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1.
A. Bryce Cooper 《Microbial ecology》1984,10(4):317-334
The in situ rates of oxygen consumption by benthic nitrifiers were estimated at 11 study sites in 4 streams. Two methods were used: an in situ respiration chamber method and a method involving conversion of nitrifying potential measurements to in situ rates. Estimates of benthic nitrogenous oxygen consumption (BNOC) rate ranged from 0–380 mmol of O2 m–2·day–1, and BNOC contributed between 0–85% of the total benthic oxygen consumption rate. The activity of nitrifiers residing in the sediments was influenced by O2 availability, temperature, pH, and substrate. Depending upon site, nitrification could approximate either first-order or zero-order kinetics with respect to ammonium concentration. The source of ammonium for benthic nitrifiers could be either totally from within the sediment or totally from the overlying water. Nitrate produced in the sediments could flux to the water above or be lost within the sediment. The sediments could act as a source (positive flux) or sink (negative flux) for both ammonium (–185 mmol·m–2·day–1 to +195 mmol·m–2·day–1) and nitrate (–135 mmol·m–2·day–1 to +185 mmol·m–2·day–1).This study provides evidence to suggest that measurements of down-stream mass flow changes in inorganic nitrogen forms may give poor estimates of in situ rates of nitrification in flowing waters. 相似文献
2.
A. M. Beal 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,164(8):629-635
Saliva was collected from the mandibular glands of anaesthetized common wombats (Vombatus ursinus) to ascertain maximal flow rates, salivary compostion and possible adaptations, particularly PO4
3- secretion, to assist digestion. After temporary catheterization of the main duct through its oral opening, salivary secretion was evoked at flow rates ranging from 0.02±0.002 (±SEM) ml·min-1 (0.7±0.07 l·min-1·kg body weight-1) to 0.4±0.05 ml·min-1(14±1.9 l·min-1·kg body weight-1) by ipsilateral intracarotid infusion of acetylcholine. The [Na+] (15±5.1 to 58±8.6 mmol·l-1) and [HCO3
-] (35±1.9 to 60±1.9 mmol·l-1) were positively correlated with salivary flow rate. The [K+] (58±5.2 to 30±2.4 mmol·l-1), [Ca2+] (10.4±1.67 to 4.1±0.44 mmol·l-1), [Mg2+] (0.94±0.137 to 0.17±0.032 mmol·l-1), [Cl-] (71±9.2 to 45±6.0 mmol·l-1), [urea] (9.3±0.79 to 5.1±0.54 mmol·l-1), H+ activity (29±1.6 to 17±1.6 nEq·l-1) and amylase activity (251±57.4 to 92±23.3 kat·l-1) were negatively correlated with flow. Both concentration and osmolality fell with increasing flow at the lower end of the flow range but osmolality always increased again by maximal flow whereas the relation between protein and flow was not consistent at the higher levels of flow and stimulation. Salivary [PO4
3+] was not correlated with flow and at 3–14% of the plasma concentration was extremely low. Thus, in contrast to its nearest relative, the koala (Phascolarctos cinereus), the wombat secretes little PO4
3+ presumably because it does not need high levels of PO4
3+ in its saliva to facilitate microbial digestion of plant fibre.Abbreviations bw
body weight
- ww
wet weight 相似文献
3.
Fusicoccin Counteracts the n-Ethylmaleimide and
Silver-Induced Stimulation of Oxygen Uptake in
Egeria densa Leaves
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It was previously shown that a number of sulfhydryl [SH] group reagents (N-ethylmaleimide [NEM], iodoacetate, Ag+, HgCl2, etc.) can induce a marked, transitory stimulation of O2 uptake (QO2) in Egeria densa leaves, insensitive to CN− and salicylhydroxamic acid and inhibited by diphenylene iodonium and quinacrine. The phytotoxin fusicoccin (FC) also induces a marked increase in O2 consumption in E. densa leaves, apparently independent of the recognized stimulating action on the H+-ATPase. In this investigation we compared the FC-induced increase in O2 consumption with those induced by NEM and Ag+, and we tested for a possible interaction between FC and the two SH blockers in the activation of QO2. The results show (a) the different nature of the FC- and NEM- or Ag+-induced increases of QO2; (b) that FC counteracts the NEM- (and Ag+)-induced respiratory burst; and (c) that FC strongly reduces the damaging effects on plasma membrane permeability observed in E. densa leaves treated with the two SH reagents. Two alternative models of interpretation of the action of FC, in activating a CN−-sensitive respiratory pathway and in suppressing the SH blocker-induced respiratory burst, are proposed. 相似文献
4.
