Search PubMed⌕ Search

Biomedical subjects

R Urbaschek

Publications and source records attributed to R Urbaschek.

At least 37 records · Page 2Linked to original sources
PubMed1993

[Detection of endotoxin in plasma: specificity and value for development and prognosis of infection].

A number of problems may be involved in the detection of endotoxin in plasma of patients using LAL (Limulus amebocyte lysate). When collecting blood or processing samples, contamination with endotoxin or its adsorption to material must be avoided. In our laboratory a kinetic LAL microtiter assay was developed that takes into account plasma-related interferences with the LAL endotoxin reaction by performing an internal standardization in each sample. Negative results do not absolutely exclude the involvement of endotoxins in the underlying disease. High levels of endotoxins do not necessarily reflect the severeness of the clinical status of the patient. Due to nonendotoxin-specific reactions with some complete lysates, false-positive levels may result, e.g., following immunoglobulin therapy. In spite of these limitations, the LAL test remains a valuable tool in the evaluation of gram-negative infections.

Endotoxins↗
PubMed1991

Isoniazid protects mice against endotoxin lethality without influencing tumor necrosis factor synthesis and release.

Treatment of NMRI mice with isoniazid (INH; 25 mg/kg) intraperitoneally induced significant protection when it was injected before or after a lethal intravenous challenge with endotoxin. The INH preparation used was not contaminated with endotoxin. Tumor necrosis factor (TNF) was not elevated in sera from NMRI mice 2 h after the injection of INH. INH did not influence TNF synthesis or release determined in human monocytes in vitro. Therefore, it is concluded that the protective effect of INH against lethal endotoxin is not due to a suppressive effect of INH on TNF production.

Animals↗
PubMed1988

[Endotoxin contents of phytopharmaceuticals: correlation with clinically observed side effects].

Four phytopharmaceutics (Carnivora, Pascotox forte-Injectopas, Esberitox N, Iascador M), which sometimes cause side effects after parenteral administration (fever, rigor, nausea), were examined for their endotoxin content by the kinetic turbidometric Limulus-amebocyte-lysate (LAL) microtitre test. Contaminations of over 10(5) EU/ml (endotoxin units; 1 EU = 0.1 ng of the FDA standard EC-5) were found in correlation with the clinical picture. In one preparation (Carnivora) very high endotoxin levels were always found; contaminations were only occasionally found in the others. These endotoxin measurements are supported by tests of endotoxin-dependent parameters in in-vivo experiments (reduction in leukocytes, acute death in hyperreactive mice). These findings underline the urgent need for a widening of the regulations on testing for pyrogens to include those parenteral preparations which now do not have to be tested because of their small volume (less than 15 ml).

Animals↗
PubMed1987

Tumor necrosis factor induced stimulation of granulopoiesis and radioprotection.

Human recombinant tumor necrosis factor, TNF, was used to assess its ability to stimulate granulopoiesis and to protect mice against lethal irradiation, effects known to be inducable with TNF-rich postendotoxin serum from BCG infected mice (BCG/ET serum). Although the endotoxin contamination of this TNF preparation is extremely low its effects were compared in endotoxin low responder C3H/HeJ mice and susceptible NMRI mice. TNF is a potent inducer of serum colony stimulating activity, CSA, in both mouse strains. In peripheral blood a marked granulocytosis with a concomitant decrease in lymphocytes and monocytopenia occurs at 2 hours after injection of TNF. Moreover, TNF induces an increase in the number of splenic myelopoietic committed stem cells (GM-CFC, granulocyte-macrophage colony forming cells) determined five days after injection. The lethality rate, registered over 30 days after exposure to 660 cGy whole body X-irradiation is reduced to 40% in C3H/HeJ mice as compared to 75% in control animals. The reduction in lethality is observed both, when TNF was injected 24 hours before or after irradiation. In vitro, TNF significantly increases the number of colonies in the presence of CSA in bone marrow cultures. TNF per se does not effect colony growth. The studies reported here demonstrate that TNF is a myelopoiesis stimulating factor in mice which may be related to the reduction in lethality following whole body irradiation.

