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1.
Donald C. Jackson Henry D. Prange 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1979,134(4):315-319
Summary Ventilation and metabolic rate were measured during exercise in adult female green turtles at Tortuguero, Costa Rica. Six turtles were studied at night on the beach while actively covering their nests. Five turtles, captured after nesting, were studied at rest, during 20 min of spontaneous activity, and during recovery from the activity. Arterial blood samples were obtained from the latter animals and analyzed for pH,
, O2 concentration and lactate concentration. Blood was obtained by heart puncture from 8 turtles immediately after nesting and analyzed for blood lactate. Active metabolism (
) in both groups was almost 10 times the standard resting value (0.024 l/kg·h). The increase in ventilation during exercise, due exclusively to higher breathing frequency, exceeded the increase in
, so that the ratio
(the air convection requirement), more than doubled. The respiratory exchange ratio,
, that averaged 0.56 in the resting turtles, increased to 1.08 during exercise in the captured turtles and was 0.90 in the nesting animals. Arterial
and O2 saturation remained unchanged during exercise, indicating efficient gas exchange in the lungs. Pre-exercise values of all variables were restored 1 h after the end of exercise. Blood acid-base changes associated with activity in the captive turtles were variable and not statistically significant, but suggested partially compensated metabolic acidosis. Lactate concentrations were significantly elevated in the nesting turtles. 相似文献
2.
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
3.
Guido van den Thillart Fanja Kesbeke Aren van Waarde 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,136(1):45-52
Summary Goldfish, acclimated to 20°C and normal
= 130 mmHg) and low (
= 19 mmHg) oxygen levels, were exposed to different periods of hypoxia and anoxia. Experiments were carried out at night. ATP, ADP, AMP, IMP, CrP, glycogen and lactate were determined in red muscle, white muscle and liver. Acclimation to hypoxia resulted in a marked increase of the energy charge of liver and red muscle and of the glycogen content of red and white muscle, indicating an increased anaerobic capacity. Short exposures to anoxia, up to 1 h, had little influence on the value of the measured parameters. Long-term exposures (12 h) to anoxia caused a significant decrease of CrP and glycogen levels in all tissues examined. The energy-charge of red and white muscle was hardly affected by a 12 h exposure to anoxia, but in liver tissue the energy charge decreased from 0.60 to 0.32. It is concluded that during anoxia muscle tissues are able to maintain high energy-charges, probably by means of a yet unknown anaerobic energy-producing system.Abbreviations
CrP
creatine phosphate
-
EC
energy charge
-
IMP
inosine monophosphate
-
I.U.
International Unit (mole/min) 相似文献
4.
Øivind Andersen Johan B. Steen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(6):823-828
Summary Nest humidity (
) under an incubating bantam hen was measured at ambient
ranging from 1.3 to 25.0 mmHg. Weight loss of eggs was recorded in clutches of varying size. Nest
and ambient
were also measured in wild incubating willow ptarmigan nests in dry and wet habitats.Nest
increased linearly with ambient
in a way predictable on the assumption that the water vapour conductance (
) of brood patch skin, plumage and eggs were constant and independent of ambient
. Nest
was also dependent of clutch size. Egg dehydration was quantitatively predicted from measured values and the laws of diffusion.Our findings confirm earlier conclusions that the adult bird does not actively regulate nest
at varying ambient
. Birds can presumably achieve appropriate egg dehydration by a strategy combining nest site, nest construction, egg shell conductance and incubation behaviour which meets the requirements of their breeding climate.Abbreviations
water vapur pressure
-
water vapur conductance
-
water flux 相似文献
5.
Gregory K. Snyder Wesley W. Weathers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1977,117(3):291-301
Summary Resting rates of O2 consumption
against
, exercise endurance times and
during recovery from vigorous exercise were measured inSceloporus occidentalis captured near sea level and inS. graciosus captured above 2850 m. Oxygen consumption against
was also measured inS. occidentalis captured above 2850 m. When
was recorded continuously, as ambient
was slowly reduced from 155 Torr, it became directly dependent upon ambient
between 110 and 120 Torr. The critical
for the high altitude lizards was lower than that for the lowland lizards, which enabled the former to maintain relatively higher
's when ambient
was reduced below 120 Torr. The high altitude lizards also had significantly greater endurance when stimulated to exercise at 1600 m (
130 Torr). Both the higher
under hypoxia and the greater endurance roughly parallel a significantly greater maximum
in the high altitude lizards. At a simulated altitude of 3600 m (
100 Torr), maximum
and rate of recovery of the O2 debt calculated from post active
were significantly reduced in the lowland but not the high altitude lizards. The effects of simulated altitude conditions on the lowland but not the mountaine animals indicate adaptations to altitude in these sceloporine lizards. We did not find any consistent relationship between organ/body weight ratios or hematocrit and our measures of
endurance or the altitude at which the lizards were captured. 相似文献
6.
