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1.
Cooper AR Morris S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2004,174(3):223-236
Haemoglobin function and respiratory status of sub-adult sharks, Heterodontus portusjacksoni was investigated for up to 1 week following transfer from 100% to either 75% or 50% seawater. Metabolic rates were unusually low and arterial–venous differences in blood O2 small. Haemodilution from osmotic inflow lowered haematocrit and reduced blood O2 content by up to 50%. There was no change in O2 consumption rate, blood O2 partial pressure, cardiac output, or the arterial-venous O2 content difference, and thus O2 delivery was maintained. Ventilation was acutely elevated but returned to normal within 24 h. The O2 delivery to the tissues was facilitated by decreased blood O2-affinity that could not be simply ascribed to changes in the osmolyte concentration. The Hb was unaffected by changes in intra-erythrocyte fluid urea or trimethylamine-N-oxide (TMAO) but was sensitive to changes in NaCl. The Bohr shifts in whole blood were low and there was little role for pH in modulating O2 transport. Venous Hb saturation remained close to 65%, at the steepest part of the in vivo O2 equilibrium curve, such that O2 unloading could be facilitated by small reductions in pressure without increasing cardiac or ventilatory work. H. portusjacksoni tolerated 50% seawater for at least 1 month, but there was little evidence of respiratory responses being adaptive which instead appeared to be consequential on changes in osmotic and ionic status.Abbreviations
a–v
arterial–venous
-
CO
2
CO2 content
-
C
a
O
2
content of O2 in arterial blood
-
C
v
O
2
content of O2 in venous blood
-
%E
branchial O2 extraction efficiency
-
f
v
ventilatory frequency
-
GTP
guanosine triphosphate
-
Hct
haematocrit
-
[Hb]
haemoglobin concentration
-
ITP
inosine triphosphate
-
met[Hb]
methaemoglobin
-
oxygen consumption
-
NTP
nucleoside triphosphate
-
OEC
oxygen equilibrium curve
-
P
a
O
2
partial pressure of O2 in arterial blood
-
P
e
O
2
partial pressure of expired O2
-
P
i
O
2
partial pressure of inspired O2
-
P
in
O
2
inflow partial pressure of O2
-
PO
2
partial pressure of O2
-
P
out
O
2
outflow partial pressure of O2
-
pH
a
arterial blood pH
-
pH
pl
whole blood pH
-
PV
plasma volume
-
P
v
CO
2
partial pressure of CO2in venous blood
-
P
v
O
2
partial pressure of O2in venous blood
-
cardiac output
-
SW
seawater
-
TMAO
trimethylamine-N-oxide
-
ventilation volume
Communicated by G. Heldmaier 相似文献
2.
Ashley R Cooper Stephen Morris 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》1998,119(4):694
The effects of caudal cannulation on the blood physiology of the Port Jackson shark, Heterodontus portusjacksoni, were investigated in sharks given between 4 and 72 h to recover from surgery. Neither the PaO2–PvO2 difference nor the CaO2–CvO2 difference of cannulated sharks fluctuated throughout the sampling period. The plasma acidosis exhibited 4 h after surgery was partially compensated after 24 h by a respiratory (hyperventilatory) alkalosis and after 72 h by a marked metabolic alkalosis. Whilst H. portusjacksoni exhibited some cell swelling after surgery the haematological status of cannulated sharks generally varied little throughout the recovery period. In contrast, marked changes in plasma and erythrocyte ion concentrations were indicative of increased branchial and erythrocyte ion permeability. The blood status of H. portusjacksoni given 72 h to recover from surgery was also compared with sharks sampled by caudal puncture. The respiratory and acid-base status of sharks sampled by caudal puncture was comparable to that of cannulated sharks. In contrast, the plasma ion concentrations of the cannulated sharks were markedly elevated and the erythrocyte ion concentrations concomitantly reduced when compared with punctured sharks. The apparent increase in the water and ion permeability of cannulated sharks was reflected by the reduced [Hb] and mean cell haemoglobin concentrations (MCHC). Blood sampling by caudal puncture appeared to reduce the haematological and ionic perturbations that resulted from surgery and thus provided a less invasive and reliable method for obtaining samples from ‘non-disturbed’ elasmobranchs. 相似文献
3.
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
4.
