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S Muto

Publications and source records attributed to S Muto.

At least 73 records · Page 4Linked to original sources
PubMed1999

Effect of protamine on ion selectivity of superficial and juxtamedullary proximal straight tubules.

Protamine is known to inhibit cation selectivity of the paracellular shunt pathway in several leaky nephron segments. Ion permeability of the superficial (SF) proximal straight tubules (PST) is selective to Cl(-), whereas that of the juxtamedullary (JM) PST is selective to Na(+). Protamine was used to estimate the contribution of the paracellular shunt pathway to ion selectivity in these segments. PSTs were isolated from the kidneys of Japanese white rabbit and microperfused in vitro. The ratio of Na(+) to Cl(-) permeability (P(Na)/P(Cl)) was estimated from the diffusion potential (dV(T)) generated by NaCl gradients. When 300 microg/ml protamine was added to the lumen, P(Na)/P(Cl) was decreased from 0.33 to 0.26 in SF-PST and from 1.80 to 1.29 in JM-PST, respectively, as the results of inhibition of cation selectivity. Addition of 30 U/ml heparin to the lumen, which neutralizes protamine, returned the ratios toward the control levels. Protamine exhibited similar effect on P(Na)/P(Cl) in the presence or the absence of ouabain in the bath, indicating that the observed voltage deflections were independent of the transcellular active transport process. Although P(Na)/P(Cl) was different between SF- and JM-PST, protamine inhibits Na(+) permeability in both segments. Preferential Cl(-) permeability in the SF-PST may be intrinsic to the paracellular route of this segment. The mechanism of this anion selectivity remains to be established.

Algorithms↗
PubMed1999

Human mannose-binding lectin preferentially binds to human colon adenocarcinoma cell lines expressing high amount of Lewis A and Lewis B antigens.

The binding of human mannose-binding lectin (MBL) to human colon adenocarcinoma cell lines and leukemia cell lines was analyzed by flow cytometry using specific antibodies against MBL. MBL binding was observed in 3 of 7 colon adenocarcinoma cell lines (Colo205, Colo201 and DLD-1), but not in any of 3 leukemia cell lines tested. The binding of MBL to these cell lines was sugar-specific and calcium-dependent, since it was almost completely inhibited in the presence of 10 mM EDTA or 50 mM mannose. The MBL binding to Colo205 cells was more strongly reduced by the pretreatment of the cells with an O-linked glycosylation inhibitor, benzyl-2-acetamide-2-deoxy-alpha-galactopyranoside (Bz-alpha-GalNAc), rather than an N-linked glycosylation inhibitor, tunicamycin. The degree of MBL binding was well correlated with the expression of Lewis A and Lewis B antigens on these cell lines. Moreover, MBL binding to Colo205 cells was inhibited by anti-Lewis A and anti-Lewis B antibodies. These results suggest that MBL could bind to some human colon adenocarcinoma cell lines through their Lewis A and Lewis B moieties.

Adenocarcinoma↗
PubMed1999

[A case of recurrent breast cancer successfully treated with docetaxel].

A 53-year-old female underwent mastectomy for left breast cancer in April, 1993. She was given oral tamoxifen but this had to be discontinued due to its side effects. In March, 1998, she developed bone and lung metastases, in spite of treatment with combination chemotherapy (CEF). We thus treated here with docetaxel 90 mg three times and 40 mg six times. After the chemotherapy, she achieved complete remissions of the lung metastases and a decrease in serum CEA, CA 15-3, NCC-ST439, and BCA225. Adverse reactions to docetaxel were grade 2 alopecia, grade 4 neutropenia, dysgeusia, and fluid retention. All were tolerable. This new agent may play an important future role in chemotherapy for recurrent breast cancer.

Antineoplastic Agents, Phytogenic↗
PubMed1998

In vivo detection of mutations induced by aflatoxin B1 using human CYP3A7/HITEC hybrid mice.

