Total Number Of Neurons Research Articles

Deficiency of DDX3X results in neurogenesis defects and abnormal behaviors via dysfunction of the Notch signaling

The molecular mechanisms underlying the neurodevelopmental disorders (NDDs) caused by DDX3X variants remain poorly understood. In this study, we validated that de novo DDX3X variants are enriched in female developmental delay (DD) patients and mainly affect the evolutionarily conserved amino acids based on a meta-analysis of 46,612 NDD trios. We generated a ddx3x deficient zebrafish allele, which exhibited reduced survival rate, DD, microcephaly, adaptation defects, anxiolytic behaviors, social interaction deficits, and impaired spatial recognitive memory. As revealed by single-nucleus RNA sequencing and biological validations, ddx3x deficiency leads to reduced neural stem cell pool, decreased total neuron number, and imbalanced differentiation of excitatory and inhibitory neurons, which are responsible for the behavioral defects. Indeed, the supplementation of L-glutamate or glutamate receptor agonist ly404039 could partly rescue the adaptation and social deficits. Mechanistically, we reveal that the ddx3x deficiency attenuates the stability of the crebbp mRNA, which in turn causes downregulation of Notch signaling and defects in neurogenesis. Our study sheds light on the molecular pathology underlying the abnormal neurodevelopment and behavior of NDD patients with DDX3X mutations, as well as providing potential therapeutic targets for the precision treatment.

Tyrosine hydroxylase expression and neuronal loss in the male and female adolescent ventral tegmental area

Adolescence is a critical period of development characterized by numerous behavioral and neuroanatomical changes. While studies of adolescent neurodevelopment typically compare adolescent age groups with young adults, there are fewer studies that assess developmental trajectories within the adolescent period. In the adolescent prefrontal cortex, some maturational changes take place linearly/chronologically, while others are associated specifically with pubertal onset. The adolescent ventral tegmental area (VTA), a primary source of forebrain dopamine, is relatively understudied during this period. In the present study, dopamine neuron number, total neuron number and tyrosine hydroxylase expression are assessed in the male and female rat VTA at three timepoints: postnatal day(P) 30 (pre-pubertal), P40 (post-pubertal for females, pre-pubertal for males) and P60 (post-pubertal). There was a non-significant trend for a reduction in total VTA neuron number between P30 and P60, but there was a significant reduction in dopamine neuron number across age. The expression of tyrosine hydroxylase did not change with age. However, in a second cohort of subjects, brain tissue was collected pre-pubertal, from recently post-pubertal males and females, and young adults. In this cohort, there was a sex-specific and transient decrease in tyrosine hydroxylase expression in recently post-pubertal males. These results suggest a selective pruning of VTA dopamine cells between early adolescence and young adulthood, while pubertal onset may coincide with a rapid maturation of these neurons. These findings may have implications for psychiatric disorders associated with dopamine dysfunction that tend to manifest during adolescence.

Changes in AmotL2 Expression in Cells of the Human Enteral Nervous System in Oxaliplatin-Induced Enteric Neuropathy.

Gastrointestinal (GI) toxicity is a common side effect in patients undergoing oxaliplatin (OxPt)-based chemotherapy for colorectal cancer (CRC). Frequently, this complication persists in the long term and could affect the efficacy of the treatment and the patient's life quality. This long-term GI toxicity is thought to be related to OxPt-induced enteral neuropathy. AmotL2 is a member of the Angiomotin family of proteins, which play a role in cell survival, neurite outgrowth, synaptic maturation, oxidative stress protection, and inflammation. In order to assess the role of AmotL2 in OxPt-induced enteral neuropathy, we studied the expression of AmotL2 in cells of the enteric nervous system (ENS) of untreated and OxPt-treated CRC patients and its relationship with inflammation, using immunofluorescence confocal microscopy. Our results in human samples show that the total number of neurons and glial cells decreased in OxPt-treated patients, and TNF-α and AmotL2 expression was increased and colocalized in both neurons and glia. AmotL2 differential expression between OxPt-treated and untreated CRC patients shows the involvement of this scaffold protein in the inflammatory component and toxicity by OxPt in the ENS.

