Biomedical subjects

Y Okamura

Publications and source records attributed to Y Okamura.

At least 19 recordsLinked to original sources

PubMed2006

[Evaluation of aortic valve replacement involving small severely calcified aortic annulus in elderly patients].

We performed aortic valve replacement in 24 patients aged over 70 with small calcified valves. The surgical management of such patients remains controversial as the extensive calcification compromises implantation. Hence, we used an ultrasonic debridement instrument to remove calcium and selected a small prosthesis with the largest possible orifice without enlargement of the aortic annulus. Echocardiography showed significant reductions in left ventricular mass index compared with preoperative values. Early and mid-term prognosis has been relatively good.

Aged↗

PubMed2006

[Effects of additional pulmonary blood flow after bidirectional Glenn procedure].

Thirteen cases of functional single ventricle who had undergone bidirectional Glenn procedure were divided into 2 groups according to presence (5) or absence (8) of additional pulmonary blood flow. Additional flow was preserved in cases with relatively small pulmonary artery index (PA index), and their sources were antegrade pulmonary blood flow (2), and Blalock-Taussig (BT) shunt (3). In the control group, PA index was reduced to about 70% of the preoperative value, while in the additional group, pulmonary artery growth was recognized without significant elevation of mean pulmonary artery pressure. However, atrioventricular valve regurgitation progressed and systemic ventricular volume did not decrease after Glenn in the additional group. Therefore special consideration for the timing of Fontan procedure is mandatory.

Anastomosis, Surgical↗

PubMed2006

[Effects of octreotide acetate on intractable chylothorax after surgery for congenital heart diseases].

We experienced 2 infants in whom octreotide acetate was effective on intractable chylothorax after surgery for congenital heart diseases. They were 8- and 5-month-old. They were diagnosed as having corrected transposition of the great arteries (TGA) and tetralogy of Fallot respectively, and underwent bidirectional Glenn anastomosis and right modified Blalock Taussig shunt. Chylothorax was revealed on the 11th and the 1st postoperative day, and was not improved by any conventional therapy in either case. Then octreotide acetate was infused continuously with 0.1-0.6 micorg/kg/hour for 24 and 7 days. Chylothorax disappeared completely without any complications such as disturbance of blood sugar level or growth retardation. Octreotide acetate was effective and safe even in infants in intractable chylothorax after surgery for congenital heart diseases, as long as used for short period.

Cardiac Surgical Procedures↗

PubMed2006

[Surgical stabilization of multiple rib fracture and flail chest].

The experience of 14 cases with surgical stabilization of multiple rib fracture and flail chest was reported. They were 11 men and 3 women of 31 to 87 years of age. Paradoxical chest movement was noted in 10 patients. Thirteen of 14 patients successfully weaned from the ventilator less than 7 days after surgery. Of 14, 4 cases were treated with internal fixation and the others were with acetabular reconstruction plates with or without rib stapler. No case of death was experienced. Ten patients who were performed fixation with acetabular reconstruction plate weaned from the ventilator earlier than cases treated by internal fixation, suggesting the superiority of the acetabular reconstruction plate. Improvement of rib stapler and the development of a titanium plate of specific use for rib is expected in the future.

Adult↗

PubMed2005

Characterization and potential application of purified aldehyde oxidase from Pseudomonas stutzeri IFO12695.

The molecular weight of purified aldehyde oxidase from Pseudomonas stutzeri IFO12695 was estimated to be 160 kDa by a gel filtration method. SDS-PAGE showed that the enzyme consisted of three non-identical subunits with molecular weights of 18, 38, and 83 kDa. The enzyme exhibited an absorption spectrum with maxima at 277, 325, 365, 415, 450, 480, and 550 nm and possessed molybdenum, CMP, iron, sulfur, and FAD as its cofactors, indicating that it belonged to the xanthine oxidase family. A variety of aliphatic and aromatic aldehydes were oxidized; and among them n-hexylaldehyde gave the most rapidly action. When 10 mM formaldehyde was treated with the aldehyde oxidase in the presence of catalase for 240 min, the formaldehyde concentration was reduced to 0.8 mM, suggesting this enzyme might be effective for the removal of formaldehyde contained in wastewater.

