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S Sakuma

Publications and source records attributed to S Sakuma.

At least 145 records · Page 8Linked to original sources
PubMed1995

Hypoxia-induced vascular endothelial growth factor expression in normal rat astrocyte cultures.

Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen, which also enhances vascular permeability. Because this angiogenic factor has been suggested to play a role in brain tumor biology, we have begun to investigate the regulation of VEGF expression in cultures of rat type I astrocytes. In this report, we have focused on the influence of hypoxia on VEGF expression. Under standard in vitro conditions (21% O2) VEGF expression in astrocytes in barely detectable by northern analysis. However, after exposure to 0.2% O2 for as little as 3 h VEGF mRNA levels are markedly increased reaching a maximum by approximately 8 h of exposure. Treatment of astrocytes with CoCl2 or desferrioxamine results in a similar induction of VEGF, suggesting that the oxygen sensor regulating VEGF expression in astrocytes is a heme-containing molecule. Although acute treatment with TPA (6 h) induces VEGF expression, chronic exposure to TPA (24 h) to deplete PKC activity does not reduce the hypoxia-induced VEGF expression. These data indicate that VEGF induction in astrocytes can proceed through PKC-dependent and -independent pathways. Furthermore, chronic exposure to TPA or treatment with herbimycin A results in the enhancement of the hypoxia-mediated increase in VEGF mRNA levels. These results suggest that PKC and herbimycin-sensitive tyrosine kinase may serve as negative regulators of the hypoxia-activated signal transduction pathway that leads to the induction of VEGF expression. However, treatment of astrocytes with the nonspecific kinase inhibitors H7 and H8 reduced the level of VEGF induction by hypoxia, indicating that some type of kinase activity is required in this signaling pathway.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Diagnostic usefulness of chest computed radiography--film versus cathode-ray tube images.

Seventy-one plain chest images obtained by computed radiography (CR) with an imaging plate were interpreted on film and two kinds of cathode-ray tube (CRT) monitors installed separately at two facilities (1,024 x 1,536 pixels, 8 bits, and 1,024 x 1,280 pixels, 10 bits) by 20 radiologists and four chest internists. The clinical categories of these 71 cases included pulmonary nodules and interstitial abnormalities. Image reading sessions were held over a total of 4 days, ie, 2 days and then another 2 days, 3 weeks later. Twenty-four observers formed four groups with six members each. Two groups read either films or CRT images at one of the two facilities. In the second experiment, 26 of 71 images were compressed at 10:1, 19 of 71 were compressed at 20:1, and 26 were not compressed. Analyses of the areas under the receiver-operating characteristic curves showed no significant differences in detection of pulmonary abnormalities between film and CRT. In detecting interstitial pulmonary abnormalities, film was more sensitive than CRT monitor. There were no significant differences in observers' performances between the two different kinds of CRT workstation. Subjective evaluation of image quality showed that images irreversibly compressed to the ratios of 10:1 and 20:1 were inferior to original images. Although further considerations are needed with regard to spatial resolution requirements, image processing, and image compression, the utilization of CR CRT image as a substitute for CR film image will be possible.

Data Display↗
PubMed1995

Effects of fatty acids and fatty acyl CoA esters on Cu(2+)-induced conversion of xanthine dehydrogenase to oxidase in rabbit liver.

Effects of various fatty acids and fatty acyl CoA esters on Cu(2+)-induced conversion of xanthine dehydrogenase to oxidase in rabbit liver were examined. Cu2+ (2-10 microM) brought about the conversion of xanthine dehydrogenase to oxidase in a dose-dependent manner. Oleic, arachidonic, eicosapentaenoic, and docosahexaenoic acids (50-200 microM) prevented the conversion of xanthine dehydrogenase to oxidase catalyzed by 6 microM-Cu2+. The effect of these four fatty acids was concentration-dependent, whereas palmitic, stearic, and linoleic acids had no effect on the conversion of xanthine dehydrogenase to oxidase at the same concentration range. On the other hand, palmitoyl, linoleoyl, and arachidonoyl CoAs elicited the inhibition of 6 microM-Cu(2+)-induced conversion of xanthine dehydrogenase to oxidase at concentrations of 50, 100, and 200 microM. These results suggest that oleic, arachidonic, eicosapentaenoic and docosahexaenoic acids, and fatty acyl CoAs have the potential to inhibit the conversion of xanthine dehydrogenase to oxidase in rabbit liver.

