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Biomedical subjects

Y Takakura

Publications and source records attributed to Y Takakura.

At least 109 records · Page 6Linked to original sources
PubMed1998

Uptake and gene expression of naked plasmid DNA in cultured brain microvessel endothelial cells.

Cellular uptake and gene expression of plasmid DNA and its cationic liposome complexes were studied using primary cultures of bovine brain microvessel endothelial cells (BMEC) developed as an in vitro model of the blood-brain barrier. An avid association of naked plasmid DNA with the BMEC monolayer was observed at 37 degreesC, which is comparable to that of the DNA/liposome complex. The cellular association significantly decreased at low temperature (4 degreesC). The binding at 4 degreesC was saturable and significantly inhibited by polyanions involving polyinosinic acid and dextran sulfate, typical ligands for the macrophage scavenger receptors, but not by polycytidylic acid or in the presence of EDTA. Unexpectedly, a significant gene expression in the BMEC was obtained by transfection with naked plasmid DNA although the expression level was lower than that obtained by plasmid DNA/cationic liposome complex. Taken together, cultured capillary endothelial cells derived from the brain are able to take up naked plasmid DNA via a scavenger receptor like-mediated mechanism for polyanions and gene expression in the cells takes place.

Animals↗
PubMed1998

Pharmacokinetic characteristics and therapeutic effects of mitomycin C-dextran conjugates after intratumoural injection.

The pharmacokinetics and therapeutic effects of macromolecular prodrugs of mitomycin C (MMC), MMC-dextran conjugates (MMC-D) were studied after intratumoural injection in rats bearing Walker 256 carcinosarcoma. As the first step, the intratumoural disposition characteristics of these drugs were delineated in perfusion experiments employing a tissue-isolated tumour preparation. While MMC immediately disappeared from the tumour preparation following direct intratumoural injection, cationic and anionic MMC-D were retained in the tumour longer, demonstrating that the intratumoural clearance of MMC can be greatly retarded by dextran conjugation. The effect was more pronounced in the case of the cationic conjugate. Venous outflow data in the perfusion experiments were analyzed based on a compartment model in which the tumour tissue was assumed to consist of two compartments, one well- and the other poorly-perfused. The pharmacokinetic analysis revealed that macromolecular conjugation reduced elimination of MMC from the poorly-perfused region rather than well-perfused region. Simulation of conjugated and free MMC levels in the tissue using the calculated parameters clearly showed that intratumoural injection of MMC-D, especially the cationic form, can maintain a certain level of active free MMC in the tissue for a much longer time period. The long retention of cationic MMC-D in tumour after intratumoural injection was also confirmed by an in vivo pharmacokinetic study and whole body autoradiography in rats bearing subcutaneous Walker 256 carcinosarcoma. In addition, superior antitumour activity of cationic MMC-D was observed against subcutaneous tumours after intratumoural injection. Together with the finding that MMC is selectively toxic to hypoxic tumour cells at low concentrations, these pharmacokinetic studies strongly support the therapeutic efficacy of the macromolecular prodrugs.

Animals↗
PubMed1998

Pharmacokinetic analysis of hepatic uptake of galactosylated bovine serum albumin in a perfused rat liver.

Hepatic uptake of 111In-labelled galactosylated bovine serum albumin (Gal-BSA) with different number of galactose residues per BSA were studied in rat liver perfusion experiments. During a single-pass constant infusion mode, [111In]Gal-BSAs (0.1-2.0 micrograms/ml) were continuously extracted by the liver and its extraction ratio at steady-state (Ess) was lowered as the inflow concentration increased. Hepatic clearance of [111In]Gal-BSAs increased significantly according to the increase in the number of galactose residues per BSA at an inflow concentration of 0.7 micrograms/ml. The outflow patterns of [111In]Gal-BSAs at various inflow concentrations were simultaneously fitted to a one-organ pharmacokinetic model, by which we can characterize their binding to the cell surface and internalization processes separately. The parameters obtained were varied significantly among [111In]Gal-BSAs depending on the number of galactose residues and indicate that not only the binding to the receptors but also the internalization after the binding are regulated by the number of galactose residues per BSA during hepatic uptake.

Animals↗
PubMed1998

Age-related changes of element contents in the human meniscus.

The relative contents (RCs) of elements in the human menisci from 23 subjects in the age range between 65 and 93 yr were analyzed by inductively coupled plasma atomic emission spectrometry. The RCs of sulfur, calcium, and phosphorus in menisci increased progressively until the 80s, being the highest in the 80s, and thereafter decreased. The RCs of magnesium in menisci increased progressively until the 90s. Regarding the medial and lateral menisci, higher RCs of magnesium and iron, and a lower RC of phosphorus were found in lateral menisci in comparison with those in medial menisci. There were sexual differences in the RCs of calcium and phosphorus of medial and lateral menisci. The RCs of calcium and phosphorus were about 50% higher in women's menisci than in men's. Histological examinations showed that structureless mucoid masses were observed in the menisci, with very high RCs of calcium and phosphorus being detected.

