Lipopolysaccharides (LPS) of gram-negative bacilli are known to protect mice against unrelated bacterial infections and to be nonspecific mitogens of murine bone marrow-derived (B-) lymphocytes. For ...assessment of the role of these cells in the mechanism of LPS-induced resistance to infection with Klebsiella, various nontoxic mitogens were assayed. In contrast to LPS or lipid A, the nontoxic mitogens did not protect mice. Experiments were also performed with LPS in nude mice and in mice treated with immunosuppressants. Stimulation by LPS was decreased after administration of hydrocortisone or cyclophosphamide under conditions that inhibited the in vitro activation of lymphocytes by mitogens. Moreover, nude mice and mice treated with 6-mercaptopurine were more resistant to Klebsiella than were control mice.
Following administration of anti-digoxin Fab fragments, monitoring unbound digoxin concentrations may help ensure appropriate dosing, and prevent recrudescent toxicity. Ultrafiltration by using ...Centrifree system and measurement of digoxin in the ultrafiltrate is considered as reference technique. However, ultrafiltration method is cumbersome, costly, and some immunoassays are affected by matrix differences. Another approach is to analyse the serum directly by digoxin immunoassays without ultrafiltering it. The validity of results obtained depends on the architecture of the immunoassay and the amount of Fab in the sample. The old radioimmunoassays and usually the other competitive immunoassays give inaccurate results. The fluorescence polarization immunoassay (FPIA) slightly underestimates the total digoxin concentrations. Total digoxin levels obtained at 24 hours and 48 hours after treatment permit measurement of the half-life of digoxin Fab complexes and can be used to estimate when the patient can be redigitalized, if necessary. The sequential immunoassays usually overestimate the free digoxin concentrations. The differences observed are >25% and cannot be explained solely by albumin binding (normal range, 20% +/- 5%). To date, ultrafiltration remains the best strategy for accurate determination of digoxin concentrations in the presence of antidigoxin Fab fragments.
Le tabagisme peut être dépisté en dosant les métabolites urinaires de la nicotine. Les performances des immunodosages EIA Microgenics et Immulite 2000 DPC ont été évaluées comparativement à la ...colorimétrie. La précision des immunodosages a été satisfaisante avec une répétabilité (coefficients de variation) de 10,2 à 3,8 % avec des étalons de 100 à 500 μg/L (EIA) et de 8,7 à 9,3 % avec des étalons de 50 à 500 μg/L (Immulite 2000). L’étude clinique a été réalisée à partir de prélèvements urinaires de 61 volontaires sains (39 fumeurs et 22 non fumeurs). Pour un seuil de positivité choisi pour donner une spécificité de 100 %, les sensibilités ont été de 97,4 % pour l’EIA (seuil de positivité : 100 μg/L), 100 % pour l’immulite 2000 (seuil de positivité : 100 μg/L) et de 92,3 % pour la colorimétrie (seuil de positivité : 1000 μg/L). Le dépistage du tabagisme a été également réalisé sur 154 urines de transplantés cardiaques. La spécificité des immunodosages a été plus élevée que celle de la colorimétrie. En conclusion, les immunodosages EIA et Immulite 2000 sont des techniques fiables pour dépister les fumeurs.
Smoking can be detected by the determination of nicotine metabolites in urine. The performances of EIA Microgenics and Immulite 2000 DPC immunossays were evaluated in comparison with the colorimetric method. The precision of immuno-assays was satisfactory with an intra-assay precision coefficients of variation from 10.2 to 3.8% using calibrators ranging from 100 to 500 μg/L (EIA) and, from 8.7 to 9.3% using calibrators from 50 to 500 μg/L (Immulite 2000). The clinical comparison was done using urine specimens from 61 healthy volunteers (39 smokers and 22 non smokers). At cut-off levels chosen to yield a specificity of 100%, the sensibilities were 97.4% for EIA (cut-off: 100 μg/L), 100% for Immulite 2000 (cut-off: 100 μg/L) and, 92.3% for colorimetric method (cut-off: 1000 μg/L). Smoking status were also determined in 154 urines from heart transplant recipients. The specificity of immuno-assays was higher than that of colorimetric method. In conclusion, immuno-assays EIA and Immulite 2000 were reliable techniques to determine smoking status.
