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Biomedical subjects

H Hayakawa

Publications and source records attributed to H Hayakawa.

At least 163 records · Page 9Linked to original sources
PubMed1996

[Advances in the diagnosis of arrhythmia Holter's ECG].

Holter electrocardiography (ECG) is a non-invasive test widely used to evaluate variety of cardiac arrhythmias. The ability to record changing dynamic cardiac electrical phenomena, that often are transient and of brief duration, is the major clinical advantage of Holter ECG. The Holter ECG historically became an important clinical diagnostic tool for the recording of cardiac arrhythmias, but its use has evolved to include signal-averaged ECG and linear or non-linear analysis of heart beat variability. These uses provides insight into the substrate, modulator and the trigger of arrhythmias. This chapter will review the advances in technology and interpretation of Holter ECG recording within the context of its application to cardiac electrophysiology and arrhythmias.

Arrhythmias, Cardiac↗
PubMed1996

Low calcium (1.25 mmol/L) dialysate can normalize relative hypoparathyroidism in CAPD patients with low bone turnover.

Recently, several reports have suggested that there is a higher incidence of low turnover bone in the absence of aluminium exposure in peritoneal dialysis patients than in hemodialysis patients. Relative hypoparathyroidism with mild hypercalcemia, induced by a positive calcium balance, is considered to be one of the major causes of this disorder. Thus, we recruited 9 continuous ambulatory peritoneal dialysis (CAPD) patients with relative hypoparathyroidism and low bone turnover [intact parathyroid hormone (iPTH) < 50 pg/mL, intact osteocalcin < 10.0 ng/mL] who had been prescribed 1.75 mmol/L calcium (Ca) dialysate for 5.0 +/- 0.3 years. They were then treated by low Ca (1.25 mmol/L) dialysate for nine months without vitamin D and aluminum administration. Intact PTH and bone metabolic markers [intact osteocalcin, alkaline phosphatase (ALP)] were measured every three months. Intact PTH levels increased from 21.1 +/- 3.8 to 159.2 +/- 32.8 pg/mL after the first three months; thereafter, those levels were maintained at around 150 pg/mL. On the other hand, intact osteocalcin levels rose consecutively from 6.7 +/- 1.2 to reach 22.0 +/- 3.8 ng/mL after nine months. Interestingly, the pattern of time course changes between PTH and intact osteocalcin was different. ALP activity did not change during the nine-month period. Corrected serum calcium was significantly decreased (p < 0.001) to approximately 0.25 mmol/L within one month, and the level remained almost the same thereafter. The serum phosphate level did not change without adjusting the original dose of calcium carbonate as a phosphate binder. We concluded that low Ca dialysate (1.25 mmol/L) is effective for the treatment of CAPD-related hypoparathyroidism with low bone turnover.

Aged↗
PubMed1996

[Continuous ambulatory peritoneal dialysis ameliorated metabolic disturbances of a patient with chronic renal failure caused by glycogen storage disease type I].

A 30-year-old woman with chronic renal failure (CRF) due to glycogen storage disease Type I (GSD I) was admitted for dialysis. Hemodialysis (HD) was introduced as the primary therapeutic modality. However, maintenance HD was very difficult to conduct because of hypotension during the HD sessions. Furthermore, hypoglycemia and metabolic disturbances persisted. After changing from HD to CAPD, fasting blood sugar was significantly elevated through a continuous glucose supply from the dialysate. The values of ketone, non-esterified fatty acid, blood urea nitrogen/creatinine (BUN/ Cr), and glucagon were improved. CAPD not only controlled uremia, but also ameliorated the metabolic disturbances of GSD I. Therefore, we conclude that CAPD is superior to HD as a dialytic modality for patients with CRF due to GSD I.

Adult↗
PubMed1996

[Follicular bronchiolitis associated with rheumatoid arthritis].

A 52-year-old man with an 8-year history of rheumatoid arthritis was admitted to the hospital because of coughing and purulent sputum. A chest X-ray film obtained on admission showed small nodular shadows without overinflation in both lower lung fields, and a high-resolution CT scan showed many micronodular shadows in the centrilobular regions. Follicular bronchiolitis was diagnosed from the results of an open-lung biopsy, and prednisolone therapy was started at a dosage of 40 mg/day. Sinusitis developed 4 years later. Five years after the start of steroid therapy, dilation of bronchi and thickening of bronchial walls appeared on a CT scan, which also showed areas of low attenuation that were presumed to be bronchiolitis obliterans. These findings suggest that the pattern of airway disease can vary during the course of rheumatoid arthritis.

