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Biomedical subjects

K Tai

Publications and source records attributed to K Tai.

At least 37 records · Page 2Linked to original sources
PubMed1994

[The effects of diltiazem on neuromuscular transmission].

The effects of intravenous diltiazem (0.5 and 1.0 mg.kg-1) on muscle compound action potential (CAP) elicited from gastrocnemius muscle by sciatic nerve stimulation in cats were investigated. Analysis was performed on the amplitude of CAP, recovery curve (RC) and train-of-four ratio (TOFR). There was no response in any parameter after administering 0.5 mg.kg-1. On the other hand, diltiazem 1.0 mg.kg-1 produced significant depression only in the amplitude of CAP, but no change was observed in both RC and TOFR. It is concluded that approximately ten times the therapeutic dose of diltiazem is necessary to modify the neuromuscular transmission.

Action Potentials↗
PubMed1993

Mutagenesis of the fourth calcium-binding domain of yeast calmodulin.

The fourth calcium-binding domain (domain IV) of the yeast (Saccharomyces cerevisiae) calmodulin is unable to bind Ca2+ (Matsuura, I., Ishihara, K., Nakai, Y., Yazawa, M., Toda, H., and Yagi, K. (1991) J. Biochem. (Tokyo) 109, 190-197). The functional significance of Ca2+ binding to domain IV was investigated by site-directed mutagenesis or recombinant DNA techniques. A recognition site for the restriction enzyme ClaI was introduced at the homologous position of Ile130 in the nucleotide sequence of chicken and yeast calmodulin cDNA, and chimeric proteins of the yeast and the vertebrate calmodulin were prepared. One of the resulting mutants named C4Y consisted of Ala1-Ile130 of chicken calmodulin and Asp131-Lys148 of yeast calmodulin. The mutant C4Y showed the yeast-type feature, and its enzyme activation profiles were similar to those of yeast calmodulin. A single substitution of Glu for Gln140 was carried out in the mutant C4Y. The resulting mutant (C4Y140E) bound 4 mol of Ca2+ and showed the vertebrate-type enzyme activation. Therefore, the alterations of 3 residues in the Ca(2+)-binding loop of the yeast-type domain IV, Ser129-->Asp, insertion of Ile130, and Gln140-->Glu, were enough for the recovery of Ca2+ binding and enzyme activation. Ca2+ binding to domain IV may induce the active conformation of the C-terminal half-molecular domain.

Amino Acid Sequence↗
PubMed1990

[Study of neuromuscular transmission with evoked electromyography--10. Comparison of the responses during partial blockade by bungarotoxin and non-depolarizing relaxants].

Effects of alpha-bungarotoxin (alpha BuTX) on muscle compound action potentials (CAPs) which were elicited from gastrocnemius muscle by sciatic nerve stimulation in cats were studied, and the results were compared with those of non-depolarizing relaxants including d-tubocurarine, pancuronium and vecuronium. The amplitude of CAP by the second member of the paired stimuli (test response) was compared with that evoked by the first component (conditioning response). The interval between the two components of the paired stimuli (the pair interval) was increased stepwise from 7 to 1,000 msec and a curve (recovery curve, RC) was obtained by relating the changes in pair interval to the difference in amplitude of the test and conditioning responses. The following results were obtained. (1) A progressive and irreversible neuromuscular block was observed after intravenous administration of alpha BuTX. During the progress of the blockade, RC of CAPs showed a pattern which was characterized by profound potentiations of test responses at shorter intervals of paired stimuli, followed by gradual recovery to similar amplitude with conditioning responses at 500 msec or over of pair interval. (2) With non-depolarizing relaxants, RC changed to the pattern of slight potentiation at a very short interval of stimuli, followed by a notable depression at longer intervals. (3) The mechanism of the development of these difference of RCs between alpha BuTX and the relaxants was discussed, and it is concluded that the notable depression of RCs derived from muscle relaxants may be caused by inhibitory effect on nerve terminals of these relaxants, and the inhibition was more prominent with d-tubocurarine than with other two relaxants.

Action Potentials↗
PubMed1989

Iodine-131 MIBG scintigraphy in small cell lung cancer.

There is a well documented relationship between small cell carcinoma of the lung and the amine precursor uptake and decarboxylation system of endocrine cells (APUD). We attempted to exploit this association by employing the unique radiopharmaceutical, 131I-MIBG, which is recognized and taken up by the APUD system to monitor disease activity in patients with small cell carcinoma of the lung. A total of eight patients with biopsy proven, metastatic small cell carcinoma of the lung were studied. 131I-MIBG was synthesized in our laboratory by reacting metaiodobenzylamine hydrochloride with cyanamide with subsequent solid phase radioiodination. A dose of 0.5 mCi radiopharmaceutical was injected and images obtained on a large field of view gamma camera with a high energy parallel hole collimator at 2, 24, and either 48 or 72 h. Images were compared with known focal areas of metastatic disease demonstrable on computed tomographic scan, chest roentgenogram or bone scan. We were unable to detect reproducible correlations between the images produced by conventional radiographic techniques and the images produced by our radiopharmaceutical. We conclude that this agent will probably not be useful for localization of metastatic small cell lung carcinoma.

3-Iodobenzylguanidine↗
PubMed1988

Comparison between a new acceleration transducer and a conventional force transducer in the evaluation of twitch responses.

An acceleration transducer elicits an output voltage proportional to the deformation of the piezo crystal, in accordance with the twitch responses of the applied fingers. The reliability of such a transducer was evaluated by comparing induced twitch responses with those from a force transducer applied on the contralateral arm of an individual during neuromuscular block with vecuronium. The results obtained from twitch responses with the acceleration transducer during neuromuscular block were almost identical to those obtained with the force transducer. Also, the twitch heights due to acceleration of the examined thumb correlated extremely well with the twitch height due to twitch tension with the force transducer. It is concluded that the acceleration transducer may be a useful and reliable device for monitoring neuromuscular block, although responses during tetanic stimulation such as tetanic fade cannot be determined by the transducer.

Adolescent↗