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Biomedical subjects

P Ludwig

Publications and source records attributed to P Ludwig.

At least 37 records · Page 2Linked to original sources
PubMed1991

Experience with the particulate prostaglandin endoperoxide synthase assay for testing non-steroidal antiinflammatory drugs.

A microsomal prostaglandin endoperoxide synthase preparation was obtained from sheep vesicular glands and used as a test system for non-steroidal antiinflammatory drugs. The activity was measured oxygraphically with arachidonic acid as substrate. The assay conditions were optimized with respect to the concentrations of enzyme, substrate and hydroperoxidase co-substrate as well as preincubation. The validity of the test was assessed by eight known prostaglandin H synthase inhibitors and two antiinflammatory drugs not acting on this enzyme. Sodium diclofenac proved to be the most potent inhibitor. As shown with indometacin as example the test shows a good reproducibility. The data were fitted to a kinetic mathematical model assuming two distinct inhibitor binding sites with different affinities. This model gave in most cases a good fitting of the experimental data.

Animals↗
PubMed1991

Inhibition of rabbit erythroid 15-lipoxygenase and sheep vesicular gland prostaglandin H synthase by gallic esters.

Gallic acid esters possessing a varying chain length of their alcohol moiety were tested for their inhibitory potencies on 15-lipoxygenase from rabbit reticulocytes and prostaglandin H synthase from sheep vesicular glands. Octyl gallate and decyl gallate proved to be the most powerful inhibitors of both enzymes showing concentrations of half-inhibition of about 0.25 mumol/l for the reticulocyte lipoxygenase and of about 25 mumol/l for the prostaglandin H synthase.

Animals↗
PubMed1991

Actions of gallic esters on the arachidonic acid metabolism of human polymorphonuclear leukocytes.

Gallic esters with a varying chain length of its alcohol moiety produced strong inhibition of the conversion of [1-14C]-arachidonic acid to 5S-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5-HETE) by isolated human polymorphonuclear leukocytes. Octyl gallate and decyl gallate were the most powerful inhibitors with a concentration of half-inhibition of about 1 mumol . 1-1. Additionally these compounds caused however at 10 mumol . 1-1 a complete inhibition of the incorporation of arachidonic acid in triacylglycerols and phospholipids which is assumed to be a consequence of the damage to the energy metabolism of the cells. In contrast, the other gallic esters enhance the incorporation of arachidonic acid in the ester lipids in addition to moderate inhibition of the 5-lipoxygenase pathway.

Arachidonic Acid↗
PubMed1990

[Fundamental research in ultrasonic surgery. IX. Splenic surgery using cavitation ultrasound--an experimental animal study of aspiration and sealing technics with ligament FIMOMED].

A farther alternative for the conservation of the spleen represents the ultrasonic aspiration and sealing technique by means of the monomeric tissue adhesive Ligament Fimomed. The effectiveness of the method was proved by histomorphologic investigations in animal experiment with the porcine spleen. The method was effective in nearly all injuries across to the longitudinal axle of the organ even with a larger parenchymal defect and also in case of splenic tumor. The control of hemorrhage succeeded promptly and surely. Not any postoperative complication appeared.

Animals↗
PubMed1990

The erythroid arachidonate 15-lipoxygenase in rat reticulocytes.

Rat reticulocytes contain an arachidonate 15-lipoxygenase which attacks submitochondrial particles in an identical way as the corresponding enzyme from rabbit reticulocytes. It shows immunological cross-reactivity with a polyclonal antiserum against the rabbit reticulocyte lipoxygenase. It differs from the rabbit enzyme with respect to some kinetic properties and its isoelectric point.

Animals↗
PubMed1989

Occurrence of the erythroid cell specific arachidonate 15-lipoxygenase in human reticulocytes.

Human reticulocytes obtained from patients suffering from various haemolytic disorders convert exogenous [1-14C]-arachidonic acid to 15-hydroxy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid (15-HETE). Immunological studies (dot blot, Western blot) indicated that human reticulocytes contain a lipoxygenase which cross-reacts with a polyclonal antiserum against the rabbit reticulocyte lipoxygenase. Northern blotting with a cloned lipoxygenase cDNA probe shows that the specific mRNA is also present. Reaction of the lipoxygenase with submitochondrial particles caused inactivation of respiratory enzymes. The occurrence of an erythroid cell specific lipoxygenase of similar type in reticulocytes of various mammals and man suggests the general role of this enzyme in the maturational degradation of mitochondria.

