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1.
Frank B. Jensen Hans Malte 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(5):483-490
Summary Intermoult crayfish (Astacus astacus) were exposed to acid (pH 4), soft water ([Ca++]=100 mol·l–1) in the absence and presence of aluminium (25 mol·l–1) for variable time periods (up to 21 days) in order to assess the consequences for acid-base and electrolyte balance and haemolymph gas transport. Haemolymph osmolality and concentration of major ions decreased drastically and to a similar extent in acid and acid-aluminium water. Muscle tissue ion concentrations were, however, regulated at an almost constant level. A severe metabolic acidosis was gradually developed, attaining a haemolymph metabolic acid load of 6–7 mequiv·l–1 after 12–21 days. The acidosis was partially compensated by ventilatory means, with the postbranchial haemolymph PCO2 decreasing earlier in acidaluminium-exposed than in acid-exposed specimens. Hyperventilation seemed to be a direct acid-base regulatory response, since the rise in postbranchial PCO2 had only minimal influence on haemolymph O2 transport. The Bohr effect of Astacus astacus haemocyanin was low (log P50/GdpH=-0.24), and the mean P50 only increased from 15 to 19 mmHg after 21 days of acid exposure. The decrease in O2 affinity with decreasing pH was accompanied by a decrease in the cooperativity of O2 binding. The haemolymph haemocyanin concentration was not affected by acid and acid-aluminium exposure, but decreased after 21 days due to starvation. Muscle tissue aluminium concentrations were unaffected, whereas gill tissue concentrations increased in acid-aluminium exposed crayfish, most likely due to accumulation of aluminium on the gill surface. Mortality was low, and an internal hypoxia and lactacidosis was not developed in either of the experimental groups. This suggests that the gas transfer qualities of the chitincovered gills of crayfish are much less sensitive to acid and acid-aluminium stress than the gills of teleost fish.Abbreviations
Hc
haemocyanin
- SO2
saturation of Hc with O2
-
P
50
oxygen tension of haemolymph at 50% SO2
-
n
50
Hills coelficient around 50% SO2 相似文献
2.
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
3.
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
4.
A. T. Marshall 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1989,159(5):609-616
Summary The lachrymal salt glands of hatchlings of the green sea turtle (Chelonia mydas) secrete a hyperosmotic (up to 2000 mosmol·kg–1) NaCl solution. X-ray microanalysis of frozen-hydrated glands showed that during secretion intracellular Na+ concentration in the principal cells increased from 13 to 34 mmol·l–1 of cell water, whilst Cl– and K+ concentrations remained unchanged at 81 mmol·l–1 and 160–174 mmol·l–1, respectively. The high Cl– concentration and the change in Na+ concentration are consistent with the prevailing paradigm for secretion by the structurally and functionally similar elasmobranch rectal gland. Concentrations of Na+, Cl– and K+ in the lumina of secretory tubules of secreting (Na+ 122, Cl– 167, K+ 38 mmol·l–1) and non-secreting (Na+ 114, Cl–1 174, K+ 44 mmol·l–1) glands were similar and the fluid was calculated to be approximately isosmotic with blood. In the central canals Na+ and Cl– concentrations were similar but K+ concentration was lower (11–15 mmol·l–1). It is concluded that either a high transepithelial NaCl gradient in secretory tubules and central canals is very rapidly dissipated during the short time between gland excision and freezing, or that ductal modification of an initial isosmotic secretion occurs. 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.
A. M. P. M. Bovens M. A. van Baak J. G. P. M. Vrencken J. A. G. Wijnen F. T. J. Verstappen 《European journal of applied physiology and occupational physiology》1993,66(3):281-284
The purpose of this study was to investigate criteria for maximal effort in middle-aged men and women undertaking a maximal exercise test until they were exhausted if no measurements of oxygen uptake are made. A large group of 2164 men and 975 women, all active in sports and aged between 40 and 65 years, volunteered for a medical examination including a progressive exercise test to exhaustion on a cycle ergometer. In the 3rd min of recovery a venous blood sample was taken to determine the plasma lactate concentration ([la–]p, 3min). Lactate concentration and maximal heart rate (f
c, max) were lower in the women than in the men (P<0.001). Multiple regression analyses were performed to assess the contribution of sex to [la–]p, 3 min, independent of age and f
c max, It was found that [la–]p,3 min was about 2.5 mmol·l–1 lower in women than in men of the same age and f
c, max. In our population 88% of the men and 85% of the women met a combination of the following f
c, max and [la–]p, 3min criteria: f
c, max equal to or greater than 220 minus age beats·min–1 and/or [la–]p, 3min equal to or greater than 8 mmol·l–1 in the men and f
c, max equal to or greater than 220 minus age beats·min–1 and/or [la–]p, 3min equal to or greater than 5.5 mmol·1–1 in the women. 相似文献
7.
