Fine Structure of the Eye of a Nudibranch Mollusc, Hermissenda Crassicornis

1967 ◽  
Vol 2 (3) ◽  
pp. 349-358
Author(s):  
R. M. EAKIN ◽  
JANE A. WESTFALL ◽  
M. J. DENNIS
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Optic Nerve ◽  
Light And Electron Microscopy ◽  
The Other ◽  
Sensory Cells ◽  
Nerve Fibres ◽  
Supporting Cells ◽  
Small Bodies ◽  
Receptor Cells

The eye of a nudibranch, Hermissenda crassicornis, was studied by light and electron microscopy. Three kinds of cells were observed: large sensory cells, each bearing at one end an array of microvilli (rhabdomere) and at the other end an axon which leaves the eye by the optic nerve; large pigmented supporting cells; and small epithelial cells, mostly corneal. There are five sensory cells, and the same number of nerve fibres in the optic nerve. The receptor cells contain an abundance of small vesicles, 600-800 Å in diameter. The lens is a spheroidal mass of osmiophilic, finely granular material. A basal lamina and a capsule of connective tissue enclose the eye. In some animals the eye is ‘infected’ with very small bodies, 4-5 µ in diameter, thought to be symbionts.

scholarly journals The Olfactory Mucosa of the Sheep

1970 ◽  
Vol 23 (2) ◽  
pp. 447 ◽  
Author(s):  
Jean E Kratzing
Keyword(s):  
Electron Microscopy ◽  
Lamina Propria ◽  
Light And Electron Microscopy ◽  
Free Edge ◽  
Cell Types ◽  
Olfactory Nerve ◽  
Olfactory Mucosa ◽  
Basal Cells ◽  
Supporting Cells ◽  
Receptor Cells

The olfactory mucosa of the sheep was studied by light and electron microscopy. The epithelium conforms to the general vertebrate pattern and consists of olfactory receptor cells, supporting, and basal cells. The free edge of the epithelium is made up of long microvilli from the supporting cells and olfactory rods of the receptor cells, each carrying 40-50 cilia. All cell types contain large dark granules which may be the site of olfactory pigment. The basement membrane is not visible in light microscopy and is fine and discontinuous in electron microscopy. Bowman's glands are simple, tubular, mucus-secreting glands in the lamina propria. Their cells contain basal granules resembling those in the epithelial cells. The lamina propria also contains bundles of fine, unmyelinated, olfactory nerve fibres which are the proximal continuations of the receptor cells.

Fine structure of the pecten oculi of the mallard (Anas platyrhynchos)

1990 ◽  
Vol 68 (3) ◽  
pp. 427-432 ◽  
Author(s):  
Charlie R. Braekevelt
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Endothelial Cell ◽  
Optic Nerve ◽  
Blood Vessels ◽  
Anas Platyrhynchos ◽  
Light And Electron Microscopy ◽  
Mallard Duck ◽  
Pecten Oculi ◽  
Region Form

The pecten oculi of the mallard duck (Anas platyrhynchos) has been examined by light and electron microscopy. In this species, the pecten is of the pleated type and 12–14 accordion folds are joined apically by a heavily pigmented bridge of tissue which holds the pecten in a fanlike shape, widest at the base. It is situated over the optic nerve head and extends out into the vitreous. The entire pecten is enclosed by a fine basal lamina and hyalocytes are often present on its outer surface. Within each fold are numerous capillaries, larger blood vessels, and melanocytes. The capillaries are surrounded by thick fibrillar basal laminae which often contain pericytes. These capillaries display extensive microfolds on both the luminal and abluminal borders. The endothelial cell bodies are extremely thin, with most organelles present in a paranuclear location. The melanocytes, which are most plentiful in the bridge region, form an incomplete sheath around the capillaries and other blood vessels. The morphology of the pecten in the mallard is indicative of a heavy involvement in the transport of materials.

