Biomedical subjects

T Yoshioka

Publications and source records attributed to T Yoshioka.

At least 19 recordsLinked to original sources

PubMed1992

The expression of presynaptic t-ACPD receptor in rat cerebellum.

The expression of a receptor subtype for one type of excitatory amino acid agonist, t-ACPD, was examined in developing Purkinje cells of cerebellar slices. The t-ACPD-induced responses were compared with those induced by QA in current response, single cell Ca2+ imaging and changes in the miniature currents in the same preparation. It was found that t-ACPD induced a single component of inward current, and an increase in the frequency of miniature currents associated with the presence of external Ca2+, but was ineffective at mobilizing intracellular Ca2+ even in the presence of external Ca2+. The present study suggests the expression of at least two types of metabotropic receptors in the Purkinje cell region, one of which, expressed in the Purkinje cell dendrites, is highly sensitive to QA, but relatively insensitive to t-ACPD, and the other of which is a t-ACPD-sensitive receptor expressed on the presynaptic terminals of the neurons making synapses onto Purkinje cells.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1992

Long-term transformation of an inhibitory into an excitatory GABAergic synaptic response.

For a constant membrane potential, a predominantly inhibitory GABAergic synaptic response is shown to undergo long-term transformation into an excitatory response after pairing of exogenous gamma-aminobutyric acid (GABA) with postsynaptic depolarization or pairing of pre- and postsynaptic stimulation. Current- and voltage-clamp experiments suggest that this synaptic transformation is due to a shift from a net increase of conductance to a net decrease of conductance in response to GABA. GABA-induced elevation of intracellular calcium is prolonged after the same stimulus pairing and may, therefore, contribute to this synaptic transformation via Ca(2+)-activated phosphorylation pathways. This synaptic transformation, which does not follow unpaired stimulus presentations, occurs in a neuronal compartment spatially separated from the soma, which also changes during stimulus pairing.

Animals↗

PubMed1992

Neutrophil priming by granulocyte colony stimulating factor and its modulation by protein kinase inhibitors.

Upon stimulation by various ligands, freshly isolated human peripheral neutrophils (PMN) respond in a variety of ways, such as superoxide (O2-.) generation, phagocytosis enzyme release, migration etc. Chemotactic peptide formylmethionyl-leucyl-phenylalanine (FMLP) and opsonized zymosan activate neutrophils by a receptor-mediated mechanism, while phorbol myristate acetate and dioctanoylglycerol activate the cells by a mechanism involving Ca(2+)-and phospholipid-dependent protein kinase (PKC). Receptor-mediated but not PKC-mediated O2-. generation in PMN was enhanced by the priming of recombinant human granulocyte colony stimulating factor (G-CSF). FMLP-dependent luminol chemiluminescence was also enhanced by G-CSF. However, no appreciable enhancement was observed in FMLP-induced intracellular calcium ion concentration ([Ca2+]i). Enhancement of FMLP-induced generation of O2-. by G-CSF was inhibited by genistein or alpha-cyano-3-ethoxy-4-hydroxy-5-phenylthiomethylcinnamamide (ST 638), inhibitors of tyrosine kinase (TK), and was stimulated by staurosporine and 1-(5-isoquinolinesulfonyl)-3-methyl-piperazine (H-7), inhibitors of PKC. The ED50 values of genistein and ST 638 for the inhibition of the FMLP-induced O2-. generation from G-CSF were 0.5 and 5 microM, respectively. In contrast, O2-. generation by PKC activation without G-CSF priming was inhibited by stauroporine and H-7, but was stimulated by genistein and ST 638. These results suggested that the enhancing effect of G-CSF on receptor-mediated generation of the O2-. might be regulated by protein kinases, such as TK and PKC, and that the TK inhibitor selectively inhibited the G-CSF-primed receptor-mediated O2-. generation of neutrophils.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1992

Augmentation of transient low-threshold Ca2+ current induced by GTP-binding protein signal transduction system in GH3 pituitary cells.

