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Biomedical subjects

J Seki

Publications and source records attributed to J Seki.

At least 55 records · Page 3Linked to original sources
PubMed1996

Dimethyl sulfoxide and related polar compounds enhance infection of human T cells with HIV-1 in vitro.

We observed the enhancing effect of dimethylsulfoxide (DMSO) on infection of human T cells with human immunodeficiency virus type 1 (HIV-1). Similar enhancing effects were also found in related polar chemicals such as dimethylformamide, hexamethylenebisacetamide, sodium butyrate and retinoic acid. In acute infection of the human MT-4 T cell line, DMSO at a concentration of 1% reduced the amounts of HIV-1 required to establish similar infection by one log. Furthermore, infection of peripheral blood lymphocytes with HIV-1 was also augmented several times by DMSO. HIV-1 production from persistently infected human T cell lines, but not monocytic cell lines, was enhanced by DMSO and related polar chemicals. DMSO enhanced transcription of HIV-1 RNA in persistently infected T cell lines, and the enhancing effect of DMSO on HIV-1 production was inhibited by staurosporine, a protein kinase inhibitor. These findings suggested that DMSO enhanced HIV-1 infection of T cells mainly at the step of transcription of viral RNA.

Acetamides↗
PubMed1996

Antianginal effects of FR144420, a novel slow nitric oxide-releasing agent.

The aim of this study was to compare the antianginal effects of two compounds that release nitric oxide (NO) spontaneously, i.e. (+/-)-N-[(E)-4-ethyl-3-[(Z-hydroxyimino]-5-nitro-3-hexenyl] -3-pyridinecarboxamide (FR144420) and (+/-)-(E)-ethyl-2-[(E)-hydroxyimino] -5-nitro-3-hexenamide (FK409), in two different rat models of coronary vasospasm. In the rat methacholine-induced coronary vasospasm model, FR144420 suppressed the elevation of the ST segment dose dependently and significantly at 1.0 mg/kg, i.d. 185 min after its administration. FK409 suppressed the ST elevation only 5 min after its administration at 1.0 mg/kg, i.d. FR144420 and FK409 significantly decreased mean blood pressure at all doses tested only 5 min after their intraduodenal administration, but did not change heart rate at any time. Although the suppression of the ST elevation by FK409 had the same duration as its hypotensive effect, the FR144420-induced suppression of the ST elevation lasted longer than its hypotensive effect. In the rat vasopressin-induced coronary vasospasm model, FR144420 (32 mg/kg) significantly inhibited the depression of the ST segment both 60 min and 120 min after oral administration, whereas FK409 (32 mg/kg) significantly inhibited this ST depression only 60 min after oral administration. These data suggest that FR144420 inhibits coronary vasospasm for longer than FK409 does and particularly shows more prolonged antianginal effects than hypotensive effects in the methacholine-induced coronary vasospasm model. Thus FR144420 is expected to be a useful NO releaser for investigating the in vivo actions of NO.

Animals↗
PubMed1996

The anti-platelet and anti-thrombotic effects of FK633, a peptide-mimetic GPIIB/IIIA antagonist.

The anti-platelet and anti-thrombotic properties of FK633, a peptide mimetic GPIIb/IIIa antagonist were studied. In human platelet rich plasma, FK633 inhibited ADP-, collagen-, thrombin-, and PAF-induced platelet aggregation with IC50 values of 103, 87, 98, and 239 nM, respectively. RGDS acted similarly, but it's potency was about 1,000 times weaker than FK633, FK633 inhibited 125I-fibrinogen binding to human washed platelet with an IC50 of 88 nM. FK633 did not inhibit alphavbeta3, alpha5beta1, and alphavbeta1 integrin-mediated cellular adhesion up to 1.0mM, while RGDS inhibited all these interactions. In dogs, bolus injection of FK633 at 0.1 mg/kg significantly suppressed ex vivo ADP-induced platelet aggregation (>40% inhibition) and thrombus formation at stenosed and injured coronary artery, but did not prolong template bleeding time. However, FK633 inhibited >90% ADP-induced aggregation at 0.32 mg/kg, causing significant prolongation of the bleeding time. Thus, FK633 is a specific GPIIb/IIIa antagonist with potent anti-thrombotic effect in vivo, but careful dosing study might be necessary to avoid the bleeding complications in the clinic.

