flow velocity in the rat pial microvessels and their temporal changes were measured in vivo using Doppler OCT technique (Doppler optical coherence tomography). The OCT system used in this study has axial resolution of 11 μm and lateral resolution about 14 μm in the cortical tissue. The velocity distributions along the vertical diameter of pial microvessels in a cranial window of the rats were measured at short time intervals by scanning the OCT sampling point repeatedly. The velocity profiles obtained in the pial …arterioles were parabolic at any phase, although the centerline velocity pulsated following heart beats with amplitude as large as 50% of the temporal mean velocity. It indicates that the blood flow in the pial microvessels is a quasi-steady laminar flow, which is consistent with the flow expected for the case of a small Reynolds number and a small frequency parameter. The stimulus-induced increase in velocity pulsation was much larger than the increase in the mean velocity, which places a restriction on the mechanism of regulating the regional cerebral blood flow and blood volume. The results obtained in this study showed that the Doppler OCT has a potential of measuring velocity profiles and their temporal changes with both high temporal and spatial resolutions for the pial microvessels with diameter up to 200 μm. Show more

Keywords: Velocity profile, Doppler optical coherence tomography, pial microvessel, cardiac pulsation, electrical stimulation, functional hyperemia

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 233-239, 2006

Authors: Sun, Bao-Liang | An, Wei | Xia, Zuo-Li | Zheng, Cheng-Bi | Li, Wen-Xia | Yang, Ming-Feng | Zhao, Tong | Ye, Wen-Jing

Article Type: Research Article

Abstract: This study was aimed to evaluate the influence of an antagonist of heme oxygenase, zinc protoporphyrin IX (ZnPPIX), on the production of endogenous carbon monoxide (CO) and the secondary cerebral injury after subarachnoid hemorrhage (SAH). Wistar rats were divided into non-SAH, SAH, and ZnPPIX groups. Autologus arterial hemolysate was injected into rat cisterna magna to induce SAH. CO and cyclic guanosine monophosphate (cGMP) levels in the brain, and lactate dehydrogenase (LDH) activity in serum were determined 24 hours and 72 hours after cisternal injection. It was found that 24 hours and 72 hours after SAH, the CO contents in SAH …group were increased by 20.76% and 37.36%, respectively. CO content in ZnPPIX group was statistically lower than that in SAH group. No obvious change of cGMP content in SAH group was found. However, cGMP content in ZnPPIX group was lower than that in SAH group. Serum LDH activity increased significantly after induction of SAH. LDH activity in ZnPPIX group increased to a greater extent. It was concluded that ZnPPIX aggravates the cerebral injury secondary to experimental SAH by inhibiting the production of endogenous CO. The activation of HO/CO pathway is an intrinsic protective mechanism against cerebral ischemic injury after SAH. Show more

Keywords: Subarachnoid hemorrhage, carbon monoxide, zinc protoporphyrin IX, heme oxygenase

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 241-246, 2006

Authors: Niimi, Hideyuki | Komai, Yutaka | Yamaguchi, Saburo | Seki, Junji

Article Type: Research Article

Abstract: Flow disturbance due to microembolism in the cerebral microvasculature with an arcadal network was studied by a numerical simulation. A mathematical model for flow in the arcadal network was developed, based on in vivo data of cat cerebral microvasculature and flow velocity. The network model consisted of 45 vessel segments, and 25 branching points. To simulate microvascular responses to blood flow, the following three types of responses to wall shear stress were considered; non-reactive (solid-like), cerebral arteriole, and skeletal muscle arteriole-like responses. The numerical calculation was carried out in the condition where a feeding arteriole was occlused. Flow changes in …efferent vessels were evaluated for assessment of blood supply to the local area of cerebral tissue. The present simulation has demonstrated that blood flow in efferent vessels was influenced by the topology of the vascular network and the response pattern in single vessels. The arcadal structure of arterioles might be most effective in response to flow disturbances in efferent vessels. Show more

Keywords: Arcadal network, flow disturbance, cerebral microcirculation, flow-induced response, microembolism

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 247-255, 2006

Authors: Sasaki, Rie | Whitt, Stevan P. | Huxley, Virginia H.

