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Biomedical subjects

Y Sawasaki

Publications and source records attributed to Y Sawasaki.

At least 19 recordsLinked to original sources
PubMed1998

Increased secretion of urokinase-type plasminogen activator by human lung microvascular endothelial cells.

Human lung microvascular endothelial cells (HLMECs) secreted 1.5-15 times more urokinase-type plasminogen activator (uPA) antigen than human hepatic microvascular endothelial cells, human umbilical vein endothelial cells (HUVECs), angioma endothelial cells, and lung fibroblasts. All of these cells also secreted a 100-fold greater amount of plasminogen activator inhibitor-1 than of uPA antigen, and uPA activities were not detected in the culture medium. The expression of uPA mRNA in HLMECs was higher (100-fold) compared with HUVECs, angioma endothelial cells, and lung fibroblasts. HLMECs secreted uPA antigen on both the luminal and basal sides of the cells. On the other hand, HLMECs secreted a 10- to 15-fold lower amount of tissue-type plasminogen activator than HUVECs, mostly on the luminal side. After stimulation with interleukin (IL)-1beta, HLMECs secreted a six- to ninefold amount of uPA antigen. In contrast, no stimulatory effect was observed in HUVECs even under high IL-1beta concentrations. The secretion of uPA and plasminogen activator inhibitor-1 from HLMECs was also enhanced by tumor necrosis factor-alpha and IL-2. These results suggest that HLMECs may contribute not only to the patency of lung vessels but also to the maintenance of alveolar functions through the production and secretion of uPA, especially in the presence of inflammatory cytokines.

Cells, Cultured↗
PubMed1996

Characterization of single chain urokinase-type plasminogen activator with a novel amino-acid substitution in the kringle structure.

ECV304 is a cell line established by a spontaneous transformation of endothelial cells of a human umbilical vein. It was shown that ECV304 secretes single chain urokinase-type plasminogen activator (scu-PA). A subclone, ECV304 clone 15, was obtained by acclimatization of parental clone to serum-free medium followed by limiting dilution. The clone was found to produce approximately five times as much scu-PA (approximately 20 IU/10(6) cells per day) as the parental clone after a 40 days' culture. Though the biochemical characteristics of the purified scu-PA were indistinguishable from those of the native scu-PA, it had a lower affinity for fibrin clots under the employed conditions. Molecular cloning of a cDNA encoding the scu-PA has identified a novel substitution from C to T in the nucleotide sequence encoding the kringle structure. The substitution resulted in an alteration from Pro (CCG) to Leu (CTG) at amino-acid position 121, which may be directly or indirectly involved in the decrease in the apparent affinity.

Amino Acid Sequence↗
PubMed1996

The restoration of the functions of serially passaged calf hepatocytes by spheroid formation.

A serial cultivation system of hepatocytes was established for the first time using calf liver as a cell source and, repeating passage of more than 30 cumulative population doublings (PDs), was obtained in the presence of long-acting ascorbic acid derivative (L-ascorbic acid 2-phosphate) and epidermal growth factor. The complete purification of hepatocytes was achieved by repeating ethylenediaminetetraacetic acid (EDTA) treatment, by which hepatocytes were easily detached from the culture dish, leaving most of the nonparenchymal cells on the dish. As the population cumulatively doubled, the cell density and albumin-synthesizing ability decreased gradually, and doubling time has exceeded 120 h at about 30 cumulative PDs. In serially passaged cells, the hepatocyte-specific histochemical and biochemical markers-including glucose-6-phosphatase, ornithine carbamoyltransferase, glutamate dehydrogenase, and ammonia-metabolizing activities-have been lost after 20 cumulative PDs. However, when these passaged cells were allowed to form spheroids, the morphologic and biochemical characteristics of hepatocytes have rapidly been restored to levels comparable to those in younger generations. Because no extrinsic factor was needed for this restoration, three-dimensional cell-cell interaction would be indispensable for the differentiation of the hepatocytes. The routine serial cultivation of hepatocytes and their redifferentiation by spheroid formation will be useful for studying metabolism, gene regulation, and transplantation of hepatocytes.

Animals↗
PubMed1996

Trans-kingdom conjugation between Agrobacterium tumefaciens and Saccharomyces cerevisiae, a bacterium and a yeast.

For conjugation between prokaryotic Agrobacterium tumefaciens and eukaryotic Saccharomyces cerevisiae, we constructed two novel conjugative plasmids. A. tumefaciens transmitted the plasmids to S. cerevisiae with the aid of tra genes on a helper plasmid. The transmitted plasmids retained their original structure and function in transconjugant yeasts. The presence of Ti plasmid barely affected the trans-kingdom conjugation.

