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Biomedical subjects

Satoru Suzuki

Publications and source records attributed to Satoru Suzuki.

At least 19 recordsLinked to original sources
PubMed2007

Distribution and diversity of tetracycline resistance genes encoding ribosomal protection proteins in Mekong river sediments in Vietnam.

We investigated the distribution and diversity of tetracycline resistance genes encoding ribosomal protection proteins (RPPs) in river and channel sediments of the Mekong Delta in Vietnam. The sediment samples were taken from nine sites in the Hau River in southern Vietnam and from 1 site in a channel in Can Tho City in May 2004 using an Ekman-Birge sediment surface sampler. The RPP genes were amplified using PCR with DNA templates obtained directly from the sediments. The tet(M), tet(S), and tet(W) genes were detected by PCR in most sediment samples. Denaturing gradient gel electrophoresis analysis of these genes and sequencing of the resulting bands showed that tet(S) and tet(W) had only one genotype each, but that tet(M) had at least two, which were tentatively called type 1 and type 2. Type 1 tet(M) was identical to the gene encoded in various plasmids and transposons of gram-positive and gram-negative bacteria, and type 2tet(M) was similar to the gene encoded in Tn1545 of Enterococcus faecalis (99% identity, 170 bp/171 bp). This study showed that various RPP genes were widely distributed in the river and channel sediments of the Mekong Delta.

Amino Acid Sequence↗
PubMed2006

Synergistic regulation of the mouse orphan nuclear receptor SHP gene promoter by CLOCK-BMAL1 and LRH-1.

Small heterodimer partner (SHP; NR0B2) is an orphan nuclear receptor and acts as a repressor for wide variety of nuclear hormone receptors. We demonstrated here that mouse SHP mRNA showed a circadian expression pattern in the liver. Transient transfection of the mSHP promoter demonstrated that CLOCK-BMAL1, core circadian clock components, bound to E-box (CACGTG), and stimulated the promoter activity by 4-fold. Liver receptor homologue-1 (LRH-1; NR5A2) stimulated the mSHP promoter, and CLOCK-BMAL1 synergistically enhanced the LRH-1-mediated transactivation. Interestingly, SHP did not affect the CLOCK-BMAL1-mediated promoter activity, but strongly repressed the synergistic activation of CLOCK-BMAL1 and LRH-1. Furthermore, in vitro pull-down assays revealed the existence of direct protein-protein interaction between LRH-1 and CLOCK. In summary, this study shows that CLOCK-BMAL1, LRH-1 and SHP coordinately regulate the mSHP gene to generate the circadian oscillation. The cyclic expression of mSHP may affect daily activity of other nuclear receptors and contribute to circadian liver functions.

ARNTL Transcription Factors↗
PubMed2006

Attention induces synchronization-based response gain in steady-state visual evoked potentials.

When attention is voluntarily directed to a spatial location, visual sensitivity increases at that location. What causes this improved sensitivity? Studies of single neuron spike rates in monkeys have provided mixed results in regard to whether attending to a stimulus increases its effective contrast (contrast gain) or multiplicatively boosts stimulus-driven neural responses (response or activity gain). We monitored frequency-tagged steady-state visual evoked potentials (SSVEPs) in humans and found that voluntary sustained attention multiplicatively increased stimulus-driven population electrophysiological activity. Analyses of intertrial phase coherence showed that this attentional response gain was at least partially due to the increased synchronization of SSVEPs to stimulus flicker. These results suggest that attention operates in a complementary manner at different levels; attention seems to increase single-neuron spike rates in a variety of ways, including contrast, response and activity gains, while also inducing a multiplicative boost on neural population activity via enhanced response synchronization.

Adult↗
PubMed2006

Inhibition of LXRalpha signaling by vitamin D receptor: possible role of VDR in bile acid synthesis.

