共查询到20条相似文献,搜索用时 31 毫秒
1.
Summary The tetrazolium salt procedure of van Gelder (1965) for the demonstration of GABA transaminase (GABAT; the most important
GABA degrading enzyme) was adapted for microphotometric measurements of GABAT activities in brain sections using the hippocampus
of rats as selected brain region. The final incubation medium consisted of 50 mM GABA, 5 mM α-ketoglutarate, 7 mM NAD, 10 mM sodium azide, 6 mM nitroblue tetrazolium chloride, 20 mM malonate and 15% polyvinyl alcohol in 0.05 M Hepes buffer; the final pH was 8.0. There was a linear relationship between GABAT activity and section thickness up to 14
μm and between GABAT activity and reaction time at least up to 20 min (kinetic and end-point measurements). Phenazine methosulfate
as an exogenous electron carrier and pyridoxal-5-phosphate as coenzyme of GABAT did not enhance the demonstrable GABAT activities,
whereas sodium azide as a blocker of the respiratory chain resulted in an increase of demonstrable enzyme activities. A coreaction
of succinate dehydrogenase was excluded by the use of malonate (competitive inhibitor). Using the incubation medium described
GABAT activities were demonstrated via the endogenous enzymes succinic semialdehyde dehydrogenase and NADH tetrazolium reductase
which were shown to be not rate limiting and seems to be similarly localized as GABAT.
Supported by the Deutsche Forschungsgemeinschaft (Ku 541/2-2) 相似文献
2.
Chi D. Ha Peggy G. Lemaux Myeong-Je Cho 《In vitro cellular & developmental biology. Plant》2001,37(1):6-11
Summary An efficient method to produce highly regenerative tissues from seeds of a previously recalcitrant cultivar of Kentucky bluegrass
(Poa pratensis L. ev. Kenblue) was established under dim-light conditions (10–30 μE m−2s−1, 16-h light) using media supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D; 4.5 or 9.0 μM), 6-benzylaminopurine (BA; 0.44 or 2.2 μM), and a high level of cupric sulfate (5.0 μM). The tissues were co-transformed with three plasmids containing the genes for hygromycin phosphotransferase (hpt), β-glucuronidase (uidA; gus), and a synthetic green fluorescent protein gene [sgfp(S65T)]. From 463 individual explants bombarded, 10 independent transgenic events (2.2%) were obtained after a 3–4-month selection
period for hygromycin resistance using 30–100 mg l−1 hygromycin B; of the 10 independent events, seven (70%) were regenerable. Stable integration of the transgene(s) in transgenic
plants was confirmed by polymerase chain reaction and DNA blot hybridization analyses. Coexpression frequency of all three
genes was 20%; for two transgenes, either hpt/uidA or hpt/sgfp(S65T), coexpression frequency was 30–40%. 相似文献
3.
Summary An efficient and reproducible procedure for the large-scale propagation of Pseudoxytenanthera stocksii is described. High-frequency multiple shoot induction was achieved from nodal shoot segments collected from superior/elite
genotypes on Murashige and Skoog (MS) liquid medium supplemented with 1-naphthaleneacetic acid (NAA; 2.68 μM) and 6-benzylaminopurine (BA; 4.40 μM) at 28±1°C and 60 μmol m−2 s−1 light intensity under 12h photoperiod. In vitro-differentiated shoots were multiplied on MS liquid medium fortified with NAA (2.68 μM), BA (2.21 μM) and additives: ascorbic acid (283.93 μM), citric acid (118.10 μM), cysteine (104.04 μM), and glutamine (342.24 μM). Subculturing was carried out every 2wk on fresh shoot multiplication medium. About 125–150 shoots per culture flask were
harvested within 45–50d. In vitro-differentiated shoot clumps (three or four shoots) were successfully rooted on half-strength MS basal liquid medium with
indole-3-butyric acid (4.90 μM), BA (0.44 μM), and additives. This is the first report where in vitro- and in vivo-(through tillers) raised clonal plants were acclimatized and established in the field, where they exhibited normal growth. 相似文献
4.
