Evidence for apical-basal transition in the delay of the reflection components of otoacoustic emissions.

Stimulus-frequency, transient-evoked, and distortion product otoacoustic emissions (OAEs) have been measured in eight normal-hearing human ears over a wide stimulus level range, with high spectral resolution. The single-reflection component of the response was isolated using time-frequency filtering, and its average delay was measured as a function of frequency and stimulus level. The apical-basal transition was studied by fitting the average delay of the filtered single-reflection OAEs, expressed in number of cycles, to a three-slope power-law function with two knot frequencies. The results show that the scale-invariant prediction of constant dimensionless delay approximately holds only over a narrow intermediate frequency range (1-2.5 kHz). Below 1 kHz, and, to some extent, above 2.5 kHz, the dimensionless delay increases with frequency, at all stimulus levels. Comparison with the numerical simulations of a delayed-stiffness active cochlear model show that the increase of tuning with frequency reported by behavioral experiments only partly explains this result. The low-frequency scaling symmetry breaking associated with the deviation of the Greenwood tonotopic map from a pure exponential function is also insufficient to explain the steep low-frequency increase of the OAE delay. Other sources of symmetry breaking, not included in the model, could therefore play a role.

Functional anatomy of the human vagina.

Anatomy studies normally precede physiology. While the anatomy of the penis and the biochemical and molecular regulation of erection are largely known, the exact anatomical description of the human clitoris was produced in 1998, the taxonomy of female sexual dysfunctions classified in 1999, and biochemistry of female excitation described only in 2002. There are various reasons for this. Female sexual physiology is much more complex than that of the male, and cultural and religious considerations have discouraged the scientific study of female sexuality. However, it is now apparent that modern sexology cannot be truly 'medical' if female sexual anatomy and the physiology of female sexual response are unknown.

Increased expression of thyroid hormone receptor isoforms in end-stage human congestive heart failure.

Thyroid hormone plays an important role on myocardial development and function. The local effects of thyroid hormone are mediated by the receptor isoforms ultimately driving the expression of cardiac-specific genes. Although overt and subclinical thyroid dysfunction causes well-known changes in the cardiovascular system, little is known about local thyroid hormone action in normal and failing human myocardium. With a newly developed multiplex competitive RT-PCR method, we evaluated the expression of thyroid hormone receptor (TR) isoforms alpha-1, alpha-2, and beta-1 in normal human hearts and in end-stage congestive heart failure. A statistically significant difference in the expression of all three TR isoforms was observed among samples from normal subjects, ischemic heart disease (IHD), and dilated cardiomyopathy (DCM). In DCM, compared with normal, the studied TR isoforms were significantly increased. In IHD, the increased expression was found significant only for alpha-1 and alpha-2 isoforms. No differences were observed between the pathologic groups. In conclusion, a coordinated increment in the expression of the TR isoforms was observed in both DCM and IHD by multiplex competitive RT-PCR. The observed changes could represent a compensatory mechanism to myocardial failure or to locally altered thyroid hormone action.