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Biomedical subjects

M Yamazaki

Publications and source records attributed to M Yamazaki.

At least 667 records · Page 37Linked to original sources
PubMed1989

Osmoelastic coupling in biological structures: a comprehensive thermodynamic analysis of the osmotic response of phospholipid vesicles and a reevaluation of the "dehydration force" theory.

A comprehensive thermodynamic analysis of the osmotic response of phospholipid vesicles is presented, using the Gibbs free energy of a vesicle suspension including the elastic contribution of the bilayer membrane. The results indicate that, in addition to the hydrostatic pressure difference across the membrane and the interbilayer pressure due to electrostatic repulsion, the elastic pressure arising from the coupling between the osmotic stress and the elasticity of the membrane (osmoelastic coupling) should participate in the osmotic response of phospholipid vesicles. The data of Cowley et al. [Cowley, A. C., Fuller, N. L., Rand, R. P., & Parsegian, V. A. (1978) Biochemistry 17, 3163-3168] and of Parsegian et al. [Parsegian, V. A., Fuller, N., & Rand, R. P. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 2750-2754] on the osmotic shrinkage of multilayer vesicles are discussed in terms of the elastic pressure and the interbilayer pressure, and the proposed "dehydration force" theory is reevaluated from the viewpoint of the present analysis.

Elasticity↗
PubMed1989

Osmoelastic coupling in biological structures: decrease in membrane fluidity and osmophobic association of phospholipid vesicles in response to osmotic stress.

Poly(ethylene glycol)- (PEG-) induced change in membrane fluidity and aggregation of phospholipid vesicles were studied. A threshold concentration of PEG was required to induce the aggregation. This concentration increased with a decrease in the molecular weight of PEG, e.g., from 5% (w/w) with PEG 6000 (PEG with an average molecular weight of 7500) to more than 30% (w/w) with PEG 200. The aggregation was reversible upon dilution of PEG if the initial PEG concentration was smaller than a certain value, e.g., 22% (w/w) for PEG 6000. Addition of PEG caused a decrease in membrane fluidity of the vesicles detected by fluorescence anisotropy of diphenylhexatriene and by electron spin resonance of a spin-labeled fatty acid. The anisotropy change of diphenylhexatriene fluidity change had an inflection point at approximately 5% (w/w) of PEG 6000, which might suggest that the aggregation would make the decrease of membrane fluidity smaller. Transfer of lipid molecules between phospholipid vesicles was enhanced by the PEG-induced aggregation. The enhancement occurred not only upon direct addition of PEG to the suspending medium, but also upon dialysis of the vesicle suspension against a high concentration of PEG. All these features are consistent with osmoelastic coupling in the phospholipid membranes and the subsequent osmophobic association of the vesicles. The imbalance of osmolarity between the region adjacent to the vesicle surface (exclusion layer) and the bulk aqueous phase, which results from the preferential exclusion of PEG from the exclusion layer in the case of direct addition of PEG, exerts an osmotic stress on the vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Elasticity↗
PubMed1989

Pancreatic vagal functional distribution in the secretion of insulin evoked by portal infusion of D-glucose.

The vagus glucose signal pathway relevant to hepatic portal control of insulin secretion was examined in bilaterally adrenalectomized rats. The increase in the insulin concentration after portal glucose injection was completely blocked by vagotomy of the hepatic branch which is bifurcated from the ventral vagus trunk at the subdiaphragmatic level. At the cervical level, the reduction in the insulin concentration showed no laterality following vagotomy on either side. The insulin response was mainly suppressed by prior section of the branch of the ventral vagus trunk at the celiac level. These results suggest that the hepatic glucose signal evoking insulin release has a specific pathway from the liver to the pancreas, and that there is functional laterality in this pathway in the visceral cavity.

Adrenalectomy↗
PubMed1989

Augmentation of release of cytotoxin from murine bone marrow and peritoneal macrophages by tumor transplantation.

