Biomedical subjects

H Oka

Publications and source records attributed to H Oka.

At least 109 records · Page 6Linked to original sources

PubMed1999

[Postoperative sore throat and intracuff pressure: comparison among endotracheal intubation, laryngeal mask airway and cuffed oropharyngeal airway].

We studied which device is most useful to reduce postoperative sore-throat. We investigated the relationship between intracuff pressure and postoperative sore-throat in using endotracheal intubation (ET), the laryngeal mask airway (LMA) and the cuffed oropharyngeal airway (COPA) in adult patients. We classified sore-throat into categories; pain at rest, hoarseness and dysphasia. We evaluated pain at rest by the score (0: no pain, 1: mild discomfort, 2: mild pain, 3: severe pain). Pain at rest (scores 1, 2, 3) was complained by 10 patients in ET group, 3 in LMA group, 5 in COPA group on the day of operation, showing significantly lower incidence of pain at rest in LMA group than in ET group. Hoarseness was complained by 15 patients in ET group, 2 in LMA group and 4 in COPA group, showing significantly lower incidence of hoarseness in LMA and COPA groups than in ET group. Dysphasia was complained by 3 in ET group, 1 in LMA group and 2 in COPA group, showing no significant difference. These results suggest that LMA is most appropriate to reduce postoperative sore-throat.

Adult↗

PubMed1998

Separation of lac dye components by high-speed counter-current chromatography.

High-speed counter-current chromatography has been successfully applied to the separation of the lac dye components. A 25-mg quantity of the sample was separated using a two-phase solvent system composed of tert.-butyl methyl ether-n-butanol-acetonitrile-water (2:2:1:5). The fractions were analyzed by high-performance liquid chromatography and electrospray tandem mass spectrometry. The separation yielded 2.6 mg of 97.2% pure laccaic acid C, 9.5 mg of 98.1% pure laccaic acid A, 3.6 mg of 98.2% pure laccaic acid B, and 0.5 mg of a 95.0% pure anthraquinonedicarboxylic acid with a molecular mass of 360.

Azo Compounds↗

PubMed1998

Separation of antibiotics by counter-current chromatography.

This paper reviews recent applications of counter-current chromatography (CCC) to the separation of antibiotics. It also covers the recent development of CCC instruments and the optimization of the two-phase solvent system. The CCC technique offers a high resolving power when the proper solvent system is carefully selected and becomes a powerful tool to separate various components from antibiotics complexes.

Anti-Bacterial Agents↗

PubMed1998

Mass spectrometric analysis of tetracycline antibiotics in foods.

We will review recent developments in mass spectrometric analysis of tetracycline antibiotics (TCs) in foods. The mass spectrometric techniques discussed are as follows: the collision-activated decomposition mass-analysed ion kinetic energy spectrometry (CAD MIKES), thin-layer chromatography (TLC)- fast atom bombardment (FAB) mass spectrometry (MS), particle beam (PB) liquid chromatography (LC)-MS, LC-fit FAB MS, thermospray (TSP) LC-MS, atmospheric chemical ionization (APCI) LC-MS and tandem electrospray (ESI) LC-MS. Their advantages and limitations are described in the confirmation of TCs in foods: CAD MIKES can confirm TCs with high sensitivity; however, its practical application is questionable because of uncommon instrumentation. TSP has a problem in reproducibility of the mass spectrum. Although TLC-FAB-MS can be applied to any kind of samples, it cannot be used for the quantitative analysis. LC-frit FAB-MS is a useful technique for the confirmation of TCs in honey, but it cannot be applied to animal tissues because of a lack of sensitivity. PB negative chemical ionization, APCI, and ESI-MS-MS can reliably confirm TCs in foods with good reproducibility.

Anti-Bacterial Agents↗

PubMed1998

Application of ion-exchange cartridge clean-up in food analysis. I. Simultaneous determination of thiabendazole and imazalil in citrus fruit and banana using high-performance liquid chromatography with ultraviolet detection.

