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1.
Aporn Bualuang Kanteera Soontharapirakkul Aran Incharoensakdi 《Journal of applied phycology》2010,22(2):123-129
The activity of Na+/H+ exchanger to remove toxic Na+ is important for growth of organisms under high salinity. In this study, the halotolerant cyanobacterium Aphanothece halophytica was shown to possess Na+/H+ exchange activity since exogenously added Na+ could dissipate a pre-formed pH gradient, and decrease extracellular pH. Kinetic analysis yielded apparent K
m (Na+) and V
max of 20.7 ± 3.1 mM and 3,333 ± 370 nmol H+ min−1 mg−1, respectively. For cells grown under salt-stress condition, the apparent K
m (Na+) and V
max was 18.3 ± 3.5 mM and 3,703 ± 350 nmol H+ min−1 mg−1, respectively. Three cations with decreasing efficiency namely Li+, Ca2+, and K+ were also able to dissipate pH gradient. Only marginal exchange activity was observed for Mg2+. The exchange activity was strongly inhibited by Na+-gradient dissipators, monensin, and sodium ionophore as well as by CCCP, a protonophore. A. halophytica showed high Na+/H+ exchange activity at neutral and alkaline pH up to pH 10. Cells grown at pH 7.6 under high salinity exhibited higher Na+/H+ exchange activity than those grown under low salinity during 15 days of growth suggesting a role of Na+/H+ exchanger for salt tolerance in A. halophytica. Cells grown at alkaline pH of 9.0 also exhibited a progressive increase of Na+/H+ exchange activity during 15 days of growth. 相似文献
2.
Active excretion of ammonia across the gills of the shore crab Carcinus maenas and its relation to osmoregulatory ion uptake 总被引:1,自引:0,他引:1
D. Weihrauch W. Becker U. Postel S. Riestenpatt D. Siebers 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(5):364-376
The mechanism of transbranchial excretion of total ammonia of brackish-water acclimated shore crabs, Carcinus maenas was examined using isolated, perfused gills. Applying physiological gradients of NH4Cl (100–200 μmol · l−1) directed from the haemolymph space to the bath showed that the efflux of total ammonia consisted of two components. The
saturable component (excretion of NH4
+) greatly exceeded the linear component (diffusion of NH3). When an outwardly directed gradient (200 μmol · l−1) was applied, total ammonia in the perfusate was reduced by more than 50% during a single passage of saline through the gill.
Effluxes of ammonia along the gradient were sensitive to basolateral dinitrophenol, ouabain, and Cs+ and to apical amiloride. Acetazolamide (1 mmol · l−1 basolateral) or Cl−-free conditions had no substantial effects on ammonia flux, which was thus independent of both carbonic anhydrase mediated
pH regulation and osmoregulatory NaCl uptake. When an inwardly directed gradient (200 μmol · l−1) was employed, influx rates were about 10-fold smaller and unaffected by basolateral ouabain (5 mmol · l−1) or dinitrophenol (0.5 mmol · l−1). Under symmetrical conditions (100 μmol · l−1 NH4Cl on both sides) ammonia was actively excreted against the gradient of total ammonia, which increased strongly during the
experiment and against the gradient of the partial pressure of NH3. The active excretion rate was reduced to 7% of controls by basolateral dinitrophenol (0.5 mmol · l−1), to 44% by basolateral ouabain (5 mmol · l−1), to 46% by Na+-free conditions and to 42% by basolateral Cs+ (10 mmol · l−1), indicating basolateral membrane transport of NH4
+ via the Na+/K+-ATPase and K+-channels and a second active, apically located, Na+ independent transport mechanism of NH4
+. Anterior gills, which are less capable of active ion uptake than posterior gills, exhibited even increased rates of active
excretion of ammonia. We conclude that, under physiological conditions, branchial excretion of ammonia is a directed process
with a high degree of effectiveness. It even allows active extrusion against an inwardly directed gradient, if necessary.
Accepted: 11 March 1998 相似文献
3.
