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Biomedical subjects

R Pethig

Publications and source records attributed to R Pethig.

50 records · Page 3Linked to original sources
PubMed1984

Radiofrequency thermotherapy, local chemotherapy, and arterial occlusion in the treatment of nonresectable cancer.

Localized radiofrequency thermotherapy (RFTT) has been effective by itself in debulking cancers but has not accomplished total eradication by itself. Occlusion of the regional artery supplying the tumor drastically reduces the arterial pressure distal to occlusion and further impairs tumor blood flow leading to an accentuation of the temperature differentiation achieved by the normal tissue and tumor. Radiofrequency thermotherapy with vascular occlusion is combined with direct injection of an effective chemotherapeutic agent into the tumor. Radiofrequency thermotherapy is performed after injection of chemotherapy using bleomycin and mitomycin C for squamous cell cancers and Adriamycin and mitomycin C for adenocarcinoma. There are no adverse systemic responses to the small dose of chemotherapy used and the combination therapy is effective in destroying the tumor.

Antineoplastic Agents↗
PubMed1983

Ascorbate-quinone interactions: electrochemical, free radical, and cytotoxic properties.

Standard midpoint potentials have been determined for p-benzoquinone, methoxy-p-benzoquinone and 2,3-, 2,5-, and 2,6-dimethoxy-p-benzoquinones in aqueous solution. ESR studies have been made of the ascorbate and semiquinone radicals produced when these quinones interact with sodium ascorbate. Direct correlations are found between the electrochemical potentials, generated semiquinone lifetimes, and cytotoxic action in Ehrlich ascites-bearing mice.

Animals↗
PubMed1983

Radiofrequency-induced hyperthermia: computer simulation of specific absorption rate distributions using realistic anatomical models.

A description is given of a computer simulation technique which predicts the specific absorption rate (SAR) distribution within the human body resulting from the application of radiofrequency electromagnetic energy. The method uses an extension to the principle of over-relaxation of electric potentials and the basis of the simulation is a realistic three-dimensional model derived from both dielectric and anatomical data. Two of the principal means of applying radiofrequency hyperthermia, namely the use of capacitive electrodes and inductive coils, have been provided for. The accuracy of the simulation has been favourably tested using an agar split-phantom and an infrared thermograph camera. The simulations can be used to assist the design and clinical use of radiofrequency applicators, and examples are given of the application of both an inductive coil and switched capacitive electrodes to heat the thorax.

Computers↗
PubMed1981

Water structure-dependent charge transport in proteins.

Dielectric and conductivity measurements are reported for bovine serum albumin as a function of hydration. Strong evidence is found for the existence of mobile charges whose short- and long-range hopping motion strongly depends on the physical state of the protein-bound water. These charges are considered to be protons. Insights into the nature of the electrical properties of protein-methylglyoxal complexes are provided, and the possibilities for correlated proton-electron motions are outlined.

Animals↗
PubMed1980

Spectroscopic studies of the protein-methylglyoxal adduct.

Spectroscopic measurements are reported for the effects of pH, time, solvent, and chemical modification of arginine and lysine side chains on the reaction of proteins with methylglyoxal. The reaction responsible for the appearance of a brown coloration and increased submolecular electronic activity in the proteins involves the epsilon-amino groups of the lysine residues. It is concluded that the primary step in the reaction involves the formation of a Schiff base linkage between the lysine side chain and methylglyoxal. These findings reaffirm the concept that, by the formation of Schiff bases, aldehydes can act as electron acceptors in charge transfer interactions with proteins.

Aldehydes↗
PubMed1978

Electronic properties of some protein--methylglyoxal complexes.

Steady-state conductivity measurements and dielectric measurements in the frequency range 10(-5) to 100 Hz are reported for samples of bovine serum albumin, casein, and lysozyme complexed with methylglyoxal. Compared with the untreated proteins, the brown complexed proteins exhibit an increased conductivity and free electron spin density, together with a low-frequency dielectric dispersion. These results can be taken as evidence that the interaction with methylglyoxal results in the proteins possessing an increased electronic activity associated with the creation of mobile electron holes within the valence band states of the protein molecules.

Aldehydes↗
PubMed1978

Electronic and dielectric properties of protein--methylglyoxal complexes.

Steady-state conduction and dielectric measurements over the frequency range 10(-5) to 10(5) Hz are reported for several proteins that have been complexed with methylglyoxal. Compared with the normal (white) proteins the brown protein--methylglyoxal complexes exhibit a marked increase in electronic conductivity and a pronounced low-frequency dielectric dispersion. The intensity of the brown colour and the electronic activity is directly related to the number of free lysine groups available to react with the methylglyoxal. It is proposed that the methylglyoxal molecules form Schiff bases with the epsilon-amino groups of lysine residues and that these Schiff bases then form a charge-transfer complex with a neighbouring peptide unit. For collagen, in particular, it is found that the electron 'holes' so formed in the polypeptide backbone are capable of long range motion in what can be interpreted as being the valence band of extended electronic states of the protein structure. The protein--methylglyoxal complexes have electronic and dielectric properties similar to those exhibited by the perylene-chloranil charge-transfer complex.

Aldehydes↗
PubMed1977

Electronic properties of the casein-methylglyoxal complex.

Measurements of the electron spin resonance, direct current conductivity, microwave permittivity, and electronic transference number are reported for the brown casein-methylglyoxal complex. Compared with normal white casein, the colored casein complex exhibits an increased electronic activity. This is considered to arise from the electron-accepting action of the methylglyoxal in separating electronic charge from an otherwise completely occupied electronic ground state of the casein macromolecule.

Aldehydes↗