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Biomedical subjects

O Tochikubo

Publications and source records attributed to O Tochikubo.

At least 91 records · Page 5Linked to original sources
PubMed1990

Fully automatic, noninvasive measurement of cardiac output by means of the CO2 rebreathing method and its clinical application to hypertensive patients.

A new device (called a hemodynamometer) employing the principle of the CO2 rebreathing method has been developed for the noninvasive automatic measurement of pulmonary blood flow (cardiac output = CO). The device can also measure oxygen consumption (VO2) and indirect blood pressure and record electrocardiographs (heart rate) at the same time and can automatically calculate total peripheral vascular resistance (TPR) by means of a computer. In this study, the hemodynamometer was used in 28 normotensive subjects and 42 patients with essential hypertension (27 with WHO stage I and 15 with WHO stage II) to evaluate hemodynamics during rest or ergometer exercise. To evaluate accuracy, the dye-dilution (cuvette) method was simultaneously employed in some subjects. The correlation coefficient (r) between CO measured by means of the hemodynamometer and CO measured by the cuvette method was 0.96 (n = 39) with a differential of 0.08 +/- 0.53 l/min and reproducibility was good (r = 0.88, n = 70). The average CO index for normotensive subjects at rest was 3.22 +/- 0.37 l/min/m2 (VO2 = 210 +/- 30 ml/min/m2) and agreed with previously reported values. A significant difference was observed between the hemodynamics (CO and TPR indices) of the WHO-I group and those of the WHO-II group during rest or mild exercise (25-watt load). Because it can measure CO and TPR easily and noninvasively, the hemodynamometer is considered useful for evaluating hemodynamic changes in hypertensive patients.

Adult↗
PubMed1990

[Adrenal tumors associated with renal cell carcinoma].

We experienced two cases with renal cell carcinoma who showed enlargement of the contralateral adrenal gland. In case 1, the enlarged adrenal gland was a non-functioning adrenal adenoma, and in case 2, it was a metastatic adrenal tumor. Non-functioning adrenal adenomas are benign tumors of the adrenal cortex often found incidentally at autopsy or on computed tomography (CT) studies of the upper abdomen. Adrenal adenomas have been reported to occur in 9.5-14% of patients with renal cell carcinoma, while the incidence being 1.5-8.7% in the general population. Since metastases of renal cell carcinoma to the adrenal glands are not uncommon, it is important to distinguish between non-functioning adrenal adenomas and metastatic tumors. Therefore, we studied the incidence of adrenal tumors (including metastatic tumors and benign tumors) in patients with renal cell carcinoma who underwent the abdominal CT study in our hospital. From 1982 to 1989, CT had been performed in 67 patients with renal cell carcinoma. Six adrenal masses were identified with CT in these patients. Three out of the 6 patients probably had metastatic tumors and one of the 3 adrenal masses was pathologically diagnosed as metastatic tumor. The other three masses were benign on pathology and only one of them was pathologically diagnosed as non-functioning adrenal adenoma. The incidence of adrenal adenomas on the CT study was lower than that of previous studies based on autopsy. The reasons of this difference in results between their studies and ours are not clear.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1989

Age-related changes in muscle sympathetic nerve activity in essential hypertension.

To investigate the pathophysiological role of the sympathetic nervous system in essential hypertension, this study recorded the muscle sympathetic nerve activity (MSNA) of the tibial nerve and examined the age-related changes in patients with essential hypertension and in normotensive persons. There were 43 normotensive subjects (16-69 years old) and 63 patients with essential hypertension (18-67 years old) in the study. The MSNA at rest, recorded by microneurography, was evaluated by burst rate (bursts/min), burst incidence (bursts/100 heart beats), and spike frequency (spikes/min). The MSNA recording showed a high reproducibility with a correlation coefficient of 0.86 (p less than 0.01) in repeated studies. The MSNA was significantly greater in the hypertensive patients than in the normotensive subjects, irrespective of activity units (p less than 0.01), and this finding was consistent in the young (30 years old or less), middle-aged (31-50 years old), and old groups (51 years old or more). Furthermore, MSNA showed a significant positive correlation with age both in the normotensive subjects (r = 0.43, p less than 0.01 for burst rate; r = 0.49, p less than 0.01 for burst incidence; and r = 0.50, p less than 0.01 for spike frequency) and in the hypertensive patients (r = 0.40, p less than 0.01 for burst rate; r = 0.44, p less than 0.01 for burst incidence; and r = 0.40, p less than 0.01 for spike frequency).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Angiotensin II inhibits baroreflex control of muscle sympathetic nerve activity and the heart rate in patients with essential hypertension.

