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Biomedical subjects

A Mizushima

Publications and source records attributed to A Mizushima.

At least 19 recordsLinked to original sources
PubMed2001

Ca(2+)-sensor region of IP(3) receptor controls intracellular Ca(2+) signaling.

Many important cell functions are controlled by Ca(2+) release from intracellular stores via the inositol 1,4,5-trisphosphate receptor (IP(3)R), which requires both IP(3) and Ca(2+) for its activity. Due to the Ca(2+) requirement, the IP(3)R and the cytoplasmic Ca(2+) concentration form a positive feedback loop, which has been assumed to confer regenerativity on the IP(3)-induced Ca(2+) release and to play an important role in the generation of spatiotemporal patterns of Ca(2+) signals such as Ca(2+) waves and oscillations. Here we show that glutamate 2100 of rat type 1 IP(3)R (IP(3)R1) is a key residue for the Ca(2+) requirement. Substitution of this residue by aspartate (E2100D) results in a 10-fold decrease in the Ca(2+) sensitivity without other effects on the properties of the IP(3)R1. Agonist-induced Ca(2+) responses are greatly diminished in cells expressing the E2100D mutant IP(3)R1, particularly the rate of rise of initial Ca(2+) spike is markedly reduced and the subsequent Ca(2+) oscillations are abolished. These results demonstrate that the Ca(2+) sensitivity of the IP(3)R is functionally indispensable for the determination of Ca(2+) signaling patterns.

Adenosine Triphosphate↗
PubMed2000

Characterization of human junctophilin subtype genes.

Junctophilin (JP) subtypes, namely JP-1, 2, and 3, have been currently identified in excitable cells and constitute a novel family of junctional membrane complex proteins. Our studies have suggested that JPs take part in the formation of junctional membrane complexes by spanning the membrane of the intracellular Ca(2+) store and interacting with the cell-surface membrane. In this report we describe the primary structures, genomic organization, and tissue distribution of human JP subtypes. By cloning and analyzing human genomic DNA segments, the protein-coding sequence interrupted with four introns was defined in each JP gene. The deduced human JP subtypes shared characteristic structural features with their rabbit and mouse counterparts. Genomic mapping demonstrated that JP genes do not cluster on the human genome. RNA blot hybridization indicated that tissue-specific expression patterns of JP genes in human are essentially the same as those in mouse; skeletal muscle contained both JP-1 and JP-2 mRNAs, the heart predominantly expressed JP-2 mRNA, and the brain specifically contained JP-3 mRNA. In the light of this, we propose intramolecular domains of JP subtypes based on the structural and functional characteristics.

Amino Acid Sequence↗
PubMed2000

Adverse effects of an active fragment of parathyroid hormone on rat hippocampal organotypic cultures.

Adverse effects of an active fragment of parathyroid hormone (PTH(1 - 34)), a blood Ca(2+) level-regulating hormone, were examined using rat hippocampal slices in organotypic culture. Exposure of cultured slice preparations to 0.1 microM PTH(1 - 34) for 60 min resulted in a gradual increase in the intracellular Ca(2+) concentration ([Ca(2+)](i)); this effect was most obvious in the apical dendritic region of CA1 subfield. When PTH(1 - 34) at a lower concentration (1 nM) was added to the culture medium and its toxic effects examined using a propidium iodide intercalation method, significant toxicity was seen 3 days after exposure and increased with time. Cells in the CA1 region seemed more vulnerable to the hormone than cells in other regions. At 1 week of exposure, the toxic effects were dose-dependent over the range of 0.1 pM to 0.1 microM, the minimum effective dose being 10 pM. The adverse effects were not induced either by the inactive fragment, PTH(39 - 84), or by an active fragment of PTH-related peptide (PTHrP(1 - 34)), an intrinsic ligand of the brain PTH receptor. The PTH(1 - 34)-induced adverse effects were significantly inhibited by co-administration of 10 microM nifedipine, an L-type Ca(2+) channel blocker, but not by co-administration of blockers of the other types of Ca(2+) channel. The present study demonstrates that sustained high levels of PTH in the brain might cause degeneration of specific brain regions due to Ca(2+) overloading via activation of dihydropyridine-sensitive Ca(2+) channels, and suggests that PTH may be a risk factor for senile dementia. British Journal of Pharmacology (2000) 129, 21 - 28

Animals↗
PubMed2000

[Perioperative management of a patient with general lymph-congestion following total spondylectomy with posterior and anterior fusion for first thoracic vertebral hemangioma].

