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M Nicol

Publications and source records attributed to M Nicol.

At least 55 records · Page 3Linked to original sources
PubMed1992

[Toxicity of chloroform and vitamin A status in the rat].

After a chloroform intraperitoneal injection, lactate dehydrogenase, alanine aminotransferase and particularly aspartate aminotransferase serum activities are much more raised in deficient animals. Liver ornithine decarboxylase (ODC) activity normally decreases in rats between the 4th. and the 7th. month after the weaning. In vitamin A deficient animals, basal values of the enzyme activity are lower and the decrease is deeper. But even at month 7, liver sustains a partial capacity of ODC recovery if retinol is fed during 15 days. Chloroform administration strongly enhances liver ODC activity in normal rats. In the deficiency, stimulation is lower in absolute value but relatively higher if referred to basal level. After retinol refeeding, chloroform stimulates enzyme activity to nearly normal values. Vitamin A deficiency impairs obviously liver ODC activity and its response to chloroform stimulation in rats, but the stroke is at least partially reversible in our conditions. Moreover, deficient animals maintain a non negligible capacity of ODC response under chloroform stimulation.

Alanine Transaminase↗
PubMed1991

Dose-dependent effects of angiotensin II, acetylcholine and vasopressin on the cytosolic concentration of Ca2+ in suspension primary cultures of zona fasciculata/reticularis cells from bovine adrenal cortex.

The effects of angiotensin II (AII), acetylcholine and vasopressin on the intracellular concentration of Ca2+ have been little studied in adrenocortical cells from the zona fasciculata/reticularis (ZFR). Primary cultures of bovine ZFR cells maintained in suspension cultured for 72 h produce cortisol in response to AII (0.1 microM), acetylcholine (0.1 mM) and vasopressin (1 microM). This response is accompanied by a breakdown of membrane phosphoinositides from [3H]inositol-prelabelled cells. Using cells loaded with the Ca2+ indicator fura-2, the intracellular concentration of Ca2+ was measured in response to increasing doses of all three agonists and found to increase in a graded fashion in each case. The basal intracellular concentration of Ca2+ was 75 +/- 3 nM (mean +/- S.E.M., n = 52), rising to a maximum 1.82 +/- 0.14-fold (n = 6) for AII (0.1 microM), 1.35 +/- 0.05-fold (n = 7) for acetylcholine (0.1 mM) and 1.27 +/- 0.10-fold (n = 6) for vasopressin (1 microM). In the case of AII and acetylcholine, agonists were added sequentially in medium of normal extracellular Ca2+ concentration (1.2 mM) or in medium in which the Ca2+ concentration was buffered to approximate to the intracellular concentration of Ca2+ (75-100 nM). Evidence was thereby obtained that both AII and acetylcholine mobilize a common intracellular pool of Ca2+. Our findings suggest that these three agonists, all of which stimulate phospholipase C, increase intracellular Ca2+ through a mechanism which depends, at least in part, on the release of Ca2+ from a common intracellular pool.

Acetylcholine↗
PubMed1991

Modulation of the functional properties of human thyrocytes in monolayer or follicle culture: effects of some anaesthetic drugs.

It is well known that some volatile anaesthetic drugs, such as halothane and isoflurane, alter the functions of the human thyroid gland, but the action of other anaesthetic drugs, such as thiopental, midazolam and ketamine, on thyroid function is still unknown. We have investigated the effects of these three drugs on the functional properties of human thyrocytes cultured in monolayers or follicles and stimulated by TSH. Thiopental, midazolam and ketamine induced total suppression or a partial reduction, depending on the dose administered, of cyclic AMP (cAMP), follicular thyroglobulin (Tg) and free tri-iodothyronine (FT3) production. In contrast, free thyroxine levels increased in the medium of thyrocytes cultured as follicles. Small doses of the drugs did not affect thyrocyte production. The inhibiting effect of thiopental, midazolam and ketamine on Tg and FT3 production seems to result from the inhibition of cAMP production and 5'-deiodinase.

Cell Survival↗
PubMed1991

Comparison of thyroperoxidase and microsomal antibody assays in sera from patients with Graves disease.

Anti-microsomal (anti-Mic Ab) and anti-thyroperoxidase antibody activities (anti-TPO Ab) were compared by using commercially available radioassay kits. Sera were collected from 52 patients with Graves disease before and after administration of carbimazole (1-methyl-2-thio-3-carbethoxyimidazole). The two antibody concentrations were significantly correlated, both before treatment (r = 0.835, P less than 0.001, n = 52) and at the end of treatment (r = 0.584, P less than 0.001, n = 52). Twenty-nine (Group I) of the 52 patients were in remission for two years after drug withdrawal, whereas 23 (Group II) relapsed. Within each group, the anti-Mic and anti-TPO Ab concentrations were significantly correlated (Group I: r = 0.781, P less than 0.0001; Group II: r = 0.866, P less than 0.0001). Relapse vs nonrelapse was linked to the antibody positivities measured before treatment: 91% vs 65% (chi 2 = 4.75, P less than 0.02) for anti-Mic Ab and 87% vs 62% (chi 2 = 4.05, P less than 0.02) for anti-TPO Ab. We conclude that assays of anti-Mic and anti-TPO Ab are equally reliable analytically and equally informative clinically. Because of its rapid implementation, the anti-TPO assay may advantageously replace anti-Mic Ab assay, especially for forming a prognosis of Graves disease.

