Synergistic effect of magnesium and calcium ions in the activation of phospholipase A2 of liver macrophages

In cell-free extracts of rat liver macrophages (Kupffer cells) phospholipase A2 was found to be strongly activated at free Ca2+ concentrations from 100 nM to 1 microM in the presence of 4 mM free Mg2+. This is within the range of intracellular free Ca2+ reported for basal and various stimulated conditions, respectively. Ca2+ alone increased phospholipase A2 activity at high Ca2+ concentrations (1 mM) whereas Mg2+ alone had only little stimulatory effect. Calmodulin does not seem to participate in the regulation of phospholipase A2 although it relieved the inhibition of phospholipase A2 activity by calmodulin antagonists.

Endotoxin-refractory liver macrophages secrete tumor necrosis factor-alpha upon viral infection

Rat liver macrophages (Kupffer cells) secrete tumor necrosis factor-alpha (cachectin) after exposure to Newcastle disease virus or bacterial endotoxin. Macrophages treated with endotoxin become refractory and fail to release tumor necrosis factor-alpha to a secondary challenge with endotoxin. The acquisition of the refractory state is dose-dependent, requires the continuous presence of endotoxin for a minimum of 8 h, is transient, and reversible. Endotoxin, however, renders Kupffer cells unresponsive only to itself. When endotoxin-refractory macrophages are activated by Newcastle disease virus, they still secrete tumor necrosis factor-alpha in amounts expected with this stimulus. Immunoprecipitation studies show that the precursor of tumor necrosis factor-alpha is found only in lysates of endotoxin-sensitive, but not in refractory macrophages, thus arguing against a post-translational regulatory process. Whereas prostaglandin E2 inhibits the production of tumor necrosis factor-alpha in response to endotoxin and viruses, it does not appear to mediate the refractory state.

Regulation of nitric oxide production by stimulated rat Kupffer cells

Macrophages have been described to release nitric oxide (NO) as a cytotoxic radical. This highly unstable substance is as well known as endothelium-derived relaxing factor produced by vascular endothelial cells. Because of its cytotoxic activity the synthesis of NO by rat Kupffer cells, the liver macrophages, upon stimulation with endotoxin (lipopolysaccharide; LPS) and tumor necrosis factor-alpha (TNF-alpha) in combination with prostaglandin E2 (PGE2) and dibutyryl cAMP (dBcAMP) was studied. Kupffer cells were stimulated after 48 h of primary culture. NO was quantified as NO2- in the cell medium 24 h after stimulation. LPS stimulated NO generation 5- to 10-fold over the basal level. This increase could be further enhanced by PGE2 and dBcAMP, especially when added 1 h after LPS. NO generation after stimulation with LPS or LPS + PGE2 depended on the simultaneous production of PGE2 by the stimulated Kupffer cells. It could be partly inhibited by anti-PGE2 antibody or acetylsalicylic acid. While murine TNF-alpha did not stimulate NO synthesis significantly, added PGE2 raised NO synthesis about 6-fold. The addition of dBcAMP to TNF-alpha in the same concentration as with LPS, however, had no effect. Thus, stimulation by LPS + PGE2 equals that of LPS + dBcAMP whereas TNF-alpha + PGE2 does not equal TNF-alpha + dBcAMP, indicating differences in the mode of action of PGE2 on LPS- or TNF-alpha-treated Kupffer cells.

Interleukin-6 release by rat liver macrophages

Tissue macrophages of the liver (Kupffer cells) release interleukin-6 (IL-6) in vitro. Since Kupffer cells reside in close proximity to hepatocytes, which are major target cells of IL-6, the regulation of IL-6 release by hepatic macrophages has been investigated in this study. Using the hybridoma growth test to detect IL-6, we found that Kupffer cells already maximally release IL-6 at endotoxin concentrations as low as 1.0 ng/ml. The stimulated secretion of IL-6 was increased 4-8-fold by endotoxin when compared to the control macrophages incubated in serum-containing medium alone. The preincubation of macrophages with interferon-gamma enhanced the capacity of Kupffer cells to respond to endotoxin. The secretion of IL-6 could also be induced by interleukin (IL)-1 beta and tumor necrosis factor (TNF-alpha). The most potent inducers, however, were the paramyxoviruses Newcastle Disease Virus and Sendai Virus. The release of IL-6 by macrophages upon stimulation with endotoxin was almost completely inhibited by 1 microM dexamethasone. Whereas 100 nM of prostaglandin E2 (PGE2) inhibited the release of TNF-alpha in rat Kupffer cells, it did not affect the secretion of IL-6.

