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Biomedical subjects

H Miyata

Publications and source records attributed to H Miyata.

At least 325 records · Page 18Linked to original sources
PubMed1990

SPECT imaging with Tl-201 and Ga-67 in myocardial sarcoidosis.

Two patients with myocardial sarcoidosis are presented, both of whom underwent SPECT imaging with Tl-201 and Ga-67. The first had Ga-67 myocardial uptake with a Tl-201 defect, which disappeared with corticosteroid therapy. The second had multiple Tl-201 defects without Ga-67 uptake, which persisted despite corticosteroid therapy. Therefore, the combination of Tl-201 and Ga-67 imaging may be useful for recognizing myocardial sarcoidosis and for predicting the response to corticosteroid therapy.

Adrenal Cortex Hormones↗
PubMed1990

Pattern of end growth of the fission yeast Schizosaccharomyces pombe.

The patterns of end growth of individual cells of Schizosaccharomyces pombe, wild-type cells (strain 972 h-), cells exposed to 8 mM hydroxyurea, and cdc mutants (cdc11-123 and cdc2-33), were investigated by time-lapse photomicrography. It was reconfirmed that there are three patterns of end growth: cells growing at the old end, at the new end, and at both ends from the beginning of the cell cycle. Cells that initiated growth at the old (new) end increased their growth rate at the new (old) end and became constant in their growth rate at the old (new) end when cells had their growth rate higher than a critical value: 0.08, 0.09, 0.08, and 0.11 microns/min in wild-type cells, cells exposed to hydroxyurea, cdc11-123 cells, and cdc2-33 cells, respectively. The critical value is proportional to the doubling time in length.

Cell Division↗
PubMed1990

[Assessment of drug effects on memory by delayed discrimination responses in rats].

Delayed discrimination experiments were conducted to examine drug effects on memory in rats. Three kinds of experimental situations: a Y-maze, an operant chamber with two retractable levers, and an operant chamber with two fixed levers were used. A discriminative stimulus light either on the left or the right side of a stimulus panel was presented for a brief period in each situation. After a certain delay time following extinguishment of the light, a choice response to the previously lighted side was termed as a correct choice. Scopolamine at 0.015-0.06 mg/kg, s.c., decreased the correct choice ratio in trials with a delay time of 0 sec in the Y-maze situation and in trials with longer delay times in the operant chamber situations. Nicotine at 0.06-1 mg/kg, s.c., decreased the correct choice ratio in trials with a delay time of 0-4 sec in the Y-maze situation, a delay time of 4 sec in the retractable-lever operant chamber situation, and a delay time of 0.1 sec in the fixed-lever operant chamber situation. Using this delayed discrimination procedure, drug effects on the relationship between delay time and correct choice ratio were observed. From these results, the present procedure was found to be useful for the evaluation of drug effects on memory in rats.

Animals↗
PubMed1990

Virucidal effect of ozone treatment of laboratory animal viruses.

An ozonization method was used to inactivate the viral pathogens of laboratory animals. Ozone at a concentration of over 100 ppm with high humidity was highly virucidal against 4 RNA viruses: HVJ, Theiler's murine encephalomyelitis virus (TMEV), Reo type 3 virus (RV) and murine hepatitis virus (MHV). For the ozone tests, 0.1 ml of a virus suspension in deionized water or saline and was placed in 35-mm dishes. The titer of 10(6) plaque-forming units of TMEV in a liquid-phase, which was highly stable against physical treatments, was reduced within 1 hr to a level of 0 by 300 ppm of ozone at 80% humidity and 22-25 degrees C. HVJ and MHV were more susceptible than TMEV to the ozone treatment. RV was the most resistant of the 4 viruses. The ozonization method may be a good way to disinfect not only for the laboratory animal RNA-viruses (both of enveloped and unenveloped viruses) but also animal rooms, clean rooms and even safety cabinets.

Animals↗
PubMed1990

HVJ infection in alveolar macrophages of various laboratory animals.

