Design-based stereology in neuroscience

Erythropoietin reduces neuronal cell death and hyperalgesia induced by peripheral inflammatory pain in neonatal rats

Painful stimuli during neonatal stage may affect brain development and contribute to abnormal behaviors in adulthood. Very few specific therapies are available for this developmental disorder. A better understanding of the mechanisms and consequences of painful stimuli during the neonatal period is essential for the development of effective therapies. In this study, we examined brain reactions in a neonatal rat model of peripheral inflammatory pain. We focused on the inflammatory insult-induced brain responses and delayed changes in behavior and pain sensation. Postnatal day 3 pups received formalin injections into the paws once a day for 3 days. The insult induced dysregulation of several inflammatory factors in the brain and caused selective neuronal cell death in the cortex, hippocampus and hypothalamus. On postnatal day 21, rats that received the inflammatory nociceptive insult exhibited increased local cerebral blood flow in the somatosensory cortex, hyperalgesia, and decreased exploratory behaviors. Based on these observations, we tested recombinant human erythropoietin (rhEPO) as a potential treatment to prevent the inflammatory pain-induced changes. rhEPO treatment (5,000 U/kg/day, i.p.), coupled to formalin injections, ameliorated neuronal cell death and normalized the inflammatory response. Rats that received formalin plus rhEPO exhibited normal levels of cerebral blood flow, pain sensitivity and exploratory behavior. Treatment with rhEPO also restored normal brain and body weights that were reduced in the formalin group. These data suggest that severe inflammatory pain has adverse effects on brain development and rhEPO may be a possible therapy for the prevention and treatment of this developmental disorder.

Early behavioral changes and quantitative analysis of neuropathological features in murine prion disease: stereological analysis in the albino Swiss mice model

Behavioral and neuropathological changes have been widely investigated in murine prion disease but stereological based unbiased estimates of key neuropathological features have not been carried out. After injections of ME7 infected (ME7) or normal brain homogenates (NBH) into dorsal CA1 of albino Swiss mice and C57BL6, we assessed behavioral changes on hippocampal-dependent tasks. We also estimated by optical fractionator at 15 and 18 weeks post-injections (w.p.i.) the total number of neurons, reactive astrocytes, activated microglia and perineuronal nets (PN) in the polymorphic layer of dentate gyrus (PolDG), CA1 and septum in albino Swiss mice. On average, early behavioral changes in albino Swiss mice start four weeks later than in C57BL6. Cluster and discriminant analysis of behavioral data in albino Swiss mice revealed that four of nine subjects start to change their behavior at 12 w.p.i. and reach terminal stage at 22 w.p.i and the remaining subjects start at 22 w.p.i. and reach terminal stage at 26 w.p.i. Biotinylated dextran-amine BDA-tracer experiments in mossy fiber pathway confirmed axonal degeneration, and stereological data showed that early astrocytosis, microgliosis and reduction in the perineuronal nets are independent of a change in the number of neuronal cell bodies. Statistical analysis revealed that the septal region had greater levels of neuroinflammation and extracellular matrix damage than CA1. This stereological and multivariate analysis at early stages of disease in an outbred model of prion disease provided new insights connecting behavioral changes and neuroinflammation and seems to be important to understand the mechanisms of prion disease progression.

Effects of Human Alpha-Synuclein A53T-A30P Mutations on SVZ and Local Olfactory Bulb Cell Proliferation in a Transgenic Rat Model of Parkinson Disease

A transgenic Sprague Dawley rat bearing the A30P and A53T α-synuclein (α-syn) human mutations under the control of the tyrosine hydroxylase promoter was generated in order to get a better understanding of the role of the human α-syn mutations on the neuropathological events involved in the progression of the Parkinson's disease (PD). This rat displayed olfactory deficits in the absence of motor impairments as observed in most early PD cases. In order to investigate the role of the mutated α-syn on cell proliferation, we focused on the subventricular zone (SVZ) and the olfactory bulbs (OB) as a change of the proliferation could affect OB function. The effect on OB dopaminergic innervation was investigated. The human α-syn co-localized in TH-positive OB neurons. No human α-syn was visualized in the SVZ. A significant increase in resident cell proliferation in the glomerular but not in the granular layers of the OB and in the SVZ was observed. TH innervation was significantly increased within the glomerular layer without an increase in the size of the glomeruli. Our rat could be a good model to investigate the role of human mutated α-syn on the development of olfactory deficits.

Accelerated human mutant tau aggregation by knocking out murine tau in a transgenic mouse model

Many models of human tauopathies have been generated in mice by expression of a human mutant tau with maintained expression of mouse endogenous tau. Because murine tau might interfere with the toxic effects of human mutant tau, we generated a model in which a pathogenic human tau protein is expressed in the absence of wild-type tau protein, with the aim of facilitating the study of the pathogenic role of the mutant tau and to reproduce more faithfully a human tauopathy. The Tg30 line is a tau transgenic mouse model overexpressing human 1N4R double-mutant tau (P301S and G272V) that develops Alzheimer's disease-like neurofibrillary tangles in an age-dependent manner. By crossing Tg30 mice with mice invalidated for their endogenous tau gene, we obtained Tg30xtau(-/-) mice that express only exogenous human double-mutant 1N4R tau. Although Tg30xtau(-/-) mice express less tau protein compared with Tg30, they exhibit signs of decreased survival, increased proportion of sarkosyl-insoluble tau in the brain and in the spinal cord, increased number of Gallyas-positive neurofibrillary tangles in the hippocampus, increased number of inclusions in the spinal cord, and a more severe motor phenotype. Deletion of murine tau accelerated tau aggregation during aging of this mutant tau transgenic model, suggesting that murine tau could interfere with the development of tau pathology in transgenic models of human tauopathies.

Brazilian psychiatric brain bank: a new contribution tool to network studies

There is an urgent need for expanding the number of brain banks serving psychiatric research. We describe here the Psychiatric Disorders arm of the Brain Bank of the Brazilian Aging Brain Study Group (Psy-BBBABSG), which is focused in bipolar disorder (BD) and obsessive compulsive disorder (OCD). Our protocol was designed to minimize limitations faced by previous initiatives, and to enable design-based neurostereological analyses. The Psy-BBBABSG first milestone is the collection of 10 brains each of BD and OCD patients, and matched controls. The brains are sourced from a population-based autopsy service. The clinical and psychiatric assessments were done by an expert team including psychiatrists, through an informant. One hemisphere was perfused-fixed to render an optimal fixation for conducting neurostereological studies. The other hemisphere was comprehensively dissected and frozen for molecular studies. In 20 months, we collected 36 brains. A final report was completed for 14 cases: 3 BDs, 4 major depressive disorders, 1 substance use disorder, 1 mood disorder NOS, 3 obsessive compulsive spectrum symptoms, 1 OCD and 1 schizophrenia. The majority were male (64%), and the average age at death was 67.2 ± 9.0 years. The average postmortem interval was 16 h. Three matched controls were collected. The pilot stage confirmed that the protocols are well fitted to reach our goals. Our unique autopsy source makes possible to collect a fairly number of high quality cases in a short time. Such a collection offers an additional to the international research community to advance the understanding on neuropsychiatric diseases.

