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Biomedical subjects

A Trouet

Publications and source records attributed to A Trouet.

At least 109 records · Page 6Linked to original sources
PubMed1979

Fate of plasma membrane during endocytosis. I. Uptake and processing of anti-plasma membrane and control immunoglobulins by cultured fibroblasts.

The uptake and processing by cultured rat embryo fibroblasts of control rabbit immunoglobulins (C IgG) or IgG directed against plasma membrane constituents (anti-PM IgG), and labeled with fluorescein (F) or with radioactive acetate (A), have been investigated by cell fractionation and immunological techniques. Both F and A anti-PM IgGs become bound to the cell surface, by a process that is slow, but largely temperature-independent. In the presence of an excess of high-affinity antibodies, binding reaches an absolute limit which corresponds to extensive coating of the plasma membrane. The anti-PM IgGs remain attached to the membrane for at least several days, even at 37 degrees C, with no significant transfer to lysosomes or degradation. In contrast, C IgGs are handled very differently by the fibroblasts, and their fate is strikingly affected by the type of labeling used. AC IgG is taken up slowly, at a rate proportional to its concentration, and is subsequently broken down in what appears to be lysosomes. Part of the AC IgG also binds to the plasma membrane. FC IgG is taken up many times faster than AC IgG, though with the same strict linearity as a function of concentration. Most of the FC IgG taken up is stored in cytoplasmic granules which behave like lysosomes. For reasons that are not understood, only about half of the stored FC IgG can be broken down. Cells exposed simulatnaously to AC IgG and FC IgG, or to A anti-PM IgG and FC IgG, handle each type of IgG in its characteristic fashion. Kinetic analysis of these results indicates that Ac IgG could be taken up by fluid endocytosis, but that FC IgG must be interiorized by a selective mechanism, presumably adsorptive in nature. That anti-PM antibodies remain stably bound to the plasma membrane and do not interfere with the uptake of FC IgG is interpreted to indicate either that two distinct membrane domains are involved in the two phenomena, or that membrane patches coated with anti-PM IgG participate in endocytosis, and are recycled back to the cell surface after delivering their contents intracellularly.

Animals↗
PubMed1979

Fate of plasma membrane during endocytosis. II. Evidence for recycling (shuttle) of plasma membrane constituents.

Cultured rat embryo fibroblasts were first allowed to store for 24 h fluorescein-labeled goat immunoglobulins directed against rabbit immunoglobulins (F anti-R IgG), and were subsequently exposed for 24 h to [(3)H]acetylated rabbit immunoglobulins known to bind to the cell membrane either specifically (anti-plasma membrane IgG: A anti-PM IgG) or unspecifically (contol IgG: AC IgG). As a result of immunological interaction between the two antibodies (no effect was found if the cells had been preloaded with control goat FC IgG), a substantial portion of the stored F anti-R IgG was unloaded from its intracellular storage site, appearing in the medium in the form of soluble immune complexes with rabbit A IgG. Part of the unloaded F anti-R IgG also was recovered in association with the plasma membrane, but only when A anti-PM IgG was used. In addition, significant reverse translocation of AC IgG from plasma membrane to lysosomes or some related intracellular storage compartment was also observed. With A anti-PM IgG, this translocation was less marked and affecte at the same time the plasma membrane marker 5'- nucleotidase. Cells that had stored horseradish peroxidase (HRP) simultaneously with F anti-R IgG did not unload HRP when exposed to A anti-PM IgG. These results support strongly, though not unequivocally, the concept that plasma membrane patches interiorized by endocytosis are recycled, or shuttled, back to the cell surface. In the framework of this concept, recycling antibody-coated membrane is taken to serve as vehicle for the selective intracellular capture and extracellular discharge of immunologically bound F anti-R IgG. The alternative explanation of regurgitation triggered off by immune complexes is considered less likely in view of the lack of HRP unloading.

Animals↗
PubMed1979

Endocytosis and chloroquine accumulation during the cell cycle of hepatoma cells in culture.