CYP3A7-M10 mouse is a transgenic mouse carrying human CYP3A7 cDNA, in which CYP3A7 is expressed in the small intestine but not in the kidney. HITEC mouse is a transgenic mouse developed to detect mutagenic potency of various chemicals in vivo. The M10/HITEC mouse was established by crossmating of these two strains of mice. When a 9,000 x g supernatant fraction prepared from the small intestine was added to an incubation mixture for Ames test with Salmonella typhimurium TA98 strain to examine the mutagen-producing activity from aflatoxin B1 (AFB1), the mutagen-producing activities of the 9, 000 x g supernatant fraction from the small intestine was found to be 1.7-fold higher in the M10/HITEC mice than in HITEC mice. Such a difference in the capacity to activate AFB1 was not seen with the 9, 000 x g supernatant fraction from the kidney from both strains of mice. Male M10/HITEC mice of 8 weeks old were treated with a single i.p. injection of AFB1 ( 8 mg/kg body weight). The mutation of the introduced rpsL gene in the genomic DNA from the small intestine and the kidney was analyzed. The mutation frequency in the small intestine of M10/HITEC mice was significantly higher (p<0.05) than that of HITEC mice, while the mutation frequency in both strains was similar in the kidney. These results provide the first evidence for the toxicological function of CYP3A7 in vivo.

Aflatoxin B1↗
PubMed1998

Determination of transmembrane topology of an inward-rectifying potassium channel from Arabidopsis thaliana based on functional expression in Escherichia coli.

We report here that the inward-rectifying potassium channels KAT1 and AKT2 were functionally expressed in K+ uptake-deficient Escherichia coli. Immunological assays showed that KAT1 was translocated into the cell membrane of E. coli. Functional assays suggested that KAT1 was inserted topologically correctly into the cell membrane. In control experiments, the inactive point mutation in KAT1, T256R, did not complement for K+ uptake in E. coli. The inward-rectifying K+ channels of plants share a common hydrophobic domain comprising at least six membrane-spanning segments (S1-S6). The finding that a K+ channel can be expressed in bacteria was further exploited to determine the KAT1 membrane topology by a gene fusion approach using the bacterial reporter enzymes, alkaline phosphatase, which is active only in the periplasm, and beta-galactosidase. The enzyme activity from the alkaline phosphatase and beta-galactosidase fusion plasmid showed that the widely predicted S1, S2, S5, and S6 segments were inserted into the membrane. Although the S3 segment in the alkaline phosphatase fusion protein could not function as an export signal, the replacement of a negatively charged residue inside S3 with a neutral amino acid resulted in an increase in alkaline phosphatase activity, which indicates that the alkaline phosphatase was translocated into the periplasm. For membrane translocation of S3, the neutralization of a negatively charged residue in S3 may be required presumably because of pairing with a positively charged residue of S4. These results revealed that KAT1 has the common six transmembrane-spanning membrane topology that has been predicted for the Shaker superfamily of voltage-dependent K+ channels. Furthermore, the functional complementation of a bacterial K+ uptake mutant in this study is shown to be an alternative expression system for plant K+ channel proteins and a potent tool for their topological analysis.

Alkaline Phosphatase↗
PubMed1998

Prognostic and Therapeutic Implications of the MIB-1 Labeling Index in Breast Cancer.

BACKGROUND: Assessment of tumor proliferative activity is considered to be the most powerful prognostic factor aside from axillary lymph node status. The purpose of this study is to assess the clinical value of measurement of proliferative activity using the MIB-1 labeling index in patients with breast cancer. METHODS: Surgical specimens from 36 patients with benign breast disorders and146 patients with breast cancer were investigated. The MIB-1 labeling index wasdetermined on the specimens stained by immunohistochemical methods as much as possible. Clinical factors associated with the MIB-1 labeling index were reviewed. RESULTS: The MIB-1 labeling index for non-proliferative disorders, proliferative disorders, and breast cancer was 3.4 +/-1.9%, 8.9 +/-6.2% and 20+/-12%, respectively. The MIB-1 labeling index and tumor size, lymph node metastasis status, and clinical stage according to the TNM classification correlated significantly. Survival rate was inversely correlated with the MIB-1 labeling index. No patientwith an MIB-1 labeling index of less than 10% had lymph node metastases, and all are alive without recurrence. Patients with an MIB-1 labeling index of over 30% had an extremely poor prognosis. CONCLUSION: The MIB-1 labeling index is very useful for predicting both either extremely good or extremely poor prognosis, and axillary lymph node metastasis

Journal Article↗
PubMed1998

Effects of hyperosmolality on Na, K-ATPase gene expression in vascular smooth muscle cells.

