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Biomedical subjects

H Miyata

Publications and source records attributed to H Miyata.

At least 253 records · Page 14Linked to original sources
PubMed1994

Two distinct types of reticular cells in the pig sheathed artery.

The morphology of reticular cells of the sheathed arteries, in the red pulp of pig spleen, was studied by using transmission electron microscopy; and their histochemical reactivity with periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP). The phagocytic ability was evaluated by injecting colloidal carbon into the splenic artery. Reticular cells of the sheathed arteries were classified as type I and type II cells. Type I cells have a nucleus with scanty chromatin, and the cytoplasm reacts positively to PA-TCH-SP. The PA-TCH-SP-positive granules are considered to be subunits of beta-glycogen particles based on their morphological features. Type II cells have a nucleus with abundant chromatin and are not stained by PA-TCH-SP. Both types of reticular cells are connected with reticular fibers. Results of the colloidal carbon injection showed that type I reticular cells did not ingest carbon particles during the time frame of the experiment, whereas type II reticular cells are phagocytic and ingested carbon.

Animals↗
PubMed1994

Effects of methamphetamine, dopamine and noradrenaline administered into the nucleus accumbens of rats discriminating subcutaneous methamphetamine.

Since the nucleus accumbens has been hypothesized to centrally mediate the discriminative effects of psychomotor stimulants, the discriminative effects of methamphetamine (MA) as well as dopamine (DA) and noradrenaline (NA) were observed by intracerebral administration of these drugs into the nucleus accumbens in rats discriminating subcutaneous MA from saline. These rats were trained and maintained to discriminate between MA at 0.5 mg/kg, s.c. and saline under a fixed ratio 10 schedule for food reinforcement in a 2-lever operant chamber situation. Guide cannulae were implanted bilaterally into the nucleus accumbens. In the substitution tests, the drug was administered into the nucleus accumbens. MA at 10 micrograms per rat substituted for subcutaneous MA in 4 out of 5 rats but neither DA at 10-40 micrograms per rat (n = 7) nor NA at 10-40 micrograms per rat (n = 4) substituted for subcutaneous MA. On the other hand, the same drugs administered into the nucleus accumbens induced increased spontaneous motor activity as also observed in six other untrained rats. MA, DA or NA alone each at 10 micrograms per rat increased spontaneous motor activity. The discriminative effects of MA are considered to be mediated in the nucleus accumbens of rats. Although DA or NA alone administered into the nucleus accumbens showed similar increasing motor activity effects as those of MA, the discriminative effects of exogenous DA or NA alone administered into the same brain area were different from those of MA in the present experimental condition.

Animals↗
PubMed1994

Ca2+ waves and intracellular Ca2+ concentration in guinea pig and rat myocytes.

We measured [Ca2+]i of guinea pig and rat myocytes with Ca2+ waves, using fura-2 fluorescence image processing. In guinea pig myocytes, Ca2+ waves were absent during the control perfusion period, but could be induced by the addition of strophanthidin (100 microM) or sodium cyanide (NaCN: 2 mM) to the perfusate. The [Ca2+]i increased from the control values of 69 +/- 5 nM and 46 +/- 2 nM, to 263 +/- 9 (p < 0.05 vs. control) nM and 225 +/- 20 (p < 0.05) nM, respectively, when cells exhibited Ca2+ waves. Although 13% (16 of 121) of the rat myocytes displayed Ca2+ waves during the control perfusion, the [Ca2+]i with Ca2+ waves (56 +/- 9 nM) did not differ from [Ca2+]i in the absence of Ca2+ waves (54 +/- 3 nM). Ca2+ waves were induced by the perfusion with a high Ca2+ solution (24.5 microM) or NaCN (2 microM), and [Ca2+]i increased from the control values of 67 +/- 11 nM and 74 +/- 5 nM, to 231 +/- 41 (p < 0.05 vs. control) nM and 266 +/- 64 nM, respectively, when cells exhibited Ca2+ waves. The Ca2+ waves were abolished by the removal of extracellular Ca2+, or by the perfusion with ryanodine (10 microM) or caffeine (20 mM). In conclusion, it was shown that Ca2+ waves were due to oscillatory Ca2+ release and that the absolute value of [Ca2+]i is important for the appearance of Ca2+ waves in guinea pig and rat myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Rotational behavior induced by methamphetamine and cocaine in rats with unilateral 6-hydroxydopamine lesions of the nigrostriatal dopamine system].

