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Biomedical subjects

H Iida

Publications and source records attributed to H Iida.

At least 19 recordsLinked to original sources
PubMed1995

Cooperation of calcineurin and vacuolar H(+)-ATPase in intracellular Ca2+ homeostasis of yeast cells.

Saccharomyces cerevisiae VMA genes, encoding essential components for the expression of vacuolar membrane H(+)-ATPase activity, are involved in intracellular ionic homeostasis and vacuolar biogenesis. We report here that the immunosuppressants FK506 and cyclosporin A cause general growth inhibition of the vma3 mutant. Upon addition of the drugs, the mutant grew neither in the presence of more than 5 mM Ca2+ nor above pH 6.0. The action of the immunosuppressants is dependent on their binding proteins and ascribable to inhibition of calcineurin activity; a mutation of a calcineurin subunit (cnb1) shows synthetic lethal interaction with the vma mutation. The addition of FK506 decreases the cytosolic free concentration of Ca2+ in the vma3 mutant cells. Consequently, FK506 induces an 8.9-fold elevation of a nonexchangeable Ca2+ pool. These results suggest that calcineurin controls calcium homeostasis by repression of Ca2+ flux into a cellular compartment(s) and that the vacuolar H(+)-ATPase is essential for cell growth cooperating with calcineurin to regulate the cytosolic free concentration of Ca2+.

Base Sequence↗
PubMed1995

Calmodulin-dependent protein kinase II and calmodulin are required for induced thermotolerance in Saccharomyces cerevisiae.

We show here that yeast mutants lacking calmodulin-dependent protein kinase II fail to fully acquire induced thermotolerance. A similar result was also obtained with mutants depending solely on either the N-terminal half or the C-terminal half of calmodulin. These findings indicate that both calmodulin-dependent protein kinase II and calmodulin are required for induced thermotolerance.

Calcium↗
PubMed1995

Error analysis of table look-up method for cerebral blood flow measurement by 123I-IMP brain SPECT: comparison with conventional microsphere model method.

While N-isopropyl-p-[123I]iodoamphetamine (IMP) is commonly used as a flow tracer, significant clearance from the brain causes underestimation of CBF as compared with true CBF when conventional microsphere model analysis is applied. We previously reported a simple "table look-up" method for CBF measurement using IMP taking into account this clearance effect. The method is based on a two-compartment model, the K1 (corresponding to CBF) and k2 constants being obtained from a table from the ratio of the 1st SPECT (40 min) to the 2nd SPECT (180 min) counts. Arterial input data used were obtained by one point blood sampling 10 min after IMP infusion against the standard input function. In the present study, this approach was compared with conventional microsphere model analysis. For 30 subjects, the latter method entailed 8 min continuous arterial blood sampling after IMP infusion and the use of SPECT data at the end of this period, calibrated by a count ratio of 8 min/40 min planar images of whole brains. A good correlation was observed between the two methods (r = 0.88), but an overestimation of table look-up method CBF as compared with microsphere model CBF was observed contrary to theoretical predictions. Limitations in the estimation of SPECT data at 8 min, obtained with SPECT data at 40 min for calibration of the count ratio of 8 min/40 min whole brain planar images, might be responsible for this.

Amphetamines↗
PubMed1995

Regional cerebral blood flow, blood volume, oxygen extraction fraction, and oxygen utilization rate in normal volunteers measured by the autoradiographic technique and the single breath inhalation method.

