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The build-up of neurosecretory material in the median neurosecretory cells and fibre tracts of cultured cockroach brains was demonstrated by staining and bioassay. Examination of the cultured brains by electron microscopy showed active production of neurosecretory granules after 3 days in vitro. The close correlation of the results obtained by these different methods of assay leaves little doubt that a neurohormone is being synthesized and stored. 相似文献
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The biodistribution and pharmacokinetics of vanadium following i.p. administration of vanadocene dichloride (VDC), a representative of a new class of organometallic anticancer agents, is reported for Strain A mice. A convenient flameless atomic absorption spectroscopic assay is described and is used to determine kinetic profiles for vanadium in blood, kidney, liver, small intestine and brain tissue for times up to 24 h after administration. For a VDC dose of 80 mg/kg, vanadium concentration decreases rapidly from both the blood and small intestine, and the data can be fit to a phenomenological exponential function (blood: t1/2 = 118 +/- 43 min; small intestine: t1/2(alpha) = 18.10 +/- 0.14 min, t1/2(beta) = 341 +/- 45 min). In contrast, vanadium accumulates in both the kidney and liver up to a maximal concentration (1.12 +/- 0.06 mM and 0.56 +/- 0.06 mM after 12 and 8 h, respectively), and is then excreted with estimated half-lives of 7.9 +/- 0.7 and 12.1 +/- 0.1 h, respectively. No detectable levels of vanadium are found in the brain tissue over the temporal course of the experiment. These results are compared to previous mammalian studies with cis-dichlorodiammineplatinum(II) (CDDP) and related 'second generation' platinum derivatives; there are both qualitative similarities between the vanadium and platinum systems as well as important quantitative differences. 相似文献
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K. L. Marks 《BMJ (Clinical research ed.)》1954,1(4869):1018-2,1018
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Kazimierz S. Kasprzak Michael P. Waalkes Lionel A. Poirier 《Biological trace element research》1987,13(1):253-273
Interactions between the physiologically essential metals calcium, magnesium, and zinc and the carcinogenic metals nickel
and cadmium were investigated to help elucidate the mechanisms of action of the carcinogenic metals. Bioassay studies revealed
several significant findings, including: (1) the ability of magnesium and calcium to inhibit nickel-induced elevation of pulmonary
adenoma incidence in strain A mice; (2) the ability of magnesium, but not of calcium, to prevent cadmium-induced subcutaneous
sarcoma formation; and (3) the ability of magnesium, but not of calcium, to inhibit nickel-induced muscle tumor formation.
Biochemical studies indicated a direct relationship between the antitumorigenic potential of magnesium and the capacity of
this metal to: (1) inhibit nickel and cadmium uptake by the target tissues in vivo; (2) inhibit nickel-induced disturbances
in DNA synthesis in vivo; (3) inhibit nuclear and cytosolic uptake of nickel by the target tissue cells in vivo; and (4) inhibit
nickel and cadmium binding to DNA in vitro. Calcium, which in most cases did not prevent carcinogenesis, had no consistent
influence on the uptake of carcinogenic metals or their biochemical effects in the target tissues. Magnesium and zinc, but
not calcium, were also found to attenuate the acute toxic effects of nickel, indicating a possible correlation between prevention
of acute effects and reduction in tumorigenicity. Zinc, which antagonizes cadmium tumorigenicity in the rat testis, was found
to reduce markedly cadmium uptake into isolated testicular interstitial cells. Also, zinc was found to inhibit strongly cadmium
binding to DNA in vitro. 相似文献