Alveolar macrophages (AM) in bronchoalveolar lavage derived 6 species of laboratory animals (mouse, rat, Syrian hamster, Mongolian gerbil, guinea pig, and rabbit) were cultivated in vitro and were infected with HVJ, parainfluenza virus type 1, for the purpose of studying virus reproduction in these cells. Using infectivity assay, fluorescent antibodies and hemadsorption techniques, three categories were proposed depending on the potential of virus replication and antigen production. Category 1 (mouse, Syrian hamster, and guinea pig AM) was the most susceptible group to HVJ infection. All AM became antigen positive, and more than 10(6) PFU/ml of virus infectivity in the culture fluids was noted at 4 days after the virus infection. Rat and Mongolian gerbil AM were grouped into Category 2. Their AM showed a moderate virus yield (average 10(5) PFU/ml of infectivity) and antigen production. On the other hand, Category 3 (rabbit AM), exhibited no production of an infectious virus. It was likely that the virus penetrated into the AM but did not replicate complete virus. However, antigen positive cells ranging from 10 to 50% depended on the multiplicity of the infection to the AM. These findings suggest that HVJ infection in the rabbit AM was abortive (incomplete virus replication), since trypsin treatment of the culture fluids, which may contain incomplete HVJ particles, did not induce infectivity.

Animals↗
PubMed1990

Theiler's murine encephalomyelitis virus--characterization of newly isolated viruses from Japanese mouse colonies.

The hemagglutinating-inhibition (HI) test was used to detect antibodies for Theiler's murine encephalomyelitis virus (TMEV), and the virus was isolated from sero-positive mice derived from colonies in Japan. HI antibody was detected in conventional mice (38.7%; 137/354) at titers ranging from 1:8 to 1:512, but it not in SPF mice (0/90). To isolate the virus, weanling mice inoculated intracerebrally with samples obtained from sero-positive mice were sacrificed and 10% brain homogenates were subcultured. New isolates designated as YOC and AB strains were obtained, and their physicochemical and biological properties were characterized. The results indicated that the new isolates were similar to Theiler's original (TO) strain according to the following observations of persistent paralysis of the hind limbs, resistance to ether treatment, a particles size of 10 approximately 50 nm in diameter, stability at pH 3, a density of 1.35 g/cm3 and three major and one minor viral proteins, (VPO; 38 Kd, VP 1; 33 Kd, VP2; 32Kd, VP3; 25 Kd). Immunoblotting analysis also showed that VP 2 of YOC and encephalomyocarditis virus of the Cardiovirus group, reacted strongly with the antisera against the viruses as well as with the GDVII strain. These results suggest that TMEV infection does exist in conventional mouse colonies in Japan, and that these viruses resemble the TO strain of TMEV.

Animals↗
PubMed1990

[Effects of scopolamine and diazepam on delayed discrimination behavior in rats].

The effects of subcutaneously administered scopolamine and diazepam on simultaneous as well as delayed light-dark discrimination behavior were studied in a Y-maze situation using rats. In simultaneous discrimination behavior, running responses to the lighted side of either the right or left arm of the Y-maze were regarded as correct choices. In delayed discrimination behavior, running responses to the lighted side at several delay times (0. 2, 4, and 8 sec) after extinguishment of the light were regarded as correct choices. In the saline test, the percentage of correct choices decreased as the delay time was extended. Scopolamine at 0.03 mg/kg decreased the percentage of correct choices as the delay time was extended within the range of 0 sec through 4 sec. Diazepam both at 1 mg/kg and at 2 mg/kg decreased the percentage at the delay times of 0, 2, and 4 sec but this decreasing effect was not dependent on the delay time. The same doses of these drugs had no effect on simultaneous discrimination behavior. These results suggest that scopolamine at 0.03 mg/kg and diazepam both at 1 mg/kg and at 2 mg/kg disrupt delayed discrimination behavior in different ways.

Animals↗
PubMed1990

[Breast carcinoma metastasis to perineal neurofibroma].