Labeling of precursor pools for glycosphingolipid biosynthesis. Incorporation of [3H]galactose by rat hepatocytes in primary culture

UDP-galactose and UDP-glucose are the immediate sources of monosaccharide residues in glycosphingolipid biosynthesis. The incorporation of [6-3H]D-galactose into these compounds was measured in primary cultures of rat hepatocytes, which take up and metabolize galactose rapidly. The UDP-glucose and UDP-galactose content of hepatocytes, determined enzymatically and by the HPLC-analysis of UDP-sugars, was 1.87 +/- 0.22 and 0.51 +/- 0.06 nmol/mg protein, respectively. Galactose concentrations in the medium of up to 7.5 microM did not influence the intracellular levels of UDP-glucose and UDP-galactose. Although the specific radioactivity of these precursor pools did not reach a constant plateau, conditions were defined that allow the calculation of rates of glycolipid synthesis from added labeled galactose. They include the replacement of glucose in the culture medium by sodium pyruvate and D-galactose.

Activation of GD3 synthase by sex steroid hormones in cultured rat hepatocytes

The influence of sex steroid hormones on the activities of GM3 and GD3 synthases in isolated hepatocytes was studied. Progesterone (0.1 - 2.0 microM), beta-estradiol (0.1 - 1 microM), and testosterone (0.1 - 1 microM) activate GD3 but not GM3 synthase when added directly to hepatocytes cultured in modified William's E medium.

Sialyltransferase activities in cultured rat hepatocytes

Previous studies on the age and sex dependency of the ganglioside patterns in rat liver in vivo and the concomitant determination of the activities of some enzymes involved in these pathways revealed the prominent role of the sialylation of GM3 to GD3 in determining the flow to the mono (a)- and polysialo (b)-series, respectively. Here, the influence of hormones on the activities of GM3 and GD3 synthases in isolated hepatocytes was studied. The combination of several factors (insulin, glucagon, epidermal growth factor, glucocorticoids) was found to be necessary for maintaining in vivo activity levels of GD3- but not of GM3-synthase.

Virus-vs endotoxin-induced activation of liver macrophages

The response of liver macrophages (Kupffer cells) to distinct pathogenic material was investigated by comparing virus- and endotoxin-induced macrophage activation. Endotoxin-induced stimulation and induction with Newcastle disease virus (NDV) or Sendai virus led to the release of the same pattern of prostanoids characterized by a predominant production of prostaglandin E2 (PGE2). With respect to peptide mediators, hepatic macrophages secreted tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 after viral induction and endotoxin treatment, respectively. In response to viruses, however, much more interleukin-6 and TNF-alpha was detected than after endotoxin stimulation. Interferon type I (interferon-alpha/beta), on the other hand, was only detected in the supernatants of macrophages infected with viruses, but not of those exposed to endotoxin. This study also revealed that rat TNF-alpha exists in several soluble species, some of which are glycosylated.

Interdependence of tumor necrosis factor, prostaglandin E2, and protein synthesis in lipopolysaccharide-exposed rat Kupffer cells

