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1.
This study focuses on selective feeding by developmental stages of two oceanic copepods, Calanus finmarchicus and Calanus helgolandicus from nauplii to adults. A mixture of four algal species of different biochemical composition, Prorocentrum nanum (dinoflagellate), Thalassiosira minima (diatom), Rhodomonas baltica (cryptophyte) and Dunaliella tertiolecta (chlorophyte), added in an equal biovolume, was used in three different experimental set-ups. In set-up 1 the algal species
were present as single cells of similar size (14 μm). In set-up 2 the diatom T. minima was present in chains of two or three cells and was therefore larger than the other algae, while the biovolume of all species
remained the same. In set-up 3, the diatom T. minima was excluded from the mixture. Feeding selectivity of the copepods was assessed in relation to the quality of the algal species
expressed in terms of carbon and nitrogen content, fatty acid composition, and chain length of the diatom. The results show
that younger stages and adult females of C. finmarchicus and C. helgolandicus did not show a preference for an algal species when the algae were of similar size. In the feeding experiments where the
diatoms were offered as chains, both copepod species showed a selective behaviour only on the basis of algal size. Individual
ingestion rates increased from 0.4 to 0.7 μg C day–1 for nauplii of both species to 5 μg C day–1 for adult females of C. helgolandicus to 12 μg C day–1 for C. finmarchicus. Individual filtration rates ranged from 5 ml day–1 for C. finmarchicus nauplii to 70–98 ml day–1 for adult females, and from 3 ml day–1 for C. helgolandicus nauplii to 35–46 ml day–1 for adult females. Ingestion and filtration rates per unit body carbon decreased gradually in both copepod species with increasing
body carbon. The daily ingested amount of food decreased for C. finmarchicus from 124–134% of the body carbon for nauplii to 19% of the body carbon for adult females, and for C. helgolandicus from 117–137% of the body carbon for nauplii to 13–26% of the body carbon of adult females.
Electronic Publication 相似文献
2.
Purified β-glucosidase fromCellulomonas biazotea had an apparentK
m andV for 2-nitrophenyl β-d-glucopyranoside (oNPG) of 0.416 mmol/L and 0.22 U/mg protein, respectively. The activation energy for the hydrolysis of pNPG
of β-glucosidase was 65 kJ/mol. The inhibition by Mn2+
vs. oNPG of parental β-glucosidase was of mixed type with apparent inhibition constants of 0.19 and 0.60 μmol/L for the enzyme
and enzyme-substrate complex, respectively. Ethanol at lower concentrations activated while at higher concentrations it inhibited
the enzyme. The determination of apparent pK
a’s at different temperatures and in the presence of 30 % dioxane indicated two carboxyl groups which control theV value. The thermal stability of β-glucosidase decreased in the presence of 10 % ethanol. The half-life of β-glucosidase in
1.75 mol/L urea at 35 °C was 145 min, as determined by 0–9 mol/L transverse urea gradient-PAGE.
This work was financed in part by a grant made by theUS Agency for International Development under PSTC proposal 6-163,USAID grant no. 9365542-G-00-89-42-00, and PAEC. 相似文献
3.
Phyto/zooplankton composition, chlorophyll a, and some water quality parameters were investigated in a spring-originated pond in Central Anatolia between February 2001
and January 2002. Water temperature, pH, dissolved oxygen, Secchi depth, total and calcium hardness, nitrate-nitrogen, nitrite-nitrogen,
ammonia-nitrogen, total phosphorus, and soluble reactive phosphorus levels were analyzed. A total of 49 species belonging
to Bacillariophyceae, Chlorophyceae, Cyanophyceae, Cryptophyceae, and Dinophyceae were identified. The highest phytoplankton
abundance was found in August, whereas the lowest was determined in January. Phytoplankton abundance increased from February
to August and declined in the following months. The Bacillariophyceae were dominant in the phytoplankton community. A total
of 21 species of Rotifera, 2 species of Cladocera, and 1 genus of Copepoda were found. The zooplankton community was dominated
by Rotifera. The highest abundance of zooplankton was recorded in July and the lowest value in November. The annual mean concentration
of chlorophyll a was measured as 1.90 μg l−1. In spite of these eutrophic levels (mean values of total phosphorus and nitrate-nitrogen: 0.069 mg P l−1 and 0.68 mg N l−1), phytoplankton cannot grow satisfactorily because of the short water retention time (0.6 day−1). The shallowness of the pond together with the low phytoplankton biomass and the high concentrations of nutrients are discussed. 相似文献
4.
