Search PubMed⌕ Search

Biomedical subjects

W Zingg

Publications and source records attributed to W Zingg.

At least 55 records · Page 3Linked to original sources
PubMed1981

Determination of the Surface tension of proteins. I. Surface tension of native serum proteins in aqueous media.

The desorption patterns of serum proteins in hydrophobic chromatography suggest that serum proteins that remain immersed in an aqueous medium and do not become in a protein-air interface are very hydrophilic. Contact angle measurements on fairly thick layers of hydrated serum proteins, formed on ultrafiltration membranes, yield surface tensions that correlate well with the degree of hydrophilicity derived from desorption data obtained by hydrophobic chromatography. For further confirmation the absorptivity of four human serum proteins was measured with respect to surfaces of different polymers of various surface tensions, for solution in aqueous solvents of different surface tensions. The surface tension of the solvent from which a dissolved protein adsorbs to precisely the same extent onto all solid substrates (regardless of their surface tensions) is equal to the surface tension of that protein. The surface tensions found by the contact angle (first value given) and by the protein adsorption methods (second value given) were. in erg/cm2; alpha 2-macroglobulin, 71.0, 71.0; serum albumin, 70.5, 70.2; immunoglobulin M, 69.5, 69.4; immunoglobulin G, 67.4, 67.7.

Adsorption↗
PubMed1981

Determination of surface tensions of proteins. II. Surface tension of serum albumin, altered at the protein-air interface.

Serum albumin, which itself has a surface tension of congruent to 70.3 erg/cm2, when dissolved in water lowers the surface tension of water from 72.5 to congruent to 50 erg/cm2, as measured by a variety of means, including the pendant drop, the Wilhelmy plate and the platinum ring methods. Equally low and even lower surface tensions are found with the contact angle method, on a thin layer of albumin that had been adsorbed onto a low energy surface and subsequently exposed to air. Surface tensions of drops of albumin solutions varying in concentration from 0.01 to 5.5% (w/v) yielded, with a contact angle method, values that only varied between 67 and 61 erg/cm2. With the pendant drop, the Wilhelmy plate and the platinum ring methods, one essentially measures the surface tension at the air-liquid interface, at which proteins tend to adsorb, and where reversible or irreversible reorientation can be expected. The same holds for a thin layer of protein adsorbed onto a low energy surface, exposed to air. Thus, when through the very act of surface tension measurement, or after adsorbing protein onto a substrate, protein is exposed at the air-liquid interface, it apparently loses the pronounced hydrophilicity characteristic of its native hydrated state and manifests through reorientation a much more hydrophobic tertiary configuration.

Air↗
PubMed1981

Patency of heparinized SBS shunts at high shear rates.

The patency of 50 cm long, 1.7 mm ID heparin-polyvinyl alcohol (PVA) coated SBS arterio-venous shunts in pigs at shear rates greater than 1000 s-1 was found to be not different from that of identical shunts coated with PVA but without heparin. This was attributed to the absence of any measureable effect of surface bound heparin on platelet related thrombus formation at high shear rates. On the other hand, platelet adhesion values determined in the absence of flow by the open static method decreased with increasing heparin content in heparin-PVA films. The low overall patency (average life of 170 minutes) of the PVA coated SBS shunts (with and without heparin) was presumed to be related to the absence of circulating heparin during surgery and the consequent presence of tissue thromboplastin or cellular debris during the immediate postoperative period. Alternative protocols are needed to test heparinized materials at low shear rates in the absence of systemic heparin to properly assess the potential thrombo-resistance of such materials.

Animals↗
PubMed1980

Concanavalin A agglutinability of dextran gel spheres. A physical model for cells agglutination.

Dextran is a polysaccharide which can interact with concanavalin A, and insolubilized dextran spheres are available with different degrees of swelling in water. One grade of these dextran gel spheres can be agglutinated extensively by concanavalin A, while another grade with the same binding constant is not affected. Photomicrographs and measurement by capillary suction show that deformability and good contact between these gel spheres can be correlated with their agglutinability.

Agglutination↗
PubMed1980

Kinetic and thermodynamic aspects of platelet adhesion from suspension to various substrates.

Kinetics of platelet adhesion from suspension to various substrates leads to Langmuir isotherm types of curves, both for suspensions in which the platelets were isolated by means of gel filtration as well as by centrifuging and washing. The level of platelet adhesion increases with increasing surface tension of the substrate. These results cannot be explained on the basis of the theoretical transport model of Ruckenstein et al. The plot of the platelet adhesion at equilibrium vs. gamma SV brings the observations in yet closer agreement with thermodynamic predictions based on free energy calculations than was found previously for the adhesion of platelets after short contact times between platelet suspension and substrate.

Animals↗
PubMed1979

Surface thermodynamics of leukocyte and platelet adhesion to polymer surfaces.