Caloric restriction attenuates age-related changes of DNA methyltransferase 3a in mouse hippocampus

Recent studies have suggested that DNA methylation is implicated in age-related changes in gene expression as well as in cognition. DNA methyltransferase 3a (Dnmt3a), which catalyzes DNA methylation, is essential for memory formation and underlying changes in neuronal and synaptic plasticity. Because caloric restriction (CR) and upregulation of antioxidants have been suggested as strategies to attenuate age-related alterations in the brain, we hypothesized that both a diet restricted in calories and transgenic overexpression of normal human Cu/Zn superoxide dismutase 1 (SOD) attenuate age-related changes in Dnmt3a in the aging mouse hippocampus. For this purpose, we performed qualitative and quantitative analyses of Dnmt3a-immunoreactivity (IR) for the hippocampal dentate gyrus (DG), CA3 and CA1-2 regions in 12- and 24-month-old mice from 4 groups, i.e. (1) wild-type (WT) mice on a control diet (WT-CD), (2) SOD-CD mice, (3) WT mice on CR (WT-CR), and (4) SOD-CR. Qualitative analyses revealed two types of Dnmt3a immunoreactive cells: type I cells--present throughout all hippocampal cell layers showing moderate levels of nuclear Dnmt3a-IR, and type II cells--a subpopulation of hippocampal cells showing very intense nuclear Dnmt3a-IR, and colocalization with Bromodeoxyuridine. Quantitative analyses indicated that the age-related increase in Dnmt3a-IR within the CA3 and CA1-2 in type I cells was attenuated by CR, but not by SOD overexpression. In contrast, the density of type II Dnmt3a immunoreactive cells showed an age-related reduction, without significant effects of both CR and SOD. These changes in Dnmt3a levels in the mouse hippocampus may have a significant impact on gene expression and associated cognitive functioning.

Age-related changes of neuron numbers in the frontal cortex of a transgenic mouse model of Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disorder, characterized by amyloid plaque accumulation, intracellular tangles and neuronal loss in selective brain regions. The frontal cortex, important for executive functioning, is one of the regions that are affected. Here, we investigated the neurodegenerative effects of mutant human amyloid precursor protein (APP) and presenilin 1 (PS1) on frontal cortex neurons in APP/PS1KI mice, a transgenic mouse model of AD, expressing two mutations in the human APP, as well as two human PS1 mutations knocked-in into the mouse PS1 gene in a homozygous (ho) manner. Although the hippocampus is significantly affected in these mice, very little is known about the effects of these mutations on selective neuronal populations and plaque load in the frontal cortex. In this study, cytoarchitectural changes were characterized using high precision design-based stereology to evaluate plaque load, total neuron numbers, as well as total numbers of parvalbumin- (PV) and calretinin- (CR) immunoreactive (ir) neurons in the frontal cortex of 2- and 10-month-old APP/PS1KI mice. The frontal cortex was divided into two subfields: layers II–IV and layers V–VI, the latter of which showed substantially more extracellular amyloid-beta aggregates. We found a 34% neuron loss in layers V–VI in the frontal cortex of 10-month-old APP/PS1KI mice compared to 2-month-old, while there was no change in PV- and CR-ir neurons in these mice. In addition, the plaque load in layers V–VI of 10-month-old APP/PS1KI mice was only 11% and did not fully account for the extent of neuronal loss. Interestingly, an increase was found in the total number of PV-ir neurons in all frontal cortical layers of single transgenic APP mice and in layers II–IV of single transgenic PS1ho mice between 2 and 10 months of age. In conclusion, the APP/PS1KI mice provide novel insights into the regional selective vulnerability in the frontal cortex during AD that, together with previous findings in the hippocampus, are remarkably similar to the human situation.

A novel animal model of hippocampal cognitive deficits, slow neurodegeneration, and neuroregeneration

Long-term adrenalectomy (ADX) results in an extensive and specific loss of dentate gyrus granule cells in the hippocampus of adult rats. This loss of granule cells extends over a period of weeks to months and ultimately results in cognitive deficits revealed in a number of tasks that depend on intact hippocampal function. The gradual nature of ADX-induced cell death and the ensuing deficits in cognition resemble in some important respects a variety of pathological conditions in humans. Here, we characterize behavioural and cellular processes, including adult neurogenesis, in the rat ADX model. We also provide experimental evidence for a neurogenic treatment strategy by which the lost hippocampal cells may be replaced, with the goal of functional recovery in mind.

Genetic-based, differential susceptibility to paraquat neurotoxicity in mice

Paraquat (PQ) is an herbicide used extensively in agriculture. This agent is also suspected to be a risk factor for Parkinson's disease (PD) by harming nigro-striatal dopamine neurons. There is likely, genetic-based, individual variability in susceptibility to PQ neurotoxicity related PD. In this study, we measured the delivery of PQ to the brain after three weekly injections of PQ at 5 mg kg(-1), PQ-related neural toxicity after three weekly injections of PQ at 1 mg kg(-1)or 5 mg kg(-1), PQ-related iron accumulation and PQ-related gene expression in midbrain of DBA/2J (D2) and C57BL/6J (B6) inbred mouse strains after a single injection of PQ at 15 mg kg(-1) and 10 mg kg(-1), respectively. Results showed that compared to controls, PQ-treated B6 mice lost greater numbers of dopaminergic neurons in the substantia nigra pars compacta than D2 mice; however, distribution of PQ to the midbrain was equal between the strains. PQ also significantly increased iron concentration in the midbrain of B6 but not D2 mice. Microarray analysis of the ventral midbrain showed greater PQ-induced changes in gene expression in B6 compared to D2 mice. This is the first study to report genetically-based differences in susceptibility to PQ neurotoxicity and to understanding individual differences in vulnerability to PQ neurotoxicity and its relation to PD in humans.

Nuclear factor-kappa B activity regulates brain expression of P-glycoprotein in the kainic acid-induced seizure rats

This study was aimed to investigate the effect of NF-κB activity on the seizure susceptibility, brain damage, and P-gp expression in kainic acid- (KA-) induced seizure rats. Male SD rats were divided into saline control group (NS group), KA induced epilepsy group (EP group), and epilepsy group intervened with NF-κB inhibitor-pyrrolidine dithiocarbamate salt (PDTC group) or with dexamethasone (DEX group). No seizures were observed in the rats of NS group. Compared with NS group, increased P-gp expression and NF-κB activation in the rat brain of the EP group were observed after KA micro-injection. Both PDTC and DEX pre-treatment significantly increased the latency to grade III or V seizure onset compared to EP group but failed to show neuron-protective effect as the number of survival neurons didn't significantly differ from that in EP group. Furthermore, PDTC pre-treatment significantly decreased P-gp expression along with NF-κB activation in the hippocampus CA3 area and amygdala complex of rats compared with the EP group, implying that NF-κB activation involved in the seizure susceptibility and seizure induced brain P-gp over-expression. Additionally, DEX pre-treatment only decreased P-gp expression level without inhibition of NF-κB activation, suggesting NF-κB independent pathway may also participate in regulating seizure induced P-gp over-expression.

