The reason why the Pyr neurons in the layer V of the cerebral cortex showed intense PS mRNA expression is unclear. Heggli et al. reported that the most pronounced effect of systemic injection of KA induces necrosis and neuronal degeneration in the piriform cortex, amygdaloid complex, hippocampus and septum, but with no mention about the cerebral cortex. In the present study, almost all neurons in the cerebral cortex showed increased PS mRNA expression after KA injection. In particular, layer-V Pyr neurons, which have a wide dendritic area that receives intense stimulation from many neurons following KA injection, produce a large amount of PS. PS mRNA expression in the choroid plexus of normal control animals was strong, as reported previously. This observation is reinforced by the finding that cerebrospinal fluid in normal animals contains a significant amount of PS. Furthermore, 3 days after KA injection, the hybridization signal in the choroid plexus was very strong. These results indicate that PS is produced in the choroid plexus and may be secreted into the cerebrospinal fluid after direct or indirect KA stimulation to the choroid plexus. There is an increasing interest in magnesium -based alloys as implantable orthopedic medical devices because of their biodegradability and good biocompatibility. Compared with other metal biomaterials, e.g., stainless steel, titanium alloys, and cobalt-chromium alloys, Mg alloys have several advantages for orthopedic application. First, their physical and mechanical properties including density, elastic modulus, and compressive yield strength, are much closer to that of natural bone, and therefore can avoid the stress shielding effect. Second, Mg is an essential element for many biological activities including enzymatic reaction, formation of apatite, and bone cells adsorption. Third, Mg alloys can eliminate the necessity of a second surgery to remove the permanent bone implants. The success of an medical implant is largely dependent on the interaction between the surface of the implant and the surrounding tissues. Both surface chemistry and topography of implants can affect biological activities such as osteoblasts metabolism, collagen synthesis, and alkaline phosphatase activity. Cells often display distinctive morphological and metabolic properties when they are in contact with materials with different surface roughness. It is a general consensus that cells cannot directly recognize bare metal materials in vitro or in vivo. It is the biomacromolecules absorbed on metal materials serve as a bridge connecting cells to the solid surface. Therefore, the adsorption of ECM proteins and subsequent structure changes may lead to different cell fate. Collagen as the most abundant ECM protein is the major component of natural bone. It plays an important role in cell attachment, mechanical support, and apatite nucleation. The mean weight percent of collagen in modern mammal bone is around 20.8%, and 90% of the organic matrix in bone is comprised of collagen. Studies have been carried out in the past with respect to the Dabrafenib 1195765-45-7 self-assembly characteristic of collagen and application of type I collagen as coating materials. Fang et al. showed that different mica surfaces affect D-period during collagen self-assembly. Nassif et al. reported that collagen-apatite matrix is necessary for organization of collagen fibrils into 3-D scaffolds and nucleation of hydroxyapatite. However, the information on collagen and Mg biomaterial interaction is still missing in the literature. Previous studies showed that biodegradable Mg alloys enhanced bone-implant strength and osseointegration compared to titanium alloys.