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Biomedical subjects

M Eto

Publications and source records attributed to M Eto.

At least 37 records · Page 2Linked to original sources
PubMed2001

Cyclophosphamide-induced tolerance in rat orthotopic liver transplantation.

BACKGROUND: We previously established a cyclophosphamide (CP)-induced tolerance system in rodent skin graft models. In this study, we applied this system to rat liver transplantation. METHODS: Lewis recipients were inoculated on day -2 with spleen and bone marrow cells (SC+BMC) from Dark Agouti (DA) donors, followed by 100 mg/kg CP on day 0. On day 25, DA livers were orthotopically grafted. We assessed the alloresponses to the donors of the long-term surviving recipients, using the second skin grafting and in vitro assay. RESULTS: The recipients that had been treated with SC+BMC and CP survived for more than 165 days. None of control group that received SC+BMC alone (mean survival times [MST]=13.8 days), CP alone (MST=40.0), SC+BMC from third-party PVG rats and CP (MST=45.0), or no treatment (MST=13.8) survived over 50 days. The donor-specific tolerance was confirmed by second skin grafts onto recipients with permanent DA liver grafts, which accepted DA skins (MST>75) but not PVG (MST=8.3). However, the lymphocytes from the tolerant recipients showed alloresponse to DA in vitro. To investigate whether the T helper type 2 deviation contributed to this "split tolerance," we assessed the production of cytokines in mixed lymphocyte reaction. Interleukin 2 and interferon-gamma were detected but interleukin 4 was not. CONCLUSIONS: These data showed that this protocol induced split tolerance in rat liver transplantation and, furthermore, the mechanism of split tolerance was not due to T helper 2 deviation.

Animals↗
PubMed2001

Estrogen prevents oxidative stress-induced endothelial cell apoptosis in rats.

BACKGROUND: Estrogen replacement attenuates the increased risk of cardiovascular disease in postmenopausal women. Recent studies using an in vitro culture system have shown that estrogen inhibits endothelial cell (EC) apoptosis. The in vivo relevance of this finding, however, is not defined. To do so, we have developed a rat vascular injury model in which EC apoptosis induced by hydrogen peroxide plays a role. METHODS AND RESULTS: Intracarotid arterial administration of 0.01 mmol/L hydrogen peroxide for 5 minutes evoked EC apoptosis after 6 to 24 hours, determined by nuclear staining with Hoechst 33342, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling, and electron microscopy. Apoptosis was associated with EC loss and was followed by EC regeneration at 72 hours and neointima formation at 1 to 2 weeks. Estradiol replacement in ovariectomized female Wistar rats decreased the rate of apoptotic ECs by approximately 50%, assayed by nuclear morphology of en face specimens, resulting in increased remaining ECs and decreased neointima formation. Progesterone did not influence the effects of estradiol on EC apoptosis. CONCLUSIONS: These results provide new insight into the cardioprotective action of estrogen as well as a paradigm of the response-to-injury hypothesis.

Animals↗
PubMed2001

Downregulation of the voltage-dependent calcium channel (VDCC) beta-subunit mRNAs in pancreatic islets of type 2 diabetic rats.

The present study was undertaken to determine whether altered expression of the VDCC beta-subunits in pancreatic beta-cells could play a role in the changes in beta-cell sensitivity to glucose that occur with diabetes. Application of competitive RT-PCR procedure revealed that in normal Wistar rats, LETO and prediabetic OLETF rats, the beta(2)-subunit mRNA levels were 60-200-fold greater than the levels for the beta(3)-subunit. These findings suggest that the beta(2)-subunit as well as the beta-cell type VDCC1 alpha(1)-subunit may be the predominant form of the VDCC expressed in pancreatic beta-cells. The levels of mRNA encoding the beta-subunits and the beta-cell type alpha(1)-subunit as well as insulin were significantly reduced in diabetic rats. Perfusion experiments revealed that diabetic rats showed the higher basal insulin secretion and profoundly impaired insulin secretory responses to glucose compared with non-diabetic rats. Alternatively, impaired insulin secretory responses to glucose in high dose glucose-infused rats were recovered partly with the elevation of mRNA levels of the VDCC beta(2)- and beta(3)-subunits as well as the alpha(1)-subunit by the treatment with diazoxide. Thus, considering the possibility that the most striking effect of the VDCC alpha(1) beta-subunit coexpression in pancreatic beta-cells might occur on activation kinetics like the skeletal muscle, the impairment of further activation of the VDCCs to acute glucose challenge caused by the reduced expressions of the alpha(1) beta-subunits mRNAs in type 2 diabetic animals might be at least partly associated with the alterations in beta-cell sensitivity to glucose.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2001

Identification of novel inhibitors of calling and in vitro [14C]acetate incorporation by pheromone glands of Plodia interpunctella.

