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Biomedical subjects

Takeshi Ikegami

Publications and source records attributed to Takeshi Ikegami.

8 recordsLinked to original sources
PubMed2006

A selective Sema3A inhibitor enhances regenerative responses and functional recovery of the injured spinal cord.

Axons in the adult mammalian central nervous system (CNS) exhibit little regeneration after injury. It has been suggested that several axonal growth inhibitors prevent CNS axonal regeneration. Recent research has demonstrated that semaphorin3A (Sema3A) is one of the major inhibitors of axonal regeneration. We identified a strong and selective inhibitor of Sema3A, SM-216289, from the fermentation broth of a fungal strain. To examine the effect of SM-216289 in vivo, we transected the spinal cord of adult rats and administered SM-216289 into the lesion site for 4 weeks. Rats treated with SM-216289 showed substantially enhanced regeneration and/or preservation of injured axons, robust Schwann cell-mediated myelination and axonal regeneration in the lesion site, appreciable decreases in apoptotic cell number and marked enhancement of angiogenesis, resulting in considerably better functional recovery. Thus, Sema3A is essential for the inhibition of axonal regeneration and other regenerative responses after spinal cord injury (SCI). These results support the possibility of using Sema3A inhibitors in the treatment of human SCI.

Animals↗
PubMed2006

Doppler-free spectroscopy using a continuous-wave optical frequency synthesizer.

A continuous-wave (cw) optical frequency synthesizer is demonstrated by using a monolithic-type cw optical parametric oscillator (cw-OPO) and an optical frequency comb. The cw-OPO is phase locked to an optical frequency comb that is phase locked to an atomic clock. The output frequency of the cw-OPO is frequency shifted with an electro-optic modulator, which makes it possible to tune the frequency continuously over 10 GHz. Furthermore, Doppler-free spectroscopy is performed using the optical frequency synthesizer for a cesium D1 line at 895 nm. The observed linewidth of 5 MHz is the natural linewidth of cesium. The center frequency of the line is consistent with a previous report.

Journal Article↗
PubMed2005

In vivo imaging of engrafted neural stem cells: its application in evaluating the optimal timing of transplantation for spinal cord injury.

Neural stem/progenitor cells (NSPCs) hold promise in neural tissue replacement therapy after spinal cord injury. However, understanding the survival time of grafted NSPCs and determining the extent of migration away from transplantation sites are essential for optimizing treatment regimens. Here, we used in vivo bioluminescence imaging to noninvasively assess the survival and residence time of transplanted NSPCs at the injury sites in living animals, and we used histologic analyses to assess cell integration and morphology. Third-generation lentiviral vectors enabled efficient transduction and stable expression of both luciferase and a variant of green fluorescent protein in primary cultured NSPCs. Signals from these cells were detectable for up to 10 months or more after transplantation into the injured spinal cords of C57BL/6J mice. Histological and functional data supported the imaging data and suggest that the timing of NSPC transplantation may be a key determinant of the fates and function of integrated cells since cell survival and migration depended on the time of transplantation relative to injury. Optimization of cell therapies can be greatly accelerated and refined by imaging, and the methods in the present study can be widely applied to various research fields of regeneration medicine, including transplantation study.

Animals↗
PubMed2005

Ultrastable cesium atomic clock with a 9.1926-GHz regeneratively mode-locked fiber laser.

We describe an ultrastable cesium (Cs) atomic clock with a 9.1926-GHz regeneratively mode-locked fiber laser obtained by use of an optically pumped Cs beam tube. By adopting a 1-m-long Cs beam tube with a linewidth of 110 Hz, we have successfully obtained frequency stabilities of 4.8 x 10(-12) for tau = 1 s and 6.3 x 10(-13) for tau = 50 s for a 9.1926-GHz microwave output signal. This Cs atomic clock can generate an optical pulse train with the same stability as that of the obtained microwave, which allows us to deliver a frequency standard optical signal throughout the world by means of optical fiber networks.

Journal Article↗
PubMed2005

Chondroitinase ABC combined with neural stem/progenitor cell transplantation enhances graft cell migration and outgrowth of growth-associated protein-43-positive fibers after rat spinal cord injury.

