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Biomedical subjects

K Tsuzuki

Publications and source records attributed to K Tsuzuki.

At least 145 records · Page 8Linked to original sources
PubMed1987

Temporal raphe of the retinal nerve fiber layer revealed by medullated fibers.

Three cases of medullated nerve fibers of the retina were seen. They had medullated nerve fibers in both the upper and lower quadrants of the temporal retina, whereby the temporal raphe of the retinal nerve fiber layer could be visualized. Some nerve fibers from the upper and lower quadrants crossed each other on the horizontal meridian. The structure of the temporal raphe reported by Vrabec through anatomical studies was confirmed by ophthalmoscopy.

Adult↗
PubMed1986

Activation of Clostridium botulinum type E toxin purified by two different procedures.

Clostridium botulinum type E toxin was purified from culture supernates and from cell extracts by two methods. The specific activity [2 X 10(4) mouse LD50 (mg protein)-1] of the toxin purified from cell extract under slightly acidic conditions was lower than that [3 X 10(5) LD50 (mg protein)-1] of the toxin purified from culture supernate under slightly alkaline conditions. Both toxin preparations were activated by trypsin treatment, but to different extents, the degree of activation of the toxin from cell extract being about 30-fold higher than that of the toxin from culture supernate. The two toxin preparations had the same electrophoretic mobility on SDS-polyacrylamide gels and antigenic specificity as revealed by agar gel double-immunodiffusion tests. The antigenic specificity of the two toxin preparations was unaltered by trypsin treatment. In SDS-polyacrylamide gel electrophoresis, a single band of Mr 144,000 was demonstrated before trypsin treatment and two bands of Mr 100,000 and 55,000 appeared after trypsin treatment. The two toxin preparations were labelled with 125I and chymotryptic peptide maps were obtained before and after trypsin treatment. The two toxin preparations without trypsin treatment demonstrated many differences in their peptide maps, but the preparations after trypsin activation had similar peptide maps. These results indicate that the toxin obtained from culture fluid was a partially activated form, and that its molecular conformation was different from that of the toxin from cell extract. Differences in specific activity and activation ratio by trypsin treatment may be due to differences in the conformation of the toxin molecules.

Botulinum Toxins↗
PubMed1985

Inhibition and level-tolerant frequency tuning in the auditory cortex of the mustached bat.

For echolocation the mustached bat, Pteronotus parnellii, emits complex orientation sounds (pulses), each consisting of four harmonics with long constant-frequency components (CF1-4) followed by short frequency-modulated components (FM1-4). The CF signals are best suited for target detection and measurement of target velocity. The CF/CF area of the auditory cortex of this species contains neurons sensitive to pulse-echo pairs. These CF/CF combination-sensitive neurons extract velocity information from Doppler-shifted echoes. In this study we electrophysiologically investigated the frequency tuning of CF/CF neurons for excitation, facilitation, and inhibition. CF1/CF2 and CF1/CF3 combination-sensitive neurons responded poorly to individual signal elements in pulse-echo pairs but showed strong facilitation of responses to pulse-echo pairs. The essential components in the pairs were CF1 of the pulse and CF2 or CF3 of the echo. In 68% of CF/CF neurons, the frequency-tuning curves for facilitation were extremely sharp for CF2 or CF3 and were "level-tolerant" so that the bandwidths of the tuning curves were less than 5.0% of best frequencies even at high stimulus levels. Facilitative tuning curves for CF1 were level tolerant only in 6% of the neurons studied. CF/CF neurons were specialized for fine analysis of the frequency relationship between two CF sounds regardless of sound pressure levels. Some CF/CF neurons responded to single-tone stimuli. Frequency-tuning curves for excitation (responses to single-tone stimuli) were extremely sharp and level tolerant for CF2 or CF3 in 59% of CF1/CF2 neurons and 70% of CF1/CF3 neurons. Tuning to CF1 was level tolerant in only 9% of these neurons. Sharp level-tolerant tuning may be the neural basis for small difference limens in frequency at high stimulus levels. Sharp level-tolerant tuning curves were sandwiched between broad inhibitory areas. Best frequencies for inhibition were slightly higher or lower than the best frequencies for facilitation and excitation. We thus conclude that sharp level-tolerant tuning curves are produced by inhibition. The extent to which neural sharpening occurred differed among groups of neurons tuned to different frequencies. The more important the frequency analysis of a particular component in biosonar signals, the more pronounced the neural sharpening. This was in addition to the peripheral specialization for fine frequency analysis of that component. The difference in bandwidth or quality factor between the excitatory tuning curves of peripheral neurons and the facilitative and excitatory tuning curves of CF/CF neurons was larger at higher stimulus levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1984

Development of a highly sensitive enzyme-immunoassay for serum carbonic anhydrase-III.

A highly sensitive sandwich enzyme-immunoassay (EIA) for human muscle carbonic anhydrase isozyme III (CA-III) has been developed using microplate as a solid-phase and peroxidase as a labelled enzyme. The assay can detect levels as low as 2 ng/ml when 20 microliter of sample sera were used. Sera from patients with various neurological diseases were studied using this method, and elevated serum CA-III levels were found in patients with Duchenne muscular dystrophy, limb-girdle dystrophy, fascioscapulohumeral dystrophy, polymyositis and amyotrophic lateral sclerosis. The values correlated well with the results of radioimmunoassay (RIA), with a correlation coefficient of 0.92 (P less than 0.001). We feel EIA is preferable to RIA for its simple methodology.

Carbonic Anhydrases↗