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Biomedical subjects

C Legrand

Publications and source records attributed to C Legrand.

At least 181 records · Page 10Linked to original sources
PubMed1979

Relationships among placental, uterine, and circulating concentrations of progesterone and fetal survival in the ovariectomized pregnant rat.

Pregnant rats were ovariectomized or sham operated on day 15 postcoitum. Four days later, progesterone was measured by RIA in peripheral and uterine vein plasma, in uteri, and in placentae. Maintenance of pregnancy was not critically affected by ovariectomy, since fetal survival was 65.7 +/- 5.1% (mean +/- SEM) despite a large decrease of peripheral plasma progesterone from 115.7 +/- 3.4 to 9.3 +/- 0.5 ng/ml. Peripheral and uterine vein plasma progesterone (8.3 +/- 0.9 ng/ml) were identical. In contrast, placental progesterone decreased only slightly, although significantly, from 27.3 +/- 1.3 to 20.3 +/- 1.0 ng/mg. The concentrations of uterine progesterone were variable and positively correlated with the concentrations of peripheral plasma progesterone. It was concluded that uterine progesterone originates from peripheral blood but not from placentae and that fetal survival is positively correlated with residual progesterone concentrations in peripheral plasma and in uterus but not in placentae.

Animals↗
PubMed1978

Binding of 14C-ADP to normal human and thrombasthenic platelet membranes. Study of the dissociation of the nucleotide from its receptors.

Normal and thrombasthenic platelet membranes are able to specifically bind 14C-ADP (12). According to the concentration of ADP present in the medium, 'high affinity binding sites' (Ka = 0.5 X 10(6) M-1 and 'low affinity-binding sites' (Ka = 0.05 X 10(6) M-1) can be recognized. In the present study, dissociation of ADP from the 'high affinity binding sites' was measured with six normal and with three thrombasthenic platelet membrane preparations. A 1:100 dilution was used to dissociate the membrane-bound 14C-ADP and the kinetics of the dissociation was determined. The same profile of dissociation (with T 1/2 = 4--10 min at 37 degrees C) was observed using normal or thrombasthenic membranes. With both preparations, the rate of dissociation was increased (up to T 1/2 = 1--3 min) when unlabelled ADP (at concentration higher than 10(-5) M) was added in the diluting medium. The results confirm the presence of normal ADP binding sites on thrombasthenic platelet membrane and possibly suggest the existence of cooperative interactions between the sites on normal as well as on thrombasthenic membranes.

Adenosine Diphosphate↗
PubMed1978

Histoenzymological studies of 3beta- and 17beta-hydroxysteroid dehydrogenases in the placentae and adrenal glands of bilaterally ovariectomized rats.

The distribution and activities of 5-unsaturated-3beta- and 17beta-hydroxysteroid dehydrogenases (HSD) have been studied during the pregnancy of normal and ovariectomized rats on days 17, 19 and 21 post coitum. No hormonal substitution was provided after bilateral ovariectomy on day 15 post-coitum. 5-Unsaturated-3beta-HSD was characterized with pregnenolone, 17alpha-hydroxypregnenolone and dehydroepiandrosterone as substrates; oestradiol-17beta and testosterone were used for the investigation of 17beta-HSD activity. With these substrates, it was found that the placental and adrenal activities and distribution of 5-unsaturated-3beta- and 17beta-HSD did not differ in ovariectomized and control rats and it is suggested that increased placental or adrenal steroidogenesis does not supplement deficient ovarian function in order to maintain pregnancy. In the pregnant rat, the ovaries do not control the activities of 5-unsaturated-3beta- and 17beta-HSD in the placenta.

17-Hydroxysteroid Dehydrogenases↗
PubMed1978

Acquired IgG antibody occurring in a thrombasthenic patient: its effect on human platelet function.

In subagglutinating amounts, an IgG antibody isolated from the plasma of a polytransfused thrombasthenic patient (L) inhibited ADP-, epinephrine-, collagen-, and thrombin-induced aggregation of normal human platelets. The inhibition of ADP-induced aggregation was strongly diminished following the prior incubation of the antibody with control human platelet stroma but not with the stroma prepared from the platelets of two different thrombasthenic patients. The IgG(L) did not affect the binding of 14C-ADP to control human platelet membranes and did not inhibit the ADP-induced shape change. Bovine factor VIIIVWF-induced agglutination and ristocetin-induced aggregation of control human platelets were not inhibited in the presence of the antibody. The IgG(L) strongly inhibited ADP-induced retraction of reptilase clot and thrombin-induced clot retraction. This antibody therefore induced a thrombasthenialike state in normal human platelets, suggesting that the antigenic site recognized by the antibody plays a central role in the later stages of the mechanism of platelet aggregation induced by physiologic aggregation-inducing agents.

