Attachment studies of aquatic Hyphomycetes

1991 ◽  
Vol 334 (1271) ◽  
pp. 449-457 ◽  
Keyword(s):  
Radial Flow ◽  
Flow Chamber ◽  
Aquatic Hyphomycetes ◽  
Shear Stresses ◽  
Initial Attachment ◽  
Subsequent Formation ◽  
Contact Points ◽  
Tetracladium Marchalianum

The strength of attachment of conidia of eight species of freshwater Hyphomycetes ( Anguillospora crassa, Articulospora tetracladia, Dimorphospora foliicola, Lemonniera aquatica, Mycentrospora filiformis, Tetracladium marchalianum, Tumularia aquatica and Varicosporium elodeae ) was examined in a Fowler Radial Flow Chamber up to 24 hours after settlement. It was shown that conidium morphology, particularly the number of contact points made by the conidium to the substratum, had an effect on initial attachment and therefore that tetraradiate conidia were initially the most strongly attached. It was also shown that the subsequent formation of appressoria significantly increased the strength of attachment at the higher shear stresses examined.

scholarly journals L-Selectin–Dependent Leukocyte Adhesion to Microvascular But Not to Macrovascular Endothelial Cells of the Human Coronary System

Blood ◽  
1997 ◽  
Vol 89 (9) ◽  
pp. 3228-3235 ◽  
Author(s):  
A. Zakrzewicz ◽  
M. Gräfe ◽  
D. Terbeek ◽  
M. Bongrazio ◽  
W. Auch-Schwelk ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Time Course ◽  
Leukocyte Adhesion ◽  
Flow Chamber ◽  
Shear Stresses ◽  
Selectin Ligands ◽  
Tnf Α ◽  
Factor Α

Abstract To characterize L-selectin–dependent cell adhesion to human vascular endothelium, human cardiac microvascular endothelial cells (HCMEC) and human coronary endothelial cells (HCEC) were isolated from explanted human hearts. The adhesion behavior of human (NALM-6) and mouse (300.19) pre-B cells transfected with cDNA encoding for human L-selectin was compared with that of the respective nontransfected cells in a flow chamber in vitro. More than 80% of the adhesion to tumor necrosis factor-α (TNF-α)–stimulated HCMEC at shear stresses <2 dyne/cm2 was L-selectin dependent and could be equally well blocked by an anti–L-selectin antibody or a L-selectin-IgG-chimera. No L-selectin dependent adhesion to HCEC could be shown. The L-selectin dependent adhesion to HCMEC was insensitive to neuraminidase, but greatly inhibited by addition of NaClO3 , which inhibits posttranslational sulfation and remained elevated for at least 24 hours of stimulation. E-selectin dependent adhesion of HL60 cells to HCMEC was blocked by neuraminidase, but not by NaClO3 and returned to control levels within 18 hours of HCMEC stimulation. It is concluded that microvascular, but not macrovascular endothelial cells express TNF-α–inducible sulfated ligand(s) for L-selectin, which differ from known L-selectin ligands, because sialylation is not required. The prolonged time course of L-selectin dependent adhesion suggests a role in sustained leukocyte recruitment into inflammatory sites in vivo.

Invited Review: Effects of flow on vascular endothelial intracellular calcium signaling of rat aortas ex vivo

2000 ◽  
Vol 89 (4) ◽  
pp. 1657-1662 ◽  
Author(s):  
Chauying J. Jen ◽  
Shuo-Ju Jhiang ◽  
Hsiun-Ing Chen
Keyword(s):  
Shear Stress ◽  
Intracellular Calcium ◽  
Calcium Influx ◽  
Ex Vivo ◽  
Flow Chamber ◽  
Shear Stresses ◽  
Dependent Manner ◽  
Intracellular Calcium Signaling ◽  
Flow Effects ◽  
Dose Dependent

To study the effects of flow on in situ endothelial intracellular calcium concentration ([Ca2+]i) signaling, rat aortic rings were loaded with fura 2, mounted on a tissue flow chamber, and divided into control and flow-pretreated groups. The latter was perfused with buffer at a shear stress of 50 dyns/cm2 for 1 h. Endothelial [Ca2+]i responses to ACh or shear stresses were determined by ratio image analysis. Moreover, ACh-induced [Ca2+]i elevation responses were measured in a calcium-free buffer, or in the presence of SKF-96365, to elucidate the role of calcium influx in the flow effects. Our results showed that 1) ACh increased endothelial [Ca2+]i in a dose-dependent manner, and these responses were incremented by flow-pretreatment; 2) the differences in ACh-induced [Ca2+]i elevation between control and flow-pretreated groups were abolished by SKF-96365 or by Ca2+-free buffer; and 3) in the presence of 10−5 M ATP, shear stress induced dose-dependent [Ca2+]i elevation responses that were not altered by flow-pretreatment. In conclusion, flow-pretreatment augments the ACh-induced endothelial calcium influx in rat aortas ex vivo.