A 51-year-old woman as admitted to our department because of multiple palpable tumors that were noted on the left breast, the perineum, and the neck, shoulders, arms, and legs. The breast tumor showed ulceration on the surface. The perineal tumor was 30 x 15 cm in size and had group slowly for 17 years. A chest X-ray revealed a bilateral coin lesion. She was diagnosed as having a left breast cancer with a skin lung metastasis and a perineal benign tumor. A simple mastectomy and a resection of the perineal tumor were performed. A postoperative examination revealed an adenocarcinoma of the breast and a fibroneurinoma of the perineum with a metastasis from the breast cancer.

Adenocarcinoma↗
PubMed1989

Purification and characterization of a third isoform of myosin I from Acanthamoeba castellanii.

A third isoform of myosin I has been isolated from Acanthamoeba and designated myosin IC. Peptide maps and immunoassays indicate that myosin IC is not a modified form of myosin IA, IB, or II. However, myosin IC has most of the distinctive properties of a myosin I. It is a globular protein of native Mr approximately 162,000, apparently composed of a single 130-kDa heavy chain and a pair of 14-kDa light chains. It is soluble in MgATP at low ionic strength, conditions favoring filament assembly by myosin II. Myosin IC has high Ca2+- and (K+,EDTA)-ATPase activities. Its low Mg2+-ATPase activity is stimulated to a maximum rate of 20 s-1 by the addition of F-actin if its heavy chain has been phosphorylated by myosin I heavy chain kinase. The dependence of the Mg2+-ATPase activity of myosin IC on F-actin concentration is triphasic; and, at fixed concentrations of F-action, this activity increases cooperatively as the concentration of myosin IC is increased. These unusual kinetics were first demonstrated for myosins IA and IB and shown to be due to the presence of two actin-binding sites on each heavy chain which enable those myosins I to cross-link actin filaments. Myosin IC is also capable of cross-linking F-actin, which, together with the kinetics of its actin-activated Mg2+-ATPase activity, suggests that it, like myosins IA and IB, possesses two independent actin-binding domains.

Acanthamoeba↗
PubMed1989

Dual loading of the fluorescent indicator fura-2 and 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF) in isolated myocytes.

Isolated rat heart myocytes were loaded with both the Ca2+ sensitive fluorescent probe fura-2/AM and the fluorescent pH indicator 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF/AM). Changes in [Ca2+]i and pHi were measured simultaneously using digitized video fluorescence microscopy. In measurement of [Ca2+]i and pHi, the ratios of dual-loaded cells were not different from single-loaded cells. Using this method, [Ca2+]i and pHi in myocytes were 48 +/- 7 nM and 7.17 +/- 0.05. It is concluded that [Ca2+]i and pHi could be measured simultaneously in isolated myocyte using dual-loading of fura-2 and BCECF.

Animals↗
PubMed1989

Plasma membrane association of Acanthamoeba myosin I.

Myosin I accounted for approximately 2% of the protein of highly purified plasma membranes, which represents about a tenfold enrichment over its concentration in the total cell homogenate. This localization is consistent with immunofluorescence analysis of cells that shows myosin I at or near the plasma membrane as well as diffusely distributed in the cytoplasm with no apparent association with cytoplasmic organelles or vesicles identifiable at the level of light microscopy. Myosin II was not detected in the purified plasma membrane fraction. Although actin was present in about a tenfold molar excess relative to myosin I, several lines of evidence suggest that the principal linkage of myosin I with the plasma membrane is not through F-actin: (a) KI extracted much more actin than myosin I from the plasma membrane fraction; (b) higher ionic strength was required to solubilize the membrane-bound myosin I than to dissociate a complex of purified myosin I and F-actin; and (c) added purified myosin I bound to KI-extracted plasma membranes in a saturable manner with maximum binding four- to fivefold greater than the actin content and with much greater affinity than for pure F-actin (apparent KD of 30-50 nM vs. 10-40 microM in 0.1 M KCl plus 2 mM MgATP). Thus, neither the MgATP-sensitive actin-binding site in the NH2-terminal end of the myosin I heavy chain nor the MgATP-insensitive actin-binding site in the COOH-terminal end of the heavy chain appeared to be the principal mechanism of binding of myosin I to plasma membranes through F-actin. Furthermore, the MgATP-sensitive actin-binding site of membrane-bound myosin I was still available to bind added F-actin. However, the MgATP-insensitive actin-binding site appeared to be unable to bind added F-actin, suggesting that the membrane-binding site is near enough to this site to block sterically its interaction with actin.

