Effects of compound injection of Pyrola rotundifolia L and Astragalus membranaceus Bge on experimental guinea pigs' gentamicin ototoxicity

In attempting to find drugs effective in preventing and remedying ototoxic injury caused by aminoglycoside antibiotics, we relied on the theory that the induction of ototoxic injury by aminoglycoside antibiotics is related to a decrease of cyclic adenosine monophosphate and RNA content in the cochlea or a dysfunction of the kidney. We selected Pyrola rotundifolia L and Astragalus membranaceus Bge from traditional Chinese herbal medicine, made a compound injection of them, and observed the effect on the pattern of gentamicin ototoxicity in guinea pigs. By electrocochleography and morphology by scanning electron microscopy, the experimental results indicated that the Chinese herbal compound possessed the definite effect of protecting the guinea pig cochlea. The determination of blood urea nitrogen, urinary N-acetyl-D-aminoglucosidase, and urinary protein and observation of renal morphology showed that it also protected the kidney against nephrotoxic nephritis of gentamicin. The conjecture that protection of the kidney by the Chinese herbs may be one of the important factors in preventing ototoxicity supports some explanations of ototoxic mechanisms induced by aminoglycoside antibiotics.

[Hair cell damage and regeneration in the quail cochlea following kanamycin ototoxicity]

Forty-day old quails were given kanamycin (KM) at a dose of 400mg/kg per day for ten days. Evoked potential thresholds induced by both click and tone burst were obtained at 1 day or 1, 2, 3, 4 and 6 weeks respectively after the last injection, and compared with the thresholds of age-matched control animals. The cochlea of the animals was examined by scanning electron microscopy (SEM). The results showed that the application of KM for 10 days produced massive destruction of the basilar papilla at 1 day posttreatment. The damaged region began at the base and extended apically to the position about 50-70% of the total distance along the papilla, with most severe damage in the basal end. The auditory thresholds measured at the same time revealed a significant elevation at 2 and 4 kHz. However, the number of hair cells in the damaged region recovered rapidly with time, and so did the function. By the end of 3 weeks postinjection, almost all the hair cells reappeared in the pathologic region and the function improved further, with nearly normal thresholds at all frequencies but 4kHz. Six weeks after KM treatment, the basilar papilla showed a nearly normal appearance, but there was no further functional improvement at 4kHz, with the threshold shift by 17.5 dB (P < 0.01). The results of the present study demonstrated that structural recovery was faster than functional one.

Origin in tobacco smoke of N'-nitrosonornicotine, a tobacco-specific carcinogen

To evaluate risk factors and to approach methods of reduction of the carcinogenic potential of cigarette smoke, the transfer rate of N-nitrosonornicotine in a popular U.S. blended cigarette into mainstream smoke was quantitatively determined. The mean transfer rate was 11.3%; thus approximately 46% of the tobacco-specific carcinogen in the smoke came from the tobacco, and the remainder was synthesized during smoking.

Separation of aza-arenes by high-pressure liquid chromatography

Fast, efficient liquid chromatographic separations of aza-arenes were obtained using both, reversed-phase, and adsorbent packings. Aza-arenes with 2-5 rings are separated within 20 minutes. Sample recovery is quantitative and permits subsequent uv and fluorescence spectrophotometric identifications. The detection limit for most aza-arenes was 1 ng with a 254-nm uv detector. An application to an air pollution problem demonstrates the usefulness of this approach.