Increased tissue survival in experimental skin flaps in mast cell-deficient rats.

Aim: The role of mast cells and their principal mediator, histamine, in surgical skin flap survival was investigated using mast cell-deficient (Ws/Ws); their congenic littermates wild-type (+/+), and Wistar rats.

Methods: A standardized dorsal skin flap was raised and sutured back into position, and 6 days later the percentage of flap survival was assessed. Moreover, endogenous histamine concentration in the dorsal skin during the surgical preparation was determined using in vivo microdialysis technique together with high performance liquid chromatography-fluorometry.

Absence of mast cell involvement in active systemic anaphylaxis in rats.

This study investigates the role of mast cells in the hypotension induced by antigen-mediated anaphylaxis, compound 48/80 and dextran in mast cell-deficient white spotting (Ws/Ws) and normal wild type (+/+) rats. Rats were sensitized with 10 microg of intraperitoneal ovalbumin in saline or saline alone (sham-sensitized). Sensitized rats, both Ws/Ws and +/+ but not sham-sensitized rats, challenged intravenously with ovalbumin exhibited hypotensive responses.

Heparin-binding protein (HBP/CAP37): a missing link in neutrophil-evoked alteration of vascular permeability.

Polymorphonuclear leukocyte infiltration into tissues in host defense and inflammatory disease causes increased vascular permeability and edema formation through unknown mechanisms. Here, we report the involvement of a paracrine mechanism in neutrophil-evoked alteration in endothelial barrier function. We show that upon neutrophil adhesion to the endothelial lining, leukocytic beta2 integrin signaling triggers the release of neutrophil-borne heparin-binding protein (HBP), also known as CAP37/azurocidin, a member of the serprocidin family of neutrophil cationic proteins.

Engagement of beta2 integrins induces surface expression of beta1 integrin receptors in human neutrophils.

Induction of beta1 integrin (CD49/CD29) expression in polymorphonuclear leukocytes (PMN) has been shown to be associated with transendothelial migration recently. Yet, beta1 integrin expression is relatively insensitive to cell activation with soluble agonists, such as N-formyl-methionyl-leucyl-phenylalanine (fMLP). We hypothesized that beta2 integrins (CD11/CD18), critically involved in PMN adhesion and extravasation, may play a role in regulating 1 integrin expression in PMN.

Spontaneous leukocyte rolling in rat and mouse microvessels is independent of mast cell activity.

Objective And Design: The role of mast cells in spontaneous leukocyte rolling in venules of the mouse cremaster muscle and rat mesentery was investigated.

Materials: The experiments were carried out using mast cell-deficient rats (Ws/Ws), WBB6F1 mice (W/Wv), and their congenic littermates (wild type).

Treatment: Administration of compound 48/80 intraperitoneally (50 microg) in rats and intrascrotally (5 microg) in mice, 4 h prior to the experiments.

Signaling via beta(2) integrins triggers neutrophil-dependent alteration in endothelial barrier function.

Activation of polymorphonuclear leukocytes (PMNs) and adhesion to the endothelial lining is a major cause of edema formation. Although known to be dependent on the function of beta(2) integrins (CD11/CD18), the precise mechanisms by which adherent PMNs may impair endothelial barrier capacity remain unclear. Here, the role of transmembrane signaling by beta(2) integrins in PMN-induced alterations in tight junctional permeability of cultured endothelial cell (EC) monolayers was investigated.

Integrin alpha(2)beta(1) (VLA-2) is a principal receptor used by neutrophils for locomotion in extravascular tissue.

Cell adhesion molecules are critically involved in the multistep process of leukocyte recruitment in inflammation. The specific receptors used by polymorphonuclear leukocytes (PMN) for locomotion in extravascular tissue have as yet not been identified. By means of immunofluorescence flow cytometry and laser scanning confocal microscopy, this study demonstrated that surface expression of the alpha(2)beta(1) (VLA-2) integrin, though absent on blood PMN, is induced in extravasated PMN collected from human skin blister chambers, and rat PMN accumulated in the peritoneal cavity after chemotactic stimulation.

Influence of local haemodynamics on leucocyte rolling and chemoattractant-induced firm adhesion in microvessels of the rat mesentery.

Tissue hyperaemia, oedema formation and leucocyte accumulation are characteristic features of the inflammatory process referable to changes at the microcirculatory level. Here, we used intravital fluorescence video microscopy to assess relationships among haemodynamical parameters, leucocyte rolling, and chemoattractant-induced firm adhesion in small venules (13-24 microM) of the rat mesentery. The rolling leucocyte flux in these vessels was directly proportional to the total leucocyte flux (r = 0.

Kinetics of leukocyte-induced changes in endothelial barrier function.

1. Extravasation of polymorphonuclear leukocytes (PMN) and associated plasma leakage are key events in the inflammatory process. The kinetics of PMN-induced changes in endothelial barrier function were studied by means of confluent monolayers of bovine aorta or human umbilical vein endothelial cells (EC), cultured on permeable membranes and mounted in a two-compartment diffusion chamber.

beta1 integrins are critically involved in neutrophil locomotion in extravascular tissue In vivo.

Recruitment of leukocytes from blood to tissue in inflammation requires the function of specific cell surface adhesion molecules. The objective of this study was to identify adhesion molecules that are involved in polymorphonuclear leukocyte (PMN) locomotion in extravascular tissue in vivo. Extravasation and interstitial tissue migration of PMNs was induced in the rat mesentery by chemotactic stimulation with platelet-activating factor (PAF; 10(-7) M).

