Biomedical subjects

Y Kanai

Publications and source records attributed to Y Kanai.

At least 109 records · Page 6Linked to original sources

PubMed1999

Disruption of E-cadherin-mediated cell adhesion systems in gastric cancers in young patients.

The aim of this study was to elucidate the pathogenetic backgrounds of early-onset gastric cancers. Mutations of the E-cadherin and beta-catenin genes were analyzed by subjecting microdissected cancer cells and corresponding non-cancerous epithelial cells obtained from 9 gastric cancer patients under 35 years old to polymerase chain reaction-single strand conformation polymorphism analysis. Somatic, but no germline, E-cadherin gene mutations were detected in 6 (67%) of the patients. The cancer cells of 2 patients were exon 9-deleted E-cadherin molecule-immunoreactive. Neither somatic nor germline mutations in exon 3 of the beta-catenin gene were observed in any patient. One patient lacked beta-catenin immunoreactivity and the cancer cells of 6 others showed cytoplasmic beta-catenin immunoreactivity. The E-cadherin-mediated cell adhesion system in the cancer cells of all the patients examined appeared to be disrupted, indicating that somatically acquired dysfunction of this system plays an important role in early-onset diffuse-type gastric cancers. Helicobacter pylori infection was observed in 6 (67%) of our 9 patients, an incidence higher than the average in young Japanese individuals. Thus, early-onset gastric cancers may be attributable to environmental factors such as Helicobacter pylori infection.

Adult↗

PubMed1999

Immunoadsorption plasmapheresis as a treatment for pregnancy complicated by systemic lupus erythematosus with positive antiphospholipid antibodies.

PROBLEM: Our purpose was to study the effect of maternal immunoadsorption plasmapheresis (IA) on the outcome of pregnancies complicated by systemic lupus erythematosus (SLE) with positive antiphospholipid antibodies, which were known to have a strong correlation with abortion or stillbirth. METHOD OF STUDY: Eight pregnancies in 7 patients with SLE were treated according to our protocol. They were all positive for the lupus anticoagulant. The treatments provided in these cases were as follows: an oral low-dose steroid; oral low-dose aspirin; and IA. The outcomes of the pregnancies were then studied. RESULTS: Of eight pregnancies, seven resulted in preterm deliveries, and cesarean sections were performed at 26-36 weeks of gestation. In one case, intrauterine fetal death occurred at 24 weeks of gestation. The other seven pregnancies resulted in live births (survival rate of 87.5%). CONCLUSION: IA improves the outcome of pregnancy complicated by SLE with positive antiphospholipid antibodies, without increasing steroid dosage.

Adult↗

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

[Amino acid transporter molecule as a drug target].

Amino acids, especially essential amino acids are required for protein synthesis and as energy sources in all living cells. Since most amino acids are hydrophilic, special membrane proteins are necessary for their transmembrane transport particularly in transformed cells. We cloned a cDNA encoding L-type amino acid transporter, and named it LAT1. LAT1 is highly expressed in most tumor cells and in a few normal tissues such as the bone marrow, spleen, placenta and brain. As a homolog of LAT1, we also cloned LAT2 which is expressed in various normal tissues. In order to clarify the role of LAT1 in tumor cells, we tested a relatively specific inhibitor to LAT1, BCH (2-aminobicyclo-2(2,2,1)-heptane-2-caboxylic acid), and found that BCH inhibited mortality of mice treated with sarcoma cells. In addition, BCH also suppressed strongly T24 carcinoma cell growth. Moreover, LAT1 transports amino acid mimetic drugs. Thus, these results indicate that amino acid transporter molecule such as LAT1 can be a drug target.

Amino Acid Transport Systems↗

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↗

PubMed1999

T-1095, an inhibitor of renal Na+-glucose cotransporters, may provide a novel approach to treating diabetes.

T-1095A and T-1095 are synthetic agents derived from phlorizin, a specific inhibitor of Na+-glucose cotransporters (SGLTs). Unlike phlorizin, T-1095 is absorbed into the circulation via oral administration, is metabolized to the active form, T-1095A, and suppresses the activity of SGLTs in the kidney. Orally administered T-1095 increases urinary glucose excretion in diabetic animals, thereby decreasing blood glucose levels. Indeed, the postprandial hyperglycemia after a meal load was shown to be suppressed by this compound in streptozotocin (STZ)-induced diabetic rats. With long-term T-1095 treatment, both blood glucose and HbA1c levels were reduced in STZ-induced diabetic rats and yellow KK mice. In addition, there was amelioration of abnormal carbohydrate metabolism, i.e., hyperinsulinemia and hypertriglyceridemia, and of the development of microalbuminuria, in yellow KK mice. Thus, T-1095 may be a useful antidiabetic drug, providing a novel therapeutic approach for diabetes.

