Atypical mitochondria in the lung of newts, Triturus alpestris, Laur

Fibrous component of yeast mitochondria

An intramitochondrial fibrous component (IMF) was consistently detected by electron microscopy in all eight strains of yeast examined, either respiratory competent or deficient, and including two species, Saccharomyces cerevisiae and S. uvarum. IMF was always found assembled into a layer 20 nm in thickness. In respiratory-deficient mutants, multiple IMF layers roll up concentrically to give rise to cylindrical inclusion bodies which attain several micrometers in length. In normal respiring yeasts, IMF occurs in close association with cristae to elaborate composite structures in which multiple parallel IMF layers are sandwiched between a pair of cristae. Evidence is presented to demonstrate the extramitochondrial origin of IMF.

[Giant mitochondria in the A cells of the pancreas of a lizard: Varanus niloticus]

Pancreatic A cells of the lizard Varanus niloticus are characterized by the presence of two types of mitochondria: (a) normal, small mitochondria (about 0.4 X 1 micron), and (b) giant mitochondria, measuring up to 9 micron in length and 1 micron in diameter. Giant mitochondria show various shapes. Their matrix is filled with tubules, filaments, and dense granules. Transverse sections of tubules are polygonal in shape and about 20 nm in diameter. They are grouped in bundles. The filaments, about 9-10 nm in diameter, are arranged in parallel layers crossing each other at a 57 degree angle. In a closely related species, Varanus exanthematicus, pancreatic A cells do not show these peculiar features.

Mitochondrial abnormalities in cortical dendrites from patients with early forms of subacute sclerosing panencephalitis (SSPE)

Biopsy fragments from the frontal cortex of two patients with early forms of subacute sclerosing panencephalitis (SSPE) were studied with ultrastructural methods. Special attention was given to mitochondrial abnormalities observed in dendrites from the three superficial cortical layers. Some of the mitochondria presented atypical elongated cristae parallel to the longer axis of the organelle and closely opposite each other. The surface of these cristae is undulated, and the intracristal space is regularly septate. As these abnormal mitochondria appeared in dendrites, which in later stages of the disease are supposed to degenerate, it is advanced that these abnormalities could be precursors of dendritic changes and be possibly related to the precocious, insidious mental changes which characterize the early forms of the disease, as it is known that the disruption of the dendritic domain is linked with neuronal dysfunction.