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Biomedical subjects

K Mito

Publications and source records attributed to K Mito.

At least 37 records · Page 2Linked to original sources
PubMed1992

Blood velocity distributions within intact canine arterial bifurcations.

As local variations in blood flow are implicated in atherogenesis at bifurcations, we measured in vivo blood velocities in different planes within exposed iliofemoral arterial bifurcations in 8 dogs using 20-MHz, 80-channel Doppler ultrasound velocimetry. Cardiac frequency was fixed at 2 Hz by pacing. Local geometry was characterized using 25-MHz, B-mode ultrasound images, photographs, and methacrylate casts. The bifurcations were asymmetrical and planar to within 5 degrees, the diameter ratios of the daughter vessels ranged from 1.47 to 2.00, and the angles between them ranged from 40 to 76 degrees. Measured velocities indicated that just upstream of the bifurcation mean peak Reynolds numbers ranged from 196 to 564 and Womersley (frequency) parameters ranged from 2.00 to 4.1. At the level of the bifurcation, secondary flows were insignificant in the normal plane but strong in the plane of the bifurcation. As a result, two-dimensional velocity fields, reconstructed by vector addition of velocities measured in the plane of the bifurcation, differed markedly from the one-dimensional profiles calculated assuming flow parallel to the vessel axis. In the two-dimensional velocity fields, forward flow was directed toward the flow divider and reversal occurred earliest near the outer wall. Wide spatial and temporal variations in the shear stress at the endothelium are implied by these detailed, in vivo measurements of the bifurcation velocity fields.

Animals↗
PubMed1990

A laser Doppler catheter for monitoring both phasic and mean coronary vein flow.

A new catheter-type laser Doppler velocimeter has been developed to monitor coronary vein flow. A thin graded-index multimode optical fiber (outer diameter of 125 microns) is set inside a 5-F catheter, and eight elastic silicon rubber spikes are arranged radially toward the vessel wall to fix the catheter tip in or near the axial region of the coronary vein. He-Ne laser light (wave length = 632.8nm) is introduced into the blood through the optical fiber, and reflected light is collected by the same fiber. The Doppler signal is detected by a spectrum analyzer. To avoid any effect by the spikes on flow, the fiber is extended from the catheter tip by 3 mm at the time of measurement. Straight and curved tubing was used to examine the accuracy of flow measurement. The flow velocities recorded by the catheter, which were measured by an electromagnetic flowmeter, exhibited excellent linearity (r = straight; 0.982, curved: 0.996). The blood flow velocity in the great cardiac vein was measured by this method in five dogs. The predominantly systolic waveform, which is a characteristic of the coronary vein flow, was observed in all of the dogs. The great cardiac vein velocity increased around the beginning of the ventricular ejection and decreased gradually after the peak formation at mid- or end-diastole. In addition to this main peak, small flow components were frequently observed during isovolumic contraction and the atrial contraction phase, although these flow components varied in individual dogs. Following left anterior descending artery occlusion, the great cardiac vein flow velocity decreased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Mechanical control of coronary artery inflow and vein outflow.

To analyze the origin of the coronary artery inflow and the coronary vein outflow, we measured the intramyocardial artery flow and the epicardial small vein flow by means of a laser Doppler velocimeter with an optical fiber. The functional characteristics of the intramyocardial capacitance vessels were investigated by analyzing the responses of coronary vein flow after stepwise changes in coronary artery pressure during long diastole. Then the effect of the intramyocardial capacitance vessels on coronary artery inflow and vein outflow was evaluated. Intramyocardial artery flow was found to be almost exclusively diastolic with frequent systolic reverse flow, whereas peripheral coronary vein flow was almost systolic exclusively. The intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. When the unstressed volume was saturated, the intramyocardial displacable blood volume impeded the coronary artery inflow, but promoted vein outflow.

Animals↗
PubMed1988

Piezoelectric polymer curvature sensor for measurement of regional curvature radius of LV wall.

To evaluate regional myocardial function, we developed a curvature sensor for direct and instantaneous measurement of the regional curvature radius of the LV wall. The sensor is a bimorph of two sheets of thin piezoelectric polymer film. The relation between output voltage of the sensor and the reciprocal of the known curvature radius has been shown to be linear. In anesthetized dogs, we inserted the curvature sensor into the subepimyocardium with a specially designed introducer. Special care was taken to insert it parallel to the epicardial surface. Circumferential regional curvature radius, which is defined as the reciprocal of regional curvature, showed the same phasic changes as the short-axis diameter under control conditions. Under regional ischemia caused by transient occlusion of the coronary artery, amplitude of the phasic change in regional curvature radius decreased, whereas that of the short-axis diameter did not change or slightly increased. Phasic changes in regional curvature radius cannot be estimated from short-axis diameter during regional ischemia. We calculated regional wall tension from the directly measured regional curvature radius and LV pressure and found that tension-length loop clearly differentiates between regional myocardial function under control and ischemic conditions. We have concluded that our newly developed curvature sensor is accurate, that its practical use is feasible, and that measurement of the regional curvature radius of the LV wall provides detailed and accurate information on regional shape and function of the left ventricle.

