Biomedical subjects

K Kon

Publications and source records attributed to K Kon.

At least 73 records · Page 4Linked to original sources

PubMed1990

Binding sites for calcium-activated neutral protease on erythrocyte membranes are not membrane phospholipids.

In order to explore the binding sites for calcium-activated neutral protease (CANP) with high calcium sensitivity (muCANP) on the inner surface of human erythrocyte membranes, we analyzed the binding of muCANP to two kinds of membranes modified by treatment with phospholipase C or Triton X-100. Binding analyses were performed using an immunoblot technique. The amount of muCANP bound to phospholipase C-treated inside-out vesicles was essentially the same as that bound to untreated inside-out vesicles. It was also observed that muCANP binds to Triton X-100-treated membranes, in which most of the integral proteins and glycerophospholipids are removed while the lining proteins remain intact. In both types of modified membrane, the bound muCANP was rapdily converted to an active form by autolysis at physiological free Ca2+ concentrations. These results indicate that the binding sites for muCANP on the inner surface of erythrocyte membranes consist of components other than membrane phospholipids. In addition, it is suggested that one of the binding sites for muCANP is some lining protein.

Animals↗

PubMed1990

Age-related changes in the uptake of calcium channel blockers by brain capillary endothelial cells and synaptosomal fractions.

The effects of aging on the uptake of calcium channel blockers through brain capillaries to brain parenchyma were investigated. Two different piperazine derivatives, flunarizine and 1-[bis(fluorophenyl)-methyl]-4-(2,3,4-trimethoxybenzyl)piperazine (abbreviated as KB-2796), were orally administered to young and aged rats. The concentrations of the blockers in plasma, endothelial cells of the brain capillaries and synaptosomal fractions of the three brain regions were determined by high-performance liquid chromatography. Flunarizine was more incorporated into brain tissues than KB-2796 in both young and aged rats. The uptake efficiency of KB-2796 from the circulation to the brain decreased more remarkably than that of flunarizine in aged rats. The partition coefficients between n-octanol and water indicated that KB-2796 was less hydrophobic than flunarizine. These results suggest that the uptake of the chemicals seems to be influenced by their hydrophobicity and the age of animals given.

Aging↗

PubMed1990

Increased levels of lipid peroxides in aged rat brain as revealed by direct assay of peroxide values.

Lipid peroxide concentrations in brain tissues of young and aged rats were determined by a direct method for measuring peroxide values. Three different brain regions were analyzed for lipid peroxides. The peroxide levels increased in all three regions of aged as compared to those of young rats, while lipid peroxides in plasma appeared to be stable along with age. Lipid peroxides in cerebrum and cerebellum increased 1.6-2.0 times in aged brains compared with young ones, and about 3-fold in the brain stem. Increased levels of lipid peroxides in aged brains seem not merely due to increased pools of precursor polyene fatty acids, but rather due to altered protection systems for lipid peroxidase formation.

Aging↗

PubMed1990

Isolation and characterization of extremely minor gangliosides, GM1b and GD1 alpha, in adult bovine brains as developmentally regulated antigens.

In addition to ganglioside GM1b, an unusual and extremely minor ganglioside, GD1 alpha, was efficiently isolated from bovine brain by combination of Q-Sepharose and Iatrobeads column chromatographies. In the course of purification steps, the presence of the sialidase-labile ganglioside was proved by a highly sensitive TLC/enzyme-immunostaining method. The structure was characterized by gas-liquid chromatography, permethylation study, sialidase degradation, immunostaining with specific antibodies, fast atom bombardment-mass spectrometry, and proton magnetic resonance spectrometry. The content of the ganglioside was very small (0.016%) in the total gangliosides. This finding suggests that a synthetic pathway of asialo GM1----GM1b----GD1 alpha may exist in mammalian brains. A monoclonal antibody NA-6 that was obtained by immunizing mice with purified GM1b reacted specifically with GM1b but showed no cross-reactivity with other structurally related gangliosides such as GM1a, GD1a, and so on. Using the method of TLC/immunostaining with NA-6, GM1b was found to be strongly expressed during embryonic days 14-17 in chick brains. Thus, it is assumed that extremely minor gangliosides like GM1b and GD1 alpha found in adult brains are characterized as embryonic molecules.

Animals↗

PubMed1990

Effects of high alpha-linolenate and linoleate diets on erythrocyte deformability and hematological indices in rats.

