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Biomedical subjects

A Tsuji

Publications and source records attributed to A Tsuji.

At least 73 records · Page 4Linked to original sources

Sensitive and selective determination of tetracaine and its metabolite in human samples by gas chromatography-mass spectrometry.

A sensitive and reliable method was developed for the determination of tetracaine and its metabolite, p-butylaminobenzoic acid, in human samples. Tetracaine and the metabolite, effectively extracted using a liquid-liquid extraction procedure from 0.5 g of sample, were analyzed by gas chromatography-mass spectrometry. Tetracaine was analyzed without derivatization, and the metabolite was analyzed after tert-butylolimethylsilyl derivatization. Dibucaine and p-dimethylaminobenzoic acid were used as internal standards for tetracaine and the metabolite, respectively. The calibration curve for each compound was linear in the concentration range from 10 to 1,000 ng/0.5 g, and the lower limits of detection were 10 ng/g for tetracaine and 0.6 ng/g for the metabolite in whole blood and tissues. The accuracy and precision of the method were evaluated in whole blood and brain at the concentrations of 50 ng/0.5 g and 500 ng/0.5 g for tetracaine and 10 ng/0.5 g and 100 ng/0.5 g for the metabolite. The coefficients of variation ranged from 0.8 to 3.0% for tetracaine and 2.4 to 9.8% for the metabolite. We used this method to determine tetracaine and its metabolite in human whole blood and tissues of an autopsied patient who died during spinal anesthesia induced by tetracaine.

4-Aminobenzoic Acid↗

Faropenem transport across the renal epithelial luminal membrane via inorganic phosphate transporter Npt1.

We previously showed that the mouse inorganic phosphate transporter Npt1 operates in the hepatic sinusoidal membrane transport of anionic drugs such as benzylpenicillin and mevalonic acid. In the present study, the mechanism of renal secretion of penem antibiotics was examined by using a Xenopus oocyte expression system. Faropenem (an oral penem antibiotic) was transported via Npt1 with a Michaelis-Menten constant of 0.77 +/- 0.34 mM in a sodium-independent but chloride ion-sensitive manner. When the concentration of chloride ions was increased, the transport activity of faropenem by Npt1 was decreased. Since the concentration gradient of chloride ions is in the lumen-to-intracellular direction, faropenem is expected to be transported from inside proximal tubular cells to the lumen. So, we tested the release of faropenem from Xenopus oocytes. The rate of efflux of faropenem from Npt1-expressing oocytes was about 9.5 times faster than that from control water-injected Xenopus oocytes. Faropenem transport by Npt1 was significantly inhibited by beta-lactam antibiotics such as benzylpenicillin, ampicillin, cephalexin, and cefazolin to 24.9, 40. 5, 54.4, and 26.2% of that for the control, respectively. Zwitterionic beta-lactam antibiotics showed lesser inhibitory effects on faropenem uptake than anionic derivatives, indicating that Npt1 preferentially transports anionic compounds. Other anionic compounds, such as indomethacin and furosemide, and the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid significantly inhibited faropenem uptake mediated by Npt1. In conclusion, our results suggest that Npt1 participates in the renal secretion of penem antibiotics.

Animals↗

In situ and in vitro evidence for stereoselective and carrier-mediated transport of monocarboxylic acids across intestinal epithelial tissue.

The present study was designed to establish the significance of carrier-mediated transport in the intestinal absorption of monocarboxylic acids by examining the stereoselectivity of transepithelial transport of chiral monocarboxylic acids. The transport of L- and D-lactic acids was examined in vitro using rat intestinal tissue sheets and in situ by means of intra-jejunal administration, followed by measurement of the plasma concentration. Both the absorptive and secretory transport of L-[14C]lactic acid across the intestinal epithelial tissues of rats was significantly greater than that of the D-isomer. The secretory transport of the L-isomer was significantly greater than the absorptive transport, implying net transport in the secretory direction. When L- and D-[14C]lactic acids were administered to the rat jejunum, the absorption ratio of the L-isomer was lower than that of the D-isomer at 15 min after administration. The concentration-dependence of absorption for both L- and D-[14C]lactic acids indicated the involvement of both saturable and nonsaturable processes. The saturable process showed a higher affinity and lower capacity for L-lactic acid compared with the D-isomer, while no significant difference between the isomers was observed in the nonsaturable process. The absorption of L-lactic acid was inhibited by chiral 2-hydroxymonocarboxylic acids in a stereoselective manner. Chiral monocarboxylic acids were shown to cross the intestinal epithelial tissues and to be absorbed in a stereoselective manner after oral administration, suggesting the involvement of specific carrier-mediated transport mechanism(s) in their intestinal absorption in vivo.

