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1.
Protoplasts were isolated from embryogenic suspension cultures derived from avocado (Persea americana Mill.) zygotic embryos and nucellus in an enzyme digestion solution consisting of 1% cellulase Onozuka RS, 1% Macerase R10,
0.2% Pectolyase Y-23, 0.7 M mannitol. 24.5 mM CaCl2, 0.92 mM NaH2PO4 and 6.25 2-[N-morpholino]ethanesulfonic acid (1.5 ml) mixed with 0.7 M MS–8P (2.5 ml). MS-8P medium consisted of Murashige and Skoog salts without NH4NO3, 1 mg l–1 thiamine HCl, 100 mg l–1 myo-inositol, 3.1 g l–1 glutamine and 8P organic addenda. Medium osmolarity was adjusted with 0.15 M sucrose and 0–0.55 M mannitol. Protoplast yields of 3.5×106 protoplasts g–1 were obtained. Growth and development of the protoplasts were significantly affected by osmolarity, nitrogen source, plating
density and culture medium dilution. Under optimum conditions, proembryos developed directly from embryogenic protoplasts
and subsequently into somatic embryos. Optimum conditions for somatic embryo development included the culture of protoplasts
at a density of 0.8–1.6×105 ml–1 in 0.4 M MS–8P for 2–3 weeks, followed by subculture in 0.15 M MS–8P at a diluted density of 20–40× for 1 month in darkness to obtain somatic embryos. Mature somatic embryos were recovered
on semisolid medium; however, a low frequency of plantlet recovery (≤1%) from protoplast-derived somatic embryos was observed.
Received: 9 February 1998 / Revision received: 4 May 1998 / Accepted: 15 May 1998 相似文献
2.
Uptake of inorganic ions and compatible solutes in cultured mangrove cells during salt stress 总被引:6,自引:0,他引:6
Eri Yasumoto Kyoko Adachi Misako Kato Hiroshi Sano Hamako Sasamoto Shigeyuki Baba Hiroshi Ashihara 《In vitro cellular & developmental biology. Plant》1999,35(1):82-85
Summary Callus of the mangrove plant, Sonneratia alba J. Smith, established from pistils of flower buds were cultured on solid Murashige and Skoog medium supplemented with 0 to
500 mM NaCl. Maximum growth was observed with 50 mM NaCl, and net growth of callus occurred for concentrations up to 200 mM NaCl. At 500 mM NaCl, growth of callus was completely inhibited, although a part of the tissue was still alive after 30 d. Cellular levels
of Na+ and Cl− were greatly increased by the treatment with NaCl. Uptake of K+ was also enhanced and was accompanied by increasing levels of Na+ and Cl− so that the Na+/K+ ratio was almost constant (4.1–4.2) in callus grown with 50–200 mM NaCl. Levels of Mg2+ and Ca2+ were not changed significantly with 50–200 mM NaCl, whereas levels of free NH
4
+
, NO
3
−
and SO
4
2−
ions, which are convertible to organic compounds, were lowest in callus grown with 50 mM NaCl. The rate of conversion of 15NH
4
+
into macromolecules during 30 d culture with 0–100 mM NaCl did not vary greatly, but 200 mM NaCl reduced the biosynthesis of macromolecules from this ion. The highest rate of conversion of 15NO
3
−
into macromolecules was observed at 50 mM NaCl. Identification of compatible solutes with NMR-spectroscopy indicated that mannitol is the compatible solute for intact
plants of Sonneratia alba, but no accumulation of mannitol was found in calluses, not even in those grown at high concentrations of NaCl. 相似文献
3.
Indirect evidence has suggested that lignin peroxidase (LiP) of the white-rot fungus Phanerochaete chrysosporium catalyses oxidative decolourisation and depolymerisation of macromolecules from brown coal in vivo. In this study we show
that LiP catalyses these transformations in vitro. Unmethylated (USC45 coal) and methylated (MWSC6 coal) fractions of solubilised
macromolecules (M
r > 30 000) from a brown coal were treated with a semi-purified preparation of LiP isozymes from P. chrysosporium. Both coal fractions were decolourised, losing between 26% and 39% of their absorbance at both 280 nm and 400 nm, in reactions
that had an absolute requirement for H2O2 and veratryl alcohol. Neither coal fraction was transformed when the enzyme was heat-inactivated or in the presence of the
LiP inhibitor metavanadate. Gel-permeation chromatography showed that MWSC6 coal but not USC45 was depolymerised and yielded
low-molecular-mass (M
r < 30 000) fragments. Nine monomeric products were identified by GC-MS.
