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Ultrastructural features of apoptosis
1Istituto di Morfologia Umana Normale, Univ. Chieti, Italy.
Abstract:
Apoptosis is a gene-directed physiological and programmed process of cell deletion aimed at the regulation of tissue and organ development. It affects different cell types and is triggered by a variety of stimuli all inducing closely comparable structural changes. Despite the deeply different morphology and metabolism of the cell models and the various inducers and their initial effects, a convergence seems to take place in a common metabolic pathway that, in most cases, involves the activation of a Ca2+ dependent endonuclease. A growing body of data is now available on the molecular events that lead to DNA damage. DNA cleavage in nucleosomic or oligonucleosomic fragments is related to the appearance of unusual and very characteristic ultrastructural changes. The nucleus is especially affected, and shows chromatin rearrangements consisting of cup-shaped marginations, sharply separated from diffuse chromatin areas. Nuclear fragmentation subsequently appears, finally followed by the formation of numerous micronuclei. Cytoplasmic damage appears at a very late stage and the process takes place despite good preservation of plasma membrane and cytoplasm.
Insights
Apoptosis, a programmed cell death process, regulates tissue development via specific molecular pathways. This study details the nuclear changes, including DNA fragmentation and chromatin rearrangement, characteristic of this essential biological mechanism.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Apoptosis is a fundamental, gene-directed process for regulating tissue and organ development.
- Diverse stimuli trigger apoptosis, leading to conserved structural changes across various cell types.
- A common metabolic pathway, often involving Ca2+-dependent endonuclease activation, is observed despite varied initial triggers.
Purpose of the Study:
- To elucidate the molecular events and ultrastructural changes associated with DNA damage during apoptosis.
- To characterize the specific nuclear alterations occurring during programmed cell death.
- To investigate the temporal sequence of cellular damage in apoptosis.
Main Methods:
- Analysis of molecular events leading to DNA damage.
- Microscopic examination of ultrastructural changes in apoptotic cells.
- Observation of nuclear and cytoplasmic alterations during the process.
Main Results:
- DNA cleavage into nucleosomic or oligonucleosomic fragments is a hallmark of apoptosis.
- Characteristic nuclear changes include chromatin marginations, fragmentation, and micronuclei formation.
- Cytoplasmic damage is a late event, with plasma membrane integrity often maintained.
Conclusions:
- Apoptosis involves specific molecular pathways culminating in DNA fragmentation and distinct nuclear morphology.
- The observed ultrastructural changes provide key indicators of programmed cell death.
- Understanding these events is crucial for comprehending tissue homeostasis and development.