Mitotic cell division in the extraadrenal chromaffin system of various species

Mitotic activity often has been reported in embryonic and fetal sympathetic neuroblasts, principal sympathoblasts, and primitive sympathetic cells in various species at different stages of development. Postnatal adrenal medullary cells also are known to undergo mitosis, but such dividing capabilities rarely have been observed in the true postnatal extraadrenal chromaffin system. Although few in number, this work nevertheless has clearly identified such cells in varying stages of the mitotic cycle in the young dog, Syrian hamster, mouse, rabbit, and rat. The dividing cells were noted in paraaortic chromaffin organs, paraganglia, and within the inferior mesenteric ganglion as well. They displayed the morphological character usually associated with their adrenal medullary catecholaminergic counterparts, including numerous dense-cored vesicles known to be the harbingers of catecholamines and various peptides. Nerve endings were not noticed upon the mitotic cells. The phenomenon of dividing extraadrenal chromaffin cells augments existing data and perhaps suggests that these cells are more endocrine than neural in type and subservient to the adrenal medulla in its classic endocrine function.     

Distribution of neurotrophin and TrK receptor-like immunoreactivity in the adrenal gland of birds

The occurrence and localization of neurotrophins and their specific TrK receptor-like proteins in the adrenal gland of chicken, duck and ostrich were examined by immunohistochemical methods. In all species studied NGF-, TrK A- and TrK C-like immunoreactivity was observed in neurons and fibers of adrenal ganglia. Thin TrK A- and TrK C-like immunoreactive fibers were also observed among chromaffin cells. NT-3-like immunoreactivity was detected in chromaffin cells as revealed by the double immunolabelings NT-3/chromogranin A and NT-3/DbetaH. The interrenal tissue never showed IR to any neurotrophins and TrK tested, and none of the adrenal structures displayed immunoreactivity to BDNF and TrK B. Double immunolabelings NGF/TrK A, NGF/TrK C and TrK A/TrK C showed colocalization in some neurons and fibers in adrenal ganglia. In adrenal glands of the species studied, the distribution of neurotrophins and TrK receptors could suggest an involvement of NT-3 on neuronal populations innervating adrenal ganglia by means of its high affinity receptor TrK C and low affinity receptor TrK A. In addition, NGF could be utilized by neuronal populations of adrenal ganglia through its preferential receptor TrK A by an autocrine or paracrine modality of action.     

An electron-microscopic study of cholinesterase distribution in the rat adrenal medulla

The distribution of cholinesterase activity in the rat adrenal medulla was studied after initial fixation with glutaraldehyde, which preserves the osmiophilia of the noradrenaline-containing cells. Staining for true cholinesterase activity was associated with all the identifiable elements of the preganglionic sympathetic innervation. The morphology and enzyme staining of the endings on the chromaffin cells was similar to that seen in cholinergic synapses in the central nervous system. The endings contained occasional dense-cored vesicles and the possible significance of such vesicles at an undoubted cholinergic synapse is discussed. Staining for pseudocholinesterase activity, by contrast, was associated particularly with the Schwann cells and to a lesser extent with the chromaffin cells, but not with the axons and their processes.     

Adrenal chromaffin cells as transplants in animal models of parkinson's disease

The field of neural transplantation has moved rapidly forward in the last decade. Initially, fetal cells were used as implants to investigate their potential to ameliorate deficits in animal models of Parkinson's disease. However, because of the moral and legal problems associated with the use of fetal tissues in humans, alternative sources of donor tissue were sought which possessed the structural and functional characteristics needed to improve motor function in Parkinsonian patients. To date, one of the most promising tissues being investigated is the adrenal medulla, whose chromaffin cells possess an inherent plasticity of form and function. Transplanted chromaffin cells currently are being studied by a variety of approaches, including electron microscopy, in mouse, rat, and primate models of Parkinson's disease. An overview of the role of the chromaffin cell in this exciting and clinically important arena is briefly reviewed, with an emphasis on the fine structure of implanted chromaffin cells.     

Ultrastructural demonstration of exocytosis in the intact rat adrenal medulla

Evidence is presented for morphological proof of exocytosis in the rat adrenal medulla in situ. Techniques were modified to allow perfusion of the intact adrenal gland with secretagogues (or electrical stimulation) followed by tannic acid. Unstimulated specimens demonstrated exocytotic (omega-shaped) profiles filled with flocculent material. This flocculation was also seen in the intercellular space. Stimulation of the adrenal medulla also resulted in the appearance of exocytotic profiles and an accumulation of the flocculent mass. This was often most evident in the subendothelial space. This is the first demonstration of exocytosis in the rat adrenal medulla by electron microscopy. The techniques used in this study will be useful for studying the pathway of secretory products of the adrenal chromaffin cell before they enter the vascular system.     