Aldehyde Oxidase↗

PubMed2005

GABAergic synaptic transmission modulates swimming in the ascidian larva.

To examine the role of the amino acid GABA in the locomotion of basal chordates, we investigated the pharmacology of swimming and the morphology of GABA-immunopositive neurones in tadpole larvae of the ascidians Ciona intestinalis and Ciona savignyi. We verified that electrical recording from the tail reflects alternating muscle activity during swimming by correlating electrical signals with tail beats using high-speed video recording. GABA reversibly reduced swimming periods to single tail twitches, while picrotoxin increased the frequency and duration of electrical activity associated with spontaneous swimming periods. Immunocytochemistry for GABA revealed extensive labelling throughout the larval central nervous system. Two strongly labelled regions on either side of the sensory vesicle were connected by an arc of labelled fibres, from which fibre tracts extended caudally into the visceral ganglion. Fibre tracts extended ventrally from a third, more medial region in the posterior sensory vesicle. Two rows of immunoreactive cell bodies in the visceral ganglion extended neurites into the nerve cord, where varicosities were seen. Thus, presumed GABAergic neurones form a network that could release GABA during swimming that is involved in modulating the time course and frequency of periods of spontaneous swimming. GABAergic and motor neurones in the visceral ganglion could interact at the level of their cell bodies and/or through the presumed GABAergic fibres that enter the nerve cord. The larval swimming network appears to possess some of the properties of spinal networks in vertebrates, while at the same time possibly showing a type of peripheral innervation resembling that in some protostomes.

Animals↗

PubMed2005

Opposing effects of oestradiol and progesterone on intracellular pathways and activation processes in the oxidative stress induced activation of cultured rat hepatic stellate cells.

BACKGROUND: Oxidative stress, including the generation of reactive oxygen species (ROS), is involved in hepatofibrogenesis. The authors' previous studies have shown that oestradiol suppresses hepatic fibrosis in animal models and attenuates the activation of cultured rat hepatic stellate cells (HSCs), which possess oestrogen receptor subtype beta and are also activated by ROS. AIMS: To define the mechanisms by which female sex hormones play an antifibrogenic role in activated HSCs, the effects of oestradiol and progesterone on ROS generation processes and intracellular pathways, leading to the activation of HSCs undergoing oxidative stress, was examined. METHODS: HSCs, isolated from rats, were cultured for 7 days with oestradiol or progesterone for 24 hours as pretreatment, and oxidative stress was then induced by exposure to low doses of hydrogen peroxide for another 24 hours. RESULTS: Oestradiol inhibited ROS generation and antioxidant enzyme loss via the suppression of NADH/NADPH oxidase activity, and attenuated hydrogen peroxide induced transforming growth factor-beta1 (TGF-beta1) expression, HSC proliferation and transformation, and the activation of mitogen activated protein kinase (MAPK) pathways and transcription factors. Progesterone exerted a stimulatory effect through the progesterone receptor on the induction of ROS generation processes and intracellular pathways, resulting in TGF-beta1 expression and HSC activation, and fibrogenic effects were inhibited by oestradiol. CONCLUSION: These findings show for the first time that oestradiol inhibits the activation of transcription factors by suppressing ROS generation processes and the MAPK pathways, and inactivates the downstream transcription processes involved in TGF-beta1 expression and HSC activation, whereas progesterone acts in opposition to the favourable effects of oestradiol and its effects are blocked by oestradiol.

Animals↗

PubMed2005

[Sutureless technique for oozing type postinfarction left ventricular free wall rupture].

We report our experience using a sutureless technique for oozing type postinfarction left ventricular free wall rupture. Several materials such as fibrin seat, autologous or heterologous pericardial patch, fibrin glue, and geratin-resorcin-formaldehyde (GRF) glue have been used. Nine patients, who developed postinfarction left ventricular free wall rupture, underwent surgical repair using a sutureless technique between 1999 and 2004. All patients survived and discharged our hospital without any postoperative complications. And all are alive an exellent condition in 5 to 44 months. A sutureless technique for the treatment of oozing type postinfarction left ventricular free wall rupture is simple, effective, and associated with a favorable outcome.

Aged↗

PubMed2005

[Microwave coagulation therapy with potassium titanyl phosphate (KTP) laser therapy for airway stenosis from a recurrent tracheocarinal tumor].

