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Biomedical subjects

Y Kudo

Publications and source records attributed to Y Kudo.

At least 199 records · Page 11Linked to original sources
PubMed1994

Hydroxyl group of Tyr13 is essential for the activity of omega-conotoxin GVIA, a peptide toxin for N-type calcium channel.

A series of analogs of omega-conotoxin GVIA, a peptide neurotoxin having 27 amino acid residues with three disulfide bridges, were synthesized by replacing each amino acid residue except for Cys and Hyp with Ala. CD spectra were virtually identical between native and all of the analogs, indicating the overall conformations were not changed by the substitutions. The inhibitory effects of these analogs on 125I-omega-conotoxin GVIA binding to chick brain synaptic plasma membranes showed that replacement of Tyr13 with Ala drastically lowered the affinity of the toxin to the N-type Ca2+ channel. Substitution of Tyr13 with Phe also showed reduction of the affinity, indicating that the hydroxyl group of Tyr13 is critical for binding. Since Lys2 is also important for binding (Sato, K. Park, N.-G., Kohno, T. Maeda, T., Kim, J.-I., Kato, R., and Takahashi, M. (1993) Biochem. Biophys. Res. Commun. 194, 1292-1296), we propose a two-point binding model in which Tyr13 and Lys2 interact with specific amino acid residues of the Ca2+ channel through hydrogen bonding and ionic interaction, respectively.

Amino Acid Sequence↗
PubMed1994

Endothelin increased [Ca2+]i in cultured neurones and slices of rat hippocampus.

We reported here the first evidence that endothelin (ET)-1 and ET-3 produced an increase in intracellular Ca2+ concentrations ([Ca2+]1), consisting of a transient and a sustained component, in cultured neurones and in slices of the rat hippocampus. In the neurones, the removal of Ca2+ or the addition of Cd2+ remarkably inhibited the ET-3-evoked sustained but not the transient response. The [Ca2+]i increased by ETs was observed in the dentate gyrus and in the vicinity of CA1 and CA3 pyramidal cell layer in the hippocampus, findings in good accord with regions where the glutamate receptor agonists have an elevated [Ca2+]i. The possible causal link between ETs and the increased [Ca2+]i in the development of hippocampal neuronal death is discussed.

Animals↗
PubMed1994

Implication that potassium flux and increase in intracellular calcium are necessary for the initiation of sperm motility in salmonid fishes.

Flux of K+ and changes in intracellular Ca2+ in the sperm of salmonid fishes were measured with spectrophotometry, ion electrode, microscopic fluorometry, and radioisotope accumulation. Release of K+ occurred at the initiation of sperm motility which is induced by decrease in external K+ and the K+ efflux and sperm motility were inhibited by K+ channel blockers. Intracellular Ca2+ increased within a short period in K(+)-free condition, and the accumulation of 45Ca in sperm cells was higher in motile sperm than that in immotile sperm. The efflux of K+ and the increase in intracellular Ca2+ were suppressed when external K+ concentration increased, i.e., sperm remained immotile. These results suggest that efflux of K+ through K+ channel and subsequent increase in intracellular Ca2+ are prerequisite for the initiation of sperm motility.

4-Aminopyridine↗
PubMed1994

Endothelin-3 stimulates inositol 1,4,5-trisphosphate production and Ca2+ influx to produce biphasic dopamine release from rat striatal slices.

1. Real-time monitoring of dopamine (DA) release from rat striatal slices demonstrated that endothelin (ET)-3 (0.1-10 microM) produced a biphasic DA release consisting of transient and sustained components. When extracellular Ca2+ was removed, the sustained but not transient response remarkably decreased. 2. ET-3 (1-10 microM) stimulated an increase in the intracellular Ca2+ concentration ([Ca(2+)]i), which also consisted of two components. The external Ca2+ depletion inhibited primarily the sustained component of the Ca2+ response to ET-3. 3. ET-3 increased inositol 1,4,5-trisphosphate (IP3) concentrations in striatal slices. This response peaked at 10 to 20 sec and returned to the basal level 2 min after stimulation, an event which was in good accord with a prompt and transient phase of both cytosolic Ca2+ activity and DA release evoked by ET-3. 4. Thus, ET-3 produces a transient and a sustained release of DA from striatal slices by stimulating intracellular Ca2+ mobilization via IP3 formation and extracellular Ca2+ influx, respectively.

Animals↗
PubMed1994

Automated collection of conditioned medium from organotypically cultured brain slice.

