Microcirculation, endothelium, and lymphatics最新文献

Two lines of evidence are presented demonstrating propagated constriction in mouse pial arterioles. First, a 2 second microapplication from a 6 micron pipette tip of approximately 12 nanoliters of BaCl2 or uridine triphosphate produced constrictions which spread to points 300 microns or more upstream from the point of application. Second, constrictions were elicited between 2 points of endothelial injury, each made with a focused laser beam 18 microns wide. A helium-neon laser was used in the presence of intravascular Evans blue. The constrictions were produced when a very brief exposure at a downstream site was followed by a more prolonged exposure at an upstream site 300 to 1100 microns from the downstream injury. In approximately half the cases the upstream damage elicited a local platelet aggregate. Therefore, vasoconstrictors released by aggregating platelets may have played a role in initiating constriction. Constriction was limited to the segment between the two endothelial injuries. The necessity for 2 injuries, rather than one, suggests that local losses of endothelium derived vasodilators also played a role in initiating constriction and/or permitting its propagation. Abrupt cessation of constriction at the sites of endothelial damage suggests that endothelium plays a role in propagation of constriction. Propagated constriction may play a role in amplifying the spasmotic effects of local subarachnoid hemorrhage or in the spread of constriction beyond local areas of reduced metabolic demand.

A detailed description is made of an acute closed cranial window method. The method is used for the study of cerebral pial microcirculation by intravital microscopy in the rat. Using these methods and techniques, the effects of systemic hypotension by SNP, i.v., on pial microvessel hemodynamics and on ICP were simultaneously measured and characterized under normophysiological conditions. The pH, PO2, PCO2 and temperature of the artificial cerebrospinal fluid (CSF) in the closed cranial window, intermittently measured, remained relatively constant, 30 to 60 min following the period of stabilization of the preparation. The infusion of SNP (6.2-35.0 micrograms/kg/min, 0.02% sol., i.v.) significantly decreased BP (52.1 +/- 13.4 mm Hg, mean +/- SD). From measurement of microvessels internal diameter (I. D.) and microhemodynamics, significant increases in pial arteriolar I.D. (from 35.4 +/- 10.1, microns, to 47.1 +/- 5.7, microns, mean and S.D., 33.0%) and estimated bulk flow (51.2%), occurred during the hypotension. The changes in hemodynamic parameter were predominantly in the arteriolar system. Only minimal changes in the venular diameter occurred during the SNP hypotension. The observed moderate (22.0%) increase in ICP during SNP hypotension in pentobarbital anesthetized rat correlates well with the microhemodynamic changes of the cerebral microcirculatory system.

Previous studies have suggested an uneven distribution of alpha-adrenergic receptors within the coronary arterial tree. We hypothesized that stimulation of these receptors would alter the regional and microregional variability of oxygen supply and utilization. Accordingly, we measured the heterogeneity of coronary blood flow to 0.5 g tissue samples and O2 saturation of small cardiac veins during coronary alpha-adrenergic stimulation. In 14 dogs we cannulated and perfused a branch of the left coronary artery. In seven dogs, an intracoronary infusion of the alpha-adrenergic agonist phenylephrine was established after prior beta-adrenergic blockade. Phenylephrine infusion decreased subendocardial venous O2 saturation (41.6 +/- 5.6 vs 45.4 +/- 5.8% saturated, P less than 0.05). It did not change the heterogeneity or distribution of the O2 saturations relative to the normally-perfused region (coefficient of variation = 22.4 +/- 6.7 vs. 19.7 +/- 4.8%, P = 0.20). Regional blood flows were made during control, beta-adrenergic blockade, and phenylephrine infusion conditions in the remaining dogs. The coefficient of variation of blood flow to samples from the perfused region was 27.1 +/- 9.8, 27.8 +/- 10.8, and 24.7 +/- 7.5% (P greater than 0.25), respectively. The results indicate that coronary alpha-adrenergic stimulation does not alter O2 supply/utilization heterogeneity, and suggest a fairly uniform distribution and/or effect of alpha-adrenergic receptors within the coronary resistance vessels.

Neurokinin A and neurokinin B may play a role in control of the peripheral circulation in either physiological or pathophysiological conditions. We have infused these peptides intra-arterially at three infusion rates each to assess their actions on vascular pressures, blood flows and total and segmental resistances in skin and skeletal muscle in the canine forelimb. Neurokinin A infusions (.01, .1, and 1 micrograms/min) decreased total forelimb resistance; transiently, 26% and 57%, respectively. The decrease in resistance was equally distributed between the skin and skeletal muscle circulations and was manifest in both large artery and small vessel resistances. Systemic and forelimb arterial pressures were decreased in a dose-dependent manner. Neurokinin B infusions (.5, 1 and 5 micrograms/min) decreased total forelimb resistance 29%, 31%, and 52%, respectively. The decrease in resistance was equally distributed between the skin and skeletal muscle circulations and was the result of decreases in both large artery and small vessel resistances. Systemic and forelimb arterial pressures were decreased in a dose-dependent manner. The potent effect of neurokinins on vascular resistance and their concentration in perivascular nerves innervating the resistance vessels of the circulation suggests a potential role for these neuropeptides in circulatory control.

