We have studied the experimental tachyarrhythmia in an improved isolated rat atrial preparation for the optical mapping of excitation spread. The atrial preparation, including the right or left auricle, was dissected from the adult rat heart, and an artificial hole was made in the center of the preparation. The preparation was then stained with a fast merocyanine-rhodanine voltage-sensitive dye (NK2761). Using a multi-element (16 × 16) photodiode array, the spread of excitation was assessed optically by timing the initiation of the action potential–related extrinsic absorption changes. In comparison with the intact isolated right atrial preparation, which we used previously, the mapping of the excitation spread was much easier and more precise because of the simple structure of the preparation. The electrical stimulation applied by a bipolar electrode evoked the sustained excitation with a fast rhythm, which we termed “experimental tachyarrhythmia” (ET). We optically mapped the spatiotemporal patterns of the spread of excitation during the initiation and the maintenance phases of ET. In most cases, a rotation of the excitatory wave around the artificial hole, i.e., a circus movement of the excitatory wave, was observed. These maps suggest that this circus movement resembles the basic mechanism of the tachycardia-like excitation observed in the intact isolated right atrial preparation. On the other hand, the appearance of an ectopic pacemaker with a fast rhythm was also observed. In some examples, two ectopic pacemakers appeared simultaneously. We consider that the experiment using the improved preparation is a superb in vitro model of atrial arrhythmia.

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Previous studies have demonstrated that Ar⁺ laser irradiation shows a more selective blocking effect on the generation of anode-break-excitation (AE) than on cathode-make-excitation (CE), and that the effects of laser irradiation closely resemble those following the application of hyperpolarization-activated current (Ih) blocker, ZD7288. We therefore examined the effects of ZD7288 and tetrodotoxin (TTX) on polar excitations to reveal whether such a selective effect of ZD7288 on AE is specific in frog sciatic nerve. Supramaximal stimuli (10-ms pulse) were applied while for 30 min each channel blocker was applied to the stimulating sites. Analyses of chronological changes in polar excitations were performed using CEs induced by positive stimuli and AEs induced by negative stimuli, because both were generated on the same stimulating grid against the recording grids. TTX application (1 mM) decreased all types of polar excitations at 30 min after initiation of the application. When ZD7288 (1 mM) was applied, the amplitude of AE displayed a significant decrease after 30 min. When TTX or ZD7288 was applied to the middle portion between the stimulating and recording electrode grids, TTX showed the conduction block, but the latter yielded almost no effect. Western blotting analyses demonstrated expressions of the second and the third subunits of hyperpolarization-activated and cyclic-nucleotide-gated nonselective cation channels in frog sciatic nerve. Ih channels thus exist in the frog sciatic nerve, and its specific blocker, ZD7288, has the potential to selectively block the generation of AE.

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The oligomeric structure and the residual propeptide are distinct characteristics of cathepsin C from other members in the papain superfamily. In this study, we examined the physiological role of the cathepsin C propeptide. The stable overexpression of cathepsin C propeptide significantly decreased the activities of intestinal alkaline phosphatase (IAP) and sucrase in human Caco-2 intestinal epithelial cells, whereas it did not change the proliferation and cathepsin C activity. The overexpression of cathepsin C propeptide significantly decreased the amounts of IAP protein in differentiated Caco-2 cells, compared with the transfection of mock vector, whereas the amounts of IAP transcripts were not changed. Pulse-chase analysis confirmed that the reduction in IAP activity was due to an increase in IAP degradation, but not a decrease in IAP expression. For the mechanism of the enhanced IAP degradation, we identified proteins interacting with cathepsin C propeptide in Caco-2 cells by immunoprecipitation and mass spectrometry. Cathepsin C propeptide interacted with proteins with a molecular mass of approximately 70 kDa, including IAP and heat shock cognate protein 70. Our present results suggest that the propeptide of cathepsin C may stimulate the sorting to the lysosome, at least in part, contributing to the degradation of IAP in Caco-2 cells.