Ciborinia gentianae sp. nov., the causal organism of sclerotial flower blight of cut-flower gentians
A new Ciborinia causing sclerotial flower blight of cut-flower gentians (Gentiana triflora var. japonica and interspecific hybrids between related species or varieties) is described as Ciborinia gentianae on the morphological basis of sclerotia and apothecia. The characteristics of Ciborinia gentianae are (1) an abundant production of spermodochia in the hollow cavity of host stems; (2) flat and thin sclerotia produced beneath
the epidermis and the inclusion of host vascular remnants within their medulla; (3) globose cells composed of ectal excipulum
of apothecia; (4) elongated cells with a slight apical swelling in ectal excipulum at the apothecial margin; and (5) tetra
nucleate ascospores. Asci and ascospores mounted in Melzer's reagent measured 156–208 × 8–12 μm and 11.8–15 × 5.5–7.1 μm,
respectively. 相似文献
5.
To evaluate the species specificity of Cd accumulation and the relationship of Cd with other essential metals and metallothionein
(MT), the concentrations of Cd, Zn, Cu, and Fe in the liver and kidney and the MT concentrations in the soluble fractions
of the liver and kidney were determined in Cd-uncontaminated nonhuman primates (11 species, 26 individuals) kept in a zoo
and two wild-caught Japanese macaques. The compositions of metal-binding proteins in the soluble fractions were also investigated
by high-performance liquid chromatography (HPLC). The hepatic Cd concentration was 0.03–14.0 μg/g and the renal Cd concentration was 0.35–99.0 μg/g, both varying greatly and being higher in nonhuman primates, which were more closely related to man. The hepatic Zn concentration
was 24.0–176 μg/g and the renal Zn concentration was 13.5–138 μg/g, showing 7- to 10-fold differences, and a correlation (r=0.558, p<0.01) was found between renal Zn and renal Cd concentrations.
It was proved that in the liver, MT is more closely correlated with Zn (r=0.795, p<0.001) than with Cd (r=0.492, p<0.01) and that in the kidney MT is correlated with both Cd (r=0.784, p<0.001) and Zn (r=0.742, p<0.001). HPLC analysis of metals bound to MT-like protein in chimpanzees, de Brazza’s monkeys, and Bolivian squirrel monkeys
showed that more than 90% of Cd in both the liver and kidney, approx 40% of Zn in liver and 28–69% of Zn in kidney were bound
to MT-like protein. The higher percentage Zn was bound to high-molecular protein. 相似文献
6.
T. E. Tautorus M. M. Lulsdorf S. I. Kikcio D. I. Dunstan 《In vitro cellular & developmental biology. Plant》1994,30(1):58-63
Summary Embryogenic cell cultures ofPicea mariana (black spruce) and the species complexPicea glauca-engelmannii (interior spruce) were maintained either as suspensions in liquid medium in 250 or 500-ml-capacity shake-flasks, 7-liter-capacity
airlift or mechanically stirred bioreactors, or on agar-solidified medium. Cultures from each of the maintenance conditions
were subsequently transferred to agar-solidified LP medium containing 40μM (±) -abscisic acid for maturation into cotyledonary stage embryos. For both species, the highest maturation frequency resulted
from cultures grown in the airlift bioreactor. With black spruce cells grown in the airlift bioreactor containing LP medium
with 60 mM sucrose, a maximum of 7.1 g·liter−1 dry weight and 2892 embryos·ml−1 were obtained after 15 days. For interior spruce cells, a maximum dry weight of 5.9 g·liter−1 and 2698 embryos·ml−1 were obtained after 21 to 30 days. During culture over 2 wk, ammonia was almost completely utilized by both species, wherease
nitrate was depleted to 40% of the initial concentration. Sucrose was rapidly hydrolyzed to glucose and fructose by both species.
