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T Sekine

Publications and source records attributed to T Sekine.

At least 91 records · Page 5Linked to original sources
PubMed1999

Transport properties of nonsteroidal anti-inflammatory drugs by organic anion transporter 1 expressed in Xenopus laevis oocytes.

Organic anion transporter 1 (OAT1) is the para-aminohippurate (PAH) transporter in the basolateral membrane of the proximal tubule. The present study investigated whether or not nonsteroidal anti-inflammatory drugs (NSAIDs) are transported by OAT1. All of the NSAIDs tested inhibited [14C]PAH uptake via OAT1 expressed in Xenopus laevis oocytes. Ibuprofen, indomethacin, salicylurate, and naproxen showed the strongest potency to inhibit [14C]PAH uptake (Ki approximately 2-10 microM); acetylsalicylate, salicylate, and phenacetin exhibited moderate potency (Ki approximately 300-400 microM), and acetaminophen (paracetamol) exhibited the weakest inhibitory potency (Ki approximately 2 mM). Radiolabeled acetylsalicylate, salicylate, and indomethacin were taken up by OAT1 and the uptake rate of these three NSAIDs was enhanced by the outwardly directed dicarboxylate gradient. The efflux of the preloaded [14C]PAH from the oocytes via OAT1 was trans-stimulated by PAH and glutarate added to the media. The addition of salicylate, acetylsalicylate, or salicylurate into the media also trans-stimulated the efflux of PAH, whereas indomethacin did not. The present study indicates that OAT1 is responsible for the renal uptake and secretion of NSAIDs.

Animals↗
PubMed1999

Transport of ochratoxin A by renal multispecific organic anion transporter 1.

In the present study, we investigated the transport of ochratoxin A (OTA) by kidney-specific organic anion transporter 1 (OAT1). When expressed in Xenopus laevis oocytes, OAT1 mediated sodium-independent uptake of OTA (Km = 2.1 microM). Piroxicam, which has been shown to prevent the nephrotoxicity of OTA, inhibited OAT1-mediated uptake of OTA. By contrast, another protective compound, aspartame, did not. Using a cell line derived from the mouse kidney terminal proximal tubule (S3) transfected with OAT1 cDNA, we investigated the transport of OTA and also its effect on cell proliferation and cell viability. S3 cells expressing OAT1 mediated the saturable transport of OTA (Km = 0.57 microM). Cell proliferation was suppressed in S3 cells expressing OAT1 when exposed to 2 and 10 microM OTA. This suppression was rescued by the coaddition of 1 mM p-aminohippurate in the media. The present study indicates that OTA is transported by OAT1 and that the accumulation of OTA via OAT1 in proximal tubular cells is the primary event in the development of OTA nephrotoxicity.

Animals↗
PubMed1999

The interaction and transport of beta-lactam antibiotics with the cloned rat renal organic anion transporter 1.

In the present study, we investigated the interactions between antibiotics, especially beta-lactam antibiotics, and rat renal organic anion transporter 1 (OAT1). [(14)C]p-Aminohippurate (PAH) uptake via OAT1 expressed in Xenopus laevis oocytes was inhibited by all of the penicillins and cephalosporins tested. Penicillin G, carbenicillin, cephaloridine, cephalothin, cefazolin, and cephalexin inhibited [(14)C]PAH uptake via OAT1 in a competitive manner (K(i) = 0.29-2.33 mM). Cinoxacin, a quinolone gyrase inhibitor, also inhibited PAH uptake via OAT1. Other antibiotics, such as gentamicin, streptomycin, and vancomycin, which do not contain anionic moieties, did not interact with OAT1. [(3)H]Penicillin G and [(14)C]cephaloridine were demonstrated to be transported via OAT1. Using the cells that stably expressed OAT1, we analyzed the cytotoxicity of several beta-lactam antibiotics. Cells expressing OAT1 showed higher susceptibility to cephaloridine (a potentially nephrotoxic beta-lactam antibiotic) toxicity than did control cells. The present study suggests that OAT1 is the major organic anion transporter in the kidney that is responsible for the renal secretion of antibiotics, especially that of beta-lactam antibiotics. Furthermore, the culture cell system expressing OAT1 was revealed to be useful for the prediction of the nephrotoxicity of beta-lactam antibiotics.