E. Król 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):503-507
Body temperature and oxygen consumption were measured in the eastern hedgehog,Erinaceus concolor Martin 1838, during summer at ambient temperatures (T
a) between-6.0 and 35.6°C.E. concolor has a relatively low basal metabolic rate (0.422 ml O2·g-1·h-1), amounting to 80% of that predicted from its body mass (822.7 g). Between 26.5 and 1.2°C, the resting metabolic rate increases with decreasing ambient temperature according to the equation: RMR=1.980-0.057T
a. The minimal heat transfer coefficient (0.057 ml O2·g-1·h-1·°C-1) is higher than expected in other eutherian mammals, which may result from partial conversion of hair into spines. At lower ambient temperature (from-4.6 to-6.0° C) there is a drop in body temperature (from 35.2 to 31.4° C) and a decrease in oxygen consumption (1.530 ml O2·g-1·h-1) even though the potential thermoregulation capabilities of this species are significantly higher. This is evidenced by the high maximum noradrenaline-induced non-shivering thermogenesis (2.370 ml O2·g-1·h-1), amounting to 124% of the value predicted. The active metabolic rate at ambient temperatures between 31.0 and 14.5° C averages 1.064 ml O2·g-1·h-1; at ambient temperatures between 14.5 and 2.0° C AMR=3.228-0.140T
a.Abbreviations AMR
active metabolic rate
- bm
body mass
- BMR
basal metabolic rate
-
h
heat transfer coefficient
- NA
noradrenaline
- NST
non-shivering thermogenesis
- NSTmax
maximum rate of NA-induced non-shivering thermogenesis
- RMR
resting metabolic rate
- RQ
respiratory quotient
- STPD
standard temperature and pressure (25°C, 1 ATM)
-
T
a
ambient temperature
-
T
b
body temperature 相似文献
5.
D. Siebers C. Lucu K. Böttcher K. Jürss 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(1):16-22
Isolated posterior gills (no. 7) of shore crabsCarcinus maenas acclimated to brackish water of a salinity of 10 S were bathed and perfused with 50% sea water (200 mmol·l-1 Na+), and the internal perfusate collected during subsequent periods of 5 min. During a single passage through the gill the pH of the perfusion medium decreased from ca. 8.1 to ca. 7.7, a result implying that the gill possesses structures which recognize unphysiologically high pH values in the haemolymph and regulates them down to physiological values of ca. 7.7. The calculated apparent proton fluxes from the epithelial cells into the haemolymph space amounted to 17.9 mol·g fw-1·h-1, a value of only 3.8% of net Na+ fluxes observed under comparable conditions. When 0.1 mmol·l-1 KCN, an inhibitor of mitochondrial cytochrome oxidase, or 5 mmol·l-1 ouabain, a specific inhibitor of Na+/K+-ATPase were applied in the internal perfusate, down-regulation of pH was no longer observed and the gill was completely depolarized, i.e. transepithelial potential differences dropped from-7.8 to 0 mV (haemolymph space negative to bath). Regulation of pH was completely inhibited by antagonists of carbonic anhydrase (0.1 mmol·l-1 acetazolamide or 0.01 mmol·l-1 ethoxyzolamide) applied in the perfusate. Inhibitors of Na+/H+ exchange, 0.1 mmol·l-1 amiloride applied in the external bathing medium or in the internal perfusate, and symmetrical 0.01 mmol·l-1 5-(N-ethyl-N-isopropyl)amiloride, as well as inhibitors of Cl-/HCO3
- exchange and Na+/HCO3
- cotransport, 0.5 mmol·l-1 4,4-diisothiocyanatostilbene-2,2-disulphonate or 0.3 mmol·l-1 4-acetamido-4-isothiocyanatostilbene 2,2-disulphonate applied on both sides of the gill, and inhibitors of H+-ATPase, 0.05 mmol·l-1
N-ethylmaleimide and 0.1 mmol·l-1
N,N-dicyclohexylcarbodiimide —applied on both sides of the gill — did not alter the acidification of the perfusate observed in controls. Using artificial salines buffered to pH 8.1 with 0.75 mmol·l-1 tris (hydroxymethyl) aminomethane instead of 2 mmol·l-1 HCO3
-, apparent proton fluxes were reduced to 11% of controls, a result suggesting that pH regulation by crab gills needs the presence of HCO3
-. The findings obtained suggest that pH regulation by crab gills depends on the oxidative metabolism of the intact branchial epithelium and that carbonic anhydrase plays a central role in this process. Na+/H+ exchange, anion exchange or cotransport and active proton secretion seem not to be involved. While unimpaired active ion uptake is a prerequisite for pH regulation, ion transport itself is independent of it.Abbreviations acetazolamide
(N-[sulphamoyl-1, 3, 4-thiadiazol-2-yl]-acetamide)
- amiloride
3,5-diamino-6-chloropyrazinoyl-guanidine
- CA
carbonic anhydrase
- DBI
dextrane-bound inhibitor thiadiazolesulphonamide
- DCCD N
N dicyclohexylcarbodiimide
- DIDS
4,4-diisothiocyanato-stilbene-2,2-disulphonate
- EIPA
5-(N-ethyl-N-isopropyl) amiloride
- ethoxyzolamide
6-ethoxy-2-benzothiazole-sulphonamide
- fw
fresh weight
-
J
H
+
apparent proton flux
- NEM
N-ethylmaleimide
- PD
transepithelial potential difference
- PEG-STZ
polyethylene-glycol-thiadiazolesulphonamide
- STTS
4-acetamido-4-isothiocyanatostibene 2,2-disulphonate
- SW
sea water
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
6.
