PubMed Health⌕ Search

Biomedical subjects

C Rampini

Publications and source records attributed to C Rampini.

At least 19 recordsLinked to original sources
PubMed1995

Stimulation of phosphatidylethanolamine synthesis during the last stages of the G1 phase in concanavalin A-activated human peripheral lymphocytes.

Phospholipid synthesis was investigated in concanavalin A-activated human peripheral lymphocytes up until 72 h following cell activation, i.e., during the G1 and S phases of the cell cycle. Using [32P]phosphate pulse experiments (5 h), striking differences were observed between phosphatidylethanolamine (PE) and phosphatidylcholine (PC) synthesis. Both the incorporation of [32P]phosphate into PE and the PE/PC incorporation ratio were greatly enhanced, 16-fold and 8-fold, respectively, after 48 h of incubation with the mitogen. This increase in PE synthesis was still observed when cell entry into the S phase was inhibited by an excess of concanavalin A; thereby it must be related to the late stages of the G1 phase. The stimulation of the incorporation into PE was the same for both [14C]ethanolamine and [32P]phosphate, therefore suggesting the involvement of the phosphoethanolamine synthesis pathway. Kinetics of continuous incorporation of [32P]phosphate into PE and PC indicated that the PE/PC net synthesis ratio was enhanced in activated cells, which corresponds to PE enrichment in lymphocyte membranes. The stimulation of PE synthesis in late G1 may be of importance for cell progression through the cell cycle by changing the membrane physical properties. Furthermore, it may serve as a test for checking lymphocyte reactivity to mitogens.

Cells, Cultured↗
PubMed1995

A monoclonal antibody against Meningococcus group B polysaccharides used to immunocapture and quantify polysialylated NCAM in tissues and biological fluids.

Polysialylated isoforms of neural cell adhesion molecule (PSA-NCAM) are transiently expressed in many tissues during development and in discrete areas of the adult central nervous system. In pathological situations, they are expressed by poorly differentiated tumor cells of neuroectodermal origin and by regenerating muscle. An ELISA is introduced here to estimate the relative concentrations of PSA-NCAM expressed by tissues or released into biological fluids. In this double-sandwich assay, an anti-PSA antibody (anti-MenB) was adsorbed onto plastic plates and permitted the immunocapture of PSA-bearing molecules. It is demonstrated that these molecules are major NCAM. The second antibody was directed against an amino acid sequence shared by NCAM isoforms in several species. The standard curves were established using Nonidet P40 extracts of human or mouse embryonic brain known to be rich in PSA-NCAM. The sensitivity of the assay allows for quantitation of PSA-NCAM in muscle during regeneration and in small samples of cerebrospinal fluid from patients with medulloblastoma metastasis.

Animals↗
PubMed1987

Effect of AY 9944 and chlorpromazine on Concanavalin A-induced stimulation of human lymphocytes.

Amphiphilic molecules AY 9944 and chlorpromazine (CPZ) inhibited DNA synthesis in Concanavalin A-stimulated lymphocytes in a dose-dependent manner. While AY 9944 strongly decreased 7-dehydrocholesterol conversion to cholesterol, CPZ did not significantly affect this reaction. Moreover, the inhibitory effect of AY 9944 and CPZ on DNA synthesis took place in the presence of cholesterol in the culture medium. These findings suggest that the mechanism of inhibition of DNA synthesis by AY 9944 or CPZ is not related to endogenous cholesterol synthesis or exogenous cholesterol supply. Results are discussed in relation to the amphiphilic properties of AY 9944 and CPZ and to the interaction of these drugs with membranes or other intracellular targets such as calmodulin.

Autoradiography↗
PubMed1984

Phosphate depletion decrease mitogen-mediated stimulation of phospholipid synthesis in human peripheral lymphocytes.

Concanavalin A-mediated stimulation of 32P-phosphate incorporation into phospholipids of human peripheral lymphocytes is comparatively studied in normal and phosphate-depleted media. In the phosphate-depleted medium, 2 hours after the start of cell activation, the stimulation sharply decreases for phosphatidylinositol (6.5-fold) and for phosphatidylcholine (in the latter case, the stimulation is even replaced by a slight inhibition of the incorporation). These results must be related to the rate-limiting effect of inorganic phosphate on ATP formation and thus on phospholipid synthesis, an effect which may be particularly pronounced when there is both phosphate depletion and cell activation.

Humans↗
PubMed1984

Changes in ganglioside metabolism during in vitro differentiation of quail embryo myoblasts.