Jonathan C. Allen Sharon J. Vaillancourt Lisa Haedrich 《Biological trace element research》1993,39(2-3):229-243
The objective was to determine if a mammary cell line shows glucocorticoid stimulation of Zn uptake, and to determine whether
polyamines mediate this stimulation.65Zn uptake by COMMA-1D mouse mammary epithelial cells over a 24-h period increased significantly in cells administered 10−7 or 10−6
M hydrocortisone. Incorporation of65Zn over a 1-h period was not hydrocortisone-responsive, suggesting that these incubation times represent uptake into different
pools. The rate of entry into the cells over a 15-min period was significantly increased by supplementing cells with hydrocortisone
with or without prolactin. Initially, cells grown in lactogenic hormone-supplemented media (10−6
M hydrocortisone+5μg/mL ovine prolactin) had up to 65% greater65Zn uptake over 24 h than cells in nonsupplemented growth media.65Zn uptake from hormone media with the spermidine synthesis inhibitor methylglyoxal-bis-(guanylhydrazone) (MGBC, 10−5
M) added was less than from growth media. Exogenous spermidine (10−6-10−3
M) added to the MGBG+hormone media increased65Zn uptake. Difluoromethylornithine (DFMO), an inhibitor of spermidine synthesis that blocks ornithine decarboxylase, caused
a slight dose-dependent decrease in65Zn uptake over the range 10−6-5×10−3
M(p<0.002) and tended to decrease65Zn-uptake in lactogenic hormone-stimulated cells with 8 h of incubation, but not at other times. These data show that Zn uptake
in mammary epithelial cells can be hormonally mediated by glucocorticoids and suggest that polyamines may be intracellular
mediators of this effect. 相似文献
5.
Summary Micropropagation of Arnica montana L. using Murashige and Skoog (MS) medium supplemented with N6-[2-isopentenyl]adenine (2iP), zeatin and α-naphthaleneacetic acid (NAA) in different concentrations does not ensure the formation
of a high number of regenerated plants; a maximum of 3.2 neoplantlets per explant were obtained. After 4 wk of culture on
medium with zeatin (4.5 μM) and NAA (5.3 μM), plants were 3.06 cm in length. The following step was to improve the clonal propagation of this species. Micropropagation
of Arnica montana L., initiated from nodal segments using semisolid media (4 g l−1 agar), was obtained. Explants were inoculated on MS medium supplemented with NAA (5.3 μM), 2iP (5.0 μM), maize extract (1.0 ml l−1), phloroglucinol (0.6 mM) or adenine sulfate (0.2 mM). Only 3 wk after the inoculation, plant multiplication as well as induction of roots were obtained, the optimal variant
being that containing NAA (5.3 μM), 2iP (5.0 μM) and maize extract (1.0 ml l−1). Six weeks after the inoculation plants were transferred to Perlite, with 80% plant survival being obtained. By isoesterase
pattern we concluded that we have obtained the clonal propagation of Arnica montana, because the pattern of several individuals belonging to different clones was the same. Only one region with esterase activity
that is present in all individuals has been identified. 相似文献
6.
U. Carpentieri J. Myers C. W. Daeschner M. E. Haggard 《Biological trace element research》1988,16(2):165-176
The effects of simultaneous changes of calcium, magnesium, iron, copper, and zinc concentrations were evaluated in normal
human T and B lymphocytes, cultured in cation-depleted media. Optimal concentrations for thymidine incorporation (TI) in both
cell populations were Fe and Zn 15 μM and Cu 5 μM; for t cells Ca 2 mM and Mg 4 mM; for B cells Ca 4 mM and Mg 6 mM. TI decreased with increasing molarity of cations and the decrease was particularly apparent with Cu. Minimal amounts of
Ca and Mg (0.5 mM) were necessary for growth, even in presence of optimal concentrations of Fe, Cu, and Zn. Fe and Cu showed synergistic stimulatory
effects at low concentrations and synergistic inhibitory effects at high concentrations. Antagonism between Fe and Zn, Cu
and Zn, and Ca and Zn was also demonstrated. CD4/CD8 increased with PHA stimulation in presence of Zn, and decreased with
ConA stimulation in presence of Zn or Fe. The results demonstrate: (1) the relationship and interdependence of Fe, Cu, and
Zn concentrations in modulating the growth of normal lymphocytes; (2) the stimulatory effects of Fe on B cells and Zn on CD8
positive cells; (3) the inhibitory effect of Cu at concentrations lower than those of Fe and Zn; (4) the requirement of Ca
and Mg in certain concentration and ratio for the action of the other cations; and (5) the Ca and Mg requirement for the growth
of B cells higher than T cells. 相似文献
7.
