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Biomedical subjects

M Munakata

Publications and source records attributed to M Munakata.

At least 145 records · Page 8Linked to original sources
PubMed1993

Theophylline affects three different potassium currents in dissociated rat cortical neurones.

1. The effects of theophylline in pyramidal neurones acutely dissociated from the rat frontal cortex were investigated in the whole-cell configuration, using the nystatin-perforated patch-clamp technique. 2. Ten millimolar theophylline evoked triphasic responses: a small slow outward current (Iso), then a large transient outward current (Ito) and finally a slow sustained inward current (Isi). The reversal potentials of the three current components shifted 56-58 mV for a 10-fold change in extracellular K+ concentration, thereby indicating that all these current components were predominantly carried by K+. 3. Iso had no voltage dependence, whereas Ito showed a steep outward rectification. Iso was relatively resistant to tetraethylammonium (TEA) with an IC50 of 10 mM. Ito was susceptible to submillimolar TEA with an IC50 of 0.8 mM. 4. Isi was a net inward current mainly resulting from suppression of the M-current (IM). 5. These three current components had a distinct concentration dependence; in particular, Isi was evoked at a relatively lower concentration range. 6. Ito was not observed when the intracellular Ca2+ was chelated by 1,2-bis(O-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) of 10 mM, using the conventional whole-cell recording configuration, whereas both Iso and Isi were retained but gradually diminished. 7. In Ca(2+)-free external solution, these responses were fully elicited by the first application of theophylline. However, Ito disappeared during successive applications and Iso, but not Isi, also decreased. Similar results were obtained in the presence of ryanodine. 8. Theophylline apparently affects three different kinds of K+ currents in rat cortical neurones. Both Iso and Ito depend on internal calcium mobilized from an intracellular Ca2+ store by theophylline, while Isi was not primarily mediated by a change in [Ca2+]i.

Action Potentials↗
PubMed1993

Ambulatory blood pressure of adults in Ohasama, Japan.

We performed a cross-sectional study in a small town in northern Japan to evaluate the distribution, reference values, and daily variation in ambulatory blood pressure. A total of 705 subjects (229 men aged 61.3 +/- 13.4 years [mean +/- SD] and 476 women aged 57.5 +/- 13.3 years; 41.1% of the regional adult population, n = 1716), including those treated with antihypertensive drugs (n = 231, 66.5 +/- 9.5 years) as well as untreated subjects (n = 474, 55.0 +/- 13.5 years), participated in the study. Both ambulatory and screening blood pressures were measured in 659 subjects. Ambulatory blood pressure was measured with an automatic device (Colin ABPM-630). The 24-hour ambulatory blood pressure in the total population was 121.7 +/- 13.0/71.1 +/- 7.6 mm Hg (95th percentile value [95%] = 146/85 mm Hg). The corresponding value in the untreated subjects was 119.4 +/- 12.5/70.1 +/- 7.4 mm Hg (95% = 144/83 mm Hg). The 24-hour average ambulatory blood pressure was 118.0 +/- 11.1/69.4 +/- 6.8 mm Hg (95% = 139/81 mm Hg) in subjects identified as normotensive by their screening blood pressure (n = 448, 57.2 +/- 13.1 years) and 133.6 +/- 14.2/78.9 +/- 8.8 mm Hg in those identified as hypertensive by their screening blood pressure (n = 73, 63.1 +/- 10.6 years). Based on the mean+SD of the 24-hour ambulatory blood pressure in the normotensive subjects by their screening blood pressure (129/76 mm Hg), the 24-hour ambulatory blood pressures in 25 (34.2%) of these 73 hypertensive subjects by screening blood pressure were below this level. Nine (2%) of 448 normotensive subjects by screening blood pressure were above the mean+2 SDs (140/83 mm Hg) of the 24-hour ambulatory blood pressure in the normotensive group by screening blood pressure. Ambulatory and screening blood pressures increased with age. The age-dependent increase in ambulatory blood pressure was less apparent in men. The 24-hour average pulse rate decreased with age. The daily variation in ambulatory blood pressure (standard deviation) increased with age, whereas that of pulse rate decreased with age. Increases in blood pressure variation were observed in nighttime and daytime blood pressure values. The differences between day versus night ambulatory blood pressures decreased with age in men but not in women.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Acute rise in serum immunoglobulin E concentration in pulmonary thromboembolism.