The metabolism of gangliosides was studied during the in vitro differentiation of both normal quail myoblasts and myoblasts which have been transformed by a temperature-sensitive mutant of Rous sarcoma virus (RSV). These transformed cells can be maintained undifferentiated if incubated at 35 degrees C, but they will differentiate when shifted to 41 degrees C. (D. Montarras and M. Y. Fiszman (1983) J. Biol. Chem. 258, 3882-3888). The analysis of [14C]Glucosamine-labeled gangliosides by two-dimensional thin-layer chromatography reveals variations in the metabolism of the gangliosides during the process of differentiation. During the formation of myotubes, it was observed that the accumulation of GD1a is reduced, while the accumulation of GD3 is increased. Therefore, this results in the variation of the ratio GD3/GD1a which increases from 1.8 to 25 in the case of clones of transformed myoblasts, and from 0.5 to 1.7 in the case of uninfected myoblasts. These variations which have been observed seem to be specific of the myogenic differentiation since they cannot be reproduced when differentiation is inhibited by BUdR treatment or when fibroblasts reach confluency and are blocked in the G1 phase of cell cycle. Furthermore, the transformed myoblasts in vitro are shown to be a good model system since their gangliosides composition is very similar to that of muscle cells in vivo.

Animals↗
PubMed1978

[32P incorporation into phospholipids of EHSVi transformed fibroblasts, with regard to adherence to the support].

The rate of 32P incorporation into phospholipids of EHSVi transformed fibroblasts was studied by pulse experiments (2 hours) in cells which are detached from the support by trypsin and either maintained in suspension or replated and in the process of adhering. This is performed comparatively to cells in monolayers. Cells are taken during or after the log phase. Both global incorporation into phospholipids and, in the case of cells in log phase, percentage of incorporation into phosphatidylinositol are lowered, after detachment from the support, in suspended cells. They are stimulated by a new contact with the support. In the same conditions, percentages of incorporation into phosphatidylethanolamine and phosphatidylcholine remain at values they have in cells in monolayers. These values are characteristic of the physiological state of cells in monolayers, in relation with medium factors exhaustion.

Cell Adhesion↗
PubMed1978

Phospholipid metabolism of 3T3 mouse fibroblasts after serum stimulation and through the G1 and S cell cycle phases : incorporation and disappearance of 32P.

Phospholipid metabolism of 3T3 mouse fibroblasts has been studied after serum stimulation of arrested cells. The study of [32Pi] incorporation shows : a) in the case of PE and PC an early peak of incorporation in the G1 phase of the cell cycle, 6 hours after serum addition; b) in the case of PI an intense initial increasing of the incorporation which continues up to a S phase peak. The study of the disappearance of [32P] Phosphate from the different phospholipids points out: a) at the beginning of serum stimulation, an intense breakdown of PI, that continues through the G1 and S phases. Except at the onset, the breakdown of PI, is at any time exactly compensated for by synthesis : the two phenomena are closely linked; b) a synthesis of PE, from PC probably, at the G1 phase, 4 hours after the serum addition and the beginning of the chase experiment.

Animals↗
PubMed1978

[Characterization of the partial inhibition, by deficiency in serum factors, of multiplication of SV3T3 transformed fibroblasts].

Partial inhibition, by serum starvation, of multiplication of SV3T3 transformed fibroblasts was studied by cultivating cells in a medium containing 1% of serum. Two different and successive states are described: a first step, with a rate of multiplication for 24 hrs, which is lowered (2 instead of 3 in a normal medium containing 10% of serum) but which remains constant (i.e. exponential multiplication), the observed inhibition being reversed by normal medium; a second step, where the rate of multiplication for 24 hrs, decreases very fast, and which is not reversible.

Blood↗
PubMed1977

[Sensitivity of transformed EHSVi fibroblasts to the antibody-complement lytic system. Cooperation between the lytic units, and existence of a cellular defense].

The sensitivity of transformed EHSVi fibroblasts to the antibody-complement lytic system was evaluated, at various antibody concentrations (Ac), in conditions in which a variation of the lytic activity proportional to Ac3, 1 may be observed. This points out, not the expected cooperation between IgG molecules in activating C1 within a definite lytic unit, but a cooperation between the lytic units themselves, and therefore the existence of a cell defence.

Antibodies↗
PubMed1975

[Hydrolysis of diphosphatidylglycerol in situ in E. coli by activation of specific phospholipase D].

E coli cells are harvested at early stationary phase and, first, incubated in phosphate buffer without energetic metabolites, conditions which invole the formation of an excess of diphosphatidylglycerol. If, in a second stage, they are cultivated again in normal medium, the diphosphatidylglycerol is metabolized very fast. It is mainly hydrolyzed, by activation of a specific phospholipase D, with formation of phosphatidylglycerol and phosphatidic acid. The latter is immediatly metabolized in bacteria in phosphatidylglycerol and phosphatidylethanolamine, both about equal in amount.

Culture Media↗