Serotonergic projections to the orbitofrontal and medial prefrontal cortices differentially modulate waiting for future rewards

Optogenetic activation of serotonergic neurons in the dorsal raphe nucleus (DRN) enhances patience when waiting for future rewards, and this effect is maximized by both high probability and high timing uncertainty of reward. Here, we explored which serotonin projection areas contribute to these effects using optogenetic axon terminal stimulation. We found that serotonin stimulation in the orbitofrontal cortex (OFC) is nearly as effective as that in the DRN for promoting waiting, while in the nucleus accumbens, it does not promote waiting. We also found that serotonin stimulation in the medial prefrontal cortex (mPFC) promotes waiting only when the timing of future rewards is uncertain. Our Bayesian decision model of waiting assumed that the OFC and mPFC calculate the posterior probability of reward delivery separately. These results suggest that serotonin in the mPFC affects evaluation of time committed, while serotonin in the OFC is responsible for overall valuation of delayed rewards

Effect of extracts from selected Kenyan plants on traits of metabolic syndrom in Wistar rats fed a high-fat high fructose diet

Purpose: To examine the potential of extracts from selected herbs used in African traditional medicine in diabetes patients, and to determine their effect on traits of metabolic syndrome in rats fed a high-fat and high-fructose diet.Methods: Ethanol and aqueous extracts were prepared from Mangifera indica (MI), Lonchocarpus eriocalyx (LE), Urtica massaica (UM), Schkuhria pinnata (SP) and Launaea cornuta (LC). Ethanol extracts (1:100 dilution) were examined for inhibition of pancreatic lipase and α-glucosidase activity invitro. Furthermore, aqueous extracts were administered for 74 days to male Wistar rats fed a high-fat and high-fructose diet to assess their effect on traits of metabolic syndrome.Results: Ethanol extracts showed at least 30 % inhibition of pancreatic lipase in vitro but no effect on α- glucosidase activity. Administration of the aqueous extracts caused significant reduction in liver triglycerides (except for LE). Muscle triglycerides and fat were also reduced, with the most pronounced effect elicited by LE. Urinary glucose excretion and plasma triglycerides, but not hyperinsulinemia and insulin resistance, were reduced by UM compared to control.Conclusion: This exploratory study indicates that UM may be considered a candidate for the prevention and management of type 2 diabetes. Keywords: Kenyan traditional medicine, High-fat diet, High fructose, Insulin resistance, Triglycerides, Diabetes, Liver steatosi

Mbi Crater (Cameroon) illustrates the relations between mountain and lowland forests over the past 15,000 years in western equatorial Africa

International audienc

A 90,000-year record of Afromontane forest responses to climate change

International audiencePollen records from African highlands are scarce; hence, the paleoecology of the Afromontane forest and its responses to glacial cycles are poorly known. Lake Bambili (Cameroon) provides a record of vegetation changes in the tropical mountains of Africa over the past 90,000 years, with high temporal resolution. Pollen data and biome reconstructions show a diverging response of forests to climate changes; the upper tree line was extremely unstable, shifting substantially in response to glacial-interglacial climate alternation, whereas the transition between the montane and lowland forests remained remarkably stable. Such ecological instability may have had a critical influence on species richness in the Afromontane forests

Altitudinal distribution of pollen, plants and biomes in the Cameroon highlands

Pollen–plant–biome relationships have been studied from 48 new soil surface samples taken along an altitudinal gradient in the Cameroon highlands in order to capture the major features of the tropical montane vegetation. Although our study is based on a relatively feeble number of samples due to difficulties to access natural landscapes in this area, the main vegetation belts are accurately reconstructed. Comparison between pollen and plant distribution has been used to identify taxa characteristic of the mountain forest and to identify eventual bias due to pollen productivity and transport. Taking that into account, we have shown that there is a potential for reliable biome reconstruction of the Afromontane forest the upper and lower limits of which are correctly reconstructed. Our study fills the gap in reconstructing African biomes from pollen data, thus providing elements to capture the vulnerability of Afromontane ecosystems to climate changes

Genetic association study of exfoliation syndrome identifies a protective rare variant at LOXL1 and five new susceptibility loci.

Exfoliation syndrome (XFS) is the most common known risk factor for secondary glaucoma and a major cause of blindness worldwide. Variants in two genes, LOXL1 and CACNA1A, have previously been associated with XFS. To further elucidate the genetic basis of XFS, we collected a global sample of XFS cases to refine the association at LOXL1, which previously showed inconsistent results across populations, and to identify new variants associated with XFS. We identified a rare protective allele at LOXL1 (p.Phe407, odds ratio (OR) = 25, P = 2.9 × 10-14) through deep resequencing of XFS cases and controls from nine countries. A genome-wide association study (GWAS) of XFS cases and controls from 24 countries followed by replication in 18 countries identified seven genome-wide significant loci (P < 5 × 10-8). We identified association signals at 13q12 (POMP), 11q23.3 (TMEM136), 6p21 (AGPAT1), 3p24 (RBMS3) and 5q23 (near SEMA6A). These findings provide biological insights into the pathology of XFS and highlight a potential role for naturally occurring rare LOXL1 variants in disease biology