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Biomedical subjects

J Araki

Publications and source records attributed to J Araki.

At least 55 records · Page 3Linked to original sources
PubMed1997

Mechanoenergetics of the negative inotropism of isoflurane in the canine left ventricle. No O2 wasting effect.

BACKGROUND: The mechanisms underlying the negative inotropic effects of isoflurane are incompletely understood. One suggested mechanism is that isoflurane may decrease Ca2+ sensitivity of contractile proteins. If so, more free calcium would be needed to activate contractile proteins to the same degree, which would impose a greater requirement for myocardial oxygen consumption used in the cycling of calcium. In this study, the authors use the excised, cross-circulated, canine heart model and the volume servopump technique to measure the effects of isoflurane on Emax (a contractile index) and on the relationship between pressure-volume area (PVA, a measure of total mechanical energy) and myocardial oxygen consumption per beat (VO2). METHODS: Effects of intracoronary isoflurane infused via a precoronary oxygenator on myocardial mechanoenergetics were studied during isovolumic contractions. The authors measured left ventricular (LV) pressure, LV volume, coronary flow, and arteriovenous oxygen content difference and computed Emax, VO2 and PVA at 0, 1.0, 1.5, and 2.0% isoflurane. From these data, the authors obtained oxygen costs of PVA and Emax in control subjects and in those receiving 2.0% isoflurane. RESULTS: Emax, PVA, and VO2 dose-dependently decreased by similar degrees (P < 0.05). Isoflurane did not change the oxygen costs at 1.5% and 2.0% concentration (P < 0.05). CONCLUSIONS: These mechanoenergetic findings suggest that the primary method by which isoflurane decreases contractility is not by decreasing Ca2+ sensitivity of contractile proteins but mainly by decreasing Ca2+ handling in the excitation-contraction coupling without myocardial oxygen wasting effect.

Anesthetics, Inhalation↗
PubMed1997

Effects of intracoronary fentanyl on left ventricular mechanoenergetics in the excised cross-circulated canine heart (revised publication).

BACKGROUND: It is still unclear whether fentanyl directly alters left ventricular (LV) contractility and oxygen consumption. This is because of the difficulty in defining and evaluating contractility and energy use independently of ventricular loading conditions and heart rate in beating whole hearts. METHODS: This study was conducted to clarify the mechanoenergetic effects of intracoronary fentanyl in six excised cross-circulated canine hearts. The authors used the framework of the Emax (a contractility index)-PVA (systolic pressure-volume area, a measure of total mechanical energy)-VO2 (myocardial oxygen consumption per beat) relationship practically independent of ventricular loading conditions. The authors measured LV pressure, volume, coronary flow, and arteriovenous oxygen content difference to calculate Emax, PVA, and VO2. They first obtained the VO2-PVA relationship for varied LV volumes at control Emax. The authors then obtained the VO2-PVA relationship at a constant LV volume, whereas coronary blood fentanyl concentration was increased in steps up to 240 ng/ml. Finally, they obtained the VO2-PVA relationship for varied LV volumes at the final dose of fentanyl. RESULTS: Fentanyl at any concentrations did not significantly change Emax, PVA, and VO2 from the control. The linear end-systolic pressure-volume relations and their slopes were virtually the same between the control and fentanyl volume loading in each heart. Further, either the slope (oxygen cost of PVA) or the VO2 intercept (unloaded VO2) of the linear VO2-PVA relationship remained unchanged by fentanyl. CONCLUSIONS: These results indicate that intracoronary fentanyl produces virtually no effects on LV mechanoenergetics for a wide range of its blood concentration.

Anesthetics, Intravenous↗
PubMed1997

Mechanism of constant contractile efficiency under cooling inotropy of myocardium: simulation.

We have reported that, in canine hearts, cardiac cooling to 29 degrees C enhanced left ventricular contractility but changed neither the contractile efficiency of cross-bridge (CB) cycling nor the excitation-contraction coupling energy. The mechanism of this intriguing energetics remained unknown. To get insights into this mechanism, we simulated myocardial cooling mechanoenergetics using basic Ca2+ and CB kinetics. We assumed that both adenosinetriphosphatase (ATPase)-dependent sarcoplasmic reticulum (SR) Ca2+ uptake and CB detachment decelerated with cooling. We also assumed that all the ATPase-independent SR Ca2+ release, Ca2+ binding to and dissociation from troponin, and CB attachment remained unchanged. The simulated cooling shifted the CB force-free Ca2+ concentration curve to a lower Ca2+ concentration, increasing the Ca2+ responsiveness of CB force generation, and increased the maximum Ca(2+)-activated force. The simulation most importantly showed that these cooling effects combined led to a constant contractile efficiency when Ca2+ uptake and CB detachment rate constants changed appropriately. This result seems to account for our experimentally observed constant contractile efficiency under cooling inotropy.

