Cytoplasmic,but not nuclear,expression of the neuronal nuclei (NeuN) antibody is an exclusive feature of Dogiel type II neurons in the guinea-pig gastrointestinal tract

This study aimed to reveal if NeuN, a neuronal nuclei (NeuN) antibody, is a selective marker of intrinsic primary afferent neurons (IPANs) in the guinea-pig gastrointestinal tract as previously hypothesised. The NeuN immunoreactivity was found in the enteric nervous system with exception of the esophagus. Two groups of NeuN-expressing neurons were observed: neurons with immunostained nuclei and cytoplasm (NeuN_NC) and neurons only expressing immunoreactivity in their nuclei (NeuN_N). The NeuN_N-immunoreactive neurons were found in the myenteric plexus of the stomach and the colon. In the stomach, none of the NeuN_N-expressing neurons, of which 55±3% co-expressed calbindin, had a Dogiel type I or II morphology. The NeuN_N-positive neurons of the colon, which did not express calbindin, did not resemble a Dogiel type II morphology either, but were small-sized neurons. The NeuN_NC-immunoreactive neurons were observed in both the small and large intestine. These neurons were smooth-contoured and bigger-sized, resembling a Dogiel type II morphology. Some of these neurons co-expressed calbindin. The present data reveal the existence of two populations of Dogiel type II neurons, exhibiting NeuN_NC⁺ /calbindin⁺ or NeuN_NC⁺/calbindin⁻ immunoreactivity, in the intestine. Assuming that all IPANs exhibit a Dogiel type II morphology, we conclude that the cytoplasmic expression of NeuN is an exclusive feature of IPANs.     

Human Hippocampal Neurogenesis Persists throughout Aging

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Benzodiazepine-refractory status epilepticus,neuroinflammation, and interneuron neurodegeneration after acute organophosphate intoxication

Nerve agents and some pesticides such as diisopropylfluorophosphate (DFP) cause neurotoxic manifestations that include seizures and status epilepticus (SE), which are potentially lethal and carry long-term neurological morbidity. Current antidotes for organophosphate (OP) intoxication include atropine, 2-PAM and diazepam (a benzodiazepine for treating seizures and SE). There is some evidence for partial or complete loss of diazepam anticonvulsant efficacy when given 30?min or later after exposure to an OP; this condition is known as refractory SE. Effective therapies for OP-induced SE are lacking and it is unclear why current therapies do not work. In this study, we investigated the time-dependent efficacy of diazepam in the nerve agent surrogate DFP model of OP intoxication on seizure suppression and neuroprotection in rats, following an early and late therapy. Diazepam (5?mg/kg, IM) controlled seizures when given 10?min after DFP exposure (“early”), but it was completely ineffective at 60 or 120?min (“late”) after DFP. DFP-induced neuronal injury, neuroinflammation, and neurodegeneration of principal cells and GABAergic interneurons were significantly reduced by early but not late therapy. These findings demonstrate that diazepam failed to control seizures, SE and neuronal injury when given 60?min or later after DFP exposure, confirming the benzodiazepine-refractory SE and brain damage after OP intoxication. In addition, this study indicates that degeneration of inhibitory interneurons and inflammatory glial activation are potential mechanisms underlying these morbid outcomes of OP intoxication. Therefore, novel anticonvulsant and neuroprotectant antidotes, superior to benzodiazepines, are desperately needed for controlling nerve agent-induced SE and brain injury.     

Intraneuronal amyloid-beta plays a role in mediating the synergistic pathological effects of apoE4 and environmental stimulation

The allele E4 of apolipoprotein E4 (apoE4), which is the most prevalent genetic risk factor of Alzheimer's disease (AD), inhibits synaptogenesis and neurogenesis and stimulates apoptosis in brains of apoE4 transgenic mice that have been exposed to an enriched environment. In the present study, we investigated the hypothesis that the brain activity-dependent impairments in neuronal plasticity, induced by apoE4, are mediated via the amyloid cascade. Importantly, we found that exposure of mice transgenic for either apoE4, or the Alzheimer's disease benign allele apoE3, to an enriched environment elevates similarly the hippocampal levels of amyloid-beta peptide (Abeta) and apoE of these mice, but that the degree of aggregation and spatial distribution of Abeta in these mice are markedly affected by the apoE genotype. Accordingly, environmental stimulation triggered the formation of extracellular plaque-like Abeta deposits and the accumulation of intra-neuronal oligomerized Abeta specifically in brains of apoE4 mice. Further experiments revealed that hippocampal dentate gyrus neurons are particularly susceptible to apoE4 and environmental stimulation and that these neurons are specifically enriched in both oligomerized Abeta and apoE. These findings show that the impairments in neuroplasticity which are induced by apoE4 following environmental stimulation are associated with the accumulation of intraneuronal Abeta and suggest that oligomerized Abeta mediates the synergistic pathological effects of apoE4 and environmental stimulation.     

Ectopic recombination in the central and peripheral nervous system by aP2/FABP4-Cre mice: Implications for metabolism research

aP2-Cre mice have amply been used to generate conditional adipose selective inactivation of important signaling molecules. We show that the efficiency of Cre mediated recombination in adipocytes and adipose selectivity is not always guaranteed. In particular, Cre activity was found in ganglia of the peripheral nervous system (PNS), in adrenal medulla and in neurons throughout the central nervous system (CNS). Because these tissues have an important impact on adipose tissue, care should be taken when using aP2-Cre mice to define the role of the targeted genes in adipose tissue function.     

Methyl CpG Binding Domain Ultra‐Sequencing: a novel method for identifying inter‐individual and cell‐type‐specific variation in DNA methylation

Experience‐dependent changes in DNA methylation can exert profound effects on neuronal function and behaviour. A single learning event can induce a variety of DNA modifications within the neuronal genome, some of which may be common to all individuals experiencing the event, whereas others may occur in a subset of individuals. Variations in experience‐induced DNA methylation may subsequently confer increased vulnerability or resilience to the development of neuropsychiatric disorders. However, the detection of experience‐dependent changes in DNA methylation in the brain has been hindered by the interrogation of heterogeneous cell populations, regional differences in epigenetic states and the use of pooled tissue obtained from multiple individuals. Methyl CpG Binding Domain Ultra‐Sequencing (MBD Ultra‐Seq) overcomes current limitations on genome‐wide epigenetic profiling by incorporating fluorescence‐activated cell sorting and sample‐specific barcoding to examine cell‐type‐specific CpG methylation in discrete brain regions of individuals. We demonstrate the value of this method by characterizing differences in 5‐methylcytosine (5mC) in neurons and non‐neurons of the ventromedial prefrontal cortex of individual adult C57BL/6 mice, using as little as 50 ng of genomic DNA per sample. We find that the neuronal methylome is characterized by greater CpG methylation as well as the enrichment of 5mC within intergenic loci. In conclusion, MBD Ultra‐Seq is a robust method for detecting DNA methylation in neurons derived from discrete brain regions of individual animals. This protocol will facilitate the detection of experience‐dependent changes in DNA methylation in a variety of behavioural paradigms and help identify aberrant experience‐induced DNA methylation that may underlie risk and resiliency to neuropsychiatric disease.