Localization of ion-regulatory epithelia in embryos and hatchlings of two cephalopods 总被引:1,自引:0,他引:1
Marian Y. Hu Elliott Sucré Mireille Charmantier-Daures Guy Charmantier Magnus Lucassen Nina Himmerkus Frank Melzner 《Cell and tissue research》2010,339(3):571-583
The tissue distribution and ontogeny of Na+/K+-ATPase has been examined as an indicator for ion-regulatory epithelia in whole animal sections of embryos and hatchlings
of two cephalopod species: the squid Loligo vulgaris and the cuttlefish Sepia officinalis. This is the first report of the immunohistochemical localization of cephalopod Na+/K+-ATPase with the polyclonal antibody α (H-300) raised against the human α1-subunit of Na+/K+-ATPase. Na+/K+-ATPase immunoreactivity was observed in several tissues (gills, pancreatic appendages, nerves), exclusively located in baso-lateral
membranes lining blood sinuses. Furthermore, large single cells in the gill of adult L. vulgaris specimens closely resembled Na+/K+-ATPase-rich cells described in fish. Immunohistochemical observations indicated that the amount and distribution of Na+/K+-ATPase in late cuttlefish embryos was similar to that found in juvenile and adult stages. The ion-regulatory epithelia (e.g.,
gills, excretory organs) of the squid embryos and paralarvae exhibited less differentiation than adults. Na+/K+-ATPase activities for whole animals were higher in hatchlings of S. officinalis (157.0 ± 32.4 μmol gFM−1 h−1) than in those of L. vulgaris (31.8 ± 3.3 μmol gFM−1 h−1). S. officinalis gills and pancreatic appendages achieved activities of 94.8 ± 18.5 and 421.8 ± 102.3 μmolATP gFM−1 h−1, respectively. High concentrations of Na+/K+-ATPase in late cephalopod embryos might be important in coping with the challenging abiotic conditions (low pH, high pCO2) that these organisms encounter inside their eggs. Our results also suggest a higher sensitivity of squid vs. cuttlefish
embryos to environmental acid-base disturbances. 相似文献
4.
Liu J Liu WD Zhao XL Shen WJ Cao H Cui ZL 《Applied microbiology and biotechnology》2011,89(4):1083-1092
A metagenomic library consisting of 3,024 bacterial artificial chromosome clones was prepared in Escherichia coli DH10B with high-molecular-weight DNA extracted from red soil in South China. A novel cellulase gene with an open reading
frame of 1,332 bp, cel5G, encoding an endo-β-1,4-glucanase was cloned using an activity-based screen. The deduced enzyme, Cel5G, belongs to the
glycosyl hydrolase family 5 and shares <39% identity with endoglucanases in the GenBank database. cel5G was expressed in E. coli BL21, and the recombinant enzyme Cel5G was purified to homogeneity for enzymatic analysis. Cel5G hydrolyzed a wide range
of β-1,4-, β-1,3/β-1,4-, or β-1,3/β-1,6-linked polysaccharides, amorphous cellulose, filter paper, and microcrystalline cellulose.
Its highest activity was in 50 mM citrate buffer, pH 4.8, at 50°C. Cel5G is stable over a wide range of pH values (from 2.0
to 10.6) and is thermally stable under 60°C. It is highly tolerant and active in high salt concentrations and is stable in
the presence of pepsin and pancreatin. The K
m and V
max values of Cel5G for carboxymethyl cellulose are 19.92 mg/ml and 1,941 μmol min−1 mg−1, respectively. These characteristics indicate that Cel5G has potential for industrial use. 相似文献
5.
Wheat leaf growth is known to be spatially affected by salinity. The altered spatial distribution of leaf growth under saline
conditions may be associated with spatial changes in tissue mineral elements. The objective of this study was to evaluate
the spatial distributions of mineral elements and their net deposition rates in the elongating and mature zones of leaf 4
of the main stem of spring wheat (Triticum aestivum L. cv. Lona) during its linear growth phase under saline soil conditions. Plants were grown in an illitic-chloritic silty
loam with 0 and 120 mM NaCl. Three days after emergence of leaf 4, sampling was begun at 3 and 13 h into the 16-h light period.
Spatial distributions of fresh weight (FW), dry weight (DW), and Na+, K+, Cl−, NO−
3, Ca2+, Mg2+, total P, and total N in the elongating and mature tissues were determined on a millimeter scale. The patterns of spatial
distribution of Na+, Cl−, K+, NO3
−, and Ca2+ in the growing leaves were affected by salinity, while those of Mg2+, total P, and total N were not. Sodium, K+, Cl−, Ca2+, Mg2+, and total N concentrations (mmol · kg−1 FW) were consistently higher at 120 mM NaCl than at 0 mM NaCl along the leaf axis from the leaf base, whereas NO3
− concentration was lower at 120 mM NaCl. Deposition rates of all nutrients were greatest in the elongation zone. The elongation
zone was the strongest sink for mineral elements in the leaf tissues. Local net deposition rates of Na+, Cl−, Ca2+, and Mg2+ (mmol · kg−1 FW · h−1) in the most actively elongating zone were enhanced by 120 mM NaCl, whereas for NO3
− this was depressed. The lower supply of NO−
3 to growing leaves may be responsible for the inhibition of growth under saline conditions. Higher tissue concentrations of
Na+ and Cl− may cause ion imbalance but probably did not result in ion toxicity in the growing leaves. Potassium, Ca2+, Mg2+, total P, and total N are less plausibly responsible for the reduction in leaf growth in this study. Higher tissue K+ and Ca2+ concentrations at 120 mM NaCl are probably due to the presence of high Ca2+ in the soil of this study.
