Trace metals deficiency

Most trace metals may be precipitated with phosphate into insoluble metal phosphates (Table 7.5). Most metal phosphates have low solubility. High localization of phosphates reduces the bioavailability of Zn in arid soils. The banded application of P near the seeds depresses Zn uptake by com (Adriano and Murphy, 1970 Grant and Bailey, 1993), causing Zn deficiency. However, both N and P fertilizers increase Cd concentration in plants. Cadmium and Zn are antagonistic in root uptake and distribution within plants. 

Falchuk, K. 1988. Zinc deficiency and the E. gracilis chromatin. Pages 75-91 in A.S. Prasad (ed.). Essential and Toxic Trace Metals in Human Health and Disease. Alan R. Liss, NY. 

The availability of the trace metals is easily determined without any of the above risks, and the results used to assess both deficiencies and toxici-ties. The metals need to be removed from the sites where they are bound to the soil particles by use of an even stronger binding agent than the soil. This is achieved with two possible complexing reagents EDTA and DTPA. They are a class of chemicals known as complexones, which form complex molecules with metals in a cage-like structure called a chelate. 

Plant roots are known to exude a fluid containing a number of amino and carboxylic acids, the amount of the exudate increasing under conditions of metal deficiency. Chlorotic plants, i.e. those suffering from iron defidency, have been found to contain more of the citric and malic acids than their normal green counterparts.21 Differences in the susceptibilities of plant species to trace metal deficiencies have indeed frequently been attributed to variations in organic acid production. 

Probably the most popular and, as it proved to be, the most contentious use of hair analysis was its application to the evaluation of nutritional deficiencies. Many food faddists, pharmacists, nutritionists, and some physicians were convinced that a person s well being was influenced by the concentration of trace metals in his hair. The demands for hair analysis became very large. Many laboratories, some with dubious competence, were estabhshed to satisfy what seemed to be a limitless, ever growing service demand. With the passage of time, however, proponents of this... 

The association between metal exposure and renal failure can be approached from two points of view. On the one hand environmental/industrial exposure to heavy metals, more particularly, lead, cadmium and mercury and other inorganic substances such as silicon has been linked to a reduced renal function and/or the development of acute or chronic renal failure [1]. This issue has been dealt with in other chapters of this book. On the other hand patients with chronic renal failure, especially those treated by dialysis are at an increased risk for trace element disturbances (Figure 1). Indeed in these subjects the reduced renal function, the presence of proteinuria, metabolic alterations associated with renal insufficiency, the dialysis treatment, medication etc. all may contribute to either accumulation or deficiency of trace metals. With regard to aluminum intensive research on the element s toxic effects has been performed in the past. Recently, new metal-containing medications have been introduced of which the potential toxic effects should be considered and put in a justified context. 

Trace metal disturbances may be due to the uremia per se. Indeed, as the urinary excretion route is an important pathway of elimination of many trace elements, i.e. silicon, strontium, aluminum,... impairment of the kidney will be an important determinant of their accumulation, whilst in the presence of a reabsorptive defect a number of trace elements, especially those that are reabsorbed because of their essential role, be lost resulting in a deficient state. The presence of proteinuria may reasonably result in losses of protein bound elements. It has also been shown also that residual renal funchon may importantly alter the accumulation and hence toxic effects of aluminum [2]. In uremia translocation of a particular metal from one tissue to another may also occur. As an example, under normal circumstances the kidney is an important target organ for cadmium. In chronic renal failure however, possibly as a consequence of a reduction in binding proteins (e.g. metallothionein), the concentrahon of cadmium in this tissue decreases to extremely low levels which... 

Compared to patients treated by hemodialysis, data on trace element accumulation/ deficiency in CAPD are rather scanty and less documented. In CAPD the total volume of dialysis fluid patients get in contact with during treatment is much lower. Hence, the potential amount of trace metals that can be exchanged during treatment is much less than in hemodialysis. Therefore, CAPD patients must be considered at a lower risk for trace element accumulation/ toxicity as compared to hemodialysis a statement which is also reflected by the data presented of Padovese et al. [21] comparing the estimated exposure of forty-four trace elements in both patient groups. Distinct differences have been noted in the trace metal content between CAPD and hemodialysis fluids. Also the trace metal content of CAPD fluids may greatly differ between each other, which has been ascribed to the wide range of trace... 

