Effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation in rats depend on the blood glucocorticoid hormone level

The effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation were investigated before and after administration of indomethacin at ulcerogenic dose in adrenalectomized rats with or without corticosterone replacement and in sham-operated animals. We estimated the blood flow velocity in submucosal microvessels; the diameters and permeability of mucosal venous microvessels as parameters of gastric microcirculation. Desensitization of capsaicin-sensitive neurons was performed with capsaicin at the dose 100 mg/kg two weeks before the experiment. Adrenalectomy was created one week before experiment. In vivo microscopy technique for the direct visualization of gastric microcirculation and the analysis of the blood flow was employed. Indomethacin at ulcerogenic dose decreased the blood flow velocity in submucosal microvessels, caused dilatation of superficial mucosal microvessels and increased their permeability. Desensitization of capsaicin-sensitive afferent neurons potentiated indomethacin-induced microvascular disturbances in gastric submucosa-mucosa. These potentiated effects of the desensitization are obviously promoted by concomitant glucocorticoid deficiency. Thus, glucocorticoid hormones have a beneficial effect on gastric microcirculation in rats with desensitization of capsaicin-sensitive afferent neurons.     

盐酸戊乙奎醚对大白兔耳微循环的影响

目的 通过观察盐酸戊乙奎醚(长托宁)注射液对清醒状态大白兔耳微循环的影响,对盐酸戊乙奎醚改善微循环的作用作初步探讨和研究.方法 用微循环观测仪观测用药前大白兔耳廓微循环血管管径、血流速度、血流量等进行综合评估出正常微循环血流指标作为对照,观察盐酸戊乙奎醚用药后对家兔耳微循环血流量变化,并用山莨菪碱作药效对照.结果 两组...     

Role of gastric microcirculation in the gastroprotection by glucocorticoids released during water-restraint stress in rats

Our previous investigations demonstrated that glucocorticoids released in response to stress protect gastric mucosa against stress-induced ulceration. This study was designed to determine whether gastric microcirculation is involved in the mechanism of gastroprotective glucocorticoid action. For this we evaluated the effects of deficiency of glucocorticoid production during 3 hr water-restraint stress and corticosterone replacement on the stress-induced gastric erosions, gastric microcirculation and arterial pressure in rats. The stress was produced in awake rats and gastric microcirculation and arterial pressure were evaluated in animals anesthetized in 3 hr after the onset of water-restraint stress. An in vivo microscopy technique for the direct visualization of gastric microcirculation was employed. The gastric submucosal and the superficial mucosal microvessels were monitored on television screen through a microscope and the pictures were stored by microfilming for the analysis of red blood cell velocity and vessel diameter. Gastric microcirculation was estimated on the base of both the volume blood flow velocity in submucosal microvessels and the diameter of superficial mucosal venous microvessels. Gastric erosions were quantitated by measuring the area of damage. Plasma corticosterone levels were also measured after 3 hr stress by fluorometry. Water-restraint stress induced an increase in corticosterone level, an appearance of gastric erosions, a decrease in volume blood flow velocity of submucosal microvessels, a dilatation of superficial mucosal microvessels, a decrease in arterial pressure. The deficiency of glucocorticoid production during water-restraint stress promoted the stress-induced gastric ulceration, a dilatation of mucosal microvessels, a decrease of blood flow velocity in submucosal microvessels and of arterial pressure. Corticosterone replacement eliminated the effects of deficiency of glucocorticoid production on all of the parameters under study. Thus, the stress-induced corticosterone rise decreased gastric ulceration, restricted both the reduction of blood flow velocity in submucosal microvessels and a dilatation of superficial mucosal venous microvessels during water-restraint stress. These data suggest that the gastroprotective action of glucocorticoids during stress may be provided by the maintenance of gastric blood flow.     

