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Biomedical subjects

G Milhaud

Publications and source records attributed to G Milhaud.

At least 91 records · Page 5Linked to original sources
PubMed1986

Calcium induced potassium efflux in erythrocytes of marine teleosts.

The effect of the calcium-ionophore A23187+ Ca++ on the K+ transport in the intact erythrocytes of sea-water fishes was investigated. A23187+ Ca++ induced a significant increase in the cell-membrane permeability for potassium ion, while A23187+ Mg++ was ineffective. Addition of EGTA to the medium blocked the ionophore+ Ca++ effect. Quinidine inhibited the A23187+ Ca++-induced K+ transport in the nucleated fish red cell. Propranolol is effective in the fish RBC in presence of Ca++ and EGTA. The relationship of the calcium-induced alkali cation transport in nucleated red cell to that in human red cell is discussed.

Animals↗
PubMed1985

Elucidation of the nucleotide sequence of chicken calcitonin mRNA: direct evidence for the expression of a lower vertebrate calcitonin-like gene in man and rat.

Calcitonin shows considerable divergence in amino acid sequence between lower vertebrates and higher vertebrates. Immunoreactive salmon-like calcitonin molecules are present in the thyroid of man and rat. Elucidation of the almost complete sequence of chicken calcitonin mRNA revealed that the calcitonin precursor in chickens had the same organisation as in higher vertebrates (man and rat) but showed considerable differences in amino acid sequence. cDNA probes specific for chicken calcitonin mRNA hybridized to poly(A)-rich RNA extracted from a case of medullary carcinoma of the thyroid and from murine thyroid. These results suggest the expression in man and rat of a gene coding for an avian calcitonin-like precursor.

Amino Acid Sequence↗
PubMed1985

Cell surface analyses of the age-dependent changes in the electrokinetic properties of human peripheral blood lymphocytes.

The age-dependent changes in the surface electrical charge of human peripheral blood lymphocytes were analyzed by establishing the differences between the surface density of four types of chemical groups on lymphocytes isolated from the blood of individuals of increasing ages. Similar determinations were carried out on cord blood lymphocytes which were shown previously to exhibit either a low or a high electrical charge density reflected in the experimentally determined parameter, the anodic electrophoretic mobility (EPM), differing by about 30%. The surface density of carboxyl group of N-acetylneuraminic acid (NANA), protein side chain epsilon-amino groups, and phosphate groups were different for the two subpopulations of CBL. Differences were also observed between the surface density of these groups on the two subpopulations of CBL and the lymphocytes of older individuals, with the exception of carboxyl groups. In some experiments on lymphocytes from adults, the carboxyls of NANA were much more numerous on nearly 1% of the cells.

Adult↗
PubMed1985

Epitopes of the 44-68 human parathyroid hormone fragments: the importance of specific hydrophilic peptide sequences.

Several pentapeptides included in the 44-68 sequence of human parathyroid hormone (hPTH) were synthesized simultaneously on benzhydrylamine and m-nitrobenzhydrylamine resins. The first polymer gave the free peptide and the second the peptidyl-resin complex. An ELISA test carried out with each peptidyl-resin complex showed that all the anti-44-68 hPTH antibodies raised in different animal species are directed against the same hPTH pentapeptidic sequence. This sequence is very hydrophilic and is specific to the hormone. This study demonstrates the importance of specific peptide chains in an epitope.

Amino Acid Sequence↗
PubMed1985

Calcium-regulating hormones modulate carbonic anhydrase II in the human erythrocyte.

The effect of calcitonin (CT) and parathyroid hormone (PTH) on carbonic anhydrase (carbonate hydrolyase, EC 4.2.1.1.) activity was tested in human erythrocyte hemolysates and with purified carbonic anhydrases I and II. The most important effect was on carbonic anhydrase II: CT showed a 2-fold increase and PTH showed a 50% decrease of carbonic anhydrase activity. This effect was observed at low hormonal concentrations and suggests the importance of CT in regulating carbonic anhydrase activity in the two important sites of CO2 exchange, erythrocyte and lung.

Calcitonin↗
PubMed1985

Circadian variations in plasma calcium and calcitonin: effect of calcium deficiency and fasting.

