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Biomedical subjects

J Araki

Publications and source records attributed to J Araki.

At least 73 records · Page 4Linked to original sources
PubMed1995

Sinusoidal and exponential decays of postextrasystolic transient alternans in excised blood-perfused canine hearts.

We have recently reported that the postextrasystolic contractile potentiation decays in alternans after a compensatory pause in canine left ventricles even under normal coronary and contractile conditions. The transient alternans appears to consist primarily of a small-magnitude exponential decay and a large-magnitude sinusoidal decay. We, therefore, hypothesized that the contractility (y) of the postextrasystolic alternans beats (beat number x) could be expressed as y = a x exp[-(x-1)/b] + c x exp[-(x-1)/d] x sin[pi(x-0.5)] + yo, where a and c are the normalized magnitudes (relative to the preceding regular beat) of the two exponential terms in the first postextrasystolic beat, b and d are their time constants, and yo is the normalized magnitude of the post-alternans regular beat (approximately 1). The first exponential term represents the monotonic decay. The sine term multiplied by the second exponential term represents the alternating decay. Mathematical curve-fitting indicated: 1) the above equation very closely fitted the alternans data with a squared correlation coefficient of 0.9996 on average, 2) c was 7 times on average greater than a, indicating dominance of the sine component, 3) b and d were 2.5 and 1.0 beats on average, indicating a faster decay of the sine component, and 4) this b was comparable to the time constant of the exponential decay of the postextrasystolic potentiation after no compensatory pause. This study suggests that myocardium has a mechanism to switch the postextrasystolic potentiation between the exponential and alternans decays depending on the first postextrasystolic interval.

Animals↗
PubMed1994

Postextrasystolic transient contractile alternans in canine hearts.

We found that postextrasystolic potentiated contractility after a spontaneous extrasystole most frequently decayed as a transient alternans over several beats in excised, cross-circulated, atrially paced canine hearts. This type of heart preparation; which we have been using consistently in mechanoenergetic studies, had normal coronary blood perfusion pressure as well as flow and mechanoenergetic performance. Spontaneous atrial and ventricular extrasystoles occurred occasionally in every heart. Arrhythmic changes in left ventricular (LV) pressure at a fixed volume reflected corresponding changes in contractility. We analyzed nearly 3,600 cases of postextrasystolic potentiation in 68 hearts; 84% decayed as transient alternans, 6% decayed exponentially, and 10% belonged to neither type. We found that a postextrasystolic compensatory pause always preceded the transient alternans after either an atrial or ventricular extrasystole at any constant atrial pacing rate (85-188 beats/min). The decay was either exponential or nonalternating when the pause did not exist after an atrial extrasystole during occasional pacing failure. Therefore, the compensatory pause after either an atrial or ventricular extrasystole seems essential for the postextrasystolic transient alternans of LV contractility in the type of canine heart preparation we have been using.

Animals↗
PubMed1994

Energetics of the negative and positive inotropism of pentobarbitone sodium in the canine left ventricle.

OBJECTIVE: Pentobarbitone (sodium) is an anaesthetic widely used in animal experiments. It is known to be a cardiovascular depressant and a coronary dilator, but its effects on myocardial energetics in relation to its negative and positive (due to Gregg's phenomenon) inotropism have not been studied. The aim of this study was therefore to determine whether and how pentobarbitone affects cardiac mechanoenergetics compared with other negative inotropic agents for which data are already available. METHODS: The effects of graded doses of intracoronary pentobarbitone on mechanoenergetics were studied in the excised cross circulated left ventricles of 12 dogs. The framework of the Emax (a contractility index)--VO2 (myocardial oxygen consumption)--PVA (systolic pressure-volume area, a measure of total mechanical energy) relationships was fully utilised. RESULTS: Pentobarbitone increased Emax at low doses in five of the 12 hearts. In two of these five hearts, a marked coronary dilatation was found. Pentobarbitone decreased Emax dose dependently at high doses in all the hearts and lowered the VO2 intercept but not the slope (oxygen cost of PVA) of the VO2-PVA relation. There was no difference in oxygen cost of Emax between pentobarbitone and CaCl2, although they have opposite inotropism. These findings suggest that pentobarbitone depresses myocardial mechanoenergetics via suppression of total calcium handling in the excitation-contraction-relaxation coupling. CONCLUSIONS: Pentobarbitone at low doses partly acts as a positive inotropic agent, but at high doses it acts as a negative inotropic agent like beta blockers and calcium antagonists on cardiac mechanoenergetics in canine blood perfused hearts.

