Biomedical subjects

K Miyamoto

Publications and source records attributed to K Miyamoto.

At least 109 records · Page 6Linked to original sources

PubMed2001

Image analysis of the effects of gonadectomy on colloidal carbon uptake in vivo by sinusoidal cells in liver and spleen of the mouse.

PROBLEM: The presence of androgen and estrogen receptors in macrophages was recently described. This suggests that both sex hormones directly act on reticuloendothelial system (RES) activity. Studies of the effect of gonadectomy on uptake and clearance of foreign materials make clear a role of the testis and ovary in RES regulation. However, there is still some disagreement as to the gonadal influence on RES. METHOD OF STUDY: We applied a computed image analysis system to the investigation of the effects of gonadectomy on colloidal carbon uptake by the liver and spleen sinusoidal cells in mice. Mice were gonadectomized or sham-operated. After a few weeks, they received colloidal carbon with or without pretreatment with lipopolysaccharide (LPS). Thereafter, livers and spleens were taken for quantitative determination of the amounts of endocytosed carbon in the sinusoidal cells by means of digital image analysis. RESULTS: Ovariectomy did not significantly affect hepatic and splenic RES activities compared with sham-operated controls. Treatment of mice with LPS after ovariectomy also caused no significant changes of the RES activities compared with sham-operated and LPS-injected controls. In contrast, orchidectomy resulted in significant enhancement of splenic RES activity compared with sham-operated males, while hepatic RES activity did not significantly change with orchidectomy alone. However, LPS treatment to orchidectomized mice significantly augmented both hepatic and splenic RES activities compared with sham-operated and LPS-injected controls. CONCLUSION: The significant augmentation of RES activity by orchidectomy, but not by ovariectomy, indicates that male RES activity is physiologically downregulated in the presence of the testes. Furthermore, splenic RES is more sensitive to orchidectomy than hepatic RES.

Animals↗

PubMed2001

Selective delivery of estradiol to bone by aspartic acid oligopeptide and its effects on ovariectomized mice.

We have developed a novel osteotropic prodrug of estradiol (E(2)) conjugated with L-Asp-hexapeptide (E(2).3D(6)), which has very low affinity for estrogen receptors, and in this study, we examined its pharmacokinetic behavior and pharmacological potential. After a single iv injection of E(2) x 3D(6) to mice, the half-time for elimination from plasma was about 100 min; however, E(2) was selectively delivered to the bone and eliminated very slowly, declining to the endogenous level at about 7 days. After a single iv injection of E(2), the half-time in plasma was about 70 min, whereas E(2) was highly distributed to the uterus, and the bone concentration of E(2) was only slightly increased at 6 h. When E(2) (0.37 micromol/kg, sc, every third day) or E(2) x 3D(6) (0.11 to 1.1 micromol/kg, sc, every seventh day) was administered to OVX mice for 4 weeks, E(2) increased the bone mineral density (BMD) together with weights of liver and uterus, whereas E(2) x 3D(6) increased only the BMD, in a dose-dependent manner. E(2) x 3D(6) enhanced the expression of messenger RNAs of bone matrix proteins (osteopontin, bone sialoprotein, type I collagen alpha) of OVX mice at 4 h after administration, but E(2) did very slightly. These results indicate that the E(2) prodrug was delivered to the bone, where it gradually released E(2), thereby ameliorating bone loss. This acidic oligopeptide appears to be a good candidate for selective drug delivery to bone.

Animals↗

PubMed2001

Cloning and characterization of gonadotropin-inducible ovarian transcription factors (GIOT1 and -2) that are novel members of the (Cys)(2)-(His)(2)-type zinc finger protein family.

