Biomedical subjects

Y Takakura

Publications and source records attributed to Y Takakura.

At least 181 records · Page 10Linked to original sources

PubMed1994

In vivo and in vitro analysis of skin penetration enhancement based on a two-layer diffusion model with polar and nonpolar routes in the stratum corneum.

In vitro and in vivo skin penetration of three drugs with different lipophilicities and the enhancing effects of 1-geranylazacycloheptan-2-one (GACH) were studied in rats. In vivo drug absorption profiles obtained by deconvolution of urinary excretion profiles were compared to the corresponding in vitro data obtained with a diffusion experiment. In vivo skin penetration of lipophilic butylparaben was considerably greater than that observed in vitro, while hydrophilic mannitol and acyclovir showed low penetration in both systems without GACH pretreatment. On the other hand, GACH enhanced mannitol and acyclovir penetration, especially in the in vivo system. Analysis of absorption profiles, using a two-layer skin model with polar and nonpolar routes in the stratum corneum, suggested that the diffusion length of a viable layer (viable epidermis and dermis) was shorter in vivo than in vitro and the effective area of the polar route in the stratum corneum was larger in vitro without GACH pretreatment. GACH increased the partitioning of acyclovir into the nonpolar route to the same extent in both systems. In addition, GACH increased the effective area of the polar route in vivo, probably because of enhanced water permeability; however, this effect was smaller in vitro since the stratum corneum was already hydrated even without GACH pretreatment.

Acyclovir↗

PubMed1994

Skin penetration enhancement of acyclovir by prodrug-enhancer combination.

The effectiveness of prodrug-enhancer combination in skin penetration enhancement was studied using acyclovir and its lipophilic prodrug, acyclovir butyrate, with octanol/water partition coefficient of 0.0123 and 0.402, respectively. In the in vitro diffusion experiment with rat skin, the total amount of acyclovir appearing in the receptor phase after administration of the aqueous suspension of acyclovir butyrate was smaller than that obtained after administration of acyclovir, but their permeability coefficients were almost equal. An enhancer, 1-geranylazacycloheptan-2-one (GACH) did not show a large penetration enhancement of acyclovir (3.37-fold) but demonstrated extensive enhancement effect on the prodrug (12.3-fold). Most of the prodrug appeared in the form of acyclovir in the receptor phase without GACH, but the appearance ratio of acyclovir to total flux decreased with an increase in pretreatment doses of GACH.

Acyclovir↗

PubMed1994

Long circulating emulsion carrier systems for highly lipophilic drugs.

With the aim of developing of emulsion carrier systems for lipophilic drugs with the potential for prolonged circulation in the blood or hepatic targeting, the in vivo disposition of four model compounds, i.e., [3H]prostaglandin E1, [3H]retinoic acid, [14C]cholesterol, and [14C]cholesteryl oleate with calculated log PC(oct) values of 2.15, 6.61, 9.46, and 18.3, respectively, injected with various emulsion formulations, were studied in mice. Small sized emulsions of about 100 nm in diameters, with compositions of egg phosphatidylcholine (PC): soybean oil = 1:1 (small PC emulsion) and PC: egg sphingomyelin (SM): soybean oil = 0.7:0.3:1 (small SM emulsion), and a conventional emulsion with a diameter of about 250 nm and a composition of PC: soybean oil = 1:1 (large PC emulsion) were compared. Highly lipophilic [14C]cholesteryl oleate, a marker of emulsion particles, indicated diverse in vivo behaviors; i.e., the small SM emulsion produced prolonged circulation in the blood, and the small PC emulsion followed this, while the large PC emulsion was rapidly uptake by the liver. Thus, a reduction in size and coating with SM on the surface of oil droplets resulted in avoidance of the reticuloendothelial system (RES). Disposition profiles of other test compounds differed, depending on their lipophilicities: [14C]cholesterol showed disposition patterns in all formulations similar to those of [14C]cholesteryl oleate, but moderately lipophilic [3H]prostaglandin E1 and [3H]retinoic acid showed common disposition profiles, regardless of emulsion types, suggesting their rapid release from the emulsion carriers. These results suggest that small SM emulsion and large PC emulsion can act respectively as long circulating and liver targeting carriers for highly lipophilic drugs with log PC(oct) larger than 9.

