Overview on nickel Carcinogenesis

Background: Acute exposure to nickel alters the pattern of gene expression in normal cells and induces a pattern of gene expression similar to that found in nickel-induced cancers. This study aims to review various mechanisms in nickel carcinogenesis. Materials and Methods: A systematic search on the Pubmed and Google scholar databases was done on the carcinogenic potency of nickel compounds in animal models and rodent cells in vitro. Results: Published evidence confirmed that the epigenetic activity of nickel carcinogenic compounds may be exerted with a modulation of gene expression. Nickel plays a role in the derivation of cells with neoplastic properties. Many researches demonstrated that nickel depletes intracellular ascorbate and may be able to replace the iron in the active site of hypoxia inducible factor-1a (HIF-1a) hydroxylases, which results in the inhibition of prolyl hydroxylase activity, activation of of hypoxia inducible factor-1a (HIF-1a), a protein known to be over-expressed in a variety of cancers and expression of hypoxia-inducible genes such as Cap43 gene. Cap43 gene was found to be highly inducible by hypoxia and over-expressed in cancer cells. These studies demonstrate that human exposure to Nickel turns on signaling for hypoxic stress, which may be important in its carcinogenesis. Conclusion: The major epigenetic effects of nickel are depletion of ascorbate, inhibition of prolyl hydroxylase enzyme activity, the stabilization of hypoxia inducible factor-1a (HIF-1a and expression of hypoxia-inducible genes such as Cap43 gene

Scaffold percolative efficiency: in vitro evaluation of the structural criterion for electrospun mats

Fibrous scaffolds of engineered structures can be chosen as promising porous environments when an approved criterion validates their applicability for a specific medical purpose. For such biomaterials, this paper sought to investigate various structural characteristics in order to determine whether they are appropriate descriptors. A number of poly(3-hydroxybutyrate) scaffolds were electrospun; each of which possessed a distinguished architecture when their material and processing conditions were altered. Subsequent culture of mouse fibroblast cells (L929) was carried out to evaluate the cells viability on each scaffold after their attachment for 24 h and proliferation for 48 and 72 h. The scaffolds’ porosity, pores number, pores size and distribution were quantified and none could establish a relationship with the viability results. Virtual reconstruction of the mats introduced an authentic criterion, “Scaffold Percolative Efficiency” (SPE), with which the above descriptors were addressed collectively. It was hypothesized to be able to quantify the efficacy of fibrous scaffolds by considering the integration of porosity and interconnectivity of the pores. There was a correlation of 80% as a good agreement between the SPE values and the spectrophotometer absorbance of viable cells; a viability of more than 350% in comparison to that of the controls