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Biomedical subjects

H Sandermann

Publications and source records attributed to H Sandermann.

At least 37 records · Page 2Linked to original sources
PubMed1999

Tumor promoters in commercial indoor-plant cultivars of the Euphorbiaceae.

Certain decorative indoor-plant cultivars are derived from toxic wild plant species. Native members of the Euphorbiaceae (spurge) contain highly irritating and tumor-promoting diterpene esters. Plant breeders and gardeners are constantly searching for less toxic cultivars of the popular Euphorbiaceae indoor plants. In this investigation, 22 commercial cultivars of Euphorbiaceae indoor plants were examined for tumor promoter contents by high-performance liquid chromatography (HPLC). Cultivars of E. milii (E. lomii hybrids), and in particular E. leuconeura, contained ingenol derivatives, whereas cultivars of E. pulcherrima and Codiaeum variegatum were devoid of these compounds. Tumor-promoting activity was assessed by induction of a luciferase reporter gene, which was placed under the control of an Epstein-Barr virus early antigen promoter. The response was closely correlated with ingenol ester content; the latex of the two E. leuconeura cultivars tested gave the strongest response. The HPLC and bioassay methods used in this study provide a basis for the development of nontoxic indoor-plant cultivars and perhaps for consumer-oriented labeling.

Carcinogens↗
PubMed1998

The lipid/protein interface as a target site for general anesthetics: a multiple-site kinetic analysis of synaptosomal Ca2+-ATPase.

There is a long-standing controversy on whether membrane lipids or proteins are the target for general anesthetics. The plasma membrane-associated Ca2+-ATPase of synaptosomes has recently been established as a model system for general anesthesia, the protein interior being the proposed target site (M.M. Lopez, D. Kosk-Kosicka, J. Biol. Chem. 270 (1995) 28239-28245). Multiple-site kinetics is now applied as a mechanistic tool to analyze inhibition by organic solvents and general anesthetics. A close fit to the experimental data points was achieved using the complex equations for a competitive displacement of lipid activators from multiple sites on the protein surface. Inhibitor dissociation constants were about 1. 6x105-fold higher than the microscopic lipid dissociation binding constants that are derived here for the first time. Binding of lipid therefore is by -7.1 kcal/mole favored over that of the tested inhibitors. The latter are nevertheless effective because in the model used displacement of only few of the lipid solvation molecules cause complete inhibition. The lipid/protein interface rather than protein or lipid alone appeared to be the anesthetic target site.

Anesthetics, General↗
PubMed1998

Defense activation and enhanced pathogen tolerance induced by H2O2 in transgenic tobacco.

Transgenic tobacco deficient in the H2O2-removing enzyme catalase (Cat1AS) was used as an inducible and noninvasive system to study the role of H2O2 as an activator of pathogenesis-related (PR) proteins in plants. Excess H2O2 in Cat1AS plants was generated by simply increasing light intensities. Sustained exposure of Cat1AS plants to excess H2O2 provoked tissue damage, stimulated salicylic acid and ethylene production, and induced the expression of acidic and basic PR proteins with a timing and magnitude similar to the hypersensitive response against pathogens. Salicylic acid production was biphasic, and the first peak of salicylic acid as well as the peak of ethylene occurred within the first hours of high light, which is long before the development of tissue necrosis. Under these conditions, accumulation of acidic PR proteins was also seen in upper leaves that were not exposed to high light, indicating systemic induction of expression. Short exposure of Cat1AS plants to excess H2O2 did not cause damage, induced local expression of acidic and basic PR proteins, and enhanced pathogen tolerance. However, the timing and magnitude of PR protein induction was in this case more similar to that in upper uninfected leaves than to that in hypersensitive-response leaves of pathogen-infected plants. Together, these data demonstrate that sublethal levels of H2O2 activate expression of acidic and basic PR proteins and lead to enhanced pathogen tolerance. However, rapid and strong activation of PR protein expression, as seen during the hypersensitive response, occurs only when excess H2O2 is accompanied by leaf necrosis.

Catalase↗
PubMed1998

Where does cholesterol act during activation of the nicotinic acetylcholine receptor?

