Biomedical subjects

K Sakai

Publications and source records attributed to K Sakai.

At least 379 records · Page 21Linked to original sources

PubMed1998

The inhibitory components from Artocarpus incisus on melanin biosynthesis.

The inhibitory effects of methanol extracts of heartwood of 23 Papua New Guinean wood species on tyrosinase activity were examined. The extract of Artocarpus incisus showed the strongest tyrosinase inhibitory activity which was equivalent to kojic acid. The extract apparently inhibited melanin biosynthesis of both cultured B16 melanoma cells without any cytotoxicity and in the back of a brown guinea pig without skin irritation. Thus, the potentiality of the extracts of heartwood of A. incisus both as material of a useful skin whitening agent and as a remedy for disturbances in pigmentation is evident. Tyrosinase inhibitory activity-guided fractionation led to the isolation of seven active compounds including a new compound which has been characterized as 6-(3"-methyl-1"-butenyl)-5,7,2',4'-tetrahydroxyflavone, named isoartocarpesin. Other active compounds were (+)-dihydromorin, chlorophorin, (+)-norartocarpanone, 4-prenyloxyresveratrol, artocarbene, and artocarpesin, These compounds are probably responsible for the melanin biosynthesis inhibitory effects.

Animals↗

PubMed1998

Dietary fructooligosaccharides increase calcium absorption and levels of mucosal calbindin-D9k in the large intestine of gastrectomized rats.

BACKGROUND: In gastrectomized rats intestinal calcium absorption and bone calcium levels markedly decrease and the levels recover as a result of feeding fructooligosaccharides (FOS). In the present study we examined the effects of gastrectomy and dietary FOS on intestinal calbindin-D9k (CaBP) levels. METHODS: One group of rats was subjected to a sham operation and fed a control diet. Two other groups of rats were gastrectomized, and those in one group were fed the control diet, whereas those in the other group were fed a diet containing 10% FOS. Intestinal calcium, magnesium, and phosphorus absorption levels and intestinal CaBP levels were measured. RESULTS: Gastrectomy increased CaBP levels in the distal small intestine, cecum, and colorectum but markedly decreased calcium absorption. Dietary FOS increased CaBP levels in the cecum and colorectum in the case of gastrectomized rats and improved calcium absorption. CONCLUSIONS: The results suggest that dietary FOS not only improve intestinal calcium absorption but also serve to maintain local calcium homeostasis in the intestine by increasing mucosal CaBP levels in the large intestine of gastrectomized rats.

Animals↗

PubMed1998

Substance P receptor (NK1) gene expression in synovial tissue in rheumatoid arthritis and osteoarthritis.

The distribution of messenger RNA coding for substance P receptor (NK1) in rheumatoid synovia and the relationship between signal intensity of NK1 mRNA and clinical parameters of disease activity were investigated. The synovia from 10 patients with rheumatoid arthritis (RA) and 7 patients with osteoarthritis was investigated by in situ hybridization histochemistry. In rheumatoid synovia, strong hybridization signal of NK1 mRNA was detected in 80% of the cells in both the lining layer and the interstitial layer. Moreover, the signal intensities of NK1 mRNA positively correlated with serum C-reactive protein levels and radiographic grade of joint destruction. These results provide histochemical evidence that rheumatoid synoviocytes strongly express NK1 gene, and the positive relation of the signal intensity of NK1 mRNA with CRP and radiographic severity suggests that the facilitation of NK1 gene expression in rheumatoid synovium relate the disease progression of RA.

Adult↗

PubMed1998

Decreased mitogen response of splenic lymphocytes in obese Zucker rats is associated with the decreased expression of glucose transporter 1 (GLUT-1).