Received: 13 March 1997 / Accepted: 9 June 1997 相似文献
6.
Ging Kuo Wang Joanna Calderon Shiow-Jiin Jaw Sho-Ya Wang 《The Journal of membrane biology》2009,229(1):1-9
Articaine is widely used as a local anesthetic (LA) in dentistry, but little is known regarding its blocking actions on Na+ channels. We therefore examined the state-dependent block of articaine first in rat skeletal muscle rNav1.4 Na+ channels expressed in Hek293t cells. Articaine exhibited a weak block of resting rNav1.4 Na+ channels at −140 mV with a 50% inhibitory concentration (IC50) of 378 ± 26 μM (n = 5). The affinity was higher for inactivated Na+ channels measured at −70 mV with an IC50 value of 40.6 ± 2.7 μM (n = 5). The open-channel block by articaine was measured using inactivation-deficient rNav1.4 Na+ channels with an IC50 value of 15.8 ± 1.5 μM (n = 5). Receptor mapping demonstrated that articaine interacted strongly with a D4S6 phenylalanine residue, which is known
to form a part of the LA receptor. Thus the block of rNav1.4 Na+ channels by articaine is via the conserved LA receptor in a highly state-dependent manner, with a ranking order of open (23.9×) > inactivated
(9.3×) > resting (1×) state. Finally, the open-channel block by articaine was likewise measured in inactivation-deficient
hNav1.7 and rNav1.8 Na+ channels, with IC50 values of 8.8 ± 0.1 and 22.0 ± 0.5 μM, respectively (n = 5), indicating that the high-affinity open-channel block by articaine is indeed preserved in neuronal Na+ channel isoforms. 相似文献
7.
F. Trischitta M. G. Denaro C. Faggio M. Mandolfino T. Schettino 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):1-8
The fundus of an eel stomach was mounted in an Ussing chamber and bathed with control Ringer on the serosal side and with
unbuffered solution on the mucosal side. The gastric mucosa exhibited a mucosa negative transepithelial voltage (V
t), a “short circuit” current (I
SC) and a small spontaneous acid secretion rate (J
H). All these parameters were abolished by cimetidine treatment. Bilateral ion substitution experiments in tissues lacking
spontaneous acid secretion suggested that a net Cl− transport from serosa to mucosa was responsible for the genesis of the I
SC in the absence of H+ secretion. Serosal application of histamine (10−4 mol · l−1) or carbachol (10−4 mol · l−1) stimulated both I
SC and J
H. The action of carbachol was independent of histamine. The control as well as the histamine-stimulated I
SC was sensitive to both serosal bumetanide (10−5 mol · l−1), inhibitor of the Na+-K+-2Cl− cotransport, and 4,4-diisothiocyano-stilbene-2,2-disulphonic acid (DIDS, 5 · 10−4 mol · l−1), inhibitor of the Cl−-HCO−
3 exchange, while the I
SC stimulated by carbachol was nullified by serosal DIDS. These data suggested that the non-acidic Cl− uptake across the serosal membrane was linked to the activity of both Na+-K+-2Cl− cotransport and Cl−-HCO−
3 antiporter; histamine stimulated both transporters while carbachol was limited to the anion exchanger. The finding that the
acid secretion was strictly dependent on serosal Cl− and was completely blocked by serosal DIDS suggested that the Cl− accompanying H+ secretion entered the cell through the serosal membrane by the Cl−-HCO−
3 exchange. In addition, the acid secretion stimulated by carbachol was also dependent on serosal Na+ and sensitive to the application of 5-N-N-dimethyl-amiloride in the serosal bath, suggesting that the increased activity of the Cl−-HCO−
3 during carbachol treatment was linked to the activation of serosal Na+-H+ exchange. The inhibitory effect of luminal omeprazole (10−4 mol · l−1) on acid secretion suggested the presence of the H+-K+ pump on the luminal membrane.
