Quantitative interaction

If there are specific data germane to the assumption of dose-additivity (e g., if two compounds arc present at the same site and it is known that the combination is five times more toxic than the sum of the toxicitics for the two compounds), then tire development of the hazard index should be modified accordingly. The reader can refer to the EPA (1986b) mi.xiure guidelines for discussion of a hazjird index equation that incorporates quantitative interaction data. If data on chemical interactions are available, but arc not adequate to support a quantitative assessment, note the information in the assumptions being documented for the risk assessment. 

The controller and its quantitative interaction with the system will not be covered in this text. Numerous books have been written about this, and most chemical engineering curricula have a course that is devoted solely to the topic. 

Knittler MR, Dirks S, Haas IG (1995) Molecular chaperones involved in protein degradation in the endoplasmic reticulum quantitative interaction of the heat shock cognate protein BiP with partially folded immunoglobulin light chains that are degraded in the endoplasmic reticulum. Proc Natl Acad Sd USA 92 1764-1768... 

ICH makes the distinction between quantitative and qualitative interactions. A quantitative interaction refers to the situation where the treatment difference is consistently in one direction (for example A is always better than B), but there are differences in terms of magnitude. A qualitative interaction is where the treatment difference is in a different direction for some centres (for example A is better than B in some centres but B is better than A in other centres). The previous example is an example of a quantitative interaction. Had the A mean in centre 4 been 3.9 and the B mean 5.0, then the treatment difference (A — B) would equal —1.1 and we would have a qualitative interaction. 

Note however that the hazard ratio in both high and low baseline LDL cholesterol subgroups is below 1.00 indicating a benefit of pravastatin (a quantitative interaction), although this benefit is marginal in those patients presenting with LDL cholesterol <4.0mmol/l. 

Figure 13.7 Effect of punch design and compression force on tablet strength - quantitative interaction...

If what we saw in Figure 13.7 was quantitative interaction , then Figure 13.8 may be said to show qualitative interaction . 

The selected fiber-cation complexes were stirred into emulsions containing fatty acids and subsequently examined. Figure U illustrates the results where it may be seen that the ferric-fiber complex caused a clear separation of phases apparently due to an almost quantitative interaction between ferric-fiber and fatty acids. The ferric-fiber broke the emulsion, bound virtually all the fatty acid present in the system and floated to the top thus creating a clear solution. The aluminum-fiber caused only partial separation while the H+, Ca2+ and Fe2+ neutralized fibers did not separate or show any preference for the hydrophobic or hydrophylic phase and formed a homogeneous dispersion. 

Although numerous precolumn derivatization techniques have been introduced in the last 35 years, none complies with the criteria of an ideal procedure providing rapid and quantitative interaction in aqueous media, permitting mild conditions, ensuring interaction with both primary and secondary AAs, and resulting in single and stable derivatives in the case of all AAs. 

Because of the different and low stability of the isoindoles obtained from the reaction of AAs with OPA/MCE reagent, alternative precolumn derivat-izations reagents, such as 3-mercaptopropionic acid (MPA) and several N-alkyl-L/o-cysteines, were proposed. The OPA/MPA and OPA/N-acetyl-L-cysteine (NAC) reagents provide more stable isoindoles compared to those formed with the OPA/MCE, and the optical resolution of enantiomeric AAs with the OPA/NAC, as well as with further N-alkyl-L/o-cysteine reagents, have opened a new area in separation of AA enantiomers. Due to robotic autosamplers, which provide excellent reproducibility even for moderately quantitative interactions, most AA analyses are performed with the OPA derivative. The unexplainable contradictions of this most popular process - relating to the particularly low stability of the OPA derivatives of six very important AAs (glycine, y-aminobutyric acid (GABA), jS-alanine,... 

L. KAt6 and B. Gozsy, Quantitative Interaction between Dextran and Antihistamines in the Rat, Fedn Proc. Fedn Am. Socs exp. Biol. 20, 256 (1961). 

Rosen JF, Pounds JG (1989) Quantitative interactions between Pb and Ca homeostasis in cultured osteoclastic bone cells. Toxicol Appl Pharmacol 98 530-543. 

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