The effect of hydroxyurea on DNA synthesis of Tipula iridescent virus and Estigmene acrea cells

1983 ◽  
Vol 29 (2) ◽  
pp. 254-260 ◽  
Author(s):  
Malgorzata Kloc ◽  
Peter E. Lee
Keyword(s):  
Electron Microscopy ◽  
Dna Synthesis ◽  
Light Microscope ◽  
Nuclear Dna ◽  
Stages Of Development ◽  
Iridescent Virus ◽  
Estigmene Acrea ◽  
Microscope Autoradiography

Viral-specific DNA synthesis of Tipula iridescent virus (TIV) was not affected in Estigmene acrea cells which were continuously exposed to 300 μg/mL hydroxyurea (HU) as detected by light microscope autoradiography. Electron microscopy of such cells showed viroplasmic centres with virions in various stages of development. In nor mal cells similarly exposed to HU, nuclear DNA synthesis was reduced by 70–80%.

scholarly journals CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

1964 ◽  
Vol 22 (3) ◽  
pp. 505-513 ◽  
Author(s):  
D. R. Wolstenholme ◽  
W. Plaut
Keyword(s):  
Electron Microscope ◽  
Dna Synthesis ◽  
Light Microscope ◽  
Tritiated Thymidine ◽  
Amoeba Proteus ◽  
Electron Microscope Autoradiography ◽  
Cytoplasmic Dna ◽  
Microscope Autoradiography ◽  
Normal Particle ◽  
Labeling Pattern

The application of electron microscope autoradiography to Amoeba proteus cells labeled with tritiated thymidine has permitted the identification of morphologically distinct particles in the cytoplasm as the sites of incorporated DNA precursor. The particles correspond to those previously described from light microscope studies, with respect to both H3Tdr incorporation and distribution in centrifugally stratified amoebae. Ingested bacteria differ from the particles, in morphology as well as in the absence of associated label. Attempts to introduce a normal particle labeling pattern by incubating amoebae with labeled sediment derived from used amoeba medium failed. The resultant conclusion, that the particles are maintained in the amoeba by self-duplication, is supported by the presence of particles in configurations suggestive of division.

Cytoplasmic DNA Synthesis at Meiotic Prophase in Lilium henryi

1979 ◽  
Vol 27 (3) ◽  
pp. 273 ◽  
Author(s):  
DR Smyth ◽  
T Shaw
Keyword(s):  
Hydrochloric Acid ◽  
Dna Synthesis ◽  
Meiotic Prophase ◽  
Light Microscope ◽  
Dnase I ◽  
Rnase A ◽  
Chromosomal Dna ◽  
Cytoplasmic Dna ◽  
Microscope Autoradiography ◽  
Small Clusters

Extensive cytoplasmic DNA synthesis has been discovered at meiotic prophase in Lilium henryi. Explanted microsporocytes were cultured in medium containing I3H]thymidine. Light microscope autoradiography revealed many small clusters of grains (< 3 μm) in the cytoplasm of premeiotic and pachytene cells. There were about 10 to 20 clusters per cell in each section. Most of the cyto- plasmic label was extracted by hot hydrochloric acid and DNase I, but not by RNase A or pronase. Thus the grains reflect DNA synthesis, and not incorporation of products of thymidine catabolism which is extensive in this tissue. These localized centres of DNA synthesis, previously unreported, might result from mitochondrial or plastid replication, or from amplification of excised chromosomal DNA.

scholarly journals Microbubbles in replicating nuclear deoxyribonucleic acid from Physarum polycephalum

1979 ◽  
Vol 183 (2) ◽  
pp. 477-480 ◽  
Author(s):  
D A F Gillespie ◽  
N Hardman
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Dna Synthesis ◽  
Physarum Polycephalum ◽  
Deoxyribonucleic Acid ◽  
Nuclear Dna ◽  
S Phase ◽  
Dna Structures ◽  
Nuclear Deoxyribonucleic Acid

Clusters of microbubbles, represent probable sites of newly initiated DNA synthesis, were identified in nuclear DNA from Physarum polycephalum by using the electron microscope. Their presence is associated specifically with S-phase. Each microbubble corresponds in size to a replicating segment of DNA about 100-5000 nucleotide residues in length. The DNA structures containing microbubbles are metastable, and revert to native DNA in the presence of moderate concentrations of formamide used to prepare samples for electron microscopy. It is suggested that each cluster of microbubbles may correspond to a unit of replication (a replicon) in Physarum DNA.

DNA is replicated at the nuclear cage

1980 ◽  
Vol 46 (1) ◽  
pp. 365-386 ◽  
Author(s):  
S.J. McCready ◽  
J. Godwin ◽  
D.W. Mason ◽  
I.A. Brazell ◽  
P.R. Cook
Keyword(s):  
Electron Microscopy ◽  
Dna Synthesis ◽  
Hela Cells ◽  
Membrane Structure ◽  
Structural Unit ◽  
Nuclear Dna ◽  
Short Pulses ◽  
Restriction Endonuclease Ecori ◽  
Endonuclease Ecori ◽  
Average Size

Structures resembling nuclei are released when HeLa cells are lysed in a detergent and 2 M salt. These nucleoids, which lack any organized membrane structure, contain all the nuclear DNA packaged within a cage of RNA and protein. Their DNA is supercoiled so that the linear DNA must remain unbroken and looped during lysis. Following digestion with the restriction endonuclease, EcoRI, cages and associated DNA were filtered free of unattached DNA. Pulse-labelled (i.e. newly synthesized) DNA remains preferentially associated with the cages. This association has been confirmed by autoradiography. When nucleoids are prepared for electron microscopy by the Kleinschmidt procedure the DNA spills out to form a skirt around the flattened cage. Labelling, which is restricted to the region of the cage after short pulses, extends out into the skirt as the labelling time increases. A model, based on the premise that replication takes place at the nuclear cage, is presented in the Appendix. The results of the biochemical experiments and electron microscopy both indicate that the average size of the unit of replication is approximately 2 micrometer. This is about one-quarter the size of the average structural unit - the loop. Therefore sequences in the loop must become attached to the nuclear cage prior to the initiation of DNA synthesis.

scholarly journals AUTORADIOGRAPHIC EVIDENCE FOR MANY SEGREGATING DNA MOLECULES IN THE CHLOROPLAST OF OCHROMONAS DANICA

1973 ◽  
Vol 59 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Sarah P. Gibbs ◽  
Ronald J. Poole
Keyword(s):  
Cell Cycle ◽  
Chloroplast Dna ◽  
Exponential Growth ◽  
Light Microscope ◽  
Nuclear Dna ◽  
Serial Sections ◽  
Dna Molecules ◽  
Ochromonas Danica ◽  
Microscope Autoradiography ◽  
S Period

Light-grown cells of Ochromonas danica, which contain a single chloroplast per cell, were labeled with [methyl-3H]thymidine for 3 h (0.36 generations) and the distribution of labeled DNA among the progeny chloroplasts was followed during exponential growth in unlabeled medium for a further 3.3 generations using light microscope autoradiography of serial sections of entire chloroplasts. Thymidine was specifically incorporated into DNA in both nuclei and chloroplasts. Essentially all the chloroplasts incorporated label in the 3-h labeling period, indicating that chloroplast DNA is synthesized throughout the cell cycle. Nuclear DNA has a more limited S period. Both chloroplast DNA and nuclear DNA are conserved during 3.3 generations. After 3.3 generations in unlabeled medium, grains per chloroplast followed a Poisson distribution indicating essentially equal labeling of all progeny chloroplasts. It is concluded that the average chloroplast in cells of Ochromonas growing exponentially in the light contains at least 10 segregating DNA molecules.

Epoxy Resin Embedment

1968 ◽  
Vol 26 ◽  
pp. 100-101
Author(s):  
J. G. Adams ◽  
M. M. Campbell ◽  
H. Thomas ◽  
J. J. Ghldonl
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
Epoxy Resin ◽  
Light Microscope ◽  
Epoxy Resins ◽  
Image Contrast ◽  
Tissue Preservation ◽  
Resin System ◽  
Excellent Quality

Since the introduction of epoxy resins as embedding material for electron microscopy, the list of new formulations and variations of widely accepted mixtures has grown rapidly. Described here is a resin system utilizing Maraglas 655, Dow D.E.R. 732, DDSA, and BDMA, which is a variation of the mixtures of Lockwood and Erlandson. In the development of the mixture, the Maraglas and the Dow resins were tested in 3 different volumetric proportions, 6:4, 7:3, and 8:2. Cutting qualities and characteristics of stability in the electron beam and image contrast were evaluated for these epoxy mixtures with anhydride (DDSA) to epoxy ratios of 0.4, 0.55, and 0.7. Each mixture was polymerized overnight at 60°C with 2% and 3% BDMA.Although the differences among the test resins were slight in terms of cutting ease, general tissue preservation, and stability in the beam, the 7:3 Maraglas to D.E.R. 732 ratio at an anhydride to epoxy ratio of 0.55 polymerized with 3% BDMA proved to be most consistent. The resulting plastic is relatively hard and somewhat brittle which necessitates trimming and facing the block slowly and cautiously to avoid chipping. Sections up to about 2 microns in thickness can be cut and stained with any of several light microscope stains and excellent quality light photomicrographs can be taken of such sections (Fig. 1).

Comparative strengths and weaknesses of peroxidase and colloidal gold in pre- and post-embedding immunolabeling techniques

1987 ◽  
Vol 45 ◽  
pp. 1002-1005
Author(s):  
D. R. Abrahamson ◽  
P. L. St.John ◽  
E. W. Perry
Keyword(s):  
Electron Microscopy ◽  
Horseradish Peroxidase ◽  
Light Microscopy ◽  
Colloidal Gold ◽  
Light Microscope ◽  
Ultrastructural Localization ◽  
The Other ◽  
Quantitative Studies ◽  
Dense Suspension ◽  
Antigen Localization

Antibodies coupled to tracers for electron microscopy have been instrumental in the ultrastructural localization of antigens within cells and tissues. Among the most popular tracers are horseradish peroxidase (HRP), an enzyme that yields an osmiophilic reaction product, and colloidal gold, an electron dense suspension of particles. Some advantages of IgG-HRP conjugates are that they are readily synthesized, relatively small, and the immunolabeling obtained in a given experiment can be evaluated in the light microscope. In contrast, colloidal gold conjugates are available in different size ranges and multiple labeling as well as quantitative studies can therefore be undertaken through particle counting. On the other hand, gold conjugates are generally larger than those of HRP but usually can not be visualized with light microscopy. Concern has been raised, however, that HRP reaction product, which is exquisitely sensitive when generated properly, may in some cases distribute to sites distant from the original binding of the conjugate and therefore result in spurious antigen localization.

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.

Use of Antibody to aid Visualization of Protein at the Termini of Bacteriophage Ø29 DNA

1980 ◽  
Vol 38 ◽  
pp. 540-541
Author(s):  
Dwight Anderson ◽  
Charlene Peterson ◽  
Gursaran Notani ◽  
Bernard Reilly
Keyword(s):  
Electron Microscopy ◽  
Bacillus Subtilis ◽  
Dna Synthesis ◽  
Restriction Endonuclease ◽  
Protein Complex ◽  
Protein Product ◽  
Viral Dna ◽  
Small Proteins ◽  
Antibody Labeling ◽  
Subtilis Bacteriophage

The protein product of cistron 3 of Bacillus subtilis bacteriophage Ø29 is essential for viral DNA synthesis and is covalently bound to the 5’-termini of the Ø29 DNA. When the DNA-protein complex is cleaved with a restriction endonuclease, the protein is bound to the two terminal fragments. The 28,000 dalton protein can be visualized by electron microscopy as a small dot and often is seen only when two ends are in apposition as in multimers or in glutaraldehyde-fixed aggregates. We sought to improve the visibility of these small proteins by use of antibody labeling.

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