Investigation of morphological and functional changes during neuronal differentiation of PC12 cells by combined hopping probe ion conductance microscopy and patch-clamp technique

PC12 cells derived from rat pheochromocytoma can differentiate into sympathetic-neuron-like cells in response to nerve growth factor (NGF). These cells have been proved to be a useful cell model to study neuronal differentiation. NGF induces rapid changes in membrane morphology, neurite outgrowth, and electrical excitability. However, the relationship between the 3D morphological changes of NGF-differentiated PC12 cells and their electrophysiological functions remains poorly understood.In this study, we combined a recently developed Hopping Probe Ion Conductance Microscopy (HPICM) with patch-clamp technique to investigate the high-resolution morphological changes and functional ion-channel development during the NGF-induced neuronal differentiation of PC12 cells. NGF enlarged TTX-sensitive sodium currents of PC12 cells, which associated with cell volume, membrane surface area, surface roughness of the membrane, and neurite outgrowth. These results demonstrate that the combination of HPICM and patch-clamp technique can provide detailed information of membrane microstructures and ion-channel functions during the differentiation of PC12 cells, and has the potential to become a powerful tool for neuronal research.     

S-100 proteins in the human peripheral nervous system

This article reviews the distribution of S100 proteins in the human peripheral nervous system. The expression of S100 by peripheral glial cells seems to be a distinctive fact of these cells, independently of their localization and their ability to myelinate or not. S100 proteins expressing cells include satellite cells of sensory, sympathetic and enteric ganglia, supporting cells of the adrenal medulla, myelinating and non-myelinating Schwann cells in the nerve trunks, and the Schwann-related cells of sensory corpuscles. In addition, S100 proteins are expressed in peripheral neurons. Most of them express S100alpha protein, and a subpopulation of sensory neurons in dorsal root ganglia contains S100beta protein or S100alpha plus S100beta proteins.     

Developmental potency of cultured pineal cells: an approach to pineal developmental biology

The pineal organ is still an enigma in regard to its developmental and phylogenetic origin. Little is known of the mechanism involved in determination and differentiation of pineal cells and virtually no studies have been done on the induction and tissue interactions during pinealogenesis. Interest is also centered on the evolutional transformation in structure and function, which may be related to the developmental alterations in pineal morphogenesis between the lower and higher vertebrate species. For developmental studies, avian embryos have great advantages for various experimental manipulations, such as cell and organ culture, surgical operation, and in situ transfection of developmental genes. The present review describes our cell culture studies, which have been done on developing rat and quail pineal organs, in order to elucidate the developmental potency of pineal cells and the regulatory mechanism involved in the phenotypic expression of cell properties. A number of phenotypes including numerous neuron-specific substances are shown immunohistochemically to be expressed only under culture conditions, and not observed in the mature pineal organ. As development proceeds, some of the potencies for cell differentiation are lost; hence, in the mature pineal organs most neuronal phenotypes are not expressed. Numerous factors were discovered which affect phenotypic expression of cultured pineal cells in a cell-type-specific manner. These findings, together with immunohistochemical observations on developing pineal organs, reveal that the developing pineal organ is a unique and useful model system for developmental neurobiology and that cell culture techniques offer a powerful tool for the understanding of development and cell differentiation of this particular organ.     

Neurotrophins and their receptors in the primary olfactory neuraxis

The primary olfactory pathway is an elegant and simple system in which to study neurogenesis and neuronal plasticity because of the simple fact that olfactory receptor neurons (ORNs) are continually generated throughout the adult lifetimes of vertebrates. Thus, neuronal birth, differentiation, survival, axon pathfinding, target recognition, synapse formation, and cell death are developmental events that can be examined in the mature olfactory epithelium (OE). Neurotrophins (nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3, and 4/5) are a family of bioactive peptides that exert their effects by interacting with high- and low-affinity receptors on the surfaces of responsive cells, and have been implicated in several stages of neuronal development throughout the central and peripheral nervous system (CNS and PNS). There has been significant interest within the olfactory community as to how these multifunctional peptides might regulate the cycle of degeneration and regeneration of olfactory receptor neurons. The focus of this review is to highlight what is known about the actions of neurotrophins in the primary olfactory pathway, and to pinpoint future directions that will enable us to further understand their role in olfactory receptor neuron development and turnover.     

