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Biomedical subjects

K Arasaki

Publications and source records attributed to K Arasaki.

At least 19 recordsLinked to original sources
PubMed2006

Reversible splenial lesion with restricted diffusion in a wide spectrum of diseases and conditions.

OBJECTIVE: Reversible lesion in the central area of the splenium of the corpus callosum (SCC) is a unique phenomenon occurring particularly in patients with encephalitis or encephalopathy and in patients receiving antiepileptic drugs (AED). We report MR imaging findings, clinical courses, and outcomes in eight patients with various diseases and conditions. MATERIALS AND METHODS: Eight patients with a reversible SCC lesion with transiently restricted diffusion were reviewed retrospectively. Diseases and conditions that were associated with a reversible lesion included epilepsy receiving AED (n=1), seizure from eclampsia receiving AED (n=1), mild infectious encephalitis (n=2), hypernatremia resulting in osmotic myelinolysis (n=1), and neoplasm (n=3) such as acute lymphocytic leukemia, spinal meningeal melanocytoma, and esophageal cancer. We evaluated MR imaging findings and clinical findings. RESULTS: Seven patients had isolated SCC lesions; one patient with osmotic myelinolysis showed additional parenchymal lesions. The reversible SCC lesion shape was oval (n=6) or extended (n=2). The mean apparent diffusion coefficient value of the splenial lesion was 0.40+/-0.16 x 10-3 mm2/s, ranging from 0.22 to 0.64 x 10-3 mm2/s. In a patient with osmotic myelinolysis, additional white matter lesions, shown as restricted diffusion, were revealed as not reversible on follow-up MR imaging. Neurological courses and outcomes were good in seven patients with isolated SCC lesions, but poor in one with osmotic myelinolysis. CONCLUSION: Reversible SCC lesion with restricted diffusion is apparent in a wide spectrum of diseases and conditions. Neurological courses and outcomes are good, particularly in patients with isolated SCC lesions. Knowledge of MR imaging findings and the associated spectrum of diseases and conditions might prevent unnecessary invasive examinations and treatments.

Adolescent↗
PubMed2002

Longitudinal study of functional spinal alpha motor neuron loss in amyotrophic lateral sclerosis.

Using a microstimulation technique for obtaining motor unit number estimates (MUNEs) of the hypothenar and extensor digitorum brevis (EDB) muscles, we performed a longitudinal study on the natural course of change in the clinical rating scale (Appel score) and of loss of functional spinal alpha motor neurons in amyotrophic lateral sclerosis. The Appel score increased to about 150% of normal at 12 months after onset, about 225% at 18 months after onset, and about 370% at 24 months after onset. By contrast, MUNEs decreased to about 27% of normal at 12 months after onset, about 12% at 18 months after onset, and about 5% at 24 months after onset. The relative merits of these different approaches in detecting changes in the disease process in its early phase are discussed.

Action Potentials↗
PubMed1999

Blood brain barrier destruction in hyperglycemic chorea in a patient with poorly controlled diabetes.

A case of hemichorea in a patient with poorly controlled diabetes is reported. T1-weighted magnetic resonance imaging (MRI) showed an unusual homogeneous high-intensity area in the corpus striatum. Of interest in the case was the fact that the globus pallidus, which was enhanced with gadolinium at the onset of hemichorea, showed homogeneous high-intensity on a subsequent T1-weighted image. This indicated that blood brain barrier destruction preceded the signal intensity change in the basal ganglia. As far as the authors could determine, this is the first reported case showing such enhancement during the course of diabetic hemichorea.

Anti-Dyskinesia Agents↗
PubMed1999

[A motor unit number estimate (MUNE)--a quantitative and pathophysiologic parameter for amyotrophic lateral sclerosis (ALS)].

We performed rate studies to develop a new method to obtain a MUNE reflecting the number of spinal alpha-motor neurons (MN). In the physiological part, six unitary muscle action potential (uMAPs) of the medial gastrocnemius muscle (MG) were averaged to obtain the mean uMAP, and a MUNE was calculated by dividing the area of its compound muscle action potential (CMAP) by the area of the mean uMAP. In the anatomical part, cholera toxin was injected into the MG muscle, and we counted the number of MG MNs identified by immunohistochemical staining of the toxin in their somata. We found that a MUNE of the MG muscle was consistent with the number of MG MNs. In the clinical application, we obtained MUNEs in 10 patients with ALS and 20 control subjects. In each patient we recorded 10 uMAPs and CMAP at each of the hypothenar and extensor digitorum brevis muscles using fine needle electrodes placed in these nerves. MUNEs for these muscles were calculated in the same way as described above. In the ALS patient group at one year post-onset of symptoms, the MUNEs for these two muscles were decreased to about 30% of the norm. We concluded that progression of ALS could be quantified by MUNEs.

