脑磁扫描反应与从自相关和双耳互相关函数中得到的因子的关系

利用脑电磁图示（MEG）的方法对听觉诱发磁场（AEFs）与由自相关系数（ACF）以及由双耳互相关系数（IACF）中导出的因子的关系加以检验．首先，检验ACF，φ1的峰值对AEFs的影响，发现音调的强度与φ1良好相关，而当刺激开始后大约100ms时在左右颞叶上发现的N1m的振幅则随φ1的增加而增大．此结果表明较强声调感的声音导致N1m幅值的增加．此外，对IACC以及τIACC对AEFs的作用也加以检验，发现人类侧向声音定位的能力随IACC的减小而变差．当IACC为0．95时，N1m幅值随τIACC的增加而增加，而当IACC为0．5时，τIACC对N1m幅值的作用不显著．此结果表明侧向声音定位的能力可由N1m的幅值来反映．     

Insect olfactory receptors are heteromeric ligand-gated ion channels

In insects, each olfactory sensory neuron expresses between one and three ligand-binding members of the olfactory receptor (OR) gene family, along with the highly conserved and broadly expressed Or83b co-receptor. The functional insect OR consists of a heteromeric complex of unknown stoichiometry but comprising at least one variable odorant-binding subunit and one constant Or83b family subunit. Insect ORs lack homology to G-protein-coupled chemosensory receptors in vertebrates and possess a distinct seven-transmembrane topology with the amino terminus located intracellularly. Here we provide evidence that heteromeric insect ORs comprise a new class of ligand-activated non-selective cation channels. Heterologous cells expressing silkmoth, fruitfly or mosquito heteromeric OR complexes showed extracellular Ca2+ influx and cation-non-selective ion conductance on stimulation with odorant. Odour-evoked OR currents are independent of known G-protein-coupled second messenger pathways. The fast response kinetics and OR-subunit-dependent K+ ion selectivity of the insect OR complex support the hypothesis that the complex between OR and Or83b itself confers channel activity. Direct evidence for odorant-gated channels was obtained by outside-out patch-clamp recording of Xenopus oocyte and HEK293T cell membranes expressing insect OR complexes. The ligand-gated ion channel formed by an insect OR complex seems to be the basis for a unique strategy that insects have acquired to respond to the olfactory environment.     

Deregulation of a Ca2+/calmodulin-dependent kinase leads to spontaneous nodule development

Induced development of a new plant organ in response to rhizobia is the most prominent manifestation of legume root-nodule symbiosis with nitrogen-fixing bacteria. Here we show that the complex root-nodule organogenic programme can be genetically deregulated to trigger de novo nodule formation in the absence of rhizobia or exogenous rhizobial signals. In an ethylmethane sulphonate-induced snf1 (spontaneous nodule formation) mutant of Lotus japonicus, a single amino-acid replacement in a Ca2+/calmodulin-dependent protein kinase (CCaMK) is sufficient to turn fully differentiated root cortical cells into meristematic founder cells of root nodule primordia. These spontaneous nodules are genuine nodules with an ontogeny similar to that of rhizobial-induced root nodules, corroborating previous physiological studies. Using two receptor-deficient genetic backgrounds we provide evidence for a developmentally integrated spontaneous nodulation process that is independent of lipochitin-oligosaccharide signal perception and oscillations in Ca2+ second messenger levels. Our results reveal a key regulatory position of CCaMK upstream of all components required for cell-cycle activation, and a phenotypically divergent series of mutant alleles demonstrates positive and negative regulation of the process.