Article Type: Research Article

Abstract: Whether insulin influences microvascular exchange is important in understanding its specific role in insulin resistance and the treatment of diabetes. We investigated whether insulin could induce changes in the microvascular flux of albumin from the mesenteric venules of anesthetized male and female Sprague-Dawley rats (n=11). After catheterization for monitoring of mean arterial pressure (MAP), a loop of small intestine was exteriorized. The mesentery was draped over a coverslip for observation and suffused continuously with bicarbonate-buffered solution (BBS) (pH 7.4, 37°C). After intravenous injection of Alexa 594™ labeled bovine serum albumin (BSA, 8 mg/kg), fluorescence intensity (If ) was recorded on …videotape for 30 minutes BBS suffusion and 75 minutes suffusion of BBS plus 0.02 U/ml porcine insulin. Microvascular flux of BSA was measured as a leak index (LI) of If in a 10×30 μm window over a postcapillary venule relative to If of the adjoining tissue. Insulin induced a rapid 34% decrease in LI within 5 minutes (p<0.05) that was sustained for the next 30 minutes. We also observed gender and age differences in the permeability response to insulin, as there was a sustained ∼59% decrease in LI in adult females (n=5) after 25 minutes, whereas there was an acute, transient (15 min) 45% decrease in LI in juvenile males (n=6). We conclude that insulin reduces mesenteric venule permeability differently in males and females. Further studies are needed to differentiate the permeability responses with respect to age and gender. Show more

Keywords: Permeability, microcirculation, endothelium, insulin, diabetes

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 259-263, 2006

Authors: Futrakul, Narisa | Butthep, Punnee | Patumraj, Suthiluk | Siriviriyakul, Prasong | Futrakul, Prasit

Article Type: Research Article

Abstract: This paper was aimed to study biomarkers of endothelial injury in chronic kidney diseases. Fifty chronic kidney disease patients were subject to the following determinations: (i) circulating endothelial cells, (ii) soluble VCAM-1, (iii) transforming growth factor beta (TGFB), and (iv) intrarenal hemodynamics. Increased number of circulating endothelial cells was significantly observed. A significant depletion of vascular endothelial growth factor (VEGF) or a depleted VEGF/TGFB ratio was also documented. Results showed that sVCAM was not significantly different from normal control. Intrarenal hemodynamic alteration demonstrated a characteristic of hemodynamic maladjustment. Since increased number of circulating endothelial cells is a sensitive biomarker for …endothelial cell injury in chronic kidney diseases, such injury is supported by the depletion of VEGF. The endothelial cell loss correlates with the glomerular endothelial dysfunction characterized by hemodynamic maladjustment at the efferent arteriole and reduction in peritubular capillary flow. In conclusion, correction of such hemodynamic maladjustment with multidrug vasodilators can effectively restore renal function in chronic kidney diseases. Show more

Keywords: Endothelial cell injury, microvascular disease, hemodynamics, chronic kidney disease, VEGF, transforming growth factor beta (TGFB)

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 265-271, 2006

Authors: Tigno, Xenia T. | Ding, Shi Ying | Hansen, Barbara C.

Article Type: Research Article

Abstract: Although microvascular complications are frequent in diabetes, the pathogenesis underlying these morbidities remains unclear. Chronic inflammation appears to play a role both in the development of vascular dysfunction and diabetes. Evaluation of microvascular status in the prediabetic stages would provide a better insight into the natural progression of the disease, both from the vascular and metabolic perspective. Microvascular function was assessed in sixty rhesus monkeys using laser Doppler fluximetry. These included monkeys who had been calorie-restricted (CR); normal non-diabetic ad libitum fed (N) monkeys; Prediabetic (PreDM) monkeys with either impaired fasting glycemia, glucose intolerance or insulin resistance; and overtly diabetic …monkeys (DM) with fasting glucose levels above 126 mg/dl. Body weight, per cent body fat, fasting glucose and insulin levels, glucose disposal rate during an intravenous glucose tolerance test (Kglucose ), and insulin sensitivity (M-rate) as assessed by the euglycemic, hyperinsulinemic clamp procedure were measured. Routine clinical chemistry and hematology were also performed. Our results show that in prediabetes, dermal microvascular flow is characterized by an increase in response to thermogenic provocation. We further show that this paradoxical increase is significantly and highly correlated with circulating high sensitivity CRP levels. The study demonstrates that both mild chronic inflammation and elevated skin microvascular perfusion precede overt diabetes. Show more