The Elongation and Orientation of Cultured Endothelial Cells in Response to Shear Stress

1985 ◽  
Vol 107 (4) ◽  
pp. 341-347 ◽  
Author(s):  
M. J. Levesque ◽  
R. M. Nerem
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Cell Elongation ◽  
Vascular Endothelial Cells ◽  
Flow Direction ◽  
Flow Chamber ◽  
Shear Stresses ◽  
Cell Alignment ◽  
Aortic Endothelial Cells ◽  
Time Required

Vascular endothelial cells appear to be aligned with the flow in the immediate vicinity of the arterial wall and have a shape which is more ellipsoidal in regions of high shear and more polygonal in regions of low shear stress. In order to study quantitatively the nature of this response, bovine aortic endothelial cells grown on Thermanox plastic coverslips were exposed to shear stress levels of 10, 30, and 85 dynes/cm2 for periods up to 24 hr using a parallel plate flow chamber. A computer-based analysis system was used to quantify the degree of cell elongation with respect to the change in cell angle of orientation and with time. The results show that (i) endothelial cells orient with the flow direction under the influence of shear stress, (ii) the time required for cell alignment with flow direction is somewhat longer than that required for cell elongation, (iii) there is a strong correlation between the degree of alignment and endothelial cell shape, and (iv) endothelial cells become more elongated when exposed to higher shear stresses.

Adhesive Characteristics of Hemoglobin SC Red Blood Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3780-3780
Author(s):  
Ai C. Chien ◽  
Rahima Zennadi ◽  
Laura M. De Castro ◽  
Marilyn J. Telen
Keyword(s):  
Red Blood Cells ◽  
Blood Cells ◽  
Matrix Protein ◽  
Physiological Stress ◽  
Flow Chamber ◽  
Extracellular Matrix Protein ◽  
Shear Stresses ◽  
Αvβ3 Integrin ◽  
Adhesive Properties ◽  
Hb S

Abstract Hemoglobin (Hb)-S containing red blood cells (RBCs) adhere abnormally to the vascular wall; this phenomenon is postulated to contribute to vaso-occlusive crisis and serious tissue damage. Patients homozygous for Hb S experience the most severe form of SCD, whereas heterozygous patients carrying Hb S and another hemoglobin variant, Hb C, experience somewhat milder clinical courses. Laminin is the extracellular matrix protein to which SS RBCs bind most avidly and is the ligand for the BCAM/Lu receptor. αvβ3 integrin is one of the major integrins on endothelial cells (ECs) and is the counter-receptor for LW on SS RBCs. Epinephrine activates both LW and BCAM/Lu on SS RBCs and thereby induces increased SS RBC adhesion to both ECs and laminin via a cAMP-dependent pathway. We have now compared the adhesive properties of Hb SC RBCs to SS RBCs. We measured the expression of RBC adhesion receptors, BCAM/Lu and LW, and assayed adhesion of SC RBCs to laminin and ECs (with and without prior stimulation of RBCs by epinephrine). Blood samples from Hb SC and SS patients in steady state and from normal controls (Hb AA) were collected into citrate tubes and were washed to remove plasma and buffy coat before use. The levels of BCAM/Lu and LW expression on RBCs were measured by flow cytometry using monoclonal antibodies to BCAM/Lu and anti-LW. SC RBCs expressed higher levels of BCAM/Lu (MFI 476.2, n=13) than did SS RBCs (MFI 332.3, n=33) and AA RBCs (MFI=225.5, n=16), but none of these differences were statistically significant (all p values &gt;0.05). The levels of LW expression were also similar on AA, SC, and SS RBCs. Adhesion to laminin and ECs was measured as previously described, in a graduated height flow chamber. Non-treated, sham-treated, and epinephrine-treated RBCs were each infused into a flow chamber fitted with a slide coated with laminin or ECs. After washing at a constant rate, adherent RBCs were quantitated at points of different shear stresses. Adhesion of SC RBCs to laminin (mean of 53.1 cells/mm2 at 1 dyne/cm2, n=9) was lower than that of SS RBCs (mean of 69.0 cells/mm2 at 1 dyne/cm2, n=6, p=0.459) but was markedly higher than the adhesion seen with AA RBCs (mean of 0.03 cells/mm2 at 1 dyne/cm2, n=3, SC vs AA p=0.011). A positive correlation was found between BCAM/Lu expression and SC RBC adhesion to laminin (r=0.638, p=0.047). While epinephrine induced an increase in SC RBC adhesion to laminin in only 10% of all SC patient samples tested (compared to 50% of SS patients), epinephrine upregulated SC RBC adhesion to ECs approximately 10-fold in all samples tested (n=3). We conclude that SC RBCs represent an intermediate adhesive phenotype compared to AA and SS RBCs. While BCAM/Lu-mediated adhesion to laminin was lower on SC RBCs than on SS RBCs, unstimulated BCAM/Lu adhesive function was strikingly enhanced in relation to AA RBCs. Most importantly, epinephrine uniformly increased SC RBC adhesion to ECs, suggesting that in Hb SC disease, physiological stress may induce SC RBC adhesion and vaso-occlusive crises by mechanisms similar to those postulated to occur as a result of stress in Hb SS disease.

