Biomedical subjects

T Akita

Publications and source records attributed to T Akita.

At least 19 recordsLinked to original sources

PubMed2006

[Aortic valve replacement for the small aortic annulus].

Aortic valve surgery for the small aortic annulus is still challenging for surgeons. Recently, the new types of high performance prosthesis have been developed and the chance of an aortic root enlargement (ARE) is decreasing. In this study, we propose the ideal strategy of the aortic surgery for the small aortic annulus. We analyzed the clinical records of 158 patients who underwent aortic valve replacement from August 1999 to October 2005 in our institution. The small aortic annulus was observed in 38 patients (24%). Fourteen patients of this group underwent ARE. Patient-prosthesis mismatch (PPM) was less frequently observed in patients with ARE compared to those without ARE. The additional time required for ARE was not considerable, and neither ischemic time nor cardiopulmonary bypass time was significantly prolonged by ARE. In conclusion, we have to select a prosthesis with sufficient orifice area to avoid PPM, otherwise we should choose an option of ARE. For this consideration, we definitely need the chart that demonstrates the relationship between the nominal size of various types of prostheses and the size of a patient's annulus that those prostheses actually fit.

Aged↗

PubMed2005

Three-dimensional mesoporous titanosilicates prepared by modified sol-gel method: Ideal gold catalyst supports for enhanced propene epoxidation.

Mesoporous titanosilicates with 1-12 mol % Ti content and with three-dimensional wormhole-like mesoporosity are prepared by a modified sol-gel technique. Sorption analysis shows that there is little change in the surface properties with increasing Ti concentration in the samples, implying that Ti atoms either are well-dispersed on the walls of the silica matrix or are present inside the framework with no pore blocking effect. Spectroscopic analysis shows that the Ti atoms are atomically dispersed in the silica matrix even at very high Ti concentration and there is no observable Ti aggregate (anatase) present in the samples. These titanosilicate samples after Au deposition followed by trimethylsilylation (for enhanced hydrophobicity) are highly efficient catalysts for vapor-phase propene epoxidation using O2 and H2. It was possible to achieve commercially desirable performance with about 7% propene conversion, >90% propene oxide selectivity, and about 40% hydrogen efficiency.

Journal Article↗

PubMed2005

[Short-term results of the Fontan operation in patients with Down syndrome].

Despite an extensive experience with Fontan operation, there is a paucity of information to guide the indication of the procedure in patients with Down syndrome. Of 79 patients who had undergone a Fontan operation in our hospital between 1995 and 2003, 3 had Down syndrome. All 3 patients had complete atrioventricular septal defect with single ventricular physiology. Two patients survived, and 1 died of chylothorax and respiratory infection. The 2 survivors have done well in the short-term without complications. We consider that in appropriately selected patients with Down syndrome in whom biventricular repair is precluded, the Fontan operation is the choice of the procedures.

Child, Preschool↗

PubMed2005

[Repair of tetralogy of Fallot with obstruction of right pulmonary artery; report of a case].

Patients with tetralogy of Fallot showing unilateral obstruction of a pulmonary artery, especially the right pulmonary artery, are a high-risk group for pulmonary hypertension after repair. This case of tetralogy of Fallot with the obstruction of the right pulmonary artery received a Blalock-Taussig shunt at 7 months old, and the occluded right pulmonary artery caused empyema after surgery. At 2 years old, a cardiac catheter study showed a pulmonary artery index of 193.6 mm2/m2, so we undertook intracardiac repair. After the repair, she showed a relativery favorable clinical course. Systolic pulmonary artery pressure and right ventricular pressure were about 30 and 50 mmHg, respectively. We considered that tetralogy of Fallot with obstruction of right pulmonary artery could be repaired, as long as the pulmonary artery index was within the limits of indication and the left ventricle was well-developed.

Arterial Occlusive Diseases↗

PubMed2003

Central and peripheral concentrations of tumor necrosis factor-alpha in Chinese Meishan pigs stimulated with lipopolysaccharide.