Acyl Coenzyme A↗
PubMed1995

Effects of fatty acyl coenzyme A esters on lipoxygenase and cyclooxygenase metabolism of arachidonic acid in rabbit platelets.

The effects of fatty acyl coenzyme A (CoA) esters (palmitoyl-, stearoyl-, oleoyl-, linoleoyl- and arachidonoyl--CoA) on the activities of lipoxygenase and cyclooxygenase in rabbit platelets were examined. Palmitoyl-, stearoyl-, oleoyl- and linoleoyl- CoA were potent inhibitors of platelet lipoxygenase activity. In addition to the lipoxygenase, the four fatty acyl-CoA esters elicited inhibitory activity on platelet cyclooxygenase, although the inhibition was a little weaker. The CoA derivative of the icosanoid precursor arachidonic acid (AA) showed little inhibition on lipoxygenase and cyclooxygenase. Palmitic, stearic and oleic acids had little or no effect on lipoxygenase and cyclooxygenase, in contrast with their CoA derivatives. Linoleic acid was more potent than linoleoyl-CoA as an inhibitor of the cyclooxygenase, but it was a weak inhibitor of the lipoxygenase. These results suggest that the CoA derivatives of palmitic, stearic, oleic and linoleic acids have the potential to modulate both platelet lipoxygenase and cyclooxygenase activities and may have functional effects within platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1995

Immunohistochemical observations on the kinetics of macrophages and myofibroblasts in rat renal interstitial fibrosis induced by cis-diamminedichloroplatinum.

It has been speculated elsewhere that growth factors produced by macrophages in response to tissue damage induce a modulation of pre-existing fibroblasts into myofibroblasts, leading to fibrosis. The development of these cells in cis-diamminedichloroplatinum (CDDP)-induced rat renal interstitial fibrosis was observed immunohistochemically. In the cortico-medullary junction, nuclear changes and epithelial necrosis of the proximal renal tubule (mainly the P3 segment) were seen on days 1 and 4 after a single dose (6 mg/kg body weight) of CDDP, and regenerating epithelium appeared on day 7. Gradually developing fibrosis was observed around the affected tubules on days 14 and 28. The increase in fibrosis was confirmed by histometrical analysis. The number of ED-1 (primary antibody) positive macrophages reached a peak in the affected cortico-medullary junction on day 7 and this was accompanied by an increase in muscle actin-positive myofibroblasts. On days 14 and 28, macrophages had declined in number, but the number of muscle actin-positive myofibroblasts in the fibrotic area was still high as compared with control values. Cytoplasmic myofilaments were observed in myofibroblasts by electron microscopy. These findings suggest that the myofibroblasts participate in renal interstitial fibrosis in the rat, and that their appearance may be related to macrophage infiltration in response to tubular injury, at least in the early stages of fibrosis.

Actins↗
PubMed1995

Expression of gicerin in development, oncogenesis and regeneration of the chick kidney.

Neurite outgrowth factor, which promotes neurite extension from neuronal cells, is an extracellular matrix glycoprotein belonging to the laminin family. Gicerin is a protein that binds neurite outgrowth factor. Its cDNA cloning has revealed that it is a novel cell adhesion molecule belonging to the immunoglobulin super-family. Functional analysis demonstrates that gicerin possesses homophilic binding activity as well as heterophilic binding activity with neurite outgrowth factor. We examined the role and expression of neurite outgrowth factor and gicerin in chick kidney during development. In the embryonic kidney, gicerin was found to be highly expressed both on ureteric bud cells and metanephrogenic mesenchymal cells, when the mesenchymal cells become condensed to be converted into polarized epithelial cells. In the adult kidney, the expression of gicerin was decreased and restricted to the glomerulus, proximal tubule and medullary loop. On the other hand, neurite outgrowth factor was constitutively expressed in the basement membranes of tubules and the matrices of glomeruli during development. As some molecules which are expressed during embryogenesis and suppressed after maturation are re-expressed in tumor cells or tissues during regeneration, we also examined the expression of gicerin in chicken Wilms' tumor and regenerating kidney in interstitial nephritis. Gicerin was remarkably upregulated in Wilms' tumor and re-expressed in collecting ducts recovering from interstitial nephritis. These findings suggest that gicerin could play a role not only in normal renal development but also in oncogenesis and regeneration.