A 50-year-old healthy woman was scheduled for surgery of the first thoracic vertebral (T 1) hemangioma accompanying rapidly aggravated neurological deficit in three months. Anesthesia was induced with intravenous fentanyl and propofol and maintained with isoflurane-oxygen-air inhalation, followed by propofol infusion combined with sevoflurane inhalation. Following posterior decompression of T 1 with fusion of C 6-T 3, consecutive total spondylectomy of T 1 with anterior fusion of C 7-T 2 was carried out. At the end of surgery, marked edema was noticed on her face, neck and bilateral upper extremities, possibly due to long manipulation around the left jugular angle. Next morning the edema spread to her whole body and the elevation of both diaphragms and the mediastinal expansion were recognized. Mechanical ventilation in the mode of IMV was performed until subsiding of edema on the fifth postoperative day. During this period, hypoxemia was frequently observed in spite of appropriate respiratory support. On the third postoperative day, bronchoscopic bronchial toilet was performed which brought the improvement of blood oxygenation. The occasional administration of furosemide was not effective to reduce general edema, but served for the acceleration of lymphatic drainage after the release of the thoracic duct obstruction and the patient was extubated uneventfully on the sixth postoperative day.

Anesthesia, Intravenous↗
PubMed1999

Comparison of anesthetic methods for microlaparoscopy in women with unexplained infertility.

STUDY OBJECTIVE: To evaluate the effectiveness of ketamine compared with fentanyl as analgesia or sedation for microlaparoscopy. DESIGN: Prospective, randomized study (Canadian Task Force classification I). SETTING: University-affiliated hospital. PATIENTS: Forty-one infertile women. INTERVENTIONS: Twenty-one patients were randomly assigned to have analgesia with fentanyl and 20 sedation with ketamine during microlaparoscopy. Maximum doses were 0.2 and 200 mg, respectively. Local anesthesia was provided with 0.25% bupivacaine 5 ml injected into cannula sites. MEASUREMENTS AND MAIN RESULTS: Abnormal findings such as endometriosis and periadnexal adhesions were identified in 24 patients. Ablation, coagulation, and adhesiolysis were easily performed in 14 (82.4%) of 17 women receiving ketamine, but difficulties were encountered in operating on 16 patients receiving fentanyl. Ketamine was administered to 10 patients (47.6%) in the fentanyl group because anxiety and pain were not sufficiently controlled by fentanyl. There were no significant differences in visual analog scale scores and recovery time between groups. On questionnaire, 19 (95%) of 20 patients receiving ketamine indicated they would choose the same anesthesia again if offered, compared with only 4 (19%) of 21 receiving fentanyl (p <0.001). CONCLUSION: Microlaparoscopy in infertile women was performed more effectively under sedation with ketamine than with fentanyl.

Analgesia↗
PubMed1998

Effect of antisense oligonucleotides against cholesteryl ester transfer protein on the development of atherosclerosis in cholesterol-fed rabbits.

Cholesteryl ester transfer protein (CETP) is the enzyme that facilitates the transfer of cholesteryl ester from high density lipoprotein (HDL) to apolipoprotein B (apoB)-containing lipoproteins. However, the exact role of CETP in the development of atherosclerosis has not been determined. In the present study, we examined the effect of the suppression of increased plasma CETP by intravenous injection with antisense oligodeoxynucleotides (ODNs) against CETP targeted to the liver on the development of atherosclerosis in rabbits fed a cholesterol diet. The ODNs against rabbit CETP were coupled to asialoglycoprotein (ASOR) carrier molecules, which serve as an important method to regulate liver gene expression. Twenty-two male Japanese White rabbits were used in the experiment. Eighteen animals were fed a standard rabbit chow supplemented with 0.3% cholesterol throughout the experiment for 16 weeks. At 8 weeks, they were divided into three groups (six animals in each group), among which the plasma total and HDL cholesterol concentrations did not significantly change. The control group received nothing, the sense group were injected with the sense ODNs complex, and the antisense group were injected with the antisense ODNs complex, respectively, for subsequent 8 weeks. ASOR. poly(L-lysine) ODNs complex were injected via the ear veins twice a week. Four animals were fed a standard rabbit diet for 16 weeks. The total cholesterol concentrations and the CETP mass in the animals injected with antisense ODNs were all significantly decreased in 12 and 16 weeks compared with those injected with sense ODNs and the control animals. The HDL cholesterol concentrations measured by the precipitation assay did not significantly change among the groups fed a cholesterol diet, and triglyceride concentrations did not significantly change in the four groups. However, at the end of the study, when the HDL cholesterol concentrations were measured after the isolation by ultracentrifugation and a column chromotography, they were significantly higher in the animals injected with antisense ODNs than in the animals injected with sense ODNs and in the control animals. A reduction of CETP mRNA and an increase of LDL receptor mRNA in the liver were observed in the animals injected with antisense ODNs compared with those injected with sense ODNs and the control animals. Aortic cholesterol contents and the aortic percentage lesion to total surface area were significantly lower in the animals injected with antisense ODNs than in the animals injected with sense ODNs and in the control animals. These findings showed for the first time that suppression of increased plasma CETP by the injection with antisense ODNs against CETP coupled to ASOR carrier molecules targeted to the liver could thus inhibit the atherosclerosis possibly by decreasing the plasma LDL + very low density lipoprotein (VLDL) cholesterol in cholesterol-fed rabbits.

