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T Sekine

Publications and source records attributed to T Sekine.

At least 73 records · Page 4Linked to original sources
PubMed2000

Purinoceptor-mediated calcium mobilization and cellular proliferation in cultured bovine corneal endothelial cells.

In the present study, we investigated the effect of adenosine triphosphate (ATP) on cytosolic free calcium mobilization and mitogenic activity in cultured bovine corneal endothelial cells (BCEC). The [Ca2+]i was determined using a Ca2+ sensitive indicator, Fura-2/AM, and cell proliferation was evaluated by counting the cell number. ATP, its metabolites and analogs caused transient increase in [Ca2+]i in a concentration-dependent manner (10(-7) M-10(-3) M) and the potency of agonists was ordered as follows: 2-methylthio-ATP > uridine triphosphate > ATP > adenosine diphosphate. Adenosine monophosphate and adenosine did not affect [Ca2+]i. ATP (10(-4) M) also promoted the accumulation of inositol trisphosphate (IP3). The ATP-induced transient [Ca2+]i increase and IP3 accumulation were attenuated by pretreatment with a phospholipase C inhibitor, U-73122 (5 microM), for 30 min. ATP (10(-5) M) significantly enhanced the proliferation of BCEC. ATP-induced [Ca2+]i increase and cell proliferation were inhibited by a purinoceptor antagonist, suramin (10(-4) M). Thus, the present study indicates that BCEC contain P2 purinoceptors that regulate their proliferation.

Adenosine Triphosphate↗
PubMed2000

Accumulation of identical T cell clones in the right and left lobes of the thyroid gland in patients with Graves' disease: analysis of T cell clonotype in vivo.

To elucidate the involvement of intrathyroidal T cells in the thyroid antigen-specific immune response in Graves' disease (GD), we investigated whether identical T cell clonotypes accumulate clonally in the right and left lobes of thyroid glands of GD patients. mRNAs extracted from thyroid glands of five females patients with GD were reverse-transcribed to cDNA and then the genes coding the T cell receptor B chain variable (V-NDN-J) region were amplified using polymerase chain reaction. Single strand conformation polymorphism analysis and subsequently nucleotide sequencing were also performed to determine the clonotype of accumulating T cells. T cells infiltrating the thyroid glands showed oligoclonal expansion. The expanded T cell clonotypes were not detected in peripheral blood of the same patients. Importantly, the majority of expanding T cell clonotypes in the two lobes of the thyroid glands were identical. Our findings suggest that the clonal expansion of identical T cell clonotypes in the two lobes is driven by factors common to both lobes, such as thyroid-specific antigens, in patients with Graves' disease.

Adult↗
PubMed2000

Rat multispecific organic anion transporter 1 (rOAT1) transports zidovudine, acyclovir, and other antiviral nucleoside analogs.

Organic anion transporter 1 (OAT1) is a p-aminohippurate/dicarboxylate exchanger that plays a primary role in the tubular secretion of endogenous and exogenous organic anions. OAT1 is located in the basolateral membrane of the proximal tubular cells and mediates the uptake of various organic anions from the peritubular fluid. In this study, we investigated the transport of antiviral nucleoside analogs via rat OAT1 (rOAT1) using a heterologous expression system in Xenopus laevis oocytes. Oocytes injected with rOAT1 cRNA showed significantly higher uptake of zidovudine (AZT) and acyclovir (ACV) than control oocytes. rOAT1-mediated uptake of AZT and ACV was probenecid-sensitive and increased by the outwardly directed gradient of glutarate. The affinity of rOAT1 for AZT and ACV was determined to be 68 and 242 microM, respectively. Five other antiviral agents that we studied (zalcitabine, didanosine, lamivudine, stavudine, and trifluridine) were also shown to be transported by rOAT1, whereas foscarnet, a phosphate analog, was not. The aforementioned nucleoside analogs lack a typical anionic group and are not very hydrophobic. This study demonstrates extension of the substrate spectrum of rOAT1 and provides a molecular basis for the pharmacokinetics of antiviral nucleoside analogs.