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
8.
F. Trischitta M. G. Denaro C. Faggio F. Fucile T. Schettino 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1994,164(4):286-291
The sensitivity to external pH of Cl- absorption was studied in isolated stripped intestinal mucosa of the eel, Anguilla anguilla, mounted in Ussing chambers. Short-circuit current, transepithelial potential difference and conductance were measured in bathing solutions containing various combinations of HCO3
--concentration (0–25 mmol·l-1), partial pressure of CO2 (0–76 mm Hg) and pH (6.9–7.9). A linear relationship was found between pH and short-circuit current in the range of pH studied both in HCO3
-/CO2 Ringer and in Hepes Ringer. The pH effect was almost completely reversible. It was not affected by the presence of mucosal Ba2+ (10-3 mol·l-1) but it was inhibited by the presence of luminal (10-5 mol·l-1) or serosal (10-4 mol·l-1) bumetanide. The results obtained suggest that the Cl- absorption in the European eel intestine is pH sensitive. The data do not indicate whether the pH affects directly the Na+–K+–Cl- cotransport and/or the basolateral Cl- conductance or other mechanisms indirectly linked to Cl- absorption.Abbreviations g
t
transepithelial conductance
- Hepes
N-2-Hydroxyethylpiperazine-N'-2-ethanesulfonic acid
-
I
sc
short circuit current
-
R
t
transepithelial resistence
-
V
t
transepithelial potential difference 相似文献
9.
M. M. Babiker 《Hydrobiologia》1984,110(1):351-363
The respiratory behaviour and partitioning of O2 uptake between air and water were investigated in Polypterus genegalus using continuous-flow and two-phase respirometers and lung gas replacement techniques P. senegalus rarely resorts to aerial respiration under normal conditions. Partitioning of O2 consumption depends on the activity and age of fish and the availability of aquatic oxygen. Immature fish (12–22 g) cannot utilize aerial O2 but older fish exhibit age-dependent reliance on aerial respiration in hypoxic and hypercarbic waters. Pulmonary respiration accounts for 50% of the total requirement at aquatic O2 concentrations of about 3.5 mg · l–1 (or CO2 of about 5%) and fish rely exclusively on aerial respiration at O2 concentrations of less than 2.5 mg · l–1. Branchial respiration is initially stimulated by hypercarbia (CO2: 0.5–0.8%) but increased hypercarbia (CO2 – 1%) greatly depresses (by over 90%) brancial respiration and initiates (CO2: 0.5%) and sustains pulmonary respiration. 相似文献
10.
