Transient Phenomena in Gene Expression after Induction of Transcription

When transcription of a gene is induced by a stimulus, the number of its mRNA molecules changes with time. Here we discuss how this time evolution depends on the shape of the mRNA lifetime distribution. Analysis of the statistical properties of this change reveals transient effects on polysomes, ribosomal profiles, and rate of protein synthesis. Our studies reveal that transient phenomena in gene expression strongly depend on the specific form of the mRNA lifetime distribution

Health and Pleasure in Consumers' Dietary Food Choices: Individual Differences in the Brain's Value System

Taking into account how people value the healthiness and tastiness of food at both the behavioral and brain levels may help to better understand and address overweight and obesity-related issues. Here, we investigate whether brain activity in those areas involved in self-control may increase significantly when individuals with a high body-mass index (BMI) focus their attention on the taste rather than on the health benefits related to healthy food choices. Under such conditions, BMI is positively correlated with both the neural responses to healthy food choices in those brain areas associated with gustation (insula), reward value (orbitofrontal cortex), and self-control (inferior frontal gyrus), and with the percent of healthy food choices. By contrast, when attention is directed towards health benefits, BMI is negatively correlated with neural activity in gustatory and reward-related brain areas (insula, inferior frontal operculum). Taken together, these findings suggest that those individuals with a high BMI do not necessarily have reduced capacities for self-control but that they may be facilitated by external cues that direct their attention toward the tastiness of healthy food. Thus, promoting the taste of healthy food in communication campaigns and/or food packaging may lead to more successful self-control and healthy food behaviors for consumers with a higher BMI, an issue which needs to be further researched

The abnormal structure induced in nodules on lucerne (Medicago sativa L.) by the supply of sodium nitrate to the host plant

It was shown in a recent paper (Thornton and Nicol, 1936) that the application of sodium nitrate to inoculated lucerne grown in sand, produced two effects upon the development of nodules. Firstly, the number of nodules was reduced and, secondly, their mean size was diminished. Both these effects increased with the nitrate dose, but, with weak doses of nitrate, it was the reduction in mean nodule size that principally affected the total mass of bacterial tissue carried by the host plant. Nevertheless, the action of nitrates in reducing the number of nodules, that is, their influence upon root infection, has occupied the attention of many workers, whereas but few have studied the growth of nodules on roots supplied with nitrates. The action of nitrate in diminishing root-hair infection by the nodule organism was recently investigated by one of us (Thornton, 1936). Infection is preceded by an increased and irregular growth of the root-hairs which is induced by secretions of the bacteria. Without this irregular growth the root-hairs remain uninfected. Nitrate inhibits this action of the bacterial secretions in stimulating irregular root-hair growth, and so checks infection. The action of nitrate upon legume root-hairs is thus superficially analogous to its action upon the already formed nodule, where it inhibits or checks the growth, which is normally stimulated by the presence of the contained bacteria. Only by a close study of the detailed effects of nitrate upon nodule growth could the significance of this analogy be disclosed. The action of nitrate in reducing the irregular growth of root-hairs exposed to the sterile secretions of nodule bacteria, can to some extent be counteracted by the simultaneous supply of dextrose to the roots (Thornton, 1936). This suggests that the inhibitory action of the nitrate upon root-hair growth is an indirect one, due to the building up of protein within the plant resulting in a shortage of carbohydrate supply to the root-hairs. One might thus expect, by analogy, that the reduction of nodule growth in a nitrate-fed plant could also be explained as being due to carbohydrate deficiency. Fred and Wilson (1934) indeed found that the size of individual nodules on soybeans was reduced by sodium nitrate manuring, but that this effect could largely be overcome by enriching the carbon dioxide supply to the leaves. This hypothesis would be supported if the structure of nodules on nitrate-manured plants showed evidences of carbohydrate shortage. A somewhat different explanation of the nitrate effect was put forward by Giöbel (1926) who supposed that the concentration of nitrate in the tissues of the host plant checked the removal of the products of nitrogen fixation, which thus accumulated in the nodule until they become toxic to the bacteria. On this hypothesis, nodules on plants given nitrate should perhaps show evidence of the accumulation of nitrogenous compounds, such as protein, in the nodule cells. It seemed, therefore, that a comparison of the detailed structure of nodules on plants grown with and without nitrate might supply facts, by which the above hypotheses could be tested, or which would suggest some other explanation of the inhibitory action of nitrate. RESP-109