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K Sakai

Publications and source records attributed to K Sakai.

At least 199 records · Page 11Linked to original sources
PubMed2000

The 5 alpha-reductase inhibitory components from heartwood of Artocarpus incisus: structure-activity investigations.

The methanol extract of heartwood of Artocarpus incisus showed potent 5 alpha-reductase inhibitory activity. We investigated the 5 alpha-reductase inhibitory effects of nine compounds isolated from A. incisus. Chlorophorin (IC50 = 37 microM) and artocarpin (IC50 = 85 microM) showed more potent inhibitory effects than did alpha-linolenic acid, which is known as a naturally occurring potent inhibitor. Structure-activity investigations suggested that the presence of an isoprene substituent (prenyl and geranyl) would enhance 5 alpha-reductase inhibitory effects.

5-alpha Reductase Inhibitors↗
PubMed2000

Identification of CYP3A4 as the predominant isoform responsible for the metabolism of ambroxol in human liver microsomes.

1. In humans, ambroxol is metabolized to dibromoanthranilic acid (DBAA) and 6,8-dibromo-3-(trans-4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazoli ne (DHTQ). The formation of DHTQ proceeds non-enzymatically, whereas that of DBAA requires NADPH. Studies have been performed to identify the CYP isozyme(s) involved in the formation of DBAA using human liver microsomes and microsomes expressing recombinant human CYP isozymes (1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4 and 4A11). 2. The apparent Vmax and Km for the formation of DBAA were 472+/-192 pmol/ min/mg protein and 248+/-40.6 microM respectively (mean +/- S.D., n = 3). 3. Of the recombinant CYP examined, only CYP3A4 metabolized ambroxol to DBAA. The apparent Vmax and Km were 1.42 pmol/min/pmol P450 and 287 microM respectively. 4. Among the CYP inhibitors examined (furafylline, sulphaphenazole, quinidine, diethyldithiocarbamic acid, ketoconazole), only ketoconazole inhibited the production of DBAA (> 80%) at 1 microM and anti-CYP3A antiserum almost completely inhibited the formation of DBAA. 5. These results suggest that CYP3A4 is predominantly involved in the metabolism of ambroxol to DBAA in humans.

Adult↗
PubMed2000

Protective effect of ginkgo extract on rat brain with transient middle cerebral artery occlusion.

It has been empirically known that Ginkgo extract is useful for reducing many symptoms associated with cerebral blood flow (CBF) insufficiency, but its mechanisms have been uncertain. In the present study, therefore, we gave Ginkgo extract to rats with per os digestion, and investigated its effect on CBF and ischemic brain damage with middle cerebral artery occlusion (MCAO). The treatment with Ginkgo extract (10 mg 100 g-1 rat) increased CBF in the normal condition, but the degree of increase in CBF was lesser during and after MCAO. TTC staining showed that infarct volume was reduced with Ginkgo treatment. TUNEL and HSP72 immunostaining confirmed the protective effect of Ginkgo treatment reducing numbers of TUNEL and HSP72 positive cells. Immunohistochemical analysis showed that caspase-3 expression was less abundant in Ginkgo treated rats. The present results suggest that Ginkgo extract contains a substance which increases normal CBF and reduces ischemic brain damage.

Animals↗
PubMed2000

Temporal profile of cytochrome c and caspase-3 immunoreactivities and TUNEL staining after permanent middle cerebral artery occlusion in rats.