Black spruce cultures preferentially metabolized glucose, whereas interior spruce preferentially metabolized fructose. Improved
growth of interior spruce cells in mechanically stirred bioreactors occurred when cultured in LP medium with 60 mM fructose as the sole carbon source.
NRCC no. 36479 相似文献
7.
Water status and gas exchange of beech (Fagus sylvatica L.) and sessile oak [Quercus petraea (Mattuschka) Liebl.] were studied in a mixed stand in the Montejo de la Sierra forest (central Iberian Peninsula), one of
the southernmost locations of both species in Europe. Gas exchange and water potential were measured in leaves at different
canopy levels over several days in two growing seasons. The daily variation pattern was established with the measurements
of three selected dates per year, representative of the soil moisture content situations in early, mid- and late summer. A
similar daily time course of leaf water potential was found for the two species. Nevertheless, beech showed a most noticeable
decrease of water potential at midmorning and maintained lower leaf water potential than oak in the early afternoon. In 1994
the sessile oak saplings showed higher values of predawn water potential (Ψpd) than beech at the end of summer, when soil moisture content was lowest (20 cm depth). Beech showed a significantly lower
net assimilation rate (A) than sessile oak for leaves under the same PPFD. Maximum net photosynthesis values (A
max) for beech and sessile oak on sunny leaves were 10.1±0.4 μmol m–2 s–1 and 17.8±1.7 μmol m–2 s–1 respectively, and those for water vapour stomatal conductance (g
wv) were 265±31 mmol m–2 s–1 and 438±74 mmol m–2 s–1. Differences in A and g
wv between the two species were maintained throughout the day on all measurement dates. No clear relationship was found between
water status of saplings and stomata performance; there was only a negative correlation between Ψpd and g
wvmid in beech. Nevertheless, a significant response to the air vapour pressure gradient between leaf and air was translated into
stomata closure on an hourly basis, more intensively in beech.
Received: 4 March 1999 / Accepted: 21 December 1999 相似文献
8.
Ademola O. Olaniran Anthony I. Okoh Stella Ajisebutu Peter Golyshin Gbolahan O. Babalola 《International microbiology》2002,5(1):21-24
Two bacterial species isolated using enrichment culture techniques from the topsoil of a main refuse dumpsite in Nigeria
were assessed for their dehalogenation potentials. The bacterial isolates were identified as belonging to the Bacillus and Pseudomonas genera. Axenic cultures of the isolates utilized monochloroacetic acid (MCA), trichloroacetic acid (TCA), trichloromethane
(CHCl3) and tetrachloromethane (CCl4) as the sole source of carbon for growth up to a final substrate concentration of 0.1% (w/v). The mean generation times of
the isolates in all the growth media ranged significantly (P<0.05) from 2.41 to 10.04 h and were generally higher than that observed in glucose medium (1.46–1.51 h). The numbers of the
chloride atoms in the different organochlorides were negatively correlated with the ability of the organisms to degrade the
compounds. Dehalogenase specific activities of the cell-mediated cultures ranged from 0.1 to 0.96 μg ml–1 chloride release (mg protein)–1 h–1 and were significantly (P <0.05) higher than that of the cell-free extract [0.09–0.8 μg ml–1 chloride release (mg protein)–1 h–1]. The optimal pH of the dehalogenase activity was found to be 8.0, and the optimal temperature was between 30 and 35 °C.
Electronic Publication 相似文献
9.