Administration, Oral↗

PubMed1999

[Plasmapheresis for collagen diseases].

Recently plasmapheresis has been performed for connective tissue disease. Double-filtration plasmapheresis (DFPP) has mainly been performed for rheumatoid arthritis (RA) and systemic lupus erythematosus (SEL) since 1980. In DFPP, autoantibodies and immune complex are removed by the second filter. The adaptation of plasmapheresis is commonly for cases (1) which are resistant to some medications, (2) which have a high titer of antibodies or immune complex, (3) in which the medication must be decreased or stopped because of side effects and complications, or (4) which are in the acute active phase. We suggest DFPP to be useful as a treatment for connective tissue disease.

Antigen-Antibody Complex↗

PubMed1999

Reduction of integrin beta4 and enhanced migration on laminin in association with intraepithelial spreading of urinary bladder carcinomas.

PURPOSE: The aim of the present study was to investigate the biological and molecular basis of intraepithelial spreading (IES) of carcinomas in situ (CIS) of the urinary bladder, which were considered to be precursors of nodular invasive carcinomas. MATERIALS AND METHODS: The propensity for IES of human transitional carcinoma cells was examined by inoculation into murine renal pelvis and urinary bladder, and the biological character of the cells with a high propensity for IES was explored in vitro. RESULTS: Three of 6 cell lines exhibited a high propensity for IES. When cultured on laminin, these IES cells scattered, whereas 3 non-IES cells and 2 immortalized transitional epithelial cells did not. IES cells showed strong adhesiveness, haptotaxis and enhanced migration on laminin compared with both non-IES and immortalized transitional epithelial cells. In IES cells, expression of the integrin beta4 subunit was markedly reduced and the integrin alpha6beta1 complex was predominant compared with the integrin alpha6beta4 complex. Transfection of IES cells with integrin beta4 subunit cDNA inhibited their ability to migrate on laminin and their propensity for IES. In addition, expression of the integrin beta4 subunit was reduced in surgically resected specimens of CIS of the urinary bladder. CONCLUSION: The results indicate that a reduction in integrin beta4 plays a role in IES of CIS of the urinary bladder through enhanced migration on laminin.

Antigens, CD↗

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↗

PubMed1998

Randomization of left-right asymmetry due to loss of nodal cilia generating leftward flow of extraembryonic fluid in mice lacking KIF3B motor protein.

Microtubule-dependent motor, murine KIF3B, was disrupted by gene targeting. The null mutants did not survive beyond midgestation, exhibiting growth retardation, pericardial sac ballooning, and neural tube disorganization. Prominently, the left-right asymmetry was randomized in the heart loop and the direction of embryonic turning. lefty-2 expression was either bilateral or absent. Furthermore, the node lacked monocilia while the basal bodies were present. Immunocytochemistry revealed KIF3B localization in wild-type nodal cilia. Video microscopy showed that these cilia were motile and generated a leftward flow. These data suggest that KIF3B is essential for the left-right determination through intraciliary transportation of materials for ciliogenesis of motile primary cilia that could produce a gradient of putative morphogen along the left-right axis in the node.

Animals↗

PubMed1998

Cloning and characterization of the human beta4-integrin gene promoter and enhancers.

The cell-surface adhesion molecule alpha6beta4-integrin is a receptor for laminins and a component of hemidesmosomes. beta4-Integrin expression is restricted to proliferating basal keratinocytes in the epidermis and is suppressed when differentiation commences. Altered beta4-integrin expression levels correlate significantly with the aggressive behavior of cancers. In order to clarify the mechanisms that regulate transcription of the beta4-integrin gene, we cloned its 5'-flanking region. This 5'-flanking region was found to have a high G + C content and not to contain either TATA or CAAT boxes. Nested delimitation and reporter analyses mapped a basal promoter to nucleotides -106 to +105, surrounding the most proximal transcription initiation site. Gel retardation and mutational analyses revealed that cooperation between AP1 and Ets, interacting with other factors, mediated the promoter activity. In addition to the promoter element, enhancer activity was found in the first intron (+1905/+3933) and in a sequence upstream of the promoter region (-414/-107). These findings should facilitate our understanding of the regulation of beta4-integrin gene expression in processes such as cell growth and differentiation, apoptosis, and cancer development and metastasis.

Antigens, CD↗

PubMed1998

Reduced p27Kip1 expression in hepatocellular carcinomas.

