FINE STRUCTURE OF NUCLEOLI AND RNA-CONTAINING CHROMOSOME REGIONS OF SALIVARY GLAND CHROMOSOMES OF CHIRONOMIDS AND THEIR INTERRELATIONSHIP

1964 ◽  
Vol 42 (6) ◽  
pp. 1147-1155 ◽  
Author(s):  
V. I. Kalnins ◽  
H. F. Stich ◽  
S. A. Bencosme
Keyword(s):  
Fine Structure ◽  
Salivary Gland ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Messenger Rna ◽  
Balbiani Ring ◽  
Electron Microscopic ◽  
Chironomid Species ◽  
Balbiani Rings ◽  
Chromosome Regions

Electron microscope studies of salivary gland nuclei of four chironomid species have shown that the RNA-containing chromosome regions and associated structures, which by light microscopy exhibit a great variety of structures such as bands, granules, micronucleoli, nucleoli, puffs, and Balbiani rings, consist of only few basic units: pars amorpha, nucleolonema, and Balbiani ring granules. The fine structure of the nucleoli and spherical micronucleoli located at various chromosome regions appears to be identical, consisting of pars amorpha, which contains fibers of varying diameters, and strands of nucleolonema composed of fibers and ribosome-like granules. The arrangement of pars amorpha and nucleolonema of nucleoli and spherical micronucleoli follows a consistent pattern. Chromosome fibers are closely associated with pars amorpha, whereas strands of nucleolonema border only the surfaces of pars amorpha. Balbiani ring granules, which have a diameter of 300 Å to 500 Å and are characterized by a particular structure, accumulate in Balbiani rings, in many chromosome regions, and in nuclear sap. In the Balbiani ring these granules seem to be attached to 100 Å chromosome fibers. They are absent in nucleoli and micronucleoli. The possible correlation between our electron microscopic observations and the present-day concept of ribosomal and messenger RNA production is discussed.

The fine structure of the vertical lobe of Octopus brain

1970 ◽  
Vol 258 (827) ◽  
pp. 379-394 ◽  
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Synaptic Vesicles ◽  
Structural Organization ◽  
Amacrine Cells ◽  
Large Cell ◽  
Inhibitory Effect ◽  
Tactile System

Although much is known about the structural organization and connexions of the various lobes of the octopus brain from light microscopy, this is the first attempt at a detailed analysis of one of the lobes— the vertical lobe, with the electron microscope. The vertical lobe consists of five lobules. The median superior frontal (MSF) axons enter each lobule from the MSF lobe. The MSF axons contain both microtubules and neurofilaments. The varicosities of the MSF axons contain both agranular and dense-cored vesicles and synapse with trunks of the amacrine cells. These trunks run together in bundles termed amacrine tracts into the centres of the lobules. The amacrine trunks contain microtubules but no neurofilaments. The trunks contain large and small agranular synaptic vesicles and synapse with what are in all probability branches of the trunks of the large cells. These trunks contain microtubules but no neurofilaments. They run out through the bases of the lobules probably without forming synaptic contacts within the lobule. Fibres signalling ‘pain’ (nocifensor) enter the lobules from below. They can be recognized by their content of neurofilaments. Their terminals contain numerous very small synaptic vesicles and a few larger and dense-cored ones. These ‘pain’ fibres appear to synapse mostly with processes of the large cells. J. Z. Young has shown that the vertical lobe is especially concerned with the integrative action of the visual system, linked with the chemo-tactile system. Electron microscopy supports Young’s suggestion that the superior frontal and interconnected vertical lobe systems constitute a loop which could sustain a positive feed-back mechanism (MSF —> amacrine -> large cell -> lateral superior frontal -> MSF) while the ‘pain’ (nocifensor) input could exert a suppressor (inhibitory) effect on the loop by its action on the large cells.

scholarly journals The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Blood ◽  
1975 ◽  
Vol 45 (5) ◽  
pp. 709-724 ◽  
Author(s):  
L Pinteric ◽  
JF Manery ◽  
IH Chaudry ◽  
G Madapallimattam
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Microscopic Study ◽  
Electron Microscopic Study ◽  
Ethylenediaminetetraacetic Acid ◽  
Human Erythrocytes ◽  
Erythrocyte Membranes ◽  
Electron Microscopic ◽  
Osmotic Hemolysis ◽  
Ionic Calcium

Abstract Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1–5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.

