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J H Dussault

Publications and source records attributed to J H Dussault.

At least 19 recordsLinked to original sources
PubMed1992

Expression of thyroid hormone receptors mRNAs in rat cerebral hemisphere neuronal cultures.

We have studied the expression of the alpha and beta thyroid receptors mRNAs (TR-mRNAs) in cerebral hemisphere neuronal cultures, initiated from 15-day-old rat embryos, by northern analysis. In the cultures grown in the absence of L-triiodothyronine (L-T3), the alpha 2 TR-mRNAs were the predominant form of TR-mRNAs and were approximately 8 to 20-fold higher than the levels of the alpha 1 TR-mRNAs, depending on the age of the cultures. The levels of alpha 2 TR-mRNAs significantly increased by 1.8 fold between day 8 and 15 and remained on a plateau value thereafter until day 22. Over the same time period, there were no significant changes on the levels of alpha 1 TR-mRNAs. The ratio alpha 1/alpha 1 + alpha 2 TR-mRNAs decreased between day 8 and 15. The beta 1 TR-mRNAs increased by 8 fold between day 8 and day 22. On day 8, the beta 1 TR-mRNAs were 1.8 fold lower than the levels of the alpha 1 TR-mRNAs while they were 6 fold higher on day 22. L-T3 treatment of the cultures had no effect on the levels of the alpha 1, alpha 2 and beta 1 TR-mRNAs. The differential temporal expression of the alpha 1 and beta 1 TR-mRNAs suggests distinct functions for both types of T3 receptors in neuronal maturation.

Animals↗
PubMed1992

Immunocytochemical localization of beta thyroid receptor in the rat cerebellum.

Using a specific antibody, we report here the immunocytochemical localization of the beta thyroid receptor (TR beta) in the adult rat cerebellum. We show that the immunoreactivity is specifically located in the Purkinje cells while the internal granular layer and the molecular layer are devoid of staining. In Purkinje cells, the immunoreactivity is either limited in the nuclei, or predominantly located in the perinuclear region and the cytoplasm. The presence of thyroid receptor is correlated with the presence of TR beta mRNAs as determined by Northern analysis.

Animals↗
PubMed1992

The expression of nuclear 3,5,3' triiodothyronine receptors is induced in Schwann cells by nerve transection.

The effects of thyroid hormones on the nervous system are mediated by the presence of nuclear T3 receptors (NT3R). In this study, the expression of NT3R was investigated in spinal cord, dorsal root ganglia (DRG), or sciatic nerve of adult rats after immunostaining with a 2B3-NT3R monoclonal antibody which recognizes both alpha and beta types of NT3R. The specificity of this monoclonal antibody was confirmed by Western blots. The 2B3-NT3R monoclonal antibody recognized one band corresponding to a molecular weight of 57 kDa in extract of spinal cord or DRG. No staining was observed on immunoblot of intact sciatic nerve. In the spinal cord, the nuclei of the neurons and glial cells including both astrocytes and oligodendrocytes exhibited 2B3-NT3R immunoreactivity. While all the nuclei of the DRG sensory neurons expressed the NT3R, all the nuclei of the satellite and Schwann cells were devoid of any immunoreaction. In the sciatic nerve, the nuclei of the Schwann cells also lacked 2B3-NT3R-immunoreactivity. After sciatic nerve transection in vivo, Schwann cell nuclei, which never expressed NT3R in intact nerves of adult rats, displayed a clear 2B3-NT3R immunoreaction in proximal and distal stumps adjacent to the section. Double immunostaining with antibodies raised to 3-sulfogalactosylceramide or S100 confirmed that most of the NT3R containing nuclei belong to Schwann cells. In dissociated cell cultures grown in vitro from sciatic nerves, Schwann cells exhibited 2B3-NT3R immunoreactivity. These data suggest that the inhibition of NT3R expression in Schwann cells ensheathing axons in intact nerve is reversed when the axons are degenerating or lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Identification of nuclear triiodothyronine receptors in the thymic epithelium.

