°13C shift referred to TMS.respectively.33 The effect of self-association is probably negligible, since the concentration of the solute is low (1 mol %) in polar solvents. Then it is found that the 14N shifts of imidazole in acetone and DMSO (proton acceptors) are shifted downfield with respect to methanol, water, and trifluoroacetic acid (proton donors). The difference of 14N shifts is 6-9 ppm over the range of the experimental error.Similarly upfield 14N shifts of 6 ± 3 ppm and 7.4 ± 3-9.8 ± 5 ppm are observed in pyrazole and 1,2,4-triazole, respectively. These values are recognized as about half of the corresponding values for A-methyl derivatives, taking into account the argument described above.Sometimes difficulty arises in observing 14N shifts in protonated species, because a longer correlation time due to protonation tends to broaden nmr lines and make the two-and three-bond N-H couplings unobservable. Protonation shifts on imidazole and thiazole are obtained by the decoupling of one-bond N-H couplings. The upfield 14N shifts are 41 ± 3 ppm and 123.1 ± 3 (34) H.

No abstract

The binding of concanavqlin A to T but not B mouse spleen lymphocytes increases Ca-2+ uptake in these cells which is measurable by 45 s and complete by 1 min. Dibutyrl cyclic AMP, but not sodium azide inhibits induced Ca-2+ uptake, wheras dibutyryl cyclic GMP enhances it. B cell mitogens do not cause a similar Ca-2+ uptake in mouse B lymphocytes. The induction of increased Ca-2+ uptake by T cells is discussed in terms of gated membrane channels for Ca-2+.

Since decompression from depth is known to produce a fall in platelet count, the effect of altitude decompression and high-altitude exposure on platelets was investigated. Sixteen subjects decompressed without hypoxia to 20,000 ft simulated altitude for two hours showed a significant (P less than 0.01) drop in circulating platelet count of approximately 10% for three days following decompression. Four of five subjects similarly exposed had a shortened autologous platelet survival compared to that prior to exposure. Subjects exposed to 9,800 ft and then 17,600 ft in a mountain environment showed a significant mean decrease in platelet count on day 2 of 7% and 25% respectively, which had returned to control by day 5. Nonhypoxic and hypoxic decompressed rabbits which received homologous chromium-51-labeled platelets had an increase in lung radioactivity compared with sea-level controls. It is postulated that altitude decompression produces platelet reductions similar to these seen after decompression from depth, and that platelets sequester in the pulmonary vascular bed.

and antibodies directed against p-azobenzenephosphonate was shown not to be due to any possible conformational changes caused by modification of amino groups outside of the antibody combining sites since loss of sites could be prevented completely by the presence of hapten during maleylation, and since the modification of all the amino groups in antibodies prepared against a neutral hapten (3-azopyridine) and against a positively charged hapten (p-azophenyltrimethylammonium) resulted in no change in either their number of antibody combining sites or their average binding constants. These results establish the presence of two kinds of chemically different combining sites in antibodies against negatively charged haptens, those containing an amino group and those that do not. In addition they establish the absence of amino groups in the combining sites of antibodies prepared against a positively charged and a neutral hapten.for amino groups. Maleic anhydride modifies essentially all of the amino groups present in protein molecules, and can be easily removed by acid hydrolysis.This report describes the effect on antibody combining sites following chemical modification of all of the free amino groups in antibody molecules by maleic anhydride under mild conditions. The results demonstrate the direct involvement, in varying amounts, of amino groups in the combining sites of antibodies prepared against certain negatively charged haptens (p-azobenzenearsonate, p-azobenzenephosphonate, and p-azobenzoate), and the absence of amino groups in the combining sites of antibodies prepared against a positively charged (p-azophenyltrimethylammonium) and a neutral (3-azopyridine) hapten. Materials and MethodsBuffers. The buffers used in this study included: Tris buffer (pH 8.0) (0.1 m Tris-HCl, 0.002 m EDTA), Tris-NaCl buffer (pH 8.0) (0.02 m Tris-HCl, 0.15 m NaCl, 0.002 m EDTA), and borate buffer (pH 9.0) 1941