Biomedical subjects

A Yamada

Publications and source records attributed to A Yamada.

At least 73 records · Page 4Linked to original sources

PubMed2001

Vitamin D receptor gene polymorphism detected by digestion with Apa I influences the parathyroid response to extracellular calcium in Japanese chronic dialysis patients.

BACKGROUND: To play its physiological role, 1,25(OH)2D3 must bind to a specific vitamin D receptor (VDR) in the nucleus. We have previously reported that VDR gene polymorphism influences the parathyroid function in patients with end-stage renal disease (ESRD). In the present study, we have investigated the relationship between the parathyroid responsiveness and VDR gene polymorphism, as detected by the Apa I restriction enzyme, by changing the concentration of Ca2+ in the dialysate. METHODS: 58 Japanese ESRD patients undergoing renal replacement therapy in our institution were evaluated. Genomic DNA was extracted from peripheral leukocytes and digested at the intron between exon 8 and exon 9 of the VDR gene using Apa I enzyme. Then alleles were classified into genotype A (undigested allele) and genotype a (digested allele). Extracellular ionized calcium ([Ca2+]e), serum phosphate, and intact parathyroid hormone (PTH) were measured before and after each hemodialysis (HD) session with dialysates having different concentrations of Ca2+ (1.5 or 1.25 mmol/l). The significance of differences in statistical analyses was defined within confidence limits of 5.0%. RESULTS: The AA, Aa, and aa genotypes were observed in 7/58 patients (12.1%), 23/58 patients (39.6%), and 28/58 patients (48.3%), respectively. The PTH reduction after HD with the 1.5-mmol/l Ca dialysate did not differ significantly between group AA+Aa and group aa. On the other hand, the PTH increase was significantly higher in group aa than in group AA+Aa after HD with the 1.25-mmol/l Ca dialysate (p = 0.0107), despite a similar PTH level before HD. Similarly, the percent increase of PTH after HD with the 1.25-mmol/l Ca dialysate was significantly higher (p = 0.0112) in group aa (50.2 +/- 9.4%) than in group AA+Aa (19.7 +/- 7.2%). There were no significant differences between the two groups in [Ca2+]e nor in serum phosphorus (Pi) before and after HD with either dialysate. Group AA+Aa and group aa did not show statistically significant differences in age, female/male ratio, ratio of diabetic nephropathy, or dialysis period. CONCLUSIONS: The study results showed that the patients in group aa were more sensitive to changes in [Ca2+]e than those in group AA+Aa. Moreover, they suggested that the VDR gene polymorphism may affect parathyroid responsiveness to changes in [Ca2+]e, which in turn may influence onset and progression of hyperparathyroidism in ESRD patients.

Alleles↗

PubMed2001

Vascular endothelial dysfunction resulting from L-arginine deficiency in a patient with lysinuric protein intolerance.

Although L-arginine is the only substrate for nitric oxide (NO) production, no studies have yet been reported on the effect of an L-arginine deficiency on vascular function in humans. Lysinuric protein intolerance (LPI) is a rare autosomal recessive defect of dibasic amino acid transport caused by mutations in the SLC7A7 gene, resulting in an L-arginine deficiency. Vascular endothelial function was examined in an LPI patient who was shown to be a compound heterozygote for two mutations in the gene (5.3-kbp Alu-mediated deletion, IVS3+1G-->A). The lumen diameter of the brachial artery was measured in this patient and in healthy controls at rest, during reactive hyperemia (endothelium-dependent vasodilation [EDV]), and after sublingual nitroglycerin administration (endothelium-independent vasodilation [EIV]) using ultrasonography. Both EDV and NO(x) concentrations were markedly reduced in the patient compared with those for the controls. They became normal after an L-arginine infusion. EIV was not significantly different between the patient and controls. Positron emission tomography of the heart and a treadmill test revealed ischemic changes in the patient, which were improved by the L-arginine infusion. Thus, in the LPI patient, L-arginine deficiency caused vascular endothelial dysfunction via a decrease in NO production.

Adult↗

PubMed2001

B7-dependent T-cell costimulation in mice lacking CD28 and CTLA4.

