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Biomedical subjects

Y Ishiyama

Publications and source records attributed to Y Ishiyama.

At least 19 recordsLinked to original sources
PubMed2000

Differential responses of circulating and tissue adrenomedullin and gene expression to volume overload.

BACKGROUND: Adrenomedullin (AM), which is produced by various tissues and organs, also circulates in the blood. Circulating AM levels increase during disease states such as essential hypertension, heart failure, and renal failure. However, little is known about how circulating AM or AM production responds to volume overload (VOL). METHODS AND RESULTS: Progressive VOL was induced in rats by an aortocaval shunt (AC) or by an aortocaval shunt with banding of the abdominal aorta distal to the shunt (AC + B), which created a larger shunt volume. Plasma and tissue AM concentrations, as well as AM gene expression levels, were measured at 1, 5, and 14 days after operation. Plasma concentrations of atrial natriuretic peptide (ANP), aldosterone, and renin activity (PRA) were also examined. Pulmonary congestion, pleural effusion, and ascites rapidly progressed in the AC + B group, suggesting that VOL caused more rapid heart failure under these conditions. Plasma AM concentrations in the AC + B and AC groups at day 1 compared with those in sham-operated rats were increased by 300% and 140%, respectively, and then gradually declined. The time course of plasma AM over 14 days was similar to that of plasma aldosterone and PRA, but not of plasma ANP or intracardiac filling pressure. The increase in plasma AM was accompanied by upregulated AM gene expression in the lung and aorta and by decreased AM concentrations in the atrium, ventricle, and adrenal gland. Cardiac AM gene expression levels were increased in the hypertrophied ventricles of AC and AC + B rats. CONCLUSIONS: The major findings of the present study were 1) a rapid increase in plasma AM after the imposition of VOL in association with increased plasma aldosterone and PRA, 2) the contribution of several organs to this increase, and 3) a late increase in the AM messenger RNA (mRNA) level in the ventricles as VOL-induced ventricular hypertrophy developed.

Adrenomedullin↗
PubMed2000

[Estimation of sympathetic skin response using DC servo-amplifier].

The aims of this paper are to make clear the characteristics of sympathetic skin response(SSR) wave. The records of SSR wave were obtained using a DC servo-amplifier with the frequency response of DC to 30 Hz and drift level of 10 microV/10 min. The SSR from the palm of 10 normal control subjects(6 males and 4 females, age range 21-25 yrs) were elicited by electrical stimulation of the median nerve at upper arm. The results that the peak latency and the duration of SSR were approximately 6.32 +/- 2.5 s and 47.5 +/- 7.5 s respectively were obtained experimentally with the amplifier, though the results of AC recordings with time constant of 0.3 s were about 1.0 s and 2.0 s respectively. It can be considered that exact peak latency and duration of SSR are much longer than those data of previous studies. These findings suggest that electric stimulation should be applied at longer intervals than 60 s for rejection of the remaining potential level of SSR and the habituation.

Action Potentials↗
PubMed1999

Increased plasma proadrenomedullin N-terminal 20 peptide in patients with essential hypertension.

The novel hypotensive peptide, proadrenomedullin N-terminal 20 peptide (PAMP), is processed from the adrenomedullin precursor. Recently, we identified PAMP-12 [PAMP(9-20)] from the porcine adrenal medulla as a major endogenous and biologically active peptide. Using a new, sensitive radioimmunoassay which recognizes the C-terminal region of PAMP-20 [PAMP(1-20)], we investigated the role of PAMP in patients with essential hypertension who had normal renal function, and whether PAMP-12 is present in humans. The mean PAMP plasma concentration, like that of adrenomedullin, was significantly higher in hypertensive [1.51 fmol/mL, standard error of the mean (SEM) 0.09 fmol/mL] than normotensive participants (1.08 fmol/mL, SEM 0.05). The increase in plasma PAMP concentration in patients with organ damage accompanied by hypertension was significantly higher than that in patients without organ damage. The PAMP concentration had a significant positive correlation with mean blood pressure and adrenomedullin concentration. The immunoreactive PAMP in human tissue and plasma was characterized by reverse-phase high-performance liquid chromatography. PAMP-12, as well as PAMP-20, was abundant in the phaeochromocytoma tissue. These findings suggest that PAMP plays some pathophysiological role against the development of essential hypertension.

Adrenomedullin↗
PubMed1998

Decrease in circulating and urine adrenomedullin concentrations in stroke-prone spontaneously hypertensive rats.