Cultured vascular smooth muscle cells (VSMC) from rat thoracic aortas were exposed to hyperosmotic media to determine the effects on Na, K-ATPase alpha1- and beta1-mRNA expression. Hyperosmotic media (500 mOsm/kgH2O) supplemented with glucose or mannitol increased alpha1-mRNA levels threefold at 24 hr and beta1-mRNA levels sevenfold at 12 hr. In sharp contrast, hyperosmotic urea medium had no effect at any time. Both the protein synthesis inhibitor cycloheximide and the RNA transcription inhibitor actinomycin D reduced alpha1- and beta1-mRNA upregulation induced by hyperosmotic glucose or mannitol media. Protein kinase C (PKC) inhibitors (staurosporine A or calphostin C) or tyrosine kinase (TK) inhibitors (genistein or herbimycin A) had no effect on the alpha1-mRNA upregulation induced by hyperosmotic glucose or mannitol media. Hyperosmotic glucose or mannitol media (500 mOsm/kgH2O) significantly increased alpha1- and beta1-subunit protein levels and Na, K-ATPase activity, whereas hyperosmotic urea medium had no effect. Transfection experiments with the 5'-flanking sequences of the alpha1- or beta1-subunit genes linked to the luciferase reporter gene revealed that hyperosmolar glucose medium increased luciferase activity 2.9- and 3.7-fold, respectively. Similarly, hyperosmotic mannitol medium increased such activity 2.7- and 3.4-fold, respectively. These results demonstrate that: (i) hyperosmolality induced by the poorly permeating solutes (glucose and mannitol) stimulates alpha1- and beta1-mRNA accumulation, alpha1- and beta1-subunit protein accumulation, and Na, K-ATPase activity, whereas the rapidly permeating solute (urea) has no effect; (ii) the upregulation of alpha1- and beta1-mRNA in response to hyperosmotic glucose or mannitol media requires, at least in part, de novo synthesis of intermediate regulatory proteins; (iii) the hyperosmolality-induced alpha1-mRNA upregulation occurs through PKC- and TK-independent mechanisms, whereas the hyperosmolality-induced beta1-mRNA upregulation occurs through activation of PKC and TK; and (iv) hyperosmolality induced by glucose or mannitol increases promoter activities of the alpha1- and beta1-subunit genes.

Animals↗
PubMed1998

Mastoparan induces an increase in cytosolic calcium ion concentration and subsequent activation of protein kinases in tobacco suspension culture cells.

Mastoparan induced a transient elevation of cytosolic free Ca2+ concentration ([Ca2+]cyt) in tobacco suspension culture cells. The mastoparan-induced [Ca2+]cyt elevation was inhibited by 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate-HCl and neomycin but not by depletion of extracellular Ca2+, suggesting that the elevation was the result of Ca2+ release from the intracellular stores caused by stimulation of phosphoinositide turnover. Hydrogen peroxide which has been shown to induce an oxidative burst in soybean cells by mastoparan treatment [L. Legendre, P.F. Heinstein, P.S. Low, Evidence for participation of GTP-binding proteins in elicitation of the rapid oxidative burst in cultured soybean cells, J. Biol. Chem., 267 (1992) 20140-20147], also induced a transient [Ca2+]cyt elevation in the tobacco cells. However, mastoparan did not induce an oxidative burst in the tobacco cells. Activation of a 50, a 75 and a 80 kDa protein kinases after the mastoparan-induced [Ca2+]cyt elevation was shown by an in-gel protein kinase assay. This activation was inhibited by neomycin, suggesting that the [Ca2+]cyt elevation is necessary for the mastoparan-induced activation of the protein kinases. The activation was inhibited also by pretreatment with staurosporine and was sustained by pretreatment with calyculin A, suggesting that the protein kinase activity is regulated by protein phosphorylation/dephosphorylation. The present report shows that mastoparan induces an increase in [Ca2+]cyt without oxidative burst and subsequent activation of protein kinases in tobacco cells.

Aequorin↗
PubMed1998

A comparison of prosthetic materials used to repair abdominal wall defects.

Large abdominal wall defects may require a prosthesis for closure. The aim of our study was to identify the best material for abdominoplasty in pediatric patients. One hundred twenty-eight Wistar KY strain male rats (3 weeks old) were used. All animals underwent celiotomy via a midline skin incision. They were divided into seven groups as follows: the animals in groups 1 through 6 underwent full-thickness abdominal wall excision 3 cm in diameter. The animals in group 1 underwent primary closure. In groups 2 through 6 the defect was closed with prosthetic material. In Group 7, a sham operation was performed. Daily weights were measured. The animals were killed after 3 and 9 weeks. Adhesion scores were assigned for each group. Vicryl mesh resulted in the fewest adhesions and had no effect on weight gain in the developing rats.