Acyclovir↗
PubMed2000

Artificial trachea and long term follow-up in carinal reconstruction in dogs.

We have already reported successful carinal reconstruction of the trachea with an observation period of 1 - 2 years. In this study, we evaluate the long-term safety and efficacy of the reconstruction after 5-years of follow-up. The Y-shaped Marlex mesh tube was reinforced with a polypropylene spiral and coated with atelocollagen made from porcine skin. The prosthesis was 60 mm long with an outer diameter of 18 mm. Replacement of the tracheobronchial bifurcation was preformed through a right thoracotomy in a beagle dog. Bronchoscopical examination and sampling of the tracheal epithelium was performed periodically to check the function of cilia. The implanted prothesis was promptly infiltrated by the surrounding connective tissue and completely incorporated by the host trachea and bronchus. Bronchoscopically, sufficient epithelization was confirmed from the upper to the lower site of anastomosis. After 5 years neither stenosis nor dehiscence was observed. In spite of there being mesh-exposure at the luminal surface, the dog had no clinical symptoms until sacrifice for pathological examination. The bent frequency of the cilia was maintained within the normal range, indicating functional recovery of the regenerating airway. Our tracheal prosthesis is promising for clinical repair of the tracheobronchial bifurcation.

Animals↗
PubMed2000

[Characteristics of Papaver somniferum L. cv. ikkanshu cultivated in Izu].

The seeds of Papaver somniferum L. cv. Ikkanshu were sown in November (Autumn sowing: AS) and March (Spring sowing: SS) in a field at Izu Experimental Station for Medicinal Plants of National Institute of Health Sciencs, and both AS and SS plants were cultivated to investigate their growth, opium yield and alkaloid content in the opium. Growing periods from the sowing to the opium harvest were approximately six months for AS plants and three months for SS plants. Sizes of plants and capsules in AS were bigger than those in SS, reflecting their growth period. Opium yields per an are in AS and SS were 212.09 g and 142.03 g, respectively. The opium was able to be collected four times in the AS plants though the SS plants ceased to exude opium after the second incision. Therefore higher yield of opium in AS plants seems to be attributed to an amount of opium in the third and fourth incision. Average morphine content in the total opium was 15.61% in AS plants and 15.04% in SS plants, and the estimated amounts of morphine per an are in AS and SS plants were 33.16 g and 21.38 g, respectively.

Government Agencies↗
PubMed1999

Developmental conversion of inotropism by endothelin I and angiotensin II from positive to negative in mice.

Inotropic effects on isolated neonatal and adult mouse myocardium of endothelin I and angiotensin II were examined. Endothelin I produced a sustained positive inotropic response in the neonate but a sustained negative response in the adult. Both were concentration-dependent and were inhibited by the endothelin ETA receptor antagonist, BQ-123 (Cyclo(D-a-aspartyl-L-prolyl-D-valyl-L-leucyl-D-tryptophyl)). Angiotensin II produced a sustained positive inotropic response in the neonate while a sustained negative response in the adult. Both were concentration-dependent and were inhibited by the angiotensin AT1 receptor antagonist, YM358 (2,7-diethyl-5-((2'-(1 H-tetrazol-5-yl)biphenyl-4-yl)methyl-5H-pyrazolo(1,5-b)(1,2,4)tria zole potassium salt monohydrate). These results indicate that inotropic responses of the mouse heart to cardioactive peptides are unique among experimental animal species and may be reversed during development.

Age Factors↗
PubMed1999

Molecular cloning and characterization of a new multispecific organic anion transporter from rat brain.

