A deep dig-hindsight on Holocene plant composition from ancient environmental DNA

Want a glimpse at past vegetation? Studying pollen and other plant remains, which are preserved for example in lake sediments or mires for thousands of years, allows us to document regional occurrences of plant species over radiocarbon-dated time series. Such vegetation reconstructions derived from optical analyses of fossil samples are inherently incomplete because they only comprise taxa that contribute sufficient amounts of pollen, spores, macrofossil or other evidences. To complement optical analyses for paleoecological inference, molecular markers applied to ancient DNA (aDNA) may help in disclosing information hitherto inaccessible to biologists. Parducci etal. (2013) targeted aDNA from sediment cores of two lakes in the Scandes Mountains with generic primers in a meta-barcoding approach. When compared to palynological records from the same cores, respective taxon lists show remarkable differences in their compositions, but also in quantitative representation and in taxonomic resolution similar to a previous study (JOrgensen etal. 2012). While not free of assumptions that need critical and robust testing, notably the question of possible contamination, this study provides thrilling prospects to improve our knowledge about past vegetation composition, but also other organismic groups, stored as a biological treasure in the ground.

Energetic and metabolic cost of growth in Gambian infants.

The aim of the study was to measure the energy used for growth of healthy fullterm and breast-fed Gambian infants. The weight gain (WG) of 14 infants (mean age +/- SEM 17 +/- 1 d, weight 3.581 +/- 0.105 kg) was measured over a 2-week period; the energy intake (EI) from breast milk was assessed for 24 h in the middle of the study period by weighing the infant before and after each breast-feed. On the same day, sleeping energy expenditure (SEE) and respiratory quotient (RQ) were measured for 30 min on five occasions through the 24-h period. EI averaged 502 +/- 25 kJ/kg.d, and SEE 230 +/- 6 kJ/kg.d; thus, an average of 272 kJ/kg.d were available for physical activity and the energy stored for growth. The total energy spent by infants while sleeping and for periods of physical activity was calculated to be 1.7 x SEE. The mean RQ measured on five occasions averaged 0.879 +/- 0.009. SEE was correlated with WG (r = 0.747, P less than 0.005), with a slope of the regression line of 5.5 kJ/g; this value can be considered as an estimate of the energy spent for new tissue synthesis in the resting infant. The efficiency of weight gain was lower in this study (67%) than in studies conducted on fast-growing preterm infants or children recovering from malnutrition.

Role of substrate utilization and thermogenesis on body-weight control with particular reference to alcohol.

Alcohol (ethanol; EtOH) provides fuel energy to the body (29.7 kJ (7. 1 kcal)/g, 23.4 kJ (5.6 kcal)/ml), as do other macronutrients, but no associated essential nutrients. The thermogenic effect of EtOH (on average 15 % of its metabolizable value) is much greater than that of the main substrates utilized by the body, i.e. fat and carbohydrates (CHO), suggesting a lower net efficiency of energy utilization for EtOH than for fat and CHO. EtOH cannot be stored in the body and is toxic, so that there is an obligatory continuous oxidation of EtOH and it becomes the priority fuel to be metabolized. In contrast to CHO, its rate of oxidation does not depend on the dose ingested. As with CHO intake, it engenders a shift in postprandial substrate utilization (decrease in fat oxidation), but by a non-insulin-mediated mechanism. A limited amount of EtOH can be converted to fatty acids by hepatic de novo lipogenesis (as occurs with high levels of CHO feeding) from acetate production, which inhibits lipolysis in peripheral tissues. There is no evidence that EtOH consumed under normoenergetic conditions (i.e. isoenergetically replacing CHO or fat) leads to greater body fat storage than fat or CHO. However, there is still a lack of experimental studies on the influence of EtOH on the level of spontaneous physical activity in man. This effect may well depend on the dose of EtOH consumed as well as other intrinsic factors.