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1.
Zinc, cadmium, and copper are known to interact in many transport processes, but the mechanism of inhibition is widely debated,
being either competitive or noncompetitive according to the experimental model employed. We investigated the mechanisms of
inhibition of zinc transport by cadmium and copper using renal proximal cells isolated from rabbit kidney. Initial rates of65Zn uptake were assessed after 0.5 min of incubation. The kinetics parameters of zinc uptake obtained at 20°C were a Jmax of 208.0±8.4 pmol· min−1·(mg protein)−1, aK
m of 15.0±1.5 μM and an unsaturable constant of 0.259±0.104 (n=8). Cadmium at 15 μM competitively inhibited zinc uptake. In the presence of 50 μM cadmium, or copper at both 15 and 50 μM, there was evidence of noncompetitive inhibition. These data suggest that zinc and cadmium enter renal proximal cells via
a common, saturable, carrier-mediated process. The mechanisms of the noncompetitive inhibition observed at higher concentrations
of cadmium or with copper require further investigation, but may involve a toxic effect on the cytoskeleton. 相似文献
2.
Cerovic A Miletic I Sobajic S Blagojevic D Radusinovic M El-Sohemy A 《Biological trace element research》2007,116(1):61-71
Zinc is an important mineral that is required for normal bone development. However, the direct effects of zinc on the mineralization
of bone cells of human origin are not clear. The objective of this study was to determine the effects of zinc on the differentiation
of SaOS-2 human osteoblast-like cells and the formation of mineralized bone nodules. Cells were cultured for 8 d and then
transferred to zinc-free medium and treated with varying concentrations (0–50 μM) of zinc. Alkaline phosphatase (ALP) activity was used as a measure of osteoblast differentiation, and bone nodules were
detected by von Kossa staining. After 4, 6, and 8 d of treatment, zinc increased ALP activity at 1 and 10 μM, but decreased activity at 50 μM. After 9 d of treatment, zinc increased both the number and area of mineralized bone nodules at low concentrations (1 and
10 μM), but decreased both at higher concentrations (25 and 50 μM). These findings demonstrate that zinc has biphasic effects on the differentiation and mineralization of human osteoblast-like
cells. 相似文献
3.
Angelos Evangelou Vicky Kalfakakou Jaques Benveniste Bernard Arnoux 《Biological trace element research》1995,50(1):43-55
PAF-acether is a phospholipid synthesized by most animal tissues and exerting a strong decrease on the heart’s contractile
force and coronary flow. PAF-acether (10−9 and 10−10
M) was administered to isolated guinea pig hearts perfused via the Langendorff apparatus with Chenoweth solution. Zinc (1.5
μM) is known to benefit heart function thus, Zn2+ (1.5, 7.5, and 30 μM) was added in the perfusing solution before or after PAF-acether administration. Contractile force, coronary flow, and heart
rate were recorded by means of a Narco MK-IV Physiograph throughout all modes of perfusion. Calcium inhibitor (Verapamil 10−10
M) and Pb2+ Co2+ (1.5×10−6
M) were used subsequently in the perfusing solutions in order to elucidate some of the Zn and PAF interactions observed. All
hearts were analyzed for their Zn and Ca content by means of an Atomic Absorption Spectrophotometry (AAS). Our data suggest
that low concentrations of zinc (1.5 μM) can strongly inhibit PAF-induced decrease of contractile force and coronary flow. Zinc-inhibiting effects on PAF's negative
inotropic action (myocytic level) is not exerted through Zn−Ca antagonism. Nevertheless, a Zn−Ca antagonism in the arteriolar
level cannot be excluded. Zinc inhibits PAF selectively only if it is administered before PAF injection and this strongly
suggests a receptor interaction between the metal and the phospholipid at the heart level. 相似文献
4.
