Leukocytes In Blood Vessels Research Articles

Synergistic Regulation Mechanism of Selectin and Integrin on Leukocyte Adhesion Under Shear Flow

Abstract In the process of inflammation, the hydrodynamic process of circulating leukocyte recruitment to the inflammatory site requires the rolling adhesion of leukocytes in blood vessels mediated by selectin and integrin molecules. Although a number of experiments have demonstrated that cooperative effects exist between selectins and integrins in leukocyte rolling adhesion under shear flow, the mechanisms underlying how the mechanics of selectins and integrins synergistically may govern the dynamics of cell rolling is not yet fully resolved. To address this issue, here we theoretically investigate selectin and integrin jointly mediated rolling adhesion of leukocyte in shear flow, by considering two pairs’ binding/unbinding events as Markov processes and describing kinetics of leukocyte by the approach of continuum mechanics. Through examining the dynamics of leukocyte rolling as a function of relative fraction of selectin and integrin pairs, we show that, during recruitment, the elongation of intermittent weak selectin bonds consuming the kinetic energy of rolling leukocyte decelerates the rolling speed and enables the integrin pairs to form strong bonds, therefore achieving the arrestment of leukocyte (firm adhesion). The co-existence of selectins and integrins may also be required for effective phase transition from firm adhesion to rolling adhesion due to dynamic competition in pairs’ formation and elongation. These results are verified by the relevant Monte Carlo simulations and related to reported experimental observations.

Pathogens in Vasculitis: Is It Really Idiopathic?

Vasculitis is an autoimmune disease characterized by the infiltration of leukocytes in blood vessels.An increasing number of studies on human and animal models have implicated various microorganisms in the pathogenesis of vasculitis. Previous studies have shown the presence of infectious agents, including viruses, bacteria, and fungi, in diseased vessels. However, despite continued research, the link between infection and vasculitis is not fully understood, possibly owing to the lack of appropriate animal models that mirror human disease and the technical limitations of pathogen detection in blood vessels. Among the pathogen-induced animal models, Candida albicans water-soluble fraction (CAWS)-induced coronary arteritis is currently considered one of the representative models of Kawasaki (KD) disease. Advances in metagenomic next-generation sequencing have enabled the detection of all nucleic acids in tissue, which can help identify candidate pathogens, including previously unidentified viruses. In this review, we discuss the findings from reports on pathogen-associated vasculitis in animal models and humans, with a specific focus on the investigation of the pathogenesis of vasculitis. Further studies on animal models and microbes in diseased vessels may provide important insights into the pathogenesis of vasculitis, which is often considered an idiopathic disease.

Self‐Alignment of Beads and Cell Trapping in Precipitate Tubes

Propagating reaction fronts allow the formation of materials in self-sustained, steep concentration gradients, which would otherwise rapidly decay. These conditions can result in macroscopic, noncrystallographic structures, such as tubes with large aspect ratios. For hollow silica/Zn(OH)2 tubes, we report the inclusion of diverse mesoscopic building blocks ranging from polymer beads to biological cells. For agarose beads, we observe spontaneous alignment along vertical tracks; the nearly periodic spacing of the beads along these tracks follows a log-normal distribution. We interpret this patterning in terms of hydrodynamic recruitment and discuss similarities to the adhesion dynamics of leukocytes in blood vessels. For diatoms and other cells, we observe novel surface textures, and yeast tagged with a green fluorescent protein shows strong fluorescence activity after trapping. The inclusion of these guest units should improve the possibilities for the application of these tubes in microfluidics and biotechnology.

Effects of Simvastatin, Ezetimibe, and Their Combination on Histopathologic Alterations Caused by Adjuvant-Induced Arthritis

The objective of the present study was to investigate the effects of monotherapy with simvastatin or ezetimibe compared with those of an ezetimibe + simvastatin combination on the histopathologic aspects of arthritis induced by Complete Freund's Adjuvant in rats. The characteristics of diarthrosis were analyzed 7 and 28 days after arthritis induction with regard to the regularity and integrity of articular cartilage, the presence of leukocytes in blood vessels at the inflammation site, and the cytokine levels in articular tissue. Monotherapy with simvastatin or ezetimibe and the ezetimibe + simvastatin combination effectively reduced the cytokine levels (interleukin-6 and tumor necrosis factor) and articular lesions that are characteristic of this experimental disease. Although the results did not reveal significant differences between the monotherapy and the combined therapy, they suggest that these drugs have considerable antiinflammatory properties, as reflected by an attenuation of articular cartilage lesions mediated by a reduction in the levels of proinflammatory cytokines.

