Postsynaptic effects of nickel ions at the insect neuromuscular junction

Ionotropic glutamate receptors mediate juvenile hormone synthesis in the cockroach, Diploptera punctata

By monitoring changes in the cytosolic [Ca2+](i) and rates of juvenile hormone (JH) synthesis in response to L-glutamate agonists and antagonists, we identified and characterized glutamate receptor subtypes in corpus allatum (CA) cells of the cockroach, Diploptera punctata. During the first ovarian cycle, corpora allata exhibited a cycle of changes in sensitivity to L-glutamate correlated to cyclic changes in rates of JH synthesis. When exposed to 60 microM L-glutamate in vitro, the active corpora allata of day-4 mated females produced 60% more JH, while inactive corpora allata at other ages showed 10-20% stimulatory response. Pharmacological characterization using various L-glutamate receptor agonists and antagonists indicated that several ionotropic subtypes of L-glutamate receptors were present in the CA. The CA showed an increase in rates of JH synthesis in response to NMDA, kainate, and quisqualate, but not to AMPA in both L-15 medium and minimum incubation medium. In contrast, applications of the metabotropic receptor-specific agonist trans-ACPD failed to elicit a change in the cytosolic [Ca2+](i) and JH production. An elevation of cytosolic calcium concentration, followed by 20-30% rise in JH production, was observed when active CA cells were exposed to 10-40 microM kainate. Kainate had no stimulatory effect on JH synthesis in calcium-free medium. The kainate-induced JH synthesis was blocked by 20 microM CNQX but was not affected by 20 microM NBQX. Kainate-stimulated JH production was not suppressed by MK-801 (a specific blocker of NMDA-receptor channel), nor was NMDA-stimulated JH production affected by CNQX (a specific antagonist of kainate receptor). These data suggest that active CA cells are stimulated to synthesize more JH by a glutamate-induced calcium rise via NMDA-, kainate- and/or quisqualate-sensitive subtypes of ionotropic L-glutamate receptors. The metabotropic-subtype and ionotropic AMPA-subtype L-glutamate receptors are unlikely to be present on active CA cells.

Heavy metal content (Hg2+, Cd2+, Pb2+) in various body parts: its impact on cholinesterase activity and binding glycoproteins in the grasshopper Aiolopus thalassinus adults

Various toxicological symptoms were observed in Aiolopus thalassinus (Fabr.) adults which resulted from either contaminated soil or from being fed HgCl2-, CdCl2-, and PbCl2-treated diet. Many insects had abnormal wings which were present until the F3 untreated generation. Heavy metals were stored in different body parts, most of Cd2+ and Hg2+ were found in the testes, followed by the gut. Lead was enriched in all organs and body parts of the treated grasshoppers compared to the control. The highest lead concentrations were found in testes, wings, gut, and ovaries. In the treated generation ChE activity was reduced to about 23% compared to the untreated grasshoppers. In contrast to this, lead increased ChE activity to about 14%. In the following F2 untreated adults, ChE activity was normal; no long-term effect was found. In the supernatant of treated adults a Cd-type glycoprotein was found which can bind Cd ions; its MW was determined by electrophoresis and reference proteins at about 14,450 Da.