Animals↗
PubMed1987

No evidence for endotoxin transfer across high flux polysulfone membranes.

Recently, there has been some concern that high-flux membranes may expose dialysis patients to the risk of endotoxin transfer secondary to backfiltration within the dialyzer. To evaluate the safety of high-flux polysulfone dialyzers, we examined in an in vitro recirculation system whether lipopolysaccharides (LPS) and lipid A respectively penetrate from the dialysate to the blood compartment and vice versa using a F-60 hemofilter (Fresenius AG). For the detection of endotoxin, a sensitive, kinetic limulus amebocyte lysate (LAL) microtiter test was used. It can be concluded that LPS and lipid A do not pass from either side through the filter system used when saline was recirculated for more than 10 h on both sides of the membrane.

Blood↗
PubMed1984

Deficient Kupffer cell phagocytosis and lysosomal enzymes in the endotoxin-low-responsive C3H/HeJ mouse.

Various substances, including lysosomal enzymes, are produced by Kupffer cells and other macrophages; their release has been implicated in the toxic response to endotoxins. C3H/HeJ mice exhibit little or no response to doses of endotoxin that are lethal in syngeneic C3HeB/FeJ mice. To explore the nature of this deficient response, the Kupffer cells of these mice were studied using in vivo microscopic as well as histochemical and electron microscopical methods. In vivo, the rate of phagocytosis of single 0.8 micron latex particles was measured in individual Kupffer cells as was the number of phagocytic cells per microscopic field. Frozen sections of livers were stained for a variety of lysosomal enzymes and liver specimens also were processed for electron microscopy. In comparison to the endotoxin-sensitive C3HeB/FeJ mice, the livers of the C3H/HeJ mice contained 60% fewer Kupffer cells that phagocytosed latex. However, the rate of phagocytosis by these cells was not statistically different and ranged from 19-26 sec. The volume density of acid-phosphatase-positive Kupffer cells was 40% less in the C3H/HeJ mice. Similar differences were observed with other lysosomal enzymes including cathepsins B and H and dipeptidyl peptidases I and II. However, light and electron microscopy revealed a relatively normal number of Kupffer cells in livers stained for peroxidase, a nonlysosomal enzyme. The results suggest that the insensitivity of C3H/HeJ mice to endotoxin may be related in part to a lysosomal enzyme deficiency and a paucity of phagocytic Kupffer cells in these animals.

Animals↗
PubMed1984

Species differences in Kupffer cells and endotoxin sensitivity.

The relative species sensitivity to Escherichia coli O111:B4 endotoxin was found to be guinea pig greater than hamster greater than mouse greater than rat. The 50% lethal dose of this endotoxin correlated with both the rate at which single latex particles were phagocytosed by individual Kupffer cells and the number of Kupffer cells in hepatic lobules that phagocytosed latex. The results suggests that the intrahepatic density and the level of activation of Kupffer cells participate in determining endotoxin sensitivity.

Animals↗
PubMed1984

Protective effects and role of endotoxin in experimental septicemia.

An experimental model was used in mice in which septicemia develops following invasion of the animals' own intestinal flora after cecal ligation and puncture. Pretreatment with 1 microgram of endotoxin administered 24 hours before surgery significantly reduced the rate of lethality. Bacteria were counted and differentiated in cardiac blood at various times throughout a 48-hour period after induction of septicemia in mice, with and without pretreatment. Endotoxin levels and plasma-related interference of the Limulus-amebocyte-lysate (LAL)-endotoxin reaction also were determined as were hematologic and metabolic parameters. A shift from mixed gram-positive and gram-negative to predominantly gram-negative bacteria occurred in both groups. In pretreated mice, a reduction in aerobic bacterial counts and reduced hyperglycemia were seen in the initial phase; and a decrease in anaerobic and aerobic bacteria and in endotoxin levels were observed at the end of the experiment. This appears to be related to endotoxin-induced increased resistance against the consequences of intraabdominal sepsis. These studies also indicate that the measured amount of circulating endotoxin does not necessarily correlate to the severeness of infection. Individual differences in plasma-related interference with the LAL-endotoxin reaction also emphasize the requirement for sample-internal standardization in order to reliably quantify endotoxin in plasma.