We characterized the effects of thyrotropin-releasing hormone (TRH; 500 nM) and guanosine 5'-0-3-thiotriphosphate (GTP gamma S; 50 microM) on two types of Ca2+ currents in pituitary-hormone-secretory GH3 cells and were surprised to find marked increases in transient, low-threshold Ca2+ currents (T currents) induced by extracellularly applied TRH or intracellularly applied GTP gamma S. The effect of TRH was blocked by intracellularly applied guanosine 5'-0-2-thiodiphosphate (GDP beta S; 100 microM). The increase in the T current was found to be accompanied by a decrease in long-lasting, high-threshold Ca2+ current (L-current), in response to both TRH or GTP gamma S. These indicate that the enhancement of Ca2+ influx by TRH (500 nM) is largely conferred by T currents in GH3 cells. A reduced concentration of TRH (5 nM) still markedly increased the T current, but failed to decrease the L current. These data suggest that the augmentation of the T currents as well as depression of the L currents by TRH (500 nM), through the activation of a GTP-binding protein, may constitute an important regulatory mechanism of sustained pituitary hormone secretion in GH3 cells.

Animals↗

PubMed1992

Partial purification and characterization of membrane-associated diacylglycerol kinase of Drosophila heads.

A membrane-associated diacylglycerol kinase of Drosophila heads was purified to near homogeneity from the KCl extract of Drosophila heads. The purification procedure involved chromatography on Q-Sepharose, ammonium sulfate fractionation, Superose 12, hydroxyapatite and ATP-agarose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of fractions after the ATP-agarose column chromatography showed that only a 115 kDa protein correlated well with the enzyme activity. The apparent Km values of partially purified DG kinase were 220 microM for ATP and 540 microM for diolein, respectively. The activity of the DG kinase was inhibited by deoxycholate and was not activated by Ca2+.

Animals↗

PubMed1992

Dynamic aspects of ovarian superoxide dismutase isozymes during the ovulatory process in the rat.

To investigate the role of superoxide dismutase (SOD) in the ovulatory process, SOD isozymes and their mRNAs were determined in the ovary of 22-day-old rats. After treatment with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG), ovarian activity of Mn-SOD decreased markedly while Cu/Zn-SOD remained unchanged. However, the ovarian level of mRNA for Mn-SOD markedly increased after hCG-treatment while that for Cu/Zn-SOD decreased only slightly. Ovulation was inhibited by intravenous injection of a long-acting SOD. These results suggested that superoxide radicals in the ovary might play a critical role in the mechanism for hCG-induced ovulation.

Animals↗

PubMed1992

Effects of GTP analogues and activation of endogenous protein kinases on photoaffinity labeling with [3H](+)PN200-110 of crude membranes from rat heart and brain.

The effects of GTP analogues and conditions in which various endogenous protein kinases were activated on photoaffinity labeling with [3H](+)PN200-110 (PN) of crude membranes from rat cardiac muscle and whole brain were investigated. Photoaffinity labeling with 20 nM [3H](+)PN of these crude membranes was decreased by 100 microM GTP-gamma-S, but not by 100 microM GTP or 100 microM GDP-beta-S. Similar results were obtained on the effects of GTP and its analogues on the specific binding of 20 nM [3H](+)PN to these crude membranes under the same conditions. Activation of endogenous protein kinases in these crude membranes did not influence the photoaffinity labeling with [3H](+)PN. These results suggested the binding sites, or DPH-sensitive, or L-type, calcium channels in curde membranes from rat cardiac muscle and whole brain are directly or indirectly modulated by endogenous GTP-binding protein, but not by various endogenous protein kinases in these crude membranes.

Affinity Labels↗

PubMed1992

Cloning of the Drosophila prospero gene and its expression in ganglion mother cells.

The Drosophila central nervous system comprises an enormous diversity of neurons that are originated from neuronal stem cells, neuroblasts. They generate a specific series of ganglion mother cells, each of which is once cleaved into a pair of neurons. Among genes known to control neurogenesis, prospero (pros) was recently identified as a gene required for gene expression specifying properties of some identified neurons. Here we report that pros encodes a nuclear protein containing a homeodomain-like sequence. In neuronal lineages of the central nervous system, pros protein is specifically detected in ganglion mother cells, although their parental neuroblasts have begun expressing a significant level of pros transcripts, suggesting a post-transcriptional control of pros expression. Our results provoke that in neuronal cell differentiation ganglion mother cells might play a pivotal role associating with the pros function.