Vicky P. Kalfakakou Angelos M. Evangelou Jacques Benveniste Bernard Arnoux 《Biological trace element research》1993,38(3):289-299
Isolated guinea pig hearts were perfused, by the Langendorff technique, with 30, 15, 7.5, and 1.5 μM Zn2+ in Chenoweth solution. Contractile force, coronary flow, and heart rate were recorded by means of Narco IV Physiograph. Calcium
inhibitor (Verapamil 1 μM) and anion inhibitor (DIDS: 0.1, 1, and 5 μM) were used subsequently in the perfusing solutions in order to distinguish some of the possible mechanisms that Zn2+ uses to exert its action on cardiac myocytes. Isomolar to zinc concentration of Pb (II) and Co (II) were used to elucidate
whether zinc effects on heart are specific for this metal. All hearts were used to estimate their zinc and calcium content
by means of AAS (Atomic Absorption Spectrometry).
Our findings suggest that the higher the Zn2+ concentration, the more toxic effects on heart are expressed by rapid reversible contractile force reduction and reversible
specific changes of heart rate and flow. Zinc 1.5 μM in the perfusing solution benefits heart performance, but not significantly. Furthermore, the metal exerts specific effects
on guinea pig heart, and it is rather possible that these effects on cardiac myocytes are held through cell membrane receptors. 相似文献
5.
The effect of the acrodermatitis enteropathica mutation on zinc uptake in human fibroblasts 总被引:1,自引:0,他引:1
The acrodermatitis enteropathica (AE) mutation affects intestinal zinc absorption. Our goal was to determine whether the AE
mutation affects zinc uptake in human fibroblasts. Zinc uptake was determined during initial rates of uptake (10 min) following
incubation in HEPES/saline buffer. Zinc uptake (from 0.25 to 1 μM) into normal fibroblasts was significantly greater than into the AE fibroblasts (p<0.05). In order to identify factors that may alter cellular zinc uptake and be affected by the AE mutation, zinc uptake in
the presence of albumin or bicarbonate was measured. Albumin restricted zinc uptake in both normal and AE fibroblasts, whereas
bicarbonate stimulated zinc uptake in the normal fibroblasts. The effect of bicarbonate on zinc uptake in the AE fibroblasts
was significantly reduced in both the Pronase-sensitive and Pronase-resistant compartments. Following loading of the fibroblasts
with 1 μM zinc for 60 min, zinc efflux and retention were measured. The AE mutation did not affect zinc retention compared to normal
fibroblasts. We conclude that the AE mutation affects both zinc binding to the cell surface and its translocation across the
plasma membrane into the cell, possibly mediated through a defective anionic exchange mechanism. 相似文献
6.
Duong Tan Nhut Bui Van Le K. Tran Thanh Van 《In vitro cellular & developmental biology. Plant》2001,37(1):44-49
Summary Excised tissues from transverse young stem sections of Lilium longiflorum were cultured on Murashige and Skoog medium supplemented with growth regulators at various concentrations. After 45 d in
culture, the presence of α-naphthaleneacetic acid (NAA) in the culture medium at 5.4 μM resulted in bulblet formation while 2,4-dichlorophenoxyacetic acid (2,4-D) at 2.2 μM resulted in root formation. The presence of IBA (indole-3-butyric acid) in the culture medium at 1.0 μM resulted in shoot formation while plantlet formation occurred when IBA was added at a concentration of 2.0 μM. When 1-phenyl-3-(1,2,3-thiadiazol-5-yl)-urea (TDZ) was added to the culture medium at 1.1 μM, protocorm-like bodies (PLBs) formed, while 2.2 μM resulted in shoot formation (on abaxial and adaxial surfaces). The presence of NAA and TDZ in the culture medium at 5.4 μM and 0.4, 1.1 or 2.2 μM, respectively, resulted in somatic embryo formation while NAA- and 6-benzylaminopurine-(BA) containing culture medium formed
callus or bulblets. The establishment of different regeneration systems when explants are exposed to various growth regulators
demonstrates that the choice of growth regulator combinations and concentrations are of significance in determining the morphogenetic
response and plant regeneration capacity. 相似文献
7.
