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1.
Matti Tolonen Seppo Sarna Markku Halme Seppo E. J. Tuominen Tuomas Westermarck Ulla-Riitta Nordberg Mirja Keinonen Jaap Schrijver 《Biological trace element research》1988,17(1):221-228
An “anti-oxidant cocktail” consisting of betacarotene, vitamins B6, C, E, zinc, and selenium or corresponding placebos were given for one y as daily dietary supplements to 45 elderly residents
of a nursing home. Initially, the serum TBA reactant levels were higher (2.7±0.7 μmol/L) than those of an ad hoc control group
of healthy younger adults (2.3±0.6 μmol/L),p<0.01. After three mo supplementation, the levels among the verum elderly had decreased to 2.2±0.6 μmol/L, and they remained
at this lower level until the end of the study period, whereas the placebo group showed no change.
A significant inverse correlation (r=−0.428,p<0.01) existed between the concentrations of serum TBA reactants and whole blood selenium (B-Se), but only B-Se levels above
200 μg/L were associated with a decrease in serum lipid peroxides. Serum alpha-tocopherol concentration also correlated inversely
with serum TBA reactants but this correlation (r=−0.273,p<0.76) was not as strong as that of B-Se.
Deficient vitamin B6 status, in biochemical terms, was observed in 25% of the elderly; a daily supplement of 2 mg B6 fully cured all cases of deficiency. The verum group improved slightly in several psychological tests, whereas subjects on
placebo remained unchanged or deteriorated during the follow-up period. Clinical amelioration among the verum subjects was
reported by the nurses; no toxic side effects were reported. In conclusion, the elderly benefited biochemically and clinically
of dietary antioxidant supplements. 相似文献
2.
Julius Brtko Peter Filipčík Soňa Hudecová Anastázia Brtková Janette Bransová 《Biological trace element research》1998,62(1-2):43-50
The present study was undertaken to investigate the effects of selenite (SeIV) and selenate (SeVI) on the all-trans retinoic acid (RA)-nuclear retinoic acid receptor (RAR) complex formation in rat liver. We also present
the data on the in vitro effects of SeIV on the RARα and the type I iodothyronine 5′-deiodinase gene expression in the GH4C1 rat pituitary tumor cells. SeIV at 1.0 μmol/L was found to reduce (p<0.05) the RA specific binding to RAR in rat liver. Dithiothreitol (DTT), a protective agent for sulfhydryl groups, was found
to be slightly effective in protecting the RAR binding properties when affected by SeIV. SeVI at 0.1 μmol/L reduced (p<0.05) the RA specific binding to RAR in liver, as well. Seleno-l-methionine (Se-II) when compared tol-methionine did not exert any inhibitory effect on the formation of the RA-RAR complex. SeIV (up to 2.5 μmol/L) has no inhibitory effect on GH4C1 cell proliferation as well as the prolactin secretion. SeIV at 1.0 μmol/L significantly decreases the rate of mRNA synthesis and/or degradation of the α form of the RAR and causes the
enhancement of the type I iodothyronine 5′-deiodinase gene expression in GH4C1 cells.
The results based on in vitro experiments suggest that inorganic selenium may affect the RA specific binding to their cognate
receptor molecules, and it may reduce expression of the gene encoding the RARα, with the cell vitality and the cell growth
remaining unchanged. 相似文献
3.
