Haemolytic disease of the newborn caused by anti-Lan antibody

The first recorded example of anti-Lan associated with haemolytic disease of the newborn is reported. This emphasizes the importance of screening for atypical antibodies early in pregnancy, even though prophylactic use of anti-D immunoglobulin will eventually reduce the incidence of haemolytic disease due to anti-D antibody.

Studies on the mode of action of diphtheria toxin. VII. Toxin-stimulated hydrolysis of nicotinamide adenine dinucleotide in mammalian cell extracts

When diphtheria toxin and NAD are added to soluble fractions containing aminoacyl transfer enzymes isolated from rabbit reticulocytes or from HeLa cells, free nicotinamide is released and, simultaneously, an inactive ADP ribose derivative of transferase II is formed. The reaction is reversible, and in the presence of excess nicotinamide, toxin catalyzes the restoration of aminoacyl transfer activity in intoxicated preparations. In living cultures of HeLa cells, the internal NAD concentration is sufficiently high to account for the rapid conversion, catalyzed by a few toxin molecules located in the cell membrane, of the entire cell content of free transferase II to its inactive ADP ribose derivative. Completely inactive ammonium sulfate fractions containing soluble proteins isolated from cells that have been exposed for several hours to excess toxin, can be reactivated to full aminoacyl transfer activity by addition of nicotinamide together with diphtheria toxin. Transferase II appears to be a highly specific substrate for the toxin-stimulated splitting of NAD and thus far no other protein acceptor for the ADP ribose moiety has been found.

Studies on the mode of action of diphtheria toxin. VI. Site of the action of toxin in living cells

Using the technique of radioautography, it has been shown that a probable maximum of only 25-50 molecules iodine-125-labeled toxin per cell is bound by human HeLa cells treated with approximately 10(7) molecules of toxin per cell, or just under one saturating dose. Radioautographs of sections from labeled cells locate most if not all of the toxin molecules fixed to the outer cell membrane. Under identical conditions far less label is taken up by mouse L cells. It is probable that the resistance of this species to diphtheria toxin can be accounted for in terms of the failure of mouse cells to bind the toxin protein. The irreversible inhibition of protein synthesis in a living cell culture by a few molecules of toxin located at the cell surface is discussed in relation to the known interaction between toxin, NAD, and transferase II in mammalian cell extracts.

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.