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Mitochondrial granules: are they reliable markers for heavy metal cations?
Abstract:
Mitochondrial granules have been used as markers for heavy metal cations, but since such granules can also be found in tissues in the absence of such cations, an attempt was made to define conditions under which these different granules might be visualised. The tissue used was the smooth muscle of the central ear artery of the rabbit. In all studies, the presence or absence of mitochondrial granules was determined by several observers, using coded specimens so that the previous treatment of the specimens was not at the time known to the observers. Paired tissues were exposed for 30 or 90 minutes at 20, 30 or 39 degrees C to an incubate containing either 10 mmol/l barium or a control barium-free solution. After fixation in osmium tetroxide, there was no difference between the two groups; in both cases granules appeared more frequently the longer the time and the higher the temperature of incubation. In a further series where glutaraldehyde was the fixative, granules were identified in 23 out of 41 tissues incubated with barium, but in only 1 out of 41 control tissues (P less than 0.001). Electron probe microanalysis showed that granules in osmium-fixed tissues contained osmium as the main element, whereas granules in glutaraldehyde-fixed tissues which had been incubated with barium showed barium as the predominant cation. Thus mitochondrial granules can be reliable markers for heavy metal cations, but only under carefully controlled conditions.
Insights
Mitochondrial granules can reliably mark heavy metal cations like barium, but only when specific conditions are met. Careful control of tissue fixation and incubation is crucial for accurate visualization of these important cellular markers.
Area of Science:
- Cell Biology
- Biochemistry
- Histology
Background:
- Mitochondrial granules have been utilized as indicators for heavy metal cations.
- However, their presence in tissues without these cations complicates their use as reliable markers.
- Defining conditions for differentiating these granules is essential.
Purpose of the Study:
- To establish conditions under which mitochondrial granules can be reliably visualized as markers for heavy metal cations.
- To investigate the influence of incubation time, temperature, and fixative type on granule formation.
- To determine the elemental composition of granules under different experimental conditions.
Main Methods:
- Smooth muscle tissue from rabbit central ear artery was used.
- Tissues were incubated with barium or a control solution at varying times and temperatures.
- Fixation was performed using osmium tetroxide or glutaraldehyde.
- Granule presence was assessed by blinded observers.
- Electron probe microanalysis was employed to determine elemental composition.
Main Results:
- Granule frequency increased with longer incubation times and higher temperatures, irrespective of the fixative.
- Glutaraldehyde fixation significantly increased granule detection in barium-incubated tissues compared to controls (P < 0.001).
- Osmium-fixed granules primarily contained osmium, while glutaraldehyde-fixed, barium-incubated granules showed barium as the predominant cation.
Conclusions:
- Mitochondrial granules can serve as dependable markers for heavy metal cations.
- Reliable identification necessitates carefully controlled experimental conditions, particularly regarding fixation and incubation.
- The choice of fixative is critical for distinguishing cation-specific granules.