To examine whether B7 costimulation can be mediated by a molecule on T cells that is neither CD28 nor CTLA4, we generated mice lacking both of these receptors. CD28/CTLA4(-/-) mice resemble CD28(-/-) mice in having decreased expression of T-cell activation markers in vivo and decreased T-cell proliferation in vitro, as compared with wild-type mice. Using multiple approaches, we find B7-dependent costimulation in CD28/CTLA4(-/-) mice. The proliferation of CD28/CTLA4(-/-) T cells is inhibited by CTLA4-Ig and by the use of antigen-presenting cells lacking both B7-1 and B7-2. CD28/CTLA4(-/-) T-cell proliferation is increased by exposure to Chinese hamster ovary cells transfected with B7-1 or B7-2. Finally, administration of CTLA4-Ig to CD28/CTLA4(-/-) cardiac allograft recipients significantly prolongs graft survival. These data support the existence of an additional receptor for B7 molecules that is neither CD28 nor CTLA4.

Abatacept↗

PubMed2001

Somatic mutations of the MEN1 gene and microsatellite instability in a case of tertiary hyperparathyroidism occurring during high phosphate therapy for acquired, hypophosphatemic osteomalacia.

Somatic mutations of the MEN type 1 (MEN1) gene were recently shown to be responsible for tumorigenesis in 13-26% of sporadic, nonfamilial primary hyperparathyroidism. However, it is unknown whether these mutations are also involved in tumorigenesis of parathyroid glands occurring during high phosphate therapy for hypophosphatemic rickets or osteomalacia. A male patient with adult-onset, hypophosphatemic osteomalacia had been treated with 1alpha-OHD3 and oral phosphate for 13 yr when tertiary hyperparathyroidism developed. After total resection of four enlarged parathyroid glands and autotransplantation of a hyperplastic gland, the patient has continued to do well for the last 2 yr. Sequence analysis of the coding exons of MEN1 gene revealed a 36-bp deletion with a 2-bp insertion (exon 2) in the right upper parathyroid gland accompanied with loss of heterozygosity at 11q13 locus and a heterozygous mutation of 2-bp deletion (AG) in exon 10 in the right lower gland, in which microsatellite instability was also found. No MEN1 gene mutation was detected in the other two hyperplastic parathyroid glands or in the peripheral blood. These findings indicate that MEN1 gene mutations contributed to tumorigenesis of the right upper parathyroid gland in this case of phosphate-induced tertiary hyperparathyroidism. Very recently a bone tumor was found in the right femoral neck, and the tumor (chondroblastoma) was resected.

Adult↗

PubMed2001

Usefulness and limitation of DiBAC4(3), a voltage-sensitive fluorescent dye, for the measurement of membrane potentials regulated by recombinant large conductance Ca2+-activated K+ channels in HEK293 cells.

The usefulness of bis-(1,3-dibutylbarbituric acid)-trimethine oxonol (DiBAC4(3)), a voltage-sensitive fluorescent dye, for the measurement of membrane potentials (MPs) was evaluated in HEK293 cells, where alpha or alpha plus beta1 subunits of large conductance Ca2+-activated K+ (BK) channels were expressed (HEKBK alpha and HEKBK alphabeta). The fluorescent intensity of DiBAC4(3) was measured at various potentials under voltage-clamp for calibration to estimate the absolute MP semi-quantitatively. The resting MPs measured with DiBAC4(3) were roughly comparable to those recorded with a microelectrode; the MP in HEKBK alphabeta was 10-20 mV more negative than that in native HEK. In HEKBK alpha, the membrane hyperpolarization induced by 10 microM Evans blue, a BK channel opener, was detected with DiBAC4(3). NS-1619, another BK channel opener, induced gradual but substantial change in F/F(K) even in native HEK, while the BK channel opening effect was detected. Oscillatory membrane hyperpolarization was induced in HEKBK alphabeta by application of 10 microM acetylcholine via increase in intracellular Ca2+ concentration. The oscillatory hyperpolarization was, however, detected only as a slow hyperpolarization with DiBAC4(3). It can be concluded that relatively slow effects of BK channel modulators can be semi-quantitatively measured by use of DiBAC4(3) in HEKBK, while the limited temporal resolution and possible artifacts should be taken into account.