S. N. Mukhopadhyay A. Ornelas Vale E. Camargo Rubio G. Cassarubias Arcos 《Applied microbiology and biotechnology》1978,6(1):55-66
Summary Submerged batch cultivation under controlled environmental conditions of pH 3.8, temperature 30°C, and KLa200 h–1 (above 180 mMO2
l
–1 h–1 oxygen supply rate) produced a maximum (12.0 g·l
–1) SCP (Candida utilis) yield on the deseeded nopal fruit juice medium containing C/N ratio of 7.0 (initial sugar concentration 25 g·l
–1) with a yield coefficient of 0.52 g cells/g sugar. In continuous cultivation, 19.9 g·l
–1 cell mass could be obtained at a dilution rate (D) of 0.36 h–1 under identical environmental conditions, showing a productivity of 7.2 g·l
–1·h–1. This corresponded to a gain of 9.0 in productivity in continuous culture over batch culture. Starting with steady state values of state variables, cell mass (CX–19.9 g·l
–1), limiting nutrient concentration (Cln–2.5 g·l
–1) and sugar concentration (CS–1.5 g·l
–1) at control variable conditions of pH 3.8, 30°C, and KLa 200 h–1 keeping D=0.36 h–1 as reference, transient response studies by step changes of these control variables also showed that this pH, temperature and KLa conditions are most suitable for SCP cultivation on nopal fruit juice. Kinetic equations obtained from experimental data were analysed and kinetic parameters determined graphically. Results of SCP production from nopal fruit juice are described.Nomenclature Cln
concentration of ammonium sulfate (g·l
–1)
- CS
concentration of total sugar (g·l
–1)
- CX
cell concentration (g·l
–1)
- D
dilution rate (h–1)
- Kln
Monod's constant (g·l
–1)
- m
maintenance coefficient (g ammonium sulfate cell–1 h–1)
- m(S)
maintenance coefficient (g sugar g cell–1 h–1)
- t
time, h
- Y
yield coefficient (g cells/g ammonium sulfate)
- Ym
maximum of Y
- YS
yield coefficient based on sugar consumed (g cells · g sugar–1)
- YS(m)
maximum value of YS
-
µm
maximum specific growth rate constant (h–1) 相似文献
11.
P. Szigligeti C. Pankucsi T. Bányász A. Varró P. P. Nánási 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(2):150-155
The effect of action potential duration and elevated cytosolic sodium concentration on the forcefrequency relationship in isolated rabbit, guinea pig and rat papillary muscle preparations was studied. Shortening of action potential duration in guinea pig and rabbit from 150–200 ms to values characteristic of rat (20–40 ms), using the K(ATP) channel activator levkromakalim (15 mol·l–1), markedly reduced the force of contraction and converted the positive force-frequency relationship into negative one at longer pacing cycle lengths. This conversion was greatly enhanced in the presence of acetylstrophanthidin (0.2–1 mol·l–1), an inhibitor of the Na-K pump. Acetylstrophanthidin (1 mol·l–1) alone, however, had no effect on the forcefrequency relationship. Prolongation of action potential duration in rat with inhibitors of cardiac K channels (4-aminopyridine [10 mmol·l–1] plus tetraethylammonium [2 mmol·l–1) increased the force of contraction and abolished the negative force-frequency relationship observed in rat at longer pacing-cycle lengths. It is concluded that both action potential duration and cytosolic sodium concentration are major determinants of the force-frequency relationship in mammalian myocardium.Abbreviations
AC
acetylstrophanthidin
-
APD
action potential duration
-
APD
50 and APD
90
action potential duration measured at 50% and 90% level of repolarization, respectively
-
SR
sarcoplasmic reticulum 相似文献
12.
R. J. Maughan J. H. Owen S. M. Shirreffs J. B. Leiper 《European journal of applied physiology and occupational physiology》1994,69(3):209-215
This study examined the effects on water balance of adding electrolytes to fluids ingested after exercise-induced dehydration. Eight healthy male volunteers were dehydrated by approximately 2% of body mass by intermittent cycle exercise. Over a 30-min period after exercise, subjects ingested one of the four test drinks of a volume equivalent to their body mass loss. Drink A was a 90 mmol·l–1 glucose solution; drink B contained 60 mmol·l–1 sodium chloride; drink C contained 25 mmol·l–1 potassium chloride; drink D contained 90 mmol·l–1 glucose, 60 mmol·l–1 sodium chloride and 25 mmol·l–1 potassium chloride. Treatment order was randomised. Blood and urine samples were obtained at intervals throughout the study; subjects remained fasted throughout. Plasma volume increased to the same extent after the rehydration period on all treatments. Serum electrolyte (Na+, K+ and Cl–) concentrations fell initially after rehydration before returning to their pre-exercise levels. Cumulative urine output was greater after ingestion of drink A than after ingestion of any of the other drinks. On the morning following the trial, subjects were in greater net negative fluid balance [mean (SEM);P<0.02] on trial A [745 (130) ml] than on trials B [405 (51) ml], C [467 (87) ml] or D [407 (34) ml]. There were no differences at any time between the three electrolyte-containing solutions in urine output or net fluid balance. One hour after the end of the rehydration period, urine osmolality had fallen, with a significant treatment effect (P=0.016); urine osmolality was lowest after ingestion of drink A. On the morning after the test, subjects were in greater net negative sodium balance (P<0.001) after trials A and C than after trials B and D. Negative potassium balance was greater (P<0.001) after trials A and B than after C and D. Chloride balance was positive after drink D and a smaller negative balance (P<0.001) was observed after drink B than after A and C. These results suggest that although the measured blood parameters were similar for all trials, better whole body water and electrolyte balance resulted from the ingestion of electrolyte-containing drinks. There appeared, however, to be no additive effect of including both sodium and potassium under the conditions of this experiment. 相似文献
13.
