The nutritional significance of tea is confined to certain vitamins and minerals. Tea is able to contribute riboflavin, folic acid, β-carotene, α-tocopherol and phylloquinone, and is also one of the more significant sources of fluoride in the UK diet. The pharmacological action of caffeine in tea is so modified, probably by its interaction with polyphenols, that the beneficial properties of the alkaloid may be enjoyed without harmful side effects. Beneficial effects attributed to tea polyphenols acting synergistically with ascorbic acid include the strengthening of capillary blood vessels and an anti-atherosclerosis action. The potential value of tea has been well recognised in Russia but has received scant attention in the West.

The nutritional and therapeutic value of tea—a review

δ-ALA-D is a metalloenzyme that has 3 vicinal thiol/thiolate groups that coordinate with Zn(II). The proximity between the sulfhydryl groups renders δ-ALA-D extremely sensitive to oxidation by soft electrophiles, such as Pb(II), Hg(II), As(III) and organoseleno and organotellurium compounds. In fact, blood δ-ALA-D is a classical biomarker of lead exposure in humans. The inhibition of δ-ALA-D can increase the concentration of 5-aminolevulinate (δ-ALA), which is a pro-oxidant compound. δ-ALA can generate oxidative stress that can further increase δ-ALA-D inhibition. Recently, data have been obtained indicating that the δ-ALA-D could be a marker of oxidative stress in human pathologies. In summary, considering its high sensitivity to pro-oxidant situations, δ-ALA-D can be considered a universal marker of oxidative stress.

Aminolevulinate dehydratase (δ-ALA-D) as marker protein of intoxication with metals and other pro-oxidant situations

The concentrations of lead, cadmium, and manganese in the tissues of cattle egrets (Bubulcus ibis) and laughing gulls (Larus atricilla) gathered from the Galveston Bay region of Texas were compared, to determine if different patterns of accumulation exist. Their levels in these species were within the range reported for other bird species. Lead levels in bone were comparable, but gulls had more lead in brain, kidney and liver tissues than the egrets, which suggested a higher rate of accumulation or exposure. Due to their high abundance and comparable positions in the estaurine and terrestrial food webs, it is suggested that Bubulcus ibis and Larus atricilla may serve as convenient biological indicators to monitor potentially toxic substances in these ecosystems.

Environmentally acquired lead, cadmium, and manganese in the cattle egret, Bubulcus ibis, and the laughing gull, Larus atricilla.

The increasing exposure of human populations to excessive levels of metals continues to represent a matter of public health concern. Several biomarkers have been studied and proposed for the detection of adverse health effects induced by lead (Pb), arsenic (As), and manganese (Mn); however, these studies have relied on exposures to each single metal, which fails to replicate real-life exposure scenarios. These three metals are commonly detected in different environmental, occupational, and food contexts and they share common neurotoxic effects, which are progressive and once clinically apparent may be irreversible. Thus, chronic exposure to low levels of a mixture of these metals may represent an additive risk of toxicity. Building upon their shared mechanisms of toxicity, such as oxidative stress, interference with neurotransmitters, and effects on the hematopoietic system, we address putative biomarkers, which may assist in assessing the onset of neurological diseases associated with exposure to this metal mixture.

Lead, Arsenic, and Manganese Metal Mixture Exposures: Focus on Biomarkers of Effect.

Background and Aims 
Hereditary disorders associated with metal overload or unwanted toxic accumulation of heavy metals can lead to morbidity and mortality. Patients with hereditary hemochromatosis or Wilson disease for example may develop severe hepatic pathology including fibrosis, cirrhosis or hepatocellular carcinoma. While relevant disease genes are identified and genetic testing is applicable, liver biopsy in combination with metal detecting techniques such as energy-dispersive X-ray spectroscopy (EDX) is still applied for accurate diagnosis of metals. Vice versa, several metals are needed in trace amounts for carrying out vital functions and their deficiency due to rapid growth, pregnancy, excessive blood loss, and insufficient nutritional or digestive uptake results in organic and systemic shortcomings. Established in situ techniques, such as EDX-ray spectroscopy, are not sensitive enough to analyze trace metal distribution and the quantification of metal images is difficult.
Methods 
In this study, we developed a quantitative biometal imaging technique of human liver tissue by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in order to compare the distribution of selected metals in cryo-sections of healthy and fibrotic/cirrhotic livers.
Results 
Most of the metals are homogeneous distributed within the normal tissue, while they are redirected within fibrotic livers resulting in significant metal deposits. Moreover, total iron and copper concentrations in diseased liver were found about 3-5 times higher than in normal liver samples.
Conclusions 
Biometal imaging via LA-ICP-MS is a sensitive innovative diagnostic tool that will impact clinical practice in identification and evaluation of hepatic metal disorders and to detect subtle metal variations during ongoing hepatic fibrogenesis.

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Novel bioimaging techniques of metals by laser ablation inductively coupled plasma mass spectrometry for diagnosis of fibrotic and cirrhotic liver disorders.

Lead and cadmium were administered intraperitoneally, singly and jointly, to the mice. The levels of cadmium, copper, manganese, lead and zinc were determined in liver, kidney and brain by atomic absorption spectrophotometric technique and deltaaminolevulinic acid dehydratase (ALA-D) activity was determined in erythrocytes. The tissue levels of some of these metals were found significantly altered by cadmium and lead both, but cadmium was found to have no effect on blood on ALA-D activity.

The effect of lead and cadmium on liver, kidney, and brain levels of cadmium, copper, lead, manganese, and zinc, and on erythrocyte ALA-D activity in mice

An investigation was carried out to estimate the amount of lead extracted by storing acetic acid in 231 pieces of glazed earthenware pottery. The average concentration of lead was found to be 4.2 mg/litre and the range was 1.0 to 6.5 mg/litre. The amount of lead extracted increased sharply between 70° to 90°C. Hence storage of hot beverages in pottery for long periods may pose health hazards due to chronic lead toxicity.

T.D. Seth

Papers

The effect of lead and cadmium on liver, kidney, and brain levels of cadmium, copper, lead, manganese, and zinc, and on erythrocyte ALA-D activity in mice

Studies on lead extraction from glazed pottery under different conditions

Bioaccumulation of HCH isomers in different tissues of young and old rats: a comparison.

Determination of cadmium, cobalt, copper, lead, manganese, nickel and zinc in animal feed by atomic absorption spectrophotometery

Evaluation of lead hazards from paints and pigments