Agrobacterium tumefaciens↗
PubMed1996

Transcytosis of lipid microspheres by human endothelial cells.

Human endothelial cells were cultivated on microporous membranes mimicking the luminal and basal spaces of blood vessels. When fluorescence-labeled lipid microspheres (LM) were added to the upper chambers of the model cultures, confluent monolayers of endothelial cells transported considerable levels of fluorescence to lower chambers. The transport was time dependent and was diminished by the addition of cytochalasin B. The uptake of LM into the endothelial cytoplasm was confirmed by electron microscopy and laser scanning confocal imaging. The amounts of fluorescence in the lower chamber were reduced when the endothelial cell layer was fixed with formaldehyde. These observations suggest that endothelial cells can transport LM by transcytosis. Endothelial cells seem to carry the LM without processing, since only minimal amounts of free fluorescence were detected even after longer cultivation periods. The fluorescence in the lower chambers of cell cultures treated with interleukin 1 beta was 3.7-fold higher than that of untreated cells; interleukin 2 and tumor necrosis factor alpha treatments had no discernible effect on LM transport. The interleukin 1 beta induced increase of transcytosis in endothelial cells would explain why LM preferentially accumulate in inflammatory tissues.

Biological Transport↗
PubMed1996

Cyclic pentapeptide endothelin A receptor antagonists with attenuated in vivo clearance.

A series of analogues of BQ-123 (1), a potent cyclic pentapeptide endothelin A receptor antagonist, with amino acids linked to the side-chain of the Pro residue via an ester linkage was synthesized. All analogues synthesized exhibited potent endothelin A receptor binding affinity similar to that of 1. Of the synthesized analogues, the Lys, Arg and N alpha,N epsilon-dimethyllysine analogues, 9d-f, exhibited about a three-fold attenuation of in vivo clearance compared with 1. In rats, these analogues exhibited a 3-fold-higher plasma concentration and a longer retention time in plasma as compared with those of 1. The attenuated in vivo clearance was thought to be a consequence of decreased extraction of the compounds from the blood via the hepatic anion transport system, which efficiently extracts 1 from the blood.

Amino Acid Sequence↗
PubMed1996

Carrier-mediated active transport of BQ-123, a peptidic endothelin antagonist, into rat hepatocytes.

The hepatic uptake mechanisms and pharmacokinetics of BQ-123, an anionic cyclopentapeptidic endothelin ET(A) receptor antagonist, were studied in rats. Elimination of BQ-123 from plasma after intravenous injection of the compound was very rapid as evidenced by high total body clearance (CLtot, 50 ml/min/kg), which is comparable with hepatic blood flow rate. Within 1 hr after injection, 86% of the dose was excreted as its intact form in the bile. BQ-123 was taken up extensively by isolated rat hepatocytes both Na(+)-dependently and Na(+)-independently. The Na(+)-dependent system transported BQ-123 with higher affinity than did the Na(+)-independent system (Km; 6 and 12 microM, respectively), but its capacity was lower (Vmax; 140 and 390 pmol/min/10(6) cells, respectively). Both uptake systems were found to be active transport systems because of explicit inhibition by metabolic inhibitors. BQ-485, an anionic linear tripeptide, strongly inhibited BQ-123 uptake with Ki values of 1.6 and 2.5 microM for Na(+)-dependent and Na(+)-independent systems, respectively, whereas BQ-587, a cationic cyclopentapeptide, inhibited BQ-123 uptake only slightly. Considering this in vitro finding and the low in vivo CLtot of BQ-587 together, the carrier systems for BQ-123 seem to recognize negatively charged substances selectively. Both Na(+)-dependent and Na(+)-independent uptake of BQ-123 were competitively inhibited by a bile acid (taurocholate) and an organic anion (dibromosulfophthalein). The Ki values were comparable with the Km values of taurocholate and dibromosulfophthalein transport, which suggests that the Na(+)-dependent system corresponds to the bile acid transporter and that the Na(+)-independent system corresponds to the organic anion transporter.

Animals↗
PubMed1992

Lung capillary endothelial cells produce and secrete urokinase-type plasminogen activator.

Bovine lung capillary endothelial cells (BLuEC) were isolated, and their ability to produce plasminogen activator (PA) in vitro was demonstrated. BLuEC secreted more than 10 times as much as urokinase-type PA (u-PA) as did bovine aortic, hepatic capillary and adrenal capillary endothelial cells, and lung fibroblasts. BLuEC secreted u-PA on both sides of the cell layer, the luminal surface, and the basic surface attached to the basement membrane. u-PA mRNA was detected in BLuEC by Northern blotting, but not in endothelial cells from other tissues and fibroblasts. These results suggest that BLuEC may contribute not only to the patency of lung vessels but also to the maintenance of alveolar functions through the production and secretion of u-PA.

