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Biomedical subjects

I Ishii

Publications and source records attributed to I Ishii.

At least 37 records · Page 2Linked to original sources
PubMed1998

Metabolism of dacarbazine by rat liver microsomes contribution of CYP1A enzymes to dacarbazine N-demethylation.

The N-demethylation of dacarbazine in liver microsomes was significantly increased by treatment of rats with beta-naphthoflavone, dexamethasone, or phenobarbital. However, the extent of increase in the N-demethylation observed in beta-naphthoflavone-treated rats was much greater than that observed in dexamethasone-treated rats. A good correlation between N-demethylation of dacarbazine and O-deethylation of phenacetin was observed when a low concentration of phenacetin was used. Furthermore, the activity of dacarbazine N-demethylase in rat liver microsomes was highly correlated with the amounts of CYP protein immunochemically determined with anti-rat CYP1A2 antibodies. In addition, antibodies to rat CYP1A2, and furafylline and alpha-naphthoflavone, which are known inhibitors of CYP1A enzymes, exhibited inhibitory effects on dacarbazine N-demethylation. These results indicated that CYP1A enzymes may be responsible for N-demethylation of dacarbazine in rat liver microsomes.

Animals↗
PubMed1998

Steroid hydroxylation by human fetal CYP3A7 and human NADPH-cytochrome P450 reductase coexpressed in insect cells using baculovirus.

Human fetal CYP3A7 and human NADPH-cytochrome P450 reductase were coexpressed in insect cells, TN-5, infected with a recombinant baculovirus carrying both cDNAs. The expression of reductase in TN-5 cells was shown to be sufficient for the CYP3A7 dependent 16 alpha-hydroxylation of dehydroepiandrosterone. However, the extra addition of cytochrome b5 and phospholipid was necessary to obtain a maximal activity of CYP3A7 catalyzing the reaction. CYP3A7 expressed in TN-5 cells was capable of metabolizing testosterone, cortisol and dehydroepiandrosterone 3-sulfate as well as dehydroepiandrosterone. The apparent Vmax for 6 beta-hydroxylations of testosterone was similar to that obtained for 6 beta-hydroxylation of cortisol (2.9 versus 2.5 nmol/nmolP450/min). In contrast, the apparent Vmax for 16 alpha-hydroxylation of dehydroepiandrosterone and its 3-sulfate were 20 and 2 times greater than those observed for steroid 6 beta-hydroxylations, respectively (67.5 and 5.8 versus 2.5-2.9 nmol/nmol P450/min). On the other hand, the apparent K(m) for 6 beta-hydroxylations of testosterone and cortisol were greater than those for 16 alpha-hydroxylations (120 and 860 versus 46-58 microM). Thus, CYP3A7 was active for steroid 6 beta-hydroxylations and 16 alpha-hydroxylations, but there were greater differences in Vmax/K(m) ratios between these reactions.

Animals↗
PubMed1998

[A case of choroidal malignant melanoma in which 123I-IMP scintigraphy was useful for diagnosis].

A case of choroidal malignant melanoma in which N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) scintigraphy was useful for diagnosis is reported. A 62-year-old man first visited our hospital 3 years ago complaining of decreases in left eyesight. CT showed a tumor with an arcuate high attenuation area on the aural side of the optic disk in the left eye. A crescent high attenuation area, evidence of retinal detachment, was also observed on the nasal side of the optic disk. T1-weighted MR images showed low signal intensity in most of the tumor and a high signal intensity area was seen in the center, T2-weighted MR images showed homogeneous and marked low signal intensity area. Differentiation from a hematoma or a vascular tumor associated with bleeding was impossible based on CT and MRI. However, because late-phase images obtained on 123I-IMP scintigraphy showed marked high accumulation in an area corresponding to almost the entire left eye, left eye enucleation was undertaken under a diagnosis of malignant melanoma. Histopathologic examinations showed tumor growth mainly in the subretinal area. The melanin content of the tumor was high in the periphery and relatively low in the center. Infiltration was observed into the sclera and around the vortex vein outside the eyeball, but this change could not be detected by CT or MRI. 123I-IMP scintigraphy was useful not only for qualitative diagnosis of choroidal malignant melanoma, but for the determination of the extent of the lesion as well.

Choroid Neoplasms↗
PubMed1998

Stimulation of cholesterol release from rabbit foam cells by the action of a new inhibitor for acyl CoA:cholesterol acyltransferase (ACAT), HL-004.