Some octopamine agonists were found to suppress in vitro biosynthesis of the calling pheromone of the Indian meal moth, Plodia interpunctella. Isolated pheromone-gland preparations incorporated sodium [14C]acetate at a linear rate for 3 h when incubated with the pheromone biosynthesis activating neuropeptide (PBAN). This incorporation was dependent on the dose of PBAN (up to 0.5 microM). Thin-layer chromatography of a pheromone-gland extract revealed quantitative incorporation of radioactivity into a product exhibiting the same mobility as (Z,E)-9,12-tetradecadienyl acetate, the main component of the calling pheromone of P interpunctella. Twenty-seven octopamine agonists were initially screened using a calling behaviour bioassay of female P interpunctella. Four derivatives with activity in the nanomolar range were identified which were, in order of decreasing pheromonostatic activity: 2-(2,6-diethylphenylimino)thiazolidine > 2-(2,6-diethylphenylimino)oxazolidine > 2-(2,6-dimethylphenylimino)thiazolidine > 2-(2-ethylphenylimino)oxazolidine. These compounds also showed in vitro inhibitory activity in intracellular de novo pheromone biosynthesis. The results of the present study indicate that these derivatives could provide useful information in the characterization and differentiation of octopaminergic receptor types and subtypes.

Adenylyl Cyclases↗
PubMed2001

Induction of nuclear orphan receptor NGFI-B gene and apoptosis in rat vascular smooth muscle cells treated with pyrrolidinedithiocarbamate.

NGFI-B is one of the orphan nuclear receptors, and its gene is implicated in the apoptosis of T cells. The aim of this study was to investigate the expression and the role of NGFI-B in vascular smooth muscle cells (VSMCs). Pyrrolidinedithiocarbamate (PDTC) is a modulator of an oxidative state and is reported to induce apoptosis only when the density of VSMCs is low. Under low VSMC density (10 000 cells/cm(2)), addition of PDTC (0.1 to 10 micromol/L) caused apoptosis of VSMCs, which was confirmed by Hoechst 33258 staining under fluorescence microscopy. At low VSMC density, expression of NGFI-B mRNA was induced 1 hour after the addition of PDTC, peaking at 6 hours, and persisted for up to 12 hours. The protein level of NGFI-B was increased 4 hours after PDTC addition and persisted for up to 12 hours. Under low VSMC density, PDTC-induced expression of NGFI-B mRNA was correlated with the magnitude of apoptosis, which was quantified by enzyme immunoassay for histone-associated DNA fragments. In contrast, when the density of VSMCs was high (50 000 cells/cm(2)), PDTC did not induce apoptosis, and the expression of NGFI-B was only transient. This transient expression pattern was also seen when VSMCs were treated with phorbol ester, calcium ionophore, hydrogen peroxide, or angiotensin II, even at low cell density. We next investigated whether the NGFI-B gene may act as a transcription factor under treatment with PDTC by measuring the promoter activity of luciferase reporter plasmids that contained typical NGFI-B-responsive elements. The PDTC-induced transcriptional activity of NGFI-B was 2-fold higher at low cell density than at high cell density. These data demonstrate that NGFI-B can be induced in VSMCs and suggest that NGFI-B may play a role in PDTC-induced VSMC apoptosis.

Animals↗
PubMed2001

[Early and mid-term results after cardiac or thoracic aortic surgery in patients aged 70 years and older--survival and quality of life].

The early and mid-term survival after cardiac or thoracic aortic surgery and influence of age to the operative mortality were examined in 168 consecutive patients aged 70 years and older from August 1994 to December 1998, together with assessment of postoperative quality of life (QOL). The mean age was 74.1 +/- 3.7 years old (70 to 86 years). 80 patients had IHD, 59 had VHD, 28 had TAA. Preoperative risk score was classified in 5 groups (good, fair, poor, high, extremely high) based on Parsonnet method. Current QOL of the survivors was assessed using Asanoi method with questionnaire by a letter. There were 9 early deaths (5.4%). Following the Parsonnet model observed mortality was absolutely lower than predicted mortality. When age score was excluded in the Parsonnet model, the observed mortality became almost equal with the predicted mortality. There were 22 late deaths (6.9%/P-Y). The actuarial survival rate of age 70 to 74 group was significantly higher than the age 75 years and older group (p = 0.0021). The actuarial survival rate of TAA group was significantly lower than the VHD or IHD group (p < 0.02). Postoperative NYHA and activity score of TAA group were better than VHD or IHD group. We got satisfactory answers for operation in 95% current survivors. Patients aged 70 years and older will be undergone cardiac or thoracic aortic surgery at a reasonable risk and well satisfaction.

