Electron Microscopic Examination of Subcellular Fractions

Abstract

Large granule fractions, containing about 80 % of the cytochrome oxidase of the tissue, were isolated from rat liver and used to prepare thin pellicles of packed particles which were submitted to quantitative electron microscopic examination. Various parameters describing the mitochondrial population were determined by measuring the size and number of mitochondrial profiles in sections, and the ratio of the inner to the outer membrane area. The mean particle radius and volume were found to be respectively 0.38 /p and 0.29 3; the average areas per mitochondrion were 2 and 5 2 for the outer and inner membranes respectively. On the basis of the cytochrome oxidase activity recovered in the particulate fractions, the results were extrapolated to the whole liver, and it was concluded that rat liver contains about 5.1011 mitochondria per gram; this corresponds to a volume of 0.14 ml/g and to an area of 2.5 and 1 m 2 /g for the inner and outer membranes respectively. The validity and the accuracy of these determinations is discussed and the results are compared to the information which has been obtained by independent methods or by other investigators.

Intergrated stereological and biochemical studies of hepatocytic membranes. I. Membrane recoveries in subcellular fractions

“…This can be explained either by swelling or by fragmentation; the fact that the diameter of mitochondria in fractions is close to the diameter but much smaller than the length of intact mitochondria, makes fragmentation the more likely process. This is further supported by the findings of greater mitochodnrial number (as questionable as this parameter may be) and smaller mean volume in fractions (4,35). Fragmentation could, however, split off variable parts of mitochondrial membranes which would then form vesicles or sheets, morphologically no longer identifiable as of mitochondrial origin; in our analysis, they would be assigned to the class of "smooth membranes."…”

Sedimentation Properties of Rat Liver Mitochondria

“…The size of native mitochondria in situ is unknown . Estimates of mitochondrial size, moreover, differ markedly according to the particular techniques of measurement employed (7,18,24,25) . Nevertheless, examination of both sections of 9 If the mitochondrion enlarges by the imbibition of water alone instead of the sucrose-containing medium in which it is suspended, the ratio v'/v will clearly be still less .…”

“…4 Baudhuin and Berthet have recently shown that mitochondria isolated in 0 .25 M sucrose have an average volume of 2 .9 X 10 -13 cm3 (18) . From these data it can be calculated that for mitochondria in 0 .25 M sucrose : V,,, = 0 .404 X 2 .9 X 10-13 = 1 .17 X 10-13 cm3 , and Vo = 0 .107 X 2 .9 X10-13=0 .31X10-13 cm3 .…”

“…VOLUME 46, 1970 . pages 1 [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]was shown to produce a three-to fourfold increase in the volume of the average liver mitochondrion. Although there is an increase in mitochondrial size, there is a concomitant reduction in the number of mitochondria per cell, the total mitochondrial material per cell remaining approximately constant .…”

A New Stereological Method for Determination of the Size of Spherical objects in Electron Microscopy: Its Application to Small Lymphocytes of the Mouse Thymus

“…For determination of the size of spherical objects the stereological methods thus far used have been based on the measurement of the diameter distribution of the sectional profiles (EACH, 1967;BAUDHUIN and BERTHET, 1967;ELIAS and HENNIG, 1967;SALTIKOV, 1967;COUPLAND, 1968). In practice, however, the precise measurement of the diameters is often attended by some difficulties, because the objects presumed to be spherical in biological specimens are not always found to be perfectly circular on sections.…”