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Biomedical subjects

M Munakata

Publications and source records attributed to M Munakata.

At least 199 records · Page 11Linked to original sources
PubMed1989

Modulation of cardiovascular depressant action of clonidine by pentobarbital anesthesia in rats.

The influence of pentobarbital anesthesia (5 mg/100 g, i.p.) on the cardiovascular depressor effect of clonidine administered intracerebroventricularly (i.c.v.) and intravenously (i.v.) was examined in rats. In conscious rats the hypotensive potency of i.v. clonidine [effective dose of clonidine which induced a decrease in blood pressure of 15 mmHg; ED15 = 7 (micrograms/kg)] is greater than that of i.c.v. clonidine (ED15 = 24.3), while in anesthetized rats that of i.c.v. clonidine (ED15 = 0.7 microgram/kg) was greater than that of i.v. clonidine (ED15 = 3.5 micrograms/kg). Pentobarbital anesthesia potentiated the hypotensive potency of i.c.v. clonidine in conscious rats by 50 times, while it potentiated that of i.v. clonidine only by 2 times. The bradycardic potency of i.v. and i.c.v. clonidine was also potentiated by pentobarbital anesthesia. These pieces of evidence suggest that in conscious rat, the hypotensive action of i.c.v. clonidine is opposed by a centrally mediated hypertensive effect of the drug and that pentobarbital anesthesia suppresses the clonidine sensitive pressor center and so potentiates the hypotensive effect of i.c.v. clonidine.

Anesthesia↗
PubMed1989

Similarity in amplitude of the nocturnal fall in blood pressure in old and young patients with essential hypertension.

The influence of age on the nocturnal fall in blood pressure (BP) was examined in essential hypertensive patients as well as normal subjects. BP was monitored every 5 min for 24 hr by means of a finger volume oscillometric device. Average daytime BP was similar in the 3 age groups [young: less than 40 (years), n = 49, average daytime systolic BP (ASBP) = 132 +/- 20 mmHg, average daytime diastolic BP (ADBP) = 82 +/- 17 mmHg; adult: 40 less than or equal to less than 60, n = 110, ASBP = 127 +/- 19 mmHg, ADBP = 86 +/- 13 mmHg; old: 60 less than or equal to, n = 33, ASBP = 131 +/- 17 mmHg. ADBP = 83 +/- 11, mean +/- S.D.]. The nocturnal fall in BP was observed in all age groups and its amplitude (delta BP = average daytime BP - average nighttime BP) in the old patients (delta SBP = 13 +/- 11 mmHg, delta DBP = 10 + 8 mmHg) was similar to that in the young patients (delta SBP = 11 +/- 8 mmHg, delta DBP = 10 +/- 8 mmHg). The results suggests that information on the nocturnal behavior of BP is valuable in treating aged essential hypertensives to prevent cerebral and/or myocardial ischemia during sleep.

Adolescent↗
PubMed1989

The circadian variation of blood pressure and heart rate in patients with hyperthyroidism.

The circadian variation of blood pressure (BP) and heart rate (HR) was examined in 18 normal subjects, 15 patients with essential hypertension treated with beta-blockers and 21 patients with hyperthyroidism. Most of the patients with hyperthyroidism were also treated with beta-blockers. The 24 hr BP was measured with an ambulatory blood pressure monitoring device (UBP-100) every 5 min. A nocturnal fall in BP and HR was observed in the patients with essential hypertension treated with beta-blockers and the patients with mild to moderate hyperthyroidism as well as normal subjects. On the other hand, in patients with severe hyperthyroidism the nocturnal fall was observed in HR alone, and the fall was small in its amplitude. There was a significant negative correlation between triiodothyronine (T3) level and percentage amplitude of the nocturnal fall in systolic BP (n = 21, r = -0.5, p less than 0.01). However, this relation was not significant in diastolic BP and HR. These results indicate that excess thyroid hormone may modulate the circadian variation of BP and HR.

Adrenergic beta-Antagonists↗
PubMed1989

Exogenous glucocorticoid eliminates or reverses circadian blood pressure variations.

