Inflammatory ascites formation induced by macromolecules in mice and rats.

Different macromolecules were administered intraperitoneally to stimulate formation of protein-rich ascitic fluid in rodents. Stimulatory effect of plant lectins depended on the attachment to cell surface carbohydrates, Canavalia ensiformis (ConA) lectin was used in the majority of experiments. The time course of ConA-induced ascites was divided into an early (up to 4 h) and a late (from 6 h on) phase, with a transitional period between the two. Water and protein accumulation showed parallel time courses: volume of the ascitic fluid peaked at around 3 h, and fibrin threads appeared after 6 h. Viscosity of the ascitic fluid and its supernatant increased with time, reaching maximal fibrinogen concentration at around 16 h. Peritoneal permeability, followed by pleural and pericardial effusions, was elicited only by lectins that form soluble complexes with serum glycoproteins, whereas the effect of serum-precipitating lectins was restricted to the peritoneum. Macromolecules with serial positive charges (e.g., polylysine or polyethyleneimine) enhanced peritoneal permeability by ionic interactions with cell surface molecules. Viscosity of the polycation-induced ascitic fluid did not tend to increase with time and corresponded to the early phase of the ConA-induced ascites. Polyglutamate, a polyanionic macromolecule, inhibited the effect of polycations, but not that of ConA. The most efficient stimulatory macromolecules appear to induce ascites by noncovalent cross-linking of cell surface glycoproteins or glycosaminoglycans or both. A similar mechanism may operate in the maintenance of basal secretion to prevent eventual desiccation. Noncovalent cross-linking appears to be a common denominator of both basal and enhanced permeability.

Failure of oral E. coli O83 lipopolysaccharide to influence intestinal morphology and cell proliferation in rats: short communication.

It is known that bacterial lipopolysaccharide (LPS) is not absorbed from the gastrointestinal tract in significant quantities. However, the question remained whether oral LPS modified the structure or function of the gut. In the present experiment Escherichia coli 083 LPS was administered to growing rats in repeated oral doses of 400 mg/kg body weight (b. w.), every 8 h. After three days of treatment, morphometric and histochemical examinations of the small intestine did not show significant differences between treated and control rats. It is concluded that repeated oral administration of high doses of E. coli 083 LPS had no demonstrable effect on intestinal structure and cell proliferation in a rat model.

Mediation of inflammatory ascites formation induced by macromolecules in mice.

The first 60-min phase of inflammatory ascites formation was studied by intraperitoneally (i.p.) administered macromolecular inducers: yeast cell wall zymosan binds to specific macrophage receptors, polyethyleneimine (PEI) and concanavalin A (ConA), produces non-covalent cross-links on the surface of various cells, while λ-carrageenan may function as a contact activator. Depletion of peritoneal macrophages was performed by overnight pretreatment with diphtheria toxin in transgenic mice, resulting in a significant (p < 0.01) decrease in the induced formation of ascitic fluid. It was shown that induced ascites is mediated partly (PEI, ConA, and carrageenan) or completely (zymosan) by peritoneal macrophages. Inhibition of prostanoid synthesis with indomethacine or of the kallikrein/bradykinin system with aprotinin also produced a significant (p < 0.01) but incomplete inhibition. A slight additivity occurred between the different inhibitory effects. In another series of experiments, the i.p. administration of bradykinin (without a macromolecular inducer) also produced marked ascites, which was not affected by macrophage depletion. The origin of the macrophage-independent part of the induced ascites is best explained by the deformation of the mesothelial cell surface, resulting in signal transfer to the underlying endothelium and the passage of ascitic fluid in the opposite direction. The soluble mediators are represented by prostanoids, bradykinin and other, unidentified agonists.

Effect of intraperitoneally administered plant lectins on leukocyte diapedesis and visceral organ weight in rats and mice.

