Localization of NADPH-diaphorase activity in the pancreatic ganglia of the young chick

NADPH-diaphorase activity was localized in pancreatic ganglia of the young chick. At 1 day posthatching, 60% of the neurons in the pancreatic ganglia were NADPH-diaphorase positive. In each neuron, the NADPH-diaphorase labelling was localized mainly in the cytoplasm of the cell body and its proximal processes, but not in the cell nucleus. There was a gradation in the labelling for the enzyme, with some neurons being heavily labelled while others were lightly to moderately labelled. At 7 days post-hatching, 100% of the pancreatic neurons showed NADPH-diaphorase activity and the average size of the NADPH-diaphorase positive neurons had also increased. By 14 days post-hatching, all the neurons present were heavily labelled for NADPH-diaphorase activity. Some of the labelled nerve processes traversed long distances and finally terminated on other ganglia as well as on the exocrine acinar or endocrine cells. It is concluded that this increase in NADPH-diaphorase/NOS activity in the pancreatic neurons is possibly correlated to the increase in modulation of neurotransmission in the young chick.

Localization of thymosin beta 4 to the neural tissues during the development of Xenopus laevis, as studied by in situ hybridization and immunohistochemistry

Thymosin beta 4, a polypeptide of 5 kDa, is known to have capacity to regulate actin polymerization by binding to an actin monomer. Distribution of Xenopus laevis thymosin beta 4 (XT beta 4) in the developing Xenopus larva was examined by means of in situ hybridization and immunohistochemistry. Analysis with in situ hybridization revealed that XT beta 4 mRNA becomes gradually localized to the neural tissues, notochord and inner epidermis during neurula stages. Intense accumulation of XT beta 4 mRNA was observed in the ganglions of cranial nerves and in the dorsal region of the spinal cord from stage 26 and onwards. XT beta 4 immunoreactivity (XTI) was observed in larvas at all developmental stages later than stage 26, tail bud embryo. Immunoreactivity was initially distributed to the ganglion of cranial nerve V and Rohon-Beard cells. As the development progressed, the XTI appeared in other neuronal groups. By late tadpole stages (stages 42-47) the XTI was found in the pineal body, oculomotor and trochlear motoneurons of the midbrain, various neurons in the rhombencephalon, ganglions of cranial nerves V, VII/VIII and IX/X. In the spinal cord the XTI was observed in Rohon-Beard cells, dorsal root ganglion cells, motoneurons and other spinal cord neurons. Immunoreactivity was seen in both cell bodies and axons of the neurons. These findings suggest that thymosin beta 4 plays a role in the development of neurons, especially of sensory neurons.

Primary olfactory fibres project to the ventral telencephalon and preoptic region in trout (Salmo trutta): a developmental immunocytochemical study

We studied the development of the primary olfactory system of a teleost, the brown trout, with the aims of clarifying whether the caudal projection pertains to the olfactory or to the terminal nerve system, of identifying the brain regions receiving this projection, and of investigating its possible functional significance. As olfactory markers (OMs) we used two polyclonal antibodies (to substance P and to alpha-melanocyte-stimulating hormone) that were found to label the olfactory projection strongly after preadsortion of the antibody with the corresponding antigen (OMs), and as a terminal nerve marker we used an antiserum to FMRF-amide peptide. OM labelling was observed in both perikarya and axons of olfactory neurons. In adults, olfactory neurons projected not only to olfactory glomeruli in the olfactory bulb but also, as has been reported previously, to more caudal targets in the forebrain through the medial olfactory tract. Our results show that these targets include the ventral and commissural nuclei of the area ventralis telencephali, the periventricular preoptic region, and the organum vasculosum laminae terminalis. Glomeruli were not observed before hatching, and the extrabulbar olfactory projections appear late in development. Extensive periventricular preoptic olfactory plexuses and olfactory innervation of the organum vasculosum laminae terminalis did not appear until adulthood. The cells of the ganglion nervus terminalis, which form ganglionic groups along the olfactory nerves, were not stained with these olfactory markers at any developmental stage studied, nor was the medial olfactory tract FMRP-amide peptide immunoreactive. Our results thus confirm the existence of primary olfactory projections to extrabulbar targets in trout. The target regions identified in this study are implicated in sexual behaviour: We discuss the related possibility that, in teleosts, these extrabulbar olfactory projections (rather than projections of the terminal nerve, as is widely held) are the primary mediators of neuroendocrine response to pheromones.