Cytotoxin release by bone marrow-adherent cells and peritoneal macrophages was transiently augmented by i.p. inoculation of syngeneic tumor cells, but not normal cells. These effects were maximal 24-48 h after tumor transplantation. The cytotoxin released from bone marrow-adherent cells obtained 24 h after tumor inoculation had a molecular weight of about 70,000. Peritoneal macrophages obtained 24 h after tumor inoculation released mainly a cytotoxin with a molecular weight of about 55,000, whereas 48-h peritoneal macrophages released both Mr 55,000 and 70,000 cytotoxins. Activities of these three cytotoxins were inhibited by the addition of rabbit anti-murine tumor necrosis factor antibody. No change in expression of antigens on cells producing the cytotoxin was detected in bone marrow-adherent cells obtained 24 h after tumor inoculation, compared to normal bone marrow-adherent cells. However, expression of surface antigens of peritoneal macrophages obtained 24 h after tumor inoculation differed from that of peritoneal macrophages obtained 48 h later. Antigen expression of 48-h peritoneal macrophages producing the cytotoxin was similar to that of 24-h bone marrow-adherent cells producing the cytotoxin. Taken together with the cytotoxin data, it appears that some cells in 48-h peritoneal macrophages may originate from 24-h bone marrow macrophages. These data suggest that the local tumor burden stimulates the central macrophages in bone marrow as well as the local macrophages and that stimulated macrophages in bone marrow may then mobilize to the local site of the tumor transplantation.

Animals↗
PubMed1989

Neutral lipid accumulation in macrophages during lipid-induced macrophage growth.

We previously reported that lipids such as cholesterol esters, triglycerides, and some phospholipids that are components of cell membranes or serum lipoproteins induced the growth of mouse peritoneal macrophages in vitro. Here, we report that macrophage growth was directly induced by lipids without any soluble factors and that the continuous presence of lipids was required for their growth during culture. When macrophages were cultured with several phospholipids that stimulated macrophage growth, their triglyceride content was dramatically increased during culture, whereas their contents of phospholipids, cholesterol, and esterified cholesterols were scarcely changed. On the other hand, phosphatidylcholine and sphingomyelin, which did not stimulate macrophage growth, caused less accumulation of triglycerides in the cells. Macrophages in which triglycerides accumulated resembled foam cells, since they contained many particles that stained with oil red O. Macrophages that cultured with cholesteryl linoleate also contained many oil red O-stainable particles. These data suggest that accumulation of lipid droplets is correlated with macrophage growth induced by lipids and that foam cells in pathological states such as those in atherosclerotic or xanthoma lesions might proliferate in situ.

Animals↗
PubMed1989

Epidermal growth factor as a regulatory hormone maintaining a low pH microclimate in the rat small intestine.

This study was designed to determine the effect of epidermal growth factor (EGF) in the lumen on the pH of the intestinal surface in the rat jejunum, which is referred to as "microclimate-pH". In the control experiment, a significant pH gradient was observed between the mucosal surface (approximately pH 6.8) and the bulk phase (approximately pH 7.3). The microclimate-pH was decreased by 0.2-0.6 pH units after addition of higher concentrations of EGF (3-100 nM) to the lumen. The microclimate-pH thus decreased recovers to the control value by replacing EGF with TES buffer, suggesting that the EGF effect is reversible. Considering that the Na+-H+ exchanger exists on the luminal membrane of the intestinal cells, the decrease in the microclimate-pH which was induced by EGF added to the luminal side may be due to the activation of Na+-H+ exchanger.

Animals↗
PubMed1989

Purification and characterization of an antibacterial and antineoplastic protein secretion of a sea hare, Aplysia juliana.

The fetid secretion of a sea hare, Aplysia juliana, was lethal to crabs and also inhibited the growth of bacteria. When the secretion was partitioned between water and n-hexane, only the n-hexane layer, which had a nauseating odor, was lethal to crabs. The water-soluble fraction showed strong antibacterial activity and inhibited the growth of both Gram-positive and Gram-negative bacteria. Antibacterial activity of the water-soluble fraction was destroyed by heating at 50 degrees C for 15 min, but was resistant to treatment with proteolytic enzymes. The active principle, named julianin-S, was purified by gel filtration and ion exchange chromatography. The purified specimen gave a single protein showing a mol. wt of approximately 67,000, as determined by gel filtration. Julianin-S inhibited the growth of Bacillus subtilis by 50% at a concentration of 70 ng protein/ml. It was also cytotoxic to murine tumor cells and inhibited in vitro growth of L1210 cells by 50% at a concentration of 8 ng protein/ml.

Animals↗
PubMed1989

Dopamine inhibition of superoxide anion production by polymorphonuclear leukocytes.