The effects of intraperitoneally administered plant lectins were examined in rats and mice. Intraperitoneally injected ConA transiently decreased the leukocyte count in the peritoneal cavity, due to the agglutination and attachment of cells to the peritoneal lining. Subsequently the total cell count was increased for hours, exceeding initial values. Peritoneal fluid aspartate transaminase (AST) concentration showed little change during the accumulation of ascitic fluid. The most marked histological alterations were found when wheat germ lectin was injected ip. (WGA, 10 mg/kg, 6 h). Neutrophil granulocytes migrated across the wall of both arterioles and venules, but the response was highly variable among adjacent vessels. The wall of the arterioles may have impeded the migration of neutrophil granulocytes, resulting in their accumulation in the muscular layer. Granulocyte accumulation was also observed in patches under the mesothelium and in other sites of the interstitium. Marked dilatation and thrombosis of a few venules were also observed. Kidney bean lectin (PHA) induced similar but less pronounced changes. The neutrophil diapedesis suggests the release of mediator(s) from mesothelial cells and/or peritoneal white cells. The cytokine-induced neutrophil chemoattractant CINC-1, injected as control, resulted in the diapedesis of predominantly mononuclear cells in the omentum within 40 minutes. In rats ip. injected ConA increased the wet weight of spleen and liver within 6 and 10 h, respectively, but kidney weight did not change. Intravascular clumping of red blood cells, thrombosis and organ weight changes also suggest the absorption of ConA into the circulation. The experiments show that plant lectins, used as models of bacterial lectins, can reproduce some aspects of peritonitis.

Transmission of antibodies from mother to young: Evolutionary strategies in a proteolytic environment.

Transmission of antibody from mother to young is an essential process. Maternal proteins provide both food (if digested) and immune protection (undigested antibody) for the offspring. The processes for transfer changed and diversified during vertebrate evolution, using receptor-dependent and -independent mechanisms pre- and postnatally. Transmission frequently proceeds in a proteolytic environment and different mechanisms evolved for the protection of antibody. The present review focuses on the relationship of acquisition of passive immunity to other physiological processes.

Contribution of the Kallikrein/Kinin System to the Mediation of ConA-Induced Inflammatory Ascites.

Intraperitoneal administration of concanavalin A (ConA, 25 mg/kg b.w.), a cell-binding plant lectin was used for inducing inflammatory ascites, and potential inhibitors were tested in 1 h and 2.5 h experiments, i.e. still before the major influx of leucocytes. At the end of the experiment the peritoneal fluid was collected and measured. The ConA-induced ascites was significantly (p<0.01) and dose-dependently inhibited by icatibant (HOE-140), a synthetic polypeptide antagonist of bradykinin receptors. Aprotinin, a kallikrein inhibitor protein also had significant (p<0.01), but less marked inhibitory effect. L-NAME, an inhibitor of NO synthesis, and atropine methylnitrate, an anticholinergic compound, were ineffective. It is concluded, that the kallikrein/kinin system contributes to the mediation of the ConA-induced ascites by increasing subperitoneal vascular permeability, independent of the eventual vasodilation produced by NO. It is known, that membrane glycoproteins are aggregated by the tetravalent ConA and the resulting distortion of membrane structure may explain the activation of the labile prekallikrein. Complete inhibition of the ConA-induced ascites could not be achieved by aprotinin or icatibant, which indicates the involvement of additional mediators.

Modulation of ConA-induced inflammatory ascites by histamine - short communication.

The early phase of the ConA-induced inflammatory ascites was studied, with special reference to histamine. Concanavalin A (ConA), a cell-surface binding lectin was injected i.p. (25 mg/kg bw) to mice. After 1 h the animals were killed, the ascitic fluid collected and measured. Other agents were injected s.c., 10 min before the ConA-challenge. Exogenous histamine markedly inhibited the ConA-induced ascites. Release of endogenous vasoactive agents from the mast cells by Compound 48/80 had a similar, but slight effect. Cromolyn, a mast cell stabilizing agent, and chloropyramine, a histamine H1 receptor antagonist was ineffective. Although histamine increases endothelial permeability, it did not enhance the formation of ascitic fluid, on the contrary, it inhibited the ConA-induced ascites, presumably due to its known hypotonic effect. It is concluded that ConA-induced ascites is not mediated by mast cell histamine.

Suppression of ConA-induced inflammatory ascites by lipopolysaccharide (LPS) in mice.

The effect of pre-treatment with Escherichia coli O83 lipopolysaccharide (LPS) on concanavalin A-induced ascites was examined. The LPS was injected intraperitoneally (i.p.) in different doses to mice, and then ascites was induced by i.p. administration of concanavalin A (ConA) (25 mg/kg b.w.). After 2.5 h the mice were killed and the ascitic fluid was collected and measured. The LPS produced a marked and dose-dependent inhibition of ConA-induced ascites and the effect of pre-treatment lasted up to almost a week. Complete inhibition could not be achieved. If administered alone, LPS did not produce ascites.It is well known that LPS enhances vascular permeability in several tissues, but the present work shows that peritoneal permeability is not enhanced by this agent. Suppression of ConA-induces ascites may be explained by the hypotonic effect of LPS.