Biomedical subjects

K Hirota

Publications and source records attributed to K Hirota.

At least 379 records · Page 21Linked to original sources

PubMed1990

Changes in total fiber numbers of disused soleus muscle on rats.

In this study, by use of technique that was modified from Morey method, we discussed the histological influence on the soleus muscle of the rats caused by disuse. This study is characterized by the calculating of total numbers of muscle fibers. ST (slow-twitch) and FT (fast-twitch) fibers in total muscular cross-sectional area were classified by their difference in intensity of staining of actomyosin adenosinetriphosphatase (myosin ATPase). During the experiment, average fiber diameter of ST and FT fibers declined when compared to control group (p less than 0.01). A 54% decrease in the total number of ST fibers was observed in the experimental group (p less than 0.01). Conversely, the total number of FT fibers increased to 362% of the control value (p less than 0.01). These results of the changes evoked in ST and FT fibers indicate 34% decrease in total muscular cross-sectional area, and showed that muscular function shifted toward a faster muscle in disused soleus muscle.

Animals↗

PubMed1990

[Relationship between exercise-induced changes in serum and hepatic cholesterol metabolism in rats].

The purpose of the present study was to determine the effects of exercise training on serum cholesterol level and hepatic cholesterol metabolism in rats. Twenty-four male Wistar strain rats, aged 6 weeks, were assigned to one of three experimental groups; control (n = 8), exercised 20 minutes a day (E20, n = 8), and exercised 60 minutes a day (E60, n = 8). Rats were sacrificed after ten weeks exercise. The levels of serum total cholesterol and HDL-cholesterol in the group E20 and group E60 were lower than that of control, 8% and 24% (p less than 0.01) for the total cholesterol and 10% and 24% (p less than 0.05) for the HDL-cholesterol, respectively. The activity of HMG-CoA reductase in liver microsome was significantly higher in the group E60 than that of control. The hepatic microsomal HMG-CoA reductase activity was negatively related to serum total (r = -0.62, p less than 0.01) and HDL (r = -0.58, p less than 0.01) cholesterol levels. From these results, we concluded that the enhancement of the cholesterol metabolism in the liver by exercise is a major course of the exercise-induced change in serum cholesterol of Wistar rats.

Animals↗

PubMed1990

Loss of viability after disulfiram treatment without preceding depletion of intracellular GSH.

Effects of disulfiram (DSF) on freshly isolated hepatocytes were examined. Its effects on the cellular reduced form of glutathione (GSH) were triphasic; GSH decreased instantly after the addition of DSF, returned to subnormal levels within 30 min, and then declined gradually. The initial decrease in GSH after DSF treatment and the subsequent recovery of GSH were accompanied by an increase and decrease in the oxidized form of glutathione (GSSG), respectively. Decreases in cell viability brought about by 0.4 mM of DSF were correlated with the later gradual decrease in GSH. The loss of viability by DSF treatment seemed to appear when the initial GSH levels became lower than approximately 5 nmole/10(6) cells. Hepatocyte toxicity of DSF was potentiated by diethylmaleate (GSH depletor) and inhibited by N-acetylcysteine (GSH biosynthesis precursor). 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of GSH reductase, inhibited the GSH recovery and potentiated the toxicity. Respiration of hepatocytes was also inhibited by DSF. Free sulfhydryl groups other than GSH showed similar changes to those of GSH. From these results, it seemed that DSF reacted with cellular GSH and other free sulfhydryl groups to form diethyldithiocarbamate and GSSG, GSSG was reduced back to GSH by glutathione reductase, and the decrease in the viability was dependent on the initial loss of GSH.

Animals↗

PubMed1990

[Effects of the dynorphin derivative "E2078" on hemodynamics and plasma catecholamines in dogs].

