Differences In Neuronal Density Research Articles

Sex-specific dendritic morphology of hippocampal pyramidal neurons in the adolescent and young adult rats.

CA1 and CA3 pyramidal neurons are the major sources of hippocampal efferents. The structural features of these neurons are presumed to be involved in various normal/abnormal cognitive and emotional outcomes by influencing the pattern of synaptic inputs and neuronal signal processing. Although many studies have described hippocampal structure differences between males and females, these reports mainly focused on gross anatomical features in adult or aged models, and such distinctions on neuronal morphology and dendritic spine density during adolescence, a period of high vulnerability to neurodevelopmental disorders, have received much less attention. In this work, we analyzed dendritic architecture and density of spines in CA1 and CA3 neurons of male and female rats in early adolescence (postnatal day, PND 40) and compared them with those in late adolescence/young adulthood (PND 60). On PND 40, CA1 neurons of male rats showed more Sholl intersections and spine density in apical and basal dendrites compared to those in females. The Sholl intersections in basal dendrites of CA3 neurons were also more in males, whereas the number of apical dendrite intersections was not significantly different between sexes. In male rats, there was a notable decrease in the number of branch and terminal points in the basal dendrite of CA1 neurons of young adults when compared to their sex-matched adolescent rats. On the other hand, CA1 neurons in young adult females also showed more Sholl intersections in apical and basal dendrites compared to adolescent females. Meanwhile, the total cable length, the number of branches, and terminal points of apical dendrites in CA3 neurons also exhibited a significant reduction in young adult male rats compared to their sex-matched adolescents. In young adult rats, both apical and basal dendrites of CA3 neurons in males showed fewer intersections with Sholl circles, but there were no significant differences in dendritic spine density or count estimation between males and females. On the other hand, young adult female rats had more Sholl intersections and dendritic spine count on the basal dendrites of CA3 neurons compared to adolescent females. Although no significant sex- and age-dependent difference in neuronal density was detected in CA1 and CA3 subareas, CA3 pyramidal neurons of both male and female rats showed reduced soma area compared to adolescent rats. Our findings show that the sex differences in the dendritic structure of CA1 and CA3 neurons vary by age and also by the compartments of dendritic arbors. Such variations in the morphology of hippocampal pyramidal neurons may take part as a basis for normal cognitive and affective differences between the sexes, as well as distinct sensitivity to interfering factors and the prevalence of neuropsychological diseases.

Duration of fetoscopic spina bifida repair does not affect the central nervous system in fetal lambs

Prenatal spina bifida aperta (SBA) repair improves neurologic outcomes, yet comes with a significant risk of prematurity and uterine scar-related complications. To reduce those, different fetoscopic techniques, e.g. with varying number of ports, are being explored. This has an impact on the duration of the procedure, potentially affecting central nervous system (CNS) development. Both the condition and anesthesia can impact the CNS, particularly the hippocampus, a region vital for prospective and episodic memory. Previous animal studies have shown the potential influence of anesthesia, premature delivery, and maternal surgery during pregnancy on this area. To compare the effects of 2- versus 3-port fetoscopic SBA repair in the fetal lamb model using neuron count of the hippocampus as primary outcome. Based on the hippocampal neuron count from previous lamb experiments, we calculated that we required five animals per group to achieve a statistical power of ≥ 80%. A SBA defect was created in fetal lambs at 75 days of gestation (term: 145 days). At 100 days, fetuses underwent either a 2-port or 3-port fetoscopic repair. At 143 days, all surviving fetuses were delivered by cesarean section, anesthetized and transcardially perfused with a mixture of formaldehyde and gadolinium. Next, they underwent neonatal brain and spine MRI following which these organs were harvested for histology. Hippocampus, frontal cortex, caudate nucleus, and cerebellum samples were immunostained to identify neurons, astrocytes, microglia, and markers associated with cell proliferation, myelination, and synapses. The degree of hindbrain herniation and the ventricular diameter were measured on MRI images and volumes of relevant brain and medulla areas were segmented. Both treatment groups included five fetuses and nine unoperated littermates served as normal controls. The durations for both skin-to-skin (341 ± 31 vs 287 ± 40 min; P=0.04) and fetal surgery (183 ± 30 vs 128 ± 22; P=0.01) were longer for the 2-port than for the 3-port approach. There were no significant differences in neuron density in the hippocampus, frontal cortex and cerebellum. In the caudate nucleus, the neuron count was higher in the 2-port group (965 ± 156 vs. 767 ± 92 neurons/mm2, P=0.04). There were neither differences in proliferation, astrogliosis, synaptophysin, or myelin. The tip of the cerebellar vermis was closer to the foramen magnum in 2-port animals compared to 3-port animals (-0.72 ± 0.67 mm vs. -2.47 ± 0.91 mm, P=0.009). There were no significant differences in the ratio of hippocampus, caudate nucleus, or cerebellar volume to body weight. For the spine, no differences were noted in spine volume/body weight ratio for the lower (L1/L2), mid (L3/L4), and higher (L5/6) levels. Compared to controls, in repaired animals the cerebellar vermis tip lays closer to the foramen magnum, parietal ventricles were enlarged and medulla volumes were reduced. In the experimental spina bifida fetal lamb model, a 2-port repair took 40% longer than a 3-port repair. There was however no indication of any relevant morphologic differences in the fetal brain.

