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Biomedical subjects

M Machida

Publications and source records attributed to M Machida.

At least 19 recordsLinked to original sources
PubMed1992

Magnetic coil stimulation of the spinal cord in the dog. Effect of removal of bony structure on eddy current.

Magnetic coil stimulation applied to the spine excites the lumbosacral roots rather than the spinal cord itself. To evaluate the mechanism responsible for this phenomenon, the effects of volume conduction on the activation of neural elements were studied. In ten intact dogs compound muscle action potentials could be recorded in the soleus muscle only when the magnetic coil was placed over the cauda equina. After laminectomy and pediculotomy, compound muscle action potentials also could be elicited when the magnetic coil was placed over the spinal cord. These findings suggest that the bony structure surrounding the spinal cord interferes with the spread of magnetically induced eddy currents to the spinal cord.

Action Potentials↗
PubMed1991

The importance of precise positioning of negatively charged carboxylate in the catalytic action of human lysozyme.

The role of aspartic acid 53 of human lysozyme (peptidoglycan N-acetylmuramoylhydrolase, EC 3.2.1.17) has been investigated by a site-directed mutagenesis. In order to clarify the importance of precise positioning of the negatively charged carboxylate group in the active site geometry, both the three-dimensional structure and the enzymatic function of glutamic acid 53 human lysozyme (Glu-53 human lysozyme) have been characterized in comparison with those of wild type enzyme. Glu-53 human lysozyme was crystallized and analysed by X-ray crystallography. No remarkable difference in the conformation of whole molecule except the side chain of 53rd residue was observed. In spite of full retention of the binding activities against either beta-1,4-linked trisaccharide of N-acetylglucosamine ((GlcNAc)3) or the corresponding hexasaccharide ((GlcNAc)6), the conversion of Asp-53 to Glu reduced the enzymatic activities against both bacterial cell substrate and p-nitrophenyl penta-N-acetyl-beta(1----4)-chitopentaoside (p-NO2-(GlcNAc)5) to a few percent of the activities of wild type enzyme. Calculation of electrostatic potential around the reaction center predicted that no significant change in pKa of Glu-35 was caused by the mutation. These results indicate that the precise positioning of the negatively charged carboxylate in the geometry of reaction center is essential for the rate enhancement in the catalytic action of lysozyme, and suggest that Asp-53 of human lysozyme participates in the catalytic action not simply in an electrostatical manner but partly in a nucleophilical manner.

Aspartic Acid↗
PubMed1991

Synthesis and structure-activity relationships of 2',3'-dideoxypurine nucleosides as potential antiretroviral agents.

In order to study the structure-activity relationships of 2',3'-dideoxypurine nucleosides as potential anti-retroviral agents, various purine derivatives have been synthesized and tested against rous sarcoma virus (RSV) in chick embryo fibroblast (CEF) cells, and against human immunodeficiency virus (HIV) in human CD4+ T cells (ATH8). Some of the new purine derivatives found to be significant antiretroviral activities. And the correlations of activity between anti-RSV and anti-HIV have shown fairly good values so far.

Animals↗
PubMed1991

Magnetic stimulation: examination of motor function in patients with cervical spine or cord lesion.

In 20 patients with cervical spine or cord lesions, we examined motor evoked potentials (MEPs) by transcranially applied magnetic stimulation to the motor cortex. We used a large-diameter (12 cm) coil to induce equal current in both left and right hemispheres. The MEPs were recorded simultaneously from multiple muscles covering the C5 to C8 myotome distribution bilaterally. The MEP abnormalities correlated well with clinical muscle weakness in 15 patients. In two patients, MEP revealed abnormalities in muscles of normal strength. Three patients with sensory but without motor deficit had normal MEPs. We conclude that magnetic stimulation is a useful adjunct in confirming and objectifying motor weakness, and in localizing the level of dysfunction in cervical spine lesions.

Adult↗
PubMed1991

[Proton magnetic resonance study on the interaction of lidocaine derivatives with lecithin vesicles].

The interaction of lidocaine hydrochloride or lidocaine ester derivatives with lecithin vesicles was investigated by proton magnetic resonance (1H-NMR) spectroscopy. Signal broadening of drug indicated the incorporation of the drug into the vesicle membrane. Positively charged nitrogen of lidocaine hydrochloride interacted with polar part of the lecithin vesicles. On the other hand, lidocaine ester derivatives indicated interaction with lecithin vesicles not only by positive charge of nitrogen but also by electrostatic effect of ester carbonyl group. This may be related with the prolonged duration of lidocaine ester derivatives.

Lidocaine↗
PubMed1991

[Functional diagnosis of brachial plexus injuries].