Summary The giant salamanders of North America include 4 genera, all of which are aquatic. We have compared the efficacy of aquatic
O2 uptake among them by measuring theVO2 while submerged and determining the responses to progressive hypoxia at 10–240 mmHg at 20° C. Both species ofAmphiuma were metabolic O2 conformers over the entire range ofPO2. About half ofSiren lacertina were conformers over this range, and half were regulators with an average critical O2 tension of 92 mmHg. There were no short-term changes (days) in the response ofSiren to progressive hypoxia, but one animal switched from conformation to regulation after 4–5 months. Neither genus is considered
to have an exceptionally low metabolic rate. The “whole-body O2 conductance”, defined asΔVO2/ΔPO2(μl O2 · g−1 · h−1 · mmHg−1) in the range of metabolic O2 conformity, was least in the species most dependent upon air-breathing and most likely to be found in hypoxic waters (e.g.,
0.076 forAmphiuma), and greatest in those that airbreathe less frequently and/or are found in relatively normoxic waters (e.g., 0.429 forNecturus). These conductances are considered to be adaptive in terms of preventing O2 loss through the skin, or in facilitating its uptake, as correlated with the O2 tensions normally prevailing in the environment of each species. 相似文献
10.
Mitochondria from Trigonella foenum-graecum seedlings grown independently in the presence of either selenium (0.75 ppm) or mimosine (0.1 mM) exhibited respiration-stimulated energy-dependent uptake of Ca2+. Uptake studies were carried out independently at a series of Ca2+ concentrations at two different levels: (1) 1–20 μM and (2) 25–1500 μM. Levels of uptake were 50–100% higher in the mitochondria of seedlings of both the Se and mimosine groups. Detailed kinetic
analyses revealed negative cooperative effects operative during uptake of Ca2+ at 25–1500 μM given in the medium. Hill coefficients for Ca2+ uptake by the mitochondria of different groups remained unchanged (nH, 0.75). Biphasic Scatchard plots were concave upward,
suggestive of two classes of binding sites. High-affinity binding sites were estimated to be 16 nmol/mg protein with dissociation
constant (K
Ca) of 2.5×109 L/mol. In contrast, graphical analyses of the uptake of Ca2+ in the range 1–20 μM in the medium revealed cooperative effects of positive nature. The present study demonstrates mixed
cooperative effects during Ca2+ uptake by mitochondria from seedlings of T. foenum-graecum 相似文献
11.
S. Moharekar S. Moharekar R. Tanaka K. I. Ogawa A. Tanaka T. Hara 《Photosynthetica》2007,45(2):259-265
Arabidopsis thaliana L., ch1-1 (chlorophyll b-less mutant), gi-1 (GI deficient mutant), cry2-1 (blue-light-photoreceptor CRY2 deficient mutant), and Columbia (Col; wild ecotype) were grown under broad range of irradiances (I) from the beginning of germination and the effect of I on the survival, development, and flowering was studied. Under low and moderate I (<300 μmol m−2 s−1), flowering time and plant size at flowering showed great variations among ch1-1, gi-1, cry2-1, and Col, whereas under higher I (>500 μmol m−2 s−1), these characteristics were almost the same. Hence under high I, development and flowering of ch1-1, gi-1, cry2-1, and Col converged to almost the same state. Flowering time was negatively correlated with I, and under high I acclimation in A. thaliana was associated with a decrease in chlorophyll (Chl) content and increases in xanthophyll cycle pool and membrane-bound APX
activity (EC 1.11.1.11) suggesting that an increase in oxidative stress induces earlier flowering. The plants of gi-1 and cry2-1 survived but Col and ch1-1 died under 1 000 μmol m−2 s−1, showing that mutants deficient in GI or CRY2 are more photo-stress-tolerant than Col and the Chl b-less mutant. Hence high I promotes in plants of Arabidopsis raised from germination till flowering the development and flowering time involving modulation of the photosynthetic apparatus,
and this promoting effect is independent of the functions of flower-inducing GI or CRY2 gene. This can be regarded as photo-acclimation of A. thaliana for survival and reproduction under high I. 相似文献
12.
B. L. Lad S. Jayasankar F. Pliego-Alfaro P. A. Moon R. E. Litz 《In vitro cellular & developmental biology. Plant》1997,33(4):253-257
Summary Embryogenic nucellar cultures were established on B5 major salts, MS minor salts and organics, 400 mg/l−1 glutamine, 60 g/l−1 sucrose, 2 g/l−1 gellan gum, and 4.5 μM 2,4-dichlorophenoxyacetic acid (2,4-D). There was no clear relationship between developmental age of the nucellar explants
and induction of embryogenic cultures. The temporal requirements for culture initiation and for induction of embryogenic competence
from nucellar explants were determined by pulsing the cultures for 0, 7, 14, 21, 28, 35, 42, 49, 56, and 63 d. Culture initiation
required a minimum 7–14 d pulse with 2,4-D, and was maximum after a 56-d pulse; however, embryogenic competence was optimum
after a minimum of 28 d exposure to 2,4-D. Somatic embryogenesis occurred directly from the nucellar explants at low frequencies.
Somatic embryo maturation only occurred following plating of suspensions onto semisolid medium, and was stimulated by 2.4–4.8
μM kinetin and 4.4 μM 6-benzyladenine. 相似文献
13.
The effects of different spectral region of excitation and detection of chlorophyll (Chl) a fluorescence at room temperature on the estimation of excitation energy utilization within photosystem (PS) 2 were studied
in wild-type barley (Hordeum vulgare L. cv. Bonus) and its Chl b-less mutant chlorina f2 grown under low and high irradiances [100 and 1 000 μmol(photon) m−2 s−1]. Three measuring spectral regimes were applied using a PAM 101 fluorometer: (1) excitation in the red region (maximum at the wavelength of 649 nm) and detection in the far-red region beyond 710 nm, (2) excitation in the blue region (maximum at the wavelength of 461 nm) and detection beyond 710 nm, and (3) excitation in the blue region and detection in the red region (660– 710 nm). Non-photochemical quenching of maximal (NPQ)
and minimal fluorescence (SV0), determined by detecting Chl a fluorescence beyond 710 nm, were significantly higher for blue excitation as compared to red excitation. We suggest that
this results from higher non-radiative dissipation of absorbed excitation energy within light-harvesting complexes of PS2
(LHC2) due to preferential excitation of LHC2 by blue radiation and from the lower contribution of PS1 emission to the detected
fluorescence in the case of blue excitation. Detection of Chl a fluorescence originating preferentially from PS2 (i.e. in the range of 660–710 nm) led to pronounced increase of NPQ, SV0, and the PS2 photochemical efficiencies (FV/FM and FV′/FM′), indicating considerable underestimation of these parameters using the standard set-up of PAM 101. Hence PS1 contribution to the minimal fluorescence level in the irradiance-adapted state may reach up to about 80 %. 相似文献
14.
Seasonal reproduction in some Arctic Laminariales coincides with increased UV-B radiation due to stratospheric ozone depletion and relatively high water temperatures during polar spring. To find out the capacity to cope with different spectral irradiance, the kinetics of photosynthetic recovery was investigated in zoospores of four Arctic species of the order Laminariales, the kelps Saccorhiza dermatodea, Alaria esculenta, Laminaria digitata, and Laminaria saccharina. The physiology of light harvesting, changes in photosynthetic efficiency and kinetics of photosynthetic recovery were measured by in vivo fluorescence changes of Photosystem II (PSII). Saturation irradiance of freshly released spores showed minimal I
k
values (photon fluence rate where initial slope intersects horizontal asymptote of the curve) values ranging from 13 to 18 μmol photons m−2 s−1 among species collected at different depths, confirming that spores are low-light adapted. Exposure to different radiation spectra consisting of photosynthetically active radiation (PAR; 400–700 nm), PAR+UV-A radiation (UV-A; 320–400 nm), and PAR+ UV-A+UV-B radiation (UV-B; 280–320 nm) showed that the cumulative effects of increasing PAR fluence and the additional effect of UV-A and UV-B radiations on photoinhibition of photosynthesis are species specific. After long exposures, Laminaria saccharina was more sensitive to the different light treatments than the other three species investigated. Kinetics of recovery in zoospores showed a fast phase in S. dermatodea, which indicates a reduction of the photoprotective process while a slow phase in L. saccharina indicates recovery from severe photodamage. This first attempt to study photoinhibition and kinetics of recovery in zoospores showed that zoospores are the stage in the life history of seaweeds most susceptible to light stress and that ultraviolet radiation (UVR) effectively delays photosynthetic recovery. The viability of spores is important on the recruitment of the gametophytic and sporophytic life stages. The impact of UVR on the zoospores is related to the vertical depth distribution of the large sporophytes in the field. 相似文献
15.
Juan Luis Gómez-Pinchetti Ziyadin Ramazanov Agustín Fontes Guillermo García-Reina 《Journal of applied phycology》1992,4(1):11-15
Photosynthetic characteristics of Dunaliella salina with high (red form) and low β-carotene (green form) concentrations were studied. D. salina growing in brine saltworks exhibited a high level of β-carotene (15 pg cell−1). The rate of oxygen evolution as a function of irradiance was higher in the red than in the green form (on chlorophyll basis).
Photosynthetic inhibition of the green form was observed above 500 μmol m−2 s−1. The red form appeared more resistant to high irradiance and no inhibition in O2 evolution was observed up 2000 μmol m−2 s−1. However, when these results are expressed on a cell number basis the rate of oxygen evolution was significantly higher in
the green form.
Carbonic anhydrase (CA) activity (total, soluble, membrane bound) was found in red and green forms. CA was higher in the red
form on a chlorophyll basis, but lower if expressed on a protein basis. The light dependent rate of oxygen evolution and photoinhibition
depends on the concentration of β-carotene in D. salina cells. 相似文献
16.
Structural and grazing responses of zooplankton community to biomanipulation of some Dutch water bodies 总被引:9,自引:9,他引:0
Structure and grazing activities of crustacean zooplankton were compared in five lakes undergoing manipulation with several
unmanipulated eutrophic (shallow) and mesotrophic (deep) lakes in The Netherlands. The biomanipulated lakes had lesser number
of species and their abundance, both of rotifers and crustaceans, and had much larger mean animal size (3–11 μg C ind.−1) than in the unmanipulated eutrophic lakes (0.65 μG C ind.−1). WhereasD. hyalina (=D. galeata) andD. cucullata generally co-occurred in the unmanipulated lakes, in the manipulated lakes bothD. hyalina and other large-bodied daphnids,D. magna,D. pulex (=D. pulicaria), were the important grazers. In the biomanipulated lakes an increase in the individual crustacean size and of zooplankton
mass were reflected in a decrease in seston concentration, higher Secchi-disc depth and a marked decrease in the share in
phytoplankton biovolume of cyanobacteria. Biomass relationship between seston (150 μm) and zooplankton indicated a Monod type
relationship, with an initial part of the curve in which the zooplankton responds linearly to the seston increase up to aboutca. 2 mg C l−1, followed by a saturation of zooplankton mass (0.39 mg C l−1) at 3–4 mg C l−1 seston, and an inhibitory effect on zooplankton mass at seston levels>4 mg C l−1. This latter is related to predominance in the seston of cyanobacteria.
In the biomanipulated lakes, the zooplankton grazing rates often exceeded 100% d−1, during the spring, and food levels generally dropped to <0.5 mg C l−1. The computed specific clearance rate (SCR) of zooplankton of 1.9 l mg−1 Zoop C is well within the range of SCR values (1.7–2.2 l mg−1 Zoop C) from deep and mesotrophic waters, but about an order of magnitude higher than in the eutrophic lakes, with the food
levels 10-fold higher. For 25% d−1 clearance of lake seston between 35 and 60 ind. l−1 are needed in the biomanipulated lakes against 1200–1300 ind. l−1 in eutrophic lakes. Similarly, about 10 to 15 times more crustacean grazers are required to eliminate the daily primary production
in the eutrophic lakes than in the biomanipulated lakes. These numbers are inversely related to the differences in animal
size. The corresponding biomass values of zooplankton needed to clear the daily primary production in the eutrophic waters
were 0.1–0.2 mg C l−1 in the biomanipulated lakes, but about 0.45 mg C l−1 in the unmanipulated eutrophic waters.