A simple, rapid and reproducible analytical method for thiabendazole (TBZ) and imazalil (IMA) in citrus fruit and banana has been developed. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of TBZ and IMA from citrus fruits spiked at levels of 10 microgram/g and 5 microgram/g were in the range of 94-98% and 93-98% with coefficients of variation of 0.5-2.2% and 1.6-2.7%, respectively. The recoveries of TBZ and IMA from banana spiked at levels of 3 microgram/g and 2 microgram/g were 94% and 94% with coefficients of variation 1.1% and 4.9%, respectively. The detection limits for TBZ and IMA were 0.1 microgram/g in citrus fruit and 0.05 microgram in banana.

Anthelmintics↗

PubMed1998

Differential distribution of TRP Ca2+ channel isoforms in mouse brain.

Mammalian homologues of the Drosophila TRP proteins, which are essential for light-activated, phosphatidyl-inositide (PI)-dependent Ca2+ conductance in Drosophila photoreceptors, were molecularly identified, to investigate receptor-activated Ca2+ influx in the mammalian nervous system. Two cloned mouse TRP homologues, TRP3 and TRP4, structurally related to the voltage-dependent Na+ channel, were expressed predominantly in the brain, where a sharp contrast in the distribution of the RNA transcripts for TRP isoforms was demonstrated by in situ hybridization analysis. TRP3 mRNA was concentrated in cerebellar Purkinje cells and sparsely localized in the cerebellar granule layer, pontine nuclei, and thalamus, whereas TRP4 mRNA was abundantly expressed in hippocampal CA1 pyramidal neurons, dentate gyrus granule cells, and cerebral cortical neurons, and in the septal nuclei and the mitral layer of olfactory bulb. The distinct spatial patterns of TRP isoforms implicate that neurons are highly heterogeneous in receptor-activated Ca2+ influx responsible for the second phase of PI-mediated rise in intracellular Ca2+.

Amino Acid Sequence↗

PubMed1998

Myocardial glucose metabolism in patients with hypertrophic cardiomyopathy: assessment by F-18-FDG PET study.

In an investigation of myocardial metabolic abnormalities in hypertrophic myocardium, the myocardial glucose metabolism was evaluated with F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET) in 32 patients with hypertrophic cardiomyopathy, and the results were compared with those in 9 patients with hypertensive heart disease. F-18-FDG PET study was performed in the fasting and glucose-loading states. The myocardial regional %dose uptake was calculated quantitatively. The average regional %dose uptake in the fasting state in the patients with asymmetric septal hypertrophy and dilated-phase hypertrophic cardiomyopathy was significantly higher than that in the patients with hypertensive heart disease (0.75 +/- 0.34%, 0.65 +/- 0.25%, and 0.43 +/- 0.22%/100 g myocardium, respectively). In contrast, the average %dose uptake in the glucose-loading state in the patients with asymmetric septal hypertrophy and dilated-phase hypertrophic cardiomyopathy was not significantly different from that in patients with hypertensive heart disease (1.17 +/- 0.49%, 0.80 +/- 0.44% and 0.99 +/- 0.45%, respectively). The patients with apical hypertrophy had also low %dose uptake in the fasting state (0.38 +/- 0.21%) as in the hypertensive heart disease patients, so that the characteristics of asymmetric septal hypertrophy and dilated-phase hypertrophic cardiomyopathy are considered to be high FDG uptake throughout the myocardium in the fasting state. Patients with apical hypertrophy are considered to belong to other disease categories metabolically. F-18-FDG PET study is useful in the evaluation of the pathophysiologic diagnosis of patients with hypertrophic cardiomyopathy.

Blood Glucose↗

PubMed1998

Telomerase activity in adrenal cortical tumors and pheochromocytomas with reference to clinicopathologic features.

