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1.
Peter G. Bushnell Richard W. Brill 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(2):131-143
Summary Responses to acute hypoxia were measured in skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) (1–3 kg body weight). Fish were prevented from making swimming movements by a spinal injection of lidocaine and were placed in front of a seawater delivery pipe to provide ram ventilation of the gills. Fish could set their own ventilation volumes by adjusting mouth gape. Heart rate, dorsal and ventral aortic blood pressures, and cardiac output were continuously monitored during normoxia (inhalant water (PO
2>150 mmHg) and three levels of hypoxia (inhalant water PO
2130, 90, and 50 mmHg). Water and blood samples were taken for oxygen measurements in fluids afferent and efferent to the gills. From these data, various measures of the effectiveness of oxygen transfer, and branchial and systemic vascular resistance were calculated. Despite high ventilation volumes (4–71·min-1·kg-1), tunas extract approximately 50% of the oxygen from the inhalant water, in part because high cardiac outputs (115–132 ml·min-1·kg-1) result in ventilation/perfusion conductance ratios (0.75–1.1) close to the theoretically ideal value of 1.0. Therefore, tunas have oxygen transfer factors (ml O2·min-1·mmHg-1·kg-1) that are 10–50 times greater than those of other fishes. The efficiency of oxygen transfer from water in tunas (65%) matches that measured in teleosts with ventilation volumes and order of magnitude lower. The high oxygen transfer factors of tunas are made possible, in part, by a large gill surface area; however, this appears to carry a considerable osmoregulatory cost as the metabolic rate of gills may account for up 70% of the total metabolism in spinally blocked (i.e., non-swimming) fish. During hypoxia, skipjack and yellowfin tunas show a decrease in heart rate and increase in ventilation volume, as do other teleosts. However, in tunas hypoxic bradycardia is not accompanied by equivalent increases, in stroke volume, and cardiac output falls as HR decreases. In both tuna species, oxygen consumption eventually must be maintained by drawing on substantial venous oxygen reserves. This occurs at a higher inhalant water PO2 (between 130 and 90 mmHg) in skipjack tuna than in yellowfin tuna (between 90 and 50 mmHg). The need to draw on venous oxygen reserves would make it difficult to meet the oxygen demand of increasing swimming speed, which is a common response to hypoxia in both species. Because yellowfin tuna can maintain oxygen consumption at a seawater oxygen tension of 90 mmHg without drawing on venous oxygen reserves, they could probably survive for extended periods at this level of hypoxia.Abbreviations BPda, BPva
dorsal, ventral aortic blood pressure
-
C
aO2, C
vO2
oxygen content of arterial, venous blood
-
DO2
diffusion capacity
- Eb, Ew
effectiveness of O2 uptake by blood, and from water, respectively
- Hct
hematocrit
- HR
heart rate
-
PCO2
carbon dioxide tension
-
P
aCO2, P
vCO2
carbon dioxide tension of arterial and venous blood, respectively
-
PO2
oxygen tension
-
P
aO2, P
vO2, P
iO2, P
cO2
oxygen tension of arterial blood, venous blood, and inspired and expired water, respectively
- pHa, pHv
pH of arterial and venous blood, respectively
- Pw—b
effective water to blood oxygen partial pressure difference
- Pg
partial pressure (tension) gradient
-
cardiac output
- R
vascular resistance
- SV
stroke volume
- SEM
standard error of mean
-
TO2
transfer factor
- U
utilization
-
g
ventilation volume
-
O2
oxygen consumption 相似文献
2.