Adrenomedullin (AM) is a peptide with potent vasodilatory and hypotensive properties. Plasma AM levels in rats with experimentally induced hypertension, such as Dahl salt-sensitive rats and two-kidney, one-clip hypertensive rats, are higher than those in normotensive rats. We previously noted, however, that plasma AM levels in spontaneously hypertensive rats (SHR) are similar to those in Wistar-Kyoto rats. To define the role of AM in rats with severe hypertension, we investigated changes in circulating and tissue AM levels in stroke-prone spontaneously hypertensive rats (SHRSP/Izm). The immunoreactive rat AM levels in plasma, urine, and tissue measured with a sensitive radioimmunoassay, and the AM mRNA levels in various tissues in 15-wk-old SHRSP/Izm were compared with those in age-matched Wistar-Kyoto rats (WKY/Izm). The plasma and urinary AM levels in SHRSP/Izm were significantly lower than those in WKY/Izm [plasma AM, 2.14+/-0.06 (SE) vs. 3.24+/-0.16 fmol/ml, p< 0.001; urinary AM, 16.36+/-3.21 vs. 36.12+/-6.09 fmol/ml, p< 0.01]. A negative correlation was found between the plasma AM level and the systolic blood pressure in both SHRSP/Izm and WKY/Izm. Reverse-phase high-performance liquid chromatography showed that the molecular components of plasma immunoreactive AM in SHRSP/Izm were similar to those in WKY/Izm. Furthermore, tissue AM levels in various organs in SHRSP/Izm were not lower than those in WKY/Izm. In conclusion, low levels of circulating AM may contribute to the maintenance of high blood pressure in 15-wk-old SHRSP/Izm. These low plasma AM levels may be caused by accelerated metabolism of circulating AM in SHRSP/Izm.

Adrenomedullin↗
PubMed1998

Malignant mesothelioma of the pleura with a large tumor embolus in the left atrium: an autopsy case.

Malignant mesothelioma of the pleura often involves the heart but seldom invades the intracardiac cavity. We report a 78-year-old woman with right pleural mesothelioma who died of heart failure. An autopsy revealed that the tumor was present at the right pleura and invaded the right upper lobe of the lung and the mediastinum. The tumor also extended to the left atrium via the right pulmonary vein and filled the atrial cavity. Repeated transthoracic echocardiography failed to detect the tumor, but magnetic resonance imaging was useful for diagnosis.

Aged↗
PubMed1998

[The present and future of neurophysiological examination].

This paper discusses the following routine examinations and new neurophysiological examinations that will likely be adopted in future. 1) EEG: a) The source derivation method and intracranial EEG recording method are useful for the detection of the exact focus in epileptic seizure. b) Polysomnography is applied to sleep disorders (ex. apnea syndrome). c) EEG topograph mapping and brain electric source analysis (BESA) are not only applied to neurological disorders, but also used for the detection of electrical equivalent dipole source localization. 2) Evoked potential (EP): ABR, SSEP and P-VEP by routine techniques are useful for the diagnosis of brain tumors and demyelinating diseases. Recently, event-related potential (ERP) has attracted attention in examining human recognition. 3) EMG and evoked EMG: a) MUP analysis with the template-matching method and single fiber EMG are topics of electromyography. b) M wave of evoked EMG has been used for the measurement of maximum nerve conduction velocity. Furthermore, the collision technique and microneurography can be applied to many kinds of nerves with different conduction velocities. c) The technique of magnetically stimulating the motor cortex was applied for the measurement of central motor conduction time (CMCT). 4) In the near future, neurophysiological examinations will include an EEG automatic diagnostic support system, neurophysiological network system, paperless digital EEG machine and non-invasive functional mapping with multichannel near infrared spectroscopic topography et al.

Electroencephalography↗
PubMed1997

Purification and characterization of PAMP-12 (PAMP[9-20]) in porcine adrenal medulla as a major endogenous biologically active peptide.

