Fine structure and innervation of the avian adrenal gland. 3. Non-cholinergic nerve fibers

Reduction of endogenous TGF-beta increases proliferation of developing adrenal chromaffin cells in vivo

Chromaffin cells and sympathetic neurons are derivatives of the sympathoadrenal cell lineage of the neural crest. Although they are similar with respect to many cell biological aspects, chromaffin cells, in contrast to sympathetic neurons, continue to synthesize DNA and proliferate through their whole life span. Large numbers of neural and hormonal signals have been implicated in the regulation of chromaffin cell proliferation based on in vitro studies. We have previously shown that chromaffin cells synthesize and release transforming growth factor-beta (TGF-beta) and that exogenously applied TGF-beta suppresses chromaffin cell proliferation in vitro. We show now that TGF-beta is also a physiologically relevant factor in the control of cell division in developing chromaffin cells. We have neutralized endogenous TGF-beta in quail embryos using a monoclonal antibody recognizing all three TGF-beta isoforms, TGF-beta1, -beta2, and -beta3. Embryos deprived of TGF-beta show a prominent increase in numbers of tyrosine hydroxylase (TH)-immunoreactive adrenal chromaffin cells and TH-positive cells incorporating 5'-bromo-2'deoxyuridine. This is the first documentation of the physiological significance of a factor that has been suggested to play a role in the regulation of chromaffin cell mitosis based on in vitro experiments.

Screening of adrenal medullary neuropeptides for putative neurotrophic effects

Chromaffin granules, the secretory organelles of the neuron-like adrenal medullary chromaffin cells, have previously been shown to store and liberate neurotrophic activities that support in vitro survival of several neuron populations including those innervating the adrenal medulla. Molecules resembling fibroblast growth factor and ciliary neurotrophic factor have been identified among these activities. Since chromaffin granules store a variety of neuropeptides and many neuropeptides can have pleiotropic effects on neuronal growth and maintenance we have tested 24 different neuropeptides for their capacities to promote survival of embryonic chick ciliary, dorsal root and sympathetic ganglionic neurons. Peptides tested included several derivatives of proenkephalin (Leu- and met-enkephalin, fragments BAM 22, B, F and E), somatostatin, substance P, neuropeptide Y, neurotensin, VIP, bombesin, secretin, pancreastatin, dynorphin B, dynorphin 1-13, beta-endorphin, alpha-, beta-, and gamma-MSH. Control cultures received saturating concentrations of ciliary neurotrophic or nerve growth factor (CNTF; NGF), or no trophic supplements. At 1 x 10(-5) M leu- and met-enkephalin as well as somatostatin supported sympathetic neurons to the same extent as NGF. At the same concentrations, leu-enkephalin, the proenkephalin fragments BAM 22 and E, and somatostatin maintained about half of the dorsal root ganglionic neurons supported by NGF, but were not effective on ciliary neurons. VIP promoted the survival of approximately 50% of the ciliary and embryonic day 10 dorsal root ganglionic neurons as compared to saturating amounts of CNTF, but required the presence of non-neuronal cells in the cultures to be effective. Neurotensin (1 x 10(-5) M had a small effect on ciliary neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoelectron microscopic study of tyrosine hydroxylase immunoreactive nerve fibers and ganglion cells in the rat adrenal gland

The present immunocytochemical study used an antiserum to tyrosine hydroxylase (TH), the first enzyme in the biosynthetic pathway of catecholamines, and revealed TH immunoreactivity in the ganglion cells and in the varicose nerve fibers of the cortex and medulla in the rat adrenal gland. TH immunoreactive nerve fibers in the cortex and medulla contained large and small granular vesicles, and also small clear vesicles. The immunoreactive nerve fibers were in close apposition to cortical cells in the cortex and in apposition to smooth muscle cells of blood vessels in both the cortex and medulla. Furthermore, TH immunoreactive nerve fibers were sometimes in close apposition to pericytes of blood vessels in the cortex and chromaffin cells in the medulla. The present results suggest that the catecholaminergic nerve fibers in the rat adrenal gland may be both intrinsic and extrinsic in origin.

Differentiation of embryonic chick sympathetic neurons in vivo: ultrastructure, and quantitative determinations of catecholamines and somatostatin

The ultrastructural and transmitter development of lumbar sympathetic ganglia was studied in embryonic day-6 through -18 chick embryos. At embryonic day 6, ganglia are populated by two morphologically distinct types of neuronal cells and Schwann cell precursors. The neuronal populations basically comprise a granule-containing cell and a developing principal neuron. Granule-containing cells have an irregularly shaped or oval nucleus with small clumps of chromatin attached to the inner nuclear membrane and numerous large (up to 300 nm) membrane-limited granules. Developing principal neurons display a more rounded vesicular nucleus with evenly distributed chromatin, prominent nucleoli, more developed areas of Golgi complexes, and rough endoplasmic reticulum and large dense-core vesicles up to 120 nm in diameter. There are granule-containing cells with fewer and smaller granules which still display the nucleus typical for granule-containing cells. These granule-containing cells may develop toward developing principal neurons or the resting state of granule-containing cells found in older ganglia. Both granule-containing cells and developing principal neurons proliferate and can undergo degeneration. At embryonic day 9 there are far more developing principal neurons than granule-containing cells. Most granule-containing cells have very few granules. Mitotic figures and signs of cell degeneration are still apparent. Synapse-like terminals are found on both developing principal neurons and granule-containing cells. Ganglionic development from embryonic day 11 through 18 comprises extensive maturation of developing principal neurons and a numerical decline of granule-containing cells. Some granule-containing cells with very few and small granules still persist at embryonic day 18. The mean catecholamine content per neuron increases from 0.044 femtomol at embryonic day 7 to 0.22 femtomol at embryonic day 15. Concomitantly, there is a more than 6-fold increase in tyrosine hydroxylase activity. Adrenaline has a 14% share in total catecholamines at embryonic day 15. Somatostatin levels are relatively high at embryonic day 7 (1.82 attomol per neuron) and are 10-fold reduced by embryonic day 15. Our results suggest the presence of two morphologically distinct sympathetic neuronal precursors at embryonic day 6: one with a binary choice to become a principal neuron or to die, the other one, a granule-containing cell, which alternatively may develop into a principal neuron, acquire a resting state or die.