Received: 20 March 1998 / Received revision: 3 September 1998 / Accepted: 3 September 1998 相似文献
4.
Sabria Defnoun Maurice Ambrosio Jean-Louis Garcia Alfred Traoré Marc Labat 《Current microbiology》2003,46(1):0047-0052
A syntrophic consortium was enriched in a basal medium containing cinnamate as the carbon and energy source. It was found
to consist of three morphologically distinct microbes, viz., a short, rod-shaped, non-motile bacterium with distinctly pointed
ends, Papillibacter cinnamivorans; a rod-shaped, motile bacterium with rounded ends, Syntrophus sp.; and a methanoarchaeon, Methanobacterium sp. This methanogen was then replaced by a collection strain of Methanobacterium formicicum. A syntrophic interdependency of the three partners of the consortium was observed during growth on cinnamate. In the presence
of bromoethanesulfonic acid (BESA), cinnamate was transformed to benzoate, whereas under methanogenic conditions without BESA,
cinnamate was first transformed to benzoate via β-oxidation and subsequently completely degraded into acetate, CH4, and CO2. Papillibacter cinnamivorans was responsible for benzoate production from cinnamate, whereas a syntrophic association between Syntrophus sp. and the methanogen degraded benzoate to acetate, CH4, and CO2. A new anaerobic degradation pathway of cinnamate into benzoate via β-oxidation by a pure culture of P. cinnamivorans is proposed.
Received: 27 December 2001 / Accepted: 28 March 2002 相似文献
5.
Hydrolysis of organic phosphates by corn and soybean roots 总被引:1,自引:0,他引:1
Because of the importance of organic phosphates as sources of P for plants, this work was performed to study the hydrolysis
of nine organic phosphates by sterile, intact corn (Zea mays L.) and soybean (Glycine max L.) roots. Results showed that the rates of hydrolysis ofp-nitrophenyl phosphate (PNP) in buffered solutions by roots of three varieties of corn and three varieties of soybean ranged
from 13 to 22 μmol PO4−P g−1 root h−1 and from 2.1 to 2.2 μmol PO4−P 0.1 g−1 root h−1, respectively. The average rate of hydrolysis of PNP in nonbuffered solutions was 2- to 3-fold lower for corn roots and 6-
to 10-fold lower for soybean roots as compared with those obtained with buffered solutions. The orthophosphate released from
hydrolysis of organic P compounds in buffered solutions during a 48-h incubation of corn roots showed that the maximum rate
of hydrolysis of PNP was 4 to 6 times greater than the commonly used substrates: α- and β-glycerophosphates, phenolphthalein
diphosphate, and glucose-6-phosphate. The rates of hydrolysis of glucose-6-phosphate and glucose-1-phosphate were similar
and about 6- to 12-fold lower than that of PNP. Phosphoethanolamine and phosphocholine were hydrolyzed slightly, ando-carboxyphenyl phosphate was not hydrolyzed. The rates of hydrolysis of organic P compounds in nonbuffered solutions by corn
and soybean roots were 1 to 3 and 1 to 10 times lower than those in buffered solutions, respectively. The trends in rates
of hydrolysis by soybean roots of buffered organic P substrates were similar to those observed with corn roots, with the exception
of glucose-1-phosphate and phosphoethanolamine. 相似文献
6.
