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N Hazemoto

Publications and source records attributed to N Hazemoto.

16 recordsLinked to original sources
PubMed1998

[Cationic liposomes in gene delivery].

Cationic liposomes have been extensively explored as gene delivery vector for several reasons. It is because disadvantages of viral vectors include risk of replication, possible immunogenicity, and the difficulty of obtaining a large quantity of viral vectors. Currently, a variety of cationic components for liposome formulations have been developed. The components are broadly divided into two classes based on the chemical structure of hydrophobic moieties: long aliphatic (saturated or unsaturated) hydrocarbons and cholesterol ring. A variety of hydrophilic moieties also include tertiary amines, ammonium salt and spermine. The role of liposomes is to condense DNA to form complexes with high affinity to cell surfaces where possible fusion or destabilization of the membrane and/or endocytosis are involved. However, at present, little structure-activity relationships are known. Some vectors are on clinical trials approved by NIH.

Cations↗
PubMed1993

Effect of phosphatidylcholine and cholesterol on pH-sensitive liposomes.

We previously reported that liposomes composed of phosphatidylethanolamine (PE) and fatty acid exhibited pH-dependent leakage, aggregation and fusion (N. Hazemoto, M. Harada, N. Komatubara, M. Haga and Y. Kato, Chem. Pharm. Bull., 38, 748 (1990)). In this study, we have examined the effects of phosphatidylcholine (PC) and cholesterol (Chol) on the pH-sensitivity of liposomes. Contents-leakage from liposomes was always accompanied by a change in light-scattering, suggesting that aggregation or fusion of liposomes causes the leakage. The pH-sensitivity was observed only when liposomes contained less than 32 mol% of PC. The leakage vs. pH curves shifted to the more acidic regions as the PC content of the liposomes increased, but the maximum leakage (%) did not change. The effect of cholesterol on the pH-sensitivity depended on the PC/PE ratio of the liposomes. Addition of cholesterol to PC/PE/oleic acid (OA) liposomes system induced two effects, that is, aggregation of liposomes via the reduction in PC content and the stabilization of the liposomal membrane. It was shown that pH-sensitivity can be controlled by addition of the appropriate amount of PC and/or Chol to liposomal lipids.

Cholesterol↗
PubMed1992

Enantiomeric difference in percutaneous penetration of propranolol through rat excised skin.

The percutaneous penetration of R-(+)- and S-(-)-propranolol (PL) through rat excised skin was investigated in vitro. The flux of S-(-)-PL after application to normal skin was high compared with that of R-(+)-PL. On the other hand, in damaged rat skin, the flux of R-(+)-PL was almost equivalent to that of S-(-)-PL. It is suggested that there is an enantiomeric difference between S-(-)- and R-(+)-PL in terms of penetration through rat stratum corneum.

Animals↗
PubMed1990

An improved chemiluminescence-based liposome immunoassay involving apoenzyme.

An improved liposome immunoassay system (LIS) combining the chemiluminescence-based LIS with an apoenzyme reactivation immunoassay system (ARIS) was developed. A low-molecular-weight co-factor, FAD (flavin adenine dinucleotide), was incorporated into liposomes instead of the high-molecular-weight enzyme GOD (glucose oxidase). FAD released from liposomes by cytolysin-hapten conjugates bound to Apo-GOD and regenerated GOD. The system allowed detection of 10 pM digoxin, the model analyte and was linear over 10 pM to 13 nM digoxin. This sensitivity was about 300 times higher than that of the homogeneous system using GOD-containing liposomes and 30 times higher than that of the heterogeneous system which we reported previously. The time required for incubation during the detection of digoxin was reduced from 20 to 3 h.

Apoenzymes↗
PubMed1990

pH-sensitive liposomes composed of phosphatidylethanolamine and fatty acid.

pH-induced destabilization, aggregation and fusion of liposomes composed of phosphatidylethanolamine (PE) and various fatty acid were studied. Destabilization was examined as a fluorescent change caused by leakage of coencapsulated aminonaphthalene-3,6,8-trisulfonic acid (ANTS) and N,N-p-xylylenebispyridinium bromide (DPX). Fusion was monitored by two different methods, that is, intermixing assay of internal aqueous contents of liposomes, and lipid dilution assay of liposomes labeled with fluorescent phospholipids. Contents leakage from liposomes was observed by lowering the pH, and pH where the leakage began depended on fatty acid used. Fifty percent leakage of contents from PE liposomes containing alpha-hydroxypalmitic acid or alpha-hydroxy-stearic acid was observed at pH 5.5, that from liposomes containing stearic acid or palmitic acid was observed at pH 6.5-6.7, and that from ricinoleic acid at pH 7.2. Aggregation and fusion of the respective liposomes also occurred at a similar pH region. These results were interpreted by the notion that the protonation of the fatty acid triggers a series of pH-sensitive events. The liposomes developed in this study may be useful as a drug carrier which could release the contents in response to pH changes in their environment.

Chemical Phenomena↗
PubMed1989

Plasma-polymerized membrane electrode for the determination of dextromethorphan and dimemorfan.

Ion-selective electrodes (ISEs) responsive to the antitussives dextromethorphan and dimemorfan were constructed by the fixation of an ion-exchanger, ammonium tetraphenylborate, on a Millipore membrane by means of a plasma-polymerization technique. The electrodes showed a Nernstian response over the range of 10(-5)-10(-2) M dextromethorphan and dimemorphan, and the working pH range was 5-7. The interference from common cations such as Na+, K+ and Ca2+ was negligible but some organic cations interfered weakly. The electrodes were applied successfully for the determination of the drugs in pharmaceutical preparations.

Dextromethorphan↗
PubMed1985

Light and dark adaptation of halorhodopsin.

Dark incubation of envelope vesicles derived from a strain of Halobacterium halobium that lacks bacteriorhodopsin but contains halorhodopsin and a third rhodopsin-like pigment caused a decrease in the flash yield [the amplitude of a transient absorbance change of flash reactive component(s) by flash] of halorhodopsin but not the rhodopsin-like pigment. The flash yield decreased to reach a low steady level after incubation for about 4 days in the dark. The flash yield of halorhodopsin at any stage of dark incubation was increased by actinic illumination of the vesicles. The flash yield at 490 nm (absorbance increase) was found to be approximately proportional to that at 590 nm (absorbance decrease). These results indicate that halorhodopsin in the envelope vesicles has two forms, dark and light adapted, and that the halorhodopsin phototransient absorbing at 490 nm is originated from the light-adapted form. A difference spectrum between these two forms of halorhodopsin shows that the light-adapted halorhodopsin was red-shifted from the dark-adapted form. The light-induced membrane potential was measured by tetraphenylphosphonium uptake. The uptake by the dark-adapted vesicles was slower than that by the light-adapted vesicles, suggesting that only the light-adapted halorhodopsin has ion-transporting activity.

Adaptation, Biological↗
PubMed1984

Suggestion of existence of two forms of halorhodospin in alkaline solution.

Illumination of halorhodopsin (hR590) with orange light in alkaline solution produced a 410 nm absorbing species (hR410), which returned to hR590 upon blue light illumination. The amount of the flash-reactive species of hR590 was estimated by the flash-yield. Illumination with orange light decreased the flash yield, due to the formation of hR410. Blue light illumination of this sample led to the increase of the yield, which was larger than that before orange light illumination. In dark, the yield decreased gradually in 3-4 days. The scheme is proposed in which there exist two forms of hR590.

Bacteriorhodopsins↗
PubMed1984

Effect of salt on photocycle and ion-pumping of halorhodopsin and third rhodopsinlike pigment of Halobacterium halobium.

The cytoplasmic membranes of Halobacterium halobium contain at least three retinal pigments: bacteriorhodopsin (bR), halorhodopsin (hR), and a third rhodopsinlike pigment (tR). The amplitudes of the phototransient in the photolysis of hR and tR were measured in various salt solutions. Halogen ion (except fluoride) was required to retain the photocycle of hR. Parallels between the amplitude of the phototransient of hR and the magnitude of the photo-induced tetraphenylphosphonium (TPP+) uptake suggests that hR is a light-driven halogen pump, which supports the hypothesis by Schobert and Lanyi (J. Biol. Chem., 1982, 257:10306-10313). The order of effectiveness of halogen was Br- greater than Cl- greater than I-. On the other hand, no specific ion was required to retain the photocycle of tR, and tR was concluded to be nonelectrogenic.

Anions↗
PubMed1983

Light-induced delta pH of envelope vesicles containing halorhodopsin measured by use of a spin probe.