Adhesion of leukocytes and platelets to solid substrates of different surface tensions and hence different wettability is studied from a thermodynamic point of view. A simple thermodynamic model predicts that a cellular adhesion should increase with increasing surface tension of the solid substrate if the surface tension of the medium in which the cells are suspended is lower than the surface tension of the cells. If the surface tension of the suspending medium is higher than that of the cells, the opposite behavior is predicted. These predictions are borne out completely by neutrophil adhesion tests, where the surface tension of the aqueous suspending medium is varied by addition of dimethyl sulfoxide (DMSO). Platelet adhesion experiments also confirm these predictions, the only difference being that surface tensions of the suspending medium above that of the platelets cannot be realized, owing to exudation of surface active solutes from the platelets. Utilization of the thermodynamic prediction that cellular adhesion should become independent of the surface tension of the substrate when the surface tensions of the cells and that of the suspending medium are equal leads to a value of the surface tension of neutrophils of 69.0 erg/cm(2), in excellent agreement with the value obtained from contact angles measured on layers of cells.

Cell Adhesion↗
PubMed1979

Thermodynamic studies of cellular adhesion.

Cellular adhesion of granulocytes and of platelets to solid substrates of different surface tensions has been studied from a thermodynamic aspect. A simple thermodynamic model predicts that cellular adhesion should increase as the surface tension of the solid substrate increases provided that the surface tension of the liquid medium in which the cells are suspended is lower than the surface tension of the cells themselves. If, however, the surface tension of the liquid medium is higher than the surface tension of the cells, then a decrease in cell adhesion with increasing substrate surface tension can be predicted. These predictions are completely substantiated by granulocyte adhesion tests in which the surface tension of the suspending liquid medium is varied through the addition of different volumes of dimethyl sulfoxide (DMSO). Platelet adhesion experiments also confirmed these predictions, the only difference being that it is not possible to obtain a suspending liquid medium with a surface tension higher than that of platelets themselves, as a consequence of the exudation of surface active substances by the platelets.

Blood Platelets↗
PubMed1978

Increased serum immunoreactive gastrin levels in idiopathic hypertrophic pyloric stenosis.

The serum immunoreactive gastrin (IRG) level in infants with confirmed idiopathic hypertrophic pyloric stenosis (IHPS) has been determined and compared to that found in vomiting infants without IHPS, in normal infants, and in normal adults. The mean serum IRG level of normal infants (103 +/- 9 pg/ml (mean +/- SEM) exceeded that of normal adults (28 +/- 5 pg/ml). The preoperative mean serum IRG level in IHPS infants (256 +/- 26 pg/ml) was significantly higher than that of both normal infants and vomiting infants without IHPS (93 +/- 9 pg/ml). Twenty-five per cent (5/20) of the IHPS infants had serum IRG levels within the upper range of normal infants. Fasting serum IRG levels in IHPS infants were not altered immediately by pyloromyotomy. The results from this study suggest a relationship between gastrin and idiopathic hypertrophic pyloric stenosis.

Adolescent↗
PubMed1977

Platelet adhesion to solid surfaces. The effects of plasma proteins and substrate wettability.

Platelet adhesion tests were performed using protein-free washed pig platelet suspensions in conjunction with a simple open-static method on smooth, well-defined protein-coated glass and polymer surfaces and bare glass and polymer surfaces. A normalization technique was introduced in an attempt to correct day-to-day variations in platelet reactivity. Protein coatings reduced platelet adhesion (to glass as well as polymer surfaces) to such a low level that the platelet density on one protein/substrate combination could not be distinguished from that on any other protein/substrate combination. Specifically, albumin and fibrinogen behaved identically regardless of the substrate on which they were coated. The addition of albumin and gamma-globulin to the platelet-suspension also significantly reduced platelet adhesion to glass surfaces. Whereas the extent of platelet adhesion from protein-free suspensions to bare glass and polymer surfaces depended on their wettability, the presence of specific chemical groups in the proteins, such as (-CONH-), may have an overriding effect on platelet adhesion to solid surfaces.

Blood Proteins↗
PubMed1977

Relation of proteins, platelets, and gas nuclei in adhesion to a synthetic material.

We report the result of exposing silicone rubber to washed pig platelet suspensions that contained on average 0.018 mg of proteins/ml in solutions. This protein content is sufficiently low to reasonably neglect the protein adhesion to the material. On comparing the measured platelet adhesion from the platelet suspensions with that from blood, we find that when the gas nuclei normally present in the surface roughness of the material are removed the number of adhering platelets is the same. Thus, in the absence of the gas nuclei, the proteins in blood plasma play a negligible role in the platelet adhesion. In contrast, when both the gas nuclei and proteins are present, the maximum platelet adhesion was observed. From this and the above observation, it appears the gas nuclei affect one or more of the proteins, and this brings about an increased platelet adhesion. Finally, the platelet adhesion from the platelet suspensions was reduced after the removal of the gas nuclei. Thus the platelets themselves sense the change in the surface resulting from the removal of the gas nuclei.

Animals↗