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1.
P. Arbeille D. Sigaudo A. Pavy Le Traon S. Herault M. Porcher C. Gharib 《European journal of applied physiology and occupational physiology》1998,78(3):208-218
The first objective of this study was to confirm that 4 days of head-down tilt (HDT) were sufficient to induce orthostatic
intolerance, and to check if 4 days of physical confinement may also induce orthostatic intolerance. Evidence of orthostatic
intolerance during tilt-up tests was obtained from blood pressure and clinical criteria. The second objective was to quantify
the arterial and venous changes associated with orthostatic intolerance and to check whether abnormal responses to the tilt
test and lower body negative pressure (LBNP) may occur in the absence of blood pressure or clinical signs of orthostatic intolerance.
The cerebral and lower limb arterial blood flow and vascular resistance, the flow redistribution between these two areas,
and the femoral vein distension were assessed during tilt-up and LBNP by ultrasound. Eight subjects were given 4 days of HDT
and, 1 month later, 4 days of physical confinement. Tilt and LBNP test were performed pre- and post-HDT and confinement. Orthostatic
intolerance was significantly more frequent after HDT (63%) than after confinement (25%, P<0.001). Cerebral haemodynamic responses to tilt-up and LBNP tests were similar pre- and post-HDT or confinement. Conversely,
during both tilt and LBNP tests the femoral vascular resistances increased less (P<0.002), and the femoral blood flow reduced less (P<0.001) after HDT than before HDT or after confinement. The cerebral to femoral blood flow ratio increased less after HDT
than before (P<0.002) but remained unchanged before and after confinement. This ratio was significantly more disturbed in the subjects who
did not complete the tilt test. The femoral superficial vein was more distended during post-HDT LBNP than pre-HDT or after
confinement (P<0.01). In conclusion, 4 days of HDT were enough to alter the lower limb arterial vasoconstriction and venous distensibility
during tilt-up and LBNP, which reduced the flow redistribution in favour of the brain in all HDT subjects. Confinement did
not alter significantly the haemodynamic responses to orthostatic tests. The cerebral to femoral blood flow ratio measured
during LBNP was the best predictor of orthostatic intolerance.
Accepted: 12 December 1997 相似文献
2.
R. M. Bevan P. J. Butler 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(5):349-354
Arterial blood pressure was monitored in voluntarily diving tufted ducks. Mean arterial blood pressure while diving increased during the pre-dive tachycardia, fell to resting levels on submersion, then gradually increased before peaking on surfacing. Estimated total peripheral resistance fell during the pre-dive and post-dive tachycardia, presumably to allow the oxygen stores to be loaded and replenished respectively and/or for carbon dioxide levels to be reduced. Changes in mean arterial blood pressure and total peripheral resistance suggest that peripheral vasoconstriction occurs in some vascular beds during a dive. An increase in arterial blood pressure (and therefore perfusion pressure) may be employed to increase blood flow and oxygen delivery to the active leg muscles.Abbreviations ecg
Electrocardiogram, f
H, heart rate
- MABP
mean arterial blood pressure
-
P
b
blood pressure(s)
- TPR
total peripheral resistance
-
V
b
cardiac output 相似文献
3.
Geneviève Florence Marc Lemenn Sylvain Desert Fran?ois Bourron André Serra Richard Bonnier Jean-Pierre Blanquie Robert Charbonné Jacques Seylaz 《European journal of applied physiology and occupational physiology》1998,77(5):469-478
We studied the effect of gravity on cerebral cortical blood flow (CBF), mean arterial blood pressure () and heart rate in six rabbits exposed to parabolic flights. The CBF was obtained using a laser-Doppler probe fixed on to
a cranial window. Before weightlessness, the animals were exposed to chest-to-back directed acceleration (1.8–2.0 g). The CBF values were expressed as a percentage of CBFo (mean CBF during 60 s before the 1st parabola). Propranolol (1 mg · kg−1 IV) was given after the 11th parabola and pentobarbital (12–15 mg · kg−1 IV) after the 16th parabola. Before the administration of the drugs, CBF increased (P < 0.01) during hypergravity [i.e. maximal CBF 151 (SD 64)% CBFo. Simultaneously increased [maximal , 119 (SD 11) mmHg (P < 0.01)]. At the onset of weightlessness, CBF and reached maximal values [194 (SD 96)% CBFo (P < 0.01) and 127 (SD 19) mmHg, (P < 0.01) respectively]. The microgravity-induced increase in CBF was transient since CBF returned to its baseline value after
8 (SD 2) s of microgravity. After propranolol administration, CBF was not statistically different during hypergravity but
an elevation of CBF was still observed in weightlessness. The increases in CBF and also persisted during weightlessness after pentobarbital administration. These data would indicate that CBF of nonanesthetized
rabbits increases during the first seconds of weightlessness and demonstrate the involvement of rapid active regulatory mechanisms
since CBF returned to control values within 8 (SD 2) s. We concluded that this elevation in blood flow was not related to
stress because it persisted after the administration of propranolol and pentobarbital.