The response of trout and zebrafish embryos to low and high boron concentrations is U-shaped 总被引:2,自引:0,他引:2
Fish in the embryo-larval stage of development have been shown to be sensitive to boron (B) at both ends of the dose-response
curve (1,2). The present study evaluated the health effects of low and high B concentrations on rainbow trout (Oncorhynchus mykiss), a cold water species, and zebrafish (Danio rerio), a warm water species. Rainbow trout embryos were incubated from day 1 until 2 wk posthatch in Type 1 ASTM ultrapure-grade
water (12.5°C) supplemented with only B (0-500 μM) as boric acid, or together with CaCO3 (0–2 mM) to increase water hardness. Embryonic growth was stimulated by B in a dose-dependent manner at all Ca concentrations
(p < 0.001). Chronic exposures below 9 μmol B/L impaired embryonic growth and above 10 mmol B/L caused death (p < 0.001). Thus, the safe range of exposure for the rainbow trout was between the adverse effect concentrations of 9 μmol
B/L and 10 mmol B/L. Zebrafish were maintained for 6 mo in ultrapure water containing <0.2 μmol B/L to determine the effect
of low-level exposure. High-level exposure was assessed by exposing zygotes, derived from parents maintained at 46 μmol B/L,
to graded concentrations of boric acid up to a concentration of 75 mmol B/L from fertilization until they were free feeding
(96 h). Fertilization occurred, but zygotes failed to survive when water contained <0.2 umol B/L (p < 0.001). Death occurred at and above 9.2 mmol B/L. Thus, the safe range of B exposure for zebrafish was between the adverse
effect concentrations of 0.2 μmol B/L and 9.2 mmol B/L. The dose-response for both species was thus U-shaped.
Part of this work was previously published in abstract form and presented at Experimental Biology 97, April 6–9, New Orleans,
LA (Eckhert, C. [1997] Embryonic trout growth and boron exposure,FASEB J.
11, A406 [abstract]). 相似文献
4.
Alma E. Rodriguez Estrada Hyun-Ju Lee Robert B. Beelman Maria del Mar Jimenez-Gasco Daniel J. Royse 《World journal of microbiology & biotechnology》2009,25(9):1597-1607
Antioxidants are molecules that may reverse, prevent or slow cellular damage caused by free radicals. Increasing dietary intake
of antioxidants is thought to reduce oxidative stress that may contribute to the development of several diseases. Mushrooms
are known to contain antioxidants such as selenium, ergothioneine and phenolics that may serve this role. Here we sought to
enhance selenium and ergothioneine concentration in Pleurotus eryngii var. eryngii basidiomata by modifying the techniques used for their commercial cultivation. To enhance selenium content in mushrooms,
substrates were supplemented with sodium selenite (Na2SeO3) to reach selenium concentrations of 5 and 10 μg/g. Basidiomata of one commercial isolate (WC888) accumulated selenium up
to 4.6 and 9.3 μg/g (d.w.), respectively. Therefore, a serving size (85 g) of fresh P. eryngii mushrooms produced on substrates supplemented with 5 and 10 μg/g of Na2SeO3 would supply 70.4 and 116.3% of the daily value of selenium (DV = 70 μg), respectively. Since selenium-enriched mushrooms
would supply more than 20% of the DV, they could be considered an excellent source of selenium. Ergothioneine concentration
was enhanced in mushrooms produced on low-moisture (55%) substrate compared to the commonly used 60% (high-moisture) in commercial
cultivation. Mushrooms produced on low-moisture substrate had ergothioneine concentrations of 3.0 mg/g, while mushrooms produced
on high-moisture substrate contained 2.2 mg/g or less. Use of a casing overlay for mushroom production resulted in significant
yield increases on low-moisture substrate but not on high-moisture substrate. 相似文献
5.
Jetmund Ringstad Synnøve F. Knutsen Odd R. Nilssen Yngvar Thomassen 《Biological trace element research》1993,36(1):65-71
Depressed selenium and Vitamin E levels may contribute to hepatic injury through lipid peroxidation. To study the effect of
moderate alcohol drinking (32.4±23.6 g ethanol/d) on serum selenium and serum vitamin E concentrations, we conducted a matched-pair
study of 73 healthy, well-nourished risk drinkers and healthy controls with little or no alcohol consumption. Among risk drinkers,
serum selenium was significantly lowered (1.49 vs 1.67 μmol/L;p<0.001) compared with controls. Difference in α-tocopherol concentrations did not, however, reach statistical significance
(22.8 vs 24.9 μmol/L;p=0.06). Nutritional and life-style factors differed very little between the two groups. We conclude that even moderate alcohol
consumption lowers selenium status. Selenium may thus represent a link joining the hepatotoxic and nutritional backgrounds
of alcoholic liver disease. 相似文献
6.