For the analysis of neural activity over a long period of time, the organotypic culture of mammalian brain slices provides excellent specimens. To effectively utilize the slice culture, we developed a device for automatic sampling of the culture medium. This device is a computer-controlled combination of a multichannel peristaltic pump to remove the media from the glass culture containers, a fraction collector designed to allow quick freezing of the samples, and a multichannel syringe pump to deliver new media to the containers. Using this device, substances released as results of neural activities can be collected at regular intervals over several days. We monitored the circadian release of arginine-vasopressin from cultured suprachiasmatic nuclei. We also monitored tonic releases of lactate dehydrogenase from cultured hippocampi phasically treated with an excitotoxin and from those transiently deprived of oxygen/glucose.

Animals↗
PubMed1994

Regulation and physiological role of insulin-like-growth-factor-binding protein-1 in human granulosa cells.

The present study was undertaken to elucidate the physiological role and the regulation of insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) in human luteinizing granulosa cells. IGFBP-1 abolished IGF-I-stimulated estradiol production by luteinizing granulosa cells in a dose-dependent manner with a 50% inhibitory concentration (IC50) of 0.27 nM. Similarly, IGFBP-1 inhibited 125I-IGF-I binding to granulosa cells. IGFBP-1 was identified by Western immunoblot and specific enzyme immunoassay in the granulosa-cell-conditioned medium after 24 h culture. Immunoreactive IGFBP-1 released into the medium was inhibited by both IGF-I and follicle-stimulating hormone dose-dependently with an IC50 of 0.14 and 0.13 nM, respectively, while human chorionic gonadotropin-stimulated IGFBP-1 release with a 50% effective dose (ED50) of 0.6 nM. These results suggest that IGFBP-1 is involved in follicular development and granulosa cell differentiation in the human ovary and that gonadotropins may influence IGF-I action by modifying IGFBP-1 levels within the ovary.

Binding, Competitive↗
PubMed1994

Effect of methylprednisolone on plasma lipid peroxidation induced by lipopolysaccharide.

The effects of methylprednisolone succinate (MP) on plasma lipid peroxidation, plasma SOD activity and superoxide production in polymorphonuclear leukocytes (PMNs) induced by lipopolysaccharide (LPS) were examined in rats in vivo and in vitro. In rats subjected to LPS treatment, plasma phosphatidylcholine hydroperoxide (PCOOH) levels significantly increased, and the plasma Cu,Zn-SOD activity decreased by about 75%. When rats were given 30 mg/kg of MP intravenously, MP suppressed the elevation of plasma PCOOH levels and partially inhibited the decrease in plasma Cu,Zn-SOD activity. MP also suppressed PMA-induced superoxide production in PMNs primed by LPS. In in vitro experiments, low concentrations of MP had no effect on NADPH-dependent lipid peroxidation, but 4 mM MP produced 50% inhibition. MP had little effect on PMA-induced superoxide production in PMNs primed by LPS. Moreover, MP had no radical-trapping effect on superoxide, hydroxyl radical and stable DPPH radical. These results suggest that the suppressive effect of plasma lipid peroxidation by MP is not due to radical-trapping effects or preventive anti-oxidation, but may involve the suppression of the lipid chain reaction in liver membrane resulting from PMA-induced superoxide anions generated by PMNs.

Animals↗
PubMed1994

[Detection of Aspergillus fumigatus DNA by polymerase chain reaction in the clinical samples from individuals with pulmonary aspergillosis].

Aspergillosis is a disastrous cause of mortality and morbidity in patients in an immunocompromised state and old lung tuberculosis. However, the diagnosis of aspergillosis remains unsettled. In the present study, we developed a test to detect the Aspergillus fumigatus DNA using polymerase chain reaction (PCR) in clinical samples including sputum and bronchial aspirations from the patients with aspergillosis. We selected 2 pairs of oligonucleotide primers and the DNA for the small subunit ribosomal RNA of aspergillus fumigatus and they were significantly amplified. Although isolation of Aspergillus DNA may reflect contamination and colonization without infection, no aspergillus DNA was found in sputum or bronchial aspirations from the patients with lung cancer or interstitial lung diseases except a case of pulmonary fibrosis associated with rheumatoid arthritis chronically received 20 mg of corticosteroid. There was a 100% correlation between the culture results and the nested PCR results in the patients with pulmonary aspergillosis. These findings indicate that PCR detection of aspergillus fumigatus might be valuable for the diagnosis of aspergillosis.

Aged↗
PubMed1994

[Residential movement of persons with senile dementia within one year prior to death].