Circadian fluctuations of plasma calcium and immunoassayable calcitonin levels were studied in normal and calcium-deficient 2-month-old rats. The relationship between these parameters was also studied in animals which had been fasted for short periods. The plasma calcium rhythm persisted and was even amplified in rats placed on a 4-week calcium-deficient diet. In these rats, as in normal rats, the plasma calcium concentration diminished during the dark period. Calcitonin levels increased at the onset of the feeding period in normal rats but, in calcium-deficient rats, the pattern changed completely, with a major peak at the end of the light period and remaining at a low level during the dark feeding period. This modification of calcitonin rhythmicity appeared to be dependent on the degree of calcium deficiency. Fasting had little effect on calcitonin rhythms in either normal or calcium-deficient rats. It is concluded that the calcitonin rhythm is relatively independent of feeding per se and that there appears to be no simple relationship between plasma calcium and calcitonin concentrations. It is suggested that the results may best be interpreted as reflecting the presence of rhythmic endogenous phenomena which are intrinsic to calcium metabolism and its regulation in the rat.

Animals↗
PubMed1985

[Risk of vertebral fracture after menopause: identification of subjects at high risk by dual photon absoprtionometry].

Dual photon absorptionometry of bone is used to detect in an exposed population those subjects who are high risk of fracture and also to follow up the evolution of these patients. 37 women who have suffered fractures have been compared to 41 women without fractures of similar age distribution. A highly significant correlation between body height and Bone Mineral Content (BMC) of the lumbar spine is found in the control group thus allowing the calculation of the expected BMC value for each patient. A crushing index is defined as the ratio of the observed BMC value to the expected one. Using this index, instead of the two more usual modes of BMC expression, leads to an improvement of the predictive estimation of fracture risk. The predictive value of such indices should still be improved. With this aim, further determinations of indices are desirable. The following requirements should be borne in mind: The physical data should be easily obtainable e.g. body height and weight and the meaning of the index based on these easily verifiable factors they should be easily understood.

Aged↗
PubMed1985

[Value of bone scintigraphy].

Artificial radioactivity enables visualisation of the principal organs in the form is scintiscans, introduces a new order of sensitivity in quantitative hormonal analysis, thanks to radio-immunology, and remains unrivalled in compartmental analyses of the various metabolism of the diagnosis of local skeletal conditions is reviewed, and the indications for this quantitative examination are described for the diagnosis of numerous bony metabolic diseases. Finally, mono- and bi- photonic absorptiometries, the latest developments in isotopic techniques, are introduced. They are likely to provide numerical data on the state of mineralisation of bony tissue. The use of these nuclear techniques for the diagnosis and surveillance of osteoporosis is detailed.

Bone Diseases↗
PubMed1985

[Experimental study of fluorosis in lambs].

Eighty-four lambs weaned at birth were randomised to three groups, each of 28 animals. The amount of fluoride contained in the feed was carefully assessed. Two groups were administered with sodium fluoride. The dose was calculated so as to administer a quantity of fluoride close to the quantity that lambs would ingest in consuming alfalfa containing from 125 to 250 ppm fluoride. The daily amount of fluoride administered to the 1st group rose progressively between week 3 and week 8 from 0.45 to 2 mg/kg/day, then remained fixed until the animals were slaughtered. Group 2 received double amounts: from 0.90 mg/kg/day to 4 mg/kg/day between week 3 and week 8, at which level the amount was fixed. The treatment had no effect on the growth of the lambs: at week 17 their average weight was about 29 kg. Plasma levels of ionic fluorine rose steadily up to week 9, at which they remained fixed at about 0.40 mg/l in group 1 and 0.75 mg/l in group 2, whereas they ranged between 0.10 and 0.15 mg/l in the controls. Ionic fluorine averaged 28% of the total fluoride in the controls, 42% in group 1 and 47% in group 2. Fluoride levels in the bones were very high (up to 2760 ppm in the mandibles in group 2). Reversely, fluoride levels in the muscles were very low: 1.00 ppm in group 2. The biochemical paremeters calcium, phosphorus, magnesium, transaminases, phosphatases and gamma glutamyl transferases greatly varied in relation to the age of the animal but were not affected by fluoride intake.

Animals↗
PubMed1984

The effect of calcitonin on prolactin secretion during gestation.

The relationship between calcitonin (CT) and prolactin (PRL) was studied by means of the injection of salmon calcitonin (SCT) i.p. on day 1 of gestation. An estrogen inhibitor - clomiphene - was also administered to certain groups of animals on day 4 and 5 of gestation. SCT did not affect PRL levels on day 1 of gestation nor on days 5 or 7, but it prevented the rise of PRL levels observed in animals submitted to injection stress on days 4 and 5. In animals treated with clomiphene, the inhibition by SCT on PRL increase after injection stress was partially abolished. SCT while not affecting basal PRL level prevented the rise observed after stress and this effect occurred some days later. Thus SCT could exercise a delayed neuroendocrine control. This action of SCT seemed to be partially dependent upon the presence of estrogens.

