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Biomedical subjects

A Pouplard

Publications and source records attributed to A Pouplard.

At least 19 recordsLinked to original sources
PubMed1996

Binding interactions of leukemia inhibitory factor and ciliary neurotrophic factor with the different subunits of their high affinity receptors.

Leukemia inhibitory factor (LIF) and ciliary neurotrophic factor (CNTF) share common components in their multimeric receptors. Both cytokine receptors contain gp130/interleukin-6-receptor transducer as well as gp190/low affinity LIF receptor. For CNTF, addition of a third subunit, or alpha subunit, defines the high-affinity CNTF receptor. In the present study, we analyzed the binding interactions of LIF and CNTF in human cell lines and showed a mutual displacement for LIF and CNTF toward the trimeric high-affinity CNTF receptor. Similar results were obtained in the JEG cell line, which only expressed the gp130/gp190 high-affinity LIF receptor, by adding a soluble form of the alpha CNTF receptor to the system to reconstitute the high-affinity-type CNTF receptor. The different receptor subunits were then expressed separately in transfected cells and their binding capacities analyzed. The results showed that the heterocomplex CNTF/alpha CNTF receptor bound to gp130 with an affinity of 3-5 x 10(-10)M, whereas LIF interacted mainly with gp190. In summary, the observed competition between LIF and CNTF does not result from the binding to a common site or receptor subunit, but rather to the interaction of the three receptor components to create a conformational site common to both LIF and CNTF.

Animals↗
PubMed1994

Expression and functionality of the trkA proto-oncogene product/NGF receptor in undifferentiated hematopoietic cells.

The expression of the low-affinity NGF receptor (p75) and the trkA proto-oncogene product was analyzed in a series of human hematopoietic cell lines at protein and RNA levels. We did not detect any form of NGF receptor in cell lines displaying a myelomonocytic phenotype (HL60 and U937). In contrast, cells displaying a more immature erythroleukemic phenotype (TF1 and K562) expressed TrkA in the absence of detectable p75. Scatchard analysis showed a single high-affinity site for NGF (kd = 10(-10) mol/L), with a copy number ranging from 300 to 3,000 sites per cell depending on the studied cell line. In addition, NGF induced autophosphorylation of TrkA and could substitute for granulocyte-monocyte colony-stimulating factor to trigger the proliferation of the TF1 cell line, with a half-maximal signal observed at 50 pmol/L, indicating that p75 is not required for DNA synthesis in this cell line. The physiologic relevance of NGF in early hematopoiesis was confirmed by showing that 12% to 15% of progenitor blood cells from mice treated with 5-fluorouracil expressed TrkA and that these cells could be induced to proliferate and differentiate in response to NGF in association with macrophage colony-stimulating factor. Our study demonstrates for the first time that trkA proto-oncogene expression and activation is not restricted to the nervous system, but is also an important element in early hematopoiesis.

Animals↗
PubMed1994

Involvement of gp130/interleukin-6 receptor transducing component in interleukin-11 receptor.

The recently cloned interleukin (IL)-11 displays many biological properties in common with those reported for IL-6. In order to analyze the nature and the functionality of the IL-11 receptor we developed a proliferative assay using the human multifactor-dependent cell line TF1. We showed that a blocking monoclonal antibody GPX7 raised against the gp130/IL-6 receptor transducing subunit was also able to inhibit the IL-11-triggered TF1 line proliferation. In addition, involvement of gp130 in IL-11 signaling was demonstrated by an induction of the transducing protein phosphorylation in response to IL-11, as observed for IL-6. In contrast, the blocking monoclonal antibody B-R6, which recognized the gp80/IL-6 binding subunit failed to interfere with the IL-11 proliferative signal in the TF1 cell line. Similarly, we did not observe any competition between IL-6 and IL-11 for a putative common binding site on the cell surface. These results suggest that the IL-11 binding component is different from the gp80/IL-6 receptor. In conclusion, IL-11, along with IL-6, leukemia inhibitory factor, oncostatin M and ciliary neurotrophic factor, belongs to the same family of cytokines, using gp130 as a transducing protein.

Antibodies, Monoclonal↗
PubMed1988

An ELISA technique for the measurement of C1q in cerebrospinal fluid.

Determination of the C1q content of cerebrospinal fluid (CSF) may be of value in understanding the immunological reactions occurring within the central nervous system (CNS). A double sandwich ELISA method has been developed for the detection of C1q in human serum and CSF. It uses polyclonal antibodies and is sensitive in the nanogram range. The mean concentrations of C1q were determined to be 127 micrograms/ml in serum and 0.4 microgram/ml in CSF. These results suggest that increased levels of C1q in the CSF play a role in some neurodegenerative disorders.

Adolescent↗
PubMed1987

Transient hypoparathyroidism induced by synthetic human parathyroid hormone-(1-34) treatment.

