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.

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.

Fine structure of the pecten oculi of the common loon (Gavia immer)

1986 ◽  
Vol 64 (10) ◽  
pp. 2181-2186 ◽  
Author(s):  
C. R. Braekevelt
Keyword(s):  
Electron Microscopy ◽  
Basal Lamina ◽  
Light And Electron Microscopy ◽  
Gavia Immer ◽  
Common Loon ◽  
Luminal Surface ◽  
Pecten Oculi ◽  
The Common ◽  
Diving Bird ◽  
Region Form

The pecten oculi of a diurnally active diving bird, the common loon (Gavia immer), was studied by light and electron microscopy. In this species the pecten consists of a pleated, highly vascular, pigmented structure that is situated over the optic nerve head and projects into the vitreous chamber. Fourteen to 15 accordion folds are joined apically by a heavily pigmented bridge of tissue, which holds the pecten in a fanlike shape, widest at the base. A distinct basal lamina encloses the entire pecten. Within each fold are numerous capillaries, melanocytes, and larger blood vessels that are often difficult to differentiate as either arterioles or venules. The capillaries are surrounded by basal laminae separated from the endothelial cells by several fibrillar layers. Pericytes are often enclosed within the basal lamina. These capillaries display numerous microfolds on their luminal surface, with a slightly reduced number of processes on the abluminal border. The endothelial cell body is extremely thin and most organelles are in the paranuclear region. The melanocytes, which are most numerous in the bridge region, form an incomplete sheath around these capillaries. As in other species, the morphology of the pecten in the loon indicates 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.

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.

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.

In situ studies on the cytochemistry and ultrastructure of a symbiotic marine dinoflagellate

1968 ◽  
Vol 48 (2) ◽  
pp. 349-366 ◽  
Author(s):  
D. L. Taylor
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Light And Electron Microscopy ◽  
Structural Morphology ◽  
Invertebrate Species ◽  
Algal Symbionts ◽  
Anemonia Sulcata ◽  
Mode Of Life ◽  
Structural Adaptations

The intertidal actinian Anemonia sulcata is known to harbour yellow-brown algal symbionts which are similar in appearance to the zooxanthellae of hermatypic, or reef-building, corals and a number of other invertebrate species. The cytochemistry and structural morphology of the zooxanthella has been studied by light and electron microscopy, to help define it taxonomically and to reveal something about its relations with the actinian. These investigations confirm that it is a dinoflagellate and have revealed several structural adaptations which are formed as a result of the peculiar mode of life adopted by this alga. Of significance is the fine structure of the periplast, which may have a considerable bearing upon the type of relationship which can exist between the host and its symbiont. These findings are discussed in terms of other known instances of algal-invertebrate symbiosis.

scholarly journals THE FINE STRUCTURE OF THE NUCLEOLUS DURING MITOSIS IN THE GRASSHOPPER NEUROBLAST CELL

1965 ◽  
Vol 24 (3) ◽  
pp. 349-368 ◽  
Author(s):  
Barbara J. Stevens
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Light Microscope ◽  
Light And Electron Microscopy ◽  
Peripheral Zone ◽  
Structural Components ◽  
Thin Sections ◽  
Nucleolar Material ◽  
Central Regions ◽  
Homogeneous Background

The behavior of the nucleolus during mitosis was studied by electron microscopy in neuroblast cells of the grasshopper embryo, Chortophaga viridifasciata. Living neuroblast cells were observed in the light microscope, and their mitotic stages were identified and recorded. The cells were fixed and embedded; alternate thick and thin sections were made for light and electron microscopy. The interphase nucleolus consists of two fine structural components arranged in separate zones. Concentrations of 150 A granules form a dense peripheral zone, while the central regions are composed of a homogeneous background substance. Observations show that nucleolar dissolution in prophase occurs in two steps with a preliminary loss of the background substance followed by a dispersal of the granules. Nucleolar material reappears at anaphase as small clumps or layers at the chromosome surfaces. These later form into definite bodies, which disappear as the nucleolus grows in telophase. Evidence suggests both a collecting and a synthesizing role for the nucleolus-associated chromatin. The final, mature nucleolar form is produced by a rearrangement of the fine structural components and an increase in their mass.

Gross anatomy and fine structure of the gut of the marine mysid shrimp Mysis stenolepis Smith

1986 ◽  
Vol 64 (2) ◽  
pp. 431-441 ◽  
Author(s):  
J. A. Friesen ◽  
K. H. Mann ◽  
J. H. M. Willison
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Digestive Tract ◽  
Fine Particles ◽  
Light And Electron Microscopy ◽  
Gross Anatomy ◽  
Lower Chamber ◽  
Pyloric Stomach ◽  
Mysid Shrimp ◽  
Upper Chamber

The structure of the digestive tract of Mysis stenolepis was studied by light and electron microscopy. The cardiac portion of the stomach is armed with dorsal, lateral, and ventral chitinous ridges. The pyloric stomach is divided by ridges and stiff hairs into an upper chamber through which most of the food passes and a lower chamber containing only fluid and fine particles. The hepatopancreas consists of five paired lobes that open into the junction of the stomach and midgut in such a way that only the fluid and fine particles from the ventral chamber of the stomach enter its tubules. Other material passes from the dorsal chamber to the midgut and is eventually voided. The fine structure of the hepatopancreas and other parts of the gut are described.

Electron microscopy of the glio-vascular organization of the brain of octopus

1969 ◽  
Vol 255 (797) ◽  
pp. 13-32 ◽  
Keyword(s):  
Electron Microscopy ◽  
Smooth Muscle ◽  
Blood Vessels ◽  
Light And Electron Microscopy ◽  
Muscle Cells ◽  
Medium Size ◽  
Muscle Fibres ◽  
Special Importance ◽  
Form Complex ◽  
Large Neurons

The glio-vascular organization of the octopus brain has been studied by light and electron microscopy. The structure of the walls of the blood vessels has been described. Two types of neuroglia can be recognized, the fibrous and protoplasmic glia; also enigmatic dark cells. Most blood vessels in the neuropil are surrounded by extracellular zones containing collagen. These zones give off glio-vascular tunnels (strands) that penetrate the neuropil in a complex network. The extracellular zones and tunnels contain in addition to collagen, smooth muscle cells and fibrocytes. Glial processes surround the extracellular zones and incompletely partition them from the neuropil. The small neuronal perikarya have no glial folds around them. The medium-size cells have thin glial sheets or finger processes related to their surfaces, which may indent the cells to form small trophospongia. The large neurons of the suboesophageal lobe have complex glial sheaths interspersed with extracellular channels. Both penetrate the neurons to form complex trophospongia. A new form of extracellular material has been observed in these extracellular channels. The occurrence of trophospongia in vertebrate and invertebrate neurons may be correlated with the absence of dendrites. Special problems discussed include the nature of the trophospongial function, the question of fluid-filled extracellular zones and their possible function as lymph channels, and the presence in some of them of haemocyanin molecules identical with those in the blood vessels. Perhaps of special importance is the observation that the lobes of the octopus brain are permeated with extracellular tunnels containing smooth muscle fibres, but it still needs to be determined whether or not the muscle cells in the tunnels of the neuropil actively contract and massage the neuropil to facilitate metabolic and other exchanges.

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