Stress Analysis of a Radial-Flow Rotor

1962 ◽  
Vol 84 (1) ◽  
pp. 124-130 ◽  
Author(s):  
M. J. Schilhansl
Keyword(s):  
Stress Analysis ◽  
Radial Flow ◽  
Mutual Interference ◽  
Circumferential Direction ◽  
Shear Stresses ◽  
Torsional Vibrations ◽  
Normal Stresses ◽  
Centrifugal Forces ◽  
High Speeds ◽  
Predominant Effect

A radial-flow rotor consisting of a disk and exactly radial blades experiences normal stresses in radial and circumferential direction and shear stresses by virtue of centrifugal forces and the torque, respectively. The following investigation is restricted to the analysis of the effect of the centrifugal forces, primarily because this is the predominant effect at high speeds at least so long as the rotor is not subjected to torsional vibrations. Special attention is being paid to the mutual interference of disk and blades.

Heat and Mass Transfer on the Unsteady Magnetohydrodynamic Flow Due to a Porous Rotating Disk Subject to a Uniform Outer Radial Flow

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Mustafa Turkyilmazoglu
Keyword(s):  
Heat Transfer ◽  
Radial Flow ◽  
Magnetic Interaction ◽  
Rotating Disk ◽  
Transient Behavior ◽  
Temperature Fields ◽  
Shear Stresses ◽  
Surface Shear ◽  
Entire Family ◽  
Integration Algorithm

An unsteady flow and heat transfer of an incompressible electrically conducting fluid over a porous rotating infinite disk impulsively set into motion are studied in the present paper. The disk finds itself subjected to a uniform normal magnetic field. The particular interest lies in searching for the effects of an imposed uniform outer radial flow far above the disk on the behavior of the physical flow. The governing Navier–Stokes and Maxwell equations of the hydromagnetic fluid, together with the energy equation, are converted into self-similar forms using suitable similarity transformations. A compact, unconditionally stable, and highly accurate implicit spectral numerical integration algorithm is then employed in order to resolve the transient behavior of the velocity and temperature fields. The time evolution and steady state case of some parameters of fundamental physical significance such as the surface shear stresses in the radial and tangential directions and the heat transfer rate are also fully examined for the entire family of magnetic interaction, radial flow, and suction/blowing parameters.

scholarly journals Differential L-Selectin Binding Activities of Human Hematopoietic Cell L-Selectin Ligands, HCELL and PSGL-1

2001 ◽  
Vol 276 (50) ◽  
pp. 47623-47631 ◽  
Author(s):  
Charles J. Dimitroff ◽  
Jack Y. Lee ◽  
Kenneth S. Schor ◽  
Brenda M. Sandmaier ◽  
Robert Sackstein
Keyword(s):  
Flow Chamber ◽  
Hematopoietic Cell ◽  
Shear Stresses ◽  
Parallel Plate Flow Chamber ◽  
Hematopoietic Stem ◽  
Selectin Ligands ◽  
Selectin Ligand ◽  
Structural Biochemistry ◽  
Adhesive Interactions ◽  
Selectin Binding

