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1.
The growth of the anaerobic acetogenic bacterium Acetobacterium woodii DSM 1030 was investigated in fructose-limited chemostat cultures. A defined medium was developed which contained fructose, mineral salts, cysteine · HCl and Ca pantothenate (1 mg · 1–1) supplied in a vitamin supplement. Growth at high dilution rates was dependent on the presence of CO2 in the gas phase. The
max was found to be 0.16 h–1 and the fructose maintenance requirement was 0.1 to 0.13 mmol fructose · (g dry wt)–1 · h–1. A growth yield of 61 g dry wt · (mol fructose)–1, corrected for the cell maintenance requirement and for incorporation of fructose carbon into cell biomass, was determined from the fructose consumption. A corresponding growth yield of 69 g dry wt · (mol fructose)–1 was calculated from the acetate production assuming that fructose fermentation was homoacetogenic. A YATP of 12.2 to 13.8 g dry wt · (mol ATP)–1 was calculated from these growth yields using a value of 5 mol ATP · (mol fructose)–1 as an estimate of the amount of ATP synthesised from fructose fermentation. The addition of yeast extract (0.5 g · 1–1) to the medium did not influence the
max or cell yield. After prolonged growth under fructose-limited conditions the requirement of the culture for CO2 in the gas phase was reduced.Abbreviations YE
yeast extract
- IC
inorganic carbon
- D
fermenter dilution rate : h–1
- MX
maintenance requirement for X: mmol X · (g dry wt)–1 · h–1
- X
may be fructose (Fruct), fructose consumed in energy metabolism (Fruct [E]), acetate (Ac)
- ATP
CO2, NH
inf4
sup+
or Pi
- qX
specific rate of utilisation or consumption of X: mmol X · (g dry wt)–1 · h–1
- V
fermenter volume: litre
- rC
· Cell, fermenter cell carbon production: mmol C · h–1
- YX
yield of cells on X: g dry wt · (mol X)–1
- Y
infx
supmax
the yield corrected for cell maintenance: g dry wt · (mol X)–1
- SATP
stoichiometry of ATP synthesis from fructose: mol ATP · (mol frucose)–1
- x
cell concentration: g dry wt · 1–1
-
specific growth rate : h–1
-
max
maximum specific growth rate: h–1 相似文献
2.
Exchange of CO2 and O2 and chlorophyll fluorescence were measured in the presence of 360 1 · 1–1 CO2 in nitrogen in Helianthus annuss L. leaves which had been preconditioned in the dark or at a photon flux density (PFD) of 24 mol · m–2 · s–1 either in 21 or 0% O2. An initial light-dependent O2 outburst of 6 mol · m–2 was measured after aerobic dark incubation. It was attributed to the reduction of electron carriers, predominantly plastoquinone. The maximum initial rate of O2 evolution at PFD 8000 mol · m–2 · s–1 was 170 mol · m–2 · s–2 or about four times the steady CO2-and light-saturated rate of photosynthesis. Fluorescence measurements showed that the rate was still acceptor-limited. Fast O2 evolution ceased after electron carriers were reduced in the dark-adapted leaf, but continued for a short time at the lower rate of 62 mol · m–2 · s–1 in the light-adapted leaf. The data are interpreted to show that enzymes involved in 3-phosphoglycerate reduction are dark-inhibited, but were fully active in low light. In a dark-adapted leaf, respiratory CO2 evolution continued under nitrogen; it was partially inhibited by illumination. Prolonged exposure of a leaf to anaerobic conditions caused reducing equivalents to accumulate. This was shown by a slowly increasing chlorophyll fluorescence yield which indicated the reduction of the PSII acceptor QA in the dark. When the leaf was illuminated, no O2 evolution was detected from short light pulses, although transient O2 production was appreciable during longer light pulses. This indicates that an electron donor (pool size about 2–3 e/PSII reaction center) became reduced in the dark and the first photons were used to oxidise this donor instead of water.Abbreviations Chl
chlorophyll
- CRC
carbon reduction cycle
- GAPDH
NADP-glyceraldehyde-phosphate dehydrogenase
- PFD
photon flux density
- PGA
3-phosphoglycerate
- RuBP
ribulose bisphosphate
- TCA
tricarboxylic acid cycle
To whom correspondence should be addressedThis work received support by the Estonian Academy of Sciences, the Gottfried-Wilhelm-Leibniz Program of the Deutsche For-schungsgemeinschaft and the Sonderforschungsbereich 251 of the University of Würzburg. 相似文献
3.
