摘要:

ABSTRACTStudy of the microcirculation began with microscopic anatomy in the 17th century, but it was not until the mid‐19th century that the concept of microcirculatory exchange was developed, in association with the great expansion in knowledge of physical chemistry and cell biology. In the first half of the 20th century, the roles of diffusion and osmosis (ultrafiltration) were put on a quantitative foundation and the physiological basis for regulation of the microcirculation was established. During the past 40 years, our understanding of transvascular exchange has been deepened and widened through two major developments: 1) the application of electron microscopy to the study of microvascular structure and 2) the use of sophisticated physical and mathematical models of passive transport processes to analyze and interpret experimental data. In the past few years, the focus of microvascular research has been returning to cell biology and the role of endothelial cells in controlling transvascular exchange. The 21st century holds promise of many exciting new development

ISSN:1073-9688    

DOI:10.3109/10739689409148270

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:The renal fractional clearance of [3H]DEAE dextran has been widely used to substantiate the charge selective model for renal permselectively, although there has only been one reported study on this type of clearance. This study sets out to examine the fractional clearance and glomerular processing of DEAE dextran.Methods:Fractional clearance studies were performed using isolated perfused rat kidneys. The glomerular processing of DEAE dextran was assessed by examining the kinetics of DEAE dextran uptake in glomerluli isolated post perfusion.Results:The fractional clearance of DEAE dextran used in the concentration range of 15–150 μg/ml in the perfusate of the isolated perfused kidney did not produce the classicalin vivofacilitated transport of DEAE dextran as compared to dextran as observed by Bohrer et al. The fractional clearance curve displays retarded clearance of low molecular weight (small radii) DEAE dextran, giving the appearance of a ‘flat curve’. Similar results were obtained when an oxygen free radical scavenger cocktail was included in the perfusate. These results may be due to the fact that DEAE dextran binds to the glomeruli (at an order of magnitude greater than dextran sulfate). Perfused kidneys with [3H]DEAE dextran for 1 h followed by a five minute perfusion with unlabelled DEAE dextran revealed no significant change in the glomerular levels of [3H]DEAE dextran (unlike dextran sulfate). Perfusion of rat kidneys with 15 μg/ml DEAE dextran produced no changes in the electron microscopical morphology of the glomerulus and no changes in the fractional clearance of dextran.Conclusions:These results do not support the glomerular charge selectivity model that involves a non‐binding electrostatic interaction of the charged dextran with the fixed anion charges of the glomerular capil

ISSN:1073-9688    

DOI:10.3109/10739689409148271

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:The influx of polymorphonuclear leukocytes (PMNs) that occurs at the onset of reperfusion of postischemic tissue is a multistep mechanism that includes initial rolling of PMNs, a progressive reduction in PMN rolling velocity, and ultimately PMN adhesion and emigration. In this study we assessed whether mast cells play a role in reperfusion‐induced PMN recruitment with emphasis on PMN rolling, adhesion, and emigration.Methods:Cat small intestinal venules were visualized using intravital microscopy during control, 60 min of ischemia (intestinal blood flow 20% of control), and 60 min of reperfusion in untreated and cromolyn‐ (mast cell stabilizer) pretreated animals.Results:Between 1 and 5 min of reperfusion, there was a very dramatic rise in PMN rolling which persisted for the next 60 min. In cromolyn‐pretreated animals, the flux of rolling PMNs increased in the very early (5 min) reperfusion period, but by 10 min the number of rolling leukocytes was significantly reduced, an event that persisted for the next 60 min. PMNs rolled at a velocity of 40% of control values for the first 10 min of reperfusion without a change in hemodynamic values but returned toward control values by 60 min of reperfusion. An identical velocity profile was observed for the cromolyn‐treated animals. In untreated animals, PMN adhesion and emigration was significantly increased throughout the reperfusion period, whereas the cromolyn‐pretreated animals had reduced adhesion (60 min of reperfusion) and a reduced rate of emigration throughout the reperfusion period.Conclusions:Interstitial mast cells contribute significantly to the multistep recruitment (rolling, adhesion, and emigration) of PMNs from blood to postischemic tissues and raise the possibility that antiallergy agents such as cromolyn may be a useful form of therapy in the postischemic

ISSN:1073-9688    

DOI:10.3109/10739689409148272

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:Exercise training produces regional increases in blood flow capacity among muscle fibers that experience increased activity during exercise. We tested the hypothesis that this increase is partially due to capillary angiogenesis among muscle fibers with large increases in activity during exercise training bouts.Methods:Two training programs were evaluated: a program consisting of 10–12 weeks of exposure to low‐intensity (30 m/min, 0 incline, 60 min/day) (LET) exercise bouts, 5 days/week, and a second program consisting of 8–10 weeks of exposure to repetitive bouts (6/day) of sprint (60 m/min, 15% incline) exercise, alternating running (2.5 min) and recovery (4.5 min), 5 days/week (IST). Cage‐confined rats were utilized (SED) as controls. After training was completed, rat hindquarters were perfusion‐fixed with modified Karnovsky's fixative. Transverse sections from soleus (Sol), and red (GR), mixed (GM), and white (GW) portions of gastrocnemius muscle were prepared to evaluate capillarization. Sections were analyzed using the Olympus Cue 2 Image Analyzer to determine capillary/muscle fiber ratio (C/F), number of capillary profiles per square millimeter of muscle area (CND), capillary surface area per volume of tissue, and capillary volume density.Results:Average area per muscle fiber and sarcomere length did not differ among groups. LET did not affect capillarization of the GW, whereas increasing C/F in GM(2.3 ± 0.1 versus 2.1 ± 0.1 for SED) and GR(3.0 ± 0.1 versus 2.6 ± 0.1 for SED). IST increased C/F and CND in GW(1.6 ± 0.1 versus 1.3 ± 0.0 for SED and 657 ± 74 versus 418 ± 53 for SED, respectively) and increased C/F ratio in GM(2.3 ± 0.1 versus 2.1 ± 0.1 for SED). IST did not increase capillarization of the GR. The capillarization of the soleus muscle was not affected by either exercise training program.Conclusions:IST increased capillarization in muscle tissue composed of a high percentage of fast glycolytic fibers (GWand GM) and LET increased capillarization of muscle tissue composed of a high percentage of fast oxidative‐glycoly

ISSN:1073-9688    

DOI:10.3109/10739689409148273

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:To determine the contribution of either endothelium‐derived nitric oxide (EDNO) or prostaglandins in the functional vasodilation of first‐order arterioles of the hamster cremaster muscle.Methods:First‐order arterioles dilated from 72 ± 3 μm to 93 ± 4 μm in response to contraction of the cremaster muscle for 1 min (n= 7). After EDNO inhibition by topical application of 10 μMNω‐nitro‐l‐arginine methyl ester (L‐NAME), the resting diameter decreased to 66 ± 3 μm and functional dilation was attenuated to 75 ± 3 μm (P0.05). Inhibition of prostaglandin synthesis by topical application of indomethacin (28 μM) resulted in no significant changes in the resting diameter but functional vasodilation was attenuated from 89 ± 2 to 81 ± 3 μm (n= 7,P<0.05).Conclusions:These results suggest that EDNO is important for the resting tone of arterioles and that prostaglandins are important in modulating the functional dilation of the first‐orde

ISSN:1073-9688    

DOI:10.3109/10739689409148274

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY