牛の神経原性筋脂肪症の2例

北海道留萌保健所天塩支所ウブシ駐在所（〒098-3311　北海道天塩郡天塩町字ウブシ5324-1）

（1998年10月26日受付・1999年5月10日受理）

要　　　　　約 　腰麻痺を示したホルスタイン種乳牛（2歳）と無症状のマリーグレー種肥育牛（3歳）に筋脂肪症を認めた．病変は左右対称性で，きわめて多量の脂肪組織が筋実質内に存在し，前者では横隔膜筋を含むほとんどすべての骨格筋に，後者では僧帽筋において認められた．筋肉固有容積の減少はなかった．組織学的に，筋組織は脂肪細胞によって広範囲に置換され，筋線維をほとんど欠く筋束もみられた．残存筋組織中には散在性に変性・壊死線維がみられ，ときに扁平あるいは角ばった小径化筋線維が核の中央移動や増加を伴って孤在性あるいは小集団単位で観察され，脱神経支配による筋線維萎縮像と考えられた．筋線維の再生像や結合組織線維の増殖は認められなかった． ―キーワード：牛，骨格筋，脂肪症． --------------------日獣会誌　52，525〜528（1999） Neurogenic Muscular Steatosis in Cattle Susumu OHFUJI Ubushi substation, Teshio branch of Hokkaido Rumoi Health Centre, 5324-1 Ubushi, Teshio, Hokkaido 098-3311, Japan SUMMARY 　A 2-year-old Holstein-Friesian cow with posterior weakness and an apparently normal 3-year-old Murray Grey steer were pathologically found to have steatosis in the skeletal muscles at meat inspection. In the Holstein-Friesian case, almost all the skeletal and diaphragmatic muscles of the carcasses contained considerable adipose tissue, whereas the trapezius muscle only was involved in the Murray Grey case. In both cases, steatotic lesions were distributed bilaterally and symmetrically without noticeable reduction in the original muscle volume. Microscopic feature common to the affected muscles in both cases was replacement of muscle fibers by fat cells, being so extensive as to reveal nearly complete absence of muscle fibers in some fascicles. Degenerative/necrotic muscle fibers were scattered in the recognizable muscle tissue. Frequently muscle fiber alteration was characteristic of denervation, showing sharply angulated or flattened atrophied muscle fibers, arranged singly or in small groups occasionally in association with internal nuclei or apparently increased number of nuclei. Neither regenerated muscle fibers nor proliferation of the stromal connective tissue were found. ―Key words : cattle, skeletal muscle, steatosis. --------------------J. Jpn. Vet. Med. Assoc., 52, 525〜528(1999)