The objective of this study was to investigate the presence of tumor necrosis factor-alpha (TNF-alpha) in the central nervous system and the effects of lipopolysaccharide on central and peripheral concentrations of TNF-alpha, behavioral conditions (standing or lying), elimination scores (defecation or urination), rectal temperature, and food intake (as-fed basis) in Chinese Meishan pigs. Intravenous injections of lipopolysaccharide resulted in increased (P < 0.05) plasma concentrations of TNF-alpha and cortisol. Although urination was not affected by the administration of lipopolysaccharide, defecation was stimulated (P < 0.05). Lipopolysaccharide increased (P < 0.05) rectal temperature and standing rate, and inhibited (P < 0.05) food intake in pigs. To determine whether TNF-alpha is present in the porcine central nervous system as well as in peripheral blood, TNF-alpha and its specific transcripts in brain tissues (hypothalamus, amygdala, or hippocampus) and the pituitary were determined. The abundance of TNF-alpha messenger RNA and immunoreactive TNF-alpha were observed in all tissues, and the concentrations of TNF-alpha were increased (P < 0.05) by the intramuscular injection of lipopolysaccharide. These results suggest that TNF-alpha is present in the central nervous system, and plays some roles in its biological regulation in Chinese Meishan pigs.

Animals↗

PubMed2003

[Long-term results of Fontan type operation].

We had experienced 41 Fontan type operations between 1977 and 2002. Twelve patients had an atriopulmonary connection (APC), 3 patients had a lateral tunnel connection, and 2 had internal conduit repair and 24 patients received an external conduit repair. There were 3 operative deaths and 5 late deaths (5 months to 24 years). Kaplan-Meier analysis shows good 5-years survival in both group of atriopulmonary connection and that of total cavoplumonary connection (TCPC). However, survival and clinical status of APC patients deteriorated after 7 years. Atrial fibrillation and right pulmonary vein stenosis by giant right atrium become common in these patients. We recommend that patients with single ventricle have the TCPC type operation and patients with giant right atrium and poor clinical status after APC have the TCPC conversion.

Blood Vessel Prosthesis Implantation↗

PubMed2002

Ca(2+)-dependent Ca(2+) clearance via mitochondrial uptake and plasmalemmal extrusion in frog motor nerve terminals.

Ca(2+) clearance in frog motor nerve terminals was studied by fluorometry of Ca(2+) indicators. Rises in intracellular Ca(2+) ([Ca(2+)](i)) in nerve terminals induced by tetanic nerve stimulation (100 Hz, 100 or 200 stimuli: Ca(2+) transient) reached a peak or plateau within 6-20 stimuli and decayed at least in three phases with the time constants of 82-87 ms (81-85%), a few seconds (11-12%), and several tens of seconds (less than a few percentage). Blocking both Na/Ca exchangers and Ca(2+) pumps at the cell membrane by external Li(+) and high external pH (9.0), respectively, increased the time constants of the initial and second decay components with no change in their magnitudes. By contrast, similar effects by Li(+) alone, but not by high alkaline alone, were seen only on 200 stimuli-induced Ca(2+) transients. Blocking Ca(2+) pumps at Ca(2+) stores by thapsigargin did not affect 100 stimuli-induced Ca(2+) transients but increased the initial decay time constant of 200 stimuli-induced Ca(2+) transients with no change in other parameters. Inhibiting mitochondrial Ca(2+) uptake by carbonyl cyanide m-chlorophenylhydrazone markedly increased the initial and second decay time constants of 100 stimuli-induced Ca(2+) transients and the amplitudes of the second and the slowest components. Plotting the slopes of the decay of 100 stimuli-induced Ca(2+) transients against [Ca(2+)](i) yielded the supralinear [Ca(2+)](i) dependence of Ca(2+) efflux out of the cytosol. Blocking Ca(2+) extrusion or mitochondrial Ca(2+) uptake significantly reduced this [Ca(2+)](i)-dependent Ca(2+) efflux. Thus Ca(2+)-dependent mitochondrial Ca(2+) uptake and plasmalemmal Ca(2+) extrusion clear out a small Ca(2+) load in frog motor nerve terminals, while thapsigargin-sensitive Ca(2+) pump boosts the clearance of a heavy Ca(2+) load. Furthermore, the activity of plasmalemmal Ca(2+) pump and Na/Ca exchanger is complementary to each other with the slight predominance of the latter.