Only if the water was kept persistently clear by zooplankton was there a balanced seston budget between the inputvia primary production and elimination by zooplankton. Mostly, however, the input exceeded the assimilatory removal by zooplankton,
such that the estimated seston loss could be attributed to sedimentation and mineralization. 相似文献
17.
P. Serrano-Ortiz A. S. Kowalski F. Domingo A. Rey E. Pegoraro L. Villagarcía L. Alados-Arboledas 《Photosynthetica》2007,45(1):30-35
Carbon and water fluxes in a semiarid shrubland ecosystem located in the southeast of Spain (province of Almería) were measured
continuously over one year using the eddy covariance technique. We examined the influence of environmental variables on daytime
(photosynthetically active photons, F
P >10 μmol m−2 s−1) ecosystem gas exchange and tested the ability of an empirical eco-physiological model based on F
P to estimate carbon fluxes over the whole year. The daytime ecosystem fluxes showed strong seasonality. During two solstitial
periods, summer with warm temperatures (>15 °C) and sufficient soil moisture (>10 % vol.) and winter with mild temperatures
(>5 °C) and high soil moisture contents (>15 % vol.), the photosynthetic rate was higher than the daytime respiration rate
and mean daytime CO2 fluxes were ca. −1.75 and −0.60 μmol m−2 s−1, respectively. Daytime evapotranspiration fluxes averaged ca. 2.20 and 0.24 mmol m−2 s−1, respectively. By contrast, in summer and early autumn with warm daytime temperatures (>10 °C) and dry soil (<10 % vol.),
and also in mid-winter with near-freezing daytime temperatures the shrubland behaved as a net carbon source (mean daytime
CO2 release of ca. 0.60 and 0.20 μmol m−2 s−1, respectively). Furthermore, the comparison of water and carbon fluxes over a week in June 2004 and June 2005 suggests that
the timing—rather than amount—of spring rainfall may be crucial in determining growing season water and carbon exchange. Due
to strongly limiting environmental variables other than F
P, the model applied here failed to describe daytime carbon exchange only as a function of F
P and could not be used over most of the year to fill gaps in the data. 相似文献
18.
Paul G. Braunschweiger Vathsala S. Basrur Dayna Cameron Laura Sharpe Octavio Santos James P. Perras Bernd-Uwe Sevin Arnold M. Markoe 《Biotherapy》1997,10(2):129-137
The modulation of cisPlatin cytotoxicity by interleukin-1 (IL-1α) was studied in cultures of SCC-7 tumor cells with and without
tumor macrophages to examine potential mechanisms for the synergistic antitumor activity of cisPlatin and IL-1α in SCC-7 solid
tumors. Neither IL-1α nor tumor macrophages affected the survival of clonogenic tumor cells and IL-1α had no direct effect
on tumor cell growthin vitro. Macrophages had no direct effect on cisPlatin sensitivity (IC90=6.0 μM), but, the addition of IL-1α (500–2000U/ml) to co-cultures of cisPlatin pretreated tumor cells and resident tumor
macrophages increased cell killing (IC90=3.1 μM). Similar responses were seen in primary cultures treated with cisPlatin before IL-1α. The modulation of cisPlatin
cytotoxicity by IL-1α exhibited a biphasic dose response that paralleled the IL-1α dose dependent release of H2O2by resident tumor macrophages. Further, IL-1α modification of cisPlatin cytotoxicity was prompt and inhibited by catalase.