Thymic epithelial cell physiology is known to be under neuroendocrine control. In particular, thyroid hormones modulate thymic hormone secretion by thymic epithelial cells in vivo and in vitro, thus suggesting the existence of specific receptors for those hormones in this component of the thymic microenvironment. Yet, thyroid hormone-binding sites have previously been detected only in crude thymus fractions and lymphocytes. We, thus, decided to search for T3 receptors in the thymic epithelium, by using an antinuclear T3 receptor monoclonal antibody. In situ immunohistochemical analysis of thymic frozen sections showed nuclear labeling of both lymphoid and nonlymphoid cells in the cortex and medulla. Moreover, in vitro studies using thymic epithelial cell lines and the so-called thymic nurse cells revealed a positive reaction in the chromatin, with nucleoli remaining negative. Immunoblot data clearly showed a single protein band of 57K reactive with the antinuclear T3 receptor antibody in murine thymus extracts as well as in the thymic epithelial cell lines. Lastly, in vitro treatment of these cells with T3 resulted in a transient, yet profound, down-modulation of the receptor. In conclusion, our findings provide molecular evidence that the action of thyroid hormones on thymic epithelium occurs via the typical 57K nuclear T3 receptors.

Animals↗
PubMed1991

Immunocytochemical localization of thyroid hormone receptors in the adult rat brain.

It is generally accepted that thyroid hormones act at the genomic level through an interaction with specific nuclear receptors. Using a monoclonal antibody raised against the rat liver nuclear L-T3 receptor (NTR), we report here the immunocytochemical localization of T3 receptors in the adult rat brain. The strongest NTR immunoreactivity was found in the olfactory bulb, the hippocampus, the dentate gyrus, the amygdala areas, and the neocortex (layers III-VI). An intermediate NTR immunoreactivity was found in the hypothalamus, whereas the thalamus, the caudate-putamen, and the pallidum were weakly NTR-immunoreactive. In the cerebellum, a strong NTR immunoreactivity was found in the nuclei of Purkinje cells, in the internal granular layer, and in some nuclei of cells located in the molecular layer. In the brainstem, a strong NTR immunoreactivity was found in the lateral mamillary nucleus and the interstitial nucleus. A weak to moderate NTR immunoreactivity was observed in the central gray matter, while the substantia nigra and the interpeduncular nucleus were weakly stained. Furthermore, we also found NTR immunoreactivity in the nuclei of ependymocytes, epithelial cells of the choroid plexus, and cells located in the white matter. At the electron microscope level, we confirm that the immunoreactivity was not only localized in the nuclei of neurons but also in the nuclei of astrocytes and medium oligodendrocytes. This study provides new information concerning the distribution of NTR in the rat brain: (1) NTR are present not only in neurons but also in glial and ependymal cells, and (2) there is a regional and cellular heterogeneity in the distribution of NTR in the central nervous system.

Animals↗
PubMed1991

Production of a specific polyclonal antibody against the rat beta thyroid receptor, using synthetic peptide as antigen.

We have developed a polyclonal antibody to a synthetic peptide corresponding to the deduced amino acid residues 67-80 of the amino terminal sequence of the rat thyroid receptor beta cDNA. Immunopositive sera were identified by radioimmunoassay and purified by affinity chromatography. The antibody specifically immunoprecipitated the labelled thyroid receptor beta synthetized in vitro but not the rat thyroid receptor alpha. Furthermore, 38% of the L-T3 binding capacity of the rat liver nuclear receptor were immunoabsorbed by this antibody. By immunocytochemistry, this antibody stained specifically the nuclei of hepatocytes while no staining was observed in the rat testis. This study presents a specific polyclonal antibody against the thyroid receptor beta. This antibody will be of a great help in determining the role of the beta receptors in the mechanism of action of thyroid hormone.

Animals↗
PubMed1990

Influence of soluble environmental factors on the development of fetal brain acetylcholinesterase-positive neurons cultured in a chemically defined medium: comparison with the effects of L-triiodothyronine (L-T3).

In cerebral hemisphere neuronal cultures derived from 15-day-old rat embryos, the addition of L-triiodothyronine (L-T3) or nerve growth factor (NGF) enhanced the expression of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities in a dose-dependent manner. When cultures were supplemented with both agents at maximal effective concentrations, the stimulation in ChAT and AChE activities was significantly greater than the sum of the individual effects. Conversely, when the cultures were exposed to astrocyte conditioned medium grown in the presence or absence of L-T3 (CM + L-T3 or CM-L-T3). laminin and fibroblast growth factor (FGF), ChAT and AChE activities were not stimulated above those of control cultures when added alone or in combination with L-T3. Furthermore, L-T3, NGF, CMs, laminin and FGF did not affect AChE+ cell survival, but significantly increased neurite outgrowth and branching with NGF and L-T3 being the most powerful agents followed by CMs, laminin and FGF. Additionally, the simultaneous addition of L-T3 with either laminin or FGF in culture, caused an additive effect of L-T2 in the neurite density of AChE+ cells with both agents. This study shows that (1) thyroid hormones do not act through the regulation of soluble neurotrophic factors produced by astroglial cells, (2) thyroid hormones interact with the effect of NGF on ChAT and AChE activities, (3) the regulation of ChAT and AChE activities and the neurite outgrowth are independently regulated. and (4) the regulation of ChAT and AChE activities is very specific compared with that of neurite outgrowth.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1990