Accepted: 6 November 1997 相似文献
4.
S. Thomas R. Fritsche S. F. Perry 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):451-458
Simultaneous venous (pre-branchial) and arterial (post-branchial) extracorporeal blood circulations were utilized to monitor continuously the rapid and progressive effects of acute environmental hypercapnia (water partial pressure of CO2 4.8±0.2 torr) or hypoxia (water partial pressure of O2 25±2 torr) on oxygen and carbon dioxide tensions and pH in the blood of rainbow trout (Oncorhynchus mykiss). During hypercapnia, the CO2 tension in the arterial blood increased from 1.7±0.1 to 6.2±0.2 torr within 20 min and this was associated with a decrease of arterial extracellular pH from 7.95±0.03 to 7.38±0.03; the acid-base status of the mixed venous blood changed in a similar fashion. The decrease in blood pH in vivo was greater than in blood equilibrated in vitro with a similar CO2 tension indicating a significant metabolic component to the acidosis in vivo. Under normocapnic conditions, venous blood CO2 tension was slightly higher than arterial blood CO2 tension difference was abolished or reversed during the initial 25 min of hypercapnia indicating that CO2 was absorbed from the water during this period. Arterial O2 tension remained constant during hypercapnia; however, venous blood O2 tension decreased significantly (from 22.0±2.6 to 9.0±1.0 torr) during the initial 10 min. Hypercapnia elicited the release of catecholamines (adrenaline and noradrenaline) into the blood. The adrenaline concentration increased from 6±3 to 418±141 nmol · l-1 within 25 min; noradrenaline concentration increased from 3±0.5 to 50±21 nmol · l-1 within 15 min. During hypoxia arterial blood O2 tension declined progressively from 108.4±9.9 to 12.8±1.7 torr within 30 min. Venous blood O2 tension initially was stable but then decreased abruptly as catecholamines were released into the circulation. The release of catecholamines occurred concomitantly with a sudden metabolic acidosis in both blood compartments and a rise in CO2 tension in the mixed venous blood only.Abbreviations
CCO2
plasmatotal carbondioxide
-
CtO2
blood oxygen content
-
PO2
partial pressure of oxygen
-
PCO2
partial pressure of carbon dioxide
-
PaO2
arterial bloodPO2
-
PaCO2
arterial bloodPCO2
-
PvCO2
venous bloodPCO2
-
PwO2
waterPO2
-
PwCO2
waterPCO2
- Hb
haemoglobin
-
SHbO2
haemoglobin oxygen saturation
- HPLC
high-performance liquid chromatography
- rbc
red blood cell(s)
- Hct
haematocrit 相似文献
5.
To testwhether the contribution of endothelin-B (ET-B) receptors to restingvascular tone differs between genders, we administered the ET-Breceptor antagonist BQ-788 into the forearm skin of 11 male and 11 female subjects by intradermal microdialysis. Skin blood flow wasmeasured using laser-Doppler flowmetry at the microdialysis site. Theprobe was perfused with Ringer solution alone, followed by BQ-788 (150 nM) and finally sodium nitroprusside (28 mM) to effect maximalcutaneous vasodilation. Cutaneous vascular conductance (CVC) wascalculated (laser-Doppler flowmetry/mean arterial pressure) andnormalized to maximal levels (%max). In male subjects, baseline CVCwas (mean ± SE) 19 ± 3%max and increased to 26 ± 5%max with BQ-788 (P < 0.05 vs. baseline). In femalesubjects, baseline CVC was 13 ± 1%max and decreased to 10 ± 1%max in response to BQ-788. CVC responses to BQ-788 differed withgender (P < 0.05); thus the contribution of ET-Breceptors to resting cutaneous vascular tone differs between men andwomen. In men, ET-B receptors mediate tonic vasoconstriction, whereas,in women, ET-B receptors mediate tonic vasodilation. 相似文献
6.
Sandblom E Axelsson M Davison W 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(2):165-173
Catecholamines increase arterial pressure by increasing cardiac output (Q) and stroke volume (V
s), while angiotensin II (ang II) also increases vascular resistance (R
sys) in the Antarctic fish Pagothenia borchgrevinki. Adrenaline, phenylephrine and ang II (Asn1, Val5) were injected into P. borchgrevinki. Cardiovascular variables, including central venous pressure (P
cv) and mean circulatory filling pressure (P
mcf; an index of venous capacitance), were recorded to investigate if venous vasoconstriction can explain the increased V
s and Q and the arterial pressor response in this species. Routine P
cv and P
mcf were 0.11 ± 0.01 and 0.18 ± 0.02 kPa, respectively. All of the drugs caused moderate increases in P
cv and P
mcf and the responses were attenuated after α-adrenergic blockade with prazosin. Although dorsal aortic pressure (P
da) also increased in response to all agonists, the mechanisms differed. Adrenaline caused sustained increases in V
s and Q, while R
sys only rose transiently. Ang II had a slower effect than adrenaline and increased both R
sys and Q, while phenylephrine only increased R
sys. This study demonstrates that P
cv is positive and controlled by an α-adrenergic mechanism in P. borchgrevinki. However, given the relatively small venous response to adrenaline it seems more likely that the increases in V
s and Q from this agonist are due to direct effects on the heart. 相似文献
7.
