Single heart cells of mouse models provide powerful tools for heart research. However, their isolation is not easy, and it imposes a significant bottleneck on their use in cellular studies of the heart. Aiming to overcome this problem, this report introduces a novel technique that reproducibly isolates healthy heart cells from mouse models. Using simple devices that ensure easy handling and the rapid aortic cannulation of a small mouse heart, cell isolation was done under physiological conditions without using the “KB” medium or 2,3-butanedione monoxime (BDM). The isolated cells consistently had a healthy appearance and a high viability of 75 ± 5% (mean ± SD) in Tyrode solution containing 1.8 mM Ca²⁺. After 8 h of storage at 37°C, they still had a viability of 45 ± 12%. The cells showed normal contraction properties when field-stimulated, and they generated normal action potentials and membrane currents under the whole-cell clamp condition. The β-adrenergic signal transduction of the cells was also normal when it was examined with the isoproterenol enhancement of the L-type Ca²⁺ current.

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Normoxic hypercapnia may increase high-frequency (HF) power in heart rate variability (HRV) and also increase respiratory sinus arrhythmia (RSA). Low-frequency (LF) power may remain unchanged. In this study, 5-min ECG recordings (N = 10) were analyzed in time and frequency domains while human subjects breathed normoxic 5% CO₂ (5%CO₂) or room air (RA). Tidal volume (V_T), inhalatory (T_I), and exhalatory (T_E) times of breaths in the final minute were measured. ECG time domain measures were unaffected by CO₂ inhalation (P > 0.05). Following natural logarithmic transformation (LN), LF_LN was unaltered (RA: 7.14 ± 0.95 vs. 5%CO₂: 7.35 ± 1.12, P > 0.05), and HF_LN increased (RA: 7.65 ± 1.37 vs. 5%CO₂: 8.58 ± 1.11, P < 0.05) with CO₂ inhalation. When changes in total power (NU) were corrected, LF_NU decreased (RA: 34.4 ± 22.9 vs. 5%CO₂: 23.8 ± 23.1, P < 0.01), and HF_NU increased (RA: 56.5 ± 22.3 vs. 5%CO₂: 66.8 ± 22.9, P < 0.01) with CO₂ inhalation. T_I (RA: 2.0 ± 1.0 vs. 5%CO₂: 1.9 ± 0.8 s) and T_E (RA: 2.5 ± 1.1 vs. 5%CO₂: 2.4 ± 0.9 s) remained unchanged, but V_T increased with CO₂ inhalation (RA: 1.1 ± 0.3 vs. 5%CO₂: 2.0 ± 0.8 L, P < 0.001). Heart rates during inhalation (RA: 35.2 ± 4.4, 5%CO₂: 34.5 ± 4.8 beats min⁻¹) were different from heart rates during exhalation (RA: 28.8 ± 4.4, 5%CO₂: 29.1 ± 3.1 beats min⁻¹). Hypercapnia did not increase the clustering of heart beats during inhalation, and we suggest that the HF component may not adequately reflect RSA.

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The aim of this study was to ascertain the influence of cysteine derivatives on pro-antioxidant equilibrium and to compare the antioxidant effectiveness of N-acetylcysteine, α-lipoic acid, and taurine by using Loverro’s coefficient (pro-antioxidant ratio) in healthy men exposed to intensity-resistance exercise. Fifty-five men were randomly assigned to one of four groups: control (CON, placebo), N-acetylcysteine (NAC 1.8 g·day⁻¹, 3 days), α-lipoic acid (LIP 1.2 g·day⁻¹, 3 days), or taurine (TAU 3 g·day⁻¹, 3 days). The erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities, lipid peroxidation products (TBARS), and plasma protein thiol concentrations were evaluated. The P/A ratio was determined from the mean values of TBARS, SOD, GPx, and CAT. The applied exercise at maximal intensity induced the significant changes in pro-antioxidant equilibrium toward peroxidation, which was proved by a 25% increase in TBARS concentration in the CON group. The peroxidation was significantly diminished by NAC (–14%) and LIP (–16%), whereas TAU had no effect on the TBARS concentration. Cysteine derivatives administration prevented exercise-induced decline in SOD activity and increased in GPx activity during exercise. CAT activity changed only in the LIP group. The estimation of P/A ratio showed the lowest level of pro-antioxidant equilibrium after LIP administration. In the CON group, P/A ratio was directly correlated with the protein thiols level (r = 0.495, p < 0.001). These data confirm the antioxidant action of tested cysteine derivatives, particularly lipoic acid, and demonstrate the practical application of P/A ratio to evaluate the effectiveness of antioxidants in athletes.