Proadrenomedullin N-terminal 20 peptide (PAMP-20) is a potent hypotensive peptide processed from the adrenomedullin (AM) precursor. We developed a specific radioimmunoassay which recognizes the C-terminal region of PAMP-20. Using this radioimmunoassay, the distribution of immunoreactive (ir-) PAMP was determined in porcine tissues. High concentrations of ir-PAMP were observed in the adrenal medulla and in the atrium, and these values were comparable to the corresponding concentrations of ir-AM. The concentration of ir-PAMP was almost the same as that of ir-AM in the kidney, while ir-PAMP was significantly lower than ir-AM in the ventricle, lung, and aorta. Reversed-phase high performance liquid chromatography in each porcine tissue sample revealed that two major peaks of ir-PAMP existed: one emerged at a position identical to that of authentic porcine PAMP-20; the other unknown peak was eluted earlier. The unknown peptide was purified to homogeneity from porcine adrenal medulla, and its complete amino acid sequence was determined. This peptide was found to be PAMP[9-20] with a C-terminal amide structure, and was named PAMP-12. Intravenous injections of PAMP-12 in anesthetized rats showed a significant hypotensive effect in a dose-dependent fashion, and the effect was comparable to that of PAMP-20. These data indicate that PAMP-12, a major component of ir-PAMP, is processed from the AM precursor, as is PAMP-20, and may participate in cardiovascular control.

Adrenal Medulla↗
PubMed1997

Effect of chronically infused adrenomedullin in two-kidney, one-clip hypertensive rats.

The hypotensive effect of chronically infused adrenomedullin, a potent vasodilator peptide, was examined in conscious two-kidney, one-clip (2K-1C) hypertensive and sham-operated rats. They were infused with 1.0 microgram/h of synthetic human adrenomedullin for 14 days by means of osmotic minipumps. Control groups were infused on the same schedule with 0.9% saline. Systolic blood pressure was measured before and during the infusion. Plasma renin activity, aldosterone and human adrenomedullin concentrations were determined at day 14 of the infusion. A significant reduction of systolic blood pressure was observed in the adrenomedullin-infused 2K-1C rats at day 4, and systolic blood pressure remained significantly lower throughout the experiment compared to that of the control 2K-1C. A similar hypotensive effect was seen in the adrenomedullin-infused sham-operated rats. Both the plasma renin activity and aldosterone concentrations of the adrenomedullin-infused 2K-1C and sham groups were significantly reduced compared to those of the respective control, whereas, the plasma human adrenomedullin concentration in the adrenomedullin-infused groups was found to be within the physiological range. These findings demonstrated that chronically infused adrenomedullin had a hypotensive effect accompanied by significant reductions of plasma renin activity and plasma aldosterone concentration in 2K-1C hypertensive and sham-operated rats.

Adrenomedullin↗
PubMed1997

Changes in cardiac adrenomedullin concentration in renovascular hypertensive rats.

We assessed changes in tissue and plasma adrenomedullin levels in two-kidney, one-clip renovascular hypertensive rats. Four weeks after clipping, adrenomedullin concentrations were significantly higher in the cardiac ventricles and lower in the left atrium than the respective values in sham-operated rats. The left ventricular adrenomedullin concentration significantly correlated with systolic blood pressure and the degree of cardiac hypertrophy. No difference was noted in the adrenomedullin concentrations of the adrenal gland, aorta, lung, kidneys, or plasma between the two groups. These findings indicate possible involvement of cardiac adrenomedullin in this model of hypertension.

Adrenomedullin↗
PubMed1997

[Stimulating conditions of cold air caloric test].

This study is to clarify the effects of stimulating conditions on caloric response evoked by cold air stimulation. The five parameters of caloric nystagmus (latency, maximum slow phase velocity [Max. spv], Max. spv arrival time, frequency and duration) were examined. The different stimulating air temperature(0 degree C, 5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C), flow rate (3.0, 4.0, 5.0, 6.0 l/m) and period(30, 45, 60, 90 sec) were used to evoke caloric nystagmus in normal subjects. 1. Effect to temperature When the intensity of air irrigation temperature increased, Max. spv, frequency and duration also tended to increase. Out of the five parameters, the duration of caloric nystagmus was the most relevant to the intensity of irrigation temperature. 2. Effect of stimulating period When the period of caloric stimuli increased, the Max. spv and its duration also increased. But, when the stimulating period was 90 seconds, the slow phase velocity reached to the maximum responses 60 seconds after starting the stimulation. Therefore, it is not necessary to stimulate for more than 60 seconds. 3. Caloric response evoked by 60 sec, 5.0 l/m at 5 degrees C air irrigation showed the same response as the caloric nystagmus provoked by 20 ml of water at 20 degrees C for 20 sec.

Adult↗
PubMed1997

[The data processing of neurophysiological examination and the diagnostic support system].

