Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.)

Fasting and refeeding effects on gastrointestinal morphology and digestive enzyme activities of Atlantic salmon, held in tanks of seawater at 9°C and 31‰ salinity, were addressed in two trials. Trial 1: Fish (mean body mass 1190 g) were fasted for 40 days and intestines sampled at day 0, 2, 4, 11, 19 and 40. Trial 2: Fish (1334 g), fasted for 50 days, were refed and sampled at day 0, 3 and 7. Mass, length, protein, and maltase, lactase, and leucine aminopeptidase (LAP) activities were analyzed for stomach (ST), pyloric caeca (PC), proximal (PI), mid (MI), and distal intestine (DI). PC contributed 50% of gastrointestinal mass and 75% of enzyme capacity. Fasting decreased mass and enzyme capacities by 20–50% within two days, and 40–75% after 40 days. In PC, specific brush border membrane (BBM) maltase activity decreased whereas BBM LAP increased during fasting. Upon refeeding, enzyme capacities were mostly regenerated after one week. The results suggest that refeeding should start slowly with about 25% of estimated feed requirement during the first 3 days, but may then be stepped up rapidly. Investigations of digestive processes of fed fish should only be performed when intestines are feed-filled to avoid bias due to effects of fasting.     

An isomorphic mapping hypothesis of the grid representation

We introduce a grid cell microcircuit hypothesis. We propose the ‘grid in the world’ (evident in grid cell discharges) is generated by a ‘grid in the cortex’. This cortical grid is formed by patches of calbindin-positive pyramidal neurons in layer 2 of medial entorhinal cortex (MEC). Our isomorphic mapping hypothesis assumes three types of isomorphism: (i) metric correspondence of neural space (the two-dimensional cortical sheet) and the external two-dimensional space within patches; (ii) isomorphism between cellular connectivity matrix and firing field; (iii) isomorphism between single cell and population activity. Each patch is a grid cell lattice arranged in a two-dimensional map of space with a neural : external scale of approximately 1 : 2000 in the dorsal part of rat MEC. The lattice behaves like an excitable medium with neighbouring grid cells exciting each other. Spatial scale is implemented as an intrinsic scaling factor for neural propagation speed. This factor varies along the dorsoventral cortical axis. A connectivity scheme of the grid system is described. Head direction input specifies the direction of activity propagation. We extend the theory to neurons between grid patches and predict a rare discharge pattern (inverted grid cells) and the relative location and proportion of grid cells and spatial band cells.     

Right atrial appendage tachycardia: A rare cause of tachycardia induced cardiomyopathy in a 4-year-old child

We present a rare case of tachycardiomyopathy in a 4-year-old girl. The child had incessant atrial tachycardia (AT) and refractory heart failure. Right atrial appendage (RAA) was localised as the source of the ectopic tachycardia. The child underwent successful radiofrequency ablation (RFA) using 3-D electroanatomical mapping. Fluoroscopy was used sparingly only to rule out underlying anomalies. The left ventricular functions returned to normal by one month after the procedure. RAA AT is rare in very young children and usually necessitates surgical appendectomies. RFA is a challenge in such age groups and there are very few published literature on RAA AT in very young children.     

Sectoral Aggregation Error in the Accounting of Energy and Emissions Embodied in Trade and Consumption

Correctly accounting for the energy and emissions embodied in consumption and trade is essential to effective climate policy design. Robust methods are needed for both policy making and research—for example, the assignment of border carbon adjustments (BCAs) and greenhouse gas emission reduction responsibilities rely on the consistency and accuracy of such estimates. This analysis investigates the potential magnitude and consequences of the error present in estimates of energy and emissions embodied in trade and consumption. To quantify the error of embodied emissions accounting, we compare the results from the disaggregated Global Trade Analysis Project (GTAP 8) data set, which contains 57 sectors to results from different levels of aggregation of this data set (3, 7, 16, and 26 sectors), using 5,000 randomly generated sectoral aggregation schemes as well as aggregations generated using several commonly applied decisions rules. We find that some commonly applied decision rules for sectoral aggregation can produce a large error. We further show that an aggregation scheme that clusters sectors according to their energy, emissions, and trade intensities (net exports over output) can minimize error in embodied energy and emissions accounting at different levels of aggregation. This sectoral aggregation scheme can be readily used in any input‐output analysis and provide useful information for computable general equilibrium modeling exercises in which sector aggregation is necessary, although our findings suggest that, when possible, the most disaggregated data available should be used.