Adenosine Triphosphatases↗
PubMed1997

Hybrid logistic characterization of isometric twitch force-time curve of intact blood-perfused canine right ventricular papillary muscle.

We previously found that a ventricular isovolumic pressure-time curve could be well fitted by the difference between two S-shaped logistic curves for the pressure rising and falling components, and called it "hybrid logistic" function: P(t)=A/[1+exp[-(4B/A)(t-C)]]-D/[1+exp[-(4E/D)(t-F)]]+G. We reported that the parameters of this hybrid logistic function are useful to characterize left ventricular contraction and relaxation comprehensively. In this study, we investigated how well this hybrid logistic function could fit the isometric twitch force-time curves of cross-circulated right ventricular papillary muscles of 7 dogs. This function precisely fitted the isometric force curves with correlation coefficients above 0.9996, much better than another fitting function (F(t)=C(t/A)(B)exp[1-(t/A)(B)]) proposed by Nwasokwa. The present results indicate that our hybrid logistic function can also reasonably express the canine right ventricular papillary muscle isometric twitch force-time curve. We suggest the possibility that the parameters of this hybrid logistic function are also useful to comprehensively characterize right ventricular papillary muscle twitch contraction and relaxation.

Animals↗
PubMed1997

Ryanodine decreases internal Ca2+ recirculation fraction of the canine heart as studied by postextrasystolic transient alternans.

We tested our hypothesis that the O2 wasting of Ca2+ handling in the excitation-contraction (E-C) coupling in ryanodine-treated failing hearts could be reflected by a decrease in the internal Ca2+ recirculation fraction (RF). We have reported, using canine excised cross-circulated hearts, that intracoronary ryanodine (40 nmol/l blood) halved left ventricular contractility without decreasing myocardial O2 consumption for the E-C coupling. We previously suspected this mechanoenergetic state to manifest energy wasting of Ca2+ handling due to ryanodine causing leakage of Ca2+ from the sarcoplasmic reticulum. To test this hypothesis, we analyzed all the sporadic spontaneous cases of postextrasystolic potentiation (PESP) obtained during the ryanodine experiments. We calculated RF from the beat constant of the exponential decay component of not only the monotonic type but also the transient alternans type of PESP. Results showed that ryanodine significantly decreased the beat constant in both types of PESP from about 2 to 1.5 beats and hence RF from 0.6 to 0.5 on the average, supporting the hypothesis. This organ-level systems approach to Ca2+ handling using transient alternans PESP as well as monotonic PESP may help obtain better insights into the mechanoenergetics of failing hearts.

Animals↗
PubMed1996

Logistic character of myocardial twitch force curve: simulation.

We found that the isovolumic pressure-time curve of the canine left ventricle closely fitted the difference of two logistic function curves and that the isovolumic relaxation-pressure curve segment was more reliably characterized by a logistic time constant than by the conventional exponential time constant. We therefore hypothesized that the calcium (Ca) transient and the Ca-troponin (Tn) binding and crossbridge (CB) kinetics underlay the logistic character of the ventricular isovolumic pressure curve. We tested this hypothesis with a computer simulation of a simple Ca and CB kinetics model of myocardial isometric twitch force development. We assumed the instantaneous number of attached CBs that was theoretically given as the difference between the cumulative CB attachment and detachment curves. We radically changed the Ca transient, Ca-Tn binding, and CB kinetic parameters. We always found that both the cumulative CB attachment and detachment curves closely fitted logistic functions. The difference curve of these two best-fit logistic functions closely fitted the theoretical F curve with certain combinations of the Ca transient, the Ca-Tn binding, and the CB kinetic parameters. These results seem to support our hypothesis.

Animals↗
PubMed1996

Optimal schedule for administering granulocyte colony-stimulating factor in chemotherapy-induced neutropenia in non-small-cell lung cancer.