Animals↗
PubMed1996

Conformational and stacking properties of 3'-5' and 2'-5' linked oligoribonucleotides studied by CD.

Comparative CD studies have been carried out to characterize the properties of 2'-5' and 3'-5' oligoriboadenylates and oligoribouridylates from dimer to decamer. The CD band of the 3'-5' oligoribonucleotides was larger than that of the 2'-5' oligoribonucleotides and increased with the increase in chain length, while the CD band of the 2'-5' oligoribonucleotides increased little beyond the dimer level. The CD analysis of the chain length dependency revealed that the 3'-5' oligoribonucleotides adopt mainly the base-base stacking interaction, while the base-sugar interaction is predominant in the 2'-5' oligoribonucleotides. The CD intensity of 3'-5' oligoribonucleotides decreased to a larger extent at elevated temperatures or in the presence of ethanol compared to that of the 2'-5' counterparts. Mg2+ or Mn2+ ion enhanced the magnitude of the CD of 3'-5' octariboadenylate, while a small decrease in the CD was observed by the presence of Mg2+ or Mn2+ ion to the 2'-5' octariboadenylate. The 3'-5' oligoribonucleotide is likely conformationally flexible and can form helical ordered structure with strong base-base stacking depending on changes in the environment such as temperature the presence of Mg2+ ion, or hydrophobicity of the solution.

Circular Dichroism↗
PubMed1996

Comparative studies of duplex and triplex formation of 2'-5' and 3'-5' linked oligoribonucleotides.

We have studied double and triple helix formation between 2'-5' or 3'-5' linked oligoriboadenylates and oligoribouridylates with chain length 7 or 10 by CD spectrometry. The complex formation depends on the type of linkage of oligoribonucleotides, chain length, concentration and molar ratio of the strands, temperature and the cationic concentration. Mixture of any linkage isomers of oligo(rA) and oligo(rU) in 1:1 molar ratio form duplex at 0.1 M NaCl. The duplex stability largely depends on the type of the linkages and is in the following order, [3'-5'] oligo(rA)-[3'-5'] oligo(rU) > [2'-5'] oligo(rA)-[3'-5'] oligo(rU) > [3'-5'] oligo(rA)-[2'-5'] oligo(rU) > [2'-5'] oligo(rA)-[2'-5'] oligo(rU). The higher cationic concentrations, 0.5 M MgCl2, stabilize the complex and either duplex or triplex is formed depending on the input strand ratio and the type of linkage. Thermodynamic parameters, DH and DS, for the complex formation between linkage isomers of oligo(rA) and oligo(rU) showed a linear relationship indicating an enthalpy-entropy compensation phenomena. The duplex and triplex composed of [2'-5'] oligo(rA) and [2'-5'] oligo(rU) exhibit different CD spectra compared to those of any others containing 3'-5' linkage, suggesting that the fully 2'-5' duplex and triplex may possess a unique conformation. We describe prebiological significance of the linkage isomers of RNA and selection of the 3'-5' linkage against 2'-5 linkage.

Circular Dichroism↗
PubMed1996

Regulation of beta1-integrin function in cultured human vascular smooth muscle cells.

Avidity modulation and function of beta1-integrin receptors in cultured human vascular smooth muscle cells (SMCs) were investigated using monoclonal antibody (mAb) 8A2, which binds to the beta1 subunit of integrin heterodimers and induces a high avidity state. The adhesion of SMCs to extracellular matrix proteins, but not to poly-L-lysine, was enhanced by pretreatment with mAb 8A2. A qualitative alteration of beta1 integrin was assessed with mAb 15/7, which binds to an activation-dependent epitope on the beta1 subunit. Binding of mAb 15/7 was enhanced by mAb 8A2 in a dose-dependent manner. Arg-Gly-Asp peptide and soluble fibronectin also enhanced expression of the 15/7 epitope, suggesting that the 15/7 epitope is closely related to the ligand-occupied state of beta1 integrin. Platelet-derived growth factor (PDGF)-AA and -BB increased SMC adhesion to type I collagen but did not augment mAb 15/7 binding, suggesting that PDGFs increase binding avidity by a postreceptor mechanism. In addition, mAb 8A2 inhibited PDGF-BB-induced SMC migration through Matrigel-coated filters. These results suggest that avidity modulation of beta1 integrin may play an important role in the function of SMCs.