Recently, a dynorphin derivative (E2078) is synthesized as a kappa-agonist. Unlike dynorphin, E2078 is easily inactivated by peptidases. In this study, hemodynamic effects of E2078 were investigated in 54 adult mongrel dogs under enflurane anesthesia. They were divided into 6 groups according to the dose of E2078 administrated. In the small dosage groups (0.05, 0.1 mg.kg-1), systemic blood pressure was reduced due to cardiac depression. In the large dosage groups (1.0 mg.kg-1, 10 mg.kg-1), the systemic blood pressure decreased due to vasodilation while the cardiac output increased. In the 1.0 mg.kg-1 group, the heart rate decreased, but it increased in the 10 mg.kg-1 group. This difference could be caused by decreased plasma catecholamines in the 1.0 mg.kg-1 group, and their increase in the 10 mg.kg-1 group. The changes in plasma catecholamine levels might be a factor contributing to circulatory depression due to decreased norepinephrine release from the sympathetic nerve endings by E2078 as observed following administration of other kappa-ligands. Another factor for hemodynamic depression would be a direct action of E2078 to dilate vascular bed.

Analgesics↗

PubMed1990

Enzyme immunoassay and monoclonal antibodies for immunological studies of the mutans group of streptococci.

Monoclonal antibodies (MAbs) were prepared from myeloma cells and splenocytes of mice immunized with Streptococcus cricetus HS1 or Streptococcus downei MF25 cells. Various makes of immunoplates were coated with whole cells or purified polysaccharide antigens of oral streptococcal strains and tested for reactivity in enzyme immunoassay (EIA) using the Mabs. It was revealed that different immunoplates had different reactivities. It was also shown that the EIA system and MAbs were useful for the immunological study and identification of oral streptococci.

Antibodies, Monoclonal↗

PubMed1990

[Effect of maxillary protracting bow appliance on reversed occlusion in deciduous dentition].

Previously we investigated the frequency of malocclusion in children who visited the Pedodontic Clinic of Kyushu University and the types of appliances to treat the reversed occlusion in deciduous dentition. The purpose of this study was to evaluate the effects of the maxillary protracting bow appliance to the reversed occlusion in deciduous dentition. Patients at the Hellman's dental age IIA and without molar cross-bite were selected. Eleven patients (6 males and 5 females) were treated with the maxillary protracting bow appliance, and 9 patients (5 males and 4 females) were treated with the chin cap. The controls were 15 patients (5 males and 10 females) without, distal step type of terminal plane, caries and malocclusion. For the sake of evaluation, the study models and lateral cephalograms were analyzed, which were taken before and after the correction of reversed occlusion. The results were as follows: 1. The effects of maxillary protracting bow appliance were the maxillary forward movement associated with counter-clockwise rotation of the nasal floor and the mandibular backward movement associated with clockwise rotation. 2. The maxillary protracting caused the labial inclination of the primary incisors in the maxilla, but the dental arch length was reduced by the mesial movement of the primary second molars in the maxilla. 3. From the results of multiple regression analysis in the maxillary protracting group, it was indicated that the increase of the overjet was attributable to the change of angles of SN-GN, SNB, SNA and GZN.

Cephalometry↗

PubMed1990

[Effects of halothane on membrane potential, Ca2+ current and intracellular cAMP content in single guinea pig ventricular myocytes].

In order to assess directly the actions of halothane on myocardium, especially on the Ca2+ channel we studied effects of halothane on electrophysiological and biochemical properties in single ventricular myocytes isolated enzymatically from guinea pig hearts. Membrane potentials and the slow inward Ca2+ current (ICa) were recorded with a suction microelectrode technique and a whole cell voltage clamp technique. The plateau duration of the action potential, maintained by ICa, and ICa was depressed by 2% halothane (to 58% and 29% of control respectively). To define the site on which halothane acts in the cell membrane, we measured cyclic adenosine monophosphate (cAMP) content of single ventricular myocytes using radioimmunoassay. One percent (1%) and 2% halothane directly produced a dose-dependent decrease in myocardial cAMP content (79% and 65% of control respectively). In conclusion, the present results suggest that the decrease of ICa by halothane participates in the observed depression of the action potential plateau phase and demonstrate that halothane depression of ICa is in part due to an inactivation of phosphorylation dependent gate in the Ca2+ channel resulting from the decrease in cAMP content by halothane.

