Nutritional chain

Radioactive aerosols (particularly aerosols of fission products) which fall out from smoke containing radioactive gaseous products and enter nutritional chains. 

Chlorinated dibenzo-p-dioxines and dibenzofurans are tricyclic aromatic compounds [4], characterized by a high chemical resistance and an ability to be accumulated in the nutritional chain. Some of them are extremely toxic, teratogenic, mutagenic and probably also carcinogenic. The most studied substances in this group are 2,3,7,8-tetrachloro-dibenzodioxine (TCDD) and 2,3,7,8-tetrachloro-dibenzofuran (TCDF), which are among the most toxic substances... 

Heavy metal ions are concentrated in nutritional chains with a possibility of a fatal involvement only of a higher member of the chain by the accumulation of the toxic metal in organisms, such as occurs even in man (the diseases itai-itai, minamata). 

The formation of alkylmercurials from elementary mercury and from its inorganic substances in waters of oceans and lakes is the basic element in the whole chain of mercury conversion in the nature. In the upper sedimentation layers of the sea or lake bottom, methylation of elementary mercury or of mercuric ions occurs with the formation of methyl mercury. The methyl mercury is retained by small aquatic organisms which either serve as feed for fish or die, and during their decomposition dimethyl mercury vapours are released into the atmosphere. In the atmosphere, in acid medium (acid rain) dimethyl mercury can be demethylated to form methyl mercury, which can re-enter the nutritional chain in water. 

One advantage of organophosphate insecticides lies in their fairly rapid biological and chemical degradation in plants and animals to non-toxic substances. They are also not accumulated in nutritional chains. The persistence of chlorinated hydrocarbons, organophosphates and of the other commonly used pesticides in water and fish is presented in Table 9.5 [28]. 

Polycyclic aromatic hydrocarbons are a large group of carcinogens, which enter the hydrosphere in the case of an escape of petroleum products. In general, since these substances can hardly be decomposed biologically, they are accumulated in aquatic organisms, and through the nutritional chain they are thus potentially hazardous to the man. In oysters collected... 

The content of elements in the nutritional chain is affected by chemical characteristics of the elements, soil composition, plant species, time of harvesting and many other factors. For example, changes of pH of soils after applications of calcium can be manifested in plants by an increased intake of molybdenum and reduced concentrations of copper, iron, manganese and zinc. An increased intake of phosphorus, nitrogen and potassium by plants is manifested by a reduction in the intake of sodium and magnesium by farm animals. Intense fertilization with nitrogen-containing compounds also induces a decrease of the content of copper and zinc in plants, which is manifested adversely in the intake of these elements by animals [5]. 

TWjce elements and toxic metals are very important factors in the environment. In the organism, they can affect metabolic processes positively as well as negatively. Due to the pollution of particular components of the environment by a wide spectrum of elements as a result of human activity, these substances enter the human nutritional chain. 

The increased use of fertilizers makes a large contribution to the penetration of elements into the nutritional chain. The fertilizers can contain, depending on their production and origin, high amounts of particular elements, including toxic ones. By the application of such fertilizers, the content of these elements in the soil is increased and they enter plants via their root system. Certain types of fertilizers, particularly natural superphosphates, contain more than 30 mg kg of cadmium and lead. Depending on the soil pH, absorption of these metals and their accumulation in particular parts of plants is encountered. The increased global use of fertilizers fortified by certain microelements has considerably increased their contents in the soil and foodstuffs. 

For the study of the entry of toxic elements into the nutritional chain, it is necessary to foUow geochemical changes resulting from the development of industry and technologies, where wastes can contaminate particular components of the environment, involving relevant biocycles. 

Therefore the sampled plants were not cleaned from adhering soil and dust particles, because animals harvesting these plants as fodder do not clean them either. This procedure is recommended if the entry of contaminants into the nutrition chain is under consideration (Markert, 1995). After a microwave digestion the samples were analyzed using Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS). Approximately 9% of the sampled plants were contaminated with arsenic >2 ppm (Fig. 5). 

However, considering the obvious and at some places extreme arsenic contamination of the soil, the arsenic content of the plants appears to be surprisingly moderate. As a result of this study the authors concluded that a dangerous contamination of the nutrition chain by arsenic via plant uptake was not observed. 

Hemp is also a good crop to grow on soils polluted with heavy metals. An experiment has shown [11] that providing the soil shows good agricultural quality, hemp can extract and accumulate substantial amounts of elements such as copper, lead, zinc and cadmium with no detrimental effect on the quantity and quality of the crop. The total calculated, extracted and fixed copper and lead can reach 377 g and 141 g per hectare, respectively [12]. This results in gradual remediation of the soil and eliminates the threat of introduction of heavy metals to the nutritive chain of humans and livestock. 

Fatty acids are susceptible to oxidative attack and cleavage of the fatty acid chain. As oxidation proceeds, the shorter-chain fatty acids break off and produce progressively higher levels of malodorous material. This condition is known as rancidity. Another source of rancidity in fatty foods is the enzymatic hydrolysis of the fatty acid from the glycerol. The effect of this reaction on nutritional aspects of foods is poorly understood andhttie research has been done in the area. 

Plants, in contrast to animals, have the ability to convert carbon dioxide from the atmosphere and inorganic components of the earth direcdy into high energy carbohydrates (qv), fats, and proteins (qv). These plant materials are absolutely essential to human nutrition as well as to the nutrition of other animal species. Thus consumption of plant matter, either directly or through a food chain, is essential to animal life and humans are totally dependent on agricultural endeavors, ie, the culture and harvesting of plant matter. 

In Parenteral and Enteral Nutrition. Amino acid transfusion has been widely used since early times to maintain basic nitrogen metaboHsm when proteinaceous food caimot be eaten. It was very difficult to prepare a pyrogen-free transfusion from protein hydrolysates. Since the advances in L-amino acid production, the crystalline L-amino acids have been used and the problem of pyrogen in transfusion has been solved. The formulation of amino acid transfusion has been extensively investigated, and a solution or mixture in which the ratio between essential and nonessential amino acid is 1 1, has been widespread clinically. Special amino acid mixtures (eg, branched chain amino acids-enriched solution) have been developed for the treatment of several diseases (93). 

The rate of mitochondrial oxidations and ATP synthesis is continually adjusted to the needs of the cell (see reviews by Brand and Murphy 1987 Brown, 1992). Physical activity and the nutritional and endocrine states determine which substrates are oxidized by skeletal muscle. Insulin increases the utilization of glucose by promoting its uptake by muscle and by decreasing the availability of free long-chain fatty acids, and of acetoacetate and 3-hydroxybutyrate formed by fatty acid oxidation in the liver, secondary to decreased lipolysis in adipose tissue. Product inhibition of pyruvate dehydrogenase by NADH and acetyl-CoA formed by fatty acid oxidation decreases glucose oxidation in muscle. 

The red microalga genus Porphyridium is a source of biochemicals possessing nutritional and therapeutic values. The biochemicals include polysaccharides that have anti-inflammatory and antiviral properties, long-chain polyunsaturated fatty acids, carotenoids such as zeaxanthin, and fluorescent phycobiliproteins. 

While quality was formerly achieved by inspection of final products, it is accomplished now by prevention through controlling critical steps in the production processes along the agri-food chain. Hazard analysis critical control points (HACCP) represent a typical example of such a preventive approach. Although this concept was developed primarily to assure food safety, the basic principle is also applicable to assuring non-safety quality attributes such as color, flavor, and nutritional value. " This section translates the HACCP principles into a critical quality control point (CQP) concept that can be part of a system to assure food quality. 

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