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Myocardial intracellular calcium (Ca²⁺) transients (CaTs) regulate tension generation and relaxation. Isometric tension curves are often analyzed using exponential equations; however, we previously demonstrated that hybrid logistic (HL) functions, which describe the difference between two S-shaped logistic functions, provide more accurate representations. In the present study, we investigated the potential application of HL functions for analyzing CaTs directly. CaTs were measured using the calcium-sensitive bioluminescent protein, aequorin, in 7 isolated rabbit right ventricular and 15 isolated mouse left ventricular papillary muscles. CaT data were fit by the least-squares method using HL and polynomial exponential (PE) function equations. The mean correlation coefficient (r) values of HL and PE fits were 0.9934 vs. 0.9523 in rabbit and 0.9980 vs. 0.9407 in mouse, respectively. The Z transformation of r value and the adjusted coefficient of determination (r squares) were higher, and the residual mean squares and Akaike information criterion values, which estimate goodness of fit between functions with different numbers of parameters, were lower for the HL curves than for the PE curves in both rabbit and mouse. There were significant correlations between the calculated values from the best-fit HL function curve and the primary CaT data. Thus the HL function curves more accurately described the amplitudes and time courses of CaTs in both rabbit and mouse papillary muscles. We speculate that the first logistic component curve reflects the concentration and time course of Ca²⁺ inflow into the cytoplasmic space, and that the second logistic component curve reflects the concentrations and time courses of Ca²⁺ removal from the cytoplasmic space as well as Ca²⁺ binding to troponin. This approach might provide a more robust model for studying CaTs and cardiac cycle regulation.

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Changed vascular functions have been reported in several pathological conditions, such as chronic regional pain syndrome, obstructive vascular disease, and inflammation. Our previous experiments also showed that electrical stimulation of the lumbar sympathetic trunk (sympathetic stimulation: SS), which normally induces a decrease in blood flow (BF), caused a BF increase in about half of the measured sites in rats persistently inflamed with complete Freund’s Adjuvant (AI rats). We also showed that the BF-increase response was only partially suppressed by the α1 antagonist at a higher dosage, suggesting the involvement of nonadrenergic mechanisms. We hypothesize that nonadrenergic mechanisms mediating vasodilatation might involve a vasodilating neuropeptide such as substance P (SP) that is released from sympathetic nerve terminals. In this experiment, we conducted an examination using an NK-1 receptor antagonist to determine whether SP plays any role in changed response to SS in AI rats, and also an immunohistochemical examination of whether SP is expressed in the lumbar sympathetic nerve ganglia (SG) of AI rats. The administration of an NK-1 receptor antagonist, CP-96,345, significantly reduced the BF-increase response to SS in AI rats, but its inactive enantiomer, CP-96,344, had no effect. Immunohistochemistry for SP revealed that SP-ir positive SG neurons (mean 13 neurons/rat) were found in 5 of 8 AI rats, whereas only one neuron was stained in 8 control rats. These results suggest that NK-1 receptor activation is involved in the BF-increase response to SS, and that this activation is in part mediated by SP from lumbar SG that was synthesized de novo in inflamed animals.

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Although closing volume is regarded as a clinical test for the early detection of peripheral airway closure, its grounds are not clear. There have been no simulation studies for phase IV in the single-breath nitrogen washout (SBNW) curve, even though several mathematical models for phase III have been proposed. We modeled the lung tissue deformation during slow expiration in which the tissue was regarded as a porous elastic body similar to a sponge. We assigned the maximum tissue density of lung parenchyma over which the lung tissue could not be contracted according to several experimental reports in literature. SBNW curves were then simulated by computing expired air volume and nitrogen concentration for respective acini in the lung model. The simulated SBNW curves well reproduced phase IV, cardiac oscillation, and its postural changes. We found that the higher lung compliance increased closing volume, but decreased residual volume. The smaller maximum tissue density generated larger closing volume and larger residual volume. It suggested that phase IV reflected the alveolar contractility, and the increase of closing volume in emphysema could be explained by an insufficient contraction of alveoli. We also found that the distribution of maximum tissue density affected the onset of Phase IV. A constant value of density generated a clear onset, but a wide distribution of it corresponding to peripheral airway closure obscured it. We suggest that the airway closure was not necessary for phase IV appearance in both normal and emphysematous lung.

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The effects of acupuncture-like stimulation of a hind limb on heart rate were examined in anesthetized rats. An acupuncture needle, having a diameter of either 160 or 340 μm, was inserted into the skin and underlying muscles at a depth of about 5 mm and twisted right and left twice every second for 1 min. Stimulation by a needle with a diameter of either 160 or 340 μm produced a decrease in heart rate. Severance of the femoral and sciatic nerves ipsilateral to the hind-limb stimulation completely abolished the bradycardiac response. Also, heart rate was significantly decreased by acupuncture-like stimulation of the hind-limb muscles alone, but was not significantly influenced by the stimulation of the hind-limb skin alone. The bradycardiac response induced by acupuncture-like stimulation was not influenced by bilateral severance of the vagal nerves at the cervical level, but was abolished by bilateral stellectomy. Acupuncture-like stimulation of the hind limb induced a decrease in the activity of the cardiac sympathetic efferent nerve as well as a decrease in heart rate. These results indicate that the decrease in heart rate induced by acupuncture-like stimulation of a hind limb is a reflex response. The afferent pathway is composed of hind-limb muscle afferents, and the efferent pathway is composed of cardiac sympathetic nerves.

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Cerebral cortical extracellular NGF was collected and measured every 100 min using microdialysis and ELISA in anesthetized rats. The NGF level, which was stable at rest, increased in the ipsilateral cortex at 200–500 min after the end of focal electrical stimulation to the unilateral NBM for 100 min.

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