Michel Dauça

Peroxisome through cell differentiation and neoplasia

Summary— Peroxisomes are essential in cellular metabolism as their dysgenesis or defects in single enzymes or impairment of multiple peroxisomal enzymatic functions have been found in several inherited metabolic diseases with serious clinical sequelae. The assembly and formation of these cytoplasmic organelles constitute a major and intringuing research topic. In the present study the biogenesis of peroxisomes and the developmental patterns of their enzymes have been reviewed during embryonic and/or post‐embryonic ontogenesis of lower (amphibians) and higher (avians, mammals) vertebrates. In developing vertebrates, epithelial cell differentiation is accompanied by increases in frequency and size of peroxisomes. The tissue‐specific expression of peroxisomal enzymes contributes substantially to the biochemical maturation of epithelial cells. The relationship between biogenesis of peroxisomes, expression of peroxisomal enzymes and structural and functional cellular phenotype has also been investigated in differentiating epithelial cells along the crypt‐villus axis of the adult rat intestine. Cytochemical studies at the ultrastructural level have provided evidence that peroxisomes are already present in proliferating cells of the intestinal crypt region before they begin to differentiate. Migration and differentiation of intestinal epithelial cells from crypt to villus compartments are marked by significant increases in number and size of catalase‐positive structures. Increasing activity gradients from crypt to surface areas are found for the peroxisomal oxidases examined (enzymes of the peroxisomal β‐oxidation system, d‐amino acid oxidase and polyamine oxidase). Thus, peroxisomes are more and more involved in oxidative metabolic pathways as intestinal epithelial cells differentiate. Finally, we have analyzed the peroxisomal behaviour in human neoplastic epithelial cells. The presence of peroxisomes has been cytochemically revealed in human breast and colon carcinomas. Peroxisomal enzyme specific activities are significantly lower in human breast and colon carcinomas than in the adjacent healthy mucosa. Furthermore, a relationship is found between the specific activities of some peroxisomal enzymes and the histological tumour grades.

Peroxisomes in human colon carcinomas : a cytochemical and biochemical study

SummaryThe presence of peroxisomes and their enzymic content were investigated and compared in healthy and neoplastic human colon epithelial cells using cytochemical studies at the ultrastructural level as well as biochemical analyses. Catalase-positive organelles were found to be more numerous in normal than in colonic neoplastic cells. Biochemical assays revealed that no Daminoacid oxidase or L-α-hydroxyacid oxidase activity was detected in normal or tumor tissues. The specific activities of catalase, fatty-acyl CoA oxidase and enoyl-CoA hydratase/3 hydroxyacyl-CoA dehydrogenase (the so-called peroxisomal bifunctional enzyme of the β-oxidation system) were found to be diminished in carcinoma cells compared with the control tissue. The fall in catalase activity correlated well with tumor stage according to Dukes, suggesting that this peroxisomal enzyme could be used as a potential prognostic marker.

The effect of clofibrate on amphibian hepatic peroxisomes

Summary— Liver peroxisomes of two anuran amphibian species, Rana esculenta and Xenopus laevis, were studied in untreated and in clofibrate‐treated adults by means of complementary technical approaches, ie, ultrastructural cytochemistry, cell fractionation and marker enzyme activity assays. In untreated adults, hepatic peroxisomes were found to be very scarce in Xenopus when compared to Rana. Activities of catalase, d‐amino acid oxidase and of the three first enzymes of the peroxisomal β‐oxidation system were detected in the light mitochondrial fractions enriched in peroxisomes and prepared from livers of both species. Administration of clofibrate at a daily dose level of 60 mg (Rana) and 90 mg (Xenopus) during ten days induced a drastic peroxisome proliferation in Rana hepatocytes but had no visible effect on the hepatic peroxisomal population of Xenopus. The catalase activity and the peroxisomal β‐oxidation system of liver cells were enhanced in Rana as well as in Xenopus. The hepatic d‐amino acid oxidase specific activity was increased in Rana whereas it remained rather constant in Xenopus. Taking advantage of the behaviors of Rana and Xenopus hepatic peroxisomes, the molecular mechanisms of clofibrate induction are now investigated in the target liver cells of the two amphibian species.