Accepted: 18 September 1997 相似文献
8.
Alkaliphilic and halophilic Bacillus sp. BG-CS10 was isolated from Zabuye Salt Lake, Tibet. The gene celB, encoding a halophilic cellulase was identified from the genomic library of BG-CS10. CelB belongs to the cellulase superfamily
and DUF291 superfamily, with an unknown function domain and less than 58% identity to other cellulases in GenBank. The purified
recombinant protein (molecular weight: 62 kDa) can hydrolyze soluble cellulose substrates containing beta-1,4-linkages, such
as carboxylmethyl cellulose and konjac glucomannan, but has no exoglucanase and β-glucosidase activities. Thus, CelB is a
cellulase with an endo mode of action and glucomannanase activity. Interestingly, the enzyme activity was increased approximately
tenfold with 2.5 M NaCl or 3 M KCl. Furthermore, the optimal temperatures were 55°C with 2.5 M NaCl and 35°C without NaCl,
respectively. This indicates that NaCl can improve enzyme thermostability. The K
m
and k
cat values of CelB for CMC with 2.5 M NaCl were 3.18 mg mL−1 and 26 s−1, while the K
m
and k
cat values of CelB without NaCl were 6.6 mg mL−1 and 2.1 s−1. Thus, this thermo-stable, salt and pH-tolerant cellulase is a promising candidate for industrial applications, and provides
a new model to study salt effects on the structure of protein. 相似文献
9.
D. G. Butler R. Zandevakili G. Y. Oudit 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(3):213-224
The vertebrate renin-angiotensin system controls cardiovascular, renal and osmoregulatory functions. Angiotensin II (ANG
II) is the most potent hormone of the RAS but in some vertebrate animals angiotensin III (Val4-ANG III) may be a hormone. We studied the effects of some angiotensins and mammalian ANG II receptor antagonists on nasal
salt gland function and arterial blood pressure in conscious white Pekin ducks. Nasal salt gland fluid secretion (NFS) was
induced by a 10 ml · kg−1 bw i.v. injection of a NaCl solution (1000 mosmol · kg−1 H2O) and maintained by a continuous i.v. infusion of the same solution at a rate of 0.97 ml · min−1. There was a positive linear correlation between nasal fluid [Na+] and osmolality, between [Na+] and [K+], and also between the rate of NFS and [Na+] and [K+]. [Asp1,Val5]-ANG II (1 nmol · kg−1 i.v.) inhibited NFS but did not change ionic concentrations. Val4-ANG III (1 or 5 nmol · kg−1) and ANG I (1-7) (20 nmol · kg−1) had no effect on NFS. [Sar1, Ile8]-ANG II (SARILE) acted as an ANG II receptor agonist and resulted in a prolonged and complete inhibition of NFS. The AT1 receptor antagonist, losartan (DuP 753) and the AT2 receptor antagonist, PD 123319 both failed to block the inhibitory effect of [Asp1, Val5]-ANG II on the nasal salt glands.
[Asp1,Val5]-ANG II (2 nmol · kg−1 i.v.) increased mean arterial blood pressure (MABP), whereas the same dose of [Asn1,Val5]-ANG II (teleost) had only 30% of the pressor potency of the avian ANG II. Neither 1 nor 5 nmol · kg−1 of Val4-ANG III i.v. nor 20 nmol · kg−1 of ANG I (1-7) had any measurable effect on MABP. SARILE blocked completely the pressor response to [Asp1,Val5]-ANG II but the AT1 antagonists losartan and CGP 48933 and the AT2 antagonist PD 123319 all failed to block the pressor response to [Asp1,Val5]-ANG II. These results have substantiated an important role of the nasal salt gland in potassium regulation and highlighted
a pharmacological dimorphism of saralasin, namely agonist and antagonist to angiotensin II-mediated inhibition of nasal salt
gland function and pressor response, respectively. Using specific nonpeptidergic angiotensin II receptor antagonists, we have
confirmed the distinct pharmacology of the avian angiotensin II receptors in a nongallinaceous species and the absence of
significant angiotensin I (1-7) and angiotensin II effects on the cardiovascular system and nasal salt gland.
Accepted: 6 November 1997 相似文献
10.