Animals↗
PubMed1988

Dual-fiber laser Doppler velocimeter and its application to the measurements of coronary blood velocity.

To obtain a smaller sample volume and a suitable sample position for the measurement of blood velocity, we fabricated a laser Doppler velocimeter (LDV) with a dual-fiber pickup. The two fibers (clad: 62.5 micron and core: 50 micron) were placed side by side. An He-Ne laser was introduced into the blood through one fiber and the backscattered light was collected by the other fiber. The Doppler signal was analyzed by a spectrum analyzer. The spectrum of the Doppler shift frequency showed a sharp peaked pattern for both forward and reverse flows and exhibited an excellent correlation with the known blood velocity. The blood velocity in the poststenotic portion of canine coronary artery was successfully measured by the dual-fiber LDV. These results indicate that the dual-fiber LDV is useful for measuring blood velocity accurately with a small sample volume even in disturbed flow fields.

Animals↗
PubMed1987

Effect of breast feeding on responses of systemic interferon and virus-specific lymphocyte transformation in infants with respiratory syncytial virus infection.

In order to elucidate the mechanisms of breast-feeding-induced resistance to respiratory syncytial virus (RSV) infection, groups of breast-fed and bottle-fed infants with this infection were tested at the onset of illness and then again 1 and 2 weeks later for the presence of interferon (IFN) as well as of virus-specific lymphocyte transformation (LTF) activity. Alpha-IFN was detected in nine out of ten breast-fed infants, while it was found in only 11 out of 21 bottle-fed subjects. The rate of the detection of IFN was significantly higher in the former group (P less than .05). Mean levels of IFN activity were also higher in breast-fed infants than in bottle-fed subjects during the course of the illness. It was noted, however, that previous breast feeding elicited little enhancing effect on the IFN response of infants with RSV infection. Combining the two feeding groups, suppressed LTF activity to RSV seemed to be related to a positive IFN response, although the association was not statistically significant. These observations suggest that breast feeding has unique mechanisms for modulating the immune response of infants with RSV infection.

Breast Feeding↗
PubMed1987

An optical-fiber laser Doppler velocimeter and its application to measurements of coronary blood flow velocities.

In this paper we describe a laser Doppler velocimeter (LDV) with an optical fiber that measures blood flow velocities accurately in a small sample volume. The principle, optical arrangement, spatial and the temporal resolutions and accuracy for blood flow measurements are delineated, followed by a report of the results of measurements of coronary artery and vein blood flow velocities in dogs. Finally, we touch upon some recent progress made in the LDV with an optical fiber pickup.

Blood Pressure↗
PubMed1986

Functional characteristics of intramyocardial capacitance vessels during diastole in the dog.

In order to evaluate the functional characteristics of the intramyocardial capacitance vessels during prolonged diastole, we analyzed the response of coronary vein flow after stepwise changes of coronary artery pressure in anesthetized open-chest dogs by using our newly developed laser Doppler velocimeter with an optical fiber. The peripheral portion of the great cardiac vein was isolated and the optical fiber tip was inserted into the vessel. The left anterior descending coronary artery was cannulated and connected to a reservoir to regulate coronary perfusion pressure. Intracoronary adenosine administration was carried out to avoid any change in coronary vasomotor tone. After 15 seconds of occlusion of the perfusion route, the heart was arrested by pacing-off. Two seconds later, coronary perfusion pressure was increased stepwise to a preset target pressure. This procedure was repeated by changing target pressure at 4 (or 5) different pressure levels (31-105 mm Hg). The great cardiac vein flow became zero due to the cardiac arrest and remained at zero for a moment (dead time) after the initiation of reperfusion. Then the flow reappeared and increased with first order time delay. The presence of dead time indicates the existence of unstressed volume, and the first order time delay represents the product of resistance and capacitance. The unstressed volume with a minimal vasomotor tone for perfusion pressure of 60-90 mm Hg was 5.2 +/- 2.2 ml per 100 g left ventricle, which is comparable to coronary blood flow for several beats. The capacitance at perfusion pressure of 60-90 mm Hg was 0.08 +/- 0.04 ml/mm Hg per 100 g left ventricle, while that at low perfusion pressure (30-50 mm Hg) was 0.14 +/- 0.09 ml/mm Hg per 100 g left ventricle. These results indicate that the intramyocardial capacitance vessels have two functional components, and that the phasic nature of coronary vein flow is solely the result of the myocardial squeezing of the blood in the capacitance vessels.

Animals↗
PubMed1986

Evaluation of human coronary blood flow with an 80 channel 20 MHz pulsed Doppler velocimeter and zero-cross and Fourier transform methods during cardiac surgery.

