Axonal site of spike initiation enhances auditory coincidence detection

Neurons initiate spikes in the axon initial segment or at the first node in the axon. However, it is not yet understood how the site of spike initiation affects neuronal activity and function. In nucleus laminaris of birds, neurons behave as coincidence detectors for sound source localization and encode interaural time differences (ITDs) separately at each characteristic frequency (CF). Here we show, in nucleus laminaris of the chick, that the site of spike initiation in the axon is arranged at a distance from the soma, so as to achieve the highest ITD sensitivity at each CF. Na+ channels were not found in the soma of high-CF (2.5-3.3 kHz) and middle-CF (1.0-2.5 kHz) neurons but were clustered within a short segment of the axon separated by 20-50 microm from the soma; in low-CF (0.4-1.0 kHz) neurons they were clustered in a longer stretch of the axon closer to the soma. Thus, neurons initiate spikes at a more remote site as the CF of neurons increases. Consequently, the somatic amplitudes of both orthodromic and antidromic spikes were small in high-CF and middle-CF neurons and were large in low-CF neurons. Computer simulation showed that the geometry of the initiation site was optimized to reduce the threshold of spike generation and to increase the ITD sensitivity at each CF. Especially in high-CF neurons, a distant localization of the spike initiation site improved the ITD sensitivity because of electrical isolation of the initiation site from the soma and dendrites, and because of reduction of Na+-channel inactivation by attenuating the temporal summation of synaptic potentials through the low-pass filtering along the axon.     

Inhibition of angiotensin I converting enzyme and kininase in rabbit plasma by bradykinin potentiating peptide B (Pyr-Gly-Leu-Pro-Arg-Pro-Lys-Ile-Pro-Pro)

Zusammenfassung Das Bradykinin-potenzierende Peptid B (Pyr-Gly-Leu-Pro-Pro-Arg-Pro-Lys-Ile-Pro-Pro) verhindert in vitro und in vivo die Aktivität der Plasmakininase und des «converting»-Enzyms.

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Acknowledgment. The authors wish to thank Dr. H.Kato of Institute for Protein Research, Osaka University, for his kind supply of BPP. Thanks also Dr. S.Sakakibara of Institute for Protein Research, Osaka University, for his kind supply of synthetic angiotensin I and bradykinin.     

Inhibitory effect of bile acids on renin angiotensinogen reaction system

Zusammenfassung Die Wirkung verschiedener synthetischer Derivate der Gallensäure wurden auf die Reninaktivität in Form des Angiotensin in vitro untersucht und es wird darauf hingewiesen, dass die 7-Desoxyform der Gallensäuren für die Renininhibition wesentlich ist.

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The authors wish to thank Dr.T. Hoshita of Department of Biochemistry, Hiroshima University, for his kind supply of cholic acid.     

Stepwise radial complexation of imine groups in phenylazomethine dendrimers

Dendrimers are highly branched organic macromolecules with successive layers or 'generations' of branch units surrounding a central core. Organic-inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. The unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior, which can give rise to an energy gradient that directs the transfer of charge and energy from the dendrimer periphery to its core. Here we show that tin ions, Sn(2+), complex to the imine groups of a spherical polyphenylazomethine dendrimer in a stepwise fashion. This behaviour reflects a gradient in the electron density associated with the imine groups, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed. By attaching an electron-withdrawing group to the dendrimer core, we are able to change the complexation pattern, so that the core imines are complexed last. By further extending this strategy, it should be possible to control the number and location of metal ions incorporated into dendrimer structures, which might find uses as tailored catalysts or building blocks for advanced materials.     

Identification of a disulfide bonded protein from cytoplasm ofBacillus subtilis

Conclusion In this study, P23 was found to be a disulfide-bonded cytoplasmic protein, abundant in late exponential phase and stationary phase cells, and was hardly detected in early exponential phase cells, the cells of sporulation process and spores. Therefore, synthesis of P23 was regulated by some specific factors or/and cellular environment. Conclusively, cytoplasm has a mechanism to catalyze the formation of disulfide bonds, which is consistent with Dermanet al. ’s conclusion from mutation experiment^[1].     

Shadow free texture acquisition of a large scale scene for city modeling

Texture acquisition of a large scale scene is one of the critical research areas in computer vision and can be used in other application areas such as computer graphics (CG), the intelligent transportation system (ITS) and the 3D geographic information system (GIS). Moreover, to acquire texture without noise (e. g. , a shadow, an obstacle body) is vital for such work. Although obstacles can be removed by using 3D geometric data, shadow elimination is still a difficult problem and strongly required for the CG and ITS community, especially for city modeling and simulation purposes. In this paper, we propose an automatic multiple image fusion technique and an efficient and simple shadow removing technique to retrieve high quality texture images of an urban area. The image fusion can be efficiently achieved by epipolar plane image (EPI) analysis, and the shadow elimination can be successfully carried out by an illumination-independent color clustering technique. The strength of this algorithm is that we can successfully fuse multiple images and eliminate shadows from the fused single image, especially in low dynamic range images, which have proven difficult using previous techniques.     

硝化-反硝化生物滤器处理城市污水的启动和运行效果

实验室废水处理反应器处理实际城市污水运行75 d .主要系统为包含两部份的上流式生物滤器.生物滤器上部曝气,用于硝化;下部缺氧,用于反硝化.为了避免自养硝化菌和异养微生物的竞争,采用新式间接启动方法实现硝化仅用时两周.该生物滤器在室温下运行,溶解于水中总有机碳(DOC)的去除率可达到75 %,总固体悬浮物的去除率可达88·5 %,总氨氮和总氮可分别去除94 %和60 %.     

Evolution of genes and genomes on the Drosophila phylogeny

Comparative analysis of multiple genomes in a phylogenetic framework dramatically improves the precision and sensitivity of evolutionary inference, producing more robust results than single-genome analyses can provide. The genomes of 12 Drosophila species, ten of which are presented here for the first time (sechellia, simulans, yakuba, erecta, ananassae, persimilis, willistoni, mojavensis, virilis and grimshawi), illustrate how rates and patterns of sequence divergence across taxa can illuminate evolutionary processes on a genomic scale. These genome sequences augment the formidable genetic tools that have made Drosophila melanogaster a pre-eminent model for animal genetics, and will further catalyse fundamental research on mechanisms of development, cell biology, genetics, disease, neurobiology, behaviour, physiology and evolution. Despite remarkable similarities among these Drosophila species, we identified many putatively non-neutral changes in protein-coding genes, non-coding RNA genes, and cis-regulatory regions. These may prove to underlie differences in the ecology and behaviour of these diverse species.