Animals↗

PubMed1990

[Usefulness of continuous SV(-)O2 monitoring during hepatectomy].

The mixed venous oxygen saturation (SV(-)O2) was continuously monitored during hepatectomy including the resection and reconstruction of great vessels in five patients. During the artificial bypass, the inadequacy of venous return due to failed bypass and/or hemorrhage was detected by the monitoring of SV(-)O2. Low cardiac function and the effect of a vasodilator were also confirmed by this monitoring. The conventional monitoring, such as blood pressure and heart rate, did not always reflect the acute changes in patients' hemodynamics. The monitoring of SV(-)O2 is useful in the anesthetic management during the surgeries which are accompanied with acute hemodynamic changes.

Adult↗

PubMed1989

A comparison of competitive enzyme immunoassay and precipitin inhibition tests in the analysis of polysaccharide antigenic determinants of oral streptococci.

A rapid and convenient method of competitive enzyme immunoassay (EIA) was explored for the immunological analysis by MAbs of polysaccharide antigens prepared from the mutans group of streptococci, and optimal conditions for it were established. These included the concentrations of antigen, monoclonal antibodies (MAbs) and labelled antibody, temperature, pH and reaction time. The results were compared with those obtained by precipitin inhibition tests using the classical quantitative precipitin reaction, and they were found to be consistent with the latter method. It was concluded that the EIA system can be extended to the immunological study of polysaccharide antigens of oral streptococci using MAbs which perform poorly in precipitation reactions.

Animals↗

PubMed1989

Directional immobilization of sodium- and potassium-activated ATPase to expose its cytoplasmic part to the liquid phase on microtiter plates by wheat germ agglutinin.

A convenient method for highly efficient and directional immobilization of intact sodium- and potassium-activated ATPase (Na,K-ATPase) using wheat germ agglutinin linked on microtiter plates was developed. Wheat germ agglutinin, which bound tightly to the beta-subunit of Na,K-ATPase and had no effect on the Na,K-ATPase activity, the potassium-activated p-nitrophenylphosphatase activity, or the inhibitory action of ouabain, was covalently linked to microtiter plates and used as an immobilizer of the enzyme. The amount of Na,K-ATPase coupled to microtiter plates in this immobilizing system was more than 10-fold greater than that used in the direct immobilizing system (O. Urayama, M. Nakao, H. Nagamune, and H. Sugiyama, (1984) Anal. Biochem. 141, 194-198). Also in this system, the cytoplasmic domain of Na,K-ATPase was exposed to the liquid phase. This technique was useful for investigating the reactivities of monoclonal antibody specific for the cytoplasmic domain of the enzyme. Moreover, because this technique was used successfully in the immobilization of periodic acid--Schiff positive staining glycoprotein 1 prepared from human erythrocytes and human alpha 2-macroglobulin, the technique should also be useful for other membrane or secreted proteins that possess N-linked sugar chains containing bisecting N-acetylglucosamine or a high amount of sialic acid.

Animals↗

PubMed1989

Purification of ATP diphosphohydrolase from bovine aorta microsomes.

ATP diphosphohydrolase (EC 3.6.1.5) hydrolyzes pyrophosphate bonds of nucleoside di- and triphosphates in the presence of divalent cations. We purified the enzyme from the vessel wall of bovine aortas. The procedure gave a homogeneous preparation of ATP diphosphohydrolase for the first time from an animal source. Bovine aorta microsomes were treated with 50 mM bicarbonate buffer (pH 10.0) containing 0.025% Triton X-100. The enzyme was then solubilized from the microsomes with 0.5% Triton X-100 and purified to homogeneity by DEAE-Sepharose CL-6B chromatography and 5'AMP-Sepharose 4B affinity chromatography. The apparent molecular mass of the pure enzyme was 110 kDa. The activity recovered was 6% of that of the microsomes. The enzyme was more active with Ca2+ than Mg2+. The sensitivity of ADPase activity to divalent cations was higher than that of ATPase activity. The enzyme had broad substrate specificity to nucleoside di- and triphosphates.