Gonadotropins are essential for ovarian follicular development and differentiation. To identify genes that are rapidly induced by gonadotropin in the immature rat ovary, ovarian genes were screened by a subtraction cloning procedure. cDNA clones encoding novel members of the (Cys)(2)-(His)(2)-type zinc finger protein family GIOT1 and -2 (gonadotropin-inducible transcription factor 1 and 2), were identified. Two isoforms of GIOT2 (GIOT2 alpha and 2 beta), which are probably produced by alternative splicing, also exist. Nucleotide sequence analysis revealed that GIOT1, but not GIOT2, contains the krüppel-associated box-A domain at the NH(2) terminus. RNA analyses revealed that these mRNAs were rapidly and temporarily induced by gonadotropins in the rat testis as well as in the ovary. In situ hybridization study revealed that expression of GIOT1 was induced in theca interna cells in the ovary and Leydig cells in the testis. Interestingly, the gene expression of GIOT1 is restricted to the pituitary, adrenal, testis, and ovary, while GIOT2 gene is expressed ubiquitously. A functional analysis of GIOT1 and -2 by a GAL4-based mammalian one-hybrid system revealed that GIOT1, but not GIOT2, is a transcriptional repressor and that the krüppel-associated box-A domain of GIOT1 is responsible for the transcriptional repressor activity. A GAL4-based yeast two-hybrid system was also used to identify proteins that interact with the rat GIOT1. We cloned genes encoding rat homologs of human I-mfa domain containing protein and transcriptional intermediary factor 1 beta, both of which are transcription-regulatory proteins. Interaction of these proteins with GIOT1 was directly demonstrated by GST pull-down assay. Our data strongly suggest that GIOT1 may function as a novel transcriptional repressor by working with rat homologs of human I-mfa domain containing protein and transcriptional intermediary factor 1 beta proteins and may play a significant role at the transcription level in the folliculogenesis.

3T3 Cells↗

PubMed2001

Tectorigenin, an isoflavone of Pueraria thunbergiana Benth., induces differentiation and apoptosis in human promyelocytic leukemia HL-60 cells.

Cytotoxic effects of six isoflavonoids, tectorigenin, glycitein, tectoridin, glycitin, 6''-O-xylosyltectoridin, and 6''-O-xylosylglycitin isolated from the flower of Pueraria thunbergiana Benth. together with genistein, a known differentiation and apoptosis inducer, were examined. Among these isoflavonoids, tectorigenin and genistein exhibited cytotoxicity against various human cancer cells; glycitein showed only mild cytotoxicity. These results suggest that the isoflavone structure and 5-hydroxyl group are crucial for the cytotoxic properties and that glycosides are inactive. Moreover, tectorigenin induced differentiation of human promyelocytic leukemia HL-60 cells to granulocytes and monocytes/macrophages, and caused apoptotic changes of DNA in the cells, as did genistein. Tectorigenin also inhibited autophosphorylation of epidermal growth factor (EGF) receptor by EGF and decreased the expression of Bcl-2 protein, with less activity than genistein. From these results, tectorigenin may be a possible therapeutic agent for leukemia.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

Phosphodiesterase 4 isoenzyme inhibitory activity of 3-phenylxanthines and 4-pheny.

On the basis of our study on the structure-activity relationships of 1,3,7-alkylxanthines and condensed-purines on cAMP-phosphodiesterase 4 (PDE 4) isoenzyme inhibitor, we investigated the synthesis and the inhibitory activity of 3-phenylxanthine and 4-phenyl[i]condensed-purine derivatives. Xanthines and condensed-purines with the phenyl group exhibited potent and selective PDE 4 inhibitory activity.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed2001

[Studies on the mechanism of subcellular distribution of basic drugs based on their lipophilicity].

This paper described the studies on the mechanism of subcellular distribution of lipophilic weak bases. Although the tissue distribution of basic drugs appeared to decrease with time simply in parallel with their plasma concentration, their subcellular distribution in various tissues exhibited a variety of patterns. Basic drugs were distributed widely in various tissues, but were concentrated in lung granule fraction, where their accumulation was dependent on their lipophilicity and lysosomal uptake. As the plasma concentration of drugs decreased after maximum level, the contribution of lysosomes to their subcellular distribution increased. The uptake of the basic drugs into lysosomes depended both on their intralysosomal pH and on the drug lipophilicity. As the lipophilicity of the basic drugs increased, they accumulated more than the values predicted from the pH-partition theory and raised the intralysosomal pH more potently, probably owing to their binding with lysosomal membranes with or without additional intralysosomal aggregation. These phenomena should be considered as a basis of drug interaction in clinical treatments.

Animals↗

PubMed2001

Role of relative myocardial perfusion reserve for evaluating stenosis severity in patients with single-vessel coronary artery disease using.

