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Biomedical subjects

T Yamane

Publications and source records attributed to T Yamane.

At least 109 records · Page 6Linked to original sources
PubMed2000

Computational fluid dynamics analysis of a centrifugal blood pump with washout holes.

The authors studied avoidance of coagulation occurrence using computational fluid dynamics (CFD) analysis from the fluid dynamical point of view. Concerning centrifugal pumps, blood coagulation sometimes occurs at the region behind the impeller where the flow is generally stagnant. Therefore, we conducted a thorough study with the specimen pump with and without washout holes, mocking up the Nikkiso HPM-15. As the result, the model with washout holes indicated that the fluid rotates rapidly at the vicinity of the shaft and generates washout effects near the stationary rear casing. On the other hand, the model without washout holes showed that fluid cannot be quickly shipped out of the area behind the impeller and rotates mildly around the shaft. To clarify the moving relations between the impeller and the fluid, validation studies by comparing the results of CFD analysis and flow visualization experiments are ongoing; thus far, the studies show that CFD results are similar to the results from flow visualization experiments.

Centrifugation↗
PubMed2000

A jump in cycle length of orthodromic common atrial flutter during catheter ablation at the isthmus between the inferior vena cava and tricuspid annulus; evidence of dual isthmus conduction directed to dual septal exits.

INTRODUCTION: In orthodromic common atrial flutter (AFL), details of intraseptal propagation of the flutter (FL) wave exiting from the isthmus between the inferior vena cava and tricuspid annulus (IVC-TA isthmus) remain unknown. We hypothesized the existence of dual septal exits of the FL wave from the IVC-TA isthmus to both the anterior, coronary sinus ostium (CSO-TA) isthmus, and the posterior septal (IVC-CSO) isthmus, and that the IVC-TA isthmus might consist of dual muscle bundles directed to both septal isthmuses over the eustachian ridge; therefore, segmental ablation of the IVC-TA isthmus could change intraseptal FL wave propagation. METHODS AND RESULTS: To test the hypothesis, we investigated the influence of segmental ablation of the IVC-TA isthmus on intraseptal FL wave propagation. In seven of 40 (18%) consecutive patients, segmental ablation of the ventricular side of the IVC-TA isthmus during orthodromic common AFL led to sudden prolongation of the flutter cycle length (FCL) (from 266 +/- 33 ms to 291 +/- 45 ms) associated with changes in intraseptal activation sequences. They consisted of prolongation of the interval between the IVC-TA isthmus and the CSO (from 38 +/- 13 ms to 86 +/- 25 ms), shortening of the interval between the CSO and His (from 31 +/- 15 ms to 9 +/- 15 ms), and atrial electrogram polarity change at the His-bundle recording site. Morphological change in the FL wave was also seen on the 12-lead ECG. CONCLUSIONS: In some patients, segmental ablation of the IVC-TA isthmus can lead to a jump in FCL and changes in intraseptal activation sequences of FL waves due to anterior-to-posterior shifting of the septal exit. This indicates that the IVC-TA isthmus may contain dual circumferential muscle bundles as conduction pathways directed to dual septal exits both anterior and posterior to the CSO.

Atrial Flutter↗
PubMed2000

EmPLiCS: an empirical approach for structure-based design of natural peptide drugs.

The computer implementation of a peptide drug-design strategy has been developed. The system is named EmPLiCS (Empirical Peptide Ligand Construction System) according to the strategy of the system, which searches for peptide-ligand structures by referring to empirical rules that are derived from known protein 3D structures. The system was tested on several known peptide-protein complexes. The results demonstrated the ability of this system to detect key residues of peptides that are crucial for interaction with their specific proteins. The system also showed the ability to detect the main chain trace of these peptides. Some of the main chain atoms were detected even though the complete primary structures were not reproduced, suggesting that main chain structure is important in peptide-protein recognition. The results of the present study demonstrated that the empirical rules-based system can generate significant information for use in the design of natural peptide drugs.

Algorithms↗
PubMed2000

Retroperitoneal laparoscopic lateral approach to the lumbar spine: a new approach, technique, and clinical trial.

A retroperitoneal laparoscopic (retroperitoneoscopic) lateral approach to achieve decompression for a far lateral disk lesion in the lumbar spine or to remove a paravertebral neurinoma without disrupting the facet is described. The operating space is maintained using a powered mechanical lift and a flat inflatable retractor mainly to make a longitudinal separation between the psoas major and the quadratus lumborum. This technique has been performed successfully in 22 cases using retroperitoneoscopy. The best indications of this new procedure are lateral disk herniation at the L5-S1 level or around the conus medullaris at the L1-L2 level. The described procedure provides adequate exposure necessary for extraforaminal exploration, discectomy, and nerve root decompression, and it is sufficient for treating extreme lateral lumbar herniation localized to the L1-S1 level and spinal nerve root tumors.

