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Biomedical subjects

H Hayashi

Publications and source records attributed to H Hayashi.

At least 685 records · Page 38Linked to original sources
PubMed1996

Electrical heterogeneity and conduction block in reoxygenated guinea pig papillary muscles.

To investigate the changes in electrical activity after reoxygenation, guinea pig papillary muscles were reoxygenated with 5 mM glucose solution after various durations (30-120 min) of substrate-free hypoxia. Action potential duration recovered to the control level on reoxygenation following 30-120 min hypoxia. The recovery of developed tension or resting tension was incomplete after reoxygenation following longer periods of hypoxia. There was a high incidence of arrhythmias on reoxygenation after 60 min hypoxia, which have been shown to be triggered activities due to delayed afterdepolarizations. In some muscles reoxygenated after prolonged hypoxia (90-120 min), there was electrical heterogeneity which was shown by variable action potential durations and configurations. There was also conduction block around the microelectrode site in muscle. It was suggested that the electrical heterogeneity and conduction block could predispose to reentry, and that triggered activities and reentry could be involved in the genesis of arrhythmias on reperfusion.

Action Potentials↗
PubMed1996

Increases in gastric acidity in response to electroacupuncture stimulation of the hindlimb of anesthetized rats.

Acupuncture treatment has been used as physiotherapy to treat gastrointestinal disorders in traditional Oriental medicine. In the present study, we selected anesthetized animals as the subjects of this experiment in order to eliminate emotional factors, and investigated the responses to acupuncture stimulation at only a single point by changing animal conditions. 1) There was marked enhancement of gastric acid secretion by electroacupuncture stimulation of the hindlimb based on pH values of the perfusate. However, the enduring response after the momentary initial decrease suggested the existence of humoral factors. 2) The electroacupuncture-specific response was not observed in rats after sciatic nerve denervation. However, the pH values of the perfusate decreased in response to electroacupuncture stimulation of the hindlimb on the sciatic nerve intact side of the same rat. This suggests that the input pathway of acupuncture stimulation was a somatic nerve efferent pathway from the hindlimb. 3) No response to electroacupuncture stimulation was observed in the rats after vagotomy, but a clear enhancement response was seen after sympathectomy. These findings show that the major efferent path of the responses to acupuncture stimulation is the vagus nerve. The results of this experiment suggest that electroacupuncture stimulation of the hindlimb of anesthetized rats increases gastric acid secretion with somatic nerves as the afferent pathway and branches of the vagus nerve to the stomach as the efferent pathway.

Animals↗
PubMed1996

Expression of CD45-restricted form B in (NZW x BXSB) F1 and MRL/Mp-lpr/lpr mice.

Expression of CD45RB on CD4+ or CD8+ cells in combination with TCRV beta usages (V beta 6, V beta 8.1, V beta 8.2, V beta 11 and V beta 17a) in normal mouse strains (BALD/c and C57BL/6) was compared with autoimmune-prone strains (NZW x BXSB) F1 and MRL/lpr) at young and old ages. The frequencies, and also the numbers of CD45RB- cells in CD4+ T cells with various TcR repertoires was significantly less in the autoimmune-prone stains at old ages, while, in normal control strains, they remained unchanged. Furthermore, CD4+/CD45RB- cells are CD44high and CD62L (L- selectin).low These findings suggest that most T cells, especially CD4+ T cells, in old W/BF1 and old MRL/lpr mice, were activated and this may reflect the elevation of autoantibodies and the progress of autoimmune status in aged autoimmune-prone mice. This will be discussed in relation to the progress of the autoimmune diseases.

Aging↗
PubMed1996

Improved production of phenomycin by a genetically engineered Escherichia coli.

We established an improved production of an antitumor polypeptide anti biotic, phenomycin (PHM), by using a genetically engineered Escherichia coli. Phenomycin consists of 89 natural amino acids without intramolecular disulfide bridge. PHM gene was synthesized as a fusion gene in which PHM at the C-terminus and the residues 1 approximately 20 of Hirudin variant 1 (HV1) at the N-terminus connected by a factor Xa recognition sequence (Ile-Glu-Gly-Arg). E coli JM 109 transformed with a plasmid containing the synthesized gene expressed a fusion protein and the trypsinization of the fusion protein purified by ultrafiltration and ion-exchange chromatography gave efficiently recombinant PHM at a final yield of 50 mg/liter of culture. This PHM yield was six times higher than that obtained by a natural PHM producing strain of Streptoverticillium baldacci. Recombinant PHM was not distinguishable from natural PHM in all aspects observed.

Anti-Bacterial Agents↗
PubMed1996

[Changes in axial length after scleral buckling surgery].

