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Y Takakura

Publications and source records attributed to Y Takakura.

At least 145 records · Page 8Linked to original sources
PubMed1997

Development of targeted delivery systems for nucleic acid drugs.

Our increased understanding of disease pathogenesis is the basis for developing novel nucleic acid drugs. The main challenge encountered in this development is how to maintain therapeutically meaningful concentrations of the drugs in the vicinity of their targets for the desired periods. The intrinsic difficulty arises from the fact that nucleic acid drugs are not readily transported across membranes. Hence, their delivery and transport characteristics at the whole body, organ and cellular levels need to be thoroughly examined. Liposomes and receptor-mediated polycation systems are promising carriers for their delivery in vivo. There are many barriers to be overcome for successful antisense and gene therapies. Along with other factors, disposition, stability against nucleases, binding to cell surface receptor and internalization, and intracellular trafficking affect the in vivo delivery and efficacy of nucleic acid drugs. This review article discusses the delivery and transport of these compounds.

Animals↗
PubMed1997

[Cancer gene therapy by direct intratumoral injection: gene expression and intratumoral pharmacokinetics of plasmid DNA].

Pharmacokinetic properties and gene expression of naked plasmid DNA and its cationic liposome complexes after intratumoral injection were studied. Using Walker 256 tissue-isolated tumor perfusion system, we quantified the recovery of naked plasmid DNA and cationic liposome complexes in the tumor, leakage from the tumor surface and the venous outflow after intratumoral injection. Approximately 50% of naked plasmid DNA was eliminated from the tumor at 2 hr after injection, while more than 90% of plasmid DNA was retained in the tumor when complexed with cationic liposome. However, distribution of these complexes in the tumor was restricted only in the vicinity of the injection site. Furthermore, we have examined the expression of chloramphenicol acetyltransferase (CAT) DNA constructs (naked pCMV-CAT) and its cationic liposome (DC-chol) complexes after intratumoral injection into subcutaneous rat Walker 256 carcinosarcoma. Significant gene expression was observed in both cases, but localization of gene expressing cells in the tumor tissue was limited to the vicinity of the injection site. Thus the pharmacokinetic and gene expression studies have demonstrated that in vivo gene expression in the tumor can be achieved by direct injection of naked plasmid DNA. In addition, there is a possibility that restricted localization of naked DNA and its cationic liposome complexes in tumor inhibits gene expression.

Animals↗
PubMed1997

Nonviral vectors for in vivo gene delivery: physicochemical and pharmacokinetic considerations.

The use of nonviral vectors is an attractive in vivo gene delivery strategy that is simpler than, and lacks some risks inherent in, viral systems. Liposomes and receptor-mediated polycation systems are promising carriers for delivery and expression of plasmid DNA encoding genes into the target cells. Many barriers need to be overcome for successful in vivo DNA delivery using these carrier systems. Such factors as extent of DNA condensation, particle size of the DNA complex, route of administration, stability against nucleases, target sites, in vivo disposition, binding to cell surface receptor and internalization, and intracellular trafficking affect in vivo gene delivery and expression. This review will provide a critical discussion of the merits and limitations of liposomal and polycationic carrier systems for gene transfer from the viewpoints of their physicochemical and pharmacokinetic properties.

Animals↗
PubMed1996

A long-term study of the donor-site ankle after vascularized fibula grafts in children.

We reviewed the long-term course of the donor-site ankle after vascularized fibula grafts in 13 children. The preventive and therapeutic effects of the tibio-fibular metaphyseal synostosis (T-F synostosis) against valgus ankle deformity, which is one of the postoperative donor-site problems, were evaluated based on three radiologic and clinical parameters. Thirteen patients were divided into two groups: patients with or without simultaneous T-F synostosis when the fibula was taken. Three patients underwent T-F synostosis secondarily after the development of the valgus deformity. Follow-up periods averaged 12.4 years. In the patients with primary T-F synostosis, valgus deformity was only observed in one case. No functional disorder of the ankle joints was observed after T-F synostosis. In the patients without T-F synostosis, all the patients younger than 8 years old showed valgus deformity, in which the tilting angle averaged 6.3 degrees. In the three patients who underwent T-F synostosis secondarily, the tilting angle normalized in cases in which the fixation was performed when the lateral wedging was in a mild stage. There was a statistically significant difference in valgus tilt angle between the two groups (with or without T-F synostosis).

Adolescent↗
PubMed1996

Histological and biochemical evaluation of osteogenic response in porous hydroxyapatite coated alumina ceramics.