Animals↗
PubMed1999

[Successful total laryngectomy in three cases with severe motor and intellectual disabilities syndrome for the management of repetitive lower respiratory tract infections].

Total laryngectomy was successfully performed for the management of repetitive lower respiratory tract infections in three cases with severe motor and intellectual disabilities syndrome. The patients were thirteen, ten and nine years of age and had cerebral palsy, mental retardation and epilepsy which resulted from neonatal asphyxia and seizures. To treat repetitive lower respiratory tract infections, the patients underwent the operation at the age of nine years and a month, seven years and six months, and six years and eleven months, respectively. Postoperatively, the respiratory tract infections were remarkably reduced for two to four years. Total laryngectomy is one of the best methods for the prevention of aspiration pneumonia, because it separates trachea and esophagus completely. The operation is indicated for children with influx of saliva into trachea and gastroesophageal reflux. The family should recognize that this operation causes permanent loss of voice and speech. The bronchoscopy, upper gastrointestinal tract barium studies and esophageal pH monitoring should be performed before the operation. Our cases fulfilled all of these indications. Laryngectomy should be considered as an effective method of respiratory management for cases of severe motor and intellectual disabilities syndrome, although its application should be carefully examined from the point of improvement of quality of life for patients.

Adolescent↗
PubMed1999

Temperature sensitive effects of alpha-adrenergic stimulation in mouse ventricular myocardia.

The effects of alpha- and beta-adrenergic stimulation on the contractile force and L-type Ca2+ channel current were studied in mouse ventricular myocardia at two different temperatures. In ventricular tissue, at 35-36 degrees C, phenylephrine, in the presence of propranolol, produced a sustained negative inotropic response with no change in the time course of contraction and relaxation. These effects were greatly reduced at 22-23 degrees C. Isoproterenol produced marked positive inotropic responses accompanied by shortening of the time required for relaxation. In isolated ventricular myocytes, phenylephrine, in the presence of propranolol, significantly increased the L-type Ca2+ channel current (I(Ca)) at 35-36 degrees C, but the effect was small at 22-23 degrees C. Isoproterenol increased I(Ca) similarly at both temperatures. These results suggest that, in mouse ventricular myocardia, alpha-adrenoceptor mediated regulation of the contractile force and I(Ca) involve temperature-dependent mechanisms different from those of beta-adrenoceptor-mediated mechanisms.

Adrenergic Agonists↗
PubMed1998

Molecular cloning and characterization of high-affinity carnitine transporter from rat intestine.

Carnitine is an essential component for mitochondrial beta-oxidation of fatty acid. Using the degenerate primers designed for organic anion transporters and an organic cation transporter, we isolated a novel cDNA encoding a carnitine transporter (CT1) from rat intestine. CT1 encodes a 557-amino-acid protein with 12 putative membrane-spanning domains. When expressed in Xenopus oocytes, CT1 mediated a high-affinity transport of L-carnitine (Km = 25 microM). The replacement of extracellular sodium with Li reduced CT1-mediated L-carnitine uptake to 19.8%. CT1 did not transport typical substrates for either organic anion or organic cation transporters, such as p-aminohippurate and tetraethylammonium. Octanoylcarnitine, acetylcarnitine, and gamma-butyrobetaine showed potent inhibitory effects on CT1-mediated L-carnitine uptake; betaine and d-carnitine showed moderate inhibition. CT1 mRNA was strongly expressed in the testis, colon, kidney, and liver and weakly in the skeletal muscle, placenta, small intestine, and brain. No CT1 expression was detected in the heart, spleen, or lung. The present study provides the molecular basis of carnitine transport in the body.

Amino Acid Sequence↗
PubMed1998

Identification of multispecific organic anion transporter 2 expressed predominantly in the liver.

In the present study, we demonstrate that NLT (novel liver-specific transport protein) is a multispecific organic anion transporter of the liver. The amino acid sequence of NLT shows 42% identity to that of the renal multispecific organic anion transporter, OAT1. When expressed in Xenopus laevis oocytes, NLT mediated uptake of organic anions, such as salicylate, acetylsalicylate, PGE2, dicarboxylates and p-aminohippurate. [14C]Salicylate uptake via NLT was saturable (Km = 88.8 +/- 23.4 microM) and sodium-independent. Expression of the mRNA of NLT was detected in the liver and kidney (liver >> kidney). We propose that NLT be renamed OAT2.

