A characteristic membrane protein of liver peroxisomes inducible by clofibrate

In sodium dodecyl sulfate polyacrylamide electrophoresis the membranes of rat liver peroxisomes show nine main protein bands (40 000--100 000 dalton); the 40 000-dalton polypeptide cannot be resolved from the membrane by deoxycholate. Treatment of the rats with clofibrate largely increases this protein and another one (about 80 000 dalton) in the peroxisomal but not in the endoplasmic reticulum membrane. Proliferation of peroxisomes seems to be connected with the insertion of specific proteins into the membrane.

Beta-oxidation in peroxisomes of brown adipose tissue

Peroxisomes and mitochondria from brown adipose tissue of the rat were separated by differential pelleting and isopycnic gradient centrifugation. Both fractions oxidized palmitoyl-CoA with comparable specific activities. Unlike the mitochondrial beta-oxidation the peroxisomal activity was not influenced by carbon monoxide. Peroxisomal beta-oxidation together with carnitine acetyl-transferase, which is also located in peroxisomes, might be involved in chemical thermogenesis by delivering acetyl groups to the mitochondria.

Catalase positive particles from pig lung. Biochemical preparations and morphological studies

In pig lung tissue catalase positive particles (CPs) are abundant especially in type II pneumocytes and in Clara cells. In both cell types they occur as circular, oval or elongated membrane profiles surrounding a moderately electron dense matrix lacking a crystalline core. In Clara cells and in part of type II pneumocytes they are located as individual particles without any evident morphological relation to other cell organelles. In part of type II pneumocytes 5-8 particles are forming a group and their close relation to agranular endoplasmic reticulum cisterns is evident. The particles can be purified from lung homogenates by fractionated pelleting and subsequent rate sedimentation in a sucrose gradient using a zonal rotor. The catalase rich fraction bands in the middle of the gradient whereas cytochrome oxidase and part of the acid phosphatase sediments at its heavy end. A second part of acid phosphatase stays at the light end of the gradient and--according to morphological control--seems to correspond to lamellar bodies of the type II pneumocytes. The purified catalase positive particles do not contain hydroxyacid and D-aminoacid oxidases thought to be characteristic H2O2 producing enzymes of peroxisomal systems. The buoyant density of the particles (d = 1.195 g/cm3) is lower than that of liver peroxisomes. Cytochemical controls of the peroxisomal pellets exhibit the particles partly uniformly filled with reaction product, partly irregularly stained.

[Recurrence of pseudotumour cerebri (intracranial hypertension) after renal transplantation (author's transl)]

The case report is presented of a 24-year-old male who developed the clinical signs and syptoms of pseudotumour cerebri (intracranial hypertension) twice during the course of protracted rejection 1 and 4 months after renal transplantation. Clinically, headache, nausea, hypertensive crisis and, finally, severe coma with an acute mid-brain syndrome was observed. Neurologically a mild left-sided hemiparesis was found on the second occasion. Examination of the fundi revealed bilateral papilloedema. Electroencephalograms showed pathological changes of a diffuse nature, later followed by abnormal delta range activity in the right frontotemporal projection. The withdrawal of corticosteroid therapy may have been responsible for the pseudotumour cerebri in this case.

Preparation of peroxisomes from carp liver by zonal rotor density gradient centrifugation

Peroxisomes from carp liver can be separated by isopycnic density gradient centrifugation in sucrose. Without reaching complete sedimentation equilibrium, the purification by this method is quite successful. There is a 40-fold enrichment of catalase, the peroxisomal marker, with a total yield of 27%. No pretreatment of animals is necessary for separation from lysosomes, which, besides high fragility, show lower buoyant densities than peroxisomes. The enzyme content of carp liver peroxisomes is similar to that of rat liver, with the exception of alpha-glycerophosphate dehydrogenase, which in this tissue is a completely soluble cytoplasmic enzyme. Total activities are much lower than in the rat, for the characteristic peroxisomal oxidases the difference being in the range of one order of magnitude.

Enzymic and morphological studies on catalase positive particles from brown fat of cold adapted rats

Brown adipose tissue of normal and cold-adapted adult rats has been investigated morphologically and cytochemically. In thin-sections catalase-positive particles appear as circular, oval or elongated profiles lying either as single particles or forming groups. Biochemical studies on peroxisomal enzymes show an increase of catalase activity to the tenfold amount after cold adaptation. The tissue is devoid of D-aminoacid oxidase and glycolate oxidase, while low activities of middle-chain-alpha-hydroxyacid oxidases could be detected. The catalase-positive particles were purified by differential and is lower than that of the liver peroxisomes. Enzymic investigations of the fractions render it probably that particles contain carnitine acetyltransferase, whereas they are lacking NAD-dependent glycerophosphate dehydrogenase. The pellets derived from the gradient centrifugation have been checked morphologically for purity. After performing DAB-cytochemistry for identification of the peroxidatic activity of catalase, most of the particles were shown to be structurally intact and homogeneously filled with reaction product.