Christian-Serge Degoute M.-P. Preckel Christian Dubreuil Vincent Banssillon Roland Duclaux 《European journal of applied physiology and occupational physiology》1997,75(4):326-332
The purpose of this work was to show that regulation of the blood flow to the cochlea by the sympathetic nervous system occurs
in humans at the level of the cochlear microcirculation during increases in blood pressure and that its involvement depends
on the pressure level. Eight anaesthetized patients undergoing tympanoplasty for hearing disease took part in a pharmacological
protocol of stimulation and inhibition of the autonomic nervous system (ANS) to provide variations in systolic blood pressure
(BPS) and cochlear blood flow (CBF). The CBF was measured by laser-Doppler flowmetry. Changes in autonomic nerve activity were
brought about by changes in baroreceptor activity (BR) initiated by the injection of an α adrenergic agent before and after
sympathetic and parasympathetic blockade. The CBF variations (δCBF) were plotted against BPS increases at each stage of the ANS inhibition. The BR diminished significantly after α blockade, after α and β blockade,
and after α and β blockade and atropine, by 50% (P < 0.01), 29% (P < 0.05), and 95% (P < 0.001) respectively. The BPS increased significantly (P < 0.01) by 36 (SD 9)%, 47 (SD 1)%, and 67 (SD 16)% respectively. The CBF response to an increase in BPS exhibited two opposing variations in the patients: CBF decreased significantly in one group, and increased significantly
in the other group. In both groups, δCBF decrease and δCBF increase, respectively, were significant after ANS blockade; even
so the decrease and increase, respectively, levelled off at BPS around 160 mmHg before ANS blockade. For BPS below 160 mmHg, correlations between δCBF and BPS were significant before inhibition and after inhibition of ANS. For BPS above 160 mmHg, BPS and δCBF were not correlated before inhibition of ANS, and were significantly correlated after inhibition of ANS. For BPS below 160 mmHg, CBF response to the BPS increase was the same before and after ANS blockade, i.e. ANS control did not predominate; even so, for BPS above 160 mmHg, the CBF response to BPS increase was different before and after ANS blockade: CBF varied significantly after ANS blockade as it varied for BPS below 160 mmHg, while it remained constant before ANS blockade that elicited ANS control of CBF. In conclusion, sympathetic
nerve regulation via its vasomotor tone at the level of cochlear microcirculation occurred markedly when the blood pressure
was above 160 mmHg; the autonomic nervous system would appear to control the cochlear blood flow against large variations
in blood flow in response to hypertensive phenomena.
Accepted: 7 October 1996 相似文献
8.
Gmitrov J 《International journal of biometeorology》2007,51(4):345-344
Spreading evidence suggests that geomagnetic field (GMF) modulates artificial magnetic fields biological effect and associated
with increased cardiovascular morbidity. To explore the underlying physiological mechanism we studied 350 mT static magnetic
field (SMF) effect on arterial baroreflex-mediated skin microcirculatory response in conjunction with actual geomagnetic activity,
reflected by K and K
p
indices. Fourteen experiments were performed in rabbits sedated by pentobarbital infusion (5 mg/kg/h). Mean femoral artery
blood pressure, heart rate, and the ear lobe skin microcirculatory blood flow, measured by microphotoelectric plethysmogram
(MPPG), were simultaneously recorded before and after 40 min of NdFeB magnets local exposure to sinocarotid baroreceptors.
Arterial baroreflex sensitivity (BRS) was estimated from heart rate/blood pressure response to intravenous bolus injections
of nitroprusside and phenylephrine. We found a significant positive correlation between SMF-induced increase in BRS and increment
in microvascular blood flow (ΔBRS with ΔMPPG, r=0.7, p<0.009) indicated the participation of the arterial baroreflex in the regulation of the microcirculation and its enhancement
after SMF exposure. Geomagnetic disturbance, as opposed to SMF, decreased both microcirculation and BRS, and counteracted
SMF-induced increment in microcirculatory blood flow (K-index with ΔMPPG; r
s=−0.55, p<0.041). GMF probably affected central baroreflex pathways, diminishing SMF direct stimulatory effect on sinocarotid baroreceptors
and on baroreflex-mediated vasodilatatory response. The results herein may thus point to arterial baroreflex as a possible
physiological mechanism for magnetic-field cardiovascular effect. It seems that geomagnetic disturbance modifies artificial
magnetic fields biological effect and should be taken into consideration in the assessment of the final effect.