Animals↗

PubMed2002

[Experience of coronary artery bypass grafting on the beating heart with right heart bypass; 3 cases of octogenarian].

Right heart bypass (RHB) yields more stable hemodynamics by increasing left ventricular preload and collapse right ventricular chamber during the displacement of the heart on beating heart coronary artery bypass grafting (CABG). Recently beating heart CABG gaining popularity, and the indications for CABG have increasingly expanded to elderly person. Using RHB while exposing posterior branches by displacing the beating heart, we have attempted to make total revascularization in beating heart CABG. We performed beating heart CABG with RHB in 3 cases of octogenarian. All patients had left main trunk lesion and needed revascularization of posterior vessels. Introduction of RHB enabled us to approach to posterior target vessels in better exposure and under greater hemodynamic stability. All three patients had no complications postoperatively. Strictly speaking CABG with RHB is not off-pump CABG, but RHB system does not include either artificial lung or manipulation of the aorta. Therefore we think it is very effective support system which enables multiple coronary revascularization for elderly person.

Aged↗

PubMed2001

TEM and HAADF-STEM study of a Au catalyst supported on a TiO2 nano-rod.

Gold nanoparticles were deposited on TiO2 nano-rods by a deposition precipitation method. This Au/TiO2 nano-rods catalyst is active for CO oxidation even at temperatures less than 273K and is as active as the catalyst of Au supported on conventional TiO2 particles. Transmission electron microscopy (TEM) showed that the TiO2 nano-rods were composed of a single anatase crystal and had a pillar shape with an axis along the <111> direction surrounded by flat four [101] planes. High angle annular dark field scanning TEM (HAADF-STEM) also revealed that a Au platelet with a thickness of 0.5-1 nm was formed at the interface between TiO2 nano-rods. The Au platelet was not observed when conventional round particles of TiO2 were used as a support.

Journal Article↗

PubMed2001

Effect of zinc deficiency on betacyanin production in a cell suspension culture of table beet (Beta vulgaris L.).

The effect of microelements in the Linsmaier-Skoog (LS) medium on betacyanin production was investigated in suspension cultures of table beet (Beta vulgaris L.). Removing zinc from the medium resulted in a high betacyanin content of the cells, the betacyanin content of the cells decreasing with increasing zinc concentration in the medium. The betacyanin content of cells cultured in the medium without zinc was twice as high as that in the medium containing 0.03 mM of zinc. In the revised LS medium without zinc, the maximum betacyanin yield was obtained of 590 mg/l from a 21-day culture.

Betalains↗

PubMed2001

Congestive heart failure caused by aortocaval fistula after nephrectomy.

We treated a 66-year-old man and a 69-year-old woman with high output cardiac failure due to aortocaval fistula. They underwent nephrectomy 40 and 36 years ago, respectively. They suffered from heart failure for a very long time. However, the etiology was not elucidated until recently. The aortogram revealed massive shunt from the aorta to the inferior vena cava via the right renal artery. Three-dimensional computerized tomography clearly delineated the aortocaval fistula. Surgical closure of the fistula promptly improved heart failure. We stress the importance of history taking concerning nephrectomy and the importance of abdominal auscultation in high output cardiac failure.

Aged↗

PubMed2000

Pig cloning by microinjection of fetal fibroblast nuclei.

Pig cloning will have a marked impact on the optimization of meat production and xenotransplantation. To clone pigs from differentiated cells, we microinjected the nuclei of porcine (Sus scrofa) fetal fibroblasts into enucleated oocytes, and development was induced by electroactivation. The transfer of 110 cloned embryos to four surrogate mothers produced an apparently normal female piglet. The clonal provenance of the piglet was indicated by her coat color and confirmed by DNA microsatellite analysis.

