Protective effect of oleic acid against very long-chain fatty acid-induced apoptosis in peroxisome-deficient CHO cells

Very long-chain fatty acids (VLCFAs) are degraded exclusively in peroxisomes, as evidenced by the accumulation of VLCFAs in patients with certain peroxisomal disorders. Although accumulation of VLCFAs is considered to be associated with health issues, including neuronal degeneration, the mechanisms underlying VLCFAs-induced tissue degeneration remain unclear. Here, we report the toxic effect of VLCFA and protective effect of C18: 1 FA in peroxisome-deficient CHO cells. We examined the cytotoxicity of saturated and monounsaturated VLCFAs with chain-length at C20-C26, and found that longer and saturated VLCFA showed potent cytotoxicity at lower accumulation levels. Furthermore, the extent of VLCFA-induced toxicity was found to be associated with a decrease in cellular C18:1 FA levels. Notably, supplementation with C18:1 FA effectively rescued the cells from VLCFA-induced apoptosis without reducing the cellular VLCFAs levels, implying that peroxisome-deficient cells can survive in the presence of accumulated VLCFA, as long as the cells keep sufficient levels of cellular C18:1 FA. These results suggest a therapeutic potential of C18:1 FA in peroxisome disease and may provide new insights into the pharmacological effect of Lorenzo's oil, a 4:1 mixture of C18:1 and C22:1 FA.

Nonspecific phospholipase C3 of radish has phospholipase D activity towards glycosylinositol phosphoceramide

Glycosylinositol phosphoceramide (GIPC) is a major sphingolipid in the plasma membranes of plants. Previously, we found an enzyme activity that produces phytoceramide 1-phosphate (PC1P) by hydrolysis of the D position of GIPC in cabbage and named this activity as GIPC-phospholipase D (PLD). Here, we purified GIPC-PLD by sequential chromatography from radish roots. Peptide mass fingerprinting analysis revealed that the potential candidate for GIPC-PLD protein was nonspecific phospholipase C3 (NPC3), which has not been characterized as a PLD. The recombinant NPC3 protein obtained by heterologous expression system in Escherichia coli produced PC1P from GIPC and showed essentially the same enzymatic properties as those we characterized as GIPC-PLD in cabbage, radish and Arabidopsis thaliana. From these results, we conclude that NPC3 is one of the enzymes that degrade GIPC.

Estimation of Arterial Mechanical Properties from Aortic and Tonometric Arterial Pressure Waveforms

Although arterial mechanical properties have been evaluated using arterial input impedance, the relative difficulty in accurate flow measurement made the value of impedance somewhat limited. To develop an alternative method to evaluate arterial mechanical properties, we analyzed the aortic pressure (AoP)-radial arterial pressure (RAP) relationship because of relative ease in obtaining peripheral pressure waveform by tonometry. In 8 patients we simultaneously recorded aortic root and radial arterial pressure waveforms. We calculated the transfer function from AoP to RAP. We then fitted the transfer function to a model of a lossless uniform elastic tube terminated with a modified Windkessel model. The fact that the model transfer function predicted AoP from RAP waveform with considerable accuracy indicated that the model represented the arterial mechanical properties well. We conclude that we can estimate the arterial mechanical properties by the pressure-pressure transfer function analysis.

Translational neurocardiology: preclinical models and cardioneural integrative aspects

Neuronal elements distributed throughout the cardiac nervous system, from the level of the insular cortex to the intrinsic cardiac nervous system, are in constant communication with one another to ensure that cardiac output matches the dynamic process of regional blood flow demand. Neural elements in their various 'levels' become differentially recruited in the transduction of sensory inputs arising from the heart, major vessels, other visceral organs and somatic structures to optimize neuronal coordination of regional cardiac function. This White Paper will review the relevant aspects of the structural and functional organization for autonomic control of the heart in normal conditions, how these systems remodel/adapt during cardiac disease, and finally how such knowledge can be leveraged in the evolving realm of autonomic regulation therapy for cardiac therapeutics.

