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R J Ulevitch

Publications and source records attributed to R J Ulevitch.

At least 145 records · Page 8Linked to original sources
PubMed1981

New function for high density lipoproteins. Isolation and characterization of a bacterial lipopolysaccharide-high density lipoprotein complex formed in rabbit plasma.

The addition of bacterial lipopolysaccharide (LPS) from Salmonella minnesota R595 to rabbit plasma results in a marked reduction of the hydrated buoyant density of the parent R595 LPS, from 1.38 to less than 1.2 g/cm3. Using immunopurified anti-R595 LPS antibody covalently linked to Sepharose 4B, we were able to separate the altered R595 LPS (d less than 1.2 g/cm3) from the remainder of the plasma proteins by elution of the bound material with 2.5 M KSCN. The KSCN eluate was shown to have a d less than 1.2 g/cm3 and to contain both R595 LPS as well as protein and lipid characteristic of high density lipoprotein (HDL). The major protein in the KSCN eluate is a single polypeptide chain with an apparent molecular weight of 26,000 in sodium dodecyl sulfate and an amino acid composition essentially identical to that of apoprotein AI, the major protein of rabbit HDL. The lipid composition of the KSCN eluate is similar to that of HDL, although marked differences in the cholesterol ester/cholesterol ration and the phosphatidyl choline/phosphatidyl ethanolamine ratio were observed when the KSCN eluate and rabbit HDL were compared. The formation of this R595 LPS-protein-lipid complex in plasma accounts for the marked reduction in buoyant density found when LPS is added to plasma.

Amino Acids↗
PubMed1981

The induction of a unique procoagulant activity in rabbit hepatic macrophages by bacterial lipopolysaccharides.

Disseminated intravascular coagulation (DIC) is a common occurrence during clinical sepsis and can be induced in the experimental host by LPS. Fibrin deposition in the hepatic microcirculation has been observed within 30 min of i.v. injection of LPS. Because mononuclear phagocytes have been shown to produce a PCA after exposure to LPS, we have examined the ability of a homogeneous population of explanted hepatic macrophages to express PCA. Addition of as little as 10 ng/ml of LPS stimulated a 15- to 20-fold increase in PCA over control culture levels within 7 1/2 hr post-treatment. The PCA was found to be membrane-associated, with approximately 90 to 95% of the total PCA present in the cellular lysates, and more than 85% was inhibited by pretreatment of the cells with the diazonium salt of sulfanilic acid, an inhibitor of ecto-enzymes. In contrast to tissue thromboplastin produced by other M phi populations, the H-M phi PCA was found to be markedly sensitive both to heat inactivation at 56 degrees C and to inhibition by 1 mM DFP. Additionally, assays involving both a 1-stage coagulation test as well as an enzyme assay with a Factor Xa-specific substrate (using normal and deficient human plasmas) demonstrated that the H-M phi PCA appears to activate Factor X directly. Unlike tissue thromboplastin, the H-M phi PCA is non-dependent of Factor VII activation. These studies: 1) demonstrate the LPS induces a unique PCA in the H-M phi, and 2) support a role for the H-M phi in the initiation of DIC in endotoxemic shock.

Animals↗
PubMed1981

Interactions of bacterial lipopolysaccharides with tissue macrophages and plasma lipoproteins.

Several of the cellular and molecular interactions of LPS within the experimental host have been examined in an attempt to elucidate the potential role of these interactions in initiating the pathophysiologic events of endotoxemia. Using 125I-LPS, the clearance of LPS from the blood and its tissue, cellular and subcellular localization was established. The H-Mø was found to be the major host site of intravenous LPS localization and, subsequently, the effect of LPS on explanted H-Mø was demonstrated to be both directly cytotoxic and stimulatory of a selective increase in several cellular enzymes. Both the depression in H-Mø function and the stimulation of release of local and systemic mediators by LPS give the H-Mø a potential central role in initiating endotoxemic shock and DIC. Finally, the marked reduction in the clearance rate of LPS remaining in plasma after the initial rapid tissue localization was found to coincide with a density shift to less than 1.2 g/cm3 for the parent LPS. This density shift was found to be dependent upon binding of the LPS to HDL in the serum or plasma and, with the presence of cellular HDL receptors, accounts for a shift in tissue localization to the adrenals. A postulated effect of direct adrenal damage by LPS can thus be invoked as contributing to the endotoxemic syndrome.

Acid Phosphatase↗
PubMed1981

The response of isolated rabbit hepatic macrophages (H-M macrophage) to lipopolysaccharide (LPS).