Acid and alkaline phosphatase activities were evaluated using batch fermenter cultues ofPenicillium citrinum, an organism used in studies of fungal functioning in soil. Fungal activity was assessed by monitoring rates of O2 utilization, glucose utilization, dry weight changes over time, and lengths of FDA-stained hyphae. At low growth rates (7 g dry wt increases·h–1·ml–1) and low culture activity, phosphatase activity at both pH 8.5 and 5.5 tended to decrease with culture age, with the exception that phosphatase activity at pH 8.5 peaked during early stationary phase. At higher growth rates (25 g dry wt increase·h–1·ml–1) and high culture activity, phosphatase activity tended to remain constant throughout the course of the experiment. The relationship between phosphatase activity and other measures of fungal activity was consistent only at low growth rates for acid phosphatase. These results suggest that phosphatase measurements will be of limited utility in assessing activity, except at low growth rates. 相似文献
4.
A technique has been developed for the enzymatic isolation of leaf cells from the Crassulacean acid-metabolism plant Sedum telephium. The cells exhibited high activity in both 14CO2 incorporation (30–70 mol CO2 mg-1 chlorophyll h-1) and O2 evolution in the presence of bicarbonate (60–110 mol O2 mg-1 chlorophyll h-1). Half-maximum saturation of 14CO2 incorporation occurred at a bicarbonate concentration of ca. 2 mM (20 M CO2) at pH 8.4 and 30°C. Two types of light-dependent O2 evolution are reported: O2 evolution in the absence of exogenously supplied bicarbonate (endogenous O2 evolution), and bicarbonate-stimulated O2 evolution. Oxygen evolution in the presence of approximately ambient concentrations of CO2 appeared to be a combination of the endogenous O2 evolution and O2 evolution from fixation of the exogenously supplied CO2.Abbreviations CAM
Crassulacean acid metabolism
- cirlo
chlorophyll
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- PEP
phosphoenolpyruvate
- RuDP
ribulose-1,5-diphosphate 相似文献
5.
The effects of medium strategies [maintenance (M), intermediary (G), and production (P) medium] on cell growth, anthraquinone (AQ) production, hydrogen peroxide (H2O2) level, lipid peroxidation, and antioxidant vitamins in Morinda elliptica cell suspension cultures were investigated. These were compared with third-stage leaf and 1-month-old callus culture. With P medium strategy, cell growth at 49 g l–1, intracellular AQ content at 42 mg g–1 DW, and H2O2 level at 9 mol g–1 FW medium were the highest as compared to the others. However, the extent of lipid peroxidation at 40.4 nmol g–1 FW and total carotenoids at 13.3 mg g–1 FW for cultures in P medium were comparable to that in the leaf, which had registered sevenfold lower AQ and 2.2-fold lower H2O2 levels. Vitamin C content at 30–120 g g–1 FW in all culture systems was almost half the leaf content. On the other hand, vitamin E content was around 400–500 g g–1 FW in 7-day-old cultures from all medium strategies and reduced to 50–150 g g–1 FW on day 14 and 21; as compared to 60 g g–1 FW in callus and 200 g g–1 FW in the leaf. This study suggests that medium strategies and cell growth phase in cell culture could influence the competition between primary and secondary metabolism, oxidative stresses and antioxidative measures. When compared with the leaf metabolism, these activities are dynamic depending on the types and availability of antioxidants.Abbreviations AQ Anthraquinone - DW Dry cell weight - FW Fresh cell weight - G Intermediary medium - M Maintenance medium - MDA Malondialdehyde - P Production medium - ROS Reactive oxygen species - TBA Thiobarbituric acid - td Doubling time 相似文献
6.
Nitrogen fixation was measured in four subarctic streams substantially modified by beaver (Castor canadensis) in Quebec. Acetylene-ethylene (C2H2 C2H4) reduction techniques were used during the 1982 ice-free period (May–October) to estimate nitrogen fixation by microorganisms colonizing wood and sediment. Mean seasonal fixation rates were low and patchy, ranging from zero to 2.3 × 10–3 µmol C2H4 · cm–2 · h–1 for wood, and from zero to 7.0 × 10–3 µmol C2H4 · g AFDM–1 · h–1 for sediment; 77% of all wood and 63% of all sediment measurements showed no C2H2 reduction. Nonparametric statistical tests were unable to show a significant difference (p > 0.05) in C2H2 reduction rates between or within sites for wood species or by sediment depth.Nitrogen contributed by microorganisms colonizing wood in riffles of beaver influenced watersheds was small (e.g., 0.207 g N · m–2 · y–1) but greater than that for wood in beaver ponds (e.g., 0.008 g N · m–2 · y–1) or for streams without beaver (e.g., 0.003 g N · m–2 · y–1). Although mass specific nitrogen fixation rates did not change significantly as beaver transform riffles into ponds, the nitrogen fixed by organisms colonizing sediment in pond areas (e.g., 5.1 g N · m–2 · y–1) was greater than that in riffles (e.g., 0.42 g N · m–2 · y–1). The annual nitrogen contribution is proportional to the amount of sediment available for microbial colonization. We estimate that total nitrogen accumulation in sediment, per unit area, is enhanced 9 to 44 fold by beaver damming a section of stream. 相似文献
7.
