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Biomedical subjects

R Shimizu

Publications and source records attributed to R Shimizu.

At least 91 records · Page 5Linked to original sources
PubMed1996

Characterization of a ligand for receptor protein-tyrosine kinase HTK expressed in immature hematopoietic cells.

HTK is a receptor tyrosine kinase that belongs to the Eph subfamily. An extensive screening using BIAcore system revealed that a colon cancer cell line, C-1, expressed the ligand for HTK. From the conditioned medium of C-1 cells, a soluble form of ligand was purified by receptor affinity chromatography, and the isolation of full-length cDNA revealed that this ligand is identical to the human HTK ligand (HTKL) previously reported. HTK receptor tyrosine phosphorylation was induced by membrane-bound or clustered soluble HTKL but not by unclustered soluble HTKL, indicating that HTKL requires cell-to-cell interaction for receptor activation. Binding analysis demonstrated that HTKL binds to HTK with a much higher affinity (Kd: 1.23 nM) than the other transmembrane-type ligand for Eph family, LERK-2/ELKL (Kd: 135 nM). The expression of HTK in cord blood cells was upregulated after the culture in the presence of stem cell factor. Clustered soluble HTKL stimulated the proliferation of sorted HTK+ cord blood cells and a hematopoietic cell line, UT-7/EPO from which HTK was isolated. These findings suggest the involvement of HTK-HTKL system in the proliferation of HTK+ hematopoietic progenitor cells in the hematopoietic environment.

Amino Acid Sequence↗
PubMed1996

Role of c-jun in the inhibition of erythropoietin receptor-mediated apoptosis.

Human bone marrow cells express both a truncated and full-length form of the erythropoietin receptor (EpoR-T and EpoR-F, respectively). Transfection experiments using the murine interleukin (IL)-3-dependent cell line, Ba/F3, revealed that the cells coexpressing EpoR-F and EpoR-T (Ba/F3-FT) were more likely to undergo programmed cell death (apoptosis) than cells expressing EpoR-F (Ba/F3-FF), even in the presence of erythropoietin (Epo). When Ba/F3-FF cells were stimulated with Epo or IL-3, rapid induction of c-myc, c-fos, c-jun and junB genes was observed. A similar effect was also seen in IL-3 stimulated Ba/F3-Ft cells. However, in Ba/F3-FT cells expression of the c-jun gene was not induced by Epo stimulation. Administration of Epo could prevent apoptosis induced by IL-3 deprivation in Ba/F3-FT cells expressing ectopic c-Jun protein. These results indicate that induction of c-Jun through the Epo signaling pathway has an important role in the inhibition of apoptosis.

Animals↗
PubMed1996

Fluorimetric determination of nicorandil in human plasma by a high-performance liquid chromatographic-postcolumn ultraviolet irradiation [corrected] system equipped with on-line back-pressure tubing.

For the determination of nicorandil in plasma, a fluorometric technique using HPLC-postcolumn UV radiation [corrected] has been developed. The chromatographic system consisted of a single pump, photoreactor and on-line back-pressure tubing. The system was suitable for the separation of nicorandil under the present reaction conditions. The calibration graph was linear over the range 6.5-1170 ng ml-1 using an injected volume of 100 microliters. The pretreatment of the plasma samples consisted only of deproteinizing steps by adding perchloric acid. The mean recovery from plasma was 90.2%.

Administration, Oral↗
PubMed1996

Failed spinal anaesthesia: cause identified by MRI.

PURPOSE: To determine the cause of failed spinal anaesthesia, magnetic resonance images of the lumbar spine were examined. CLINICAL FUTURES: A 28-yr-old woman, scheduled for closure of a rectal fistula under spinal anaesthesia, hyperbaric tetracaine 12.5 mg injected into the subarachnoid space at L3-4 repeatedly resulted in restricted sacral spread. Magnetic resonance imaging showed that the cylindrical dimension of the lumbar spinal canal was wider than in normal subjects, suggesting a larger volume of CSF within the dural sac below the termination of the cord. The summit of the lumbar convexity was located at L3, which was more cephalad than the L3-4 puncture site. CONCLUSION: The uncommon anatomical characteristics of the lumbar spinal canal identified by magnetic resonance imaging were considered to be the reason for the restricted sacral spread observed repeatedly in this patient.