Acanthamoeba↗
PubMed1989

Effects of strophanthidin on intracellular Ca2+ concentration and cellular morphology of guinea pig myocytes.

To study the role of cytosolic calcium concentration [( Ca2+]i) in the pathophysiology of Ca2+ overload, we used a digital image of calcium indicator signals (fura-2 fluorescence) from guinea pig myocytes. [Ca2+]i increased from 69(SEM 5) nmol.litre-1 (n = 15) to 204(45) nmol.litre-1 (n = 14) after 10 min perfusion with 100 mumol.litre-1 strophanthidin. The effects of strophanthidin on cellular morphology were associated with variable increases in [Ca2+]i of myocytes. [Ca2+]i was 263(9) nmol.litre-1 in the spontaneous contracting cells with "Ca2+ wave", and 784(103) nmol.litre-1 in rounded cells. There was a significant relationship (r = 0.77, p less than 0.001) between elevation of [Ca2+]i and shortening of longitudinal length of the cells. After 20 min pretreatment with 10 mumol.litre-1 ryanodine, strophanthidin (100 mumol.litre-1) did not cause spontaneous contractile activity, and induced a slower increase in [Ca2+]i than found previously with strophanthidin alone. We suggest that [Ca2+]i played a primary role in mediating irreversible injury in this study, and that the absolute value of [Ca2+]i was correlated with morphological changes. We also suggest that the Ca2+ release from the sarcoplasmic reticulum was related to the increase in [Ca2+]i and the spontaneous contracting activity.

Animals↗
PubMed1989

Effects of hydrogen peroxide on action potentials and intracellular Ca2+ concentration of guinea pig heart.

Oxygen free radicals and Ca2+ overload have been implicated in the genesis of reperfusion induced arrhythmia and injury. Effects of hydrogen peroxide (H2O2) on action potentials and intracellular Ca2+ concentration ([Ca2+]i) were studied using guinea pig papillary muscles and ventricular myocytes. High concentration of H2O2 (10 mmol.litre-1) caused delayed afterdepolarisations in all six papillary muscles, and induced triggered activity in 3/6 preparations. Pretreatment with ryanodine (1 mumol.litre-1) abolished delayed afterdepolarisations and triggered activity induced by H2O2. [Ca2+]i and morphological changes in isolated ventricular myocytes of guinea pig were measured using fura-2. Quiescent and rod shaped myocytes became shortened and rounded (contracture) after the application of 0.1 and 1 mmol.litre-1 H2O2. [Ca2+]i increased from the control values of 53 (SEM 4) and 62(8) nmol.litre-1 to 110(29) and 105(24) nmol.litre-1 (p less than 0.05 v control) when cells were shortened during perfusion with 0.1 and 1 mmol.litre-1 H2O2, respectively. The values were 130(26) nmol.litre-1 (p less than 0.05 v control) and 100(18) nmol.litre-1 (p less than 0.05 v control) when the cells became rounded during perfusion with 0.1 and 1 mmol.litre-1 H2O2. We suggest that the arrhythmia caused by Ca2+ overload was induced by H2O2, possibly by lipid peroxidation of cell membrane. H2O2 was also shown to shorten cells and cause cell contracture (rounding). The mechanism of cell injury is not likely to be due to the Ca2+ overload, since the increase in [Ca2+]i during perfusion with H2O2 was not large.

Action Potentials↗