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A Masuda

Publications and source records attributed to A Masuda.

At least 181 records · Page 10Linked to original sources
PubMed1994

[Effects of sevoflurane on contraction, membrane ionic currents and intracellular cyclic AMP concentration in canine single ventricular cells].

The effects of sevoflurane (SV) on contraction, membrane ionic currents and intracellular cAMP concentration were studied in single canine ventricular cells. The authors demonstrated first that SV depressed contractile response of single ventricular cells in a dose-dependent manner. In electrophysiological studies, SV depressed the plateau height and duration of action potentials. Whole-cell voltage clamp experiments revealed that SV depressed voltage-dependent Ca2+ currents in a dose-dependent manner but SV (1%, 2%) did not change Na+ currents. Further, SV (1%, 2%) did not reduce intracellular cAMP concentrations. We conclude that the decrease of myocardial contractile response in single canine cardiac cells by SV is mainly due to the inhibition of voltage-dependent L-type of Ca2+ channels at the sarcolemma and not through changes in intracellular cAMP levels.

Animals↗
PubMed1993

Modification of BHA forestomach carcinogenesis in rats: inhibition by diethylmaleate or indomethacin and enhancement by a retinoid.

The long-term effects of butylated hydroxyanisole (BHA), in combination with various other chemicals on the development of forestomach lesions in rats were investigated. BHA is a synthetic antioxidant, and the other agents included the glutathione-depleting agent diethylmaleate (DEM), the anti-inflammatory drugs indomethacin (IM), dexamethazone (DEX), 6-aminocaproic acetate (6-ACA) and FOY (gabexate mesilate), and the vitamin all-trans-retinol acetate (RA). Concurrent treatment with BHA (1% in diet) and DEM, IM, DEX or FOY for 52 weeks inhibited development of forestomach epithelial hyperplasia as compared to BHA alone, while simultaneous treatment with RA enhanced hyperplastic development. However, the inhibition by DEX or FOY was only partial and in the DEX case, in particular, might have been due to weight loss. Since the most effective inhibitory influence on BHA-induced forestomach lesions exerted in this 1-year experiment was by DEM, a further 2-year experiment was conducted to confirm whether DEM actually can exert inhibitory effects on BHA (2% in diet)-induced forestomach carcinogenesis. The results demonstrated that induction of forestomach hyperplasias and papillomas by BHA was significantly reduced by combination treatment with DEM. Both multiplicity and incidence of forestomach papillomas were significantly decreased, while squamous cell carcinoma development showed a tendency for decrease only.

Animals↗
PubMed1993

Effects of 100% O2 exposure on hypoxic ventilatory response.

Comparison of the slope of progressive isocapnic hypoxia obtained with and without prior O2 exposure (termed + and -O2 runs, respectively) placed our subjects into two groups. Positive responders had a significantly lower slope in -O2 runs compared with similar runs in negative responders, but they also improved hypoxic ventilatory response (HVR) significantly after O2 exposure. Negative responders had a high -O2 slope that did not alter significantly after O2 exposure. We conclude that ambient air hypoxic depression is active in positive responders who are O2 sensitive.

Adult↗
PubMed1993

Percutaneous discectomy in athletes.

Percutaneous discectomy has been widely used for the lumbar disc herniation in recent years because it is a simple and safe procedure. This report evaluates the postoperative return to the original level of activity among athletes who compete in their sports on a national level. It has been thought that the recovery rate was poor in the conventional surgery but there have been few studies. The postoperative results using percutaneous discectomy were rated as excellent in 4 athletes, good in 5, poor in 4. The patients generally returned to full sports activity 2 months after surgery. The authors conclude that percutaneous discectomy may be considered if conservative treatments fail to relieve pain in athletes.

Adolescent↗
PubMed1993

Complete remission of neuroleptic-induced Meige's syndrome by botulinum toxin treatment: a case report.

A botulinum A toxin injection has beneficial effects on patients suffering from facial and cervical spastic disorders. However, its effect almost completely disappears within three months. We have reported a case of a 23-year-old schizophrenic patient with severe neuroleptic-induced Meige's syndrome in whom botulinum toxin treatment exerted a marked effect which lasted more than 15 months after the final injection of botulinum toxin in spite of continuous neuroleptic medication. It is concluded that botulinum can be recommended as a treatment of choice in neuroleptic-induced Meige's syndrome.

Adult↗
PubMed1993

Gender differences in cochlear response time: an explanation for gender amplitude differences in the unmasked auditory brain-stem response.