T cells sense biophysical cues using lamellipodia and filopodia to optimize intraluminal path finding

Intraluminal crawling is considered to be important for extravasation of leukocytes in blood vessels, but biochemical/biophysical cues guiding the crawling of leukocytes have not been clearly understood. Here we provide evidence that T cells sense the topography of luminal surfaces and the nuclei of endothelial cells (ECs) using lamellipodia and filopodia, respectively, to optimize path finding during intraluminal crawling. Well-aligned EC layers or replicas of EC layers, which exhibit topography similar to that of EC layers, were fabricated, and flow was applied either parallel or perpendicular to the orientation of EC alignment. T cells crawled along the valleys of the topographical landscapes of the EC layers, while avoiding nuclei of ECs regardless of flow direction. Pharmacological inhibitor treatments revealed that sensing of topography and nuclei of EC layers was mediated by lamellipodia and filopodia, respectively. Lamellipodia or filopodia-inhibited T cells crawled significantly longer distances for extravasation than did normal T cells, indicating that sensing biophysical cues are critical for optimizing routes for extravasation.

The Attachment, Internalization, and Time-Dependent, Intracellular Distribution ofClostridium difficileToxin A in Porcine Intestinal Explants

Toxin A (TcdA), secreted by toxigenic strains of Clostridium difficile, produces lesions typical of C. difficile-associated disease (CDAD) in susceptible mammal species. Porcine colon explants maintained for 2 hours with TcdA developed severe lesions characterized by cell swelling, swelling of mitochondria and other organelles, distension of cytoplasmic vesicles, expansion of paracellular spaces, apoptosis, and necrosis. Severity of lesions was proportional to the dosage of toxin. No lesions were present in uninoculated control tissues after 2 hours. Receptor-mediated endocytosis is the keystone event in the pathogenesis of the toxin, and susceptibility of a given species is thought to depend on the presence of receptors in intestinal epithelial cells. The fate of TcdA applied to viable colon explants was determined by transmission electron microscopy in an anti-toxin-labeled gold assay. At 5 minutes postinoculation, the presence of TcdA was indicated at the membrane of microvilli or in the cytoplasm of epithelial cells. TcdA was also indirectly observed within endosomes or attached at their margin. A 30-minute inoculation period was associated with many more gold particles labeling structures inside the cell, although some were still attached to microvilli. Within the cell, most TcdA was associated with mitochondria of epithelial cells, but some gold particles decorated the nuclei. Endothelial cells of the lamina propria had evidence of TcdA at both their lumenal and basal aspects, as well as in the cytoplasm and, occasionally, nuclei. Gold particles also labeled the lumen of such vessels as well as leucocytes in blood vessels and the lamina propria.

Cellular-Level Characterization of Lymph Vessels in Live, Unlabeled Corneas by In Vivo Confocal Microscopy

To determine whether in vivo confocal microscopy (IVCM) of the cornea can be used for the label-free detection and monitoring of lymph vessels in live corneas. Parallel corneal hemangiogenesis and lymphangiogenesis was induced by the placement of a single suture in one cornea of male Wistar rats. Fourteen days after suture placement and under general anesthesia, laser-scanning IVCM was performed in the vascularized region. Corneas were subsequently excised for flat-mount double immunofluorescence with a pan-endothelial marker (PECAM-1/CD31) and a lymphatic endothelial specific marker (LYVE-1). Using the suture area and prominent blood vessels as points of reference, the identical microscopic region was located in both fluorescent and archived in vivo images. Additionally, vessel diameter, lumen contrast, and cell diameter and velocity within vessels were quantified from in vivo images. Comparison of identical corneal regions in fluorescence and in vivo revealed prominent CD31(+)/LYVE-1(3+) lymph vessels that were visible in vivo. In vivo, corneal lymph vessels were located in the vascularized area in the same focal plane as blood vessels but had a darker lumen (P < 0.001) sparsely populated by highly reflective cells with diameters similar to those of leukocytes in blood vessels (P = 0.61). Cell velocity in lymph vessels was significantly reduced compared with blood particle velocity (P < 0.001). Morphologic characteristics enabled subsequent identification of corneal lymphatics in live, vascularized rat corneas before immunofluorescence labeling. IVCM enabled the nondestructive, label-free, in vivo detection of corneal lymphatics. IVCM provides the possibility of observing lymphatic activity in the same live corneas longitudinally and, as a clinical instrument, of monitoring corneal lymphatics in live human subjects.

