Biomedical subjects

M Hayashi

Publications and source records attributed to M Hayashi.

At least 343 records · Page 19Linked to original sources

PubMed2000

Cytotoxic alkaloids of Pachysandra terminalis.

Four steroidal alkaloids, epipachysamines B (1) and E (2), pachystermine A (3) and pachysamine E (4), were isolated as cytotoxic principles from the MeOH extract of the stems of Pachysandra terminalis SIEB. et ZUCC. (Buxaceae). These alkaloids showed cytotoxic activity against P388 and P388/ADR leukemia cells in vitro. Three of the alkaloids (1-3) were previously isolated from this plant material, and this is the first report of their cytotoxic activity. Pachysamine E (4) is a new alkaloid.

Alkaloids↗

PubMed2000

Species differences in oral bioavailability of methotrexate between rats and monkeys.

The contributions of incomplete absorption and a first-pass effect to the low bioavailability (BA) of methotrexate (MTX) were evaluated pharmacokinetically in rats and monkeys which respectively have a lower and higher aldehyde oxidase (AO) activity than humans. Plasma concentration profiles of MTX in rats showed linear and nonlinear pharmacokinetics respectively after intravenous (i.v.) and oral dosing of 0.1, 0.5 or 2.5 mg/kg MTX. In rats, most of the dose was excreted as the parent compound into bile and urine after i.v. dosing of 0.5 mg/kg MTX, while the radioactivity was largely eliminated in expired air after oral dosing of 0.5 mg/kg 14C-MTX. Elimination in expired air fell markedly following antibiotics treatment. 7-Hydroxymethotrexate (7-OH-MTX), formed from MTX by AO, was detected in monkey plasma after i.v. and oral dosing of 0.5 mg/kg MTX, but not in rat plasma. The ratio of the cumulative urinary excretion of 7-OH-MTX to MTX in monkeys was higher after oral dosing than after i.v. dosing. The low BA in rats (10% at 0.5 mg/kg) was shown to be mainly due to incomplete absorption, including limited absorption and degradation to 2,4-diamino-N10-methylpteroic acid (DAMPA) and glutamic acid (Glu) by the carboxypeptidase of intestinal bacteria. The low BA in monkeys (5% at 0.5 mg/kg) was shown to be mainly due to the extensive first-pass effect, including metabolism to 7-OH-MTX.

Animals↗

PubMed2000

Evaluation of absorbability of poorly water-soluble drugs: validity of the use of additives.

Apparent membrane permeation coefficients (Papp) of poorly water-soluble drugs such as indomethacin (IDM) and triamterene (TAT) were obtained by the chamber method using an isolated rat intestinal tissue after solubilization of the drugs by additives. For the additives, sodium deoxycholate (DOC), polyethylene glycol 600 (PEG 600), dimethylsulfoxide (DMSO), ethanol (EtOH), propylene glycol (PG), and rat bile were examined. Their concentrations were determined in ranges considered to be appropriate from the results of in vivo experiments and physiological findings. From the correspondence between this membrane permeability and in vivo bioavailability, we evaluated the validity of our in vitro experiment. On the basis of these evaluations, it was shown that 5% DMSO and 10% PEG 600, which did not affect the membrane integrity, were most appropriate additives for chamber experiments. Papp of IDM was greater than that of TAT, indicating that the order corresponded with that of in vivo bioavailability after oral administration of their PEG 600 solutions. Accordingly, it was concluded that Papp obtained by our in vitro system can be used to assess the in vivo bioavailability.

Absorption↗

PubMed2000

The effects of absorption enhancers on the pulmonary absorption of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in rats.

Pulmonary absorption of recombinant human granulocyte colony-stimulating factor (rhG-CSF) with various surfactants and protease inhibitors were examined in rats. The relative bioavailabilities of rhG-CSF with surfactants, such as polyoxyethylene 9-lauryl ether (Laureth-9) and sodium glycocholate (SGC), after intratracheal (i.t.) administration by intravenous (i.v.) and subcutaneous (s.c.) means were 37% (i.v.), 88% (s.c.), 84% (i.v.) and 197% (s.c.), respectively. These values were evaluated from the ratio of the area under the curve (AUC) of the plasma rhG-CSF concentration versus time for 8 h. In the presence of various kinds of protease inhibitors, such as (p-amidinophenyl) methanesulfonyl fluoride x HCl (p-APMSF), aprotinin and bestatin, an increase in the plasma rhG-CSF concentration was observed, and the effect with p-APMSF was maximal. The relative bioavailabilities of rhG-CSF with p-APMSF after i.t. administration by i.v. and s.c. means were increased about 2-fold. To clarify the absorption mechanism of rhG-CSF, rhG-CSF was intratracheally administered with both Laureth-9 and p-APMSF. The AUC of rhG-CSF increased with both agents, and was approximately equal to that with SGC, which has both an enhancing effect on membrane permeation and an inhibitory effect on enzymatic degradation after i.t. administration. Consequently, it was considered that permeation and enzymatic degradation were rate-determining steps in the pulmonary absorption of rhG-CSF after i.t. administration.

