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We previously showed that immunization of various strains of mice with three types of antigen--PC-Hy (nominal antigen), F6-Hy (Ab2 alpha-Hy, and 4C11-Hy (Ab2 beta-Hy)--induces a differential PC-specific, T15-Id+ antibody response. In this report, the in vitro phosphorylcholine (PC)-specific B cell responses induced by these three antigens were studied. A hemocyanin-specific long-term T helper cell line was used to provide help for primary and secondary in vitro T cell-dependent B cell responses. At low doses (0.005 to 0.5 micrograms/ml) of antigen, a significant increase in the proliferation of PC-OVA-primed BALB/c B cells was observed with Ab2-Hy or PC-Hy conjugate, but not unconjugate, antigens. Similar low doses of antigen could stimulate naive B cells to secrete IgM and stimulate PC-OVA- or 4C11-Hy-primed B cells to secret IgM and IgG1 anti-PC antibodies. The percentage of T15-Id of the PC-specific antibodies produced in the in vitro T-B culture was found to be less dominant than that produced by in vivo immunization, suggesting that certain regulatory mechanisms occur in the in vivo environment that may help to maintain the T15-Id dominance. Taken together, our in vivo and in vitro results indicate that idiotope antigens can function like nominal antigens to induce antigen-specific B cell responses. The mechanisms of thymic-dependent B cell activation induced by idiotope and nominal antigen are similar in that the T-B interaction is MHC-restricted and requires cognate recognition.

The chemical structure of AMG-1 was isolated during our search for an effective compound to overcome the untoward effects of complete ischemia. The duration of gasping was prolonged significantly and dose-dependently in mice by the administration of AMG-1, the efficacy being 1000 times that seen with adenosine. However, AMG-1 had no effect on ischemia-induced passive avoidance impairment and histopathological degradation in CAl neurons in the hippocampus. The relationship between adenosine and its analogue and cerebral ischemia is discussed.

Two methods for determination of the acoustic nonlinearity parameter B/A in biological media are presented. One is the finite amplitude insert-substitution method (FAIS), considering the influence of both the sound attenuation of samples and the diffraction of the transducer on the experimental measurement. The other is the improved thermodynamic method (ITD), based on the measurement of phase shifts in the acoustic wave due to the change of ambient pressure. The nonlinearity parameter B/A has been measured for various biological solutions and soft tissues using these two methods. Some results of dependence of B/A values on the concentration and temperature are also presented here.

Kinetics of chromium transformations under typical environmental conditions were systematically investigated using batch, microcosm and column experiments. Oxidation and reduction rates were evaluated in single phase water systems and in two phase water-solid systems. Natural and reference waters, sediments and soils representing a broad range of characteristics were used. Some of the investigated reactions, such as the reduction of Cr(VI) by S2- or Fe2+ ions under anaerobic conditions, were instantaneous and the experimental results exactly followed the stoichiometric and equilibrium calculations. Other reactions, such as the reduction of Cr(VI) by organics in sediments and soils, or the oxidation of Cr(III) by MnO2, were much slower and clearly exhibited kinetic controls. Reduction of Cr(VI) by organics was dependent on both the type and amount of organic material. Dissolved oxygen by itself did not induce measurable oxidation of Cr(III), spiked to the experimental waters, after 128 days. Slow Cr(III) oxidation to Cr(VI) was only noted in one of the natural waters and sediments with half-lives ranging from 2 to 9 years. In all cases the extent of Cr(III) oxidation did not exceed 15% of the initial Cr(III) present. The overall results indicate that the transport and transformation of chromium can be predicted using kinetics data derived from a simplified laboratory experiment, the Eh-pH data and the aquatic system characteristics. Results of the microcosm and laboratory experiments were in good agreement with the predicted concentrations.