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681.
Lead (Pb), depositing primarily in astroglia in the brain, is a well-known neurotoxicant and a risk factor for neurologic disorders. Pb has been reported to induce oxidative stress by probably the disturbance of copper (Cu) homeostasis in astroglia. Thus, we hypothesized that Pb-induced oxidative stress is initiated by interfering with Cu transporter in astroglia. In this study, we observed Pb-induced oxidative stress as indicated by reactive oxygen species (ROS) augmentation and GRP78 and GRP94 protein induction, and it was parallel to Cu accumulation intracellularly by Pb. To further address Cu transporter as a potential Pb target, a heavy metal-binding (HMB) domain of Cu-transporting ATPase (Atp7a) was overexpressed and purified. Evidence showed that one molecule of HMB chelated 11 Pb ions or seven Cu ions and that Pb competed with Cu for binding to HMB. These findings suggest that Pb-induced oxidative stress results from the impairment of Cu metabolism by Pb targeting of Atp7a. 相似文献
682.
The pharyngeal arches are one of the defining features of the vertebrates, with the first arch forming the mandibles of the jaw and the second forming jaw support structures. The cartilaginous elements of each arch are formed from separate migratory neural crest cell streams, which derive from the dorsal aspect of the neural tube. The second and more posterior crest streams are characterized by specific Hox gene expression. The zebrafish has a larger overall number of Hox genes than the tetrapod vertebrates, as the result of a duplication event in its lineage. However, in both zebrafish and mouse, there are just two members of Hox paralogue group 2 (PG2): Hoxa2 and Hoxb2. Here, we show that morpholino-mediated "knock-down" of both zebrafish Hox PG2 genes results in major defects in second pharyngeal arch cartilages, involving replacement of ventral elements with a mirror-image duplication of first arch structures, and accompanying changes to pharyngeal musculature. In the mouse, null mutants of Hoxa2 have revealed that this single Hox gene is required for normal second arch patterning. By contrast, loss-of-function of either zebrafish Hox PG2 gene individually has no phenotypic consequence, showing that these two genes function redundantly to confer proper pattern to the second pharyngeal arch. We have also used hoxb1a mis-expression to induce localized ectopic expression of zebrafish Hox PG2 genes in the first arch; using this strategy, we find that ectopic expression of either Hox PG2 gene can confer second arch identity onto first arch structures, suggesting that the zebrafish Hox PG2 genes act as "selector genes." 相似文献
683.
Atchison WD 《Journal of bioenergetics and biomembranes》2003,35(6):507-532
Voltage-gated Ca2+ channels are targets of the number of naturally occurring toxins, therapeutic agents as well as environmental toxicants. Because of similarities of their chemical structure to Ca2+ in terms of hydrated ionic radius, electron orbital configuration, or other chemical properties, polyvalent cations from aluminum to zinc variously interact with multiple types of voltage-gated Ca2+ channels. These nonphysiological metals have been used to study the structure and function of the Ca2+ channel, especially its permeability characteristics. Two nonphysiological cations, Pb2+ and Hg2+, as well as their organic derivatives, are environmental neurotoxicants which are highly potent Ca2+ channel blockers. These metals also apparently gain intracellular access in part by permeating through Ca2+ channels. In this review the history of Ca2+ channel block produced by Pb2+ and Hg2+ as well as other nonphysiological cations is traced. In particular the characteristics of Ca2+ channel block induced by these environmental neurotoxic metals and the consequences of this action for neuronal function are discussed. 相似文献
684.
Phytochelatins (PCn) are thiol-containing peptides with general structure (-Glu-Cys)n-Gly enzymatically synthesized by plants and algae in response to metal exposure. They are involved in the cellular detoxification mechanism for their capability to form stable metal-phytochelatin complexes. The speciation of Cd and Pb complexes with phytochelatins has been studied in laboratory cultures of the marine diatom Phaeodactylum tricornutum. An approach based on size-exclusion chromatography (SEC) with off-line detection of phytochelatins, by reverse-phase HPLC, and metal ion, by atomic absorption spectrometry, has been used. The formation of Cd- and Pb-PCn complexes with n-value from 3 to 6 was demonstrated. The metal-PCn complexes formed with Cd appear to be different from those formed with Pb for the number of molecules of peptide involved in the complex and for the amount of the metal ion bound. The chromatographic behaviour of metal-PCn complexes is consistent with Pb-PCn complexes in which only a molecule of peptide binds the metal ion, and with Cd-PCn complexes containing two or more molecules of peptide. The metal/peptide molar ratio in Cd-PCn complexes was higher that in Pb-PCn complexes. The formation of Cd- or Pb-PC2 complexes was not demonstrated, probably for a dissociation during the cellular extract preparation. The effectiveness of phytochelatins in the detoxification of these two metal ions in this alga is discussed. 相似文献
685.
Shulkin V. M. Kavun V. Ya. Tkalin A. V. Presley B. J. 《Russian Journal of Marine Biology》2002,28(1):43-51
The relationship between the concentration of Pb, Cu, Cd, Zn, and Ag in soft tissues of mytilids Crenomytilus grayanus and Modiolus kurilensis and in bottom deposits was studied to determine the potential and limitations in the use of these molluscs as bioindicators of contamination of coastal waters near Vladivostok (northwest of the Sea of Japan). It was found that the mussel C. grayanus began to accumulate Pb and Cu after certain threshold concentrations of these metals (60 and 150 g/g respectively) in fine fractions of sediments was reached. Accumulation of Pb and Cu by M. kurilensis also depended on the level of sediment contamination, but the higher initial metal content in tissues and the higher individual variability reduced the sensitivity of this species as a bioindicator. Accumulation of Cd and especially of Zn in mytilid tissues is adjusted by the organism, which restricts the opportunity of their use for tracking the anthropogenic input of bioavailable forms of these metals. 相似文献
686.