Events mediated by immunoglobulin E (IgE) may be related to platelet activation and aggregation, and there may be an association between IgE and pulmonary thromboembolism (PTE). Fourteen patients with PTE were studied with regard to serum concentrations of IgE, IgA, IgG, IgM, fibrinogen, and D-dimer and with regard to blood neutrophil, lymphocyte, platelet, and eosinophil counts during acute and recovery phases. The serum IgE concentration increased during the acute phase to 402 +/- 310 IU/ml and decreased afterwards in all patients. The increase in serum IgE concentration lagged a few days behind that of the serum D-dimer concentration, indicating later IgE production than thrombus formation and lysis. Infarction and pleural fluid accumulation developed in patients with a high initial serum IgE concentration. These results indicated a relationship between serum IgE concentration and the pathophysiology of PTE. Serum IgE may be an indicator of the severity of PTE and provide insight into its pathogenesis, thereby facilitating the diagnosis of PTE.

Adult↗
PubMed1993

Female asthmatics have increased hypercapnic chemosensitivity during the luteal phase which is not associated with decline in airway function.

To examine whether changes in respiratory chemosensitivity during the menstrual cycle are related to worsening of airway functions, hypoxic and hypercapnic ventilatory and P0.1 responses, airway function, and serum progesterone levels were studied in 11 female asthmatic patients in both the follicular and luteal phases. Plasma progesterone levels were 30-fold higher in the luteal phase than in the follicular phase (p < 0.0001). The PaCO2 decreased from 37.1 +/- 0.98 (SE) mm Hg to 35.1 +/- 0.89 mm Hg (p = 0.05) and HCO3- decreased from 22.4 +/- 0.44 mEq/L to 20.8 +/- 0.61 mEq/L (p < 0.001), from the follicular phase to the luteal phase, respectively. From the follicular to the luteal phase, delta VE/delta PACO2 tended to increase from 1.57 +/- 0.12 L/min/mm Hg to 1.91 +/- 0.26 L/min/mm Hg (p = 0.08) and delta P0.1/delta PACO2 increased from 0.25 +/- 0.05 cm H2O/mm Hg to 0.37 +/- 0.08 cm H2O/mm Hg (p = 0.05). During hyperoxic hypercapnia in the luteal phase, VE, f, and mean inspiratory flow increased and TI and TE decreased (p < 0.05). There were no differences in the hypoxic ventilatory and P0.1 responses and airway functional parameters (FEV1, PEF, V50, V25, and Raw) of the two phases. The increases in hypercapnic ventilatory and P0.1 responses were correlated to the improvement in FEV1 and PEF (p = 0.05 and p < 0.01, respectively). These results suggest that, although there is an augmentation of hypercapnic chemosensitivity during the luteal phase in female asthmatic patients, this is not associated with the decline in airway functions.

Adult↗
PubMed1993

Two-year follow up on the protective value of dust masks against farmer's lung disease.

Some advocate moving away from the farm environment for farmers affected with farmer's lung disease (FLD), but most affected farmers still live on farms. In this study, we evaluated the practicality of dust masks and their effectiveness in prevention of FLD. The dust masks we chose were practically used and no new severe episodes of FLD developed in 20 of 21 farmers with FLD using the masks during a 2-year period. When the farmers took off the dust masks in a farming environmental provocation test, statistically significant reductions in FVC (mean 3.43 to 3.351, p < 0.01), DLco (mean 19.6 to 18.2 ml/torr/min, p < 0.01), and DL/VA (mean 5.1 to 4.8 (x10(-3)) 1/torr/min, p < 0.01) were observed several hours after exposure. These findings suggest that the dust masks were used practically during routine dairy farming and were effective in protection against FLD.

Adult↗
PubMed1993

[Bronchial asthma--airway inflammation and asthma--role of airway epithelium].

The importance of airway inflammation in the pathophysiology of bronchial asthma has been recognized recently. This inflammation is organized by the interaction between inflammatory cells and the cells which compose airway structures. We studied the role of airway epithelium in airway hyperresponsiveness and airway inflammation, which are the major characteristics of bronchial asthma, and demonstrated a close relationship between them. On the bases of these data and the data reported by many other researchers, and from the point of view of airway inflammation, we discussed the possible roles of airway epithelium in bronchial asthma.

Animals↗
PubMed1993

[Causes of idiopathic interstitial pneumonia (IIP): inhaled dust as environmental problem].

