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Biomedical subjects

L Vroman

Publications and source records attributed to L Vroman.

At least 19 recordsLinked to original sources
PubMed1991

Is the Vroman effect of importance in the interaction of blood with artificial materials?

The successive displacement of plasma proteins adsorbed to artificial surfaces (biomaterials) is well documented, mostly by specially designed experiments that stretch out the effect in time and space. Analysis of displacement has been focused principally on molecular events on the adsorbing surface. In this paper attention is directed rather to the antecedent transport phenomena necessary to deliver successive proteins to a surface. The different limitations on protein arrival fixed by the total quantity present and by the rates of transport of super-sufficient quantities are distinguished. The transport perspective is then used to ask, and partly answer, the question: Can protein displacement be responsible for patterns of thrombus formation and cellular adhesion that are seen on the blood-wetted surfaces of devices found in medical practice: artificial organs and vascular prostheses? Calculations and a small amount of preliminary data suggest that such patterns may form when blood is introduced into these devices, particularly in the neighborhood of boundary shapes that cause separated flows.

Adsorption↗
PubMed1986

Rapid identification of proteins on flat surfaces, using antibody-coated metal oxide suspensions.

Suspensions of Fe3O4 (black), Fe2O3 (red), and Cr2O3 (green) were exposed to solutions of protein A, and then each to a different antiserum to one of the following human proteins: fibrinogen, high molecular weight kininogen (HMK), albumin or immunoglobulins (IgG). Test surfaces were patterns of human proteins adsorbed out of solutions or out of plasma, onto glass as well as onto polyvinylchloride slides. They were exposed to single or mixed suspensions of the treated oxides for about 30 s and rinsed. Adhesion of each oxide onto each matching protein of these patterned test surfaces resulted, thus identifying each protein by color.

Antibodies↗
PubMed1985

Lack of exchange among plasma proteins in narrow spaces on glass, demonstrated with metal oxide coatings.

Onto 'activating' surfaces, intact normal plasma deposits an overlapping sequence of proteins, each being desorbed by the next. Ultimately, high molecular weight kininogen (HMK) is deposited unless contact was too short, or space between 2 surfaces too narrow. Thus, injected between a glass slide and a convex lens, intact plasma will leave a disk of HMK with a center of fibrinogen. We describe here how the exchange of proteins on the surface can be demonstrated by staining the adsorbate with a metal oxide suspension. Subsequent flooding of the preparation with more normal plasma causes lift-off of the oxide where underlying fibrinogen is being displaced by the HMK of the newly applied plasma. Kininogen-deficient plasma fails to remove any oxide, while normal plasma can remove nearly all of the oxide and adsorbate, left on glass by HMK-deficient plasma.

Adsorption↗
PubMed1984

The effect of high molecular weight kininogen on surface-adsorbed fibrinogen.

High molecular weight kininogen (HMWK) plays an important role in altering the association of plasma fibrinogen with surfaces. Plasma initially deposits fibrinogen onto most materials, but on hydrophilic surfaces within 10 min adsorbed plasma fibrinogen cannot be detected on the surface by anti-fibrinogen antisera. However, using HMWK-deficient plasma, fibrinogen remains immunologically identifiable. The interrelationship of adsorbed plasma fibrinogen with kininogen on hydrophilic surfaces is studied further using glass slides stained for protein with Coomassie Blue, and oxidized silicon crystal slices in an automated ellipsometer. On glass slides when plasma that is deficient in both low molecular weight kininogen (LMWK) and HMWK, is reconstituted with HMWK (0.04 Units/ml), fibrinogen is no longer detected on the surface. This finding is specific for HMWK, since, when the same plasma is reconstituted with LMWK (220 micrograms/ml), the amount of fibrinogen detected on the surface is unchanged. The alteration of surface-adsorbed fibrinogen by HMWK is not due to plasmin-induced fibrinolysis, since it occurs in plasminogen-free plasma. In the ellipsometer, surface adsorption of normal plasma is associated with a significantly less (p less than 0.0005) thick protein layer (1.99 +/- 0.08 degree change in azimuth) than plasmas deficient in HMWK (2.32 +/- 0.11). Using ellipsometry, HMWK in plasma is shown to shorten the time in which immunologically detectable surface-adsorbed fibrinogen was removed or altered. These studies in a whole plasma system present further evidence that HMWK specifically modifies the association of plasma fibrinogen with hydrophilic surfaces.

Adsorption↗
PubMed1982

Immunologic technic.

Explore the source record for details and available documents.

Blood Coagulation Tests↗
PubMed1980

Interaction of high molecular weight kininogen, factor XII, and fibrinogen in plasma at interfaces.

Using ellipsometry, anodized tantalum interference color, and Coomassie blue staining in conjunction with immunologic identification of proteins adsorbed at interfaces, we have previously found that fibrinogen is the main constituent deposited by plasma onto many man-made surfaces. However, the fibrinogen deposited from normal plasma onto glass and similar wettable materials is rapidly modified during contact activation until it can no longer be identified antigenically. In earlier publications, we have called this modification of the fibrinogen layer "conversion," to indicate a process of unknown nature. Conversion of adsorbed fibrinogen by the plasma was not accompanied by marked change in film thickness, so that we presumed that this fibrinogen was not covered but replaced by other protein. Conversion is now showen to be markedly delayed in plasma lacking high molecular weight kininogen, slightly delayed in plasma lacking factor XII, and normal in plasma that lack factor XI or prekallikrein. We conclude that intact plasma will quickly replace the fibrinogen it has deposited on glass-like surfaces by high molecular weight kininogen and, to a smaller extent, by factor XII. Platelets adhere preferentially to fibrinogen-coated surfaces; human platelets adhere to hydrophobic nonactivating surfaces, since on these, adsorbed firbinogen is not exchanged by the plasma. The adsorbed fibrinogen will be replaced on glass-like surfaces during surface activation of clotting, and platelets failing to find fibrinogen will not adhere.

Adsorption↗