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Biomedical subjects

A Bourdeau

Publications and source records attributed to A Bourdeau.

60 records · Page 4Linked to original sources
PubMed1978

[Biological effects and activity threshold of a long-acting purified porcine calcitonin in the child].

The biologic effects of a purified long-acting porcine calcitonin (pTCT) were investigated in 45 children without any known renal, skeletal, endocrine, or metabolic disorder. pTCT was given as a single im injection at dose levels varying from 1 to 150 MRC u/1.73 m2. Administration of the highest dose was followed by a decrease in serum calcium and phosphorus concentrations and in tubular reabsorption of phosphorus, serum calcium and phosphorus concentrations and in tubular reabsorption of phosphorus. Mean maximal variation of serum calcium was -- 13.8 +/- 2.1 mg/l in children less than 3 years old, versus -- 8.2 +/- 0.9 mg/l (p less than 0.01) in older ones. Such an age-related differences was not observed for the hypophosphatemic action of pTCT. In 40 subjects aged 3 to 14 years the threshold for pTCT hypocalcemic activity was between 1 and 5 MRC u/1.73 m2. No significant differences in the effects on serum calcium of either 10, 25, 75 or 150 MRC u/1.73(2) m could be found. The threshold for pTCT hypophosphatemic activity was between 10 and 25 MRC u/1.73 m2 with, similary, no dose-response relationship for doses varying from 25 to 150 MRC u/1.73 m2. The present data demonstrate the high sensitivity of children, especially those younger than 3 years, to pTCT; furthermore, the lack of a dose-response relationship indicates that the pharmacological use of pTCT in pediatrics at doses higher than 10 to 25 MRC u/1.73 m2 is unnecessary.

Adolescent↗
PubMedDate not supplied

Umbilical vein and placental vessels from newborns with hereditary haemorrhagic telangiectasia type 1 genotype are normal despite reduced expression of endoglin.

Hereditary haemorrhagic telangiectasia, HHT, is an autosomal dominant disorder that affects approximately 1 in 8000 people. HHT1 is associated with mutations in the ENG (Endoglin) gene and with haploinsufficiency. The disorder is characterized by focally dilated vessels, which can lead to arteriovenous malformations and serious complications even in young children. In the current study, umbilical cord and placenta samples from newborns with ENG mutations were analyzed to estimate the level of corresponding protein and look for potential vascular dysplasia. We confirmed, using metabolic labelling and flow cytometry, that endoglin levels were significantly reduced to median values of 47 per cent (range 32-56 per cent) and 58 per cent (46-90 per cent), respectively, in human umbilical vein endothelial cells derived from newborns with ENG mutations (HHT1 group; n=18) relative to samples from newborns shown not to have the familial mutation (non-HHT group). We also quantified the relative expression of endoglin by estimating the endoglin/PECAM-1 staining ratio in tissue sections. We observed significantly lower values in the HHT1 group, compared to the non-HHT group for the umbilical vein (n=9; median 0.6 vs 0.9; ranges 0.2-1.0 and 0.5-1.5) and for placental stem villus vessels (n=9 and 10; median 0.42 vs 0.93; ranges 0.24-0.58 and 0.56-1.18). No differences in the estimated umbilical vein cross-sectional area and in the proportion of vessels present in placental villi were observed in sections from the HHT1 group relative to the non-HHT group. Thus, blood vessels from HHT1 individuals are maintained intact in the umbilical vein and placenta during pregnancy and delivery, despite a significant reduction in endoglin expression.

Antigens, CD↗
PubMedDate not supplied

The calcium receptor in health and disease.

The recent cloning of a G-protein-coupled, extracellular calcium [(Ca2+)e]-sensing receptor (CaRG) from the parathyroid, kidney and brain of several species has clarified the molecular mechanisms underlying Ca2+-sensing by parathyroid and other cell types. It has long been suspected that such a receptor existed on parathyroid cells, coupled to intracellular second messengers through guanine nucleotide regulatory (G) protein which is able to recognize and respond to (Ca2+)e. Recently, functional screening of a cDNA library constructed from bovine parathyroid mRNA led to the isolation of a 5.3-kb clone expressing maximal Ca2+-stimulated Cl- currents in oocytes. This 5.3-kb cDNA encodes a protein of 1,085 amino acids with three principal predicted structural domains. The CaRG protein is present in chief parathyroid cells, in C cells of the thyroid, in the cortical thick ascending limb (TAL) and collecting duct of the kidney, and in discrete brain areas. CaRG may play several physiological roles. It is a central element in the control of both parathyroid and calcitonin secretion by (Ca2+)e. Moreover, functional evidence for its participation in the regulation of renal Ca2+ reabsorption in TAL and water reabsorption in the collecting duct has been obtained. Mutations of the CaRG gene are responsible for hereditary and familial parathyroid disorders, and a decrease in CaRG expression has been documented in primary and secondary uremic hyperparathyroidism. The expression of CaRG in several additional organs and tissues allows speculation on the potential involvement in other pathologies.

Calcium-Binding Proteins↗
PubMedDate not supplied

[Dysregulation of plasma 1,25(OH)2D in calcium restriction in hypercalciuric children].

BACKGROUND: The effect of calcium restriction on the plasma concentration of 1,25(OH)2D in normo- and hypercalciuric children remains unknown. METHODS: We studied phosphate and calcium metabolism of 8 normocalciuric and 8 hypercalciuric children aged 4 to 16 years, under 3 conditions: on a normal dietary calcium intake after a 5-day calcium-restricted diet, and after oral calcium loading. The healthy, normocalciuric children had histories that included no renal failure of abnormalities of phosphate and calcium metabolism. Four of the 8 hypercalciuric children had urolithiasis, 1 had hematuria and the 3 others had idiopathic hypercalciuria. Blood samples were analyzed for calcium, creatinine, immunoreactive parathyroid hormone, cAMP, 25(OH)D and 1,25(OH)2D concentrations. Urine samples were analyzed for calcium, phosphorus, creatinine and cAMP. RESULTS: On the normal dietary calcium intake, the hypercalciuric children had higher urinary calcium excretion and plasma 1,25(OH)2D levels and lower TmP that did the controls. The 1,25(OH)2D levels of the normocalciuric children were significantly increased after 5 days of dietary calcium deprivation, but those of the hypercalciuric children were not. The other parameters (essentially PTH, cAMP and TmP) varied similarly in the two groups. CONCLUSION: The results suggest that: a) calcium restriction influences 1,25(OH)2D levels in normocalciuric subjects via a PTH- and phosphor-independent mechanism; b) dietary control of renal vitamin D metabolism is impaired in hypercalciuric patients.

Adolescent↗