We compared the osteogenic response in porous alumni (Al) and hydroxyapatite coated porous alumni ceramic (HA/Al) by grafting rat bone marrow cells with these implants subcutaneously in the back of syngeneic rats. The ceramics did not show any bone formation without marrow, but did when combined with marrow cells. The osteogenesis in HA/Al began directly on the ceramic surface, but in Al began away from the ceramic surface, and fibrous tissue interposition was seen between the de novo bone and its surface. Alkaline phosphatase activity and bone specific bone gla protein content in HA/Al with marrow were both about three times higher than in Al with marrow. These results indicate that HA/Al has excellent osteoconductive properties and that a composite of marrow and HA/Al is clinically applicable osteogenic biomaterial.

Alkaline Phosphatase↗
PubMed1996

Theoretical design of prodrug-enhancer combination based on a skin diffusion model: prediction of permeation of acyclovir prodrugs treated with 1-geranylazacycloheptan-2-one.

PURPOSE: A theoretical design of percutaneous penetration enhancement in which prodrug derivation and enhancer application are combined is proposed based on the skin diffusion model and it is experimentally verified. METHODS: Employing acyclovir as a model drug, the hypothesis was tested by synthesis of its prodrugs and evaluation of their in vitro permeation in the rat skin, with or without a penetration enhancer, 1-geranylazacycloheptan-2-one(GACH). RESULTS: Among five acyclovir prodrugs, those with higher lipophilicities (propionate, butyrate, valerate, and hexanoate prodrugs) showed greater skin penetration than those of hydrophilic prodrugs (acetate), when administered in combination with GACH. Furthermore, the observed enhancement ratios were in good agreement with those predicted by theoretical consideration. CONCLUSIONS: Thus, skin permeation of prodrugs applied with an enhancer can be predicted and optimized by model analysis.

Acyclovir↗
PubMed1996

Development and pharmacokinetics of galactosylated poly-L-glutamic acid as a biodegradable carrier for liver-specific drug delivery.

PURPOSE: A biodegradable carrier for the liver-specific delivery of drugs was developed using poly-L-glutamic acid (PLGA) modified with galactose (galactosylated PLGA or Gal-PLGA), and its feasibility was investigated in mice. METHODS: 111In-PLGA and 111In-Gal-PLGAs were injected in mice and their distribution and biodegradation properties were studied. RESULTS: After intravenous injection. 111In-PLGA was rapidly eliminated from the plasma and recovered mainly in the kidneys and urine. Approximately 15% of the dose was recovered in the liver, predominantly in the nonparenchymal cells. 111In-Gal-PLGAs were taken up by the liver parenchymal cells. Derivatives having 16 or more galactose residues were taken up by the liver to a higher extent (> 60% of the dose). The hepatic clearance of 111In-Gal-PLGAs correlated with their number of galactose residues. 111In-Gal18-PLGA was degraded into low-molecular weight products in the liver. CONCLUSIONS: The advantageous in vivo properties of Gal-PLGA as a liver-specific biodegradable carrier of drugs were demonstrated in mice.

Animals↗
PubMed1996

Pharmacokinetic analysis of drug disposition after intratumoral injection in a tissue-isolated tumor perfusion system.

PURPOSE: The purpose of this study was to establish an experimental system for evaluation of the intratumoral behavior of drugs after intratumoral injection using perfused tissue-isolated tumor preparations of Walker 256 carcinoma (3.46-9.73g, n = 16). METHODS: We quantified the recovery of Phenol Red (model drug) in the tumor, leakage from the tumor surface and the venous outflow after intratumoral injection using perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model in which the tumor tissue was assumed to be divided into two compartments, i.e., well- and poorly-perfused regions. RESULTS: In small tumors (Type 1, 5.42 +/- 0.39 g), the drug appeared immediately in the venous outflow, and the amount remaining in the tumor tissue at 2 hr after injection was small. In contrast the venous appearance rate reached a significantly lower peak a few minutes after injection, and a large amount of injected drug remained in some large tumors (Type 2.8.17 +/- 0.51 g). Pharmacokinetic analysis revealed that there was a correlation between tumor weight and the rate constants of transfer from the poorly-perfused region to the well-perfused region, and between the rate constants of transfer from the well-perfused region to the venous outflow and dosing ratios into the well-perfused region. CONCLUSIONS: An experimental system and analytical method were established for the evaluation of the intratumoral behavior of drugs after intratumoral injection using a tissue-isolated tumor perfusion system. This experimental system will be useful in analyzing the antitumor drug disposition after intratumoral injection.

Animals↗
PubMed1996

Disposition characteristics of plasmid DNA in the single-pass rat liver perfusion system.