Autoantibodies↗
PubMed1990

Effect of vitamin A deficiency on the in vitro transfer of mannose and N-acetylglucosamine in rat liver nuclei.

Liver nuclei, prepared from normal and vitamin A-deficient rats, were incubated in the presence of GDP-(14C)mannose or UDP-N-acetyl(14C)glucosamine and the labelled glycoproteins analysed by SDS PAGE. Fluorographic analysis has shown that (14C) mannose labelling is enhanced by vitamin A deficiency whereas N-acetyl(14C)glucosamine transfer remains approximately at the same level regardless of the vitamin A status; we did not notice any modification when the proteins were monitored by Coomassie blue or by silver nitrate.

Acetylglucosamine↗
PubMed1990

Vasopressin stimulates cortisol secretion and phosphoinositide catabolism in cultured bovine adrenal fasciculata/reticularis cells.

Cells isolated from the zona fasciculata/reticularis (ZFR) of the bovine adrenal cortex and maintained in culture were found to secrete cortisol in response to vasopressin stimulation. The increased cortisol secretion was dose dependent, with a threshold response at 1 nM and a maximal response (1.68-fold over basal) at 0.1 microM. In cells cultured in the presence of [3H]inositol (to prelabel the membrane phosphoinositide pool), stimulation with vasopressin in the presence of LiCl (10 mM) resulted in a similar dose-dependent increase in labelling of the phosphoinositol fraction, with a maximal response (1.45-fold over basal) at 10 nM. The increased labelling of the phosphoinositol fraction was independent of extracellular Ca2+ as it was not abolished in medium with [Ca2+] buffered to intracellular resting levels. This suggests that vasopressin stimulation results in the activation of a phosphoinositidase C. It is probable that cortisol secretion by bovine ZFR cells in response to vasopressin is dependent upon activation of this Ca2(+)-independent phosphoinositidase C. However, the small magnitude of the cortisol secretory response makes it unlikely that vasopressin is a primary regulator of cortisol secretion in vivo.

Acetylcholine↗
PubMed1989

Effect of amiodarone and propranolol on the functional properties of human thyroid follicles cultured in collagen gel.

Amiodarone and propranolol have been known to inhibit the peripheral conversion of thyroxine (T4) to 3,5,3'-triiodothyronine (T3) but their direct effect on the thyroid gland is not understood. We therefore investigated the action of the two drugs on the functional properties of human thyroid follicles embedded in collagen gel. Amiodarone and propranolol induced a dose-dependent reduction or blocking of the follicular production of cyclic AMP (cAMP), thyroglobulin (Tg) and free triiodothyronine (FT3) under 200 microU/ml medium. Small drug doses and the drug solvents did not affect the follicular secretion. The inhibiting effect of amiodarone and propranolol on follicular production of cAMP, Tg and FT3 appears to result from several factors: (1) inhibition of thyroid 5'-deiodinase; (2) amiodarone high iodine content; (3) a quinidine-like effect of propranolol involving a membrane-stabilizing mechanism.

Amiodarone↗
PubMed1989

T-cell-mediated protection of mice against virulent Mycobacterium tuberculosis.

We sought to protect CBA mice against tuberculosis using in vivo transfer of a T-cell line previously shown to be capable of I-A-restricted recognition of peritoneal macrophages infected in vitro with Mycobacterium tuberculosis. This line induces total bacteriostasis in vitro. In mice that received 500 rads of irradiation 48 h before infection, the T-cell line caused significant prolongation of life when given intravenously with a challenge dose of 5 x 10(6) organisms. Similar experiments with two other T-cell lines showed that these lines offered no protection. Bacterial load at the time of death was inversely related to the time of survival. Thus, death occurred at a lower bacterial load in adoptively protected mice, implying the contribution of an immunopathological component in these animals. The protective T-cell line, which was CD4+ CD8-, had no effect on the rate of growth of strain BCG in CBA nu/nu mice or M. tuberculosis in fully T-cell-deprived mice. This could indicate that CD8+ cells play a role in this system or that there is a need for the recruitment of interleukin 2-producing cells in the recipient. Experiments with monoclonal antibodies to selectively deplete T-cell subsets in normal CBA mice showed that depletion of CD4+ cells strikingly shortened survival, whereas depletion of CD8+ cells did not. However, CD8-depleted mice died with a lower bacterial load than those found in nondepleted controls, and the lesions in CD8-depleted mice were histopathologically distinct. These results suggest that the CD8+ cells either down-regulate bacteriostasis or cause immunopathology in this model and that it is the CD4+ cells that are the major protective subset in long-term protection experiments.

