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Biomedical subjects

I A Feuerstein

Publications and source records attributed to I A Feuerstein.

At least 19 recordsLinked to original sources
PubMed1994

Role of P-selectin and leukocyte activation in polymorphonuclear cell adhesion to surface adherent activated platelets under physiologic shear conditions (an injury vessel wall model).

Carbohydrate moieties on leukocytes adhere to activated platelets via P-selectin under static binding condition studies. We characterize polymorphonuclear cell (PMN) surface interactions with surface adherent platelets and the PMNs response, under physiologic flow conditions corresponding to a shear of 100 s-1, in an in vitro flow chamber. Fluorescent labeled PMNs with red blood cells were drawn through a transparent flow channel and visually quantitated over 30 minutes, interacting with a confluent monolayer of activated, shear-spread platelets expressing P-selectin. PMN adhesion was saturable (2,250 +/- 350/mm2), and time and cation (Ca2+, Mg2+) dependent, and PMNs did not bind to the experimental surface in the absence of a platelet monolayer. P-selectin antibodies completely abolished PMN adhesion in a concentration-dependent manner with half inhibition at 70 micrograms/mL. Antibodies to a putative P-selectin receptor CD15 (80H5 and MMA) maximally inhibited PMN adhesion by 73% and 10%, respectively. Adherent PMNs appeared morphologically activated and flow cytometric analysis of adherent PMNs confirmed activation because CD11b and CD18 surface expression was upregulated (100% and 27%, respectively), whereas L-selectin was downregulated (55%) compared with control nonadherent PMNs. In the presence of the metabolic inhibitor sodium azide (0.02% and 0.1%) there was a 23% +/- 9% and 51% +/- 3% decrease, respectively, in PMN adhesion at 100 s-1. Thus, P-selectin is required for PMN adhesion to a pathophysiologic surface of activated adherent platelets at physiologic shear rates. Furthermore, a secondary step involving PMN activation after platelet binding appears necessary for complete (irreversible) adhesion to occur. This unique flow cell provides a model to explore, under controlled conditions, biologic mechanisms and ligands involved in leukocyte-platelet binding that play important roles in PMN localization at sites of thrombosis and vascular injury.

Antibodies, Monoclonal↗
PubMed1994

Adherent platelet morphology on adsorbed fibrinogen: effects of protein incubation time and albumin addition.

The composition of the protein layer adsorbed to a polymer has been thought to be important for the adhesion of platelets. The state of activation of adherent platelets is an additional factor that may be a predictor of biocompatibility. Activation refers to the degree of change from discoid shape to any of several spread shapes. The conformation and orientation of adsorbed adhesive proteins, which interact with receptors on the membrane of platelets, such as fibrinogen, fibronectin, and von Willebrand factor, may also be important for platelet adhesion and activation. This work deals with the behavior of fibrinogen adsorbed to PMMA alone, where the experimental variable was incubation time with the substrate, and with adsorbed fibrinogen mixed with albumin, where the experimental variable was the molar percent of fibrinogen in the adsorption solution. Shorter protein incubation times and increased albumin levels in the initial fibrinogen adsorption solution enhanced the percentages of activated platelet morphologies and increased adsorbed fibrinogen redistribution by the platelet. Lower concentrations of albumin in the initial adsorption solution enhanced platelet adhesion numbers; fibrinogen incubation time had no effect. Together, these factors can contribute to the biocompatibility of a biomaterial through their effect on platelet adhesion and activation.

Adenosine Diphosphate↗
PubMed1994

In vitro leukocyte adhesion to modified polyurethane surfaces: III. Effect of flow, fluid medium, and platelets on PMN adhesion.

