Enzyme histochemical changes in retinal ganglion cells and the optic nerve after goldfish optic nerve lesion. A regenerative and hypertrophic phenomena study

After sectioning of the goldfish optic nerve a number of enzyme histochemical changes are observed in the hypertrophied retinal ganglion cells and in the optic nerve. Between one and eighteen days postoperatively an increase in the amount of acid phosphatase reaction product is noted. The enhanced activity decreased to normal first in the optic nerve, followed by the optic tract and tectum. Four days postoperatively higher levels of activity were noted in the hypertrophic retinal ganglion cells for the enzymes NADH tetrazolium reductase, cytochrome oxidase, glutamate dehydrogenase and lactate dehydrogenase. The same enzymes also showed an activity increase in the lesioned optic nerve after four to ten days postoperatively, beginning at the cut and gradually spreading towards the optic tectum. Between fifteen and eighteen days the activity dropped to normal in the hypertrophic retinal ganglion cells, while in the lesioned nerve raised levels of reaction products could be seen till days thirty-five and/or forty-five. It was concluded that the degeneration of the optic pathway is marked by the increase of acid phosphatase activity, whereas the process of regeneration is characterized by an increase of NADH tetrazolium reductase, cytochrome oxidase, glutamate dehydrogenase and lactate dehydrogenase activities. The possible functional implications of these enzymes in the regenerative phenomena are discussed.     

A distinct effect of transient and sustained upregulation of cellular factor XIII in the goldfish retina and optic nerve on optic nerve regeneration

Unlike in mammals, fish retinal ganglion cells (RGCs) have a capacity to repair their axons even after optic nerve transection. In our previous study, we isolated a tissue type transglutaminase (TG) from axotomized goldfish retina. The levels of retinal TG (TG(R)) mRNA increased in RGCs 1-6weeks after nerve injury to promote optic nerve regeneration both in vitro and in vivo. In the present study, we screened other types of TG using specific FITC-labeled substrate peptides to elucidate the implications for optic nerve regeneration. This screening showed that the activity of only cellular coagulation factor XIII (cFXIII) was increased in goldfish optic nerves just after nerve injury. We therefore cloned a full-length cDNA clone of FXIII A subunit (FXIII-A) and studied temporal changes of FXIII-A expression in goldfish optic nerve and retina during regeneration. FXIII-A mRNA was initially detected at the crush site of the optic nerve 1h after injury; it was further observed in the optic nerve and achieved sustained long-term expression (1-40days after nerve injury). The cells producing FXIII-A were astrocytes/microglial cells in the optic nerve. By contrast, the expression of FXIII-A mRNA and protein was upregulated in RGCs for a shorter time (3-10days after nerve injury). Overexpression of FXIII-A in RGCs achieved by lipofection induced significant neurite outgrowth from unprimed retina, but not from primed retina with pretreatment of nerve injury. Addition of extracts of optic nerves with injury induced significant neurite outgrowth from primed retina, but not from unprimed retina without pretreatment of nerve injury. The transient increase of cFXIII in RGCs promotes neurite sprouting from injured RGCs, whereas the sustained increase of cFXIII in optic nerves facilitates neurite elongation from regrowing axons.     

Ganglion cell axon pathfinding in the retina and optic nerve

The eye is a highly specialized structure that gathers and converts light information into neuronal signals. These signals are relayed along axons of retinal ganglion cells (RGCs) to visual centers in the brain for processing. In this review, we discuss the pathfinding tasks RGC axons face during development and the molecular mechanisms known to be involved. The data at hand support the presence of multiple axon guidance mechanisms concentrically organized around the optic nerve head, each of which appears to involve both growth-promoting and growth-inhibitory guidance molecules. Together, these strategies ensure proper optic nerve formation and establish the anatomical pathway for faithful transmission of information between the retina and the brain.     

Radiation retinopathy: electron microscopy of retina and optic nerve.

A 4 1/2 year old female was treated for embryonal rhabdomyosarcoma of the left orbit in 1975 with radiation (59.5 Gy in 5 weeks), followed by chemotherapy. An electroretinogram (ERG) in March, 1988 revealed cone responses 3% of normal and no rod responses in the left eye, and normal responses in the right eye. The eye was enucleated in April 1988. In the fovea no choroidocapillaris was seen at the intact Bruch's membrane, and the pigment epithelium was preserved only in small patches. No photoreceptor cells were seen in the areas devoid of pigment epithelial cells. The parafoveal and peripheral (30 degrees eccentricity) retina was better preserved. The thickness of the layer of rods and cones and of Henle's fiber layer was reduced. Very few outer segments were present. Macrophages had invaded the retinal tissue in moderate numbers. The retinal vessels were ensheathed by several layers of collagen fibrils. The spatial densities of pigment epithelial, cone, rod, and bipolar cells had been reduced. The optic nerve contained a total number of 1,022,000 nerve fibers.     