Role of nerve growth factor in the olfactory system

Olfactory neurons are unique in the mammalian nervous system because of their capacity to regenerate in adult animals. It has been shown that olfactory receptor cells located in the olfactory epithelium are replaced on a continuous basis and in response to injury throughout the life span of most species. NGF, which is one of the neurotrophic factors, is present in many areas of the central and peripheral nervous system. It has been shown that NGF in the olfactory bulb plays a role in the survival of cholinergic neurons in the horizontal limb of the diagonal band (HDB). Recent studies of NGF in the olfactory bulb suggest that it is involved in the development, maintenance, and regeneration of olfactory receptor cells. In this study, we review reports examining the relationship between NGF in the olfactory bulb and neuronal regeneration and development in the mammalian olfactory systems. Low- and high-affinity NGF receptor immunoreactivity is markedly expressed during regeneration and at different stages of development in the mouse olfactory system. This level of immunoreactivity is no longer present after completion of regeneration and at maturation. Other findings indicate that NGF injected into the olfactory bulb is transported retrogradely to the olfactory epithelium. It has also been shown that continuous anti-NGF antibody injection into the olfactory bulb causes degeneration and olfactory dysfunction. Administration of NGF directory into nasal cavity results in an increase in the expression of olfactory marker protein within the olfactory epithelium in axotomized rats. These findings suggested that the presence of NGF in the olfactory bulb plays an essential role in regeneration, maintenance, and development in the olfactory system of mammals.     

Immunocytochemical localization of neuropeptides in the adrenal medulla

The distribution of neuropeptides exhibits pronounced interspecies heterogeneity. Neuropeptides may function as hormones secreted from chromaffin cells or as neurotransmitters/neuromodulators released from nerve terminals. However, other possible functions such as trophic or intracellular effects should also be considered. Thus, to understand the role of neuropeptides, it is important to explore their localization in different species. The distribution of enkephalins, neurotensin, neuropeptide Y, calcitonin gene-related peptide, and galanin in the adrenal medulla of rat, cat, hamster, and mouse is presented in detail.     

SCO-spondin, a glycoprotein of the subcommissural organ/Reissner's fiber complex: evidence of a potent activity on neuronal development in primary cell cultures

In the cattle, SCO-spondin was shown to be a brain-secreted glycoprotein specifically expressed in the subcommissural organ (SCO), an ependymal differentiation located in the roof of the Sylvian aqueduct. Furthermore, SCO-spondin makes part of Reissner's fiber (RF), a structure present in the central canal of the spinal cord. Sequencing of overlaping cDNA inserts after successive screening of a cattle SCO cDNA expression library allowed characterization of the complete sequence of this novel protein. Conserved domains were identified including twenty-six thrombospondin type 1 repeats (TSRs), nine low-density lipoprotein receptor LDLr type A domains (LDLRA), two epidermal growth factor EGF-like domains, and homologies to mucins and the von Willebrand factor were found in the amino- and carboxy- termini. In addition, SCO-spondin shows a unique arrangement "in mosaic" of these domains. The putative function of SCO-spondin in neuronal differentiation is discussed regarding these features and homologies with other developmental molecules of the central nervous system exhibiting TSR domains, and involved in axonal guidance.To correlate molecular and functional features of SCO-spondin, we tested the effect of oligopeptides whose sequences include highly conserved regions of the TSRs, LDLRA repeats, and a potent site of attachment to glycosaminoglycan, on cortical and spinal cord neurons in primary cell cultures. Peptides corresponding to SCO-spondin TSRs markedly increased adhesivity and neuritic outgrowth of cortical neurons and induced disaggregation of spinal cord neurons. Thus, SCO-spondin is a candidate to interfere with neuronal development and/or axonal guidance during ontogenesis of the central nervous system in modulating side-to-side and side-to-substratum interactions, and in promoting neuritic outgrowth. RF proper has a wide range of activity on neuronal differentiation, including survival, aggregation, and disaggregation effects and neurite extension of cortical and spinal cord neurones "in vitro." Thus, the SCO/RF complex may interact with developmental processes of the central nervous system including the posterior commissure and spinal cord differentiation.     

