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We examined the morphological changes in fibers, localization of apoptotic cells, and protein expression of αB-crystallin in the lens of Morioka cataract (MCT) mice, a novel cataract model. Using a scanning electron microscope, swollen lens fibers and enlarged spaces between lens fibers were observed in the lens of 3-week-old MCT mice. At 2 weeks of age (before cataract), the single-strand DNA (ssDNA)-positive (indicating apoptosis) cell ratio of the lens epithelium was significantly higher in MCT than in wild-type ddY mice. At 2 and 4 weeks of age, αB-crystallin protein expression of the lens in MCT mice was significantly lower than that in wild-type ddY mice. These findings suggest that increase in apoptosis and reduction in αBcrystallin level are involved in the cataractogenesis of MCT mice.

Effects of low protein intake on the development of the remaining kidney in subtotally (5/6) nephrectomized immature rats were examined. Three week-old weaning rats were kept on a diet containing either 12% (Lp rats) or 18% (Np rats) protein for 4 or 8 weeks after subtotal nephrectomy. Blood urea nitrogen (BUN) concentration was determined at 2, 4, 6, and 8 weeks after 5/6 nephrectomy. At 4 or 8 weeks after the operation, glomerular sclerosis and tubulointerstitial damage were assessed by a standard semiquantitative analysis and were expressed as the glomerular sclerosis index (GSI) and interstitial fibrosis score (IFS), respectively. The localization of DNA fragmented cells in the kidney was examined by the terminal deoxynucleotidyl transferase (TdT) -mediated d-UTP-biotin nick end labeling (TUNEL) method and the localization of the epidermal growth factor (EGF) by immunohistochemical methods. BUN concentration was significantly lower in the Lp rats compared with that in the Np rats. Both 4 and 8 weeks after subtotal nephrectomy, GSI and incidence of TUNEL positive cells in the distal tubules were significantly lower in the Lp rats than in the Np rats. Four weeks after the operation, IFS was significantly lower in the Lp rats than in the Np rats. Four and 8 weeks after the operation, EGF positive cells in the distal tubules were more observed in the Lp rats than in the Np rats. These findings reveal that protein restriction is effective in preventing renal tubular scarring in immature rats and that EGF is involved in the process of this prevention.

The present study was designed to explore whether maternal uninephrectomy affects development of the collecting ducts in fetal kidney. Localization of DNA fragmented cells in the kidney of fetal rats from uninephrectomized mothers were examined by the terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP-biotin nick end labeling (TUNEL) method. Immunohistochemistry was used to examine the localizations of bcl-2 gene products. The gene expressions for bcl-2, p53, and WT1 mRNAs were examined by using the semi-quantitative reverse transcript-polymerase chain reaction. TUNEL positive cells were more numerous in the medullary collecting ducts of the fetuses from uninephrectomized mothers than in those of the fetuses from sham-operated ones. The expressions of bcl-2, p53, and WT1 mRNAs were lower in the fetuses from uninephrectomized mothers than in the fetuses from sham-operated ones. Cells in the medullary collecting ducts showed positive reactions to anti-bcl-2 gene products antibody with the reactions being weaker in the fetuses from uninephrectomized mothers. These results showed that maternal uninephrectomy accelerated the development of fetal rat kidney and it was associated with the lowered the expression of bcl-2 in fetal rat kidney.

Localization of apoptotic cells in the kidney of perinatal rats was examined by the terminal deoxynucleotidyl transferase-mediated d-UTP-biotin nick end labeling (TUNEL) method and electron microscopy. Perinatal changes in the percentage of kidney cells with DNA fragmentation were determined by flow cytometric analysis. Through observation of two successive sections, the relationship between the localization of the epidermal growth factor receptor (EGFR) positive cells and TUNEL positive cells in the kidney was determined. From fetal day 18 to neonatal day 5, TUNEL positive cells were noted in immature glomeruli, collecting ducts and interstitium. Electron microscopically, chromatin condensed nuclei and apoptotic bodies were seen in the same tissue component as the TUNEL positive cells. The percentage of DNA fragmented cells significantly increased from fetal days 18 to 20 and significantly decreased from fetal days 20 to 22, while they still remained low in the neonatal period. The TUNEL positive cells in immature glomeruli and collecting ducts were not reactive to the EGFR antibody. The TUNEL positive cells were not observed in the proximal tubular cells, which were positive to EGFR antibody. These results indicate that apoptotic cells are present in the kidney throughout the perinatal period in the rat and that EGF plays an important role in perinatal development of the rat kidney.