Why agonist-induced activation of the nicotinic acetylcholine receptor (nAcChoR) fails completely in the absence of cholesterol is unknown. Affinity-purified nAcChoRs from Torpedo reconstituted into 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine/1, 2-dioleoyl-sn-glycero-3-phosphate/steroid bilayers at mole ratios of 58:12:30 were used to distinguish between three regions of the membrane where cholesterol might act: the lipid bilayer, the lipid-protein interface, or sites within the protein itself. In the bilayer, the role of fluidity has been ruled out and certain neutral lipids can substitute for cholesterol [C. Sunshine, M.G. McNamee, Biochim. Biophys. Acta 1191 (1994) 59-64]; therefore, we first tested the hypothesis that flip-flop of cholesterol across the membrane is important; a plausible mechanism might be the relief of mechanical bending strain induced by a conformation change that expands the two leaflets of the bilayer asymmetrically. Cholesterol analogs prevented from flipping by charged groups attached to the 3-position's hydroxyl supported channel opening, contrary to this hypothesis. The second hypothesis is that interstitial cholesterol binding sites exist deep within the nAcChoR that must be occupied for channel opening to occur. When cholesterol hemisuccinate was covalently 'tethered' to the glycerol backbone of phosphatidylcholine, channel opening was still supported. Thus, if there are functionally important cholesterol sites, they must be very close to the lipid-protein interface and might be termed periannular.

Animals↗
PubMed1998

Memory effects in the action of ozone on conifers.

Conifers are known to possess relative ozone tolerance in short-term experiments. A scenario for ozone damage of conifers is now derived from the first exposure experiments in which both the initial biochemical response phase and delayed visible symptom development were studied. A number of early biochemical ozone responses could be detected in Norway spruce (Picea abies [L.] Karst.) and Scots pine (Pinus sylvestris L.). The stress metabolite catechin persisted over several months. In the year following ozone treatment of spruce, decreases in pigment content and photosynthetic capacity, as well as development of visible symptoms (chlorosis, banding), were determined in the needle age classes previously exposed to an accumulated hourly ozone dose above 40 ppb (AOT40) of >/=60-80 ppm small middle doth. The visible symptoms developed during spring emergence of the new flush. In the case of Scots pine, an ozone dose (AOT40) of >/=30 ppm small middle doth caused the premature shedding of needles 9 months after treatment. The delayed symptoms of both spruce and pine occurred during known phases of endogenous stress. The symptoms appeared to reflect an ozone "memory" imprinted by the induced early stress reactions. Ambient AOT40 ozone doses in Central Europe are in the range 4 and 50 ppm small middle doth per growing season. Ozone is proposed to potentially damage conifers through memory effects ("abiotic" pathway) or through predisposition for pathogen attack ("biotic" pathway).

Catechin↗
PubMed1998

Cytochrome P450 monooxygenases for fatty acids and xenobiotics in marine macroalgae.

The metabolism of xenobiotics has mainly been investigated in higher plant species. We studied them in various marine macroalgae of the phyla Chlorophyta, Chromophyta, and Rhodophyta. Microsomes contained high oxidative activities for known cytochrome (Cyt) P450 substrates (fatty acids, cinnamic acid, 3- and 4-chlorobiphenyl, 2, 3-dichlorobiphenyl, and isoproturon; up to 54 pkat/mg protein). The presence of Cyt P450 (approximately 50 pmol/mg protein) in microsomes of the three algal families was demonstrated by CO-difference absorption spectra. Intact algal tissue converted 3-chlorobiphenyl to the same monohydroxy-metabolite formed in vitro. This conversion was 5-fold stimulated upon addition of phenobarbital, and was abolished by the known P450 inhibitor, 1-aminobenzotriazole. It is concluded that marine macroalgae contain active species of Cyt P450 and could act as a metabolic sink for marine pollutants.

Animals↗
PubMed1998

A new intermediate in the mineralization of 3,4-dichloroaniline by the white rot fungus Phanerochaete chrysosporium.

Phanerochaete chrysosporium ATCC 34541 has been reported to be unable to mineralize 3,4-dichloroaniline (DCA). However, high mineralization is now shown to occur when a fermentation temperature of 37 degrees and gassing with oxygen are used. Mineralization did not correlate with lignin peroxidase activity. The latter was high under C limitation and low under N limitation, whereas the reverse was true for mineralization. The kinetics of DCA metabolism was studied in low-N and low-C and C- and N-rich culture media by metabolite analysis and 14CO2 determination. In all cases, DCA disappeared within 2 days, and a novel highly polar conjugate termed DCAX accumulated in the growth medium. This metabolite was a dead-end product under C and N enrichment. In oxygenated low-C medium and in much higher yield in oxygenated low-N medium, DCAX was converted to DCA-succinimide and then mineralized. DCAX was purified by high-performance liquid chromatography and identified as N-(3,4-dichlorophenyl)-alpha-ketoglutaryl-delta-amide by high-performance liquid chromatography and mass spectroscopy, gas chromatography and mass spectroscopy, and nuclear magnetic resonance spectroscopy. The formation of conjugate intermediates is proposed to facilitate mineralization because the sensitive amino group of DCA needs protection so that ring cleavage rather than oligomerization can occur.

