Identification and localization of ryanodine binding proteins in the avian central nervous system

Ryanodine binding proteins of the CNS have been identified using monoclonal antibodies against avian skeletal muscle ryanodine binding proteins. These proteins were localized to intracellular membranes of the dendrites, perikarya, and axons of cerebellar Purkinje neurons using laser confocal microscopy and immunoelectron microscopy. Ryanodine binding proteins were not found in dendritic spines. Immunoprecipitation and [3H]epiryanodine binding experiments revealed that the cerebellar ryanodine binding proteins have a native molecular weight of approximately 2000 kd and are composed of two high molecular weight (approximately 500 kd) polypeptide subunits. A comparable protein having a single high molecular weight polypeptide subunit was observed in the remainder of the brain. If the ryanodine binding proteins in muscle and nerve are similar in function, then the neuronal proteins may participate in the release of calcium from intracellular stores that are mechanistically and spatially distinct from those gated by inositol trisphosphate receptors.

Sex differences among oxytocin-immunoreactive neuronal systems in the mouse hypothalamus

Serial frontal sections of male and female mouse hypothalamus were immunostained with an antiserum to oxytocin, in order to study the topographical distribution of oxytocinergic perikarya and processes. Numbers of immunostained perikarya were counted in various hypothalamic regions. The oxytocin content of microdissected hypothalamic tissue samples was measured in radioimmunoassays. While the overall topographical distribution of oxytocin neurons in the classical magnocellular nuclei was similar in both genders, quantitative differences could be observed. The numbers of immunostained perikarya and the amounts of oxytocin found in females exceeded by far the numbers and amounts found in males. Male mice had fewer oxytocin-immunostained axons, projecting within the brain, than females. This was especially apparent in parts of the limbic system. Oxytocin-immunostained neurons in the perifornical region, the lateral hypothalamus and the ventral ansa lenticularis were mostly absent in males. It is possible that the observed sex differences in oxytocin immunoreactive brain architecture are due to the different hormonal conditions in males and females.

Evidence for the colocalization of the axonal mitogen for Schwann cells and oligodendrocytes

Axons that normally will encounter either CNS or PNS glia have been shown to contain a powerful mitogen for both Schwann cells and oligodendrocytes. The normally nonmyelinated, nonglial ensheathed cerebellar granule cells have been shown to possess a proliferative signal for Schwann cells, suggesting that a glial mitogen is common to all axons. To determine if a glial mitogen capable of stimulating both Schwann cells and oligodendrocytes is colocalized on all types of axons we have (1) cocultured granule cells with oligodendrocytes, (2) incubated oligodendrocytes with granule cell membranes, and (3) evaluated the ability of heparin extracts of granule cell membranes, splenic nerve microsomes, and axolemma-enriched fractions isolated from rat and bovine CNS to stimulate mitosis of cultured oligodendrocytes. Neither the intact granule cells nor the granule cell membrane fraction stimulated cultured oligodendrocytes to divide. However, heparin extracts of the granule cell membranes were significantly mitogenic to the cultured oligodendrocytes. Heparin extracts of splenic nerve microsomes were more mitogenic than the comparable extract obtained from bovine CNS axolemma-enriched fractions. These results suggest that the neuronal mitogen for oligodendroglia is colocalized with the neuronal mitogen for Schwann cells.

Use of the biotin-avidin system for labelling, isolation and characterization of neural cell-surface proteins

We describe a method for the selective labelling, isolation and electrophoretic analysis of cell-surface molecules and extracellular matrix components. Intact tissues are reacted with activated esters of biotin and the labelled surface molecules identified on Western blots with horseradish-peroxidase-coupled or 35S-labelled streptavidin. Alternatively, the biotinylated proteins can be purified from tissue homogenates by affinity chromatography on an avidin-agarose column. Evidence is presented to show that this method is indeed specific for membrane and matrix components. Its practical application to embryonic neural tissues is demonstrated.

Innervation of somatostatin synthesizing neurons by adrenergic, phenylethanolamine-N-methyltransferase (PNMT)-immunoreactive axons in the anterior periventricular nucleus of the rat hypothalamus

The adrenergic innervation of somatostatin synthesizing neurons located in the anterior region of the rat hypothalamic periventricular nucleus was studied by means of a light and electron microscopic immunocytochemical double labelling technique. This region which is the source of hypophysiotrophic somatostatin immunoreactive (IR) neurons also receives a dense plexus of adrenergic axons as determined by immunocytochemistry of phenylethanolamine-N-methyltransferase (PNMT), the marker enzyme for the central adrenergic system. The simultaneous detection of PNMT and somatostatin antigens in hypothalamic sections of colchicine pretreated animals revealed a congruency in the distribution of the labelled elements and also close juxtaposition of PNMT-IR axons to somatostatin producing neurons. At the ultrastructural level, axo-somatic and axo-dendritic synaptic connections were found between PNMT-containing axons and somatostatin expressing neurons. These morphological findings support the view that the central adrenergic system might influence the production and secretion of growth hormone in the pituitary gland by a direct monosynaptic interaction with somatostatin synthesizing neurons.

Ca2+ binding by Myxicola neurofilament proteins

Titrimetric, 45Ca dialysis, and autoradiographic methods were used to examine how axoplasmic proteins from the giant neuron of the marine annelid Myxicola infundibulum bind calcium. Following the autoradiographic method of Maruyama et al., the 150-160 kD neurofilament subunits were identified as prominent intracellular Ca-binding peptides. Using equilibrium dialysis, extracts of axoplasmic proteins (greater than 50% neurofilament subunits) were examined in 300 mM KCl at different concentrations of free Ca and Mg, and at different pH. Axoplasmic proteins showed a high affinity Ca binding site (K1/2 3-6 microM, capacity 3-7 mumole g-1 protein) at pH 6.8 or pH 7.5. Changing the Mg concentration from 0 to 5 mM had no effect on the Ca binding. Elevating the dialysis pH from 7.0 to 9.0 reduced the apparent number of binding sites for Ca. Using microelectrodes to record the free Ca, microtitrations of axoplasmic proteins were completed by adding small amounts of CaCl2 to 100 microliters volumes of protein solutions. In a medium containing ionic constituents closely resembling those of the Myxicola axon, a Ca binding capacity of 5.0 mumole g-1 protein and a K1/2 of approximately 1 microM were measured.

Glutamate-like immunoreactivity in the retina of a marine teleost, the dragonet

The localisation of endogenous glutamate in the dragonet retina was investigated by light microscopic postembedding silver-enhanced immunogold labeling after incubation with an anti-glutamate antiserum. Rod and cone inner segments and synaptic terminals, as well as the inner plexiform layer, are moderately labeled. Bipolar cells and ganglion cell bodies show strong labeling. In the dorsal inner plexiform layer, the levels with square-patterned bipolar synaptic boutons can be identified by their prominent glutamate-immunoreactivity. These results support the idea that the majority of the neurons that constitute the direct, centripetal pathways through the retina use glutamate as their neurotransmitter.

Effect of excitatory amino acids on microtubule-associated proteins in cultured cortical and spinal neurones

The effect of excitatory amino acid stimulation on the cytoskeleton of cultured spinal cord and cortical neurons was monitored with antibodies against microtubule-associated proteins tau and MAP2. In unstimulated cultures tau-1 immunoreactivity was restricted to axon-like processes. Stimulation with glutamate (0.1-1 mM) or N-methyl-D-aspartate (NMDA) (0.1 mM) resulted in a dramatic increase in the intensity of tau labelling in axons and the appearance of staining within a proportion of neuronal cell bodies and dendrites. Quisqualate or kainate stimulation resulted only in an increase in tau immunoreactivity within axons. The NMDA mediated events were calcium dependent and the effects of all excitatory amino acids could be blocked by specific antagonists. In contrast, following stimulation with excitatory amino acids, MAP2-immunoreactivity was associated with filaments which formed a complex network within the cell body. This suggests that the different excitatory amino acid receptor subtypes can have differential effects on the neuronal cytoskeleton.

