bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hebbian Learning in a Random Network Captures Selectivity Properties of the Prefrontal Cortex
Authors: Lindsay Grace W. , Rigotti Mattia , Warden Melissa R. , Miller Earl K. , Fusi Stefano 
Published: October 2017

Complex cognitive behaviors, such as context-switching and rule-following, are thought to be supported by the prefrontal cortex (PFC). Neural activity in the PFC must thus be specialized to specific tasks while retaining flexibility. Nonlinear “mixed” selectivity is an important neurophysiological trait for enabling complex and context-dependent behaviors. Here we investigate (1) the extent to which the PFC exhibits computationally relevant properties, such as mixed selectivity, and (2) how such properties could arise via circuit mechanisms. We show that PFC cells recorded from male and female rhesus macaques during a complex task show a moderate level of specialization and structure that is not replicated by a model wherein cells receive random feedforward inputs. While random connectivity can be effective at generating mixed selectivity, the data show significantly more mixed selectivity than predicted by a model with otherwise matched parameters. A simple Hebbian learning rule applied to the random connectivity, however, increases mixed selectivity and enables the model to match the data more accurately. To explain how learning achieves this, we provide analysis along with a clear geometric interpretation of the impact of learning on selectivity. After learning, the model also matches the data on measures of noise, response density, clustering, and the distribution of selectivities. Of two styles of Hebbian learning tested, the simpler and more biologically plausible option better matches the data. These modeling results provide clues about how neural properties important for cognition can arise in a circuit and make clear experimental predictions regarding how various measures of selectivity would evolve during animal training.SIGNIFICANCE STATEMENTThe prefrontal cortex is a brain region believed to support the ability of animals to engage in complex behavior. How neurons in this area respond to stimuli—and in particular, to combinations of stimuli (“mixed selectivity”)—is a topic of interest. Even though models with random feedforward connectivity are capable of creating computationally relevant mixed selectivity, such a model does not match the levels of mixed selectivity seen in the data analyzed in this study. Adding simple Hebbian learning to the model increases mixed selectivity to the correct level and makes the model match the data on several other relevant measures. This study thus offers predictions on how mixed selectivity and other properties evolve with training.
SK Channels Regulate Resting Properties and Signaling Reliability of a Developing Fast-Spiking Neuron
Authors: Zhang Yihui , Huang Hai 
Published: October 2017

Reliable and precise signal transmission is essential in circuits of the auditory brainstem to encode timing with submillisecond accuracy. Globular bushy cells reliably and faithfully transfer spike signals to the principal neurons of the medial nucleus of the trapezoid body (MNTB) through the giant glutamatergic synapse, the calyx of Held. Thus, the MNTB works as a relay nucleus that preserves the temporal pattern of firing at high frequency. Using whole-cell patch-clamp recordings, we observed a K+conductance mediated by small-conductance calcium-activated potassium (SK) channels in the MNTB neurons from rats of either sex. SK channels were activated by intracellular Ca2+sparks and mediated spontaneous transient outward currents in developing MNTB neurons. SK channels were also activated by Ca2+influx through voltage-gated Ca2+channels and synaptically activated NMDA receptors. Blocking SK channels with apamin depolarized the resting membrane potential, reduced resting conductance, and affected the responsiveness of MNTB neurons to signal inputs. Moreover, SK channels were activated by action potentials and affected the spike afterhyperpolarization. Blocking SK channels disrupted the one-to-one signal transmission from presynaptic calyces to postsynaptic MNTB neurons and induced extra postsynaptic action potentials in response to presynaptic firing. These data reveal that SK channels play crucial roles in regulating the resting properties and maintaining reliable signal transmission of MNTB neurons.SIGNIFICANCE STATEMENTReliable and precise signal transmission is required in auditory brainstem circuits to localize the sound source. The calyx of Held synapse in the mammalian medial nucleus of the trapezoid body (MNTB) plays an important role in sound localization. We investigated the potassium channels that shape the reliability of signal transfer across the calyceal synapse and observed a potassium conductance mediated by small-conductance calcium-activated potassium (SK) channels in rat MNTB principal neurons. We found that SK channels are tonically activated and contribute to the resting membrane properties of MNTB neurons. Interestingly, SK channels are transiently activated by calcium sparks and calcium influx during action potentials and control the one-to-one signal transmission from presynaptic calyces to postsynaptic MNTB neurons.
GFP-Mutant Human Tau Transgenic Mice Develop Tauopathy Following CNS Injections of Alzheimer's Brain-Derived Pathological Tau or Synthetic Mutant Human Tau Fibrils
Authors: Gibbons Garrett S. , Banks Rachel A. , Kim Bumjin , Xu Hong , Changolkar Lakshmi , Leight Susan N. , Riddle Dawn M. , Li Chi , Gathagan Ronald J. , Brown Hannah J. , Zhang Bin , Trojanowski John Q. , Lee Virginia M.-Y. 
Published: October 2017