The spin-labeled amine, 4-amino-2,2,6,6-tetramethyl-piperidino-N-oxyl was used to measure the photoinduced delta pH in the envelope vesicles derived from mutant cells of Halobacterium halobium. The cells contain halorhodopsin (hR) and are spectroscopically free from bacteriorhodopsin (bR). The EPR signals from the extravesicular populations of the probe was quenched by ferricyanide. The membrane bound population of the probe was less than 1% of the amount of the probe entrapped within the vesicle. Hence, we can monitor continuously the concentration of the intravesicular populations of the probe and delta pH can be calculated from the line height of the signal. The kinetic analysis indicated that the time course of the change in the EPR signal represents faithfully delta pH of the vesicle. At pH 7.5, the photoinduced delta pH showed a maximum. The kinetic constant of pH change also displayed a peak at this pH. Addition of uncoupler did not increase either the rate nor magnitude of delta pH at this pH, but at other pH, especially at lower pH, uncoupler showed its effect. A theoretical equation was derived which correlated the photocycle of hR with delta pH. According to the analysis by use of this equation, the time constant of the photocycle was suggested to be constant in pH ranging from 5.5 to 8.25. The maximum in photoinduced delta pH observed at pH 7.5 was concluded to be due to the permeability dependence of ions, especially of H+ on pH. The temperature dependence of delta pH was measured. As the temperature decreased, delta pH was, surprisingly, found to be increased. The rate constant of the photocycle analyzed by the equation, however, decreased with decrease of temperature.

Bacterial Proteins↗
PubMed1983

Photochemistry of two rhodopsinlike pigments in bacteriorhodopsin-free mutant of Halobacterium halobium.

Two photocycles due to two different pigments were found in membrane vesicles of a bacteriorhodopsin-free mutant of Halobacterium halobium. A pigment absorbing approximately 590 nm halorhodopsin (HR) underwent a faster photocycle with a phototransient at approximately 490 nm (half-time of decay, tau 1/2 = 10 ms). Another third rhodopsinlike pigment (TR) absorbing approximately 580 nm underwent a slower photocycle accompanying a phototransient absorbing below 410 nm (tau 1/2 = 0.8s). The photocycles were measured under various conditions of temperature, NaCl concentration, pH, and in the presence of cholate. All results obtained support the notion that the two photocycles are independent of each other, and the fast or the slow cycle can be abolished after these treatments. At alkaline pH, the wavelength of maximum absorbance of both pigments shifted to blue, but the magnitude of the shift of the pigment undergoing the slow photocycle was much greater than the other. The ratio of the content of the two pigments varies among bacteriorhodopsin-free mutants.

Bacteriorhodopsins↗
PubMed1976

Electrode sensitive to sulfa drugs.

An electrode sensitive to sulfa drugs was constructed by using the iron(II)-bathophenanthroline chelate embedded in a liquid membrane. Rapid and Nernstian responses were exhibited against solutions of sulfamerazine and sulfisomidine ranging between 10(-3) and 10(-1) M in concentration. High selectivity was observed in the presence of urea, glycine, aminopyrine, or p-amino-benzoic acid. These chemicals are known to interfere in the usual colorimetric analysis of sulfa drugs.

Chemical Phenomena↗
PubMed1976

Ion selective electrode for 2,4-dichlorophenoxyacetic acid.

An electrode responsive to 2,4-D (2,4-dichlorophenoxyacetic acid) was constructed by dissolving tetrazolium derivatives as an ion exchanger in a liquid membrane. The electrode exhibited rapid and Nernstian response to solutions of 2,4-D over the concentration range 10(-1) to 10(-4)M. The presence of diverse substances such as acetate, benzoate, and 3-indoleacetate showed no appreciable effect on the electromotive force of the electrode.

2,4-Dichlorophenoxyacetic Acid↗
PubMedDate not supplied

Astrocytic contributions to blood-brain barrier (BBB) formation by endothelial cells: a possible use of aortic endothelial cell for in vitro BBB model.

Astrocytic contribution of endothelial cell monolayer permeability was examined in two blood-brain barrier (BBB) models, using the coculture in a double chamber system: rat astrocytes and bovine aortic endothelial cells (BAECs) or bovine brain endothelial cells (BBECs). In system 1, where astrocytes were separated from endothelial cells, a 40% reduction in L-glucose permeability of the BBEC monolayer, but not the BAEC monolayer, was observed by cocultivation with astrocytes. Although several passages of BBEC in culture elicited morphological transformation from spindle-shapes to cobblestone-like features, the passaged BBECs remained responsive to astrocytes in coculture in system 1 (37% reduction of the L-glucose permeability). By contrast, in system 2, where respective endothelial cells and astrocytes layered on the upper and lower surfaces of a membrane, the permeability of both BAEC and BBEC monolayers was reduced by cocultivation with astrocytes (75% reduction for BAEC and 40% reduction for BBEC). BAECs in this contiguous coculture (system 2) with astrocytes showed numerous tight junction-like structures characteristic of the BBB in vivo. These results suggest that primary cultured BBECs, which had been primed by astrocytes in vivo, retain a higher sensitivity to astrocytes possibly through an astrocytic soluble factor (s) to exhibit BBB-specific phenotypes, and that even BAEC from extra-neural tissues, when cultured with astrocytes in close proximity in vitro, may acquire the similar phenotypes and serve for an extensive use of BBB model in vitro.

Animals↗