Identification and isolation of an axonal plasma membrane enriched fraction from cerebellar granule cell neurites

A procedure is described to isolate a fraction enriched in cerebellar granule cell neuritic membranes. Morphological markers that are specific for either the granule cell perikarya or neuritic membranes have been identified. Concanavalin A (Con A) has been shown to bind predominantly to the granule cell neurites whereas, the enzymes acetylcholinesterase (AChE) and 2',3',cyclic nucleotide-3'-phosphohydrolase (CNPase) are localized predominantly in the neuronal cell bodies. The membrane fraction enriched in Con A binding has been used to generate a monoclonal antibody which morphologically recognized the cerebellar granule cell neuritic membrane. Following fractionation of the granule cells, each marker was used to identify the cellular origin of the fractions. The neuritic markers Con A and the neuritic membrane antibody MR2 bound predominantly to membranes found in the 29.1% and 31.5% region of the sucrose gradient. The perikaryal markers, CNPase and AChE activity were most enriched in membrane fractions found at a sucrose concentration of 23% and 21%, respectively. Morphological examination of the neuritic enriched fraction shows that it contains predominantly membranous material with few subcellular organelles. The protein profiles of the cerebellar granule cell fractions are unique when compared with the protein profiles of other neuronal and non-neuronal fractions. The membrane fraction isolated from the cerebellar granule cells should prove useful in furthering our understanding of the axonal influence on glial development.

Identification of early developing axon projections from spinal interneurons in the chick embryo with a neuron specific beta-tubulin antibody: evidence for a new 'pioneer' pathway in the spinal cord

The early development of interneurons in the chick embryo spinal cord was studied using a monoclonal antibody against a neuron-specific beta-tubulin isoform. Early developing interneurons were divided into two cell groups on the basis of their location and the pattern of growth of their axons. One group is composed of cells that establish a primitive longitudinal pathway (PL-cells), whereas the other group contains cells constituting a circumferential pathway (C-cells). The onset of axonal development in both cell groups occurs at stage (st.) 15 (embryonic day, (E), 2) in the branchial segments, which is prior to axonogenesis of motoneurons. PL-cells develop in the region between the floor plate and the motoneuron nucleus. Their axons are the first neuronal processes ('pioneer axons') to arrive in the ventrolateral marginal zone and they project both rostrally and caudally to establish a primitive longitudinal association pathway at the ventrolateral surface of the neural tube. This pathway is formed before axons of C-cells arrive in the ventrolateral region. The first C-cells are initially located in the most dorsal portion of the neural tube, whereas later appearing C-cells are also located in both intermediate and ventral regions of the neural tube. The axons of C-cells project ventrally, without fasciculating, along the lateral border of the neural tube. Some of their axons enter the ipsilateral ventrolateral longitudinal pathway at st. 17. We often observed apparent contacts and interactions between preexisting axons of PL-cells and newly arriving axons of C-cells. The axons of commissural C-cells first enter the floor plate at st. 17 and cross the midline at st. 18. Axons of C cells begin to join the contralateral ventrolateral longitudinal pathway at st. 18+ to st. 19. In the floor plate region, contacts between growth cones and axons were often observed. However, axons in the floor plate at these stages were not fasciculated. These observations establish the timing and pattern of growth of axons from two specific populations of early developing interneurons in the chick spinal cord. Additionally, we have identified an early and apparently previously undescribed 'pioneer' pathway that constitutes the first longitudinal pathway in the chick spinal cord.

Computerized quantification of immunofluorescence-labeled axon terminals and analysis of co-localization of neurochemicals in axon terminals with a confocal scanning laser microscope

The confocal scanning laser microscope (CSLM) offers improved optical resolution and contrast, high photometric precision, and the ability to make optical sections. These benefits were explored for use in quantitative analysis of immunofluorescence-labeled axon terminals. Guidelines were obtained for adjustments of the CSLM parameters. In the present applications, bleaching of the fluorescence did not represent a serious obstacle to analysis with the CSLM. A method was developed to distinguish the background fluorescence from the specific fluorescence labeling. This procedure made way for the development of automated quantification of immunolabeled axon terminals. The automated procedures substantially reduced the man-hour expenditure for analysis and provided highly reproducible quantifications compared with manual methods. The increased resolution and contrast of the CSLM allowed measurements of the fluorescence signal strength of individual axon terminals. The CSLM also allowed detection of co-localized neurochemicals in axon terminals.

Optic nerves in plethodontid salamanders (amphibia, urodela): neuroglia, fiber spectrum and myelination

In five species of lungless salamanders, family Plethodontidae, which all show highly developed visual abilities, the ultrastructure of the optic nerve was investigated and the total number of retinal ganglion cell axons, the percentage of myelinated axons, and the volume densities of glia and axons were determined. More than 80% of all axons were smaller than 0.4 micron and only 2-3% were larger than 0.8 micron. In individual nerves the degree of myelination varied between 1 and 9% which is in the range reported for other amphibian species. The miniaturized and highly paedomorphic species Batrachoseps attenuatus was an exception because only very few or even no myelinated axons were present in the nerve, which is unique among gnathostome vertebrates. The five investigated species had total numbers of axons ranging from 26,000 in Batrachoseps attenuatus to about 50,000 in Plethodon jordani. These numbers are the lowest found among vertebrates with an elaborated visual system. The amount of glial material in the optic nerve varied between 25 and 50%, with larger nerves possessing more glia than smaller ones. Ultrastructural analysis revealed that the optic nerve of each species contained both astrocytes and oligodendrocytes, although often in immature form. In Batrachoseps attenuatus the glia showed features of both astrocytes and oligodendrocytes which reflect an undifferentiated state.

The development of a simple scaffold of axon tracts in the brain of the embryonic zebrafish, Brachydanio rerio

We have examined neuronal differentiation and the formation of axon tracts in the embryonic forebrain and midbrain of the zebrafish, between 1 and 2 days postfertilisation. Axons were visualised with three techniques; immunocytochemistry (using HNK-1 and antiacetylated tubulin antibodies) and horseradish peroxidase (HRP) labelling in whole-mounted brains, and transmission electron microscopy. Differentiation was monitored by histochemical staining for acetylcholinesterase (AChE). These independent methods demonstrated that a simple grid of tracts and commissures forms the initial axon scaffold of the brain. At 1 day, the olfactory nerve, four commissures, their associated tracts and three other non-commissural tracts are present. By 2 days, these tracts and commissures have all greatly enlarged and, in addition, the optic nerve and tract, and three new commissures and their associated tracts have been added. Small applications of HRP at various sites revealed the origins and projections of some of these earliest axons. Retrogradely labelled cell bodies originated from regions that were also positive for AChE activity. At 1 day, HRP-labelled axons were traced: (1) from the olfactory placode through the olfactory nerve to the dorsal telencephalon; (2) from the telencephalon into the tract of the anterior commissure and also to the postoptic region of the diencephalon; (3) from the hindbrain through the ventral midbrain and diencephalon to the postoptic commissure; (4) from the dorsal diencephalon (in or near the epiphysis) to the tract of the postoptic commissure; (5) from ventral and rostral midbrain through the posterior commissure. Three new projections were demonstrated at 2 days: (1) from the retina through the tract of the postoptic commissure to the tectum; (2) from the telencephalon to the contralateral diencephalon; and (3) from the telencephalon to the ventral flexure. These results show that at 1 day, the zebrafish brain is impressively simple, with a few small, well-separated tracts but by 2 days the brain is already considerably more complex. Most of the additional axons added onto pre-existent tracts rather than pioneered new ones supporting the notion that other axons play a crucial role in the guidance of early central nervous system (CNS) axons.