M. Christopher Barnhart 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(3):347-354
Summary Control of extracellular acid-base status was examined during activity and dormancy inOtala lactea (Pulmonata, Helicidae). Active snails showed little variation in hemolymph pH and
at constant temperature. With increase of temperature, hemolymph
increased from about 6 Torr at 5°C to 13 Torr at 24°C and pH decreased by about 0.017 pH units/°C, a pattern consistent with alphastat regulation of pH via ventilatory control of
.During dormancy, mean hemolymph
increased to about 50 Torr. Venous pH declined by about 0.4 units due to hypercapnia and fluctuated more widely than in active snails due to variability of
. Hemolymph pH declined further in prolonged dormancy due to progressive metabolic acidosis; after one year of dormancy the mean hemolymph pH was about 0.8 units lower than that of active snails at similar temperature.Active snails exposed experimentally to high
showed a large increase in hemolymph [HCO
3
–
]. However, [HCO
3
–
] declined by up to 50% during dormancy, despite the naturally occurring hypercapnia. Hemolymph osmolality and the concentrations of solutes other than [HCO
3
–
] increased with increasing duration of dormancy. Concentrations of magnesium and calcium increased about 2.5 times more rapidly than those of sodium and chloride, indicating that acidosis is partially offset by the dissolution of carbonates from the shell or tissues. 相似文献
7.
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
8.
Jack P. Hayes 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(4):453-459
Summary I compared the maximal aerobic metabolic rates (
), field metabolic rates (FMR), aerobic reserves (
-FMR), and basal metabolic rates (BMR) of wild and recently captured deer mice from low (440 m) and high (3800 m) altitudes. To separate the effects of the thermal environment from other altitudinal effects, I examined mice from different altitudes, but similar thermal environments (i.e., summer mice from high altitude and winter mice from low altitude). When the thermal environment was similar,
, FMR, and aerobic reserve of low and high altitude mice did not differ, but BMR was significantly higher at high altitude. Thus, in the absence of thermal differences, altitude had only minor effects on the aerobic metabolism of wild or recently captured deer mice.At low altitude, there was significant seasonal variation in
, FMR, and aerobic reserve, but not BMR. BMR was correlated with
, but not with FMR. The significant positive correlation of BMR with
indicates a cost of high
, because higher BMR increases food requirements and energy use during periods of thermoneutral conditions.Abbreviations
BMR
basal metabolic rate
-
FMR
field metabolic rate
-
partial pressure of oxygen
-
T
a
ambient temperature
-
T
b
body temperature
-
T
e
operative temperature
-
maximal aerobic metabolic rate 相似文献
9.
Pierre Dejours Jean-Paul Truchot 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(3):387-391
Summary In the intertidal shore crab,Carcinus maenas, pH and
values of the prebranchial venous hemolymph,
and
, the PO2 values of the arterialized cardiac hemolymph,
, were measured, and the ventilatory activity was assessed by measuring the hydrostatic pressures at the exits of the epibranchial cavities, under four environmental conditions: normoxic water, normoxic air, hypoxic gas, hyperoxic gas.In the crab breathing normoxic air,
was lower and
higher than in animals breathing normoxic water. With the switch to hypoxic gas, ventilation increased and
and
decreased. With the switch to hyperoxic gas, ventilation decreased,
and
increased and
decreased.Thus these crabs breathing air were not as well oxygenated as when breathing air-equilibrated water, and because of their low
, they were relatively hypervetilating and hypocapnic compared to air-breathing vertebrates. Hyperoxic breathing, increasing
and reducing ventilatory drive, led to increased
. Conversely,
was reduced by hypoxic breathing. These observations suggest that the gas exchanger of intertidal crabs is not as successfully designed for air breathing as that of land-colonizing insects and air-breathing vertebrates. 相似文献
10.
