PubMed Health⌕ Search

Biomedical subjects

M Kumakura

Publications and source records attributed to M Kumakura.

At least 19 recordsLinked to original sources
PubMed1994

Appearance of high enzyme activity in immobilized urease disc by electron beam irradiation technique.

A new preparation method of immobilized urease discs for biomedical applications, which was a thin circular film (200 microns, 50mm phi), was developed. The method was achieved by electron beam irradiation of polyethyleneglycol diacrylate monomers in the addition of paper disc and bean powder as protective substance for irradiation by which a denaturation of the enzyme by irradiation was effectively prevented. The immobilized enzyme disc with a high enzyme activity (remaining activity yield), about 90%, was obtained. The enzyme activity was varied by the preparation conditions such as the thickness of paper disc, monomer concentration etc. The enzymes were trapped near the surface of the disc to be easily reacted with substrate. The trapped state of the enzymes appeared to be affected by a hydrophilicity of the polymers.

Electrons↗
PubMed1994

An ultrastructural study of the dorsal lingual epithelium of the rat snake, Elaphe quadrivirgata.

The histological characteristics and ultrastructure of the dorsal lingual epithelium of the rat snake, Elaphe quadrivirgata, were investigated by light microscopy and scanning and transmission electron microscopy. Most of the surface of the bifurcated part of the tongue was relatively smooth. Dome-shaped, hemispherical bulges were compactly arranged on the epithelial cell surface of the basal area of this region. Intercellular borders were clearly recognizable as striations. Microridges were densely distributed on the epithelial cell surface of the lingual body. Intercellular borders were thickened. A keratinized layer was clearly visible in the epithelium of the anterior bifurcated area, namely, at the apex of the tongue. Although keratohyalin granules were not found in any layer of the epithelium in this area, the cells of the surface layer were filled with keratin filaments. The dorsal lingual epithelium of the posterior area, namely, the lingual body, did not show any evidence of keratinization. Each cell on the surface side still had a large, oval nucleus and intact organelles, such as mitochondria, rough endoplasmic reticulum, ribosomes, tonofibrils, and tonofilaments. Cellular interdigitation was evident between adjacent cells and clear microridges or microvilli were observed on the cell membranes on the free-surface side of cells located in the surface layer. The phylogenetic relevance of these findings is discussed.

Animals↗
PubMed1994

Three-dimensional fine structure of the lingual papillae and their connective tissue cores in the human tongue.

The three-dimensional structure of the four types of lingual papillae and their connective tissue cores (CTCs) in the human tongue was studied by scanning electron microscopy after removal of the epithelial cell layer, and was compared to those of other mammalian species. Filiform papillae are densely distributed on the dorsal surface of the anterior two-thirds of the tongue. Each filiform papilla has numerous slender protrusions on the top. After removal of the epithelium, the CTC of the filiform papilla has a columnar primary core with 10-30 rod-shaped small secondary cores surrounding an upper central depression. A few long spine-like protrusions are frequently found in the center of this upper depression. The number, thickness and length of each secondary protrusion of the filiform CTC show some variations at the region distributed on the tongue. Fungiform papillae with spherical heads are scattered among these filiform papillae and are numerous at the anterior margin of the tongue. The CTC of the fungiform papilla shows a coralliform structure with numerous small rod-shaped protrusions on the lateral surface, and its branched top has flat areas with a few small round depressions harboring taste buds. It must be emphasized that human fungiform papilla has some taste buds not only in the young, but also in the adult age. Several to 12 vallate papillae are distributed in front of the terminal groove and had the CTC of pinecone-like structure with numerous small thorns (secondary connective tissue cores). Foliate papillae consist of 10-15 parallel folds at the posterior margin of the tongue. The CTC of the foliate papillae appears as ridges and grooves. Small protrusions are scattered on the surface of the ridges. The underside view of the exfoliated epithelium of the vallate as well as the foliate papillae revealed numerous taste buds arranged in single file in the lateral epithelium. The dorsal surface of the root of the tongue has evenly distributed short rod-shaped protrusions of the connective tissue.

Adolescent↗
PubMed1993

Dose-dependency of radiation on enzyme production in Trichoderma reesei.