T. H. Dietz D. H. Neufeld H. Silverman S. H. Wright 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(2):87-95
The effect of ambient osmolality on the height of lateral ciliated cells from the gills of two freshwater bivalve species
(Dreissena polymorpha, Toxolasma texasensis) was directly observed microscopically. The addition of 1 mmol · l−1 KCl to an artificial pondwater (APW) superfusion medium resulted in an increase in cell height. When the superfusion solution
was made hyperosmotic (∼90 mmol · kg−1 H2O) by the addition of 45 mmol · l−1 NaCl to APW, the cell height decreased by about 20–30% and there was no evidence of a regulatory volume increase over 20–30 min.
In contrast, when 1 mmol · l−1 KCl was added to the hyperosmotic medium the cell height always partially (40–50%) recovered. When the gill tissue was returned
to APW following the hyperosmotic treatment the cells returned to the original cell height. Bivalve gills superfused with
the hyperosmotic NaCl and KCl solution in the presence of 1 mmol · l−1 ouabain experienced a similar 25% decrease in cell height. When the ouabain-treated tissues were returned to APW the cells
swelled, overshooting the original cell height. These results indicate these freshwater bivalves have a limited ability for
cellular volume regulation using inorganic ions, but depend on a suitable balance of Na+ and K+ in the environment to effect regulatory volume changes.
Accepted: 17 October 1997 相似文献
11.
Protective effects of prostaglandins in the isolated gastric mucosa of the eel, Anguilla anguilla 总被引:1,自引:0,他引:1
Faggio C Denaro MG Lionetto MG Trischitta F 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(5-6):357-363
The protective effect of endogenous prostaglandins on the fish gastric mucosa was evaluated by studying the effect of indomethacin
and aspirin, known cyclooxigenase inhibitors, on the mucosal ulceration in the isolated gastric sacs of Anguilla anguilla. Gastric sacs devoid of muscle layers were incubated in the presence of indomethacin (10−4 mol · l−1) or aspirin (10−4 mol · l−1) in different experimental conditions. Both the anti-inflammatory drugs produced ulcers, but the effects were more severe
in the presence of histamine and in the absence of HCO3
− in the incubation bath. The effects of prostaglandin E2 (PGE2) on acid secretion rate (JH) and on alkaline secretion rate (JOH) were evaluated (with the aid of the pH stat method) in isolated gastric mucosa mounted in Ussing chambers. We found that
PGE2 (10−8–10−5 mol · l−1) increased JH in a dose-dependent manner. In tissues pretreated with luminal omeprazole (10−4 mol · l−1), PGE2 stimulated gastric alkaline secretion. It was nullified by serosal removal of HCO3
− or Na+ and by serosal ouabain (10−4 mol · l−1). These results suggested that prostaglandins also exert their protective effects in fish gastric mucosa. This protection
seems partially due to a stimulation of exogenous HCO3
− transport from the serosal to the mucosal side. It is likely that this transport is an active transcellular mechanism coupled
to Na+ transport.
Accepted: 14 April 2000 相似文献
12.
Takashi Imanishi Kayoko Matsushima Akinori Kawaguchi Hajime Asano Yoshinori Funakami Tetsuyuki Wada Takashi Masuko Shigeru Yoshida Seiji Ichida 《Neurochemical research》2009,34(5):1011-1019
Characteristics for the up-regulated response in the concentration of intracellular calcium ion ([Ca2+]
i
) and in the sodium ion (Na+) current by serotonin (5-HT) were investigated in differentiated neuroblastoma × glioma hybrid NG108-15 (NG) cells. The results
for the changes in [Ca2+]
i
by 5-HT were as follows, (1) The 5-HT-induced Ca2+ response was inhibited by 3 × 10−9 M tropisetron (a 5-HT3 receptor blocker), but not by other types of 5-HT receptor blockers; (2) The 5-HT-induced Ca2+ response was mainly inhibited by calciseptine (a L-type Ca2+ blocker), but not by other types of Ca2+ channel blockers or 10−7 M TTX (a voltage-sensitive Na+ channel blocker); (3) When the extracellular Na+ was removed by exchange with choline chloride or N-methyl-d-glucamine, the 5-HT-induced Ca2+ response was extremely inhibited. The results for the 5-HT-induced Na+ current by the whole cell patch-clamp technique were as follows, (1) The 5-HT-induced Na+ current in differentiated cells was significantly larger than that in undifferentiated cells; (2) The ED50 value for 5-HT-induced Na+ current in undifferentiated and differentiated cells was almost the same, about 4 × 10−6 M each other; (3) The 5-HT-induced Na+ current was completely blocked by 3 × 10−9 M tropisetron, but not by other 5-HT receptor antagonists and 10−7 M TTX. These results suggested that 5-HT-induced Ca2+ response in differentiated NG cells was mainly due to L-type voltage-gated Ca2+ channels allowing extracellular Na+ to enter via 5-HT3 receptors, but not through voltage-gated Na+ channels. 相似文献
13.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
14.