Nitric oxide influences red blood cell velocity independently of changes in the vascular tone

Nitric oxide (NO) plays a key role in regulation of vascular tone and blood flow. In the microcirculation blood flow is strongly dependent on red blood cells (RBC) deformability. In vitro NO increases RBC deformability. This study hypothesized that NO increases RBC velocity in vivo not only by regulating vascular tone, but also by modifying RBC deformability. The effects of NO on RBC velocity were analysed by intra-vital microscopy in the microcirculation of the chorioallantoic membrane (CAM) of the avian embryo at day 7 post-fertilization, when all vessels lack smooth muscle cells and vascular tone is not affected by NO. It was found that inhibition of enzymatic NO synthesis and NO scavenging decreased intracellular NO levels and avian RBC deformability in vitro. Injection of a NO synthase-inhibitor or a NO scavenger into the microcirculation of the CAM decreased capillary RBC velocity and deformation, while the diameter of the vessels remained constant. The results indicate that scavenging of NO and inhibition of NO synthesis decrease RBC velocity not only by regulating vascular tone but also by decreasing RBC deformability.     

Momentum integral method for studying flow characteristics of blood through a stenosed vessel

Taking into consideration the slip velocity at the wall of a blood vessel, a mathematical model is developed in the paper for the study of blood flow through a mammalian blood vessel in the presence of a stenosis. By employing the momentum integral technique, analytical expressions for the velocity profile, pressure gradient and skin-friction are derived. The condition for an adverse pressure gradient is also deduced. It is observed that the slip velocity bears the potential to influence the velocity distribution of blood to a remarkable extent and to reduce considerably the pressure-gradient as well as the skin-friction.     

Nitric oxide influences red blood cell velocity independently of changes in the vascular tone

Abstract

Nitric oxide (NO) plays a key role in regulation of vascular tone and blood flow. In the microcirculation blood flow is strongly dependent on red blood cells (RBC) deformability. In vitro NO increases RBC deformability. This study hypothesized that NO increases RBC velocity in vivo not only by regulating vascular tone, but also by modifying RBC deformability. The effects of NO on RBC velocity were analysed by intra-vital microscopy in the microcirculation of the chorioallantoic membrane (CAM) of the avian embryo at day 7 post-fertilization, when all vessels lack smooth muscle cells and vascular tone is not affected by NO. It was found that inhibition of enzymatic NO synthesis and NO scavenging decreased intracellular NO levels and avian RBC deformability in vitro. Injection of a NO synthase-inhibitor or a NO scavenger into the microcirculation of the CAM decreased capillary RBC velocity and deformation, while the diameter of the vessels remained constant. The results indicate that scavenging of NO and inhibition of NO synthesis decrease RBC velocity not only by regulating vascular tone but also by decreasing RBC deformability.     

The effects of slip velocity on a micropolar fluid through a porous channel with expanding or contracting walls

In this paper, a simple mathematical model depicting blood flow in the deforming porous channel is developed with an emphasis on the permeability property of the blood vessel and slip boundary based on Beavers and Joseph slip condition. In this study, the blood is represented by a micropolar fluid. With such an ideal model, the governing equations are reduced to ordinary ones by introducing suitable similar transformations. Homotopy analysis method is employed to obtain the expressions for velocity and microrotation fields. Graphs are sketched for some values of parameters such as slip coefficient and expansion ratio, and the associated dynamic characteristics are analysed in detail.     

Effect of nonaxisymmetric hematocrit distribution on non-Newtonian blood flow in small tubes

Hematocrit distribution and red blood cell aggregation are the major determinants of blood flow in narrow tubes at low flow rates. It has been observed experimentally that in microcirculation the hematocrit distribution is not uniform. This nonuniformity may result from plasma skimming and cell screening effects and also from red cell sedimentation. The goal of the present study is to understand the effect of nonaxisymmetric hematocrit distribution on the flow of human and cat blood in small blood vessels of the microcirculation. Blood vessels are modeled as circular cylindrical tubes. Human blood is described by Quemada's rheological model, in which local viscosity is a function of both the local hematocrit and a structural parameter that is related to the size of red blood cell aggregates. Cat blood is described by Casson's model. Eccentric hematocrit distribution is considered such that the axis of the cylindrical core region of red cell suspension is parallel to the axis of the blood vessel but not coincident. The problem is solved numerically by using finite element method. The calculations predict nonaxisymmetric distribution of velocity and shear stress in the blood vessel and the increase of apparent viscosity with increasing eccentricity of the core.     

