Analysis of Histological Features of the Cerebral Cortex and Hippocampus of Albino Rats Using Haematoxylin & Eosin Stain- An Observational Study

Background: The study determined the histological layers of the cerebral cortex and hippocampus of the albino rat brain samples has been used in the study. The Cerebral cortex is composed of the Molecular layer, external granular, external pyramidal layer, internal granular layer and interior pyramidal layer. The layers of the hippocampus are alveus, stratum oriens, stratum pyramidale, stratum radiatum, stratum lacunosum and stratum moleculare. The aim of the study is to analyze the detailed histological features of the cerebral cortex and hippocampus layers of albino rats at the magnification of 10X,100X,40X. By using haematoxylin and eosin stain as an observational study. Materials and Methods: The samples were preserved and fixed with the formalin and stained by haematoxylin and eosin and observed with a light microscope. Results: The molecular layer is the superficial layer containing neurons. The outer granular layer of the cells are densely packed. Outer pyramidal layer contains rich pyramidal cells, Inner granular layer contains stellate cells, Inner pyramidal layer contains glial cells and the deeper multiform layer is composed of pyramidal cells. The hippocampus contains three layers of cornu Ammonia CA1, CA2, CA3. CA1 responds to memory and is covered by the choroid plexus. CA2 contains 3 major cell dentate gyrus, pyramidal cells, pyramidal neurons and CA3 composed of stratum lucidum. Conclusion: The study of brain analysis of histological features of the cerebral cortex and hippocampus of the brain adds a greater insight in understanding the histology of various types of layers in rat brain and morphology of brain cells.

Effect of Oral Administration of Paraquat Pesticide on the Hippocampus and Substantia Nigra in Wistar Rats' Brains: تأثير التجريع الفموي للمبيد العشبي (الباراكوات) على الحصين والمادة السوداء في أدمغة جرذان الويستر

This study aimed to detect the neurohistological damages of chronic exposure to low levels of pesticide (paraquat) in the hippocampus, and substantia nigra in Wistar rats' brains. The neurotoxic effects of acute poisoning are well established but the possibility that low level exposure causes different diseases is controversialIt is important to get a clear answer to this question as more individuals are at risk of low level exposure than acute poisoning. The anatomical and histological of current study to affected brains showed cells display the cytological changes of herbisecticides-lesioned brain tissue, such as a significant decrease in the size of the brain was observed, as most of its external features disappeared. in addition, we detected vacuolization around cells that degenerated because many reasons like apoptosis or necrosis, and the intracellular neurofibrillary tangles were observed at many regions such as the hippocampus and substantia nigra. Moreover extracellular amyloid plaques take fibers form were detected. we also observed degenerated in CA1, CA2 and CA3 regions (molecular layer, polymorphic layer and pyramidal layer) by pigmenting degenerated neurons with silver nitrate with increased astrocytes of glia cells.

IMPACT OF INSTITUTIONAL ENVIRONMENT AND PYRAMIDAL LAYER ON COMPLETION OF CHINESE SOES’ MIXED-OWNERSHIP TRANSACTIONS

This paper utilizes Chinese SOEs that undertake mixed-ownership transactions in 2019 as its research objects and discusses the impact of institutional environment (including the degree of marketization and governmental hierarchy) on the completion of mixed-ownership transactions. In addition, this study explores the moderating effect of pyramidal layer and the munificence of payment on the above relationships. The empirical results show that the main effect hypothesis is supported. Furthermore, pyramidal layer weakens the positive correlation between the marketization and the completion of mixed-ownership transactions, and strengthens the negative correlation between governmental hierarchy and the completion of mixed-ownership transactions. The munificence of payment has no significant moderating effect on the relationship between marketization and completion of mixed-ownership transactions; however, it weakens the negative correlation between the governmental level and the completion of mixed-ownership transactions.

The Hybrid Drive: a chronic implant device combining tetrode arrays with silicon probes for layer-resolved ensemble electrophysiology in freely moving mice

Understanding the function of brain cortices requires simultaneous investigation at multiple spatial and temporal scales and to link neural activity to an animal's behavior. A major challenge is to measure within- and across-layer information in actively behaving animals, in particular in mice that have become a major species in neuroscience due to an extensive genetic toolkit. Here we describe the Hybrid Drive, a new chronic implant for mice that combines tetrode arrays to record within-layer information with silicon probes to simultaneously measure across-layer information. The flexible, open-source design allows custom spatial arrangements of tetrode arrays and silicon probes to generate areas-specific layouts. We show that large numbers of neurons and layer-resolved local field potentials can be recorded from the same brain region across weeks without loss in electrophysiological signal quality. The drive's light-weight structure (3.5 g) leaves animal behavior largely unchanged during a variety of experimental paradigms, enabling the study of rich, naturalistic behaviors. We demonstrate the power of the Hybrid Drive in a series of experiments linking the spiking activity of CA1 pyramidal layer neurons to the oscillatory activity across hippocampal layers.

