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Biomedical subjects

T Araiso

Publications and source records attributed to T Araiso.

At least 37 records · Page 2Linked to original sources
PubMed1989

Oxygen diffusion through mitochondrial membranes.

The effect of the mitochondrial membrane on the oxygen supply to the interior of mitochondria was analyzed with a cylinder model of diffusion. This estimation is based on the assumption that cytochrome a,a3 is distributed only on the inner surface of the mitochondrial inner membrane. The diffusion coefficient in the mitochondrial membrane was approximated from the fluorescently-determined viscosity of rat mitochondrial membrane. A pico-second time-resolved fluorometer at 37 degrees C gave values of 43.8 cp for intact mitochondria and 51.4 cp after phospholipase A2 treatment. Using the mean oxygen consumption rate of 10 ml O2/100 g tissue/sec in beating heart, oxygen gradients of 3.9 and 4.6 nmol was predicted across the intact and phospholipase-A2 treated mitochondrial membranes, respectively. The increased oxygen consumption during systole will yield oxygen gradients of 11.6 and 13.7 nmol. These gradients were much larger than the values estimated in a hypothetical case using the diffusion coefficient for the mitochondrial membrane of 1.5 x 10(-5) cm2/sec. The predicted oxygen gradient suggests a non-uniform distribution of oxygen in the myocardial cell and may be of importance in understanding the relationship between oxygen supply and myocardial function in hypoxia. Phospholipase A2, which is known to be activated in ischemia, destroys the microstructure of myocardial cells, seems deleterious to oxygen transport to cytochrome a,a3.

Animals↗
PubMed1989

Membrane viscosity of lymphocytes and influence of phytohemagglutinin.

The membrane viscosity of peripheral blood lymphocytes (PBLs) of equine, bovine and canine was measured by the use of time-resolved fluorescence depolarization technique with 1, 6-diphenyl-1,3,5-hexatriene (DPH). The viscosity values were 0.55, 0.59 and 0.50 poise for equine, bovine and canine PBLs, respectively. These values were compared with steady-state anisotropies and order parameters measured from electron spin resonance (ESR) of 5-doxyl stearic acid. Both values were increased with increase of viscosity. The fluid property of the membranes stimulated with phytohemagglutinin-P (PHA) was measured with steady-state fluorescence anisotropy and ESR. Little change of membrane fluidity was recognized with both methods during the stimulation with PHA. It appears that PHA activation process for these lymphocytes does not included large increase of the membrane fluidity which significantly accelerate the diffusion velocity of receptors in the plasma membrane.

Animals↗
PubMed1988

Diffusion pathway of oxygen in ox lung.

The diffusion coefficients of cell membranes of pneumocytes plus endothelial cells, cytosol plus blood plasma, erythrocyte membranes, and hemoglobin solution in erythrocytes were estimated from the fluorometrically measured membrane viscosity. The time course of oxygen partial pressure distribution was numerically calculated in a model for the pathway of oxygen in the lung. The high viscosity of the phospholipid bilayers seems to cause a reduction in the rate of oxygenation of the hemoglobin solution.

Animals↗
PubMed1988

Effects of alpha-tocopherol-nicotinate administration on the microdynamics of phospholipids of erythrocyte membranes in human subjects.

The effects of alpha-tocopherol-nicotinate on the microdynamic parameters, membrane viscosity, and wobbling angle of phospholipid molecules of healthy human erythrocyte membranes were studied with a nanosecond time-resolved fluorometer. The incorporation of alpha-tocopherol was achieved by oral administration of alpha-tocopherol-nicotinate for one month with dosage of 400 mg/day. The increase in alpha-tocopherol concentration in erythrocytes was confirmed in two subjects. The membrane viscosity in seven healthy subjects decreased significantly from 1.015 +/- 0.137 to 0.888 +/- 0.133 mPa.s. But no changes in the wobbling angle of phospholipid molecules were observed.

Adult↗
PubMed1988

A new analysis method for the membrane viscosity from steady-state fluorescence depolarization.

The absolute value of the viscosity in membrane lipid bilayers, which is different from the microviscosity advocated by Shinitzky, could be calculated from steady-state fluorescence depolarization of a hydrocarbon fluorophore, 1,6-diphenyl-1,3,5-hexatriene (DPH). This method was based on the theory of time-resolved fluorescence anisotropy and empirical relationships between fluorescence life time and the anisotropy parameters such as half cone angle in wobbling motion and wobbling diffusion rate of the fluorescent probe. Obtained viscosity values of various membranes from this method were consistent with those from time resolved method within experimental error.

Animals↗
PubMed1988

Fluidity and osmotic sensitivity changes of phospholipase A2-treated liposomes.

