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H Tsubone

Publications and source records attributed to H Tsubone.

At least 73 records · Page 4Linked to original sources
PubMed1992

ECG changes under hyperkalemia with nephrectomy in the rat.

Electrolyte abnormalities have become an increasingly important cause of arrhythmias. Although the electrocardiographic (ECG) changes under hyperkalemia in the rat are poorly understood, it is conceivable that excess plasma potassium may also alter the cardiac excitations in the rat. Further, effects of hyperkalemia on ECG in the rat may differ from other species that have ST-segment and longer QT intervals in ECG. The present study was designed to determine the diagnostic criteria for ECG manifestations to various levels of plasma potassium concentration. For this purpose, hyperkalemia was induced by nephrectomy with and without infusions. Because it was difficult to produce various levels of plasma potassium concentration by only nephrectomy, we used two kinds of infusions to obtain especially moderate levels of nephrectomy-induced hyperkalemia. ECGs were recorded 24, 36, and 48 hours after nephrectomy. Plasma potassium concentration and number of abnormal ECGs were increased time-dependently. Increased T wave amplitude was present with mild hyperkalemia. The typical T wave change observed with so-called sinoventricular conduction levels of potassium concentration in species with long QT intervals did not occur in the rat. PR interval and QRS duration became slightly shorter within moderate hyperkalemia. P wave disappeared in most rats at potassium levels above 8.0 mEq/l. In advanced hyperkalemia (plasma potassium concentration above 7.5 mEq/l), conduction in all parts of the heart was suppressed. Moreover, sinoventricular conduction appeared. Thus, the diagnostic criteria for ECG manifestations to various levels of plasma potassium concentration in the rat were demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Characteristics of ventricular activation and recovery patterns in the rat.

Bipolar or unipolar epicardial and intraseptum electrograms were recorded from the in situ rat hearts with spontaneous sinus rhythm or myocardial electrical stimulation of 400 bpm in order to investigate the sequence and duration of cardiac activation in the rat. The ventricular epicardial isochronous maps in the rat showed the activation sequence comparable to those in humans and dogs, although the activation time (6 to 13 msec) of epicardium was approximately one-third of those of such species. The delay of activation between septum and ventricular surface in the rat was 5 to 8 msec, which was also shorter as compared with those in humans and dogs. However, the conduction velocity of the ventricular epicardium in the rat was approximately 40 cm/sec, mostly equal to that of humans. These findings might be accounted for by the possible presence of the bundle branch-purkinje system, at least functionally, similar to humans. The local QT interval in the septum were relatively longer (69 to 123 msec), compared with that of the ventricular surface (50 to 98 msec), and such durations of ventricular epicardium and septum were considerably less than those of dogs and humans. These results are consistent with the configuration of QRS-T on the limb lead ECG.

Animals↗
PubMed1992

Vagal afferent activities and respiratory reflexes during drug-induced bronchoconstriction in the guinea pig.

Vagal afferent activities and respiratory reflexes during drug-induced bronchoconstriction were studied in 31 anesthetized, spontaneously breathing or artificially ventilated guinea pigs. Histamine (5, 10, 20 micrograms/kg), ACh (10, 20, 40 micrograms/kg) and endothelin-1 (2 micrograms/kg) were intravenously injected to the animals in order to induce the bronchoconstriction. In spontaneously breathing and vagi intact animals, a considerable respiratory change characterized by rapid-shallow breathing was elicited by histamine. Such respiratory change was abolished by bilateral vagotomy, indicating that the vagal pathway fairly participated in the respiratory change during bronchoconstriction. Indeed, recordings of electrical activities of single vagal afferent nerve fibers from pulmonary stretch and irritant receptors elucidated that the bronchoconstriction by the three drugs markedly influenced these receptor activities. The response of stretch receptors to bronchoconstriction was grouped into four types: two of those types showed a marked increase in their activities and the other two a decrease or no change. Such uneven response was assumed to be derived from heterogenous contraction and aeration among the intrapulmonary small airway. On the other hand, irritant receptors were invariably stimulated by increased transmural pressure during bronchoconstriction. Administration of isoproterenol (20 micrograms/kg) which inhibited the smooth muscle contraction abolished stimulatory effect of the drugs to irritant receptors, suggesting that the effect was due to indirect action through the muscle contraction rather than their direct action to the nerve endings.

Acetylcholine↗
PubMed1991

Laryngeal afferent activity and reflexes in the guinea pig.

