Optical and electron microscopic changes in ultraviolet irradiated chromosome segments.

Area of Science:

• Cell Biology
• Molecular Biology
• Radiation Biology

Background:

• Chromosomes are essential for cellular function and heredity.
• Understanding how external factors like radiation affect chromosome structure is crucial.
• Previous studies indicated changes in cellular components after irradiation.

Purpose of the Study:

• To investigate the effects of heterochromatic ultraviolet light on urodele cell chromosomes.
• To characterize the substance lost from chromosomes after irradiation.
• To elucidate the process of DNA-steresis at a molecular and structural level.

Main Methods:

• Irradiation of urodele cells with ultraviolet light.
• Staining techniques including Feulgen, pyronine-methyl-green, and Alfert-Geschwind.
• Spectrophotometric analysis of irradiated chromosome segments.
• Electron microscopy of fixed cells (formalin-fixed, phosphotungstic acid stained).

Main Results:

• Irradiation led to loss of substance in chromosome segments.
• Affected segments showed reduced staining and decreased absorption at 2400-2800 A.
• Electron microscopy revealed a reduction in a homogeneous component (component-A) presumed to contain DNA.
• The process was termed DNA-steresis, indicating deoxyribonucleic acid loss.

Conclusions:

• Heterochromatic ultraviolet light induces DNA-steresis in urodele chromosomes.
• DNA-steresis involves the loss of deoxyribonucleic acid and associated material.
• The structural alterations observed are significant for understanding radiation-induced cellular damage.