Central neural influence on precapillary microvessels and sphincter.

The responses to central nervous system (CNS) stimulation of consecutive segments of arterioles down to the precapillary sphincter were measured in the mesoappendix and/or cremaster of nine male rats with indwelling electrodes. Under pentobarbital sodium anesthesia, vasoactive sites were stimulated at threshold for maximal constriction or lumen closure of the precapillary sphincter and/or immediately preceding precapillary arteriole (metarteriole). In all experiments, CNS stimulation induced blood pressure elevation and constriction of three consecutive segments of precapillary vessels and of the sphincter. A threefold increase in rate of vasomotion of precapillary sphincter and metarteriole was the rule, but this was noted infrequently in larger arterioles. In addition to an overall influence of the CNS on microcirculation, the data show a gradient of responses to stimulation, the slope of which is negatively related to the size of the vessels and sphincter, in both tissues studied. A complete lumen closure of the metarteriole and precapillary sphincter (when present) in response to CNS stimulation implies active participation in the regulation of local blood flow. No evidence was foun for central neural regulation of the precapillary sphincter independent of arteriolar control.     

The vascular architecture of the supravaginal and vaginal parts of the human uterine cervix: a study using corrosion casting and scanning electron microscopy

The aim of this study was to visualize and describe the vascular architecture of the vaginal and supravaginal parts of the human uterine cervix. Uteri collected at autopsy (n = 42) were perfused via the afferent vessels with fixative followed by Mercox resin. After polymerization of the resin, corrosion was performed. The obtained vascular casts of the cervix, visualizing all vessels including capillaries, were examined using scanning electron microscopy. Both in the vaginal and supravaginal parts of the cervix, four distinct vascular zones were distinguished – the outer zone containing large arteries and veins, the arteriole and venule zone, the endocervical mucosal capillaries zone and the pericanalar zone containing small veins and capillaries. In the pericanalar zone ran small veins, responsible for draining the mucosal capillaries. Both in the muscular layer, as well as in the pericanalar zone, arterioles and venules passed close to each other, often adjoining. This study introduces the idea of two systems responsible for draining blood from the mucosal capillaries. It is also the first to suggest the possible existence of a countercurrent transport between adjoining veins and arteries.     

抗疲劳复方中药提取物对小鼠骨骼肌微血管管径及血流速度的影响

目的 :研究抗疲劳复方中药提取物 (EAFF)对小鼠骨骼肌微循环的影响。方法 :采用我室建立的小鼠骨骼肌微循环观察方法 ,以肾上腺素作为引起微循环障碍的激动剂模拟骨骼肌疲劳。局部应用EAFF ,观察其对微血管管径及血流速度的影响。结果 :应用EAFF后 ,骨骼肌微动脉管径、微静脉血流速度以及毛细血管管径及血流速度与对照组比较均有明显改善 ,差异具有显著性意义 (P均 <0 .0 5 )。结论 :EAFF具有改善骨骼肌微循环障碍的作用     

Correlation of the directly observed responses of mesenteric vessels of the rat to nerve stimulation and noradrenaline with the distribution of adrenergic nerves

1. The effects of nerve stimulation and of the topical application of noradrenaline on arteries, capillaries and veins of the mesentery of the anaesthetized rat were examined by direct observation under a microscope. The distribution of adrenergic nerves to the vessels of the mesentery was studied using the fluorescence histochemical method.

2. Principal arteries, small arteries and terminal arterioles were all innervated by a network of adrenergic fibres and they all constricted in response to the stimulation of paravascular nerves and to exogenous noradrenaline. Few adrenergic fibres accompanied the smaller, precapillary arterioles; these vessels did not respond to nerve stimulation, although they were constricted by concentrations of noradrenaline as low as 10^-10 g/ml.

3. The capillaries did not respond to nerve stimulation or to applied noradrenaline. All veins were constricted by noradrenaline, but only those veins greater than about 30 μm in internal diameter responded to nerve stimulation.