Animals↗

PubMed1989

Effect of disuse on the ultrastructure of the achilles tendon in rats.

We examined the influence exerted, through disuse of the hindlimb, on the collagen fibres of the achilles tendon in rats. With disuse the body mass decreased by 28%, and the mass of soleus muscle decreased by 20%. A decrease in the surface area and diameter was observed in the experimental group when compared to the control group. A histogram of the collagen fibres showed a decrease of the thick fibres in the experimental group. The maximum surface area of collagen fibres in the experimental group was seen to be only 43% of that of the control group. These results showed a decrease in the thickness of the collagen fibres of the achilles tendon through disuse. This seemed to suggest that resistance to tension is decreased by disuse.

Achilles Tendon↗

PubMed1989

Effects of exercise on hypocholesterolemia of stroke-prone spontaneously hypertensive rats.

The effects of exercise on hypocholesterolemia, one of the risk factors of cerebrovascular disorders, were examined. 47-51-day-old stroke-prone spontaneously hypertensive rats (stroke-prone SHRs) were assigned to 2 groups, sedentary or exercise, and raised for 8 weeks. The total serum cholesterol level of the exercised group was 17-18% higher (P less than 0.01) than the control group, and the level of cholesterol synthesis in the liver of the former group significantly higher than in the latter. On the other hand, the level of intestinal cholesterol synthesis in the exercised group was significantly lower. The activity of HMG-CoA reductase in the liver microsomes was significantly increased by exercise, but the activity of this enzyme in the small intestine was not affected. A significant correlation was observed between the rate of cholesterol synthesis in the liver and the amount of radiolabeled cholesterol released into the serum. From these results, we conclude that the enhancement of the synthesis and the release of cholesterol in the liver by exercise is a major cause of the exercise-induced increase in serum cholesterol of stroke-prone SHRs.

Animals↗

PubMed1989

Type-specific antigen of Streptococcus rattus strains (KAY1, FA1 and BHT). II. Ultrastructural localization.

Streptococcus rattus strains (KAY1, FA1 and BHT) were examined by electron microscopy in whole cell-mounted samples and ultrathin sections for the localization of the type-specific antigen, using specific antiserum and ferritin-labelled anti-rabbit IgG as secondary antibody. In thin sections as well as whole cell-mounted samples the antigen was observed as irregular masses over the entire surface of the cells, in particular in the septal region between cells. The localization of the antigen was also examined in thin sections of a cell wall fraction prepared by treating the whole cells with glass beads in a disintegrator. Ferritin particles were observed around the outer surface, but not as many in number as those in whole cell-mounted or sectioned samples and rarely on the inner surface of the cell wall.

Antigens, Bacterial↗

PubMed1989

Effects of halothane on membrane ionic currents in guinea pig atrial and ventricular myocytes.

We studied the effects of halothane on membrane potentials and ionic currents in single guinea pig atrial and ventricular cells prepared by an enzymatic dispersion procedure. In both atrial and ventricular cells, action potential overshoot and its plateau phase were significantly decreased by halothane (2%) without change in resting potential. However, the duration of the ventricular action potential measured at 90% repolarization was markedly shortened by halothane (2%) (to 60% of control), whereas that of the atrial action potential did not change significantly. Corresponding voltage clamp experiments demonstrated that in atrial cells halothane (2%) significantly depresses the time- and voltage-dependent outward K+ current (IK) (to 46% of control); and that in ventricular cells IK is then nearly absent. In both atrial and ventricular cells halothane had no effect on the inwardly rectifying K+ current (IK1). On the other hand, halothane (2%) decreased the slow inward Ca2+ current (ICa) in both atrial and ventricular cells (to 36% and 29% of control, respectively). The results suggest that the shortened action potential in ventricular cells by halothane may well be responsible for the decrease of the plateau phase resulting from the depression of ICa; and that in atrial cells the depression of IK and ICa by halothane had no significant effect on the duration of action potential.