Keywords: Type 2 diabetes, inflammation, microcirculation, CRP, prediabetes, metabolic syndrome, laser Doppler flow

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 273-282, 2006

Authors: Jariyapongskul, Amporn | Rungjaroen, Tippawan | Kasetsuwan, Ngamjit | Pathumraj, Suthiluk | Niimi, Hideyuki

Article Type: Research Article

Abstract: This study was aimed to investigate chronic changes of the iris microvasculature in streptozotocin (STZ)-induced diabetic rats. Diabetes was induced in male Wistar-Furth rats by intravenous injection of STZ (55 mg/kg.bw). The rats were divided into control (CON) and diabetic (STZ) groups. The experiments were performed at 8, 12, 24 and 36 weeks after the injection of STZ. The iris microcirculation was visualized under a fluorescence videomicroscope. Intraluminal diameters of microvessels were measured based on the FITC-dextran images. Leukocyte adhesion to the microvascular endothelium was evaluated by counting leukocytes (labeled with rhodamine 6G). The iris blood perfusion was measured using …laser Doppler flowmetry. Tissue lipid peroxidation of the eye was evaluated. The results demonstrated that the lipid peroxidation increased significantly after the injection of STZ. Both the diameters of arterioles (or precapillaries) and the iris blood perfusion decreased significantly in STZ rats, compared to the control levels. Adherent leukocytes increased significantly at 8, 12, 24 and 36 week after the injection of STZ, compared with the control levels. This indicates that the increased in oxygen-derived free radicals may be a major contributor for iris vascular endothelial dysfunction in diabetes mellitus, including leukocyte adhesion and reducing the arteriolar diameter. The present model may be useful for assessing long-term effects of therapeutic agents on diabetic retinopathy. Show more

Keywords: Diabetes, endothelial dysfunction, fluorescence videomicroscopy, iris microcirculation, leukocyte adhesion, STZ-induced diabetic rat

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 283-294, 2006

Authors: Amatyakul, Supathra | Chakraphan, Daroonwan | Chotipaibulpan, Siriporn | Patumraj, Suthiluk

Article Type: Research Article

Abstract: The purpose of this study was to determine the role of exercise training on blood flow in diabetic dental pulp. Male Spraque-Dawley rats were divided into three groups of control (CON), diabetes (STZ), and diabetes with exercise-trained (STZ + Ex) groups. Diabetes was induced by intravenous injection of streptozotocin (STZ; 55 mg/kg.bw). The exercise training protocol consisted of treadmill running, 5 times/week with the velocity of 13–15 m/min for 30 min. At 12 weeks (wks) and 24 wks after the STZ injection, the laser Doppler flowmeter (Model ALF 21, USA) was used to measure pulpal blood flow (PBF) while the …animals were anesthetized with sodium pentobarbital (50 mg/kg.bw). The results showed that STZ rats developed hyperglycemia, hypertriglyceridemia, higher mean arterial blood pressure, higher heart weight, body weight loss, and lower of PBF in the intact right lower incisor. Exercise training has beneficial effect on physiological characteristics of diabetic condition including triglyceride level, mean arterial blood pressure, heart rate, and heart weight. Interestingly, reduction of the PBF was restored in STZ + Ex rats. In conclusion, our observations indicate that exercise training can prevent the reduction in PBF of STZ-induced diabetic rats. Show more

Keywords: Diabetes, exercise training, laser Doppler flowmetry, pulpal blood flow