Kupffer cells are the main producers of tumor necrosis factor-alpha (TNF; cachectin) and eicosanoids in the liver exposed to lipopolysaccharide (endotoxin; LPS). A very rapid but transient release of TNF is followed by a slow, steady synthesis of prostaglandin E2 (PGE2). TNF itself is able to provoke eicosanoid synthesis in Kupffer cells; the rate and pattern of prostaglandin production are similar to those observed after treatment with LPS. Anti-TNF antibodies completely neutralize TNF action on Kupffer cells, thus ruling out any participation of contaminating LPS. LPS stimulation of PGE2 production in Kupffer cells is reduced by the antiserum to 50%, indicating an involvement of TNF in the stimulatory action of LPS. On the other hand, PGE2, a potent inhibitor of LPS-elicited TNF release, is able to suppress LPS- but not TNF-stimulated eicosanoid synthesis in rat Kupffer cells. In addition to this autocrine circuit, extrahepatic factors participate in the regulation of Kupffer cell activation: glucocorticoids not only inhibit TNF or prostaglandin production, they also reverse the LPS-specific changes in the prostaglandin pattern of Kupffer cells. LPS, TNF or cycloheximide when given alone in the concentration range applied in this study do not affect the viability of rat Kupffer cells. However, the combinations of cycloheximide and either LPS or TNF cause rapid death of the cultured cells. The cytolytic potential of either combination cannot be alleviated by treatment with glucocorticoids.

Ganglioside biosynthesis in rat liver: different distribution of ganglioside synthases in hepatocytes, Kupffer cells, and sinusoidal endothelial cells

The activities of five glycolipid-glycosyltransferases, GL2, GM3, GM2, GM1, and GD1a synthase, were determined in a cell-free system with homogenate protein of total rat liver, isolated hepatocytes, Kupffer cells, and sinusoidal endothelial cells. In rat liver parenchymal and nonparenchymal cells ganglioside synthases were distributed differently. Compared to hepatocytes, Kupffer cells expressed a nearly sevenfold greater activity of GM3 synthase, but only 14% of GM2, 19% of GM1, and 67% of GD1a synthase activity. Sinusoidal endothelial cells expressed a pattern of enzyme activities quite similar to that of Kupffer cells with the exception of higher GM2 synthase activity. Activity of GL2 synthase was distributed unifromly in parenchymal and nonparenchymal cells of rat liver, but differed by sex. It was 1 to 2 orders of magnitude below that of all the other ganglioside synthases investigated. The results indicate GL2 synthase regulates the total hepatic ganglioside content, and hepatocytes but not nonparenchymal liver cells have high enzymatic capacities to form a-series gangliosides more complex than GM3.

[Microbiology studies of intra- and postoperative autotransfusion in orthopedics]

In order to determine the risk of bacterial contamination of blood during autotransfusion, blood samples were taken from the autotransfusion system of 25 consecutive total hip replacements at various stages and at different times (9 samples per patient). According to the same principle, samples were taken from the identical system after processing the postoperative drainage blood. Since the danger of contamination depends on the quality of the air which is sucked into the autotransfusion system along with the blood, we also measured the amount of bacteria in the air in two different operating rooms: Horizontal laminar air flow was provided for 20, conventional ventilation for a further 5 operations. Evaluation of airborne contamination in the operating rooms showed at most 656 cfu/m3 in the conventionally ventilated room and at most 344 cfu/m3 in the room with laminar air flow. Micrococci and peptococci were cultivated from 2 samples out of 225. The isolates were derived from 2 different patients (1 in the LAF-OR, 1 in the conventionally ventilated OR); both samples were taken from the retransfusion bag towards the completion of surgery. From these results we conclude that even in a conventionally ventilated operating room during primarily aseptic surgery intraoperative autotransfusion does not involve an increased risk of infection. This also applies to the retransfusion of processed blood from Redon drainages using the identical autotransfusion set.

Mikrobiologische Untersuchungen bei intra- und postoperativer Autotransfusion in der Orthopädie