Augmentation of H2 photoproduction in Rhodopseudomonas palustris by N-heterocyclic aromatic compounds 总被引:1,自引:0,他引:1
Increases of 23- (5.6 mmol acetylene reduced mg dry wt–1) and 16- (4 mmol acetylene reduced mg dry wt–1) fold in nitrogenase activity and 12- (671 l H2 mg dry wt–1 h–1) and 6- (349 l mg dry wt–1 h–1) fold in H2 photoproduction in Rhodopseudomonas palustris JA1 over 24 h were achieved with pyrazine 2-carboxylate (3 mM) and 3-picoline (3 mM), respectively, and were higher than earlier reports of enhancement (1.5 to 5- fold) in biological H2 production using various alternative methods. 相似文献
8.
Sylvie Ferrario Marie-Hélène Valadier Jean-François Morot-Gaudry Christine H. Foyer 《Planta》1995,196(2):288-294
Transformed Nicotiana plumbaginifolia plants with constitutive expression of nitrate reductase (NR) activity were grown at different levels of nitrogen nutrition. The gradients in foliar NO
3
–
content and maximum extractable NR activity observed with leaf order on the shoot, from base to apex, were much decreased as a result of N-deficiency in both the transformed plants and wild type controls grown under identical conditions. Constitutive expression of NR did not influence the foliar protein and chlorophyll contents under any circumstances. A reciprocal relationship between the observed maximal extractable NR activity of the leaves and their NO
3
–
content was observed in plants grown in nitrogen replete conditions at low irradiance (170 mol photons·m–2 ·s–1). This relationship disappeared at higher irradiance (450 mol photons·m–2·S–1) because the maximal extractable NR activity in the leaves of the wild type plants in these conditions increased to a level that was similar to, or greater than that found in constitutive NR-expressors. Much more NO
3
–
accumulated in the leaves of plants grown at 450 mol photons·m–2·s–1 than in those grown at 170 mol photons·m–2·s–1 in N-replete conditions. The foliar NO
3
–
level and maximal NR activity decreased with the imposition of N-deficiency in all plant types such that after prolonged exposure to nitrogen depletion very little NO
3
–
was found in the leaves and NR activity had decreased to almost zero. The activity of NR decreased under conditions of nitrogen deficiency. This regulation is multifactoral since there is no regulation of NR gene expression by NO
3
–
in the constitutive NR-expressors. We conclude that the NR protein is specifically targetted for destruction under nitrogen deficiency. Consequently, constitutive expression of NR activity does not benefit the plant in terms of increased biomass production in conditions of limiting nitrogen.Abbreviations Chl
chlorophyll
- N
nitrogen
- NR
NADH-nitrate reductase
- WT
wild type 相似文献
9.