B. McMahon Fiona Sinclair C. D. Hassall P. L. deFur P. R. H. Wilkes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,128(2):109-116
Summary Frequencies of scaphognathite (ventilatory,f
sc) and heart (f
h) pumping, oxygen consumption (
), and hemolymph oxygen, carbon dioxide and pH levels were measured in adult Dungeness crabs (Cancer magister) during 7–10 day periods of exposure to 7, 12, and 17°C seawater. Ventilation volume (
) was calculated for individual animals fromf
sc and a previously determined relationship between stroke volume and animal mass.
increases (Q10=2.3) with temperature were associated with larger increases inf
sc (Q10=3.3) and
(Q10=3.5) and smaller increases inf
h (Q10=1.5). The incidence of unilateral scaphognathite pumping and pausing decreased as temperature rose.Postbranchial oxygen tension was maintained in vivo but hemolymph oxygen content decreased both in vivo and in vitro as temperature rose. Postbranchial carbon dioxide tension did not change significantly but relative alkalinity was maintained as temperature rose by loss of hemolymph bicarbonate. The effects of increased ventilation volume and potential mechanisms of bicarbonate regulation are discussed.The responses of the essentially subtidalCancer magister are compared with those of subtidal, intertidal and terrestrial crabs demonstrating that the concepts of acid-base regulation developed for water and air breathing vertebrates are also applicable to water and air breathing crabs, and that intertidal crabs may exhibit transitional states.This work was supported by Grant No. A.5762 National Research Council of Canada 相似文献
3.
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
4.
Ole Brix Gunnar Lykkeboe Kjell Johansen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1979,129(2):97-103
Summary Oxygen binding properties of the hemocyanin-containing blood ofBuccinum undatum were examined in vitro and in vivo under normoxic (
150 mmHg) and hypoxic (
50 mmHg) conditions at 10°C. Blood pH and
showed a decrease in vivo under hypoxic conditions. Oxygen uptake at high water
, was about 18 ml O2/kg·h (wet weight) and the critical oxygen tension between 25 and 50 mm Hg. In vitro the O2 binding to hemocyanin showedn-values independent of pH, while both O2 affinity and oxygen carrying capacity were strongly pH dependent. Oxygen affinity increased below pH=8.1 and thus showed a pronounced reversed Bohr shift in the physiological pH range (7.5<pH<8.1). The oxygen carrying capacity similarly increased markedly with falling pH in the physiological pH range (reversed Root shift). Astrup titration curves showed a metabolic and respiratory acidosis under hypoxic conditions (
50 mm Hg). The role of hemocyanin in the transport of oxygen in relation to ambient O2 availability is discussed. 相似文献
5.
Nathan H. Phillips Ralph J. Berger 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(3):311-318
Summary To test the hypothesis that nocturnal body temperature (Tb) and metabolic rate (MR) in the pigeon are regulated during sleep at levels proportional to energy reserves, continuous recordings of Tb, oxygen consumption (
O2), carbon dioxide production, and electrophysiological measures were taken from five pigeons subjected to two separate 4-day fasts. Energy reserves were depleted differentially during the fasts by 12-h diurnal infusions of either saline or isosmotic glucose solutions. Although Tb and
O2 were closely correlated,
O2 declined throughout the fast during diurnal and nocturnal phases of the 12:12 light-dark cycle whereas significant declines in Tb were restricted to the night. Diurnal thermal conductance declined over days of fasting, especially during saline infusions, and was reduced to minimal levels each night. The durations and distributions of arousal states did not change during the fast or differ between conditions. The results were consistent with the hypothesis of a nocturnal regulation of Tb and metabolic rate proportional to energy reserves.Abbreviations
C
1
thermal conductance
-
EEG
electroencephalogram
-
EMG
electromyogram
-
EOG
electrooculogram
-
LD
light-dark
-
MHP
metabolic heat production
-
MR
metabolic rate
-
REM
rapid eye movement sleep
-
RQ
respiratory quotient
-
SWS
slow wave sleep
-
T
a
ambient temperature
-
T
b
body temperature
-
TRT
total recording time
-
TST
total sleep time
-
O2
oxygen consumption 相似文献
6.
