Tatsuyuki Otoshi

Renal lesions induced in F344/DuCrj rats by 4-weeks oral administration of dimethylarsinic acid

The nephrotoxicity of dimethylarsinic acid (cacodylic acid, DMA) was examined in male and female F344/DuCrj rats. DMA administered perorally at doses of 113, 85, and 57 mg/kg for 4 weeks produced dose-related decreases in body weight and survival rate in both sexes. Mortality was higher and appeared more quickly in females than in males. Histopathological findings in the kidney were proximal tubular degeneration and necrosis, as well as papillary necrosis, and hyperplasia of the epithelium covering the papillae. Since extensive proximal tubular necrosis was observed only in dead animals of both sexes, and not in survivors or the controls, it was therefore concluded that the main cause of death could be attributed to nephrotoxicity of DMA. The results thus show that DMA is nephrotoxic to both male and female rats.

Morphological studies of mesothelial cells in CAPD effluent and their clinical significance

We studied the mesothelial cells in the effluent of patients undergoing continuous ambulatory peritoneal dialysis (CAPD) and their relationship with CAPD duration, peritoneal function, peritoneal sclerosis (PS), and sclerosing encapsulating peritonitis (SEP) in 49 patients (26 men, 23 women) treated for 3 to 161 months with CAPD. Three patients had SEP and five patients had PS. The overnight effluent was drained and centrifuged. The cell differentiation and surface area of mesothelial cells were studied by a computed light microscope system after cytospin preparation staining. The surface area of 50 cells was measured. The mesothelial cells were classified into three types according to their morphological appearance: normal cell type, with a mean surface area of 335.6+/-31.0 microm2 and mean nucleocytoplasmic ratio (N/C ratio) of 0.66+/-0.01; dyskaryotic cell type, with a mean surface area of 570.5+/-35.9 microm2 and N/C ratio 0.58+/-0.06; and giant cell type, with a mean surface area of 1,821.0+/-68.8 microm2 and N/C ratio of 0.06+/-0.01. There was a low but significant correlation between the fast peritoneal equilibration test and surface area (r=0.495; P=0.0120) and a highly significant correlation between CAPD duration and mean surface area (r=0.719; P < 0.0001). This increased cell surface area was because of both an increased surface area of normal and dyskaryotic cells and an increase in the number of dyskaryotic and giant cells. The mean surface area in patients with SEP was 709.3+/-125.4 microm2 and that in patients with PS was 586.6+/-55.2 microm2. Giant cells were found in the effluent of all three patients with SEP and three of the patients with PS. In conclusion, a marked correlation was found between the surface area of effluent mesothelial cells and the duration of CAPD. Giant cells were almost always found in the effluent of patients with SEP and PS. The surface area of mesothelial cells in the effluent might reflect morphological changes in the peritoneum during CAPD. These morphological changes and the measurement of the size of mesothelial cells may predict critical derangement of peritoneal membrane.

Correlation between Peritoneal Mesothelial Cell Cytology and Peritoneal Histopathology with Respect to Prognosis in Patients on Continuous Ambulatory Peritoneal Dialysis

Background: Sclerosing encapsulating peritonitis (SEP) is a serious complication seen in patients on long-term continuous ambulatory peritoneal dialysis (CAPD). We have previously reported that mesothelial cells in effluent dialysate significantly increased in size as the duration of CAPD progressed. In this study, we investigated the relationship between mesothelial cytology, histopathology of the peritoneum, and clinical outcomes of 34 CAPD patients. Methods: When peritoneal dialysis catheters were inserted (n = 7) or removed (n = 27), a peritoneal biopsy was performed and results compared with mesothelial cytology in effluent dialysate. Results: A significant positive correlation was noted between the duration of CAPD and the surface area of peritoneal mesothelial cells (r = 0.721, p < 0.0001). The surface area of mesothelial cells in peritoneal sclerosis (n = 9; 584 ± 97 µm2) was significantly greater than in peritoneal fibrosis (n = 14; 389 ± 26 µm2, p < 0.05), pathologic acute peritonitis (n = 3; 223 ± 10 µm2, p < 0.005), and normal peritoneum (n = 7; 247 ± 12 µm2, p < 0.001). The surface area in sclerosing peritonitis (n = 1; 1,200 µm2) was greater than that of all the others. Giant cells were found in the 1 case with sclerosing peritonitis and in 3 of 9 cases with peritoneal sclerosis, although they were found in only 1 of 14 patients with peritoneal fibrosis and in none of those with pathologic acute peritonitis or normal peritoneum. As the surface area of mesothelial cells increased to more than 400 µm2 and giant cells appeared in the effluent, the frequency of peritoneal sclerosis and/or clinical SEP increased. Conclusion: An increase in the mesothelial cell surface area and the emergence of giant cells in the effluent indicate advanced peritoneal histopathology, and may be useful indicators to determine appropriate timing of discontinuation of CAPD to prevent the development of SEP.

Validation of silver-stained nucleolar organizer regions for evaluation of invasive character of urinary bladder carcinoma in rats and mice

A series of 8 rat and 16 mouse invasive bladder carcinomas were investigated for the presence of silverstained nucleolar organizer regions (AgNORs) to clarify whether this parameter is applicable to the estimation of their invasive character. With regard to number of AgNORs per cell, neither rat nor mouse carcinomas showed any difference between invasive and noninvasive sites within the same tumor. However, the frequency of cancer cells bearing bizarre dots, irregular in size and shape, was significantly higher at sites of actual invasion. Quantitative data generated using an image analyzer revealed significantly lower values for NOR roundness and significantly larger NOR size in invasive sites than in noninvasive sites in all groups. Double staining for the proliferation marker proliferating cell nuclear antigen (PCNA) and AgNORs was performed on eight rat carcinomas and a close correlation between the two was confirmed. Thus the number of AgNORs in PCNA-positive cells was significantly greater than in PCNA-negative cells. Furthermore, a particularly strong correlation was observed for incidences of PCNA-positive cells and bizarre dots (P<0.01). The quantitative data also demonstrated significant differences in size and shape of dots. It is concluded that AgNORs have diagnostic value for the invasive character of bladder carcinomas.