This study was designed to determine whether changes in p27Kip1 expression are involved in human hepatocarcinogenesis. We examined the p27Kip1 mRNA expression in hepatocellular carcinomas and surrounding non-cancerous liver tissue samples from 21 patients using a reverse-transcriptase polymerase chain reaction assay. The mean p27Kip1 mRNA expression levels (ratio of p27Kip1/beta-actin mRNA) were significantly lower in hepatocellular carcinomas than in non-cancerous liver tissues (0.49 +/- 0.24 versus 0.57 +/- 0.22, P < 0.05). p27Kip1 mRNA expression was reduced in 11 (52%) of the 21 hepatocellular carcinomas when compared with the surrounding non-cancerous liver tissues. These findings suggest that reduced p27Kip1 expression may be at least partly responsible for human hepatocarcinogenesis.

Adult↗

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

Expression cloning and characterization of a transporter for large neutral amino acids activated by the heavy chain of 4F2 antigen (CD98).

A cDNA was isolated from rat C6 glioma cells by expression cloning which encodes a novel Na+-independent neutral amino acid transporter designated LAT1. For functional expression in Xenopus oocytes, LAT1 required the heavy chain of 4F2 cell surface antigen (CD98), a type II membrane glycoprotein. When co-expressed with 4F2 heavy chain, LAT1 transported neutral amino acids with branched or aromatic side chains and did not accept basic amino acids or acidic amino acids. The transport via LAT1 was Na+-independent and sensitive to a system L-specific inhibitor 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid. These functional properties correspond to those of the classically characterized amino acid transport system L, a major nutrient transporter. In in vitro translation, LAT1 was shown to be a nonglycosylated membrane protein consistent with the property of 4F2 light chain, suggesting LAT1 is at least one of the proteins formerly referred to as 4F2 light chain. LAT1 exhibits relatively low but significant amino acid sequence similarity to mammalian cationic amino acid transporters and amino acid permeases of bacteria and yeasts, indicating LAT1 is a new member of the APC superfamily. Because of highly regulated nature and high level of expression in tumor cell lines, LAT1 is thought to be up-regulated to support the high protein synthesis for cell growth and cell activation. The cloning of LAT1 is expected to facilitate the research on the protein-protein interaction in the transporter field and to provide a clue to the search for still unidentified transporters.

Amino Acid Sequence↗

PubMed1998

Involvement of NGF in the induction of increased noradrenergic innervation of the ureter in neonatally capsaicin-treated rats.

Neonatal denervation of primary afferents with capsaicin leads to increased sympathetic innervation of the rat ureter. In the present study the development and the immunohistochemical characterization of this sympathetic hyperinnervation as well as the specific involvement of nerve growth factor (NGF) was investigated. Noradrenaline levels were found elevated in neonatally capsaicin-treated rats by 2 weeks of age and remained at that high level into adulthood. Injections of an anti-NGF antiserum during postnatal days (PN) PN 8-14, PN 13-19 or during PN 17-23 counteracted the capsaicin effect and reduced noradrenaline towards control levels. Immunohistochemical localization of tyrosine hydroxylase (TH), a marker for sympathetic nerve fibres, revealed that the capsaicin-induced hyperinnervation was mainly represented by fibres in deeper muscle layers and to a smaller extent by fibres in the submucosa. In control animals and in rats treated with capsaicin and anti-NGF antiserum fibres were mainly distributed in the adventitia and in the outer part of the smooth muscle layer. These results show that NGF is responsible for the development of an increased noradrenergic innervation in the rat ureter after neonatal capsaicin treatment.

Adrenergic Fibers↗

PubMed1998

Apocrine Carcinoma of the Breast: Clinicopathological Analysis and Histological Subclassification of 12 Cases.

BACKGROUND: Apocrine carcinoma is rare and most of its clinicopathological features are still unknown. The purpose of this study was to identify the clinicopathological characteristics of apocrine carcinoma. METHODS: We clinicopathologically analyzed apocrine breast carcinomas resected from 12 Japanese women and subclassified them histopathologically. RESULTS: The average age of the patients at diagnosis was 60.1 years (range: 38-78). Tumor diameters ranged from 0.5 to 4.5 cm (median 2.4). Mammography revealed tumor shadows without microcalcifications in all patients. Two (17%) of the12 patients were lymph node metastasis-positive, and lymphatic permeation by tumor cells was observed in 3 (25%). Apocrine carcinoma in this study could be classified into three subtypes according to predominant histopathological growth pattern: type I, intraductal spreading type (4 patients); type II, adenosis-associated type (3 patients); and type III, infiltrating type (5 patients). Types I and II showed no lymph node metastasis and had an excellent prognosis, whereas theinfiltrating type was associated with lymph node metastasis and death from cancer. Estrogen receptors and progesterone receptors were positive in 17% (1/6) and 60% (3/5), respectively, of the tumors tested. CONCLUSION: In the present study, apocrine carcinoma of the breast was characterized by higher patient age and tumor shadows without microcalcifications on mammography. However, the tumors were heterogenous with regard to pattern of local spread.

Journal Article↗