Effect of irradiation dose on the production of cellulase and amylase related enzymes in Trichoderma reesei was studied, in which post-irradiation time response pattern was measured. The damage of the cells irradiated with certain irradiation doses (1.40 +/- 0.20 x 10(5), 2.20 +/- 0.10 x 10(5), 3.00 +/- 0.50 x 10(5) and 3.50 +/- 0.20 x 10(5) rad) was rapidly recovered. The increased enzyme production in the culture of the irradiated cells resulted from the recovery of radiation damage after irradiation. The function of cell growth was not affected by irradiation below dose of 5 x 10(5) rad, though the function of enzyme synthesis was drastically affected.

Amylases↗
PubMed1993

Recognition of microbial cells by the surface of polymers with oxyethylene units.

The recognition of microbial cells by the surface of polymers with oxyethylene units was investigated using the organism Trichoderma reesei, in which the surface was modified by the radiation polymerization method. The cells were recognized by their adhesion to the surface of the polymer giving a bioaffinity similar to cell fusion. The adhesion was affected by the molecular structure of the surface relating to the length of the oxyethylene unit, and enzyme productivity from the adhered cell walls was affected by the property of the polymer.

Cell Adhesion↗
PubMed1991

A new biodegradable copolymer of glycolic acid and lactones with relatively low molecular weight prepared by direct copolycondensation in the absence of catalysts.

Relatively low-molecular-weight copolyesters of glycolic acid (GA) with lactones such as gamma-butyrolactone (BL), delta-valerolactone (VL), and epsilon-caprolactone (CL) were synthesized by copolycondensation without catalysts. The resulting copolyesters are intended as carriers for drug delivery systems. Copolyesters with approximately 85 mol% GA (number-average molecular weight (Mn): 2900 +/- 100) are crystalline and solid and show a parabolic-type in vivo degradation pattern. The in vivo degradation of amorphous-pasty poly (GA/CL) (approximately 50/50 mol%) changed from parabolic-type to linear-type to S-type pattern as their molecular weight increased. A luteinizing hormone-releasing hormone agonist, [D-Leu6, des-Gly10]-LHRH ethylamide monoacetate (LHRH agonist), was incorporated into small cylinders with these copolyesters. An initial burst of LHRH agonist was observed for cylinders prepared with parabolic-type degrading copolyesters, in contrast to a marked delay in LHRH agonist release for cylinders prepared with S-type degrading copolyesters. The resulting daily dose of drug was maintained an approximately constant, though decreasing stepwise with time. For example, the daily amount of LHRH agonist released in vivo from a cylinder prepared with poly(GA/CL) (50/50 mol%; Mn = 4500) was 61 +/- 39 micrograms/day throughout an experimental period of 10 weeks with a corresponding pharmacological effect on the rat prostate.

Animals↗
PubMed1991

In vivo characteristics of high molecular weight copoly(L-lactide/glycolide) with S-type degradation pattern for application in drug delivery systems.

Amorphous copoly(L-lactide)/glycolide, 70/30 mol%) with weight average molecular weights of 16,900-41,300 were synthesized by ring-opening polymerization in the presence of catalysts using a molecular weight moderator lauryl alcohol. The in vivo degradation profiles of the copolyesters, which were evaluated by implanting them subcutaneously in the back of rats, showed a typical S-type degradation pattern. A luteinizing hormone-releasing hormone agonist (LH-RH agonist), des-Gly10-[Leu6]-LH-RH ethylamide monoacetate, was incorporated into the small cylinders of copoly (L-lactide/glycolide) with a weight average molecular weight of 24,000. The cumulative amount of drug released in vivo from the cylinders showed an S-type profile in analogy with the in vivo degradation pattern. This was demonstrated from data such as serum drug level and pharmacological influence on rat prostates.

Animals↗
PubMed1991

Evaluation of new pasty-type implantable devices consisting of poly(epsilon-caprolactone/delta-valerolactone) and Estracyt or estramustine.

Biodegradable pasty-type copolyesters with a relatively low molecular weight of 4500 were synthesized by direct copolycondensation of epsilon-caprolactone (CL) and delta-valerolactone (VL) in the absence of catalysts to evaluate in vivo capabilities of the polymer for implantable controlled release devices in drug delivery systems. The devices in cylindrical shape were prepared by the melt-pressing technique using pasty-type copoly(CL/VL) with 53 mol% CL unit, in which Estracyt and estramustine were used as a water soluble and insoluble drug, respectively. The degradation and drug release in vivo of the devices were examined by subcutaneous implantation in the backs of male rats. The degradation of the device was remarkably accelerated by the presence of hydrophilic Estracyt, and was slightly suppressed by hydrohobic estramustine. The estramustine release profile roughly corresponded to the polymer degradation one. It was found that the degradation of the polymer in the device was affected by hydrophilicity of the drug. A reasonable release of estramustine from the device was kept for a period of more than 20 weeks. Furthermore, the release of the drugs in vivo was able to lead to an atrophy of accessory sex organs such as ventral prostates (VP) and right-side seminal vesicle (SV), resulting in pharmacological influence.