Herbert R. L. Drouin 《European biophysics journal : EBJ》1999,28(7):600-604
A new ion-selective liquid membrane microelectrode, based on the neutral carrier 1,1′-bis(2,3-naphtho-18-crown-6), is described
that shows the dependence of EMF on the activity of divalent putrescine cations a
Put, with the linear slope s
Put = 26 ± 3 mV/decade (mean ± SD, N = 18), in the range 10−4–10−1 M at 25 ± 1 °C. Values of potentiometric putrescine cation selectivity coefficients of logK
Pot
Put
j
(mean ± SD, N) are obtained by the separate solution method for the ions K+ (1.0 ± 0.4, 10), Na+ (−1.2 ± 0.4, 8), Ca2+ (−2.3 ± 0.5, 10) and Mg2+ (−2.5 ± 0.5, 7). The microelectrode can be applied for the direct analysis of the activities of free divalent putrescine
cations in the range 5 × 10−4 to 10−1 M in an extracellular ionic environment. Established analytical methods, e.g. high performance liquid chromatography, determine
the total concentration of the derivatives of free and bound putrescine.
Received: 20 December 1998 / Revised version: 7 May 1999 / Accepted: 27 May 1999 相似文献
15.
Samia Oueslati Najoua Karray-Bouraoui Houneïda Attia Mokded Rabhi Riadh Ksouri Mokhtar Lachaal 《Acta Physiologiae Plantarum》2010,32(2):289-296
Mentha pulegium L. is a medicinal and aromatic plant belonging to the Labiatae family present in the humid to the arid bioclimatic regions
of Tunisia. We studied the effect of different salt concentrations on plant growth, mineral composition and antioxidant responses.
Physiological and biochemical parameters were assessed in the plant organs after 2 weeks of salt treatment with 25, 50, 75
and 100 mM NaCl. Results showed that, growth was reduced even by 25 mM, and salt effect was more pronounced in shoots (leaves
and stems) than in roots. This growth decrease was accompanied by a restriction in tissue hydration and K+ uptake, as well as an increase in Na+ levels in all organs. Considering the response of antioxidant enzymes to salt, leaves and roots reacted differently to saline
conditions. Leaf and root guaiacol peroxidase activity showed an increase by different concentration of NaCl, but superoxide
dismutase activity in the same organs showed a slight modification in NaCl-treated leaves and roots. Moreover, polyphenol
contents and antioxidant activity were analysed in M. pulegium leaves and roots under salt constraint. The analysis showed an increase of total polyphenol content (2.41–8.17 mg gallic
acid equivalent g−1 dry weight) in leaves. However, methanol extract of leaves at 100 mM NaCl displayed the highest DPPH· scavenging ability
with the lowest IC50 value (0.27 μg ml−1) in comparison with control which exhibited IC50 equal to 0.79 μg ml−1. 相似文献
16.
This study examined the thermoregulatory responses of men (group M) and women (group F) to uncompensable heat stress. In
total, 13 M [mean (SD) age 31.8 (4.7) years, mass 82.7 (12.5) kg, height␣1.79␣(0.06) m, surface area to mass ratio 2.46␣(0.18) m2 · kg−1 · 10−2, Dubois surface area 2.01 (0.16) m2, %body fatness 14.6 (3.9)%, V˙O2peak 49.0 (4.8) ml · kg−1 · min−1] and 17 F [23.2 (4.2) years, 62.4 (7.7) kg, 1.65 (0.07) m, 2.71 (0.14) m2 · kg−1 · 10−2, 1.68 (0.13) m2, 20.2 (4.8)%, 43.2 (6.6) ml · kg−1 · min−1, respectively] performed light intermittent exercise (repeated intervals of 15 min of walking at 4.0 km · h−1 followed by 15 min of seated rest) in the heat (40°C, 30% relative humidity) while wearing nuclear, biological, and chemical
protective clothing (0.29 m2 ·°C · W−1 or 1.88 clo, Woodcock vapour permeability coefficient 0.33 i
m). Group F consisted of eight non-users and nine users of oral contraceptives tested during the early follicular phase of
their menstrual cycle. Heart rates were higher for F throughout the session reaching 166.7 (15.9) beats · min−1 at 105 min (n = 13) compared with 145.1 (14.4) beats · min−1 for M. Sweat rates and evaporation rates from the clothing were lower and average skin temperature () was higher for F. The increase in rectal temperature (T
re) was significantly faster for the F, increasing 1.52 (0.29)°C after 105 min compared with an increase of 1.37 (0.29)°C for
M. Tolerance times were significantly longer for M [142.9 (24.5) min] than for F [119.3 (17.3) min]. Partitional calorimetric
estimates of heat storage (S) revealed that although the rate of S was similar between genders [42.1 (6.6) and 46.1 (9.7) W · m−2 for F and M, respectively], S expressed per unit of total mass was significantly lower for F [7.76 (1.44) kJ · kg−1] compared with M [9.45 (1.26) kJ · kg−1]. When subjects were matched for body fatness (n = 8 F and 8 M), tolerance times [124.5 (14.7) and 140.3 (27.4) min for F and M, respectively] and S [8.67 (1.44) and 9.39 (1.05) kJ · kg−1 for F and M, respectively] were not different between the genders. It was concluded that females are at a thermoregulatory
disadvantage compared with males when wearing protective clothing and exercising in a hot environment. This disadvantage can
be attributed to the lower specific heat of adipose versus non-adipose tissue and a higher percentage body fatness.
