Colocalization of neurons in optical coherence microscopy and Nissl-stained histology in Brodmann's area 32 and area 21.

Optical coherence tomography is an optical technique that uses backscattered light to highlight intrinsic structure, and when applied to brain tissue, it can resolve cortical layers and fiber bundles. Optical coherence microscopy (OCM) is higher resolution (i.e., 1.25 µm) and is capable of detecting neurons. In a previous report, we compared the correspondence of OCM acquired imaging of neurons with traditional Nissl stained histology in entorhinal cortex layer II. In the current method-oriented study, we aimed to determine the colocalization success rate between OCM and Nissl in other brain cortical areas with different laminar arrangements and cell packing density. We focused on two additional cortical areas: medial prefrontal, pre-genual Brodmann area (BA) 32 and lateral temporal BA 21. We present the data as colocalization matrices and as quantitative percentages. The overall average colocalization in OCM compared to Nissl was 67% for BA 32 (47% for Nissl colocalization) and 60% for BA 21 (52% for Nissl colocalization), but with a large variability across cases and layers. One source of variability and confounds could be ascribed to an obscuring effect from large and dense intracortical fiber bundles. Other technical challenges, including obstacles inherent to human brain tissue, are discussed. Despite limitations, OCM is a promising semi-high throughput tool for demonstrating detail at the neuronal level, and, with further development, has distinct potential for the automatic acquisition of large databases as are required for the human brain.

The nucleus pararaphales in the human, chimpanzee, and macaque monkey.

The human cerebral cortex and cerebellum are greatly expanded compared to those of other mammals, including the great apes. This expansion is reflected in differences in the size and organization of precerebellar brainstem structures, such as the inferior olive. In addition, there are cell groups unique to the human brainstem. One such group may be the nucleus pararaphales (PRa); however, there is disagreement among authors about the size and location of this nucleus in the human brainstem. The name "pararaphales" has also been used for neurons in the medulla shown to project to the flocculus in the macaque monkey. We have re-examined the existence and status of the PRa in eight humans, three chimpanzees, and four macaque monkeys using Nissl-stained sections as well as immunohistochemistry. In the human we found a cell group along the midline of the medulla in all cases; it had the form of interrupted cell columns and was variable among cases in rostrocaudal and dorsoventral extent. Cells and processes were highly immunoreactive for non-phosphorylated neurofilament protein (NPNFP); somata were immunoreactive to the synthetic enzyme for nitric oxide, nitric oxide synthase, and for calretinin. In macaque monkey, there was a much smaller oval cell group with NPNFP immunoreactivity. In the chimpanzee, we found a region of NPNFP-immunoreactive cells and fibers similar to what was observed in macaques. These results suggest that the "PRa" in the human may not be the same structure as the flocculus-projecting cell group described in the macaque. The PRa, like the arcuate nucleus, therefore may be unique to humans.

Cytoarchitecture of the spinal cord of the postnatal (P4) mouse.

Interpretation of the new wealth of gene expression and molecular mechanisms in the developing mouse spinal cord requires an accurate anatomical base on which data can be mapped. Therefore, we have assembled a spinal cord atlas of the P4 mouse to facilitate direct comparison with the adult specimens and to contribute to studies of the development of the mouse spinal cord. This study presents the anatomy of the spinal cord of the P4 C57Bl/6J mouse using Nissl and acetyl cholinesterase-stained sections. It includes a detailed map of the laminar organization of selected spinal cord segments and a description of named cell groups of the spinal cord such as the central cervical (CeCv), lateral spinal nucleus, lateral cervical, and dorsal nuclei. The motor neuron groups have also been identified according to the muscle groups they are likely to supply. General features of Rexed's laminae of the P4 spinal cord showed similarities to that of the adult (P56). However, certain differences were observed with regard to the extent of laminae and location of certain cell groups, such as the dorsal nucleus having a more dispersed structure and a more ventral and medial position or the CeCv being located in the medial part of lamina 5 in contrast to the adult where it is located in lamina 7. Motor neuron pools appeared to be more tightly packed in the P4 spinal cord. The dorsal horn was relatively larger and there was more white matter in the P56 spinal cord.

In situ hybridization and immunofluorescence on resin-embedded tissue to identify the components of Nissl substance.