Neurodegenerative proteinopathies characterized by intracellular aggregates of tau proteins, termed tauopathies, include Alzheimer's disease (AD), frontotemporal lobar degeneration (FTLD) with tau pathology (FTLD-tau), and related disorders. Pathological tau proteins derived from human AD brains (AD-tau) act as proteopathic seeds that initiate the templated aggregation of soluble tau upon intracerebral injection into tau transgenic (Tg) and wild-type mice, thereby modeling human tau pathology. In this study, we found that aged Tg mice of both sexes expressing human tau proteins harboring a pathogenic P301LMAPTmutation labeled with green fluorescent protein (T40PL-GFP Tg mouse line) exhibited hyperphosphorylated tau mislocalized to the somatodentritic domain of neurons, but these mice did not developde novoinsoluble tau aggregates, which are characteristic of human AD and related tauopathies. However, intracerebral injections of either T40PL preformed fibrils (PFFs) or AD-tau seeds into T40PL-GFP mice induced abundant intraneuronal pathological inclusions of hyperphosphorylated T40PL-GFP. These injections of pathological tau resulted in the propagation of tau pathology from the injection site to neuroanatomically connected brain regions, and these tau inclusions consisted of both T40PL-GFP and WT endogenous mouse tau. Primary neurons cultured from the brains of neonatal T40PL-GFP mice provided an informativein vitromodel for examining the uptake and localization of tau PFFs. These findings demonstrate the seeded aggregation of T40PL-GFPin vivoby synthetic PFFs and human AD-tau and the utility of this system to study the neuropathological spread of tau aggregates.SIGNIFICANCE STATEMENTThe stereotypical spread of pathological tau protein aggregates have recently been attributed to the transmission of proteopathic seeds. Despite the extensive use of transgenic mouse models to investigate the propagation of tau pathologyin vivo, details of the aggregation process such as the early seeding events leading to new tau pathology have remained elusive. This study validates the use of GFP-labeled tau expressed by neuronsin vivoandin vitroas models for investigating mechanisms underlying the seeded transmission of tau pathology as well as tau-focused drug discovery to identify disease-modifying therapies for AD and related tauopathies.
The Lateral Habenula and Its Input to the Rostromedial Tegmental Nucleus Mediates Outcome-Specific Conditioned Inhibition
Authors: Laurent Vincent , Wong Felix L. , Balleine Bernard W. 
Published: October 2017

