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A Chatelain

Publications and source records attributed to A Chatelain.

At least 37 records · Page 2Linked to original sources
PubMed1986

[Influence of heparin on the radioimmunological assay of ACTH].

Heparin traps plasma ACTH, promoting the formation of aggregates with apparent high molecular weight as shown by chromatography on Sephadex G 50 fine columns. The percentage of 125I-ACTH which appeared in the void volume of the column, increased linearly with the log. dose of heparin. Heparin at concentrations of up to 100 IU/ml does not impair ACTH adsorption on either silicic acid or Quso G 32 as well as further elution by acetic acid/acetone/water (I : 40 : 59; V/V) or HCl O.I N. Silicic acid traps selectively ACTH but not heparin. Heparin interferes with direct RIA-ACTH in the plasma by decreasing 125I-ACTH binding to the antibodies and modifying the slope of the standard curve. Unsuitable artefacts induced by heparin, as overestimation or underestimation of plasma ACTH levels by RIA, can be avoid by previous hormone extraction from heparinized plasmas. Such results emphasized the importance of the sample preparation in order to obtain consistent results.

Adrenocorticotropic Hormone↗
PubMed1986

Immunoreactive forms of ACTH released by the adenohypophysis of the rat during the perinatal period in vivo and in vitro studies.

Immunoreactive ACTH levels were determined in whole plasma, eluate fractions of plasma and perfusates of anterior lobe extracts subjected to chromatography on Sephadex G-50 fine. In the fetal plasma, ACTH levels were higher on day 19 than on days 17, 18, 20 and 21. After birth, ACTH concentrations dropped to reach the lowest values in one week old newborns; thereafter they increased until weaning on day 21. They were then similar to those of non pregnant adult females. Three peaks of immunoreactive ACTH were present in all the chromatograms; the first one eluted near the void volume ("big" ACTH, PM approximately 44,000), the third one coeluted with human ACTH (1-39) ("little" ACTH, PM approximately 4,500) and the second one eluted midway between the 2 previous peaks ("intermediate" ACTH, PM approximately 13,000). During the last days of pregnancy, the proportion of the "little" form of ACTH in the fetal plasma showed a gradual increase whereas that of the "big" one decreased. On days 17, 19 and 21 of gestation the anterior lobes of fetal pituitary glands released in vitro these 3 forms of immunoreactive ACTH in the same proportions as those observed in the anterior lobes. In contrast, the proportions of the circulating forms of ACTH were quite different; the "little" one gradually increased and the "big" one decreased as gestation progressed. In vitro controlled tryptic digestion of the isolated "big" form led to the appearance of "intermediate" and "little" forms suggesting some transformations in the circulation of the ACTH forms released by the fetal hypophysis in vivo.

Adrenocorticotropic Hormone↗
PubMed1985

Heterogeneity of adrenocorticotrophin in the pituitary gland and plasma during the perinatal period.

Three immunoreactive forms of ACTH are characterized by their apparent molecular weight (MW) and bioactivity when acid extracts of the anterior or of the neurointermediate lobe of fetal and newborn rat pituitary glands are subjected to gel filtration on Sephadex G50 fine columns. The "big" ACTH form which shows an apparent MW close to 44 000 hardly stimulates the in vitro release of corticosterone by perifused fetal adrenals. In contrast, the "intermediate" (MW: congruent to 13 000) and "little" (MW: congruent to 4 500) forms show high biological activity by eliciting corticosterone secretion which is log-dose-dependent. During the perinatal period, the relative proportions between these different molecular forms of ACTH change in both the anterior and neurointermediate lobes. "Big" ACTH is the main form in the neurointermediate lobe of the fetal rat pituitary. After birth, the "big" ACTH/total ACTH ratio regularly decreases until postpartum week 4; it is not very different then from that of pregnant adult females. The three immunoreactive forms of ACTH are present in the anterior lobe throughout the perinatal period. The gradual increase of the "intermediate" and "little" forms is accompanied by a correlative decrease in the "big" form. The anterior lobes of 17, 19 and 21-day old fetuses, stimulated in vitro by an acid extract of adult hypothalamus, release the three immunoreactive forms of ACTH in the same proportions as those observed in corresponding extracts of anterior lobes. On days 17, 19 and 21 of gestation, fetal plasma contains all the immunoreactive forms of ACTH previously observed in pituitary glands. The proportion of the "little" ACTH form gradually increases, whereas that of the "big" form decreases as gestation progresses. At term, the relative proportion of "little" ACTH is greater in the plasma than in the fetal pituitary. Controlled trypsic digestion of pituitary "big" ACTH results in a conversion to the "intermediate" and "little" immunoreactive forms. When "intermediate" ACTH is submitted to tryptic digestion under the same conditions, there is continuous loss of immunoreactivity but no change of hormonal form. These findings strengthen the hypothesis that "big" ACTH is a precursor of "intermediate" and "little" ACTH; in contrast, the "intermediate" form is not a precursor of the "little" one. The high molecular-weight form of ACTH might be converted endogenously into lower MW forms in the fetal circulation at term as well as in newborns. In fetal plasma, immunoreactive ACTH levels reach peak values on day 19 of gestation and decrease thereafter until day 21.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗
PubMed1985