Assessment of phosphorus leaching losses from arable land 总被引:12,自引:0,他引:12
Phosphorus (P) losses from soil to water by erosion and surface runoff have been much studied and quantified. However, P losses
by leaching have received much less attention, mainly because, until recently, the quantities involved were not considered
to be of environmental significance. Furthermore, P leaching losses, unlike P losses from erosion or surface runoff were not
believed to be related to rates of P addition, as inorganic fertilizer or manures. Here we report results from a number of
field and laboratory experiments, designed to assess the significance of P leaching losses from soil to water. Annual cumulative
total P losses in drainage waters from four UK field sites ranged from about 0.03 to 5 kg P ha−1 during 2001–2002. Molybdate reactive P ranged from 45–57%, soluble organic P from 10–13% and particulate P from 29–45% of
total P on the two sites (Broadbalk and Woburn) where they could be accurately measured. The proportions of these different
P forms were comparable in all treatments, including drainage waters from the unfertilised soils and soils receiving long-term
applications of farmyard manure or inorganic fertilizer. In all soils, there was indication of an Olsen- (0.5 M NaHC03-, pH 8.5) extractable P concentration, (termed the Change-Point), where P measured in field drainage waters or in laboratory
soil extracts of 0.01 M CaCl2 began to increase linearly as Olsen-P increased. There was also some agreement between drainage water-P or CaCl2-P and the Olsen-P concentration where the Change-Point occurred. This suggests that CaCl2-extractable P may provide an approximate indicator of soil P concentrations above which significant quantities of P may be
lost by leaching under field conditions. There were positive linear relationships between soil dithionate-extractable Al and
soil organic C with the Change-Point: [Change Point = [(0.049)[Al3+] minus (9.2)(% organic C)] accounting for 93% of the variance
in the data. If this relationship holds under further testing it could well be a useful predictor of Change-Points in different
soils. Phosphate sorption isotherms were used to study the soil P concentrations above which P was at risk of moving from
soil to water. They showed that soil solution P concentrations were significantly lower between pH 6.9–7.2 than between pH 7.7–8.1,
with implications for P loss from soil to water. 相似文献
7.
The effects of root-induced pH changes on the depletion of inorganic and organic phosphorus in the rhizosphere 总被引:6,自引:0,他引:6
A new method allowing control of rhizosphere pH and mineral nutrition was applied to study depletion of various organic and inorganic phosphorus fractions extractable sequentially with 0.5M KHCO3 (pH 8.5), 0.1M NaOH and residual P extractable with 6M H2SO4 from the rhizosphere soil.Soil pH was affected about 2 mm from the root mat. Depletion zones of inorganic P (KHCO3-Pi) extractable with 0.5M KHCO3 extended up to about 4 mm but the depletion zones of all other P fractions were about 1 mm only. The root-induced decrease of soil pH from 6.7 to 5.5 increased the depletion of total P from all fractions by 20% and depletion of KHCO3-Pi and residual P by 34% and 43%, respectively. Depletion of organic P (KHCO3-Po) extractable with 0.5M KHCO3 was not affected by a change in rhizosphere pH. With constant or increased pH, depletion of inorganic P (NaOH-Pi) was 17% and organic P (NaOH-Po) was 22% higher than with decreased pH. Only 54–60% of total P withdrawn from all fractions was from KHCO3-Pi. Substantial amounts of KHCO3-Po and NaOH-Po were mineralized and withdrawn from the rhizosphere within 1 mm from the root mat, as 11–15% of total P withdrawn originated from the organic P fractions. A remaining 11–16% was derived from NaOH-Pi, and 15–18% from residual P fractions likely to be rather immobile. Thus, 40–46% of the P withdrawn near the root mat of rape originated from non-mobile P fractions normally not included in 0.5M NaHCO3 extraction used to obtain an index of plant-available soil P. 相似文献
8.
The effects of low concentrations of aluminium on the growth and uptake of nitrate-N by white clover 总被引:1,自引:0,他引:1
Summary The effects of aluminium (Al3+) at concentrations of 0, 25, 50 and 100 μM on the growth of white clover, dependent upon N supplied as NO
3
−
, were examined in flowing solution culture. Plants were established with a normal nutrient supply for 7 weeks and then grown
with carefully controlled pH (at 4.5) and P concentrations, and with 0, 25, 50 or 100 μM Al3+ for a further three weeks. There were rapid visual effects (i.e. symptoms of P deficiency and reduction in root extension) and the dry weights of shoots and roots were reduced at 50 and
100 μM. Less than 10% of Al absorbed from solution was transported to the shoots. The uptake of P, and its transport between roots
and shoots, were reduced in plants grown with Al. The uptake of NO
3
−
stopped immediately after the introduction of 50 or 100 μM Al, and was significantly reduced at 25 μM after three weeks.
