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Biomedical subjects

Y Ishida

Publications and source records attributed to Y Ishida.

At least 217 records · Page 12Linked to original sources
PubMed1998

Effects of local anesthetics on acetylcholine-induced desensitization of guinea pig ileal longitudinal muscle.

We investigated which of the major actions of local anesthetics (i.e., inhibition of phospholipase A2, interaction with Ca++ channels or blockade of receptor) was responsible for the inhibition of acetylcholine-induced desensitization in guinea pig ileal longitudinal muscle. Desensitization was inhibited by amine local anesthetics and related compounds in the order of potency quinacrine > chloroquine > tetracaine > procaine. Potent phospholipase A2 inhibitors, manoalide (1 microM) and p-bromophenacyl bromide (5 microM) had no effect on desensitization. The rank order of interaction of local anesthetics with Ca++ channels did not agree with the potency order of inhibition of desensitization. These data indicated that local anesthetics did not inhibit desensitization through their inhibition of phospholipase A2 or their interaction with Ca++ channels. Quinacrine, chloroquine, tetracaine and procaine inhibited [3H]N-methylscopolamine binding to solubilized membrane with pKi values of 7.03 +/- 0.10, 6.59 +/- 0.02, 5.40 +/- 0.10 and 5.03 +/- 0.04 and reduced receptor occupancy by agonist from 99.0% (without inhibitor) to 96.8%, 95.1%, 89.4% and 49.8%, respectively, under the conditions where each drug induced half-maximum inhibition of desensitization, indicating that they (except for procaine) did not effectively block muscarinic receptors. However, the combined dose-ratio test showed that some of these drugs (quinacrine and chloroquine) interacted noncompetitively at muscarinic receptors. Therefore, these drugs could have bound to an allosteric site on the receptor, modified agonist-receptor interaction and thus inhibited the pathway specific to the desensitization process.

Acetylcholine↗
PubMed1998

Finite element analysis of the lower lumbar neural arch under facet loading.

To evaluate the mechanical effect of the direction of facet load on the isthmus stresses of the lower lumbar neural arch, stress analyses were performed by using three-dimensional finite element models of isolated L4 and L5 vertebrae with particular emphasis on accurate discretization of the posterior elements. The bilateral symmetric or unilateral facet loads, with a constant magnitude, were applied within the sagittal and transverse planes. The largest maximal principal stress in the neural arch (the largest sigma(max)) tended to be qualitatively similar in L4 and L5. At the physiologic range, the largest sigma(max), observed on the anterior surface of the isthmus, was relatively insensitive to the sagittal plane loadings but sensitive to the transverse plane loadings. The values of the largest sigma(max) of L4 and L5 were low at the more frontally directed facet load. The magnitude and direction of the largest sigma(max) depended upon the facet loadings mainly on the ipsilateral side and partly on the opposite side. The results suggest that the direction of facet load, which may be characterized by the facet orientation, can have mechanical effects on the occurrence and direction of isthmic crack.

Computer Simulation↗
PubMed1998

Evaluation of the function of primary human hepatocytes co-cultured with the human hepatic stellate cell (HSC) line LI90.

Most bioartificial liver devices utilise primary hepatocytes alone although some have considered the use of non parenchymal cells in addition. However the effects of co-culture of human hepatocytes with different sinusoidal cell types has not been fully investigated. In this study we have examined the influence of co-culturing primary human hepatocytes with the human hepatic stellate cell (HSC) line, LI90. Cultures were monitored by light microscopy and on days 4, 8 and 14 urea synthesis and cytochrome P450 activity were measured. Morphologically LI90 cells proliferated to fill spaces between and into adjacent islands of hepatocytes. On day 14 cytochrome P450 activity in co-culture was significantly improved compared to hepatocytes cultured alone. By contrast, urea synthesis in hepatocytes was unaffected by single or co-culture. Therefore it can be concluded that a combination of primary human hepatocytes with LI90 cells is beneficial for growth and some stability of hepatocytes and may therefore be appropriate for seeding bioartificial liver devices.

Cell Division↗
PubMed1998

Impaired regional fatty acid uptake and systolic dysfunction in hypertrophied right ventricle.