Amino Acid Sequence↗

PubMed1992

Effect of extracellular phosphatidylinositol on c-myc gene-expressed human renal cancer cell line.

Effect of exogenously added soybean phosphatidylinositol on c-myc gene expressed and unexpressed human cancer cell lines was investigated. When phosphatidylinositol liposomes were introduced into culture media, viability of c-myc unexpressed cells was reduced, while that of c-myc expressed cells was not. Death of c-myc unexpressed cells by phosphatidylinositol liposomes was found to be caused by abnormally accumulated intracellular Ca2+, and it seemed to be related to reduction of protein kinase C activity.

Calcium↗

PubMed1992

Supra-neuroectodermal cells and fibers on the primary nasal cavity and in the fourth ventricle of mouse and human embryos: scanning and transmission electron microscopic studies.

Neuroectoderm-derived epithelia of the primary nasal cavity and the fourth ventricular floor and roof were observed by scanning (SEM) and transmission electron microscopy (TEM) and SEM-TEM correlative views in mouse embryos of 9th to 13th days of gestation, and in 38 externally normal human embryos ranging at Carnegie stages from 13 to 18 (about 5 to 7 weeks of gestation). Smooth-surfaced spindle-shaped cells with one or more cytoplasmic processes and cord-like cytoplasmic structures were observed by SEM on the wall of the primary nasal cavity of both species. They had morphological features similar to those of neuronal type 1 supraependymal (SE) cells and SE fibers on the floor and roof of the fourth ventricle in both species. Type 1 SE cells, SE fibers, and corresponding structures in the primary nasal cavity were localized in relation to the underlying developing nerve and vascular systems. Furthermore, their processes and fibers ran roughly parallel to these underlying structures and they penetrated the epithelial layer at the ends, suggesting a connection with underlying structures. From TEM and SEM-TEM correlative observations, SE fibers in the fourth ventricle and cord-like structures in the primary nasal cavity, both with a larger diameter, were deduced as single axon-like processes or bundles of processes. Those fibers and cord-like structures of smaller diameters were interpreted as elongated telophase bridges; both contained parallel packed microtubules and connected distant cells. Since these processes and fibers were generally longer and became fewer at later developmental stages, they appeared to be transient neuronal structures. They may play a development-related role in such morphogenetic cell movements as in the developing nerve and vascular systems in the epithelial and/or subepithelial layers, but not as direct rudiments of adult nerve tissues.

Animals↗

PubMed1992

Activities of creatine kinase isoenzymes in single skeletal muscle fibres of trained and untrained rats.

Biochemical changes in the creatine kinase isoenzyme compositions in single muscle fibres of different types in rats were induced by endurance running training. Single muscle fibres were dissected from the soleus and extensor digitorum longus muscles of Wistar-strain male rats trained on a motor-driven treadmill for 16 weeks. Each fibre was typed histochemically (SO, slow-twitch oxidative; FOG, fast-twitch oxidative glycolytic; FG, fast-twitch glycolytic), and the activities of total creatine kinase and its four isoenzymes (CK-MM, -MB, -BB, and mitochondrial creatine kinase) were measured. The endurance training did not affect the total creatine kinase activity, but resulted in significantly increased activities of CK-MB and CK-BB in SO and FOG fibres, and the mitochondrial enzyme activity in FOG and FG fibres. Endurance training induced biochemical changes in the isoenzyme compositions, specifically in FOG fibres. These results suggest that changes in creatine kinase isoenzymes with endurance training reflect changes in the energy metabolism in the different muscle fibres, supporting the hypothesis that the different isoenzymes play different roles in energy transduction.

Animals↗

PubMed1992

Morphological and functional alterations of the hypothalamic-pituitary system in brain death with long-term bodily living.