We have investigated the various sensory modalities represented in the laryngeal nerves of the guinea pig. In addition, we have examined the defensive responses to mechanical stimuli and capsaicin instillation into the laryngeal lumen of the same species. Recording from both the whole superior laryngeal nerve and from single units of the same nerve revealed the presence of afferent activity related (1) to the contraction of laryngeal muscles and/or the 'tracheal tug', (2) to transmural pressure changes, either positive or negative and (3) to mechanical and chemical irritants. The irritant type receptors of this species, when challenged with water solutions, show two distinct patterns of activation: some behave as osmoreceptors, some respond to the lack of chloride ions. Challenges with capsaicin solutions activated one ending with the characteristics of a C-fiber receptor that failed to respond to a subsequent trial. This behavior is consistent with the reflex apnea, dependent on an intact laryngeal innervation, induced by capsaicin instillation that was not elicitable on repeating the challenge. Cough to mechanical probing of the supraglottic area depended on an intact SLN, whereas cough elicited from the subglottic area depended on an intact RLN. Cough to mechanical stimulation could not be desensitized by capsaicin. These findings suggest the presence of two independent afferent pathways for defensive responses.

Afferent Pathways↗
PubMed1991

The respiratory activity of the superior laryngeal nerve in the rat.

The aim of this study was to characterize the laryngeal afferent activity of the rat. The animals were anesthetized and breathing spontaneously. Laryngeal afferent activity was recorded from both the whole superior laryngeal nerve (SLN) and from single fibers isolated from this nerve. An overall inspiratory augmenting activity was observed in the whole SLN during tracheostomy breathing, tracheal occlusion and upper airway breathing, but an expiratory augmenting activity was present during upper airway occlusion. The inspiratory modulated activity was abolished by bilateral section of the hypoglossal nerves but not the recurrent laryngeal nerves. A great number of receptors (46/80, 58%) were identified as 'drive' receptors, and others as 'pressure' (22/80, 28%) and 'irritant' type receptors (9/80, 11%). Nineteen pressure receptors were stimulated by positive transmural pressure, while only three stimulated by negative pressure. Nine drive receptors were also stimulated by positive pressure and inhibited by negative pressure. Such response to pressure was further evaluated by applying maintained pressures to the functionally isolated upper airway. These results are essentially consistent with findings obtained in the rabbit, but differ from those reported for the dog.

Afferent Pathways↗
PubMed1991

Afferent activity in the external branch of the superior laryngeal and recurrent laryngeal nerves.

We investigated the presence of respiratory-modulated receptors in the recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (ExtSLN) in anesthetized, spontaneously breathing dogs. Of 39 receptors recorded from the ExtSLN, the vast majority responded with a slowly adapting discharge to compression of the cricothyroid muscle, and only 1 responded to probing of the laryngeal mucosa. Ten receptors showed a respiratory modulation. All 30 receptors recorded from the RLN responded to probing of the laryngeal lumen, most of them (60%) with a rapidly adapting response. Seven of the slowly adapting receptors exhibited a respiratory modulation; 38% of the receptors tested were stimulated by water, and only 15% by smoke. No receptors stimulated by laryngeal cooling were identified in either nerve. Our study indicates that in the RLN and the ExtSLN there are relatively few afferents responding to changes in transmural pressure and mechanical irritation, as compared to the internal branch of the SLN. The relative scarcity of receptors responding to transmural pressure and irritant stimuli is consistent with previous observations in dogs that indicate a preponderant role for afferents in the internal branch of the SLN in the reflex responses to laryngeal stimulation.

Afferent Pathways↗
PubMed1991

Characteristics of electrocardiographic changes with some representative antiarrhythmic drugs in adult rats.

The characteristics of ECG changes with representative antiarrhythmic drugs; procainamide (PA) (class Ia), lidocaine (LC) (class Ib), propranolol (PN) (class II), and verapamil (VP) (class IV) were investigated in adult rats. Action potential (AP) was also recorded from myocardial cells during electrical stimuli with frequencies of 1-5 Hz. All the four drugs produced ECG abnormalities which contained AV and SA blocks at middle and high dose levels. Three drugs except VP induced a prolongation of QRS complex and notched QRS at low or middle dose level. As compared such effects with those in dogs and humans, some differences were noted as follows: (1) a dose-dependent prolongation of QT interval by LC and PN, and (2) a shortening of RR interval by VP at the dose of 0.6 mg/kg or less. LC and PN elongated the QT interval in the unipolar precordial chest lead ECGs at right anterior chest positions. These two drugs did not affect the duration of AP (APD90), whereas maximum upstroke velocity (Vmax) decreased. These results suggest that the prolongation of QT interval with LC and PN was due to a delay in local ventricular conduction time, especially on the right ventricle. The shortening of RR interval by VP was clearly blocked by the pretreatment with PN, indicating that this shortening reflected the sympathetic nervous reflex presumably due to the peripheral vasodilation effect of VP.

