Physiological significance

Until separation techniques such as chromatography (28,29) and counter-current extraction had advanced sufficientiy to be of widespread use, the principal alkaloids were isolated from plant extracts and the minor constituents were either discarded or remained uninvestigated. With the advent of, first, column, then preparative thin layer, and now high pressure Hquid chromatography, even very low concentrations of materials of physiological significance can be obtained in commercial quantities. The alkaloid leurocristine (vincristine, 22, R = CHO), one of the more than 90 alkaloids found in Catharanthus roseus G. Don, from which it is isolated and then used in chemotherapy, occurs in concentrations of about 2 mg/100 kg of plant material. 

The Physiological Significance of Cooperative Binding of Oxygen by Hemoglobin... 

We can determine quantitatively the physiological significance of the sigmoid nature of the hemoglobin oxygen-binding curve, or, in other words, the biological importance of cooperativity. The equation... 

Their biological and physiological significance have only recently been broadly recognized20). 

The TAAR receptor system has also been associated with body temperature regulation on the basis of putative thyroid hormone metabolites and their synthetic derivatives (thyronamines) activating TAAR1 in rodents. However, as these effects are only observed with thyronamine concentrations several orders of magnitude above physiological levels, and as the specificity of these compounds has not been determined, the physiological significance of these observations is unclear. 

The physiological significance of the growth requirements for established animal cell lines in serum-free medium is still an unresolved matter. Cultures of... 

Functional Groups That Are Weak Acids Have Great Physiologic Significance... 

Peroxidation is also catalyzed in vivo by heme compounds and by lipoxygenases found in platelets and leukocytes. Other products of auto-oxidation or enzymic oxidation of physiologic significance include oxysterols (formed from cholesterol) and isoprostanes (prostanoids). 

The lipids of major physiologic significance are fatty acids and their esters, together with cholesterol and other steroids. 

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