Animals↗
PubMed1983

In vivo microscopic observations of the responses of Kupffer cells and the hepatic microcirculation to Mycobacterium bovis BCG alone and in combination with endotoxin.

Kupffer cell function and hepatic microvascular hemodynamics were studied by in vivo microscopy in Mycobacterium bovis BCG-infected NMRI mice before and after treatment with minute (0.01 mu mg) tolerance-producing doses and doses causing 70% lethality (0.5 micrograms) of Escherichia coli 0111:B5 endotoxin alone and in combination. BCG-induced granulomas distorted the hepatic microvasculature and impeded blood flow in many sinusoids; flow also was altered further by leukocytes adhering to the sinusoidal walls and by enlarged Kupffer cells that bulged into the lumen. Nevertheless, in BCG-infected mice, the ratio of Kupffer cells which phagocytosed latex to sinusoids containing blood flow and capable of delivering these particulates to Kupffer cells was significantly greater than that in uninfected mice. The phagocytosis of single latex particles by individual Kupffer cells also was more rapid. This indicated an expansion of the numbers and activation of Kupffer cells. In this hyperreactive state, the tolerance-inducing dose of endotoxin produced no change in the rate of phagocytosis after 2 h. In contrast, the 70% lethal dose reduced the rate by 123%, unless tolerance was induced, in which case there was no reduction in the rate of phagocytosis. Twenty-four hours after injection of the tolerance-inducing dose, however, the rate of phagocytosis was accelerated slightly (17%). This suggested that the Kupffer cells had been activated and perhaps were more effective in clearing subsequent endotoxin from the blood but without sufficient release of toxic substances to be lethal. That some mediators were released, however, was suggested by the microvascular alterations that accompanied the above phagocytic responses. These results further support the concept of a central role for Kupffer cells in endotoxin-mediated, nonspecific host defense mechanisms.

Animals↗
PubMed1983

Ability of various adsorbents to bind endotoxins in vitro and to prevent orally induced endotoxemia in mice.

The efficacy of various adsorbents for endotoxin was tested in vitro and in vivo using a murine experimental model of gut-derived endotoxemia. A quantitative limulus amebocyte lysate microtiter test and the limulus amebocyte lysate tube test were used to determine intestinal and circulating levels of endotoxin. Kaopectate, kaolin/pectin mixture, kaolin, pectin, bentonite, charcoal particles, and lactulose were tested for their ability to bind endotoxins both in vitro and in vivo. The most effective material in the prevention of endotoxemia provided to be bentonite followed by Kaopectate and charcoal particles. Kaolin least effectively bound endotoxin at similar concentrations, while lactulose and pectin had minimal effects. Good correlation was shown between the ability of these drugs to bind endotoxin in vitro as compared with in vivo action.

Aluminum Silicates↗
PubMed1983

[Quantitative endotoxin determination. Automated kinetic Limulus amebocyte lysate microtiter test with measurement of sample-related interferences].

A turbidometric, automated limulus amoebocyte lysate (LAL) microtiter test has been developed based on the evaluation of the LAL-endotoxin reaction kinetics. The maximal increase in optical density of each reaction mixture within 1 min is recorded. With this method an endotoxin standard curve is achieved which is linear over a concentration range of six decades. With presently available LAL methods sample-related inhibition or enhancement of the LAL endotoxin reaction may be overlooked and lead to false results. The quality of interfering factors can be characterized with our methods by spiking serial dilutions of the sample with constant endotoxin concentrations. The additional introduction of an internal standardization in our system allows the determination of endotoxin with simultaneous detection of quality and quantity of sample-induced interference. This procedure is based on a mathematic model which describes interference-caused alterations of the reaction revealed by addition of endotoxin in increasing concentrations. In comparison to the LAL tube test and the turbidometric determination at a given time the advantages of the developed method are demonstrated using three different samples (gelatin solution, adenine-HCl solution and a concentrate of coagulation factors (PPSB)). These are paradigmaticly selected because and enhancement of the LAL endotoxin reaction.

