Biomedical subjects

Aya Takahashi

Publications and source records attributed to Aya Takahashi.

7 recordsLinked to original sources

PubMed2006

A SNP in the ABCC11 gene is the determinant of human earwax type.

Human earwax consists of wet and dry types. Dry earwax is frequent in East Asians, whereas wet earwax is common in other populations. Here we show that a SNP, 538G --> A (rs17822931), in the ABCC11 gene is responsible for determination of earwax type. The AA genotype corresponds to dry earwax, and GA and GG to wet type. A 27-bp deletion in ABCC11 exon 29 was also found in a few individuals of Asian ancestry. A functional assay demonstrated that cells with allele A show a lower excretory activity for cGMP than those with allele G. The allele A frequency shows a north-south and east-west downward geographical gradient; worldwide, it is highest in Chinese and Koreans, and a common dry-type haplotype is retained among various ethnic populations. These suggest that the allele A arose in northeast Asia and thereafter spread through the world. The 538G --> A SNP is the first example of DNA polymorphism determining a visible genetic trait.

ATP-Binding Cassette Transporters↗

PubMed2006

Volitional hyperventilation during ramp exercise to exhaustion.

The purpose of this study was to determine whether volitional hyperventilation at 20 L x min(-1) above normal exercise values affected exercise duration while performing ramp exercise to exhaustion. Nine healthy subjects performed a ramp exercise test to exhaustion. On a subsequent test they hyperventilated, with the aid of visual and audio feedback, at 20 L x min(-1) greater than their initial test. Ramp exercise time to exhaustion was substantially reduced from 771.6 +/- 85.2 s to 726.6 +/- 86.6 s (p < 0.002) with the additional hyperventilation. Subjects underwent 2 more ramp exercise tests and performed a 5 s maximum voluntary ventilation or a forced vital capacity test at work rates corresponding to rest, below lactate threshold (LT), above LT, immediately after exercise, and 3 min recovery. Generally, the flow rates were not affected by exercise below LT and were enhanced during above-LT exercise, exhaustion, and recovery. This indicated a change in pulmonary function that is dependent on exercise intensity. In spite of this increased ability to generate high flow rates, exercise performance was diminished when respiratory muscle work was increased volitionally by 20 L x min(-1), indicating a strong coupling between respiratory muscle work and fatigue during ramp exercise in normal subjects.

Adult↗

PubMed2005

A high-frequency null mutant of an odorant-binding protein gene, Obp57e, in Drosophila melanogaster.

We have found a null mutant of an odorant-binding protein, Obp57e, in Drosophila melanogaster. This frameshift mutation, which is a 10-bp deletion in the coding region, is at a high frequency in the Kyoto population and is also present in Taiwan and Africa. We have sequenced a 1.5-kb region including the tandemly duplicated gene, Obp57d, from 16 inbred lines sampled in Kyoto, Japan. The analyses showed a peak of nucleotide diversity and strong linkage disequilibrium around this mutation. This pattern suggests an elevated mutation rate or an influence of balancing selection in this region. The level of nucleotide divergence between D. melanogaster and D. simulans does not support the former possibility. Thus, this presence/absence polymorphism may be due to balancing selection, which takes advantage of the relatively weak functional constraint in members of a large gene family. In addition, the Obp57d gene region showed an excess of high-frequency-derived mutants that is consistent with a pattern predicted under positive natural selection.

Alleles↗

PubMed2004

Genetic basis of sexual isolation in Drosophila melanogaster.

Sexual isolation between Zimbabwe (abbreviated as Z) and cosmopolitan (abbreviated as M) races exists in Drosophila melanogaster. Typically, when given a choice, the females from the Zimbabwe race mate only with males from the same race, whereas females from the cosmopolitan race mate readily with males from both races non-discriminatorily. Genetic tools available in this experimental organism permit the detail genetic analyses of the sexual isolation behavior. On the other hand, the search for the actual signaling systems involved in the mate recognition is still limited in this system. In this paper, we review the studies, which attempt to dissect the genetic basis of the sexual isolation system, and document the complex features of the genetic architecture and the behavioral traits that evolved at an incipient stage of speciation. The evolution and the maintenance of this behavioral polymorphism are also discussed.

Alleles↗

PubMed2003

Genetic variation versus recombination rate in a structured population of mice.

The correlation between genetic variation and recombination rate was investigated in a structured mouse population. Nucleotide sequence data from 19 autosomal DNA loci from eight inbred strains of mouse (Mus musculus) sampled from three major subspecies were analyzed. The recombination rate was estimated from the comparison of genetic and physical map distances between markers flanking a 10-cM region of each locus. The strains were categorized into four groups (subpopulations) based on geography. By partitioning the genetic diversity into within-group and among-group variation, we detected a positive correlation between the recombination rate and nucleotide diversity within groups. The level of nucleotide differentiation among groups (G(ST)) showed a negative correlation with the rate of recombination. There was no significant correlation between recombination rate and nucleotide diversity when data from different subpopulations were pooled. No correlation was detected between recombination rate and nucleotide divergence of M. musculus and M. spicilegus. These patterns deviate from the strict neutral expectation under the constant nucleotide substitution rate, and they are likely to have been formed either by a hitchhiking effect of positively selected mutants or by background selection of deleterious mutants occurring in a subdivided population. Our series of comparisons show that because a real population always has some structure, incorporation of its information is important in detecting non-neutral evolution.

Animals↗

PubMed2002

A mutation in the promoter of desaturase 2 is correlated with sexual isolation between Drosophila behavioral races.

Examples of genes governing behavioral isolation are scarce. Here we report that a regulatory mutation in desaturase 2, known to determine a pheromonal polymorphism in Drosophila melanogaster females, may be such an example. This mutation is strongly correlated with the mating pattern between the Zimbabwe and cosmopolitan races of this species. These two behavioral races appear to be at the incipient stage of speciation. The desaturase 2 mutation may be one of the many loci underlying the behavioral differences between the two races.

Animals↗

PubMed2002

Effects of ischaemia on subsequent exercise-induced oxygen uptake kinetics in healthy adult humans.

Leg muscles were occluded (33 kPa) prior to exercise to determine whether the induced metabolic changes, and reactive hyperaemia upon occlusion release just prior to the exercise, would accelerate the subsequent oxygen consumption (VO2) response. Eight subjects performed double bouts (6 min duration, 6 min rest in-between) of square wave leg cycle ergometry both below and above their lactate threshold (LT). Prior to exercise, large blood pressure cuffs were put around the upper thighs. Occlusion durations were 0 min (control), 5 min and 10 min. Ischaemia was terminated within 5 s prior to exercise onset. Heart rate, VO2, ventilatory rate (V(E)), electromyogram (EMG) and haemoglobin/myoglobin (Hb/Mb) saturation were recorded continuously. Single exponential modelling demonstrated that, compared to control (time constant = 53.9 +/- 13.9 s), ischaemia quickened the VO2 response (P < 0.05) for the first bout of exercise above LT (time constant = 48.3 +/- 14.5 s) but not to any other exercise bout below or above LT. The 3-6 min integrated EMG (iEMG) slope was correlated to the 3-6 min VO2 slope (r = 0.73). Hb/Mb saturation verified the ischaemia but did not show a consistent relation to the VO2 time course. Reactive hyperaemia induced a faster VO2 response for work rates above LT. The effect, while significant, was not large considering the expected favourable metabolic and circulatory changes induced by ischaemia.

Adult↗