A prospective randomized study was conducted to determine the optimal schedule of rhG-CSF (recombinant human granulocyte colony-stimulating factor). A group of 33 lung cancer patients treated with MVP therapy (mitomycin, vindesine, and cisplatin) were randomly assigned to three groups: an early prophylaxis group in which rhG-CSF was initiated on day 2 of the MVP cycle; a late prophylaxis group in which rhG-CSF was initiated on day 8; and a therapeutic group in which rhG-CFS was initiated after the onset of neutropenia. Ten patients who had received MVP therapy without rhG-CSF were also analyzed as a no-support group. The incidence of neutropenia was 80% (16/20 courses) in the early prophylaxis group, 44% (8/18) in the late prophylaxis group, 94% (17/18) in the therapeutic group, and 94% (16/17) in the no-support group. The incidence of neutropenia in the late prophylaxis group was less than in the early prophylaxis group (P<0.05), the therapeutic group (P<0.01), and the no-support group (P<0.01). The late prophylactic rhG-CSF schedule was therefore more effective in countering neutropenia than either the early prophylactic or therapeutic schedule.

Aged↗
PubMed1996

[Invasive pulmonary aspergillosis caused by aspiration of polluted water after nearly drowning].

A 21-year-old male nearly drowned in a reservoir by a traffic accident and he aspirated a large mount of polluted water containing Aspergillus fumigatus. On admission to our hospital, he was alert but cyanotic. Chest rentogenograms showed scatter infiltrative shadows in bilateral lung fields. We administered methylpredonizolon and antimicrobial agents immediately because of respiratory failure which was rapidly progressing. During the following six days, infiltrative shadows diminished but multiple nodular shadows in both lung fields appeared. The diagnosis of pulmonary aspergillosis was confirmed by serological and microbiological studies. Intravenous amphotericin B and oral itraconazol were administrated, and clinical improvement was observed.

Adult↗
PubMed1996

[Two cases of pulmonary dirofilariasis in Nagasaki Prefecture].

We reported two cases of pulmonary dirofilariasis in Nagasaki Prefecture. Each case was admitted to our hospitals for evaluation of an abnormal shadow on chest X-ray film taken for examination. We strongly suspected lung cancer before operation. It was resected in order to confirm the pathological diagnosis. There was a Dirofilaria immitis in the vessels surrounded by the necrotic tissues. The case of pulmonary dirofilariasis tends to increase in Japan, but the positive rate of dogs with Dirofilaria immitis tends to decrease, because of decreasing breeding places of mosquitoes by the spread of the public sewage system in Nagasaki City.

Adult↗
PubMed1995

Logistic time constant of isovolumic relaxation pressure-time curve in the canine left ventricle. Better alternative to exponential time constant.

BACKGROUND: The time constant of left ventricular (LV) relaxation derived from a monoexponential model has been widely used as an index of LV relaxation rate or lusitropism, although this model has several well-recognized problems. In the present study, we proposed a logistic model and derived a "logistic" time constant (TL) as a better alternative to the conventional "exponential" time constant (TE). METHODS AND RESULTS: A total of 189 beats (147 isovolumic and 42 ejecting beats) were investigated in seven canine excised cross-circulated heart preparations. We found that the logistic model fitted much more precisely all the observed LV isovolumic relaxation pressure-time [P(t)] curves than the monoexponential model (P < .05). The logistic model also fitted well both the time curve of the first derivative of the observed P(t) (dP/dt) and the dP/dt-P(t) phase-plane curve. Like TE, TL indicated that volume loading depressed LV lusitropism and that increasing heart rate and ejection fraction augmented it. TL was independent of the choice of cutoff point defining the end of isovolumic relaxation; TE was dependent on that choice. CONCLUSIONS: We conclude that the logistic model better fits LV isovolumic relaxation P(t) than the monoexponential model in the present heart preparation. We therefore propose TL as a better alternative to TE for evaluating LV lusitropism.

Animals↗
PubMed1995

Suppression of myocardial mitochondrial respiratory function in acute failing hearts made by a short-term Ca2+ free, high Ca2+ coronary perfusion.

We made acute cardiac failure in excised cross-circulated canine hearts by a new coronary perfusion protocol consisting of Ca2+ free Tyrode perfusion for the first 10 min, high Ca2+ (16 mmol/l) Tyrode perfusion for the next 5 min, and normal Tyrode perfusion for the last 5 min interrupting blood cross circulation. After 50 min from the blood recirculation, left ventricular contractility was stably depressed to 60% of control. We studied mechanoenergetics of these acute failing hearts for the next 1-3 h. Then, we prepared mitochondria from these excised failing hearts and the support dogs' normal hearts to examine their mitochondrial respiratory function by the respiratory control index (RCI) and the oxygen consumption rate in state III (State III O2). RCI and State III O2 were significantly smaller in the failing hearts than in the normal hearts. However, sham protocol consisting of normal Tyrode coronary perfusion for 20 min did not affect RCI and State III O2. These results revealed that the mitochondrial respiratory function was moderately impaired in these acute failing hearts made by the new short-term Ca2+ intervention. However, no ultrastructural injuries of mitochondria were detected in these failing hearts.