P. Pärt C. M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(1):37-45
Using primary cultures of gill pavement cells from freshwater rainbow trout, a method is described for achieving confluent monolayers of the cells on glass coverslips. A continuous record of intracellular pH was obtained by loading the cells with the pH-sensitive flourescent dye 2,7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and mounting the coverslips in the flowthrough cuvette of a spectrofluorimeter. Experiments were performed in HEPES-buffered media nominally free of HCO3. Resting intracellular pH (7.43 at extracellular pH=7.70) was insensitive to the removal of Cl– or the application of 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l–1), but fell by about 0.3 units when Na+ was removed or in the presence of amiloride (0.2 mmol·l–1). Exposure to elevated ammonia (ammonia prepulse; 30 mmol·l–1 as NH4Cl for 6–9 min) produced an increase in intracellular pH (to about 8.1) followed by a slow decay, and washout of the pulse caused intracellular pH to fall to about 6.5. Intracellular non-HCO
3
–
buffer capacity was about 13.4 slykes. Rapid recovery of intracellular pH from intracellular acidosis induced by ammonia prepulse was inhibited more than 80% in Na+-free conditions or in the presence of amiloride (0.2 mmol·l–1). Neither bafilomycin A1 (3 mol·l–1) nor Cl removal altered the intracellular pH recovery rate. The K
m for Na+ of the intracellular pH recovery mechanism was 8.3 mmol·l–1, and the rate constant at V
max was 0.008·s–1 (equivalent to 5.60 mmol H+·l–1 cell water·min–1), which was achieved at external Na+ levels from 25 to 140 mmol·l–1. We conclude that intracellular pH in cultured gill pavement cells in HEPES-buffered, HCO
3
–
-free media, both at rest and during acidosis, is regulated by a Na+/H+ antiport and not by anion-dependent mechanisms or a vacuolar H+-ATPase.Abbreviations
BCECF
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein
-
BCECF/AM
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein, acetoxymethylester
-
Cholin-Cl
choline chloride
-
DMSO
dimethyl sulfoxide
-
EDTA
ethylene diamine tetra-acetic acid
-
FBS
foetal bovine serum
-
H
+
-ATPase
Proton-dependent adenosine triphosphatase
-
HEPES
N-[2-hydroxyethyl]piperazine-N[2-ethanesulfonic acid]
-
pH
i
intracellular pH
-
pH
e
extracellular pH
-
PBS
phosphate-buffered saline
-
SITS
4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid 相似文献
14.
Brad A. Seibel Fabienne Chausson Francois H. Lallier Franck Zal James J. Childress 《Experimental Biology Online》1999,4(1):1-10
The functional properties of the haemocyanin ofVampyroteuthis infernalis (Cephalopoda: Vampyromorpha), measured at 5 °C, are reported and discussed in relation to hypoxia. The oxygen affinity of this haemocyanin (P50=0.47−0.55 kPa) is higher than any previously measured for a cephalopod. The high cooperativity (n50=2.20−2.23) and Bohr coefficient (−0.22) suggest a true transport function for this haemocyanin. This high-affinity haemocyanin, in conjunction with moderate gill diffusion capacity, provides a sufficient oxygen gradient from the environment to the blood to support the low routine oxygen consumption rate of V. infernalis 相似文献
15.