About 2 years after right lower lobectomy for anadenocarcinoma in the right lung, an 80-year-old man had a reccurent tumor in tracheocarinal lymph nodes. Although concurrent chemoradiotherapy was performed, there was no change (NC) and the tumor grew back slowly. He was admitted to our hospital with exertional dyspnea and stridor 2 years later. The bronchoscopic microwave coagulation therapy was performed in the right main bronchus. After potassium titanyl phosphate (KTP) laser therapy had been performed in the tracheocarinal lumen, an expandable metallic stent was performed. The postopertive course was uneventful.

Adenocarcinoma↗

PubMed2005

[Blalock-Taussig shunt and pulmonary artery angioplasty for isolated unilateral absence of the right pulmonary artery; report of a case].

A 7-month-old girl was referred to us for further examination of absence of the right pulmonary artery. She had no symptom at that time. Diagnosis was made by chest computed tomography (CT) and cardiac catheterization. Though the size of the right pulmonary artery was not apparent, right pulmonary vein wedge angiography revealed the distal portion of right pulmonary artery sufficient for surgical repair. But the distance between the pulmonary trunk and right pulmonary artery was too far to perform direct anastomosis, and some systemic collaterals had already been recognized. Pulmonary vasculature was also not inadequate. Therefore we planned a palliative procedure. At the age of 7 months, right modified Blalock-Tausig shunt using 5mm expand-polytetrafluoroethylene (ePTFE) tube and angioplasty of the distal portion of right pulmonary artery using autologous pericardium roll with Dacron mesh was performed. Postoperative course was uneventful. She has been followed up for 6 months after the palliation. In the near future the completion of the definitive repair will be considered.

Anastomosis, Surgical↗

PubMed2005

[Jatene procedure with arch repair; usefulness of rapid two-stage repair].

Four cases of Jatene procedure with arch repair were performed since 2000 in our department. Two-stage repair was used in all cases and the extended end-to-end anastomosis and pulmonary artery banding (PAB) were performed in 3 cases as the initial repair. In a recent case of TGA type I with coarctation of the aorta (CoA), only subclavian flap aortoplasty was performed when he was 6-day-old and patent ductus arteriosus (PDA) was preserved and rapid two-stage Jatene procedure was performed when he was 8-day-old. There was no hospital or late death, or reoperation. The results of the two-stage Jatene procedure with arch repair was good and safe. Rapid two-stage repair was thought to be a useful choice especially for TGA type I with arch anomaly.

Aorta, Thoracic↗

PubMed2003

[The surgical technique of heart displacement during off-pump coronary artery bypass grafting in the exposure of the anastomotic site of posterior descending artery].

Heart displacement during off-pump coronary artery bypass grafting (OPCAB) is necessary to expose the anastomotic site. However, such displacement causes hemodynamic deterioration especially in the exposure of the circumflex branches and posterior descending artery (PDA). In this study we present two different cardiac positioning for the exposure of the anastomotic site of PDA. To expose the mid-portion of PDA the heart is vertically displaced by fixing the suction cup of the heart positioner on apex. To expose the proximal portion of PDA the suction cup is attached on the acute margin of the right ventricle (off apex). By using these 2 different techniques properly, hemodynamic deterioration can be avoided during OPCAB for PDA.

Anastomosis, Surgical↗

PubMed2001

Induction of ascidian peripheral neuron by vegetal blastomeres.

