ISSN:1073-9688    

DOI:10.3109/10739689409148256

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:1073-9688    

DOI:10.3109/10739689409148257

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

ISSN:1073-9688    

DOI:10.3109/10739689409148258

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: The objective is to determine the contributions of electrostatic charge, endothelial cell adhesion glycoproteins (P‐ and E‐selectins), and histamine to lactoferrin‐induced leukocyte adhesion in postcapillary venules.Methods: Rat mesentery was prepared for intravital microscopic observation. Erythrocyte velocity, vessel diameter, leukocyte rolling velocity, number of adherent and emigrated leukocytes, and velocity, flux, and number of rolling leukocytes were monitored in mesenteric venules (25–35 μm initial diameter). After control measurements were obtained for all parameters, lactoferrin, other cationic proteins (histone or α‐chymotrypsinogen A), or transferrin (an anionic iron‐binding protein) were infused into the superior mesenteric artery, with repeat measurements taken 20 min into the infusion period. In other lactoferrin experiments, animals were treated with either a monoclonal antibody (MAb) directed against P‐ or E‐selectin, an H1‐ or H2‐histamine receptor antagonist, or diamine oxidase (histaminase).Results: Increased numbers of rolling and adherent leukocytes were observed during infusion of lactoferrin, histone, or α‐chymotrypsinogen A but not with transferrin. The leukocyte‐endothelial cell adhesion (LECA) elicited by lactoferrin was substantially greater than that induced by histone and α‐chymotrypsinogen A. The P‐selectin MAb completely prevented lactoferrin‐induced LECA, whereas the E‐selectin MAb had no effect. Diamine oxidase and the H1−(but not the H2−) receptor antagonist were also effective in attenuating lactoferrin‐induced LECA.Conclusions: These results indicate that lactoferrin‐induced LECA results from histamine‐mediated expression of P‐selectin on venular endothelial cells. The cationic nature of lactoferrin accounts f

ISSN:1073-9688    

DOI:10.3109/10739689409148259

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: To test the capillary recruitment hypothesis for the brain with control and hypoxic rats.Methods: Local cerebral blood flow (LCBF) was sharply raised by respiring 10% O2(hypoxia). LCBF as well as local influx rate constants (K1) and permeability‐surface area (PS) products of14C‐antipyrine and14C‐3‐O‐methyl‐d‐glucose (30MG) were estimated for capillary systems in 44 brain areas.Results: With this testing, an increase in PS product would be suggestive of capillary recruitment. In all brain areas, LCBF was increased by 30–90% by hypoxia. Hypoxia modestly raised the influx of antipyrine in brain but did not appreciably alter its PS products. With hypoxia,K1's and PS products of 30MG were significantly lowered (5–25%) throughout the brain, and the blood levels of glucose were sizeably raised. The latter increase would diminish the transfer of 30MG across the blood‐brain barrier by the hexose transporter because of increased glucose competition. By applying a glucose‐concentration correction to the data, the apparent PS product of 30MG for the hypoxic group became equal to that for the controls, which agrees with the antipyrine PS product results.Conclusions: Hypoxia, thus, leads to virtually no increase in PS products and no capillary recruitment in brain, and elevates LCBF mainly, perhaps exclusively, by raising the velocity of flow through already

ISSN:1073-9688    

DOI:10.3109/10739689409148260

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: Amino acid transport and its regulation in vascular endothelial cells remains a largely unexplored area. In this study, we evaluated alanine transport in bovine aortic endothelial cells to assess possible mechanisms of regulation.Methods: Alanine transport into confluent monolayers of endothelial cells was measured using 100 μM [3H]alanine in the presence and absence of external Na+, in cells deprived of serum for 24 hr (SD), and in SD cells exposed to 10% serum (S) for 3 hr (SD + S cells).Results: Our results indicate that although SD did not significantly affect the Na+‐independent transport of alanine when compared to normal cells, serum addition to serum‐deprived cells markedly stimulated the Na+‐dependent uptake of this amino acid through system A. The stimulation of alanine transport pathway(s) by serum was totally abolished by pretreatment of endothelial cells with 10 μM. cycloheximide, suggesting a role of protein synthesis. Serum also induced a marked increase in calcium recycling at the cell membrane, suggesting that calcium is a key element of the serum signaling pathway. Indeed, both BAPTA (20 μM), a cellular calcium chelator, and thapsigargin (1 μM), an agent that depletes intracellular calcium stores, prevented the stimulation of alanine uptake by serum. Finally, pertussis toxin (400 ng/ml), an agent known to inactivate certain G‐protein‐dependent pathways, significantly reduced the serum‐dependent45Ca uptake and [3H]alanine entry. However, the protein kinase C activator PMA (100 nM), significantly reduced the stimulation of alanine uptake by serum but did not affect the stimulation of calcium uptake.Conclusions: Altogether these findings suggest that cell calcium is involved in the regulation of system A by serum in vascular en

