Introduction

1978 ◽  
Vol 36 (3) ◽  
pp. 543-544
Author(s):  
W. Bernard
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Nucleic Acid ◽  
Gene Mapping ◽  
Molecular Genetics ◽  
Cell Biology ◽  
Gene Activity ◽  
Close Connection ◽  
Basic Information ◽  
Simple Systems

In comparison to many other fields of ultrastructural research in Cell Biology, the successful exploration of genes and gene activity with the electron microscope in higher organisms is a late conquest. Nucleic acid molecules of Prokaryotes could be successfully visualized already since the early sixties, thanks to the Kleinschmidt spreading technique - and much basic information was obtained concerning the shape, length, molecular weight of viral, mitochondrial and chloroplast nucleic acid. Later, additonal methods revealed denaturation profiles, distinction between single and double strandedness and the use of heteroduplexes-led to gene mapping of relatively simple systems carried out in close connection with other methods of molecular genetics.

Historic nucleic acids isolated by Friedrich Miescher contain RNA besides DNA

2021 ◽  
Vol 402 (10) ◽  
pp. 1179-1185
Author(s):  
Andreas Thess ◽  
Ingmar Hoerr ◽  
Benyamin Yazdan Panah ◽  
Günther Jung ◽  
Ralf Dahm
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Molecular Genetics ◽  
Phosphorus Content ◽  
Cell Types ◽  
Significant Percentage ◽  
Dna And Rna ◽  
Large Molecular Weight ◽  
New Type ◽  
High Phosphorus Content

Abstract One hundred fifty years ago, Friedrich Miescher discovered DNA when he isolated “Nuclein”—as he named it—from nuclei of human pus cells. Miescher recognized his isolate as a new type of molecule equal in importance to proteins. He realised that it is an acid of large molecular weight and high phosphorus content. Subsequently, he discovered Nuclein also in the nuclei of other cell types, realised that it chemically defines the nucleus, and speculated on its role in proliferation, heredity and fertilisation. While now universally recognised as the discoverer of DNA, whether Miescher also discovered RNA has not yet been addressed. To determine whether his isolation also yielded RNA, we first reproduced his historic protocols. Our resulting modern Nuclein contained a significant percentage of RNA. Encouraged by this result, we then analysed a sample of Nuclein isolated by Miescher from salmon sperm. Assuming that the RNA present in this sample had degraded to nucleobases, we tested for the presence of uracil in the historic Nuclein. Detection of significant levels of uracil by LC-UV-MS demonstrates that Miescher isolated both forms of nucleic acid—DNA and RNA—and underlines the fundamental nature of his discovery for the field of molecular genetics.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Electron microscopy of the replicative events of A25 bacteriophages in group A streptococci

1972 ◽  
Vol 18 (1) ◽  
pp. 93-96 ◽  
Author(s):  
S. E. Read ◽  
R. W. Reed
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Electron Microscope ◽  
Nucleic Acid ◽  
Group A Streptococcus ◽  
Group A Streptococci ◽  
Virulent Phage ◽  
Acid Pool ◽  
Group A ◽  
A Cell

The replicative events of a virulent phage (A25) infection of a group A Streptococcus (T253) were studied using the electron microscope. The first intracellular evidence of phage replication in a cell occurred 30 min after infection with arrest of cell division and increase in the nucleic acid pool. Phage heads were evident in the nucleic acid pool of the cells 45 min after infection. Release of phages occurred by splitting of the cell wall along discrete lines. This appeared to be at sites of active wall synthesis, i.e., near the region of septum formation. Many phage components were released but relatively few complete phages indicating a relatively inefficient replicative system.

Toxoplasma as a Model Apicomplexan Parasite: Biochemistry, Cell Biology, Molecular Genetics, Genomics and Beyond

2000 ◽  
pp. 143-167 ◽  
Author(s):  
David S. Roos ◽  
John A. Darling ◽  
Mary G. Reynolds ◽  
Kristin M. Hager ◽  
Boris Striepen ◽  
...  
Keyword(s):  
Molecular Genetics ◽  
Cell Biology ◽  
Apicomplexan Parasite

scholarly journals Effect of kinetin on nucleic acid synthesis in senescing and young leaves in Brassica oleracea L. var. gongylodes L.

