共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
Taylor JR Whittamore JM Wilson RW Grosell M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2007,177(6):597-608
The effects of feeding on both acid–base and ion exchange with the environment, and internal acid–base and ion balance, in
freshwater and seawater-acclimated flounder were investigated. Following voluntary feeding on a meal of 2.5–5% body mass and
subsequent gastric acid secretion, no systemic alkaline tide or respiratory compensation was observed in either group. Ammonia
efflux rates more than doubled from 489 ± 35 and 555 ± 64 μmol kg−1 h−1 under control conditions to 1,228 ± 127 and 1,300 ± 154 μmol kg−1 h−1 post-feeding in freshwater and seawater-acclimated fish, respectively. Based on predictions of gastric acid secreted during
digestion, we calculated net postprandial internal base gains (i.e., HCO3− secreted from gastric parietal cells into the blood) of 3.4 mmol kg−1 in seawater and 9.1 mmol kg−1 in freshwater-acclimated flounder. However, net fluxes of ammonia, titratable alkalinity, Na+ and Cl− indicated that branchial Cl−/HCO3− and Na+/H+ exchange played minimal roles in counteracting these predicted base gains and cannot explain the absence of alkaline tide.
Instead, intestinal Cl−/HCO3− exchange appears to be enhanced after feeding in both freshwater and seawater flounder. This implicates the intestine rather
than the gills as a potential route of postprandial base excretion in fish, to compensate for gastric acid secretion. 相似文献
3.
Alex M. Zimmer C. Michele Nawata Chris M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(8):1191-1204
Recently, a “Na+/NH4
+ exchange complex” model has been proposed for ammonia excretion in freshwater fish. The model suggests that ammonia transport
occurs via Rhesus (Rh) glycoproteins and is facilitated by gill boundary layer acidification attributable to the hydration
of CO2 and H+ efflux by Na+/H+ exchanger (NHE-2) and H+-ATPase. The latter two mechanisms of boundary layer acidification would occur in conjunction with Na+ influx (through a Na+ channel energized by H+-ATPase and directly via NHE-2). Here, we show that natural ammonia loading via feeding increases branchial mRNA expression
of Rh genes, NHE-2, and H+-ATPase, as well as H+-ATPase activity in juvenile trout, similar to previous findings with ammonium salt infusions and high environmental ammonia
(HEA) exposure. The associated increase in ammonia excretion occurs in conjunction with a fourfold increase in Na+ influx after a meal. When exposed to HEA (1.5 mmol/l NH4HCO3 at pH 8.0), both unfed and fed trout showed differential increases in mRNA expression of Rhcg2, NHE-2, and H+-ATPase, but H+-ATPase activity remained at control levels. Unfed fish exposed to HEA displayed a characteristic reversal of ammonia excretion,
initially uptaking ammonia, whereas fed fish (4 h after the meal) did not show this reversal, being able to immediately excrete
ammonia against the gradient imposed by HEA. Exposure to HEA also led to a depression of Na+ influx, demonstrating that ammonia excretion can be uncoupled from Na+ influx. We suggest that the efflux of H+, rather than Na+ influx itself, is critical to the facilitation of ammonia excretion. 相似文献
4.