Amino Acid Sequence↗
PubMed1992

Renin inhibitors. II. Synthesis and structure-activity relationships of N-terminus modified inhibitors containing a homostatine analogue.

The synthesis and structure-activity relationships of N-terminus modified renin inhibitors containing the homostatin analogue, (2RS,4S,5S)-5-amino-2-ethyl-4-hydroxy-7-methyloctanoic acid, are described. The compounds having a 3-alkyl (or aryl)sulfonylpropionyl residue at the N-terminus are found to be potent inhibitors which contain two amino acids. (2RS,4S,5S)-N-Isobutyl-5-[N-[(2S)-3-ethylsulfonyl-2-(1- naphthylmethyl)propionyl]-L-norleucyl]-amino-2-ethyl-4-hydroxy-7- methyloctanamide (20) has an IC50 of 0.5 nM against human plasma renin and the oral bioavailability of 20 is 0.73% in rats. Interaction between renin and the N-terminus of 1 and 20 is discussed in molecular modeling studies.

Amino Acids↗
PubMed1992

Basic fibroblast growth factor promotes proliferation of rat glomerular visceral epithelial cells in vitro.

Glomerular visceral epithelial cells (vGEC) play an important role in the synthesis of the glomerular basement membrane (GBM), and together with glomerular endothelial cells and the GBM, in glomerular ultrafiltration. Therefore clarification of the properties of vGEC is essential to investigations of glomerular morphology and function in both physiologic and pathologic conditions. This article demonstrates that basic fibroblast growth factor (bFGF) is mitogenic to vGEC in vitro. Its effect was found at concentrations as low as 1.25 ng/ml, and was synergistic with epidermal growth factor (EGF). In contrast, EGF by itself had no demonstrable mitogenic effect at concentrations of 1.25-100 ng/ml. In addition, mRNA for bFGF was identified in cultured vGEC by the method of reverse transcriptase polymerase chain reaction and the immunoreactivity of bFGF was found in GEC of the Sprague-Dawley rat kidney. These results suggest that bFGF stimulates the proliferation of vGEC in an autocrine manner in vivo. A unique relationship similar to that observed in endothelial cells may also exist among bFGF, vGEC, and the extracellular matrix (ECM). In a word, bFGF may be produced by vGEC and stored in the ECM, that is the GBM, and may be one factor that stimulates vGEC to proliferate when vGEC are injured and lost in vivo.

Animals↗
PubMed1991

Close similarity between cultured human omental mesothelial cells and endothelial cells in cytochemical markers and plasminogen activator production.

The mesothelial cells obtained from human omental adipose tissue showed a typical cobblestone monolayer and reacted strongly with keratin, but did not have Von Willebrand factor. Ultrastructurally these cells revealed the existence of desmosome-like cell junctions as well as intracellular canaliculi, tubular structures surrounded by microvilli, and tonofilament-like filaments. The mesothelial cells grew much faster in the medium containing epidermal growth factor, actively took up acetylated-low density lipoprotein into their cytoplasm, and released angiotensin-converting enzyme. They also released urokinase-type plasminogen activator, but only half as much as do human umbilical vein endothelial cells; release of tissue-type plasminogen activator was not observed. Inasmuch as the mesothelial cells also released plasminogen activator inhibitor-1, as do human umbilical vein endothelial cells, we could not detect u-PA activity in culture medium. u-Pa may play a role in the protection against adhesion among visceral organs. These observations indicate that cultured human mesothelial cells have characteristics closely related to those found in human endothelial cells.

Adipose Tissue↗
PubMed1991

Hypolipidemic effects of NB-598 in dogs.

NB-598, a new inhibitor of mammalian squalene epoxidase, was found to be a potent inhibitor of microsomal squalene epoxidase from dog liver. Hypolipidemic effects of NB-598 were compared with those of simvastatin (MK-733, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor) in dogs. NB-598 was found to decrease serum total cholesterol levels and increase serum squalene levels in a dose-dependent manner. MK-733 decreased serum total cholesterol and squalene levels. Both NB-598 and MK-733 decreased all classes of lipoprotein cholesterol, and they decreased low density lipoprotein cholesterol most potently. Both drugs decreased phospholipid levels in parallel with cholesterol levels. NB-598 also decreased triacylglycerol levels. After termination of drug administration, these levels returned to the control levels. The potency of NB-598 is thought to be as great or greater than that of MK-733. Moreover, NB-598 increased squalene concentrations in the feces and gallbladder bile, but it did not affect neutral sterol and bile acid concentrations. NB-598 did not affect the lithogenic index.

Animals↗
PubMed1990

NB-598: a potent competitive inhibitor of squalene epoxidase.