Neurophysiological examinations include EEG, EMG, Evoked Potential (EP) and ENG. In this paper, EEG and EP data processing, and the diagnostic support system using these findings were discussed. The FFT and AR model for analysis of frequency, and the pattern recognition for spike or spindle detection are the technical methods for application to EEG data processing of the first order. Amplitude or phase mapping techniques, as a second order data processing, were not only applied to the diagnosis of neurological disorders, but also used for detection of electrical equivalent dipole source localization which was inversely reconstructed in the cerebral cortex from the distribution of EEG potentials on the scalp. The averaging technique was used for detection of small evoked potentials (EP) such as SEP or ABR. The following items were included in the diagnostic support system applied to data processing. 1) Topographic analysis in the brain mapping of SEP to median nerve stimulation was applied to the identification of the central sulcus during a neurosurgical procedure to maintain the QOL of patient. 2) The usefulness of EEG automatic reporting system with Japanese sentences and brain topographic mapping was described. 3) Digital EEG in a data filing system using magneto optical disks was used for data analysis and diagnostic support system after EEG examination.

Algorithms↗
PubMed1996

Chronic effect of beta-adrenoceptor blockade on plasma levels of brain natriuretic peptide during exercise in essential hypertension.

Many factors have been reported to stimulate the release of brain natriuretic peptide (BNP) as well as atrial natriuretic peptide (ANP). In hypertensive patients, however, little is known about whether these factors differ from those in normotensive subjects or if they are influenced by antihypertensive treatment. We measured the plasma concentrations of BNP and ANP in 12 hypertensive patients and examined the chronic effects of beta-adrenoceptor blockade on BNP secretion during exercise with a bicycle ergometer. The exercise raised both plasma BNP and ANP with concomitant increases in systolic blood pressure, heart rate (HR) and plasma norepinephrine (NE) and epinephrine (Epi) before and after treatment. Before treatment, the changes in ANP and BNP correlated with that in HR (p < 0.05). After treatment 4 wk of treatment, the change in ANP correlated with those in NE and Epi as well as HR. Multivariate regression analysis indicated that only NE was a significant stimulus for ANP secretion during the treatment period. As for BNP, HR was the only significant stimulant for its secretion both before and after treatment. In essential hypertension, beta-adrenergic receptor blockade affected the factors stimulating exercise-induced ANP release but not those stimulating BNP release. BNP release, therefore, seems to be stimulated by similar but distinct factors from those that stimulate ANP release.

Adrenergic beta-Antagonists↗
PubMed1995

Plasma adrenomedullin in patients with primary aldosteronism.

Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from the pheochromocytoma tissue of humans. To examine the pathophysiological role of AM in primary aldosteronism (PA), the plasma concentration of AM in patients with PA was measured with a specific radioimmunoassay and compared to that in age- and sex-matched healthy normotensive subjects. In addition, the concentrations of AM as well as catecholamines in the plasma from both the adrenal vein and the inferior vena cava (IVC) were measured to determine whether or not the circulating AM in these PA patients is supplied from the adrenal medulla, which contains a much higher concentration of AM than any other human tissue does. The plasma concentration of AM in the PA patients (4.57 +/- 0.32 fmol/mL, n = 6) was significantly (P < .01) higher than that in the healthy subjects (3.06 +/- 0.20 fmol/mL, n = 12). A significant positive correlation (r = 0.62, P < .01) was observed between the mean blood pressure and the plasma AM level. The AM concentration in plasma from the adrenal vein was almost the same level as that from the IVC although the concentrations of both epinephrine and norepinephrine in the adrenal vein were much higher than those in the IVC. Therefore, it seems unlikely that the plasma AM in the PA patients is mainly supplied from the adrenal medulla. Judging from the potent hypotensive activity of AM, the present findings suggest that AM participates in defense mechanisms acting against the elevation of blood pressure in the patients with PA.

Adrenal Glands↗
PubMed1995

Haemodynamic responses to rat adrenomedullin in anaesthetized spontaneously hypertensive rats.

