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Biomedical subjects

K Kuroda

Publications and source records attributed to K Kuroda.

At least 343 records · Page 19Linked to original sources
PubMed1988

Effects of cadralazine on contractions induced by norepinephrine, serotonin, angiotensin II and K+ in rabbit aortic and renal arterial strips.

Antagonistic effects of the new antihypertensive agent cadralazine (ethyl(+/-)-6-[ethyl(2-hydroxypropyl)-amino]-3-pyridazinecarbazate ) and its metabolite ISF-2405 [+/-)-6-[ethyl(2-hydroxypropyl)amino]-3-hydrazinopyridazine) on norepinephrine (NE), 5-hydroxytryptamine (serotonin), angiotensin II (angio II) and KCl induced contractions of rabbit abdominal aortic and renal arterial strips were compared with those of hydralazine. Substantially, cadralazine does not exert any effect on cumulative dose-response curves of these agonists in both vessel preparations even with the highest concentration of 10(-4) mol/l. ISF-2405 and hydralazine at concentrations of 10(-5) and 10(-6) mol/l showed non-competitive antagonism, depending not only on the dose but also on the length of the pretreatment time, on NE-induced contractions of abdominal aorta and renal artery. The two drugs attained maximal pD2 values with 60 min pretreatment without showing significant difference between the two vessel preparations, suggesting that the inhibitory effect of these drugs does not show vascular bed-related difference against NE-induced contractions. 60 min pretreatment with 10(-6) and 10(-5) mol/l of ISF-2405 and hydralazine also manifested non-competitive antagonism on contractile responses to serotonin, angio II, and K+ for both compounds. The degree of antagonistic effects of ISF-2405 and hydralazine on these agonists is similar, the order being angio II greater than serotonin greater than NE greater than K+. These results suggest that ISF-2405 and hydralazine exert direct vasodilating effects by the same mode of action at a site other than receptors against Ca2+ mobilization.

Angiotensin II↗
PubMed1988

Effects of cadralazine on contractions induced by Ca2+ and norepinephrine in isolated rabbit aortic strips.

Antagonistic effects of the new antihypertensive agent cadralazine (ethyl(+/-)-6-[ethyl(2-hydroxypropyl)-amino]-3-pyridazinecarbazate ) and its metabolite ISF-2405 [+/-)-6-[ethyl(2-hydroxypropyl)amino]-3-hydrazinopyridazine) on contractile responses to CaCl2 in K+-depolarised medium and to norepinephrine (NE) in Ca2+-free medium were compared with those of hydralazine using isolated rabbit abdominal aortic strips. Even at high doses of cadralazine (10(-4) mol/l), ISF-2405 (10(-5) mol/l) and hydralazine (10(-5) mol/l), only less than 10% inhibition was observed on dose-dependent contractions induced by CaCl2, 0.05 to 6.4 mmol/l, in K+ 40 mmol/l medium. NE produced dose-dependent contractions even in Ca2+-free medium at concentrations of 10(-9) to 3 X 10(-5) mol/l, and the maximal response was diminished to about 45% of the response in the presence of Ca2+. Cadralazine 10(-4) mol/l exerted no effect on Ca2+-free NE-induced contractions, while ISF-2405 and hydralazine at concentrations of 10(-7) to 10(-5) mol/l were equipotent, showing marked dose-dependent, non-competitive inhibition on NE-induced contractions. These results suggest that ISF-2405 and hydralazine show vasodilating effect through the inhibition of the Ca2+-release from intracellular storage but not via inhibition of the potential dependent Ca2+ influx.

Animals↗
PubMed1987

Dynamic aspects of the contractile system in Physarum plasmodium. III. Cyclic contraction-relaxation of the plasmodial fragment in accordance with the generation-degeneration of cytoplasmic actomyosin fibrils.