The operation of filters used to remove leukocytes from red cell concentrates may depend on the adhesion and mechanical trapping of leukocytes. If adhesion is a major component of filtration then filter materials which augment leukocyte adhesion will be useful. In previous leukocyte adhesion studies, done without flow, poly(ethyleneimene) (PEI) modified polyurethane (PU) films were shown to have greater adhesion when compared with unmodified PU. Since filtration is done under flow conditions, it was decided to study PMN adhesion at a number of flow rates using an established parallel plate flow cell. The influence of divalent cations, plasma and platelets were investigated in the presence of red cells, 40% Hematocrit. The number of adherent PMNs to the PEI modified films was always substantially higher than that for the unmodified ones when the shear rate was set at 30 s-1. When using Tyrode's solution containing albumin, with or without divalent cations, a maximum in PMN adhesion was found between the shear rates of 10 and 100 s-1. With Tyrode's solution containing albumin and with 10% (v/v) plasma in saline, the addition of platelets increased PMN adhesion when divalent cations were absent. Adhesion levels with 10% (v/v) plasma in saline were reduced when compared to Tyrode's solution containing albumin without divalent cations. These results support the use of filtration conditions where the concentration of plasma is reduced and the concentration of divalent cations is increased. Detailed evaluation of filter function with flow rate is also recommended. A cell adhesion promoting polymer coating, such as PEI, may be useful in improving filter efficiency.

Cell Adhesion↗
PubMed1993

States in adherent platelet morphology and the processing of adsorbed protein on biomaterials.

This study evaluates the range of adherent platelet morphologies and their relationship to preadsorbed protein. Fluorescently labelled protein was used so changes in its distribution could be followed along with morphological states assessed with modulation-contrast microscopy. Our particular concern was with the quantitative relationship between the platelet and the fluorescent image. The findings from this study continue to support the idea that platelets do interact with adsorbed protein so that protein redistribution occurs and that thrombin accelerates this. Evidence is also presented to support platelet shrinkage, membrane vesicle formation and destruction as a result of thrombin. The shrinking of adherent platelets causes areas free of pre-adsorbed protein to be exposed. This process will be important determining the nature of the substrate available to cells contacting surfaces along with other adsorbed protein-related processes, e.g. reversible adsorption and post-adsorptive transitions.

Adsorption↗
PubMed1992

Platelet adherence and detachment with adsorbed fibrinogen: a flow study with a series of hydroxyethyl methacrylate-ethyl methacrylate copolymers using video microscopy.

The adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) with preadsorbed fibrinogen. Observations of the interactions of acridine-orange-labeled washed platelets with these surfaces from a flowing (500 s-1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). In some cases preadsorbed materials were incubated for 24 h, during which little or no loss of protein occurred. Protein surface concentration, by itself, was a poor indicator of expected cell adhesion and morphology. Surface chemistry was a second important factor which must be considered. A third observation is that for the 100% EMA copolymer, 24 h of incubation led to a large reduction in platelet adhesion when compared to the 100% EMA material without incubation. For the 0% and 100% EMA polymers, the percentage of contacting platelets which adhere and detach is greater for the 24-h incubation cases than for those not incubated. These results led to the conclusion that our most hydrophilic surface favors adhesion with detachment, transient cell contact, over long-term adhesion, as does incubation of adsorbed protein. A brief discussion is presented of a possible connection between this behavior and platelet consumption in vivo for hydrogels.

Adsorption↗
PubMed1992

Epifluorescent video microscopy (EVM) for platelet-biomaterial interactions: elimination of photoactivation and dye effects.

The use of two intracellular dyes for epifluorescent video microscopy (EVM) in observations of cell-surface interactions is evaluated and discussed. This methodology permits determinations of cell adhesion, detachment and movement at the surfaces of biomaterials in the presence of flow and physiological haematocrit. Two tests, one which examines for the effect of incident light on platelet adhesion and one which checks for sufficient light for accurate observation of cells, have been designed. Evaluations were made of the adhesion of platelets labelled with the fluorescent dyes mepacrine and acridine orange, used singly and in combination. The use of a number of light level-dye level combinations with glass and several polymers and the addition of a plasma level of fibrinogen did not show any photoactivation effects. This methodology paves the way for longer than previous exposures to light with our system, from 1 min up to 30 min now. Washed platelet suspensions are preferred; these allow for the selective labelling of specific cells and the removal of dye from the surface of the cell.