The effects of phosphorus, Zn2+, CO2, and light intensity on growth, biochemical composition, and the activity of extracellular carbonic anhydrase (CA) in Isochrysis galbana were investigated. A significant change was observed when the concentration of phosphorus in the medium was increased from
5 μmol/L to 1000 μmol/L affecting I. galbana’s cell density, biochemical composition, and the activity of extracellular CA. Phosphorous concentration of 50 μmol/L to 500
μmol/L was optimal for this microalgae. The Zn2+ concentration at 10 μmol/L was essential to maintain optimal growth of the cells, but a higher concentration of Zn2+ (≥ 1000 μmol/L) inhibited the growth of I. galbana. High CO2 concentrations (43.75 mL/L) significantly increased the cell densities compared to low CO2 concentrations (0.35 mL/L). However, the activity of extracellular CA decreased significantly with an increasing concentration
of CO2. The activity of extracellular CA at a CO2 concentration of 43.75 mL/L was approximately 1/6 of the activity when the CO2 concentration was at 0.35 mL/L CO2. Light intensity from 4.0 mW/cm2 to 5.6 mW/cm2 was beneficial for the growth, biochemical composition and the activity of extracellular CA. The lower and higher light intensity
was restrictive for growth and changed its biochemical composition and the activity of extracellular CA. These results indicate
that phosphorus, Zn2+, CO2, and light intensity are important factors that impact growth, biochemical composition and the activity of extracellular
CA in I. galbana. 相似文献
7.
Dose-related influence of sodium selenite on apoptosis in human thyroid follicles in vitro induced by iodine, EGF, TGF-β, and H2O2 总被引:1,自引:0,他引:1
Lehmann P Rank P Hallfeldt KL Krebs B Gärtner R 《Biological trace element research》2006,112(2):119-130
Apoptosis of thyroid follicular cells is induced by high doses of iodide, epidermal growth factor (EGF), transforming growth
factor-β (TGF-β), as well as H2O2 and might be attenuated by antioxidants. Therefore, we examined the apoptotic index induced by these substances in selenium-treated
vs untreated human thyroid follicular cells. Reconstituted human thyroid follicles were incubated with sodium selenite (10
or 100 nM) for 72 h; controls received none. The follicles were then distributed to 24-well plates and incubated with potassium iodide
(5, 10, or 20 nM), EGF (5 ng/mL), TGF-β (5 ng/mL), or H2O2 (100 μM). Apoptosis was determined by a mitochondrial potential assay and the number of apoptotic cells counted by two independent,
experienced technicians and the glutathione peroxidase (GPx) activity was determined. A significant increase of apoptic cells
was obtained in control thyroid follicles treated with iodine (5, 10, or 20 μM), thyroid-stimulating hormone (TSH) 1, or 10 mU/mL in combination with 5 and 10 μM iodine, EGF (5 ng/mL) and TGF-β (5 ng/mL), or H2O2 (100 μM) (p<0.001). In contrast, in thyroid follicles preincubated with 10 or 100 nM sodium selenite, the apoptototic index was identical to the basal rate. In H2O2-treated follicles, the apoptotic index was still significantly elevated but 50% lower compared to control cells. The GPx
activity increased from 1.4±0.2 to 2.25±0.4 mU/μg DNA with 10 nM selenite and 2.6+0.4 mU/μg DNA with 100 nM selenite. Sodium selenite might increase the antioxidative potential in human thyroid follicles in vitro and therefore diminish
the apoptosis induced by TGF-β, EGF, iodide, and even H2O2 相似文献
8.
The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied
in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as
sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations
of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of
revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene,
and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na2SeO3 reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic
selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion.
Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na2SeO4 inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that
form and concentration are important factors in this trace element's efficacy. 相似文献
9.