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 295-301, 2006

Authors: Okano, Hideyuki | Ohkubo, Chiyoji

Article Type: Research Article

Abstract: The involvement of plasma nitric oxide metabolites (NOx ) in hypertension was examined in stroke-resistant spontaneously hypertensive rats during the development of hypertension. Continuous application of a static magnetic field (SMF; a maximum magnetic flux density of 180 millitesla, a peak magnetic gradient of 133 millitesla/mm) to the left carotid sinus baroreceptors of rats was carried out for 6 weeks using a disc-shaped magnetic implant (4.4 mm in diameter, 2.2 mm in height). An L-type voltage-gated Ca2+ channel blocker, nicardipine (2 mg/kg) was administered intraperitoneally three times a week for 6 weeks, and then 15 min after each injection, …mean arterial blood pressure (MAP), heart rate (HR), skin blood flow (SBF), skin blood velocity (SBV) and plasma NOx were monitored. The nicardipine significantly decreased MAP, and increased HR, SBF and SBV in the nicardipine-treated rats compared with the control rats (p<0.001) without changing plasma NOx levels. The SMF exposure alone significantly suppressed or retarded the development of hypertension in SMF-exposed rats compared with the control rats (p<0.05). The SMF significantly promoted the nicardipine-induced MAP decrease (p<0.001) and induced a significant increase in plasma NOx levels (p<0.01) in SMF-exposed, nicardipine-treated rats compared with the unexposed, nicardipine-treated rats. The SMF did not significantly induce any changes in the SBF and SBV in nicardipine-treated nor untreated rats. These results suggest that the SMF may enhance nicardipine-induced hypotension by more effectively antagonizing the Ca2+ influx through the Ca2+ channels compared with the nicardipine treatment alone. In addition, the enhanced antihypertensive effects of the SMF on the nicardipine-treated rats might be, at least in part, related to the increased NOx , primarily due to the upregulation of inducible nitric oxide synthase. Show more

Keywords: Nitric oxide, static magnetic fields, Ca$^{2+}$ channel blocker, antihypertensive effects, baroreceptor, spontaneously hypertensive rats

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 303-308, 2006

Authors: Chanawirat, Atchareeya | Khemapech, Sirima | Patumraj, Suthiluk | Siriviriyakul, Prasong

Article Type: Research Article

Abstract: The objective of this study is to examine roles of genistein in postmenopausal induced-endothelial dysfunction and bone loss, the ovariectomized (OVX) rat model was used. The animals were divided into three groups of sham treated with vehicle (DMSO 100 μl/day; Shamveh ), OVX treated with vehicle (OVXveh ) and OVX treated with genistein (0.25 mg/kg/day; OVXgen ). At 3 and 7 weeks after the surgery, endothelial dysfunction in mesenteric microcirculation of each group was determined by using intravital fluorescence microscopy and analyzed with digital image software. The parameters of bone mass density (BMD) and bone formation marker were represented by …percentage of ash/dry matter and osteocalcin activity (using radioimmunoassay (RIA)), respectively. Mean arterial pressures (MAP) in OVXveh groups were significantly increased compared to their aged-matched sham groups (p<0.05). Interestingly, the treatment of genistein could significantly attenuate this abnormality (p<0.001). Besides, it could increase the vascular response to acetylcholine (Ach; 10−6 M) significantly compared to OVX-rats (p<0.05). Moreover, BMD and osteocalcin activity were significantly increased in Ovxgen as well. Therefore, our findings suggested that genistein supplementation could effectively prevent endothelial dysfunction and bone loss in OVX-rat model. Show more