Membrane fluidity and osmotic sensitivity were examined in DPPC liposomes treated with phospholipase A2 (PL.A2) in the presence of Ca2+ or Mg2+. The amount of liposome phospholipid hydrolyzed differed with the two ions. Embedded DPH, a rod-like fluorescent probe, was employed in the determination of membrane fluidity. Membrane fluidity decreased according to the degree of phospholipid hydrolization in liposomes by PL.A2. The reciprocal value of absorption at 450 nm was measured as the index of osmotic sensitivity of liposomes. Intact sonicated liposomes showed osmotic insensitivity. PL.A2-treated liposomes in which about 40% of total phospholipid was hydrolyzed showed osmotic sensitivity. No change in the membrane fluidity was obtained when PL.A2-treated liposomes were exposed to hypertonic or hypotonic solution. These results suggested that the motion of the acyl-chain of phospholipids and free fatty acids was resisted in PL.A2-treated liposomes. The resistance may be due to a phase separation between phospholipids and free fatty acids. The pore for water permeation might be induced in the border between phase-separated domains in PL.A2-treated liposomes.

Calcium↗
PubMed1987

Dynamic structure of phospholipid bilayers on the path for oxygen diffusion in the ox lung.

The dynamic properties of the phospholipid bilayer of cell membranes were studied with a nanosecond fluorometer to obtain information on the microstructure of the path for oxygen diffusion in the ox lung. The viscosity in membranes of pneumocytes, endothelial cells from pulmonary artery, and erythrocytes was 47, 54 and 162 mPa . sec respectively. The wobbling angle representing the oscillation of phospholipid molecules was 47, 44 and 38 degrees, respectively.

Animals↗
PubMed1987

Dynamics of membrane structure of frog erythrocyte ghosts measured with a nanosecond fluorometer.

The dynamics of membrane microstructure was studied as molecular motions of phospholipids for bullfrog erythrocyte ghosts by the DPH fluorescence depolarization technique with a nanosecond fluorometer. The bullfrog erythrocyte ghosts were obtained by hypotonic lysis and collagenase treatment. The constituents of membrane proteins were confirmed by the disk gel electrophoresis. The viscosity of erythrocyte membrane ghosts was estimated to be 3.3 +/- 1.0 at 10 degrees C, and 2.1 +/- 0.1 at 20 degrees C and 1.3 +/- 0.2 at 30 degrees C in the unit of poise and the wobbling angle of lipid molecule was 35 +/- 1, 41 +/- 1 and 43 +/- 1 degree at the respective temperatures on an average and +/- S.D. The viscosity is lower than that of human erythrocytes. The relatively low viscous phospholipid bilayer may be one of the factors for the deformability of bullfrog erythrocytes.

Animals↗
PubMed1987

Intensification of rheological destruction of rat fibrosarcoma KMT 17 cells by elimination of divalent cations.

In an effort to find a method to intensify the rheological destruction of tumor cells, rat fibrosarcoma KMT 17 cells in ascitic form were exposed to rheological stresses in test solutions; modified Eagle medium with EDTA, and phosphate buffer solution without divalent cations or with verapamil. KMT 17 cells were exposed to a uniform shear stress produced by the rotation of a rotating cone plate viscometer for 1 to 2 hours and to the strong deformation by the passage through Nuclepores of 10, 8 and 5 micrometer. KMT 17 cells suspended in the test solutions were more effectively destroyed by the stresses than those suspended in normal solutions containing divalent cations without any other calcium-suppressing agents. These results suggest that the elimination of divalent cations and/or the block of calcium ion channels of cell membranes intensify the rheological destruction of tumor cells migrating in the circulatory system.

Animals↗
PubMed1987

[Peroxidase].

Explore the source record for details and available documents.

Peroxidases↗
PubMed1986

Oxygen diffusion coefficient of cell membranes.

The microviscosity was measured in erythrocyte membranes of different animal species and in lung cells and myocytes of bull frogs by means of the nanosecond fluorescence depolarization technique with a rod-like fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH). The diffusion coefficient of oxygen molecules (DO2) was estimated from the microviscosity and an equation for the relation between viscosity and diffusion coefficient. The DO2 value of erythrocyte ghosts was remarkably different among species; 0.84 in sheep, 1.29 in human, 1.49 in rat and 1.92 X 10(-7) cm2/sec in rabbit, while the wobbling diameter Wd was 10.7, 11.5, 12.1 and 10.7A in respective species. The DO2 value in frogs was different among organs; 1.07 in erythrocyte ghosts, 2.18 in lung cells, 2.64 X 10(-7) cm2/sec in myocytes. The Wd value was 12.2, 12.6 and 13.4A in respective organs at 30 C. A comparison between sizes of moving area of phospholipid molecules in membrane and in ideal fluid state suggested that the actual DO2 values in cell membranes may probably be ten times larger than the present values.

Animals↗
PubMed1986

Viscosity and order in erythrocyte membranes studied with nanosecond fluorometry.