A new inhibitor of acyl CoA:cholesterol acyltransferase (ACAT), HL-004 [N-(2, 6-diisopropylphenyl)tetradecylthioacetamide], suppressed the synthesis of cholesterol [14C]oleate at 10(-9) approximately 10(-7) M in a concentration-dependent manner in both THP-1 cell-derived macrophages and foam cells prepared from aortic intima of rabbits fed a high cholesterol diet. Incorporation of [3H]cholesterol oleate-beta very low density lipoproteins was not inhibited by HL-004 at 10(-9) approximately 10(-7) M. Release of radioactivity from the cells loaded with [3H]cholesterol oleate-beta very low density lipoproteins was increased by the inhibition of ACAT activity with HL-004. HL-004 did not affect on acid and neutral cholesterol esterases. As a result, cholesterol ester content in foam cells decreased. These data suggested that HL-004 decreases cholesterol ester in foam cells by increasing the release of cholesterol and therefore might suppress atherosclerotic lesions.

Acetanilides↗
PubMed1997

Malignant transformation by overproduction of translation initiation factor eIF4G.

N4G3, a cell line that overexpresses translation initiation factor eIF4G, one of the components of eIF4F, was made by stable transfection of the human eIF4G cDNA into NIH3T3 cells. The cells expressed 80-100 times greater levels of eIF4G mRNA than did NIH3T3 cells. N4G3 cells formed transformed foci on a monolayer of cells, showed anchorage-independent growth, and formed tumors in nude mice. These results indicate that overexpression of eIF4G caused malignant transformation of NIH3T3 cells. It is also known that overexpression of eIF4E, another component of eIF4F, causes transformation of NIH3T3 cells. However, there was no difference in the amount of eIF4E protein between N4G3 and NIH3T3 cells, indicating that cell transformation does not involve a change in eIF4E levels. The results may be due to an effect of eIF4G on translational control of protein synthesis directed by mRNAs having long 5'-untranslated region.

3T3 Cells↗
PubMed1997

Alanine exchanges of polar amino acids in the transmembrane domains of a platelet-activating factor receptor generate both constitutively active and inactive mutants.

To determine ligand-binding sites of a platelet-activating factor (PAF) receptor, alanine-scanning mutagenesis was carried out. All 23 polar amino acids in the putative 7-transmembrane (TM) domains of a guinea pig PAF receptor were individually replaced with alanine. The ligand-binding properties of mutant receptors were determined after transient expression in COS-7 cells. Mutants in TM II (N58A, D63A), TM III (N100A, T101A, S104A) and TM VII (D289A) displayed higher PAF-binding affinities than seen with the wild-type receptor. In contrast, mutants in TM V (H188A), TM VI (H248A, H249A, Q252A), and TM VII (Q276A, T278A) showed lower affinities. Representative mutants were then stably expressed in Chinese hamster ovary cells to observe PAF-induced cellular signals (arachidonate release, phosphatidylinositol hydrolysis, adenylyl cyclase inhibition). An N100A mutant with the highest affinity was constitutively active and was responsive to lyso-PAF, an inactive derivative of PAF. One nanomolar PAF induced no signals in low affinity mutants, an EC50 value for the wild-type receptor. Three histidines (His-188, His-248, His-249) might form a binding pocket for the phosphate group of PAF, since zinc effectively inhibited ligand binding. Based on these results, a three-dimensional molecular model of PAF and its receptor was generated using bacteriorhodopsin as a reference protein.

Alanine↗
PubMed1997

The differential involvement of von Willebrand factor, fibrinogen and fibronectin in acute experimental thrombosis in rat cerebral and mesenteric microvessels.

Arterial thrombi are primarily composed of platelets. Platelets are bound to injured endothelial cells, sub-endothelial matrices, and other platelets by a range of adhesive proteins. Some of these reactions are governed by shear forces. The role of adhesive proteins in the pathogenesis of arterial thrombosis is not fully understood. The aim of this study was to examine the involvement of von Willebrand factor (vWF), fibrinogen (Fg), and fibronectin (FN) in the formation of microvascular thrombi in vivo using a helium-neon laser-induced thrombosis method. Transmission electron microscopy demonstrated that laser irradiation resulted in platelet-rich thrombosis in arterioles and venules, and revealed that this occurred in the absence of endothelial denudation. The mean wall shear rates in mesenteric arterioles and venules were 641 +/- 40 and 280 +/- 20 s-1, respectively. Shear rates increased approximately fivefold in arterioles and tenfold in venules during the formation of occlusive thrombi. Antibody to vWF inhibited thrombosis in arterioles and venules. Antibodies to Fg and FN inhibited thrombosis in venules but not in arterioles. These results confirm that vWF, Fg and FN were involved in thrombogenesis in vivo and demonstrated that significantly higher shear rates were required for the reactions involving vWF than those involving either Fg or FN.