By means of a high resolution PET scanner, the regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and metabolic rate of oxygen (rCMRO2) for major cerebral gyri and deep brain structures were studied in eleven normal volunteers during an eye-covered and ear-unplugged resting condition. Regional CBF was measured by the autoradiographic method after intravenous administration of H2(15)O. Regional OEF and rCMRO2 were measured by the single inhalation of 15O2. With MR T1-weighted images as an anatomical reference, thirteen major cerebral gyri, caudate nucleus, lentiform nucleus, thalamus, midbrain, pons, cerebellum and vermis were defined on the CMRO2 images. Values were read by using circular regions of interest 16 mm in diameter. The posterior part of the cingulate gyri had the highest rCBF and rCMRO2 values among brain structures, followed by the lentiform nucleus, the cerebellum, the caudate nucleus, and the thalamus. Parahippocampal gyri had the lowest rCBF and rCMRO2 values among the cortical gyri. Regional OEF for the pontine nuclei (0.34 +/- 0.04), the midbrain (0.35 +/- 0.05), the parahippocampal gyri (0.35 +/- 0.04 for the right and 0.37 +/- 0.05 for the left), and the thalami (0.37 +/- 0.05 for the right and 0.36 +/- 0.04 for the left) were significantly lower than the mean OEF for the cerebral cortices (0.42 +/- 0.04) (p < 0.05 or less). The global CBF and CMRO2 were consistent with those obtained by the Kety-Schmidt method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Photic stimulation study of changing the arterial partial pressure level of carbon dioxide.

To investigate the effect of the level of baseline cerebral blood flow (CBF) on local CBF augmentation by activation, we have used positron emission tomography to measure regional CBF (rCBF) in 12 normal volunteers with and without photic stimulation during hypocapnia, normocapnia, and hypercapnia. The increase in rCBF in the primary visual cortex by photic stimulation was 10.8 +/- 3.1, 18.6 +/- 9.3, and 19.5 +/- 6.1 ml 100 ml-1 min-1 in hypo-, normo-, and hypercapnia, respectively. The increase was significantly smaller in hypocapnia than in normocapnia (p < 0.005). The fractional CBF increase caused by the photic stimulation was the same in all breathing conditions. This result indicates that the magnitude of the CBF increase induced by neuronal activity correlates proportionally with the level of baseline CBF.

Adult↗
PubMed1995

Latent tarsal tunnel syndrome with the provocation of flexor spasms in a paraplegic person. Case report.

A 71-year-old paraplegic woman presented with a complaint of insomnia caused by severe flexor spasms of the lower limbs at night, aggravated for a few hours by taking hot baths. Lidocaine injection of the tarsal tunnel diminished the flexor-withdrawal reflex, which was easily elicited by light pinching or sustained compression over the tarsal tunnel, and strongly suggested the existence of the tarsal tunnel syndrome. Surgical decompression of the tarsal tunnel significantly reduced the flexor spasms both in terms of frequency and of duration.

Aged↗
PubMed1995

Mechanisms of dexmedetomidine-induced cerebrovascular effects in canine in vivo experiments.

Dexmedetomidine decreases cerebral blood flow without significantly affecting cerebral oxygen consumption in anesthetized dogs. To assess the direct cerebrovascular effects of dexmedetomidine, we investigated the responses of vasomotor tone to topical application of dexmedetomidine to pial vessels in vivo, using a parietal cranial window. Forty-one dogs were anesthetized with pentobarbital. In 20 dogs, we topically applied six concentrations of dexmedetomidine solution (10(-8), 10(-7), 10(-6), 10(-5), 10(-4), 10(-3) M) and directly measured pial arterial and venous diameters. In 10 dogs, the inhibitory effects of pretreatment of pial vessels with 10(-5) M yohimbine were examined after the application of 10(-5) dexmedetomidine. In the remaining 11 dogs, the effects of 10(-3) M dexmedetomidine were evaluated in the presence of N omega-nitro-L-arginine methyl ester (L-NAME), glibenclamide, or propranolol. Dexmedetomidine significantly constricted pial arteries and veins in a concentration-dependent manner (10(-7) M to 10(-4) M; P < 0.05). Yohimbine blocked dexmedetomidine-induced constriction of pial vessels (both large and small arteries and large veins P < 0.0001; small veins P < 0.005). However, when the highest concentration of dexmedetomidine (10(-3) M) was administered under the window, pial vessel diameter was not significantly altered. In the presence of glibenclamide, 10(-7) and 10(-3) M dexmedetomidine induced a significant decrease in pial arterial diameter compared with 10(-7) and 10(-3) M dexmedetomidine solution alone, respectively (P < 0.05). L-NAME or propranolol did not affect the dexmedetomidine-induced constriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Topical↗
PubMed1995

Positron emission tomography with oxygen-15 of stunned myocardium caused by coronary artery vasospasm after recovery.