Production of nerve growth factor by brown fat in culture: relation with the in vivo developmental stage of the tissue

The regulation of nerve growth factor (NGF) production is still poorly understood. We attempt here to determine whether brown adipose tissue (BAT), which is densely innervated by sympathetic nerve fibres and can be induced to grow in adult rats by simple cold exposure, has the ability to produce NGF and thus to stimulate the growth of its innervation and, if so, whether this NGF activity is developmentally regulated. BAT at various stages of development was cocultured with NGF-sensitive sympathetic ganglia in the presence or absence of antiserum to NGF. Both undifferentiated BAT from newborn hamster and differentiated BAT from newborn rat induced neurite outgrowth by producing a neurotrophic factor which was biologically and immunologically indistinguishable from mouse submandibular gland beta (2.5S) NGF. Newborn hamster BAT and BAT from adult rats exposed to cold for 1 or 2 days showed the same high level of NGF activity, whereas the activities of newborn rat BAT, BAT from adult rats at normal room temperature or cold-exposed for 3 days or more were not significantly different from each other and were only about half as high. Newborn hamster BAT and BAT from adult rats cold-exposed for 1 or 2 days are both characterized in vivo by a rapidly increasing mitotic activity of the stromal-vascular cells, which distinguishes them from the other developing tissues tested. Our observations, therefore, suggest a relationship between NGF synthesis and proliferative activity.

Collapsin: a protein in brain that induces the collapse and paralysis of neuronal growth cones

Repulsive guidance cues can steer neuronal growth cones during development and prevent mature axons from regenerating. We have identified a 100 kd glycoprotein in the chick brain that is a good candidate for a repulsive cue. Since it induces the collapse and paralysis of neuronal growth cones in vitro, we have named it collapsin. It is effective at concentrations of approximately 10 pM. The C-terminal half of collapsin contains a single immunoglobulin-like domain and an additional highly basic region. The N-terminal half of collapsin shares significant homology with fasciclin IV, a growth cone guidance protein in grasshopper. Recombinant collapsin causes sensory ganglion growth cones to collapse but not retinal ganglion cell growth cones. We propose that collapsin could serve as a ligand that guides specific growth cones by a motility-inhibiting mechanism.

Development of substance P and neurokinin A immunoreactivity in ganglia supplying nerves to the submandibular glands of the rat

Developing submandibular, trigeminal and superior cervical ganglia, which provide innervation to the submandibular glands, were studied for substance P (SP)- and neurokinin A (NKA)-immunoreactive (IR) ganglion cells and nerve fibres in rat. These ganglia were examined by using an indirect immunofluorescence technique at daily intervals from the 16th day in utero (i.u.) until birth, and subsequently on the 2nd, 5th, 7th, 12th, 16th, 30th, 42nd postnatal day and in the adult (3 months). In the submandibular ganglion SP- and NKA-IR cells and fibres first appeared in considerable numbers on the 19th day i.u. (in one sample out of five on the 18th day i.u.), when more than 90% of the ganglion cells were immunoreactive to SP and NKA. The number stayed at more than 90% to the 7th postnatal day and then slowly decreased to the levels of adult animals (18% SP, 17% NKA). The first SP- and NKA-IR ganglion cells and fibres appeared in the trigeminal ganglion on the 18th day i.u. when they represented 7% (SP) and 4% (NKA) of the ganglion cells. The number of SP- and NKA-IR cells increased steadily, reaching a maximum at the time of birth when 68% (SP) and 74% (NKA) of the ganglion cells were immunoreactive. Thereafter they began to decrease toward the level of an adult rat (10% SP, 11% NKA). In the superior cervical ganglion only a few SP- and NKA-IR ganglion cells were detected from the 19th day i.u. to the fifth postnatal day. Positive ganglion cells were also occasionally found in the nerve trunks outside the superior cervical ganglion.(ABSTRACT TRUNCATED AT 250 WORDS)

Coordinate and noncoordinate regulation of synaptic vesicle protein genes during embryonic development