We evaluated 10 patients with verified brachial plexus injuries and root avulsion. In 100%, dermatomal somatosensory evoked potentials (DSSEPs) were abnormal. Compound muscle action potentials (CMAPs) by magnetic stimulation revealed 90% abnormal findings on the affected side, but also revealed abnormality in adjacent segments. Dissociation of CMAPs and DSSEPs revealed the apparent continuity of motor and sensory nerves. The use of both techniques for the examination of the function of proximal peripheral nerve revealed increased latencies over the motor and/or sensory pathways in all patients. The technique of non-invasive stimulation of the motor pathway therefore provides an additional tools to detect and quantify subclinical and clinically apparent lesions in patients with defined brachial plexus injuries and root avulsions.

Action Potentials↗
PubMed1990

Toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals.

A toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals was undertaken using nalidixic acid as a standard drug. Norfloxacin and nalidixic acid were subcutaneously administered to rats and rabbits, orally administered to dogs, and norfloxacin was orally dosed to monkeys once a day for 7 consecutive days. Of the dose levels tested, the minimum arthropathic doses of norfloxacin were 100, 25, and 50 mg/kg/day in rats, rabbits, and dogs, respectively. At these doses, the peak serum concentrations (Cmax) on Day 6 were 16.1, 9.73, and 5.11 micrograms/ml, and the areas under the serum concentration/time curve (AUC0----infinity) were 31.9, 22.9, and 26.2 micrograms.hr/ml, in respective animals. Monkeys showed no arthropathy with norfloxacin at doses of less than 500 mg/kg/day, at which the Cmax and AUC0----infinity were 15.6 micrograms/ml and 103 micrograms.hr/ml, respectively. The minimum arthropathic doses of nalidixic acid were 50, 100, and 25 mg/kg/day in rats, rabbits, and dogs, respectively. The Cmax and AUC0----infinity of nalidixic acid were higher than those of norfloxacin in all animals. Joint tissues took up more norfloxacin than nalidixic acid, but when arthropathy was present the articular cartilage concentrations of the two drugs were in the same range. The penetration of norfloxacin into the articular cartilage was the same regardless of the joint's anatomical locations, but differed among species, being highest in rats and lowest in monkeys. The Cmax and AUC0----infinity of norfloxacin in animals at their arthropathic doses were far higher than those measured clinically in children, whereas those of nalidixic acid in animals did not differ much from its clinical parameters.

Administration, Oral↗
PubMed1990

Effect of spinal cord ischemia on compound muscle action potentials and spinal evoked potentials following spinal cord stimulation in the dog.

We recorded the compound muscle action potentials (CMAP) from the soleus muscle and spinal evoked potentials (SpEP) from the caudal spinal cord after stimulation of the rostral spinal cord via epidural electrodes in 18 dogs. We examined the changes of CMAP and SpEP after the cord was made ischemic by clamping the aorta at different levels. Clamping the abdominal aorta below the artery of Adamkiewicz (five dogs) did not change either CMAP or SpEP significantly. When the thoracic aorta was clamped above the radicular and Adamkiewicz arteries (10 dogs), CMAP disappeared entirely within 5-10 min of occlusion, but SpEP showed only minimal latency prolongation limited to the late peaks in seven of 10 dogs. In the remaining three dogs, both CMAP and SpEP disappeared within 30 min of occlusion but with the more rapid deterioration of CMAP than of SpEP. Progressive ligation of lumbar arteries (three dogs) from caudal to rostral levels did not change CMAP until ligation of Adamkiewicz artery. Then CMAP disappeared, but SpEP remained unchanged. These findings suggest that CMAP and SpEP are mediated through different pathways and that CMAP reflect anterior cord function. The described electrophysiologic technique would be useful to monitor spinal cord motor function during surgery of the spine, spinal cord, or thoracoabdominal aorta.

Action Potentials↗
PubMed1990

[Electrophysiological diagnosis in ulnar nerve entrapment at elbow].

Using "inching technique" we recorded antidromic sensory nerve action potentials from the little finger and compound muscle action potentials from the abductor digiti minimi, first dorsal interosseous and flexor carpi ulnaris muscles in 30 entrapped ulnar nerves. In cubital tunnel syndrome, localized conduction delay occurred most commonly at a point 2 to 4 cm distal to the medial epicondyle. In other ulnar neuropathies, with the exception of cubitus valgus deformity, conduction block or delay was noted at a site just distal to the medial epicondyle. These conduction abnormalities were most commonly observed in the abductor digiti minimi and first dorsal interosseous. In contrast, conduction abnormality in tardy palsy secondary to the valgus deformity reflected mainly in the flexor carpi ulnaris. This method provides useful information in diagnosing the early involvement and precise localization of nerve entrapment, and differentiation of cubital tunnel syndrome from other ulnar nerve entrapment.