The effects of selenium, zinc, iron, chromium, and lead on telomere lengths of human cells have not been investigated. This
article adopted flow cytometry and fluorescence in situ hybridization to investigate the impact of different elements on cellular apoptosis and telomere lengths of human hepatocytes
L-02 and hepatoma cells SMMC-7721. Results showed that these trace elements under the following dosages did not have remarkable
effect on cellular apoptosis. However, sodium selenite at doses of 0.5 and 2.5 μmol/L significantly extended the telomere
length of hepatocytes L-02; 0.5 μmol/L lead acetate remarkably shortened the telomere length of L-02 cells; 80 μmol/L zinc
sulfate, 20 μmol/L ferric chloride, and 200 μmol/L chromic chloride only had slight impact on the telomere length, respectively.
Regarding hepatoma cells SMMC-7721, sodium seleite at 0.5 and 2.5 μmol/L had little impact on the telomere length; 80 μmol/L
zinc sulfate significantly accelerated the loss of telomere length, whereas 20 μmol/L ferric chloride, 200 μmol/L chromic
chloride, and 0.5 μmol/L lead acetate remarkably extended the telomere lengths, respectively. The results revealed differential
effects of each trace element on the life-span of human hepatocytes and hepatoma cell lines, which suggested further research
on somatic hepatocytes and hepatoma in vivo. 相似文献
10.
Letsiou S Nomikos T Panagiotakos D Pergantis SA Fragopoulou E Antonopoulou S Pitsavos C Stefanadis C 《Biological trace element research》2009,128(1):8-17
The trace element selenium is an essential micronutrient for human health and its low levels in serum are implicated in the
pathogenesis of several chronic diseases. Therefore, the determination of total selenium in serum may contribute to the assessment
of the health and nutritional status of certain populations. The objective of the present work was to determine total selenium
in the serum of 506 healthy volunteers that participated in the ATTICA study. Selenium was determined in serum by using the
technique of inductively coupled plasma mass spectrometry. The mean serum selenium concentration was determined to be 91.8 ± 33.7 μg/L
(N = 506); 87.6% of women and 88.5% of men had serum selenium concentration below 125 μg/L, the cutoff considered to be required
for optimal glutathione peroxidase activity. No association was found between serum selenium levels and the gender of the
participants while a significant decline of selenium with age (p < 0.0001) was observed. According to our results, no anthropometric, lifestyle, nutritional, or biochemical indices were
able to affect the association between serum selenium and age. This result may indicate that other factors such as selenium
distribution as well as retention may be affecting the relationship between serum selenium and age. 相似文献
11.
Lennart Hardell Marit Danell Carl-Axel Ängqvist Stefan L. Marklund Mats Fredriksson Anna-Lena Zakari Arne Kjellgren 《Biological trace element research》1993,36(2):99-108
Plasma selenium and glutathione peroxidase in erythrocytes were analyzed in a case-control study encompassing 441 cases with
breast cancer and 191 controls with benign breast disease. No difference in mean serum selenium level between cases and controls
on supplementary selenium intake was seen. If only individuals without supplementary intake, 278 cases and 135 controls, were
considered a preventive effect was found increasing with selenium level. This finding was significant among women 50 years
old or more with Mantel-Haenszel odds ratio=0.16 for individuals with serum selenium >1.21 μmol/L. Also for subjects with
serum selenium in the range 1.00–1.21 μmol/L a significant preventive effect was seen with odds ratio=0.38. For women under
50 years of age a nonsignificant preventive effect was seen. Glutathione peroxidase in erythrocytes did not correlate well
with serum selenium and was not a marker for the risk of breast cancer. 相似文献
12.
Eduard Kühn Rudi Van Cauwenbergh Leo Huybrechts Hendrik Deelstra 《Biological trace element research》1992,32(1-3):289-292
Plasma concentrations of cGH, T3, and T4 were not different between dwarf and normal broiler breeders. Normal hens had a liver selenium content of 710±35 ng/g, and
dwarf hens 656 ±nine ng/g (n=8). Following injections into a wing vein of different doses (1.5, 3, 6, 12, and 24 μg/kg) of the hypothalamic hormone TRH,
GH was increased after 15 min. This effect seemed to last longer in dwarf chickens. Plasma concentrations of T3 increased significantly 1 h after TRH in normal hens, but TRH was ineffective in raising T3 levels in dwarf animals. The selenium content of livers obtained following decapitation after 2 h was also increased in normal
hens up to 902±42 ng/g using the highest dose of TRH (24 μg/kg). This seemed not to be the case for dwarf animals. A much
smaller. number of hepatic cGH receptors was also found in dwarf hens, whereas the affinity of the hepatic GH receptor was
not influenced by the genotype. It is concluded that the sex-linked dwarf hens are unable to increase their hepatic T4 into T3 conversion following a TRH challenge probably because of a deficiency in hepatic GH receptors. The lower content of selenium
in dwarfs and their inability to increase its uptake after TRH seem therefore to support the hypothesis that selenium has
a direct role in the activity of the 5′-deiodinase complex. 相似文献
13.
