Neuronal Density Research Articles

FGF13 enhances the function of TRPV1 by stabilizing microtubules and regulates acute and chronic itch.

Itching is an aversive somatosensation that triggers the desire to scratch. Transient receptor potential (TRP) channel proteins are key players in acute and chronic itch. However, whether the modulatory effect of fibroblast growth factor 13 (FGF13) on acute and chronic itch is associated with TRP channel proteins is unclear. Here, we demonstrated that conditional knockout of Fgf13 in dorsal root ganglion neurons induced significant impairment in scratching behaviors in response to acute histamine-dependent and chronic dry skin itch models. Furthermore, FGF13 selectively regulated the function of the TRPV1, but not the TRPA1 channel on Ca2+ imaging and electrophysiological recordings, as demonstrated by a significant reduction in neuronal excitability and current density induced by TRPV1 channel activation, whereas TRPA1 channel activation had no effect. Changes in channel currents were also verified in HEK cell lines. Subsequently, we observed that selective modulation of TRPV1 by FGF13 required its microtubule-stabilizing effect. Furthermore, in FGF13 knockout mice, only the overexpression of FGF13 with a tubulin-binding domain could rescue TRP channel function and the impaired itch behavior. Our findings reveal a novel mechanism by which FGF13 is involved in TRPV1-dependent itch transduction and provide valuable clues for alleviating pathological itch syndrome.

Social hierarchy differentially influences the anxiety-like behaviors and dendritic spine density in prefrontal cortex and limbic areas in male rats

Social hierarchy is a fundamental feature of social organization that can influence brain and emotional processing regarding social ranks. Several areas, including the medial prefrontal cortex (mPFC), the hippocampus, and the basolateral nucleus of the amygdala (BLA), are recognized to be involved in the regulation of emotional processing. However, its delicate structural correlates in brain regions are poorly understood. To address this issue, social hierarchy in home-caged sibling Wistar rats (three male rats/cage) was determined by employing a social confrontation tube test (postnatal weeks 9–12). Then, locomotor activity and anxiety-like behaviors were evaluated using an open-field test (OFT) and elevated plus-maze (EPM) at 13 weeks of age. The rapid Golgi impregnation method was conducted to quantify the spine density of the first secondary branch of the primary dendrite in 20 µm length. The results indicated that dominant rats had significantly higher anxiety-like behaviors compared to subordinates, as was evident by lower open-arm entries and time spent in the EPM and lower entries and time spent in the center of OFT. The spine density analysis revealed a significantly higher number of spines in subordinates compared to the dominant rats in dmPFC pyramidal neurons and the apical and basal dendrites of hippocampal CA1 pyramidal neurons. However, the spine density of pyramidal-like neurons in the BLA was higher in dominant rats. Our findings suggest that dominant social rank is associated with higher anxiety and differential density of the dendritic spine in the prefrontal cortex and limbic regions of the brain in male rats.

CXCL10 is a crucial chemoattractant for efficient intranasal delivery of mesenchymal stem cells to the neonatal hypoxic-ischemic brain

BackgroundHypoxic-Ischemic Encephalopathy (HIE) is a leading cause of mortality and morbidity in newborns. Recent research has shown promise in using intranasal mesenchymal stem cell (MSC) therapy if administered within 10 days after Hypoxia-Ischemia (HI) in neonatal mice. MSCs migrate from the nasal cavity to the cerebral lesion in response to chemotactic cues. Which exact chemokines are crucial for MSC guidance to the HI lesion is currently not fully understood. This study investigates the role of CXCL10 in MSC migration towards the HI-injured brain.MethodsHI was induced in male and female 9-day-old C57BL/6 mice followed by intranasal MSC treatment at day 10 or 17 post-HI. CXCL10 protein levels, PKH26-labeled MSCs and lesion size were assessed by ELISA, immunofluorescent imaging and MAP2 staining respectively. At day 17 post-HI, when CXCL10 levels were reduced, intracranial CXCL10 injection and intranasal PKH26-labeled MSC administration were combined to assess CXCL10-guided MSC migration. MSC treatment efficacy was evaluated after 18 days, measuring lesion size, motor outcome (cylinder rearing task), glial scarring (GFAP staining) and neuronal density (NeuN staining) around the lesion. Expression of the receptor for CXCL10, i.e. CXCR3, on MSCs was confirmed by qPCR and Western Blot. Moreover, CXCL10-guided MSC migration was assessed through an in vitro transwell migration assay.ResultsIntranasal MSC treatment at day 17 post-HI did not reduce lesion size in contrast to earlier treatment timepoints. Cerebral CXCL10 levels were significantly decreased at 17 days versus 10 days post-HI and correlated with reduced MSC migration towards the brain. In vitro experiments demonstrated that CXCR3 receptor inhibition prevented CXCL10-guided migration of MSCs. Intracranial CXCL10 injection at day 17 post-HI significantly increased the number of MSCs reaching the lesion which was accompanied by repair of the HI lesion as measured by reduced lesion size and glial scarring, and an increased number of neurons around the lesion.ConclusionsThis study underscores the crucial role of the chemoattractant CXCL10 in guiding MSCs to the HI lesion after intranasal administration. Strategies to enhance CXCR3-mediated migration of MSCs may improve the efficacy of MSC therapy or extend its regenerative therapeutic window.