Animals↗

Blood-brain barrier transport of H1-antagonist ebastine and its metabolite carebastine.

The transport mechanism of the non-sedative H1-antagonist ebastine and its first-pass carboxylic acid metabolite carebastine at the blood-brain barrier (BBB) was studied. In rats, the brain uptake index (BUI) value of [14 C]carebastine was significantly lower than that of [14 C]ebastine. The BUI value of [14 C]carebastine was greatly increased by the addition of non-labeled carebastine. The steady-state uptake of [14 C]carebastine by P-glycoprotein-overexpressing K562/ADM cells was significantly lower than that by their parental drug-sensitive cell line K562. The decreased steady-state uptake of [14 C]carebastine by K562/ADM cells was reversed by verapamil. Steady-state uptake of [14 C]carebastine by primary cultured bovine brain capillary endothelial cells (bovine BCECs) was increased in the presence of metabolic inhibitors and verapamil. Non-labeled carebastine increased the steady-state uptake of a P-glycoprotein substrate, [3 H]vincristine, by bovine BCECs. The initial uptake of [3 H]mepyramine by bovine BCECs and RBEC1 (an immortalized cell line from rat brain capillary endothelial cells) was strongly inhibited by ebastine, while zwitterionic carebastine was slightly inhibitory. The values of brain-to-plasma unbound concentration ratio (Kp,f) in mdr1a(-/-) mice were increased 5.3-fold and 4.2-fold for [14 C ebastine and for [14 C]carebastine, respectively, compared with those in mdr1a(+/+) mice. Non-radiolabeled carebastine increased the Kp,f values of [14 C]carebastine in both types of mice. In conclusion, carebastine was shown to be a substrate for P-glycoprotein-mediated efflux from the brain at the BBB. A second efflux system may also be involved. The relatively low affinity of the uptake transport system for carebastine also limits the brain distribution of ebastine/carebastine.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

Function and expression of multidrug resistance-associated protein family in human colon adenocarcinoma cells (Caco-2).

Several organic anions are actively extruded from intestinal epithelial cells into the lumen and vascular sides. To examine the role of the multidrug resistance-associated protein (MRP) family in the intestinal efflux of organic anions, the function and expression of these proteins were investigated with Caco-2, a human adenocarcinoma cell line that retains many of the characteristics of normal enterocytes. [(3)H]2,4-Dinitrophenyl-S-glutathione (DNP-SG) and [(3)H]17beta-estradiol 17-beta-D-glucuronide (E(2)17betaG), typical substrates for MRP1 and cMOAT (canalicular multispecific organic anion transporter)/MRP2, were taken up into brush-border membrane vesicles (BBMVs) from Caco-2 in an ATP-dependent manner, with K(m) values of 16.9 +/- 7.2 and 9.4 +/- 1.2 microM, respectively. The uptake of [(3)H]DNP-SG into BBMVs was osmotically sensitive and stimulated to some extent by other nucleotide triphosphates (GTP, CTP, and UTP) but not by ADP or AMP. An ATPase inhibitor, vanadate, inhibited the ATP-dependent uptake of [(3)H]DNP-SG to some extent. Reverse-transcriptase polymerase chain reaction resulted in the amplification of MRP1, MRP3, and MRP5. Northern blot analysis indicated extensive expression of cMOAT/MRP2 and MRP3 and only minimal expression of MRP1 and MRP5. Although cMOAT/MRP2 was continuously expressed throughout the culture period, MRP3 was not expressed immediately after the confluent state was reached. Collectively, the presence of ATP-dependent transport systems for DNP-SG and E(2)17betaG was demonstrated in Caco-2 cells. Because cMOAT/MRP2 and MRP3 may be expressed on brush-border and basolateral membranes in epithelial cells, respectively, the transport activity associated with BBMVs may result from the function of cMOAT/MRP2.

