Both growth hormone-releasing peptide 6 （GHRP-6） and growth hormone-releasing hormone （GHRH） have potent GH-releasing activity in animals. We have previously demonstrated that the administration of a plasmid encoding the GHRH gene to pregnant mice and pig augmented long-term growth in first generation progeny,and that the administration of GHRP-6 results in growth augmentation in mice and rabbits. However,it has not yet been reported if GHRP-6 induces intergenerational growth effects in pigs. Ploy lactic-co-glycolic acid （PLGA） microsphere adsorption of treatment proteins enhances gene expression,genetic immunization and the ability to protect plasmid DNA and peptides from degradation. The cur-rent study was conducted to determine the growth performance of piglets born to gilts treated with GHRP-6 incorporated into thermosensitive PLGA-PEG-PLGA triblock copolymers. Gilts were injected intra-muscularly once at day 85 of gestation with 30 mg of GHRP6-loaded thermosensitive PLGA-PEG-PLGA triblock copolymers. Piglets were weighed periodically between birth and 28 days. Mean body weights of piglets born to GHRP-6-treated gilts were 6. 58% to 18. 89% （P 〈 0. 05 ） greater than those of piglets born to control gilts. This study confirms that enhanced maternal GHRP-6 mediated by thermosensitive PLGA-PEG-PLGA can augment growth of piglets.
Small bioactive peptides, with diverse biological functions, have received increasing attention as physiologically beneficial substances in animal production. The main obstacle to wide application of small bioactive peptides is a lack of costeffective methods for mass production. In this study, we mass-production method for small bioactive peptides. used glycyl-glutamine （Gly-Gln） as a test case to develop a novel The oligonucleotide encoding Gly-Gln pro-peptide （Gpp） was designed and synthesized. Gpp includes 3 Gly-Gln dipeptides and 2 enzymatic sites for pepsin and trypase, allowing direct digestion and absorption of Gly-Gln in the gastrointestinal tract. The Gpp oligonucleotides were linked to generate an oligomeric oligonucleotide segment containing 12 tandem copies of Gpp. This 12Gpp segment was cloned and expressed in Escherichia coli vector pET32a. By optimizing culture conditions [0.1 mmol L^-1 isopropyl-β-D- thiogalactopyranoside （IPTG）, 50 μg mL^-1 ampicillin （Amp）, 30℃ for 12 h], the thioredoxin fusion peptides reached 40% of total bacterial protein. After purification, the fusion protein was fed to Kunming mice to determine its effect on mouse immune function. The results showed that similar to Gly-Gln dipeptide, Gpp polymer protein could significantly suppress the proliferation of T and B lymphocytes in blood and spleen, and additionally could significantly improve interleukin-2 （IL-2） and interleukin-6 （IL-6） secretion of blood and spleen lymphocytes. These effects were not observed in mice fed a 2 amino acids mix （glycine and glutamine）. These evidences indicated that an efficient digestion of Gpp polymer protein could be achieved when ingested into the animal gut. The expression system in this study provides a potential production method for not only Gly-Gln dipeptide but also other short bioactive peptides.
XU Ping-wen FANG Xin-ling SHU Gang ZHU Xiao-tong LUO Zeng-fu JIANG Qing-yan GAO Ping ZHANG Yong-liang
Bone marrow mesenchymal stem cells （BMSCs） could differentiate into various cell types including adipocytes and myocytes, which had important scientific significance not only in the field of tissue regeneration, but also in the field of agricultural science. In an attempt to exhibit the characterization and differentiation into adipocytes and myocytes of porcine BMSCs, we isolated and purified porcine BMSCs by red blood cell lysis method and percoll gradient centrifugation. The purified cells presented a stretched fibroblast-like phenotype when adhered to the culture plate. The results of flow cytometry analysis and immunofluorescence staining demonstrated that the isolated cells were positive for mesenchymal surface markers CD29, CD44 and negative for hematopoietic markers CD45 and the adhesion molecules CD31. Cells were induced to differentiate into adipocytes with adipogenic medium containing insulin, dexamethasone, oleate and octanoate. Oil Red O staining demonstrated that the porcine BMSCs successfully differentiated to adipocytes. Moreover, the findings of real-time PCR and Western blotting indicated that the induced cells expressed adipogenic marker genes （PPAR-y, C/EBP-c~, perilipin, aP2） mRNA or proteins （PPAR-3,, perilipin, aP2）. On the other hand, porcine BMSCs were induced into myoctyes with myogenic medium supplemented with 5-azacytidine, basic fibroblast growth factor, chick embryo extract and horse serum. Morphological observation by hochest 33342 staining showed that the induced cells presented as multi-nucleus muscular tube structure. And myogenic marker genes （Myf5, desmin） mRNA or proteins （MyfS, MyoD, myogenin, desmin） were found in the induced cells. In addition, the results of immunofluorescence staining revealed that myogenic marker （Myf5, MyoD, myogenin, desmin, S-MyHC） proteins was positive in the induced cells. Above all, these results suggested that the isolated porcine BMSCs were not only consistent with the characterization of mesenchymal stem cells, but also e
