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C Mizuno

Publications and source records attributed to C Mizuno.

11 recordsLinked to original sources
PubMed1996

Trehalase in the spermatophore from the bean-shaped accessory gland of the male mealworm beetle, Tenebrio molitor: purification, kinetic properties and localization of the enzyme.

Trehalase from the bean-shaped accessory glands of the male mealworm beetle, Tenebrio molitor, was purified by acid treatment, with subsequent chromatography on columns of DEAE-cellulofine and Sephacryl S-300. The molecular masses of the native and the denatured forms were estimated to be 43 and 62 kDa by gel filtration and SDS-PAGE, respectively, an indication that the trehalase may be composed of a single polypeptide. The optimum pH of the reaction catalyzed by trehalase was 5.6-5.8. The Km for trehalose was 4.4 mmol.1(-1). Immunohistochemical experiments with trehalase-specific antiserum showed that the enzyme was localized in one specific type of secretory cell in the bean-shaped accessory gland epithelium and within the semisolid secretory mass that was a precursor to the wall of spermatophore. SDS-PAGE and immunoblotting analysis revealed the presence of a polypeptide of about 62 kDa in the spermatophore. Immunohistochemical observations showed that the trehalase was located at the outgrowth in the anterior portion of the spermatophore. When a fresh spermatophore was immersed in phosphate-buffered saline it discharged sperm in the same manner as in the bursa copulatrix of the female. Before the rupture of the expanded bulb of the spermatophore, almost all of the trehalase had dissolved in the phosphate-buffered saline. The addition of validoxylamine A to the saline, a specific inhibitor of trehalase, did not affect the expansion and evacuation of the spermatophore. These results demonstrate that trehalase, synthesized by a specific type of secretory cell in the bean-shaped accessory gland epithelium, is actively passed into the lumen of the bean-shaped accessory gland and then incorporated into the spermatophore. Trehalase appears to be one of the structural proteins of the spermatophore, although the possibility can not yet be completely ruled out that the trehalase-trehalose system functions for the nourishment and/or activation of the sperm in the bursa copulatrix of the female.

Acetates↗
PubMed1994

Periodicity of long-term context can influence gap detection.

Temporal gap detection in bands of noise is a basic paradigm to investigate auditory temporal resolution. This study further examined the role of the long-term temporal organization for gap detection. Our experiments aimed at determining whether a gap superimposed on an amplitude-modulated noise was easier to detect when the amplitude modulation was regular--or periodic--than when it was not. Care was taken to ensure that the stimulus portion, where the gap was inserted, was exactly the same for both periodic and aperiodic conditions. Results show that gap detection in periodically modulated white noise (125 Hz fundamental frequency, or 8 ms duration from peak to peak) is easier (with a threshold 4.7 ms lower) than in an aperiodically modulated noise (modulation randomly varied from 5 to 18 ms). This effect is observed for variations of the modulation frequency from 125 to 1000 Hz. These results indicate that the regularity of long-term temporal organization of amplitude modulations in noise can improve the detection of a gap.

Acoustic Stimulation↗
PubMed1992

Some chemical properties of the HCl-methanol extract from the puparial cuticle of Drosophila melanogaster.

1. The HCl-methanol (HCl-MeOH) soluble fraction from the puparial cuticle of yellow, black and ebony of D. melanogaster was hydrolyzed in hydrochloric acid and examined for beta-alanine, ketocatechol, and acetic acid. 2. Between beta-alanine and ketocatechol and between beta-alanine and acetic acid, a quantitatively inverse relationship was found, respectively. The former relationship was further confirmed by the feeding experiment of beta-alanine to black. 3. Of total beta-alanine in the HCl-MeOH extract, the proportion of those having free amino group was 74.8 per cent. 4. All these results indicate that the HCl-MeOH soluble fraction of the puparial cuticle may be useful for investigating the cross-link structure of the cuticle.

Acetates↗
PubMed1992

[Estimation of energy expenditure and the validity of pitch counting during walking and jogging by piezoelectric materials].