We reported previously that obesity is a risk factor for deteriorating cellular immune functions in aging. However, the mechanism by which obesity decreases cellular immunity remains to be elucidated. To determine the mechanism of the decrease in cellular immunity with obesity, lean (Fa/?) and obese (fa/fa) 12-mo-old Zucker rats were used. The mitogen response of splenic lymphocytes in obese Zucker rats was significantly lower than that of lean Zucker rats, which was not restored by in vitro treatment with indomethacin (10 micromol/L), an inhibitor of prostaglandin E2 (PGE2). In addition, PGE2 production by splenic lymphocytes was not greater in obese than in lean Zucker rats. Glucose consumption by splenic lymphocytes after in vitro incubation with concanavalin A (conA) for 48 h was also significantly lower in obese Zucker rats. Expression of glucose transporter 1 (GLUT-1), analyzed by Western blot analysis, was lower in splenic lymphocytes of obese than in lean Zucker rats. However, the expression of the conA receptor in splenic lymphocytes, analyzed by flow cytometry with fluorescein isothiocyanate-conjugated conA, was not significantly different between lean and obese Zucker rats. In conclusion, the decreased mitogen response of splenic lymphocytes in obese Zucker rats may be due in part to the decreased uptake of glucose as the main energy source for lymphocytes at the stage of proliferation and may be associated with the decreased expression of GLUT-1.

Animals↗

PubMed1998

Patterns of care study of radiation therapy for cervix cancer in Japan: the influence of the stratification of institution on the process.

BACKGROUND: To improve the quality of radiation oncology in Japan, Patterns of Care Study (PCS), a widely known quality assurance (QA) program in the USA, was introduced. The feasibility was tested by collecting nationwide data by extramural audit for cervix cancer. METHODS: From July 1996 through February 1997, PCS audits were performed for 29 institutions nationwide. On the basis of the facility survey by Tsunemoto, 13 institutions were classified as A1 (university hospital/cancer center), 10 as B1 (other institutions treating >120 patients/year) and six as B2 (other institutions treating <120 patients/year). Medical charts for the patients treated for cervix cancer between 1992 and 1994 were reviewed based on the data format of the US PCS. The total number of patients surveyed was 432. RESULTS: Simulation was used for >90% of the patients in both A1 and B1-2 institutions. However, in B1-2, planning for 5% of the patients was performed with only a clinical set-up (p = 0.0287). A daily fraction with a size of 200 cGy was given to >65% of patients in A1 and to <47% in B1-2. On the other hand, >50% of those in B1-2 were treated with daily fractions of 180 cGy and less compared with 25% in A1 institutions (p < 0.0001). Brachytherapy was utilized more frequently for patients in Stages II (p = 0.0365), III (p = 0.0015) and IV (p = 0.0483) in A1 than in B1-2. As for external beam equipment, linear accelerators with 10 MV or more were used for 83% of the patients in A1. However, in B1-2 institutions, machines with lower energy were used for 38% of the patients (p < 0.0001). The median number of full-time-equivalent (FTE) radiation oncologists was 2.7 in A1, 0.65 in B1 and 0.2 in B2. CONCLUSIONS: Institutional stratification, including equipment and personnel, was found to affect significantly the patterns of care for cervix cancer. Therefore, to improve the quality of radiation therapy nationwide, improvements in equipment and in supply of FTE personnel are extremely important. PCS was found to have great potential for a practical evaluation of how much improvement will be required in Japan.

Adult↗

PubMed1998

Functional role of focal adhesion kinase in the process of implantation.

The expression and function of focal adhesion kinase (FAK) in human decidual cells were investigated. This kinase is localized to focal adhesions in fibroblasts, and is phosphorylated on tyrosine in normal and src-transformed fibroblasts. Immunofluorescent staining revealed that the cultured decidual cells expressed high levels of FAK at the cell periphery. Double stainings for FAK and phosphotyrosine, FAK and talin, and FAK and beta1 integrin demonstrated that FAK co-localized with integrins in cellular focal adhesions. Mouse blastocysts became attached to cultured decidual cells after embryos hatched from the zona pellucida. The majority of hatched blastocysts attached to human decidual cells within 24 h of culture. Blastocysts attached to decidual cells exhibited extensive outgrowth after 48 h. Treatment of decidual cells with herbimycin A, a tyrosine kinase inhibitor, did not affect the rate of hatching or attachment of blastocysts. However, the outgrowth of embryos on the decidual cells was inhibited by the addition of herbimycin A in a dose-dependent manner, implying that blastocyst attachment and outgrowth are mediated by different mechanisms. This study suggests that tyrosine phosphorylation of FAK on decidual cells may be important in development and differentiation following attachment.