An erratum to this article can be found at 相似文献
9.
Margarthe Brummermann Randi Eidsmo Reinertsen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):16-22
Summary Body temperatures, metabolic rate, haemostatic parameters, and cardiovascular reactions to thoracic skin cooling were compared between incubating (broody) and non-broody Bantam hens. Under resting conditions, without thoracic skin cooling, cardiac output of broody hens was twice that of non-broody hens. However, their metabolic rate
was increased by only one-third over that of non-broody hens, and the arteriovenous difference in oxygen concentration was smaller for broody birds. This indicates a higher rate of non-nutrient blood flow during incubation. A higher thoracic skin temperature (T
ths) for broody hens compared to non-broody hens suggests that brood patches are the probable site of this increased flow through arteriovenous anastomoses (AVAs). Thoracic skin cooling increased metabolic rate and
significantly more in broody hens, but did not increase AVA blood flow. The relation between metabolic rate and total peripheral resistance indicated more intense vasodilation for broody hens at the relatively low metabolic rates during moderate cooling, and more intense vasoconstriction for the broody hens at the high metabolic rates during stronger cooling. This corresponds to T
ths measurements indicating dilation of brood patch AVAs with moderate cooling and AVA constriction with severe cooling. During moderate cooling, vasoconstriction in the feet and wattles of broody hens (but not of non-broody hens) freen non-nutrient blood flow for redistribution to the brood patches. Thus, the cardiovascular system of the hen seems to adjust to the special demands of incubation by a permanent increase of AVA flow in the brood patch, and by an additional capacity for brood patch vasodilation induced by cold stimuli in the range from 35 to 25°C. This corresponds well to the temperature range for development of galliform embryos.Abbreviations AVAs
arteriovenous anastomoses
- BP
arterial blood pressure
-
CaO2 and CvO2
arterial and venous oxygen concentrations, respectively
- HR
heart rate
- MAP
mean arterial blood pressure
-
cardiac output
- SV
stroke volume
-
T
bs
back skin temperature
-
T
c
cofon temperature
-
T
f
foot temperature
-
T
ths
thoracic skin temperature
- TPR
total peripheral resistance
-
T
w
wattle temperature
-
oxygen consumption 相似文献
10.
Steve F. Perry Serge Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(5):489-497
Summary An extracorporeal circulation of rainbow trout (Oncorhynchus mykiss) was utilized to continuously monitor the rapid and progressive effects of endogenous or exogenous catecholamines on blood respiratory/acid-base status, and to provide in vivo evidence for adrenergic retention of carbon dioxide (CO2) in fish blood (cf. Wood and Perry 1985). Exposure of fish to severe aquatic hypoxia (final P
wO2=40–60 torr; reached within 10–20 min) elicited an initial respiratory alkalosis resulting from hypoxia-induced hyperventilation. However, at a critical arterial oxygen tension (P
aO2) between 15 and 25 torr, fish became agitated for approximately 5 s and a marked (0.2–0.4 pH unit) but transient arterial blood acidosis ensued. This response is characteristic of abrupt catecholamine mobilization into the circulation and subsequent adrenergic activation of red blood cell (RBC) Na+/H+ exchange (Fievet et al. 1987). Within approximately 1–2 min after the activation of RBC Na+/H+ exchange by endogenous catecholamines, there was a significant rise in arterial PCO2 (P
aCO2) whereas arterial PO2 was unaltered; the elevation of P
aCO2 could not be explained by changes in gill ventilation. Pre-treatment of fish with the -adrenoceptor antagonist phentolamine did not prevent the apparent catecholamine-mediated increase of P
aCO2. Conversely, pre-treatment with the -adrenoceptor antagonist sotalol abolished both the activation of the RBC Na+/H+ antiporter and the associated rise in P
aCO2, suggesting a causal relationship between the stimulation of RBC Na+/H+ exchange and the elevation of P
aCO2. To more clearly establish that elevation of plasma catecholamine levels during severe hypoxia was indeed responsible for causing the elevation of P
aCO2, fish were exposed to moderate hypoxia (final P
wO2=60–80 torr) and then injected intraarterially with a bolus of adrenaline to elicit an estimated circulating level of 400 nmol·l-1 immediately after the injection. This protocol activated RBC Na+/H+ exchange as indicated by abrupt changes in arterial pH (pHa). In all fish examined, P
aCO2 increased after injection of exogenous adrenaline. The effects on P
aO2 were inconsistent, although a reduction in this variable was the most frequent response. Gill ventilation frequency and amplitude were unaffected by exogenous adrenaline. Therefore, it is unlikely that ventilatory changes contributed to the consistently observed rise in P
aCO2. Pretreatment of fish with sotalol did not alter the ventilatory response to adrenaline injection but did prevent the stimulation of RBC Na+/H+ exchange and the accompanying increases and decreases in P
aCO2 and P
aO2, respectively. These results suggest that adrenergic elevation of P
aCO2, in addition to the frequently observed reduction of P
aO2 are linked to activation of RBC Na+/H+ exchange. The physiological significance and the potential mechanisms underlying the changes in blood respiratory status after addition of endogenous or exogenous catecholamines to the circulation of hypoxic rainbow trout are discussed.Abbreviations
P
aCO2
arterial carbon dioxide tension
-
P
aO2
arterial oxygen tension
-
P
da
dorsal aortic pressure
-
pHa
arterial pH
-
P
wO2
water oxygen tension
-
RBC
red blood cell
-
V
f
breathing frequency 相似文献
11.