During peak thermogenesis of anthesis, high rates of respiration by the sterile male florets on the spadix ofPhilodendron selloum significantly reduce the oxygen tension (PO
2) and raise CO2 tension between the florets. Nevertheless, respiration is not limited by the availability of O2 under natural conditions. At experimental PO
2 below about 17 kPa, however, florets begin to show decreased O2 consumption. A respiratory exchange ratio of 0.83 indicates that the major energy source is not starch, but is probably lipid.Abbreviations and symbols
capacitance of the gas phase for O2 (ml O2 cm-3 kPa-1)
- DO
2
binary diffusion coefficient of O2 in air (cm2 min-1)
- KO
2
Krogh's diffusion coefficient (ml O2 cm-2 min-1 kPa-1 cm)
- PO
2 PCO
2
partial pressures of O2 and CO2 (kPa)
-
rate of O2 consumption (ml O2 g-1 h-1)
- Fgas
fractional gas volume
- P80
O2 partial pressure at which
falls below 80% of maximum
- RE
respiratory exchange ratio
相似文献
7.
The effect of short-term fasting and a single meal on protein synthesis and oxygen consumption in cod,Gadus morhua 总被引:2,自引:0,他引:2
A. R. Lyndon D. F. Houlihan S. J. Hall 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(3):209-215
Summary Rates of protein synthesis and oxygen consumption (
O2) in cod were compared in both fasted and refed animals. During a 14-day fast both protein synthesis and respiration rates fell to stable values after 6 days. When a meal of whole sandeel at 6% body weight was fed to fish fasted for 6 days, protein synthesis and (
O2) increased to a maximum at between 12 and 18 h after feeding. Peak (
O2) was about twice the pre-feeding values, while whole animal protein synthesis increased four-fold. There were differences between tissues in the timing of maximum protein synthesis; the liver and stomach responded faster than the remainder of the body. Maximum protein synthesis rates in the liver and stomach occurred at 6 h after feeding, at which time their calculated contribution to total (
O2) was 11%. Similar calculations suggested that the integrated increment in whole animal protein synthesis contributed between 23% and 44% of the post-prandial increase in (
O2). It was concluded that protein synthesis is an important contributor to increased (
O2) after feeding in cod.Abbreviations
A
s
absolute rate of protein synthesis
- ASDA
apparent specific dynamic action
- ATP
adenosine triphosphate
-
k
s
fractional rate of protein synthesis
-
k
s/RNA
amount of protein synthesized per unit RNA
- (
O2)
oxygen consumption
- PCA
perchloric acid
- RNA
ribonucleic acid 相似文献
8.
S. S. Madsen B. K. Larsen F. B. Jensen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(2):101-109
Osmoregulation, acid-base balance and respiratory parameters were investigated in whitefish following transfer from freshwater to salt water. Whitefish acclimated successfully to 25 ppt brackish water but died after direct transfer to 32 ppt sea water. Transfer to brackish water induced rapid (<6 h) and permanent increases in plasma [Na+], [Cl–], total [Ca] and [Mg]. The extracellular hyperosmolality effected a transient (<3 days) muscle tissue dehydration and red blood cell shrinkage. Exposure to brackish water decreased both the arterial O2 tension and whole body O2 uptake. The extracellular acid-base status changed from an initial respiratory acidosis at 1 h towards a pronounced metabolic acidosis at 48 h of brackish water exposure. Red cell pHi decreased in parallel with extracellular pHe, but the in vivo pHi/pHe was only 0.26, suggesting some selective protection of red cell pHi. Plasma cortisol concentration and gill Na+, K+-ATPase activity increased after exposure to high ambient salinity, reflecting the induction of hypo-osmoregulatory mechanisms. The physiological changes in whitefish are discussed in relation to salinity-induced effects in other salmonid fishes.Abbreviations
CO2 solubility in plasma
-
water O2 capacitance coefficient
-
BW
brackish water
-
C
T
total CO2 content in plasma
-
FW
fresh water
-
Hb
hemoglobin
-
Hct
hematocrit
-
M
b
body mass of fish
-
MCHC
mean cellular hemoglobin concentration
-
PCO2
carbon dioxide tension
-
pH
e
extracellular pH
-
pH
i
intracellular pH
-
PO2 in
oxygen tension in water flowing in
-
PO2 out
oxygen tension in water flowing out
-
ppt
parts per thousand
-
RBC
red blood cell(s)
-
SW
sea water
-
V
m
water flows through chamber
-
OV
2
ml O2 consumed per kg per hour 相似文献
9.