Although apoptotic pathways play important roles in ischemic neuronal injury, exact mechanism of apoptotic enzyme cascade has not been fully studied. Immunohistochemical stainings for cytochrome c and caspase-3, and histochemical staining for a terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP-biotin nick end-labeling method (TUNEL) were examined in a rat model of permanent middle cerebral artery (MCA) occlusion. Cytochrome c was strongly induced in neurons of the ischemic penumbra from 3 h after MCA occlusion, and caspase-3 began to be induced in the same area from 3 h with a peak at 8 h. Neuronal cells in MCA area became TUNEL positive at delayed time, reaching a peak at 24 h. Thus, the peak of induction of cytochrome c preceded that of caspase-3, and these two peaks were also precedence of the peak of DNA-fragmentation. Western blot analysis showed cytosolic expression of cytochrome c from mitochondria. This study demonstrated 1. Rapid release of cytochrome c from mitochondria to the cytosol, mainly in neurons of the cortex at 3 h after ischemia. 2. Subsequent peaks of caspase-3 and TUNEL in this order. These temporal profiles suggest a serial cascadic activation of apoptotic pathways in neuronal death after permanent MCA occlusion of rats.

Animals↗
PubMed2000

Walnuts lower serum cholesterol in Japanese men and women.

Recent studies have shown that incorporating moderate quantities of walnuts into the recommended cholesterol-lowering diet in the U.S. decreased serum concentrations of total cholesterol in normal American men. To explore whether walnut consumption would also prove effective as part of the Japanese diet, we studied the effects of walnut consumption on serum lipids and blood pressure in Japanese subjects. We randomly assigned 20 men and 20 women to two mixed natural diets, each to be consumed for 4 wk in a crossover design. Both diets conformed to the average Japanese diet (reference diet) and contained identical foods and macronutrients, except that 12.5% of the energy of the walnut diet was derived from walnuts (43-57 g/d) (offset by lesser amounts of fatty foods, meat and visible fat). Total cholesterol concentration was 0.16 mmol/L lower for men (P = 0.05) and 0.21 mmol/L lower for women (P<0.01) when they consumed the walnut diet than when they consumed the reference diet. The LDL cholesterol concentrations were 0.18 mmol/L lower for men (P = 0.13) and 0.22 mmol/L lower for women (P<0.01) when they consumed the walnut diet. The ratio of LDL cholesterol to HDL cholesterol and the apolipoprotein B concentration were also lowered by the walnut diet (P<0.05). Blood pressures did not differ between the walnut and reference diet periods. Incorporating moderate quantities of walnuts into the average Japanese diet while maintaining the intake of total dietary fat and energy decreases serum total cholesterol concentrations and favorably modifies the lipoprotein profile in Japanese, particularly in women.

Adult↗
PubMed2000

The cecum and dietary short-chain fructooligosaccharides are involved in preventing postgastrectomy anemia in rats.

Dietary short-chain fructooligosaccharides (Sc-FOS) stimulate absorption of calcium and magnesium in the large intestine of rats. In this study, we examined whether Sc-FOS stimulate iron absorption in the large intestine by monitoring recovery from anemia in gastrectomized rats, with or without cecectomy. The rats were divided into four groups, i.e., sham-operated (Sham), gastrectomized only (GX), cecectomized only (CX) and both gastrectomized and cecectomized (GCX). Half of the rats in each group were fed a control diet (AIN-93G) and the other half were fed a Sc-FOS-containing diet (75 g/kg diet) for 28 d. Hematocrit (Ht) and hemoglobin concentration (Hb) were measured at the start, and on d 14 and 28 after the start of feeding. On the final day of the study, total blood was collected. Gastrectomy significantly decreased Ht and Hb, but cecectomy did not influence these variables. Dietary Sc-FOS prevented the decrease in Ht and Hb significantly. In the gastrectomized rats, the effectiveness of Sc-FOS in preventing postgastrectomy anemia was significantly diminished by cecectomy. These results suggest that the effect of Sc-FOS in increasing absorption of iron in gastrectomized rats takes place in part in the cecum. The cecum plays an important role in the mechanism by which Sc-FOS prevent postgastrectomy anemia.

Analysis of Variance↗
PubMed2000

Presence of two trans-o-hydroxybenzylidenepyruvate hydratase-aldolases in naphthalenesulfonate-assimilating Sphingomonas paucimobilis TA-2: comparison of some properties.

