Prediction of The Marbled Beef Quality before Fattening up Japanese Black Cattle

大理石牛肉(Shimofuri-Niku)在日本是一种备受推崇的畜产品，其中的肌肉纤维与精细的脂肪组织相互作用。由于其柔软多汁的质地，大理石牛肉的交易价格高于普通牛肉。为了生产大理石纹牛肉，农民花了大量的精力和金钱来育肥具有良好遗传背景的小牛。由于这种脂肪组织在肌肉纤维中形成的确切机制尚不清楚，因此，被认为具有良好遗传背景的小牛，其品质差异很大。肉牛育肥前的牛肉品质预测是日本畜牧业的一项重要技术。脂肪细胞与骨细胞、软骨细胞和平滑肌细胞属于间充质细胞谱系，并根据微环境的不同而与结缔组织中的普通干细胞区分开来。目前已建立了许多具有间充质干细胞潜能的细胞系，其中3T3F442a是一种…更多这样的细胞系。在本研究中，我们首次发现将体外培养的3T3F442a细胞移植到裸鼠皮下形成脂肪垫，在其中分化良好的脂肪细胞带有丰富的微血管。生长因子如碱性成纤维细胞生长因子、血小板衍生生长因子、胰岛素样生长因子和生长激素刺激脂肪垫的形成，但单独注射这些生长因子不能诱导脂肪垫的形成。然而，当这些生长因子与重组的基底膜成分(Matrigel)一起注射时，在没有外源前体细胞的情况下形成了发育良好的FAD垫。这表明生长因子被困在重建的基底膜中，这为间充质干细胞增殖和分化为脂肪细胞创造了一个微环境。碱性成纤维细胞生长因子联合Matrigel诱导仅由脂肪细胞组成的PAD，而生长激素联合Matrigel诱导仅由脂肪细胞组成的PAD，但生长激素联合Matrigel诱导肌纤维与脂肪细胞共同组成的PAD。这为在日本黑牛的理想部位诱导大理石纹牛肉提供了一种新的技术。我们克隆了牛C/EBPalpha、C/EBPbeta、C/EBPGamma和PRAYGamma2基因，并获得了针对其重组产物的多克隆抗体。这些基因编码与脂肪细胞分化的遗传控制密切相关的交易因子，并在脂肪组织形成的早期表达。我们还建立了在为大理石纹牛肉生产育肥之前检测小牛脂肪细胞前体的免疫组织化学方法。较少

The marbled beef (Shimofuri-niku)is a highly appreciated livestock product in Japan, in which muscle fibers are interpositioned with fine adipose tissues. Because of its soft and juicy texture, the marbled beef is dealt at higher price than usual beef. For the production of marbled beef, farmers spend a large effort and money to fatten up calves having good genetic background. Since the exact mechanism of such adipose tissue formation in muscle fibers is not known, the quality of marbeled beef varies widely amoung calves beleived to have good genetic background. Prediction of the beef quality before fattening up calves is an important technology for the stockbreeders in Japan.Adipocytes belong to the mesenchymal cell lineage together with osteocytes, chondrocytes and smooth muscle cells, and differentiate from a common stem cells in connective tissue depending on the microenvironment. Many cell lines with the potential of mesenchymal stem cell have been established and 3T3 F442A is one … More of such cell lines. In this study, we first found that transplantation of in vitro cultured 3T3 F442A cells subcutaneously into nude mice forms a fat pad in which well differentiated adipocytes are delivered with abundant micro-capillaries. The growth factors such as bFGF,PDGF,IGF-1 and growth hormone stimulated this fat pad formation but injection of those growth factor alone did not induce fat pad. When these growth factors were injected in combination with the reconstitutted basement membrane components(Matrigel), however, well developed fad pad was formed in the absence of exogenous precursor cells. This shows that growth factors are trapped in the reconstituted basement membrane and this creates a microenvironment where the mesenchymal stem cells proliferate and differentiate into adipocytes. bFGF in combination with Matrigel induced the pads composed of only adipocytes but growth hormone in combination with Matrigel induced the pads composed of only adipocytes but growth hormone in combination with Matrigel induced muscle fibers together with adipocytes. This suggested a new technology of inducing marbled beef at desired site of Japanese black cattle. We have cloned bovine C/EBPalpha, C/EBPbeta, C/EBPgamma and PRAYgamma2 genes and obtained polyclonal antibodies against their recombinant products. These genes encodes transacting factors deeply related to the genetic control of adipocyte differentiation and are expressed at early stage of adipose tissue formation. We also established immunohistochemical method to detect adipocyte presursors in calves before fattening up for the prodution of marbled beef. Less