1. The haemodynamic effects of rat adrenomedullin (AM), a novel hypotensive peptide, were examined in anesthetized 16-18 week old spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). 2. An intravenous injection of rat AM dose-dependently reduced the mean blood pressure (MBP) with a concomitant fall in total peripheral resistance index (TPRI) and an increase in cardiac index (CI) in both strains of rats. Percent changes in MBP, TPRI and CI were not different between SHR and WKY. 3. The plasma half-life of rat AM in SHR was similar to that in WKY when it was administered at the dose of 1.0 nmol/kg. 4. These findings indicate that AM has a potent vasorelaxant activity in both SHR and WKY. The haemodynamic responsiveness to exogenous AM and its pharmacokinetics in SHR were comparable with those in WKY.

Adrenomedullin↗
PubMed1995

Exercise-induced secretion of brain natriuretic peptide in essential hypertension and normal subjects.

To determine the major stimuli for the release of brain natriuretic peptide (BNP) and atrial natriuretic peptide (ANP), we measured their plasma concentrations in 14 normal subjects and 19 patients with essential hypertension during exercise with a bicycle ergometer. The plasma levels of both hormones at baseline were significantly higher in the hypertensive group than in the controls (p < 0.05). The exercise raised both the plasma BNP and ANP, with concomitant increases in systolic blood pressure (SBP), heart rate (HR) and plasma norepinephrine (NE) or epinephrine (Epi) in each group. In the controls the change in ANP correlated with those in SBP, HR and NE (p < 0.05), and similarly the change in BNP with those in SBP, HR, NE and Epi (p < 0.05). In multivariate regression analysis only NE was found to be a significant stimulus for ANP secretion, whereas SBP or Epi was related to BNP release. In the hypertensives the change in ANP correlated with those in HR and NE, but on multivariate regression analysis the change in ANP correlated only with that in HR. The change in BNP in the hypertensives correlated only with that in HR. These findings indicate that in normal subjects the exercise-induced release of BNP and ANP is more sensitive to a similar but slightly different sympathetic stimulus, whereas in hypertensives the major stimulus for the release of both hormones is heart rate, indicating that the mediators for BNP or ANP release are altered by some factors involved in hypertension.

Adult↗
PubMed1995

[The effect of local transient cooling on anodermal blood flow].

To clarify the regulatory mechanism of blood flow of anodermal mucosal layers responding to the localized and transient coolong stimulation (around -4 degrees C), we examined the change of anodermal blood flow with use of Laser Doppler Flowmeter (Periflux, Perimed). The cooling stimulation was applied to anoderm by the insertion of chilled cold stick (Poscool, Maruho) into the anus of 11 healthy male volunteer, aged 20-25 years. Experimental results obtained are as follow; 1) The anodermal blood flow of healthy subjects are variant in degree and widely distributed from 30 to 80 Perfusion Unit (PU). 2) After cooling for five minutes by the insertion of a frozen Poscool, anodermal blood flow were increased in 8 cases out of eleven (72.7%). The changes corresponds to be 1.4 to 5.2 times. 3) Eight cases are divided into two groups on the basis of the time course after cooling: the one is "delayed responding group" (there is a delay 10-40 minutes before the blood flow is increasing) and the other is "rapid responding group" (the blood flow is immediately increasing). These results indicate that the anodermal blood flow, which are exposed to cooling, of healthy subjects is regulated not only by nervous mechanism but by humoral mechanism. Then, based on the Lewis reaction (cold vasodilatation), it is suggested that the short time cooling of anoderm should be appreciated as a conservative therapy of hemorrhoids and anal fissures.

Adult↗
PubMed1995

Plasma adrenomedullin in various diseases and exercise-induced change in adrenomedullin in healthy subjects.

Adrenomedullin is a novel hypotensive peptide recently discovered in human pheochromocytoma. In the present study, we measured the plasma immunoreactive adrenomedullin of healthy subjects and patients with various diseases. Immunoreactive adrenomedullin was found to circulate in blood of the healthy subjects at a considerable concentration (3.3 +/- 0.3 fmol/ml). Plasma adrenomedullin was significantly increased in the patients with congestive heart failure (5.4 +/- 0.3 fmol/ml), essential hypertension (5.3 +/- 0.4 fmol/ml) and renal disease (4.9 +/- 0.4 fmol/ml). In healthy volunteers physical exercise significantly increased the plasma adrenomedullin concentration. The increase of adrenomedullin was inversely related to systolic blood pressure. These findings indicate that adrenomedullin participates in the circulation control in both physiological and diseased conditions. Although the exact origin of circulating adrenomedullin is still unknown, it is thought to be released rapidly by acute exercise, thereby regulating the cardiovascular system by its vasodilating activity.

Adrenomedullin↗