Adult↗
PubMed1996

Sevoflurane anaesthesia for a patient with adult polyglucosan body disease.

PURPOSE: Adult polyglucosan body disease (APBD) is a rare neurological disorder of unknown cause characterized by four manifestations: upper motor neuron signs, peripheral neuropathy with motor and sensory loss, urinary incontinence, and dementia. The purpose of this report is to present a patient with APBD anaesthetized successfully with sevoflurane and nitrous oxide. CLINICAL FEATURE: A 51-yr-old man with APBD was scheduled for haemorrhoidectomy. Paraesthesia, dysaesthesia, distal muscular atrophy and fasciculation were recognized in the extremities. Dementia, bulbar paralysis and respiratory insufficiency were basent. Anaesthesia was induced with inhalation of sevoflurane and nitrous oxide, and the trachea was intubated without the use of muscle relaxants. Maintenance of anaesthesia was performed with sevoflurane (inspired concentration: 1.5-2.5%) and nitrous oxide (50%). Emergence from anaesthesia and the postoperative course were uneventful, and no exacerbation of neurological signs and symptoms was recognized. No postoperative analgesia was required. CONCLUSION: General anaesthesia and tracheal intubation with sevoflurane and nitrous oxide provided safe anaesthesia for a patient with APBD.

Anesthesia↗
PubMed1996

Convulsions associated with epidural analgesia during sevoflurane anaesthesia.

A three-year-old girl who underwent an operation for adrenal neuroblastoma was anaesthetized with sevoflurane and epidural analgesia. In the immediate recovery period she had convulsions. The convulsions were successfully treated with thiopentone and sevoflurane, there were no neurological sequelae. The convulsions were considered to be a manifestation of mepivacaine toxicity because of a high plasma mepivacaine concentration. Complications of paediatric regional analgesia and manifestations of mepivacaine toxicity under sevoflurane anaesthesia are discussed.

Analgesia, Epidural↗
PubMed1996

Anatomical configuration of the spinal column in the supine position. III. Comparison of adolescent and adult volunteers.

To clarify the anatomical configuration of the spinal column in the adolescent in the supine position, we have studied 10 adolescent (13-17 yr) and 10 adult (26-38 yr) volunteers using magnetic resonance imaging. T1-weighted sagittal midline magnetic resonance images of the spinal column were obtained with subjects in the supine position. The maximum angles of decline of the lumbar spinal canal did not differ between the adolescent (mean 13.6 (SD 3.3) degrees) and adult (12.4 (3.8) degrees) groups. The maximum angles of incline of the upper thoracic spinal canal were smaller in the adolescent group (15.9 (4.7) degrees) than in the adult group (26.4 (5.8) degrees). The median highest point of the lumbar spinal canal was located at L4 (range L3-4 to L4-5) in both groups. The lowest points of the thoracic spinal canal in the adolescent and adult groups were located at T8-9 (T7 to T9) and T8 (T6-7 to T9), respectively. This study showed that thoracic kyphotic curvature in adolescents was reduced significantly in the supine position compared with that in adults. This minimized thoracic kyphosis may explain, in part, the enhanced cephalad spread of subarachnoid hyperbaric anaesthetic solutions in adolescents.

Adolescent↗
PubMed1996

Airway management for patients with a tracheal bronchus.

A tracheal bronchus is an aberrant, accessory or ectopic bronchus arising almost invariably from the right lateral wall of the trachea, causing hypoxaemia, atelectasis, or both, during anaesthesia. We describe two patients with a tracheal bronchus found before anaesthesia. One tracheal bronchus was found by tracheobronchoscopy and the other by chest x-ray. Because of recognition of the anomaly before operation, anaesthesia was uneventful in each patient.