UNLABELLED: Little information is available regarding the determinants of systolic contractile function of the hypertrophied right ventricle (RV). The purpose of this study was to clarify the relationship between myocardial metabolism and contractile function in the hypertrophied RV due to pulmonary hypertension (PH). METHODS: Iodine-123-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) and 99mTc-sestamibi (MIBI) SPECT were performed to calculate the RV-to-left ventricle (LV) tracer uptake ratio (RV/LV) in 21 patients with PH (6 with primary PH and 15 with chronic thromboembolic PH). The patients also underwent electron-beam CT to assess RV ejection function (RVEF) and percentage systolic wall thickening (%SWT) and right heart catheterization to measure mean pulmonary arterial pressure (mPAP). RESULTS: There were significant positive correlations between mPAP and MIBI-RV/LV (r = 0.89, p < 0.001) and between mPAP and BMIPP-RV/LV (r = 0.86, p < 0.001). However, 8 patients showed lower BMIPP-RV/LV than MIBI-RV/LV, indicating the impairment of myocardial fatty acid uptake in the RV. These patients had lower RVEF and %SWT compared to those with normal myocardial fatty acid uptake (RVEF = 28% +/- 10% compared to 40% +/- 9% and %SWT = 33% +/- 27% compared to 74% +/- 30%, respectively; p < 0.05 for both comparisons). Although mPAP did not differ between the groups, the RVEF-mPAP and %SWT-mPAP regression lines drawn from the patients with impaired myocardial fatty acid uptake were located below the lines from the patients with normal myocardial fatty acid uptake, suggesting disproportionately decreased RV myocardial contractility for a given mPAP in patients with impaired myocardial fatty acid uptake. The patients with the impaired fatty acid uptake in the RV had a significantly higher death rate (log-rank test, p < 0.05). CONCLUSION: The results from this preliminary study suggest that myocardial fatty acid uptake is impaired in the failing hypertrophied RV due to PH.

Fatty Acids↗
PubMed1998

Sympathetic reinnervation demonstrated on serial iodine-123-metaiodobenzylguanidine SPECT images after cardiac transplantation.

The transplanted heart is without autonomic nervous control in the early postsurgical period. We present here a case of cardiac transplantation in which 123I-metaiodobenzylguanidine (MIBG) SPECT and an exercise-loading test were used to monitor the sympathetic reinnervation. The distribution of myocardial 123I-MIBG uptake extended with time from 1 to 2 yr after surgery. However, functional improvement, estimated by the heart rate response to exercise, was not discernable during this period. The findings in this case suggest the feasibility of 123I-MIBG SPECT imaging in the serial monitoring of sympathetic reinnervation after transplantation and that scintigraphic evidence of reinnervation precedes functional recovery.

3-Iodobenzylguanidine↗
PubMed1998

In vitro and in vivo effects of KT6352, a derivative of indolocarbazole compounds, on murine megakaryocytopoiesis.

We investigated the in vitro and in vivo effects of KT6352, a derivative of indolocarbazole compound, on murine megakaryocytopoiesis. When serum-free megakaryocyte (Meg) colony assay was performed with 100 U/mL of recombinant mouse interleukin-3 (rmIL-3), the addition of 1x10(-11)M to 1x10(-9)M of KT6352 increased the number of Meg colonies. An additional increase of Meg colonies by KT6352 was observed in the serum-free culture containing rmIL-3 plus recombinant mouse interleukin-6 or rmIL-3 plus recombinant mouse stem cell factor. KT6352 did not stimulate Meg colony formation without rmIL-3. When KT6352 was administered intraperitoneally to normal BALB/c male mice at a dose of 10 mg/kg daily for 5 consecutive days, a 2.1-fold increase in the platelet count was observed on day 14, and the prolonged thrombocytopoiesis was detectable from 9 to 27 days after KT6352 administration. A marked increase in the white blood cell count was also observed from 5 to 14 days after KT6352 treatment. Before the gradual increase of platelet counts, 8 days after KT6352 administration, a marked increase in the number of colony-forming units of megakaryocytes (CFU-Megs) in bone marrow and spleen was observed, and a substantial increase in the number of splenic CFU-Megs was observed 14 and 23 days after KT6352 administration. Bone marrow Meg ploidy analysis by two-color flow cytometry showed a shift in the modal ploidy class from 16 to 32 and an increase in the frequency of 64 cells in KT6352-treated mice. These results suggest a possible therapeutic benefit of KT6352 in the management of thrombocytopenia.

Animals↗
PubMed1998

[Application of a semi-automatic ROI setting system for brain PET images to animal PET studies].

