In vitro alkylation of calf thymus DNA by acrylonitrile. Isolation of cyanoethyl-adducts of guanine and thymine and carboxyethyl-adducts of adenine and cytosine

Reaction of the rodent carcinogen acrylonitrile (AN) at pH 5.0 and/or pH 7.0 for 10 and/or 40 days with 2'-deoxyadenosine (dAdo), 2'-deoxycytidine (dCyd), 2'-deoxyguanosine (dGuo), 2'-deoxyinosine (dIno), N6-methyl-2'-deoxyadenosine (N6-Me-dAdo) and thymidine (dThd) resulted in the formation of cyanoethyl and carboxyethyl adducts. Adducts were not detected after 4 h. The adducts isolated were 1-(2-carboxyethyl)-dAdo (1-CE-dAdo), N6-CE-dAdo, 3-CE-dCyd, 7-(2-cyanoethyl)-Gua (7-CNE-Gua), 7,9-bis-CNE-Gua, imidazole ring-opened 7,9-bis-CNE-Gua, 1-CNE-dIno, 1-CE-N6-Me-dAdo and 3-CNE-dThd. Structures were assigned on the basis of UV spectra and electron impact (EI), chemical ionization (CI), desorption chemical ionization (DCI) and Californium-252 fission fragment ionization mass spectra. Evidence is presented which strongly suggests that N6-CE-dAdo was formed by Dimroth rearrangement of 1-CE-dAdo during the reaction between AN and dAdo. The carboxyethyl adducts resulted from initial cyanoethylation (by Michael addition) at a ring nitrogen adjacent to an exocyclic nitrogen atom followed by rapid hydrolysis of the nitrile moiety to a carboxylic acid. It was postulated that the facile hydrolysis is an autocatalyzed reaction resulting from the formation of a cyclic intermediate between nitrile carbon and exocyclic nitrogen. AN was reacted with calf thymus DNA (pH 7.0, 37 degrees C, 40 days) and the relative amounts of adducts isolated were 1-CE-Ade (26%), N6-CE-Ade (8%), 3-CE-Cyt (1%), 7-CNE-Gua (26%), 7,9-bis-CNE-Gua (4%), imidazole ring-opened 7,9-bis-CNE-Gua (19%) and 3-CNE-Thy (16%). Thus a carcinogen once adducted to a base in DNA was shown to be subsequently modified resulting in a mixed pattern of cyanoethylated and carboxyethylated AN-DNA adducts. Three of the adducts (1-CE-Ade, N6-CE-Ade and 3-CE-Cyt) were identical to adducts previously reported by us to be formed following in vitro reaction of the carcinogen beta-propiolactone (BPL) and calf thymus DNA. The results demonstrate that AN can directly alkylate DNA in vitro at a physiological pH and temperature.

Synthesis of prostanoids and cyclic nucleotides by phagocytosing rat Kupffer cells

Rat Kupffer cells in monolayer culture were allowed to phagocytose unopsonized zymosan granules. They responded with a strongly stimulated synthesis and release of prostanoids, mainly the immunologically determined prostaglandins PGE2 and PGF2 alpha. The same response could be obtained by treatment with the calcium ionophore A23187. The effects of the ionophore and the zymosan particles were of the same magnitude but not additive. The rapid uptake of Ca2+ after contact with phagocytosable material recently described by us [(1983) Eur. J. Biochem. 131, 539-543] appears to mediate the enhanced prostaglandin synthesis. That response was suppressed not only by indomethacin but also by trifluoperazine which does not inhibit Ca2+ entry in the Kupffer cells. Similar effects by R24571 and 4-bromophenacyl bromide support the participation of calcium-calmodulin and of phospholipase A2. The calcium channel blocker Verapamil did not influence the zymosan-provoked production of prostaglandin PGE2 nor were any indications obtained for a feedback inhibition by PGE1 or PGE2. Contact with zymosan resulted in a rapid but transient rise of the intracellular levels of cAMP and cGMP: 10 nM indomethacin completely blocked the increase of both cyclic nucleotides while trifluoperazine elicited different responses in the cAMP and cGMP levels. The stimulated release of prostaglandin E2 was inhibited in a dose-dependent manner by nordihydroguaiaretic acid, an inhibitor of 5-lipoxygenase and by FPL 55712, known as a receptor antagonist for some leukotrienes. This suggests a regulatory role for its metabolites on prostaglandin synthesis.