Anemia↗
PubMed1989

[Basic studies of ultrasound surgery. VIII. Experimental animal studies of power ultrasound surgery of the swine pancreas].

The technique of the power ultrasound was tested in vitro and in vivo in 20 porcine pancreas. Simultaneous temperature measurements and laboratory tests do not produce any restriction. Enzymatic disorders were provable adequate to the clinical course. The ultrasonic effect guarantees a nearly riskless dissection in the layer. Joining processes, by adding Ligament-FIMOMED, produced a waterproof occlusion of parenchymal wounds. The cross-section of the pancreas with the pancreatic duct was sealed sufficiently. Also the jointed pancreato-jejunostomy remained sufficient. The reaction of the pancreatic parenchyma to the power ultrasound was small. A scarred metaplasia evolved immediately at the adhesive as a chronic atrophic interstitial pancreatitis. Only in case of occlusion of the pancreatic duct this alteration comprehended the whole pancreas.

Animals↗
PubMed1988

The biological dynamics of lipoxygenase in rabbit red cells in the course of an experimental bleeding anaemia. Unexpected effects of the calcium ionophore A 23187.

The lipoxygenase activity of red cell lysates with linoleic acid as substrate, the concentration of immunologically detectable lipoxygenase protein as well as the metabolization of external [1-14C]arachidonic or -linoleic acid by intact cells were determined during bleeding anaemia and the recovery period of rabbits. All three criteria behaved in a parallel manner. Before bleeding no lipoxygenase was detectable. After the third day of strong bleeding high amounts and activities of lipoxygenase appeared in parallel to the appearance of megaloreticulocytes. As few as about a million of cells were sufficient to detect the utilization of [1-14C]polyenoic fatty acids via the lipoxygenase pathway in intact cells in the absence of ionophore A 23187. After discontinuation of strong bleeding the amount and activity of the lipoxygenase declined gradually but persisted for 2-3 months corresponding to the presumed life-span of red cells. Several types of evidence indicate the identity of the lipoxygenase of red cells during the recovery period with that of reticulocytes during strong bleeding: (1) comparable specific activity, (2) Western blot analysis, (3) identical cellular products from [1-14C]-linoleic and -arachidonic acid which were identified by means of HPLC analysis to be 13 S-hydroxyoctadecadienoic acid (13 S-HODE) and 15 S-hydroxyeicosatetraenoic acid (15 S-HETE), respectively. Use of large amounts of cells during the recovery period (5.10(9) cells) led to an apparent masking of the polyenoic fatty acid added. Haemolysis of the cells or addition of calcium and ionophore A 23187 abolished or reduced this masking. Both masking and influence of haemolysis or ionophore disappeared at sufficiently low concentrations of cells. Under these conditions the rate of the formation of lipoxygenase products in intact cells corresponded to the lipoxygenase activity measured in membrane-free cell lysates. In red cells during the recovery period but not during strong bleeding, calcium and ionophore A 23187 stimulated the secondary conversion of 15 S-HETE to more polar products after arachidonic acid had been exhausted. The implications of the results on the performance and the interpretation of the effects of the calcium ionophore A 23187 on cellular arachidonic acid metabolism are discussed.

Anemia↗
PubMed1987

A kinetic model for lipoxygenases based on experimental data with the lipoxygenase of reticulocytes.

A comprehensive kinetic model for lipoxygenase catalysis is proposed which includes the simultaneous occurrence of dioxygenase and hydroperoxidase activities and is based on the assumption of a single binding site for substrate fatty acid and product. The aerobic reaction of purified lipoxygenase from rabbit reticulocytes with 9,12(Z,Z)-octadecadienoic acid (linoleic acid) as substrate was studied. The rate constants and the dissociation constants of this enzyme were calculated for the model from progress curves; the model describes correctly the experimental data. The following kinetic features of the reticulocyte enzyme are assumed to apply generally to lipoxygenases. (a) The enzyme shows autoactivation by its product. (b) The rate-limiting step is the hydrogen abstraction. (c) Both substrate fatty acid and its product are competitive inhibitors of the lipoxygenase. (d) Lowering the oxygen concentration enhances the degree of substrate inhibition, whereas product inhibition is not influenced. (e) If substrate is in excess the oxygen concentration determines the share of dioxygenase and hydroperoxidase activities of the enzyme. As predicted from the model it was found that at low concentrations of oxygen the regio- and stereo-specificities of the dioxygenation are diminished. During the autoactivation phase the steady-state approximation does not hold.