Antibodies, Monoclonal↗
PubMed1996

Oral biological activities of spontaneous nitric oxide releasers are accounted for by their nitric oxide-releasing rates and oral absorption manners.

We examined whether p.o. biological activities of (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (FK409), a spontaneous nitric oxide (NO) releaser, and the derivatives, i.e., (+/-)-[(E)-4-ethyl-3-[(Z)-hydroxyimino]-5-nitro-3-hexenyl]-3 - pyridinecarboxamide (FR144420) and (+/-)-N-[(E)-4-ethyl-3-[(Z)-hydroxyimino]-6-methyl-5- nitro-3-heptenyl]-3-pyridinecarboxamide (FR146801), could be accounted for by their NO-releasing rates and p.o. absorption manners. These compounds spontaneously released NO with the rates in the rank order of FK409 > FR144420 > FR146801. Total contribution of these drugs as NO donors in vivo was almost the same from the determination of urinary nitrite/nitrate (NOx) levels after p.o. administration of the compounds at 10 mg/kg to rats. Plasma NOx level after p.o. administration of FK409 at 10 mg/kg to rats reached maximal level at 120 min, and decreased gradually. On the other hand, plasma NOx levels time-dependently increased during 360 min after p.o. administration of FR144420 and FR146801 at the same dose. FK409 and FR144420 showed hypotensive effects immediately after p.o. administration at 10 mg/kg to rats, and the maximum response of FR144420 was less and the duration of the effect was longer than those of FK409, respectively. On the other hand, FR146801, which is most stable in solution, did not show any significant hypotensive effect during 240 min after p.o. administration at the same dose. In conclusion, the response and the duration of biological activity after p.o. administration of three spontaneous NO releasers can be closely accounted for by their NO-releasing rates and p.o. absorption manners.

Absorption↗
PubMed1996

Pentamidine is a specific, non-peptide, GPIIb/IIIa antagonist.

Pentamidine was previously shown to act on glycoprotein (GP) IIb/IIIa (Cox et al., Thromb Haemost 1992; 68: 731). In this paper we study the effect of pentamidine on other RGD-dependent receptors. In a cell adhesion assay, pentamidine was 500 times more potent than RGDS at inhibiting platelet adhesion to fibrinogen. While RGDS inhibited platelet adhesion to fibronectin, endothelial cell adhesion to vitronectin or fibronectin, 293 cell adhesion to vitronectin, IMR 32 cell adhesion to fibronectin and C32 cell adhesion to vitronectin; pentamidine failed to inhibit these interactions at doses as high as 1 mM. Resting platelets fixed in the presence of 1 mM RGDS had increased binding of fibrinogen, i.e., RGDS activated GPIIb/IIIa, while pentamidine at 100 microM had no effect. Similarly, RGDS induced the binding of an anti-LIBS monoclonal antibody, while pentamidine had no effect. Pentamidine partially, but significantly, inhibited lysosome and alpha-granule release induced by the thrombin agonist peptide, while RGDS had no effect. Neither pentamidine nor RGDS affected ADP-induced Ca2+ influx. Pentamidine had no effect on ADP-induced intracellular pH changes while RGDS prevented the pH from returning to normal. Thus, pentamidine is a non-peptide GPIIb/IIIa antagonist that is non-activating and is specific for GPIIb/IIIa.

Amino Acid Sequence↗
PubMed1996

Regulation and function of an activation-dependent epitope of the beta 1 integrins in vascular cells after balloon injury in baboon arteries and in vitro.

