Tadashi Hashimoto

Alginate Enhances Elongation of Early Regenerating Axons in Spinal Cord of Young Rats

Freeze-dried alginate sponge cross-linked with covalent bonds has been demonstrated to enhance nerve regeneration in peripheral nerves and spinal cords. The present study examined, at early stages after surgery, the outgrowth of regenerating axons and reactions of astrocytes at the stump of transected spinal cord in young rats. Two segments (Th7-8) were resected, and alginate was implanted in the lesion. As controls, collagen gel was implanted in place of alginate or the lesion was left without implantation. Two and 4 weeks after surgery, nerve outgrowth and astrocyte reactions were examined. Many regenerating axons, some of which were accompanied by astrocytic processes, were found to extend from the stump into the alginate-implanted lesion. In the all nonimplanted animals, large cystic cavities were formed at both interfaces with no definite axonal outgrowth into the lesion. In collagen-implanted animals, cavity formation was found in some rats, and regenerating axons once formed at the stumps did not extend further into the lesion. Astrocytic processes extending into alginate-implanted lesion had no basal laminae, whereas those found in control experiments were covered by basal laminae. These findings suggest that alginate contributed to reducing the barrier composed of connective tissues and reactive astrocytic processes, and served as a scaffold for the outgrowth of regenerating axons and elongation of astrocytic processes.

Reconstruction of rat peripheral nerve gap without sutures using freeze-dried alginate gel†

Many materials have been used for artificial tubular prostheses to assist peripheral nerve gap reconstruction. However, the clinical use of these devices has been restricted because a microsurgical procedure requires specialized techniques and expensive equipment, such as operating microscope systems. Therefore the authors developed a new gluing method, without sutures, that uses freeze-dried alginate gel. A 7-mm gap in the sciatic nerve of rats was bridged with freeze-dried alginate gel. Regeneration was evaluated by electrophysiologic testing and histologic study. Eighteen weeks after surgery, functional reinnervation of motor and sensory nerves had occurred, as demonstrated by recovery of compound muscle action potentials (CMAP), compound nerve action potentials (CNAP), and somatosensory-evoked potentials (SEP). Histologically, many regenerated nerve fasciculi, including myelinated and unmyelinated fibers, were observed and the implanted alginate gel had disappeared. In conclusion, a gluing technique using alginate gel is a potential alternative to the conventional nerve autograft technique. Advantages include simple application and rapid repair. Freeze-dried alginate gel is a promising material for artificial nerve guides for peripheral nerves and also could be used for repair of disrupted pathways in central nervous tissue that is amorphous and cannot be sutured.

Human V5 demonstrated by magnetoencephalography using random dot kinematograms of different coherence levels.

To investigate the cortical mechanisms for motion perception in human V5, we measured visual evoked magnetic fields in response to random dot kinematograms (RDKs) of three different coherence levels (50, 70 and 100%) using a 122-channel whole-head magnetometer. As the coherence level increased, the peak amplitude measured by the root mean square (RMS) of the local response increased significantly (7.4+/-1.0, 9.5+/-1.5 and 15.5+/-3.2 fT/cm on the right, 6.4+/-0.3, 7.8+/-0.7 and 12.5+/-0.9 fT/cm on the left; for the coherence level of 50, 70 and 100%, respectively). There was no significant difference between the hemispheres. As for the peak latency, there was no significant difference in terms of coherence levels or hemispheres. The response was localized posterior to the junction of the ascending limb of the inferior temporal and lateral occipital sulci (human V5). These findings indicate that processing of global motion in terms of the synchronized portion correlates well with the response amplitude but not with its latency. Thus, we could estimate the magnetic responses of human V5 non-invasively by presenting different coherence levels of the visual motion stimuli. Hemispheric laterality was recognized, although the dominant side varied among subjects.

Temporal profile of visual evoked responses to pattern-reversal stimulation analyzed with a whole-head magnetometer.

