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Biomedical subjects

M Asano

Publications and source records attributed to M Asano.

At least 307 records · Page 17Linked to original sources
PubMed1992

Effects of cromakalim on the contraction and the membrane potential of the circular smooth muscle of guinea-pig stomach.

1. The effects of cromakalim on mechanical and electrical activities of the circular smooth muscles of guinea-pig stomach antrum were observed. 2. Cromakalim (greater than 1 x 10(-7) M) decreased the amplitude of spontaneous rhythmic contractions and also the acetylcholine-enhanced spontaneous contractions. Cromakalim was less effective against the 25.9 mM and 35.9 mM K(+)-induced tonic contractions. 3. Glibenclamide (1 x 10(-6) M) itself caused no detectable change in the spontaneous contractions, those potentiated by acetylcholine or tonic contractions induced by high K+ solutions, but attenuated the actions of cromakalim. On the other hand, charybdotoxin (3 x 10(-8) M) increased the amplitude of spontaneous contractions but failed to affect the actions of cromakalim. 4. Cromakalim (greater than 1 x 10(-6) M) decreased the amplitude and duration of slow waves, and hyperpolarized the membrane. These actions of cromakalim were completely antagonized by 1 x 10(-6) M glibenclamide, whereas part of the effects of cromakalim on mechanical activity was resistant to glibenclamide. 5. The results suggest that the inhibition by cromakalim of the electrical activity and the hyperpolarization, which may be associated with the opening of glibenclamide-sensitive K+ channel, are responsible for its inhibitory action on circular smooth muscle of guinea-pig stomach. Further, some effects independent of glibenclamide-sensitive K+ channel may also be responsible for the mechanical effect.

Acetylcholine↗
PubMed1992

Cerebral microcirculatory changes after cerebral embolization induced by glass bead injection in rabbits.

The authors investigated microcirculatory changes in cerebral embolization induced by an injection of glass beads (mesh size 20/400, 15 mg/body) using intravital microscopy and reflectance spectrophotometry in normal rabbits. Cerebral embolization with the glass bead injection reduced the inner diameter of cerebral arterioles, the index of cerebral hemoglobin concentration (IHb), and the index of oxygen saturation (ISO2). Moreover, platelet aggregation rates and plasma levels of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) appreciably increased. During observation of the pial vasculature, "white bodies" became visible at the entrance of arteriolar branchings two to three minutes after the glass bead injection. After indomethacin administration (3 mg/kg, IV), they could not observe white bodies, and platelet aggregation rates were significantly reduced. The plasma levels of TXB2 and 6-keto-PGF1 alpha were also significantly reduced. These findings suggest that glass beads do injury to the microvascular endothelial cells leading to development of white bodies, ie, "flying thrombi." Therefore, the cerebral microvascular embolization induced by the glass bead injection appears to be an experimental model for evaluating efficacy of remedies for the cerebral microcirculatory disorders.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Studies on the chemical modification of monensin. IV. Synthesis, sodium ion permeability, and biological activity of 7-O-acyl- and 7-O-alkylmonensins.

7-O-Acyl-(4a-e) and 7-O-alkylmonensins (5a-d) were prepared from monensin (1). Their lipophilicity, sodium ion permeability in human erythrocytes, antibacterial activity and effect on rat tail artery were examined. There was a correlation between lipophilicity and sodium ion permeability as well as between lipophilicity and antibacterial activity. We also found that the compound having larger sodium ion permeability, showed stronger contraction of rat tail artery. 7-O-Benzylmonensin (5c) exhibited higher lipophilicity and larger sodium ion permeability than monensin (1) among the tested monensin derivatives. In addition, antibacterial activity and contractile effect on rat tail artery of 5c were comparable to those of 1.

Animals↗
PubMed1992

Syntheses of 2-(3,4-dimethoxyphenyl)ethylamine derivatives and their antiulcer activities.

A series of acyl derivatives of 2-(3,4-dimethoxyphenyl)ethylamine (4) were synthesized and evaluated for their effectiveness to prevent water-immersion stress-induced gastric ulceration when given intraperitoneally to rats. Among them N-[2-(3,4-dimethoxyphenyl)ethyl]-2-phenylaminoacetamide hydrochloride (15) had significant antiulcer activity. Further modification of the four parts of 15 revealed that only the introduction of a carbamoyl group into 2- or 3-position of the phenylamino part gave compounds (49-51, 54 and 55) which retained antiulcer activity comparable to the lead compound. However, the compounds (49-51 and 54) did not exert a prophylactic effect when administered orally except for the 3-substituted bezamide derivative 55. Alkyl substitution on the nitrogen of benzamide gave 3-[[[2-(3,4-dimethoxyphenyl)ethyl]carbamoyl]methyl] amino-N-methylbenzamide (66, DQ-2511) and the related compounds (67, 70, 74 and 77) which all had potent antiulcer activities at oral doses of 50-400 mg/kg.