Isolation and partial characterization of plasmid DNA from Arthrobacter oxidans

A method for the extraction of the high molecular weight plasmid AO 1 from the gram-positive soil bacterium Arthrobacter oxidans is presented. Following digestion of this DNA with the restriction endonucleases AccI, Bam HI, Eco RI and Hind III, an average molecular mass of 157.8 kb was estimated. This value is in good agreement with the 160 kb size determined previously by electron microscopy (Brandsch et al. 1982). Using the same method, no plasmid DNA was found in strains of the genus Arthrobacter which do not degrade nicotine, e.g., A. albidus, A. globiformis and A. auricans.

Calmodulin content and activity of Ca2+-ATPase and phospholipase A2 in rat Kupffer cells

A protein resembling calmodulin was isolated from non-parenchymal and parenchymal cells of rat liver by affinity chromatography. The biological activity of the purified protein was assessed by the bovine brain cAMP phosphodiesterase assay. A highly sensitive radioimmunoassay as well as the cAMP phosphodiesterase method were employed to determine the calmodulin content of crude extracts from monolayer cultures of rat Kupffer cells and hepatocytes. An ATP-dependent, calmodulin-enhanced calcium transport was demonstrated in a membrane fraction of the non-parenchymal cells. Phospholipase A2 activity specific for 2-arachidonoyl phosphatide and with a pH optimum of 8.1 was measured in homogenized Kupffer cells; it was stimulated by agents previously shown to enhance prostaglandin synthesis in Kupffer cells, e.g. zymosan particles and lipopolysaccharide isolated from Salmonella minnesota. The increase in activity was completely prevented by pretreatment with or simultaneous addition of R 24571, a known calmodulin antagonist. However, if this inhibitor or calmodulin was added to the cell-free extract phospholipase A2 activity was not influenced. Phospholipase A1 activity could be detected at pH 5 only, showing a slight decrease in the homogenate of stimulated macrophages. Acyltransferase activity was high but independent of treatment of the Kupffer cells.

On the mechanism of lactate dehydrogenase leakage from normal and D-galactosamine-treated hepatocytes in monolayer culture

Synthesis, degradation and leakage of lactate dehydrogenase and of total protein was measured using D-galactosamine-treated rat hepatocytes in monolayer culture. The kinetics of [3H]leucine incorporation into trichloroacetic acid-precipitable material and into isolated lactate dehydrogenase of cells and of the extra-cellular space revealed a similar extent of inhibition of both synthesis and leakage following exposure to D-galactosamine. Hepatocyte cultures that had been labeled before D-galactosamine treatment lost intracellular protein-associated radioactivity almost as rapidly as control cells up to the time of measurable enzyme leakage; thereafter, the rate of 3H-loss increased in the treated cells. Lactate dehydrogenase present in the medium is degraded less rapidly than the enzyme in the intracellular space. This explains the apparent increase of total lactate dehydrogenase activity in D-galactosamine-treated as compared to control cultures. Following [3H]leucine addition to D-galactosamine-treated cultures, the specific radioactivity of the leaked lactate dehydrogenase in the medium was never greater than that of the enzyme in the cytosolic compartment. The data rule out a direct excretion of newly synthesized enzyme as a result of D-galactosamine action.

[Man and the chair - radiography of the lumbar vertebrae and pelvis in sitting position]

Radiographs of the lumbar spine in sitting and standing positions demonstrate sliding movements of the vertebral bodies to an unexpected extent, as a sign of the instability of the lumbar spine. These observations suggest some ideas for the construction of chairs.

Induction of acute phase proteins by dexamethasone in rat hepatocyte primary cultures

The effect of dexamethasone on the synthesis of acute phase proteins has been studied in primary cultures of rat hepatocytes. In the absence of dexamethasone no detectable amounts of alpha 2-macroglobulin were synthesized by hepatocytes cultured for 1 day. alpha 2-Macroglobulin synthesis was induced by dexamethasone concentrations of 10(-8) M or higher with a maximum at a concentration of 10(-7) M. alpha 1-Acid glycoprotein was synthesized in the absence of dexamethasone; however, its synthesis was also greatly stimulated by dexamethasone concentrations of 10(-8)-10(-6) M. Synthesis of alpha 1-proteinase inhibitor was stimulated only 1.4-fold at a dexamethasone concentration of 10(-7) M. The kinetics of induction of alpha 2-macroglobulin and alpha 1-acid glycoprotein were studied at a dexamethasone concentration of 10(-7) M. After an initial lag phase of 3 h the synthesis of both proteins showed a steady increase during 2 days. Synthesis of albumin remained unchanged under these experimental conditions. Unlike alpha 2-macroglobulin and alpha 1-acid glycoprotein tyrosine aminotransferase activity increased already during the first 3 h of induction by dexamethasone with a maximum at 12 h followed by a slight decrease.

