Interneurons of the sympathetic ganglia, in organotypic culture. A suggestion as to their function, based on three types of study

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.

Development of chick paravertebral sympathetic ganglia. I. Fine structure and correlative histofluorescence of catecholaminergic cells

Paravertebral sympathetic ganglia from the lumbosacral region of a series of chick embryos have been studied with electron microscopic methods, including aldehyde-osmium and permanganate fixatives, and correlative histofluorescence (Grillo et al, '74). Our purpose was to assess the differentiation of catecholaminergic (CA) cells during histogenesis in ovo. Examination of comparable adult ganglia as a baseline for differentiating stages confirmed that the principal sympathetic neuron (PN) is similar to those of other species in that it contains predominately small dense-cored vesicles (SDCV) preserved only by permanganate, and does not histofluoresce following the method of Grillo et al. ('74). At embryonic day (E) 7--8, when ganglia have just formed, areas fluorescing bright yellow-green are correlated with two types of cells: 1) Neuroblasts with vesicular nuclei and large dense-cored vesicles (LDCV) are common. As the neuroblasts grow and differentiate, LDCV move away from perikaryal cytoplasm into developing processes. Around E13-15, LDCV appear in the neuroblasts which continue to develop until they resemble miniature adult PN in late embryos and hatchlings. 2) Granule (GR) cells with clumped chromatin and sparse cytoplasm are clustered in te ganglionic periphery at E7-8, but are rare. The GR cells increase somewhat in size and numbers by E11, but retail essentially the same characteristics as at earlier stages. Neither bright fluorescence nor GR cells appear later than stages E13-15. These results are interpreted to mean that when chick sympathetic stem cells have migrated from the primary ganglia into the paravertebral ganglia, they give rise to two separate lines of CA cells, one of which is not maintained and subsequently disappears. The results are significant as a basis for understanding how a mixed population of CA cells might arise within sympathetic ganglia in situ.

The development and ultrastructure of previously dissociated embryonic chick corpus striatum cultured on feeder layers of liver cells

Embryonic chick corpus striatum neurons were dissociated and maintained on liver feeder layers in culture. Although some large dark-cored vesicles were present in many nerve processes and presynaptic boutons they were substantially less numerous than chick spinal cord neurons grown under identical conditions. Paraformaldehyde-induced fluorescence, although observed in a few culture batches in aggregates of corpus striatum neurons, was otherwise absent and no decisive evidence was obtained to suggest that fluorescent corpus striatum neurons were commonly developed on liver feeder layers in culture. Microtubules filled most cell bodies and nerve processes, and extended well into synaptic boutons often approaching the active zones. They were much more abundant in cultures of corpus striatum than in comparable spinal cord preparations and formed the principal organelle of many nerve fibres. These differences between chick spinal cord and corpus striatum neurons are both interesting and difficult to interpret. It is possible that fewer appropriate cholinergic neurons are available for transformation into adrenergic neurons within the corpus striatum, and that excessive numbers of dark-cored vesicles indicate only a greatly increased rate of acetylcholine production and storage.

A cytochemical and ultrastructural study of the "S.I.F." cells in cat sympathetic ganglia

According to the hypothesis of Eccles and Libet, the small intensely fluorescent cells (S.I.F. cells) in the sympathetic ganglion would represent an essential element in the inhibition of the principal neuron. As a contribution to the study of this important problem, we have investigated serial sections in superior cervical (S.C.G.) and celiac (C.G.) ganglia of the cat, a species that has not been extensively studied up to now, both by fluorescence and electron microscopy. We have shown that the "S.I.F." cells are three times fewer in the cat S.C.G. than in the rat S.C.G. There are five times more "S.I.F." cells in the C.G. of the cat than in the S.C.G. of the same species. Moreover we have described two types of "S.I.F." cells. Type I is composed of cells characterized by highly polymorphous large dense-cored vesicles. These cells lack processes and are grouped in clusters centered on fenestrated capillaries. They could be endocrine function cells. Type II is formed of isolated cells which exibit long processes and establish synaptic junctions with the dendrites of the principal neurons. In this case, the dense-cored vesicles are very regular and much smaller. These cells could be equivalent to interneurons. Type I very strongly predominates in the S.C.G. and C.G. of the cat where it represents more than 90% of the "S.I.F." cell total observed by fluorescence microscopy. A priori such a quantitative and qualitative heterogeneity hardly consistent with Eccles and Libet's hypothesis based on the existence of dopaminergic interneurons only, allows the question to be raised as to the functional significance of the "S.I.F." cells in ganglion physiology. The notion of modulation of ganglionic transmission does not seem to be quiered by these new data but could be founded on different forms of action embodied in the broader conception of the neuromodulation phenomenon.

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.

The ultrastructure of paraganglia associated with the inferior mesenteric ganglia in the guinea-pig

The paraganglia of the inferior mesenteric ganglia in the guinea-pig are composed of small chromaffin cells containing an abundance of granule-containing vesicles. The chromaffin cells are almost completely surrounded by satellite cells. In areas in which satellite cell processes do not intervene, the membranes of adjacent chromaffin cells are closely apposed and often form specialized attachment zones. The paraganglia contain a dense capillary network, the endothelial cells of which are often extremely attenuated and show areas of fenestration. The processes of chromaffin cells approach close to the capillary walls and are often bare of satellite cells covering on the side facing the capillary. Evidence has been obtained for the exocytotic release of the contents of chromaffin cell vesicles into pericapillary spaces. Synapses of cholinergic and noradrenergic axons are seen on the chromaffin cells. The cholinergic axons degenerate when the praganglia are decentralized, but the noradrenergic axons, which appear to arise from the local inferior mesenteric ganglia, remain intact. The results suggest that the paraganglia have an endocrine function.