Rats were fed either a high alpha-linolenate diet or a high linoleate diet from weaning to 4 mon of age. Soybean oil was used as a control. Phospholipid compositions of erythrocytes from the three dietary groups were not significantly different. However, the difference in the alpha-linolenate (18:3n-3)/linoleate (18:2n-6) ratio of the diets was reflected in the n-3/n-6 ratios of the 20 and 22 carbon highly unsaturated fatty acids except for docosahexaenoic acid (22:6n-3) in the phospholipids. Despite the significant differences in the fatty acid compositions of phospholipids, no measurable differences were detectable in erythrocyte deformability, whole blood viscosity and hematological indices of the three dietary groups. These results indicate that the beneficial effects of the high alpha-linolenate diet, as compared with the high linoleate diet, are exerted without significant changes in these parameters.

Animals↗

PubMed1990

Erythrocyte rheology.

Two main subjects of erythrocyte rheology, deformation and aggregation, are discussed in detail, on the basis of biochemical structure. The close relationship between the life span (or cell aging) and the rheology of individual erythrocytes is also briefly described. A currently important problem is emphasized, that is, the molecular aspect of the dynamic cytoskeletal structure and the mechanism of its regulation. This concerns not only the rheological function and the survival of circulating erythrocytes, but also the pathophysiology of abnormal erythrocytes.

Blood Viscosity↗

PubMed1990

Deformation response of red blood cells in oscillatory shear flow.

The characteristics of red cell deformation were studied, focusing on deformation response of the cells subjected to oscillatory shear stress. Red blood cells were fractionated into subpopulations of different densities, i.e., low-density and high-density cells. The deformation response of the fractionated cells was evaluated with a rheoscope varying their intracellular viscosity and oscillation frequency of the applied shear stress, and determinants of the deformation response were compared with those of whole cell deformation under stationary shear stress. When the fractionated cells were exposed to sinusoidally oscillated shear stress, the cells underwent oscillatory deformation. The degree of deformation of the low-density cells correspond to the magnitude of the applied shear stress up to an oscillation frequency of 2.7 Hz. Meanwhile, such an oscillatory deformation as to correspond to the applied shear stress was observed up to 1.7 Hz for the high-density cells. It was suggested that intracellular viscosity was an important factor to determine the deformation response of red cells to oscillatory shear stress.

Cell Survival↗

PubMed1990

Synthesis and cytostatic activity of the antitumor antibiotic chartreusin derivatives.

In order to overcome the rapid biliary excretion of chartreusin, which diminished its activity when administered iv, a series of 3',4'-O-substituted derivatives of chartreusin were synthesized. Exo-type of 3',4'-O-benzylidene-chartreusin was found active both by ip and iv administration. Therefore, this compound was selected for further modification on its 6-phenol to obtain broader spectra and better pharmacokinetic parameters than the original compound. Several 6-O-acyl-3',4'-O-exo-benzylidene-chartreusins had high antitumor activity against some murine tumors both by iv and po administration.

Aminoglycosides↗

PubMed1989

Structure of phosphonoglycosphingolipid containing pyruvylated galactose in nerve fibers of Aplysia kurodai.

A phosphonoglycosphingolipid, designated as FGL-IIb, was identified in nerve fibers of Aplysia kurodai by two-dimensional thin layer chromatography (Abe, S., Araki, S., and Satake, M. (1986) Biomed. Res. (Tokyo) 7, 47-51). FGL-IIb was isolated from the nervous system of A. kurodai by Iatrobeads column chromatography using three solvent systems. Pyruvic acid was identified by thin layer chromatography as its 2,4-dinitrophenylhydrazone and established by permethylation studies to be attached as a ketal to O-3 and O-4 of the terminal galactose of the oligosaccharide chain in FGL-IIb. By sugar analysis, permethylation studies, fast atom bombardment-mass spectrometry, and proton magnetic resonance spectrometry, the structure of FGL-IIb was concluded to be [3,4-O-(1-carboxyethylidene)]Gal beta 1----3GalNAc alpha 1----3(Fuc alpha 1----2) (2-aminoethylphosphonyl----6)Gal beta 1----4Glc beta 1----1ceramide. Its major aliphatic components were palmitic acid, octadeca-4-sphingenine and anteisononadeca-4-sphingenine. This is the first report of the occurrence of pyruvylated galactose as a constituent of animal sphingolipid.

Acidic Glycosphingolipids↗

PubMed1989

Rheological properties of erythrocytes in recombinant human erythropoietin-administered normal rat.

Recombinant human erythropoietin [rhEPO (180 iu/micrograms); 1 or 10 micrograms polypeptide equivalent/kg] was intravenously administered daily to 6-week-old normal rats for 1 week. Rheologically, (1) blood viscosity at shear rate of 40-380 s-1 increased in a manner entirely dependent upon the haematocrit, (2) no change in erythrocyte deformability was detected by high shear rheoscopy, and (3) the velocity of rouleau formation in autologous plasma (at 7.5 s-1) decreased. Haematologically, rhEPO administration induced considerable polycythaemia with reticulocytosis in a dose-dependent manner, accompanying increased cell volume and decreased intracellular haemoglobin concentration, thus the density distribution of erythrocytes shifted towards low specific gravity. Plasma viscosity and plasma protein composition were unaffected by rhEPO-administration. In erythrocyte metabolism, no drastic alteration in the level of 2.3-DPG or ATP was detected.

