ISSN:1073-9688    

DOI:10.3109/10739689609148298

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWe describe a simple new method for computing two‐dimensional velocity vector fields of blood flows in microvascular networks. This method, known as optical flow, requires a time sequence of two or more images obtained by a process such as conventional videomicroscopy. There is no need to distinguish individual cells provided clear variations in the light intensity levels are present in the images. The result of the computation reveals the velocity distribution in the microvascular network and the geometry of the blood vessels. Although various implementations of the optical flow technique exist, we have found that the spatial correlation algorithm of Anandan performs best for microcirculatory flows. This report is an introduction to the application of optical flow to the microcirculation and provides instructions on how to obtain and run the code

ISSN:1073-9688    

DOI:10.3109/10739689609148299

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: Previous work in our laboratory has shown that retinal vein pressure is significantly greater than intraocular pressure in the cat. Our purpose here is to evaluate the potential of an active mechanism being responsible for the control of vein pressure in the cat retina.Methods: A double‐lumen, concentric barrel micropipette assembly designed for operation within the eye of a spontaneously breathing anesthetized cat was developed. The micropipette, initially filled with hypertonic saline for use with a servonull pressure measuring system, was used to determine intravascular pressure. With the tip of the micropipette still situated in the lumen of the vessel the solution in the micropipette was exchanged for papaverine, a potent smooth muscle dilator. Following vasodilation in the distal portion of a major retinal vein, the papaverine was exchanged for hypertonic saline and intravascular pressures were measured in the dilated vessel.Results: Microinjection of papaverine caused visible dilation of the major retinal vein downstream from the site of microinjection. This indicates a relaxation of the smooth muscle yet papaverine caused no change in measured retinal vein pressure.Conclusions: Vein pressure in the cat retina is maintained above intraocular pressure by mechanisms other than active control. A passive high‐resistance segment resides somewhere within the optic nerve possibly within the lamina cribosa or prelaminar reg

ISSN:1073-9688    

DOI:10.3109/10739689609148300

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: Polymorphonuclear leukocytes (PMN) have been found to be less deformable in humans with non‐insulin‐dependent diabetes. It has therefore been hypothesized that white blood cells (WBC) may affect the development of diabetic microangiopathy. This study was designed to determine whether PMN or small and large lymphocytes were less deformable in a large animal model of diabetes—chronically hyperglycemic pancreatectomized cats.Methods: Venous blood was withdrawn from 13 normal and 14 diabetic cats. The diabetic cats had been kept in poor metabolic control since their pancreatectomy (7‐113 months before this study). Blood cell counts, hemoglobin concentration, hematocrit, erythrocyte volume, and WBC differential counts were obtained from the blood samples. Purified mononuclear WBC and PMN fractions were obtained by separating the blood on a discontinuous Percoll gradient. The deformability of each cell fraction was determined using a Cell Transit Analyzer (ABX, Montpellier, France) that measures the transit time of cells through 7.5‐μm pores. By varying the sampling rate of the CTA and the pressure difference across the filter, the subpopulations of the mononuclear fractions (small and large lymphocytes) could be identified and each subpopulation analyzed separately.Results: Median transit times for the PMN and small lymphocytes were significantly greater for the diabetic cats, but no difference was found in the large lymphocyte fractions.Conclusions: These results are in accordance with the finding that PMN are less deformable in humans with diabetes. We also showed that the small lymphocytes from diabetic cats have prolonged transit times. The results suggest that PMN may contribute to the development of microangiopathies like diabetic retinopathy. Diabetic cats may prove useful for testing potential therapies to improve WBC def

