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Biomedical subjects

J J Russo

Publications and source records attributed to J J Russo.

25 records · Page 2Linked to original sources
PubMed1990

Na(+)-K(+)-ATPase in adipocyte differentiation in culture.

Differentiation of 3T3-L1 cells from a fibroblast to an adipocyte phenotype results in an approximately 50% decline in Na(+)-K(+)-ATPase activity and ouabain-sensitive 86Rb uptake. Kinetic analysis revealed a K 1/2 for Na+ of approximately 14 mM, a Km for ATP of approximately 0.4 mM, and maximal activation by sodium dodecyl sulfate at a 0.05 (wt/wt) detergent/protein ratio in both mature fibroblasts and adipocytes. Both fibroblasts and adipocytes exhibited Na(+)-K(+)-ATPase activity with an inhibition constant (Ki) for ouabain of approximately 10(-4) M. In addition, adipocytes exhibited a second component representing 30% of total activity with a Ki of approximately 5 x 10(-7) M. The emergence of biphasic ouabain inhibition kinetics in adipocytes raised the possibility of a change in alpha-subunit isoform composition with cytodifferentiation. This inference was evaluated by isoform-specific mRNA analysis (Northern blots) and by alpha-isoform-specific immunoassays (Western blots). Northern blots revealed a modest decrease in mRNA alpha 1, a striking increase in mRNA alpha 2, and a significant loss of mRNA beta content with differentiation of fibroblasts to adipocytes. By immunoassay, fibroblasts exhibited the alpha 1-isoform. Adipocytes exhibited an admixture of alpha 1- and alpha 2-isoforms, with alpha 2 being the more abundant isoform. There was no one-to-one correspondence either between the mRNA isoform and alpha-subunit abundances or between alpha-subunit abundances and enzymatic activity, suggesting that regulation occurs at multiple levels in this system. Findings indicate, however, that a shift in alpha-isoform composition accompanied by a change in ouabain inhibition kinetics occurs with cytodifferentiation.

Adipose Tissue↗
PubMed1989

A cytochrome P450 immunochemically related to P450c,d (P450I) localized to the smooth microsomes and inner zone of the guinea pig adrenal.

In addition to their capacity for steroid synthesis, guinea pig adrenal microsomes have a well documented ability to metabolize foreign compounds. The capacity for metabolism of foreign compounds is localized to the smooth endoplasmic reticulum-filled cells of the inner zone. However, it has not been clear whether they possess cytochrome P450(s) specific for this function, distinct from the two known steroid hydroxylases, P450(21) and P450(17)alpha. Multiple prominent protein bands in the mol wt range of known cytochrome P450s are seen on sodium dodecyl sulfate gels of guinea pig adrenal microsomes. Most are more intense in smooth microsomes, where the concentration of cytochrome P450 is highest. However, one band (52K) appears unique to the smooth microsomes. This band is also characteristic of microsomes obtained from the inner zone. This protein and two others (54K and 50K) are concentrated in the membrane pellet after carbonate treatment of the microsomes, indicating that they are integral membrane proteins. All three decrease in intensity after treatment of the animals with spironolactone, a compound known to cause depletion of adrenal cytochrome P450s. On Western blots of microsomal proteins the 54K and 50K proteins react with antibodies specific for P450(17) alpha and P450(21), respectively. The 52K protein, characteristic of the smooth microsomes and inner zone, does not react with anti-P450(21) or anti-P450(17) alpha, but does react with polyclonal antibody raised against microsomal cytochrome P450s induced by methylcholanthrene in rat liver (P450c,d). These results suggest that there is at least one additional cytochrome P450 in adrenal microsomes which is immunochemically distinct from P450(21) and P450(17) alpha. Its localization to the smooth microsomes and inner zone microsomes correlates with the high activity for ethylmorphine metabolism detected in these fractions. This suggests that this cytochrome P450, which is immunochemically related to members of the P450I subfamily, may be associated with the ability of guinea pig adrenal microsomes to metabolize foreign compounds.

Adrenal Glands↗
PubMed1987

Characterization and use of polyclonal antibody to Na+,K+-ATPase: immunocytochemical localization in salt glands of the duck.

The amount of Na+,K+-ATPase of the avian salt gland increased concomitantly with plasma membrane surface area during salt feeding of ducklings (adaptation), and both enzyme content and membrane surface area decreased upon return to fresh water (deadaptation). In a further study of the enzyme, a marker for plasma membrane biogenesis, polyvalent antibodies were raised to the denatured alpha-subunit of the purified ATPase. Antisera did not inhibit enzymatic activity but immunoprecipitated the phosphorylated intermediate of the alpha-subunit. Furthermore, the alpha-subunit, which was not glycosylated, was immunoprecipitated from homogenates of tissue slices metabolically labelled with [35S]-methionine, using antisera raised against either duck salt gland or dog kidney alpha-subunit. The former antisera also recognized the alpha-subunit in the brain, heart, kidney, liver, intestine and skeletal muscle of the duck. Immunocytochemistry with the antisera raised to the duck salt gland alpha-subunit revealed reaction at basolateral as well as apical plasma membrane in the duck salt gland principal cells, with essentially no deposits on peripheral cells, fibroblasts, erythrocytes, endothelial cells and neural elements. Within the principal cells, immunolabelling was also detected on small vesicles, multivesicular bodies and lysosomes; deposits on extracellular debris and vesicles in the lateral and lumenal spaces were also apparent. The labelling patterns were qualitatively but not quantitatively similar in salt glands of control, adapted and deadapted ducklings, and are discussed in the context of a model for plasma membrane biogenesis and turnover in which degradative events may play a major role.

Adaptation, Physiological↗
PubMed1980

Stereological analysis of the guinea pig adrenal: effects of dexamethasone and ACTH treatment with emphasis on the inner cortex.

This paper describes the morphological responses of adult male guinea pig adrenals to dexamethasone (DEX) and adrenocorticotrophic hormone (ACTH), in both qualitative and quantitative terms. Most organelles and inclusions are affected, but their responses often vary in the different cell types examined: zona fasciculata externa and interna, and zona reticularis. Following DEX the volume of lipid droplets increases in cells of zona fasciculata externa but decreases in zona reticularis; smooth endoplasmic reticulum decreases in fasciculata externa but increases in reticularis. Following ACTH, exactly the opposite occurs. This strongly suggests differing functions for these subcellular entities in each cell type, particularly for the smooth reticulum, as well as for the cells themselves. The volume of the Golgi complex markedly decreases following DEX in all cells but increases only in zona fasciculata interna and zona reticularis following ACTH. These deeper cortical cells are known to secrete at least one sulfated steroid, dehydroepiandrosterone sulfate, and these changes in the Golgi complex strengthen the suggestion that the Golgi plays a role in sulfation of steroids. Mitochondrial volume and number decrease in all cells following DEX, supporting their role in steroidogenesis. Further decreases in their volume, accompanied by increases in their number following ACTH, may be related to a proliferation of mitochondria in response to ACTH. Changes in peroxisome volume and number, following DEX and ACTH, suggest a possible role for these organelles in steroid cell metabolism. Lysosomes decrease in volume in all cells following ACTH. This does not support the recently suggested concept that they play a role in steroid secretion.

Adrenal Cortex↗