CYTOCHEMICAL STUDIES OF NUCLEAR METABOLISM IN BIOLOGICAL SYSTEMS
With the aid of track autoradiographi, using an election sensitive liquid emulsion it was possible to follow the intracellular incorporation of a labelled precursor like adenine-8-C/sup 14/ which is specific for nucleic acids. The incorporation was determined on the basis of the topographical emission of ionizing particles in particular eganelles of the cell. The balance of evidence points to the fact thai in oocytes of the newt the nucleolus incorporates adenine with marked rapidity in the RNA. However, the fact that there is a high specific radioactivity in the nucleolus does not necessarily imply that the site of synthesis of RNA is centered in this intranuclear structure since in the actively dividing mersystematic cells of Vicia faba there is a preferential uptake of the labelled adenine in the heterochromatic and nucleolar organizing (SAT) regions of the long chromosonaes. From this it would appear that the nucleolus acts as a reservoir of RNA and that actual synthesis supervenes in the heterochromatic regions and SATloci of particular chromosomes. In an attempt to understand the mechanics of chromosome replication, cytologists have made many assumptions, the validity of which has not been tested on cytochemical grounds until very recently. Although it his been known for lung that during mitosis there is a doubling of chromosomes followed by an equipartition of chromosomal substance between the two daughter nuclei, no decisive technique has so far demonstrated whether the original chromosome produces by a self-duplicating process a replica of itself from available new material or whether the original chromosomal substance is equally distributed between the daughter nuclei. However, with the availability of specific precursors, like thymidine-2-C/sup 14/ of DNA and refinement in autoradiographic techniques it is now possible to selectively label particular components of chromosomes and follow the fate of the tagged atoms in successive mitotic cycles. In this way evidence is accumulating to suggest the operation of a template process in chromosome synthesis and duplication, at any rate in the somatic mitoses of Vicia faba and Luzula species. The cytological implications of such a synthesis are further discussed. (C.H.)
- Research Organization:
- Atomic Energy Establishment, Trombay, India
- NSA Number:
- NSA-13-006235
- OSTI ID:
- 4288357
- Report Number(s):
- A/CONF.15/P/1646
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-59
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ADENINE
BIOCHEMISTRY
CARBON 14
CHROMOSOMES
CYTOLOGY
DNA
ELECTRONS
EMISSION
IONIZATION
LABELLED COMPOUNDS
LIQUIDS
METABOLISM
MITOSIS
NUCLEAR EMULSIONS
NUCLEIC ACIDS
NUCLEOLI
ORGANIC NITROGEN COMPOUNDS
PARTICLES
PLANTS
RADIOACTIVITY
RADIOAUTOGRAPHY
RIBONUCLEIC ACID
SENSITIVITY
THYMIDINE
VICIA