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Biomedical subjects

J Dornand

Publications and source records attributed to J Dornand.

At least 73 records · Page 4Linked to original sources
PubMed1984

Paradoxical production of mouse thymocyte activating factor by ouabain-treated human mononuclear cells.

At concentrations as low as 10(-7) M, the cardiotonic glycosteroid ouabain, a specific inhibitor of the membrane Na+, K+-ATPase, is known to inhibit in vitro human lymphocyte proliferation produced in mixed lymphocyte cultures or induced by various stimulating agents (PHA, Con A, PWM, soluble antigens), while mouse lymphocyte proliferation is unaffected at this concentration. Ouabain inhibits most of proliferative response parameters at all stages of the transformation. This observation prompted us to suggest that ouabain could also act through inhibition of interleukin production which is known to occur during the first hours after T-cell stimulation in the presence of monocytes. In order to check the possible influence of ouabain on interleukin production, conditioned media from stimulated human mononuclear cells, prepared in the presence or in the absence of inhibitor, were tested for their ability to promote a mouse thymocyte response to PHA. Instead of the expected inhibition, we found that ouabain, even at high concentrations (2 X 10(-6) M) enhanced the stimulatory effect and/or the production of murine thymocyte activating factor(s). Moreover conditioned media from serum-free cultures of unstimulated human mononuclear cells exposed for 24 hr to low ouabain concentrations (10(-8) to 10(-7) M) showed a high activating effect on the response of murine thymocytes to PHA. This soluble factor produced upon ouabain treatment is produced by adherent cells and appears to be functionally similar to interleukin 1.

Animals↗
PubMed1984

Characterization of peanut agglutinin receptors of murine thymocytes.

Murine thymocytes can be separated on the basis of their agglutinability by peanut agglutinin (PNA) into two broad subpopulations assimilated to immunoincompetent agglutinated PNA+ cells and immunocompetent nonagglutinated PNA- cells. Seven surface membrane components have been isolated by immunoprecipitation using rabbit anti-PNA IgG and Staphylococcus aureus bearing protein A, from PNA-coated radiolabeled immature cells. These components (apparent molecular weights of 180, 175, 130, 115, 65, 26, and 23 kDa) labeled by the galactose oxidase/tritiated sodium borohydride method and by 125I-iodination are glycoproteins which are PNA-receptor sites normally exposed on the surface membrane of PNA+ thymocytes. The nonagglutinated PNA- cells also possess on their surface unmasked receptors for the lectin (175-180 kDa) but in lower amounts. Neuraminidase treatment prior to galactose oxidase/tritiated sodium borohydride labeling shows that the majority of PNA receptors is present on the PNA-thymocyte surface but are masked by sialic acid residues on the terminal position of the oligosaccharidic chains.

Animals↗
PubMed1983

Cell affinity chromatography with ligands immobilized through cleavable mercury-sulfur bonds.

A new methodology for cell separation by affinity chromatography is described. We have conjugated the organomercurial mersalyl to trisacryl beads bearing primary amino groups. Thiolated ligands can be immobilized on this matrix through cleavable Hg-S bonds. Two model studies of cell separation are reported: (i) concanavalin A thiolated with N-succinimidyl-3-(2-pyridyldithio)-propionate and immobilized on mersalyl-trisacryl; mouse thymocytes bound to Con A-mersalyl-trisacryl were eluted from the support by short thiol treatment which preserved cell viability; (ii) anti-dinitrophenyl antibodies modified with S-acetyl-mercaptosuccinic anhydride and immobilized on mersalyl-trisacryl; sheep erythrocytes, previously labelled with trinitrobenzene sulfonic acid, bound to this support and were easily recovered by thiol treatment without hemolysis. This methodology should overcome difficulties frequently encountered in cell affinity chromatography. Cell support multivalent interactions or high affinity of cell-ligand bindings often require drastic elution conditions which prevent viable cell recovery.

