Pharmacological studies of a new analgesic, dl-erythro-1-phenyl-2-(o-chlorophenyl)-2-[4-(p-methoxybenzyl)-1-piperazinyl] ethanol dihydrochloride, in experimental animals.

dl-Erythro-1-phenyl-2-(o-chlorophenyl)-2-[4-(p-methoxybenzyl)-1-piperazinyl] ethanol dihydrochloride showed orally a definite analgesic activity, without producing the significant morphine-like physical dependence liability, and its analgesic potency was about a half that of codeine and far superior to aminopyrine in experimental animals.     

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.     

Further evidence for the dissociation of digoxin-like immunoreactivity from Na+, K+-ATPase inhibitory activity

Summary The effects of adrenalectomy or nephrectomy, carried out one hour previously, on the levels of endogenous digitalis-like factors were determined in rat plasma. Factors were assayed by digoxin-like immunoreactivity and direct Na⁺, K⁺-ATPase inhibitory activity. Digoxin-like immunoreactivity significantly decreased one hour after bilateral ablation of adrenals, while Na⁺, K⁺-ATPase inhibitory activity remained unaltered. There were no changes in either activity one hour after bilateral nephrectomy. These results suggest that digoxin-like immunoreactivity may be derived from the adrenal gland or under adrenal control and the major substances detected by digoxin-like immunoreactivity and direct Na⁺, K⁺-ATPase inhibitory activity may be different.     

Crystal structure of the human centromeric nucleosome containing CENP-A

In eukaryotes, accurate chromosome segregation during mitosis and meiosis is coordinated by kinetochores, which are unique chromosomal sites for microtubule attachment. Centromeres specify the kinetochore formation sites on individual chromosomes, and are epigenetically marked by the assembly of nucleosomes containing the centromere-specific histone H3 variant, CENP-A. Although the underlying mechanism is unclear, centromere inheritance is probably dictated by the architecture of the centromeric nucleosome. Here we report the crystal structure of the human centromeric nucleosome containing CENP-A and its cognate α-satellite DNA derivative (147 base pairs). In the human CENP-A nucleosome, the DNA is wrapped around the histone octamer, consisting of two each of histones H2A, H2B, H4 and CENP-A, in a left-handed orientation. However, unlike the canonical H3 nucleosome, only the central 121 base pairs of the DNA are visible. The thirteen base pairs from both ends of the DNA are invisible in the crystal structure, and the αN helix of CENP-A is shorter than that of H3, which is known to be important for the orientation of the DNA ends in the canonical H3 nucleosome. A structural comparison of the CENP-A and H3 nucleosomes revealed that CENP-A contains two extra amino acid residues (Arg?80 and Gly?81) in the loop 1 region, which is completely exposed to the solvent. Mutations of the CENP-A loop 1 residues reduced CENP-A retention at the centromeres in human cells. Therefore, the CENP-A loop 1 may function in stabilizing the centromeric chromatin containing CENP-A, possibly by providing a binding site for trans-acting factors. The structure provides the first atomic-resolution picture of the centromere-specific nucleosome.     

Timing of action of sperm proteases in ascidian fertilization

Summary The timing of action of three sperm proteases, acrosin, spermosin, and a chymotrypsin-like enzyme, in the fertilization of the ascidian,Halocynthia roretzi, was examined by adding specific protease inhibitors at various times after insemination. The results indicate that the last two enzymes both function at the early stage of the process of sperm penetration through the egg investment, while acrosin functions at the late stage.Acknowledgments. We are indebted to Dr M. Hoshi of Tokyo Institute of Technology for his helpful discussion, and to Dr T. Someno of Nippon Kayaku Kogyo Co. for his generous gifts of Z-Val-Pro-Arg-H and leupeptin. This work was supported by Grants-in-Aid from the Ministry of Education, Science and Culture of Japan, and from Naito Research Foundation.     

Observations on calcareous corpuscles using a scanning electron microscope

Summary Calcareous corpuscles were observed in a scanning electron microscope, and the presence of Ca was examined by means of elemental X-ray analysis.     

Ascidian sperm chymotrypsin-like enzyme; participation in fertilization

The action of a chymotrypsin-like enzyme from sperm extract from the ascidian Halocynthia roretzi was studied using several substrates. It was found that the most susceptible substrate had the most powerful inhibitory effect on fertilization in this animal. Among the substrates, the order of susceptibility coincided with the order of inhibitory ability, which indicates that the enzyme is involved in the fertilization process.     

Bayesian image superresolution and hidden variable modeling

<正> Superresolution is an image processing technique that estimates an original high-resolutionimage from its low-resolution and degraded observations.In superresolution tasks,there have beenproblems regarding the computational cost for the estimation of high-dimensional variables.Theseproblems are now being overcome by the recent development of fast computers and the developmentof powerful computational techniques such as variational Bayesian approximation.This paper reviewsa Bayesian treatment of the superresolution problem and presents its extensions based on hierarchicalmodeling by employing hidden variables.     

Structural basis for recognition of acidic-cluster dileucine sequence by GGA1

GGAs (Golgi-localizing, gamma-adaptin ear homology domain, ARF-interacting proteins) are critical for the transport of soluble proteins from the trans-Golgi network (TGN) to endosomes/lysosomes by means of interactions with TGN-sorting receptors, ADP-ribosylation factor (ARF), and clathrin. The amino-terminal VHS domains of GGAs form complexes with the cytoplasmic domains of sorting receptors by recognizing acidic-cluster dileucine (ACLL) sequences. Here we report the X-ray structure of the GGA1 VHS domain alone, and in complex with the carboxy-terminal peptide of cation-independent mannose 6-phosphate receptor containing an ACLL sequence. The VHS domain forms a super helix with eight alpha-helices, similar to the VHS domains of TOM1 and Hrs. Unidirectional movements of helices alpha6 and alpha8, and some of their side chains, create a set of electrostatic and hydrophobic interactions for correct recognition of the ACLL peptide. This recognition mechanism provides the basis for regulation of protein transport from the TGN to endosomes/lysosomes, which is shared by sortilin and low-density lipoprotein receptor-related protein.