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H Michishita

Publications and source records attributed to H Michishita.

16 recordsLinked to original sources
PubMed1997

Structure-activity relationships of cyclic enediynes related to dynemicin A. I. Synthesis and antitumor activity of 9-acetoxy enediynes equipped with aryl carbamate moieties.

A series of the 9-acetoxy enediyne compounds, 6a-k which were simplified from natural dynemicin A, and designed to be equipped with various aryl carbamate moieties, was synthesized and evaluated for DNA-cleaving ability, in vitro cytotoxicity, and in vivo antitumor activity. As a result of this study of the structure-activity relationships (SAR) with regard to the Rt substituent, both compounds 6a and 6f with the phenyl carbamate and 4-chlorophenyl carbamate moiety, respectively, were found to exhibit significant activity (T/C > 200%) against murine P388 leukemia in mice, in spite of having IC50 values in the micromolar range. In particular, compound 6f showed the most potent activity with a maximum T/C of 256% at a daily dosage of 4.0 mg/kg for four days. Furthermore, both compounds 6a and 6f were effective against Meth A sarcoma in mice and inhibited 71 and 77% of the tumor growth at 2.0 and 3.0 mg/kg dosages, respectively. In contrast to 6f, compound 6i possessing the 2-nitrophenyl carbamate moiety showed only a slight in vivo activity, while it had about one order of magnitude higher in vitro cytotoxicity than 6f. For the stereochemistry-activity relationships at the C9 position, the (9R*)-isomers of 6c, 6g, and 6j were found to show higher in vitro and in vivo potencies than the corresponding (9S*)-isomers.

Animals↗
PubMed1997

Structure-activity relationships of cyclic enediynes related to dynemicin A. II. Synthesis and antitumor activity of 9- and 12-substituted enediynes equipped with aryl carbamate moieties.

Novel enediyne compounds 4-8, simple analogues of dynemicin A (1) equipped with the phenyl or 4-chlorophenyl carbamate moiety, were synthesized and evaluated for DNA-cleaving ability, in vitro cytotoxicity, and in vivo antitumor activity. As a result of the SAR study, it was revealed that the size and character of the substituents (R1 and R2) at the C9 position critically influenced both the stability and antitumor activity of the enediyne compounds. We found that the 9-deoxy compound 6a, a stable and less bulky enediyne having a hydrogen as the R1 and R2 substituents, showed a significant in vivo activity with a T/C of 215% at a daily dosage of 2.0 mg/kg for 4 days. The incorporation of an oxygen-containing functional group as the R3 substituent on a benzene ring resulted in considerable abolishing of both the in vitro and in vivo potencies. In a series of 9-acyloxy compounds, incorporation of the basic aromatic moiety such as 8e was effective for the in vitro activity, but it was ineffective for the in vivo activity. Furthermore, for the stereochemistry-activity relationships at the C9 position, the (9R*)-isomers of 8c, 8e, and 8f were found to show higher both in vitro and in vivo than the corresponding (9S*)-isomers. For the mechanistic studies, compound 6a underwent Bergman cycloaromatization via a diradical pathway under acidic conditions, whereas it scarcely showed DNA-cleaving activity due to the chemical stability of the aryl carbamate moiety under neutral conditions.

Animals↗
PubMed1997

Synthesis and antitumor activity of water-soluble enediyne compounds related to dynemicin A.

The enediyne compounds 9-14, simple dynemicin A (1) analogues equipped with aryl carbamate moieties with various aliphatic amino or hydroxy groups at the C9 position, were synthesized and evaluated for DNA-cleaving ability, in vitro cytotoxicity, and in vivo antitumor activity. We found that the water-soluble compounds, in which the tert-amines such as the 2-(dimethylamino)ethyl (10b, 14b), 2-(pyrrolidino)ethyl (10c), or 1-azabicyclo[3.3.0]oct-5-ylmethyl (10d, 12d, 14d) group were attached, showed not only the enhanced in vivo antitumor activity but also the decreased toxicity compared to the corresponding 9-acetoxy enediyne compounds 6-8. In particular, compound 10c showed the most enhanced in vivo antitumor activity (T/C = 222% at a daily dose of 1.25 mg/kg for 4 days) at about half of the dose of 6. These results suggest that both the enhanced antitumor activity and the reduced toxicity might be due to the improved bioavailability or disposition of compounds 6-8 by their water-solubilization.

Animals↗
PubMed1997

Synthesis and biological evaluation of novel cyclic enediyne compounds related to dynemicin A as antitumor agents.

