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T Araiso

Publications and source records attributed to T Araiso.

At least 19 recordsLinked to original sources
PubMed1998

Change of motion and localization of cholesterol molecule during L(alpha)-H(II) transition.

Formation of the inverted hexagonal (H(II)) phase from the lamellar (L(alpha)) phase of bovine brain-extracted phosphatidylcholine (BBPC) and phosphatidylethanolamine (BBPE) was investigated using 31P-NMR with or without cholesterol. When the ratio of BBPC to BBPE was 1:1, the H(II) formation was observed in the presence of 33 mol% cholesterol (i.e., BBPC:BBPE:cholesterol = 1:1:1) at 47 degrees C. The fraction of the H(II) phase in the BBPC/BBPE/cholesterol system could be controlled by the addition of dioleoylglycerol. The change of molecular motion of cholesterol affected by the H(II) formation was measured at various ratios of the L(alpha) to H(II) phase with the time-resolved fluorescence depolarization method, using dehydroergosterol as a fluorescent probe. It is observed that the motion of cholesterol became vigorous in the mixture state of the L(alpha) and the H(II) phases compared to that in the L(alpha) or the H(II) phase only. These facts show that cholesterol has the strong ability to induce the H(II) phase, probably by special molecular motion, which includes change of its location from the headgroup area to the acyl-chain area.

Animals↗
PubMed1997

Restricted motion of photoexcited bacteriorhodopsin in purple membrane containing ethanol.

The molecular motion of retinal within the purple membrane was investigated by flash-induced absorption anisotropies with or without ethanol. In the absence of ethanol, the measured anisotropies at several wavelengths exhibited almost the same slow decay. This slow decay was attributed to only the rotation of purple membrane sheet itself in the aqueous suspension. In the presence of ethanol, however, we observed the wavelength-dependent anisotropies. The fluidity of the purple membrane, investigated with a fluorescence anisotropy method, was increased by the addition of ethanol. These facts indicated that the characteristic motion of bacteriorhodopsin is induced in perturbed purple membrane with ethanol. The data analysis was performed, taking account of the overlapping of absorption from ground-state bacteriorhodopsin and photointermediates. The results showed that the rotational motion of photointermediates within the membrane was more restricted than that of nonexcited bacteriorhodopsin. The addition of ethanol facilitated the rotation of nonexcited protein, whereas it did not significantly affect the motion of photointermediates. The restricted motion of photointermediates is probably caused by a conformational change in them, which may hinder the rotation of monomer protein and/or induce the interaction between photointermediate and neighboring proteins.

Bacteriorhodopsins↗
PubMed1996

Biosynthesis of B2-integrin, intracellular calcium signalling and functional responses of normal and CD18-deficient bovine neutrophils.

1Biosynthesis of CD11/CD18 in bovine leucocytes, intracellular Ca2+ ([Ca2+]i) signalling, chemiluminescent responses and membrane fluidity of neutrophils and the effects of D-mannose on neutrophils from control heifers and a heifer with bovine leucocyte adhesion deficiency (BLAD) were measured. The synthesis of CD11/CD18 complex was clearly detected in leucocytes from a normal heifer, but not in a BLAD-affected heifer. The transient phase of increased [Ca2+]i was clearly detected in neutrophils from a heifer with BLAD stimulated with opsonised zymosan, aggregated bovine immunoglobulin G or concanavalin A, whereas the sustained phase was deficient or significantly decreased compared with control heifers. [Ca2+]i signalling of neutrophils from control heifers and a heifer with BLAD stimulated with phorbol myristate acetate via an 11b/CD18-independent pathway showed no transient phase, and the subsequent increase in [Ca2+]i was almost identical in neutrophils from affected and control heifers. [Ca2+]i concentration and chemiluminescent responses of neutrophils from a control heifer were clearly decreased by treatment with anti-CD18 and anti-IgG antibodies. No differences in membrane fluidity were detected between neutrophils derived from control and CD18-deficient cattle. D-mannose binds mainly to Fc rather than CD18 receptors, and decreased Agg-IgG induced [Ca2+]i and the chemiluminescent response of neutrophils. The [Ca2+]i responses and Agg-IgG induced chemiluminescent responses of neutrophils from control heifers and a BLAD-affected heifer were inhibited by D-mannose. The characteristic changes of [Ca2+]i signalling and functional responses of B2-integrin-deficient neutrophils were demonstrated.