Chandra P Lecluyse EL Brouwer KL 《In vitro cellular & developmental biology. Animal》2001,37(6):380-385
Summary This study was undertaken to examine the influence of time and volume of collagen overlay, type of media, and media additives
on taurocholate (TC) accumulation and biliary excretion in hepatocytes cultured in a collagen-sandwich configuration. Hepatocytes
were isolated from male Wistar rats by in situ perfusion with collagenase, seeded onto collagencoated 60-mm dishes, overlaid
with gelled collagen, and cultured for 4 d. Experiments to examine the influence of time and volume of collagen overlay were
conducted in Dulbecco's modified Eagle's medium (DMEM)+1.0μM dexamethasone (DEX)+5% fetal bovine serum (FBS). Hepatocytes were overlaid at 0 h with 0.1 or 0.2 ml collagen, or at 24 h
with 0.1 or 0.2 ml collagen. The influence of media type and additives was examined in hepatocytes overlaid at 0 h with 0.2
ml collagen and incubated in DMEM+0.1μM DEX, DMEM+0.1μM DEX+5% FBS, Williams' medium E+0.1μM DEX+1% ITSΘ+, DMEM +1.0μM DEX, DMEM+1.0 μM DEX+5% FBS, or modified Chee's medium (MCM)+0.1 μM DEX+1% ITSГ+. [3H] TC accumulation by hepatocytes in Hank's balanced salt solution (HBSS) and Ca2+-free HBSS was measured, and the biliary-excretion index (BEI: percentage of accumulated TC localized in the canalicular compartment)
was calculated. Light microscopy and carboxydichlorofluorescein fluorescence were employed to examine the cellular and canalicular
morphologies. The volume of collagen used for both the substratum and the overlay did not affect TC accumulation or biliary
excretion. The BEI tended to be higher in cells overlaid at 24 h (BEI=0.649 [0.1 ml collagen]; BEI=0.659 [0.2 ml collagen])
compared with those overlaid at 0 h after seeding (BEI=0.538 [0.1 ml collagen]; BEI=0.517 [0.2 ml collagen]), although the
differences were not statistically significant. Hepatocytes cultured in MCM produced consistently the lowest BEI of TC (BEI=0.396).
Differing DEX concentration (0.1 μM versus 1.0 μM) with or without 5% FBS did not appear to have a significant effect on the BEI of TC. 相似文献
8.
Summary Although pineapple plants have been found to produce proteases ex vitro, most of the biotechnological investigations of this crop have been focused on propagation. The procedure involving the use
of temporary immersion bioreactors is one of the most outstanding because of its high multiplication rate. We previously recorded
specific protease activity in the culture medium during the pre-elongation step of this protocol. Therefore, we decided to
modify the culture medium composition of this phase looking for an increase in protease excretion. Four independent experiments
were performed to evaluate the effects of different levels of sucrose (0–350.4 mM), inorganic salts [0–200% Murashige and Skoog (MS) salt strength], inositol (0–2.20 mM), and thiamine (0–1.2μM). The following indicators were recorded: shoot fresh mass per bioreactor; and protein concentration, proteolytic activity,
and specific protease activity in culture media. Specific protease activity, the most important indicator recorded, was highest
with 262.8 mM sucrose, 100% MS salt strength, 0.3 μM thiamine and no inositol. Results shown here demonstrate that conditions adequate for propagation purposes (87.6 mM sucrose, 100% MS salt strength, 0.55 mM inositol, 0.3 μM thiamine) are not always adequate for protease excretion. 相似文献
9.
Zinc (Zn) is an essential nonredox metal that has been regarded as having antioxidant properties. Some epidemiological indications
and therapeutic results point to a role of Zn in restricting the development and the progression of some diseases. Redox-active
metals like iron and copper are involved in oxidative injury mechanisms, and a decrease in the Zn∶Cu ratio may be associated
with certain pathologies. We studied the effect of Zn on the copper-induced lipid peroxidation in diluted human plasma. Lipid
peroxidation was evaluated by measuring the formation of conjugated dienes and of thiobarbituric acid reactive products. We
found that 20 μM Zn reduced the 125-μM copper-dependent formation of conjugated dienes by 27% and of thiobarbituric acid reactive products by 49%, during a 3-h
incubation period. The inhibition of lipid peroxidation by 125 μM Zn is almost total in the same conditions. The time-course study of the inhibitory effect of 125 μM Zn showed that it lasted for 7 h, which was the maximum incubation period tested. We also found that Zn had an inhibitory
effect on the spontaneous lipid peroxidation in rat brain whole homogenates. Our results support the antioxidant properties
of Zn, which may be potentially relevant to the protection of human plasma constituents, competing with the transition metals
for redox reactions. 相似文献
10.
