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Biomedical subjects

E Hamada

Publications and source records attributed to E Hamada.

At least 37 records · Page 2Linked to original sources
PubMed1995

17beta-Estradiol inhibits the voltage-dependent L-type Ca2+ currents in aortic smooth muscle cells.

To elucidate the mechanisms of estrogens-induced relaxation effects on vascular smooth muscle cells, the effects of estrogens and the related hormones were examined in cultured rat thoracic aortic smooth muscle cell lines (A7r5), using the whole-cell voltage clamp technique. The patch pipette was filled with 140 mM CsCl- or KCl-containing internal solution. With CsCl-internal solution, 17beta-estradiol and synthetic estrogens, ethynylestradiol and diethylstilbestrol (0.1-30 mu M) inhibited the Ba2+ inward current (IBa) through the voltage-dependent L-type Ca2+ channel in a concentration-dependent and reversible manner. The potency of the inhibitory effects on IBa was 17beta-estradiol < ethynylestradiol < diethylstilbestrol. 17beta-Estradiol (10 mu M) appeared to reduce the maximal conductance of IBa with only a slight shift of voltage-dependency of inactivation and to affect IBa in a use-independent fashion. On the other hand, testosterone and progesterone (30 mu M) failed to affect IBa. At a holding potential of -40 mV, both vasopressin and endothelin-1 (100 nM) activated a long-lasting inward current. After endothelin-1 (100 nM) activated the current, the additional application of vasopressin (100 nM) could not induce it furthermore, suggesting that each agonist activates the same population of the channels. The reversal potential of the current was about 0 mV and was not significantly altered by replacement of [Cl-]i or [Cl-]0 and the inward current was also observed even when extracellular cations are Ca2+, proposing that it was a Ca2+-permeable non-selective cation channel (IN.S.). La3+ or Cd2+ (1 nM) completely abolished IN.S., however, nifedipine (10 mu M) failed to inhibit it at all. Diethylstilbestrol (1-30 mu M) suppressed the IN.S. evoked by both endothelin-1 and vasopressin in a concentration-dependent manner, while 17beta-estradiol, ethynylestradiol, progesterone and testosterone (30 mu M) failed to inhibit it significantly. In addition, at a holding potential of +0 mV, 17beta-estradiol by itself did not affect the holding currents, and did not inhibit K+ currents evoked by endothelin-1 or vasopressin, possibly due to the Ca2+ release from the storage sites. These results suggest that 17beta-estradiol may play a role in regulating vascular tone, selectively by inhibiting the voltage-dependent L-type Ca2+ current in vascular smooth muscle cells.

Animals↗
PubMed1995

Regional differences in transient outward current density and inhomogeneities of repolarization in rabbit right atrium.

BACKGROUND: Recent experimental and clinical studies on atrial flutter have demonstrated that the crista terminalis (CT) plays an important role in the genesis of atrial reentry. To elucidate the underlying mechanism of its role, we characterized the electrophysiological repolarization properties of CT cells by comparing them with those of the pectinate muscles (PM). METHODS AND RESULTS: After action potential properties of both regions were compared by conventional microelectrode technique in multicellular atrial tissues, the whole-cell clamp experiments were applied in atrial cells isolated from both regions. Action potential duration (APD) was more prolonged in CT than in PM in multicellular preparations (APD90 77 +/- 5 ms versus 52 +/- 8 ms at 1 Hz, P < .01), though the other properties did not differ significantly. Similarly, in isolated atrial cells, APD was more prolonged in CT cells than in PM cells (APD90 63 +/- 7 ms versus 41 +/- 6 ms at 0.1 Hz, P < .01). Isolated single cells were larger in CT than in PM. The whole-cell clamp recordings showed no definite distinctions in the density of the voltage-dependent L-type Ca2+ current and the inwardly rectifying K+ current between these cells but revealed a significant reduction of the density of the 4-aminopyridine-sensitive transient outward current (Ito) in CT cells compared with that in PM cells (6.3 +/- 0.7 pA/pF versus 10.3 +/- 0.8 pA/pF at +20 mV, P < .05). However, no differences in the kinetics or the voltage dependence of Ito were observed between the cells. The time course of recovery from inactivation of Ito was also similar in both types of cells. CONCLUSIONS: These results suggest that the preferential reduction in the density of Ito in the CT cells could contribute to prolong their APD, which may be related to the genesis of atrial reentry.

