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Search Results: 1 - 10 of 1409 matches for " Hiroaki Matsunami "
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Taste and pheromone perception in mammals and flies
Hiroaki Matsunami, Hubert Amrein
Genome Biology , 2003, DOI: 10.1186/gb-2003-4-7-220
Abstract: Feeding is initiated in terrestrial animals with the detection of volatile (airborne) chemicals. Generally referred to as odorants, these chemicals are released from food sources towards which animals move by monitoring the concentration gradient of a particular odor. Naturally, noxious volatile substances are also detected by the same sensory epithelia, in this case leading to avoidance of the odor source. In both mammals and insects, volatile cues are detected by odorant receptor proteins, which are G-protein-coupled receptors (GPCRs) encoded by a single large gene family expressed in the cognate olfactory epithelia in the nose and antenna of mammals and insects, respectively. The odorant receptor gene family consists of about 1,000 genes in mice and 60 in Drosophila. Surprisingly, the odorant receptor genes in mammals and insects are not related to each other at the sequence level (beyond encoding GPCRs), even though they recognize a largely overlapping array of chemical compounds. The olfactory systems of insects and mammals have analogous anatomical features and use similar molecular logic for olfactory coding, however [1].Once a potential food source is identified, animals taste it by means of contact between chemicals from the source and chemosensory receptors located in the gustatory (taste) organs, predominantly the tongue in mice and the labellum (proboscis) in Drosophila (both species also have secondary taste organs). Distinct sets of taste-receptor proteins in specific taste cells allow the organism to discriminate between 'delicious' food, generally associated with rich nutrition, and bitter-tasting substrates, typically present in contaminated, non-edible food sources.Courtship and mating are also initiated by chemosensory signals, better known as pheromones, although other sensory systems are also important for these behaviors. Pheromones are sometimes sex-specific and are secreted by specialized glands or cells to trigger distinct behavioral and end
Calreticulin: Roles in Cell-Surface Protein Expression
Yue Jiang,Sandeepa Dey,Hiroaki Matsunami
Membranes , 2014, DOI: 10.3390/membranes4030630
Abstract: In order to perform their designated functions, proteins require precise subcellular localizations. For cell-surface proteins, such as receptors and channels, they are able to transduce signals only when properly targeted to the cell membrane. Calreticulin is a multi-functional chaperone protein involved in protein folding, maturation, and trafficking. However, evidence has been accumulating that calreticulin can also negatively regulate the surface expression of certain receptors and channels. In these instances, depletion of calreticulin enhances cell-surface expression and function. In this review, we discuss the role of calreticulin with a focus on its negative effects on the expression of cell-surface proteins.
Functional Evolution of Mammalian Odorant Receptors
Kaylin A. Adipietro,Joel D. Mainland,Hiroaki Matsunami
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002821
Abstract: The mammalian odorant receptor (OR) repertoire is an attractive model to study evolution, because ORs have been subjected to rapid evolution between species, presumably caused by changes of the olfactory system to adapt to the environment. However, functional assessment of ORs in related species remains largely untested. Here we investigated the functional properties of primate and rodent ORs to determine how well evolutionary distance predicts functional characteristics. Using human and mouse ORs with previously identified ligands, we cloned 18 OR orthologs from chimpanzee and rhesus macaque and 17 mouse-rat orthologous pairs that are broadly representative of the OR repertoire. We functionally characterized the in vitro responses of ORs to a wide panel of odors and found similar ligand selectivity but dramatic differences in response magnitude. 87% of human-primate orthologs and 94% of mouse-rat orthologs showed differences in receptor potency (EC50) and/or efficacy (dynamic range) to an individual ligand. Notably dN/dS ratio, an indication of selective pressure during evolution, does not predict functional similarities between orthologs. Additionally, we found that orthologs responded to a common ligand 82% of the time, while human OR paralogs of the same subfamily responded to the common ligand only 33% of the time. Our results suggest that, while OR orthologs tend to show conserved ligand selectivity, their potency and/or efficacy dynamically change during evolution, even in closely related species. These functional changes in orthologs provide a platform for examining how the evolution of ORs can meet species-specific demands.
Sour Taste Responses in Mice Lacking PKD Channels
Nao Horio,Ryusuke Yoshida,Keiko Yasumatsu,Yuchio Yanagawa,Yoshiro Ishimaru,Hiroaki Matsunami,Yuzo Ninomiya
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020007
Abstract: The polycystic kidney disease-like ion channel PKD2L1 and its associated partner PKD1L3 are potential candidates for sour taste receptors. PKD2L1 is expressed in type III taste cells that respond to sour stimuli and genetic elimination of cells expressing PKD2L1 substantially reduces chorda tympani nerve responses to sour taste stimuli. However, the contribution of PKD2L1 and PKD1L3 to sour taste responses remains unclear.
Genetic Variation of an Odorant Receptor OR7D4 and Sensory Perception of Cooked Meat Containing Androstenone
Kathrine Lunde, Bj?rg Egelandsdal, Ellen Skuterud, Joel D. Mainland, Tor Lea, Margrethe Hersleth, Hiroaki Matsunami
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035259
Abstract: Although odour perception impacts food preferences, the effect of genotypic variation of odorant receptors (ORs) on the sensory perception of food is unclear. Human OR7D4 responds to androstenone, and genotypic variation in OR7D4 predicts variation in the perception of androstenone. Since androstenone is naturally present in meat derived from male pigs, we asked whether OR7D4 genotype correlates with either the ability to detect androstenone or the evaluation of cooked pork tainted with varying levels of androstenone within the naturally-occurring range. Consistent with previous findings, subjects with two copies of the functional OR7D4 RT variant were more sensitive to androstenone than subjects carrying a non-functional OR7D4 WM variant. When pork containing varying levels of androstenone was cooked and tested by sniffing and tasting, subjects with two copies of the RT variant tended to rate the androstenone-containing meat as less favourable than subjects carrying the WM variant. Our data is consistent with the idea that OR7D4 genotype predicts the sensory perception of meat containing androstenone and that genetic variation in an odorant receptor can alter food preferences.
