Biomedical subjects

R P Quintana

Publications and source records attributed to R P Quintana.

At least 19 recordsLinked to original sources

PubMed1997

Radiochemical studies on contact lens soilation. I. Lens uptake of 14C-lysozyme from simple and complex artificial tear solutions.

A systematic study has been made of the uptake of lysozyme by various contact lens materials. Lens uptake of 14C-methylated lysozyme was assessed using simple to complex artificial tear solutions. The data reflect prominent uptake by Group IV (ionic, high-water-content) hydrogel lenses, consistent with the literature. This includes protein on the lens surface and in the lens matrix, the former being estimated at about 33% of the total deposit for the DuraSoft 3 lenses used. Uptake appears to be contingent upon the nature of the lens material, the composition of the deposit model used, and the duration of lens exposure to the artificial tear solution.

Animals↗

PubMed1997

Radiochemical studies on contact lens soilation. II. Lens uptake of cholesteryl oleate and dioleoyl phosphatidylcholine.

Employing an artificial tear preparation composed of six proteins and six lipids as a deposit model, uptake of the lipids 3H-cholesteryl oleate and 14C-dioleoyl phosphatidylcholine was measured on contact lenses representative of the four FDA hydrogel groups and on select RGP lenses. Cholesteryl oleate uptake after 24 h at 37 degrees C generally was less than 1 microgram/lens although occasionally reaching 1-2 micrograms. DuraSoft 3 lenses (Group IV) accumulated the deposits in greater amounts (p = 0.04) with other lens groups not differing significantly from each other. Ionic DuraSoft 2 and 3 lenses bound more phosphatidylcholine (also < 1 microgram) than other lens groups, possibly reflecting an interaction between the positively charged choline residue and the negative surface of the lens. Lysozyme deposition, measured simultaneously with cholesteryl oleate, bound to a far greater extent to Group IV lenses (e.g., DuraSoft 3, mean surface deposit 279 micrograms) than to other lens types (p < 0.01). Multiple application of the artificial tear solution did not produce a statistically significant increase in cholesteryl oleate accumulation.

Cholesterol Esters↗

PubMed1986

Interrelationships between the chemical structure of synthetic entities, their platelet aggregation inhibitory potency and their cellular toxicity, based on in vitro experiments.

Striking relationships were observed, in vitro, between the molecular constitution of synthetic entities, their aggregation-inhibitory potency (as determined in ADP-induced human blood platelet aggregation), and their cellular toxicity (as assessed by their inhibition of cultured mouse fibroblast L-cell growth). Effects exerted on platelets tended to reflect interactions between the molecules' aggregation-inhibitory specific functions and the platelets' corresponding target sites, while fibroblasts were generally more susceptible to the molecular constitution's hydrophobic character. The hyperbolic relationships between concentrations effecting 50% inhibition and slopes of concentration-response curves reflect net activity from both specific and nonspecific receptor site interactions, with the latter being dominant, and indicated that the assays approximated equilibrium systems. Plotting logarithm values of concentrations effecting 50% inhibition against logarithms of reciprocal slopes for concentration response curves yielded multiple regression coefficients of R = 0.97 (platelet aggregation-inhibitory potency) and R = 0.98 (fibroblast growth-inhibitory potency).

Alkanes↗

PubMed1984

Relationships between the chemical constitution of aggregation inhibitors and human blood platelet response profile.

Gradually altered synthetic entities were employed as molecular probes, and arachidonic acid, ADP, human alpha-thrombin and the Ca2+ ionophore A23187 as aggregation-inducing agents, in a comprehensive study on the response profile of human blood platelets with an emphasis on the effects of exogenous and increased intracellular Ca2+. Corroborating further previous conclusions, some representative carbamoylpiperidine derivatives, at concentrations effecting substantial inhibition of ADP-induced aggregation, failed to retain that effect when 5.0 mM Ca2+ was introduced into the otherwise identical test medium; reference compounds chlorpromazine and propranolol registered corresponding inhibitory patterns. At increased concentrations the compounds' inhibitory potency was regenerated even in the presence of 5 mM Ca2+. In fact, in sufficiently high concentrations, the compounds were even capable of inhibiting aggregation elicited by 15 microM of the ionophore A23187; so did chlorpromazine and propranolol. Another set of congeners revealed the striking sensitivity of ionophore A23187-induced human blood platelet aggregation to the surface active potencies of inhibitor molecules. The loss in inhibitory potency was directly related to the lesser hydrophobic character of the molecule.

Adenosine Diphosphate↗

PubMed1982

Surface activity and human blood platelet aggregation-inhibitory potency.

Surface and interfacial activity is correlated with molecular constitution and inhibitory potency of mono- and bis(carbamoylpiperidino)alkanes and aralkanes, and of some corresponding quaternary pyridinium congeners, in ADP-induced human blood platelet aggregation. The measurements of surface and interfacial tension were carried out at concentrations and pH-values approximating those employed in the hemodynamic study. The effect of changes in chemical structure, ranging from relatively minor variations in a specific functional group to the alteration of major components in molecular constitution, was examined and interpreted in terms of contemporary theoretical chemistry.

Humans↗

PubMed1980