Migration and proliferation of endothelial cells (ECs) and smooth muscle cells (SMCs) contribute to the response to injury in damaged and atherosclerotic vessels. These events might be regulated by cellular interactions with extracellular matrix through the expression and activation of integrins. To study the functions of beta 1 integrins in the vessel wall, we used monoclonal antibody (MAb) 15/7, which recognizes an activation epitope of beta 1 integrin subunits, and MAb 8A2, which induces a high affinity form of beta 1 integrins recognized by MAb 15/7. Immunohistochemical analyses were done on samples of normal baboon saphenous arteries and from arteries subjected to balloon injury. EC and SMC expressed the activation epitope of beta 1 integrin in uninjured arteries. By contrast, in balloon-injured arteries 6 weeks after injury, regenerating EC did not express the activation epitope, and there was no decrease in the expression of total beta 1 integrin, whereas SMC migrating into the intima exhibited decreased expression of the total and activated beta 1 integrin. Flow cytometer analysis of cultured cells indicated that baboon EC and SMC weakly express the activation epitope of beta 1 integrin. Next, we determined by utilizing MAb 8A2 the effects of increased expression of activation epitope of beta 1 integrin on the functions of SMC and EC. The activation of beta 1 integrins on SMC induced by MAb 8A2 enhanced SMC adhesion and suppressed SMC migration in a Boyden chamber assay. SMC proliferation was inhibited by MAb 8A2 dose-dependently. Similarly, MAb 8A2-induced activation of beta 1 integrins on EC suppressed EC migration into a wound. However, MAb 8A2 did not affect the basic fibroblast growth factor-induced proliferation of EC, although it blocked the decrease in EC number caused by the removal of basic fibroblast growth factor. These results suggest that activation of beta 1 integrins in vascular cells is regulated in a cell-type dependent manner and plays an important role in modulating vascular cell functions.

Animals↗
PubMed1996

Effects of NO-donors on thrombus formation and microcirculation in cerebral vessels of the rat.

Sodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne) laser. SNP infused at doses from 10 micrograms/kg/h significantly inhibited thrombus formation in a dose dependent manner. This inhibition of thrombus formation was suppressed by methylene blue. SIN-1 at a dose of 100 micrograms/kg/h also demonstrated a significant antithrombotic effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity and vessel diameters was increased significantly during infusion. In contrast, mean wall shear rates in the arterioles and venules were not changed by SNP infusion. The results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst SNP increased cerebral blood flow without changing wall shear rate. The findings suggest that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection of cerebral infarction.

Animals↗
PubMed1995

FK409, a new nitric-oxide donor, suppresses smooth muscle proliferation in the rat model of balloon angioplasty.

The effect of FK409, a new nitric-oxide (NO) donor, on neointimal formation of rat carotid arteries following balloon injury was studied. The intimal thickening at 14 days was strongly suppressed by twice daily administration of FK409 at 10 mg/kg from 2 days before to 13 days after injury. The neointima area and neointima/media ratio were decreased by 48.0% (P < 0.01) and 38.5% (P < 0.01), respectively, compared with control. On the other hand, isosorbide dinitrate (ISDN), a classical nitro-vasodilator, did not suppress intimal thickening even at 100 mg/kg twice a day. An in vivo 5-bromo-2'-dedoxyuridine (BrdU) uptake study revealed that FK409 inhibited the proliferative response of smooth muscle cells (SMC) in media at early stage of injury. In fact, the neointimal formation at 14 days was inhibited by the short term administration of FK409 only from the day of injury to 4 days after at 10 mg/kg twice a day. In cultured rat SMC, FK409 (1-10 mumol/l) markedly enhanced intracellular c-GMP and inhibited the proliferation in 10% FBS-containing medium. These results suggest that FK409 suppresses intimal thickening following balloon injury of the rat carotid artery by inhibition of SMC proliferation.

Angioplasty, Balloon↗
PubMed1995

Effect of TFC-612, a 7-thia prostaglandin E1 derivative, on a peripheral arterial occlusive disease model in rats.

