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Biomedical subjects

E C Horning

Publications and source records attributed to E C Horning.

At least 19 recordsLinked to original sources
PubMed1987

Metabolism of bromobenzene. Analytical chemical and structural problems associated with studies of the metabolism of a model aromatic compound.

Our studies of bromobenzene metabolism have shown that the 3,4-oxide is metabolized to 3- and 4-bromophenol through an extended glutathione pathway. The mechanism of sulfur elimination from a dihydrobromobenzene metabolite is not known, although it is known that the aromatization reaction will occur in a 9000-g supernatant fraction of rat liver. The hepatotoxic and nephrotoxic metabolites of bromobenzene are most likely bromthiocatechols and a bromothiopyrogallol, respectively.

Animals↗
PubMed1987

Analytical methods for the study of urinary thioether metabolites in the rat and guinea pig.

Methods are described for the isolation and identification of three classes of bivalent sulfur metabolites characterized as neutral methylthio ethers, ethyl acetate-soluble acidic thioethers and ethyl acetate-insoluble acidic thioethers from rat and guinea pig urine. After extraction of the metabolites by the ammonium carbonate-ethyl acetate procedure, the individual metabolites are separated by capillary gas chromatography and/or by high-performance liquid chromatography with both mu Bondapak C18 and Porasil columns. Identification of the metabolites is based on gas chromatography-mass spectrometry (electron impact) and on fast atom bombardment mass spectrometry. Interesting species differences in metabolism were observed. The major ethyl acetate-soluble acidic thioethers in rat urine are mercapturic acids. In contrast, in the guinea pig a new pathway involving mercaptopyruvic, mercaptolactic and mercaptoacetic acids is operative. The thioether metabolites of styrene oxide and phenanthrene are described, but the procedures have been applied in studies of several drugs and environmental chemicals in our laboratory.

Animals↗
PubMed1983

High-performance liquid chromatography and gas chromatography-mass spectrometry determination of specific lipid peroxidation products in vivo.

Peroxidation of membrane lipids has been implicated in the toxicity of reactive oxygen intermediates and of several hepatotoxins, but the specific products of this peroxidation in vivo have not been chemically identified. A method for the isolation, identification, and quantitation of specific lipid hydroperoxy and hydroxy acids formed in vivo has been developed. Hydroxylated derivatives of linoleic, arachidonic, and docosahexaenoic acids formed in mouse liver phosphatidylcholines following carbon tetrachloride administration were isolated by high-pressure liquid chromatography and identified as the trimethylsilyl ether methyl ester derivatives by gas chromatography-mass spectrometry. This methodology should be important for the investigation of the role of lipid peroxidation in a variety of normal physiologic and pathologic processes.

Animals↗
PubMed1978

Metabolism of biphenyl in the rat.

The metabolism of biphenyl in the rat has been studied by using gas chromatographic and mass spectrometric methods. The free and conjugated urinary metabolites were characterized. Eight new metabolites were isolated: a dihydrodiol and two hydroxydihydrodiols were characteristic for the epoxide--diol pathway. There were two dihydroxybiphenyls, a trihydroxybiphenyl, a trihydroxymethoxybiphenyl and 4,4'-dihydroxy-3-methylthiobiphenyl. The mass spectra of the trimethylsilyl derivatives of the metabolites exhibited characteristic doubly charged and metastable ions.

Animals↗
PubMed1978

Children absorb tris-BP flame retardant from sleepwear: urine contains the mutagenic metabolite, 2,3-dibromopropanol.

The flame retardant, tris(2,3-dibromopropyl)phosphate (tris-BP), which is a mutagen and causes cancer and sterility in animals is absorbed from fabric by people. 2,3-Dibromopropanol, a metboloite of tris-BP and a mutagen itself, has been found in the urine samples of ten children who were wearing or who had worn tris-BP-treated sleepwear. Eight of these children were wearing well-washed sleepwear and the possibility of absorption of tris-BP from well-washed sleepwear discussed. 2,3-Dibromopropanol was not found in the urines of one child and one adult who had never worn tris-BP-treated garments.

1-Propanol↗
PubMed1978

Metabolism of diethylstilbestrol in the C3H mouse: chromatographic systems for the quantitative analysis of DES metabolic products.

Initial excretion studies with orally administered [monoethyl-1-3H] DES demonstrated the feces to be the principal mode of elimination of DES in the C3H mouse. Metabolic studies with tritiated DES and/or [UL-14C] DES were performed with orally dosed C3H high (MTV+) and low (MTV-) titer MMTV female mice. Extraction and partitioning of the fecal radioactivity demonstrated 77 to 86% (n = 4) to be benzene soluble and the remainder H2O soluble. The principal product in the organic phase following Sephadex LH-20 and HPLC purification was DES. The aqueous phase was resolved by LH-20 into two conjugate fractions that were partially hydrolyzed by beta-glucuronidase. The principal aglycone was chromatographically identical with authentic DES. The urinary conjugates were resolved into six fractions. The four major fractions were 80% hydrolyzable with beta-glucuronidase. Two of these fractions had trans-DES as the principal aglycone, whereas the other two had a major peak similar to but not chromatographically coincident with cis-DES. In certain experiments mice were sequentially dosed with tritium (24 hr) followed by a 14C dose (24 hr). Two mice (MTV+) were also previously fed 1000 ppb DES prior to these experiments. The tritated and 14C products were combined and analyzed simultaneously. This experiment did not reveal significant differences in the metabolism due to the modes of radioactive labeling, MMTV titer, or the prior feeding of DES. The developed methodology was judged to purify quantitatively 90% or more of the DES radioactive products.