Effect of reinfusions of autologous blood on the systemic and portal circulation in acute blood loss in rats

The experiments on rats using the method of contact luminescent biomicroscopy coupled with the ultrasonic measurement of systemic blood pressure and blood flow velocity in the portal vein and hepatic artery have revealed that portal micro- and macrocirculation reflects the degree of efficacy of acute hemorrhage treatment with autoblood. Autoblood infusion in animals with compensatory type of posthemorrhagic period restored systemic blood pressure and blood flow velocity in the portal vein and hepatic artery, promoting the development of erythrocyte aggregation and local microcirculation disturbances in the central zone of hepatic functional elements.     

电磁水对血白细胞、红细胞、血小板及血管内皮细胞影响的研究

血管中白细胞等的粘附、聚集问题能够影响微循环的血流速度,是损伤血管内皮细胞乃至形成血栓的主要因素之一。在内毒素注射大白鼠的随机、对照实验中,发现电磁水能够减轻内毒素所致的炎症刺激,并能够降低白、红细胞和血小板的粘附、聚集,能降低白细胞的渗出,能提高红细胞的电泳率,能抑制血流速度的减慢和能够减轻血管内皮细胞的损伤。t检验,差异显著(P<0.01)以及差异明显(P<0.05)。揭示电磁水能够提高血细胞和血管内皮细胞的表面负电荷密度,并可以减轻外因(如,内毒素)对体内细胞和血管的损伤。说明电磁水能够改善微循环,维系正常血流和防止血栓形成。     

Dynamic Alterations of Cerebral Pial Microcirculation During Experimental Subarachnoid Hemorrhage

The study aimed to investigate the involvement of cerebral microcirculation turbulence after subarachnoid hemorrhage (SAH). Wistar rats were divided into non-SAH and SAH groups. Autologous arterial hemolysate was injected into rat’s cisterna magna to induce SAH. Changes of pial microcirculation within 2 h were observed. It was found that there were no obvious changes of the diameters, flow velocity, and fluid state of microvessels in non-SAH group. With the exception of rare linear-granular flow in A4 arteriole, linear flow was observed in most of the arterioles. There was no blood agglutination in any of the arterioles. After SAH, abnormal cerebral pial microcirculation was found. Spasm of microvessels, decreased blood flow, and agglutination of red blood cells occurred. Five minutes following the induction of SAH, the diameters of the arterioles and venules significantly decreased. The decreased diameters persisted for 2 h after cisternal injection. Decreased flow velocity of venules was found from 5 to 90 min after induction of SAH. Spasm of the basilar artery and increased brain malondialdehyde were also found after SAH. We concluded that cerebral microcirculation turbulence plays an important role in the development of secondary cerebral ischemia following SAH.     

Study of dynamic microcirculatory problems in ‘blackfoot disease’ -emphasizing its differences from arteriosclerosis

The cutaneous microcirculation can be divided into thermoregulatory shunt vessels and nutritive skin capillaries. Flux in nonnutritional shunt vessels dominates the signal recorded by the laser Doppler flowmeter. Computerized videophotometric capillaroscopy is a sensitive method for assessing cutaneous nutritive microcirculation. Using patients with blackfoot disease and arteriosclerosis as disease models, we evaluated the sensitivity and clinical usefulness of these relatively new techniques for peripheral vascular disorders. In blackfoot disease, blood flux measured by the laser Doppler flowmeter in the affected toe was lower than that in the nonaffected toe. In symptom-free fingers, blood flow was not significantly different between blackfoot disease and arteriosclerosis. However, blood flow in both diseases was lower than that of the control group. Patients who had the same status of thermoregulatory flow and eyeground arteriosclerotic classification underwent a 1-min arterial occlusion of the digits. The postocclusive reactive hyperemia response (PRH) of nailfold capillary loops was evaluated. All parameters for PRH for the cutaneous nutrient microcirculation including resting capillary blood cell velocity (rCBV), peak capillary blood cell velocity (pCBV) and time to pCBV were more significantly disturbed in the blackfoot disease group than in the arteriosclerotic group. On the basis of the results of this study, dynamic capillaroscopy provides a new approach for the early detection of circulatory disturbances resulting from different mechanisms.     