ISSN:1073-9688    

DOI:10.3109/10739689609148301

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: Apigenin is a flavonoid that effectively blocks intercellular adhesion molecule‐1 (ICAM‐1) upregulation and leukocyte adhesion in response to cytokinesin vitro.In the present study, we characterized the effects of tumor necrosis factor (TNF) on ICAM‐1 expression in different tissues of the rat. We then assessed whether apigenin alters this response.Methods: ICAM‐1 expression was measured under baseline conditions or 5 h after treatment with rTNF. We used125I‐labeled anti‐rat ICAM‐1 monoclonal antibody (mAb) and an isotype‐matched control mAb labeled with131I to correct for nonspecific accumulation of the binding mAb. Animals were pretreated with either placebo, apigenin, narigenin (a flavonoid without inhibitory effectin vitro), or vehicle. Additional groups of animals were treated with either allopurinol, glutathione, dimethyl‐thiourea, or an anti‐CD18 monoclonal antibody in order to assess possible actions of flavonoids that were mediated via free radical scavenging or through interference with neutrophil function.Results: Treatment with rTNF resulted in a marked increase in ICAM‐1 expression in all organs studied. The magnitude of the response varied in different organs and increases ranged from onefold (lung) to threefold (muscle). Treatment with apigenin blocked ICAM‐1 upregulation in organs with low to intermediate responses to rTNF and it significantly attenuated the increased ICAM‐1 expression in organs that normally exhibit more marked upregulation. Treatment with narigenin or vehicle did not affect rTNF‐induced ICAM‐1 upregulation in all tissues studied. Pretreat‐ment with either allopurinol, free radical scavengers, or anti‐CD18 monoclonal antibody did not affect the ICAM‐1 upregulatory response to rTNF.Conclusions: TNF‐induced ICAM‐1 upregulationin vivoeffectively is blocked by apigenin through a mechanism that is unrelated to free r

ISSN:1073-9688    

DOI:10.3109/10739689609148302

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The purpose of this study was to develop a model for microscopicin situobservation of the murine peripheral lymph node (LN) microcirculation and to characterize the function of the lymphocyte homing receptor L‐selectin (CD62L) and the peripheral node addressin (PNAd). The latter is a high‐affinity ligand for L‐selectin in LN high endothelial venules (HEV).Methods: The subiliac (superficial inguinal) LN was microsurgically dissected in anesthetized adult mice. The nodal microvascular architecture and venular hemodynamics were characterized by bright field and epifluorescence video microscopy. L1‐2 pre‐B cells that were either mock transfected (L1‐2Vector) or stably transfected to express human L‐selectin (L1‐2L‐selection) were labeled fluorescently and injected into a feeding artery. Cell adhesion in LN venules was studied in both the presence and absence of neutralizing monoclonal antibodies (MAb) to PNAd and L‐selectin.Results: The preparation allowed a detailed analysis of hemodynamic parameters and leukocyte adhesion in LN microvessels. L1‐2Vectorcells did not interact with LN microvessels. In contrast, L1‐2L‐selectincells rolled efficiently in venules but not in arterioles or capillaries. Rolling was most prominent in subcortical HEV (orders III to V) and was less frequent but consistently detectable in downstream medullary and hilus venules (orders I and II). Rolling interactions were abrogated by MAb DREG‐56 to the lectin domain of L‐selectin and were markedly reduced by the anti‐PNAd MAb MECA‐79.Conclusions: The present study develops a new intravital microscopy model forin vivovisualization of leukocyte interactions with microvessels in murine LN. The preparation permitted an analysis of biophysical and molecular mechanisms of leukocyte adhesion to high endothelial cells. The data support the concept that L‐selectin and PNAd are the predominant receptor/ligand pair responsible for lymphocyte rolling in HEV. The model will be useful for high‐resolution analysis of intra

ISSN:1073-9688    

DOI:10.3109/10739689609148303

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: As a first step in modeling microvascular exchange in the renal medulla, we developed mathematical models to explore the effects of blood flow, permeability, and anatomical arrangement of microvessels on the steady‐state distribution of solute in the blood and the interstitial fluid (ISF).Methods: Single capillaries and countercurrent capillary loops were used to model microvessels that were surrounded by a secretory epithelium over either the whole or part of the capillary length. Solute concentration in the vessels and the ISF were derived analytically. We also derived approximate solutions that ignored axial diffusion of solute.Results: The full and approximate solutions were in good agreement with data based on measurements in the renal medulla. Model results revealed that concentration in the ISF falls rapidly with distance beyond the region of solute secretion and equilibrates with the concentration in capillaries, even with countercurrent exchange between the two limbs of the capillary loop. The ratio of the product of the permeability and area to the flow of the afferent limb, γ1, is an important parameter. When γ1>4, countercurrent exchange in a capillary loop facilitates a greater ISF concentration gradient than with a single capillary. Changes in flow also have a greater effect on this gradient.Conclusion: The model of countercurrent exchange presented here not only demonstrates the sensitivity of interstitial concentration gradients of solute to flow through capillary loops but also reveals the importance of the absolute value of γ1in determining the magnitude and direction of these gradi