Adrenocorticotrophic hormone in the anterior and neurointermediate lobes of the rat during the perinatal period: polymorphism, biological and immunological activities of ACTH.

When acid extracts (0.1 N HCl) of the anterior or neurointermediate lobes of fetal and newborn rat pituitary were subjected to gel filtration on Sephadex G-50 fine columns, polymorphism of ACTH was revealed by radioimmunoassay. At every stage of pregnancy and after birth three main ACTH forms were observed. The first form ('big' ACTH) eluted near the void volume of the column; its apparent molecular weight was 45,000. The second form ('little' ACTH) coeluted with synthetic human ACTH1-39 and 125I human ACTH. As the latter marker eluted more slowly than the former, 'little' ACTH, which showed an apparent molecular weight near 5,000, could not be a single entity. The third form ('intermediate' ACTH) eluted between 'big' and 'little' ACTH; its apparent molecular weight was near 13,000. During the perinatal period, the relative proportions between these different molecular forms of ACTH changed in both anterior and neurointermediate lobes. Thus the gradual increase of 'intermediate' and 'little' forms was accompanied by a decrease of 'big' ACTH. The perfusion of fetal adrenal glands with the same immunological quantities of 'big', 'intermediate' and 'little' ACTH showed that the 'little' and 'intermediate' forms have greater biological potency in eliciting corticosterone secretion than the 'big' ACTH form.

Adrenocorticotropic Hormone↗
PubMed1984

Effect of norepinephrine on the pituitary adrenocorticotrophic activation by ether stress and on the in vitro release of ACTH by the adenohypophysis of male and female newborn rats.

The effect of norepinephrine (NOR) has been investigated in 8-day-old newborn rats of both sexes subjected to stress by 2 min ether inhalation or sham stress. The animals were sacrificed either before or 2 and 32 min after the stress or the sham stress procedure was started. Investigations were also performed on newborns bearing neurotoxic lesions of the arcuate nucleus by neonatal treatment with monosodium-L-glutamate. The effect of NOR was also investigated in vitro on incubated pars distalis. ACTH concentrations in the pituitary, plasma, and the incubation medium were determined by radioimmunoassay. NOR at the dose of 0.2 microgram/g was unable to affect plasma ACTH levels during a period of 60 min in unstressed newborns, in contrast to higher doses (0.5, 1, and 5.0 micrograms/g) which elicited a sharp rise in plasma ACTH levels. Then, NOR was injected (0.2 microgram/g) to male and female pups 15 min before the stress or sham stress procedure. 32 min after the beginning of ether inhalation, the pituitary response was greater in NOR-injected than in saline-injected males; in NOR-treated females the rise in plasma ACTH levels was higher at 2 and 32 min than in saline-injected animals. At this latter time, plasma ACTH levels were similar in NOR-treated males and females, while in saline-treated newborns, the response to ether stress was greater and more longlasting in females than in males. No significant rise in plasma ACTH levels was observed in sham-stressed pups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1984

In-vitro effects of corticosterone, synthetic ovine corticotrophin releasing factor and arginine vasopressin on the release of adrenocorticotrophin by fetal rat pituitary glands.