Because the formation of a mature nerve terminal requires the accumulation of large quantities of synaptic vesicles, the expression of synaptic vesicle proteins would be expected to correlate with synaptogenesis. However, previous studies have provided conflicting evidence on this point. We have examined the developmental pattern of expression of mRNA and protein for three RNAs derived from two genes coding for synaptic vesicle membrane proteins. For these experiments, we cloned a chick p65 (synaptotagmin) cDNA using a reduced stringency screen with a rat p65 cDNA probe. We examined p65 expression in chick forebrain in conjunction with that of synaptophysin II. RNase protection assays for p65 and the two isoforms of synaptophysin II (Bixby, 1992) show essentially coordinate increases of these three mRNAs in embryonic forebrain during the peak period of synaptogenesis (E17 to E20). However, each of the three mRNAs has a distinct temporal pattern of expression during the early stages of embryogenesis. In the ciliary ganglion, upregulation of synaptophysin II mRNA correlates very well with synaptogenesis. Our results suggest that the regulation of expression of vesicle membrane protein mRNA can serve as a marker for synaptogenesis, despite temporal differences in early expression patterns. In contrast to mRNA expression, assays for vesicle protein expression show a relatively steady rise in both p65 and synaptophysin II throughout the embryonic period, without a sharp increase corresponding to that seen in message levels. These results suggest that the expression both of the p65 and of the synaptophysin II proteins is post-transcriptionally regulated.

Development of dopaminergic neurons is insensitive to optic nerve section in the neonatal rat retina

The development of tyrosine-hydroxylase-immunoreactive (TH-IR) cells was studied in pre- and postnatal rat retinas. Using a modified staining method, TH-IR cells were first detectable in retinal wholemounts at embryonic day 19 (E19), much earlier than previously reported. By E20, TH-IR cells were present in every retina examined. These 'early' TH-IR cells were always concentrated at the peripheral dorsal part of the retina, in contrast to the expected distribution predicted by the center to peripheral gradient of retinal development. The development of TH-IR cells and their pattern of distribution were insensitive to optic nerve section, indicating that the postnatal development of dopaminergic neurons is independent of the presence of ganglion cells.

Grafting in acute spinal cord injury: morphological and immunological aspects of transplanted adult rat enteric ganglia

We have studied allogeneic transplants of adult rat enteric ganglia in order to evaluate their use as donor tissue for eventual autografts in rodent spinal cord injury models. Female Sprague-Dawley rats of similar weights served either as transplant donors or as recipients. A glass micropipette of 0.8 mm diameter was used to create a local penetrating injury of the lower thoracic spinal cord and the transplant material was pressure injected through the pipette within the neural parenchyma. Ganglia of the myenteric plexus adhering to the stratum longitudinal muscularis were dissected from portions of the jejunum and ileum. Following partial enzymatic digestion and mechanical disruption of the myenteric plexus and muscle tissue (labeled with adherent rhodamine conjugated microbeads), reaggregates of myenteric plexus and muscle were suspended in growth medium and cultured in vitro for one to two days prior to transplantation. Transplants were examined at three, four, six, and eight weeks after surgery. Some of the donor tissue was grown in vitro, in order to determine its cellular composition. These cultured explants were fixed after 10 days, and like myenteric plexus and muscle grafts, were stained histochemically for acetylcholinesterase and observed by fluorescence and light microscopy. At the earlier post-transplantation periods, grafts contained several clusters of enteric ganglion cells that were positive for acetylcholinesterase and exhibited ultrastructural features characteristic of the enteric nervous system. They had well-defined boundaries. Reactive astrocytes and their processes remained located within the host spinal cord adjacent to the boundary region of the grafts. Likewise, macrophages were located in areas abutting the graft. Newly formed vasculature penetrated the graft interior and appeared to be continuous with the host vessels. Grafts grown for at least eight weeks were characterized by interdigitating boundaries. Finger-like protrusions of graft tissue containing fibroblasts and collagen intermixed with adjacent gray and white matter of the host cord. Such transplants also had reactive astrocytes and ED1-positive macrophages. At this later stage, several groups of ganglion cells were identified that were intensely acetylcholinesterase-positive; however, only two of four grafts were recovered, whereas two of the transplants degenerated. We postulate that degeneration of allogeneic grafts may occur as a result of ongoing immune responses of the host which could be prevented by use of autogeneic enteric ganglia. Our studies show that fully differentiated enteric ganglia can survive transplantation to acutely injured spinal cord of adult rats.