Animals↗
PubMed1998

Stroke due to a fusiform aneurysm of the cervical vertebral artery: case report.

Aneurysms of the cervical vertebral artery (VA) are uncommon; they are often caused by trauma or spontaneous dissection. A fusiform aneurysm without evidence of atherosclerosis or dissection has not been reported previously. A 46-year-old man presented with a pontine infarct. Imaging revealed a fusiform aneurysm of the left VA at the C5-6 level, with occlusion of the basilar artery. Associated minor anomalies included fusion of the vertebral bodies of C5 and C6, cervical rib and platybasia. The left VA arose directly from the aortic arch and entered the transverse foramen at the C4 level. Hyperextension and left lateral flexion of the neck caused kinking of the VA proximal to the aneurysm. Turbulent flow in the aneurysm lumen was noted on angiography.

Cerebral Angiography↗
PubMed1998

Esophageal strictures in children with recessive dystrophic epidermolysis bullosa: experience of balloon dilatation in nine cases.

BACKGROUND: Recessive dystrophic epidermolysis bullosa is a rare disorder characterized by extreme vulnerability of the squamous epithelium and mucous membranes. Minor trauma such as is caused by swallowing solid food is followed by blistering and scarring. Stricture formation at the pharyngoesophageal junction (C6 or C7) is the severest complication of this disease. METHODS: We evaluate the effectiveness of Microvasive Rigiflex balloon dilatation and extensive nutritional support as a primary treatment for this condition. Nine of 21 recessive dystrophic epidermolysis bullosa patients developed esophageal strictures at the level of the pharyngo-esophageal junction (C6). We treated them with intensive nutritional therapy followed by balloon dilatation, which produces longitudinal pressure and provides prompt relief from esophageal stricture. Eleven balloon dilatations have been performed in 9 patients. RESULTS: All patients had poor physical development and were severely malnourished; extensive nutritional support was required before treatment could begin. Balloon dilatation was performed once in seven patients and twice in two patients. No recurrent stricture formation was observed after balloon dilatation. CONCLUSION: Intensive nutritional support followed by balloon dilatation is the first choice of treatment for esophageal strictures complicating recessive epidermolysis bullosa. By following this regime, invasive surgery can be avoided.

Adolescent↗
PubMed1997

Urinary excretion of aquaporin-2 water channel protein in human and rat.

Previous studies by the authors demonstrated that the response of urinary aquaporin-2 (AQP2) excretion to dDAVP (deamino-8-D-arginine vasopressin) infusion is an index of vasopressin action on the kidney (N Engl J Med 332: 1540-1545, 1995). In the study presented here, the characteristics of urinary excretion of AQP2 were examined further. An RIA suitable for AQP2 in the urine was established. Relatively high concentrations of detergent and bovine serum albumin in the RIA buffer allowed analysis of urine samples with a wide range of concentrations and increased the sensitivity of the assay. AQP2 in the urine existed as a high molecular weight form of approximately 190 kD by HPLC analysis. The mean urinary AQP2 concentration corrected for creatinine in spot urine samples of healthy subjects who voided in the morning was 1081 +/- 699 fmol/mg creatinine (mean +/- SD, n = 208). The amount of daily excretion of AQP2 in the urine was the same in men and women. Urinary AQP2 content was not affected by age of the subjects and showed a positive correlation with urine osmolality. Finally, the fraction of AQP2 excreted in the urine compared with whole kidney content was determined in the rat. Approximately 3% of AQP2 in the kidney was excreted daily, and this fraction did not change when rats were dehydrated for 3 d. These data demonstrate the necessity of establishing well-designed protocols to use urinary AQP2 as a marker of AVP action.