Exercise training plus calorie restriction causes synergistic protection against cognitive decline via up-regulation of BDNF in hippocampus of stroke-prone hypertensive rats

One of the important organ damage of hypertension is cognitive decline. Cognitive function is determined by the function of hippocampus, and previous studies have suggested that the decrease in brain-derived neurotrophic factor (BDNF) in the hippocampus causes cognitive decline. Protection against cognitive decline is reported not only in pharmacological therapy but also in exercise training or calorie restriction. The aim of the present study was to determine whether exercise training plus calorie restriction cause synergistic protection against cognitive decline via BDNF in the hippocampus or not. Exercise training for 28 days improved cognitive decline determined by Morris water maze test via up-regulation of BDNF in the hippocampus of stroke-prone spontaneously hypertensive rats, whereas calorie restriction for 28 days did not. However, exercise training plus calorie restriction causes the protection against cognitive decline to a greater extent than exercise training alone. In conclusion, exercise training plus calorie restriction causes synergistic protection against cognitive decline via up-regulation of BDNF in the hippocampus of stroke-prone hypertensive rats.

Intravascular parasympathetic cardiac nerve stimulation prevents ventricular arrhythmias during acute myocardial ischemia

Although previous animal studies clearly demonstrated antiarrhythmic effects of vagal stimulation during acute myocardial ischemia, highly invasive nature of vagal stimulation limited its clinical use. Recently, intravascular parasympathetic cardiac nerve stimulation (IPS) has emerged as a novel approach to the cardiac autonomic nervous system. We hypothesized that IPS might prevent ventricular arrhythmias during acute myocardial ischemia.

METHODS

The IPS (36 V, 10 Hz) was performed in superior vena cava using an expandable electrode-basket catheter. In 18 open-chest dogs, left anterior descending coronary artery ligation was performed without IPS (control group, n= 6), with IPS (IPS group, n= 6) and with IPS and right atrial pacing at 180/min (IPS+P group, n=6). The ECGs were monitored for 60 min. The incidence and severity of ventricular arrhythmias were analyzed.

RESULTS

The IPS significantly decreased the frequency of premature ventricular contractions (control group: 9.1 &#177; 4.6/min, IPS group: 0.2 &#177; 0.4 /min, IPS+P group: 10.6 &#177; 4.2 / min; p&lt;0.05). The frequency of ventricular tachycardia was lower in IPS group (0 &#177; 0 /min) than in control group (0.15 &#177; 0.18 /min, p&lt;0.05) and than in IPS+P group (0.17 &#177; 0.12 /min, p<0.05). The incidence of ventricular fibrillation was lower in IPS group (0%) than in control group (33.3%) and than in IPS+P group (33.3%).

CONCLUSIONS

The IPS suppressed ventricular arrhythmias during acute ischemia mainly through its bradycardiac effect.

Experimental 'jet lag' causes sympathoexcitation via oxidative stress through AT1 receptor in the brainstem

Circadian disruptions through frequent transmeridian travel, rotating shift work, and poor sleep hygiene are associated with an array of physical and mental health maladies, including the abnormal autonomic nervous system. We have demonstrated that the oxidative stress through AT(1) receptor in the brain activates sympathetic nervous system. The aim of the present study was to determine whether experimental 'jet lag' causes sympathoexcitation via oxidative stress through AT(1) receptor in the cardiovascular center of the brainstem (rostral ventrolateral medulla; RVLM) or not. Experimental 'jet lag' was made to normotensive (Wister-Kyoto rat; WKY rat) and hypertensive rats (stroke-prone spontaneously hypertensive rats; SHRSP) by the exposure to a 12 hour phase advance for 5 days. In WKY, 'jet lag' increases blood pressure and the activity of sympathetic nervous system via oxidative stress through angiotensin II type 1 receptor in the RVLM for 2 days only, and the changes are improved at 3 day after the initiation of 'jet lag'. In SHRSP, 'jet lag' also increases blood pressure and the activity of sympathetic nervous system via oxidative stress through angiotensin II type 1 receptor in the RVLM, and the changes are greater compared to those in WKY, and are maintained for the period of 'jet lag'. These results suggest that experimental 'jet lag' causes sympathoexcitation via oxidative stress through AT(1) receptor in the brain, especially in hypertension.

Poly I:C-induced expression of intercellular adhesion molecule-1 in intestinal epithelial cells

Intercellular adhesion molecul-1 (ICAM-1) is a transmembrane glycoprotein belonging to the immunoglobulin superfamily of adhesion molecules and plays perdominant roles in recruitment and trafficking of leucocytes to sites of inflammation. ICAM-1 expression in intestinal epithelial cells (IECs) is enhanced by several stimuli, such as proinflammatory cytokines, bacterial infections or pathogen-associated molecular patterns. One of these stimuli, double-stranded RNA (dsRNA), is a by-product of viral replication and can be recognized by its cognate receptor Toll-like receptor 3 (TLR-3). In spite of expression of both TLR-3 and ICAM-1 in IECs, correlation between TLR-3-signalling and ICAM-1 expression has never been examined in IECs. In the present study, we investigated whether poly I:C, an analogue of dsRNA, can stimulate the expression of ICAM-1 in IEC line, HT-29. Poly I:C-stimulation up-regulated the expression of ICAM-1 mRNA by real-time polymerase chain reaction. Enhanced expression of ICAM-1 was confirmed in protein level by immunofluoresense cell staining and enzyme-linked immunosorbent assay by measuring the released soluble ICAM-1 in culture supernatant. As the stimulation effect was reduced by pre-treatment of the cells with anti-TLR-3 antibody, poly I:C-binding signal was thought to be sensed by TLR-3 on the surface of HT-29. The results of luciferase assay and nuclear factor kappa-b (NF-kappaB) inhibitor treatment experiments indicated that the downstream signal was mainly transduced by transcription factor, NF-kappaB. All these results demonstrated the connection between TLR-3 signalling and ICAM-1 expression in HT-29 cells and indicated the importance of coordinated function of both innate and adaptive immunity against viral infections.

An intravenous replenishment of salivary components decrease water intake and increases feed intake in freely drinking large-type goats fed on dry forage

This research utilized two treatments to investigate if feed intake is reduced by changes in humoral factors induced by dry forage feeding in large-type goats given free access to water. In the control treatment (NI), a solution was not infused. The artificial parotid saliva i.v. infusion (ASI) treatment consisted of an i.v. infusion of artificial parotid saliva in order to replenish NaHCO3 and fluids lost from the blood to the rumen due to increased saliva secretion volume during initial stages of dry forage feeding. The ASI treatment significantly mitigated the decreases in circulating plasma volume caused by saliva secretion. Thirst was lower in the ASI-treated group, as indicated by the lower water intake (NI, 3894 mL 2 h-1; ASI, 3100 mL 2 h-1). Decreases with time in dry forage intake were significantly reduced by the ASI treatment (2134g 2 h-1) compared with the NI control (1756 g 2 h-1). These results indicate that under free drinking conditions, dry forage intake of large-type goats may likely be suppressed by the decrease in plasma volume and increase in water intake following saliva secretion during the initial stages of feeding. Key words: Dry forage intake, water intake, large-type goat

Characterization of ouabain-induced noradrenaline and acetylcholine release from in situ cardiac autonomic nerve endings

AIM

Although ouabain modulates autonomic nerve ending function, it is uncertain whether ouabain-induced releasing mechanism differs between in vivo sympathetic and parasympathetic nerve endings. Using cardiac dialysis, we examined how ouabain induces neurotransmitter release from autonomic nerve ending.

METHODS

Dialysis probe was implanted in left ventricle, and dialysate noradrenaline (NA) or acetylcholine (ACh) levels in the anaesthetized cats were measured as indices of neurotransmitter release from post-ganglionic autonomic nerve endings.

RESULTS

Locally applied ouabain (100 microm) increased in dialysate NA or ACh levels. The ouabain-induced increases in NA levels remained unaffected by cardiac sympathetic denervation and tetrodotoxin (Na+ channel blocker, TTX), but the ouabain-induced increases in ACh levels were attenuated by TTX. The ouabain-induced increases in NA levels were suppressed by pretreatment with desipramine (NA transport blocker) and augmented by reserpine (vesicle NA transport blocker). In contrast, the ouabain-induced increases in ACh levels remained unaffected by pretreatment with hemicholinium-3 (choline transport blocker) but suppressed by vesamicol (vesicle ACh transport blocker). The ouabain-induced increases in NA levels were suppressed by pretreatment with omega-conotoxin GVIA (N-type Ca2+ channel blocker), verapamil (L-type Ca2+ channel blocker) and TMB-8 (intracellular Ca2+ antagonist). The ouabain-induced increases in ACh levels were suppressed by pretreatment with omega-conotoxin MVIIC (P/Q-type Ca2+ channel blocker), and TMB-8.

CONCLUSIONS

Ouabain-induced NA release is attributable to the mechanisms of regional exocytosis and/or carrier-mediated outward transport of NA, from stored NA vesicle and/or axoplasma, respectively, while the ouabain-induced ACh release is attributable to the mechanism of exocytosis, which is triggered by regional depolarization. At both sympathetic and parasympathetic nerve endings, the regional exocytosis is because of opening of calcium channels and intracellular calcium mobilization.

A sieve electrode as a potential autonomic neural interface for bionic medicine

We examined the applicability of a sieve electrode to the autonomic nervous system as a potential neural interface for bionic medicine. We developed, using a Si-semiconductor process, a sieve electrode having a square diaphragm (1 mm in one side, 12 microm in thickness) with 30-81 penetrating square holes (50-100 microm in one side). In the first protocol, we implanted the sieve electrode to the vagal nerve in rats. One hundred and twenty days after the implantation, cuff electrodes were attached to the vagal nerve proximal and distal to the sieve electrode under halothane anesthesia. The evoked action potential was recorded from the sieve electrode by nerve stimulation via the cuff electrodes. The evoked action potential was also recorded from the cuff electrodes by nerve stimulation via the sieve electrode. In the second protocol, we implanted the sieve electrode to the renal sympathetic nerve in rabbits. Forty days after the implantation, the spontaneous action potential or sympathetic nerve activity was recorded under pentobarbital anesthesia. In conclusion, we were able to record the evoked and spontaneous action potentials using the sieve electrode. The sieve electrode will provide a useful neural interface for recording and stimulating the autonomic nervous system.

Insignificant effects of plasma catecholamines on dynamic heart rate regulation by the cardiac sympathetic nerve

Although plasma catecholamines such as norepinephrine (NE) and epinephrine (Epi) increase during severe exercise, the effects of high levels of plasma catecholamines on dynamic heart rate (HR) regulation by the cardiac sympathetic nerve remains unknown. The aim of the present study was to examine the effects of plasma catecholamines on the transfer function from sympathetic nerve stimulation to HR. In anesthetized rabbits, we randomly stimulated the right cardiac sympathetic nerve according to a binary white noise signal while measuring HR. The effects of intravenous NE administration at 1 and 10 mugmiddotkg^-1middoth^-1 were examined in 6 rabbits. The effects of intravenous Epi administration at 1 and 10 mugmiddotkg^-1middoth^-1 were examined in different 6 rabbits. Although plasma NE increased 10 times as high as the baseline level during the NE administration at mugmiddotkg^-1middoth^-1 , dynamic gain of the transfer function was not changed significantly (7.1plusmn1.2, 6.9plusmn1.1, and 7.7plusmn1.1 beatsmiddotmin^-1middotHz^-1). Similarly, although plasma Epi increased 10 times as high as the baseline level during the Epi administration at 10 mugmiddotkg^-1middoth^-1, dynamic gain of the transfer function was not changed significantly (7.5plusmn0.8, 7.9plusmn0.8, and 7.6plusmn1.2 beatsmiddotmin^-1middotHz^-1). In conclusion, plasma catecholamines of physiologically-relevant high concentrations did not interfere with the dynamic HR regulation by the cardiac sympathetic nerve.

Transfer function analysis of carotid sinus baroreceptor transduction

The carotid sinus baroreflex is one of the most important negative feedback systems that regulate arterial pressure. The neural arc transfer function from carotid sinus pressure (CSP) input to efferent sympathetic nerve activity shows a gain increase of approximately 10 dB when input frequency increases from 0.01 to 0.5 Hz. The transfer gain of the neural arc decreases in the frequency range above 0.8 Hz. The aim of the present study was to elucidate the extent of contribution of the carotid sinus baroreceptor transduction to the determination of the neural arc dynamic characteristics. In 7 anesthetized rabbits, we isolated the right carotid sinus and controlled CSP while recording afferent nerve activity (ANA) from the carotid sinus nerve. CSP was randomly assigned to either 80 or 120 mmHg with a switching interval of 50 ms according to a binary white noise signal for 15 min. The transfer function from CSP to ANA was estimated in the frequency range from 0.01 to 3 Hz. The transfer function showed a gain increase of approximately 4.6 dB when input frequency increased from 0.01 to 0.3 Hz. The transfer gain remained relatively constant up to 3 Hz. These results suggest that the carotid sinus baroreceptor transduction partly contributes to the gain increase of the baroreflex neural arc in the frequency range from 0.01 to 0.5 Hz but not the gain decrease above 0.8 Hz.

A comprehensive physiological model of circulation enables automatic piloting of hemodynamics in patients with acute heart failure

A comprehensive physiological model of the whole circulation is mandatory to quantitatively diagnose pathophysiology and to guide an appropriate treatment. Such a model would enable automatic piloting of hemodynamics in patients with acute heart failure. By extending Guyton's model, so as to deal with heart failure predominantly affecting left heart and to quantify left atrial pressure, we constructed such a model consisting of a venous return (VR) surface and a cardiac output (CO) curve. VR surface, the integrated property of systemic and pulmonary vascular beds, relates VR and left and right atrial pressures (P(LA), P(RA)) linearly as VR = V/W - G(R)P(RA) - G(L)P(LA), given total blood volume (V). CO curve, the pumping ability of hearts, relates CO and either P(LA) or P(RA) approximately by logarithmic functions, respectively, as CO = S(L) [ln (P(LA)- B(L)) + C(L)] = S(R) [ln (P(RA) - B(R)) + C(R)]. The slopes (S(R) and S(L)) of CO curve mainly describes the pump performance. W, G(R), G(L), B(R), B(L), C(R) and C(L) are parameters. We validate the model with animal experiments. Parameters W, G's, B's and C's were relatively constant in 19 dogs. In other 8 dogs, with or without acute left heart failure, we determined V and S's from a single set of CO, P(RA), P(LA) and standard parameter values. We then predicted hemodynamics (CO, P(RA), P(LA)) for altered V from -8 to +8 ml/kg. We identified standard values of parameters as W (0.13 min), G(R) (19.6 ml/min/kg/mmHg), G(L) (3.5 ml/min/kg/mmHg). B(L) (2.1 mmHg), C(L) (1.9), B(R) (2.0 mmHg) and C(R) (0.80). Using these, we could accurately predict CO (y = 0.93x + 6.5, r2 = 0.96, Figure 2), P(RA) (y = 0.87x + 0.4, r2 = 0.91) and P(LA) (y = 0.90x + 0.48, r2 = 0.93). Our comprehensive physiological model of circulation is useful in accurately predicting hemodynamics from the measurement of a single set of CO, P(RA) and (P(LA) following blood volume changes. Therefore, this model enables continuous monitoring of blood volume and pump performance for automatic hemodynamic piloting.

High resolution optical mapping of cardiac action potentials in freely beating rabbit hearts

Optical mapping of action potentials (APs) has become important tools for the cardiac electrophysiology. However, cardiac contraction unavoidably produces motion artifacts (MA) in optical signal. We developed a method to suppress motion artifacts without arresting the hearts.

METHODS

Using a dual-wavelength optical mapping system, APs were recorded on the surface of an isolated rabbit heart. Transmembrane APs were simultaneously recorded using glass microelectrodes. We eliminated MA in a frontal plane by a motion tracking technique. Subsequently, a dual-wavelength ratiometric method was used to remove MA in a vertical direction to a frontal plane.

RESULTS

MA were effectively removed from optical signals. Action potential duration measured from optical signals corresponded with those measured from microelectrodes (r2=0.9677). Our method enables us to map action potentials in freely beating hearts.

Immunohistochemical detection of ubiquitin-positive intracytoplasmic eosinophilic inclusion bodies in diffuse alveolar damage

AIMS

To clarify the relationship between ubiquitin-positive pneumocytes and intracytoplasmic eosinophilic inclusion bodies (IB) in patients who died of diffuse alveolar damage (DAD).

METHODS AND RESULTS

Eighteen patients with DAD were studied, in whom hyaline membranes were present in one or more out of five sections from each lobe of the lungs and 15 patients with no DAD. Light microscopy revealed hyaline membrane in over 25% of lobes from 18 patients with DAD. The cytoplasm of pneumocytes from six of 18 cases of DAD contained IB. Immunohistochemically, all IBs were characteristically positive for both ubiquitin (Ub) and cytokeratin KL-1. Cytoplasmic granules were also Ub+ in four cases of DAD without IB. IB+ or Ub+ pneumocytes were undetectable in non-DAD patients. We evaluated DAD severity based on hyaline membrane formation; the mean score in DAD with IB (3.60; n = 6) was significantly higher than that in Ub- (2.92; n = 8). Ub+ pneumocytes were found with or without IB among those cases with high DAD scores.

CONCLUSIONS

These findings suggest that disordered proteolysis in the Ub-mediated proteasome system leads to the accumulation of abnormal ubiquitinated protein, which includes cytokeratin, in pneumocytes. This is the first report to suggest that Ub+ pneumocytes are associated with disease severity in patients with DAD.

Filter cigarette smoking and lung cancer risk; a hospital-based case--control study in Japan

Recent changes in the histology of lung cancer, namely a relative increase of adenocarcinoma compared to squamous cell carcinoma, might be due to a temporal shift from nonfilter to filter cigarettes. To investigate the association between type of cigarette and lung cancer by histological type, we conducted a case–control study in Japan, comprising 356 histologically confirmed lung cancer cases and 162 controls of male current smokers, who provided complete smoking histories. Overall, logistic regression analysis after controlling for age and prefecture revealed decreased risk, as shown by adjusted odds ratios, for both squamous cell carcinoma and adenocarcinoma among lifelong filter-exclusive smokers as compared to nonfilter or mixed smokers. This decrease was greater for squamous cell carcinoma than for adenocarcinoma. Among men under 54 years, filter-exclusive smokers displayed increased risk of adenocarcinoma, but decreased risk of squamous cell carcinoma. The recent shift in histology from squamous cell carcinoma to adenocarcinoma, particularly among younger smokers, might be due to changes in cigarette type. However, among subjects aged 65 years or more, no differences in histological type appeared related to type of cigarette smoked, implying that other factors are associated with increases in adenocarcinoma among older Japanese population.

Bezold-Jarisch Reflex Blunts Arterial Baroreflex via the Shift of Neural Arc toward Lower Sympathetic Nerve Activity

Although the Bezold-Jarisch (BJ) reflex is potentially evoked during acute myocardial ischemia or infarction, its effects on the static characteristics of the arterial baroreflex remain to be analyzed in terms of an equilibrium diagram between the neural and peripheral arcs. The neural arc represents the static input-output relationship between baroreceptor pressure input and efferent sympathetic nerve activity (SNA), whereas the peripheral arc represents that between SNA and arterial pressure (AP). In 8 anesthetized rabbits, we increased carotid sinus pressure stepwise from 40 to 160 mmHg in increments of 20 mmHg at one-minute intervals while measuring renal SNA and AP under control conditions and during the activation of the BJ reflex by intravenous administration of phenylbiguanide (PBG, 100 microg.kg(-1).min(-1)). The neural arc approximated a sigmoid curve whereas the peripheral arc approximated a straight line. PBG decreased AP at the operating point from -91.3 +/- 2.4 to -71.7 +/- 3.1 mmHg (P < 0.01), and attenuated the total loop gain at the operating point from -1.31 +/- 0.44 to -0.51 +/- 0.14 (P < 0.05). The equilibrium diagram indicated that PBG caused a parallel shift of the neural arc toward lower SNA such that the maximum SNA was reduced to approximately 60% of control. PBG decreased neural and peripheral arc gains at the operating point to approximately 43% and 77%, respectively. In conclusion, the BJ reflex blunts arterial baroreflex via the shift of the neural arc toward lower SNA.

Attenuation of hypercapnic carbon dioxide chemosensitivity after postinfarction exercise training: possible contribution to the improvement in exercise hyperventilation

OBJECTIVE

To elucidate the responsible mechanisms of increased slope of minute ventilation relative to carbon dioxide production (VE/VCO(2)) during exercise after acute myocardial infarction without overt signs of heart failure, patients who had an acute myocardial infarction were examined after participating in a three month supervised exercise training programme.

DESIGN

Exercise testing, hypercapnic CO(2) chemosensitivity measurement (rebreathing method), and pulmonary function test were repeated at entry and after three months in 50 acute myocardial infarction patients with neither symptoms nor signs of heart failure who completed the training programme. Ten patients who performed initial inhospital training served as controls.

RESULTS

Age, peak oxygen uptake, left ventricular ejection fraction, CO(2) chemosensitivity, respiratory parameters (percentage of predicted normal vital capacity (%VC), forced expiratory volume in one second, and carbon monoxide transfer factor (%TLCO)) were all significantly correlated with VE/VCO(2) slope. Multivariate regression analysis showed that age (beta = 0.29, p = 0.01), %TLCO (beta = -0.27, p = 0.01), and CO(2) chemosensitivity (beta = 0.49, p < 0.001) were independent determinants of VE/VCO(2) slope. After three months, there was no significant change in these parameters in the control group. Peak oxygen uptake, %TLCO, and %VC and attenuation in CO(2) chemosensitivity increased significantly in the training group. The VE/VCO(2) slope decreased marginally (p = 0.11). The changes in VE/VCO(2) slope were correlated only with those in CO(2) chemosensitivity (r = 0.50, p < 0.001).