Barbiturates↗

PubMed2001

marY2N, a LINE-like non-long terminal repeat (non-LTR) retroelement from the ectomycorrhizal homobasidiomycete Tricholoma matsutake.

A LINE-like non-LTR retroelement designated marY2N was cloned from the ectomycorrhizal homobasidiomycete Tricholoma matsutake. marY2N has open reading frames that correspond to gag and pol, and a putative promoter and consensus sequences common to those of the mutators from fruit flies. While it is common to T. matsutake and Tricholoma magnivelare, marY2N does not reside in any other species of Tricholoma tested.

Base Sequence↗

PubMed2001

Detection of B virus infection in cynomolgus monkeys by ELISA using simian agent 8 as alternative antigen.

The use of simian agent 8 (SA8) as an antigen for B virus (BV) antibody detection was evaluated in cynomolgus monkeys. Seventy-two sera judged as positive using BV antigen were all positive when the SA8 antigen was used. Out of 28 BV-negative sera 2 were positive against the SA8 antigen and one serum was classified as indeterminate. The present data indicates that detection of BV antibody can be achieved accurately and safely by enzyme-linked immunosorbent assay (ELISA) using SA8 antigen.

Animals↗

PubMed2001

Evaluation of central nervous system involvement in nasal lymphomas.

OBJECTIVES: To clarify the usefulness of evaluating central nervous system (CNS) involvement in patients with nasal lymphomas at the initial staging procedure, and of CNS prophylaxis for patients with clinical stage I/II. PATIENTS AND METHODS: We retrospectively reviewed 43 patients with nasal lymphomas who had been treated from 1973 through 1999. The staging procedure included mainly computed tomography (CT), ultrasonography, gallium scintigraphy, upper gastrointestinal study, magnetic resonance (MR) imaging, and bone marrow biopsy. Forty-two patients received radiotherapy, and 25 patients received chemotherapy. All 38 patients with stage I/II were not subjected to CNS prophylaxis. RESULTS: Four patients demonstrated CNS involvement at the staging procedure. MR imaging demonstrated the tumor had directly infiltrated the skull base in 3 patients, but CT demonstrated CNS infiltration in only one patient. In another patient, cerebrospinal fluid (CSF) cytologic analyses demonstrated CNS involvement, but MR imaging and CT did not. These 4 patients complained of frontonasal pain and/or cerebral nerve dysfunction. No patient with stage I/II developed CNS relapse. CONCLUSIONS: MR imaging and CSF cytologic analyses should be performed at the initial staging of nasal lymphomas, especially in patients with frontonasal pain and/or cerebral nerve dysfunction. Patients with stage I/II might not need CNS prophylaxis.

Adult↗

PubMed2001

Induction of cellular immune responses to tumor cells and peptides in colorectal cancer patients by vaccination with SART3 peptides.

The tumor-rejection antigen SART3 possesses two antigenic epitopes (SART3(109-118) and SART3(315-323)) capable of inducing HLA-A24-restricted and tumor-specific CTLs. To determine its safety and ability to generate antitumor immune responses, 12 patients with advanced colorectal cancer were administered s.c. vaccinations of these peptides. No severe adverse events were associated with the vaccinations. Significant levels of increased cellular immune responses to both HLA-A24+ colon cancer cells and the vaccinated peptide were observed in the postvaccination peripheral blood mononuclear cells in 7 of 11 and 7 of 10 patients tested, respectively, and the higher responses were observed in those patients vaccinated with the highest dose (3 mg/injection) of the peptides. These results encourage further development of SART3 peptide vaccine for colorectal cancer patients.

Adult↗

PubMed2000

Identification of SART3-derived peptides capable of inducing HLA-A2-restricted and tumor-specific CTLs in cancer patients with different HLA-A2 subtypes.

