Clusters Of Ganglion Cells Research Articles

Concurrent ependymal and ganglionic differentiation in a subset of supratentorial neuroepithelial tumors with EWSR1-PLAGL1 rearrangement

Neuroepithelial tumors with fusion of PLAGL1 or amplification of PLAGL1/PLAGL2 have recently been described often with ependymoma-like or embryonal histology respectively. To further evaluate emerging entities with PLAG-family genetic alterations, the histologic, molecular, clinical, and imaging features are described for 8 clinical cases encountered at St. Jude (EWSR1-PLAGL1 fusion n = 6; PLAGL1 amplification n = 1; PLAGL2 amplification n = 1). A histologic feature observed on initial resection in a subset (4/6) of supratentorial neuroepithelial tumors with EWSR1-PLAGL1 rearrangement was the presence of concurrent ependymal and ganglionic differentiation. This ranged from prominent clusters of ganglion cells within ependymoma/subependymoma-like areas, to interspersed ganglion cells of low to moderate frequency among otherwise ependymal-like histology, or focal areas with a ganglion cell component. When present, the combination of ependymal-like and ganglionic features within a supratentorial neuroepithelial tumor may raise consideration for an EWSR1-PLAGL1 fusion, and prompt initiation of appropriate molecular testing such as RNA sequencing and methylation profiling. One of the EWSR1-PLAGL1 fusion cases showed subclonal INI1 loss in a region containing small clusters of rhabdoid/embryonal cells, and developed a prominent ganglion cell component on recurrence. As such, EWSR1-PLAGL1 neuroepithelial tumors are a tumor type in which acquired inactivation of SMARCB1 and development of AT/RT features may occur and lead to clinical progression. In contrast, the PLAGL2 and PLAGL1 amplified cases showed either embryonal histology or contained an embryonal component with a significant degree of desmin staining, which could also serve to raise consideration for a PLAG entity when present. Continued compilation of associated clinical data and histopathologic findings will be critical for understanding emerging entities with PLAG-family genetic alterations.

Choroidal Ganglioneuroma: An Unexpected Diagnosis

Abstract Introduction/Objective Ganglioneuromas are rare, fully differentiated, benign neuronal tumors arising from neural crest cells anywhere along the sympathetic nervous system. However, they can undergo dedifferentiation and give rise to malignant neuroblastoma and ganglioneuroblastoma. Choroidal ganglioneuroma is exceptionally rare and usually an unexpected histopathological diagnosis. We report a pediatric patient with neurofibromatosis type 1, who underwent evisceration of a painful blind eye with subsequent histopathological examination confirming a diagnosis of choroidal ganglioneuroma. Methods/Case Report A 15-year-old boy with a medical history of neurofibromatosis type 1, plexiform neurofibroma of the right face and right orbit, right optic pathway glioma, and right painful blind eye secondary to congenital glaucoma underwent evisceration of the right eye with placement of orbital implant. On histopathological examination a choroidal lesion was identified adjacent to the pigmented retinal epithelium. This lesion showed proliferation of spindle-shaped cells admixed with clusters of ganglion cells. There were no signs of atypia, necrosis, or pleomorphism. The ganglion cells showed abundant cytoplasm with large vesicular nucleus and prominent nucleoli. The spindle cells were positive for S-100 immunostain and the ganglion cells were positive for synaptophysin. These findings were diagnostic of choroidal ganglioneuroma. Results (if a Case Study enter NA) NA Conclusion Choroidal ganglioneuroma, in addition to being a clinically unsuspected diagnosis, is exceptionally rare in patients with neurofibromatosis type 1. Medical literature on choroidal ganglioneuroma is sparse, however, it is reported that these benign tumors can locally recur with malignant transformation, and therefore close follow-up is advised.

Ovarian Teratomas in Women With Anti-N-methyl-D-Aspartate Receptor Encephalitis: Topography and Composition of Immune Cell and Neuroglial Populations Is Compatible With an Autoimmune Mechanism of Disease.