The in-vitro release of ACTH by fetal rat pituitary glands on days 17, 19 and 21 of pregnancy was measured using radioimmunoassay. The spontaneous release of ACTH, expressed in pg ACTH/gland per h, increased with fetal age, in correlation with the sharp rise in pituitary ACTH content. However, since pituitary ACTH content was nearly sevenfold higher at term than on day 17, while basal release of ACTH was only threefold higher, one can speculate that the spontaneous release of ACTH was proportionally greater on day 17 than on day 21 of gestation. As corticosterone, at a physiological concentration (865 nmol/l), reduced ACTH release, it was concluded that the pituitary gland was one site of the negative feedback action of the corticosteroids during fetal life. Quantities of synthetic ovine corticotrophin releasing factor (CRF) which gave concentrations of 0.3-30 nmol/l in the incubation medium induced a sharp rise in ACTH release which was log-dose dependent between 0.3 and 3 nmolCRF /1 on day 17 and between 0.3 and 30 nmolCRF /1 on days 19 and 21. The response to CRF increased with fetal age. Quantities of arginine vasopressin (AVP) which gave concentrations of 2-200 nmol/l stimulated ACTH release at all stages of gestation investigated. However, the response to AVP was much lower than that to CRF. Potentiation of CRF-induced ACTH release was not observed when whole pituitary glands from 21-day-old fetuses were incubated with AVP (20 nmol/1) + CRF ( 3nmol /1). Such results were correlated with the ontogenesis of immunoreactive vasopressin- and CRF-containing fibres in the median eminence of the rat fetus, as well as with the CRF-like immunoreactivity present in adult rat pituitary portal plasma and the AVP content of the fetal rat hypophysis.

Adrenocorticotropic Hormone↗
PubMed1983

Normal development of cells with somatostatin immunoreactivity in the pancreas and duodenum of the rat fetus and newborn. Effect of hypophysectomy and intrauterine growth retardation.

Immunohistochemistry was employed to study the development of somatostatin-containing cells in the pancreas and duodenum of rat fetuses and of 1-7 day-old newborns. Immunoreactive cells were first detected in the pancreatic islets on day 17 of gestation and in the duodenum on day 18. Somatostatin cells were numerous in the pancreas and gut at term and in early postnatal stages. The development of somatostatin-containing cells in both pancreatic islets and duodenum was not affected by either fetal hypophysectomy on day 16 or intrauterine growth retardation induced by ligature of the main uterine vessels on day 17 of gestation.

Animals↗
PubMed1983

Late pregnancy maternal and fetal time-course of plasma ACTH and corticosterone after continuous ether inhalation by pregnant rats. Cytoimmunological study of fetal hypophyseal cells.

In order to compare the time-course and the amplitude of the hypophyseal-adrenal response to stress in both the mother and the fetus, female rats on day 20 of pregnancy were subjected to continuous ether inhalation and killed at different time intervals after the onset of stress (5, 10, 20, 30, 40 and 60 min). Plasma ACTH was determined by radioimmunoassay and plasma corticosterone by a competitive binding radioassay. In normal pregnant rats subjected to ether stress, the release of ACTH is tenfold higher than in the fetus, but the amplitude of maternal and fetal corticosterone release after this stimulus is very similar; the response occurs faster in the mother than in the fetus. In pregnant rats adrenalectomized 4 h before ether stress procedure, the ACTH release is smaller than in normal mothers and the plasma corticosterone values, despite the adrenalectomy, are close to those observed in resting rats at the same time of day. The fetal corticosterone release is still elevated under this stimulus and occurs faster than in fetuses from normal mothers. The cytoimmunological study of fetal hypophysis revealed both hypertrophy and hyperplasy of ACTH-containing cells during the first minutes of ether anesthesia.

Adrenalectomy↗
PubMed1981

Activity of the pituitary-adrenal system in rat fetuses subjected to encephalectomy in early or late stages of pregnancy.

The corticostimulating activity of the fetal rat hypophysis was studied on day 21, in fetuses deprived of their hypothalami by total removal of the brain (encephalectomy) in early (day 16) or late (day 19) stages of gestation. On day 19, the fetal manipulation was performed either on intact or adrenalectomized dams. The data show that: (1) Compared to controls, encephalectomy does not alter pituitary ACTH content in fetuses of intact mothers but that pituitary ACTH content does not significantly increase in encephalectomized fetuses of adrenalectomized mothers whereas it does in the littermate control fetuses. (2) Compared to controls, circulating ACTH levels are reduced by encephalectomy on both day 16 and day 19; an increase in ACTH levels occurs in both fetal groups in response to maternal adrenalectomy. Decapitation removes this fetal source of ACTH. (3) Adrenal glands are not as much atrophied by encephalectomy as by decapitation on day 16, whereas adrenal weight is decreased to the same extent by encephalectomy and by decapitation on day 19. However, the marked increase in circulating ACTH in both control and encephalectomized fetuses caused by maternal adrenalectomy is probably the cause of the significant increase in adrenal weight in these groups. (4) Adrenal corticosterone content in all the groups but not always adrenal weight, is a fairly accurate reflection of the ACTH levels measured. The results suggest that: (1) Pituitary ACTH content is not a sensitive measure of dynamic changes in synthesis and secretion in rat fetuses. (2) Changes in basal plasma ACTH in response to fetal encephalectomy show the presence of both an autonomous corticotropic function and a cephalic regulation of the corticotropic function from day 16 of fetal life and beyond. Pituitary autonomy seems higher in earlier than in later stages of gestation. (3) There is feedback of corticosterone into the pituitary of fetal rats; a marked increase in ACTH release is caused by the removal of the maternal corticosteroids.