Um die Gefahr der bakteriellen Kontamination des Blutes während der Autotransfusion zu untersuchen, wurden bei 25 konsekutiven Hüftprothesenimplantationen zu verschiedenen Zeitpunkten und von unterschiedlichen Stellen Proben aus dem Autotransfusions-system entnommen (9 Proben pro Patient). Nach dem gleichen Prinzip erfolgte die Probenentnahme nach Aufbereitung des postoperativen Drainageblutes aus demselben System. Da die Kontaminationsgefahr von der Qualität der Luft abhängt, die zusammen mit dem Blut angesaugt wird, bestimmten wir auch den Keimgehalt der Luft in zwei unterschiedlichen Operationssälen: 20 Operationen fanden in einem Raum mit Laminar Flow, 5 in einem mit konventioneller Belüftung statt. Bei den Raumluftmessungen lagen die Werte im konventionell belüfteten OP maximal bei 656, im Raum mit Laminar Flow bei 344 KBE/m3. Von insgesamt 225 Proben wurden in 2 Proben von verschiedenen Patienten (einmal aus dem LAF-OP, einmal aus dem konventionell belüfteten OP) in der Anreicherungskultur aus dem Retransfusions-beutel bei Operationsende Mikrokokken bzw. Peptokokken isoliert. Wir schlieβen aus den Ergebnissen, daβ bei der Anwendung der intraoperativen Autotransfusion auch unter den Bedingungen eines konventionell belüfteten OP bei primär aseptischen Eingriffen kein erhöhtes Infektionsrisiko besteht. Dies gilt auch für die Retransfusion von postoperativ aufbereitetem Blut aus Redon-Drainagen mit dem identischen Autotransfusions-Set.

The activity of GD3 synthase modulates the ganglioside pattern in rat liver

Variations of the ganglioside composition in the livers of Wistar rats correlated with the activity of GD3 synthase in the corresponding liver homogenates. With increasing enzyme activity, higher proportions of b-series gangliosides (GD3, GD1b, GT1b) were detected. No significant changes in the activity of GM2 synthase or GM1 synthase were observed, indicating a regulatory function for GD3 synthase in this tissue. Young animals showed an average GD3 synthase activity of 0.5-0.6 nmol.h-1.mg protein-1 without sex-dependent variations. Among the older animals, however, males expressed an activity five-fold higher than females, suggesting that this enzyme might be affected by hormones.

Theory in action. The geriatric assessment team

The scientific principles of homeodynamics explain the older person in terms of unique wholeness; continuous interaction, and growth. Assessing the functional status of the older adult requires evaluation of both the person and the environment. Comparing the older adult to himself is often more accurate than comparing findings to so-called norms. The role of the clinical nurse specialist as a member of the geriatric assessment team is clarified when nursing actions are theory-based.

Fc receptors mediate prostaglandin and superoxide synthesis in cultured rat Kupffer cells

Latex beads with covalently bound bovine serum albumin were prepared and coated with anti-BSA immunoglobulin G. These particles were shown to possess on their surfaces a defined quantity of the antibody with the Fc portions exposed to the medium. One homologous and two heterologous antibodies of the G class were used and compared in terms of their binding to the rat Kupffer cells and their ability to elicit the typical phagocytotic responses. These particles were phagocytosed by rat Kupffer cells and elicited synthesis of prostaglandins and superoxide anion radicals. A significant release of superoxide into the medium was observed in the presence of cytochalasin B only. The data presented here suggest that a) Fc-carrying particles can be bound to Kupffer cells and elicit responses via specific receptors; b) coating with the homologous antibody yields the most effective particles; c) superoxide release into the surrounding medium is most abundant when the particle-binding membrane areas are prevented from forming phagocytotic vesicles.

4-Bromophenacyl bromide inhibits prostaglandin D2 synthesis from arachidonic acid rather than phospholipase A2 activity in liver macrophages

4-Bromophenacyl bromide at a concentration of 50 microM does not inhibit phospholipase A2 activity in liver macrophages. Rather, this compound increases the amount of radioactivity released from [3H]arachidonate-prelabeled Kupffer cells and leads to the formation of small amounts of thromboxane, prostaglandin D2 and prostaglandin E2. Also the zymosan-induced formation of thromboxane and prostaglandin E2 from endogenous sources which is thought to involve phospholipase A2 remains unaffected in the presence of this compound. The generation of superoxide and the formation of prostaglandin D2 from arachidonate and after stimulation of the cells with zymosan, however, are blocked by 4-bromophenacyl bromide. Furthermore, this compound suppresses the incorporation of externally added arachidonate into membrane lipids of the cells. 4-Bromophenacyl bromide seems, therefore, not to be a useful tool to demonstrate the involvement of phospholipase A2 in complex biological systems.