Abdominal Muscles↗
PubMed1998

Corticosterone and 11-dehydrocorticosterone stimulate Na,K-ATPase gene expression in vascular smooth muscle cells.

BACKGROUND: In mineralocorticoid target tissues such as kidney and colon, the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta OHSD) catalizes the reversible conversion of corticosterone (CS) to inactive 11-dehydrocorticosterone (DHCS) in rats, and cortisol to inactive cortisone in humans. This enzyme is also expressed in vascular smooth muscle cells (VSMC). METHODS: In cultured VSMC from rat thoracic aortae, we examined the effects of CS and DHCS on Na,K-ATPase alpha 1- and beta 1-mRNA accumulation by Northern blot analysis, on alpha 1- and beta 1-subunit protein accumulation by Western blot analysis, and on Na,K-ATPase activity by the coupled assay method. RESULTS: In VSMC, CS and DHCS (10(-6) M) increased alpha 1-mRNA level 2.6- and 2.5-fold at 48 hours and beta 1-mRNA level 9.2- and 9.1-fold at 12 hours, respectively. The RNA transcription inhibitor (actinomycin D) abolished both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The glucocorticoid receptor antagonist (RU38486) and the mineralocorticoid receptor antagonists (ZK91587) inhibited both CS- and DHCS-mediated alpha 1- and beta 1-mRNA induction. The 11 beta OHSD inhibitor (carbenoxolone) inhibited DHCS-mediated alpha 1- and beta 1-mRNA induction, whereas it caused no effect on CS-mediated alpha 1- or beta 1-mRNA induction. The addition of CS or DHCS to VSMC significantly increased alpha 1- and beta 1-subunit protein levels and Na,K-ATPase activity. When adrenalectomized rats were treated with CS or DHCS for 12 hours, aorta alpha 1- and beta 1-mRNA levels increased 3.0- and 8.7-fold or 3.4- and 8.4-fold, respectively. CONCLUSIONS: In VSMC, both CS and DHCS stimulate Na,K-ATPase alpha 1- and beta 1-mRNA accumulation, alpha 1- and beta 1-subunit protein accumulation, and Na,K-ATPase activity. The CS-mediated alpha 1- and beta 1-mRNA induction occurs independently of 11 beta OHSD, whereas the DHCS-mediated alpha 1- and beta 1-mRNA induction occurs through 11 beta OHSD-dependent mechanisms, possibly via conversion of inactive DHCS into active CS.

Animals↗
PubMed1998

Salicylic acid induces a cytosolic Ca2+ elevation in yeast.

Cytosolic free calcium ion concentration ([Ca2+]cyt) after a salicylic acid (SA)-stimulus was monitored in cells of the yeast Saccharomyces cerevisiae expressing apoaequorin, which constitutes a Ca(2+)-sensitive luminescent protein, aequorin, when combined with coelenterazine. SA induced a transient [Ca2+]cyt elevation that was dependent on the concentration of SA and pH of the SA solution. The SA-induced [Ca2+]cyt elevation was not reduced in Ca(2+)-deficient medium, suggesting that Ca2+ was mobilized from an intracellular Ca2+ store(s). Benzoic acid, butyric acid and sorbic acid did not induced a [Ca2+]cyt elevation.

Aequorin↗
PubMed1998

[Toremifene sensitized the effect of adriamycin on human breast cancer cell lines].

A experimental study was reported here to clarify the chemosensitizing effect of Toremifene (Tor) on human breast cancer cell lines. MCF7, estrogen dependent adriamycin (ADM) resistant cell, and MDA-MB231, estrogen independent cell, were preincubated for 8 hours with Tor 0, 4 or 10 microM, then with ADM 0-10 micrograms/ml for one hour. After that, cells were cultured for 24 hours, and their cell cycle and growth were analyzed with flow-cytometry and MTT assay, respectively. Furthermore, the ADM concentrations of these cells were measured by high-performance liquid chromatographic assay (HPLC). Although flowcytometric analysis showed the enhancement of Gz block only in MCF7 at the ADM concentration with 5 micrograms/ml, the sensitizing effect was revealed by MTT assay, and the elevation of ADM concentration was found in HPLC assay in both cells. The chemosensitizing effect of Toremifene was observed in estrogen dependent and independent cell lines.

Antibiotics, Antineoplastic↗
PubMed1997

An increase in cytosolic calcium ion concentration precedes hypoosmotic shock-induced activation of protein kinases in tobacco suspension culture cells.