Animals↗
PubMed1977

Development and use of analytical systems based on mass spectrometry.

Contemporary analytical systems based on mass spectrometry include as components a gas chromatograph, a mass spectrometer, and a computer. The form of operation is usually in electron impact ionization mode for identification and structural studies, and in chemical ionization mode for quantitative analyses. Important stages in the development of these systems included the design of "molecule separators" for the concentration of solutes in the gas phase, the use of mass spectrometers as specific ion detectors, the introduction of chemical ionization techniques, and the development of computer-based operation, data acquisition, and data analysis capabilities. A current line of investigation is concerned with the design and use of systems based on atmospheric pressure ionization. Samples are ionized in a small reaction chamber external to the low-pressure region of a quadrupole mass analyzer. The primary source of electrons is a 63Ni foil or a corona discharge. The ionization process leading to positive ions involves a sequence of ion molecule reactions, usually electrons leads to carrier gas ions leads to reagent ions leads to sample component ions. Negative ions may be formed by direct electron attachment, or by ion molecule reactions that include new types of elimination reactions. The source will accept a variety of gases and solvents. The sample may be introduced in the gas phase without solvents, by probe injection, or in the effluent stream from a gas chromatograph. Samples may be introduced in the liquid phase in solvents by injection after the fashion of gas chromatography or in the effluent stream from a high-performance liquid chromatograph. The novel aspects of atmospheric pressure ionization mass spectrometry lie in its versatility and high sensitivity of detection. Few clinical chemistry laboratories now use these systems. Significant future uses are likely to be in analytical work involving therapeutic drug monitoring and studies of drug metabolism, and in analyses for environmental biohazards including pesticides, herbicides, polyhalobiphenyls, dibenzodioxins, and other toxic compounds.

Anions↗
PubMed1976

Gas chromatographic study of free polyols and aldoses in cataractous human lens tissue.

An analytical procedure for the qualitative and quantitative analysis of human lens tissue for polyol and aldose content is described. Profile samples are obtained by direct derivatization of lyophilized lenses. The components are analyzed as per-O-acetylpolyols (from the polyols) and per-O-acetylaldononitriles (from the aldoses). This procedure converts each component into a single derivative and terminal dissymmetry for each aldose is retained. The derivatives form in quantitative yield, give good chromatographic peaks, are thermally stable and readily volatilized. They are not subject to adsorption on gas chromatographic columns and are suitable for both qualitative and quantitative analytical studies. Six non-cataractous lenses and fourteen lenses from patients with senile cataract (in seven instances complicated by diabetic pathology) were analyzed. Thermostable borosilicate glass open-tubular capillary columns, coated with the nonpolar phase SE-30, and containing dispersed particles of silanized silicic acid, were used for the gas chromatographic separations. The results are discussed in relation to what is known from earlier studies of human and animal cataracts. A gas chromatographic method for determining the polyol and aldose excretion levels of controlled diabetics is also reported along with a typical metabolic profile.

Cataract↗
PubMed1975

Concurrent determination of alpha-tocopherol and free fatty acids in human plasma by glass open tubular capillary column gas chromatography.

A new gas chromatographic procedure was developed for the concurrent analysis of mixtures of long-chain acids (as methyl esters), cholesterol (as the trimethylsilyl ether) and the tocopherols (as trimethylsilyl ethers). This method was used in a study of free fatty acids and alpha-tocopherol in the plasma of normal subjects and stroke patients. The chromatographic separation was based upon the use of thermostable glass open tubular capillary columns prepared with Silanox (procedure of Lin, Pfaffenberger and Horning) and a new polar liquid phase (Schwartz-Mathews polyphenyl ether sulfone phase). The German-Horning injection system was used in a modified gas chromatograph.

Adult↗
PubMed1975

Analysis of long-chain acids or human plasma phosphatidylcholines (lecithins) and cholesteryl esters by glass open tubular capillary column gas chromatography for stroke patients and for normal subjects.

Methods are described for long-chain acid compositional analyses of human plasma phosphatidylcholines and plasma cholesteryl esters. Conventional procedures were employed for the isolation of these lipids and for the preparation of methyl esters of the acids. The gas chromatographic analytical procedure was based upon the use of thermostable glass open tubular capillary columns with a new polar phase. The methods were used in a study of plasma lipids in stroke patients and in normal young adult subjects.

Cerebrovascular Disorders↗
PubMed1975

High-resolution biomedical gas chromatography. Determination of human urinary steroid metabolites using glass open tubular capillary columns.

Recently developed analytical procedures for the qualitative and quantitative analysis of human urine for major and minor steroid metabolites are described. Steroid profile samples were obtained by enzymic hydrolysis with beta-glucuronidase and sulfatase. Methoxime-trimethylsilyl ether derivatives of steroid metabolites were prepared; the recommended procedure converts all ketone groups (except the 11-one group) into methoxime groups and all hydroxyl groups into trimethylsily ether groups. These derivatives are thermally stable, readily volatilized, not subject to dehydration or adsorption on gas chromatographic columns, and suitable for both quanlitative and quantitative analytical studies. Thermostable glass open tubular capillary columns, coated with the non-polar phase SE-30, and containing dispersed particles of silanized silicic acid, were used for the gas chromatographic separation. Illustrations of profiles for normal female and male subjects, and patients with a testosterone-secreting ovarian tumor, congenital adrenal insufficiency and a dehydroepiandrosterone-secreting adrenal tumor are included.

Adrenal Gland Neoplasms↗