During a second phase of the experiment, plants previously grown at 0, 25, 50 and 100 μM Al, were grown for a further 2 weeks either with NO
3
−
(with and without 50 μM Al3+) or without NO
3
−
but with inoculation by Rhizobia (and with or without 50 μM Al3+). The effects of the previous treatments with Al on N uptake were small during the second phase, but uptake by all plants
was restricted when Al was present. Inoculation did not result in nodulation in the second phase when Al3+ was present in the solution, but Al already in the plant from the first phase did not prevent nodulation in the absence of
Al during the second phase. 相似文献
9.
The β-casein (CN) human milk fraction is comprised of a single protein phosphorylated at levels from 0 to 5. Component interactions
are dependent on the phosphorylation level. Here, 3 mg/ml of β-CN-0P, β-CN-2P, β-CN-4P, a 2P/4P 1:1 (wt:wt) mixture, or a
mixture of all six forms in the ratio in human milk, were mixed with bovine κ-CN at a κ/β molar ratio of 0.33. Measurements
were with 0, 5 and 10 mM Ca+2 and 4 and 8 mM added inorganic phosphate (Pi). The turbidity (OD400 nm) and a lack of precipitation as T increased from 4 to 37°C was an index of micelle formation. The results indicate: (1) while micelles will form with Ca+2 alone, added Pi has a significant enhancing effect on micelle formation; (2) the patterns of micelle formation as a function of T are influenced by the β-CN-0P and β-CN-1P forms of β-CN to an unexpected extent. 相似文献
10.
Summary
In vitro methods were applied to the only remaining plant of the Meelup Mallee (Eucalyptus phylacis), a critically endangered species from the southwest of Western Australia. Shoot explants were initiated into culture using
a 1/2 MS [Murashige and Skoog basal medium (BM) for all experiments] liquid medium supplemented with 1% (w/v) activated charcoal,
which was replenished twice daily, followed by transfer of explants to agar medium supplemented with 0.5 μM zeatin. Explants were cultured under low intensity lighting (PPFD of 5–10 μmol m−2s−1) to minimize blackening of tissues, and some explants were induced to produce nodular green calluses in response to BM supplemented
with 5 μM thidiazuron. Nodular green calluses were induced to form adventitious shoots following transfer to medium supplemented with
0.5 μM zeatin and 1 μM gibberellic acid, A4 isomer (GA4). Development of shoots was completed on 1 μM zeatin + 0.1 μM 6-benzylaminopurine (BA) in vented culture tubes. Regenerated shoots were sequentially cultured on medium containing 0.5
μM zeatin + 0.2 μM indoleacetic acid (IAA) followed by either 0.5 μM zeatin + 1μM GA4 for shoot elongation or 1 μM zeatin + 0.5 μM IAA to optimize shoot growth. Rooted microshoots were produced after 4 weeks on 5 μM indolebutyric acid (IBA) and survived acclimatization and transfer to potting mixture. 相似文献
11.