The expression of cholesterol 7alpha-hydroxylase (CYP7alpha), the rate-limiting enzyme in the catabolism of cholesterol to bile acid, is stimulated by oxysterol receptor, liver X receptor alpha (LXRalpha) and negatively regulated by a bile acid receptor, farnesoid X receptor. In the current study, we demonstrated that 1,25-(OH)(2)D3 blunted the LXRalpha-mediated induction of CYP7alpha mRNA in H4IIE rat hepatoma cells. In co-transfection experiments in HepG2 cells, VDR repressed the activity of rat CYP7alpha promoter in a ligand-dependent manner through inhibition of LXRalpha signaling. We also confirmed the ability of VDR to repress LXRalpha transcriptional activation using a synthetic LXRalpha responsive reporter. Deletion analyses revealed that the ligand-binding domain of VDR was required for the suppression and the DNA-binding domain was dispensable. Given the fact that VDR can be activated by the secondary bile acid as well as 1,25-(OH)(2)D3, the crosstalk between LXRalpha and VDR signaling in regulation of bile acid metabolism provides a possible contribution of VDR to modulate bile acid and cholesterol homeostasis, and highlights a physiological function of VDR beyond calcium metabolism in the body.

Animals↗
PubMed2006

Degradation of tributyltin in microcosm using Mekong River sediment.

The degradation of tributyltin (TBT) and changes of bacterial number and community structures were investigated in microcosms using the sediment collected from the Mekong River, Vietnam. Concentrations of TBT in sediments were less than 0.62 ng/g (dry wt), lower than those reported from other areas. TBT-resistant bacteria were found in the three sampling sites, and the occurrence rates were 11-16% out of the total viable count. In this microcosm experiment, initial concentration of TBT [1.0-1.4 microg/g (dry wt)] decreased to 0.6 microg/g (dry wt) during 150 days, whereas that in the control microcosm with autoclaved sediment did not change, indicating that Mekong River sediment contains high TBT-degrading activity by microorganisms. The occurrence of TBT-resistant bacteria and the bacterial community structures monitored by denaturing gradient gel electrophoresis were almost the same between test and control groups, indicating that the addition of TBT had little influence on microbial community structure. Mekong River sediment seems to have a stable microbial community against TBT pollution.

Bacteria↗
PubMed2006

Adenoviral mediated MyoD gene transfer into fibroblasts: myogenic disease diagnosis.

MyoD, a master regulatory gene for myogenesis, converts mesoderm derived cells to the skeletal muscle phenotype MyoD gene transfer into skin fibroblasts has been attempted in an effort to diagnose genetic muscle diseases. Although the gene transduction efficiency of adenoviral gene delivery systems is higher than that of various other systems, the rate of myo-conversion is insignificant. Since high adenovirus doses are cytotoxic and exogenous MyoD expression is insufficient for skin fibroblasts to re-differentiate into muscle cells, we constructed the novel adeno-MyoD vector, Ad.CAGMyoD using the recombinant CAG promoter. Even at a lower multiplicities of infection most skin fibroblasts infected with Ad.CAGMyoD could convert into myotubes without vector-induced cytotoxicity. The converted cells expressed muscle-specific desmin and full-length dystrophin, both of which were detected by Western blotting. Genetic and immunohistochemical analyses using skin fibroblasts and our vector system are reliable and useful for the clinical diagnosis of genetic muscle diseases.

Adenoviridae↗
PubMed2006

Metabolic syndrome and age-related dementia: endocrinological aspects of adaptation to aging.

Metabolic syndrome is one of the determinants of lifespan in Japan. In order to prevent the acute vascular events, intervention is recommended. However, management of patients with this syndrome increased the number of patients with cognition decline and depressive state. Endocrinological studies with human and experimental animals showed that there is a negative relationship between progression of metabolic syndrome and occurrence of mental disorders. In this review, we summarize our clinical and experimental data, and discuss on the mechanism of the metabolic syndrome prevention of progression of age-related mental disorder.