Animals↗

PubMed1994

Manipulation of renal disposition of human recombinant superoxide dismutase by chemical modification.

The renal disposition characteristics of superoxide dismutase (SOD) and its derivatives, including macromolecular conjugates with polyethylene glycol and carboxymethyl-dextran, a cationized derivative, and glycosylated derivatives with galactose and mannose, were studied in the isolated perfused rat kidney. Renal disposition processes, such as glomerular filtration, tubular reabsorption, and uptake from the capillary side, were quantitatively determined by single-pass indicator dilution experiments under filtering and nonfiltering kidney conditions. Native SOD had a high glomerular filtration rate (40% of that of inulin) and was effectively reabsorbed in the tubules, while no significant uptake was observed from capillary side. Macromolecular conjugates showed restricted glomerular filtration due to an increase in molecular size. Cationization of SOD greatly enhanced its association with the tissue, not only from the luminal side but also from the capillary side, based upon electrostatic interaction. Galactosylated and mannosylated SOD showed reduced tubular reabsorption and increased exposure of the luminal surface to the enzyme. In addition, a small but significant uptake of mannosylated SOD from the capillary side was observed. This uptake was dose-dependent and completely inhibited by mannan, suggesting that mannose receptor-mediated endocytosis existed in the capillary side of the kidney. Thus, we can manipulate the renal disposition profiles of SOD by changing its physicochemical or biological properties through chemical modification.

Animals↗

PubMed1994

Control of in vivo fate of albumin derivatives utilizing combined chemical modification.

Three types of bovine serum albumin (BSA) derivatives such as lactosylated BSA (LBSA), mannosylated BSA (Man-BSA), and cationized BSA (cBSA) were synthesized and their hepatic disposition characteristics in mice were evaluated by pharmacokinetic analysis. At lower doses (< or = 1 mg/kg), LBSA and Man-BSA were very rapidly eliminated from the blood circulation due to uptake by parenchymal and nonparenchymal cells of the liver, respectively, via receptor-mediated endocytosis (Nishikawa et al., 1992; Nishida et al., 1991a, b). These uptake processes were nonlinear and the apparent hepatic uptake clearances (CLliver) were decreased at administered doses higher than 1 mg/kg, e.g. 10, 20, and 100 mg/kg. The liver accumulation of cBSA was also nonlinear, but its binding and/or uptake capacity in the liver was larger than those of LBSA and Man-BSA; i.e., CLliver decreased at doses higher than 20 mg/kg. In the next step, we modified these BSA derivatives by attaching polyethylene glycol (PEG), a modifier known to reduce the hepatic uptake and increase plasma retention, to achieve precise control of the in vivo disposition characteristics of BSA derivatives. By conjugation with PEG having a molecular weight of 10 kDa, the CLliver values of LBSA, Man-BSA, and cBSA were decreasing to one-seventh, one-fortyfifth, and one-onehundredthirtieth, respectively. However, liver accumulation of PEG modified LBSA and Man-BSA at 24 h after i.v. injection was not significantly different from unmodified BSA derivatives. These results suggest that it is possible to control the hepatic uptake of protein drugs by a combination of introduction of charge or sugar moieties and PEG conjugation.

Animals↗

PubMed1994

Improvement of therapeutic effect of human recombinant superoxide dismutase on ischemic acute renal failure in the rat via cationization and conjugation with polyethylene glycol.