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune syndrome in young women that is often accompanied by an ovarian teratoma (NMDAR-E teratoma). A prevailing theory implicates that the generation of autoantibodies to NMDAR on neurons in the central nervous system is triggered by neuroglial tissue in the associated teratoma. The histopathology of NMDAR-E teratomas has not been fully elucidated but limited studies have focused on alterations in neuroglial tissues and immune cell populations. We hypothesized that evidence of antibody generation in NMDAR-E teratomas could be detected by colocalized neuroglial tissue and lymphoid aggregates with germinal centers as well as by alterations in the composition and morphology of neuroglial tissues. The study compared 12 NMDAR-E teratomas (11 ovarian, 1 mediastinal) with 61 control teratomas containing neuroglial tissue from women without NMDAR-E. NMDAR-E teratomas were significantly smaller and were composed of a higher percentage of neuroglial tissue than control teratomas. Many NMDAR-E teratomas did not exhibit typical gross pathologic features of a mature cystic teratoma, but were composed of predominately solid tissue (so-called Rokitansky nodule). Colocalized neuroglial tissue and lymphoid aggregates with germinal centers were present in 11/12 NMDAR-E teratomas, predominantly within the Rokitansky nodule, but only in 4/61 control teratomas (P<0.0001). There was a relative paucity of mature neurons in NMDAR-E teratomas as well as a hypercellular astrocyte population, while there were less prominent or no differences in the presence or composition of diffuse inflammatory infiltrates, lymphoid aggregates without germinal centers, ganglion cell clusters or oligodendrocytes between NMDAR-E teratomas and control teratomas. We conclude that the presence of colocalized neuroglial tissue and lymphoid aggregates with germinal centers along with a general paucity of neurons should prompt clinical consideration for NMDAR-E even in asymptomatic women, as the symptoms may occasionally develop after an otherwise incidental oophorectomy. Tissue sampling should be directed to the Rokitansky nodule, when present, to identify neuroglial tissues; complete microscopic examination of the ovarian specimen should be considered if gross pathologic features of teratoma are not present. The significance of the altered neuroglial cell populations and potential relationship to the pathogenesis of NMDAR-E merit further study.

Duodenal Gangliocytic Paraganglioma: A Rare Neuroendocrine Tumor

Gangliocytic paragangliomas, predominantly found in the second part of duodenum, are rare, usually benign tumors with occasional lymph node metastasis. Clinical presentation varies from incidental finding upon endoscopy, or abdominal pain and upper gastrointestinal bleeding. A 73-year old woman with past medical history of non-Hodgkin's lymphoma, presented with intermittent post-prandial epigastric pain, radiating to right upper quadrant, without any weight loss or melena. Physical examination was unremarkable. Laboratory analysis was normal. Cross-sectional imaging of abdomen revealed a possible duodenal diverticulum. Esophagogastroduodenoscopy revealed 17mm, sessile polyp in second part of duodenum. Endoscopic ultrasound (EUS) showed a hypoechoic mass, measuring 17mm x 13mm, extending from mucosa to submucosa and having well-defined margins. EUS-guided fine needle aspiration (FNA) cytology was consistent with a neuroendocrine tumor with immunohistochemical stains positive for synaptophysin, chromogranin and CD56 antibodies. A decision was made to proceed with endoscopic mucosal resection (EMR) which revealed a hypoechoic intramural lesion, appearing to originate from submucosa, overlaid by focal ulcerating flattened duodenal mucosa. The pathology was remarkable for variable admixture of bundles of spindle cells, clusters of ganglion cells and epithelial cells. Immunohistochemical stains showed positive S100 protein in the spindle cells; the epithelioid cells were positive for synaptophysin and CD56 consistent with neuroendocrine differentiation; and the ganglion cells positive for calretinin. Gangliocytic paragangliomas, first reported by Dahl et al. in 1957, is a peculiar neuroendocrine tumor thought to be derived from neural crest with 88% reported lesions located in the second part of duodenum. These tumors are benign and consist of variable admixture of spindle cells, epithelioid cells, and ganglion cells. Rare malignant cases have been reported with regional lymph node metastasis. The epithelioid component was found to be present in the patients with lymph node metastasis; the causal relationship of which is unclear. Due to the submucosal location of the tumor, diagnosis is difficult on endoscopic biopsy which emphasizes the role of EMR in the diagnosis. As most of these tumors are benign and non-functional, EMR is therefore the treatment of choice especially in cases in which the tumor may be removed in its entirety with negative margins.Figure: A 17mm x 13mm, hypoechoic intramural lesion, appearing to originate from submucosa.Figure: Duodenal mass showing variable admixture of ganglion cells, spindle cells, and epithelioid cells (arrow shows ganglion cell). H&E X 100.Figure: Well-controlled immunostain with antibody to synaptophysin shows strong positivity for epithelioid cells. Synaptophysin X 100.

