Tadakazu Yamauchi

Dual immunoassay of human chorionic gonadotropin and human placental lactogen at a miocrofabricated substrate by scanning electrochemical microscopy

Abstract A dual immunoassay of human chorionic gonadotropin (HCG) and human placental lactogen (HPL) at a microfabricated substrate was studied using scanning electrochemical microscopy (SECM). Anti-HCG and anti-HPL were microspotted on 50 × 50 μ m 2 raised flat squares separated from each other by 150 μm at a glass substrate. A 10 μl sample solution containing HCG and/or HPL was then dropped onto the substrate followed by treatment with a solution of horseradish peroxidase (HRP)-labeled anti-HCG and HRP-labeled anti-HPL. The SECM measurements were carried out at 0.05 V vs. Ag/AgCl in the presence of ferrocenylmethanol (FMA) and H 2 O 2 to detect FMA + generated by the HRP reaction. The SECM images of the substrates showed clearly the large response areas which corresponded to the squares with HCG and/or HPL. The detection limits were 0.1 IU ml −1 for HCG and 3 ng ml −1 for HPL.

Platelet-derived growth factor-b expression induced after rat peripheral nerve injuries

Schwann cells are crucially important for peripheral nerve regeneration. These cells synthesize several factors that are supposed to enhance axonal regeneration when injured. Platelet‐derived growth factor (PDGF) B‐chain and its β‐receptor are expressed in Schwann cells in both normal peripheral nerves and culture. To elucidate the role of PDGF‐B in peripheral nerve regeneration, we investigated its expression in cut or crush‐injured rat sciatic nerves for up to 28 days. Northern blotting identified substantial increase of PDGF B‐chain transcripts in injured nerves. Immunohistochemistry demonstrated that protein products of the transcripts were augmented at the distal tip of swollen axons in proximal nerve segments and in regenerating axons. Soon after both types of injury, considerable amounts of PDGF‐B accumulated in numerous Schwann cells in distal segments of both models. With restoration of the axon–Schwann cell relationship in the crush model, levels of PDGF‐B tended to decrease, eventually returning to normal. In the cut model in which the relationship cannot be restored, the PDGF‐B was depleted to a very low level. The spatiotemporal correlation between PDGF‐B and cell proliferation was very close throughout the study. These results differed strikingly from those of our previous study of rat optic nerve transection, in which PDGF‐B was expressed only in a few recruited macrophages and glial cells. Augmented PDGF‐B expression after sciatic nerve injury might contribute to peripheral nerve regeneration because PDGF‐B is a mitogen and survival factor for Schwann cells and because it has trophic activity on neurons. GLIA 38:303–312, 2002.