TFC-612, methyl 6-[((1R,2S,3R)-3-hydroxy-2-[(1E,3S,5R)-3-hydroxy-5- methyl-1-nonenyl)-5-oxocyclopentyl]-thio]-hexanoate, inhibited the progression of the lesion in a lauric acid-induced peripheral arterial occlusive model at 1.0 mg/kg p.o. or 1.0 microgram/rat/h s.c. in rats. Aspirin (32 mg/kg, p.o.), an anti-platelet drug, did not suppress the lesion growth. On the other hand, ketanserin (10 mg/kg, p.o.), a 5-HT2 antagonist, also inhibited the progression of the lesion. In vitro, TFC-612 inhibited rat platelet aggregation induced by collagen and ADP with IC50 values of 5.4 ng/mL and 9.5 ng/mL, respectively. Aspirin also inhibited collagen-induced aggregation with an IC50 value of 6.3 micrograms/mL, but not ADP-induced aggregation at 180 micrograms/mL. Ketanserin had no effect on either aggregation at 40 micrograms/mL. In ex vivo experiments, aspirin inhibited platelet aggregation induced by collagen at 10 and 32 mg/kg in rats. However, TFC-612 showed significant inhibition only at 10 mg/kg. TFC-612 and ketanserin increased dermal blood flow in the rat paw at 1.0 microgram/kg i.v. and 100 micrograms/kg i.v., respectively. Aspirin had no effect on blood flow at 3.2 mg/kg i.v. These results suggest that the improvement of microcirculation, in addition to anti-platelet action by TFC-612, contributes to its inhibitory effect in a peripheral arterial occlusive model in rats.

Alprostadil↗
PubMed1994

Effect of TFC-612, a 7-thia prostaglandin E1 derivative, on intimal thickening after endothelial injury with balloon catheter in rats.

The effect of TFC-612, methyl-6-[(1R,2S,3R)-hydroxy-2-](1E,3S,5R)-3- hydroxy-5-methyl-1-nonenyl]-5-oxocyclopentyl)thio] hexanoate, on intimal thickening of carotid artery 14 days after endothelium denudation with a balloon catheter was examined in rats. This compound significantly suppressed the neointimal area and the ratio of intimal and medial layer by 41.1% and 31.4%, respectively, at 3.2 micrograms/rat/h s.c. infusion. At this dose, this compound did not inhibit platelet aggregation induced by either collagen or ADP. It did not inhibit bromodeoxyuridine incorporation into medial smooth muscle cells at 3 days after injury. In in vitro experiments, TFC-612 did not inhibit the [3H]thymidine uptake into cultured smooth muscle cells, but it showed significant inhibition of smooth muscle cell migration induced by platelet-derived growth factor (PDGF) at more than 10(-9) M. This compound increased cyclic AMP levels dose dependently in cultured smooth muscle cells at more than 10(-8) M. These results suggest that TFC-612 inhibits intimal thickening by inhibition of smooth muscle cell migration from media to intima through cyclic AMP elevation.

Alprostadil↗
PubMed1994

AP-811, a novel ANP-C receptor selective agonist.

AP-811 is a derivative of the Phe8-Ile15 region of atrial natriuretic peptide (ANP) and is one of the smallest linear ligands for ANP receptors. The binding and agonist activities of AP-811 have been compared with those of other ANP analogs for the ANP-A and ANP-C receptors. AP-811 binds with a high binding affinity to and is a strong agonist for the ANP-C receptor, indicating that the binding and agonist sites for this receptor are the same or near each other in the ANP sequence. In contrast, AP-811 showed no agonistic effect for the ANP-A receptor, although it could bind to this receptor. Comparing the biological activities of AP-811 with those of other ANP analogs, we propose that the binding and agonist sites for the ANP-A receptor may consist of separate regions of ANP. In conclusion, AP-811 is the smallest C-receptor-selective agonist.

Adenylyl Cyclase Inhibitors↗
PubMed1994

Flow pulsation and network structure in mesenteric microvasculature of rats.