PURPOSE: To define the hepatic uptake mechanism of a plasmid DNA, we quantitated the uptake of pCAT (plasmid DNA encoding chloramphenicol acetyltransferase reporter gene fused to simian virus 40 promoter), a model plasmid, after a single pass through the perfused rat liver using albumin- and erythrocyte-free Krebs-Ringer bicarbonate buffer (pH 7.4). METHODS: [32P]pCAT was introduced momentarily into this system from the portal vein as a bolus input or constant infusion mode, and the outflow patterns and hepatic uptake were evaluated using statistical moment analysis. RESULTS: The venous outflow samples had electrophoretic bands similar to that of the standard pCAT, suggesting that the plasmid is fairly stable in the perfusate during liver perfusion. In bolus experiments, pCAT was largely taken up by the liver and the uptake was decreased with increase in injected dose. Statistical moment analysis against outflow patterns demonstrated that the apparent volume of distribution of pCAT was greater than that of human serum albumin, indicating a significant reversible interaction with the tissues. The results of collagenase perfusion experiments suggest that the hepatic accumulation of pCAT occurred preferentially in the nonparenchymal cells (NPC). The amount of total recovery in the liver decreased substantially by preceding administration of polyinosinic acid, dextran sulfate, succinylated bovine serum albumin, but not by polycytidylic acid. This suggests that pCAT is taken up by the liver via scavenger receptors for polyanions on the NPC. In constant infusion experiments, the presence of 2,4-dinitrophenol and NH4Cl caused a significant increase in the outflow concentration of [32P]pCAT and decrease by half in the total hepatic recovery than that of plasmid DNA administered alone, suggesting that plasmid DNA may undergo internalization by the NPC. CONCLUSIONS: The liver plays an important role in the elimination of plasmid DNA and a successful delivery system will be required to avoid its recognition by the scavenger receptors on the liver NPC.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1996

Macromolecular carrier systems for targeted drug delivery: pharmacokinetic considerations on biodistribution.

This review article describes the current status and future perspectives of site-specific drug delivery by means of macromolecular carrier systems. Basic aspects and recent advances of targeted delivery of 1) conventional drugs, 2) protein drugs, and 3) gene medicines including antisense oligonucleotides and plasmid DNA, are reviewed from a pharmacokinetic perspective. Successful in vivo application of macromolecular carrier systems requires pharmacokinetic considerations at whole body, organ, cellular and subcellular levels. The integration of simultaneous research progress in the multidisciplinary fields such as biochemistry, cell and molecular biology, pharmacology, and pharmacokinetics will accelerate the emergence of marketed drugs with macromolecular carrier systems.

Animals↗
PubMed1996

Uptake characteristics of oligonucleotides in the isolated rat liver perfusion system.

The objective of this study was to examine the hepatic disposition characteristics of 20-mer model phosphodiester oligonucleotide (PO) and its partially phosphorothioated (PS3) and fully phosphorothioated (PS) derivatives in the single-pass isolated rat liver perfusion system. [32P]-labeled oligonucleotides were momentarily introduced into this system through the portal vein as a bolus input mode, and the venous outflow patterns were evaluated using statistical moment analysis. The apparent volumes of distribution of these oligonucleotides were greater than those of reference substances for vascular space (erythrocytes) and extracellular space (human serum albumin), indicating a significant interaction between oligonucleotides and the liver. Significant hepatic uptake of oligonucleotides was also observed. About 20%, 36%, and 52% of the injected dose (3 micrograms/rat) was taken up by the liver during a single passage after bolus injection of PO, PS3, and PS, respectively. In the case of PS injection, slow efflux from the liver was observed in the latter phase of perfusion. This suggests that the hepatic uptake process of these oligonucleotides greatly depended on their types. The results of collagenase perfusion experiments suggest that PS3 oligonucleotides were taken up by both liver parenchymal and nonparenchymal cells. The amount of total recovery in the liver decreased substantially by coadministration of polyinosinic acid, dextran sulfate, polycytidic acid and 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid. This suggests that PS3 was taken up by the liver as an anionic molecule in a nonspecific manner.

Animals↗
PubMed1996

Isolated first naviculocuneiform joint coalition.

Clinical analysis was performed on 60 feet in 40 patients with isolated first naviculocuneiform coalitions. The most common symptom was a mild pain at the medioplantar site of the first naviculocuneiform joint. Fifteen feet (25%) were asymptomatic. Some cases had been treated erroneously as osteoarthritis or bony cyst before diagnosis. We divided coalitions morphologically into three patterns based on computed tomography findings: irregular, cystic, and combined pattern. Based on the mean age of each pattern, we hypothesized that initial irregular coalitions gradually develop into cystic and, finally, combined patterns. Considering the modest number of reported cases, this condition might easily be overlooked in many patients or may be related to ethnic characteristics. We suggest that the actual incidence of first naviculocunei-form coalitions should be investigated again.