Aniline Compounds↗
PubMed1997

A thermodynamic analysis of the partitioning of cholesterol and related compounds between trioleoylglycerol and egg phosphatidylcholine bilayers.

The free energy of transfer of a number of alcohols, including cholesterol, from a bulk isotropic lipid phase, trioleoylglycerol (TG), to an anisotropic lipid phase, egg phosphatidylcholine (PC), was determined. n-Alkane-1-ols partitioned preferentially into the bilayer phase; for example, the free energy of transfer of octanol-1 from TG to PC was about -1.0 kcal/mol. This preference declined with increasing number of carbons at a rate of 40 cal/mol of CH2. Cholesterol had a much stronger preference for the bilayer with a free energy of -1.3 kcal/mol, compared to an extrapolated value of -0.2 kcal/mol for a normal alkane-1-ol with the same number of carbon atoms. Thus, the excess free energy of -1.1 kcal/mol represents the favourable interaction of the cholesterol skeleton with the bilayer phase. This conclusion was confirmed by comparing cholesterol 3-hemisuccinate to oleic acid. Substituting TG for water as the standard state has eliminated the large hydrophobic effect and has permitted us to identify for the first time the subtle binding increment of the steroid ring system.

Alcohols↗
PubMed1997

Molecular cloning of ozone-inducible protein from Pinus sylvestris L. with high sequence similarity to vertebrate 3-hydroxy-3-methylglutaryl-CoA-synthase.

We have isolated a Pinus sylvestris cDNA encoding a globular protein of 474 amino acids with a predicted molecular weight of 52,995 Da. The deduced amino acid sequence showed 41.9% identity and 13.6% similarity to mammalian cytosolic 3-hydroxy-3-methylglutaryl-CoA-synthase (HMGS). Treatment of Scots pine seedlings with ozone resulted in a transient increase of a 1.95 kb transcript, whereas a 1.2 kb mRNA decreased transiently, indicating a possible influence of ozone on isoprenoid biosynthesis.

Amino Acid Sequence↗
PubMed1997

Differential transcript induction of parsley pathogenesis-related proteins and of a small heat shock protein by ozone and heat shock.

Parsley (Petroselinum (crispum L.) is known to respond to pathogen attack by the synthesis of furanocoumarins and to UV irradiation by the synthesis of flavone glycosides whereas ozone treatment results in the induction of both pathways. A cDNA library from parsley plants was differentially screened using labelled reverse-transcribed poly(A)+ RNA isolated from ozone-treated parsley plants. This resulted in the isolation of 13 independent cDNA clones representing ozone-induced genes and of 11 cDNA clones representing ozone-repressed genes. DNA sequencing of several clones resulted in the identification of pathogenesis-related protein 1-3 (PR1-3), of a new member of PR1 cDNAs (PRI-4) and of a small heat shock protein (sHSP). Northern blot analyses showed a transient induction of the three mRNA species after ozone fumigation. In contrast, heat shock treatment of parsley plants resulted in an increase of sHSP mRNA whereas no increase for transcripts of PR1-3 and PR1-4 could be observed. This is the first characterized sHSP cDNA clone for plants induced by heat shock, as well as by oxidative stress caused by ozone.

Amino Acid Sequence↗
PubMed1997

An ozone-responsive region of the grapevine resveratrol synthase promoter differs from the basal pathogen-responsive sequence.

Stilbene synthase (STS) is an enzyme involved in the biosynthesis of stilbenes, which are synthesized in various plants in response to pathogen attack, UV irradiation or exposure to ozone. We describe analysis of an ozone inducible STS transcript and its corresponding promoter (Vst1), combined with the beta-glucuronidase (GUS) reporter gene. A single ozone pulse (0.1 microliter/l, 10 h) resulted in 11-fold GUS expression. Histochemical localization of GUS activity revealed small spots distributed over the whole leaf. Cross-sections of leaf tissue showed that the Vst1 promoter was induced in palisade and spongy parenchyma cells and to a lesser extent in epidermal cells. Deletions at the 5' end showed that a partial promoter sequence between position -430 and -280 constituted the ozone-responsive region, whereas for effective pathogen-inducibility sequences from -280 to -140 have been shown to be necessary.

Acyltransferases↗
PubMed1997

Maize glutathione-dependent formaldehyde dehydrogenase cDNA: a novel plant gene of detoxification.