Animals↗
PubMed1995

Familial risk factors for a second primary malignancy in endometrial or ovarian carcinoma.

OBJECTIVE: To elucidate the risk factor for a second primary carcinogenesis in endometrial or ovarian carcinoma patients. METHODS: Endometrial and ovarian carcinoma patients treated from 1975 through 1990 were analyzed clinicopathologically. RESULTS: The incidence of patients with a second primary malignancy was 10.5% (28/267) in endometrial carcinoma cases, and 9.0% (13/144) in ovarian carcinoma cases. Endometrial carcinoma patients whose parents, siblings, and/or children had developed malignant diseases were at risk for a second primary malignancy. This familial factor is also believed to be a risk factor for ovarian carcinoma patients, but the results lacked statistical significance. There also was no statistical significance with respect to smoking and/or alcohol consumption. More than one-half of the second primary carcinomas were breast, colon, or stomach carcinomas. CONCLUSIONS: Cancer patients with this familial high-risk factor should be carefully and regularly followed up by monitoring at every anatomic site, especially the breast, stomach, and colon, in order that the development of a second primary carcinoma can be detected as early as possible, and not be overlooked in examinations.

Endometrial Neoplasms↗
PubMed1995

Ca(2+)-free, high-Ca2+ coronary perfusion suppresses contractility and excitation-contraction coupling energy.

We studied the mechanoenergetic effects of a short-term Ca(2+)-free, high-Ca2+ Tyrode solution coronary perfusion in eight excised, cross-circulated canine hearts. The perfusion protocol consisted of coronary perfusion with Ca(2+)-free Tyrode solution for 10 min followed by high-Ca2+ (16 mM) Tyrode solution for 5 min. This new protocol successfully induced acute contractile failure in seven hearts, without myocardial ultrastructural changes. We studied the end-systolic pressure-volume relation (slope = Emax, a contractility index) and the relation between oxygen consumption per beat (VO2) and systolic pressure-volume area (PVA) in these failing hearts. These hearts had no increase in end-diastolic pressure at a given volume, a 40% decrease in Emax and a proportional decrease in the PVA-independent VO2 for 1-4 h, but no decrease in the oxygen cost of PVA, defined as the slope of the VO2-PVA relation. The oxygen cost of Emax for Ca2+ handling, defined as the slope of the relation between PVA-independent VO2 and Emax, was unchanged in the failing hearts. We conclude that the present protocol induced left ventricular contractile failure, primarily involving the suppression of Ca2+ handling energy for excitation-contraction coupling.

Animals↗
PubMed1995

Detection of Cryptococcus neoformans in bronchial lavage cytology: report of four cases.

Four cases of pulmonary cryptococcosis were diagnosed by cytological detection of Cryptococcus neoformans in bronchial lavage. Three patients had underlying diseases, but not HIV infection. The chest X-rays showed 2 patients with nodular lesions and 2 with cavitary lesions. The cryptococcal antigen in the serum was positive in all four patients. In the cytology of bronchial lavage, Cryptococcus neoformans was detected after period-acid-Schiff (PAS) staining and was cultured in Sabouraud-dextrose agar. The cytology of bronchial lavage is useful for the rapid diagnosis of pulmonary cryptococcosis.

Adult↗
PubMed1995

Logistic characterization of left ventricular isovolumic pressure-time curve.

Although some investigators have attempted to express the left ventricular pressure-time curve by mathematical functions such as exponential and sinusoidal functions, none of them reasonably fits the left ventricular pressure-time curve. In the present study, we hypothesized that a ventricular isovolumic pressure-time curve could be expressed as the difference between two S-shaped curves for pressure rising and falling, and proposed a new "hybrid logistic" function to express the left ventricular isovolumic pressure-time curve. We investigated how well this hybrid logistic function fits left ventricular isovolumic pressure curves experimentally observed under physiological preload and contractility in the excised cross-circulated left ventricles of 10 dogs. The new function precisely fitted the isovolumic pressure curves regardless of preload and contractility with correlation coefficients above 0.9996, much better than the previously proposed functions. The observed values characterizing the magnitude and time course of the isovolumic pressure curve such as peak +/- dP/dt also closely correlated with the corresponding theoretical values calculated by the present best-fit function. We conclude that our new hybrid logistic function reasonably characterizes the canine left ventricular isovolumic pressure-time curve within physiological ranges of preload and contractility. The present results indicate that this hybrid logistic function is useful to evaluate left ventricular contraction and relaxation comprehensively.

Animals↗