Targeting pathological cells with senolytic drugs reduces seizures in neurodevelopmental mTOR-related epilepsy

Cortical malformations such as focal cortical dysplasia type II (FCDII) are associated with pediatric drug-resistant epilepsy that necessitates neurosurgery. FCDII results from somatic mosaicism due to post-zygotic mutations in genes of the PI3K-AKT-mTOR pathway, which produce a subset of dysmorphic cells clustered within healthy brain tissue. Here we show a correlation between epileptiform activity in acute cortical slices obtained from human surgical FCDII brain tissues and the density of dysmorphic neurons. We uncovered multiple signatures of cellular senescence in these pathological cells, including p53/p16 expression, SASP expression and senescence-associated β-galactosidase activity. We also show that administration of senolytic drugs (dasatinib/quercetin) decreases the load of senescent cells and reduces seizure frequency in an MtorS2215F FCDII preclinical mouse model, providing proof of concept that senotherapy may be a useful approach to control seizures. These findings pave the way for therapeutic strategies selectively targeting mutated senescent cells in FCDII brain tissue.

Cortical dysmorphology and reduced cortico-collicular projections in an animal model of autism spectrum disorder.

Autism spectrum disorder is a neurodevelopmental disability that includes sensory disturbances. Hearing is frequently affected and ranges from deafness to hypersensitivity. In utero exposure to the antiepileptic valproic acid is associated with increased risk of autism spectrum disorder in humans and timed valproic acid exposure is a biologically relevant and validated animal model of autism spectrum disorder. Valproic acid-exposed rats have fewer neurons in their auditory brainstem and thalamus, fewer calbindin-positive neurons, reduced ascending projections to the midbrain and thalamus, elevated thresholds, and delayed auditory brainstem responses. Additionally, in the auditory cortex, valproic acid exposure results in abnormal responses, decreased phase-locking, elevated thresholds, and abnormal tonotopic maps. We therefore hypothesized that in utero, valproic acid exposure would result in fewer neurons in auditory cortex, neuronal dysmorphology, fewer calbindin-positive neurons, and reduced connectivity. We approached this hypothesis using morphometric analyses, immunohistochemistry, and retrograde tract tracing. We found thinner cortical layers but no changes in the density of neurons, smaller pyramidal and non-pyramidal neurons in several regions, fewer neurons immunoreactive for calbindin-positive, and fewer cortical neurons projecting to the inferior colliculus. These results support the widespread impact of the auditory system in autism spectrum disorder and valproic acid-exposed animals and emphasize the utility of simple, noninvasive auditory screening for autism spectrum disorder.

Regional and Sex Differences in the Mouse Colonic Innervation Assessed Using a Computerized Quantitative Approach in Three-dimension of the Enteric Nervous System (ENS)