Complement-associated loss of CA2 inhibitory synapses in the demyelinated hippocampus impairs memory

The complement system is implicated in synapse loss in the MS hippocampus, but the functional consequences of synapse loss remain poorly understood. Here, in post-mortem MS hippocampi with demyelination we find that deposits of the complement component C1q are enriched in the CA2 subfield, are linked to loss of inhibitory synapses and are significantly higher in MS patients with cognitive impairments compared to those with preserved cognitive functions. Using the cuprizone mouse model of demyelination, we corroborated that C1q deposits are highest within the demyelinated dorsal hippocampal CA2 pyramidal layer and co-localized with inhibitory synapses engulfed by microglia/macrophages. In agreement with the loss of inhibitory perisomatic synapses, we found that Schaffer collateral feedforward inhibition but not excitation was impaired in CA2 pyramidal neurons and accompanied by intrinsic changes and a reduced spike output. Finally, consistent with excitability deficits, we show that cuprizone-treated mice exhibit impaired encoding of social memories. Together, our findings identify CA2 as a critical circuit in demyelinated intrahippocampal lesions and memory dysfunctions in MS.

Complement-associated loss of CA2 inhibitory synapses in the demyelinated hippocampus impairs memory

The complement system is implicated in synapse loss in the MS hippocampus, but the functional consequences of synapse loss remain poorly understood. Here, in post-mortem MS hippocampi with demyelination we find that deposits of the complement component C1q are enriched in the CA2 subfield, are linked to loss of inhibitory synapses and are significantly higher in MS patients with cognitive impairments compared to those with preserved cognitive functions. Using the cuprizone mouse model of demyelination, we corroborated that C1q deposits are highest within the demyelinated dorsal hippocampal CA2 pyramidal layer, and co-localized with inhibitory synapses engulfed by microglia/macrophages. In agreement with the loss of inhibitory perisomatic synapses, we further found that Schaffer collateral feedforward inhibition but not excitation was impaired in CA2 pyramidal neurons and accompanied by a reduced spike output. Ultimately, we show that these electrophysiological changes were associated with an impaired encoding of social memories. Together, our findings identify CA2 as a critical circuit in demyelinated intrahippocampal lesions and memory dysfunctions in MS.

Inhibitory microcircuits for top-down plasticity of sensory representations

Rewards influence plasticity of early sensory representations, but the underlying changes in circuitry are unclear. Recent experimental findings suggest that inhibitory circuits regulate learning. In addition, inhibitory neurons are highly modulated by diverse long-range inputs, including reward signals. We, therefore, hypothesise that inhibitory plasticity plays a major role in adjusting stimulus representations. We investigate how top-down modulation by rewards interacts with local plasticity to induce long-lasting changes in circuitry. Using a computational model of layer 2/3 primary visual cortex, we demonstrate how interneuron circuits can store information about rewarded stimuli to instruct long-term changes in excitatory connectivity in the absence of further reward. In our model, stimulus-tuned somatostatin-positive interneurons develop strong connections to parvalbumin-positive interneurons during reward such that they selectively disinhibit the pyramidal layer henceforth. This triggers excitatory plasticity, leading to increased stimulus representation. We make specific testable predictions and show that this two-stage model allows for translation invariance of the learned representation.

DeepCINAC: a deep-learning-based Python toolbox for inferring calcium imaging neuronal activity based on movie visualization

Two-photon calcium imaging is now widely used to infer neuronal dynamics from changes in fluorescence of an indicator. However, state of the art computational tools are not optimized for the reliable detection of fluorescence transients from highly synchronous neurons located in densely packed regions such as the CA1 pyramidal layer of the hippocampus during early postnatal stages of development. Indeed, the latest analytical tools often lack proper benchmark measurements. To meet this challenge, we first developed a graphical user interface allowing for a precise manual detection of all calcium transients from imaged neurons based on the visualization of the calcium imaging movie. Then, we analyzed the movies using a convolutional neural network with an attention process and a bidirectional long-short term memory network. This method is able to reach human performance and offers a better F1 score (harmonic mean of sensitivity and precision) than CaImAn to infer neural activity in the developing CA1 without any user intervention. It also enables automatically identifying activity originating from GABAergic neurons. Overall, DeepCINAC offers a simple, fast and flexible open-source toolbox for processing a wide variety of calcium imaging datasets while providing the tools to evaluate its performance.Significance statementInferring neuronal activity from calcium imaging data remains a challenge due to the difficulty in obtaining a ground truth using patch clamp recordings and the problem of finding optimal tuning parameters of inference algorithms. DeepCINAC offers a flexible, fast and easy-to-use toolbox to infer neuronal activity from any kind of calcium imaging dataset through visual inspection.