Biomedical subjects

K Obayashi

Publications and source records attributed to K Obayashi.

At least 37 records · Page 2Linked to original sources

PubMed1999

Unusual self-association properties of transthyretin Y114C related to familial amyloidotic polyneuropathy: effects on detection and quantification.

We performed biochemical and immunological examinations of heterozygotic carriers of the transthyretin (TTR) mutant Y114C associated with familial amyloidotic polyneuropathy (FAP). The total serum TTR levels in Y114C TTR carriers were extremely low when analyzed by single radial immunodiffusion (SRID), whereas by indirect enzyme-linked immunosorbent assay (ELISA) procedure, their total TTR concentrations were increased. Recombinant homozygotic Y114C TTR showed no immunoreactivity towards a TTR antibody when analyzed by SRID, whereas by the ELISA procedure presented the same degree of reactivity as that of normal TTR or isolated serum heterozygotic Y114C TTR. These results indicate that immunodifusion based techniques cannot properly determine TTR serum levels in Y114C carriers. Analyses of serum TTR of the Y114C TTR carriers by electrospray ionization mass spectrometry (ESI-MS) with the orifice corn voltage at 60 V revealed a small peak of the free Y114C TTR in addition to large TTR peaks of normal TTR. The levels of the free mutant TTR increased with the orifice corn voltage at 90 V. In contrast, increase in orifice voltage from 60 to 90 V produced a reduction in the level of normal TTR. The results suggest a different pattern of association between monomers in Y114C relative to normal TTR.

Adult↗

PubMed1999

On the mechanism of genistein-induced activation of protein kinase A-dependent Cl- conductance in cardiac myocytes.

Genistein, an inhibitor of protein tyrosine kinase (PTK), enhanced the activation of the cardiac isoform of the protein kinase A (PKA)-regulated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- conductance in guinea-pig ventricular cells. We examined the mechanism(s) underlying this excitatory action of genistein by using patch-clamp techniques. The CFTR Cl- conductance, activated by isoproterenol (ISO, 10 nM; [Cl-] 153 mM extracellular, 21 mM intracellular; 36 degrees C), was enhanced by 20 microM genistein. Daidzein, a structural analogue of genistein with little inhibitory action on PTK, also enhanced CFTR Cl- currents. After maximal activation of the Cl- conductance by a cocktail of adenosine 3', 5'-cyclic monophosphate, 3-isobutyl-1-methylxanthine and okadaic acid or vanadate plus forskolin in the pipette, genistein was no longer stimulatory but was rather slightly inhibitory at 100 microM. Direct exposure of myocytes to higher concentrations of genistein (50-100 microM) elicited outwardly rectifying currents with a reversal potential of -47 mV in the absence of ISO. In the presence of 50 microM H-89, a PKA inhibitor, genistein had no effect. Vanadate in the pipette at a concentration (100 microM) inhibiting phosphotyrosine phosphatases alone did not prevent the action of genistein. In contrast, no conductance was activated by tyrphostins B42 or 51 or lavendustin A, other PTK inhibitors. Genistein's stimulation of cardiac CFTR Cl- conductance appears to be independent of the PTK pathway and to be due to its direct interaction with CFTR Cl- channels.

1-Methyl-3-isobutylxanthine↗

PubMed1999

Effects of amlodipine and cilnidipine on cardiac sympathetic nervous system and neurohormonal status in essential hypertension.