Plasmodial fragments of Physarum polycephalum, excised from anterior regions of a thin-spread plasmodium, contracted-relaxed cyclicly with a period of 3-5 min. The area of the fragments decreased approximately 10% during contraction. In most cases, there was little endoplasmic streaming which indicates that contractions were synchronized throughout the fragment. By both polarized light and fluorescence microscopy, the organization and distribution of the cytoplasmic actomyosin fibrils in the fragments changed in synchrony with the contraction cycle. The fibrils formed during the contraction phase, and finally became a highly organized framework consisting of a three-dimensional network of numerous fibrils with many converging points (the nodes). During relaxation, the fibrils degenerated and disappeared almost completely, though some very weak fibrils remained near the nodes and the periphery. The results obtained by fluorometry of the fragments, stained with rhodamine-phalloidin, suggested that the G-F transformation of actin is not the main underlying process of the fibrillar formation.

Actomyosin↗
PubMed1987

[A case of hepatocellular carcinoma with extrahepatic portal vein obstruction due to tumor invasion, responsive to oral administration of UFT].

A 38-year-old male was admitted to Ikeda Municipal Hospital because of thrombocytopenic purpura and abnormal liver function. Computed tomography and ultrasonography of the liver showed a 5 by 5 cm mass in the right lobe of the liver. Hepatic angiography revealed a hypervascular tumor in the right lobe of the liver and extrahepatic portal venous obstruction. A diagnosis of hepatocellular carcinoma with extrahepatic portal venous obstruction due to tumor invasion was made. Endoscopic examination showed marked esophageal varices with red color sign. Oral administration of UFT at a daily dose of 400 mg was started. Though ascites and frequent hemorrhage from esophageal varices were observed, these symptoms disappeared completely after 8 months administration of UFT. Endoscopic examination revealed disappearance of the esophageal varices, and recanalization of the extrahepatic portal vein was confirmed by the second hepatic angiography. Computed tomography showed no growth of the liver tumor. These data suggest that UFT was effective in this case.

Administration, Oral↗
PubMed1987

Inhibitory effect of fumaric acid on hepatocarcinogenesis by thioacetamide in rats.

An inhibitory effect of fumaric acid (FA) on hepatocarcinogenesis was examined in rats fed thioacetamide (TAA). A group of male DONRYU rats were fed TAA at a level of 0.035% in the diet for 40 weeks and then fed a basal diet for 40 weeks. Hepatic carcinomas developed in 9 of 41 animals of this group fed TAA alone. The effect of FA on the carcinogenesis was examined in 2 groups fed both TAA and FA; one group of rats were fed FA at 1% in a basal diet after ingestion of TAA, and another group of rats were fed TAA plus a supplement of 1% FA in the diet. The inhibitory effect of FA on TAA carcinogenesis was so marked that no hepatic carcinomas were found in both groups fed FA in combination with TAA.

Acetamides↗
PubMed1986

Phosphorylation of Amoeba G-actin and its effect on actin polymerization.

Mass culture of Amoeba proteus enabled us to do biochemical studies on this organism. Actin and profilin were purified from Amoeba to examine actin phosphorylation and polymerization. The apparent molecular weight of Amoeba actin was 44,000, and its isoelectric point was 5.8. The apparent molecular weight of Amoeba profilin was 12,000, and its isoelectric point was 4.9. It reduced the rate of actin polymerization as reported in the cases of profilins from other organisms. A protein of Mr = 44,000 (44 K protein) was phosphorylated in a Ca2+-dependent manner in cell homogenate of Amoeba without being inhibited by calmodulin antagonists. Using the homogenate as a kinase, purified Amoeba G-actin could be phosphorylated in proportion to the amount of actin. However, neither Amoeba F-actin nor rabbit skeletal muscle G-actin was phosphorylated. The phosphorylation of Amoeba actin with a kinase partially purified from A. proteus increased with dilution of the actin concentration. When Amoeba profilin was added, more than 80% of the actin was phosphorylated. By viscometry, electron microscopy, and ultracentrifugation analysis it was demonstrated that Amoeba G-actin phosphorylated in the presence of profilin and kinase did not polymerize in this solution. High-performance liquid chromatography analysis showed that phosphorylated Amoeba actin remained in a monomeric state even under conditions favorable for actin polymerization.

