Evidence for catecholamine involvement in the suppression of locomotor activity due to hypoxia

Locomotor activity of mice under 12 or 21% oxygen in nitrogen was measured. Under 12% oxygen there was a decrease in locomotor activity which was not reversed by administration of amphetamine; however, administration of a sub-threshold dose of l-dopa in combination with a peripheral decarboxylase inhibitor before the amphetamine restored the locomotor stimulant action of the drug under hypoxia. In contrast to amphetamine, the increase in locomotor activity after the administration of a combination of noradrenaline and dopamine receptor stimulating agents, Clonidine plus apomorphine respectively, was not inhibited by hypoxic conditions. Data suggest an involvement of central catecholamine neurotransmission in the disruption of locomotor activity due to hypoxia.

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.