Animals↗
PubMed1987

[Basic research in ultrasound surgery. VII. Comparative animal experiments after intestinal anastomosis by suturing, ligament gluing with Fimomed and ultrasound sealing with ligament Fimomed].

Animal experimental anastomoses in the small intestine of Mini-Lewe-pigs showed that even sufficient anastomoses free of stenosis can be obtained by using the sticking respectively the ultrasound sealing method. The foreign-body reaction in the surroundings of the suture was approximately equally strong as on the gluten. All animals did not show any specialty in the postoperative course. The use of butylcyanidacrylic is possible in the human intestine as also shown in the literature. The use is indicated if advantages are to be expected in face of a suture anastomosis in clinical sight.

Anastomosis, Surgical↗
PubMed1987

[Ultrasonic sealing of the lung parenchyma after atypical resection].

Surfaces of lung parenchyma after resection or lesion can be sealed reliably by means of monomeric tissue adhesive with immediate polymerization by ultrasound sealing. No bronchopleural fistula was observed during the animal experimental testing. Necrotic areas of the lung parenchyma are avoidable extensively. This technique is simple. It offers reliability for patient and operator in emergency situations.

Animals↗
PubMed1986

The stoichiometry of oxygen uptake and conjugated diene formation during the dioxygenation of linoleic acid by the pure reticulocyte lipoxygenase. Evidence for aerobic hydroperoxidase activity.

Simultaneous measurements of oxygen uptake and conjugated diene formation (increase in the absorbance at 234 nm) during the dioxygenation of linoleic acid by the pure reticulocyte lipoxygenase gave a nearly theoretical stoichiometry of 1.1 in a temperature range from 5 to 30 degrees C and a wide range of concentrations of both oxygen and linoleic acid. At low concentrations of either oxygen or linoleic acid or both, secondary processes occurred such as linoleic acid-supported lipohydroperoxidase reactions leading to the disappearance of conjugated dienes and to the formation of oxodienes, linoleic acid dimers and epoxyhydroxy derivatives. Under these conditions marked deviations of the stoichiometry between oxygen uptake and conjugated diene formation appeared. The formation of conjugated oxodienoic fatty acids absorbing at 285 nm occurred only under conditions of high concentrations of linoleic acid and limiting oxygen supply. The results indicate that lipohydroperoxidase reactions catalyzed by the pure reticulocyte lipoxygenase do not only take place under strictly anaerobic conditions but also under conditions of limiting concentrations of either linoleic acid or oxygen or both.

Aerobiosis↗
PubMed1985

Circular dichroism observations on the lipoxygenase from reticulocytes.

CD spectra of reticulocyte lipoxygenase were recorded at various times during aerobic incubation, which leads to loss of catalytic activity, and after inactivation by the reaction product, 13-LS-hydroperoxylinoleic acid. Neither process showed any correlation with a decrease in the alpha-helix content, which was only observed over much longer times. It is concluded that inactivation of reticulocyte lipoxygenase by the suicidal reaction with 13-LS-hydroperoxylinoleic acid is not accompanied by gross structural alterations.

Animals↗
PubMed1985

Two modes of irreversible inactivation of the mitochondrial electron-transfer system by tetradecanoic acid.

Bovine heart submitochondrial particles were incubated for 2-6 h at 37 degrees C with various concentrations of tetradecanoic acid, and the effects on the activities, the total acid-labile sulphide content and EPR spectra of the electron transfer system were studied. Two distinct time-dependent processes of the slow irreversible inactivation of the electron-transfer system were found. They differ in the concentration of tetradecanoic acid required. The more specific effect, induced by 100-400 nmol tetradecanoic acid per mg protein, consists of a selective blockage of electron transfer between the Fe-S clusters of the NADH dehydrogenase and ubiquinone, without damage to any of the Fe-S clusters. Higher concentrations of tetradecanoic acid caused gradual destruction of all Fe-S clusters of NADH dehydrogenase and of the 3-Fe cluster of succinate dehydrogenase, leading to complete inactivation of both NADH and succinate oxidation.

Animals↗