摘要:

ABSTRACTThe tracheobronchial microcirculation consists of a subepithelial capillary network and in some species deeper capacitance vessels and an adventitial network. Postcapillary venules are the main site of plasma extravasation in inflammatory conditions. There are surprising species differences. The subepithelial capillary network is dense in species such as sheep and dog but relatively scanty in rabbit and humans. Sheep have conspicuous capacitance vessels or blood sinuses, especially in the trachea and at points of bronchial branching with walls that lack smooth muscle. The rabbit also has a well‐developed capacitance system but the blood sinuses have thick muscular walls. Although the capacitance system in humans has not been studied much it is probably present with muscular walls. It is absent in rats but present in guinea pigs. Thus, in some species the tracheobronchial vasculature may give the mucosa an erectile capacity, as in the nose of each species. Arteriovenous anastomoses (AVA) cannot be demonstrated physiologically in sheep but they seem to be present as thoroughfare vessels in rats and guinea pigs. Whether they exist in humans is not known. The absence of AVA might indicate a weak or absent thermoregulatory and air conditioning role for the lower airway vasculature.Extensive studies of neurogenic inflammation in rodents show that sensory neuropeptides can open gaps between the endothelial cells of postcapillary venules and the same change can be caused by a large number of inflammatory mediators. These opened gaps cause extravasation of plasma into the interstitium. Small increases in interstitial pressure lead to spaces opening between the epithelial cells and exudation of plasma into the airway lumen.The role of the airway microvasculature in asthma is controversial. Cold and hyperosmolar solutions cause vasodilatation as do the mediators released in the mucosal inflammation of asthma. However, quantitation of the thickening of the airway wall due to vascular engorgement, mucosal edema, or increased luminal liquid does not prove that these changes are a cause of airway obstruction. The contraction of airway smooth muscle superimposed on the mucosal inflammatory pathology might lead to a synergistic mechanism to increase airway resistanc

ISSN:1073-9688    

DOI:10.3109/10739689609148283

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe microvasculature is an extremely adaptable structure that is capable of architectural and functional adjustments in response to multiple biochemical and mechanical stimuli. Inadequate or inappropriate adjustments often result in pathophysiology. Recent work has brought increasing recognition of the importance of microvascular remodeling in widespread disease states such as hypertension, tumor growth, diabetes, and progressive coronary artery occlusion. Much work has been done to characterize the cells and molecules with putative roles in microvascular remodeling, but little is known regarding the mechanotransduction processes that might link hemodynamic stresses such as wall shear stress and circumferential wall stress to structural and functional changesin vivo.Two primary approaches have been employed:in vitrostudies that use cultured cells and allow molecular biologic analysis of signaling pathways and gene expression; andin vivoexperiments aimed at understanding vessel adaptations in the intact tissue. This article reviews the structural adaptations exhibited by microvessels and the information available fromin vitroandin vivoapproaches. The formation of new arterioles in intact tissues is examined in detail as an example of integrative work, and the prospects for new technologies are discussed. This is a time of great opportunity for bidirectional exchange between basicin vitroadvances andin vivoexperimentation. This exchange will be essential in generating new understanding of the role of mechanical stresses in microvascular remodeling.

ISSN:1073-9688    

DOI:10.3109/10739689609148284

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The under‐agarose migration assay developed for use with endothelial cells provides a measurement of the intrinsic migratory behavior of a cell population. However, the assay is labor intensive and lacks experimental flexibility. This migration assay has been refined and tested on human microvessel endothelial cells in the presence of a migration stimulus or on differing matrix‐coated substrates.Methods: The improved assay retains the linear geometry and mathematical basis of the under‐agarose assay. Cells migrating from a cell reservoir formed with a Delrin® insert are counted using an automated image‐analysis system utilizing a high‐contrast, fluorescent nuclear stain. From the cell counts, a stochastic measure of random migration is calculated.Results: Values for random migration between the improved migration assay and the traditional under‐agarose assay were very similar. Furthermore, a stochastic measure of endothelial cell migration on fibronectin was determined.Conclusions: This improved linear migration assay permits readily obtainable measures of endothelial cell migration for a number of experimental conditions. Improvements in the assay include the use of a removable fence for forming cell reservoirs, a nuclear stain to facilitate cell counting, and a more comprehensive analysis of the ce