Gilmour KM Perry SF Esbaugh AJ Genz J Taylor JR Grosell M 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2012,182(2):259-274
In seawater-acclimated rainbow trout (Oncorhynchus mykiss), base secretion into the intestine is a key component of the intestinal water absorption that offsets osmotic water loss
to the marine environment. Acid–base balance is maintained by the matched excretion of acid equivalents via other routes,
presumably the gill and/or kidney. The goal of the present study was to examine acid–base balance in rainbow trout upon transfer
to more dilute environments, conditions under which base excretion into the intestine is predicted to fall, requiring compensatory
adjustments of acid excretion at the gill and/or kidney if acid–base balance is to be maintained. Net acid excretion via the
gill/kidney and rectal fluid, and blood acid–base status were monitored in seawater-acclimated rainbow trout maintained in
seawater or transferred to iso-osmotic conditions. As predicted, transfer to iso-osmotic conditions significantly reduced
base excretion into the rectal fluid (by ~48%). Transfer to iso-osmotic conditions also significantly reduced the excretion
of titratable acidity via extra-intestinal routes from 183.4 ± 71.3 to −217.5 ± 42.7 μmol kg−1 h−1 (N = 7). At the same time, however, ammonia excretion increased significantly during iso-osmotic transfer (by ~72%) so that
the apparent overall reduction in net acid excretion (from 419.7 ± 92.9 to 189.2 ± 76.5 μmol kg−1 h−1; N = 7) was not significant. Trout maintained blood acid–base status during iso-osmotic transfer, although arterial pH was significantly
higher in transferred fish than in those maintained in seawater. To explore the mechanisms underlying these adjustments of
acid–base regulation, the relative mRNA expression and where possible, activity of a suite of proteins involved in acid–base
balance were examined in intestine, gill and kidney. At the kidney, reduced mRNA expression of carbonic anhydrase (CA; cytosolic
and membrane-associated CA IV), V-type H+-ATPase, and Na+/HCO3
− co-transporter were consistent with a reduced role in net acid excretion following iso-osmotic transfer. Changes in relative
mRNA expression and/or activity at the intestine and gill were consistent with the roles of these organs in osmotic rather
than acid–base regulation. Overall, the data emphasize the coordination of acid–base, osmoregulatory and ionoregulatory processes
that occur with salinity transfer in a euryhaline fish. 相似文献
5.
Sunita R. Nadella Carrie C. Y. Hung Chris M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(1):27-41
An in vitro gut-sac technique and 64Cu as a radiotracer were used to characterize gastric copper (Cu) transport. Cu transport was stimulated by low luminal pH
(4.0 vs. 7.4), to a greater extent than explained by the increased availability of the free Cu2+ ion. At pH = 4.0, uptake kinetics were indicative of a low affinity (K
m = 525 μmol L−1), saturable carrier-mediated component superimposed on a large linear (diffusive and/or convective) component, with about
50% occurring by each pathway at Cu = 50 μmol L−1. Osmotic gradient experiments showed that solvent drag via fluid transport may play a role in Cu uptake via the stomach,
in contrast to the intestine. Also unlike the intestine, neither the Na+ gradient, high Ag, nor phenamil had any influence on gastric Cu transport, and a tenfold excess of Fe and Zn failed to inhibit
Cu uptake. These findings indicate that neither Na+-dependent pathways nor DMT1 are likely candidates for carrier-mediated Cu transport in the stomach. We have cloned a partial
cDNA sequence for the copper transporter Ctr1, and show its mRNA expression in all segments of the trout gastrointestinal tract, including the stomach. Based on the fact
that this transporter is functional at low pH conventionally found in the stomach lumen, we suggest Ctr1 is a pathway for gastric Cu transport in trout. Extreme hypoxia inhibited Cu uptake. High
P\textCO2 P_{{{\text{CO}}_{2} }} levels (7.5 torr) increased Cu uptake and acetazolamide (100 μmol L−1) significantly inhibited Cu uptake, indicating carbonic anhydrase activity was involved in gastric Cu transport. Transport of Cu was insensitive to bafilomycin (10 μmol L−1) suggesting a V-ATPase did not play a direct role in the process. Expression (mRNA) of H
+
, K
+-ATPase, carbonic anhydrase 2, and the α-3 isoform of Na
+–K
+-ATPase were observed in the stomach. We suggest these enzymes facilitate Cu transport in the stomach indirectly as part of a physiological
mechanism exporting H+ to the cell exterior. However, pre-treatment with the H
+
, K
+-ATPase proton pump blocker omeprazole did not affect gastric Cu transport, suggesting that other mechanisms must also be involved. 相似文献
6.
