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At least 451 records · Page 25Linked to original sources
PubMed1993

A standardized oral zinc tolerance test for assessment of zinc absorption in dogs.

Three oral zinc tolerance tests using increasing doses of elemental zinc (0.5, 0.75 and 1.0 mg/kg) given as zinc sulphate (ZnSO4.7H2O) were carried out in eight normal beagles. The zinc tolerance curves obtained were similar to those described in man, with the peak plasma zinc concentration occurring 2 h after dosing. There was a considerable variation between individual animals in the peak plasma zinc concentration achieved with each dose. This would appear to limit the value of a zinc tolerance test in assessing the efficiency of zinc absorption in individuals, although it may be of value in making comparisons between groups of dogs.

Administration, Oral↗
PubMed2004

Enhanced zinc consumption causes memory deficits and increased brain levels of zinc.

Zinc deficiency has been shown to impair cognitive functioning, but little work has been done on the effects of elevated zinc. This research examined the effect on memory of raising Sprague-Dawley rats on enhanced levels of zinc (10 ppm ZnCO3; 0.153 mM) in the drinking water for periods of 3 or 9 months, both pre- and postnatally. Controls were raised on lab water. Memory was tested in a series of Morris Water Maze (MWM) experiments, and zinc-treated rats were found to have impairments in both reference and working memory. They were significantly slower to find a stationary platform and showed greater thigmotaxicity, a measure of anxiety. On a working memory task, where the platform was moved each day, zinc-treated animals had longer latencies over both trials and days, swam further from the platform, and showed greater thigmotaxicity. On trials using an Atlantis platform, which remained in one place but was lowered on probe trials, the zinc-treated animals had significantly fewer platform crossings, spent less time in the target quadrant, and did not swim as close to the platform position. They had significantly greater latency on nonprobe trials. Microprobe synchrotron X-ray fluorescence (microSXRF) confirmed that brain zinc levels were increased by adding ZnCO3 to the drinking water. These data show that long-term dietary administration of zinc can lead to impairments in cognitive function.

Aging↗
PubMed2004

Zinc ion dependent B-cell epitope, associated with primary Sjogren's syndrome, resides within the putative zinc finger domain of Ro60kD autoantigen: physical and immunologic properties.

The Ro/La ribonucleoprotein (RNP) complex is composed of the proteins Ro60kD, Ro52kD, and La48kD that are in association with one small cytoplasmic RNA (YRNA). Specific protein-RNA and protein-protein interactions are thought to occur through the RNP and zinc-finger secondary structure elements of the Ro60kD protein. The aim of our study was to investigate the antigenic properties of the zinc finger domain of the Ro60KD autoantigen and its contribution to the formation of Ro/La RNP complex. It was found that the peptide VSLVCEKLCNEKLLKKARIHPFHILIA (Zif-1), which corresponds to the natural sequence of the zinc finger domain (301-327), and the peptide C(Acm)NEKLLKKARIC(Acm), analogous to the intermediate loop 310-319 (Zif-3) of the same domain of Ro60KD, are recognized by the majority of anti-Ro/SSA and anti-La/SSB positive sera (82.6% and 77.1%, respectively) in the absence of zinc ions. The same sera failed to react with Zif-1 peptide in the presence of Zn2+. In contrast, the addition of zinc ions was necessary for the binding of Zif-1 to recombinant Ro52KD as shown by direct binding experiments of the recombinant protein with synthetic peptides. Our data suggest the zinc finger domain of Ro60kD contains a B-cell epitope with high specificity for primary Sjogren's syndrome. Furthermore, depending on the presence of zinc ions, the zinc finger domain of the Ro60KD protein can exist in two different conformational states favoring either an interaction with the Ro52KD protein or binding with autoantibodies.

Autoantibodies↗
PubMed2005

The six zinc fingers of metal-responsive element binding transcription factor-1 form stable and quasi-ordered structures with relatively small differences in zinc affinities.

Six Cys(2)His(2) zinc fingers (F1-6) comprise the DNA binding domain of metal-responsive element binding transcription factor-1 (MTF-1). F1-6 is necessary for basal and zinc-induced expression of metallothionein genes. Analysis of NMR structural and dynamic data for an F1-6 protein construct demonstrates that each zinc finger adopts a stable betabetaalpha fold in the presence of stoichiometric Zn(II), provided that all cysteine ligands are in a reduced state. Parallel studies of protein constructs spanning the four N-terminal core DNA binding fingers (F1-4) and two C-terminal low DNA affinity fingers (F5-6) reveal similar stable zinc finger structures. In both the F1-6 and F5-6 proteins, the finger 5 cysteines were found to readily oxidize at neutral pH. Detailed spectral density and hydrodynamic analysis of (15)N relaxation data revealed quasi-ordered anisotropic rotational diffusion properties of the six F1-6 zinc fingers that could influence MTF-1 DNA binding function. A more general effect on the rotational diffusion properties of Cys(2)His(2) zinc fingers was also uncovered that is dependent upon the position of each finger within multifinger domains. Analysis of NMR (1)H-(15)N-heteronuclear single quantum coherence spectral peak intensities measured as a function of added Zn(II) in conjunction with Zn(II) binding modeling studies indicated that the Zn(II) affinities of all MTF-1 zinc fingers are within approximately 10-50-fold. These analyses further suggested that metal sensing by MTF-1 in eukaryotic cells involves multiple zinc fingers and occurs over a 100-fold or less range of accessible Zn(II) concentration.

Amino Acid Sequence↗
PubMed1983

Bioavailability of zinc in coagulated soy protein (tofu) to rats and effect of dietary calcium at a constant phytate:zinc ratio.

An assay was conducted with young albino rats to compare the bioavailability of zinc contained in calcium- and in magnesium-precipitated tofu to zinc supplied as the carbonate in egg white diets. Relative availability of zinc from both tofu preparations was 51% as measured by weight gain and 36-39% for log micrograms tibia zinc accumulation. In a separate experiment with zinc supplied at 9 mg/kg in all diets, the effect of increasing dietary calcium on weight gain and tibia zinc accumulation was tested. Performance of tofu-fed rats relative to zinc carbonate-fed rats at 0.4, 0.7 and 1.2% calcium was, respectively: 92, 67 and 48% for weight gain, and 70, 58 and 61 for tibia zinc content.

Animals↗
PubMed1990

Endogenous zinc excretion in relation to various levels of dietary zinc intake in the mink (Mustela vison).

Endogenous zinc excretion was studied in adult male mink fed experimental diets for 73 d, including a collection period from d 69 to 73. Dietary zinc levels were 2.8, 26 or 121 mg/kg wet weight. In accordance with the results of a methodological study, also reported here, the animals had an intramuscular injection of 65ZnCl2 12 d before the start of the collection period. Total fecal (endogenous + unabsorbed) zinc excretion for d 69-73 in the three groups was 2.3, 20.4 and 91.0 mg. The endogenous zinc excretion was 1.3, 2.0 and 6.4 mg, corresponding to 80.8, 10.6 and 6.4% of the zinc intake. Thus, the endogenous excretion was mainly important for the zinc homeostasis at low zinc intake, whereas at high intake the homeostasis was regulated via absorption from the digestive tract. The overall conclusion of the experiment was that mink are comparable to other species (including man) in regard to mechanisms controlling zinc homeostasis.

Absorption↗