ISSN:1073-9688    

DOI:10.3109/10739689609148285

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The majority of investigations have demonstrated a strong relationship between muscle capillarity and oxidative capacity. There is, however, evidence that die capacities for O2supply and utilization can be dissociated. Also, metabolite removal rather man O2supply may represent the predominant design constraint placed on the capillary bed in some muscles (i.e., fast‐twitch glycolytic). Recent evidence suggests mat the principal barrier to O2diffusion in skeletal muscle resides between the red blood cell and the immediately subjacent sarcolemmal space. Consequendy, if the primary design constraint placed on the capillary bed is to facilitate O2exchange, we hypothesized that capillary surface per fiber surface should be correlated with die mitochondrial volume subserved. Thus, the purpose of this study was to investigate whether one single relationship would be found between the capillary‐to‐fiber surface ratio and fiber mitochondrial volume in slow‐ (soleus) and fast‐twitch (plantaris) muscle and whether this relationship would be preserved after training.Methods: Rats were exercise‐trained on a motor‐driven treadmill up to 60 min/day, 5 days/week for 4 weeks at an intensity calculated to elicit V 75% VO2max. Following training, soleus (S) and plantaris (P) muscles were removed under deep anesthesia for citrate synthase analysis, and the contralateral limb was perfusion‐fixedin situwith glutaraldehyde and analyzed morphometrically under light and electron microscopy.Results: Training significantly (p<0.05) increased citrate synthase activity and capillary‐to‐fiber ratio both in S and P muscles. For all muscles combined (i.e., S and P, control and trained), the capillary‐to‐fiber surface ratio significantly correlated with mitochondrial volume per unit fiber length (r= 0.64).Conclusions: Our finding of a single relationship between the capillary‐to‐fiber surface ratio and fiber mitochondrial volume across the muscles is consistent with the notion that the size of the capillary bed in muscles comprised principally of either slow‐twitch oxidative or mixed fast‐twitch oxidative glycolytic and fast‐twitch glycolytic fibers is primarily designed to meet fiber requirements for O2exchange, and that an important site for O2diffusion resistance is at the capillary‐fiber interface. In addition, capillary‐to‐fiber surface and fiber mitochondrial volume increased in similar proportions, i.e., the relationship between the two variables

ISSN:1073-9688    

DOI:10.3109/10739689609148286

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: To validate the use of two‐slit velocimetry in an epiilluminated microvascular bed by demonstrating conservation of flow and to compare this validation with that provided by the literature for transilluminated beds.Methods: The brain surface vessels of mice were epiilluminated with a mercury lamp and observed with a Leitz Ultrapak objective (22X) and dipping cone. The internal diameters were measured with an ocular micrometer. The Instrumentation for Physiology and Medicine (IPM) velocimeter and cross correlator were used to measure red blood cell (RBC) velocity at the centerline of 17 different microvascular branch points. The velocity in the feeding arteriole and each branch or in the tributaries and draining venule were used, together with the respective diameters, to calculate flow in each vessel. Findings in the arterioles and venules were combined, because the results were the same in either set of vessels.Results: Flow in the main vessel (nl/sec) = 0.97 (sum of flow in branches or tributaries) +2. The correlation coefficient was 0.95. The relationship was not significantly different from an ideal slope of unity. However, in individual bifurcations the sum of flows in branches or tributaries deviated by as much as 40% from predicted values.Conclusions: On the average, conservation of flow was present. The deviations from conservation at individual bifurcations were similar to those reported by others who utilized transilluminated beds. Thus, when conservation of flow is the validating criterion, the two‐slit technique used with epiillumination is not less valid than when used with transilluminat

ISSN:1073-9688    

DOI:10.3109/10739689609148287

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: This study addresses the hypothesis that the diminished constriction of renal arterioles to angiotensin II (Ang II) and norepinephrine (NE) in diabetic rats is due to elevated activity in the polyol pathway. This activity results in reduced incorporation of myo‐inositol into membrane phospholipids and impaired signal transduction.Methods: The left ureter of female Wistar rats (140‐160 g) was surgically ligated. Four to six weeks later, streptozotocin (50 mg/kg, i.p.) was injected in half of the rats to induce diabetes. Beginning on the day of streptozotocin injection, diabetic and nondiabetic rats were fed either a standard diet or a diet enriched with 1% myo‐inositol. Seven to 10 days later, all rats were anesthetized and the hydrone‐phrotic kidney was bisected and exteriorized in a bath for direct visualization of the renal microvasculature. The constrictor responses of interlobular, afferent, and efferent arterioles to Ang II or NE (applied to the bath) were directly quantitated byin vivomicroscopy.Results: Among diabetic rats, the myo‐inositol‐enriched diet significantly enhanced the constriction of interlobular, afferent, and efferent arterioles in response to Ang II, so that the responses to the peptide were almost completely restored to normal. Constriction to NE by interlobular arteries and afferent arterioles (but not efferent arterioles) was also significantly attenuated among diabetic rats fed the standard diet. However, unlike what was observed for Ang II, the myo‐inositol‐enriched diet did not enhance constriction to NE among diabetic rats.Conclusions: These data indicate that different mechanisms are responsible for decreased renal arteriolar constriction due to Ang II and NE in early diabetes. Diminished arteriolar constriction due to Ang II, but not to NE, may be linked to altered myo‐in