Action Potentials↗
PubMed1998

The pattern of antiganglioside antibody reactivities producing myelinated nerve conduction block in vitro.

We studied the pattern of human antiganglioside antibody reactivities causing an acute conduction block in rat myelinated nerve fibers, using an in vitro preparation of the sciatic-tibial nerve. With the aid of complements, IgM antibodies reacting with the terminal disaccharide of galactose (beta1-3)N-acetylgalactosamine produced the block. These findings may help us to understand the mechanism in which the conduction block occurs in neuropathies associated with antiganglioside antibodies.

Action Potentials↗
PubMed1998

A loss of functional spinal alpha motor neurons in amyotrophic lateral sclerosis.

We obtained motor unit number estimates (MUNEs) of the hypothenar and the extensor digitorum brevis muscles in ALS patients by our new technique. One year after symptom onset, the MUNEs had decreased to +/-30% of normal. Accordingly, we suggest that 70% of functional spinal alpha motor neurons are lost in the first post-onset year in ALS.

Adult↗
PubMed1997

Validity of electromyograms and tension as a means of motor unit number estimation.

The purpose of this study was to validate three different techniques for obtaining motor unit number estimates of the rat medial gastrocnemius muscle. These consisted of two electromyographic techniques using unprocessed and digitally averaged unitary muscle action potentials, and one mechanical technique. We also injected subunit B of cholera toxin into this muscle and counted the number of spinal motor neurons labeled by the toxin. Our results revealed that a motor unit number estimate obtained by using the unprocessed unitary muscle action potential was statistically different from the actual number of motor neurons. The other two motor unit number estimates, however, were not statistically different from the actual motor neuron number. These two methods thus seem more appropriate than the first electromyographic method for obtaining an accurate motor unit number estimate.

Animals↗
PubMed1997

[Immunologic diagnosis of central nervous system viral infection].

Immunologic diagnosis of central nervous system viral infection requires paired sera, obtained at the onset of symptoms and in the convalescent period. Titers of antibodies against a particular virus in these samples should be obtained under the same conditions. As a screening test, the complement fixation or hemagglutination method is used. On the other hand, the neutralization, the enzyme-linked immunosorbent assay (ELISA) or the Western blot method is used as a confirmatory test. An antibody capture ELISA is especially effective for detecting viral antibody in the cerebrospinal fluid. Although a four-fold or greater increase in a viral antibody titer is serologically considered indicative of active viral infection, it may be clinically irrelevant. Accordingly, clinical correlation should always be sought when interpreting the results of the viral titer assay.

Central Nervous System Diseases↗
PubMed1994

Clinical evaluation of plasma exchange and high dose intravenous immunoglobulin in a patient with Isaacs' syndrome.

The clinical effects of plasma exchange and high dose intravenous immunoglobulin (IVIg) were evaluated in a 41 year old woman with Isaacs' syndrome. After double filtration plasma exchange, symptoms almost disappeared for two to three weeks and the recorded continuous muscle action potentials were considerably decreased. Symptoms recurred within a few months. On the other hand, IVIg worsened the symptoms of the disorder: during and after IVIg at a dose of 0.2 g/kg/day (total 50 g), widespread myokymia, pseudomyotonia, and muscle cramps gradually increased. Symptoms improved after another course of plasma exchange.

Action Potentials↗
PubMed1994

[Analysis of dysarthria in amyotrophic lateral sclerosis--MRI of the tongue and formant analysis of vowels].

To evaluate dysarthria in patients with ALS, we used MRI (gradient rephasing echo method) and compared it with the computed acoustic analysis. Five ALS male patients of progressive bulbar palsy type and five normal male were asked to phonate the five Japanese vowels, /a/./i/./u/./e/./o/. MRI of the sagittal tongue and vocal tract was obtained by the gradient rephasing echo method (0.2 Tesla, TR:30 ms, TE:10 ms, FA 25 degrees C, Hitachi). We could clearly visualize the change of tongue shape and the narrow site of the vocal tract for each vowel phonation. In normal subjects, the tongue shape and the narrow site of the vocal tract were distinguishable between each vowel, but unclear in ALS. Acoustic analysis showed that the first formant frequency of /i/./u/ in ALS was higher than normal and the second formant frequency of /i/./e/ in ALS was significantly lower than normal. The discrepancy from the normal first, second and third formant frequency for each vowel of ALS was most seen in /i/./e/. It was speculated that /i/ and /e/ were the most disturbed vowels in ALS. The first and second formant frequency of vowel depends on the tongue shape and the width of the oral cavity. Therefore the results of the acoustic analysis in ALS indicated poor movement of tongue in /i/./u/./e/ and were compatible with the findings of the sagittal tongue MRI. The sagittal view of the tongue in the gradient rephasing echo MRI and the acoustic analysis are useful in evaluation dysarthria in ALS.

Aged↗
PubMed1993

Acute conduction block in vitro following exposure to antiganglioside sera.