The Fusarium toxin deoxynivalenol (DON) often co-occurs along with the acetylated derivatives 3-acetyl-DON and 15-acetyl-DON in diets
for ruminants. De-epoxy-DON is formed by rumen micro-organisms, while the acetylated DON derivatives might also undergo ruminal
metabolism with de-epoxy-DON as an end product. However, despite the fact that de-epoxy-DON is the predominant substance finally
absorbed, a complete degradation of the mother compounds can not be assumed for all feeding and metabolic situations of the
cow, and thus raising the question of their possible post-absorptive effects. Hence, the aim of the study was to examine the
effects of all four compounds on the concanavalin A stimulated proliferation of bovine peripheral blood mononuclear cells
(PBMC) using MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) as indicator in vitro and ex vivo. Among
the DON-related compounds, DON and 15-acetyl-DON resulted in a similar IC50 (i.e. the concentration where the proliferation was inhibited by 50%) of 0.5 μM, whereas 3-acetyl-DON was less toxic (IC50 = 2.6 μM), while actually no IC50 could be estimated for de-epoxy-DON which was characterized by a maximum inhibition of approximately 24% at the highest tested
in vitro concentration of 18.29 μM. For the in vivo experiment, 14 Holstein cows were used and fed either an uncontaminated control diet (CON) or a diet contaminated
with Fusarium toxins, with DON being the predominating toxin for 18 weeks when blood was collected for PBMC isolation and subsequent proliferation/viability
assay. The complete diets for the CON and FUS group contained 0.4 and 4.6 mg DON/kg DM, respectively, at that time. Exposure
of dairy cows to the FUS diet resulted in maximum serum de-epoxy-DON levels of 52 ng/ml (0.19 μM), while levels of the unmetabolized DON reached maximum levels of 9 ng/ml (0.03 μM). The PBMC of these cows were slightly less viable, by approximately 18% (p = 0.057), while stimulation capability was not decreased at the same time. Although de-epoxy-DON was characterized by the
lowest in vitro toxicity among the tested DON-related compounds, there appeared to be a lower viability of the PBMC isolated
from cows fed the FUS diet, which had nearly exclusively de-epoxy DON in serum beside slight traces of unmetabolized DON.
Thus, the factors responsible for these apparent discrepancies need to be clarified. 相似文献
12.
Suleiman A. Suleiman Jeffrey B. Stevens 《In vitro cellular & developmental biology. Plant》1987,23(5):332-338
Summary Cell viability, cytochrome P-450 content, cell respiration, and lipid peroxidation were all investigated as a function of
oxygen tension in adult rat hepatocytes in short-term culture (less than 9 h). The various oxygen tensions used in this study
were obtained by equilibrating culture medium with air, air + nitrogen, or air + oxygen. Cell viability, as assessed by trypan
blue exclusion, was significantly greater at all time points tested when hepatocytes were cultured in Ham's F12 medium containing
132 μM O2, as compared to medium equilibrated with air (220 μM O2) or air + oxygen (298 μM O2). Cells cultured in 220 μM O2 (air) also exhibited a gradual loss of cytochrome P-450, so that by 9 h of incubation less than 60% of the active material
remained. This loss of P-450 was minimized when cells were cultured in 163 μM O2 and abolished when cells were cultured in 132 μM O2. The 132 μM O2 exposure conditions also maintained cell respiration at the 1 h incubation values, whereas there was a continuous loss in
cell respiration over time when the cells were cultured in either 220 μM O2 (air) or 298 μM O2 (air:O2). These cytotoxicity findings may be related to oxidative cell damage inasmuch as it was additionally demonstrated that lipid
peroxidation (as measured by malondieldehyde equivalents) was consistantly lower in hepatocytes cultured in air:N2 as compared to air or air:O2. These results suggest that hepatocyte culture in low oxygen tension improves not only cell viability but also maintains
other functional characteristics of the cell.
This work was supported by a Biomedical Research Support Grant S-S07-RR 05448 awarded to the University of Minnesota School
of Public Health by the Biomedical Research Grant Program, Division of Research and Resources, National Institutes of Health,
Bethesda, MD. 相似文献
13.
Gerald Audesirk David Shugarts Gina Nelson Julie Przekwas 《In vitro cellular & developmental biology. Plant》1989,25(12):1121-1128
Summary Neurons from brains of chick embryos and pond snails (Lymnaea stagnalis) were cultured for 3 to 4 d in the presence of no toxins, inorganic lead (PbCl2), or organic lead (trielthyl lead chloride). In chick neurons, inorganic lead reduced the percentage of cells that grew neurites
(IC50=270μM total lead, approximately 70 nM free Pb2+) but did not reduce the number of neurites per cell or the mean neurite length. Triethyl lead reduced the percentage of cells
that grew neuites (IC50=0.24 μM) and the mean neurite length (extrapolated IC50=3.6 μM) but did not reduce the number of neurites per cell. InLymnaea neurons, inorganic lead reduced the percentage of cells that grew neurites (IC50=13 μM total lead; approximately 10 nM free Pb2+). Triethyl lead reduced the percentage of cells that grew neurites (IC50=0.4 μM) and exerted significant toxicity at 0.2 μM. The two forms of lead affected neurite growth in qualitatively different ways, which suggests that their mechansms of action
are different.