Animals↗
PubMed1995

Intravenous injection of rabbit apolipoprotein A-I inhibits the progression of atherosclerosis in cholesterol-fed rabbits.

The effects of intravenous injection of purified rabbit apoA-I on the progression of aortic atherosclerosis in cholesterol-fed rabbits were examined. In experiment 1, 28 rabbits were equally divided into groups A and B and fed a 0.5% cholesterol diet for 90 days. For the last 30 days, group B received 40 mg apoA-I every week. The fatty streak lesions in group B (23.9 +/- 15.6%) were significantly suppressed compared with those in group A (46.0 +/- 24.9%) (P < .05). In experiment 2, 33 rabbits were divided into four groups (8 or 9 rabbits per group) and fed a 0.5% cholesterol diet. Group A was killed on day 105, while groups B, C, and D were maintained for an additional 60 days on a normal diet, during which time groups C and D received 1 mg apoA-I every other day or 40 mg apoA-I every week, respectively. The lesions in group C (70.2 +/- 15.4%) and group D (65.7 +/- 20.0%) were significantly suppressed compared with those in group B (86.2 +/- 13.7%) (P < .05) but were not reduced to the level of group A (50.0 +/- 22.9%). Although apparent regression was not observed under these conditions, the present study provided the first evidence for the antiatherogenic effect of homologous and apoA-I on the progression of atherosclerosis in cholesterol-fed rabbits.

Animals↗
PubMed1995

Lungworm, Filaroides osleri, infection in a dog in Japan.

A 7-month-old male Pomeranian had severe dyspnea for 2 weeks. The lateral bronchogram showed a stenosis of the trachea. Inspite of supportive therapy including supplemental oxygen, the dog died 5 days later. Six pedunculated nodules were recognized in the mucosal surface of the trachea at necropsy. The tracheal nodules were histopathologically granuloma characterized by many coiled parasites containing a little collagen fibers, lymphocytes, plasma cells and macrophages. Female parasites had a lot of embryonated eggs in the uterus. Immature worms were observed in the dilated lymph vessels of bronchial and bronchiolar wall in the lungs. The worms were identified as Filaroides osleri based on the parasitological examinations.

Animals↗
PubMed1995

p55 and p75 tumor necrosis factor receptor expression on human glioblastoma cells.

Expression of the two types of tumor necrosis factor (TNF) receptor, p55 and p75, in 12 human glioblastoma cell lines was studied. Reverse-transcription polymerase chain reaction detected messenger ribonucleic acid (mRNA) transcripts of p55 TNF receptor in all 12 cell lines tested, but p75 TNF receptor mRNA in only four cell lines. Flow cytometric analysis with anti-p55 and anti-p75 TNF receptor monoclonal antibodies demonstrated both p55 and p75 proteins in these four cell lines, but the level of expression of p75 molecule was very low. Correlation of p55 and p75 TNF receptor expression with TNF-induced growth suppression and production of bioactive molecules (interleukin-6, interleukin-8, manganase-superoxide dismutase, prostaglandin E2) showed that p55 TNF receptor mediates these TNF actions, but none of the responses were influenced by the presence of the p75 TNF receptor, which apparently has no specific role.

Base Sequence↗
PubMed1995

Vessel wall injury and arterial thrombosis induced by a photochemical reaction.