The ENS consists of the submucosal and myenteric plexus (SMP, MP) and controls a variety of gut functions. The quantitative analysis of innervation in the ENS is still a challenge because the ENS forms a mesh-like three-dimensional (3D) network embedded in the gut wall. We developed a computerized approach to perform direct, objective and automatic measurements of innervation in 3D structures of the mouse colonic ENS. The whole mounts of SMP and MP were prepared along the proximal, transverse and distal colon (pC, tC, dC) collected from 8 naïve mice (C57BL/6J, 6 weeks, 4 of each sex). Each 3D image of SMP or MP was reconstructed from Z-stack confocal images with 50-100 or 30-50 optical sections in the frame 1415×1415 or 708×708 μm and 1 μm apart. The Hu C/D, peripheral form of choline acetyltransferase (pChAT), nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH) and calcitonin gene-related protein (CGRP) immunoreactive (ir) enteric neurons or fibers were digitally traced and automatically measured with Imaris 9.7 for neuroscientists. The co-localization of pChAT and nNOS was determined with ImarisColoc tool. The densities of neurons and nerve fibers, co-localization of pChAT and nNOS were calculated from 6-8 of 3D images/marker/plexus/segment/mouse (total 2304 3D images) and expressed as the percentage of each type of neurons in total neurons, the volume of each type of nerve fibers in the volume of SMP and MP and co-labeled neurons in each type of neurons. The results demonstrate significant differences in the numbers of two major neuronal populations, their co-localization and densities of three representative nerve fibers among three colonic segments, between two plexuses and sexes. 1. pChAT- and nNOS-ir neurons in the MP: the density of pChAT-ir neurons was 1.4- and 2.1-fold lower in the pC than in the tC and dC (p<0.05, p<0.001), and 1.6- and 4.0-fold higher than that of nNOS-ir neurons in the tC and dC (p<0.001, p<0.001), respectively. In contrast, the density of nNOS-ir neurons was 1.4- or 2.3-fold higher in the pC or tC than dC (p<0.001, p<0.01). 2. Co-localization of pChAT and nNOS in the MP: Co-labeled neurons in the nNOS-ir neurons were 1.4- or 1.5-fold lower in the pC or tC than dC (p<0.05, p<0.05). 3. Nerve fibers: The density of VIP-ir fibers in the SMP was 2.4- and 1.8-fold higher in the pC than tC and dC (p<0.001, p<0.001) while 3.0- and 2.4-fold lower than in the MP in both tC and dC (p<0.001, 0.001). TH-ir fibers in the SMP were 1.6-fold lower in both tC or dC than pC (p<0.01, p<0.01), 1.6-, 2.2- and 1.4-fold lower than MP in the pC, tC and dC (p<0.001, p<0.001, p<0.05). In the MP, they were 1.8- and 1.6-fold lower in the dC than in pC and tC (p<0.001, p<0.001). CGRP-ir fibers did not show significant difference between two plexuses among three segments. 4. Sex differences: The co-labeled neurons in the pChAT-ir neurons were 2.2-, 2.7- and 2.2-fold more in the males than females in three segments (p<0.001, p<001, p<0.001) while those in the nNOS-ir neurons were 1.9-fold more in the males than females only in the dC (p<0.05). VIP-ir fibers in the dC-MP were 1.2-fold higher in the males than females (p<0.05). These data and the novel approach developed in this study will contribute to further assessments of the structure-function relationships and pathological alterations in the colon with mouse models. Supported by NIH/SPARC 1OT2OD024899-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

MRI Evaluation of Microstructural and Perfusion Changes in Patients with Hemsensory Neurological Syndromes

Background: Hemisensory syndrome is characterized by a nondermatomal sensory deficit involving one half of the body. With the conventional imaging techniques, researches find low diagnostic yield in this condition; however, with the advancements in MRI imaging, there is hope to find the pathophysiological basis of hemisensory symptoms. Objective: To evaluate microstructural and perfusion changes in brain parenchyma in patients with hemisensory syndrome on MRI with diffusion tensor imaging (DTI) and arterial spin labeling (ASL). Material and Methods: A total of 20 patients with hemisensory symptoms and 10 age-matched controls were enrolled and divided in two study groups – a) case vs. control and b) affected vs. nonaffected cerebral hemisphere in cases. Quantification of absolute cerebral blood flow (aCBF), fractional anisotropy (FA), and mean diffusivity (MD) was done in both groups. Results: On ASL, there was significantly increased aCBF in thalamus on the contralateral-affected side. DTI revealed significantly decreased FA in the thalamus and increased FA in corona radiata of the affected side. There was a significant difference for MD of corona radiata between affected and nonaffected hemisphere. The mean value of MD in corona radiata is decreased on the affected side. Conclusion: Changes in advanced neuroimaging techniques like ASL and DTI along the pain processing pathway suggest an alteration in neuronal density and activity at the microstructural level. These findings may provide an insight into the etiopathogenesis of pain syndromes.