The concentrations of cadmium, lead, selenium, and zinc in blood and seminal plasma were determined in 76 Singapore males.
Except for zinc, the concentrations were generally higher in blood than in seminal plasma (cadmium, 1.31 μg/L vs 0.61 μg/L;
lead, 82.6 μg/L vs 12.4 μg/L, and selenium, 163.6 μg/L vs 71.5 μg/L). The mean concentration of zinc in seminal plasma was
more than 30 times higher than in blood (202 mg/L vs 6.2 mg/L). Significant positive correlations were found between the concentrations
in blood and seminal plasma for the two essential trace elements: selenium (r=0.45,p<0.001) and zinc (r=0.25,p<0.05). However, no relationships were found between the concentrations in blood and seminal plasma for two toxic metals (cadmium
and lead). Significant inverse correlations were observed between Cd and Zn (r=−0.40,p<0.01), and Pb and Se (r=−0.32,p<0.05) in blood, whereas significant positive correlations were noted between Cd and Se (r=0.45,p<0.01), Cd and Zn (r=0.35,p<0.05), and Se and Zn (r=0.57,p<0.001) in seminal plasma. The physiological significance of these relationships are also discussed in this paper. 相似文献
14.
M. Torras-Llort R. Ferrer J.F. Soriano-García M. Moretó 《The Journal of membrane biology》1996,152(3):183-193
The properties of l-lysine transport in chicken jejunum have been studied in brush border membrane vesicles isolated from 6-wk-old birds. l-lysine uptake was found to occur within an osmotically active space with significant binding to the membrane. The vesicles
can accumulate l-lysine against a concentration gradient, by a membrane potential-sensitive mechanism. The kinetics of l-lysine transport were described by two saturable processes: first, a high affinity-transport system (K
mA= 2.4 ± 0.7 μmol/L) which recognizes cationic and also neutral amino acids with similar affinity in the presence or absence
of Na+ (l-methionine inhibition constant KiA, NaSCN = 21.0 ± 8.7 μmol/L and KSCN = 55.0 ± 8.4 μmol/L); second, a low-affinity transport mechanism (KmB= 164.0 ± 13.0 μmol/L) which also recognizes neutral amino acids. This latter system shows a higher affinity in the presence
of Na+ (KiB for l-methionine, NaSCN = 1.7 ± 0.3 and KSCN = 3.4 ± 0.9 mmol/L). l-lysine influx was significantly reduced with N-ethylmaleimide (0.5 mmol/L) treatment. Accelerative exchange of extravesicular labeled l-lysine was demonstrated in vesicles preloaded with 1 mmol/L l-lysine, l-arginine or l-methionine. Results support the view that l-lysine is transported in the chicken jejunum by two transport systems, A and B, with properties similar to those described
for systems b
0,+ and y+, respectively.
Received: 14 August 1995/Revised: 2 April 1996 相似文献
15.
