Perceptual organization of onsets and offsets of sounds

Several illusory phenomena in auditory perception are accounted for by using the event construction model presented by Nakajima et al. (2000) in order to explain the gap transfer illusion. This model assumes that onsets and offsets of sounds are detected perceptually as if they were independent auditory elements. They are connected to one another according to the proximity principle to constitute auditory events. This model seems to contribute to a general cross-modal theory of perception where the idea of edge integration plays an important role. Potential directions in which we can connect the present paradigm with speech perception are indicated, and possibilities to improve artificial auditory environments are suggested.     

Characterization of 4-O-methyl-ascochlorin-induced apoptosis in comparison with typical apoptotic inducers in human leukemia cell lines

Apoptosis can be induced by various stimuli such as the ligands of death receptors, chemotherapeutic drugs and irradiation. It is generally believed that chemotherapeutic drugs induce mitochondrial damage, cytochrome c release and activation of caspase-9, leading to apoptosis. Here, we found that an isoprenoid antibiotic, 4-O-methyl ascochlorin, significantly induces typical apoptotic events in Jurkat cells including the degradation of poly (ADP-ribose) polymerase, DNA fragmentation, activation of caspase-3, -9 and -8, and cytochrome c release from mitochondria. Similar to Fas stimulation, 4-O-methyl ascochlorin but not staurosporine, cycloheximide and actinomycin D, induced apoptosis in SKW6.4 cells, in which apoptosis is strongly dependent on death-inducing signaling-complex. Bcl-2 overexpression in Jurkat cells completely suppressed the apoptosis, but procaspase-9 processing was partially induced. A caspase-8 inhibitor, IETD-fmk, effectively suppressed poly (ADP-ribose) polymerase cleavage and cytochrome c release. However, 4-O-methyl ascochlorin induced apoptosis in Jurkat cells deficient of caspase-8 or Fas-associated death domain protein. These results suggest that 4-O-methyl ascochlorin induces apoptosis through the mechanism distinct from conventional apoptosis inducers.     

Molecular phylogenetic relationships of Eastern Asian Cyprinidae (Pisces: Cypriniformes) inferred from cytochrome b sequences

Cyprinidae, the largest fish family, comprises ap-proximately 210 recognized genera and 2010 species that are distributed widely in Eurasia, East Indian Is-land, Africa, and North America[1]. Species richness of this family is the greatest in East Asia, for example, China has 122 genera and more than 600 species. It is difficult to build a comprehensive phylogeny of Cy-prinidae due to the large number of genera and species. The classification of this family has been subject to revisions an…     

A new subtilisin family: nucleotide and deduced amino acid sequences of new high-molecular-mass alkaline proteases from<Emphasis Type="Italic"> Bacillus</Emphasis> spp.

Six genes encoding high-molecular-mass subtilisins (HMSs) of alkaliphilic Bacillus spp. were cloned and sequenced. Their open reading frames of 2,394–2,424 bp encoded prosubtilisins of 798–808 amino acids (aa) consisting of the prepropeptides of 151–158 aa and the mature enzymes of 640–656 aa. The deduced aa sequences of the mature enzymes exhibited 60–95% identity to those of FT protease of Bacillus sp. strain KSM-KP43, a subtilisin-like serine protease, and a minor serine protease, Vpr, of Bacillus strains. Three of the six recombinant enzymes were susceptible to proteolysis, but the others were autodigestion resistant. All enzymes had optimal pH values of 10.5–11.0, optimal temperatures of 40–45°C for hydrolysis of a synthetic substrate, and were heat labile. These alkaline proteases seem to form a new subtilisin family, as judged by their aa sequences and phylogenetic analysis.Communicated by K. Horikoshi     

Nucleotide sequence of the p53 cDNA of beluga whale (Delphinapterus leucas)