We have previously shown that intact plants and cultured plant cells can metabolize and detoxify formaldehyde through the action of a glutathione-dependent formaldehyde dehydrogenase (FDH), followed by C-1 metabolism of the initial metabolite (formic acid). The cloning and heterologous expression of a cDNA for the glutathione-dependent formaldehyde dehydrogenase from Zea mays L. is now described. The functional expression of the maize cDNA in Escherichia coli proved that the cloned enzyme catalyses the NAD(+)- and glutathione (GSH)-dependent oxidation of formaldehyde. The deduced amino acid sequence of 41 kDa was on average 65% identical with class III alcohol dehydrogenase from animals and less than 60% identical with conventional plant alcohol dehydrogenases (ADH) utilizing ethanol. Genomic analysis suggested the existence of a single gene for this cDNA. Phylogenetic analysis supports the convergent evolution of ethanol-consuming ADHs in animals and plants from formaldehyde-detoxifying ancestors. The high structural conservation of present-day glutathione-dependent FDH in microorganisms, plants and animals is consistent with a universal importance of these detoxifying enzymes.

Alcohol Dehydrogenase↗
PubMed1996

Induction of lipid-protein mismatch by xenobiotics: kinetic cooperativity.

Lipophilic inhibitors such as general anaesthetics or drugs can conceivably act by displacing boundary lipid molecules that are required by many functional membrane proteins. The resulting lipid-protein mismatch has been analyzed previously in terms of multiple site kinetics (Sandermann H. (1993) Biochim. Biophys. Acta 1150, 130-133). Expressions for kinetic cooperativity are now derived, and data for the inhibition of dog kidney Na+,K+-ATPase and Escherichia coli lactose permease by organic solvents are presented and analyzed. Half-maximal inhibitor concentrations were without diagnostic value because they were within the general range of critical solvent concentrations known for general anaesthesia and several membraneous and non-membraneous systems, as well as two specific liposomal parameters. The kinetic cooperativity of inhibition was of much higher diagnostic value because the cooperativity values for the solvent inhibition of Na+,K+-ATPase and lactose permease were characteristic for the lipid displacement mechanism, in contrast to cooperativity values of protein kinase C and luciferase. The latter enzymes are known not to require a boundary lipid layer, so that the degree of kinetic cooperativity provides a new diagnostic tool to distinguish between modes of action of lipophilic inhibitors.

Alcohols↗
PubMed1996

Ozone and plant health.

Phytotoxic effects of ozone are described with emphasis on secondary plant metabolism. Numerous ozone-induced genes, enzymes and stress metabolites of antioxidative and phytopathological defense reactions have been discovered for herbaceous plants and forest tree species. Ozone induces reactions normally elicited by viral and microbial pathogens. The molecular basis (receptors, signal chains) for induction by ozone remains to be elucidated. The induced stress reactions seem to change plant predisposition to either enhanced tolerance or susceptibility for a second stressor. The following topics are discussed: ozone and biotic disease, the role of ozone on field sites and ozone limit values.

Journal Article↗
PubMed1994

Plant biochemistry of xenobiotics: isolation and characterization of a soybean O-glucosyltransferase of DDT metabolism.

The insecticide DDT is metabolized in soybean and wheat cell cultures to the acylglucoside of 2,2-bis-(4-chlorophenyl)-acetic acid (DDA) (M. Arjmand and H. Sandermann, 1985, Pesticide Biochem. Physiol. 23, 389-397). An enzyme catalyzing the conjugation reaction has been highly purified from the soluble enzyme fraction of cultured soybean cells. After the initial ammonium sulfate fractionation, quercetin and pentachlorophenol were preferentially glucosylated. In the course of 367-fold purification, DDA became the preferred substrate. The purified enzyme was unstable. A molecular weight of approximately 50 kDa was estimated for the native enzyme (gel permeation chromatography) as well as the denatured protein (sodium dodecyl sulfate-gel electrophoresis). The isoelectric point for the enzyme was near pH 4.9. Apparent Km values of about 170 microM were determined for UDP-glucose as well as DDA. The maximal velocity was 257 microkat/kg protein, corresponding to a conjugation capacity of 855 micrograms DDA/h/g fresh weight of cells.

Chromatography, Affinity↗
PubMed1994

Higher plant metabolism of xenobiotics: the 'green liver' concept.

Xenobiotic metabolism in plants resembles that in animal liver on the levels of metabolite patterns, enzyme classes and cDNA sequences. Historical and current evidence for the 'green liver' concept of xenobiotic plant metabolism is presented. Xenobiotic residues resulting from phase I (transformation) and phase II (conjugation) are usually stored in the plant tissue in phase III (compartmentation). The following topics are discussed: residue toxicology, metabolic modelling, enzyme inducibility and enzyme evolution.

Animals↗