Ascidian tadpole larvae have a similar dorsal tubular nervous system as vertebrates. The induction of brain formation from a4.2-derived (a-line) cells requires signals from the A4.1-derived (A-line) cells. However, little is known about the mechanism underlying the development of the larval peripheral nervous system due to the lack of a suitable molecular marker. Gelsolin, an actin-binding protein, is specifically expressed in epidermal sensory neurons (ESNs) that mainly constitute the entire peripheral nervous system of the ascidian young tadpoles. Here, we address the role of cell interactions in the specification of ESNs using immunostaining with an anti-gelsolin antibody. Animal half (a4.2- and b4.2-derived) embryos did not give rise to any gelsolin-positive neurons, indicating that differentiation of ESNs requires signals from vegetal cells. Cell isolation experiments showed that A4.1 blastomeres induce gelsolin-positive neurons from a-line cells but not from b4.2-derived (b-line) cells. On the other hand, B4.1 blastomeres induce gelsolin-positive neurons both from b-line cells and a-line cells. This is in sharp contrast to the specification of brain cells which is not affected by the ablation of B4.1-derived (B-line) cells. Furthermore, basic fibroblast growth factor (bFGF) induced ESNs from the a-line cells and b-line cells in the absence of vegetal cells. Their competence to form ESNs was lost between the 110-cell stage and the neurula stage. Our results suggested that the specification of the a-line cells and b-line cells into ESNs is controlled by distinct inducing signals from the anterior and posterior vegetal blastomeres. ESNs in the trunk appear to be derived from the a8.26 blastomeres aligning on the edge of presumptive neural region where ascidian homologue of Pax3 is expressed. These findings highlight the close similarity of ascidian ESNs development with that of vertebrate placode and neural crest.

Animals↗

PubMed2001

A magnetosome-specific GTPase from the magnetic bacterium Magnetospirillum magneticum AMB-1.

Magnetic bacteria produce intracellular vesicles that envelope single domain magnetite crystals. Although many proteins are present in this intracellular vesicle membrane, five are specific to this membrane. A 16-kDa protein, designated Mms16, is the most abundant of the magnetosome-specific proteins, and to establish its function we cloned and sequenced its gene from Magnetospirillum magneticum AMB-1. This was achieved by determination of the N-terminal amino acid sequence of the protein following two dimensional polyacrylamide gel electrophoresis, and sequencing of the gene was performed by gene walking using anchored polymerase chain reaction. Mms16 contains a putative ATP/GTP binding motif (P-loop). Recombinant Mms16 with a hemagglutinin tag, was expressed in Escherichia coli and purified. Recombinant Mms16 protein could bind GTP and showed GTPase activity. GTP was the preferred substrate for Mms16-catalyzed nucleotide triphosphate hydrolysis. These results suggest that a novel protein specifically localized on the magnetic particle membrane, Mms16, is a GTPase. Mms16 protein showed similar characteristics to small GTPases involved in the formation of intracellular vesicles. Furthermore, addition of the GTPase inhibitor AlF(4)- also inhibited magnetic particle synthesis, suggesting that GTPase is required for magnetic particles synthesis.

Amino Acid Sequence↗

PubMed2001

Hepatic stellate cells contain the functional estrogen receptor beta but not the estrogen receptor alpha in male and female rats.

In an earlier study, we showed that estradiol (E2) inhibits proliferation and transformation in cultured rat hepatic stellate cells (HSCs) and that the actions of E2 are mediated through estrogen receptors (ERs). This study reports on an investigation of the cellular localization of ER subtypes ERalpha and ERbeta using immunohistochemistry in experimental fibrotic liver rats and of each ER subtype expression in cultured rat HSCs by evaluating the produced mRNA and protein. The results indicate that high levels of ERbeta expression and low or no levels of ERalpha expression were observed in normal and fibrotic livers and in quiescent and activated HSCs from both males and females. The specificity of E2-mediated antiapoptotic induction through the ERbeta was shown by dose-dependent inhibition by the pure ER antagonist ICI 182,780 in HSCs which were undergoing early apoptosis. These findings demonstrate for the first time that rat HSCs possess functional Erbeta, but not Eralpha, to respond directly to E2 exposure.

Animals↗

PubMed2001

Steroidogenic acute regulatory protein binds cholesterol and modulates mitochondrial membrane sterol domain dynamics.

