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The application of science to human nutrition over the centuries has served societies well. One example is the identification of key nutrients to overcome nutritional deficiencies, which has enhanced life expectancy. Enhanced life expectancy, however, is associated with an increased prevalence of chronic disorders related to food and nutrition. Findings of studies indicating that individual responses to nutrients differ substantially between individuals make it necessary to re-examine the relationship between nutrition and human health. The emergence of new genomic-based technologies illustrates the complexity and scale of the interactions between nutrition and genetic factors. Epigenetic modifications resulting from interactions of the genetic profile, aging, and lifestyle can influence the time course of chronic disorders and contribute to human variability in response to nutritional interventions. Developing a better understanding of human variability as it applies to human nutrition will involve embracing the approaches and principles of complex science., (© The Author(s) 2020. Published by Oxford University Press on behalf of the International Life Sciences Institute. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The noradrenaline (NA) content of the mesenteric arteries from spontaneously-hypertensive rats (SHR) are greater than those in arteries from normotensive Kyoto Wistar rats (WKY). The possibility that impaired neuronal monoamine oxidase (MAO) activity in mesenteric arteries from SHR rats was responsible for the differences in NA content was explored. The in-vitro formation of dihydroxyphenylethylene glycol (DOPEG) by intact segments of mesenteric arteries was used as an index of neuronal MAO activity. There were no differences in the production of DOPEG from endogenous NA by arteries from normotensive and hypertensive rats. Moreover, the formation of DOPEG from exogenous NA was similar in arteries from SHR and WKY rats. The neuronal uptake of NA was indistinguishable between mesenteric arteries from SHR and WKY rats. The results argue against an impairment of neuronal MAO in contributing to the enhanced content of NA in the mesenteric artery of the SHR rat.

The effect of in-vitro sympathetic denervation on the O-methylation of 2-hydroxyoestradiol was examined using the rabbit thoracic aorta. Aortic segments were exposed to 6-hydroxydopamine (400 mg litre-1, 10 min), incubated in 2-hydroxyoestradiol (5 microM, 60 min), and the 2-methoxyoestradiol formed was quantified using HPLC with electrochemical detection. Pre-exposure to 6-hydroxydopamine reduced O-methylation by 90% in intact aortic strips. However, O-methylation was also reduced (81%) in rabbit aorta that had been surgically denervated before exposure to 6-hydroxydopamine. Furthermore, the O-methylation of 2-hydroxyoestradiol (20 microM, 15 min) by partially purified soluble catechol-O-methyltransferase was inhibited by 6-hydroxydopamine (400 mg litre-1) by 95% and 51% in the absence and presence of antioxidant, respectively. These results suggest that the inhibition of catechol-O-methyltransferase by 6-hydroxydopamine reported for the purified enzyme, applies to the intact tissue and that the inhibition is dependent on oxidation of the 6-hydroxydopamine. Subsequent experiments using dialysis techniques demonstrated that the inhibition of soluble catechol-O-methyltransferase by 6-hydroxydopamine was irreversible in part, but the degree of irreversibility was influenced by pH and by the extent of in-vitro oxidation of 6-hydroxydopamine.

The use of sodium borate impregnated silica gel plates for the chromatographic separation of the catecholamines noradrenaline, adrenaline, and isoprenaline from their respective 3-0-methylated derivatives, normetanephrine, metanephrine, and methoxy-isoprenaline, is described. The parent catecholamines remain at the origin of the plates while the 3-0-methylated derivatives concentrate in discrete bands at the upper edge of the borate impregnated area (the "borate front").

The use of sodium borate impregnated thin-layer silica gel plates for the separation of noradrenaline and its 3-O-methylated metabolites is described. Its application to studies of the metabolism of tritiated I-noradrenaline by isolated tissues is illustrated for the rabbit uterus.