The σ ligand 1,3‐di‐O‐tolylguanidine (DTG) increased basal dynamin and decreased depolarization‐stimulated phosphorylation of the synaptosomal protein synapsin Ib without having direct effects on protein kinases or protein phosphatases. DTG dose‐dependently decreased the basal cytosolic free Ca2+ concentration ([Ca2+]i) and blocked the depolarization‐dependent increases in [Ca2+]i. These effects were inhibited by the σ antagonists rimcazole and BMY14802. The nitric oxide donors sodium nitroprusside (SNP) and 8‐(p‐chlorophenylthio)guanosine‐3′,5′‐cyclic monophosphorothioate decreased basal [Ca2+]i and the KCl‐evoked rise in [Ca2+]i to an extent similar to DTG. SNP, but not DTG, produced a rise in cyclic GMP levels, suggesting that the effect of DTG on [Ca2+]i was not mediated via downstream regulation of cyclic GMP levels. DTG increased 45Ca2+ uptake and efflux under basal conditions and inhibited the 45Ca2+ uptake induced by depolarization with KCl. The KCl‐evoked rise in [Ca2+]i was inhibited by ω‐conotoxin (ω‐CgTx)‐GVIA and ‐MVIIC but not nifedipine and ω‐agatoxin‐IVA. The effect of DTG on decreasing the KCl‐evoked rise in [Ca2+]i was additive with ω‐CgTx‐MVIIC but not with ω‐CgTx‐GVIA. These data suggest that DTG was producing some of its effects on synapsin I and dynamin phosphorylation and intrasynaptosomal Ca2+ levels via inhibition of N‐type Ca2+ channels.

Tyrosine hydroxylase (TOH), the rate‐limiting enzyme in catecholamine biosynthesis, is regulated by phosphorylation. Activation of histaminergic H1 receptors on cultured bovine adrenal chromaffin cells stimulated a rapid increase in TOH phosphorylation (within 5 s) that was sustained for at least 5 min. The initial increase in TOH phosphorylation (up to 1 min) was essentially unchanged by the removal of extracellular Ca2+. In contrast, the H1‐mediated response was abolished by preloading the cells with BAPTA acetoxymethyl ester (50 µM) and significantly reduced by prior exposure to caffeine (10 mM for 10 min) to deplete intracellular Ca2+. Trypticphosphopeptide analysis by HPLC revealed that the H1 response in the presence or absence of extracellular Ca2+ resulted in a major increase in the phosphorylation of Ser19 with smaller increases in that of Ser40 and Ser31. In contrast, although a brief stimulation with nicotine (30 µM for 60 s) also resulted in a major increase in Ser19 phosphorylation, this response was abolished in the absence of extracellular Ca2+. These data indicate that the mobilization of intracellular Ca2+ plays a crucial role in supporting H1‐mediated TOH phosphorylation and may thus have a potentially important role in regulating catecholamine synthesis.

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The effect on the concentrations of specific serum proteins and tumour markers, of heat-treating samples at 56°C for 30 min to inactivate HIV, was investigated. Statistically significant decreases, that may affect clinical decisions, were observed for α-1-antitrypsin, β-2-microglobulin, IgE, fibrinogen, C***1-esterase inhibitor and CA125. Statistical, but not clinically significant, changes were observed for α-1-acid glycoprotein, C3, haptoglobin, IgA, IgG, IgM and transferrin. A significant decrease in the α-1 band was observed on protein electrophoresis.