It is not clear whether the Nissl substance is present at the axon hillock. To clarify this gap in knowledge, we conducted in situ hybridization (ISH) on mouse brain tissue using 30-microm cryostat and 1-3-microm acrylic resin sections. Cryostat and rehydrated resin sections were exposed to digoxygenin-labeled glutamic acid decarboxylase 1 sense and antisense riboprobes. Consecutive sections from tissue embedded in resin were subjected to the ribosomal protein L26 primary antibody to determine the distribution of the ribo/polysomes. ISH results from the antisense riboprobe in both cryostat and resin-embedded tissue sections demonstrated an abundance of message in the neurons from the substantia nigra pars reticulate. In addition, the resin sections demonstrated hybridization signal in the axon hillock of some neurons. Immunofluorescence labeling of consecutive sections using an antibody to the most abundant ribosomal protein L26 confirmed their distribution in the cell body and the axon hillock of similar neurons. Compared with the 30-microm cryostat sections, the most striking feature of ISH in the thinner resin (2-3 microm) sections was that there was a phenomenal improvement in the overall clarity and spatial resolution. Reexamination of the axon hillock when continuous with the cell body in cryostat sections revealed that the same message was also present, except it was overlooked initially because of overlapping cell populations in thick tissue slices. As ribosomes are a component of Nissl substance, we propose that the axon hillock, like other parts of the neuron, does contain Nissl substance.

Spontaneous ganglioneuroma possibly originating from the trigeminal ganglion in a B6C3F1 mouse.

In a carcinogenicity study, a neuronal tumor in the cranial cavity was observed in a 110-week-old female B6C3F1 mouse. At necropsy, the tumor was seen at the site of the pituitary gland. Histologically, the tumor consisted of well-differentiated ganglion cells, nerve fiber/neuropil-like elements and ganglion-like cells. The tumor was composed mainly of ganglion-like cells, which were arranged in solid sheets interspersed with thin fibrovascular stroma. Nissl substance was detected at the margin in the cytoplasm of well-differentiated ganglion cells, and nerve fibers were identified by the Kluever-Barrera method. Immunohistochemically, the well-differentiated ganglion cells were positive for S-100, neurofilament protein (NF), neuron-specific enolase (NSE), synaptophysin, and chromogranin A. The nerve fiber/neuropil-like elements were positive for S-100, NF, NSE, and glial fibrillary acidic protein (GFAP), and the ganglion-like cells were strongly positive only for NSE and synaptophysin. On the other hand, there were no pituitary cells, such as prolactin-positive or adrenocorticotropic hormone (ACTH)-positive cells in the tumor tissue. Detailed histopathological examination suggested that the tumor might be a ganglioneuroma arising from the trigeminal ganglion. This report provides additional histopathological evidence of peripheral nerve neoplasms in mice.

Cytoarchitecture of the human superior olivary complex: nuclei of the trapezoid body and posterior tier.

The superior olivary complex (SOC) is a cluster of nuclei situated in the caudal brainstem tegmentum that forms an essential component of the auditory pathway. The SOC includes two principal nuclei, the medial and lateral superior olives (MSO and LSO respectively), that have clear roles in sound source localization. Surrounding the principal nuclei are a number of periolivary nuclei (PON) that vary significantly between mammalian species but function in multiple aspects of hearing. Although the PON have been studied in numerous laboratory animals, these nuclei have not been delineated in human. The major goal of this study is to, based on myeloarchitecture, location, neuronal morphology and cytoarchitecture, define the PON within the human SOC and provide estimates of neuronal number within these nuclei. Results from the study of twelve human brainstems provide evidence for six morphologically distinct cell groups: three within the trapezoid body and three along the posterior aspect of the SOC. Based on the analysis of human tissue stained for myelin, Nissl substance, or impregnated with silver, the human PON appear largely homologous to the PON described in other low-frequency hearing animals.

The rat orbital and agranular insular prefrontal cortical areas: a cytoarchitectonic and chemoarchitectonic study.

Cytoarchitectonic characterization of borders is necessary for stereological studies (e.g., total cell number estimation), in which particular cortical areas have to be defined. In this study, cytoarchitectonic characteristics are described and illustrated for the rat ventral or orbital frontal cortical areas, i.e., the lateral-, ventrolateral-, ventral- and medial-orbital areas; and for the lateral frontal cortical areas, i.e., the agranular insular and the dorsolateral orbital cortical area. Each cytoarchitectonic-defined boundary is corroborated by one or more of the immunocytochemical stainings for dopaminergic fibers, SMI-32 positive neurons, calbindin and parvalbumin positive neurons. Each immunocytochemical staining, however, shows a characteristic subset of the cytoarchitectonical borders. The dorsal agranular insular area (AId) and the dorsolateral orbital area (DLO) have been subdivided into a dorsal and a ventral part based upon differences between these parts in the Nissl and immunocytochemical stainings. The posterior part of VLO has a different structure and is, therefore, indicated as VLOp (VLO, posterior part).

