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.

scholarly journals THE FINE STRUCTURE OF Streptomyces coelicolor

1960 ◽  
Vol 8 (1) ◽  
pp. 267-278 ◽  
Author(s):  
David A. Hopwood ◽  
Audrey M. Glauert
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Light Microscope ◽  
Streptomyces Coelicolor ◽  
Nuclear Material ◽  
Average Density ◽  
Tubular Structures ◽  
Thin Sections ◽  
Nuclear Regions

Colonies and spore suspensions of Streptomyces coelicolor were fixed for electron microscopy by the method of Kellenberger, Ryter, and Séchaud (1958). In thin sections the nuclear regions have a lower average density than the cytoplasm and the outlines of these regions correspond well with the profiles of the chromatinic bodies observed with the light microscope. The nuclear regions contain fibrils, about 5 mµ in diameter. In contrast, after fixation by the method of Palade (1952) the nuclear material is coagulated into irregular dense masses and tubular structures about 20 mµ in diameter, lying in a nuclear "vacuole." The significance of these observations is discussed in relation to the observations of other workers on the fine structure of the nuclear material of other bacteria and the chromosomes of higher cells.

Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM

1978 ◽  
Vol 36 (2) ◽  
pp. 82-83 ◽  
Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Light Microscopy ◽  
Thin Sections ◽  
Transmission Electron ◽  
Identical Cell ◽  
Electron Microscopes ◽  
Scanning Electron

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).

Fine structure and possible functions of the hermaphrodite duct of some pulmonate snails (Mollusca: Gastropoda)

1990 ◽  
Vol 48 (3) ◽  
pp. 68-69
Author(s):  
Alan N. Hodgson
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Seminal Vesicle ◽  
Reproductive Biology ◽  
Light Microscope ◽  
Light Microscope Level ◽  
Transmission Electron ◽  
Standard Techniques

The hermaphrodite duct of pulmonate snails connects the ovotestis to the fertilization pouch. The duct is typically divided into three zones; aproximal duct which leaves the ovotestis, the middle duct (seminal vesicle) and the distal ovotestis duct. The seminal vesicle forms the major portion of the duct and is thought to store sperm prior to copulation. In addition the duct may also play a role in sperm maturation and degredation. Although the structure of the seminal vesicle has been described for a number of snails at the light microscope level there appear to be only two descriptions of the ultrastructure of this tissue. Clearly if the role of the hermaphrodite duct in the reproductive biology of pulmonatesis to be understood, knowledge of its fine structure is required.Hermaphrodite ducts, both containing and lacking sperm, of species of the terrestrial pulmonate genera Sphincterochila, Levantina, and Helix and the marine pulmonate genus Siphonaria were prepared for transmission electron microscopy by standard techniques.

scholarly journals STUDIES ON THE MODE OF ACTION OF EXCESS OF VITAMIN A

1963 ◽  
Vol 17 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Audrey M. Glauert ◽  
Mary R. Daniel ◽  
J. A. Lucy ◽  
J. T. Dingle
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Vitamin A ◽  
Phase Contrast ◽  
Phase Contrast Microscopy ◽  
Intact Cells ◽  
Thin Sections ◽  
Initial Effect ◽  
Contrast Microscopy ◽  
Site Of Action

Rabbit erythrocytes have been haemolysed by treatment with vitamin A alcohol and the sequence of changes in the fine structure of the cells during lysis has been investigated by phase contrast microscopy of intact cells and electron microscopy of thin sections. The initial effect of the vitamin, which occurs within 1 minute, is the production of cells of bizarre appearance which have a greatly increased surface area relative to untreated cells. Large indentations appear in the surfaces of the cells, and vacuoles are formed from the indentations by a process that resembles micropinocytosis. The cells then become spherical and loss of haemoglobin begins as breaks appear in the membranes of some cells; finally, ghosts are produced that are no longer spherical but still contain numerous vacuoles. These observations support the thesis that one site of action of vitamin A is at lipoprotein membranes.

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.

Replication factories and nuclear bodies: the ultrastructural characterization of replication sites during the cell cycle

1994 ◽  
Vol 107 (8) ◽  
pp. 2191-2202 ◽  
Author(s):  
P. Hozak ◽  
D.A. Jackson ◽  
P.R. Cook
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
S Phase ◽  
Nuclear Bodies ◽  
Nuclear Antigen ◽  
Thin Sections ◽  
Permeabilized Cells ◽  
Ultrastructural Characterization ◽  
Replication Sites ◽  
Proliferating Cell

Sites of replication in synchronized HeLa cells were visualized by light and electron microscopy; cells were permeabilized and incubated with biotin-16-dUTP, and incorporation sites were immunolabelled. Electron microscopy of thick resinless sections from which approximately 90% chromatin had been removed showed that most DNA synthesis occurs in specific dense structures (replication factories) attached to a diffuse nucleoskeleton. These factories appear at the end of G1-phase and quickly become active; as S-phase progresses, they increase in size and decrease in number like sites of incorporation seen by light microscopy. Electron microscopy of conventional thin sections proved that these factories are a subset of nuclear bodies; they changed in the same characteristic way and contained DNA polymerase alpha and proliferating cell nuclear antigen. As replication factories can be observed and labelled in non-permeabilized cells, they cannot be aggregation artifacts. Some replication occurs outside factories at discrete sites on the diffuse skeleton; it becomes significant by mid S-phase and later becomes concentrated beneath the lamina.

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.

The fine structure of Sphaerotilus nutans

1973 ◽  
Vol 19 (3) ◽  
pp. 309-313 ◽  
Author(s):  
Judith F. M. Hoeniger ◽  
H.-D. Tauschel ◽  
J. L. Stokes
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Lateral Position ◽  
Thin Sections ◽  
Liquid Cultures ◽  
Sphaerotilus Natans ◽  
Stationary Liquid ◽  
Basal Disk ◽  
Polar Organelle

Sphaerotilus natans developed sheathed filaments in stationary liquid cultures and motile swarm cells in shaken ones. Electron microscopy of negatively stained preparations and thin sections showed that the sheath consists of fibrils. When the filaments were grown in broth with glucose added, the sheath was much thicker and the cells were packed with granules of poly-β-hydroxybutyrate.Swarm cells possess a subpolar tuft of 10 to 30 flagella and a polar organelle which is usually inserted in a lateral position and believed to be ribbon-shaped. The polar organelle consists of an inner layer joined by spokes to an accentuated plasma membrane. The flagellar hook terminates in a basal disk, consisting of two rings, which is connected by a central rod to a second basal disk.

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.

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