The viscosity and the order in the interior of human erythrocyte membranes were investigated by the fluorescence depolarization technique in the nanosecond region with 1,6-diphenyl-1,3,5-hexatriene (DPH). After pulsed excitation with a polarized light, the fluorescence anisotropy ratio of DPH in membranes rapidly decreased and gave a final value (r infinity). The rate of initial decrease and the value of r infinity related to the viscosity in the interior of the membranes and a wobbling angle of DPH which reflects a size of range for the phospholipid motion relating to the order of membrane structure. For normal human erythrocyte membranes the viscosity and the wobbling angle were obtained to be 0.82 poise and 42 degrees, at 37 degrees C. Similar values were obtained for spectrin-free membranes. Hardened membranes by the cross-linking of the cytoskeletal proteins with glutaraldehyde showed a small wobbling angle of 37 degrees, but the viscosity of them was unchanged.

Blood Viscosity↗
PubMed1985

Effects of temperature and transfer from seawater to freshwater on blood microrheology in Pacific salmon.

Blood of Pacific salmon was studied with particular interest in red blood cell (RBC) deformability in relation to migration. Blood samples were taken via cardiac puncture or chronic cannula placed in the dorsal aorta and heparinized. As an index of RBC deformability the mean passage time of single RBCs through micropores of 8 micron in diameter and 10 micron in length was determined under a pressure difference of 10 cmH2O. Despite about 100 mOsmol/l difference in plasma osmolality, there was no marked difference in RBC passage time between fish in seawater and those well acclimatized to freshwater. However, it seemed probable that a transient decrease in RBC passage time, i.e., an increase in RBC deformability, occurred immediately following transfer from seawater to freshwater. Plasma osmolality decreased to about 300 mOsmol/l within 1 hr after the transfer and showed no fluctuations thereafter. The temperature dependence of RBC deformability was much smaller in comparison with those previously observed in yellowtail and carp; salmon RBCs were still highly deformable even at 5 degrees C, a possible temperature of cold river water.

Animals↗
PubMed1984

Hypoxic reduction in blood flow velocity in pulmonary arterioles and capillaries.

A small ring chamber (I.D. = 6 mm) was placed on the exposed lung of anaesthetized bullfrogs. A localized hypoxia was induced in the ring chamber by introducing nitrogen in it. Blood flow velocity in pulmonary microvessels was measured by means of a laser Doppler microscope. The mean blood flow velocity was 1.98 +/- 0.45 and 1.52 +/- 0.10 mm/sec during the control condition in arterioles and capillaries, respectively. It was then reduced by the localized hypoxia to 1.63 +/- 0.32 and 1.33 +/- 0.08 mm/sec in arterioles and capillaries, respectively. The reduction, when expressed in the percentage ratio to the control flow velocity in each blood vessel group, was significantly larger in arterioles than in capillaries. A phase delay in the pulsation of the flow velocity contour was detected only in arterioles. These differences between pulmonary arterioles and capillaries in response to the localized hypoxia may be attributed to the dense interconnection of capillary network extending beyond the localized hypoxic area to the normoxic area.

Animals↗
PubMed1984

A nanosecond fluorometer for studies of rheological aspects of biomembranes.

A nanosecond fluorometer was designed to study the microdynamics of biomembranes. The overall system consists of a nitrogen laser for excitation of fluorophores, optics consisting of polarizers, monochromators, a single photon counting system having a multichannel time to amplitude converter controlled with a microcomputer and a data processing system. The laser pulse for excitation was polarized with a polarizer. Anisotropically polarized DPH fluorescence could be measured with a time resolution smaller than 5 nsec. The parallel decay curve of DPH fluorescence was higher than the perpendicular decay curve in erythrocyte membrane over the whole decay time. No anisotropism was recorded in a tetrahydrofuran solution. These results suggested that the motion of DPH molecules in erythrocyte membranes was restrained and that the present system provided information on rheological aspects of molecular dynamic structure of biomembranes.

Diphenylhexatriene↗
PubMed1982

A kinetic study of the binding of carbon monoxide to ferrous chloroperoxidase.

The binding of carbon monoxide to ferrous chloroperoxidase in the pH range 4-6.5 is influenced by a titratable group on the enzyme having a pKA of 5.5 +/- 0.2 at 20 degrees C. The basic form of the enzyme reacts much faster with carbon monoxide than does the protonated form of the enzyme. The delta H degrees for the ionization of the functional group in the enzyme involved in carbon monoxide binding is about 8 kcal mol-1, and the delta S degrees is approximately 1 cal mol-1 K-1. These pKA and delta H degrees values suggest that this functional group is an imidazole ring associated with a histidine residue situated at the active site of the enzyme. The rates of the reaction for the formation and dissociation of the complex suggest that this histidine residue is not directly liganded to the iron atom of the heme prosthetic group. The relatively good agreement between the various kinetic approaches with several methods of experimentation, data collection, and data analysis lends strength to a proposed model in which the histidine occupies a distal site close to the sixth axial ligand position of the heme iron atom.

Carbon Monoxide↗