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F Dumont

Publications and source records attributed to F Dumont.

At least 19 recordsLinked to original sources
PubMed1992

Analogs of cyclosporin A modified at the D-Ala8 position.

The conversion of [2-deutero-3-fluoro-D-Ala8]cyclosporin A (1) to a dehydroalanine analog [delta-Ala8]cyclosporin A (2) was achieved with lithium diisopropylamide in THF at low temperature. This dehydro compound is a useful intermediate for the preparation of position 8 analogs of cyclosporin A formed from it by the conjugate addition of thiol compounds. NMR conformational studies have provided evidence for the restoration of D-stereochemistry in the modified Ala8 residues. The preparation of several of these cyclosporin analogs and their bioactivities are described.

Animals↗
PubMed1991

Is cyclophilin involved in the immunosuppressive and nephrotoxic mechanism of action of cyclosporin A?

In this report we have approached two questions relating to the mechanism of action of cyclosporin A (CsA). First, we address whether the major cytosolic protein for CsA, cyclophilin, is directly involved in mediating the immunosuppressive activity of this drug, and, in particular, whether inhibition of this protein's peptidyl-prolyl cis-trans isomerase (PPIase) activity results in inhibition of murine T cell activation. Second, we ask whether the nephrotoxicity observed with CsA is related to inhibition of PPIase-dependent pathways in cells other than lymphocytes. Using a series of 61 cyclosporin analogues, we generally found a good correlation between cyclophilin binding and immunosuppressive activity for the majority of analogues analyzed. However, a number of compounds of distinct structural classes were found that could interact with cyclophilin but were much less immunosuppressive than expected. The inability of these analogues to inhibit lymphocyte activation could not be explained by their failure to enter the cell and bind to cyclophilin under the conditions used in the cellular assays. Surprisingly, a nonimmunosuppressive analogue, MeAla-6, which bound well to cyclophilin and was active as a PPIase inhibitor, did not induce renal pathology in vivo. Furthermore, another analogue, MeBm2t, which was immunosuppressive in vitro, possessed little or no activity as a PPIase inhibitor. These findings pose serious questions concerning a direct role of cyclosporin in mediating CsA's immunosuppressive and nephrotoxic activities. In addition, they raise doubts about whether PPIase has a direct function in lymphocyte signal transduction.

Amino Acid Isomerases↗
PubMed1979

Peanut agglutinin (PNA)-binding properties of murine thymocyte subpopulation.

Surface receptors for peanut agglutinin (PNA), a lectin with D-galactose specificity, were detected on mouse thymocytes using fluorescence microscopy. Depending on mouse strain, 69-85% of unseparated thymocytes could thus be characterized as PNA+. Electrophoretic fractionation of thymocytes from normal or immunosuppressive drug-treated donors revealed an inverse relationship between PNA-binding properties and cell electrophoretic mobility (EPM). Thus, all thymocytes recovered in the lowest EPM fractions were strongly PNA+ whereas those in the highest EPM fractions were in the majority PNA-. Most of the cells collected in the intermediate EPM range were PNA+ but staining with the fluoresceinated lectin appeared weaker than for the low EPM thymocytes. Reciprocal experiments in which thymocytes were separated by PNA-mediated aggregation into fractions with different affinities for the lectin and then subjected to physical analysis, definitely established that PNA+ cells are of lower EPM than PNA- cells and that these two cell types also differ in size distribution. These data show that the four physical subpopulations of thymocytes previously described present distinctive PNA-binding properties: Th1 and Th2 cells can be classified as strongly PNA+, Th3 cells as less intensely PNA+, and Th4 cells as mostly PNA-.

Agglutination Tests↗
PubMed1979

T and B lymphocytes in pituitary dwarf Snell-Bagg mice.

The lymphocyte composition of the thymus and spleen from weaned (4 month old) hypopituitary dwarf Snell-Bagg mice were compared to those of their phenotypically normal littermates and of hormone (somatotropic hormone plus thyroxine)-treated individuals. Detection of cells bearing receptors for peanut agglutinin, physical analysis and measurement of in vitro reactivities to phytohaemagglutinin and concanavae intra-thymic lymphocyte population of dwarf mice. Examination of spleen-cell suspensions demonstrated a slightly higher frequency of T lymphocytes (Thy 1-2+ alpha-Naphthyl esterase+, high electrophoretic mobility) and lower frequency of B lymphocytes (surface immunoglobulin+, low electrophoretic mobility) in dwarf mice than in control mice. The degree of splenocyte responsiveness to T- and B-cell mitogens, however was similar in the two mouse types. High mobility (T) splenic cells were found to exhibit a smaller modal volume in dwarf mice (110 micron3) than in control mice (122 micron3) but this difference was not corrected by hormone administration. More pronounced were the quantitative differences between the spleens of hormone-deficient and normal mice. Thus, when expressed as a function of body weight, the numbers of splenic T and B lymphocytes in untreated dwarf mice were about half the corresponding values in hormone-reconstituted or normal littermates. These data suggested that in adult life, developmental hormones exert little direct effect on the thymus lymphocytes but influence the size of the pool of both peripheral T and B lymphocytes.

