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Biomedical subjects

F Loor

Publications and source records attributed to F Loor.

123 records · Page 7Linked to original sources
PubMedDate not supplied

Activity of some natural and modified (fluorescent) cyclosporins on T cells.

A simple test system for comparing the proliferation inhibition properties of cyclosporins (Cs) on susceptible T cells is described. This test was applied to a number of natural and chemically altered Cs-compounds, the latter from inactive, hypo-active and hyper-active Cs. These cyclosporins constituted standards for further comparison of the activities of new Cs such as fluorescent derivatives of the molecules, and especially for determining their mechanism of action. The use of Cs-sensitive (CsS) and Cs-resistant (CsR) cell lines permitted the distinction between specific cytostatic and generalized cytotoxic effects. Active--but not inactive--Cs were found to cause the appearance of refractive globular bodies in both CsS and CrR lymphocytes and in macrophages. When active fluorescent Cs were used, Cs detectable by fluorescence after one or several days was found to be concentrated within these globular bodies.

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PubMedDate not supplied

Basal and lipopolysaccharide-inducible membrane alkaline phosphatase of lymphoid cells from mice with immune system dysfunctions.

The expression of membrane alkaline phosphatase (mAlPase) activity is an enzymatic marker of activated but not resting B cells which can be used on unseparated lymphoid cell suspensions. It is higher in lymphoid cell suspensions from mice with higher proportions of B cells (athymic mice) or with more activated B cells (autoimmune mice) than in those of control mice.

Alkaline Phosphatase↗
PubMedDate not supplied

Cyclosporin-binding sites of murine sensitive and resistant lymphoid cell lines.

Cyclosporin (Cs)-binding sites on murine spleen lymphocytes and on Cs-sensitive (CsS) and Cs-resistant (CsR) cloned lymphoma lines were compared using a ditritiated derivative of cyclosporin C (d3H-CsC). All three types of lymphocytes displayed similar d3H-CsC-binding characteristics. There were no major differences in the d3H-CsC-binding sites in terms of their cell surface density (number per surface area), their affinity and their specificity (capacity to discriminate between different Cs forms). The presence of the presumably membranous Cs-binding site is therefore insufficient to confer susceptibility to Cs, and resistance can thus be obtained at a post-receptor level. With the CsS clone, there was a general correlation between the Cs-specific binding capacity and the Cs-specific biological activity inasmuch as Cs which were weakly or not at all cytostatic bound only very poorly to the d3H-CsC-binding site. Such a correlation could not be established in the case of a mixed spleen cell population; which implies that, in such a system, Cs processing might play a role in its activity. Binding to the receptor may be an early but only a permissive step in the mechanism of action of Cs.

Animals↗
PubMedDate not supplied

Membrane alkaline phosphatase activity: an enzymatic marker of B-cell activation.

The expression of membrane alkaline phosphatase (mAlPase) activity was studied on viable cells from mouse lymphoid organs. The low mAlPase activity level of ex vivo mouse spleen cells was markedly increased by in vitro culture in the presence of the direct B-cell mitogen lipopolysaccharide (LPS). This increase occurred nearly simultaneously with increased uptake of 3H-thymidine and an increased percentage of blasts in the culture. The T-cell-dependent B-cell pokeweed mitogen did not increase the mean level of mAlPase activity per cell, although there was an increase per culture. The T cell mitogen ConA did not cause an increase in mAlPase activity, although it was able to stimulate both cell proliferation and blast transformation. Several other mitogens and differentiating agents were tested, but did not detectably affect mAlPase expression. LPS high responder mouse strains C57BL/6 and CBA/J showed a higher LPS-induced mAlPase expression response to LPS than did LPS low responder strains BALB/c or CBA/N. These data suggest a preferential expression of mAlPase by stimulated cycling B cells. However, mAlPase expression appeared restricted to a subpopulation of cycling B cells and could not be elicited by every B-cell stimulus.

Alkaline Phosphatase↗