Neuroligin-1 knockdown reduces survival of adult-generated newborn hippocampal neurons

Survival of adult-born hippocampal granule cells is modulated by neural activity, and thought to be enhanced by excitatory synaptic signaling. Here, we report that a reduction in the synaptogenic protein neuroligin-1 in adult-born neurons in vivo decreased their survival, but surprisingly, this effect was independent of changes in excitatory synaptic function. Instead, the decreased survival was associated with unexpected changes in dendrite and spine morphology during granule cell maturation, suggesting a link between cell growth and survival

Comparison of a low carbohydrate and low fat diet for weight maintenance in overweight or obese adults enrolled in a clinical weight management program

<p>Abstract</p> <p>Background</p> <p>Recent evidence suggests that a low carbohydrate (LC) diet may be equally or more effective for short-term weight loss than a traditional low fat (LF) diet; however, less is known about how they compare for weight maintenance. The purpose of this study was to compare body weight (BW) for participants in a clinical weight management program, consuming a LC or LF weight maintenance diet for 6 months following weight loss.</p> <p>Methods</p> <p>Fifty-five (29 low carbohydrate diet; 26 low fat diet) overweight/obese middle-aged adults completed a 9 month weight management program that included instruction for behavior, physical activity (PA), and nutrition. For 3 months all participants consumed an identical liquid diet (2177 kJ/day) followed by 1 month of re-feeding with solid foods either low in carbohydrate or low in fat. For the remaining 5 months, participants were prescribed a meal plan low in dietary carbohydrate (~20%) or fat (~30%). BW and carbohydrate or fat grams were collected at each group meeting. Energy and macronutrient intake were assessed at baseline, 3, 6, and 9 months.</p> <p>Results</p> <p>The LC group increased BW from 89.2 ± 14.4 kg at 3 months to 89.3 ± 16.1 kg at 9 months (<it>P </it>= 0.84). The LF group decreased BW from 86.3 ± 12.0 kg at 3 months to 86.0 ± 14.0 kg at 9 months (<it>P </it>= 0.96). BW was not different between groups during weight maintenance (<it>P </it>= 0.87). Fifty-five percent (16/29) and 50% (13/26) of participants for the LC and LF groups, respectively, continued to decrease their body weight during weight maintenance.</p> <p>Conclusion</p> <p>Following a 3 month liquid diet, the LC and LF diet groups were equally effective for BW maintenance over 6 months; however, there was significant variation in weight change within each group.</p

Data from a pre-publication independent replication initiative examining ten moral judgement effects

We present the data from a crowdsourced project seeking to replicate findings in independent laboratories before (rather than after) they are published. In this Pre-Publication Independent Replication (PPIR) initiative, 25 research groups attempted to replicate 10 moral judgment effects from a single laboratory's research pipeline of unpublished findings. The 10 effects were investigated using online/lab surveys containing psychological manipulations (vignettes) followed by questionnaires. Results revealed a mix of reliable, unreliable, and culturally moderated findings. Unlike any previous replication project, this dataset includes the data from not only the replications but also from the original studies, creating a unique corpus that researchers can use to better understand reproducibility and irreproducibility in science

The pipeline project: Pre-publication independent replications of a single laboratory's research pipeline

This crowdsourced project introduces a collaborative approach to improving the reproducibility of scientific research, in which findings are replicated in qualified independent laboratories before (rather than after) they are published. Our goal is to establish a non-adversarial replication process with highly informative final results. To illustrate the Pre-Publication Independent Replication (PPIR) approach, 25 research groups conducted replications of all ten moral judgment effects which the last author and his collaborators had “in the pipeline” as of August 2014. Six findings replicated according to all replication criteria, one finding replicated but with a significantly smaller effect size than the original, one finding replicated consistently in the original culture but not outside of it, and two findings failed to find support. In total, 40% of the original findings failed at least one major replication criterion. Potential ways to implement and incentivize pre-publication independent replication on a large scale are discussed

Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules

Neuroligin-1 overexpression in newborn granule cells in vivo.

