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Identification of Spontaneous Feline Idiopathic Pulmonary Fibrosis: Immunohistochemistry

Electron Microscopy:
Tissues from three affected cats were prepared for electron microscopy. The samples were rinsed in 0.1 mol/L phosphate buffer and placed in osmium tetroxide (Electron Microscopy Sciences; Fort Washington, PA) for 3 h. The tissues were then rerinsed in 0.1M phosphate buffer, followed by three 10-min rinses in 30% ethanol. The tissues were transferred into 2% uranyl acetate (Electron Microscopy Sciences) for 1 h, rinsed in 30% ethanol, and dehydrated in a graded series of ethanol. The tissues were placed in propylene oxide, before being embedded in DMP-30 and araldite 501 (Electron Microscopy Sciences); 1 |j,m sections were cut on a LKB ultramicrotome (LKB; Bromma, Sweden), and stained with toluidine blue. Tissues of interest were sectioned at 600 angstroms, stained with uranyl acetate and lead citrate (Electron Microscopy Sciences), and examined on a Phillips 301 electron microscope (Phillips; Atlanta, GA).

Smooth-muscle actin (SMA) was detected using mouse monoclonal antibody and biotinylated anti-mouse antibody utilized at the dilution recommended by the manufacturer (Dako Corporation; Carpinteria, CA). These were followed by avidin-biotin conjugated horseradish peroxidase, used per instructions of the manufacturer (Vector Laboratories; Burlingame, CA). Diamino-benzidine (Sigma Chemical; St. Louis, MO) was used as the substrate for the peroxidase.
Results
Clincal Findings

A summary of the signalment and clinical signs is found in Table 1. The average age of the affected cats was 8.7 years, with an equal number of male and female animals. In nine of the cats that lived a period of time after onset of the clinical signs, the average duration of signs before death/euthanasia was 5.5 months. In the remaining cats, death occurred suddenly or after a period of days.
Table 1—Signalment and Clinical Findings in Cats With IPF

Cat No.

Age, yr

Sex

Breed

Clinical Signs and Duration

1

13

FS

Mixed

Sudden death

2

12

FS

Mixed

Tachypnea, 4 mo

3

10

FS

Persian

Sudden death

4

6

MC

Mixed

Tachypnea, 6 mo

5

9

MC

Persian

Tachypnea

6

10

FS

DLH

Tachypnea, 6 mo

7

5

MC

Mixed

Tachypnea, N/A

8

5

MC

Mixed

Tachypnea, N/A

9

12

FS

DSH

Tachypnea, 4 mo

10

7.5

FS

DLH

Tachypnea, 4 d

11

2

MC

Mixed

Tachypnea, 1 mo

12

12

MC

DSH

Tachypnea, N/A

13

6

FS

DSH

Tachypnea

14

10

MC

Mixed

NA

15

12

MC

Persian

Tachypnea, 12 mo

16

8

F

DSH

Tachypnea, 6 mo