Adrenal Glands↗
PubMed1981

Pituitary response to bilateral adrenalectomy, metyrapone treatment and ether stress in the newborn rat.

ACTH level, determined by radioimmunoassay, has been used as a reliable test to investigate pituitary response to bilateral adrenalectomy, metyrapone treatment and ether stress in 8-day-old rat newborns. The pituitary gland able to enhance ACTH release significantly, first in response to the decrease in plasma corticosteroid levels induced either by bilateral adrenalectomy or by metyrapone inhibition of the corticosteroidogenesis, and second in response to 2 min of ether exposure. This latter response was greater in females than in males but smaller in neonates than in adults. These data suggest that the steroid-feedback mechanism was operating fully at the 8th postnatal day and that central mechanisms partially responded to external signals of stress. However, a relative 'stress-non-responsive period' was evident by the 8th postnatal day. The newborn rat's hypothalamic-pituitary axis has partially matured to be responsive to stress by the end of the first week after birth.

Adrenalectomy↗
PubMed1981

Adrenocorticotrophic hormone in the anterior and neurointermediate lobes of the fetal rat pituitary gland.

The concentration of ACTH in the pars distalis and pars intermedia of the fetal rat hypophysis from days 17-21 of pregnancy was measured with a specific radioimmunoassay and a bioassay using isolated adrenal cells from adult rats. In both lobes of the pituitary gland, a significant correlation was observed between immunoreactive and bioreactive values, expressed as pg equivalents synthetic human 1-39 ACTH per microgram protein. In the pars distalis, ACTH concentrations increased steadily from days 17-20 and then remained unchanged to term. At this time they were tenfold higher than on day 17. In the neurointermediate lobe, ACTH was detected only from day 18; the concentration of ACTH increasing between days 18 and 19. At each of the stages of pregnancy examined, the concentration of ACTH in the pars distalis was greater than that in the pars intermedia. These data have demonstrated that ACTH is present in both anterior and neurointermediate lobes of the fetal rat hypophysis, that the functional differentiation of the pars distalis takes place earlier than that of the pars intermedia, and that the concentrations of corticotrophin in the pars distalis and in the pars intermedia have different patterns of development as gestation progresses.

Adrenocorticotropic Hormone↗
PubMed1981

[Hypophyseal corticotropic activity during perinatal period: ontogenesis and regulation].

1. In the fetal rat hypophysis, the "opio-melano-corticotropic" cells were immunocytologically revealed earlier in the pars distalis (day 16) than in the pars intermedia (day 17). At an early stage of embryonic development, some factors, possibly of nervous origin, could exert inductive influence on the differentiation and/or the increase in the number of immunoreactive cells. 2. Several forms of ACTH, characterized by their apparent molecular weight, bioactivity and immunoreactivity, can be observed when acid extracts are subjected to gel filtration on Sephadex G 50 fine columns. The ratios between these ACTH forms change during fetal development; the rise in bioactive ACTH content during the last days of gestation, is correlated with an increase of the "intermediate" and "little" molecular forms of ACTH and a parallel decrease of the "big" form. 3. The hypophyseal corticotropic activity is highest on days 18-19 of gestation. Between days 17 and 19, the cortico-stimulating activity is largely independent of the hypothalamus although the fetal hypothalamus shows light hypophyso-stimulating influence. In contrast, between days 19 and 21, the hypophyseal corticotropic activity is mostly under the hypothalamic control; the ACTH release is greatly reduced in its absence. 4. Circulating corticosteroids exert a negative feedback directly at the hypothalamic and pituitary levels. Such negative feedback could explain the decrease of the corticotropic activity of the pituitary during the last three days of gestation and the first postnatal days. 5. The fetus at the end of gestation, as the newborn, is responsive to stress; however, the extent of the pituitary response is weaker than in the adult.

