Reaction of endotoxin and surfactants. I. Physical and biological properties of endotoxin treated with sodium deoxycholate

Ribi, E. (Rocky Mountain Laboratory, Hamilton, Mont.), R. L. Anacker, R. Brown, W. T. Haskins, B. Malmgren, K. C. Milner, and J. A. Rudbach. Reaction of endotoxin and surfactants. I. Physical and biological properties of endotoxin treated with sodium desoxycholate. J. Bacteriol. 92:1493-1509. 1966.-Endotoxins from three species of gram-negative bacteria were shown to be dissociated by the bile salt sodium deoxycholate (NaD) into nontoxic subunits with molecular weights of about 20,000. When the bile salt was removed by dialysis, the subunits reaggregated in an orderly manner to form a relatively uniform population of biologically active endotoxin particles with average molecular weights of 500,000 to 1,000,000. If a small amount of human plasma was added to the dissociated endotoxin before removal of the NaD, reassociation apparently did not occur and the preparation remained nonpyrogenic. However, the plasma protein could subsequently be removed from the endotoxin subunits, and reaggregation to the toxic form would then occur. The studies on the physical nature of endotoxin performed with biophysical solution techniques were supplemented and confirmed by direct examination of the endotoxin polymers by electron microscopy. The results of these studies were consonant with the theory that the biologically active endotoxic elements are composed of micellar aggregates of linear lipopolysaccharide subunits.

Visual search with meaningful and non-meaningful material

Two experiments are reported which attempt to assess the effects of variations in target word, context items and instructions on performance in a visual search task. In Experiment 1, subjects were required to search through context lists of three-letter nonsense syllables (of either high or low association value) for three-letter meaningful target words (of either high or low frequency). They were given either “positive” or “negative” instructions, i.e. were told either to pick out the meaningful word or to pick out the word which was not a nonsense syllable. The results showed that visual search times were significantly influenced by both frequency of target word and association value of context items. A significant interaction was observed between type of instructions and target word frequency. The design of Experiment 2 followed that of Experiment 1, with the exceptions that nonsense syllables now became target items, and meaningful words formed the contexts. Again, nonsense syllable association value and word frequency were found to be critical in determining visual search times.

Polypeptide antibiotic 4205 from a soil bacillus

Antibiotic complex 4205, a basic polypeptide, was isolated from a nonsporulating bacillus. It was separated into two components, A and B, each composed of 2,4-diaminobutyric acid, isoleucine, leucine, phenylalanine, serine, and valine, but in different proportions, namely, 4:1:2:1:1:1 and 5:1:3:1:2:2, respectively. There was also an ether-soluble moiety in each that had the characteristics of a fatty acid. This antibiotic differed chemically from other known antibiotics. Both A and B were effective against gram-positive and gram-negative bacteria, cytotoxic for various tissue cell lines, highly toxic for mice by intraperitoneal injection, and toxic for chick embryos by the amniotic and allantoic routes, but not by yolk-sac inoculation. Antibiotic, in amounts sublethal by the allantoic route, inhibited the multiplication of 10 to 100 minimal infective doses of influenza type A, PR8, in embryonated eggs.

AN ARTHROPLASTY OF THE ELBOW

Images