Animals↗

PubMed1988

Erythrocyte aggregation as a determinant of blood flow: effect of pH, temperature and osmotic pressure.

The effect of pH, temperature and osmotic pressure on velocity of erythrocyte aggregation was quantitatively examined with a rheoscope combined with a video-camera, an image analyzer and a computer, (a) in an artificial medium containing fibrinogen and albumin and (b) in diluted autologous plasma. (1) With increasing pH of the medium, the velocity of erythrocyte aggregation increased. (2) The velocity of erythrocyte aggregation in the artificial medium increased as the temperature rose. However, in 70% autologous plasma the velocity was minimum at 15-18 degrees C, increasing both above and below this temperature (above 30 degrees C, the velocity saturated). (3) The velocity of erythrocyte aggregation decreased in hypotonic medium, while it increased in hypertonic medium (at osmotic pressures higher than 400 mOsm, the velocity decreased). The mechanism of erythrocyte aggregation is discussed with special reference to the morphological changes produced by pH, temperature and osmotic pressure, and the implications of the phenomena for oxygen transport to tissues in (patho)physiological situations are considered.

Adult↗

PubMed1988

Appearance of a novel type of ganglioside (GD1 alpha) in a differentiation-resistant clone of mouse myeloid leukemia cells, M1-R1.

Glycolipid compositions of three mouse myeloid leukemia cell clones, two that are sensitive to differentiation inducers (M1-T22 and M1-S1) and one that is differentiation-resistant (M1-R1), have been compared. The T22 and S1 clones contained glucosylceramide (GlcCer), lactosylceramide (LacCer) and gangliotriaosylceramide (Gg3Cer) as the major neutral glycolipids. The differentiation resistant clone, R1, was characterized by the appearance of globotriaosylceramide (Gb3Cer) and a decrease of Gg3Cer. There was a distinct difference in the ganglioside profile between the differentiation-inducible and -resistant clones: T22 and S1 cells contained no detectable amounts of ganglioside, whereas six different gangliosides were detected in the R1 clone. These gangliosides were isolated and identified as GM3, GM2, GM1a, GD1a, GM1b, and a unique disialoganglioside, GD1 alpha, having the following structure: (formula; see text) Based on these comparative studies, the relationship between the glycolipid composition and the differentiation potential of leukemia cells is discussed.

Animals↗

PubMed1988

Oscillatory deformation of human erythrocytes in sinusoidally modulated shear flow.

The red cell deformation under oscillatory shear stress was studied. Shear stress was sinusoidally modulated between 8 and 32 dyn/cm2, thus, the extent of cellular deformation altered sinusoidally. At a low modulation frequency (less than 1.8 Hz), intact red cells perfectly responded to the shear stress applied on cells, and they could deform as much as the deformation in stationary shear flow. Above 2 Hz, the cellular deformation could not follow changes in shear stress along up-phase in the shear stress cycle. As decreasing the intracellular hemoglobin concentration, the cellular response to oscillatory shear stress became better. Treatment of cells with low concentrations of diamide impaired the response of intact cells to oscillatory shear stress, but unaffected the response of partially hemolyzed cells. These data suggest that the cellular response to oscillatory shear stress is determined by the cytoskeletal structure and the intracellular viscosity.

Blood Viscosity↗

PubMed1988

Distribution of erythrocyte in a model vessel exposed to inhomogeneous magnetic fields.

In order to investigate magnetic field effects on blood flow, changes in the flow of erythrocytes in a model branched vessel were observed in an inhomogeneous magnetic field. The magnetic field was applied perpendicular to the straight vessel before branching. When the suspension containing paramagnetic erythrocytes with high spin methemoglobin or deoxygenated hemoglobin flowed in the model vessel, the erythrocytes were attracted towards the stronger magnetic field (i.e. to the side branch) and an excess flow of erythrocytes to the side branch was detected. This excess flow of erythrocytes to the side branch was the highest at a hematocrit of about 5% for the suspension containing erythrocytes with high spin methemoglobin. In the case of mixed suspensions containing erythrocytes with high spin methemoglobin and oxygenated erythrocytes, the excess flow of erythrocytes to the side branch reached its maximum at the "partial hematocrit" for the paramagnetic erythrocyte of around 5% and remained nearly constant with a further increase of the "partial hematocrit." The effect of magnetic field decreased as the flow velocity increased. These results are explained with the paramagnetism of erythrocytes and with the assumption of a hydrodynamic interaction among erythrocytes which are pulled in the direction of the magnetic field. It is suggested that a strong inhomogeneous magnetic field is not totally negligible to the blood circulation.