Adrenal Glands↗
PubMed1980

Absence of transplacental passage of ACTH in the rat: direct experimental proof.

In order to investigate whether ACTH can cross the placenta of the rat at term, porcine 125I-ACTH was injected into mothers or fetuses. ACTH was then extracted from maternal and fetal plasma, using QUSO G-32, 2.5, 5, 10, 15, and 20 min after the injection of labelled ACTH. Plasma samples were also chromatographed on Sephadex G-50, fine, columns, 5 and 20 min after the administration of ACTH. When 125I-ACTH was injected into the mothers, the two methods used were unable to detect any radioactivity associated with intact ACTH in the fetal plasma. The same was observed in the maternal plasma when labelled hormone was administered to the fetuses. These observations provide direct experimental proof of the absence of transplacental passage in the rat of 125I-ACTH from the mother to the fetus as well as from the fetus to the mother.

Adrenocorticotropic Hormone↗
PubMed1980

Influences of heparin on ACTH distribution and immunoreactivity in plasma of the rat. In vivo and in vitro studies.

1. Blood samples from non-pregnant female rats were incubated in vitro with porcine 125I-ACTH, and the corresponding plasmas were chromatographed on fine Sephadex G 50. When heparin was added in vivo or in vitro, almost all the radioactivity appeared in the void volume of the columns; the same was observed when labelled ACTH was added to heparin-containing saline. In contrast, when NaCl instead of heparin was added to the blood in vivo as well as in vitro, almost all the plasma radioactivity was eluted later, with 125I-ACTH. 2. When labelled ACTH was i.v. administered to pregnant females, it was eluted in the void volume in the presence of heparin, and further down in its absence. 3. The same plasma samples from non-stressed or ether-stressed females were radioimmunoassayed for ACTH, with and without heparin. The degradation of ACTH was greater in the presence of heparin, and plasma ACTH concentration was understimated for low blood levels of heparin (5 UI/ml or less) and in contrast overestimated for high ones (25 or 50 UI/ml). 4. In conclusion, the reported data clearly demonstrated firstly that heparin added to rat blood traps ACTH molecules, promoting the formation of aggregates with apparent height molecular weight; secondly that heparin interferes with the direct radioimmunoassay of ACTH in the plasma.

Adrenocorticotropic Hormone↗
PubMed1979

Ontogenesis of cells producing polypeptide hormones (ACTH, MSH, LPH, GH, prolactin) in the fetal hypophysis of the rat: influence of the hypothalamus.

The ontogenesis of cells containing polypeptide hormones (ACTH, MSH, LPH, GH and Prolactin) was investigated in the fetal rat hypophysis by immunohistochemistry using the peroxidase-antiperoxidase complex. Corticotrophs, melanotrophs and lipotropic cells were revealed earlier in the pars distalis than in the pars intermedia. In the pars distalis, cells producing LPH were found in the morning of day 15 of gestation using anti-gamma- or anti-beta-LPH sera, and in afternoon using anti-alpha- or beta-endorphin sera. Cells containing beta-MSH were observed from the afternoon of day 15. The cells stainable with the anti-alpha-MSH, anti-beta-(17--39)ACTH and anti-beta-(1--24)ACTH sera appeared on day 16. In the pars intermedia, the cells producing alpha-MSH, beta-MSH, alpha- and beta-endorphin, gamma- and beta-LPH were observed in the morning of day 17, while cells containing ACTH were only revealed in the afternoon of the same day of gestation. Based on the treatment of serial paraffin sections with various antisera, it was clearly shown that MSH, ACTH, and LPH occur in the same cells located in the pars distalis as in the pars intermedia. The development of the corticotrophs, melanotrophs and lipotropic cells does not require the presence of the fetal hypothalamus or other central nervous structures. The pituitary glands of 21 day-old fetus encephalectomized on day 16 showed as many reactive cells as those of the littermate controls. The somatotrophs were first revealed in the pars distalis in the afternoon of day 19. The cells producing prolactin were not observed before day 21 of gestation. On some cases GH and prolactin were found together in one cell. The cytodifferentiation of GH and prolactin cells is apparently not under hypothalamic control.

Animals↗