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Biomedical subjects

N Muramatsu

Publications and source records attributed to N Muramatsu.

At least 37 records · Page 2Linked to original sources
PubMed1996

Preparation of poly(D,L-lactide) and copoly(lactide-glycolide) microspheres of uniform size.

In an attempt to prepare monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres, a novel emulsification technique (membrane emulsification) was employed and the preparation conditions which might affect the monodispersity were evaluated. With this technique nearly monodisperse poly(D,L-lactide) and copoly(lactide-glycolide) microspheres were successfully prepared and their sizes were controllable only by making use of microporous glass membranes of different pore sizes. However, in the present system of emulsion (methylene chloride/water) the surfactant used was limited to ionic ones and the amount of polymers available for the formation of microspheres was inevitably too small in concentration to entrap sufficient amounts of drug. As for the drug release, the effect of particle size was not appreciable but the method of solvent removal gave a great influence; the solvent extraction method showed a more drug-sustaining effect than did the solvent evaporation method. The present results suggest the possibility of making drug-loaded and biodegradable monodisperse microspheres.

Biocompatible Materials↗
PubMed1995

Difference in surface properties between Escherichia coli and Staphylococcus aureus as revealed by electrophoretic mobility measurements.

Electrophoretic mobilities of Escherichia coli and Staphylococcus aureus were measured in media of different pH values and ionic strengths at 310 K and the results were analyzed via a new mobility formula which was derived on the assumptions of uniform charge distribution in the cell surface layer of finite thickness and ion-penetrability in the layer. E. coli was shown to have a more negatively charged and less soft surface than that of S. aureus. It is suggested that electrophoretic mobility measurements can be used to detect the difference in surface structure between gram-positive and gram-negative bacteria.

Cell Membrane↗
PubMed1995

Transitions in functional status and active life expectancy among older people in Japan.

This study analyzes the patterns and determinants of the transitions in functional status among elderly Japanese persons. Data for this research came from a two-wave national probability sample survey of persons aged 60 and over conducted between 1987 and 1990 in Japan. The study focuses on the transitions from two states of origin, "not disable" and "disabled," to three states of destination, "not disabled," "disabled," and "dead." Through multinomial logit analyses, the effects of sociodemographic factors, social relationships, health, and health behavior on transitions in functional status were examined. To assess the impact of panel attrition, the risk of nonresponse was analyzed in conjunction with health transition within the same framework. Finally, an increment-decrement active life table for Japanese elderly people was derived on the basis of the multivariate analyses. According to the life table, a Japanese older person at age 60 is expected to spend about 18.7 years (81%) in functional independence and about 4.4 years (19%) in disability throughout his or her remaining lifetime.

Age Factors↗
PubMed1995

[A case report of a 6-year-old boy with intracranial yolk sac tumor treated by VAB-6 regimen].

Several clinical trials have demonstrated that cisplatin-based chemotherapy for primary intracranial germ-cell tumors is effective as a neoadjuvant chemotherapy. In this report, we describe a 6-year-old boy, Down syndrome and Hirschsprung's disease with intracranial pure yolk sac tumor treated by combined chemotherapy with cisplatin, vinblastine, bleomycin and cyclophosphamide (modified VAB-6 regimen). He had been admitted to our hospital because of intractable vomiting, and left facial nerve palsy since 1 month before. An MRI revealed an enlarged mass, 4cm in diameter, in the left cerebello-pontine angle with uniformal enhancement by Gd-DTPA, and bilateral ventricular dilatation. He was found to have increased serum alpha-fetoprotein level (AFP 11, 786ng/ml), but not human chorionic gonadotropin beta-subunit. After a partial resection of the tumor, diagnosed as pure yolk sac tumor, and ventriculo-peritoneal shunt, three courses of combined chemotherapy with cisplatin, bleomycin, vinblastine and cyclophosphamide (modified VAB-6 therapy) were carried out. The serum AFP level returned to normal, and the tumor mass entirely disappeared (a complete response) on MRI after the second course of chemotherapy. However, cisplatin-induced vomiting and mild neutropenia and renal tubular injury developed after the third course of chemotherapy. Irrespective of administration of recombinant human G-CSF and broad spectrum antibiotics, he suffered from pneumonia and died of septic shock and multiple organ failure. Autopsy showed microscopic residual tumors. The combination chemotherapy with cisplatin, bleomycin, vinblastine and cyclophosphamide is effective for initial treatment of childhood intracranial yolk sac tumor. It is necessary, however, to reevaluate the cisplatin dosage and treatment schedule in order to reduce such side effects as bone marrow suppression and renal damage.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Phagocytosis of monosaccharide-binding latex particles by guinea-pig polymorphonuclear leucocytes.