Adolescent↗
PubMed1996

Japanese triplets with cerebrotendinous xanthomatosis are homozygous for a mutant gene coding for the sterol 27-hydroxylase (Arg441Trp).

We present the first case of triplets with cerebrotendinous xanthomatosis (CTX). A C-to-T base change identified in the genomic DNA and cDNA encoding the sterol 27-hydroxylase led to replacement of arginine by tryptophan at position 441 (Arg441Trp) in the triplets. The triplets were homozygous and their mother was heterozygous for this mutant gene. The triplets exhibited an identical phenotypic expression, which was different from that of a sporadic CTX case with the same mutation.

Adult↗
PubMed1996

[Development of drug delivery systems for macromolecular drugs].

With a rapid progress in biotechnology, a variety of endogenous macromolecular substances have become a novel class of therapeutic agents. This review will focus on the development of delivery systems for macromolecular drugs. Current status and future perspectives in this research field are reviewed mainly based on the results obtained in our laboratory. First of all, we studied pharmacokinetic characteristics of macromolecules in relation to their physicochemical properties such as molecular weight and electric charge. Based on this information, we first developed macromolecular prodrugs as a delivery system for low molecular weight drugs. An antitumor antibiotic, mitomycin C (MMC) were covalently conjugated with dextran and various types of macromolecular prodrug of MMC were developed for tumor targeting. Secondly, delivery systems for protein drugs such as soybean trypsin inhibitor, uricase, and recombinant superoxide dismutase (SOD) were developed. In particular, successful targeting of SOD to the liver, kidney and blood circulation was achieved by chemical modification of the protein drug. Finally, we have been trying to develop delivery systems for nucleic acid drugs involving antisense oligonucleotides and plasmid DNA. Prior to the development of delivery systems, we found that the pharmacokinetics of the nucleic acid drugs are decided by their physicochemical properties as polyanions even if these materials contain genetic information. Several approaches were tested to control the in vivo behavior of the oligonucleotides and plasmid DNA based on the finding. Thus, we have established the strategy for rational design of delivery systems for various types of macromolecular drugs based on the pharmacokinetic considerations. This methodology can be a formidable tool for the development of clinically applicable macromolecular drugs.

Antibiotics, Antineoplastic↗
PubMed1996

Biliary excretion of polystyrene microspheres with covalently linked FITC fluorescence after oral and parenteral administration to male Wistar rats.

To further our understanding of microspheres as a drug delivery system, the biliary excretion of covalently linked FITC fluorescence polystyrene microspheres of various diameters was investigated after oral and parenteral administration to male Wistar rats. About 36%, 16% 3% and 1% of the dose was excreted into the bile after parenteral injection of 50 nm, 500 nm, 1 micron and 3 microns diameter microspheres, respectively, over 24 h. In addition, about 30%, 11%, 1%, and 1% of the dose, respectively, was found in the blood at 24 h. After oral administration of 50 nm, 500 nm, and 1 micron microspheres, the recovery was about 18%, 8% and 1% of the dose in the bile and about 9%, 1%, and 0% in the blood, respectively. No 3 microns microspheres were detected in the bile or blood after oral administration. Particles were not detected in the urine of any group tested. Thus, the present study demonstrated that biliary excretion plays an important role in the disposition of microspheres administered by the oral or parenteral routes, and there is a size-related excretion of microspheres into the bile.

Administration, Oral↗
PubMed1996

[Infections mononucleosis with pleural effusion].

A 24-year-old man was admitted to our hospital for further examination of pleural effusion. On physical examination, he had a temperature of 39 degrees C, the pharynx was painful and liver and spleen were enlarged. The leukocyte count was 5,700/microliters (atypical lymphocyte 6%). The serum LDH, GOT, GPT, ALP and gamma-GTP levels were elevated, and antibodies to Epstein-Barr viral capsid, early, and nuclear antigens were diagnostic of a primary Epstein-Barr virus infection. The CD4/CD8 ratio of peripheral blood lymphocyte was decreased to 0.2. The pleural effusion was exudate, and infiltration of mononuclear cells was noted. The CD4/CD8 ratio of lymphocytes in the effusion also was decreased to 1.1. The result of pleural biopsy showed a perivascular infiltration of mononuclear cells and immunological stain showed that the infiltrated cells were dominantly T-lymphocytes (about 90%). These findings suggested that the pathogenesis of pleural effusion in infectious mononucleosis was a pleulitis due to the infiltration of T-lymphocytes. Pleural effusion is known as a rare complication of infectious mononucleosis.

Adult↗