Functional and Structural Investigation of Myenteric Neurons in the Human Colon

Background and aimsThe enteric nervous system independently controls gastrointestinal function including motility, which is primarily mediated by the myenteric plexus, therefore also playing a crucial role in functional intestinal disorders. Live recordings from human myenteric neurons proved to be challenging due to technical difficulties. Using the neuroimaging technique, we are able to record human colonic myenteric neuronal activity and investigate their functional properties in a large cohort of patients. MethodsActivity from myenteric neurons in wholemount preparations of different sampling sites of fresh, human colonic tissue was recorded using neuroimaging with the voltage sensitive dye Di-8-ANEPPS. Neuronal responses were analysed following stimulation with nicotine and serotonin (5-HT) for differences based on the donor’s age, the disorder indicative for surgery and the colonic region. Immunohistochemistry was performed to calculate the total neuronal numbers. ResultsStimulation with nicotine and 5-HT elicited reproducible action potential discharge in a proportion of human myenteric neurons. The responses to 5-HT were significantly greater in tissues from older patients and from those with inflammatory disorders, while neuronal activity to nicotinergic stimulation was comparable in all patients. Neuronal numbers declined with rising patient’s age and was highest in the sigmoid colon. ConclusionNeuroimaging with Di-8-ANEPPS was successfully adapted to record reproducible responses from human colonic myenteric neurons upon pharmacological stimulation. Evidence exists for an impact of age and inflammation on the serotonergic neuronal signalling and for differences in neuronal numbers in the distinct colonic regions as well as a neuronal decrease with age.

The olfactory system of sharks and rays in numbers.

Cartilaginous fishes have large and elaborate olfactory organs, but only a small repertoire of olfactory receptor genes. Here, we quantitatively analyze the olfactory system of 21 species of sharks and rays, assessing many features of the olfactory organ (OOR) (number of primary lamellae, branches of the secondary folds, sensory surface area, and density and number of sensory neurons) and the olfactory bulb (OB) (number of neurons and non-neuronal cells), and estimate the ratio between the number of neuronsin the two structures. We show that the number of lamellae in the OOR does not correlate with the sensory surface area, while the complexity of the lamellar shape does. The total number of olfactory receptor neurons ranges from 30.5 million to 4.3 billion and the total number of OB neurons from 1.5 to 90 million. The number of neuronsin the olfactory epithelium is 16 to 158 times higher (median ratio is 46) than the number of neuronsin the OB. These ratios considerably exceed those reported in mammals. High convergence from receptor neurons to neurons processing olfactory information, together with the remarkably small olfactory receptor repertoire, strongly suggests that the olfactory system of sharks and rays is well adapted to detect a limited number of odorants with high sensitivity.

Morphological and Molecular Characteristics of Perineuronal Nets in the Human Prefrontal Cortex-A Possible Link to Microcircuitry Specialization.

Perineuronal nets (PNNs) are a type of extracellular matrix (ECM) that play a significant role in synaptic activity and plasticity of interneurons in health and disease. We researched PNNs' regional and laminar representation and molecular composition using immunohistochemistry and transcriptome analysis of Brodmann areas (BA) 9, 14r, and 24 in 25 human postmortem brains aged 13-82 years. The numbers of VCAN- and NCAN-expressing PNNs, relative to the total number of neurons, were highest in cortical layers I and VI while WFA-binding (WFA+) PNNs were most abundant in layers III-V. The ECM glycosylation pattern was the most pronounced regional difference, shown by a significantly lower proportion of WFA+ PNNs in BA24 (3.27 ± 0.69%) compared to BA9 (6.32 ± 1.73%; P = 0.0449) and BA14 (5.64 ± 0.71%; P = 0.0278). The transcriptome of late developmental and mature stages revealed a relatively stable expression of PNN-related transcripts (log2-transformed expression values: 6.5-8.5 for VCAN and 8.0-9.5 for NCAN). Finally, we propose a classification of PNNs that envelop GABAergic neurons in the human cortex. The significant differences in PNNs' morphology, distribution, and molecular composition strongly suggest an involvement of PNNs in specifying distinct microcircuits in particular cortical regions and layers.