Development of Na(+)- and K(+)-currents in the cochlear ganglion of the chick embryo

The development of Na(+)- and K(+)-currents in the primary afferent neurons of the cochlear ganglion was studied using the patch-clamp technique. Cells were dissociated between days 6 and 17 of development and membrane currents recorded within the following 24 h. Outward currents were the first to appear between days 6 and 7 of embryonic development and their magnitude increased throughout development from 200 pA on day 7 to 900 pA on days 14-16. Threshold for activation decreased by 20 mV between days 8 and 14. Outward currents were absent when Cs+ replaced K+ in the pipette and were partially blocked by external tetraethylammonium. Outward currents contained at least three components: (i) a non-inactivating outward current, similar to the delayed-rectifier, predominating in mature neurons; (ii) a slowly inactivating current (tau about 200 ms), most evident in early and intermediate stages (days 7-10); and (iii) a rapidly inactivating outward current (tau about 20 ms) similar to the A-current (IA) described in other neurons, which was distinctly expressed in mature neurons. Sodium currents were identified as fast transient inward currents, sensitive to tetrodotoxin and extracellular Na(+)-removal. They appeared later than K(+)-currents and increased in size from about 100 pA between days 9-11 to 600 pA by days 13-16. The development of membrane currents in cochlear ganglion neurons corresponded to defined stages of the innervation pattern of the chick cochlea [Whitehead and Morest (1985) Neuroscience 14, 255-276]. These currents could be functionally related to the establishment of synaptic connections between transducing cells and primary afferent neurons.

Development of serotoninlike immunoreactivity in the embryonic nervous system of the snail Lymnaea stagnalis

In our initial effort to study the ontogeny of the gastropod nervous system, we used histological techniques to examine the post-embryonic development of cells which exhibit serotoninlike immunoreactivity in Lymnaea (Croll and Chiasson, J. Comp. Neurol. 230:122-142, '89). The present study complements that report by examining the embryonic development of these neurons. The first serotoninlike immunoreactive (SLIR) cells to be detected in the embryos are the paired C4 neurons of the cerebral ganglia. These cells are faintly visible at about 37-38% of embryonic development and have already produced axons which traverse the cerebral commissure. By about 2-3% later the axon tips reach the pedal ganglia and appose the next SLIR cells to appear, the EPe1 neurons. Over the next 30% of development four more pairs of cerebral neurons are added adjacent to the C4 neurons and over ten cells are added to each of the pedal ganglia. At about 70% of development SLIR fibers are first detected in the parietal and visceral ganglia forming the abdominal ring. Around this time the somata of the C1 neurons also first appear in the cerebral ganglia together with their prominent axons projecting to the buccal ganglia. The last 30% of development is marked by a massive addition of SLIR cells (up to 60) in each pedal ganglion. The early appearance of the first SLIR cells suggests that they may be among the first nerve cells to differentiate and that they may play central roles in the formation of the CNS. We hypothesize that most of the animal's neural circuitry is laid down during embryogenesis by a stereotypic ontogenetic program with post-embryonic neurogenesis subserving mostly compensatory and modulatory purposes.

Dual effects of endothelin-1 on neurite outgrowth induced by 12-O-tetradecanoylphorbol-13-acetate

The vasoactive peptide endothelin-1 (ET-1) was found to bind to a single class of binding sites in chick embryonic sensory ganglia with a Kd of 67 +/- 5 pM. Treatment of ganglia explants with 100 pM ET-1 did not affect neuronal development, but when added together with 12-O-tetradecanoylphorbol-13-acetate (TPA) a synergistic stimulation of neurite outgrowth was observed. In contrast, 10 nM ET-1 inhibited TPA-induced neurite outgrowth. Both the stimulatory and inhibitory effects were not blocked by nifedipine, a Ca2+ channel blocker. These results suggest that ET-1 can modulate the process of neurite outgrowth and its effects are not dependent on voltage-gated Ca2+ channels.