Arterial thrombosis may be initiated in an experimental animal by a photochemical reaction between transmural green light and i.v. administered Rose Bengal, a photosensitizer dye. In this study, scanning electron microscopy has been used to reveal the nature of vessel injury and the cellular composition of the photochemically induced thrombus. A 5 mm segment of the guinea pig femoral artery was occluded by a thrombus about 10 min after irradiation with green light in the presence of systemically administered Rose Bengal. Electron microscopy revealed that following photochemical reaction, endothelial cells first contract and, with further irradiation, become detached from the vessel wall, with their cell membrane being destroyed at the irradiated site where an occlusive platelet-rich thrombus was formed. Endothelial cell injury and vessel occlusion could be completely inhibited by the aminothiol, DL-cysteine administered i.v. 1 min after Rose Bengal. The mechanism of endothelial injury in this model appears to be by singlet molecular oxygen, 1O2 formed by energy transfer from the photo-excited dye to O2.

Animals↗
PubMed1995

Further metabolism of FK506 (tacrolimus). Identification and biological activities of the metabolites oxidized at multiple sites of FK506.

To characterize the metabolic pathway of FK506 (tacrolimus), FK506 or its 31-O-desmethyl metabolite was incubated with liver microsomes prepared from dexamethasone-treated rats in the presence of a NADPH-generating system under aerobic conditions. Besides the four oxidized metabolites already reported, four new metabolites were isolated and identified by HPLC, mass spectrometry, and NMR spectroscopy, and their biological activities were examined. The di-demethylated metabolites at the 15- and 31-, 13- and 31-, and 13- and 15-methoxy groups of FK506, were designated respectively as M-V, M-VI, and M-VII. The fourth, M-VIII, was the metabolite produced after O-demethylation at the 31-methoxy group and formation of a fused 10-membered ring structure through the 19- to 22-carbon of the macrolide ring after oxidation of the 19-methyl group, and of the 36- and 37-vinyl group of FK506. The immunosuppressive activity of the isolated metabolites was estimated in a mouse mixed lymphocyte reaction system and the IC50 values for M-V, M-VI, M-VII, M-VIII, and FK506 were > 1000, 8.78, > 1000, 15.27, and 0.11 ng/ml, respectively. Reactivity of the metabolites with mouse anti-FK506 monoclonal antibody was studied and immunocrossreactivity of M-V was 92.3% of FK506, but no reactivity was observed for M-VI, M-VII, and M-VIII. FK506 thus was metabolized at multiple sites by rat hepatic microsomes and the metabolites formed (M-V) - (M-VIII) exhibited weak or negligible immunosuppressive activity.

Animals↗
PubMed1995

Radiation induction of the receptor tyrosine kinase gene Ptk-3 in normal rat astrocytes.

Radiation-induced gene expression was examined in rat astrocyte cultures using differential display of mRNA via reverse transcriptase-polymerase chain reaction. A 0.3-kb cDNA that was consistently observed in irradiated cultures but not in unirradiated cultures was cloned and sequenced. It was found to be identical to Ptk-3, a receptor tyrosine kinase gene identified recently. The protein encoded by Ptk-3 is a member of a novel class of receptor tyrosine kinases whose extracellular domain contains regions of homology with coagulation factors V and VIII and complement component C1. Northern blot analysis revealed that the expression of Ptk-3 was increased in rat astrocytes by 0.5 h after exposure to 10 Gy and remained at the same elevated level for at least 24 h. The maximum increase occurred after 5 Gy. Cloning studies indicated the presence of at least two Ptk-3 mRNA transcripts, which are probably the result of an alternative splicing mechanism. The short isoform lacks a 37-amino acid sequence in the glycine/proline-rich juxtamembrane region. The splicing pattern of the Ptk-3 gene was not altered by radiation. However, the ratios of the longer to the shorter mRNA transcripts differed between adult cortex, neonatal cortex and in vitro astrocyte cultures.

Alternative Splicing↗
PubMed1994

Hereditary cerebellar vermis defect in the Lewis rat.

We report a new rat model of hereditary cerebellar vermis defect. Mutant rats exhibited hind-leg paralysis from about 14 days old. Gross pathology showed the cerebellar vermis defect, fused cerebellar hemispheres and cyst formation. Ectopic dysplastic cerebellar tissues existed in the cerebello-pontine junctional zones. Mild disarrangement of lamination was also observed in the fused cerebellar hemispheres. The present mutant may serve as a valid model for studying the cerebellar vermis defect under the genetic control.