Animals can readily learn that stimuli predict the absence of specific appetitive outcomes; however, the neural substrates underlying such outcome-specific conditioned inhibition remain largely unexplored. Here, using female and male rats as subjects, we examined the involvement of the lateral habenula (LHb) and of its inputs onto the rostromedial tegmental nucleus (RMTg) in inhibitory learning. In these experiments, we used backward conditioning and contingency reversal to establish outcome-specific conditioned inhibitors for two distinct appetitive outcomes. Then, using the Pavlovian-instrumental transfer paradigm, we assessed the effects of manipulations of the LHb and the LHb–RMTg pathway on that inhibitory encoding. In control animals, we found that an outcome-specific conditioned inhibitor biased choice away from actions delivering that outcome and toward actions earning other outcomes. Importantly, this bias was abolished by both electrolytic lesions of the LHb and selective ablation of LHb neurons using Cre-dependent Caspase3 expression in Cre-expressing neurons projecting to the RMTg. This deficit was specific to conditioned inhibition; an excitatory predictor of a specific outcome-biased choice toward actions delivering the same outcome to a similar degree whether the LHb or the LHb–RMTg network was intact or not. LHb lesions also disrupted the ability of animals to inhibit previously encoded stimulus–outcome contingencies after their reversal, pointing to a critical role of the LHb and of its inputs onto the RMTg in outcome-specific conditioned inhibition in appetitive settings. These findings are consistent with the developing view that the LHb promotes a negative reward prediction error in Pavlovian conditioning.SIGNIFICANCE STATEMENTStimuli that positively or negatively predict rewarding outcomes influence choice between actions that deliver those outcomes. Previous studies have found that a positive predictor of a specific outcome biases choice toward actions delivering that outcome. In contrast, a negative predictor of an outcome biases choice away from actions earning that outcome and toward other actions. Here we reveal that the lateral habenula is critical for negative predictors, but not positive predictors, to affect choice. Furthermore, these effects were found to require activation of lateral habenula inputs to the rostromedial tegmental nucleus. These results are consistent with the view that the lateral habenula establishes inhibitory relationships between stimuli and food outcomes and computes a negative prediction error in Pavlovian conditioning.
A Role of Endogenous Progesterone in Stroke Cerebroprotection Revealed by the Neural-Specific Deletion of Its Intracellular Receptors
Authors: Zhu Xiaoyan , Fréchou Magalie , Liere Philippe , Zhang Shaodong , Pianos Antoine , Fernandez Neïké , Denier Christian , Mattern Claudia , Schumacher Michael , Guennoun Rachida 
Published: October 2017

Treatment with progesterone protects the male and female brain against damage after middle cerebral artery occlusion (MCAO). However, in both sexes, the brain contains significant amounts of endogenous progesterone. It is not known whether endogenously produced progesterone enhances the resistance of the brain to ischemic insult. Here, we used steroid profiling by gas chromatography-tandem mass spectrometry (GC-MS/MS) for exploring adaptive and sex-specific changes in brain levels of progesterone and its metabolites after MCAO. We show that, in the male mouse brain, progesterone is mainly metabolized via 5α-reduction leading to 5α-dihydroprogesterone (5α-DHP), also a progesterone receptor (PR) agonist ligand in neural cells, then to 3α,5α-tetrahydroprogesterone (3α,5α-THP). In the female mouse brain, levels of 5α-DHP and 3α,5α-THP are lower and levels of 20α-DHP are higher than in males. After MCAO, levels of progesterone and 5α-DHP are upregulated rapidly to pregnancy-like levels in the male but not in the female brain. To assess whether endogenous progesterone and 5α-DHP contribute to the resistance of neural cells to ischemic damage, we inactivated PR selectively in the CNS. Deletion of PR in the brain reduced its resistance to MCAO, resulting in increased infarct volumes and neurological deficits in both sexes. Importantly, endogenous PR ligands continue to protect the brain of aging mice. These results uncover the unexpected importance of endogenous progesterone and its metabolites in cerebroprotection. They also reveal that the female reproductive hormone progesterone is an endogenous cerebroprotective neurosteroid in both sexes.SIGNIFICANCE STATEMENTThe brain responds to injury with protective signaling and has a remarkable capacity to protect itself. We show here that, in response to ischemic stroke, levels of progesterone and its neuroactive metabolite 5α-dihydroprogesterone are upregulated rapidly in the male mouse brain but not in the female brain. An important role of endogenous progesterone in cerebroprotection was demonstrated by the conditional inactivation of its receptor in neural cells. These results show the importance of endogenous progesterone, its metabolites, and neural progesterone receptors in acute cerebroprotection after stroke. This new concept could be exploited therapeutically by taking into account the progesterone status of patients and by supplementing and reinforcing endogenous progesterone signaling for attaining its full cerebroprotective potential.
Activation of CD4+ and CD8+ T-lymphocytes by insulin and GAD in patients with type 1 or 2 diabetes mellitus
Authors: Arneth Borros 
Published: October 2017

Background
The origin of autoimmune disease type 1 diabetes is still unknown.