Two trans-o-hydroxybenzylidenepyruvate hydratase-aldolases named tHBP HA A and tHBP HA B were purified from a cell-free extract of naphthalenesulfonate-assimilating Sphingomonas paucimobilis (formerly Pseudomonas sp.) TA-2 to an electrophoretically homogeneous state by successive column chromatographies on DEAE-cellulose, DEAE-Toyopearl 650M, Sephacryl S-100, Hydroxyapatite, and Mono Q. These enzymes were similar to each other in molecular mass (ca. 37 kDa on SDS-PAGE, ca. 110 kDa on ultracentrifugation), thermal stability (<50 degrees C) and optimum pH (pH 9.0). However, they differed from each other in N-terminal amino acid sequences, pH stability, K(m) values for trans-o-hydroxybenzylidenepyruvate (tHBP), and inhibition by p-chloromercuribenzoic acid (PCMB). tHBP HA B had a homologous N-terminal amino acid sequence with tHBP HAs from Pseudomonas vesicularis DSM 6383 (strain BN6) and Sphingomonas aromaticivorans F119, and tHBP HA A had a homologous sequence with tHBP HAs of Pseudomonas putida strain OUS82, Pseudomonas sp. strain C18 and NAH7 plasmid. tHBP HA B was inhibited by PCMB, but tHBP HA A was not. Their K(m) values for tHBP were 9 and 3 M, respectively. tHBP HA B was stable in the range of pH 7.1 to pH 10.7, and tHBP HA A was stable in the range of pH 6.0 to 9.3.

Amino Acid Sequence↗
PubMed2000

The effects of propofol with and without ketamine on human cerebral blood flow velocity and CO(2) response.

UNLABELLED: The combination of propofol and ketamine has been used for total IV anesthesia. This study was designed to clarify the effects of propofol-ketamine anesthesia on cerebral circulation by using transcranial Doppler ultrasonography. In Study 1, we examined the time course of time-mean middle cerebral artery blood flow velocity (Vmca) after ketamine (n = 10) or saline (n = 6) administration during propofol anesthesia. In Study 2, CO(2) responses were measured under the following conditions: awake (Group C, n = 7), propofol anesthesia (Group D, n = 7), and propofol-ketamine anesthesia (Group E, n = 8). Ketamine administration during propofol anesthesia administration did not affect Vmca, mean arterial pressure, or heart rate. Vmca under normocapnia in Groups D and E were 36 +/- 3 and 37 +/- 3 cm/s (mean +/- SE), respectively. The values were significantly lower than that of Group C (70 +/- 3 cm/s). The CO(2) response slopes of Groups D and E were significantly lower than that of Group C, although there was no significant difference between Groups D and E. These results suggest that ketamine does not influence Vmca or the cerebrovascular CO(2) response during propofol anesthesia administration, although the sample size in each group was small. IMPLICATIONS: Our study suggests that ketamine does not influence middle cerebral artery blood flow velocity or the cerebrovascular CO(2) response assessed by transcranial Doppler ultrasonography during propofol anesthesia administration in patients without neurological complications.

Adult↗
PubMed2000

Nicorandil metabolism in rat myocardial mitochondria.

The in vitro study using rats was carried out to clarify the hypothesis that nicorandil is denitrated and then may produce nitric oxide (NO) in myocardial mitochondria. In the presence of a NADPH-generating system, [14C]nicorandil, which was incubated in mitochondrial and microsomal fractions of the lung, heart, or liver, was converted to its main denitrated metabolite, SG-86 and other metabolites. Apparent Km and Vmax for nicorandil in mitochondrial and microsomal fractions of the heart were considerably similar to those of the lung, but completely different from those of the liver. It seems that glutathione-S-transferases (GSTs) are not primarily involved in the conversion of nicorandil to SG-86, because a known GST inhibitor, indomethacin, did not affect the nicorandil degradation in the mitochondrial fraction. Nitrite, the stable metabolite of NO, was measured by the Griess reaction. In the presence of an NADPH-generating system, nicorandil significantly increased nitrite production in myocardial mitochondria, but SG-86 did not. These data strongly indicate that nicorandil is metabolized to SG-86 in myocardial mitochondria, then releasing NO, and that GSTs are not primarily responsible for the conversion of nicorandil to SG-86.