This study examined the effects of angiotensin II (Ang II) on blood pressure, heart rate and muscle sympathetic nerve activity in patients with essential hypertension and normotensive subjects. Muscle sympathetic nerve activity was measured by a microneurographic method. Graded doses of phenylephrine (0.5 and 1.0 g/kg per min) or Ang II (5, 10 and 20 ng/kg per min) were intravenously infused into supine subjects for 10 min at 30-min intervals. Although the pressor responses to Ang II and phenylephrine were enhanced in the hypertensives compared with the normotensives (both P less than 0.05), the reduction in muscle sympathetic nerve activity during infusion of phenylephrine and Ang II and the reduction in the heart rate during infusion of phenylephrine were significantly smaller in the hypertensives than in the normotensives. The decrease in the heart rate in response to Ang II was not significant in either group. Furthermore, in the two groups, the decreases in muscle sympathetic nerve activity and the heart rate were significantly smaller during infusion of Ang II than during infusion of phenylephrine. These results suggest that angiotensin II impairs the baroreflex function in patients with essential hypertension and in normotensive subjects, and that the blunted response of sympathetic nerve activity and the heart rate observed in the hypertensives may underlie the maintenance of high blood pressure.

Angiotensin II↗
PubMed1988

Impaired baroreflex changes in muscle sympathetic nerve activity in adolescents who have a family history of essential hypertension.

To evaluate the baroreflex changes and basal sympathetic vasomotor tone among three groups of adolescent normotensives or borderline hypertensives with and normotensives without a family history of hypertension, we continuously recorded muscle sympathetic nerve activity, arterial pressure and heart interval. Baroreflex slopes were calculated either by plotting the heart interval against the preceding peak systolic arterial pressure, or by relating the percentage changes in muscle sympathetic nerve activity to the mean changes in systolic arterial pressure produced by intravenous phenylephrine. The baroreflex slopes for the heart interval were significantly smaller in borderline hypertensive offspring (14 +/- 2 ms/mmHg) than in control normotensives (23 +/- 2 ms/mmHg) or normotensive offspring (19 +/- 3 ms/mmHg), whereas those for muscle sympathetic nerve activity were significantly smaller both in normotensive offspring (-8.3 +/- 1.0%/mmHg) and borderline hypertensive offspring (-7.9 +/- 0.5%/mmHg) than in control normotensives (-16.3 +/- 1.4%/mmHg). Baseline muscle sympathetic nerve activity was higher in borderline hypertensive offspring (20.1 +/- 3.0 bursts/min) than in control normotensives (10.1 +/- 1.2 bursts/min) or normotensive offspring (12.8 +/- 1.4 bursts/min), and also the depressor responses to trimethaphan were significantly enhanced in borderline hypertensive offspring [-19.2 +/- 2 versus 14 +/- 1 (normotensive offspring) or 12 +/- 2 (control normotensives)]. These results indicate that baroreflex inhibition of muscle sympathetic nerve activity was reduced in adolescents with a family history of hypertension even when they were normotensive. This reduced reflex sympatho-inhibition could lead to the development of hypertension by increasing sympathetic vasomotor tone.

Adult↗
PubMed1988

Altered platelet alpha 2-adrenoceptors and adrenaline response in adolescents with borderline hypertension who have a family history of essential hypertension.

We studied the relationship between a family history of essential hypertension and the characteristics of platelet alpha 2-adrenoceptors in male university students. Platelet membranes were prepared by the method of U'Prichard. Tritium-rauwolscine was used for the alpha 2-adrenoceptor binding assay. The maximum number of binding sites (Bmax) of platelet alpha 2-adrenoceptors was higher in borderline hypertensives with a family history of hypertension than in normotensives without it. However, no significant difference in the Bmax was found between the normotensives without and those with a family history. Dissociation constants (Kd) were not significantly different among the three groups. The plasma concentration of adrenaline after 30 min of standing was higher in the borderline hypertensives with a family history than in the normotensives, either with or without a family history. These results suggest that alterations in the alpha 2-adrenoceptor density or affinity for antagonists of platelets may not be linked to a positive family history of essential hypertension. However, an increased alpha 2-adrenoceptor density in platelets and an enhanced adrenaline response may be involved in blood pressure elevation in borderline hypertensives with a family history of hypertension.

Adult↗
PubMed1988

A new compact 24-hour indirect blood-pressure recorder and its clinical application.

