Chemo-Mechanical Coupling in F1-ATPase Revealed by Catalytic Site Occupancy during Catalysis

F₁-ATPase is a rotary molecular motor in which the central γ subunit rotates inside a cylinder made of α₃β₃ subunits. To clarify how ATP hydrolysis in three catalytic sites cooperate to drive rotation, we measured the site occupancy, the number of catalytic sites occupied by a nucleotide, while assessing the hydrolysis activity under identical conditions. The results show hitherto unsettled timings of ADP and phosphate releases: starting with ATP binding to a catalytic site at an ATP-waiting γ angle defined as 0°, phosphate is released at ∼200°, and ADP is released during quick rotation between 240° and 320° that is initiated by binding of a third ATP. The site occupancy remains two except for a brief moment after the ATP binding, but the third vacant site can bind a medium nucleotide weakly.     

Tissue tracking imaging for identifying the origin of idiopathic ventricular arrhythmias: a new role of cardiac ultrasound in electrophysiology

Several strategies for mapping ventricular outflow tract tachycardia have been reported as useful indices for differentiating between those originating from the right and the left side. Recently, tissue tracking imaging (TTI) has been demonstrated as a novel non-invasive modality for identifying the origin of outflow tract tachycardias. Tissue tracking imaging is an ultrasonographic technique that measures the myocardial motion amplitude towards the transducer in each region during systole, identifying regional myocardial displacement on the basis of myocardial velocities using color Doppler myocardial imaging principles. In this technique, the origin of the arrhythmia could be recognized as the site where the earliest color-coded signal (ECCS) appeared on the myocardium at the onset of the systole. In preliminary studies this modality was found to be useful in differentiating outflow tract ventricular tachycardias. ECCS was always found below or at the level of the pulmonary valve in all arrhythmias which could be ablated from the right ventricular outflow tract, while in those where the ECCS was above and close to the pulmonary valve it could be ablated from the left sinus of valsalva. These results indicate that TTI can provide detailed and accurate information on the arrhythmia origin of outflow tract tachycardia and may be useful for differentiating between an outflow tract tachycardia originating from the LV epicardium remote from the LSV and that from the LSV. Newer advances in echocardiographic technologies like high resolution, high frame rate real time three dimensional echocardiography with speckle tracking may further improve the precise localization of arrhythmias in the future.     

Arabidopsis Aux/IAA genes are involved in brassinosteroid-mediated growth responses in a manner dependent on organ type

We examined whether auxin/indole-3-acetic acid (Aux/IAA) proteins, which are key players in auxin-signal transduction, are involved in brassinosteroid (BR) responses. iaa7/axr2-1 and iaa17/axr3-3 mutants showed aberrant BR sensitivity and aberrant BR-induced gene expression in an organ-dependent manner. Two auxin inhibitors were tested in terms of BR responses. Yokonolide B inhibited BR responses, whereas p-chlorophenoxyisobutyric acid did not inhibit BR responses. DNA microarray analysis revealed that 108 genes were up-regulated, while only eight genes were down-regulated in iaa7. Among the genes that were up- or down-regulated in axr2, 22% were brassinolide-inducible genes, 20% were auxin-inducible genes, and the majority were sensitive neither to BR nor to auxin. An inhibitor of BR biosynthesis, brassinazole, inhibited auxin induction of the DR5-GUS gene, which consists of a synthetic auxin-response element, a minimum promoter, and a beta-glucuronidase. These results suggest that Aux/IAA proteins function in auxin- and BR-signaling pathways, and that IAA proteins function as the signaling components modulating BR sensitivity in a manner dependent on organ type.     

Synergism between cysteinyl leukotrienes and thromboxane A2 to induce allergic late phase nasal blockage in guinea pigs

We examined whether cysteinyl leukotrienes (CysLTs) and thromboxane (TX) A2 are synergistically involved in a cedar pollen-induced allergic late phase nasal blockage in guinea pigs. Sensitized animals were repeatedly challenged by pollen inhalation once every week. Combined treatment with pranlukast (a CysLT antagonist) and seratrodast (a TXA2 antagonist) inhibited late phase nasal blockage, but the magnitude of inhibition (approximately 50%) was equal to those of the respective single treatments, suggesting that CysLTs produced late after challenge induces TXA2 production in the nasal tissue, as in the case of the lung of this species. However, pranlukast did not affect TXB2 increase in the nasal tissue. In contrast, combined intranasal instillation of LTD4 and U-46619 (a TXA2 mimetic) produced much greater nasal blockage than single administration of each agonist in sensitized animals. Therefore, allergic late phase nasal blockage should be induced by synergistic activity of CysLTs and TXA2 at the effector organ.     

Foot odor due to microbial metabolism and its control

To characterize foot odor, we analyzed its components by sensory tests, isolated microorganisms that produce it, and evaluated the mechanism of the occurrence of foot odor. As a result, foot odor was found to be derived from isovaleric acid, which is produced when Staphylococcus epidermidis, a resident species of the normal cutaneous microbial flora, degrades leucine present in sweat. In addition, Bacillus subtilis was detected in the plantar skin of subjects with strong foot odor, and this species was shown to be closely associated with increased foot odor. Therefore, we screened various naturally occurring substances and fragrant agents that inhibit microbial production of foot odor without disturbing the normal microbial flora of the human skin. As a result, we identified citral, citronellal, and geraniol as fragrant agents that inhibit the generation of isovaleric acid at low concentrations.     

Neverland is an evolutionally conserved Rieske-domain protein that is essential for ecdysone synthesis and insect growth

Steroid hormones mediate a wide variety of developmental and physiological events in multicellular organisms. During larval and pupal stages of insects, the principal steroid hormone is ecdysone, which is synthesized in the prothoracic gland (PG) and plays a central role in the control of development. Although many studies have revealed the biochemical features of ecdysone synthesis in the PG, many aspects of this pathway have remained unclear at the molecular level. We describe the neverland (nvd) gene, which encodes an oxygenase-like protein with a Rieske electron carrier domain, from the silkworm Bombyx mori and the fruitfly Drosophila melanogaster. nvd is expressed specifically in tissues that synthesize ecdysone, such as the PG. We also show that loss of nvd function in the PG causes arrest of both molting and growth during Drosophila development. Furthermore, the phenotype is rescued by application of 20-hydroxyecdysone or the precursor 7-dehydrocholesterol. Given that the nvd family is evolutionally conserved, these results suggest that Nvd is an essential regulator of cholesterol metabolism or trafficking in steroid synthesis across animal phyla.