Animals↗
PubMed1982

Alamethicin or detergent permeabilization of the cell membrane as a tool for adenylate cyclase determination.

Treatment of mouse lymphocytes with very low concentrations of alamethicin or Lubrol PX induces spontaneous permeabilization of the plasma membrane to ATP and allows determination of adenylate cyclase activity in whole cells. The permeabilized cells retain responsiveness to hormones (isoproterenol, adenosine analogs) and to fluoride. The main advantage of this new method is that it does not require any homogenization step, and thus adenylate cyclase activities can be accurately and reproducibly measured with very low amounts of cells. It should be especially useful for the study of purified lymphocyte subpopulations.

Adenylyl Cyclases↗
PubMed1981

Unmasking of membrane enzyme activities and the problem of subcellular localization of adenylate cyclase in pig lymph node lymphocytes.

A large-scale purification of plasma membranes from pig lymph node lymphocytes is described. Centrifugation on a discontinuous sucrose density gradient was performed in a zonal rotor. Adenylate cyclase activity of untreated fractions displayed a profile different from that of plasma membrane enzymatic markers and was maximal at higher density. However, when latent adenylate cyclase was unmasked by Lubrol PX treatment, its maximum was shifted to lower density and was no longer significantly different from that of plasma membrane markers. These results are discussed in terms of cell surface topography.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Adenosine-induced cyclic AMP increase in pig lymphocytes is not related to adenylate cyclase stimulation.

Adenosine-cyclic AMP relationships have been studied in pig mesenteric lymph node lymphocytes. The early 2--3-fold increase in cyclic AMP accumulation elicited by adenosine and 2-chloroadenosine, an adenosine deaminase-resistant analogue, could not be correlated to similar effects on the adenylate cyclase activity of disrupted cell preparations, but rather to the competitive inhibition of the low Km (0.17 muM) cyclic AMP phosphodiesterase. The existence of adenosine receptors coupled to lymphocyte adenylate cyclase, which had been proposed by several authors, could not be confirmed by this study Adenosine-cyclic AMP relationships do not appear to be involved in concanavalin A stimulation of pig lymphocytes.

Adenosine↗
PubMed1978

Purification and properties of 5'-nucleotidase from lymphocyte plasma membranes.

5'-Nucleotidase is purified from lymphocyte plasma membranes by two affinity chromatographies. The first one, on Lens culinaris lectin-Sepharose 4B yields a fraction of twelve lectin-binding glycoproteins (lectin-receptor fraction). The second one on 5'-AMP-Sepharose 4B leads to pure enzyme. This enzyme is a glycoprotein with a molecular weight of 130 000; it gives a single band in polyacrylamide/dodecylsulfate electrophoresis and displays a very high specific activity (2500-3000 mumol Pih-1mg-1). Some properties of purified 5'-nucleotidase are similar to those of membrane-bound enzyme: substrate specificity, temperature dependence, effects of ions and SH-blocking reagents. Others are completely different for the two systems and these differences result from an interaction between the enzyme molecule and other Lens culinaris lectin binding proteins.

Animals↗
PubMed1978

Studies of (Na+ + K+)-sensitive ATPase activity in pig lymphocytes. Effects of concanavalin A.

(Na+ + K+)-ATPase activity is demonstrated in plasma membranes from pig mesenteric lymph nodes. After dodecyl sulfate treatment plasma membranes have an 18-fold higher (Na+ + K+)-ATPase activity, while their ouabain-insensitive Mg2+-ATPase is markedly lowered. A solubilized (Na+ +K+)-ATPase fraction, obtained by Lubrol WX treatment of the membranes, has very high specific activity (21 mumol Pi/h per mg protein). Concanavalin A has no effect on these partially purified (Na+ + K+)-ATPase, while inhibits (40%) this activity in less purified fractions which still contain Mg2+-ATPase activity.

Adenosine Triphosphatases↗