Hypothalamic hormones as well as anterior pituitary hormones were detected in the peripheral plasma after the diagnosis of brain death. It is possible that residual hypothalamic tissue was functioning after satisfying the usual criteria of total brain death. To examine this possibility, endocrinological and morphological alterations of the hypothalamic-pituitary system was evaluated in 28 brain dead patients. Intrinsic ADH was depleted in the plasma shortly after the diagnosis of brain death. Anterior pituitary hormones were initially detected in all patients, but gradually disappeared. The direct TRH (thyrotropin releasing hormone) stimulation to the anterior lobe was responded to well. Morphological studies showed a partial necrosis of the anterior lobe and the preservation of the posterior lobe for as long as a week. These data prove that the pituitary is partially preserved after brain death. LH-RH (luteinizing hormone releasing hormone) was detected in the peripheral plasma of all patients and GRF (growth hormone releasing factor) was detected in half of the patients for as long as 15 days, but autopsy revealed the fact that the brain tissue including the hypothalamus became extensively necrotic after the sixth day of brain death. In order to solve this controversy it is proposed that these hormones originate from extracranial tissues such as pancreas. The detection of hypothalamic hormones after the diagnosis of brain death therefore is not contradictory to the concept of total brain death.

Adolescent↗

PubMed1992

Localization and elasticity of connectin (titin) filaments in skinned frog muscle fibres subjected to partial depolymerization of thick filaments.

The localization and elasticity of connectin (titin) filaments in skinned fibres of frog skeletal muscle were examined for changes in the localization of connectin and in resting tension during partial depolymerization of thick filaments with a relaxing solution containing increased KCl concentrations. Immunoelectron microscopic studies revealed that deposites of antibodies against connectin at a sarcomere length of 3.0 microns remained at about 0.8 microns from the M-line, until the thick filament was depolymerized to the length of approximately 0.4 microns. On further depolymerization, the bound antibodies were found to move towards the Z-line and, on complete depolymerization, were observed to be within 0.3 microns of the Z-line; a marked decrease in resting tension accompanied this further depolymerization. These results suggest that connectin filament starts from the Z-line, extends to the M-line, and contributes to resting tension. After partial depolymerization of thick filaments, the distances between the anti-connectin deposits and the Z-line and between anti-connectin deposits and the M-line increased with sarcomere length, suggesting that connectin filaments are elastic along their entire length.

Actin Cytoskeleton↗

PubMed1992

Hypothermia relieves oxidative stress in reperfused skeletal muscle following partial ischemia.

The impact of hypothermia on reperfusion-associated oxidative stress in postischemic skeletal muscle was evaluated in a small animal model of high-grade partial ischemia. The infrarenal aorta of heparinized Sprague-Dawley rats was clamped for 90 min, declamped, and then reperfused for 60 min. Previous characterization of this model with 51Cr-tagged microspheres revealed that hindlimb perfusion during aortic clamping continued at 16.6% of baseline values. Resting transmembrane potential difference (Em) and tissue malondialdehyde (MDA), lactate and high-energy phosphate content were determined in hindlimb skeletal muscle at baseline, during ischemia, and upon reperfusion. Four experimental groups (N = 7 in each group) were studied: control animals underwent aortic clamping and declamping; hypothermia animals underwent topical cooling of hindlimbs prior to aortic clamping, with muscle temperatures maintained between 5 and 15 degrees C during ischemia; sham animals underwent midline laparotomy only; and hypothermia-sham animals underwent cooling and midline laparotomy only. During ischemia, resting Em (-mV) was significantly depolarized (P < 0.05 versus baseline) in control (74.9 +/- 0.8 from 91.0 +/- 0.1), hypothermia (64.4 +/- 1.1 from 90.9 +/- 0.3), and hypothermia-sham (67.2 +/- 1.4 from 90.9 +/- 0.4) animals. Upon reperfusion, resting Em remained depolarized in control animals (74.7 +/- 1.6), while repolarization occurred in hypothermia (88.8 +/- 1.1) and hypothermia-sham (90.7 +/- 0.3) animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1992

Delayed appearance of G-protein coupled signal transduction system in developing cerebellar Purkinje cell dendrites.