Telomeres consist of short repeated sequences that are shortened on continuous cell proliferations and synthesized by telomerase, an RNA-dependent DNA polymerase. Recent molecular studies have reported that telomerase is activated in most human cancers, whereas it is not detected in most somatic cells. These findings indicate that the positive telomerase activity is closely related to the malignant potential of human tumors. In several types of human tumors, including adrenal cortical tumors and pheochromocytomas, it is very difficult to predict the malignant potential using conventional histopathologic examination. To determine whether telomerase activity is useful as a diagnostic marker, we examined telomerase activity in adrenal cortical tumors and pheochromocytomas with special reference to their clinicopathologic features. Using a highly sensitive polymerase chain reaction (PCR)-based detection method, telomerase activity was demonstrated in one of 13 adrenal cortical tumors and two of seven pheochromocytomas, whereas all seven normal portions of adrenal gland failed to showed any telomerase activity. Although none of the tumors examined in this study was associated with metastasis, these three telomerase-positive tumors were accompanied by clinicopathologic features suggesting malignant potential. Telomerase activity might be a potential marker for estimating the biologic characteristics of adrenal cortical tumors and pheochromocytomas.

Adolescent↗

PubMed1998

Pituitary adenylate-cyclase-activating polypeptide (PACAP) binding sites and PACAP/vasoactive intestinal polypeptide receptor expression in human pituitary adenomas.

Pituitary adenylate-cyclase-activating polypeptide (PACAP) stimulates release of several anterior pituitary hormones by interacting with PACAP receptors on pituitary cells. To learn more about the distribution and possible regulatory roles of PACAP and its receptors in human pituitary adenomas, we investigated the expression of vasoactive intestinal polypeptide (VIP) and PACAP binding sites using receptor autoradiography, PACAP and PACAP/VIP receptor (PVR) mRNAs by reverse transcription polymerase chain reaction (RT-PCR), conventional in situ hybridization, and catalyzed reporter deposition in situ hybridization (CARD-ISH) analyses. PACAP mRNA was expressed in normal human hypothalamus, which was used as a positive control, but not in pituitary adenomas. Receptor autoradiography showed PACAP types I and II binding sites in all groups of pituitary adenomas, except prolactinomas. The highest levels were present in gonadotroph and null cell adenomas. PVR-2 mRNA was expressed in normal pituitaries and in all groups of pituitary adenomas by RT-PCR, whereas PVR-1 and -3 mRNAs were expressed in all groups of pituitary adenomas, except for most prolactinomas. Conventional in situ hybridization studies with digoxigenin-labeled probes demonstrated weak staining for PVR-1, -2, and -3 mRNAs in most tissues. The CARD-ISH technique, which increased the sensitivity of the in situ hybridization method, also revealed PVR-2 mRNA expression in all adenomas, whereas PVR-1 and -3 mRNAs were detected in nearly all adenomas except for prolactinomas. The presence of PACAP mRNA in the hypothalamus, but not in normal anterior pituitary or in pituitary adenomas, and the differential expression of PVRs in adenomas indicate a selective regulatory endocrine and paracrine role of PACAP in normal and neoplastic anterior pituitary cells.

Adenoma↗

PubMed1998

Supersensitivity of atherosclerotic artery to constrictor effect of cigarette smoke extract.

