Biomedical subjects

F Pothier

Publications and source records attributed to F Pothier.

25 records · Page 2Linked to original sources

PubMed1989

Rabbit blastocoelic fluid regulation of tumor-cell proliferation in vitro.

To determine whether rabbit blastocoelic fluid could inhibit tumor-cell proliferation, day-9 and day-12 embryonic fluids, together with autologous and homologous sera, were collected from pregnant or pseudopregnant rabbits and tested against 13 different cell lines and on human carcinoma cells in primary culture. An inhibitory effect on cell proliferation was observed in the presence of blastocoelic fluids, but not with homologous or heterologous sera. This suppression was higher with samples collected at day 12 than at day 9 of pregnancy. No such inhibition could be detected on one-cell rabbit embryos or on freshly prepared uterine stromal or myometrial cells. In addition, the inhibitory activity on tumor cells was completely reversible upon removal of the fluids. Incorporation of 3H-thymidine, 3H-uridine and 35S-methionine revealed that, in the presence of blastocoelic fluids, both DNA and RNA syntheses were rapidly inhibited. Inhibition of protein synthesis did not occur before 24 hr of treatment. We conclude that rabbit blastocoelic fluid suppresses the proliferation of tumor cells via inhibition of RNA and DNA synthesis by a process which may involve the expression of growth-suppression gene(s).

Animals↗

PubMed1989

The effects of vasopressin and related peptides on osmoregulation in Amoeba proteus.

We describe the effects of arginine-vasopressin (AVP) and five related peptides on the contractile vacuole, the osmoregulatory organelle of the fresh water Amoeba proteus. Arginine-vasopressin, lysine-vasopressin, and SKF 101926, a synthetic antagonist of vasopressin, cause a significant increase in the rate of output of the contractile vacuole. Deamino-vasopressin (dAVP), oxytocin, and arginine-vasotocin have no such activity, although dAVP interferes with the action of AVP when present in equimolar concentration. Relatively high concentrations are required and the effect of active peptides is readily reversible. When the normal, hypotonic medium (a synthetic pond water) is replaced by isotonic sucrose, the action of AVP on the vacuole is abolished. Thus vasopressin is believed to act by increasing permeability of the Amoeba plasma membrane to water.

Amoeba↗

PubMed1989

Transgenic mice carrying the mouse mammary tumor virus ras fusion gene: distinct effects in various tissues.

Transgenic mice carrying the v-Ha-ras oncogene under the control of the mouse mammary tumor virus long terminal repeat were produced. These mice exhibit several phenotypes: mammary tumors, bilateral hyperplasia of the harderian lacrimal gland, primary bronchio-alveolar lung adenocarcinoma, and splenomegaly. High levels of the transgene RNA were detected in mammary, harderian, and lung tumors. Accumulation of cells of the myeloid lineages was found in enlarged spleens. This phenotype may represent an indirect effect of v-Ha-ras expression on myeloid progenitors. Our data illustrate the cell-specific effects of v-Ha-ras.

Animals↗

PubMed1984

ATP and the autonomy of the contractile vacuole in Amoeba proteus.

Contractile vacuole function in amoebae treated with immobilizing (5 mM) and nonimmobilizing (0.125 mM) concentrations of ATP has been studied. In ATP-immobilized amoebae, most vacuolar parameters are accelerated, especially the rate of output which passes from 30 to 70 micron3/sec. This favors the concept of an autonomous vacuole, fully functional in the absence of any bulk contribution to it from remote points of the cell. A lower concentration of ATP (0.125 mM), which does not inhibit movement, causes a still greater acceleration of vacuolar function. Work is in progress to elucidate the site and mode of action of exogenous ATP on Amoeba.

Adenosine Triphosphate↗

PubMed1981

[A controlled-temperature microscope stage for extended observations of living materials (author's transl)].

We have designed a controlled-temperature stage for the observations of live microorganisms under all magnifications of the compound microscope. The use of water-immersion objectives eliminates the need for a cover-slip and permits interventions such as liquid medium changes, microsurgery or the insertion of microelectrodes. Simple in design and relatively inexpensive this stage has an observation area of 50 X 75 mm.

Microscopy↗

PubMed1978

[Scotopic visual pigments in 3 Percidae: Perca flavescens, Stizostedion vitreum and S. canadense].

The scotopic visual pigments of three percids from Quebec waters, viz. the yellow perch (Perca flavescens), the walleye (Stizostedion vitreum) and the sauger (S. canadense), were studied in situ using a microspectrophotometer-computer complex. The difference spectra show that the three fishes possess a porphyropsin whose lambda max. is at 530 nm in the yellow perch, 533 nm in the walleye and at 536 in the sauger. This variation corresponds to the tendency of the visual pigments to fit the preferred environments. The three species studied also have different modes of life. The yellow perch inhabits mostly shallow, clear waters while the walleye and sauger prefer turbid waters. The retinal structure and responses also differ among them. Since the difference in lambda max. is so small, the differences in habitat and behaviour may be attributed to morphological differences in the retina rather than to its visual pigment content.

Adaptation, Biological↗

PubMedDate not supplied

An improved CAT assay for promoter analysis in either transgenic mice or tissue culture cells.

We have developed an improved method for determining CAT activity directed by stably (transgenic mice) or transiently (tissue culture cell lines) introduced CAT reporter gene constructs. The procedure is based on the use of a new buffer system which considerably increases the stability of the CAT enzyme during the preparation of the crude cell extracts. When compared to other procedures, our method enables an increase of up to 100-fold in the sensitivity of the assay, depending on the transgenic tissue tested. Furthermore, a strong increase (up to 23-fold) was also observed with various promoter/CAT constructs transiently transfected in established tissue culture cell lines. This increase in sensitivity provides a significant reduction in the time required to perform the CAT assay when strong promoters are studied (from 18 to 1 hr) and is also very useful for the analysis of CAT gene expression driven by weak promoters.

Animals↗