Animals↗
PubMed1991

Thermo-responsive hydrogels based on acryloyl-L-proline methyl ester and their use as long-acting testosterone delivery systems.

New thermo-responsive hydrogels were synthesized by copolymerizing acryloyl-L-proline methyl ester (A-ProOMe) with minor amounts of 2-hydroxypropyl methacrylate (HPMA) or polyethylene glycol 600 dimethacrylate (14G), using gamma-rays from a 60Co source. In water, extensive swelling of the hydrogels occurred at 10 degrees C, but there was marked deswelling as the temperature was raised to 37 degrees C. The poly(A-ProOMe-co-HPMA) hydrogel was characterized by an initial rapid shrinkage at the surface in the deswollen state; this shrinkage arose because of the formation of a rigid membrane barrier devoid of micropores. The system is therefore 'surface regulated'. In contrast, no such a barrier formed in the deswollen poly(A-ProOMe-co-14G) hydrogel. The whole matrix shrunk without the disappearance of micropores, and it is therefore a 'matrix pumping' system. Testosterone was incorporated into both these types of hydrogels, and the drug-loaded hydrogels were implanted subcutaneously into the backs of castrated rats. The daily dose of testosterone released in vivo from the poly(A-ProOMe-co-HPMA) hydrogel was constant at approximately 30 micrograms/day throughout an experimental period of 54 weeks. In contrast, drug release from the poly(A-ProOME-co-14G) hydrogel reached a maximum after one week and then decreased linearly with time down to the 7th week, when it was undetectable. These conclusions were supported by the changes in weight of the ventral prostates and right-side seminal vesicles of the rats, which were restored to normal when delivery of the testosterone was sustained.

Animals↗
PubMed1990

Sequential polydepsipeptides as biodegradable carriers for drug delivery systems.

Sequential polydepsipeptides containing both peptide and ester bonds, poly[(L-alanyl)n-gamma-ethyl L-glutamyl-L-lactyl] (n = 0, 1, 2, and 3) (poly[(Ala)n-Glu(OEt)-Lac]), were prepared for application as biodegradable carriers for drug delivery systems. The in vivo degradation of these polymers was evaluated by subcutaneous implantation in the backs of male rats, and was strongly influenced by the number (n) of Ala units in poly[(Ala)n-Glu(OEt)-Lac]. The resulting poly(Ala-Ala-Glu(OEt)-Lac) gave the highest degradability, in which 100% degradation was observed 24 weeks from the start of implantation. A luteinizing-hormone-releasing hormone agonist des-Gly10-[D-Leu6]-LH-RH ethylamide (LH-RH agonist), was incorporated into a sequential poly(Ala-Ala-Glu(OEt)-Lac) carrier by the melt-pressing technique, which gave fine cylindrical polymer formulations with different structures of drug dispersion, e.g., blend-type and sandwich-type formulations. The rate of in vivo release of LH-RH agonist from a blend-type formulation showed a linear decrease with time until its release was finished after 6 weeks' implantation. In contrast, in a sandwich-type formulation, the in vivo release rate was apparently maintained constant over a period of 16 weeks (24 +/- 14 micrograms/day).

Amino Acid Sequence↗
PubMed1990

In vivo characteristics of low molecular weight copolymers composed of L-lactic acid and various DL-hydroxy acids as biodegradable carriers for drug delivery systems.

