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Biomedical subjects

M Mezei

Publications and source records attributed to M Mezei.

At least 55 records · Page 3Linked to original sources
PubMed1986

Liposomes as drug carriers for oral ulcers.

The aim of this study was to test the potential of liposomes as drug carriers to the ulcerated oral mucosa. Radioactive triamcinolone acetonide palmitate (3H-TRMAp) was encapsulated in large multilamellar lipid vesicles and served as the test lotion. 3H-TRMAp in solution served as control. Forty-six hamsters were divided into three groups. In group I, multiple confluent ulcers in both cheek pouches were treated by topical application. In group II, single ulcers on the cheeks were treated by intramucosal injection. In group III, multiple confluent ulcers were produced in the cheek pouch on one side, with a single ulcer in the contralateral cheek pouch; no drug was applied, and the tissues were prepared for histology. Hamsters were killed at three and 24 hours, respectively, after treatment. Pouches were divided into ulcerated and intact adjacent mucosa. Cheeks were divided into ulcerated mucosa and distant mucosa. Drug levels in the four mucosal portions as well as in the blood, liver, spleen, brain, and thalamic region were determined by radioactive tracer technique. At three hours, liposomal drug concentrations were lower than in control animals in the brain and the thalamic region. At 24 hours, liposomal drug values were higher than in control animals in the ulcerated mucosa and lower than in control animals in the thalamic region. Mean drug concentrations in the ulcerated mucosa were higher in group II than group I. The results parallel those of Mezei and Gulasekharam (1980, 1982); liposomes increase local and decrease systemic drug concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1984

Monte Carlo computer simulation of the aqueous hydration of the glycine zwitterion at 25 degree C.

Monte Carlo computer simulation on a dilute aqueous solution of the glycine zwitterion are reported. The results are presented in terms of the Quasi-Component Distribution Functions (QCDF) of Ben Naim and partitioned into atomic and functional group contributions using the Proximity Criterion. The Proximity Criterion analysis has been extended to orientational properties and a new normalization procedure has been introduced for the radial distribution functions obtained by the Proximity Criterion. The solvation environment of the glycine zwitterion is found to contain, on the average, 14.4 water molecules out of which 3.2 belong to the ammonium group, 6.1 to the methylene group and 5.1 to the carboxyl group. The importance of the many-body statistical mechanical approach to hydration is emphasized by our finding that the configuration corresponding to the absolute minimum of the glycine zwitterion-water potential surface was found to have negligible statistical weight in the aqueous simulation.

Computer Simulation↗
PubMed1984

Aqueous hydration of nucleic acid constituents: Monte Carlo computer simulation studies.

Monte Carlo computer simulations were performed on dilute aqueous solutions of thymine, cytosine, uracil, adenine, guanine, the dimethyl phosphate anion in the gauche-gauche conformation and a ribose and deoxyribose derivative. The aqueous hydration of each molecule was analysed in terms of quasi-component distribution functions based on the Proximity Criterion, and partitioned into hydrophobic, hydrophilic and ionic contributions. Color stereo views of selected hydration complexes are also presented. A preliminary discussion of the transferability of functional group coordination numbers is given. The results enable to comment on two current problems related to the hydration of nucleic acids: a) the theory of Dickerson and coworkers on the role of water in the relative stability of the A and B form of DNA and b) the idea of water bridges and filaments emerging from the computer simulation results on the hydration of DNA fragments by Clementi.

Carbohydrates↗
PubMed1984

Covalent binding of antibodies to liposomes using a novel lipid derivative.

N-[3-(2-Pyridyldithio) propionyl] stearylamine (PDP-SA) was synthesized from a reaction between stearylamine and the heterobifunctional reagent N-succinimidyl-3-(2-pyridyldithio) propionate. Use of this PDP-SA to covalently couple antibodies to liposomes was investigated. The binding efficiency was found to be 24-32%. The antibodies bound to liposomes were shown to retain the specific antibody activity. This new procedure of coupling antibodies to liposomes could be an efficient means to deliver drugs to selected target organs, especially in cancer chemotherapy.

Animals↗
PubMed1983

Pharmacokinetic profile of intravenous liposomal triamcinolone acetonide in the rabbit.

The pharmacokinetics of triamcinolone [2-14C]acetonide, encapsulated in neutral multilamellar liposomes, and a control preparation of the steroid in a 3:1 solution of polyethylene glycol-water was investigated in the rabbit after single intravenous bolus injections. Blood samples were obtained at various times up to 7 hr postinjection and assayed for the drug by liquid scintillation counting. Blood drug concentration-time data showed biexponential decay and were analyzed by nonlinear, least-squares regression analysis to obtain the initial (time zero) drug concentration [(Cb)0] and the initial (fast, alpha) and terminal (slow, beta) disposition rate constants. From these estimates the central compartment volume (Vc) and the respective half-lives [(t1/2) alpha, (t1/2) beta] of the fast and slow disposition phases were calculated. The total body clearance (CLT) and the apparent distribution volume (Vd) were obtained by nonparametric analysis. Significant differences were observed between the liposome-encapsulated dosage form and the solution of the steroid in beta and Vd beta. While beta for the liposomal form was smaller than that for the solution, the apparent Vd was larger with the liposome-encapsulated drug. There was no difference in the total body clearance of the drug in the two dosage forms. Results of the study suggest that when administered by the intravenous route, liposome-encapsulated drug may exhibit extensive tissue distribution and a prolonged half-life.