ProASSIST, a semi-automatic ROI (region of interest) setting system for human brain PET images, has been modified for use with the canine brain, and the performance of the obtained system was evaluated by comparing the operational simplicity for ROI setting and the consistency of ROI values obtained with those by a conventional manual procedure. Namely, we created segment maps for the canine brain by making reference to the coronal section atlas of the canine brain by Lim et al., and incorporated them into the ProASSIST system. For the performance test, CBF (cerebral blood flow) and CMRglc (cerebral metabolic rate in glucose) images in dogs with or without focal cerebral ischemia were used. In ProASSIST, brain contours were defined semiautomatically. In the ROI analysis of the test image, manual modification of the contour was necessary in half cases examined (8/16). However, the operation was rather simple so that the operation time per one brain section was significantly shorter than that in the manual operation. The ROI values determined by the system were comparable with those by the manual procedure, confirming the applicability of the system to these animal studies. The use of the system like the present one would also merit the more objective data acquisition for the quantitative ROI analysis, because no manual procedure except for some specifications of the anatomical features is required for ROI setting.

Animals↗
PubMed1998

Fluorine-18-fluorodeoxyglucose PET identification of cardiac metastasis arising from uterine cervical carcinoma.

Cardiac metastasis of uterine cervical carcinoma is rare. We describe a patient with a past history of uterine cervical carcinoma who presented with metastasis to the heart, lungs and distant lymph nodes 3 yr after surgery and chemotherapy. Since the patient complained of chest pain and demonstrated electrocardiogram abnormalities, we performed echocardiography, electron beam CT and MRI, which revealed a tumor in the right ventricular wall. The tumor was assessed by 67Ga scintigraphy and 18F-fluorodeoxyglucose (FDG) PET scanning. The mean differential 18F-FDG uptake ratio of the tumor was 7.9, suggesting malignancy, which was later confirmed by myocardial biopsy. Information about the extent of the tumor and partial necrosis within it was provided by 18F-FDG PET. Although both radionuclide imaging techniques also detected metastatic lesions in the lungs and lymph nodes, 18F-FDG PET scanning detected small lesions more sensitively than 67Ga scintigraphy.

Adult↗
PubMed1997

Methylmercury alters the tyrosination status of tubulin in the brains of acutely intoxicated rats.

Tyrosination/detyrosination, a post-translational modification at the carboxyl terminus of alpha-tubulin, was investigated in the brain cytosol fraction of rats treated with methylmercury (MeHg) chloride (10 mg/kg per day, for 7 days). The amount of detyrosinated tubulin species, determined as the incorporation of 14C-tyrosine at the carboxyl-terminal end of alpha-tubulin, was significantly decreased throughout the experimental period of MeHg intoxication. Furthermore, the activity of tubulin-tyrosine ligase, as well as the amounts of tyrosinatable tubulin determined and calculated by a method involving pancreatic carboxypeptidase A, also decreased in the latent and symptomatic periods. Tubulin-tyrosine carboxypeptidase activity did not change during the MeHg intoxication. The total amounts of alpha- and beta-tubulins, as determined by densitometry and immunoblotting, did not show significant changes during the intoxication. These results suggest that MeHg treatment may produce perturbation of cellular activities associated with the tubulin/microtubule system by altering the tyrosination status of tubulin in the rat brain.

Animals↗
PubMed1997

An extremely heat-stable extracellular proteinase (aeropyrolysin) from the hyperthermophilic archaeon Aeropyrum pernix K1.

An extracellular metalloproteinase, which we had designated aeropyrolysin, from the aerobic marine hyperthermophilic archaeon Aeropyrum pernix K1 (JCM 9820), was purified by ammonium sulfate precipitation, anionic exchange chromatography, and gel filtration chromatography. The purified enzyme was composed of a single polypeptide chain with a molecular mass of 52 kDa as determined by SDS-PAGE. The proteinase had a broad pH optimum (pH 5-9) with a maximal activity at pH 6-8 for azocasein hydrolysis. The optimum temperature for enzyme activity was 100 degrees C in the absence of 1 mM CaCl2 and 110 degrees C in the presence of 1 mM CaCl2. The enzyme activity was completely inhibited by EDTA and EGTA, indicating that it was a metalloproteinase. The enzyme was highly resistant to the denaturing reagents urea, guanidine-HCl, dithiothreitol, 2-mercaptoethanol and SDS. The enzyme also showed a high activity with the metalloproteinase specific substrate MOCAc-Pro-Leu-Gly-Leu-A2pr(Dnp)-Ala-Arg-NH2. The enzyme was extremely thermostable showing half-lives of 2.5 h at 120 degrees C and 1.2 h at 125 degrees C in the presence of 1 mM CaCl2. These results indicate that this enzyme is one of the most thermostable extracellular proteinases reported to date.

Caseins↗
PubMed1997

Effects of hypoxia on [Ca2+]i, pHi and myosin light chain phosphorylation in guinea-pig taenia caeci.