We recently identified the SART3 antigen encoding shared tumor epitopes recognized by HLA-A2402-restricted and tumor-specific CTLs. Our study investigated whether the SART3 antigen encodes peptides recognized by the HLA-A2-restricted CTLs. The HLA-A2-restricted and tumor-specific CTL line recognized COS-7 cells co-transfected with the SART3 gene and either HLA-A0201, -A0206 or -A0207 cDNA but not those co-transfected with the SART3 gene and HLA-A2402 or -A2601 cDNA. The 2 SART3 peptides at positions 302 to 310 and 309 to 317 possessed the ability to induce HLA-A2-restricted and tumor-specific CTLs from peripheral blood mononuclear cells of cancer patients with various histological types and different HLA-A2 subtypes. Therefore, these 2 peptides could be useful for specific immunotherapy of a relatively large number of HLA-A2(+) cancer patients.

Amino Acid Sequence↗

PubMed2000

Self-augmentation effect of male-specific products on sexually differentiated progesterone metabolism in adult male rat liver microsomes.

It is well known that several 3-keto-4-ene steroids such as progesterone and testosterone are metabolized in a gender-specific or -predominant manner by adult rat liver microsomes. In the male, these steroids are primarily metabolized into two oxidized (16alpha-hydroxyl and 6beta-hydroxyl) products mainly by the respective, male-specific cytochrome P450 subforms, CYP2C11 and CYP3A2, while they are primarily metabolized into the 5alpha-reduced products by female-predominant 5alpha-reductase in the female. These sexually differentiated enzyme activities are largely regulated at the transcription level under endocrine control. In the present study, we show that unlabeled 16alpha-hydroxyprogesterone and 6beta-hydroxyprogesterone inhibited the 5alpha-reductive [(3)H]progesterone metabolism by adult male rat liver microsomes without significantly inhibiting the CYP2C11 and CYP3A2 activities producing themselves, whereas 3alpha-hydroxy-5alpha-pregnan-20-one and 5alpha-pregnane-3,20-dione not only stimulated the 5alpha-reductive metabolism producing themselves but also inhibited the male-specific oxidative metabolism. This finding compels us to propose a novel hypothesis that adult male rat liver microsomes may possess a self-augmentation system regulated by the male-specific products on sexually differentiated steroid metabolism, besides regulation by gene expressions of the related enzymes.

5-alpha-Dihydroprogesterone↗

PubMed2000

Inhibition of smooth-muscle myosin-light-chain phosphatase by Ruthenium Red.

Ruthenium Red (RuR) is widely used as an inhibitor of ryanodine receptor Ca(2+) release channels, but has additional effects such as the induction of Ca(2+) sensitization of contraction of permeabilized smooth muscles. To address the mechanism underlying this process, we examined the effects of RuR on contractility in permeabilized guinea-pig ileum and on the activity of myosin-light-chain phosphatase (MP). RuR increased the force at submaximal [Ca(2+)] (pCa 6.3) approx. 4-fold. This effect was not observed after thiophosphorylation of MP. RuR also seemed capable of preventing the thiophosphorylation of MP, suggesting a direct interaction of RuR with MP. Consistent with this possibility, smooth-muscle MP was inhibited by RuR in a concentration-dependent manner (IC(50) 23 microM). Exogenous calmodulin significantly increased RuR-induced contraction at pCa 6.3 but had little effect on contraction induced by microcystin at this [Ca(2+)]. Ca(2+)-independent contraction was induced by RuR (EC(50) 843 microM) and by microcystin (EC(50) 59 nM) but the maximal force induced by RuR was smaller than that induced by microcystin. The addition of 300 microM RuR enhanced the contraction induced by 30 nM microcystin but markedly decreased that induced by 1 microM microcystin. Such a dual action of RuR on microcystin-induced effects was not observed in experiments using purified MP. We conclude that the RuR-induced Ca(2+) sensitization of smooth-muscle contraction is due to the direct inhibition of MP by RuR.

Adenosine Triphosphate↗

PubMed2000

Reduced ventricular response irregularity is associated with increased mortality in patients with chronic atrial fibrillation.