Targeted Nanoparticles to Mitigate Radiation-Induced Blood-Brain Barrier Disruption and Cognitive Impairment

Background: Damage to neurovascular endothelium contributes to cognitive decline through increased blood-brain barrier (BBB) permeability. In our studies of mice and endothelial cells (ECs) subject to irradiation, we detect increases in mitochondrial reactive oxygen species (mtROS), mitochondrial DNA (mtDNA) damage, and cell-free release of mtDNA. Cell-free mtDNA acts as a damage associated molecular pattern (DAMP), and similarly to bacterial DNA, binds Toll-like receptor 9, triggering a pro-inflammatory and pro-oxidative response. However, these irradiation-induced effects are attenuated with TLR9 inhibition or mtROS scavenging. Our preliminary data implicate TLR9’s critical role in propagating a feedforward mechanism of sustained oxidative endothelial damage and dysfunction following radiation therapy. We hypothesize that specific inhibition of TLR9 in neurovascular ECs during radiation will prevent BBB permeability and cognitive decline. Thus, the purpose of the study is to use a novel nanoparticle (NP)-based tool to examine the sequela of cranial irradiation and provide proof-of-concept for its use as a mitigator. Methods: To target TLR9 in irradiated ECs, poly (lactic-co-glycolic acid)-based NP coated with cyclic Arg-Gly-Asp (cRGD)-peptide were designed and loaded with TLR9 antagonist (aTLR9, ODN-2088, 2.23ug/mg particle). cRGD-peptide is a ligand for integrin αvβ3, which is highly expressed in ECs post-irradiation (IR). C57Bl6 mice were administered NP-ODN-2088 (aTLR9-NP) or empty-NP (3mg injection) and subjected to unilateral cranial Xray IR (dose of 12Gy). 30d post-IR, memory and learning ability were assessed with the Novel Object Recognition (NOR) and Y-maze tests. The functionality of the NPs was assessed in vivo via BBB permeability, neuronal density, mtDNA damage, and serum levels of mtDNA and in vitro via mtROS production levels and inflammatory markers measurement in human brain microvascular endothelial cells (HBMECs) 5 days post-IR (IR dose of 4Gy). Results: In cultured HBMECs, treatment with aTLR9-NP prevented mtROS production 120hours post-IR. This correlated with attenuated inflammatory intermediates (p65, TNFa, IL6, and IL8), as compared to treatment with vehicle. In mice, aTLR9-NP treatment preserved integrity of mtDNA isolated from brain tissue and decreased blood levels of circulating cell-free mtDNA. aTLR9-NP treatment showed protective effects on BBB permeability and neuronal dropout, and these findings corresponded with preserved cognition in both, NOR and Y-maze tests. NP treatment caused no changes in alkaline phosphatase, alanine transaminase, aspartate aminotransferase, or bilirubin levels, indicating no liver injury. Conclusion: Inhibition of TLR9 in ECs was observed to prevent radiation-induced BBB permeability, neuronal dropout, and cognitive decline. Our findings support a pathway through which TLR9 links oxidative endothelial injury to neurological pathology. Currently there are no pharmacological options for treating radiation-induced normal tissue injury and targeting TLR9 poses a promising strategy. American Heart Association 2021CDA 853499. NIH R01 EY 031544-02 Veterans Affairs I01 BX000163-12. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

CNTN4 modulates neural elongation through interplay with APP.

The neuronal cell adhesion molecule contactin-4 (CNTN4) is genetically associated with autism spectrum disorder (ASD) and other psychiatric disorders. Cntn4-deficient mouse models have previously shown that CNTN4 plays important roles in axon guidance and synaptic plasticity in the hippocampus. However, the pathogenesis and functional role of CNTN4 in the cortex has not yet been investigated. Our study found a reduction in cortical thickness in the motor cortex of Cntn4 -/- mice, but cortical cell migration and differentiation were unaffected. Significant morphological changes were observed in neurons in the M1 region of the motor cortex, indicating that CNTN4 is also involved in the morphology and spine density of neurons in the motor cortex. Furthermore, mass spectrometry analysis identified an interaction partner for CNTN4, confirming an interaction between CNTN4 and amyloid-precursor protein (APP). Knockout human cells for CNTN4 and/or APP revealed a relationship between CNTN4 and APP. This study demonstrates that CNTN4 contributes to cortical development and that binding and interplay with APP controls neural elongation. This is an important finding for understanding the physiological function of APP, a key protein for Alzheimer's disease. The binding between CNTN4 and APP, which is involved in neurodevelopment, is essential for healthy nerve outgrowth.

Hyperphosphorylated tau in Alzheimer's disease disseminates along pathways predicted by the Structural Model for Cortico-cortical Connections.