Characteristics of histamine-induced leukocyte rolling in the undisturbed microcirculation of the rat mesentery.

1. The main objective of this study was to analyse the role and mode of action of the mast cell mediator histamine in leukocyte-endothelium interactions in small venules in vivo. For this purpose, we used a histological approach (combined with intravital microscopy) that allows studies of rapid mediator-induced venular leukocyte accumulation, reflecting leukocyte rolling, in the undisturbed microcirculation of the rat mesentery where rolling is normally absent.

An approach for studies of mediator-induced leukocyte rolling in the undisturbed microcirculation of the rat mesentery.

1. Although intravital microscopy is the method of choice for observation of inflammatory leukocyte rolling and adhesion in small venules in vivo, a problem with this technique is that surgical exposure of suitable tissues per se triggers the rolling mechanism. In this study, we describe an approach to investigate induction of rolling in undisturbed microvessels.

Inhibitory effect of locally administered heparin on leukocyte rolling and chemoattractant-induced firm adhesion in rat mesenteric venules in vivo.

1. Anti-inflammatory actions of heparin and related glycosaminoglycans have been described in the literature. Here, we used intravital microscopy of the rat mesentery microcirculation to examine effects of locally administered heparin on leukocyte rolling and chemoattractant-induced firm adhesion.

In vivo rolling and endothelial selectin binding of mononuclear leukocytes is distinct from that of polymorphonuclear cells.

In inflammation, rolling of leukocytes along the microvascular endothelium is a precondition for subsequent integrin-mediated firm adhesion and extravasation. Rolling characteristics of polymorphonuclear leukocytes (PMNL) and mononuclear leukocytes (MNL) in small venules (15-25 microns) of the rat mesentery were studied by intravital fluorescence microscopy under basal conditions and after intravenous treatment with an anti-rat neutrophil serum (ANS). The baseline rolling fraction of the venular total leukocyte flux was 36 +/- 15% (mean +/- SD).

Microvascular actions of histamine: synergism with leukotriene B4 and role in allergic leucocyte recruitment.

Background: Previous studies have shown that antihistamines provide little or no protection against the recruitment of leucocytes in allergic inflammation.

Objective: We wanted to examine if threshold doses of histamine can potentiate chemoattractant-induced leukocyte adhesion and if complete inhibition of histamine-induced microvascular effects is necessary to reduce allergic leucocyte recruitment.

Methods: The role of histamine in allergic leucocyte recruitment was examined by use of intravital microscopy of the hamster cheek pouch microcirculation.

Tumor cell arrest in the microcirculation: lack of evidence for a leukocyte-like rolling adhesive interaction with vascular endothelium in vivo.

Hematogenous spread of tumor cells and metastasis formation in secondary organs are insidious aspects of cancer. In the present intravital microscopic study in the rabbit mesentery, we examined the in vivo flow behavior of six human tumor cell lines of different histological origin. The tumor cells and human neutrophils were injected locally into a side branch of the superior mesenteric artery upstream of the observed microvascular area in the mesentery.

Propentofylline inhibits polymorphonuclear leukocyte recruitment in vivo by a mechanism involving adenosine A2A receptors.

Propentofylline is an atypical xanthine derivative that blocks adenosine uptake and has been shown to protect against ischemia-induced cerebral damage. We have studied the effect of propentofylline on recruitment of polymorphonuclear leukocytes during acute peritonitis induced by zymosan in mice. Following i.

Anti-IgE-induced accumulation of leukocytes, mediators, and albumin in skin chamber fluid from healthy and atopic subjects.

The aim of this study was to examine potential differences between healthy and atopic subjects with regard to IgE-mediated cutaneous inflammation. For this purpose, we analyzed histamine, tryptase, leukotriene B4, albumin, eosinophils, and total leukocytes in skin chamber fluid after challenge with anti-human IgE. We also measured gross skin reactivity (wheal, flare, and late-phase reactions), circulating IgE, and eosinophils, as well as the state of eosinophil activation.

Microvascular mechanisms of histamine-induced potentiation of leukocyte adhesion evoked by chemoattractants.

1. Intravital microscopy of the rat mesentery was used to examine interactions between histamine and the chemoattractant leukotriene B4 (LTB4) with regard to leukocyte adhesion in postcapillary venules. 2.

The promotion of patent airways and inhibition of antigen-induced bronchial obstruction by endogenous nitric oxide.

1. The aim of the present study was to investigate the role of nitric oxide (NO), histamine and leukotrienes in bronchial obstruction. For this, guinea-pigs immunised against ovalbumin were studied under anaesthesia during challenge with antigen or agonists.

Mast cell activation induces P-selectin-dependent leukocyte rolling and adhesion in postcapillary venules in vivo.

As studied by intravital microscopy, local challenge with the mast cell secretagogue compound 48/80 was found to increase the leukocyte rolling fraction, decrease rolling velocity and induce firm leukocyte adhesion in postcapillary venules of the rat mesentery. These effects of compound 48/80 were inhibited by a monoclonal anti-P-selectin antibody, but not by combined treatment with H1 and H2 histamine-receptor antagonists. Moreover, the response to compound 48/80 was not mimicked by exogenous histamine or 5-hydroxytryptamine (5-HT).