Mogens L. Glass James W. Hicks Marvin L. Riedesel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1979,131(4):353-359
Summary In late February, seven box turtles were collected with body temperatures between 7 and 9°C. Ventilation, gas exchange and end-tidal
and
were recorded at 5, 10, 15 and 25°C, the animals being at each temperature for 2 to 3 weeks. There was a pronounced diurnal rhythm of breathing frequency at all temperatures. At 5°C the mean 24-h frequency was only 3.7 breaths h–1. At 15°C the frequency was 16 times higher with a 17-fold increase of ventilation. Oxygen uptake only changed from 3.4 to 12.7 ml·kg–1·h–1. Consequently, the ratio (ventilation, ml BTPS/O2 uptake, ml STPD) increased from 12.5 at 5°C to 48 at 15°C, but decreased to 24 at 25°C. The decrease of this ratio during cold exposure contrasts with an increase of the ratio during cooling earlier reported for fresh water turtles,Pseudemys. Cutaneous CO2 elimination was important at low temperature. This caused a decrease of the pulmonary gas exchange ratio so that end-tidal
remained low at 5°C in spite of an end-tidal
of only 54 Torr. 相似文献
11.
G. M. Barnas R. E. Burger 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1984,154(4):393-397
Summary In order to determine the pH effect on the discharge of intrapulmonary chemoreceptors (IPC) not mediated through
, we determined discharge frequency-ln
relationships of 28 IPC from ten adult cockerels made acidotic by ingestion of feed containing 6% NH4Cl for 2 to 5 days. Blood buffer curves — the relationships between pH and
— from these cockerels were shifted in parallel towards acidosis by 0.24 pH units (SE=±0.05) compared to control curves. The average slope of the IPC discharge frequenc-ln
relationships was less negative than that reported for similar cockerels with normal acid-base balance and the average intercept was decreased. We conclude that pH has an effect on IPC discharge, independent of changes in
; this effect decreases IPC sensitivity to CO2. We calculate that a shift towards acidosis in the blood buffer curve of one pH unit causes the slope of the IPC discharge frequency-ln
relationship to be less negative by 14.7±3.3 imp (s·ln
)–1 and that for any acidotic shift in the blood buffer curve (pH), the average IPC discharge frequency=[–10.7+(14.7·pH)][ln(
/25.5)]+3.37. Since IPC discharge is altered by changes in acid-base balance, IPC may contribute to the implementation of respiration responses during metabolic disturbances.Abbreviation
IPC
intrapulmonary chemoreceptor 相似文献
12.
B. Grubb G. E. Folk Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,128(2):185-188
Summary The rate of oxygen consumption (
) by skeletal muscle was investigated in isolated perfused hindlimbs of laboratory rats and lemmings (Lemmus). In both species,
increased in proportion to blood flow rate, even at flow rates 4–5 times above resting level. The slope of the line relating
to skeletal muscle blood flow was significantly greater in the lemming than in the rat. This may be related to the inverse relationship between body weight and metabolic rate. These data support the hypothesis that in small animals a dependent relationship exists between blood flow and skeletal muscle
. 相似文献
13.
Roger S. Seymour David Vleck Carol M. Vleck 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(6):773-782
Summary The brush turkey (Alectura lathami) and mallee fowl (Leipoa ocellata) are megapode birds that incubate their eggs by burying them in mounds. Respiratory gas exchange between the buried eggs and the atmosphere occurs mainly by diffusion through about 60 cm of decomposing forest litter (brush turkey) or sand (mallee fowl).Gas fluxes in the brush turkey mound are greatly influenced by the respiration of thermophilic microorganisms which consume O2 at rates over eight times that of all of the eggs. The respiratory exchange ratio (
) of the microorganisms is 0.75 and theQ
10 for metabolism is 2.56. Fermentation and nitrogen fixation do not occur in the mounds.If the mound becomes too wet, gas tensions near the eggs can become critical because water increases rates of microbial respiration and impedes gas diffusion. However, field mounds are relatively dry, possibly because the adult bird modifies the shape of the mound and affects the entry of rain water. At egg level in field mounds,
and
are about 132 and 21 Torr, respectively, in both species. Embryonic respiration decreases
and increases
about 5 Torr in the immediate environment of individual eggs in late development. Due to a high eggshell gas conductance, which increases during incubation, the gas tensions within the shell of late embryos (
ca. 108 Torr,
ca. 47 Torr) are not far from the mean values found in species that nest above ground. 相似文献
14.
Stephen C. Wood Kjell Johansen Mogens L. Glass G. M. O. Maloiy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,127(4):331-336
Summary Oxygen consumption
was measured at rest and during spontaneous activity at body temperatures of 25 and 35°C in 14 fasting Savanna monitor lizards,Varanus exanthematicus ranging in weight from 172 to 7500 g. The allometric relationship between metabolic rate at 25°C and body weight (W) is given by:
(ml O2 STPD·g–1·hr–1)=0.88W
–0.43 (Fig. 2). Although statistical comparisons are equivocal, this intraspecific size dependence exceeds that reported for interspecific comparisons among reptiles and other vertebrate groups (Fig 3). A reproducible diurnal pattern of activity was observed in undisturbed animals with minimum values of
between 2400 and 0800 h (Fig. 1). Spontaneous activity and
generally reached peak values between 1200 and 2000 hrs. The average ratio of active aerobic metabolic rate (AMR) to minimum (standard) aerobic metabolic rate (SMR) was 8.2. This voluntary AMR/SMR inVaranus exceeds the AMR/SMR for most reptiles stimulated to exhaustion. The high aerobic capacity is consistent with other evidence for efficient exchange and transport of respiratory gases inV. exanthematicus; e.g., low or absent intracardiac shunt flow resulting in high arterial saturation and low ventilation
and perfusion
requirements. 相似文献
15.
Chappell Mark A. Bucher Theresa L. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(1):129-136
Summary The effects of ambient temperature (T
a) on ventilation and gas exchange in chukar partridges (Alectoris chukar) were determined after acclimation to low and high altitute (LA and HA; 340 and 3,800 m, respectively).At both LA and HA, oxygen consumption (
) increased with decreasingT
a atT
a from 20 to –20°C. AtT
a of 35 to 40°C,
increased above thermoneutral values at HA but remained constant and minimal at LA. Water loss rates increased rapidly atT
a>30°C at both altitudes as birds began to pant. Ventilation rates (f) during panting were 5-to 23-fold greater than the minimalf at thermoneutralT
a.Increased
atT
a below thermoneutrality was supported by increased minute volume (V
i) at both altitudes. The change inV
i was primarily a function of changing tidal volume (V
t), althoughf increased slightly asT
a declined. Oxygen extraction (
) remained fairly constant atT
a below 20°C at both altitudes. BothV
t and
were considerably lower when birds were panting than at lowerT
a.Chukars showed few obvious ventilatory adaptations to HA. The 35% change in
between 340 and 3,800 m was accommodated by a corresponding change inV
i (btps), most of which was accomplished by increasedf at HA, along with a slight increase in
.Abbreviations and symbols
HA
high altitude
-
LA
low altitude
-
rate of evaporative water loss
-
oxygen extraction efficiency
-
f
respiratory frequency
-
V
t
tidal volume
-
V
i
minute volume
-
BMR
basal metabolic rate
-
MHP
metabolic heat production 相似文献
16.
P. Pic 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1978,123(2):155-162
Summary In seawater (SW)-adaptedMugil andFundulus, gill effluxes of Na+
and of Cl–
and the simultaneously recorded transgill potential (P.D.) differ according to whether they are measured in stressed or rested animals.In rested animals of the two species, transfer to Ringer's solution considerably reduces the P.D. but not
. InFundulus,
is also decreased. Transfer of the two species from SW to fresh water (FW) reduces
and
by 75 to 85% and leads to a large inversion of P.D. When K+ is added to FW, a gill depolarization occurs, as well as a large increase of
and
.These results suggest that: 1) the P.D. originates primarily from the diffusion of cations, the gill permeability to Na+ (
) being greater than that to Cl– (
), 2) a Cl–/Cl– exchange independent of P.D. is associated with the Cl– pump; 3) Cl– pump activity is linked to Na+/K+ exchange which in turn is associated to a Na+/Na+ exchange diffusion mechanism.In stressed individuals of the two species, the P.D. in SW, as well as the P.D. changes observed during transfer experiments, are considerably reduced. The decrease of
and
observed after transfer from SW to FW are also minimised. Changes are smaller inFundulus. The decrease of P.D. characterizing stressed animals may be at least in part due to a 3 to 4 fold increase of
which becomes equal to
in both species.As a result of stress, the K+-activated Na+ and Cl– excretion mechanisms are totally inhibited inFundulus and partially so inMugil.Stress response seems more intense inFundulus and recovery from stress faster inMugil. 相似文献
17.