Animals↗
PubMed1983

Monte Carlo studies on water in the dCpG/proflavin crystal hydrate.

The extensive water network identified in the crystallographic studies of the dCpG/Proflavin hydrate by Neidle, Berman and Shieh (Nature 288, 129, 1980) forms an ideal test case for a) assessing the accuracy of theoretical calculations on nucleic acid--water systems based on statistical thermodynamic computer simulation, and b) the possible use of computer simulation in predicting the water positions in crystal hydrates for use in the further refinement and interpretation of diffraction data. Monte Carlo studies have been carried out on water molecules in the unit cell of dCpG/proflavin, with the nucleic acid complex fixed and the condensed phase environment of the system treated by means of periodic boundary conditions. Intermolecular interactions are described by potential functions representative of quantum mechanical calculations developed by Clementi and coworkers, and widely used in recent studies of the aqueous hydration of various forms of DNA fragments. The results are analyzed in terms of hydrogen bond topology, hydrogen bond distances and energies, mean water positions, and water crystal probability density maps. Detailed comparison of calculated and experimentally observed results are given, and the sensitivity of results to choice of potential is determined by comparison with simulation results based on a set of empirical potentials.

Acridines↗
PubMed1981

Effect of Wallerian degeneration on histamine concentration of the peripheral nerve.

One sciatic nerve of a White Leghorn hen was severed and the distal portion was allowed to undergo Wallerian degeneration. The change in histamine and DNA concentration and mast cell number was measured at different times following nerve sectioning in the proximal regenerating, distal degenerating, and intact, contralateral nerves. The experimental results revealed a significant accumulation of histamine in the proximal desheathed segment and in the contralateral "functional nerve," whereas the biogenic amine in the distal desheathed nerve significantly decreased. The pattern of change of histamine in the distal and proximal nerve sheaths was different: it dropped at 2 h and then rose in the later stages of Wallerian degeneration. In the distal desheathed nerves and in both the proximal and distal nerve sheaths DNA increased significantly by 14 days. The number of mast cells appeared to be highest in the 14-day distal nerve and in the 7-day proximal nerve sheaths. These results support a dual localization of histamine in the peripheral nerve, and are consistent with the interpretation that the amine has either some role in neurotransmission or in the process of growth and regeneration.

Animals↗
PubMed1979

Studies on 2', 3'-cyclic AMP 3'-phosphohydrolase in rabbit skin.

Previous studies indicated that 2', 3'-cyclic AMP 3'-phosphohydrolase, an enzyme which splits the 3'-phosphate bond of the 2', 3'-cyclic AMP, is primarily confined to nervous tissue. The physiological function of this enzyme is still unknown. In the present study this enzyme was found to be active in various organs of rabbit, i.e. liver, kidney, heart and skin, although to a much lesser extent than in brain and sciatic nerve. The finding of this enzyme in the skin generated further studies to measure the enzyme activity in normal and diseased skin. Chemically induced (surfactant-treated) skin disorder was used as a model for the present study. Topical application of Polysorbate 85 resulted in a two fold increase of the enzyme activity in rabbit skin. The results suggest that this enzyme may have some role in the repair mechanisms, particularly in the regeneration of damaged membranes.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1979

The 2', 3'-cyclic AMP 3'-phosphohydrolase in normal and psoriatic epidermis.

The activity of the enzyme 2', 3'-cyclic AMP 3'-phosphohydrolase is significantly greater in the 'involved' psoriatic skin than in the 'uninvolved' psoriatic skin or in skin samples taken from persons having clinically normal skin. Although the physiological function of this enzyme is not established, it is possible that, besides being associated with myelin, it may also play some role in cell proliferation and maturation, probably at the membrane level.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1978

Ontogenesis of histamine in the chick nervous system.

Tissues from the central and peripheral nervous systems of the chick were analyzed for concentration of histamine (Hm) during development. Of the three CNS organs examined, cerebral hemispheres had the highest Hm content. Expressed on the bases of wet weight, protein, and DNA concentrations, sciatic nerve and the pineal gland had the highest levels of this biogenic amine of the five tissues investigated. The concentration of Hm was higher in the cerebellum, cerebral hemispheres, and thalamus of adult animals than in the 15 to 17-day-old embryos. The level of Hm rose markedly in the sciatic nerve and pineal gland after the 15th day of embryonic development. These data might indicate a possible involvement of Hm in controlling the course of maturation of certain organs in the nervous system.

Age Factors↗
PubMed1975

In vivo method for monitoring polysorbate 85 effect on epidermal permeability.

An in vivo method of monitoring the rate of water desorption from human forearms, using "dry" nitrogen gas passed over approximately 1 cm-2 of skin was investigated with the aid of a commercial electrolytic moisture analyzer. The assembled apparatus was used to evaluate the differences in water loss rates from treated and untreated (control) forearms following surfactant application. The changes in the differences were also monitored after cessation of treatment, i.e., during the healing process. The apparatus provided an accurate, rapid, and painless method of monitoring relative water loss rates and, as such, could prove a useful tool in routine testing in experimental dermatology and cosmetology. The results confirm the earlier finding from an in vitro method with excised rabbit skin that the tested surfactant increases the permeability of the epidermis.

Adult↗