Adhesiveness↗
PubMed1997

[Multidrug-resistance by induction of inactivation for anti-cancer drugs].

There are several major groups of multidrug resistance mechanisms. 1) The multidrug resistant phenotype. 2) Glutathione S-transferences (GST) and detoxification mechanisms. 3) Topoisomerase I and II. 4) DNA repair. 5) Drug activation by cytochrome P450 (P450). In this article the biochemical functions of GST and P450 are described to show how individual enzymes contribute to resistance to carcinogens and anti-tumor drugs. Cancer cell lines indicated resistant to anti-cancer drugs, such as mitomycin C, doxorubicin, tamoxifen, cyclophosphamide and their derivatives, by a high activity of GST and a low activity of P450 in general. However, the mechanism of change of these enzyme activities is complicated and different in each drug. We show the study on the mechanism of multidrug resistance using cancer cell lines.

Animals↗
PubMed1997

Nucleotide sequence of pi class glutathione S-transferase in human fetal liver.

The GST Fpi and GST Ppi, pi class glutathione S-transferase (GST), were purified from human fetal livers and placentas, respectively. Both GST enzymes were indistinguishable each other in their subunit molecular weights, immunochemical properties and substrate specificities. Three clones (pFGP-1, pFGP-2 and pFGP-3) coding for the pi class GST purified from fetal livers were isolated from a human fetal liver cDNA library. The full-length clone encodes a polypeptide comprising 210 amino acid including the initiator methionine. All of these cDNA clones were nearly identical to a human placental cDNA clone, pGpi 2. The pFGP-1 cDNA had only a single base transition accompanied by an amino acid transition in the coding region, at position 313. The pFGP-2 and pFGP-3 cDNAs were also nearly identical to pGpi 2 cDNA, having only a single silent C-->T transition in the coding region, at position 555.

Amino Acid Sequence↗
PubMed1996

[Influence of multiple-dose administration of cefetamet pivoxil on blood and urinary concentrations of carnitine and effects of simultaneous administration of carnitine with cefetamet pivoxil].

Cefetamet pivoxil (CEMT-PI), a drug of pivaloyloxymethyl group, was investigated for its impact on the carnitine blood homeostasis and renal excretion upon administering CEMT-PI alone, and CEMT-PI simultaneously with carnitine. 500 mg of CEMT-PI (group A) and 500 mg of CEMT-PI and an equimolar amount (200 mg of carnitine) of levocarnitine chloride (group B) were administered twice a day for 7 and 1/2 consecutive days to 5 healthy volunteers (group A) and 3 healthy volunteers (group B). No serious side effects nor abnormal values in physical and laboratory tests were observed throughout the study in both groups. During the treatment period, plasma total carnitine decreased slowly down to 25.5 microM (group A) and 38.8 microM (group B) and plasma free carnitine reached steady state levels at 17.7 microM (group A) and 29.2 microM (group B) on day 5. These concentrations represent 45 and 37% in group A, 66 and 58% in group B of the average pre-treatment baseline levels. Plasma pivaloylcarnitine quickly reached plateau levels of 6.12 microM (group A) and 4.05 microM (group B) on day 4. After treatment stop, plasma total and free carnitine returned to the pretreatment baseline level within 5 days (group A) and 3 days (group B), and plasma pivaloylcarnitine was detectable until day 7 of the treatment-free follow up in both groups. Although carnitine was given concurrently at a dose equimolar to the ingested amount of pivalic acid in group B, the plasma total and free carnitine exhibited a decrease. This was considered attributable to the fact that the bioavailability of carnitine is as low as 16% when administered orally, which is considerably less compared to the 55% bioavailability of cefetamet pivoxil.

Administration, Oral↗
PubMed1995

Cholesterol metabolism in monocyte-derived macrophages from macrophage colony-stimulating factor administered rabbits.

