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

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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