The purpose of this study was to clarify what factors were affecting the residential movement of persons with senile dementia, within one year prior to their death, and to find out ways to sustain the quality of life of the terminal period. We analyzed ninety-six cases of the members of the Association of Family Caring for the Demented Elderly, who died within the period from 1989 to 1991. 1. The average age of death of the elderly persons was 83.2 years. Seventy-four percent had severe dementia. Fifty-five percent had complications of cancer, cardiopathy or apoplexy. 2. Thirty-three percent of the patients in the analyzed cases died at home, sixty percent died in hospitals, and seven percent died elsewhere. Only a few had been hospitalized for more than one year. 3. There were four major movement patterns: care at home and death at home, periodic hospitalization before death at home, periodic hospitalization before death at hospital, and hospitalization and death at hospital. Each of the four patterns had unique characteristics regarding both physical and mental disorders. 4. Those persons with periodic hospitalization before death at home had more care in regards to discharge guidance than those with periodic hospitalization before death at hospital. From the above analysis, we concluded that persons with senile dementia in their terminal period require preventative treatments against advanced dementia and the various complications. In addition they need effective discharge planning at medical institutions.

Aged↗
PubMed1993

Effects of anti-free radical interventions on phosphatidylcholine hydroperoxide in plasma after ischemia-reperfusion in the liver of rats.

The present study set out to investigate whether plasma phosphatidylcholine hydroperoxide (PCOOH) levels could accurately reflect lipid peroxidation linking to liver damage due to ischemia--reperfusion. PCOOH is a primary peroxidative product of phosphatidylcholine (PC), which is the most important functional lipid in the hepatocellular membrane, and may mediate oxidative stress. We quantified PCOOH and PC in the plasma and liver of rats subjected to hepatic ischemia-reperfusion by chemiluminescence detecting HPLC (CL-HPLC) method. Plasma PCOOH levels showed no significant rise in either the ischemia only group or in the sham-operation group, compared to controls (0.7 nmol/mL plasma). At 60 min subsequent to reperfusion, the PCOOH levels in plasma and liver, as well as the levels of several serum markers of liver injury [lactic dehydrogenase (LDH), glutamic-oxalacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT)] increased in proportion to the duration of ischemia (up to 60 min). During periods of reperfusion following 30 min of ischemia, plasma PCOOH increased biphasically (2 nmol/mL; 12-24 hr duration of reperfusion), and generally ran parallel to that in the liver after more than 60 min of reperfusion. Dose-dependent protective effects against warm ischemia (30 min)-reperfusion (12 hr) injury were clearly demonstrated in the groups treated with allopurinol, diclofenac Na, ascorbic acid (V.C), alpha-tocopherol and coenzyme Q10, but not in those treated with r-h-superoxide dismutase or betamethasone. The rises in plasma PCOOH and serum GOT, GPT and LDH of the ischemia-reperfused rats were ameliorated most in the group pretreated with diclofenac Na, and next most in the group pretreated with V.C. These results indicate that the plasma PCOOH levels are a useful index both for liver cell damage induced by oxygen free radicals generated during ischemia-reperfusion, and to investigate the efficacy of drugs against oxidative stress.

Animals↗
PubMed1993

Early mobilization of Ca2+ is not required for glucocorticoid-induced apoptosis in thymocytes.

Contradictory results have been reported on the question of the role of Ca2+ in glucocorticoid-induced apoptosis in thymocytes. To resolve this problem, we investigated the effect of dexamethasone, a synthetic glucocorticoid, on intracellular Ca2+ concentration ([Ca2+]i), by microscopic fluorometry that enables us to monitor real-time [Ca2+]i of cells loaded with fura-2, a fluorescent Ca2+ indicator, on a single cell basis. The results indicated that dexamethasone does not induce an increase in [Ca2+]i above control level both in murine and rat thymocytes at least for 1 h after the start of the culture. We also investigated whether the depletion of extracellular Ca2+ with EGTA or buffering intracellular Ca2+ with quin-2/AM inhibited glucocorticoid-induced apoptosis as reported on rat thymocytes. Dexamethasone-induced apoptosis in both murine and rat thymocytes, however, was not inhibited by EGTA. High concentrations (25 microM and over) of quin-2/AM inhibited DNA fragmentation, but failed to inhibit cytolysis. Calmodulin inhibitors, trifluoperazine and calmidazolium, also inhibited DNA fragmentation as reported, although they markedly enhanced cytolysis. Therefore, glucocorticoid-induced death is not inhibited by quin-2/AM or calmodulin inhibitors. Furthermore, we have previously found that a proper combination of the calcium ionophore, ionomycin, and the protein kinase activator, PMA, inhibits corticosterone-induced apoptosis. These results suggest that an early increase in [Ca2+]i is neither induced by glucocorticoids nor responsible for glucocorticoid-induced apoptosis in thymocytes.