ATP-Binding Cassette Transporters↗

[Preliminary clinical evaluation of low-dose CDDP and continuous 5-FU therapy for advanced gallbladder cancer].

5-fluorouracil (5-FU) has been widely used for the treatment of gastrointestinal cancers. Low-dose cisplatin (CDDP) and continuous venous infusion of 5-FU have recently shown additive or synergistic antitumor effects in experimental models. In this study, we evaluated the clinical effects of low-dose CDDP and 5-FU (low-dose FP therapy) in patients with advanced gallbladder cancer. From December, 1993 to June, 1998, 13 patients with advanced gallbladder cancer were treated with low-dose FP therapy. Patients were eligible for this study if they had a bidimensionally measurable tumor. 5-FU (160 mg/m2/day) was continuously infused over 24 hours using an implantable port, and CDDP (3 mg/m2/day) was infused for one hour. The administration schedule consisted of 5-FU for 7 consecutive days and CDDP for 5 days followed by a 2-day rest, each for four weeks according to response and tolerance. Low-dose FP therapy was given to 12 patients (92.3%). The response rate was 66.7% and the median survival time was 151 days. The regimen was tolerable, with the most common toxicity being nausea (38.5%). There were no severe side effects except for one patient who suffered from grade 3 nausea. We conclude that low-dose FP therapy may be useful as a palliative chemotherapy for cases of advanced gallbladder cancer.

Aged↗

Combination chemotherapy of continuous 5-FU infusion and low-dose cisplatin infusion for the treatment of advanced and recurrent gastric and colorectal adenocarcinomas.

We evaluate the efficacy and toxicities of low-dose FP therapy in the treatment of advanced and recurrent gastric and colorectal adenocarcinomas. 104 patients (gastric adenocarcinoma: 52, colorectal adenocarcinoma: 52) were enrolled. Low-dose FP therapy consisted of 5-FU (160 mg/m2/day every day by continuous infusion) and cisplatin (3 mg/m2/day in 100 ml of normal saline by infusion over 30 minutes on days 1-5/W). Patients were treated for 4 consecutive weeks with subsequent one-week rest period. Ninety-four of 104 patients completed this therapy, and the treatment accomplishment rate was 90%; 82% in gastric adenocarcinomas, 96% in colorectal adenocarcinomas. Two cases had CR, and 47 cases had PR, with an overall response rate of 52.1%. Response rates, 50% survival time, 1-year survival rates, and 2-year survival rates were 65.9%, 249 days, 33.7%, 19.7% in gastric adenocarcinomas, and 40.0%, 466 days, 56.7%, 29.4% in colorectal adenocarcinomas, respectively. Nausea/vomiting was the most common toxicity, occurring in 44.2% of patients treated and was predominantly mild to moderate (up to Grade 2). In 5 cases Grade 3 toxicity was observed. Low-dose FP therapy has a high antineoplastic effect and low-grade toxicity, and this therapy should become the first-choice chemotherapy for the treatment of advanced and recurrent gastric and colorectal adenocarcinomas.

Adenocarcinoma↗

[Conceptual changes in cancer chemotherapy--biochemical modulation of 5-FU].