Expression of a neurally related laminin binding protein by neural crest-derived cells that colonize the gut: relationship to the formation of enteric ganglia

In order to give rise to the enteric nervous system (ENS), cells migrating from the neural crest must find the bowel and cease migrating at appropriate locations within the gut. Previous studies of the development of the ENS in a mutant mouse have led to the hypothesis that laminin in the enteric mesenchyme may act as a signal to crest-derived cells to cease migrating and extend neurites (or glial processes). Implied in this hypothesis is the idea that crest-derived cells, as a prelude to their participation in ganglion formation, acquire a neurally related laminin receptor, which they do not express at pre-enteric stages of migration. As a partial test of this hypothesis, single and double label immunocytochemistry at light and electron microscopic (EM) levels were used to study the expression of cell surface laminin binding proteins by crest-derived cells in the process of migrating to or within the developing chick gut. Two antibodies (called 3070 and alpha-110) raised against neuronal cell surface laminin binding proteins were employed for this purpose. Laminin binding protein immunoreactivity was found to be expressed within the bowel and ganglion of Remak by a subset of crest-derived cells (identified immunocytochemically with NC-1/HNK-1 antibodies) and by all of those developing as neurons (identified immunocytochemically with antibodies to neurofilament-associated proteins). Laminin binding protein immunoreactivity was also found to be expressed in fixed neural structures elsewhere in the embryos, including cranial and spinal roots, nerves, and ganglia. In contrast, laminin binding protein immunoreactivity was not expressed by migrating crest-derived cells in the vicinity of the vagal or sacral regions of the neuraxis (from which the precursors of the ENS take origin); nor was it expressed by juxta-pharyngeal vagal crest-derived cells migrating to the foregut through the caudal branchial arches or by the caudal stream of sacral crest-derived cells approaching the hindgut. EM immunocytochemistry confirmed that laminin binding protein immunoreactivity in the bowel was located on the surfaces of crest-derived cells, and was exhibited both by those cells that could only be distinguished from their neighbors by their NC-1/HNK-1 immunoreactivity and by cells developing as neurons or glia. EM immunocytochemistry also revealed that the surfaces of crest-derived cells migrating through the enteric mesenchyme were contacted by many small osmiophilic "puffs" of laminin-immunoreactive extracellular material. These puffs coincided in location with membrane sites that expressed the immunoreactivity of the laminin binding protein. These observations are consistent with the hypothesis that laminin plays a role in the formation of enteric ganglia.

A light and electron microscopic study of the development of the Mauthner cell and vestibular nerve in the axolotl

Vestibular axons form synapses on a restricted area of the lateral dendrite of the Mauthner cell, a large, identified brainstem neuron found in fish and amphibians. The differentiation of the vestibular nerve, medullary neuropil, and Mauthner cell of the axolotl (Ambystoma mexicanum) was studied to understand better the means by which this synaptic specificity arises. The Mauthner cell first extends a medial process and then a lateral dendrite. The latter initially elongates as a simple process and later sends out branches. As the lateral dendrite grows, vestibular axons enter the brainstem to form one of the earliest of several discrete axon fascicles that course longitudinally through the neuropil. The fascicles, many of which are identifiable on the basis of their location and axonal morphology, are the precursors of the longitudinal tracts of the mature salamander. The lateral dendrite grows dorsally over the orthogonally oriented fascicles, making contact with each at a characteristic time and place. The first afferents to form synapses do so on the soma and proximal lateral dendrite; subsequent afferent groups terminate more distally. Axons within a given fascicle form synapses with the Mauthner cell in a discrete and initially homogeneous domain. As dendritic branches form and the organization of the longitudinal fascicles becomes more complex, the homogeneity of axons terminating on a given region of the Mauthner cell surface is lost, but no major rearrangement or migration of terminals is apparent. These observations are consistent with both active recognition and passive spatiotemporal models of synaptic site specificity.

Age-related differential expression of neuropeptide mRNAs in Aplysia

The basis of aging in the Aplysia nervous system is unknown. We now report age-related changes in mRNA expression of phe-met-arg-phe-NH2 (FMRFamide) and egg-laying hormone (ELH) in the abdominal ganglion, a part of the CNS, in young, mature and old Aplysia. Northern blot analysis revealed two mRNA species of 1.4 and 3.2 kb for RMRFamide and a single mRNA species of 0.8 kb for ELH. FMRFamide mRNA level increased 1.5-fold from young to mature and then decreased 3-fold in old animals. ELH mRNA gradually increased between young and mature animals and then escalated 25-fold in old animals. Age differentially affected the mRNA of these two peptides, which may contribute to behavioral changes previously reported.