Immunocytochemical localization of thyroid hormone nuclear receptors in cultured acetylcholinesterase-positive neurons: a correlation between the presence of thyroid hormone nuclear receptors and L-tri-iodothyronine morphological effects.

A monoclonal antibody against the rat liver L-tri-iodothyronine nuclear receptor and acetylcholinesterase cytochemistry were used for the localization of thyroid hormone nuclear receptors in acetylcholinesterase-positive cell nuclei in fetal rat cerebral hemisphere neuronal cultures. After 3 days in vitro, the ratio of acetylcholinesterase-positive cells that were immunoreactive for the thyroid hormone nuclear receptor to those not stained for this receptor (74-26%, respectively) remains unchanged despite an increase in the number of acetylcholinesterase-positive cells with time (from day 3 to day 21) in culture. Furthermore, the addition of 3 X 10(-8) L-tri-iodothyronine in culture did not modify this ratio or have an effect on the number of acetylcholinesterase-positive cells, but significantly increased the neurite density in those acetylcholinesterase-positive cells that were immunoreactive for the thyroid hormone receptor. Conversely, no difference in the neurite densities of those acetylcholinesterase-positive cells not stained for this receptor was observed when cultured in the presence or absence of thyroid hormone. In other experiments with the same fetal brain cultures, treatment of cultures for 8 days with L-tri-iodothyronine, beginning on culture day 20, demonstrated the presence of a critical period which occurs in vitro around day 20, since the stimulatory effect of L-tri-iodothyronine on immunoreactive acetylcholinesterase-positive cell neurite density is lost after 20 days in vitro. These results demonstrate, for the first time, the presence of L-tri-iodothyronine nuclear receptors in fetal rat acetylcholinesterase-positive neurons and the existence of a cellular heterogeneity in the distribution of the thyroid hormone receptor. The presence of these receptors in fetal brain acetylcholinesterase-positive neurons suggests that some effects of L-tri-iodothyronine on the maturation of a subpopulation of acetylcholinesterase-positive neurons may result from a direct effect of this hormone through an interaction with its specific nuclear receptors.

Acetylcholinesterase↗
PubMed1990

Interaction of sodium molybdate with the thyroid hormone receptor.

The 3,5,3'-triiodothyronine (T3) binding activity of solubilized nuclear proteins from rat liver was decreased when molybdate (10 mM) was present in the incubation medium in the absence of thiol reagents. The equilibrium affinity constant was reduced by 40%. The rate of degradation of T3-receptor complexes at 37 degrees C remained unchanged, but when the extracts were further reincubated in the presence of beta-mercaptoethanol, molybdate had a protective effect after 5 h incubation at 37 degrees C. In contrast, the thyroxine (T4) binding activity was not affected by heating at 37 degrees C or by molybdate. Ion-exchange chromatography confirmed the existence of a molybdate-receptor interaction: the T3-receptor complexes shifted from elution at 0.22 to 0.20 M NaCl with the progressive appearance of a small leader peak, whereas the T4-receptor complexes eluted in a large and split peak (0.22-0.4 M NaCl). The destabilizing effect on T3 binding induced by exogenous dephosphorylation is more efficiently reversed by beta-mercaptoethanol when the extracts were pretreated by molybdate. In controls, the loss of saturable T3 binding activity was recovered by 50% at a 10 mM concentration of beta-mercaptoethanol, but in the presence of molybdate, the loss of T3 binding activity was recovered by 50% at a 5 mM concentration of beta-mercaptoethanol. This molybdate-receptor interaction is similar to that with nuclear receptor models in term of (i) stabilization of hormone binding, (ii) dependency on a thiol, and (iii) reversibility of the destabilizing effect by exogenous dephosphorylation.

Alkaline Phosphatase↗
PubMed1989

Localization of c-ERB A proteins in rat liver using monoclonal antibodies.