Wiktoria Ratajczak Władysław Polcyn Teresa Lehmann Lech Ratajczak Małgorzata Garnczarska 《Acta Physiologiae Plantarum》1998,20(2):123-127
The incorporation of 14C-aspartate during the imbibition of yellow lupin seeds resulted in the production of 14C-alanine and 14CO2. On the basis of tracer and enzymatic assays, conducted in vitro on the extract obtained from lupin seeds, it is postulated that aspartate can be converted to oxaloacetate, then, by phosphoenolopyruvate
and pyruvate to alanine. This pathway can be catalyzed by the following enzymes: aspartate aminotransferase, phosphoenolpyruvate
carboxykinase, pyruvate kinase and alanine aminotransferase. 相似文献
7.
S. M. Thoroed K. Fugelli 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1993,163(4):307-316
About 92% of the taurine influx in flounder erythrocytes at physiological conditions in vitro (330 mosmol·l-1, 145 mmol·l-1 Na+, 0.30 mmol·l-1 taurine) is Na+-dependent. This influx is highly specific for taurine. The -amino compounds hypotaurine and -alanine were the only compounds which mimicked the inhibitory effect of taurine on influx of [14C]taurine, the former more than the latter. Counterexchange of taurine was also mediated by the taurine transporters. Reduction of osmolality per se did not affect the activity of these transporters. Non-linear regression analysis of the influx values revealed the presence of two different influx systems: a system with high affinity and low capacity and another with low affinity and high capacity. However, we cannot exclude the possibility that this influx of taurine was mediated by only one transporter which operated in different modes depending on the extracellular Na+ concentration. On the assumption that the Na+-dependent influx was mediated by two separate systems, the maximal velocity of the low capacity system was 2.55 nmol·g dry weight-1·min-1 at 145 mmol·ll-1 extracellular Na+. This capacity was about 50% lower than that of the high capacity system. The Michaelis constants were 0.013 and 1.34 mmol·l-1, respectively. Reduction of the extracellular Na+ concentration reduced maximal velocity and the affinity to taurine of both transport systems. At 10 mmol·l-1 Na+ or lower concentrations the high capacity system did not seem to operate. The activation method suggested that each taurine molecule transported by the high capacity system was accompanied by two Na+. The stoichiometry of the low capacity system was 1 taurine: 1 Na+. The Hill-coefficient for both transport systems was 1.00.Abbreviations cpm
counts per minute
- dw
dry weight
- GABA
-amino-n-butyric acid
-
K
m
Michaelis constant
- pK
b
basic dissociation constant
- SD
standard deviation
- -ABA
Dl--amino-n-butyric acid
-
V
max
maximal velocity
- ww
wet weight 相似文献
8.
