Peroxisomes and Related Particles in Animal Tissues

Morphometric (strictly stereologic) methods, based on simple mathematical formulae and elementary statistical principles, permit the synthesis of quantitative models having the coordinates of three-dimensional space, of organelle, cell, and tissue structures. This provides a sounder basis than has previously been available for the detailed comparison of the results of structural investigations with those obtained by other techniques, e.g., physiology or biochemistry. After a brief outline of the methods of determining volume and area, the estimation of numbers of objects is considered in more detail. The influence of fixatives upon results and the use of correction factors for various systematic errors are discussed. A summary of the available data on various differentiated organs in steadystate is provided, with emphasis on the liver. A description of the changes of cellularity in liver during the life cycle and in response to various stimuli (e.g., hormones, nutrition pharmaceuticals, etc.) is followed ...

Stereology of Cellular Reaction Patterns

For histologic differential diagnosis of fibrotic and cirrhotic liver changes in early infancy Zellweger's cerebro-hepato-renal syndrome has to be considered. A case is reported where a female newborn failed to thrive and developed severe muscular hypotonia, defective intelligence, and seizures. At an age of 12 months an open biopsy was taken from the enlarged liver. Biochemical tests for disorders of carbohydrate metabolism were negative. The light microscopic examination showed severe fibrosis, lobular disarray, and single cell necroses. Neither siderin nor bile pigment could be detected. There were no changes of the small bile ducts and no signs of inflammation — the child died at 18 months. A postmortem needle biopsy of the liver showed the advanced stage of micronodular cirrhosis. The electron microscopic examination of the first biopsy revealed hypertrophy of smooth endoplasmic reticulum, probably induced by anticonvulsive drugs. The mitochondria showed an increase in the density of their matrix and in the number of sometimes tubular cristae. In accordance with reports in literature, no regular peroxisomes (microbodies) could be found in the hepatocytes. Only a very few profiles with an average diameter of 0.16 μm looked like rather small peroxisomes. The cytoplasmic volume fraction of those organelles, however, amounted to 3×10−5 which is only 1/500 of the normal value in human hepatocytes. Although the significance of the absence of peroxisomes is not yet definitively proved, the term ‘Peroxisome Deficiency’ is proposed as a name which probably is more closely related to the pathogenetic mechanism than the hitherto usual designation cerebro-hepato-renal syndrome.

Licht- und Elektronenmikroskopische Leberbefunde beim Cerebro-Hepato-Renalen Syndrom nach Zellweger (Peroxisomen-Defizienz)

A comparative study has been carried out on the micro-localization of catalase in mouse tissues subsequent to treatment with a representative range of hypolipidemic drugs. A commonality of effect was shown by clofibrate (ethyl-α-p-chlorophenoxyisobutyrate), Wy-14,643 (4-chloro-6-[2,3 xylidino)-2-pyrimidinylthio] acetic acid), RMI-15,414 (5-tetradecyloxy-2-furancarboxylic acid) and aspirin (acetyl salicylic acid), in that treatments with each of these drugs was associated with the release of peroxisomal catalase into the cytoplasmic compartment of liver and kidney. It was also noticeable that this increased cytosolic activity was characterized by the presence of an ‘aged’ form of the enzyme with different mobility and activity characteristics to that of the peroxisomal enzyme. Possible molecular bases for these effects and their relationship to peroxisomal biogenesis are discussed.

Sequential alterations in the micro-localization of catalase in mouse liver after treatment with hypolipidemic drugs.

Introduction Autolysis is very often a reason for cell damage and is also superimposed on many other cell damages. Already one hour of autolysis causes serious changes in cell metabolism, which can be demonstrated morphometrically. Material and Methods Experiments were made with 10 male adult Wistar rats. 5 animals were for control purposes and 5 animals had to undergo a 1-hour's autolysis. The morphometric analysis of the liver parenchymal cells was based on the information of Weibel et al. (1968) with the help of a computer program. Results and discussion The consequence of the drop in energy caused by autolysis is an enlargement of the liver cell which is possibly due to a breakdown of the energy-dependent ionic pumps. One of the earliest observable cell changes is a so-called “Kern- wandhyperchromatosis” and chromatin condensation within the nuclei, whereby the Kernwandhyperchromatosis is seen to be a direct consequence of the increase in lactate and decrease of pH. ATP-sufficiency causes a disturbed function of mitochondrial membranes. The mitochondria are swollen, the number of mitochondrial grana is clearly reduced. An enlargement of the mitochondrial outer membrane takes place by folding while the surface of mitochondrial cristae remains unchanged. As a consequence of the altered membrane activities also the peroxisomes swell at reduced numerial density. At unchanged total volume of RER the surface of the granulated membranes of the RER decrease by 50%. This decrease caused by ribosome detachment of the granulated membranes corresponds to the enlargement of the degranulated membrane parts of the endoplasmic reticulum. The vesiculation is caused by an unspecific damage of cytoplasm. While the density of its volume and the membrane surface remain unaltered, the SER also shows a tendency to small vesiculation caused by an unspecific damage of cytoplasm. The increase in number and volume of the lysosomes and vacuoles of unknown origin speaks for a lysosomal activity. The cell compartment responsible for protein synthesis shows the most impressive morphometric and morphologic changes, which eventually can be explained by a decrease of protein synthesis which is needed to obtain enough energy for a well operating physiological equilibrium.

Einfluß einer einstündigen Autolyse auf die quantitative Zytoarchitektur der Rattenleberzelle (Eine ultrastrukturell-morphometrische Studie)

Das Reaktionsmuster der Leber-Peroxysomen (= Microbodies) im Verlaufe einer Zellschädigung

Introduction Even small quantities of lead inhibit the respiratory chain and the hemoglobin synthesis as well as the gluconeogenesis. Lead is concentrated in mitochondria and lysosomes. Therefore, it was of interest to analyse morphometrically the adaptability of liver parenchymal cells of juvenile rats to lead overload. Material and Methods 20 10-day-old male Wistar rats were used — During 2 weeks, 15 of these animals were injected i. p. 0,2 ml of a 1% lead acetate solution. Afterwards they were seperated from their mothers and given free access to food and tap water. During 2 additional weeks lead acetate was added to the tap water. 5 untreated rats served as controls. After 4 weeks the animals were sacrified. Morphometric analysis was made according to Weibel et al., 1969. Results After 4 weeks of lead overload, nuclear invaginations and intranuclear lipid inclusions occur. Giant lysosomes contain osmiophilic granular material and damaged mitochondria. Fingerprint-like mebrane whorls can be observed. The number of mitochondria per unit volume of cytoplasm decreases without changes in mean volume of mitochondria. The total surface of cristae per unit cytoplasmic volume increases by 20%. The RER increases its mebranes and volume by 50%. The volume of the free ribosomes increases, too. SER and lysosomes lose part of their volume. Discussion Under the influence of a 4 week lead overload a change in nuclear morphology occurs. The number of mitochondria decreases probably due to blocked chondriogenesis. The proliferation of cristae membranes is considered a consequence of a disintegrated membran formation. The quantitative changes of the endoplasmic reticulum and in the number of free ribosomes (polysomes) as well as the fingerprint-like membrane whorls indicate an interference of lead with protein synthesis.

H.P. Rohr

Papers

Das Reaktionsmuster der Leber-Peroxysomen (= Microbodies) im Verlaufe einer Zellschädigung

Einfluß einer Bleibelastung auf die quantitative Cytoarchitektur der Leberzelle juveniler Ratten