Therapeutic effect of superoxide dismutase (SOD) and three derivatives: a conjugate with polyethylene glycol (SOD-PEG2), a cationized derivative (cSOD), and a mannosylated derivative (Man-SOD), on acute renal failure induced by ischemia/reperfusion was studied in rats. SOD and derivatives were administered intravenously to the rat after nephrectomy of the right kidney and before and after 60 min occlusion of the left renal artery. At 48 hr after reperfusion, the renal function was evaluated by determining the urinary excretion rate of 14C-inulin injected intravenously. No therapeutic effect on the impaired renal function was shown in the case of low dose SOD (2600 unit/kg) treatment. In contrast, administration of cSOD which was shown to be taken up by the isolated perfused kidney from its capillary side and SOD-PEG2 which maintained high plasma concentration exhibited significant therapeutic effect, as did SOD at ten-fold higher dose (26,000 unit/kg). On the other hand, renal damage was promoted by Man-SOD. Thus, the present study demonstrated that chemical modification may improve the therapeutic effect of SOD on the ischemic acute renal failure and increased SOD concentration in the renal vascular space is an important factor for the improved effect.

Acute Kidney Injury↗

PubMed1994

[Control of in vivo characteristics of gene and antisense DNA disposition].

In order to construct a strategy for control of in vivo disposition characteristics of gene and antisense DNA, in vivo stability and basic pharmacokinetic properties of DNA were investigated. A model gene, plasmid DNA (pCAT), and model oligonucleotide (thymidine 10-mer; T10) derivatives with phosphoroamidate substitution at the 3' and/or 5'-terminal internucleotide linkage, were rapidly degraded in vivo after intravenous injection into mice. The degradation rates were much faster than those observed in in vitro experiments using plasma and whole blood, suggesting that they underwent enzymatic degradation in other compartments than the blood pool. More than 70% of injected pCAT was taken up by the liver within 5 minutes, and the uptake clearance was almost identical to the plasma flow rate in the liver. On the other hand, T10 derivatives were rapidly excreted in the urine and taken up by the kidney and liver. The urinary excretion clearance was close to the glomerular filtration rate. In an attempt to control T10 disposition characteristics, the oligonucleotide was conjugated to a macromolecular carrier, carboxymethyl dextran (CMD). The T10-CMD conjugate exhibited increased in vivo stability and prolonged plasma circulation time. Thus, the present study has shown that macromolecular conjugation is a useful approach to improve in vivo disposition of antisense oligonucleotides.

Animals↗

PubMed1993

Specific uptake of succinylated proteins via a scavenger receptor-mediated mechanism in cultured brain microvessel endothelial cells.

Cellular uptake of succinylated catalase (Suc-CAT; Mw 227 kDa), bovine serum albumin (Suc-BSA; Mw 70 kDa), superoxide dismutase (Suc-SOD; Mw 34 kDa) and soybean trypsin inhibitor (Suc-STI; Mw 21 kDa) was studied using primary cultures of bovine brain microvessel endothelial cells (BMECs) developed as an in vitro model of the blood-brain barrier. Large succinylated proteins (Suc-CAT, Suc-BSA) were taken up by BMECs whereas significant uptake was not observed for native proteins and small succinylated proteins (Suc-SOD, Suc-STI). Uptake of Suc-BSA was significantly inhibited at 4 degrees C and in the presence of endocytosis inhibitors. Large succinylated proteins, maleylated BSA and dextran sulfate also showed competitive inhibition against Suc-BSA uptake while small succinylated proteins and carboxymethyl dextran did not show any effect. These results indicate that microvessel endothelial cells obtained from the brain endocytose succinylated proteins via a scavenger receptor-mediated mechanism for polyanions, and in addition, the importance of molecular weight or total numbers of anionic charges per one molecule of proteins is suggested. Usefulness of direct succinylation of proteins for their delivery to the brain capillary endothelium is thus demonstrated.

Animals↗

PubMed1993

Synthesis and pharmacokinetics of a new liver-specific carrier, glycosylated carboxymethyl-dextran, and its application to drug targeting.