Adenosine Diphosphate↗
PubMed1977

Histochemical distribution of delta5-3beta- and 17beta-hydroxysteroid dehydrogenases in hamster trophoblast.

The histochemical distribution of delta5-3beta- and 17beta-hydroxysteroid dehydrogenases was demonstrated in hamster trophoblast between Days 8 and 15 of pregnancy. The delta5-3beta-hydroxysteroid dehydrogenase activity in the ectoplacental trophoblast of 8-day embryos was demonstrated by use of delta5-pregnenolone and dehydroepiandrosterone as substrates; between Days 11 and 15, activity was demonstrated in the trophoblastic giant cells of the placenta and in the intra-arterial trophoblast cells when delta5-pregnenolone was the substrate. Between Days 11 and 15, 17beta-hydroxysteroid activity was present in the spongiotrophoblast, labyrinth, placental giant cells and intra-arterial trophoblast cells, as shown by use of testosterone and oestradiol as substrates. Both enzymes were demonstrated in ectopic trophoblast cells, indicating that these activities are autonomous.

17-Hydroxysteroid Dehydrogenases↗
PubMed1976

Binding of 14C-ADP by thrombasthenic platelet membranes.

We have measured the binding of 14C-ADP to isolated human platelet membranes by a technique using 0.8-mum Millipore filters to separate unbound tracer from membrane-bound nucleotide. The binding was dependent on the time of incubation and on the nucleotide concentration in the medium. The affinity constant was found to be comprised between 0.35 x 10(6) and 0.55 x 10 (6) M-1. Platelet membranes prepared from different thrombasthenic patients bound 14C-ADP with the same kinetic parameters as those from normal subjects. The affinity constant as determined for two of these thrombasthenic platelet membrane preparations was in the normal range.

Adenosine Diphosphate↗
PubMed1976

Thyroid hormone and cell formation in the developing rat cerebellum.

Effects of neonatal hyperthyroidism on cell formation in the developing rat cerebellum were reinvestigated. Administration at birth of excessive doses of thyroxine or triiodothyronine led to an early stimulation of cell acquisition, followed by a permanent deficit of cells in the cerebellum. The corrective effects of physiological doses of thyroxine on the troubles of the histological and biochemical development of the cerebellum in thyroid-deficient animals were also studied. As early as 6 days, cell maturation and formation were already retarded in animals treated with propylthiouracil, but, as previously reported, cell formation was prolonged and the final number of cells was normal. Administration to thyroid-deficient animals of progressively increasing doses of thyroxine, nearly equal to the amounts of hormone secreted by the thyroid gland of the developing normal rat, returned the evolution of the cerebellar wet weight and of the cerebellar DNA to normal, as well as the histological maturation of the cerebellum, even if it did not entirely correct the retardation of body growth. These results are consistent with the view that thyroid hormone early stimulates maturation of the cerebellar germinative cells and subsequently interacts with cell formation in the cerebellum, and that this action is physiological.

Animals↗
PubMed1976

[The receptor of adenosine-dephosphate on the human platelet membrane (author's translation)].

The binding of 14C-ADP on the isolated platelet membrane is a saturable and reversible phenomenon which seems to implicate a protein only partially solubilised by Triton X-100. The binding is strongly reduced by mersalyl, which is known to inhibit the ATPase activity of the thrombosthenin i.e. the platelet contractile protein; this protein could be involved in the mechanism of binding of ADP on the platelet membrane. Platelets not aggregated by ADP from patients with Glanzmann's thrombasthenia, have a normal binding of 14C-ADP which is also strongly reduced by mersalyl.

Adenosine Diphosphate↗
PubMed1975

In vitro study of chorionic and ectoplacental trophoblast differentiation in the mouse.

Mouse chorioallantoic pre-placental structures alone or in association with the embryo were explanted during the 9th day of gestation (7-somite stage) and cultured in a static medium for 24 to 48 h. From the subsequent morphological study of trophoblast differentiation, using both light and electron microscopy, we draw the following conclusions. 1. The allantoic mesoderm cells migrate inside the trophoblastic population but they do not differentiate a capillary network and trophoblast cells phagocytose the existing foetal erythrocytes. 2. In the absence of allantoic mesoderm, chorionic trophoblast cells remain undifferentiated. 3. The development of the chorionic trophoblast is modified in that chorionic trophoblast cells fail to establish close junctions with ectoplacental trophoblast, and some chorionic cells initiate the formation of multinucleated syncytia. The genesis of these syncytia is discussed.

Animals↗