Red cell velocity was measured by a fiber-optic laser-Doppler anemometer microscope in microvessels of the mesentery of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto control rats (WKY) with high temporal resolution. Based on the velocity data, the propagation velocity of flow pulse along single microvessels as well as the arteriovenous distributions of the mean volumetric flow, the amplitude of flow pulsation, and the phase lag of the flow relative to the systemic pressure were analyzed in relationship to the vessel wall rheology and the network topology. The propagation velocity was 3.5-134 cm/s in arterioles of 12-43 microns in diameter, and it increased with increasing diameter. The mean volumetric flow exhibited a power law relationship to the vessel diameter, in which the exponents were 3.16 and 3.30 for arterioles and 3.03 and 2.85 for venules in SHR and WKY, respectively. The exponents for arterioles were > 3 (P < 0.1) and different between SHR and WKY (P < 0.12). The amplitude of the flow pulsation also varied in a power law with the vessel diameter, whose exponents for arterioles were 3.41 and 3.52 for SHR and WKY, respectively. The flow phase lag increased gradually with decreasing vessel diameter in arterioles and increased comparatively rapidly with increasing vessel diameter in venules, which suggests more compliant vessel walls for venules than arterioles. The slope of the increase in the flow phase lag with the vessel diameter in arterioles of SHR was larger than that for WKY (P < 0.05). This difference in the flow phase lag distribution and the difference in the exponent of the mean flow rate vs. diameter relationship may reflect that the number of small arterioles relative to large ones is reduced in SHR microvasculature compared with that in WKY.

Animals↗
PubMed1993

The anti-platelet actions of FR122047, a novel cyclooxygenase inhibitor.

The anti-platelet actions of 1-[(4,5-bis(4-methoxyphenyl)-2- thiazoyl)carbonyl]-4-methylpiperazine hydrochloride (FR122047) were investigated in vitro and in vivo. FR122047 was 100 times more potent than aspirin against arachidonic acid- and collagen-induced human and guinea-pig platelet aggregation in vitro. Its actions on platelets were a result of cyclooxygenase inhibition. The single oral dose of FR122047 inhibited arachidonic acid- and collagen-induced aggregation with an ED50 of 280 micrograms/kg and 530 micrograms/kg, respectively, in guinea-pigs. The anti-platelet action was augmented 5-10 times by repeated administration for 4 days. At 1 mg/kg the inhibitory actions were prolonged for 48 h and the drug concentration was < 0.1 ng/ml in platelet-poor plasma at 24 h and 0.282 ng/ml in platelet-rich plasma at 48 h. The safety margin in rats (minimum ulcerogenic dose/ED50 for anti-platelet aggregation) of FR122047 was more than 70, while that of aspirin was only 1.2. These results indicate that FR122047 is concentrated in platelets and may be a useful anti-platelet agent.

Animals↗
PubMed1993

Characteristics of the epitope of protein-reactive anti-peptide antibodies.

The specificity of hen egg-white lysozyme (HEL)-reactive rabbit antibodies induced by the peptide loop I.II (sequences 57-107 containing Cys64-Cys80 and Cys76-Cys94) of HEL was clarified by analyzing their cross-reactions with various avian lysozymes and their reaction with synthetic peptides (sequences 59-82) in which alanine was substituted for the amino acid at certain positions. The Arg-68 residue of HEL plays a dominant role in the binding, while Gly-71, Ser-72, Arg-73, and Pro-79 also contribute to the binding of two anti-Ploop I.II antibodies (rabbit number 125 and 126). These residues, although remote in sequence, are grouped together in the crystal structure of HEL and may form an area of contact with the antibody. Contributions by Trp-63, Ile-78, and Asn-77 to the binding of the two antibodies to HEL were excluded. These results support the idea that the anti-Ploop I.II antibodies recognize a conformational type of epitope which is similar to that of native HEL. The immunogenicity of the reduced and alkylated form of Ploop I.II was also tested, but it failed to induce an HEL-reactive antibody.

Alanine↗