N-Type calcium channel antagonists may suppress sympathetic activity. The purpose of this study was to assess the effects of amlodipine and cilnidipine on the cardiac sympathetic nervous system and the neurohormonal status of essential hypertension. 123I-metaiodobenzylguanidine (MIBG) cardiac imaging was performed and blood samples were taken to determine plasma renin activity and plasma norepinephrine concentration before and 3 months after drug administration in 47 patients with mild essential hypertension. Twenty-four of the patients were treated with 5 to 10 mg/d of amlodipine; the other 23 were treated with 10 to 20 mg/d of cilnidipine. For comparison, 12 normotensive subjects were also studied. No significant differences were found in the basal characteristics between the 2 hypertensive groups. In both hypertensive groups, both the systolic and diastolic blood pressures were significantly reduced to similar levels 3 months after drug treatment. Before the drug treatment, the 2 hypertensive groups had a significantly higher washout rate and lower heart-to-mediastinum (H/M) ratio compared with the normotensive subjects. The H/M ratio significantly increased (P<0.05) in combination with a decreased washout rate (P<0.02) after drug treatment in the cilnidipine group. In the amlodipine group, a significant decrease in washout rate (P<0. 04) was noted, without an increase in the H/M ratio. However, no significant changes were found in plasma renin activity and plasma norepinephrine concentration in either group. Thus, in patients with essential hypertension, cilnidipine suppressed cardiac sympathetic overactivity and amlodipine had a little suppressive effect. Cilnidipine may provide a new strategy for treatment of cardiovascular diseases with sympathetic overactivity.

Adult↗

PubMed1999

Pseudoxanthoma elasticum with dipyridamole-induced coronary artery spasm: a case report.

In patients with pseudoxanthoma elasticum, severe organic coronary artery stenosis often occurs without coronary risk factors. However, this report presents the case of a 49-year-old woman with pseudoxanthoma elasticum who had coronary artery spasm with an angiographically normal coronary artery. In addition, coronary artery spasm was provoked with dipyridamole thallium-201 cardiac imaging.

Coronary Angiography↗

PubMed1999

Analysis of transthyretin amyloid fibrils from vitreous samples in familial amyloidotic polyneuropathy (Val30Met).

The aim of the present study was to analyze the forms of wild type and mutated monomeric transthyretin (Val30Met) in the amyloid fibrils of patients with familial amyloidotic polyneuropathy by electrospray ionization mass spectrometry (ESI-MS). The solubility of amyloid fibrils from the vitrectomized samples was examined to determine the appropriate solution for ESI-MS. ESI-MS analysis revealed that heterozygotic Val30Met amyloid fibrils contained 14.6 +/- 7.5% normal TTR. In all samples, 3 different types of variant ATTR could be identified: Full length ATTR, and -57, and -157 (or 156) Da from ATTR Val30Met were found. The two peaks showing -57, and -157 (or 156) Da from ATTR Val30Met corresponded to the -Gly, and -Gly-Pro sequences of ATTR Val30Met from the N-terminal. The results illustrate the heterogeneity of ATTR amyloid deposits and this method may be very useful for analyzing amyloid fibrils in ATTR related amyloidosis.

Aged↗

PubMed1999

Gastrointestinal dysfunction in familial amyloidotic polyneuropathy (ATTR Val30Met)--comparison of Swedish and Japanese patients.

The aim of the present study was to compare the clinical symptoms of Swedish and Japanese patients with familial amyloidotic polyneuropathy (ATTR Val30Met), especially gastrointestinal disturbances, and to correlate the findings with survival. Seventy-three Swedish and 47 Japanese patients were available for the study. Thirty-two Swedish and 7 Japanese patients had undergone liver transplantation. The mean age at onset was 50 for Swedish and 35 for Japanese patients (P < 0.001; non-transplanted patients). Fifty-five percent of Japanese patients had gastrointestinal disturbances from onset, compared to 22% of Swedish patients (P < 0.05; whole population). The Swedish patients average survival after the onset was significantly longer than Japanese patients (P < 0.05; non-transplanted patients). An early onset of gastrointestinal symptoms was correlated to a decreased survival for Swedish, but not for Japanese patients. Age at onset was not correlated to survival neither for Swedish nor for Japanese patients. We conclude that the clinical expressions of familial amyloidotic polyneuropathy ATTR Val30Met are different in Swedish and Japanese patients. The survival after the onset was shorter for Japanese patients, who also had an earlier onset of gastrointestinal disturbances, especially diarrhea than Swedish patients.