Keywords: Genistein, endothelial dysfunction, bone, ovariectomized rat

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 309-314, 2006

Authors: Sridulyakul, Pattrin | Chakraphan, Daroonwan | Patumraj, Suthiluk

Article Type: Research Article

Abstract: This paper was aimed to study whether vitamin C supplementation reverses the diabetes-induced endothelial cell dysfunction occurred in streptozotocin (STZ)-rats or not. The animals were divided into four groups: control and diabetes rats (DM, using iv. injection of 50 mg/kg.bw STZ), and two DM rats treated with vitamin C (1 g/l) starting on day 2 (DM + VitCday2 ) and week 6th after STZ-injection (DM + VitC6wks ). The mesenteric microcirculation was observed using fluorescence videomicroscopy. Based on the recorded videoimages, microvascular responses to acetylcholine (Ach; 10–5 M) and number densities of leukocyte adhesion in venules were evaluated using the …Global Lab II image software. In DM group, blood glucose and glycosylated hemoglobin were significantly increased, while the body weight and plasma vitamin C levels were decreased significantly compared to their controls. Ach-induced vasodilation was decreased, while the number of leukocyte adhesion was increased significantly compared to their controls (p<0.01). These abnormalities induced by DM were prevented by supplementation of vitamin C in DM + VitCday2 group. Six-weeks delayed treatment of vitamin C (DM + VitC6wks ) demonstrated increase in the Ach-induced vasodilation with significant decrease in the leukocyte adhesion. It was indicated that vitamin C supplementation could reverse diabetes-induced endothelial cell dysfunction in mesenteric microcirculation. Show more

Keywords: Diabetes, endothelial dysfunction, leukocyte adhesion, vitamin C, vasodilation

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 315-321, 2006

Authors: Cheung, Anthony T. | Duong, Patricia L. | Driessen, Bernd | Chen, Peter C. | Jahr, Jonathan S. | Gunther, Robert A.

Article Type: Research Article

Abstract: Systemic function and oxygenation changes during hemorrhagic shock treatment were continuously monitored and correlated with real-time microvascular changes. After splenectomy, each dog (n=12) was hemorrhaged (MAP=∼50 mmHg; ∼40% blood loss=32–36 ml/kg) and randomly assigned to 4 resuscitation groups: autologous/shed blood, hemoglobin-based oxygen-carrier/Oxyglobin® , crystalloid/saline, and colloid/Hespan® . Systemic function and oxygenation changes were continuously monitored and measured using standard operating room protocols. Computer-assisted intravital microscopy was used to non-invasively videotape and objectively analyze and quantify real-time microvascular changes in the conjunctival microcirculation. All measurements were made during pre-hemorrhagic (baseline), post-hemorrhagic and post-resuscitation phases of the study. Pre-hemorrhagic microvascular changes were …similar in all 12 dogs (venular diameter=43±12 μm; red-cell velocity=0.6±0.2 mm/s). All dogs showed similar significant (P<0.01) post-hemorrhagic microvascular changes: ∼20% decrease in venular diameter; ∼80% increase in red-cell velocity. These microvascular changes correlated with post-hemorrhagic systemic function and oxygenation changes. The resuscitations restored microvascular changes to pre-hemorrhagic values; the microvascular reversals also correlated with post-resuscitation systemic function changes in all groups. However, only shed blood resuscitation restored oxygenation level close to pre-hemorrhagic values. All 12 dogs survived resuscitation treatments despite differences in oxygen-carrying capability between groups. Show more

Keywords: Systemic function, oxygenation, hemorrhagic shock, blood substitutes

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 325-334, 2006

Authors: Sakai, Hiromi | Tsuchida, Eishun

Article Type: Research Article

Abstract: Hemoglobin-Vesicles (HbV; diameter, 250 nm) are artificial O2 carriers encapsulating purified and concentrated human Hb solution in phospholipid vesicles (liposomes), and their safety and efficacy, as a transfusion alternative, have been studied. In this paper, we summarized the characteristics of HbV that have been clarified by the microcirculatory observations.

Keywords: Blood substitutes, liposome, microcirculation, EDRF, oxygenation

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 335-340, 2006

Authors: Maeda, Nobuji | Cicha, Iwona | Tateishi, Norihiko | Suzuki, Yoji

Article Type: Research Article

Abstract: The effect of triglyceride in plasma on RBC aggregation was examined, and the prospective influence on the flow of RBCs in microcirculation and the O2 release was discussed. To minimize the individual differences, blood samples were collected from one subject 2 hrs after high-fat and low fat meals. Triglyceride content in plasma was measured by an enzymatic method, and the rate of rouleaux formation was measured with a low shear rheoscope. The rate of rouleaux formation was increased with the increase of triglyceride concentration. Our previous findings suggested some functional impairment in microcirculation. (1) The enhanced RBC aggregation tends …to reduce flow resistance in arterioles, but results in inhomogeneous flow of RBCs in capillaries. (2) The sclerotic change of microvessels alters flow behavior of RBCs, and thereby flow resistance is increased. (3) The enhanced RBC aggregation reduces O2 release from RBCs flowing in microvessels. In conclusion, high triglyceride level in plasma not only changes flow behavior of RBCs in microcirculation and thus increases flow resistance, but also prevents homogeneous tissue oxygenation. Show more