Anti-Inflammatory Agents↗
PubMed1996

[Study of peritoneal water channel expression in rats].

Removal of excess fluid from patients with chronic renal failure is one of the major objectives of peritoneal dialysis (PD). Water movement from capillary to dialysate derives from the dialysate-to-capillary osmotic gradient across the peritoneum. To explain the mechanism of water movement driven by the osmotic gradient through the peritoneum, the notion of a water selective "ultra small pore" has been proposed. The purpose of this study was to investigate the involvement of peritoneal water channels in water movement across the peritoneum in PD. The abdominal cavity of male anesthetized rats was catheterized for administration of a series of artificial dialysates. Experimental PD was performed for 90-180 min with 25 ml of hyperosmotic dialysate generated by glucose (600 mOsm), sucrose (600 mOsm), and sodium (1800 mg/dl, 600 mOsm). Analysis of the sodium concentration and osmolality of dialysate during experimental PD showed mercurial sensitive water transport that was compatible with water channel-mediated water transport in the peritoneum. RT-PCR amplification with cDNAs constructed from peritoneal mRNA revealed the existence of both AQP1 (CHIP28) and AQP4 (MIWC) water channels in the peritoneum. PD with hyperosmotic dialysate did not affect the expression of peritoneal water channels. As a result of an in situ hybridization study to investigate the localization of the peritoneal water channels, it was found that both channels were expressed in the sub-mesothelial layer containing capillaries. The results obtained in this study suggest that peritoneal water channels might play a role in fluid removal during PD.

Animals↗
PubMed1995

Chronic forced swim stress of rats increases frontal cortical 5-HT2 receptors and the wet-dog shakes they mediate, but not frontal cortical beta-adrenoceptors.

We studied the effects of chronic forced swim stress on 5-HT2 receptors and beta-adrenoceptors in the rat frontal cortex. The number of 5-HT2 receptors was increased immediately after the last chronic stress, but not after an acute stress. In vivo, the number of wet-dog shakes induced by a 5-HT2 receptor agonist, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), was increased 24 h after the last chronic stress. However, the concentrations of 5-HT and 5-hydroxyindole acetic acid (5-HIAA), measured by high pressure liquid chromatography (HPLC), were not altered by this stress. Binding sites for [3H]CGP-12177, i.e., beta-adrenoceptor sites, were unchanged after both the acute and the chronic stress. These results suggest that, in the rat, the chronic forced swim stress increases the number of frontal cortical 5-HT2 receptors and the number of wet-dog shakes mediated by these receptors, while the number of frontal cortical beta-adrenoceptors is not increased by this treatment.

Amphetamines↗
PubMed1995

Developmental changes of alpha 1-adrenergic chronotropic action on human sinus node.

The important role of alpha 1-adrenoceptors in reperfusion ventricular arrhythmia is mentioned in the introduction. However, the present report is concerned with the sinus node. It is speculated that the decreased positive chronotropic action of alpha 1-adrenergic stimulation due to aging may contribute to the development of sick sinus syndrome.

Adolescent↗
PubMed1995

Superoxide generation by alveolar macrophages from aged rats: improvement by in vitro treatment with IFN-gamma.

Alveolar macrophages (AM) from aged rats show an impaired oxidative response, but it is unclear whether or not this is due to the inability of these cells to be activated. To elucidate this, we investigated the capacity of AM from young (16-week-old) and aged (100-week-old) rats to become primed with recombinant rat interferon-gamma (IFN-gamma) for increased phorbol myristate acetate (PMA)-elicited O2- production, utilizing an MCLA-dependent chemiluminescent assay. We also compared concanavalin A- or Bacillus Calmette Guerin (BCG)-induced IFN-gamma production by the spleen cells of young and aged animals. The data indicated that AM freshly harvested from non-sensitized aged rats produced less O2- than those from young animals. A similar result was obtained in BCG-sensitized rats. However, AM from aged rats were primed with in vitro treatment with IFN-gamma for increased rate of O2- production to an equivalent level of that by AM from young animals. In addition, the ability of spleen cells to produce IFN-gamma was well maintained in aged rats. These results suggest that AM function is suppressed in the lungs of aged animals. Our observation that the decreased AM function in aged rats can be reversed is important because it suggests that appropriate treatment may reduce the incidence and mortality of respiratory infections in the elderly.