P. Pärt C. M. Wood 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(1):37-45
Using primary cultures of gill pavement cells from freshwater rainbow trout, a method is described for achieving confluent monolayers of the cells on glass coverslips. A continuous record of intracellular pH was obtained by loading the cells with the pH-sensitive flourescent dye 2,7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein and mounting the coverslips in the flowthrough cuvette of a spectrofluorimeter. Experiments were performed in HEPES-buffered media nominally free of HCO3. Resting intracellular pH (7.43 at extracellular pH=7.70) was insensitive to the removal of Cl– or the application of 4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l–1), but fell by about 0.3 units when Na+ was removed or in the presence of amiloride (0.2 mmol·l–1). Exposure to elevated ammonia (ammonia prepulse; 30 mmol·l–1 as NH4Cl for 6–9 min) produced an increase in intracellular pH (to about 8.1) followed by a slow decay, and washout of the pulse caused intracellular pH to fall to about 6.5. Intracellular non-HCO
3
–
buffer capacity was about 13.4 slykes. Rapid recovery of intracellular pH from intracellular acidosis induced by ammonia prepulse was inhibited more than 80% in Na+-free conditions or in the presence of amiloride (0.2 mmol·l–1). Neither bafilomycin A1 (3 mol·l–1) nor Cl removal altered the intracellular pH recovery rate. The K
m for Na+ of the intracellular pH recovery mechanism was 8.3 mmol·l–1, and the rate constant at V
max was 0.008·s–1 (equivalent to 5.60 mmol H+·l–1 cell water·min–1), which was achieved at external Na+ levels from 25 to 140 mmol·l–1. We conclude that intracellular pH in cultured gill pavement cells in HEPES-buffered, HCO
3
–
-free media, both at rest and during acidosis, is regulated by a Na+/H+ antiport and not by anion-dependent mechanisms or a vacuolar H+-ATPase.Abbreviations
BCECF
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein
-
BCECF/AM
2,7-bis(2-carboxyethyl)-5(6)-carboxy-fluorescein, acetoxymethylester
-
Cholin-Cl
choline chloride
-
DMSO
dimethyl sulfoxide
-
EDTA
ethylene diamine tetra-acetic acid
-
FBS
foetal bovine serum
-
H
+
-ATPase
Proton-dependent adenosine triphosphatase
-
HEPES
N-[2-hydroxyethyl]piperazine-N[2-ethanesulfonic acid]
-
pH
i
intracellular pH
-
pH
e
extracellular pH
-
PBS
phosphate-buffered saline
-
SITS
4-acetamido-4-isothiocyanatostilbene-2,2-disulfonic acid 相似文献
10.
Rodriguez Maria E. Hozbor Daniela F. Samo Analia L. Ertola Rodolfo Yantorno Osvaldo M. 《Journal of industrial microbiology & biotechnology》1994,13(5):273-278
Summary The kinetics ofBordetella pertussis growth was studied in a glutamate-limited continuous culture. Growth kinetics corresponded to Monod's model. The saturation constant and maximum specific growth rate were estimated as well as the energetic parameters, theoretical yield of cells and maintenance coefficient. Release of pertussis toxin (PT) and lipopolysaccharide (LPS) were growth-associated. In addition, they showed a linear relationship between them. Growth rate affected neither outer membrane proteins nor the cell-bound LPS pattern.Nomenclature X
cell concentration (g L–1)
-
specific growth rate (h–1)
- m
maximum specific growth rate (h–1)
- D
dilution rate (h–1)
- S
concentration of growth rate-limiting nutrient (glutamate) (mmol L–1 or g L–1)
- Ks
substrate saturation constant (mol L–1)
- ms
maintenance coefficient (g g–1 h–1)
- Yx/s
theoretical yield of cells from glutamate (g g–1)
- Yx/s
yield of cells from glutamate (g g–1)
- YPT/s
yield of soluble PT from glutamate (mg g–1)
- YKDO/s
yield of cell-free KDO from glutamate (g g–1)
- YPT/x
specific yield of soluble PT (mg g–1)
- YKDO/x
specific yield of cell-free KDO (g g–1)
- qPT
specific soluble PT production rate (mg g–1 h–1)
- qKDO
specific cell-free KDO production rate (g g–1 h–1) 相似文献
11.
Randall M. Jones M. Renuka Prasad Dipak K. Das 《Molecular and cellular biochemistry》1990,98(1-2):161-166
Summary In this study, we examined the effects of exposure of heart fatty acid-binding protein (h-FABP) to chemically generated O2
– or OH · with respect to its oleate binding and to its electrophoretic properties. Purified rat h-FABP at 40 M scavenged as much as 30% O2
– and 85% OH ·. On the other hand, when 2 nmol (4 M) FABP were exposed to free radicals, the maximum oleate binding capacity as measured by Scatchard analysis was reduced only by 14% and 27% for O2
– and OH ·, respectively. The electrophoretic pattern of free radical-exposed FABP was not markedly different when examined either by the non-denaturing or by denaturing PAGE, suggesting the absence of any degradation or aggregation of FABP by O2
– or OH ·. It is hypothesized that O2
– or OH · in physiological concentration may not alter the function of FABP markedly in the ischemic-reperfused myocardium.Abbreviations h-FABP
Heart Fatty Acid Binding Protein
- NEFA
Non-Esterified Fatty Acids
- O2
–
Superoxide anions
- OH·
hydroxyl radicals
- OCI
hypohalite radicals
- H2O2
hydrogen peroxide
- HPLC
High Pressure Liquid Chromatography 相似文献
12.