Markus P. Look Jürgen K. Rockstroh Govind S. Rao Karl A. Kreuzer Ulrich Spengler Tilman Sauerbruch 《Biological trace element research》1997,56(1):31-41
Serum selenium levels were determined cross-sectionally in 57 HIV-infected patients who were classified according to the Centers
for Disease Control (CDC) 1993 classification system. Mean serum selenium levels were lower in CDC stage II (58.7±12.2 μg/L;p<0.01;n=18) and stage III (47.6±11.3 μg/L;p<0.01;n=19) HIV-infected patients, than in healthy subjects (80.6±9.6 μg/L;n=48) and stage I patients (73.6±16.5 μg/L;n=20). Serum selenium levels were positively correlated with CD4 count, CD4/8 ratio, hematocrit, and serum albumin (r=0.42;r=0.39;r=0.48; andr=0.45;p<0.01, respectively) and inversely with serum levels of thymidine kinase (r=−0.49;p<0.01;n=49) and β2-microglobulin (r=−0.46;p<0.001;n=49). In addition, serum selenium levels in 20 randomly selected AIDS-free individuals (CDC I:n=10; CDC II:n=10) were inversely correlated with serum concentrations of interleukin-8 (IL-8) and soluble tumor necrosis factor receptors
(sTNFR) types I and II. There was no correlation with serum immuneglobulin A and total serum protein levels. The results show
that the progressive deprivation of serum selenium in HIV-infection is associated with loss of CD4+-cells and with increased levels of markers of disease progression and inflammatory response. 相似文献
16.
Nitrogen-Use Efficiency in Relation to Different Forms and Application Rates of Se in Lettuce Plants
Juan J. Ríos Begoña Blasco Luis M. Cervilla Maria M. Rubio-Wilhelmi Miguel A. Rosales Eva Sanchez-Rodriguez Luis Romero Juan M. Ruiz 《Journal of Plant Growth Regulation》2010,29(2):164-170
The main objective of this work was to determine whether nitrogen-use efficiency (NUE) was affected by the application of
different forms and dosages of selenium (Se), to ascertain the influence of this trace element in a biofortification program
in lettuce plants. The parameters analyzed were biomass, NO3
− concentration, and total reduced N as well as those defining NUE in plants: total nitrogen accumulation (TNA), nitrogen efficient
ratio (NER), nitrogen-utilization efficiency (NUtE), and nitrogen-uptake efficiency (NUpE). According to our results, application
of Se affected NUE in lettuce plants. With the application of selenite as well as selenate NO3
− uptake was reduced, thus diminishing the NUpE and the foliar concentration of this anion. In addition, selenate application
at a rate of 20 μM and selenite at 5 μM induced N utilization, reflected by an increase in NER and NUtE; this result coincides
with augmented biomass production. Notably, our results indicate that when Se is applied at high rates, selenite is far more
phytotoxic, this being associated with a higher reduction of NUE in these plants. 相似文献
17.
A bacterium that reduces toxic and mobile selenite to insoluble elemental selenium (Se0) was isolated from a laboratory scale permeable reactive biobarrier. Biochemical tests and 16S rRNA gene sequence alignment
identified the isolate as Aeromonas salmonicida. Two colony types were isolated, one more resistant to selenite than the other. Both grew on agar plates containing 16 mM selenite, although the colony diameter was reduced to 8% of controls with the small colony type and to 18% with the large
colony type. Further study was done with the large colony type. In anaerobic culture, this bacterium was able to use nitrate
as a term electron acceptor but not selenate or selenite. In aerobic culture, when no nitrate was present, early log phase
cells removed selenite at a rate of 2.6 ± 0.42 μmol SeO3−2/mg protein/day. Reduction was retarded by 25 mM nitrate. Mutants with a diminished ability to reduce selenite to Se0 also had a reduced ability to reduce nitrate to nitrous oxide. This bacterium, or perhaps its enzymes or DNA, might be used
to remove selenite from contaminated groundwaters. 相似文献
18.