Adult↗
PubMed1997

[Anesthetic management in a child with Drash syndrome].

Drash syndrome is characterized by nephropathy, Wilms tumor and male pseudohermaphroditism. We present a child with an incomplete form of this syndrome who underwent two operations. A full-term, 3070 g female was born after a normal transvaginal delivery. At the age of 1 year and 6 months, in order to confirm the diagnosis of the infantile nephrosis, a renal biopsy was performed with halothane anesthesia. Histological findings showed diffuse mesangium sclerosis. At the age of 3 years and 8 months, a chromosomal analysis revealed XY gonadal dysgenesis. Therefore, a diagnosis was made as the incomplete Drash syndrome. At the age of 5 years and 7 months, a gonadectomy and a CAPD catheter insertion for renal failure were performed under sevoflurane anesthesia. The main problems encountered by anesthetists were severe renal dysfunction, use of steroids, anticoagulants and immunodepressants, choice of anesthetic agent, and mental health care. This patient has been followed for the potential development of Wilms tumor.

Anesthesia, Inhalation↗
PubMed1996

Contrast-enhanced MRI in spinal arteriovenous malformations and fistulae before and after embolisation therapy.

MRI was performed in six cases of spinal arteriovenous malformation (AVM) and arteriovenous fistula (AVF) before and after embolisation. Intramedullary and perimedullary AVMs showed marked vascular enhancement after embolisation. This was thought to reflect feeding vessel occlusion and correlated well with a favourable clinical outcome. In dural AVFs, contrast-enhanced studies were essential for the diagnosis, unenhanced images being nonspecific. After embolisation, enhancement of the spinal cord was reduced, although one case with a poor outcome showed persistent enhancement.

Adult↗
PubMed1996

Effect of sevoflurane anaesthesia on plasma concentrations of glutathione S-transferase.

To assess the effect of sevoflurane anaesthesia on hepatocellular integrity, we measured plasma concentrations of glutathione S-transferase (GST) before anaesthesia and 1, 3, 6 and 24 h after the end of anaesthesia in 41 healthy, Japanese patients undergoing elective, body surface surgery. Sevoflurane (approximately 1.0 MAC) was delivered in 50-66% nitrous oxide in oxygen via a circle system, with a fresh gas flow of 6 litre min-1. Ventilation was spontaneous in all patients. Mean duration of anaesthesia was 101 min. Concentrations of GST increased significantly 1 h after the end of anaesthesia (P = 0.0075), but this was not significantly different from preoperative concentrations at 3, 6 and 24 h. Three patients developed a large secondary increase in GST concentrations at 24 h. The increase observed at 1 h was probably a result of reduced total liver blood flow; the mechanism for the secondary increase at 24 h is unclear but the possibility that products of sevoflurane biotransformation are responsible cannot be excluded.

Adult↗
PubMed1996

Type D dural carotid-cavernous fistula. Results of combined treatment with irradiation and particulate embolization.

PURPOSE: To assess the efficacy of irradiation combined with particulate embolization for treating type D dural carotid-cavernous fistulas, supplied by the meningeal branches of both external (ECA) and internal carotid arteries. MATERIAL AND METHODS: Nine patients were treated by particulate embolization via the ECA branches, followed by radiation therapy with doses of 30 Gy. One of these patients with recurrent symptoms received an additional 30 Gy one year after initial treatment, making a total dose of 60 Gy. RESULTS: In all cases, symptoms were improved immediately after the particulate embolizations. In 8 cases, complete resolution of symptoms were obtained in 4-19 months and an average of 8 months after treatment. In one case, chemosis was markedly improved and persisted minimally 41 months later. CONCLUSION: Particulate embolization is effective for immediate symptomatic improvement, and complete resolution of symptoms can usually be achieved by subsequent radiation therapy.

Aged↗
PubMed1996

[Anesthetic problems in a very low birth weight infant with Kasabach-Merritt syndrome].