ISSN:1073-9688    

DOI:10.3109/10739689609148304

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The goal of the present study was to develop a method to isolate enzymatically viable arteriolar muscle cells from single cremasteric arterioles, which retain the contractile and electrophysiological phenotype of the donor microvessels.Methods: Arterioles were hand‐dissected from rat and hamster cremaster muscles and dissociated by incubation in papain and didiioerythritol for 35 min followed by incubation in collagenase, elastase, and soybean trypsin inhibitor for 10 to 25 min in solutions containing 100 μM Ca2+, 10 μM sodium nitroprusside, and 1 mg/ml albumin at 37°C.Results: Populations of single smooth muscle cells enzymatically isolated from cremasteric arterioles showed elongated fusiform morphology and intact plasmalemmal membranes as indicated by retention of calcein, by exclusion of ethidium homodimer‐1, and by high membrane resistances (11 ± 0.8 Gω,n= 36 for rat cells; 8 ± 0.6 Gω,n= 21 for hamster cells;p0.05). Families of voltage‐dependent K+currents were observed during stepwise depolarizing pulses from −60 mV to more positive potentials. Blockers of voltage‐gated and ATP‐sensitive K+channels (4‐Aminopyridine [3 mM] and glibenclamide [1 μM], respectively) inhibited membrane K+conductance, increased membrane resistance, and depolarized cells by 20 ± 4 mV (n= 8) and 14 ± 3 mV (n= 6), respectively.Conclusions: The present method permits isolation of smooth muscle cells from a single cremasteric arteriole. These cells seem to retain the contractile phenotype, α‐adrenergic signaling cascade, membrane potential, and K+conductances described for the donor arteriole. Correlating the functional and electrophysiological properties of these smooth muscle cells toin situandin vitrostudies of their donor arterioles should provide a useful extension for understanding die physiology, pathophysiology, biophysics, and cell biolo

ISSN:1073-9688    

DOI:10.3109/10739689609148305

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTObjective: The purpose of this study was to develop anin vitromodel which, compared to stagnant two‐chamber systems, is more analogous to the rheological conditions found in the vasculature and permits near simultaneous measurement of polymorphonuclear leukocytes (PMN) entrapment and endothelial monolayer permeability.Methods: A previously described cell‐column model of the vasculature was perfused with 2 ± 106PMN/ml at an average fluid velocity of 0.09 cm/s and an average estimated endothelial surface shear stress of 4.5 dyne/cm2for a total of 60 min. PMN entrapment was estimated from counts of PMN in this recirculating system. Bovine endothelial permeability was estimated from an indicator dilution analysis of the three co‐injected dyes: blue dextran (molecular weight [MW]) 2 ± 106), sodium fluorescein (MW 342) and cyanocobalamin (MW 1355).Results: Circulation of PMN through cell‐columns did not activate PMN, although the number of circulating PMN decreased at a rate of 14% per 65 cm2of endothelial surface in the first 15 min. Endothelial cell monolayer permeability did not change within 60 min. Addition of formyl‐methionyl‐leucyl‐phenylalanine (fMLP) (lO−5M) activated PMN and significandy increased entrapment of circulating PMN to 27% per 65 cm2in the first 15 min. Although the percentage of circulating PMN entrapped increased, endothelial monolayer permeability was not increased by either the addition of 10−5M fMLP or PMN + fMLP to the cell‐column perfusate.Conclusions: Over the 60‐min period studied, entrapment of PMN within a recirculating model of die microvasculature was not associated with an increase in endothelial permeability even after PM

ISSN:1073-9688    

DOI:10.3109/10739689609148306

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY