Biomedical subjects

M Yamaguchi

Publications and source records attributed to M Yamaguchi.

At least 703 records · Page 39Linked to original sources

PubMed1996

Nicotinamide nucleotide transhydrogenase: a model for utilization of substrate binding energy for proton translocation.

The energy-transducing nicotinamide nucleotide transhydrogenases of mammalian mitochondria and bacteria are structurally related membrane-bound enzymes that catalyze the direct transfer of a hydride ion between NAD(H) and NADP(H) in a reaction that is coupled to transmembrane proton translocation. The protonmotive force alters the affinity of the transhydrogenase for substrates, accelerates the rate of hydride ion transfer from NADH to NADP, and shifts the equilibrium of this reaction toward NADPH formation. Transhydrogenation in the reverse direction from NADPH to NAD is accompanied by outward proton translocation and formation of a protonmotive force. In reverse transhydrogenation, the enzyme utilizes substrate binding energy for proton pumping. Therefore, with regard to the mechanism of energy transduction, the transhydrogenase works according to the same principles as the ATP synthase complex of mitochondria and bacteria, the proton and cation ATPases, and possibly certain redox-linked proton pumps. However, the relatively simple structure of the transhydrogenase recommends it as a model for study of the utilization of binding energy for vectorial translocation of protons and other cations.

Amino Acid Sequence↗

PubMed1996

Development of a novel form of an oral 5-fluorouracil derivative (S-1) directed to the potentiation of the tumor selective cytotoxicity of 5-fluorouracil by two biochemical modulators.

We have focused our attention on the development of a novel form of a tegafur-based [FT; a prodrug of 5-fluorouracil (5-FU)] antitumor agent. We have used two biochemical and pharmacological modulators of 5-FU to improve its overall activity. To potentiate the antitumor activity of FT, 5-chloro-2,4-dihydroxypyridine (CDHP) was used as a potent reversible inhibitor of 5-FU degradation. The reduction of gastrointestinal (GI) toxicity, induced in the host by 5-FU, was modulated by potassium oxonate (Oxo), an inhibitor of orotate phosphoribosyltransferase that catalyzes the phosphorylation of 5-FU, a process believed to be responsible for the toxic effects of 5-FU. When CDHP and FT were simultaneously given orally to Yoshida sarcoma-bearing rats in various molar ratios, the antitumor effect of FT was significantly potentiated by the combination consisting of at least a 0.2 versus 1 molar ratio of CDHP to FT, respectively. This augmentation of an antitumor activity was supported by potent and prolonged inhibition of dihydrouracil dehydrogenase activity (5-FU degrading activities) in the liver of tumor-bearing rats after oral CDHP (0.2:0.8 molar ratio) and furthermore by elevation and over 12 h retention of 5-FU levels in the tumors following combined administration of FT and CDHP at a molar ratio of 1:0.4, respectively. Moreover, to reduce the severe GI injury and subsequent loss of body weight, observed in parallel with an increased antitumor efficacy, Oxo was given orally to Yoshida sarcoma-bearing rats and nude rats xenografted with H-81 human gastric carcinoma, during consecutive administration of the FT-CDHP mixture. Combined treatment with Oxo and FT (1:2 molar ratio) supplemented with 0.4 molar CDHP resulted in protection of body weight loss without affecting the high antitumor efficacy of the FT-CDHP mixture. When [2-14C]FT plus CDHP was administered with Oxo, the 14C-labeled fluoronucleotide content was objectively decreased in the GI tract of the tumor-bearing rats but not in the tumor and bone marrow, which supports our initial hypothesis. Based on these promising data, we propose a suitable formulation of a FT-based anticancer drug, called S-1, and consisting of FT, CDHP and Oxo at a 1:0.4:1 molar ratio and showing tumor-selective cytotoxicity of 5-FU.

Animals↗

PubMed1996

Thymic carcinoma of the thyroid.

A highly malignant case of intrathyroidal thymic carcinoma showing morphological and biochemical evidence identical with mediastinal thymoma is presented. A 32-year-old female, who had previously undergone total colectomy with ileo-proctostomy due to familial adenomatous polypnosis, was operated on for a tumor (3.4 x 4.5 cm) originating from the left thyroid lobe. A minute focus (diam. 0.8 cm) of papillary adenocarcinoma also existed in the upper pole of the right lobe. The main tumor was morphologically an epithelial thymoma with scanty lymphocyte intermixing and showed medullary differentiation with apparent Hassall's corpuscles. Mitosis was frequent and numerous tumor thrombi were in the subcapsular veins. Five months after the total thyroidectomy and lymph node dissection, a subcutaneous recurrence of the tumour (diam. 2.3 cm) appeared in the anterior cervical region. The cystic contents of the recurrent tumor revealed a high titer of thymosin alpha 1-Other organs, including thymus, lungs, and adrenals, had all been free of neoplastic changes clinically and radiologically for 5 months after her first admission until the local tumor recurrence.

Adult↗

PubMed1996

Effect of in vitro aging on Campylobacter rectus lipopolysaccharide-stimulated PGE2 release from human gingival fibroblasts.

OBJECTIVE: We examined the influence of in vitro aging on Campylobacter rectus (C. rectus) lipopolysaccharide (LPS)-stimulated prostaglandin (PG), E2 release frOm human gingival fibroblasts (HGFs). MATERIALS AND METHODS: LPS was prepared from C. rectus ATCC33238. HGFs were established from healing gingival tissue removed from three patients (donors A, B and C), aged 10-12 years. Aging of the cells in culture was determined with increasing population doubling. The cells were cultured until confluence, then stimulated with LPS (1.0 micrograms ml-1), and the levels of PGE2 in the medium were measured after 24 h by radioimmunoassay. RESULTS: The LPS-stimulated PGE2 production in each old cell (passage 17-20) was significantly increased to about 1.6-2.6 times than that in the corresponding young cells (passage 5-6). The gene expression of cyclooxygenase-2 mRNA in the old cells was higher than that in the young cells in response to LPS. In the absence of LPS, PGE2 production levels in both the young and old cells were very low, and also at the same level. However, there was a higher level of LPS-stimulated PGE2 production in the young cells from donor C compared to that in the old cells from donor B. The LPS-stimulated PGE2 production in each young cell from donors A and C was almost equal to that in each old cell from donors B and A, respectively. CONCLUSIONS: The results suggested that aging in HGFs may be one of the factors that take part in the stimulation of C. rectus LPS-stimulated PGE2 production in old cells.

Analysis of Variance↗

PubMed1996

H2O2 modulates twitch tension and increases Po of Ca2+ release channel in frog skeletal muscle.

The effect of H2O2 was examined to elucidate the basis of muscle injury after exercise. Exposure of single fibers to 1.5-6 mM H2O2 led to twitch potentiation followed by a marked decrease. Then, fibers contracted spontaneously. BAY K 8644 augmented twitch potentiation and slowed the decay of twitches. In 5 mM dithiothreitol (DTT), twitch potentiation and spontaneous contraction were not observed on H2O2 addition. Cytoplasmic application of 1.5-3 mM H2O2 to heavy sarcoplasmic reticulum (SR) vesicles incorporated into planar lipid bilayers increased the open probability of Ca2+ release channels, an effect reversed by DTT. We investigated oxidation of sulfhydryl groups on proteins in SR membrane by H2O2 with N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide. Pretreatment of light and heavy SR membranes with 1.5 mM H2O2 exponentially increased fluorescence intensity. The time constant of the intensity increase was increased markedly only in heavy SR in solution containing 50 microM cytoplasmic Ca2+, so Ca2+ release was associated with protein oxidation by H2O2. Thus extracellular H2O2 probably acts by oxidizing sulfhydryls of proteins at two distinct sites: the dihydropyridine receptors, oxidation of which elicits potentiation and subsequent inhibition of twitches, and Ca2+ release channels, whose oxidation elicits spontaneous contraction, resulting in muscle dysfunction.

Animals↗

PubMed1996

Heparin-like glycosaminoglycans inhibit leukocyte adhesion to endotoxin-activated human vascular endothelial cells under nonstatic conditions.

Since heparin-like glycosaminoglycans (GAGs) have been reported to possess anti-inflammatory effects, we tested effects of heparin-like GAGs on cell adhesion between endothelial cells (ECs) and leukocytes. Effects of heparin-like GAGs on adhesion molecule expression and leukocyte adhesion were analyzed using cultured human umbilical vein ECs stimulated by endotoxin. Expression of adhesion molecules on ECs was unchanged, but adherence of leukocytes to ECs was significantly reduced by heparin-like GAGs under nonstatic conditions. These results suggest that heparin-like GAGs may act as anti-inflammatory agents partly by inhibition of leukocyte adherence to stimulated ECs under nonstatic conditions and may prevent critical conditions caused by endotoxin.

Anti-Inflammatory Agents↗

PubMed1996

Cardiac rod body: hypertrophic Z-line in an aged pony.

Numerous rod bodies were found in a heart sample from a 33-year-old pony by a conventional electron-microscopic technique. The rod bodies were concentrated in localized areas of both atria and ventricles, without a specific pattern of distribution. The rods appear to have a typical crystalline-like structure which presumably contains actin backbone filaments and alpha-actinin as major protein constituents. Diminution, fragmentation, and disorganization of the myofibrils, random expansion of electron-dense materials, especially at the fasciae adherens of the intercalated disc, an increase of intercellular space, frequently associated with connective tissue elements, and accumulation of glycogen granules, lipofuscin, mitochondria, and nonviable organelles in the rod body-containing cells suggested that rod-containing myocytes are in a degenerating stage and that rod body formation occurs in atrophic cardiomyocytes rather than normal or hypertrophic cardiomyocytes in the aged pony heart.

Aging↗

PubMed1996

Myocardial bridge muscle on left anterior descending coronary artery differs from subepicardial myocardium of the left ventricle in dogs.

The myocardial bridge (MB) is a muscle band found sporadically above the coronary artery (CA) in humans and certain animals such as the dog, cat and sheep. The purpose of our study was to compare the structure of the MB muscle with that of tissue from the subepicardial myocardium. The histological studies included toluidine blue staining of 1-micron-thick sections and Gomori's trichrome staining of canine cardiac samples. The MB muscle of the dog heart is characterized by a distinctive spatial arrangement, with individual fibers separated by substantial elements of intercellular connective tissue in cross-section. Longitudinally, the long, slender fibers are aligned continuously with intermediation of intercalated disks lying perpendicular to the long axis of the fibers. In other regions of the left ventricular subepicardial myocardium, each myocyte is tightly packed in transverse view. There is great variation in the thickness (0.11-2.24 mm, average 0.45 mm) of MBs and the distance (24-236 microns, average 103 microns) between MBs and the left anterior descending coronary artery (LAD) among the 13 affected dogs examined, with no apparent relationship between the occurrence of MBs and either age or sex. These results on MB alignment suggest that the MB muscle generates force along the long axis of the fiber orientation as skeletal muscle does, and with minimal constriction of the CA; if so, the function of MB myocytes may differ from that of common cardiac myocytes, as does the structure. Then, the long-supposed downward compressive force of MBs on the LAD would be minimal in most cases; however, when the MB produces a systolic narrowing of the LAD known as the milking effect, the degree of lateral compression and its influence should depend not only on the substantial size of the MB muscle but also on the distance between the MB muscle and LAD. The environment surrounding the LAD may be a crucial factor in determining whether the MB influences the induction of heart disorders or not.

Animals↗

PubMed1996

Myocardial bridging as a factor in heart disorders: critical review and hypothesis.

The purpose of this report is to review the previous and current methods for the detection of a MB and to summarize results of work by other investigators as well as our own recent morphological studies with emphasis on work since 1983. We will discuss the presumable association of MBs with heart disorders, on the basis of significant publications. We describe the importance of both basic and clinical research for the assessment of MB influence in various heart disorders. Aspects covered are: (1) historical background of MBs and the relationship between the MB and CA; (2) general characteristics of MBs; (3) methods for studying MBs; (4) compressive effect of the MB on the CA; (5) clinical symptoms including myocardial ischemia, angina pectoris, myocardial infarction, development of atherosclerosis and thrombosis, ventricular fibrillation and sudden death; (6) treatment of MB-associated heart disorders by resection of MBs and (7) future research trends.

Animals↗

PubMed1996

Effects of different magnitudes of tension-force on alkaline phosphatase activity in periodontal ligament cells.

Alkaline phosphatase (ALP) activity is involved in the process of calcification in various mineralizing tissues, and it is found at much higher levels in the periodontal ligament (PDL) than in other connective tissues. Since the PDL lies between hard tissues and functions as a cushion mitigating mechanical stress, such as occlusal and orthodontic forces, this stress may modulate ALP activity in PDL cells, which themselves may affect adjacent alveolar bone metabolism. The objective of this study was to determine the level of ALP activity and the gene expression of liver/bone/kidney (L/B/K) ALP in human PDL fibroblasts in response to cyclic tension-forces. Human PDL cells were cultured on flexible-bottomed plates and placed on a Flexercell Strain Unit. Cells were flexed at 6 cycle/min (5 sec strain, 5 sec relaxation) at 6 levels of tension-force (9%, 12%, 15%, 18%, 21%, and 24% increase in surface area) for 5 days. There was no significant difference in cell proliferation between the cells subjected to the tension-force and the controls. There was a 10% and 42% decrease, respectively, in the ALP activity in PDL cells exposed to low (9%) and high (24%) tension-forces, and these decreases were dependent on the magnitude of the tension-force. The finding of inhibited ALP activity in response to tension-force was consistent with the observation that L/B/K ALP mRNA levels were decreased in response to cyclic tension-force. These results suggest that tension-force may affect PDL metabolism, depending on the functional role of ALP.