M. Lauerer D. Saftic W. P. Quick C. Labate K. Fichtner E. -D. Schulze S. R. Rodermel L. Bogorad M. Stitt 《Planta》1993,190(3):332-345
Tobacco (Nicotiana tabacum L.) plants transformed with antisense rbcS to decrease the expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) have been used to investigate the contribution of Rubisco to the control of photosynthesis in plants growing at different irradiances. Tobacco plants were grown in controlled-climate chambers under ambient CO2 at 20°C at 100, 300 and 750 mol·m–2·s–1 irradiance, and at 28°C at 100, 300 and 1000 mol·m–2·s–1 irradiance. (i) Measurement of photosynthesis under ambient conditions showed that the flux control coefficient of Rubisco (C
infRubisco
supA
) was very low (0.01–0.03) at low growth irradiance, and still fairly low (0.24–0.27) at higher irradiance. (ii) Short-term changes in the irradiance used to measure photosynthesis showed that C
infRubisco
supA
increases as incident irradiance rises, (iii) When low-light (100 mol·m–2·s–1)-grown plants are exposed to high (750–1000 mol·m–2·s–1) irradiance, Rubisco is almost totally limiting for photosynthesis in wild types. However, when high-light-grown leaves (750–1000 mol·m–2·s–1) are suddenly exposed to high and saturating irradiance (1500–2000 mol·m–2·s–1), C
infRubisco
supA
remained relatively low (0.23–0.33), showing that in saturating light Rubisco only exerts partial control over the light-saturated rate of photosynthesis in sun leaves; apparently additional factors are co-limiting photosynthetic performance, (iv) Growth of plants at high irradiance led to a small decrease in the percentage of total protein found in the insoluble (thylakoid fraction), and a decrease of chlorophyll, relative to protein or structural leaf dry weight. As a consequence of this change, high-irradiance-grown leaves illuminated at growth irradiance avoided an inbalance between the light reactions and Rubisco; this was shown by the low value of C
infRubisco
supA
(see above) and by measurements showing that non-photochemical quenching was low, photochemical quenching high, and NADP-malate dehydrogenase activation was low at the growth irradiance. In contrast, when a leaf adapted to low irradiance was illuminated at a higher irradiance, Rubisco exerted more control, non-photochemical quenching was higher, photochemical quenching was lower, and NADP-malate dehydrogenase activation was higher than in a leaf which had grown at that irradiance. We conclude that changes in leaf composition allow the leaf to avoid a one-sided limitation by Rubisco and, hence, overexcitation and overreduction of the thylakoids in high-irradiance growth conditions, (v) Antisense plants with less Rubisco contained a higher content of insoluble (thylakoid) protein and chlorophyll, compared to total protein or structural leaf dry weight. They also showed a higher rate of photosynthesis than the wild type, when measured at an irradiance below that at which the plant had grown. We propose that N-allocation in low light is not optimal in tobacco and that genetic manipulation to decrease Rubisco may, in some circumstances, increase photosynthetic performance in low light.Abbreviations A
rate of photosynthesis
- C
infRubisco
supA
flux control coefficient of Rubisco for photosynthesis
- ci
internal CO2 concentration
- qE
energy-dependent quenching of chlorophyll fluorescense
- qQ
photochemical quenching of chlorophyll fluorescence
- NADP-MDH
NADP-dependent malate dehydrogenase
- Rubisco
ribulose-1,5-bisphosphate carboxylase-oxygenase
- RuBP
ribulose-1,5-bisphosphate
This work was supported by the Deutsche Forschungsgemeinschaft (SFB 137). 相似文献
13.
E. Molina Grima J. A. Sánchez Pérez F. Garcia Camacho J. L. Garcia Sánchez D. López Alonso 《Applied microbiology and biotechnology》1993,38(5):599-605
Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid productivities from chemostat cultures of an isolate of Isochrysis galbana have been studied. The productivities reached in the interval of dilution rates between 0.0295 h–1 and 0.0355 h–1 were 1.5mg·1–1·h–1 for lipids, 300 g·1–1·h–1 for EPA and 130g1·1–1·h–1 for DHA. Furthermore, light attenuation by mutual shading, and agitation speed influences on growth and fatty acid composition were analysed. A model relating steady-state dilution rates to internal average light intensity has been proposed, the parameter values of which obtained by non-linear regression were: maximum specific growth rate (max)=0.0426 h–1; the affinity of cells to light (Ik) = 10.92 W·m–2; the exponent (n) = 5.13; regression coefficient (r
2)=0.9999.
Correspondence to: E. Molina Grima 相似文献
14.
Leaves of Populus balsamifera grown under full natural sunlight were treated with 0, 1, or 2 l SO2·1-1 air under one of four different photon flux densities (PFD). When the SO2 exposures took place in darkness or at 300 mol photons·m-2·s-1, sulfate accumulated to the levels predicted by measurements of stomatal conductance during SO2 exposure. Under conditions of higher PFD (750 and 1550 mol·m-2·s-1), however, the predicted levels of accumulated sulfate were substantially higher than those obtained from anion chromatography of the leaf extracts. Light-and CO2-saturated capacity as well as the photon yield of photosynthetic O2 evolution were reduced with increasing concentration of SO2. At 2 l SO2·1-1 air, the greatest reductions in both photosynthetic, capacity and photon yield occurred when the leaves were exposed to SO2 in the dark, and increasingly smaller reductions in each occurred with increasing PFD during SO2 exposure. This indicates that the inhibition of photosynthesis resulting from SO2 exposure was reduced when the exposure occurred under conditions of higher light. The ratio F
v/F
M (variable/maximum fluorescence emission) for photosyntem II (PSII), a measure of the photochemical efficiency of PSII, remained unaffected by exposure of leaves to SO2 in the dark and exhibited only moderate reductions with increasing PFD during the exposure, indicating that PSII was not a primary site of damage by SO2. Pretreatment of leaves with SO2 in the dark, however, increased the susceptibility of PSII to photoinhibition, as such pretreated leaves exhibited much greater reductions inF
V/F
M when transferred to moderate or high light in air than comparable control leaves.Abbreviations and symbols A1200
photosynthetic capacity (CO2-saturated rate of O2 evolution at 1200 mol photons·m-2·s-1)
- Fo
instantaneous fluorescence emission
- FM
maximum fluorescence emission
- FV
variable fluorescence emission
- PFD
photon flux density (400–700 nm)
- PSII
photosystem II 相似文献
15.
W. S. Marshall S. E. Bryson J. S. Burghardt P. M. Verbost 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1995,165(4):268-277
We examined transepithelial transport of Ca2+ across the isolated opercular epithelium of the euryhaline killifish adapted to fresh water. The opercular epithelium, mounted in vitro with saline on the serosal side and fresh water (0.1 mmol·l–1 Ca2+) bathing the mucosal side, actively transported Ca2+ in the uptake direction; net flux averaged 20–30 nmol·cm–2·h–1. The rate of Ca2+ uptake varied linearly with the density of mitochondria-rich cells in the preparations. Ca2+ uptake was saturable, apparent K
1/2 of 0.348 mmol·l–1, indicative of a multistep transcellular pathway. Ca2+ uptake was inhibited partially by apically added 0.1 mmol·l–1 La3+ and 1.0 mmol·l–1 Mg2+. Addition of dibutyryl-cyclic adenosine monophosphate (0.5 mmol·l–1)+0.1 mmol·l–1 3-isobutyl-l-methylxanthine inhibited Ca2+ uptake by 54%, but epinephrine, clonidine and isoproterenol were without effect. Agents that increase intracellular Ca2+, thapsigargin (1.0 mol·l–1, serosal side), ionomycin (1.0 mol·l–1, serosal side) and the calmodulin blocker trifluoperazine (50 mol·l–1, mucosal side) all partially inhibited Ca2+ uptake. In contrast, apically added ionomycin increased mucosal to serosal unidirectional Ca2+ flux, indicating Ca2+ entry across the apical membrane is rate limiting in the transport. Verapamil (10–100 mol·l–1, mucosal side), a Ca2+ channel blocker, had no effect. Results are consistent with a model of Ca2+ uptake by mitochondria rich cells that involves passive Ca2+ entry across the apical membrane via verapamil-insensitive Ca2+ channels, intracellular complexing of Ca2+ by calmodulin and basolateral exit via an active transport process. Increases in intracellular Ca2+ invoke a downregulation of transcellular Ca2+ transport, implicating Ca2+ as a homeostatic mediator of its own transport.Abbreviations
DASPEI
2-(4-dimethylaminostyryl)-N-ethylpyridinium iodide
-
db-cAMP
dibutyryl-cyclic adenosine monophosphate
-
FW
fresh water
-
G
t
transepithelial conductance
-
I
sc
short-circuit current
-
IBMX
3-isobutyl-1-methylxanthine
-
SW
sea water
-
TFP
trifluoperazine
-
V
t
transepithelial potential 相似文献
16.