These experiments were supported by grants from the Environmental Protection Agency, Washington, DC, and the National Institutes
of Environmental Health Science, Research Triangle Park, NC. 相似文献
14.
Functional characterisation of an engineered multidomain human P450 2E1 by molecular Lego 总被引:1,自引:0,他引:1
Michael Fairhead Silva Giannini Elizabeth M. J. Gillam Gianfranco Gilardi 《Journal of biological inorganic chemistry》2005,10(8):842-853
The human cytochrome P450s constitute an important family of monooxygenase enzymes that carry out essential roles in the metabolism
of endogenous compounds and foreign chemicals. We present here results of a fusion between a human P450 enzyme and a bacterial
reductase that for the first time is shown does not require the addition of lipids or detergents to achieve wild-type-like
activities. The fusion enzyme, P450 2E1–BMR, contains the N-terminally modified residues 22–493 of the human P450 2E1 fused
at the C-terminus to residues 473–1049 of the P450 BM3 reductase (BMR). The P450 2E1–BMR enzyme is active, self-sufficient
and presents the typical marker activities of the native human P450 2E1: the hydroxylation of p-nitrophenol (K
M=1.84±0.09 mM and k
cat of 2.98±0.04 nmol of p-nitrocatechol formed per minute per nanomole of P450) and chlorzoxazone (K
M=0.65±0.08 mM and k
cat of 0.95±0.10 nmol of 6-hydroxychlorzoxazone formed per minute per nanomole of P450). A 3D model of human P450 2E1 was generated
to rationalise the functional data and to allow an analysis of the surface potentials. The distribution of charges on the
model of P450 2E1 compared with that of the FMN domain of BMR provides the ground for the understanding of the interaction
between the fused domains. The results point the way to successfully engineer a variety of catalytically self-sufficient human
P450 enzymes for drug metabolism studies in solution. 相似文献
15.
Ten soils collected from the major arable areas in Britain were used to assess the availability of soil sulphur (S) to spring
wheat in a pot experiment. Soils were extracted with various reagents and the extractable inorganic SO4-S and total soluble S(SO4-S plus a fraction of organic S) were determined using ion chromatography (IC) or inductively-coupled plasma atomic emission
spectrometry (ICP-AES), respectively. Water, 0.016 M KH2PO4, 0.01 M CaCl2 and 0.01 M Ca(H2PO4)2 extracted similar amounts of SO4-S, as measured by IC, which were consistently smaller than the total extractable S as measured by ICP-AES. The amounts of
organic S extracted varied widely between different extractants, with 0.5 M NaHCO3 (pH 8.5) giving the largest amounts and 0.01 M CaCl2 the least. Organic S accounted for approximately 30–60% of total S extracted with 0.016 M KH2PO4 and the organic C:S ratios in this extract varied typically between 50 and 70. The concentrations of this S fraction decreased
in all soils without added S after two months growth of spring wheat, indicating a release of organic S through mineralisation.
All methods tested except 0.5 M NaHCO3-ICP-AES produced satisfactory results in the regression with plant dry matter response and S uptake in the pot experiment.
In general, 0.016 M KH2PO4 appeared to be the best extractant and this extraction followed by ICP-AES determination was considered to be a good method
to standardise on. 相似文献
16.
Terry L. Riss' David A. Sirbasku 《In vitro cellular & developmental biology. Plant》1989,25(2):136-142
Summary The effect of 17β-estradiol (E2) on growth of GH4C1 rat pituitary tumor cells was investigated under serum-free conditions and with medium containing charcoal-extracted serum.