Absorption↗

PubMed2000

Brain natriuretic peptide predicts chronic atrial fibrillation after ventricular pacing in patients with sick sinus syndrome.

Chronic atrial fibrillation (AF) is one of the main complications of sick sinus syndrome (SSS). As previously reported, plasma brain natriuretic peptide (BNP), reflects hemodynamic changes in different pacing modes, as does plasma atrial natriuretic peptide (ANP), so the present study investigated whether plasma BNP or ANP can predict chronic AF after single-chamber ventricular (VVI) pacemaker implantation in patients with SSS. Plasma ANP and BNP levels were measured before and 1-3 months after implantation in 99 SSS patients. Long-term follow-up was conducted with chronic AF as an endpoint. Chronic AF occurred in 19 patients during a mean follow-up of 5.1 years. Plasma ANP and BNP were significantly higher in the patients who developed chronic AF after implantation than in those who did not, despite similar ANP and BNP levels between the 2 groups before implantation. Post-implant high BNP and a history of paroxysmal AF were independent predictors of chronic AF by a multivariate Cox proportional hazards analysis. Plasma BNP can predict the development of chronic AF after VVI pacemaker implantation in patients with SSS because increased levels may reflect latent hemodynamic abnormalities, which may contribute to the development of AF after VVI pacemaker implantation.

Actuarial Analysis↗

PubMed2000

New anthocyanins from purple pods of pea (Pisum spp.).

Two new anthocyanins were isolated from purple pods of pea (Pisum spp.). Their structures were identified as delphinidin 3-xylosylgalactoside-5-acetylglucoside and its deacetylated derivative by the usual chemical degradation methods and by spectroscopic methods such as UV-VIS, MS and NMR. Both pigments showed moderate stability and antioxidative activity in a neutral aqueous solution.

Anthocyanins↗

PubMed2000

The effects of calcium channel blockers on nuclear factor kappa B activation in the mesangium cells.

It has been reported that calcium channel blockers (CCBs) have an inhibitory action on cell growth and transcriptional changes induced by cytokines and hormones. In this study, we examined the effects of CCBs on nuclear factor kappa B (NFkappaB), which plays a key role in the intracellular signaling of various growth factors and cytokines. The activity of NFkappaB was determined by luciferase assay with the transfection of the reporter gene, which has six NFkappaB-recognizing sequences in the upstream of herpes simplex virus thymidine kinase promoter. In cultured human mesangial cells, increased intracellular calcium concentration by calcium ionophore, A23187, showed a stimulatory effect on the phorbor 12-myristate 13-acetate (PMA)-induced activation of NFkappaB, while L-type calcium channel agonist, Bay K 8644, did not have any significant effects on either basal or PMA-stimulated activity of NFkappaB. At a higher concentration (10 microM), nifedipine, verapamil, or efonidipine showed an inhibitory effect on the activation of NFkappaB by PMA and A23187, while at a lower concentration (1 microM), only efonidipine showed a significant inhibitory effect. From these results, we conclude that CCBs have an inhibitory effect on NFkappaB via the independent pathway of an L-type calcium channel and that the potency of this effect is variable among L-type calcium channel blockers.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed2000

Wortmannin, a radiation sensitizer, enhances the radiosensitivity of WKAH rat cells but not that of LEC rat cells.

No significant cytotoxic effect was observed in WKAH rat cells by the treatment of wortmannin, a radiation sensitizer, at concentrations lower than 30 microM for 24 hr. The relative surviving fractions of LEC rat cells were slightly, but significantly, lower than those of WKAH rat cells at each concentration of wortmannin. When the wortmannin-treated WKAH rat cells were X-irradiated, the relative surviving fractions decreased in a wortmannin concentration-dependent manner. On the contrary, no significant difference was observed between the survival curves of untreated and wortmannin-treated LEC rat cells after X-irradiation.

Androstadienes↗

PubMed2000

Effects of antioxidants on induction of apoptosis in bursal cells of Fabricius during in vitro cultivation.