The eye lengthens after scleral buckling surgery for retinal detachment. We investigated the changes in axial length and refraction after scleral buckling. A total of 89 eyes from 88 patients which were all scheduled to undergo scleral buckling were included in this study. The eyes were classified into four groups based on the type of buckling procedures:1 local buckling, 2 encircling, 3 encircling with vitrectomy, and 4 encircling with local buckling. We examined the axial length of these eyes using ultrasonography, preoperatively and at 1, 3, and 6 months postoperatively. The refractive changes were also examined. Depending on the type of scleral buckling procedure employed, the eyes in Groups 2, 3, and 4 clearly lengthened, but those of Group 1 did not. The amount of axial lengthening in Groups 2, 3, and 4 was significantly greater than in Group 1 at 3 and 6 months after surgery. In the spherical equivalent, a myopic shift occurred in the eyes in Groups 2, 3, and 4, and this shift was significantly greater than in Group 1 In addition, the correlation between the extent of axial lengthening and myopic shift was significant. In conclusion, the axial length increases with a myopic shift due to encircling, whereas local buckling changed the axial length only slightly.

Adolescent↗
PubMed1996

[Measurement of serum catalase activity and its clinical significance].

Catalase (CAT) is an enzyme to scavenge H2O2 and to protect peroxidation of cell wall lipid and lipoproteins. The increase in its activity has been observed in several diseases as an compensating reaction. The decrease in its activity may be related to some pathophysiologies of diseases. However, there has been few reports on the measurement of serum CAT activity. We formerly reported the method to measure CAT accurately with an automated analyzer. In the present experiment, we measured CAT in various kinds of diseases and healthy controls by this method. By an analysis of serum samples which were obtained from randomly selected 1,051 patients at Chibune Hospital for 12 months (from January to December, 1993), we obtained following results. The CAT of neuromuscular, cardiovascular and metabolic diseases were significantly high (p < 0.01). The CAT of psychiatric and otorhinopharyngologic diseases were significantly low (p < 0.01). There was significant relationship between CAT and some biochemical markers. CAT is thought as a protector against tissue injuries or circulatory insufficiencies. These results indicate that CAT increases in some kinds of diseases as a protection reaction to the injury, and that the decrease of CAT may cause some kinds of diseases.

Cardiovascular Diseases↗
PubMed1996

[Virtual CT endoscopy "Cruising Eye View": development and clinical applications].

We have developed a virtual CT endoscopy, designated as "Cruising Eye View (CEV)", which have generated from spiral volumetric CT data and reconstracted using a new three-dimensional image reconstruction technique. Using this new method, we have reconstructed the inner image of patients with aortic dissection (2 cases) and arteriosclerosis obliterance (3 cases). The view point and view direction could be set arbitrarily in the vessel, so that the site, configuration, and/or degree of the intravascular abnormalities were recognized at first glance. Virtual CT endoscopy with CEV method is a promising, non-invasive strategy for archiving the inner image of diverse aorto-arterial pathologies.

Aortic Dissection↗
PubMed1996

[Transesophageal echocardiography (Part 2): Basic concepts in Doppler techniques].

Cardiac Doppler techniques provide information on blood flow dynamics by applying Doppler frequency shift analysis to echo signals from moving red blood cells. Velocity and direction of blood flow can be determined and instantaneously displayed on a monitor screen. These techniques include pulsed-wave Doppler (PWD), continuous wave Doppler (CWD) and color Doppler imaging (CDI). In PWD, short bursts of ultrasound waves are emitted at a pulse-repetition frequency (PRF), and velocity and direction of blood flow can be measured at specific locations in the heart. This technique enables measurement with high spatial resolution. By its nature as a sampling system, however, PWD can not accurately measure Doppler shift frequency exceeding the Nyquist limit (PRF/2). In CWD, ultrasound pulses are continuously emitted and received by two separate transducers. Precise localization of a sampling volume is impossible in this technique, but CWD can determine higher flow velocity without ambiguity than that detected by PWD. CWD is useful to evaluate high-velocity blood flows such as those seen with valvular diseases or shunt lesions. CDI displays two-dimensional patterns of blood flow in colors, superimposed on the two-dimensional images of the heart structures. Thus, the velocity, direction and location of blood flows can be visualized in real-time. This technique facilitates detection of abnormal blood flows in the heart and major blood vessels, and it is also utilized to evaluate the severity of valvular regurgitation.

Blood Flow Velocity↗
PubMed1996

[Transesophageal echocardiography (Part 1): Basic concepts in two-dimensional imaging and M-mode].

