Biomedical subjects

Eiji Abe

Publications and source records attributed to Eiji Abe.

5 recordsLinked to original sources

PubMed2004

Quasicrystals as cluster aggregates.

Quasicrystals are solids that exhibit symmetries long thought forbidden in nature. Since their discovery in a rapidly solidified Al-Mn alloy in 1984, the central issue in the field has been to understand why they form. Are they energetically stable compounds or stabilized by entropy? In recent years, major strides have been made in determining atomic structure, largely by direct imaging using advanced electron microscopy. One system is now known to be energetically stabilized, and quasicrystals are therefore firmly established as a new physical state of matter. They represent a unique packing of atomic clusters some tens of atoms in size, with substantial localized fluctuations, referred to as phasons. Understanding phasons may in future allow their unique macroscopic properties to be tailored for useful materials applications.

Crystallization↗

PubMed2003

Multicentric osteosarcoma with long-term survival.

We present a 14-year-old girl with multicentric osteosarcoma who has survived for over 9 years to date. The patient first noticed right knee pain in 1992. Radiographs showed a destructive and sclerotic lesion of the right distal femur. Similar small sclerotic lesions were seen in the proximal metaphysis of the right femur, proximal site of the right humerus, and mid-posterior of the left humerus. A diagnosis of multicentric osteosarcoma was made on a biopsy of the right distal femur. The sclerotic lesions of the bilateral humeri disappeared after systemic chemotherapy (T-20), and thus wide excisions of the right distal femur and proximal femur were performed in 1993. New lesions appeared in the left iliac bone and the first lumbar vertebra on bone scintigraphy 24 months after the first surgery. Chemotherapy and wide excisions of the left iliac bone and the first lumbar vertebra were performed. The patient was well at the latest follow-up in April 2003, with no evidence of local recurrence or distant metastasis, but recently renal dysfunction appeared.

Adolescent↗

PubMed2003

Nontraumatic acute complete paraplegia resulting from cervical disc herniation: a case report.

STUDY DESIGN: A case report of nontraumatic acute complete paraplegia resulting from cervical disc herniation. OBJECTIVES: To describe a rare case of nontraumatic paraplegia resulting from enlargement of a herniated disc in the cervical spine and to outline appropriate management of a patient with severe spinal cord compression secondary to disc herniation with developmental spinal canal stenosis. SUMMARY OF BACKGROUND DATA: Acute progression of myelopathy into complete paraplegia resulting from disc herniation is rare. There are only four reported cases of nontraumatic acute myelopathy secondary to cervical disc herniation. No other report has described magnetic resonance imaging findings noted before and after the onset of acute myelopathy. METHODS: A cervical disc herniation at C6-C7 is reported in a 29-year-old man who had nontraumatic acute complete paraplegia. Neurologic and magnetic resonance imaging findings are evaluated and discussed. RESULTS: Disc herniation at C6-C7 enlarged nontraumatically, resulting in complete paraplegia. Emergent anterior decompression followed by secondary posterior multilevel decompression was performed. Magnetic resonance imaging studies revealed localized high signal intensity change in the spinal cord. No neurologic recovery was achieved 3 years post-surgery. CONCLUSION: We emphasize that there is a possibility of acute, irreversible progression of paralysis secondary to nontraumatic enlargement of cervical disc herniation with canal stenosis. In these cases, immediate early decompressive surgery is crucial to the prevention of severe myelopathy.

Acute Disease↗

PubMed2003

Direct observation of a local thermal vibration anomaly in a quasicrystal.

Quasicrystals have long-range order with symmetries that are incompatible with periodicity, and are often described with reference to a higher-dimensional analogue of a periodic lattice. Within the context of this 'hyperspace' crystallography, lattice dynamics of quasicrystals can be described by a combination of lattice vibrations and atomic fluctuations--phonons and phasons. However, it is difficult to see localized fluctuations in a real-space quasicrystal structure, and so the nature of phason-related fluctuations and their contribution to thermodynamic stability are still not fully understood. Here we use atomic-resolution annular dark-field scanning transmission electron microscopy to map directly the change in thermal diffuse scattering intensity distribution in the quasicrystal, through in situ high-temperature observation of decagonal Al72Ni20Co8. We find that, at 1,100 K, a local anomaly of atomic vibrations becomes significant at specific atomic sites in the structure. The distribution of these localized vibrations is not random but well-correlated, with a quasiperiodic length scale of 2 nm. We are able to explain this feature by an anomalous temperature (Debye-Waller) factor for the Al atoms that sit at the phason-related sites defined within the framework of hyperspace crystallography. The present results therefore provide a direct observation of local thermal vibration anomalies in a solid.

Journal Article↗

PubMed2002

Effects of dantrolene on extracellular glutamate concentration and neuronal death in the rat hippocampal CA1 region subjected to transient ischemia.

BACKGROUND: Excessive extracellular glutamate produced by cerebral ischemia has been proposed to initiate the cascade toward neuronal cell death. Changes in extracellular glutamate concentration are closely linked to changes in intracellular calcium ion concentration. Dantrolene inhibits calcium release from intracellular calcium stores. In this study, the authors investigated the effects of dantrolene on extracellular glutamate accumulation and neuronal degeneration in a rat model of transient global forebrain ischemia. METHODS: Male Wistar rats weighing 230-290 g were anesthetized with halothane in nitrous oxide-oxygen and were subjected to 10 min of transient forebrain ischemia using a four-vessel occlusion technique. Fifteen minutes before ischemic injury, dantrolene sodium (5 mm), dimethyl sulfoxide as a vehicle for dantrolene, or artificial cerebrospinal fluid as a control was intracerebroventricularly administered (n = 8 in each group). In the hippocampal CA1 subfield, the extracellular glutamate concentration in vivo was measured during the periischemic period with a microdialysis biosensor, and the number of intact neurons was evaluated on day 7 after reperfusion. RESULTS: Both dantrolene and dimethyl sulfoxide significantly reduced the ischemia-induced increase in glutamate concentration to a similar extent, i.e., by 53 and 51%, respectively, compared with artificial cerebrospinal fluid (P < 0.01). The number of intact hippocampal CA1 neurons (mean +/- SD; cells/mm) in dantrolene-treated rats (78 +/- 21) was significantly higher than that in artificial cerebrospinal fluid- (35 +/- 14; P < 0.001) and dimethyl sulfoxide-treated (56 +/- 11; P < 0.05) animals. Dimethyl sulfoxide also significantly increased the number of preserved neurons in comparison with artificial cerebrospinal fluid (P < 0.05). CONCLUSIONS: Intracerebroventricular dantrolene prevents delayed neuronal loss in the rat hippocampal CA1 region subjected to transient ischemia; however, this neuroprotection cannot be accounted for only by the reduced concentrations of extracellular glutamate during ischemia.

Animals↗