The effect of glucocorticoid on circadian variations of blood pressure was examined. In untreated patients with essential hypertension, a clear nocturnal fall in blood pressure and heart rate was observed and this was unaffected by combined treatment with antihypertensive drugs. The circadian blood pressure variation in patients with chronic glomerulonephritis (CGN) not receiving glucocorticoid treatment was essentially the same as that in patients with essential hypertension. In both groups there was a positive correlation between blood pressure and heart rate. On the other hand, in patients with CGN and systemic lupus erythematosus (SLE) who were treated with glucocorticoid, there was no nocturnal fall in blood pressure, and often a significant rise. In these patients the blood pressure was lowest in the afternoon and began to rise from then, and during the night, attaining a peak level in the morning. Despite this changed pattern of blood pressure variations, the heart rate in these patients was clearly reduced at night. In 10 patients with CGN and SLE, circadian rhythm of blood pressure and heart rate was examined before and during treatment with prednisolone (40.2 +/- 17.0 mg/day for 58.0 +/- 19.4 days, mean +/- s.d.). Prednisolone abolished the nocturnal fall of blood pressure, while the nocturnal fall of heart rate remained. There was no correlation between blood pressure and heart rate in patients with glucocorticoid treatment. These results suggest that the circadian blood pressure variation is influenced by the hypothalamo-pituitary-adrenal axis, probably through its action on the autonomic nervous system.

Adult↗
PubMed1988

Difference in the nocturnal behaviour of blood pressure between monitorings with the arm-cuff method and with the finger-volume oscillometric method.

The nocturnal behaviour of blood pressure obtained by a new portable device for monitoring ambulatory blood pressure (ABPM 630) was compared with that obtained by a finger-volume oscillometric device (BP-100); the former uses a conventional arm-cuff inflated by CO2 gas to eliminate the noise of the motorized pump, and is based on a cuff-oscillometric as well as the Korotkoff sound technique (microphone method). With the microphone method in ABPM 630, the mean differences from the conventional auscultatory method were -0.28 +/- 6.15 mmHg (mean +/- s.d.) for systolic and 0.96 +/- 6.28 mmHg for diastolic blood pressure, and there was a highly significant correlation between blood pressure values measured by the ABPM 630 and by the auscultatory method. In 40 patients with mild to moderate hypertension 24-h blood pressure was monitored simultaneously with the ABPM 630 and BP-100. The daytime average of systolic blood pressure measured with the ABPM 630 was similar to that measured with the BP-100, whereas the night-time average assessed by the former was significantly higher than that assessed by the latter. Arm-cuff inflation by ABPM 630 caused some degree of sleep disturbance in 35 of 40 subjects, whereas finger-cuff inflation scarcely disturbed the sleep. The performance of the ABPM 630 was excellent.

Arm↗
PubMed1988

Reversed circadian rhythm of blood pressure in adult spontaneously hypertensive rats.

The diurnal rhythms of blood pressure and heart rate were examined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) when they were 5-6 weeks old (young), 17-20 weeks old (adult) and 30-32 weeks old (old). Blood pressure was recorded continuously for 24 h in conscious, unrestrained rats. Hourly averages of blood pressure and heart rate were calculated by an on-line computer. The circadian variation of blood pressure and heart rate remained unchanged regardless of age in WKY, but the difference in blood pressure between the daytime average and the night-time average decreased as they grew older. A well-defined circadian variation of blood pressure and heart rate was observed in young rats of both strains, i.e. a nocturnal rise in blood pressure and heart rate. An inverted circadian variation of blood pressure, a nocturnal fall in blood pressure, was observed in adult and old SHR, whereas the ordinary circadian variation of the heart rate remained unchanged. A significant positive correlation was observed between the hourly averages of blood pressure and heart rate in WKY in all the age groups (r = 0.9, P less than 0.001 in each age group) and a weak positive correlation was observed in young SHR (r = 0.6, P less than 0.05, 5-6 weeks old). This positive correlation disappeared in adult and old SHR and, instead, a negative correlation was observed (r = -0.5, P less than 0.02 for 17-20-week-old rats: r = -0.8, P less than 0.001 for 30-32-week-old rats).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1988

Osmotic stimuli induce epithelial-dependent relaxation in the guinea pig trachea.

Epithelium in airways, like endothelium in blood vessels, may regulate responses of adjacent smooth muscle. To study the intact trachea from guinea pigs we developed an in vitro preparation that permits independent stimulation from either the inner epithelial surface or the outer serosal surface. The whole guinea pig trachea was excised, cannulated, and perfused at a constant flow with Krebs-Henseleit (KH) solution that was in direct contact with the inner epithelial-lined surface. The outer serosal surface of the trachea was immersed in a separate system (bath) containing KH solution. Tracheal responses were assessed by measuring the pressure drop between the tracheal inlet and the outlet under conditions of constant flow. When the trachea was precontracted with carbachol or KCl, hyperosmolar stimuli (KCl, mannitol, urea, or NaCl) produced concentration-dependent relaxation when applied to the inner epithelial surface. Relaxation was not produced when the hyperosmolar stimulus was applied to the serosal surface and was markedly reduced or abolished when the epithelial surface had been physically damaged or removed. These results indicate that hyperosmotic stimuli induce epithelial-dependent relaxation of trachea. A defect in this mechanism may be partially responsible for the bronchoconstriction seen in asthmatic subjects after exercise.

