Micro-connectomics: probing the organization of neuronal networks at the cellular scale.

Defining the organizational principles of neuronal networks at the cellular scale, or micro-connectomics, is a key challenge of modern neuroscience. In this Review, we focus on graph theoretical parameters of micro-connectome topology, often informed by economical principles that conceptually originated with Ramón y Cajal's conservation laws. First, we summarize results from studies in intact small organisms and in samples from larger nervous systems. We then evaluate the evidence for an economical trade-off between biological cost and functional value in the organization of neuronal networks. Various results suggest that many aspects of neuronal network organization are indeed the outcome of competition between these two fundamental selection pressures.This work was supported by the National Institute of Health Research (NIHR) Cambridge Biomedical Research Centre.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Nature Publishing Group

Effects of silicon, citrate and the fastin state on the intestinal absorption of aluminium in rats

1. The effect of silicon (Si) contained in drinking water and solid food on the intestinal absorption of aluminium (Al) remains a matter of debate. The present study was designed to readdress this issue in the experimental animal, and to examine concomitantly the effects of citrate and the fasting state, respectively. 2. Three groups of young, non-fasted rats (n = 8 per group) were gavaged by solutions containing 3.8 ng of 26Al, 63 ng of 27Al, and either distilled water (&amp;lt;0.1 mg/l Si) or commercial mineral water with a medium (6 mg/l) or high (14 mg/l) Si concentration. 3. Two other groups of eight non-fasted rats each received the same distilled water or high-Si gavage solution, respectively, together with a high citrate concentration (62 g/l). In each case the animals had free access to drinking water for 5 days before and 2 days after the gavage, containing the same Si concentration as in the gavage solution. A sixth group of eight rats was gavaged by low-Si, Al and distilled water in the fasted state. 4. The animals were killed 48 h after gavage, and blood, tissue and urine samples were collected for 26Al measurements by accelerator mass spectrometry. 5. We found that the fraction of absorbed 26Al retained in the skeleton (0.025–0.030%) was of the same order of magnitude as the fraction excreted in the 48 h urine (0.035-0.037%). High Si concentrations in the drinking water failed to depress the 26Al fraction absorbed, as estimated on the basis of skeletal accumulation and urinary excretion. 6. The administration of citrate-containing fluid enhanced 26Al absorption 5- to 10-fold (P &amp;lt; 0.005), but again the Si content of drinking water did not interfere. Finally, the intestinal absorption of 26Al was approximately 15 times higher in the fasted than in the non-fasted state. 7. In conclusion, the provision of large amounts of Si in the drinking water failed to modify physiological intestinal Al absorption under basal conditions or after its stimulation by citrate. However, a prolonged fast greatly enhanced Al absorption, compared with the non-fasted state.</jats:p

Immediate reuse of patch-clamp pipettes after ultrasonic cleaning

The patch-clamp technique has revolutionized neurophysiology by allowing to study single neuronal excitability, synaptic connectivity, morphology, and the transcriptomic profile. However, the throughput in recordings is limited because of the manual replacement of patch-pipettes after each attempt which are often also unsuccessful. This has been overcome by automated cleaning the tips in detergent solutions, allowing to reuse the pipette for further recordings. Here, we developed a novel method of automated cleaning by sonicating the tips within the bath solution wherein the cells are placed, reducing the risk of contaminating the bath solution or internal solution of the recording pipette by any detergent and avoiding the necessity of a separate chamber for cleaning. We showed that the patch-pipettes can be used consecutively at least ten times and that the cleaning process does not negatively impact neither the brain slices nor other patched neurons. This method, combined with automated patch-clamp, highly improves the throughput for single and especially multiple recordings

The AMS facility at Gif-sur-Yvette: progress, perturbations and projects

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