To examine the modulatory effects of catecholamines on the respiratory burst in polymorphonuclear leukocytes (PMNs), dopamine was tested for its capacity to modify the superoxide anion (O2-) production by PMNs under their stimulation with several stimuli. Dopamine inhibited the O2- production by PMNs when PMNs were stimulated with N-formylated chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol myristate acetate, or opsonized zymosan, whereas dopamine did not alter the PMN mobility. The values of percentage inhibition of the O2- production by FMLP-stimulated PMNs were 57% under treatment with 10(-5) mol/L and 83% with 10(-4) mol/L of dopamine. Isoproterenol also inhibited PMN O2- production in response to FMLP. Although a beta-adrenergic blockade, propranolol, diminished the isoproterenol-induced inhibition of the O2- production, it did not affect the inhibitory effect of dopamine. The increase in intracellular cyclic AMP levels in dopamine-treated PMNs was much smaller than the increase in isoproterenol-treated cells. Furthermore, dopamine inhibited the reduced nicotinamide-adenine dinucleotide phosphate-dependent O2- production by subcellular particles. These results indicate that dopamine inhibits PMN O2- production through its effect on PMN reduced nicotinamide-adenine dinucleotide phosphate-oxidase system rather than through its beta-adrenergic action.

Chemotaxis, Leukocyte↗
PubMed1989

Purification of dolabellanin-C an antineoplastic glycoprotein in the body fluid of a sea hare, Dolabella auricularia.

An antineoplastic factor, dolabellanin C, inducing tumor lysis was purified to apparent homogeneity from the body fluid of the sea hare Dollabella auricularia. Purified dolabellanin C is a glyco-protein of 215 K daltons containing 3 subunits of 70 K daltons. The amino acid sequence of the amino terminal region was also determined. This factor was active even at 0.38 ng protein/ml, but did not lyse normal white or red blood cells.

Amino Acid Sequence↗
PubMed1989

Poly(ethylene glycol)-induced shrinkage of Sephadex gel. A model system for quantitative analysis of osmoelastic coupling.

Shrinkage of Sephadex gels caused by addition of a high-molecular weight molecule, poly(ethylene glycol) (PEG) was studied. A quantitative analysis based on the cross-linked network theory by Flory and Tanaka (Tanaka, T. 1978. Phys. Rev. Lett. 40:820-823) showed that the shrinkage is due to a mechanochemical coupling between the elasticity of the network and the osmotic stress arising from preferential exclusion of PEG. These results may provide good evidence for "osmoelastic coupling", the coupling between elasticity of macromolecular structures and osmotic stress, which has been predicted in some biological systems such as phospholipid bilayer membranes (Ito, T., M. Yamazaki, and S. Ohnishi. 1989. Biochemistry. 28:5626-5630; Yamazaki, M., S. Ohnishi, and T. Ito. 1989. Biochemistry. 28:3710-3715) or actin filaments.

Biopolymers↗
PubMed1989

Granulocyte-macrophage colony-stimulating factor and human neutrophils: role of guanine nucleotide regulatory proteins.

The addition of granulocyte-macrophage colony-stimulating factor (GM-CSF) to human neutrophils causes a rapid increase in the basal and fMet-Leu-Phe-stimulated Na+ influx and an increase in intracellular pH. The increase can be seen as early as 5 min after the addition of GM-CSF. Changes produced by GM-CSF are totally inhibited by amiloride and are significantly reduced in pertussis toxin-treated cells. The stimulation of the Na+/H+ exchange mechanism by GM-CSF inhibits further stimulation of this system with either fMet-Leu-Phe or phorbol 12-myristate 13-acetate. In addition, membrane preparations isolated from GM-CSF-treated neutrophils have higher basal and stimulated GTPase activities. The basal and the fMet-Leu-Phe- or platelet-activating factor-stimulated GTPase activities are reduced in pertussis toxin-treated cells. Cells pretreated with GM-CSF accumulate more radioactive phosphate than control cells, and this increase is diminished by pertussis toxin treatment. In addition, GM-CSF causes a rapid increase in the tyrosine phosphorylation levels of five proteins with molecular masses of 118 kDa, 92 kDa, 78 kDa, 54 kDa, and 40 kDa. These results clearly show that GM-CSF, on its own, can initiate several changes and that these changes are mediated in part by the pertussis toxin-sensitive guanine nucleotide regulatory protein.

Amiloride↗
PubMed1989

Phorbol 12-myristate 13-acetate inhibits binding of leukotriene B4 and platelet-activating factor and the responses they induce in neutrophils: site of action.