Effects of zinc (12–180 μM) alone and in mixtures with 12 μM Cd on metal accumulation, dry masses of roots and shoots, root
respiration rate, variable to maximum fluorescence ratio (FV/FM), and content of photosynthetic pigments were studied in hydroponically cultivated chamomile (Matricaria recutita) plants. The content of Zn in roots and shoots increased with the increasing external Zn concentration and its accumulation
in the roots was higher than that in the shoots. While at lower Zn concentrations (12 and 60 μM) the presence of 12 μM Cd
decreased Zn accumulation in the roots, treatment with 120 and 180 μM Zn together with 12 μM Cd caused enhancement of Zn content
in the root. Presence of Zn (12–120 μM) decreased Cd accumulation in roots. On the other hand, Cd content in the shoots of
plants treated with Zn + Cd exceeded that in the plants treated only with 12 μM Cd. Only higher Zn concentrations (120 and
180 μM) and Zn + Cd mixtures negatively influenced dry mass, chlorophyll (Chl) and carotenoid content, FV/FM and root respiration rate. Chl b was reduced to a higher extent than Chl a. 相似文献
11.
Summary Callus cultures were established from pith tissue of Coryphantha elephantidens (Lem.) Lem. on Murashige and Skoog (MS) basal medium supplemented with 9.05 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.3 μM kinetin. Highest shoot regeneration frequency was observed on a medium containing 6.9 μM kinetin and 2.3 μM 2,4-D under 30 μE m−2 s−1 light intensity with a 16-h photoperiod. Calluses retained organogenic potential throughout several passages of subculture
(18 mo.). Shoots were rooted on MS medium without plant growth regulators. All (100%) plantlets transplanted to soil survived
acclimatization. Regenerated plants showed good overall growth and were morphologically similar to the mother plants. 相似文献
12.
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
13.
J. Liu W. C. Kershaw C. D. Klaassen 《In vitro cellular & developmental biology. Plant》1990,26(1):75-79
Summary The effect of Zn-induced metallothionein (MT) on the toxicity, uptake, and subcellular distribution of cadmium (Cd) was examined
in rat primary hepatocyte cultures and compared to results obtained earlier in this laboratory from intact animals. Hepatocytes
were isolated and grown in monolayer culture for 22 h and subsequently treated with ZnCl2 (100 μM) for 24 h, which increased MT concentration about 15-fold. After Zn pretreatment, hepatocytes were exposed to Cd for 24 h.
Cytotoxicity was assessed by enzyme leakage, intracellular potassium loss, and cellular glutathione content. The toxicity
of Cd was much less in Zn-pretreated cells than in control cells, similar to that previously demonstrated in the intact animal.
Zn pretreatment had no appreciable effect on the hepatocellular uptake of109Cd, but markedly altered its subcellular distribution, with more Cd accumulating in the cytosol and less in the nuclear, mitochondrial,
and microsomal fractions. In the cytosol of Zn-pretreated cells, Cd was associated mainly with MT; in contrast, cytosolic
Cd in control cells was mainly associated with non-MT macromolecules. Zn-induced changes in the subcellular distribution of
Cd in vitro are identical to those observed in vivo in Zn-pretreated rats challenged with Cd. In summary, Zn pretreatment
of rat primary hepatocyte cultures protects cells against Cd toxicity. Protection seems to be due to MT-promotes sequestration
of Cd and reduction of the amount of Cd associated with critical organelles and proteins. These observations are similar to
those noted in the whole animal. These results indicate that cultured hepatocytes are an ideal model for examining MT-induced
tolerance to Cd hepatotoxicity.
This work was supported by grant ES-01142, and WCK was supported by training grant ES-07079, both from the Public Health Service,
Department of Health and Human Services. 相似文献
14.
Masahiro Miyazaki Yoshihiko Handa Yasunori Suzuki Jiro Sato 《In vitro cellular & developmental biology. Plant》1987,23(1):2-9
Summary Ten barbituric acid (BA) derivatives were synthesized and tested for their potency for supporting survival of functional hepatocytes
from adult rats in primary culture. Of the 10 BA derivatives, 7 compounds (C-2, 3, 4, 5, 6, 9, and 10) efficiently supported
hepatocyte survival for at least 2 wks in primary culture. Especially C-5, 6, and 9 showed excellent efficiency for such action.