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We estimated the time taken for a repletion of the junctional sarcoplasmic reticulum (JSR) Ca²⁺ stores from a family of mechanical restitution curves after twitches of various magnitudes in the cardiac muscle of hypertensive rats (SHR), using a method described previously (Tameyasu et al. Jpn J Physiol. 2004;54:209-19), to evaluate abnormality in Ca²⁺ handling by cardiac JSR in hypertension. We found no differences in contractility or in the time course of mechanical restitution between SHR and the controls (WKY) at 3 weeks of age. In comparison to WKY, 7- and 20-week-old SHR showed a greater rested state contraction (RST) and similar or smaller rapid cooling contracture, suggesting that their JSR contains a similar amount of Ca²⁺ at saturation, but releases more Ca²⁺ upon stimulation. The adult SHR and WKY showed similar mechanical restitution time courses, but the adults had longer pretwitch latencies. The function G(t) representing the time course of JSR Ca²⁺ store repletion in adult SHR exceeded the WKY value at t ≤ 0.5 s, but the function H(t) representing JSR [Ca²⁺] change corresponding to the mechanical restitution after RST was smaller in the adult SHR at t ≤ 0.5 s, resulting in smaller H(t)/G(t) in adult SHR at t ≤ 0.5 s. Deviations of G(t), H(t), and H(t)/G(t) from WKY were greater at 20 weeks than at 7. The results suggest an acceleration of JSR Ca²⁺ store repletion and an alternation of the Ca²⁺-induced release of Ca²⁺ from the JSR in young adult SHR.

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In some lymph nodes, water and water-soluble substances of smaller molecular weight are known to be absorbed into blood vessels, and consequently the protein concentration of lymph within the nodes increases. In this study, we examined pressure-flow relationships of lymph nodes in situ and exchange properties of water and water-soluble substances through the nodes with special reference to inflamed lymph nodes. A lymph perfusion model through the lymph node in situ was constructed by cannulating one of the afferent lymphatics and an efferent lymphatic. Increasing infusion pressure (0 to 150 cmH₂O) or decreasing outflow pressure (10 to −5 cmH₂O) in the model caused a significant increase of the lymph outflow rate through the node. This rate was also increased significantly with increases in both intranodal venous pressure (range: control, 20, 30, and 40 mmHg) and prenodal lymph albumin concentration (range: 0%, 2.6%, and 10%). When formyl-Met-Leu-Phe-OH (fMLP)–mediated acute inflammation was produced in the lymph nodes, the lymph outflow rate through the node was significantly decreased. These results indicate that colloid osmotic pressure and hydrostatic pressure within the lymph node may play important roles in the transport of water and water-soluble substances through the node. Acute fMLP-mediated inflammation of lymph nodes also produced a significant decrease of the lymph flow rate through lymph nodes.

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The present experiments examined the effects of electrical stimulation of the superior ovarian nerve (SON) and the ovarian plexus nerve (OPN) on the ovarian estradiol secretion in rats. The rats were anesthetized on the day of estrus, and the ovarian venous blood was collected intermittently. The secretion rate of estradiol from the ovary was calculated from differences in the estradiol concentration between ovarian venous plasma and systemic arterial blood plasma, and from the flow rate of ovarian venous plasma. Either an SON or OPN, ipsilateral to the ovary from which ovarian venous blood was collected, was electrically stimulated at a supramaximal intensity for C-fibers. The secretion rate of estradiol was significantly decreased by 47 ± 6% during SON stimulation, but it was not significantly changed during OPN stimulation. These results suggest that autonomic nerves, which reach the ovary via the SON, have an inhibitory role in ovarian estradiol secretion.

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Nicotine, like several other abused drugs, is known to act on the reward system in the brain. Smoking-associated cues produce smoking urges and cravings accompanied by autonomic dysfunction to these cues in smokers. The present study was aimed at investigating whether cues related to smoking elicit the autonomic response in smokers. The subjective and physiological reactivity of 7 smokers and 12 nonsmokers in a supine position to smoking-related visual cues was assessed under indirect dim light using a self-assessment manikin and a specially designed pupillometer. The experimental procedure consisted of the elicitation and measurement of pupil size (PS) while the subjects viewed a smoking image and images from three valence-defined categories (i.e., pleasant, unpleasant, and neutral), based on normative affective ratings selected from the International Affective Picture System. Both groups produced significantly larger PS increases in response to pleasant or unpleasant images compared to neutral images. Smokers, viewing smoking-related visual cues but no other affective images, produced significantly larger PS's compared to nonsmokers. Moreover, smokers rated the smoking image with more pleasure and arousal than nonsmokers. These findings suggest that cues related to smoking induce not only a subjective emotional alteration, but also sympathetic activation, measured by the time-series PS data in smokers.

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We tested the hypothesis that the biphasic ventilatory response to poikilocapnic hypoxia shows circadian variation and contribution of histamine H1 receptors in mice. Initial increases in ventilation were augmented during dark periods. H1 receptors had no major relationship with circadian variation, but affected the declined phase.

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