Phagocytosis of monosaccharide-binding latex particles by guinea-pig polymorphonuclear leucocytes (PMNs) was investigated. When neuraminic acid or glucuronic acid was chemically bound to the surface of latex particles the degree of phagocytosis was somewhat lower than that for bare, glucose-, mannose- or rhamnose-binding latex particles. These experimental findings were interpreted in terms of the kind of monosaccharide and the surface potential and surface hydrophobicity of latex particles. As a result, it was concluded that the inhibitory action of neuraminic acid or glucuronic acid on phagocytosis arises from an increase in the surface hydrophilicity of latex particles brought about by the hydroxyl groups and negative charges on the chemically bound neuraminic acid or glucuronic acid molecules. Physically adsorbed glucuronic acid molecules were also found to decrease the degree of phagocytosis of latex particles by PMNs, though not so remarkable as the chemically bound monosaccharide molecules.

Animals↗
PubMed1993

Preparation of heat responding artificial cells.

Enzyme-loaded microcapsules were prepared and treated with dimyristoylphosphatidylcholine molecules so as to control the permeation of substrates through the microcapsule membranes. The activities of enclosed enzymes increased with increase in ambient temperature, but gave an abrupt change at around the phase transition temperature of the lipid. The experimental results indicate the possibility of making artificial cells which respond to the temperature change of the surrounding medium.

Capsules↗
PubMed1992

An interpretation of cell separation mechanism on polyamine graft copolymers.

Interaction between polyamide microcapsules having different balances of negative and positive charges on their surface, that is, different isoelectric points and copolymers with different numbers of polyamine macromer of a definite chain length grafted on poly(2-hydroxyethyl methacrylate) backbone was studied by measuring the amount adhered of the microcapsules onto the surface of copolymer-coated glass beads at different pH values. Maximum microcapsule adhesion was observed for a proper combination of microcapsule and copolymer to suggest that separation of a specified cell population from others on the surface of copolymer-coated glass beads can be explained in terms of preferential adhesion through electrostatic interaction of the specified cells with the copolymer.

Cell Separation↗
PubMed1991

Effect of particle size on phagocytosis of latex particles by guinea-pig polymorphonuclear leucocytes.

The effect of the size of foreign particles on phagocytosis by guinea-pig polymorphonuclear leucocytes (PMNs) was investigated using latex particles having approximately the same surface potentials but different sizes. Two types of latexes with different negative surface potentials, those having amino groups (Ami-latexes) and those having carboxylic acid groups (Ca-latexes), were used in this experiment. Since Ca-latexes had different surface potentials for different particle sizes, the carboxylic acid groups were modified by the carbodiimide method to make the surface potentials almost equal. Phagocytosis was estimated by the rate of oxygen consumption. It was found that the phagocytosis reached its maximum when the latex particle size was about 0.5 microns. This finding was plausibly explained by considering the two probabilities that a latex particle comes into contact with a PMN surpassing a potential barrier and the contact takes place at certain receptor areas favourable to phagocytosis on the PMN surface.

Animals↗
PubMed1991

Adsorption of negatively charged microcapsules to a poly(2-hydroxyethylmethacrylate)/polyamine graft co-polymer surface.

The electrokinetic properties of artificial particles--microcapsules--were compared with those of the rat lymphocyte sub-populations, T and B cells, and similar results were obtained. The affinity of the microcapsules to the polyamine graft co-polymer, which was claimed to be capable of separating the cells efficiently, was measured and it revealed that not the magnitude of the surface negative charge and the kind of dissociable groups, but the balance of the anionic and cationic charges on the microcapsule surface played a key role in their adsorption to the co-polymer.