The purpose of this study was to compare the ability of intravenously administered methamphetamine and cocaine to facilitate dopaminergic transmission, based on the ability of these drugs to induce rotational behavior in rats with unilateral 6-hydroxydopamine lesions of the substantia nigra. The doses of methamphetamine and cocaine ranged from 0.25 mg/kg to 4 mg/kg which was equivalent to 50% of the minimum dose which caused convulsion. Methamphetamine induced more marked ipsilateral rotational behavior than did cocaine. The present results suggest that methamphetamine produces longer duration of the facilitation of dopaminergic transmission both in the nucleus accumbens and in the striatum than does cocaine.

Animals↗
PubMed1994

Histochemical fiber composition of cat's tail muscles.

A histochemical analysis was performed on the activity of myofibrillar ATPase following preincubation at pH 10.3 with NADH-diaphorase in the cat tail muscles (ECM; extensor caudae medialis, ECL; extensor caudae lateralis, ACE; abductor caudae externus, ACI; abductor caudae internus, FCL; flexor caudae longus, and FCB; flexor caudae brevis). Muscles contained three types of muscle fibers: FG (fast-twitch glycolytic) showed high reaction of myofibrillar ATPase staining and low reaction in NADH-diaphorase staining; FOG (fast-twitch oxidative glycolytic) showed high reaction in myofibrillar ATPase staining and high reaction in NADH-diaphorase staining; and SO (slow-twitch oxidative) showed low reaction in myofibrillar ATPase staining and high reaction in NADH-diaphorase staining. All 6 tail muscles were composed of these three types of fibers, but proportions differed in each tail muscle. Proportions of SO and FG fibers were highest in ECL (SO: 38.6 +/- 2.3, S.D. %) and ACI (FG: 59.2 +/- 5.0%), respectively. The diameters of the fibers were also measured (SO; 50.47 +/- 3.12, FOG; 58.18 +/- 2.78, FG; 70.91 +/- 3.40, S.D. microns).

Adenosine Triphosphatases↗
PubMed1994

An antiallergic drug, pemirolast potassium, inhibits inositol 1,4,5-trisphosphate production and Ca2+ mobilization in antigen-stimulated rat basophilic leukemia (RBL-2H3) cells.

An antiallergic drug, pemirolast potassium (TBX) at concentrations between 0.01 and 10 micrograms/ml inhibited antigen (Ag)-stimulated degranulation in RBL-2H3 cells, which have the properties of mucosal mast cells. At the same concentrations, the drug suppressed both the formation of inositol 1,4,5-trisphosphate and the mobilization of Ca2+, indicating the prevention of phospholipase C activation. The production of 1,2-diacylglycerol and phosphatidic acid, which was mainly due to phosphatidylcholine hydrolysis, was also suppressed. Moreover, TBX reduced Ag-induced liberation of arachidonic acid, a precursor of eicosanoids, implying the inhibition of phospholipase A2. These data suggest that TBX inhibits the activation of phospholipase C, leading to decreased formation of the signal transducing molecules necessary for cell activation.

Animals↗
PubMed1994

[A study on the causes of the physical and mental disabilities in children].

The causes and time of onset of physical and mental disabilities in children were investigated. Among 72 subjects, the causes of the disabilities were clearly verified in 43 cases, that is, 21 cases of hypoxic ischemic encephalopathy (29%), 12 cases of cerebral malformations (17%), 7 cases of other congenital malformations (10%), and 3 cases of intrauterine infections (4%). In 10 cases from the remaining 29 subjects, the disorders during perinatal period were strongly suggested from the findings of CT and MRI.

Brain↗
PubMed1993

Involvement of tyrosine phosphorylation in IgE receptor-mediated phospholipase D activation in rat basophilic leukemia (RBL-2H3) cells.

The effect of protein tyrosine phosphorylation on phospholipase D (PLD) activation measured by the formation of radiolabeled phosphatidylbutanol (PBut) was examined in rat basophilic leukemia (RBL-2H3) cells stimulated with antigen. The PLD activation elicited by antigen was attenuated dose-dependently by pretreatment with protein tyrosine kinase inhibitors, genistein and ST638. In parallel, tyrosine phosphorylation of 72 kDa protein was inhibited by the same pretreatment. These results, taken together with little effect of genistein on phosphoinositide hydrolysis, suggest that tyrosine kinase may be implicated in the IgE-mediated PLD activation which is regulated by a protein kinase C-independent process.

Animals↗
PubMed1993

Effect of soft diet and aging on rat masseter muscle and its motoneuron.