Independent regulation of thromboxane and prostaglandin synthesis in liver macrophages

Incubation of liver macrophages with zymosan, phorbol ester and calcium ionophore A 23187 led to the formation of thromboxane, prostaglandin E2 and prostaglandin D2, whereas after external addition of arachidonic acid prostaglandin E2 and prostaglandin D2 only were found. This was confirmed by the use of labeled arachidonic acid given together with the stimuli. When the liver macrophages were prelabeled with [3H]arachidonic acid, and zymosan and [14C]arachidonic acid were added simultaneously, [3H]-label only was found in thromboxane whereas both [3H]- and [14C]-labeled PGE2 and PGD2 were detected in the cell medium. These data suggest that in cultured rat liver macrophages externally added arachidonic acid is accessible to the cyclooxygenase supplying prostaglandin H2 for prostaglandin E2 and D2 synthesis but not for thromboxane synthesis.

The sulfhydryl reagent thimerosal elicits human platelet aggregation by mobilization of intracellular calcium and secondary prostaglandin endoperoxide formation

The effect of the sulfhydryl (SH) group inhibitor ethylmercurithiosalicylate (thimerosal) on the function of human platelets was investigated. In contrast to known SH reagents such as p-chloromercuribenzoate or N-ethylmaleimide, thimerosal elicited both aggregation and [3H]serotonin release of washed human platelets at low micromolar concentrations (greater than or equal to 2 microM). Only a significant higher dose (greater than or equal to 15 microM) was effective when platelets were pretreated with the cyclooxygenase inhibitor aspirin, indicating an amplification of the proaggregatory effect of thimerosal by secondary prostaglandin (PG) endoperoxide and/or thromboxane (TX) formation. Consistent with this notion, thimerosal induced endogenous platelet arachidonic acid (20:4) metabolism which could be attributed to enhanced 20:4 liberation, presumably by activation of phospholipase A2. The latter effect was mediated by mobilization of intracellular calcium (Ca2+), and was not affected by removal of extracellular Ca2+. In the presence of aspirin, the thimerosal-induced Ca2+ elevation was completely reversed by dithiothreitol (DTT) which implicates SH groups in intracellular Ca2+ transport. In contrast to previous observations with other SH reagents, thimerosal had no effect on the inositoltrisphosphate (IP3)-mediated release or the sequestration (and/or extrusion) of intracellular Ca2+ following stimulation with thrombin, indicating an action on an as yet undefined CA2+ transport system.

Comparative study of cytotoxicity, tumor necrosis factor, and prostaglandin release after stimulation of rat Kupffer cells, murine Kupffer cells, and murine inflammatory liver macrophages

Macrophages (Mphi) and Mphi-depleted (nonadherent) nonparenchymal cells (NPC) of the liver were examined for their cytotoxic potential against tumor cells, production of tumor necrosis factor (TNF), and release of prostaglandins (PG) following stimulation by lipopolysaccharide (LPS), interferon-gamma (IFN gamma), and zymosan. Resident murine liver macrophages had no natural cytotoxicity for the TNF-resistant target cell line P815. Activation of these cells was only obtained by a combination of IFN gamma and LPS. Inflammatory murine macrophages were in a primed stage and could be activated by LPS alone in the absence of IFN gamma. Rat resident macrophages resembled functionally the inflammatory macrophages of the mouse liver rather than the resident macrophages. They displayed natural cytotoxicity against all targets tested and were further activated by LPS in the absence of IFN gamma. Similar results were obtained with respect to macrophage-depleted nonadherent NPC: Mouse NPC had a low level of NK activity against Yac-1 cells. Treatment with pyran copolymer resulted in a strong increase of cytotoxicity against Yac-1; furthermore, a TNF-dependent killing of Wehi 164 and TNF-independent cytotoxicity against P815 cells were now acquired. In the rat NPC prepared from unstimulated animals expressed high levels of natural cytotoxicity against all targets. No major differences could be observed between inflammatory Mphi and Kupffer cells of rat and mouse liver with regard to TNF production and TNF-dependent killing of Wehi 164 tumor cells. The same was true for the spectrum of secreted prostanoids. Upon activation of all cell populations a marked shift toward the production of PGE2 occurred. Experiments involving the cyclooxygenase inhibitor indomethacin showed enhanced TNF-dependent tumor cell killing by nonactivated Mphi in the absence of prostanoid production.