The steroidogenic acute regulatory protein (StAR) mediates the rate-limiting step of steroidogenesis, delivery of cholesterol to the inner mitochondrial membrane. However, the mechanism whereby cholesterol translocation is accomplished has not been resolved. Recombinant StAR proteins lacking the first N-terminal 62 amino acids comprising the mitochondrial-targeting sequence were used to determine if StAR binds cholesterol and alters mitochondrial membrane cholesterol domains to enhance sterol transfer. First, a fluorescent NBD-cholesterol binding assay revealed 2 sterol binding sites (K(d) values near 32 nm), whereas the inactive A218V N-62 StAR mutant had only a single binding site with 8-fold lower affinity. Second, NBD-cholesterol spectral shifts and fluorescence resonance energy transfer from StAR Trp residues to NBD-cholesterol showed (i) close molecular interaction between these molecules (R(2/3) = 33 A) and (ii) sensitized NBD-cholesterol emission from only one of the two sterol binding sites. Third, circular dichroism showed that cholesterol binding induced a change in StAR secondary structure. Fourth, a fluorescent sterol transfer assay that did not require separation of donor and acceptor mitochondrial membranes demonstrated that StAR enhanced mitochondrial sterol transfer as much as 100-fold and induced/increased the formation of rapidly transferable cholesterol domains in isolated mitochondrial membranes. StAR was 67-fold more effective in transferring cholesterol from mitochondria of steroidogenic MA-10 cells than from human fibroblast mitochondria. In contrast, sterol carrier protein-2 (SCP-2) was only 2.2-fold more effective in mediating sterol transfer from steroidogenic cell mitochondria. Taken together these data showed that StAR is a cholesterol-binding protein, preferentially enhances sterol transfer from steroidogenic cell mitochondria, and interacts with mitochondrial membranes to alter their sterol domain structure and dynamics.

4-Chloro-7-nitrobenzofurazan↗

PubMed2001

The maternal transcript for truncated voltage-dependent Ca2+ channels in the ascidian embryo: a potential suppressive role in Ca2+ channel expression.

Ca2+ entry during electrical activity plays several critical roles in development. However, the mechanisms that regulate Ca2+ influx during early embryogenesis remain unknown. In ascidians, a primitive chordate, development is rapid and blastomeres of the muscle and neuronal lineages are easily identified, providing a simple model for studying the expression of voltage-dependent Ca2) channels (VDCCs) in cell differentiation. Here we isolate an ascidian cDNA, TuCa1, a homologue of the alpha(1)-subunit of L-type class Ca2+ channels. We unexpectedly found another form of Ca2+ channel cDNA (3-domain-type) potentially encoding a truncated type which lacked the first domain and a part of the second domain. An analysis of genomic sequence suggested that 3-domain-type RNA and the full-length type have alternative transcriptional start sites. The temporal pattern of the amount of 3-domain-type RNA was the reverse of that of the full-length type; the 3-domain type was provided maternally and persisted during early embryogenesis, whereas the full-length type was expressed zygotically in neuronal and muscular lineage cells. Switching of the two forms occurred at a critical stage when VDCC currents appeared in neuronal or muscular blastomeres. To examine the functional roles of the 3-domain type, it was coexpressed with the full-length type in Xenopus oocyte. The 3-domain type did not produce a functional VDCC current, whereas it had a remarkable inhibitory effect on the functional expression of the full-length form. In addition, overexpression of the 3-domain type under the control of the muscle-specific actin promoter in ascidian muscle blastomeres led to a significant decrease in endogenous VDCC currents. These findings raise the possibility that the 3-domain type has some regulatory role in tuning current amplitudes of VDCCs during early development.

Amino Acid Sequence↗

PubMed2001

The extra domain A of fibronectin activates Toll-like receptor 4.

Cellular fibronectin, which contains an alternatively spliced exon encoding type III repeat extra domain A (EDA), is produced in response to tissue injury. Fragments of fibronectin have been implicated in physiological and pathological processes, especially tissue remodeling associated with inflammation. Because EDA-containing fibronectin fragments produce cellular responses similar to those provoked by bacterial lipopolysaccharide (LPS), we examined the ability of recombinant EDA to activate Toll-like receptor 4 (TLR4), the signaling receptor stimulated by LPS. We found that recombinant EDA, but not other recombinant fibronectin domains, activates human TLR4 expressed in a cell type (HEK 293 cells) that normally lacks this Toll-like receptor. EDA stimulation of TLR4 was dependent upon co-expression of MD-2, a TLR4 accessory protein. Unlike LPS, the activity of EDA was heat-sensitive and persisted in the presence of the LPS-binding antibiotic polymyxin B and a potent LPS antagonist, E5564, which completely suppressed LPS activation of TLR4. These observations provided a mechanism by which EDA-containing fibronectin fragments promote expression of genes involved in the inflammatory response.

Animals↗