Phagocytosis of hepatocyte mitochondria by rat Kupffer cells in vitro

Kupffer cells in primary culture bind and endocytose rapidly added rat liver mitochondria. Using phase contrast microscopy various stages of the uptake and digestion of these organelles were documented. Activities of mitochondrial enzymes within the Kupffer cells increased during the early phase of phagocytosis; they later declined, reaching the endogenous level of the Kupffer cell mitochondria after 3 to 4 h. The uptake was enhanced in the presence of heparin or rat serum, while iodoacetate, cytochalasin B or anti-fibronectin antisera were inhibitory. The transient presence of enzymatically active hepatocyte mitochondria renders Kupffer cells capable of producing urea. This mechanism partially explains earlier observations of urea formation in non-parenchymal rat liver cells.

Enzymatic determination of several D-amino acids using luminol-mediated chemiluminescence

A method for the quantitative determination of several D-amino acids in the range of 0.05-1 nmol per assay (0.25-5 microM) is described. It is insensitive to the presence of excesses of the respective L-amino acids. The assay system employs D-amino-acid oxidase (hog kidney), peroxidase (horse radish) and luminol; the total photon output elicited by the oxidation of the D-amino acids is determined. The different reactivity of individual D-amino acids with D-amino-acid oxidase limits the applicability of the assay. Indications for the usefulness of immobilized enzymes in D-amino-acid analysers are also given.

1-deoxynojirimycin impairs oligosaccharide processing of alpha 1-proteinase inhibitor and inhibits its secretion in primary cultures of rat hepatocytes

1-Deoxynojirimycin was found to inhibit oligosaccharide processing of rat alpha 1-proteinase inhibitor. In normal hepatocytes alpha 1-proteinase inhibitor was present in the cells as a 49,000 Mr high mannose type glycoprotein with oligosaccharide side chains having the composition Man9GlcNAc and Man8GlcNAc with the former in a higher proportion. Hepatocytes treated with 5 mM 1-deoxynojirimycin accumulated alpha 1-proteinase inhibitor as a 51,000 Mr glycoprotein with carbohydrate side chains of the high mannose type, containing glucose as measured by their sensitivity against alpha-glucosidase, the largest species being Glc3Man9GlcNAc. Conversion to complex oligosaccharides was inhibited by the drug. In addition, increasing concentrations of 1-deoxynojirimycin inhibited glycosylation resulting in the formation of some alpha 1-proteinase inhibitor with two instead of three oligosaccharide side chains. 5 mM 1-deoxynojirimycin inhibited the secretion of alpha 1-proteinase inhibitor by about 50%, whereas secretion of albumin was unaffected. The oligosaccharides of alpha 1-proteinase inhibitor secreted from 1-deoxynojirimycin-treated cells were characterized by their susceptibility to endoglucosaminidase H, incorporation of [3H]galactose, and [3H]fucose and concanavalin A-Sepharose chromatography. It was found that 1-deoxynojirimycin did not completely block oligosaccharide processing, resulting in the formation of alpha 1-proteinase inhibitor molecules carrying one or two complex type oligosaccharides. Only these alpha 1-proteinase inhibitor molecules processed to the complex type in one or two of their oligosaccharide chains were nearly exclusively secreted. This finding demonstrates the importance of oligosaccharide processing for the secretion of alpha 1-proteinase inhibitor.

Ganglioside biosynthesis in rat liver. Characterization of UDPgalactose--glucosylceramide galactosyltransferase and UDPgalactose-GM2 galactosyltransferase

The conditions for the quantitative determination of UDP-Gal:glucosylceramide galactosyltransferase and of UDP-Gal:GM2 galactosyltransferase in Golgi-enriched preparations of rat liver were optimized. Triton X-100 was the detergent routinely used as octyl glucoside acted as a galactose acceptor forming octyl lactoside. Manganese ions were required for full activity, but Co2+ and Mg2+ could substitute to some extent. The nucleotide pyrophosphatase activity of the Golgi preparations which interfered with the GL2-synthase assay was inhibited by addition of 20 mM IMP; the latter is without appreciable effect on the rate of GL2 synthesis. Apparent Km values for UDP-Gal were 130 microM and 140 microM with Gl2-synthase and Gm1-synthase, respectively. That for glucosylceramide was 80 microM with GL2-synthase; for GM2 it was 10 microM with GM1-synthase. Competition experiments with variable concentrations of the lipid acceptors showed that the two synthase activities are independent catalytic entities. The specific activity of GM1-synthase exceeds that of GL2-synthase by a factor of ca. 25 under the optimized conditions used here.