A cDNA encoding the new member of the multispecific organic anion transporter family, OAT3, was isolated by the reverse transcription-polymerase chain reaction cloning method. Degenerate primers were designed based on the sequences conserved among OAT1, OAT2, and organic cation transporter 1 (OCT1), and reverse transcription-polymerase chain reaction was performed using rat brain poly(A)+ RNA. The 536-amino acid protein sequence encoded by OAT3 showed 49, 39, and 36% identity to those of OAT1, OAT2, and OCT1, respectively. Northern blot analysis revealed that rat OAT3 mRNA is expressed in the liver, brain, kidney, and eye. When expressed in Xenopus laevis oocytes, OAT3 mediated the uptake of organic anions, such as p-aminohippurate (Km = 65 microM), ochratoxin A (Km = 0.74 microM), and estrone sulfate (Km = 2.3 microM) and a cationic compound, cimetidine. OAT3-mediated uptake of [3H]estrone sulfate was sodium-independent. para-Aminohippuric acid, estrone sulfate or ochratoxin A did not show any trans-stimulatory effect on either influx or efflux of [3H]estrone sulfate via OAT3. Organic anions such as sulfobromophthalein, probenecid, indocyanine green, bumetanide, piroxicam, furosemide, azidodeoxythymidine, 4, 4'-diisothiocyanostilbene-3,3'-disulfonic acid, and benzylpenicillin inhibited OAT3-mediated estrone sulfate uptake, while ouabain and digoxin did not. Organic cations such as tetraethylammonium, guanidine, verapamil, and quinidine did not interact with OAT3. Acidic metabolites of neurotransmitters derived from dopamine, epinephrine, norepinephrine, and serotonin inhibited the uptake of estrone sulfate via OAT3. These results suggest an important role of OAT3 in the excretion/detoxification of endogenous and exogenous organic anions, especially from the brain.

Amino Acid Sequence↗
PubMed1999

RGS7 and RGS8 differentially accelerate G protein-mediated modulation of K+ currents.

The recently discovered family of RGS (regulators of G protein signaling) proteins acts as GTPase activating proteins which bind to alpha subunits of heterotrimeric G proteins. We previously showed that a brain-specific RGS, RGS8 speeds up the activation and deactivation kinetics of the G protein-coupled inward rectifier K+ channel (GIRK) upon receptor stimulation (Saitoh, O., Kubo, Y., Miyatani, Y., Asano, T., and Nakata, H. (1997) Nature 390, 525-529). Here we report the isolation of a full-length rat cDNA of another brain-specific RGS, RGS7. In situ hybridization study revealed that RGS7 mRNA is predominantly expressed in Golgi cells within granule cell layer of cerebellar cortex. We observed that RGS7 recombinant protein binds preferentially to Galphao, Galphai3, and Galphaz. When co-expressed with GIRK1/2 in Xenopus oocytes, RGS7 and RGS8 differentially accelerate G protein-mediated modulation of GIRK. RGS7 clearly accelerated activation of GIRK current similarly with RGS8 but the acceleration effect of deactivation was significantly weaker than that of RGS8. These acceleration properties of RGS proteins may play important roles in the rapid regulation of neuronal excitability and the cellular responses to short-lived stimulations.

Amino Acid Sequence↗
PubMed1999

Intraoperative irradiation after surgery for locally recurrent rectal cancer.

PURPOSE: This study retrospectively evaluated the effects of intraoperative electron beam irradiation on patients with locally recurrent (pelvic) rectal cancer. METHODS: From November 1, 1975, to December 31, 1997, 51 patients underwent surgery for locally recurrent rectal or rectosigmoid cancer, and 27 patients received intraoperative electron beam irradiation. The intraoperative electron beam irradiation dose was 15 to 30 Gy. Kaplan-Meier survival estimates at three and five years were analyzed for the 47 patients who recovered postoperatively. RESULTS: Statistically significant factors related to survival included intraoperative electron beam irradiation vs. no intraoperative electron beam irradiation (P=0.0007), amount of residual tumor (slight vs. gross; P=0.0022), and symptom status (P=0.0024). Factors not associated with survival included distant metastases at reoperation, type of surgery for the recurrent tumor, external beam irradiation, pathologic grade, age, and gender. Surgical resection without intraoperative electron beam irradiation resulted in three-year and five-year survival rates of 5 and 0 percent, respectively. For patients who received intraoperative electron beam irradiation, the three-year survival rate was 43 percent and five-year survival rate was 21 percent. Intraoperative electron beam irradiation was a statistically significant factor related to survival in patients with and without distant metastasis (P=0.04 and P=0.0035, respectively), with slight residual tumor (P=0.0003), or with palliative surgery (P=0.0276). CONCLUSION: The trends seen in resection with intraoperative electron beam irradiation are encouraging with regard to improvements in survival as compared with studies not using intraoperative electron beam irradiation treatment.