Animals↗
PubMed1996

Culture temperature affects the molecular motion of bacteriorhodopsin within the purple membrane.

We measured the absorption anisotropies of bacteriorhodopsin (bR) within a purple membrane suspension after photo-excitation in the millisecond time range. The purple membranes used were isolated from Halobacterium salinarium grown at three different culture temperatures, 37.0, 43.0 and 47.5 degrees C. For the membranes from the 37.0 degrees C culture, the observed anisotropies at wavelengths of 410, 570 and 680 nm showed almost the same slow decay. The slow decaying of the anisotropies originated from the rotation of the membrane itself. Using the membranes from the 43.0 and 47.5 degrees C culture, however, we found that the anisotropy change varied at each wavelength measured. In these cases, it is shown from detailed data analysis that 1) the rotational motion of photo-intermediates within the membrane is more restricted than that of non-excited bR and 2) the distorted arrangements of the proteins within the membrane remain, even after photo-intermediates return to ground-state bR. This restricted motion is probably caused by the conformational changes in photo-intermediates, which prevent the rotation of the monomer protein and/or lead photo-intermediates to bind with neighboring proteins.

Bacteriorhodopsins↗
PubMed1995

The molecular motion of bacteriorhodopsin mutant D96N in the purple membrane.

We measured the flash-induced absorption anisotropies of mutant bacteriorhodopsin (bR), D96N, in the purple membrane suspension. The measured anisotropy decay at 410 nm differed from that at 570 nm. These wavelength-dependent anisotropies show that the motion of absorption dipole of non-excited bR is faster than that of M-intermediate. The motion of non-excited bR is considered as the rotational motion of whole protein in the purple membrane. This fact suggests that the photo-excitation induces the conformational change of the protein and/or the inter-protein interaction within the membrane, which prevents the motion of M-intermediate.

Anisotropy↗
PubMed1995

Fluidity of glycerol skeletal region in phospholipid bilayers: a time-resolved fluorescence depolarization study.

The fluidity of glycerol skeletal region in phospholipid bilayer was investigated by the time-resolved fluorescence depolarization technique with L-alpha-dihexadecanoyl-sn-glycero-3-phospho-[N-(4-nitrobenzo-2-oxa-1,3- diazole)]ethanolamine (NBD-PE) as a fluorescent probe. In this probe, the fluorescent moiety, 4-nitrobenz-2-oxa-1,3-diazole (NBD), is attached to a nitrogen atom at the polar head group of phosphatidylethanolamine molecule. When this probe is embedded in a lipid bilayer, the NBD moiety locates near the glycerol skeletal region. The time courses of fluorescence anisotropy of NBD-PE in dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) bilayers were analyzed using a wobbling-in-cone model, in which the molecular motion is characterized by a half cone angle (theta c) and a wobbling diffusion rate (Dw). Values of Dw of NBD moiety in phospholipid bilayers were found to be on the order of 10(7) s-1 at the physiological temperatures, which is almost the same value as that of the hydrocarbon chain in lipid bilayers. This fact indicates that the fluidity in the glycerol skeletal region is similar to that in the hydrocarbon layer.

Anisotropy↗
PubMed1995

Effects of Ca2+ and Mg2+ on dynamics of the polar head group of phosphatidylserine bilayers.

The effects of Ca2+ and Mg2+ on the molecular motion of the polar head group in phosphatidylserine (PS) bilayers were measured by the time-resolved fluorescence depolarization method probed by 1,2-dihexadecanoyl-sn-glycero-3-phospho-[N-(4-nitrobenzo- 2-oxa-1,3-diazole)]ethanolamine [formula: see text] (NBD-PE). By this method, the rate and width of the molecular motion at the fluorescent moieties in the probe molecules could be evaluated as the wobbling diffusion rate (Dw, s-1) and the half cone angle of the wobbling cone (theta c, degree). The values of Dw and theta c measured for NBD-PE embedded in bovine brain phosphatidylserine bilayers were 3.7 x 10(7) s-1 and 46 degrees in the absence of divalent cations at 25 degrees C. When 3 mM of Ca2+ was added, both Dw and theta c distinctly dropped to 1.7 x 10(7) s-1 and 38 degrees, respectively. By the addition of 3 mM of Mg2+, however, only Dw decreased to 2.7 x 10(7) s-1 and theta c remained unchanged. These results show that both Ca2+ and Mg2+ decrease the rate of motion at the head part in PS molecules, but only Ca2+ narrows the distance between the neighboring head groups. Since Mg2+ does not promote vesicle fusion, it appears that the deformation at the head group region in the bilayer structure induced by Ca2+ is an important step in the membrane fusion process.