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
8.
Exposure of rat hepatocytes to cadmium below 50 μM for a short period (10 min) resulted in cellular acidification. Conversely, exposure to Cd more than 50 μM for a long period (60 min) caused cellular alkalinization accompanied by membrane damage as reflected by decrease in cellular
K content and loss of intracellular lactic dehydrogenase. In hepatocytes exposed to 5 μM Cd, a concentration sufficient to induce acidification without cytotoxicity, the metal was preferentially associated with
the crude nuclei and cell debris fractions, suggesting an interaction between Cd and cell membranes to cause acidification.
Omission of bicarbonate from the incubation medium induced cellular acidification. The presence of Cd in this medium did not
potentiate the medium-induced acidification. Mg-ATP (25 μM) induced cellular acidification in relation to an increase in the concentration of cytosolic free Ca. The coexistence of
Mg-ATP and Cd at the concentrations which had no effect on cellular pH in the presence of either agants induced cellular acidification.
These observations suggest that Cd induced cellular acidification by modulating the process connected with the rise in cytosolic
free Ca via interaction with plasma membranes. This acidification had no strong immediate cytotoxic actions but led to subsequent
cellular alkalinization accompanied with severe cytotoxicity and membrane breakage. 相似文献
9.
S. R. Thengane D. K. Kulkarni V. A. Shrikhande K. V. Krishnamurthy 《In vitro cellular & developmental biology. Plant》2001,37(2):206-210
Summary Regeneration of adventitious shoots from the medicinal plant Nothapodytes foetida (Weight) Sleumer Syn. Mappia foetida (family Ieacinaceceae) has been achieved using different seedling explants. Direct, regeneration of shoot buds was observed
in Murashige and Skoog's (MS) basal medium supplemented with various concentrations of thidiazuron. The optimum levels of
thidiazuron concentrations were 0.91–4.45 μM. Leaf explants formed more shoots followed by hypocotyls or cotyledons. The shoot buds elongated and rooted on MS basal medium
with N6-benzyladenine (0.88–2.22 μM) and indole-3-butyric acid (0.49 μM). 相似文献
10.
External phosphorus requirements of five tropical grain legumes grown in flowing-solution culture 总被引:4,自引:0,他引:4
Summary Five tropical grain legume species were grown for periods from 4 to 20 days in flowing-solution culture at 7 maintained phosphorus
(P) concentrations, ranging from 0.25 μM to 16 μM. Critical external P requirements were 0.8 μM for cowpea cv. Vita 4 and soybean cv. Fitzroy, 1.0 μM for pigeon pea cv. Royes, 2.0 μM for mungbean cv. Regur and 3.0 μM for guar cv. Brooks. Plant responses to P deficiency included reduced growth rate, increased root percentage, and increased
P uptake potential. The long-term P uptake rates of guar plants were lower than those of the other species at each external
P concentration. Guar plants had a low P uptake potential as indicated by short-term32CP-labelled uptake rate studies from 15 μM P solutions. Cowpea by contrast had high short-term uptake rates indicating a high P uptake potential. 相似文献
11.