Novel cyclic enediyne compounds, which are simple functional analogs of dynemicin A (1) having the bicyclo-[7.3.1]tridec-4-ene-2,6-diyne system, were synthesized and evaluated for the DNA-cleaving ability, in vitro cytotoxicity and in vivo antitumor activity. All of the sulfones 19-24, which were equipped with a 2-(arylsulfonyl)-ethoxycarbonyl group or the 2-(methylsulfonyl)ethoxycarbonyl group as a triggering device, showed both potent DNA-cleaving activity and cytotoxicity against various tumor cell lines. However, these compounds were entirely inactive or only slightly active against murine P388 leukemia in mice. On the other hand, the enediyne 2a having a phenyl carbamate moiety as a stable N-protecting group showed effective antitumor activity both in vitro and in vivo. In particular, it exhibited significant antitumor activity against Lewis lung carcinoma in mice. These results show that the character of the carbamate moiety of the cyclic enediynes strikingly affects their biological activities, that is, the sulfonylethyl carbamate moiety is an effective triggering device for both DNA-cleaving activity and cytotoxicity, and the phenyl carbamate moiety is significant for antitumor activity in vivo. As part of a mechanistic study, the reactivities of 2a and 21 were examined under a weakly basic condition (pH 9.3); both compounds failed to give the Bergman cycloaromatization product.

Alkynes↗
PubMed1994

Effects of recombinant superoxide dismutase on manganese superoxide dismutase gene expression in gerbil hippocampus after ischemia.

BACKGROUND AND PURPOSE: We reported that recombinant human superoxide dismutase ameliorates delayed neuronal death in the postischemic gerbil hippocampus. Since postischemic induction of copper-zinc superoxide dismutase messenger RNA was abolished by this treatment, oxygen radicals generated on reperfusion may induce the expression of this gene. In the present study we examined whether oxygen radicals also induce the expression of manganese superoxide dismutase messenger RNA in the postischemic brain. METHODS: We induced transient cerebral ischemia by occluding the bilateral common carotid arteries of gerbils. Recombinant human superoxide dismutase (8 x 10(5) U/kg) or apo-superoxide dismutase was administered intravenously 1 minute before a 5-minute occlusion of the carotid arteries. We analyzed both copper-zinc and manganese superoxide dismutase RNA by in situ hybridization histochemistry and by Northern and dot blot analyses using radioisotope-labeled oligonucleotide probes. RESULTS: Hybridization with the manganese superoxide dismutase messenger RNA occurred at the limit of detection in normal CA1 neurons. We observed striking increases in the labeling of CA1 up to 24 hours after 5 minutes of ischemia. The hybridization occurred anew in glial cells of the CA1 layer during 3 to 7 days. Pretreatment with recombinant human superoxide dismutase had no effect on the postischemic induction of manganese superoxide dismutase messenger RNA, whereas the same treatment significantly attenuated (P < .01) the increase in copper-zinc superoxide dismutase messenger RNA. CONCLUSIONS: Our results demonstrated temporal postischemic induction of manganese superoxide dismutase messenger RNA. The inducer may not be superoxide radicals but may be other chemical mediators such as cytokines.

Amino Acid Sequence↗
PubMed1994

Pharmacodynamics and tumoricidal effect of adriamycin entrapped in ceramide sulfate-containing liposomes.

Ceramide sulfate (N-acylsphingosine-1-O-sulfate), which lacks the galactose residue of sulfatide, was examined as a possibly preferable constituent of liposomes for drug delivery. Multilamellar vesicles prepared from phosphatidylcholine, cholesterol, and N-lignoceroylsphingosine-1-O-sulfate in a molar ratio of 5:4:1 efficiently entrapped adriamycin, and the retention of the drug in the liposomes in saline at 4 degrees C for 8 d was nearly 100%. In terms of entrapment efficiency and retention of the drug in liposomes, N-lignoceroylsphingosine-1-O-sulfate was superior to N-stearoylsphingosine-1-O-sulfate. A pharmacodynamic study revealed that the blood level of adriamycin was far higher with the drug encapsulated in N-lignoceroylsphingosine-1-O-sulfate-containing liposomes than with the free drug. The drug level in the heart was remarkably reduced with the liposome-entrapped drug, which is advantageous in reducing the cardiotoxicity of this drug. The effect of N-lignoceroylsphingosine-1-O-sulfate-containing liposomes on the blood level of adriamycin was superior to that of sulfatide-containing liposomes, though the effect of the former on the heart level was comparable to that of the latter. The tumoricidal effect on ascitic P388 leukemia and Lewis lung carcinoma was higher with adriamycin entrapped in N-lignoceroylsphingosine-1-O-sulfate-containing liposomes than with the free drug.

