Yasushi Nakao

Keio University, Edo, Tōkyō, Japan

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Publications (12)13.49 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Schwann cells are glial cells of the peripheral nervous system. There are two known subtypes of Schwann cells: those that are myelin-forming; and those that are non-myelin-forming. In this study, we looked at the expression of cell adhesion molecules in Schwann cells to determine whether other subtypes might exist. We used immunohistological analysis of femoral nerve segments containing sensory and motor fascicles, stained with anti-HNK-1, M6749 and anti-neural cell adhesion molecule (NCAM) monoclonal antibodies. Anti-HNK-1 and M6749 were positive in the motor fascicle, while anti-NCAM was positive in the sensory fascicle. Immunoblot analysis with the anti-HNK-1 and M6749 antibodies showed stronger immunoreactivity in the motor fraction than in the sensory fraction in the 100 kDa band. With the anti-NCAM antibody, the 140 and 120 kDa bands were seen in the sensory fascicle fraction, but not in the motor fascicle fraction. HNK-1-positive-cells were seen in motor fascicles 7 days after transection. However, the level of immunoreactivity diminished at 14 days, and no immunoreactivity was seen at 21 days. NCAM-positive cells were not observed 3 days after transection. In development, HNK-1-positive-cells and NCAM-positive cells were seen after P-21. These results suggest that the Schwann cells from the motor and the sensory fascicles have different subtypes. The motor and sensory Schwann cells may play different roles and function in a different way during peripheral nerve regeneration. In addition, there could be more stages of Schwann cell differentiation than previously thought; it is possible that myelin-forming Schwann cells differentiate into HNK-1-positive-cells (motor myelin-forming Schwann cells) and HNK-1-negative-cells (sensory myelin-forming Schwann cells), and non-myelin-forming Schwann cells differentiate into NCAM-positive cells (sensory non-myelin-forming Schwann cells) and NCAM-negative cells (autonomic non-myelin-forming Schwann cells).
    Neuroscience Research 12/2005; 53(3):314-22. DOI:10.1016/j.neures.2005.08.006 · 1.94 Impact Factor
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    ABSTRACT: The ulnar-shortening procedure has been adopted widely to reduce pressure between the ulna and ulnar carpus in ulnocarpal abutment syndrome. The hammock-like structure of the triangular fibrocartilage complex (TFCC), which supports and connects the ulnocarpal and distal radioulnar joint (DRUJ), variably is torn in this condition. The degree to which the torn TFCC may be tensioned to restabilize the DRUJ with ulnar recession is uncertain. This study examined changes in the stabilizing effect of the ulnar-shortening procedure in several TFCC tear conditions. Six fresh-frozen cadaver arms amputated at the midportion of the humerus were used. The skin, muscles, and capsuloligamentous structures below the elbow all were preserved. The ulna and humerus were affixed firmly to a custom mount that allowed 60 degrees of forearm rotation. An external fixator was attached to the distal ulna leaving space for a 10-mm resection of the ulna to allow progressive shortening. The radius was attached to a materials testing machine. The load-displacement curves were obtained while translating the distal radius dorsally or palmarly with respect to the ulna at 1.25 mm/s. Stiffness in dorsopalmar displacement was recorded at 1-mm intervals through 6 mm of length. These measurements then were compared with controls (0 mm shortening of the intact specimens) at 60 degrees pronation, neutral position, and 60 degrees supination. The tests then were repeated after sectioning either the dorsal or palmar portion of the radioulnar ligament (RUL) and then after complete sectioning of the RUL. Each portion was sectioned at its attachment to the ulnar fovea. The stiffness of the DRUJ increased significantly in all 3 rotatory positions after shortening the ulna. A shortening of 6 mm resulted in a 26% to 44% increase in DRUJ stiffness. The stiffness decreased after partial sectioning of the RUL but increased with further ulnar shortening in all 3 positions. The DRUJ stiffness with the partially sectioned RUL after a shortening of 3 to 6 mm was as large as that of the intact specimens. The stiffness of the DRUJ after the complete section of the RUL was significantly smaller than that of the intact specimens even after shortening of 6 mm. The ulnar-shortening procedure can stabilize the DRUJ by increasing intrastructural tension of the TFCC, only when the RUL is attached totally or partially to the ulnar fovea. If the RUL is avulsed completely then stability of the DRUJ no longer is obtained by the ulnar-shortening procedure.