BACKGROUND-Variations in the ventricular response interval (VRI) during atrial fibrillation (AF) may be reduced in patients with adverse clinical outcomes. The properties of VRI dynamics associated with prognosis remain undetermined. METHODS AND RESULTS-In 107 patients with chronic AF (age, 64+/-9 years), we analyzed a 24-hour ambulatory ECG for VRI variability (SD, SD of successive differences, and SD of 5-minute averages) and VRI irregularity (Shannon entropy of histogram, symbolic dynamics, and approximate entropy of beat-to-beat and minute-to-minute fluctuations [ApEn(b-b) and ApEn(m-m)]). During a follow-up period of 33+/-16 months, 18 patients died (17%), 9 from cardiac causes, 7 from fatal strokes, and 2 from malignancies. Reductions in all VRI variability and irregularity measures were associated with an increased risk for cardiac death but not for fatal stroke. A significant association with cardiac death was also found for ejection fraction (relative risk, 1.10; 95% confidence interval [CI], 1.04 to 1.17, per 1% decrement) and ischemic AF (relative risk, 6.52; 95% CI, 1.62 to 26. 3). After adjustment for these clinical variables, all irregularity measures except symbolic dynamics had predictive value (relative risks [95% CIs] per 1SD decrement: Shannon entropy of histogram, 2. 03 [1.14 to 3.61]; ApEn(b-b), 1.72 [1.14 to 2.60]; and ApEn(m-m), 1. 90 [1.03 to 3.52]); however, the predictive power of variability measures was no longer significant. When the patients were stratified with the 33rd and 67th percentile values of ApEn(b-b) (1. 83 and 1.94, respectively), the 5-year cardiac mortality rates for the upper, middle, and lower tertiles were 0%, 13%, and 43%, respectively (log-rank test, P=0.04). CONCLUSIONS-Reduced VRI irregularity in a 24-hour ambulatory ECG has an independent prognostic value for cardiac mortality during long-term follow-up in patients with chronic AF.

Adult↗

PubMed2000

Complementation of defective translesion synthesis and UV light sensitivity in xeroderma pigmentosum variant cells by human and mouse DNA polymerase eta.

Defects in the human gene XPV result in the variant form of the genetic disease xeroderma pigmentosum (XP-V). XPV encodes DNA polymerase eta, a novel DNA polymerase that belongs to the UmuC/DinB/Rad30 superfamily. This polymerase catalyzes the efficient and accurate translesion synthesis of DNA past cis-syn cyclobutane di-thymine lesions. In this report we present the cDNA sequence and expression profiles of the mouse XPV gene and demonstrate its ability to complement defective DNA synthesis in XP-V cells. The mouse XPV protein shares 80.3% amino acid identity and 86.9% similarity with the human XPV protein. The recombinant mouse XPV protein corrected the inability of XP-V cell extracts to carry out DNA replication, by bypassing thymine dimers on template DNA. Transfection of the mouse or human XPV cDNA into human XP-V cells corrected UV sensitivity. Northern blot analysis revealed that the mouse XPV gene is expressed ubiquitously, but at a higher level in testis, liver, skin and thymus compared to other tissues. Although the mouse XPV gene was not induced by UV irradiation, its expression was elevated approximately 4-fold during cell proliferation. These results suggest that DNA polymerase eta plays a role in DNA replication, though the enzyme is not essential for viability.

Amino Acid Sequence↗

PubMed2000

Identification of a new endoplasmic reticulum-resident protein recognized by HLA-A24-restricted tumor-infiltrating lymphocytes of lung cancer.

To help clarify the molecular basis of tumor immunology in lung cancer, we have investigated antigens recognized by HLA-A24-restricted CTLs established from T cells infiltrating into lung adenocarcinoma and report a new gene encoding tumor epitopes recognized by the CTLs. This gene was located on chromosome 4q31.22 and encoded an unreported endoplasmic reticulum-resident protein with 412 deduced amino acids. This protein had a molecular mass of 46 kDa and was expressed in the majority of malignant cells and tissues tested, with the exception of T-cell leukemia cells, but was not expressed in a panel of normal cells and tissues, except in those of the testis, placenta, and fetal liver. Two peptides at positions 13-20 and 75-84 were recognized by the CTLs and had an ability to induce HLA-A24-restricted and tumor-specific CTLs in peripheral blood mononuclear cells of lung cancer patients. Thus, these peptides might be appropriate molecules for use in the specific immunotherapy of HLA-A24+ patients with lung and other cancers.

