Use of backscattered electron imaging on developed radioautographic emulsions: Application to viewing rat incisor enamel maturation pattern following45calcium injection
✍ Scribed by McKee, M. D. ;Warshawsky, H. ;Nanci, A.
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1987
- Tongue
- English
- Weight
- 836 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0741-0581
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✦ Synopsis
Backscattered electron imaging (BED can be used to obtain compositional contrast in biological structures because it detects differences in concentration of elements with different atomic number. Rat incisor enamel shows a banded pattern in the maturation zone when radioautography is used to reveal the location of injected 45Ca at the enamel surface. The bands of developed silver grains in the photographic emulsion that coats the enamel surface are ideal for atomic number contrast. The purpose of this study was to use BE1 to analyze the radioautographic pattern with SEM resolution. Onemonth-old rats were injected with 45Ca and sacrificed at early (1 min, 5 min, 30 min), intermediate (4 h, 8 h), and late (1 day, 4 days) time intervals after injection. Whole incisors were dissected, the enamel organs were removed, and the enamel surface was coated with photographic emulsion and processed for radioautography. These radioautographed teeth were examined with a JEOL JSM-840 SEM equipped with a JEOL backscatter annular-type detector. At the early time intervals, light microscopic examination showed five or six broad black bands running obliquely across the teeth. These were separated by narrow white bands of unlabeled enamel. BE1 resolved the presence of a delicate subbanding pattern within each dark band. At the intermediate time intervals, although the incisal bands persisted, only a diffusely blackened apical area was seen by light microscopy. BE1 resolved bands in this apical region, but these showed no subbanding pattern. At the late time intervals, both light microscopy and BE1 showed no banding, and the enamel was uniformly labeled. The significantly improved resolution obtained with BE1 on surface radioautographs has revealed a previously undetected substructure in the 45Ca-labeled banding pattern seen in enamel maturation.