To determine the effect of a soft diet and aging on the masticatory motor unit, we investigated the morphologic and metabolic properties of the superficial masseter muscle and its motoneurons in rats. Twenty rats were divided into four groups of five rats: rats fed a hard diet until 4 months after birth (hard, young), rats fed a soft diet until 4 months after birth (soft, young), rats fed a hard diet until 22 months after birth (hard, old), and rats fed a soft diet until 22 months after birth (soft, old). The diameter of the fast-twitch oxidative glycolytic muscle fiber was significantly smaller in the soft than the hard, and in the old than the young groups. The glycolytic enzyme (phosphofructokinase) activity of the muscle was significantly weaker in the old than the young group. There was no significant difference in soma diameter of the motoneurons between the soft and hard group, while the diameter was significantly larger in the old than in the young group. There was no significant difference in NADH-diaphorase activity of the motoneurons between the soft and hard group, while significantly less activity was demonstrated in the old than in the young group. The reduction in motor unit activity caused by the soft diet is considered to influence the morphologic and metabolic properties in the superficial masseter muscle but not in its motoneurons. The reduction in the oxidative enzyme activity of motoneurons with aging may occur regardless of the reduction in motor unit activity.

Aging↗
PubMed1993

Orientation of actin monomers in moving actin filaments.

We have visualized, under an optical microscope, the orientations of actin monomers in individual actin filaments undergoing Brownian motion in solution, actively sliding past myosin molecules, or immobile on a surface. For the visualization, two strategies have been adopted. One is to exploit the fluorescence polarization of a fluorescent probe firmly attached to actin. Using the probe phalloidin-tetramethylrhodamine, the fluorescence was clearly polarized along the filament axis, showing alignment of the probe molecules along the filament axis. Within our temporal resolution of 33 ms and spatial resolution of better than 1 micron (average over approximately 10(2) actin monomers), the orientation of the probe (hence of actin monomers) did not change upon interaction of the filament with heavy meromyosin; myosin-induced reorientation was estimated to be a few degrees at most. This first method, while highly sensitive to small reorientations of monomers off or toward the filament axis, does not report on reorientations around the axis. To detect rotation around the filament axis, we adopted the second strategy in which we attached small plastic beads to the actin filaments. Axial turns would be immediately apparent from the movement of the beads. Preliminary observations indicate that actin filaments can slide over a heavy meromyosin-coated surface without axial rotations. Since rotations have been implicated in different experiments, we are currently investigating the source of the apparent discrepancy. The attached bead also serves as a handle through which we can apply force, via optical tweezers, on the filament. By letting the sliding actin filament pull the bead against the optical force, we were able to estimate the sliding force and its fluctuation.

Actin Cytoskeleton↗
PubMed1993

Changes in myosin heavy chain isoform expression of overloaded rat skeletal muscles.

1. The effect of functional overload produced by tenotomy of synergistic gastrocnemius muscle on the expression of myosin heavy chain (MHC) isoforms in the plantaris and soleus muscles of the rat was studied using gradient sodium dodecyl sulfate-acrylamide gel electrophoresis. 2. Five weeks tenotomy, the plantaris and soleus muscle weights induced by tenotomy of the gastrocnemius muscle were 44.3% (P < 0.005) and 37.4% (P < 0.005), respectively, heavier than the contralateral control muscles. 3. Although four types of MHC isoforms were observed in both control and experimental plantaris, the percentage of MHC isoforms in the control and experimental muscles differed; the hypertrophied plantaris muscle contained more HCI (P < 0.05), HCIIa and HCIId (P < 0.05) and less HCIIb (P < 0.05) than the control muscle. 4. The control soleus muscle contained two MHC isoforms, HCI and HCIIa. However, there was only a single HCI isoform in the hypertrophied soleus muscle. 5. These results indicate that overloading a skeletal muscle by removing its synergists produces not only the muscle hypertrophy but also the changes in the expression of MHC isoforms.

Animals↗
PubMed1993

Cardiovascular effects of NSP-804 and NSP-805, novel cardiotonic agents with vasodilator properties.