Adaptation, Physiological↗
PubMed2006

Single-walled carbon nanotube growth from highly activated metal nanoparticles.

We demonstrate that any metal, even gold, silver, and copper, can act as a catalyst for SWCNT synthesis in chemical vapor deposition (CVD). Metal nanoparticles 3 nm or less in diameter, introduced into CVD ambience immediately after heat treatment at 800-950 degrees C in air, produce SWCNTs. The activation method is effective for copper and various noble metals as well as for iron-family elements. This implies that any metal particle may produce SWCNTs when its size becomes 1-3 nm. In other words, carbon atoms can form SWCNTs in a self-assembling fashion on nanoparticles without the specific functions of iron-family elements.

Journal Article↗
PubMed2006

Independent representation of parts and the relations between them: evidence from integrative agnosia.

Whether objects are represented as a collection of parts whose relations are coded independently remains a topic of ongoing discussion among theorists in the domain of shape perception. S. M., an individual with integrative agnosia, and neurologically intact ("normal") individuals learned initially to identify 4 target objects constructed of 2 simple volumetric parts. At test, the targets were mixed with distractors, some of which could be discriminated from the targets on the basis of a mismatching part, whereas the rest could be discriminated only on the basis of the altered spatial arrangements of parts. S. M. learned to identify the target objects, although at a rate slower than that of the normal participants. At test, he correctly rejected distractors on the basis of mismatching parts but was profoundly impaired at rejecting distractors made of the same local components but with mismatching spatial arrangements. These results suggest that encoding the spatial arrangements of parts of an object requires a mechanism that is different from that required for encoding the shape of individual parts, with the former selectively compromised in integrative agnosia.

Adult↗
PubMed2006

A -786T>C polymorphism in the endothelial nitric oxide synthase gene reduces serum nitrite/nitrate levels from the heart due to an intracoronary injection of acetylcholine.

We identified a -786T>C polymorphism in the eNOS gene, and this polymorphism was strongly associated with coronary spasm. The present study aimed to elucidate whether the -786T>C polymorphism or acetylcholine (ACh)-induced coronary spasm affects serum nitrite/nitrate (NOx) levels. The study population comprised three groups: (i) 26 patients without coronary spasm in the left anterior descending coronary artery (LAD) with the T/T genotype (group A); (ii) 20 patients with coronary spasm in the LAD with the T/T genotype (group B); and (iii) 16 patients with coronary spasm in the LAD with the C/T genotype (group C). Paired blood samples were obtained from the coronary sinus (CS) and the aortic tract (Ao) before and after an intracoronary injection of ACh. Serum NOx and plasma lactate levels were measured. The delta NOx level was calculated as the serum concentration of NOx in the CS minus that in the Ao. We compared lactate extraction ratios (LERs) and delta NOx levels between the three groups. The LERs after the provocation test in groups A, B and C were 18.9+/-2.4%, -0.5+/-3.9% and -13.5+/-4.2%, respectively. The LER in group C was significantly lower than in group B. The delta NOx levels after the provocation test in groups A, B and C were 11.5+/-1.7 micromol/l, 10.4+/-3.5 micromol/l and -2.1+/-4.8 micromol/l, respectively. The delta NOx levels in group C were significantly lower (P<0.05). Although the NOx level was significantly increased after the provocation test in group A (P<0.05), the NOx level was significantly decreased after the provocation test in group C (P=0.001). In group B, the provocation test did not significantly change the delta NOx level. In conclusion, the -786T>C polymorphism reduces the NOx level from the heart due to an intracoronary injection of ACh, and thereby predisposes the patients to severe coronary spasm.

Acetylcholine↗
PubMed2006

Microarray-mediated transcriptome analysis of the tributyltin (TBT)-resistant bacterium Pseudomonas aeruginosa 25W in the presence of TBT.

