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1.
Tree species and wood ash application in plantations of short-rotation woody crops (SRWC) may have important effects on the
soil productive capacity through their influence on soil organic matter (SOM) and exchangeable cations. An experiment was
conducted to assess changes in soil C and N contents and pH within the 0–50 cm depth, and exchangeable cation (Ca2+, Mg2+, K+, and Na+) and extractable acidity concentrations within the 0–10 cm depth. The effects of different species (European larch [Larix decidua P. Mill.], aspen [Populus tremula L. × Populus tremuloides Michx.], and four poplar [Populus spp.] clones) and wood ash applications (0, 9, and 18 Mg ha−1) on soil properties were evaluated, using a common garden experiment (N = 70 stands) over 7 years of management in Michigan’s Upper Peninsula. Soils were of the Onaway series (fine-loamy, mixed,
active, frigid Inceptic Hapludalfs). The NM-6 poplar clone had the greatest soil C and N contents in almost all ash treatment
levels. Soil C contents were 7.5, 19.4, and 10.7 Mg C ha−1 greater under the NM-6 poplar than under larch in the ash-free, medium-, and high-level plots, respectively. Within the surface
layer, ash application increased soil C and N contents (P < 0.05) through the addition of about 0.7 Mg C ha−1 and 3 kg N ha−1 with the 9 Mg ha−1 ash application (twofold greater C and N amounts were added with the 18 Mg ha−1 application). During a decadal time scale, tree species had no effects—except for K+—on the concentrations of the exchangeable cations, pH, and extractable acidity. In contrast, ash application increased soil
pH and the concentration of Ca2+ (P < 0.05), from 5.2 ± 0.4 cmolc kg−1 (ash-free plots) to 8.6 ± 0.4 cmolc kg−1 (high-level ash plots), and tended to increase the concentration of Mg2+ (P < 0.1), while extractable acidity was reduced (P < 0.05) from 5.6 ± 0.2 cmolc kg−1 (ash-free plots) to 3.7 ± 0.2 cmolc kg−1 (high-level plots). Wood ash application, within certain limits, not only had a beneficial effect on soil properties important
to the long-term productivity of fast-growing plantations but also enhanced long-term soil C sequestration. 相似文献
2.
Nicola D’Amelio Luca Fontanive Fulvio Uggeri Furio Suggi-Liverani Luciano Navarini 《Food biophysics》2009,4(4):321-330
Caffeine complexation by chlorogenic acid (3-caffeoylquinic acid, CAS Number [327-97-9]) in aqueous solution as well as caffeine–chlorogenate
complex in freshly prepared coffee brews have been investigated by high-resolution 1H-NMR. Caffeine and chlorogenic acid self-associations have also been studied and self-association constants have been determined
resorting to both classical isodesmic model and a recently introduced method of data analysis able to provide also the critical
aggregation concentration (cac). Furthermore, caffeine–chlorogenate association constant was measured. For the caffeine, the
average value of the self-association constant determined by isodesmic model (K
i = 7.6 ± 0.5 M−1) is in good agreement with the average value (K
a = 10 ± 1.8 M−1) determined with the method which permits the determination of the cac (8.43 ± 0.05 mM). Chlorogenic acid shows a slight
decreased tendency to aggregation with a lower average value of association constants (K
i = 2.8 ± 0.6 M−1; K
a = 3.4 ± 0.6 M−1) and a critical concentration equal to 24 ± 1 mM. The value of the association constant of the caffeine–chlorogenate complex
(30 ± 4 M−1) is compatible with previous studies and within the typical range of reported association constants for other caffeine–polyphenol
complexes. Structural features of the complex have also been investigated, and the complex conformation has been rediscussed.
Caffeine chemical shifts comparison (monomeric, complexed, coffee brews) clearly indicates a significant amount of caffeine
is complexed in beverage real system, being chlorogenate ions the main complexing agents. 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.
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
5.