In Alzheimer´s disease (AD), hyperphosphorylated tau spreads along the cerebral cortex in a stereotypical pattern that parallels cognitive deterioration. Tau seems to spread transsynaptically along cortico-cotical pathways that, according to synaptic tract-tracing studies in nonhuman primates, have specific laminar patterns related to the cortical type of the connected areas. This relation is described in the Structural Model. In the present article, we study the laminar distribution of hyperphosphorylated tau, labeled with the antibody AT8, along temporal cortical types in postmortem human brains with different AD stages to test the predictions of the Structural Model. Brains from donors without dementia had scant AT8-immunorreactive (AT8-ir) neurons in allo-, meso-, and isocortical types. In early AD stages, the mesocortical dysgranular type, including part of the transentorhinal cortex, had the highest AT8 immunostaining and AT8-ir neurons density. In advanced AD stages, AT8 immunostaining increased along the isocortical types until reaching the auditory koniocortex. Regarding laminar patterns, in early AD stages there were more AT8-ir neurons in supragranular layers in each de novo involved neocortical type; in advanced AD stages, AT8-ir neurons were equally distributed in supra- and infragranular layers. These AT8-ir laminar patterns are compatible with the predictions of the Structural Model. In summary, we show that hyperphosphorylated tau initially accumulates in allo-, meso-, and isocortical types, offer a proof of concept for the validity of the Structural Model to predict synaptic pathway organization in the human cerebral cortex, and highlight the relevance of nonhuman primate tract-tracing studies to understand human neuropathology.

Sparse Asymmetry in Locus Coeruleus Pathology in Alzheimer's Disease.

Tau accumulation in and neurodegeneration of locus coeruleus (LC) neurons is observed in Alzheimer's disease (AD). We investigated whether tangle and neuronal density in the rostral and caudal LC is characterized by an asymmetric pattern in 77 autopsy cases of the Rush Memory and Aging Project. We found left-right equivalence for tangle density across individuals with and without AD pathology. However, neuronal density, particularly in the caudal-rostral axis of the LC, is asymmetric among individuals with AD pathology. Asymmetry in LC neuronal density may signal advanced disease progression and should be considered in AD neuroimaging studies of LC neurodegeneration.

Methamphetamine and the Synthetic Cathinone 3,4-Methylenedioxypyrovalerone (MDPV) Produce Persistent Effects on Prefrontal and Striatal Microglial Morphology and Neuroimmune Signaling Following Repeated Binge-like Intake in Male and Female Rats.

Psychostimulants alter cellular morphology and activate neuroimmune signaling in a number of brain regions, yet few prior studies have investigated their persistence beyond acute abstinence or following high levels of voluntary drug intake. In this study, we examined the effects of the repeated binge-like self-administration (96 h/week for 3 weeks) of methamphetamine (METH) and 21 days of abstinence in female and male rats on changes in cell density, morphology, and cytokine levels in two addiction-related brain regions-the prefrontal cortex (PFC) and dorsal striatum (DStr). We also examined the effects of similar patterns of intake of the cocaine-like synthetic cathinone derivative 3,4-methylenedioxypyrovalerone (MDPV) or saline as a control. Robust levels of METH and MDPV intake (~500-1000 infusions per 96 h period) were observed in both sexes. We observed no changes in astrocyte or neuron density in either region, but decreases in dendritic spine densities were observed in PFC pyramidal and DStr medium spiny neurons. The microglial cell density was decreased in the PFC of METH self-administering animals, accompanied by evidence of microglial apoptosis. Changes in microglial morphology (e.g., decreased territorial volume and ramification and increased cell soma volume) were also observed, indicative of an inflammatory-like state. Multiplex analyses of PFC and DStr cytokine content revealed elevated levels of various interleukins and chemokines only in METH self-administering animals, with region- and sex-dependent effects. Our findings suggest that voluntary binge-like METH or MDPV intake induces similar cellular perturbations in the brain, but they are divergent neuroimmune responses that persist beyond the initial abstinence phase.

PRG ameliorates cognitive impairment in Alzheimer's disease mice by regulating β-amyloid and targeting the ERK pathway