Animals↗
PubMed1993

Adrenoceptor coupling mechanisms which regulate salivary secretion during aging.

In parotid slices and membranes from Wistar rats 2, 12 and 24 months old, changes are noted in adrenoceptor-stimulated K+ fluxes, formation of [3H]inositol phosphates ([3H]IPs), cAMP production, and membrane environment. Norepinephrine-stimulated K+ efflux and formation of [3H]IPs in the slices proceed through an alpha 1-adrenergic mechanism and are reduced 20% and 40% during aging, respectively. In beta-adrenoceptor stimulation with isoproterenol, no age changes were observed in K+ influx and cAMP production. The cholesterol content in membranes was reduced with age; concomitantly, the membrane viscosity decreased with age. These results indicate that the alterations in the membrane environment may provide age-dependent modulation of alpha 1-adrenoceptor coupling mechanisms and their functions.

Aging↗
PubMed1991

Dynamics of the bilayer-water interface of phospholipid vesicles and the effect of cholesterol: a picosecond fluorescence anisotropy study.

The motion of the head group of phospholipid molecules in the bilayer structure was investigated by a picosecond fluorescence anisotropy technique using a newly synthesized fluorescent phospholipid, dipalmitoyl-L-alpha-phosphatidyl-(3-p-methoxyphenyl)umbelliferone (DPPU). In this phospholipid, a coumarin derivative is attached covalently to the phosphate moiety. The motion of the acyl chain of the phospholipid was also investigated by the same method using 1-palmitoyl-2-(3-diphenylhexatrienyl)-propanoyl-L-alpha-phospha tid ylcholine (DPHpPC). From fluorescence anisotropy decay the wobbling diffusion rate (Dw) of DPPU and DPHpPC in DPPC vesicles at 45 degrees C was calculated to be 2.7 x 10(9) s-1 and 5.1 x 10(7) s-1 using the wobbling-in-cone-model. The range of the motion was calculated as the cone angle (theta c), which is half of the angle of the cone in which the fluorophore can diffuse. The cone angle of the coumarin skeleton of DPPU in DPPC vesicles at 45 degrees C was 64 degrees, which was larger than that of the DPH skeleton of DPHpPC, 40 degrees. These results indicate that the motion of the head group is much faster and wider than that of the acyl chain. When cholesterol was added to the DPPC vesicles, the range of motion of the acyl chain decreased, but that of the head group increased. These facts show that cholesterol restricts the motion of the acyl chain but enhances that of the head group in the phospholipid bilayer.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Dynamic microstructure of mitochondrial membranes from rabbit heart subjected to reperfusion after ischemia.

The effects of ischemia combined with reperfusion on the dynamic microstructure of mitochondrial membranes were studied in the hearts of anesthetized open-chest rabbits by means of time-resolved fluorometry. The fluorescence of diphenyl hexatriene (DPH) and its anisotropic decay were used to calculate membrane viscosity, wobbling angle of phospholipids and fluorescence life time. The anterior descending branch of the coronary artery was occluded for 15 min and reperfused for 15 min. Mitochondria from the area of the left ventricular wall exposed to ischemia-reperfusion and from an unexposed control area were separately isolated in 8 rabbits. For comparison, mitochondria from ventricular wall exposed to ischemia but not to reperfusion were obtained from 5 rabbits. The membrane viscosity increased from 0.44 to 0.49 poise and the wobbling angle of phospholipids tended to decrease from 59 to 56 degrees at 37 degrees C. The amount of peroxidized lipid rose from 1.5 to 4.3 nmol/mg-protein as expressed with MDA in the mitochondria exposed to ischemia-reperfusion. The fluorescence life time of DPH was slightly longer in the latter than in mitochondria from the control area. None of these parameters was altered in mitochondria exposed only to ischemia. The increase in viscosity observed in mitochondria from the ischemic-reperfused area probably produces a decrease in the diffusion of molecules through mitochondrial membranes. The concurrent tendency of the decrease in wobbling angle of membrane phospholipids suggests a decrease in the size of molecules which can permeate membranes. Limitations in diffusion will affect the metabolic activity of mitochondria and finally, overall cardiac function.