ISSN:1073-9688    

DOI:10.3109/10739689609148288

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The consequential implications of the leukocyte‐endothelial cell adhesion reaction, as well as the subsequent migratory activity of the leukocytes within the interstitium proper, are currently known only in general phenomenological terms. Our objective was to carry out a detailed quantitative analysis of transendothelial and interstitial migration.Method: We incorporated several new features, such as the video recording of time‐lapse photography in conjunction with the time history of individual leukocytes under the influence of representative stimulators and inhibitors. The mesentery was suffused with the chemical activator N‐formyl‐met‐leu‐phe (fMLP, 5 ± 10−8M) and histamine (10−6M) for periods up to 3 h. This leads to an attachment of neutrophils preferentially to the walls of small postcapillary venules followed by migration into the adjacent interstitium.Results: The time interval between the initial neutrophil adhesion to the luminal side of the venules and their first appearance on the abluminal side of the venule wall was about 25 min. The time interval for the actual physical migration across the endothelium was only about 1‐2 min. There was an initial increase in the number of neutrophils migrating across the wall per unit time after the application of fMLP. However, this effect then gradually decreased over the course of 1 h. In the extravascular tissue, the neutrophils appeared to migrate along random pathways with an average trajectory away from the venular wall. When histamine (1 μM) was applied topically in conjunction with fMLP, the overall migratory flux across the venular wall increased, although the cells migrated comparatively short distances into the interstitium. After pretreatment with phalloidin (25 μg/kg), an actin cross‐linking agent, neutrophil adhesion and migration in response to fMLP stimulation was reduced. The mast cell stimulator 48/80 (25 mg/ml) resulted in rapid degranulation, which was accompanied by an insignificant increase in neutrophil diapedesis. After fMLP stimulation there was reduced neutrophil emigration in the presence of mast cell inhibitors, such as lodoxamide (1 μg/kg) and ketotifin (1 μg/kg).Conclusions: Our results demonstrate that both the endothelial cells and interstitial mast cells are involved in the rate of transvascular migration of leukocytes across postcapillary venules a

ISSN:1073-9688    

DOI:10.3109/10739689609148289

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: In several systems, exogenous ascorbate (reduced vitamin C) has been shown to protect against microvascular injury induced by reactive oxygen species. Since skeletal muscle is relatively resistant to oxidative injury, it is possible that under physiological conditions endogenous ascorbate in the muscle microvasculature affords such protection. To examine the ability of microvascular endothelium to accumulate ascorbate, we aimed (1) to develop anin vitromodel of microvascular endothelial cells derived from rat hindlimb skeletal muscles and (2) to investigate the uptake and steady‐state concentration of ascorbate in these cells.Methods: Microvascular cells were enzymatically dissociated, isolated on a density gradient, and grown in serum‐supplemented medium. After passaging, they were tested for formation of tube‐like structures, coagulation factor VIII antigen expression,Griffonia simplicifolialectin I‐isolectin B4binding, and acetylated low‐density lipoprotein (LDL) uptake. Concentrations of reduced ascorbate were measured by high‐performance liquid chromatography (HPLC) with electrochemical detection. Transport activity was assessed on the basis of the initial rate of [14C]ascorbate uptake.Results: The cultured cells tested positively for factor VIII antigen expression, lectin binding, LDL uptake, and tube formation. Although these cells did not synthesize ascorbatede novo, they accumulated reduced vitamin C when it was added to the culture medium. The initial rate of [14C]ascorbate uptake was 0.9 μ‐mol/g cell protein 10 min when cells were incubated with 10 μM of the radiolabeled vitamin. This uptake was Na+‐dependent and was blocked by the organic anion transport inhibitor sulfinpyrazone, but was not acutely affected by glucose. Following incubation with a physiological concentration of vitamin C (100 μM L‐ascorbate), cells accumulated a high concentration of ascorbate within 6 h (approximately 16 mM at steady‐state). Steady‐state cellular ascorbate concentration was also dependent on extracellular Na+and sensitive to sulfinpyrazone.Conclusions: Microvascular cells derived from rat hindlimb muscles demonstrated endothelial characteristics. These cells accumulated reduced vitamin C by means of Na+‐dependent ascorbate transporters, which are distinct from hexose carriers. The high endothelial ascorbate concentration at steady‐state is consistent with the role of ascorbate as a major antioxidant in the skel

ISSN:1073-9688    

DOI:10.3109/10739689609148290

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:1073-9688    

DOI:10.3109/10739689609148291

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

ISSN:1073-9688    

DOI:10.3109/10739689609148292

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY