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H Nishide

Publications and source records attributed to H Nishide.

36 records · Page 2Linked to original sources
PubMed1992

Oxygen-transport and solution properties of polylipid/Hb vesicles (ARC).

Polymerized phospholipid vesicle encapsulating Hb (polylipid/Hb vesicle) was prepared from a mixture of unsaturated phospholipid, cholesterol and unsaturated fatty acid and polymerization by gamma-ray irradiation. The average radius of resulting vesicles was 203 +/- 39 nm and concentrated Hb (30 wt%) was efficiently encapsulated. gamma-Ray polymerization proceeds theoretically at low temperature (4 degrees C). P50 and oxygen transporting efficiency were adjusted to 40 mmHg and 40%, respectively. Oncotic pressure and solution viscosity can be controlled to the same values as blood.

Blood Substitutes↗
PubMed1991

Structure/activity relationship of eel calcitonin. A study using a newly devised method for designing analogs.

A series of analogs of eel calcitonin (eCT) was synthesized according to a newly devised scheme, 'the insertion-inactivation method', to clarify the structure/activity relationship of a given peptide. This method consists of two steps: the deletion of a residue of the peptide is first chosen and then a series of analogs with the residue reinserted into serial positions is synthesized and biological activities are assessed in each step. An analog lacking Lys18 (dK), selected as a deleted analog for the first step, showed marked loss of activities determined by inhibition of 125I-eCT binding, growth inhibition, and cAMP production in a porcine kidney cell line LLC-PK1. Activities of a set of 20 analogs with the reinserted lysine residue at serial positions from 12 to 32 (K12-K32) were then evaluated. The results showed the following three patterns of the expression of activities according to the position of the reinsertion: (a) analogs K12-K16 (positions 12-16) and K25 (position 25) showed lower activities than eCT in all assays; (b) K17-K24 (positions 17-24) showed slightly lower activities than eCT in the receptor binding and the growth inhibition and similar level in cAMP production; (c) K26-K32 (positions 26-32) showed considerably lower activities in the former two assays and slightly lower activity in cAMP production. Further, analogs considerably less active than eCT showed unchanged alpha-helix contents and destroyed amphiphilicity by the insertion of a lysine residue, indicating that amphiphilicity is one of important factors for expressing the activity. The results obtained here lead to a conclusion on the significance of each region of eCT molecule as follows: (a) the presence of Lys18 is necessary for the complete expression of biological activity; (b) the length of amphiphilic alpha-helix to be required for the activity is at most 10 residues ranging from position 8 to position 17; (c) the receptor binding region is located within 9 residues ranging from position 24 to position 32.

Amino Acid Sequence↗
PubMed1990

Growth inhibition and morphological changes of LLC-PK1 induced by ultimobranchial calcitonins.

Ultimobranchial calcitonins (CTs), known to stimulate cAMP production, inhibited the growth of a porcine kidney cell line LLC-PK1. This inhibition was accompanied by degenerative changes including vacuole formation and cell detachment. The electron microscopic study revealed marked swelling of rough endoplasmic reticulum (RER). Other cAMP-increasing agents such as human CT, arginine, vasopressin, and forskolin showed less growth inhibitory activities and no induction of the degenerative changes. These results indicate that the growth inhibition of LLC-PK1 by ultimobranchial CTs is mainly due to cellular death caused by the swelling of RER via a signalling pathway other than the cAMP-dependent event(s).

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Liposome/heme as a totally synthetic oxygen carrier.

We synthetically derived protoheme (oxygen-binding site of hemoglobin) to an amphiphilic heme compound and embedded it in the phospholipid bilayer of liposomes, not in an aqueous inside region of liposomes. This liposome/heme transports oxygen efficiently under physiological conditions. Characteristics of our totally synthetic liposome/heme as an artificial oxygen carrier, are summarized as follows. (i) Oxygen-binding is reversible and very rapid. (ii) The oxygen volume dissolved in the fluid is similar or superior to that of blood. (iii) The oxygen-binding affinity is close to that of blood. (iv) The particle size is smaller than 0.1 micron. (v) It is physically and mechanically stable under shear stress and storage. (vi) The components are synthetic derivatives of protoheme and phospholipid originated in nature. The advantages (i)-(iii) and brilliant red color of the solution are derived from the fact that our totally synthetic liposome/heme, transports oxygen in the same principle of red blood cells. When the liposome/heme solution was mixed with human blood, the liposome/heme delivered oxygen to blood in the mixture system. The oxygen-exchanging of the liposome/heme with blood was also tested ex-vivo using an artificial lung apparatus. The oxy liposome/heme was circulated through A-V of a dog leg, and the oxygen concentration was kept at a high level. This demonstrates the fact that the synthetic liposome/heme transports and delivers oxygen to the muscle tissue. Application to extracorporeal circulation and transfusion test will also be reported.

Animals↗
PubMed1987

Clearance and tissue distribution of functionalized polymeric liposomes from the blood stream of rats.

Polymeric liposomes containing a synthetic porphinato-iron-imidazole complex (hemoglobin or red blood cell model) were labeled by introducing 1,2-di[1-14C]palmitoyl-sn-glycero-3-phosphocholine into their polymerized bilayers. After intravenous injection into rats, their clearance from a blood stream was measured. The apparent half-life time (50% disappearance time) was about 14 +/- 2 h. Their tissue distribution was determined with time by whole autoradiographic measurement.

Animals↗
PubMed1986

Interactions of functionalized polymeric liposomes having a porphinato-iron complex with some biological cells and components in vitro.

The hemocompatibility of functionalized polymeric liposome particles (diameter: 20-32 nm), which have a synthetic porphinato-iron complex in their polymerized bilayers and can carry oxygen, was studied in vitro. The ultramicroparticles did not induce hemolysis, platelet aggregation and plasma coagulation directly and were stable against hydrolysis by phospholipases A2 and D.

Animals↗
PubMed1984

Enzymatic reduction of synthetic polymer-bound hemin derivatives: efficient method to prepare a heme-oxygen adduct in cooled aqueous medium.

Synthetic polymer-bound hemin (iron(III) protoporphyrin IX) derivatives were effectively reduced by ferredoxin and ferredoxin-NADP reductase system. The resultant polymer-bound heme (iron(II) protoporphyrin IX) derivatives formed oxygen adducts with a lifetime of ca. 1 hr in aqueous solution at -30 degrees C. The reduction rate is discussed in terms of the structure of the hemin derivatives.

Animals↗
PubMed1983

Liposomal heme as oxygen carrier under semi-physiological conditions. Orientation study of heme embedded in a phospholipid bilayer by an electrooptical method.

The meso-tetra(alpha,alpha,alpha,alpha(o-pivalamidophenyl]porphinato iron-mono(1-lauryl-2-methylimidazole) complex embedded in the bilayer of dimyristoylphosphatidylcholine (liposomal heme) binds molecular oxygen reversibly at pH 7 and 37 degrees C. Orientation of the iron porphyrin complex in the phospholipid bilayer was studied by electric birefringence and dichroism. It was observed that both the phospholipid bibilayer of liposome and the porphyrin plane are oriented nearly in parallel to the electric field. Therefore the angle between the porphyrin plane and the bilayer is considered to be practically small.

Circular Dichroism↗
PubMed1977

Dissociation of aggregated ferroheme complexes and protoporphyrin IX by water-soluble polymers.

The ferroheme-pyridine complex, ferroheme and protoporphyrin IX form the aggregates by the hydrophobic interaction in aqueous solutions. We found by spectrophotometric and fluorometric measurements that the aggregates dissociated into the monomers by the addition of water-soluble polymers, such as, poly(ethyleneoxide), poly(vinylalcohol), poly(vinylpyrrolidone) and poly(styrene sulfonate). The dissociation by the polymers proceeded as their hydrophobicities increased. The aggregated ferroheme was effectively dissociated by the copolymers of 4-vinylpyridine which were water-soluble polymer-ligands.

Binding Sites↗
PubMedDate not supplied

Surface modification of hemoglobin vesicles with poly(ethylene glycol) and effects on aggregation, viscosity, and blood flow during 90% exchange transfusion in anesthetized rats.

Poly(ethylene glycol) (PEG5000)-conjugated phosphatidylethanolamine was introduced onto the surface of hemoglobin vesicles (HbV); phospholipid vesicles encapsulating concentrated Hb (d = 0.257 +/- 0.087 micron; P50 = 32 Torr). The obtained PEG-modified HbV (HbV-PEG) was studied for use as a red cell substitute from the viewpoint of rheology, surface properties, and hemodynamics. The viscosity of the unmodified HbV suspended in saline ([Hb] = 10 g/dL) was 2.6 cP (shear rate = 358 s-1, 37 degrees C), less than that of human blood (4 cP). However, when suspended in a 5 g/dL albumin solution (HbV/ albumin), it increased to 8 cP due to the molecular interaction between albumin and vesicles, and the viscosity increased with decreasing shear rate, e.g., 37 cP at 0.58 s-1. As for the HbV-PEG/albumin, on the other hand, the viscosity was 3.5 cP at 358 s-1 and was comparable with that of human blood. Optical microscopy showed formless flocculated aggregates of the unmodified HbV, while no aggregates were confirmed for the HbV-PEG. The steric hindrance of PEG chains seemed to be effective in preventing intervesicular access and the resulting aggregation. To estimate the flow profiles in the capillaries, the suspensions were allowed to penetrate through isopore membrane filters (pore size = 0.4-8 microns, cf. capillary diameter = 4-10 microns). The penetration rate of the HbV-PEG/albumin was higher than that of the unmodified HbV/albumin due to the suppression of aggregation, whereas both of them were significantly higher than that of human blood due to the smaller size of vesicles than RBC. Ninety percent exchange transfusion was performed with the HbV-PEG/albumin or HbV/albumin in anesthetized Wistar rats (n = 6). The blood flow in the abdominal aorta increased 1.5 times, and the total peripheral resistance decreased in the HbV-PEG/albumin-administered group in comparison with the HbV/albumin group. As for the blood gas parameters, the base excess and pH remained at higher levels in the HbV-PEG/albumin group, and the O2 tension in mixed venous blood for the HbV-PEG/albumin group tended to be maintained at a higher level than that for the HbV/albumin group. Thus, the PEG modification of HbV reduced the viscosity by the suppression of aggregation and resulted in prompt blood circulation in vivo.

Adsorption↗
PubMedDate not supplied

Properties of and oxygen binding by albumin-tetraphenylporphyrinatoiron(II) derivative complexes.

A hydrophobic tetraphenylporphyrinatoiron(II) derivative bearing a covalently bound axial imidazole [Fe(II)P] was efficiently and noncovalently bound into human serum albumin (HSA) up to an average of eight Fe(II)P molecules per HSA molecule. The aqueous solutions of the HSA-Fe(II)P complex provided a reversible and relatively stable oxygen adduct under physiological conditions (pH 7.4 and 37 degrees C). The half-life of the oxygen adduct (tau 1/2) was 1 h at 37 degrees C in an air atmosphere. With Fe(II)-TpivPP (the so-called "picket-fence heme") having no axial base, an oxygenated HSA-Fe(II)TpivPP complex was obtained using a 20-fold molar excess of 1,2-dimethylimidazole, but the tau 1/2 was very short (ca. 10 min at 37 degrees C). The oxygen affinity [P 1/2(O2)] and oxygen transporting efficiency (OTE) of HSA-Fe(II)P at 37 degrees C were 30 Torr and 22%, respectively. Furthermore, the oxygen-binding and dissociation rate constants (kon and koff) are extremely high in comparison with those of hemoglobin. The HSA molecule binding eight Fe(II)P molecules can transport about 3.4 mL/dL of oxygen under physiological conditions, corresponding to about 60% of the oxygen transporting amount of human blood.

Blood Substitutes↗
PubMedDate not supplied

Methemoglobin formation in hemoglobin vesicles and reduction by encapsulated thiols.

The hemoglobin vesicle (HbV) is a red cell substitute encapsulating purified concentrated Hb in a phospholipid vesicle. In order to suppress metHb formation or autoxidation, for the long-term maintenance of the oxygen transporting capability, a series of thiols (cysteine, Cys; glutathione, GSH; homocysteine, Hcy; and acetylcysteine, Acy) were studied as reductants of metHb. Hcy and GSH showed a good suppressive effect on metHb formation, while Cys adversely accelerates the metHb formation at a rate twice that of the Hb solution without any reductants and Acy showed no change. The significant suppression by the coaddition of superoxide dismutase (SOD) and catalase to Cys indicated that Cys was easily oxidized by oxygen and simultaneously generates a large amount of active oxygens. The effective suppression of metHb formation by SOD and catalase was not observed for HbV containing no reductants, indicating that the generation of active oxygens from Hb itself is not significant. The coencapsulation of Hcy with Hb resulted in a low rate of metHb formation in HbV (initial rate, 1%/h) in vitro at an oxygen partial pressure (Po2) of 142 Torr. The rate increased with decreasing Po2, showed a maximum (2.2%/h) around Po2 = 23 Torr, and then decreased to 0%/h at 0 Torr. From these results, it is suggested that the fast metHb formation rate in the blood circulation of Wistar rats injected with 20 vol % of the HbV solution would be mainly caused by the exposure of HbV to the low Po2.

Animals↗
PubMedDate not supplied

Physical properties of hemoglobin vesicles as red cell substitutes.

Hemoglobin vesicles (HbV) as red cell substitutes were prepared from a purified carbonylhemoglobin (HbCO) solution and a lipid mixture composed of phospholipids, cholesterol, and alpha-tocopherol. The diameter was controlled to 251 +/- 87 nm using an extrusion method; the vesicles penetrated through the membrane filters with regulated pore sizes. After the ligand exchanging reaction (HbCO-->HbO2), the oxygen affinity (P50) of HbV was 32 Torr, which was controlled with the coencapsulation of pyridoxal 5'-phosphate. The rate of metHb formation in HbV was nonenzymatically reduced with the coencapsulation of DL-homocysteine. The Hb concentration of the HbV suspension, which was dispersed in a phosphate buffered saline solution (pH 7.4), was controlled at 10 g/dL. At this concentration, the total lipid concentration was 6.2 g/dL and the viscosity, 2.6 cP (230 s-1), was lower than that of the blood (4.4 cP). The HbV suspension showed a typical non-Newtonian flow for a particle dispersion and agreed well with the Casson model. The viscosity at shear rates lower than 23 s-1 showed a maximum with increasing the mixing ratio of human blood, plasma, or albumin, while no maximum was observed for the mixture with washed red blood cells. The aggregates of HbV are formed by interaction with plasma proteins, including albumin, while the aggregates reversibly dissociate at higher shear rate.

Blood Substitutes↗
PubMedDate not supplied

Construction of artificial methemoglobin reduction systems in Hb vesicles.