Acridine Orange↗
PubMed1991

Platelet adherence and detachment: a flow study with a series of hydroxyethyl methacrylate-ethyl methacrylate copolymers using video microscopy.

The adhesion and detachment of platelets were studied on glass coatings of a series of copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA). Observations of the interactions of mepacrine labelled washed platelets with these surfaces from a flowing (500 s-1 wall shear rate) suspension in Tyrode's solution containing albumin and red cells were made with epifluorescent video microscopy (EVM). Total platelet adhesion, including platelets which adhere on first contact and platelets which attach temporarily before adhesion, and the number of detaching platelets were minimal for the 0 and 20% EMA copolymers, reached a maximum for the 50% EMA copolymer and showed reduced values for the 80% and 100% EMA copolymers. For the 50, 80, and 100% EMA copolymers, the adhesion values expressed, as a percentage of total contacting platelets, were not different. Albumin adsorption to these copolymers shows a continuous increase from the 0% to the 100% EMA copolymer. It is likely that the peak in platelet adhesion at the 50% EMA composition is related to: low protein adsorption on the 0 and 20% EMA copolymers, too little albumin adsorption to block adhesion on the 50% EMA copolymer, and full-scale blocking on the 80 and 100% EMA copolymers due to greater albumin adsorption.

Adult↗
PubMed1991

Platelets process adsorbed protein: a morphological study.

The nature of the adsorbed protein on a non-biological biomaterial surface is known to influence cell adhesion. This work deals with the contribution of adherent platelets towards the redistribution of preadsorbed proteins. A redistribution was only observed with spread platelets on adsorbed fibrinogen and fibronectin, but not with adsorbed beta-lactoglobulin. The labelled protein images showed a dark outer ring with an inner region having fluorescent areas, with greater intensity than regions not covered by platelets. The fluorescent patterns observed may be a result of the binding of adsorbed fluorescent protein to the glycoprotein IIb/IIIa receptors of platelets, followed by their redistribution within the plasma membrane.

Adsorption↗
PubMed1990

Adhesion and aggregation of thrombin prestimulated human platelets: evaluation of a series of biomaterials characterized by ESCA.

Five materials of interest in blood contact applications (PVC, Silastic, Biomer and siliconized glass) were internally coated on glass tubes and exposed to suspensions of platelets and red cells. Uncoated glass was also examined. Thrombin was added (prestimulation) to some suspensions before exposure to the biomaterial surfaces. The three polymeric surfaces were characterized by electron spectroscopy for chemical analysis (ESCA). Prestimulation with thrombin leads to increased adhesion of single platelets only with Silastic. With a wide range of surface types, thrombin prestimulation consistently leads to higher levels of platelet accumulation in the form of aggregates; the PVC-coated material showed the highest levels. ESCA analysis of PVC, however, suggested our coating was impure or an oxidized material.

Biocompatible Materials↗
PubMed1989

Adhesion of polymorphonuclear leukocytes to protein-coated and platelet adherent surfaces.

Since protein adsorption and platelet adhesion are likely to precede significant contact of leukocytes with the surfaces of artificial organs, we have chosen to study polymorphonuclear leukocyte (PMN) adhesion in a sequential manner. The work presented here deals with the effects of flow and surface type on PMN adhesion to fibrinogen- and albumin-coated glass. We compared direct adhesion to adsorbed protein with adhesion to adsorbed protein having adherent platelets. These experiments were designed to see if PMN's might preferentially adhere to albumin or fibrinogen and whether a particular morphological form of adherent platelet could promote PMN adhesion. The adhesion of PMN's to spread platelets on albumin or fibrinogen occurs to a greater extent than in the absence of platelets. Adhesion of PMN's to spread platelets may be an important mechanism for their depletion from the circulation during artificial organ use.

Adult↗
PubMed1989

Microcomputer-based interactive tracking of blood cells at biomaterial surfaces.

A microcomputer-based system for analyzing the motion of human platelets and leukocytes at synthetic surfaces from a sequence of video frames on tape is described. The software is designed to provide convenient interaction with an operator to reduce the burden of manual analysis. In addition, the system computes and stores the cell movement data on disk for subsequent statistical analysis. Measurement include the number and nature of cell-to-surface collisions, residence times, and distances traveled.

