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Biomedical subjects

W D Lehmann

Publications and source records attributed to W D Lehmann.

At least 55 records · Page 3Linked to original sources
PubMed1995

Increased generation of cysteinyl leukotrienes in Kawasaki disease.

Endogenous cysteinyl leukotriene synthesis was assessed in 10 patients with Kawasaki disease and 10 healthy controls by measuring excretion of leukotriene E4 (LTE4) in urine. LTE4 was increased more than fivefold in patients with Kawasaki disease compared with controls (median (range) 55.3 (31.8-120.6) v 10.2 (7.1-14.9) nmol/mol creatinine); this suggests that cysteinyl leukotrienes are involved in the pathophysiology of Kawasaki disease. Leukotriene synthetase inhibition or receptor antagonism may therefore offer a new potential therapeutic approach in children with this disease.

Child, Preschool↗
PubMed1994

Possible involvement of arachidonic acid and eicosanoids in metamorphic events in Hydractinia echinata (Coelenterata; Hydrozoa).

Upon induction of metamorphosis, larvae of the marine hydroid Hydractinia echinata release [14C]-arachidonic acid from previously labeled endogenous sources. The lipoxygenase inhibitors nordihydroguaiaretic acid and 5,8,11,14-eicosatetraynoic acid inhibited metamorphosis induced by Cs+ and 1,2-sn-dioctanoylglycerol, whereas the inhibitors of cyclooxygenase, indomethacin, and acetylsalicylic acid were ineffective, suggesting a role for lipoxygenase metabolites of arachidonic acid in induction of metamorphosis. Lipoxygenase products in Hydractinia echinata were isolated and identified by gas chromatography/mass spectrometry. 8- and 12-HETE were the most abundant metabolites. In cytosolic fractions from larvae activity of an arachidonic acid metabolizing enzyme, presumably a lipoxygenase, was found. The metabolic product was identified by 1H-NMR and chiral phase HPLC as 8(R)-HETE. Its production was strongly inhibited by NDGA, but not by indomethacin.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

Regio- and stereochemistry of the dioxygenation reaction catalyzed by (S)-type lipoxygenases or by the cyclooxygenase activity of prostaglandin H synthases.

Investigations on the regio- and stereochemistry of the reactions of mammalian lipoxygenases and of prostaglandin H synthases are reviewed. The results and concepts are summarized as two reaction box models. The structures of all known (S)-type lipoxygenase products of long-chain fatty acids carrying an all-cis-1,4-diene structural element including mono-, di-, and tri-hydroxyl products can be accommodated by this model. The model also provides an explanation for leukotriene formation by mammalian lipoxygenases and for the substrate specificity of lipoxygenases towards esterified fatty acids. The reaction box model for the first dioxygenation step of the cyclooxygenase activity of prostaglandin H synthase is stereochemically different from the (S)-type lipoxygenase box model.

Animals↗
PubMed1993

Metabolism of 15-(4'-[123I]iodophenyl)pentadecanoic acid ([123I]IPPA) in the rat heart; identification of new metabolites by high pressure liquid chromatography and fast atom bombardment-mass spectrometry.

The metabolism of 15-(4'-iodophenyl)pentadecanoic acid (IPPA) in the heart muscle is commonly believed to end at 4-iodobenzoic acid as the main and final product of beta-oxidation. However, investigation of the metabolic fate of IPPA in Langendorff rat hearts using high pressure liquid chromatography (HPLC) and negative fast atom bombardment mass spectrometry (FAB-MS) revealed new results. After perfusing isolated rat hearts with [123I]IPPA, metabolites were monitored by HPLC using simultaneous detection of gamma-radioactivity and u.v. absorbance. The identification of HPLC separated metabolites was based on their nominal molecular weights as determined by negative FAB-MS. According to these measurements five catabolites were identified with decreasing concentration: 3-(4'-iodophenyl)propanoic acid >> 3-(4'-iodophenyl)propanoic acid = 5-(4'-iodophenyl)-3-hydroxypentanoic acid >> 4-iodobenzoic acid. Additionally, an anabolic metabolite was found exclusively in the lipid ester fraction. From the hydrolysed heart lipids this compound was identified as 11-(4'-iodophenyl)undecanoic acid. Its formation is explained by the action of cytosolic fatty acid synthetase on IPPA catabolites. This metabolic behaviour may be of importance for the interpretation of sequential heart scintigraphy performed with [123I]IPPA.