Adult↗
PubMed2000

Delayed stochastic systems

Noise and time delay are two elements that are associated with many natural systems, and often they are sources of complex behaviors. Understanding of this complexity is yet to be explored, particularly when both elements are present. As a step to gain insight into such complexity for a system with both noise and delay, we investigate such delayed stochastic systems both in dynamical and probabilistic perspectives. A Langevin equation with delay and a random-walk model whose transition probability depends on a fixed time-interval past (delayed random walk model) are the subjects of in depth focus. As well as considering relations between these two types of models, we derive an approximate Fokker-Planck equation for delayed stochastic systems and compare its solution with numerical results.

Journal Article↗
PubMed2000

Crystallization and preliminary X-ray analysis of high-alkaline pectate lyase.

Pel-15, a high-alkaline pectate lyase (pectate transeliminase; E.C. 4.2.2.2) from Bacillus sp. strain KSM-P15, has been crystallized using the hanging-drop vapour-diffusion method at 277 K. Two different crystal forms were obtained and preliminary X-ray diffraction data were collected from each crystal form at 100 K. Both forms belong to the orthorhombic space group P2(1)2(1)2(1) and contain one molecule per asymmetric unit. The unit-cell parameters of form I are a = 43.2 (2), b = 60.2 (2), c = 82.2 (2) A and those of form II are a = 42.9 (1), b = 43.4 (1), c = 105.9 (3) A. Diffraction data to a resolution of 1.5 A were collected from form II crystals using a synchrotron-radiation source.

Bacillus↗
PubMed2000

Crystallization and preliminary X-ray diffraction analysis of a eumenine mastoparan toxin: a new class of mast-cell degranulating peptide in the wasp venom.

Mastoparans are tetradecapeptides found to be the major component of vespid venoms. A mastoparan toxin isolated from the venom of Anterhynchium flavomarginatum micado has been crystallized and X-ray diffraction data collected to 2.7 A resolution using a synchrotron-radiation source. Crystals were determined to belong to the space group P6(2)22 (P6(4)22). This is the first mastoparan to be crystallized and will provide further insights into the conformational significance of mastoparan toxins with respect to their potency and activity in G-protein regulation.

Cell Degranulation↗
PubMed2000

Mid-term follow-up of endocardial biventricular pacing.

Biventricular (BV) pacing is a promising treatment of end-stage heart failure. This article describes our experience with a strictly endocardial BV pacing system in patients with severe congestive heart failure. Three women and eight men (age 65 +/- 9 years) with drug-resistant end-stage CHF underwent implantation of an endocardial BV pacing system. In the first seven patients, the left ventricular lead was placed via a combined femoral and internal jugular approach. In the last four patients, the transseptal puncture was directly performed via the right internal jugular vein with a dedicated kit. The procedure was successful in all 11 patients. The acute left ventricular and BV thresholds were 1.3 +/- 0.6 V and 2.4 +/- 1 V, respectively. The QRS duration decreased from 214 +/- 57 to 176 +/- 25 ms. A functional improvement was noted in ten patients with a decrease in mean NYHA functional class from 3.7 +/- 0.5 before, to 2.6 +/- 0.9 after system implantation. A significant decrease in pulmonary capillary wedge pressure and increase in cardiac output were measured in eight patients. During follow-up, four patients died from CHF (n = 3) or ventricular fibrillation (n = 1). Under oral anticoagulation, no thromboembolic event was observed but one transient ischemic attack occurred in one patient whose anticoagulation was interrupted. Endocardial BV pacing is technically feasible and appears safe, though further studies are needed before it is used on a longer scale.

Aged↗
PubMed2000

Multiple sources initiating atrial fibrillation from a single pulmonary vein identified by a circumferential catheter.

The pulmonary veins are the predominant source of ectopic activity initiating AF. The reproducibility of intrapulmonary vein activation during ectopic activity and/or initiation of multiple AF episodes was examined. Eighty-nine pulmonary veins (PVs) among 29 patients undergoing radiofrequency ablation of AF were studied with a 15- to 20-mm diameter, circumferential PV catheter equipped with ten electrodes and a deflectable shaft. Local electrograms were recorded simultaneously during sinus rhythm, ectopic activity, or AF onset, spontaneously or induced via the catheter left in a stable position. Fifty-four arrhythmogenic veins were identified, 39 showing isolated ectopy, and 8 displayed repetitive ectopy (in salvos). The earliest site of activation and the sequence of intra-PV activation during isolated ectopy was identical to that observed during consecutive ectopic complexes in 77% and variable in 23% during isolated ectopy. The earliest activity was sometimes limited to a single bipole. During repetitive ectopy and AF initiation, multiple sources and/or variable activation patterns were noted in 53% of instances, indicating the presence of multiple arrhythmogenic foci within the same PV. Simultaneous electrogram recordings with a circumferential PV catheter identified the presence of multiple arrhythmogenic foci within a single PV.