[Cholinergic innervation of vasopressin-containing cells of the blood vessels of the brain in man]

By means of immunochemical method the presence of vasopressin in the melanocytes of the man's brain arteries was found. The terminals of the cholinergic axons come to an end on the surface of these cells. It is suggested that the melanocytes take part in the regulation of the brain arteries mobility.

[Ultrastructural features of somatostatin-containing neurons of the hypothalamus of rats with protein insufficiency]

The electron microscopic investigation was performed to analyze somatostatin-contained nerve terminals in the median eminence of 21 days old malnourished rats' hypothalamus. In nerve terminals of malnourished animals in compared with controls ones there was found the increased density of granular vesicles (11.62 +/- 0.40 and 8.56 +/- 0.39 in 1 micron2, respectively) and decreased density of electron lucent vesicles with 120-160 nm diameter (1.66 +/- 0.18 and 3.43 +/- 0.26 in 1 micro2, respectively). The revealed increase in density of granular vesicles in axon terminals with positive immunohistochemical reaction to somatostatin in malnourished rats was explained by slow somatostatin release.

Association of dopaminergic fibers with corticotropin releasing hormone (CRH)-synthesizing neurons in the paraventricular nucleus of the rat hypothalamus

Catecholamines are known to exert a central influence on the hypothalamo-hypophyseal-adrenal neuroendocrine system. The selective dopaminergic innervation of the hypothalamic paraventricular nucleus (PVN) and putative relationships between dopaminergic fibers and corticotropin releasing hormone (CRH)-synthesizing neurons were studied in the male rat by means of immunocytochemistry following the elimination of noradrenergic and adrenergic inputs to the hypothalamus. A 3.0-mm-wide coronal cut was placed unilaterally in the brain at the rostral level of the mesencephalon. All neuronal structures from the cortex to the ventral surface of the brainstem, including the ascending catecholaminergic fiber bundles were transected. This surgical intervention resulted in the accumulation of dopamine-beta-hydroxylase (DBH)-immunoreactivity in axons proximal to the cut, and an almost complete disappearance of DBH activity in those located distal to the lesion. Two weeks following the operation, DBH immunoreactivity was significantly diminished in the PVN located on the side of lesion, while tyrosine hydroxylase (TH)-immunoreactivity was present in a substantial number of fibers in the same nucleus. Both DBH- and TH-immunoreactive axons were preserved in the contralateral PVN. Simultaneous immunocytochemical localization of either DBH- or TH-IR fibers and corticotropin releasing hormone-synthesizing neurons in the hypothalami from brainstem-lesioned, colchicine treated animals revealed that the distribution of catecholaminergic fibers and CRH neurons is homologous within the PVN of the intact side. Only a few scattered DBH-immunoreactive axons were detected among CRH-producing neurons in the PVN on the side of the lesion. In contrast, many tyrosine hydroxylase containing neurons and neuronal processes were observed on the lesioned side and the TH-IR fibers established juxtapositions with CRH-synthesizing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Membrane proteins of synaptic vesicles and cytoskeletal specializations at the node of Ranvier in electric ray and rat

Binding sites for antibodies against membrane proteins of synaptic vesicles have been shown to be enhanced at nodes of Ranvier in electromotor axons of the electric ray Torpedo marmorata and sciatic nerve axons of the rat, using indirect immunofluorescence and monoclonal antibodies against the synaptic vesicle transmembrane proteins SV2 and synaptophysin (rat) or SV2 (Torpedo). In the electric lobe of Torpedo, vesicle-membrane constituents occurred at higher density in the proximal axon segments covered by oligodendroglia cells than in the distal axon segments where myelin is formed by Schwann cells. Antibody binding sites were enhanced at nodes forming the borderline of the central and peripheral nervous systems. Filamentous actin was present in the Schwann-cell processes covering both the nodal and the paranodal axon segments as suggested by the pattern of phalloidin labelling. Furthermore, in rat sciatic nerve, Schmidt-Lanterman incisures were intensely labelled by phalloidin. A similar nodal distribution was found for binding sites of antibodies against actin and myosin. Binding of antibodies to tubulin was enhanced at nodes in Torpedo electromotor axons. The apparent nodal accumulation of constituents of synaptic vesicle membranes and the presence of filamentous actin and of myosin are discussed in relation to the substantial constriction of the axoplasm at nodes of Ranvier.

Immunohistochemical evidence for reorganization of tau in the plaques and tangles in Alzheimer's disease

Cytochemical and biochemical techniques have been used to assess the relationship of epitopes on the microtubule-associated protein, tau, to the cytoskeletal pathology of Alzheimer's disease. The main probes were Tau-1 and Alz-50, two monoclonal antibodies which recognize tau and a potentially related 68 kDa protein. Sequential treatment of tissue slices with combinations of the antibodies showed that each blocked the binding of the other to neurofibrillary tangles and neuritic plaques but not to normal axons. Western blot analysis of tau proteins isolated from Alzheimer's disease brains did not reveal such blocking patterns. The issue of steric hindrance affecting antibody binding in tissue sections was addressed by using Alz-50 in combination with Tau-2, another monoclonal antibody recognizing tau on blots and in Alzheimer's disease pathology. Neither antibody blocked the binding of the other to neurofibrillary tangles and neuritic plaques. These data suggest that the Alz-50 and Tau-1 epitopes are selectively organized in the tangles and plaques to be in close proximity which supports the hypothesis that in Alzheimer's disease pathology, tau is modified.

Immunohistochemical differential distribution of S-100 alpha and S-100 beta in the peripheral nervous system of the rat

The localization of the alpha subunit of the S-100 protein (S-100 alpha) and beta subunit (S-100 beta) was studied in the peripheral nervous system of the rat. In peripheral nerves, S-100 alpha and S-100 beta were found in the cytoplasm of Schwann cells. Axons were positively stained in part by S-100 alpha and almost totally by S-100 beta. In the dorsal root ganglia, S-100 alpha was found in satellite cells and their processes and in some neurons. S-100 beta was found in more of the large neurons, but almost all of the small neurons were negative for S-100 beta. In the anterior horn cells, S-100 beta staining was stronger than that of S-100 alpha. In Schwann cells, both S-100 alpha and S-100 beta were present on the rough endoplasmic reticulum, free ribosomes, and nucleus, as seen by electron microscopy. The S-100 alpha and S-100 beta in axons were associated with microtubules and neurofilaments.