Some cytochemical and cytological features of the so-called SIF cells of the superior cervical ganglion of the rat

The properties of uptake and storage of dopamine and noradrenaline of the SIF cells of the superior cervical ganglion of the rat were tested, using the radioautographic method. Their ability to store exogenous catecholamines appears very poor under the present experimental conditions, in spite of the great number of storage vesicles they usually contain. This situation may be related either to the absence of a high affinity uptake mechanism in the SIF cell membrane or to a normal saturation of SIF cells in catecholamine. Cytological peculiarities of nerve terminals on SIF cells were pointed out. Dense patches attached to the inner face of the SIF cell membrane suggest a local release of vesicular contents, with further functional implications.

Visual identification of two kinds of nerve cells and their synaptic contacts in a living autonomic ganglion of the mudpuppy (Necturus maculosus)

1. Many of the nerve cells comprising the cardiac parasympathetic ganglion of the mudpuppy are spread out in a thin, transparent sheet of tissue, enabling one to see cellular details in living preparations with differential interference contrast optics. The aim of this study was twofold: to establish the morphology of the nerve cells and their synaptic connections by light and electron microscopy, and to determine which aspects of the ganglion's structure could be reliably identified in the living tissue. 2. There are two types of neurones in the ganglion: (a) principal cells that send post-ganglionic axons to cardiac muscle fibres, and (b) interneurones whose processes are confined to the ganglion. 3. Interneurones are distinguished from principal cells by the presence of numerous granular vesicles seen with the electron microscope, and by intense formaldehyde-induced fluorescence. The interneurones are thus similar to catecholamine-containing interneurones in autonomic ganglia of other vertebrates. 4. Principal cells are innervated by processes that terminate mainly on the cell body, forming up to forty-five synaptic boutons and covering, on the average, 5% of the perikaryal surface. The synaptic terminals are derived from three sources: (a) axons from the vagus nerves, (b) interneurones and (c) other principal cells. Vagal terminals contacting principal cells contain agranular vesicles typical of preganglionic cholinergic endings. At regions of contact between processes of interneurones and principal cells, the interneurones have granular vesicles focused at membrane specializations; in addition there are small areas of close plasma membrane apposition, probably gap junctions. Some of the contacts between principal cells are characterized by gap junctions; others are structurally similar to vagal endings but persist after vagal degeneration. 6. Interneurones are innervated by axons that make contact mainly with their processes. The axon terminals on processes of interneurones contain agranular vesicles similar to vagal terminals on principal cells. 7. In live preparations principal cells are distinguished from interneurones by their size and the appearance of their organelles. Synaptic contacts on principal cells could often be identified and, in some cases, large contacts from interneurones or those from other nearby principal cells could be traced back to their cell bodies of origin. The validity of these identifications was confirmed by subsequent electron microscopic examination of the same cells.

The culture of previously dissociated embryonic chick spinal cord cells on feeder layers of liver and kidney, and the development of paraformaldehyde induced fluorescence upon the former

Spinal cord cells from embryonic chicks were cultured upon liver and kidney feeder layers of similar species origin. Successful cultures were obtained with inocula of cord cells containing as few as 15 000 cells ml(-1), whereas without feeder layers at least 200 000 ml(-1) are ordinarily required. Upon liver, many neurons and processes became intensely fluorescent, a property seldom shared by those grown upon kidney. Many processes upon liver contained large numbers of dense-cored vesicles, significantly larger and more numerous than in those grown upon kidney. We conclude that association with liver feeder layers has the consequence of producing in cord cells fluorescence and ultrastructural characteristics appropriate to catecholamine content, through a mechanism as yet unknown.

Ultrastructural observations on human cerebral capillaries in organ culture

The use of an organotypic-in the strictly literal meaning of the word, nervous tissue culture device has allowed the identification and ultrastructural study of various types of developing capillaries in human cerebellum and olfactory bulb in vitro. Most capillaries were similar to those already described by other authors or by us, in human or animal embryos and fetuses. Large Type I Capillaries. Their luminal diameters were greater than 8 microns. The basement membranes were thin and discontinous. Numerous interendothelial junctions were either plate-like attachments or contained pentalaminar zones. Type II Capillaries. Their lumina were between 2 and 8 microns in diameter. The basement membranes were wider than those of type I capillaries and were sometimes continuous. The interendothelial junctional complexes of type II capillaries included pentalaminar portions. Many simple or complex vascular sprouts (type IV and V capillaries) had small or non-patent lumina. Their basement membranes were absent or very thin and discontinuous. Their interendothelial junctions were similar to those of type I capillaries. Some of the less frequently encountered capillary types seen in developing human nervous tissue were absent in culture. Some pathological features were seen-especially in long-term cultures-in type I and II capillaries containing degenerating blood cells or processes sometimes obviously related to histiocytic cells. They consisted mainly of an accumulation of microfilaments and modifications of the rough endoplasmic reticulum in the endothelial cells. These pathological changes did not modify the main characteristics of the capillaries. The origin of the vascular sprouts, the exact nature of the interendothelial junctions and the significance of the pathological changes are discussed. This model may prove useful for the study of cerebral vasculogenesis, the development of the blood-brain barrier and the physiological or pathological properties of the human brain capillaries in tissue culture.

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.