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M Webb

Publications and source records attributed to M Webb.

At least 199 records · Page 11Linked to original sources
PubMed1977

The effect of selenium on the brain uptake of methylmercury.

Twenty-four h after the subcutaneous administration of 0.5 mumoles selenite labelled with 75Se to rats of 200 g body weight, the retention of selenium at the injection site was significantly increased by the presence of equimolar amounts of methylmercury in the injection solution. The retention of Me203HgCl was not affected by the presence of selenite. The most significant shift caused by interaction was a decrease in the blood content and an increase in the brain content of 203Hg. The brain content of 75Se was also increased to a lesser extent. The shift in the distribution--which was the same whether the two metals were injected at the same site or separately--continuously decreased from 6-48 h. The same interaction pattern was observed when methylmercury and selenite were administered by gastric gavage and differences in distribution increased when the dose was increased from 1.25 mumoles/kg to 2.5 mumoles/kg. The increase in the brain content of mercury caused by selenite was not restricted to simultaneous administration and occurred when selenite was given 2-7 days after methylmercury.

Animals↗
PubMed1976

The interaction between cadmium, mercury and zinc--administered subcutaneously in a single injection.

The interaction between three heavy metals, cadmium, mercury and zinc was investigated. The metals were injected subcutaneously into the hind leg of male rats of approximately 200 g body weight in a volume of 0.2 ml either alone or in combination with another metal. It has been shown that interaction started at the site of injection, at which the retention of one metal was increased by the presence of the other over a 48 h period. Besides this local interaction, probably based on competition for a carrier compound, there were differences in distribution. Analysis of the data indicates that metals injected simultaneously can influence the distribution of each other and, although each of the studied metal is able to induce thionein, the observed interactions cannot be explained by a single mechanism.

Animals↗
PubMed1976

Differences in distribution and excretion of selenium and cadmium or mercury after their simultaneous administration subcutaneously in equimolar doses.

Forty-eight hours after the simultaneous administration of either 1.8 mumoles Se (as Na2SeO3) to 200 g male rats with equivalent doses of Cd (as CdCl2) or 0.5 mumoles Se with equivalent doses of Hg (as HgCl2) the retention of selenium at the subcutaneous injection site was affected only when it was given in a single injection with the heavy metal. The retention of cadmium was increased only if selenium was injected separately and the retention of mercury was increased both in single and separate injections. When there was an increase in retention at the site of injection, this made up less than 8% of the dose for selenium and mercury and 3% for cadmium and thus could not explain either changes in distribution or the reported protective effects by one metal against the other. The shift in the distributionpattern of one metal caused by the other metal was similar, and independent of whether they were injected in single or separate injections. However the shift in the distribution of interacting metals showed some differences indicating that interaction could not be mediated through the formation of a stable complex between selenium on the one hand and mercury or cadmium on the other.

Animals↗
PubMed1976

Cadmium-thionein and the protection by cadmium against the nephrotoxicity of mercury.

Uptake of Hg2+ into the renal and hepatic metallothioneins of rats is increased by pretreatment with Cd2+. This increased uptake occurs both by displacement of Cd2+ (and of Zn2+) from the presynthesized cadmium-thionein, and by further synthesis of thionein. The former mechanism predominates in the kidney of the male rat, which is more sensitive than the female to Hg2+. The latter mechanism, which occurs particularly in the kidney of the female, also is considered to involve an initial displacement of Cd2+ from cadmium-thionein, but is followed by further synthesis of the metalloprotein, which is induced by the liberated cation. Pretreatment with Cd2+ increases not only the incorporation of Hg2+ into the renal metallothionein, but also the uptake of Hg2+ into other components of the kidney. At dose levels of Hg2+ at which Cd2+-pretreatment gives complete protection against the nephrotoxicity in male and female rats, the increase in Hg2+-uptake into both the particulate components and into the soluble fraction of the kidney is greater than into metallothionein. It is concluded, therefore, that binding of Hg2+ by pre-induced cadmium-thionein alone cannot explain the protection by Cd2+ against the nephrotoxicity of Hg2+.

Animals↗
PubMed1976

Influence of dietary cadmium on the distribution of the essential metals copper, zinc and iron in tissues of the rat.

The effect of long-term dietary cadmium treatment upon the distribution of the metals copper, iron and zinc has been compared in various organs of male and female rats. The renal accumulation of cadmium was similar in both sexes without a plateau being reached. In contrast, the hepatic accumulation of cadmium was higher in the female than in the male rat and a plateau was observed after 30-35 weeks of dietary cadmium treatment. Most of the cadmium which accumulated in these organs was recovered in the metallothionein fraction andthe concentration of hepatic cadmiumthionein in the female rat was correspondingly higher than in the male rat. Accumulation of cadmium was associated with an increased zinc concentration in the liver and an increased copper concentration in the kidney; these increases were correlated with increases in liver and kidney metallothioneins induced by cadmium. Uptake of cadmium into organs other than liver and kidney occurred to a small extent but was not associated with changes in the concentration of copper and zinc. Cadmium also accumulated in the intestinal mucosa where it could be recovered in a fraction corresponding to metallothionien. A loss of iron from the liver and kidney was also observed following dietary cadmium treatment and involved mainly a loss of iron from ferritin.

Administration, Oral↗
PubMed1975

Induced synthesis of metallothionein by pig kidney cells in vitro in response to cadmium.

Cells of a line (K7), derived from the cortex of the adult pig kidney, synthesize and accumulate high levels of metallothionein when grown in vitro in the presence of low concentrations (0.5 mug/ml) of Cd2+. This indicates that the accumulation of this protein in the kidneys of animals exposed to cadmium is due at least partly to synthesis in situ, and not solely to uptake by the renal cells of metallothionein produced by the liver. It is suggested that the ability to synthesize large amounts of metallothionein indicates the tubular origin of the cells of this line.

Animals↗
PubMed1975

Cadmium.

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Animals↗