To develop a new carrier system for hepatic targeting, carboxymethyl-dextran (CMD) was modified with galactose and mannose residues (Gal-CMD, Man-CMD), and their disposition characteristics were studied in mice using 14C-labeled dextran. At a dose of 1 mg/kg, i.v.-injected Gal-CMD and Man-CMD rapidly accumulated in the liver parenchymal and nonparenchymal cells, respectively, because of their preferential uptake via carbohydrate receptors in these cells. Pharmacokinetic analysis revealed that their uptake rates were sufficiently large for selective drug targeting. Targeting of cytosine beta-D-arabinoside (araC) was studied using Gal-CMD as a specific carrier to the hepatocytes. From the conjugate of araC with Gal-CMD, araC was released with a half-life of 36 hr in phosphate buffer (pH 7.4) and 23 hr in plasma. An in vivo biodistribution study demonstrated a disposition profile of the conjugated araC similar to that of the carrier, and selective delivery to hepatocytes of up to 80% of the dose was achieved. These findings suggest that glycosylated CMDs are carriers with a high affinity to liver parenchymal or nonparenchymal cells without any affinity to other tissues.

Animals↗

PubMed1993

Disposition characteristics of protein drugs in the perfused rat kidney.

The renal disposition characteristics of 111In-labeled neocarzinostatin (NCS), soybean trypsin inhibitor (STI), and superoxide dismutase (SOD) were studied in the perfused rat kidney. In a single-pass indicator dilution experiment, venous and urinary recovery profiles and tissue accumulation of proteins were determined under filtering or nonfiltering conditions. In the nonfiltering kidney perfusion experiment, no significant tissue accumulation was observed, suggesting minimal uptake from the glomerular and peritubular capillary sides. Therefore, tissue recovery corresponded to that with tubular reabsorption after glomerular filtration. The total amount of NCS or STI being filtrated through glomeruli, the sum of tissue and urinary recoveries, was similar to that of inulin, but that of SOD was about half. Similarly, the steady-state distribution volumes (Vd) of NCS and STI obtained by moment analysis of their venous outflow curves were similar to that of inulin, while the Vd value of SOD was significantly lower. These results suggest the restricted passage of SOD through the glomerular and postglomerular capillary wall. The tubular reabsorption ratio of proteins against the total filtrated amount decreased with an increase in the administered dose, suggesting nonlinearity of reabsorption. SOD had the largest reabsorption ratio. Thus, this experimental system is useful for quantitative analysis of renal disposition of proteins.

Animals↗

PubMed1993

Disposition characteristics of model macromolecules in the perfused rat kidney.

The disposition characteristics of model macromolecules such as dextran (70 kDa), bovine serum albumin (BSA), and their charged derivatives were studied in the perfused rat kidney. In a single-pass indicator dilution experiment, venous and urinary recovery patterns and tissue accumulation of radiolabeled compounds were evaluated under filtering or nonfiltering conditions. In the filtering kidney, cationic macromolecules such as diethylaminoethyl-dextran (DEAE-dex) and cationized BSA (cBSA) accumulated in the kidney to a great extent whereas anionic and neutral macromolecules such as BSA, carboxymethyl-dextran (CM-dex), and dextran showed only small uptake. DEAE-dex and cBSA were distributed to both the medulla and cortex regions of the kidney and their recoveries in the kidney decreased as the injected dose increased. Similar tissue uptake was observed in the nonfiltering kidney perfusion system suggesting that they were mainly taken up by the kidney from the renal capillary side based on electrostatic interaction. In addition, the steady-state distribution volumes of cationic macromolecules calculated from venous outflow patterns were larger than those of the intravascular volume estimated from the distribution volumes of neutral and anionic macromolecules, suggesting their reversible interaction with the vascular wall. On the other hand, dextran derivatives with molecular weight distribution were excreted into urine based on glomerular permselectivity; i.e., cationic DEAE-dex and anionic CM-dex showed enhanced and restricted urinary excretion, respectively, compared with neutral dextran. In contrast, no significant excretion was observed for BSA and cBSA. The utility of the isolated rat kidney perfusion experiment for studying the renal disposition of macromolecular drugs was thus demonstrated.

Animals↗

PubMed1993

Controlled biodistribution of highly lipophilic drugs with various parenteral formulations.