Autistic-like behaviour and changes in thalamic cell numbers a rat model of valproic acid-induced autism; A behavioural and stereological study

The contribution of the thalamus to the development and behavioural changes in autism spectrum disorders (ASD), a neurodevelopmental syndrome, remains unclear. The aim of this study was to determine the changes in thalamic volume and cell number in the valproic acid (VPA)-induced ASD model using stereological methods and to clarify the relationship between thalamus and ASD-like behaviour.Ten pregnant rats were administered a single dose (600 mg/kg) of VPA intraperitoneally on G12.5 (VPA group), while five pregnant rats were injected with 5 ml saline (control group). Behavioural tests were performed to determine appropriate subjects and ASD-like behaviours. At P55, the brains of the subjects were removed. The sagittal sections were stained with cresyl violet and toluidine blue. The thalamic and hemispheric volumes with their ratios, the total number of thalamic cells, neurons and non-neuronal cells were calculated using stereological methods. Data were compared using a t-test and a Pearson correlation analysis was performed to examine the relationship between behaviour and stereological outcomes.VPA-treated rats had lower sociability and sociability indexes. There was no difference in social novelty preference and anxiety. The VPA group had larger hemispheric volume, lower thalamic volume, and fewer neurons. The highest percentage decrease was in non-neuronal cells. There was a moderate positive correlation between the number of non-neuronal cells and sociability, thalamic volume and the number of neurons as well as the time spent in the light box.The correlation between behaviour and stereological data suggests that the thalamus is associated with ASD-like behaviour.

The IC87201 (a PSD95/nNOS Inhibitor) Attenuates Post- Stroke Injuries.

N-methyl-D-aspartate receptor-dependent excitotoxicity is one of the most important mechanisms underlying stroke injury and the resulting neuronal death. In the present study, in order to reduce post-stroke brain injury and improve behavioral performance, a new molecule named IC87201, which acts as an inhibitor of PSD95/nNOS interaction in the intracellular signaling pathway of NMDA receptors, was administered. Using the middle cerebral artery occlusion (MCAO) technique, 24 adult male rats were subjected to one hour of cerebral ischemia. Animals were randomly divided into sham, MCAO, MCAO + DXM, and MCAO + IC87201 groups, and in the last two groups, intraperitoneal injection of dextromethorphan hydrobromide monohydrate (DXM), as an NMDA antagonist, and IC87201 was performed after ischemia. Neurobehavioral scores were evaluated for seven days, and on the last two days, the rats' memory performance was appraised using the passive avoidance test. On seventh day, the brain tissue was properly prepared for stereological analysis. Stereological studies of the hippocampus CA1 and CA3 regions revealed that changes in the total and infarcted volumes, total number of neurons, non-neurons, and dead neurons are the consequences of cerebral ischemia. Also, following cerebral ischemia, neurobehavioral and memory function impairments which were assessed by modified neurological severity scores (mNSS) and passive avoidance test, were observed. The aforementioned impairments were recovered after administration of IC87201 significantly and more potently than DXM. Based on our findings, IC87201 successfully attenuated post-ischemia damages. Therefore, this molecule can be considered as a new therapeutic approach in future research.

Properties of the Caudal Pontine Reticular Nucleus Neurons Determine the Acoustic Startle Response in Cntnap2 KO Rats.

