Melanized dopaminergic neurons are differentially susceptible to degeneration in Parkinson's disease

In idiopathic Parkinson's disease massive cell death occurs in the dopamine-containing substantia nigra. A link between the vulnerability of nigral neurons and the prominent pigmentation of the substantia nigra, though long suspected, has not been proved. This possibility is supported by evidence that N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its metabolite MPP+, the latter of which causes destruction of nigral neurons, bind to neuromelanin. We have directly tested this hypothesis by a quantitative analysis of neuromelanin-pigmented neurons in control and parkinsonian midbrains. The findings demonstrate first that the dopamine-containing cell groups of the normal human midbrain differ markedly from each other in the percentage of neuromelanin-pigmented neurons they contain. Second, the estimated cell loss in these cell groups in Parkinson's disease is directly correlated (r = 0.97, P = 0.0057) with the percentage of neuromelanin-pigmented neurons normally present in them. Third, within each cell group in the Parkinson's brains, there is greater relative sparing of non-pigmented than of neuromelanin-pigmented neurons. This evidence suggests a selective vulnerability of the neuromelanin-pigmented subpopulation of dopamine-containing mesencephalic neurons in Parkinson's disease.

Radiochemical micro assays for the determination of choline acetyltransferase and acetylcholinesterase activities

1. The methods for the assay of choline acetyltransferase were based on the reaction between labelled acetyl-CoA and unlabelled choline to give labelled acetylcholine. 2. Both synthetic acetyl-CoA and acetyl-CoA formed from sodium [1-(14)C]acetate or sodium [(3)H]acetate by incubation with CoA, ATP, Mg(2+) and extract from acetone-dried pigeon liver were used. 3. [1-(14)C]Acetylcholine was isolated by extraction with ketonic sodium tetraphenylboron. 4. [(3)H]Acetylcholine was precipitated with sodium tetraphenylboron to remove a ketone-soluble contaminant in sodium [(3)H]acetate and then extracted with ketonic sodium tetraphenylboron. 5. The values of choline acetyltransferase activity obtained in the presence of sodium cyanide or EDTA and synthetic acetyl-CoA were similar to those obtained with acetyl-CoA synthesized in situ. 6. The assay of acetylcholinesterase was based on the formation of labelled acetate from labelled acetylcholine. The labelled acetylcholine could be quantitatively removed from the acetate by extraction with ketonic sodium tetraphenylboron. 7. The methods were tested with samples from central and peripheral nervous tissues and purified enzymes. 8. The blank values for choline acetyltransferase and acetylcholinesterase corresponded to the activities in 20ng. and 5ng. of brain tissue respectively.

Impaired long-term potentiation, spatial learning, and hippocampal development in fyn mutant mice

Mice with mutations in four nonreceptor tyrosine kinase genes, fyn, src, yes, and abl, were used to study the role of these kinases in long-term potentiation (LTP) and in the relation of LTP to spatial learning and memory. All four kinases were expressed in the hippocampus. Mutations in src, yes, and abl did not interfere with either the induction or the maintenance of LTP. However, in fyn mutants, LTP was blunted even though synaptic transmission and two short-term forms of synaptic plasticity, paired-pulse facilitation and post-tetanic potentiation, were normal. In parallel with the blunting of LTP, fyn mutants showed impaired spatial learning, consistent with a functional link between LTP and learning. Although fyn is expressed at mature synapses, its lack of expression during development resulted in an increased number of granule cells in the dentate gyrus and of pyramidal cells in the CA3 region. Thus, a common tyrosine kinase pathway may regulate the growth of neurons in the developing hippocampus and the strength of synaptic plasticity in the mature hippocampus.

Integrated biomarker response: a useful tool for ecological risk assessment

A battery of biomarkers is often used to evaluate the effects of exposure to chemical contaminants and detect responses to environmental stress. Unfortunately, field application of biomarkers is subject to various constraints (e.g., the availability of living material) that can limit data acquisition and prevent the use of multivariate methods during statistical analysis. In these circumstances, a simple method is needed to summarize biomarker responses and simplify their interpretation in biomonitoring programs. The present study used star plots to display results for the panel of biomarkers used for each station and survey. Integrated biomarker response (IBR) was then computed as the star plot area. Star plots using IBR values instead of biomarker data make it possible to visualize between-site and/or between-survey differences for comparison with exposure conditions. This approach was applied to sites in the Baltic Sea and the Seine Estuary, English Channel. In both cases, IBR values were visually compared to polycyclic aromatic hydrocarbons (PAH) or polychlorobiphenyls (PCB) levels measured in mussel or fish tissues. The IBR, as an indicator of environmental stress, appears to be a useful tool for scientists and managers in assessing ecological risk.

Architectonic subdivision of the human orbital and medial prefrontal cortex

The structure of the human orbital and medial prefrontal cortex (OMPFC) was investigated using five histological and immunohistochemical stains and was correlated with a previous analysis in macaque monkeys [Carmichael and Price (1994) J. Comp. Neurol. 346:366-402]. A cortical area was recognized if it was distinct with at least two stains and was found in similar locations in different brains. All of the areas recognized in the macaque OMPFC have counterparts in humans. Areas 11, 13, and 14 were subdivided into areas 11m, 11l, 13a, 13b, 13m, 13l, 14r, and 14c. Within area 10, the region corresponding to area 10m in monkeys was divided into 10m and 10r, and area 10o (orbital) was renamed area 10p (polar). Areas 47/12r, 47/12m, 47/12l, and 47/12s occupy the lateral orbital cortex, corresponding to monkey areas 12r, 12m, 12l, and 12o. The agranular insula (areas Iam, Iapm, Iai, and Ial) extends onto the caudal orbital surface and into the horizontal ramus of the lateral sulcus. The growth of the frontal pole in humans has pushed area 25 and area 32pl, which corresponds to the prelimbic area 32 in Brodmann's monkey brain map, caudal and ventral to the genu of the corpus callosum. Anterior cingulate areas 24a and 24b also extend ventral to the genu of the corpus callosum. Area 32ac, corresponding to the dorsal anterior cingulate area 32 in Brodmann's human brain map, is anterior and dorsal to the genu. The parallel organization of the OMPFC in monkeys and humans allows experimental data from monkeys to be applied to studies of the human cortex.

Histochemically distinct compartments in the striatum of human, monkeys, and cat demonstrated by acetylthiocholinesterase staining

We here report observations on the distribution of acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7) in the striatum of the adult human, the rhesus monkey, and the cat. By the histochemical staining methods of Geneser-Jensen and Blackstad and of Karnovsky and Roots, compartments of low cholinesterase activity were identified in parts of the striatum in all three species. In frontal sections, these enzyme-poor zones appeared as a variable number of weakly stained approximately 0.5-mm-wide zones embedded in a darkly stained background. The zones varied in cross-sectional shape from round to elongated and were sometimes branched. They were most prominent in the head of the caudate nucleus. Three-dimensional reconstructions of serial sections through the caudate nucleus in the human and cat suggest that over distances of at least several millimeters, the zones of low enzyme activity form nearly continuous labyrinths.

Architectonic subdivision of the orbital and medial prefrontal cortex in the macaque monkey

The orbital and medial prefrontal cortex (OMPFC) of macaque monkeys is a large but little understood region of the cerebral cortex. In this study the architectonic structure of the OMPFC was analyzed with nine histochemical and immunohistochemical stains in 32 individuals of three macaque species. The stains included Nissl, myelin, acetylcholinesterase, Timm, and selenide stains and immunohistochemical stains for parvalbumin, calbindin, a nonphosphorylated neurofilament epitope (with the SMI-32 antibody), and a membrane-bound glycoprotein (with the 8b3 antibody). In addition to patterns of cell bodies and myelinated fibers, these techniques allow the visualization of markers related to metabolism, synapses, and neurotransmitters. A cortical area was defined as distinct if it was differentiated in at least three different stains and, as described in later papers, possessed a distinct set of connections. Twenty-two areas were recognized in the OMPFC. Walker's areas 10, 11, 12, 13, and 14 [J. Comp. Neurol. (1940) 73:59-86] have been subdivided into areas 10m, 10o, 11m, 11l, 12r, 12l, 12m, 12o, 13m, 13l, 13a, 13b, 14r, and 14c. On the medial wall, areas 32, 25, and 24a,b,c have been delineated, in addition to area 10m. The agranular insula also has been recognized to extend onto the posterior orbital surface and has been subdivided into medial, intermediate, lateral, posteromedial, and posterolateral agranular insula areas. The OMPFC, therefore, resembles other areas of primate cortex, such as the posterior parietal and temporal cortices, where a large number of relatively small, structurally and connectionally distinct areas have been recognized. Just as the area-specific neurophysiological properties of these parietotemporal areas underlie broader regional functions such as visuospatial analysis, it is likely that the many small areas of the OMPFC also make differential contributions to the general mnemonic, sensory, and affective functions of this region.

Limbic and sensory connections of the inferior parietal lobule (area PG) in the rhesus monkey: a study with a new method for horseradish peroxidase histochemistry

The caudal part of the inferior parietal lobule (area PG) was injected with horseradish peroxidase (HRP) in 6 hemispheres of 5 rhesus monkeys. The retrograde transport of HRP resulted in the labeling of neurons in diverse cortical and subcortical areas. In cortex, labeled neurons were noted in prefrontal cortex (areas 8, 45, 46), in the banks of the intraparietal and superior temporal sulci, in medial parietal cortex, in cingulate cortex, in the retrosplenial area, in area TF and the caudal portions of the parahippocampal region. Subcortical sites with labeled neurons included the necleus basalis of the substantia innominata, the claustrum, the pulvinar and intralaminar thalamic nuclei, the pretectal area, the nucleus locus coeruleus and the raphe nuclei. Although many of the labeled neurons were seen in layers IIIc and V, each cortical area had an individual laminar pattern of labeled neurons. In these experiments, a benzidine dihydrochloride (BDHC) method was used which yields a blue reaction-product at sites containing HRP. BDHC affords superior visibility of labeled neurons, and a significant improvement in sensitivity when compared to a diaminobenzidine procedure in matching series of sections. Additional sections were also stained with a method which allows the simultaneous demonstration of HRP (blue) and acetylcholinesterase (reddish-brown). These revealed that virtually all substantia innominata (nucleus basalis) neurons which project to area PG are also rich in the enzyme acetycholinesterase. These afferents of PG may be classified into 'sensory association', 'limbic' and 'reticular' categories. It is argued that this arrangement of afferent imput may afford a convergence of limbic and sensory information in area PG and that this may subserve a significant function in the process of sensory attention.

Innervation of "painful" lumbar discs

STUDY DESIGN

The authors investigated the innervation of discographically confirmed degenerated and "painful" human intervertebral discs.

OBJECTIVE

To determine the type and distribution patterns of nerve fibers present in degenerated human intervertebral discs.

SUMMARY OF BACKGROUND DATA

The innervation of intervertebral discs has previously been extensively described in fetal and adult animals as well as humans. However, little is yet known about the innervation of severely degenerated human lumbar discs. The question may be posed whether a disc that has been removed for low back pain possesses an increased innervation compared with normal discs.

METHODS

The presence of nerve fibers was investigated using acetylcholinesterase enzyme histochemistry, as well as neurofilament and substance P immunocytochemistry. From 10 degenerated and 2 control discs, the anterior segments were excised and their nerve distribution studied by examining sequential sections.

RESULTS

In all specimens, nerve fibers of different diameters were found in the anterior longitudinal ligament and in the outer region of the disc. In 8 of 10 degenerated discs, fibers were also found in the inner parts of the disc. Substance P-immunoreactive nerve fibers were sporadically observed in the anterior longitudinal ligament and the outer zone of the anulus fibrosus.

CONCLUSIONS

Findings indicate a more extensive disc innervation in the severely degenerated human lumbar disc compared with normal discs. The nociceptive properties of at least some of these nerves are highly suggested by their substance P immunoreactivity, which provides further evidence for the existence of a morphologic substrate of discogenic pain.

Establishment of functional clonal lines of neurons from mouse neuroblastoma

Clonal lines of neurons were obtained in culture from a mouse neuroblastoma. The neuroblastoma cells were adapted to culture growth by the animal-culture alternate passage technique and cloned after single-cell plating. The clonal lines retained the ability to form tumors when injected back into mice. A striking morphological change was observed in the cells adapted to culture growth; they appeared as mature neurons, while the cells of the tumor appeared as immature neuroblasts. Acetylcholinesterase and the enzymes for the synthesis of neurotransmitters, cholineacetylase and tyrosine hydroxylase were assayed in the tumor and compared with brain levels; tyrosine hydroxylase was found to be particularly high, as described previously in human neuroblastomas. The three enzymes were found in the clonal cultures at levels comparable to those found in the tumors. Similarly, there were no remarkable differences between the three clones examined.

Visualization of detailed acetylcholinesterase fiber and neuron staining in rat brain by a sensitive histochemical procedure

A sensitive method for acetylcholinesterase (AChE) histochemistry has been developed which permits simultaneous observation of fine fiber processes and neuron cell bodies. In rat brain, distinctive configurations can be observed which have been difficult to see by other techniques. The staining procedure involves two steps. Tissue sections are incubated first in Karnovsky and Roots medium diluted one-hundredfold; and then with a mixture containing diaminobenzidine (DAB) and H2O2. The reaction product of the first step induces cleavage of hydrogen peroxide in the second step, with a resulting oxidation of DAB to yield a fine precipitate. Addition of metal ions, such as nickel, to the DAB-H2O2 mixture produces high-contrast, Golgi-like images of neuron structures. The technique is much more sensitive than previous methods and greatly reduces background staining caused by crystallization of reaction products. Many potential applications exist for this new technique, in addition to the initial results described here.

Autonomic nerves, mast cells, and amine receptors in human brain vessels. A histochemical and pharmacological study

The studies were performed on operation material from 17- to 63-year-old patients and on fetuses at 19-23 weeks gestational age. Formaldehyde histofluorescence showed the presence of numerous perivascular adrenergic nerves around pial and intracerebral vessels, the carotid system being better supplied than the vertebral system. Cholinergic nerves, visualized by the cholinesterase technique, followed the adrenergic fibers in the plexus formations of the pial arterial system. Histamine-containing mast cells, often with a perivascular distribution, were located with the o-phthaldiadehyde method. Transmural electrical stimulation of the perivascular nerves contracted isolated pieces of pial arteries in a frequency-dependent manner, and the response was inhibited by the adrenergic nerve blocking agent, guanethidine. On the basis of the relative potency of various amines and related compounds in producing a motor response of isolated pial arteries, and the mode of inhibition caused by specific antagonists, various amine receptors could be demonstrated: adrenergic alpha-receptors (mediating contraction) and beta-receptors (dilation), cholinergic muscarinic receptors (dilation) and histamine H2-receptors (mediating dilation). Thus, the amine mechanisms demonstrated in human brain vessels appear to be principally the same of those shown in more extensive studies on laboratory animals.