Animals↗
PubMed1993

Impaired degradation of leukotrienes in patients with peroxisome deficiency disorders.

The degradation of leukotrienes by beta-oxidation from the omega-end proceeds in peroxisomes (Jedlitschky et al. J. Biol. Chem. 1991. 266:24763-24772). Peroxisomal degradation of leukotrienes was studied in humans by analyses of endogenous leukotrienes in urines from eight patients with biochemically established peroxisome deficiency disorder and eight age- and sex-matched healthy infant controls. Leukotriene metabolites were separated by high-performance liquid chromatography, quantified by radioimmunoassays, and identified as well as quantified by gas chromatography-mass spectrometry. Urinary leukotriene E4 (LTE4) and N-acetyl-LTE4 excretions, relative to creatinine, were increased > 10-fold in the patients in comparison to healthy infants. The beta-oxidation product omega-carboxy-tetranor-LTE3 averaged 0.05 mumol/mol creatinine in the controls but was not detectable in the patients. However, omega-carboxy-LTE4 (median 13.6 mumol/mol creatinine) was significantly increased in the patients' urine, whereas LTB4 (median 0.07 mumol/mol creatinine) and omega-carboxy-LTB4 were detected exclusively in the urines of the patients. These data indicate an impairment of the inactivation and degradation of both LTE4 and LTB4 in patients with peroxisomal deficiency. The increased levels of the biologically active, proinflammatory mediators LTE4 and LTB4 might be of pathophysiological significance in peroxisome deficiency disorders. This is the first and so far only condition with a pronounced urinary excretion of omega-carboxy-LTE4, omega-carboxy-LTB4, and LTB4. This impaired catabolism of leukotrienes and the altered pattern of metabolites may be of diagnostic value. These findings underline the essential role of peroxisomes in the catabolism of leukotrienes in humans.

Chromatography, High Pressure Liquid↗
PubMed1992

Profiling assay for lipoxygenase products of linoleic and arachidonic acid by gas chromatography-mass spectrometry.

A method for determination of the lipoxygenase products of linoleic acid (9- and 13-hydroxyoctadecadienoic acid; 9-HODE, 13-HODE) and of arachidonic acid (5-, 8-, 9-, 11-, 12-, and 15-hydroxyeicosatetraenoic acid; 5-, 8-, 9-, 11-, 12-, and 15-HETE) is described. The method combines solid-phase extraction, derivatization to the corresponding fully hydrogenated methylester/trimethylsilylether derivatives and capillary gas chromatography coupled with electron impact mass spectrometry. Each regioisomeric HODE and HETE shows a unique pair of mass spectrometric fragment ions originating from fission of the fatty acid carbon chain at the hydroxylated position. The carboxyl-terminal fragment is used for quantification relative to a carboxyl-18O2-labeled analogue added as internal standard and the methyl-terminal fragment is monitored for confirmation. The assay can be extended for quantification of the complete hydroxylation profile of linoleic and arachidonic acid. Applications of this assay are demonstrated for the quantification of HODEs and HETEs in normal, hyperplastic, and neoplastic mouse epidermis. In mouse epidermis papilloma, the tissue levels of 8- and 12-HETE were found to be increased by one to two orders of magnitude compared to levels in normal epidermis.

Animals↗
PubMed1991

Peroxisomal degradation of leukotrienes by beta-oxidation from the omega-end.

