We analyzed the frequency distribution of the left ventricular (LV) mechanical efficiency of individual arrhythmic beats during electrically induced atrial fibrillation (AF) in normal canine hearts. This efficiency is the fraction of the external mechanical work (EW) in the total mechanical energy measured by the systolic pressure-volume area (PVA). The mean, median, and mode of this efficiency (EW/PVA) were as high as 78%, 80%, and 81%, respectively, on average in six hearts. These high efficiencies were comparable to that of the regular beats in these hearts. The frequency distribution of the EW/PVA during AF tended to skew to the higher side in all the hearts. Since the EW/PVA is directly related to both the ventriculo-arterial (or afterload) coupling ratio (E_a/E_max; E_a = effective arterial elastance, E_max = end-systolic ventricular elastance) and the ejection fraction on a per-beat basis, we also analyzed their frequency distributions. We found them to skew enough to account for the rightward skewed frequency distribution of the EW/PVA during AF with the unexpectedly high mean EW/PVA. These results indicate that the LV arrhythmia during AF per se does not directly suppress the mean level of LV mechanical efficiency in normal canine hearts.

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The purpose of this study was to determine the cardioprotective effects of the repetitive pretreatment of acupuncture in rats with myocardial ischemia and reperfusion (MIR). Experimental MIR was produced by ligating and reperfusing the left anterior descending coronary artery in the rats. The elevated ST segments of electrocardiogram (ECG), cardiac arrhythmias, and ratio of infarct size/risk zone were compared among the normal control (NC), ischemia and reperfusion (IR), electro-acupuncture (EA), electro-acupuncture plus propranolol (EAP), and EA at nonacupoint (EAN) groups. Before the experiment, EA was applied at bilateral Neiguan acupoints (PC6) in the forelimbs in EA and EAP groups for 30 min once a day for 3 consecutive days. In the EAN group, the same EA treatment was administered at bilateral nonacupoints in the hind limbs. In the EAP group, propranolol, a nonspecific antagonist of β-adrenoceptors, was administered intraperitoneally 15 min before each EA pretreatment. The results showed that the elevated ST segment of ECG, cardiac arrhythmia score, and ratio of infarct size/risk zone were significantly attenuated in the EA group when compared with those in the IR group (P < 0.05), indicating a cardioprotection of EA pretreatment. When propranolol was given before each EA pretreatment in the EAP group, the cardioprotective effect of EA pretreatment was abolished, showing an involvement of β-adrenoceptors in mediating the effect of EA pretreatment. There was no significant cardioprotective effect observed in the EAN group. The results suggest that pretreatment may be a better way to apply acupuncture in the prevention and treatment of coronary heart disease.

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This paper studies calcitonin (CT) transport across the C-cell–blood (CCB) barrier in normal rats. The efficiency of this transport is expressed as endogenous calcitonin bioavailability (F_CT), i.e., that portion of CT molecules extruded by the thyroid C-cell basal pole that enters the circulating blood. Because currently F_CT cannot be estimated directly, a novel methodology was used for its estimation. The essence of this methodology is to assess the CT level before and after the CCB barrier, to study these input-output CT relationships mathematically, and to find the F_CT range allowed by the relationships. In this context, the subplasmalemmal granule numerical density in the C-cell basal pole (X) and the CT concentration in the right ventricular blood (Y) were found to be highly correlated: r_xy = 0.922, P < 0.001; the covariance coefficient ρ_xy = 0.9980, P < 0.0001. Clearly, the overall variance of these input-output relationships in the covariance model (√(Var_xy) = 6.32) is explained, specifically, by CT retention (R_CT) variability at the CCB transport stages. The greater the R_CT mean value in the studied rats, the greater is the impact of R_CT variability on Var_xy. The estimated variance caused by R_CT (Var_CCBR) makes it possible to determine R_CT and F_CT (F_CT = 100% − R_CT). Thus we estimated Var_CCBR as Var_CCBR < Var_xy − CV_RIA², where CV_RIA² is CT assay variance: √(Var_CCBR) = 6.00% (P ≥ 0.95). We then estimated F_CT as the value range that does not contradict the Var_CCBR obtained: 62% < F_CT < 100% (P ≥ 0.95).