We have reported that patients with IIP can be roentgenologically grouped into two subtypes, typical (type-A) and atypical (type-B). The characteristic feature of X-ray findings in type-A is marked restriction of the lung, especially of the lower lobes, and in type-B is emphysematous changes in addition to the findings of type-A. In this study, to clarify the pathological findings of these two subtypes, 60 IIP patients in whom open lung biopsy and/or autopsy were performed were studied both clinically and pathologically. The following results were obtained. 1) Pathological features of type-A were alveolitis, marked restriction of the lung secondary to atelectasis and fibrosis of lung parenchyma, and honeycombing as a result of remodeling. 2) The features of type-B were intra-alveolar organization and secondary emphysema after intra-alveolar inflammation (pneumonia) overlapped the pathological changes of type-A. 3) Patients with a history of dust inhalation were much more frequently observed in type-B than in type-A (p < 0.01). These results suggest that inhaled dust may be a causative factor of IIP, especially of type-B.

Dust↗
PubMed1993

[Transvenous pacemaker implantation for sick sinus syndrome with mirror-image dextrocardia].

A case of sick sinus syndrome with mirror-image dextrocardia which was associated with bilateral superior vena cava and an absent inferior vena cava with azygos continuation is reported. A 45-year-old woman was referred to our hospital with the chief complaints of dizziness and palpitation. The electrocardiogram showed a atrial fibrillation with a 4-second period of asystole. A permanent endocardial bipolar demand pacemaker was inserted through the left superior vena cava. Since anomaly of venous system is commonly associated with mirror-image dextrocardia, the angiogram is necessary prior to permanent pacemaker implantation.

Dextrocardia↗
PubMed1993

[A case of subpulmonary membranous stenosis associated with atrial septal defect].

The patient was a 5 years old male who had had the cyanosis and congestive heart failure from his neonatal period. Dopamine, digitalis and diuretics disappeared his symptoms and he had been followed up as the out-patient. Preoperative cardiac catheterization revealed atrial septal defect and moderately pulmonary stenosis with two-staged systolic pressure gradient in a right ventricular cavity. Right ventriculogram showed subpulmonary crescent-shaped, linear filling defect. Ventricular septal defect was not detected. He was underwent open heart surgery and subpulmonary membranous stenosis was found out. Pressure gradient across the right ventricular outflow tract was diminished by the resection of the membranous structure. Atrial septal defect without lower margin was closed directly. Postoperative course was uneventful. Right ventricular apical systolic pressure was decreased to the degree of 27 mmHg postoperatively.

Child, Preschool↗
PubMed1992

Novel Ca2+ currents in mammalian CNS neurons.

Voltage-dependent Ca2+ currents (ICa) in neurons can be classified into T-, N- and L-types. In the CA1 pyramidal neurons freshly dissociated from rat hippocampus we found an additional tetrodotoxin (TTX)-sensitive Ca2+ current (termed 'TTX-ICa'). The TTX-ICa showed a heterogeneous distribution, preferentially in the dorsal site of CA1 region. Activation and inactivation processes of the TTX-ICa were highly potential-dependent, and the latter was fitted by a double exponential function. The TTX-ICa was activated at a threshold potential of about -55 mV and reached full activation at -30 mV. The steady-state inactivation of TTX-ICa could be fitted by a Boltzmann equation with a slope factor of 6.0 mV and a half-inactivation voltage of -72.5 mV. When the peak amplitudes of TTX-ICa were plotted as a function of extracellular Ca2+ concentration ([Ca2+]o), the current amplitude increased linearly without showing any saturation. The ratio of peak amplitude in the individual I-V relationships of Ca2+, Sr2+ and Ba2+ currents passing through the TTX-sensitive Ca(2+)-conducting channel was 1:0.33:0.05, although the current kinetics were much the same. TTX inhibited the TTX-ICa in time- and concentration-dependent manner without affecting the current kinetics. Lignocaine inhibited the TTX-ICa in a second in a concentration-dependent manner, with accelerating the inactivation process. The concentrations of half-inhibition (IC50) were 3.5 x 10(-9) M for TTX and 3.6 x 10(-4) M for lignocaine. Scorpion toxin prolonged the inactivation phase of TTX-ICa in a time- and concentration-dependent manner. In the toxin-treated neurons, both the slow time constant of inactivation (tau is) and its functional contribution to the total current increased with increasing the toxin concentration.