Biocompatible Materials↗
PubMed1986

Adhesion and aggregation of thrombin prestimulated human platelets: evaluation of surface-bound fibrinogen and surface-bound albumin.

The effect of prestimulation of human washed platelets with thrombin on their ability to adhere to and form aggregates on fibrinogen- and albumin-coated glass has been studied. Prestimulation of platelets does not alter platelet adhesion to surface bound albumin and fibrinogen. Our data for both protein coatings support a mechanism of adherence of single prestimulated platelets before formation of surface-bound aggregates from single platelets arriving from the flow. When whole blood contacts an artificial surface, thrombin will likely influence the platelet component of thrombus formation.

Cell Membrane↗
PubMed1986

Platelet adherence and detachment--in what ways is surface-bound albumin different from surface-bound fibrinogen?

The adhesion and detachment of platelets on surface-bound albumin and surface-bound fibrinogen were studied. Fluorescent video-microscopy of platelets labelled with mepacrine was used to provide continuous information. Glass tubes (I.D. 1.3 mm) were precoated with either human albumin or human fibrinogen before exposure to a suspension of washed platelets and red cells. Observations were made 0.5 cm from the tube's entrance over a 1370 micron 2 portion of lumen. The rate at which cells leave the measurement area and the percent of initially attaching cells which leave are independent of protein coating but increase with flow rate. The percent of initially attaching platelets which permanently adhere is equal for both protein coatings but the pathways leading to this result can be different. For the lower shear rate studied, 80 s-1, the percent of cells which permanently adhere on first contact is less for albumin than for fibrinogen; the percent of initially attaching cells which adhere and then move before permanent adhesion is greater for albumin. The mechanism of detachment and reattachment leads to the equality of the overall adhesion efficiencies for the two protein coatings at 80 s-1. For the higher shear rate studied, 456 s-1, the adhesion pathways for both coatings were the same.

Chromium Radioisotopes↗
PubMed1986

Blood platelet surface interactions on fibrinogen under flow as viewed with fluorescent video-microscopy.

The interaction of fluorescently labeled blood platelets with fibrinogen-coated glass was studied in Poiseuille flow at 3 wall shear rates, 40, 80 and 944 s-1. Observations were made via video-microscopy at a distance of 0.5 cm from a tube's entrance over a 1370 microns 2 portion of luminal area. The rates of arrival and detachment, and the net rate of adhesion of cells increased nonlinearly with flow rate. The fraction of arriving cells, first contacts, which adhered without subsequent movement and the fraction of arriving cells which adhered, moved to new positions and then remained adherent, were maximal at 80 s-1. For platelets which adhere and then move to a number of new positions, the likelihood of permanent adhesion is greater than 85 percent. The adhesion process is one in which 40-60 percent of cells permanently adhere on first contact with an additional 30 percent adhering after several moves along the surface. Cells contacting where a platelet was previously adherent had a greater chance of adhering than they would on an unaltered fibrinogen surface. The efficiency of platelet adhesion is greater for second contacts than for first contacts on unaltered fibrinogen coated surface.

Analysis of Variance↗
PubMed1986

Platelet adhesion to fibrinogen-coated glass at an abrupt tubular expansion viewed with fluorescent video-microscopy.

The adhesion and detachment of human washed platelets was studied on the surface of the larger tube of a tubular expansion. Measurements were made within the vortex, at the reattachment point and downstream of the vortex. Fluorescent video-microscopy of mepacrine labelled platelets was used to record data continuously. Flow was from the smaller to the larger tube at Reynolds numbers (based on upstream conditions) of 75.4 and 212.2. Measurements of the adhesion efficiency for initially contacting cells and an overall adhesion efficiency were made. These efficiencies decreased with increasing Reynolds number. There was a pattern of variability for both efficiencies with respect to position and Reynolds number which is consistent with the generation of the unstable flow at the reattachment point.

Analysis of Variance↗