Recently, the demand for more useful therapies for cancer patients has increased. We describe in this paper a therapeutic modality based on a self-rescuing concept (SRC), and which features dual activity, i.e., an effect-enhancing activity and an adverse reaction-reducing activity. We present the theory and practice of S-1, a novel oral fluoropyrimidine anticancer agent designed to enhance anticancer activity and reduce gastrointestinal toxicity through the deliberate combination of the following components: the oral fluoropyrimidine agent tegafur; a DPD inhibitor (CDHP) which is more potent than uracil, which is used in UFT; and an ORTC inhibitor (Oxo) which localizes in the gastrointestinal tract. S-1 is a combination drug with a molar ratio of 1:0.4:1 in FT, CDHP, and Oxo, respectively. A clinical pharmacology study was conducted to examine blood concentrations of 5-FU after twice-a-day administration of S-1 at a dose of 40 mg/m2. Blood concentrations of 5-FU were found to be 60 to 200 ng/ml in all twelve patients examined. The overall response rate was 44.6% (45/101). In addition, the incidence of adverse reactions judged to be grade 3 or higher was 10% or less. We have also reported a combination therapy with 5-FU (civ) (5-FU: 250 to 350 mg/body, 24-hour cvi, consecutive days) and low-dose cisplatin (CDDP: 3 to 5 mg/body, i.v., 5 days/week), in which CDDP was used as a modulator of 5-FU. Low-dose FP therapy provided response rates as high as 40 to 60% in 163 patients with various gastrointestinal cancers other than pancreas cancer. The incidence of the adverse reactions of nausea and vomiting which were judged to be grade 3 or higher was 2.5% (4/163). The incidences of other adverse reactions were 1% or less. In line with the theory and practice of combination therapy with 5-FU (cvi) 24 hr cvi; 5-FU: 750 to 1,000 mg/body/day on Monday, Wednesday, and Friday (withdrawal on Tuesday, Thursday, Saturday and Sunday) intermittent administration and low-dose CDDP (3 to 5 mg/body/day day 1-5/w) consecutive administration was utilized in which there was a difference in cell cycle between gastrointestinal mucosal cell and tumor cell, or between bone marrow cell and tumor cell. Few adverse reactions, e.g., diarrhea and stomatitis, were observed despite the overall response rate being as high as 52.4% (22/42). The incidence of adverse reaction judged to be grade 3 or higher was as low as 9.3% (5/54), with an incidence of 9.3% (5/54) in Grade 3 or higher myelotoxicity. We intend in the future to combine the abovementioned therapeutic modalities, which provoke fewer adverse reactions and are easy on patients with cancer in an effort to further increase their life expectancy.

Administration, Oral↗

Limited distribution of new quinolone antibacterial agents into brain caused by multiple efflux transporters at the blood-brain barrier.

Transport of new quinolone antibacterial agents (quinolones) at the blood-brain barrier (BBB) was studied in vitro by using immortalized rat brain capillary endothelial cells RBEC1, and in vivo by using the brain perfusion method in rats and multidrug-resistant mdr1a/1b gene-deficient mice. The permeability coefficient of grepafloxacin measured by brain perfusion was increased by an excess of unlabeled grepafloxacin, suggesting a participation of a saturable BBB efflux system. Uptake coefficients of [(14)C]grepafloxacin, [(14)C]sparfloxacin, and [(14)C]levofloxacin by RBEC1 cells at the steady state were increased in the presence of the unlabeled quinolones. The steady-state uptake of [(14)C]grepafloxacin was increased in the presence of various quinolones. Brain distributions of [(14)C]grepafloxacin and [(14)C]sparfloxacin evaluated in terms of the brain-to-plasma free concentration ratio in mdr1a/1b gene-deficient mice were significantly higher than those in wild-type mice, demonstrating an involvement of P-glycoprotein as the efflux transporter. Anionic compounds, including 4, 4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and genistein, increased the steady-state uptake of [(14)C]grepafloxacin by RBEC1 cells. Because [(14)C]grepafloxacin was transported by multidrug resistance-associated protein (MRP), in MRP1-overexpressing cells and because RBEC1 and primary cultured brain capillary endothelial cells expressed MRP1, this protein may be an additional efflux transporter for quinolones. Furthermore, the permeability coefficient of [(14)C]grepafloxacin across the BBB was increased by DIDS or in the absence of bicarbonate ions in the brain perfusion method. DIDS or bicarbonate ion did not affect MRP1 function. Accordingly, the brain distribution of quinolones is restricted by the action of multiple efflux transporters, including P-glycoprotein, MRP1, and an unknown anion exchange transporter.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

Traumatic false aneurysm of the descending aorta which ruptured to right thoracic cavity.

A 54-year-old male, who had been involved in a traffic accident one week earlier, suddenly died in hospital without any warning. Autopsy revealed right hemothorax due to rupture of a subpleural hematoma of the right lung which was connected to a false aneurysm of the descending aorta. It is likely that the false aneurysm began to grow just after the traffic accident, forming an aortopleural fistula due to preceding adhesion. This led to the formation of a hematoma in the right subpleural space, which ruptured one week after the traffic accident. The present case indicates that the natural course and pathogenesis of traumatic false aneurysm depends upon the preceding local anatomical circumferences.