S. Thomas S. F. Perry 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(5):383-389
The effects of ambient O2 partial pressure and CO2 partial pressure on the intensity of rainbow trout (Oncorhynchus mykiss) red blood cell -adrenergic Na+/H+ exchange were investigated. This was accomplished in vitro by continuously monitoring whole blood extracellular pH, partial pressures of O2 and CO2 and by measuring red blood cell water content and Na+ concentration before and 30 min after the addition of a catecholamine mixture (final nominal concentrations: 250 nmol·l-1 adrenaline and 20 nmol·l-1 noradrenaline). The experiments were performed under six different initial conditions combining two ambient partial pressures of CO2 (1.50 and 6.75 torr) and three ambient partial pressures of O2 (15, 30 and 150 torr). The activation of red blood cell Na+/H+ exchange (as indicated by marked reductions of whole blood pH) was followed by transient reductions in blood partial pressures of CO2 and O2 (2 min) resulting from the shift of the CO2/HCO3
- equilibrium within the cell and the subsequent binding of O2 to the haemoglobin. The initial reduction in blood CO2 partial pressure was followed by a rise reflecting the titration of plasma HCO3
- by extruded H+. At low partial pressure of CO2 (1.50 torr) there was a pronounced stimulatory effect of hypoxia on the initial intensity of the extracellular acidification (5 min), whereas at high CO2 partial pressure (6.75 torr) hypoxia actually lowered the extent of the initial acidification. In all cases, Na+/H+ exchange activation was accompanied by increases in cell water content and red blood cell Na+ levles when measured 30 min after addition of catecholamines. Both hypercapnia and hypoxia increased the magnitude of these changes although the largest changes in cell water content and Na+ levels were observed under hypercapnic conditions. Thus, the long-term activity (as determined by measuring cell water and Na+ levels) of the Na+/H+ exchanger was enhanced both by hypercapnia and hypoxia regardless of the initial CO2 partial pressure. The initial activity (5 min), on the other hand, although stimulated by hypercapnia was influenced by hypoxia in opposing directions depending upon the initial CO2 partial pressure of the blood.Abbreviations RBC
red blood cell(s)
- Hb
haemoglobin
- pHe
extracellular pH
-
P
bCO2
blood partial pressure of CO2
-
P
bO2
blood partial pressure of O2 相似文献
5.
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
6.
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
7.
Pillans RD Good JP Anderson WG Hazon N Franklin CE 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2005,175(1):37-44
This study examined the osmoregulatory status of the euryhaline elasmobranch Carcharhinus leucas acclimated to freshwater (FW) and seawater (SW). Juvenile C. leucas captured in FW (3 mOsm l–1 kg–1) were acclimated to SW (980–1,000 mOsm l–1 kg–1) over 16 days. A FW group was maintained in captivity over a similar time period. In FW, bull sharks were hyper-osmotic regulators, having a plasma osmolarity of 595 mOsm l–1 kg–1. In SW, bull sharks had significantly higher plasma osmolarities (940 mOsm l–1 kg–1) than FW-acclimated animals and were slightly hypo-osmotic to the environment. Plasma Na+, Cl–, K+, Mg2+, Ca2+, urea and trimethylamine oxide (TMAO) concentrations were all significantly higher in bull sharks acclimated to SW, with urea and TMAO showing the greatest increase. Gill, rectal gland, kidney and intestinal tissue were taken from animals acclimated to FW and SW and analysed for maximal Na+/K+-ATPase activity. Na+/K+-ATPase activity in the gills and intestine was less than 1 mmol Pi mg–1 protein h–1 and there was no difference in activity between FW- and SW-acclimated animals. In contrast Na+/K+-ATPase activity in the rectal gland and kidney were significantly higher than gill and intestine and showed significant differences between the FW- and SW-acclimated groups. In FW and SW, rectal gland Na+/K+-ATPase activity was 5.6±0.8 and 9.2±0.6 mmol Pi mg–1 protein h–1, respectively. Na+/K+-ATPase activity in the kidney of FW and SW acclimated animals was 8.4±1.1 and 3.3±1.1 Pi mg–1 protein h–1, respectively. Thus juvenile bull sharks have the osmoregulatory plasticity to acclimate to SW; their preference for the upper reaches of rivers where salinity is low is therefore likely to be for predator avoidance and/or increased food abundance rather than because of a physiological constraint. 相似文献
8.
Ionic responses to alteration in external and internal pH were examined in an organism from a marine-like environment. Vacuolar pH (pHv) is about 4.9–5.1, constant at external pH (pHo) 5–8, while cytoplasmic pH (pHc) increases from 7.3 to 7.7. pHc regulation fails above pHo 9, and this is accompanied by failure of turgor regulation. Na+ increases above pHo 9, while K+ and Cl– decrease. These changes alone cannot however explain the alterations in turgor. Agents known to affect internal pH are also tested for their effect on ion relations.Abbreviations Ci
ion concentration
- CCCP
carbonyl cyanide m-chlorophenyl hydrazone
- DCCD
dicyclohexylcarbodiimide
- DES
diethylstilbestrol
- DMO
5,5-dimethyloxazolidine-2,4-dione
- DNP
2,4-dinitrophenol
- pHo
external pH
- pHc
cytoplasmic pH
- pHv
vacuolar pH
- i
osmotic pressure
-
turgor pressure 相似文献
9.
C. L. Beckmann J. G. Mitchell L. Seuront D.A.J. Stone C. Huveneers 《Journal of fish biology》2014,85(3):944-952
The muscle and liver fatty acid composition of young‐of‐the‐year (YOY) Port Jackson sharks Heterodontus portusjacksoni were investigated to determine the effects of a known dietary lipid source v. maternal input as demonstrated by egg yolk fatty acid profiles. Ten Heterodontus portusjacksoni egg yolks were collected in situ and compared with four hatched H. portusjacksoni fed a known diet in a controlled feeding experiment of 185 days. This study demonstrated that fatty acids are probably conservatively transferred from egg yolks to YOY H. portusjacksoni, while diet did not have a large effect on the fatty acid composition of the liver or muscle. 相似文献
10.
N. C. Jørgensen 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(6):450-457
Simultaneous net uptake of Na+ and net extrusion of H+, both inhibited by amiloride, could be stimulated in red blood cells of the frog, Rana temporaria, either by intracellular acidification or cellular shrinkage. Net transports of Na+ and H+ were transient, dying out after 10–20 min (20°C) when stimulated by intracellular acidification but developing more slowly and proceeding for more than 60 min (20°C) when stimulated by cellular shrinkage. Evidence is presented suggesting a coupling between the transports of Na+ and H+ with an exchange ratio of 1:1 Na+/H+ exchange, stimulated by intracellular acidification, was able to readjust intracellular pH also when operating in parallel to a fully working anion exchanger in CO2/HCO
3
-
-buffered media. Inhibition of anion exchange resulted in reduced cellular net uptake of Na+.Abbreviations
DIDS
4,4-diisothiocyanatostilbene-2,2-disulphonate
-
DMSO
dimethylsulphoxide
-
IU
international unit
-
pH
e
extracellular pH
-
pH
i
intracellular pH
-
RBC
red blood cell 相似文献
11.
Information is given concerning two standard buffer solutions suitable as pH references in 30, 40, and 50 mass% dimethyl sulfoxide (DMSO)/H2O mixed solvents at subzero temperatures from −20 to 0 °C, with the intention of establishing a pH (designated pH*) scale. The two buffers selected were the ampholytes N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid (“bes”) and N-tris(hydroxymethyl)methylglycine (“tricine”), and the reference standard consisted of equal molal quantities of the buffer and its respective sodium salt. The assignment of pH* values was based on measurements of the emf of cells without liquid junction of the type: Pt;H2(g,1 atm) ¦Bes, Na Besate, NaCl ¦ AgCl;Ag and Pt;H2(g,1 atm) ¦Tricine, Na Tricinate, NaCl ¦AgCl;Ag and the pH* was derived from a determination of K2, the equilibrium constant for the dissociation process (Buffer)±/ai (Buffer)− + H+. 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.
Niels Thomas Eriksen Frederik Kier Riisgård William Stuart Gunther Jens Jørgen Lønsmann Iversen 《Journal of applied phycology》2007,19(2):161-174
Growth of the green algae Chlamydomonas reinhardtii and Chlorella sp. in batch cultures was investigated in a novel gas-tight photobioreactor, in which CO2, H2, and N2 were titrated into the gas phase to control medium pH, dissolved oxygen partial pressure, and headspace pressure, respectively.
The exit gas from the reactor was circulated through a loop of tubing and re-introduced into the culture. CO2 uptake was estimated from the addition of CO2 as acidic titrant and O2 evolution was estimated from titration by H2, which was used to reduce O2 over a Pd catalyst. The photosynthetic quotient, PQ, was estimated as the ratio between O2 evolution and CO2 up-take rates. NH4
+, NO2
−, or NO3
− was the final cell density limiting nutrient. Cultures of both algae were, in general, characterised by a nitrogen sufficient
growth phase followed by a nitrogen depleted phase in which starch was the major product. The estimated PQ values were dependent on the level of oxidation of the nitrogen source. The PQ was 1 with NH4
+ as the nitrogen source and 1.3 when NO3
− was the nitrogen source. In cultures grown on all nitrogen sources, the PQ value approached 1 when the nitrogen source was depleted and starch synthesis became dominant, to further increase towards
1.3 over a period of 3–4 days. This latter increase in PQ, which was indicative of production of reduced compounds like lipids, correlated with a simultaneous increase in the degree
of reduction of the biomass. When using the titrations of CO2 and H2 into the reactor headspace to estimate the up-take of CO2, the production of O2, and the PQ, the rate of biomass production could be followed, the stoichiometrical composition of the produced algal biomass could be
estimated, and different growth phases could be identified. 相似文献
14.
R. W. Wilson E. W. Taylor 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(1):38-47
Acutely lethal (24 h) exposure of adult rainbow trout (Oncorhynchus mykiss) to 4.9 mol copper·l-1 in fresh water (pH 7.9, [Ca2+]0.8 mEq·l-1) caused a rapid decline of plasma Na+ and Cl- and arterial O2 tension, and initially a pronounced tachycardia. The internal hypoxia probably resulted from histopathologies observed in the gills of fish exposed to copper, such as cell swelling, thickening and curling of the lamellae, and haematomas. Copper cannot therefore be considered purely as an ionoregulatory toxicant during acutely lethal conditions. Mortality during exposure to copper could not simply be explained by the plasma ionic dilution, nor by the internal hypoxia, since arterial O2 content remained relatively unchanged. Secondary to the ionoregulatory and respiratory disturbances were a number of deleterious physiological responses which included a massive haemoconcentration (haematocrit values as high as 60%) and a doubling of the mean arterial blood pressure. The time-course of these changes suggest that cardiac failure was the final cause of death. In this respect copper exposure resembles low pH exposure in freshwater trout (Milligan and Wood 1982). Copper and H+ appear to be similar in both the primary site of their toxic action (the gills) and the secondary physiological consequences which result from acutely lethal exposures. Furthermore, the acute toxicity syndrome observed may be common to many metals which cause ionoregulatory and/or respiratory problems in freshwater fish.Abbreviations
C
aO2
arterial oxygen content
- FR
water flow rate
- Hb
haemoglobin
- Hct
haematocrit
- H
m
+
net metabolic acid load
- IU
international unit
- MABP
mean arterial blood pressure
- MCHC
mean corpuscular haemoglobin content
-
MO2
rate of oxygen consumption
-
P
aCO2
arterial carbon dioxide tension
-
P
aO2
arterial oxygen partial pressure
-
T
amm
total ammonia (=NH3+NH
4
+
)
-
TCO2
total carbon dioxide
-
TOC
total organic carbon
- %Hb–O2
percentage of haemoglobin saturated with oxygen 相似文献
15.
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
16.
Müller F Aschenbach JR Gäbel G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):337-343
This study sought to investigate effects of short-chain fatty acids and CO2 on intracellular pH (pHi) and mechanisms that mediate pHi recovery from intracellular acidification in cultured ruminal epithelial cells of sheep. pHi was studied by spectrofluorometry using the pH-sensitive fluorescent indicator 2′,7′-bis (carboxyethyl)-5(6′)-carboxyfluorescein
acetoxymethyl ester (BCECF/AM). The resting pHi in N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES)-buffered solution was 7.37 ± 0.03. In HEPES-buffered solution,
a NH4
+/NH3-prepulse (20 mM) or addition of butyrate (20 mM) led to a rapid intracellular acidification (P < 0.05). Addition of 5-(N-ethyl-N-isopropyl)-amiloride (EIPA; 10 μM) or HOE-694 (200 μM) inhibited pHi recovery from an NH4
+/NH3-induced acid load by 58% and 70%, respectively. pHi recovery from acidification by butyrate was reduced by 62% and 69% in the presence of EIPA (10 μM) and HOE-694 (200 μM),
respectively. Changing from HEPES- (20 mM) to CO2/HCO3
−-buffered (5%/20 mM) solution caused a rapid decrease of pHi (P < 0.01), followed by an effective counter-regulation. 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS; 100 μM) blocked
the pHi recovery by 88%. The results indicate that intracellular acidification by butyrate and CO2 is effectively counter-regulated by an Na+/H+ exchanger and by DIDS-sensitive, HCO3
−-dependent mechanism(s). Considering the large amount of intraruminal weak acids in vivo, both mechanisms are of major importance
for maintaining the pHi homeostasis of ruminal epithelial cells.
Accepted: 8 March 2000 相似文献
17.
Hemolymph oxygen content,oxyhemocyanin, protein levels and ammonia excretion in the shrimp Penaeus monodon exposed to ambient nitrite 总被引:1,自引:0,他引:1
J. C. Chen S. Y. Cheng 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,164(7):530-535
Subadult Penaeus monodon (21.03±3.19 g) were exposed individually in sea water (30 mg·ml-1) to 0.02 (control), 1.04, 5.02, 10.11 and 20.06 mg·l-1 nitrite-N for 24h. Hemolymph pH, partial pressures of oxygen and carbon dioxide, bicarbonate concentration, oxyhemocyanin and protein levels, and whole animal ammonia-N excretion and nitrite-N uptake were determined. Ammonia-N excretion and hemolymph oxygen partial pressure increased, whereas hemolymph pH, HCO
3
-
, oxyhemocyanin, protein and the ratio of oxyhemocyanin/protein levels decreased with increasing ambient nitrite-N. It is suggested that accumulated nitrite of P. monodon following exposure to ambient nitrite causes reduction of oxyhemocyanin, protein and the ratio of oxyhemocyanin/protein in the hemolymph, and affects nitrogen metabolism and acid-base balance at low hemolymph pH.Abbreviations bw
body weight
- EC50
concentration reducing growth rate by 50% that of controls
- LC50
median lethal concentration
- nitrite-N
nitrite concentration measured as nitrogen
-
PO2
partial pressure of O2 in hemolymph
-
PCO2
partial pressure of CO2 in hemolymph
- sw
sea water
- ww
wet weight 相似文献
18.
The influence of cytosolic pH (pHi) in controlling K+-channel activity and its interaction with cytosolic-free Ca2+ concentration ([Ca2+]i) was examined in stomatal guard cells ofVicia faba L. Intact guard cells were impaled with multibarrelled microelectrodes and K+-channel currents were recorded under voltage clamp while pHi or [Ca2+]i was monitored concurrently by fluorescence ratio photometry using the fluorescent dyes 2,7-bis (2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF) and Fura-2. In 10 mM external K+ concentration, current through inward-rectifying K+ channels (IK,in) was evoked on stepping the membrane from a holding potential of –100 mV to voltages from –120 to –250 mV. Challenge with 0.3-30 mM Na+-butyrate and Na+-acetate outside imposed acid loads, lowering pHi from a mean resting value of 7.64 ± 0.03 (n = 25) to values from 7.5 to 6.7. The effect on pHi was independent of the weak acid used, and indicated a H+-buffering capacity which rose from 90 mM H+/pH unit near 7.5 to 160 mM H+/pH unit near pHi 7.0. With acid-going pHi, (IK,in) was promoted in scalar fashion, the current increasing in magnitude with the acid load, but without significant effect on the current relaxation kinetics at voltages negative of –150 mV or the voltage-dependence for channel gating. Washout of the weak acid was followed by transient rise in pHi lasting 3–5 min and was accompanied by a reduction in (IK,in) before recovery of the initial resting pHi and current amplitude. The pHi-sensitivity of the current was consistent with a single, titratable site for H+ binding with a pKa near 6.3. Acid pHi loads also affected current through the outward-rectifying K+ channels (IK,out) in a manner antiparallel to (IK,in) The effect on IK, out was also scalar, but showed an apparent pKa of 7.4 and was best accommodated by a cooperative binding of two H+. Parallel measurements showed that Na+-butyrate loads were generally without significant effect on [Ca2+]i, except when pHi was reduced to 7.0 and below. Extreme acid loads evoked reversible increases in [Ca2+]i in roughly half the cells measured, although the effect was generally delayed with respect to the time course of pHi changes and K+-channel responses. The action on [Ca2+]i coincided with a greater variability in (IK,in) stimulation evident at pHi values around 7.0 and below, and with negative displacements in the voltage-dependence of (IK,in) gating. These results distinguish the actions of pHi and [Ca2+]i in modulating (IK,in) they delimit the effect of pHi to changes in current amplitude without influence on the voltage-dependence of channel gating; and they support a role for pHi as a second messenger capable of acting in parallel with, but independent of [Ca2+]i in controlling the K+ channels.Abbreviations BCECF
2,7-bis (2-carboxyethyl)-5(6)-carboxy fluorescein
- [Ca2+]i
cytosolic free Ca2+ concentration
- gK
ensemble (steady-state) K+-channel conductance
- IK,out, IK,in
outward-, inward-rectifying K+ channel (current)
- IN
current-voltage (relation)
- Mes
2-(N-morpholinolethanesulfonic acid
- pHi
cytosolic pH
- V
membrane potential 相似文献
19.
Isolated characean internodal cells of Nitellopsis obtusa can be stored in artificial pond water for many days, but they cannot survive in 100mol m?3 NaCl solution unless more than several mol m?3 Ca2+ is added. Short-term effects of NaCl stress on the cytosolic concentration of Ca2+ ([Ca2+]c), cytosolic pH (pHc) and vacuolar pH (pHv) were studied in relation to the external concentration of Ca2+ ([Ca2+]e). Changes in [Ca2+]c were measured with light emission from a Ca2+-sensitive photoprotein, semisynthetic fch-aequorin which had been injected into the cytosol. Both pHc and pHv were measured with double-barrelled pH-sensitive microelectrodes. When internodal cells were treated with 100 mol m?3 NaCl (0–1 mol m?3 NaCl (0.1 mol m?3 [Ca2+]e), [Ca2+]c increased and then recovered to the original level within 60 min. The time course of the transient change in [Ca2+]c was not influenced by the level of [Ca2+]c (0.1 and 10 mol m?3). In some cases, the transient increase in [Ca2+]c was induced only by increasing external osmotic pressure with sorbitol. In response to treatment with 100 mol m?3 NaCl (0.1 mol m?3 [Ca2+]c), pHc decreased by 0.1–0.2 units after 10min but recovered after 30–60 min, while pHv increased by 0.4–0.5 units after 2–50 min and tended to recover after 60 min. The initial changes in both pHc and pHv were suppressed when [Ca2+]e was raised from 0.1 to 10mol m?3. These results show that the charophyte alga Nitellopsis can regulate [Ca2+]c, pHc and pHv under NaCl stress in the short term and that the protective effect of Ca2+ on salinity stress is apparently unrelated to perturbation of Ca2+ and pH homeostasis. 相似文献
20.
Concanamycin 4-B, a macrolide antibiotic with an 18-membered lactone ring, is known as a specific inhibitor of the vacuolar type of H+-ATPase, as is bafilomycin A1. The drug was tested for its effect on regulation of the vacuolar pH (pHv) of internodal cells of a fresh water characean alga, Chara corallina, under normal conditions and under salt stress. The pHv was measured either on isolated vacuolar sap with a conventional pH electrode or directly by inserting a pH-sensitive glass microelectrode into the vacuole. Proton-pumping into tonoplast vesicles was almost completely inhibited by concanamycin 4-B at 1 nM. Concanamycin 4-B at 1 μM significantly increased pHv while bafilomycin A1 was ineffective when applied at 1 μM. Concanamycin 4-B did not affect pHv when applied at 0.1 μM and increasing the concentration to 10 μM did not amplify the degree of alkalization. Concanamycin 4-B also inhibited pHv regulation under NaCl stress. When Chara cells were treated with 100 mM NaCl, pHv promptly increased and then recovered to the original level. The reacidification was completely inhibited by concanamycin 4-B (1 μM), suggesting that the reacidification was achieved by the H+-ATPase of the tonoplast. 相似文献