The metabolism of beta-very-low-density lipoproteins (beta-VLDL) in macrophages from the blood monocytes of rabbits, which had been administered macrophage colony-stimulating factor (M-CSF) in vivo, was investigated in order to clarify the mechanism of the suppressive effect of M-CSF on cholesterol accumulation in macrophages. Cholesterol ester content after incubation with beta-VLDL, and [3H]cholesterol oleate-beta-VLDL incorporation remarkably increased in cultured macrophages from blood monocytes in the high cholesterol diet control group compared to those in the normal diet control group. Those in macrophages from M-CSF-treated groups, both normal diet and high cholesterol diet, were the same as in the normal diet control group. The ratio of released [3H]cholesterol to incorporated [3H]cholesterol oleate-beta-VLDL in macrophages from control was smaller than that from the M-CSF group. The acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity was enhanced in the high cholesterol diet groups, and the activity in M-CSF-treated groups decreased. The neutral cholesterol esterase activity was enhanced in the M-CSF-treated groups compared with that in the non-treated control groups. These results suggest that high cholesterol diet induced further cholesterol esterification and that M-CSF treatment enhanced cholesterol clearance in macrophages.

Animals↗
PubMed1995

Genetic differences of lipid metabolism in macrophages from C57BL/6J and C3H/HeN mice.

Cholesterol metabolism in macrophages from atherosclerosis-prone C57BL/6J mice was compared with that in macrophages from atherosclerosis-resistant C3H/HeN mice. Plasma total cholesterol levels of both types of mice were significantly increased, but HDL cholesterol level was increased only in C3H/HeN mice when a high-cholesterol diet (1% cholesterol) was fed for 5 weeks. After incubation of macrophages from male and female mice on the high-cholesterol diet with beta-VLDL for 24 hours, cholesterol content in macrophages from C57BL/6J was approximately 1.5- to 2.0-fold higher than in those from C3H/HeN mice. [3H]Cholesterol oleate-beta-VLDL incorporation into macrophages from C57BL/6J mice on the high-cholesterol diet was greater than incorporation into those from C3H/HeN mice. The release of [3H]cholesterol from macrophages from C57BL/6J mice on the high-cholesterol diet was one seventh that from macrophages from C57BL/6J mice on the basal diet or that from macrophages from C3H/HeN mice on the basal or high-cholesterol diet. Acid cholesterol esterase activity was almost the same in macrophages from any group. Acyl CoA:cholesterol acyltransferase activity in macrophages from C57BL/6J mice on the high-cholesterol diet increased compared with that from macrophages from C57BL/6J mice on the normal diet. Neutral cholesterol esterase activity in macrophages from C57BL/6J mice was about half of that in macrophages from C3H/HeN mice independent of the type of diet. There were no sex differences in these metabolisms. Considered with our previous data, these results suggested that a high-cholesterol diet may cause metabolic changes to accumulate cholesterol ester in macrophages from C57BL/6J mice in accordance with genetic abnormalities.

Animals↗
PubMed1995

Regulation of neutral cholesterol esterase activity by phospholipids containing negative charges in substrate liposome.

The effect of phospholipids on cholesteryl ester hydrolysis by neutral cholesterol esterase in alveolar macrophages was studied. Among the phospholipids used as emulsifiers, those with a negative charge, such as phosphatidylserine, phosphatidic acid, phosphatidylinositol, and cardiolipin, gave a higher level of hydrolysis by neutral cholesterol esterase than other less negatively charged phospholipids, such as phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, and sphingomyelin. Phospholipase D treatment of liposomes emulsified with phosphatidylcholine produced phosphatidic acid and enhanced cholesteryl ester hydrolysis. Phospholipase A2 treatment produced lysophosphatidylcholine and decreased the hydrolysis. The hydrolysis of cholesteryl ester in lipid droplets obtained from cholesterol-laden macrophages elicited by thioglycollate in the rat peritoneal cavity was low compared to artificial liposomes emulsified with phosphatidylcholine. The reason for this was speculated to be that lipid droplets were low in total phospholipids and poor in phospholipids with strong negative charges but rich in phosphatidylethanolamine and sphingomyelin. These results suggest that the polar heads of phospholipids may play an important role in cholesteryl ester hydrolysis by neutral cholesterolesterase.

Animals↗
PubMed1994

Possible involvement of GTP-binding proteins in 1 alpha,25-dihydroxyvitamin D3 induction of tissue transglutaminase in mouse peritoneal macrophages.

