A further study of the fine structure and membrane properties of neuroglia in the optic nerve of Necturus

The optic nerve of Necturus maculosus consists of a homogeneous population of astroglia and bundles of unmyelinated axons. The glial cell processes ramify within the nerve roughly delineating fascicles of axons and come together at the periphery to form a complete external limiting membrane interrupted only by narrow clefts between adjacent processes. They are frequently “attached” to one another, forming specialized junctions. Blood vessels are entirely outside the nerve which is surrounded by a basal lamina. The temperature dependence of the glial membrane potential is accurately predicted by the Nernst relation. The membrane potential is unaffected by changes in Cl, Na, Li, and guanidinium which are apparently impermeant. The permeability of the glial membrane to other cations is in the sequence Tl> K> Rb> Cs> NH₄. This suggests that the chemical nature of the site of potassium permeability in glial cells is similar to that in the neuron.     

A further study of the fine structure and membrane properties of neuroglia in the optic nerve of Necturus.

The optic nerve of Necturus maculosus consists of a homogeneous population of astroglia and bundles of unmyelinated axons. The glial cell processes ramify within the nerve roughly delineating fascicles of axons and come together at the periphery to form a complete external limiting membrane interrupted only by narrow clefts between adjacent processes. They are frequently "attached" to one another, forming specialized junctions. Blood vessels are entirely outside the nerve which is surrounded by a basal lamina. The temperature dependence of the glial membrane potential is accurately predicted by the Nernst relation. The membrane potential is unaffected by changes in Cl, Na, Li, and guanidinium which are apparently impermeant. The permeability of the glial membrane to other cations is in the sequence Tl greater than K greater than Rb greater than Cs greater than NH4. This suggests that the chemical nature of the site of potassium permeability in glial cells is similar to that in the neuron.     

The fine structure of the collar cells in the optic tentacles of Helix aspersa

Summary At the base of the optic tentacular ganglion there is a group of large monopolar cells containing numerous secretory inclusions. These are the collar cells. Secretory material can be seen accumulating in swollen portions of the granular endoplasmic reticulum. It is postulated that this material is transported to the Golgi bodies and thus the limiting membrane of the inclusions is derived from the Golgi membranes. The Golgi bodies appear to be polarized and small vesicles resembling secretory inclusions are associated with one face of these organelles. The secretory inclusions fuse together to form large membrane-bound secretory pools in the perikaryon. The collar-cell processes are packed with secretory inclusions. These processes traverse the digital extensions of the tentacular ganglion and pass into the epithelium covering the tip of the tentacle. The secretory inclusions do not resemble neurosecretory inclusions in other situations. The collar cell processes receive a nerve supply from single axons containing granular and agranular vesicles. The evidence that these cells may be modified neurons is only minimal.This work was supported by the Australian Research Grants Committee.     

Juvenile pilocytic astrocytoma of the optic nerve diagnosed by fine needle aspiration biopsy

Fine needle aspiration biopsy of an orbital mass was performed under CT guidance in a nine-year-old boy presenting with rapidly increasing proptosis of the right eye with lateral displacement and no light perception. The cytologic findings consisted of bipolar astrocytes with cytoplasmic fibrillated processes intermingled with Rosenthal fibers. A cytologic diagnosis of juvenile pilocytic astrocytoma was advanced; this was confirmed by subsequent histologic study of the surgical specimen. The differential diagnosis among juvenile pilocytic astrocytoma, neurilemmoma and meningioma of the optic nerve are discussed.     

The fine structure of nerve endings on rat thyroid follicular cells

Summary Axon profiles in thyroid glands obtained from adult male Wistar rats were studied electron-microscopically, using common and serial thin sections.Bouton profiles of nerve fibers, resembling the terminal or en passant type, often appeared closely associated with vascular smooth muscle cells via basement membranes. These structures are probably adrenergic, since they contained mainly small-core vesicles (mean diameter: 41.2 nm), in addition to a few large-core (mean diameter: 88.4 nm) and flattened vesicles.Nerve fibers containing microtubules and sometimes mitochondria and vesicles were seen lying between basement membranes and follicular cells. The incidence of nerve fiber contacts on profiles of follicular cells was 0.0177±0.0092 (S.D.). Using serial sections, follicles were seen to have up to two nerve endings, separated from the plasma membranes of the follicular cells by a gap of 22 nm. They contained mainly flattened vesicles and several large-core vesicles (mean diameter: 95.1 nm). Small-core vesicles were rarely seen in these nerve endings. Furthermore, subsurface cistern-like rough endoplasmic reticulum was found immediately under the plasma membranes of follicular cells facing membranes of nerve endings. These results suggest that the nerve fibers in contact with follicular cells are different from the adrenergic type.     