Animals↗
PubMed1978

Differential effect of hydrocortisone on lymphocyte populations in the mouse spleen.

The cellular composition of the spleen from CBA mice was investigated two days after administration of increasing doses of hydrocortisone acetate (HC), this using the presence of surface-immunoglobulin and the electrophoretic mobility as criteria for identification of lymphocyte populations. The B cell content was found to decrease more rapidly than did the T cell content. However, a significant diminution of the modal volume of both B and T cells was observed which suggests that HC acted similarly on each of these lymphocyte compartments by removing the larger elements. On the other hand, the in vitro reactivities to the B cell mitogens LPS and PPD were strongly depressed by HC injection while the reactivities to the T cell mitogens Con A and PHA remained relatively unchanged. Therefore, HC treatment appears to affect both B and T lymphocyte populations in the mouse spleen but the former to a greater extent than the latter.

Animals↗
PubMed1977

Electrokinetic properties and mitogen responsiveness of mouse splenic B and T lymphocytes following hydrocortisone treatment.

CBA mice recieved a single intraperitoneal injection of hydrocortisone acetate (OHC) in a dose of 125 mg/kg body weight. At various times therafter, electrophoretic mobility (EPM), surface immunoglobulin (SIG) and in vitro DNA synthetic reactivity to concanavalin A (ConA), phytohemagglutinin (PHA), lipopolysaccharide (LPS) and tuberculin (PPD) were investigated on splenic lymphocytes. OHC was found to deplete rapidly the spleen to a minimum of 18% of control cellularity by day 4 posttreatment. At this time, the proportions of low mobility (LM) and SIG-bearing lymphocytes (B cells) were reduced respectively to 28% (control 54%) and 20% (control 45%). The proportion of high mobility (HM) lymphocytes (T cells) was increased to 72% (control 45%). While the mean EPM of LM cells (0.71) was only slightly and transiently reduced, that of HM cells was significantly augmented (1.24) over control value (1.16). This latter finding was interpreted as indicating the selective removal by OHC of a T cell subpopulation with a mean EPM around 1.10. Changes in mitogenic responsiveness were consistent with these alterations of B and T cell compartments. Despite a marked drop in spontaneous 3H-thymidine uptake, the absolute response to T cell mitogens ConA and PHA remained relatively unchanged. By contrast, the reactivity to B cell mitogens LPS and PPD was strongly depressed. Starting by day 12, regeneration and normalizaiton of lymphocyte populations proceeded slowly and were not achieved before day 26-34.

Animals↗
PubMed1977

Changes in the electrophoretic mobility of mouse lymph node lymphocytes during ontogeny.

The electrokinetic properties of peripheral lymph node (LN) cells from C3H and nude mice aged 1, 3 or 10 weeks, were investigated by means of preparative and analytical cell electrophoresis. Two groups of cells were distinguishable throughout the age interval examined. The first group, with low-mobility (LM) included the majority of surface-immunoglobulin positive lymphocytes, was predominant in athymic nude mice and is thus likely to represent B cells. The other group, with higher mobility (HM), was sensitive to anti-Thy 1-2 serum, made up the major LN population in C3H mice and normal nude littermates and thus probably corresponds to T cells. In C3H mice, the relative proportion of LM cells was found to increase with age of LN donors (from 9-22%). Moreover, significant alterations in the mean electrophoretic mobility (EPM) of both lymphocyte populations were detected in the course of development. While the EPM of LM cells diminished from 0-81-0-70 micrometer.s-1.V-1.cm, that of HM cells increased from 1-11-1-22 micrometer.s-1.V-1.cm as the animals grew from 1-10 weeks. These observations indicate a relationship between the degree of maturity of peripheral B- and T-cell populations and their electrokinetic properties.

Animals↗
PubMed1976

Dose-related effect of hydrocortisone treatment on the electrokinetic properties and mitogen responsiveness of mouse thymocytes.