Midkine gene transfer protects against focal brain ischemia and augments neurogenesis

Background and purpose Midkine is a heparin-binding growth factor having various biological activities including chemotaxis of inflammatory cells, angiogenesis and migration of neuronal cells. These biological activities are expected to have a great impact on the pathology of brain infarction in subacute phase. Therefore, we investigated the effect of post-ischemic gene transfer of midkine in the phase. Methods Brain ischemia was produced by the photothrombotic distal middle cerebral artery occlusion in spontaneously hypertensive rats. We measured cerebral blood flow by laser Doppler flowmetry. At 90 min after induction of brain ischemia, adenovirus vectors encoding mouse midkine (AdMK) or enhanced green fluorescence protein (AdGFP) were injected into the lateral ventricle. At 7 days after brain ischemia, the infarct volume, angiogenesis, inflammation and neuronal regeneration were evaluated. Results There were no differences in cerebral blood flow changes between AdMK and AdGFP groups. However, infarct volume of AdMK group was significantly smaller than AdGFP group by 33%. The vascular density, the numbers of leukocytes in blood vessels, infiltrated macrophages and proliferated neuronal precursor cells were not significantly different between both groups. Contrastingly the numbers of migrating neuronal precursor cells toward the brain infarction were significantly increased in AdMK group than AdGFP group. Conclusions Neuroprotective effect of midkine gene transfer persisted until the subacute phase of brain infarction. Midkine may contribute to neuronal regeneration. These results suggest the usefulness of midkine gene transfer for treatment of brain infarction.

In VivoCell Tracking With Video Rate Multimodality Laser Scanning Microscopy

Studies of biological processes, such as disease progression and response to therapy, call for live imaging methods that allow continuous observation without terminating the study subject for histological tissue processing. Among all current imaging modalities, optical microscopy is the only method capable of probing live tissue with cellular and subcellular resolution. We present a video-rate (30 frames/s), multimodality imaging system that is designed specifically for live animal imaging and cell tracking. In vivo depth-sectioned, high-resolution images are obtained using confocal and nonlinear optical techniques that extract structural, functional, and molecular information by combining multiple contrast mechanisms, including back scattering, fluorescence (from single- and two-photon excitation), second harmonic generation, and coherent anti-Stokes Raman scattering. Simultaneous use of up to three modalities is possible and eliminates the need for coregistration, especially on large-scale images. A real-time movement correction algorithm was developed to extend integration times in cases where the image needs to be stabilized against subject movement. Finally, imaging of fast moving leukocytes in blood vessels is made possible with a modification that permits operation at 120 frames/s over a smaller area. Sample imagery obtained in vivo with the microscope is presented to illustrate the capabilities.

Method of pathology recognition in bio-organs by multifrequency ultrasound signals

Ultrasound methods of pathology recognition in bio-organs are proposed. They are based on the application of multichannel sounding signals (or wide band signals). The peculiarities of the proposed methods take into account the specific character of the biomedium in the ultrasound diagnostic. The nuances of the effective application in the ultrasound diagnostic of the following method of recognition are analyzed: application of the natural resonance frequencies of the bio-organs without signal form recollection (vessel, red corpuscles, leucocytes, etc.), by apportionment of complex poles of the Laplas transformation function (R. Prony’s method), application of the stepped influence with organ boundary restoration by impulse reaction and by the algorithm of the form restoration with projection (J. Young’s method and V. Bojarsky’s method, J. Radon transformation), structure methods of the two-dimensional bio-organ form picture (the grammar method), multichannel irradiation of the bio-organ with its phase-frequency characteristic synthesis of three-dimensional bio-organ transformation by its Ess. in LF, MF, HF bands. The numerical data concerning the form compensation of the spherical and elliptical elastic objects and recognition of the red corpuscles and leucocytes in blood vessels are deduced. Frequency band: 1–10 MHz, feeler length: one period, discrete radiation: 1, 2, 4, 6, 8, 10 MHz.

