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51.
Yamazaki F Matsumura F Nagata J Ando A Imura T 《European journal of applied physiology》2001,85(3-4):208-213
The purpose of this study was to elucidate the effect of raised body temperature per se during acute heat stress on the spontaneous
arterial baroreflex control of heart rate (f
c) in humans. To investigate whether unloading of cardiopulmonary baroreceptors during whole-body heating would alter the arterial
baroreflex control of f
c, we controlled loading of the cardiopulmonary baroreceptors by head-down tilt (HDT) at angles of 5°, 10°, 15°, and 30° during
heat stress produced by hot-water-perfused suits. The sensitivity of the arterial baroreceptor-cardiac reflex was calculated
from the spontaneous changes in beat-to-beat arterial pressure and f
c. As an index of cardiopulmonary baroreceptor loading, the left atrial diameter (LAD) was measured by echocardiography. During
whole-body heating, the LAD decreased with the rising body core temperature and increased with the HDT. The decreased LAD
during heating almost recovered to the normothermic control level by 10° HDT. In the supine position, cardiac baroreflex sensitivity
remained unchanged during heating. Arterial pressure, f
c and cardiac baroreflex sensitivity were not changed by HDT ranging from 5° to 30° during heating. These results suggest that
cardiac baroreflex sensitivity remain unchanged during graded loading of the cardiopulmonary baroreceptors in heat-stressed
humans. Also, we conclude that the sensitivity of the spontaneous arterial baroreflex controlling the f
c is not influenced by raised body temperature per se during acute heat stress.
Electronic Publication 相似文献
52.
A. Maillet A. Pavy-Le Traon A. M. Allevard D. Sigaudo R. L. Hughson C. Gharib G. Gauquelin 《European journal of applied physiology》1994,68(6):497-503
Endocrine regulation of hormones and electrolytes during 37.5 h of –6° head down tilt (HDT) was studied in 13 men. The acute effects of simulated weightlessness are today well documented, but no study has been made concerning the hormone changes between 12 h and 2 days of HDT. Plasma volume showed a maximal increase of 9.23 (SEM 1.97) % after 6.5 h (P<0.01) and had returned to prestudy levels after 13.5 h of HDT. From 1.5 h to 4 h of HDT, C-terminus and N-terminus atrial natriuretic peptide (ANP) concentrations in plasma were increased by about 50% (P<0.01) and thereafter declined to pre-HDT levels. Plasma renin activity (PRA) was decreased by 47% (P<0.05) after 4 h of HDT; PRA increased after 23.5 h to 60%; noradrenaline concentration decreased immediately and remained low up to 37.5 h. Diuresis and natriuresis were evident during the 1st day of HDT, resulting in a marked increase in the urinary Na+. These results showed that the initial hormone (ANP, PRA) changes during HDT did not last more than 13.5 h and that after 24 h a new state would seem to have been established to adapt the body to hypovolaemia. 相似文献
53.
Gerasimos Gavrielatos Konstantinos P. Letsas Loukas K. Pappas Panagiotis Dedeilias Elias Sioras Fotis Kardaras 《Cardiovascular pathology》2007,16(6):365-367
Myxoma is the most common type of primary tumors of the heart in adults. The majority of patients with myxomas may experience symptoms due to central or peripheral embolism or intracardiac obstruction, while in some cases, they may be completely asymptomatic. Rarely, patients develop unusual symptoms that complicate the diagnostic evaluation. Herein, we describe the case of a 70-year-old patient with a long-lasting low-grade fever due to a large left atrial myxoma revealed during a transthoracic echocardiography. 相似文献
54.
Sheikh-Zade YR Galenko-Yaroshevskii PA Cherednik IL 《Bulletin of experimental biology and medicine》2002,134(1):1-4
We propose a new mechanism of atrial fibrillation basing on the results of 30 series of acute experiments on anesthetized cats. In brief, combination of two or more arrhythmogenic factors shortens the interval between the inward and outward ionic currents in cardiomyocytes to a critical value. Under these conditions repolarization of cardiomyocyte membrane reaches the excitation threshold before complete inactivation of the depolarizing currents. This inevitably results in autoexcitation of myocytes (or extrasystole), that in turn promotes repolarization. Once occurred, autoexcitation turns into self-triggering activity resembling tachyarrhythmia paroxysm. 相似文献
55.
K. Ando N. Umetani T. Kurosawa S. Takeda Y. Katoh F. Marumo 《Journal of molecular medicine (Berlin, Germany)》1988,66(17):768-772
Summary A highly sensitive radioimmunoassay to measure atrial natriuretic peptide (ANP) concentration in urine has been established, and its clinical usefulness is presented. ANP in urine was stable at 4° C for several days and was easily measured by our radioimmunoassay. The average ANP excretion in 65 healthy persons was 25.0±1.4 ng/day (mean ± SEM) and the fractional excretion of ANP was 0.7±0.05%. In 14 patients with congestive heart failure, the average ANP excretion was 119.2±29.4 ng/day, which decreased to 53.3±11.0 after successful treatment.Abbreviations ANP
atrial natriuretic peptide
- hANP
human atrial natriuretic peptide
- RIA
radioimmunoasay
- NSB
non specific bound
- FEANP
the fractional excretion of atrial natriuretic peptide
- FENa
the fractional excretion of sodium
- SIADH
the syngrome of inappropriate secretion of antidiuretic hormone 相似文献
56.
Among other characteristics, the steady-state current-voltage relationship of patch-clamped single atrial myocytes from guinea-pig hearts is defined by an outward current hump in the potential region –15 to +40mV. This hump was reversibly suppressed by Co2+ (3 mM) or nitrendipine (5 M) and enhanced by Bay K 8644 (5 M). The maintained outward current component suppressed by Co2+ extended between –15.2±1.9 mV and +39.5 ±1.7 mV (mean±SEM of 14 cells) and has an amplitude of 95.7±9.4 pA at +10 mV. In isochronal I-V curves, the hump was already visible at 400 ms with essentially the same amplitude as at 1500 ms. The Co2+ -sensitive outward current underlying the hump was poorly time-dependent during 1.5 s voltage pulses but slowly relaxed upon repolarization. Tail currents reversed near the K+ equilibrium potential under our experimental conditions. The current hump of the steady-state I-V curve was also abolished by caffeine (10 mM) or ryanodine (3 M), both drugs that interfere with sarcoplasmic reticulum function. Apamin (1 M) or quinine (100 M) but not TEA (5–50 mM) markedly reduced its amplitude. However, at similar concentrations as required to inhibit the hump, both apamin and quinine appeared to be poorly specific for Ca2+ -activated K+ currents in heart cells since they also inhibited the L-Type Ca2+ current. It is concluded that a long lasting Ca2+ -activated outward current, probably mainly carried by K+ ions but not sensitive to TEA, exists in atrial myocytes which is responsible for the current hump of the background I-V curve. 相似文献
57.
We examined the action of high (2×10–8M) and low (6×10–9M) concentrations of atrial natriuretic factor (ANF) on water and urea transport in the rat inner medullary collecting duct (IMCD) using the in vitro microperfusion technique. We measured the hydraulic conductivity (Lp ×10–6 cm/atm per second) and both lumen-to-bath (P
u(lb)) and bath-to-lumen (P
u(bl)) 14C-urea permeabilities (P
u× 10–5 cm/s) in the absence and in the presence of vasopressin (VP). High concentrations of ANF were able to inhibit the maximum activity of (50 U/ml) VP-stimulated L
p but physiological concentration of ANF inhibit only submaximum activity (10 U/ml) of VP-stimulated L
p. The hydrosmotic effect of dibutyryl-cyclic 3,5 adenosine monophosphate (cAMP) (10–4M) was unchanged by high concentrations of ANF (2×10–8M). Also we found that high (10–4M) and low (10–6M) concentrations of exogenous cyclic 3,5-guanosine monophosphate (GMP) while unable to change the Lp in the absence of VP, decreased the maximum activity of VP-stimulated Lp significantly. We also found that ANF inhibits partially and in a reversible manner the VP-stimulated P
u(lb) but not the VP-stimulated P
u(bl). These results demonstrated that plasma concentrations of ANF observed during volume expansion (10–10M) are able to inhibit submaximum activity of VP-stimulated (10 U/ml) L
p in the rat IMCD, this effect seems to occur before cAMP formation and it appears to be mediated by cGMP. ANF (6× 10–9M) also reduced the VP-stimulated urea outflux. Therefore, the increase in water excretion produced by ANF could be explained, at least in part, by the inhibition by ANF of vasopressin effects on water and urea transport in the IMCD.This study was presented in part at the VI Latin American Congress of Nephrology, Brazil, October 1985 and at the Xth International Congress of Nephrology, London, July 1987. 相似文献
58.