A. M. Beal 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):611-619
Summary The effects of carbonic anhydrase inhibitors on secretion by macropodine parotid and mandibular glands were investigated using anaesthetized red kangaroos. In the parotid gland, acetazolamide (500 mol·l-1) reduced a stable acetylcholine-evoked, half-maximal flow rate of 2.02±0.034 to 0.27±0.023 ml·min-1 (87% reduction). Concurrently, salivary bicarbonate concentration and secretion fell (129.4±1.46 to 80.9±1.63 mmol·l-1 and 264.8±7.96 to 22.3±2.30 mol·min-1, respectively), phosphate and chloride concentrations rose (14.0±0.79 to 27.6±0.85 mmol·l-1 and 5.6±0.25 to 27.5±1.32 mmol·l-1, respectively), sodium concentration and osmolality were unaltered, and potassium concentration fell (8.8±0.33 to 6.4±0.29 mmol·l-1). High-rate cholinergic stimulation during acetazolamide blockade was unable to increase salivary flow beyond 11±0.9% of that for equivalent unblocked control stimulation. However, superimposition of isoprenaline infusion on the acetylcholine stimulation caused a three-fold increase in the blocked flow rate. These treatments were accompanied by small increases in salivary phosphate and chloride concentrations but not bicarbonate concentration. Methazolamide infusion caused similar changes in parotid secretion. In the mandibular gland, acetazolamide infusion had no effect on salivary flow rate during either low- or high-level acetylcholine stimulation. Acetazolamide caused no alterrations in salivary electrolyte secretion at low flow rates, but curtailed the rise in bicarbonate concentration associated with high-level acetylcholine stimulation. Acetazolamide administration did not affect the increase in salivary flow rate associated with isoprenaline infusion, but did block the concomitant increase in bicarbonate concentration and secretion substantially. It was concluded that neither cholinergic nor adrenergic stimulation of mandibular fluid secretion depends on secretion of bicarbonate derived from catalysed hydration of CO2, but a substantial proportion of the increase in bicarbonate secretion during isoprenaline administration, which is probably ductal in origin, is so dependent. In contrast to other salivary glands, including the ovine parotid, fluid secretion by the kangaroo parotid gland during cholinergic stimulation is largely dependent (about 90%) on secretion of bicarbonate derived from hydration of CO2 catalysed by glandular carbonic anhydrase. Fluid secretion during adrenergic stimulation is not bicarbonate dependent.Abbreviations b.w.
body weight
- PAH
p-aminohippurate
-
PCO2
partial pressure carbon dioxide
-
PCO2
partial pressure of oxygen 相似文献
16.
M. L. Glass K. Johansen A. S. Abe 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1981,142(4):509-514
Summary Pulmonary CO-diffusing capacity (D
l
CO), lung volume, pulmonary perfusion and O2-uptake were measured by non-invasive techniques in the lizardsVaranus exanthematicus andTupinambis teguixin (mean body weight 2.2 kg for both species).The CO-diffusing capacity was at 25–27°C 0.059 mlstpd·kg–1·min–1·Torr–1 inVaranus, which is 47% greater than the value of 0.040 mlstpd·kg–1·min–1·Torr–1 inTupinambis. The lung volume ofVaranus was 36 ml·kg–1 and that ofTupinambis 20 ml·kg–1. At 35–37°C the diffusing capacity of lizard lungs are about 25% of those for mammals of comparable size.InVaranus pulmonary CO-diffusing capacity increased with temperature from 0.027 mlstpd·kg–1·min–1·Torr–1 at 17–19 °C to 0.075 mlstpd·kg–1·min–1·Torr–1 at 35–37 °C. This change closely matched a concomitant increase of O2-uptake. Pulmonary perfusion increased from 27 ml·kg–1·min–1 to 55 ml·kg–1·min–1 within this temperature range.The study emphasizes that pulmonary diffusing capacity cannot be fully evaluated without information on pulmonary perfusion and O2-uptake. In reptiles and other ectotherms diffusing capacity must be reported at specified body temperature. 相似文献
17.