Atrial Fibrillation↗
PubMed2000

Concealed left pulmonary vein potentials unmasked by left atrial stimulation.

Pulmonary vein potentials (PVPs), though obvious during ectopic activity, are frequently invisible during sinus rhythm when they need to be distinguished from left atrial (LA) potentials to perform successful ablation procedures. Thirty-six patients with paroxysmal atrial fibrillation underwent circumferential PV mapping with a circular ten-electrode catheter during sinus rhythm, and during pacing from the right atrium, proximal and distal coronary sinus (CS), and LA. Ablation was performed at the ostium of the PV, the procedural endpoint consisting of electrical disconnection of the PV from the LA. A total of 93 PVs (excluding the right inferior PV) were mapped. During sinus rhythm, distinct right PVPs were present in all instances, while they were concealed within the electrograms recorded from the left inferior and superior PV in 23 (64%) patients. Distal CS or LA appendage pacing unmasked and separated left PV from LA potentials by a mean of 19 +/- 14 ms; the LA-to-left-PV potential interval measured 36 +/- 14 ms. The number of deflections also increased from 2.1 +/- 0.7 during sinus rhythm to 3 +/- 1.4 during LA stimulation. However, in the right superior PV, pacing caused overlapping of atrial potentials with right superior PVPs. RF ablation of the left PVPs was performed during distal or LA pacing in 23 patients, while in the right superior PV it was performed during sinus rhythm eliminating all, including unmasked, left PVPs, providing proof of their PV origin. Distal CS or LA pacing is required to recognize left PVPs in approximately 2/3 of patients and facilitates RF ablation.

Atrial Fibrillation↗
PubMed2000

Left ventricular diastolic dysfunction in patients with so-called lone atrial fibrillation.

Lone atrial fibrillation (AF) is defined by the absence of identifiable causes of AF, but its hemodynamics have not been investigated. Twenty-eight patients with lone AF were compared with 14 control patients referred for Wolff-Parkinson-White ablation. Transthoracic and transesophageal echocardiography were performed to rule out structural heart disease, followed by transseptally performed complete hemodynamic evaluation of the left heart systolic and diastolic function. There was no evidence of diastolic dysfunction according to echocardiographic criteria in AF and control patients. There was no difference in echocardiographic measurements, except for a significantly higher inferosuperior left atrial dimension seen in the four-chamber apical view in AF patients (51+/-10 vs 40+/-6 mm, P = 0.03). Hemodynamic evaluation showed that end-diastolic left ventricular pressure and the nadir of the left atrial Y descent were significantly higher in lone AF patients versus controls: 13+/-5 versus 8+/-3 mmHg (P = 0.001) and 6.7+/-3 versus 4.6+/-2.7 mmHg (P = 0.05). Our results demonstrated the presence of diastolic left heart dysfunction in patients with so-called lone AF.

Adult↗
PubMed2000

In vitro analysis of roles of a disulfide bridge and a calcium binding site in activation of Pseudomonas sp. strain KWI-56 lipase.

The expression of lipase from Pseudomonas sp. strain KWI-56 (recently reclassified as Burkholderia cepacia) had been found to be dependent on an activator gene (act) downstream of its structural gene (lip). In this work, the mature lipase was synthesized in an enzymatically active form with a cell-free Escherichia coli S30 coupled transcription-translation system by expressing a recombinant lipase gene (rlip) encoding the mature lipase in the presence of its purified activator or by coexpression of rlip and act. The in vitro expression systems were used for studying the folding process of the lipase. The addition of dithiothreitol in the expression systems decreased the activity dramatically without affecting the synthesis level of the lipase, whereas the in vitro-synthesized active lipase was relatively stable even in the presence of dithiothreitol. This phenomenon was further investigated by constructing mutant lipase genes only in vitro by PCR without gene cloning. Replacements of cysteine residues (Cys190 and Cys270) forming a sole putative disulfide bond to serine residues decreased the lipase activity greatly, suggesting that the disulfide bond was essential for the proper folding of the lipase. In addition, replacing Asp242 and Asp288, which were deduced to be part of a Ca(2+) binding site, also greatly decreased the activities of the in vitro-synthesized lipases. The role of the Ca(2+) binding site in the activation of the lipase is also discussed.

Base Sequence↗