OBJECTIVE: The aim of this study was to assess whether contractile response of arteries to aqueous component of cigarette smoke extract (CSE) may be modulated in atherosclerotic arteries. METHODS: Thoracic aortas were isolated from control rabbits and from 1.5% cholesterol-fed rabbits, all of which had visible advanced atheromatous surface changes on the aortas. CSE was prepared by bubbling main stream of smoke from one cigarette with filter into 2 ml of phosphate-buffered saline. The thoracic aortic rings were suspended in organ chambers and tested with CSE (0.01-3.0 microliters/ml buffer in the organ chamber) after precontraction with 0.1 mumol/l of phenylephrine (PE). RESULTS: The contractile response to CSE was significantly greater in atherosclerotic aortas than in control aortas (the maximal contraction expressed as % of the precontraction; control aortas 10.8 +/- 2.8%, atherosclerotic aortas 42.6 +/- 4.7%; P < 0.01). The magnitude of the precontractions by PE was not different between control and atherosclerotic aortas. Exogenous addition of superoxide dismutase (SOD) significantly attenuated the CSE-induced contraction in both control and atherosclerotic aortas and pretreatment of aortic rings with diethyldithiocarbamate to deplete of endogenous vascular CuZn-SOD activity potentiated the CSE-induced contraction in control aortas, while it had no significant effect in atherosclerotic aortas. The vascular SOD activity was significantly lower in atherosclerotic aortas than in control aortas ((U/mg protein): control aortas 38.2 +/- 3.3, atherosclerotic aortas 18.5 +/- 2.4; P < 0.01). CONCLUSION: These results indicate that atherosclerotic arteries may be supersensitive to the constrictor effect of superoxide anion derived from CSE. The decrease in endogenous vascular SOD activity may partly contribute to the increased susceptibility to oxidative stress in atherosclerotic arteries.

Animals↗

PubMed1998

Membrane properties of dissociated trigeminal mesencephalic neurons of the adult rat.

Electrophysiological properties of pseudounipolar trigeminal mesencephalic (Me5) neurons, dissociated from the rat brain, were studied under current-clamp conditions using the whole-cell configuration. Almost all Me5 neurons (37/38, 97%) exhibited a rapid adaptation in response to long depolarizing current pulses. Another firing type, slowly-adapting, was observed in only 3% of neurons (1/38). Most Me5 neurons (42/43) generated an overshooting action potential without a hump on the falling phase, and the remaining neuron (1/43) showed an action potential with a small hump. The action potential of Me5 neurons was reversibly blocked by 1 microM tetrodotoxin (TTX) or by removing Na+ from the bathing medium. When the outward K+ current was suppressed, two types of Ca2+ spikes were revealed. According to characteristic thresholds and sensitivity to inorganic (Ni2+, Cd2+) and organic (nifedipine, omega-conotoxin GVIA) Ca2+ channel blockers, these Ca2+ spikes were identified as T-type LTS (low-threshold spike) and L-type HTS (high-threshold spike). Also, a time-dependent inward rectification was observed in all Me5 neurons. It is concluded that the majority of Me5 neurons are of the rapidly-adapting type and generate a TTX-sensitive Na+ spike with negligible contribution of Ca2+, showing that the electrophysiological properties of Me5 neurons are more similar to those of CNS neurons than to those of PNS ganglion cells which have similar morphological features to Me5 neurons.

Action Potentials↗

PubMed1998

The effect of neuronal perturbation on the uptake of [18F]2-fluoro-2-deoxy-D-glucose in brain slices of the rat.

The positron-emitting radionuclide 18F was used to label 2-fluoro-2-deoxy-D-glucose producing [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG), and subsequently applied to sagittally-sectioned brain slices of the rat to evaluate the activity of neurons for up to 7 h in living brain slices. The amount of [18F]FDG uptake, which is proportional to the activity of neurons, was monitored every 20 min in five representative brain regions: frontal cortex, caudate-putamen, thalamus, hippocampus and cerebellum. The uptake of [18F]FDG linearly increased with time in these areas, showing constant glucose utilization. The rate of uptake was reversibly decreased by tetrodotoxin (TTX) regardless of brain region, but some uptake was insensitive to TTX. There was a tendency for the uptake to be decreased in Ca2+-free, 5 mM Mg2+ (2 mM EGTA) solution, suggesting some remaining functional synapses. Thus in sagittally-sectioned brain slices, most glucose metabolism is dedicated to neuronal firings and some metabolism to synaptic activities and to other functions of neurons and glial cells. When Cd2+ was applied to brain slices at 0.1-1 mM, the curve of [18F]FDG uptake irreversibly declined, indicating its toxic effect rather than its blocking action of transmitter release at synapses. The cerebellum was the most sensitive to Cd2+, and the caudate-putamen was the least sensitive. The present method, therefore, can be also used as a rapid examination system for checking neurotoxicity of substances.