13C, 15N, and 31P NMR studies on 6-hydroxy-L-nicotine oxidase from Arthrobacter oxidans

The interaction between the apoprotein of 6-hydroxy-L-nicotine oxidase from Arthrobacter oxidans and the prosthetic group FAD has been investigated by 13C, 15N, and 31P NMR techniques. The FAD prosthetic group was selectively enriched in 13C and 15N isotopes by adding isotopically labeled riboflavin derivatives to the growth medium of riboflavin-requiring mutant cells. In the oxidized state the chemical shift of the C(7) and C(8) atoms indicates that the xylene moiety of the isoalloxazine ring is embedded in a hydrophobic environment. The polarization of the isoalloxazine ring as a whole is, however, much more comparable to that of free flavin in a polar and protic environment than to free flavin in an apolar environment. The polarization of the ring system can be ascribed to strong hydrogen bonds between the apoprotein and the two carbonyl groups. The binding of the competitive inhibitor, 6-hydroxy-D-nicotine, influences the resonances of the C(4a) and the N(5) atoms strongly. It is suggested that these shifts are due to a strong hydrogen-bonding interaction between the N(5) atom and the inhibitor. On reduction all resonances, except those of the C(10a) and the N(1) atoms, shift upfield, indicating the increased electron density in the ring system. In the dithionite-reduced enzyme, the ring system is bent at the N(5) position. Due to the bending of the N(5) atom and the sp2 hybridized N(10) atom, electron density from the N(10) atom is reallocated at the C(4) carbonyl group. In contrast, in the substrate-reduced enzyme the N(5) atom is almost completely sp2 hybridized, yielding a rather planar isoalloxazine ring.(ABSTRACT TRUNCATED AT 250 WORDS)

The release of tumor necrosis factor from endotoxin-stimulated rat Kupffer cells is regulated by prostaglandin E2 and dexamethasone

Evidence is presented that upon stimulation with endotoxin (lipopolysaccharide, LPS), Kupffer cells, the body's largest pool of sessile macrophages, synthesize and liberate a factor whose immunological, cytotoxic and chemical properties are those described for tumor necrosis factor (TNF)-alpha. Hepatocytes and sinusoidal endothelial cells do not produce detectable amounts of this protein. Ten nanograms of LPS per ml medium are sufficient to stimulate a substantial release of this mediator. Recombinant interferon-gamma (rIFN gamma) per se is a poor inducer of TNF release. Costimulation with endotoxin and rIFN gamma shows only a slight increment in the release of this cytotoxic factor, relative to LPS alone. Exposure of Kupffer cells to the Ca2+ ionophore A23187 or to elicitors of the oxidative burst and superoxide production, e.g. zymosan or phorbol 12-myristate 13-acetate, stimulates only a fraction (20%) of the TNF release seen after endotoxin challenge. Prostaglandin E2, the synthesis of which is strongly enhanced after challenge of rat Kupffer cells with LPS, suppresses the release of TNF by these cells. This autoregulatory mechanism may explain the kinetics of TNF production by stimulated Kupffer cells. Dexamethasone is another important mediator capable of reducing the LPS-elicited TNF formation. An effect of the glucocorticoid hormone can still be provoked if it is added simultaneously with or shortly after LPS. This rapid action requires a mechanism that is different from the time-consuming one leading to the inhibition of prostaglandin synthesis in Kupffer cells.

[Incidence and significance of pathogen detection in Douglas fluid in non-inflammatory genital diseases]

Between 1976 and 1986 the secretions from the pouch of Douglas of 1,219 patients with non-inflammatory genital diseases were microbiologically studied. Microorganisms were detected in 3.4%. In the majority of cases they were physiological skin organisms, with a count of less than 10 per ml of Douglas fluid. These findings support the view, that secondary contamination of the specimens occurred during removal, transportation, or laboratory processing.