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Biomedical subjects

J Higuchi

Publications and source records attributed to J Higuchi.

32 records · Page 2Linked to original sources
PubMed1988

Inter-organ relation between salivary gland and kidney in lithium excretion. I. Effects of continuous stimulation of salivation on salivary, renal and systemic clearances of lithium in dog.

The effects of continuous stimulation of salivation on salivary, renal and systemic clearances of lithium were investigated following bolus intravenous administration of lithium chloride (0.145 meq/kg) in three beagle dogs. The salivation was frequently stimulated with citric acid solution, then parotid saliva and mandibular-sublingual saliva were collected separately by means of permanent fistulae. Although the continuous stimulation of salivation markedly increased the salivary clearance of lithium, no significant change was observed in plasma concentrations or systemic clearance of lithium. This was because the decrement in the renal clearance of lithium canceled out the effect of increased salivary clearance. It is suggested that the reabsorption of lithium in the renal tubule was enhanced under the continuous stimulation of salivation, and this seemed to be caused by loss of water or sodium through the salivary glands.

Animals↗
PubMed1983

Dynamics of cardiac output and systolic time intervals in supine and upright exercise.

Transient and steady-state responses of stroke volume (SV), heart rate (HR), cardiac output (Q), left ventricular ejection time (LVET), preejection period (PEP), and the ratio of LVET to PEP during bicycle exercises of 50 and 100 W were studied in four healthy male subjects in supine and upright postures. A computer-based system in which impedance cardiography was incorporated served to determine the above parameters on a 10-s interval basis. SV remained almost unchanged in response to exercises in a supine posture, whereas it increased significantly in an upright posture, although the individual differences among subjects were found to be large. The half-response times of variables to a step work load were determined. An approximate accordance was observed among the response times for HR, Q, and LVET/PEP. There was an inverse relationship between LVET and HR, the slope of which was found to be steeper in the supine posture than in the upright posture, reflecting the difference between the SV responses in both postures. LVET fell shortly after the cessation of exercise despite the decreasing HR. Inasmuch as the paradoxical reduction of LVET was also found in the case where SV remained unchanged in response to exercise, no changes in SV can be the cause thereof. Thus, a transient increase in ejection rate, which is due to either the increased myocardial contractility or decreased peripheral vascular resistance, may be responsible for the phenomenon.

Adult↗
PubMed1982

Dynamics of cardiac, respiratory, and metabolic function in men in response to step work load.

Stroke volume, heart rate, cardiac output, tidal volume, respiratory frequency, minute ventilation, end-tidal tensions of O2 and CO2, O2 uptake, CO2 output, and respiratory exchange ratio were measured simultaneously in healthy male volunteers before, during, and after upright bicycle exercise from 0 to 360 and 720 kpm/min. The circulatory variables were determined continuously once per 20 cardiac cycles and the respiratory variables breath by breath using separate computer-based systems in which an impedance pneumograph and an impedance cardiograph were incorporated. Stroke volume, heart rate, and cardiac output started to increase without measurable delay at the onset of exercise. Stroke volume increased by 20% from resting control value in response to the mildest exercise and essentially leveled off with a further increase in work load. Time constant for cardiac output increased with the increasing work load. Time constant for minute ventilation was much longer than that for cardiac output and independent of work intensity. A good synchronization between the ventilation and cardiac output responses at an initial period of transitions from rest to exercise and from exercise to rest seems to support the concept of cardiodynamic hyperpnea.

Adult↗
PubMed1982

The dynamic response of the cardiopulmonary parameters to passive head-up tilt.

Transitional changes in stroke volume, heart rate, and cardiac output resulting from head-up tilt were measured in healthy male subjects, using impedance cardiography. Respiratory frequency, tidal volume, ventilation rate, end-tidal O2 and Co2 tensions, O2 uptake, CO2 output, and exchange ratio were also determined breath-by-breath. When the subject was tilted upward from a supine to an upright position, the stroke volume was decreased while the heart rate was increased. The time required to attain the steady state was shorter in the stroke volume change than in the heart rate. In addition, since the heart rate was not increased so high as to be inversely related to the stroke volume, the cardiac output decreased by tilting upward. The ventilation rate remained almost unchanged within a tilt angle of 60 degrees or so. Thus, both the O2 and CO2 fractions in expired air showed transitory changes. As the original body position was restored, the cardiac output was increased to the initial level, the tidal volume showing a transient increase. During the recovery process, PCO2, in expired air increased and PO2 decreased, showing that the change in cardiac output exceeded that in ventilation in quantity. The change in ventilation moreover, preceded that of expired PCO2 by ca. 10 sec, suggesting that the enhancement of ventilation occurred through some agent(s) other than the chemical drive.

Adult↗