Yoshio Morikawa

Perinatal development of the rat kidney : Proliferative activity and epidermal growth factor

The immunolocalization of proliferating cell nuclear antigen (PCNA), epidermal growth factor (EGF) and its receptor (EGFR) was examined in the perinatal rat kidney. As the index of proliferative activity, PCNA-positive cell ratios in glomeruli and proximal tubules were determined. The PCNA-positive ratios in both glomeruli and proximal tubules decreased significantly during the perinatal period and tended to decrease as the glomerular developmental stage proceeded as well. PCNA-positive cells were seen predominantly in the nephrogenic zone of the kidney throughout the period examined. They were noted in the collecting ducts of the nephrogenic zone and were rarely seen in those of the central zone of the kidney. On the other hand, PCNA-positive cells were noted in the straight portion of the proximal tubules and were rarely seen in the convoluted one. EGF-positive cells were seen in the proximal tubules, distal tubules and collecting ducts, though EGF-positive cells in the proximal tubules decreased after birth. EGFR-positive cells were seen along the entire length of the proximal tubules and collecting ducts as well as in immature glomeruli, not in mature ones. These results indicate that marked cell proliferation occurs in the collecting ducts in the peripheral area and in the proximal tubules in the central area of the kidney, that the proliferative activity decreases with age during the perinatal days and that EGF plays an important role in the proliferation of glomerular cells, and in both proliferation and maturation of the cells in the proximal tubules and collecting ducts.

Light- and Electron-Microscopic Studies on the Gastric Parietal Cells in Perinatal Rats

Perinatal changes of the gastric parietal cells were studied under normal and various experimental conditions. Histologic examination revealed that the parietal cells appeared markedly increased in number from late fetal to early neonatal days. When premature newborn rats were delivered by cesarean section and were nursed by foster mothers for 1 or 2 days, the degree of increase of these cells reached nearly that in the normal neonates. On the other hand, in fetuses retained in utero 1 day beyond the normal gestation, these cells appeared not increased in number. When these postmature fetuses were delivered, the parietal cells turned to increase in number in a degree similar to that in the normal neonates. Milk given to the premature newborn rats caused 6 h later a marked increase in the number of the parietal cells. Milk given to fetuses in utero also caused an increase of these cells. The results suggest that the development of the parietal cells in perinatal rats is accelerated by the intake of milk and that the fetal parietal cells are ready to respond to milk given at least 1 day before birth.

Growth-Factor-Like Substance in Amniotic Fluid in the Rat: Effect on the Development of Fetal Colonic Goblet Cells

Extra- and intrauterine fetuses were studied to explore the effect of amniotic fluid on the development of colonic goblet cells. Significant differences in the density of goblet cells in developing colon were observed during fetal days 19-22 between these two groups, suggesting that amniotic fluid affects the development of the colonic goblet cells, especially during the period between days 19 and 21 when rat fetuses began to swallow amniotic fluid, as demonstrated by injecting India ink into the amniotic cavity. By immunological dot blot analysis, the amniotic fluid and gastric juice from intrauterine fetuses were positive for epidermal growth factor (EGF), whereas maternal abdominal serous fluid and gastric juice from extrauterine fetus were negative for EGF. The present results indicate that the amniotic fluid during late gestation greatly affects the development of the colonic goblet cells in rat fetuses and that the trophic factors for the cells seems to be EGF or an EGF-like substance in the amniotic fluid.

Development of the proximal tubule of the fetal rat kidney : Morphometry and ultrastructural findings

The development of the kidney in fetal rats was investigated morphometrically and ultrastructurally. Both the length and volume of the proximal tubule increased with age. The total volume of functional glomeruli increased markedly from fetal day 20 onward. The ratio of total glomerular volume to total proximal tubular volume decreased with age and was less than 1 from fetal day 20 onward. The cells of the proximal tubule had numerous microvilli on their free surfaces and vacuoles in the apical region of the cytoplasm after fetal day 20. These findings indicate that the relative growth of the proximal tubule has exceeded that of the glomeruli by fetal day 20, and that increased filtration induces both the growth and the differentiation of the proximal tubule during development of the fetal rat kidney.

Morphometrical changes in the apical surface of the colonic absorptive cells in perinatal rats with special reference to the effect of fetal oral administration of milk in utero

Perinatal changes in the apical surface of the colonic absorptive cells in the rat were studied morphometrically. Cell microvilli length increased from day 20 through neonatal day 3, during which a maximum incremental growth rate was noted between fetal day 22 and neonatal day 1. Microvilli width remained almost constant throughout the period. Enlargement of the apical surface of the microvilli showed a similar developmental pattern as was seen from the measurement of length and surface area of any one of the microvilli. Fetal oral administration of milk in utero caused incremental growth in length and surface area, as well as an associated apical surface enlargement. The present study indicates that the function of the colonic absorptive cells, which is acquired later on in utero, is activated by ingestion of maternal milk after birth.