The cardiovascular properties of NSP-804 (4,5-dihydro-6-[4-[(2-methyl-3-oxo-1-cyclopentenyl)-amino] phenyl]-3(2H)-pyridazinone) and NSP-805 (4,5-dihydro-5-methyl-6-[4-[(2-methyl-3-oxo-1-cyclopentenyl) amino]phenyl]-3(2H)-pyridazinone), novel cardiotonic agents, were investigated in vitro and in vivo in comparison with those of other cardiotonic agents. In isolated guinea pig left atria, the positive inotropic EC50 values (microM) in order of potency were about 0.18 (NSP-805), 0.39 (indolidan), 1.1 (MCI-154), 1.7 (NSP-804, milrinone), 2.0 (denopamine), 4.0 (papaverine), 4.4 3-isobutyl-1-methylxanthine, IBMX, 6.5 (imazodan), and 27 (amrinone). In anesthetized dogs, intravenous (i.v.) injection of NSP-804 and NSP-805 produced dose-dependent increases in left ventricular VVdp/dtmax and decreases in aortic blood pressure (ABP) with relatively small increases in heart rate (HR). The ED50 values (micrograms/kg) for LVdP/dtmax of NSP-804, NSP-805, denopamine, milrinone, MCI-154, and indolidan were 15, 12, 22, 23, 15, and 7.3, respectively. When the drugs were administered intraduodenally to anesthetized dogs, the ED50 values (micrograms/kg) for LVdP/dtmax of NSP-804, NSP-805, milrinone and indolidan were approximately 30, 10, 200, and 25 respectively. In the propranolol-induced heart failure model, NSP-804 and NSP-805 completely improved the hemodynamic state of heart failure to normal levels. The in vitro positive inotropic effects of NSP-804 and NSP-805 were accompanied by increases in tissue cyclic AMP and abolished by carbachol. NSP-805 was the most potent and selective inhibitor of guinea pig cardiac phosphodiesterase (PDE) III among the agents examined, and NSP-804 was a potent and selective inhibitor of PDE III similar to indolidan. The cardiovascular properties determined in this study suggest that both NSP-804 and NSP-805 may have beneficial effects for treatment of congestive heart failure (CHF).

Animals↗
PubMed1993

The chemoluminescence response of human polymorphonuclear leukocytes to Escherichia coli O and K antigens.

The interactions between Escherichia coli O or K antigens and polymorphonuclear leukocyte function were studied. Five types of O antigen and three types of K antigen were extracted from E. coli. These included O1, O6, O75 and K1 antigens from pyelonephritopathogenic strains, O44 and K74 antigens from an enteropathogenic strain and O14 and K7 antigen from a standard strain. The antigens all reacted specifically to their specific antisera and no cross-reactions were observed. The O1 or O44 antigen stimulated a significantly greater chemoluminescence response in polymorphonuclear leukocytes obtained from normal volunteers than O75, O6 or O14 antigen. In addition, the K1 or K74 antigen stimulated polymorphonuclear leukocytes significantly more than K7 antigen. These results suggest that pyelonephritopathogenic or enteropathogenic E. coli may produce severe tissue damage as a result of the response to their O or K antigens, as well as via adhesive agents such as pyelonephritopathogenic P-pili or the enteroadhesive factor, and exotoxins such as hemolysin or verotoxin.

Antigens, Bacterial↗
PubMed1993

Effects of phospholipase C on action potentials and intracellular Ca2+ concentration in guinea pig heart.

To clarify the role of phospholipase C (PLC) in arrythmias and cell injury during myocardial ischemia/reperfusion, we studied its effects on electrophysiology and [Ca2+]i in guinea pig hearts. After exposure to PLC (1 and 2 U/ml), the action potential durations of right ventricular papillary muscles were decreased. Delayed afterdepolarizations were observed in all of the preparations, and some developed into triggered activities. Developed tension decreased after an initial increase for the first 5 min, while resting tension increased consistently. The effects of PLC (0.02, 0.1, and 0.2 U/ml) on [Ca2+]i of ventricular myocytes were measured using fura-2 fluorescence. The ratio of rod-shaped cells to all cells decreased in a time- and a concentration-dependent manner. Perfusion with 0.1 U/ml PLC elevated [Ca2+]i from 56 +/- 5 nM to 245 +/- 47 nM before cell rounding, and to 1167 +/- 172 nM after cell rounding, suggesting that PLC causes Ca2+ overload. In conclusion, activation of PLC may play a role in arrhythmias and cell injury during ischemia/reperfusion. The increase in [Ca2+]i during ischemia/reperfusion may activate phospholipase, which would further increase [Ca2+]i to form a vicious cycle.

Action Potentials↗
PubMed1993

[Effect of tranilast ophthalmic solution on allergic conjunctivitis in guinea pigs].

The effect of the ophthalmic solution of tranilast, an anti-allergic agent, on allergic conjunctivitis was studied in passively sensitized guinea pigs. We determined the content of uranine dye and histamine in tears and histopathologically examined palpebral conjunctiva. After instillation of antigen into the conjunctival sac, inflammation of the palpebral conjunctiva, an increase in leaked dye and the release of histamine were found. In the histopathological study, tranilast (1.0%) suppressed the appearance of edema and infiltration of inflammatory cells. Tranilast suppressed the leakage of uranine in a dose-dependent manner. A 0.5% solution of diphenhydramine also showed the inhibitory effect on the leakage of uranine. The inhibitory effect of 0.5% tranilast on antigen-induced dye leakage and histamine release lasted for 6 hr. These results suggest that topically applied tranilast is effective for allergic conjunctivitis.

Animals↗