Summary Some environmental affects on cell aggregation described in the literature are briefly summarized. By means of a biomass recirculation culture (Contact system), using the yeast Torulopsis glabrata, the aggregation behavior of cells in static and in dynamic test systems is described. Sedimentation times required to obtain 50 g · l–1 yeast dry matter in static systems were always higher than in dynamic ones.In addition to, influencing the biomass yield, the specific growth rate of the yeast also affected cell aggregation. The specific growth rate and therefore the aggregation could be regulated by the biomass recirculation rate as well as by the sedimenter volume.Abbreviations fo
Overflow flow rate (l·h–1)
- fR
Recycle flow rate (l·h–1)
- ft0t
Total flow rate through the fermenter (l·h–1)
- g
Gram
- h
Hour
- DR
Fermenter dilution rate due to recycle (h–1)
- DS
Fermeter dilution rate due to substrate (h–1)
- Dtot
Total fermenter dilution rate (h–1)
- l
Liter
-
Specific growth rate (h–1)
- PF
Fermenter productivity (g·l–1·h–1)
- PFS
Overall productivity (g·l–1·h–1)
- RpM
Rates per minute
- RS
Residual sugar content in the effluent with respect to the substrate concentration (%)
- Y
Yield of biomass with respect to sugar concentration (%)
-
Sed 50
Sedimentation time to reach a YDM of 50 g·l–1 (min)
- V
Volume (l)
- VF
Fermenter volume (l)
- VSed
Sedimenter volume (l)
- VVM
Volumes per volume and minute
- XF
YDM in the fermenter (g·l–1)
- XF
YDM in the recycle (g·l–1)
- XS
Yeast dry matter due to substrate concentration (g·l–1)
- YDM
Yeast dry matter (g·l–1) 相似文献
17.
L. Oliveira 《Planta》1992,188(3):279-288
Germination of aplanospores in Vaucheria longicaulis Hoppaugh var. macounii Blum proceeds through three stages of development. Stage I begins with the initiation of germination and lasts approx. 2 h. During this stage germinating filaments grow at an accelerated rate (266 ± 12 m · h–1). Stage II is characterized by a sharp decline in the growth rate of germinating filaments (96 ± 4 m · h–1) and lasts 4 h. This is followed, during the next 4 h, by a recovery in the growth rate (168 ± 8 m · h–1) of germinating filaments, stage III. Growth rates stabilize and remain unchanged during subsequent development (Oliveira and Fitch, 1988, J. Submicrosc. Cytol. Pathol. 20, 397–406). The Ca2+-influx modulators LaCl3, nifedipine and methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4 (2-trifluoromethylphenyl)-pyridine-5-carboxylate (Bay K-8644), the ionophore calcimycin (A23187), the intracellular Ca2+-release antagonist 8-N-N'-(diethylamino)-octyl-3,4, 5-trimethoxybenzoate (TMB-8), the Ca2+-uptake inhibitor ruthenium red and the phosphoinositide-cycle modulators LiCl and myo-inositol show that the events required for the initiation are distinct from those required for the completion of each stage of germination. These studies in conjunction with microinjection of germinating filaments with inositol 1,4,5-trisphosphate, the natural ligand for Ca2+ release from Ca-storing organelles (endoplasmic reticulum, vacuole), and treatment with chlorotetracycline (CTC), to visualize the distribution of membrane-bound Ca2+ reveal that both the initiation and completion of each stage of germination are controlled by Ca2+ signals which are restricted to well-defined time intervals and are modulated by the origin (source) of Ca2+.Abbreviations BAPTA
1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid
- Bay K-8644
methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4(2-trifluoromethylphenyl)-pyridine-5-carboxylate
- CTC
chlorotetracycline
- InsP3
inositol 1,4,5-trisphosphate
- RR
ruthenium red
- TMB-8
8-N-N-(diethylamino)-octyl-3,4,5-trimethoxybenzoate
The author wishes to express his gratitude to the technical group of the Immunocytochemistry Unit for their help with the microinjection studies. This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada (grant A-7844). 相似文献
18.