Stunned myocardium is often observed after unstable angina, myocardial infarction, thrombolysis, angioplasty, and bypass surgery but rarely after coronary vasospasm. A case of stunned myocardium caused by diffuse coronary artery vasospasm and mimicking myocardial infarction is reported. The patient had an emergency coronary angiography, which showed no pathological coronary disease, but the left ventricular ejection fraction showed severe left ventricular dysfunction. Repeat coronary angiography 24 days later after medical treatment (diltiazem and nitrates) showed complete recovery of wall function, and a diffuse vasospasm was induced in both coronary arteries (left anterior and right coronary arteries). Two days later the patient underwent a positron emission tomography study with water labelled with oxygen-15 to evaluate the viable myocardium and oxygen-15 to evaluate oxidative metabolism. The results showed normal myocardial blood flow and perfusable tissue density, confirming that the myocardium was viable, and normal myocardial oxidative metabolism, reflecting the recovery of the left ventricular function.

Aged↗
PubMed1995

Effect of spinal cord stretching due to head flexion on intramedullary pressure.

The effect of the longitudinal stretching force of the spinal cord on intramedullary pressure was investigated using our method for measuring intramedullary pressure of the spinal cord with implanted balloons. The transverse compressive force against the posterior wall of the spinal column was excluded by measuring the intramedullary pressure during flexion of the head with the middle and lower cervical spine in the neutral position. The intramedullary pressure of the cervical spinal cord was measured simultaneously at the C-2, C-4, and C-6 levels in 10 mongrel dogs, in three head positions: neutral, and head extension and flexion. Head flexion caused significant increases in the intramedullary pressure at C-2, C-4, and C-6. The pressure increase in the middle to lower cervical cord must have been due to the transmission of the longitudinal stretching force of the cord itself, and may be a factor in the development of intramedullary disorders such as syringomyelia and intramedullary neoplasms.

Animals↗
PubMed1995

Spinal cord intramedullary pressure: direct cord traction test.

Spinal cord intramedullary pressure was measured in eight mongrel dogs using a balloon method. The neck of the animals was maintained in the neutral position. Following cervical laminectomy, the cervical spinal cord was drawn dorsally using a small plastic saddle inserted ventral to the spinal cord at the C-5 level. The cord pressure at C-5 increased with traction load. The cord pressure at C-6 not in direct contact with the plastic saddle also increased to about one third the increase at C-5. These findings indicate that spinal cord intramedullary pressure is increased by mechanical compression on the anterior structure of the spinal canal and stretching of the cord to some extent. This phenomenon might be important in cord insult in patients with spinal column lesions located anterior to the spinal cord and presenting with neurological signs extending over several segments.

Animals↗
PubMed1995

[The effects of systemic bupivacaine on baroreflex sensitivity in dogs].

To evaluate the effects of systemic bupivacaine on the baroreflex control of heart rate, we investigated the baroreflex sensitivity assessed with a pressor and a depressor test using phenylephrine and nitroglycerin in pentobarbital anesthetized dogs (n = 12). Intravenous injection of bupivacaine (mean plasma concentration of 2.4 +/- 0.9 micrograms.ml-1) caused a significant suppression of the baroreflex sensitivity, defined by the slopes of regression line (in msec of RR interval change per mmHg increase or decrease in systolic blood pressure). The sensitivity obtained with the pressor and the depressor tests decreased from 6.0 +/- 2.3 to 3.5 +/- 1.7, from 2.4 +/- 1.3 to 1.3 +/- 0.8 msec.mmHg-1, respectively (P < 0.01). Suppression of the baroreflex sensitivity during epidural anesthesia with bupivacaine could be due not only to cardiac sympathectomy but also to a direct effect of bupivacaine on the reflex arch including the receptors, the afferent nerve pathways, the CNS, the efferent pathway, and the effector organs. Therefore, the hemodynamic responses to reduction of blood pressure are likely to be inhibited by epidural bupivacaine.