Kainate and NMDA toxicity for cultured developing and adult rat spiral ganglion neurons: further evidence for a glutamatergic excitatory neurotransmission at the inner hair cell synapse

In the inner ear, the excitatory amino acid glutamate is a proposed neurotransmitter acting at the synapse between hair cells and afferent auditory neurons. Using cultures of 5-day-old rat auditory neurons, we show that the afferent auditory neuronal population can be divided, on the basis of its sensitivity to the neuronotoxic effect of glutamate and its analogs, in at least 3 subpopulations, one responding to N-methyl-D-aspartate (NMDA), one responding to kainate and a third minor one unresponsive to NMDA, kainic acid and glutamate. No toxic effect of quisqualate is observed. The use of specific antagonists (kynurenate and 2-amino-5-phosphonovalerate (DAP-5) demonstrates the specificity of the receptors to the excitatory amino acids on the afferent auditory neurons. Afferent auditory neurons from adult rats can also be cultured and in these preparations only the large neurons are sensitive to glutamate, kainate and NMDA while the small neurons are not responsive, suggesting that a glutamatergic neurotransmission occurs only at this synapse between the inner hair cells and the large radial afferent auditory neurons. We also show that, in vitro, the organ of Corti releases, in response to an increased potassium concentration and in the presence of calcium, a toxic activity for the afferent auditory neurons that is antagonized by kynurenate and DAP-5. Pathophysiological implications are discussed.

The regulation of transmitter expression in postembryonic lineages in the moth Manduca sexta. II. Role of cell lineage and birth order

The expression of GABA is restricted to the progeny of only six of the 24 identified postembryonic lineages in the thoracic ganglia of the tobacco hornworm, Manduca sexta (Witten and Truman, 1991). It is colocalized with a peptide similar to molluscan small cardioactive peptide B (SCPB) in some of the neurons in two of the six lineages. By combining chemical ablation of the neuroblasts at specific larval stages with birth dating of the progeny, we tested whether the expression of GABA and the SCPB-like peptide was determined strictly by cell lineage or involved cellular interactions among the members of individual clonal groups. Chemical ablation of the six specific neuroblasts that produced the GABA-positive neurons (E, K, M, N, T, and X) or of the two that produced the GABA + SCPB-like-immunoreactive neurons (K, M) prior to the generation of their lineages resulted in the loss of these immunoreactivities. These results suggest that regulation between lineages did not occur. Ablation of the K and M neuroblasts after they had produced a small portion of their lineages had no effect on the expression of GABA, but did affect the pattern of the SCPB-like immunoreactivity. Combining birth-dating techniques with transmitter immunocytochemistry revealed that it was the position in the birth order and not interactions among the clonally related neurons that influenced the peptidergic phenotype. These results suggest that cell lineage is involved in establishing the GABAergic phenotype and that both cell lineage and birth order influence the determination of the peptidergic phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Laminin-like immunoreactivity in the snail Helisoma: involvement of approximately 300 kD extracellular matrix protein in promoting outgrowth from identified neurons

Polyclonal antibodies directed against laminin (LM), and against the A and B chains of reduced LM were used to identify antigenically related proteins in the extracellular matrix (ECM) of the snail Helisoma trivolvis. Immunofluorescence of snail central ganglionic rings using either the anti-LM or anti-B chain antibodies labeled the ECM within ganglionic sheaths as well as basal laminae surrounding the ganglia. Both the anti-LM and anti-B chain antibodies recognized a prominent, approximately 300-kD protein on immunoblots of a snail central ganglion preparation enriched in ECM components. The anti-A chain antibody failed to label any structures in sections of snail ganglia or to recognize any proteins on immunoblots of ganglionic ECM. A polyclonal antibody was raised against the approximately 300-kD snail protein. Immunofluorescence of snail ganglia with the anti- approximately 300-kD antibody gave a distribution of labeled structures comparable to that obtained with the anti-LM antibody. Immunofluorescent labeling of sections of snail muscle and salivary gland with the anti- approximately 300-kD antibody revealed a distribution of reactive protein characteristic of an ECM component. Probing immunoblots of ganglionic ECM with the anti- approximately 300-kD antibody revealed the recognition of the same approximately 300-kD protein as identified by the anti-LM antibodies. Media conditioned by Helisoma central ganglionic rings (CM) contains an unidentified neurite outgrowth promoting factor (NOPF). Immunoblots of CM probed with the anti-B chain and anti- approximately 300-kD antibodies reveal the recognition of a soluble approximately 300-kD protein similar to the approximately 300-kD protein identified in snail ECM. The ganglionic ECM preparation containing the approximately 300-kD protein supported outgrowth from cultured snail buccal neurons B5, and addition of anti- approximately 300-kD Fab fragments to CM abolished its outgrowth promoting activity. These results suggest that the approximately 300-kD ECM protein may be the NOPF in CM and/or functions in promoting neurite outgrowth.