Treatment with the copper compound CuATSM has no significant effect on motor neuronal pathology in patients with ALS.

Although the orally available brain-penetrant copper compound CuATSM has demonstrated promising effects in SOD1-linked mouse models, the impact of CuATSM on disease pathology in patients with amyotrophic lateral sclerosis (ALS) remains unknown. The present study set out to address this deficit by performing the first pilot comparative analysis of ALS pathology in patients that had been administered CuATSM and riluzole [N = 6 cases composed of ALS-TDP (n = 5) and ALS-SOD1 (n = 1)] versus riluzole only [N = 6 cases composed of ALS-TDP (n = 4) and ALS-SOD1 (n = 2)]. Our results revealed no significant difference in neuron density or TDP-43 burden in the motor cortex and spinal cord of patients that had received CuATSM compared with patients that had not. In patients that had received CuATSM, p62-immunoreactive astrocytes were observed in the motor cortex and reduced Iba1 density was found in the spinal cord. However, no significant difference in measures of astrocytic activity and SOD1 immunoreactivity was found with CuATSM treatment. These findings, in this first postmortem investigation of patients with ALS in CuATSM trials, demonstrate that in contrast to that seen in preclinical models of disease, CuATSM does not significantly alleviate neuronal pathology or astrogliosis in patients with ALS.

Cholinergic Hub Vulnerability in Typical and Atypical Alzheimer’s Disease Presentations

AbstractBackgroundThe nucleus basalis of Meynert (nbM) is a critical hub that supplies cholinergic input throughout the cortex. Prior to even entorhinal cortex involvement, the nbM is observed to be vulnerable to tau pathology. Neuropathologic and neuroimaging studies provide strong evidence suggesting evaluation of nbM volume may be highly informative as an early biomarker of Alzheimer’s disease.MethodThe relevant AD biomarker literature with neuropathologic validation will be highlighted. Data will be provided from the FLorida Autopsied Multi‐Ethnic (FLAME) series of neuropathologically diagnosed AD cases. To enhance translational neuropathologic studies of the nbM, differences in neuronal density will be compared in the context of both typical and atypical (non‐memory) clinical presentations of AD using digital pathology to quantify nbM neurons in the postmortem tissue.ResultIn the FLAME series, we observed greater nbM neuronal loss in individuals with atypical clinical presentations (median=23/mm2) compared to typical AD dementia (median=26; p=0.002). Atypical clinical variants will be compared to provide a didactic learning experience, in addition to discussing the nbM’s influence on cortical tangle accumulation. Moreover, we will emphasize the paradoxical nature of greater nbM neuronal loss in young‐onset AD (median=21) compared to late‐onset AD (median=28; p<0.001).ConclusionEvaluation of cholinergic hub vulnerability may greatly inform our understanding of clinical heterogeneity in AD and provide key insight into early biomarker interpretation.

Quantitative and qualitative evaluation of the hippocampal cytoarchitecture in adult cats with regard to the pathological diagnosis of hippocampal sclerosis

Cats are known to be affected by hippocampal sclerosis, potentially causing antiseizure drug(s) resistance. In order to lay the foundation for a standardized, systematic classification and diagnosis of this pathology in cats, this prospective study aimed at evaluating normal reference values of cellular densities and the cytoarchitecture of the feline hippocampus. Three transverse sections (head, body and tail) of each left hippocampus were obtained from 17 non-epileptic cats of different brachycephalic and mesocephalic breeds and age classes (range: 3–17 years). Histological (hematoxylin and eosin, Nissl) and immunohistochemical (NeuN, GFAP) staining was performed to investigate neuron and astroglial cell populations, as well as the layer thickness of the pyramidal cell layer and granule cell layer. Significant differences in neuronal density (in CA2-CA4 and the granule cell layer) and layer thickness (in CA1-CA3 and the granule cell layer) were evidenced throughout the longitudinal hippocampal axis (p<0.05); on the other hand, the astrocyte density did not differ. Moreover, reference ranges were defined for these parameters in the pyramidal cell layer and in the granule cell layer. The findings did not differ according to breed or age. In veterinary medicine these parameters have not been evaluated in cats so far. As surgical treatment may become a therapeutic option for cats with temporal lobe epilepsy, estimating normal values of the hippocampal cytoarchitecture will help in the standardized histopathological examination of resected hippocampal specimens to reach a diagnosis of hippocampal sclerosis.