Variations of endocytic and of lysosomal functions during the cell cycle have been investigated in synchronized hepatoma cells (derived from Morris hepatoma 7288c) by following the cellular uptake of horseradish peroxidase, dextran (mol wt. 70,000), and chloroquine. Cell fractionation and cytochemistry show that in asynchronously growing cells exposed for 1 h to 5 mg/ml peroxidase, the bulk of the enzyme taken up by the cells is found in phagosomes. By using the same experimental system with synchronized HTC cells, large variations of endocytosis are observed during the cell cycle. Peroxidase uptake is lowest during mitosis, increases 5--10 times during G1 phase, reaches a plateau, and finally decreases at the end of S phase and during G2 phase. A similar evolution is observed for the uptake of dextran (0.5 or 1 mg/ml), but it is likely that a significant part of the polysaccharide is still associated with the pericellular surface after 1 h. Moreover, dextran is transferred more slowly than peroxidase to lysosomes. Cellular accumulation of chloroquine is related to intralysosomal pH or to the buffering capacity of lysosomes. Our results show that this drug is taken up more rapidly during G1 and S phases while the rate of accumulation is lowest in mitotic cells. The results are discussed in relation to the modifications of the physical properties of lysosomes during the cell cycle observed previously by cell fractionation and electron microsocopy, and to the possible role of lysosomes in the initiation of mitosis. Cyclic changes of endocytosis in actively dividing cells are demonstrated by our observations and may induce large differences in the uptake rate of extracellular substances.

Animals↗
PubMed1979

Clinical studies with daunorubicin-DNA and adriamycin-DNA complexes: a review.

The clinical results presently available on the use of daunorubicin (DNR)-DNA and Adriamycin (ADR)-DNA are reviewed in light of the most recent experimental data regarding the anthracycline-DNA complexes. Three randomized trials indicate that ADR-DNA is superior to DNR-DNA in combination therapy for acute lymphoblastic leukemia, that DNR-DNA equals DNR in the treatment of acute nonlymphoblastic leukemia, and that ADR-DNA might be equal to ADR in the chemotherapy for anaplastic bronchogenic carcinoma. Increasing evidence suggests that the anthracycline-DNA complexes are less cardiotoxic than the corresponding free drugs.

Animals↗
PubMed1979

Pharmacokinetic, toxicologic, and chemotherapeutic properties of detorubicin in mice: a comparative study with daunorubicin and adriamycin.

We have studied the stability, pharmacology, toxicology, and therapeutic activity in mice of detorubicin, a new semisynthetic derivative of daunorubicin. In vitro, detorubicin remains stable under acidic conditions while it is very quickly hydrolyzed into Adriamycin under neutral pH conditions. In vivo, the hydrolysis of detorubicin into Adriamycin occurs in the bloodstream a few minutes after iv injection. The tissue distribution of detorubicin in mice is, however, very distinct from that observed after administration of Adriamycin and daunorubicin. The therapeutic effect of detorubicin on the sc implanted L1210 leukemia is superior to that of daunorubicin and at least equal to that of Adriamycin. Detorubicin can thus be considered a prodrug of Adriamycin with very distinct pharmacokinetic and perhaps therapeutic properties.

Animals↗
PubMed1979

Effects of daunorubicin and doxorubicin, free and associated with DNA, on hemopoietic stem cells.

We have compared daunorubicin (DNR)-DNA with free DNR and doxorubicin (DOX)-DNA with free DOX for their effects in vivo in mice on pluripotent stem cells and granulocytic committed stem cells. Dose-survival, time-survival, and recovery curves were obtained after one i.v. injection of either drug. The dose-survival curves of colony-forming units-spleen (CFU-S) and colony-forming units-committed stem cells (CFU-C) were exponential in shape with both agents. DNR-DNA appeared more toxic to the hemopoietic precursor cells than did free DNR. In contrast, DOX-DNA was less toxic toward CFU-S and as toxic as DOX toward CFU-C. Time-survival curves indicated a minimum level of CFU-S and CFU-C at about 33 hr. After that, the recovery of CFU-S was rapid for DNR-treated mice but remained below 50% of the controls on Day 12 for the DNR-DNA-treated group. In mice previously given injections of DOX or DOX-DNA, the recovery of the CFU-S was more protracted in time with a better recovery in mice treated with DOX-DNA. Both DNR and DNR-DNA induced an initial CFU-C decrease followed by a rapid but transient rise with a maximum on Day 4 after chemotherapy. On Day 12, the CFU-C recovery was still incomplete in both DNR- and DNR-DNA-treated mice. In the groups treated with DOX, the CFU-C recovery was more important after DOX-DNA complex than after free DOX. The results are discussed in view of the "lysosomotropic chemotherapy" hypothesis.