Appendicular Biopsy in Total Colonic Aganglionosis: A Histologically Challenging and Inadvisable Practice.

Background The reliability of intraoperative evaluation of ganglion cells in the appendix as a guide to a diagnosis of total colonic aganglionosis is unclear. Objective To evaluate the diagnostic utility of appendicular innervation in colonic Hirschsprung disease (HD) and TCA. Methods Prospective, systematic study of ganglion cells and the neural plexii in appendices from cases (HD and TCA) and age matched controls with frozen and paraffin sections, rapid acetylcholinesterase (AChE) and immunohistochemistry. Results A total of 48 appendices (28 controls, 20 cases; 19 frozen) were evaluated. Of these 48, 30 were neonates. Ganglion cell clusters were smaller in controls (28) and HD (6) than those in the rectum, distorted at places and mimicked lymphocytes and endothelial cells, especially in neonates. Complete study of 13 appendices in TCA showed absence of ganglion cells, hypertrophic nerves, AChE activity, and calretinin staining. In 2/13 TCA, an erroneous frozen section identification of ganglia was later corrected based on AChE histochemistry and a panel of IHC stains. Ileal biopsies guided the placement of a ganglionic ileostomy in all. One case each of skip segment aganglionosis in a TCA and variable hypoganglionosis in long segment colonic HD is reported. Conclusion Intraoperative characterization of appendicular innervation as a guide to the diagnosis of TCA is unreliable, in part because of the possibility of skip segment disease/variable hypoganglionosis. We propose terminal ileal biopsies for diagnosis and leveling of aganglionosis. AChE on frozen/calretinin on paraffin tissue is the best approach to avoid diagnostic errors.

Rapid and coordinated processing of global motion images by local clusters of retinal ganglion cells.

Even when the body is stationary, the whole retinal image is always in motion by fixational eye movements and saccades that move the eye between fixation points. Accumulating evidence indicates that the brain is equipped with specific mechanisms for compensating for the global motion induced by these eye movements. However, it is not yet fully understood how the retina processes global motion images during eye movements. Here we show that global motion images evoke novel coordinated firing in retinal ganglion cells (GCs). We simultaneously recorded the firing of GCs in the goldfish isolated retina using a multi-electrode array, and classified each GC based on the temporal profile of its receptive field (RF). A moving target that accompanied the global motion (simulating a saccade following a period of fixational eye movements) modulated the RF properties and evoked synchronized and correlated firing among local clusters of the specific GCs. Our findings provide a novel concept for retinal information processing during eye movements.

Acromegaly associated with mixed pituitary adenoma-gangliocytoma and rathke's cleft cyst

Gangliocytoma of the pituitary gland is a rare lesion that often occurs in combination with pituitary adenomas and the exact origin is the subject of discussion. We report a rare case of an intrasellar mass of combined gangliocytoma/ pituitary adenoma coexistent with Rathke's cleft cyst. A 50-year-old female was admitted to our hospital with headache, mild acromegaly, and bitemporal hemianopsia. Histologically the tumor was composed of triphasic component of pituitary adenoma, clusters of ganglion cells and small cysts embedded in a variably dense neuropil substrate. Immunohistochemical analysis revealed the ganglion cells and adenoma cells were positive for synaptophysin and neurofilament. The lining of Rathke's cleft cyst was immunoreactive for cytokeratin 8. The exact pathogenesis of combined sellar pathology is not clear yet. However, a common stem/progenitor cell origin of both the adenomatous and neuronal component of these lesions has been suggested.

Fine Spatial Information Represented in a Population of Retinal Ganglion Cells

Detailed measurement of ganglion cell receptive fields often reveals significant deviations from a smooth, Gaussian profile. We studied the effect of these irregularities on the representation of fine spatial information in the retina. We recorded from nearby clusters of ganglion cells, testing their ability to determine the location of small flashed spots, and we compared the results to the prediction of a Gaussian receptive field model derived from reverse correlation. Despite considerable receptive field overlap, almost all ganglion cell pairs signaled nearly independently. For groups of five cells with highly overlapping receptive fields, the measured light-evoked currents encoded ∼33% more information than predicted by the Gaussian receptive field model. Including measured local irregularities in the receptive field model increased performance to the level observed experimentally. These results suggest that instead of being an unavoidable defect, irregularities may be a positive design feature of population neural codes.