Miriam Altstein Tal Gabay Orna Ben-Aziz Shai Daniel Irina Zeltser Chaim Gilon 《Invertebrate neuroscience : IN》1999,4(1):0033-0040
The binding of [3H]tyrosyl-PBAN28-33NH2 to pheromone gland membranes of the moth Heliothis peltigera was investigated. The study describes the development of a pheromone biosynthesis-activating neuropeptide (PBAN) radioreceptor
assay and demonstrates the presence of a putative PBAN binding site on the pheromone gland. It also describes synthesis of
a radioligand and optimization of binding conditions with respect to membrane preparation, number of gland equivalents, kinetics
of ligand binding and composition of the binding solution. Binding was found to be optimal when membranes were freshly prepared
from frozen glands, incubated at a concentration of one gland equivalent per reaction tube in the presence of 10 mM HCO3
− ions. Equilibrium of ligand binding was obtained after 20 min. Presence of other components such as NaCl, KCl or SH reagents
did not have any effect on binding. Binding was found to be saturable, with a Kd of 5.73 ± 1.05 × 10−6 M and a Bmax of 1.85 ± 0.22 nmol/mg protein. Binding was effectively displaced by unlabeled PBAN1-33NH2 and PBAN28-33ΝΗ2 with a Ki of 4.3 ± 1.1 × 10−6 M and 4.9 ± 2.6 × 10−6 M, respectively.
Accepted: 4 February 1999 相似文献
6.
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
7.
T Roukas 《Journal of industrial microbiology & biotechnology》1999,22(6):617-621
Aureobasidium pullulans P56 was investigated using an adaptation technique and a mixed culture system. The adaptation of A. pullulans and the mixed cultures of A. pullulans and/or Lactobacillus brevisX20, Debaryomyces hansenii 194 and Aspergillus niger did not increase the production of polysaccharide. Enzymic hydrolysis of lactose in deproteinized whey gave a higher polysaccharide
concentration and polysaccharide yield than acidic hydrolysed lactose. Maximum polysaccharide concentration (11.0 ± 0.5 g L−1), biomass dry weight (10.5 ± 0.4 g L−1), polysaccharide yield (47.2 ± 1.8%) and sugar utilization (93.2 ± 2.8%) were achieved using enzyme-hydrolysed whey (pH 6.5)
containing 25 g L−1 lactose and supplemented with K2HPO4 0.5%, L-glutamic acid 1%, olive oil 2.5%, and Tween 80 0.5%. In this case the pullulan content of the crude polysaccharide was 40%.
Received 16 December 1997/ Accepted in revised form 12 March 1999 相似文献
8.
S A Shaikh J M Khire M I Khan 《Journal of industrial microbiology & biotechnology》1997,19(4):239-245
A thermostable β-galactosidase was produced extracellularly by a thermophilic Rhizomucor sp, with maximum enzyme activity (0.21 U mg−1) after 4 days under submerged fermentation condition (SmF). Solid state fermentation (SSF) resulted in a nine-fold increase
in enzyme activity (2.04 U mg−1). The temperature range for production of the enzyme was 38–55°C with maximum activity at 45°C. The optimum pH and temperature
for the partially purified enzyme was 4.5 and 60°C, respectively. The enzyme retained its original activity on incubation
at 60°C up to 1 h. Divalent cations like Co2+, Mn2+, Fe2+ and Zn2+ had strong inhibitory effects on the enzyme activity. The K
m and V
max for p-nitrophenyl-β- D-galactopyranoside and o-nitrophenyl-β - D-galactopyranoside were 0.39 mM, 0.785 mM and 232.1 mmol min−1 mg−1 respectively. The K
m and V
max for the natural substrate lactose were 66.66 μM and 0.20 μ mol min−1 mg−1.
Received 10 March 1997/ Accepted in revised form 17 July 1997 相似文献
9.
Water conductance of the cuticular membrane (CM) of mature sweet cherry fruit (Prunus avium L. cv. Sam) was investigated by monitoring water loss from segments of the outer pericarp excised from the cheek of the fruit.
Segments consisted of epidermis, hypodermis and several cell layers of the mesocarp. Segments were mounted in stainless-steel
diffusion cells with the mesocarp surface in contact with water, while the outer cuticular surface was exposed to dry silica
(22 ± 1 °C). Conductance was calculated by dividing the amount of water transpired per unit area and time by the difference
in water vapour concentration across the segment. Conductance values had a log normal distribution with a median of 1.15 × 10−4 m s−1 (n=357). Transpiration increased linearly with time. Conductance remained constant and was not affected by metabolic inhibitors
(1 mM NaN3 or 0.1 mM carbonylcyanide m-chlorophenylhydrazone) or thickness of segments (range 0.8–2.8 mm). Storing fruit (up to 42 d, 1 °C) used as a source of
segments had no consistent effect on conductance. Conductance of the CM increased from cheek (1.16 ± 0.10 × 10−4 m s−1) to ventral suture (1.32 ± 0.07 × 10−4 m s−1) and to stylar end (2.53 ± 0.17 × 10−4 m s−1). There was a positive relationship (r2=0.066**; n=108) between conductance and stomatal density. From this relationship the cuticular conductance of a hypothetical astomatous
CM was estimated to be 0.97 ± 0.09 × 10−4 m s−1. Removal of epicuticular wax by stripping with cellulose acetate or extracting epicuticular plus cuticular wax by dipping
in CHCl3/methanol increased conductance 3.6- and 48.6-fold, respectively. Water fluxes increased with increasing temperature (range
10–39 °C) and energies of activation, calculated for the temperature range from 10 to 30 °C, were 64.8 ± 5.8 and 22.2 ± 5.0 kJ
mol−1 for flux and vapour-concentration-based conductance, respectively.