Animals↗
PubMed1979

Cellular uptake and subcellular distribution of two non-steroidal anti-inflammatory drugs: indomethacin and ketoprofen.

The cellular uptake and intracellular localization of indomethacin and ketoprofen were studied on rat embryo fibroblasts in vitro. The two drugs are taken up by the cells, but to a lesser extent for ketoprofen than for indomethacin. Inside fibroblasts ketoprofen is rapidly metabolized whereas indomethacin seems accumulated as such inside the cells. After different incubation times, ketoprofen is partly associated to the cytosol and partly to another cellular component, probably the endoplasmic reticulum. Indomethacin on the other hand is almost exclusively distributed inside the cytosol. No clear association of the two drugs can be found with the lysosomes.

Animals↗
PubMed1978

Analytical fractionation of cultured hepatoma cells (HTC cells).

Homogenates of HTC cells have been fractionated by differential centrifugation (in four particulate fractions: N, M, L, P, and a supernatant S) or isopycnic banding in linear sucrose gradients. On this basis, the following subcellular organelles may be characterized: (i) Mitochondria, detected by cytochrome oxidase and succinodehydrogenase, are collected in the M and L fractions, and equilibrate, as a narrow band, at a median buoyant density of 1.18 g/cm3. (ii) Lysosomes, detected by the latent hydrolases beta-glycerophosphatase and N-acetyl-beta-glucosaminidase, are largely sedimented in the M and L fractions, and display a broad density distribution pattern with a median value of 1.17 g/cm3. This density is decreased or increased after cultivation of the cells in presence of Triton WR-1339 or Dextran 500, respectively. The behavior of cathepsin D is somewhat at variance with that of the two other hydrolases. (iii) Plasma membrane is tentatively detected by alkaline phosphodiesterase I. Largely recovered in the P fraction, this enzyme equilibrates at a median density close to that of the lysosomal hydrolases; the bulk of cholesterol and about half of the leucyl-2-naphthylamidase are closely associated with alkaline phosphodiesterase I; HTC cells do not contain typical 5'-nucleotidase. (iv) Catalase-bearing particles, of high buoyant density (1.22 g/cm3) are present, but 30-40% of the catalase is also found readily soluble. NADPH- and NADH: cytochrome c reductase, and RNA show more complex distributions. It is suggested that the former enzyme is associated with the endoplasmic reticulum; as in liver, NADH reductase activity is shared between the endoplasmic reticulum and the mitochondria; half of the RNA is associated with free ribosomes of polysomes. True glucose-6-phosphatase could not be detected.

Animals↗
PubMed1978

Cellular uptake and metabolism of daunorubicin as determined by high-performance liquid chromatography. Application to L1210 cells.

The metabolism of daunorubicin (DNR) to daunorubicinol and daunomycinone in murine leukaemia cells has been examined by means of high-performance liquid chromatography. A rapid and efficient extraction method has been developed that permits the recovery of the drug and its metabolites from cell homogenates. By means of high-performance liquid chromatography daunorubicinol and daunomycinone have been separated from DNR and the intracellular concentration of the compounds determined. The method developed is very rapid and sensitive, and amounts as small as 30 pg of DNR can be detected. The results indicate that the aldo-keto reductase is not very active in L1210 cells in culture, the main intracellular product found being DNR.

Animals↗