Kasabach-Merritt syndrome is characterized by thrombocytopenia and bleeding tendency leading to disseminated intravascular coagulation with giant hemangiomas. We present a very low birth weight infant with this syndrome who underwent four operations. A male baby (1179 g, 37 cm) was born at a gestational age of 28 weeks and 6 days by caesarean section. A large hemangioma, 7 x 8 cm in size, was recognized on the left thigh. As associated consumption coagulopathy (Kasabach-Merritt syndrome) was diagnosed with platelet count 5.1 +/- 10(4) mm-3 and fibrinogen 49 mg.dl-1. Despite treatment with liniac X-ray radiation, systemic steroid and component transfusion, coagulopathy became worse with extremely low platelet count of 1.1 x 10(4) mm-3. Infusion of dopamine and dobutamine was necessary for high output cardiac failure. On day 9, PDA ligation was performed. Cerebro-ventricular drainage, ventricuro-peritoneal shunt and shunt revision were required on day 15, 49 and 88, respectively, for hydrocephalus due to intraventricular hemorrhage. Main anesthetics used were fentanyl and sevoflurane. Major problems encountered by anesthetists were: bleeding tendency, water and electrolyte management, body temperature control, and immaturity and fragility of premature infant. Coagulopathy in Kasabach-Merritt syndrome must be a risk factor for intraventricular hemorrhage, which is a characteristic complication of a very low birth weight infant.

Anesthesia, General↗
PubMed1996

[Anesthetic problems in a 480 g infant for ventriculo-peritoneal shunt surgery].

A 480 g, 38-day-old female infant underwent ventriculo-peritoneal shunt surgery for hydrocephalus after intra-ventricular hemorrhage. The patient was born at a gestational age of 25 weeks and 5 days, weighing 600 g, as one of twins by a cesarean section. Although respiratory distress syndrome developed, it was relieved with surfactant. The esophagus was easily perforated by a gastric tube. At the age of 7 days, PDA was closed conservatively with indomethacin. Anesthesia was induced and maintained with fentanyl (induction dose 4 micrograms.kg-1, total dose 6 micrograms.kg-1) and vecuronium. Ventilation was controlled with oxygen and air (FIO2 0.21-0.25). The main problems encountered by anesthetists in the perioperative period were; fluid management (hyperkalemia, hyponatremia, infusion volume), bradycardia due to increased intracranial pressure, body temperature control (hypothermia), and transport to the operating room. In anesthesia for extremely low birth weight (extremely premature) infants, utmost care and proficient procedure are required because of their immaturity, fragility and smallness.

Adjuvants, Anesthesia↗
PubMed1995

Functional mapping of the sensorimotor cortex: combined use of magnetoencephalography, functional MRI, and motor evoked potentials.

Combined use of magnetoencephalography (MEG), functional magnetic resonance imaging (f-MRI), and motor evoked potentials (MEPs) was carried out on one patient in an attempt to localise precisely a structural lesion to the central sulcus. A small cyst in the right frontoparietal region was thought to be the cause of generalised seizures in an otherwise asymptomatic woman. First the primary sensory cortex was identified with magnetic source imaging (MSI) of somatosensory evoked magnetic fields using MEG and MRI. Second, the motor area of the hand was identified using f-MRI during hand-squeezing. Then transcranial magnetic stimulation localised the hand motor area on the scalp, which was mapped onto the MRI. There was a good agreement between MSI, f-MRI and MEP as to the location of the sensorimotor cortex and its relationship to the lesion. Multimodality mapping techniques may thus prove useful in the precise localisation of cortical lesions, and in the preoperative determination of the best treatment for peri-rolandic lesions.

Adult↗
PubMed1995

[Unexpected intraoperative respiratory distress; an infant who developed tracheomalacia and fatal aortoesophageal fistula due to unrecognized vascular ring].

Vascular rings cause respiratory distress and dysphasia by tracheoesophageal compression. We present a case of tracheomalasia and fatal aortoesophageal fistula due to unrecognized vascular ring. A 3-month-old (7.3 kg) boy underwent V-P shunt operation under sevoflurane anesthesia. The trachea was intubated easily using vecuronium with a relatively large-size tube with a diameter of 4.5 mm, because of leakage. Gastric intubation was difficult. During scrubbing of the head, an asthma-like respiratory distress suddenly occurred. The condition responded poorly to ventilatory support and pharmacological interventions. Although intraoperative fiberscopy through the tracheal tube and chest X-ray showed no tracheobroncheal abnormality, postoperative fiberscopy revealed a tracheomalacia. Adequate ventilation was possible only when the tip of the tracheal tube was located between the stenotic part and the tracheal carina. On the 9th postoperative day, during respiratory management with a tracheal tube, fatal esophageal hemorrhage broke out. Postmortern examination revealed a double aortic arch with tracheal stenosis and aortoesophageal fistula. The nasogastric tube may have led to fistula formation by compression of the esophageal wall against an anomalous vessel. When anesthetists encounter an infantile respiratory distress, even in perioperative period, vascular rings should be taken into consideration.

Aorta, Thoracic↗