Aged↗
PubMed2001

Dynamic retentive force of a mandibular unilateral removable partial denture framework with a back-action clasp.

PURPOSE: The purpose of this study was to investigate the dynamic retentive force of a mandibular unilateral distal-extension partial denture framework with a back-action clasp that was designed in a buccally tilted cast on a dental surveyor. The retention mechanism of this framework was analyzed in comparison with other typical unilateral and bilateral frameworks for the mandibular Kennedy class II case. MATERIALS AND METHODS: Experimental gold alloy frameworks of three designs were repositioned to the master cast, and lifted upward to the vertical direction to the occlusal plane. The load required to dislodge each framework was recorded. The retentive force of each framework was determined by the maximum load in a dislodgment cycle. The bending strength of a plain clasp pattern of the same length as the clasp arm used in each framework was also measured by cantilever beam test. RESULTS: The mean retentive force of the unilateral framework with a back-action clasp of relatively low bending strength was significantly higher (P < 0.01) than that of the unilateral framework with two Akers clasps of relatively high bending strength, and 70 to 80% of the bilateral framework with two Akers clasps on the edentulous side and a double Akers clasp on the contralateral side. The unilateral framework with a back-action clasp showed the greatest early load resistance in the dislodgment cycle among the three designs. CONCLUSION: The reasonable retention mechanism was demonstrated by the unilateral framework with a back-action clasp.

Dental Abutments↗
PubMed2000

Advanced glycation end products-induced gene expression of scavenger receptors in cultured human monocyte-derived macrophages.

We investigated the effects of advanced glycation end products (AGEs) on the expression of oxidized low-density lipoprotein (OxLDL) receptors in human monocyte-derived macrophages and THP-1 cells treated with PMA. Both RT-PCR procedure and Northern blot analysis revealed that AGEs induced not only the gene expression of two major OxLDL receptors, macrophage scavenger receptor (MSR) class A and CD36, but also MSR-B I and lectin-like oxidized low-density lipoprotein receptor 1. Also, as a result of gel shift assay, AGEs increased transcriptional activities of AP-1, NF-kappaB, and peroxisome proliferator-activated receptor gamma. These findings indicate that AGEs-induced enhancement of these transcriptional activities might be involved in increased levels of mRNA for some of OxLDL receptors in THP-1-cells treated with PMA. The upregulated surface expression of these receptors on macrophage membranes was closely associated with increased uptake of modified LDL, and culminated in enhanced foam cell transformation. Thus, AGEs may be involved in the cause of variable levels of foam cell formation via the increased numbers of OxLDL receptors in accelerated atherosclerotic lesions of individuals with diabetes.

Blotting, Northern↗
PubMed2000

Enhancement of kondo effect in quantum dots with an even number of electrons

We investigate the Kondo effect in a quantum dot with almost degenerate spin-singlet and triplet states for an even number of electrons. We show that the Kondo temperature as a function of the energy difference between the states Delta reaches its maximum around Delta = 0 and decreases with increasing Delta. The Kondo effect is thus enhanced by competition between singlet and triplet states. Our results explain recent experimental findings. We evaluate the linear conductance in the perturbative regime.

Journal Article↗
PubMed2000

Kondo effect in an integer-spin quantum dot

The Kondo effect--a many-body phenomenon in condensed-matter physics involving the interaction between a localized spin and free electrons--was discovered in metals containing small amounts of magnetic impurities, although it is now recognized to be of fundamental importance in a wide class of correlated electron systems. In fabricated structures, the control of single, localized spins is of technological relevance for nanoscale electronics. Experiments have already demonstrated artificial realizations of isolated magnetic impurities at metallic surfaces, nanoscale magnets, controlled transitions between two-electron singlet and triplet states, and a tunable Kondo effect in semiconductor quantum dots. Here we report an unexpected Kondo effect in a few-electron quantum dot containing singlet and triplet spin states, whose energy difference can be tuned with a magnetic field. We observe the effect for an even number of electrons, when the singlet and triplet states are degenerate. The characteristic energy scale is much larger than in the ordinary spin-1/2 case.

Journal Article↗
PubMed2000

Agonists trigger G protein-mediated activation of the CPI-17 inhibitor phosphoprotein of myosin light chain phosphatase to enhance vascular smooth muscle contractility.