Stillbirth/perinatal weak calf syndrome: preliminary pathological, microbiological and biochemical findings.

Microbiological, biochemical and pathological data collected from 293 calves which were either stillborn, or born alive and either failed to breathe or failed to breathe for more than about 10 minutes are presented. No bacteria were recovered from 96 of the calves (32.7 per cent), and bacteria which were considered significant were isolated from only four (1.4 per cent). Evidence of leptospiral infection was found in 75 calves (25.5 per cent). Of 64 calves examined for bovine virus diarrhoea (BVD) and infectious bovine rhinotracheitis (IBR) antigens, two were positive for BVD virus and none for IBR virus. The mean (+/- sd) liver vitamin E and kidney selenium concentrations, determined in 148 of the calves, were 2.0 +/- 0.76 micrograms/g wet matter and 0.47 +/- 0.17 micrograms/g wet matter, respectively. The thyroid iodine concentration in 15 of 71 calves (21 per cent) was less than 300 micrograms/g wet matter and the mean (+/- sd) thyroid weight of 266 of the calves was 18.5 +/- 11.6 g. Evidence of severe trauma was found in 19 of the calves (6.5 per cent). Histological findings included thyroid epithelial hyperplasia, hepatic haemosiderosis, erythrophagocytosis in the spleen, perivascular haemorrhage in brain and adrenal glands, and accumulation of leucocytes in blood vessels.

Effects of oestradiol-17 beta on testicular microcirculation in rats.

The effect of oestradiol-17 beta on testicular microcirculation in intact and hypophysectomized rats was studied before and after treatment with human chorionic gonadotrophin (hCG). Treatment of intact rats with oestradiol-17 beta for 5 days did not influence vasomotion but decreased testicular interstitial fluid volume (IFV). Treatment of intact rats with 50 IU hCG 8 h before the experiment began induced an increase in testicular IFV, abolished vasomotion and increased the accumulation of polymorphonuclear leucocytes in the testicular venules and interstitium. These changes were unaffected by pretreatment with oestradiol-17 beta, despite the decreased testosterone production. However, pretreatment with oestradiol-17 beta potentiated the hCG-induced migration of polymorphonuclear leucocytes to the interstitium. The interstitial fluid volume and number of polymorphonuclear leucocytes in blood vessels were decreased in hypophysectomized rats, and vasomotion was abolished. Daily treatment with 5 IU hCG increased the IFV and the number of polymorphonuclear leucocytes in blood vessels, and preserved vasomotion. Treatment of hypophysectomized rats with oestradiol-17 beta decreased testosterone production but did not influence basal IFV, vasomotion or the changes in IFV and vasomotion induced by 5 IU hCG. The present study shows that the regulation of testicular vascular permeability and vasomotion may not be directly related to testicular steroidogenesis, and that oestrogens are probably not involved as a mediator of the hCG-induced changes in testicular microcirculation.

Avoidance of host defences by Treponema pallidum in situ and on extraction from infected rabbit testes.

Electron microscopic observations of acutely infected rabbit testes showed that the majority of Treponema pallidum were extracellular, and confined to interstitial regions of the tissue. Organisms were often adjacent to small blood vessels, where they should be freely accessible to non-specific humoral and cellular defence mechanisms. However, there was no accumulation of leucocytes in blood vessels or infiltration of inflammatory cells into infected areas. Inoculation of live treponemes into perforated plastic chambers which had been implanted subcutaneously in rabbits or guinea-pigs did not incite significant infiltration into the chamber fluid of inflammatory cells, in contrast to that seen after inoculation of Neisseria gonorrhoeae. Interaction of antibody from infected rabbits with live treponemes freshly extracted from rabbit testes could not be detected by an indirect fluorescent antibody method. These observations suggest that T., pallidum escapes recognition by host defences.