Loong AM Chew SF Wong WP Lam SH Ip YK 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2012,182(4):491-506
The freshwater climbing perch, Anabas testudineus, is an obligatory air-breathing teleost which can acclimate to seawater, survive long period of emersion, and actively excrete
ammonia against high concentrations of environmental ammonia. This study aimed to clone and sequence the Na+:K+:2Cl− cotransporter (nkcc) from the gills of A. testudineus, and to determine the effects of seawater acclimation or exposure to 100 mmol l−1 NH4Cl in freshwater on its branchial mRNA expression. The complete coding cDNA sequence of nkcc from the gills of A. testudineus consisted of 3,495 bp, which was translated into a protein with 1,165 amino acid residues and an estimated molecular mass
of 127.4 kDa. A phylogenetic analysis revealed that the translated Nkcc of A. testudineus was closer to fish Nkcc1a than to fish Nkcc1b or Nkcc2. After a progressive increase in salinity, there were significant
increases in the mRNA expression and protein abundance of nkcc1a in the gills of fish acclimated to seawater as compared with that of the freshwater control. Hence, it can be concluded that
similar to marine teleosts, Cl− excretion through basolateral Nkcc1 of mitochondrion-rich cells (MRCs) was essential to seawater acclimation in A. testudineus. Exposure of A. testudineus to 100 mmol l−1 NH4Cl for 1 or 6 days also resulted in significant increases in the mRNA expression of nkcc1a in the gills, indicating a functional role of Nkcc1a in active ammonia excretion. It is probable that NH4
+ enter MRCs through basolateral Nkcc1a before being actively transported across the apical membrane. Since the operation of
Nkcc1a would lead to an increase in the intracellular Na+ concentration, it can be deduced that an upregulation of basolateral Na+/K+-ATPase (Nka) activity would be necessary to compensate for the increased influx of Na+ into MRCs during active NH4
+ excretion. This would imply that the main function of Nka in active NH4
+ excretion is to maintain intracellular Na+ and K+ homeostasis instead of transporting NH4
+ directly into MRCs as proposed previously. In conclusion, active salt secretion during seawater acclimation and active NH4
+ excretion during exposure to ammonia in freshwater could involve similar transport mechanisms in the gills of A. testudineus. 相似文献
7.
Sohn Y Yoo KY Park OK Kwon SH Lee CH Choi JH Hwang IK Seo JY Cho JH Won MH 《Neurochemical research》2011,36(12):2459-2469
The maintenance of intracellular pH is important in neuronal function. Na+/HCO3
− cotransporter (NBC), a bicarbonate-dependent acid–base transport protein, may contribute to cellular acid–base homeostasis
in pathophysiological processes. We examined the alterations of NBC immunoreactivity and its protein levels in the hippocampal
CA1 region after transient cerebral ischemia in gerbils. In the sham-operated group, moderate NBC immunoreactivity was detected
in CA1 pyramidal neurons, and, 12 h after I/R, the immunoreactivity in the pyramidal neurons was markedly increased over controls.
Three days after I/R, NBC immunoreactivity nearly disappeared in the CA1 pyramidal neurons. However, NBC immunoreactivity
was detected in the non-pyramidal neurons of the ischemic CA1 region at 3 days after I/R. From double immunofluorescence study
with glial markers, NBC immunoreactivity was detected in astrocytes, not in microglia, at 4 days after I/R. NBC protein level
in the CA1 region was significantly increased at 12 h post-ischemia and significantly decreased at 2 days post-ischemia. Thereafter,
NBC protein level was again increased and returned to the level of the sham-operated group at 4 days post-ischemia. On the
other hand, treatment with 4,4′-diisothiocyanatostilbene-2,2′-disulfonate (DIDS), an inorganic anion exchanger blocker including
Cl-bicarbonate exchanger, protected CA1 pyramidal neurons from I/R injury at 4 days post-ischemia. These results indicate
that changes in NBC expressions may play an important role in neuronal damage and astrocytosis induced by transient cerebral
ischemia. 相似文献
8.
