Local changes in potassium ions regulate input integration in active dendrites.

During neuronal activity, the extracellular concentration of potassium ions ([K+]o) increases substantially above resting levels, yet it remains unclear what role these [K+]o changes play in the dendritic integration of synaptic inputs. We here used mathematical formulations and biophysical modeling to explore the role of synaptic activity-dependent K+ changes in dendritic segments of a visual cortex pyramidal neuron, receiving inputs tuned to stimulus orientation. We found that the spatial arrangement of inputs dictates the magnitude of [K+]o changes in the dendrites: Dendritic segments receiving similarly tuned inputs can attain substantially higher [K+]o increases than segments receiving diversely tuned inputs.

Gather your neurons and model together: Community times ahead.

Bottom-up, data-driven, large-scale models provide a mechanistic understanding of neuronal functions. A new study in PLOS Biology builds a biologically realistic model of the rodent CA1 region that aims to become an accessible tool for the whole hippocampal community.

Modeling apical and basal tree contribution to orientation selectivity in a mouse primary visual cortex layer 2/3 pyramidal cell.

Pyramidal neurons, a mainstay of cortical regions, receive a plethora of inputs from various areas onto their morphologically distinct apical and basal trees. Both trees differentially contribute to the somatic response, defining distinct anatomical and possibly functional sub-units. To elucidate the contribution of each tree to the encoding of visual stimuli at the somatic level, we modeled the response pattern of a mouse L2/3 V1 pyramidal neuron to orientation tuned synaptic input.

Illuminating dendritic function with computational models.

Dendrites have always fascinated researchers: from the artistic drawings by Ramon y Cajal to the beautiful recordings of today, neuroscientists have been striving to unravel the mysteries of these structures. Theoretical work in the 1960s predicted important dendritic effects on neuronal processing, establishing computational modelling as a powerful technique for their investigation. Since then, modelling of dendrites has been instrumental in driving neuroscience research in a targeted manner, providing experimentally testable predictions that range from the subcellular level to the systems level, and their relevance extends to fields beyond neuroscience, such as machine learning and artificial intelligence.

Dendritic action potentials and computation in human layer 2/3 cortical neurons.

The active electrical properties of dendrites shape neuronal input and output and are fundamental to brain function. However, our knowledge of active dendrites has been almost entirely acquired from studies of rodents. In this work, we investigated the dendrites of layer 2 and 3 (L2/3) pyramidal neurons of the human cerebral cortex ex vivo.

Contribution of apical and basal dendrites to orientation encoding in mouse V1 L2/3 pyramidal neurons.

Pyramidal neurons integrate synaptic inputs from basal and apical dendrites to generate stimulus-specific responses. It has been proposed that feed-forward inputs to basal dendrites drive a neuron's stimulus preference, while feedback inputs to apical dendrites sharpen selectivity. However, how a neuron's dendritic domains relate to its functional selectivity has not been demonstrated experimentally.

Optically Induced Calcium-Dependent Gene Activation and Labeling of Active Neurons Using CaMPARI and Cal-Light.

The advent of optogenetic methods has made it possible to use endogeneously produced molecules to image and manipulate cellular, subcellular, and synaptic activity. It has also led to the development of photoactivatable calcium-dependent indicators that mark active synapses, neurons, and circuits. Furthermore, calcium-dependent photoactivation can be used to trigger gene expression in active neurons.

Resistance to sliding in orthodontics: misconception or method error? A systematic review and a proposal of a test protocol.

Resistance to sliding (RS) between the bracket, wire, and ligature has been largely debated in orthodontics. Despite the extensive number of published studies, the lack of discussion of the methods used has led to little understanding of this phenomenon. The aim of this study was to discuss variables affecting RS in orthodontics and to suggest an operative protocol.

Basal tree complexity shapes functional pathways in the prefrontal cortex.

While the morphology of basal dendritic trees in cortical pyramidal neurons varies, the functional implications of this diversity are just starting to emerge. In layer 5 pyramidal neurons of the prefrontal cortex, for example, increased basal tree complexity determines the recruitment of these neurons into functional circuits. Here, we use a modeling approach to investigate whether and how the morphology of the basal tree mediates the functional output of neurons.

A simulation study on the effects of dendritic morphology on layer V prefrontal pyramidal cell firing behavior.

Pyramidal cells, the most abundant neurons in neocortex, exhibit significant structural variability across different brain areas and layers in different species. Moreover, in response to a somatic step current, these cells display a range of firing behaviors, the most common being (1) repetitive action potentials (Regular Spiking-RS), and (2) an initial cluster of 2-5 action potentials with short interspike interval (ISIs) followed by single spikes (Intrinsic Bursting-IB). A correlation between firing behavior and dendritic morphology has recently been reported.

Dendritic nonlinearities reduce network size requirements and mediate ON and OFF states of persistent activity in a PFC microcircuit model.

Technological advances have unraveled the existence of small clusters of co-active neurons in the neocortex. The functional implications of these microcircuits are in large part unexplored. Using a heavily constrained biophysical model of a L5 PFC microcircuit, we recently showed that these structures act as tunable modules of persistent activity, the cellular correlate of working memory.