In order to assess the effect of opioid receptor antagonists, naloxone and noradrenaline, on renal cortical microcirculation,
India ink infusion was made through the renal artery, one hour after treatment with each drug, in dogs subjected to haemorrhagic
shock. Naloxone (1 mg/kg) treatment showed a dual beneficial effect of significant improvement (P < 0.001) in the mean arterial pressure without increasing the renal resistance as indicated by the presence of ink particles
in about 75% of the cortical glomeruli. However, in the case of noradrenaline (2 Μ/kg/min)-treated animals, although mean
arterial pressure increased significantly (P < 0.001) only very few glomeruli (25%) in the cortical region showed ink particles, demonstrating severe vasoconstriction.
In the control group infused only with saline, although most of the glomeruli (92%) were filled with ink particles, there
was a significant decline in the mean arterial pressure (P < 0.001). 相似文献
12.
S. Aota D. J. Randall 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(2):138-146
Ventilation frequency, opercular pressure amplitude, heart rate, dorsal aortic pressure, arterial pH, arterial O2 tension, and plasma catecholamine levels were recorded in rainbow trout, Oncorhynchus mykiss, during normoxia (19.7 kPa, 148 mmHg) or hyperoxia (51.2 kPa, 384 mmHg) after injection of various concentrations of catecholamines. In normoxic fish, adrenaline injection resulted in a depression of arterial O2 tension, hypoventilation due to a drop in ventilation frequency, and a drop in heart rate, while dorsal aortic pressure increased. Noradrenaline depressed ventilation frequency, but opercular pressure amplitude increased to a far greater extent, and dorsal aortic pressure increased. During hyperoxia, adrenaline injection lowered ventilation frequency, opercular amplitude and heart rate, but dorsal aortic pressure increased. The stimulatory effects of noradrenaline on ventilation were abolished during hyperoxia, but the cardiac responses were similar to those seen during normoxia. These results indicate that catecholamines can modify the ventilatory output from the respiratory centre, and modification of ventilation frequency can occur independently of opercular pressure amplitude.Abbreviations
f
g
ventilation frequency
- HPLC
high performance liquid chromatography
-
P
op
opercular pressure amplitude
-
f
h
heart rate
-
P
DA
dorsal aortic pressure
- pHa
arterial pH
-
P
aO2
arterial oxygen tension
-
PO2
oxygen tension 相似文献
13.
Valérie Maxime Jean-Pierre Pennec Claude Peyraud 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):557-568
Summary The effects of increased ambient salinity (35 mg · ml-1) were studied at 1, 6, and 24 h after direct transfer of rainbow trout from freshwater to seawater. Two series of experiments were carried out successively. The first series was designed to simultaneously study all the respiratory (except Hb affinity for O2), circulatory, and acid-base variables in each fish. In this series, fish were fitted with catheters chronically inserted into the cardiac bulbus, the dorsal aorta, and the opercular and buccal cavities. In the second series, designed to study haemoglobin O2 affinity, fish were fitted with only a dorsal aorta catheter. The ventilatory flow (
) was markedly increased just after transfer (by 55% at 1 h), then more moderately (by 20% at 6 h and 32% at 24 h). The initial hyperventilation peak was associated with frequent couphing motions. These ventilatory changes resulted essentially from increase in ventilatory amplitude. Initially, standard oxygen consumption (MM}O2) decreased slightly, the moderately increased (by 12% at 24 h), so that the oxygen convection requirement (
) increased substantially. In spite of an increased ventilation, the partial pressure of oxygen in arterial blood (P
aO2) decreased slightly at 1 h, prior to returning to control levels, while partial pressure of carbon dioxide in arterial blood (P
aCO2) was not significantly decreased. Gill oxygen transfer factor decreased substantially at 1 h (by 35%) then more moderately (by 7% at 1 h and 12% at 24 h). These results suggest a decrease in gas diffusing capacity of the gills. As P
aCO2 remained approximatively unchanged, the gradual decrease in arterial pH (pHa) from 7.94 to 7.67 at 24 h must therefore be regarded as a metabolic acidosis. The strong ion difference decreased markedly because the concentration of plasma chloride increased more than that of sodium. Arterial O2 content (C
aO2) gradually decreased (by 38% at 24 h) simultaneously with the decrease in pHa, while the ratio P
aO2/C
aO2 increased. In parallel, seawater exposure induced a marked decrease in affinity of haemoglobin for O2, so that at 24 h, P50 was increased by 26% above the value obtained in freshwater-adapted trout. The increase in
could be ascribed initially (at 1 h) to the decrease of P
aO2 and later to a stimulation of respiratory neurons resulting from the lowered medullary interstitial pH. The decrease in C
aO2 could be interpreted mainly as a consequence of a decreased affinity of haemoglobin for O2, likely to be due to the blood acidosis and a predictable increase in chloride concentration within erythrocytes. Cardiac output (
) slightly decreased at 1 h, then progressively increased by 30% at 24 h. Branchial vascular resistance increased at 1 h by 28%, then decreased by 18% of the control value at 24 h. Systemic vascular resistance decreased markedly by 40% at 24 h. As heart rate (HR) remained significantly unchanged, the cardiac stroke volume initially decreased then increased in relation to the changes in
. The increase of
, allowing compensation for the effect of decreased C
aO2 in tissue O2 supply, was interpreted as a passive consequence of the decrease in total vascular resistance occurring during seawater exposure.Abbreviations a.u.