Evolutionary implications of duplications and Balbiani rings in Drosophila. A study of Drosophila serrata

Genome ◽  
1990 ◽  
Vol 33 (4) ◽  
pp. 478-485 ◽  
Author(s):  
P. Mavragani-Tsipidou ◽  
N. Kyrpides ◽  
Z. G. Scouras
Keyword(s):  
Salivary Gland ◽  
Larval Development ◽  
Chromosomal Rearrangements ◽  
Balbiani Ring ◽  
Intercalary Heterochromatin ◽  
Developmental Profile ◽  
Balbiani Rings ◽  
Drosophila Serrata ◽  
Tandem Duplications

Drosophila serrata, a species of subgroup montium, exhibits in its salivary-gland chromosomes a high number of inverted tandem duplications and a well-formed Balbiani ring. A photographic map, the duplications, and the Balbiani ring of this species are presented. Also presented are the most prominent puffs during normal larval development and after ecdysone treatment, as well as intercalary heterochromatin regions of the above chromosomes. These data are discussed and compared with those of Drosophila auraria, another species of subgroup montium. All the inverted tandem duplications found in both species are homozygous and are not accompanied by other types of chromosomal rearrangements. These results argue in favor of the relatively old origin of these structures. The similarity of the structure and the developmental profile of the Balbiani ring 1 in both species may indicate a necessary role served by the Balbiani ring 1 and hence its selection during evolution.Key words: Drosophila, duplications, Balbiani ring, ecdysone, intercalary heterochromatin.

Observations on healing tissue: A combined light and electron microscopic investigation

1963 ◽  
Vol 246 (733) ◽  
pp. 305-325 ◽  
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Light Microscopy ◽  
Secretory Activity ◽  
Microscopic Investigation ◽  
Electron Microscopic Investigation ◽  
Foreign Body Giant Cell ◽  
Electron Microscopic ◽  
Adventitial Cells

1. The process of healing in the rabbit ear chamber has been investigated in detail by correlating light microscopy, mainly in vivo , and electron microscopy. 2. During healing new vessels are formed from existing vessels by a process of sprouting and anastomosis, with subsequent remodelling of the loops so formed. 3. The fundamental process in the formation of vessels by sprouting is the mitotic division of existing endothelium, during which it retains its characteristic properties. 4. Blood vessel sprouts are composed of strands of tightly apposed cells formed in continuity with the walls of existing vessels. The subsequent canalization of such strands takes place extra-cellularly by a series of events largely as described by Billroth (1856). 5. The endothelium of recently formed vessels has a fine structure which distinguishes it clearly from that of more mature vessels. Certain features of this structure are compatible with a secretory activity by the endothelium during the formation of new vessels. 6. Evidence was obtained that in the course of differentiation of recently formed vessels fibroblast-like cells are incorporated into vessel walls to become adventitial cells, and that adventitial cells may undergo conversion to vascular smooth muscle cells. 7. Lymphatic endothelium exhibits properties during regeneration that confirm the specificity of this form of endothelium. 8. Cells with the characteristic fine structure of fibroblasts were frequently found in mitosis. The fibroblasts in the regions of active fibrogenesis had a highly developed cisternal form of endoplasmic reticulum. Vesicles and corresponding caveolae identifiable in such fibroblasts may provide a communication between the endoplasmic reticulum and the sites of fibrogenesis at the external surfaces of the cells. 9. Cells sharing characteristic features of fine structure formed a series which grouped together the monocyte, macrophage and foreign body giant cell. 10. Highly fibrillary intracytoplasmic tracts were found in both fibroblasts and macrophages. These tracts were equated with the fibroglial fibres of light microscopy. 11. ‘ Clear spaces ’ in advance of the growing fringe of blood vessels were temporary structures lined by a pavement of mesothelium-like cells. 12. No evidence was found of the formation of primitive mesenchymal tissue during healing in the mammal.

scholarly journals Electron Microscopic Studies of Spermatozoa I. The Morphology of the Spermatozoon of the Common Domestic Fowl (Gallus Domesticus)

1949 ◽  
Vol 2 (3) ◽  
pp. 271 ◽  
Author(s):  
GW Grigg ◽  
AJ Hodge
Keyword(s):  
Electron Microscope ◽  
Light Microscopy ◽  
Domestic Fowl ◽  
Gallus Domesticus ◽  
Distilled Water ◽  
Electron Microscopic ◽  
Enzymic Digestion ◽  
Microscopic Studies ◽  
The Common

The morphology of the fowl spermatozoon, as revealed by use of the electron microscope and such techniques as partittl enzymic digestion and disruption with distilled water, is described in detail, and compared with that observable by light microscopy.

The fine structure and method of feeding of the tissue parasitizing stages ofHistomonas meleagridis

Parasitology ◽  
1969 ◽  
Vol 59 (1) ◽  
pp. 171-184 ◽  
Author(s):  
D. L. Lee ◽  
P. L. Long ◽  
B. J. Millard ◽  
J. Bradley
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Technical Assistance ◽  
Proteolytic Enzymes ◽  
Succinic Dehydrogenase ◽  
Host Cells ◽  
Vegetative Stage ◽  
Small Particles

The structure, method of feeding and relationship with the host cells of the tissue parasitizing stages ofHistomonas meleagridishave been studied by means of light microscopy, cytochemistry and electron microscopy. The invasive stage is amoeboid, lacks flagella but has what appears to be remnants of the flagella apparatus, and feeds by phagocytosis. The vegetative stage is a round quiescent form. It apparently feeds by secreting proteolytic enzymes, which carry out extra-corporeal digestion of the host's tissues, and then taking up small particles of disrupted host cells by means of pinocytosis and probably by diffusion. The vegetative stage also contains remnants of flagella apparatus. Neither the invasive stage nor the vegetative stage contains mitochondria and succinic dehydrogenase is absent. It is concluded that there is no resistant stage.The reaction of the host's tissues to the parasites has been briefly described.The authors are grateful to Dr C. C. D. Shute for permission to use the electron microscope, to Mrs B. Fisher and Mr M. Shirley for technical assistance and to Mr P. Rogers for assistance with the photography.

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Blood ◽  
1975 ◽  
Vol 45 (5) ◽  
pp. 709-724
Author(s):  
L Pinteric ◽  
JF Manery ◽  
IH Chaudry ◽  
G Madapallimattam
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Microscopic Study ◽  
Electron Microscopic Study ◽  
Ethylenediaminetetraacetic Acid ◽  
Human Erythrocytes ◽  
Erythrocyte Membranes ◽  
Electron Microscopic ◽  
Osmotic Hemolysis ◽  
Ionic Calcium

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1–5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.

scholarly journals AN ELECTRON MICROSCOPIC STUDY OF THE DEVELOPMENT OF SYNAPSES IN CULTURED FETAL MOUSE CEREBRUM CONTINUOUSLY EXPOSED TO XYLOCAINE

1971 ◽  
Vol 49 (2) ◽  
pp. 362-371 ◽  
Author(s):  
Pat G. Model ◽  
Murray B. Bornstein ◽  
Stanley M. Crain ◽  
George D. Pappas
Keyword(s):  
Cerebral Cortex ◽  
Fine Structure ◽  
Electron Microscope ◽  
Impulse Activity ◽  
Morphological Differentiation ◽  
Bioelectric Activity ◽  
Electron Microscopic ◽  
Fetal Mouse ◽  
Electrical Impulse ◽  
Mouse Cerebral Cortex

Explants of fetal mouse cerebral cortex, continuously exposed to the local anesthetic Xylocaine from the time of explantation to the time of fixation, were examined in the electron microscope to determine whether morphologically normal synapses and potentially functional interneuronal synaptic networks can form in the absence of electrical impulse activity. Morphological differentiation of complex synaptic networks proceeds normally, and the drug does not alter the fine structure of the formed synapses. These observations are consonant with the electrophysiological data which show that the potential for complex bioelectric activity can develop in the absence of its expression. The development and maturation of functional synaptic networks, then, is not contingent upon prior electrical impulse activity. These data support the concept that organized neuronal assemblies are formed in forward reference to their ultimate function.

An electron-microscope study of centrioles in differentiating motor neuroblasts

Development ◽  
1968 ◽  
Vol 20 (3) ◽  
pp. 343-354
Author(s):  
Katherine M. Lyser
Keyword(s):  
Nineteenth Century ◽  
Fine Structure ◽  
Electron Microscope ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Morphological Differentiation ◽  
Nerve Cells ◽  
Electron Microscopic ◽  
Mitotic Apparatus ◽  
Mature Neurons

Mature neurons with centrioles were first described at the end of the nineteenth century and have been observed in many animals (see Cajal, 1911; Ariëns Kappers, Huber & Crosby, 1936). As mitosis rarely, if ever, occurs after morphological differentiation of the neuroblast begins, the function of the centrioles in nerve cells posed a problem which has yet to be resolved. Held (1909) described centrosomes in differentiating neuroblasts as being associated with the ‘fibrillogenous zone’, which suggests a role for the centriole in the differentiation of neurofibrils. Recently, electron-microscopic observations have refocused attention on the possibility of morphological and functional association between the centrioles of nerve cells and the fibrillar elements, especially neurotubules, which appear to be similar in fine structure to microtubules of other types of cells and to spindle tubules of the mitotic apparatus.

scholarly journals RNA TRANSPORT FROM NUCLEUS TO CYTOPLASM IN CHIRONOMUS SALIVARY GLANDS

1966 ◽  
Vol 31 (1) ◽  
pp. 55-77 ◽  
Author(s):  
Barbara J. Stevens ◽  
Hewson Swift
Keyword(s):  
Nuclear Envelope ◽  
Messenger Rna ◽  
Rna Transport ◽  
Central Channel ◽  
Balbiani Ring ◽  
Apparent Effect ◽  
Nuclear Pores ◽  
Balbiani Rings ◽  
Rna Puffs ◽  
Chironomus Thummi

The fine structure and cytochemistry of the extremely large RNA puffs, or Balbiani rings, in salivary gland nuclei of midge, Chironomus thummi, larvae have been investigated. The Balbiani rings are composed of a diffuse mass of electron-opaque 400 to 500 A granules, short threads about 180 to 220 A in diameter and associated fine chromatin fibrils. These components appear to be organized into brushlike elements which form the ring. Electron microscope cytochemistry has shown that the granules and short threads contain RNA. After ribonuclease digestion, only 50 to 100 A chromatin fibrils were apparent in the Balbiani ring, and the granules were no longer demonstrable. Deoxyribonuclease digestion had no apparent effect on these structures. Observations indicate that the granules are formed from the short threads and released into the nucleoplasm in which they are evenly distributed. At the nuclear envelope, many granules have been observed partially or completely within the nuclear pores. These granules become elongated and are shown to penetrate the center of the pore in a rodlike form, about 200 A in diameter. The Balbiani ring granules are not normally visible within the cytoplasm adjacent to the nuclear envelope, but have been rarely found in this region. It is suggested that the granules represent the product of the Balbiani ring, possibly a messenger RNA bound to protein, and that they regularly pass into the cytoplasm through a narrow central channel in the pores of the nuclear envelope.

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