Aged↗
PubMed1998

Effect of particle size and charge on the disposition of lipid carriers after intratumoral injection into tissue-isolated tumors.

PURPOSE: Pharmacokinetic properties of various lipid carriers (liposome and emulsions) after intratumoral injection were studied in perfusion experiments using tissue-isolated tumor preparations of Walker 256 carcinosarcoma. METHODS: Four types of lipid carriers, large emulsion (254 nm), small emulsion (85 nm), neutral liposomes (120 nm) and cationic liposomes (125 nm) were prepared. We quantified their recovery from the tumor, leakage from the tumor surface and venous outflow after intratumoral injection into perfused tissue-isolated tumors, and analyzed venous appearance curves based on a pharmacokinetic model. RESULTS: In contrast to the small emulsion and neutral liposomes, which immediately appeared in the venous outflow perfusate following intratumoral injection, the appearance of the cationic liposomes and the large emulsion was highly restricted, clearly demonstrating that intratumoral clearance of these formulations can be greatly retarded by the cationic charge and large particle size, respectively. The venous appearance rate-time profiles were fitted to equations derived from a two-compartment model by nonlinear regression analysis. When the calculated parameters were compared among these four formulations, the venous appearance rate did not exhibit such a large difference; however, the rate of transfer from the injected site to the compartment which involves clearance by venous outflow was all very different. CONCLUSIONS: The results of this study indicate that the determining factor which alters the pharmacokinetic properties of these lipid carriers after intratumoral injection is not the rate of transfer from the interstitial space to the vascular side but the rate of intratumoral transfer from the injection site to the well-vascularized region.

Animals↗
PubMed1998

Cellular uptake properties of oligonucleotides in LLC-PK1 renal epithelial cells.

The objective of this study was to clarify the renal uptake characteristics of oligonucleotides at a cellular level using LLC-PK1 renal epithelial cells derived from the proximal tubule. The association of [35S]-labeled 20-mer phosphodiester (PO) and phosphorothioate (PS) oligonucleotides with the monolayers of polarized LLC-PK1 cells cultured on polycarbonate filter was characterized after apical or basolateral application. The cellular association of PO and PS at both apical and basolateral membranes was time dependent and temperature dependent, and the apparent association amount of PS was larger than that of PO. The PO and PS association after apical application was saturable, with the apparent Km and Vmax values determined to be 5.4 microM and 0.14 nmol/mg protein for PO and 0.22 microM and 0.11 nmol/mg protein for PS, respectively. In contrast, almost linear kinetics were observed after basolateral application within a tested concentration range. The association was inhibited significantly by sodium azide and chloroquine, suggesting that an energy-dependent endocytotic process was involved. Internalization and subsequent transport to endosome and lysosome compartments of FITC-labeled oligonucleotides were shown by confocal laser scanning microscopy. The present study has demonstrated that both types of oligonucleotides are taken up by LLC-PK1 cells from both apical and basolateral surfaces probably via an endocytosis mechanism.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1998

Cationic liposome-mediated efficient induction of type I interferons by a low dose of poly I:poly C in mouse cell lines.

Double-stranded polyriboinosinic acid:polyribocytidylic acid (poly I:poly C) is a powerful inducer of type I interferons (IFNs). However, the dose of poly I:poly C required for efficient IFN induction is so high as occasionally to be cytotoxic. In this work, we examined the IFN-inducibility of poly I:poly C complexed with several cationic reagents in mouse fibroblast L cells and found that Lipofectin and LipofectACE can induce the production of a substantial amount of type I IFNs (mostly beta-type) even at a two-order lower dose compared with poly I:poly C alone. Such effects of poly I:poly C were optimal at 0.1 microgram/ml for 2-10 microgram/ml of Lipofectin and LipofectACE. These conditions caused no significant cytotoxicity in the recipient cells. Furthermore, a short treatment (less than 10 min) with the complexes was sufficient for the maximum induction. This IFN induction method was applicable to other cell types and other species including human. Hence, our observations may pave the way for clinical application of the IFN inducer.

Animals↗
PubMed1998

Histopathological study of nonosseous tarsal coalition.

Histopathological analysis was performed on 55 feet in 48 patients with nonosseous tarsal coalitions. Histological findings were similar to those observed at the tendinous attachment site of Osgood-Schlatter disease, accessory navicular, and bipartite patellae. No nerve elements were observed in the fibrocartilaginous tissue at the coalition. Nerve elements were present only in periosteum and articular capsule surrounding the coalition. Pain in the tarsal coalition is not mediated by nerve elements at the coalition site itself. It is assumed that the pain is caused by mechanical abnormality that results from incomplete coalition. Incomplete coalition produces microfractures and remodelings on the boundaries between bone and the coalition, which then lead to degenerative changes. This mechanical abnormality seems to induce pain via free nerve endings in the periosteum and in the articular capsule surrounding the coalition.

Adolescent↗
PubMed1998

Hepatic disposition characteristics of recombinant human interleukin-11 (rhIL-11) in the perfused rat liver.