Summary Methyl jasmonate (MeJA) interacted significantly with both indole-3-acetic acid (IAA) and 6-benzylaminopurine (BA) to influence
cell growth of cultured Onosma paniculatum cells. Cell growth decreased with increasing concentrations of MeJA from 0.004–4.45 μM with or without IAA and BA. The same concentrations of MeJA (0–4.45 μM) increased the cell growth with IAA and BA, when administered to the cultured cells in M9 medium. This was found to enhance the production of shikonin. The optimum time for MeJA addition for enhanced shikonin formation
was 4 d after cell inoculation in M9 medium. Furthermore, shikonin formation was affected significantly by both MeJA/IAA and MeJA/BA combinations. Shikonin content
was enhanced by increasing MeJA concentrations with IAA concentrations in the range of 0–28 μM and with BA concentrations in the range of 0–44.38 μM in MeJA/BA experiments, respectively. The optimal combination of MeJA and IAA was 4.45 μM and 0.28 μM, while MeJA and BA concentrations of 4.45 μM and 2.22 μM were optimal for shikonin formation. The result also showed that MeJA increased phenylalanine ammonia-lyase (PAL) and p-hydroxybenzoic acid-geranyltransferase (PHB-geranyltransferase) activites during the course of shikonin formation, but decreased
the activity of PHB-O-glucosyltransferase within 9 d after inoculation. These results suggest that enhanced shikonin formation in cultured Onosma paniculatum cells induced by MeJA involves regulation of the key enzyme activities. 相似文献
12.
Summary Sodium chloride-tolerant plantlets of Dendrocalamus strictus were regenerated successfully from NaCl-tolerant embryogenic callus via somatic embryogenesis. The selection of embryogenic
callus tolerant to 100 mM NaCl was made by exposing the callus to increasing (0–200 mM) concentrations of NaCl in Murashige and Skoog medium having 3% (w/v) sucrose, 0.8% (w/v) agar, 3.0 mg l−1 (13.6 μM) 2,4-dichlorophenoxyacetic acid (2,4-D), and 0.5mg l−1 (2.3μM) kinetin (callus initiation medium). The tolerance of the selected embryogenic callus to 100 mM NaCl was stable through three successive transfers on NaCl-free callus initiation medium. The tolerant embryogenic callus
had high levels of Na+, sugar, free amino acids, and proline but a slight decline was recorded in K+ level. The stable 100 mM NaCl-tolerant embryogenic callus differentiated somatic embryos on maintenance medium [MS medium +3% sucrose +0.8% agar +2.0
mg l−1 (9.0 μM) 2,4-D+0.5 mg l−1 (2.3 μM) kinetin] supplemented with different (0–200 mM) concentrations of NaCl. About 39% of mature somatic embryos tolerant to 100 mM NaCl germinated and converted into plantlets in germination medium [half-strength MS+2% sucrose+0.02 mg l−1 (0.1 μM) α-naphthaleneacetic acid +0.1 mg l−1 (0.49 μM) indole-3-butyric acid] containing 100 mM NaCl. Of these plantlets about 31% established well on transplantation into a garden soil and sand (1:1) mixture containing
0.2% (w/w) NaCl. 相似文献
13.
Jerome Honnorat Michele Accominotti Christiane Broussolle Andree-Carole Fleuret Jean-Jacques Vallon Jacques Orgiazzi 《Biological trace element research》1992,32(1-3):311-316
Zinc status was assessed in 53 diabetic patients: 18 insulin-dependent diabetic patients (IDDM), 22 noninsulin-dependent diabetic
patients (NIDDM) treated with oral antidiabetic agents, and 13 insulin-treated, noninsulin-dependent diabetic patients (IRDM).
Plasma zinc concentrations were in the usual range for healthy subjects in these three groups (15.3±0.9 μmol/L). Urinary zinc
excretions were elevated in the IDDM group (18.3±4.1 μmol/24 h;p<0.01 vs normal) and in the NIDDM group (17.5±3.5 μmol/24 h;p<0.01 vs normal), but normal in the IRDM group (11.3±2.4 μmol/24 h). In 14 NIDDM patients treated with transient continuous
sc insulin injections, urinary zinc decreased from 16.5±2.2 μmol/24 h before insulin treatment to 11.5±0.3 μmol/24 h after
insulin treatment without any modification in plasma zinc concentrations. 相似文献
14.