BMP signaling regulates murine enteric nervous system precursor migration, neurite fasciculation, and patterning via altered Ncam1 polysialic acid addition

The enteric nervous system (ENS) forms from migrating neural crest-derived precursors that differentiate into neurons and glia, aggregate into ganglion cell clusters, and extend neuronal processes to form a complex interacting network that controls many aspects of intestinal function. Bone morphogenetic proteins (BMPs) have diverse roles in development and influence the differentiation, proliferation, and survival of ENS precursors. We hypothesized that BMP signaling might also be important for the ENS precursor migration, ganglion cell aggregation, and neurite fasciculation necessary to form the enteric nervous system. We now demonstrate that BMP signaling restricts murine ENS precursors to the outer bowel wall during migration. In addition, blocking BMP signaling causes faster colonization of the murine colon, reduces ganglion cell aggregation, and reduces neurite fasciculation. BMP signaling also influences patterns of neurite extension within the developing bowel wall. These effects on ENS precursor migration and neurite fasciculation appear to be mediated at least in part by increased polysialic acid addition to neural cell adhesion molecule (Ncam1) in response to BMP. Removing PSA enzymatically reverses the BMP effects on ENS precursor migration and neurite fasciculation. These studies demonstrate several novel roles for BMP signaling and highlight new functions for sialyltransferases in the developing ENS.

Operating Behind Denonvilliers' Fascia for Reliable Preservation of Urogenital Autonomic Nerves in Total Mesorectal Excision: A Histologic Study Using Cadaveric Specimens, Including a Surgical Experiment Using Fresh Cadaveric Models

Little is known about which urogenital nerves are liable to be injured along surgical planes in front of or behind Denonvilliers' fascia. Using semiserial histology for five fixed male pelves, we demonstrated that: 1) left/right communicating branches of bilateral pelvic plexuses run immediately in front of Denonvilliers' fascia; and 2) a lateral continuation of Denonvilliers' fascia separates the urogenital neurovascular bundle from the mesorectum. Notably, the mesorectum contains no or few extramural ganglion cells. At the level of the seminal vesicles, incision in front of Denonvilliers' fascia seems likely to injure superior parts of the pelvic plexus and the left/right communication. Moreover, at the prostate level, this incision misleads the surgical plane into the neurovascular bundle. Fresh cadaveric dissections of five unfixed male pelves confirmed that the surgical plane in front of Denonvilliers' fascia continues to a fascial space for the pelvic plexus containing ganglion cell clusters lateral and/or inferior to the seminal vesicles. To preserve all autonomic nerves for urogenital function, optimal total mesorectal excision for rectal cancer requires dissection behind Denonvilliers' fascia.

Ganglion cell containing pituitary adenomas: signs of neuronal differentiation in adenoma cells

Ganglion cell containing pituitary adenomas are rare. They represent tumors originating in the sella turcica which are composed of adenomatous and neuronal components. Recently accumulated information suggests a common origin for their neuronal and pituitary constituents. The objective of this study was to report the clinical and morphologic findings of pituitary gangliocytomas and study their immunoprofile using neuronal markers. Seven cases of pituitary gangliocytomas retrieved from 1,322 sellar lesions were studied. All tumors were removed from patients with mild acromegaly. Histologically they were biphasic composed of pituitary adenoma and clusters of ganglion cells embedded in a variably dense neuropil substrate. All adenomas belonged to the category of sparsely granulated somatotroph adenoma and were positive for growth hormone, whereas in five tumors, a few adenoma cells were also positive for prolactin. Ganglion cells were immunoreactive for NSE, synaptophysin and neurofilament protein (NFP). NFP-reactive fibrils were observed in the neuropil substrate and varied in number among the cases. Interestingly, all tumors contained varying numbers of adenoma cells with NFP-positive, dot-like areas of cytoplasmic reactivity, mostly tiny paranuclear, a finding not previously reported in human pituitary gangliocytomas. The presence of NFP in pituitary adenomas indicates neuronal differentiation in adenoma cells, suggesting a common origin for neuronal and pituitary adenoma cell elements in gangliocytomas.

