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Further evidence to suggest that microbodies do not exist as individual entities
Abstract:
Male wild-type mice (Cs(a) strain) were treated with ethyl-alpha-p-chlorophenoxyisobutyrate (CPIB), a hypolipidemic drug which enhances hepatic catalase synthesis and induces rapid and significant increase in the number of microbody (peroxisome) profiles in liver cells. Numerous microbody profiles, several of them appearing in clusters and retaining membranous continuities, were observed in liver cells of CPIB-treated mice. They showed a significant variation in size and configuration, and the presence or absence of the nucleoid or core did not appear to bear any relation to the size or shape of microbody profiles. Nucleoids were encountered frequently in microbody profiles measuring as small as 0.1 mu in diameter. Numerous continuities between two or more anucleoid and/or nucleoid-containing microbody profiles of different sizes and shapes were seen. These findings are inconsistent with the concept that the smaller peroxisomes are the possible precursors or progenitors of their larger counterparts. Detailed examination of numerous electron micrographs revealed irregular dilatations and tortuosities of the endoplasmic reticulum (ER) containing electron-opaque peroxisomal material displaying the characteristic appearance of matrix and usually containing irregular cores. Transitions of rough ER to smooth ER in which microbody proteins accumulated were also apparent. Numerous continuities between several microbody profiles and continuities between microbody profiles and ER are interpreted as accumulations of peroxisomal proteins in dilated tortuous channels of ER. These observations strongly suggest that the microbody proteins constitute a common pool, circulating constantly in the dilated ER channels. The size, shape and number of microbody profiles appear to reflect the amount of peroxisomal proteins present in the pool. These observations clearly suggest that the microbodies do not exist as individual entities.
Insights
Ethyl-alpha-p-chlorophenoxyisobutyrate (CPIB) treatment in mice revealed that microbodies (peroxisomes) do not exist as individual entities. Instead, they form from a common pool of peroxisomal proteins within the endoplasmic reticulum (ER).
Area of Science:
- Cell Biology
- Hepatology
- Biochemistry
Background:
- Peroxisomes, also known as microbodies, are vital organelles involved in various metabolic processes.
- The biogenesis and structural dynamics of peroxisomes have been a subject of ongoing research.
- Ethyl-alpha-p-chlorophenoxyisobutyrate (CPIB) is a hypolipidemic drug known to influence hepatic peroxisome proliferation.
Purpose of the Study:
- To investigate the structural dynamics and biogenesis of hepatic microbodies (peroxisomes) in mice treated with CPIB.
- To examine the relationship between the endoplasmic reticulum (ER) and microbody formation.
- To challenge the prevailing concept of peroxisomes as independent entities.
Main Methods:
- Male wild-type mice (Cs(a) strain) were treated with ethyl-alpha-p-chlorophenoxyisobutyrate (CPIB).
- Liver cells were examined using electron microscopy to observe microbody morphology and distribution.
- Analysis focused on the presence of nucleoids, membranous continuities, and connections between microbodies and the ER.
Main Results:
- CPIB treatment led to a significant increase in the number and variation in size and shape of microbody profiles.
- Membranous continuities were observed between microbodies and between microbodies and the endoplasmic reticulum (ER).
- Electron-opaque peroxisomal material was found within dilated ER channels, suggesting ER as a source of peroxisomal proteins.
Conclusions:
- The findings suggest that microbodies (peroxisomes) do not exist as individual entities but arise from a common pool of proteins within the ER.
- The size, shape, and number of microbody profiles appear to reflect the dynamics of this peroxisomal protein pool.
- This challenges the traditional view of peroxisome biogenesis and suggests a more interconnected origin.