Hypoosmotic shock induced a transient increase in cytosolic free calcium concentration [Ca2+]cyt and subsequent activation of 50-, 75- and 80-kDa protein kinases in tobacco (Nicotiana tabacum L.) suspension culture cells. Depletion of external calcium suppressed both the elevation of [Ca2+]cyt and the activation of protein kinases in response to hypoosmotic shock, indicating that the elevation of [Ca2+]cyt is prerequisite for the activation of protein kinases. Pharmacological analysis indicated that the hypoosmotic shock-activated protein kinases were activated by phosphorylation, suggesting that the activities of these protein kinases are regulated by putative protein kinases. These results suggest that the hypoosmotic signal is transduced to protein kinase cascades which are triggered by [Ca2+]cyt elevation.

Aequorin↗
PubMed1997

A low-Na+ diet enhances expression of mRNA for epithelial Na+ channel in rat renal inner medulla.

The purpose of the present study was to determine whether the renal inner medulla expresses mRNA for the rat epithelial Na+ channel (rENaC) and, if so, to define its regulatory properties using a low-Na+ diet model. We detected alpha, beta and gamma subunit mRNA in rat renal inner medulla using reverse transcriptase-polymerase chain reaction (RT-PCR) with primers specific for rENaC alpha, beta and gamma subunits. Moreover, we have developed a specific probe for the alpha subunit using RT-PCR with rENaC alpha-subunit-specific primers. The resulting cDNA was verified by sequencing and was then used in Northern blot analysis of distal colon, whole kidney and inner medulla. The probe for the rENaC alpha subunit hybridized not only to distal colon RNA but also to inner medulla RNA derived from rats fed a normal diet. Furthermore, we examined the effect of a low-Na+ diet on alpha, beta and gamma subunit mRNA expression of rENaC using full-length cDNA as a probe. A marked elevation of rENaC alpha subunit mRNA abundance in the inner medulla was observed in response to a high plasma aldosterone concentration induced by dietary Na+ deprivation. On the other hand, neither beta nor gamma subunit mRNA expression was enhanced by a low-Na+ diet. From these results, it is suggested that rENaC is responsible for Na+ transport in the renal inner medulla and that is probably regulated via transcriptional control of the alpha subunit of ENaC.

Animals↗
PubMed1997

Serum transcriptionally regulates Na(+)-K(+)-ATPase gene expression in vascular smooth muscle cells.

The present study was designed to examine the effects of serum on Na(+)-K(+)-ATPase alpha 1- and beta 1-subunit gene expression in cultured vascular smooth muscle cells (VSMC) from rat thoracic aortas. Addition of 10% serum to VSMC for 24 h increased Na(+)-K(+)-ATPase activity 1.5-fold and alpha 1- and beta 1-subunit protein levels 1.9-fold. Serum (10%) caused a 3.5-fold increase in alpha 1-mRNA levels and a 6.7-fold increase in beta 1-mRNA levels, with peak elevations at 12 h. The protein synthesis inhibitor cycloheximide abolished serum-mediated beta 1-mRNA induction but did not affect serum-mediated alpha 1-mRNA induction. Protein kinase C (PKC) inhibitors (staurosporine A or calphostin C) or tyrosine kinase (TK) inhibitors (genistein or herbimycin A) significantly reduced serum-mediated beta 1-mRNA induction but had no effect on serum-mediated alpha 1-mRNA induction. Transfection experiments with the 5'-flanking sequences of the alpha 1- or beta 1-subunit genes linked to the luciferase reporter gene revealed that 10% serum caused 2.8- and 6.5-fold increases in luciferase activity, respectively. Among growth factors, only basic fibroblast growth factor (FGF) enhanced luciferase activities for the alpha 1- and beta 1-subunit genes. We conclude that 1) serum stimulates alpha 1- and beta 1-mRNA expression, alpha 1- and beta 1-subunit protein accumulation, and Na(+)-K(+)-ATPase activity; 2) serum-mediated beta 1-mRNA induction partly requires de novo synthesis of intermediate regulatory proteins and activation of PKC and TK, whereas serum-mediated alpha 1-mRNA induction occurs through PKC- and TK-independent mechanisms; 3) the 5'-flanking regions of the alpha 1- and beta 1-subunit genes are serum responsive; and 4) FGF mimics stimulatory effects of serum on promoter activities for the alpha 1- and beta 1-subunit genes.

Animals↗