Animals↗
PubMed1994

[A case of MRSA sepsis treated by the sequential combination therapy netilmycin and minocycline].

A sixteen year old female was feverish from June 12, 1993. Methicillin-resistant Staphylococcus aureus was isolated from the blood, the diagnosis of MRSA sepsis was established. Vancomycin (2 g/day) was administered for eighteen days, but MRSA was not eradicated in the blood culture. Then she was administered a combination therapy of arbekacin (200 mg/day) and imipenem/cilastain (1 g/day) for seven days, but MRSA in the blood was cultured continuously. The sequential combination therapy of netilmycin (200 mg/day) and minocycline (200 mg/day) was started, MRSA was eradicated from the blood culture after four days. The sequential combination therapy netilmycin and minocycline was seemed to be effective for MRSA infection.

Adolescent↗
PubMed1994

[A case of brain abscess associated with enterococcal endocarditis].

Enterococcal infections involving the central nervous system are uncommon clinical entities. A 74-year-old male was admitted to our hospital on November 3, 1991 for high fever. Nuchal rigidity was observed at neurological examination. All four blood cultures yielded E. faecalis. The MIC value of ABPC against the isolated E. faecalis was 0.25 microgram/ml. Vegetation on the mitral valve and mitral regurgitation were revealed by an echocardiogram. Enhanced CT scan showed low density area with ring enhancement in the right basal ganglia and a CSF examination suggested bacterial meningitis. He became better after ABPC 8 g/day was intravenously administered. Then the vegetation on the mitral valve and the brain abscess disappeared. He was discharged with no complications. We reported a rare case of brain abscess associated with enterococcal endocarditis.

Aged↗
PubMed1994

[A comparison of pathohistological findings of transbronchial lung biopsy specimens between Mycobacterium tuberculosis and mycobacteria other than Mycobacterium tuberculosis infections].

The pathohistological findings of transbronchial lung biopsy (TBLB) were compared between Mycobacterium tuberculosis infection (group A) and Mycobacteria other than Mycobacterium tuberculosis (MOTT) infections (group B). The number of positive pathological findings in TBLB were 14 (70%) in group A and 2 (16%) in group B, respectively. Eleven cases (55%) in group A were positive for acid-fast bacilli in TBLB by Ziehl-Neelsen stain, and 3 cases of group A showed granulomatous lesion in TBLB. In pathohistological findings of group B, 2 cases (16%) were granulomatous lesion, 4 cases (33%) were fibrosis, and 3 cases (25%) were inflammatory changes. The pathohistological examination of TBLB was more useful for the diagnosis of pulmonary tuberculosis than for MOTT infection.

Adult↗
PubMed1994

[An autopsy case of urinary bladder carcinoma with pulmonary infarction and subacute cor pulmonale caused by tumor embolization].

Pulmonary tumor embolism is a common finding at autopsy but is difficult to diagnose clinically antemortem. We report an autopsy case of urinary bladder carcinoma associated with tumor emboli of the pulmonary arteries and subsequent pulmonary infarctions. An eighty-six-year-old man with bloody sputum showed multiple infiltrates on chest X-ray and multiple pleural based parenchymal lesions with truncated apex on computed tomography. The patient had a history of radiation therapy against urinary bladder carcinoma two years earlier. Transitional type carcinoma cells were identified from a urine sample obtained on admission. Three weeks later, the patient developed subacute cor pulmonale and died in severe respiratory distress. Postmortem examination revealed primary carcinoma of the urinary bladder. Multiple tumor emboli of pulmonary arteries and subsequent pulmonary infarctions were visible microscopically. There was a large amount of effusion in both the pleural and the abdominal space. The heart contained focal scarring and mild right ventricular hypertrophy and there was congestion of the lungs, liver, kidneys and spleen. Pulmonary tumor embolization may present at any stage of the patient's illness but rarely causes subsequent pulmonary infarctions. Cytologic examination of blood samples obtained from Swan-Ganz catheters may be useful in the diagnosis of tumor embolization.

