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[Electron microscopic study of the minichromosomes in murine fibroblast cells fixed in situ]
Abstract:
The ultrastructure and differential staining of minute chromosomes (MC) from mouse fibroblasts line C3H10T1/2 (LS9/0.1) was studied. MC in mitotic cells of this line contain R-positive material and are not stained according to the G- and C-methods. Reconstruction of ultrathin serial sections made it possible to identify MC in situ. It is shown that the basic structural unit of MC is a DNP fibril 20-30 nm in diameter. The density of packing of the MC material corresponds to that of normal chromosomal arms. In some cases the fibrillar material is present between MC and normal chromosomes. It is suggested therefore that some MC may be structurally linked to a normal chromosome arm. The MC structure is discussed in terms of the ultrastructural properties of R- and C-positive segments.
Insights
Minute chromosomes (MC) in mouse fibroblasts contain R-positive material and resist G- and C-staining. Their structure, composed of DNP fibrils, suggests potential links to normal chromosome arms.
Area of Science:
- Cell Biology
- Genetics
- Chromosomal Ultrastructure
Background:
- Minute chromosomes (MC) are small chromosomal structures observed in certain cell lines.
- Understanding the ultrastructure of MC is crucial for comprehending their origin and function.
- Differential staining properties of MC provide clues to their composition.
Purpose of the Study:
- To investigate the ultrastructure of minute chromosomes (MC) in mouse fibroblasts (C3H10T1/2 line).
- To analyze the differential staining characteristics of MC using G-, C-, and R-banding methods.
- To elucidate the structural relationship between MC and normal chromosomes.
Main Methods:
- Ultrastructural analysis using electron microscopy on ultrathin serial sections.
- Differential staining techniques (G-banding, C-banding, R-banding) applied to MC.
- Reconstruction of MC 3D structure from serial sections.
Main Results:
- MC in C3H10T1/2 cells contain R-positive material and are negative for G- and C-banding.
- The fundamental structural unit of MC is a deoxynucleoprotein (DNP) fibril, 20-30 nm in diameter.
- MC exhibit packing densities similar to normal chromosomal arms, with some showing fibrillar connections to normal chromosomes.
Conclusions:
- MC possess a distinct ultrastructure characterized by DNP fibrils.
- The R-positive nature of MC suggests a specific chromatin composition.
- Evidence indicates that MC may be structurally integrated with normal chromosome arms, potentially originating from them.