c-Myc and Mxi1 immunoreactivities in the calcifying areas of the epiphyseal-plate cartilage matrix of growing rats.

We looked for the protooncogene protein, c-Myc, its dimerization partner, Max, and the repressors of its transactivation activity, Mad1 and Mxi1, in the epiphyseal-plate cartilage matrix of growing rats by immunocytochemistry in the electron microscope. c-Myc and Mxi1 immunoreactivities were found in the calcifying areas of the cartilage matrix only. There was no immunolabeling in response to anti-Max or anti-Mad1 antibodies.

Structural characteristics of supramolecular assemblies formed by guanidinium-cholesterol reagents for gene transfection.

We have recently discovered that cationic cholesterol derivatives characterized by guanidinium polar headgroups are very efficient for gene transfection in vitro and in vivo. In spite of being based on some rationale at the molecular level, the development of these new synthetic vectors was nevertheless empirical. Indeed, the factors and processes underlying cationic lipid-mediated gene transfer are still poorly understood.

Expression of Bcl-2 protein in the epiphyseal plate cartilage and trabecular bone of growing rats.

The protooncogene protein, Bcl-2, protects cells from apoptosis and ensures their survival in vitro by inhibiting the action of the apoptosis-inducer, Bax. Its expression in proliferative and long-lived cells in vivo also indicates that it protects against cell death. The chondrocytes of the epiphyseal plate cartilage undergo a series of maturation steps and deposit mineral in the cartilage matrix before dying.

Expression and subcellular localization of the Myc superfamily proteins: c-Myc, Max, Mad1 and Mxi1 in the epiphyseal plate cartilage chondrocytes of growing rats.

The changes in the expressions of the protooncogene protein c-Myc, its dimerization partner Max and the competitive inhibitors Mad1 and Mxi1 during the terminal differentiation of chondrocytes in vivo were investigated by immunocytochemistry. The four immunoreactivity patterns in the epiphyseal plate cartilage of growing rats, as they appeared under the light microscope, showed differences in protein expression level and intracellular distribution, with the chondrocyte developmental stage. c-Myc immunoreactivity was intense and mainly in the nuclei of proliferative chondrocytes.

Ultrastructural localization of alpha-parvalbumin in the epiphyseal plate cartilage and bone of growing rats.

The distribution of the calcium-binding protein, alpha-parvalbumin, in the epiphyseal plate cartilage and bone of growing rats was examined by electron microscope immunocytochemistry of undecalcified samples. Parvalbumin immunoreactivity, as revealed by gold particles, increased with maturation of chondrocytes and was maximal in the zone of calcification. It was found in the cytoplasm of chondrocytes, osteoblasts and osteocytes, corroborating light microscope observations.

Localization of the Ca(2+)-binding alpha-parvalbumin and its mRNA in epiphyseal plate cartilage and bone of growing rats.

This study describes the localization of alpha-parvalbumin, in undecalcified tibial epiphyseal cartilage and bone of growing rats by immunocytochemistry in the light microscope, and of parvalbumin mRNA by in situ hybridization. They were compared to the distribution of the calbindin-D9K and its mRNA in rat epiphyseal cartilage. All the chondrocytes of the epiphyseal cartilage were parvalbumin-immunopositive, but there was no parvalbumin immunoreactivity in the uncalcified or calcified extracellular cartilage matrix.

Calbindin-D28K and -D9K and 1,25(OH)2 vitamin D3 receptor immunolocalization and mineralization induction in long-term primary cultures of rat epiphyseal chondrocytes.

Rat epiphyseal plat chondrocytes were grown on glass slides, as nonadhering monolayer cultures for up to 6 weeks. Chondrocyte growth, differentiation and maturation, matrix formation and mineralization, and the temporospatial distribution of the vitamin D-dependent calcium-binding proteins, calbindin-D9K and -D28K, and the 1,25(OH)2D3 receptor (VDR), were all monitored. Chondrocytes became confluent in 2.

Zonal variations of types II, IX and XI collagen mRNAs in rat epiphyseal cartilage chondrocytes: quantitative evaluation of in situ hybridization by image analysis of radioautography.

The spatial-temporal distribution of the mRNAs for type IX and type XI collagens were compared to that of type II collagen mRNA in the tibial epiphyseal plate cartilage of normal growing rats. The mRNAs were detected by in situ hybridization with radio-labelled specific probes and visualized by radioautography. The areas covered by the resulting silver grains were quantified by computer assisted image analysis.

Relationship between vitamin D status and deposition of bound calcium in skeletal muscle of the rat.

The effects of vitamin D on the intramuscular distribution of total and bound calcium, phosphate and on available cytosolic calcium, were investigated in skeletal muscle. Total calcium and phosphorus were measured on ashed subcellular fractions of muscles from vitamin D-repleted and vitamin D-deprived rats. The variations in available calcium were followed by determining the activities of calcium-sensitive enzymes in isolated cytosol.

Impact on energy metabolism of quantitative and functional cyclosporine-induced damage of kidney mitochondria.

In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies).

The reoxidation of cytochrome P-450 by paraquat inhibits aldosterone biosynthesis from 18-hydroxycorticosterone.

Paraquat is an artificial electron carrier that captures electrons from reduced cytochrome P-450 instead of the natural acceptors, thus decreasing the concentration of reduced mitochondrial cytochrome P-450. In the present study, paraquat inhibited the biosynthesis of aldosterone from 18-hydroxycorticosterone by mitochondria from duck adult adrenal gland, under aerobic conditions. Since paraquat did not induce any change in the absorption spectrum of highly purified cytochrome P-450 11 beta, the possibility of a displacement of steroid by the drug is ruled out.

Stimulation of oxygen consumption at the cytochrome A3 level inhibits aldosterone biosynthesis from 18-hydroxycorticosterone.

A mitochondrial preparation from duck adrenal gland was used, under aerobic conditions, to show that the oxygen requirement for the last step of aldosterone biosynthesis (transformation of 18-hydroxycorticosterone into aldosterone) is at the cytochrome P-450 level only. Vitamin C and tetramethyl-p-phenylene-diamine (TMPD) were used to increase oxygen consumption at the cytochrome a3 level, thereby decreasing its availability to cytochrome P-450. The vitamin C plus TMPD system acts as an 'oxygen trap'.

Degenerative processes in skeletal muscle of Cd2+-treated rats and Cd2+ inhibition of mitochondrial Ca2+ transport.

In rat skeletal muscle, chronic exposure to 50 ppm Cd2+ in drinking water produced both ultrastructural and functional damage, which took place successively and increased gradually with duration of treatment. Ultrastructurally, the first effect was a regression of the sarcoplasmic reticulum, mitochondrial cristae, and glycogen granules. Then, the number of mitochondria diminished and a degeneration of myofilaments appeared.

Mitochondria alterations in Cd2+-treated rats: general regression of inner membrane cristae and electron transport impairment.

Young adult rats absorbed 50 p.p.m.

Relation between energy metabolism in mitochondria and conversion of 18 hydroxycorticosterone to aldosterone in adrenals.

The purpose of this study was to see whether there was any link between conversion of 18 hydroxycorticosterone to aldosterone and mitochondrial energy metabolism. In vitro incubations of duck adrenal mitochondria with 18 OH B were used in this study. Results show that 18 oxidation is inhibited by compounds blocking electron transport (antimycin A, cyanide, rotenone, amytal).

[In vitro calcium binding by isolated brush border vesicles of rat jejunum and ileum].

A new procedure for isolation of the Rat jejunum and ileum brush border vesicles is described. Several calcium transport conditions have been established. A previous incubation with ATP induces an increased calcium binding.