Neurochemical Profile of Enteric Neurons in the Submucosal Plexuses of Pig vs. Human Colon

The enteric nervous system (ENS), the neural network that controls gastrointestinal functions, varies among species. This is particularly evident for the submucosal plexus that is multilayered in humans but single layered and much less developed in rodents and guinea pigs often used for ENS studies. The submucosal plexus plays a major role in the control of gut functions. The pig has many homologies with humans, including a well‐developed submucosal plexus with an inner submucous plexus (ISP) near the mucosa and an outer submucous plexus (OSP) near the circularmuscle, as in humans. We have previously shown that in the adult pig colon, the density of enteric neurons is significantly higher in the ISP than OSP in ascending (AC) and descending (DC) colon, and that neurons in both plexuses contain choline acetyltransferase (ChAT) immunoreactivity (IR) and neuronal nitric oxide synthase (nNOS)‐IR, markers of the major excitatory (acetylcholine) and inhibitory (nitric oxide) transmitters with a small subpopulation containing both transmitters (Cell Tissue Res. 2021;383(2):645‐654). In this study, we compared the density and neurochemical profile of enteric neurons of the ISP and OSP in the AC and DC of the adult pig (16 Yucatan pigs, 3 F,25‐30 kg) and humans. Human specimens were obtained from 14 patients (6 F, age 48‐86) undergoing elective surgery for colon adenocarcinoma and were taken from the uninvolved resection margin. We used HuC/D (pan‐neuronal marker), ChAT, nNOS and substance P (SP) antibodies in whole mount preparations of the submucosa, confocal imaging and Imaris software for quantification. In both pig and human colon, the highest density of neurons was observed in the ISP of the AC, though the overall density of HuC/D‐IR neurons was about 4 times higher in pig vs. human. As observed in the pig colon, the density of HuC/D‐IR neurons in the ISP of the AC was significantly higher than the ISP of the DC (P&lt;0.01), whereas neuronal density in OSP of AC and DC were not significantly different. The ganglia were also smaller in human ISP and OSP throughout the colon (average ranging from 13‐28 neurons/ganglion) compared to pig where average neurons/ganglion ranged from 30‐120. The % of ChAT‐IR neurons in human (38‐44%) and pig (30‐44%) colon was comparable with no differences between ISP and OSP in AC and DC. The % of nNOS‐IR neurons in human colon was similar in the ISP and OSP of AC and DC (16‐22%), which differs from the pig, where the % of nNOS‐IR neurons in the ISP of AC was significantly lower than OSP (15% vs. 45%) and both ISP and OSP of DC (38‐42%). Overall, the density of nNOS‐IR neurons in human colon was lower compared to the pig colon. The % of SP‐IR neurons was slightly lower in human (15‐20%) vs. pig (23‐26%) colon in both plexuses in the AC and DC. There were dense SP‐IR varicosities through the ganglia in both pig and human colon. SP‐IR mostly colocalized with ChAT‐IR but was also observed in a subpopulation of nNOS‐IR and of nNOS/ChAT‐IR neurons in both human and pig colon. Overall, except for a few differences in neuronal density, there are neurochemical similarities that support the validity of the pig as pre‐clinical model for translational research to explore neuromodulation in colonic disorders in humans.

Do Hippocampal Neurons Really Count for Comorbid Depression in Patients With Mesial Temporal Lobe Epilepsy and Hippocampal Sclerosis? A Histopathological Study.