Animals↗
PubMed1991

Protective effects of idebenone against alterations in dynamic microstructure induced by lipid peroxidation in rat cardiac mitochondria.

The antioxidative effect of idebenone was studied in isolated mitochondria from the rat heart. Variables for dynamic microstructure, membrane viscosity and wobbling angle of phospholipids, were measured by means of a nanosecond time-resolved fluorometer. Exposure of isolated cardiac mitochondria to oxidative conditions in vitro caused significant alterations in lipid peroxidation, wobbling angle of phospholipids and membrane viscosity. Exposure of mitochondria to oxidative conditions after idebenone pretreatment resulted in no significant alterations in membrane viscosity and wobbling angle of phospholipids. Alterations in these variables seemed to be related to the amount of peroxidized lipid. Protection of phospholipids against peroxidation by antioxidative substances is effective in maintaining nearly normal physical properties in the dynamic microstructure of cardiac mitochondrial membranes.

Animals↗
PubMed1990

Membrane viscosity correlates with alpha 1-adrenergic signal transduction of the aged rat cerebral cortex.

We investigated, using adult (2-month-old) and senescent (12- and 24-month-old) rats, the effects of aging on the relationship between the alpha 1-adrenergic coupling system and the membrane viscosity of the cerebral cortex. There was no age-related difference in the KD values of [3H]prazosin binding on the membranes. The Bmax values of [3H]prazosin binding were reduced with advanced age. Norepinephrine-induced formation of 3H-labeled inositol phosphates (3H-IPs) in the slices increased with advanced age. The EC50 values for norepinephrine to stimulate the formation of 3H-IPs at advanced age were lower than that at adult age. The cholesterol content in membranes increased with advanced age. No changes in the phospholipid content in membranes were observed with advanced age. Concomitantly, an increase of the molar ratio of cholesterol to phospholipids was observed with advanced age. The membrane viscosity as measured by 1,6-diphenyl-1,3,5-hexatriene increased with advanced age. These results indicate that the altered cholesterol content and/or viscosity in cortical membranes of the aged rat may account for the loss of alpha 1-adrenergic receptor density and/or compensatory changes in the receptor-phospholipase C coupling system.

Aging↗
PubMed1990

Microdynamics of outer and inner membranes of mitochondria from bullfrog myocardium.

Outer and inner mitochondrial membranes were separated from bullfrog myocardium. Membrane viscosity and wobbling angle of phospholipids were measured with a nanosecond time-resolved fluorometer using a fluorophore, DPH, in each membrane. Measurements were also made on liposomes prepared from lipids extracted from each membrane. The anisotropy decay curve for DPH fluorescence was assumed to represent a mean value of decays in several microenvironments in membranes. Phospholipid constituents in membranes were analyzed by HPLC. A high proportion of PE and CL, both of which contain large amounts of unsaturated acyl chain, were found in the inner membrane. The low viscosity and large wobbling angle of phospholipids in the liposome from the inner membrane were consistent with the probable high content of unsaturated acyl chains and the low content of cholesterol in the inner membrane. Measurements of the dynamic microstructure of mitochondrial membranes suggested multifactorial characteristics probably resulting from the lipid-protein interactions. The average viscosity was found to be 0.39 +/- 0.08 P in the outer membrane and 0.58 +/- 0.01 P in the inner membrane. The wobbling angle of phospholipids in the outer and the inner membrane was, respectively, 47 and 49 degrees (non-significant difference). The liposomes prepared from lipid extracts of the membranes showed a lower viscosity and/or higher wobbling angle of phospholipids compared with the membranes themselves. The difference in the viscosity and wobbling angle between the mitochondrial membrane and its respective liposome was large in the inner membrane. These results suggest that the motion of phospholipids is limited by membrane proteins and the limitation of molecular motion of phospholipids results in an increase in the average viscosity. The results also suggest that the microdynamic values obtained in the inner membrane fraction reflect the interaction between phospholipid and protein which is abundant in the inner membrane.