Animals↗
PubMed2000

Increased expression after X-irradiation of MUC1 in cultured human colon carcinoma HT-29 cells.

The effect of X-irradiation on production of MUC1 was studied with human colon carcinoma HT-29 cells. As evaluated by immunocytochemical staining, the percentages of MUC1-positive cells in cells at 4 days after 6 Gy irradiation and in unirradiated control cells were 52 +/- 3.5% (n = 6) and 26 +/- 2.8% (n = 6), respectively. Flow-cytometric analysis of living cells showed that MUC1 began to rise from day 1, reaching a plateau by day 4 after 6 Gy irradiation. Western blot analysis with monoclonal antibody MY.1E12 against glycosylated MUC1 (mature form) showed dose-dependent increases of two bands (500 and 390 kDa) corresponding to two polymorphic MUC1 alleles. Premature forms of MUC1 (350 and 240 kDa) were detectable with monoclonal antibody HMFG-2 only in irradiated cells, suggesting that new core protein synthesis had been induced. The transcriptional activity of the MUC1 gene was analyzed in terms of transient expression of MUC1-CAT reporter plasmids containing 5'-flanking sequences of the MUC1 gene fused to the bacterial chloramphenicol acetyltransferase (CAT) gene. The results of CAT assay indicate that enhanced expression of MUC1 in irradiated HT-29 cells was due to upregulation of MUC1 transcription, and required the upstream promoter.

Antibodies, Monoclonal↗
PubMed2000

Effect of suplatast tosilate (IPD-1151T) on a mouse model of asthma: inhibition of eosinophilic inflammation and bronchial hyperresponsiveness.

BACKGROUND: Suplatast tosilate (IPD) is a newly developed 'anti-allergic' drug. It seems to be a unique compound because of its ability to suppress IgE but not IgG or IgM production in vivo and cytokine production from type 2 helper T cells (Th2) in vitro. However, information on its in vivo effect on an animal model of asthma is limited. METHOD: BALB/c mice sensitized to ovalbumin (3 times, 2-week interval) were challenged with ovalbumin by inhalation (50 mg/ml for 20 min, once a day for 6 days). In this study, we explored the influence of IPD on eosinophil infiltration into the airways, bronchial hyperresponsiveness (BHR) to methacholine, specific IgE antibody production, and cytokines in bronchoalveolar lavage fluid (BALF) using this murine model. RESULTS: Treatment with IPD significantly reduced the number of total cells and eosinophils in BALF (around -40%) and almost completely inhibited the development of antigen-induced BHR. Histological findings confirmed the reduction of submucosal cell infiltration in the lung, and disclosed the marked inhibition of bronchial epithelial cell damage. Ovalbumin-specific IgE was slightly but significantly reduced. The levels of IL-4, IL-5 and IL-13 in BALF were significantly decreased in mice treated with the compound compared to those in untreated mice. CONCLUSION: These results suggest that IPD is capable of inhibiting the production of Th2 cytokines, which inhibit eosinophil infiltration into the murine airway, IgE synthesis, and development of BHR, in a murine model of asthma.

Animals↗
PubMed2000

Effect of aerosolized docosahexaenoic acid in a mouse model of atopic asthma.