Mark A. Chappell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(8):722-730
Summary Ventilation was measured across a range of O2 consumption rates in four sciurid rodents: Tamias minimus (47 g), Spermophilus lateralis (189 g), S. beecheyi (531 g), and Marmota flaviventris juveniles (1054 g) and adults (2989 g). Maximum thermogenic oxygen consumption was measured for all but adult M. flaviventris. Aerobic scopes (maximum/minimum O2 consumption rates) were 4.6, 3.8, 5.4, and 4.8 in T. minimus, S. lateralis, S. beecheyi, and juvenile M. flaviventris, respectively. Aerobic scope was at least 4.1 in adult M. flaviventris. Ventilatory accommodation of changing O2 consumption rate was qualitatively similar in the four species, with the bulk of accommodation resulting from changes in minute volume. Nevertheless, there were significant differences in the relative importance of frequency, tidal volume, and O2 extraction in accommodation. In all species, frequency and minute volume were strongly correlated to O2 consumption rate. Tidal volume was significantly correlated to O2 consumption rate in T. minimus and S. beecheyi, but not in the other species. Oxygen extraction was not significantly correlated to O2 consumption rate in any species. Analysis of factorial ventilation changes across a standardized 3.8-fold change in O2 consumption rate revealed significant differences among species in frequency and O2 extraction, but not in tidal or minute volume. When compared to a generalized allometry for mammalian resting ventilation, the four sciurid species had consistently lower respiration frequency and higher O2 extraction than predicted, perhaps because the sciurid measurements were made on unrestrained animals. There was no indication that ventilation constrained maximum O2 consumption rate.Abbreviations BMR
basal metabolic rate
- BTPS
body temperature and pressure saturated
-
EO2
oxygen extraction
-
f
respiration frequency
- MMR
minimal metabolic rate
- RH
relative humidity
- STPD
standard pressure and temperature, dry
-
T
a
ambient temperature
-
T
b
body temperature
-
minute volume
-
tidal volume
-
maximum rate of oxygen consumption 相似文献
10.
J. Iba?ez R. Rama M. Riera M. T. Prats L. Palacios 《European journal of applied physiology and occupational physiology》1993,67(1):7-13
The effect of severe acute hypoxia (fractional concentration of inspired oxygen equalled 0.104) was studied in nine male subjects performing an incremental exercise test. For power outputs over 125 W, all the subjects in a state of hypoxia showed a decrease in oxygen consumption (
O2) relative to exercise intensity compared with normoxia (P < 0.05). This would suggest an increased anaerobic metabolism as an energy source during hypoxic exercise. During submaximal exercise, for a given
O2, higher blood lactate concentrations were found in hypoxia than in normoxia (P < 0.05). In consequence, the onset of blood lactate accumulation (OBLA) was shifted to a lower
O2 (
O2 1.77 l·min–1 in hypoxia vs 3.10 l·min–1 in normoxia). Lactate concentration increases relative to minute ventilation (
E) responses were significantly higher during hypoxia than in normoxia (P < 0.05). At OBLA,
E during hypoxia was 25% lower than in the normoxic test. This study would suggest that in hypoxia subjects are able to use an increased anaerobic metabolism to maintain exercise performance. 相似文献
11.