Action Potentials↗
PubMed1995

Ionic basis of neurokinin-A-induced depolarization in single smooth muscle cells isolated from guinea-pig trachea.

Neurokinin A (NKA) caused single tracheal smooth muscle cells (TSMCs) to contract. The effects of NKA on the electrical activity of guinea-pig TSMCs were examined using the tight-seal whole-cell patch-clamp technique. Under current-clamp conditions at rest, the membrane potential of TSMCs spontaneously oscillated at about -40 mV and NKA rapidly depolarized the membrane potential to nearly 0 mV, which then gradually repolarized to about -20 mV in the presence of NKA. The oscillations in potential disappeared transiently during the rapid phase of depolarization in response to NKA and reappeared during the sustained phase of depolarization. Under voltage-clamp conditions, NKA evoked an inward current which faded quickly. Subsequently, the cell conductance in the presence of NKA at potentials greater than -40 mV decreased gradually. The reversal potential of the NKA-induced inward current was about 0 mV, and shifted with changes in the Cl- equilibrium potential. The Cl- current was not elicited by NKA when using a pipette solution containing 10 mM ethylenebis(oxonitrilo)tetraacetic acid (EGTA). During the sustained phase, K+ currents evoked by depolarizing voltage steps were inhibited by NKA. The present results indicate that NKA causes rapid and sustained depolarization of TSMCs by two distinct mechanisms: (1) initial transient activation of the Ca(2+)-dependent Cl- current, and (2) sustained inhibition of K+ currents.

Animals↗
PubMed1995

Hepatocyte growth factor is the most potent endogenous stimulant of rabbit gastric epithelial cell proliferation and migration in primary culture.

Various growth factors are suggested to be involved in gastric mucosal repair. Our previous studies have shown that exogenous hepatocyte growth factor (HGF) has a proliferative effect on gastric epithelial cells. In the present study, comparison of the maximum proliferative effects and the optimum concentrations of several growth factors revealed that HGF was the most potent mitogen for gastric epithelial cells, as is the case for hepatocytes. Restitution of gastric epithelial cell monolayers was assessed using a round wound restitution model. HGF was the most effective agent for facilitating gastric epithelial restitution among those tested. A binding assay revealed specific binding of HGF to its receptor on gastric epithelial cells. Northern blot analysis confirmed the expression of specific HGF receptor mRNA (c-met) by gastric epithelial cells but not by gastric fibroblasts. To investigate endogenous HGF production, we determined the effect of gastric fibroblast-conditioned medium on epithelial proliferation and restitution. The conditioned medium produced similar effects to HGF and its activity was neutralized by an anti-HGF antibody. In addition, expression of HGF mRNA was detected in gastric fibroblasts but not in gastric epithelial cells. Our immunohistochemical study confirmed these in vitro data by means of demonstrating the existence and localization of HGF at human native gastric mucosa. HGF was localized at fibroblasts under the epithelial cell layer around gastric ulcers. These results suggest that HGF may be a potent endogenous promotor of gastric epithelial cell proliferation and migration, and may contribute to gastric mucosal repair through a paracrine mechanism.

Animals↗
PubMed1995

Flecainide inhibits the transient outward current in atrial myocytes isolated from the rabbit heart.

We examined the effects of flecainide, a class Ic antiarrhythmic agent, on membrane currents in single rabbit atrial myocytes, using the tight-seal whole cell voltage-clamp technique. Under the current-clamp condition, flecainide (1-100 microM) prolonged the action potential duration at both the early and the late phases of repolarization in a concentration-dependent manner without affecting the resting membrane potential. In the presence of 4-aminopyridine, however, the drug affected the atrial action potential duration differently than it did in the absence of 4-aminopyridine: it shortened the early phase and only slightly lengthened the late phase of the atrial action potential. Under the voltage-clamp condition, flecainide suppressed the 4-amino-pyridine-sensitive, Ca(++)-insensitive transient outward current in a concentration-dependent fashion (the concentration for the half-maximal effect was approximately 17 microM). The drug also slightly inhibited the voltage-dependent L-type Ca++ current and delayed outward K+ current. Flecainide apparently accelerated the inactivation time course of the transient outward current but did not affect the voltage-dependence of its steady-state inactivation. These actions of flecainide on the transient outward current could be described by a voltage-dependent first-order interaction of the drug with the channel.