Prevalence of thrombophilia in asymptomatic individuals with a family history of thrombosis.

Objective: The present study investigates the prevalence of thrombophilia in individuals with first or/and second degree family history of thromboembolism.

Material-methods: The study group consisted of 68 individuals with a first or second degree family history of venous or arterial thromboembolism, but without a personal history of thrombosis. The activity of ATIII, PC, PS, FVIII, FΧΙΙ and total homocysteine was measured on the ACL Advance coagulation analyzer.

Modulatory effects of inhibition on persistent activity in a cortical microcircuit model.

Neocortical network activity is generated through a dynamic balance between excitation, provided by pyramidal neurons, and inhibition, provided by interneurons. Imbalance of the excitation/inhibition ratio has been identified in several neuropsychiatric diseases, such as schizophrenia, autism and epilepsy, which also present with other cognitive deficits and symptoms associated with prefrontal cortical (PFC) dysfunction. We undertook a computational approach to study how changes in the excitation/inhibition balance in a PFC microcircuit model affect the properties of persistent activity, considered the cellular correlate of working memory function in PFC.

Induction and modulation of persistent activity in a layer V PFC microcircuit model.

Working memory refers to the temporary storage of information and is strongly associated with the prefrontal cortex (PFC). Persistent activity of cortical neurons, namely the activity that persists beyond the stimulus presentation, is considered the cellular correlate of working memory. Although past studies suggested that this type of activity is characteristic of large scale networks, recent experimental evidence imply that small, tightly interconnected clusters of neurons in the cortex may support similar functionalities.

Coding and decoding with dendrites.

Since the discovery of complex, voltage dependent mechanisms in the dendrites of multiple neuron types, great effort has been devoted in search of a direct link between dendritic properties and specific neuronal functions. Over the last few years, new experimental techniques have allowed the visualization and probing of dendritic anatomy, plasticity and integrative schemes with unprecedented detail. This vast amount of information has caused a paradigm shift in the study of memory, one of the most important pursuits in Neuroscience, and calls for the development of novel theories and models that will unify the available data according to some basic principles.

Is Post-ERCP Pancreatitis a Genetically Predisposed Complication?

Background/Objectives. Pancreatitis remains the most common complication of ERCP. History of post-ERCP pancreatitis is an independent risk factor for a new episode, suggesting a genetic background.

Molecular and epidemiological characterization of HIV-1 infection networks involving transmitted drug resistance mutations in Northern Greece.

Objectives: To determine the contribution of transmission clusters to transmitted drug resistance (TDR) in newly diagnosed antiretroviral-naive HIV-1-infected patients in Northern Greece during 2000-07.

Methods: The prevalence of TDR was estimated in 369 individuals who were diagnosed with HIV-1 infection in the period 2000-07 at the National AIDS Reference Laboratory of Northern Greece. Phylogenetic analysis was performed using a maximum likelihood method on partial pol sequences.

Designation of the European Working Group on Legionella Infection (EWGLI) amplified fragment length polymorphism types of Legionella pneumophila serogroup 1 and results of intercentre proficiency testing Using a standard protocol.

The utility of amplified fragment length polymorphism (AFLP) analysis as a genotyping method for the epidemiological typing of Legionella pneumophila serogroup 1 has been previously demonstrated. This study (i). reports recommendations for the designation of the European Working Group on Legionella Infections (EWGLI) AFLP types, (ii).

Genetic variation of the protease and reverse transcriptase genes in HIV-1 CRF04_cpx strains.

To gain information about the genetic variation of the protease and reverse transcriptase gene-coding regions in HIV-1 strains belonging to CRF04_cpx, genotyping and drug susceptibility testing were performed on serum samples derived from seven patients carrying sequences belonging to this circulating recombinant form. Substitutions classically associated with resistance to antiretroviral drugs were observed in six of seven samples, including G48V, V82A, L90M, M46I in the protease protein, and K70R, D69D/N, M184V, T215F, K103N in the reverse transcriptase protein. Genotypic resistance patterns of CRF04_cpx samples were found to be similar to those identified in subtype B viruses, suggesting that the drug-selective pressure has similar effects on both subtype B and CRF04_cpx.

HIV-1 subtypes and circulating recombinant forms (CRFs) in Northern Greece.

In order to understand the genetic diversity of virus isolates associated with the human immunodeficiency virus type one (HIV-1) epidemic in Northern Greece, 51 specimens from HIV-1 infected individuals were classified into subtypes by sequence-based phylogenetic analysis of the polymerase (pol) region of the viral genome. Forty two (82.3%) specimens were identified as pol subtype B, three (5.

Application of polymerase chain reaction for detection of Legionella pneumophila in serum samples.

OBJECTIVE: To apply the polymerase chain reaction (PCR) to serum samples for the rapid diagnosis of Legionnaire's disease using the L5SL9 and L5SR93 primers designed to generate a 104-base-pair (bp) fragment from the 5S RNA gene of Legionella spp. The amplified product was detected by electrophoresis and by hybridization with the L5S-1-specific probe. METHODS: Single specimens of serum obtained from 24 patients with confirmed legionellosis, at different stages of their disease, were tested by PCR.