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At least 19 recordsLinked to original sources
PubMed1960

A method for titrating endotoxic activity in the skin of rabbits.

The primary inflammatory response of rabbits to intradermal injection of bacterial products has been used as the basis of a sensitive assay for endotoxins. Injection of materials into the skin of the lateral surfaces, rather than the ventral surface of the abdomen, was essential. The method was evaluated by comparison with the mouse toxicity test. Statistical examination revealed an excellent correlation between the mean threshold dose for producing skin lesions in rabbits (SLD(50)) and the median lethal dose for mice (LD(50)). For potent endotoxins (LD(50) = 0.2-0.3 mg.) the skin test dose was about one-thousandth of the lethal dose for mice. Thereafter the LD(50) increased in the proportion of about 0.3 mg. per 1 microg. increase in SLD(50). The method of testing was devised for endotoxins prepared in various ways from Salmonella enteritidis and S. typhosa but was directly applicable to endotoxins from several other species of enteric Gram-negative bacteria.

Animals↗
PubMed1961

Preparation and host-reactive properties of endotoxin with low content of nitrogen and lipid.

Endotoxins of low lipid content prepared from S. enteritidis by the aqueous ether method have been further treated to remove bound lipid by non-hydrolytic procedures. Such endotoxins, containing as little as 2 per cent lipid A, were as potent in stimulating a variety of physiological responses as those prepared by the well known phenol-water or Boivin procedures which yield products containing as much as 30 per cent lipid A. To verify the difference in lipid content between the aqueous ether preparations and other types of endotoxins, three different methods of lipid analysis were employed: determination of chloroform-soluble material released by hydrolysis with hydrochloric acid (lipid A) or with acetic acid (lipid W), and estimation of total bound fatty acids. These methods were in accord in showing the magnitude of the difference. No more than one-half of the fatty acids present in endotoxin were associated with the fraction designated lipid A. Methods are described for the preparation of potent endotoxins with analytical values for nitrogen, phosphorus, hexosamine, carbohydrate, and fatty acid which do not differ appreciably from those of the classical, non-toxic, haptenic polysaccharides.

Antitoxins↗
PubMed1961

Biological properties of parent endotoxins and lipoid fractions, with a kinetic study of acid-hydrolyzed endotoxin.

The biological potencies of a number of lipid fractions separated from endotoxins by acid hydrolysis, including the material known as lipid A, were determined in parallel with those of their parent endotoxins, employing bio-assays based on the following dose-related host responses: fever, resistance to infection, tumor damage, primary inflammation of skin, and lethality. Without exception, lipid fractions dispersed by detergents exerted less than 1 per cent of the biological activity of the potent endotoxins from which they were derived. A study was made of the rate at which biologic activities diminished in relation to the release of bound lipid during progressive hydrolysis of Salmonella enteritidis endotoxin with dilute acid. Each of the five assays for endotoxin revealed that biological activity had been reduced to negligible proportions prior to any significant liberation from the endotoxin of water-insoluble firmly bound lipid. The major pharmacological activity of endotoxins, therefore, is acid-labile and cannot be accounted for in isolated lipids. This conclusion is also supported by the finding that lipids with activity similar to that of lipid A could be obtained by non-hydrolytic methods without diminishing the potency of the parent endotoxins.

Antitoxins↗