Development of the optic nerve in Xenopus laevis

Development ◽  
1982 ◽  
Vol 72 (1) ◽  
pp. 225-249
Author(s):  
Charles Cima ◽  
Philip Grant
Keyword(s):  
Electron Microscopy ◽  
Optic Nerve ◽  
Xenopus Laevis ◽  
Ganglion Cell ◽  
Light And Electron Microscopy ◽  
Near Neighbour ◽  
Dorsoventral Axis ◽  
Fibre Size ◽  
Autoradiographic Analysis ◽  
Young Old

Development of the Xenopus laevis optic nerve was studied by light and electron microscopy from embryonic stage 26, before the retina has formed, to juveniles, 8 months post-metamorphic. Low-power EM photographs of sections through the retinal optic nerve (RON), middle optic nerve (MON) and chiasmatic optic nerve (CON) were prepared at different stages and the areas containing large axons (0·5 μm) were traced in optic nerve reconstructions. Ordering of fibre size along a dorsoventral axis was noted in the embryonic nerve, and this pattern persisted throughout development. Most large fibres, myelinated and unmyelinated, occupy an eccentric dorsocentral position in the MON while small axons are seen in a ventral peripheral crescent. In the CON, the dorsal one third to one half is occupied by large fibres while the ventral CON contains small fibres exclusively. If, as assumed, large axons are older than small axons (0·1–0·3 μm), then patterns of large and small axons along the nerve might reveal a chronotopic fibre ordering. Chronotopic ordering was confirmed by autoradiographic analysis of the distribution of old, labelled fibres and young, unlabelled newly arriving fibres in optic nerves between stage 51 and 57. The young—old labelling pattern corresponds to the small and large axon patterns respectively, in all sections of the optic nerve. Chronotopic ordering of fibres in the developing optic nerve can be explained, in part, by the dorsoventral asymmetric marginal growth of the developing retina and the phenomenon of fibre following as ganglion cell axons join near neighbour fascicles in the retina, converge at the optic disc and grow through the optic nerve.

The Biology of Bothrimonus (=Diplocotyle) (Pseudophyllidea: Cestoda): Detailed Morphology and Fine Structure

1974 ◽  
Vol 31 (2) ◽  
pp. 147-153 ◽  
Author(s):  
M. D. B. Burt ◽  
I. M. Sandeman
Keyword(s):  
Electron Microscopy ◽  
Nervous System ◽  
Fine Structure ◽  
Functional Morphology ◽  
Light And Electron Microscopy ◽  
Nerve Fibers ◽  
Fish Host ◽  
Extensive System ◽  
And Function

Light and electron microscopy were used to describe the functional morphology of Bothrimonus sturionis in detail. In particular, the musculature, nervous system, osmoregulatory system, and tegument are dealt with, and the findings compared with those of other workers. The musculature of the scolex consists of several interrelated systems, the structure of each being discussed in relation to its function. Associated with the regular nervous system, considered typical of cestodes, is an extensive system of giant nerve fibers. The osmoregulatory system is unusual in that there are lateral "excretory" pores in many proglottides which open directly to the exterior of the worm. The microtriches of the tegument are long, like those of other primitive cestodes, and are covered by a noncellular sheath while the worm is in its gammarid host. The sheath is lost when the worm becomes established in its fish host; the nature and function of the sheath are discussed.

Probable mechanoreceptor structures of osphradia in marine Caenogastropoda

2020 ◽  
Vol 30 (1) ◽  
pp. 33-39
Author(s):  
N. N. Kamardin
Keyword(s):  
Electron Microscopy ◽  
Apical Surface ◽  
Supporting Cells ◽  
Receptor Cells ◽  
Single Receptor

TEM and SEM electron microscopy have been used to study osphradia in 6 species of marine Caenogastropoda. The ultrastructural features of mechanoreceptor cells that perform the Littorina osmoreception function in osphradium organs are presented. Mechanoreception is based on a possible change in the volume of cisterns of microvilli of supporting cells, which can be transmitted by the cilia of nearby mechanoreceptor cells. These cells obviously, have mechanosensory channels on the apical surface. It has been first discovered in predatory molluscs actively searching for food, that single receptor cells with a mobile sensilla consisting of several cilium were joined together. They are located along the groove zone and follow the direction and force of the movement of water along the osphradium petals.