Effect of clofibrate application on morphology and enzyme content of liver peroxisomes

Male albino rats (Sprague Dawley) were fed for 2-6 weeks on a diet containing 0.75% clofibrate. Liver cell fractions obtained from these animals were assayed for peroxisomal enzymes. In the cell homogenate the catalase activity was doubled, whereas the activity of urate oxidase was found to be only slightly depressed. The activity of carnitine acetyltransferase increased several times. In liver peroxisomes purified by isopycnic gradient centrifugation the specific activity of urate oxidase decreased appreciably showing that peroxisomes formed under the proliferative influence of clofibrate are not only modified with respect to their morphological characteristics but also to their enzymic equipment. This is also obvious from the changes in peroxisomal carnitine acetyltransferase activity which was enhanced by clofibrate to more than the fivefold amount. In purified mitochondria this enzyme was even more active: clofibrate advances both, the peroxisomal and the mitochondrial moiety of carnitine acetyltransferase. Morphological and cytochemical studies showed an increase in the number of microbodies and as compared to the controls microbodies were lying in groups more frequently. Small particles located closely adjacent to "normal" sized peroxisomes were found particularly after short feeding periods. While the number of coreless microbodies increased studies gave no clear evidence for an increase in marked shape irregularities of the peroxisomes.

Phenacetin and the liver. The influence of phenacetin in acute and chronic doses on membrane-bound mitochondrial enzymes in the rat

Following the administration of phenacetin in single and in multiple high doses, enzymes bound to the inner mitochondrial membrane of the liver were determined. Acute doses of phenacetin (75% of oral LD50) failed to produce any effect. The chronic administration of phenacetin provoked a small but statistically significant decrease in the TD-trnashydrogenase activity. This observation indicates that liver damage may occur in patients with phenacetin abuse.

An experimental study of acute and chronic effects of phenacetin on the rat kidney, using clinical-chemical and biochemical methods

In rats, changes in urinary enzymatic activities (AP, SP, LAP, beta-GLU, MUR) were recorded following the administration of phenacetin in acute doses (4.75 and 7.15 mmol/kg). Urinary AP and LAP activities were measured over 77 days in which 3.35 mmol phenacetin/kg were given daily. The results revealed immediate and delayed effects of phenacetin, depending upon the quality of the drug used. In the chronic series, changes in urinary enzymatic activities were less pronounced. Concomitant biochemical investigations of kidney cell fractions revealed the occurrence of mitochondrial damage under the influence of chronic phenacetin administration. Following acute doses of phenacetin, destructive alterations in the plasma membrane of kidney cells were encountered. Investigations of serum enzymatic activities 24 h after phenacetin administration did not reveal any significant changes.

Influence of subtotal hepatectomy on peroxisomes and peroxisomal enzymes of rat liver and isolated liver cell fractions

The activities of peroxisomal enzymes of rat liver were followed 1 to 10 days after subtotal (60-70%) hepatectomy in homogenates prepared from regenerating livers and in cell fractions isolated from them. Catalase activity was found to be depressed in the total liver homogenate (H) as well as in the mitochondrial (M) and soluble (S) fractions, while it did not change appreciably in the microsomal (Mc) and lysosomal (L) fractions. Alpha-hydroxyacid oxidase behaved in a similar fashion. In contrast to these enzymes, urate oxidase activity remained unchanged in H, whereas it was decreased in M and increased in L and Mc during the first 5 days after operation. These results agree well with the assumption that microbody proliferation is initiated by the fragmentation of large peroxisomes. The different relations of peroxisomal enzyme activities during regeneration time are discussed with respect to the possible existence of various kinds of peroxisomes with different enzyme equipments and with different turnover rates. Biochemical examinations ions were paralleled to morphological and histochemical studies. An early increase in number of peroxisomes was found to occur during the first day after partial hepatectomy, which is accompanied by decrease in particle size. During the first mitotic wave (24-36 hrs post op.) the number of peroxisomes per cell was reduced to about the half. After this time number and size of the particles began to increase. Positive staining of ribosomes was frequently observed in the vicinity of peroxisomes after the application of the cytochemical catalase reaction (alkaline diaminobenzidine medium). This phenomenon is interpreted to represent rather a diffusion artifact than the cytochemical identification of newly synthesized catalase.