4. At stimulus frequencies greater than 4 Hz the flow of blood through the microvasculature usually ceased, although there was never complete closure of these vessels. The maximum constriction observed in principal arteries was usually between 50 and 70% of the control internal diameter, and in small arteries and terminal arterioles was between 40 and 65% of the control internal diameter.

5. It is concluded that the principal arteries and small arteries of the mesenteric vasculature are important in the control of blood flow through this vascular bed during sympathetic stimulation and following topical application of noradrenaline, and that the precapillary arterioles are important vessels determining the rate of blood flow through the capillary bed under resting conditions.

     

“芬舒雅”对微循环和血液流变性的影响

“芬舒雅”吸入剂能扩张小白鼠脑膜及家兔球结膜的微小动、静脉,增加微血管密度,并使全血粘度和血浆粘度下降,血沉减慢.     

Correlation of the directly observed responses of mesenteric vessles of the rat to nerve stimulation and noradrenaline with the distribution of adrenergic nerves

1. The effects of nerve stimulation and of the topical application of noradrenaline on arteries, capillaries and veins of the mesentery of the anaesthetized rat were examined by direct observation under a microscope. The distribution of adrenergic nerves to the vessels of the mesentery was studied using the fluorescence histochemical method.2. Principal arteries, small arteries and terminal arterioles were all innervated by a network of adrenergic fibres and they all constricted in response to the stimulation of paravascular nerves and to exogenous noradrenaline. Few adrenergic fibres accompanied the smaller, precapillary arterioles; these vessels did not respond to nerve stimulation, although they were constricted by concentrations of noradrenaline as low as 10(-10) g/ml.3. The capillaries did not respond to nerve stimulation or to applied noradrenaline. All veins were constricted by noradrenaline, but only those veins greater than about 30 mum in internal diameter responded to nerve stimulation.4. At stimulus frequencies greater than 4 Hz the flow of blood through the microvasculature usually ceased, although there was never complete closure of these vessels. The maximum constriction observed in principal arteries was usually between 50 and 70% of the control internal diameter, and in small arteries and terminal arterioles was between 40 and 65% of the control internal diameter.5. It is concluded that the principal arteries and small arteries of the mesenteric vasculature are important in the control of blood flow through this vascular bed during sympathetic stimulation and following topical application of noradrenaline, and that the precapillary arterioles are important vessels determining the rate of blood flow through the capillary bed under resting conditions.     

The cytoarchitecture of the wall and the innervation pattern of the microvessels in the rat mammary gland: A scanning electron microscopic observation

This report describes the morphology of the smooth muscle cells, pericytes, and the perivascular autonomic nerve plexus of blood vessels in the rat mammary gland as visualized by scanning electron microscopy after removal of connective-tissue components. From the differences in cellular morphology, eight vascular segments were identified: (1) terminal arterioles (10–30 μm in outer diameter), with a compact layer of spindle-shaped and circularly oriented smooth muscle cells; (2) precapillary arterioles (6–12 μm), with a less compact layer of branched smooth muscle cells having circular processes; (3) arterial capillaries (4–7 μm), with “spidery” pericytes having mostly circularly oriented processes; (4) true capillaries (3–5 μm), with widely scattered pericytes having longitudinal and several circular processes; (5) venous capillaries (5–8 μm), with spidery pericytes having ramifying processes; (6) postcapillary venules (10–40 μm), with clustered spidery pericytes; (7) collecting venules (30–60 μm), with a discontinuous layer of circularly oriented and elongated stellate or branched spindle-shaped cells which may represent primitive smooth muscle cells; and (8) muscular venules (over 60 μm), with a discontinuous layer of ribbon-like smooth muscle cells having a series of small lateral projections. No focal precapillary sphincters were found. The nerve plexus appears to innervate terminal arterioles densely and precapillary arterioles less densely. Fine nerve fibers are only occasionally associated with arterial capillaries. Venous microvessels in the rat mammary gland seemingly lack innervation.     