arbitrary units
-
C
aO2
arterial oxygen content
- pH50
arterial pH at P50
-
C
vO2
venous oxygen content
- Hb
haemoglobin
- HR
heart rate
- Hct
hematocrit
- nHill
Hill coefficient
- O2
standard oxygen consumption
-
P
aCO2
arterial partial pressure of carbon dioxide
-
P
aO2
arterial partial pressure of oxygen
-
P
vO2
oxygen partial pressure in mixed venous blood
- P50
oxygen tension at half saturation of haemoglobin
-
P
VA, P
DA
blood pressure in ventral and dorsal aorta
- pHa
arterial pH
-
PIO2, PEO2
oxygen partial pressure of inspired and expired water
-
PO2
oxygen partial pressure
-
cardiac output
- SEM
standard error of mean
- S.I.D.
strong ion difference
- SV
cardiac stroke volume
- TO2
gill oxygen transfer factor
- U
oxygen extraction coefficient
- VA
ventilatory amplitude
- VF
ventilatory frequency
- VRG, VRS
branchial and systemic vascular resistances
-
ventilatory flow
-
ventilatory oxygen convection requirement 相似文献
14.
S. F. Perry C. J. Montpetit A. E. Julio K. Moore 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):335-343
The effect of long-term (7 day) anaemia on catecholamine release was examined in rainbow trout (Oncorhynchus mykiss) in vivo during acute exposure to hypoxia and in situ using a perfused post-cardinal vein preparation. The first goal was
to distinguish among reductions in blood O2 partial pressure, O2 concentration and haemoglobin percentage saturation as potential stimuli for, or correlates of, catecholamine secretion during
hypoxia. The second goal was to elucidate the role of these factors in promoting enhanced chromaffin cell responsiveness in
trout subjected to chronic hypoxia (Montpetit and Perry 1998). Anaemic fish (haematocrit lowered from 28.4±2.4% to 11.9±1.6%)
displayed a marked reduction in haemoglobin-O2 binding affinity [P
50 (P
aO2 at 50% Hb-O2 saturation) was increased from 14.7 mm Hg to 24.3 mm Hg]. Upon exposure to hypoxia, the anaemic fish released catecholamines
into their circulation at higher values of arterial O2 partial pressure (∼52 mm Hg versus ∼18 mm Hg) and haemoglobin O2 saturation (<70% versus <55%) than did control fish. In addition, anaemic fish achieved significantly greater circulating
levels of total catecholamines (noradrenaline plus adrenaline) during acute hypoxia (294.8±67.3 versus 107.0±35.6 nmol l−1). These results do not support the view that catecholamine release is triggered by a reduction in haemoglobin O2 saturation or arterial PO2, per se. Nor are they consistent with the idea that catecholamine release occurs at a threshold value of arterial PO2 corresponding to a critical reduction in blood O2 concentration. The effects of the non-selective cholinergic receptor carbachol on catecholamine secretion from chromaffin
tissue were assessed using perfused posterior cardinal vein preparations derived from control or anaemic fish. For adrenaline
secretion, there was no statistically significant change in the ED50 (dose eliciting 50% response). For noradrenaline secretion however, preparations originating from anaemic fish displayed
an enhanced responsiveness to carbachol as indicated by a significant 4.5-fold reduction in the carbachol ED50 value from 2.53 × 10−6 mol kg−1 to 5.67 × 10−7 mol kg−1. These results demonstrate that anaemia-induced hypoxaemia, in the absence of any lowering of PO2, is able to modulate the responsiveness of chromaffin cells to cholinergic stimulation.
Accepted: 21 April 1999 相似文献
15.