Aged↗
PubMed1993

Ca2+ sensitivity of contractile machinery and Ca2+ handling energy. Simulation.

Myocardial Ca2+ handling during excitation-contraction coupling has been modelled mathematically to gain a better insight into the expectation that Ca2+ sensitization of contractile machinery may save myocardial energy utilization for Ca2+ handling. The basic model of myocardial Ca2+ kinetics and mechanoenergetics involved the sarcoplasmic reticulum (SR), sarcoplasm, troponin C (Tn) and crossbridges (CB). The relations among the released Ca2+ ions from the SR, peak concentrations of sarcoplasmic free Ca2+ ([Ca2+]i) and Ca(2+)-bound troponin ([TnCa]) and peak contractile force were computed, based upon the assumptions that the released Ca2+ ions diffuse as free Ca2+ in sarcoplasm, bind kinetically with Tn with an association rate constant of k1, dissociate from TnCa with a dissociation rate constant of k2, and are sequestered into the SR with consumption of ATP. TnCa was associated with CB cycling to develop force with a set of given on and off rate constants. The association constant Ka (= k1/k2) of TnCa as an index of Ca2+ sensitivity of Tn was varied 32-fold from 0.25 to 8/microM. Results showed that Ca2+ sensitization from a lower Ka level could most sharply decrease the total Ca2+ release required to develop the same contractile force. Thus, it would reduce the total Ca2+ handling energy that the SR uses to maintain the same contractility.

Calcium↗
PubMed1993

Nipradilol depresses cardiac contractility and O2 consumption without decreasing coronary resistance in dogs.

Nipradilol (3,4-dihydro-8-(2-hydroxy-3-isopropylamino) propoxy-3-nitroxy-2H-1-benzopyran) is a newly synthesized chemical agent designed to possess beta-adrenoceptor blocking and vasodilating actions. Nipradilol decreased left ventricular contractility index (Emax, slope of the ventricular end-systolic pressure-volume relation), systolic pressure-volume area (PVA, a measure of ventricular total mechanical energy) and oxygen consumption in cross-circulated excised dog hearts. However, nipradilol did not decrease total coronary resistance. These results indicate that nipradilol, like propranolol, depresses myocardial mechanoenergetics and that the vasodilating action of nipradilol could not be detected in the present study.

Adrenergic beta-Antagonists↗
PubMed1993

Left ventricular ORS widening decreases Emax without lowering VO2-PVA relation in dog hearts.

We observed a few rare spontaneous cases of a suddenly widened QRS wave of left ventricular ECG associated with a simultaneous decrease in left ventricular (LV) contractility (Emax, end-systolic pressure-volume ratio) in excised cross-circulated dog heart experiments. The decreased Emax was not associated with a descent of the relation between cardiac oxygen consumption (VO2) and LV systolic pressure-volume area (PVA, a measure of total ventricular mechanical energy). This result is intriguing because ventricular VO2-PVA relation generally changes its elevation in proportion to Emax under various inotropic interventions. We suspected the unusual observation to reflect no change in myocardial contractility despite ventricular asynchrony augmented by an intraventricular conduction defect.

Animals↗
PubMed1993

[Physiology of cardiac performance].

We previously proposed i) Emax (end-systolic maximum elastance of the ventricle) as an index of contractility independent of preload and afterload and ii) PVA (systolic pressure-volume area of the ventricle) as a measure of the total mechanical energy generated by the ventricular contraction. Emax is defined as the slope of the end-systolic pressure-volume relation, which is relatively linear within the normal working range of the left ventricle. A working pressure-volume point starts from the end-diastolic pressure-volume curve, comes close to or slightly exceeds the end-systolic pressure-volume line, and returns to the end-diastolic curve. Thus, the end-diastolic and end-systolic pressure-volume curves envelop a family of pressure-volume trajectories of variously loaded contractions in a stable contractility. Emax increases with enhanced contractility and decreases with depressed contractility. PVA is an area between the end-diastolic and end-systolic pressure-volume curves on the origin side of the systolic pressure-volume trajectory. PVA linearly correlates with myocardial oxygen consumption regardless of ventricular loading conditions in a given Emax and this load-independent oxygen consumption-PVA relation is elevated with an enhanced Emax. Consequently, Emax and PVA have proved to be key measures and concepts in the physiology of cardiac performance.