The tributyltin (TBT)-resistant bacterium, Pseudomonas aeruginosa 25W, which was isolated in seawater from the Arabian Sea, was subjected to transcriptome analysis in the presence of high concentrations of TBT. Only slight effects were observed at TBT concentration of 50 microM, but exposure to 500 microM resulted in the upregulation of 6 genes and the downregulation of 75. Among the 75 downregulated genes, 53% (40 out of 75) were of hypothetical function, followed by 14 transcriptional regulation- and translation-associated genes. The results of this study indicated that although the 25W strain was highly resistant to TBT, high concentrations of TBT result in toxic effect on the transcriptional and translational levels. The target genes likely belong to a specific category of transcription- and translation-associated genes rather than to other gene categories.

Down-Regulation↗
PubMed2006

[C-reactive protein, white blood cell and body temperature following cardiovascular surgery, as predicting factors of postoperative infection].

The aim of this study is to clarify the relationship between CRP and postoperative infection after cardiovascular surgery. We had 5 cases of surgical site infection, and 3 cases of infective endocarditis (IE) among 57 patients selected for this study out of 405 patients who had undergone cardiovascular surgery from May 1995 to March 2005. CRP, WBC and body temperature (BT) were evaluated during 1 week after the operation. Our results showed not only that the mean value of CRP level in the 49 non-infection patients attained the peak on the 2nd or 3rd day after the operation (18.2 +/- 4.7 and 17.7 +/- 5.7 mg/dl), but also that each patient in this group showed the same pattern of CRP sequence. CRP in the 5 cases of postoperative infection showed different patterns from that in the non-infection group. CRP in 3 cases of valve replacement for IE showed significantly higher level than that in 16 cases of valve replacement without IE through 1 week after the surgery. WBC level in the non-infection group reached the peak just after the operation (11.3 +/- 4.4 x 10(3)/microl) and then decreased gradually during 1 week after the operation. WBC in the 3 cases of valve replacement for IE, did not show different sequence pattern from that in the 16 cases of valve replacement without IE. WBC in a case of postoperative mediastinal infection showed a similar pattern of sequence to that in the non-infection group although it showed a remarkably high level of CRP sequence through 1 week after the surgery. BT in the non-infection group became the lowest just after the operation and reached the peak 8 hours after the operation. It then decreased gradually during 1 week after the operation. Our study demonstrates that CRP sequence after the surgery might be useful to detect postoperative infection after cardiovascular surgery.

Aged↗
PubMed2005

Direct effects of aldosterone on cardiomyocytes in the presence of normal and elevated extracellular sodium.

It is now recognized that aldosterone is potentially cardiotoxic, although its local effects in the heart are not well understood. We examined the effects of aldosterone on cultured neonatal rat cardiomyocytes in the presence of normal and elevated extracellular Na+ ([Na+]o). We evaluated the intracellular volume of cardiomyocytes in the presence of normal (141 mEq/liter) and elevated (146 mEq/liter) [Na+]o by measuring cell size. Intracellular Na+ was measured using sodium-binding-benzofuran-isophthalate as a fluorescent sodium indicator, and cardiac hypertrophy was assessed using B-type natriuretic peptide transcription and (3)H-leucine incorporation. Cardiomyocytes shrank in the presence of 146 mEq/liter Na+ due to the increased extracellular osmolarity at early phase. Aldosterone (10(-7) mol/liter) mitigated the shrinkage by stimulating Na+ uptake by the cells. This effect of aldosterone was blocked by SM 20220, a Na+/H+ exchanger 1 (NHE1) inhibitor, but not by eplerenone, a mineralocorticoid receptor blocker. Seventy-two hours of exposure to aldosterone in the presence of 146 mEq/liter Na+ led to increases in cardiomyocyte size, 3H-leucine incorporation, and B-type natriuretic peptide and NHE1 transcription that were significantly greater than were seen in the presence of 141 mEq/liter Na+. All but the last were blocked by either eplerenone or SM 20220; the increase in NHE1 transcription was blocked only by eplerenone. Aldosterone exerts a beneficial effect via NHE1 to block cardiomyocyte shrinkage in the presence of elevated [Na+]o at early phase, but long-time exposure to aldosterone in the presence of elevated [Na+]o leads to cardiomyocyte hypertrophy via genomic effects mediated by the mineralocorticoid receptor.