Alkaline Phosphatase↗

PubMed1996

Differences in mechanisms for cell-free NADPH oxidase activation between arachidonate and sodium dodecyl sulfate.

Mechanisms for the cell-free activation of NADPH oxidase by sodium dodecyl sulfate (SDS) and arachidonate were compared in relation to their responsiveness to short chain diacylglycerols. The plasma membrane and cytosol prepared from guinea pig neutrophils were used for the cell-free system. The activation of NADPH oxidase by SDS was enhanced about 5- to 10-fold by 1,2-dioctanoylglycerol (diC8), but not by either 1,2-dihexanoylglycerol (diC6) or 1,2-didecanoylglycerol (diC10). However, none of these diacylglycerols potentiated the NADPH oxidase activation by arachidonate. The maximal extent of activation by the combination of SDS and diC8 was similar to that by arachidonate alone. In the presence of sufficient amounts of diC8 and SDS, GTP gamma S potentiated the activation of NADPH oxidase. The potentiating activity of diC8 was preserved in the membrane fraction, not in the cytosol fraction. These results suggest that arachidonate may possess the functions of both SDS and diC8 in the activation. In addition, diC8 and GTP gamma S seem to independently enhance the NADPH oxidase activation.

Animals↗

PubMed1996

High-performance liquid chromatographic determination of human serum albumin in plasma and urine by post-column fluorescence enhancement detection using 8-anilino-1-naphthalenesulfonic acid.

A method for the quantitative determination of human serum albumin in plasma and urine by post-column high-performance liquid chromatography with fluorescence detection is presented. Human serum albumin in plasma and urine is separated by gel-permeation column chromatography, which is followed by fluorescence detection. The detection uses the fluorescence enhancement observed when 8-anilino-1-naphthalenesulfonic acid binds to human serum albumin. The method is rapid to perform and is highly sensitive (detection limit is 2.5 ng/injection volume at a signal-to-noise ratio of three.

Adult↗

PubMed1996

Assay for tryptophan hydroxylase activity in rat brain by high-performance liquid chromatography with fluorescence detection.

A highly sensitive and selective liquid chromatographic (HPLC) method with post-column fluorescence detection has been developed for the determination of tryptophan 5-monooxygenase activity in rat brain tissue homogenate. 5-Hydroxytryptophan, formed enzymatically from tryptophan (incubation time, 20 min), is extracted with perchloric acid and determined by HPLC. Detection is performed fluorometrically after post-column derivatization by a reaction with benzylamine in the presence of potassium hexacyanoferrate (III). The lower limit of detection for 5-hydroxytryptophan formed enzymatically is 100 fmol at a signal-to-noise ratio of three.

5-Hydroxytryptophan↗

PubMed1996

Purification, characterization, and crystallization of single molecular species of beta-conglycinin from soybean seeds.

Four major molecular species of beta-conglycinin, alpha 3, alpha 2 beta, alpha beta 2, and beta 3, were isolated and purified from seeds of an alpha' subunit-deficient strain of soybeans (Glycine max). All components were found to be homogeneous by high pressure liquid chromatography, SDS-polyacrylamide gel electrophoresis, and amino acid and amino terminal sequence analyses. The amino acid compositions of the alpha 3 and beta 3 components agreed fairly well with the compositions deduced from the cDNA sequences, and all of the components were highly glycosylated. The alpha 3 and beta 3 components were compared regarding their secondary structures. The secondary structure of the alpha 3 component deduced from CD measurements showed a higher alpha-helix content than that of the beta 3 component. The beta 3 component was crystallized by decreasing the ionic strength from 0.5 to 0.14 in phosphate buffer, pH 7.3, and the crystals grew to a size (1.0 mm x 0.2 mm x 0.2 mm) suitable for X-ray crystallographic analysis. A preliminary X-ray analysis showed that the crystal belonged to an orthorhombic crystal system having the space group P2(1)2(1)2(1) and unit cell dimensions of a = 185.1 A, b = 107.9 A, and c = 97.6 A.

Amino Acid Sequence↗

PubMed1996

Equine synovial villi: distinctive structural organization of vasculature and novel nerve endings.