NB-598, (E)N-ethyl-N-(6,6-dimethyl-2-hepten-4-ynyl)-3-[(3,3'-bith iophen-5-yl)methoxy]benzene-methanamine, was found to inhibit human microsomal squalene epoxidase (from Hep G2 cells) in a competitive manner. NB-598 inhibited cholesterol synthesis from [14C]acetate dose dependently in Hep G2 cells and increased the intracellular radioactivity of squalene. A single oral administration of NB-598 inhibited cholesterol synthesis from [14C]acetate in rats. Moreover, multiple oral administration of NB-598 to dogs decreased serum total and low density lipoprotein cholesterol levels and increased serum squalene levels. After termination of treatment, the reduced serum cholesterol and increased squalene levels returned to their control values.

Animals↗
PubMed1990

Spontaneous transformation and immortalization of human endothelial cells.

A new cell line from the human umbilical vein has been established and maintained for more than 5 yr (180 generations; 900 population doublings). This strain, designated ECV304, is characterized by a cobblestone monolayer growth pattern, high proliferative potential without any specific growth factor requirement, and anchorage dependency with contact inhibition. Karyotype analysis of this cell line reveals it to be of human chromosomal constitution with a high trisomic karyotype (mode 80). Ultrastructurally, endothelium-specific Weibel-Palade bodies were identified. Although one of the endothelial cell markers, Factor VIII-related antigen (VIIIR:Ag) was negative in this cell line, immunocytochemical staining for the lectin Ulex europaeus I (UEA-I), and PHM5 (anti-human endothelium as well as glomerular epithelium monoclonal antibody) was positive, and angiotensin-converting enzyme (ACE) activity was also demonstrated. In addition, ECV304 displayed negativity for alkaline and acid phosphatase and for the epithelial marker keratin. All of these findings suggest that ECV304 cells originated from umbilical vein endothelial cells by spontaneous transformation. Ultrastructurally, no viruslike particles have been detected intracellularly. Nude mouse tumorigenicity and rabbit cornea tests were both positive. This is a report on a novel case of phenotypic alteration of normal venous endothelial cells of human origin in vitro, and generation of a transformant with indefinite life spans. This line may be useful in studies of some physiologically active factors available for medical use.

Cell Division↗
PubMed1990

Effect of simvastatin (MK-733) on sterol and bile acid excretion in rabbits.

The effects of Simvastatin (MK-733), an inhibitor of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, on fecal and biliary excretion of sterols and bile acids were examined using rabbits. Multiple doses of MK-733 (10 mg/kg/day) for 7 days were found to increase fecal concentrations of neutral sterols in cholesterol-fed rabbits, but not to affect those of bile acids. Multiple doses of cholestyramine (750 mg/kg/day), a bile acid sequestrant, for 7 days increased fecal concentrations of neutral sterols and bile acids in normally fed and cholesterol-fed groups. MK-733 did not affect biliary neutral sterols and total bile acids in normally fed and cholesterol-fed groups. Cholestyramine decreased biliary concentrations of neutral sterols in both diet groups. Cholestyramine altered fecal and biliary composition of bile acids, but MK-733 did not. It was considered that MK-733 inhibited the absorption of cholesterol, resulting in an increase of the fecal concentration of neutral sterols in cholesterol-fed rabbits. The mechanism of action of MK-733 in the inhibition of cholesterol absorption is considered to be clearly different from that of cholestyramine. These results confirmed the conclusion in the previous experiment.

Animals↗
PubMed1989

Effects of MK-733 (simvastatin), an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on intestinal acylcoenzyme A:cholesterol acyltransferase activity in rabbits.

MK-733 (simvastatin), a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, was found to inhibit the absorption of cholesterol from the gastrointestinal tract in cholesterol-fed rabbits (Ishida et al. (1988) Biochim. Biophys. Acta 963, 35-41). To clarify the mechanism of action, the effects of MK-733 on acyl coenzyme A:cholesterol acyltransferase (ACAT) and cholesterol esterase activities, which are thought to participate in the absorption of cholesterol, were examined. Dietary administration (0.03% in a 1% cholesterol diet for 7 days, approx. 10 mg/kg) of MK-733 to cholesterol-fed rabbits was found to inhibit the increase in serum total cholesterol levels, and caused a 70% reduction in ACAT activity in microsomes of intestinal mucosa relative to those observed in concurrent control rabbits. MK-733 did not affect cholesterol esterase activity in the cytosol of the intestinal mucosa. The inhibitory effect of MK-733 on cholesterol absorption in cholesterol-fed rabbits is though to be related to a reduction in microsomal ACAT activity in the intestinal mucosa.

Animals↗