双斑蟋复眼和视叶的显微结构

【目的】为探索昆虫视觉信号处理的重要神经结构,详细观察和描述了直翅目(Orthoptera)蟋蟀科(Gryllidae)代表性昆虫双斑蟋Gryllus bimaculatus De Geer复眼和视叶的组织学结构特征。【方法】利用扫描电镜技术和组织学切片技术,观察分析了30只双斑蟋的复眼和视叶组织学结构。【结果】双斑蟋复眼约有3400个小眼,均为六边形结构,小眼间隙内分布有机械感受器——感觉毛和钟形感受器。每个小眼均由角膜、晶锥、感杆束、6个网膜细胞及基膜等构成。视叶呈两个扇形结构,由三大神经纤维网构成,分别为神经节层、外髓、内髓。【结论】双斑蟋复眼表面具有少量感觉毛和钟形感受器,每个小眼均由角膜、晶锥、感杆束、6个网膜细胞及基膜等构成,属并列像眼,视叶由三大神经纤维网构成。     

The fine structure of myelinated nerve cell bodies in the bulbus olfactorius of man

Summary In the bulbus olfactorius of man numerous myelinated nerve cell bodies occur in the stratum plexiforme internum and stratum granulosum internum. In many respects they resemble the neighbouring granule cells: small chromatin clumps border on more than half of the circumference of the nucleus, the thin cytoplasmic rim contains abundant polysomes and sometimes pigment complexes with numerous light vacuoles, the cells often show a process which extends up to the stratum glomerulosum, the perikarya are devoid of synaptic contacts whereas the proximal segment of the peripheral processes display rare contacts. The myelin sheath varies in thickness, consisting of 2 to 24 lamellae with distances between the major dense lines ranging from 9.3 to 11.3 nm. The myelin sheath may enclose the cell body completely or partially and accompany the proximal segment of the process arising from the perikaryon. On partially enveloped perikarya, the myelin lamellae end in formations like those of the node of Ranvier, though often less regularly. Within the compact myelin sheath all of its lamellae may be distended for a short distance by glial cytoplasm as in the Schmidt-Lanterman incisures of peripheral nerve fibres. Adjacent to the outermost myelin lamella myelinated axons and cell bodies, tentatively identified as oligodendrocytes, as well as granule cells may be closely joined.Supported by the Deutsche Forschungsgemeinschaft (Br. 634/1)     

Primary structure of limulus anticoagulant anti-lipopolysaccharide factor

A potent anticoagulant, anti-lipopolysaccharide (LPS) factor, found in limulus hemocytes inhibits the LPS-mediated activation of limulus coagulation cascade and shows an antibacterial action against R-types of Gram-negative bacteria (Morita, T., Ohtsubo, S., Nakamura, T., Tanaka, S., Iwanaga, S., Ohashi, K., and Niwa, M. (1985) J. Biochem. (Tokyo) 97, 1611-1620). The complete amino acid sequence of this substance was determined by sequencing the peptides obtained by selective proteolytic cleavage. The NH2-terminal end of anti-LPS factor was pyroglutamic acid. Anti-LPS factor had two variant residues at position 36 and the COOH-terminal end, respectively. The following sequence was assigned to anti-LPS factor, and it was also confirmed by fast atom bombardment mass spectrometry. less than EGGIWTQLALALVKNLATLWQSGDFQFLGHE (formula; see text) Limulus anti-LPS factor consisted of a single chain of 102 residues with 2 half-cystines in disulfide linkage. Its NH2-terminal region up to 20 residues was highly hydrophobic, and positively charged residues were clustered mainly within the disulfide loop. By searching the homologous sequence in known protein sequences with that of anti-LPS factor, we found a structural homology between anti-LPS factor and alpha-lactalbumin/lysozyme family.     

The fine structure of the nerve cord of Myxicola infundibulum (annelida,polychaeta)

Summary Ultrastructural observations of the giant axon of Myxicola infundibulum reveal that the axoplasm contains neurofilaments, a few neurotubules and mitochondria. Finger-like projections issuing from the glial cells of the sheath encircle the giant axon at various angles. The space between the axolemma and sheath is 125 Å. Branches of the giant axon are also surrounded by a glial sheath as they course through the neuropil. Some branches of the giant axon seem to fuse with certain neurons, creating a syncytial arrangement between the giant axon and these neurons.Many small nerve fibers course longitudinally in the neuropil of the nerve cord. Most of these axons are separated from each other by a space of 200 Å without intervening glial processes. Synapses in the neuropil have both clear 600 Å vesicles and larger dense core vesicles suggesting chemical transmission. Some, but not all, of the synaptic areas show thickened membranes and dense material in the synaptic cleft.This study was supported in part by PHS NS-07740 to R.L.P., J.A.B. is a NDEA Predoctoral Fellow in the Department of Physiology.     