S. K. Maloney T. J. Dawson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):464-472
The emu is a large, flightless bird native to Australia. Its habitats range from the high snow country to the arid interior of the continent. Our experiments show that the emu maintains a constant body temperature within the ambient temperature range-5 to 45°C. The males regulate their body temperature about 0.5°C lower than the females. With falling ambient temperature the emu regulates its body temperature initially by reducing conductance and then by increasing heat production. At-5°C the cost of maintaining thermal balance is 2.6 times basal metabolic rate. By sitting down and reducing heat loss from the legs the cost of homeothermy at-5°C is reduced to 1.5 times basal metabolic rate. At high ambient temperatures the emu utilises cutaneous evaporative water loss in addition to panting. At 45°C evaporation is equal to 160% of heat production. Panting accounts for 70% of total evaporation at 45°C. The cost of utilising cutaneous evaporation for the other 30% appears to be an increase in dry conductance.Abbreviations
A
r
Effective radiating surface area
- BMR
basal metabolic rate
-
C
dry
dry conductance
- CEWL
cutaneous evaporative water loss
- EHL
evaporative heat loss
- EWL
evaporative water loss
- FECO2
fractional concentration of CO2 in excurrent air
- FFH2O
water content of chamber excurrent air
- FEO2
fractional concentration of O2 in chamber excurrent air
- FICO2
fractional concentration of CO2 in incurrent air
- FIO2
fractional concentration of O2 in chamber incurrent air
- MHP
metabolic heat production
- MR
metabolic rate
- REWL
respiratory evaporative water loss
- RH
relative humidity
- RQ
respiratory quotient
;
- SA
surface area
- SEM
standard error of the mean
- SNK
Student-Newman-Keuls multiple range test
- STPD
standard temperature and pressure dry
-
T
a
ambient temperature(s)
-
T
b
body temperature(s)
-
T
e
surface temperature(s)
-
flow rate of air into the chamber
-
carbon dioxide production
-
oxygen consumption
-
vapour pressure of water 相似文献
12.
C. Carey O. Dunin-Borkowski F. Leon-Velarde D. Espinoza C. Monge 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,163(8):649-656
Oxygen consumption, air cell gases, hematology, blood gases and pH of Puna teal (Anas versicolor puna) embryos were measured at the altitude at which the eggs were laid (4150 m) in the Peruvian Andes. In contrast to the metabolic depression described by other studies on avian embryos incubated above 3700 m, O2 consumption of Puna teal embryos was higher than even that of some lowland avian embryos at equivalent body masses. Air cell O2 tensions dropped from about 80 toor in eggs with small embryos to about 45 toor in eggs containing a 14-g embryo; simultaneously air cell CO2 tension rose from virtually negligible amounts to around 26 torr. Arterial and venous O2 tensions (32–38 and 10–12 toor, respectively, in 12- to 14-g embryos) were lower than described previously in similarly-sized lowland wild avian embryos or chicken embryos incubated in shells with restricted gas exchange. The difference between air cell and arterial O2 tensions dropped significantly during incubation to a minimum of 11 torr, the lowest value recorded in any avian egg. Blood pH (mean 7.49) did not vary significantly during incubation. Hemoglobin concentration and hematocrits rose steadily throughout incubation to 11.5 g · 100 ml-1 and 39.9%, respectively, in 14-g embryos.Abbreviations PO2
partial pressure gradient of O2
- BM
body mass
-
D
diffusion coefficient
-
G
gas conductance (cm3·s-1·torr-1)
-
conductance to water vapor
- IP
internal pipping of embryos
-
P
ACO2
partial pressure of carbon dioxide in air cell
-
P
AO2
partial pressure of oxygen in air cell
-
P
aCO2
partial pressure of carbon dioxide in arterial blood
-
P
aCO2
partial pressure of oxygen in arteries
-
P
H
barometric pressure (torr)
-
PCO2
partial pressure of carbon dioxide
-
P
IO2
partial pressure in ambiant air
-
PO2
partial pressure of oxygen
-
P
VCO2
venous carbon dioxide partial pressure
-
P
VO2
mixed venous oxygen partial pressure
- SE
standard error
-
VO
2
oxygen consumption 相似文献
13.
Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus) 总被引:2,自引:1,他引:1
Mark A. Chappell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1985,155(6):751-758
Summary The effects of different ambient temperatures (T
a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).At both low and high altitude, oxygen consumption (
) decreased with increasingT
a atT
a from –10 to 30 °C. The
was 15–20% smaller at high altitude than at low altitude atT
a below 30 °C.Increased
atT
a below thermoneutrality was supported by increased minute volume (
) at both low and high altitude. At mostT
a, the change in
was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V
T) or oxygen extraction efficiency (O2EE). AtT
a=0 °C and below at high altitude,
was constant due to decliningV
T and O2EE increased in order to maintain high
.At high altitude,
(BTP) was 30–40% higher at a givenT
a than at low altitude, except atT
a below 10 °C. The increased
at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT
a below 0 °C. The
(STP) was equivalent at high and low altitude atT
a of 10 °C and above. At lowerT
a,
(STPD) was larger at low altitude.At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT
a (20–30 °C).Abbreviations
EHL
evaporative heat loss
-
f
respiration frequency
-
HL
a
heat loss from warming tidal air
-
HL
e
evaporative heat loss in tidal air
-
HL
total respiratory heat loss
-
MHP
metabolic heat production
-
O
2
EE
oxygen extraction efficiency
-
RQ
respiratory quotient
-
T
a
ambient temperature
-
T
b
body temperatureT
lc lower critical temperature
-
carbon dioxide production
-
evaporative water loss
-
oxygen consumption
-
minute volume
-
V
T
tidal volume 相似文献
14.
Evidence for improved myocardial oxygen delivery and function during hypoxia in the mole rat 总被引:2,自引:0,他引:2
Y. Edoute R. Arieli E. Nevo 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(5):575-582
Summary The high capillary density of the hypoxic adapted mole rat may provide an efficient oxygen extraction system that permits the maintenance of a normal metabolic rate during hypoxia. We compared myocardial function and energetics in the isolated working heart of the mole rat with that of the white rat during oxygenation (567 torr O2) and 3 hypoxic periods of 319, 232 and 155 torr O2, each followed by a reoxygenation period. Control hearts were perfused for a similar time but with oxygenated buffer. The control oxygenated mole rat heart had higher coronary flow (CF), systolic pressure and myocardial O2 consumption
and lower coronary resistance compared with the heart of the white rat. The hypoxic heart of the mole rat had higher CF, aortic flow, stroke volume,
, mechanical power and efficiency, and lower coronary resistance compared with the hypoxic heart of the white rat. The better performance of the hypoxic mole rat heart was not due to a more efficient O2 extraction but was associated with a lower coronary resistance. The findings correlate with the known cardiac physiology of the intact mole rat. 相似文献
15.
Ekkehard Liefke Dieter Kaiser Ulfert Onken 《Applied microbiology and biotechnology》1990,32(6):674-679
Summary Influence of pressure (P) and oxygen partial pressure (
) on cultivation of various Streptomyces spp. and Micromonospora purpurea was examined in pressurized air-lift and stirred tank fermenters. The maximum
was 2100 mbar. Growth and product formation of all cultures tested were markedly influenced by
higher than 1000 mbar. There is evidence that wild strains are more oxygen tolerant than production strains. At a certain
the metabolic activities of all cultures were inhibited. However, results obtained with S. aureofaciens and S. rimosus indicated an increase in specific product formation rate at elevated pressure. With increase in oxygen tension incorporation of oxygen into tetracycline molecules was enhanced. Since elevated oxygen tension can either show inhibiting effects or may be used for regulation of product formation and selectivity, the influence of
should be determined in an appropriate experimental set-up for each process.Offprint requests to: U. Onken 相似文献
16.