We studied the role of antiganglioside antibodies in the pathogenesis of autoimmune neuropathies using an in vitro preparation of a rat sciatic nerve. Human and rabbit sera with high titers of the antibodies were applied to a restricted segment of the sciatic nerve mounted in a recording chamber, and the compound nerve action potentials of the myelinated and unmyelinated fibers were observed. Myelinated fiber conduction became blocked at the segment within a few hours, whereas the unmyelinated fiber conduction remained unchanged. These results suggest that antiganglioside sera directly produce an acute conduction block only in myelinated nerve fibers and that this in vitro model is useful for studying the ionic mechanism by which the acute conduction block occurs.

Action Potentials↗
PubMed1992

Maximal and minimal motor nerve conduction velocities determined by a collision method: correlation with axonal conduction velocity of type-identified motor units.

Maximal and minimal motor nerve conduction velocities of the medial gastrocnemius (MG) muscle nerve were measured by a new collision method in 20 rats of 8-9 weeks of age; the rate of tension increase produced by the muscle was also recorded. Single motor unit analysis in the other 20 rats obtained axonal conduction velocity and contractile properties of type-identified MG motor units. Comparison of the data from these experiments revealed that the maximal and minimal motor nerve conduction velocities obtained by this collision method were most likely to be the axonal conduction velocity of fast-twitch and slow-twitch motor units, respectively. Therefore, these motor nerve conduction velocities in man may also be used as functional parameters of human fast-twitch and slow-twitch motor units, respectively.

Action Potentials↗
PubMed1992

[A case of distal myopathy with rimmed vacuole formation, progresses into proximal-dominant muscle involvement].

A case of 55-year-old male with distal myopathy with rimmed vacuole formation is reported. He first noticed dragging of his legs at the age of forty-three. Two years later, he was evaluated to have muscle wasting and weakness in lower legs. In another ten years, he became unable to stand or walk unaided. On physical examination, proximal limb muscles were more severely affected than distal limb muscles. Notably, muscle strength of the quadriceps femoris muscles were weak (MRC Scale 3/5), compared to hamstrings, tibialis anterior muscle and gastrocnemius muscle (4/5). Serum creatine kinase, electromyography, nerve conduction velocities were all compatible with this diagnosis. A computed tomography of the musculoskeletal system was consistent with physical findings. Muscle biopsy revealed many fibers with typical rimmed vacuoles (approximately 6% of fibers). Additionally, small amount of ragged-red fibers (0.5%) was noted. Histochemical reaction showed a focal deficiency of cytochrome c oxidase. This case suggests that during the longstanding course of the illness, proximal limb muscles may be more severely affected, and quadriceps femoris muscle may be predominantly involved.

Cytochrome-c Oxidase Deficiency↗
PubMed1991

Normal maximal and minimal motor nerve conduction velocities in adults determined by a collision method.

Using a new collision method, we measured motor nerve conduction velocities of the ulnar nerve in the forearm and the action potential amplitude of the abductor digiti minimi muscle on 60 adults, ages 20 to 82 years and apparently free from diseases of the peripheral nervous system. Both maximal and minimal motor nerve conduction velocities were linear functions of age; 64.42-0.05 age and 60.45-0.12 age, respectively. The percentage of the minimal to the maximal motor nerve conduction velocities was expressed as 94.45-0.13 age. The maximum amplitude of evoked muscle action potentials was also correlated with age. This novel method may be useful in detecting pathology of motor nerve fibers which results in a decrease in submaximal conduction velocities.

Action Potentials↗
PubMed1991

Maximal and minimal motor nerve conduction velocities in patients with motor neuron diseases: correlation with age of onset and duration of illness.

We measured the maximal and minimal motor nerve conduction velocities of the ulnar nerve in 17 patients with spinal muscular atrophy (SMA), 27 patients with amyotrophic lateral sclerosis (ALS), and 40 age-matched control subjects. Crude values of the maximal and minimal motor nerve conduction velocities were reduced in both patient groups, but their difference in each patient was not statistically different from that of a control subject. The conduction velocities adjusted according to each patient's age were faster in SMA patients than in ALS patients. Among patients with either ALS or SMA, the age-adjusted conduction velocities were larger in those who had developed the disease at younger ages and suffered from it for shorter periods of time. These findings suggest that the motor nerve fibers regenerate more in younger patients in the early stages of the disease, particularly in SMA.

Action Potentials↗
PubMed1989

Selective neurotoxicity of clioquinol on the function of the posterior column nuclei.

In the gracile nucleus of clioquinol-treated rats, the presynaptic inhibition was remarkably diminished, and the excitatory synaptic transmission was less intensely inhibited by a conditioning sural nerve volley. These changes may be the pathophysiology responsible for paresthesia and/or dysesthesia in patients with subacute optico-myelo-neuropathy (SMON).

Action Potentials↗