Adult↗

PubMed1998

Purification and some properties of 2-hydroxychromene-2-carboxylate isomerase from naphthalenesulfonate-assimilating Pseudomonas sp. TA-2.

A 2-hydroxychromene-2-carboxylate isomerase was purified from a cell-free extract of naphthalenesulfonate-assimilating Pseudomonas sp. TA-2 to an electrophoretically homogeneous state by successive column chromatography on DEAE-cellulose, DEAE-Toyopearl 650M, Sephadex G-75, Hydroxyapatite, and Mono Q. The enzyme had a molecular mass of 25 and 27 kDa as estimated by SDS-PAGE and Superdex 200, respectively. Its N-terminal 30 amino acid sequence had high homology with the deduced amino acid sequences of the 2HC2CA isomerase of nahD (a gene of naphthalene metabolism), pahD (a gene of naphthalene and phenanthrene metabolism), and doxJ (a gene of dibenzothiophene metabolism). The enzymatic product was a trans isomer. The isomerase activity was inhibited in the presence of monoiodoacetate or Hg2+, but not by preincubation with monoiodoacetate or N-ethylmaleimide. GSH functioned as a cofactor and activated the enzyme at above 0.15 mM.

Amino Acid Sequence↗

PubMed1998

Molecular characterization and physiological role of a glyoxysome-bound ascorbate peroxidase from spinach.

cDNAs encoding two cytosolic and two chloroplastic ascorbate peroxidase (AsAP) isozymes from spinach have been cloned recently [Ishikawa et al. (1995) FEBS Lett. 367: 28, (1996) FEBS Lett. 384: 289]. We herein report the cloning of the fifth cDNA of an AsAP isozyme which localizes in spinach glyoxysomes (gAsAP). The open reading frame of the 858-base pair cDNA encoded 286 amino acid residues with a calculated molecular mass of 31,507 Da. By determination of the latency of AsAP activity in intact glyoxysomes, the enzyme, as well as monodehydroascorbate (MDAsA) reductase, was found to be located on the external side of the organelles. The cDNA was overexpressed in Escherichia coli (E. coli). The enzymatic properties of the partially purified recombinant gAsAP were consistent with those of the native enzyme from intact glyoxysomes. The recombinant enzyme utilized ascorbate (AsA) as its most effective natural electron donor; glutathione (GSH) and NAD(P)H could not substitute for AsA. The substrate-velocity curves with the recombinant enzyme showed Michaelis-Menten type kinetics with AsA and hydrogen peroxide (H2O2); the apparent Km values for AsA and H2O2 were 1.89 +/- 0.05 mM and 74 +/- 4.0 microM, respectively. When the recombinant enzyme was diluted with AsA-depleted medium, the activity was stable over 180 min. We discuss the H2O2-scavenging system maintained by AsAP and the regeneration system of AsA in spinach glyoxysome.

Amino Acid Sequence↗

PubMed1998

Vascular levels and cGMP-increasing effects of nicorandil administered orally to rats.

We examined a relation between cyclic guanosine monophosphate (cGMP) production in thoracic aorta, as an indicator probably reflecting the vascular response, and the vascular as well as plasma levels of nicorandil administered orally to rats. Nicorandil (3 mg/kg) given orally was rapidly absorbed, reaching the maximal plasma (approximately 2,600 ng/ml) and vascular concentrations (approximately 176 ng/g) at 15 min after the dosing and thereafter decreased rapidly. Even 2 h after the dosing, the level of the vascular cGMP formation in vivo remained significantly higher (approximately 1,000 fmol/mg increase from the control level) in the nicorandil-treated group, compared with the vehicle-treated one, and was enough to develop pronounced muscle relaxation in in vitro aortic preparations. However, it seems that the vascular cGMP increase in vivo was not always correlated to the plasma concentration of nicorandil, because the plasma concentration (approximately 750 ng/ml corresponding to 3.5 microM) at 2 h after the dosing, caused only relatively low cGMP production (300-400 fmol/mg increase from the control level), when tested in in vitro aortic preparations. Our study may indicate, therefore, that the vascular cGMP elevation in vivo is due to the content of nicorandil effectively remaining at its vascular targets of action as well as the plasma nicorandil concentration.