Summary The in vivo induction of H2O2 production was tested on tobacco cell suspension cultures (Nicotiana tabacum cv. Bright Yellow-2). The measurement of H2O2 was based on the oxidation of 3,5-dichloro-2-hydroxybenzensulfonic acid by endogenous peroxidases and spectrophotometric detection after reaction with 4-aminoanti-pyrine. The phosphatase inhibitor cantharidin induced a transient increase in H2O2 synthesis. The timing of the H2O2 production, the level of induction by cantharidin and the background H2O2 production were dependent on the tobacco cell concentration used. A concentration curve of cantharidin revealed saturating kinetics for the H2O2 detection (E50=46 to 70 M, Emax=101 to 128 mol/h·g fresh weight). An inhibitor study with the tobacco BY-2 cells showed high inhibitions of the H2O2 induction with the flavin analogues diphenylene iodonium (I50=1.26M) and acridine orange and with membrane-permeative thiol reagents (N-ethyl maleimide, N-pyrene maleimide, iodoacetate); whereas the nonpermeative thiol reagentp-chloromercuribenzoic acid was ineffective. Therefore, the induction of H2O2 production with phosphatase inhibitors (cantharidin) showed comparable properties to the elicitor-induced oxidative-burst response in other plant cells.Abbreviations AcOr
acridine orange
- AOS
active-oxygen species
- BY-2
Bright Yellow-2
- pCMBS
p-chloromercuribenzoic acid
- DHBS
3,5-dichloro-2-hydroxybenzenesulfonic acid
- DMSO
dimethylsulfoxide
- DPI
diphenylene iodonium
- EtOH
ethanol
- H2O2
hydrogen peroxide
- HRP
horseradish peroxidase
- MS
Murashige and Skoog
- NEM
N-ethyl maleimide
- NPM
N-pyrene maleimide
- O
2
–
superoxide
- SOD
superoxide dismutase 相似文献
19.
In C4 grasses belonging to the NADP-malic enzyme-type subgroup, malate is considered to be the predominant C4 acid metabolized during C4 photosynthesis, and the bundle sheath cell chloroplasts contain very little photosystem-II (PSII) activity. The present studies showed that Flaveria bidentis (L.), an NADP-malic enzyme-type C4 dicotyledon, had substantial PSII activity in bundle sheath cells and that malate and aspartate apparently contributed about equally to the transfer of CO2 to bundle sheath cells. Preparations of bundle sheath cells and chloroplasts isolated from these cells evolved O2 at rates between 1.5 and 2 mol · min–1 · mg–1 chlorophyll (Chl) in the light in response to adding either 3-phosphoglycerate plus HCO
3
–
or aspartate plus 2-oxoglutarate. Rates of more than 2 mol O2 · min–1 · mg–1 Chl were recorded for cells provided with both sets of these substrates. With bundle sheath cell preparations the maximum rates of light-dependent CO2 fixation and malate decarboxylation to pyruvate recorded were about 1.7 mol · min–1 · mg–1 Chl. Compared with NADP-malic enzyme-type grass species, F. bidentis bundle sheath cells contained much higher activities of NADP-malate dehydrogenase and of aspartate and alanine aminotransferases. Time-course and pulse-chase studies following the kinetics of radiolabelling of the C-4 carboxyl of C4 acids from 14CO2 indicated that the photosynthetically active pool of malate was about twice the size of the aspartate pool. However, there was strong evidence for a rapid flux of carbon through both these pools. Possible routes of aspartate metabolism and the relationship between this metabolism and PSII activity in bundle sheath cells are considered.Abbreviations DHAP
dihydroxyacetone phosphate
- NADP-ME(-type)
NADP-malic enzyme (type)
- NADP-MDH
NADP-malate dehydrogenase
- OAA
oxaloacetic acid
- 2-OG
2-oxoglutarate
- PEP
phosphoenolpyruvate
- PGA
3-phosphoglycerate
- Pi
orthophosphate
- Ru5P
ribulose 5-phosphate 相似文献
20.
J. H. Becking 《Plant and Soil》1979,53(4):541-545
Summary Nitrogenase activity as assayed by acetylene reduction was observed in detachedRubus ellipticus J. E. Smith root nodules collected in the field and tested under ambient conditions. The nitrogenase activity was 8.4 moles C2H4.gfr. wt nodule–1.h–1 or 24.0 moles C2H4.g dry wt nodule–1.h–1 being at a rate comparable with that measured in some other non-legumes assayed in Java at the same time under similar conditions. Nodule morphology bore little resemblance to the root nodules of other non-leguminous plants and nodule structure was different from the other rosaceous examples.The endophyte inhabiting the root nodules was actinomycetal. 相似文献