In order to evaluate the possible role of the hepatic macrophage (H-M macrophage) in lipopolysaccharide-induced shock and disseminated intravascular coagulation (DIC), a technique has been developed for the isolation and maintenance in culture of rabbit H-M macrophage. Characterization of the resultant cell population by morphology, nonspecific esterase staining, phagocytosis of latex beads, by presence of Fc and C3b membrane receptors confirms a pure population of M macrophage without outgrowth of other cell types for up to 10 days in culture. The exposure in vitro of the H-M macrophage to LPS (either Salmonella minnesota R595 or Escherichia coli 0111:B4) stimulates a selective increase in activity of several cellular enzyme: LDH, lysozyme, plasminogen activator, and a procoagulant factor, with minimal changes in acid phosphatase and beta-glucuronidase detected. Concomitantly, both in vivo and in vitro treatment with LPS produces an apparent direct cellular toxicity. The combined effect of toxicity and selective stimulation and release of mediators in LPS-stimulated H-M macrophage may play a central role in the endotoxemic shock syndrome.

Animals↗
PubMed1980

Rabbit prekallikrein. Purification, biochemical characterization, and mechanism of activation.

Rabbit prekallikrein (RPK) was purified from rabbit plasma by ion exchange and lectin column chromatography and preparative polyacrylamide gel electrophoresis. A 1500-fold purification was routinely achieved with a final yield of 5-10%. The purified RPK was found to be a glycoprotein with an apparent molecular weight of 88,000. Activation of RPK with either trypsin or rabbit Hageman factor (active) occurs by limited proteolytic cleavage, producing two disulfide-linked polypeptide chains with molecular weights of 55,000 and 35,000. Both chains contain carbohyrate and the 35,000-molecular-weight polypeptide was shown to incorporate [3H]DFP. Activation of RPK in kaolin-treated plasma was shown to proceed by an analogous mechanism yielding 55,000- and 35,000-molecular-weight polypeptide chains.

Amino Acids↗
PubMed1980

Role of C3 in the regulation of a splenic PFC response in rabbits.

The effects of in vivo C3 depletion on the immune response were examined in rabbits by assaying for splenic PFC after immunizing normal or cobra venom factor-treated animals with aggregated human gamma-globulin. The response to this T-dependent antigen has previously been shown to be regulated such that several cycles of PFC appear following a single intravenous injection of antigen. C3 depletion had no effect on the first peak of PFC (appearing 5 days after injection), but resulted in depression of the second peak of PFC (day 13). In rabbits depleted of C3, antigen localization in splenic germinal centers was markedly decreased. Delaying C3 depletion until after antigen localization had occurred resulted in no depression of the second peak of PFC. These results suggest that one mechanism by which C3 affects immune responses in vivo is via its role in influencing the persistence of antigen. In the absence of C3, no significant localization of antigen occurs, resulting in interference with the cyclical production of antibody.

Animals↗
PubMed1980

The distribution of lipopolysaccharide in normocomplementemic and C3-depleted rabbits and rhesus monkeys.

To examine the role of complement (C3) in determining the fate of lipopolysaccharide (LPS) in vivo, the distribution of LPS was studied in normocomplementemic (NC) and C3-depleted animals (pretreated with cobra venom factor [CoF]) after intravenous injection of highly purified, radioiodinated Salmonella minnesota R595 LPS. After injection of a lethal (250 micrograms) or nonlethal (5 micrograms) dose of LPS in NC and CoF rabbits and a lethal (5 mg/kg) dose of LPS in rhesus monkeys, the LPS disappeared from blood in a biphasic manner. In all cases, a substantial portion of the dose was removed from blood in an initial disappearance phase (t1/2 < 15 minutes), which, in some cases, was accelerated in CoF-treated animals. LPS remaining in blood beyond 30 minutes persisted with a much increased half-life (> 5 hours). Liver contained the major portion (40%) of tissue-bound LPS (determined by use of 131I-BSA blood marker) in animals killed 3--5 hours after injection. The distribution of LPS in rabbits was found to be dose-indpendent and only minimally changed by prior depletion of C3. In addition, the tissue distribution and cellular localization of LPS in monkeys was similar to that we have reported previously for R595 LPS in NC rabbits and was not substantially changed by prior CoF treatment. These results indicate that binding of C3 to intravenously injected LPS is not required for the initial rapid disappearance from blood. Further, the uptake of LPS by cellular targets, notably the hepatic macrophages (Kupffer cells), is not altered by in vivo decomplementation.

Animals↗
PubMed1979

New function for high density lipoproteins. Their participation in intravascular reactions of bacterial lipopolysaccharides.