Administration, Oral↗

PubMed1998

Neonatal urinary ascites caused by urinary tract obstruction: two case reports.

Two cases of neonatal urinary ascites are reported, one (case 1) caused by posterior urethral valves associated with right vesicoureteral reflux, and the other (case 2) secondary to bilateral obstructed megaureter--a very rare cause. Abdominal distension, electrolyte imbalance, and an elevated BUN/serum creatinine ratio were noted at the time of hospitalization in both cases. These laboratory values promptly returned to normal after the establishment of appropriate urinary drainage, accomplished through bladder catheterization in case 1 and bilateral percutaneous nephrostomy in case 2. In case 1, transurethral resection of the posterior urethral valves was followed by resumption of normal urination. In case 2, bilateral ureteroneocystostomy with ureteral tapering was performed successfully. These are only the fifth and sixth cases of neonatal urinary ascites reported in the Japanese literature.

Ascites↗

PubMed1998

Enhancement of the vasodepressor response to adenosine by nicorandil in rats: comparison with cromakalim.

The effect of nicorandil on systemic blood pressure (SBP) and heart rate (HR) responses to adenosine was compared with that of cromakalim, an adenosine triphosphate (ATP)-sensitive K+ channel opener, in anesthetized rats. Intravenous (i.v.) adenosine in doses of 1-100 micrograms/kg elicited dose-dependent decreases in SBP, accompanied by decreases in HR. Potentiation of adenosine action by i.v. infusion of either nicorandil (10 or 30 micrograms/kg per min) or cromakalim (0.1 microgram/kg per min) occurred in all of the animals tested. After i.v. treatment with glibenclamide (20 mg/kg), an ATP-sensitive K+ channel blocker, not only adenosine action but also the enhancement of adenosine action by nicorandil and cromakalim were significantly attenuated. The present result indicates that the enhancement of the adenosine action by nicorandil and cromakalim appears to occur at least partly through ATP-sensitive K+ channel activation.

Adenosine↗

PubMed1998

Potentiating effect of nicorandil on the adenosine A2 receptor-mediated vasodepression in rats: potential role for KATP channels.

The effects of nicorandil on systemic blood pressure (SBP) and heart rate (HR) responses to adenosine were compared with those to N6-cyclopentyladenosine (CPA), a selective adenosine A1 receptor agonist, and 5'-(N-cyclopropyl)-carboxamidoadenosine (CPCA), a selective adenosine A2 receptor agonist, in anesthetized rats. When injected intravenously (i.v.), single bolus doses of CPCA (0.01-1.0 micrograms/kg), like adenosine (30 micrograms/kg), elicited dose-dependent decreases in SBP scarcely affecting HR, while CPA (0.03-1.0 micrograms/kg) produced only reduction of HR without influencing SBP. The enhancement of the vasodepressor response to CPCA, like adenosine, was induced by the i.v. infusion of either nicorandil (10 micrograms/kg per min) or cromakalim (0.1 micrograms/kg per min), but the response to CPA in HR remained unmodified during the infusion of nicorandil as well as cromakalim. After i.v. treatment with glibenclamide (20 mg/kg), and adenosine triphosphate (ATP)-sensitive K+ channel blocker, or 3,7-dimethyl-1-propargylxanthine (DMPX) (1 mg/kg), a selective antagonist of adenosine A2 receptor, not only CPCA action but also the enhancement of CPCA action by nicorandil and cromakalim were significantly attenuated. Similar results were obtained in the case of single bolus i.v. adenosine. The present result indicates that the augmentation of the adenosine action by nicorandil appears to be mediated by activation of ATP-sensitive K+ channels, closely linked with stimulation on A2 receptors by adenosine.

