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E Larras-Regard

Publications and source records attributed to E Larras-Regard.

12 recordsLinked to original sources
PubMed1990

Thyroid hormones induce hemopoietic pluripotent stem cell differentiation toward erythropoiesis through the production of pluripoietin-like factors.

We have previously reported that E pluripoietins are produced in mice after a single 20-mg injection of cytosine arabinoside (Ara-C) and that they are able to initiate the determination of hemopoietic pluripotent stem cells (CFU-S) toward the erythrocytic lineage. However, the mechanism of E pluripoietin release is still unclear. Since the stimulating effect of thyroid hormone on erythropoiesis is well known, we postulated a link between this hormone and the E pluripoietins. In previous papers we demonstrated that L-triiodothyronine (LT3) exhibits the capacity of inducing CFU-S differentiation toward erythropoiesis in vitro. Two series of data presented here suggest that LT3 acts indirectly on CFU-S determination by promoting the release of E pluripoietin-like factors. First, the Ara-C injection which induces the production of E pluripoietins in mice also promotes an increase in the LT3 plasma level. Second, medium conditioned with bone marrow cells exposed in vitro for 90 min to LT3 (even though this medium does not contain LT3) has E pluripoietin-like effects, inducing CFU-S differentiation toward the erythrocytic lineage.

Animals↗
PubMed1989

[Respective contributions of atomic emission spectrometry (AES) and secondary ion mass spectrometry (SIMS) to trace element quantification].

By means of Secondary Ion Mass Spectrometry (SIMS) it is possible to measure in situ the relative concentration of a given element in a volume of 1 micron 3. Atomic Emission Spectrometry (AES) allows absolute quantitation of tissue homogenates. The use of both techniques lead to correlate relative and absolute elemental concentrations. These methods have been applied to lithium and manganese quantitation after treatments at a therapeutic dose. The results assess the sensibility of SIMS analysis, around 0.1 ppm in biological specimens, and confirm the adequacy of the instrument to trace elements study.

Animals↗
PubMed1988

[Methods of quick-freezing and cryosubstitution of biological tissues in analytical ion microscopy].

The localization and relative concentration of diffusible ions (Li+, K+) or bound but easily displaceable ions (Ca2+) have been studied in myocardium prepared by rapid-freeze fixation and compared with results from chemically prepared samples. Contrary to chemical fixation which gives diffused potassium imaging, cryofixation enables elemental precise mapping in cellular compartment. Bound displazable external calcium, extracted by chemical fixation, is visualized after rapid-freeze fixation. Its localization is distinguished by a bright cellular outline, which corresponds to the glycocalix. Intracellular calcium is less emissive and has the same distribution and concentration whatever the sample preparation. Very movable and present at low concentration in tissues, lithium is localized after rapid-freeze fixation. Those qualitative and quantitative results show the adequation of rapid freeze fixation and freeze substitution to the study of diffusible ions by means of analytical ion microscopy.

Animals↗
PubMed1988

Changes in iodine mapping in rat thyroid during the course of iodine deficiency: imaging and relative quantitation by analytical ion microscope.

The analytical ion microscope (AIM) makes possible imaging and relative quantitation of multiple stable or labeled elements on an even tissue section, according to their mass. The purpose of this work was to follow at the rat thyroid follicle level the changes in 127I mapping during low iodine diet (LID) in relation to the ability of thyroid to pick up radioiodine (129I) and to synthesize Tg from its precursor, 2H-labeled leucine. The overall picture of images and countings of 127I shows a progressive decrease of the luminal iodine concentration which on day 80 was 10-fold lower than that of control value. In control rat thyroid cell, concentration was 10-fold lower than that of follicular lumina and was unchanged until 35 days, but the size of the cytoplasmic compartment increased, suggesting a redistribution of iodine stores between thyroid cells and follicular lumina. 129I was always found in colloid as well as in cells at all stages. After 35 days of LID, cytoplasmic and luminal radioiodine concentrations decreased. In control rats, [2H]leucine was found mainly in the cells. During LID its localization was evidenced progressively in most of the lumina. The most striking fact was the presence up to 35 days of some large residual follicles with high 127I concentration and low 129I and 2H incorporation. These data demonstrate the follicular heterogeneity of thyroid response to progressive chronic TSH stimulation induced by LID.

Animals↗
PubMed1986

[Crystalline inclusions of the mouse thyroid. Effect of chronic treatment with lithium gluconate].

Intracytoplasmic crystalline bodies of various sizes are found in thyroid cells of 10-month-old mice and in younger animals under chronic lithium treatment. They are frequently surrounded by small microvesicles and dense bodies or enclosed in larger vesicles having a dense content. The crystalline skeleton is a network of protein fibers assembled in a characteristic axis with a periodicity of 8 nm. A deficiency of thyroid cell metabolism related to aging or lithium gluconate treatment would lead to an accumulation of substances of a crystalline pattern.

Aging↗
PubMed1985

[Kinetic study of the distribution of stable iodine and radioiodine in the thyroid vesicle and cell using analytical ionic microscopy].

Images of the distribution of 127I and 129I have been obtained by means of SIMS, in Mouse thyroid gland, after tracer injection. Profiles analysis performed on 60 microns area express the relative amount of iodine in thyroid vesicles. Isotopic ratio show a large discrepancy from a follicle to an other which is in situ in agreement with the functional heterogeneity of the gland. The interest of the method to study the kinetics of iodine pools is discussed.

Animals↗
PubMed1984

[Localization of iron and sulfur in the lysosomes of thyroid epithelium using electron probe microanalysis and X-ray spectrometry].

Thyroid lysosomes have been studied by means of EPMA combined with an electron microscope. In 4 months old mice, lysosomes are a few number and contain very low iodine concentrations and sulfur load is not significant. In 10 months old mice, iodine only or associated with sulfur is observed in homogeneous lysosomes varying in size and density. Those two types of localizations reflect two eventual steps in hormonal metabolism pathway of iodine.

Animals↗
PubMed1984

[Analytical ion microscopy, a new approach to the study of iodine and sulfur in the thyroid gland].

Images of distribution of stable iodine and sulfur in mouse thyroid gland have been obtained by ion microscopy. These images give new information related to iodine and sulfur load of thyroglobulin and to the intensity of iodine concentration in lysosomes of thyroid cells. In 4 month old mice, the lumen of some follicles is practically deprived of iodine, but rich in thyroglobulin, whereas all are iodinated in adult mice of 10 months.

Aging↗
PubMed1982

[Effects of exogenous TSH on the thyroid activity of adult or neotenic amphibians].

In adult Anuran and neotenic Urodela, bred in laboratory conditions, the levels of plasma thyroid hormones are undetectable (T3 less than 50 ng/100 ml, T4 less than 5 ng/100 ml). Thyroid function can be reactivated after ovine TSH treatment. Under those conditions, metamorphosis is induced in the axolotl and T4 plasmatic levels reaches 0,53 +/- 0,13 micrograms/100 ml and those of T3 9 +/- 2,64 ng/100 ml. In adult Anuran, thyroid reactivation under thyrotropic treatment determines an increased secretion of T4 whereas T3 remains below the limits of detection of the assay procedure. This aptitude of adult Anuran thyroid to answer thyrotropic stimulation suggests a cyclic function of the gland after metamorphosis.

Ambystoma↗