Daily injections of low doses of a synthetic fragment of human PTH [hPTH-(1-34) have increased iliac trabecular bone volume when used in the treatment of osteoporosis. In approximately 50 patients no major side-effects had occurred. However, during daily sc 100-micrograms injections of the peptide, one patient repeatedly developed parathyroid hypofunction which resolved each time treatment was stopped. Specific immunoglobulin G (IgG) antibodies binding [125I]hPTH-(1-34) were identified in the patient's serum, and positive immunohistochemical reactions were obtained when bovine parathyroid sections were exposed to the patient's IgG. After adsorption with PTH, the patient's IgG, free of anti-PTH antibodies, reacted with renal cell membranes, as demonstrated by indirect immunofluorescence and blocked renal PTH-dependent adenylate-cyclase activation in vitro. These results support the hypothesis that anti-PTH receptor as well as anti-PTH antibodies were generated during hPTH-(1-34) treatment, which led to the development of hypoparathyroidism when their titers were high.

Adenylyl Cyclases↗
PubMed1987

Glucose counterregulation in pre-school-age diabetic children with recurrent hypoglycemia during conventional treatment.

To determine whether immature or defective glucose counterregulation was responsible for the severe recurrent hypoglycemic episodes (3.6 per patient per year) observed during conventional therapy (CT) in six pre-school-age diabetic children, we investigated their metabolic and hormonal responses to insulin infusion (40 mU/kg i.v. for 60 min). Counterregulation was considered adequate because no patient experienced symptoms requiring discontinuation of the test, and blood glucose (BG) nadirs averaged 42 +/- 5 mg/dl. Glucose production rate decreased from 4.2 +/- 0.2 to 2.6 +/- 0.6 mg X kg-1 X min-1. Blood 3-hydroxybutyrate levels were elevated (approximately 3 mM) and did not change during insulin infusion. The responses of epinephrine (from 137 +/- 37 to 393 +/- 143 pg/ml), norepinephrine (from 145 +/- 33 to 347 +/- 152 pg/ml), and growth hormone (from 6.0 +/- 1.5 to 20.3 +/- 5.1 ng/ml) were normal for this age group. As previously observed in diabetic adults, glucagon response was deficient (from 117 +/- 30 to 114 +/- 18 pg/ml). The six children were subsequently treated with continuous subcutaneous insulin infusion (CSII), which resulted in a 20-fold decrease in the number of severe hypoglycemic reactions. Predisposition to severe hypoglycemia in this subset of diabetic children, which remains a refractory problem even after considerable efforts have been made to decrease them, may thus be sharply decreased with CSII therapy. During this therapy, a significant inverse correlation appeared between the individual frequency of BG values less than 40 mg/dl and BG nadir during the insulin infusion test (r = .94, P less than .001).

Blood Glucose↗
PubMed1985

Antigonadotropic cell antibodies in the serum of cryptorchid children and infants and of their mothers.

An indirect immunofluorescence test allowed us to study circulating antigonadotropin-cell antibodies in patients with cryptorchidism. Antigonadotropin-cell activity was found in the serum in 14 of 23 cryptorchid boys aged 1 to 11 years and in 12 of 23 infants aged 1 to 3 months; in most of them the antibodies persisted during short-term follow-up. Results of paired study of the mother and infant were concordant in 14 of 15 cases. No such antibodies were found in 24 control male children. These data support the possible role of pituitary autoimmunity in the child and the mother as a factor in testicular maldescent. We found no correlation between the presence or absence of antibodies and the partial luteinizing hormone-Leydig cell deficiency usually found in cryptorchidism.

Adolescent↗
PubMed1983

[Paget's bone disease. Preliminary serological study].

A serological study has been carried out in Paget's bone disease where the etiology still remains uncertain. Previous work on patients with the disease revealed specific osteoclast inclusions that could be linked to the presence of a virus of the paramyxovirus group. Conventional methods for exploring humoral immunity reveal no great differences in the concentration of antibodies against the various viral strains tested on sera from 46 patients with Paget's bone disease and from 46 paired controls. The viral origin of Paget's bone disease is reconsidered in the light of the results obtained. The eventuality of sub-threshold viral infection and the possible action of incomplete or defective virus leading to the chronic nature of the disease are discussed.

Aged↗
PubMed1983

[Paget's bone disease. Preliminary serological study].

A serological study has been carried out in Paget's bone disease where the etiology still remains uncertain. Previous work on patients with the disease revealed specific osteoclast inclusions that could be linked to the presence of a virus of the paramyxovirus group. Conventional methods for exploring humoral immunity reveal no great differences in the concentration of antibodies against the various viral strains tested on sera from 46 patients with Paget's bone disease and from 46 paired controls. The viral origin of Paget's bone disease is reconsidered in the light of the results obtained. The eventuality of sub-threshold viral infection and the possible action of incomplete or defective virus leading to the chronic nature of the disease are discussed.

Aged↗
PubMed1983

[Circulating human pituitary prolactin cell autoantibodies and Alzheimer's disease].

