Biomedical subjects

Dipa Joshi

Publications and source records attributed to Dipa Joshi.

3 recordsLinked to original sources

PubMed2006

Olfactory sensitivity for enantiomers and their racemic mixtures--a comparative study in CD-1 mice and spider monkeys.

Using a conditioning paradigm, the olfactory sensitivity of six CD-1 mice for the enantiomers of carvone and of limonene as well as for their racemic mixtures was investigated. With all six stimuli, the animals significantly discriminated concentrations <or=0.1 ppm (parts per million) from the odorless solvent, and with five of the six stimuli, the best-scoring animals were even able to detect concentrations <or=1 ppb (parts per billion). Five spider monkeys tested in parallel were found to detect the same stimuli at concentrations <1 ppm, and with two of the stimuli, they were also able to discriminate concentrations <1 ppb from the solvent. The results showed 1) both CD-1 mice and spider monkeys to have a well-developed olfactory sensitivity for the stimuli tested, with no systematic difference in performance between species; 2) the effect of chirality on detectability of the enantiomers to be substance specific; 3) no systematic effect of the presence (carvone) or absence (limonene) of a functional carbonyl group on detectability of the enantiomers; and 4) that spider monkeys detected the racemic mixtures of both carvone and limonene at lower concentrations compared to the unmixed compounds, whereas the mice failed to do so. These findings lend support to the growing body of evidence suggesting that between-species comparisons of the relative size of olfactory brain structures do not allow us to reliably predict olfactory sensitivity. As mice and spider monkeys are thought to share a similar number of functional olfactory receptor genes, the findings further suggest that differences in the relative abundance of chiral-specific olfactory receptor types might account for the observed difference in mixture additivity at threshold level between the two species. These threshold data may provide useful information for the choice of adequate stimulus concentrations in electrophysiological or imaging studies of the olfactory system or investigations of the discriminative abilities of mice and spider monkeys.

Animals↗

PubMed2005

Olfactory sensitivity for aliphatic aldehydes in CD-1 mice.

Using a conditioning paradigm, the olfactory sensitivity of CD-1 mice for a homologous series of aliphatic aldehydes (n-butanal to n-nonanal) was investigated. With all six odorants, the animals significantly discriminated concentrations below 4 ppb (parts per billion) from the odorless solvent, and with n-butanal, n-heptanal, and n-nonanal the best-scoring animals were even able to detect concentrations below 40 ppt (parts per trillion). The results showed (a) CD-1 mice to have a well-developed olfactory sensitivity for aliphatic aldehydes which for the majority of substances is higher than that of other mammalian species, (b) a limited concentration range of about 1 log unit from threshold to near saturation which is similar to that shown at the single receptor cell level, (c) no significant correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of the aldehydes tested, and (d) no systematic effect of preexposure to an aldehyde on sensitivity. These findings suggest that CD-1 mice are highly sensitive to non-pheromonal odorants that are abundant in plant odors. Further, the results demonstrate that sensitivity for members of a homologous series of substances is not a simple function of vapor pressure as threshold values did not correlate with molecular weight. These threshold data may provide useful information for the choice of adequate stimulus concentrations in electrophysiological or imaging studies of the olfactory system or investigations of the discriminative abilities of the mouse.

Aldehydes↗

PubMed2004

Age-related hearing loss and its association with reactive oxygen species and mitochondrial DNA damage.

Age-related hearing loss, known as presbyacusis, is characterized by the progressive deterioration of auditory sensitivity associated with the aging process and is the leading cause of adult auditory deficiency in the USA. Presbyacusis is described as a progressive, bilateral, high-frequency hearing loss that is manifested on audiometric assessment by a moderately sloping pure tone audiogram. Approximately 23% of the population between 65 and 75 years of age, and 40% of the population older than 75 years of age are affected by this condition. It was estimated in 1980 that 11% of the population was 76 years or older and this number is expected to almost double by the year 2030. When one considers that the population over 65 years of age is experiencing the most accelerated development of hearing loss, the potential socioeconomic ramifications are staggering. Curiously, the frequency of presbyacusis varies across different societies. This discrepancy has been attributed to many factors including genetics, diet, socioeconomic factors, and environmental variables. The purpose of this article is to review the various molecular mechanisms underlying presbyacusis and to offer insights into potential methods of mitigating the effects of aging on hearing impairment.

Animals↗