Aldosterone↗
PubMed2005

Stochastic resonance in binocular rivalry.

When a different image is presented to each eye, visual awareness spontaneously alternates between the two images--a phenomenon called binocular rivalry. Because binocular rivalry is characterized by two marginally stable perceptual states and spontaneous, apparently stochastic, switching between them, it has been speculated that switches in perceptual awareness reflect a double-well-potential type computational architecture coupled with noise. To characterize this noise-mediated mechanism, we investigated whether stimulus input, neural adaptation, and inhibitory modulations (thought to underlie perceptual switches) interacted with noise in such a way that the system produced stochastic resonance. By subjecting binocular rivalry to weak periodic contrast modulations spanning a range of frequencies, we demonstrated quantitative evidence of stochastic resonance in binocular rivalry. Our behavioral results combined with computational simulations provided insights into the nature of the internal noise (its magnitude, locus, and calibration) that is relevant to perceptual switching, as well as provided novel dynamic constraints on computational models designed to capture the neural mechanisms underlying perceptual switching.

Adaptation, Ocular↗
PubMed2005

Cobalt-filled apoferritin for suspended single-walled carbon nanotube growth with narrow diameter distribution.

Cobalt-filled apoferritin (Co-ferritin) was, for the first time, used as a wet catalyst for the synthesis of single-walled carbon nanotubes (SWNTs) with narrow diameter distribution. Co-ferritins were spin-coated and converted to cobalt nanoparticles by calcination. Using chemical vapor deposition, suspended networks of SWNTs were formed on pillar-structured substrates. The suspended SWNTs show narrow tube diameter distribution with a relatively good graphite structure. By virtue of the low diffusion coefficient of cobalt, Co-ferritin might be more useful for narrow diameter SWNTs growth than ferritins, which encase iron particles.

Animals↗
PubMed2005

An anti-apoptosis gene of the Bcl-2 family from Marine Birnavirus inhibiting apoptosis of insect cells infected with baculovirus.

VP5 is a 15-kDa nonstructural protein encoded by a small open reading frame in 5'-terminal of segment A of the Marine Birnavirus (MABV) (strainY-6) genome. Comparisons of the amino acid sequence of the VP5 with other Bcl-2 family member proteins indicated that the VP5 protein contains Bcl-2 homology (BH) domains BH1, BH2, BH3, and BH4, but without the transmembrane region. The VP5 gene from MABV was fused to enhancing green fluorescence protein (eGFP) gene and inserted into the baculovirus genome under the control of polyhedrin gene promoter, and then was highly expressed in insect cells. The expressed VP5 was capable of enhancing insect cell viability, prevented membrane blebbing and delayed DNA internucleosomal cleavage when cells were infected with the recombinant virus. The results suggested that the VP5 of MABV is a novel anti-apoptosis gene, which could regulate the cell apoptosis-off system.

Amino Acid Sequence↗
PubMed2005

Rare complication of dissection of Valsalva sinus with aorto-left atrial fistula in active aortic valve endocarditis.

We present a rare case of dissection of the sinus of Valsalva associated with an aortic annular abscess that perforated into the left atrium. A 61-year-old patient with infective endocarditis underwent emergent operation due to progressive heart failure, in whom echocardiography showed the dissection of sinus of Valsalva with aorto-left atrial communication. Procedure included autologous pericardial patch repair of the dissecting sinus of Valsalva and bioprosthetic valve replacement with a successful outcome. Microscopic examination showed excessive neutrophil infiltration in the aortic valve and annulus without involvement of the sinus of Valsalva.

Abscess↗