Adult↗
PubMed1999

Intrathoracic esophageal replacement in the dog with the use of an artificial esophagus composed of a collagen sponge with a double-layered silicone tube.

OBJECTIVES: Intrathoracic esophageal replacement with an artificial esophagus is considered difficult. We attempted to replace the intrathoracic esophagus with an artificial esophagus composed of a collagen sponge with a double-layered silicone tube and examined the state of host tissue regeneration. METHODS: A 5-cm long gap was created in the intrathoracic esophagus in 9 dogs and repaired by interposition of our prosthesis. The dogs were fed only by intravenous hyperalimentation for 28 days. The silicone tube was removed at 29 days after the operation, and oral feeding was reintroduced. RESULTS: One dog was put to death at each of the following times: 1, 2, 3, 3, 6, 12, and 24 months after the operation. One dog is still surviving without problems after more than 26 months. One dog died of malnutrition at 10 months. In all dogs, the host regenerated tissue had replaced the resulting gap at the time of silicone tube removal. The mucosa had fully regenerated within 3 months and the glands within 12 months. The process of stenosis and shrinkage was complete within 3 months and did not advance thereafter. The lamina muscularis mucosae were observed as islets of smooth muscle within 12 months. Although the skeletal muscle regenerated close to the anastomoses, it did not extend to the middle of the regenerated esophagus even after 24 months. CONCLUSIONS: Use of a collagen sponge with a double-layered silicone tube was shown to be feasible even in the thorax and to allow the regenerated host tissue, consisting of the mucosa, glands, and lamina muscularis mucosae, to replace the esophageal gap.

Anastomosis, Surgical↗
PubMed1999

Production of radioactive endovascular stents by implantation of 133Xe ions.

A coronary stent was made radioactive by implantation of 133Xe ions for the purpose of suppressing the renarrowing of the part of blood vessel in which the stent is implanted. Electrons of relatively low energies emitted in the decay of 133Xe may give an antiproliferative effect of ionizing radiation to the intimal cells within a limited range of 1 mm. A 133Xe+ beam accelerated at 40 or 60 keV was directed to several stainless steel stents mounted on a target-holder table that could revolve and move up and down to distribute the 133Xe+ ions within a stent as well as among the stents. The radioactive stents produced contained up to 100 kBq of 133Xe and were implanted into the abdominal aortas of rabbits. Neointimal thickening was analyzed by histomorphometry for samples taken 4 weeks after stent implantation. The results indicate that the radioactive stents have a potential to suppress neointimal hyperplasia in rabbits.

Angioplasty, Balloon, Coronary↗
PubMed1999

Low BCL-2 expression in acute leukemia with t(8;21) chromosomal abnormality.