Action Potentials↗

PubMed1998

Long-term functional outcome of suprasellar germinomas: usefulness and limitations of radiotherapy.

We investigated the long-term functional outcome of patients with suprasellar germinoma after radiotherapy to determine the usefulness and limitations of radiotherapy for these tumors. From among 54 cases of intracranial germ cell tumor at Kitasato University Hospital, 12 patients with suprasellar germinoma who were treated with radiotherapy but not chemotherapy retrospectively investigated for mental, hormonal and visual functions. The follow-up period ranged from 63 to 262 months (mean, 161.1 months). The mortality rate was zero and there was no recurrence of tumors. However, three patients treated with local irradiation alone showed metastasis to the ventricles or spinal cord. With regard to mental function, 50% of the patients showed remarkably low mental function after radiotherapy. With regard to pituitary hormonal function, deficiency of ADH, GH, ACTH, and TSH was documented in 75%, 41.7%, 16.7% and 8.3% of the patients, respectively, before radiotherapy. Prolactin was elevated in 50% of the patients. After radiotherapy, 91.7% needed hormone replacement. With regard to visual function, most patients showed an improvement or no change after radiotherapy. In conclusion, radiotherapy for suprasellar germinomas gave long-time survival. However, such radiotherapy may cause mental and pituitary hormonal dysfunction. Our results show that while radiotherapy is useful for treating suprasellar germinomas, its dose have some limitations.

Adolescent↗

PubMed1998

Preoperative superselective embolization of skull-base meningiomas: indications and limitations.

We evaluated the clinical significance of preoperative superselective embolization for skull-base meningiomas. The subjects consisted of 20 patients with skull-base meningiomas, and were classified into a preoperative embolized group and a non-embolized group. The volume of blood transfused during the operation, the length of the operative procedure and the neurological outcome were compared between the two groups. The results showed that, in tumors smaller than 6 cm, the blood lost during the operation was significantly less in the embolized group. In tumors larger than 6 cm, there was not difference in blood lost, perhaps because larger meningiomas tend to have tiny blood vessels that are unsuitable for preoperative embolization. There was no difference in the length of the operation between the two groups. The embolized group tended to show a better clinical outcome than the non-embolized group.

Adult↗

PubMed1998

Aberrant expression and phosphorylation of beta-catenin in human colorectal cancer.

The cytoplasmic domain of cadherins is known to associate with the intracellular proteins, catenins, which link cadherins to the actin-based cytoskeleton. In this study, we immunohistochemically investigated the expression of beta-catenin as well as E-cadherin and alpha-catenin in 86 human colorectal cancers, and we analysed their coexpression pattern and relationship to clinicopathological factors. In cancerous tissues, the frequency of reduced expression of beta-catenin (28 of 86, 33%) was similar to that of E-cadherin (19 of 86, 22%), but less than that of alpha-catenin (47 of 86, 55%). All three molecules were expressed strongly, as was the normal epithelium, in 36 cases (42%), whereas the rest (50 cases, 58%) showed reduction in one of the molecules. The reduction of beta-catenin expression was significantly correlated with dedifferentiation, Duke's stage, lymph node metastasis and liver metastasis. Next, we examined tyrosine phosphorylation in the protein complex immunoprecipitated with E-cadherin, as E-cadherin function is down-regulated by receptor-type tyrosine kinase in vitro. It was of interest that up-regulation of tyrosine phosphorylation of beta-catenin was more frequently observed in cancerous tissues than in the matching normal mucosa. These results suggest that beta-catenin may have important regulatory roles within an E-cadherin-mediated adhesion system in human colorectal cancers.