Action Potentials↗
PubMed1991

Reflex activities of the upper airway muscles during experimental nasal occlusion in anesthetized dogs.

Reflex responses of the upper airway muscles during experimental nasal and tracheal occlusions were studied in 21 anesthetized dogs breathing through the nose or a tracheostomy (tracheal cannula). Out of them, five animals were examined for maintained negative and positive pressures applied to the isolated upper airway. When the nose was occluded at end-expiration during three consecutive breathings, the electromyographic (EMG) activity of alae nasi (AN) and posterior cricoarytenoid (PCA) muscle markedly increased. The upper airway was subjected to negative pressure, -2.41 approximately -3.04 kPa (n = 34) by these nasal occlusions. The activity of upper airway muscles was also increased by tracheal occlusions. However, such augmentation of PCA activity was much less in tracheal occlusions than nasal occlusions, whereas there was the smaller difference in AN activity between both occlusions. During nasal occlusions, a prolongation of the inspiratory time (TI) was observed. Furthermore, maintained negative pressure applied to the isolated upper airway provoked an augmentation of PCA activity. Such an augmented EMG activity of PCA and the prolongation of TI were largely diminished by sectioning the superior laryngeal nerves. These results proves that the upper airway muscles play an important role to protect the upper airway from collapsing by nasal occlusions. In addition, it is suggested that a lack of lung volume feedback is substantially concerned with the activation of AN, while negative pressure in the upper airway is essential to stimulate PCA.

Airway Obstruction↗
PubMed1991

Evaluation of a new tail-cuff method for blood pressure measurements in rats with special reference to the effects of ambient temperature.

We evaluated a recently developed tail-cuff apparatus for the indirect blood pressure measurement in rats with special reference to the effects of ambient temperature. For this purpose, we designed two preparations 1) an intact preparation to determine the effect of ambient temperature on blood pressure measurements and 2) an anesthetized and catheterized preparation for comparison of the values of blood pressure obtained by the indirect and by the direct method. This apparatus also required enough pulse volume oscillations to measure the accurate value of blood pressure. Sufficient pulse volume oscillations were obtained within 20 min at 30 and 40 degrees C. At 40 degrees C, the values of blood pressure, pulse rate and rectal temperature were significantly higher than those at 30 degrees C. Correlation between blood pressure and rectal temperature was significant, and blood pressure increased with rectal temperature dependently. The values of the indirect measurement were close to the values measured directly, and these correlations were highly significant. Thus, we showed the effects of temperature for indirect blood pressure measurement. This tail-cuff apparatus could measure the accurate value of indirect blood pressure without thermal stress at 30 degrees C.

Animals↗
PubMed1990

Nasal 'pressure' receptors.

This study was performed to identify, recording from single fibers of the ethmoidal nerve, nasal receptors which respond to changes in the upper airway pressure during nasal occlusion. In 15 anaesthetized rats breathing through the nose, three consecutive nasal occlusions were performed while recording the afferent activity of ethmoidal nerve fibers, the EMG activity of an external intercostal muscle, temperature in the nose and upper airway pressure. Twenty-two afferent fibers were activated during the three inspiratory efforts with occlusions applied at end-expiration, when the upper airway was subjected to negative pressure (-1.93, -2.16 and -2.22 kPa at the 1st, 2nd and 3rd effort, respectively). The number of impulses was 24, 22 and 20 (n = 22) at the 1st, 2nd and 3rd effort, respectively. The pressure threshold were measured as -0.73, -0.87 and -0.96 kPa (n = 22) in each effort. Three fibers were also stimulated by positive pressure during occlusions performed at end-inspiration. In 5 rats breathing through a tracheostomy, maintained negative (-0.1-3.7 kPa) and positive (0.8-3.0 kPa) pressures were applied to the isolated upper airway. All the 12 fibers tested were activated by the maintained negative pressure, whereas three of them were also activated by the maintained positive pressure. However, none of fibers tested were stimulated by tracheal occlusions. These results indicate that the ethmoidal branch of the trigeminal nerve contains fibers connected to nasal 'pressure' receptors, mostly 'negative pressure' receptors, that may play a role in the maintenance of upper airway patency.