The hepatic disposition characteristics of recombinant human interleukin-11 (rhIL-11) were investigated in perfused rat liver to clarify the mechanism of hepatic clearance which is a major contributor to the rapid clearance of rhIL-11 in vivo. We analyzed the disposition characteristics of [(111)In]-labeled rhIL-11 using a single-pass constant infusion mode at different concentrations of rhIL-11. The venous outflow rapidly reached a steady-state condition at every concentration. Liver extraction ratio at steady-state (Ess) was decreased with increase in the concentration, suggesting that there is a saturable interaction between the liver cells and rhIL-11 molecule. Cellular localization experiments demonstrated that rhIL-11 was taken up by both liver parenchymal and nonparenchymal cells depending on their surface area, suggesting that this uptake was mediated by electrostatic interaction due to cationic charges in the cytokine.

Animals↗
PubMed1998

Control of plasma cholesterol-lowering action of probucol with various lipid carrier systems.

In order to explore the relationship between the pharmacokinetic properties and pharmacological actions of lipophilic drugs injected with lipid carrier systems, probucol was selected as a model drug with high lipophilicity, and the effect of disposition control on cholesterol-lowering activities was evaluated. Both large emulsion, with mean diameter of 280 nm, and long-circulating type small emulsion containing egg sphingomyelin with mean diameter of 100 nm, showed stable incorporation of probucol. The former produced rapid accumulation of probucol in the liver, while the latter demonstrated prolonged systemic circulation and gradual hepatic uptake. On the other hand, injection of a micellar solution with HCO-60 (polyoxyethylene hydrogenated castor oil) showed a rapid decrease in plasma concentration and a high hepatic uptake of probucol, similar to injections with serum, suggesting the rapid release of the drug from the micelles. However, probucol in a micellar solution showed higher cholesterol-lowering action than that in emulsion formulations. These results suggested that the pharmacological action of probucol in the liver might be affected by the uptake mode and sequential disposition in the organ, depending on the drug retention properties of the lipid carrier particles.

Animals↗
PubMed1998

Tarsal tunnel syndrome caused by coalition associated with a ganglion.

We examined seven patients with tarsal tunnel syndrome in one foot caused by talocalcaneal coalition and a ganglion. We excised the coalition and the ganglion in six of them. All the patients had pain, sensory disturbance in the sole, and a positive Tinel's sign. Older patients with a long history showed atrophy and weakness of the plantar muscles. Talocalcaneal coalition can be diagnosed on a plain lateral radiograph and an anteroposterior radiograph externally rotated 20 degrees, and confirmed by CT. MRI is also useful for diagnosis. The coalitions were medial, and the ganglion had developed from the incomplete part of the coalition; it was multilocular in some patients. After resection, there was early pain relief but sensory disturbances and Tinel's sign persisted. The postoperative results were excellent in one patient, good in four and fair in one.

Adolescent↗
PubMed1998

Subtalar arthrography in acute injuries of the calcaneofibular ligament.

We treated 43 acute tears of the calcaneofibular ligament by operation in 43 patients after subtalar arthrography. There were 22 men and 21 women with a mean age of 22.3 years (14 to 61). Anteroposterior (AP), lateral and oblique views were obtained with the foot in 45 degrees of internal rotation and the ankle in the neutral position. Any communication or leakage to the ankle, tendon sheaths, subcutaneous tissue and sinus tarsi was recorded. We examined an oblique view of the microrecess along the interosseous ligament and an AP view of the lateral recess just under the distal end of the fibula. We also studied a control group of 27 patients with isolated injuries of the anterior talofibular ligament without rupture of the calcaneofibular ligament. The findings in the two groups were significantly different when examined for leakage to the ankle (p=0.0002), to the peroneal tendon sheaths (p=0.0347) and to the subcutaneous tissue (p=0.0222), absence of the microrecess (p=0.0055) and presence of the lateral recess (p=0.0012). Many ankle sprains which involve tearing of the calcaneofibular ligament are accompanied by injuries of the subtalar joint. Combined injuries of the anterior talofibular ligament and calcaneofibular ligament, and isolated injury of the anterior talofibular ligament should be differentiated.

Adolescent↗
PubMed1998

Results of opening-wedge osteotomy for the treatment of a post-traumatic varus deformity of the ankle.

We performed a one-stage opening-wedge valgus osteotomy in nine patients to correct a post-traumatic progressive varus deformity of the ankle. The osteotomy site was stabilized with two, three, or four Kirschner wires or with a plate and screws (in one patient). The site of the osteotomy united within two months after the operation in eight patients and at six months in one patient who was fifty-nine years old. The average duration of follow-up was seven years and four months (range, two years and four months to thirteen years and two months). Postoperatively, the range of motion of the ankle was decreased in six patients and remained unchanged in three. However, none of the patients reported any limitation in the activities of daily living, and the four adolescent patients were able to participate in sports activities. The result was graded as excellent for four ankles, good for two, and fair for three.

Activities of Daily Living↗