We previously reported that the transplantation of neural stem/progenitor cells (NSPCs) can contribute to the repair of injured spinal cord in adult rats and monkeys. In some cases, however, most of the transplanted cells adhered to the cavity wall and failed to migrate and integrate into the host spinal cord. In this study we focused on chondroitin sulfate proteoglycan (CSPG), a known constituent of glial scars that is strongly expressed after spinal cord injury (SCI), as a putative inhibitor of NSPC migration in vivo. We hypothesized that the digestion of CSPG by chondroitinase ABC (C-ABC) might promote the migration of transplanted cells and neurite outgrowth after SCI. An in vitro study revealed that the migration of NSPC-derived cells was inhibited by CSPG and that this inhibitory effect was attenuated by C-ABC pre-treatment. Consistently, an in vivo study of C-ABC treatment combined with NSPC transplantation into injured spinal cord revealed that C-ABC pre-treatment promoted the migration of the transplanted cells, whereas CSPG-immunopositive scar tissue around the lesion cavity prevented their migration into the host spinal cord in the absence of C-ABC pre-treatment. Furthermore, this combined treatment significantly induced the outgrowth of a greater number of growth-associated protein-43-positive fibers at the lesion epicentre, compared with NSPC transplantation alone. These findings suggested that the application of C-ABC enhanced the benefits of NSPC transplantation for SCI by reducing the inhibitory effects of the glial scar, indicating that this combined treatment may be a promising strategy for the regeneration of injured spinal cord.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2004

Cervical peridural calcification in patients undergoing long-term hemodialysis. Report of two cases.

The authors report on two patients undergoing long-term hemodialysis in whom cervical myelopathy was caused by calcification related to the cervical dural sac. The lesions were demonstrated on plain computerized tomography (CT) scans as dotted curvilinear bands outlining the dural sacs in almost the whole of their cervical spines. During posterior decompressive surgery in both cases, the CT scanning--documented curvilinear bands were identified as calcified plaques infiltrating the fibrous membranes beneath the ligamenta flava, constricting the cervical dural tube. In each case, the spinal cord could not be decompressed by merely enlarging the osseous spinal canal; rather, it required removal of the calcified membrane from the posterior surface of the dura. Based on the operative findings, the lesion should be described as cervical peridural calcification.

Aged↗
PubMed2003

Results of skip laminectomy-minimum 2-year follow-up study compared with open-door laminoplasty.

STUDY DESIGN: Results of skip laminectomy and open-door laminoplasty for cervical spondylotic myelopathy were compared. OBJECTIVES: To verify that skip laminectomy is less invasive to the posterior extensor mechanism of the cervical spine including the deep extensor muscles than conventional laminoplasty and is effective in preventing postoperative problems often seen after conventional laminoplasty of the cervical spine such as persisting axial pain, restriction of neck motion, and loss of cervical lordosis. SUMMARY OF BACKGROUND DATA: A preliminary short-term follow-up study on skip laminectomy demonstrated that the procedure successfully prevented such postoperative problems, while achieving adequate decompression of the spinal cord. METHODS: Since December 1998, more than 100 patients with cervical spondylotic myelopathy underwent skip laminectomy, and 43 who were followed for more than 2 years (average of 2 years and 6 months) (Group A) were included in this study. Fifty-one patients who underwent open-door laminoplasty (Group B) in the authors' institutes before December 1998 served as controls. Japanese Orthopaedic Association scores and incidence of newly developed or deteriorated axial pain were recorded. Preoperative and postoperative ranges of neck motion were measured on lateral flexion and extension radiographs. Preoperative and postoperative cervical curvature indices were calculated according to Ishihara's method. For quantitative analysis of damage to the posterior cervical muscles, atrophy rates were calculated from cross-sectional areas of the deep extensor muscles on preoperative and postoperative axial magnetic resonance images. RESULTS: Using Japanese Orthopaedic Association scores, the average recovery rates were 59.2% for Group A and 60.1% for Group B. Only one patient (2%) in Group A had newly developed axial pain, whereas 33 patients (66%) in Group B had postoperative development or deterioration of axial pain. Postoperative range of neck motion averaged 98% of the preoperative measurement in Group A and 61% in Group B. There was no significant difference between preoperative and postoperative cervical curvature index in Group A, whereas the mean value of postoperative index (16.0) was significantly smaller than that of preoperative one (11.8) in Group B (P < 0.05). The atrophy rate of the deep extensor muscles in Group A averaged 13%, whereas that in Group B was 59.9%. CONCLUSIONS: Skip laminectomy was less invasive to the posterior extensor mechanism including the deep extensor muscles than open-door laminoplasty. This new procedure was effective in preventing postoperative morbidities often seen after conventional laminectomy and laminoplasty with adequate decompression of the spinal cord.

Adult↗