Thyroid critical organ

Special precautions Store this radioisotope behind 3 mm thick lead shielding. The effective biological half-life in humans is around 140 days. The thyroid gland is the critical organ in terms of dose, and one would be well... 

EPA Environmental standards for management and storage of spent nuclear fuel, high-level and transuranic radioactive wastes —applicability and definitions Whole body Thyroid Other critical organs 25 mrem 75 mrem 25 mrem EPA 2001 i 40CFR191, Subpart A... 

The consequences of accidents are expressed in terms of dose, which can be calculated using standard atmospheric dispersion and dose calculation software, such as those based on the Canadian standard (CSA, 1991). Stochastic doses are usually expressed in terms of the effective and thyroid doses for emergencies that involve the release of radioactive iodine. For emergencies that do not involve iodine, the critical organ dose would be based on the main radionuclide most likely to be released. For the calculation of deterministic health effects, it is important to use organ-specific equivalent doses because the effective dose concept is not applicable to doses this high. It is also important to consider the rate at which the dose is received because the thresholds for deterministic effects vary with the exposure rate. 

The concept of cis-trans (Z-E) isomerism, originally used for the description of the relative geometry of olefins, has been extended to many other functions which feature a double bond character (pseudo double bonds), such as amides, as well as single bonds with a partial or complete limited rotation due to steric or stereoelec-tronic effects. Cis-trans isomerization (CTI) therefore exists in non-re-bonded or overcrowded molecules that switch from a given stable conformational state to another. This is the case of biaryl compounds which have been utilized in organic chemistry as the basis of molecular switches and rotors [1,2]. Nature has also exploited CTI of single bonds to increasing molecular diversity, in particular with the bulky thyroxin, a thyroid hormone, and the well-known disulfide bond which plays a critical role in the structure of peptides and in the conformation of proteins. 

The alterations in morphological organization of the brain resulting from hypothyroidism have been documented [10-13]. Numerous biochemical parameters are affected by altered thyroid states (for review see 14-16). Recent biochemical data on the effect of thyroid hormones on nerve cell differentiation indicate that they regulate microtubule assembly by changing the concentration and/or the activity of MAPS (tau fraction) [17]. The critical period of effectiveness of thyroid hormones in brain maturation raises a special problem. The correct organization of... 

Raw materials. Raw materials from natural origin may be highly contaminated with micro-organisms especially spore-forming bacteria and moulds and in some cases with more critical Enterobacteriaceae. Soon after a publication on salmonellosis in more than 200 persons caused by the contamination of thyroid tablets with two types of Salmonella originating from the raw material [53], proposals for the examination of non-sterile pharmaceutical preparations and acceptance criteria were published [54]. 

The overall effect of these cellular and systemic actions is to stimulate respiratory and other enzyme synthesis, which results in increased oxygen consumption and resultant increased basal metabolic rate. This affects heart rate, respiratory rate, mobilization of carbohydrates, cholesterol metabolism, and a wide variety of other physiological activities. In addition, thyroid hormones stimulate growth and development and, as noted earlier, are critical for the normal proliferation, growth, and development of brain cells. Table 2 shows the estimated iodine concentration in selected organs. 

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