Animals↗
PubMed1992

[Studies on cardiac ingredients of plants. X. Preparation of nitrates of tetrahydroproscillaridin and their pharmacological activities].

To reduce the vascular contracting effect of the hydrogenated cardiac glycosides, 20-(R)- and 20-(S)-tetrahydroproscillaridins (THPs, 1a, 1b), and to extend the concentration-dependent range, mono- and dinitrates of THPs were prepared. The pharmacological activities of the nitrates of THP were evaluated by use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase preparations from dog kidney. Furthermore, the effect for smooth muscle was examined using the helical strips isolated from 13-week-old spontaneously hypertensive rat. The positive inotropic effects of mononitrates (11a, 11b, 2a, 2b, 8a, and 8b) were more potent than those of THPs. Nitration of the sugar moiety in THPs resulted in a vascular relaxing effect unobserved in the case of THPs.

Animals↗
PubMed1992

Possible involvement of nuclear oncoproteins in regulation of DNA replication.

Polyomavirus DNA replication requires its enhancer which contains an AP-1 site. We have shown that protooncogenes, c-jun and c-fos, whose products form heterodimeric transcription activator, AP-1, strongly stimulate polyomavirus DNA replication through the AP-1 site. The mechanisms by which this enhancer stimulates replication and transcription are different. By replacing the enhancer with the oligonucleotides representing the binding site of a transcription factor of interest, any transcription factor with the known binding sequence can be characterized in this replication assay. When Rel protein was examined, we were able to reveal a new domain in v-Rel protein which can stimulate replication strongly. Whether this domain also coincides with transforming potential of v-Rel protein is currently under investigation.

Animals↗
PubMed1992

[Solitary infected renal cyst: a case report].

A 48-year-old man was admitted to our hospital because of high fever and left flank pain. Laboratory findings revealed a high white blood cell count, high C-reactive protein level, and severe pyuria. Sonographic examination revealed an enlargement of the cyst at the upper pole of the left kidney that had already been detected. Percutaneous drainage was performed for the cyst and 60 ml of purulent fluid was obtained. Bacterial culture of the fluid was positive for Propionibacterium acnes and gamma-Streptococcus. The drainage and administration of povidone-iodine was continued for 7 days. The size of the cyst was reduced with disappearance of symptoms.

C-Reactive Protein↗
PubMed1992

A 5-lipoxygenase inhibitor, FR110302, suppresses airway hyperresponsiveness and lung eosinophilia induced by Sephadex particles in rats.

To study the role of chemical mediators in airway hyperresponsiveness and simultaneous eosinophilia, we examined effects of a potent 5-lipoxygenase inhibitor FR110302 and those of prednisolone, indomethacin, platelet-activating factor (PAF) antagonist (RP-59227) and leukotriene C4 (LTC4) antagonist (ONO-1078) on airway hyperresponsiveness and lung eosinophilia induced by Sephadex particles. Sephadex G200 particles (2.5 mg/kg) were injected intravenously to rats and 3 days later the airway hyperresponsiveness to acetylcholine (ACh) and the eosinophilia in the bronchoalveolar lavage (BAL) fluids were observed. FR110302 (10 mg/kg b.i.d.p.o.) significantly suppressed both of these indicators of asthma. The amounts of immunoreactive LTB4,C4 (i-LTB4, C4) in the BAL fluid were measured by radioimmunoassay. The amounts of i-LTB4,C4 in the FR110302-treated rats were significantly less compared with that in the Sephadex-injected controls. Prednisolone completely inhibited the airway hyperresponsiveness. PAF antagonist and LTC4 antagonist partially inhibited the airway hyperresponsiveness, and indomethacin had no effect. The results indicate that 5-lipoxygenase products play important roles in the Sephadex-induced airway hyperresponsiveness and lung eosinophilia in rats.

Acetylcholine↗
PubMed1992

[Function, molecular structure and gene expression of fibroblast growth factor (FGF/HBGF)].

The structure and function of members of the fibroblast growth factor (FGF) gene family and their receptors are reviewed. All the member of this gene family bind heparin, and therefore, are also called the as heparin-binding growth factor (HBGF). In this review, the structural features of FGF/HBGF are summarized first, and general features of the structure and function of their receptors are then described briefly. After biological effects of FGF/HBGF on adult-type tissues and cultured cells are reviewed, effects of FGF on the mesodermal induction in amphibian (Xenopus laevis) embryonic system are reviewed in more detail. Emphasis is given on the experiments with Xenopus animal cap assay system and also on the injection into Xenopus fertilized eggs of mRNA of dominant defect mutant of FGF receptor, which leads to the formation of embryos with abnormal axial mesoderm.