Airway Resistance↗
PubMed1988

Altered circadian blood pressure rhythm in patients with Cushing's syndrome.

The circadian blood pressure rhythm was compared in patients with Cushing's syndrome, essential hypertension, and primary aldosteronism. In patients with essential hypertension or primary aldosteronism, a clear nocturnal fall in systolic and diastolic blood pressure and heart rate was observed. This fall was seen in untreated subjects as well as in patients receiving combined treatment with a calcium antagonist, diuretic, converting enzyme inhibitor, alpha-blocker and beta-blocker, or sympatholytic drug. In these groups, there was a positive correlation between heart rate and systolic or diastolic blood pressure. On the other hand, in patients with Cushing's syndrome, there was no nocturnal fall in blood pressure but in some patients a rise was observed. In all patients there was a nocturnal fall in heart rate. Thus, there was no significant correlation between heart rate and blood pressure in these patients. Exogenous glucocorticoid eliminated the normal nocturnal fall of blood pressure in patients with chronic glomerulonephritis or systemic lupus erythematosus. These results suggest that the changed circadian blood pressure pattern in patients with Cushing's syndrome is not due to antihypertensive treatment or to the mineralocorticoid excess accompanying this disease, but it is attributable to excess glucocorticoid or the associated disturbance in the adrenocorticotropic hormone-glucocorticoid system (or both). This conclusion also implies that the normal circadian rhythm of blood pressure may be regulated at least in part by the adrenocorticotropic hormone-glucocorticoid system.

Adolescent↗
PubMed1988

The hypotensive mechanism of percutaneous transluminal dilatation (PTD) in renovascular hypertension due to bilateral renal artery stenosis.

The hypotensive mechanism of percutaneous transluminal dilatation (PTD) in renovascular hypertension due to bilateral renal artery was investigated in two patients. Blood pressure was monitored continuously before, during and after PTD by use of a new automated blood pressure monitoring device based on finger volume-oscillometry. Plasma renin activity was measured repeatedly before, during and after PTD. A hypotensive effect appeared immediately after PTD and blood pressure remained low in the following observation period without any hypotensive medication. In these cases, the hypotension was accompanied by a transient decrease in heart rate immediately after PTD. The hypotensive response to PTD was not parallel to the basal plasma renin activity, suggesting that the renin-angiotensin system is not necessarily involved in the maintenance of the hypertension before PTD. The autonomic nervous system seemed to play a certain role. Since the hypotension was accompanied by a transient decrease in heart rate immediately after PTD, the hypotension may be induced either by a decrease in sympathetic tone or by an increase in vagal tone at least just after PTD. It is hypothesized that these changes in autonomic nervous activity are mediated centrally through the renal afferent mechanism in response to rapid changes in renal hemodynamics induced by PTD.

Adult↗
PubMed1988

Involvement of the hypothalamo-pituitary-adrenal axis in the control of circadian blood pressure rhythm.

The circadian blood pressure rhythm was compared between patients with Cushing's syndrome and those with essential hypertension or primary aldosteronism. In patients with essential hypertension or primary aldosteronism, clear nocturnal falls in systolic and diastolic blood pressure and the heart rate were observed. In contrast, in patients with Cushing's syndrome there was no nocturnal fall in blood pressure, and even a rise in some cases. In all cases with Cushing's syndrome, there was a nocturnal fall in the heart rate. Exogenous glucocorticoid abolished a nocturnal fall of blood pressure in patients with chronic glomerulonephritis or systemic lupus erythematosus, but did not affect nocturnal falls in the heart rate. These results indicate that the normal circadian rhythm of blood pressure may be regulated, at least in part, by the hypothalamopituitary-adrenal system.

Blood Pressure↗
PubMed1988

Hypertensive episodes and circadian fluctuations of blood pressure in patients with phaeochromocytoma: studies by long-term blood pressure monitoring based on a volume-oscillometric method.

A new portable device for the indirect measurement of arterial blood pressure was successfully applied to detect paroxysmal hypertension and circadian fluctuation of blood pressure in patients with phaeochromocytoma. The device utilizes the volume-oscillometric technique, it is equipped with a microprocessor and allows long-term automatic monitoring of indirect blood pressure in the human finger. Compared with conventional fully automated portable devices of the arm-cuff type, our current equipment is lighter, less noisy, and causes less discomfort. With this device repeated measurements can be made without causing stress or discomfort, and without disturbing sleep. The arterial pressure measurement obtained using this device was reliable and reproducible. In some patients certain symptoms, possibly due to phaeochromocytoma, had been observed for several years before the study, although hypertension had not been identified. While these patients had consistently high circulating catecholamine levels, nocturnal falls in blood pressure were clearly documented. This suggests that plasma catecholamines released from the phaeochromocytoma, though excessive, may be of less physiological importance than other regulatory mechanisms concerned with circadian fluctuation of blood pressure, e.g. the sympathetic nervous system and/or hypothalamo-pituitary-adrenal system. This new device has proved to be a reliable means of monitoring long-term blood pressure and is useful in the diagnosis of paroxysmal hypertension in patients with phaeochromocytoma.