Received: 23 March 2000 / Accepted: 28 July 2000 相似文献
10.
C. Lydersen K. M. Kovacs M. O. Hammill 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1997,167(2):81-88
In this study we measured growth and milk intake and calculated energy intake and its allocation into metabolism and stored
tissue for hooded seal (Cystophora cristata) pups. In addition, we measured mass loss, change in body composition and metabolic rate during the first days of the postweaning
fast. The mean body mass of the hooded seal pups (n = 5) at the start of the experiments, when they were new-born, was 24.3 ± 1.3 kg (SD). They gained an average of 5.9 ± 1.1.
kg · day−1 of which 19% was water, 76% fat and 5% protein. This corresponds to an average daily energy deposition of 179.8 ± 16.0 MJ.
The pups were weaned at an average body mass of 42.5 ± 1.0 kg 3.1 days after the experiment was initiated. During the first
days of the postweaning fast the pups lost an average of 1.3 ± 0.5␣kg of body mass daily, of which 56% was water, 16% fat
and 28% protein. During the nursing period the average daily water influx for the pups was 124.6 ± 25.8 ml · kg−1. The average CO2 production during this period was 1.10 ± 0.20 ml · g−1 · h−1, which corresponds to a field metabolic rate of 714 ± 130 kJ · kg−1 · day−1, or 5.8 ± 1.1 times the predicted basal metabolic rate according to Kleiber (1975). During the postweaning fast the average
daily water influx was reduced to 16.1 ± 6.6 ml · kg−1. The average CO2 production in␣this period was 0.58 ± 0.17 ml · g−1 · h−1 which corresponds to a field metabolic rate of 375 ± 108 kJ · kg−1 · day−1 or 3.2 ± 0.9 times the predicted basal metabolic rate. Average values for milk composition were 33.5% water, 58.6% fat and
6.2% protein. The pups drank an average of 10.4 ± 1.8␣kg of milk daily, which represents an energy intake of 248.9 ± 39.1
MJ · day−1. The pups were able to store 73.2 ± 7.7% of this energy as body tissue.
Accepted: 15 August 1996 相似文献
11.
Human FcγRI (CD64) is an integral membrane glycoprotein functioning as a high-affinity receptor binding to monomeric IgG.
In this study, the extracellular region of FcγRI, which is the actual part that interacts with IgG, was expressed as aglycosylated
recombinant human FcγRI (rhFcγRI) in Escherichia coli. The soluble form of aglycosylated rhFcγRI was expressed in the periplasm of E. coli. The production of soluble aglycosylated rhFcγRI was increased by low induction levels. Furthermore, this production was
increased by low translational efficiency, controlled by modification of the putative region between the ribosome binding
site and initiation codon of rhFcγRI fusing signal peptide (MalE, PelB, or TorT) of the expression vector. By the optimization
of induction and translational efficiency, the production of soluble aglycosylated rhFcγRI was up to approximately 0.8 mg/l
of culture medium. Surface plasmon resonance analysis revealed that the binding affinities of aglycosylated rhFcγRI for human
IgG1 (equilibrium dissociation constant K
D = [1.7 ± 0.2] × 10−10 M) and IgG3 (K
D = [1.1 ± 0.2] × 10−10 M) were similar to those of glycosylated rhFcγRI. 相似文献
12.
Zanaty R. Komy Rabei M. Gabar Ahmed A. Shoriet Rehab M. Mohammed 《World journal of microbiology & biotechnology》2006,22(9):975-982
Summary The ability of Pseudomonas
aeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pK
i
=1.66±3.26×10−3, 1.92±1.63×10−4 and 2.16±3.79×10−4) and binding constant of cadmium metal ions (pK
M1=1.99±2.45×10−3 and pK
M2=1.67±4.08×10−3) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pK
f) constant is 2.04±2.1×10−5 suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (q
max) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10−3± 2.10×10−3, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains. 相似文献
13.