Animals↗
PubMed1998

Intrasarcomere [Ca2+] gradients and their spatio-temporal relation to Ca2+ sparks in rat cardiomyocytes.

1. Line-scan analyses of spontaneous Ca2+ sparks, non-propagating local rises in Ca2+ concentration, and the early phase of Ca2+ transients in cardiomyocytes were performed with a rapid-scanning laser confocal microscope (Nikon RCM8000) and fluo-3. 2. On electrical stimulation, points at which rise in Ca2+ began earliest were observed at regular spacings of 1.82 +/- 0.26 micron (mean +/- S.D.) along the longitudinal axis of the cell. The points were heavily stained with di-2-ANEPEQ, which stains the T-tubules, indicating that they were at the Z-line. 3. The points where spontaneous Ca2+ sparks originated coincided with the points which showed faster Ca2+ elevation, i.e. the Z-line. 4. In some cases where a Ca2+ spark had occurred within about 30 ms before the evoked Ca2+ transient, fast elevation of Ca2+ was not observed at the corresponding Z-line, indicating the presence of a refractory period in Ca2+ release from the SR. 5. The present results provide visual evidence for Ca2+ release from the junctional sarcoplasmic reticulum in cardiomyocytes. The presence of a refractory period in Ca2+ release after Ca2+ sparks provided new evidence that the normal Ca2+ transient may be the summation of Ca2+ sparks.

Aniline Compounds↗
PubMed1998

Frequent clonal expansion of peripheral T cells in patients with autoimmune diseases: a novel detecting system possibly applicable to laboratory examination.

To investigate T cell involvement in antigen-specific immune responses, it is important to detect accumulating T cells at a clonal level in vivo. However, thus far the clinical application of such analyses has been limited. Here we have established novel primers to anneal with T cell receptor (TCR) beta genes of multiple Vbeta families and applied them to reverse transcription-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis to evaluate peripheral T cell clonality of autoimmune disease patients. As a result, the new Vbeta primers could detect accumulating T cell clones in the periphery of healthy individuals and patients. It was revealed that patients with autoimmune diseases such as systemic lupus erythematosus (SLE) had a larger number of clonal accumulations of peripheral T cells compared with normal individuals. Thus, the RT-PCR-SSCP system using the new multifamily Vbeta primers is the first such laboratory examination to detect T cell clonal expansion, and will provide a simple and sensitive tool to aid in the diagnosis and also in the investigation of the pathogenesis of autoimmune diseases.

Adult↗
PubMed1998

Myeloproliferative disease in a calf.

A myeloproliferative disease was found in a 128-day-old Holstein female calf. The tumour consisted chiefly of primitive cells, and more mature cells, many of which were positive for haemoglobin, were admixed with them. Binucleated cells at various stages of maturation were occasionally seen, and siderosomes were confirmed in both primitive cells and more mature cells by electron microscopy. The primitive cells resembled proerythroblasts, and this tumour, thought to be an acute type neoplasm of the erythroid system, was distinguishable from chronic erythremic myelosis and polycythemia vera.

Animals↗
PubMed1998

Role of sarcoplasmic reticulum in myocardial contraction of neonatal and adult mice.