    The Journal Of Hand Surgery 08/2005; 30(4):719-26. DOI:10.1016/j.jhsa.2005.04.015 · 1.67 Impact Factor
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    ABSTRACT: Open repair technique of the ulnar disruption of the triangular fibrocartilage complex is described. This technique is indicated for a fresh or a relatively fresh (less than 1 year after the initial injury) ulnar foveal detachment tear, horizontal tear, and proximal slit tear of the triangular fibrocartilage complex, all of which are accompanied by severe dorsal, palmar, or multidirectional instability of the distal radioulnar joint. A chronic tear greater than 1 year from initial injury and a fresh triangular fibrocartilage complex tear without distal radioulnar joint instability, such as central slit tear, are excluded from our indications. A dorsal C-shaped skin incision, a longitudinal incision of the radial edge of the extensor carpi ulnaris subsheath and the dorsal distal radioulnar joint capsule, exposes the distal radioulnar joint. A small, 5-mm longitudinal incision at the origin of the radioulnar ligament exposes its fovea detachment and/or the proximal slit tear of the triangular fibrocartilage complex. The disrupted radioulnar ligament is sutured in a pullout fashion to the ulna with a 3-dimensional double mattress technique through 2 bone tunnels that is precisely made at the central portion of the fovea with 1.2-mm K-wire. An additional horizontal mattress suture is used for closure of the small incision made at the radioulnar ligament, then the extensor carpi ulnaris is repaired. This open-repair technique is complex and requires precise technical skills; however, early results have been more rewarding than the conservative treatment.
    Techniques in Hand and Upper Extremity Surgery 07/2004; 8(2):116-23. DOI:10.1097/01.bth.0000126573.05697.29
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    ABSTRACT: The purpose of this study is to promote nerve regeneration across a peripheral nerve gap, using a biologic, tissue-engineered nerve (TEN), containing a high density of viable Schwann cells (SCs) in the absence of supportive foreign materials and a tubular system. Isolated SCs from adult rat sciatic nerve were seeded onto biodegradable constructs and implanted into the backs of nude mice to create TENs. Six weeks later, the constructs were harvested, implanted into surgically created sciatic nerve gaps in rats without supportive artificial conduits and compared with both an autograft group and a silicone conduit group using SCs. Two months later, functional assessment was evaluated by walking track analysis and the implanted lesions were imaged by transmission electron microscopy. The axonal number and sciatic function index of the TEN were significantly higher than those of the silicone group and achieved a comparable level to the autograft group. The results indicate that the large number of SCs within their own extracellular matrix appeared sufficient to enable neuronal growth across a nerve gap in the absence of an artificial conduit and that these circumstances may have a positive effect on the supplement of growth factors from the surrounding tissues of implanted TEN.
    Journal of Neuroscience Methods 05/2004; 134(2):133-40. DOI:10.1016/j.jneumeth.2003.11.020 · 2.05 Impact Factor
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    ABSTRACT: The effect of number of fascicles on axonal regeneration in cable grafts was examined in the rat cable graft model. The study comprised three experimental groups: the 5f-group, which received 5 fascicles, larger than the host; the 3f-group, in which the total area of the graft fascicles was similar to that of the host; and the 1f-group, which received one fascicle cable graft, smaller in diameter than the host nerve. At the graft segment, well-myelinated fibers were observed both inside and outside the graft fascicles. The three groups showed no difference in morphometric and functional assessment, suggesting that the fibers which regenerated through the outside of the graft might be effectively induced into the distal host. The disproportionate enlargement of the graft fascicle of the 1f-group also increased the fibers passing through it. These findings suggest that a small number of fascicles can induce a larger population of regenerated fibers in the 20-mm cable graft model.
    Microsurgery 01/2004; 24(5):400-7. DOI:10.1002/micr.20052 · 2.42 Impact Factor
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    ABSTRACT: The use of an artificial nerve conduit containing viable Schwann cells (SCs) is one of the most promising approaches to repair nerve injuries. Obtaining a large number of viable SCs in a short period is demanded for the clinical use of this technique. However, the previous methods using mitogens are not clinically acceptable, and other methods that do not require mitogens, failed to isolate adult SCs effectively or required a long period of time. In this study, we have developed a novel technique to isolate SCs from adult rat peripheral nerves for an artificial nerve conduit without mitogens, which has produced a total number of 1.21 x 10(5) cells per mg, with an average purity of 93.0+/-0.58% at 21 days in vitro. The Bottenstein-Sato (BS) medium used in this study, had originally been developed for oligodendrocyte culture, but here it is shown to have an effect on SC proliferation and survival. By changing fetal bovine serum (FBS) concentrations from 0 to 10% serially, SCs could be isolated maximally from the predegenerated nerves while suppressing fibroblast overgrowth. The combination of this technique and the altered medium promoted the migration and proliferation of SCs selectively by utilizing the supporting cells of SCs instead of discarding them by changing the culture dishes and media.