Chain shortening via beta-oxidation from the omega-end has been recognized as the major pathway for the degradation of cysteinyl leukotrienes as well as leukotriene B4 (LTB4). The metabolic compartmentation of this pathway was studied using peroxisomes purified from normal and clofibrate-treated rat liver. beta-Oxidation products of omega-carboxy-LTB4, including omega-carboxy-dinor-LTB4 identified by gas chromatography-mass spectrometry, were formed by the isolated peroxisomes. The reaction was dependent on CoA, ATP, and NAD and was stimulated by FAD. NADPH was necessary for the further metabolism of omega-carboxy-dinor-LTB4. Together with microsomes a degradation of omega-carboxy-LTB4 also proceeded in isolated mitochondria in the presence of CoA, ATP, and carnitine. beta-Oxidation of the cysteinyl leukotriene omega-carboxy-N-acetyl-leukotriene E4 was observed only with isolated peroxisomes in combination with lipid-depleted microsomes. Direct photoaffinity labeling using omega-carboxy-[3H] LTB4 and omega-carboxy-N-[3H]acetyl-LTE4 served to identify peroxisomal leukotriene-binding proteins. The bifunctional protein (EC 4.2.1.17 and 1.1.1.35) and 3-ketoacyl-CoA thiolase (EC 2.3.1.16) of the peroxisomal beta-oxidation system were the predominantly labeled polypeptides as revealed by precipitation with monospecific antibodies. In vivo studies with N-acetyl-[3H2]LTE4, N-acetyl-[3H8]LTE4, and N-[14C]acetyl-LTE4 after treatment with the peroxisome proliferator clofibrate indicated formation and biliary excretion of large amounts of metabolites more polar than omega-carboxy-tetranor-N-acetyl-LTE3 including omega-carboxy-tetranor-delta 13-N-acetyl-LTE4 and omega-carboxy-hexanor-N-acetyl-LTE3. Increased formation of beta-oxidized catabolites of N-acetyl-LTE4 and LTB4 was also observed in hepatocytes isolated after clofibrate treatment. Our results indicate that peroxisomes play a major role in the beta-oxidation of leukotrienes from the omega-end. Whereas omega-carboxy-LTB4 was beta-oxidized both in isolated peroxisomes and mitochondria, the cysteinyl leukotriene omega-carboxy-N-acetyl-LTE4 was exclusively degraded in peroxisomes.

Affinity Labels↗
PubMed1991

Characterization of an 8-lipoxygenase activity induced by the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate in mouse skin in vivo.

An enzymatic activity has been found in cytosolic preparations from mouse epidermis which catalyzes the formation of 8-hydroperoxyeicosatetraenoic acid/8-hydroxyeicosatetraenoic acid (8-HPETE/8-HETE) from arachidonate. In contrast to 12-lipoxygenase this enzyme activity was not detectable in normal (untreated) mouse skin but only after in vivo treatment with the phorbol ester tumor promoter TPA (12-O-tetradecanoylphorbol-13-acetate). The induction showed a maximum at 24 h after TPA treatment strictly depended on the age of the mice and the TPA dose and was prevented by cycloheximide. The primary product formed from arachidonic acid was 8-HPETE, and the enzyme seems not to possess a significant peroxidase activity. This result as well as studies with specific inhibitors and its cytosolic localization indicates this enzyme to be a member of the lipoxygenase family. Most of the 8-lipoxygenase activity is located in cells of the suprabasal compartment of the epidermis. In spite of being a cytosolic enzyme 8-lipoxygenase appeared to be lipophilic to some extent and was activated by lecithin. The enzyme did not require calcium ions or ATP and showed a pH optimum at 7.5-8.0. 8-HPETE/8-HETE levels in mouse epidermis in vivo were determined by gas chromatography-mass spectrometry and found to be strongly increased after phorbol ester treatment, in agreement with the induction of 8-lipoxygenase observed.

Aging↗
PubMed1990

Ferrioxamine and its hexadentate iron-chelating metabolites in human post-desferal urine studied by high-performance liquid chromatography and fast atom bombardment mass spectrometry.