Accepted: 31 October 1997 相似文献
17.
Schröder B Vössing S Breves G 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(7):487-494
From various in vivo and in vitro studies it has been shown that the rumen represents a significant site of Ca2+ absorption in sheep and goats. It was the aim of the present study to further characterize the underlying mechanisms. Unidirectional
flux rates of Ca2+ across rumen wall epithelia of sheep were measured in vitro by applying the Ussing-chamber technique in the absence of electrochemical
gradients. Under these conditions, significant Ca2+ net flux rates (Jnet) clearly indicate the presence of active mechanisms for Ca2+ transport. Short chain fatty acids (SCFAs) caused highest stimulation of Ca2+ Jnet (6.3 ± 1.9 nmol · cm−2 · h−1) when used as a mixture of acetate, proprionate and butyrate in physiological proportions (36, 15, 9 mmol · l−1, respectively). The effect of 30 mmol · l−1 butyrate (3.2 ± 0.6 nmol · cm−2 · h−1) was higher than respective amounts of propionate and acetate (0.6 ± 0.8 nmol · cm−2 · h−1 and 0.9 ± 0.8 nmol · cm−2 · h−1, respectively). Eliminating SCFAs resulted in Ca2+ Jnet of 0.4 ± 1.1 nmol . cm−2 . h−1. Addition of Ca channel blocker verapamil (mucosal 1 mmol · l−1) had no significant effect on SCFA-stimulated Jnet of Ca2+, whereas application of Na+/H+ inhibitor amiloride (mucosal 1 mmol · l−1) further enhanced the Ca2+ Jnet by >65%. The Ca2+-pump inhibitor vanadate had no significant effect on Jnet of Ca2+. Dietary Ca depletion enhanced calcitriol plasma concentrations but had no effect on active Ca2+ absorption across the rumen wall of sheep. In addition, no effect on active Ca2+ absorption could be observed during early lactation. In conclusion, there is clear evidence for the rumen as a main site
for active Ca2+ absorption in sheep. Our results suggest the presence of a Ca2+/H+ exchange mechanism in the apical membrane of rumen epithelial cells which depends on SCFA absorption and which does not seem
to be under the control of calcitriol. Basolateral Ca2+ extrusion occurs independently from Ca2+-pump activity and may be accomplished via Na+/Ca2+ exchange.
Accepted: 29 June 1999 相似文献
18.