A new portable noninvasive recorder (4 X 6.5 X 14 cm in size, 390 g in weight) was developed for monitoring 24-hour blood pressure and its clinical applicability was investigated. Employing an ordinary-size cuff, this is the lightest and the most compact apparatus of its kind ever developed. It is powered by a rechargeable battery. The cuff is pressurized by a miniature, low-noise, rotary micropump. To eliminate noises resulting from body motion, two microphones are used to distinguish Korotkoff sounds. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) are measured automatically at intervals of 1 to 60 min throughout 24 hours. These data can be stored as many as 600 times in the recorder's semiconductor memory. After measurement, mean values; standard deviations (SD); and trendograms of SBP, DBP, and HR are printed out by means of an appurtenant, miniature analyzer measuring 5 X 7.5 X 15 cm. A comparison of values obtained with this new instrument and the values obtained with a conventional auscultatory method showed average errors of -1.2 +/- 4.7 (SD)mmHg for SBP and -2.7 +/- 5.0 mmHg for DBP. The correlation coefficient (r) of values obtained by two methods was r = 0.99 for SBP and r = 0.96 for DBP (n = 185). In 38 male and 31 female normotensive subjects (average casual BP: male 126 +/- 11/76 +/- 7 mmHg; female 116 +/- 13/69 +/- 10 mmHg), average 24-hour BP values recorded by the new recorder were 115 +/- 7.5 (SBP)/70 +/- 6 (DBP)mmHg for the males and 106 +/- 6/63 +/- 5 mmHg for the females. The new recorder seems to be convenient, easy to operate, and clinically useful in ambulatory monitoring.

Adult↗
PubMed1988

Neurogenic abnormalities in young borderline hypertensives.

Although neurogenic abnormalities have been postulated to be involved in the pathogenesis of borderline hypertension, no direct evidence has been documented. We continuously recorded muscle sympathetic nerve activity (MSNA) using a microelectrode in the tibial nerve, along with arterial pressure (AP) and heart rate (HR) during the cold pressor or isometric handgrip test in 16 male adolescents with borderline hypertension (BHT) and 10 normotensive adolescents (NT). Baroreflex changes in MSNA were also assessed during the pressor responses to intravenous phenylephrine. During the cold pressor test, both MSNA and AP gradually increased, but the HR responses were inconsistent. The resulting changes in MSNA, AP and HR were all augmented in BHT compared with NT. By contrast during the isometric handgrip test, MSNA, AP, and HR increased in both groups, but none of the differences between the groups was significant. Furthermore, baroreflex inhibition of MSNA were significantly reduced in BHT. Thus, some neurogenic abnormalities exist in BHT, which can be easily detected by recording MSNA.

Adolescent↗
PubMed1987

Effect of ramipril on 24-hour variability of blood pressure and heart rate in essential hypertension.

Nonrestricted blood pressure recording was performed invasively or noninvasively, using new portable devices, for a period of 24 hours in 4 patients with essential hypertension before and after 6- to 17-day treatment with ramipril at an initial dosage of 1.25 mg daily. Ramipril produced a steady decrease in blood pressure without changing heart rate. Before initiation of ramipril treatment, the blood pressure was lower during the night than during the day. This day to night difference was not affected by ramipril. In addition, analysis of the standard deviation of the mean for each time point examined during 24 hours revealed no effect of ramipril on circadian variation of blood pressure.

Adult↗
PubMed1987

Mathematical evaluation of 24-hour blood-pressure variability in young, middle-aged and elderly hypertensive patients.

The characteristics of 24-hour blood pressure variation in hypertensive patients were assessed using new indices of variability. Blood pressure of 43 inpatients with essential hypertension was measured using a portable device without disturbing daily behaviors. Variances in systolic and diastolic pressure values obtained for a day (SDd2), and short-term (SDh2) and long-term (SD24(2) variances were calculated; their relationship was expressed as SDd2 = SDh2 + SD24(2). SDh and SD24 were expedient in assessing the relatively fast and slow blood-pressure variations, respectively. The results showed that the ratio SDh2/SDd2 (percentile of the short-term variance in a whole-day variance) increased and therefore SD24(2)/SDd2 decreased as age increased for both systolic and diastolic pressures. It was found, moreover, that systolic SDh was significantly related to age and baroreflex sensitivity, and systolic SD24 to the heart rate during waking hours. The physiological and clinical significance of SDh and SD24 is discussed, briefly, including arterial wall stiffness.

Adult↗
PubMed1987

Measurements of base blood pressure during sleep and its clinical significance in hypertensive patients.

The intra-arterial blood pressure (BP) was measured during 24 hours on 52 patients with essential hypertension using a portable device. The minimum BP inherent to each subject (base BP) was determined from the systolic and diastolic BP histograms during sleep. In this study the systolic and diastolic BPs were presented as a mean BP (BP) and a base BP, and the average of BPs during waking hours was considered as the sum of the base BP and the additional BP increment. The clinical significance of the base BP and BP increment was examined by comparing them with the results of clinical examinations. The comparison showed that the base BP was closely related with the left ventricular hypertrophy and severity of hypertension, while the BP increment correlated with the baroreflex sensitivity and plasma norepinephrine concentration. In this paper, a new tonometry was developed to indirectly record the BP of the superficial temporal artery. The tonometry correlated well with the intra-arterial BP measurement, and was available for the indirect base BP evaluation at an outpatient-clinic.