Anesthesia, General↗
PubMed1996

Soft tissue anatomy within the vertebral canal in pregnant women.

To clarify pregnancy-induced changes in soft tissue anatomy within the vertebral canal, we have studied magnetic resonance (MR) images of the lumbar spine in three women. In each subject, T2-weighted axial MR images were obtained both before pregnancy and at 32 weeks' gestation, and the paired images were compared. The extradural venous plexus was engorged significantly in supine parturients. In addition, the engorged extradural venous plexus displaced the dura away from the wall of the vertebral canal in a posterior direction, which resulted in a decrease in the volume of the cerebrospinal fluid in the dural sac. These findings confirmed the long-held concept that the engorged extradural venous plexus in supine parturients decreases the effective capacity of the extradural and subarachnoid spaces.

Adult↗
PubMed1996

Inflammatory changes after extradural anaesthesia may affect the spread of local anaesthetic within the extradural space.

We have assessed cephalad spread of analgesia in 491 patients undergoing extradural anaesthesia at the L2-3 or L3-4 interspace. Patients were classified into one of three groups based on the number of previous lumbar extradural anaesthesia procedures: none (group I, n = 339), one (group II, n = 82), and two or more (group III, n = 70). Cephalad spread of analgesia was greater in group I than in groups II and III, regardless of the puncture site. In addition, we examined the extradural space using a flexible extraduroscope in 32 patients who were excluded from the analysis of spread. Extraduroscopy showed the extradural space to be patent in patients with no history of prior lumbar extradural anesthesia, but it was not clearly identified in patients who had received extradural anaesthesia one or more times because of aseptic inflammatory changes, including proliferation of connective tissue, adhesions between the dura mater and the ligamentum flavum, granulation and changes in the ligamentum flavum. Extradural anaesthesia may cause aseptic inflammatory changes in the extradural space which may reduce the spread of analgesia.

Adult↗
PubMed1996

Acid-base state of cerebrospinal fluid during pregnancy and its effect on spread of spinal anaesthesia.

To assess the possible relationship between changes in acid-base state of cerebrospinal fluid (CSF) and enhanced spread of spinal anaesthesia during pregnancy, we have measured CSF pH, carbon dioxide tension (PCO2) and HCO3- values in 73 women undergoing spinal anaesthesia with hyperbaric amethocaine 8 mg. Patients were allocated to one of four groups according to gestational period: non-pregnant group (n = 13), first trimester group (8-13 weeks, n = 19), second trimester group (14-26 weeks, n = 11) and third trimester group (27-39 weeks, n = 30). The pH of the CSF was greater in the second and third trimester groups than in the non-pregnant group. CSF PCO2 decreased by 0.53-0.8 kPa throughout pregnancy. CSF HCO3- was decreased throughout pregnancy. Overall, no clinically significant correlation was found between maximum cephalad spread of analgesia and CSF pH, PCO2 or HCO3-. We conclude that pregnancy-induced changes in acid-base state of CSF have little effect on the spread of spinal anaesthesia, although there is a clinically different spread of spinal anaesthesia between non-pregnant and pregnant states.

Acid-Base Equilibrium↗
PubMed1996

Atrioventricular conduction during adenosine-induced hypotension in dogs anaesthetized with sevoflurane.

We have studied the effects of adenosine-induced hypotension on A-H interval (atrioventricular (AV) nodal conduction time during sinus rhythm), St-H interval (intra-atrial plus AV nodal conduction time during atrial pacing), H-V interval (His-Purkinje conduction time) and H-S interval (total ventricular conduction time) by His-bundle electrocardiography in addition to surface electrocardiogram during both sinus rhythm and atrial pacing in nine dogs anaesthetized with 1 MAC of sevoflurane. Stepwise increases in infusion rates of adenosine to 0.1, 0.3, 0.5 and 1.0 mg kg-1 min-1 produced a dose-related decrease in mean arterial pressure from 91 (6) to 38 (2) mm Hg. Adenosine significantly increased the A-H interval at infusion rates of 0.5 mg kg-1 min-1 and above, and the St-H interval at 1.0 mg kg-1 min-1. The H-V and H-S intervals remained unchanged. Heart rate decreased significantly only at 1.0 mg kg-1 min-1 with a significant increase in the PR interval. Adenosine-induced hypotension did not have deleterious effects on AV conduction times and the surface electrocardiogram in dogs anaesthetized with 1 MAC of sevoflurane. This may indicate that the effects of adenosine on AV conduction were small and therefore are unlikely to be a contraindication to the use of adenosine for inducing hypotension in patients with initially normal conduction during sevoflurane anaesthesia.