Rats with a loss-of-function mutation in the contactin-associated protein-like 2 (Cntnap2) gene have been validated as an animal model of autism spectrum disorder (ASD). Similar to many autistic individuals, Cntnap2 knock-out rats (Cntnap2-⁣/-) are hyperreactive to sound as measured through the acoustic startle response. The brainstem region that mediates the acoustic startle response is the caudal pontine reticular nucleus (PnC), specifically giant neurons in the PnC. We previously reported a sex-dependent genotypic effect in the sound-evoked neuronal activity recorded from the PnC, whereby female Cntnap2-⁣/- rats had a dramatic increase in sound-evoked responses compared with wildtype counterparts, but male Cntnap2-⁣/- rats showed only a modest increase in PnC activity that cannot fully explain the largely increased startle in male Cntnap2-⁣/- rats. The present study therefore investigates activation and histological properties of PnC giant neurons in Cntnap2-⁣/- rats and wildtype littermates. The acoustic startle response was elicited by presenting rats with 95 dB startle pulses before rats were euthanized. PnC brain sections were stained and analyzed for the total number of PnC giant neurons and the percentage of giant neurons that expressed phosphorylated cAMP response element binding protein (pCREB) in response to startle stimuli. Additionally, in vitro electrophysiology was conducted to assess the resting state activity and intrinsic properties of PnC giant neurons. Wildtype and Cntnap2-⁣/- rats had similar total numbers of PnC giant neurons and similar levels of baseline pCREB expression, as well as similar numbers of giant neurons that were firing at rest. Increased startle magnitudes in Cntnap2-⁣/- rats were associated with increased percentages of pCREB-expressing PnC giant neurons in response to startle stimuli. Male rats had increased pCREB-expressing PnC giant neurons compared with female rats, and the recruited giant neurons in males were also larger in soma size. Recruitment and size of PnC giant neurons are important factors for regulating the magnitude of the acoustic startle response in Cntnap2-⁣/- rats, particularly in males. These findings allow for a better understanding of increased reactivity to sound in Cntnap2-⁣/- rats and in CNTNAP2-associated disorders such as ASD.

The combination treatment of hypothermia and intranasal insulin ameliorates the structural and functional changes in a rat model of traumatic brain injury.

The present study aimed to investigate the combination effects of hypothermia (HT) and intranasal insulin (INS) on structural changes of the hippocampus and cognitive impairments in the traumatic brain injury (TBI) rat model. The rats were divided randomly into the following five groups (n = 10): Sham, TBI, TBI with HT treatment for 3h (TBI + HT), TBI with INS (ten microliters of insulin) treatment daily for 7days (TBI + INS), and TBI with combining HT and INS (TBI + HT + INS). At the end of the 7th day, the open field and the Morris water maze tests were done for evaluation of anxiety-like behavior and memory performance. Then, after sacrificing, the brain was removed for stereological study. TBI led to an increase in the total volume of hippocampal subfields CA1 and DG and a decrease in the total number of neurons and non-neuronal cells in both sub-regions, which was associated with anxiety-like behavior and memory impairment. Although, the combination of HT and INS prevented the increased hippocampal volume and cell loss and improved behavioral performances in the TBI group. Our study suggests that the combined treatment of HT and INS could prevent increased hippocampal volume and cell loss in CA1 and DG sub-regions and consequently improve anxiety-like behaviors and memory impairment following TBI.

Nuclear parcellation and numbers of orexinergic neurons in five species of larger brained birds.