    Journal of Neuroscience Methods 02/2003; 122(2):195-200. DOI:10.1016/S0165-0270(02)00320-5 · 2.05 Impact Factor
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    ABSTRACT: The abductor digiti minimi (ADM) opponensplasty is used widely as a standard technique of opponensplasty for congenital hypoplastic thumb. Functional results, however, are not always satisfactory in cases of marked laxity of the thumb metacarpophalangeal (MP) joint. The authors have developed a modified procedure of ADM opponensplasty to stabilize the thumb MP joint and to obtain appropriate opponens function. The first step of their modification is to retain the maximum length of transferred ADM muscle. The origin of the ADM is shifted radially and is reattached to the transverse carpal ligament. In our modification the ADM tendon is passed underneath the extensor pollicis longus tendon and is sutured to the adductor pollicis tendon at the ulnar side of the thumb MP joint. By this modified anchoring point the transferred ADM tendon runs across the ulnar side of the thumb MP joint and is expected to act as if it were an ulnar collateral ligament.
    Techniques in Hand and Upper Extremity Surgery 01/2003; 6(4):166-70. DOI:10.1097/00130911-200212000-00002
  • Yasushi Nakao · Shinichiro Takayama · Yoshiaki Toyama ·
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    ABSTRACT: A new technique of endoscopic release of the ulnar nerve at the elbow was designed for cubital tunnel syndrome. After three 5 mm incisions were made along the line of the ulnar nerve, the skin and subcutaneous tissue were lifted up using a fine tape to produce a provisional space. An endoscope was inserted through the one incision, and the constricting ligaments and fascia were released using a retrograde knife inserted through the other incision under endoscopic vision. Eight patients were treated using this method, and successful results were achieved. No neurovascular complications occurred, and all pre-operative complaints were resolved within three weeks. Our surgical series indicated an earlier return to work and daily activity due to early healing of incisions and minimal post-operative pain.
    Hand Surgery 01/2002; 6(2):199-203. DOI:10.1142/S0218810401000679
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    ABSTRACT: We report on a case of a 19-year-old male student who sustained a hyperextension injury to his left knee while playing rugby, which resulted in a traction injury of the common peroneal nerve and multiple ligamentous injuries at the knee joint. The damaged part of the common peroneal nerve was resected, and an end-to-end suture was performed, because the gap between the nerve ends was small enough to allow closure with little mobilization. Now, 2.5 years after the surgery, the patient shows remarkable recovery. This result suggests that end-to-end suture is an ideal procedure for nerve traction injury, if the nerve ends can be closed without tension, without excessive flexion of the adjacent joint.
    Microsurgery 01/2002; 22(8):339-42. DOI:10.1002/micr.10069 · 2.42 Impact Factor
  • Hirokazu Tochigi · Yasushi Nakao · Yukio Horiuchi · Yoshiaki Toyama ·

    Hand Surgery 08/2000; 5(1):69-72. DOI:10.1142/S0218810400000156

  • Techniques in Hand and Upper Extremity Surgery 07/1998; 2(2):115-8. DOI:10.1097/00130911-199806000-00005
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    ABSTRACT: We examined radiographs of the elbows of the pitching arms of 79 professional baseball pitchers (mean age, 25.1 years; mean duration of professional career, 4.7 years) and noted the frequency and size of spurs, bone fragments, and intra-articular loose bodies according to site. The influence of duration of professional baseball career on these osteoarthritic changes was also investigated. The olecranon tip was the most frequent site of spurs (62/79; 78.5%), and fragmentation of the spur was detected in 17 joints. The frequency of spurs was also high at the medial margin of the olecranon, the tip of the coronoid process, the medial margin of the sigmoid notch, the medial margin of the trochlea and the olecranon fossa. In 38 subjects, spurs were observed at the distal portion of the radial notch of the ulna. However, few pitchers had osteoarthritic changes in the humeral capitellum or radial head. Intra-articular loose bodies were detected in 4 of 79 joints (5.1%), and bone fragments were present below the medial humeral epicondyle in 25 of 79 joints (31.6%). Osteoarthritic changes in the elbow joint appeared to be attributable mainly to traction stress and impingement associated with extension and valgus strain. Significant osteoarthritic changes were often found in professional pitchers whose careers exceeded 5 years.
    Journal of Orthopaedic Science 10/1997; 2(6):372-377. DOI:10.1007/BF02488924 · 0.94 Impact Factor