4-Aminopyridine↗
PubMed1994

Effects of azelastine on membrane currents in tracheal smooth muscle cells isolated from the guinea-pig.

Azelastine [4-(p-chlorobenzyl)-2-(hexahydro-1-methyl -1H-azepin-4-yl)-1-(2H)-phthalazinone hydrochloride], an anti-allergic agent, inhibited the high K(+)-induced contraction in tracheal smooth muscle cells isolated from the guinea-pig. In order to investigate the ionic mechanisms, we examined the effects of azelastine on membrane currents, using the tight-seal whole cell voltage clamp technique. Azelastine (1-100 microM) caused an inhibition of the Ba2+ inward current (IBa) through the voltage-dependent L-type Ca2+ channel in a concentration-dependent manner. The inhibitory effect of azelastine on IBa was fully reversible. The IC50 value for azelastine-induced inhibition of IBa was approximately 8 microM, and 100 microM azelastine completely suppressed IBa. Azelastine exerted mainly a tonic block of IBa but did not show use dependence. Azelastine (10 microM) shifted the quasi-steady-state inactivation curve of IBa to more negative membrane potentials by approximately -20 mV, suggesting that the inhibitory effect of azelastine on IBa was voltage-dependent. In addition, azelastine produced inhibitory actions on other membrane currents (i.e. the voltage-dependent transient outward K+ current and the Ca(2+)-activated oscillatory K+ current) at doses higher than 10 microM. These results suggest that azelastine inhibits the voltage-dependent L-type Ca2+ current in single tracheal smooth muscle cells, which may contribute to the anti-allergic actions of azelastine in airways.

Animals↗
PubMed1994

Laparoscopic deroofing for symptomatic liver cysts: report of a case.

We present herein the case of a 73-year-old woman with symptomatic liver cysts and cholelithiasis for whom successful deroofing of the liver cysts and cholecystectomy were performed via laparoscopy. Histopathological diagnosis of the resected cyst wall and direct observation of the inner surface of the remaining cyst wall confirmed that they were benign biliary cysts. The laparoscopic deroofing of liver cysts is therefore not only an effective means of treatment, but it also facilitates the establishment of an exact differential diagnosis.

Aged↗
PubMed1994

Churg-Strauss syndrome (allergic granulomatous angiitis) with multiple perforating ulcers of the small intestine, multiple ulcers of the colon, and mononeuritis multiplex.

A case of Churg-Strauss syndrome with multiple perforations of the small intestine is described. A 31-year-old woman was admitted with a complaint of epigastric pain. She had a history of bronchial asthma. One week before admission, white blood cell count was 20,800/mm3 with 59% eosinophils. Neurological examination on admission disclosed mononeuritis multiplex with paresthesia in both the lower and upper extremities. At colonoscopy, there were scattered aphthous ulcers in the colon. Ophthalmological examination revealed allergic conjunctivitis. After admission, hypereosinophilia increased to as high as 36,000/mm3. Oral administration of prednisolone (60 mg/day) was begun. On the 3rd day of the treatment, the eosinophil count decreased dramatically, to 400/mm3, while severe abdominal pain developed. Since abdominal X-ray film revealed free air in the abdominal cavity, emergency laparotomy was performed and multiple intestinal ulcers with perforations were found. Partial ileectomy was performed. Pathological findings of the resected specimen were interpreted as a necrotizing angiitis with extravascular granuloma. Since the operation, the patient has been asymptomatic, except for neurological symptoms. Hypereosinophilia has decreased without treatment to counts averaging 270/mm3, within 3 months. On the basis of the clinical features and histopathological findings, a diagnosis of Churg-Strauss syndrome was established.

Adult↗
PubMed1994

A case of primary gastric choriocarcinoma and a review of the Japanese literature.

A 63-year old woman who had experienced melena for 2 weeks was admitted to Tokyo University Hospital. Gastric adenocarcinoma was diagnosed endoscopically and histologically, and a total gastrectomy was performed soon thereafter. Pathological examination of the resected stomach revealed choriocarcinoma of the stomach. Although chemotherapy was administered after surgery, she died 3 months after admission. Autopsy confirmed the diagnosis of primary gastric choriocarcinoma, a rare, but highly malignant tumor. It is characteristic; macroscopically it forms a necrotic mass with bleeding, and microscopically it often consists of adenocarcinoma and choriocarcinoma. Since its prognosis is extremely poor, we must take into account the possibility of primary gastric choriocarcinoma when a hemorrhagic gastric tumor with necrosis is found.