CONCLUSION

After acute myocardial infarction, exercise hyperventilation is seen in association with aging, enhanced hypercapnic CO(2) chemosensitivity, and reduced TLCO, even in the absence of overt heart failure. The correlation of VE/VCO(2) attenuation after training with the reduction in CO(2) chemosensitivity suggests that exercise training may reduce increased VE/VCO(2) slope, at least partially by reducing CO(2) chemosensitivity.

Changes in single unit activity in the lateral hypothalamic area of goats during feeding

In order to clarify the location of feeding centers in the ruminant brain, this study used a single-unit activity (SUA) recording electrode to investigate the existence of appetite-regulating neurons in the lateral hypothalamic area (LHA) in goats. Seven male Japanese Saanen goats were used in the experiment. The animals were fed twice daily, once in the morning (1000 to 1200) with 1.5 kg of roughly crushed alfalfa hay cubes, and once in the afternoon (1600 to 1800) with 200 g of commercial ground concentrate feed. The animals were allowed free access to drinking water. In this study, the animals were surgically operated on to position the recording electrode in the LHA. Recordings of SUA were carried out continuously over a 2.25-h period beginning 15 min prior to the commencement of morning feeding. The eating rates of crushed alfalfa hay cubes were highest 10 min after feeding commencement, but decreased sharply by the time 40 min had elapsed. The cumulative feed intake after the completion of the 2-h feeding period was 1164 +/- 38 g. The cumulative water intake upon the conclusion of the 2-h feeding period was 2422 +/- 107 mL. This study recorded 31 units, of which five showed a response to feeding and altered their firing rates. In response to a sharp increase in eating rates, all five units increased their firing rates to a level higher than that of prefeeding (P < 0.05). As the animals reached a level of satiety (eating rates declined to very low levels), firing of units I and II stopped completely, while the firing rates of units III, IV, and V decreased. Examination of a serial histological section confirmed that the five units in which changes in firing rates with feeding were observed were all located in the dorsolateral hypothalamic area close to the fornix. The LHA neurons recorded in this experiment characteristically showed neuronal activity increases at high levels of feeding, but decreases at low levels. The results suggest that there are cells located in the LHA of goats that are active in the physiological regulation of hay (dry forage) intake.

Gene-specific response of dynamic ventricular repolarization to sympathetic stimulation in LQT1, LQT2 and LQT3 forms of congenital long QT syndrome

AIMS

Differences in the sensitivity of the genotype of the congenital long QT syndrome to sympathetic stimulation have been suggested. This study compared the influence of sympathetic stimulation on continuous corrected QT (QTc) intervals between LQT1, LQT2 and LQT3 forms of the congenital long QT syndrome.

METHODS AND RESULTS

We recorded a 12-lead electrocardiogram continuously before and after bolus injection (0.1 microg x kg(-1)) of epinephrine followed by continuous infusion (0.1 microg x kg(-1) min(-1)) in 12 LQT1, 10 LQT2, 6 LQT3, and 13 control patients. The QT intervals and previous RR intervals of all beats were measured semi-automatically, and the QTc intervals of all beats were calculated by Bazett's method. The dynamic response of the RR interval to epinephrine was no different between the four groups. The QTc was prolonged remarkably (477+/-42 to 631+/- 59 ms; P<0.0005, % delta prolongation =+32%) as the RR was maximally decreased (at peak of epinephrine), and remained prolonged at steady state conditions of epinephrine (556+/-56 ms; P<0.0005 vs baseline, +17%) in LQT1 patients. Epinephrine also prolonged the QTc dramatically (502+/-23 to 620+/-39 ms; P<0.0005, +24%) at peak of epinephrine in LQT2 patients, but this shortened to baseline levels at steady state (531+/-25 ms; P=ns vs baseline, +6%). The QTc was much less prolonged at peak of epinephrine in LQT3 (478+/-44 to 532+/-41 ms; P<0.05, +11%) and controls (394+/-21 to 456+/-18 ms; P<0.0005, +16%) than in LQT1 and LQT2 patients, and shortened to the baseline levels (LQT3; 466+/-49 ms, -3%, controls; 397+/-16 ms, +1%; P=ns vs baseline) at steady state.