Animals↗

PubMed2000

Quantitative trait loci (QTL) analysis in a Meishan x Göttingen cross population.

In order to locate the genetic regions in the swine genome that are responsible for economically important traits, a resource population has been constructed by mating two female Meishan pigs with a male Göttingen miniature pig. In subsequent generations, 265 F2 offspring were produced from two F1 males and 19 F1 females. The F2 offspring were scored for eight traits including growth rate, teat number, vertebra number and backfat thickness, and genotyped for 318 genetic markers spanning the swine genome. Least-square analysis revealed quantitative trait loci (QTL) effects for vertebra number on chromosomes 1 and 2; for teat number on chromosomes 1 and 7; for birth weight on chromosome 1; for average daily gain between 4 and 13 weeks of age on chromosomes 9 and 10; for backfat thickness on chromosome 7; and for backskin thickness on chromosome 3.

Animals↗

PubMed2000

Functional coupling of Ca(2+) channels to ryanodine receptors at presynaptic terminals. Amplification of exocytosis and plasticity.

Ca(2+)-induced Ca(2+) release (CICR) enhances a variety of cellular Ca(2+) signaling and functions. How CICR affects impulse-evoked transmitter release is unknown. At frog motor nerve terminals, repetitive Ca(2+) entries slowly prime and subsequently activate the mechanism of CICR via ryanodine receptors and asynchronous exocytosis of transmitters. Further Ca(2+) entry inactivates the CICR mechanism and the absence of Ca(2+) entry for >1 min results in its slow depriming. We now report here that the activation of this unique CICR markedly enhances impulse-evoked exocytosis of transmitter. The conditioning nerve stimulation (10-20 Hz, 2-10 min) that primes the CICR mechanism produced the marked enhancement of the amplitude and quantal content of end-plate potentials (EPPs) that decayed double exponentially with time constants of 1.85 and 10 min. The enhancement was blocked by inhibitors of ryanodine receptors and was accompanied by a slight prolongation of the peak times of EPP and the end-plate currents estimated from deconvolution of EPP. The conditioning nerve stimulation also enhanced single impulse- and tetanus-induced rises in intracellular Ca(2+) in the terminals with little change in time course. There was no change in the rate of growth of the amplitudes of EPPs in a short train after the conditioning stimulation. On the other hand, the augmentation and potentiation of EPP were enhanced, and then decreased in parallel with changes in intraterminal Ca(2+) during repetition of tetani. The results suggest that ryanodine receptors exist close to voltage-gated Ca(2+) channels in the presynaptic terminals and amplify the impulse-evoked exocytosis and its plasticity via CICR after Ca(2+)-dependent priming.

Animals↗

PubMed2000

Functional triads consisting of ryanodine receptors, Ca(2+) channels, and Ca(2+)-activated K(+) channels in bullfrog sympathetic neurons. Plastic modulation of action potential.

Fluorescent ryanodine revealed the distribution of ryanodine receptors in the submembrane cytoplasm (less than a few micrometers) of cultured bullfrog sympathetic ganglion cells. Rises in cytosolic Ca(2+) ([Ca(2+)](i)) elicited by single or repetitive action potentials (APs) propagated at a high speed (150 microm/s) in constant amplitude and rate of rise in the cytoplasm bearing ryanodine receptors, and then in the slower, waning manner in the deeper region. Ryanodine (10 microM), a ryanodine receptor blocker (and/or a half opener), or thapsigargin (1-2 microM), a Ca(2+)-pump blocker, or omega-conotoxin GVIA (omega-CgTx, 1 microM), a N-type Ca(2+) channel blocker, blocked the fast propagation, but did not affect the slower spread. Ca(2+) entry thus triggered the regenerative activation of Ca(2+)-induced Ca(2+) release (CICR) in the submembrane region, followed by buffered Ca(2+) diffusion in the deeper cytoplasm. Computer simulation assuming Ca(2+) release in the submembrane region reproduced the Ca(2+) dynamics. Ryanodine or thapsigargin decreased the rate of spike repolarization of an AP to 80%, but not in the presence of iberiotoxin (IbTx, 100 nM), a BK-type Ca(2+)-activated K(+) channel blocker, or omega-CgTx, both of which decreased the rate to 50%. The spike repolarization rate and the amplitude of a single AP-induced rise in [Ca(2+)](i) gradually decreased to a plateau during repetition of APs at 50 Hz, but reduced less in the presence of ryanodine or thapsigargin. The amplitude of each of the [Ca(2+)](i) rise correlated well with the reduction in the IbTx-sensitive component of spike repolarization. The apamin-sensitive SK-type Ca(2+)-activated K(+) current, underlying the afterhyperpolarization of APs, increased during repetitive APs, decayed faster than the accompanying rise in [Ca(2+)](i), and was suppressed by CICR blockers. Thus, ryanodine receptors form a functional triad with N-type Ca(2+) channels and BK channels, and a loose coupling with SK channels in bullfrog sympathetic neurons, plastically modulating AP.