Accidents, Traffic↗

An autopsy case of accidental asphyxiation in a storage room for apples.

A 12-year-old boy died in a storage room and his mother was rescued from the same storage room, where many apples were being stored. The atmosphere in the room was strictly controlled and the concentration of oxygen (O2) was recorded. The cause of death was suffocation. According to the records, the concentration of O2 was about 2.7% when the boy died. On the other hand, it was about 3.4% when his mother entered the room and she survived, although she remained unconscious for about four hours. These findings show that the absolute concentration of O2 causing acute death due to O2 deficiency is approximately 2.5-3.0%.

Accidents↗

Tissue selective drug delivery utilizing carrier-mediated transport systems.

This paper describes some successful examples of a tissue selective drug delivery by utilizing specialized transporter(s) expressed in the targeted tissue cells. These are as follows: (1) oral delivery via H(+)/oligopeptide transporter, rat or human Pept1, in the intestine for beta-lactam antibiotics and a newly synthesized dipeptide, L-dopa-L-phenylalanine; (2) tumor cell specific delivery via the newly discovered H(+)/oligopeptide transporter(s) expressed in human fibrosarcoma cell line HT-1080 for model oligopeptides, glycylsarcosine and carnosine; (3) oral and hepatic delivery via an H(+)/monocarboxylate transporter in the intestine and an organic anion transporter in the liver for HMG-CoA reductase inhibitor, pravastatin; and (4) lung selective delivery via some type of transporter and avoidance of transfer into the brain via P-glycoprotein at the blood-brain barrier for a new quinolone antibacterial, HSR-903.

Animals↗

Mossy fiber sprouting in the dentate gyrus in a newly developed epileptic mutant, Ihara epileptic rat.

We examined the correlation between seizure activity and development of mossy fiber sprouting in the hippocampal formation using Timm staining in a newly developed Ihara epileptic rat (IER). The sprouting of mossy fibers were clearly shown in the inner molecular portion of the dentate gyrus and in the stratum oriens of CA3 pyramidal cell layer with repeated seizures. A positive correlation between the frequency of generalized tonic and clonic convulsions and the Timm staining score in molecular layer of dentate gyrus was revealed. Sprouting of mossy fiber in IER seems to be linked with seizure activities resulting from epileptic bursts, not to the genetic mutation.

Animals↗

Genetic dissection of "OLETF," a rat model for non-insulin-dependent diabetes mellitus: quantitative trait locus analysis of (OLETF x BN) x OLETF.

To identify genetic determinants relevant to non-insulin-dependent diabetes mellitus (NIDDM), we performed a genome-wide analysis for quantitative trait loci (QTLs) using 359 backcross progeny of the Otsuka Long-Evans Tokushima Fatty (OLETF) rat. The OLETF strain is a well-studied animal model of obese NIDDM, with features of hyperinsulinemia, hyperglycemia, insulin resistance, and abundant abdominal fat. Our extensive genomic scanning with 218 markers revealed nine significant QTLs, including a strong determinant of obesity on chromosome 1 (Dmo1: LOD = 13.99, for body weight). Two highly significant QTLs for glucose homeostasis were found, one on chromosome 1 (Dmo4 LOD = 7.16, for postprandial glucose level) and the other on chromosome X (Dmo11/Odb1: LOD = 7.81, for postprandial glucose level). These data are comparable to results of our previous studies of the OLETF rat.

Adipose Tissue↗

Carrier-mediated or specialized transport of drugs across the blood-brain barrier.

In the drug development process, it remains a difficult task to regulate the entry of the drugs. However, recent progress in studies of the transporter-mediated influx and efflux of endogenous and exogenous compounds, including synthetic drugs, across the blood-brain barrier (BBB) is beginning to provide a rational basis for controlling drug distribution to the brain. This paper describes mechanisms established in the last decade for carrier-mediated influx and efflux of drugs and endocytosis of biologically active peptides across the BBB. The transport systems at the BBB described here are the uptake transporters for nutrients, such as amino acids and hexoses, monocarboxylates, amines, carnitine and glutathione and efflux transporters, such as P-glycoprotein and multiple organic anion transporters. Delivery of cationized peptides across the BBB via adsorptive-mediated endocytosis is also described. By utilizing such highly specific transport mechanisms, it should be possible to establish strategies to regulate the entry of candidate drugs, including peptides, into the brain.

