The Experimental Study On The Diagnostic Ultrasound Affecting Hearing Development In Fetal Guinea Pigs

Objective: To investigate whether diagnostic ultrasound could affect the development of hearing in fetal guinea pigs. Methods : The experiments consist of three part.The diagnostic ultrasound was used to irradiate the uteri of pregnant guinea pigs, which were divided randomly early exposed group, late exposed group and non-exposed control groups. The pregnant guinea pigs in early exposed group were irradiated for five minutes daily during the first 15 days of gestation and those in late exposed group were irradiated for five minutes daily from fortieth to fiftieth-five day of gestation.The electrophysiological study on hearing function: The threshold of the auditory brainstem response (ABR) and the cochlear microphonics (CM) in offspring of the animals were recorded to evaluate alteration of hearing.The morphological study on cochlea: The number of hair cells was calculated using succinic dehydrogenase staining , the soft surface specimen spreading and computer image analysis technigue. The surface change of hair cells in fetal guinea pigs (with 5 animals of each group) was observed with scanning electron microscope(SEM).Results: Compared with non-exposed control group, the threshold of ABR and CM were elevated in two exposed groups. In early exposed group, the threshold of ABR was higher than that in late exposed group. There were all significantly differences (P<0.05). The threshold of CM were nosignificantly differences (P<0.05) between two exposed group. The threshold of ABR did not demonstrate a significant alteration during 1,2,3,5 days post-birth.Compared with non-exposed control group, the number of total hair cells was lower in two exposed groups ,there were all significantly differences (P<0.05), especially in the second turn, the third turn and the fourth turn of cochlear base membrane, the number of total hair cells was much lower(P<0.01). In early exposed group, the number of total hair cells was about same as that in late exposed group, there were no significantly differences (P<0.05) between two exposed group. It were observed that irradiation of the diagnostic ultrasound induce some inside hair cells (IHC) and outside hair cells (OHC)loss, especially outside hair cells (OHC) were missing.Conclusion: (1) Result show that diagnostic ultrasound for certain times could cause injury of the development of hearing in fetal guinea pigs. Hearing impairment of diagnostic ultrasound in early stage of pregnancy was higher than that in late stage of pregnancy. There were not significant alterations of impaired hearing function during first 5 days post-birth. (2) Diagnostic ultrasound for certain times could cause injury of the development of cochlear hair cell in fetal guinea pigs. Damaged region was mainly at the bottom of cochlear base membrane. Hair cells' impairment of diagnostic ultrasound in early stage of pregnancy was the same as that in late stage of pregnancy.