Low molecular weight and amorphous copolyesters composed of 70 mol% L-lactic acid and 30 mol% DL-hydroxy acids such as DL-lactic acid, DL-alpha-hydroxy-n-butyric acid, DL-alpha-hydroxyisovaleric acid and DL-alpha-hydroxyisocaproic acid were synthesized by direct copolycondensation in the absence of catalysts, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. For this purpose, the copolyester was moulded into a small cylindrical specimen under melt-pressing technique and implanted subcutaneously in the back of male adult rats. The in vivo degradation pattern can be subdivided into three types: the formations of parabolic type (L-LA/DL-HBA copolymer), linear type (L-LA/DL-LA copolymer) and S type (L-LA/DL-HIVA and L-LA/DL-HICA copolymers). A luteinizing hormone-releasing hormone agonist, des-Gly10-(D-Leu6)-LH-RH ethylamide monoacetate (LH-RH agonist), was incorporated into the small cylinders of copolyester formulations, of which the strongest pharmacological influence was observed in a copoly(L-LA/DL-HICA) formulation system, resulting in the maintenance of effective pharmacological influence throughout an experimental period of 15 wk, at which the in vivo release rate of LH-RH agonist was held constant at approximately 45 micrograms/d.

Animals↗
PubMed1990

Effects of Z-100 on mice exposed to gamma-irradiation: a preliminary report.

Subcutaneous administration of Z-100 twice a week starting immediately after supralethal whole-body irradiation of mice produced a prolongation of survival time. The effect of Z-100 on the hematopoietic system was thought to have contributed to the prolongation and was thus investigated. A single subcutaneous dose of Z-100 immediately after irradiation inhibited reduction of the total number of nucleated cells in the femoral bone marrow of the treated mice, although the inhibition was not by promotion of the proliferation of specific cells but by promotion of the recovery of multiple cell lines. Treatment with Z-100 promoted colony formation in the spleen of the treated mice and CFU-S formation in the femoral bone marrow, indicating that the drug accelerated the recovery of hematopoietic stem cells. The recovery of CFU-C count was also promoted by Z-100, which suggested that the drug has a restoring effect on the recovery of granulocytic and macrophagic precursor cells. Furthermore, Z-100 produced a greater increase in the CSF activity in the serum of irradiated mice, leading to the presumption that CSF induced by Z-100 was greatly involved in promoting the recovery of the above-mentioned hematopoietic stem cells. We conclude that Z-100 prolonged survival time of irradiated mice by promoting recovery of hematopoiesis of the mice.

Animals↗
PubMed1989

In vivo characteristics of low molecular weight copoly (D,L-lactic acid) formulations with controlled release of LH-RH agonist.

Amorphous and crystalline copolymers with a relatively low molecular weight of 1800 were synthesized by direct copolycondensation of D-lactic acid and L-lactic acid in the absence of a catalyst, to evaluate their in vivo capabilities as biodegradable carriers for drug delivery systems. A luteinizing hormone-releasing hormone agonist, des-Gly10-(D-Leu6)-LH-RH ethylamide, was incorporated in a fine cylindrical copolymer formulation, under melt-pressing technique, a mild heat-pressure condition. This formulation was implanted subcutaneously in the back of male rats. The rate of in vivo degradation of amorphous copolymer was much faster than that of crystalline copolymer. Contrary to this tendency, the in vivo release of the drug from this amorphous formulation was held constant over a longer period, compared with the crystalline formulation. This can be closely related to the difference in dispersion of the drug in the formulation.

Animals↗
PubMed1986

Mechanical properties of polymeric membranes obtained by radiation cast-polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers.

Polymeric membranes have been prepared by radiation cast-polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers, and the mechanical properties of the membranes before and after swelling have been studied as a function of the molecular structure of the monomers. The degree of hydration of the polymers from hydroxypolyethyleneglycol methacrylate monomers increased with increasing the number of ethyleneglycol units in the monomers, and that from hydroxyalkyl methacrylate monomers decreased with an increase in the number of methylene units. The mechanical properties such as tensile strength, tear strength, Young's modulus, and elongation at break varied with the length of the methylene and ethyleneglycol units in the monomers. It was found that flexible polymeric membranes having various properties for medical applications could be obtained by radiation cast-polymerization of hydroxyalkyl and hydroxypolyethyleneglycol methacrylate monomers.

Acrylates↗
PubMed1984

Preparation by irradiation of a solid support for enzyme immunoassay.

Reagents (immobilized anti-alpha-fetoprotein discs) having a porous structure were prepared for enzyme immunoassay of alpha-fetoprotein by radiation polymerization at low temperatures. Discs were attached to sticks for easy handling. The activity (determined by absorbance at 492 nm) of the discs varied with the hydrophilic properties and size of the disc. The discs are sufficiently sensitive and precise for enzyme immunoassay of alpha-fetoprotein.

Animals↗