The addition of the platelet-activating factor (PAF) to neutrophils causes an increase in cytoskeletal actin, a rise in the intracellular concentration of free calcium, release of arachidonic acid, and the synthesis of PAF. The PAF synthesis in human neutrophils stimulated by PAF is greatly potentiated by the human granulocyte-macrophage colony-stimulating factor. Incubation of human neutrophils with the tumor copromoter phorbol 12-myristate 13-acetate (PMA) for 3 min prior to the addition of the stimulus inhibits all these responses produced by PAF. The inhibition is prevented when the cells are incubated with protein kinase C inhibitors such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine for 5 min prior to the addition of PMA. The rise in the intracellular concentration of free calcium in human neutrophils stimulated with leukotriene B4 is also inhibited by PMA, and this inhibition is prevented by protein kinase C inhibitors such as staurosporine. Unlike PMA, the inactive ester 4 alpha-phorbol 12,13-didecanoate has no inhibitory effect on the stimulated rise in the intracellular concentration of free calcium. The binding of either PAF or leukotriene B4 to intact cells is inhibited by PMA. The most important finding of the present studies is that PMA interferes with the binding of PAF and leukotriene B4 to their respective receptors. Whether PMA inhibits the binding of these lipid mediators by activating protein kinase C or by perturbing the membrane directly remains to be elucidated.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Surface hydrophobicity of spores of Bacillus spp.

The surface hydrophobicity of 12 strains of Bacillus spp. was examined in a hexadecane-aqueous partition system. Mature and germinated spores of Bacillus megaterium QM B1551 transferred to the hexadecane layer, while vegetative and sporulating cells did not. Wild-type spores were more hydrophobic than spores of an exosporium-deficient mutant of B. megaterium QM B1551, although the mutant spores were shown to be hydrophobic to some extent by using increased volumes of hexadecane. This result suggests that the exosporium is more hydrophobic than the spore coat and that the surface hydrophobicity of spores depends mainly on components of the exosporium. The surface hydrophobicity of spores of nine other species of Bacillus was also examined, and spores having an exosporium were more hydrophobic than those lacking an exosporium. Thus measurement of the hydrophobicity of spores by the hexadecane partition method may provide a simple and rapid preliminary means of determining the presence or absence of an exosporium.

Alkanes↗
PubMed1989

Binding of hydrochlorothiazide to erythrocytes.

Hydrochlorothiazide (HCT) was administered orally to healthy volunteers and intravenously to rabbits. HCT concentrations in plasma (Cp) and erythrocytes (Ce) were determined by a high-performance liquid chromatographic method. Ce was about 9-fold that of Cp 24 h after the administration to volunteers, and 8-fold 6 h after the administration to rabbits. From the results of the in vitro binding study which was done with rabbit erythrocytes, at least the presence of three kinds of binding site for HCT was expected. The first binding site was characterized by extremely high affinity and very low capacity, and was unaffected by acetazolamide, known as a carbonic anhydrase inhibitor. The second one was characterized by medium affinity and medium capacity, and disappeared under the presence of acetazolamide and may be due to the carbonic anhydrase of erythrocytes. The third one was characterized by low affinity, but its binding capacity was extremely high and apparently unsaturable in the HCT concentration range studied (0.5-100 micrograms/ml = 1.68-336 microM). The binding of HCT to erythrocytes seems to be dominated by the second binding site in the therapeutic range (under 1 microgram/ml of plasma).

Adult↗
PubMed1989

Isolation of a new tremorgenic indoloditerpene, 1'-O-acetylpaxilline, from Emericella striata and distribution of paxilline in Emericella spp.

The distribution of a tremorgenic mycotoxin, paxilline (1), was investigated in 19 species belonging to the genus Emericella. It was found that Emericella desertorum, E. foveolata, and E. striata produced paxilline (1). A new type of indoloditerpene, emindole DA (4), was also found in E. quadrilineata. A new tremorgenic indoloditerpene, 1'-O-acetylpaxilline (3), was isolated from the mycelium of E. striata. Its structure was established on the basis of spectroscopic investigations.

Acetylation↗
PubMed1989

Studies on the monoamine oxidase (MAO) inhibitory potency of TL-1, isolated from a fungus, Talaromyces luteus.

The compound tentatively named TL-1 was isolated from Talaromyces luteus as a metabolite having monoamine oxidase (MAO) inhibitory potency. TL-1 showed mixed-type inhibition of MAO in mouse liver when kynuramine was used as a substrate, and the IC50 was 6.6 microM. The inhibition constants (Ki) for MAO-A and -B in mouse liver were 39.9 and 7.85 microM, respectively. On the other hand, the Ki values for MAO-A and -B in mouse brain were 74.0 and 0.71 microM, respectively. Despite the marked structural resemblance between TL-1 and 7-episclerotiorin, the latter compound had little inhibitory effect on MAO.

Animals↗