In de novo t(8;21) AML which shows terminal neutrophilic differentiation, the BCL-2 expression was found to be significantly lower than that in types of other AML regardless of the phenotypic differentiation status. An inverse correlation between BCL-2 expression and the S/G2/M population cells was observed in AML. The S/G2/M population in t(8;21)AML was larger than in the other types of AML. In t(8;21)AML, spontaneous apoptosis after a 12-h liquid culture was prominent, and the autonomous DNA synthesis after a 72-h liquid culture was low. G-CSF and IL-5 promoted the colony formation of t(8;21)AML cells. The data suggest that, in vivo, the low BCL-2 in t(8;21)AML induced entry of cells from the G0/G1 phase to S phase, but the cells easily die by apoptosis, in vitro. The low BCL-2 expression and the supportive effects of G-CSF and IL-5 in t(8;21)AML is thought to be a key phenomenon which might be related to the formation of the in vivo blood picture, such as prominent neutrophilic differentiation and eosinophilia. Cellular extracts from t(8;21)AML cell line Kasumi-1 bound to both the AML1 and CRE binding sites in the bcl-2 promoter, but none of the cellular extracts from de novo t(8;21)AML bound to either of these sites. The DNA binding activity of transactivators in de novo t(8;21)AML is different from that in Kasumi-1 cells probably due to the phosphorylation status.

Acute Disease↗
PubMed1999

Role of organic anion transporter 1 (OAT1) in cephaloridine (CER)-induced nephrotoxicity.

UNLABELLED: Role of organic anion transporter 1 (OAT1) in cephaloridine (CER)-induced nephrotoxicity. BACKGROUND: Cephaloridine (CER) has been used to elucidate the mechanisms of cephalosporin antibiotic-induced nephrotoxicity. Organic anion transporters have been thought to mediate CER uptake by the proximal tubule. The purpose of this study was to elucidate the possible involvement of organic anion transporter 1 (OAT1) in CER-induced nephrotoxicity. METHODS: A mouse terminal proximal straight tubule (S3) cell line stably expressing rat OAT1 (S3 rOAT1) was established and used in this study. The cellular uptake of [14C]-para-aminohippuric acid (PAH), a prototype organic anion, and that of [14C]-CER were measured. The effects of CER on the viability of the cells and the amount of lipid peroxidation were estimated. RESULTS: S3 rOAT1 expressed a functional organic anion transporter in the cytoplasmic membrane, and exhibited CER uptake activity. CER treatment resulted in a more significant decrease in the viability and a more significant increase in the amount of lipid peroxidation in S3 rOAT1 than in S3 cells transfected with an expression vector lacking the rOAT1 insert. Probenecid, an inhibitor of organic anion transport, and probucol, an antioxidant, significantly suppressed the decrease in viability and increase in the amount of lipid peroxidation in S3 rOAT1 treated with CER. The effects of various cephalosporin antibiotics on the uptake of [14C]PAH were correlated significantly with the effects of these drugs on cell viability. CONCLUSIONS: These results suggest that rOAT1 is, at least in part, responsible for the cellular uptake of CER and therefore CER-induced nephrotoxicity.

Animals↗
PubMed1999

Increased choline kinase activity and elevated phosphocholine levels in human colon cancer.

Nuclear magnetic resonance spectroscopy has detected elevated phosphocholine levels in human tumor tissues and cells, and in cells that were transformed with the activated Ha-ras gene and stimulated in vitro with growth-promoting factors such as platelet-derived growth factor, epidermal growth factor, and phorbol ester. However, the mechanism of the elevation and the function of the increased phosphocholine levels have not been clearly demonstrated. We studied phosphocholine levels enzymatically and analyzed the activity of choline kinase, which catalyzes the phosphorylation of choline to produce phosphocholine, in human colon cancer and adenoma. Both choline kinase activity and phosphocholine levels were increased in colon cancer and adenoma tissue. The activation of choline kinase and the increased levels of choline kinase alpha were partly responsible for the elevated phosphocholine levels. This study suggests that choline kinase might play a role in growth promotion or signal transduction in carcinogenesis.

Adult↗
PubMed1999

Type II collagen is a target antigen of clonally expanded T cells in the synovium of patients with rheumatoid arthritis.