Morphological properties of mouse retinal ganglion cells

The mouse retina offers an increasingly valuable model for vision research given the possibilities for genetic manipulation. Here we assess how the structural properties of mouse retinal ganglion cells relate to the stratification pattern of the dendrites of these neurons within the inner plexiform layer. For this purpose, we used 14 morphological measures to classify mouse retinal ganglion cells parametrically into different clusters. Retinal ganglion cells were labeled in one of three ways: Lucifer Yellow injection, ‘DiOlistics’ or transgenic expression of yellow fluorescent protein. The resulting analysis of 182 cells revealed 10 clusters of monostratified cells, with dendrites confined to either On or Off sublaminae of the inner plexiform layer, and four clusters of bistratified cells, dendrites spanning the On and Off sublaminae. We also sought to establish how these parametrically identified retinal ganglion cell clusters relate to cell types identified previously on the basis of immunocytochemical staining and the expression of yellow fluorescent protein. Cells labeled with an antibody against melanopsin were found to be located within a single cluster, while those labeled with the SMI-32 antibody were in four different clusters. Yellow fluorescent protein expressing cells were distributed within 13 of the 14 clusters identified here, which demonstrates that yellow fluorescent protein expression is a useful method for labeling virtually the entire population of mouse retinal ganglion cells. Collectively, these findings provide a valuable baseline for future studies dealing with the effects of genetic mutations on the morphological development of these neurons.

Phospholipase C isozymes are differentially distributed in the rat adrenal medulla

Immunohistochemistry has been used to examine the distribution of selected phospholipase C (PLC) isozymes within the adrenal medulla of the rat. PLCβ isozymes were expressed at moderate levels in the chromaffin cells but more strongly in association with ganglion cell clusters. PLCβ2 and PLCβ3 staining of clusters did not overlap suggesting selective PLC isozyme expression in two distinct ganglionic types. The distribution of PLCβ4 immunoreactivity was very similar to PLCβ3 with the strongest staining observed in the same cell clusters. Antibodies to PLCβ1 labelled multiple bands on Western blots and were not therefore used for immunohistochemistry. The chromaffin cells were also immunoreactive for PLCγ1, although the strongest staining with this antibody was seen in cells surrounding large sinus vessels. PLCδ1 and PLCδ2 had quite distinct distributions, with the former selectively localized to an endothelial cell population surrounding the chromaffin cells. This observation was supported by experiments on isolated bovine adrenal medullary cells where PLCδ1 expression was lost when the cell preparation was enriched for chromaffin cells. Antibodies to PLCδ2 labelled a network of nerve fibres throughout the medulla and clusters of ganglion cells located primarily at the medullary-cortical boundary. PLCδ2 immunoreactivity was also present in nerve fibres within the adrenal capsule where it appeared to be co-localized with PLCβ4 staining.

Interindividual Variation in Distribution of Extramural Ganglion Cells in the Male Pelvis: A Semi-Quantitative and Immunohistochemical Study Concerning Nerve-Sparing Pelvic Surgery

Objective: We examined distribution and numbers of extramural ganglion cells in the male pelvis, classifying them as sympathetic or parasympathetic. Methods: Specimens were obtained from 14 formalin-fixed donated male cadavers. Semiserial sections were processed for histologic examination, and for immunohistochemistry using anti-tyrosine hydroxylase (TH) or anti-peptide histidine isoleucine (PHI). Results: Like those along the sacral sympathetic trunk, most other pelvic ganglion cells were located in and along nerve components. Yet the ganglion cell clusters attached to pelvic viscera accounted for 22% to 38% of ganglion cells. These were seen at the dorsal aspect of the bladder, the bladder/prostate junction, the dorsal aspect of the seminal vesicle, and along the prostate, but not along the extrapelvic pudendal nerve, cavernous tissues including the penile hilum, the rhabdosphincter, retropubic fat or recto-urethral muscle. Two fold interindividual variation was seen for total ganglion cell number (3044 to 6522) in the pelvis. TH-positive and PHI-positive cells intermingled at various ratio in every ganglion cell cluster. Sympathetic TH-positive proportions tended to be site-specific. Conclusions: Pelvic autonomic cells exist not only in nerve components but also along viscera. Even nerve-sparing radical prostatectomy can compromise visceral ganglia. Simple classification of pelvic nerve components as sympathetic or parasympathetic would seem misleading given coexistence of both cell types in a ganglion.

