scholarly journals Heterochromatin in Triton

1942 ◽  
Vol 130 (860) ◽  
pp. 324-335 ◽  
Keyword(s):  
Nucleic Acid ◽  
Low Temperature ◽  
Crossing Over

When subjected to low temperature, certain segments of the chromosomes of Triton vulgaris , T. palmatus and T. cristatus are heterochromatic. At mitosis these segments are undercharged and at meiosis uncharged with nucleic acid. These segments show the same type of allocyclic behaviour as do similar segments in Paris , Trillium and Fritillaria . They form Feulgen-positive chromocentres in all diffuse nuclei except pachytene, which is diffuse in Triton . The availability of nucleic acid at the stage when the chromosomes normally spiralize is now shown to be a condition of that spiralization. The diffuse pachytene without chromocentres is followed by meiosis with unspiralized heterochromatin: the diffuse resting nucleus with chromocentres is followed by mitosis with spiralized heterochromatin. With certain exceptions heterochromatin seems to be confined to those parts of chromosomes where chiasmata and crossing-over rarely occur.

Polydopamine-coated nucleic acid nanogel for siRNA-mediated low-temperature photothermal therapy

Biomaterials ◽  
2020 ◽  
Vol 245 ◽  
pp. 119976 ◽  
Author(s):  
Fei Ding ◽  
Xihui Gao ◽  
Xiangang Huang ◽  
Huan Ge ◽  
Miao Xie ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Low Temperature ◽  
Photothermal Therapy

THE EFFECTS OF THE IONIC ENVIRONMENT ON THE CHROMATIN STRUCTURES OF BACTERIA

1956 ◽  
Vol 2 (3) ◽  
pp. 245-260 ◽  
Author(s):  
J. F. Whitfield ◽  
R. G. E. Murray
Keyword(s):  
Escherichia Coli ◽  
Nucleic Acid ◽  
Low Temperature ◽  
Shigella Dysenteriae ◽  
Regulatory Mechanisms ◽  
Metabolic Inhibitors ◽  
Permanent Damage ◽  
Ionic Environment ◽  
Wild Yeast ◽  
Normal Configuration

The aggregation of bacterial chromatin into compact masses under a variety of circumstances (exposure to high salt concentrations, low temperature, ultraviolet irradiation, metabolic inhibitors, and starvation) is a function of the concentration of electrolytes in the environment of the cell. This effect can be prevented or reversed in an environment deficient in salts. The observations indicate that chromatin aggregation is a consequence of interaction of cations (Na+ and K+, in particular) and polymerized desoxyribose nucleic acid, which behaves as an anionic gel. The organisms used (Shigella dysenteriae, Escherichia coli, Bacillus cereus, Caryophanon latum, a wild yeast, and a Geotrichum sp.) were able to maintain their "normal" configuration of chromatin in salt-deficient media and in media with up to 3% salt as long as their metabolism was intact. Disruption of metabolism by exposure to cold or metabolic inhibitors produced aggregation or dispersion of chromatin according to the ionic environment. This range of change in nuclear form can be produced in the living cell without apparent or permanent damage to viability. These studies indicate that bacterial and fungal cells share with cells of higher organisms the ability to regulate the influx and efflux of cations. Chromatin serves as a sensitive indicator of the integrity of these ion regulatory mechanisms. Some implications of these observations are discussed.

What does the biologist want from the physical scientist?

1987 ◽  
Vol 45 ◽  
pp. 538-539
Author(s):  
Michael Beer
Keyword(s):  
Nucleic Acid ◽  
Low Temperature ◽  
Protein Complexes ◽  
Simultaneous Detection ◽  
Inorganic Ions ◽  
Chemical Processes ◽  
X Ray ◽  
Carbon To Nitrogen Ratio ◽  
Acid Protein ◽  
Nitrogen Ratio

The Biologist is interested in discovering and then understanding the chemical processes in organisms. Crucial in his analysis is a knowledge of the structure of the system at various levels. At the level of the cell he must recognize the positions of particular macromolecules. For proteins or nucleoproteins this is best done with labeled antibodies. Inorganic ions like calcium or sodium can be localized by X-ray microprobe or EELS. From the designer he requires instruments in which the distribution of these species is not altered by the data collection. Specimen stability is favored by low temperature and efficient collection of data. That means simultaneous detection of all possible scattering events. Rapid display of the results as abundances requires computers of sufficient capability.Similar procedures look promising in the analysis of the structure of nucleic acid-protein complexes. Nucleic acids can be traced through phosphorus and protein through sulphur or perhaps carbon to nitrogen ratio.

Nucleic acid synthesis in microsporocytes of Lilium cv. cinnabar: events in the nucleus

1982 ◽  
Vol 57 (1) ◽  
pp. 229-246
Author(s):  
E.K. Porter ◽  
J.M. Bird ◽  
H.G. Dickinson
Keyword(s):  
Nucleic Acid ◽  
Chromosome Pairing ◽  
Rna Synthesis ◽  
Dna Amplification ◽  
Acid Synthesis ◽  
Autoradiographic Study ◽  
Crossing Over ◽  
Electron Microscopic ◽  
Dna And Rna ◽  
Dna And Rna Synthesis

In an electron microscopic autoradiographic study of DNA and RNA synthesis during meiosis isolated Lilium microsporocytes were supplied with [3H]thymidine and [3H]uridine. DNA synthesis occurred in the nucleus during the zygotene and pachytene intervals of meiotic prophase. Most of the activity was associated with the chromatin, but some synthesis early in zygotene was located at the nucleolus. RNA synthesis occurred throughout prophase until diplotene, when all activity ceased until after division. The newly synthesized RNA was found mostly in association with the chromosomal peripheries or in the space between chromosomes. There was also a peak of [3H]uridine incorporation at the nucleolus, which followed shortly after the synthesis of DNA at that site. The localization of DNA and RNA synthesis at the various stages of meiosis is discussed in relation to current concepts of chromosome pairing, crossing-over, ribosomal DNA amplification and cycles of RNA metabolism.

A Method for the Hybridization of Nucleic Acid Molecules at Low Temperature*

Biochemistry ◽  
1967 ◽  
Vol 6 (12) ◽  
pp. 3650-3653 ◽  
Author(s):  
James Bonner ◽  
Grace Kung ◽  
Isaac Bekhor
Keyword(s):  
Nucleic Acid ◽  
Low Temperature
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