A statistically significant correlation was observed between the severity of anatomic stenosis and coronary flow reserve in experimental animals. A similar correlation in human coronary artery disease (CAD) was shown using positron emission tomography (PET) and pharmacologic vasodilator stress. The present study tested whether the concept of relative myocardial perfusion reserve (MPR) might be superior to absolute MPR in correlating coronary stenosis determined by quantitative coronary arteriography in patients with single vessel CAD using [13N]ammonia and PET. The study group comprised 21 patients (62 +/-10 years old; 15 men, 6 women) with normal left ventricular function who underwent angioplasty for isolated left anterior descending coronary artery stenosis. Absolute MPR, the ratio of dipyridamole-induced hyperemic blood flow to baseline blood flow by [13N]ammonia PET, and relative MPR, the ratio of MPR in regions supplied by stenosed coronary arteries to MPR in remote regions, were measured before and 3 months after angioplasty. The percent diameter stenosis was also quantified on coronary arteriograms just before the angioplasty and again at 3 months after. The study found that absolute MPR (r=0.755; p<0.0001) and relative MPR (r=0.814; p<0.0001) were inversely and nonlinearly correlated with the percent stenosis on angiography. The fitting curve of the correlation between relative MPR and coronary stenosis on angiography was identical to that observed in animal models. Therefore, relative MPR measured by [13N]ammonia PET more accurately and specifically describes stenosis severity in patients with CAD compared with absolute MPR, probably because of its independence from hemodynamic variations and the effects of coronary risk factors.

Adult↗

PubMed2001

H2 production from algal biomass by a mixed culture of Rhodobium marinum A-501 and Lactobacillus amylovorus.

To produce hydrogen from starch accumulated in an algal biomass, we used a mixed culture of the lactic acid bacterium, Lactobacillus amylovorus, and the photosynthetic bacterium, Rhodobium marinum A-501. In this system L. amylovorus, which possesses amylase activity, utilized algal starch for lactic acid production, and R. marinum A-501 produced hydrogen in the presence of light using lactic acid as an electron donor. Algal starch accumulated in the marine green alga Dunaliella tertiolecta, and the freshwater green alga Chlamydomonas reinhardtii, was more suitable for lactic acid fermentation by L. amylovorus than an authentic starch sample. Consequently, the yields of hydrogen obtained from starch contained in D. tertiolecta and C. reinhardtii were 61% and 52%, respectively, in the mixed culture of L. amylovorus and R. marinum A-501. These values were markedly superior to those obtained using a mixed culture of Vibrio fluvialis T-522 and R. marinum A-501 described previously. The yield and production rate of hydrogen by R. marinum A-501 from the lactic acid fermentates were higher than from authentic lactic acid, suggesting that the fermentates contain a factor(s) which promotes H2 production by this bacterium.

Journal Article↗

PubMed2001

Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta.

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.

Journal Article↗

PubMed2001

Bioassay for neutron-dose estimations of three patients in the JCO criticality accident in Tokai-mura by measuring beta-ray emitters.

The measurement of beta-emitters in biological samples (hair, urine and bone) from three patients in the JCO criticality accident was performed to assess the neutron dose to individuals. The result of the measurements of 32P in hair and urine collected immediately after the accident showed that sufficient 32P activities had been induced in the hair by fast neutrons and in the urine by thermal neutrons to know the severity of the exposure to the individuals and to the position. From the measurement of 32P and 45Ca in bone from various anatomical parts of two patients who died 82 and 210 days after the accident, it was suggested that the distribution of the induced beta-emitters activities could prove the position and posture of the patients at the moment of exposure.

Beta Particles↗

PubMed2001

Cloning, sequencing, and expression of the gene encoding an intracellular beta-D-xylosidase from Streptomyces thermoviolaceus OPC-520.

The intracellular beta-xylosidase was induced when Streptomyces thermoviolaceus OPC-520 was grown at 50 degrees C in a minimal medium containing xylan or xylooligosaccharides. The 82-kDa protein with beta-xylosidase activity was partially purified and its N-terminal amino acid sequence was analyzed. The gene encoding the enzyme was cloned, sequenced, and expressed in Escherichia coli. The bxlA gene consists of a 2,100-bp open reading frame encoding 770 amino acids. The deduced amino acid sequence of the bxlA gene product had significant similarity with beta-xylosidases classified into family 3 of glycosyl hydrolases. The bxlA gene was expressed in E. coli, and the recombinant protein was purified to homogeneity. The enzyme was a monomer with a molecular mass of 82 kDa. The purified enzyme showed hydrolytic activity towards only p-nitrophenyl-beta-D-xylopyranoside among the synthetic glycosides tested. Thin-layer chromatography analysis showed that the enzyme is an exo-type enzyme that hydrolyze xylooligosaccharides, but had no activity toward xylan. High activity against pNPX occurred in the pH range 6.0-7.0 and temperature range 40-50 degrees C.

Amino Acid Sequence↗

PubMed2001

Enzymatically enantioselective hydrolysis of prochiral 1,3-diacyloxyglycerol derivatives.

An enzymatically enantioselective ester hydrolysis of prochiral 1,3-diacyloxy-2-substituted-2-propanol to chiral 1-acyloxy-2,3-propanediol was studied. The (R)-monoester was prepared by selection of a suitable lipase and alkyl chain length of the substrate diester. Lipase D from Rhizopus delemer gave (R)-1-isobutyryloxy-2-(2,4-difluorophenyl)-2,3-propanediol with 97%ee and 87% yield at 15 degrees C and pH 5.5. The (R)-monoester is a key intermediate of azole antifungal agents.

Biochemistry↗

PubMed2001

Enhancement of endothelial nitric oxide production by chenodeoxycholic acids in patients with hepatobiliary diseases.

The purpose of this study was to clarify whether physiological concentrations of bile acids could affect endothelial nitric oxide production. We investigated the relationships between clinical concentrations of individual bile acids observed in patients with hepatobiliary diseases and endothelial nitric oxide production induced by each bile acid. Fifteen serum bile acids were measured using high-performance liquid chromatography combined with enzymatic fluorometry in 8 patients with liver cirrhosis, obstructive jaundice, and 8 healthy subjects. The effects of individual bile acids on nitric oxide production were examined in human umbilical endothelial cells by measuring the concentration of NO2- in the cultured medium. NO release in the blood was also determined by measuring the NO2-/NO3- concentration in these patients. In patients with hepatobiliary diseases, the plasma concentrations of chenodeoxycholic acid, ursodeoxycholic acid and cholic acid (free acid, taurine and glycine conjugates) were markedly elevated. Incubation of cells with chenodeoxycholic acid and deoxycholic acid (free acid, taurine and glycine conjugates) enhanced NO2- production in a concentration-dependent manner, while cholic acid (free and its conjugates) did not. The effects of individual bile acids on nitric oxide production were additive. Patients with liver cirrhosis and obstructive jaundice had higher plasma levels of NO2-/NO3- levels than the control subjects. These results suggest that increased plasma concentrations of chenodeoxycholic acid (free, taurine and glycine conjugates) in patients with hepatobiliary diseases may induce endothelial nitric oxide production. Thus, nitric oxide production induced by bile acids may be involved in the pathogenesis of circulatory abnormalities in patients with liver diseases.

Aged↗

PubMed2001

Evaluation of plasma clearance of inulin in clinically normal and partially nephrectomized cats.

OBJECTIVE: To evaluate accuracy of measuring plasma clearance of inulin as an alternative renal function test for estimation of glomerular filtration rate (GFR) in cats. ANIMALS: 10 cats, first studied with intact kidneys and subsequently studied following partial nephrectomy. PROCEDURE: Clearance studies were performed in 10 clinically normal cats; those same cats then underwent partial nephrectomy, and clearance studies were performed again. Plasma concentration of inulin was determined after administration at 50 mg/kg of body weight to cats while renally intact and 45 mg/kg after the partial nephrectomy. Plasma clearance of inulin (PCin) was determined by dividing the dose by the area under the plasma inulin concentration versus time curve. Results for PCin were compared with values obtained simultaneously for urinary clearance of exogenously administered creatinine (Ccr), a widely accepted method for measurement of GFR in cats with intact kidneys and cats with reduced renal mass. RESULTS: Results of PCin were strongly correlated (r2 = 0.912, P < 0.001) with Ccr. Repeatability of determination of PCin was similar to that of Ccr. Sensitivity and specificity of PCin were superior and equivalent to that of Ccr, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Determination of PCin provides a reliable estimate of GFR in cats and is a promising alternative to determining Ccr in cats.

Animals↗

PubMed2001

Use of plasma clearance of iohexol for estimating glomerular filtration rate in cats.

OBJECTIVE: To determine whether plasma clearance of iohexol (PCio) can be used to estimate glomerular filtration rate (GFR) in cats. ANIMALS: 4 renal-intact and 6 partially nephrectomized adult cats. PROCEDURE: Plasma clearance of iohexol was determined after IV administration of iohexol; plasma concentrations of iodine were measured by use of a colorimetric assay. Results for PCio were compared with simultaneously obtained values for urinary clearance of creatinine (CCr). RESULTS: The colorimetric assay used to measure plasma iodine concentrations was extremely precise. Results of PCio for all cats, renal-intact cats, and partially nephrectomized cats were closely associated with results of CCr. Mean difference between CCr and PCio determined for all cats was 0.95 ml/min/kg, which was < 30% of mean CCr for renal-intact cats. Coefficients of variance for PCio (5%) and CCr (8%) in renal-intact cats were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma clearance of iohexol determined by use of a simple colorimetric assay provided an estimation of GFR in cats that was not significantly different from that provided by CCr. Moreover, PCio more reliably estimates renal function than BUN and plasma creatinine concentrations. Because determination of PCio is less labor intensive and invasive, compared with CCr, it may be easier to perform in a clinical setting.

Animals↗

PubMed2001

Novel drug delivery system to bone using acidic oligopeptide: pharmacokinetic characteristics and pharmacological potential.

We synthesized fifteen oligopeptides consisting of Asp or Glu conjugated with a fluorescent probe, 9- fluorenylmethylchloroformate (Fmoc). In the in vitro binding assay to putative hydroxyapatite (HA), the affinities of these conjugates depended only on the number of amino acid residues, not on their optical characters (L or D) or their species (Asp or Glu). In an in vivo experiment involving a single i.v. injection of Fmoc-D-Asp oligopeptides into mice, peptides consisting of over six Asp residues were selectively distributed to the bone. Then, we synthesized estradiol-17 beta-succinate-(L-Asp)6 [E2-(L-Asp)6] and studied its pharmacokinetic characteristics and its antiosteoporotic effects on ovariectomized (OVX) mice. Although the distribution volume of E2-(L-Asp)6 was significantly smaller than that of E2, E2-(L-Asp)6 was selectively distributed in the bone after i.v. injection and gradually decreased during 7 days. E2-(L-Asp)6 effectively prevented OVX-induced bone loss, without altering the uterine weight, in the dosage range of 0.11 to 1.1 mumol/kg once a week, while E2 increased both the bone mineral density and uterine weight at 0.37 mumol/kg every third day. The results suggest that acidic oligopeptide may be useful for drug delivery to bone and E2-(L-Asp)6 is a good candidate as an anti-osteoporosis drug without the adverse side effects of E2.

Acids↗

PubMed2001

Removal of broken pedicle screws. Technical note.

The authors describe a simple, new method for removing broken pedicle screws. Under microscopic visualization a straight, narrow slot is etched in the broken surface of the pedicle screw by using a power drill with a 2-mm diamond burr. A minus screwdriver is then inserted into the slot, and the broken screw is rotated and removed. There is no need to enlarge the screw hole around the broken screw or to use any special devices. The authors succeeded in removing broken screws in two cases, and there were no complications. This method allows preservation of both the pedicle and the screw hole. Consequently, it is possible to insert new pedicle screws into the same hole without losing the strength and stability of pedicle screw fixation. The authors recommend this simple and new method for removal of broken pedicle screws.

Bone Screws↗

PubMed2001

Beneficial effect of the active form of vitamin D3 against LPS-induced DIC but not against tissue-factor-induced DIC in rat models.

1Alpha,25-dihydroxyvitamin D3 (active form of vitamin D3; vitamin D3) has been reported to induce the upregulation of thrombomodulin and downregulation of tissue factor (TF) on monocytes. The possibility exists that vitamin D3 prevents the development of disseminated intravascular coagulation (DIC). In particular, monocyte TF production plays an important role in the pathophysiology of DIC in septic patients. We have attempted to determine whether vitamin D3 is effective against DIC in a rat model induced by lipopolysaccharides (LPS) (30 mg/kg, 4 h) or TF (3.75 U/kg, 4 h) using selective hemostatic parameters, markers of organ dysfunction and pathological findings (assessment of glomelular fibrin deposition). Vitamin D3 was administered orally each day at a dose of 2.0 mg/kg/day for 3 days, or low molecular weight heparin (LMWH 200 u/kg; i.v.) was given 10 min before the injection of TF or LPS in each treatment group. Vitamin D3 was effective against DIC in the rat model induced by LPS only, whereas LMWH was effective against DIC in both rat models induced by either TF or LPS. The anti-DIC effect of vitamin D3 was equal to (or more potent than) that of LMWH. The results suggested that vitamin D3 was useful for the treatment of LPS-induced DIC, and that the assessment of a drug's efficacy should be done carefully given the markedly different results obtained according to the agents used to induce DIC.

Administration, Oral↗