Using two mouse-mouse hybridoma cell lines, the response to ammonia step and serial changes was investigated in batch and continuous cultures with serum-free medium. The inhibitory effect of ammonia on cell growth depended on the cultivation mode, and differed markedly between cell lines. The cell line, 4C10B6 producing IgG monoclonal antibody against Pseudomonas, showed a high adaptation ability to ammonia. The 4C10B6 cells could grow under ammonia concentration as high as 21 mmol/l NH4Cl with a viability of 80% in the continuous culture with serial increase in ammonia concentration. Whereas, in the batch culture with ammonia step change the cell growth completely ceased at 12 mmol/l NH4Cl. The other cell line, TO-405 producing IgG monoclonal antibody against hepatitis B surface antigen, could not adapt to ammonia, and the cell growth did not occur at 9 mmol/l NH4Cl even under the ammonia serial change.List of symbols DFeed
d-1 Dilution rate of fresh feed medium (=Fo/V)
- DOut
d-1 Dilution rate of cell suspension (=F1/V)
- F1
ml·d-1 Volumetric discharge rate of cell suspension
- F0
ml·d-1 Volumetric flow rate of fresh feed medium
- kD
h-1 Specific death rate
- P
mmol·l-1 Product concentration
- S
mmol·l-1 Substrate concentration in culture broth
- S0
mmol·l-1 Substrate concentration in feed medium
- t
d Cultivation time
- V
ml Working volume of reactor
- X0
cells·ml-1 Total cell density
- XV
cells·ml-1 Viable cell density
- YP/S
mmol·mmol-1 Yield of product from substrate
- YX/S
cells·mmol-1 Yield of cells from substrate
-
mmol·cell-1·h-1 Specific production rate
-
h-1 Specific growth rate
-
mmol·cell-1·h-1 Specific consumption rate of substrate 相似文献
9.
Summary Sulfhydryl blockers, such as N-ethylmaleimide, iodoacetate and heavy metals induce a transitory stimulation of O2 consumption and H2O2 production (oxidative burst) and a rapid release of electrolytes in leaves of various aquatic plants. The correlation between these two responses to N-ethylmaleimide or to Ag+ in separate organs and stages of leaf development was investigated inEgeria densa. Only adult leaves were able to respond to the sulfhydryl blockers with an oxidative burst, whereas this response was absent in immature growing leaves and in stem and root segments. In N-ethyl-maleimide- as well as in Ag+-treated adult leaves the oxidative burst was constantly associated with a relevant electrolyte leakage. These data are consistent with a model in which the SH reagent would first interact with a plasmalemma protein, leading to an increase in passive permeability to ions and to the activation of an oxidative enzyme of the type of the superoxide synthase described for granulocytes. In its turn, active-oxygen species produced by the activated oxidase might further damage the plasma membrane, increasing its passive permeability. Digitonin and nystatin, two reagents known to cause a permeabilization of lipid membranes, induced in adultE. densa leaves a transient increase in the rate of O2 consumption and H2O2 production and an electrolyte leakage very similar to those induced by sulfhydryl blockers. These effects, however, were not influenced by the flavin analogues diphenylene iodonium and quinacrine, and were partially inhibited by the presence of CN– and salicylhydroxamic acid, thus suggesting the involvement of a different oxidase in the oxidative burst elicited by these reagents.Abbreviations BTP
1,3-bis-tris(hydroxymethyl)methylaminopropane
- CCCP
carbonylcyanide-chlorophenylhydrazone
- DCMU
3-(3,4 dichloropheny 1)-1,1-dimethylurea
- DPI
diphenylene iodonium
- NEM
N-ethylmaleimide
- QO2
O2 uptake 相似文献
10.
Jonas Collén Miguel Jiménez Del Rio Guillermo García-Reina Marianne Pedersén 《Planta》1995,196(2):225-230
Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H2O2 was light dependent with a production of 1.2 mol·g FW–1·h–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m–2·s–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW–1·h–1) but at pH 9.0 the production was 5.0 mol·g FW–1·h–1. The production of H2O2 was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H2O2 was checked and found to be seven times higher at 08.00 hours than other times of the day. The H2O2 concentration in the cultivation tank (density: 2 g FW·l–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H2O2 formation. The H2O2 is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW–1·h–1 at pH 8.2 and 90 mmol·g FW–1·h–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H2O2 production. The H2O2 production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL
artificial, continuous light
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- GNL
greenhouse
- LDC
Luminol-dependent chemiluminescence
- SOD
Superoxide dismutase
This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain. 相似文献
11.