Action Potentials↗

PubMed1989

Mechanism of release of beta-endorphin from rat pituitary cells. Role of lipoxygenase products of arachidonic acid.

We investigated the effects of metabolites of arachidonic acid on the release of beta-endorphin-like immunoreactivity (beta-end-IR) from rat anterior pituitary cells. Anterior pituitary cells from female rats cultured with arachidonic acid released beta-end-IR in a dose- and time-dependent manner. To determine which metabolites of arachidonic acid stimulated the release of beta-end-IR, we examined the effects of an inhibitor of the cyclooxygenase, indomethacin, and an inhibitor of the 5-lipoxygenase, 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA-861). beta-end-IR release from pituitary cells induced by arachidonic acid was inhibited about 37% by AA-861, but was not affected by indomethacin. Other lipoxygenase inhibitors (eicosatetraynoic and nordihydroguaiaretic acid) also reduced the release of beta-end-IR induced by arachidonic acid. The effects of the 5-lipoxygenase products 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) and leukotrienes (LTA4, B4, C4, and D4) on the release of beta-end-IR from rat pituitary cells were also examined. 5-HETE (1-50 microM) elicited a dose-dependent release of beta-end-IR from cultured pituitary cells, and 50 microM 5-HETE induced beta-endorphin release time dependently. LTA4 and LTB4 also significantly stimulated the release of beta-end-IR, but LTC4 and LTD4 had no effect. Other lipoxygenase products (12-hydroxy-5,8,10,14-eicosatetraenoic acid, 12-HETE; 15-hydroxy-5,8,10,14-eicosatetraenoic acid, 15-HETE) were also secretagogues at concentrations of above 1 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Involvement of extracellular calcium and arachidonate in [3H] dopamine release from rat tuberoinfundibular neurons.

The mechanism of [3H]dopamine [( 3H]DA) release was investigated using primary cultures of dispersed cells from the rat tuberoinfundibular region, which contains tyrosine hydroxylase (TH)-like immunoreactive neurons. The calcium ionophore A23187 at 10 nM and above caused a significant and dose-dependent increase in [3H]DA release. In the presence of 50 microM A23187, [3H]DA release was detectable within 30 s and reached a plateau in 15 min. The induction of [3H]DA release by 50 microM A23187 was abolished by lowering the extracellular calcium concentration with 2 mM EDTA. Maitotoxin, another calcium-channel activator, also increased [3H]DA release at a concentration of 50 ng/ml. Exogenous additions of 100 mIU/ml phospholipase A2 and 10 microM arachidonate caused significant release of [3H]DA. Furthermore, A23187 stimulated [3H]arachidonate release from tuberoinfundibular dopaminergic (TIDA) neurons in a dose- and time-dependent manner. These results suggest that extracellular calcium and arachidonate are involved in the process of [3H]DA release from rat TIDA neurons.

Animals↗

PubMed1989

Anticoagulant activity of immobilized thrombomodulin.

Bovine lung thrombomodulin was partially purified, and immobilized on agarose gel (Sepharose 4B). Immobilized thrombomodulin inhibited the procoagulant activity of thrombin, and enhanced the thrombin-catalyzed protein C activation. The plasma recalcification time test showed that immobilized thrombomodulin prolonged plasma clotting time. It is suggested that the immobilization of thrombomodulin will provide an antithrombogenic biomaterial able to convert thrombin from a procoagulant to an anticoagulant enzyme.

Animals↗