Tissue cultures of Armoracia rusticana L., both transformed with Agrobacterium rhizogenes and nontransformed, were screened for peroxidase activity. Most of the derived and tested strains exhibited 20 times higher activity [from 99 to 723 U g−1(d.m.)] than the root of the intact plant [(30 U g−1 (d.m.)]. The highest peroxidase activity was found in tumour culture growing on the medium without growth regulators. The influence of the addition of sugars and heavy metal ions in the medium on peroxidase production was tested. Increase in peroxidase activity was observed after cultivation of horseradish culture with cadmium, cobalt, nickel or lead ions.This work is supported by Grant Agency of Czech Republic Project No. 526/04/0135. 相似文献
687.
We determined the hepatic and renal concentrations of Cd, Pb, Zn, Cu, and Fe in (1) marine mammals (three bottle-nosed dolphins,
six California sea lions, and one sea otter), (2) freshwater and brackish-water mammals (one Oriental short-clawed otter and
four European river otters), and (3) sea birds (three rock-hopper penguins, two king penguins, three Humboldt penguins, four
Macaroni penguins, and four Magellanic penguins), all of which were kept in a zoo and an aquarium in Japan. We investigated
the species-specificity of Cd accumulation in these aquatic animals. We also presented the basic data on metal concentrations.
The concentrations of Cd in liver and kidney tended to be higher in marine mammals than in freshwater mammals. Many penguins,
sea birds, showed high Cd concentrations. These results suggest that the habits of these animal species may be involved in
accumulation of Cd. Pb concentrations were below the detection limit or low in both liver and kidney [not detected (ND)=0.132
μg/g and ND=0.183 μg/g, respectively]. The hepatic concentrations of Zn and Cu were high in young animals. In penguins, a
positive correlation was found between the Zn and Cd concentrations in the liver and kidney and between the Cu and Cd concentrations
in the liver. Individual variation was large in Fe concentration (48–3746 μg/g in the liver and 51–980 μg/g in the kidney). 相似文献
688.
This comparative study of the intestinal absorption of four toxic metals (aluminum, manganese, nickel, and lead) carried out
in rats using the in situ intestinal perfusion technique was able to measure the partition of each metal between the intestine (intestinal retention),
the blood circulation, and target tissues after 1 h. The perfused metal solutions were at concentrations likely to occur during
oral intoxication. It was found that aluminum (48 and 64 mM), even as a citrate complex, crossed the brush border with difficulty (0.4% of the perfused amount); about 60% of this was
retained in the intestine and the remainder was found in target tissues (about 36%). Conversely, lead (4.8–48 μM) penetrated the intestine more easily (about 35% of the perfused amount), was slightly retained (about 12% of the input),
and was soon found in the tissues (about 58% of the input) and to a lesser degree in circulation (about 29%). Within the same
concentration range, nickel and manganese showed certain similarities, such as a reduced crossing of the brush border proportional
to the increase in the concentration perfused (0.17–9.5 mM). There was similar intestinal retention and absorption (about 80% and 20% of the input, respectively). Manganese crossed
the brush border more easily and was diffused more rapidly into tissues. Finally, the addition of equimolar amounts of iron
(4.7 mM) produced opposite effects on the absorption of the two elements, inhibiting manganese and showing a trend to increase in
nickel absorption. This could be the result of competition between Fe2+ and Mn2+ for the same transcellular transporters and the slight predominance of paracellular mechanism in the event of “Fe2+-Ni2+” association. 相似文献
689.
The ability of the filamentous fungus Verticillium marquandii for Zn2+ and Pb2+ uptake from aqueous solution was studied. The 24-h-old living mycelium bound Zn2+ and Pb2+ (206.2 and 324.5 mg/g dry weight, respectively) effectively, in contrast to a very low Zn2+ uptake by autoclaved mycelium (20.2 mg/g). The most effective results were noted when the metals were introduced as acetates
and incubated with mycelium for 24 h in case of Zn2+ while Pb2+ achieved the maximum level of metal binding after as early as 3 h. The cell wall was the main site of effective Zn2+ and Pb2+ binding by V. marquandii mycelium (91.0–93.6% of metals were located in cell wall after 24 h of exposure). The metabolic inhibitors: antimycin A and
sodium azide had a strong limitation effect on Zn2+ uptake by a 24-h-old living mycelium, whereas Pb2+ binding did not decrease to a large extent. The freshly obtained protoplasts accumulated Zn2+ and Pb2+ on a low level in comparison with cells at different stages of cell wall regeneration. The use of regenerating protoplasts
showed that resynthesis of cell wall was necessary for high binding of Zn2+, whereas Pb2+ uptake on the significant level took place during cell wall regeneration.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
690.
Using intracellular recording, we studied the effects of lead ions on the synaptic responses of neurons of the superior cervical ganglion (SCG) of the rat. Three groups of SCG neurons were found; they differed from each other in directions of the changes evoked by Pb2+ applications and in their sensitivity to this agent. In two groups of the phasic SCG neurons, Pb2+ decreased the amplitude of EPSP evoked by stimulation of the cervical sympathetic nerve with EC50 of (2.2 ± 0.2) · 10-6 M and (3.55 ± 0.29) · 10-5 M, respectively. In the tonic neurons, 2 · 10-6 M Pb2+ increased the EPSP amplitude by 27 ± 2%, on average, as compared with the control values. We postulate that the specificity of responses of these three groups of SCG neurons to the action of Pb2+ is determined by the different subunit composition of the nicotinic cholinoreceptors in the membrane of these cells. 相似文献