Differential expression of the noradrenaline transporter in adrenergic chromaffin cells, ganglion cells and nerve fibres of the rat adrenal medulla

Expression of the noradrenaline transporter (NAT) was identified in various cell and fibre populations of the rat adrenal medulla, examined with immunohistochemistry and confocal microscopy. Immunoreactivity for the catecholamine biosynthetic enzymes tyrosine hydroxylase (TH), aromatic- l-amino-acid decarboxylase (AADC) and dopamine β-hydroxylase (DBH) was present in all chromaffin cells, while phenylethanolamine N-methyltransferase (PNMT) was used to determine adrenergic chromaffin cell groups. Labelling with NAT antibody was predominantly cytoplasmic and colocalised with PNMT immunoreactivity. Noradrenergic chromaffin cells were not NAT immunoreactive. Additionally, NAT antibody labelling demonstrated clusters of ganglion cells (presumably Type I) and nerve fibres. Expression of TH, AADC, DBH, PNMT and NAT mRNA was examined using reverse transcription-polymerase chain reaction (RT-PCR) from adrenal medulla punches and single chromaffin cells, and results were consistent with those obtained with immunocytochemistry. Chromaffin cells and fibres labelled with antibodies against growth associated protein-43 (GAP-43) were not NAT immunoreactive, while ganglion cells were doubled labelled with the two antibodies. The presence of NAT in adrenergic chromaffin cells, and its absence from noradrenergic cells, suggests that the adrenergic cell type is primarily responsible for uptake of catecholamines in the adrenal medulla.

Spindle Cell Sarcoma of the Kidney with Ganglionic Elements (Malignant Ectomesenchymoma) Associated with Chromosomal Abnormalities and a Review of the Literature

Malignant ectomesenchymomas are tumors that exhibit both mesenchymal and neuroectodermal elements (1). We report a case thought to represent a malignant ectomesenchymoma arising in the kidney with cytogenetic abnormalities that may provide insight into the biologic basis for this unusual tumor. We discuss the clinical features, histopathologic findings, cytogenetics, treatment, and outcome of a child with a malignant ectomesenchymoma arising in the kidney. An asymptomatic 16-month-old boy had a large abdominal mass. The resected tumor contained sheets of spindled cells that expressed mesenchymal markers and cartilaginous differentiation, interspersed with clusters of ganglion cells that expressed neural markers. No blastemal or epithelial elements were demonstrated. Cytogenetic analysis of the tumor revealed a hyperdiploid count with multiple numerical and structural abnormalities, including a translocation between chromosomes 12 and 15. In addition to the surgical resection, the patient was successfully treated with adjuvant chemotherapy and local radiation therapy. This is the first report of which we are aware of an ectomesenchymoma arising within the kidney. A subset of malignant ectomesenchymomas may be related to the Ewing's family of tumors (EFTs) (2), but this case did not exhibit cytogenetic features consistent with EFT. Thus, the malignant ectomesenchymoma phenotype probably represents a heterogeneous group of tumors with different genotypes and origins. Cytogenetic analysis may be instrumental in determining the appropriate therapeutic approach when faced with such a neoplasm. The outcomes of 12 other children with ectomesenchymoma are reviewed.

Positional Determination of the Naso-Temporal Retinal Axis Coincides with Asymmetric Expression of Proteins along the Anterior–Posterior Axis of the Eye Primordium