Summary A method of micropropagation through multiple shoot formation from axillary buds of mature tree and rootstock growths of Crataeva adansonii (DC.) Prodr. (a multipurpose tree) has been developed. Factors affecting multiplication rate included season, age of explant
source, explant type, type of bud, position of bud on the foliage twig, type of medium, various additives, and explant implantation
on the medium. The maximum number of buds was produced from the sixth to 10th axillary buds taken from foliage twigs of 40–50-d-old
rootstock growth in the months of October to December. At this time of the year the contamination was minimum. Optimum response
was recorded on Murashige and Skoog (MS) medium supplemented with 6-benzyladenine (BA; 3 mgl−1, 13.3μM) and 1-naphthaleneacetic acid (NAA; 0.05 mgl−1, 0.27 μM) after 21 d of culture. Shoot buds were further multiplied and maintained on BA (1–1.5 mgl−1, 4.4–6.7 μM) while shoots elongated on BA (0.1–0.5 mgl−1, 0.44–2.2 μM) supplemented medium. The number of shoots was further multiplied by using nodal segments of in vitro-regenerated shoots as microcuttings and repeated subculturing of stumps after excising the microshoots. In vitro rooting on growth regulator-free MS medium was possible with 70% of microshoots after 4 wk. From one nodal segment 150 plantlets
were produced within 14 wk. 相似文献
15.
Women with preeclampsia have been shown to have elevated blood levels of the metabolite homocysteine, and alterations in blood
levels of zinc and copper have also been reported. This study measured plasma levels of zinc, copper, and homocysteine in
women with preeclampsia and in women with healthy, normotensive pregnancies.
For the patients with preeclampsia compared with controls, significantly higher mean plasma levels were found of homocysteine
(16.39 vs 9.45 nmol/mL; p≤0.001), zinc (15.53 vs 11.93 μg/g protein; p < 0.05), and copper (47.90 vs 31.60 μg/g protein; p=0.001). The ratio of plasma Cu/Zn levels tended to be higher in preeclamptic women and could be taken as an index of inflammatory
reaction, but the difference was not significant. Homocysteine concentrations correlated positively with plasma zinc concentrations
in women with preeclampsia (r=0.588, p=0.003) but not in women with healthy pregnancies. No correlations were observed between plasma levels of homocysteine and
copper.
Thus, the present study found evidence that preeclampsia might be associated with hyperhomocysteinemia and elevated blood
levels of zinc and copper. Furthermore, elevated blood levels of zinc were significantly associated with hyperhomocysteinemia
in preeclampsia. More studies are warranted to investigate further any relationship between altered homocysteine metabolism
and levels of zinc and copper in preeclampsia. 相似文献
16.
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
17.
Cell-free extracts (CFEs) of chromium-resistant bacterium Bacillus sphaericus AND 303 isolated from serpentine soil of Andaman, India reduced Cr(VI) in in vitro condition, and the reductase activity was solely localized in the soluble cell-fractions (S12, S32, and S150). The enzyme was constitutive as the CFEs from cells grown in Cr(VI)-free and Cr(VI)-containing media reduced a more or less
equal amount of Cr(VI). Optimum Cr(VI) reductase activity was obtained at an enzyme (S150) concentration equivalent to 4.56 mg protein/mL, 300 μM Cr(VI) and pH 6.0 after 30 min incubation at 30°C. The enzyme was heat labile; 80% of its activity was lost when exposed
at 70°C for 15 min. Kinetics of Cr(VI) reductase activity fit well with the linearized Lineweaver-Burk plot and showed a Vmax of 1.432 μmol Cr(VI)/mg protein/min and Km of 158.12 μM Cr(VI). The presence of additional electron donors accelerated Cr(VI) reductase activity of CFE, and an increase of 28% activity
over control was recorded with 1.0 μM NADH. Heavy metal ions such as Ni(II), Cu(II), and Cd(II) were strong inhibitors of Cr(VI) reductase unlike that of 100 μM Co(II), which retained 93% activity over control. 相似文献
18.
