Mitochondrial alterations

What is it about?

Morphological alterations of mitochondria may be related to metabolic and energy deficiency in neurons in Alzheimer’s disease (AD) and other neurodegenerative disorders. In previous studies on the morphological and morphometric estimation of mitochondria in AD, electron microscopy revealed substantial morphological and morphometric changes in the hippocampus, the acoustic cortex, the frontal cortex, and the cerebellum. This study extends this observation to subcortical centers, namely the thalamus, the globus pallidus, the red nucleus, and the locus caeruleus in 10 brains of patients who suffered from AD. The morphological alterations consisted of very obvious changes of the mitochondrial cristae, accumulation of osmiophilic material and decrease of their size, in comparison with the normal controls. Mitochondrial alterations were particularly prominent in neurons, which showed loss of dendritic spines and abbreviation of the dendritic arborization. The ultrastructural study of a large number of neurons in the thalamus and the red nucleus revealed that the mitochondrial alterations did not coexist with cytoskeletal pathology and accumulation of amyloid deposits. However, they were prominent in neurons, which demonstrated fragmentation of the cisternae of the Golgi apparatus. The morphological alterations of the mitochondria presumably suggest oxidative damage in neurons in AD brains.

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Why is it important?

The ultrastructural study of the thalamus, globus pallidus, red nucleus, and locus coeruleus revealed an impressive polymorphism of the mitochondria in the soma of the nerve cells as well as in the axonal and dendritic profiles of the majority of neurons . The mitochondria demonstrated a wide variation of size and shape in comparison with those of the normal control brains.Some dendritic profiles included mitochondria, which showed an impressive polymorphism in the arrangement of the cristae. The cristae sometimes showed a concentric configuration, or they were arranged in a parallel way to the long axis of the organelle. The polymorphism of the mitochondria was particularly impressive in dendritic profiles of neurons of the locus caeruleus (Figure 3), where morphological alterations of the mitochondria coexisted with fragmentation of the Golgi apparatus. Small, round mitochondria intermixed with dense bodies were seen in a large number of neurons in the globus pallidus. Morphological alterations of the mitochondria were seen in the soma, the perivascular astrocytic processes, and the astrocytic sheaths in AD brains in contrast to normal controls, where the mitochondria appeared normal.

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