Animals↗
PubMed1984

Rapid increase of calcitonin-specific mRNA after acute hypercalcemia.

The regulation of calcitonin (CT) secretion by calcium was studied by measuring CT mRNA extracted from thyroids of normal rats subjected to acute calcium stimulation in vivo. The 15000-Mr primary translation product of CT mRNA was identified by immunoprecipitation using specific antibodies. While total mRNA and total radioactivity incorporated after translation of total mRNA remained unaffected by the calcium stimulation, a fourfold increase in radioactivity incorporated in CT primary translation product occurred as early as 2 min after calcium administration. This peak coincided with a rise in plasma levels of the hormone and preceded a detectable decrease in tissue stores. These results suggest that calcium ion, either directly or indirectly via its action on intracellular stores of the hormone or its precursors, causes a rapid increase in cell levels of translatable CT mRNA. In view of the extremely short time (2 min) in which this increase occurs, the action is probably at the post-transcriptional level as no increase in CT mRNA levels could be detected by hybridization assay using a specific cDNA probe for human CT mRNA.

Acute Disease↗
PubMed1984

The complete sequence of human preprocalcitonin.

DNA complementary to mRNA extracted from the thyroid glands of patients suffering from medullary carcinoma of the thyroid (MCT), a calcitonin-producing tumour, was inserted in the Pst site of pBR 322 by G-C tailing. The recombinant plasmids were used to transform Escherichia coli DP 50. Ampicillin-resistant clones were screened using a 32P-labelled cDNA to mRNA extracted from a case of MCT particularly rich in calcitonin (CT) mRNA. Positive clones were subsequently rescreened using a 32P poly(T) probe. Eighty clones were thus purified, and the inserts obtained by digestion with PstI were subjected to positive hybridization selection with subsequent translation in vitro. An insert stimulating synthesis of the protein and containing restriction sites compatible with the previously published complete sequence of calcitonin mRNA from rat was sequenced. This cDNA insert contained the entire coding region of 426 bp, 70 bp at the 5'-end, and 295 bp upstream from the poly(A) tail. The complete amino acid sequence of human preprocalcitonin could thus be deduced.

Amino Acid Sequence↗
PubMed1984

Ultimobranchial gland of the domestic fowl. Two types of secretory cells involved in calcitonin metabolism.

The ultimobranchial gland (UBG) of birds is particularly rich in calcitonin, the hypocalcaemic hypophosphataemic hormone, that is secreted by the C-cells of the mammalian thyroid. The principal cells of the UBG have a striking resemblance with the mammalian C-cells, i.e., they possess small intracytoplasmic dense-core secretory granules, 150-300 nm in diameter. The gland also contains a second, morphologically distinct, endocrine cell type with larger granules, 500-800 nm in diameter. A sensitive immunocytochemical reaction was developed with the use of antibodies against salmon calcitonin. By means of this technique the presence of calcitonin-immunoreactive molecules was demonstrated in both secretory cell types of the UB gland of the chicken. This gland can thus be considered as a homogeneous calcitonin-producing tissue. Whether the secretory products are identical is discussed and differences in the secretory pathways are suggested.

Animals↗
PubMed1984

Dichloromethylene diphosphonate (Cl2MDP) reduces natural killer (NK) cell activity in mice.

Daily administration of dichloromethylene diphosphonate (Cl2MDP) to (C57BL/6 X DBA/2) F1 hybrid mice, from two days of age (10 mg of P/kg body weight), resulted in a marked impairment of natural killer (NK) activity of spleen cells against YAC-1 lymphoma cells. The suppressive effect increased with the duration of the treatment. Cessation of the treatment led to a rapid recovery (in 2 weeks) of NK activity while the osteopetrotic bone lesions persisted. Thus, the loss of natural killing cannot be explained by the simple reduction of bone marrow volume secondary to Cl2MDP-induced osteopetrosis. However, as NK cells are considered to be dependent on the bone marrow because they cannot be sustained by extramedullary production, a direct effect of Cl2MDP on the generation of NK cell precursors by the bone marrow was not excluded. Cl2MDP was not directly toxic to the fully differentiated splenic NK cells, since the addition of Cl2MDP to the in vitro assay (10(-5)-10 micrograms/ml) did not reduce cytotoxicity. These studies suggest that impairment of NK activity during Cl2MDP treatment may have clinical toxicologic implications since NK cells have been suggested to play an important role in natural host defenses against infection and neoplasia.

Animals↗