The blood vascular architecture of the salamander external gill: a scanning electron microscopic study of corrosion casts

The blood vascular architecture in three-paired external gills of salamander tadpoles, Hynobius dunni Tago, was demonstrated with special reference to metamorphosis by scanning electron microscopy of vascular corrosion casts. In the fully developed gill, each of the three-paired afferent branchial arteries gave off secondary afferent filament arterioles. The afferent filament arteriole drained toward the efferent filament arteriole, forming the loop at the posterior extremity of the gill filament. The branched capillaries from the afferent filament arteriole formed two plates of respiratory capillary networks with irregular honeycomb-shaped meshes. In addition, there were non-respiratory shunts as bypass of the blood circulation between the afferent and efferent branchial arteries without branching filament arterioles. Furthermore, the deep venous plexus and subepithelial capillary plexus were seen around each efferent branchial artery. The filament central venule in the central part of the filament merged into the venous plexus. Nutritive capillaries branched from efferent branchial arteries also drained toward the venous plexus. Such general vascular architecture is simpler than that of the fish. During metamorphosis, the pattern of the vascular distribution, especially filament net capillaries became irregular, and then markedly tortuous or convoluted blood vessels occurred in the absorbing gill. At the metamorphic climax, the capillary network practically disappeared in the remnant of the gill but the bypass shunt as a non-respiratory artery remained almost unchanged.     

A Model of NO/O<Subscript>2</Subscript> Transport in Capillary-perfused Tissue Containing an Arteriole and Venule Pair

The goal of this study was to investigate the complex co-transport of nitric oxide (NO) and oxygen (O₂) in a paired arteriole–venule, surrounded by capillary-perfused tissue using a computer model. Blood flow was assumed to be steady in the arteriolar and venular lumens and to obey Darcy’s law in the tissue. NO consumption rate was assumed to be constant in the core of the arteriolar and venular lumen and to decrease linearly to the endothelium. Average NO consumption rate by capillary blood in a unit tissue volume was assumed proportional to the blood flux across the volume. Our results predict that: (1) the capillary bed, which connects the arteriole and venule, facilitates the release of O₂ from the vessel pair to the surrounding tissue; (2) decreasing the distance between arteriole and venule can result in a higher NO concentration in the venular wall than in the arteriolar wall; (3) in the absence of capillaries in the surrounding tissue, diffusion of NO from venule to arteriole contributes little to NO concentration in the arteriolar wall; and (4) when capillaries are added to the simulation, a significant increase of NO in the arteriolar wall is observed.     

Microcirculation of the bulbar conjunctiva in the goat implanted with a total artificial heart: effects of pulsatile and nonpulsatile flow

A new system to observe the microcirculation on the bulbar conjunctiva was developed using a digital high definition microscope to investigate the influence of the flow patterns on the microcirculation in a goat with a total artificial heart (TAH). The undulation pump TAH was implanted into the goat. When the whole body condition became stable, the flow pattern was modulated between the pulsatile and the nonpulsatile mode, and the changes in the microcirculation were observed. When the flow pattern was changed from pulsatile to nonpulsatile mode, the erythrocyte velocity in capillaries dropped from 526+/-83 to 132+/-41 microm/s and remained at a low level. The number of perfused capillaries decreased as well. Then the nonpulsatile flow mode was maintained for 20 minutes. After the flow pattern was returned to the pulsatile mode again, the erythrocyte velocity recovered to the initial level (433+/-71 microm/s). In many cases, the flow of the nonperfused capillaries in the nonpulsatile mode recovered to the initial level after the flow pattern was changed to the pulsatile mode again. The perfused capillary density in the nonpulsatile mode (19.7+/-4.1 number of capillaries/mm) was significantly lower than that in the pulsatile mode (34.7+/-6.3 number of capillaries/mm). It is thought that the basal and flow stimulated endothelium derived nitric oxide release in the microvessels decreased because of the disappearance of pulsatility and that the nitric oxide induced the constriction of arterioles after the flow pattern was changed to the nonpulsatile mode. At the same time, the baroceptors might sense the decrease in the arterial peak pressure or dp/dt, and the sympathetic nerve increases activities and induce the constriction of arterioles. Then, the erythrocyte velocity in capillaries would decrease. Because of the flow pattern further in the chronic phase, it is important to follow the change in the microcirculation.     

