Ikuyo Sugimoto

Evidence That the PsbK Polypeptide Is Associated with the Photosystem II Core Antenna Complex CP43

PsbK is encoded by the chloroplast psbK gene and is one of the small polypeptides of photosystem II (PSII). This polypeptide is required for accumulation of the PSII complex. In the present study, we generated an antibody against recombinant mature PsbK of Chlamydomonas and used it in Western blots to localize PsbK in the PSII core complex. PsbK was found in the thylakoid membranes, and purification of the PSII core complex from detergent-solubilized thylakoid membranes showed that PsbK is tightly associated with the PSII core complex. We used potassium thiocyanate to separate PSII into subcore complexes, including the D1/D2/cytochrome b559 reaction center complex, CP47, and CP43, and we found that PsbK co-purifies with one of the core antenna complexes, CP43, during ion exchange chromatography. Subsequent gel filtration chromatography of the purified CP43 confirmed that PsbK is tightly associated with CP43. Steady-state levels of PsbK were also determined in Chlamydomonas mutants expressing various levels of PSII. Quantitative Western blotting revealed that the levels of PsbK in these mutants are approximately equal to those of CP43, suggesting that PsbK is stable only when associated with CP43 in the chloroplast. Together, our results indicate that PsbK is an integral part of the PSII complex and may participate in the assembly and stability of the PSII complex.

A microfluidic device to reduce treatment time of intracytoplasmic sperm injection

OBJECTIVE To develop a microfluidic device that can reduce the intracytoplasmic sperm injection (ICSI) treatment time by increasing sperm concentration. DESIGN We compared the ICSI treatment time required for porcine sperm using a method employing the microfluidic device and one using the conventional microdroplet method. SETTINGS Academic research laboratories at Okayama University. ANIMAL(S) Reproductive cells of porcine sperm, oocytes, and embryos. INTERVENTION(S) Cell manipulations, ICSI, and embryo culture. MAIN OUTCOME MEASURE(S) Average ICSI treatment time and sperm concentration. RESULT(S) The average ICSI treatment time (mean ± SEM) using the method with the microfluidic device for poor-quality semen (sperm concentration, 2.0 × 10(4) cells/mL) was significantly shorter than the treatment time using the conventional microdroplet method (265 ± 15 seconds [n = 43] vs. 347 ± 19 seconds [n = 50]). When diluted semen with a sperm concentration of 2.0 × 10(5) cells/mL was used, no significant difference was observed between the two methods (n = 50 and n = 48). CONCLUSION(S) The microfluidic device can reduce the time required for ICSI treatment that is used to increase sperm concentration in poor-quality semen samples. The results suggest that this device may be clinically useful for ICSI treatment in human assisted reproductive technology.

Microfluidic Device Increases Sperm Concentration by Optimization of Chamber Structure

Microfluidic Device Increases Sperm Concentration by Optimization of Chamber Structure Intracytoplasmic sperm injection (ICSI) is an extremely timeconsuming and tedious procedure in cases of oligozoospermia, because it is difficult to obtain a sufficient number of motile sperms. To circumvent this difficulty, we previously developed a microfluidic device to increase sperm concentration and reduce time required for ICSI. Here, we improved this device by carefully optimizing its dimensions. We achieved a 10–13-fold enrichment ratio in non-motile human sperms (1.0 × 104 cells/ml) when a chamber height of 1.4 mm was used, and we described a mathematical model to explain the relationship between sperm concentration and enrichment ratio. However, this model was unable to explain the decrease in the enrichment ratio when a chamber height of 1 mm was used.

Electrode fabrication using conductive nano-ink and microfluidic technology for bio-applications

Printed electronics technology, which is used to economically prepare printing conductive patterns onto flexible materials, is both fundamental and crucial for the successful integration of electronics with textiles or fluidics. Conductive channels can be prepared using conventional printing technologies and conductive inks. These preparation methods would cost less, and they are convenient for prototyping of microdevices. The use of hydrophilic organic-inorganic hybrid nanoparticles (NPs), dispersed in water, enables the simplification of the electrode preparation process at room temperature. In this study, we developed a transparent breadboard and NP microelectrodes in the microfluidic channel to measure the number of particles. The electrode fabrication in the microfluidic channel can be acquired using conventional laboratory equipment without the need for expensive ultra-vacuum deposition instruments. We integrated the equipment with electrical measurement systems to count cells and/or microparticles. By using a parallel electric-circuit model (diluted case) or Langmuir isotherm model (saturated case), the particle concentration between two NP electrodes can be analyzed by measuring the capacitance of the total circuit. The microfluidic fabrication of electrodes and electrical measurement technologies may be potentially applied to the technology for micro-nano fluidics and bio-applications such as cell counting or ion sensing.