Journal and Proceedings of
The Royal Society of New South Wales
Volume 135 Parts 3 and 4
Dietary Chemicals and Brain Function
Liversidge Lecture – 2003
Professor Graham Johnston AM
Abstract: Phytochemicals in our diet may play a vital role in maintaining the brain's chemical balance by influencing the function of receptors for the major inhibitory neurotransmitter GABA.
The flavonoids apigenin and epigallocatechin gallate, found in chamomile and green tea respectively, influence the way in which GABA receptors are modulated by drugs such as diazepam. Resveratrol, a flavonoid-like polyphenol found in red wine, acts on a subtype of GABA receptors consistent with its action as a cognitive enhancer. Bilobalide from Ginkgo biloba, a herb used in cognitive therapy, also influences GABA receptors. α-Thujone, a terpenoid in the alcoholic beverage Absinthe, acts in a similar manner to bilobalide on GABA receptors. (+)-Borneol and other terpenoids from Valerian, a herb used to promote sleep, enhance the effects of GABA. The effects of these phytochemicals on GABA receptors are consistent with the overall actions of the beverages and herbal preparations that contain them, thus providing a rational basis for the use of these beverages and herbal preparations.
These studies provide evidence that chemicals in our diet may influence brain function in a positive way. The chemical nature of these substances may lead to the development of new therapeutic agents for the treatment of anxiety, epilepsy, memory disorders and insomnia.
Keywords
Brain function, chemicals, diet, balance, dosage
Ionic Combating Mechanisms and their Comparative Effects on Seed Hardening under Simulated Supra-Optimal Environmental Conditions
M.A. Kader
Abstract: Heat extremes and limited moisture are two of the most dominant environmental factors impacting stand establishment of rainfed sorghum (Sorghum bicolor L. Moench). Hardening is the process of exposing plants to gradual levels of stress and acclimation to foster better response to post-treatment stress factors. Three experiments were carried out under phytotron and germination cabinet conditions to test the effects of osmotic soaking of sorghum seeds with sodium chloride (NaCl) on germination and growth under simulated heat stress. The hypothesis was that the NaCl treatment forms an acclimation to stress by inducing hormonal responses to ionic toxicity caused by salt. This acclimation would lead to a lowered degree of response when the seed is exposed to future stress; namely, heat and/or drought. Independent variables included NaCl concentration, treatment duration, storage and genotype, whereas germination and growth were dependent variables. Further experiments tested various methods of achieving the initial acclimation "signaling" whilst reducing ionic toxicity through combating ions. Longer soaking treatment durations (2-3 days) and higher NaCl concentrations (16 g NaCl L-1) were detrimental to germination in comparison to lower concentrations (8 g NaCl L-1) and shorter durations (1 day). An interaction between concentration and duration of treatment existed where high concentrations performed better at lower treatment durations and vice versa. Combining 10 g NaCl L-1 with 5 g calcium sulphate L-1 to combat ionic toxicity produced a greater advancement of germination than NaCl alone. Drying duration of seeds did not affect subsequent germination nor did storage for 10 days to 1 month. The effects of osmotic conditioning are discussed and could have potential for improving sorghum success rates in harsh arid environments.
Keywords
ions, acclimation, stress, sorghum, germination