The electrophoretic mobility (EPM) and the ability to synthesize DNA in vitro either spontaneously or in response to concanavalin A (Con A) and phytohemagglutinin (PHA) were investigated on thymocytes from adult female Swiss/B mice which had received intraperitoneally, 2 days previously, various doses (10-750 mg/kg body weight) of hydrocortisone acetate (OHC). A first group of thymocytes, highly sensitive to OHC, rapidly decreased in proportion following administration of increasing doses of OHC (10-125 mg/kg body weight) and included the totality of low-EPM thymocytes (EPM less than 1.0 mum sec-1 V-1 cm) together with about 70% of the high-EPM thymocytes encountered in the normal thymus. The second group of thymocytes (4% of the initial cellularity), which resisted to OHC at 125 mg/kg body weight and was only reduced by half with doses of OHC 6-fold larger, was composed essentially of high-EPM cells. The mean EPM of both groups tended to increase with increasing doses of OHC which suggests that among these two groups thymocytes are all the more OHC-sensitive as they possess a low surface charge. Spontaneous DNA synthesis, measurable on the first 24 h of in vitro cultivation, markedly dropped after treatment with OHC at doses higher than or equal to 62 mg/kg body weight. This loss of early spontaneous proliferation coincided with the disappearance of medium-EPM thymocytes. By contrast, proliferative response of thymocytes to mitogens was enhanced by OHC pretreatment of donors and roughly paralleled the enrichment in high-EPM cells. However, administration of the largest amounts of OHC diminished this mitogen responsiveness, although PHA reactivity was less affected than Con A reactivity.

Animals↗
PubMed1976

Electrokinetic properties of splenic lymphocytes from the low-lipopolysaccharide responder C3H/Hej mice.

Spleen cells from C3H/Hej mice (H-2k) respond poorly to the B-cell mitogen lipopolysaccharide in vitro as compared to the related strains C3H/Tif (H-2k) and CBA/Orl (H-2k). The electrokinetic properties of splenic lymphocytes from these 3 strains were investigated in parallel, in order to both quantitate low-mobility B cell and high-mobility T cell populations and measure their mean electrophoretic mobilities. C3H/Hej mice were found to possess the same proportion (55%) of LM cells as C3H/Tif and CBA/Orl mice. Therefore, the low LPS-responsiveness of C3H/Hej is not due to a numerical deficiency in B cells. Whereas the mean EPM of HM cells was identical in the 3 strains, that of LM cells was slightly (6%) but significantly (Student's t test, P less than 0.01) lower in C3H/Hej than in the high LPS-responder controls. This suggests that the membrane-structure required for activating interaction with LPS might contribute to B-cell electronegative surface-charge.

Animals↗
PubMed1975

Effect of treatment with cyclophosphamide on the electrophoretic mobility and mitogen responsiveness of mouse thymus cells.

Two days after a single intraperitoneal injection of cyclophosphamide (CY) in a dose of 300 mg/kg of body weight, the cellularity of the thymus from adult female CBA mice was reduced to 17% of its normal value. The electrophoretic mobility (EPM) analysis of the surviving cells revealed a decrease in the proportion of the slow-moving cells together with a significant diminution of their mean EPM. The proportion of fast-moving cells, which were shown to correspond to the hydrocortisone-resistant and mitogen-responsive pool of mature thymocytes, was correlatively increased by 2-3 fold. Despite this enrichment in cells with a high surface charge, the thymocytes from CY-treated mice exhibited a diminished reactivity "in vitro" to both concanavalin A and phytohemagglutinin. The possible significance of theses results is discussed with reference to the known mitostatic properties of CY.

Animals↗
PubMed1975

Electrophoretic mobility and surface immunoglobin of albumin gradient fractionated mouse spleen cells.

Spleen cells from normal CBA mice, containing B and T lymphocytes, cyclophosphamide-treated CBA mice, containing almost exclusively T lymphocytes, and athymic nudemice, containing only B lymphocytes, were fracitonated by differential flotation in adiscontinuous albumin gradient. In all three cases, four density fractions were regularly obtained. The electrophoretic mobility (EPM), which allows distinction betweenslow-EPM (B) cells and fast-EPM (T) cells and the presence of surface immunoglobulins (sIg) detectable by direct immunofluorescence, characterizing B lymphocytes, were investigated on these fractions. Both B and T cells were recovered throughout the gradient, but in different proportions. Thus, B cells (slow-EPM, sIg-bearing) were enriched in the light density fractions while T cells (fast-EPM)were more numerous in the denser fraction. The mean EPM of slow-moving cells decreased, whereas that of fast-moving cells increased, as their buoyant density increased. Less nude spleen (B) cells were found to bear sIg in the light density fractions than in the denser fractions. These findings suggest the existence of lymphocyte subpopulations with distinct physicochemical properties which might represent stages in the maturation and differentiation of B- and T-cell lineages.

Animals↗
PubMedDate not supplied

Effect of stimulation with bacterial lipopolysaccharide on the surface-charge of mouse B-lymphocytes.

Nude spleen (B) cells were cultivated in vitro in a serum-free medium, without or with lipopolysaccharide (LPS) and their surface-charge was measured by cell electrophoresis. In the absence of LPS, surface-charge did not vary significantly with time, whereas, in the presence of LPS a biphasic modification was observed. Thus, after 4 hours of culture with LPS, surface-charge was diminished by 14%. Subsequently, when DNA synthesis and blast formation were activated, it increased by up to 19-23% over control value, whether LPS was present continuously in the medium or had been eliminated by washing after 4 hours of incubation.

Animals↗