Derived narrow-band auditory brain-stem responses (ABRs) in young normal-hearing subjects revealed a significant gender difference in response time between frequency regions of the cochlea. Females showed shorter delays than males between derived bands. This differential has not been previously reported. As in many early studies, the unmasked amplitude of the wave V complex was significantly larger (30%) in females than males. However, differences in amplitudes of the narrow-band responses were too small to account for the differential in the unmasked response. It is hypothesized that the larger amplitude of the unmasked wave V complex in females occurs because of a faster response time across the cochlea leading to better neural synchrony and, therefore, larger amplitudes. Furthermore, results can be explained by assuming that the stiffness gradient in the cochlea is 13% larger in females than in males. If males and females have the same cochlear tonotopic mapping, the female cochlea should be 13% shorter. This prediction is highly consistent with recent anatomical studies of cochlear length and gender. The results of the present study indicated possibly important cochlear mechanisms that influence the main parameters of ABRs. An understanding of these cochlear mechanisms may improve the diagnostic capabilities of ABRs in patients with peripheral hearing loss.

Acoustic Stimulation↗
PubMed1993

[Preoperative collection of autologous blood with recombinant human erythropoietin therapy].

The major problems in liquid storage of donated blood are the limitation of blood volume preserved and the time consumed. We studied on the usefulness of utilization of recombinant human erythropoietin (rH-EPO) for preoperative collection of autologous blood. Patients were divided into 2 groups: Group 1 (12 patients) received 3000 unit of rH-EPO intravenously every day. Group 2 (10 patients) was not treated with rH-EPO. All the patients were given ferrous sulfate 100 mg of iron orally every day. As a rule, 400 ml blood was donated two or three times a week for rH-EPO treated group, while, for control group 400 ml blood was collected once a week. Some patients did not donate 400 ml because of their critical condition. The blood volume preserved became 780.9 +/- 284.1 ml in Group 1, and 910.8 +/- 263.9 ml in Group 2. However, the number of days until operation were significantly shorter in Group 1 (8.7 +/- 3.6 days) than in Group 2 (26.2 +/- 11.2 days). Hemoglobin and Hematocrit levels recovered promptly in rH-EPO treated group. In control group, 2 patients complained of nausea and vomiting caused by severe anemia. On the other hand, no one with rH-EPO therapy did not show any side effects and complications. Our study indicates that the administration of rH-EPO enables us to collect an adequate volume of autologous blood preoperatively in a shorter period of time.

Anemia↗
PubMed1993

Clinical significance of hypocitraturia in kidney stone patients.

Although a low concentration of urinary citrate is cited as one of the risk factors promoting stone formation or recurrence among patients with urinary stones, its clinical significance remains obscure. We studied 62 kidney stone patients with a low urinary citrate excretion (hypocitraturia) of less than 320 mg/day, without any apparent cause. The incidence of hypocitraturia in 722 kidney stone patients followed up at our stone clinic was 14.6%. Among the 62 patients, 37 had an uncomplicated hypocitraturia as the sole abnormality, while 25 had other associated stone risk factors, including hypercalciuria in 11% (7/62), hyperuricosuria in 24% (15/62), hyperoxaluria in 5% (3/62) and hypomagnesuria in 24% (15/62). The rate of urinary stone recurrence was 38% (14/37) in uncomplicated hypocitraturia, and 52% (13/25) in complicated hypocitraturia, but no statistical difference was observed. Regarding the outcome of stones, more stones were managed with lithotripsy and more passed spontaneously in the hypocitraturic patients than in the control patients with normal urinary citrate excretion. The diagnosis of hypocitraturia complicated with additional stone risks urged us to treat patients more vigorously with lithotripsy and medication, resulting in a prompt cure.

Citrates↗
PubMed1993

[Inhibitory action of bupivacaine on cardiac contraction].

We studied the effects of bupivacaine on the contractility and membrane potentials in isolated dog papillary muscle. Bupivacaine (10(-6)-10(-4) M) produced dose-dependent depression of twitch tension elicited by electrical stimulation. These inhibitory effects were greater at high frequencies of stimulation (2, 3 Hz) than at low frequencies (less than 1 Hz). Bupivacaine did not alter the resting membrane potential, but produced a reduction in Vmax of the action potentials, in a dose-dependent and reversible manner (concentrations from 10(-6) to 10(-4) M). Bupivacaine 10(-4) M often blocked the fast action potentials in normal Tyrode's solution. In high K+ (26 mM) Tyrode's solution, bupivacaine inhibited both slow action potentials and associated contractions in the presence of isoproterenol. These results suggest that low concentrations of bupivacaine decreases the contraction mainly due to Na+ channel block, whereas at higher concentration, this anesthetic may block Ca2+ channels. In addition, isoproterenol may be clinically effective in the treatment of bupivacaine cardiotoxicity due to stimulation of Ca2+ mediated slow action potentials through beta-receptors.

Animals↗
PubMed1993

Expression of proto-oncogenes and tumor suppressor genes in in vitro cell lines derived from a thymus, thymoma, and malignant thymoma of rats.