BACKGROUND: Docosahexaenoic acid (DHA) found in fish oil is known to depress inflammation-related mediators. We investigated a novel delivery method of tridocosahexaenoyl-glycerol (DHA-TG). METHODS: BALB/c mice (6-8 weeks old) were primed intraperitoneally with ovalbumin (OVA) and Al(OH)(3) on days 0 and 7, and with aerosolized OVA on day 7. Primed mice were challenged by repeated exposure to aerosolized OVA on days 15-17. Just before each exposure to aerosolized OVA, the mice were also exposed to an aerosol of emulsified DHA-TG or soybean oil, or saline (days 7 and 15-17). Bronchial hyperresponsiveness (BHR) to methacholine was measured, and bronchoalveolar lavage fluid was obtained 24 h after the last challenge (day 18). Lungs were histologically examined. RESULTS: Bronchoalveolar lavage fluid of saline-treated mice showed an increased cellularity with predominant eosinophils. Exposure to DHA-TG significantly reduced the total cell number and the eosinophil percentage in lavage fluid, whereas soybean oil did not. CONCLUSION: DHA but not soybean oil exposure reduced BHR and cell infiltration to bronchovascular bundles. This type of DHA administration could be studied in clinical trials.

Aerosols↗
PubMed2000

Bezafibrate increases prebeta 1-HDL at the expense of HDL2b in hypertriglyceridemia.

Prebeta1-high density lipoprotein (prebeta1-HDL), the initial acceptor of cell-derived cholesterol, can be generated from HDL(2) by hepatic lipase. Because bezafibrate elevates lipase activity, it may increase prebeta1-HDL at the expense of HDL(2). To answer this question, we determined the apolipoprotein A-I (apoA-I) distribution in 20 hypertriglyceridemics (triglycerides>2.26 mmol/L) and 20 sex-matched normolipidemics by native 2-dimensional gel electrophoresis. At baseline, prebeta1-HDL was 70% higher in hypertriglyceridemics than in normolipidemics (123.5+/-49.9 versus 72.5+/-34.1 mg/L apoA-I, P<0.01). Prebeta1-HDL was positively correlated with triglyceride (r=0.624, P<0.0001). A 4-week bezafibrate treatment (400 mg daily) increased prebeta1-HDL by 30% (160.2+/-64.5 mg/L apoA-I, P<0.05) but decreased HDL(2b) by 31% (from 188.8+/-94.9 to 129.3+/-78.7 mg/L apoA-I, P<0.05). Hepatic lipase activity increased by 24% (P<0.005). Prebeta1-HDL was generated either from ultracentrifugally isolated HDL(2) or from plasma during incubation with triglyceride lipase. In conclusion, bezafibrate increases prebeta1-HDL at the expense of HDL(2). We speculate that such an effect might partly contribute to the antiatherogenic action of bezafibrate.

Adult↗
PubMed2000

Angiotensin in the nucleus tractus solitarii contributes to neurogenic hypertension caused by chronic nitric oxide synthase inhibition.

Activation of the sympathetic nervous system and renin-angiotensin system has been suggested to contribute to the hypertension caused by chronic nitric oxide synthase inhibition. The aim of the present study was to determine whether angiotensin within the nucleus tractus solitarii (NTS) plays a role in activation of the sympathetic nervous system in this model. Rats were treated with N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 mg. kg(-1). d(-1) in drinking water) for 2 weeks. Experiments were performed on anesthetized rats with denervated arterial and cardiopulmonary baroreceptors. Arterial pressure, heart rate, and renal sympathetic nerve activity (RSNA) were measured. Microinjection of an angiotensin II type 1 (AT(1)) receptor antagonist (CV11974) or an angiotensin II type 2 (AT(2)) receptor antagonist (PD123319) into the depressor region within the NTS (identified by prior injection of L-glutamate) was performed. Microinjection of CV11974, but not of PD123319, produced greater decreases in arterial pressure, heart rate, and RSNA in L-NAME-treated rats than in control rats. The administration of hexamethonium resulted in a larger fall in arterial pressure in L-NAME-treated rats than in control rats. The ACE mRNA level in the brain stem was greater in L-NAME-treated rats than in control rats. These results suggest that increased sympathetic nerve activity plays a role in hypertension caused by chronic nitric oxide synthase inhibition and that activation of the renin-angiotensin system in the NTS is involved at least in part in this increased sympathetic nerve activity via AT(1) receptors.

