Mutwiri G K, Butler D G, Rosendal S, Woodward B
Department of Veterinary Microbiology and Immunology, University of Guelph, Ontario.
Can J Vet Res. 1995 Jan;59(1):40-5.
A paired feeding experiment was conducted to investigate if reduced food intake is a reason for the body weight loss previously observed in severe combined immunodeficient beige (SCID bg) mice infected with Mycobacterium paratuberculosis. Mice were paired on the basis of age, litter and sex. One of each pair was injected intraperitoneally with 10(5) viable M. paratuberculosis organisms. The remainder served as uninfected pairfed mates. Each uninfected mouse was restricted to the amount of food (per gram body weight) that its infected paired mate ate in the previous 24 hour period starting at four weeks postinfection until 12 weeks postinfection when the mice were necropsied. The mean body weights of the two groups were not significantly different (p < 0.05) at the start of the experiment (infected 27.6 +/- 2.1 g, pairfed 27.3 +/- 3.4 g) but the pairfed group weighed less after 12 weeks of restricted food intake. Mycobacterium paratuberculosis was isolated from the spleen, liver, gut and fecal pellets of the infected but not the uninfected mice. Acid-fast bacilli were seen histologically in the liver, spleen and intestines of the infected mice only. Analysis of carcass compositions indicated that both infected and pairfed mice lost dry matter. Despite the loss in dry matter, the infected mice appeared to have maintained their body weights due to an increased retention of body water (presumably due to edema of inflammation). These results suggest that infection of SCID bg mice with M. paratuberculosis causes a reduction in their food intake (presumably due to reduced appetite) which, in turn, contributes to a loss in dry matter. We suggest that this loss in dry matter is one of the initial events that eventually lead to cachexia, and that it precedes the body weight loss that inevitably occurs in SCID bg mice chronically affected with M. paratuberculosis.
进行了一项配对喂养实验，以研究食物摄入量减少是否是先前在感染副结核分枝杆菌的严重联合免疫缺陷米色（SCID bg）小鼠中观察到体重减轻的原因。小鼠根据年龄、窝别和性别进行配对。每对中的一只小鼠腹腔注射10(5) 个活的副结核分枝杆菌。其余小鼠作为未感染的配对喂养伙伴。从感染后四周开始，直到感染后12周小鼠进行尸检时，每只未感染的小鼠被限制摄入其感染的配对伙伴在前24小时内所吃的食物量（每克体重）。在实验开始时，两组小鼠的平均体重没有显著差异（p < 0.05）（感染组27.6 +/- 2.1克，配对喂养组27.3 +/- 3.4克），但在限制食物摄入12周后，配对喂养组的体重较轻。在感染小鼠的脾脏、肝脏、肠道和粪便颗粒中分离出了副结核分枝杆菌，而未感染小鼠中未分离到。仅在感染小鼠的肝脏、脾脏和肠道中在组织学上观察到抗酸杆菌。胴体成分分析表明，感染小鼠和配对喂养小鼠都损失了干物质。尽管干物质有所损失，但感染小鼠由于身体水分保留增加（可能是由于炎症性水肿）似乎维持了体重。这些结果表明，SCID bg小鼠感染副结核分枝杆菌会导致其食物摄入量减少（可能是由于食欲下降），这反过来又导致干物质损失。我们认为，这种干物质损失是最终导致恶病质的最初事件之一，并且它先于长期感染副结核分枝杆菌的SCID bg小鼠不可避免地出现的体重减轻。