Keywords: Red blood cell aggregation, plasma triglycerides, cell-free layer, flow resistance, O$_{2}$ release

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 341-346, 2006

Authors: Zheng, Xiaoxiang | Ning, Gangmin | Yang, Yong

Article Type: Research Article

Abstract: To reveal the intracellular distribution of nitric oxide (NO) in single cell and to detect NO quantitatively in animal models, various methods are developed. A confocal microscope and 3D visualization technique were applied to visualize NO concentration in arbitrary directions and in different sections of cells. It was shown that NO distributions in cultured neurons of rat hipopocampus were not homogeneous. A kind of highly sensitive and selective NO electrode was utilized to measure the NO concentration in SD rat hippocampus, simultaneously with blood pressure and ECG recording. By the administration of NG -nitro-L-arginine methylester (L-NAME), the changes of NO …level in the hippocampus in vivo were detected. It was shown that the NO level decreased greatly when NOS was inhibited by L-NAME with significant increase in blood pressure. The developed methods may be helpful to investigate the physiological mechanism of NO and its role in pathology. Show more

Keywords: NO detection, confocal microscope, NO electrode

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 347-352, 2006

Authors: Shin, S. | Park, M.S. | Ku, Y.H. | Suh, J.S.

Article Type: Research Article

Abstract: Though the aggregation of red blood cells (RBCs) is a major determinant of blood viscosity, there have not been any available techniques to measure the effect of RBC aggregation on blood viscosity over a range of shear rates. The microfluidic shearing technique with vibration has been applied to an aggregometer for measuring the dynamic aggregation characteristic of RBCs. In measuring backscattered light intensity I(t) and pressure p(t) over time, both aggregation and the stress–shear rate information can be determined simultaneously. The feasibility and accuracy of the new aggregation measurement technique has been demonstrated to correlate with blood viscosity for normal …and heated blood. We found that RBC aggregability showed shear-dependent behavior, which can be correlated directly with shear-thinning blood viscosity. The present measurements of the dynamic aggregation characteristic over shear rate enable the interpretation of the shear-rate dependent blood viscosity, which is greatly affected by RBC aggregation. Show more

Keywords: Microfluidics, shear, aggregation, red blood cell, vibration

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 353-361, 2006

Authors: Ning, Gangmin | Bai, Yan | Yan, Weimin | Zheng, Xiaoxiang

Article Type: Research Article

Abstract: This paper was aimed to apply telemetry technology to investigate the cardiovascular activity of rats. A subminiature radio transducer was implanted in the body of rat to measure beat to beat blood pressure, ECG, body temperature, as well as the activity of rat continuously. Mathematic tools were developed to extract beat to beat cardiovascular parameters. Accordingly, spectral analysis of blood pressure variability and heart rate variability was performed to analyze cardiovascular activity in both normotensive and hypertensive rats. New indices were also established to assess the fluctuation of blood pressure of hypertensive rats and thus the effect of anti-hypertensive medication. …The ratio of low frequency power to high frequency power in heart rate variability of normotensive rats was much lower than that of hypertensive rats. In hypertensive rats, the blood pressure variability demonstrated significant increase. Furthermore, the circadian rhythm of blood pressure and heart rate variability also altered in hypertensive rats. After the treatment, the blood pressure of hypertensive rats dropped significantly. Meanwhile, the developed indices, such as 24h smoothness index were consistent with the behavior of blood pressure satisfactorily. The results suggest that the developed methods are powerful in studying cardiovascular system as well as evaluating the effects of antihypertensive medication objectively. Show more

Keywords: Telemetry, cardiovascular activity, blood pressure variability, heart rate variability, smoothness index

Citation: Clinical Hemorheology and Microcirculation, vol. 34, no. 1-2, pp. 363-371, 2006