Biological Significance of

Most estimates of the thyroidal radiation dose consequent to exposure are based upon metabolic parameters determined for other radioiodines. For example, Colard et al. (1965) calculated thyroidal burdens from chronic (1 iiCi h ) absorption for a number of radioiodines, assuming a stable iodine intake of 100 //g d . In the case of I, such an exposure was estimated to lead to the deposition of 5700 / Ci in the thyroid. Because of its low specific activity, however, one /iCi of represents 5.9 mg of iodine. Hence, the data of Colard et al. (1965) would require the deposition of 34 g of iodine (all as I) in the thyroid. This quantity corresponds to several thousand times the average value of 0.012 g iodine in the thyroid (ICRP, 1975). The intake per day for the maximum permissible dose is discussed in Section 4.7. 

In a similar fashion, a single administration of one microcurie of I would be expected to reduce the uptake of iodine by the thryoid. Several investigators have examined the effect of large doses of stable iodine ( I) on I uptake (Hamilton, 1942 Adams and Bonnel, 1962 Saxena et al., 1962 Cuddihy, 1964 Blum and Eisenbud, 1967 Stem-thal et al., 1980). Since the uptake of radioiodine by the thyroid is inversely related to the intake of I, the fraction of ingested I taken up by the thyroid would be expected to decrease as the amount of I ingested increases. 

Over the range of I dosages, there was a 5-fold decrease in peak thyroidal uptake, from about 27 percent of the administered dose in controls receiving 0.2 mg I in their diets to 5.2 percent in the group receiving an additional 5 mg I. The rate of release from the thyroid 

For humans, the effect of on thyroidal iodine metabolism can be similarly estimated. From the data of Blum and Eisenbud (1967), wherein was administered to suppress intake, and for a dietary intake of 150 mg d , the relationship of the 24-h uptake (Y) in percent, to the total iodine intake (X) in mg was computed to be 

(5-2) may be utilized in estimating thyroidal uptake. If a daily intake of 0.15 mg is assumed, then thyroidal uptakes at 24 hours would remain at about 27 percent for dosages of less than 1 nCi (5.9 ng iodine). However, at higher dosages of there would be a considerable reduction in thyroidal uptake, to about 10 percent from 0.1 ltd I (0.59 mg -I- 0,15 mg), to about 3 percent from 1 tCi (5.9 mg -I- 0.15 mg). Since the radiologic dose to the thyroid is determined by the concentration in the gland, a similar decrease in dose per unit intake would be predicted. 

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Distinctive coordination chemistry and biological significance of complexes with macrocyclic ligands. D. H. Busch, Acc. Chem. Res., 1978,11, 392-400 (61). 

The widespread occurrence and biological significance of polyoxygenated carbocycles provided the impetus to apply RCM to sugar-derived dienes. Carbohydrate carbocyclization based on a sequence of Vasella reductive opening of iodo-substituted methyl glycosides [25], and RCM of the dienes available from the resulting unsaturated aldehydes, were used to prepare a series of natural compounds (Schemes 5-7). 

The biological significance of chitosan biomaterials in the hiunan body depends largely on the actions that certain hydrolases exert on them. The resulting chitoohgomers stimulate various cells, while the released monomers are phosphorylated and incorporated into hyaluronan, keratan sulphate and chondroitin sulphate, components of the intracellular matrix and connective tissue [348]. 

Jameel, A., Skilton, R.A., Campbell, T.A., Chander, S.K., Coombes, R.C., Luzmani, Y.A. (1992). Clinical and biological significance of hsp89 alpha in human breast cancer. Inti. J. Cancer 50, 409-415. 

SALUNKHE D K, JADHAV s J, KADAM s s, CHAVAN J K (1982) Chemical, biochemical, and biological significance of polyphenols in cereals and legumes. Crit Rev Food Sci Nutr. 17 277-305. 

Luan J, Shattuck-Brandt R, Haghnegahdar H, et al. Mechanism and biological significance of constitutive expression of MGSA/GRO chemokines in malignant melanoma tumor progression. J Leukoc Biol 1997 62(5) 588-597. 

The ratio of peaks for peptides derived from 42 high abundance yeast proteins was examined for the wild type versus cln2 mutant strains (Oda et al., 1999). Only two of the proteins, a peroxisomal membrane protein and S-adenosylmethionine synthase 2, exhibited significant differences in expression between the strains. The biological significance of this observation is not yet known but the study does indicate that changes of >20% in expression levels can be detected using the technique (Oda et al., 1999). 

The results also showed that the age-related increase in serum creatinine was earlier and faster and more linear among subjects in the highest quartile than among those in the lowest quartile. Based on the results, Kim et al. (1996a) concluded that low-level exposure to lead may impair renal function in middle-aged and older men however, the biological significance of a 0.08 mg/dL increase in serum creatinine is unknown. 

To provide useful ancillary information when the biological significance of the bioassay result is uncertain... 

We are attempting to understand the biological significance of the large variations in frequency of putative LDRs, whether between different types of bacteria or archaea, or between pro- and eukaryota. We have carefully studied the literature of more than 90 example proteins selected from our disordered protein databases and found reports on the functions of most of the disordered regions (Dunker et al., 2002). The observed functions and the number of examples in each functional class are given in Table VI. As indicated, four major functional classes were found molecular recognition, molecular assembly or disassembly, protein modification, and entropic chains. 

In Z-DNA, guanine residues are syn, whereas cytosine and thymine residues are anti. Eukaryotic DNA contains several alternating purine-pyrimidine sequences consistent with die Z-DNA conformation however, the biologic significance of Z-DNA is still unclear. 

Price K R, Johnson IT and Fenwick G R (1987), The chemistry and biological significance of saponins in food and feeding stuffs , Crit Rev Food Sci Nutr, 26, 27-133. 

The biological significance of glycoporphyrins, their limited natural occurrence, and their widespread applications have made the availability of such compounds a scientific challenge for several research groups. Synthetic approaches have consisted in the direct glycosylation of prefunctionalized porphyrins or chemical synthesis from suitable glycoconjugates precursors. 

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