Changes in action potential parameters by and inotropic responses to nicardipine, verapamil, ryanodine and cyclopiazonic acid were examined in isolated ventricular myocardial preparations from neonatal and adult mice. The action potential of both neonatal and adult mice had a unique configuration with little evidence of a plateau at depolarized membrane potential; the action potential duration was significantly larger in neonatal preparations. Nicardipine had no effect on action potential parameters in the adult while it significantly shortened the action potential duration at 50% repolarization in the neonate. Ryanodine significantly shortened the action potential duration at 80% repolarization at both ages: the shortening was significantly larger in the adult when compared with the neonate. The contraction of ventricular preparations from adult mice were relatively resistant to nicardipine and verapamil. Nicardipine or verapamil, even at 10(-5) M, only decreased the contractile force to 70% of control values; the decrease was much less than that reported in other experimental species such as chick, guinea pig or rabbit. In the neonate, 10(-5) M nicardipine or verapamil decreased the contractile force to 30% of control values. Ryanodine had a potent negative inotropic effect both in the neonate and adult; the effect was significantly larger in the adult. Cyclopiazonic acid produced a decrease in contractile force and prolongation of the time required for relaxation; both effects were significantly larger in the adult. These results suggest that the contraction of the adult mouse myocardium is highly dependent on SR function and less dependent on transsarcolemmal Ca2+ influx when compared with the myocardium of the neonatal mouse and that of other species.

Age Factors↗
PubMed1998

Functional characterization of renal chloride channel, CLCN5, mutations associated with Dent'sJapan disease.

BACKGROUND: The annual urinary screening of Japanese children above three years of age has identified a progressive renal tubular disorder characterized by low molecular weight proteinuria, hypercalciuria and nephrocalcinosis, and this represents a variant of Dent's disease. Hitherto, 12 mutations of the X-linked renal specific chloride channel, CLCN5, have been reported in the Dent'sJapan variant. To further identify such CLCN5 mutations and to define the structure-function relationships of this channel, we have investigated five unrelated, non-consanguinous Japanese families with this disorder. METHODS: Leukocyte DNA from probands was used with CLCN5 primers for PCR amplification of the coding region, and the DNA sequences of the products determined. Functional studies were performed by expressing the mutants in Xenopus oocytes. RESULTS: Five CLCN5 mutations consisting of two nonsense (R648X and R704X), two missense (S270R and L278F) and one acceptor splice site mutation (ag-->cg) in intron 4 were identified. The missense and splice site mutations represent novel abnormalities. Heterologous expression in Xenopus oocytes of wild-type and the missense mutants demonstrated that the mutations, which were translated, either abolished or markedly reduced chloride conductance. CONCLUSIONS: These results expand the spectrum of CLCN5 mutations associated with this renal disorder and provide insight into possible structure-function relationships. For example, both the missense mutations are located within a short putative loop between two transmembrane domains, and our results suggest that this region may have an important functional role in the regulation of channel activity.

Adolescent↗
PubMed1998

P2 purinoceptor localization along rat nephron and evidence suggesting existence of subtypes P2Y1 and P2Y2.

Effects of extracellular ATP on intracellular free calcium concentration([Ca2+]i) were examined in rat single nephron segments using the fura 2-AM. ATP (10 ¿M) induced a significant transient increase in [Ca2+]i in the glomerulus, the early proximal convoluted tubule (S1), the cortical collecting tubule (CCT), and the outer medullary collecting tubule (OMCT). The magnitude of the response was the greatest in the OMCT among four segments. ATP induced an increase in the [Ca2+]i in a dose-dependent manner in S1 and OMCT. In the OMCT, ATP caused a biphasic increase in [Ca2+]i consisting of an initial rapid rise and a sustained phase. Removal of calcium from the medium resulted in an attenuation of the sustained phase of [Ca2+]i and an approximately 30% reduction in the height of the initial [Ca2+]i peak in response to 10 ¿M ATP. Effects of ATP, its analogs, and its metabolites were tested in the S1 and OMCT. ATP, 2-methylthio-ATP (2-MeS-ATP), ADP, and UTP increased [Ca2+]i dose dependently. AMP and adenosine did not affect [Ca2+]i in the S1 and OMCT. The ATP- or 2-MeS-ATP-induced [Ca2+]i increase was inhibited by the pretreatment of the S1 and OMCT with suramin or reactive blue 2. Neomycin, a phospholipase C inhibitor, attenuated the ATP-induced [Ca2+]i increase. To investigate the hormonelike action of ATP in OMCT, a heterologous cross desensitization was performed. The pretreatment of OMCT with ATP inhibited increases in vasopressin-, ANG II-, endothelin-1-, or bradykinin-induced[Ca2+]i increase. These findings suggest that ATP might affect the above peptidyl agonist-activated calcium mobilizations.