Depression is the most frequent psychiatric comorbidity seen in mesial temporal lobe epilepsy (MTLE) patients with hippocampal sclerosis (HS). Moreover, the HS is the most frequent pathological hallmark in MTLE-HS. Although there is a well-documented hippocampal volumetric reduction in imaging studies of patients with major depressive disorder, in epilepsy with comorbid depression, the true role of the hippocampus is not entirely understood. This study aimed to verify if patients with unilateral MTLE-HS and the co-occurrence of depression have differences in neuronal density of the hippocampal sectors CA1–CA4. For this purpose, we used a histopathological approach. This was a pioneering study with patients having both clinical disorders. However, we found no difference in hippocampal neuronal density when depression co-occurs in patients with epilepsy. In this series, CA1 had the lowest counting in both groups, and HS ILAE Type 1 was the most prevalent. More studies using histological assessments are needed to clarify the physiopathology of depression in MTLE-HS.

Fetally‐injected drugs for immobilization and analgesia do not modify fetal brain development in a rabbit model

During fetal surgery, fetuses receive medication (atropine-fentanyl-curare) to prevent fetal pain, movement and bradycardia. Although essential there has been no detailed review of potential side effects. Herein we aimed to assess the effects of this medication cocktail on fetal brain development in a rabbit model. Pregnant does underwent laparotomy at 28 days of gestation. Two pups of each horn were randomized to an ultrasound guided injection with medication (atropine-cisatracurium-fentanyl, as clinically used) or saline (sham). The third pup was used as control. At term, does were delivered by cesarean. Outcome measures were neonatal biometry, neuromotoric functioning and neuro-histology (neuron density, synaptic density and proliferation). Maternal vital parameters remained stable during surgery. Fetal heart rates did not differ before and after injection, and were comparable for the three groups. At birth, neonatal body weights and brain-to-body weight ratios were also comparable. Both motor and sensory neurobehavioral scores were comparable. There were no differences in neuron density or proliferation. Sham pups, had a lower synaptic density in the hippocampus as compared to the medication group, however there was no difference in the other brain areas. In the rabbit model, fetal medication does not appear to lead to short-term neurocognitive effects.

Maternal surgery during pregnancy has a transient adverse effect on the developing fetal rabbit brain

Recently, the US Food and Drug Administration called for cautious use of anesthetic drugs during pregnancy. In 0.2-2% of pregnancies, nonobstetric surgery is being performed. The consequences of anesthesia during pregnancy on fetal development remain unclear, and preclinical studies in relevant animal models may help to elucidate them. To assess the effect of maternal anesthesia and surgery during pregnancy on the developing fetal brain, using a rabbit model. This is a randomized, sham-controlled study in time-mated pregnant does at 28 days of gestation (term= 31 days), which corresponds to the end of the second trimester in humans. Anesthesia was induced in 14 does (155 pups) with propofol and maintained with 4 vol% (equivalent to 1 minimum alveolar concentration) sevoflurane for 2 hours, and a laparotomy with minimal organ manipulation was performed (surgery group). Maternal vital signs (blood pressure, heart rate, peripheral and cerebral oxygen saturation, temperature, end-tidal CO2, pH, lactate) were continuously monitored. Sham controls consisted of 7 does (74 pups) undergoing invasive hemodynamic monitoring for 2 hours without sedation. At term, does underwent cesarean delivery under ketamine-medetomidine sedation and local anesthesia. Pups either underwent motor and sensory neurologic testing followed by euthanasia at day 1 or daily neurodevelopment testing for 2 weeks and extensive neurologic assessment at 5 and 7 weeks (open field and object recognition test, T-maze, and radial-arm maze). Brains were harvested for histologic assessment of neuron density and synaptophysin expression. Blood gases and vital parameters were stable in both groups. On postnatal day 1, surgery pups had significant lower motor (25 ± 1 vs 23 ± 3; P= .004) and sensory (16 ± 2 vs 15 ± 2; P= .005) neurobehavioral scores and lower brain-to-body weight ratios (3.7% ± 0.6% vs 3.4% ± 0.6%; P= .001). This was accompanied by lower neuron density in multiple brain regions (eg, hippocampus 2617 ± 410 vs 2053 ± 492 neurons/mm2; P= .004) with lower proliferation rates and less synaptophysin expression. Furthermore, surgery pups had delayed motor development during the first week of life, for example with hopping appearing later (6 ± 5 vs 12 ± 3 days; P= .011). Yet, by 7 weeks of age, neurobehavioral impairment was limited to a reduced digging behavior, and no differences in neuron density or synaptophysin expression were seen. In rabbits, 2 hours of maternal general anesthesia and laparotomy, with minimal organ and no fetal manipulation, had a measurable impact on neonatal neurologic function and brain morphology. Pups had a slower motoric neurodevelopment, but by 7 weeks the effect became almost undetectable.

Longitudinal Characterization of mGluR5 Using 11C-ABP688 PET Imaging in the Q175 Mouse Model of Huntington Disease.