Blood Circulation↗

PubMed1987

High-performance liquid chromatography of underivatized gangliosides.

High-performance liquid chromatographic systems have been developed which use DEAE-Iatrobeads and Aquasil SS or amino-silica gel to attain fine separation of gangliosides in a short time. Two UV-transparent solvent systems containing potassium chloride or tetramethylammonium chloride were devised and optimized, especially for the separation of polysialogangliosides.

Animals↗

PubMed1987

New solvent system for high-performance thin-layer chromatography and high-performance liquid chromatography of gangliosides.

New solvent systems consisting of acetonitrile, isopropanol and aqueous 50 mM potassium chloride or 2.5 M ammonium hydroxide were developed for the separation of gangliosides by high-performance thin-layer chromatography. These solvent systems seem to be superior for the resolution of polysialogangliosides such as tetra-, penta- and hexasialo species, as compared to chloroform-methanol-aqueous salt systems. The order of mobility of gangliosides in the ammoniacal solvent system is GD3 greater than GD1a greater than GM1 greater than GT1b greater than GD1b as compared with GM1 greater than GD3, GD1a greater than GD1b greater than GT1b in the neutral septem. A combination of these two solvent systems provides excellent two-dimensional separations of complex ganglioside mixtures. The neutral solvent system, acetonitrile-isopropanol-aqueous 50 mM potassium chloride, can be used for the separation of underivatized gangliosides by high-performance liquid chromatography on an Aquasil SS silica gel column. Ganglioside elution can be monitored at 208 nm because of the good UV-transparency of the effluent.

Chromatography, High Pressure Liquid↗

PubMed1987

Characterization of sulfated glucuronic acid containing glycolipids reacting with IgM M-proteins in patients with neuropathy.

In some patients with neuropathy and plasma cell dyscrasia, the serum IgM M-proteins are known to bind to the myelin associated glycoprotein and to peripheral nerve glycolipids. We have isolated two acidic glycolipids which bind to the M-protein from human cauda equina by DEAE-Sephadex, Iatrobeads, and high performance liquid column chromatographies. The major acidic glycolipid migrated between GM1 and GD1a and the minor acidic glycolipid migrated between GD1a and GD1b. Their structures were elucidated by sugar analysis, enzymatic digestion, mild acid hydrolysis, permethylation, fast atom bombardment mass spectrometry, and NMR studies. Their core structure was confirmed to be paragloboside by high performance thin-layer chromatography-immunostaining using anti-paragloboside monoclonal antibody. Both acidic glycolipids lacked sialic acid but contained sulfated glucuronic acid as their acidic moiety. The sulfate group in the glucuronic acid was established by periodate oxidation and permethylation studies to be attached to the 3 position. The structures of the two acidic glycolipids are therefore consistent with the following: IV3GlcUA(3-sulfate)nLcOse4Cer and VI3GlcUA(3-sulfate)nLcOse6Cer. Additionally, the free carboxyl group on the glucuronic acid residue was shown to be necessary to bind the IgM M-proteins from neuropathy patients.

Antibodies, Monoclonal↗

PubMed1987

A kinetic study on functional impairment of nitric oxide-exposed rat erythrocytes.

In acute in vivo exposure of rats to 25 to 250 ppm nitric oxide (NO) by use of a small exposure chamber for a single rat, the kinetic parameters of nitrosylhemoglobin (Hb-NO) and methemoglobin (MetHb) formation were estimated (with the aid of computer simulation) on the basis of experimental data. The biochemical and rheological injuries of erythrocytes were also examined. The time course of Hb-NO and MetHb formation in blood was compared with that simulated by a simplified kinetic model. The rate of MetHb formation from Hb-NO was much faster than MetHb reduction to ferrous form and dissociation of Hb-NO; thus, MetHb content was always greater than Hb-NO content. The activity of MetHb reduction decreased on exposure to a high concentration of NO, but the activity was recovered when rats were placed in clean air. Rheologically, the blood viscosity was scarcely altered, but a few undeformed cells were detected at high shear stress. Morphologically, echinocytic transformation was observed to some extent. Biochemically, the crosslinking of membrane proteins and the alteration of acyl chain composition of membrane phospholipids were not detected in the in vivo exposure, though the in vitro exposure of rat erythrocytes to high concentrations of NO revealed remarkable oxidative crosslinking among membrane proteins and hemoglobin. In conclusion, both for persistent methemoglobinemia and for membrane damage, the maintenance of reductive activity in erythrocytes is the most important determinant factor for the protection of NO-induced oxidative injury.

Animals↗