Adolescent↗

PubMed1998

Post-translational modification of transthyretin in plasma.

To determine the behavior of transthyretin (TTR) in blood circulation, TTR purified from normal subjects' plasma was injected to rats, and blood and urine were collected time dependently. Although TTR in plasma was proven to be a predominantly cysteine (Cys) conjugated form by electrospray ionization mass spectrometry (ESI-MS) analysis, it was gradually converted into free, 32 Da (dihydroxylation), 80 Da (phosphorylation), and 306 Da (glutathionylation), increased forms in molecular weight of TTR. The plasma levels of TTR were decreased in a time-dependent manner with the half life of 72.4 min. No secretion of TTR into the urine was observed by ESI-MS. In conclusion, this method can be simply performed without loading a radioactive molecule to the targeted protein. It offers a possibility to determine natural protein behaviors in the blood stream.

Animals↗

PubMed1998

Visceral orthostatic hypotension in patients with severe autonomic dysfunction.

Although changes in the blood flow of the cerebral vessels and the peripheral vessels in the extremities after changing body postures have been well examined in patients with orthostatic hypotension (OH), such changes in visceral vessels have not been well investigated. To elucidate the effect of autonomic dysfunctions on changes in the abdominal blood flow, the blood flow velocity of the portal vein was measured by Doppler ultrasonography in 11 patients with familial amyloidotic polyneuropathy (FAP) (Met30), 3 with pandysautonomia, 1 with Shy-Drager syndrome, and 10 healthy controls, in the supine and at the upright position. Among the 15 patients with the above-mentioned autonomic disorders, 5 of the patients showed a marked decrease in blood flow after standing, and one of these 5 patients exhibited transient hepatic and intestinal ischemia during intensive rehabilitation because of a severe decrease in visceral blood flow. Another 7 patients exhibited moderate decreases in the blood flow after standing. In contrast, no such change was observed in the 10 healthy controls. The FAP patients with L-threo-3,4-dihydroxyphenylserine (L-threo-DOPS) administration showed no significant correlation between the degree of OH and the decrease in the blood flow of the portal vein, and the patients without the drug exhibited a weak correlation. On the contrary, the pandysautonomia and Shy-Drager syndrome patients exhibited a linear positive correlation. These results suggest that FAP is a disease for which this kind of ultrasonographic examination should be applied, and that Doppler ultrasonography may be a helpful tool to evaluate visceral OH.

Adult↗

PubMed1998

Genistein inhibits slow component delayed-rectifier K currents via a tyrosine kinase-independent pathway.

In single guinea pig ventricular cells, genistein, a potent inhibitor of protein tyrosine kinase (PTK), was found to suppress the delayed-rectifier K (IK) current. The present study was carried out to examine the underlying mechanism. Ventricular myocytes were voltage-clamped in the conventional whole-cell mode (36 degrees C). The amplitudes of tail and steady-state (2-s pulse) currents were measured as IK. Genistein (10-100 microM) reversibly inhibited both basal and intrapipette cAMP (1 mM)-enhanced IK currents in a concentration-dependent manner with a half-maximum inhibitory concentration (IC50) at approximately 30 microM. In contrast, lavendustin A (10 microM; n = 5) and tyrphostin 51 (100 microM; n = 5) had no effect on the currents. The inhibitory action of genistein was also seen after IK currents were activated by forskolin (500 nM) plus intrapipette orthovanadate (500 microM). The intrapipette cAMP-enhanced IK was also reduced to a lesser degree by daidzein, an inactive analogue of genistein. Envelope tail and short pulse protocols revealed that genistein inhibits the slow component of IK (IKs). Thus, the inhibitory action of genistein is not mediated via an inhibition of PTK but may be due to the block of IKs channels.

1-Methyl-3-isobutylxanthine↗

PubMed1998

Accentuated antagonism by angiotensin II on guinea-pig cardiac L-type Ca-currents enhanced by beta-adrenergic stimulation.

