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Table 3 Histopathological findings of the lung, peritoneum and pleura in rats exposed to MWNT-7 for 104 weeks

From: Lung carcinogenicity of inhaled multi-walled carbon nanotube in rats

 

Male

Peto test

Female

Peto test

Group (mg/m3)

0

0.02

0.2

2

0

0.02

0.2

2

Number of animals examined

50

50

50

50

 

50

50

50

50

 

Neoplastic lesions

 Lung

          

  Bronchiolo-alveolar carcinoma

1

1

8 #

10 ##

↑↑

0

1

0

5 ##

↑↑

  Adenosquamous carcinoma

0

0

0

1

 

0

0

0

1

 

  Poorly differentiated adenocarcinoma

0

0

0

0

 

0

0

0

1

 

  Squamous carcinoma

0

0

0

0

 

0

0

0

1

 

  Total carcinoma

1

1

8 #

11 ##

↑↑

0

1

0

8 ##

↑↑

  Bronchiolo-alveolar adenoma

1

1

7 #

5

 

3

1

4

3

 

  Total adenoma and/or carcinoma

2

2

13 ##

16 ##

↑↑

3

2

4

11 #

↑↑

 Peritoneum

          

  Malignant mesothelioma

0

3

1

1

 

0

0

0

0

 

Non-neoplastic lesions

 Lung

          

  Bronchiolo-alveolar hyperplasia

2 (1.5)

6 (1.3)

13 * (1.2)

22 ** (1.0)

 

3 (1.3)

3 (1.0)

8 (1.1)

12 * (1.1)

 

  Atypical hyperplasia

0

0

1 (1.0)

10 ** (1.3)

 

0

0

0

14 ** (1.1)

 

  Alveolar hyperplasia

0

2 (1.0)

13 ** (1.0)

41 ** (1.0)

 

1 (1.0)

1 (1.0)

6 (1.0)

41 ** (1.1)

 

  Bronchiolar hyperplasia

0

0

4 (1.0)

8 ** (1.0)

 

0 (1.0)

0 (1.0)

4 (1.0)

26 ** (1.0)

 

  Accumulation: alveolar macrophage

2 (1.0)

7 (1.0)

5 (1.0)

48 ** (2.0)

 

2 (1.0)

6 (1.0)

9 (1.0)

48 ** (1.8)

 

  Focal fibrosis: alveolar wall

0

2 (1.0)

43 ** (1.0)

48 ** (1.8)

 

0

3 (1.0)

44 ** (1.0)

49 ** (1.2)

 

  Granulomatous change

0

5 (1.0)

42 ** (1.0)

50 ** (1.9)

 

0

3 (1.0)

45 ** (1.0)

50 ** (1.8)

 

 Pleura

          

  Simple mesothelial hyperplasia

3 (1.0)

3 (1.0)

7 (1.0)

12 * (1.0)

 

3 (1.0)

2 (1.0)

6 (1.0)

10 (1.0)

 

  Focal fibrosis: parietal (diaphragm)

0

0

2 (1.0)

6 * (1.0)

 

0

0

0

3 (1.0)

 

  Focal fibrosis: ventral (lung)

0 (1.0)

2 (1.0)

4 (1.0)

19 ** (1.1)

 

0

2 (1.0)

2 (1.0)

20 ** (1.0)

 

Inflammation: mediastinum

15 (1.0)

18 (1.0)

21 (1.0)

26 * (1.0)

 

17 (1.0)

17 (1.0)

16 (1.0)

19 (1.0)

 

  Inflammation: diaphragm

0

0

1 (1.0)

1 (1.0)

 

0

1 (1.0)

1 (1.0)

1 (1.0)

 
  1. Values indicate number of animals bearing the lesion
  2. Values in parentheses are the average of severity grade indexes of the lesions in affected animals. The average of severity grade indexes are calculated with a following equation. 〔Σ(grade × number of animals with grade)〕÷number of affected animals. Grade: 1 = slight, 2 = moderate, 3 = marked, 4 = severe
  3. Significant difference; *: p≦0.05, **: p≦0.01 by Chi-square Test, #: p≦0.05, ##: p≦0.01 by Fisher Exact Test, ↑: p≦0.05, ↑↑: p≦0.01 by Peto’s Test