K+-conductive pathways were evaluated in isolated surface and crypt colonic cells, by measuring 86Rb efflux. In crypt cells, basal K+ efflux (rate constant: 0.24 ± 0.044 min−1, span: 24 ± 1.3%) was inhibited by 30 mM TEA and 5 mM Ba2+ in an additive way, suggesting the existence of two different conductive pathways. Basal efflux was insensitive to apamin,
iberiotoxin, charybdotoxin and clotrimazole. Ionomycin (5 μM) stimulated K+ efflux, increasing the rate constant to 0.65 ± 0.007 min−1 and the span to 83 ± 3.2%. Ionomycin-induced K+ efflux was inhibited by clotrimazole (IC50 of 25 ± 0.4 μM) and charybdotoxin (IC50 of 65 ± 5.0 nM) and was insensitive to TEA, Ba2+, apamin and iberiotoxin, suggesting that this conductive pathway is related to the Ca2+-activated intermediate-conductance K+ channels (IKca). Absence of extracellular Ca2+ did neither affect basal nor ionomycin-induced K+ efflux. However, intracellular Ca2+ depletion totally inhibited the ionomycin-induced K+ efflux, indicating that the activation of these K+ channels mainly depends on intracellular calcium liberation. K+ efflux was stimulated by intracellular Ca2+ with an EC50 of 1.1 ± 0.04 μM. In surface cells, K+ efflux (rate constant: 0.17 ± 0.027 min−1; span: 25 ± 3.4%) was insensitive to TEA and Ba2+. However, ionomycin induced K+ efflux with characteristics identical to that observed in crypt cells. In conclusion, both surface and crypt cells present
IKCa channels but only crypt cells have TEA- and Ba2+-sensitive conductive pathways, which would determine their participation in colonic K+ secretion. 相似文献
19.
Na+/H+ antiporters are ubiquitous membrane proteins and play a central role in cell homeostasis including pH regulation, osmoregulation,
and Na+/Li+ tolerance in bacteria. The microbial communities in extremely hypersaline soil are an important resource for isolating Na+/H+ antiporter genes. A metagenomic library containing 35,700 clones was constructed by using genomic DNA obtained from the hypersaline
soil samples of Keke Salt Lake in Northwest of China. Two Na+/H+ antiporters, K1-NhaD, and K2-NhaD belonging to NhaD family, were screened and cloned from this metagenome by complementing
the triple mutant Escherichia coli strain KNabc (nhaA
−
, nhaB
−
, chaA
−) in medium containing 0.2 M NaCl. K1-NhaD and K2-NhaD have 75.5% identity at the predicted amino acid sequence. K1-NhaD has
78% identity with Na+/H+ antiporter NhaD from Halomonas elongate at the predicted amino acid sequence. The predicted K1-NhaD is a 53.5 kDa protein (487 amino acids) with 13 transmembrane
helices. K2-NhaD has 73% identity with Alkalimonas amylolytica NhaD. The predicted K2-NhaD is a 55 kDa protein (495 amino acids) with 12 transmembrane helices. Both K1-NhaD and K2-NhaD
could make the triple mutant E. coli KNabc (nhaA
−
, nhaB
−
, chaA−) grow in the LBK medium containing 0.2–0.6 M Na+ or with 0.05–0.4 M Li+. Everted membrane vesicles prepared from E. coli KNabc cells carrying K1-NhaD or K2-NhaD exhibited Na+/H+ and Li+/H+ antiporter activities which were pH-dependent with the highest activity at pH 9.5. Little K+/H+ antiporter activity was also detected in vesicles form E. coli KNabc carrying K1-NhaD or K2-NhaD. 相似文献
20.
Juan Fuentes F. B. Eddy 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(6):438-443
Drinking in Atlantic salmon (Salmo salar) juveniles was investigated in fresh water and following transfer to sea water. There was a significant effect of fish size
on drinking, and smolts (20–30 g) imbibed about ten times less water than alevins of 0.2–0.3 g. Freshwater smolts drank at
a rate of 0.15 ± 0.03 ml · kg−1 · h−1 and administration of doses of 10 or 20 mg · kg−1 of papaverine (stimulator of the renin- angiotensin system RAS) or [Asn1, Val5]-Angiotensin II (0.4 μmol · kg−1) resulted in significant increases in drinking, while administration of the angiotensin converting enzyme inhibitor, enalapril
(50 mg · kg−1) had no effect on drinking. Transfer of Atlantic salmon smolts to 1/3, 2/3 and full strength sea water resulted in significant
increases in drinking to 1.06 ± 0.12, 1.24 ± 0.0.16 and 3.89 ± 0.28 ml · kg−1 · h−1, respectively. In sea water, stimulation of the endogenous RAS by administration of papaverine (20 mg · kg−1) resulted in a 20% increase in drinking, while administration of enalapril to doses of 50 and 200 mg · kg−1 lowered drinking to 1.99 ± 0.48 and 0.32 ± 0.06 ml · kg−1 · h−1, respectively. All treatments were without effect on blood plasma levels of Na+ and Cl− in fresh water, while in sea water smolts both stimulation and inhibition of drinking resulted in hemoconcentration of Na+ and Cl−. The role of the renin angiotensin system in control of drinking and hydromineral balance in Atlantic salmon is discussed.
Accepted: 27 February 1997 相似文献