Angiotensin Receptor Antagonists↗
PubMed2000

Overexpression of eNOS in NTS causes hypotension and bradycardia in vivo.

The role of nitric oxide (NO) in the brain in the control of blood pressure and the sympathetic nervous system is debated. This study examined the effect of overexpression of endothelial NO synthase (eNOS) in the nucleus tractus solitarii (NTS) on blood pressure in conscious rats. Adenovirus vectors encoding either eNOS (AdeNOS) or ss-galactosidase were transfected into the NTS in vivo. In the AdeNOS-treated rats, the local expression of eNOS in the NTS was confirmed by immunohistochemical staining and Western blot analysis for the eNOS protein and by increased production of nitrite/nitrate in the NTS measured by in vivo microdialysis. Blood pressure and heart rate, monitored by the use of a radiotelemetry system in a conscious state, were significantly decreased in the AdeNOS-treated group at day 5 to day 10 after the gene transfer. Urinary norepinephrine excretion also was decreased at day 7 after the gene transfer in the AdeNOS-treated group. Our results indicate that overexpression of eNOS in the NTS decreases blood pressure, heart rate, and sympathetic nerve activity in conscious rats.

Animals↗
PubMed2000

Dialysis membranes for blood purification.

All of the artificial membranes in industrial use, such as a reverse-osmosis membrane, dialysis membrane, ultrafiltration membrane, microfiltration membrane and gas separation membrane, also have therapeutic applications. The most commonly used artificial organ is the artificial kidney, a machine that performs treatment known as hemodialysis. This process cleanses the body of a patient with renal failure by dialysis and filtration, simple physicochemical processes. Hemodialysis membranes are used to remove accumulated uremic toxins, excess ions and water from the patient via the dialysate, and to supply (deficit) insufficient ions from the dialysate. Dialysis membranes used clinically in the treatment of patients with renal failure account for by far the largest volume of membranes used worldwide; more than 70 million square meters are used a year. Almost all dialyzers now in use are of the hollow-fiber type. A hollow-fiber dialyzer contains a bundle of approximately 10000 hollow fibers, each with an inner diameter of about 200 microm when wet. The membrane thickness is about 20-45 microm, and the length is 160-250 mm. The walls of the hollow fibers function as the dialysis membrane. Various materials, including cellulose-based materials and synthetic polymers, are used for dialysis membranes. This paper reviews blood purification, hemodialysis and dialysis membranes.

Biocompatible Materials↗
PubMed2000

Novel bifunctional polymer with reactivity and temperature sensitivity.

To introduce reactive groups into temperature-responsive polymeric chains of poly(N-isopropylacrylamide) (PIPAAm), IPAAm is copolymerized with other monomer such as acrylic acid (AAc). IPAAm homopolymer exhibited temperature-responsive properties and phase transition at 32 degrees C, however, the lower critical solution temperature (LCST) of the IPAAm-AAc copolymer shifts to a higher temperature and the phase transition becomes insensitive with increasing AAc content. To achieve a useful bifunctional copolymer containing both reactivity and temperature-sensitivity, we assumed that the homopolymer-like structure in the polymer chain would be required to maintain a sensitive temperature response with functional groups. Therefore, we designed a reactive monomer, 2-carboxyisopropylacrylamide (CIPAAm), and investigated its copolymerization with IPAAm. The important characteristic of the poly(IPAAm-co-CIPAAm) structure is that it was composed of the same polymer backbone and isopropylamide groups and some additional carboxyl groups. The transmittance measurement of the polymer aqueous solution revealed that phase transition of IPAAm-co-CIPAAm random copolymer occurred within a very narrow temperature range in pH 6.4, 7.4, and also even 9.0 phosphate buffered solution. These profiles were almost same as that of IPAAm homopolymer. While, under the same conditions, phase transition properties of poly(IPAAm-co-AAc)s solution were considerably influenced by small AAc content. We succeeded with the preparation of bifunctional polymer that possessed reactive functional groups and very sensitive response to temperature change.

Acrylamides↗