The cDNA (DNA complementary to RNA) of the p53 gene of the beluga whale (Delphinapterus leucas) was sequenced by the method of 5'- and 3'-rapid amplification of cDNA ends (RACE) with the cDNA made for the RNA obtained from fresh peripheral blood leukocytes isolated from two animals. Primers for the RACE method were synthesized based on the sequence of the DNA of beluga whale corresponding to exon 5 of the human p53 gene, which was determined after amplification of the DNA isolated from the liver from a beluga whale by using a pair of primers for the human sequence. The sequenced cDNA had a 2150-nucleotide length and contained the whole region corresponding to human exons 1 through 11. The reading frame was 1164 bp (base pair) long and began in exon 2 and ended in exon 11, coding for a 387-amino acid protein. The nucleotide sequence of the reading frame showed high similarity over 85% with pig, sheep, cow, and human genes. The similarities with the former two animals at the amino acid level were also more than 85%. Lower similarity of the beluga whale p53 gene was also found with those of lower tetrapods, fish and invertebrates.     

A new polypeptide toxin from the nematocyst venom of an Okinawan sea anemone Phyllodiscus semoni (Japanese name "unbachi-isoginchaku")

The venomous sea anemone Phyllodiscus semoni causes cases of severe stinging. We isolated Phyllodiscus semoni toxin 20A (PsTX-20A), a hemolytic and lethal polypeptide (20 kDa), from the nematocyst venom of this species for the first time. Furthermore, we sequenced the cDNA encoding PsTX-20A. The deduced amino acid sequence of PsTX-20A showed that this toxin was a new member of the actinoporin family, which consists of several cytolytic polypeptides originating from sea anemones. PsTX-20A showed lethal toxicity to the shrimp Palaemon paucidens when administered via intraperitoneal injection (LD50, 50 microg/kg) and hemolytic activity toward 0.8% sheep red blood cells (ED50, 80 ng/ml).     

Cloning and expression of the exo-beta-D-1,3-glucanase gene (exgS) from Aspergillus saitoi

A gene of exo-1,3-beta-D-glucanase (exgS) was cloned from a koji mold, Aspergillus saitoi, genomic DNA using PCR. The exgS has an ORF comprising 2832 bp, which contains one intron of 45 bp, and encodes 945 amino acids. The deduced amino acid sequences showed that the ExgS has a non-homologous linker region consisting of 180 amino acids, which encompassed highly conserved regions observed in Exg homologues from filamentous fungi. A recombinant protein (ExgS) has been recovered from the cultural filtrate of an Aspergillus oryzae strain that carried an expression vector containing full length of the exgS. The N-terminal amino acid sequences of the recombinant exo-1,3-beta-D-glucanase (ExgS) were identical to that of native ExgS from A. saitoi.     

Spatial and temporal aspects of Ca2+ signaling mediated by P2Y receptors in cultured rat hippocampal astrocytes

ATP produces a variety of Ca2+ responses in astrocytes. To address the complex spatio-temporal Ca2+ signals, we analyzed the ATP-evoked increase in intracellular Ca2+ concentration ([Ca2+]i) in cultured rat hippocampal astrocytes using fura-2 or fluo-3 based Ca2+ imaging techniques. ATP at less than 10 nM produced elementary Ca2+ release event "puffs" in a manner independent of extracellular Ca2+. Stimulation with higher ATP concentrations (3 or 10 micro M) resulted in global Ca2+ responses such as intercellular Ca2+ wave. These Ca2+ responses were mainly mediated by metabotropic P2Y receptors. ATP acting on both P2Y1 and P2Y2 receptors produced a transient Ca2+ release by inositol 1,4,5-trisphosphate (InsP3). When cells were stimulated with ATP much longer, the transient [Ca2+]i elevation was followed by sustained Ca2+ entry from the extracellular space. This sustained rise in [Ca2+]i was inhibited by Zn2+ (<10 micro M), an inhibitor of capacitative Ca2+ entry (CCE). CCE induced by cyclopiazonic acid or thapsigargin and Ca2+ entry evoked by ATP share the same pharmacological profile in astrocytes. Taken together, the hierarchical Ca2+ responses to ATP were observed in hippocampal astrocytes, i.e., puffs, global Ca2+ release by InsP3, and CCE in response to depletion of InsP3-sensitive Ca2+ stores. It should be noted that these Ca2+ signals and their modulation by Zn2+ could occur in the hippocampus in situ since both ATP and Zn2+ are rich in the hippocampus and could be released by excitatory stimulation.