Adenosine↗
PubMed1998

Cloning, functional characterization, and localization of a rat renal Na+-dicarboxylate transporter.

We report here the isolation, functional characterization, tissue distribution, and membrane localization of rat renal Na+-dicarboxylate transporter (rNaDC-1). rNaDC-1 consists of 2,245 nucleotides, and the deduced amino acid sequence showed 73% and 75% identity to rabbit and human NaDC-1, respectively. When expressed in Xenopus laevis oocytes, rNaDC-1 mediated sodium-dependent uptake of di- and tricarboxylates. Substrates of rNaDC-1 evoked inward currents in oocytes expressed with rNaDC-1; succinate, alpha-ketoglutarate, and glutarate were relatively high-affinity substrates, and citrate was a low-affinity substrate of rNaDC-1. The coupling ratio of citrate to charge was determined to be 1:1 at pH 7.4; influx of one positive charge per citrate molecule suggests a symport of three Na+ with a divalent citrate. Expression of rNaDC-1 mRNA was detected in the kidney and the small and large intestines. Immunohistochemistry using polyclonal antibodies raised against the 14 amino acids at the COOH terminus of rNaDC-1 revealed that rNaDC-1 is localized exclusively in the luminal membrane of S2 and S3.

Amino Acid Sequence↗
PubMed1998

Evaluation of shikonin on granulation tissue formation compared with carrageenan.

The effect of shikonin (SK) on granulation tissue formation was biochemically evaluated and the biological effect of SK on cotton pellet induced granulation tissue formation and the induction of hind paw edema was compared with that of lambda-carrageenan (carrageenan) in rats. The dry weight of granulation tissue formed was increased by SK. The amounts of hemoglobin and hydroxyproline in granulation tissue were also increased by SK. These results suggest that SK has an enhancing effect on the formation of granulation tissue, accompanied by the proliferation of capillaries and the increased production of collagen in rats. SK showed mild stimulation toward swelling when injected into the hind paws of rats, as did carrageenan, while it showed a marked enhancing effect on granulation tissue formation compared with carrageenan. These results suggest that the mechanism underlying the biological effect of SK on granulation tissue formation is different from that of carrageenan, though the mild stimulation by SK might still contribute in part to the enhancing effect on granulation tissue formation.

Animals↗
PubMed1998

[Effect of shikonin and alkannin on hydroxyl radical generation system concerned with iron ion].

The effects of shikonnin (SK) and its optical isomer alkannin (AK) on the hydroxyl radical (HO.) generation system including iron ions were evaluated using the spin trap method by ESR spectroscopy. 5,5-Dimethyl-1-pyrroline-1-oxide (DMPO) was used as a spin trap agent and HO. was generated by a reaction between an iron ion and hydrogen peroxide, which is called Fenton reaction system. SK inhibited the HO. spin adduct (DMPO-OH) yielded in a dose-dependent manner. In this effect no difference was observed between SK and AK. When different concentrations of DMPO were used for the confirmation of its competitive reaction, no difference was also observed in the concentration of SK required to reduce the amount of the DMPO-OH by 50% (ID50). These findings suggested that the inhibitory effect of SK against the thus yielded DMPO-OH was not generated by the scavenging for HO., but by the inhibition on the Fenton reaction system. The mechanism of the inhibition on this system may be based on the formation of a complex between SK and the iron ion. The molar ratio of SK to the iron ion in the complex was considered 2 to 1 (2:1), because the concentrations of the observed ID50 and the used iron ion exhibited the same value. In addition, the same result was also obtained from the study using spectroscopic analysis.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

[Anti-dermaptophyte activity of phenolic compounds in "mokusaku-eki"].

"Mokusaku-eki," a kind of pyroligneous acid, is a dark brown color solution obtained from the charcoal burner of such Quercus spp. woods as a by-product. This is used as a folk medicine in water eczema. The n-hexane fraction of this solution contained several phenolic compounds such as 4-ethyl-2-methoxyphenol (3) and 2,6-dimethoxyphenol (4), which could not be found in the fresh woods. Among these compounds, 3 has the highest anti-dermaptophyte activity against Trichophyton mentagrophytes at minimum inhibitory concentration (MIC) 150 micrograms/ml.

Alkaloids↗