The hemoglobin vesicle (HbV) is a red cell substitute encapsulating purified concentrated Hb in a phospholipid vesicle. In order to suppress metHb formation for the long term maintenance of oxygen transporting capability in vivo, thiols (cysteine, Cys; homocysteine, Hcy) were studied as reductants of metHb. Hcy showed a suppressive effect on metHb formation, while Cys adversely accelerates metHb formation at the rate of twice the Hb solution without any reductants. The suppression of Cys-induced metHb formation by the addition of superoxide dismutase (SOD) and catalase indicated that Cys was easily oxidized by oxygen and simultaneously generated a large amount of active oxygens. The rate of metHb formation was influenced by PO2 and pH. Furthermore, the reducing systems (methylene blue (MB), NADH or ascorbic acid) were added to the outer aqueous phase of HbV, and the artificial reduction systems constructed through the bilayer membrane were evaluated.

Blood Substitutes↗
PubMedDate not supplied

Liposome-embedded-heme as a totally artificial oxygen carrier.

To produce a totally artificial oxygen carrying substance, a synthetic iron-porphyrin (heme) complex that is analogous to the oxygen binding site (protoheme) of hemoglobin was embedded in the phospholipid bilayer of a liposome. The O2 carrying capacity of this liposome-embedded-heme (L/H) was examined by exchange transfusions in beagles. Six beagles were divided into two groups. In Group I, 15 ml/kg of blood was removed, and the same amount of L/H solution was injected intravenously. In Group II, 30 ml/kg of blood was withdrawn, and the same amount of the L/H solution was injected intravenously. The mean L/H concentration in the blood was 0.9 mM in Group I and 1.5 mM in Group II. The oxygen volume transported by 1 mM of the L/H at 1 L/min of cardiac output in Groups I and II were 15 and 17 ml/mM.L.min, respectively. The oxygen volume consumed from 1 mM of the L/H at 1 L/min of cardiac output in Groups I and II were 7.7 and 8.3 ml/mM.L.min, respectively. O2 volume transported by the L/H in Groups I and II were 8 and 15%, respectively. O2 volume consumed from the L/H in Groups I and II were 12 and 24%, respectively. Thus, this liposome-embedded-heme has the ability to combine with oxygen, to transport it to the tissue, and to release it in the tissue. The oxygen volumes transported by and consumed from the L/H were proportional to the L/H concentration in the blood.

Animals↗
PubMedDate not supplied

Evaluation of the capabilities of a hemoglobin vesicle as an artificial oxygen carrier in a rat exchange transfusion model.

Encapsulation of hemoglobin within a liposome is one of the strategies in the development of artificial oxygen carriers. It maintains the oxygen transporting properties of hemoglobin and, at the same time, eliminates the side effects of cell free hemoglobin. Hemoglobin vesicles (HbV) are a type of liposome encapsulated hemoglobin. They have a particle size of approximately 250 nm, a hemoglobin concentration of 10 g/dl, and the oxygen affinity, P50, is regulated to 32 Torr. In this study the authors examined the oxygen transporting capability of HbV in vivo, by performing exchange transfusions in rats. Exchange transfusion (90% of the estimated circulatory volume) with HbV suspended in 5% albumin (containing 160 mEq/L, sodium and 107 mEq/L, chloride) was carried out in male Wistar rats. Mean arterial pressure and heart rate were monitored through the arterial catheter. Arterial blood samples for gas analyses were also obtained from the arterial catheter. Abdominal aortic blood flow was measured by an ultrasonic pulsed Doppler flowmeter as an indicator of cardiac output. The oxygen tension of blood withdrawn from the right atrium was measured as an indicator of mixed venous oxygen tension. These values were employed to calculate oxygen delivery and consumption. Renal cortical and skeletal muscle tissue oxygen tensions were monitored as indicators of tissue perfusion. Five percent albumin and washed rat red blood cells suspended in 5% albumin containing 10 g/dl of hemoglobin; were employed as controls. At the completion of a 90% exchange transfusion, renal cortical and skeletal muscle tissue oxygen tensions, along with oxygen delivery and consumption, were sustained almost equally well with the HbV suspension compared to the washed rat red blood cell suspension, but declined significantly with the albumin suspension. The results indicate that the oxygen transporting capability of HbV was almost equivalent to that of rat red blood cells.

Animals↗