Adsorption↗
PubMed1990

Possible application of polyamine graft copolymer to targeting drug delivery.

Polystyrene microspheres were coated with polyamine graft copolymer and mixed with rat lymphocyte suspension. In the mixture of T and B cells, the microspheres formed large aggregates, while they were fairly well dispersed in the T cell suspension. This result was understood to be the result of preferential adsorption of B cells to the microspheres, indicating it would be possible to deliver drugs to B cells alone with these copolymer-coated microspheres.

Animals↗
PubMed1989

Hidden self-association of proteins.

Sedimentation equilibrium measurements were carried out on solutions of bovine serum albumin, aldolase, and ovalbumin in phosphate-buffered saline, pH 7.2, at 10 degrees C. The data obtained for each protein were analyzed to yield the dependence of apparent weight-average molecular weight upon protein concentration, over a concentration range of ca 1-200 g/L. Using the approximate theory of Chatelier and Minton [1987) Biopolymers 26, 507-524), models are formulated for the dependence of apparent weight-average molecular weight upon concentration in non-ideal solutions containing proteins which may self-associate according to a monomer/n-mer or a monomer/dimer/tetramer scheme. The concentration dependence data for serum albumin may be accounted for, assuming either no self-association or weak monomer/dimer association. The data for aldolase may be accounted for assuming either weak monomer/dimer or weak monomer/trimer association. The data for ovalbumin may be accounted for assuming either weak monomer/trimer or weak monomer/dimer/tetramer association. The associations do not approach saturation at the highest concentrations studied, and the standard-state free energy changes accompanying self-association amount to less than 4 kcal/mol of intermolecular contacts, suggesting that non-specific clustering of protein molecules at high concentration rather than the formation of specific complexes is being observed.

Animals↗
PubMed1989

Phagocytosis by guinea pig polymorphonuclear leukocytes of liposomes stabilized with polysaccharides.

Hemolysate-loaded liposomes were prepared with their surface coated by polysaccharides, carboxymethylchitin, carboxymethylcellulose and carboxymethylchitosan. Phagocytosis by guinea pig polymorphonuclear leukocytes of these coated liposomes was measured in view of electrostatic interactions between the cells and the liposomes. This view revealed to hold at least in quite an early stage of phagocytosis, but some specific interactions were assumed to exist between the cells and the liposomes. N-acetyl groups of the chitin molecules were suggested to play a role in the complex processes of phagocytosis.

Animals↗
PubMed1988

An automated method for rapid determination of diffusion coefficients via measurements of boundary spreading.

The use of a simple device by which a layer of solvent may be deposited onto a solution of an optically absorbing solute in a cylindrical quartz tube, without substantial mixing of solution and solvent, is described. The spreading of the boundary thus formed may be monitored as a function of time using an automated absorbance scanning device previously described [A. K. Attri and A. P. Minton (1983) Anal. Biochem. 133, 142-152]. A semiautomatic procedure for determining the diffusion coefficient from the time dependence of the shape of the boundary is described and is particularly well-suited for real-time data analysis with a laboratory microcomputer. The diffusion coefficients of several proteins have been measured using the technique reported, and the results are generally in good agreement with values reported in the literature. The feasibility of using this technique in combination with a previously described method for measuring the sedimentation coefficient [A. K. Attri and A. P. Minton (1984) Anal. Biochem. 136, 407-415] to rapidly determine the molecular weight of a protein is established.

Diffusion↗
PubMed1988

Tracer diffusion of globular proteins in concentrated protein solutions.

The diffusion of tracer proteins at low concentration was measured in solutions containing "background" proteins at concentrations of up to 200 g/liter. The fractional reduction of the diffusion coefficient of tracer in the presence of a given weight/volume concentration of background species generally increases with increasing size of tracer species and with decreasing size of background species. The dependence of the diffusion constants of three out of four tracer species upon the concentrations of four background species is accounted for semiquantitatively by a simple hard particle model. Extrapolation of model calculations to higher background concentrations suggests that in solutions containing proteins at concentrations comparable to those found in biological fluid media, the diffusive transport of larger proteins and aggregates may be slower than in dilute solution by several orders of magnitude.

Algorithms↗