Grazyna Perko Jes F. Schmidt Jorgen Warberg Niels H. Secher 《European journal of applied physiology》1996,73(5):459-464
To evaluate influences on blood volume distribution, atrial natriuretic peptide concentrations (ANP) and thoracic and leg electrical impedance at 2.5 (TI2.5 and LI2.5, respectively) and 100 kHz (TI100 and LI100, respectively) were monitored during administration of ketanserin, noradrenaline and trimetaphan combined with lower body negative pressure (LBNP) in 12 subjects. Administration of clinically relevant doses of ketanserin alone did not induce changes in mean arterial pressure (MAP) or in the central blood volume, as electrical impedance and ANP concentrations did not change. During continued infusion of ketanserin an increase in MAP from a mean of 90 (range 83–108) to 113 (range 98–138) mmHg was induced by noradrenaline, but TI2.5 [mean 45.6 (range 39.3–54.2)] and TI100 [mean 33.8 (range 27.5–38.5) ] remainded stable until ganglionic blockade and LBNP were applied, when they increased by a mean of 3.1 (range 2.0–6.1) and 2.7 (range 1.1–4.2) , respectively (P < 0.05). Conversely, LI2.5 [mean 79.6 (range 74.1–89.4)] and LI100 [mean 56.7 (range 52.4–63.3) ] decreased by a mean of 3.2 (range 1.2–8.0) and 2.3 (range 0.9–3.9) ANP from a mean of 27.7 (range 10.2–62.7) to 12.7 (range 7.1–27.5) pmol· 1–1 and MAP fell to a mean of 62 (range 42–70) mmHg (P < 0.05). The heart rate was a mean of 75 (range 69–77) beats -min-' and did not change until LBNP, when it increased to a mean of 102 (range 78–104) beats · min–1, as presyncopal symptoms appeared. The data indicated that serotonergic blockade by ketanserin and -sympathetic stimulation by noradrenaline did not affect blood volume distribution in normal humans, but that ganglionic blockade combined with LBNP reduced the central blood volume as leg volume increased; during central hypovolaemia tachycardia induced by ganglionic blockade did not prevent the fall in MAP, and thereby the appearance of presyncopal symptoms. 相似文献
59.
本研究旨在探讨茶黄烷醇(TF)对离体缺血再灌注鼠心心律失常的作用。结果表明,对照组缺血后再灌注初期心律失常发生率高达91.67%(11/12),显著高于TF组(P<0.005),TF组心律失常发生率仅为23.08%(3/13);对照组心律失常持续时间平均为27.91±6.94min,TF组平均为9.83±6.21min,两组比较差异显著(P<0.001)。上述结果表明TF具有显著的抗缺血再灌性心律失常作用。 相似文献
60.
Yoshihisa Kurachi Toshiaki Nakajima Tsuneaki Sugimoto 《Pflügers Archiv : European journal of physiology》1987,410(3):227-233
The short-term desensitization of the acetylcholine (ACh)-induced K+ channel current was examined in single atrial cells of guinea-pig heart. The tight-seal whole cell voltage clamp technique was used. The solution in the pipettes contained GTP or guanosine-5-O-(3-thiotriphosphate) (GTP-S, a non-hydrolyzable GTP analogue). In GTP-loaded cells, ACh evoked a specific K+ channel current via GTP-binding proteins (G) in a dose-dependent manner. The K+ current showed agonist-dependent desensitization similar to those reported in other cardiac tissues (Nilius 1983; Carmeliet and Mubagwa 1986). The cellular response to ACh was also desensitized by activation of P1-purinergic receptors with adenosine (Ado). In GTP-S-loaded cells, the K+ current was gradually induced even in the absence of agonists, probably due to direct activation of G proteins by GTP-S. In the early phase of the spontaneous current increase, ACh evoked a large current transiently. As the GTP-S-induced activation of the current progressed, the magnitude of the ACh-evoked current transient became smaller and finally negligible. Similar results were obtained when Ado was used as an agonist instead of ACh to induce the K+ current. Therefore, it is indicated that the agonistreceptor interaction may not be essential for the desensitization of ACh-induced K+ current in atrial myocytes. 相似文献