The fine structure of daphnid supraesophageal and optic ganglia,and its possible functional significance

Neurosecretory activity and fine structure of the supraesophageal and optic ganglia of Daphnia schødleri Sars were studied. The relative amount of paraldehyde fuchsin stainable material present was determined at “daylight” and at one and three hours following for animals maintained under photoperiods of 7.5, 10.5, 13.5, and 16.5 hours. More material was found after one hour in both ganglia and there was a tendency for more in the optic ganglion under 7.5- and 10.5-hour photoperiods. Sections made at two levels in the supraesophageal ganglion and one level in the optic ganglion were examined with an electron microscope. Posterior and anterior parts of the supraesophageal ganglion contain apparent nerve processes at the edge of the ganglion, parallel to the anterior-posterior axis; these have large granules. Neurons in both areas contain patches of presumed polysaccharide granules. In the posterior region are a dorsolateral and a ventrolateral glandular cell, presumably these occur on both sides of the brain. They have very well-developed endoplasmic reticulum and some large granules. The dorsal cell is usually at the tip of a glial attenuation. Concentric lamellar systems are located in dilated nerve processes of the first optic ganglion neuropile. Large whorls (about 3.5 μ) are composed of concentric lamellae. When lamellae do not form complete rings, they end in loops or in dilated tubules that are sometimes constricted as vesicles. Small whorls (1.5 μ) typically have lamellae joined into two or three thick layers. Mitochondria are frequently associated with the whorls. It is proposed that the whorls are active in synthesis, possibly neurohumor production.     

The fine structure of the olfactory mucosa and nerve in the teleost Carassius carassius L.

Summary Morphological studies on teleost olfactory mucosa confirm the findings of previous authors regarding the general arrangement of conventional cell types, viz. receptor, sustentacular, mucous and basal, but teleosts show certain distinct differences. The receptor cells have the general mammalian bipolar shape but their peripheral dendrite does not project beyond the epithelial surface. In addition to numerous typical cilia, an exceptional ciliary formation was observed in which the filaments, instead of forming individual cilia, are grouped together in clusters and are enveloped in a single limiting membrane.At the junction between the finger-like process and the mucosal fold myelinated nerve fibres are observed within the subepithelial stroma.Within the postero-medial zone of the mucosa is a conspicuous well-differentiated new cell type. A thick rim of electron-dense cytoplasm, bounded by an outer trilaminar membrane, encloses prominent foliate (leaf-like) organelles, a basal nucleus, numerous mitochondria and vacuolar spaces. These foliaceous cells communicate with the external environment through a small stoma, their close association with epithelial components suggesting a possible secretory or absorptive function. Their intricate morphology, however, suggests that they may be receptors, but their role and neural connections still require definition.Supported by Grant 5 RO 5 TWOO 154-02 from the National Institutes of Health, United States Public Health Service.The authors are indebted to Dr. A. S. Wilson for his helpful criticism and gratefully acknowledge the photographic technical assistance of Mr. J. Simmons and Mr. S. Frank.     

The fine structure ofPhycomyces

Summary The cytological organization of the apices of sporangiophores and hyphae ofPhycomyces Blakesleeanus was studied by means of light- and electron microscopy. The sporangiophore apex in growth stage I contains a mass of cytoplasm in which is embedded a cluster of lipid globules. Within the plug several zones are differentiated by the grouping of organelles. These zones are not separated by membranes. The most apical zone is low in nuclei and vesicles but rich in mitochondria and dense bodies. Below this zone lies a compact group containing up to several hundred nuclei. Along the midline of the cell, below these nuclei, lies an ovoid region from which vesicles, nuclei and mitochondria are excluded. In this ovoid exclusion zone lies the cluster of lipid globules mentioned above. Lateral to the exclusion zone (i.e. in the peripheral region of the cell) the cytoplasm is rich in nuclei, mitochondria, dense bodies, and especially in developing autophagic vesicles. Of these vesicles, the most mature are found farthest from the cell apex. The region between the exclusion zone and the upper end of the cell's large central vacuole is occupied largely by mature, swollen autophagic vesicles. In addition to the zonal organization described above, microtubules are found to run along the cylindrical cell's axis at a distance from the cell wall, and extend to the extreme apex of the cell. Similar tubules occur in growing hyphae, together with dense bodies, and the hyphal apex contains non-autophagic vesicles that increase in size with distance from the hyphal tip. The hyphae lack the zonation shown by sporangiophore apices. Perinuclear masses of cisternae are described and related to the dictyosomes of higher plants. The findings are discussed in relation to the function of the apices in tip growth and sporulation.This work was supported in part by a National Science Foundation Graduate Fellowship to the author, and in part by grant No. GB 3241 from the National Science Foundation to ProfessorKenneth V.Thimann.