After physically disrupting cell contacts, apoptosis of bursal cells of Fabricius was induced during in vitro cultivation. The percentage of apoptotic cells increased with incubation time and approximately 70% cells represented apoptosis after 6 hr of incubation. The induction of apoptosis was significantly inhibited by treatment of the cells with ascorbic acid (vitamin C), but not with trolox, a vitamin E analog. An intense DNA ladder pattern was shown at 6 hr post-isolation, which is a biochemical hallmark of apoptosis. Treatment of the cells with ascorbic acid inhibited the DNA fragmentation, but trolox did not. To monitor the intracellular production of reactive oxygen species (ROSs), the intensity of fluorescence emitted from DCFH-DA was measured. The intensity of fluorescence from cells incubated for 0.5-2 hr was approximately 2-fold higher than that from cells at 0 hr. The relative intensity of fluorescence decreased immediately after the addition of ascorbic acid to the cells. The intensity from the cells treated with ascorbic acid was 20-30% of that from the control cells at each incubation time. For trolox, the intensity was 50-70% of that from the control cells at each 1 to 2 hr incubation time. When ROSs-induced lipid peroxidation was assessed using cis-parinaric acid (PnA) as a monitor molecule, lipid peroxidation was found to occur in the control cells after isolation of the bursal cells. Treatment of the cells with trolox reduced lipid peroxidation, but treatment with ascorbic acid enhanced peroxidation.

Animals↗

PubMed2000

Inhibitory effects of long-wave ultraviolet radiation of isolated chicken liver nuclei on the Mg2+-dependent transition of chromatin structure.

Since the turbidity of nuclear suspensions is known to be correlated with the nuclear morphology, the effects of long-wave ultraviolet (UVA) radiation on Mg2+-dependent structural transition of chromatin in isolated chicken liver nuclei were monitored by measuring the relative turbidity of nuclear suspensions. UVA radiation of the nuclei inhibited the Mg2+-dependent change in relative turbidity of nuclear suspensions in a UVA dose-dependent manner under aerobic conditions but not under N2 conditions. No inhibitory effect of UVA radiation on the change in relative turbidity was observed in the presence of 50 mM NaN3, which scavenges singlet oxygen (1O2) and hydroxyl radicals (*OH). In contrast, 100 mM dimethyl sulfoxide, which primarily scavenges *OH, did not show the inhibitory effect of UVA radiation. The amounts of DNA-protein crosslinks increased with UVA dose under aerobic conditions but not under N2 conditions. The present study showed that UVA radiation of isolated nuclei inhibited the Mg2+-dependent unfolding of condensed chromatin and that O2 is likely to be involved in this process. Furthermore, the formation of DNA-protein crosslinks may contribute to the inhibition.

Animals↗

PubMed2000

A leaf-peroxisomal protein, hydroxypyruvate reductase, is produced by light-regulated alternative splicing.

Hydroxypyruvate reductase (HPR) is localized in leaf peroxisomes in plants, and it plays an important role in the glycolate pathway of photorespiration. In this laboratory, two highly homologous cDNAs for pumpkin HPR (HPR1 and HPR2) have been obtained, and appear to be produced from the same primary transcript by alternative splicing. Analyses at the mRNA level showed that the amounts of the two HPR mRNAs is changed in response to light, suggesting that light changes the splicing pattern of HPR pre-mRNA from almost equal amounts of two HPR mRNAs to greater production of HPR2 mRNA. From the sequences of the two HPR cDNAs, the HPR1 protein, but not the HPR2 protein, was found to have a targeting sequence into peroxisomes at the carboxy terminus. Analyses of transgenic Arabidopsis thaliana expressing fusion proteins with green fluorescent protein confirmed the different subcellular localizations of the two HPR proteins. These findings indicate the presence of light-regulated alternative splicing of HPR pre-mRNA, which controls the subcellular localizations of two HPR proteins in pumpkin cells.

Alcohol Oxidoreductases↗

PubMed2000

Transport of peroxisomal proteins synthesized as large precursors in plants.

Plant peroxisomes contain at least four proteins, namely, citrate synthase, malate dehydrogenase, long-chain acyl-CoA oxidase, and 3-ketoacyl-CoA thiolase, which are synthesized as large precursors with an N-terminal cleavable presequence. Each presequence has a conserved domain (R[I/L/Q]-X5-HL) that is homologous to peroxisomal targeting signal 2 from mammals and yeasts. In addition, a cysteine residue is found at the C-terminal ends of the presequences, whose function has not yet been described. The authors analyzed the function of the presequences and the conserved amino acids using transgenic Arabidopsis plants, which accumulate beta-glucuronidase carrying the presequence of the peroxisomal proteins from plants. Immunological and immunocytochemical studies on the transgenic plants showed that a conserved sequence in the extrapeptides is essential for targeting to peroxisomes, and a cysteine residue at the cleavage site is involved in the processing of the presequence. These results suggest that the presequences of the peroxisomal proteins function as targeting signals, and are necessary for the recognition of the processing.

Amino Acid Sequence↗

PubMed2000

Functional transformation of plant peroxisomes.