To investigate the relation between the function of Ca(2+)-activated K+ channels and phosphoinositide turnover, we have examined the physiological and pharmacological characteristics of ionotropic and metabotropic quisqualate (QA) receptors in rat cerebellar Purkinje cells during development using the slice-patch method combined with Ca2+ imaging. The typical response to QA obtained from a rat on postnatal day (PND) 21 consisted of three components: (1) a fast inactivating inward current, (2) a slow inward current, and (3) a slow outward current. The slow inward current was abolished in Ca(2+)-free medium, while the fast inactivating inward current and the slow outward current remained unaffected. The slow outward current which appeared to be activated via a metabotropic receptor was not observed in the Purkinje cell of PND 7 rat, in which dendrites were poorly developed but its amplitude increased linearly with PND. QA caused significant increases in [Ca2+]i in the fully developed dendritic region of the Purkinje cells even in Ca(2+)-free medium, suggesting a dendritic localization of the metabotropic receptors.

Animals↗

PubMed1992

A strategy of cystine stone management.

Simple mechanical disintegration of cystine calculi by extracorporeal shock wave lithotripsy and/or percutaneous nephrolithotomy is being performed widely around the world. However, it cannot be denied that the cystine calculus is one of the most difficult stones for mechanical disintegration. We previously reported the oral medical chemolysis of cystine calculi in 1982 and a third of the patients became stone-free. In another third of the patients the cystine component was replaced by apatite during the medical treatment and apatite stones formed in this manner are easily disintegrated. In view of the complications of mechanical disintegration, oral medical treatment for chemolysis should be recommended before simple destruction of cystine calculi.

Adult↗

PubMed1992

The role of calcium in prolonged modification of a GABAergic synapse.

Caudal hair cell impulses cause postsynaptic inhibition of ipsilateral type B photoreceptors in the snail Hermissenda. This inhibition is shown to be GABAergic according to a number of criteria. HPLC, mass spectrophotometric, and immunocytochemical techniques demonstrated the presence of GABA in the hair cells and their axons. GABA agonists and antagonists mimic and block the synaptic effect in a manner consistent with endogenous GABAergic transmission. Other properties, including I-V relations, conductance changes and reversal potentials, are comparable for exogenous GABA responses and endogenous effects of the hair cell impulses. This inhibitory synapse has been found to undergo a long-lasting transformation into an excitatory synapse if GABA release is paired with post-synaptic depolarization. GABA, via GABAA and GABAB receptors in the B cell, causes the opening of calcium sensitive chloride and potassium channels that leads to the post-synaptic hyperpolarization. GABA also induces a long-lasting intracellular calcium elevation at the terminal branches of the B cell that greatly outlasts the voltage responses. Synaptic transformation induced by pairings is caused by a decrease in both GABA induced chloride and potassium conductances in the post-synaptic B cell, as well as a significant prolongation of the intracellular calcium accumulation in the B cell's terminal axonal branches.

Animals↗

PubMed1992

Reduced activity of antioxidant enzymes underlies contrast media-induced renal injury in volume depletion.

Oxidant-mediated renal injury has been suggested as an important mechanism of acute renal failure induced by contrast media. Since volume depletion has been recognized as a predisposing factor for contrast media nephropathy, the present study was designed to characterize host-defense mechanisms against oxidant-mediated renal injury during volume depletion. Antioxidant enzyme activities in renal cortex were compared between acutely water deprived (WD, 72 hours) and non-WD rats. WD rats had reduced activities of catalase and superoxide dismutase activities (on average, 48% and 60% of values in non-WD, respectively). In separate groups of WD rats, saline or one of three different contrast media, namely diatrizoate meglumine/diatrizoate sodium (DTZ), ioxaglate meglumine/ioxaglate sodium (IXG), and iohexol (IHX) was injected. Both GFR and renal plasma flow rate, measured 24 hours later, was some 50% less in DTZ-injected than saline-injected WD rats. WD rats treated with IXG and IHX had similar GFR to saline-treated rats. In DTZ-treated WD rats, specific products of membrane lipid peroxidation, phosphatidylcholine and phosphatidylethanolamine hydroperoxide, determined by chemiluminescent HPLC, were more than two-fold higher than saline, IXG, or IHX-treated WD rats. DTZ did not induce renal dysfunction and enhance lipid peroxidation in non-WD rats. Therefore, DTZ appeared to induce oxidant-mediated injury only in WD rats. When WD rats were pretreated with polyethylene glycol-coupled catalase (1.4 mg x 2 days), renal cortical catalase activity remained at a level similar to that of non-WD rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