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Histaminergic neurons in the hypothalamus are well documented as being involved in the control of autonomic functions, such as the balance of energy metabolism and circadian rhythm. We tested the hypothesis that an activation of the histamine type-1 (H1) receptor is required for the control of ventilation during the course of a day in free-moving mice. Ventilation, aerobic metabolism, and electroencephalogram were measured by a whole-body-plethysmograph, a magnetic-type mass spectrometry system, and a telemetry system, respectively, in H1 receptor-knockout (H1RKO) and wild-type mice. Both genotypes showed daily oscillations in minute ventilation (V_E) and oxygen consumption (Vo₂), with greater values during the dark period compared to the light period. In the latter, H1RKO mice showed increased V_E and CO₂ excretion (Vco₂) relative to wild-type mice, and V_E was comparable to the Vco₂ increase. However, there was no change in Vo₂ in H1RKO mice, suggesting that differences in Vco₂ between genotypes are responsible for differences in V_E during the light period. During the dark period, Vco₂ was elevated in H1RKO mice compared with WT mice. Because there was no difference in V_E, the ratio of V_E to Vco₂ was reduced in H1RKO mice. Electroencephalogram results suggested that this might be due to a depressed arousal state in H1RKO mice because the ratio of delta to theta band power spectrum densities was greater in H1RKO mice than in wild-type mice. We concluded that histamine modulates ventilation by affecting metabolism and arousal state via H1 receptors.

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Alpha₁-adrenoceptor stimulation (α₁ARS) shows a positive inotropic effect in most mammalian myocardium. In mouse myocardium, however, α₁ARS showed the negative inotropic effect, of which intracellular mechanisms are not fully clarified. The purpose of this study is to investigate the intracellular mechanism of the negative inotropic effect by α₁ARS in C57BL/6 mouse myocardium. We used isolated ventricular papillary muscles of C57BL/6 strain mouse which is widely used for genetic manipulation. We simultaneously measured isometric tension and intracellular Ca²⁺ concentration ([Ca²⁺]_i) using the aequorin method. In twitch contraction, phenylephrine concentration-dependently (1–100 μM) decreased tension without significant changes in the Ca²⁺ transient, and these effects were completely blocked by prazosin (3 μM) or calphostin C (a PKC inhibitor, 1 μM). Phorbol 12-myristate 13-acetate (PMA) (a PKC activator, 1 μM) decreased tension as observed in phenylephrine. After PMA application, the negative inotropic effect of phenylephrine disappeared. To estimate the Ca²⁺ sensitivity, tetanic contraction was produced, and the relation between [Ca²⁺]_i and tension at a steady state was measured. Phenylephrine (10 μM) decreased the Ca²⁺ sensitivity, and PMA showed a similar Ca²⁺ desensitizing effect. These results suggest that the negative inotropic effect of phenylephrine in mouse myocardium can be explained by the decrease in the Ca²⁺ sensitivity through the activation of PKC. The present result indicates that the effect of α₁ARS differs among species and strains of experiment animals. Thus, we should be careful about using the results of mouse myocardium to understand the functions of the human heart.

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The purpose of this study was to characterize the effects of prior swim exercise on glucose uptake in isolated skeletal muscles of mice. Male and female mice (C57BL/6) performing 180 min of swimming had significantly decreased glycogen concentration compared to resting controls in soleus, extensor digitorum longus (EDL), and epitrochlearis muscles, regardless of gender. Glucose uptake by isolated muscles was measured using [³H]-2-deoxyglucose without insulin or with 180 pmol/l insulin (20, 75, or 200 min post-exercise and sedentary) or 12,000 pmol/l (20 or 200 min post-exercise and sedentary) in the soleus and EDL and without insulin or with 12,000 pmol/l insulin (20 or 200 min post-exercise and sedentary) in the epitrochlearis. Glucose uptake was higher (P ≤ 0.01) for female versus male mice at each insulin concentration in the soleus and EDL, but not the epitrochlearis. Although prolonged (180 min) swim exercise did not alter subsequent glucose uptake, a shorter duration exercise protocol (60 min) tested in male mice (20 min post-exercise) led to a 1.5-fold increase in insulin-independent glucose uptake in EDL muscles. However, insulin-stimulated (180 pmol/l) glucose uptake was not altered by 60 min exercise in EDL or soleus. In light of these results, swim exercise is not recommended to evaluate the exercise-induced improvement in insulin-stimulated glucose uptake of muscles of C57BL/6 mice.

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A power spectrum density (PSD) analysis was performed on electroencephalograms (EEG) of sleeping epileptic El mice and non-epileptic ddY mice. A respiratory peak at 3.13 Hz was detected in the EEGs of both categories. The PSD analysis revealed a peak at 8.59 Hz in the El mice, which was associated with interictal discharges. This peak may be helpful in diagnosing epilepsy.

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GV01 is one of the most effective acupoints to treat diarrhea in humans and animals. The present study showed that skin on the GV01 acupoint reveals tenderness and neurogenic inflammation in colonic inflammatory states, but not in normal healthy states.

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Six subjects performed two trials of incremental cycling to exhaustion under normoxic and hypoxic conditions. The lactate threshold and onset of muscle deoxygenation were highly correlated under both conditions, and during the hypoxic condition both variables shifted leftward.

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