Aged↗
PubMed1994

Molecular mechanism of cibenzoline-induced anticholinergic action in single atrial myocytes: comparison with effect of disopyramide.

The anticholinergic effects of cibenzoline were examined and compared with those of disopyramide in atrial myocytes isolated from guinea pig heart. The tight-seal whole-cell voltage clamp technique was performed with a patch pipette filled with guanosine-5'-triphosphate (GTP) or guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S). In GTP-loaded cells, both acetylcholine (ACh) and adenosine (Ado) induced a specific K channel current through GTP-binding proteins by binding to the muscarinic and Ado receptors, respectively. Both cibenzoline and disopyramide suppressed the ACh-induced K current effectively in a concentration-dependent manner. The concentrations for half-maximal inhibition of the current (EC50) caused by cibenzoline and disopyramide were 8 and 3 microM, respectively. In GTP gamma S-loaded cells, the K current was irreversibly activated because GTP binding proteins were directly elicited by GTP gamma S. Cibenzoline effectively caused a decrease in the GTP gamma S-induced K current, whereas the extent of disopyramide action on the GTP gamma S-induced K current was much less. Cibenzoline also caused significant inhibition of Ado-induced K current in GTP-loaded cells. However, the action of disopyramide was less effective in inhibiting Ado-induced K current. These results indicate that cibenzoline has less potent anticholinergic effects than disopyramide in atrial myocytes. In addition, cibenzoline effectively inhibits the muscarinic K channel itself and/or GTP-binding proteins coupled to the channel, whereas the effect of disopyramide is attributed mainly to blockade of muscarinic receptors. These findings provide novel understanding of the molecular mechanism of anticholinergic action of cibenzoline.

Animals↗
PubMed1993

Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1993

Percutaneous ethanol injection therapy for hepatocellular carcinoma: results in 146 patients.

OBJECTIVE: Sonographically guided percutaneous ethanol injection therapy has been used widely in the treatment of hepatocellular carcinoma. However, few reports have been published on the results of this treatment in large numbers of patients. Accordingly, we describe our experience with 146 patients who had this treatment. The study is an update of our previous reports on this subject. SUBJECTS AND METHODS: We used ethanol injection, with or without transcatheter arterial embolization, 1048 times in 146 patients who had 242 lesions of hepatocellular carcinoma. In 98 patients, ethanol injection was used to attempt a cure of the disease. In the remaining 48 patients, ethanol injection was used palliatively only to reduce the tumor burden. In most cases, 2-8 ml of absolute ethanol was injected in one treatment session. Patients were given the injections two or three times each week until ethanol was injected throughout the lesion. When tumors were greater than 2 cm in diameter, ethanol was injected into the edges of the lesion. RESULTS: Histopathologic examination after treatment in 21 cases showed that the lesion was completely necrotic in 15 cases, 90% necrotic in five cases, and 70% necrotic in the remaining case. Follow-up angiography performed in 69 cases showed no contrast stains in the treated tumors in 60 cases. Elevated serum levels of alpha-fetoprotein decreased in 39 of 43 cases. The 1-, 2-, 3-, 4-, and 5-year survival rates of all 146 patients were 79%, 64%, 46%, 38%, and 38%, respectively. Among 98 patients in whom ethanol injection was used as a potentially curative therapy, these rates were 85%, 70%, 62%, 52%, and 52%, respectively. After ethanol injection, the cancer recurred frequently; the 1-, 2-, 3-, 4-, and 5-year recurrence rates in the potentially curative group were 26%, 38%, 51%, 60%, and 60%, respectively. However, 84% of recurrences were new lesions in different portions of the liver; recurrence of lesions treated by ethanol injection was rare. Major complications of the treatment were peritoneal bleeding in two cases and pleural effusion in one case. CONCLUSION: Histopathologic examination, angiography, and serum levels of alpha-fetoprotein showed that percutaneous ethanol injection is a valuable treatment of hepatocellular carcinoma. The therapy increased the long-term survival of patients who have this disease.