Three iron-containing fractions were detected by high-performance liquid chromatography (HPLC) on a reverse-phase column in the 24-h urine of two patients with hereditary hemochromatosis following the injection of deferoxamine mesylate (Desferal). These fractions have virtually identical absorption spectra in the visible range, with a broad maximum around 430 nm. Molecular weight determination of these fractions was performed by fast atom bombardment mass spectrometry (FAB-MS), which gave intense ion signals for the protonated molecular ions of the intact iron chelates, namely, at m/z 614 for ferrioxamine (FOA; Mr 613), at m/z 629 for metabolite I (FOA-MI; Mr 628), and at m/z 601 for metabolite II (FOA-MII; Mr 600). The molecular weight of FOA-MI is compatible with deamination of the terminal amino function and oxidation of the adjacent carbon atom to a carboxyl group; the molecular weight of FOA-MII is compatible with loss of a C2H4 unit from FOA-MI by beta oxidation. Quantification of iron in post-Desferal urine samples either by atomic absorption spectrometry (AAS) or by HPLC leads to results which are identical within experimental error. In ten subsequent 12-h urine samples of a patient under therapy (subcutaneous infusion of Desferal), the following distribution of urinary iron was found: FOA-MI, 58.4 +/- 4.7% (arithmetic mean +/- SD); FOA, 33.2 +/- 4.9%; FOA-MII, 8.4 +/- 1.7%. Addition of 2 mM ethylenediaminetetraacetic acid (EDTA) to the chromatographic solvents was used as a stability test for FOA and its two metabolites MI and MII.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1990

[Early amniocentesis].

Preliminary clinical experience with early amniocentesis is reported. Fifty-two amniocenteses were performed before the end of the 14th week following the last menstrual period. Cytogenetic and biochemical analyses (AFP, AChE) were performed. Increasing experience with amniotic fluid samples containing small-cell populations and the use of combined culture media improved the poor initial results to a 100% level, thus enabling the use of this technique for diagnostic purposes. The sampling technique and the post-procedural evolution of twelve amniocenteses in pregnant women, whose pregnancy is to be continued, are presented. The possibility of performing amniocentesis in early pregnancy is discussed with reference to anatomical aspects (amniotic and chorionic cavity).

Acetylcholinesterase↗
PubMed1988

Iron absorption in man calculated from erythrocyte incorporation of the stable isotope iron-54 determined by fast atom bombardment mass spectrometry.

The methodology of precise isotope abundance determinations of erythrocyte iron by fast atom bombardment mass spectrometry and signal averaging is established. For the determination of the 54Fe/56Fe ratio a relative precision of 0.5% and an absolute precision of 0.03% is achieved. After oral loading with 54Fe-enriched samples in the range between 5 and 25 mg per subject, the 14-day erythrocyte incorporation of 54Fe has been determined in five individuals, namely, two adults, two children, and one infant. In the two adults, the oral dose of 54Fe was simultaneously labeled with a trace amount of carrier-free 59Fe. In these double-isotope loading tests, a good agreement was observed between the absorption data determined on the basis of whole body retention of 59Fe and on the basis of the 54Fe erythrocyte incorporation. The stable isotope methodology applied allows measurement of the iron absorption using highly enriched 54Fe at a dose of 25 mg for an adult or at a dose of 5 mg for infants of about 1 year of age.

Adult↗
PubMed1987

[Transabdominal chorionic biopsy: indications and timing of the procedure].

The article reports on the introduction of transabdominal chorionic biopsy in the Gynaecological Hospital of Ludwigshafen in cooperation with the Department of Human Genetics at the University of Heidelberg. After completion of a pilot study 15 diagnostic transabdominal chorionic biopsies were performed between the 15th and 23rd pregnancy week. Sampling was successful in all cases; the median estimated weight of the biopsied samples was 35 mg. Cytogenic, biochemical and molecular-genetic examinations were conducted. No complications were seen except for one subserous haematoma. Indications and time of performance are discussed. The transabdominal chorionic biopsy is easier to conduct in the 2nd trimenon than during the first, and can therefore be considered to be a favorable "entry" into the technique. Shifting the biopsy to an earlier date, namely, into the first trimenon, can be aimed at as the familiarity with the technique increases. The obvious advantages of transabdominal removal of villi compared with the transcervical method lead us to expect that in course of the time the transcervical method will be replaced by the transabdominal one. No indication for invasive prenatal diagnosis should be implied without previous detailed genetic counselling.

Adult↗
PubMed1986

Metabolic conversion of L-[U-14C]phenylalanine to respiratory 14CO2 in healthy subjects, phenylketonuria heterozygotes and classic phenylketonurics.