Optical fractionation of chlorophyll and primary production for coastal waters of the Southern Ocean 总被引:1,自引:1,他引:0
Our objective was to quantify the potential variability in remotely sensed chlorophyll a (Chl a) and primary productivity in coastal waters of the Southern Ocean. From data collected throughout the springs/summers of
1991–1994, we calculated the proportion of water column Chl a and primary productivity within the upper optical attenuation length (K −1
par) and the satellite-weighted depth. The temporal variability was resolved every 2–3 days and was observed to be greater within
years than between years. Three-year averages (n=223) revealed that 10.2 ± 3.6% of total Chl a and 14.8 ± 6.5% of production occurred within satellite-weighted depth in predominantly Case I waters. The average values
were twice as high within K −1
par, 24.1 ± 8% of total Chl a and 34 ± 9% of production respectively. Masked in these long-term averages are very large changes occurring on short time
scales of seasonal blooms. We observed that the patterns of Chl a vertical distribution within blooms are also subject to taxonomic influence and dependent upon the physiological state of
the phytoplankton. Highest proportions of water column Chl a in the first optical depth were measured during the rapid onset of surface cryptophyte blooms each year, i.e. 50% within
K −1
par and 30% above the satellite-weighted depth. Lowest fractions, 6% and 2% of biomass within K −1
par and satellite-weighted depth respectively, were associated with peak bloom conditions independent of taxonomy. Our analyses
suggest that satellite-dependent models of Chl a and subsequent chlorophyll-dependent primary production will be challenging to develop for the near-shore Southern Ocean,
especially given the potentially high natural variability in the vertical distribution of Chl a driven by physical forcing, the photoadaptive abilities of polar phytoplankton, and taxonomic influences.
Accepted: 27 August 1999 相似文献
14.
Juozas Kulys Kastis Krikstopaitis Arturas Ziemys 《Journal of biological inorganic chemistry》2000,5(3):333-340
N -substituted phenothiazines (PTs) and phenoxazines (POs) catalyzed by fungal Coprinus cinereus peroxidase and Polyporus pinsitus laccase were investigated at pH 4–10. In the case of peroxidase, an apparent bimolecular rate constant (expressed as k
cat/K
m) varied from 1 ×107 M−1 s−1to 2.6×108 M−1 s−1 at pH 7.0. The constants for PO oxidation were higher in comparison to PT. pH dependence revealed two or three ionizable
groups with pK
a values of 4.9–5.7 and 7.7–9.7 that significantly affected the activity of peroxidase. Single-turnover experiments showed
that the limiting step of PT oxidation was reduction of compound II and second-order rate constants were obtained which were
consistent with the constants at steady-state conditions. Laccase-catalyzed PT and PO oxidation rates were lower; apparent
bimolecular rate constants varied from 1.8×105 M−1 s−1 to 2.0×107 M−1 s−1 at pH 5.3. PO constants were higher in comparison to PT, as was the case with peroxidase. The dependence of the apparent
bimolecular constants of compound II or copper type 1 reduction, in the case of peroxidase or laccase, respectively, was analyzed
in the framework of the Marcus outer-sphere electron-transfer theory. Peroxidase-catalyzed reactions with PT, as well as PO,
fitted the same hyperbolic dependence with a maximal oxidation rate of 1.6×108 M−1 s−1 and a reorganization energy of 0.30 eV. The respective parameters for laccase were 5.0×107 M−1 s−1 and 0.29 eV.
Received: 20 September 1999 / Accepted: 24 February 2000 相似文献
15.
Submerged aquatic higher plants maintain acropetal water transport to the young leaves in active growth to satisfy their
demand for nutrients and hormones derived from the roots. We here present the first measurements of hydraulic properties for
a submerged plant, the monocotyledon Sparganium emersum Rehman. The hydraulic conductance per unit length, Kh, was measured in leaf segments without the leaf tip and shown to be greater in old, fully developed leaves (1.5 · 10−10 · m4 · MPa−1 · s−1) than in young leaves (1.0 · 10−10 · m4 · MPa−1 · s−1). In leaves with intact leaf tips, however, Kh was significantly greater in the youngest leaves, which suggests that the leaf tip with the hydathode influences resistance
and thus flow. Microscopy confirmed that the hydathodal area, which is an apical opening, undergoes structural changes with
leaf age; a matrix of microorganisms develops in the older leaves and probably restricts water flow by clogging the hydathodes.