Valérie Maxime Marguerite Peyraud-Waitzenergger Guy Claireaux Claude Peyraud 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(1):31-39
Summary Oxygen consumption, gill ventilation, blood acid-base/ionic status and haemoglobin oxygen affinity were studied in seawater-adapted adult salmon (Salmo salar) during five weeks after transfer into fresh water. Freshwater exposure induced the following changes: Standard oxygen consumption (
) and ventilatory flow (
) decreased markedly during the first days after transfer, then decreased more gradually until a new steady-state was achieved at which
and
were about 80% and 56% of the control values, respectively. The marked increase in oxygen extraction coefficient (Ew
O
2) and the marked decrease in the oxygen convection requirement (
) were associated with a reduction in the partial pressure of carbon dioxide in arterial blood (Pa
CO
2), in spite of a decrease of both ventilatory flow and water CO2 capacitance. These results suggested that transfer into fresh water induced an increase in branchial diffusive conductance. A biphasic pattern was observed in the time-course of the changes in both plasma ion concentration and acid-base status. During the first 10 days, plasma Na+, K+, and Cl– concentrations fell abruptly, then more gradually. [Cl–] decreased more than [Na+] resulting in a progressive increase in the [Na+]/[Cl–] ratio. During the second phase of acclimation to fresh water plasma Na+, K+, and Cl– concentrations progressively increased. [Cl–] increased more than [Na+], so that [Na+]/[Cl–] ratio decreased. Transfer into fresh water did not significantly change plasma lactate concentration. Upon exposure to fresh water, blood pH increased from 7.94±0.04 to 8.43±0.06 at day 10 and then decreased to 8.08±0.03 at day 34. The increase in blood pH induced by transfer to fresh water initially represented a mixed metabolic/respiratory alkalosis. However, after 15 days Pa
CO
2 had returned to pretransfer values and the alkalosis was purely metabolic. The metabolic component of the alkalosis was associated with appropriate changes in the plasma strong ion difference (S.I.D.). Blood alkalosis moved the oxygen dissociation curve to the left, so that P50 was decreased by 30% below the value in seawater for the maximal increase in blood pH. This rise in haemoglobin affinity for O2, associated with a marked increase in blood buffer capacity, are regarded as adaptative processes allowing the salmon to cope with the markedly increased energy expenditure required for upstream migration. 相似文献
17.
Lars Bo Andersen Jóhanna Haraldsdóttir 《European journal of applied physiology and occupational physiology》1993,67(4):315-320
In a randomly selected sample of 88 men and 115 women, aged 23–27 years from Denmark, maximal oxygen uptake (
O2max), maximal voluntary isometric contraction (MVC) in four muscle groups and physical activity were studied. The
O2max was 48.0 ml · min–1 kg–1 and 39.6 ml · min–1 · kg–1 for the men and the women, respectively. The MVC was 10% lower than in a comparable group of Danes of the same age and height studied 35 years ago. Only in men was sports activity directly related to
O2max (ml · min–1 · kg–1; r=0.31, P<0.01). The MVC of the knee extensors was related to
O2max in the men (r=0.31, P<0.01), but there was no relationship between the other measurements of MVC and
O2max. In the women
O2max (ml · min–1 · kg–1) was only related to body size, i.e. body mass index, percentage body fat and body mass [(r= –0.47, –0.48 (both P<0.001) and –0.34. (P<0.01), respectively)]. There were differences in
O2max in the men, according to education and occupation. Blue collar workers and subjects attending vocational or trade schools in 1983 had lower
O2max and more of them were physically inactive. In the women differences were also found, but there was no clear pattern among the groups. More of the women participated regularly in sports activity, but more of the men were very active compared to the women. 相似文献
18.
Effect of temperature and humidity on evaporative water loss in Anna's hummingbird (Calypte anna) 总被引:1,自引:0,他引:1
Donald R. Powers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(1):74-84
Summary Evaporative water loss (EWL), oxygen concumption
, and body temperature (Tb) of Anna's Hummingbirds (Calypte anna; ca. 4.5g) were measured at combinations of ambient temperature (Ta) and water vapor density (va) ranging from 20 to 37 °C and 2 to 27 g·m-3, respectively. The EWL decreased linearly with increasing va at all temperatures. The slopes of least squares regression lines relating EWL to va at different temperatures were not significantly different and averaged-0.50 mg H2O·m-3·g-2·h-1 (range:-0.39 to-0.61). Increased va restricted EWL in C. anna more than has been reported for other endotherms in dry air. The percent of metabolic heat production dissipated by evaporation (
) was lower than that of other birds in dry air, but higher than that for other birds at high humidity when Ta 33 °C. When Ta>33 °C the effect of humidity on
was similar to that in other birds. Calypte anna might become slightly hyperthermic at Ta>37 °C, which could augment heat transfer by increasing the Tb-Ta gradient. Body temperature for C. anna in this study was 43 °C (intramuscular) at Tas between 25 and 35 °C, which is above average for birds. It is estimated that field EWL is less than 30% of daily water loss in C. anna under mild temperature conditions (<35 °C).Abbreviations BMR
basal metabolic rate
- EWL
evaporative water loss
-
percent of metabolic heat production dissipated by evaporation
-
ambient water vapor density
-
body surface water vapor density
- RMR
resting metabolic rate
- Ta
ambient-temperature
- Tb
body temperature
- Td
dew-point temperature
- TNZ
thermoneutral zone
- Ts
body surface temperature
-
carbon dioxide production
-
oxygen consumption 相似文献
19.
