In human hepatocellular carcinoma cells the total membrane surface area of each major organelle is a particular allometric function of the cytoplasmic volume. A morphometric study

Morphometric analysis by both light and electron microscopy was performed in cells from five cases of human, hepatocellular carcinoma (HCC) and in three control cases. In each case, three fragments were examined individually and the following morphometric parameters evaluated: a) nuclear, cytoplasmic and cell volumes; b) volume density and absolute volume of the rough ER, smooth ER, mitochondria, Golgi apparatus, peroxisomes, dense bodies and cytoplasmic matrix; c) surface density, surface/ volume ratio, and total surface area of rough ER, smooth ER and outer mitochondrial membranes. The parameters obtained from HCC cases showed ample scatter of data, all control values lying within the interval between the extreme values for the various parameters. Both the original and the logarithmically transformed data on volume and total membrane surface area of organelles (y) and of the cytoplasmic volume (x) were regressed using first degree regression equations. The original values for volume and total surface area of rough ER, total ER and mitochondria were linearly related to the corresponding values for cytoplasmic volume. The allometric analysis carried out with the logarithms also revealed significant regressions between cytoplasmic volume and smooth ER parameters not detectable when using the original x and y values. It showed, in addition, that in progressively larger cytoplasmic volumes, the cisternae of both rough and smooth ER tend to appear more compacted and a higher portion of the total ER membrane tends to be constituted of smooth ER. Within the wide range of variation in cytoplasmic volume of the HCC cells, the volume and total surface of the organelles do not vary randomly. These data indicate that in the small, normal-sized and large tumoral cells the mechanisms responsible for the cytoplasmic volume and for the corresponding total volume and membrane surface area of each major organelle are interdependent. Such an interdependence gives no support to ideas implying that the variation in size of cancer cells, an element of pleomorphism, would result of anarchical intracellular synthetic and/or degradative conditions.

Development of the cloacal bursa in the domestic fowl. II. A quantitative and fine structural analysis of the follicular cortex and medulla

The estimated volumes of the follicular medulla (x) and cortex (y) from 14-day-old embryos till 28-day-old White Leghorn chicks were associated through the allometric formula y = bxk or log y = log b + k log x. Two successive allometric growth stages (I and II) are discernable, being hatching the transition region between them. The volumetric growth of the cortex is 2.49 times greater than that of the medulla in stage I, whereas cortex and medulla grow isometrically in stage II. The curve fitting procedure analysis of the absolute cortical and medullary growth confirmed these results. The fine structure of the cell types in the follicular medulla revealed that: a) in the allometric stage I pre-existing, bud precursor (Pr) cells appear to give rise to basal (Ba) and medullary epithelial (ME) cells, in both cases showing lucent and dark varieties. A medullary cytoreticulum is established at the onset of this stage. b) The marked lymphocyte proliferation during stage II occurs among the thin and short cytoplasmic processes of BA cells. These processes extend towards the centre of the medulla and also show many lateral interdigitating processes. During this same stage, the cytoplasmic processes of ME cells elongate and become thinner promoting a widening of the cytoreticulum interstices. The fine structural analysis of the cortical cytoarchitectural arrangement showed that: a) before the onset of stage I (14-day-old embryos) the cortex consists mainly of typical fibroblasts (F) and a few blastic (Pr?) cells. Later in this stage I, a poorly defined cortical framework is made up of typical fibroblasts, few cortical branching (CB) cells of the epithelial variety (which seem to be derived from Pr cells) and CB cells of the fibroblast-like variety. These cells are interspersed with mature and immature lymphocytes. b) Allometric stage II of the cortex is characterized by the presence of very thin and long cytoplasmic processes from CB cells of both epithelial and fibroblast-like varieties. The arrangement of CB cell profiles, visualized in electron micrographic montages, is remarkably similar to that of the ME cells profiles which are known to form a cytoreticulum. We thus propose that the mature follicular cortex is endowed with a cellular framework forming wide interstices in which packed mature lymphoid cells are lodged.