Effects of intra-uterine and early extra-uterine malnutrition on seizure threshold and hippocampal morphometry of pup rats

We evaluate the influence of different malnutrition paradigms (intra-uterine × extra-uterine) in body and brain weight, in seizure threshold and in hippocampus morphometry, in developing rats. Intra-uterine malnutrition model consisted in reduction by half of the ration offered to pregnant female; extra-uterine malnutrition consisted of progressive limitation of lactation, from P2 to P15. Seizure induction was accomplished by exposure to flurothyl, at P15. At the same day animals were sacrificed. Morphometric analysis was based on hippocampal pyramidal and granular cells estimate number, through volume calculation and cellular density. Extra-uterine malnutrition significantly reduced pups body and brain weight, seizure threshold and neuronal number in CA4 region only. Intra-uterine malnutrition reduced neuronal number in CA2, CA4 and DG regions regarding well-nourished and extra-uterine malnourished animals. In CA3, CA4 and dentate gyrus, a significant cell increase was observed in groups exposed to seizures, regarding similar control groups.

Efficient and stable transduction of dopaminergic neurons in rat substantia nigra by rAAV 2/1, 2/2, 2/5, 2/6.2, 2/7, 2/8 and 2/9

Dysfunction of the nigrostriatal system is the major cause of Parkinson's disease (PD). This brain region is therefore an important target for gene delivery aiming at disease modeling and gene therapy. Recombinant adeno-associated viral (rAAV) vectors have been developed as efficient vehicles for gene transfer into the central nervous system. Recently, several serotypes have been described, with varying tropism for brain transduction. In light of the further development of a viral vector-mediated rat model for PD, we performed a comprehensive comparison of the transduction and tropism for dopaminergic neurons (DNs) in the adult Wistar rat substantia nigra (SN) of seven rAAV vector serotypes (rAAV 2/1, 2/2, 2/5, 2/6.2, 2/7, 2/8 and 2/9). All vectors were normalized by titer and volume, and stereotactically injected into the SN. Gene expression was assessed non-invasively and quantitatively in vivo by bioluminescence imaging at 2 and 5 weeks after injection, and was found to be stable over time. Immunohistochemistry at 6 weeks following injection revealed the most widespread enhanced green fluorescence protein expression and the highest number of positive nigral cells using rAAV 2/7, 2/9 and 2/1. The area transduced by rAAV 2/8 was smaller, but nevertheless almost equal numbers of nigral cells were targeted. Detailed confocal analysis revealed that serotype 2/7, 2/9, 2/1 and 2/8 transduced at least 70% of the DNs. In conclusion, these results show that various rAAV serotypes efficiently transduce nigral DNs, but significant differences in transgene expression pattern and level were observed.

Changes in cholinergic amacrine cells after rodent anterior ischemic optic neuropathy (rAION)

PURPOSE

Displaced cholinergic amacrine cell neurons comprise a significant fraction of the retinal ganglion cell (RGC) layer. Rodent anterior ischemic optic neuropathy (rAION) is an optic nerve infarct, which results in RGC loss in mice. The goal was to determine whether rAION produces changes in amacrine cell neurons.

METHODS

rAION was generated in transgenic mice carrying a cyan fluorescent reporter protein (CFP) gene linked to the Thy-1 promoter, which expresses CFP in RGCs. rAION was induced with standard parameters. Retinas were examined pre-and post-induction by retinal fundus microscopy. rAION induction severity was scored by changes in retinal transparency and RGC loss. Cholinergic amacrine cells were identified via choline acetyltransferase (ChAT) immunohistochemistry. ChAT and CFP expression was evaluated in flat-mounted retinas examined by confocal microscopy and western analysis.

RESULTS

Moderate rAION induction levels (defined as early retention of retinal transparency and <70% RGC loss) did not alter amacrine cell numbers in the RGC layer, but changed the relative levels of ChAT expression by immunohistochemistry. No changes in total ChAT protein were seen. Severe rAION induction (defined as loss of retinal transparency and >70% RGC loss) resulted in a trend toward amacrine cell loss and decreased ChAT protein levels.

CONCLUSIONS

There is wide disparity in mouse rAION induction levels using standardized parameters. Moderate rAION induction levels without direct retinal compromise produces isolated RGC loss, with displaced amacrine cell changes likely due to changes in RGC-amacrine communication. Severe rAION induction results in both RGC and amacrine cell loss, possibly due to intra-retinal ischemic changes.

Stereological approaches to identifying neuropathology in psychosis

The challenges involved in identifying the neuropathological substrates of the clinical syndrome recognized as schizophrenia are well known. Stereological sampling provides a means to obtain accurate and precise quantitative estimates of components of neural circuits and thus offers promise of an enhanced capacity to detect subtle alterations in brain structure associated with schizophrenia. In this review, we 1) consider the importance and rationale for robust quantitative measures of brain abnormalities in postmortem studies of schizophrenia; 2) provide a brief overview of stereological methods for obtaining such measures; 3) discuss the methodological details that should be reported to document the robustness of a stereological study; 4) given the constraints of postmortem human studies, suggest how to approach the limitations of less robust designs; and 5) present an overview of methodologically sound stereological estimates from postmortem studies of schizophrenia.

Anterior cingulate synapses in prefrontal areas 10 and 46 suggest differential influence in cognitive control

Dorsolateral prefrontal areas 46 and 10 are involved in distinct aspects of cognition. Area 46 has a key role in working memory tasks, and frontopolar area 10 is recruited in complex multitask operations. Both areas are innervated by the anterior cingulate cortex (ACC), a region associated with emotions and memory but is also important for attentional control through unknown synaptic mechanisms. Here, we found that in rhesus monkeys (Macaca mulatta) most axon terminals labeled from tracers injected into ACC area 32 innervated spines of presumed excitatory neurons, but ∼20-30% formed mostly large synapses with dendritic shafts of presumed inhibitory neurons in the upper layers (I-IIIa) of dorsolateral areas 10, 46, and 9. Moreover, area 32 terminals targeted preferentially calbindin and, to a lesser extent, calretinin neurons, which are thought to be inhibitory neurons that modulate the gain of task-relevant activity during working memory tasks. Area 46 was distinguished as a recipient of more (by ∼40%) area 32 synapses on putative inhibitory neurons. Area 10 stood apart as recipient of significantly larger (by ∼40% in volume) area 32 terminals on spines of putative excitatory neurons. These synaptic specializations suggest that area 32 has complementary roles, potentially enhancing inhibition in area 46 and strengthening excitation in area 10, which may help direct attention to new tasks while temporarily holding in memory another task.

The neurotoxicity of DOPAL: behavioral and stereological evidence for its role in Parkinson disease pathogenesis

BACKGROUND

The etiology of Parkinson disease (PD) has yet to be fully elucidated. We examined the consequences of injections of 3,4-dihydroxyphenylacetaldehyde (DOPAL), a toxic metabolite of dopamine, into the substantia nigra of rats on motor behavior and neuronal survival.