Synthesis of rat-liver lactate dehydrogenase and characterization of its mRNA

Rat liver lactate dehydrogenase (LDH) has been synthesized in hepatocytes and in a cell-free translation system. The subunit synthesized in both systems displayed the same electrophoretic mobility upon sodium dodecyl sulfate/polyacrylamide slab gel electrophoresis. Sequence analysis of the subunits translated in vitro and synthesized in vivo indicated N-acetyl-alanyl-alanine for both N termini. Thus, the newly synthesized subunit does not exhibit an amino-terminal extension. The mRNA for the lactate dehydrogenase subunit was exclusively found in free polysomes. A size of 2120 +/- 240 nucleotides was estimated for the mRNA. Only about 50% of these nucleotides are needed to code for the polypeptide chain of the enzyme.

Purification of the flavoproteins 6-hydroxy-D- and 6-hydroxy-L-nicotine oxidase using hydrophobic affinity chromatography

A systematic study of the homologous series of omega-aminoalkyl-agaroses revealed differences in the affinities of 6-hydroxy-D- and 6-hydroxy-L-nicotine oxidase. In contrast to supports with nonpolar alkyl chains, omega-aminoalkyl-agarose showed high affinity towards the L-specific enzyme, while the D-specific oxidase was bound most firmly by omega-aminododecyl-agarose. 6-Hydroxy-L-nicotine oxidase could be desorbed by 1.3M NaCl only in the presence of the substrate L-6-hydroxynicotine. Using the omega-aminoalkyl-agarose, a complete separation of the enantiozymes was accomplished and an efficient purification procedure for both oxidases established.

Luminometric determination of FAD in subpicomole quantities

Very small quantities of FAD were able to reactivate apo-D-amino acid oxidase. In the presence of D-alanine, luminol, horseradish peroxidase, and an excess of the apoenzyme, a quantitative luminometric determination of FAD was possible. The maximal photon emission measured in a bicarbonate buffer, pH 9.2, at 37 degrees C was proportional to the amount of FAD added. FMN, riboflavin, or 5-deazaflavin produced no chemiluminescence and had no inhibitory effect in the assay when added together with FAD. With this method, FAD could be quantitatively determined with high accuracy in perchloric acid extracts of animal tissue and bacteria.

Ca2+ flux as an initial event in phagocytosis by rat Kupffer cells

Ca2+ uptake by monolayer cultures of rat Kupffer cells was strongly stimulated immediately after contact with phagocytosable material, e.g. zymosan particles. The intensity of the luminol-mediated chemiluminescence following zymosan addition was dependent on extracellular Ca2+; addition of the Ca2+-ionophore A 23187 did not further increase the zymosan-elicited response. The superoxide-mediated chemiluminescence was not inhibited by indomethacin but could be suppressed by compounds known to inhibit Ca2+-calmodulin-dependent reactions. Analysis of their efficiency, however, suggests that the O-2 production is mediated by Ca2+ rather than Ca2+-calmodulin and that the inhibitors exert another, e.g. membrane-directed influence.

Quantitation of immunoadsorbed flavoprotein oxidases by luminol-mediated chemiluminescence

The detection of the flavoenzymes 6-hydroxy-L-nicotine oxidase and 6-hydroxy-D-nicotine oxidase at the sub-femtomol level was achieved by coupling the reaction of the immunoadsorbed proteins to the peroxidase-catalysed oxidation of luminol. The H2O2-producing oxidases retained their full activity when bound to the respective immobilized antibodies. This fact allowed the concentration of the enzymes from very dilute solutions and the quantitative assay of their activities in the microU range. Due to strict stereoselectivity and the absence of immunological cross-reactivity, the two flavoproteins could be determined in the same solution. This method was used to measure the 6-hydroxy-D-nicotine oxidase and 6-hydroxy-L-nicotine oxidase activities in Escherichia coli RR1 and different Arthrobacter strains cultured under non-inducing conditions. The same activity ratio of 6-hydroxy-L-nicotine oxidase/6-hydroxy-D-nicotine oxidase as in D L-nicotine-induced cells of A. oxidans was observed in non-induced wild type and in riboflavin-requiring (rf-) mutant cells of this aerob.