Journal Article↗

Mechanism of hepatorenal syndrome in rats of Long-Evans Cinnamon strain, an animal model of fulminant Wilson's disease.

Rats of Long-Evans Cinnamon (LEC) strain were used as a hepatorenal syndrome model of fulminant Wilson's disease. Copper levels in the kidneys increased markedly from 16 to 126 microg Cu/g from 12 to 16 weeks, and remained at the same level at 16 and 19 weeks when the rats suffered from severe renal dysfunction and also at 20 weeks in some other normal rats. The above findings imply that the renal dysfunction may have been induced independently of the copper level in the kidneys. The present study suggested the following mechanism: immediately after copper-induced hepatic dysfunction, plasma copper-metallothionein (CuMT), which was released from the liver, became elevated. The elevation was closely related to the increases in alkaline phosphatase, glucose and amino acids, all in the urine. The above findings suggest that plasma CuMT, which was released from the liver into the blood upon copper-induced hepatic dysfunction, was subsequently filtered at the glomeruli due to its smaller molecular weight, and then caused dysfunction of the brush border membrane of the renal proximal tubules probably after splitting into radical copper and amino acids in acidic vesicles close to the membrane. The critical concentration of plasma CuMT required to induce renal dysfunction was estimated as 1 microg Cu/l.

Animals↗

Differences in the hepatobiliary transport of two quinolone antibiotics, grepafloxacin and lomefloxacin, in the rat.

The biliary excretion of grepafloxacin (GPFX) was compared with that of lomefloxacin (LFLX) in rats. The biliary clearances (Cl(plasma)(bile)) of GPFX was 2.9 times greater than LFLX based on the plasma concentration reached during constant intravenous (i.v.) infusion. The liver-plasma unbound concentration ratio, K(pu), of GPFX (1.7) was also higher than that of LFLX (0.7). The hepatic uptake clearance, assessed from an integration plot analysis, of GPFX was comparable with the hepatic blood flow rate, and 1.5 times that of LFLX, indicating that membrane transport in the uptake process is more efficient for GPFX. This was also supported by the difference between the uptake clearance of GPFX and LFLX in isolated rat hepatocytes. The bile-liver unbound concentration ratio of GPFX and LFLX was approximately 6 and 3, respectively, and the biliary clearance based on the unbound liver concentration of GPFX was 1.8 times that of LFLX. These results suggest that the concentrative transport of GPFX also across the canalicular membrane was more efficient than that of LFLX. Thus, the membrane transport activity via both sinusoidal and canalicular membranes determines the net excretion of each compound.

Animals↗

Loss of wild-type carrier-mediated L-carnitine transport activity in hepatocytes of juvenile visceral steatosis mice.

Juvenile visceral steatosis (JVS) mice, which show systemic L-carnitine deficiency, may be an animal model of Reye's syndrome because of its phenotype of fat deposition and mitochondrial abnormalities in the liver. In this study, we compared the characteristics of the L-carnitine transport in isolated hepatocytes from wild-type and JVS mice. The uptake of L-carnitine by wild-type hepatocytes was saturable and the Eadie-Hofstee plot showed 2 distinct components. The apparent Michaelis constant (K(m)) and the maximum transport rate (V(max)) were 4.6 micromol/L and 59.5 pmol/15 min/10(6) cells, respectively, for the high-affinity component, and 404 micromol/L and 713 pmol/15 min/10(6) cells, respectively, for the low-affinity component. The high-affinity L-carnitine uptake occurred via an active carrier-mediated transport mechanism, which is characterized by Na(+)-, energy-, and pH-dependency. On the other hand, the high-affinity uptake was absent in JVS hepatocytes, and the values of K(m) and V(max) for the low-affinity uptake were 475 micromol/L and 557 pmol/15 min/10(6) cells, respectively. The hepatic carnitine transport properties in wild-type hepatocytes were similar to those of high-affinity mouse Octn2-transfected HEK293 cells. This study suggests that Octn2-type carnitine transporter is dysfunctional in hepatocytes of JVS mice.

2,4-Dinitrophenol↗