Air Pressure↗
PubMed1989

Nasal 'flow' receptors of the rat.

This study was performed to identify trigeminal nasal 'flow' receptors and to investigate their firing characteristics. For this purpose, single unit afferent activity was recorded from the anterior ethmoidal nerve in anesthetized rats breathing through the nose or a tracheostomy. In fourteen rats breathing through the nose, 40 of 73 endings tested were identified as 'flow' receptors for the following characteristics: their spontaneous activity had an inspiratory modulation that disappeared during nasal occlusions, they were markedly stimulated by exposure to cold air and inhibited by warm air. In eleven rats breathing through a tracheostomy, 85 endings were identified as 'flow' receptors being stimulated by a constant nasal airflow (100-300 ml/min) with room air (22-26 degrees C) or cold air (0-15 degrees C), but inhibited with warm air (30-45 degrees C). Fifty-five 'flow' receptors (Type R1 and R2) exhibited a dynamic response to the constant airflow, while the other 30 receptors (Type S) showed a static response. A large proportion of 'flow' receptors (more than 52%) were responsive to tactile stimuli. For all the flow receptors, a decrease in intranasal temperature was the primary factor to excite them. These results suggest that the trigeminal nerve has a number of 'flow' receptors which operate as thermoreceptors.

Action Potentials↗
PubMed1988

Contraction of trachealis muscle and activity of tracheal stretch receptors.

This study examined the relationship between tracheal slowly adapting stretch receptor discharge and smooth muscle activity in a preparation in which the efferent supply to the airway was essentially intact. In 7 anesthetized, paralyzed, artificially ventilated dogs, smooth muscle activity was assessed by measuring the pressure of a water-filled cuff placed in the extrathoracic trachea and action potentials originating from 19 extrathoracic tracheal stretch receptors were recorded from the superior laryngeal nerve. Challenges were: hypercapnia (FI = 0.05 and FI = 0.10), hypoxia (FI = 0.10 and FI = 0.05) and asphyxia. Concurrent increases in cuff pressure and receptor discharge were present in 18 of the endings studied in response to all the challenges presented. The remaining receptor increased its rate of discharge with 10% CO2 and asphyxia; neither receptor discharge or cuff pressure increased with 5% CO2 and hypoxia. Following block of the recurrent laryngeal nerves, baseline values of both cuff pressure and receptor discharge, as well as the responses to asphyxia, decreased; any residual response was eliminated by atropine. Of the 17 receptors whose location could be precisely ascertained, 14 were found in the proximal third of the extrathoracic trachea, and the remaining 3 in the middle third. The temperature at which the nervous conduction was blocked was determined for 3 slowly adapting receptors; it ranged from 4.5 to 12.5 degrees C. Of 5 extrathoracic tracheal rapidly adapting receptors encountered during the course of the experiments, 3 were tested with asphyxia and found to be unaffected. This study shows that tracheal slowly adapting stretch receptors are activated by smooth muscle contractions reflexly induced by chemoreceptor stimulation.

Animals↗
PubMed1987

Respiratory activity in the superior laryngeal nerve of the rabbit.

We studied the respiratory modulation of laryngeal afferents and their response to transmural pressure in 24 anesthetized, spontaneously breathing rabbits. Laryngeal afferent activity has a predominant inspiratory augmentation during tracheal breathing or tracheal occlusion that can be accounted for by the respiratory movement transmitted to the larynx through the trachea. During upper airway breathing or upper airway occlusion SLN afferent activity increases in expiration and decreases in inspiration. This respiratory modulation is due to changes in upper airway pressure (Pua). In fact, positive pressure stimulates SLN afferent activity, while negative pressure inhibits it. Mechanical restriction of epiglottal movement reduced the response to Pua changes during upper airway occlusion and application of maintained positive (0.1-0.5 kPa) and negative (-0.1 to -0.5 kPa) pressures (P less than 0.005). Furthermore, surgical removal of epiglottis decreased the baseline activity of SLN to 16.5% of control. These experiments suggest that in the rabbit the epiglottis is the main source of SLN afferent activity and that its displacement, due to changes in Pua, is the most important factor for modulating SLN activity. Most of the laryngeal receptors showed an inspiratory augmentation with tracheal breathing and occlusion, were stimulated by positive pressure and inhibited by negative pressure, reflecting the behavior observed in the whole nerve.

Animals↗
PubMed1986

Characteristics of vagal afferent activity in rats: three types of pulmonary receptors responding to collapse, inflation, and deflation of the lung.