Animals↗
PubMed1992

Laminoplasty versus subtotal corpectomy. A comparative study of results in multisegmental cervical spondylotic myelopathy.

A comparative study of surgical results was used to determine the treatment of choice for multisegmental cervical spondylotic myelopathy. Forty-one patients who received subtotal corpectomy and strut grafting (SCS) and forty-two undergoing laminoplasty were followed up for at least 2 years after surgery. Regarding factors known to affect surgical prognosis (age at surgery, duration of symptoms, severity of neurologic deficit, anteroposterior canal diameter, transverse area of the cord at the site of maximum compression, number of levels involved), the two groups were statistically comparable with each other. The severity of neurologic deficits was assessed by the Japanese Orthopaedic Association scale. Results were evaluated in terms of postoperative score and recovery rate. The difference between the recovery rate and final score between the two groups was not statistically significant. Surgical complications were more frequent in the subtotal corpectomy and strut grafting group than in the laminoplasty group. The most frequent complications encountered in the subtotal corpectomy and strut grafting group were related to bone grafting. Spinal alignment worsened in six patients of the laminoplasty group, but none of them suffered from neurologic deterioration. Another disadvantage of subtotal corpectomy and strut grafting was the longer postoperative period of bed rest needed to secure graft stability. We conclude that laminoplasty should be the treatment of choice for multisegmental cervical spondylotic myelopathy when neurologic results, incidence of complications, and postoperative treatment are taken into consideration.

Aged↗
PubMed1992

[Effects of prostaglandin E1 and epidural block on circulatory, hepatic and renal functions during anesthesia for major upper abdominal surgeries].

The effects of low dose (0.02 microgram.kg-1.min-1) prostaglandin E1 (PGE1), epidural block (EP) or combination of PGE1 and EP (PGE1 + EP) under general anesthesia on circulatory, hepatic and renal functions were studied in 31 patients undergoing major upper abdominal surgeries without hepatic or renal dysfunction preoperatively. Mean arterial pressure decreased by 10% in PGE1 and EP groups, while 20% in PGE1 + EP group. Cardiac output decreased significantly in EP group, increased in PGE1 group and was unaltered in PGE1 + EP group during anesthesia and the operation. The arterial ketone body ratio as a hepatic function test increased following the administration of PGE1 or epidural block. Urine output, osmotic clearance and free water clearance were higher in PGE1 + EP group during the operation. These results suggest that the combination of low dose PGE1 and epidural block maintain cardiac output and organ blood flow during anesthesia and surgery in spite of a greater decrease in arterial blood pressure.

Abdomen↗
PubMed1992

Modulation of hepatic and pulmonary drug-metabolizing enzyme activities of rabbits by dietary cholesterol.

Modulation of the activities of drug-metabolizing enzymes by dietary cholesterol was studied in rabbits. In male rabbits fed a 1.5% cholesterol-diet, an elevated levels of serum cholesterols and triglycerides were observed from the early phase of cholesterol-feeding. At 12 weeks after the onset of cholesterol feeding, a marked increase was observed in the wet weights of livers but not of lungs, while total contents of lipids and cholesterols were elevated in both tissues in cholesterol-fed animals. The content of collagen was increased significantly in livers, but not in lungs and the phase I drug-metabolizing enzyme activities were significantly reduced in livers but remained unchanged in lungs by cholesterol feeding. On the other hand, the phase II drug-metabolizing enzyme activities varied depending on the enzymes in both tissues. The results demonstrate that dietary cholesterol induces different effects on rabbit liver and lung and that the modulation of the hepatic enzymes by dietary cholesterol in rabbits differs from that in rats, mice and guinea pigs in which the activity of the enzymes are elevated by dietary cholesterol.

Animals↗
PubMed1991

Activin receptor mRNA is expressed early in Xenopus embryogenesis and the level of the expression affects the body axis formation.

Activin is a member of the transforming growth factor beta (TGF-beta) and possesses various activities in cellular control phenomena. During Xenopus embryonic development, activin is thought to act as a natural mesoderm-inducing factor. We isolated here the Xenopus activin receptor cDNA from Xenopus tadpole cDNA library and examined the expression of the Xenopus activin receptor gene during the course of early embryonic development. The Xenopus activin receptor has an 87% homology at the level of deduced amino acid sequence with the mouse activin receptor, and using the cDNA obtained, three bands of mRNA with different lengths were detected in Xenopus embryos throughout early embryogenesis. We synthesized activin receptor mRNA in vitro and tested the effect of the injection of the mRNA into Xenopus fertilized eggs on subsequent development. When the synthetic mRNA was injected into uncleaved fertilized eggs, embryos with reduced trunk structure were formed. However, when the mRNA was injected into the ventral blastomeres at the 16-cell stage, embryos with a secondary body axis were formed. These results indicate the importance of the function of activin receptor in the regulatory mechanism for body axis formation.

Activin Receptors↗