Monoclonal antibodies were raised against the nuclear thyroid hormone receptors encoded by c-ERB A genes and against a purified nuclear receptor fraction. These antibodies recognize the c-ERB A protein in nuclear extracts from rat liver and are able to compete with thyroid hormone in Scatchard analyses. In sections of rat liver they react with all the hepatocyte nuclei as well as with the cells of the hepatic bile ducts. Comparison with another putative T3 receptor antibody, described previously, showed that distinct 57 kD proteins with a different cellular distribution were recognized.

Animals↗
PubMed1989

Immunocytochemical localization of nuclear 3,5,3'-triiodothyronine (L-T3) receptors in astrocyte cultures.

By means of a monoclonal antibody (mab) against the rat liver nuclear L-T3 receptor (NT3R) and a polyclonal anti-GFAp serum, it has been possible to demonstrate nuclear thyroid hormone receptors in astrocyte cultures. On day 3, 47% of GFAp+ cell nuclei were labeled by 2B3 mab. Between day 3 and day 15, the number of GFA+ cell nuclei stained by 2B3 mab increased from 47 to 75%. Thyroid hormone nuclear receptors were present in fibrous and protoplasmic astrocytes. However, they developed asynchronously in both types of astrocytes. Indeed, 60% of fibrous astrocytes were stained by 2B3 mab on day 3 and this percentage reached 77% after 8 days in vitro. In contrast, only 30% of protoplasmic astrocytes were immunoreactive for 2B3 mab on day 3 and this percentage increased slowly reaching 47% on day 8 and around 75-80% on day 15. By immunoblotting, the monoclonal antibody recognized two bands of proteins with a molecular weight of 57 and 45 kDa respectively. These proteins have the same electrophoretic mobility as [125I]bromoacetyl-LT3 rat liver nuclear L-T3 receptor. This paper presents the first immunocytochemical localization of nuclear L-T3 receptors in astrocyte cultures. Furthermore, we show that thyroid hormone receptors develop more rapidly in fibrous than in protoplasmic astrocytes.

Animals↗
PubMed1989

Immunocytochemical localization of thyroid hormone nuclear receptors in cultured hypothalamic dopaminergic neurons.

By means of a monoclonal antibody against the rat liver L-triiodothyronine nuclear receptor and a polyclonal anti-tyrosine hydroxylase serum, it has been possible to demonstrate thyroid hormone nuclear receptors in immunoreactive tyrosine hydroxylase cell nuclei in fetal rat hypothalamic cultures. After 8 days in vitro, the ratio of tyrosine hydroxylase cells that were immunoreactive for the thyroid hormone receptor to those not stained for this receptor (64% to 36% respectively) remains unchanged despite an increase in the number of tyrosine hydroxylase-positive cells with time (from day 8 to day 21) in culture. The presence of thyroid hormone nuclear receptor in dopaminergic neurons is correlated with a morphological effect of L-triiodothyronine in this neuronal population. Our results demonstrate, for the first time, the presence of triiodothyronine nuclear receptors in fetal rat dopaminergic neurons and the existence of a cellular heterogeneity in the distribution of the thyroid hormone receptor. The presence of these receptors in fetal hypothalamic dopaminergic neurons suggests that some effects of L-triiodothyronine on the maturation of DA neurons may result from a direct effect of this hormone through an interaction with its specific nuclear receptors.

Animals↗
PubMed1989

Immunocytochemical localization of the nuclear 3,5,3'-triiodothyronine receptor in the adult rat: liver, kidney, heart, lung and spleen.

A monoclonal antibody was used for the localization of the nuclear T3 receptor in different tissues of the adult rat: the liver, kidney, heart, lung, spleen, testis, and pituitary. In the liver, the immunoreactivity was found uniformly distributed in the nuclei of hepatocytes. Sections incubated with a control ascitic fluid or with the same ascitic fluid pre-adsorbed with purified receptor showed no specific staining. In the kidney, the immunoreactivity was higher in the epithelial cell of the proximal convoluted tubes and juxtaglomerular cells. In the heart, only the myocardial cells were stained. In the lung, the immunoreactivity was confined to type II pneumocytes and alveolar macrophages. In the spleen, only a few mature lymphocyte and macrophage cell nuclei were stained. These results show that: 1) the abundance of the nuclear T3 correlates with previous studies using hormone binding techniques; 2) the nuclear T3 receptor is selectively located in certain cell types, which possess a precise local function.