Adenosine↗

PubMed1998

Comparison of the potentiating effects of nicorandil and its denitrated metabolite (SG-86) on the adenosine-induced vasodepression in rats.

The potentiating activity of SG-86[N-(2-hydroxyethyl)nicotinamide], a denitrated metabolite of nicorandil, on the adenosine-induced vasodepression was compared with that of nicorandil in anesthetized rats. Single bolus i.v. adenosine (3-100 micrograms/kg) produced dose-dependent reductions of blood pressure, accompanied by slight decreases (except for 100 micrograms/kg) in heart rate. The adenosine-induced vasodepression was significantly enhanced during i.v. infusion of either SG-86 (100 micrograms/kg per min) as well as nicorandil (10 micrograms/kg per min). The enhancement of adenosine action by them did not occur in the presence of glibenclamide (20 mg/kg i.v.). Single bolus i.v. injections of SG-86 (0.3-30 mg/kg), except for 30 mg/kg, which caused a glibenclamide-sensitive decrease by about 5-10 mmHg in mean arterial blood pressure, had no effects on blood pressure and heart rate, whereas those of nicorandil (30-300 micrograms/kg) elicited overt reduction of blood pressure, accompanied by decreases in heart rate. The present results revealed that SG-86, like nicorandil, significantly enhanced the vasodepressor response to adenosine, probably in part through KATP channel activation, and that the activity of SG-86 was about 10 times less potent than that of nicorandil.

Adenosine↗

PubMed1998

Ultrastructural localization of nicorandil in the heart of rats.

To examine the intracellular localization of nicorandil in the heart, [14C]nicorandil and [3H]nicorandil (3 mg kg(-1)) were given orally to rats. The maximum concentration (Cmax) of nicorandil in the myocardium was reached 15 min after the oral dosing. At this time subcellular localization of nicorandil was examined. Nicorandil and its denitrated metabolite, SG-86 were found in mitochondrial fractions and in cytosolic and microsomal fractions of the heart. Electron-microscopic autoradiograms recorded 15min after oral dosing of 3 mg kg(-1) [3H]nicorandil to rats also showed the presence of silver grains generated by the radioactive nicorandil or its metabolites in the mitochondria of the heart. We conclude that nicorandil given orally to rats is distributed in mitochondria of the heart.

Administration, Oral↗

PubMed1998

Differential effects of nicorandil on the vasodepressor responses to vasoactive polypeptides administered intravenously to rats.

The effects of nicorandil on vasodepressor responses to vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and substance P have been examined in anaesthetized rats. Intravenous bolus injections of VIP (0.3 microg kg(-1)), CGRP (0.1 microg kg(-1)) and substance P (0.1 microg kg(-1)) induced reductions of blood pressure accompanied by slight increases (less than 5%) in heart rate. Nicorandil infused intravenously at 10 or 30 microg kg(-1) min(-1) significantly augmented the vasodepressor responses to VIP and CGRP but did not modify the responses to substance P and acetylcholine (0.1 microg kg(-1)). Intravenous treatment with glibenclamide (20 mg kg(-1)) [corrected] significantly attenuated not only the vasodepression caused by VIP and CGRP, but also the enhancement of the effects of the agents by nicorandil. These results indicate that nicorandil can enhance the action of VIP and CGRP, in rats, at least partly through ATP-sensitive K+-channel activation.

Animals↗

PubMed1998

Interrelationship of cardiovascular effects, plasma levels of nicorandil, and vascular cGMP formation in conscious rats.