Aim
This study assessed the activation of CD4+ and CD8+ T-lymphocytes by human insulin and human glutamate decarboxylase (GAD) in patients with type 1 or type 2 diabetes mellitus (DM) and healthy volunteers.

Materials and methods
The expression of CD69, a marker of T-lymphocyte activity, was determined in whole blood samples by flow cytometry after 12 h of incubation with or without insulin or GAD. The analysis included samples from 12 type 1 DM patients, 14 type 2 DM patients and 12 healthy volunteers.

Results
Significant increases in the number of activated CD4+ and CD8+ T-lymphocytes following pre-incubation of whole blood samples with human insulin or GAD were observed in samples from patients with type 1 DM, whereas no activation of these cells was detected in samples from either type 2 DM patients or healthy subjects.

Discussion
These results indicated that latent pre-activation of CD4+ and CD8+ T-lymphocytes in response to insulin or GAD epitopes occurred in type 1 DM patients.

Conclusion
These findings suggest that pre-immunization against insulin and/or GAD might be associated with the development of type 1 DM. Alternatively, these results might reflect a non-specific, bystander autoimmune response.
Preoperative selective vs non-selective α-blockade in PPGL patients undergoing adrenalectomy
Authors: Liu Caojie , Lv Qingguo , Chen Xinlei , Ni Guangcheng , Hu Liru , Tong Nanwei , Zhang Yuwei 
Published: October 2017

Purpose
Preoperative preparation for adrenalectomy for pheochromocytomas and paragangliomas (PPGL) is universally recognized as necessary, while the optimal strategy remains controversial. Our aims were to increase intraoperative hemodynamic stability, expedite postoperative recovery, decrease side effects and reduce costs for patients with PPGL undergoing adrenalectomy.

Methods
We identified 526 patients undergoing open adrenalectomy for PPGL in the West China Hospital of Sichuan University between May, 2007 and December, 2016. 149 patients received preoperative selective α-blockade with phenoxybenzamine, and 377 patients received non-selective α-blockade with prazosin, doxazosin or terazosin. There were no statistical differences between groups regarding preoperative patient and tumor characteristics. Operations were planned once hypertensive patients were well-controlled with blood pressure ≤130/85 mmHg. Intraoperatively, all patients received arterial blood pressure monitoring, and indwelling urinary catheters to record urine output. We recorded intraoperative hemodynamics, status in the postanesthesia or intensive care unit, postoperative recovery and complications.

Results
Patients in the non-selective group showed a more significant decline in postoperative systolic blood pressure than the selective group (P = 0.041). Also, patients in the non-selective group appeared to receive a long-term anti-hypertensive effect, especially for diastolic blood pressure (P = 0.037), which was a novel finding, based on the current literature.

Conclusions
Our results confirmed that non-selective α-blockade produced a more significant anti-hypertensive effect than selective α-blockade. However, we found no significant difference in intraoperative hemodynamic instability, postoperative recovery and postoperative complications between groups.
Metabolomic Analysis Reveals That the Drosophila melanogaster Gene lysine Influences Diverse Aspects of Metabolism
Authors: St. Clair Samantha L , Li Hongde , Ashraf Usman , Karty Jonathan A , Tennessen Jason M 
Published: October 2017