METHODS/PRINCIPAL FINDINGS

A total of 800 nl/rat of DOPAL (1 µg/200 nl) was injected stereotaxically into the substantia nigra over three sites while control animals received similar injections of phosphate buffered saline. Rotational behavior of these rats was analyzed, optical density of striatal tyrosine hydroxylase was calculated, and unbiased stereological counts of the substantia nigra were made. The rats showed significant rotational asymmetry ipsilateral to the lesion, supporting disruption of dopaminergic nigrostriatal projections. Such disruption was verified since the density of striatal tyrosine hydroxylase decreased significantly (p<0.001) on the side ipsilateral to the DOPAL injections when compared to the non-injected side. Stereological counts of neurons stained for Nissl in pars compacta of the substantia nigra significantly decreased (p<0.001) from control values, while counts of those in pars reticulata were unchanged after DOPAL injections. Counts of neurons immunostained for tyrosine hydroxylase also showed a significant (p=0.032) loss of dopaminergic neurons. In spite of significant loss of dopaminergic neurons, DOPAL injections did not induce significant glial reaction in the substantia nigra.

CONCLUSIONS

The present study provides the first in vivo quantification of substantia nigra pars compacta neuronal loss after injection of the endogenous toxin DOPAL. The results demonstrate that injections of DOPAL selectively kills SN DA neurons, suggests loss of striatal DA terminals, spares non-dopaminergic neurons of the pars reticulata, and triggers a behavioral phenotype (rotational asymmetry) consistent with other PD animal models. This study supports the "catecholaldehyde hypothesis" as an important link for the etiology of sporadic PD.

Synergistic effects of age and stress in a rodent model of stroke

Ageing and stress represent critical influences on stroke risk and outcome. These variables are intricately linked, as ageing is frequently associated with gradual dysregulation of the hypothalamic-pituitary-adrenal axis. This study determined the effects of stress on motor function in aged rats, and explored possible interactions of age and stress on motor recovery following stroke in a rat model. Young adult (4 months) and aged (18 months) male Wistar rats were tested in skilled and non-skilled movement before and after focal ischemia in motor cortex. One group of each age received restraint stress starting seven days pre-lesion until three weeks post-lesion. Aged rats were less mobile and stress further diminished their overall exploratory activity. Aged rats were also less proficient in motor skill acquisition and slower to improve after lesion. Stress diminished post-lesion improvement and prevented recovery of endpoint measures. The larger functional loss in aged rats vs. young rats was accompanied by greater damage of cortical tissue and persistent elevations in corticosterone levels. The behavioural and physiological measures suggest limited ability of aged animals to adapt to chronic stress. These findings show that age or stress alone can modulate motor performance but may have greater influence by synergistically affecting stroke recovery.

N-acetylcysteine prevents loss of dopaminergic neurons in the EAAC1-/- mouse

OBJECTIVE

Dopaminergic neuronal death in Parkinson's disease (PD) is accompanied by oxidative stress and preceded by glutathione depletion. The development of disease-modifying therapies for PD has been hindered by a paucity of animal models that mimic these features and demonstrate an age-related progression. The EAAC1(-/-) mouse may be useful in this regard, because EAAC1(-/-) mouse neurons have impaired neuronal cysteine uptake, resulting in reduced neuronal glutathione content and chronic oxidative stress. Here we aimed to (1) characterize the age-related changes in nigral dopaminergic neurons in the EAAC1(-/-) mouse, and (2) use the EAAC1(-/-) mouse to evaluate N-acetylcysteine, a membrane-permeable cysteine pro-drug, as a potential disease-modifying intervention for PD.

METHODS

Wild-type mice, EAAC1(-/-) mice, and EAAC1(-/-) mice chronically treated with N-acetylcysteine were evaluated at serial time points for evidence of oxidative stress, dopaminergic cell death, and motor abnormalities.

RESULTS

EAAC1(-/-) mice showed age-dependent loss of dopaminergic neurons in the substantia nigra pars compacta, with more than 40% of these neurons lost by age 12 months. This neuronal loss was accompanied by increased nitrotyrosine formation, nitrosylated α-synuclein, and microglial activation. These changes were substantially reduced in mice that received N-acetylcysteine.

INTERPRETATION

These findings suggest that the EAAC1(-/-) mouse may be a useful model of the chronic neuronal oxidative stress that occurs in PD. The salutary effects of N-acetylcysteine in this mouse model provide an impetus for clinical evaluation of glutathione repletion in PD.

Altered expression of parvalbumin and calbindin in interneurons within the primary visual cortex of neonatal enucleated hamsters

In the present study, we tested the hypothesis that the expression of calcium binding proteins (CaBPs), parvalbumin (PV), calretinin (CR) and calbindin (CB), is dependent upon sensory experience as emphasized in visual deprivation and deafferentation studies. The expression of CaBPs was studied in interneurons within the primary and extrastriate visual cortices (V1, V2M, V2L) and auditory cortex (AC) of adult hamsters enucleated at birth. The effects of enucleation were mainly confined to area V1 where there was a significant volume reduction (26%) and changes in the laminar distribution of PV and CB immunoreactive (IR) cells. The density of PV-IR cell bodies was significantly increased in layer IV and reduced in layer V. Moreover, the density of CB-IR neurons was inferior in layer V of V1 in enucleated hamsters (EH) compared to controls. These results suggest that some features of the laminar distribution of specific CaBPs, in primary sensory cortices, are dependent upon or modulated by sensory input.

Measurements of neuron soma size and density in rat dorsal striatum, nucleus accumbens core and nucleus accumbens shell: differences between striatal region and brain hemisphere, but not sex

Both hemispheric bias and sex differences exist in striatal-mediated behaviors and pathologies. The extent to which these dimorphisms can be attributed to an underlying neuroanatomical difference is unclear. We therefore quantified neuron soma size and density in the dorsal striatum (CPu) as well as the core (AcbC) and shell (AcbS) subregions of the nucleus accumbens to determine whether these anatomical measurements differ by region, hemisphere, or sex in adult Sprague-Dawley rats. Neuron soma size was larger in the CPu than the AcbC or AcbS. Neuron density was greatest in the AcbS, intermediate in the AcbC, and least dense in the CPu. CPu neuron density was greater in the left in comparison to the right hemisphere. No attribute was sexually dimorphic. These results provide the first evidence that hemispheric bias in the striatum and striatal-mediated behaviors can be attributed to a lateralization in neuronal density within the CPu. In contrast, sexual dimorphisms appear mediated by factors other than gross anatomical differences.

Induction of striatal neurogenesis and generation of region-specific functional mature neurons after ischemia by growth factors

Object

The capacity to replace lost neurons after insults is retained by several regions of adult mammalian brains. However, it is unknown how many neurons actually replace and mature into region-specific functional neurons to restore lost brain function. In this paper, the authors asked whether neuronal regeneration could be achieved efficaciously by growth factor treatment using a global ischemia model in rats, and they analyzed neuronal long-term maturation processes.