Ke-Gui Li Zhen-Dong Cao Jiang-Lan Peng Shi-Jian Fu 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(5):661-671
Feeding and exhaustive exercise are known to elevate metabolism. However, acid–base status may be oppositely affected by the
two processes. In this study, we first investigated the acid–base response of Chinese catfish to feeding (the meal size was
about 8% of body mass) to test whether an alkaline tide (a metabolic alkalosis created by gastric HCl secretion after feeding)
would occur. We then determined the combined effects of feeding and exhaustive exercise on excess post-exercise oxygen consumption
and acid–base status to determine whether the alkaline tide induced by feeding protects against acid–base disturbance during
exhaustive exercise and affects subsequent recovery. Arterial blood pH increased from 7.74 ± 0.02 before feeding to 7.88 ± 0.02
and plasma [HCO3
−]pl increased from 5.42 ± 0.29 to 7.83 ± 0.37 mmol L−1 6 h after feeding, while feeding had no significant effect on
P\textCO2 P_{{{\text{CO}}_{2} }} . Exhaustive exercise led to a significant reduction in pH by 0.46 units and a reduction of [HCO3
−]pl by ~3 mmol L−1. Lactate concentrations in white muscle and plasma increased by 2.4 mmol L−1 and 13.4 μmol g−1, respectively. Fed fish had a higher pH and [HCO3
−]pl than fasting fish at rest, and the reductions in pH (0.36 units) and [HCO3
−]pl (~2 mmol L−1) were thus lower after exhaustive exercise. However, the recovery of acid–base status and metabolites were similar in digesting
and fasting fish. Overall, a significant alkaline tide was found in Chinese catfish after feeding. The alkaline tide elicited
by feeding significantly prevented the decreases in pH and [HCO3
−]pl immediately after exhaustive exercise, but recovery from exhaustive exercise was not affected by digestion. 相似文献
9.
The sodium bicarbonate cotransporter (NBC1) is essential for bicarbonate transport across plasma membranes in epithelial
and nonepithelial cells. The direction of the NaHCO3 movement in secretory epithelia is opposite to that in reabsorptive epithelia. In secretory epithelia (such as pancreatic
duct cells) NBC is responsible for the transport of bicarbonate from blood to the cell for eventual secretion at the apical
membrane. In reabsorptive epithelia (such as kidney proximal tubule cells) NBC is responsible for the reabsorption of bicarbonate
from cell to the blood. In nonepithelial cells this transporter is mainly involved with cell pH regulation. Recent molecular
cloning experiments have identified the existence of four NBC isoforms (NBC1, 2, 3 and 4) and two NBC-related proteins AE4
and NCBE (Anion Exchanger 4 and Na-dependent Chloride-Bicarbonate Exchanger). All but AE4 are presumed to mediate the cotransport
of Na+ and HCO3
− under normal conditions and may be functionally altered in certain pathologic states. NBC1 shows a limited tissue expression
pattern, is electrogenic and plays an important role in bicarbonate reabsorption in kidney proximal tubule. In addition to
the kidney, NBC1 is expressed in pancreatic duct cells, is activated by cystic fibrosis transmembrane conductance regulator
(CFTR) and plays an important role in HCO3
− secretion. NBC2 and NBC3 have a wider tissue distribution than NBC1, are electroneutral, and are involved with cell pH regulation.
The characterization of NBC4 is incomplete. The NBC-related protein called NCBE mediates Na-dependent, Cl−/Bicarbonate Exchange. The purpose of this review is to summarize recent advances on the cloning of NBC isoforms and related
proteins and their role and regulation in physiologic and pathologic states.
Received: 26 February 2001/Revised: 14 May 2001 相似文献
10.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
11.
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
12.
There are numerous reports on the accumulation of ammonia in the mounds of soil-feeding termites. Here, we provided direct
evidence for an effective mineralization of nitrogenous soil organic matter in the gut of Cubitermes spp., which gives rise to enormous ammonia concentrations in the intestinal tract. In Cubitermes ugandensis, the ammonia content of the nest material [24.5 μmol (g dry wt.)−1] was about 300-fold higher than that of the parent soil. Large amounts of ammonia were present throughout the intestinal
tract, with lowest values in the extremely alkaline gut sections (pH >12) and highest values posterior hindgut [185 μmol (g dry wt.)−1]. Results obtained with other Cubitermes species were similar. Ammonia concentrations in the posterior hindgut of these humivorous species (up to 130 mM) are among
the highest values ever reported for soil macroinvertebrates and are matched only by insects feeding on an extremely protein-rich
diet (e.g., the sarcophageous larvae of blowflies). Volatilization of ammonia [about 10 nmol (g fresh wt.)−1 h−1], either directly by emission from the termite body or indirectly from their feces, led to NH3 concentrations in the nest atmosphere of C. ugandensis that were three orders of magnitude above the ambient background – a relative accumulation that is considerably higher than
that observed with CH4 and CO2. Together with previous results, these observations document that through their feeding activity and due to the physicochemical
and biochemical properties of their digestive system, soil-feeding termites effectively catalyze the transformation of refractory
soil organic nitrogen to a plant-available form that is protected from leaching by adsorption to the nest soil. Nitrogen mineralization
rates of soil-feeding termites may surpass those effected by tropical earthworms and should contribute significantly to nitrogen
fluxes in tropical ecosystems. 相似文献
13.