2015 ◽  
Vol 44 (4) ◽  
pp. 553-565
Author(s):  
J. Legocka ◽  
A. Szweykowska
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Acid Synthesis ◽  
Inhibitory Effect ◽  
Rrna Synthesis ◽  
Low Molecular Weight ◽  
Chlorophyll B ◽  
Mature Leaves ◽  
Young Leaves ◽  
Brassica Oleracea L

In detached kohlrabi leaves senescing in the dark, the decrease in chlorophyll to was more pronounced than in chlorophyll a. The retardation by kinetin of the chlorophyll loss was also markedly stronger in the case of chlorophyll b. Using the fractionation of nucleic acids on polyacrylamide gels it has been shown that during leaf senescence the level of all RNA species decreased, whereas the amount of DNA was more or less constant. In the presence of kinetin, the loss of RNA was inhibited and the incorporation of precursor into the cytoplasmic rRNA as well as into low molecular weight RNA species was supported. Chloroplast rRNA synthesis has not been detected in mature leaves and kinetin showed no effect in this respect. In young expanding leaves detached and kept in light, the synthesis of cytoplasmic rRNA was strongly stimulated by kinetin, whereas in the case of Chloroplast rRNA only an inhibitory effect of kinetin could be found. The results suggest that the cytokinins are primarily involved in processes of the synthesis of cytoplasmic rRNA and low molecular RNA fractions, and in this way affect the development of plastids, in particular the course of their senescence.

scholarly journals CORP: Using transgenic mice to study skeletal muscle physiology

2020 ◽  
Vol 128 (5) ◽  
pp. 1227-1239
Author(s):  
C. Brooks Mobley ◽  
Ivan J. Vechetti ◽  
Taylor R. Valentino ◽  
John J. McCarthy
Keyword(s):  
Skeletal Muscle ◽  
Transgenic Mice ◽  
Research Program ◽  
Gene Function ◽  
Cell Biology ◽  
Muscle Physiology ◽  
Basic Information ◽  
Adult Skeletal Muscle ◽  
Tissue Specific ◽  
Muscle Research

The development of tissue-specific inducible transgenic mice has provided a powerful tool to study gene function and cell biology in almost any tissue of interest at any given time within the animal’s life. The purpose of this review is to describe how to use two different inducible transgenic systems, the Cre-loxP system and the Tet-ON/OFF system, that can be used to study skeletal muscle physiology. Myofiber- and satellite cell-specific Cre-loxP transgenic mice are described as is how these mice can be used to knockout a gene of interest or to deplete satellite cells in adult skeletal muscle, respectively. A myofiber-specific Tet-ON system is described as is how such mice can be used to overexpress a gene of interest or to label myonuclei. How to effectively breed and genotype the transgenic mice are also described in detail. The hope is this review will provide the basic information necessary to facilitate the incorporation of tissue-specific inducible transgenic mice into a skeletal muscle research program.

Direct Isolation of High-Quality Low Molecular Weight RNA of Pear Peel from the Extraction Mixture Containing Nucleic Acid

2009 ◽  
Vol 44 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Xin-wei Wang ◽  
Ai-sheng Xiong ◽  
Quan-hong Yao ◽  
Zhen Zhang ◽  
Yu-shan Qiao
Keyword(s):  
Molecular Weight ◽  
Nucleic Acid ◽  
Low Molecular Weight ◽  
High Quality ◽  
Extraction Mixture

scholarly journals DEVELOPMENT OF AN IMPROVED MEDIUM FOR THE ISOLATION OF LIVER MITOCHONDRIA

1956 ◽  
Vol 2 (5) ◽  
pp. 609-624 ◽  
Author(s):  
M. S. C. Birbeck ◽  
E. Reid
Keyword(s):  
Adverse Effect ◽  
Molecular Weight ◽  
Electron Microscope ◽  
Acid Phosphatase ◽  
Mitochondrial Fraction ◽  
Liver Mitochondria ◽  
High Concentration ◽  
Mitochondrial Fractions ◽  
Sucrose Medium ◽  
Optimal Medium

In view of the unsatisfactory appearance, under the electron microscope, of liver mitochondria isolated in isotonic sucrose medium, alternative media have been examined. It was found to be advantageous to replace sucrose by raffinose, and to add levan or, preferably, dextran, together with heparin in suitable concentration. With the optimal medium, the constituents of which are raffinose, versene (optional), dextran of high molecular weight, heparin, and AMP (optional), most of the mitochondria in the osmium-fixed pellet are apparently intact, and show the membranes characteristic of mitochondria as seen in cell sections. The optimal medium has no adverse effect on the activity of the several tissue enzymes which have been studied, except that Mg++-activated ATPase is partially inhibited if the medium is present in high concentration in the assay system. Mitochondrial fractions isolated in the new medium have, in common with sucrose fractions, appreciable "free" ATPase activity, this activity being evidently a poor criterion of mitochondrial integrity. Use of the new medium does not decrease the proportion of cytoplasmic ATPase which fails to sediment with the mitochondria, but does give a mitochondrial fraction low in RNA and in acid phosphatase activity and little contaminated with microsomal material. Particles tentatively identified as "lysosomes" have been seen in certain sections.

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