Figure 10.7. Experiments with different chelators and a wide range of trace metal concentrations demonstrate that trace metal toxicity and deficiency are determined by metal-ion activities and not total concentrations. Motility data of the dinoflagellate Gonyaulax tamarensis as a function of total copper [Cul and cupric ion activity [Cu ] for two chelators, Tris and EDTA. (Adapted from Anderson and Morel, 1978).

Tn recent years there has been an increased interest in assessing the human health effects from environmental exposure to trace metals. Studies of occupational exposures and dietary intakes of trace metals have required the refinement and development of analytical techniques for the analyses of low elemental concentrations in complex matrices. Molybdenum is one of the trace metals that has been the subject of intensive study because it is an essential trace element in both plant and animal nutrition. It is an integral constituent of several metalloenzymes including xanthine oxidase, which is the last enzyme in the catabolic pathway of purines. Extensive ingestion of molybdenum has been shown to cause molybdenosis in cattle. Many of the features of this condition can be ascribed to induced copper deficiency. Whether biochemical changes or adverse health effects in humans can be attributed to excessive exposure to molybdenum is not known. 

Nutritional status Many antioxidants are present in the diet (e.g., vitamin E, vitamin C, peptides for the synthesis of glutathione, trace metals, and minerals like zinc). However, poor nutrition or malabsorption leads to deficiency of these key vitamins and antioxidants. This may impair the antioxidative defense capacity, leading to drug-induced oxidative stress and lower threshold for DILL In a preclinical study, a mere 1.6- and 2.1-fold increase in liver zinc content was associated with an increase in liver metallothionein between 50- and 200-fold.38 Metallothionein is a key antioxidant protein in vivo capable of scavenging most common kinds of oxidative species.39 It is therefore conceivable that a lack of sufficient dietary available zinc could compromise a patient s hepatic metallothionein levels and his or her antioxidant reserve capabilities in liver. 

There are two types of trace metal supplements the pharmaceutical prepared formulation and the non-pharmaceutical formulation. The metals present in pharmaceutical preparations are chelated or bonded to organic compounds to achieve maximum beneficial effects to the body. Manufacturers claim that supplements are needed to augment the deficiencies caused by our modem agricultural methods and that healthy people also need them. 

Prevention of iron deficiency in populations not sustaining chronic blood loss is possible by judicious selection of diets which enhance the bioavailability of dietary iron. The recent decades have produced significant research on the availability of iron as it is affected by various dietary components, those which enhance as well as those which inhibit iron absorption. This has allowed for the first time the quantification of dietary effects on a trace metal and the development of a model whereby the quantity of bioavailable iron in a diet may be estimated. 

One coal ash from the Kanawha River Valley of eastern Kentucky (EKY-FA) was evaluated. Trace-metal concentrations were low in this leachate and also low in the whole ash analysis. Ca, Mg, Na and K concentrations were deficient in the leachate in comparison to the other ash leachates. 

Modern-day diets are composed of foods from all five Continents and often reflect the elemental compositions of the soil used to grow those crops and to raise the animals, as mentioned in Chapter 2, it has been estimated that a human eats approximately 8 kg of soil during a lifetime. Thus, a varied and ample diet will probably protect against trace-metal deficiencies for most of a lifetime. However, the reduction in physical activity, in circulation, and in appetite in later life, may lead to less trace elements being taken in. Thus, it is often advisable to increase the concentrations of such trace metals for older persons, to counteract their lower presence in the smaller diets see Wound Dressings, page 70). 

Pharmaceuticals that require metal ions for their specific activity and in which the metals have a very active role are fewer in number but hold far greater fascination. The metal ion may be present because it has the ability, coupled with its coordination chemistry properties, to direct covalent bonds or because it is a source of positive charge density or because the metal is able to form specific bonds to an active site in the biochemistry of the diseased organ. Furthermore, it is frequently necessary to raise the concentration of the total amount of the trace metal present in tissue in order to allay the symptoms of a deficiency condition. This means that the metal ion has to be made bioavailable such that it can pass from the gastrointestinal tract into the bloodstream. 

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