Animals↗
PubMed1982

Histopathology of mixed anaerobic intraabdominal infection in mice.

This study characterized acute peritonitis and chronic abscess formation resulting from experimental mixed anaerobic infection with Bacteroides melaninogenicus and Fusobacterium necrophorum. At intervals after infection liver and spleen samples were obtained, fixed, and processed for histological examination. An acute to chronic infection progressed in mice infected with this mixture of anaerobic bacteria, whereas, no infection resulted when either organism was injected alone. Acute inflammatory cell infiltrates were noted in tissue samples at 12 h postinfection. Small, discrete areas of liver cell necrosis with neutrophilic infiltrates were observed as early as 24 h. By 48 h after infection the liver parenchyma was infiltrated with both acute and chronic inflammatory cells, with moderate to severe hepatocyte degeneration recognized at 72 h. Large intrahepatic abscesses were present in the subphrenic (upper lobe) area 2 to 6 weeks after experimental infection.

Animals↗
PubMed1982

Aspects of beneficial endotoxin-mediated effects.

The status of hyperreactivity and hyporeactivity following the administration of endotoxin in a susceptible host represents phenomena which are of interest in an attempt to understand the role of endotoxins in pathophysiological events in general. Two experimental approaches designed to examine these events are reported herein; i.v. injection with minute concentrations of endotoxin (10 ng of a BOIVIN endotoxin from E. coli 0111) induces tolerance against lethal doses of endotoxin (0.5 microgram or 5.0 microgram) within 24 h in hyperreactive NMRI mice that were infected 14 days before with BCG. Transfer of post-endotoxin serum from BCG infected mice, which contains a myriad of macrophage mediators and which induces nonspecific resistance to X-irradiation, renders a strain of mice (C3H/HeJ) that is hyporeactive to endotoxins, susceptible to the lethal effect of endotoxin. Studies of the role of the macrophage and its mediators in the experimental models described here may contribute to a further understanding of the mechanisms underlying endotoxin-induced biological activities.

Animals↗
PubMed1982

In vivo microscopic studies of the responses of the liver to endotoxin.

In vivo microscopic methods concomitant with electron microscopic and histochemical procedures are being used to explore the sequelae of responses of Kupffer cells and the hepatic microvasculature to endotoxins. To gain further insight into the role of the liver in host defense and nonspecific resistance, the effects of endotoxin also are being studied in animals sensitized to endotoxin (BCG infection) or tolerant to endotoxin (pretreated with detoxified endotoxin, low doses of endotoxin, or in C3H/HeJ mice). The results to date, have demonstrated that endotoxin induces significant alterations in the hepatic microcirculation due to swelling of Kupffer and endothelial cells and the adhesion of leukocytes and platelets to the sinusoid wall. Lymphocytes frequently are associated with the Kupffer cells. Phagocytosis also is affected; following a brief period of stimulation, the rate of phagocytosis by Kupffer cells is depressed. In BCG infected animals all of these responses are exaggerated but can be minimized by pretreatment with detoxified endotoxin or minute concentrations of endotoxin 24 h prior to the challenge dose of endotoxin. The responses are not seen in the endotoxin low-responder, C3H/HeJ mouse which was found to have a deficiency in lysosomal enzymes and a paucity of functional Kupffer cells. The results provide some insight into the sequelae of cellular and microvascular events that occur in the liver during endotoxemia, endotoxin-related host defense mechanisms and non-specific resistance. In addition, support is provided for the central role of Kupffer cells in these events and that lysosomal enzymes participate in the toxic response elicited by endotoxin.

Animals↗