Myosin light chain phosphatase (MLCP) plays a pivotal role in smooth muscle contraction by regulating Ca(2+) sensitivity of myosin light chain phosphorylation. A smooth muscle phosphoprotein called CPI-17 specifically and potently inhibits MLCP in vitro and in situ and is activated when phosphorylated at Thr-38, which increases its inhibitory potency 1000-fold. We produced a phosphospecific antibody for this site in CPI-17 and used it to study in situ phosphorylation of endogenous CPI-17 in arterial smooth muscle in response to agonist stimulation. In the intact femoral artery, CPI-17 phosphorylation was negligible at the resting state and was not increased during contraction induced by K(+) depolarization. The Ca(2+)-sensitizing agonists histamine and phenylephrine induced nearly equivalent contractions, but histamine generated significantly higher levels of CPI-17 phosphorylation. In alpha-toxin-permeabilized strips at pCa 6.7, contractile force and CPI-17 phosphorylation were proportional in response to histamine, guanosine 5'-O-(gamma-thiotriphosphate), and histamine plus guanyl-5'-yl thiophosphate, implying that histamine increased CPI-17 phosphorylation through activation of G proteins. Inhibitors of Rho-kinase (Y27632) and protein kinase C (PKC; GF109203X) reduced contraction and CPI-17 phosphorylation in parallel, suggesting that CPI-17 functions downstream of Rho kinases and PKC. The results show that agonists such as histamine signal through phosphorylation of CPI-17 to produce Ca(2+) sensitization of smooth muscle contraction.

Amides↗
PubMed2000

Red wine polyphenols inhibit proliferation of vascular smooth muscle cells and downregulate expression of cyclin A gene.

BACKGROUND: Red wine polyphenols have been shown to contribute to the "French paradox" phenomenon, which consists of lower morbidity and mortality from coronary heart disease in the French population. Although vascular smooth muscle cell (VSMC) proliferation plays an important role in the progression of atherosclerotic lesions, the effects of red wine polyphenols on VSMC proliferation have not been elucidated. METHODS AND RESULTS: We extracted the total polyphenolic fraction from red wine (RW-PF) by column chromatography. Treatment with RW-PF showed a potent inhibitory effect on the proliferation and DNA synthesis of cultured rat aortic smooth muscle cells (RASMCs). In contrast, the inhibitory effect of RW-PF on the proliferation of bovine carotid endothelial cells was observed only at much higher concentrations. To elucidate the molecular mechanisms of this antiproliferative effect of RW-PF on RASMCs, we investigated the effects of RW-PF on cell cycle regulation. RW-PF downregulated the expression of cyclin A mRNA and cyclin A promoter activity. In addition, RW-PF decreased the binding of nuclear proteins to the activating transcription factor (ATF) site in the cyclin A promoter and downregulated the mRNA levels of transcription factors, cAMP-responsive element-binding protein (CREB), and ATF-1. CONCLUSIONS: These results suggest that the downregulation of cyclin A gene expression may contribute to the antiproliferative effect of red wine polyphenols on RASMCs through the inhibition of transcription factor expression.

Animals↗
PubMed2000

Prostanoids regulate proliferation of vascular smooth muscle cells induced by arginine vasopressin.

The aim of the present study was to investigate the effect of arginine [Arg(8)]vasopressin (vasopressin) on proliferation of vascular smooth muscle cells and the mechanisms underlying the action of vasopressin. To clarify these issues, we used two different types of vascular smooth muscle cells, cultured adult rat aortic smooth muscle cells and A10 cells, a cell line derived from fetal rat aorta. Vasopressin (10(-8) to 10(-6) M) significantly stimulated the proliferation of rat aortic smooth muscle cells in a dose-dependent manner. In contrast, vasopressin significantly inhibited the proliferation of A10 cells. This inhibition was abolished when A10 cells were treated with indomethacin. Vasopressin stimulated the production of prostanoids several-fold in A10 cells but not in rat aortic smooth muscle cells. These effects were completely blocked by the vasopressin V(1) receptor antagonist, 1-¿1-[4-(3-acetylamino-propoxy)benzoyl]4-piperidyl¿-3, 4-dihydro-2(1H)-quinolinone (OPC21268), but not by the vasopressin V(2) receptor antagonist, (+/-)-5-dimethylamino-1-[4-(2-methylbenzoylamino)benzol]-2, 3,4,5-tetrahydro-1H-benzazepine hydrochloride (OPC31260). These results indicate that vasopressin has diverse effect on proliferation of vascular smooth muscle cells through the vasopressin V(1) receptor, depending on the production of growth regulatory prostanoids.

6-Ketoprostaglandin F1 alpha↗
PubMed2000

Inhibition of myosin/moesin phosphatase by expression of the phosphoinhibitor protein CPI-17 alters microfilament organization and retards cell spreading.