Animals↗
PubMed1990

Dynamic microstructure and hydration of peroxidized membrane of rat cardiac mitochondria and effects of adriamycin.

Nanosecond time-resolved fluorometry of diphenyl hexatriene, DPH, fluorescence was used to study the effects of lipid peroxidation caused by NADH or adriamycin treatment on the dynamic microstructure of mitochondrial membranes from rat myocardium. Isolated mitochondria were incubated with NADH, FeCl3, and ADP, or with adriamycin. Parameters for microdynamics were calculated from the fluorescence intensity and anisotropy decay curves for DPH fluorescence. Peroxidized lipids were measured as malondialdehyde (MDA) resulting from the thiobarbiturate reaction. As peroxidized lipids accumulated, the membrane viscosity increased and the wobbling angle of the phospholipids decreased. The structural changes induced in unsaturated phospholipids by peroxidation probably increased the friction of neighboring phospholipids and restricted the range of their wobbling motion. The fluorescence intensity and fluorescence lifetimes decreased significantly when MDA was higher than 10 nmol/mg protein. These alterations in the behavior of DPH fluorescence strongly suggest that the hydration of the phospholipid layer of the mitochondria is occurring as a consequence of lipid peroxidation, since the fluorophore, DPH, is hydrophobic and its fluorescence is known to be quenched by increasing the dielectric constant of the surrounding media. The present results provide experimental supports to the hypothesis of membrane hydration induced by lipid peroxidation.

Animals↗
PubMed1990

Dynamic microstructure of plasma and mitochondrial membranes from bullfrog myocardium--a nanosecond time-resolved fluorometric study.

The viscosity of the phospholipid bilayer and the wobbling angle of the phospholipid molecules of mitochondrial membranes and plasma membranes from bullfrog myocardium were measured with a nanosecond time-resolved fluorometer using pulsed excitation of a hydrophobic fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene (DPH). The mean +/- S.D. in the viscosity of the mitochondrial and plasma membranes was 0.54 +/- 0.9 and 0.37 +/- 0.03 P, respectively, at 30 degrees C. The wobbling angle of phospholipid molecules was 42 +/- 1 and 47 +/- 1 degree, respectively. Cholesterol content was lower in mitochondria (6.4 micrograms/mg protein) than in plasma membranes (43.7 micrograms/mg protein) but phosphatidylethanolamine concentration was higher in mitochondria (31.8%) than in plasma membranes (27.3%). Cardiolipin was contained only in mitochondria. The results of these lipid analyses appear consistent with the measurements of membrane viscosity and phospholipid wobbling angle. When the results are compared with those from a previous study on the erythrocyte membranes from bullfrogs, viscosity is found to increase in the order mitochondrial membranes less than plasma membranes less than erythrocyte membranes. The complex requirements of biomembranes of organelles performing different functions appear to be met by the particular dynamic microstructure of the biomembrane. The effect of membrane viscosity on oxygen diffusion through membranes is discussed.

Adenosine Triphosphatases↗
PubMed1990

Analysis for the molecular motion of phospholipid bilayer with picosecond fluorometry.

The viscosity and the molecular motion of phospholipid molecule in biological and artificial phospholipid bilayers were studied using picosecond fluorescence depolarization method with rod-like fluorophore, DPH. From the relationship between the viscosity in the lipid bilayer and the free space of phospholipid acyl-chain, it is concluded that the viscosity is determined mainly by the range of wobbling motion of the acyl-chain. Motion of polar head group was also measured by the same method with a newly synthesized fluorescent phospholipid, dipalmitoyl-phosphatidyl-umbelliferone. The rate and the range in the motion of head group were faster and larger than those of acyl-chain and gave the viscosity of head group layer to be 0.03 poise, which was about one tenth of that of acyl-chain layer in the liquid crystalline phase. This fact indicates that the head group layer would not resist the lateral diffusion of molecules in membrane and that the lateral diffusion rate of molecules could be estimated from the viscosity in the acyl-chain layer.

1,2-Dipalmitoylphosphatidylcholine↗
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↗