Abstract Magnetoencephalography (MEG) has become accepted as a useful method for non-invasively studying brain functions, including visual perception. The present study used MEG to elucidate information processing following pattern-reversal stimulation by analyzing the origins and properties of visual evoked magnetic fields (VEFs). The VEFs of ten healthy adults were recorded in a magnetically shielded room using a 122-channel whole-head magnetometer. The visual stimulation of checkerboard-pattern reversal at 1.7 Hz was presented to the subject’s right hemifield. Visual evoked potentials (VEPs) were recorded simultaneously, and 150 responses were each averaged for VEFs and VEPs. For the contrast profile study, pattern-reversal stimuli at five different contrast levels from 96% to 8% were used. In all subjects, the VEFs showed three components with latencies of approximately 95, 120, and 160 ms. The equivalent current dipoles for the first and the third components were located and were oriented close to each other in the left occipital lobe, but these dipoles were separated from that of the second component, which showed an opposite direction. Stimuli at a moderate contrast level markedly reduced the first component, but not the third. These findings indicate that the first and the third components of VEFs appear to originate from anatomically closely situated, almost identical, sources, but that their physiological properties differ.

Adsorption of glycated proteins by boronic copolymer-coated adsorbents

The presence of glycated proteins in the plasma of diabetic patients may play a role in serious complications such as nephritis, retinosis, and nerve disorders. We evaluated the adsorption properties of copolymers of styreneboronic acid and styrenesulfonic acid for glycated protein and glycated lipoprotein. Porous glass with pore sizes of 50 and 100nm and cellulose gel were coated with or bound to the copolymer of styreneboronic acid, styrenesulfonic acid, and glycidyl methacrylate. These adsorbents showed selective adsorptivity for glycated albumin and glycated lipoprotein, depending on their boronic acid content. Copolymer composition affects the adsorption properties in a different manner for glycated albumin and glycated lipoprotein, suggesting that not only boronic acid but also sulfonic acid moieties play an important role in adsorption. The copolymer of styreneboronic acid and hydroxyethyl methacrylate had a smaller adsorption capacity than the copolymer of styreneboronic acid and styrenesulfonic acid without positive participation of the hydroxyethyl methacrylate moiety, which also showed the need for sulfonic acid in selective adsorption. Furthermore, these adsorbents had less capacity to activate the intrinsic blood coagulation cascade. Therefore, it may be possible to use these adsorbents to prevent the complications of diabetes by plasmapheresis.The presence of glycated proteins in the plasma of diabetic patients may play a role in serious complications such as nephritis, retinosis, and nerve disorders. We evaluated the adsorption properties of copolymers of styreneboronic acid and styrenesulfonic acid for glycated protein and glycated lipoprotein. Porous glass with pore sizes of 50 and 100nm and cellulose gel were coated with or bound to the copolymer of styreneboronic acid, styrenesulfonic acid, and glycidyl methacrylate. These adsorbents showed selective adsorptivity for glycated albumin and glycated lipoprotein, depending on their boronic acid content. Copolymer composition affects the adsorption properties in a different manner for glycated albumin and glycated lipoprotein, suggesting that not only boronic acid but also sulfonic acid moieties play an important role in adsorption. The copolymer of styreneboronic acid and hydroxyethyl methacrylate had a smaller adsorption capacity than the copolymer of styreneboronic acid and styrenesulfonic acid without positive participation of the hydroxyethyl methacrylate moiety, which also showed the need for sulfonic acid in selective adsorption. Furthermore, these adsorbents had less capacity to activate the intrinsic blood coagulation cascade. Therefore, it may be possible to use these adsorbents to prevent the complications of diabetes by plasmapheresis.

Design of a new disposable ERG electrode.

A new electrode for electroretinography (ERG) has been produced. The new device made of gold filament was applied as corneal and noncorneal electrod. Flash ERG and pattern ERG were recorded in normal subjects using this new electrode and compared with those made by available electrodes. There were so significant differences in amplitude and latency between the new electrode placed on the cornea and the JET-type electrode. For pattern ERG there were no significant differences between the new electrode placed in the lower fornix and a gold-foil-type electrode. As this new electrode is less expensive and more comfortable than the available electrodes, it is clinically useful.