Aging↗
PubMed1995

The activation gate of cardiac Na+ channel modulates voltage- and pH-dependent unbinding of disopyramide.

To assess the drug unbinding process from receptor sites in cardiac Na+ channels, we examined the recovery kinetics of disopyramide-blocked Na+ current (INa) in isolated guinea-pig ventricular myocytes using the whole-cell variation of the patch-clamp technique. In the presence of disopyramide (20 microM), the time course of INa recovery from use-dependent block (unbinding) was described by a double exponential function. Although the time constant for the fast phase (tau f) of recovery was unchanged at different membrane voltages, the slow phase (tau s) increased with hyperpolarizing membrane potential: 4.4 +/- 0.2 s at a holding potential of -90 mV and 6.4 +/- 0.3 s at -140 mV (n = 10, P < 0.01). The slow time constant of INa recovery was also increased by acidification. These findings suggest that disopyramide molecules can escape from the receptor site through the hydrophobic pathway after deprotonation, because slowing of recovery from use-dependent block by acidification is caused by a decreased deprotonation rate of receptor-bound drug molecules. In addition to the hydrophobic escape, the roles of the fast inactivation gate and activation gate (m-gate) were evaluated during the recovery process. After inhibition of the fast inactivation process of INa by pretreatment with chloramine-T (2 mM), the fast phase of recovery from use-dependent block by disopyramide was abolished.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1995

Increased procoagulant and antifibrinolytic activities in the lungs with idiopathic pulmonary fibrosis.

To elucidate the pathophysiology of idiopathic pulmonary fibrosis (IPF), we examined procoagulant (tissue factor:TF), fibrinolytic (tissue type plasminogen activator:t-PA and urokinase type plasminogen activator:u-PA) and antifibrinolytic (plasminogen activator inhibitor-1:PAI-1 and PAI-2) activities in bronchoalveolar lavage (BAL) supernatant fluids and BAL cell lysates obtained from IPF patients. The results indicated that TF levels in BAL supernatant fluids from IPF patients were higher than those of normal subjects, especially in patients with progressive disease, suggesting that TF levels in the lung correlate with disease activity. PAI-1 levels in BAL supernatant fluids were significantly higher in IPF patients than in normal subjects (1.7 +/- 4.1 vs 0 ng/mg protein). PAI-2 levels in BAL cell lysates were also significantly higher in IPF patients than those in normal subjects (14.4 +/- 12.2 vs 3.0 +/- 3.0 ng/mg protein). However, u-PA levels in both BAL supernatant fluids and BAL cell lysates did not differ between the two groups. These observations suggest that u-PA inhibition exceeded u-PA activity in alveolar lining fluid resulting in an antifibrinolytic condition. Immunohistochemical analysis showed that TF was intensely stained in cuboidal epithelial cells and PAIs were positively stained in alveolar macrophages (AMs) and cuboidal epithelial cells, suggesting that cuboidal epithelial cells as well as AMs contribute to the increased procoagulant and antifibrinolytic activities in the lungs of IPF patients.

Aged↗
PubMed1995

Direct measurements of endothelium-derived nitric oxide release by stimulation of endothelin receptors in rat kidney and its alteration in salt-induced hypertension.