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

Observations on the nephridial system of the cestode Moniezia expansa (Rud., 1805)

Parasitology ◽  
1969 ◽  
Vol 59 (2) ◽  
pp. 449-459 ◽  
Author(s):  
R. E. Howells
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Connective Tissue ◽  
Intercellular Space ◽  
Technical Assistance ◽  
Light And Electron Microscopy ◽  
Flame Cell ◽  
Research Scholarship ◽  
Research Facilities

The nephridial system of M. expansa has been studied using light and electron microscopy, and a number of histochemical techniques have been used on sections of the worm. The organization of the nephridial system and the fine structure of the flame cells and the nephridial ducts are described. Pores, which connect the nephridial lumen to the intercellular space of the connective tissue, exist at the junction of a flame cell and a nephridial duct. These pores may be considered nephrostomes and the system therefore is not protonephridial as defined by Hyman (1951).The epithelium lining the nephridial ducts has a structure which suggests that it is metabolically active. It is postulated that the beating of the cilia of the flame cells draws fluid into the ducts via the nephrostomes, with absorption and/or secretion of solutes being carried out by the epithelial cells of the duct walls. The function of the nephridial system is discussed.I am grateful to Professor James Brough for the provision of research facilities at the Department of Zoology, University College, Cardiff, andtoDrD. A. Erasmus for much helpful advice during the course of the work. I wish to thank Professors W. Peters and T. Wilson for critically reading the manuscript and Miss M. Williams and Mr T. Davies for expert technical assistance.I also wish to thank the Veterinary Inspector and his staff at the Roath Abattoir, Cardiff, for their kind co-operation and assistance in obtaining material.The work was carried out under the tenure of an S.R.C. research scholarship.

The fine structure of ampullary electric receptors in Amiurus

1964 ◽  
Vol 160 (980) ◽  
pp. 345-359 ◽  
Keyword(s):  
Fine Structure ◽  
Lateral Line ◽  
Cell Group ◽  
Sensory Cells ◽  
Receptor Cells ◽  
Pit Organ ◽  
Accessory Cells ◽  
Myelinated Nerves ◽  
Square Array ◽  
Small Nerve

The small pit-organs of Amiurus have been included in the group of ampullary lateral-line organs. On morphological and physiological grounds these ampullary organs are thought to be electric receptors and not mechano-receptors; thus they can be distinguished from all other types of acoustico-lateralis organs of vertebrates. Each small pit-organ consists of a duct leading from the surface of the skin to an ampulla, beneath which there is a group of cells lying at the base of the epidermis. There are two main types of cells in this group: the receptor and the accessory cells. The apical surfaces of the receptor cells bear microvillae but no cilia: these microvillae project into the lumen of the ampulla. Myelinated nerves supply the organs at the base ; they lose their myelin sheaths before entering the cell group where they branch and innervate the receptor cells. Small nerve terminals are closely applied to the surface of the receptor cells and in some places are thought to be in synaptic contact. Near these regions characteristic dense bodies are found in the base of the receptor cells. The bodies are surrounded by an accumulation of small vesicles of about 300 to 500 Å in diameter; they resemble structures found in corresponding situations in other types of sensory cells. Dense inclusions are found in some receptor cells: these inclusions have a highly ordered fine structure which in some sections appears as a square array of dense dots having a centre-to-centre spacing of about 75 Å. These observations are discussed in relation to the supposed activity of small pit-organs as electric receptors and to their position in the group of ampullary lateral-line organs.

scholarly journals The Fine Structure of the Wheat Scutellum During Germination

1972 ◽  
Vol 25 (3) ◽  
pp. 469 ◽  
Author(s):  
JG Swift ◽  
TP O'brien
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Epithelial Cells ◽  
Light And Electron Microscopy ◽  
Cell Types ◽  
Wall Material ◽  
Cytological Evidence ◽  
Starch Grains ◽  
Parenchyma Cells ◽  
Cytological Changes

The cytological changes that take place in the scutellar epithelium and parenchyma during the first 5 days of germination are described by light and electron microscopy. Within 6 hr small starch grains appear in the plastids of both cell types and the size and number of starch grains increase gradually as germination proceeds. Later in germination starch disappears again from the plastids in the epithelial cells, but large starch grains still remain in the parenchyma cells. The reserves of the protein bodies are hydrolysed and the residual vacuoles undergo extensive coales-cence. Modifications in the appearance of the wall material of the epithelial cells as these cells elongate are illustrated and possible functional bases for these changes are suggested. The cells of the scutellar epithelium show no cytological evidence for their known functions of diastase secretion and nutrient absorption.

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