Influence of splanchnic nerve on reserpine action in avian adrenal medulla

Reserpine at three doses (0.05, 0.2, and 0.8 mg/100 g body wt) has been injected intraperitoneally to seven unilaterally splanchnic denervated avian species, in order to ascertain the neural regulation of its action in avian adrenal medulla. The adrenomedullary catecholamines (CA) were estimated at 24 hr after reserpine injection. The findings revealed that reserpine at high doses caused 66-92% depletion of total CA from both the innervated and the denervated glands in all the species investigated. The low dose of reserpine in the passerine (common myna and bulbul) birds resulted in 40-84% reduction of both norepinephrine (NE) and epinephrine (E) from the adrenal glands irrespective of its nerve supply. As a contrast, it depleted 60-80% of both NE and E from the innervated glands as compared to 17-43% reduction from the denervated glands in nonpasserine (woodpecker, parakeet, and koel) birds. Interestingly, in other nonpasserine (pigeon and duck) birds, the low dose of reserpine depleted 66-71% of NE from the innervated glands as compared to only 2-13% reduction from the denervated glands. But in these birds, 60-85% depletion of E, however, occurred independent of neural regulation. The findings suggest that at high doses depletion of CA by reserpine is controlled by some nonneurogenic mechanisms. Generally speaking, at a low dose of reserpine, the splanchnic nerve probably modulates depletion of CA from the adrenal medulla of the nonpasserine birds while the same is governed by some nonneurogenic mechanisms in the passerine birds.

Neuroblastoma cells contain a trophic factor sharing biological and molecular properties with ciliary neurotrophic factor

Ciliary neurotrophic factor (CNTF) is a protein supporting the in vitro survival of a characteristic spectrum of embryonic chicken and rat peripheral neurons. High-speed supernatants of extracts from two neuroblastoma (NB) cell lines--the mouse C 1300 N2a and the human IMR 32--mimic the effects of CNTF on identical target neurons. Promotion of survival is dose-dependent with an ED50 of 80 micrograms (IMR 32) and 140 micrograms (C 1300 N2a) of protein per ml and saturable at plateau values for surviving neurons identical to those achieved with purified CNTF. Small amounts of a CNTF-like material are also detectable in medium conditioned by NB cells. The activity is destroyed by heat and trypsin and not blocked by antibodies to (mouse) nerve growth factor. Unlike the neurite-promoting and neuronal-survival modulating agent laminin, it cannot be depleted on poly(L-alpha-ornithine)-coated plastic surfaces. NB IMR 32 cell extracts were electrophoresed using NaDodSO4/PAGE and transferred to nitrocellulose. Ciliary ganglion neurons seeded on the blotting paper in culture medium lacking CNTF ("cell blot") exclusively survive on two distinct bands with apparent molecular masses of 24 and 48 kDa. Twenty-four kilodaltons is the molecular mass of a CNTF purified from rat sciatic nerve. These results suggest that NB cells may contain a CNTF-like protein and provide further evidence that neurons may store neurotrophic factors. Purified (chicken) CNTF failed to affect proliferation and neurite growth of NB cells. The biological relevance of CNTF for NB cells, therefore, remains to be elucidated.

Nerve endings in human sympathetic ganglia

Forty-eight human sympathetic ganglia from 22 sympathectomies were examined ultrastructurally after one of three different fixations: (1) glutaraldehyde + osmium tetroxide, (2) glutaraldehyde + potassium dichromate + osmium tetroxide, or (3) potassium permanganate. Three different kinds of synapsing nerve ending could be identified after all fixation schedules. Type 1: "Cholinergic," containing small, agranular vesicles 40-60 nm in diameter (75% of all vesicles) and some large granular vesicles (100 nm in diameter). The number of type 1 profiles decreased with increasing age. Type 2: "Adrenergic," containing small granular vesicles 40-70 nm in diameter (over 90% of the vesicles). Type 3: "Nonadrenergic, noncholinergic," characterized by large opaque vesicles 80 -160 nm in diameter (over 50% of all vesicles). The frequencies of the types were counted after potassium permanganate fixation: type 1 - 71%, type 2 - 23%, and type 3 - 6%. In addition, at least two types of nerve profiles were observed which did not form synapses: (1) profiles entirely filled with mitochondria (mitochondrial accumulation), and (2) large nerve profiles full of different kinds of vesicles, myelin figures, and mitochondria (axonal dilatation). It is concluded that the sympathetic ganglion cells receive cholinergic and adrenergic innervation and also a third type of innervation, the possible peptidergic nature of which is discussed.