Daniel T. Clemens 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(1):57-66
Summary Rosy finches (Leucosticte arctoa) breed at altitudes above 3500 m in eastern California. House finches (Carpodacus mexicanus) belong to the same subfamily (Carduelinae), but breed at much lower elevations. Oxygen consumption (
) and ventilatory parameters of these two species were measured over a wide range of ambient temperatures (T
a) at low altitude (LA; 150 m) and at high altitude (HA; 3800 m).Minimal nighttime
's of rosy finches and house finches at LA (T
a=30°C) were close to allometrically predicted values for passerine birds. At both altitudes,
increased linearly with decreasingT
a betweenT
a=20 and –10°C. Resting
's were slightly higher at HA than at LA on average.In both species, minute volume (
) was inversely related toT
a.T
a-correlated increases in
resulted from significant increases in both ventilatory frequency (f) and tidal volume (V
T) at both altitudes. Oxygen extraction efficiency (
) was independent ofT
a in rosy finches at LA, but declined significantly with decreasingT
a in rosy finches at HA and in house finches at both altitudes.At a givenT
a, both species had significantly greater
(BTPS) at HA than at LA. Altitude-correlated increases in
resulted primarly from increases inf with little change inV
T.
was significantly greater at HA than at LA in both species.In spite of the difference in altitudinal distributions of rosy finches and house finches, there were few conspicuous interspecific differences in metabolic or ventilatory adaptation to altitude or lowT
a over the range of conditions examined.Symbols and abbreviations
BMR
basal metabolic rate
-
BTPS
at body temperature and pressure, saturated
-
oxygen extraction efficiency
-
f
ventilation frequency
-
h
mean coefficient of heat transfer
-
HA
high altitude
-
instantaneous oxygen consumption
-
LA
low altitude
-
RH
relative humidity
-
SMR
standard metabolic rate
-
STPD
standard temperature and pressure, dry
-
T
temperature
-
a
ambient
-
b
body
-
lc
lower critical of thermoneutral zone
-
minute volume
-
V
T
tidal volume 相似文献
20.
The purpose of this study was to test a theoretical model (Stein et al. 1986) which suggested that minimizing the rate of metabolic energy consumption (
O2) is related to minimizing jerk (third derivative of position) during human movement. At a given speed of walking,
O2 has been shown to increase curvilinearly as stride length (SL) is varied from freely chosen stride length (FCSL). It was hypothesized that the jerk-cost, or JC (area under squared jerk curve), would exhibit similar behavior. Subjects (n=24) walked (1.75 m ·. s–1) on a treadmill at FCSL, and at SL derivations at ± 10 and ±20% of leg length from FCSL until steady-state
O2 was attained. Videotaping (60 Hz) in the sagittal plane and subsequent digitizing of relevant markers produced position coordinates which were smoothed and normalized in both distance and time before calculating the third time derivative to obtain two-dimensional JC values. The expected response of
O2 to deviations in SL was found (minimum at FCSL), but JC increased with SL except at the two longest SL conditions. A weak but statistically significant negative correlation was found between
O2 and JC, suggesting that smoothness and economy are not complementary performance criteria during walking. 相似文献