The degradation potential of trichloroethene by the aerobic methane- and ammonia-oxidizing microorganisms naturally associated
with wetland plant (Carex comosa) roots was examined in this study. In bench-scale microcosm experiments with washed (soil free) Carex comosa roots, the activity of root-associated methane- and ammonia-oxidizing microorganisms, which were naturally present on the
root surface and/or embedded within the roots, was investigated. Significant methane and ammonia oxidation were observed reproducibly
in batch reactors with washed roots incubated in growth media, where methane oxidation developed faster (2 weeks) compared
to ammonia oxidation (4 weeks) in live microcosms. After enrichment, the methane oxidizers demonstrated their ability to degrade
150 μg l−1 TCE effectively at 1.9 mg l−1 of aqueous CH4. In contrast, ammonia oxidizers showed a rapid and complete inhibition of ammonia oxidation with 150 μg l−1 TCE at 20 mg l−1 of NH4
+-N, which may be attributed to greater sensitivity of ammonia oxidizers to TCE or its degradation product. No such inhibitory
effect of TCE degradation was detected on methane oxidation at the above experimental conditions. The results presented here
suggest that microorganisms associated with wetland plant roots can assist in the natural attenuation of TCE in contaminated
aquatic environments. 相似文献
14.
Gilmour KM Collier CL Dey CJ Perry SF 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(4):501-515
Fish compensate for acid–base disturbances primarily by modulating the branchial excretion of acid–base equivalents, with
a supporting role played by adjustment of urinary acid excretion. The present study used metabolic acid–base disturbances
in rainbow trout, Oncorhynchus mykiss, to evaluate the role played by cortisol in stimulating compensatory responses. Trout infused with acid (an iso-osmotic solution
of 70 mmol L−1 HCl), base (140 mmol L−1 NaHCO3) or saline (140 mmol L−1 NaCl) for 24 h exhibited significant elevation of circulating cortisol concentrations. Acid infusion significantly increased
both branchial (by 328 μmol kg−1 h−1) and urinary (by 5.9 μmol kg−1 h−1) net acid excretion, compensatory responses that were eliminated by pre-treatment of trout with the cortisol synthesis inhibitor
metyrapone (2-methyl-1,2-di-3-pyridyl-1-propanone). The significant decrease in net acid excretion (equivalent to enhanced
base excretion) of 203 μmol kg−1 h−1 detected in base-infused trout was unaffected by metyrapone treatment. Acid- and base-infusions also were associated with
significant changes in the relative mRNA expression of branchial and renal cytosolic carbonic anhydrase (tCAc) and renal membrane-linked
CA IV (tCA IV). Cortisol treatment caused changes in CA gene expression that tended to parallel those observed with acid but
not base infusion. For example, significant increases in renal relative tCA IV mRNA expression were detected in both acid-infused
(~2x) and cortisol-treated (~10x) trout, whereas tCA IV mRNA expression was significantly reduced (~5x) in base-infused fish. Despite changes in CA gene expression in acid- or base-infused fish, neither acid nor base infusion
affected CAc protein levels in the gill, but both caused significant increases in branchial CA activity. Cortisol treatment
similarly increased branchial CA activity in the absence of an effect on branchial CAc protein expression. Taken together,
these findings provide support for the hypothesis that in rainbow trout, cortisol is involved in mediating acid–base compensatory
responses to a metabolic acidosis, and that cortisol exerts its effects at least in part through modulation of CA. 相似文献
15.