Anesthesia, Epidural↗
PubMed1995

[Spinal multiple sclerosis mimicking a spinal cord tumor: a case report].

Since the advent of magnetic resonance imaging (MRI), to visualize lesions of multiple sclerosis has become easy to do. However, in some cases with primary spinal cord multiple sclerosis, it is not always easy to obtain a diagnosis in the first instance. We reported a case of primary spinal multiple sclerosis diagnosed through histological examination of a surgical specimen taken by an open biopsy. A 35-year-old woman was admitted with complaints of two-months duration of progressive weakness and sensory disturbance in the legs and buttocks. On radiological examinations including metrizamide CT myelography and MRI, enlargement of the conus medullaris was the only positive finding. Respective to her clinical course, intramedullary spinal cord tumor could not be ruled out, so an open biopsy was performed. Histological examination revealed that the cord lesion was acute demyelination with perivascular inflammation. Her neurological signs were almost completely cured with administration of corticosteroid, though new brainstem signs took place two months later and then a concrete diagnosis of her having multiple sclerosis was finally achieved. Since preoperative examinations can not differentiate spinal cord tumor from any other intramedullary cord lesions such as demyelinating foci of multiple sclerosis, surgical intervention would be approved in such atypical primary spinal cord multiple sclerosis.

Adult↗
PubMed1995

[Kinetics of glucose metabolism in central neurocytomas].

To estimate proliferating activity of central neurocytoma, we measured kinetic rate constants and glucose metabolic rate (kinetic-rCMRGI) using dynamic positron emission tomography (PET), as well as autoradiographic rCMRG1 (arg-rCMRG1), in patients with histologically verified central neurocytoma. The subject included five patients, four males and one female, aged from 23 to 53 years with a mean age of 41 years old. All tumors were located in the lateral ventricle and two extended into the third ventricle through the forearm of Monro. Tumor lesion on the PET images was determined using CT or MRI, which was performed at levels equivalent to those for the PET scans. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three compartment 18F-fluorodeoxyglucose (FDG) model. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter. Tumor k1 and k2 values were similar to or higher than those of the contralateral gray matter, suggesting high permeability due to lack of blood-brain barrier. Tumor k3 value, an indicator of hexokinase activity, and kinetic-rCMRG1 were exceedingly lower in three of five patients. These three patients have been free from tumor recurrence or regrowth, postoperatively. The other two patients, tumor kinetic-rCMRG1 was similar to or higher than that of the contralateral gray matter. One patient suffered from tumor regrowth shortly after resection, and the other has been followed up postoperatively. Thus, k3 and kinetic-rCMRG1 are indicative parameters of proliferative activity in central neurocytoma.

Adult↗
PubMed1995

Annexin V is localized in association with Z-line of rat cardiac myocytes.

OBJECTIVE: The aim of this study was to characterize a 33-kDa protein (p33) isolated from bovine liver and to determine the subcellular localization of the protein in rat cardiocytes as well as in non-cardiac tissues. METHODS: Cycles of calcium-induced precipitation coupled with EGTA-resolubilization were used to isolate crude annexins from bovine and rat tissues. Column chromatography was performed to purify the p33 from the crude annexins. The protein was identified as annexin V by partial amino acid sequence determination. Specificity of anti-annexin V antibody was examined by using Western blotting after one- or two-dimensional electrophoresis. For characterization of the protein, immunofluorescence microscopy and actin-binding assays were carried out. RESULTS: Immunofluorescence microscopy showed that annexin V was stained as a striated pattern along myofibrils on frozen sections of both atria and ventricles of adult rats. The striations were seen more clearly in cultured rat atrial myocytes. Examination of doubly stained cardiocytes with anti-annexin V and anti-alpha-actinin by a confocal laser scanning microscope suggests that annexin V is localized in association with the Z-line of rat cardiac myocytes. We also found that annexin V was stained intensely in actin-rich regions of non-cardiac tissues such as bile canaliculi of rat liver and brush border-terminal web region in the epithelial cells of both small intestine and kidney proximal tubular cells. F-actin binding experiments revealed that annexin V failed to bind to F-actin directly in vitro. CONCLUSION: Our results suggest that annexin V is a new component of the Z-line in rat cardiocytes and might be involved in regulation of its organization.