1. Hypoxia (achieved by bubbling with N2 instead of O2) reduces the force of a KCl (40 mM)-induced contracture to approximately 10% of the control value in guinea-pig taenia caeci. The underlying mechanism of this relaxation in response to hypoxia was investigated by measuring the major cell signalling parameters, intracellular Ca2+ concentration ([Ca2+]i) and myosin regulatory light chain (LC20) phosphorylation (MLC-P1), as well as intracellular pH (pHi), a factor often suggested to mediate hypoxic relaxation of muscle. 2. [Ca2+]i, measured using the ratiometric fluorescent dye fura-2, increased when 40 mM KCl was added to physiological saline solution (PSS) (peak value assigned 100%), and the steady state after 15 min was 92.8%. There were no detectable decreases in [Ca2+]i during hypoxia. 3. MLC-Pi, measured using isoelectric focusing-polyacrylamide gel electrophoresis and identified using Western blotting, increased from 9% of the total LC20 in Ca(2+)-free PSS to a peak value of 51% in 40 mM KCl-PSS. The steady-state value in hypoxia of 43% was not significantly different from that in control oxygenated conditions at the same point in time. 4. pHi, measured using the ratiometric fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxy-fluorescein (BCECF), under quiescent conditions (Ca(2+)-free PSS) was 7.23 and increased to 7.36 with 40 mM KCl. After imposition of hypoxia pHi remained unchanged despite the known increase in both lactate content and production. 5. As [Ca2+]i and MLC-Pi, key factors in activation, were not decreased by hypoxia and changes in pHi were minor, hypoxic relaxation in guinea-pig taenia caeci appears to be directly related to energy limitation rather than any oxygen-sensing mechanism.

Animals↗
PubMed1997

A case of internal carotid artery occlusion complicating embolization of the external carotid artery system.

A case of visual disturbance by embolization through the external carotid artery (ECA) after internal carotid artery (ICA) occlusion is reported. A 65-year-old female presented left ICA occlusion 14 years ago. She was admitted with acute deterioration of left visual acuity. Ophthalmologically, the retinal central artery was occluded. Cerebral angiography disclosed an irregular wall at the left ICA stump and stenosis of the maxillary artery. Carotid endarterectomy of the common carotid artery, ECA and residual ICA was performed and atheromatous plaque with ulceration was removed. The postoperative course was uneventful. We discuss cases of ICA occlusion in relation to visual impairment.

Aged↗
PubMed1997

Simplified method for the determination of 25-hydroxy and 1alpha,25-dihydroxy metabolites of vitamins D2 and D3 in human plasma. Application to nutritional studies.

A simplified method for the determination of 25-hydroxy and 1alpha,25-dihydroxy metabolites of vitamins D2 and D3 in human plasma was developed. Plasma samples were deproteinizated and applied to a Bond Elut C18OH cartridge to separate 25-hydroxyvitamin D (25-OH-D) and 1alpha,25-dihydroxyvitamin D [1,25(OH)2D] fractions. The 25-OH-D fraction was purified by a Bond Elut C18 cartridge and 25-OH-D2 and 25-OH-D3 were assayed by HPLC using a Zorbax SIL column. The 1,25(OH)2D fraction obtained above was subsequently applied to HPLC using a Zorbax SIL column to separate 1,25(OH)2D2 and 1,25(OH)2D3 fractions which were determined by a radioreceptor assay (RRA) using calf thymus receptor. The method was applied to nutritional studies.

25-Hydroxyvitamin D 2↗
PubMed1997

Effects of area postrema lesion and abdominal vagotomy on interleukin-1 beta-induced norepinephrine release in the hypothalamic paraventricular nucleus region in the rat.

Peripherally administered interleukin-1 beta (IL-1 beta) has been shown to increase extracellular norepinephrine (NE) concentration in the paraventricular nucleus (PVN) of the hypothalamus. The present study was carried out using an in vivo microdialysis technique in conscious rats in order to examine the possible involvement of the area postrema (AP) and the abdominal vagal afferent nerves in this effect. Extracellular NE concentrations in the PVN region were measured by high performance liquid chromatography with electrochemical detection. In AP-lesioned or abdominal-vagotomized rats, the NE increase was significantly attenuated compared to that in sham-operated rats; this reduction was greater in abdominal-vagotomized rats than in AP-lesioned rats. The results suggest that the AP as well as the abdominal vagal afferent nerves is involved in intraperitoneal (i.p.) administered IL-1 beta-induced NE release in the PVN region.

Abdomen↗