RESUMO
Objective To study the effects of chronic manganism on hearing and cochlear cells in rats by using animal model of chronic manganism .Methods Sixty adult SD rats were randomly divided into Mn - exposed and controlgroups.RatsweretreatedwithMnCl24H2O(100mg·kg -1·d-1)ordeionizedwaterbygastricperfusion, lasted for 12 weeks .The Mn concentration in peripheral blood was measured respectively at 4 weeks ,8 weeks and 12 weeks after treatment .At 12 weeks after treatment ,the auditory brainstem response was recorded ,the hair cells morphology and counting were examined by stretched preparation of basilar membrane stained with FITC -phalloi-din ,and the spiral ganglion cells morphology and counting were studied by HE staining ,the ultrastructure changes of hair cells and spiral ganglion cells were detected by transmission electron microscopy .Results The blood Mn concentration increased gradually with time after treatment .ABR thresholds at 4 ,8 ,16 ,24 and 32 kHz were sig-nificantly increased at 12 weeks after treatment ,especially in the high-frequency range .Morphological study at 12 weeks after treatment showed loss of outer hair cells ,mainly in the basal turn of the cochlea ,and decreased number of spiral ganglion cells .The ultrastructure changes of outer hair cells and spiral ganglion cells included the break -ups ,disappearance or vacuolar change of mitochondria cristas .Conclusion Our data demonstrate that chronic man-ganism can cause loss of outer hair cells and spiral ganglion cells in cochlear in rats ,leading to hearing loss .
RESUMO
Objective The study aimed to explore the relationship between AIF related pathway and the inju-ring of cultured SGNs (spiral ganglion neurons)by glutamate toxicity,and to find AIF expression and distribution changes in SGNs.Methods SGNs of 40 newborn rats within 3 day were obtained and cultured in vitro.Cultured cells were divided into four groups:the normal control group,10 mM,20 mM and 40 mM glutamate injured group, separately.After 48 h hours culturing,optical microscopy,immune fluorescence staining and real-time fluores-cence quantitative PCR were used to observe the morphology,AIF distribution,and AIF,calpain,Caspase3 expres-sion changes in SGNs in vitro.TUNEL was used to verify the cell apoptosis.ResuIts Noticeable morphological chan-ges and cell apoptosis were occurred in 20 mM glutamate group,with AIF nuclear translocation.AIF gene expression was significantly higher than normal after glutamate administration (P0.05). ConcIusion In the process of cultured SGNs injured by glutamate,AIF participated in the cell apoptosis.Noticeable cell apoptosis were occurred in 20 mM glutamate group with AIF nuclear translocation.Calpain up-expression also contributed to excitatory neurotransmitter injury on SGNs,but Caspase 3 had no obvious effects.