Ten healthy volunteers, 12 classic phenylketonuria (PKU) heterozygotes, and 5 classic phenylketonurics have been loaded orally with a mixture of 5 microCi of L-[U-14C]phenylalanine plus 25 mg/kg of L-[2H5]phenylalanine. For 3 h thereafter, carbon-14 activity in expired air and total carbon dioxide were measured continuously and the levels of L-phenylalanine and L-tyrosine in plasma were determined in six blood samples. After 3 h, 15.1 +/- 2.1% of the applied dose of radioactivity was recovered in the expired air of the healthy subjects, compared to 10.1 +/- 2.2% for PKU heterozygotes and 0.32 +/- 0.18% for classic phenylketonurics. The integrated activity expired provides a discrimination between normals and PKU heterozygotes with a classification error of about 13% compared to an error of about 9% based on the fasting L-phenylalanine over L-tyrosine ratio. A combination of these two parameters in a two-dimensional discriminatory analysis reduces the classification error to less than 1%. An intraindividual correlation between the absolute activity expired and the formation of L-[2H4]tyrosine formed is shown, confirming that ring hydroxylation of L-phenylalanine to L-tyrosine is mandatory in the catabolism of L-phenylalanine to carbon dioxide.

Breath Tests↗
PubMed1986

The NIH-shift in the in vivo hydroxylation of ring-deuterated L-phenylalanine in man.

Oral loading with L-[ring-2H5]phenylalanine has been performed at a dose of 25 mg/kg for detection of heterozygotes for classic phenylketonuria. Using three differently labeled batches of ring-deuterated L-phenylalanine, quantitative analysis of deuterium-labeled L-phenylalanine and L-tyrosine in plasma revealed different label distributions. Three different reaction mechanisms for the 4-hydroxylation of L-phenylalanine to L-tyrosine were used as the basis for model calculations of the transformation of the L-phenylalanine label distribution into that of L-tyrosine. The best agreement between observed and calculated distributions was found for the mechanism involving a migration of the 4-substituent into the 3- or 5-position (NIH-shift), followed by a random loss of the 4-/3- or the 4-/5-substituent from this intermediate structure.

Adult↗
PubMed1986

Impaired phenylalanine-tyrosine conversion in patients with iron-deficiency anemia studied by a L-(2H5)phenylalanine-loading test.

Ten patients with manifest iron deficiency and without documented relationship to phenylketonuria patients were orally loaded with 25 mg/kg of L-(2H5)phenylalanine. Before loading, the fasting phenylalanine-tyrosine plasma ratio was determined and after loading, the concentrations of labeled and nonlabeled phenylalanine and tyrosine were determined in five consecutive plasma samples. With respect to the fasting phenylalanine-tyrosine ratio and to the post-load ratios of labeled phenylalanine over labeled tyrosine, the iron-deficient patients showed data intermediate between those of normals and heterozygotes for phenylketonuria. Compared to a 100% in vivo activity of phenylalanine hydroxylase in normals and a circa 37% activity in heterozygotes for classic phenylketonuria, iron-deficient patients with an average hemoglobin of 8.6 +/- 1 g/dl showed an activity of circa 56%. After normalization of their iron status, four patients were subjected again to the L-(2H5)phenylalanine-loading test. For three of these individuals, test results shifted into the range of normal.

Adult↗
PubMed1985

Oral versus intravenous L-phenylalanine loading compared by simultaneous application of L-[2H5] and L-[15N]phenylalanine.

Oral loading with 1.5 g of L-[15N]phenylalanine was performed simultaneously with an intravenous infusion of 1.5 g of L-[2H5]phenylalanine in two healthy volunteers with normal phenylalanine-hydroxylase activity. For both volunteers peak levels of oral L-[15N]phenylalanine were about 20 micrograms/ml compared to peak levels of around 50 micrograms/ml for intravenous L-[2H5]phenylalanine. Throughout the four hours following application, the plasma levels of the intravenously administered phenylalanine were higher than the plasma levels of the phenylalanine administered orally. In contrast, similar plasma levels of L-[15N]tyrosine and of L-[2H4]tyrosine formed in vivo by hydroxylation of the corresponding stable isotope labelled L-phenylalanine precursors were observed during the test, indicating that about equal fractions of both the oral and of the intravenous L-phenylalanine are converted into L-tyrosine.

Administration, Oral↗