Effects of maternal uninephrectomy on the development of fetal rat kidney: Numerical and volumetric changes of the glomerulus and formation of the anionic site in the glomerular basement membrane

Developmental processes of the fetal rat kidney from uninephrectomized mothers were studied. The uninephrectomy was performed on day 5 of gestation. Glomerular number and volume in the fetal kidneys on days 18, 20, and 22 of gestation were morphometrically determined. To investigate the anionic site formation in the glomerular basement membrane, distribution of cationized ferritin (CF) in the fetal glomerulus was examined electron microscopically after CF injection. Blood urea nitrogen (BUN) concentration in the pregnant rats was also determined on various days after uninephrectomy. On fetal days 20 and 22, the glomerular volume was significantly larger in the fetuses from uninephrectomized mothers than in those from sham‐operated ones. On fetal day 20, the CF particles were clustered in the laminae rarae interna and externa of the glomerular basement membrane in the fetuses from uninephrectomized mothers, while the clusters were arrayed in three to four layers in the glomerular basement membrane in the fetuses from sham‐operated ones. On fetal day 22, the CF particles noted in the lamina rara externa in the fetuses from uninephrectomized mothers were slightly larger in number than such particles in the age‐matched control fetuses. The BUN concentration of the uninephrectomized pregnant rats was significantly higher than that of the sham‐operated pregnant ones on each postoperative day. These results suggest that the development of the fetal renal glomerulus is accelerated by the elevated BUN level following maternal uninephrectomy when the fetal kidney is functional in effective filtration in the rat. J. Morphol. 238:337–342, 1998.

Effects of maternal uninephrectomy on the development of fetal rat kidney: apoptosis and the expression of oncogenes.

ABSTRACT    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.

Effects of maternal uninephrectomy on the development of fetal rat kidney with special reference to the proliferative activity and epidermal growth factor (EGF).

ABSTRACT Immunolocalization of proliferating cell nuclear antigen (PCNA), epidermal growth factor (EGF) and EGF receptor (EGFR) in the kidney of fetal rats from uninephrectomized mothers were examined. As the index of proliferative activity, PCNA positive cell ratios in glomeruli and proximal tubules were determined. In the fetuses from uninephrectomized mothers and sham‐operated mothers, the PCNA positive cells were seen predominantly in the nephrogenic zone of the kidney. On fetal day 22, the PCNA positive cell ratio in the glomerulus of the fetus from uninephrectomized mothers (E fetus) was significantly lower than that in the glomerulus of the fetus from sham‐operated ones (C fetus). The proximal tubular cells showed positive reaction to EGF and EGFR antibodies in both fetuses. On fetal day 22, the reactions of the proximal tubules to EGF and EGFR antibodies were stronger in E fetus than in C fetus.

Morphometrical Studies on Perinatal Development of Glomerular Components in Rat

Perinatal development of rat glomerulus was studied morphometrically. The percentage volumes of the five glomerular components (epithelial cells, capillary, mesangium, glomerular basement membrane, and Bowmans space) were determined by point counting and the surface area of glomerular basement membrane per unit volume of glomerulus was done by intercept counting. Percentage volume of Bowmans space was significantly decreased between days 20 and 21 of gestation, indicating the rapid growth of glomerular tuft during the prenatal period. Though both the length of glomerular capillary per unit volume of glomerulus (Lv) and surface area of glomerular basement membrane per unit volume of glomerulus were gradually increased from fetal day 20 to neonatal day 3, remarkable increase in Lv was observed between fetal day 22 and neonatal day 1. This indicates that the rat glomerulus develops rapidly during this period to adapt to extrauterine environment after birth.

Perinatal Development of Brunner’s Glands in the Rat: Morphometrical Study

Perinatal changes of the Brunners glands in rats from fetal day 20 through neonatal day 3 were studied morphometrically and electron-microscopically. Percentage volume of secretory granules of the gland cells did not change from fetal day 20 through neonatal day 1 and increased significantly from neonatal days 1-2; this level was maintained through neonatal day 3. Electron-microscopically, the gland cells during the fetal days were rich in free ribosomes. The Golgi apparatus and rough-surfaced endoplasmic reticulum (RER) were poorly developed during fetal days. After birth, however, the cells showed active formation of secretory granules, which was evidenced by well-developed Golgi apparatus, distended RER and accumulation of granules in the apical cytoplasm. Furthermore, light microscopy revealed that strongly PAS-positive material increased for the first time after birth, indicating remarkable formation of the secretory granules. Thus, the present study indicates that the cell of the Brunners glands become active in secretory granule formation just after birth by responding to ingested material following birth.