The relationship between the dual activity of nicorandil (KATP channel-opening activity and nitrate-like action), plasma levels, and changes in vascular cGMP levels and cardiovascular parameters was investigated in conscious rats. Nicorandil (3 mg kg(-1), p.o.) was rapidly absorbed and caused a significant reduction in blood pressure, lasting for at least 1 h, increases in heart rate and femoral blood flow, and decreases in femoral vascular resistance. These were entirely abolished by intravenous glibenclamide (20 mg kg(-1)). The plasma concentration of nicorandil reached a maximum 30 min after dosing. After administration of nicorandil, a correlation was observed between blood pressure and plasma nicorandil level or femoral vascular resistance. A significant increase (P < 0.05) in the cGMP content of the thoracic aorta occurred 15 min after administration of nicorandil, and persisted for at least 2 h. These results imply that nicorandil induces vasodilatation by opening KATP channels in peripheral resistance vessels, leading to overt reduction of blood pressure, but acts on conductance vessels mainly through nitrate-like activity.

Administration, Oral↗

PubMed1998

Purification and characterization of three thermostable endochitinases of a noble Bacillus strain, MH-1, isolated from chitin-containing compost.

A thermophilic and actinic bacterium strain, MH-1, which produced three different endochitinases in its culture fluid was isolated from chitin-containing compost. The microorganism did not grow in any of the usual media for actinomyces but only in colloidal chitin supplemented with yeast extract and (2, 6-O-dimethyl)-beta-cyclodextrin. Compost extract enhanced its growth. In spite of the formation of branched mycelia, other properties of the strain, such as the formation of endospores, the presence of meso-diaminopimelic acid in the cell wall, the percent G+C of DNA (55%), and the partial 16S ribosomal DNA sequence, indicated that strain MH-1 should belong to the genus Bacillus. Three isoforms of endochitinase (L, M, and S) were purified to homogeneity and characterized from Bacillus sp. strain MH-1. They had different molecular masses (71, 62, and 53 kDa), pIs (5.3, 4.8, and 4.7), and N-terminal amino acid sequences. Chitinases L, M, and S showed relatively high temperature optima (75, 65, and 75 degreesC) and stabilities and showed pH optima in an acidic range (pH 6.5, 5.5, and 5.5, respectively). When reacted with acetylchitohexaose [(GlcNAc)6], chitinases L and S produced (GlcNAc)2 at the highest rate while chitinase M produced (GlcNAc)3 at the highest rate. None of the three chitinases hydrolyzed (GlcNAc)2. Chitinase L produced (GlcNAc)2 and (GlcNAc)3 in most abundance from 66 and 11% partially acetylated chitosan. The p-nitrophenol (pNP)-releasing activity of chitinase L was highest toward pNP-(GlcNAc)2, and those of chitinases M and S were highest toward pNP-(GlcNAc)3. All three enzymes were inert to pNP-GlcNAc. AgCl, HgCl2, and (GlcNAc)2 inhibited the activities of all three enzymes, while MnCl2 and CaCl2 slightly activated all of the enzymes.

Amino Acid Sequence↗

PubMed1998

Exercise training restores decreased cellular immune functions in obese Zucker rats.

This study investigated whether exercise training had a beneficial effect on the decreased mitogen response and improved a decreased expression of glucose transporter 1 (GLUT-1) in splenocytes from obese Zucker rats. Experimental groups were lean and sedentary and exercise-trained obese Zucker rats. Exercise training, running on a motor-driven treadmill for 5 days/wk for 40 wk, did not induce a significant decrease in body weight in obese Zucker rats. The plasma insulin concentration, showing a significant increase compared with lean Zucker rats, was unaffected by exercise training. However, the plasma triglyceride concentration in obese Zucker rats was significantly depressed by exercise training, whereas it was still higher than that in lean Zucker rats. In addition, natural killer cell activity and concanavalin A-induced mitogenesis of splenic lymphocytes of obese Zucker rats were significantly restored. In these splenic lymphocytes, glucose uptake was significantly lower compared with that in lean Zucker rats, which was also improved by exercise training. Although the expression of GLUT-1, the major glucose transporter in immune cells, was depressed in splenic lymphocytes of obese Zucker rats, exercise training induced a significant improvement. These results suggest that exercise training has a beneficial effect on the decreased cellular immune functions in obese Zucker rats, which is associated, in part, with the improvement in GLUT-1 expression.

Animals↗