Methods

Rat global ischemia using a modified 4-vessel occlusion model was used to induce consistent ischemic neuronal injury in the dorsolateral striatum. To potentiate the proliferative response of neural progenitors, epidermal growth factor and fibroblast growth factor–2 were infused intraventricularly for 7 days from Day 2 after ischemia. Six weeks after ischemia, the number of neurons was counted in the defined dorsolateral striatum. To label the proliferating neural progenitors for tracing studies, 5-bromo-2′-deoxyuridine (BrdU; 150 mg/kg, twice a day) was injected intraperitoneally from Days 5 to 7, and immunohistochemical studies were conducted to explore the maturation of these progenitors. Migration of the progenitors was further studied by enhanced green fluorescent protein retrovirus injection. The effect of an antimitotic drug (cytosine arabinoside) on the neuronal count was also evaluated for contribution to regeneration. To see electrophysiological changes, treated rats were subjected to slice studies by whole-cell recordings. Finally, the effect of neural regeneration was assessed by motor performance by using the staircase test.

Results

Following epidermal growth factor and fibroblast growth factor–2 infusion into the lateral ventricles for 7 days beginning on Day 2, when severe neuronal loss in the adult striatum was confirmed (2.3% of normal controls), a significant increase of striatal neurons was observed at 6 weeks (~ 15% of normal controls) compared with vehicle controls (~ 5% of normal controls). Immunohistochemical studies by BrdU and enhanced green fluorescent protein retrovirus injection disclosed proliferation of neural progenitors in the subventricular zone and their migration to the ischemic striatum. By BrdU tracing study, NeuN- and BrdU-positive new neurons significantly increased at 6 and 12 weeks following the treatment. These accounted for 4.6 and 11.0% of the total neurons present, respectively. Antimitotic treatment demonstrated an approximately 66% reduction in neurons at 6 weeks. Further long-term studies showed dynamic changes of site-specific maturation among various neuronal subtypes even after 6 weeks. Electrophysiological properties of these newly appeared neurons underwent changes that conform to neonatal development. These regenerative changes were accompanied by a functional improvement of overall behavioral performance.

Conclusions

Treatment by growth factors significantly contributed to regeneration of mature striatal neurons after ischemia by endogenous neural progenitors, which was accompanied by electrophysiological maturation and improved motor performance. Recognition and improved understanding of these underlying dynamic processes will contribute to the development of novel and efficient regenerative therapies for brain injuries.

Stereological estimation of numerical densities of glutamatergic principal neurons in the mouse hippocampus

Recent studies have emphasized functional dissociations between dorsal and ventral hippocampus in learning, emotion, and affect. A rigorous quantitative analysis concerning lamellar cytoarchitecture would be important for promoting further research on the regional differentiation of the hippocampus. Here, we stereologically estimated the numerical densities (NDs) of glutamatergic principal neurons in the mouse hippocampus and encountered the significant differences along the dorsoventral axis. In the CA1 region, the NDs of CA1 pyramidal neurons were almost three times higher at the dorsal level (447.5 x 10(3)/mm(3)) than at the ventral level (180.5 x 10(3)/mm(3)); meanwhile, along the transverse axis, the NDs were significantly higher in the proximal portion than in the distal portion both at the dorsal and ventral levels. An EF-hand calcium-binding protein, calbindin D28K, was expressed in approximately 45% of CA1 pyramidal neurons both at the dorsal and ventral level. In the CA3 region, there were no significant differences in the NDs along the dorsoventral and transverse axes (dorsal, 165.2 x 10(3)/mm(3); ventral, 172.4 x 10(3)/mm(3)). In the dentate gyrus (DG), the NDs of granule cells were significantly higher at the dorsal level (916.7 x 10(3)/mm(3)) than at the ventral level (788.9 x 10(3)/mm(3)). The significant differences were observed only in the suprapyramidal blade, but not in the infrapyramidal blade. Then, we calculated the total neuron numbers contained in a 300-microm-thick hypothetical transverse slice of the hippocampus and found that the ratios of GABAergic to glutamatergic neuron numbers were two to three times higher in the ventral slice than in the dorsal slice. The ratios of numbers of eight GABAergic neuron subtypes to principal cells indicate structural dissociations in the neural network between dorsal and ventral slices. These findings provide an essential quantitative basis for elucidating mechanisms of distinct neural circuits underlying various hippocampal functions.

Association of the severity of cortical damage with the occurrence of spontaneous seizures and hyperexcitability in an animal model of posttraumatic epilepsy

Posttraumatic epilepsy is a common consequence of traumatic brain injury in humans. Major predictors for the development of posttraumatic epilepsy include the severity of injury and occurrence of cortical contusions. The effect of the size or location of the cortical lesion on the risk of epileptogenesis, however, is poorly understood. Here, we investigated the extent and location of cortical damage and its association with a lowered seizure threshold and the occurrence of spontaneous seizures in rats (n=77) that had experienced moderate or severe lateral fluid-percussion brain injury (FPBI) 12 months earlier. Spontaneous seizures were detected with video-electroencephalography monitoring and a lowered seizure threshold was determined based on a pentylenetetrazol (PTZ) test. Cortical atrophy was evaluated from thionin-stained sections using the Cavalieri estimation in four different experiments in which rats developed either spontaneous recurrent seizures (i.e., epilepsy) or a lowered seizure threshold. Our data show that damage to the cortex ipsilateral to the injury was more severe and extended more caudally in epileptic animals than in those without epilepsy (p<0.05 and p<0.001 for 2 independent experiments). Further, the extent of the cortical damage correlated positively with chronically increased hyperexcitability (number of spikes in PTZ test) in animals with traumatic brain injury (r=-0.54, p<0.05; r=-0.72, p<0.01 for 2 independent experiments). Specifically, cortical lesions located at the level of the perirhinal, entorhinal, and postrhinal cortices were associated with a lowered seizure threshold and seizures. The severity of the cortical injury did not correlate with the severity of hippocampal damage. These findings indicate that, like in humans, the severity of cortical injury correlates with epileptogenesis and epilepsy in an experimental model of posttraumatic epilepsy.

Von Economo neurons in autism: a stereologic study of the frontoinsular cortex in children

The presence of von Economo neurons (VENs) in the frontoinsular cortex (FI) has been linked to a possible role in the integration of bodily feelings, emotional regulation, and goal-directed behaviors. They have also been implicated in fast intuitive evaluation of complex social situations. Several studies reported a decreased number of VENs in neuropsychiatric diseases in which the "embodied" dimension of social cognition is markedly affected. Neuropathological analyses of VENs in patients with autism are few and did not report alterations in VEN numbers. In this study we re-evaluated the possible presence of changes in VEN numbers and their relationship with the diagnosis of autism. Using a stereologic approach we quantified VENs and pyramidal neurons in layer V of FI in postmortem brains of four young patients with autism and three comparably aged controls. We also investigated possible autism-related differences in FI layer V volume. Patients with autism consistently had a significantly higher ratio of VENs to pyramidal neurons (p=0.020) than control subjects. This result may reflect the presence of neuronal overgrowth in young patients with autism and may also be related to alterations in migration, cortical lamination, and apoptosis. Higher numbers of VENs in the FI of patients with autism may also underlie a heightened interoception, described in some clinical observations.