The optimum concentrations of the BA derivatives for observing the morphological and biochemical effects differed from each
other. The maintenance of hepatocytes was attained only in the continuous presence of the BA derivatives in the medium. The
morphologic features of hepatocytes surviving in the presence of the BA derivatives resembled those of hepatocytes 24 h after
inoculation. The surviving hepatocytes secreted remarkably large amounts of albumin into the culture media. Tyrosine aminotransferase
(TAT) activity was higher in the 1-wk-old cultures treated with C-5, 6, and 9 than in the freshly isolated hepatocytes. The
addition of dexamethasone (10 μM) caused a 1.7 to 2.1-fold induction in TAT activity. The basal levels of TAT activity and the induction rates increased in
the cultures treated with C-5 and 6 from Week 1 to 2 of primary culture. 相似文献
15.
G. Vengadesan N. Selvaraj R. Prem Anand V. Gaba A. Ganapathi 《In vitro cellular & developmental biology. Plant》2005,41(6):789-793
Summary Suspension culture of cucumber (Cucumis sativus L.) has been an inefficient method for production of somatic embryos owing to problems with embryo maturation and conversion.
Embryogenic callus of cv. Green Long was induced on semisolid Murashige and Skoog (MS) medium containing 6.8 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.2 μM 6-benzylaminopurine (BA). A large number of globular somatic embryos were obtained on transfer of the callus to MS liquid
medium supplemented with 87.6 mM sucrose, 1.1 μM 2,4-D, and improved by the addition of 342.4 μM
l-glutamine. MS medium supplemented with 87.6 mM sucrose was more effective in somatic embryo production than other sugars. Subsequent development led to the formation of
heart-and torpedo-shaped embryos. Maturation of somatic embryos occurred on plant growth regulator-free MS semi-solid medium
containing 175.2 mM sucrose and 0.5 gl−1 activated charcoal. Conversion of embryos into plants was achieved on half-strength MS semi-solid medium containing 87.6
mM sucrose and 1.4 μM gibberellic acid (GA3) in a 16h photoperiod. Twenty-seven percent of embryos were converted into normal plants. 相似文献
16.
Microphotometric determination of enzymes in brain sections 总被引:1,自引:1,他引:0
P. Kugler 《Histochemistry and cell biology》1990,93(3):295-298
Summary A histochemical procedure was established for the microphotometric determination of hexokinase (HK) in sections of the rat hippocampus, which served as an exemplary brain region. For this quantitative procedure, slides were coated with glucose 6-phosphate dehydrogenase (G6PDH) as an auxiliary enzyme and sections were mounted onto this enzyme film. The sections were then incubated with the following adapted incubation medium: 5 mM
d-glucose, 1.5 mM NADP, 7.5 mM ATP, 4 mM nitroblue tetrazolium chloride, 10 mM NaN3, 10 mM MgCl2, 0.25 mM phenazine methosulfate, 1 U/ml G6PDH, 22% polyvinyl alcohol in 0.05 M Hepes buffer; the final pH was 7.5. A linear response of the reaction was observed in the initial 10 min of reaction (kinetic and end-point measurements). The relationship between HK activity and section thickness was linear up to 5 m. The need for such thin sections is discussed in relation to the limited penetration of the auxiliary enzyme into the section. It is concluded that the quantitative demonstration of HK in brain sections could be a valuable tool for studying the local metabolic entrance of glucose in the glycolytic pathway.Supported by the Deutsche Forschungsgemeinschaft (Ku 541/2-1, 2-2) 相似文献
17.
Summary Embryogenic calluses were induced from 73% of Phalaenopsis shoot-tip explants excised from flower stalk buds by culturing for 7 mo. on New Dogashima Medium (NDM) containing 0.5 μM α-naphthaleneacetic acid (NAA), 4.4 μM 6-benzylaminopurine and 29.2 mM sucrose. The sucrose concentration was increased to 58.4 mM 4 mo. after initiation of the callus culture. These calluses were successfully subcultured as cell suspension cultures in
liquid NDM supplemented with 5.4μM NAA and 58.4 mM sucrose. By simply reducing the sucrose concentration to 29.2 mM, the cells grew into plantlets through a developmental process similar to that of Phalaenopsis seedlings. The occurrence of somaclonal variants was less than 10% in six out of eight genotypes examined. These results
suggest that the embryogenic callus and cell suspension culture could be utilized as the materials for micropropagation and
breeding of Phalaenopsis orchids. 相似文献
18.