Serum-free TRM-1 medium was a 1∶1 (vol/vol) mixture of F12-DME supplemented with 50 μg/ml gentamicin, 15 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 10 μg/ml insulin, 10 μg/ml transferrin, 10 ng/ml selenous acid, 10 nM 3,5,3′-triiodothyronine (T3), 50 μM ethanolamine, and 500 μg/ml bovine serum albumin. The cells grew continuously in TRM-1 but were E2 responsive only when growth was retarded by reducing the T3 concentration to 10 pM (TRM-MOD). Addition of 1 to 10 nM E2 to TRM-MOD increased growth by 0.3 to 0.9 cell population doublings over controls in 9 d. By using medium supplemented with
charcoal-extracted sera, basal growth became 1 to 1.5 cell population doublings in 9 d. Addition of 0.1 pM E2 to medium containing charcoal-extracted serum caused a significant increase in cell number whereas pM-nM concentrations stimulated 200 to 570% increases over controls. The effect of steroid hormone was the same in phenol-red-containing
and indicator-free medium. The data presented confirm that the major requirements for demonstration of estrogenic effects
in culture were optimum concentrations of thyroid hormones and the presence of yet-to-be-characterized serum factors.
This work was supported by National Cancer Institute (Bethesda, MD) grants CA-26617 and CA-38024, American Cancer Society
grant BC-255, and grant 2225 from The Council for Tobacco Research, U.S.A., Inc. 相似文献
17.
The reactions of trees to wind, rockfall, and snow and debris flow depend largely on how strong and deformable their anchorage
in the soil is. Here, the resistive turning moment M of the root–soil system as a function of the rotation ϕ at the stem base plays the major role. M(ϕ) describes the behavior of the root–soil system when subject to rotational moment, with the maximum M(ϕ) indicating the anchorage strength M
a of the tree. We assessed M(ϕ) of 66 Norway spruce (Picea abies L. Karst) by pulling them over with a winch. These 45- to 170-year-old trees grew at sites of low and high elevation, with
a diameter at breast height DBH = 14–69 cm and a height H = 9–42 m. M(ϕ) displayed a strong nonlinear behavior. M
a was reached at a lower ϕ for large trees than for small trees. Thus overhanging tree weight contributed less to M
a for the large trees. Overturning also occurred at a lower ϕ for the large trees. These observations show that the rotational ductility of the root–soil system is higher for small trees.
M
a could be described by four monovariate linear regression equations of tree weight, stem weight, stem volume and DBH
2
·H (0.80 < R
2 < 0.95), and ϕ at M
a, ϕ
a, by a power law of DBH2·H (R
2 = 0.85). We found significantly higher M
a for the low-elevation spruces than for the high-elevation spruces, which were more shallowly anchored, but no significant
difference in ϕ
a. The 66 curves of M(ϕ), normalized (n) by M
a in M-direction and by ϕ
a in ϕ-direction, yielded one characteristic average curve: . Using and the predictions of M
a and ϕ
a, it is shown that M(ϕ) and the curves associated with M(ϕ) can be predicted with a relative standard error ≤25%. The parameterization of M(ϕ) by tree size and weight is novel and provides useful information for predicting with finite-element computer models how
trees will react to natural hazards. 相似文献
18.
Soluble Organic Nitrogen Pools in Forest soils of Subtropical Australia 总被引:15,自引:0,他引:15
Soil soluble organic N (SON) plays an important role in N biogeochemical cycling. In this study, 22 surface forest soils (0–10 cm)
were collected from southeast Queensland, Australia, to investigate the size of SON pools extracted by water and salt solutions.
Approximately 5–45 mg SON kg−1, 2–42 mg SON kg−1 and 1–24 SON mg kg−1 were extracted by 2 M KCl, 0.5 M K2SO4 and water, on average, corresponding to about 21.1, 13.5 and 7.0 kg SON ha−1 at the 0–10 cm forest soils, respectively. These SON pools, on average, accounted for 39% (KCl extracts), 42% (K2SO4 extracts) and 43% (water extracts) of total soluble N (TSN), and 2.3% (KCl extracts), 1.3% (K2SO4 extracts) and 0.7% (water extracts) of soil total N, respectively. Large variation in SON pools observed across the sites
in the present study may be attributed to a combination of factors including soil types, tree species, management practices
and environmental conditions. Significant relationships were observed among the SON pools extracted by water, KCl and K2SO4 and microbial biomass N (MBN). In general, KCl and K2SO4 extracted more SON than water from the forest soils, while KCl extracted more SON than K2SO4. The SON and soluble organic C (SOC) in KCl, K2SO4 and water extracts were all positively related to soil organic C, total N and clay contents. This indicates that clay and
soil organic matter play a key role in the retention of SON in soil. 相似文献
19.