Stem cells in the development and differentiation of the human adrenal glands

There are no studies on stem cells (SCs) and development and differentiation (DD) of the human adrenal glands. The SCs in DD of the adrenal glands were herein investigated histochemically and immunohistochemically in 18 human embryonic adrenal glands at gestational week (GW) 7–40. At 7 GW, the adrenal glands were present, and at 7 GW, numerous embryonic SCs (ESCs) are seen to create the adrenal cortex. The ESCs were composed exclusively of small cells with hyperchromatic nuclei without nucleoli. The ESCs were positive for neural cell adhesion molecule, KIT, neuron‐specific enolase, platelet‐derived growth factor receptor‐α, synaptophysin, and MET. They were negative for other SC antigens, including chromogranin, ErbB2, and bcl‐2. They were also negative for lineage antigens, including cytokeratin (CK)7, CK8, CK18, and CK19, carcinoembryonic antigen, carbohydrate antigen 19‐9, epithelial membrane antigen, HepPar1, mucin core apoprotein (MUC)1, MUC2, MUC5AC, and MUC6, and cluster differentiation (CD)3, CD45, CD20, CD34, and CD31. The Ki‐67 labeling index (LI) was high (Ki‐67 LI = around 20%). α‐Fetoprotein was positive in the ESCs and adrenal cells. The ESC was first seen in the periphery of the adrenal cortex at 7–10 GW. The ESC migrates into the inner part of the adrenal cortex. Huge islands of ESC were present near the adrenal, and they appeared to provide the ESC of the adrenal. At 16 GW, adrenal medulla appeared, and the adrenal ESCs were present in the periphery or the cortex, in the cortical parenchyma, corticomedullary junctions, and in the medulla. The adrenal essential architecture was established around 20 GW; however, there were still ESCs. At term, there are a few ESCs. These data suggest that the adrenal glands were created by ESCs. Microsc. Res. Tech., 78:59–64, 2015. © 2014 Wiley Periodicals, Inc.     

Neurotrophins and development of the rod pathway: an elementary deduction

The rodent retina is a particularly attractive model for the study of neuronal developmental processes since considerable neurogenesis, cellular migration, phenotypic differentiation of retinal cell types and synaptogenesis occurs postnatally. In addition, the retina is readily accessible to surgical intervention, pharmacological manipulation, and local suppression of gene expression-tools that can be utilized to study mechanisms underlying the development of retinal neurons and their interconnections that form distinct functional circuits. Here, I review our studies describing the ontogeny of a specific retinal interneuron, the AII amacrine cell, an integral element in the rod (scotopic) pathway. Specifically, we used a number of approaches to examine the potential role of neurotrophic factors on the morphological and neurochemical differentiation of the AII.     

Cytochrome b558 (p22phox) in the guinea-pig adrenal medulla.

Paraganglionic cells are sensitive to hypoxia, and the involvement of a plasmalemmal cytochrome b558-like protein in oxygen sensing by these cells has been suggested, but neither the identity of the immunoreactive protein detected by immunohistochemistry nor its anticipated subcellular (i.e., plasmalemmal) localization were directly proven. Thus, we extended these studies to the largest paraganglion, i.e., the adrenal medulla, in the guinea-pig, which, due to its size and accessibility, allowed us to address both of these issues utilizing antisera raised against synthetic peptides of the small (22 kD) subunit of cytochrome b558, p22phox. Cytochrome b558 was originally identified in granulocytes and macrophages, and antisera against this phagocyte p22phox were utilized. Immunoreactivity to p22phox was observed in all adrenal medullary endocrine cells, and the identity of the immunoreactive protein to the small cytochrome b558-subunit was confirmed by Western blotting. Immuno-electron microscopy of ultrathin cryosections and of resin-embedded tissue demonstrated its subcellular localization in the dense core vesicles of endocrine A-cells but not in the plasma membrane. In conclusion, the present study documents the presence of the small subunit of cytochrome b558 in guinea-pig adrenal medullary cells, but its subcellular vesicular localization does not support the initial interpretation of cytochrome b558 serving as a plasmalemmal oxygen sensor.     