Animals↗
PubMed1994

Risk factors for carotid atherosclerosis and platelet activation.

Thromboxane A2 biosynthesis was studied in healthy subjects, in patients in whom the extent of carotid atherosclerosis was determined, and in patients receiving chronic aspirin treatment, to determine what factors activate platelets to develop carotid atherosclerosis. Urinary 11-dehydrothromboxane B2, a major metabolite of thromboxane A2, was measured by radioimmunoassay after purification by reverse-phase HPLC. The extent of carotid atherosclerosis was determined by real-time B-mode ultrasonography. The severity of carotid atherosclerosis in each subject was evaluated by plaque score, which was computed by summing the maximum thickness of plaque measured in millimeters. Urinary excretion of 11-dehydrothromboxane B2 in healthy subjects was higher (P < 0.01) in cigarette smokers (1063 +/- 244 ng/g creatinine) than in non-smokers (815 +/- 183 ng/g creatinine). Aspirin significantly suppressed 11-dehydrothromboxane B2 excretion (266 +/- 114 ng/g creatinine). In the 24 patients in whom the plaque score was measured, multivariate analysis indicated a significant positive correlation between urinary excretion of 11-dehydrothromboxane B2 and plaque score, age, smoking and hypercholesteremia. Our results indicate that risk factors such as age, hypercholesteremia, atherosclerosis and smoking activate platelets in vivo to develop carotid atherosclerosis.

Adult↗
PubMed1993

Induction of copper-zinc superoxide dismutase in gerbil hippocampus after ischemia.

To assess the role of Cu-Zn superoxide dismutase (CuZnSOD) in regulating cellular antioxidant defenses, we studied the induction of CuZnSOD mRNA by an in situ hybridization technique and of CuZnSOD protein by an immunocytochemical method in the gerbil hippocampus following 5 min of transient global ischemia. For hybridization, we synthesized 48-mer oligonucleotide (base 465-512) complementary to rat CuZnSOD mRNA. Northern blot analysis showed hybridization to a single band of molecular weight 0.65 kb. After 5 min of ischemia, the signal became stronger at 3 and 24 h and returned to the control level 3 days later. In situ hybridization histochemistry revealed an increase in labeling throughout the hippocampus, especially in the granular layer 3 h following ischemia. The increase was prolonged only in the CA1 pyramidal layer after 24 h and was eliminated within 3 days or later. Conversely, analysis by Western blotting revealed that the insult produced few effects on the induction of CuZnSOD protein. Immunocytochemistry for CuZnSOD revealed a reduced immunostaining in the CA1 pyramidal layer at 24 h of recirculation when the persistent expression of CuZnSOD mRNA was shown in the same area. Our findings suggest that the expression of endogenous CuZnSOD is temporarily stimulated by an ischemic insult without increasing the protein level. The prolonged increase in mRNA and the decrease in the protein of CuZnSOD in the CA1 neurons seem to imply an important role of the endogenous antioxidant enzyme that protects against the detrimental effects of superoxide radicals on delayed neuronal death.

Animals↗
PubMed1993

Do anger and aggression affect carotid atherosclerosis?

BACKGROUND AND PURPOSE: Although a number of metabolic and psychosocial factors have been identified as coronary risk factors, no studies have evaluated the relation between personality and cerebrovascular disease. The purpose of the present study was to elucidate the relation between the characteristics of anger or aggression and the severity of carotid atherosclerosis on the basis of the findings of B-mode ultrasonography. METHODS: The Cornell Medical Index was used to measure anger in 34 patients with signs of atherosclerosis or at least one of four recognized risk factors for atherosclerosis (hypertension, hypercholesterolemia, diabetes mellitus, and cigarette smoking). The Rosenzweig Picture Frustration Study and Yatabe-Guilford Personality Test were used to evaluate aggression. High-resolution B-mode ultrasonography was performed, and the severity of carotid atherosclerosis was determined by plaque score. The occurrence of risk factors for carotid atherosclerosis was compared among the patients. RESULTS: The correlation of plaque score with one item that endorses anger was r = .65 (P < .01) and with "extrapersistive" in aggression was r = .50 (P < .01). Multivariate analysis identified significant correlations between plaque score and age, hypercholesterolemia, and anger. CONCLUSIONS: Our results suggest that anger and, perhaps, aggression may be risk factors for cerebrovascular disease.

