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Intramitochondrial inclusions in the kidney of the pygmy mouse
Abstract:
Intramitochondrial inclusions averaging 1000 A in diameter were observed in the cells of the proximal convoluted tubules in samples of kidneys from pygmy mice, Baiomys taylori. Electron microscopic study of unstained sections and mitochondrial fractions showed that these inclusions are lipid and found at a S.G. 1.37 in a linear sucrose gradient. Renal glycogen, inorganic phosphate and plasma sodium were significantly higher in the pygmy mouse and plasma calcium was lower, as compared with the laboratory mouse. We believe these intramitochondrial inclusions to be lipid which accumulates divalent cations, particularly calcium, which acts as a sodium pump allowing the pygmy mouse to conserve water and adapt to its environment.
Insights
Pygmy mice possess unique intramitochondrial lipid inclusions. These inclusions aid in calcium accumulation, facilitating water conservation and adaptation to arid environments.
Area of Science:
- Cell Biology
- Animal Physiology
- Biochemistry
Background:
- Mitochondria play crucial roles in cellular energy metabolism and ion homeostasis.
- The unique physiological adaptations of pygmy mice (Baiomys taylori) to arid environments are not fully understood.
- Intramitochondrial inclusions have been observed in various cell types, but their composition and function remain unclear in many contexts.
Purpose of the Study:
- To investigate the nature and potential function of intramitochondrial inclusions observed in the kidney proximal convoluted tubules of pygmy mice.
- To correlate the presence of these inclusions with the known water-conserving adaptations of Baiomys taylori.
Main Methods:
- Electron microscopy was employed to examine kidney tissue samples from pygmy mice.
- Unstained sections and isolated mitochondrial fractions were analyzed.
- Density gradient centrifugation was used to characterize the inclusions.
Main Results:
- Intramitochondrial inclusions, approximately 1000 Angstroms in diameter, were identified in proximal convoluted tubule cells.
- These inclusions were characterized as lipidic, with a specific gravity of 1.37.
- Pygmy mice exhibited significantly higher renal glycogen, inorganic phosphate, and plasma sodium levels, along with lower plasma calcium, compared to laboratory mice.
Conclusions:
- The intramitochondrial inclusions in pygmy mice are likely lipid in nature.
- These lipid inclusions appear to accumulate divalent cations, particularly calcium.
- This calcium accumulation may function as a sodium pump, contributing to the pygmy mouse's remarkable water conservation abilities and adaptation to its environment.