The orexinergic/hypocretinergic system, while having several roles, appears to be a key link in the balance between arousal and food intake. In birds, to date, this system has only been examined anatomically in four species, all with brains smaller than 3.5g and of limited phylogenetic range. Here, using orexin-A immunohistochemistry, we describe the distribution, morphology, and nuclear parcellation of orexinergic neurons within the hypothalami of a Congo gray and a Timneh gray parrot, a pied crow, an emu, and a common ostrich. These birds represent a broad phylogeny, with brains ranging in size from 7.85 to 26.5g. Within the hypothalami of the species studied, the orexinergic neurons were organized in two clusters, and a densely packed paraventricular hypothalamic nucleus cluster located within the medial hypothalamus (Hyp), but not contacting the ventricle, and a more loosely packed lateral hypothalamic cluster in the lateral Hyp. Stereological analysis revealed a strong correlation, using phylogenetic generalized least squares regression analyses, between brain mass and the total number of orexinergic neurons, as well as soma parameters such as volume and area. Orexinergic axonal terminals evinced two types of boutons, larger and the smaller en passant boutons. Unlike the orexinergic system in mammals, which has several variances in cluster organization, that of the birds studied, in the present and previous studies, currently shows organizational invariance, despite the differences in brain and body mass, phylogenetic relationships, and life-histories of the species studied.

Differences in enteric neuronal density in the NSE-Noggin mouse model across institutes

The enteric nervous system (ENS) is a large and complex part of the peripheral nervous system, and it is vital for gut homeostasis. To study the ENS, different hyper- and hypo-innervated model systems have been developed. The NSE-Noggin mouse model was described as one of the few models with a higher enteric neuronal density in the colon. However, in our hands NSE-Noggin mice did not present with a hyperganglionic phenotype. NSE-Noggin mice were phenotyped based on fur appearance, genotyped and DNA sequenced to demonstrate transgene and intact NSE-Noggin-IRES-EGFP construct presence, and RNA expression of Noggin was shown to be upregulated. Positive EGFP staining in the plexus of NSE-Noggin mice also confirmed Noggin protein expression. Myenteric plexus preparations of the colon were examined to quantify both the overall density of enteric neurons and the proportions of enteric neurons expressing specific subtype markers. The total number of enteric neurons in the colonic myenteric plexus of transgenic mice did not differ significantly from wild types, nor did the proportion of calbindin, calretinin, or serotonin immunoreactive myenteric neurons. Possible reasons as to why the hyperinnervated phenotype could not be observed in contrast with original studies using this mouse model are discussed, including study design, influence of microbiota, and other environmental variables.

Efficacy of coenzyme Q10 and curcumin on antioxidant enzyme activity and hippocampal alteration following exposure to cyclophosphamide in male rat

Coenzyme Q10 (KQ10) and curcumin (KUR) supplements are extensively used for their potential antioxidant, anticancer, and antiapoptotic properties. The present study investigated the neuroprotective potential of KQ10 and KUR against the side effect of cyclophosphamide (SF) (150mg/kg) on the hippocampus of male Wistar albino rats. Forty-nine 10–12 weeks old rats were randomly divided into seven groups: control, olive oil (OL), SF, KQ10, KUR, SF+KQ10, and SF+KUR. Our biochemical finding showed a significant decrease in superoxide dismutase (SOD) level in the SF group compared to the control group (p<0.05). There was also a significant reduction in the total number of the hippocampal pyramidal neurons in the CA1, CA2, and CA1-3 regions in the SF group compared to the control group (p<0.05). In the SF+KQ10 group, we found a significant increase in serum SOD level and the total number of the hippocampal pyramidal neurons in the CA1, CA2, and CA1-3 regions compared to the SF group (p<0.05). Immunohistochemical and histopathological examination exhibited noteworthy findings in the hippocampus tissues. Our findings showed that KQ10 administration significantly mitigated the hippocampal alteration caused by SF through enhancing antioxidant enzyme activity and reducing apoptosis. However, we found no protective activity of KUR on the hippocampus tissue, which may be due to its weak antioxidative activity.

Phenotyping of light-activated neurons in the mouse SCN based on the expression of FOS and EGR1.