Action Potentials↗
PubMed1989

Purification and characterization of a nuclear factor which binds specifically to the upstream activation sequence of Saccharomyces cerevisiae enolase 1 gene.

The nuclear factor which specifically binds to the upstream activation sequence (UAS) of the enolase 1 gene (ENO1) of yeast Saccharomyces cerevisiae was purified by sequence-specific affinity chromatography. The purified factor gave two closely migrated bands at 32 kDa on SDS/PAGE. The binding activities were eluted from a gel filtration column at molecular masses of 110 kDa and 60 kDa, suggesting a dimeric and a tetrameric assembly of the factor in the native form. The region protected by the purified factor against deoxyribonuclease I digestion contained the sequence ACCCAAACACC which is highly similar to the consensus sequence present in the 5'-flanking region of the ribosomal protein genes (RPG box). We also identified the other factor specific to the ENO1 UAS which gave a single peak at a molecular mass of 120 kDa in gel filtration. We suggest the existence of multiple binding to the ENO1 UAS by at least two factors: one is the factor which we purified with a molecular mass of 32 kDa on SDS/PAGE and the other is the factor like RAP1 protein which generally recognizes the RPG-box-like sequence.

Base Sequence↗
PubMed1989

Compound muscle action potentials and spinal evoked potentials in experimental spine maneuver.

In this study, the authors evaluated the effects of spine manipulations, similar to those used in scoliosis surgery, on the compound muscle action potential (CMAP) and spinal evoked potential (SEP) in 25 cats: a distraction maneuver was performed in ten, a rotation in five, and a combined (distraction and rotation) procedure in ten cats. Compound muscle action potential was only minimally changed by the rotation maneuver alone in all five cats. Distraction resulted in earlier deterioration of CMAP than SEP; when CMAP was no longer elicitable in ten cats, seven still showed measurable SEP. All ten cats became paraplegic. With the combined procedure, both CMAP and SEP were abolished earlier than with distraction alone. This was observed in all ten cats becoming paraplegic. The authors further extended the study to ten rabbits having experimentally induced scoliosis. Following corrective surgery with distraction and derotation, eight rabbits lost both CMAP and SEP. Two lost CMAP with still recordable SEP. All ten rabbits became paraplegic. These findings suggest that monitoring CMAP is a more sensitive measure than SEP, and that the spinal cord is more vulnerable to a combined distraction and derotation maneuver than to either one alone.

Action Potentials↗
PubMed1989

[Bolus and maintenance infusion of high-dose methotrexate].

For 17 patients with bone and soft tissue sarcoma, 32 bolus and maintenance infusions of high-dose methotrexate (MTX) were performed to induce rapid elevation of plasma MTX concentration and to maintain it. At the doses of 200-300 mg/kg, plasma MTX concentrations were measured by enzyme assay. It needed four hours to reach the steady state by five hours' constant rate infusion, with the plasma plateau concentration at about 1 X 10(-3) M/L. On the other hand, bolus infusion of MTX needed only one hour to reach over 5 X 10(-4) M/L, and the plateau concentration lasted during the maintenance infusion period. By the constant rate infusion as well as bolus infusion, it was possible to maintain the plasma concentration over 1 X 10(-4) M/L for 12 hours, but both infusions can not maintain 1 X 10(-3) M/L for a long time. From these results, clinical effects of high dose MTX against sarcomas seemed to be evaluated by the plasma MTX plateau concentration and the maintenance time.

Bone Neoplasms↗
PubMed1988

The protein factor which binds to the upstream activating sequence of Saccharomyces cerevisiae ENO1 gene.

Using a gel retardation assay it was shown that the 87 bp DNA fragment (UAS87) containing the upstream activating sequence (UAS) of S. cerevisiae EN01 gene and a nuclear extract gave rise to three migration-retarded species specific to UAS87. Heat- or proteinase-treatment of the nuclear extract revealed that these species were protein-DNA complexes. The precise binding region of the protein identified by DNaseI protection analysis was found to include a CCAAACA sequence which forms a dyad-symmetrical structure. The amount of one of the three migration-retarded species significantly increased when cells were grown in medium containing a gluconeogenic carbon source. The introduction of pGCR8, a multicopy plasmid containing GCR1 gene, a regulatory gene controlling the expression of several glycolytic enzymes, showed no effect on the amount of three migration-retarded species.

Base Sequence↗