The regulation of transmitter expression in postembryonic lineages in the moth Manduca sexta. I. Transmitter identification and developmental acquisition of expression

The majority of the neurons in the adult nervous system of Manduca sexta are born postembryonically, during larval life. Stereotypic arrays of identifiable neuroblasts generate their clonal families or lineages commencing at the end of the second larval instar through pupal day 2, when the neuroblasts die (Booker and Truman, 1987a). We have used immunohistochemical techniques to follow the neurochemical differentiation of GABA and a peptide similar to molluscan small cardioactive peptide B (SCPB) in identified lineages. We report here the distribution and developmental acquisition of the expression of these putative transmitters. There are 24 postembryonic lineages in the second thoracic ganglion of the larvae (Booker and Truman, 1987a). Immunoreactivity against GABA and SCPB is seen only in a subset of these 24 clonal families. GABA immunoreactivity is confined to the progeny of the E, K, M, N, T, and X neuroblasts and is expressed by most or all of the neurons in these lineages. The SCPB-like immunoreactivity is found in a subset of the neurons in only two clonal groups, the K and M groups, and is colocalized with GABA. These results show that, though heterogeneity in transmitter type exists (GABA, GABA/SCPB), members of a given lineage share at least some features (GABA) in common. The onset of transmitter expression was followed in detail for the K- and M-lineage neurons. During the larval stages, the postembryonic lineage cells are developmentally arrested in a partially differentiated state (Booker and Truman, 1987a) and do not express transmitter immunoreactivity at this time. Their maturation resumes with the onset of metamorphosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Internalization of gap junctions between neuron and glial cell and formation of annular lamellar bodies in Chinese leech Whitmania pigra

This paper reveals the formation of annular lamellar body (ALB) in the ganglion of leech by means of in situ fixation and the lanthanum nitrate tracer technique. This formation involves both wrapping and internalization of the gap junctions between glial processes themselves, as well as between neuron and glial process. The results indicate that there is probably an active process of internalization of membrane structures involving gap junctions between neuron and glial cell in the central nervous system in leech. The functions of ALB are discussed.

An autoradiographic analysis of neurogenesis in juvenile Aplysia californica

In developing Aplysia californica, a dramatic proliferation of new neurons occurs throughout the central nervous system (CNS) surprisingly late in juvenile development (Cash and Carew, 1989). In the present study, we investigated the source of these new neurons. Using tritiated thymidine autoradiography, we examined two different juvenile stages: stage 11 (before the large-scale proliferation) and stage 12 (at the peak of proliferation). Previous results implicated the body wall as a source for neurons in developing Aplysia (McAllister, Scheller, Kandel, and Axel, 1983; Jacob, 1984). Thus, we focused our attention on the body wall adjacent to a specific central ganglion, the abdominal ganglion. We found that in stage 11 there was uniform labelling of cells across the entire body wall. However, in stage 12 there was significantly more labelling in the body wall region immediately adjacent to the abdominal ganglion compared to flanking regions. Thus, at the time of neuronal proliferation, specific and highly localized regions of the body wall immediately opposite their target in the CNS show a significant increase in cell division. We also examined the distribution of labelled cells in the abdominal ganglion at survival times of 1 and 7 days after thymidine injection. In both stage 11 and stage 12, the fraction of labelled cells on the surface of the ganglion decreased over time, with a corresponding significant increase in the fraction observed on the inside. Our results support the hypothesis that specific regions of body wall are significantly up-regulated in juvenile Aplysia development, giving rise to widespread neuronal proliferation. These neurons then migrate from the body wall to their target ganglion, and from there continue migrating into the ganglion to achieve their final position.

