Eicosanoids, signal molecules of liver cells

The information that has been accumulated in recent years about metabolism and function of eicosanoids in the liver does not yet allow the presentation of a comprehensive picture. It suffices, however, to attribute to these mediators an important role in signal transduction between the different cells of the liver, especially in inflammatory reactions, in immunologic disorders, and in septic shock. Much knowledge has been gained in recent years about the biochemistry and physiology of eicosanoids in many other tissues; the methodology of the analysis of eicosanoids, their metabolites, and their cellular functions is rapidly improving. This will assist in the elucidation of the signal functions of arachidonic acid derivatives in the liver.

[Nonpuerperal mastitis]

The medical history of 37 women with nonpuerperal mastitis, who had been treated between January 1980 and July 1983 at the Dept. of Obstetrics and Gynaecology of the University of Tübingen, was reviewed because of the increasing prevalence of this disease. Defined by different history and clinical symptoms, two groups of patients were seen: 25 women with acute nonpuerperal mastitis and 12 women with chronic recurring nonpuerperal mastitis. The average age of the patients was 30 years. The inflammation was located mostly subareolar and around the nipple. The main symptoms were pain, erythema and swelling, in acute cases accompanied by fever and abscess formation. This process was strongly related to the interval between the onset of symptoms and the initiation of treatment. Anaerobes and Staphylococcus aureus could be cultured mainly from women with acute nonpuerperal mastitis. In females with chronic recurrent mastitis, mostly anaerobes were found. Women were treated with a prolactin inhibitor (bromocriptine), if abscess formation, leukocytosis or fever were absent. In patients with leukocytosis and/or fever this regimen was combined with antibiotics. Abscesses were treated surgically, in some cases in combination with prolactin inhibition and antibiotic administration. The results show that an early conservative treatment is important to prevent abscess formation. It seems that this treatment can reduce the rate of recurrences.

[Nuclear magnetic resonance tomography of the spine]

The present paper deals with the results of 48 MR examinations of known spinal abnormalities. The use of a method strictly related to the individual problem helps to reduce the duration of the examination. Sagittal cuts are particularly useful for demonstrating much of the spinal canal. The spin-echo method is used for all examinations. Demonstration of the cord was performed by using short repetition and echo times (TR, TE). For showing the outer margin of the spinal canal, longer TR and TE should be selected. Surface coils are important for demonstrating spinal disease, since the larger images can be performed without increasing the duration of the examination.

Toxicity of D-galactosamine for rat hepatocytes in monolayer culture

Hepatocellular injury was induced by exposure of primary cultures of rat hepatocytes to 4 mM D-galactosamine. The cell damage was very similar to that seen in vivo and in the isolated perfused rat liver, both in biochemical and in structural terms. The severity of the lesions caused by D-galactosamine was dependent on the age of the culture being treated. Less severe damage was found with older cultures. Since the primary metabolic effects of D-galactosamine were age-independent, the reduction in cell damage seems to be due to progressive cell dedifferentiation. Dexamethasone (1 microM) suppressed the full development of the injury, while 1 microM triiodo-L-thyronine enhanced it. A protection of hepatocytes by alpha 2-macroglobulin against the effects of D-galactosamine could be observed neither in vivo nor in vitro. Direct cytotoxic effects of endotoxin from Salmonella minnesota R 595 could be demonstrated only on hepatocytes in the early phases of primary culture using rather high doses of the purified lipopolysaccharide. It is unlikely that they play a major role in the hepatocellular injury seen following endotoxinemia in vivo. Lowering of extracellular Ca2+ concentration and additions of calcium/calmodulin inhibitors did not prevent cell injury after treatment with D-galactosamine. The results suggest that cell death is not due to an increased influx of Ca2+ into the cells.

Unglycosylated rat alpha 1-proteinase inhibitor has a six-fold shorter plasma half-life than the mature glycoprotein

The plasma half-lives of glycosylated and unglycosylated alpha 1-proteinase inhibitor-radioactively labeled with [35S]methionine in rat hepatocyte primary cultures - were determined in the rat. Unglycosylated alpha 1-proteinase inhibitor was synthesized by hepatocytes in the presence of tunicamycin. Media from hepatocytes containing 35S-labeled glycosylated or unglycosylated alpha 1-proteinase inhibitor were injected into the tail veins of rats. At different times after injection alpha 1-proteinase inhibitor was isolated from plasma by affinity chromatography with anti-alpha 1-proteinase inhibitor Sepharose. Radioactivity measurements revealed a plasma half-life of 170 min for glycosylated alpha 1-proteinase inhibitor and of 30 min for the unglycosylated form of the inhibitor.

Biosynthesis and secretion of alpha 1 acute-phase globulin in primary cultures of rat hepatocytes

Experimental inflammation in rats led to a sevenfold increase in serum levels of alpha 1 acute-phase globulin. This increase is correlated with elevated levels of translatable mRNA for alpha 1 acute-phase globulin in the liver. Biosynthesis and secretion of alpha 1 acute-phase globulin were studied in rat hepatocyte primary cultures. An intracellular form of alpha 1 acute-phase globulin with an apparent relative molecular mass of 63 500 and a secreted form of 68 000 were found. The intracellular form of alpha 1 acute-phase globulin could be deglycosylated by endoglucosaminidase H treatment indicating that its oligosaccharide chains were of the high-mannose type. The secreted form of alpha 1 acute-phase globulin was not sensitive to endoglucosaminidase H, but was susceptible to the action of sialidase reflecting carbohydrate side-chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the high-mannose and the complex type alpha 1 acute-phase globulin. In the hepatocyte medium newly synthesized alpha 1 acute-phase globulin was detected 30 min after the pulse. Unglycosylated alpha 1 acute-phase globulin was found in the cells as well as in the medium when the transfer of oligosaccharide chains onto the polypeptide chains was blocked by tunicamycin. Tunicamycin led to a marked delay in alpha 1 acute-phase globulin secretion.

Induction of rat alpha 2-macroglobulin in vivo and in hepatocyte primary cultures: synergistic action of glucocorticoids and a Kupffer cell-derived factor

Turpentine injection into rats elicits enhanced secretion of acute phase proteins including alpha 2-macroglobulin (alpha 2M). Hypophysectomized rats, however, do not respond in this way unless dexamethasone is given together with turpentine. On the other hand, dexamethasone injection alone did not result in an induction of alpha 2M synthesis. When a medium of Kupffer cell cultures was added to hepatocytes, a dose-dependent stimulation of alpha 2M synthesis of up to 4-fold after 10-12 h was observed. However, the presence of low concentrations (10(-9)M) of dexamethasone was essential for the stimulatory effect. We conclude that the acute phase induction of alpha 2M in hepatocytes requires the synergistic action of glucocorticoids and a non-dialysable factor secreted by Kupffer cells.

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.