OBJECTIVE: To investigate whether type II collagen (CII) is recognised by oligoclonally expanded synovial T cells of patients with rheumatoid arthritis (RA). METHODS: Peripheral blood mononuclear cells (PBMC) from 15 RA patients were stimulated with CII in vitro. T cell clones expanded by such stimulation were compared with the clonally expanded synovial T cells by using T cell receptor (TCR) B chain gene specific reverse transcription-polymerase chain reaction and subsequent single strand conformation polymorphism analyses. RESULTS: Stimulation of the heterogeneous peripheral T cells with CII induced clonal expansion of T cells. In three of 15 patients, a proportion of these clones (approximately 17% to 25%) was found to be identical to expanded T cell clones in the synovium in vivo. CONCLUSION: T cell clones that had TCR CDR3 sequences identical to those induced by purified CII were found in a proportion of RA patients. This finding suggests that CII is recognised by T cells that accumulate clonally in RA joints. Oligoclonal T cell expansion in RA joints is probably driven, at least in part, by intra-articular components such as CII.

Aged↗
PubMed1999

Molecular cloning and functional expression of a multispecific organic anion transporter from human kidney.

Recently, we isolated the multispecific organic anion transporter (OAT1) from the rat kidney, which plays important roles in the renal elimination of endogenous and exogenous organic anions including clinically important drugs. In the present study, we cloned and characterized human OAT1. Two cDNA clones, hOAT1-1 cDNA and hOAT1-2 cDNA, were isolated from a human kidney cDNA library, whose amino acid sequences were 86.0% and 87.8% identical to that of rat OAT1, respectively. When expressed in Xenopus laevis oocytes, hOAT1 mediated sodium-independent uptake of p-aminohippurate (PAH) (Km = 9. 3 +/- 1.0 microM). hOAT1-mediated PAH uptake was inhibited by bulky inorganic anions, various xenobiotics, and endogenous substances, including benzylpenicillin, furosemide, indomethacin, probenecid, phenol red, urate, and alpha-ketoglutarate. Northern blot analysis revealed that hOAT1 mRNA is strongly expressed in human kidney; transcripts of different sizes are expressed in skeletal muscle, brain, and placenta. Immunohistochemical analysis using rabbit IgG antibody against the carboxy-terminal 14 peptides of hOAT1 revealed that hOAT1 is expressed at the basolateral membrane of the proximal tubule. hOAT1 gene was located on human chromosome 11q13.1 by fluorescent in situ hybridization analysis. These results indicate that hOAT1 is a multispecific organic anion transporter on the basolateral membrane of the proximal tubule in human kidney.

Amino Acid Sequence↗
PubMed1999

Immunohistochemical localization of multispecific renal organic anion transporter 1 in rat kidney.

Renal proximal convoluted tubules have an important role, i.e., to excrete organic anions, including numerous drugs and endogenous substances. Recently, multispecific organic anion transporter 1 (OAT1) was isolated from rat kidney. In this study, the cellular and subcellular localization of OAT1 in rat kidney was investigated. Kidneys from normal rats were perfused and fixed with periodate-lysine-paraformaldehyde solution and were then processed for immunohistochemical analysis using the labeled streptavidin-biotin method, preembedding horseradish peroxidase method, and immunogold method. Light microscopic examination revealed immunostaining for OAT1 in the middle portion of the proximal tubule (S2 segment), but not in the initial portion of the proximal convoluted tubule, next to the glomerulus. Nephron segments other than the S2 segment and the renal vasculature were not stained with antibody to OAT1. Electron-microscopic observation using a preembedding method revealed that OAT1 was exclusively expressed in the basolateral membrane of S2 segments of proximal tubules. The immunogold method showed no labeling for OAT1 in the cytoplasmic vesicles, suggesting that OAT1 may not move together with organic anions into the cells. These results are consistent with previous physiologic data showing that organic anions, including para-aminohippurate, are taken up by the basolateral Na+-independent organic anion/dicarboxylate exchanger and excreted at S2 segments. In conclusion, OAT1 was localized to the basolateral membrane of S2 segments of proximal tubules in rat kidneys.

Animals↗