E. Savin J. Siegelova B. Fisher P. Bonnin 《European journal of applied physiology and occupational physiology》1997,76(3):289-293
The intra- and extracerebral Doppler artery blood velocity responses to a 10-mmHg abrupt blood pressure (BP) decrease in ten
healthy men were studied. This decrease was obtained using two cuffs placed over both thighs. First, cuffs were inflated to
pressures greater than the arterial BP for 5 min. Next, they were deflated to 60 mmHg in order to prevent venous return from
the legs. We obtained a decrease in mean arterial BP of from 101 (10) to 90 (10) mmHg [mean (SD), P < 0.01] without modifications in the heart rate [HR, 88 (14) beats min−1]. Middle cerebral artery mean blood velocity (MCAmv) decreased immediately from 50 (10) to 42 (12) cm s−1 (P < 0.05). Simultaneously, temporal superficial artery mean blood velocity (TSAmv) decreased from 11 (3) to 7 (2) cm s−1 (P < 0.05) and common carotid artery blood flow (CCAbf ) decreased from 305 (23) to 233 (33) ml min−1 (P < 0.05). After 5 s, MCAmv and CCAbf returned to baseline values, whereas TSAmv [8 (2) cm s−1], mean arterial BP [86 (10) mmHg] remained low and HR increased [92 (12) beats min−1]. TSAmv, BP and HR returned to baseline values in 1 min. These data confirm that cerebral blood flow (CBF) is very rapidly
regulated but that blood flow in extracranial territories is not and that it follows the arterial BP changes.
Accepted: 8 April 1997 相似文献
16.
Thermoregulatory reflexes and cutaneous active vasodilation during heat stress in hypertensive humans 总被引:1,自引:0,他引:1
Kellogg D. L. Jr.; Morris S. R.; Rodriguez S. B.; Liu Y.; Grossmann M.; Stagni G.; Shepherd A. M.M. 《Journal of applied physiology》1998,85(1):175-180
During dynamic exercise in the heat, increasesin skin blood flow are attenuated in hypertensive subjects whencompared with normotensive subjects. We studied responses to passiveheat stress (water-perfused suits) in eight hypertensive and eightnormotensive subjects. Forearm blood flow was measured byvenous-occlusion plethysmography, mean arterial pressure (MAP) wasmeasured by Finapres, and forearm vascular conductance (FVC) wascalculated. Bretylium tosylate (BT) iontophoresis was used to blockactive vasoconstriction in a small area of skin. Skin blood flow was indexed by laser-Doppler flowmetry at BT-treated and untreated sites,and cutaneous vascular conductance was calculated. In normothermia, FVCwas lower in hypertensive than in normotensive subjects(P < 0.01). During heat stress, FVCrose to similar levels in both groups(P > 0.80); concurrent cutaneousvascular conductance increases were unaffected by BT treatment(P > 0.60). MAP was greater in hypertensive than in normotensive subjects during normothermia (P < 0.05, hypertensive vs.normotensive subjects). During hyperthermia, MAP fell in hypertensivesubjects but showed no statistically significant change in normotensivesubjects (P < 0.05, hypertensive vs.normotensive subjects). The internal temperature at which vasodilationbegan did not differ between groups (P > 0.80). FVC is reduced during normothermia in unmedicatedhypertensive subjects; however, they respond to passive heat stress ina fashion no different from normotensive subjects. 相似文献
17.
Cold-induced vasodilation and vasoconstriction in the finger of tropical and temperate indigenes 总被引:1,自引:0,他引:1
While heat acclimatization reflects the development of heat tolerance, it may weaken an ability to tolerate cold. The purpose of this study was to explore cold-induced vasodilation (CIVD) responses in the finger of tropical indigenes during finger cold immersion, along with temperate indigenes. Thirteen tropical male indigenes (subjects born and raised in the tropics) and 11 temperate male indigenes (subjects born and raised in Japan and China) participated. Subjects immersed their middle finger at 4.3±0.8 °C water for 30 min. Rectal temperature, skin temperatures, finger skin blood flow, blood pressure and subjective sensations were recorded during the test. The results showed that: (1) the tropical group demonstrated a lower minimum (Tmin), maximum (Tmax) and mean finger temperature (Tmean) compared to those of the temperate group (P<0.05); (2) seven tropical indigenes demonstrated a late-plateau type of CIVD pattern, which is characterized by a pronounced 1st vasoconstriction and a single CIVD with a faint and weak 2nd vasoconstriction, whereas no temperate indigene demonstrated the late-plateau type; and (3) the hand temperature at the end of finger immersion was 3 °C lower in the tropical than the temperate group (P<0.05). These results indicate that tropical indigenes have less active responses of arterio-venous anastomoses in the finger and weaker vasoconstrictions after the first CIVD response during finger cold immersion, which can be considered as being more vulnerable to cold injury of the periphery in severe cold. 相似文献
18.