5‐Hydroxytryptamine‐induced microvascular pressure transients in lungs of anaesthetized rabbits

We determined lung microvascular pressure transients induced by 5‐hydroxytryptamine (5HT), by the micropuncture technique. We mechanically ventilated anaesthetized (halothane 0.8%), open‐chested rabbits, in which we recorded pulmonary artery (PA), left atrial (LA) and carotid artery pressures and cardiac output. For 4‐min periods of stopped ventilation, we constantly inflated the lung with airway pressure of 7 cmH₂O, then micropunctured the lung to determine pressures in arterioles and venules of 20–25 μm diameter. An intravenous bolus infusion of 5HT (100 μg), increased total pulmonary vascular resistance by 59%. Prior to 5HT infusion, the arterial, microvascular and venous segments comprised 30, 50 and 19% of the total pulmonary vascular pressure drop, respectively. However 14 s after 5HT infusion, the PA‐arteriole pressure difference (arterial pressure drop) increased 46%, while the venule‐LA pressure difference (venous pressure drop) increased >100%. The arteriole–venule pressure difference (microvascular pressure drop) was abolished. The increase in the arterial pressure drop was maintained for 4.8 min, whereas the increased venous pressure drop reverted to baseline in <1 min. We conclude that in the rabbit lung in situ, a 5HT bolus causes sustained arterial constriction and a strong but transient venous constriction.     

TA-Fe法媒染骨骼肌微血管及肌纤维的光镜研究

目的　光镜下观察骨骼肌微血管构筑及其与肌纤维的关系。方法　应用单宁酸媒染固定液灌流大鼠 ,取髂腰肌 ,冰冻切片 ,氯化铁显色 ,光镜下观察。结果　髂腰肌内微动脉以一定角度进入肌束内 ,形成毛细血管前微动脉或毛细血管营养纤维 ,毛细血管可同向走行 ,亦可呈反向或爪形分支 ,常见两条或者几条毛细血管互相吻合成网 ,多数毛细血管长距离直行于肌纤维之间 ,偶见波浪状走行者 ,毛细血管呈双线条状 ,可见细胞核 ,肌纤维保存完好 ,横纹清晰。结论　TA Fe法可清晰的显示髂腰肌微血管和肌纤维 ,血管内皮细胞和肌细胞的核明显     

Resistance vessels supplying the median eminence of the rabbit, rat, and cat

The ultrastructure of arterioles supplying the median eminence of eight rats, eight rabbits, and two cats was studied after vascular perfusion with phosphate buffered aldehyde fixatives. There were terminal arterioles with a lumen diameter of 50-70 micron within the pars tuberalis. Smaller arterioles (precapillary sphincters and metarterioles) with a lumen diameter of 15-20 micron were present on the surface of the median eminence. Arterioles were not observed to penetrate the neuropil but were seen to supply the external capillary plexus of the median eminence. Direct innervation of arterioles supplying the median eminence was not present and hence regulation of median eminence blood flow by peripheral sympathetic mechanisms appears unlikely. Resistance vessels were found to be closely related to axon terminals on the surface of the median eminence and to fenestrated capillaries of the external plexus. In addition, the endothelial cells of arterioles were characterized by the presence of pits and vesicles which may play a role in transendothelial transport. These findings suggest two mechanisms by which blood flow into the median eminence can be regulated: (a) by central catecholaminergic systems terminating in the median eminence and (b) by catecholamine secretions from the adrenal medulla.     