Echocardiography↗
PubMed1992

Metabolic activation of lidocaine and covalent binding to rat liver microsomal protein.

Incubation of [14C]lidocaine with rat liver microsomes in the presence of an NADPH-generating system resulted in covalent bindings of a 14C-labelled material to microsomal protein. The covalent binding of radioactivity needed NADPH and atmospheric oxygen, and was diminished by purging of carbon monoxide and the addition of SKF-525A. Hence the covalent binding of a 14C-labelled material resulting from a reactive metabolite of lidocaine formed by cytochrome P450-dependent monooxygenation. The covalent binding measured at various concentrations of lidocaine (2.5-30 microM) followed Michaelis-Menten kinetics, and the Km value (4.52 microM) of the activation reaction was close to the Km value (1.78 microM) of lidocaine 3-hydroxylation. The metabolism-dependent covalent binding of lidocaine to microsomal protein as well as lidocaine 3-hydroxylase activity was much lower in the Dark Agouti strain rat, which is known as a poor-metabolizer animal model of debrisoquine 4-hydroxylation, than in the Wistar rat for the corresponding sexes. The covalent binding in male rats was greater than that in females of both strains, but the extent of the sex difference in the binding was smaller than that of the lidocaine N-deethylase activity in Wistar rats. Propranolol and quinidine, specific inhibitors of debrisoquine 4-hydroxylase, markedly inhibited lidocaine 3-hydroxylase activity of Wistar male rats, but not N-deethylase activity. These compounds also inhibited the metabolism-dependent covalent binding of lidocaine to microsomal protein. These strain difference and inhibition studies showed that the reaction converting lidocaine to a reactive metabolite capable of binding covalently to microsomal protein was related to lidocaine 3-hydroxylation, and may be catalysed by cytochrome P450 isozyme(s) belonging to the CYP2D subfamily. The covalent binding of radioactivity to rat liver microsomal protein was diminished by nucleophiles, reduced glutathione and cysteine, indicating that the reactive metabolic intermediate of lidocaine is an electrophilic metabolite such as an arene oxide.

Animals↗
PubMed1992

[A case of mediastinitis and bilateral pyothorax, following acute epiglottitis with concurrent Aspergillus infection].

Life threatening mediastinitis as a complication of acute epiglottitis is very rare. A 38-year-old male in previously good health was admitted to our hospital in a state of unconsciousness. Seven days prior to admission he had complained of a sore throat, dysphagia, high fever and dyspnea. A chest X-ray on admission showed widening of the mediastinum, mediastinal emphysema, subcutaneous emphysema and left pleural effusion. Bronchoscopy showed the swelling of supraglottic structures. He was diagnosed as having acute mediastinitis and pyothorax as a complication of acute epiglottitis, but pathogens were not identified. The blood was hyperglycemic and insulin therapy was started. Though he gradually improved by massive antibiotic therapy, steroid therapy, tracheotomy and surgical drainage of both the left thoracic cavity and the mediastinum, he died suddenly of massive hemoptysis. Autopsy revealed that the acute mediastinitis had healed, but that the Aspergillus infection was present in both lungs and the pericardium. The Aspergillus infection was not lethal in the present case, and it seemed that death had resulted from arterial hemorrhage caused by erosion of the trachea. The present case suggests the need for antifungal therapy even in non-immunocompromised patients in particular when massive doses of antibiotics and steroids are administered.

Acute Disease↗
PubMed1992

Prevalence of HTLV-I antibody in pulmonary cryptococcosis.