The structural arrangement and cellular distribution of endothelial and lining cells of the synovial villi were studied in the equine palmar/plantar recess of the metacarpo- and metatarsophalangeal joints by light microscopy and electron microscopy. The extent and distribution of blood vessels varied with villous shape and length. The majority of vessels formed concentric circles in cross and longitudinal sections and probably are arranged in a convoluted, spiral or helical pattern. The villi do not contain smooth muscle cells or typical capillaries as observed in other organs. Under the electron microscope, the endothelium is surrounded by connective tissue and discontinuous circular cells, presumably fibroblasts. The outermost layer was sometimes surrounded by type A and/or B synovial cells. The lumen of the blood vessels at the top of villus appeared to be constricted in most cases, with a diameter of about 12 +/- 3 microns. Blood vessels formed by more than six endothelial cells in the middle portion of villus generally were not constricted. Well-developed cytoplasmic processes extended into the lumen of blood vessels. The constriction of blood vessels with no apparent smooth muscle presence and the observation of numerous intermediate filaments in the cytoplasm of the endothelial cells suggests that these villous blood vessels constrict through contraction of their own endothelial cells. Lining cells were distributed unevenly even within a single villus; the villous lining cells seemed to have directional preferences with domination of synovial type A cells. Surprisingly, structures resembling myelinated nerve ends (approximately 0.2 microns) were observed between juxtaposed endothelial cells as well as directly on an endothelial cell, suggesting that these nerve endings may be a sensor detector of either pressure or temperature or have a proprioceptive-like function. Synovial villi have a distinctive structural arrangement of vessels, lining cells, and nerve endings.

Animals↗

PubMed1996

Regulation of mouse placental lactogen secretion by factors secreted from the pituitary in vitro.

The effect of factors secreted from the pituitary on mouse placental lactogen I (mPL-I) and mPL-II secretion in vitro was examined. Co-culture of mouse placental cells from day 7 of pregnancy with the pituitary cells of the mother significantly stimulated mPL-I secretion but did not regulate mPL-II secretion. The effect on mPL-I secretion was dependent on the number of pituitary cells. The conditioned medium of pituitary cells also significantly stimulated mPL-I secretion but did not regulate mPL-II secretion. The stimulatory effect of mPL-I secretion was dependent on the volume of the conditioned medium. The number of cells containing mPL-I assessed by immunocytochemistry was increased by the co-culture in a cell number-dependent manner. Northern blot analysis for mPL-I indicated that treatment of placental cells with the pituitary-conditioned medium results in an increase of mPL-I gene expression. These findings suggest that factors secreted from the pituitary directly regulate mPL-I secretion, but not mPL-II secretion, before midpregnancy in vivo.

Animals↗

PubMed1996

Cyclic AMP regulates expression of activin and inhibin subunit mRNAs in the mouse placenta and decidua: a short communication.

We examined whether cAMP regulates expression of activin/inhibin subunit mRNAs in the mouse placenta and decidua. 8-Bromo-cAMP inhibited expression of inhibin alpha-subunit mRNA but stimulated expression of activin/inhibin beta A- and beta B-subunit mRNAs in placenta and decidua by the 3rd day of culture. Forskolin and cholera toxin also regulated expression of activin/inhibin subunit mRNAs in the same manner. However, activin-A did not affect expression of activin/inhibin subunit mRNAs. These findings suggest that cAMP inhibits inhibin production but stimulates activin production in the mouse placenta and decidua.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1996

8-Bromo-cAMP inhibits glucose transport activity in mouse placental cells in culture.

Glucose plays an important role in fetal development and energy metabolism. Facilitative glucose transporter-1 (GLUT1) has been found in placenta. However, little is known about GLUT1 modulation in placental cells. To examine changes in mouse placental GLUT1 levels caused by 8-bromo-cAMP, we performed 2-deoxyglucose uptake experiments, Northern blot analysis and immunoblot analysis using a primary mouse placental cell culture. Immunohistochemical analysis showed that GLUT1 was localized to the ectoplacental cone and the labyrinth zone of mouse placentas on days 7 and 11 of pregnancy respectively. Treatment of mouse placental cells with 250 mumol/l 8-bromo-cAMP resulted in a significant (P < 0.01) decrease in glucose uptake on days 2-5 of culture. The inhibitory effect of 8-bromo-cAMP on glucose uptake was concentration-dependent. Glucose uptake was also inhibited by 100 micrograms/l cholera toxin and by 0.1 mmol/l forskolin. Northern blot and immunoblot analysis revealed that both GLUT1 mRNA and protein levels were also decreased by 8-bromo-cAMP. These findings suggest that 8-bromo-cAMP inhibits glucose transport activity in mouse placental cells in culture.

8-Bromo Cyclic Adenosine Monophosphate↗