Peroxisomes and Peroxisomal Enzymes in the Human Fetal Small Intestine

The appearance and development of peroxisomes and the expression of their enzymes in the human fetal intestine have been investigated between 11 and 22 weeks of gestation. In the youngest samples (11-16 weeks of age), cytochemistry at the ultrastructural level revealed the presence of rare, mostly circular peroxisomes. From 16 weeks of gestation onwards, an increase was noted in the number of peroxisomes. Two peroxisomal types were distinguished: round to oval forms and elongated and/or tailed organelles. Biochemical assays revealed that total and specific intestinal catalase activities increased gradually between 11 and 20 weeks of gestation. The activity of fatty acylCoA oxidase, the first enzyme of the peroxisomal beta-oxidation system, was detectable as early as 11 weeks of gestation. Thereafter, total and specific activities of the enzyme increased steadily. Activities of other peroxisomal oxidases (D-amino acid oxidase, L-alpha-hydroxyacid oxidase) appeared more slowly in the fetal intestine during the period studied. This investigation establishes the presence and the morphological changes that occur in intestinal peroxisomes during human fetal development as well as the developmental patterns of associated enzymes.

Evaluation of the elements in the intestinal epithelial cells of rat during the development by x-ray microanalysis

A Cen t r i f uga l Displacement P rope r t t (CDP), responsible fo r the GV t rans loca t ion in oocytes prevented from undergoing resumption of meiosis was shown to be corre la ted wi th a motive force provided by the microf i lament cytoskeleton and counteracted by a Prote in Kinase A-enhanced s t a b i l i z a t i o n of the cytoplasmic microtubular network (CHTC) (Alexandre et a l . , 1989). The se t t ing up of CDP is shown to take place concomitant ly wi th the meiot ic competence and the motive force to be dependent on ATP production and on pro te in synthesis and phosphorylat ion. In order to know whether a s i m i l a r mechanism is involved in movement of other membrane bounded organel les, we fol lowed the d i s t r i b u t i o n of c o r t i c a l granules and mitochondria by f luorescent microscopy wi th spec i f i c probes, LCA-biotin-Texas red-s t rep tav id in and Rhodamin 123 respec t ive ly . Desorganisat ion of the microtubular network by colcemid in both maturing and metabol ica l ly GV-arrested oocytes (by e i the r isobuty lmethylxanthine (IBMX) or 6-dimethylaminopurine (6-DMAP)) has no e f fec t on the submembranar d i s t r i b u t i o n of the c o r t i c a l granules but induces dispersal of mitochondria i n i t i a l l y located in the per inuc lear region. On the cont rary , c~tochalasin D exerts no e f fec t on the mitochondria d i s t r i bution but induces a huge desorganisat ion of ~hecor t i ca l granules d i s t r i b u t i o n . In re l a t i on to i t s cytoskeleton reorganisat ion e f f ec t , TPA induces an asymetric aggregation of both organel les in the v i c i n i t y of the nuclear membrane. In conclusion, c o r t i c a l granules d i s t r i b u t i o n as wel l as GV t rans locat ion i s dependent on a microf i lament mediated mechanism whi le mitochondrta are relocated by the more c lass ica l microtubule-associated motor molecules.

Immunolocalization of Fibronectin and Laminin in the Amphibian Intestine During Spontaneous and Triiodothyronine‐Induced Metamorphosis

Fibronectin and laminin were detected by indirect immunofluorescence in the intestine of Alytes obstetricans (anuran amphibian) during triiodothyronine (T3)‐induced metamorphosis and spontaneous post‐embryonic development. Fibronectin was first detected between a small number of connective tissue cells. As T3‐treatment and spontaneous development progressed, fibronectin became detectable as a fine network extending throughout the whole thickness of the connective tissue and particularly in the core of the developing epithelial folds. During the first week of T3‐treatment and throughout the spontaneous larval period, laminin was present as a linear band within the basement membrane. Between day 6 and 12 of hormonal treatment, an increase in the laminin fluorescent staining was noted. After hormonal treatment for two weeks and at the end of spontaneous metamorphosis, laminin staining was localized within the basement membrane of the folded epithelium and around muscle fibers. These observations indicate that variations in the density and distribution of extracellular matrix molecules are closely related spatiotemporarily to the structural changes occurring in the connective and muscle tissues of the intestine during metamorphosis.