High-power, low-noise, Yb-doped, cladding-pumped, three-level fiber sources at 980 nm.

We present results on a high-power, cladding-pumped, Yb-doped fiber emitting at 977 nm in laser and ampllified-spontaneous-emission source configurations. We obtained up to 1.4 W of fiber-coupled, single-mode output power and slope efficiency as high as 68%. To our knowledge these are the highest powers efficiencies achieved from a single-mode fiber laser at approximately 980 nm and the first demonstrated results on a high-power amplified-spontaneous-emission source in this wavelength range. High power and high slope efficiency are achieved by using a high numerical aperture (> 0.7), a jacketed air-clad fiber, and a high-brightness pump source. Both types of sources exhibit relative intensity noise below -130 dB/Hz and are thus suitable for a wide range of applications.

The expression of apoptosis-related proteins in the aged cochlea of Mongolian gerbils.

OBJECTIVE: Apoptotic changes have been reported in the aged gerbil cochlea and are speculated to be one of the principal causes of presbyacusis. The objective of the study was to determine the underlying mechanism of apoptotic change in the aged gerbil cochlea. STUDY DESIGN: Prospective controlled animal study. METHODS: We examined the tissue distribution of bcl-2, bax, caspase-3p20, and caspase-3p32 using immunohistochemical techniques in the young and aged gerbil cochlea, together with the measurement of the distortion product of otoacoustic emission (DPOAE). RESULTS: Aged gerbils showed a significant reduction of the DPOAE amplitude as compared with that of the young gerbils, suggesting a disturbance of the auditory function in the aged cochlea. There was a significant decrease in the number of bcl-2-positive cells in the aged gerbils. The expression of bax in the aged group was slightly increased but did not significantly differ from that in the young gerbils. A significantly increased number of caspase-3p20-positive cells was observed in the organ of Corti, spiral ganglion, and lateral wall of cochlea in the aged gerbils as compared with those of the young gerbils. There was no significant difference in the expression levels of caspase-3p32 between the young and aged groups. In the aged cochlea, the degree of deterioration of DPOAE responses was compatible with those of both the reduction of bcl-2 and the activation of caspase-3p20. CONCLUSION: These data suggest that the suppression of bcl-2 protein expression may lead to apoptosis-induced presbyacusis through activation of caspase-3 in the aged gerbil cochlea.

Cisplatin-induced apoptotic cell death in Mongolian gerbil cochlea.

Cisplatin is well known to cause cochleotoxicity. In order to determine the underlying mechanisms of cisplatin-induced cell death in the cochlea, we investigated the apoptotic changes and the expression of bcl-2 family proteins controlling apoptosis. Mongolian gerbils were administered 4 mg/kg/day cisplatin consecutively for 5 days. The cisplatin-treated animals showed a significant deterioration in the responses of both distortion product otoacoustic emissions and the endocochlear potential as compared with those of the age-matched controls, suggesting outer hair cell and stria vascularis dysfunction. The presence of DNA fragmentation revealed by a terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling method was recognized in the organ of Corti, the spiral ganglion, and the stria vascularis in the cisplatin-treated animals whereas almost negative results were obtained in the control animals. The nuclear morphology obtained by Hoechst 33342 staining revealed pyknotic and condensed nuclei, confirming the presence of the characteristic features of apoptosis. A significant increase and reduction in the number of bax- and bcl-2-positive cells, respectively, following cisplatin treatment was observed in the cells of the organ of Corti, the spiral ganglion, and the lateral wall. These findings suggest a critical role for bcl-2 family proteins in the regulation of apoptotic cell death induced by cisplatin. The underlying mechanisms of the cisplatin-induced cell death are discussed.

Acute effects of combined administration of kanamycin and furosemide on the stria vascularis studied by distortion product otoacoustic emission and transmission electron microscopy.

Acute effects of kanamycin and/or furosemide administration on the stria vascularis of the guinea pig cochlea were assessed by distortion product otoacoustic emission (DPOAE) and transmission electron microscopy. Kanamycin alone failed to affect the DPOAE levels and ultrastructural changes. Furosemide alone caused a rapid but reversible fall of the DPOAE levels. No remarkable pathological changes in the strial vascularis were observed after a complete recovery of the DPOAEs. On the other hand, furosemide injection following kanamycin with a 2 hour interval resulted in two patterns of significant changes in the DPOAEs, namely, a sudden drop in the DPOAE levels 2 to 3 hours after furosemide injection and a gradual fall in the DPOAE levels immediately after the incomplete recovery from the furosemide-induced decrease of the DPOAE levels. Ultrastructural changes in the stria vascularis included numerous vacuoles in the strial marginal cells and increased electron density of the intermediate and basal cells. These physiological and morphological changes in the stria vascularis may imply new ototoxic features induced by kanamycin potentiated by furosemide.

Study of the presence of rabies virus in indigenous bats.

One hundred and thirteen fruit eating and insectivorous bats were captured from different parts of Bangladesh. Antemortem and post mortem examinations of the bats for rabies were conducted. Microscopic studies and biological tests were carried-out with bat's brain for the detection of rabies virus. The results were negative. It may therefore, be concluded that the insectivorous and fruit eating bats from different parts of Bangladesh do not act as the reservoir for rabies virus.

Mycotic keratitis.

Specimens of swabs from corneal ulcers from forty-nine patients were studied to isolate and identify fungus. Direct microscopy revealed the presence of fungal elements in eight (16.32 per cent) cases, whereas culture yielded growth of fungus in eleven (22.44 per cent) cases. Aspergillus species was isolated in eight of the eleven cases.

Studies of the presence of rabies virus among stray dogs in Dhaka City.

One hundred and thirty one stray dogs were captured from Dhaka City. Anti-mortem as well post-mortem examination of the dogs for rabies were conducted. Microscopic studies and biological tests were carried-out with dog's brain for the detection of rabies virus. One dog was found to have rabies virus in its brain. The stray dogs under Dhaka Municipal Corporation area therefore, seem to harbour rabies virus in their brains and could be a source of potential danger to the community after the full development of the disease.

Candida as a cause of diarrhoea in children.

In a study of 134 children under 12 years of age suffering from diarrhoea, candida was responsible either directly or indirectly in 23 (17.1%) cases. Mixed incidence of candida and shigella were found in 2 (1.7%) cases. Candida species were isolated in 78(58.2%) specimens. Shigella and salmonella were recovered from 10(7.4%) children suffering from diarrhoea.