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Biomedical subjects

A Suganuma

Publications and source records attributed to A Suganuma.

At least 19 recordsLinked to original sources
PubMed1996

Effect of E5510 on anastomotic intimal hyperplasia and platelet aggregation in dogs.

We examined the effect of an antiplatelet agent, E5510, which inhibits both platelet aggregation and release of platelet-derived growth factor (PDGF), on anastomotic intimal hyperplasia and platelet aggregation. Twenty Beagle dogs underwent infrarenal aortic reconstruction with an expanded polytetrafluoroethylene (ePTFE) graft 5 mm in diameter and 3 cm long. The dogs were divided into three groups: placebo (control group, 7 dogs), E5510 1 mg/day (1-mg group, 6 dogs), and E5510 4 mg/day (4-mg group, 7 dogs). E5510 was administered orally 2 h before operation and once daily for 3 months after operation. Grafts were harvested 3 months after operation. All 13 grafts in the treated groups remained patent without evidence of intimal hyperplasia, whereas only 4 of 7 grafts (57%) remained patent in the control group, including 1 graft with > 50% stenosis. Three occluded grafts showed severe intimal hyperplasia at the anastomoses. The platelet aggregation ratio (PAR) with collagen (100 micrograms/ml) before drug administration at 3 months in the 4-mg group was significantly lower than that in the control and 1-mg groups. PAR after drug administration at 3 months in the 1- and 4-mg groups was significantly lower than that in the control group. Intimal thickness at the distal anastomosis was 817 +/- 190 microns in the control group, 240 +/- 80 microns in the 1-mg group, and 197 +/- 28 microns in the 4-mg group. Intimal thickness in the control group was significantly greater than that in the 1- and 4-mg groups. Smooth muscle cell (SMC) values in the intima at the distal anastomosis were 65.6 +/- 4.4% extinction (%E) in the control group, 47.6 +/- 3.4%E in the 1-mg group, and 51.3 +/- 3.5%E in the 4-mg group. SMC value in the control group was significantly greater than that in the 1- and 4-mg groups. E5510 inhibited PAR and reduced the degree of anastomotic intimal hyperplasia.

Anastomosis, Surgical↗
PubMed1995

Multiple elements in the 5' untranslated region down-regulate c-sis messenger RNA translation.

Expression of the platelet derived growth factor (PDGF) B-chain, the product of the c-sis proto-oncogene, is regulated both at the transcriptional and translational level. Previous studies have shown that the long 5' untranslated region (UTR) of the c-sis mRNA strongly inhibits synthesis of the PDGF-B chain. However, the assignments of down-regulatory regions within the 5' UTR were ambiguous. Expression of several site-directed point and deletion mutants of the 5' UTR of the c-sis mRNA in COS1 cells revealed that the UTR inhibited PDGF-B chain synthesis in a more complex manner than indicated by the previous studies. Abrogation of the three upstream short open reading frames by mutating each of the AUGs did not have any effect on the synthesis of the PDGF-B chain. Expression of deletion mutants revealed two partially overlapping regions, nucleotides 1-651 and 475-1022, each of which independently inhibited c-sis mRNA translation as effectively as the entire 5' UTR. Each of these regions contains a potentially strong stem-loop structure and a GC-rich element. These elements of the alternate down-regulatory regions could interact within the same region and/or with the elements of the other regulatory region to block c-sis mRNA translation. We show, in contrast to the previous reports, that the inhibition of c-sis mRNA translation cannot be attributed exclusively to any particular predicted secondary structure or a GC-rich element within the 5' UTR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Acquired nephrogenic diabetes insipidus secondary to distal renal tubular acidosis and nephrocalcinosis associated with Sjögren's syndrome.

A 52-year-old woman was referred to our hospital because of 16-year history of polyuria and polydipsia. Hyposthenuria, hyperchloremic metabolic acidosis and the inabilities to acidify the urine after acid-loading test and to concentrate the urine in responses to water-deprivation and antidiuretic hormone administration allowed us to diagnose renal tubular acidosis and nephrogenic diabetes insipidus. Radiographic examinations revealed bilateral nephrocalcinosis. The patient was also found to have clinical and laboratory findings characteristic for Sjögren's syndrome. Thus the longstanding, poorly monitored distal renal tubular acidosis associated with Sjögren's syndrome was considered to result in very rare renal complications-nephrocalcinosis and nephrogenic diabetes insipidus. In patients with renal tubular acidosis and/or nephrogenic diabetes insipidus of unknown etiology, therefore, Sjögren's syndrome should be considered as one of primary disorders.

Acidosis, Renal Tubular↗
PubMed1994

Localization of sugar-binding sites in Staphylococcus aureus using gold-labeled neoglycoprotein.