CONCLUSION

Our data suggest that the dynamic response of ventricular repolarization to sympathetic stimulation differs between LQT1, LQT2 and LQT3 syndromes, and may explain why the trigger of cardiac events differs between the genotypes.

Heart rate-independent vagal effect on end-systolic elastance of the canine left ventricle under various levels of sympathetic tone

BACKGROUND

Although we have shown that in rabbits the direct (heart rate [HR]-independent) vagal effect on left ventricular end-systolic elastance (E(es)) was negligible under minimal sympathetic tone, how underlying sympathetic tone modulates the inotropic response to vagal stimulation remains unknown.

METHODS AND RESULTS

We used an isolated canine heart preparation with functioning autonomic nerves. We examined the direct vagal inotropic effect by measuring E(es) under fixed-rate atrial pacing with or without concomitant sympathetic nerve stimulation. Right and left vagal stimulation at 20 Hz decreased HR by 27+/-3% and 14+/-2%, respectively, and decreased E(es) by 11+/-2% and 6+/-2%, respectively. When we fixed HR by atrial pacing, right and left vagal stimulation at 20 Hz did not decrease E(es) (0.01+/-0.3% and 0.3+/-0.4%; NS). Concomitant left sympathetic nerve stimulation at 4 Hz enhanced direct vagal negative inotropism to -19+/-3% and -34+/-5% for 20-Hz right and left vagal stimulation (interaction, P<0.01).

CONCLUSIONS

Direct vagal negative inotropism was unobservable with minimal sympathetic tone in dogs but was enhanced with concomitant sympathetic stimulation.

Effects of ketamine on in vivo cardiac sympathetic nerve endings

Using the dialysis technique, we examined the effect of ketamine on dialysate norepinephrine (NE) levels in the myocardial interstitial space in anesthetized cats. Dialysis probes were implanted in the left ventricular myocardium, and we measured the dialysate NE levels serving as an indicator of NE output at the cardiac sympathetic nerve endings. During local administration of ketamine (10 mM), we examined the time-course of the change in dialysate NE levels and the dialysate NE response to coronary occlusion. Dialysate NE levels significantly increased from 39+/-7 pg/ml at control to 133+/-22 pg/ml 30 min after beginning the ketamine administration. Addition of either omega-conotoxin GVIA (N-type calcium channel blocker) at 10 microg/kg intravenously or desipramine (neuronal NE transport blocker) at 100 microM did not inhibit the increment in dialysate NE evoked by ketamine. These findings suggest that the increase in dialysate NE evoked by ketamine is dependent neither on the activity of NE exocytosis nor on the neuronal NE transport. Left descending coronary artery occlusion evoked increments in dialysate NE. The addition of ketamine augmented the dialysate NE response to coronary occlusion. A ketamine-induced increment in dialysate NE might occur as a consequence of NE exocytosis independent or membrane NE transport insensitive efflux of NE.

In vivo assessment of acetylcholine-releasing function at cardiac vagal nerve terminals

We examined whether the ACh concentration measured by cardiac microdialysis provided information on left ventricular ACh levels under a variety of vagal stimulatory and modulatory conditions in anesthetized cats. Local administration of KCl (n = 5) and ouabain (n = 7) significantly increased the ACh concentration in the dialysate to 4.3 +/- 0.8 and 7.3 +/- 1.3 nmol/l, respectively, from the baseline value of 0.6 +/- 0.5 nmol/l. Intravenous administration of phenylbiguanide (n = 5) and phenylephrine (n = 6) significantly increased the ACh concentration to 5.4 +/- 0.9 and 6.0 +/- 1.5 nmol/l, respectively, suggesting that the Bezold-Jarisch and arterial baroreceptor reflexes affected myocardial ACh levels. Modulation of vagal nerve terminal function by local administration of tetrodotoxin (n = 6), hemicholinium-3 (n = 6), and vesamicol (n = 5) significantly suppressed the electrical stimulation-induced ACh release from 20.4 +/- 3.9 to 0.6 +/- 0.1, 7.2 +/- 1.9, and 2.7 +/- 0.6 nmol/l, respectively. Increasing the heart rate from 120 to 200 beats/min significantly reduced the myocardial ACh levels during electrical vagal stimulation, suggesting a heart rate-dependent washout of ACh. We conclude that ACh concentration measured by cardiac microdialysis provides information regarding ACh release and disposition under a variety of pathophysiological conditions in vivo.