Prolactin cell autoantibodies (PRL cells Ab) were detected in 96 p. cent of 27 cases of Alzheimer's presenile dementia and senile dementia, as defined by clinical criteria and data from CT scans. The very high frequency of these autoantibodies appears to be even more significant of Alzheimer's disease in that they were found with a similar frequency in patients with Down's syndrome aged from 13 to 33 years. The frequency of PRL cells Ab is very low in the general population including patients with endocrine disorders. Current evidence indicates that higher levels exist only in cases of arteriopathic dementia, in subjects over 80 years and in subjects with isolated organic memory disturbances, though their frequency may be such that it suggests the probability of Alzheimer's disease. The etiopathogenic significance of these autoantibodies is not clear, but they support a role of autoimmune factors in Alzheimer's disease.

Aged↗
PubMed1981

[Viral origin of Paget's disease of bone. Contribution of electron microscopy and immunocytology of the aetiological diagnosis (author's transl)].

Despite considerable research work the cause of Paget's disease of bone remains uncertain. In a study of bone tissue from 100 patients with Paget's disease electron microscopy demonstrated alterations of the cells involved in bone remodelling. Osteoblasts showed distinct signs of hyperactivity, and the fibrillar arrangement of the osteoid tissue they produce was irregular. Osteoclasts were very large with numerous nuclei, and their bone-resorption activity was abnormal. Microcylindric inclusions visible in the cytoplasma and nuclei were morphologically comparable to the nucleocapsids of measles virus observed in experimental infections or in human pathology. Immunocytology tests confirmed the presence in osteoclasts of an antigenic material belonging to the measles virus group and cross-reacting with it. The hypothesis of a viral origin for Paget's disease of bone is supported by the chronic course of the condition, the histopathology of bone tissue, the ultrastructural changes in osteoclasts and the immunological results. A virus of the measles virus group probably plays a major role in the etiology of the disease.

Animals↗
PubMed1981

Lymphocytes from diabetics suppress insulin release in vitro.

The insulin response of isolated islet cells to glucose and theophylline in vitro was studied after incubation with lymphocytes. The test was employed to explore cell-mediated immunity in diabetics. A significant inhibition of insulin response to glucose and theophylline as compared to insulin release in a "basal" medium was found after incubation with blood lymphocytes from 21 out of 23 insulin-dependent diabetics (mean secretion index 18 +/- 18 versus 118 + 8 (SEM) % in control subjects). Most of the patients studied had associated autoimmune diseases: all of these displayed inhibition of insulin release. In six cases, the diabetes had a recent onset with no associated autoimmune disease: four of them displayed the same inhibition. No inhibition was found in the 26 control subjects and in seven non-insulin-dependent diabetics (mean secretion index 134 +/- 17 versus 145 +/- 23 (SEM) % in four control subjects). Lymphocytes inhibiting islet cell response were not cytotoxic against mouse fibroblasts. Twenty-two insulin-dependent diabetics showed islet cell antibodies to human and/or mouse pancreatic islets. However, an inhibition of insulin release was found with no detectable islet cell antibodies in one case, and the converse in two cases. Lymphocyte cytotoxicity to islet cells could play a role in the natural history of insulin-dependent diabetes.

Adolescent↗
PubMed1981

Towards a viral etiology for Paget's disease of bone.

The etiology of Paget's disease of bone has long remained obscure. The recent discovery in electron microscopy of specific inclusions in the cytoplasm and nuclei of osteoclasts in tissue from patients with Paget's bone disease has been the starting point of investigations into a possible viral origin. The inclusions, made up of microcylinders, described by several authors as being found only in osteoclasts in Paget's bone disease, present a close morphological analogy with nucleocapsids of paramyxovirus of the measles group. Immunocytological methods have provided a complementary approach to the problem. It has been demonstrated that the osteoclasts in Paget's bone disease contain antigenic material which reacts positively with sera containing measles antibodies. Both the morphological and the immunocytological evidence is strongly in favour of a viral etiology for Paget's bone disease.

Humans↗
PubMed1981

Complement-fixing Islet cell antibodies from some diabetic patients alter insulin release in vitro.

To explore humoral immunity in insulin-dependent diabetic (IDDM) patients, we studied insulin release from isolated mouse islets stimulated by glucose + theophylline after incubation with the sera of these patients and complement. Eleven of 21 IDDM sera suppressed the stimulated insulin release while the arginine-stimulated glucagon release remained unchanged. Morphologic evidence and the trypan-blue exclusion test suggested that the suppression of insulin release was due to a cytotoxic effect of the sera. No beta-cell inhibition of morphologic damage was detectable in the presence of sera from 30 healthy subjects, 8 non-insulin-dependent diabetic patients, and 5 nondiabetic patients with autoimmune diseases. Beta-cell inhibition by IDDM sera was not observed when complement was omitted. After serum fractionation, the cytotoxic potency of IDDM sera was located in the immunoglobulin G fraction. Using human islets, insulin release was suppressed by 3 of 6 IDDM sera. Complement-dependent cytotoxicity was found in 1 of 5 recent-onset IDDM patients and 11 of 16 IDDM patients with autoimmune phenomena. It was associated in all cases with the presence of islet cell antibodies as detected by immunofluorescence, and with the presence of circulating lymphocytes which suppressed insulin release in vitro. Complement-fixing antibodies may contribute to the selective beta-cell damage in IDDM.

Adolescent↗