To analyze the processes of the development of thymoma and malignant thymoma from normal thymic epithelial cells, we have examined the expression of 15 proto-oncogenes and tumor suppressor genes in seven in vitro epithelial cell lines established from a normal thymus (TuD1-1, TuD1-3, and TuD1-5), thymoma (TaD1-3 and TaD1-8), and malignant thymoma (MTHC-1 and MTHC-3) of rats. Northern blot analysis indicated that most of these genes examined were transcribed at similar levels. However, higher levels of transcription of epidermal growth factor receptor (EGFR) were observed in TuD1-1, TuD1-3, TuD1-5, TaD1-3, and TaD1-8 cells than in MTHC-1 and MTHC-3 cells. Conversely, four of the former five cell lines showed no TGF-beta transcription while the latter two cell lines had high levels of its expression. In addition, c-fos proto-oncogene was highly expressed in TuD1-5 cells, which showed the fastest growth rate among the seven cell lines. These results denote that some molecular changes in the regulation of gene expression occurred in the processes of malignant transformation of thymic epithelial cells.

Animals↗
PubMed1993

[Electrophysiological effects of ketamine on Ca(2+)-activated K+ channel in single rabbit portal vein cell].

The effects of ketamine on Ca(2+)-activated K+ channel currents were studied in dispersed single smooth muscle cells from rabbit portal vein using inside-out patch clamp technique. In a near physiological K+ and Ca2+ gradient, three populations of outward rectangular single currents were recorded in isolated cell membrane of rabbit portal vein at +60 mV membrane potential. These currents were judged as Ca(2+)-activated K+ channel currents since application of EGTA or Apamin in the internal solution inhibited these currents. Application of 10(-5)M or 10(-4)M ketamine inhibited the number of occurrences of channel opening and decreased open times, but did not reduce the amplitudes. When the 10(-3)M ketamine was applied, the Ca(2+)-activated K+ channel currents were abolished. We suggest that the depression of Ca(2+)-activated K+ channel currents may explain the continuous contraction observed in rabbit portal vein at a clinical concentration of ketamine from a point of electrophysiological K+ current study.

Animals↗
PubMed1993

Percutaneous diskectomy for lumbar disk herniation. A preliminary report.

Percutaneous diskectomy is a new method for reducing lumbar disk herniation. This procedure is simple, safe, and only semiinvasive since it causes no direct damage to the dura or nerve roots. This technique employs a nucleotome (blunt-tipped, suction-cutting probe) with a rotating electric shaver (3 mm in diameter) that was specially developed for this procedure. It was applied to 117 patients with lumbar disk herniation whose sciatica had not been relieved by conservative treatments. The results of the technique were considered effective in 94 patients (80.3%). The improvements were even more marked in patients with protrusion or prolapse type herniation. Reviewed with postoperative examinations using magnetic resonance imaging (MRI), excision of the herniated disk, resulting in decompression of the nerve root, may be correlated with the relief of symptoms.

Adolescent↗
PubMed1993

[A rare case of infraclinoid aneurysm accompanied with pituitary adenoma extending over the extrasellar space].

A 39 year-old female patient suffering from amenorrhea over the course of the last 14 years was admitted to our hospital on Dec. 12, '89. Computed Tomography revealed a relatively high-density mass extending over the suprasellar portion and the sphenoid sinus. Enlargement and destruction of the sella turcica was demonstrated clearly by the plain craniogram ++. Right carotid angiography demonstrated an open siphon and a medially pointing aneurysm on the right anterior siphon. Two staged operations were performed. On Jan. 23, '90, a transsphenoidal operation was performed to remove the part of the tumor invading the sphenoid sinus. Two weeks later, on Feb. 9, '90, a transcranial operation was carried out for extirpation of the residual adenoma and direct neck clipping of the aneurysm. The tumor was subtotally removed through a left fronto-lateral craniotomy. By drilling away the tuberculum sellae and the planum sphenoidal the aneurysm was completely clipped via a contralateral approach. The postoperative neuroradiological examinations demonstrated that the aneurysm was clipped successfully and the adenoma was extirpated almost totally.

Adenoma↗
PubMed1993

[The anesthetic management of Arnold-Chiari malformation with spinal cord injury].

A rare case of spinal cord injury at C3 level associated with Arnold-Chiari malformation is reported. A 33 year old male was admitted with a complaint of walking difficulty. MRI revealed cerebellar herniation, and a plain X-ray showed spinous process adhesion of C2-3 and slight scoliosis. Percent vital capacity was reduced to 69%, and blood cell count showed a slight anemia. The patient was anesthetized for an orthopedic surgery with pethidine 70 mg, thiamylal 200 mg, 60% nitrous oxide, 40% oxide, and 0.5-1.2% isoflurane. There was a mild decrease in arterial blood pressure during surgical procedures, but this could be easily treated by fluid therapy, and there was no episode of autonomic hyperreflexia. Postoperative course of the patient was uneventful, except a transient pneumonia and urinary tract infection. The key in the anesthetic management of Arnold-Chiari malformation with spinal cord injury is the control of intracranial pressure, care for respiratory dysfunction and the prevention of infection as well as autonomic hyperreflexia.

Adult↗