Irregular activity arises as a natural consequence of synaptic inhibition.

Irregular neuronal activity is observed in a variety of brain regions and states. This work illustrates a novel mechanism by which irregular activity naturally emerges in two-cell neuronal networks featuring coupling by synaptic inhibition. We introduce a one-dimensional map that captures the irregular activity occurring in our simulations of conductance-based differential equations and mathematically analyze the instability of fixed points corresponding to synchronous and antiphase spiking for this map. We find that the irregular solutions that arise exhibit expansion, contraction, and folding in phase space, as expected in chaotic dynamics. Our analysis shows that these features are produced from the interplay of synaptic inhibition with sodium, potassium, and leak currents in a conductance-based framework and provides precise conditions on parameters that ensure that irregular activity will occur. In particular, the temporal details of spiking dynamics must be present for a model to exhibit this irregularity mechanism and must be considered analytically to capture these effects.

Essential fats for future health. Proceedings of the 9th Unilever Nutrition Symposium, 26-27 May 2010.

The 9th Unilever Nutrition Symposium entitled 'Essential fats for future health', held on 26-27 May 2010, aimed to review the dietary recommendations for essential fatty acids (EFA); discuss the scientific evidence for the roles of EFA in cognition, immune function and cardiovascular health; and to identify opportunities for joint efforts by industry, academia, governmental and non-governmental organizations to effectively improve health behaviour. This paper summarizes the main conclusions of the presentations given at the symposium. Linoleic acid (LA) and α-linolenic acid (ALA) are EFA that cannot by synthesized by the human body. Docosahexaenoic acid (DHA) is considered as conditionally essential because of its limited formation from ALA in the human body and its critical role in early normal retinal and brain development and, jointly with eicosapentaenoic acid (EPA), in prevention of cardiovascular disease (CVD). Some evidence for possible beneficial roles of n-3 fatty acids for immune function and adult cognitive function is emerging. A higher consumption of polyunsaturated fatty acids (PUFA; >10%E), including LA, ALA and at least 250-500 mg per day of EPA+DHA, is recommended for prevention of coronary heart disease (CHD). Two dietary interventions suggest that EFA may affect CVD risk factors in children similarly as in adults. To ensure an adequate EFA intake of the population, including children, public health authorities should develop clear messages based on current science; ensure availability of healthy, palatable foods; and collaborate with scientists, the food industry, schools, hospitals, health-care providers and communities to encourage consumers to make healthy choices.

Normalization of triglycerides in type IV hyperlipoproteinemia fails to correct low levels of high-density-lipoprotein cholesterol.

High-density-lipoprotein (HDL) cholesterol protects against coronary heart disease, and ways to raise low HDL values are being sought. Cross-sectional population surveys have shown that HDL cholesterol is inversely related to plasma triglycerides, yet to our knowledge no longitudinal studies have shown that a decrease in elevated triglycerides will raise depressed HDL levels. We therefore used dietary therapy to lower the triglyceride levels of 29 men with Type IV hyperlipoproteinemia and evaluated the effects on HDL-cholesterol levels. Despite a reduction in triglyceride levels from 697 +/- 90 to 333 +/- 37 mg per deciliter (P < 0.01), initially low HDL-cholesterol values did not change (29 +/- 1 to 30 +/- 1 mg per deciliter). Even in a subgroup of 12 men whose triglyceride levels fell to normal (from 670 +/- 99 to 170 +/- 7, P < 0.01) and whose weight and triglycerides remained stable for two years, HDL cholesterol remained unchanged (29 +/- 1 vs. 32 +/- 1). The persistently low HDL-cholesterol level in the presence of normalization of triglycerides suggests that depressed HDL cholesterol may be an independent metabolic abnormality in Type IV hyperlipoproteinemia.