We studied post- and pre-embedding staining of sugar-binding sites on thin sections of Staphylococcus aureus with an electron microscopic neoglycoprotein-gold technique. Although gold particles of cellobiosyl bovine serum albumin (BSA)-glycosylated BSA-, lactosyl BSA-, and melibiosyl BSA-gold did not label, heavy labeling of N-acetylglucosaminide-BSA-gold was observed in both the cell wall and the cytoplasm on Spurr-embedded thin sections of S. aureus. Inhibition of labeling with wheat germ agglutinin-biotin and N-acetylglucosaminidase indicated that the labeling was due to N-acetylglucosamine. These data suggested that molecules that bind specifically with N-acetylglucosamine occur in the cell wall and cytoplasm of S. aureus. Pre-embedding staining revealed that these molecules are abundant at the surface of the cell wall and that the abundance differs depending on the bacterial strain. An N-acetylglucosamine-specific lectin-like substance, glucosaminidase, and toxins are proposed as candidates for molecules responsible for the labeling, and the possible functional significance of the findings is discussed briefly.

Binding Sites↗
PubMed1992

Mass contents of inositol 1,4,5-trisphosphate and 1,2-diacylglycerol in human platelets stimulated with a thromboxane analogue and thrombin.

Mass contents of inositol 1,4,5-trisphosphate (IP3) and 1,2-diacylglycerol (DG) were measured in U46619-stimulated human platelets. 1 microM of U46619 induced maximum responses in aggregation, 5-hydroxytryptamine (5HT) secretion and increase in intracellular free Ca2+ concentration ([Ca2+]i). Aggregation was almost comparable to that induced by maximal dose (1 U/ml) of thrombin, while 5HT release was almost half. The initial [Ca2+]i peak in response to U46619 was about half of thrombin stimulation. Production of IP3 and DG was, however, less than one tenth of that seen in thrombin stimulation. The profile (time course and concentration-dependency) of IP3 formation did not correlate with that of [Ca2+]i, suggesting that U46619 stimulates IP3-dependent and -independent Ca2+ mobilization. DG production was small but sustained for more than 5 min. These findings support the recent hypothesis that aggregation is regulated by a delayed accumulation of DG. The low level of 5HT secretion could be explained by the low production of second messengers, IP3 and DG.

Blood Platelets↗
PubMed1992

Ultrastructure of Staphylococcus aureus as revealed by microwave fixation.

The ultrastructure of the cell wall of Staphylococcus aureus was examined at electron microscopic level using new chemical fixation techniques during microwave irradiation and the results obtained were compared with those obtained by other conventional techniques. By using microwave fixation the concentric circular or zipper-like structure was observed in the cell wall. This structure was observed also with the spray-freeze-etch technique but not in thin section of the cells chemically fixed by conventional technique. For chemical fixative, glutaraldehyde is more advantageous than OsO4 as a concomitant fixative during microwave irradiation and postfixation by OsO4 is unnecessary and rather harmful for the preservation of the ultrastructure. The function of the observed structure is briefly discussed.

Fixatives↗
PubMed1991

Thrombin induces a biphasic 1,2-diacylglycerol production in human platelets.

The 1,2-diacylglycerol (DAG) mass content was measured in thrombin-stimulated human platelets. Thrombin stimulates a biphasic accumulation of DAG, with an early phase reaching a peak at 10 s and a later phase reaching a peak at 2-3 min. The time course of first-phase DAG production corresponded well to that of Ins(1,4,5)P3 formation, which was rapid and transient. The second phase of DAG accumulation occurred after the level of Ins(1,4,5)P3 returned to nearly basal. Thrombin stimulated the decrease in PtdIns and phosphatidylcholine contents. The source of second-phase DAG was examined in platelets prelabelled with three radioactive fatty acids, i.e. arachidonic, palmitic and myristic. Thrombin stimulated the increase in radioactivity of DAG with decline of PtdIns in platelets labelled with [3H]arachidonic acid or [3H]palmitic acid, in which PtdIns was considerably labelled. In contrast, significant accumulation of [3H]DAG was not observed in [3H]myristic acid-labelled platelets, in which PtdIns was poorly labelled. In platelets prelabelled with [3H]inositol, an increase in InsP in response to thrombin was seen for more than 5 min. In contrast, upon stimulation, significant increases in [3H]phosphocholine and [3H]choline were not observed in [methyl-3H]choline-labelled platelets. Thrombin induced a small production of phosphatidylethanol, when ethanol was present during stimulation. However, the formation of DAG and phosphatidic acid was not significantly affected by ethanol. These results suggest that thrombin stimulates a biphasic accumulation of DAG, initially from PtdInsP2 and later from PtdIns in human platelets.

