https://stacks.cdc.gov/view/cdc/37676/cdc_37676_DS1.pdf

Toxicological Profile for Lead

Publisher Summary This chapter discusses separate pools of CNS zinc, which are, vesicular zinc, free zinc, and protein-bound zinc Vesicular zinc is the one which is sequestered in the presynaptic vesicles of a special class of neurons, the zinc-containing neurons, which are found primarily in limbic, cerebrocortical, and corticofugal systems This vesicular zinc can be selectively stained by several histochemical procedures and is, therefore, accessible to histological and histoanalytical studies The second pool, free zinc, is an entirely hypothetical pool of ionic Zn +2 in the cytosol or interstitial fluid that may or may not be present in normal, healthy brain tissue The third pool of zinc is that which is bound firmly into the structure of the many zinc-containing enzymes in the brain The enzymatic zinc is, therefore, a stable pool, involved only in the specific function of the zinc-containing enzymes Zinc metalloenzymes are essential to the normal biology of brain cells, and any experimental treatment that is extreme enough to affect the metalloenzymes, such as prolonged zinc undernutrition or administration of chelators, can disrupt brain function through metalloenzymatic effects

Neurobiology of zinc and zinc-containing neurons.

Zinc is essential to the structure and function of myriad proteins, including regulatory, structural and enzymatic. It is estimated that up to 1% of the human genome codes for zinc finger proteins. In the central nervous system, zinc has an additional role as a neurosecretory product or cofactor. In this role, zinc is highly concentrated in the synaptic vesicles of a specific contingent of neurons, called "zinc-containing" neurons. Zinc-containing neurons are a subset of glutamatergic neurons. The zinc in the vesicles probably exceeds 1 mmol/L in concentration and is only weakly coordinated with any endogenous ligand. Zinc-containing neurons are found almost exclusively in the forebrain, where in mammals they have evolved into a complex and elaborate associational network that interconnects most of the cerebral cortices and limbic structures. Indeed, one of the intriguing aspects of these neurons is that they compose somewhat of a chemospecific "private line" of the mammalian cerebral cortex. The present review outlines (1) the methods used to discover, define and describe zinc-containing neurons; (2) the neuroarchitecture and synaptology of zinc-containing neural circuits; (3) the physiology of regulated vesicular zinc release; (4) the "life cycle" and molecular biology of vesicular zinc; (5) the importance of synaptically released zinc in the normal and pathological processes of the cerebral cortex; and (6) the role of specific and nonspecific stressors in the release of zinc.

/pdf/importance-of-zinc-in-the-central-nervous-system-the-zinc-fsnzl8oic3.pdf

Importance of Zinc in the Central Nervous System: The Zinc-Containing Neuron

Zinc Metabolism in the Brain: Relevance to Human Neurodegenerative Disorders ☆

http://cleanaircarolina.org/wp-content/uploads/2011/06/Mercury-exposure-and-childrens-health.pdf

Mercury Exposure and Children’s Health

Monochromated synchrotron radiation (SXRF), 17.5 keV photons from an X-ray tube (XRF) with Mo anode and 3 MeV protons (PIXE) were used to excite X-ray spectra from thin samples of standard reference materials. Relative detection limits derived from these X-ray spectra were calculated to compare the different excitation modes. XRF shows the highest detection limits, while protons and synchrotron radiation monochromated to 16.5 keV are comparable. Much lower detection limits (down to 0.1 ppm) are experimentally shown with synchrotron radiation monochromated to 9.1 keV. Results are in agreement with theoretical predictions. The advantage of the polarization of the synchrotron radiation has been discussed theoretically and shown experimentally.

Experimental comparison of synchrotron radiation with other modes of excitation of X rays for trace element analysis

Incorporation routes of elements into human hair; implications for hair analysis used for monitoring

The effect of dietary zinc deficiency on the mossy fiber zinc content of the rat hippocampus was investigated using PIXE (Particle Induced X-Ray Emission) spectroscopy. Using the proton microbeam (60×60 μm), 2 mm linescans were made on hippocampal sections and the data were expressed as absolute zinc concentrations. Values of 55 and 136 ppm (dry weight) were found for the mean background zinc level and the maximum mossy fiber zinc level, respectively, in animals fed a control diet containing 50 ppm zinc. Treatment of these animals with dithizone caused about 50% reduction in the maximum mossy fiber zinc level. Feeding a zinc-deficient diet for 28 days did not cause a decrease in the mossy fiber zinc level, however, feeding the zinc-deficient diet for 90 days reduced the maximum mossy fiber zinc level by about 30%. The results are discussed in relation to the behavioral abnormalities that have been observed in zinc-deficient animals.

The effect of dietary zinc deficiency on the mossy fiber zinc content of the rat hippocampus. A microbeam PIXE study. Particle Induced X-Ray Emission.

A focussing monochromator for synchrotron-radiation microprobe analysis has been made by bending and fixation of a Si(111) crystal onto an ellipsoidal mould produced by numerically controlled diamond cutting. Experiments were performed using 15 keV radiation from the SRS dipole line. Measured beam profiles, topograms and fluxes are compared with the results of a ray-tracing program. In the experiment the spot size has been reduced, if compared with a flat monochromator, by a factor of 1000 horizontally and by a factor of 15 vertically, in agreement with the calculations. The measured photon-flux density is 104 photons/(s mA μm2), suited for detecting trace elements of sub-ppm concentration in an organic matrix with a detection volume of the order of 10 μm diameter.

Ellipsoid X-ray focussing for synchrotron-radiation microprobe analysis at the SRS, Daresbury, UK

We present the computer program TTPIXAN, developed recently in our group as a tool for quantitative thick target PIXE analysis. Our intention was to develop an accurate and general computer code which could be useful in all aspects of PIXE analysis, i.e. either for choosing optimal working conditions when planning an experiment, or afterwards, when performing quantitative analysis for a wide range of sample types and thicknesses. The program is suitable for proton excitation as well as for deuterons and He ions in the common range of excitation energies (0.5–4 MeV).

R.D. Vis

Papers

Experimental comparison of synchrotron radiation with other modes of excitation of X rays for trace element analysis

Incorporation routes of elements into human hair; implications for hair analysis used for monitoring

The effect of dietary zinc deficiency on the mossy fiber zinc content of the rat hippocampus. A microbeam PIXE study. Particle Induced X-Ray Emission.

Ellipsoid X-ray focussing for synchrotron-radiation microprobe analysis at the SRS, Daresbury, UK

TTPIXAN — A package of computer programs for quantitative thick target PIXE analysis