To examine mechanism(s) underlying the accentuated antagonism by angiotensin II (A-II) on twitch tension, we recorded L-type Ca2+ currents (ICa,L) using conventional patch-clamp techniques in single, guinea-pig, ventricular myocytes. ICa,L was recorded by a step-pulse protocol after eliminating K+ conductances (internal Cs+ plus tetraethylammonium chloride and K+-free extracellular solution). A-II (100 nM) did not affect basal ICa,L, but inhibited ICa,L that had been enhanced (approximately 200% of control) by (ISO, isoproterenol 100 nM). The inhibitory action of A-II was concentration dependent (concentration eliciting 50% inhibition 88+/-9 pM, n=41) and the ISO-enhanced component of ICa,L was completely blocked by A-II at concentrations above 10 nM. CV-11974 (500 nM), an A-II type-1 receptor (AT1) antagonist, prevented the inhibitory action of A-II. Pre-incubation with pertussis toxin (PTX) abolished the inhibitory effect of A-II. A-II also inhibited the ICa, L enhanced by histamine (500 nM) and forskolin (1 microM), but failed to affect ICa,L enhanced by intracellular cyclic adenosine monophosphate (1 mM). The inhibitory action of A-II may therefore involve AT1 receptors/PTX-sensitive, guanine nucleotide-binding (G) proteins (Gi)/adenylate cyclase and partially explains the A-II-dependent accentuated antagonism of inotropy.

Adrenergic beta-Antagonists↗

PubMed1998

Successful radiofrequency current catheter ablation of accessory atrioventricular pathway after tricuspid replacement in Ebstein's anomaly.

A 15-year-old female with Ebstein's anomaly was referred to hospital for radiofrequency (RF) current catheter ablation of her refractory paroxysmal supraventricular tachycardia (PSVT) after tricuspid valve replacement. A surface ECG showed ventricular preexcitation of type B Wolff-Parkinson-White (WPW) syndrome. In a baseline electrophysiological study, two types of PSVT with left and right bundle branch block (LBBB and RBBB) configurations were induced. The LBBB type was antidromic and the RBBB type was orthodromic atrioventricular reciprocating tachycardia (AVRT) with a right posterolateral accessory pathway. RF current was successfully delivered at the posterolateral site above the prosthetic valve (V-delta interval = -30 msec). The patient has been free from arrhythmias during a follow-up period of 9 months. RF current ablation seems to be useful for AVRT patients with corrected Ebstein's anomaly.

Adolescent↗

PubMed1997

Changes in nitrite and nitrate (NO2-/NO3-) levels in cerebrospinal fluid of patients with multiple sclerosis.

To compare the change in nitric oxide (NO) metabolism in patients with multiple sclerosis (MS) in different clinical stages, such as exacerbation, remission, and 1-2 months after methylpredonisolone administration, we measured the nitrite and nitrate (NO2-/NO3-) levels in the cerebrospinal fluid (CSF). In the extreme stage of MS exacerbation, those levels were remarkably elevated, compared with those both after methylpredonisolone administration and remission. These results suggest that, in addition to MRI study, measurement of NO metabolites in the CSF may give information to help us understand the activity of MS and effect of drugs on the disease.

Adult↗

PubMed1997

Detection of different forms of variant transthyretin (Met30) in cerebrospinal fluid.

To detect the variant transthyretin (TTR; Met30) in cerebrospinal fluid (CSF) of familial amyloidotic polyneuropathy (FAP) patients, we have applied a new method using a centrifugal concentrator device and electrospray ionization mass spectrometry (ESI-MS). Only 100 microl of CSF and 30 microl of the antibody for TTR was needed for the analysis. After preparation of the samples with anti-TTR antibody, they were passed through a 1000 kDa cut-off centrifugal concentrator which retained the antibody. By analyzing the obtained filtrate with ESI-MS, three predominant forms of normal and their variant forms of TTR were detected in CSF samples. TTR (Met30), with a molecular weight 32.0 Da higher than the normal form of TTR, was found in all FAP patients' materials. Although the ratio of the three major peaks of TTR were different in each individual, they were always found in CSF and sera. This method will contribute to make a diagnosis of neurologic disorders having a mutant protein in CSF as well as serum.