Expression of L-selectin on human hematopoietic cells (HC) is associated with a higher proliferative activity and a more rapid engraftment after hematopoietic stem cell transplantation. Two L-selectin ligands are expressed on human HCs, P-selectin glycoprotein ligand-1 (PSGL-1) and a specialized glycoform of CD44 (hematopoietic cell E- and L-selectin ligand, HCELL). Although the structural biochemistry of HCELL and PSGL-1 is well characterized, the relative capacity of these molecules to mediate L-selectin-dependent adhesion has not been explored. In this study, we examined under shear stress conditions L-selectin-dependent leukocyte adhesive interactions mediated by HCELL and PSGL-1, both as naturally expressed on human HC membranes and as purified molecules. By utilizing both Stamper-Woodruff and parallel-plate flow chamber assays, we found that HCELL displayed a 5-fold greater capacity to support L-selectin-dependent leukocyte adherence across a broad range of shear stresses compared with that of PSGL-1. Moreover, L-selectin-mediated leukocyte binding to immunopurified HCELL was consistently >5-fold higher than leukocyte binding to equivalent amounts of PSGL-1. Taken together, these data indicate that HCELL is a more avid L-selectin ligand than PSGL-1 and may be the preferential mediator of L-selectin-dependent adhesive interactions among human HCs in the bone marrow.

Characterization of a Sudden Expansion Flow Chamber to Study the Response of Endothelium to Flow Recirculation

1995 ◽  
Vol 117 (2) ◽  
pp. 203-210 ◽  
Author(s):  
George A. Truskey ◽  
Kevin M. Barber ◽  
Thomas C. Robey ◽  
Lauri A. Olivier ◽  
Marty P. Combs
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Recirculation Zone ◽  
Numerical Solutions ◽  
Flow Chamber ◽  
Sudden Expansion ◽  
Shear Stresses ◽  
Stress Gradients ◽  
Wall Shear

In order to simulate regions of flow separation observed in vivo, a conventional parallel plate flow chamber was modified to produce an asymmetric sudden expansion. The flow field was visualized using light reflecting particles and the size of the recirculation zone was measured by image analysis of the particles. Finite element numerical solutions of the two and three-dimensional forms of the Navier-Stokes equation were used to determine the wall shear stress distribution and predict the location of reattachment. For two different size expansions, numerical estimates of the reattachment point along the centerline of the flow chamber agreed well with experimental values for Reynolds numbers below 473. Even at a Reynolds number of 473, the flow could be approximated as two-dimensional for 80 percent of the chamber width. Peak shear stresses in the recirculation zone as high as 80 dyne/cm2 and shear stress gradients of 2500 (dyne/cm2)/cm were produced. As an application of this flow chamber, subconfluent bovine aortic endothelial cell shape and orientation were examined in the zone of recirculation during a 24 h exposure to flow at a Reynolds number of 267. After 24 h, gradients in cell orientation and shape were observed within the recirculation zone. At the location of reattachment, where the wall shear stress was zero but the shear stress gradients were large, cells plated at low density were still aligned with the direction of flow. No preferred orientation was observed at the gasket edge where the wall shear stress and shear stress gradients were zero. At higher cell densities, no alignment was observed at the separation point. The results suggest that endothelial cells can respond to spatial gradients of wall shear stress.

scholarly journals Microscopic Monitoring of Erythrocytes Deformation under Different Shear Stresses Using Computerized Cone and Plate Flow Chamber: Analytical Study of Normal Erythrocytes and Iron Deficiency Anemia

2018 ◽  
Vol 2018 ◽  
pp. 1-5
Author(s):  
Mohamed A. Elblbesy
Keyword(s):  
Iron Deficiency ◽  
Iron Deficiency Anemia ◽  
Hemoglobin Concentration ◽  
Flow Chamber ◽  
Deficiency Anemia ◽  
Shear Stresses ◽  
Microscopic Technique ◽  
Mean Cell Volume ◽  
Elongation Index ◽  
The Mean

Erythrocytes deformation is one of the exciting properties of erythrocytes. It is still under investigation by many of the researchers in different disciplines. The clinicians and researchers are still looking for a simple and efficient method to monitor and tracking the erythrocytes deformation. This research article represented a microscopic technique that could be a helpful tool in evaluation and studying of erythrocytes deformation under different shear stresses. This technique was used to compare the deformation of normal erythrocytes and iron deficiency anemia. Elongation index was calculated and used in the quantitative analysis of erythrocytes deformation. It was found that the deformability of normal erythrocytes was higher than that of iron deficiency anemia. Normal erythrocytes and iron deficiency anemia showed strong negative correlations with the mean cell volume and the mean cell hemoglobin concentration under different shear stresses. This study introduces more understanding of the erythrocytes deformation by using a simple microscopic technique. The elongation index could be used as a measurable parameter to evaluate the deformability of the erythrocyte in normal and abnormal cases.

Sign in / Sign up

Export Citation Format

Share Document