Adult-born dentate granule cells integrate into the hippocampal network, extend neurites and form synapses in otherwise mature tissue. Excitatory and inhibitory inputs innervate these new granule cells in a stereotyped, temporally segregated manner, which presents a unique opportunity to study synapse development in the adult brain. To examine the role of neuroligins as synapse-inducing molecules in vivo, we infected dividing neural precursors in adult mice with a retroviral construct that increased neuroligin-1 levels during granule cell differentiation. By 21 days post-mitosis, exogenous neuroligin-1 was expressed at the tips of dendritic spines and increased the number of dendritic spines. Neuroligin-1-overexpressing cells showed a selective increase in functional excitatory synapses and connection multiplicity by single afferent fibers, as well as an increase in the synaptic AMPA/NMDA receptor ratio. In contrast to its synapse-inducing ability in vitro, neuroligin-1 overexpression did not induce precocious synapse formation in adult-born neurons. However, the dendrites of neuroligin-1-overexpressing cells did have more thin protrusions during an early period of dendritic outgrowth, suggesting enhanced filopodium formation or stabilization. Our results indicate that neuroligin-1 expression selectively increases the degree, but not the onset, of excitatory synapse formation in adult-born neurons

Neuroligin-1 overexpression increases the frequency of miniature excitatory post-synaptic currents in 3-week-old granule cells.

<p>A. Representative recordings showing mEPSCs in control (GFP only) and neuroligin-1 IRES GFP infected 21-day-old neurons. An asterisk is placed next to each detected event for clarity. Scale bars: 5 pA, 1 sec. B, C. Summary data for mEPSC amplitude and frequency (shown ± SEM; control n = 15 cells, NLG-1 n = 13 cells; * p<0.05). D. Cumulative mEPSC amplitude distribution for control (GFP only) and neuroligin-1 IRES GFP infected 21-day-old cells. E. Representative average mEPSCs are depicted for control (GFP only) and neuroligin-1 overexpressing cells. Scale bars for single traces: 2 pA, 5 ms. An overlay of peak-scaled responses demonstrates similar rise and decay kinetics between conditions. F, G, H. Neuroligin-1 overexpression does not change inhibitory innervation onto 21-day-old cells. F. Representative mIPSC recordings from control and neuroligin-1 overexpressing 21-day-old granule cells. Scale bars: 20 pA, 2 sec. G, H. Summary data for mIPSC amplitudes and frequencies at 21 dpi (shown ± SEM; control n = 14, NLG-1 n = 9; p>0.6 for each measurement).</p

Neuroligin-1 overexpression increases dendritic spine number.

<p>A. Dendritic spine morphology as demonstrated from GFP expression in 21-day-old granule cells expressing GFP only (control) or HA-neuroligin-1 in conjunction with GFP. Scale bar: 5 μm. B. To control for variability between fluorophore expression levels, a subset of 21-day-old live cells was identified by GFP expression, filled with membrane-impermeant dye by patch pipette, and fixed. Images show sections of dendrite taken from 21-day-old control cells and neuroligin-1 overexpressing cells. Scale bar: 5 μm. C. The dentate middle molecular layer of an adult mouse co-injected with separate retroviruses expressing mCherry (control) or neuroligin-1 IRES GFP. The projected image shows a 21-day-old control granule cell (mCherry) next to a GFP-filled cell overexpressing neuroligin-1. Scale bar: 5 μm. D, E. Summary data of spine measurements from infected cells 21 days post-mitosis demonstrating an increase in spine density but no change in spine length. Control neurons were infected with a retrovirus expressing GFP only (data shown ± SEM; control, n = 11 cells; NLG-1, n = 10 cells; ***p<0.005).</p

Neuroligin-1 overexpression does not change granule cell soma or dendrite morphology at 21 days post-mitosis.

<p>A. Low-power images of 21-day-old granule cells labeled with retroviruses encoding GFP only (above) or neuroligin-1 IRES GFP (below). Scale bar: 50 µm. B. Tracings of the same 21-day-old neurons, used for quantification. Scale bar: 50 µm. C, D, E. Summary data for 21 day old neurons showing no difference in cell soma size, total dendritic length, or dendritic process number between conditions (shown ± SEM; control, n = 9 cells; NLG-1, n = 15 cells; n.s. all conditions). F. Dendritic branch (Sholl) analysis demonstrates a similar overall branching pattern in control and neuroligin-1 overexpressing 21-day-old cells.</p