Adenosine↗
PubMed1996

The effects of sevoflurane and isoflurane anesthesia on renal tubular function in patients with moderately impaired renal function.

Increasing evidence indicates that sevoflurane anesthesia does not impair renal function in healthy patients despite higher concentrations of plasma inorganic fluoride. However, whether sevoflurane further affects renal tubular function in patients with impaired renal function is not known. We compared the effect of sevoflurane anesthesia with that of isoflurane anesthesia on renal tubular function in patients with moderately impaired renal function. Fourteen patients with creatinine clearance between 10 and 55 mL/min were anesthetized with either sevoflurane or isoflurane using a semiclosed circuit system. Plasma inorganic fluoride concentrations and urine N-acetyl-beta-D-glucosaminidase (NAG), gamma-glutamyltranspeptidase (gamma-GTP), and beta 2-microglobulin (beta 2MG) excretions were measured up to post-anesthetic day 14. Although both the peak plasma inorganic fluoride concentrations and the areas under the curve of plasma inorganic fluoride concentration versus time were significantly greater in the sevoflurane group than in the isoflurane group, urine NAG, gamma-GTP, and beta 2MG excretions per day did not differ between the two groups. These results indicate that sevoflurane and isoflurane may have similar effects on the renal tubules in patients with moderately impaired renal function.

Acetylglucosaminidase↗
PubMed1996

Sevoflurane is equivalent to isoflurane for attenuating bupivacaine-induced arrhythmias and seizures in rats.

The effects of sevoflurane on bupivacaine toxicity have not been defined. The purpose of this study was to investigate the effects of sevoflurane and isoflurane on bupivacaine-induced arrhythmias and seizures in rats. Thirty-seven Sprague-Dawley rats received bupivacaine intravenously at a constant rate of 2 mg.kg-1.min-1 until both arrhythmias and seizures occurred while electrocardiogram (ECG) and electroencephalogram (EEG) recordings were made. The cumulative doses of bupivacaine inducing arrhythmias and seizures were determined in the presence of 1 minimum alveolar anesthetic concentration (MAC) of sevoflurane (sevoflurane group, n = 14) or isoflurane (isoflurane group, n = 10) and in the absence of anesthetic (control group, n = 13). The cumulative doses of bupivacaine inducing arrhythmias and seizures were larger in the sevoflurane and isoflurane groups than in the control group and were similar in the sevoflurane and isoflurane groups. These results indicate that sevoflurane and isoflurane attenuate bupivacaine-induced arrhythmias and seizures in rats.

Anesthetics, Inhalation↗
PubMed1996

In vivo production of nitric oxide in the canine heart in IgE-mediated anaphylaxis.

We investigated the production of nitric oxide (NO) in the canine anaphylactic heart in vivo using an NO-selective electrode. Seven dogs with positive sensitivity to Ascaris Suum were studied. Ascaris Suum was administered into the systemic circulation to induce anaphylaxis, and NO, blood pressure, heart rate, end-diastolic left ventricular pressure, cardiac output, and the maximum rate of rise of left ventricular pressure were monitored for 60 min. The electrode was placed on the surface of the left ventricle adjacent to the interventricular branches of the left coronary artery. NO concentration increased significantly during the period from 2 to 3 min, and tended to increase during the period from 4 to 15 min after antigen challenge, and almost returned to baseline after 20 min. In conclusion, increases in NO in the heart are only observed during the early phase of anaphylaxis.

Anaphylaxis↗