Summary Sugarcane (Saccharum spp. hybrid cv. CP 84-1198) seeds were germinated on modified Murashige and Skoog (MS) basal medium alone or supplemented
with 2.3, 4.5, 11.3, 22.5, and 45.0 μM thidiazuron (TDZ), or 4.5, 13.6, 22.6, and 45.0 μM 2,4-dichlorophenoxyacetic acid (2,4-D), or 4.1, 12.4, 20.7, and 41.3, μM picloram. Both auxins delayed seed germination by approximately 5 d. Maximum germination was observed on MS medium supplemented
with 45.0 μM TDZ. Callus induction occurred for seed germinated on 2,4-D and picloram-containing media, but not on TDZ medium. The greatest
amount of callus (554±198mg per seed) was produced on 4.1 μM picloram. For shoot initiation, calluses were transferred to MS medium alone or supplemented with 2.5 μM TDZ. The highest number of shoots was recorded on TDZ medium from callus that had been obtained originally from media containing
either 4.1 or 12.4 μM picloram or 13.6 μM 2,4-D (∼500). All shoots developed roots and grew to maturity on medium with 24,6 μM indolebutyric acid. 相似文献
19.
Ze-peng Y Guo-wei L Hong-yu H Yun-yu W Yong-hui S 《Biological trace element research》2005,105(1-3):215-227
This experiment was conducted to investigate the effects of zinc sulfate and zinc methionine (Zn-Met) and their levels on
apoptosis induced by glucocorticoid of thymocytes and the possible mechanism. Dexamethasone was used to make the apoptosis
model of thymocytes; zinc sulfate and zinc methionine were supplemented to the medium at levels of 0,50, 100, 500, and 1000
μM. The activity of cells,Cu,Zn superoxide dismutase (Cu,Zn-SOD), DNA ladder pattern, intracellular calcium concentration, and
the percentage of apoptosis nuclei were determined.
Both ZnSO4 and Zn-Met could modulate apoptosis; they inhibited apoptosis and decreased DNA fragmentation. The regulation was concentration
dependent. At levels of 50 and 100 μM, the effect of Zn-Met on inhibiting apoptosis was less efficient than that of ZnSO4 (p<0.05), but the activity of the cells cultured with Zn-Met was higher than those cultured with ZnSO4; they showed no difference in modulating apoptosis when added at levels of 500 and 1000 μM to the medium (p>0.05). Intracellular calcium concentrations of cells cultured with Zn-Met were higher than those cultured with ZnSO4 at the same levels. Zinc supplementation decreased the concentration of intracellular calcium significantly (p<0.05) and increased the activity of Cu,Zn-SOD in the extract of the cells (p<0.05). Both zinc sulfate and Zn-Met could modulate apoptosis of thymocytes induced by glucocorticoid; the mechanism might
involve the exchange of intracellular calcium, the redox of cells, and the two forms of zinc might go different ways in the
regulations. 相似文献
20.
Paula N. Morgan Francoise Costa Carmen M. Donangelo Janet C. King 《Biological trace element research》1994,42(2):129-142
The aim of this study was to determine whether the postprandial decline in plasma zinc concentration is altered by aging.
Eleven women, between the ages of 65 and 82 yr, participated in two separate experimental protocols: a high carbohydrate breakfast
trial and a fasting trial. Plasma zinc concentrations were measured from blood samples obtained at 8∶00am (baseline fasting) and at 30-min intervals until 1∶00pm during each trial. Following the breakfast meal, plasma zinc concentrations declined 14% from 75±1 to 65±2 μg/dL (p<0.05), reaching a nadir 2.7±0.2 h after the meal. This decline was significantly (p<0.0001) greater than the 3.6% fall observed during the fasting trial. Postprandial changes in the plasma zinc concentrations
were correlated with postprandial changes in serum glucose (r=−0.43,p<0.001), serum insulin (r=−0.17,p<0.01), and serum phosphorus(r=0.32,p<0.005). These data show that plasma zinc concentrations decline following food intake in elderly women in the same manner
as previously described for younger adult women. 相似文献