Biomedical subjects

M R Blum

Publications and source records attributed to M R Blum.

7 recordsLinked to original sources

PubMed1992

Hyperthermia-induced enhancement of melphalan activity against a melphalan-resistant human rhabdomyosarcoma xenograft.

The effects of regional hyperthermia (42 degrees C for 70 min) on the antitumor activity of melphalan were examined in athymic mice bearing melphalan-resistant human rhabdomyosarcoma (TE-671 MR) xenografts growing in the right hind limb, and results were compared with similar studies of melphalan-sensitive (TE-671) parent xenografts. Melphalan alone at a dose of 36 mg/m2 (0.5 of the 10% lethal dose) produced growth delays of 4.1 to 10.2 days in TE-671 MR xenografts and 21.8 to 28.7 days in TE-671, respectively. Hyperthermia alone produced growth delays of 0.9 days in TE-671 MR xenografts and 0.8 days in TE-671. Combination therapy with melphalan and hyperthermia produced growth delays of 7.2 to 13.3 days in TE-671 MR xenografts and 34.3 to 42.8 days in TE-671, respectively, representing a mean thermal enhancement ratio of 1.7 in TE-671 MR and 1.5 in TE-671. Measurement of glutathione levels in TE-671 MR xenografts following treatment with melphalan, hyperthermia, or melphalan plus hyperthermia revealed significant reductions in glutathione content with the nadir (60% of control values) seen 6 h following treatment. Glutathione levels in TE-671 xenografts following identical therapy revealed no differences from control values. Hyperthermia plus melphalan did not result in a higher tumor-to-plasma melphalan ratio compared with treatment with melphalan alone in either TE-671 MR or TE-671 xenografts. These studies suggest that heat-induced alterations in tumor glutathione or melphalan levels are not responsible for the increase in melphalan activity produced by hyperthermia. Combination therapy with melphalan plus regional hyperthermia offers promise for treatment of melphalan-resistant neoplasms.

Animals↗

PubMed1991

Therapeutic analysis of melphalan-resistant human rhabdomyosarcoma xenograft TE-671 MR.

Investigations with the melphalan-resistant human rhabdomyosarcoma xenograft TE-671 MR were carried out to identify patterns of cross-resistance and collateral sensitivity and to define the mechanism(s) mediating melphalan resistance. TE-671 MR was cross-resistant to thio-TEPA, mitomycin, vincristine, and cisplatin, and partially resistant to chlorambucil and cyclophosphamide. TE-671 MR and the parent line TE-671 were both resistant to 1,3-bis(2-chloroethyl)-nitrosourea and expressed similar levels of O6-alkylguanine-DNA alkyltransferase. TE-671 MR retained full sensitivity to actinomycin D and demonstrated enhanced sensitivity to VP-16 compared to TE-671. Treatment of TE-671 MR with melphalan plus VP-16 resulted in greater than additive growth delays. The frequency of hypoxic regions was similar in TE-671 MR and TE-671, respectively. Measurement of tumor-to-plasma levels at 180 min following i.p. administration of melphalan at 0.5 of the 10% lethal dosage showed mean tumor-to-plasma ratios of 3.81 in TE-671 MR and 7.38 in TE-671, respectively. The lower drug levels in TE-671 MR may be contributing to the resistance to melphalan and thus indicate the need for further studies to define the reasons for these differences in tumor drug level.

Animals↗

PubMed1979

Acyclovir kinetics after intravenous infusion.