Transesophageal echocardiography has features suitable for intraoperative use. It enables intraoperative evaluation of cardiac or thoracic aortic lesions before and after surgical intervention. It also provides real-time information on cardiac performance throughout the operation without interfering with surgical procedures. Anatomical relationship of the esophagus and the heart allows the use of high frequency ultrasound, which is advantageous to increase the resolution of echo images. An ultrasound beam emitted by a transducer is absorbed, reflected and scattered as it progresses in inhomogeneous living tissues. The reflected ultrasound waves reach the transducer, and their mechanical vibrations are converted to electronic signals. These signals are further processed by the ultrasound imaging system, and echo images are displayed on a video screen. Ultrasound imaging techniques include M-mode, two-dimensional imaging and Doppler techniques. M-mode is the most basic technique, which displays a scroll of the echo signals along a single ultrasound beam on a video screen. It has higher temporal resolution than other modes, and is therefore useful for precise timing of events and quantitative measurements of size or distance within the cardiac cycle. Two-dimensional mode produces a real-time cross-sectional view of cardiac structures, which can be easily interpreted. It is suited to visualization of anatomic structures.

Aorta, Thoracic↗
PubMed1996

[Body surface mapping].

The body-surface map provides an integral picture containing more information on the activation sequence of the heart than is available from a standard 12-lead electrocardiogram (ECG) or vectorcardiogram (VCG), because the body-surface map has a larger number of lead points that the ECG, and they are uniformly distributed over the entire thorax and back. It supplies instant-by-instant information about the distribution of the positive and negative potential areas over the body surface. Therefore, body-surface mapping is a very powerful diagnostic tool for assessing the activation sequence of the heart and is likely to play an important role in determining the focus of various arrhythmias and the site of bypass tract and also clarifying the physiological mechanism of arrhythmias.

Arrhythmias, Cardiac↗
PubMed1996

[Transesophageal echocardiography (Part 3): Clinical application Part 1].

Intraoperative transesophageal echocardiography (TEE) has a wide range of applications including monitoring of left ventricular (LV) function, evaluation of natural and prosthetic valves, detection of intracardiac thrombus, mass and vegetation, assessment of surgical repair of cardiac disease, visualization of intracardiac air, positioning of an intraaortic balloon and a coronary sinus catheter, evaluation of thoracic aortic lesions, and so on. Complications are very rare with TEE, but damage of the esophagus or stomach can occur. Gentle manipulation of the TEE probe is always required. Patients should be carefully examined prior to TEE to exclude potential esophageal or gastric lesions. Monitoring of global and regional LV function is the major application of intraoperative TEE. Fractional shortening, fractional area change, and ejection fraction are widely used estimates of global LV systolic function, but these measurements may not accurately estimate overall ventricular performance when regional wall motion abnormalities (RWMAs) exist. Regional wall motion is highly sensitive to myocardial ischemia, and a decrease or cessation of regional contraction is indicative of impaired myocardial perfusion. Assessment of RWMAs is thus very useful for diagnosis of ischemia. Although RWMAs are not always caused by acute ischemia, a new onset of RWMAs, as seen during surgery, almost certainly indicates myocardial ischemia. TEE also allows evaluation of LV diastolic function by analyzing the transmittal flow velocity.

Echocardiography, Transesophageal↗
PubMed1996

Acute dose-dependent disposition studies of nicotinic acid in rats.

The pharmacokinetics of nicotinic acid (NiAc) and nicotinuric acid (NiUAc), the major metabolite of NiAc, and the dose dependency of these pharmacokinetics were determined in rats. Intravenous injections of 2, 5, 15, and 45 mg/kg of NiAc and 5 and 15 mg/kg of NiUAc were administered, and plasma and urine samples were assayed for NiAc and NiUAc by HPLC. The plasma concentration-time profiles of NiAc showed a typical characteristic of capacity-limited elimination after higher doses. When the NiAc dose was elevated, the total plasma clearance of NiAc decreased dramatically, and the normalized area under the plasma concentration-curve increased markedly. There was no change in the volume of distribution at steady state. After the administration of NiUAc, however, the pharmacokinetics of NiUAc were linear, at least up to a dose of 15 mg/kg. With increasing doses of NiAc, the ratio for NiUAc to unchanged drug excreted in urine decreased markedly from 4.54 +/- 0.93 at 2 mg/kg to 0.37 +/- 0.12 at 45 mg/kg while the renal clearance of NiAc remained constant. An in vitro study of the plasma protein binding of NiAc showed no saturability, with a 40 to 50% bound fraction, when total NiAc concentrations were 1 to 130 micrograms/ml. Plasma NiAc profiles after the iv administration of NiAc were adequately described by the two-compartment model including the "pooled" Michaelis-Menten elimination process. The present results suggest that the nonlinear disposition of NiAc can be attributed in part to the saturation of glycine conjugation, and also, probably to amidation.

Animals↗