The relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore the relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus.</p><p><b>METHODS</b>After 28-day hind-limb unloading and muscle atrophy, we used the method of isolated muscle perfusion with different stimulated protocols to determine the changes in contractile characteristics including the isometric twitch force and tetanus force and fatigue index of slow twitch muscle in mice. The muscle myofibrillar composition and fiber type conversion were detected by immunofluorescence staining and real-time PCR.</p><p><b>RESULTS</b>The isometric twitch force and the tetanus force and fatigue index were decreased progressively in 28-day unloaded mice soleus, with the increase in fast twitch fiber subtype and the decrease in slow twitch fiber subtype.</p><p><b>CONCLUSION</b>The alteration of contractile characteristics is relevant to the slow-to-fast fiber conversion in mice soleus after 28-day hind-limb unloading.</p>

Expression, purification and refolding of streptavidin-tagged human tumor necrosis factor-alpha fusion protein / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the purification, refolding and bioactivity of streptavidin-tagged human tumor necrosis factor-alpha (SA-TNF-alpha) bi-functional fusion protein.</p><p><b>METHODS</b>SA-TNF-alpha fusion protein was expressed in BL21(DE3) host bacteria, purified using Ni-NTA affinity chromatography and refolded by dilution and dialysis followed by identification using Western blotting. The effect of SA-TNF-alpha fusion protein against L929 cells was evaluated by MTT assay. Flow cytometry was used to analyze the surface modification of biotinylated MB49 tumor cells by SA-TNF-alpha fusion protein.</p><p><b>RESULTS</b>Recombinant SA- TNF-alpha fusion protein was expressed in BL21(DE3) at about 30% of total bacterial protein, with a purity of about 95% after purification. The SA-TNF-alpha fusion protein existed as dimmers, tetramers and higher order structures after refolding. The fusion protein exhibited a bi-functionality by inhibiting L929 cells and SA-mediated high-affinity binding to biotinylated cell surfaces, with an anchor modification rate of above 90%.</p><p><b>CONCLUSION</b>The dimmers, tetramers and higher order structures of the obtained SA-TNF-alpha fusion protein all exhibit a bi-functionality, and may serve as a potential candidate therapeutic agent for tumors.</p>