To understand how plants from the Fabaceae family maintain zinc (Zn) homeostasis, we have characterized the kinetics of three
Zn transporting proteins from the ZIP family of divalent metal transporters in the model legume Medicago truncatula. Of six ZIP’s studied, MtZIP1, MtZIP5 and MtZIP6 were the only members from this family determined to transport Zn and were
further characterized. MtZIP1 has a low affinity for Zn with a Km of 1 μM as compared to MtZIP5 and MtZIP6 that have a higher affinity for Zn with Km of 0.4 μM and 0.3 μM, respectively. Zn transport by MtZIP1 was more sensitive to inhibition by copper (Cu) concentrations
than MtZIP5 and MtZIP6, because 3 μM Cu inhibited Zn transport by 80% in MtZIP1 while 5 μM Cu was required to achieve the
same inhibition of Zn transport in MtZIP5 and MtZIP6. Cadmium (Cd) had a greater effect on the ability of MtZIP1 to transport
Zn than MtZIP5 and MtZIP6, because at a concentration of 3 μM Cd, the Zn transport by MtZIP1 was inhibited 55% and the transport
of Zn by MtZIP5 and MtZIP6 was inhibited by 20–30%. However, only MtZIP6 transported Cd at higher rates than those observed
in the control plasmid pFL61, demonstrating a low affinity for Cd based on a Km of 57 μM. These results suggest that Medicago truncatula has both high and low affinity Zn transporters to maintain Zn homeostasis and that these transporters may function in different
compartments within the plant. 相似文献
19.
Véronique Marie Patrice Gonzalez Magalie Baudrimont Jean-Paul Bourdineaud Alain Boudou 《Biometals》2006,19(4):399-407
Metallothionein (MT) response to cadmium (Cd) and zinc (Zn) bioaccumulation after single or combined direct exposure was compared
in two freshwater bivalves, Dreissena polymorpha (zebra mussel) and Corbicula fluminea (Asiatic clam). Bivalves were exposed to 0.133 μM Cd and/or 15.3 μM Zn, with metal and MT concentrations analysed in the
whole soft body after 1, 3, 10 and 24 days of exposure and compared with controls. Results showed significant increase in
MT concentrations in both species exposed to Cd and Cd+Zn with a higher accumulation of the protein compared to the control
in D. polymorpha for nevertheless similar Cd levels accumulated with time. Exposure to Zn alone led to a significant increase in MT concentrations
only in C. fluminea, whereas there was a lack of MT gene induction in the zebra mussels which was confirmed by MT mRNA quantification in gills
(RT-PCR). Mussel mortality after 10 days of exposure to Zn and Cd + Zn is discussed with regard to detoxification mechanisms,
which include metallothioneins. 相似文献
20.
Summary Short-term culture of rainbow trout (Onchorhynchus mykiss) hepatocytes was used to examine the effect of dexamethasone (DEX) on microsomal CYP 1A1 protein content and 7-ethoxyresorufin-O-deethylase (EROD) activity in vitro. Hepatocytes prepared by controlled collagenase digestion and plated at a density of
0.25 × 106 cells/cm2 in plastic culture dishes precoated with trout skin extract (7.6 μg skin protein/cm2) to facilitate cell attachment were maintained at 16° C. Cells were treated with DEX (10−9 to 10−7
M) or vehicle (dimethyl sulfoxide, DMSO) at 24 h. Microsomal CYP 1A1 protein content and EROD activities were measured at 72
h. Both CYP 1A1 protein as measured by Western blots using CYP 1A1 specific anti-sera and EROD activity were significantly
lower in DEX (10−8 to 10−7
M)-treated hepatocytes compared to untreated (control) or DMSO-treated cells. The effect was dose dependent in that a gradual
decrease of CYP 1A1 protein and EROD activities were seen with increasing doses of DEX (10−8 to 10−7
M). DEX at 10−9
M was ineffective. Concomitant addition of 10−6
M RU486, a type II specific glucocorticoid receptor antagonist, to hepatocytes treated with 10−7
M DEX abolished the DEX effect. RU486 at 10−8
M was ineffective. Spironolactone (10−8 to 10−6
M), a type I specific glucocorticoid receptor antagonist, did not counteract the DEX effect. RU486 or spironolactone (10−6
M) alone had no effect on CYP 1A1 under similar conditions. DEX thus down regulates CYP 1A1 in fish cultured hepatocytes and
this regulation is mediated through the type II glucocorticoid receptor(s). 相似文献