Chunming Xu Bing Zhao Yuan Ou Xiaodong Wang Xiaofan Yuan Yuchun Wang 《World journal of microbiology & biotechnology》2007,23(7):965-970
Syringin production and related secondary metabolism enzyme activities in suspension cultures of Saussurea medusa treated with different elicitors (yeast extract, chitosan and Ag+) were investigated. All elicitors enhanced syringin production, and the optimal feeding protocol was the combined addition
of 1.5% (v/v) yeast extract, 0.2 g l−1 chitosan and 75 μM Ag+ at the 15th day of the cell culture. The highest syringin production reached 741.9 mg l−1, which was 3.6−fold that of the control. The glucose−6-phosphate dehydrogenase (EC 1.1.1.49), phenylalanine ammonia lyase
(EC 4.3.1.5) and peroxidase (EC 1.11.1.7) activities increased significantly after elicitor treatment. The maximum enzyme
activities were obtained when the treatment time was 6 h. 相似文献
16.
Changes in oxygen consumption rate and Na+/K+-ATPase activity during early development were studied in the sea urchin Paracentrotus lividus Lam. The oxygen consumption rate increased from 0.12 μmol O2 mg protein−1 h−1 in unfertilized eggs to 0.38 μmol O2 mg protein−1 h−1 25 min after fertilization. Specific activity of the Na+/K+-ATPase was significantly stimulated after fertilization, ranging up to 1.07 μmol Pi h−1 mg protein−1 in the late blastula stage and slightly lower values in the early and late pluteus stages. 相似文献
17.
Morteza Shabannejad Mamaghani Mohammad Hassan Assareh Mansoor Omidi Mohammad Matinizadeh Abbas Ghamari-Zare Shokofeh Shahrzad Massih Forootan 《Plant Growth Regulation》2009,59(3):199-205
The green twigs of 1-year-old Eucalyptus microtheca F. Muell seedlings were cultured on modified MS medium, supplemented with α-naphthalene acetic acid (NAA) and kinetin (Kin)
hormones at 12 different concentrations. After 4 weeks, the combination of 1 mg l−1 NAA + 1 mg l−1 Kin induced the highest number of axillary shoots. Meanwhile, embryogenic calli were observed in media containing 4 mg l−1 NAA + 0.5 mg l−1 Kin, without any regeneration. The hormone treatments were followed by subculturing the twigs in different levels of thidiazuron
(TDZ). The combination of 1 mg l−1 NAA + 1 mg l−1 Kin together with 0.01 mg l−1 TDZ resulted in an increase of direct shoot, while higher amounts of TDZ led to adventitious shoot induction. Somatic embryogenesis
was observed in the treatment containing 0.01 mg l−1 TDZ + 4 mg l−1 NAA + 0.5 mg l−1Kin. The peroxidase (POD) band patterns in regenerated plantlets were investigated in order to determine the effect of different
levels of TDZ on loci synthesis. A dimer locus, a tetramer locus and two epigenetic bands (a new band for NAA + Kin and the
other for TDZ) were observed in the POD profiles. In case of low (0.01 mg l−1 and 0.1 mg l−1) levels of TDZ, one heterozygote allele was disappeared from dimer locus, while at higher TDZ levels, the dimer locus lost
its stability and tetramer locus showed a high activity. Thus, POD allele patterns seems to be a feasible marker for different
types of regeneration. 相似文献
18.