BackgroundPRG is derived from Phellinus ribis and is a homogeneous polysaccharide with well-defined structural information. PRG was found to have significant in vitro neurotrophic and neuroprotective activities. Thus, PRG might be a potential treatment for Alzheimer's disease. However, the related mechanisms of action are still unclear, so deeper in vivo experimental validation and the potential mechanisms need to be investigated. PurposeThe effects of PRG on AD mice were investigated using Senescence-accelerated SAMP8 mice as an AD model to elucidate the crucial molecular mechanisms. MethodsPRG was obtained from Phellinus ribis by water-alcohol precipitation, column chromatography, and ultrafiltration. The Morris water maze and novel object recognition behavioral assays were used to evaluate the effects of PRG in AD mice. Nissl staining, the TUNEL apoptosis assay, and Golgi staining were used to assess brain neuronal cell damage, apoptosis, and neuronal status. Enzyme-linked immunosorbent assays, Western blotting, and immunofluorescence were used to explore the impacts of correlated factors and protein pathways under relevant mechanisms. ResultsThe findings suggest that PRG improved learning ability and spatial memory capacity in SAMP8 mice. PRG hastened the disintegration of β-amyloid, reduced the content and abnormal accumulation of the toxic Aβ1–42 protein, and decreased apoptosis. PRG activated the BDNF/ERK/CREB signaling pathway through a cascade, exerted neurotrophic effects, regulated cell proliferation and differentiation, increased neuronal dendritic branching and spine density, and improved synaptic plasticity. ConclusionPRG promoted β-amyloid degradation to reduce neuronal damage and apoptosis. It exerted neurotrophic effects by activating the BDNF/ERK/CREB pathway, promoting neuronal dendritic branching and dendritic spine growth, regulating cell proliferation and differentiation, and improving synaptic plasticity, which improved AD. Taken together, as a novel natural active polysaccharide with a well-defined structure, PRG affected AD symptoms in senescence-accelerated mice by interacting with multiple targets. The results indicate that PRG is a promising potential anti-AD drug candidate.

Association cortical areas in the mouse contain a large population of fast-spiking GABAergic neurons that do not express parvalbumin.

GABAergic neurons represent 10-15% of the neuronal population of the cortex but exert a powerful control over information flow in cortical circuits. The largest GABAergic class in the neocortex is represented by the parvalbumin-expressing fast-spiking neurons, which provide powerful somatic inhibition to their postsynaptic targets. Recently, the density of parvalbumin interneurons has been shown to be lower in associative areas of the mouse cortex as compared with sensory and motor areas. Modelling work based on these quantifications linked the low-density of parvalbumin interneurons with specific computations of associative cortices. However, it is still unknown whether the total GABAergic population of association cortices is smaller or whether another GABAergic type can compensate for the low density of parvalbumin interneurons. In the present study, we investigated these hypotheses using a combination of neuroanatomy, mouse genetics and neurophysiology. We found that the GABAergic population of association areas is comparable with that of primary sensory areas, and it is enriched of fast-spiking neurons that do not express parvalbumin and were not accounted for by previous quantifications. We developed an intersectional viral strategy to demonstrate that the population of fast-spiking neurons is comparable across cortical regions. Our results provide quantifications of the density of fast-spiking GABAergic neurons and offers new biological constrains to refine current models of cortical computations.

Tributyltin (TBT) toxicity: Effects on enteric neuronal plasticity and intestinal barrier of rats' duodenum

Tributyltin (TBT) is a biocide used in the formulation of antifouling paints and it is highly harmful. Despite the ban, the compound persists in the environment, contaminating marine foodstuffs and household products. Therefore, considering the route of exposure to the contaminant, the gastrointestinal tract (GIT) acts as an important barrier against harmful substances and is a potential biomarker for understanding the consequences of these agents. This work aimed to evaluate histological and neuronal alterations in the duodenum of male Wistar rats that received 20 ng/g TBT and 600 ng/g via gavage for 30 consecutive days. After the experimental period, the animals were euthanized, and the duodenum was intended for neuronal histochemistry (total and metabolically active populations) and histological routine (morphometry and histopathology). The results showed more severe changes in neuronal density and intestinal morphometry in rats exposed to 20 ng/g, such as total neuronal density decrease and reduction of intestinal layers. In rats exposed to 600 ng/g of TBT, it was possible to observe only an increase in intraepithelial lymphocytes. We conclude that TBT can be more harmful to intestinal homeostasis when consumed in lower concentrations.

Structural, Functional, and Genetic Changes Surrounding Electrodes Implanted in the Brain.