Peroxisomes in higher plant cells are known to differentiate into at least three different classes, namely, glyoxysomes, leaf peroxisomes, and unspecialized peroxisomes, depending on the cell types. In germinating fatty seedlings, glyoxysomes that first appear in the etiolated cotyledonary cells are functionally transformed into leaf peroxisomes during greening. Subsequently, the organelles are transformed back into glyoxysomes during senescence of the cotyledons. Flexibility of function is a distinct feature of plant peroxisomes. This article briefly describes recent studies of the regulatory mechanisms involved in the changes of the function of plant peroxisomes.

Adaptation, Biological↗

PubMed2000

Role of BMK1 in regulation of growth factor-induced cellular responses.

Big mitogen-activated protein kinase (MAPK) 1 (BMK1), also known as ERK5, is a recently identified member of the mammalian MAPK family. Cellular stimulation of BMK1 is induced in response to growth factors, oxidative stress, and hyperosmolar conditions. Specific members of the myocyte enhancer factor 2 family of transcription factors that regulate growth factor-induced early gene expression have been identified as direct downstream targets of BMK1 activity. Recent studies have shown that growth factors of the epidermal growth factor family mediate the sequential activation of a kinase cascade consisting of MAPK kinase kinase 3, MAPK kinase 5, and BMK1. Most importantly, the activation of this signal transduction pathway has been shown to be required for growth factor-mediated cell proliferation and cell-cycle progression. Collectively, these studies establish BMK1 as an important regulator of growth factor-induced cellular responses.

Animals↗

PubMed2000

Histopathological study of the effects of a single intratracheal instillation of surface active agents on lung in rats.

Pulmonary drug administration of most peptide/protein drugs is characterized by low bioavailability due to low permeability. Surface active agents have been tested as an absorption enhancer, but few studies have been carried out on the local toxicity of these additives. In the present study, to clarify the toxic effects of surface active agents on the lung, a relatively high concentration (1%) of polyoxyethylene 9 lauryl ether (Laureth-9) and sodium glycocholate (SGC) was given to rats in a single intratracheal instillation (100 microliters/rat), and the lung was evaluated histopathologically. In the rats treated with Laureth-9, lung lesions were observed in the bronchi to alveoli. At 1 day after administration, edema, hemorrhage and inflammatory cell infiltration due to degeneration and desquamation of epithelium were observed. At 3 and 7 days after administration, the wound healing process resulting from the lung injury, such as hyperplasia of epithelium and sporadic fibrosis, was noted. SGC also induced lung lesions with a similar histopathological nature, whereas the lesions were mostly confined to the alveoli. These results suggest that surface active agents induce acute inflammation of the lung by intratracheal instillation, that the distribution of lesions is different among surface active agents, and moreover that pathological examination is indispensable for clarifying local toxicity of absorption enhancers in pulmonary drug-delivery studies.

Absorption↗

PubMed2000

Successful resection of intracardiac invasive thymoma with right ventricular inflow tract occlusion.

A 72-year-old man presenting with the superior vena cava syndrome and intracardiac mass was admitted to our hospital. The mass was resected and confirmed to be invasive thymoma. Three years later, he was re-admitted with recurrence into the intracardiac space without any changes in the anterior mediastinum mass. The mass occupied the right atrial cavity and protruded into the right ventricle, causing right ventricular inflow tract obstruction. He underwent re-operation and irradiation. His postoperative course was uneventful, and he has remained alive. Invasive thymoma with intracardiac extension is extremely rare.

Aged↗

PubMed2000

Malignant insulinoma which expressed a unique creatine kinase isoenzyme: clinical value of arterial embolization as a palliative therapy.

A 76-year-old man with hypoglycemic coma was diagnosed as malignant insulinoma with multiple hepatic metastases. Embolization was done for two-thirds of the hepatic mass and it rapidly lowered the serum immunoreactive insulin. He was discharged without medication and has been free from hypoglycemia. After the embolization, the serum creatine kinase (CK) level increased transiently although there was no evidence of myocardial infarction. On electrophoresis, the CK activity showed an abnormal peak, suggesting mitochondrial CK. CK release after embolization has been reported in only a few cases with endocrine tumors, which might indicate some relationship between active energy metabolism and mitochondrial CK.

Aged↗

PubMed2000

Effects of progesterone on the elevation of tail skin temperature in ovariectomized rats.

We examined the effects of progesterone on the elevation of tail skin temperature (TST) in ovariectomized rats and compared them with those of estradiol. Progesterone showed only insignificant effects on the TST elevation, whereas estradiol showed complete inhibition. The TST elevation induced by ovariectomy is caused by estradiol deficiency, but progesterone plays little or no role.

Animals↗