To elucidate the characteristics of vagal afferent fibers arising from rat lungs, single-unit activity from pulmonary stretch receptors and two other types of pulmonary receptors was recorded. In the latter, one type of receptor, termed deflation-sensitive receptors in this study, was stimulated only in the expiratory phase of normal respiration. Moreover, this type of receptor exhibited persistent discharges resulting in a train or burst of impulses with collapse and forced deflation, respectively. The decrease of discharge frequency during collapse was slow and the average adaptation index was 20%, indicating a slowly adapting characteristic. Upon forced deflation, the discharge frequency increased with increasing negative pressure to -158 mm H2O intratracheal pressure. The other type of receptor, termed irritant-like receptors, responded to both deflation and inflation. In addition, they displayed rapidly adapting and irregular discharges during maintained inflation. These results indicate that rat vagus nerves deliver afferent information from at least three types of pulmonary receptors: pulmonary stretch and lung irritant-like receptors and the receptors specifically sensitive to expiration or lung deflation. Furthermore, the possibility is postulated that vagal deflation-sensitive receptors are related to the peripheral mechanism in normal respiration and Hering-Breuer deflation reflex in rats.

Afferent Pathways↗
PubMed1984

Effects of nitrate and nitrite, chemical intermediates of inhaled nitrogen dioxide, on membrane components of red blood cells of rats.

Rat blood was incubated at 37 degrees C for 60 min with either NaNO3 or NaNO2 to examine the relationship between the decrease in the hexose content and Ca2+,Mg2+-ATPase activity of red cell membranes, and NO3- and NO2-. The hexose content decreased depending on the NaNO2 concentration up to 100 microM reaching 76% (p less than 0.05) of the control value. NaNO3 had little effect on the hexose content. On the other hand, the Ca2+,Mg2+-ATPase activity decreased depending on the NaNO3 concentration up to 200 microM, where the activity reached 75% (p less than 0.01) of the control value. The effect of NaNO2 on this activity was smaller than that of NaNO3. The sialic acid content and the Na+,K+-ATPase activity did not show significant alterations by incubation with NaNO2 and NaNO3 at below 100 microM. To examine the in vivo effects of NO2- and NO3-, 50 mM NaNO3 was intravenously injected into rats five times at hourly intervals (dose: 1.0 ml/kg body weight), and blood was collected 1 hr after the last injection. The activities of Ca2+,Mg2+- and Na+,K+-ATPases of red cell membranes were decreased to 68% (p less than 0.05) and 80% of the control value, respectively. Reduction by injection of 50 mM NaNO2 was smaller than that by 50 mM NaNO3. The results show that the hexose content and the Ca2+,Mg2+-ATPase activity of red cell membranes were decreased by NO-x that increased in the blood during short-term exposure of rats to NO2.

Animals↗
PubMed1984

Changes of cardiac and respiratory rhythm in non- and tracheostomized rats exposed to nitrogen dioxide.

Cardiac and respiratory changes in non- and tracheostomized rats were examined during exposure to 20 ppm of NO2 for 150 min. The abnormal respiratory pattern consisted of rapid shallow breathing, deep breathing, and apnea, and the bradyarrhythmias were observed in the tracheostomized rats during exposure. Also, similar changes were seen in the nontracheostomized rats. A decrease in the heart rate (HR) was observed in both non- and tracheostomized rats. The decrease in HR was depressed by atropine injection, and the abnormal respiratory patterns were almost abolished by this drug. It was suggested, from these results, that the cardiac and respiratory abnormalities could be induced without the irritation to upper respiratory tracts, and that the vagal efferent pathway had an important role in the appearance of the abnormalities during exposure.

Air Pollutants↗
PubMed1984

Reflex cardiopulmonary responses by stimulation to type J receptors in rats exposed to NO2.

To examine the role of the vagal pathway on the cardiopulmonary functions in NO2-exposed rats, phenyl diguanide, which stimulates type J receptors in the lungs, was injected to control and exposed rats at a constant dose. Based on a statistical test, a decrease in the heart rate (HR) after the injection was observed in the groups exposed to 20 ppm NO2 for 1.5 h and 3h, and 10 ppm for 24 h. On the other hand, an increase in respiratory rate (RR) was observed in the groups exposed to 10 ppm for 3 h and 4 ppm for 1 wk. No change in HR and RR was found in the group exposed to 0.4 ppm for 4 wk. These results suggest that the augmentation of the reflex cardiopulmonary responses due to stimulation to the type J receptors was produced by exposures with a higher concentration of NO2.

Animals↗