Arachidonic Acid↗
PubMed1989

Mechanism of arachidonic acid liberation in platelet-activating factor-stimulated human polymorphonuclear neutrophils.

Upon stimulation of human polymorphonuclear neutrophils with platelet-activating factor (PAF), arachidonic acid (AA) is released from membrane phospholipids. The mechanism for AA liberation, a key step in the synthesis of biologically active eicosanoids, was investigated. PAF was found to elicit an increase in the cytoplasmic level of free Ca2+ as monitored by fluorescent indicator fura 2. When [3H] AA-labeled neutrophils were exposed to PAF, the enhanced release of AA was observed with a concomitant decrease of radioactivity in phosphatidylinositol and phosphatidylcholine fractions. The inhibitors of phospholipase A2, mepacrine and 2-(p-amylcinnamoyl)-amino-4-chlorobenzoic acid, effectively suppressed the liberation of [3H]AA from phospholipids, indicating that liberation of AA is mainly catalyzed by the action of phospholipase A2. The extracellular Ca2+ is not required for AA release. However, intracellular Ca2+ antagonists, TMB-8 and high dose of quin 2/AM drastically reduced the liberation of AA induced by PAF, indicating that Ca2+ is an essential factor for phospholipase A2 activation. PAF raised the fluorescence of fura 2 at concentrations as low as 8 pM which reached a maximal level about 8 nM, whereas more than nM order concentrations of PAF was required for the detectable release of [3H]AA. Pretreatment of neutrophils with pertussis toxin resulted in complete abolition of AA liberation in response to PAF. However, the fura 2 response to PAF was not effectively inhibited by toxin treatment. In human neutrophil homogenate and membrane preparations, guanosine 5'-O-(thiotriphosphate) stimulated AA release and potentiated the action of PAF. Guanosine 5'-O-(thiodiphosphate) inhibited the effects of guanosine 5'-O-(thiotriphosphate). These results suggest several points: 1) PAF stimulates human polymorphonuclear neutrophils to liberate AA mainly by the action of phospholipase A2; 2) Ca2+ mobilization alone is not sufficient to stimulate AA release, although Ca2+ is the important factor for phospholipase A2 activation; and 3) a pertussis toxin-sensitive GTP-binding protein may be implicated in activation of phospholipase A2.

Arachidonic Acid↗
PubMed1989

Primary role of calcium ions in arachidonic acid release from rat platelet membranes. Comparison with human platelet membranes.

The liberation of arachidonic acid (AA) was investigated in platelet membranes prelabelled with [3H]AA. In rat platelet membranes, Ca2+ at concentrations over several hundred nanomolar induced [3H]AA release, with a concurrent decrease in 3H radioactivity of phosphatidylethanolamine and phosphatidylcholine. Some 4-6% of total radioactivity incorporated into platelet membrane lipids was released at 1-10 microM-Ca2+, which is nearly equivalent to that attained in agonist-stimulated platelets. Formation of lysophospholipids in [3H]glycerol-labelled membranes and decrease in [3H]AA liberated by the phospholipase A2 inhibitors mepacrine and ONO-RS-082 suggest that [3H]AA release is mainly catalysed by phospholipase A2. In intact platelets agonist-stimulated [3H]AA release was markedly decreased in the absence of extracellular Ca2+ or in the presence of the intracellular Ca2+ chelator quin 2. These results indicate that in rat platelets the rise of intracellular Ca2+ plays a primary role in the activation of phospholipase A2. In contrast, Ca2+ even at high millimolar concentrations did not effectively stimulate [3H]AA release in human platelet membranes. Thus factor(s) additional to or independent of Ca2+ is required for the liberation of AA in human platelets.

Animals↗
PubMed1987

A role of diacylglycerol kinase in stimulus-secretion coupling of human platelets. Dissociation of serotonin secretion from Ca2+ mobilization.

The addition of diacylglycerol kinase inhibitor, R 59 022 (6-[2-[4-[(4-fluorophenyl)phenylmethylene]-1-piperidinyl]-7-methyl - 5H-thiazolo[3,2-alpha]pyrimidin-5-one) resulted in a marked accumulation of diacylglycerol in thrombin-stimulated platelets. Release of arachidonic acid induced by thrombin was not affected by the inhibitor. In intact platelets, the conversion of exogenously added 1-oleoyl-2-acetylglycerol to 1-oleoyl-2-acetylphosphatidic acid also was inhibited by the inhibitor. We further investigated the effects of the inhibitor on serotonin secretion and Ca2+ mobilization in thrombin-activated platelets. R 59 022 potentiated serotonin secretion induced by thrombin or 1-oleoyl-2-acetylglycerol. On the other hand, the thrombin-induced increase in cytosolic free Ca2+ concentration measured with aequorin or Quin2 was found to be depressed by R 59 022. These results indicate that diacylglycerol kinase has an important role in regulation of serotonin secretion and that Ca2+ mobilization may not be tightly coupled to serotonin secretion.