Innervation of the rabbit cornea. A histochemical and electron-microscopic study

The innervation of the rabbit cornea was investigated histochemically and electron-microscopically with special reference to the autonomic nerves. Both formaldehyde- and glyoxylic-acid-induced fluorescence methods revealed adrenergic nerves in the stroma; a few fibres were also observed between the basal epithelial cells near the limbus. Acetylcholinesterase- (AChE-) positive nerves were found both in the stroma and in the epithelium, whereas nonspecific cholinesterase (NsChE) activity appeared only in the stromal nerves. Under the electron microscope, both AChE and NsChE activities were observed to be located in the axon membranes. A weak NsChE reaction also appeared in the Schwann cells. When the specimens fixed with KMnO4 were examined under the electron microscope, most nerve fibres did not contain any special axoplasmic structures, although several axons contained mitochondria. Moreover, two vesicle-containing axon types were found in the stromal nerves; axons with small granular vesicles and axons containing small agranular vesicles. In the epithelium, two types of fibres were observed; one type containing only mitochondria while the other showed both agranular vesicles and mitochondria.     

A histochemical study of catecholamines and cholinesterases in the autonomic nerves of the human minor salivary glands

Synopsis The cholinergic and adrenergic innervation of human minor sublingual buccal and labial salivary glands has been studied with histochemical techniques for localizing acetylcholinesterase and catecholamines. A rich cholinergic innervation was observed around the acini, blood vessels and some ducts of the three glands.The adrenrgic innervation, however, was virtually absent from the parenchyma although present around the blood vessels, in marked contrast to the dense parenchymal adrenergic innervation observed in the human parotid and submandibular glands. These results suggest that the autonomic nervous mechanism which regulates salivary secretion is more elaborate in the major than in the minor salivary glands.     

A histochemical study of lysosomal enzymes in the retina of the rat

Summary Sections of retinas from albino and pigmented rats were studied histochemically by the naphthol and lead methods for lysosomal enzymes (acid phosphatase, aryl sulfatase, glucosaminidase and -glucuronidase). Activity of the enzymes studied (except -glucuronidase) is demonstrable in granules which by their staining properties are identified as lysosomes. The matrix of the lysosome stains positively in PAS preparations and is diastaae resistant. The organelles are distributed mainly in the pigment epithelium, outer limiting membrane, inner nuclear layer, ganglion layer and inner limiting membrane of the retina.This investigation was supported by a generous grant from the Nuffield Foundation.     

Expression of glutamate transporters in human and rat retina and rat optic nerve

l-Glutamate is the major excitatory transmitter in the vertebrate retina and plays a central role in the transmission of the various retinal neurons. Glutamate is removed from the extracellular space by at least five different glutamate transporters. The cellular distribution of these has been studied so far mainly using immunocytochemistry. In the present study non-radioactive in situ hybridisation using complementary RNA probes was applied in order to identify the cell types of rat retina and optic nerve expressing generic GLT1, GLT1 variant (GLT1v or GLT1B), GLAST and EAAC1. The results were compared with immunocytochemical data achieved using affinity-purified antibodies against transporter peptides. In the immunohistochemical studies the human retina was included. The study showed that in the rat retina GLT1v and EAAC1 were coexpressed in various cell types, i.e. photoreceptor, bipolar, horizontal, amacrine, ganglion and Müller cells, whereas GLAST was only detected in Müller cells and astrocytes. In the rat optic nerve GLT1v and EAAC1 were preferentially expressed in oligodendrocytes, whereas GLAST was revealed to be present mainly in astrocytes. Generic GLT1 could not be detected in the retina or optic nerve. The cellular distribution of glutamate transporters (only immunocytochemistry) in the human retina was very similar to that of the rat retina. Remarkable results of our studies were that generic GLT1 was not detectable in the rat (and human) retina and that GLT1v and EAAC1 were demonstrable in most cell types of the retina (including photoreceptor cells and their terminals).