The purpose of the present study was to assess the validity of Piezo-electric accelerometer for estimating energy expenditure in walking and jogging. Energy consumption by oxygen uptake was determined during steady state level of treadmill walking at the speed of 60, 80 and 100 m/min and jogging at the speed of 100, 120, 140, and 160 m/min for 10 subjects. There was a highly significant correlation between the energy consumption and the estimated energy expenditure by an accelerometer despite the attached position (r = 0.912 at the waist, r = 0.915 at the chest, P < 0.001), which suggests accurate estimating energy expenditure in the field.

Adult↗
PubMed1990

[Estimation of energy expenditure during walking and jogging by using an electro-pedometer].

Using an electro-pedometer which is commercially available, energy expenditure during walking and/or jogging was assessed, and was compared with that obtained by oxygen uptake (VO2). Thirteen male students and 12 female students exercised on 6 minutes duration treadmill tests which velocities were 40, 60, 80, 100, and 120m/min for walking and 100, 120, 140, 160, and 180m/min for jogging, respectively. During exercise, energy expenditure was calculated by VO2 value and respiratory exchange ratio, and was estimated by an electro-pedometer. There was a significant linear relationship between energy expenditures estimated by the pedometer and calculated by VO2 during walking and jogging. To predict energy expenditure more precisely by the electro-pedometer, it is suggested that more precise value of stride should be inputted into the pedometer. In conclusion, the present study showed that commercially available electro-pedometer is able to use for the estimation of energy expenditure with precise validity during walking and/or jogging.

Adult↗
PubMed1981

Inhibition of cell-free protein and RNA syntheses by partially purified fractions of mouse melanoma extract.

Ethanol precipitate (70-95%) of the water extract of mouse melanoma (ME) contains suppressors for melanocyte cell division. A fraction which had preferential melanocyte cell line suppressor activity (ME IV2) was shown to inhibit protein synthesis by cell-free systems and RNA synthesis by isolated nuclei of rat liver. The separation and some characterization of the inhibitory factors in ME IV2 were carried out. Upon being boiled, the factor in ME IV2 inhibiting cell-free protein synthesis became inactive, whereas that inhibiting cell-free RNA synthesis remained active. Bio-Gel p-2 column chromatography of ME IV2 gave three distinct fractions (ME IV2-A, -B and -C). ME IV2-A was inhibitory to cell-free protein synthesis but non-inhibitory to cell-free RNA synthesis. On the contrary, ME IV2-B was non-inhibitory to cell-free protein synthesis but inhibitory to cell-free RNA synthesis. ME IV2-C was non-inhibitory to cell-free protein synthesis and seemed to be somewhat inhibitory to cell-free RNA synthesis. Preliminary analyses of the components in these subfractions are also reported.

Animals↗
PubMed1980

Inactivation of tyrosinase by dopa.

Tyrosinase in a melanosome is known to be inactivated during melanin formation in vivo, and a similar inactivation was observed in vitro when melanosomes isolated from Harding Passey mouse melanoma were incubated with dopa. Tyrosinase, whether particle bound or in soluble form, was inactivated during the dopa-tyrosinase reaction and the reduction rate of its activity was proportional to the reaction time. Tyrosinase inactivation also occurred when ascorbic acid was added to the reaction system; in which dopaquinone, an oxidation product of dopa which is immediately converted back to dopa by ascorbic acid thus preventing melanin formation. When 14C-dopa or 14C-ascorbic acid were added to the reaction mixture, these radioactive substances were not recovered from the inactivated enzyme protein fraction after incubation. In addition this inactivation of tyrosinase by dopa was not inhibited by any of: 1.4-diazabicyclo[2.2.2]octane, scavenger for singlet oxygen; D-mannitol, that for hydroxyl radical; superoxide dismutase, that for superoxide anion; and catalase, cleavaging enzyme for hydrogen peroxide. Thus the inactivation of tyrosinase appears to be due to neither these radicals, nor reaction products from dopa or ascorbic acid, but to changes in the enzyme itself.

Animals↗