Aminoquinolines↗
PubMed1987

Guanine nucleotides stimulate arachidonic acid release by phospholipase A2 in saponin-permeabilized human platelets.

GTP or GTP gamma S alone caused low but significant liberation of arachidonic acid in saponin-permeabilized human platelets but not in intact platelets. GTP or GTP gamma S also enhanced thrombin-induced [3H]arachidonic acid release in permeabilized platelets. Inhibitors of the phospholipase C (neomycin)/diacylglycerol lipase (RHC 80267) pathway for arachidonate liberation did not reduce the [3H]arachidonic acid release. The loss of [3H]arachidonate radioactivity from phosphatidylcholine was almost equivalent to the increase in released [3H]arachidonic acid, suggesting the hydrolysis of phosphatidylcholine by phospholipase A2. The effect of GTP gamma S was greater at lower Ca2+ concentrations. These data indicate that the release of arachidonic acid by phospholipase A2 in saponin-treated platelets may be linked to a GTP-binding protein.

Arachidonic Acid↗
PubMed1987

Ultrastructural localization of carbohydrates on thin sections of Staphylococcus aureus with silver methenamine and wheat germ agglutinin-gold complex.

Postembedding staining of intracellular carbohydrates on thin sections of Staphylococcus aureus was studied by the silver methenamine and the wheat germ agglutinin-gold techniques. Staining of silver grains was observed on both the cell wall and the cross wall. The staining was interpreted to be due to teichoic acid. Labeling by wheat germ agglutinin-gold particles was observed on both the cell wall and the cross wall, and the staining pattern resembled that of silver methenamine staining. Therefore, the labeling was considered to be due to N-acetylglucosamine of teichoic acid. The combination of two types of cytochemical techniques was useful to localize and characterize the carbohydrates of the bacterial cell.

Carbohydrates↗
PubMed1987

Polymyxin B binding sites in Escherichia coli as revealed by polymyxin B-gold labeling.

A complex of polymyxin B, bovine serum albumin, and colloidal gold was prepared and used for the ultrastructural localization of polymyxin B binding sites on thin sections of Epon-embedded Escherichia coli cells. Gold particles were found on the outer membrane of E. coli, which is consistent with reported biochemical findings. We concluded that gold labeling with polymyxin B is useful in localizing the binding sites of polymyxin.

Binding Sites↗
PubMed1986

Aminoglycoside binding sites in Escherichia coli as revealed by neomycin-gold labeling.

A cytochemical technique for demonstration of neomycin binding sites by electron microscopy was developed and applied to Escherichia coli. Neomycin was conjugated chemically with bovine serum albumin (BSA). Colloidal gold was coated with the conjugated neomycin-BSA. The neomycin-BSA-gold was applied to thin sections of Epon-embedded E. coli and examined. Gold particles were observed on the outer membrane and the cytoplasmic membrane of E. coli. It was probably the ribosomes that were being labeled in the cytoplasm. Different cytochemical controls, including a number of inhibition tests and the use of BSA-gold, proved the specificity of this cytochemical technique and provided the biochemical significance of the observations.

Binding Sites↗
PubMed1986

B lymphocyte differentiation and suppressor activity by T lymphocytes derived from neonatal and sucking piglets.

The capacity of porcine neonatal T and B lymphocytes was studied employing a protein A haemolytic plaque assay. Only a few peripheral blood lymphocytes (PBL) from newborn piglets differentiated into immunoglobulin (Ig)-producing cells on stimulation by pokeweed mitogen (PWM). Newborn PBL also suppressed the differentiation of adult PBL into Ig-producing cells. This suppressive effect existed in T-cell enriched populations and appeared to be equally effective in the generation of IgG and IgM-producing cells. When newborn B lymphocytes were cocultured with T lymphocytes from adults in the PWM system, their differentiation into IgG and IgM-producing cells was enhanced. No such enhancement was seen in cocultures of newborn T and B lymphocytes. The generation of Ig-producing cells in PBL from suckling piglets increased with ageing, and reached about half the adult mean at six weeks old. On the other hand, the suppressor activity of T lymphocytes was observed throughout the suckling period, although it gradually decreased with ageing and was not consistently demonstrated by five weeks of age.

Animals↗