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
18.
Tamir M. Ellis Mark A. Chappell 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(3):393-402
Summary Thermogenic incubation has been documented in two large species of pythons, but the phenomenon has not been studied in small species with concomitantly large heat transfer coefficients. We describe behavior, metabolic rates, mass changes, and temperature relations for adult ball pythons (Python regius), the smallest member of the genus, during the reproductive cycle. Egg and hatchling metabolism and hatchling growth rates were also examined.Rates of oxygen consumption (
) of both gravid and non-gravid snakes showed typical ectothermic responses to changing ambient temperature (T
a). TheQ
10 forT
a's of 20–35°C was 2.2–2.3. The
of gravid females was significantly greater than that of non-gravid snakes at allT
a. Maximum oxygen consumption (
max) during forced exercise was about 12 times resting
atT
a=30°C.Eggs (5–6 per female) were laid in April. Total clutch mass was approximately 32% of the females' pre-oviposition mass. After oviposition, mother snakes coiled tightly around their clutches and remained in close attendance until the eggs hatched in June. Sudden decreases inT
a elicited abrupt but transient 2- to 4-fold increases in the
of incubating females. Similar responses were not observed in non-incubating snakes. The steady-state
of incubating females was independent ofT
a. In no case was body temperature (T
b) elevated more than a few tenths of a degree aboveT
a in steady-state conditions.The
of developing eggs increased sigmoidally through the 58–70 day incubation period. Total oxygen consumption during incubation atT
a=29.2°C was about 3.61 per egg. Young snakes quadrupled their mass during their first year of growth.Compared to larger python species which are endothermic during incubation, ball pythons have similar aerobic scopes and higher mass-specific
max. However, effective endothermy in ball pythons is precluded by high thermal conductance and limited energy stores. 相似文献
19.
S. Zielinski H. O. Pörtner 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(8):492-500
The intertidal wormSipunculus nudus was exposed to various temperatures for an analysis of the integrated changes in energy and acid-base status. Animals were
incubated in sea water or maintained for up to 8 days at 4 and 0°C while dwelling in the sediment. Cannulation of the animals
prior to experimentation allowed the analysis of blood gas parameters (
,
and pH).
fell to 0 torr within 8 days at 0°C. A simultaneous reduction of ventilatory activity was derived from measurements of the
pattern of coelomic fluid pressure changes associated with ventilatory movements. The increase in
and an onset of anaerobic metabolism, indicated by the accumulation of end products like acetate and propionate both in the
coelomic fluid and the body wall musculature, led to the development of a progressive acidosis and a deviation from the alphastat
regulation of intracellular pH seen in unburied animals. The drop in intracellular pH together with the depletion of the adenylates
and the phosphagen, phospho-l-arginine, reflect a significant decrease in the Gibb's free-energy change of ATP hydrolysis. These changes are interpreted
to indicate lethal cold injuries, because recovery was not possible when the animals were returned to 12°C after more than
2 days of exposure to 0°C. A low critical temperature indicating the onset of cold-induced anaerobiosis is concluded to exist
below 4°C owing to the insufficient response of the ventilatory system to the developing hypoxia. 相似文献
20.
Barbara Grubb G. E. Folk 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1976,110(2):217-226
Summary The purpose of this study was to determine the effect of norepinephrine (NE) on oxygen consumption (
) of perfused (constant flow) muscle in cold acclimated (CA) and control rats. Infusion of NE for a five minute period caused an increase in
of similar magnitude in both groups. Infusion of NE for 30 min resulted in an elevated steady state
in the cold acclimated group, while the control group showed only an initial increase in
followed by a continual decline during the remainder of the 30 min infusion period. These results suggest that when rats are challenged by cold exposure, the magnitude of the initial muscle response to NE by control and acclimated rats is the same, but a useful sustained higher muscle oxygen consumption is found only in the cold acclimated animals.Abbreviations CA
cold acclimated
- NE
norepinephrine 相似文献