Methylmercury: effect on serum enzymes and humoral antibody

Dosages of 20 and 10 ppm methylmercury were toxic to rabbits while 1 ppm did not produce clinical signs or death. Serum alkaline phosphatase levels were elevated in all rabbits exposed to methylmercury. Methylmercury-exposed rabbits challenged to A/PR8 influenza virus had hemagglutination inhibition titers as much as four times lower than those of controls. Histopathologic lesions were found in the cerebellum of rabbits that died. The most significant features of this study were that methylmercury chloride suppressed the humoral immune system and resulted in increased serum alkaline phosphatase levels, which may aid in diagnosis when methylmercury poisoning is suspected.     

High-peak-power room-temperature GaAs laser arrays

The current procedures that are employed in the design and fabrication of high-peak-power room-temperature GaAs laser arrays are presented. The methods of material selection and heat-sink preparation are illustrated. Specific mention is made of the laser-chip packing densities that produce effective laser-array brightness in the 100 kW/cm²region. Actual arrays have been constructed that produce 1 kW peak power with 400 amperes peak of modulator current at 1 kHz, or 600 watts peak at 300 amperes peak at 5 kHz. For modulator-current pulses less than 35 ns, these arrays can be expected to operate for 10¹⁰pulses. For field-lens apertures only a few inches in diameter, beam divergences from these arrays of only a few milliradians can be realized. Data relating the power output as a function of pulsewidth, repetition rate, and modulator current for several array configurations are presented. Differential quantum efficiency and overall power-efficiency data and curves are illustrated for typical diode and array configurations. The schemes employed to select and interface various optical components necessary to produce the desired beam divergences from reasonably sized apertures are discussed. Brief mention is made of the parameters of the laser-junction radiation densities necessary to maximize the array operating lifetime.     

Preliminary characterization and pathogenicity studies of a virus isolated from ticks (Ornithodoros coriaceus) and from tick-exposed cattle

Several viral isolates from ticks (Ornithodoros coriaceus) and from the blood of cattle which aborted after exposure to these ticks were found to be identical by reciprocal cross serum-neutralization tests. Characterization studies indicate that the virus is a member of the Togaviridae family, although specific identification is still incomplete. Whether its natural host is the tick or bovine animals is also unknown. Pregnant cows inoculated with the agent by all conventional parenteral routes, including intrafetal, delivered healthy calves at term. It was concluded, therefore, that it was not a bovine pathogen and that the abortions which occurred after tick-exposure were due to a 2nd agent in O coriaceus ticks which also harbor the virus. While several ciruses believed to be tick-borne have been isolated from cattle in various parts of the world, it is believed that the present report describes the first isolation in the Western Hemisphere for a viral agent from Argasid ticks which has been demonstrated to replicate in cattle.     

Chemical models of oxidative phosphorylation

Chemical models for coupling oxidation to phosphorylation are summarized and examined both from the standpoint of organic reaction mechanisms and with respect to their relevance to mitochondria and chloroplasts. In order to accelerate the progress of our research in bioenergetics, it is suggested to focus at least as much attention on structural biochemistry as on phenomenological observations of energy-transducing membranes.     

Studies of the reactions of anhydrosulphites of α-hydroxy acids,part IX. thermal polymerisation of anhydrosulphites of α-hydroxy α-methyl carboxylic acids

The anhydrosulphites of a series of unsymmetrically substituted α-hydroxy acids have been prepared and their susceptibility to polymerisation by thermal decomposition studied. The first order rate determining ring scission process, leading to the formation of a reactive α-lactone intermediate which then undergoes spontaneous polymerisation, is the predominant mechanism even with substituents up to C₈. As the length of the n-alkyl substituent is increased the rate of decomposition and thus polymerisation increases until a plateau value is reached at around C₃. Further increase in substituent length decreases the rate of decomposition, an effect which is attributed to steric hindrance of the leaving group by long (C₆—C₈) substituents.