Formation of ganglia in the gut of the chick embryo

We have examined the formation of myenteric ganglia in the developing avian enteric nervous system. The monoclonal antibody HNK-1 was used to identify neural-crest-derived cells in whole mounts of fore- and midgut of chick embryos. We find that the crest-derived cells extend processes to their neighbors and form a complex network in the wall of the gut. Formation of this network is an unusual behavior of crest-derived cells and suggests the gut microenvironment is critical to this behavior. This cellular network disappears after ablation of the vagal neural crest, indicating the HNK-1-stained cellular network arises from crest-derived cells. The network is found in the gut wall before the vagal nerve fibers are present. This network is first found in the primordium of the proventriculus, distal to the evagination of the lung buds, and progresses just proximal to the yolk stalk at embryonic day (E) 3.5 and almost to the ileocecal junction at E5.5. The number of cells and the complexity of the network decrease in a rostral-caudal direction down the length of the gut at these stages. The leading edge of the network consists of cells serially arranged in longitudinally running strands. The organization of the network changes with increasing embryonic age; we have focused on network changes in the proventriculus. In the primordium of the proventriculus at E3.5, the network consists of a cluster of one or two adjacent crest-derived cells, which extend processes to a number of neighboring crest-derived cells. At E5.5 large increases in the number of cells per cluster and in the length of cellular connectives between clusters are apparent. At E6.5 a crude meshwork of clusters is seen. At E10.5 the arrangement of cell clusters resembles the pattern of ganglia found in the adult myenteric plexus. This network may provide the environmental cues for the differentiation of enteric neurons and a framework for the pattern of ganglia found in the adult enteric nervous system.

Unequal competition between axons for neuronal targets

Precise wiring of the nervous system depends not only on a matching between neurons and their synaptic targets, but also upon competition between neurons for particular targets. Neurons in adult leeches regenerate synaptic connections with their usual neuronal targets in the central nervous system, selecting only those targets with which they connect during embryogenesis. Thus during development axons of nociceptive (N) sensory cells make contacts on the cell bodies of certain neurons in adjacent ganglia but not upon those same types of cells in their own ganglion. After injury the N cell axons accurately regenerate contacts on the appropriate target cells. An abnormal feature observed after injury is that N cell axons sprout and grow to make contacts upon cell bodies within their own ganglion. This is a consequence of the normal innervation of those cells having been removed, thereby eliminating the source of competition. Similar competition during embryogenesis may guide the formation of selective connections.

Novel effects of serotonin on neurite outgrowth in neurons cultured from embryos of Helisoma trivolvis

The neurotransmitter serotonin has been shown to inhibit neurite outgrowth in specific identified neurons isolated from adult Helisoma. While in vivo experiments on Helisoma embryos have supported the hypothesis that endogenous serotonin regulates neurite outgrowth during embryonic development, direct effects of serotonin on embryonic neurons have not been measured. In the present study, cultures of dissociated embryonic neurons were used to test the direct actions of serotonin on developing embryonic neurons. Serotonin arrested neurite outgrowth in a significant percentage of elongating neurites in a dose-dependent manner. Furthermore, analysis of neurons with stable, nonelongating neurites revealed a novel response. Serotonin caused the reinitiation of neurite outgrowth in a significant percentage of nonelongating neurites. The arrestment of outgrowth and reinitiation of outgrowth occurred in similar percentages of elongating and nonelongating neurites, respectively. Parallel experiments on cultures of dissociated adult neurons were carried out to determine whether serotonin could also induce both inhibitory and stimulatory responses in adult cells. Serotonin arrested neurite outgrowth in a similar percentage of neurites to that observed in cultures of embryonic neurons. In contrast, serotonin did not reinitiate neurite outgrowth in a significant percentage of adult neurites. These data support the hypothesis that serotonin regulates neurite outgrowth in developing embryonic neurons. Furthermore, only some of these regulatory effects appear to be conserved from embryonic to adult neurons.