Animals↗
PubMed1988

Detection of the thyroxine-binding globulin (TBG) gene in six unrelated families with complete TBG deficiency.

T4-binding globulin (TBG) is a glycoprotein of hepatic origin which transports thyroid hormone in serum. Inherited TBG defects in man are X-chromosome linked and are expressed in hemizygotes as complete deficiency, partial deficiency, or excess. Since TBG is not necessary for thyroid hormone action, affected subjects are healthy. Using DNA probes for human TBG, we searched for restriction fragment length polymorphisms in six affected males belonging to 6 unrelated families with inherited complete TBG deficiency and an equal number of normal males. TBG could not be detected in the serum of any of the TBG-deficient males by a specific and sensitive RIA capable of detecting as little as 5 micrograms TBG/L or 0.031% of the average normal serum TBG concentration. DNA isolated from white blood cells was digested with 11 restriction endonucleases, and the digests were submitted to DNA blot analysis using two cloned TBG-DNA probes which together covered the entire protein coding and the 5'-flanking sequences of the TBG gene. A total of 26 different bands were detected on DNA blots, identifying 18 restriction sites located within the 4.2-kilobase TBG gene, which includes intronic, exonic, and 5'-flanking sequences. This analysis, which sampled 2.3% of the total TBG genome, failed to reveal differences in fragment size among the 6 TBG-deficient and 6 normal males examined. One restriction endonuclease (NcoI) identified normal sequences at the putative promoter region of the gene, and four other endonucleases (TaqI, SstII, MspI, and HpaII) recognized the cytosine-guanine dinucleotide phosphate sequences representing potential mutation hot spots. Although C was methylated at these sites, no C to T (thymidine) transitions were found. These data suggest that large deletions, insertions, or rearrangements of the TBG gene, or mutations at sites of methylated cytosine-guanine dinucleotide phosphate dimers are not common mechanisms for inherited complete TBG deficiency in man.

Cloning, Molecular↗
PubMed1987

Somatosensory evoked potentials and auditory brain-stem responses in congenital hypothyroidism. II. A cross-sectional study in childhood. Correlations with hormonal levels and developmental quotients.

We report the results of somatosensory evoked potentials (SEPs) and auditory brain-stem responses (ABRs) done in 48 congenital hypothyroid (CH) treated children, early detected and aged 18 months, 3 and 5-9 years of age. We report also the results of SEP and ABR done in 9 3-year-old CH children, before and after a 1 month therapy interruption to reassess the thyroid status. The more frequent abnormalities were increased wave I latencies for 18 month and 3-year-old CH children. In some children, these increases were not associated with signs of otitis media. No significant difference was seen between CH children and controls for SEP latencies and ABR and SEP interpeak latencies (IPLs). Similarly, no significant difference was seen between the two recording sessions in the 9 3-year-old CH children for ABR and SEP. On an individual basis, we observed abnormalities of central conduction time for ABR and SEP in several CH children. Moreover, significant partial correlations were found between ABR and SEP IPLs and thyroxine (T4) serum levels at diagnosis and thyrotropin (TSH) serum levels at the time of recording. There was also a significant partial correlation between N19-P22 IPLs and the practical reasoning scale of the Griffiths test considering the whole group of CH children. These results indicate that SEP might eventually be used to detect CH children at risk of presenting developmental abnormalities.

Brain Stem↗
PubMed1987

Effect of transient neonatal hypothyroidism on the free aspartic acid, glutamic acid, and GABA content of different central auditory regions in the rat.

The aspartic acid, glutamic acid, and gamma-aminobutyric acid (GABA) contents were determined in four central auditory system regions in rats with transient neonatal hypothyroidism compared with control ones: the ventral and dorsal parts of the cochlear nucleus, the central nucleus of the inferior colliculus, the auditory cortex, and in an extra-auditory structure, the substantia nigra pars reticulata. The animals were sacrificed at 50 days of age, brain tissue samples were taken out by microdissection, and the free amino acids were extracted. The amino acid content was assessed by double-isotope labelling following two-dimensional thin-layer chromatography separation. GABA content was significantly decreased in both cochlear nucleus regions and glutamic acid was elevated in the inferior colliculus. Neonatal hypothyroidism had no significant effect on the aspartic acid levels in the regions studied. The results suggest an effect of neonatal hypothyroidism on regional contents of free amino acids known as candidate neurotransmitters in the auditory system.

Animals↗