CisPlatin and exogenous H2O2 (50 μM) produced more than additive SCC-7 clonogenic cell kill and hydroxyl radicals played an important role in the response.
Interleukin-1 modulation of cisPlatin cytotoxicity was schedule dependent. IL-1α treatment for 24 hrs, before cisPlatin, produced
drug resistance (IC90=11.1 μM). Our study shows that IL-1α can stimulate tumor macrophages to release pro-oxidants that modify cellular chemosensitivity
in a schedule and dose dependent fashion. Our findings may also provide a mechanistic explanation for the synergistic antitumor
activity of cisPlatin and IL-1αin vivo. 相似文献
19.
We compared the CO2- and light-dependence of photosynthesis of four tree species (Acer rubrum, Carya glabra, Cercis canadensis, Liquidambar styraciflua) growing in the understory of a loblolly pine plantation under ambient or ambient plus 200 μl l–1 CO2. Naturally-established saplings were fumigated with a free-air CO2 enrichment system. Light-saturated photosynthetic rates were 159–190% greater for Ce. canadensis saplings grown and measured under elevated CO2. This species had the greatest CO2 stimulation of photosynthesis. Photosynthetic rates were only 59% greater for A. rubrum saplings under CO2 enrichment and Ca. glabra and L. styraciflua had intermediate responses. Elevated CO2 stimulated light-saturated photosynthesis more than the apparent quantum yield. The maximum rate of carboxylation of ribulose-1,5-bisphosphate
carboxylase, estimated from gas-exchange measurements, was not consistently affected by growth in elevated CO2. However, the maximum electron transport rate estimated from gas- exchange measurements and from chlorophyll fluorescence,
when averaged across species and dates, was approximately 10% higher for saplings in elevated CO2. The proportionately greater stimulation of light-saturated photosynthesis than the apparent quantum yield and elevated rates
of maximum electron transport suggests that saplings growing under elevated CO2 make more efficient use of sunflecks. The stimulation of light-saturated photosynthesis by CO2 did not appear to correlate with shade-tolerance ranking of the individual species. However, the species with the greatest
enhancement of photosynthesis, Ce. canadensis and L. styraciflua, also invested the greatest proportion of soluble protein in Rubisco. Environmental and endogenous factors affecting N partitioning
may partially explain interspecific variation in the photosynthetic response to elevated CO2.
Received: 16 February 1999 / Accepted: 30 August 1999 相似文献
20.
A. E. Zemlyakov V. N. Tsikalova L. R. Azizova V. Ya. Chirva E. L. Mulik M. V. Shkalev O. V. Kalyuzhin M. V. Kiselevsky 《Russian Journal of Bioorganic Chemistry》2008,34(2):223-229
Phenyl, p-tolyl, and p-tert-butylphenyl β-1-thio-N-acetylglucosaminides were synthesized by the treatment of thiophenols with peracetate of α-D-glucosaminyl chloride in the presence of triethylamine or under the conditions of phase-transfer catalysis with quaternary
ammonium salts. The compounds synthesized were used for obtaining of glycosides of 4,6-O-isopropylidene-N-acetylmuramic acid, which were coupled with L-Ala-D-Glu(NH2)-OBzl and then deprotected to obtain the target aryl β-thioglycosides of N-acetylmuramyl-L-analyl-D-isoglutamine (MDP). The aryl β-thioglycosides of MDP were found to stimulate an antibacterial resistance toward Staphylococcus aureus in mice. The reliable induction of the spontaneous activity of natural killers in the population of blood mononuclear cells
was observed only for phenyl β-thio-MDP at a dose of 200 μg/ml.
Original Russian Text ? A.E. Zemlyakov, V.N. Tsikalova, L.R. Azizova, V.Ya. Chirva, E.L. Mulik, M.V. Shkalev, O.V. Kalyuzhin,
M.V. Kiselevsky, 2008, published in Bioorganicheskaya Khimiya, 2008, Vol. 34, No. 2, pp. 245–251. 相似文献