Metabotropic glutamate receptor 5 (mGluR5) represents a potential therapeutic target for Huntington disease. Using 11C-ABP688 (3-(6-methyl-pyridin-2-ylethynyl)-cyclohex-2-enone-O-11C-methyl-oxime), a noncompetitive and highly selective antagonist for mGluR5, we aimed to longitudinally characterize in vivo changes in mGluR5 by means of PET imaging in the Q175 mouse model of Huntington disease. Methods:11C-ABP688 PET imaging, followed by a CT scan, was performed on 18 heterozygous mice and 18 wild-type (WT) littermates at 3 different time points (6, 9, and 13 mo old). 11C-ABP688 nondisplaceable binding potential (BPND) was calculated for each time point in striatum and cortex using the cerebellum as the reference region. In addition, voxel-based statistical parametric mapping (SPM) analysis was performed on BPND images. Postmortem validation of mGluR5 level and neuronal density was performed on the mice at 6 mo old. Results: The 11C-ABP688 BPND of heterozygous animals was significantly reduced at all time points in the striatum (-13.1%, -13.5%, and -14.2% at 6, 9, and 13 mo, respectively; P < 0.001 for all) and in the cortex (-9.8%, -10.2%, and -10.6%, respectively; P < 0.01 for all), when compared with WT animals. Longitudinal changes in 11C-ABP688 BPND were also found in heterozygous mice, showing a reduction at 13 mo compared with 6 mo (-10.4%, P < 0.05). SPM analysis confirmed reduced BPND in heterozygous compared with WT mice, as well as a time-related decline in 11C-ABP688 binding in the striatum of heterozygous mice. Postmortem analysis confirmed a mGluR5 decrease in both striatum (-36.6%; P < 0.01) and cortex (-16.6%; P < 0.05) in heterozygous mice, whereas no difference in neuronal density was found. Conclusion: In vivo imaging of mGluR5 using 11C-ABP688 PET/CT revealed a marked reduction in ligand binding in the striatum and cortex of heterozygous mice, compared with WT mice, as well as a temporal decline. This study suggests that 11C-ABP688 PET imaging is a potential biomarker to monitor the progression of, and therapeutic strategies for, Huntington disease.

The Effects of Normal Aging on Regional Accumulation of Hyaluronan and Chondroitin Sulfate Proteoglycans in the Mouse Brain.

The brain changes in volume and composition with normal aging. Cellular components of the brain are supported by an extracellular matrix (ECM) comprised largely of hyaluronan (HA) and HA-associated members of the lectican family of chondroitin sulfate proteoglycans (CSPGs). We examined regional differences in microvascular density, neuronal and glial markers, and accumulation of HA and CSPGs in mouse brains during normal aging. The cortex, hippocampus, dentate gyrus, and cerebellum of young (4 months), middle-aged (14 months), and aged (24-26 months) brains were analyzed. Microvascular density decreased in cerebral cortex and cerebellum with age. There were no detectable differences in neuronal density. There was an increase in astrocytes in the hippocampus with aging. HA accumulation was higher in aged brain relative to young brain in the cerebral cortex and cerebellum, but not in other regions examined. In contrast, CSPGs did not change with aging in any of the brain regions examined. HA and CSPGs colocalized with a subset of neuronal cell bodies and astrocytes, and at the microvasculature. Differences in accumulation of ECM in the aging brain, in the setting of decreased microvascular density and/or increased glial activation, might contribute to age-related regional differences in vulnerability to injury and ischemia.

The Neocortex of Indian River Dolphins (Genus Platanista): Comparative, Qualitative and Quantitative Analysis

We investigated the morphology of four primary neocortical projection areas (somatomotor, somatosensory, auditory, visual) qualitatively and quantitatively in the Indian river dolphins (Platanista gangetica gangetica, P. gangetica minor) with histological and stereological methods. For comparison, we included brains of other toothed whale species. Design-based stereology was applied to the primary neocortical areas (M1, S1, A1, V1) of the Indian river dolphins and compared to those of the bottlenose dolphin with respect to layers III and V. These neocortical fields were identified using existing electrophysiological and morphological data from marine dolphins as to their topography and histological structure, including the characteristics of the neuron populations concerned. In contrast to other toothed whales, the visual area (V1) of the ‘blind' river dolphins seems to be rather small. M1 is displaced laterally and the auditory area (A1) is larger than in marine species with respect to total brain size. The layering is similar in the cortices of all the toothed whale brains investigated; a layer IV could not be identified. Cell density in layer III is always higher than in layer V. The maximal neuron density in P. gangetica gangetica is found in layer III of A1, followed by layers III in V1, S1, and M1. The cell density in layer V is at a similar level in all primary areas. There are, however, some differences in neuron density between the two subspecies of Indian river dolphins. Taken as a whole, it appears that the neocortex of platanistids exhibits a considerable expansion of the auditory field. Even more than other toothed whales, they seem to depend on their biosonar abilities for navigation, hunting, and communication in their riverine habitat.

Reduced GABA neuron density in auditory cerebral cortex of subjects with major depressive disorder

Although major depressive disorder (MDD) and schizophrenia (SZ) are closely associated with disrupted functions in frontal and limbic areas of cerebral cortex, cellular pathology has also been found in other brain areas, including primary sensory cortex. Auditory cortex is of particular interest, given the prominence of auditory hallucinations in SZ, and sensory deficits in MDD. We used stereological sampling methods in auditory cortex to look for cellular differences between MDD, SZ and non-psychiatric subjects. Additionally, as all of our MDD subjects died of suicide, we evaluated the association of suicide with our measurements by selecting a SZ sample that was divided between suicide and non-suicide subjects. Measurements were done in primary auditory cortex (area A1) and auditory association cortex (area Tpt), two areas with distinct roles in sensory processing and obvious differences in neuron density and size. In MDD, densities of GABAergic interneurons immunolabeled for calretinin (CR) and calbindin (CB) were 23–29% lower than non-psychiatric controls in both areas. Parvalbumin (PV) interneurons (counted only in area Tpt) showed a nominally smaller (16%) reduction that was not statistically significant. Total neuron and glia densities measured in Nissl stained sections did not show corresponding reductions. Analysis of suicide in the SZ sample indicated that reduced CR cell density was associated with suicide, whereas the densities of CB and other cells were not. Our results are consistent with previous studies in MDD that found altered GABA-associated markers throughout the cerebral cortex including primary sensory areas.

Distribution of Pathology in Frontal Variant Alzheimer's Disease

Atypical presentations of Alzheimer's disease (AD) have been described, including a "frontal" variant (fvAD), which presents with personality change and executive dysfunction similar to that seen in behavioral variant frontotemporal dementia (bvFTD). This clinical variation is thought to reflect the regional distribution of pathology, although few reports include autopsy confirmation. We compared three clinicopathological groups matched for age at diagnosis and disease duration; those with possible bvFTD who at autopsy had only AD (fvAD), those with typical AD clinically and pathologically, and those with typical clinical bvFTD confirmed pathologically. The density of neurons and AD-type pathology was quantified in the frontal association, occipital association, and entorhinal cortices and hippocampal CA1 regions. Immunohistochemistry for phosphorylated tau and amyloid-β deposition was used to detect neurofibrillary tangles and plaques. Of the six core clinical features of the International Consensus Criteria, disinhibition, stereotyped behaviors, and executive dysfunction were most common, occurring in five of the six fvAD patients. Other features were rare. While there was no significant difference in neuron density between groups for any of the four regions, when the ratio of frontal:occipital pathology was examined, neuronal density in fvAD was significantly less than AD but similar to bvFTD. The frontal:occipital ratio of AD-type pathology was also greater in fvAD than AD. The findings of this study suggest a frontal variant of AD exists with features that mimic bvFTD and that this reflects a differential distribution of neurodegeneration with more marked pathology in the frontal cortex compared with the occipital cortex.

Extra-cardiac neural remodeling in humans with cardiomyopathy and arrhythmias

5.1 Extra-cardiac neural remodeling in humans with cardiomyopathy and arrhythmias O.A. Ajijola, J.J. Wisco, H.W. Lambert, E.M. Stark, A. Mahajan, M.C. FIshbein, K. Shivkumar (University of California, Los Angeles, CA, USA), (West Virginia University, Morgantown, WV, USA) Background: Intra-myocardial nerve sprouting after myocardial infarction is associated with ventricular arrhythmias (VAs). Whether human stellate ganglia remodel in association with cardiac pathology was unknown. The purpose of our study was to determine whether cardiac pathology is associated with remodeling of the stellate ganglia in humans. Methods and Results: Left stellate ganglia (LSG) were collected from patients undergoing sympathetic denervation for intractable ventricular arrhythmias, and from cadavers, along with intact hearts. Clinical data on patients and cadaveric subjects were reviewed extensively. We classified ganglia from normal; scarred; and non-ischemic cardiomyopathic hearts without scar as NL (n = 3); SCAR (n = 24); and NICM (n = 7), respectively. Within LSG, we measured neuronal size, density, fibrosis, synaptic density and nerve sprouting. Nerve density and sprouting were also quantified in obtained cadaveric hearts. Mean neuronal size in NL, SCAR, and NICM groups were; 320 ± 4 μm, 372 ± 10 μm, and 435± 10 μm (p= 0.002). No significant differences in neuronal density and fibrosis were present between the groups. Synaptic density in SCAR and NICM ganglia were 57.8 ± 11.2um/mm (p= 0.039) and 44.5 ± 7.9um/mm (p= 0.084) respectively, compared to the NL, 17.8 ± 7um/mm (overall p = 0.162). There were no significant differences in LSG nerve sprouting ormyocardial nerve density between the groups. In a porcinemodel of chronic infarcts, neurochemical changes were also observed in addition to increased neuronal size. Conclusions: Neuronal hypertrophy within LSG is associated with chronic cardiomyopathy in humans. Ganglionic and myocardial nerve sprouting and nerve density were not significantly different. A porcine model recapitulates these findings, and demonstrates neurochemical rmodeling. These changes may be related to increased cardiac sympathetic signaling and VAs. Further studies are needed to determine the electrophysiologic consequences of extra-cardiac neuronal remodeling in humans. doi:10.1016/j.autneu.2013.05.030

Sources of Variability of Resting Cerebral Blood Flow in Healthy Subjects: A Study Using133Xe SPECT Measurements

Measurements of cerebral blood flow (CBF) show large variability among healthy subjects. The aim of the present study was to investigate the relative effect of established factors influencing CBF on the variability of resting CBF. We retrospectively analyzed spontaneous variability in 430 CBF measurements acquired in 152 healthy, young subjects using (133)Xe single-photon emission computed tomography. Cerebral blood flow was correlated positively with both end-tidal expiratory PCO₂ (PETCO₂) and female gender and inversely with hematocrit (Hct). Between- and within-subject CO₂ reactivity was not significantly different. Including PETCO₂, Hct and gender in the model reduced between-subject and within-subject variance by 14% and 13.5%, respectively. Within-subject variability was mainly influenced by PETCO₂ and between-subject variability mostly by Hct, whereas gender appeared to be of little added value when Hct was also accounted for. The present study confirms large between-subject variability in CBF measurements and that gender, Hct, and PETCO₂ explain only a small part of this variability. This implies that a large fraction of CBF variability may be due to unknown factors such as differences in neuron density or metabolism that could be subject for further studies.

Cell type-specific genes show striking and distinct patterns of spatial expression in the mouse brain

To characterize gene expression patterns in the regional subdivisions of the mammalian brain, we integrated spatial gene expression patterns from the Allen Brain Atlas for the adult mouse with panels of cell type-specific genes for neurons, astrocytes, and oligodendrocytes from previously published transcriptome profiling experiments. We found that the combined spatial expression patterns of 170 neuron-specific transcripts revealed strikingly clear and symmetrical signatures for most of the brain's major subdivisions. Moreover, the brain expression spatial signatures correspond to anatomical structures and may even reflect developmental ontogeny. Spatial expression profiles of astrocyte- and oligodendrocyte-specific genes also revealed regional differences; these defined fewer regions and were less distinct but still symmetrical in the coronal plane. Follow-up analysis suggested that region-based clustering of neuron-specific genes was related to (i) a combination of individual genes with restricted expression patterns, (ii) region-specific differences in the relative expression of functional groups of genes, and (iii) regional differences in neuronal density. Products from some of these neuron-specific genes are present in peripheral blood, raising the possibility that they could reflect the activities of disease- or injury-perturbed networks and collectively function as biomarkers for clinical disease diagnostics.

Extracardiac Neural Remodeling in Humans With Cardiomyopathy

Intramyocardial nerve sprouting after myocardial infarction is associated with ventricular arrhythmias. Whether human stellate ganglia remodel in association with cardiac pathology is unknown. The purpose of this study was to determine whether cardiac pathology is associated with remodeling of the stellate ganglia in humans. Left stellate ganglia were collected from patients undergoing sympathetic denervation for intractable ventricular arrhythmias and from cadavers, along with intact hearts. Clinical data on patients and cadaveric subjects were reviewed. We classified ganglia from normal, scarred, and nonischemic cardiomyopathic hearts without scar as NL (n=3), SCAR (n=24), and NICM (n=7), respectively. Within left stellate ganglia, neuronal size, density, fibrosis, synaptic density, and nerve sprouting were determined. Nerve density and sprouting were also quantified in cadaveric hearts. Mean neuronal size in normal, scarred, and nonischemic cardiomyopathic hearts without scar groups were 320 ± 4 μm(2), 372 ± 10 μm(2), and 435 ± 10 μm(2) (P=0.002), respectively. No significant differences in neuronal density and fibrosis were present between the groups. Synaptic density in ganglia from SCAR and NICM groups were 57.8 ± 11.2 μm(2)/mm(2) (P=0.084) and 44.5 ± 7.9 μm(2)/mm(2) (P=0.039), respectively, compared with the normal group, 17.8 ± 7 μm(2)/mm(2) (overall P=0.162). There were no significant differences in left stellate ganglia nerve sprouting or myocardial nerve density between the groups. Neuronal hypertrophy within left stellate ganglia is associated with chronic cardiomyopathy in humans. Ganglionic and myocardial nerve sprouting and nerve density were not significantly different. These changes may be related to increased cardiac sympathetic signaling and ventricular arrhythmias. Further studies are needed to determine the electrophysiological consequences of extracardiac neuronal remodeling in humans.

Low distribution of synaptic vesicle protein 2A and synaptotagimin-1 in the cerebral cortex and hippocampus of spontaneously epileptic rats exhibiting both tonic convulsion and absence seizure

The spontaneously epileptic rat (SER) is a double mutant (zi/zi, tm/tm) which begins to exhibit tonic convulsions and absence seizures after 6weeks of age, and repetitive tonic seizures over time induce sclerosis-like changes in SER hippocampus with high brain-derived neurotrophic factor (BDNF) expression. Levetiracetam, which binds to synaptic vesicle protein 2A (SV2A), inhibited both tonic convulsions and absence seizures in SERs. We studied SER brains histologically and immunohistochemically after verification by electroencephalography (EEG), as SERs exhibit seizure-related alterations in the cerebral cortex and hippocampus. SERs did not show interictal abnormal spikes and slow waves typical of focal epilepsy or symptomatic generalized epilepsy. The difference in neuronal density of the cerebral cortex was insignificant between SER and Wistar rats, and apoptotic neurons did not appear in SERs. BDNF distributions portrayed higher values in the entorhinal and piriform cortices which would relate with hippocampal sclerosis-like changes. Similar synaptophysin expression in the cerebral cortex and hippocampus was found in both animals. Low and diffuse SV2A distribution portrayed in the cerebral cortex and hippocampus of SERs was significantly less than that of all cerebral lobes and inner molecular layer (IML) of the dentate gyrus (DG) of Wistar rats. The extent of low SV2A expression/distribution in SERs was particularly remarkable in the frontal (51% of control) and entorhinal cortices (47%). Lower synaptotagmin-1 expression (vs Wistar rats) was located in the frontal (31%), piriform (13%) and entorhinal (39%) cortices, and IML of the DG (38%) in SER. Focal low distribution of synaptotagmin-1 accompanying low SV2A expression may contribute to epileptogenesis and seizure propagation in SER.

Hippocampal Neuronal Atrophy and Cognitive Function in Delayed Poststroke and Aging-Related Dementias

We have previously shown delayed poststroke dementia in elderly (≥75 years old) stroke survivors is associated with medial temporal lobe atrophy; however, the basis of the structural and functional changes is unknown. Using 3-dimensional stereological methods, we quantified hippocampal pyramidal neuronal volumes and densities in a total of 95 postmortem samples from demented and nondemented poststroke survivors within our prospective Cognitive Function after Stroke study and subjects pathologically diagnosed with vascular dementia, Alzheimer disease, and mixed Alzheimer disease and vascular dementia syndrome. Hippocampal CA1 but not CA2 subfield neuron density was affected in poststroke, Alzheimer disease, vascular dementia, and mixed dementia groups relative to control subjects (P<0.05). Neuronal volume was reduced in the poststroke dementia relative to poststroke nondemented group in both CA1 and CA2, although there were no apparent differences in neuronal density. Poststroke nondemented neuronal volumes were similar to control subjects but greater than in all dementias (P<0.05). Neuronal volumes positively correlated with global cognitive function and memory function in both CA1 and CA2 in poststroke subjects (P<0.01). Degrees of neuronal atrophy and loss were similar in the poststroke dementia and vascular dementia groups. However, in the entorhinal cortex layer V, neuronal volumes were only impaired in the mixed and Alzheimer disease groups (P<0.05). Our results suggest hippocampal neuronal atrophy is an important substrate for dementia in both cerebrovascular and neurodegenerative disease.