Action Potentials↗

PubMed2000

Analytical high-resolution TEM study of supported gold catalysts: orientation relationship between Au particles and TiO2 supports.

An analytical high-resolution TEM study was carried out for gold deposited on TiO2 (anatase and rutile) to obtain a structural insight into the unique catalytic properties of the system. Preferred orientations between Au particles and the TiO2 support were often observed and a model for the epitaxial orientation between the Au particles and anatase TiO2 was proposed. These results were consistent with the results calculated by the coincidence of reciprocal lattice point (CRLP) method.

Journal Article↗

PubMed2000

Hyperhomocysteinemia impairs angiogenesis in response to hindlimb ischemia.

Hyperhomocysteinemia (HH) is an independent risk factor for atherosclerosis, including peripheral arterial occlusive disease (PAOD). Because angiogenesis and collateral vessel formation are important self-salvage mechanisms for ischemic PAOD, we examined whether HH modulates angiogenesis in vivo in a rat model of hindlimb ischemia. Rats were divided into 3 groups: the control group was given tap water, the HH group was given water containing L-methionine (1 g x kg(-1) x d(-1)), and the HH+L-arg group was given water containing methionine (1 g x kg(-1) x d(-1)) and l-arginine (2.25 vol%). At day 14 of the dietary modifications, the left femoral artery and vein were excised, and the extent of angiogenesis and collateral vessels in the ischemic limb were examined for 4 weeks. Plasma homocysteine levels significantly increased (P:<0.001), and plasma and tissue contents of nitrite+nitrate as well as tissue cGMP levels significantly decreased in the HH group compared with the control group (P:<0.01). Laser Doppler blood flowmetry (LDBF) revealed a significant decrease in the ischemic/normal limb LDBF ratio in the HH group at days 7, 14, 21, and 28 (P:<0.01 versus control). Angiography revealed a significant decrease in the angiographic score in the HH group at day 14 (P:<0.001 versus control). Immunohistochemistry of ischemic tissue sections showed a significant reduction in the capillary density in the HH group (P:<0. 001 versus control). Oral l-arginine supplementation in rats with HH (HH+L-arg) restored the decreased plasma and tissue nitrite+nitrate and cGMP contents (P:<0.05) as well as angiogenesis, as assessed by LDBF (P:<0.05 versus HH), angiographic score (P:<0.01 versus HH), and capillary density (P:<0.001 versus HH). In summary, HH impaired ischemia-induced angiogenesis and collateral vessel formation in a rat model of hindlimb ischemia in vivo. The mechanism of the HH-induced impairment of angiogenesis might be mediated in part by a reduced bioactivity of endogenous NO in the HH state.

Angiography↗

PubMed2000

Cardiac tumor biopsy under the guidance of intracardiac echocardiography.

Transthoracic echocardiography or transesophageal echocardiography is sometimes useful in intracardiac tumor biopsy. Intracardiac echocardiography was used as an alternative to either of these for performing a biopsy of a right cardiac tumor in a 79-year-old woman. The procedure was well tolerated and no complications occurred. Histopathological findings and immunohistological staining were compatible with the diagnosis of neurogenic sarcoma.

Aged↗