Animals↗
PubMed1988

Functional properties of human thyroid follicles cultured within collagen gel.

Cultures of human thyroid follicles embedded in collagen gel were performed to investigate certain functional properties under bovine thyrotropin (TSH) stimulation. Follicles obtained from normal glands responded to increasing concentrations of TSH administered on day 4 in culture and for 3 days by increased amounts of cyclic AMP (cAMP), thyroglobulin (Tg) and triiodothyronine (T3) and by decreased levels of thyroxine (T4). Effect was maximal at 2000 microU/ml TSH (cAMP) or 200 microU/ml (Tg, T3, T4). When methimazole or propylthiouracil (PTU) were added, the T3 levels decreased. Follicle lumens contained a periodic acid-Schiff substance which was identified by immunoreaction as Tg. Thyroid follicles obtained from Graves' disease glands gave modified results with an earlier and intensified T3 response and no increase in Tg. These data show that (1) Tg and T3 are secretory products of functional follicles giving a cAMP-mediated response to TSH. (2) The detected T3 also derives from T4 5'-deiodination inhibited by PTU. (3) Intensified T3 response in Graves' follicles is probably due to enhanced conversion of T4 to T3.

Cells, Cultured↗
PubMed1988

Ornithine decarboxylase basal activity in liver, oesophagus and lung of vitamin A deficient rats, and the effect of retinoic acid.

Ornithine decarboxylase (ODC, EC 4.1.1.17) activity was measured, without exogenous stimulation, in the liver, oesophagus and lung of Wistar rats which were vitamin A deficient or supplemented with retinol or retinoic acid. The enzyme basal activity in such deficiency conditions was higher, when compared with controls, in the oesophagus and especially in the lungs. Retinoic acid normalized enzyme activity only at high doses (300 micrograms/day). In the liver, initial retinol deficiency did not sensitively modify ODC activity, and retinoic acid then stimulated the enzyme abnormally. This phenomenon could not be observed at later stages of vitamin deficiency (but there again without cytological abnormalities or thymidine incorporation disturbances): liver ODC response then became comparable to that of other tissues. These results highlight the particular basal hyperactivity of pulmonary ODC during the initial stages of vitamin A deficiency, indicative of an enhanced tendency to cell proliferation. A special stimulating effect of retinoic acid on ODC, contemporary with early deficiency, was observed in the liver; this effect was not observed at a later stage in normally fed rats.

Animals↗
PubMed1987

[Vitamin A status and the carcinogenic action of N-nitrosobenzyl methylamine on the esophagus in the rat].

A state of pure vitamin A deficiency, without any clinical manifestations, rapidly induces a stimulation of ornithine decarboxylase (ODC) activity and some oesophageal mucosal abnormalities (hyperkeratosis, dyskeratosis, cytonuclear abnormalities) in rats treated with N-nitrosobenzylmethylamine (NBMA). Retinol deficient rats fed with retinoïc acid (all-trans) show a mucosal ODC induction, but no morphological lesion. The association of retinoïc acid + retinol, as does retinol alone, prevents simultaneously histological lesions and enzymatic induction. In the liver of vitamin A deficient rats treated with NBMA, a stimulation of the ODC system, without any macroscopical lesions, has been observed.

Animals↗
PubMed1986

Assays for thyrotropin-receptor binding and thyroid-stimulating antibodies in sera from patients with Graves' disease.

We compared the activities of thyroid-stimulating antibodies (TSAb) measured in cultures of human thyrocytes and the values for thyrotropin-receptor antibodies (TRAb) as measured with a commercial kit based on use of radiolabeled receptors. Sera were obtained from patients with Graves' disease before, during, and after therapy with carbimazole (1-methyl-2-thio-3-carbethoxyimidazole). We found a significant correlation between the measurements of these two antibodies in patients: before treatment (r = 0.74, p less than 0.01, n = 44), after three months of treatment (r = 0.76, p less than 0.01, n = 21), and during relapse after the drug was discontinued (r = 0.64, p less than 0.01, n = 19). In all three situations, our TSAb technique was more sensitive than the TRAb method. We conclude that, even though the TRAb technique is simpler and quicker, this commercial kit is too insensitive to replace measurement of TSAb in fresh human thyrocyte cultures for management of drug therapy of patients with Graves' disease.

Adult↗
PubMed1983

[Concepts of placental hormonology].

During pregnancy, different protein (hCG and hPL) and steroid (progesterone, oestradiol, oestrone, oestriol) hormones are secreted. hCG, measured by RIA in maternal serum, is a first-trimester trophoblastic function test. The serum levels of hPL reveal the placental function during the two last trimesters of gestation. The main steroid hormones, produced by the foeto-placental unit, are progesterone, oestradiol and oestrone, which control placental function, and oestriol, a good index of foetal vitality.

Female↗