Arterial wall function is associated with different physiological and clinical factors. Changes in arterial pressure cause major changes in the arterial wall. This study presents a simple non-invasive method to quantify arterial volume distensibility changes with different arterial pressures.The electrocardiogram, finger and ear photoplethysmogram were recorded from 15 subjects with the right arm at five different positions (90°, 45°, 0°, ?45° and ?90° referred to the horizontal level). Arm pulse propagation time was determined by subtracting ear pulse transit time from finger pulse transit time, and was used to obtain arterial volume distensibility. The mean arterial blood pressure with the arm at the horizontal level was acquired, and changes with position were calculated using the hydrostatic principle that blood pressure in the arm is linearly related to its vertical distance from the horizontal level.The mean arm pulse propagation times for the five different positions were 88, 72, 57, 54 and 52 ms, with the corresponding mean arterial volume distensibility of 0.234%, 0.158%, 0.099%, 0.088% and 0.083% per mmHg. For all consecutive changes in arm position, arm pulse propagation time and arterial volume distensibility, were significantly different (all probability P<0.05). The slopes of arm pulse propagation time and arterial volume distensibility against arterial pressure decreased significantly between each consecutive arm position from 90° to ?45° (all P<0.01), indicating significant non-linearity.The experimental results fitted the physiological exponential model and Langewouters’ arctangent model well, and were also comparable to published data with arterial volume distensibility approximately tripling for transmural pressure changes from 101 to 58 mmHg.In conclusion, the inverse and non-linear relationship between arterial volume distensibility and arterial pressure has been quantified using a simple arm positioning procedure, with the greatest effect at low pressures. This work is an important step in developing a simple non-invasive technique for assessing peripheral arterial volume distensibility. 相似文献
19.
H. Acker F. Degner J. Hilsmann 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(1):73-79
Summary Elastically-suspended microelectrodes were used in the vascularly isolated blood-perfused carotid body of fetal and newborn lambs as well as of 6–7-day-old lambs to measure local blood flow velocities by means of hydrogen clearance. Fetal sheep (n=9) carotid bodies elicited mean local blood velocity values between 0.008 and 0.11 cm·s–1, whereas newborn lamb carotid bodies (n=7) showed values between 0.008 and 0.067 cm·s–1 at a perfusion pressure range between 30 and 150 mmHg. The 6–7-day-old lamb carotid bodies (n=5) were characterized by values of 0.003 and 0.049 cm·s–1 over the same perfusion pressure range. Fetal carotid body values were statistically significantly higher than the values of the 6–7-day-old lamb carotid bodies, whereas the newborn carotid body values showed no significant difference to both other groups. The flow velocity/perfusion pressure relationship peaked at perfusion pressure values between 100 and 150 mmHg in all groups with a reduced steepness in the lamb carotid body. It is concluded that local blood flow velocities in the carotid body are similar to that in other organs, and that after birth local blood flow velocities in the carotid body decrease during the first week of life, probably induced by vasoconstriction, changed blood gas values, and/or increasing shunt flow.Abbreviations
significance level
-
D
diffusion coefficient
-
i.v.
intravenous
-
n
number of experiments
-
PCO
2
carbon dioxide partial pressure
-
pH
negative logarithm of hydrogen ion concentration
-
PH
2
hydrogen partial pressure
-
Po PH2
with perfusion
-
P
PH2
without perfusion
-
PO
2
oxygen partial pressure
-
PP
perfusion pressure
-
r
radius 相似文献
20.
Gmitrov J 《Radiation and environmental biophysics》2007,46(3):281-290
Increasing evidence suggests that time-varying and static magnetic fields in the environment might affect the cardiovascular
system. To explore the underlying physiology, the effect of static magnetic fields (SMFs) on the carotid baroreflex control
of microcirculation was studied. Twenty-four hemodynamic monitorings were performed in rabbits sedated by pentobarbital infusion
(5 mg/kg/h) during experiments that lasted 120 min. Mean femoral artery blood pressure, heart rate, and ear lobe skin microcirculatory
blood flow, measured by microphotoelectric plethysmogram (MPPG), were simultaneously recorded before and after a 40 min exposure
of the sinocarotid baroreceptors to Nd2–Fe14–B alloy magnets (n = 14) or sham magnets (n = 10, control series). The local SMF field was 350 mT, at the baroreceptors’ site. Arterial baroreflex sensitivity (BRS)
was estimated from heart rate/blood pressure response to intravenous bolus injections of nitroprusside and phenylephrine.
A significant positive correlation was found between the SMF-induced increase in BRS (ΔBRS = BRSafterSMF − BRSpriorSMF) and the increment in microvascular blood flow (ΔMPPG = MPPGafterSMF − MPPGpriorSMF) (r = 0.66, p < 0.009). The SMF probably modulated the arterial baroreflex-mediated microcirculatory control. This could represent one
possible mechanism how environmental magnetic fields act on the cardiovascular system, and a method how to complexly adjust
macro- and microcirculation with potential clinical implementation. 相似文献