To evaluate local blood flow velocities accurately at many sampling points in small vessels, especially in human coronary arteries, we have developed an 80 channel 20 MHz pulsed Doppler velocimeter. Doppler signals from 80 channels are detected by a zero-cross method and a signal from an optional channel is analyzed by a fast-Fourier transform method, both in real time. Basic experiments using a model and animals have demonstrated the accuracy and utility of our method of measurement of blood flow velocity for both nondisturbed and disturbed flow. Velocity waveforms in a native coronary artery beyond a vein bypass graft insertion were measured during cardiac surgery. They showed a diastolic-predominant pattern with a small systolic component. During transient graft occlusion, the waveforms changed to a systolic-predominant pattern in a patient with severe stenosis and to a to-and-fro pattern in a patient with total occlusion. In a patient with severe aortic regurgitation, the coronary arterial velocity waveforms exhibited a systolic-predominant pattern with a broad velocity spectrum. After aortic valve replacement, however, a diastolic-predominant pattern with a narrow spectrum was observed.

Blood Flow Velocity↗
PubMed1985

Evaluation of phasic blood flow velocity in the great cardiac vein by a laser Doppler method.

In the present study, characteristics of the phasic flow pattern in the great cardiac vein and the mechanism of such pattern formation were investigated using a laser Doppler velocimeter with an optic fiber probe. The laser Doppler velocimeter allowed measurements of venous blood velocity under more physiological conditions than were possible with previous methods. Moreover, venous blood flow measurement in the great cardiac vein mirrors the effects of myocardial contraction on the venous flow more directly than does measurement in the coronary sinus. Thus, our method is considered very useful. Results obtained from the present study are as follows: 1) Measurement of the phasic flow in the great cardiac vein was made in 11 anesthetized dogs using our laser Doppler method. The blood velocity curve obtained in the great cardiac vein was always characterized by a prominent systolic flow wave (SFW). The mean value for the maximum velocities under control conditions in 11 cases was 40 +/- 13 cm/s. The blood velocity increased with the onset of left ventricular ejection and decreased gradually after the peak formation at mid- or late systole.--2) Besides the above SFW, one or two small wave components were frequently observed during the atrial contraction period and/or during the isovolumic contraction phase. On the waveform during the atrial contraction period, two cases showed forward flow, while one case showed reverse flow. The small reverse flow waves during the isovolumic contraction phase were found in seven cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Cellular immune response to infection with respiratory syncytial virus and influence of breast-feeding on the response.

Virus-specific lymphocyte transformation (LTF) activity in vitro was examined in 78 infants with various forms of illness due to respiratory syncytial virus (RSV) infection. In 73 subjects with lower respiratory tract disease, significant LTF activity was often detected within one week after onset of initial symptoms, and responses characteristic for each clinical form were observed in the subsequent rise. Thus, mean activity in subjects with tracheobronchitis increased gradually, with the maximum response being detected at the fourth week after the onset of illness. In subjects with pneumonia the response was rather low during the first week of illness, and then a sharp increase of activity was observed at the second week. Although patients with bronchiolitis elicited similar levels of the activity until the first week, the response was significantly suppressed during the subsequent two weeks. The response at the second week in this group was significantly lower than those of corresponding specimens obtained from patients with pneumonia (p less than 0.01) or tracheobronchitis (p less than 0.05), suggesting a close association of the responsiveness with underlying mechanisms of bronchiolitis induced by RSV. The present study further indicated a possibility that breast-feeding of RSV-infected infants may alter levels of the LTF activity in these subjects.

Adult↗
PubMed1983

Review of criteria for diagnosis of diabetes mellitus based on results of follow-up study.

Comparison of the 75-g oral glucose tolerance test (OGTT) method was made with the conventional 50-g method in a fixed population followed for 1--17 yr. The possibility of using the results in establishing the diagnosis of diabetes mellitus was also considered. The following results were obtained: (1) The 75-g method showed significantly higher 2-h and 3-h postchallenge plasma glucose (PG) and immunoreactive insulin values. (2) The two methods showed good correlation in PG values at various time periods, and there was no difference between the two at 1/2 h and 1 h. The 2-h standard value of 200 mg/dl used to diagnose diabetes with the 75-g method was equivalent to 180 mg/dl by the 50-g method. The upper limits of normals were 140 mg/dl and 120 mg/dl, respectively, for the two tests. (3) Those subjects diagnosed as diabetic on the basis of fasting plasma glucose (FPG) values of 140--149 mg/dl only had a high rate of reverting to normal over time. The frequency of "nondiabetic" plasma glucose values after glucose loading steadily decreases as FPG increased, with separation into two asymptotic lines at 150 mg/dl level. Thus, the logical value for diagnosis of diabetes when based only on FPG value is considered to be 150 mg/dl. (4) A smaller number of individuals had 2-h PG values that satisfied criteria for diagnosis of diabetes mellitus, but 1/2-h and 1-h values that were less than 200 mg/dl. Nevertheless, follow-up of these subjects showed a high development rate of diabetes. Thus, the 1/2-h and 1-h values are not considered necessary to establish diagnosis of diabetes mellitus.

Adult↗