Pulsatile blood flow in a rigid pulmonary alveolar sheet with porous walls

This paper deals with the pulsatile blood flow in the lung alveolar sheets by idealizing each of them as a channel covered by porous media. As the blood flow in the lung is of low Reynolds number, a creeping flow is assumed in the channel. The analytical and numerical results for the velocity and pressure distribution in the porous medium are presented. The effect of an imposed slip condition is also studied. Comparisons with the corresponding results for the steady-state case are made at the end.     

电针改善VBI所致内耳微循环障碍及对VOR的影响

目的：对照电针和西比灵（盐酸氟桂利嗪）的效应,探讨电针改善椎-基底动脉供血不足（VBI）所致内耳微循环障碍的机理及电针对前庭-眼反射（VOR）的影响。方法：组织硬化剂-775注射液注射致家兔左侧颈椎横突软组织建立椎动脉型颈椎病（VCS）模型,采用直线加速度（LA）和水平旋转（HR）诱发眼震电图（ENG）、经颅多谱勒（TCD）、激光多谱勒血流计（LDF）和血液流变学,检测VBI家兔NEG频率、基底动脉（BA）血流速度、内耳血流量（IEBF）、血液粘度和细胞流变性变化。结果：模型组ENG频率、BA血流速度和IEBF显著降低,全血中、低切变率粘度和红细胞聚集指数（EDI）显著增高。西比灵可显著降低全血粘度和EDI,加快BA收缩期血流速度（Vs）,但对舒张期血流速度（Vd）和平均血流速度（Vm）无明显作用。电针不能降低血液粘度和EDI无明显作用,但改善IEBF和LA诱发的ENG作用较西比灵显著,并有增快Vs、Vd和Vm的趋势,电针和西比灵对HR诱发的ENG均无改善作用。结论：VBI所致内耳微循环障碍可引起前庭和水平半规管功能障碍,电针可能通过神经一体液调节改善VBI,并可能主要通过增强内耳微循环局部调节改善内耳血供,恢复前庭囊斑对LA的敏感性。电针效应优于西比灵。VBI模型前庭器官内血流分配及前庭信号转导可能存在复杂的机制,有待深入研究。     

Red blood cell velocity and oxygen tension measurement in cerebral microvessels by double-wavelength photoexcitation.

Because the regulation of microcirculation in the cerebral cortex cannot be analyzed without measuring the blood flow dynamics and oxygen concentration in cerebral microvessels, we developed a fluorescence and phosphorescence system for estimating red blood cell velocity and oxygen tension in cerebral microcirculation noninvasively and continuously with high spatial resolution. Using red blood cells labeled with fluorescent isothiocyanate to visualize red cell distribution and using the oxygen quenching of Pd-meso-tetra-(4-carboxyphenyl)-porphyrin phosphorescence to measure oxygen tension enabled simultaneous measurement of blood velocity and oxygen tension. We examined how the measurement accuracy was affected by the spatial resolution and by the excitation laser light passing through the targeted microvessel and exciting the oxygen probe dye in the tissue beneath it. Focusing the excitation light into the microvessel stabilized the phosphorescence lifetime at each spatial resolution; moreover, it greatly reduced phosphorescence from the brain tissue. Animal experiments involving acute hemorrhagic shock demonstrated the feasibility of our system by showing that the changes in venular velocity and oxygen tension are synchronized to the change in mean arterial pressure. Our system measures the red cell velocity and oxygen concentration in the cerebral microcirculation by using the differences in luminescence and wavelength between fluorescence and phosphorescence, making it possible to easily acquire information about cerebral microcirculatory distribution and oxygen tension simultaneously.     

Visualization study of motion and deformation of red blood cells in a microchannel with straight,divergent and convergent sections

The size of red blood cells (RBC) is on the same order as the diameter of microvascular vessels. Therefore, blood should be regarded as a two-phase flow system of RBCs suspended in plasma rather than a continuous medium of microcirculation. It is of great physiological and pathological significance to investigate the effects of deformation and aggregation of RBCs on microcirculation. In this study, a visualization experiment was conducted to study the microcirculatory behavior of RBCs in suspension. Motion and deformation of RBCs in a microfluidic chip with straight, divergent, and convergent microchannel sections have been captured by microscope and high-speed camera. Meanwhile, deformation and movement of RBCs were investigated under different viscosity, hematocrit, and flow rate in this system. For low velocity and viscosity, RBCs behaved in their normal biconcave disc shape and their motion was found as a flipping motion: they not only deformed their shapes along the flow direction, but also rolled and rotated themselves. RBCs were also found to aggregate, forming rouleaux at very low flow rate and viscosity. However, for high velocity and viscosity, RBCs deformed obviously under the shear stress. They elongated along the flow direction and performed a tank-treading motion.     