Light-sensitive neurons are located in the ventral and central core of the suprachiasmatic nucleus (SCN), whereas stably oscillating clock neurons are found mainly in the dorsal shell. Signals between the SCN core and shell are believed to play an important role in light entrainment. Core neurons express vasoactive intestinal polypeptide (VIP), gastrin-releasing peptide (GRP), and Neuroglobin (Ngb), whereas the shell neurons express vasopressin (AVP), prokineticin 2, and the VIP type 2 (VPAC2) receptor. In rodents, light has a phase-shifting capacity at night, which induces rapid and transient expression of the EGR1 and FOS in the SCN. Methods: The present study used immunohistochemical staining of FOS, EGR1, and phenotypical markers of SCN neurons (VIP, AVP, Ngb) to identify subtypes/populations of light-responsive neurons at early night. Results: Double immunohistochemistry and cell counting were used to evaluate the number of SCN neurons expressing FOS and EGR1 in the SCN. The number of neurons expressing either EGR1 or FOS was higher than the total number of neurons co-storing EGR1 and FOS. Of the total number of light-responsive cells, 42% expressed only EGR1, 43% expressed only FOS, and 15% expressed both EGR1 and FOS. Light-responsive VIP neurons represented only 31% of all VIP neurons, and EGR1 represents the largest group of light-responsive VIP neurons (18%). VIP neurons expressing only FOS represented 1% of the total light-responsive VIP neurons. 81% of the Ngb neurons in the mouse SCN were light-responsive, and of these neurons expressing only EGR1 after light stimulation represented 44%, whereas 24% expressed FOS. Although most light-responsive neurons are found in the core of the SCN, 29% of the AVP neurons in the shell were light-responsive, of which 8% expressed EGR1, 10% expressed FOS, and 11% co-expressed both EGR1 and FOS after light stimulation. Discussion: Our analysis revealed cell-specific differences in light responsiveness between different peptidergic and Ngb-expressing neurons in different compartments of the mouse SCN, indicating that light activates diverse neuronal networks in the SCN, some of which participate in photoentrainment.

COMPARISON OF STEREOLOGY METHODS FOR ASSESSING AGE-RELATED EFFECTS ON IMMUNOSTAINED BRAIN CELLS

Abstract The primary benefit of stereology methods is quantification of well-stained biological objects in tissue sections with the ability to adjust sampling intensity to achieve desired levels of precision. The advent of hand-crafted algorithms and artificial intelligence-based deep learning (DL) provides an opportunity for more standardized collection of stereology data with enhanced efficiency and higher reproducibility compared to state-of-the-art manual stereology. We contrasted and compared the performance of four manual, semi-automatic, and fully automatic approaches for generating data for total number of Neu-N immunostained neurons in neocortex (NCTX) in the mouse brain. The gold standard for these studies was manual counts using the state-of-the-art optical fractionator method on 3-D reconstructed serial z-axis image stacks through a known tissue volume (disector stacks). To allow for direct methodological comparisons on the same images, disector stacks were automatically converted into extended depth of field (EDF) images in which all neurons in the disector stack were imaged at each cell’s maximal plane of focus. Total number of Neu-N neurons on the same EDF images were counted by a fully automatic hand-crafted method [automatic segmentation algorithm (ASA)] and a semi-automatic method [ASA counts manually corrected for false positives and negatives]. All comparison counts were done using unbiased frames and counting rules with total counts of NeuN-immunostained neurons by the optical fractionator method. The results were comparable across methods with wide variations in throughput efficiency and inter-rater agreement. These results are discussed with respect to applications to experimental studies of brain aging, neuroinflammation and neurodegenerative disease.

Loss of Aspm causes increased apoptosis of developing neural cells during mouse cerebral corticogenesis.

Abnormal spindle-like microcephaly associated (ASPM) is a causative gene of primary autosomal recessive microcephaly. Microcephaly is considered to be a consequence of a small brain, but the associated molecular mechanisms are not fully understood. In this study, we generated brain-specific Aspm knockout mice to evaluate the fetal brain phenotype and observed cortical reduction in the late stage of murine cortical development. It has been reported that the total number of neurons is regulated by the number of neural stem and progenitor cells. In the Aspm knockout mice, no apparent change was shown in the neural progenitor cell proliferation and there was no obvious effect on the number of newly generated neurons in the developing cortex. On the other hand, the knockout mice showed a constant increase in apoptosis in the cerebral cortex from the early through the late stages of cortical development. Furthermore, apoptosis occurred in the neural progenitor cells associated with DNA damage. Overall, these results suggest that apoptosis of the neural progenitor cells is involved in the thinning of the mouse cerebral cortex, due to the loss of the Aspm gene in neocortical development.

Quantitative cellular changes in multiple system atrophy brains.

Multiple system atrophy (MSA) is a neurodegenerative disorder characterised by a combined symptomatology of parkinsonism, cerebellar ataxia, autonomic failure and corticospinal dysfunction. In brains of MSA patients, the hallmark lesion is the aggregation of misfolded alpha-synuclein in oligodendrocytes. Even though the underlying pathological mechanisms remain poorly understood, the evidence suggests that alpha-synuclein aggregation in oligodendrocytes may contribute to the neurodegeneration seen in MSA. The primary aim of this review is to summarise the published stereological data on the total number of neurons and glial cell subtypes (oligodendrocytes, astrocytes and microglia) and volumes in brains from MSA patients. Thus, we include in this review exclusively the reports of unbiased quantitative data from brain regions including the neocortex, nuclei of the cerebrum, the brainstem and the cerebellum. Furthermore, we compare and discuss the stereological results in the context of imaging findings and MSA symptomatology. In general, the stereological results agree with the common neuropathological findings of neurodegeneration and gliosis in brains from MSA patients and support a major loss of nigrostriatal neurons in MSA patients with predominant parkinsonism (MSA-P), as well as olivopontocerebellar atrophy in MSA patients with predominant cerebellar ataxia (MSA-C). Surprisingly, the reports indicate only a minor loss of oligodendrocytes in sub-cortical regions of the cerebrum (glial cells not studied in the cerebellum) and negligible changes in brain volumes. In the past decades, the use of stereological methods has provided a vast amount of accurate information on cell numbers and volumes in the brains of MSA patients. Combining different techniques such as stereology and diagnostic imaging (e.g. MRI, PET and SPECT) with clinical data allows for a more detailed interdisciplinary understanding of the disease and illuminates the relationship between neuropathological changes and MSA symptomatology.

Development of the human medullary arcuate nucleus from mid-gestation to the perinatal period: A morphometric study

IntroductionDevelopment of the human medullary arcuate nucleus (AN) has not been sufficiently investigated. The present study provides morphometric data by examining the brains from preterm and perinatal infants. Materials and methodsNine brains were obtained from infants aged 21–43 postmenstrual weeks (PW). Serial celloidin sections were cut and stained using the Klüver–Barrera method. After microscopic observations, morphometric parameters [AN volume, numerical density (Nv) and total number (Nt) of neurons, and neuronal profile area (PA)] were analyzed. ResultsThe AN was found as a pair of neuronal masses on the ventral medullary surface at 21 PW. Caudally, it was ventrolateral to the pyramidal tract (PT), and rostrally, medial to the PT. In the middle, it was diminished in size or interrupted. The AN neurons were gradually enlarged with age, showing multiplicity in size and shape. The following findings had a marked asymmetry and individual variability: (1) complete or partial inclusion of the AN in the PT; (2) connection between the rostral AN and the pontine nuclei; (3) coexistence of pyknotic neurons. The AN volume increased exponentially with age, while the Nv decreased exponentially. The Nt changed along two phases (decrease–increase) after mid-gestation. The mean PA increased linearly with age. Asymmetry and/or individual variability were demonstrated in the AN volume, Nt, and mean PA. ConclusionsAsymmetry and individual variability in the AN morphology are present in fetal period. The AN may undergo neuron death and neuroblasts production in tandem after mid-gestation.

Age-dependent patterns of somatostatinergic neurons in sympathetic paravertebral ganglia

Aim. We aimed to determine the content of neurons expressing somatostatin (SST) and their colocalization with cells expressing tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in the cranial cervical ganglion (CCG) and celiac plexus in rats. Material and methods. We used 30 white male Wistar rats of six age groups (5 rats per group): newborn pups, 10-, 20-, 30-, and 60-day-old pups, and 24-month-old pups. We incubated their ganglia sections with primary antibodies against SST, NPY, and TH, as well as with secondary antibodies conjugated with fluorochromes. We evaluated the ratio between immunoreactive (IR) neurons with a visible nucleolus and excessive fluorescence and the total number of neurons, as well as the average cross-sectional area, by ImageJ software (NIH, USA).Results. SST-IR neurons were not found in the CCG. However, the immunoreaction (as granules) was revealed in most perikaryons at the celiac plexus for SST and NPY with a rather homogeneous distribution for TH. The ratio of ST-IR neurons reached 33% in pups, doubled during the first month of life, and then remained constant (70–73%). No statistically significant differences were found between the ratios of SST-IR neurons of the cranial mesenteric ganglion (CMG) and celiac ganglion (CG) for all age groups. From the moment of birth to 60 days of life, the average cross-sectional area of SST-IR neurons in the CG and CMG increased by 3.4–3.9 times and then did not change until 24 months. From the 20th day of life, the average cross-sectional area of SST-IR neurons in the CG was significantly higher than that in the CMG. All SST-IR neurons in all age groups expressed TH, while 90–94% of neurons expressed NPY. Conclusions. The content of ST-IR neurons in different sympathetic nodes is not the same: they are absent in the CCG, and their ratio and area in the celiac plexus increase during early postnatal development. This may be due to the peculiarities of innervated target organs.

Cognitive Aging and the Primate Basal Forebrain Revisited: Disproportionate GABAergic Vulnerability Revealed.

Basal forebrain (BF) projections to the hippocampus and cortex are anatomically positioned to influence a broad range of cognitive capacities that are known to decline in normal aging, including executive function and memory. Although a long history of research on neurocognitive aging has focused on the role of the cholinergic basal forebrain system, intermingled GABAergic cells are numerically as prominent and well positioned to regulate the activity of their cortical projection targets, including the hippocampus and prefrontal cortex. The effects of aging on noncholinergic BF neurons in primates, however, are largely unknown. In this study, we conducted quantitative morphometric analyses in brains from young adult (6 females, 2 males) and aged (11 females, 5 males) rhesus monkeys (Macaca mulatta) that displayed significant impairment on standard tests that require the prefrontal cortex and hippocampus. Cholinergic (ChAT+) and GABAergic (GAD67+) neurons were quantified through the full rostrocaudal extent of the BF. Total BF immunopositive neuron number (ChAT+ plus GAD67+) was significantly lower in aged monkeys compared with young, largely because of fewer GAD67+ cells. Additionally, GAD67+ neuron volume was greater selectively in aged monkeys without cognitive impairment compared with young monkeys. These findings indicate that the GABAergic component of the primate BF is disproportionally vulnerable to aging, implying a loss of inhibitory drive to cortical circuitry. Moreover, adaptive reorganization of the GABAergic circuitry may contribute to successful neurocognitive outcomes.SIGNIFICANCE STATEMENT A long history of research has confirmed the role of the basal forebrain in cognitive aging. The majority of that work has focused on BF cholinergic neurons that innervate the cortical mantle. Codistributed BF GABAergic populations are also well positioned to influence cognitive function, yet little is known about this prominent neuronal population in the aged brain. In this unprecedented quantitative comparison of both cholinergic and GABAergic BF neurons in young and aged rhesus macaques, we found that neuron number is significantly reduced in the aged BF compared with young, and that this reduction is disproportionately because of a loss of GABAergic neurons. Together, our findings encourage a new perspective on the functional organization of the primate BF in neurocognitive aging.