The addition of bacterial lipopolysaccharide (LPS) from Escherichia coli 0111:B4 or Salmonella minnesota R595 to plasma (or serum) resulted in a marked reduction of the hydrated buoyant density of the parent LPS (0111:B4 [d = 1.44 g/cm3] and R595 [d = 1.38 g/cm3]), to d less than 1.2 g/cm3. This reduction in buoyant density to less than 1.2 g/cm3 of the LPS required plasma (or serum) lipid. Delipidation of plasma (or serum) by extraction with n-butanol/diisopropyl ether (40/60, vol:vol) prevented the conversion of the parent LPS to a form with d less than 1.2 g/cm3. Reversal of the effect of delipidation was accomplished by the addition of physiologic concentrations of high density lipoprotein (HDL). In contrast, as much as two times normal serum concentration of low density or very low density lipoprotein were ineffective. The ability of normal plasma (or serum) to inhibit the pyrogenic activity of LPS, lost after delipidation, was also restored after the addition of HDL. Preliminary results suggested that prior modifications of the LPS, probably disaggregation, may be required before interaction with HDL.

Animals↗
PubMed1978

Two distinct mechanisms for the initiation of mast cell degranulation. II. A specific inhibition of amine release by serum proteins.

Our experiments have provided additional data in support of the concept that different mast cell activators follow distinct biochemical path-ways in the initiation of secretion and degranulation. To do this we have taken advantage of the observation that some serum proteins, and albumins in particular, have the capacity to inhibit selectively the release of amines from rat peritoneal mast cells initiated by some, but not all, stimuli. We show that the relative inhibition of release obtained is independent of the concentration of activator but dependent upon the concentration of albumin, indicating that the inhibitory process does not involve a direct activator--inhibitor interaction. Finally, our data demonstrate that the inhibition does not interfere with the ability of the acitivator to interact with the mast cell. Thus, cells incubated with activator in the presence of inhibitor become increasingly unresponsive, or desensitized, to subsequent challenge with activator in the absence of inhibitor. These combined data therefore provide evidence, that, in addition to a selectivity in the activation/desensitization process initiated by different mast cell stimuli, at least one of the biochemical steps subsequent to the activation step is also not shared by all mast cell stimuli.

Animals↗
PubMed1978

Role of complement in lethal bacterial lipopolysaccharide-induced hypotensive and coagulative changes.

The effect of C3 depletion on the multiple pathophysiological changes produced by a lethal dose of Serratia marcescens lipopolysaccharide (LPS) was evaluated. The injection of this LPS into rabbits resulted in biphasic hypotensive changes and thrombocytopenia. These changes were characterized by an acute, transient decrease occurring within minutes after injection followed by a second more gradual decrease beginning 30 to 60 min post-LPS. Prior depletion of C3, with the anticomplementary protein from cobra venom (CoF), did not alter the extent of either the gradual hypotensive and platelet changes or the coagulative and metabolic changes when normal and C3-depleted rabbits were compared. Importantly, the lethal effects of S. marcescens LPS were not reduced by prior depletion of C3. Only the immediate, reversible thrombocytopenia and hypotension were abrogated by C3 depletion.

Animals↗
PubMed1978

Distribution of endotoxin (lipopolysaccharide) in the tissues of lipopolysaccharide-responsive and -unresponsive mice.

We examined the distribution of bacterial lipopolysaccharide (LPS) in LPS-responsive (C3H/St) and LPS-unresponsive (C3H/HeJ) mice. The results reported here demonstrate that the rates of removal of an immunological or a toxic dose of LPS from the circulation are the same in both strains of mice. C3H/St spleens accumulated significantly more LPS than C3H/HeJ spleens after the intravenous injection of either an immunogenic or a toxic dose of LPS. There was also a greater amount of LPS associated with cells teased from C3H/St spleens compared to those from C3H/HeJ spleens. After a toxic dose of LPS, there was more LPS in C3H/St lymph nodes, adrenals, lungs, kidneys, and heart than in the corresponding C3H/HeJ tissues. The accumulation of more LPS in tissues from C3H/St mice compared to C3H/HeJ mice suggests that these tissues are involved in the pathophysiological and, ultimately, the toxic effects of LPS. The differential accumulation of LPS in the tissues of these two strains may be the reason for the decreased responses of C3H/HeJ mice to LPS.

Animals↗
PubMed1978

The modification of biophysical and endotoxic properties of bacterial lipopolysaccharides by serum.

Normal rabbit serum reduces the buoyant density of lipopolysaccharide (LPS) from Escherichia coli 0111:B4 (d = 1.44 g/cm3) and Salmonella minnesota R595 (d = 1.38 g/cm3) to a value less than g/cm3. This density shift is associated with the inhibition of a number of endotoxic activities of the LPS; namely, the pyrogenic activity, the ability to produce an immediate neutropenia in rabbits, lethality in adrenalectomized mice, and anticomplementary activity. A qualitatively similar change in buoyant density was observed to occur after intravenous injection of the LPS into rabbits. Preliminary evidence suggests that the density shift does not occur as a result of the degradation of the glycolipid backbone of the LPS. These data suggest that the interactions of LPS with plasma (or serum) components leading to reduction in buoyant density may account for a major pathway of LPS detoxification.

Animals↗