Aggression↗
PubMed1992

Protective effects of human recombinant superoxide dismutase on transient ischemic injury of CA1 neurons in gerbils.

BACKGROUND AND PURPOSE: It has been postulated that oxygen-derived free radicals are produced in significant quantities upon reperfusion of ischemic brain and that the free radicals play a pivotal role in triggering the ischemic neuronal damage causing delayed neuronal death. This study was undertaken to examine the effects of human recombinant superoxide dismutase on the delayed neuronal death of CA1 neurons and on the change in the expression of messenger ribonucleic acid for endogenous copper-zinc superoxide dismutase after transient ischemia. METHODS: Human recombinant superoxide dismutase (8 x 10(5) units/kg) or apo-superoxide dismutase was administered intravenously 1 minute before bilateral carotid artery occlusion in gerbils divided among four experimental groups. Endogenous copper-zinc superoxide dismutase messenger ribonucleic acid was analyzed by in situ hybridization histochemistry using a sulfur-35-labeled oligonucleotide probe. Immunohistochemical localizations of administered human recombinant superoxide dismutase were investigated. RESULTS: All gerbils receiving apo-superoxide dismutase exhibited almost complete destruction of CA1 neurons 7 days after 5 minutes of ischemia. The gerbils treated with human recombinant superoxide dismutase showed mild lesions (p less than 0.01). Discrete localizations were observed for endogenous copper-zinc superoxide dismutase messenger ribonucleic acid. Transient ischemia increased labeling throughout the hippocampus after 30 minutes and 24 hours of reperfusion. This increase was abolished by treatment with human recombinant superoxide dismutase. This phenomenon was confirmed by Northern blot analysis. The interneurons in CA3 and cells in the hilus were mainly stained against administered superoxide dismutase at 5 and 30 minutes, and these reactions had disappeared at 20 hours after the administration. CONCLUSIONS: Our data demonstrate protective effects of human recombinant superoxide dismutase against ischemic neuronal damage and support the hypothesis that the generated free radicals induce a vicious cycle leading to delayed neuronal death.

Animals↗
PubMed1990

Effects of proxigermanium on interferon production and 2',5'-oligoadenylate synthetase activity in the lung of influenza virus-infected mice and in virus-infected human peripheral blood mononuclear cell cultures.

Proxigermanium (SK-818) is a synthesized organic germanium compound having various biological activities. The effects of proxigermanium on interferon (IFN) production in mice infected with influenza virus and virus-infected human peripheral blood mononuclear cells (hPBMC) were investigated. Proxigermanium alone did not induce IFN production in normal mice or in hPBMC without viral infection. On the other hand, proxigermanium enhanced alpha/beta IFN production in viral-infected mice and hPBMC. Since proxigermanium is known to have antiviral activity in vivo but not in vitro, it is likely that the IFN production augumenting activity of proxigermanium is involved in its antiviral activities.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

[Bilateral internuclear ophthalmoplegia in association with basilar artery occlusive disease].

A 56 year-old man presented with vertigo and the right sided weakness. Neurological examination revealed a lethargic man with good orientation to three spheres. His neck was supple. He had anisocoria, the right pupil being larger than the left by 1.5 mm with sluggish light reaction bilaterally. He had exotropia of the right eye in primary gaze. The abduction of both eyes were full with terminal horizontal nystagmus. The adduction of both eyes were quite limited in each eye. He had a limited upward gaze with poor convergence. These were interpreted as the syndrome of the medial longitudinal fasciculus (MLF) bilaterally. He had a depressed gag reflex on the right side with tongue deviation to the right. He had a mild weakness of the right side limb and also had the right sided hemihyperesthesia including his face to pain and temperature. Twenty four hours after the onset, the left brachial angiography revealed a complete occlusion of the rostral portion of the basilar artery without visualization of the posterior cerebral and superior cerebellar arteries bilaterally. CT scans three days after the onset revealed a low density area in the mid pons with extension rostrally up to the mesencephalon. Four days later he became quadriplegic with bilateral horizontal gaze palsy. No more internuclear ophthalmoplegia is noted on both sides. The midline location of the MLF in the pons, and the separate blood supplies by different paramedian branches of the basilar artery, form the anatomical explanation for the frequent unilaterality of vascular and bilaterality of demyelinating lesions. Bilateral MLF syndrome has been considered almost pathognomonic of multiple sclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Arterial Occlusive Diseases↗