Noradrenergic and peptidergic innervation of the extrinsic vessels and microcirculation of the rat cremaster muscle

The noradrenergic and peptidergic innervation of the extrinsic vessels and microcirculation of the rat cremaster muscle was examined. Catecholamine-containing nerves were identified histochemically by glyoxylic acid-induced fluorescence and tyrosine hydroxylase immunoreactivity (TH-IR). The extrinsic pudic-epigastric artery and vein as well as the entire intramuscular arteriolar network was innervated by noradrenergic axons. The capillaries and intramuscular venules of the cremaster muscle were devoid of a noradrenergic innervation. Immunohistochemical double-labeling demonstrated that most, if not all, of the TH-IR axons also possessed neuropeptide Y immunoreactivity (NPY-IR), implying colocalization of the norepinephrine and NPY in the perivascular nerves. No vasoactive intestinal peptide immunoreactivity (VIP-IR) was found, except for occasional VIP-IR axons associated with the pudic-epigastric artery. Substance P immunoreactive (SP-IR) axons formed a sparse plexus around the arteries and larger arterioles. Calcitonin gene-related peptide immunoreactivity (CGRP-IR) had a similar distribution to the SP-IR axons. CGRP-IR was also observed in axons alongside some smaller arterioles and capillaries. The extrinsic vessels and intramuscular arteriolar network of the rat cremaster muscle are innervated by noradrenergic axons which contain NPY and by presumed sensory nerves containing SP and/or CGRP. Both types of nerves may contribute to regulation of microvascular function.

An 18-kd heparin-binding protein of developing brain that is distinct from fibroblast growth factors

An 18-kd heparin-binding protein (p18) was isolated from perinatal rat brain. Although the protein closely resembles the fibroblast growth factors in its strong binding to heparin and in its apparent molecular mass, it has a distinct structure. This was concluded from the amino-terminal sequence analysis that identified a unique structure containing a cluster of lysine residues. Antipeptide antibodies were raised in rabbits according to the sequence analysis and affinity purified using a synthetic peptide. The antibodies were shown to bind specifically to p18, which was immunochemically distinct from the basic fibroblast growth factor. The antipeptide antibodies detected p18 in brain but not in liver, kidney, heart or skeletal muscle. The content of the protein was shown to undergo a remarkable developmental change corresponding to the time period of rapid sprouting of axons and dendrites in brain. The content of p18 was rapidly increased at the time of birth until the postnatal age of approximately 1 week, after which it was decreased to values less than 10% in young adults as compared to the content found in perinatal rats. p18 also enhanced neurite outgrowth in brain neurons in vitro. The protein was stained in neurons in cells dispersed from perinatal brain. The properties of p18 suggest that it has a role in the growth and maturation of brain.

Ultrastructural localization of thyrotropin-releasing hormone immunoreactivity in the dorsal vagal complex in rat

Thyrotropin-releasing hormone-like immunoreactivity (TRH-LI) was localized at the ultrastructural level in the dorsal vagal complex (DVC: dorsal motor nucleus of the vagus (DMV) and the nucleus of the solitary tract (NST] in rat. TRH-LI was concentrated in large granular vesicles in axons, presynaptic terminals, and non-synaptic axon varicosities. TRH-LI presynaptic terminals established both asymmetric and symmetric synaptic contacts with dendrites. These observations are consistent with recently described direct inhibitory and facilitatory effects of TRH on the electrical activity of neurons in the DVC.

Distribution of phenylethanolamine N-methyltransferase cell bodies, axons, and terminals in monkey brainstem: an immunohistochemical mapping study

Adrenaline (epinephrine) is an important candidate transmitter in descending spinal control systems. To date intrinsic spinal adrenergic neurons have not been reported; thus adrenergic input is presumably derived from brainstem sites. In this regard, the localization of adrenergic neurons in the brainstem is an important consideration. Maps of adrenergic cell bodies and to a lesser extent axons and terminal fields have been made in various species, but not in monkeys. Thus, the present study concerns the organization of adrenergic systems in the brainstem of a monkey (Macaca fascicularis) immunohistochemically mapped by means of an antibody to the enzyme phenylethanolamine N-methyltransferase (PNMT). PNMT-immunostained cell bodies are distributed throughout the medulla in two principal locations. One concentration of labeled cells is in the dorsomedial medulla and includes the nucleus of the solitary tract (NTS), the dorsal motor nucleus of the vagus (X), and an area ventral to X in a region of the reticular formation (RF) known as the central nucleus dorsalis (CnD) of the medulla. A few scattered cells are observed in the periventricular gray just ventral to the IVth ventricle and on midline in the raphe. The second major concentration of PNMT-immunostained cells is located in the ventrolateral RF, lateral and dorsolateral to the inferior olive (IO), including some cells in the rostral part of the lateral reticular nucleus (LRN). Terminal fields are located in the NTS, X, area postrema (AP), and the floor of the IVth ventricle in the medulla and pons. A light terminal field is also observed in the raphe, particularly raphe pallidus (RP). A heavy terminal field is present in locus coeruleus (LC). Fibers labeled for PNMT form two major fiber tracts. One is in the dorsomedial RF extending as a well-organized bundle through the medulla, pons, and midbrain. A second tract is located on the ventrolateral edge of the medulla and caudal pons. Fibers in this tract appear to descend to the spinal cord. A comparison with maps of other catecholamine neurons in primates is discussed, confirming that the distribution of the adrenergic system in monkeys is similar to that described in the human.

Acute action of DSP-4 on central norepinephrine axons: biochemical and immunohistochemical evidence for differential effects

Previous immunohistochemical studies of the long-term effects of the noradrenergic neurotoxin DSP-4 have demonstrated a remarkably selective vulnerability of norepinephrine (NE) axons of the locus coeruleus (LC). NE axons originating in non-LC NE neurons appear to be largely resistant to the neurotoxic action of DSP-4. We conducted this study to evaluate the acute effects of DSP-4 on NE axons in four different brain regions: cerebral cortex, cerebellum, ventral forebrain, and hypothalamus. NE levels were determined by high-performance liquid chromatography (HPLC) 6 and 24 hr and 14 days after DSP-4 administration. NE axons in these brain regions were visualized in brain sections at 6 and 24 hr after drug treatment, using a specific antiserum to NE. HPLC assays revealed profound reductions of NE levels in cerebral cortex and cerebellum, but only minor decreases in ventral forebrain and hypothalamus. NE immunohistochemistry showed dramatic differences in the acute effects of DSP-4 on NE axon staining: nearly complete loss of staining in cortex and cerebellum, in contrast to an almost unchanged staining pattern in ventral forebrain and hypothalamus. This study demonstrates that NE immunohistochemistry is a valuable tool to assess the acute effects of DSP-4 on NE axons in different brain regions. The results provide the first direct evidence that NE axons are not uniformly acted on by DSP-4 and suggest that the acute effects of DSP-4 are restricted to LC axons.

Identification of protein-bound oligosaccharides on the surface of growth cones that bind to muscle cells

In the accompanying paper (Gabel, Den, and Ambron, in press) it was shown that eight populations of glycopeptides are synthesized by single neurons of Aplysia californica. To see which glycopeptides might mediate interactions with target cells, we first identified glycopeptides that are transported selectively to synapses and growth cones. The giant neuron R2 was injected intrasomatically with 3H-glucosamine. Twenty-four hours later, 3H-glycopeptides in the axon and cell body were isolated and resolved by serial lectin affinity chromatography. Of the eight populations, the biantennary-type glycopeptides (GPbi) and those that bind to WGA (GPwga) were preferentially associated with rapidly transported glycoproteins. In contrast, the glycopeptide that consists of N-acetylglucosamine O-linked to ser/thr was mostly retained in the cell body. GPbi and GPwga were also preferentially transported to growth cones. Analyses of RUQ cells, exposed to 3H-glucosamine in vitro for 36 h showed an enrichment of GPbi and GPwga at the growth cone relative to the cell body. The disposition of the various glycopeptides in growing neurons was also examined using FITC lectins. FITC-coupled WGA, Vicia vellosa, and lentil lectin showed extensive staining of the cell body, but only WGA stained the growth cones. To investigate if GPwga interacts specifically with target cells, these glycopeptides were isolated from the neurons of 180 abdominal ganglia. GPwga, other Aplysia glycopeptides, and glycopeptides prepared from ovalbumin were coupled separately to fluorescent spheres. The spheres were then added to muscle cells isolated from the auricle of the heart, which is innervated by many neurons from the ganglion. While spheres coupled to GPwga bound to the muscle cell surface, the other glycopeptides did not. These results indicate that glycopeptides class GPwga, found among rapidly transported glycoproteins and on the growth cone surface, is able to bind to muscle cells and may therefore play some role in neuron-target interactions.

Serotonin-containing axon terminals in the hypoglossal nucleus of the rat. An immuno-electronmicroscopic study

The morphology and distribution of serotonin-containing axon terminals in the rat hypoglossal nucleus (XII) was investigated immunocytochemically at the electron microscopic level. Serotonin-positive profiles were found throughout all regions of XII and included unmyelinated axons, varicosities and axon terminals. Most labeled profiles (68.1%) were nonsynaptic unmyelinated axons and varicosities, while synaptic profiles, ending on dendrites and somata, were seen less frequently (28.7%). The majority of labeled axon terminals (76.9%) ended on small-to-medium-sized dendrites. Most axodendritic terminals contained small, round agranular vesicles (20-55 microns), several large (60-100 microns) dense core vesicles, and were associated with a pronounced asymmetric postsynaptic specialization. By contrast, labeled axosomatic terminals were seen less often than those ending on dendrites (23.0%). Axosomatic terminals typically contained small, round, agranular and large dense core vesicles and were associated with a symmetric or no postsynaptic specialization. These results provide the structural substrates for elucidating the functional role of serotonin in tongue control.

Axon-myelin relationships in rat cranial nerves III, IV, and VI: a morphometric study of large- and small-fibre classes

The primary objectives of this study were to determine (1) if quantitative axon-myelin relationships are similar for large- and for small-fibre classes within individual nerves and (2) if the same axon-myelin relationships hold for equivalent fibre classes in closely similar nerves. The oculomotor, trochlear, and abducent nerves of the rat were examined since they each contain distinct large- and small-fibre classes and are similar in a wide range of anatomical and developmental respects. Accordingly, morphometric analyses of axon-myelin relationships were performed separately on large and small fibres of each of the three nerves. Within each nerve, the setting of the relationship between the two parameters was found to be different for the two fibre classes: Scatterplots relating sheath thickness to axon perimeter for large fibres were shifted upwards relative to those for small fibres. These differences were also reflected in the positions of the regression lines fitted to the plots and in the g-ratios. Significant differences were found between nerves in relation to their large fibres: Those of the abducent nerve had significantly thicker sheaths, those of the oculomotor nerve had significantly smaller axon perimeters, and the myelin sheath-axon perimeter relationship of the abducent nerve differed significantly from that of the other two. This study therefore shows that morphometric axon-myelin relationships may differ significantly between equivalent fibre classes of nerves that are closely similar in respect of morphological class, central origin, peripheral distribution, developmental environment, and function.

Reorganization of intrinsic components in the distal motor axon during outgrowth

We have studied the changes in the distribution of three intrinsic axonal components during the growth and maturation of sprouts in vivo. Neurofilaments, tubulin and synaptophysin, a synaptic vesicle protein, were visualized in motor axons and their sprouts using immunocytochemical staining of frozen longitudinal sections of muscle. We examined changes in these elements in sprouts regenerating after axonal crush injury and in those evoked from intact axons by denervation changes in muscle. Our results show that intrinsic axonal components move into newly formed motor axon sprouts in different temporal patterns. Based on the patterns of reorganization of staining of intrinsic axonal components, two types of outgrowth can be distinguished. One type, synaptic elaboration, is manifest by short, broad axonal processes that produce enlargement of the synaptic zone (synaptophysin staining) with little change in the distribution of intrinsic cytoskeletal elements. A second type of outgrowth, axonal elongation, occurs during axonal regeneration and ultraterminal sprouting and is longitudinal in form. In these sprouts there is a sequential appearance of neurofilament and then, several days later, tubulin immunostaining. Synaptophysin only accumulates in these sprouts after two weeks at points of synaptic contact with a muscle fibre.

Ultrastructural immunocytochemical localization of B-50/GAP43, a protein kinase C substrate, in isolated presynaptic nerve terminals and neuronal growth cones

Accumulating evidence indicates that the neuron-specific B-50/GAP43, a substrate for protein kinase C, plays a role in neuronal differentiation and neuritogenesis during nervous tissue development and axonal regeneration. An ultrastructural immunocytochemical study on the localization of B-50 in presynaptic terminals (synaptosomes) isolated from the frontal cortex of 6-week-old rats, and in neuronal growth cones, isolated from forebrains of 5-day-old rats, the majority of B-50 is detected at the surrounding neuronal plasma membrane. In both neuronal growth cones and synaptosomes, a relatively small fraction of B-50 in the cytoplasm was not evidently associated with internal membranes. Our results indicate that B-50 is mainly located at the cytoplasmic face of the synaptosomal and neuronal growth cone plasma membrane. The similar B-50 localization in neuronal growth cones and synaptosomes suggests that, both in extending axons and mature synaptic terminals, B-50 may exert identical functions as a protein kinase C substrate at the plasma membrane.

Differential utilization of beta-tubulin isotypes in differentiating neurites

beta-Tubulin is encoded in vertebrate genomes by a family of six to seven functional genes that produce six different polypeptide isotypes. We now document that although rat PC-12 cells express five of these isotypes, only two (classes II and III) accumulate significantly as a consequence of nerve growth factor-stimulated neurite outgrowth. In contrast to previous efforts that have failed to detect in vivo distinctions among different beta-tubulin isotypes, we demonstrate using immunoblotting with isotype-specific antibodies that three beta-tubulin polypeptides (classes I, II, and IV) are used preferentially for assembly of neurite microtubules (with approximately 70% of types I and II assembled but only approximately 50% of type III in polymer). Immunofluorescence localization shows that an additional isotype (V) is partially excluded from neurites. Distinctions in in vivo localization of the neuron-specific, class III isotype have also been directly observed using immunofluorescence and immunogold electron microscopy. The sum of these efforts documents that some in vivo functional differences between tubulin isotypes do exist.

Galanin-like immunoreactivity in sympathetic and parasympathetic neurons of the toad Bufo marinus

Immunoreactivity (IR) to galanin (GAL) was detected in a wide range of peripheral autonomic neurons in the toad Bufo marinus. Forty percent of adrenergic nerve cell bodies in paravertebral sympathetic ganglia had GAL-IR in addition to neuropeptide Y (NPY)-IR. Some of these neurons projected to systemic arteries. GAL-IR was localized in parasympathetic neurons supplying the heart, lung, pulmonary artery, bladder, rectum and tongue. Eighty-two percent of intracardiac vagal nerve cell bodies had both GAL-IR and somatostatin (SOM)-IR. GAL-IR and SOM-IR were also co-localized in cholinergic post-ganglionic vagal neurons supplying the lung musculature and the pulmonary artery, and in neurons intrinsic to the bladder. Many postganglionic glossopharyngeal neurons in the tongue contained both GAL-IR and vasoactive intestinal peptide (VIP)-IR. Therefore, in Bufo marinus, a GAL-like peptide, in combination with other peptides or with adrenaline or acetylcholine, may be involved in neurotransmission in several different functional classes of autonomic neurons.

The neuronal response to injury as visualized by immunostaining of class III beta-tubulin in the rat

The neuronal response to trauma of the brain and spinal cord was examined by staining sections of injured central nervous system (CNS) with a monoclonal antibody (TuJ1) that recognizes class III beta-tubulin exclusively. Because class III beta-tubulin is expressed by neurons and not by glia, this monoclonal antibody stains neuronal cell bodies, dendrites, axons and axonal terminations darkly with a pale staining background. Thus, the TuJ1 antibody is extremely useful, revealing the fine details of axons and their terminations, as well as significant injury-related alterations in the composition of the somatic cytoskeleton.

Immunohistochemical localization of intermediate filament and S-100 proteins in several non-endocrine cells of the human pituitary gland

The presence and distribution of glial fibrillary acidic protein, vimentin, neurofilament protein, cytokeratins No. 8 (52 Kd), No. 18 (45 Kd) and No. 19 (40 Kd) and S-100 protein in pituicytes, folliculo-stellate cells, the epithelium of the Rathke's cysts and squamous cell nests of the pars tuberalis were investigated immunohistochemically by the peroxidase-antiperoxidase (PAP) method in eleven normal human pituitary glands. An identical immunostaining pattern was expressed by both folliculo-stellate cells and pituicytes. In both cell types the immunostaining for glial fibrillary acidic protein (GFAP), S-100 protein and vimentin was strongly positive. These results indicate the probable glial origin of the folliculo-stellate cell, and enlarge the group of glial cell types expressing vimentin. The co-expression of cytokeratins No. 8 and 19, both characteristic for simple epithelia, and S-100 protein was evident in the epithelial cells lining the Rathke's cysts and the squamous cell nests of the pars tuberalis. Furthermore, some epithelial cells of the Rathke's cysts co-expressed cytokeratins, S-100 protein and GFAP, a fact seldom reported and only in relation to rare neoplasms. The cytokeratin No. 18, characteristic for glandular epithelia, was not clearly demonstrated. Finally, the neurofilament protein was detected only in axons of the neurohypophysis; no immunopositive cells could be found throughout the adenohypophysis. Similarities in the antigenic patterns of these cell populations and the possible relation with their origin and nature are discussed.

Peptide immunoreactivity of unmyelinated primary afferent axons in rat lumbar dorsal roots

The present study demonstrates calcitonin gene-related peptide (CGRP), somatostatin (SOM), bombesin (BOM), and substance P (SP) at the electron microscopic level in lumbar dorsal root axons of normal rats. The highest percentages of labeled axons were for CGRP (14%) and then, in descending order, for SP (8.6%), SOM (6.8%), and BOM (3.1%). The labeled axons were exclusively unmyelinated for SP, SOM, and BOM, and predominantly unmyelinated for CGRP. These data are consistent with the data for labeled sensory cell bodies for these same compounds. We emphasize that these peptides were immunocytochemically visualized in the dorsal roots without experimental manipulation, such as colchicine or dorsal root ligation. Quantitative sampling of this type can be used to assay changes in response to physiological stimuli in numbers of sensory axons that contain identifiable concentrations of these peptides.

Localization of GABA-like immunoreactivity in the ectostriatum of domestic chicks: GABA immunocytochemistry combined with Golgi impregnation

The distribution of GABA-like immunoreactivity (GABA-LI) in the ectostriatal core (Ec) of domestic chicks (one to two days old) was investigated using (1) preembedding GABA immunocytochemistry and (2) Golgi impregnation and gold-toning combined with postembedding GABA immunocytochemistry. Two major classes of neurons which display GABA-LI were identified in chick Ec. Firstly, large GABA immunopositive cells which comprise at least two further subtypes: an ovoid or polygonal form of 14-18 microns diameter with no apparent polarity of dendrites and a smaller cell (10-14 microns) with ovoid or basket-shaped soma and often more polarized dendritic ramification. In both subtypes the dendritic surface is smooth or sparsely spiny. Secondly, a small GABA immunopositive cell which is characterized by a round cell body of 5-8 microns diameter and thin and sparsely ramifying dendrites of smooth surface or with irregular protrusions. Based upon comprehensive descriptions of ectostriatal cytoarchitectonics (Tömböl et al., 1988c), and synaptology (Watanabe et al., 1985), we argue that the GABA-immunopositive cell types of chick Ec are likely to represent inhibitory interneurons comparable with GABAergic inhibitory cell types described in mammalian visual cortex.

The Drosophila melanogaster l(2)gl gene encodes a protein homologous to the cadherin cell-adhesion molecule family

Mutations in the recessive Drosophila tumor gene l(2)gl affect growth and structural properties of neural tissues and imaginal discs during larval development. We have analyzed the cellular localization of transcripts and a 130-kDa protein encoded by the l(2)gl gene, using in situ hybridization and immunofluorescence techniques. Transcripts of maternal origin are detected in freshly laid eggs and are homogeneously incorporated into blastoderm cells. The protein is found at low levels in all embryonic tissues after blastoderm formation. In later stages differential expression of the protein is observed, particularly in cells of the nervous system. The protein is located at the cell surface of dissociated embryonic cells. Anti-l(2)gl sera show cross-reaction to a mouse protein that is localized at cell-cell contact sites in tissue culture cells. Moreover, amino acid sequence homology to deduced amino acid sequences of members of the vertebrate cadherin cell-adhesion molecule family suggests that the l(2)gl gene product may have properties of a cell-adhesion molecule.

Dystrophic neuropeptidergic neurites in senile plaques of Alzheimer's disease precede formation of paired helical filaments

The relationship between peptidergic neurites and paired helical filaments (PHF)-positive neurites in Alzheimer's disease (AD) senile plaques (SP) was studied using combined fluorescence and bright field optics. Cryostat sections of AD hippocampi were first stained by thioflavine-S and immunolabeled with antisera raised against different neuropeptides: somatostatin 28(1-12) (som 28(1-12)), somatostatin 14 (som 14), neuropeptide Y (NPY), cholecystokinin (CCK) and substance P (sP). Secondly, using the elution-restaining procedure, sections were immunolabeled with anti-tau/PHF. In immature SP, clusters of abnormal, swollen neurites were found. The dystrophic, strongly peptidic-positive neurites contained less PHF than the poorly positive ones. Cell bodies, exhibiting a peptidic content, could be found within SP without any alteration. These results suggest the following sequence of events: an extracellular poisoning mechanism, perhaps the amyloid substance, first changes the structure of presynaptic endings and causes the formation of ballooning dystrophic neurites filled with their normal peptidic content. Subsequently, intracellular degradation occurs with formation of the PHF. Then the other structures such as dendrites and perikarya are damaged by the same mechanism. Therefore this phenomenon seems to precede any formation of PHF in SP.

Characterization of a novel 66 kd subunit of mammalian neurofilaments

A 66 kd protein, pl 5.4, was purified from the Triton-insoluble fraction of rat spinal cord. This protein formed 10 nm filaments in vitro. The 66 kd protein was unique, although it shared homology with the 70 kd neurofilament protein (NF-L) and vimentin. An antiserum (anti-66) specific to the 66 kd protein did not cross-react with any of the neurofilament triplet proteins. In the spinal cord, anti-66 intensely stained the axons of the anterior and lateral columns. However, afferents from dorsal root ganglia and the efferents from the motoneurons were negative. In the cerebellum, anti-66 intensely stained most axons. The 66 kd protein was readily detectable in homogenates of forebrain, cerebellum, brainstem, and spinal cord, but was found only in trace amounts in adult sciatic nerves and was not found in extraneural tissues. The 66 kd protein constituted 0.5% of total protein in the spinal cord, whereas NF-L constituted about 1.5%.

Effects of aldose reductase inhibitor sorbinil on neuroaxonal dystrophy and levels of myo-inositol and sorbitol in sympathetic autonomic ganglia of streptozocin-induced diabetic rats

Biochemical and ultrastructural effects of the aldose reductase inhibitor sorbinil were examined in two experimental rat models of chronic diabetic neuropathy: rats with streptozocin-induced diabetes (STZ-D) and rats fed a galactose-enriched diet. The frequency of neuroaxonal dystrophy in the superior mesenteric sympathetic ganglia of rats with untreated 8-mo STZ-D increased sevenfold compared with that in age-matched controls. Animals chronically maintained on a diet containing 50% galactose, however, did not develop neuroaxonal dystrophy in excess of that found in untreated age-matched control rats. Institution of sorbinil therapy at the time of induction of STZ-D decreased, but did not completely normalize, the frequency of neuroaxonal dystrophy without altering the severity of diabetes; this finding is based on measurements of plasma glucose, body weight, food consumption, 24-h urine volume, and levels of glycosylated hemoglobin. Sorbitol levels in the superior cervical sympathetic ganglia (SCG) of untreated 8-mo-diabetic animals increased three- to fourfold compared with levels in controls. The increase in sorbitol content of diabetic SCG was completely prevented by early institution of dietary sorbinil therapy. The myo-inositol content of 8-mo-diabetic SCG was modestly decreased compared with controls. Sorbinil administration improved but did not completely normalize diabetic SCG myo-inositol. The sorbitol content of the SCG, superior mesenteric and celiac sympathetic ganglia, and a major trunk of the superior mesenteric nerve of short-term (2.5-mo)-diabetic rats increased comparably, but only the diabetic SCG showed a decrease in myo-inositol.

Neural cell recognition molecule F11: homology with fibronectin type III and immunoglobulin type C domains

We report here the complete cDNA sequence of F11 130 kd polypeptide, a chick neural cell surface-associated glycoprotein implicated in neurite fasciculation and elongation. The predicted protein sequence of 1010 amino acids includes an amino-terminal signal peptide and a carboxy-terminal hydrophobic stretch, which is compatible with the consensus motif for covalent attachment of glycosyl-phosphatidylinositol. Accordingly, F11 lacks an intracellular domain, which is consistent with evidence obtained from protease protection experiments on isolated microsomes. In addition, the molecule comprises six domains related to the immunoglobulin domain type C and four resembling fibronectin repeat type III. Both types of repeats resemble those present in neural cell adhesion molecules L1 and N-CAM. The possible identity of F11 with the chick neural glycoprotein contactin is discussed.

Contributions from the upper cervical dorsal roots and trigeminal ganglia to the feline circle of Willis

To further define the sensory projections to the circle of Willis, we measured concentrations of immunoreactive substance P in pial arteries of cats following either bilateral removal of the C1-3 dorsal root ganglia (six cats) or bilateral removal of the trigeminal ganglia (three cats). Removal of the dorsal root ganglia decreased concentrations of the tachykinin substance P in the vertebral artery and the basilar artery and its branches by 72% and 50-66%, respectively. Bilateral removal of the trigeminal ganglia decreased substance P concentrations in all forebrain vessels including the rostral basilar artery, although only concentrations in the anterior cerebral artery were significantly lower than those in unilaterally lesioned cats (p less than 0.01). Hence, the vertebrobasilar artery and its tributaries are invested by substance P-containing fibers originating from the upper cervical dorsal root ganglia, and the anterior cerebral artery is innervated by both trigeminal ganglia. If a similar anatomy exists in humans, our data provide an explanation for the occipital localization of headaches arising from the vertebrobasilar arteries and for bilateral headaches following stimulation of the anterior cerebral artery.

A comparison of four techniques for mapping the distribution of serotonin and serotonin-containing neurons in fixed and living ganglia of the snail, Lymnaea

The distribution of serotonin and serotonin-containing neurons was studied in the ganglia of the CNS of the snail Lymnaea stagnalis. Results of the application of three different labelling techniques on wholemount preparations were compared with each other and with the serotonin content of the ganglia, measured by high-performance liquid chromatography. Serotonin immunocytochemistry resulted in the highest number of labelled neurons, but the more recently developed in vivo method of 5,6- or 5,7-dihydroxytryptamine-induced pigmentation also proved to be a reliable technique for the visualization of serotonin-containing cell bodies. In comparison with these two techniques, the glyoxylic acid fluorescence method appeared to be less sensitive. The distribution and number of serotonin-containing neurons and biochemically measured serotonin in specific ganglia showed a close correlation. By combining the results of the three labelling techniques, a detailed map of serotonin-containing neurons was constructed, and this was compared with maps of identified neurons prepared from earlier electrophysiological studies. Previously described serotonergic neurons were consistently found, as well as several new serotonin-containing cell types in the cerebral, visceral and parietal ganglia. A network of serotonin-containing inter- and intraganglionic axon tracts, and thin serotonergic fibres in the perineurium were also demonstrated. This in vivo and in vitro identification of serotonin-containing neurons will facilitate further neurophysiological analysis of serotonergic neural mechanisms in Lymnaea.

Cytoskeletal abnormalities in motor neuron disease. An immunocytochemical study

Immunocytochemistry with antibodies against cytoskeletal proteins has been used to search for molecular differences in the spinal cord from patients with motor neuron disease (MND) of amyotrophic lateral sclerosis type and normal spinal cord. Monoclonal antibodies which recognize phosphorylated neurofilament epitopes diffusely labelled a proportion of normal and MND anterior horn cells, but did not permit differentiation between normal and MND tissue. However, in some MND and control anterior horn cells, dense 'floccular' accumulations were labelled by antibodies recognizing phosphorylated neurofilament epitopes. These accumulations of phosphorylated neurofilaments suggest abnormalities of cytoskeletal regulation, but were neither a common nor a specific feature of MND. Axonal spheroids, which were as common in normal as in MND tissue, were labelled by all antineurofilament antibodies. Normal-appearing axons, but not spheroids, in MND and control tissue were identified by an antiactin antibody, indicating that actin may be absent from the cytoplasmic domain which gives rise to spheroids. In summary, we have not found specific posttranslational changes of cytoskeletal proteins in MND and, in particular, phosphorylated neurofilament epitopes are common to both MND and control anterior horn cells.

Ultrastructural localization of tyrosine hydroxylase-like immunoreactivity in the rat hippocampal formation

The light and electron microscopic localization of antigenic sites for a polyclonal antiserum directed against the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH), was examined in the hippocampal formation of the rat brain with a double-bridged peroxidase-antiperoxidase method. By light microscopy, the majority of varicose processes with intense TH-like immunoreactivity (LI) were contained in the hilus of the dentate gyrus (DG) and strata radiatum and lacunosum-moleculare of the CA3 region of the hippocampus. Only a few immunoreactive fibers were observed in the molecular and granule cell layers of the DG, in strata oriens and pyramidale of CA3, and in all layers of CA1. Electron microscopy confirmed that these labeled processes were primarily axons and axon terminals. Terminals with TH-LI were 0.4-1.1 micron in diameter and contained many small clear vesicles and from 0 to 3 larger dense-core vesicles. The number and types of associations formed by terminals with TH-LI were remarkably similar in the DG and hippocampus proper despite known differences in intrinsic cells and function. In both regions, the majority of terminals with TH-LI formed junctions on small (distal dendrites (52% of 112 in the DG; 67% of 116 in CA3) and dendritic spines (30% in the DG; 18% in CA3) that were both asymmetric and symmetric. In the DG, axosomatic junctions (2% of 112) were symmetric and occurred exclusively on the perikarya of granule cells, whereas junctions on large (proximal) dendrites were more numerous (16%), exhibited symmetric as well as asymmetric membrane specializations, and were of both granule (molecular layer) and nongranule (hilus) cell origin. In CA3, synaptic contacts on perikarya (5% of 116) and large (proximal) dendrites (10%) of both pyramidal cell and nonpyramidal cell origin were few and all symmetric. The distribution and types of synaptic associations formed by terminals with TH-LI in the CA1 region paralleled that seen in the CA3 region. In both the dentate and hippocampus proper, 10% of the terminals with TH-LI were observed closely apposed to unlabeled terminals that formed asymmetric synapses with dendrites and dendritic spines. In rare instances, TH-immunoreactive terminals were found in close association with the basement membrane of blood vessels, astrocytic processes, or with other unlabeled terminals not forming recognizable junctions. In addition TH-LI was occasionally detected within the cytoplasm of a minority of astrocytes.(ABSTRACT TRUNCATED AT 400 WORDS)

Gap junction protein in rat hippocampus: correlative light and electron microscope immunohistochemical localization

Immunohistochemical techniques and an affinity-purified antibody directed against the 27-kD gap-junctional protein (GJP) from rat liver were used to determine the ultrastructural localization of GJP in the rat hippocampus. At the light microscope level, dense GJP immunoreactivity having a stringlike appearance was seen in a very small percentage of medium-sized neuronal somata located in the stratum pyramidale, and diffuse immunostaining was seen in many small cell bodies in the stratum pyramidale, stratum oriens, and the alveus. Abundant GJP-immunoreactive (GJP-IR) varicose fibers were observed in the strata pyramidale, radiatum, and oriens but were less concentrated in the alveus. Numerous punctate GJP-IR elements were observed in all hippocampal layers. Upon EM analysis, GJP-IR neuronal somata in the stratum pyramidale were found to be, without exception, nonpyramidal neurons as judged by such distinguishing features as their fusiform perikarya, indented nucleus, and well-developed rough endoplasmic reticulum (RER). Immunostaining within these cells was largely localized to the Golgi apparatus and associated vesicular components. Small, diffusely GJP-IR cells were identified ultrastructurally as protoplasmic and fibrous astrocytes. Immunostaining within these cells was localized to the Golgi apparatus, RER, and small, ribosomelike bodies 15-25 nm in diameter. Among neuronal processes GJP immunoreactivity was found within dendrites, axons, and axonal terminals. The latter structures contained numerous GJP-IR vesicles having an average diameter of about 40 nm. A frequent observation indicating some degree of specificity of the anti-GJP antibody employed here was immunostaining of typical gap junctions between dendrites and, more commonly, between processes of glial cells. Occasionally, however, GJP-IR dendrodendritic, axodendritic, and axoaxonic contacts were found that could be considered, at best, as being gap-junction-like (gj-L). In these cases, asymmetric immunostaining of adjacent plasma membranes forming gj-L structures was not uncommon. These results confirm the existence of gap junctions between dendrites in the rat hippocampus and demonstrate that GJP immunoreactivity on cytoplasmic membranes is restricted either to typical neuronal and glial gap junctions or to gj-L structures at circumscribed sites of contact between various types of neuronal elements where GJP may contribute to a novel mechanism of neural communication.

The distribution of dopamine-beta-hydroxylase, neuropeptide Y and galanin in locus coeruleus neurons

The locus coeruleus (LC) is composed of noradrenaline-producing neurons that project widely throughout the neuraxis. Subpopulations of LC neuron perikarya have been shown to contain neuropeptide Y (NPY) and galanin (GAL). In the major terminal fields of LC projections, the cerebral cortex, dorsal thalamus and cerebellar cortex, there are differing plexuses of dopamine-beta-hydroxylase (DBH), NPY and GAL immunoreactive axons. DBH immunoreactive plexuses are found in all areas which conform in appearance to previous demonstrations of noradrenaline localization by fluorescence histochemistry. In contrast, there are few NPY immunoreactive axons in thalamus and cerebellum, and the cortical plexus, while similar to the DBH immunoreactive plexus, is not affected by 6-hydroxydopamine treatment. Similarly, there are few GAL immunoreactive axons in either cerebral cortex, dorsal thalamus or cerebellar cortex. Transection of ascending LC axons results in accumulation of DBH but not NPY or GAL immunoreactivity proximal to the lesion. These observations indicate that NPY and GAL are distributed differently in LC neurons from noradrenaline and DBH.

Evidence from dithizone and selenium zinc histochemistry that perivascular mossy fiber boutons stain preferentially "in vivo"

This paper describes a perivascular staining pattern that is obtained when dithizone or sodium selenite are used to label zinc intravitally. Our observations indicate that the perivascular staining is a result of zinc labeling in mossy fiber boutons adjacent to capillaries and suggest that there might be a special blood brain barrier in the mossy fiber regions.

Evidence for GABAergic fibers entering the superior cervical ganglion of rat from the preganglionic nerve trunk

The origin of gamma-aminobutyric acid immunoreactive (GABA-IR) nerve fibers present in the superior cervical ganglion (SCG) of rat was investigated. With immunocytochemical techniques many nerve fibers showed GABA-like positivity in the cervical sympathetic trunk, whereas similar staining could not be revealed in the internal carotid nerve or in the external carotid nerve. Ligation of the cervical sympathetic trunk for 24 h resulted a dramatic reduction in the staining density in the ganglion and in the cervical sympathetic trunk distal to the ligature. After transection of the preganglionic nerve fibers for eleven days or more, very few fibers staining for GABA were seen in the ganglion. The immunohistochemical results suggest that a major source of GABA within the SCG is a population of GABAergic axons entering from the preganglionic trunk.

Nerve growth factor-induced changes in the intracellular localization of the protein kinase C substrate B-50 in pheochromocytoma PC12 cells

High levels of the neuron-specific protein kinase C substrate, B-50 (= GAP43), are present in neurites and growth cones during neuronal development and regeneration. This suggests a hitherto nonelucidated role of this protein in neurite outgrowth. Comparable high levels of B-50 arise in the pheochromocytoma PC12 cell line during neurite formation. To get insight in the putative growth-associated function of B-50, we compared its ultrastructural localization in naive PC12 cells with its distribution in nerve growth factor (NGF)- or dibutyryl cyclic AMP (dbcAMP)-treated PC12 cells. B-50 immunogold labeling of cryosections of untreated PC12 cells is mainly associated with lysosomal structures, including multivesicular bodies, secondary lysosomes, and Golgi apparatus. The plasma membrane is virtually devoid of label. However, after 48-h NGF treatment of the cells, B-50 immunoreactivity is most pronounced on the plasma membrane. Highest B-50 immunoreactivity is observed on plasma membranes surrounding sprouting microvilli, lamellipodia, and filopodia. Outgrowing neurites are scattered with B-50 labeling, which is partially associated with chromaffin granules. In NGF-differentiated PC12 cells, B-50 immunoreactivity is, as in untreated cells, also associated with organelles of the lysosomal family and Golgi stacks. B-50 distribution in dbcAMP-differentiated cells closely resembles that in NGF-treated cells. The altered distribution of B-50 immunoreactivity induced by differentiating agents indicates a shift of the B-50 protein towards the plasma membrane. This translocation accompanies the acquisition of neuronal features of PC12 cells and points to a neurite growth-associated role for B-50, performed at the plasma membrane at the site of protrusion.