Cardiac hypertrophy is a common phenomenon observed in progressive heart disease associated with heart failure. Insulin-like growth factor receptor II (IGF-IIR) has been much implicated in myocardial hypertrophy. Our previous studies have found that increased activities of signaling mediators, such as calcium/calmodulin-dependent protein kinase II (CaMKII) and calcineurin induces pathological hypertrophy. Given
In a previous study we observed that during perfusion of normal human parathyroid tissue, the release of PTH (1-84) was modulated by ambient extracellular calcium (Ca++) and lithium (Li+) concentrations in the media and preliminary studies indicated that this stimulus-response coupling was absent in human parathyroid adenoma fragments. The present study compares the responsiveness of parathyroid adenoma fragments and isolated parathyroid adenoma cells from the same adenoma and their response to Ca++ changes and Li+ presence in culture media. The data indicate that parathyroid adenoma tissue fragments fail to respond to ambient changes in Ca++ and Li+. In contrast, dispersed parathyroid cells preparations responded with a significant increase of PTH (1-84) release (50%) under the influence of low ambient calcium concentrations. Six of the dispersed cell preparations also responded with a 45% decrease in PTH release under the influence of a high Ca concentration in the medium. Isolated parathyroid cells obtained from the same adenoma's did not respond to the presence of Li++ in the medium. These data suggest tat human parathyroid adenoma tissue functions autonomously and is not sensitive to calcium regulation in the tissue configuration as opposed to the isolated cell suspensions. The nature of this difference remains elusive.
Bio‐absorbable polymers are widely desired to be applied and used as biomaterials for surgery hemostatic and medical tissue engineering devices. Ring‐opening copolymerization reaction was applied to synthesize poly(ethylene succinate‐co‐glycolide) (PES‐b‐PGA). Stannous octoate was used as a catalyst whereas poly(ethylene succinate) was used as a macro‐initiator to react with glycolide. PES‐b‐PGA was then used as a compatibilizer to prepare the blend biomaterial of PPDO/PLGA/PES‐b‐PGA by melt blending poly(p‐dioxanone) (PPDO) with poly(lactide‐co‐glycolide) (PLGA). This would enhance the interactions of the inter‐molecular chains and intra‐molecular segments thus improving the compatibility. To obtain the biomaterial of PPDO/PLGA/PES‐b‐PGA with a regulated and controlled degradation and/or hydrolysis period, various ratios of PPDO, PLGA, and PES‐b‐PGA was blended. Behaviors of the thermal and in vitro simulated degradation, biological compatibility, cytotoxicity and subcutaneous implantation of PPDO/PLGA/PES‐b‐PGA were investigated. The results show that the in vitro hydrolytic degradation cycle is consistent with the wound healing time and that the biomaterial has slight cytotoxicity and it will do good to the cell proliferation, with 1 grade of cytotoxicity and the relative growth rate being the range from 92.5% to 96.2%. The implantation of the biomaterial into the rabbits' ears will not adversely affect the wound healing and the tissues surrounding the implanted sites. Therefore, the biomaterial has good biocompatibility and potential applications in medical tissue engineering devices.
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