Adult↗
PubMed1987

Changes in blood pressure and plasma norepinephrine during sleep in essential hypertension.

A fall in blood pressure (BP) and the presence of a period of unstable BP during sleep has been reported in humans. However the mechanisms responsible for these phenomena are unclear. In order to examine the role of the sympathetic nervous system in these phenomena, plasma norepinephrine (PNE) was measured in patients with essential hypertension. Blood pressure was monitored under unrestricted conditions by a canula inserted into the brachial artery. During sleep, systolic (SBP) and diastolic blood pressure (DBP) fell by 18.8/13.7 mmHg, respectively. The magnitude of the fall in SBP correlated significantly (p less than 0.05) with the level of PNE in the daytime and with the magnitude of the fall in PNE during sleep. The period of unstable BP and pulse rate was observed during sleep. During this unstable period, BP changed periodically with 20 to 120-second cycles associated with parallel changes in pulse rate. PNE during this period was higher (p less than 0.05) than that during the period of stable BP during sleep. These data suggest that the sympathetic nervous system may play an important role in the fall in BP and unstability of BP during sleep.

Adolescent↗
PubMed1987

Relationship between 24-hour arterial pressure and heart rate variation in normotensives, hypertensives and patients with Shy-Drager syndrome.

To investigate a relation between circadian blood pressure and heart rate variation, intra-arterial blood pressure (BP) and heart rate (HR) were recorded during 24 hours in 53 untreated essential hypertensives (EH), 8 secondary hypertensives, 10 normotensives (NT), and 3 patients with Shy-Drager syndrome. Values of systolic BP (SBP) and HR were sampled at about 10 second intervals throughout the 24-hour to calculate the coefficient of correlation between SBP and HR (rSBP-HR). A significant positive correlation was found between SBP and HR levels in each subject of EH with WHO stage I and II, along with NT (average rSBP-HR = 0.59, 0.40, and 0.54 respectively, p less than 0.001). Low coefficients of correlation were found in the EH with WHO Stage III (r = 0.16) and the patients with pheochromocytoma (r = 0.05). In contrast, a significant negative correlation was found in the patients with Shy-Drager syndrome (r = -0.44, p less than 0.001). Since HR is controlled mainly by the autonomic nervous system (ANS), the results suggest that the circadian variation of SBP is also mainly controlled by the ANS in the subjects with high rSBP-HR and that of SBP controlled by the other factors in subjects with low rSBP-HR.

Adult↗
PubMed1987

The effects of twice daily captopril and once daily enalapril on ambulatory intraarterial blood pressure in essential hypertension.

Intraarterial ambulatory pressure (AP) was recorded before and during therapy with captopril or enalapril in two groups with hypertension. Seven patients were admitted during the study. The monitoring of AP and heart rate (HR) was performed during placebo therapy and following a minimum period of 7 days of 25 mg twice daily captopril or 2.5 to 10 mg once daily enalapril. The AP and HR following percutaneous insertion of a cannula into the brachial artery were sampled then data were analyzed as reported previously. After the cannula was inserted, examinations of tilt-up, handgrip and ergometer were performed. Both drugs produced a significant reduction of ambulatory AP throughout 24 hours with preservation of the overall shape of the circadian curve. The results also demonstrated that both drugs had not affected normal daily activities. Thus, twice daily captopril and once daily enalapril can be used as the first-line therapy of hypertension.

Adult↗
PubMed1986

Management of hypertension in high school students by using new salt titrator tape.

In a blood pressure screening program involving 6589 high school students, 180 male (4.7%) and 17 female (0.6%) students were identified as borderline hypertensive. The 174 hypertensive male adolescents studied further showed pathophysiological features such as a significantly higher frequency of obesity, higher 24-hour urinary sodium excretion, higher hematocrit value, higher sodium and lower potassium concentration in red blood cells, and higher ouabain-sensitive sodium efflux compared with the control group (231 male students; p less than 0.05). When used alone, the ordinary 10-week period of counseling about a low salt diet failed to significantly reduce the blood pressure of hypertensive students. However, when education and counseling efforts were combined with self-monitoring of salt (chloride) excretion in overnight urine samples using a new salt titrator tape developed in our laboratory, 24-hour urinary sodium excretion, weight, and blood pressure decreased significantly over 10 weeks (mean reduction: 52 mEq/day for 24-hour urinary sodium excretion, 1.7 kg for weight, 12/7 mm Hg for blood pressure). These results indicate that blood pressure of borderline hypertensive adolescents could be effectively reduced with this nonpharmacological method of dietary education. Such systematic management might be of importance for the prevention of essential hypertension.

Adolescent↗