Cell migration and cytokinesis require reorganization of the cytoskeleton, involving phosphorylation and dephosphorylation of proteins such as myosin II and moesin. Myosin and moesin bind directly to a regulatory subunit of myosin/moesin phosphatase (MMP) that contains a protein type-1 phosphatase (PP1) catalytic subunit. Here we examined the role of MMP in cytoskeletal dynamics using a phosphorylation-dependent inhibitor protein specific for MMP, called CPI-17. Fibroblasts do not express CPI-17, making them a null background to study effects of expression. Wild type CPI-17 in rat embryo fibroblasts caused (1) abnormal accumulation of cortical F-actin fibers, distinct from the stress fibers induced by expression of active RhoA; (2) progressive contraction of cell area, leaving behind filamentous extensions that stained for F-actin and moesin, but not myosin; and (3) significantly retarded spreading of fibroblasts on fibronectin with elevated myosin II light chain phosphorylation. A phosphorylation site mutant CPI-17(T38A) and inhibitor-2 (Inh2), another PP1-specific inhibitor protein, served as controls and did not elicit these same responses when expressed at the same level as CPI-17. Inhibition of myosin light chain kinase by ML-9 prevented the abnormal accumulation of cortical microfilaments by CPI-17, but did not reverse shrinkage in area, whereas kinase inhibitors HA1077 and H7 prevented CPI-17-induced changes in microfilament distribution and cell contraction. These results highlight the physiological importance of myosin/moesin phosphatase regulation to dynamic remodeling of the cytoskeleton.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

Influence of sex and age on serum nitrite/nitrate concentration in healthy subjects.

Measurement of serum nitrite/nitrate (NOx) concentrations has been considered useful to estimate nitric oxide production in humans. However little is known about the physiologic range and the factors affecting serum NOx levels. The aim of this study was, thus, to investigate the influence of sex and age on serum NOx levels in healthy subjects. We selected 263 healthy subjects (118 women and 145 men, 20-69 y) from 505 consecutive subjects who received annual medical checkups at our hospital. Serum NOx levels were determined using an analyzer employing the Griess method. The linear regression analysis showed that NOx increased significantly according to age in women (r=0.22, P<0.05), but did not in men (P=NS). Women of the younger age group (<40 y) showed significantly lower NOx levels than men of the same age group (P<0.05), whereas there was no significant difference between men and women of the older age (> or =40 y). Then, to investigate whether menopause affects serum NOx levels, middle aged women (46-55 y) were selected. Multiple logistic regression analysis showed that menopause was an independent factor for increased serum NOx levels in middle aged women (r=0.4, P<0.05). These results suggest that the serum NOx concentration is affected by age in healthy women, possibly depending on menopausal state.

Age Factors↗
PubMed2000

Increased levels of advanced glycosylation end products in the kidney and liver from spontaneously diabetic Chinese hamsters determined by immunochemical assay.

Increased levels of advanced glycosylation end products (AGEs) have been reported in tissues in association with diabetes mellitus. Thus, we measured tissue AGE levels and detected an accumulation of AGEs in the kidney and liver from spontaneously diabetic Chinese hamsters (CHAD) to determine the relationship between AGEs and diabetes mellitus. Diabetic CHAD aged 12 to 13 months were studied together with age-matched nondiabetic CHAD. We used an AGE-specific noncompetitive enzyme-linked immunosorbent assay (ELISA) with polyclonal anti-AGE-bovine serum albumin (BSA) antibody to measure tissue AGE levels. The samples extracted from the kidney and liver obtained from diabetic and nondiabetic CHAD reacted with anti-AGE-BSA antibody. When the absorbance of standard AGE-BSA (0.1 microg/mL) was expressed as 1 U, AGE levels in the kidney and liver from diabetic CHAD were significantly increased as compared with nondiabetic CHAD (kidney, 0.26 +/- 0.05 v 0.10 +/- 0.03 U/microg protein, P< .01; liver, 0.20 +/- 0.03 v 0.09 +/- 0.02 U/microg protein, P< .01). Positive AGE staining was observed in the renal cortex, especially in the tubules of diabetic CHAD, but little AGE staining was observed in the glomerulus by the immunohistochemical study. AGE staining was diffuse in the hepatocytes. These AGE levels were significantly correlated with fasting plasma glucose and glycated hemoglobin (P < .01, respectively). In conclusion, we have confirmed that AGE structures were expressed in the kidney and liver from CHAD, and these AGE levels were increased in diabetic CHAD. AGE staining was observed in the renal tubules and hepatocytes. Tissue AGE levels were positively correlated with glycemic control in CHAD.

Animals↗