Neuronal density, size and shape in the human anterior cingulate cortex: a comparison of Nissl and NeuN staining.

There are an increasing number of quantitative morphometric studies of the human cerebral cortex, especially as part of comparative investigations of major psychiatric disorders. In this context, the present study had two aims. First, to provide quantitative data regarding key neuronal morphometric parameters in the anterior cingulate cortex. Second, to compare the results of conventional Nissl staining with those observed after immunostaining with NeuN, an antibody becoming widely used as a selective neuronal marker. We stained adjacent sections of area 24b from 16 adult brains with cresyl violet or NeuN. We measured the density of pyramidal and non-pyramidal neurons, and the size and shape of pyramidal neurons, in laminae II, III, Va, Vb and VI, using two-dimensional counting methods. Strong correlations between the two modes of staining were seen for all variables. However, NeuN gave slightly higher estimates of neuronal density and size, and a more circular perikaryal shape. Brain pH was correlated with neuronal size, measured with both methods, and with neuronal shape. Age and post-mortem interval showed no correlations with any parameter. These data confirm the value of NeuN as a tool for quantitative neuronal morphometric studies in routinely processed human brain tissue. Absolute values are highly correlated between NeuN and cresyl violet stains, but cannot be interchanged. NeuN may be particularly useful when it is important to distinguish small neurons from glia, such as in cytoarchitectural studies of the cerebral cortex in depression and schizophrenia.

Effects of postnatally administered inorganic lead on the tyrosine hydroxylase immunoreactive norepinephrinergic neurons of the locus ceruleus of the rat.

The neurotoxic effects of inorganic lead are known to include peripheral neuropathy in adults and encephalopathy in children. The purpose of this study was to determine the effect of inorganic lead (PbCl2) administration on norepinephrinergic neurons of the locus ceruleus in neonatal rats by immunocytochemical and electron microscopic analyses. Lead chloride solutions, 0.05%, 0.1% and 0.2% in concentrations, were prepared in distilled water and administered orally via drinking water. After 4, 8, or 12 weeks of continuous administration, the rats were sacrificed and brains were immunostained with the tyrosine hydroxylase antibody. The number of immunoreactive cell bodies in the locus ceruleus was estimated. Densitometric analysis of immunoreactive profiles visualized by electron microscopy was performed using an image analyzer. The numbers of immunoreactive neurons in the locus ceruleus were increased statistically by lead administration. The intensity of the immunoreaction, both under the light and electron microscopes was also increased. Degenerative changes, including intra-axonal vacuole formation and widening of the extracellular spaces, were found by electron microscopy in and around the tyrosine hydroxylase immunoreactive axons. Increased tyrosine hydroxylase immunoreactivity may correlate with the hyper-reactivity of lead intoxicated children. Degenerative changes may account for the reported deficits in intellectual attainment and achievement in lead intoxicated children.

Histochemical identification of cortical areas in the auditory region of the human brain.

Despite numerous studies stretching over the last 100 years there is still no general agreement on the number of auditory areas in the human cortex or even how to define them by histological methods. Full definition of these areas will require a combination of functional and histological methods but, by using six complementary histological methods, of which most have been used in the monkey, we provide a clearer description of these areas. The primary auditory area was located on the posteromedial two-thirds of the first transverse temporal (Heschl's) gyrus and was distinguished by a dense band of cytochrome oxidase activity in layer IV and the base of layer III, as well as a relatively thick, pale layer V and VI. Layers V and VI together made up 40% of the cortical thickness. Acetylcholinesterase (AChE)-containing pyramidal cells were sparsely distributed within the primary auditory area. The anterolateral third of Heschl's gyrus did not have a clear band of high cytochrome oxidase activity but contained a moderately high density of AChE-containing pyramidal cells and thus appeared to be part of the auditory belt. Within Heschl's sulcus there was a third area, which had a band of high cytochrome oxidase activity and bands of high parvalbumin immunoreactivity and AChE activity in layer IV. This area appeared to be part of the auditory core. Thus the use of staining methods for cytochrome oxidase, AChE and parvalbumin provided additional information which allowed a clearer definition of auditory areas than Nissl or myelin staining alone. Our results suggest that there are two core areas surrounded by at least six belt areas in the human auditory region.