Cadherins↗

PubMed1998

Increased serum midkine levels during hemodialysis using heparin in chronic renal failure.

The heparin-binding growth factor midkine (MK) has been implicated in neuron growth, angiogenesis, and inflammation. In this study, to elucidate the involvement of MK in the development of pathologies associated with uremia, we examined the serum MK levels in patients receiving hemodialysis (HD) by a highly sensitive enzyme-linked immunoassay. Although no significant difference was found between control serum and serum before dialysis in HD patients, serum MK levels increased significantly at the early stage of HD sessions using heparin and gradually decreased after dialysis. In normal controls, intravenous administration of heparin induced a similar sudden increase of MK, but the subsequent decrease was also rapid. In an in vitro study, MK was released in time- and heparin-dose dependent manner from cultured vessels, but not from peripheral leukocytes. These results indicate that, in HD patients, MK is released mainly from endothelial cells immediately after administration of heparin during HD and disappears gradually from blood due to renal impairment. This phenomenon might affect some complications associated with HD.

Adult↗

PubMed1998

Biphasic regulation of transcription factor nuclear factor-kappaB activity in human endothelial cells by lysophosphatidylcholine through protein kinase C-mediated pathway.

Lysophosphatidylcholine (lysoPC), which is generated in oxidized LDL (Ox-LDL) and abundantly exists in atherosclerotic arterial walls, has been shown to alter various endothelial functions and induces several endothelial genes expressed in atherosclerotic arterial walls. Nuclear factor-kappa B (NF-kappaB), a pleiotropic transcription factor, plays an important role in regulation of expression of various genes implicated in atherosclerosis. We have previously reported that lysoPC transferred from Ox-LDL to endothelial surface membrane activates endothelial protein kinase C (PKC), leading to modulated endothelial functions. This study was aimed at determining whether lysoPC could modulate activity of transcription factors in cultured human umbilical vein endothelial cells (HUVECs) by using electrophoretic mobility shift assay. LysoPC was found to increase DNA-binding activity of NF-kappaB in HUVECs within 15 minutes, which peaked at 1 to 2 hours and subsequently declined to the baseline level at 6 hours. Lower concentrations (5 to 15 micromol/L) of lysoPC markedly increased NF-kappaB activity, but higher concentration (50 micromol/L) of lysoPC inhibited the activity. Phorbol 12-myristate 13-acetate, a potent activator of PKC, also augmented NF-kappaB activity in HUVECs, mimicking the effects of lysoPC; furthermore, calphostin C and chelerythrine chloride, specific PKC inhibitors, and alpha-tocopherol, a clinically potent PKC inhibitor, suppressed the lysoPC-induced NF-kappaB activation. These results indicate that lysoPC regulates NF-kappaB activity in a biphasic manner dependent on its concentrations and incubation time in human endothelial cells and the endothelial PKC activation may in part be involved in the lysoPC-induced NF-kappaB activation. Thus, the time course and the positive and negative biphasic regulatory actions of lysoPC on NF-kappaB activity in endothelial cells might exhibit a unique effect of lysoPC in arterial walls on the different stages of atherosclerosis.

Cells, Cultured↗

PubMed1998

Astemizole-induced torsades de pointes in a patient with vasospastic angina.

Astemizole (Hismanal), an antihistamine agent, has been reported to be associated with ventricular arrhythmias. In this paper we present a case of QT prolongation and torsades de pointes (TdP) in a 77-year-old woman who had been taking astemizole (10 mg/day) for 6 months because of allergic skin disease. At the time of admission, the serum concentration of astemizole and its metabolites was markedly elevated at 15.85 ng/ml, approximately 3 times the normal level. The patient was also taking cimetidine, a known inhibitor of cytochrome P-450 enzymatic activity, and during her admission was diagnosed as having vasospastic angina. To the best of our knowledge, this is the first report of astemizole-induced QT prolongation and TdP in Japan.

Aged↗