Role of adrenocorticotropic hormone in the development and maintenance of the adrenal cortical vasculature

The adrenal cortex is a highly vascularized endocrine tissue. A dense network of blood capillaries centripetally irrigates the adrenal gland, allowing every endocrine cell to be in contact with an endothelial cell. The pituitary hormone ACTH controls the coordinated development of the vasculature and the endocrine tissue mass. This suggests that paracrine secretions between steroidogenic adrenocytes and capillary endothelial cells participate in the control of adrenocortical homeostasis. Besides its effect on the vascular tone of arteries, ACTH induces the expression of the angiogenic cytokine VEGF-A (vascular endothelial growth factor-A) in primary cultures of adrenocortical cells. This growth factor is a specific mitogen for endothelial cells and is likely to mediate the hormonal control of adrenocortical vascularization through a paracrine mechanism. The newly discovered angiogenic factor EG-VEGF (endocrine-gland-derived vascular endothelial growth factor), the expression of which is restricted to endocrine glands and which is preferentially mitogenic for endocrine tissue-derived endothelial cells, is another candidate mediator of great potential interest.     

Development and neuronal dependence of cutaneous sensory nerve formations: Lessons from neurotrophins

Null mutations of genes from the NGF family of NTs and their receptors (NTRs) lead to loss/reduction of specific neurons in sensory ganglia; conversely, cutaneous overexpression of NTs results in skin hyperinnervation and increase or no changes in the number of sensory neurons innervating the skin. These neuronal changes are paralleled with loss of specific types of sensory nerve formations in the skin. Therefore, mice carrying mutations in NT or NTR genes represent an ideal model to identify the neuronal dependence of each type of cutaneous sensory nerve ending from a concrete subtype of sensory neuron, since the development, maintenance, and structural integrity of sensory nerve formations depend upon sensory neurons. Results obtained from these mouse strains suggest that TrkA positive neurons are connected to intraepithelial nerve fibers and other sensory nerve formations depending from C and Aδ nerve fibers; the neurons expressing TrkB and responding to BDNF and NT‐4 innervate Meissner corpuscles, a subpopulation of Merkell cells, some mechanoreceptors of the piloneural complex, and the Ruffini's corpuscles; finally, a subpopulation of neurons, which are responsive to NT‐3, support postnatal survival of some intraepithelial nerve fibers and Merkel cells in addition to the muscle mechanoreceptors. On the other hand, changes in NTs and NTRs affect the structure of non‐nervous structures of the skin and are at the basis of several cutaneous pathologies. This review is an update about the role of NTs and NTRs in the maintenance of normal cutaneous innervation and maintenance of skin integrity. Microsc. Res. Tech. 2010. © 2009 Wiley‐Liss, Inc.     

Innervation of the gastric mucosa

A plethora of neuronal messengers ("classical" transmitters, gaseous messengers, amino acid transmitters, and neuropeptides) are capable of mediating or modulating gastric functions. Accordingly, the stomach is richly innervated. Gastric nerves are either intrinsic to the gastric wall, i.e., they have their cell bodies in the intramural ganglia and thus belong to the enteric nervous system, or they reach the stomach from outside, originating in the brainstem, in sympathetic ganglia, or in sensory ganglia. Topographically, the nerve fibers in the stomach reach all layers from the most superficial portions of the gastric glands to the outer smooth muscle layer. This wide distribution implies that virtually all different cell types may be reached by neuronal messengers. Within the gastric mucosa endocrine and paracrine cells (e.g., gastrin cells, ECL cells, somatostatin cells), exocrine cells (parietal cells, chief cells, mucous cells), smooth muscle cells, and stromal cells are regulated by neuronal messengers. The sensory innervation, responding to capsaicin, plays an important role in mucosal protection, and in ulcer healing. Presumably also other nerves are involved and a plasticity in the neuropeptide expression has been demonstrated at the margin of gastric ulcers. Taken together, available data indicate a complex interplay between hormones, paracrine messengers and neuronal messengers, growth factors and cytokines in the regulation of gastric mucosal activities such as secretion, local blood flow, growth, and restitution after damage.     

Tachykinins and tachykinin receptors in bone

Adrenomedullin (AM) was originally characterized in extracts of an adrenal medullary tumor. Since this original finding the peptide and its mRNA have also been found in the adrenal cortex, specifically, in the cells of the aldosterone-secreting zona glomerulosa. It is clear that the synthesis of AM is actively regulated in both cortex and medulla. Much research effort has been focused on identifying a role for AM in the adrenal gland. To date, no consistent effect on medullary catecholamine biosynthesis has been demonstrated. In the cortex the actions of AM are controversial and appear to depend on both the tissue preparation used and on the specific receptor population expressed in the individual gland. The results of further studies on the long-term actions of AM on adrenal growth and differentiation are awaited with interest.