New patterns of intracortical projections after focal cortical stroke.

Cortical strokes alter functional maps but associated changes in connections have not been documented. The neuroanatomical tracer biotinylated dextran amine (BDA) was injected into cortex bordering infarcts 3 weeks after focal strokes in rat whisker barrel (somatosensory) cortex. The mirror locus in the opposite hemisphere was injected as a control. After 1 week of survival, brains were processed for cytochrome oxidase (CO)-, Nissl-, and BDA-labeled neurons. Cortex bordering the infarct (peri-infarct cortex) had abnormal CO and Nissl structure. BDA-labeled neurons were plotted and projections were analyzed quantitatively. Animals with small strokes had intracortical projections, arising from peri-infarct cortex, not seen in normal hemispheres: the overall orientation was statistically significantly different from and rotated 157 degrees relative to the controls. Compared to the controls, significantly fewer cells were labeled in the thalamus. Thus, after focal cortical stroke, the peri-infarct cortex is structurally abnormal, loses thalamic connections, and develops new horizontal cortical connections by axonal sprouting.

Local cerebral blood flow during the first hour following acute ligation of multiple arterioles in rat whisker barrel cortex.

The objectives are to measure the early time-course of the flows of blood, red cells, and plasma in brain tissue destined to infarct following arterial occlusion. The flux of fluorescent red blood cells (fRBCs) through venules and the arteriovenous transit times (AVTT) of fluorescein-labeled plasma albumin were periodically monitored in anesthetized adult Wistar rats before and up to 60 min after permanent ligations of several small branches of the middle cerebral artery. Of note, fRBC is a function of venular erythrocyte flow and volume, whereas AVTT is a function of plasma flow and volume in visible arteriole-capillary-venule units. In another group of anesthetized rats, local cerebral blood flow (ICBF) was measured 1 h after permanent arterial occlusion by [14C]iodoantipyrine (IAP) autoradiography. With this model of focal ischemia, the lesion is highly reproducible and involves part of the whisker barrel cortex. Infarction of this area was observed in 12 of 13 rats. From 10 to 60 min after arterial occlusion, AVTT was nearly four times longer in the ischemic barrel cortex than at the same site before ligations, and fRBC flux was 25%. Neither parameter changed appreciably over this time. After 60 min of ischemia, ICBF on the ipsilateral barrel cortex was 18% of that on the contralateral side and 15% of the sham control value for the same area of the barrel cortex. Since whole blood flow in the ischemic barrel cortex was < 20% of normal at 60 min and AVTT and fRBC flux were essentially constant from 10 to 60 min, the rates of plasma and red cell flows were similarly depressed during the first hour of arteriolar occlusion. In conclusion, such lowering of red cell, plasma, and blood flows produced consistent infarctions in the barrel cortex.

Experimental brain injury induces expression of amyloid precursor protein, which may be related to neuronal loss in the hippocampus.

Previous reports have demonstrated that some focal brain injuries increase amyloid precursor protein (APP) immunoreactivity in the region surrounding the injury where it was localized, in damaged axons and in pre-alpha 2 cells of the entorhinal cortex. However, to date, APP expression in the hippocampus remote from the impact site has not been comprehensively studied. Therefore, we have evaluated APP expression not only in the locally injured cerebral cortex but also in the hippocampus remote from the impact site. In the present paper, diffuse axonal injury was induced in rats in midline fluid percussion injury. APP expression was examined post injury using Western blot analysis and immunohistochemistry. Western blot analysis demonstrated that the expression of 100-kd APP was increased in both the cerebral cortex and hippocampus 24 h after injury. It then decreased in the hippocampus, but did not change in the cerebral cortex, 7 days after injury. Immunohistochemical studies showed increased immunoreactivity of APP in the neuronal perikarya and reactive astrocytes near the region of injury in the cerebral cortex 24 h to 7 days after injury. In the hippocampus, APP accumulated in the CA3 neurons 24 h and 3 days after injury, although no hemorrhagic lesions were seen at that site. The APP positive neurons in CA3 showed shrunken cell bodies and pyknotic nuclei 3 days after injury, and some of the neurons in CA3 had disappeared by 7 days postinjury. The results of present study suggest that traumatic brain injury induces overexpression and accumulation of APP in neuronal perikarya and that these events are followed by degeneration of CA3 neurons. Further, the decline in APP expression in the hippocampus is thought to be due to neuronal loss in CA3 subsector.

Identification of a survival-promoting peptide in medium conditioned by oxidatively stressed cell lines of nervous system origin.

A survival-promoting peptide has been purified from medium conditioned by Y79 human retinoblastoma cells and a mouse hippocampal cell line (HN 33.1) exposed to H2O2. A 30 residue synthetic peptide was made on the basis of N-terminal sequences obtained during purification, and it was found to exhibit gel mobility and staining properties similar to the purified molecules. The peptide maintains cells and their processes in vitro for the HN 33.1 cell line treated with H2O2, and in vivo for cortical neurons after lesions of the cerebral cortex. It has weak homology with a fragment of a putative bacterial antigen and, like that molecule, binds IgG. The peptide also contains a motif reminiscent of a critical sequence in the catalytic region of calcineurin-type phosphatases; surprisingly, like several members of this family, the peptide catalyzes the hydrolysis of para-nitrophenylphosphate in the presence of Mn2+. Application of the peptide to one side of bilateral cerebral cortex lesions centered on area 2 in rats results in an increase in IgG immunoreactivity in the vicinity of the lesions 7 d after surgery. Microglia immunopositive for IgG and ED-1 are, however, dramatically reduced around the lesions in the treated hemisphere. Furthermore, pyramidal neurons that would normally shrink, die, or disintegrate were maintained, as determined by MAP2 immunocytochemistry and Nissl staining. These survival effects were often found in both hemispheres. The results suggest that this peptide operates by diffusion to regulate the immune response and thereby rescue neurons that would usually degenerate after cortical lesions. The phosphatase activity of this molecule also suggests the potential for direct neuron survival-promoting effects.

Survival and functional demonstration of interregional pathways in fore/midbrain slice explant cultures.

An important general question in neurobiology concerns the development and expression of the rich context of neuronal phenotypes, especially in relation to the diverse patterns of connectivity. Organotypic cultures of brain slices may offer distinct advantages for such studies if such a preparation survives, maintains a wide diversity of neuronal phenotypes and displays appropriate synaptic connections between regions. To address these requirements, we utilized long-term organotypic cultures of intact horizontal slices of rat forebrain and midbrain and assessed a variety of markers of phenotype in combination with functional tests of connectivity. This explant preparation displayed a distinct viability requirement such that the greatest explant survival was seen in slices taken from pups of less than postnatal day 7 and was independent of N-methyl-D-aspartate channel blockade. The anatomical features of the major brain regions (e.g., neocortex, striatum, septum, hippocampus, diencephalon and midbrain) were observed in their normal boundaries. The presence of cholinergic and catecholaminergic neurons was demonstrated with acetylcholinesterase histochemistry and tyrosine hydroxylase immunohistochemistry. Labelled neurons displayed multiple, regionally-appropriate cytoarchitectures and, in some cases, could be seen to project to brain regions in a manner quite similar to that seen in vivo. Finally, the direct demonstration of spontaneous and evoked interregional excitatory synaptic transmission was made using whole-cell patch-clamp recordings from striatal neurons which revealed an intact glutamate-using corticostriatal pathway. This simple explant preparation appears to contain a rich diversity of neuronal types and synaptic organization. Therefore, this preparation appears to have several distinct advantages for basic neurobiologic research since it combines long-term culture viability and many features of mature brain including complex interregional neuronal systems.

Destruction of locus coeruleus neuronal perikarya after injection of anti-dopamine-B-hydroxylase immunotoxin into the olfactory bulb of the rat.

Saporin, a ribosome-inactivating protein, was coupled to a monoclonal antibody to dopamine-B-hydroxylase (DBH) and injected unilaterally into the olfactory bulb of rats. After 4-13 days survival, the rat brain was processed histologically and the locus coerulei (LC) examined with Nissl and anti-DBH staining. There were degenerating dendrites in surviving LC neurons on the side ipsilateral to the immunotoxin-injected olfactory bulb. The number of Nissl-positive LC neurons in a transverse section through the caudal one third of the LC was reduced from 116+/-10 to 50+/-8 neurons (P < 0.01, n = 7) and the number of DBH-positive neurons in the more rostral LC sections was reduced from 13+/-2 to 5+/-1 (P < 0.05, n = 4). Our results indicate that it is possible to lesion LC neurons via retrograde intraaxonal transport of saporin-anti-DBH immunotoxin from the olfactory bulb.

Trimethyltin (TMT) neurotoxicity in organotypic rat hippocampal slice cultures.

The neurotoxic effects of trimethyltin (TMT) on the hippocampus have been extensively studied in vivo. In this study, we examined whether the toxicity of TMT to hippocampal neurons could be reproduced in organotypic brain slice cultures in order to test the potential of this model for neurotoxicological studies, including further studies of neurotoxic mechanisms of TMT. Four-week-old cultures, derived from 7-day-old donor rats and grown in serum-free medium, were exposed to TMT (0.5-100 microM) for 24 h followed by 24 h in normal medium. TMT-induced neurodegeneration was then monitored by (a) propidium iodide (PI) uptake, (b) lactate dehydrogenase (LDH) efflux into the culture medium, (c) cellular cobalt uptake as an index of calcium influx, (d) ordinary Nissl cell staining, and (e) immunohistochemical staining for microtubule-associated protein 2 (MAP-2). Cellular degeneration as assessed by densitometric measurements of PI uptake displayed a dose and time-dependent increase, with the following ranking of vulnerability of the hippocampal subfields: FD>CA4>/=CA3c>CA1>CA3ab. This differential neuronal vulnerability observed by PI uptake was confirmed by MAP-2 immunostaining and corresponded to in vivo cell stain observations of rats acutely exposed to TMT. The mean PI uptake of the cultures and the LDH efflux into the medium were highly correlated. The combined results obtained by the different markers indicate that the hippocampal slice culture method is a feasible model for further studies of TMT neurotoxicity.

The in vivo time course for elimination of adrenalectomy-induced apoptotic profiles from the granule cell layer of the rat hippocampus.

Although apoptotic cellular degeneration has been reported to be extremely rapid with the use of in vitro models, the time needed to clear apoptotic neurons in the in vivo brain is unknown. In this study we used a simple morphological approach to solve this problem. Four days after adrenalectomy (ADX), all of the operated rats morphologically displayed hippocampal granule cell apoptosis that was prevented completely by corticosterone replacement immediately after ADX. Therefore, we intravenously injected the rats with corticosterone 4 d after ADX and subsequently maintained them on corticosterone replacement in saline drinking water. This corticosterone replacement could protect healthy granule cells promptly and continuously against hormone-deficient apoptosis, because the normal glucocorticoid receptor immunoreactivity within the granule cell nuclei, which disappeared after ADX, was identified 1 hr after corticosterone replacement was started, and this effect persisted for several days. However, this corticosterone treatment could not prevent the irreversible apoptosis of the already degenerated granule cells at various stages of the same progressive apoptotic process. Then we successively traced the disappearance of apoptotic granule cells throughout the hippocampus at different time points by Nissl and silver staining. Given that the apoptotic cells at the earliest stage of the degenerating process when the ADX rats received corticosterone injection were the last to disappear, the period from corticosterone injection until the disappearance of the last degenerating debris of apoptotic cells was taken to represent the time course for elimination of apoptotic neurons in vivo. We discovered that the elimination of apoptotic granule cells took 72 hr.

Fluoro-Jade: a novel fluorochrome for the sensitive and reliable histochemical localization of neuronal degeneration.

Fluoro-Jade is an anionic fluorochrome capable of selectively staining degenerating neurons in brain slices. The histochemical application of Fluoro-Jade results in a simple, sensitive and reliable method for staining degenerating neurons and their processes. The technique will detect neuronal degeneration resulting from exposure to a variety of neurotoxic insults. Fluoro-Jade can be combined with other fluorescent methodologies including immunofluorescence, fluorescent axonal tract tracing, and fluorescent Nissl counterstaining. Compared to conventional methodologies, Fluoro-Jade is a more sensitive and definitive marker of neuronal degeneration than hematoxylin and eosin (H&E) or Nissl type stains, while being comparably sensitive yet considerably simpler and more reliable than suppressed silver techniques.

Aspects of the quantitative analysis of neurons in the cerebral cortex.

We address three problems concerning the quantitative analysis of nerve cell distribution in the cerebral cortex: (i) preparatory tissue deformation (shrinkage); (ii) difficulties in differentiating between small neurons and astroglia; and (iii) the bias introduced by the counting method. We found that staining with Richardson's solution led to no shrinkage in Vibratome-cut sections of aldehyde-fixed rat brains, but did result in staining of the neurons and left the glial cells unstained. This was in striking contrast to Nissl staining which introduced a linear shrinkage of 20-30% and stained all kinds of cortical cells indiscriminately. A computer-based unbiased counting method was implemented by taking advantage of the stereological procedure referred to as the 'optical disector' (Gundersen, H.J.G. (1986) Stereology of arbitrary particles, J. Microsc., 143: 3-45).