The acute effects of photoradiation after administering hematoporphyrin derivative (Hpd) on capillary blood flow were studied in intrahepatic tumors and normal liver. The tumors were solitary Walker carcinosarcomas implanted within the livers of Sprague-Dawley rats. Capillary flow was measured by a laser doppler monitor with its probe positioned over the tumor or over normal liver. Within a minute after intraportal Hpd injection (1.7 mg), capillary flow in the tumors began to decrease. Minimal levels of flow were maintained for as long as 15 minutes after Hpd injection with no observed recovery of flow back to control levels. Ratio of minimal flow/control flow averaged 0.36. Similar results were seen in studies on normal liver tissue. These studies demonstrate the extremely rapid vasoactive effects caused by photoradiation of Hpd. Vasoconstriction, vascular stasis and ischemia have proven to be important mechanisms in producing tumor cell destruction by photodynamic therapy.

In vitro preparations of isolated umbilical vessels are ideal for the study of vasoactive substances. These vessels display vascular reactivity in response to numerous substances, although the mechanism of action of many of these agents is unknown. The present study was undertaken to study the role of the endothelium in the vasoactivity of these preparations, and to examine their cellular integrity. Umbilical artery and vein were studied using conventional isometric techniques, and using high power light microscopy. We found that umbilical vessel rings had no relaxant response to agents believed to release endothelium-derived relaxant factor (EDRF). Mechanical and chemical treatment to remove endothelium did not significantly alter vascular response to known contractile agonists. Cellular morphology is well maintained in ring preparations. Finally, mechanical rubbing of the intima of these rings is more reliable in endothelium removal, as compared to chemical removal with the detergent saponin.

In a group of 12 subjects (5 men, 7 women) with vascular atherosclerotic disease (VAD) and in a group of 17 subjects (9 men, 8 women) with VAD and with non-insulin dependent diabetes mellitus (NIDDM) we evaluated the red cell membrane individual phospholipids and their relationships with the erythrocyte membrane fluidity. Examining the group of non diabetic subjects with VAD, it is evident that no difference is present between normals and this group regarding individual phospholipids; in this group is present a slight correlation between the erythrocyte membrane fluidity (expressed as Iex/Im ratio) and phosphatidylethanolamine only. Examining the group of VAD subjects with NIDDM it is evident that between normals and this group a significant difference is present for phosphatidylcholine and phosphatidylserine; in this group no relationship is evident between red cell membrane individual phospholipids and Iex/Im ratio.

The diameters of arterioles 30-40 microns on the surface of the mouse brain were monitored by TV microscopy with an image splitting technique. Endothelium was injured by light from a helium neon laser in the presence of intravascular Evans blue. This method was previously shown to selectively eliminate dilation by known endothelium dependent dilators which cause endothelial cells to release one or more relaxing factors (EDRFs). Dilation was produced by local application of 8 Br cGMP and dibutyryl cAMP, 10(-5) M. The response before endothelial damage was compared with the response after damage. Two separate studies were conducted. In one, 10 mice were treated with 8 Br cGMP and 10 with dibutyryl cAMP. In the second study 12 mice were treated with each nucleotide before endothelial injury and again after injury. In both studies only the response to 8 Br cGMP was impaired (p less than .01) by the endothelial injury. These data suggest that in these arterioles a portion of the response to GMP, but not to AMP, is controlled by endothelium and may reflect a role for guanylate cyclase/GMP in the synthesis/-release of an EDRF. This would provide a function for the guanylate cyclase in endothelial cells. The function of guanylate cyclase within these cells has not previously been defined.

The measuring properties of antimony electrodes were improved by the introduction of highly purified crystallographically oriented monocrystalline antimony (COMA). COMA electrodes are sensitive to pH and pO2. For measurements of either pH, pO2, or both, the pH and the pO2 sensitivities must be known and the components of the composite electrode signal must be separable. The oxygen sensitivity of COMA electrodes in vivo have been shown to be higher than in vitro in the pO2 range below 10 kPa. The present study was performed in an animal model to investigate the oxygen sensitivity and to further evaluate the tissue pO2 measuring properties of a miniaturized six channel COMA microelectrode. The results show that the COMA microelectrode has negligible drift, a response time of less than 5 s and high sensitivity and reproducibility for tissue pO2 measurements when the pH part of the electrode signal is eliminated. The oxygen sensitivity found (8.5 +/- 0.4 (mV/pO2) (mean +/- SEM)), is described by a direct linear function in the oxygen tension range studied. It is concluded that tissue pO2 can be calculated after elimination of the pH part of the electrode signal. A multichannel COMA microelectrode possess characteristics suitable for in vivo oxygen measurements and is therefore an interesting complement to traditional tissue oxygen sensors.

The precise effects ethanol (ETOH), acetaldehyde (ACT) and acetate (AC) exert on microscopic resistance and capacitance vessels in skeletal muscle is unknown. In-situ studies on the skeletal (cremaster) microvasculature of the rat, using high-resolution television microscopy, were undertaken. Acute administration (topical, intra-arterial or iv) of ethanol (0.001-10%) to young rats produced a concentration-related vasoconstriction of arterioles (18-45 microns) and muscular venules (25-50 microns), ranging from a 7 to 80% reduction in microvessel lumen sizes. Acute administration of either ACT or AC, however, produced concentration-related vasodilatation of these same microvessels. No known amine or opiate pharmacologic antagonist or cyclooxygenase inhibitor could attenuate or prevent ETOH, ACT and AC from eliciting their unique microvascular responses. These new, direct in-situ microcirculatory findings clearly demonstrate: 1) ETOH exerts constrictor, and not dilator, effects on skeletal muscle microscopic resistance and capacitance vessels; 2) both ACT and AC exert dilator, and not constrictor, effects on these muscle microvessels; and 3) the effects of alcohol can not be due to metabolism to ACT or AC. A progressive increase in ischemia of the skeletal muscle microscopic resistance and capacitance vessels, over a period of time (weeks to years), could result in the well-known syndrome of alcoholic myopathy.