Automated Measurement of Microcirculatory Blood Flow Velocity in Pulmonary Metastases of Rats

Because the lung is a major target organ of metastatic disease, animal models to study the physiology of pulmonary metastases are of great importance. However, very few methods exist to date to investigate lung metastases in a dynamic fashion at the microcirculatory level, due to the difficulty to access the lung with a microscope. Here, an intravital microscopy method is presented to functionally image and quantify the microcirculation of superficial pulmonary metastases in rats, using a closed-chest pulmonary window and automated analysis of blood flow velocity and direction. The utility of this method is demonstrated to measure increases in blood flow velocity in response to pharmacological intervention, and to image the well-known tortuous vasculature of solid tumors. This is the first demonstration of intravital microscopy on pulmonary metastases in a closed-chest model. Because of its minimized invasiveness, as well as due to its relative ease and practicality, this technology has the potential to experience widespread use in laboratories that specialize on pulmonary tumor research.     

Mathematical model of the dynamics of transport of inert gases in the microcirculatory system

A mathematical model imitating transport of inert gases in the system of microcirculation under increased pressures was constructed. It has been shown that saturation of microareas nucleus of the brain cortex of average dimensions proceeds in about 90 sec. Effect of the blood flow velocity, gases tension in arterial blood and density of the capillary net on the dynamics of mass transfer of gases in a tissue was investigated.     

The effects of desensitization of capsaicin-sensitive neurons on the blood flow in microvessels of the rat gastric serous muscular membrane with normal and insufficient contents of glucocorticoids

The effects of desensitization of capsaicin-sensitive neurons on the blood flow velocity in microvessels of the gastric muscular membrane were investigated before and after indomethacin (35 mg/kg) administration in adrenalectomized rats with or without corticosterone replacement (4 mg/kg sc) and in sham-operated animals. Desensitization of capsaicin-sensitive neurons was performed with neurotoxic dose of capsaicin (20 + 30 + 50 mg/kg sc) two weeks before the experiment. Adrenalectomy was created one week before the experiment. The in vivo microscopy technique for direct visualization of gastric microcirculation and analysis of red blood cell (RBC) velocity was employed. Indomethacin decreased the RBC velocity. Adrenalectomy by itself profoundly decreased the RBC velocity, whereas corticosterone replacement prevented this effect. Desensitization of capsaicin-sensitive neurons did not influence the RBC velocity in sham-adrenalectomized rats; however, it induced further fall of both basal and indomethacin-induced RBC velocity in adrenalectomized rats that was prevented by corticosterone. We conclude that glucocorticoid hormones have a beneficial effect on the blood flow velocity in microvessels of the gastric muscular membrane in rats with desensitization of capsaicin-sensitive neurons.     

Effect of surface roughness on slip flows in hydrophobic and hydrophilic microchannels by molecular dynamics simulation

The influences of surface roughness on the boundary conditions for a simple fluid flowing over hydrophobic and hydrophilic surfaces are investigated by molecular dynamics (MD) simulation. The degree of slip is found to decrease with surface roughness for both the hydrophobic and hydrophilic surfaces. The flow rates measured in hydrophobic channels are larger than those in hydrophilic channels with the presence of slip velocity at the walls. The simulation results of flow rate are correlated with the theoretical predictions according to the assumption of no slip boundary condition. The slip boundary condition also strongly depends on the shear rate near the surface. For hydrophobic surfaces, apparent fluid slips are observed on smooth and rough surfaces. For simple fluids flowing over a hydrophobic surface, the slip length increases linearly with shear rate for both the smooth and rough surfaces. Alternately, the slip length has a power law dependence on the shear rate for the cases of hydrophilic surfaces. It is observed that there is a no-slip boundary condition only when shear rate is low, and partial slip occurs when it exceeds a critical level.