J. M. Laplace J. P. Delgenes R. Moletta J. M. Navarro 《Applied microbiology and biotechnology》1991,36(2):158-162
Summary To investigate simultaneous alcoholic fermentation of glucose and xylose derived from lignocellulosic material by separate or co-culture processes, the effect of oxygen transfer rate (OTR) on the fermentation of 50 g/l xylose by Pichia stipitis NRRL Y 7124 and Candida shehatae ATCC 22984, and the fermentation of 50 g/l glucose by Saccharomyces cerevisiae CBS 1200 and Zymomonas mobilis ATCC 10988 was carried out in batch cultures. The kinetic parameters of the xylose-fermenting yeasts were greatly dependent on the OTR. The optimum OTR values were found to be 3.9 and 1.75 mmol·1–1·h–1 for C. shehatae and P. stipitis, respectively. By contrast the fermentative parameters of S. cerevisiae were poorly affected by the OTR range tested (0.0–3.5 mmol·l–1·h–1) Under these conditions the ethanol yields ranged from 0.41 g·g–1 to 0.45 g·g–1 and the specific ethanol productivity was around 0.70 g·g–1·h–1. Z. mobilis gave the highest fermentative performance under strictly anaerobic conditions (medium continually flushed with nitrogen): under these conditions, the ethanol yield was 0.43 g·g–1 and the average specific ethanol productivity was 2.3 g·g–1·h–1. Process considerations in relation to the effect of OTR on the fermentative performance of the tested strains are discussed.
Offprint requests to: J. P. Delgenes 相似文献
18.
Yuefei Liu Jürgen M. Steinacker Martin Stanch 《European journal of applied physiology and occupational physiology》1995,71(4):326-331
On reaching the respiratory compensation point (RCP) during rapidly increasing incremental exercise, the ratio of minute ventilation (VE) to CO2 output (VCO2) rises, which coincides with changes of arterial partial pressure of carbon dioxide (P
aCO2). Since P
aCO2 changes can be monitored by transcutaneous partial pressure of carbon dioxide (PCO2,tc) RCP may be estimated by PCO2,tc measurement. Few available studies, however, have dealt with comparisons between PCO2,tc threshold (T
AT) and lactic, ventilatory or gas exchange threshold (V
AT), and the results have been conflicting. This study was designed to examine whether this threshold represents RCP rather than V
AT. A group of 11 male athletes performed incremental excercise (25 W · min–1) on a cycle ergometer. The PCO2,tc at (44°C) was continuously measured. Gas exchange was computed breath-by-breath, and hyperaemized capillary blood for lactate concentration ([la–]b) and P
aCO2 measurements was sampled each 2 min. The T
AT was determined at the deflection point of PCO2,tc curve where PCO2,tc began to decrease continuously. The V
AT and RCP were evaluated with VCO2 compared with oxygen uptake (VO2) and VE compared with the VCO2 method, respectively. The PCO2,tc correlated with P
aCO2 and end-tidal PCO2. At T
AT, power output [P, 294 (SD 40) W], VO2 [4.18 (SD 0.57)l · min–1] and [la–] [4.40 (SD 0.64) mmol · l–1] were significantly higher than those at V
AT[P 242 (SD 26) W, VO2 3.56 (SD 0.53) l · min–1 and [la–]b 3.52 (SD 0.75), mmol · l–1 respectively], but close to those at RCP [P 289 (SD 37) W; VO2 3.97 (SD 0.43) l · min– and [la–]b 4.19 (SD 0.62) mmol · l–1, respectively]. Accordingly, linear correlation and regression analyses showed that P, VO2 and [la–]b at T
AT were closer to those at RCP than at V
AT. In conclusion, the T
AT reflected the RCP rather than V
AT during rapidly increasing incremental exercise. 相似文献
19.
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
20.
《Comparative biochemistry and physiology. C: Comparative pharmacology》1992,101(2):339-343
1. When added in vitro to crab haemolymph at concentrations of 50 or 100 mg.1−1, copper decreased both haemocyanin-O2 affinity and the cooperativity of O2 binding.2. In crabs contaminated by a lethal dose of waterborne copper (2mg.l−1), haemolymph total concentration of the metal never reached levels that could affect O2 binding properties directly.3. Exogenous copper added in vitro or entering the animal in contaminated water was found for the most part non filterable and thus probably bound to haemolymph proteins. 相似文献