Adult↗

PubMed1997

Down regulation of a harmful variant protein by replacement of its normal protein.

To compensate for the hypoprotein and hypoalbuminemia of familial amyloidotic polyneuropathy (FAP) patients, 800 ml of fresh frozen plasma (FFP) was intravenously administered and change in total and variant transthyretin (TTR) levels were measured in the plasma. After injection of FFP, total plasma TTR levels were elevated and variant TTR levels decreased from 24 to 48 h, accompanied by an elevation of plasma total protein, albumin levels and TTR levels. To elucidate the mechanism of this phenomenon, a large amount of purified normal TTR from normal human plasma was intravenously injected in mice and FAP patients. By intravenous injection of 3 mg of the purified TTR to C57Black6, the expression of TTR mRNA decreased from 6 to 24 h post injection, and gradually increased up to 48 h post injection. After injecting 400 mg of normal TTR in each of 3 FAP patients, total plasma TTR levels were elevated and variant TTR levels decreased significantly from 24 to 48 h. These results suggested that down regulation of the harmful protein by replacement of its normal form of the protein occurred by this method. This phenomenon should be applied as the basis for one of the useful methods for decreasing the harmful proteins in the circulation.

Adult↗

PubMed1997

Functional compartmentalization of ATP is involved in angiotensin II-mediated closure of cardiac ATP-sensitive K+ channels.

BACKGROUND: The effects of angiotensin II (Ang II) on ATP-sensitive K+ channels (K(ATP)) were investigated in ventricular myocytes enzymatically isolated from adult guinea pig heart. METHODS AND RESULTS: In the whole-cell and cell-attached configurations (including open-cell-attached mode) of the patch-clamp technique, K(ATP) currents (I(KATP)) were activated through metabolic poisoning by the use of inhibitors of both glycolytic and oxidative ATP productions at 37 degrees C. In the whole-cell mode, I(KATP) were reversibly suppressed by increasing extracellular glucose and Ang II (1 nmol/L). In the cell-attached mode, Ang II concentration-dependently inhibited single K(ATP) activities with an IC50 value of 3.2+/-0.5 pmol/L (Hill coefficient=1.3+/-0.3). CV11974 (100 nmol/L), an angiotensin 1 (AT1) receptor-selective antagonist, blocked the inhibitory action of Ang II. Preincubation of myocytes with pertussis toxin (5 microg/mL for > 120 min at 37 degrees C) virtually prevented subsequent Ang II action. The inhibitory effect of Ang II was also abolished in the open-cell-attached mode (achieved by a prior perfusion of streptolysin-O, 0.08 U/mL). In this mode, through tiny membrane holes, the intracellular ATP concentration can be controlled by bathing extracellular solutions containing a known ATP concentration. CONCLUSIONS: The inhibitory actions of Ang II on K(ATP) appear to be mediated by an increase in the subsarcolemmal ATP concentration that results from the inhibition of adenylate cyclase activities via AT1 receptors/PTX-sensitive G proteins.

Adenosine Triphosphate↗

PubMed1997

Angiotensin II inhibits protein kinase A-dependent chloride conductance in heart via pertussis toxin-sensitive G proteins.