Actins↗
PubMed1995

[Kinetic analysis of glucose metabolism in meningiomas--comparison with malignant gliomas].

We measured kinetic rate constants and glucose metabolic rate (kinetic-rCMRGl) using dynamic positron emission tomography (PET), as well as regional cerebral blood flow (rCBF), blood volume (rCBV), oxygen extraction fraction (rOEF), oxygen metabolic rate (rCMRO2) and autoradiographic rCMRGl (arg-rCMRGl), in patients with meningioma. Ten patients including one recurrent case, two males and eight females aged from 44 to 71 years with a mean age of 54 years old, were studied prior to surgical interventions. Histological diagnosis was as follows: seven cases of meningothelial type, two cases of angiomatous type and one fibrous type. For quantitative analysis, regions of interest (ROI) on PET images were delineated on the tumor and the contralateral gray matter in comparison with eight cases with malignant gliomas (five cases of malignant astrocytoma and three cases of glioblastoma, aged from 14 to 70 years with a mean age of 41 years old). Hemocirculation of the tumor was exceedingly higher than that of the contralateral gray matter, which corresponded to neuroradiological findings of abundant tumor vessels. Low rOEF implicated an excessive blood flow beyond oxygen demand of the tumor. The raised metabolic rate (rCMRO2/rCMRGl) suggested rather aerobic glycolysis as compared with malignant gliomas. The kinetic rate constants of tracer transport from blood to brain (k1), reverse transport from brain to blood (k2), and phosphorylation (k3) were analyzed according to the three compartment model of 18F-fluorodeoxyglucose (FDG). Tumor k1 and k2 values markedly increased in all examined cases, suggesting high permeability due to lack of blood-brain barrier and an abundant blood supply.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[Coronary artery bypass grafting in a patient with a single coronary artery].

Coronary artery bypass grafting in a patient with a single coronary artery is reported. A 61-year-old male who had chest pain and palpitation was transferred to our hospital. His ECG showed ischemic change, and CPK rose to a high level. Emergency coronary angiography revealed a type L II A (Lipton's criteria) single coronary artery and atherosclerotic stenosis on three major branches. He underwent CABG of LAD using LITA, #3 and #14 using saphenous vein grafts. Post operative angiography confirmed patent grafts, and the patient was free from symptoms.

Coronary Angiography↗
PubMed1995

Rapid calculation of regional cerebral blood flow and distribution volume using iodine-123-iodoamphetamine and dynamic SPECT.

UNLABELLED: Iodine-123-iodoamphetamine (IMP) is commonly used as a flow tracer for SPECT due to its large first-pass extraction fraction. Significant clearance from the brain, however, causes changes in distribution and underestimation of CBF values when a conventional microsphere model is applied to prolonged data acquisition. We have developed a rapid method to calculate CBF images in which clearance effects are taken into account. METHODS: A dynamic SPECT scan was obtained from five subjects (four patients with cerebral infarctions and one healthy volunteer) following intravenous injection of IMP lasting 1 min. The arterial input function was obtained by frequent blood sampling and measurement of the octanol extraction ratio. The dynamic images were weighted and integrated so that the look-up table procedures yielded values of CBF and distribution volume (Vd) simultaneously. RESULTS: Calculated values for CBF and Vd were consistent with those determined by nonlinear least squares fitting [CBF: Y = 1.03X-0.30 (ml/100 ml/min), r = 0.998, p < 0.001; Vd: Y = 0.99X-0.11 (ml/ml), r = 0.99, p < 0.001] and calculated CBF correlated significantly with CBF measured by PET [Y = 0.85X-0.15 (ml/100 ml/min), r = 0.92, p < 0.001]. CONCLUSION: This technique is valid for estimating CBF.

Amphetamines↗