Long lasting batch cultures of Azospirillum brasilense SP 7 ATCC 29145 grown in liquid malate medium for 8–14 days without any fixed nitrogen source exhibited a biphasic nitrogenase activity, when incubated under gas atmospheres of 99.0% N2 and 1.0% O2 or 99.5% N2 and 0.5% O2 respectively. Maximum specific nitrogenase activity was 1100 nmol C2H4·mg protein-1·h-1. Poly-3-hydroxybutanoic acid (PHBA) synthesis and growth of the cells also showed two phases. Maxima and minima of glutamine synthetase activity developed synchronously with nitrogenase activity, whereas those of glutamate dehydrogenase and alanine aminotransferase were reverse. During a 192 h period of growth protein increased 3–4-fold and PHBA 25 fold. At maximum accumulation of the polymer the PHBA-nitrogen ratio was 6:1 or 8:1. Azospirillum brasilense was also able to fix nitrogen on agar surfaces exposed to air, but nitrogen fixation was monophasic under these conditions during a 14 d period. Specific nitrogenase activity was dependent on the type and concentration of the source of fixed nitrogen (leucine, ammonia) in solidified media. With 1 mM leucine maximum specific nitrogenase activity was 110 nmol C2H4·mg protein-1·h-1.Non-Standard Abbreviations PHBA
poly-3-hydroxybutanoic acid
- TAPS
tris(hydroxymethyl)methylaminopropane sulfonic acid
- TES
N-tris(hydroxymethyl)methyl-2-aminoethane sulfonic acid
- TRICINE
N-tris(hydroxymethyl)methylglycine
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
12.
T. Hartmund H. Gesser 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(3):219-229
With focus on metabolism not depending on contractility in myocardial tissue from rainbow trout, Oncorhynchus mykiss, the effects of high CO2 on lactate production, phosphocreatine, creatine, ATP, ADP, AMP and intracellular pH were examined under a blockage of cell respiration either alone or in combination with a glycolytic inhibition. Irrespective of metabolic interventions, a change in CO2 from 1 to either 11 or 5% of the gas mixture perfusing the muscle bath with 15 mmol·l-1 HCO
-
3
caused a drop of intracellular pH from 7.4 to either 6.5 or 7.0, respectively. An elevation of CO2 to 11% diminished the rate of anaerobic lactate formation and slightly lowered anaerobic energy degradation. The further addition of 1 mmol·l-1 iodoacetate to inhibit glycolysis strongly enhanced the tendency of acidosis to lower energy degradation. Moreover, iodoacetate induced a parallel decrease in ATP and total concentration of phosphorylated adenylates and an increase in resting tension. These effects were all substantially dampened by acidosis and could not immediately be related to tissue content of energy-rich phosphates. Tentatively, the depression of resting tension was the prime effect and a cause of the other effects acidosis. However, these were not affected by an inhibition of resting tension development with 2,3-butadione monoxime. The results suggest that glycolysis protects the anaerobic myocardium also by means not immediately related to tissue energy state. Acidosis exerts a similar protection, which is marginal as long as glycolysis is fully active, but substantial with an inhibited glycolysis.Abbreviations
Cr
t
total tissue concentration of creatine
- G
PCr
energy liberated per mol PCr hydrolyzed
-
IAA
iodoacetate
-
PCr
phosphocreatine
-
PE
total tissue concentration of energy-rich phosphate bonds
-
pH
i
intracellular pH
-
P
i
inorganic phosphate
-
TAN
total tissue concentration of phosphorylated adenylates
- 2,3-BDM
2,3-butadione monoxime
-
SE
standard error of the mean 相似文献
13.
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
14.
G. P. Gusev N. I. Agalakova A. V. Lapin 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(3):230-237
Pathways of K+ movement across the erythrocyte membrane of frog Rana temporaria were studied using 86Rb as a tracer. The K+ influx was significantly blocked by 0.1 mmol·l-1 ouabain (by 30%) and 1 mmol·l-1 furosemide (by 56%) in the red cells incubated in saline at physiological K+ concentration (2.7 mmol·l-1). Ouabain and furosemide had an additive effect on K+ transport in frog red cells. The ouabain-sensitive and furosemide-sensitive components of K+ influx saturated as f(K+)e with apparent K
m values for external K
e
+
concentration of 0.96±0.11 and 4.6±0.5 mmol·l-1 and V
max of 0.89±0.04 and 2.8±0.4 mmol·l cells-1·h-1, respectively. The residual ouabain-furosemide-resistant component was also a saturable function of K
e
+
medium concentration. Total K+ influx was significantly reduced when frog erythrocytes were incubated in NO
-
3
medium. Furosemide did not affect K+ transport in frog red cells in NO
3
-
media. At the same K
e
+
concentration the ouabain-furosemide-insensitive K+ influx in Cl- medium was significantly greater than that in NO
-
3
medium. We found no inhibitory effect of 1 mmol·l-1 furosemide on Na+ influx in frog red cells in Cl- medium. K+ loss from the frog erythrocytes in a K+-free medium was significantly reduced (mean 58%) after replacement of Cl- with NO
-
3
. Furosemide (0.5 mmol·l-1) did not produce any significant reduction in the K+ loss in both media. The Cl--dependent component of K+ loss from frog red cells was 5.7±1.2 mmol·l-1·h-1. These results indicate that about two-thirds of the total K+ influx in frog erythrocytes is mediated by a K–Cl cotransport which is only partially blocked by furosemide.Abbreviations
DMSO
dimethyl sulphoxide
- K
e
+
external concentration of K+
-
K
m
apparent Michaelis constant for external
- K+
K
e
+
at V
max/2
-
RBC
red blood cell(s)
-
V
max
maximal velocity of the unidirectional K+ influx
- TRIS
tris(hydroxymethyl)aminomethane 相似文献
15.
W. S. Marshall S. E. Bryson J. S. Burghardt P. M. Verbost 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(4):268-277
We examined transepithelial transport of Ca2+ across the isolated opercular epithelium of the euryhaline killifish adapted to fresh water. The opercular epithelium, mounted in vitro with saline on the serosal side and fresh water (0.1 mmol·l–1 Ca2+) bathing the mucosal side, actively transported Ca2+ in the uptake direction; net flux averaged 20–30 nmol·cm–2·h–1. The rate of Ca2+ uptake varied linearly with the density of mitochondria-rich cells in the preparations. Ca2+ uptake was saturable, apparent K
1/2 of 0.348 mmol·l–1, indicative of a multistep transcellular pathway. Ca2+ uptake was inhibited partially by apically added 0.1 mmol·l–1 La3+ and 1.0 mmol·l–1 Mg2+. Addition of dibutyryl-cyclic adenosine monophosphate (0.5 mmol·l–1)+0.1 mmol·l–1 3-isobutyl-l-methylxanthine inhibited Ca2+ uptake by 54%, but epinephrine, clonidine and isoproterenol were without effect. Agents that increase intracellular Ca2+, thapsigargin (1.0 mol·l–1, serosal side), ionomycin (1.0 mol·l–1, serosal side) and the calmodulin blocker trifluoperazine (50 mol·l–1, mucosal side) all partially inhibited Ca2+ uptake. In contrast, apically added ionomycin increased mucosal to serosal unidirectional Ca2+ flux, indicating Ca2+ entry across the apical membrane is rate limiting in the transport. Verapamil (10–100 mol·l–1, mucosal side), a Ca2+ channel blocker, had no effect. Results are consistent with a model of Ca2+ uptake by mitochondria rich cells that involves passive Ca2+ entry across the apical membrane via verapamil-insensitive Ca2+ channels, intracellular complexing of Ca2+ by calmodulin and basolateral exit via an active transport process. Increases in intracellular Ca2+ invoke a downregulation of transcellular Ca2+ transport, implicating Ca2+ as a homeostatic mediator of its own transport.Abbreviations
DASPEI
2-(4-dimethylaminostyryl)-N-ethylpyridinium iodide
-
db-cAMP
dibutyryl-cyclic adenosine monophosphate
-
FW
fresh water
-
G
t
transepithelial conductance
-
I
sc
short-circuit current
-
IBMX
3-isobutyl-1-methylxanthine
-
SW
sea water
-
TFP
trifluoperazine
-
V
t
transepithelial potential 相似文献
16.
S. Marhold A. Nagel 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,164(8):636-645
Body temperature, oxygen consumption, respiratory and cardiac activity and body mass loss were measured in six females and four males of the subterranean Zambian mole rat Cryptomys sp. (karyotype 2 n=68), at ambient temperatures between 10 and 35°C. Mean body temperature ranged between 36.1 and 33.2°C at ambient temperatures of 32.5–10°C and was lower in females (32.7°C) than in males (33.9°C) at ambient temperatures of 10°C but dit not differ at thermoneutrality (32.5°C). Except for body temperature, mean values of all other parameters were lowest at thermoneutrality. Mean basal oxygen consumption of 0.76 ml O2·g-1· h-1 was significantly lower than expected according to allometric equations and was different in the two sexes (females: 0.82 ml O2·g-1·h-1, males: 0.68 ml O2·g1·h-1) but was not correlated with body mass within the sexes. Basal respiratory rate of 74·min-1 (females: 66·min1, males: 87·min-1) and basal heart rate of 200·min-1 (females: 190·min-1, males: 216·min-1) were almost 30% lower than predicted, and the calculated thermal conductance of 0.144 ml O2·g-1·h1·°C-1 (females; 0.153 ml O2·g-1·h-1·°C-1, males: 0.131 ml O2·g-1·h-1·°C-1) was significantly higher than expected. The body mass loss in resting mole rats of 8.6–14.1%·day-1 was high and in percentages higher in females than in males. Oxygen consumption and body mass loss as well as respiratory and cardiac activity increased at higher and lower than thermoneutral temperatures. The regulatory increase in O2 demand below thermoneutrality was mainly saturated by increasing tidal volume but at ambient temperatures <15°C, the additional oxygen consumption was regulated by increasing frequency with slightly decreasing tidal volume. Likewise, the additional blood transport capacity was mainly effected by an increasing stroke volume while there was only a slight increase of heart frequency. In an additional field study, temperatures and humidity in different burrow systems have been determined and compared to environmental conditions above ground. Constant temperatures in the nest area 70 cm below ground between 26 and 28°C facilitate low resting metabolic rates, and high relative humidity minimizes evaporative water loss but both cause thermoregulatory problems such as overheating while digging. In 13–16 cm deep foraging tunnels, temperature fluctuations were higher following the above ground fluctuations with a time lag. Dominant breeding females had remarkably low body temperatures of 31.5–32.3°C at ambient temperatures of 20°C and appeared to be torpid. This reversible hypothermy and particular social structure involving division of labour are discussed as a strategy reducing energy expenditure in these eusocial subterranean animals with high foraging costs.Abbreviations BMR
basal metabolic rate
- br
breath
-
C
thermal conductance
- HR
neart rate
- LD
light/dark
-
M
b
body mass
- MR
metabolic rate
- OP
oxygen pulse
- PCO2
partial pressure of carbon dioxide
- PO2
partial pressure of oxygen
- RMR
resting metabolic rate
- RR
respiratory rate
-
T
a
ambient temperature
-
T
b
body temperature
- TNZ
thermal neural zone
-
O2
oxygen consumption 相似文献
17.
Stephen Morris Peter Greenaway Brian R. McMahon 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,157(6):873-882
Summary The oxygen and carbon dioxide transporting properties of the haemolymph from an amphibious Australian crab,Holthuisana transversa were investigated. Within the temperature range 15 to 35°C increasing temperature markedly decreased oxygen affinity (H=–54 kJ·mol–1). The Bohr effect was small at all temperatures with a mean value of –0.13. Over the temperature range 15–35°C there was a significant increase in the cooperativity of oxygen binding. Changing the concentration of Ca,l-lactate or haemocyanin in the haemolymph could elicit no significant change in either O2 affinity or cooperativity of O2 binding. There was no evidence in support of a specific effect of CO2 on oxygen affinity of either non-dialysed or dialysed haemolymph.The amount of CO2 that could be carried byH. transversa haemolymph was significantly reduced by increased temperature (approx. 14 to 12.5 mmol·l–1 CO2). Comparisons of oxygenated and deoxygenated haemolymph at a fixed pH were unable to demonstrate the presence of a significant Haldane effect. Combining data from oxygenated and deoxygenated haemolymph the buffer value was calculated to be in the range –6.2 to –8.5 mmol·l–1 HCO
3
–
·pH unit–1.The insensitivity ofH. transversa haemocyanin function to all modulating influences except temperature is discussed with respect to the ecology of this crab. 相似文献
18.