ISSN:1073-9688    

DOI:10.3109/10739689409148261

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: To test the hypothesis that adenosine can increase capillary densities in developing brain tissue.Methods: Transparent tadpoles of albinoXenopus laeviswere exposed to adenosine agonists, mainly 5′‐N‐ethylcarboxamidoadenosine (NECA), and to antagonists, mainly 8‐phenyltheophylline (8PT) in aquarium water. After 2 weeks in drugs, networks of blood vessels on the dorsal surface of the optic tectum were scanned in vivo by videomicroscopy. Densities of surface capillaries and venules, of deep branches, and of deep perfused capillaries were calculated.Results: NECA initially dilated brain blood vessels and chronically increased blood flow by a simple subjective index. 8PT diminished diameters and prevented the subjective flow increase. Chronic 3 μM NECA significantly increased densities of total deep branches from pial vessels into the tectum.Conclusions: In anin vivoamphibian assay, NECA dilated brain capillaries and venules and increased their flow and density. Adenosine was present chemically and increased during metabolic stress. These results are consistent with adenosine as a metabolic signal for growth of blood vessels during brain development. In addition, it appeared that short‐term dilation and flow increase in tectal capillaries in acute NECA was followed over a period of weeks in chronic NECA by vascular remodeling and return of diameters

ISSN:1073-9688    

DOI:10.3109/10739689409148262

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: To determine whether fluid flow influences the action of soluble vasoactive agonists on vascular endothelium.Methods: Confluent monolayers of bovine aortic endothelial cells (BAEC) were cultured on glass coverslips, prelabeled with the Ca2+‐sensitive dye fura‐2, and placed in a parallel‐plate flow chamber designed to generate defined laminar fluid flow. Cytosolic free Ca2+concentration ([Ca2+];) in individual BAEC was monitored during perfusion with medium containing adenine nucleotide under defined flow conditions.Results: Continuous perfusion with ATP (0.3–3.0 μM) or ADP (0.1–1.0 μM) evoked repetitive oscillations in [Ca2+]; in individual BAEC. The frequency of the [Ca2+]; oscillations was dependent on both nucleotide concentration and levels of applied shear stress; at constant bulk concentration of nucleotide, the frequency increased with shear stress. Stopping flow in the continuous presence of agonists immediately extinguished the oscillatory response. Elimination of extracellular Ca2+did not inhibit the [Ca2+]; oscillations. In the presence of nonhydrolyzable nucleotide analog, ATPγS or ADPβS, application of flow resulted in similar shear‐dependent [Ca2+]; oscillations, suggesting that flow modulation of the [Ca2+]; response was not simply due to depletion of ATP or ADP in the vicinity of BAEC monolayers as a result of hydrolysis of nucleotides by ectonucleotidases.Conclusions: These findings suggest that local hemodynamic conditions may modulate the action of vasoactive agents on the vascular end

ISSN:1073-9688    

DOI:10.3109/10739689409148263

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTObjective: To determine if the novel cyclooxygenase, COX II, was induced by acidic fibroblast growth factor (aFGF) in rabbit cardiac muscle microvessel (RCME) endothelial cells and to determine the role of protein kinase C (PKC) activation in the mediation of the aFGF induction of COX activity.Methods: Cultured RCME cells were treated with aFGF (200 ng/ml). Induction of COX II activity was assessed by determination of COX activity (PGE2production), by immunoprecipitation of metabolically labeled COX II, and by Northern analyses. The role of PKC was assessed using phorbol myristate acetate and PKC inhibitors and by determination of PKC activity in cytosol and membrane fractions of RCME cells treated with aFGF and phorbol myristate acetate.Results: aFGF selectively induced COX II protein and mRNA. Protein kinase C activation was implicated in the transduction of the effects of aFGF for the following reasons: (1) phorbol myristate acetate (PMA), a direct activator of protein kinase C, was a potent inducer of COX II mRNA, COX activity and synthesis of COX II protein. (2) H‐7, an inhibitor of PKC, but not the inactive control, HA‐1004, blocked aFGF induction of COX II mRNA, COX II protein synthesis, and COX activity. Two additional inhibitors of PKC, calphostin C and staurosporine, also inhibited aFGF induction of COX activity. (3) Downregulation of PKC by overnight incubation with 1 μM PMA blocked subsequent induction of COX II protein synthesis by aFGF. (4) aFGF treatment of RCME cells resulted in the translocation of PKC activity from the cytosol to the membrane fraction. However, aFGF, at concentrations that elicited COX II, neither induced Ca2+mobilization from intracellular stores nor increased the accumulation of inositol phosphates.Conclusion: aFGF induces COX II in RCME and this response in mediated, at least in part, by protein kinase C activation. However, aFGF mediated activation of PKC activation must stimulate this kinase through a pathway of signal transduction distinct from inositol phospholipid accumulation or elevation of intracellular

ISSN:1073-9688    

DOI:10.3109/10739689409148264

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY