William E. Seifert

Metabolism of the Lipid Peroxidation Product, 4-Hydroxy-trans-2-nonenal, in Isolated Perfused Rat Heart*

The metabolism of 4-hydroxy-trans-2-nonenal (HNE), an α,β-unsaturated aldehyde generated during lipid peroxidation, was studied in isolated perfused rat hearts. High performance liquid chromatography separation of radioactive metabolites recovered from [3H]HNE-treated hearts revealed four major peaks. Based on the retention times of synthesized standards, peak I, which accounted for 20% radioactivity administered to the heart, was identified to be due to glutathione conjugates of HNE. Peaks II and III, containing 2 and 37% radioactivity, were assigned to 1,4-dihydroxy-2-nonene (DHN) and 4-hydroxy-2-nonenoic acid, respectively. Peak IV was due to unmetabolized HNE. The electrospray ionization mass spectrum of peak I revealed two prominent metabolites with m/z values corresponding to [M + H]+ of HNE and DHN conjugates with glutathione. The presence of 4-hydroxy-2-nonenoic acid in peak III was substantiated using gas chromatography-chemical ionization mass spectroscopy. When exposed to sorbinil, an inhibitor of aldose reductase, no GS-DHN was recovered in the coronary effluent, and treatment with cyanamide, an inhibitor of aldehyde dehydrogenase, attenuated 4-hydroxy-2-nonenoic acid formation. These results show that the major metabolic transformations of HNE in rat heart involve conjugation with glutathione and oxidation to 4-hydroxy-2-nonenoic acid. Further metabolism of the GS-HNE conjugate involves aldose reductase-mediated reduction, a reaction catalyzed in vitro by homogenous cardiac aldose reductase.

Human tissue distribution of platinum after cis-diamminedichloroplatinum

SummaryUsing X-ray fluorescence spectrometry, platinum concentrations were determined in autopsy tissue samples from 12 patients who had received cis-diamminedichloroplatinum (DDP) 20–120 mg/m2 up to 6 months antemortem. Tissue platinum concentrations were highest in liver (0.5–3.7 μg/g wet weight), prostate (1.6–3.6 μg/g), and kidney (0.4–2.9 μg/g), somewhat lower in bladder, muscle, testicle, pancreas, and spleen, and lowest in bowel, adrenal, heart, lung, cerebrum, and cerebellum, Platinum concentrations in tumors were generally somewhat lower than the concentration in the organ in which the tumor was located, with the exception of intracerebral tumors. Different metastatic sites in the same patient had substantially different platinum concentrations and hepatic metasutases had the highest concentrations. Intra-arterial administration of drug may augment tissue concentrations of platinum. In a patient undergoing therapeutic abortion 4 days after treatment, the platinum concentration was 0.5 μg/g in the placenta and 0.3 μg/g in the fetus. The data suggest that for in vitro sensitivity testing, DDP concentrations of ≦7 μg/ml should be used.

Measurement of gamma-aminobutyric acid (GABA) in blood

Abstract Blood GABA levels can be readily determined using a radioreceptor assay or gas chromatography-mass spectrometry. After withdrawal of blood, GABA levels remain stable with 25–50% of the GABA in whole blood found in the plasma fraction. Whole blood GABA concentrations range from 500 pmoles/ml to 1200 pmoles/ml in 8 mammalian species with human values being about 900 pmoles/ml. in vivo administration of aminooxyacetic acid increases both blood and brain GABA levels to a similar extent.

Neurotransmitter defects and treatment of disorders of hyperphenylalaninemia

The disordered biosynthesis of dopamine, norepinephrine, and serotonin in brain in untreated PKU is corrected by dietary restriction of phenylalanine. Low levels of biogenic amine metabolites were measured in cerebrospinal fluid from three patients with classical PKU; metabolite concentrations increased after dietary treatment. In a variant of hyperphenylalaninemia caused by deficiency of dihydropteridine reductase, there is defective metabolism of biogenic amines despite dietary restriction of phenylalanine. Two siblings with DHPR deficiency had low amine metabolite values in CSF; in one patient the metabolic defect was corrected by administration of hydroxylated amino acid precursors. Defective biosynthesis of biogenic amines in brain in disorders associated with hyperphenylalaninemia and evaluation of specific dietary treatments can be determined by analysis of neurotransmitter metabolites in CSF.