Abstract
The fruit fly Drosophila melanogaster has emerged as a powerful model for investigating the molecular mechanisms that regulate animal metabolism. However, a major limitation of these studies is that many metabolic assays are tedious, dedicated to analyzing a single molecule, and rely on indirect measurements. As a result, Drosophila geneticists commonly use candidate gene approaches, which, while important, bias studies toward known metabolic regulators. In an effort to expand the scope of Drosophila metabolic studies, we used the classic mutant lysine (lys) to demonstrate how a modern metabolomics approach can be used to conduct forward genetic studies. Using an inexpensive and well-established gas chromatography-mass spectrometry-based method, we genetically mapped and molecularly characterized lys by using free lysine levels as a phenotypic readout. Our efforts revealed that lys encodes the Drosophila homolog of Lysine Ketoglutarate Reductase/Saccharopine Dehydrogenase, which is required for the enzymatic degradation of lysine. Furthermore, this approach also allowed us to simultaneously survey a large swathe of intermediate metabolism, thus demonstrating that Drosophila lysine catabolism is complex and capable of influencing seemingly unrelated metabolic pathways. Overall, our study highlights how a combination of Drosophila forward genetics and metabolomics can be used for unbiased studies of animal metabolism, and demonstrates that a single enzymatic step is intricately connected to diverse aspects of metabolism.
Competitive Ability of Maize Pollen Grains Requires Paralogous Serine Threonine Protein Kinases STK1 and STK2
Authors: Huang Jun T , Wang Qinghua , Park Wonkeun , Feng Yaping , Kumar Dibyendu , Meeley Robert , Dooner Hugo K 
Published: October 2017

Abstract
serine threonine kinase1 (stk1) and serine threonine kinase2 (stk2) are closely related maize paralogous genes predicted to encode serine/threonine protein kinases. Pollen mutated in stk1 or stk2 competes poorly with normal pollen, pointing to a defect in pollen tube germination or growth. Both genes are expressed in pollen, but not in most other tissues. In germination media, STK1 and STK2 fluorescent fusion proteins localize to the plasma membrane of the vegetative cell. RNA-seq experiments identified 534 differentially expressed genes in stk1 mutant pollen relative to wild type. Gene ontology (GO) molecular functional analysis uncovered several differentially expressed genes with putative ribosome initiation and elongation functions, suggesting that stk1 might affect ribosome function. Of the two paralogs, stk1 may play a more important role in pollen development than stk2, as stk2 mutations have a smaller pollen transmission effect. However, stk2 does act as an enhancer of stk1 because the double mutant combination is only infrequently pollen-transmitted in double heterozygotes. We conclude that the stk paralogs play an essential role in pollen development.
Histone H3 Threonine 11 Phosphorylation Is Catalyzed Directly by the Meiosis-Specific Kinase Mek1 and Provides a Molecular Readout of Mek1 Activity in Vivo
Authors: Kniewel Ryan , Murakami Hajime , Liu Yan , Ito Masaru , Ohta Kunihiro , Hollingsworth Nancy M , Keeney Scott 
Published: October 2017

Abstract
Saccharomyces cerevisiae Mek1 is a CHK2/Rad53-family kinase that regulates meiotic recombination and progression upon its activation in response to DNA double-strand breaks (DSBs). The full catalog of direct Mek1 phosphorylation targets remains unknown. Here, we show that phosphorylation of histone H3 on threonine 11 (H3 T11ph) is induced by meiotic DSBs in S. cerevisiae and Schizosaccharomyces pombe. Molecular genetic experiments in S. cerevisiae confirmed that Mek1 is required for H3 T11ph and revealed that phosphorylation is rapidly reversed when Mek1 kinase is no longer active. Reconstituting histone phosphorylation in vitro with recombinant proteins demonstrated that Mek1 directly catalyzes H3 T11 phosphorylation. Mutating H3 T11 to nonphosphorylatable residues conferred no detectable defects in otherwise unperturbed meiosis, although the mutations modestly reduced spore viability in certain strains where Rad51 is used for strand exchange in place of Dmc1. H3 T11ph is therefore mostly dispensable for Mek1 function. However, H3 T11ph provides an excellent marker of ongoing Mek1 kinase activity in vivo. Anti-H3 T11ph chromatin immunoprecipitation followed by deep sequencing demonstrated that H3 T11ph was highly enriched at presumed sites of attachment of chromatin to chromosome axes, gave a more modest signal along chromatin loops, and was present at still lower levels immediately adjacent to DSB hotspots. These localization patterns closely tracked the distribution of Red1 and Hop1, axis proteins required for Mek1 activation. These findings provide insight into the spatial disposition of Mek1 kinase activity and the higher order organization of recombining meiotic chromosomes.