The leaf specific conductivity expressing transport capacity relative to the leaf area supplied, of S. emersum (0.1 · 10−8 to 9 · 10−8 · m2 MPa−1· s−1) was within the same range as for various species of terrestrial ferns, vines and trees. This finding does not support the
traditional concept of functionally reduced vascular transport in
Received: 15 July 1996 / Accepted: 30 November 1996 相似文献
16.
Using the cell pressure probe, the effects of temperature on hydraulic conductivity (Lp; osmotic water permeability), solute
permeability (permeability coefficient, Ps), and reflection coefficients (σs) were measured on internodes of Chara corallina, Klein ex Willd., em R.D.W.. For the first time, complete sets of transport coefficients were obtained in the range between
10 and 35 °C which provided evidence about pathways of water and solutes as they move across the plasma membrane (water channel
and bilayer arrays). Test solutes used to check for the selectivity of water channels were monohydric alcohols of different
molecular size and shape (ethanol, n-propanol, iso-propanol, and tert-butanol) and heavy water (HDO). Within the limits of accuracy, Q10 values for Lp and for the diffusive water permeability (Pd) were identical (Q10 for Lp = 1.29 ± 0.17 (± SD; n = 15 cells) and Q10 for Pd = 1.25 ± 0.16 (n = 5 cells)). The Q10 values were equivalent to activation energies of Ea = 16.8 ± 6.4 and 16.6 ± 10.0 kJ · mol−1, respectively, which is similar to that of self-diffusion or of viscous flow of water. The Q10 values and activation energies for Ps of the alcohols were significantly larger (ethanol: Q10 = 1.68 ± 0.16, Ea = 37.1 ± 5.9 kJ · mol−1; n-propanol: Q10 = 1.75 ± 0.40, Ea = 43.1 ± 15.3 kJ · mol−1; iso-propanol: Q10 = 2.12 ± 0.42, Ea = 52.2 ± 14.6 kJ · mol−1; tert-butanol: Q10 = 2.13 ± 0.56, Ea = 51.6 ± 17.1 kJ · mol−1; ±SD; n = 5 to 6 cells). Effects of temperature on reflection coefficients were most pronounced. With increasing temperature, σs values of the alcohols decreased and those of HDO increased. The data indicate that water and solutes use different pathways
when crossing the membrane. Ordinary and isotopic water use water channels and the other test solutes use the bilayer array
(composite transport model of membrane). Changes in σs values with temperature were found to be a sensitive measure for the open/closed state of water channels. The decrease of
σs with temperature was theoretically predicted from the temperature dependence of Ps and Lp. Differences between predicted and measured values of σs allowed estimation of the bypass flow (slippage) of solutes through water channels which did not completely exclude test
solutes. The permeability of channels depended on the structure and size of test solutes. It is concluded that water channels
are much less selective than is usually thought. Since water channels represent single-file or no-pass pores, solutes drag
along considerable amounts of water as they diffuse across channels. This results in low overall values of σs. The σs of HDO was extremely low. Its response to temperature was opposite to that for the σs of the alcohols. This suggested a stronger effect of temperature on the hydraulic (osmotic) than on the diffusive water flow
across individual water channels, i.e. a differential sensitivity of different mechanisms to temperature.
Received: 10 October 1996 / Accepted: 2 December 1996 相似文献
17.
A new cultivation technique for Kappaphycus alvarezii was used in the Brazilian southeastern coast (23°02′25″ S and 43°53′39″ W), the tubular netting on floating rafts. The tubular
net technique (TN) was compared with the current method of tie–tie (TT). After 47 days, the daily growth rate (mean ± SD of TN and TT = 3.4 ± 0.7% day−1), carrageenan yield (mean ± SD of TN and TT = 36 ± 1.3%), gel strength (mean ± SD of TN and TT = 730 ± 114.5 g cm2), and
viscosity (mean ± SD of TN and TT = 350 ± 60.4 cP) did not differ between the two techniques (p > 0.05). The amount of time used to plant (TT = 30.2 ± 2.3 min and TN = 13.3 ± 3.4 min) and to harvest the seedlings (TT = 36.2 ± 2.7 min
and TN = 17.8 ± 3.7 min) were lower in TN (p < 0.001). It is concluded that TN was more effective than TT, the cultivation management (time rates used to plant and harvest
the seedlings) was 53.6% faster, no seedlings were lost, the cost was lower, and an estimated return in 1 year of nearly 20%
more than that of the TT technique. 相似文献
18.
