Failure of methylprednisolone to protect lead-sensitized rats against endotoxin

The influence of low lead doses on the reticulo-endothelial system and leucocytes of mice

The half-life of the indian ink elimination (carbon clearance method) was used as a measure of the RES activity. A significant increase of the RES activity in mice was found already after a single intraperitoneal (i.p.) administration of 20, 50, or 100 micrograms PbAc/kg body weight (b.w.). A significant RES stimulation could also be demonstrated after a single or 10-day oral administration of lead at doses of 10-1,000 micrograms PbAc/kg b.w. No RES stimulation occurred, however, after 30-day oral administration of lead. On determining the reactivity of the RES to 1 microgram endotoxin/kg b.w. it was found that it was already limited after a single and 10-day oral lead administration. After 30-day oral administration of lead (doses 10-1,000 micrograms PbAc/kg b.w.) the reactivity of the RES was completely suppressed. After a single and 10-day oral administration of lead (doses 10-1,000 micrograms PbAc/kg b.w.) we observed a marked leucocytosis. This effect was most clearly seen after a dose of 100 micrograms PbAc/kg b.w.; the leucocyte counts were increased by up to 50% in comparison with controls. After 30-day oral administration of lead, such a leucocytosis was no longer detectable. In accordance with the findings on the RES, the leucocytosis that is normally induced in the animals by 1 microgram endotoxin/kg b.w. was significantly reduced or completely suppressed both after single and also after 10 and 30 days' oral administration of lead at doses of 100 and 1,000 micrograms PbAc/kg b.w. These results show that the resistance state of the mouse is impaired already by low doses of lead.

Potentiation of endotoxin-induced consumptive coagulopathy by lead acetate administration

Since chickens are naturally deficient in several clotting factors normally present in mammalian sera, the ability of lead acetate (PbAc(2)) to sensitize 11-day-old chicks to endotoxin was compared with its ability to sensitize rats. It was found that, although the chicks could tolerate only relatively low doses of PbAc(2), even those doses would produce a greater than 200-fold sensitization to the endotoxin in rats, as compared with little sensitization in the chicks. By using larger doses of PbAc(2), known to maximally sensitize rats to endotoxin, the effect of PbAc(2) sensitization on whole-blood clotting times, platelet counts, plasma factor V and VIII activities, and the appearance of fibrin degradation products was evaluated. It was found that animals treated with lethal doses of endotoxin but no PbAc(2) showed varying degrees of consumptive coagulopathy. On the other hand, the injection of minute quantities of endotoxin into PbAc(2)-sensitized rats invariably resulted in disseminated intravascular coagulation, apparently via a complete activation of the intrinsic pathway. It is concluded that the site of PbAc(2) sensitization to endotoxin is in the blood, and most probably at the level of Hageman factor activation.

Protein fraction with immunogenic potential and low toxicity isolated from the cell wall of Neisseria meningitidis group B

Several fractions were extracted from the cell envelope (CE) of Neisseria meningitidis group B and characterized with regard to their morphology, antigenicity, protein composition, and toxicity. Whole bacterial cells were suspended in a medium of low ionic strength and disrupted in a French pressure cell. The crude CE thus obtained were separated into cell membrane (CM) enriched and cell wall (CW) enriched fractions on sucrose density gradients. In addition, CM and CW fractions were separated from CE on the basis of differential solubility in the nonionic detergent, Triton X-100. The Triton-insoluble fraction, containing primarily CW components, was further treated with a mixture of Triton and ethylenediaminetetraacetic acid, which was shown to remove additional protein and most of the lipopolysaccharide. Electron microscope examination of the various fractions revealed typical unit membrane structures in the case of CM, or large, open segments in the case of CW. The Triton-insoluble and especially the Triton-ethylenediaminetetraacetic acid-insoluble fractions consisted of small vesicular structures. All fractions, except the Triton-soluble fraction, when assayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were shown to contain one major protein component accounting for more than 50% of the total. Sera from rabbits immunized with the various fractions formed precipitin lines in immunodiffusion tests against the homologous and some of the heterologous fractions. High-titer bactericidal antibodies were also demonstrated in these sera when tested against the homologous strains. Toxicity studies in rats sensitized with lead acetate indicate that the level of contamination of Triton-insoluble/Triton-ethylenediaminetetraacetic acid-insoluble fractions with lipopolysaccharide was significantly smaller than that of the other fractions.

Methylprednisolone protection against endotoxin in lead-sensitized mice

Lead-sensitized BALB/c male mice are protected against Escherichia coli endotoxin by the intraperitoneal administration of 6alpha-methylprednisolone. This protection is dependent on time of administration of the methylprednisolone.