Common Promoter Elements in Odorant and Vomeronasal Receptor Genes
Jussara S. Michaloski, Pedro A. F. Galante, Maíra H. Nagai, Lucia Armelin-Correa, Ming-Shan Chien, Hiroaki Matsunami, Bettina Malnic
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0029065
Abstract: In mammals, odorants and pheromones are detected by hundreds of odorant receptors (ORs) and vomeronasal receptors (V1Rs and V2Rs) expressed by sensory neurons that are respectively located in the main olfactory epithelium and in the vomeronasal organ. Even though these two olfactory systems are functionally and anatomically separate, their sensory neurons show a common mechanism of receptor gene regulation: each neuron expresses a single receptor gene from a single allele. The mechanisms underlying OR and VR gene expression remain unclear. Here we investigated if OR and V1R genes share common sequences in their promoter regions. We conducted a comparative analysis of promoter regions of 39 mouse V1R genes and found motifs that are common to a large number of promoters. We then searched mouse OR promoter regions for motifs that resemble the ones found in the V1R promoters. We identified motifs that are present in both the V1R and OR promoter regions. Some of these motifs correspond to the known O/E like binding sites while others resemble binding sites for transcriptional repressors. We show that one of these motifs specifically interacts with proteins extracted from both nuclei from olfactory and vomeronasal neurons. Our study is the first to identify motifs that resemble binding sites for repressors in the promoters of OR and V1R genes. Analysis of these motifs and of the proteins that bind to these motifs should reveal important aspects of the mechanisms of OR/V1R gene regulation.
A 7-Year-Old Boy with Light Cupula of the Horizontal Semicircular Canal  [PDF]
Hiroaki Ichijo
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2014, DOI: 10.4236/ijohns.2014.32018
Abstract:

Report of childhood positional vertigo is very rare. We present a 7-year-old boy who revealed persistent direction-changing geotropic positional nystagmus. In the supine position, horizontal nystagmus toward the left continued as long as the position was maintained. However, it ceased when the head was turned to the right side by 45°. With greater head turn (right-ear-down), nystagmus toward the right lasted for more than 1 minute. In the left-ear-down position, horizontal nystagmus toward the left occurred and lasted for more than 1 minute. After the disappearance of positional nystagmus, we detected canal paresis of the right ear by caloric test. We considered that the pathophysiology of the persistent type of geotropic nystagmus is a result of light debris cupulolithiasis of the horizontal canal.

Determination of Shear Center of Arbitrary Cross-Section  [PDF]
Hiroaki Katori
World Journal of Mechanics (WJM) , 2016, DOI: 10.4236/wjm.2016.68020
Abstract: In structural analysis, it is often necessary to determine the geometrical properties of cross section. The location of the shear center is greater importance for an arbitrary cross section. In this study, the problems of coupled shearing and torsional were analyzed by using the finite element method. Namely, the simultaneous equations with respect to the warping, shear deflection, angle of torsion and Lagrange’s multipliers are derived by finite element approximation. Solving them numerically, the matrix of the shearing rigidity and torsional rigidity is obtained. This matrix indicates the coupled shearing and torsional deflection. The shear center can be obtained determining the coordinate axes so as to eliminate the non-diagonal terms. Several numerical examples are performed and show that the present method gives excellent results for an arbitrary cross section.
Inverse Problems for an Euler-Bernoulli Beam: Identification of Bending Rigidity and External Loads  [PDF]
Hiroaki Katori
World Journal of Mechanics (WJM) , 2018, DOI: 10.4236/wjm.2018.85014
Abstract: We present a method for identifying the flexural rigidity and external loads acting on a beam using the finite-element method. We used mixed beam elements possessing transverse deflection and the bending moment as the primary degrees of freedom. The first step is to determine the bending moment from the transverse deflection and boundary conditions. The second step is to substitute the bending moment into the final equations with respect to the unknown parameters (flexural rigidity or external load). The final step solves the resulting system of equations. We apply this method to some inverse beam problems and provide an accurate estimation. Several numerical examples are performed and show that present method gives excellent results for identifying bending stiffness and distributed load of beam.
Vestibular Rehabilitation for the Patients with Intractable Vestibular Neuritis  [PDF]
Hiroaki Ichijo
International Journal of Otolaryngology and Head & Neck Surgery (IJOHNS) , 2018, DOI: 10.4236/ijohns.2018.76035
Abstract: Objective: To clarify whether vestibular rehabilitation is effective in improving spontaneous nystagmus in patients with intractable vestibular neuritis. Methods: The subjects were 8 patients (6 females and 2 males) with vestibular neuritis who revealed long-lasting (more than 2 months since the onset) horizontal spontaneous nystagmus toward the healthy side. We used thumbs-up head shaking for vestibular rehabilitation. This exercise involves active head shaking (1 Hz) while staring at one’s thumb nail. One set is 10 cycles. We asked the patient to do 3 sets (morning, afternoon, and night) every day. Results: The mean value of the slow-phase velocity of spontaneous nystagmus before treatment was 4.1°/s, and that 3 months after vestibular rehabilitation was 4.1°/s. No improvement was observed. Conclusion: Vestibular rehabilitation is not always effective in improving spontaneous nystagmus in patients with intractable vestibular neuritis. Therefore, clinicians should consider the possibility of long-term incomplete central compensation.
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