Lipid carrier systems are considered effective for targeting highly lipophilic drugs, but little systematic information about the effect of the physicochemical and pharmaceutical characteristics of drugs and formulations on their performance has been obtained. 3H-Retinoic acid and 14C-cholesteryl oleate with different lipophilicities (log PCoct = 6.6 and 18, respectively) were selected as model drugs and the potential of formulations such as oil in water (o/w) emulsion, micellar solution, and liposomes for controlling their biodistribution was demonstrated. After intravenous injection in mice, 3H-retinoic acid showed similar disposition profiles irrespective of formulation type, suggesting its rapid dissociation from carriers. 14C-Cholesteryl oleate with extremely high lipophilicity revealed widely varied disposition profiles reflecting the distribution patterns of carriers: micellar solution and liposomes showed large AUC values and low hepatic clearances, while the use of emulsion as a carrier resulted in rapid clearance from blood circulation into the liver. The results suggested that these formulations can be used as targeting carriers for lipophilic drugs which, however, should have a sufficiently high lipophilicity of about log PCoct 9-16.

Animals↗

PubMed1992

Therapeutic effects of superoxide dismutase derivatives modified with mono- or polysaccharides on hepatic injury induced by ischemia/reperfusion.

Therapeutic effects of four types of recombinant superoxide dismutase (SOD) derivatives, conjugates with polysaccharides, carboxymethyl (SOD-CMD) and diethylaminoethyl (SOD-DEAED) dextrans and galactosylated (Gal-SOD) and mannosylated (Man-SOD) derivatives, on hepatic ischemia/reperfusion injury were studied in rats. Hepatic injury induced by transient occlusion and subsequent reflow of hepatic blood was evaluated by the analysis of biliary excretion of bromosulfophthalein (BSP) injected intravenously. At a dose of 10000 units/kg, native SOD and SOD-DEAE did not show any significant effect and SOD-CMD showed slight effect. On the other hand, Gal-SOD and Man-SOD, targeted to the liver parenchymal and nonparenchymal cells, respectively, by a receptor-mediated endocytosis, exhibited superior inhibitory effects. These results demonstrated that these glycosylated SOD derivatives were useful for the prevention of hepatic ischemia/reperfusion injury.

Animals↗

PubMed1992

Disposition characteristics of macromolecules in the perfused tissue-isolated tumor preparation.

Disposition characteristics of model macromolecules with different physicochemical characteristics and macromolecular prodrugs of mitomycin C, namely mitomycin C-dextran conjugates, were studied in tissue-isolated tumor preparations of Walker 256 carcinoma with the use of a single-pass vascular perfusion technique. In constant infusion experiments, all radiolabeled macromolecules accumulated in the tumor tissue, but the degree and pattern of distribution greatly varied, depending on their electric charges. Positively charged macromolecules were markedly accumulated compared with those that were neutral or negatively charged. In addition, their concentrations were significantly higher in viable than in necrotic regions, while neutral and negative compounds were distributed in necrotic rather than in viable regions. Pharmacokinetic analysis of tissue concentration-time courses of positively charged diethylaminoethyl and neutral dextrans showed that their movement occurred by convective fluid flow, and that high tissue accumulation of positively charged macromolecules could be explained by strong binding due to electrostatic interaction. For neutral and anionic macromolecules with negligible affinity to the tissue, it was suggested that the final concentration gradient between the viable and necrotic regions was decided by their tissue fluid content. Thus, the present study revealed the basic disposition characteristics of macromolecules in tumor tissue relative to their physicochemical properties.

Animals↗

PubMed1992

Demonstration of the receptor-mediated hepatic uptake of dextran in mice.

To establish a rationale of designing a drug targeting system using dextran conjugation, the disposition behaviour of dextran itself was investigated in mice. At a high dose (100 mg kg-1), [14C]dextran was retained in the blood circulation for a considerably long period. However, [14C]dextran rapidly disappeared from the plasma and accumulated in the liver (up to 60% of dose in 1 h) after a dose of 1 mg kg-1. Cellular localization of [14C]dextran in the liver following intravenous administration was examined and the contribution of parenchymal cells was demonstrated as well as the case of galactosylated bovine serum albumin (Gal-BSA). Pharmacokinetic analysis based on a physiological model including Michaelis-Menten type uptake mechanisms revealed that the Michaelis constant Km,l of [14C]dextran was 100 times greater than that of Gal-BSA. Coadministration of Gal-BSA delayed the hepatic uptake of [14C]dextran and the simulation based on the physiological model suggested that [14C]dextran was taken up by the same mechanism as Gal-BSA. These results suggested that dextran conjugation of a drug might lead to its undesirable accumulation in the liver at a low dose and an appropriate modification of dextran, such as carboxymethylation, would be required in such cases.