J. T. Pearson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(6):415-424
Oxygen consumption rates were measured in chicks (0–7 days of age), and in non-brooding and brooding adults. Brooded chicks maintained a constant oxygen consumption rate at a chamber ambient temperature of 10–35°C (0–5 days of age: 2.95ml O2·g-1·h-1 and 6–17 days of age: 5.80 ml O2·g-1·h-1) while unbrooded chicks increased oxygen consumption rate at ambient temperature below 30°C to double the brooded oxygen consumption rate at 25 and 15°C for chicks < 5 days of age and>5 days of age, respectively. The massspecific oxygen consumption rate of breeding male and females (non-brooding) were significantly elevated within the thermoneutral zone thermal neutral zone (28–35°C) in comparison to non-breeding adults. Below the thermal neutral zone, oxygen consumption rate was not significantly different. The elevation in oxygen consumption rate of breeding quail was not correlated with the presence of broodpatches, which developed only in females, but is a seasonal adjustment in metabolism. Male and females that actively brooded one to five chicks had significantly higher oxygen consumption rate than non-brooding quail at ambient temperature below 30°C. Brooding oxygen consumption rate was constant during day and night, indicating a temporary suppression of the circadian rhythm of metabolism. Brooding oxygen consumption rate increased significantly with brood number, but neither adult body mass nor adult sex were significant factors in the relationship between brooding oxygen consumption rate and ambient temperature. The proportion of daylight hours that chicks were brooded by parents was negatively correlated with ambient temperature. After chicks were 5 days old brooding time was reduced but brooding oxygen consumption rate was unchanged. Heat from the brooding parent appeared to originate mainly from the apteria under the wings and legs rather than the broodpatch. The parental heat contribution to chick temperature regulation below the chicks' thermal neutral zone is achieved by increasing parental thermal conductance by a feedback control similar to that suggested for the control of egg temperature via the brood-patch. It is concluded that the brooding period is an energetic burden to parent quail, and the magnitude of the cost increases directly with brood number and inversely with ambient temperature during this period. The oxygen consumption rate of brooding parents was 5.80–6.90 ml O2·g-1·h-1 (ambient temperature 10–15°C) at night and up to 5.10 ml O2·g-1·h-1 (ambient temperature 18°C) during the day, which are 100 and 40% higher than non-brooding birds, respectively.Abbreviations bm
body mass
- SMR
standard metabolic rate
-
T
a
ambient temperature
-
T
b
body temperature
- I/O2
oxygen consumption rate
-
C
wet
wet thermal conductance
- TNZ
thermal neutral zone
- ANOVA
analysis of variance
- ANCOVA
analysis of covariance 相似文献
19.
Daniel T. Clemens Martin E. Feder 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(7):646-650
Summary Rates of O2 uptake across isolated perfused skin of bullfrogs (Rana catesbeiana) were measured in relation to blood flow at three levels of ambient O2 tension: normoxia (O2 tension=152 torr), hypoxia (12% O2, 87 torr) and hyperoxia (42% O2, 306 torr). At bulk perfusion rates ranging from 3.4 to 10.1 l·cm-2·min-1, O2 uptake was positively correlated with hemoglobin delivery rate in both normoxia and hyperoxia, but was independent of delivery rate in hypoxia. Mean O2 uptake in normoxia was 3.8 nmol O2·cm-2·min-1 at a delivery rate of 9.8 nmol·cm-2·min-1 and 6.5 nmol O2·cm-2·min-1 at a delivery rate of 28.3 nmol·cm-2·min-1. At any given bulk perfusion rate, oxygen uptake averaged about 49% lower in hypoxia than in normoxia, decreasing in proportion to the reduction of O2 tension difference between medium and blood. In hyperoxia, O2 uptake did not increase proportionally with the difference in O2 tension between blood and medium, averaging only 50% higher at a 2.4-fold greater O2 tension difference. Cutaneous diffusing capacity for O2 averaged 0.041 nmol O2·cm-2·torr-1·min-1 during the first hour of perfusion in normoxia, and was not affected by reduction of ambient O2 tension. The results indicate that cutaneous O2 uptake in hypoxia is highly diffusion limited, and consequently, increases in cutaneous perfusion can not effectively compensate for reduction of ambient O2 tension. In hyperoxia, O2 uptake may be substantially perfusion limited because of reduced blood O2 capacitance at high O2 saturations.Abbreviations
O2 capacitance
-
C
Hb
hemoglobin concentration
- D
diffusing capacity
- PO2
medium-blood PO2 difference
- Hb
flow, hemoglobin delivery rate
- Hepes
N-[2-Hydroxyethyl]piperacine-N-[2 ethanesulfonic acid]
-
L
diff
extent of diffusion limitation
-
MO2
oxygen uptake rate
-
PO2
oxygen tension
-
S
O2 saturation 相似文献
20.
The relationship between phosphate status and photosynthesis in leaves 总被引:19,自引:0,他引:19
Spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) were grown in hydroponic culture with varying levels of orthophosphate (Pi). When leaves were fed with 20 mmol·l–1 Pi at low CO2 concentrations, a temporary increase of CO2 uptake was observed in Pi-deficient leaves but not in those from plants grown at 1 mmol·l–1 Pi. At high concentrations of CO2 (at 21% or 2% O2) the Pi-induced stimulation of CO2 uptake was pronounced in the Pi-deficient leaves. The contents of phosphorylated metabolites in the leaves decreased as a result of Pi deficiency but were restored by Pi feeding. These results demonstrate that there is an appreciable capacity for rapid Pi uptake by leaf mesophyll cells and show that the effects of long-term phosphate deficiency on photosynthesis may be reversed (at least temporarily) within minutes by feeding with Pi.Abbreviation Pi
orthophosphate 相似文献