双峰驼胸膜下肺微血管构筑的扫描电镜观察

目的探讨双峰驼胸膜下肺微血管的构筑特征及其功能意义,为哺乳动物肺微血管构筑学研究积累资料。方法铸型扫描电镜技术。结果双峰驼胸膜下肺微血管根据其连续分支可以识别出4级血管：微动脉、终末微动脉、毛细血管前微动脉和毛细血管,胸膜下肺毛细血管通常由该部的毛细血管前微动脉发出,也可由终末微动脉直接发出,并最终相互吻合成胸膜下肺毛细血管网。胸膜下肺毛细血管网粗疏,网孔孔径一般大于毛细血管管径,网孔多呈六边形和五边形。胸膜下肺微动脉、终末微动脉和毛细血管前微动脉的铸型表面均显示有清晰的、环状排列的平滑肌压迹,毛细血管铸型表面可见卵圆形内皮细胞核的压痕。肺间质毛细血管与胸膜下肺微血管之间存在有广泛的、不同水平上的吻合。结论双峰驼胸膜下肺微血管构筑特征与其他哺乳动物比较,并无显著差异。     

Electron microscopical study of relaxation and constriction in frog arterioles

Mesenteric arterioles of frogs were selected under a dissecting microscope and compact vasoconstriction was induced by local application of a microdrop of epinephrine. Selected arterioles were fixed in situ at maximum constriction by flooding with buffered osmium tetroxide or glutaraldehyde. Fixation was faster than any vasoconstriction initiated by the onset of fixation. The arterioles were embedded in epoxy resin and regions of dilation and constriction were identified optically in the resin block. Ultrathin sections were cut at known levels for examination in the electron microscope. The localized constriction permitted the use of the relaxed, dilated region of the arteriole as a structural control for comparison against the fine structure of the constricted segment of the same arteriole. In constriction there was a dramatic change from the relaxed condition. The endothelial cells assumed a teardrop configuration and their nuclei protruded toward the lumen. The muscle cells and their nuclei became short and thick and demonstrated strongly indented borders, and the elastic membrane assumed a deeply pleated appearance. Both endothelium and smooth muscle cells appeared to adhere tightly to the elastic membrane for they faithfully replicated its convolutions. Bundles of thick (120 Å) and thin (70 Å) filaments were seen in the endothelial cytoplasm. The thick filaments were not contractile although the thin variety may shorten during vasoconstriction.     

Effects of electrical stimulation of the dorsal skin on systemic and mesenteric microvascular hemodynamics in anesthetized rats

The effects of electrical stimulation of the dorsal skin area on the mesenteric arterioles were investigated in anesthetized rats by the use of an intravital microscope-television system. Changes in the diameter of the mesenteric precapillary arterioles (10-40 microm in diameter) were measured with an image processor. Blood flow velocity in the mesenteric precapillary arterioles was monitored by the dual sensor method developed by the authors. Electrical stimulation was performed through two platinum electrodes placed at the right dorsal Th5-12 level skin area by the use of an electrical stimulator (0.2 ms, 20 Hz). Continuous stimulation lasting for 30 s (1-10 mA) and intermittent stimulation lasting for 10 min (3 mA) were applied. The pressor response following the depressor response was induced by a stimulus current above 8 mA. The decrease in mesenteric blood flow velocity was induced by stimulus current above 10 mA. These responses were abolished by lidocaine injection into the subcutaneous area where the electrodes were attached. No significant change in arteriolar diameter or heart rate were induced by the stimulation for 30 s. Electrical stimulation of the skin for 10 min evoked a decrease in the diameter of arterioles (-3.4 +/- 2%, p < 0.01, n = 12). In the adrenalectomized group, electrical stimulation of the skin for 10 min elicited a slight increase in the diameter (1.1 +/- 0.5%, n = 6). It is therefore suggested that electrical stimulation of the skin for 30 s reflexly evoked decreases in MAP and in blood flow velocity, and that the constriction of the mesenteric precapillary arterioles induced by the stimulation for 10 min was mediated by humoral adrenaline and noradrenaline released by somato-adrenal medullary reflex.