Dipartimento di Patologia Animale, Sez. Anatomia patologica, Facoltà di Medicina Veterinaria di Torino, Università di Torino, Via L. da Vinci 44, 10095 Grugliasco (TO), Italy.
Vet Rec. 2010 Aug 28;167(9):338-43. doi: 10.1136/vr.c3303.
Thymus atrophy and regeneration were studied in 13- to 22-month-old beef calves treated with dexamethasone (DMT), using anabolic dosages and implementing different withdrawal times. Two trials were conducted. In trial 1, group A (n=6) received 0.7 mg/day DMT orally for 40 days, group B (n=6) received 1.4 mg/day orally for 40 days and group C (n=6) was the control. In trial 2, group D (n=6) received 0.7 mg/day DMT orally for 40 days, group E (n=6) received 1.4 mg/day orally for 40 days and group K (n=6) was the control. DMT withdrawal times before slaughter were six days (groups A and B) and 26 days (groups D and E). At slaughter, thymus atrophy was severe and progressive in animals from groups A and B. In contrast, thymus weight and volume of the animals from groups D and E were almost normal. Slight atrophy was also detected in the calves in these groups. Histological changes and Ki67 immunostaining revealed a large number of positive lymphoid cells, mostly in the cortical area, associated with higher expression of apoptosis in the medulla compared with controls. This demonstrated that the thymus of beef cattle is still able to regenerate following DMT administration.
研究了用合成代谢剂量的地塞米松（DMT）处理 13-22 月龄的肉牛犊后的胸腺萎缩和再生，并实施了不同的停药时间。进行了两项试验。在试验 1 中，A 组（n=6）经口接受 0.7mg/天 DMT 治疗 40 天，B 组（n=6）经口接受 1.4mg/天 DMT 治疗 40 天，C 组（n=6）为对照组。在试验 2 中，D 组（n=6）经口接受 0.7mg/天 DMT 治疗 40 天，E 组（n=6）经口接受 1.4mg/天 DMT 治疗 40 天，K 组（n=6）为对照组。屠宰前 DMT 停药时间为 6 天（A 组和 B 组）和 26 天（D 组和 E 组）。屠宰时，A 组和 B 组动物的胸腺严重且呈进行性萎缩。相比之下，D 组和 E 组动物的胸腺重量和体积几乎正常，这些组的小牛也出现了轻微的萎缩。组织学变化和 Ki67 免疫染色显示大量阳性淋巴细胞，主要位于皮质区，与对照组相比，髓质中的细胞凋亡表达更高。这表明，在 DMT 给药后，肉牛的胸腺仍然能够再生。