BACKGROUND: Stimulation of endothelin subtype B (ETB) receptors has been proposed to induce release of endothelium-derived nitric oxide (EDNO). METHODS AND RESULTS: To obtain direct evidence of its release and its alteration in deoxycorticosterone acetate (DOCA)-salt hypertension, EDNO released from renal vessels by ET stimulation was assayed by a highly sensitive chemiluminescence method. Kidneys were isolated from DOCA-salt and control rats, and renal perfusion pressure (RPP) and EDNO (by hydrogen peroxide-luminol chemiluminescence) in the perfusate were monitored simultaneously during perfusion of ET-1, ET-3, an ETA receptor antagonist (BQ-123), and an ETB receptor agonist (BQ-3020). In control rats, ET-1 and ET-3 dose-dependently increased both RPP and NO release. Although the vasoconstricting effects of ET-1 were greater, their NO-releasing effects were comparable. The increase in NO release by ETs was inhibited by NG-monomethyl-L-arginine. After 10(-6) mol/L BQ-123 treatment, ET-1 decreased RPP and increased NO release in control kidneys. DOCA-salt rats responded to these agents with much less NO release. BQ-3020 at up to 10(-10) mol/L caused vasodilation (RPP, 10(-11) mol/L, -5.4 +/- 1.7%, P < .01) associated with increased NO release in control kidneys (+9.0 +/- 2.7 fmol.min-1.g-1 kidney wt, P < .01). However, in DOCA-salt kidneys, BQ-3020 caused renal vasoconstriction (RPP, +5.4 +/- 2.4%, P < .01 versus control) and a much smaller NO release (+1.1 +/- 0.4 fmol.min-1.g-1 kidney wt, P < .01 versus control). Northern blot analysis revealed that renal ETB mRNA was significantly decreased in DOCA-salt rat kidneys compared with controls (0.36 +/- 0.13 versus 1.00 +/- 0.23, P < .05). CONCLUSIONS: These results suggest that ET-1 and ET-3 release EDNO via ETB receptors in renal vessels. ETB-mediated NO release was reduced in DOCA-salt rats, which may modulate renal function and thus blood pressure regulation in DOCA-salt hypertensive rats.

Animals↗
PubMed1995

Generation and elimination of 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate, a mutagenic substrate for DNA synthesis, in human cells.

8-Oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP) is a potent mutagenic substrate for DNA synthesis. The present study deals with generation and degradation of 8-oxo-dGTP in the nucleotide pool of human cells. (1) 8-Oxo-dGTP can be generated not only by direct oxidation of dGTP but also by phosphorylation of 8-oxo-dGDP by nucleoside diphosphate kinase. (2) 8-Oxo-dGTP is rapidly degraded to 8-oxo-dGMP by cellular 8-oxo-dGTPase activity. 8-Oxo-dGMP thus produced cannot be rephosphorylated; guanylate kinase, which phosphorylates both GMP and dGMP to the corresponding nucleoside diphosphates, is totally inactive for 8-oxo-dGMP. (3) 8-Oxo-dGMP is further degraded to 8-oxo-deoxyguanosine by a nucleotidase. The enzyme was partially purified from an extract of human Jurkat cells, and the mode of action was elucidated. 8-Oxo-dGMP is the most preferred substrate of the enzyme, and other nucleoside monophosphates are cleaved at significantly lower rates: Km for 8-oxo-dGMP is 10 times lower than that for dGMP, the second best substrate for the enzyme. The enzyme appears to convert 8-oxo-dGMP, which accumulates in the cellular nucleotide pool, to a form readily excretable to the cell exterior.

Cell-Free System↗
PubMed1995

Characterization of the acetylcholine-sensitive muscarinic K+ channel in isolated feline atrial and ventricular myocytes.

M2-cholinergic receptor activation by acetylcholine (ACh) is known to cause a negative inotropic and chronotropic action in atrial tissues. This effect is still controversial in ventricular tissues. The ACh-sensitive muscarinic K+ channel (IK(ACh)) activity was characterized in isolated feline atrial and ventricular myocytes using the patch-clamp technique. Bath application of ACh (1 microM) caused shortening of action potential duration without prior stimulation with catecholamines in atrial and ventricular myocytes. Resting membrane potential was slightly hyperpolarized in both tissues. These effects of ACh were greater in atrium than in ventricle. ACh increased whole-cell membrane current in atrial and ventricular myocytes. The current-voltage (I-V) relationship of the ACh-induced current in ventricle exhibited inward-rectification whose slope conductance was smaller than that in atrium. In single channel recording from cell-attached patches, IK(ACh) activity was observed when ACh was induced in the pipette solution in both tissues. The channel exhibited a slope conductance of 47 +/- 1 pS (mean +/- SD, n = 14) in atrium and 47 +/- 2 pS (n = 10) in ventricle (not different statistically; NS). The open times were distributed according to a single exponential function with mean open lifetime of 2.0 +/- 0.3 msec (n = 14) in atrium and 1.9 +/- 0.3 msec (n = 10) in ventricle (NS); these conductance and kinetic properties were similar between the two tissues. However, the relationship between the concentration of ACh and single channel activity showed a higher sensitivity to ACh in atrium (IC50 = 0.03 microM) than in ventricle (IC50 = 0.15 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