Aminoquinolines↗
PubMed1993

Characterization of protein kinase C activities in postsynaptic density fractions prepared from cerebral cortex, hippocampus, and cerebellum.

Protein kinase C (PKC) activities, especially, substrates and PKC isozymes, associated with postsynaptic density (PSD) fractions isolated from rat cerebral cortex, hippocampus, or cerebellum were investigated. The 17k M(r) major substrate for PKC was associated with PSD fractions prepared from cerebral cortex and hippocampus, and several substrates including 18k M(r) protein were associated with PSD fraction isolated from cerebellum. The content of 17k M(r) substrate was extremely low in the PSD fraction prepared from cerebellum. PKCs-beta and gamma were associated with PSD fractions and PKC-alpha was virtually absent in the fraction prepared from the three different regions of the brain. All of PKCs-alpha, beta, and gamma were associated with synaptosome fractions. The 36k M(r) bands immunoreactive with anti-PKC-beta antibody, probably degradation products of native PKC-beta, were detected in both the PSD and synaptosome fractions from the three regions, and the ratio of the degradation fragments to native PKC molecule was higher in PSD fractions than in synaptosome fractions. The results suggest postsynaptic roles of PKCs-beta and gamma and involvement of proteolytic activation of PKC-beta in the postsynaptic signal processing.

Amino Acid Sequence↗
PubMed1993

Investigation of the renal injury caused by liver ischemia-reperfusion in rats.

To explain the mechanism of renal injury caused by liver ischemia-reperfusion, we investigated biochemical and morphological changes in the liver and kidney in rats. After reperfusion following 60 min of liver ischemia, numerous changes were found. The level of serum transaminases and lipid peroxide formation in the liver tissue increased significantly. Electron microscopic studies revealed that most of the hepatocytes had swollen mitochondria and clumping of the nuclear chromatin. The sinusoidal endothelium was disrupted and the sinusoidal lumen was filled with numerous erythrocytes. Blood endotoxin concentration, plasma lipid peroxide levels, and serum beta-glucuronidase activities were significantly higher than in the control group. Biochemical and morphological renal injury was also observed. Tissue lipid peroxide levels increased in both the kidney and the liver. Microscopic examination revealed damage to the renal tubules, including interstitial edema, dilatation of the lumen, and granular casts derived from necrotic cells in the proximal convoluted tubule. The levels of urinary N-acetyl-beta-D-glucosaminidase (NAG) in the liver ischemia-reperfusion group were also higher than in the control group. These results suggest that the renal injury was caused by an increase in endotoxin, lipid peroxide, and lysosomal enzymes in the blood following the liver injury induced by the ischemia-reperfusion.

Animals↗
PubMed1993

Distribution of radioisotopic beryllium in mice after administration by various routes of injection.

A 7BeCl2 solution containing 0.5 micrograms Be per mouse was injected subcutaneously, intraperitoneally, intramuscularly, intrathoracically, and intravenously, and distribution was observed for periods up to 1 wk. 7Be was excreted more rapidly following intravenous injection than by the other routes of injection. The amount of Be found in the liver or the spleen was substantial at 1 d after intraperitoneal injection. It increased more in the spleen at 7 d after either intraperitoneal or intrathoracic injection. On the other hand, the amounts of Be stayed almost constant in the kidneys, by the various routes of injection. When injected intrathoracically, the amounts of Be in the heart and the lung were greater than when administered by the other routes of injection. The amounts of Be in the femurs of mice administered by these routes of injection, except with intravenous injection, were greater than in the other organs. The percentage of 7Be in the mineralized bone was 90% of that of 7Be in the femurs when injected intraperitoneally or intrathoracically. However, the ratio of Be in the mineralized bone to that in the bone marrow was 3 to 2. Beryllium had thus a closer affinity for the femurs than for the other organs investigated, with the different modes of administration used. The amount of Be in the entire skeleton was estimated to be substantial. Within the limitations of 1 wk of exposure, the skeleton would appear to be a critical organ. This would suggest that osteosarcomas may occur following administration of Be to laboratory animals for a long-term period.

Animals↗