A retrospective study was done to determine the prevalence of anti-HTLV-I antibodies in patients with pulmonary cryptococcosis. None of the 19 patients with pulmonary cryptococcosis had underlying immunodeficiency. Anti-HTLV-I antibody was present in 6 (32%) of 19 patients with pulmonary cryptococcosis, a significantly higher prevalence than found in patients with bronchial asthma (4 (7%) of 58) (p less than 0.01, chi-square test). No statistical difference was noted when anti-HTLV-I antibody seropositivity was compared to that of patients with pulmonary tuberculosis (16% (17/105)), lung cancer (17% (22/129)) and pneumonia (9% (6/64)). A reduced cellular immunity as shown by lymphopenia, the CD4/CD8 ratio, and purified protein derivative skin test was found in only 1 (5%) of 19, 2 (12%) of 17, and 6 (33%) of 18 patients, respectively. These results do not explain the susceptibility to pulmonary cryptococcosis in HTLV-I carriers. This is the first report of high prevalence of pulmonary cryptococcosis in HTLV-I carriers and it raises the question whether HTLV-I carriers are more susceptible to opportunistic infections and other malignancies probably due to subtle immunological abnormalities.

Adolescent↗
PubMed1992

[Nd-YAG laser treatment for central airway lesions].

YAG laser treatment was conducted in 55 patients with central airway lesions over the last 8 years. The malignant lesions comprised 1 primary tracheal cancer, 1 chondroma of the trachea, 34 primary lung cancer, and 10 metastatic lung tumor. The benign lesions comprised one each of hamartoma, lipoma, bronchial lithiasis, post-tracheotomy granuloma, and bronchial web, and 3 other cases. Nd-YAG laser treatment was performed in 55 patients with airway lesions, with a success rate of 73%. The success rates in the above patients were 70% for primary lung cancer, 60% for metastatic lung tumor, 100% for primary tracheal cancer and chondroma of trachea, and 89% for benign lesions. In 34 patients with primary lung cancer, palliative widening of the airway was planned with the exception of 2 patients with endoscopically early lung cancer for whom curative vaporization was intended, 6 months-survival rate was 59.3% in patients in whom various combined treatments were performed after the laser treatment. For all patients with hamartoma or lipoma in those with benign lesions, curative vaporization was performed. The severe complication of lethal massive hemoptysis occurred in 3 patients. We consider that Nd-YAG laser treatment is a powerful therapeutic means of performing lifesaving or emergency, curative, and supplemental treatment.

Adult↗
PubMed1992

[A case of interstitial pneumonitis with hemoptysis, BOOP (bronchiolitis obliterans organizing pneumonia) pattern, granulomas and foreign body giant cells in lung biopsy].

A 66-year-old male presented to our hospital in January 1990 with chief complaints of hemoptysis and cough. These symptoms had developed 10 months previously and had gradually increased. Fine crepitations were audible over the right lower lung field. There were no results suggesting an inflammatory process such as leucocytosis, elevation of ESR or positive CRP reaction. Chest X-ray film on the first visit showed fine nodular shadows in the right lower lung field, and chest CT revealed fine nodular shadows and mild dilatation of the right lower lobe bronchus. Transbronchial lung biopsy specimens showed granulomas with multinucleated giant cells, alveolitis and Masson bodies. The open lung biopsy specimens showed numerous macrophages and foreign body giant cells, and extensive organizing exudates in the bronchioles and alveolar spaces. Proliferation of smooth muscle and fibrosis around the dilated bronchioles were also seen. Thus, this patient demonstrated BOOP pattern, with granulomas and foreign body giant cells. His hemoptysis appeared to have resulted from inflammation of dilated bronchioles. His symptoms and abnormal shadows on chest X-ray improved without any therapy after admission. After treatment with corticosteroid, the diffuse fine nodular shadows disappeared. There has been no recurrence of symptoms to date, although this patient has continued living in the same environment as prior to admission. BAL findings during his prolonged follow-up revealed decrease in lymphocytes and elevation of CD4/CD8 ratio. Although the presence of granulomas suggests the possibility of an allergic reaction, no antigenic material could be identified in this case.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