Gram-negative vaccines can elicit the production of tumor necrosis factor (TNF) in mice primed by muramyl dipeptide (MDP) or by its lipophilic derivative MDP-dipalmitoyl glycerol (MDP-GDP). In mice ...pretreated with MDP and particularly with MDP-GDP, Bordetella pertussis vaccine was shown to be more effective than typhoid vaccine. The time course of TNF production in the blood did not indicate any difference between the effect of MDP or of MDP-GDP. In both cases the cytotoxic activity reached maximal levels by 2 h after injection of the bacterial preparations and returned to normal values between 3 and 5 h after the challenge. In nude mice, high titers of circulating TNF were also produced by combined treatment with MDP-GDP and bacterial vaccine. Moreover, in tumor-bearing mice the association of MDP or of MDP-GDP to a bacterial vaccine induced a strong hemorrhagic necrosis, whereas each treatment alone was inactive. It was also found that mice were less sick when they were primed with MDP-GDP than with MDP, and when TNF was elicited by B. pertussis instead of lipopolysaccharide. Moreover, nude mice appeared more resistant to shock and to hemoconcentration than normal mice.
The metabolic fate in mice of two 14C labelled meso-A2pm containing muramyl-peptides, the muramyl-tripeptide (Ac-Mur-L-Ala-gamma-D-Glu-14C-meso-A2pm) (MTP) and the muramyl-pentapeptide ...(Ac-Mur-L-Ala-gamma-D-Glu-meso-A2pm-14C-D-Ala-14C-D-Ala) (MPP) has been studied. As with 14C-MDP, the radioactive muramyl-tripeptide and muramyl-pentapeptide disappear rapidly from the organs and the radioactivity is found mainly in the urine. In contrast to MDP, the two meso-A2pm containing muramyl-peptides are not excreted intact in the urine. In both cases labelled fragments have been identifed: meso-A2pm from MTP and the tetrapeptide gamma-D-Glu-meso-A2pm-D-Ala-D-Ala from MPP. The ability of the two muramyl-peptides to increase nonspecific resistance of mice to Klebsiella infection was also investigated. The muramyl-pentapeptide injected i.v. one day before a lethal dose of K. pneumoniae protects both adult and neonate mice, as does MDP itself; the muramyl-tripeptide is inactive.
A selective inhibition of LPS-induced tumor necrosis factor-alpha (TNF) response in mice was caused by an injection of recombinant human interleukin-1 (IL-1). The decrease in serum TNF level reached ...70 to 80 percent of the controls receiving LPS alone when IL-1 was given simultaneously or prior to the challenge. At the same time serum IL-6 release was more elevated. Ex vivo assays have shown that macrophages from IL-1 treated animals did not respond to LPS when stimulated immediately after harvesting but recovered their normal responsiveness after being cultured for 2 hours and then washed. In vitro with or without addition of IL-1, mouse elicited macrophages responded equally to LPS in releasing TNF. In the absence of a direct and lasting effect on TNF-producing cells, the host reaction responsible for the inhibitory effect of IL-1 could be related to the overproduction of corticosterone that occurred after IL-1 injection, since it was not observed in adrenalectomized animals. Indeed the blockade of corticoid secretion by indomethacin prevented the inhibition of TNF production induced by IL-1 administration before LPS challenge. TNF administration did not result in elevation of corticosterone level and in contrast to IL-1 enhanced the TNF response to LPS injection. In vitro and ex vivo assays have shown this enhanced response to LPS was linked to a direct and prolonged effect of TNF on TNF-producing cells. Muramyl dipeptide (MDP) which was used as a known priming agent for enhanced cytokine release had a similar effect on TNF-producing cells.
The nature of cellular factors in host response to endotoxin was determined by studying various phases of reactivity to endotoxin in splenectomized and sham operated mice. Spleen ablation by itself ...actually increased the resistance of animals to endotoxin lethality and the absence of spleen did not interfere with either the development or expression of tolerance to the lethal effects of the toxin. The clearance rates of carbon and of endotoxin were normal after splenectomy and increased in conjunction with RES activation associated with endotoxin tolerance, both in sham operated and the splenectomized animals. From these results, it is concluded that subtle and specific adaptations of hepatic RE elements and/or critical metabolic functions play a determining role in endotoxicosis. Furthermore, the presence of spleen does not seem to be required for opsonization, phagocytosis and removal of either nonspecific, inert colloidal particles such as carbon, or of biological materials such as endotoxin. Pertinence of these findings to splenectomized patients is indicated.
New analogues of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) have been synthesized in which the D-isoglutaminyl residue has been replaced by D-glutamine alkyl esters. They are all adjuvant active; ...however, their intravenous injection does not induce a febrile response in rabbits at a dose of 10 mg/kg, in contrast to MDP in which the minimal pyrogenic dose is 25 mu g/kg.