We used two different methodologies to examine at what stage development retinal positional specificity is established and which molecules are responsible. The first goal was achieved by removing parts of the presumptive temporal primary optic vesicle at stage 11 (40 to 45 hr of incubation) and fate mapping of tissue with presumptive nasal properties that shifted into the wound during the events of wound-healing. Participation of the shifted tissue in the healing resulted in assembly of a temporal retina with mosaic-like projection properties, as examined by retrograde double staining of the retinal ganglion cells from the optic tectum. In addition to cells with normal temporal–rostral projections, clusters of ganglion cells with nasal-like projection identities appeared labelled within the temporal hemiretina. The number of clusters increased with the amount of resected tissue, and by almost complete ablation of the presumptive temporal anlage, a temporal hemiretina with predominantly nasal retinotectal specificity was created. These neuroanatomical results suggested that neuroepithelial cells had fixed nasal and temporal positional specificities at stage 11. To examine differences in the cells derived of either half of the eye cup, we performed biochemical one-and two-dimensional gel electrophoresis of the hemianlagen at stage 11. In addition, incorporation of 35S-methionin into newly synthesized peptides was investigated. Both techniques revealed the exclusive expression of one major and three less-abundant proteins within the presumptive nasal anlage. The most abundant of these proteins has a molecular weight of about 40 kDa and is clearly distinguishable both in gel electrophoresis and autoradiography. The asymmetric protein patterns had disappeared when the retina was analysed with the same methods at the more advanced embryonic days E4 and E6. The asymmetry in the expression of proteins in the retinal primordium may be the biochemical correlate of an early positional specification of the retinal neuroepithelium. The difference in the protein expression may explain that mixing the positionally specified cells of either origins results in projection mosaics.

On the Microanatomy of the Supraoesophageal Ganglion of Some Amphinomids (Polychaeta Errantia), with Further Discussion of the Innervation and Homologues of the Polychaete Palps

AbstractEarlier papers dealing with the anatomy of the amphinomid brain were studied. Discrepancies in the studied works prompted a re‐investigation of the central nervous system of these animals. In this paper the brain commissures, the clusters of ganglion cells and the innervation of the antennae, the palps and the nuchal organs of Eurythoe complanata, Amphinome rostrata, Pherecardia striata, and Notopygos variabilis are described in some detail. The brain of Hermodice carunculata is studied more cursorily. The results, summarized in schematic diagrams, are compared with corresponding observations of the brains of ‘spiomorphic’ and ‘serpulimorphic’ polychaetes and to information given by earlier authors about structures in the Nereidiformia and Aphroditiformia. Using the major Remanian criteria for identifying homologies, equivalents in the amphinomid brain and the central nervous systems of some ‘sedentary’ and ‘errant’ families are proposed. As a consequence, some earlier opinions about the morphological value of the cephalic appendages of the amphinomids are strengthened while others are rejected. The necessity of further investigations of the polycheaete nervous system is emphasized.

The appearance of trigeminal ectopic ganglia within the surface ectoderm in the chick embryo.

Aberrant ganglion cell morphogenesis associated with the ophthalmic placode was observed within the epidermis of the chick embryo at stages 20 through 26. This process was studied using immunohistochemistry and scanning and transmission electron microscopy. Clusters of ganglion cells were covered by epidermis and seen as epidermal nodules distributed diffusely in the supraorbital region. The ganglion cell clusters found within these nodules were not delineated by basement membrane from the epidermis, and were provisionally termed ectopic ganglia. The cell bodies within the ganglia possessed neurites containing microtubules and neurofilament protein. The cell bodies were also immunoreactive to monoclonal antibodies, E/C8 and HNK-1, indicating neuronal phenotypes. The neurites were often associated with the ophthalmic nerve or its branches as well as being distributed in the ectoderm. The ectopic ganglia seemed to represent the delayed gangliogenesis of a part of the ophthalmic placode which failed to detach from the ectoderm during ophthalmic ganglion formation.

Early stages of spinal ganglion formation during tail regeneration in the newt, Notophthalmus viridescens.

Stages in the development of sensory ganglia in the regenerating newt tail after amputation are described by taking advantage of the rostrocaudal developmental gradient of the regenerating tail. A series of ganglia, beginning at the tip of the regenerate and progressing rostrally, were examined. Eight-week regenerates were used because they showed the most complete array of stages. The first recognizable ganglia appear as small clusters of cells sitting dorsally on the already established ventral roots. The cluster of ganglionic cells steadily expands with the addition of many new cells. Signs of cell differentiation within the ganglion precede the formation of the dorsal root rudiment, which assumes several different configurations but most commonly enters the cord close to the ventral root. Our material suggests that ganglion precursor cells originate in the ventral region of the developing spinal cord and migrate out of the cord by travelling along the ventral root until, at a suitable distance from the cord, they halt, proliferate, and eventually differentiate. In the regenerate, we saw no evidence of neural crest cells--such as those that give rise to ganglia in the trunk region during development--forming at the dorsal region of the regenerated neural tube. Nor was there any morphological evidence of mesenchymal contribution to the ganglion cell clusters.