scholarly journals THE FINE STRUCTURE OF THE ELECTRIC ORGAN OF TORPEDO MARMORATA

1965 ◽  
Vol 24 (1) ◽  
pp. 129-141 ◽  
Author(s):  
Michael N. Sheridan
Keyword(s):  
Fine Structure ◽  
Connective Tissue ◽  
Basement Membrane ◽  
Intercellular Space ◽  
Electric Organ ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Nerve Fibers ◽  
Nerve Endings ◽  
Torpedo Marmorata

The fine structure of the electric organ of the fish Torpedo marmorata has been examined after osmium tetroxide or potassium permanganate fixation, acetone dehydration, and Araldite embedment. This organ consists of stacks of electroplaques which possess a dorsal noninnervated and a ventral richly innervated surface. Both surfaces are covered with a thin basement membrane. A tubular membranous network whose lumen is continuous with the extracellular space occupies the dorsal third of the electroplaque. Nerve endings, separated from the ventral surface of the electroplaque by a thin basement membrane, contain synaptic vesicles (diameter 300 to 1200 A), mitochondria, and electron-opaque granules (diameter 300 A). Projections from the nerve endings occupy the lumina of the finger-like invaginations of the ventral surface. The cytoplasm of the electroplaques contains the usual organelles. A "cellular cuff" surrounds most of the nerve fibers in the intercellular space, and is separated from the nerve fibre and its Schwann cell by a space containing connective tissue fibrils. The connective tissue fibrils and fibroblasts in the intercellular space are primarily associated with the dorsal surface of the electroplaque.

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 Biosynthesis of acetyl-coenzyme A in the electric organ of Torpedo marmorata in relation to acetylcholine metabolism

1977 ◽  
Vol 166 (3) ◽  
pp. 447-453 ◽  
Author(s):  
M F Diebler ◽  
Y Morot-Gaudry
Keyword(s):  
Choline Acetyltransferase ◽  
Gel Filtration ◽  
Electric Organ ◽  
Nerve Endings ◽  
Tissue Extract ◽  
Torpedo Marmorata ◽  
Forward Reaction ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Acetylcholine Metabolism

Formation of acetyl-CoA through acetyl-CoA synthetase (forward reaction) and through choline acyltransferase (backward reaction) was investigated in tissue extract from the electric organ of Torpedo marmorata. When the tissue extract was submitted to gel filtration on Sephadex G-25, the formation of acetyl-CoA by acetyl-CoA synthetase appeared fully dependent on ATP and CoA and partially dependent on acetate (an endogenous supply of acetate is discussed). Choline acetyltransferase was a potent source of acetyl-CoA, only requiring acetylcholine and CoA, and was much more efficient than acetyl-CoA synthetase for concentrations of acetylcholine likely to be present in nerve endings.

scholarly journals THE FINE STRUCTURE OF GIARDIA MURIS

1966 ◽  
Vol 29 (2) ◽  
pp. 317-332 ◽  
Author(s):  
Daniel S. Friend
Keyword(s):  
Fine Structure ◽  
Osmium Tetroxide ◽  
Smooth Endoplasmic Reticulum ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Cell Periphery ◽  
Adhesive Disc ◽  
Medial Surfaces ◽  
Dorsal Portion ◽  
Giardia Muris

Giardia is a noninvasive intestinal zooflagellate. This electron microscope study demonstrates the fine structure of the trophozoite of Giardia muris in the lumen of the duodenum of the mouse as it appears after combined glutaraldehyde and acrolein fixation and osmium tetroxide postfixation. Giardia muris is of teardrop shape, rounded anteriorly, with a convex dorsal surface and a concave ventral one. The anterior two-thirds of the ventral surface is modified to form an adhesive disc. The adhesive disc is divided into 2 lobes whose medial surfaces form the median groove. The marginal grooves are the spaces between the lateral crests of the adhesive disc and a protruding portion of the peripheral cytoplasm. The organism has 2 nuclei, 1 dorsal to each lobe of the adhesive disc. Between the anterior poles of the nuclei, basal bodies give rise to 8 paired flagella. The median body, unique to Giardia, is situated between the posterior poles of the nuclei. The cytoplasm contains 300-A granules that resemble particulate glycogen, 150- to 200-A granules that resemble ribosomes, and fusiform clefts. The dorsal portion of the cell periphery is occupied by a linear array of flattened vacuoles, some of which contain clusters of dense particles. The ventrolateral cytoplasm is composed of regularly packed coarse and fine filaments which extend as a striated flange around the adhesive disc. The adhesive disc is composed of a layer of microtubules which are joined to the cytoplasm by regularly spaced fibrous ribbons. The plasma membrane covers the ventral and lateral surfaces of the disc. The median body consists of an oval aggregate of curved microtubules. Microtubules extend ventrally from the median body to lie alongside the caudal flagella. The intracytoplasmic portions of the caudal, lateral, and anterior flagella course considerable distances, accompanied by hollow filaments adjacent to their outer doublets. The intracytoplasmic portions of the anterior flagella are accompanied also by finely granular rodlike bodies. No structures identifiable as mitochondria, smooth endoplasmic reticulum, the Golgi complex, lysosomes, or axostyles are recognized.