Carcinoma, Hepatocellular↗
PubMed1993

Eustachian tube function tests and their diagnostic potential in normal and diseased ears.

We have summarized various methods for testing Eustachian tube function since the 1980's. There have been numerous contributions to our knowledge on Eustachian tube and middle ear functions, and the pathophysiology of disorders of the middle ear has been clarified. Understanding of the Eustachian tube function and controlling the Eustachian tube dysfunction are mandatory for adequate clinical management and for improvement of the prognosis.

Adult↗
PubMed1993

Active opening function of the human eustachian tube: comparison between sonotubometry and pressure equilibration test.

Sonotubometry and pressure equilibration test are representative test methods to evaluate the active opening capacity of the Eustachian tube. We applied these tests to 72 ears with otitis media with effusion and 21 ears with chronic otitis media. In 73 ears, both tests showed identical results (11 ears with good active function and 62 ears with poor function). Twenty ears showed good active opening by sonotubometry despite inability to relieve applied negative pressure by swallowing. This inconsistency is believed to result from a too short duration of the tubal opening, by which sound is transmitted through the Eustachian tube, without pressure change in the middle ear cavity. We propose that sonotubometry is a suitable method of detecting impairment of the tubal active opening function, but that a good result by sonotubometry does not always indicate a satisfactory pressure equilibration capacity of the Eustachian tube.

Adult↗
PubMed1993

Otitis media with effusion and eustachian tube dysfunction in adults and children.

Eustachian tube (ET) function was studied in 162 ears with otitis media with effusion (OME) and chronic otitis media (COM), using tubo-tympanoaerodynamic graphy, patency and pressure equilibration test in the inflation-deflation test. Severe impairment of active opening function was found in both OME children and adults compared with that of COM patients. This impairment in active opening was thought to result from functional obstruction of the ET in 71.8% of OME children and 51.8% of OME adults. However, 45.6% of OME adults had an organic obstruction while such was present only in 28.2% of OME children. We deduce from this study that impaired active opening function of the ET in both OME children and adults is the result of functional obstruction rather than organic obstruction, but organic obstruction is considered to be related to the pathogenesis of OME in adults.

Adolescent↗
PubMed1993

Animal model of otitis media with effusion.

A rat model of otitis media with effusion (OME) was developed by intratympanic injection of E. coli endotoxin and section of the third branch of the trigeminal nerve (V3). The period of fluid retention induced by the endotoxin was prolonged for 5 days or longer, in cases when tubal function was impaired by cutting of V3. Three Eustachian tube function tests (patency test of inflation-deflation tests, forced response test and negative pressure test) were carried out before and after the endotoxin inoculation and V3 sectioning. At 4 days after these procedures, passive opening pressure (Po), closing pressure (Pc) and tubal resistance (R2) were significantly lowered. The negative pressure test showed impaired capacity of active opening. This model of Eustachian tube dysfunction is considered to reveal functional obstruction, a condition similar to that of clinical cases of OME. The study shows that both inflammation in the middle ear and tubal dysfunction, such as functional obstruction, are factors in the development and prolongation of OME.

Animals↗
PubMed1993

A reverse-phase high-performance liquid chromatographic determination of nicarbazin residues in eggs.

A reverse-phase high-performance liquid chromatographic (HPLC) method was employed for analysis of nicarbazin [1:1 mixture of 4,4'-dinitrocarbanilide (DNC) and 2-hydroxy-4, 6-dimethyl-pyrimidine] in chicken eggs. Nicarbazin residues were analysed by determining the DNC of nicarbazin. HPLC of the DNC portion of nicarbazin was performed with a reverse-phase mu-Bondapak C18 column, using a mobile phase of acetonitrile-water (7:3, v/v). A variable-wavelength detector set at 340 nm, 0.02 AUFS, and a recorder set at 4 mm/min were used for the detection. The standard curve for nicarbazin was linear within the range 0.05-2.0 micrograms/ml. The recovery of nicarbazin added to eggs was 90.2%. The detection limit of nicarbazin in this analytical method was 0.005 micrograms/ml. Nicarbazin was detected in 10% of eggs obtained by feeding chickens with a diet contaminated with nicarbazin within the range 0.07 to 1.39 micrograms/g, but it was not detected in eggs obtained commercially.

Animal Feed↗