Atomic force microscopy (AFM) enables the topographical structure of cells and biological materials to be resolved under
natural (physiological) conditions, without fixation and dehydration artefacts associated with imaging methods in vacuo. It
also provides a means of measuring interaction forces and the mechanical properties of biomaterials. In the present study,
AFM has been applied for the first time to the study of the mechanical properties of a natural adhesive produced by a green
plant cell. Swimming spores of the green alga Enteromorpha linza (L.) J. Ag. (7–10 μm) secrete an adhesive glycoprotein which provides firm anchorage to the substratum. Imaging of the adhesive in its
hydrated state revealed a swollen gel-like pad, approximately 1 μm thick, surrounding the spore body. Force measurements revealed
that freshly released adhesive has an adhesion strength of 173 ± 1.7 mN m−1 (mean ± SE; n=90) with a maximum value for a single adhesion force curve of 458 mN m−1. The adhesive had a compressibility (equivalent to Young's modulus) of 0.54 × 106 ± 0.05 × 106 N m−2 (mean ± SE; n=30). Within minutes of release the adhesive underwent a progressive `curing' process with a 65% reduction in mean adhesive
strength within an hour of settlement, which was also reflected in a reduction in the average length of the adhesive polymer
strands (polymer extension) and a 10-fold increase in Young's modulus. Measurements on the spore surface itself revealed considerably
lower adhesion-strength values but higher polymer-extension values than the adhesive pad, which may reflect the deposition
of different polymers on this surface as a new cell wall is formed. The study demonstrates the value of AFM to the imaging
of plant cells in the absence of fixation and dehydration artefacts and to the characterisation of the mechanical properties
of plant glycoproteins that have potential utility as adhesives.
Received: 22 February 2000 / Accepted: 20 April 2000 相似文献
19.
J. B. K. Leonard J. F. Norieka B. Kynard S. D. McCormick 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(4-5):287-295
To assess the energetics of migration in an anadromous fish, adult American shad (Alosa sapidissima) were swum in a large respirometer at a range of speeds (1.0–2.3 body lengths (BL) s−1, 13–24 °C). Metabolic rate (MO2) was logarithmically related to swimming speed (Bl s−1; r
2 = 0.41, slope = 0.23 ± 0.037) and tailbeat frequency (beats × min−1; r
2 = 0.52, slope = 0.003 ± 0.0003). Temperature had a significant effect on metabolic rate (r
2 = 0.41) with a Q10 of 2.2. Standard metabolic rate (SMR), determined directly after immobilization with the neuroblocker gallamine triethiodide,
ranged from 2.2–6.2 mmolO2 kg−1 h−1 and scaled with mass (W) such that SMR = 4.0 (±0.03)W0.695(±0.15). Comparison of directly determined and extrapolated SMR suggests that swimming respirometry provides a good estimate of SMR
in this species, given the differences in basal activity monitored by the two methods. Overall, American shad metabolic rates
(MO2 and SMR) were intermediate between salmonids and fast-swimming perciforms, including tunas, and may be a result of evolutionary
adaptation to their active pelagic, schooling life history. This study demonstrates variability in metabolic strategy among
anadromous fishes that may be important to understanding the relative success of different migratory species under varying
environmental conditions.
Accepted: 3 March 1999 相似文献
20.
C. E. Crocker J. J. Cech Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):50-60
The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO2, PO2, pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia
(water PCO2 < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25–35 Torr) and a final return to normocapnia at 19 ± 0.5 °C. Acute
(≤ 2h) hypercapnia significantly increased arterial PCO2 (8-fold increase), ventilation frequency (2-fold increase), plasma HCO3
− (2.3-fold) and decreased arterial pH (to 7.15 ± 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly
increased, and arterial pH reached its nadir (7.10 ± 0.03). During the 72- and 96-h-periods, arterial PCO2 (24 ± 4.4 Torr) and ventilatory frequency (105 ± 5 breaths min−1) stabilized, HCO3
− reached its apparent maximum (23.6 ± 0.0 mmol−1), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored
arterial PCO2 (2.5 ± 0.14 Torr), HCO3
− (7.4 ± 0.59 mmol · l−1), ventilation frequency (71 ± 7 breaths · min−1), and pH (7.75 ± 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine
“spike”, and increased plasma catecholamines, cortisol, and arterial PO2. The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted
in a significantly decreased blood-O2 affinity (Bohr effect), as determined by construction of in vitro blood O2 equilibrium curves at 15 °C and 20 °C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively
affect growth of white sturgeon.
Accepted: 17 August 1997 相似文献