The effect of gyrase inhibitors and cyclic AMP on induction and glucose repression of the 6-hydroxy-nicotine oxidases in Arthrobacter oxidans

The induction by D,L-nicotine of the enantiozymes 6-hydroxy-L-nicotine oxidase and 6-hydroxy-D-nicotine oxidase in Arthrobacter oxidans was differently affected by the inhibitors of Escherichia coli gyrase, novobiocin and nalidixic acid. These compounds inhibited 6-hydroxy-L-nicotine oxidase induction slightly, but led to an increase in the level of 6-hydroxy-D-nicotine oxidase activity. Furthermore, the specific repression by glucose of 6-hydroxy-D-nicotine oxidase synthesis was not abolished by the addition of cAMP but by that of novobiocin.

[Amniotic infection syndrome after amniocentesis--a case report]

A severe amniotic infection syndrome with a septic shock and a consumption coagulopathy is reported after an amniocentesis in second trimester. In literature, the risk of an amnionitis after amniocentesis amounts to 0.1%-0.4% and the risk of a severe maternal infection reaches 0.03%-0.19%. The available data show, that the clinical symptoms (rise in temperature, signs of septic shock) start 24-36 hours after the punction. The earlier treatment (evacuation of the uterus or - if necessary - hysterectomy) is accomplished, the more favourable will be the course of the disease with respect to septic shock and DIC. Determination of germs in each amniotic fluid seems to be of prognostic value; thus treatment can be started before infection becomes detrimental for the mother.

Involvement of prostaglandin E and adenosine 3', 5'-monophosphate in lipopolysaccharide-stimulated collagenase release by rat Kupffer cells

Kupffer cells exposed to bacterial lipopolysaccharide in vitro synthesized collagenase and released the major portion of it into the extracellular space while the intracellular level of enzyme was not altered significantly. Cycloheximide prevented the appearance of collagenase in the medium indicating de novo synthesis. Indomethacin, an inhibitor of cyclooxygenase, also blocked collagenase synthesis. In line with this observation. Kupffer cells were found to synthesize substantial amounts of prostaglandin E2 when exposed to lipopolysaccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimulated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3', 5'-monophosphate as well as of prostaglandin E2 or, to a lesser extent, prostaglandin E1 allowed indomethacin-inhibited cells to resume the production of collagenase. It is proposed that in rat Kupffer cells lipopolysaccharide-elicited collagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels.

Acetyl coenzyme A and coenzyme a contents of growing clostridium kluyveri as determined by isotope assays

CoASH and some of its acyl derivatives, especially acetyl-SCoA, occupy a central position in the energy metabolism of the anaerobic Clostridium kluyveri, both as intermediates and as regulatory effectors. The steady state concentrations of these compounds were determined in growing cultures of this organism using an anaerobic and fast deproteinization technique and radio isotope assays. Acetyl-SCoA was determined as [1-14C]citrate formed in the presence of [4-14C]oxaloacetate and citrate synthase; 0.49 mumol/g cell wet wt. were found. CoASH, CoAS-SCoA after borohydride reduction, and total acyl derivatives of coenzyme A after hydrolysis of the thiol esters were converted to thioethers with [2,3-14C]N-ethylmaleimide and brought to radiochemical purity by chromatographic methods. While disulfides of coenzyme A were undetectable, 0.13 mumol CoASH and 1.17 mumol of total acyl-SCoA per g wet wt. were found. These data are consistent with the regulatory scheme of the energy metabolism of C. kluyveri previously proposed.

Ganglioside biosynthesis in rat liver. Characterization of UDP-N-acetylgalactosamine -- GM3 acetylgalactosaminyltransferase

UDP-N-acetylgalactosamine--GM3 acetylgalactosaminyltransferase (GM2-synthase) was studied in a Golgi-rich fraction from rat liver. Activity in a cell-free system required the presence of detergents; octyl glucoside was found to be the most effective in stimulating the enzyme. Optimal activity of GM2-synthase was obtained at pH 7.2, in the presence of 0.8% octyl glucoside, 10 mM Mn2+ and 5 mM CDP-choline. The latter was used to counteract the rapid sugar nucleotide hydrolysis caused by a nucleotide pyrophosphatase activity in the Golgi fraction. The apparent Km values for UDP-N-acetylgalactosamine and added GM3 were 0.035 mM and 0.1 mM, respectively. Different results were obtained if endogenous GM3 only was used as the glycolipid acceptor. In this case, the apparent Km value for UDP-N-acetylgalactosamine was 0.18 mM and Co2+ and Fe2+ exceeded Mn2+ in activating GM2-synthase. Under optimal assay conditions and in the presence of added GM3 and 5 mM CDP-choline, the specific activity of the enriched Golgi fraction was measured to be 25-30 nmol X mg protein-1 X h-1; with endogenous GM3 as the sole glycolipid acceptor, V was calculated to be 9 nmol X mg protein-1 X h-1.