The disposition and safety of the antiviral drug acyclovir were studied in 14 subjects with advanced malignancies. Acyclovir was administered by a 1-hr intravenous infusion at doses of 0.5, 1.0, 2.5, and 5.0 mg/kg. At the end of infusion, mean peak plasma levels (+/- SEM), determined by radioimmunoassay, were 6.4 +/- 0.7, 12.1 +/- 2.3, 14.9 +/- 2.7, and 33.7 +/- 7.1 microM. The plasma concentration-time profiles could be described by a biexponential equation. The half-life of acyclovir in the slow disposition phase ranged from 2.2 to 5 hr and the drug was detected in the plasma for at least 18 hr after infusion. The total body clearance ranged from 117 to 396 ml/min/1.73 m2. A proportionality between area under the curve and dose suggests that acyclovir exhibits dose-independent kinetics in the dose range studied. There was wide variation in cumulative urinary excretion of unchanged drug, ranging from 30 to 69% of the dose. From renal clearances of acyclovir, which were higher than creatinine clearances, it appears that both glomerular filtration and tubular secretion contribute to its renal excretion. Analysis of the urine by reverse-phase high-performance liquid chromatography revealed the presence of the metabolite 9-carboxymethoxymethylguanine. There was no indication of toxicity either clinically or from laboratory findings in any of the study subjects. This study demonstrates that in addition to selectivity and low toxicity, the kinetic profile and metabolic disposition of acyclovir make it an attractive candidate for therapy in a variety of herpes infections.

Aged↗

PubMed1978

Evidence for a trimodal pattern of acetylation of isoniazid in uremic subjects.

Isoniazid metabolic clearance values were calculated retrospectively and plotted on a frequency distribution histogram. A trimodal distribution pattern was observed. According to a two-allele codominant model, the mean clearance values of the slow and rapid acetylators closely predicted the mean clearance value for the intermediate acetylators. The potential clinical implications of identifying intermediate and rapid acetylators of isoniazid and its use in renal failure are discussed.

Acetylation↗

PubMed1978

Acetylation phenotype, platelet monoamine oxidase inhibition, and the effectiveness of phenelzine in depression.

The authors treated 16 depressed patients with up to 90 mg/day of phenelzine. After acetylation phenotype was determined and platelet monoamine oxidase (MAO) activity measured, no significant relationship was observed between clinical improvement and acetylation phenotype or between MAO inhibition and acetylation. Discrepant findings regarding acetylation phenotype and the effects of phenelzine are discussed. The authors do not recommend a sulfamethazine phenotype test as a predictor of outcome for phenelzine.

Acetylation↗

PubMed1976

Relationship of sulfamethazine disposition kinetics to acetylator phenotype in man. A preliminary study.

The relationship between sulfamethazine disposition kinetics and acetylation phenotype was studied in man. Sulfamethazine pharmacokinetic parameters were determined after the administration of the drug as an oral suspension. When the half-life, acetylation rate constant, or per cent available dose excreted in the urine as acetylsulfamethazine of each subject was plotted on frequency distribution histograms, bimodal distribution patterns were observed. However, when acetylation clearance values were plotted in the same manner, an apparent trimodal pattern was seen. The failure to identify the presumed homozygous rapid acetylator using the commonly employed indices of drug metabolism, i.e., half-life, metabolic rate constant, or per cent of the dose metabolized, was attributed to a significant increase in the apparent volume of distribution of this genotype, as well as the low renal clearance of sulfamethazine found in all genotypes. This preliminary study points out the value of using metabolic clearance as an index of drug metabolizing capacity and suggests its application to further pharmacogenetic studies.

Acetylation↗

PubMed1976

A radioimmunoassay for methotrexate and its comparison with spectrofluorimetric procedures.

A radioimmunoassay procedure has been developed for the direct measurement of methotrexate (MTX) in plasma, serum, cerebrospinal fluid, or urine samples. The assay is sensitive to levels of at least 100 pg of MTX and is highly specific for MTX in the presence of folinic acid (citrovorum factor), folic acid, tetrahydrogolic acid, and other folate analogs and known metabolites. Results from this procedure have been compared with those obtained with a spectrofluorimetric method, utilizing the plasma of cancer patients undergoing high-dose MTX treatment with citrovorum factor rescue. Results indicate that the method should be usful in the future in assisting individualization of dosage regimens and in the study of the pharmacokinetics and metabolism of MTX in cancer patients.

Carrier Proteins↗