Animals↗

PubMed1992

Targeted delivery of human recombinant superoxide dismutase by chemical modification with mono- and polysaccharide derivatives.

Four types of superoxide dismutase (SOD) derivatives such as SOD-carboxymethyl dextran conjugate, SOD-diethylaminoethyl dextran conjugate, galactosylated SOD and mannosylated SOD were synthesized and their potential for selective targeting to organs or cells was evaluated in mice by pharmacokinetic analysis. All SOD derivatives retained 50 to 80% of the original enzymatic activity and were stable during incubation with mouse serum retaining enzymatic activity greater than 80% for 3 hr. After intravenous injection, native SOD was rapidly excreted into urine and no significant accumulation was observed in the organs except the kidney. SOD-carboxymethyl dextran conjugate gave a long plasma half-life because of impaired glomerular filtration and tissue interaction. By contrast, galactosylated-SOD and mannosylated-SOD were very rapidly eliminated from the circulation and taken up by parenchymal and nonparenchymal cells of the liver, respectively, via receptor-mediated endocytosis. These uptake processes were nonlinear and hepatic uptake clearance decreased as the dose increased, although almost complete extraction was obtained at a dose of 0.1 mg/kg. Furthermore, the accumulation in kidney of both glycosylated SODs was drastically decreased due to reduced renal proximal tubular reabsorption and also enhanced hepatic clearance. SOD-diethylaminoethyl dextran conjugate also rapidly disappeared from plasma and distributed into liver, but its accumulation occurred due to electrostatic interaction and was nonspecific in cellular distribution. These results suggest the possibility of controlling the in vivo fate of SOD at a cellular level by chemical modification utilizing sugar moieties with varied physicochemical and/or biological characteristics.

Animals↗

PubMed1992

[Change in arterial ketone body ratio during gastrectomy and mastectomy].

We evaluated the influence of operative procedure on arterial ketone body ratio (AKBR), which indicates the function of the liver cells, in patients undergoing gastrectomy or mastectomy. AKBR during the stomach resection was significantly lower than that during the breast resection. A significant reduction in AKBR due to induced hypotension was observed in mastectomy group. SGOT and SGPT increased significantly in gastrectomy group, but unchanged in mastectomy group on the first and the seventh postoperative days. On the first post-operative day, SGOT and SGPT in gastrectomy group were significantly higher than those in mastectomy group. These findings suggest that influence of operative procedure on the liver during gastrectomy is more serious than that during mastectomy.

Adult↗

PubMed1992

Analysis of primary bone formation in porous alumina: a fluorescence and scanning electron microscopic study of marrow cell induced osteogenesis.

Porous alumina ceramics alone and combined with rat marrow cells were implanted subcutaneously in the back of syngeneic Fischer rats. Fluorochrome-labeling was performed post operatively and the ceramics were harvested 6 and 8 weeks after implantation. Undecalcified sections of the implants were observed under fluorescence microscopy and the de novo bone-ceramic interfacial areas were analyzed by a scanning electron microscope equipped with an electron probe microanalyzer. Alumina ceramics alone did not show any bone formation, while all marrow cell loaded ceramics showed new bone formation 6 and 8 weeks after implantation. Bone formation was first observed in the center of the pores and proceeded in a centrifugal direction, leading to contact with the ceramic. These results suggest that bone marrow cells have inherent osteogenic capacity and in the pore region of alumina ceramics progression of the osteogenesis causes the dissipation of intervening fibrous tissue between the de novo bone and alumina ceramic surface.

Aluminum Oxide↗