摘要:

ABSTRACTObjective:To determine superfusate‐induced changes in the distribution of plasma proteins in the perimicrovascular interstitial matrix.Methods:Rats were anesthetized with sodium pentobarbital and a mesenteric loop was exteriorized. Intravital video microspectrophotometry was performed using wavelengths of 280, 320, and 700 nm. The images were analyzed to give protein and collagen spatial distributions in vascular regions of rat mesenteric tissue. Perimicrovascular protein concentrations were fitted to an exponential decay modelci+cvexp (‐x/k), whereciis distal protein concentration,ci+cvis the protein concentration proximal to the vessel,xis the distance from the vessel wall, and k is the decay constant indicating protein gradient slope.Results:Before superfusion with 0.5‐ml normal saline,ci= 1.45 ± 0.13 g/dl,ci+cv= 4.56 ± 0.23 g/dl. After the first superfusion,cidecreased (p<0.01) to 0.53 ± 0.06 g/dl; following a second superfusion,cidecreased to 0.4 ± 0.03 g/dl; an additional final superfusion caused a further decrease to 0.33 ± 0.02 g/dl.ci+cvalso decreased significantly during repeated superfusions to 2.92 ± 0.15, 2.35 ± 0.25, and 2.1 ± 0.12 g/dl, respectively.Conclusions:Superfusion produced changes in perivascular and distal interstitial matrix protein distribution. Protein concentration proximal to the microvessel remained higher than distal concentrations. This could be due to increased gel concentrations inhibiting pro

ISSN:1073-9688    

DOI:10.3109/10739689409148265

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:Permeability of basement membrane and all other barriers contains a term for membrane thickness (Δx). This naturally leads to development of methods for measuring Δxthat are imprecise, inaccurate, expensive, subject to preparation artifact, and inattentive to variability. Although height and shape of permeability (P) vs. probe radius (α) curves are sensitive to Δx, ln(P) or ln(P/free diffusivity or Do) curves have shapes independent of Δx.It should, thus, be possible using such characteristics to determine fiber radius (rf) and void volume ratio (ε) without Δx.We developed such a method to derive membrane structure by the standard model of Ogston and present its experimental evaluation.Methods:Basement membranes were self‐assembled using 1: 1 Matrigel: 0.01 M Tris/150 mM NaCl/1.0 mM CaCl2buffer on 0.4‐μ polycarbonate supports with transport measured in diffusion chambers using FITC‐labeled hydroxyethyl starch probes from 25 to 102 Å in radius. Sampling was at 0.5 hr and then for each hour up to 5. Other membranes were measured 7 days after formation.Results:The best fit of the new technique occurred at 3 hr withR2= 0.949 ± 0.003 SEM,rf= 36.8 ± 2.4 Å, and ε = 0.87 ± 0.02. Membranes studied for 7 days showed more variability but essentially the same characteristics.Conclusions:Membrane thickness is not necessary to reduce permeability of basement membrane to structure, and optimum sa

ISSN:1073-9688    

DOI:10.3109/10739689409148266

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:Microvascular pericytes may contract in two different ways: In the first, a circumferential or radial mechanical force applied at right angles to the long axis of the vessel may constrict the underlying vessel affecting blood flow and transmural pressure. Retraction and elongation of pericyte processes may also occur tangentially and at right angles to the vessel axis and alter microvessel permeability by changing the amount of ablumenal surface covered or the openness of interendothelial junctions. In this study, cultured pericytes were utilized as a model experimental system to determine if vasoactive stimulation changes their shape in a manner consistent with this hypothesis.Methods:Pericytes cultured from isolated rate capillaries were subjected to angiotensin II and histamine. Their response was monitored by measuring the area of nonyielding substrate covered by the pericytes and the manner in which their shape changed. Shape changes were quantified by calculating the surface area: perimeter perimeter ratios.Results:Histamine significantly reduced surface area covered and the surface area: perimeter ratio. The pericyte processes retracted, resulting in elongated, spindle‐shaped cells. These effects were nullified by the H1blocker diphenhydramine suggesting a receptor‐specific response. Angiotensin II also elicited contraction and reduced surface area, but the cells contracted laterally and longitudinally. The surface area: perimeter ratios also decreased.Conclusions:These results indicate that pericytes are capable of two types of contractile responses in culture, depending on the specific vasoactive stimu

ISSN:1073-9688    

DOI:10.3109/10739689409148267

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:Although acute and chronic roles of microvascular smooth muscle cells as effectors of pulmonary vascular resistance and remodeling are well appreciated, relatively little is known regarding the direct effects of neurohumoral agents on these cells. We recently reported that microvascular smooth muscle cells isolated from distal rat lung (RPC) express mRNA and binding sites for 5HT2receptors. The objective of the current study was to determine if protein kinase C (PKC) affected 5HT‐induced changes in intracellular calcium and phosphoinositide metabolism in RPC.Methods:5HT‐induced changes in intracellular calcium ([Ca2+]i) in single RPC were determined microspectrofluorometrically using the calcium‐sensitive dye, Fura‐2.Results:Phorbol 12‐myristate 13‐acetate (PMA: 100 nM) caused a rapid desensitization of 5HT‐induced increases in [Ca2+]i. Staurosporine, a putative PKC inhibitor, abolished the PMA‐induced desensitization. Downregulation of PKC with prolonged (24 hr) PMA exposure also abolished subsequent PMA‐induced desensitization of 5HT response. Neither short‐ nor long‐term exposure of RPC to PMA affected binding of [125I]LSD. Activation of PKC by PMA was associated, however, with complete inhibition of 5HT‐induced increases in intracellular inositol monophosphate.Conclusions:These data are consistent with PKC causing desensitization of 5HT2receptors by affecting elements of signal transduction and uncoupling receptor‐G protein complex fr

ISSN:1073-9688    

DOI:10.3109/10739689409148268

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective:Renal hyperfiltration in early diabetes is often correlated with increased renal blood flow, reflecting dilation of resistance arterioles. This loss of arteriolar tone has been associated with an impaired reactivity to angiotensin II (Ang II). This study determined if outer cortical arterioles (preglomerular and/or postglomerular) of diabetic rats exhibit a diminished reactivity to Ang II and established if renal vascular prostaglandins account for the diminished responsiveness.Methods:The constriction of renal microvessels to Ang II (applied to the kidney bath) was quantitated in hydronephrotic kidneys of diabetic rats (7‐10 days after streptozotocin treatment) and nondiabetic rats byin vivovideomicroscopy.Results:Interlobular, afferent, and efferent arterioles of diabetic rats were found to be less reactive to Ang II than arterioles of nondiabetic rats. Indomethacin, added to the bath to inhibit renal vascular prostaglandin synthesis, enhanced the interlobular and efferent arteriolar reactivity to the peptide among diabetic rats. Yet, after indomethacin treatment, the afferent and efferent arterioles of diabetic rats were still less reactive than control arterioles to Ang II.Conclusions:We conclude that the blunted reactivity of afferent and efferent arterioles to Ang II among diabetic hydronephotic kidneys cannot be fully explained by the influence of renal vascular‐derived dilator prostagland

ISSN:1073-9688    

DOI:10.3109/10739689409148269

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY