Sympathetic ganglia in culture. I. Neurons

Current approaches to development of the autonomic nervous system: clues to clinical problems

A number of different approaches to autonomic development utilizing a variety of experimental models and analytical techniques have been outlined. A scheme, which attempts to delineate a series of events involving separate but sometimes overlapping mechanisms, is proposed for the complex process of formation and maintenance of functional autonomic neuroeffector junctions. The relevance of these basic mechanisms of a variety of clinical abnormalities of autonomic function is discussed.

Dendritic outgrowth of myenteric plexus neurons in primary culture

Myenteric plexus neurons derived from neonatal guinea pigs, when exposed to serum, demonstrated a characteristic pattern of growth, including a proliferating outgrowth zone of glial cells, peripheral extension of dendritic processes, and progressive dendritic growth. Serum effects upon dendritic growth, measured morphometrically, was strongly dose- and temporally dependent. Dendritic density was increased 10-fold (120 hr) by the addition of 6% serum, while mean dendritic length was increased 3-fold. Development of cholinergic function was reflected by release of [3H]ACh in response to cholecystokinin octapeptide, vasoactive intestinal peptide, substance P, and calcitonin gene-related peptide (10(-10) and 10(-8) M).

Visualisation of specific binding sites for atrial natriuretic peptide on non-neuronal cells of cultured rat sympathetic ganglia

The distribution of atrial natriuretic peptide binding sites on cells in dissociated culture preparations of neonatal rat superior cervical ganglia and in explant cultures of rat thoracic sympathetic chain ganglia has been studied. The autoradiographic visualisation of atrial natriuretic peptide binding sites has been combined with the use of specific immunocytochemical markers for glial cells (antiserum to S-100 protein), fibroblasts (antiserum to fibronectin) and neurones (antiserum to protein gene product 9.5) in order to achieve unambiguous identification of the cell types in culture. Specific binding sites for rat 125I-atrial natriuretic peptide(1-28) were observed over subpopulations of fibronectin-like-immunoreactive fibroblasts and S-100-like-immunoreactive glia in the dissociated superior cervical ganglion cultures. However, only a subpopulation of fibronectin-like-immunoreactive fibroblasts possessed atrial natriuretic peptide binding sites in the explant culture preparations. No atrial natriuretic peptide-like-immunoreactive cells were present in either culture. The distribution of autoradiographic grains over individual cell surfaces in culture was uniform, but there were distinct differences in the density of labelling of single cells of the same type. This apparent variation in the number of binding sites on glial cells and fibroblasts in culture did not seem to be related to the morphology of the cells or the surrounding cell types. No sympathetic neurones were labelled with autoradiographic grains in either the dissociated or explant culture preparations. However, the presence of atrial natriuretic peptide binding sites on non-neuronal cells of sympathetic ganglia in culture may be linked to the relationship between atrial natriuretic peptide and the sympathetic nervous system.

The use of cell and tissue culture techniques in the study of regulatory peptides

Cell and tissue culture preparations have a number of general advantages for the study of biological processes: cells are more accessible for study, diffusion delays and barriers to applied substances are minimised, the humoral and cellular components of the culture environment can be controlled and progressive changes in intracellular and intercellular events can be directly monitored. These significant advantages mean that culture preparations can provide unique opportunities for investigation of the properties and functions of regulatory peptides. Culture preparations also have disadvantages and not all cultures are suitable for use in all types of experiments; therefore, the choice of preparation must be made accordingly. Here we describe different types of culture preparation and give examples where cultures have been used to examine peptide synthesis, storage, secretion and receptor localisation, as well as the short-term and trophic actions of regulatory peptides.

Stimulatory effect of substance P on sympathetic ganglia and spinal cord in culture

Studies with organotypic culture of sympathetic ganglia and spinal cord revealed that substance P at concentrations of 10(-5) to 10(-12) M and 10(-5) to 10(-14) M exerts a marked growth-stimulating effect on sympathetic ganglia and spinal cord, respectively. In the presence of substance P, the intensity of sympathetic ganglion growth exceeds control values 3.0-4.8 times. The growth zone size of spinal cord explants increases under these conditions 2.0-5.2-fold. A feasible physiological significance of regulatory peptides in the growth and regeneration of nervous tissue as well as the role of noci-antinociceptive systems in histogenesis and regeneration are discussed.

Neuron-like derivatives of cultured F9 embryonal carcinoma cells express characteristics of parietal endoderm cells

Murine F9 embryonal carcinoma cells exposed to retinoic acid and dibutyryl cyclic AMP gradually arborize and acquire a neuron-like morphology in monolayer culture. Whether F9 cells can be induced to differentiate into cells with features specific to neural cells is controversial. We analyzed the intermediate filament content and pericellular matrix proteins of F9 cells after exposing them to retinoic acid, dibutyryl cyclic AMP, and nerve growth factor. In long-term cultures, a great majority of the cells appeared neuron-like, but showed intra- and pericellular laminin and type IV collagen, and frequently cytokeratin filaments as well. Several monoclonal antibodies to neurofilaments did not react with these cells in immunofluorescence or immunoblotting, though they recognize either all or individual mouse neurofilament triplet proteins. Polyclonal antibodies to neurofilament proteins gave a diffuse, nonfibrillar, vinblastine-resistant fluorescence in the morphologically neuron-like cells, but in immunoblotting failed to reveal polypeptides compatible with neurofilament triplet proteins. In long-term cultures, most of the cells appeared to have partially or totally lost the intermediate filaments. This was confirmed with anti-IFA antibodies which normally react with all intermediate filament proteins. The F9-derived cells did not respond to nerve growth factor in any detectable way. We conclude that the morphologically neuron-like derivatives of F9 cells display characteristics of modified parietal endoderm-like cells and do not show unequivocal features of neural cells.

Effects of opioid peptides and naloxone on nervous tissue in culture

It was shown that opioid peptides stimulate nervous tissue growth in culture in the rat, which manifests itself in augmented outgrowth of neurites from explants and in an increase in the number of glial and fibroblast-like cells in the growth zone. The effects of opioid peptides ([Leu]- and [Met]-enkephalins, beta- and gamma-endorphins and some synthetic analogues of [Leu]-enkephalin) on the growth of organotypic cultures of rat sympathetic and dorsal root ganglia and spinal cord were investigated. Neurite outgrowth, cell composition, and size of the growth zone as well as the dynamics of its formation were estimated. Changes in the survival of neurons in dorsal root ganglion cultures were determined. The experiments were performed with living cultures as well as with fixed preparations. In experiments with sympathetic ganglia, it was demonstrated that a significant growth-promoting effect is exerted by peptides taken at concentrations of 10(-8) M to 10(-14) M. Naloxone does not eliminate the effects of peptides, but stimulates the growth at 10(-5) M to 10(-7) M. Studies with spinal cord revealed that naloxone (10(-6) M) enhances the response to [Leu]-enkephalin (10(-9) M). The survival of dorsal root ganglion neurons under the influence of a [leu]-enkephalin analog (10(-9) M) exceeds control values by approximately two to four times. Thus, opioid peptides were shown to exert a strong growth-promoting effect on nervous tissue in culture. This effect is dual: in neurons the peptides stimulate the outgrowth of neurites and their survival, while in glial cells they change the rate of their migration and, probably, their proliferation. It is suggested that opioid peptides, besides their already established functions, may play a role in the development and regeneration of nervous tissue.

[Met5]enkephalin-Arg6-Phe7- and [Met5]enkephalin-Arg6-Gly7-Leu8-immunoreactive nerve fibres and neurons in the superior cervical ganglion of the rat

[Met5]enkephalin-Arg6-Phe7-(MEAP-) and [Met5]enkephalin-Arg6-Gly7-Leu8-(MEAGL-) immunoreactivity was studied by indirect immunohistochemistry in the superior cervical ganglion of the rat with specific antisera produced in rabbits against the corresponding synthetic opioid peptides. Several MEAP- and a few MEAGL-immunoreactive principal nerve cells were observed in the ganglion, while the small intensely fluorescent cells appeared as non-reactive. The superior cervical ganglion also contained dense networks of MEAP- and MEAGL-immunoreactive nerve fibres, which often formed basket-like structures around the principal nerve cells and small intensely fluorescent cells. After ligation of the preganglionic nerve trunk with simultaneous transection of the main postganglionic trunks, a distinct accumulation of both MEAP- and MEAGL-immunoreactivity was observed on both sides of the ligature. Ligation of the preganglionic nerve trunk caused a marked decrease in the number of both MEAP- and MEAGL-immunoreactive nerve fibres in the ganglion. Ligation of the main postganglionic nerve trunks with simultaneous preganglionic nerve division resulted in accumulation of MEAP- and MEAGL-immunoreactive material on the ganglionic side of the ligature in both the external and internal carotid nerve. After division of both the pre- and postganglionic nerve trunks, some immunoreactive nerve fibres and principal nerve cells were still observed in the ganglion. A few immunoreactive neurons and nerve fibres were also observed in the ganglion stellatum. A large number of MEAP- and MEAGL-immunoreactive nerve fibres was detected in the spinal cord at the levels C6-Th6. A few neurons in the intermediolateral cell column of the spinal cord at levels C8-Th1 showed MEAP- but not MEAGL-immunoreactivity. The cultured superior cervical ganglion contained a few MEAP-immunoreactive neurons, and the fibre outgrowth showed immunoreactivity both to MEAP and MEAGL. In electron microscopy, MEAGL-immunoreactivity in the superior cervical ganglion was localized in nerve fibres containing neurotubules and in principal nerve cells. The present results demonstrate that the rat superior cervical ganglion contains both extrinsic and intrinsic MEAP- and MEAGL-immunoreactive nerve fibres. Most of these fibres are of preganglionic origin. Both the principal nerve and small intensely fluorescent cells are often surrounded by MEAP- or MEAGL-immunoreactive nerve fibres and may receive innervation by these fibres. Several ganglionic neurons projecting to the sympathetic target tissues show MEAP- and/or MEAGL-immunoreactivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Urinary bladder intramural neurones: an electrophysiological study utilizing a tissue culture preparation

An enzymic dispersion technique was used to free the intramural ganglia from their usual close association with the other components of the urinary bladder wall. The isolated ganglia obtained were viable and could be kept in culture for several weeks. The development of the cultures was monitored by phase-contrast microscopy and their electrophysiological properties were investigated using intracellular recording techniques. Neurones could be visually identified after 2-3 days in culture; cell groups contained from 2-50 neurones. Three types of spontaneous activity were seen: small changes in membrane potential and action potentials, and slow oscillatory conductance changes. These events were not blocked by hexamethonium but were abolished by hyperpolarizing current. Most neurones spiked without adaptation to direct stimulation; in a few cells the train of spikes was damped out. No neurones generated long afterhyperpolarizations. Indirect stimulation produced responses in the ganglia which are consistent with synaptic activity. Summation of inputs was demonstrated. These results provide evidence for local intraganglionic circuits since the ganglia or neurone groups are unequivocally extrinsically denervated. It was concluded that the intramural ganglia have the capacity to integrate preganglionic input and the question of whether or not they might mediate reflex activity is raised.

Morphometric study of the interphase nucleus in some radiosensitive and radioresistant mammalian cells

The radiosensitive cell populations, such as resting lymphocytes from thymus, spleen, lymph node and blood, have much smaller nuclei (Vn (nuclear volume) approximately 20 to 70 microns3) compared to radioresistant G0 cells from non-lymphoid tissues (liver, kidney, brain, heart; Vn approximately 75 to 2700 microns3). It is suggested that radiation-induced disorganization of nuclear structures and cell pycnosis (interphase death) are promoted in G0 lymphocytes because in normal physiological conditions their nuclei assume a higher degree of chromatin condensation. In contrast, dispersion of chromatin into larger nuclear volumes, such as those of most non-lymphoid G0 cells, may hinder or delay radiation-induced cell death.

Intensely fluorescent cells in embryonic and postnatal superior cervical ganglia of the rat cultured with or without hydrocortisone

Pre- and postnatal superior cervical ganglia of the rat were cultured in Rose chambers for 1-7 days with or without hydrocortisone. Fibre growth of the principal nerve cells was observed by phase contrast microscopy, and the explants were then processed for formaldehyde-induced catecholamine fluorescence. The ganglia of 13-day-old embryos cultured for 7 days in the control medium did not show fibre growth and contained only one type of fluorescent cells, the weakly fluorescent, presumably principal nerve cell, while in the older ganglia the principal nerve cells formed a fibre network, and the ganglia also contained a few small intensely fluorescent cells some of which had short processes. The ganglia of 15-day-old embryos and newborn rats cultured for 1 day in a control medium contained cells that showed a continuous range of weak through bright fluorescence. In the course of the culture, the cells of intermediate fluorescence intensity disappeared, and the number of the intensely fluorescent cells greatly decreased, more slowly in the newborn than in the embryonic ganglia. The intensely fluorescent cells in the newborn, but not those in the embryonic ganglia transiently produced marked fibre growth within the explants. All embryonic ganglia and 6-day-old or younger postnatal ganglia cultured in hydrocortisone-containing medium for 7 days showed a much greater number of intensely fluorescent cells than the corresponding control ganglia. Examination of the cultures 1, 2, 4, or 7 days after the explantation showed that in both pre- and postnatal ganglia hydrocortisone resulted in the appearance of both neuroendocrine and fibre-growing types of intensely fluorescent cells. These observations support the idea that during a limited period of pre- and postnatal development, the sympathetic ganglia contain a population of cells which are able to change their phenotype in the presence of glucocorticoids.

Effect of hydrocortisone on immunohistochemically demonstrable phenylethanolamine-N-methyltransferase in cultures of embryonic and postnatal superior cervical ganglia

Pre- and postnatal superior cervical ganglia of the rat were cultured in Rose chambers for 1-7 days with or without hydrocortisone. Phenylethanolamine-N-methyltransferase (PNMT) was demonstrated by indirect immunofluorescence technique. In cultures without added hydrocortisone, no cells or fibres showed PNMT-immunoreactivity, without regard to the time in culture or the developmental stage at the time of explantation. The first PNMT-immunoreactive cells in hydrocortisone-containing cultures appeared 3 days after the explantation of E14 ganglia, or 1 day after the explantation of E15 ganglia, i.e. at the developmental stage E16-E17. The cultures of neither E14 nor E15 ganglia showed marked fibre growth from the PNMT-immunoreactive cell bodies. On the other hand, in the hydrocortisone-containing cultures of newborn or postnatal rats, there was extensive nerve fibre formation from the PNMT-immunoreactive cells in the course of the culture. PNMT-immunoreactive cells did not appear in hydrocortisone-containing cultures of ganglia taken from rats older than 17 postnatal days.

Synaptic organisation of the pelvic ganglion in the guinea-pig

A semi-quantitative electron-microscopic study of neuronal cell bodies, nerve profiles and synapses in the anterior pelvic ganglia of the guinea-pig has been carried out following in vivo labelling of adrenergic nerve endings with 5-hydroxydopamine. Ganglion cells of three main types have been distinguished: 1) the majority (about 70%) not containing granular vesicles, probably cholinergic elements; 2) those containing large granular vesicles of uniform size (80-110 nm), with granules of medium density and prominent halos; and 3) those containing vesicles of variable size (60-150 nm), with very dense eccentrically placed granular cores. Some non-neuronal 'granule-containing' cells were present, mainly near small blood vessels. Some 95% of the total axon profiles within the ganglia were cholinergic, the remaining 5% were adrenergic. However, 99% of synapses (i.e. axons within 50 nm of nerve cell membrane with pre- and post-synaptic specialisations) were cholinergic, and 1% were adrenergic. Only three examples of nerve cell bodies exhibiting both cholinergic and adrenergic synapses were observed. Unlike the para- and prevertebral ganglia, the pelvic ganglia contained large numbers of axo-somatic synapses. As many as 20% of the nucleated neuronal cell profiles displayed two distinct nuclei.

The enteric nervous system in tissue culture. II. Ultrastructural studies of cell types and their relationships

Tissue culture preparations of the myenteric plexus from the guinea pig taenia coli have been studied by electron microscopy. Three main cell types can be identified: neurons, enteric glial cells and fibroblasts. The ultrastructure of these cells resembles that of the same cells in situ. Neuronal processes form close associations with other neurons and glial cells, but not with fibroblasts. After extended periods in culture, neurons and glial cells form aggregates of cells which resemble ganglia of the myenteric plexus in situ, having a compact neuropil and synapses between neuronal elements. Aggregates are connected to each other by thick bundles of neurites. Vesicle-containing nerve profiles are common; the majority contain a predominance of small agranular vesicles, but some contain many large granular or large opaque vesicles; profiles may also contain variable mixtures of these kinds of vesicles.

The enteric nervous system in tissue culture. I. Cell types and their interactions in explants of the myenteric and submucous plexuses from guinea pig, rabbit and rat

This paper describes methods for removing the ganglionated myenteric and submucous plexuses from the mammalian gut and maintaining them as explants in tissue culture. A detailed account is given of cell types, their interactions and the development of these cultures during 5 weeks in vitro. Three major cell types were identified in the cultures: neurons, glial cells and fibroblasts. The development of the plexuses in culture was studied in detail for the myenteric plexus from the guinea pig taenia coli. It followed a characteristic pattern, in which the merging of individual ganglia into a continuous monolayer of flattened neurons was accompanied and followed by the formation of an extensive outgrowth zone of flat glial cells covered by a dense mesh of outgrowing neurites. In older cultures, neuronal migration resulted in the reformation of discrete and compact aggregates, which consisted of neurons and glial cells, and were interconnected by thick neurite bundles. This arrangement resembles in many ways the original organization of enteric nervous tissue in vivo. This is the first time the enteric ganglia have been freed from the gut wall and grown in culture as explants of nervous tissue. These preparations open many new directions for investigations of the largest and most complex division of the peripheral nervous system, including studies of the molecular nature of neuronal and glial cell surfaces, analysis of cell-cell interactions, trophic factors and developmental signals.

Catecholamine-containing neurons in Remak's ganglion: a developmental and tissue culture study

Development and maturation of the catecholamine-containing neurons of the embryonic chick and quail Remak's ganglion were studied, using the glyoxylic acid method. Fluorescent neurons were detected in the pararectal segment of the ganglion from its earliest in vivo formation, and along the whole ganglionic chain in later developmental stages. In tissue culture, a large number of catecholamine-containing neurons matured in explants of both early and more developed ganglia, producing an extensive network of outgrowing fluorescent nerve processes. Pararectal ganglia, cultured in vitro for up to 4 days, gave rise, whatever the developmental stage examined, to fluorescent migratory neurons distributed either in ganglion-like clusters or singly in a large area surrounding the explant. Many non-fluorescent neurons were intermingled with the fluorescent ones in the explants, as well as in the outgrowth. Ganglia from segments adjacent to the small intestine did not give rise to migratory neurons whatever the developmental stage. Regional differences in the development of migratory neurons may be correlated to the mechanism of the in vivo organization of the ganglionic chain. The present observations indicate that catecholamine-containing neurons in Remak's ganglion exhibit the same histochemical features as adrenergic sympathetic neurons and differentiate in short-term cultures.

Plexus muscularis profundus and associated interstitial cells. II. Ultrastructural studies of mouse small intestine

The ultrastructure of plexus muscularis profundus (PMP) of the mouse small intestine was investigated subsequent to vascular perfusion with ruthenium red-containing and routine aldehyde fixatives. Four types of nerve terminals were revealed. Type I: numerous 500-A agranular vesicles and few 1,000-A granular vesicles. Type II: predominantly large (1,000-1,500 A), granular vesicles and fewer 500-A agranular vesicles. Type III: an abundance of mitochondria and many flattened vesicles (300 A X 700-1,300 A). Type IV was identified by abundant smooth cisternae 200 A in width. Types I-III formed close (200 A), synapse-like contacts to interstitial cells of Cajal (ICC-III). Presynaptic densities were frequent in type I endings. A direct innervation of muscle cells via PMP was only very occasionally suggested. ICC-III possessed a basal lamina and numerous caveolae associated with subsurface SER-cisternae. Mitochondria were very abundant in ICC-III-processes. ICC-III formed multiple, large gap junctions with outer circular-muscle cells and with other ICC-III. Also reflexive gap junctions were observed. Fibroblastlike cells (FLC) were distinguished by their prominent GER, the frequent presence of lipid droplets, and the lack of caveolae and a basal lamina. FLC never participated in synaptic arrangements or gap junctions. Macrophage-like cells were occasionally encountered. It is concluded that possible efferent and afferent nerve terminals in PMP may chiefly, if not exclusively, innervate ICC-III, the ultrastructure of which is compatible with efferent and/or afferent modulatory actions.

Explant cultures of adult amphibian sympathetic ganglia: electrophysiological and pharmacological investigation of neurotransmitter and nucleotide action

Explant cultures from adult bullfrog sympathetic ganglia can be maintained in vitro for several months and are suitable for electrophysiological recording. The cultured neurons display morphological, electrophysiological and pharmacological characteristics similar, in most respects, to those reported for acutely isolated sympathetic ganglia. Individual cells were visualized by Nomarski optics and impaled with a glass micropipette, which was used for voltage recording and current injection. The average specific membrane properties, calculated from cell dimensions and responses to current injection, were Vm = -46 mV, Rin = 27 M omega, Rm = 1665 omega cm2, tau m = 5 msec, and Cm = 3.2 microF/cm2. Bath perfusion of the cholinergic agonist muscarine depolarized most neurons with an increase in input resistance, while carbachol depolarized neurons with both increases and decreases in input resistance. GABA depolarized all neurons tested with a decreased resistance. High concentrations of catecholamines (2-5 mM) generally hyperpolarized explanted neurons, usually in association with an increased resistance. Extracellularly or intracellularly applied cyclic AMP and two other analogues produced weak and inconsistent hyperpolarizations. In contrast, perfusion or iontophoresis of most non-cyclic purine and pyrimidine nucleotides markedly depolarized most neurons in association with an increased input resistance. UTP and UDP were most potent, revealing threshold concentrations of about 10(-8) to 5 x 10(-8) M. The related nucleosides were largely ineffective. The nucleotide-evoked depolarizations were similar to the muscarine responses but were not blocked by atropine. These results suggest that the purine or pyrimidine nucleotides should be considered for a possible involvement in neurotransmission in sympathetic ganglia.

Subpopulations of cultured chick sympathetic neurones differ in their requirements for survival factors

Peripheral autonomic and sensory neurones derived from the neural crest will survive in vitro only if the culture medium is supplemented with specific factors (for review see ref. 1). For example, the nerve growth factor (NGF), although supporting the survival of sympathetic and spinal sensory neurons, is ineffective on parasympathetic neurones, whereas medium conditioned by chick heart cells (HCM) supports the survival of all three neuronal types. We showed previously that the requirements of cultured spinal sensory ganglion neurones for survival factors changed during development, and so provided a basis for the classification of such factors. We now demonstrate that cultured post-mitotic neurones from chick paravertebral sympathetic ganglia respond differentially to NGF, HCM and medium conditioned by C6 glioma cells (GCM). Thus, there three survival factors are functionally distinct in that they support the survival in culture of discrete subpopulations of sympathetic neurones. Those subpopulations responding to HCM and NGF are shown to differ not only in their requirements for survival factors but also in their contents of the cholinergic and adrenergic marker enzymes choline acetyltransferase (ChAT) and tyrosine hydroxylase (TH).

A method for the measurement of growth of noradrenergic axons in tissue culture and the effects of colchicine thereon

Explants of superior cervical ganglia from 2-day-old mice have been cultured on collagen-coated glass coverslips in modified L15 culture medium (with foetal calf serum) for 5-day periods. Noradrenergic axons were visualized by uptake of alpha-methyl noradrenaline and subsequent treatment with buffered 2% glyoxylic acid for fluorescence microscopy. An index of axon growth was obtained by a point-counting method using a coherent multi-purpose test system graticule. The growth indices thus obtained for a sample of control cultures were normally distributed. Examination of a single batch of cultures showed that good agreement was obtained between successive counts by one observer and between counts by two observers. The method gave sufficient resolution to detect with statistical significance a small inhibition of growth by colchicine at 2 ng/ml and to obtain a concentration-effect plot for this drug. The acceptability of the method for routine use is discussed.

The neuroendocrine nature of the glomus cells: an experimental, ultrastructural, and histochemical tissue culture study

Although the carotid body is an established chemoreceptor, there is considerable evidence also for its possessing a secretory function. While adrenergic neuroendocrine cells of neuroectodermal derviation exist in the central and autonomic nervous systems, the exact histogenesis of the mammalian carotid body is unsettled. The normal human carotid body and glomus jugulare tumor have been grown in tissue culture and their constituent cells have been observed to transform from epithelial to neuronoid appearing cells with extensive dendritic processes. This conversion has been further enhanced by the addition of nerve growth factor, a polypeptide specific for neural tissue. Electron microscopy confirmed that these culus cell. Histofluorescence revealed that these in vitro cells continued to synthesize and store biogenic monoamines in culture. Comparison of the morphologic, ultrastructural and histochemical features of the glomus cell with established neuroendocrine cells (central nervous system neurons, sympathetic ganglia cells, chromaffin cells) shows striking similarities. On the basis of these findings it is concluded that the glomus cell is a modified neuron of neural crest origin. The embryology, electron microscopy and histochemistry of the carotid body and related glomera and their tumors are reviewed.

Regeneration and myelination in autonomic ganglia transplanted to intact brain surfaces

Fragments of superior cervical ganglia (SCG) from donor rats between newborn and three months of age were transplanted either into the fourth ventricle, onto the dorsal surface of the medulla or in contact with the area postrema of recipient rats aged 6--14 days (allografts) and 3--4 weeks (autografts). Except for the meninges, the entire brain surface and parenchyma was undisturbed. The regenerative capacity of the transplanted ganglia and its interaction with the brain surfaces was followed for post-operative periods between 1 h and six months. Both ependymal and glial cells reacted to the transplant even though there was no mechanical damage to the brain. Ependymal cells developed luminal fronds that projected into the ventricle and the subpial glia displayed a very subtle gliosis in the form of thin multi-laminated processes. Schwann cells from the transplant tended to cover the free surfaces of the brain. The transplants, often incorporated into the stroma of the choroid plexus, received an extensive vascular supply of both fenestrated and non-fenestrated vessels. In contrast to SCG in tissue culture, the perinatal explants quickly degenerated while all those from older donors, at least 3--4 weeks of age, regenerated briskly in the ambient cerebrospinal fluid. Thriving SCG neurons, which diminished in number over time, sprouted numerous neurites as early as one week; growth cones and synaptic contacts between cell processes were still evident at six months. The trasplanted mature SCG fragment underwent a redevelopment after an initial period of degeneration. It seems likely that the survival of the allografted ganglion cells depends on their acquisition of a target site in their new environment. By four to six months many axons became enclosed by myelin produced by SCG Schwann cells that normally do not form myelin in situ. Other Schwann cells appeared reactive in that they had a great increase in cytoplasmic filaments and formed gap junctions, two characteristics of C.N.S. astrocytes. It is possible that the proximity to the C.N.S. changes the character of certain Schwann cells or, alternatively, resulted in the migration of glial cells out of the brain. If the glial cells have migrated into the transplant, they may support alien neural tissue. This system in which the transplantation site is easily accessible with a minimum of trauma could lend itself to the study of some underlying mechanisms of the growth and regulation of both central and autonomic neurons and their supporting cells.

Light and electron microscopic histochemistry of the monoamines in the human foetal sympathetic ganglion in culture

Sympathetic ganglia of 13 to 19-week-old human foetuses were cultured in small pieces with and without nerve growth factor for up to 5 weeks in vitro. The cultures were studied using phase-contrast, fluorescence and electron microscopy. Monoamines were demonstrated with the formaldehyde-induced fluorescence method, with and without pretreatment of the cultures with catecholamines or monoamine oxidase inhibitor. In the long-term cultures, primitive sympathetic cells, sympathicoblasts of types I and II, and young sympathetic neurons showed a fine structure identical to that described earlier in vivo. There were virtually no satellite or Schwann cells in the cultures. The neurons showed a considerable capacity to grow new nerve fibres in culture, even without nerve growth factor. Nerve terminals with accumulations of synaptic vesicles were regularly observed, occasionally in synapse-like contact with other nervous structures. Large granular vesicles were regularly found in the sympathicoblasts after glutaraldehyde-osmium tetroxide fixation. After permanganate fixation, dense-cored vesicles typical of adrenergic neurons were not seen, either in the perikarya, or in the processes, although it was possible to demonstrate specific fluorescence. No small intensity fluorescent (SIF) cells were observed. Variable formaldehyde-induced fluorescence was observed in the nerve cell perikarya and nerve fibres. The intensity of the fluorescence increased after treatment of the cultures with monoamine oxidase inhibitor and after incubation with catecholamines.

A correlative histofluorescence and light microscopic study of the formation of the sympathetic trunks in chick embryos

The appearance and development of the primary and secondary sympathetic trunks in staged chick embryos was studied using the Falck-Owman histochemical method for the demonstration of primary monoamines. The earliest appearance of catecholamine (stage 20) was in individual fluorescent cells located in the region of the dorsal root ganglia about two stages prior to the formation of primary trunk aggregates. These cells are believed to be sympathetic precursor cells and correspond to formaldehyde-induced fluorescent cells observed in recent explantation experiments. Aggregates of fluorescent cells had formed bilaterally dorsolateral to the aorta at stage 22. These aggregates became continuous to form primary trunks by stage 24. The secondary sympathetic trunks were first seen in stage 25 and appeared to form at least partially by dorsal migration of cells from the primary trunks. Fluorescent cell processes were first observed at this stage. Secondary trunk formation was essentially complete by stage 28, and the primary trunks had become small and discontinuous. Definite rami communicantes could be observed by the early part of stage 28 in silver preparations. The significance of the development of two successive trunks in avians is discussed.

Establishment of a noradrenergic clonal line of rat adrenal pheochromocytoma cells which respond to nerve growth factor

A single cell clonal line which responds reversibly to nerve growth factor (NGF) has been established from a transplantable rat adrenal pheochromocytoma. This line, designated PC12, has a homogeneous and near-diploid chromosome number of 40. By 1 week's exposure to NGF, PC12 cells cease to multiply and begin to extend branching varicose processes similar to those produced by sympathetic neurons in primary cell culture. By several weeks of exposure to NGF, the PC12 processes reach 500-1000 mum in length. Removal of NGF is followed by degeneration of processes within 24 hr and by resumption of cell multiplication within 72 hr. PC12 cells grown with or without NGF contain dense core chromaffin-like granules up to 350 nm in diameter. The NGF-treated cells also contain small vesicles which accumulate in process varicosities and endings. PC12 cells synthesize and store the catecholamine neurotransmitters dopamine and norepinephrine. The levels (per mg of protein) of catecholamines and of the their synthetic enzymes in PC12 cells are comparable to or higher than those found in rat adrenals. NGF-treatment of PC12 cells results in no change in the levels of catecholamines or of their synthetic enzymes when expressed on a per cell basis, but does result in a 4- to 6-fold decrease in levels when expressed on a per mg of protein basis. PC12 cells do not synthesize epinephrine and cannot be induced to do so by treatment with dexamethasone. The PC12 cell line should be a useful model system for neurobiological and neurochemical studies.

The altrastructure of Auerbach's plexus in the guinea-pig. I. Neuronal elements

The ultrastructural features of nerve cell bodies and axon profiles within Auerbach's plexus in the stomach, ileum, caecum and colon of the guinea-pig have been examined. Nerve cell bodies have been tentatively classified into nine different types according to their size, distribution of organelles, location and relationship to satellite cells. Except for cell size, no attempt has been made to correlate ultrastructual with light microscopical observations. On the basis of vesicular size, shape and content, eight morphologically distinct types of axon profile have been identified as well as two profile types which are thought to reflect different physiological conditions. The axons contained various populations of small, mostly granular vesicles; small, round agranular vesicles; small, flattened vesicles; large flattened or elongated vesicles; and three types of large vesicle with granular contents distinguished by size. Some correlation between types of axon profile and two types of nerve cell body was recognized. However, more than one type of axon profile usually formed synapses with one type of cell body, and a precise correlation was not determined.

Effects of dbcAMP and theophylline on rat adrenal medulla grown in tissue culture

Explants of rat adrenal medulla were grown in tissue culture. The effects of various doses of dbcAMP ranging from 0.001 mM up to 1 mM and equimolar amounts of theophylline were recorded by phase contrast optics and catecholamine histochemistry (glyoxylic acid method) over six days. There was a dose-dependent inhibition of the normally occurring outgrowth of Schwann cells, "chromaffin" cells and axons from the explants. Maintenance of glyoxylic acid-induced fluorescence in "chromaffin" cells was dose-dependent, too. Since theophylline is known to enhance intracellular levels of cAMP only, these effects are probably due to the action of cAMP. cAMP obviously maintains the degree of differentiation of chromaffin cells. Thus it could be argued that a certain degree of dedifferentiation is a prerequisite for the formation of axons from these cells.

Specificity of innervation of iris musculature by sympathetic nerve fibres in tissue culture

Irides from 3-5 day old rats have been grown 1-3 mm from superior cervical or lumbar paravertebral sympathetic ganglia in modified Rose chambers. The two muscles of the iris received distinctly different innervation patterns in vitro, and these were similar to those seen in vivo. Varicose, adrenergic fibres were consistently associated with the dilator pupillae rather than with the sphincter pupillae while excitatory, cholinergic junctions developed between the nerve fibres and the muscle cells of the spincter but not the dilator. There was a lack of specificity shown by the sympathetic neurons during this innervation. Fibres from lumbar ganglia formed plexuses within the dilator similar to those formed by superior cervical fibres, and sympathetic, cholinergic fibres were able to substitute for the normal parasympathetic, cholinergic fibres in the sphincter.

Differentiation of sympathicoblasts in cultures of chick ganglia: light and electron microscopic, fluorescence and enzyme histochemical observations

Immature sympathetic ganglia prepared from 5 1/2-or 6-day-old chick embryos were cultured up to one month. The in vitro development was followed by phase microscopy, electron microscopy and using histochemistry for catecholamines, monoamine oxidase and cholinesterases. During the first week of culture extensive plexuses of nerve fibres were formed between and around the clusters of nerve cells. Mature-looking neurons were observed in the cultures by phase microscopy after three weeks, at which age the mean diameter of the perikarya was more than doubled. Varying catecholamine fluorescence was observed in the perikarya during the entire culture period. The nerve fibres showed usually only weak fluorescence, but, in the older cultures, bright varicosities were regularly found in the fibres. Monoamine oxidase activity was demonstrated already at three days of culture and the reaction was maintained positive. Weak or moderate acetyl-cholinesterase activity was demonstrated in the sympathicoblasts and young sympathetic neurons and their processes. The axolemma showed acetylcholinesterase activity also around the nerve terminals containing small dense cored vesicles. Reactions for the non-specific cholinesterases were negative. Electron microscopy of the 30-day-old cultures revealed that the clusters of nerve cells consisted of mature sympathetic neurons, which contained large (60-200 nm) and small (35-60 nm) granular catecholamine-storing vesicles. Glial cells were almost totally lacking. Large numbers of nerve terminals containing both large and small granular vesicles were observed in the clusters, often in synaptic contact with the sympathetic neurons. It is concluded that the primitive sympathicoblasts are, in favourable conditions, capable of differentiation in culture up to mature sympathetic neurons.