Zancanaro C, Merigo F, Digito M, Pelosi G
Institute of Anatomy and Histology, University of Verona, University of Padova, Italy.
J Morphol. 1996 Mar;227(3):321-34. doi: 10.1002/(SICI)1097-4687(199603)227:3<321::AID-JMOR4>3.0.CO;2-8.
In the frog, the fat body is the largest body lipid deposit and is associated with the gonad. The aim of the present work was to investigate the fine structure of the fat body at different periods of the annual cycle and during prolonged starvation. Results indicate that fat body cells of Rana esculenta caught in autumn and after winter hibernation resemble mammalian adipocytes of white adipose tissue and contain markers of adipose tissue, such as S-100 protein and lipoproteinlipase. However, unlike mammalian adipocytes, fat body adipocytes consistently show small lipid droplets associated with their single, large lipid deposits, a lack of a definite external lamina, and the presence of cellular prolongations and spicula at their surfaces. Transmission and scanning electron microscopy in association with lanthanum tracer experiments suggest that in fat body adipocytes a vesicular-tubular system connects the cytoplasm and the interstitial space. In June (i.e., during the reproductive period), fat body adipocytes appear to have lost much of their lipid deposit and adjacent adipocytes show interdigitation of their plasma membranes and prominent Golgi complexes. In starved frogs, fat body cells can be almost devoid of lipid and in regression to a near-mesenchymal state. Nevertheless, these fat bodies still contain lipoproteinlipase activity (approximately 45% of that found in lipid-filled ones), indicating persistent adipose differentiation of the cells therein. Results presented here show that the R. esculenta fat body is an adipose organ undergoing reversible extreme changes in adipocyte fat content, which are associated with definite ultrastructural features. The fat body represents a suitable model for studying adipose tissue under different and extreme physiological conditions.
在青蛙体内，脂肪体是最大的身体脂质储存部位，且与性腺相关。本研究的目的是调查一年周期中不同时期以及长期饥饿期间脂肪体的精细结构。结果表明，秋季捕获的食用蛙以及冬季冬眠后的脂肪体细胞类似于白色脂肪组织的哺乳动物脂肪细胞，并含有脂肪组织标记物，如S - 100蛋白和脂蛋白脂肪酶。然而，与哺乳动物脂肪细胞不同的是，脂肪体脂肪细胞始终显示出与其单个大脂质沉积物相关的小脂滴，缺乏明确的外部薄片，并且在其表面存在细胞延长部分和针状物。透射电子显微镜和扫描电子显微镜结合镧示踪实验表明，在脂肪体脂肪细胞中，一个囊泡 - 管状系统连接细胞质和细胞间隙。在六月（即繁殖期），脂肪体脂肪细胞似乎失去了大部分脂质沉积物，相邻的脂肪细胞显示出其质膜的相互交错和突出的高尔基体复合物。在饥饿的青蛙中，脂肪体细胞几乎可以没有脂质，并退化为接近间充质状态。然而，这些脂肪体仍然含有脂蛋白脂肪酶活性（约为充满脂质的脂肪体中发现的活性的45%），表明其中的细胞持续存在脂肪分化。此处呈现的结果表明，食用蛙脂肪体是一个脂肪器官，其脂肪细胞脂肪含量经历可逆的极端变化，这些变化与明确的超微结构特征相关。脂肪体代表了一个在不同和极端生理条件下研究脂肪组织的合适模型。