Adolescent↗
PubMed1987

Bronchoalveolar lavage during third-trimester pregnancy in patients with status asthmaticus: a case report.

Bronchial asthma is not uncommon among pregnant women. Especially, uncontrollable status asthmaticus may endanger both the lives of mother and fetus. We present a case of a late-phase pregnant woman in whom life-threatening status asthmaticus was relieved by repeated bronchoalveolar lavage (BAL) under controlled ventilation, followed by successful spontaneous vaginal delivery. This case may indicate that BAL should be considered as an option in status asthmaticus complicating pregnancy before terminating the pregnancy to save the lives of mother and fetus.

Adult↗
PubMed1987

Daily variation of blood pressure in patients with Cushing's syndrome.

The circadian rhythm of blood pressure (BP) was compared between patients with Cushing's syndrome and those with essential hypertension. In patients with essential hypertension, clear nocturnal falls in systolic and diastolic BP and heart rate (HR) were observed, and there was a positive correlation between HR and systolic or diastolic BP. On the other hand, in patients with Cushing's syndrome, there was no nocturnal fall in BP and instead a rise in some cases. In all cases with Cushing's syndrome there was a nocturnal fall in HR, and consequently no significant correlation between HR and BP in these patients. The present results imply that the normal circadian rhythm of blood pressure may be regulated at least in part by the hypothalamo-pituitary-adrenal system.

Adult↗
PubMed1987

A finger volume-oscillometric device for monitoring ambulatory blood pressure: laboratory and clinical evaluations.

A new portable device for the indirect measurement of ambulatory blood pressure in the finger was successfully applied to normotensive and hypertensive subjects in and outside a ward setting. The device uses the volume-oscillometric technique and, equipped with a microprocessor, permits long-term ambulatory monitoring of indirect systolic and mean blood pressure at desired intervals (once every 1-10 min). Systolic and mean blood pressures obtained by this method were well correlated with those measured by the direct (Oxford) and arm-cuff methods. Systolic and diastolic blood pressure obtained by the volume-oscillometric device were almost identical with those recorded by an arm-cuff. Systolic blood pressure obtained by the volume oscillometric method was, however, significantly lower than that measured by the direct method. The new device has also been used to measure blood pressure during treadmill exercise and ice-water immersion. Mean values of blood pressure and the SD of these averaged for 24 hours, or for every hour, were reproducible when the measurements were repeated under the same condition. The present device is portable, causes minimal noise, can detect rapid change in blood pressure and causes less discomfort when compared to the conventional arm-cuff method. Regular measurements can be made with minimal sleep disturbance. This fully automatic volume-oscillometric device allows reliable 24-hour monitoring of ambulatory blood pressure not only in but also outside a ward setting, and as such is useful for studies of hypertension.

Ambulatory Care↗
PubMed1987

Protein kinase C and tracheal contraction at low temperature.

During exercise or dry air-induced asthma, airway walls cool. However, the role of temperature in the regulation of airway tone is not clear. Protein kinase C (PKC) is an important second messenger in the mediation of cell responses. To explore whether changes in temperature affect pathways involving PKC in airways, we examined the effects of phorbol esters, potent activators of PKC, in guinea pig tracheal rings at various temperatures. Phorbol-12,13-diacetate (PDA) caused a reduction in tracheal tone at 37 degrees C and an increase in tone when temperature was reduced to 22 degrees C. Increases in tone were also produced by PDA when cell membranes were depolarized by ouabain (10 microM) or KCl (30 mM) at 37 degrees C. Contractions produced by PDA at 22 degrees C were inhibited by lipoxygenase inhibitors [ETYA (5,8,11,14-eicosatetraynoic acid), NDGA (nordihydroguaiaretic acid) and phenidone] and a leukotriene receptor antagonist [FPL 55712 (sodium 7-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-2-hydroxypropoxyl] -4-oxo-8-propyl-4H-1-benzopyran-2-carboxylate)]. Contractions produced by PDA at 37 degrees C or 22 degrees C in the presence of ouabain (10 mM) or KCl (30 mM) were not affected by these drugs. These results indicate that changes in temperature have profound effects on responses resulting from PKC activation. At low temperature, the lipoxygenase pathway mediates responses. Thus, cooling has the potential to modify a major intracellular pathway regulating physiological responses of the airways.

Animals↗