Implantable neurotechnology enables monitoring and stimulating of the brain signals responsible for performing cognitive, motor, and sensory tasks. Electrode arrays implanted in the brain are increasingly used in the clinic to treat a variety of sources of neurological diseases and injuries. However, the implantation of a foreign body typically initiates a tissue response characterized by physical disruption of vasculature and the neuropil as well as the initiation of inflammation and the induction of reactive glial states. Likewise, electrical stimulation can induce damage to the surrounding tissue depending on the intensity and waveform parameters of the applied stimulus. These phenomena, in turn, are likely influenced by the surface chemistry and characteristics of the materials employed, but further information is needed to effectively link the biological responses observed to specific aspects of device design. In order to inform improved design of implantable neurotechnology, we are investigating the basic science principles governing device-tissue integration. We are employing multiple techniques to characterize the structural, functional, and genetic changes that occur in the cells surrounding implanted electrodes. First, we have developed a new "device-in-slice" technique to capture chronically implanted electrodes within thick slices of live rat brain tissue for interrogation with single-cell electrophysiology and two-photon imaging techniques. Our data revealed several new observations of tissue remodeling surrounding devices: (a) there was significant disruption of dendritic arbors in neurons near implants, where losses were driven asymmetrically on the implant-facing side. (b) There was a significant loss of dendritic spine densities in neurons near implants, with a shift toward more immature (nonfunctional) morphologies. (c) There was a reduction in excitatory neurotransmission surrounding implants, as evidenced by a reduction in the frequency of excitatory postsynaptic currents (EPSCs). Lastly, (d) there were changes in the electrophysiological underpinnings of neuronal spiking regularity. In parallel, we initiated new studies to explore changes in gene expression surrounding devices through spatial transcriptomics, which we applied to both recording and stimulating arrays. We found that (a) device implantation is associated with the induction of hundreds of genes associated with neuroinflammation, glial reactivity, oligodendrocyte function, and cellular metabolism and (b) electrical stimulation induces gene expression associated with damage or plasticity in a manner dependent upon the intensity of the applied stimulus. We are currently developing computational analysis tools to distill biomarkers of device-tissue interactions from large transcriptomics data sets. These results improve the current understanding of the biological response to electrodes implanted in the brain while producing new biomarkers for benchmarking the effects of novel electrode designs on responses. As the next generation of neurotechnology is developed, it will be increasingly important to understand the influence of novel materials, surface chemistries, and implant architectures on device performance as well as the relationship with the induction of specific cellular signaling pathways.

Synergistic neuroprotective action of prolactin and 17β-estradiol on kainic acid-induced hippocampal injury and long-term memory deficit in ovariectomized rats.

The neuroprotective actions of the ovarian hormone 17β-estradiol (E2) against different brain lesions have been constantly confirmed in a variety of models including kainic acid (KA) lesions. Similarly, the pituitary hormone prolactin (PRL), traditionally associated with lactogenesis, has recently been linked to a large diversity of functions, including neurogenesis, neuroprotection, and cognitive processes. While the mechanisms of actions of E2 as regards its neuroprotective and behavioral effects have been extensively explored, the molecular mechanisms of PRL related to these roles remain under investigation. The current study aimed to investigate whether the simultaneous administration of PRL and a low dose of E2 prevents the KA-induced cognitive deficit and if this action is associated with changes in hippocampal neuronal density. Ovariectomized (OVX) rats were treated with saline, PRL, and/or E2 in the presence or absence of KA. Neuroprotection was assessed by Nissl staining and neuron counting. Memory was evaluated with the novel object recognition test (NOR). On their own, both PRL and E2 prevented short- and long-term memory deficits in lesioned animals and exerted neuroprotection against KA-induced excitotoxicity in the hippocampus. Interestingly, the combined hormonal treatment was superior to either of the treatments administered alone as regards improving both memory and neuronal survival. Taken together, these results point to a synergic effect of E2 and PRL in the hippocampus to produce their behavioral, proliferative, and neuroprotective effects.

Challenges with hippocampal MR spectroscopy as a surrogate for pre-radiotherapy assessment of neurocognitive impairment in patients with brain metastasis.