Animals↗
PubMed1994

Existence of an enzymatic pathway furnishing arachidonic acid for prostaglandin synthesis from arachidonoyl CoA in rabbit kidney medulla.

We examined whether arachidonoyl CoA (AA-CoA) can be a possible supplier of arachidonic acid (AA) for prostaglandin (PG) synthesis in rabbit kidney medulla. AA-CoA was preincubated with or without the 105,000 g supernatant (cytosol) fraction from the kidney medulla for 5 min at 37 degrees C followed by the incubation with the microsomal fraction (0.5 mg protein) (a rich source of PG synthesizing enzymes) in the presence of reduced glutathione and hydroquinone for 5 min at 37 degrees C, and the formed PGE2, F2 alpha and D2 were measured by high-pressure liquid chromatography using 9-anthryldiazomethane for derivatization. The addition of AA-CoA (20 nmol) alone changed the total PG formation (the sum of PGE2, F2 alpha and D2) from 0.14 to 1.55 ng. When the cytosolic fraction (10-100 microliters) was added together with 20 nmol-AA-CoA in the preincubation mixture, total PG formation was further increased 2- to 3-fold compared to AA-CoA alone. Experiments utilizing AA, instead of AA-CoA and boiled cytosolic fraction revealed that the stimulatory action of the cytosolic fraction on the AA-CoA-induced PG synthesis may not be due to the effect on cyclooxygenase activity and due to long-chain acyl CoA hydrolase. These results show that long-chain acyl CoA hydrolase which hydrolyzes AA-CoA to AA is present in the cytosol of rabbit kidney medulla and suggest that this enzyme activity is a potential mediator of supply of AA for PG synthesis in this region.

Acyl Coenzyme A↗
PubMed1994

Interaction of tacrolimus(FK506) and its metabolites with FKBP and calcineurin.

Tacrolimus(FK506) is a strong immuno-suppressant and shows its activity through inhibiting IL-2 mRNA transcription by forming pentameric complex with intracellular receptor(FK506 binding protein 12 kDa or FKBP12), Ca2+, calmodulin, and calcineurin. Here, we report the binding activity to FKBP12, the pentameric complex formation and Con-A response inhibiting activities of 7 metabolites. C15-demethylated metabolite(M-3) needed higher quantity to compete in Con-A assay and in pentamer formation assay, although it binds more strongly to FKBP12. The result suggests that the ability to form a pentameric complex is not a two step reaction with the first binding to FKBP12, but a single step reaction by components for the pentamer formation.

Animals↗
PubMed1994

Distinct induction of c-fos mRNA in NG108-15 cells transfected with muscarinic m1 and m3 receptors.

The differences of intracellular signalling mechanisms between muscarinic acetylcholine m1 and m3 receptors, which are coupled with polyphosphoinositide turnover, were examined by using m1- and m3-transfected NG108-15 cells. The c-fos mRNA was induced by 1 mM acetylcholine peak at 60 min in both m1 and m3 cells. The c-fos induction in m1 cells was inhibited by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (BAPTA-AM) and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7), but was not inhibited by prolonged treatment with 12-O-tetradecanoylphorbol 13-acetate (TPA), suggesting that intracellular Ca2+ and calmodulin are involved in the induction. The c-fos induction in m3 cells was inhibited by BAPTA-AM and prolonged treatment with TPA, but was not influenced by W-7, suggesting that protein kinase C is mainly involved in m3-induced c-fos expression. Acetylcholine induced an increase in inositol phosphates and a transient increase in the intracellular concentration of Ca2+ in both m1 and m3 cells. Sustained stimulation of acetylcholine strongly increased the inositol monophosphate content in m3 cells, but that of inositol trisphosphate and inositol diphosphate in m1 cells. These results suggest that the difference between m1- and m3-induced c-fos mRNA induction mechanisms is due to the difference in respective properties in polyphosphoinositide turnover.

Acetylcholine↗