Energy-dispersive X-ray fluorescence determination of platinum in plasma, urine, and cerebrospinal fluid of patients administered cis-dichlorodiammineplatinum(II)

SummaryA method involving the use of an energy-dispersive X-ray fluorescence spectrometer was developed for assaying total platinum concentrations in body fluids of patients treated with the antitumor drug cis-dichlorodiammineplatinum(II). Sample preparation by this procedure is simple, consisting in adding an internal standard (Zr) to 1 ml of biological fluid or tissue homogenate, pipetting 20 μl of the sample onto a Mylar sample holder, and drying. This produces a thin-film sample, which effectively eliminates absorption enhancement effects due to other elements in the specimen. Standard addition studies were found to be linear in the concentration range of interest (0.1–10.0 μg/ml), with correlation coefficients exceeding 0.99. Minimum detection limits range from 0.10 to 0.25 μg Pt per ml, depending on the body fluid, which is adequate for routine patient monitoring after normal chemotherapeutic doses of cis-dichlorodiammineplatinum(II). In preliminary studies with mammalian liver, standard addition experiments were found to be linear and the minimum detection limit was found to be 1.4 μg/g dry weight.

Is Phentolamine Stable in Solution with Papaverine

Although the intracorporeal injection of mixtures of phentolamine and papaverine is used commonly in the diagnosis and treatment of erectile dysfunction, pharmacological data relating to the stability of such drug mixtures are lacking. The stability of phentolamine mesylate in aqueous solution and in solution with papaverine (0.83 mg. per cc phentolamine and 25 mg. per cc papaverine) was ascertained by high performance liquid chromatography and gas chromatography with mass spectrometry. No degradation of phentolamine occurred during 40 days whether the drug or drug combination was refrigerated or stored at room temperature. Phentolamine is stable for at least 40 days when mixed with papaverine.

NEUROTRANSMITTERS IN NEUROLOGICAL DISORDERS OF CHILDHOOD

Disturbances in biogenic amine metabolism in genetic and biochemical disorders affecting the nervous system of children were studied by quantitation of metabolites of dopamine, serotonin and norepinephrine in cerebrospinal fluid before and after oral probenecid, using gas chromatographic/mass spectrometric methods.

High-performance liquid chromatographic method with electrochemical detection for the analysis of O6-methylguanine

An improved system consisting of a combination of high-performance liquid chromatographic methods with electrochemical detection for the separation and analysis of the DNA adduct O6-methylguanine (O6MG) has been developed. This adduct is produced by the interaction of methylating agents with DNA and induces mispairing in the DNA of the target cells. A good separation of modified from unmodified bases is first achieved with an HPLC system using a Partisil 10 SCX column and a salt gradient. A second HPLC step with electrochemical detection and a C18 column is used for farther separation and quantitation of O6-methylguanine. This method shows a linear response up to 15 pg of 06MG tested. The lowest amount detected was 0.5 pg of O6MG and is highly reproducible. This method is useful to study DNA damage as a product of cellular metabolism and its effects on the process of carcinogenesis.

Lipids and proteins in the Rathke's gland secretions of the North American mud turtle ( Kinosternon subrubrum )

Lipids and proteins in the Rathkes gland secretions of the North American mud turtle (Kinosternon subrubrum, Kinosternidae) were analyzed by gas chromatography-mass spectrometry (GC-MS) and SDS-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. Analysis by GC-MS indicates 2,3-dihydroxypropanal and C3-C24 free or esterified fatty acids. Analysis by SDS-PAGE indicates a major protein component with an approximate molecular mass of 60 kDa and minor components ranging from ca. 23 to 34 kDa. The major component of K. subrubrum glandular secretions exhibits a mobility that matches that of the Kemps ridley sea turtle (Lepidochelys kempi, Cheloniidae), suggesting that these proteins are evolutionarily conserved.

Faculty and Academic Institution: A Covenantal Relationship

Over the past few decades universities and academic health centers seem to be shifting from faculties composed predominantly of tenured or tenure-track faculty members to faculties who are increasingly made up of nontenure track or part-time members. This trend may have deleterious effects on the academic endeavors and other activities of the institution. This paper examines the nature of the relationship between faculty members and the educational institutions focusing on whether the relationship is contractual or covenantal. The authors conclude that the nature of the relationship is primarily covenantal and offer proposals to extend this relationship to faculty members who are either part-time or not on the tenure track.