Adenocarcinoma↗

PubMed2000

Microaerobic hydrogen production by photosynthetic bacteria in a double-phase photobioreactor.

The rate of hydrogen production by the marine nonsulfur photosynthetic bacterium, Rhodovulum sp., increased with increasing light intensity. A light intensity of 1800 W/m(2) hydrogen production rate was achieved at the rate of 9.4 micromol/mg dry weight/h. The hydrogen production of this strain was enhanced by the addition of a small amount of oxygen (12 micromol O(2)/reactor). Intracellular ATP content was most efficiently accumulated under microaerobic, dark conditions. Hydrogen production rate by Rhodovulum sp. was investigated using a double-phase photobioreactor consisting of light and dark compartments. This rate was compared with data obtained using a conventional photobioreactor. Rhodovulum sp. produced hydrogen at a rate of 0.38+/-0.03 micromol/mg dry weight/h under microaerobic conditions using the double-phase photobioreactor. The hydrogen production rate was four times greater under microaerobic conditions, as compared with anaerobic conditions using either type of photobioreactor. Hydrogen production using a double-phase photobioreactor was demonstrated continuously at the same rate for 150 h.

Adenosine Triphosphate↗

PubMed2000

Regulation of long-term potentiation by H-Ras through NMDA receptor phosphorylation.

The proto-oncogene ras plays a critical role in cell proliferation and differentiation. However, ras genes are abundantly expressed in the adult CNS, although neuronal cells normally do not proliferate. Recently, several lines of evidence implicated the involvement of Ras signaling pathway in synaptic plasticity. To explore the role of the Ras proteins in the CNS, we generated knock-out mice lacking the H-ras gene and then used them to study the roles of Ras in synaptic transmission and plasticity. An investigation of protein phosphorylation and synaptic transmission in H-ras null mutant mice has shown that the NMDA receptor is a final target molecule of the Ras protein pathway in the CNS. In the H-ras null mutant hippocampus, the tyrosine phosphorylation of NR2A (epsilon1) and NR2B (epsilon2) subunits of NMDA receptors is increased, and, correspondingly, NMDA synaptic responses are selectively enhanced. In addition, long-term potentiation is markedly enhanced in mutant mice, most likely because of a selective enhancement of NMDA synaptic responses. Therefore, although Ras proteins have been implicated in cell proliferation and differentiation, the regulation of activity-dependent synaptic plasticity in the adult animals by downregulation of the phosphorylation of the NMDA receptor may be another major and pivotal role for H-Ras protein.

Animals↗

PubMed2000

Reconstitution of damage DNA excision reaction from SV40 minichromosomes with purified nucleotide excision repair proteins.

We previously constructed the cell-free nucleotide excision repair (NER) assay system with UV-irradiated SV40 minichromosomes to analyze the mechanism of NER reaction on chromatin DNA. Here we investigate the factor that acts especially on nucleosomal DNA during the damage excision reaction, and reconstitute the damage excision reaction on SV40 minichromosomes. NER-proficient HeLa whole cell extracts were fractionated, and the amounts of known NER factors involved in the column fractions were determined by immunoblot analyses. The column fractions were quantitatively and systematically replaced by highly purified NER factors. Finally, damage DNA excision reaction on SV40 minichromosomes was reconstituted with six highly purified NER factors, XPA, XPC-HR23B, XPF-ERCC1, XPG, RPA and TFIIH, as those essential for the reaction with naked DNA. Further analysis showed that the damages on chromosomal DNA were excised as the same efficiency as those on naked DNA for short incubation. At longer incubation time, however, the damage excision efficiency on nucleosomal DNA was decreased whereas naked DNA was still vigorously repaired. These observations suggest that although the six purified NER factors have a potential to eliminate the damage DNA from SV40 minichromosomes, the chromatin structure may still have some repressive effects on NER.

DNA Damage↗