Animals↗
PubMed1992

The accuracy and performance of the A&D TM 2421, a new ambulatory blood pressure monitoring device based on the cuff-oscillometric method and the Korotkoff sound technique.

The accuracy and performance of the A&D TM 2421, a new ambulatory blood pressure (BP) monitoring device using both the cuff-oscillometric method (O) and the Korotkoff sound method (K) were evaluated. The device was tested for accuracy under static and dynamic conditions by simultaneous comparison with two observers using a standard mercury column sphygmomanometer (standard method) and by the objective recording method (ORM). The performance of the device was also evaluated under ordinary ambulatory conditions. The mean differences in BP of standard method from K-method were -1.2 +/- 4.7 mm Hg systole and 1.3 +/- 4.7 mm Hg diastole (n = 323, mean +/- SD) and those of standard method from O-method were -0.4 +/- 5.3 mm Hg systole and 1.4 +/- 5.1 mm Hg diastole (n = 323). The agreement between each of the two methods of the device and the standard method was within 10 mm Hg for more than 90% of both systolic and diastolic readings. During bicycle exercise, the mean differences in BP of standard method from K-method were -3.4 +/- 4.8 mm Hg systole and 1.8 +/- 5.2 mm Hg diastole (n = 71) and those of standard method from O-method were -1.1 +/- 7.3 mm Hg systole and 1.7 +/- 7.8 mm Hg diastole (n = 67). There was a greater scatter in the individual comparisons of the device and the standard method during exercise, especially in diastolic BP. The relation between the device and ORM was almost similar to that between the device and the standard method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

5-HT response of rat hippocampal pyramidal cell bodies.

Serotonin (5-HT) responses of pyramidal neurones freshly dissociated from rat ventral hippocampal CA1 region were investigated by using nystatin-perforated whole-cell recording. These dissociated neurones lack most of the dendrites and axons. Application of nanomolar concentrations of 5-HT induced outward current with an increase of membrane conductance at a holding potential (VH) of -40 mV. The current was mimicked by alpha-methyl-5-HT (5-HT2 receptor family agonist), but not by 8-OH-DPAT (5-HT1 receptor family agonist). Ketanserin (5-HT2 receptor family antagonist) and spiperone (5-HT1A and 5-HT2 receptor family antagonist) blocked the current in a concentration dependent manner. These results suggests that 5-HT-induced outward current is mediated by the activation of 5-HT2 receptor family in the cell bodies of hippocampal pyramidal neurones.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1992

The influence of antihypertensive agents on circadian rhythms of blood pressure and heart rate in patients with essential hypertension.

The effects of once-daily administration of calcium (Ca) channel blockers, beta-blockers and and angiotensin-converting enzyme (ACE) inhibitors on circadian rhythms of blood pressure (BP) and heart rate (HR) were studied using the cosinor method. Sixty-two recruited patients with essential hypertension (WHO stage I or II) were divided into three groups based on the class of administered drugs. In the Ca channel blocker group (n = 37, age 54 +/- 9.0 years), 18 patients were given YM 730 at a mean dose of 11 +/- 4.0 mg/day (mean +/- S.D.), 8 were given nitrendipine (11 +/- 6.7 mg/day), and 11 were given nisoldipine (8 +/- 6.4 mg/day). In the beta-blocker group (n = 15, age 42 +/- 13.5 years), 13 patients were given atenolol (44 +/- 11.0 mg/day), 1 was given nadolol (30 mg/day), and 1 was given sustained-release propranolol (60 mg/day). In the ACE inhibitor group (n = 10, age 56 +/- 8.7 years), 7 patients were given enalapril (6 +/- 2.8 mg/day), and 3 were given lisinopril (20 mg/day). Ambulatory BP monitoring (ABPM) was performed before and during treatment. Mean arterial pressure (MAP) and HR were monitored under ambulatory conditions every five minutes for 24 hr with a finger volume oscillometric device. In all three groups, the mesor of MAP decreased significantly, while the amplitude and acrophase did not change during treatment. beta-Blockers reduced the amplitude as well as the mesor of HR. Ca channel blockers increased the amplitude of HR without influencing the mesor. ACE inhibitors had no effect on the circadian rhythm parameters of HR. These results suggest that Ca channel blockers, beta-blockers and ACE inhibitors lowered BP throughout the day without changing the circadian BP rhythm. However, the three drug classes may have different influences on the autonomic nervous system that regulates circadian cardiac rhythm.

Adrenergic beta-Antagonists↗