Induction of transglutaminase was analyzed based on increases in the maximal enzymic activity and in the Northern blots of mRNA during culture of mouse resident peritoneal macrophages with active forms of hydrophobic vitamins and steroid hormones. The enzyme was induced by 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3) or retinoic acid but not by steroid hormones. The induction by 1 alpha,25-(OH)2D3 was characterized by its slow onset and marked synergism with retinoic acid induction. The induction was enhanced by protein kinase activators such as cholera toxin and phorbol 12-myristate 13-acetate but largely inhibited by pertussis toxin treatment of cells. It is suggested that pertussis toxin-linked and protein kinase-related signaling would mediate the 1 alpha,25-(OH)2D3-induced enzyme gene expression.

Animals↗
PubMed1994

Impact of monocyte colony-stimulating factor upon beta-very low density lipoprotein (beta-VLDL) cholesterol metabolism in tetradecanoyl phorbol acetate-derived THP-1 cells.

The effect of monocyte colony stimulating factor (M-CSF) on the beta-very low density lipoprotein (beta-VLDL) metabolism in THP-1 cells (human leukemia cell line) was studied. THP-1 cells treated with M-CSF decreased Latex Bead phagocytosis, but the cells incubated with 12-tetradecanoyl-phorbol-13-acetate (TPA) enhanced phagocytosis 2.5-fold. Binding activity of 125I-M-CSF to THP-1 cells was higher than that in THP-1 cells elicited with TPA. THP-1 cells incubated with M-CSF before TPA treatment were designated MT macrophages, and those incubated with M-CSF after TPA treatment were called TM macrophages. When these cells were incubated with beta-VLDL, the cholesterol ester content in MT macrophages was less than in TM macrophages. The uptake of [3H]cholesterol oleate-beta-VLDL in MT macrophages was the same as in TM macrophages. The released radioactivity from [3H]cholesterol oleate-beta-VLDL loaded MT macrophages was higher than that from TM macrophages. Acid cholesterol esterase activity and ACAT activity were the same in both types of macrophages. Neutral cholesterol esterase activity was higher in MT than in TM macrophages. These results suggested that beta-VLDL-induced cholesterol ester deposition in THP-1 cells-derived macrophages was suppressed by M-CSF, when M-CSF acted at the stage of monocytes (THP-1 cells), and that the reduction of cholesterol ester might be due to enhanced release of cholesterol from the cells with high neutral cholesterol esterase activity.

Cell Line↗
PubMed1994

Retinoic acid-induced gene expression of tissue transglutaminase via protein kinase C-dependent pathway in mouse peritoneal macrophages.

Culture of mouse resident peritoneal macrophages with retinoic acid resulted in increased expression of the tissue transglutaminase gene as revealed by increases in the maximal velocity of the enzyme reaction in the cytosol and in the enzyme mRNA level. Protein kinase C-activating phorbol esters and okadaic acid, both of which were without effect on the enzyme induction by themselves, enhanced the retinoic acid-induced gene expression, which was in turn inhibited partially by pertussis toxin and totally by inhibitors of protein kinase C in either the presence or absence of phorbol esters. Retinoic acid was more effective in the "conditioned" medium, in which macrophages had been cultured for a time longer than 4 h, than in the "fresh" medium. The retinoic acid induction of transglutaminase was accompanied by increased phosphatidylinositol turnover and phosphatidic acid generation, which were efficiently suppressed by prior exposure of cells to pertussis toxin. It is likely that certain autocrine factor(s) liberated during culture of macrophages may afford conditions favorable for retinoic acid-induced gene expression, presumably via pertussis toxin-sensitive G protein-mediated phosphoinositide metabolism leading to activation of protein kinase C.

Animals↗
PubMed1994

Intense accumulation of Tl-201 in carcinoid tumor of the thymus.

A case of carcinoid tumor of the thymus is presented in which Tl-201 SPECT demonstrated intense accumulation in the lesion. Conventional chest radiograph and CT scan in a 66-year-old man who had been experiencing cough and pain at the anterior part of the chest revealed a tumor in the anterior mediastinum, suggesting a thymoma. The tumor was clearly delineated in both early and delayed SPECT studies. On the delayed scan, the tumor was more prominently visualized with an extremely high uptake ratio of the lesion compared to the contralateral background; therefore, the tumor was believed to possess very prolonged Tl-201 retention. The pathological and immunohistochemical examinations confirmed that the area of intense Tl-201 uptake was rich in viable cells.

Aged↗