A short history of hearing research. IV: Physiology]

In 1863, Hensen concluded from measurements of the width of the basilar membrane that tones of high and low pitch were represented at the base and apex of the cochlea, respectively. According to his calculations on the tonotopic representation of sound stimuli in the cochlea Helmholtz proposed additional resonators that would transmit the amplified signal to the afferent nerve endings. He speculated that the pillar cells of the tunnel of Corti or strands of the basilar membrane might be these proposed resonators. The resonance theory was contradicted by Wien in 1905. However, further experiments by Held and Kleinknecht in 1927 and by Békésy in 1928 demonstrated that Helmholtz's ideas on the tonotopic dispersion of the vibration of the basilar membrane were correct. Békésy measured the vibration of the cochlear partition in human and animal cadavers and discovered the travelling-wave of the basilar membrane. At the turn of the century Ter Kuile noted that the vibration of the cochlear partition caused a deflection of the sensory hairs of the hair cells, the auditory receptor cells. Wever and Bray described in 1930 stimulus-evoked electrical currents near the cochlea with a wave form similar to that of the original sound stimulus. It was Adrian who later coined the term "cochlear microphonics" for this phenomenon. According to calculations of Gold (1948) and others active mechanical amplification would be required for such a sharp tuning in the cochlea. The first to measure action potentials of the afferent auditory nerve was Tasaki (1954).(ABSTRACT TRUNCATED AT 250 WORDS)     

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Impact of maternal anthropometry and smoking on neonatal birth weight

The purpose of this study was to determine the effect of maternal pre-pregnancy body mass index (BMI) and maternal smoking habits on neonatal birth weight. We reviewed 10,240 normal singleton term pregnancies between 1985 and 1995 at the University Department of Obstetrics and Gynecology, Vienna. Birth weights of infants of overweight smokers were greater than those of smokers in general and similar to birth weights of nonsmokers, but smoking did have a fetal growth-retarding effect in overweight smoking mothers. Infants of underweight mothers who increased their daily cigarette consumption during pregnancy had significantly lowest birth weight. Our results suggest that the negative effects of smoking during pregnancy cannot be mitigated by a higher pre-pregnancy BMI and/or an improved weight gain during pregnancy. Especially the infants of underweight mothers benefit from their mothers' decision to cease smoking.     

Concentration of vascular endothelial growth factor (VEGF) in the serum of patients with malignant bone tumors

BACKGROUND: Vascular endothelial growth factor (VEGF) is recognized as an important stimulator of angiogenesis. Formation of new blood vessels by angiogenic factors occurs in many biological processes, both physiological and pathological, among others in growth of primary solid malignant tumors and metastasis. This implies that the inhibition of angiogenic factors like VEGF would result in a suppression of tumor growth and metastasis formation. The aim of the present study was to compare preoperative serum VEGF levels of patients having malignant bone tumors with healthy controls to identify serum VEGF levels as a tumor marker. PROCEDURE: Blood sera from patients with high-grade osteosarcoma (n = 17), chondrosarcoma (n = 4) and Ewing sarcoma (n = 6) were taken at the time of diagnosis before biopsy and compared with sera from 129 healthy persons. To measure VEGF levels in serum, a commercially available ELISA was used (Quantikine Human VEGF Immunoassay; R&D Systems). RESULTS: The observed geometric mean VEGF levels and 95% confidence intervals are 232.0 pg ml(-1) (168.9-318.5) for patients with high-grade osteosarcoma, 325.5 pg ml(-1) (169.3-625.8) for patients with chondrosarcoma, 484.3 pg ml(-1) (284.0-826.0) for patients with Ewing sarcoma, as compared to 216.2 pg ml(-1) (192.8-242.5) for healthy individuals. CONCLUSIONS: While the sample means for the three groups of sarcoma patients were higher than the respective mean for the healthy controls, only the mean for the group with Ewing sarcoma is statistically significantly higher than the mean for the healthy controls. Despite the significant difference, VEGF levels are not suitable as a marker for Ewing sarcoma.     

Mechanical transduction in outer hair cells

The outer hair cells are responsible for the exquisite sensitivity, frequency selectivity and dynamic range of the cochlea. These cells are part of a mechanical feedback system involving the basilar membrane and tectorial membrane. Transverse displacement of the basilar membrane results in relative motion between the tectorial membrane and the reticular lamina, causing deflection of the stereocilia and modulation of the open probability of their transduction channels. The resulting current causes a change of membrane potential, which in turn produces mechanical force, that is fed back into the motion of the basilar membrane. Experiments were conducted to address mechanical transduction mechanisms in both the stereocilia and the basolateral cell membrane, as well as modes of coupling of the outer hair cell force to the organ of Corti.