Patients with multiple brain metastases (BM) benefit from hippocampal-avoiding whole brain radiotherapy (HA-WBRT), the challenging and less available form of WBRT. This study explores potential of pre-radiotherapy (pre-RT) hippocampal magnetic resonance spectroscopy (MRS) measuring hippocampal neuronal density as an imaging surrogate and predictive tool for assessing neurocognitive functions (NCF). 43 BM patients underwent pre-RT hippocampal MRS. N-acetyl aspartate (NAA) concentration, a marker for neuronal density (weighted by creatine (Cr) and choline (Cho) concentrations), and neurocognitive function (NCF) tests (HVLT and BVMT) performed by certified psychologists were evaluated. Clinical variables and NAA concentrations were correlated with pre-RT NCFs. HVLT and BVMT subtests showed pre-RT deterioration except for BVMT recognition. Significantly better NCFs were observed in women in HVLT subsets. Significantly higher NAA/Cr + Cho was measured in women (median 0.63 vs. 0.55; P=0.048) in the left hippocampus (no difference in the right hippocampus). In men, a positive correlation (0.51, P=0.018) between total brain volume and HVLT-TR, between left hippocampal NAA/Cr + Cho and HVLT-R (0.45, P=0.063), and between right hippocampal NAA/Cr + Cho and BVMT-recognition (0.49, P=0.054) was observed. In women, a borderline significant negative correlation was observed between left hippocampal NAA/Cr + Cho and BVMT-TR (-0.43, P=0.076) and between right NAA/Cr + Cho and HVLT-DR (-0.42, P=0.051). Borderline statistically significant correlations were observed with speculative interpretation underlying the challenges of hippocampal MRS as a surrogate for neurocognitive impairment. Further studies need to be done to ascertain the opportunities for imaging predictors of benefit from memory sparing radiotherapy.

Interaction between Neurogenic Pulmonary Edema and Thoracic 3 DRG Degeneration Following Spinal Subarachnoid Hemorrhage: First Experimental Study.

Neurogenic pulmonary edema (NPE) following subarachnoid hemorrhage (SAH) is still one of the most catastrophic complications with high morbidity and mortality rates. Systemic sympathetic hyperactivity has been considered in the pathogenesis, but it has not been clarified. In this study, we investigate the relationship between the degeneration of the T3 dorsal root ganglion (DRG) and the development of NPE following spinal SAH. The study was conducted on 23 rabbits. Five rabbits were used as the control group, 5 as the sham group (n = 5), and 13 as the study group. The correlation between the degenerated neuronal densities of the T3 nerve axons and neurons in the DRG and NPE scores was analyzed statistically. A correlation between the neuronal degeneration of the T3 nerve, its DRG, and high NPE scores was found in the study group and the sham group. Massive NPE was detected in the study group along with neural degeneration of T3 axons and ganglia. The present study indicates that NPE and pulmonary artery vasospasm can be prevented by reducing T3 DRG degeneration.

Dry Eye Disease Symptoms Among Glaucoma Patients at a Portuguese Hospital.

Glaucoma-related dry eye disease (DED) is often underestimated, but it is an important comorbidity affecting 40% to 59% of glaucoma patients. It may be an exacerbation of a pre-existing condition or a novel disease starting after the initiation of topical medication. The cumulative effect of medication, preservatives and excipients leads to an alteration in tear film composition and ocular surface stability. The main purpose of this investigation was to study a group of Portuguese glaucoma patients regarding the presence of DED symptoms and correlate the severity of the symptoms with the usage of different types of glaucoma topical medications. This is a cross-sectional observational study of patients diagnosed with primary and secondary open-angle glaucoma. The questionnaire Standardized Patient Evaluation of Eye Dryness (SPEED) translated to Portuguese (SPEED-Vp) was taken by patients followed in the Glaucoma Department of Unidade Local de Saúde Entre Douro e Vouga, Santa Maria da Feira, Portugal. Data was collected regarding their age, gender, type of topical medication in use as well as frequency and duration of usage. A statistical analysis was performed. A total of 75 patients answered the SPEED-Vp questionnaire. The mean age was 72 ± 7 years old. Fifty-two percent (n=39) were male, and 48% (n=36) were female patients. About 49.33% (n=37) had been on intraocular pressure (IOP)-lowering eyedrops for more than five years. About 61.43% (n=43) of patients used IOP-lowering eyedrops with preservatives. Most of the patients used prostaglandin analogs (75.71%, n=53) and beta-blockers (72.86%, n=51). SPEED score average was 2.75. About 25.33% (n=19) had no DED symptoms, 58.67% (n=44) had mild symptoms, 8% (n=6) had moderate symptoms and 8% (n=6) had severe symptoms. No statistically significant correlation was found between SPEED score and age, gender, number of eyedrop containers, number of active principles, application frequency, presence of preservatives, number of eyedrop containers with preservatives, duration of eyedrops usage or any of the medication groups. Although a high percentage of patients were on eyedrops with preservatives, this low rate of symptoms might be because patients tended to devalue these symptoms;were already on treatment with artificial tears; or have an underestimation of the sensation of dry eye due to decreased neuronal corneal nerve responses and density. These results were surprisingly positive. This might also be the result of the healthcare provider's sensibilization to this issue (early diagnosis, early prescription of artificial tears and change from preservative to preservative-free medication).