Metabolic pathways of quinoline, indole and their methylated analogs by Desulfobacterium indolicum (DSM 3383) 总被引:2,自引:0,他引:2
S. S. Johansen D. Licht E. Arvin H. Mosbæk A. B. Hansen 《Applied microbiology and biotechnology》1997,47(3):292-300
The transformation of quinoline, isoquinoline and 3-, 4-, 6- and 8-methylquinoline by Desulfobacterium indolicum was compared with that of the N-containing analogues indole and 1-, 2-, 3- and 7-methylindole. The metabolites were identified
using high-performance liquid chromatography with UV detection, thin-layer chromatography, combined gas chromatography/mass
spectrometry and proton NMR spectroscopy. All degraded compounds were initially hydroxylated at position 2 by D. indolicum. A new degradation product of quinoline was observed in the second transformation step, where 3,4-dihydro-2-quinolinone accumulated.
This ring-reduced compound was further transformed into unidentified products. The transformation pathway of indole was characterized
by well-known steps through oxindole, isatin, and anthranilic acid. No further transformation of the hydroxylated methyl analogues:
3- and 7-methyloxindole and 3- and 4-methyl-2-quinolinone, was observed within 162 days of incubation. These degradation products
accumulated in stoichiometric amounts, while 6- and 8-methyl-2-quinolinone were further degraded to 6- and 8-methyl-3,4-dihydro-2-quinolinone
in stoichiometric amounts. Isoquinoline, 2-methylquinoline and 1- and 2-methylindole were not degraded by D. indolicum. These observations indicate that a methyl group at or close to position 2 results in blockage of the microbial attack, and
that transformation of hydroxyquinolines methylated at the heterocyclic ring also was blocked or sterically inhibited. An
incomplete transformation of some methylated compounds was observed, e.g. for 3- and 6-methylquinoline and 3- and 7-methylindole,
with residual concentrations of 0.5–4 mg/l in relation to initial concentrations of 10–15 mg/l.
Received: 23 July 1996 / Received revision: 4 October 1996 / Accepted: 25 October 1996 相似文献
20.
Summary The present study reports that a revised nutrient concentration in the basal medium improved shoot bud induction and subsequent
plant regeneration in barley (Hordeum vulgare L. var. BL-2). Cultures were raised from immature embryos on MSB5 medium supplemented with picloram. Concentrations of five nutrients were varied. The effect of these nutrients was investigated
on (1) induction, (2) induction and subculture, and (3) induction, subculture and regeneration stages. The basal MSB5 medium was not optimal for each phase of barley culture. Decreased ammonium nitrate, increased potassium dihydrogen phosphate,
sodium molybdate, cobalt chloride, and addition of glycine enhanced shoot bud induction and plant regeneration. The different
media that were optimal for immature embryo culture were: MSB5 medium supplemented with 20.70 μM picloram, 10.30 mM NH4NO3, 6.25 mM KH2PO4, 2.06 μM Na2MoO4, 0.55 μM CoCl2, and 26.64 μM glycine (for induction); MSB5 medium supplemented with 12.47 μM picloram, 10.30 mM NH4NO3, and 0.55 μM CoCl2 (for subculture); and MSB5 medium supplemented with 0.2 μM picloram and 10.3 mM NH4NO3 (for regeneration). Primary cultures required 6wk (without transfer) for morphogenic callus formation. Callus required 4wk
of subculture and another 4wk on regeneration medium for optimal plant regeneration. The revised medium could also promote
regeneration of the recalcitrant barley genotype RD-2552. Histological analysis showed that the major pathway of differentiation
was through shoot bud formation. 相似文献