BACKGROUND: Angiotensin II receptors are reported to be abundant in the guinea pig ventricle; their coupling to adenylate cyclase in the heart, however, remains controversial. Therefore, we investigated the effect of angiotensin II on Cl- conductance activated by cAMP-dependent protein kinase. METHODS AND RESULTS: After minimizing the contribution of other ionic currents, exposure of single guinea pig ventricular cells to isoproterenol (40 to 50 nmol/L; 36 degrees C) elicited a typical protein kinase A-dependent Cl- conductance. Subsequent application of angiotensin II reduced the isoproterenol-induced conductance with an IC50 of 0.24 +/- 0.08 nmol/L. Angiotensin II also inhibited the Cl- currents, which were activated through stimulation of adenylate cyclase by forskolin and histamine receptors. CV-11974 (1 mumol/L), an antagonist selective for the angiotensin type 1 receptor, prevented the effect of angiotensin II. Angiotensin II did not inhibit the current that had been persistently activated by intracellular GTP gamma S (100 mumol/L), a nonhydrolyzable guanine nucleotide, plus isoproterenol. In addition, prior incubation of myocytes with pertussis toxin prevented the angiotensin II inhibitory action. Cl- conductance, when activated directly by intracellular dialysis with cAMP (1 mmol/L), was not affected by angiotensin II. Radioimmunologic measurement of cellular cAMP in the dissociated myocytes showed that angiotensin II inhibited the isoproterenol-induced increase of cAMP. CONCLUSIONS: Angiotensin II receptors negatively couple to adenylate cyclase via pertussis toxin-sensitive G proteins, thereby inhibiting cardiac protein kinase A-dependent Cl- conductance.

Adenylate Cyclase Toxin↗

PubMed1997

Endothelin-1 inhibition of cardiac ATP-sensitive K+ channels via pertussis-toxin-sensitive G-proteins.

OBJECTIVE: Secretion of endothelin-1 (ET-1) and activation of cardiac ATP-sensitive K+ (KATP) channels are facilitated under myocardial metabolic stress. The aim of this study was to investigate the effects of ET-1 on KATP channels and to assess underlying mechanisms in ventricular myocytes. METHODS: Single channel currents were measured with the voltage-clamp technique in cell-attached patches from enzymatically-isolated single guinea pig ventricular myocytes. In some experiments, the open-cell-attached mode was employed by permeating the membrane with streptolysin-O. RESULTS: ET-1 concentration-dependently inhibited single KATP channel currents, which had been activated by metabolic poisoning, with an IC50 of 3.8 +/- 0.7 pM. BQ-123, an ETA receptor-selective antagonist, reduced the effects of ET-1. ET-1 effects were largely abolished in the myocytes pre-incubated with pertussis toxin. In the open-cell-attached mode, where the intracellular ATP concentration ([ATP]) could be virtually controlled, the effects of ET-1 were abolished. Muscarinic receptor stimulation inhibited the channels in a similar manner to ET-1, whereas beta-adrenoceptor stimulation accelerated channel activation. By analogy, ouabain also inhibited KATP channel activity under metabolic stress presumably because inhibition of the Na+/K+ pump spares subsarcolemmal ATP. ET-1 inhibited the KATP channels that had been reactivated in the continuous presence of ouabain. CONCLUSIONS: ET-1 reversibly inhibited KATP channels. This effect appears to be mediated by an increase in subsarcolemmal [ATP] which results from inhibition of adenylate cyclase activities through PTX-sensitive G-proteins coupled to ETA receptors.

Adenosine Triphosphate↗

PubMed1997

[Radiation therapy for adrenal metastases].

PURPOSE: To evaluate the role of radiation therapy for adrenal metastases. MATERIALS AND METHODS: Fourteen patients, 13 with primary lung carcinoma and one with primary unknown carcinoma, received radiation therapy for adrenal metastases from 1984 to 1995 at the Hyogo Medical Center for Adults. Total dose ranged from 16 Gy to 60 Gy, and fractional dose from 1.6 Gy/ Fr to 3 Gy/Fr. RESULTS: Partial response of the local tumor was recognized in 2 of 7 patients by CT imaging. Pain relief was obtained in 7 of 8 patients. Median survival was 3 months, and 6-month survival was 28.6% in all patients. Among patients in the symptomatic group, who had complaints of pain due to adrenal mass, survival was even worse (12.5% at 6 months). There were no severe complications, but 4 patients (29%) had gastrointestinal symptoms. CONCLUSION: Radiation therapy is useful for the purpose of pain relief in adrenal metastases.

Adrenal Gland Neoplasms↗