The effect of increasing concentration of polycyclic aromatic hydrocarbon (PAH) fluoranthene (FLT; 0.1, 1 and 5 mg l−1) on the growth, ethylene production and anatomy of stems of 21-day-old pea plants cultivated in vitro in MS medium, with
or without FLT, enriched with 0.1 mg l−1 indole-3-acetic acid (IAA) or with combination of 0.1 mg l−1 IAA + 0.1 mg l−1 N6-benzyladenine (BA) were investigated. The low concentration of 0.1 mg l−1 FLT, in both IAA- and IAA + BA-treated plants, significantly stimulated the growth of pea callus, while higher concentrations
1 mg l−1 and especially 5 mg l−1 FLT significantly inhibited it. Pea shoots were significantly influenced only after application of 5 mg l−1 FLT in IAA treatment. Significantly increased production of ethylene was found in IAA + BA treatments in all concentrations
of FLT, whereas in IAA treatments in 1 and 5 mg l−1 FLT. The lysigenous aerenchyma formation in the cortex of pea stems significantly increased in all FLT treatments and its
highest proportion was found in plants exposed to 1 mg l−1 FLT. 相似文献
19.
Timothy J. Hoellein Jennifer L. Tank John J. Kelly Emma J. Rosi-Marshall 《Hydrobiologia》2010,649(1):331-345
Humans have increased the availability of nutrients including nitrogen and phosphorus worldwide; therefore, understanding
how microbes process nutrients is critical for environmental conservation. We examined nutrient limitation of biofilms colonizing
inorganic (fritted glass) and organic (cellulose sponge) substrata in spring, summer, and autumn in three streams in Michigan,
USA. Biofilms were enriched with nitrate (NO3
−), phosphate (PO4
3−), ammonium (NH4
+), NO3
− + PO4
3−, NH4
+ + PO4
3−, or none (control). We quantified biofilm structure and function as chlorophyll a (i.e., primary producer biomass) and community respiration on all substrata. In one stream, we characterized bacterial and
fungal communities on cellulose in autumn using clone library sequencing and denaturing gradient gel electrophoresis to determine
if community structure was linked to nutrient limitation status. Despite oligotrophic conditions, primary producer biomass
was infrequently nutrient limited. In contrast, respiration on organic substrata was frequently limited by N + P combinations.
We found no difference between biofilm response to NH4
+ versus NO3
− enrichment, although the response to both N-species was positively related to water column PO4
3− concentrations and temperature. Molecular analysis for fungal community composition suggested no relationship to nutrient
limitation, but the dominant members of the bacterial community on cellulose were different on NO3
−, PO43, and NO3
− + PO4
3− treatments relative to control, NH4
+, and NH4
+ + PO4
3− treatments, which matched patterns for biofilm respiration rates from each treatment. Our results show discrete patterns
of nutrient limitation dependent upon substratum type and season, and imply changes in bacterial community structure and function
may be linked following nutrient enrichment in streams. 相似文献
20.
D. S. Choi H. O. Jin D. J. Chung K. Sasa T. Koike 《Trees - Structure and Function》2008,22(5):729-735
To evaluate the effect of ectomycorrhizal colonization on growth and physiological activity of Larix kaempferi seedlings grown under soil acidification, we grew L. kaempferi seedlings with three types of ectomycorrhizae for 180 days in acidified brown forest soil derived from granite. The soil
had been treated with an acid solution (0 (control), 10, 30, 60, and 90 mmol H+ kg−1). The water-soluble concentrations of Ca, Mg, K, Al, and Mn increased with increasing amounts of H+ added to the soil. Ectomycorrhizal development significantly increased in soil treated with 10 and 30 mmol H+ kg−1 but was significantly reduced in soil treated with 60 and 90 mmol H+ kg−1. The concentrations of Al and Mn in needles or roots increased with increasing H+ added to the soil. The total N in seedlings significantly increased with increasing H+ in soil and colonization with ectomycorrhiza. The maximum net photosynthetic rate at light and CO2 saturation (P
max) was greater in soil treated with 10 mmol H+ kg−1 than in controls, and was less is soils treated with greater than with 30 mmol H+ kg−1, especially with 60 and 90 mmol H+ kg−1. However, colonization with ectomycorrhiza significantly reduced the concentration of Al and Mn in needles or roots and increased
the values of P
max and total dry mass (TDM). The relative TDM of L. kaempferi seedlings was approximately 40% at a (BC, base cation)/Al ratio of 1.0. However, ectomycorrhizal seedlings had a 100–120%
greater TDM at a BC/Al ratio of 1.0 than non-ectomycorrhizal seedlings, even though the acid treatment reduced their overall
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