scholarly journals Attachment devices and the tarsal gland of the bug Coreus marginatus (Hemiptera: Coreidae)

Zoomorphology ◽  
2021 ◽  
Vol 140 (1) ◽  
pp. 85-102
Author(s):  
Manuela Rebora ◽  
Gianandrea Salerno ◽  
Silvana Piersanti ◽  
Elena V. Gorb ◽  
Stanislav N. Gorb
Keyword(s):  
Fine Structure ◽  
Dorsal Surface ◽  
Ventral Surface ◽  
Hydraulic Pressure ◽  
Capillary Suction ◽  
Gland Cells ◽  
Tarsal Gland ◽  
Fluid Production ◽  
Adhesive Fluid ◽  
Attachment Devices

AbstractThe present ultrastructural investigation using scanning and transmission electron microscopy as well as light and fluorescence microscopy describes in detail the attachment devices and tarsal gland of the bug Coreus marginatus (L.) (Hemiptera: Coreidae). In particular, the fine structure of pulvilli reveals a ventral surface rich with pore channels, consistent with fluid emission, and a folded dorsal surface, which could be useful to enhance the pulvillus contact area during attachment to the substrate. The detailed description of the tarsal gland cells, whose structure is coherent with an active secretory function, allows us to consider the tarsal gland as the plausible candidate for the adhesive fluid production. Scolopidia strictly adhering to the gland cells are also described. On the basis of the fine structure of the tarsal gland, we hypothesise a fluid emission mechanism based on changes of the hydraulic pressure inside the gland, due to the unguitractor tendon movements. This mechanism could provide the fluid release based on compression of the pad and capillary suction, as demonstrated in other insects. The data here reported can contribute to understanding of insect adhesive fluid production, emission and control of its transport.

scholarly journals On the Origin of the Electric Organ in Malapterurus Electricus

1956 ◽  
Vol s3-97 (39) ◽  
pp. 455-463
Author(s):  
ALF G. JOHNELS
Keyword(s):  
Connective Tissue ◽  
Anterior Part ◽  
Electric Organ ◽  
Shoulder Girdle ◽  
Ventral Surface ◽  
Spinal Root ◽  
Electric Organs ◽  
Electric Fishes ◽  
Rostral Portion ◽  
Dermal Connective Tissue

The present study was made on two small specimens of Malapterurus electricus, of standard lengths 11.4 and 12.7 mm. As is well known, the postembryonic growth of electric organs in Malapterurus and other electric fishes takes place by an enlargement of the electric units and not by an increase in the number of the electric plates. In the present material, however, there is a multiplication of electric tissue elements in the rostral portion of the electric organ. The structure of this multiplication zone is described. In the anterior region the connective tissue membranes which surround the two halves of the electric organ form structures similar to tendons which are fixed to the ventral surface of the shoulder girdle on each side of the median line. A small deficiency on each side in the muscular wall in the same region was observed in adult specimens by Maurer. This deficiency is more evident in the young specimens studied in the present paper and it is covered from the outside by the multiplication zone of the electric organ. In this place the electric nerve joins the electric organ. The giant electric cell, the surface of which is penetrated by intracellular capillaries, is situated in the anterior part of the spinal cord and its axon emerges with the third ventral spinal root. In the multiplication zone the connective tissue membranes are completely independent of the dermal connective tissue and the space between the electric organ and the skin is of a conventional subdermal type. These circumstances strongly indicate that the electric organ is of myoblastic origin in Malapterurus as in all other electric fishes known in this respect. Nothing has been observed which supports the idea of an adenoid origin of the electric organ in Malapterurus.

Sign in / Sign up

Export Citation Format

Share Document