Cultures able to dechlorinate cis-1,2-dichloroethene (cDCE) were selected with ethene (3–20%, v/v) as the sole source of carbon and energy. One mixed culture (K20) could degrade
cDCE (400 μmol l–1) or vinyl chloride (100 μmol l–1) in the presence of ethene (≤ 80 μmol l–1 and ≤ 210 μmol l–1, respectively). This culture consists of at least five bacterial strains. All five strains were able to degrade cDCE cometabolically in pure culture. The mixed culture K20 was highly tolerant against cDCE (up to 6 mmol l–1 in the liquid phase). Degradation of cDCE (200 μmol l–1) was not affected by the presence of trichloroethene (100 μmol l–1) or tetrachloroethene (100 μmol l–1). Transformation yields (Ty, defined as unit mass of chloroethene degraded per unit mass of ethene consumed) of the mixed culture K20 were relatively
high (0.51 and 0.61 for cDCE and vinyl chloride, respectively). The yield for cDCE with ethene as auxiliary substrate was ninefold higher than any values reported with methane or methane/formate as auxiliary
substrate. The viability of the cells of the mixed culture K20 (0.3 mg of cells ml–1) was unaffected by the transformation of ≤ 200 μmol l–1
cDCE in 300 min.
Received: 9 March 1999 / Accepted: 21 July 1999 相似文献
19.
We studied the effects of trace elements, Mn, Mo, and Si, on vasoconstriction induced by norepinephrine (NE) or electrical
field stimulation in isolated porcine right coronary arteries. α1-Adrenoceptor (AR) antagonist prazosin dose-despondently suppressed vasoconstriction in response to NE or field stimulation
indicating an α1-AR mediated response. Mn, Mo, and Si at 0.3-3 μmol/L dosedespondently inhibited NE mediated contraction (allp < 0.05). In contrast, Mn, Mo, and Si at the same concentrations (0.3-3 μmol/L) enhanced the maximal contractile response to
field stimulation in a dose-dependent manner (allp < 0.05), but these elements at 10 μmol/L suppressed the vasoconstrictive response. The results indicate that in porcine right
coronary arteries, the α1-AR-mediated vasoconstriction by NE or electrical field stimulation was affected differently by micromolar concentrations
of Mn, Mo, and Si and that the elements might facilitate NE release presynaptically but inhibit the contractile response postsynaptically. 相似文献
20.
The study was conducted to investigate the effects of dietary maternal selenomethionine or sodium selenite supplementation
on performance and selenium status of broiler breeders and their next generation. Two hundred and forty 39-week-old Lingnan
yellow broiler breeders were allocated randomly into two treatments, each of which included three replicates of 40 birds.
Pretreatment period was 2 weeks, and the experiment lasted 8 weeks. The groups were fed the same basal diet supplemented with
0.30 mg selenium/kg of sodium selenite or selenomethionine. After incubation, 180 chicks from the same parental treatment
group were randomly divided into three replicates, with 60 birds per replicate. All the offspring were fed the same diet containing
0.04 mg selenium/kg, and the experiment also lasted 8 weeks. Birth rate was greater (p < 0.05) in hens fed with selenomethionine than that in hens fed with sodium selenite. The selenium concentration in serum,
liver, kidney, and breast muscle of broiler breeders, selenium deposition in the yolk, and albumen and tissues' (liver, kidney,
breast muscle) selenium concentrations of 1-day-old chicks were significantly (p < 0.01) increased by maternal selenomethionine supplementation compared with maternal sodium selenite supplementation. The
antioxidant status of 1-day-old chicks was greatly improved by maternal selenomethionine intake in comparison with maternal
sodium selenite intake and was evidenced by the increased glutathione peroxidase activity in breast muscle (p < 0.05), superoxide dismutase activity in breast muscle and kidney (p < 0.05), glutathione concentration in kidney (p < 0.01), total antioxidant capability in breast muscle and liver (p < 0.05), and decreased malondialdehyde concentration in liver and pancreas (p < 0.05) of 1-day-old chicks. Feed utilization was better (p < 0.05), and mortality was lower (p < 0.05) in the progeny from hens fed with selenomethionine throughout the 8-week growing period compared with those from
hens fed with sodium selenite. In summary, we concluded that maternal selenomethionine supplementation increased birth rate
and Se deposition in serum and tissues of broiler breeders as well as in egg yolk and egg albumen more than maternal sodium
selenite supplementation. Furthermore, maternal selenomethionine intake was also superior to maternal sodium selenite intake
in improving the tissues Se deposition and antioxidant status of 1-day-old chicks and increasing the performance of the progeny
during 8 weeks of post-hatch life. 相似文献