Differential involvement of the periaqueductal gray in multiple system atrophy

The periaqueductal gray (PAG) consists of distinct columns that participate in the integrated control of autonomic function. We sought to determine whether the PAG is affected in multiple system atrophy (MSA), a disorder characterized by prominent autonomic failure. Brains were obtained at autopsy from 13 MSA patients (10 M, 3 F, age 61±3 years) and 13 controls (8 M, 5 F, age 67±4 years). Transverse formalin-fixed 50 μm sections were obtained throughout the PAG and immunostained for the vesicular transporter 2 (VGLUT-2), nitric oxide synthase (NOS), or α-synuclein and co-stained with thionin. Some sections were processed for myelin or astrocyte staining. Stereological quantitation was performed separately in the ventrolateral, lateral, dorsolateral, and dorsomedial columns of the PAG. In MSA cases, there was a decrease in the total estimated number of VGLUT-2 immunoreactive neurons in the ventrolateral, lateral, and dorsomedial and to a lesser extent dorsolateral PAG compared to controls (ventrolateral PAG: 16,299±1612 vs. 27,906±2480 respectively, p<0.01; lateral PAG: 11,004±1401 vs. 16,078±1140 respectively, p<0.05; and dorsomedial PAG: 8847±1052 vs. 15,412±1097 respectively, p<0.001). The number of NOS immunoreactive neurons in the dorsolateral PAG was similar to controls. In all columns, the number of non-immunolabelled Nissl-stained cells was similar between groups. There was accumulation of glial cytoplasmic inclusions in all PAG columns in MSA. Our findings indicate involvement of the PAG columns in MSA, which may contribute to autonomic disturbances in this disorder.

ICAM-1 mediates surface contact between neutrophils and keratocytes following corneal epithelial abrasion in the mouse

Corneal epithelial abrasion elicits an inflammatory response involving neutrophil (PMN) recruitment from the limbal vessels into the corneal stroma. These migrating PMNs make surface contact with collagen and stromal keratocytes. Using mice deficient in PMN integrin CD18, we previously showed that PMN contact with stromal keratocytes is CD18-dependent, while contact with collagen is CD18-independent. In the present study, we wished to extend these observations and determine if ICAM-1, a known ligand for CD18, mediates PMN contact with keratocytes during corneal wound healing. Uninjured and injured right corneas from C57Bl/6 wild type (WT) mice and ICAM-1(-/-) mice were processed for transmission electron microscopy and imaged for morphometric analysis. PMN migration, stromal thickness, and ICAM-1 staining were evaluated using light microscopy. Twelve hours after epithelial abrasion, PMN surface contact with paralimbal keratocytes in ICAM-1(-/-) corneas was reduced to  ˜ 50% of that observed in WT corneas; PMN surface contact with collagen was not affected. Stromal thickness (edema), keratocyte network surface area and keratocyte shape were similar in ICAM-1(-/-) and WT corneas. WT keratocyte ICAM-1 expression was detected at baseline and ICAM-1 staining intensity increased following injury. Since ICAM-1 is readily detected on mouse keratocytes and PMN-keratocyte surface contact in ICAM-1(-/-) mice is markedly reduced, the data suggest PMN adhesive interactions with keratocyte-stromal networks is in part regulated by keratocyte ICAM-1 expression.

Number and nuclear morphology of TH+ and TH- neurons in the mouse ventral midbrain using epifluorescence stereology

The accurate and reliable counting of tyrosine hydroxylase positive (TH+) and tyrosine hydroxylase negative (TH-) neurons in the ventral midbrain is an important measure in studies related to Parkinson's disease and many other disorders associated with this region. Despite recent advancements, the use of stereology remains limited due to a variety of challenges for many users. We implemented a real-time fluorescence detection method and the use of an antibody to the neuron specific nuclear antigen (NeuN) to overcome some challenges for users. We found that the regional value for the two different cell types (TH+ and TH-) varied with the method of detection (chromogenic versus fluorescence) and with different nuclear markers (Nissl, DAPI, or NeuN). The number of both TH+ and TH- neurons was higher using fluorescence detection. The number of TH- neurons was higher using NeuN as a neuronal nuclear marker compared to DAPI. We identified 3 types of neuronal nuclei using NeuN staining characteristics. The method is applicable for mouse and rat. We describe a practical approach for epifluorescence-based counting of these two types of neurons that may offer significant advantages over existing methods for potential users.

Motor deficits, neuron loss, and reduced anxiety coinciding with axonal degeneration and intraneuronal Aβ aggregation in the 5XFAD mouse model of Alzheimer's disease

In the present report, we extend previous findings in the 5XFAD mouse model and demonstrate that these mice develop an age-dependent motor phenotype in addition to working memory deficits and reduced anxiety levels as demonstrated in an elevated plus maze task. Employing a variety of N- and C-terminal specific Aβ antibodies, abundant intraneuronal and plaque-associated pathology, including accumulation of pyroglutamate Aβ, was observed as early as the age of 3 months. Using unbiased stereology, we demonstrate that the 5XFAD mice develop a significant selective neuron loss in layer 5 of the cortex, leaving the overall neuron number of the total frontal cortex and hippocampus unaffected. This observation coincides with the accumulation of intraneuronal Aβ peptides only in cortical Layer 5, but not in CA1, despite comparable APP expression levels. The motor phenotype correlates with abundant spinal cord pathology, as demonstrated by abundant intraneuronal Aβ accumulation and extracellular plaque deposition. In addition, comparable to the APP/PS1KI mouse model, 5XFAD mice develop an age-dependent axonopathy likely contributing to the behavioral deficits.

Advanced microscopy techniques for quantitative analysis in neuromorphology and neuropathology research: current status and requirements for the future

Visualizing neuromorphology and in particular neuropathology has been the focus of many researchers in the quest to solve the numerous questions that are still remaining related to several neurological and neuropsychiatric diseases. Over the last years, intense research into microscopy techniques has resulted in the development of various new types of microscopes, software imaging systems, and analysis programs. This review briefly discusses some key techniques, such as confocal stereology and automated neuron tracing and reconstruction, and their applications in neuroscience research. Special emphasis is placed on needs for further developments, such as the demand for higher-throughput analyses in quantitative neuromorphology. These developments will advance basic neuroscience research as well as pharmaceutical and biotechnology research and development.

Motor axonal sprouting and neuromuscular junction loss in an animal model of Charcot-Marie-Tooth disease

Muscle weakness in Charcot-Marie-Tooth Type 1A disease (CMT1A) caused by mutations in peripheral myelin protein 22 (PMP22) has been attributed to an axonopathy that results in denervation and muscle atrophy. The underlying pathophysiological mechanisms involved are not understood. We investigated motor performance, neuromuscular junctions (NMJs), physiological parameters, and muscle morphometry of PMP22 transgenic mice. Neuromuscular junctions were progressively lost in hindlimb muscles of PMP22 transgenic mice, but their motor performance did not completely deteriorate during the observation period. There was considerable variability, including in laterality, in deficits among the animals. Cross-sectional areas and mean fiber size measurements indicated variable myofiber atrophy in hindlimb muscles. There was substantial concomitant axonal sprouting, and loss of neuromuscular junctions was inversely correlated with the accumulated length of axonal branches. Synaptic transmission studied in isolated nerve/muscle preparations indicated variable partial muscle denervation. Acetylcholine sensitivity was higher in the mutant muscles, and maximum tetanic force evoked by direct or indirect stimulation, specific force, and wet weights were markedly reduced in some mutant muscles. In summary, there is partial muscle denervation, and axons may retain some regenerative capacity but fail to reinnervate muscles in PMP22 transgenic mice.

Prefrontal cortex lesions and sex differences in fear extinction and perseveration

Electrolytic lesions of the medial prefrontal cortex (PFCX) were examined using fear conditioning to assess the recall of fear extinction and performance in the Y-maze, open field, and object location/recognition in male and female Sprague-Dawley rats. Rats were conditioned to seven tone/footshocks, followed by extinction after 1-h and 24-h delays, revealing PFCX effects and sex differences during all phases of fear conditioning. In male rats, PFCX impaired 24-h recall of fear extinction to tone, which required the 1-h delay extinction and was not attributed to nonassociative factors. In contrast, sham and PFCX females increased freezing to tone following a 24-h delay, whether or not 1-h delay tone extinction was presented. Moreover, PFCX females failed to extinguish to tone, contrasting to the robust extinction to tone that was observed for sham females, PFCX, and sham males. Also, sex differences were found during acquisition, with sham females acquiring fear conditioning slower than PFCX females. By the last tone-shock presentation, sham and PFCX females showed a slight but significant reduction in freezing to tone relative to those of sham and PFCX males. Of the other behavioral measures, PFCX females maintained exploration of a novel object during object recognition when sham females habituated. PFCX did not influence other behaviors in the remaining tasks. These findings show important sex differences in PFC function, with the PFC influencing the recall of fear extinction in males and contributing to the acquisition and maintenance of fear extinction memory in females, perhaps through altering perseveration.

Redox dysregulation affects the ventral but not dorsal hippocampus: impairment of parvalbumin neurons, gamma oscillations, and related behaviors

Elevated oxidative stress and alteration in antioxidant systems, including glutathione (GSH) decrease, are observed in schizophrenia. Genetic and functional data indicate that impaired GSH synthesis represents a susceptibility factor for the disorder. Here, we show that a genetically compromised GSH synthesis affects the morphological and functional integrity of hippocampal parvalbumin-immunoreactive (PV-IR) interneurons, known to be affected in schizophrenia. A GSH deficit causes a selective decrease of PV-IR interneurons in CA3 and dendate gyrus (DG) of the ventral but not dorsal hippocampus and a concomitant reduction of beta/gamma oscillations. Impairment of PV-IR interneurons emerges at the end of adolescence/early adulthood as oxidative stress increases or cumulates selectively in CA3 and DG of the ventral hippocampus. Such redox dysregulation alters stress and emotion-related behaviors but leaves spatial abilities intact, indicating functional disruption of the ventral but not dorsal hippocampus. Thus, a GSH deficit affects PV-IR interneuron's integrity and neuronal synchrony in a region- and time-specific manner, leading to behavioral phenotypes related to psychiatric disorders.

Retrograde amnesia for fear-potentiated startle in rats after complete, but not partial, hippocampal damage

We assessed the involvement of the hippocampus in recall of learned fear of a discrete visual stimulus using a fear-potentiated startle (FPS) procedure. Recall was measured by an increase in acoustic startle in the presence of a light that was paired with footshock. In Experiment 1, rats either received sham, dorsal, ventral, or complete (dorsal and ventral) NMDA-induced damage of the hippocampus following FPS acquisition. During the post-surgery retention test, only the rats with complete hippocampal damage showed a significant FPS deficit. In Experiment 2, we examined whether recent and remote memory for FPS would be differentially affected by complete hippocampal damage. Rats received sham or complete hippocampal damage 1- or 4-wk after FPS acquisition. During the retention test, sham rats exhibited significant FPS, whereas rats with hippocampal damage showed a large FPS deficit that was equivalent for recent and remote memories. In Experiment 3, we found that rats with complete hippocampal damage induced before conditioning showed levels of FPS that did not significantly differ from sham rats. Combined, these findings suggest that extensive damage to the hippocampus causes retrograde amnesia for a memory involving a light-shock association that is not temporally graded. The same damage does not cause anterograde amnesia in the same memory task. Partial damage of the hippocampus, whether of the dorsal or ventral region, was insufficient to cause retrograde amnesia. Thus, the hippocampus normally has a critical and long-lasting role enabling recall of fear conditioning to a discrete visual stimulus. In the absence of the hippocampus other memory systems support new learning.

Hippocampal interneuron loss in an APP/PS1 double mutant mouse and in Alzheimer's disease

Hippocampal atrophy and neuron loss are commonly found in Alzheimer's disease (AD). However, the underlying molecular mechanisms and the fate in the AD hippocampus of subpopulations of interneurons that express the calcium-binding proteins parvalbumin (PV) and calretinin (CR) has not yet been properly assessed. Using quantitative stereologic methods, we analyzed the regional pattern of age-related loss of PV- and CR-immunoreactive (ir) neurons in the hippocampus of mice that carry M233T/L235P knocked-in mutations in presenilin-1 (PS1) and overexpress a mutated human beta-amyloid precursor protein (APP), namely, the APP(SL)/PS1 KI mice, as well as in APP(SL) mice and PS1 KI mice. We found a loss of PV-ir neurons (40-50%) in the CA1-2, and a loss of CR-ir neurons (37-52%) in the dentate gyrus and hilus of APP(SL)/PS1 KI mice. Interestingly, comparable PV- and CR-ir neuron losses were observed in the dentate gyrus of postmortem brain specimens obtained from patients with AD. The loss of these interneurons in AD may have substantial functional repercussions on local inhibitory processes in the hippocampus.

A rapid and reliable method of counting neurons and other cells in brain tissue: a comparison of flow cytometry and manual counting methods

It is of critical importance to understand the numbers and distributions of neurons and non-neurons in the cerebral cortex because cell numbers are reduced with normal aging and by diseases of the CNS. The isotropic fractionator method provides a faster way of estimating numbers of total cells and neurons in whole brains and dissected brain parts. Several comparative studies have illustrated the accuracy and utility of the isotropic fractionator method, yet it is a relatively new methodology, and there is opportunity to adjust procedures to optimize its efficiency and minimize error. In the present study, we use 142 samples from a dissected baboon cortical hemisphere to evaluate if isotropic fractionator counts using a Neubauer counting chamber and fluorescence microscopy could be accurately reproduced using flow cytometry methods. We find greater repeatability in flow cytometry counts, and no evidence of constant or proportional bias when comparing microscopy to flow cytometry counts. We conclude that cell number estimation using a flow cytometer is more efficient and more precise than comparable counts using a Neubauer chamber on a fluorescence microscope. This method for higher throughput, precise estimation of cell numbers has the potential to rapidly advance research in post-mortem human brains and vastly improve our understanding of cortical and subcortical structures in normal, injured, aged, and diseased brains.

Increased neuronal cell number in the dorsal motor nucleus of the vagus in schizophrenia

Axer H, Bernstein H-G, Keiner S, Heronimus P, Sauer H, Witte OW, Bogerts B, Bär K-J. Increased neuronal cell number in the dorsal motor nucleus of the vagus in schizophrenia.

OBJECTIVE

Recently, a reduction in efferent vagal regulation has been found in schizophrenic patients.

METHODS

Therefore, the brainstems of nine schizophrenic patients and nine normal controls were stereologically analysed. The number of neurons using the optical fractionator method and nuclear volumes applying the Cavalieri principle was estimated in Nissl stained sections of the dorsal motor nucleus of the vagus (DMNV) and the hypoglossal nucleus.

RESULTS

The neurons in the right DMNV were significantly increased in the schizophrenic group compared to normal controls (p = 0.047), while the volumes of the DMNV did not differ. In contrast, no such differences were found in the hypoglossal nucleus.

CONCLUSION

Although this pilot study is limited by its small sample size, the analysis of the solitarius-ambiguus-vagus system in schizophrenic patients is an interesting target in schizophrenia research. The most reasonable background for increased neuron numbers in the DMNV could be a system-specific neurodevelopmental disturbance in schizophrenia.

Calibration of the stereological estimation of the number of myelinated axons in the rat sciatic nerve: a multicenter study

Several sources of variability can affect stereological estimates. Here we measured the impact of potential sources of variability on numerical stereological estimates of myelinated axons in the adult rat sciatic nerve. Besides biological variation, parameters tested included two variations of stereological methods (unbiased counting frame versus 2D-disector), two sampling schemes (few large versus frequent small sampling boxes), and workstations with varying degrees of sophistication. All estimates were validated against exhaustive counts of the same nerve cross sections to obtain calibrated true numbers of myelinated axons (gold standard). In addition, we quantified errors in particle identification by comparing light microscopic and electron microscopic images of selected consecutive sections. Biological variation was 15.6%. There was no significant difference between the two stereological approaches or workstations used, but sampling schemes with few large samples yielded larger differences (20.7+/-3.7% SEM) of estimates from true values, while frequent small samples showed significantly smaller differences (12.7+/-1.9% SEM). Particle identification was accurate in 94% of cases (range: 89-98%). The most common identification error was due to profiles of Schwann cell nuclei mimicking profiles of small myelinated nerve fibers. We recommend sampling frequent small rather than few large areas, and conclude that workstations with basic stereological equipment are sufficient to obtain accurate estimates. Electron microscopic verification showed that particle misidentification had a surprisingly variable and large impact of up to 11%, corresponding to 2/3 of the biological variation (15.6%). Thus, errors in particle identification require further attention, and we provide a simple nerve fiber recognition test to assist investigators with self-testing and training.

Cingulum bundle white matter in MAG-knockout mice

Myelin associated glycoprotein (MAG) is an oligodendrocyte-derived gene whose expression is decreased in schizophrenia. Several measures of white matter integrity appear abnormal in schizophrenia, specifically in the anterior cingulate gyrus. We studied mice lacking MAG as a potential model of dysmyelination. Using the stereological “Space Balls” method, we estimated myelinated fiber length density in the cingulum bundle in adult knockout and control mice. We performed diffusion anisotropy imaging in these animals, measuring fractional anisotropy (FA) in a region of the cingulum bundle. We found no differences in cingulum myelinated fiber length density between the two groups, although we did note an age-related decrease regardless of genotype. No differences were noted in FA either, but an age-related decrease was seen as well. These findings imply that MAG dysfunction alone is not sufficient to cause the white matter alterations seen in schizophrenia.

CARDIOVASCULAR RISK FACTORS AFFECT HIPPOCAMPAL MICROVASCULATURE IN EARLY AD

There is growing clinical and neuropathologic evidence suggesting that cognitive decline in early Alzheimer's disease (AD) is aggravated by a synergistic relationship between AD and cerebrovascular disease associated with cardiovascular risk factors such as diabetes and hypertension. Here we used the stereologic "Space Balls" method to investigate the relationships between AD pathology and cardiovascular risk factors in postmortem human brains of patients with hypertension and diabetes in two groups - one consisting of cases with AD diagnosis and one of cases without. Hippocampal CA1 and CA3 microvasculature length density estimates were generated to characterize quantitatively the contribution of cardiovascular risk factors to the severity of neuropathologic changes. Our main finding is that the mean and variance of length density values in the AD group were significantly increased from the non-AD group, regardless of the absence or presence of a cardiovascular risk factor. An additional finding is that in the AD group without a risk factor, dementia severity correlated with amount of length density change in the CA1 field-this correlation did not exist in the AD groups with risk factors. Our findings suggest a role for cardiovascular risk factors in quantifiable change of hippocampal CA1 field microvasculature, as well as suggest a possible role of cardiovascular risk factors in altering microvasculature pathology in the presence of AD.

Valproic acid reduces spatial working memory and cell proliferation in the hippocampus

Valproic acid (VPA) is widely used clinically, as an anticonvulsant and mood stabilizer but is, however, also known to block cell proliferation through its ability to inhibit histone deacetylase enzymes. There have been a number of reports of cognitive impairments in patients taking VPA. In this investigation we examined the relationship between cognition and changes in cell proliferation within the hippocampus, a brain region where continued formation of new neurons is associated with learning and memory. Treatment of rats by i.p. injection of VPA, reduced cell proliferation in the sub granular zone of the dentate gyrus within the hippocampus. This was linked to a significant impairment in their ability to perform a hippocampus-dependent spatial memory test (novel object location). In addition, drug treatment caused a significant reduction in brain-derived neurotrophic factor (BDNF) and Notch 1 but not doublecortin levels within the hippocampus. These results support the idea that VPA may cause cognitive impairment and provide a possible mechanism for this by reducing neurogenesis within the hippocampus.

Age-related vascular pathology in transgenic mice expressing presenilin 1-associated familial Alzheimer's disease mutations

Mutations in the presenilin 1 (PS1) gene are the most commonly recognized cause of familial Alzheimer's disease (FAD). Besides senile plaques, neurofibrillary tangles, and neuronal loss, Alzheimer's disease (AD) is also accompanied by vascular pathology. Here we describe an age-related vascular pathology in two lines of PS1 FAD-mutant transgenic mice that mimics many features of the vascular pathology seen in AD. The pathology was especially prominent in the microvasculature whose vessels became thinned and irregular with the appearance of many abnormally looped vessels as well as string vessels. Stereologic assessments revealed a reduction of the microvasculature in the hippocampus that was accompanied by hippocampal atrophy. The vascular changes were not congophilic. Yet, despite the lack of congophilia, penetrating vessels at the cortical surface were often abnormal morphologically and microhemorrhages sometimes occurred. Altered immunostaining of blood vessels with basement membrane-associated antigens was an early feature of the microangiopathy and was associated with thickening of the vascular basal laminae and endothelial cell alterations that were visible ultrastructurally. Interestingly, although the FAD-mutant transgene was expressed in neurons in both lines of mice, there was no detectable expression in vascular endothelial cells or glial cells. These studies thus have implications for the role of neuronal to vascular signaling in the pathogenesis of the vascular pathology associated with AD.