Trace deficiency

In conclusion, this symposium has been convened because of concerns about exposure of infants to toxic levels of certain elements in infant foods. I am pleased that the organizers have, at the same time, recognized the necessity of considering the other end of the spectrum. The changes in infant feeding practices in recent years have placed a clear responsibility on us to undertake extensive research to determine the optimal trace element content of infant formulas. Meanwhile, strenuous efforts are required to avoid inadvertent trace deficiencies while, at the same time, avoiding the potential hazards of over-zealous supple-mentation/fortification programs. 

Cobalt, copper, molybdenum, iodine, iron, manganese, nickel, selenium, and zinc are sometimes provided to mminants. Mineral deficiency or toxicity in sheep, especially copper and selenium, is a common example of dietary mineral imbalance (21). Other elements may be required for optimal mminant performance (22). ExceUent reviews of trace elements are available (5,22). 

The Sugars Task Force s Select Committee on Nutrition and Human Needs recommended a daily consumption of sugars at 10% of total calories, which approximates current (11%) daily intake levels in the United States. At this level, sucrose does contribute to the development of dental caries however, no firm evidence exists that it causes dietary imbalances or deficiencies of vitamins (qv), minerals, or trace nutrients (62). 

Approximately 5% of the U.S. consumption of is in agriculture. Boron is a necessary trace nutrient for plants and is added in small quantities to a number of fertilizers. Borates are also used in crop sprays for fast rehef of boron deficiency. Borates, when apphed at relatively high concentration, act as nonselective herbicides. Small quantities of borates are used in the manufacture of alloys and refractories (qv). Molten borates readily dissolve other metal oxides usage as a flux in metallurgy is an important apphcation. Other important small volume apphcations for borates are in fire retardants for both plastics and ceUulosic materials, in hydrocarbon fuels for fungus control, and in automotive antifreeze for corrosion control (see Corrosion and corrosion inhibitors). Borates are used as neutron absorbers in nuclear reactors. Several borates, which are registered with the Environmental Protection Agency (EPA) can be used for insecticidal purposes, eg, TIM-BOR. 

The strained bicyclic carbapenem framework of thienamycin is the host of three contiguous stereocenters and several heteroatoms (Scheme 1). Removal of the cysteamine side chain affixed to C-2 furnishes /J-keto ester 2 as a possible precursor. The intermolecular attack upon the keto function in 2 by a suitable thiol nucleophile could result in the formation of the natural product after dehydration of the initial tetrahedral adduct. In a most interesting and productive retrosynthetic maneuver, intermediate 2 could be traced in one step to a-diazo keto ester 4. It is important to recognize that diazo compounds, such as 4, are viable precursors to electron-deficient carbenes. In the synthetic direction, transition metal catalyzed decomposition of diazo keto ester 4 could conceivably furnish electron-deficient carbene 3 the intermediacy of 3 is expected to be brief, for it should readily insert into the proximal N-H bond to... 

When iodine dissolves in organic solvents, it produces solutions having a variety of colors. These colors arise from the different interactions between the I2 molecules and the solvent (Fig. 15.21). The element is only slightly soluble in water, unless I ions are present, in which case the soluble, brown triiodide ion, I,, is formed. Iodine itself has few direct uses but dissolved in alcohol, it is familiar as a mild oxidizing antiseptic. Because it is an essential trace element for living systems but scarce in inland areas, iodides are added to table salt (sold as iodized salt ) in order to prevent an iodine deficiency. 

H. F. Bienfait, H. J. Lubberding, P. Heutink, L. Linder, J. Visser, R. Kaptain and K. Dijkstra, Rhizosphere aeidilication by iron deficient bean plants the role of trace amounts of divalent metal ions. Plant Physiol. 90 359 (1989). 

Trace elements Provide standard parenteral trace element preparation (containing zinc, copper, manganese, chromium, and selenium) daily in PN Assess patient for any possible adjustments needed (e.g., delete copper and manganese from PN if the patient has evidence of severe cholestasis, supplemental zinc and selenium for any Gl or fistula losses) or potential deficiencies... 

Soil pH is easily tested for and determines the availability of nutrients and the success of white clover. Very acid soils (below pH 5.0) will cause a deficiency of the trace elements iron, boron, copper and molybdenum and conversely will cause injury to plant growth by increasing the availability of aluminium and manganese to toxic levels. Over-liming, on the other hand, which can raise the pH above 6.5, will reduce the availability of certain essential elements such as phosphorus, manganese and boron. 

Another important factor is the food/nutrient ratio. Many of the necessary nutrients may already be present in the aquifer, such as K, Mg, Ca, S, Na, Mn, Fe, and trace elements however, N and P may be deficient and need to be added. The optimum ratio of BOD N P is 100 5 1. It is not a good practice to inject a large quantity of nutrients in the aquifer at one go. They should be fed at the required usage rate throughout the cleanup process. Both the organic contaminants and the nutrients should be completely exhausted by the end of the in situ remediation of an aquifer. 

The so-called trace elements in general have a catalytic function or are involved in regulatory processes. Some elements exhibit contradicting properties. For example, selenium in large amounts is highly toxic, but a deficiency can have serious health repercussions. It all comes down to the dosage, but this we have known, at the latest, since Parcelsus. 

Hashmi NS, Kachru DN, Khandelwal S, et al. 1989a. Interrelationship between iron deficiency and lead intoxication Part 2. Biol Trace Elem Res 22 299-307. 

For some trace elements (e.g., Zn and Cu), high organic matter leads to Zn/Cu deficiency. Zinc deficiency has been observed in muck or peat soils... 

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. 

Crop cultivar variation in trace element uptake had been observed with com, rice, barley, wheat, and cocoa (Adriano, 1986). Wheat and soybeans showed variety-based variation of P-Zn interaction. Crop varieties with a low capacity for uptake of Zn in soils were more vulnerable to Zn deficiency by P application. Crops sensitive to Zn deficiency included beans, potatoes, peaches, flax, com, rice, soybeans, and citrus (Adriano, 2001). 

---