Actins↗
PubMed1986

Expression of the influenza virus haemagglutinin in insect cells by a baculovirus vector.

The insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) has played a major role in studies on the molecular biology of insect DNA viruses. Recently, this system has been effectively adapted as a highly efficient vector in insect cells for the expression of several mammalian genes. A cDNA sequence of the influenza (fowl plague) virus haemagglutinin gene has been inserted into the BamHI site of the pAc373 polyhedrin vector. Spodoptera frugiperda cells were co-transfected with this construct, pAc-HA651, and authentic AcNPV DNA. Recombinant virus was selected by adsorption of transfected cells to erythrocytes followed by serial plaque passages on S. frugiperda cells. We have determined the site of insertion of the haemagglutinin gene into the AcNPV genome by restriction enzyme cleavage and Southern blot hybridization analyses using haemagglutinin cDNA as a probe. The influenza haemagglutinin gene is located in the polyhedrin gene of AcNPV DNA. Immunofluorescent labelling, immunoprecipitation and immunoblot analyses with specific antisera revealed that S. frugiperda cells produce immune reactive haemagglutinin after infection with the recombinant virus. The haemagglutinin is expressed at the cell surface and has haemolytic capacity that has been activated by post-translational proteolytic cleavage. When chickens were immunized with S. frugiperda cells expressing haemagglutinin, they developed haemagglutinin-inhibiting and neutralizing antibodies and were protected from infection with fowl plague virus. These observations demonstrate that the haemagglutinin is processed in insect cells in a similar fashion as in fowl plaque virus-infected vertebrate cells and that it has full biological activity.

Amino Acid Sequence↗
PubMed1986

Mutations blocking the transport of the influenza virus hemagglutinin between the rough endoplasmic reticulum and the Golgi apparatus.

Mutants ts1 and ts227 of fowl plague virus have a temperature-sensitive defect in the transport of the hemagglutinin from the rough endoplasmic reticulum to the Golgi apparatus. The primary structure of the hemagglutinin of the mutants and of a number of revertants derived from them has been analysed by nucleotide sequencing. The transport block of the hemagglutinin of ts227 can be attributed to a single amino acid exchange. It involves the replacement of aspartic acid at position 457 by asparagine thereby introducing a new glycosylation site which appears to be located in a cryptic position in the lower part of the hemagglutinin stalk. Attachment of carbohydrate to this site is temperature-dependent. At permissive temperature only a small fraction of the monomers (approximately 30%) is glycosylated in this position, whereas at nonpermissive temperature this is the case with all subunits. The data suggest that under the latter conditions the new oligosaccharide interferes by steric hindrance with the trimerization of the hemagglutinin. The hemagglutinin of ts1 has an essential amino acid exchange at position 275 where serine is replaced by glycine. This substitution may increase the flexibility of the molecule in the hinge region between the globular domain and the stalk. The exchange of a conserved glutamic acid residue at position 398 that is involved in the interaction between different monomers contributes also to the structural instability of the ts1 hemagglutinin. These observations support the notion that the transport of the hemagglutinin from the rough endoplasmic reticulum to the Golgi apparatus depends on trimer assembly.

Animals↗
PubMed1986

Spermatogenesis in Snell dwarf, little and congenitally hypothyroid mice.

The status of spermatogenesis in Snell dwarf, little and congenitally hypothyroid mice was studied. In all of these mice with a hormone deficiency the seminiferous tubules were smaller in size and contained fewer spermatogonia, spermatocytes, spermatids and spermatozoa than did those of normal control mice. There was no substantial difference in the Johnsen score between the hormone-deficient mice and normal control mice, but the former had underdeveloped seminiferous tubules with a corresponding paucity of germ cells, which may be partly responsible for the infertility of these mice. In the present study, growth hormone and thyroxine were administered separately to growth hormone-deficient and thyroxine-deficient mice, respectively. Such replacement therapy brought about an increase in cell counts of the seminiferous tubules and in sperm counts in both groups.

Animals↗