Biomedical subjects

E L Manchester

Publications and source records attributed to E L Manchester.

6 recordsLinked to original sources

PubMed1987

Receptor radioligand system for measuring digoxin activity.

The purpose of this study was to develop and evaluate a receptor radioligand assay (RRA) for the measurement of digoxin, its metabolites, and endoxin and to compare the results of this assay with those of a fluorescence polarization immunoassay (FPIA) for digoxin. The within-run coefficients of variations for the RRA at digoxin concentrations of 2.0 and 5.0 nmol/L were 21 and 10%, respectively. Serum samples collected from 33 volunteers (not on digoxin medication) measured in the RRA resulted in levels less than 1.23 nmol/L digoxin equivalents (1.23 nmol/L is the lower level of sensitivity for this system). Serum samples collected from 29 patients receiving digoxin for therapeutic purposes and measured in the RRA gave a mean of 3.39 nmol/L digoxin equivalents. The samples collected from the patients receiving digoxin were also measured using FPIA with a mean of 1.75 nmol/L digoxin. The interference of progesterone, 11-alpha-hydroxyprogesterone, cortisone, and six digoxin metabolites on the binding of 3H-ouabain in the RRA was also evaluated.

Animals↗

PubMed1984

Benzodiazepine ([3H])-flunitrazepam) binding sites in cerebellar and cerebral cortical slices of mouse brain.

We have characterized and quantified the specific binding of [3H]-flunitrazepam ( FNZ ) to thick (230 micron) slices of mouse brain. The binding site has the characteristics of a benzodiazepine receptor, i.e., binding of FNZ is reversible, stereospecific, saturable and of high affinity. Clonazepam, but not R05 -4864, readily displaces the label. In contrast to results from homogenate assays, neither GABA nor bicuculline has any effect on [3H]- FNZ binding. However, as previously reported, the slice assay confirms the lower number of benzodiazepine receptors in "emotional" mouse brain. In addition, we have confirmed that the neurotoxin DSP4 can modify [3H]- FNZ binding though in our hands this compound elevates rather than reduces binding. The speed, simplicity and minimal tissue preparation involved suggests that this slice assay could be a valuable addition to neurochemical studies of neurotransmitter receptors.

Animals↗

PubMed1983

Strain differences in brain alpha2- and beta-adrenergic receptor binding in dystrophic mice.

We have examined alpha 2-adrenergic [( 3H]-clonidine) and beta-adrenergic [( 3H]-dihydroalprenolol; DHA) binding in brain membranes from four different dystrophic mouse mutants: 129/ReJ-dy; 129 B6F1/J-dy; C57BL/6J-dy and C57BL/6J-dy2J. As shown previously, male 129/ReJ-dy mice have significantly fewer brain [3H]-DHA binding sites than their littermate controls. In marked contrast, the remaining three mutants showed no differences in [3H]-DHA binding when compared to their respective controls although there were inter-strain differences, e.g., C57BL/6J-dy2J mice have significantly fewer binding sites than the 129B6F1/J-dy mice. On the other hand, we saw no strain differences in alpha 2-binding. In one mutant, however, (129 B6F1/J-dy) we observed a 50% increase in alpha 2-binding sites compared to littermate controls. We conclude that weight loss or undernutrition may be an important factor in determining brain levels of adrenergic binding sites in dystrophic mouse brain.

Animals↗

PubMed1983

Activation of ovine fetal adrenal function by pulsatile or continuous administration of adrenocorticotropin-(1-24). II. Effects on adrenal cell responses in vitro.

We have examined 1) the effects of mode of ACTH administration to fetal sheep in vivo on the pattern of corticosteroid output by dispersed adrenal cells in vitro, and 2) the time course of fetal adrenal activation during pulsatile ACTH administration to the fetus. Fetal sheep received the same amount of ACTH either as a continuous infusion (C-ACTH; 0.5 microgram/h) or as 15-min pulses every 2 h for 72 h (P-ACTH). Other fetuses received P-ACTH until labor occurred (mean, 100 h) or saline for 72 or 100 h. Adrenal cells from fetuses that received C-ACTH for 72 h produced more corticosterone from endogenous precursors after the addition of ACTH in vitro and after the addition of 0.3 microM progesterone (P4) or pregnenolone (P5) than cells from fetuses treated with P-ACTH for 72 h. There was no difference in cortisol (F) response between the two groups, although in both groups F output was greater than in controls. Adrenal cells from control fetuses produced more P4 in vitro during incubation with ACTH plus guanosine-5'-(beta, gamma-imido)triphosphate [Gpp(NH)p] or N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate [(Bu)2cAMP] than after ACTH alone. There was no significant F response to the agonists, and F output was quantitatively less than that of P4. After 72-h P-ACTH, the mean P4 output after ACTH addition was not significantly different from that after ACTH plus Gpp(NH)p or (Bu)2cAMP. By 100 h of P-ACTH, the output of F exceeded that of P4 and was not different in response to ACTH, ACTH plus Gpp(NH)p, or (Bu)2cAMP. After 72 h of P-ACTH, incorporation of exogenous P4, but not P5, 17 alpha-hydroxyprogesterone, or 17 alpha-hydroxypregnenolone, into F was greater than that in cells from control fetuses. By 100 h of P-ACTH, incorporation of all substrates into F was greater than that after P-ACTH for 72 h. We conclude that 1) both C-ACTH and P-ACTH for 72 h increase fetal adrenal responses, but the pattern of corticosteroid output in vitro is determined by the mode of ACTH administration in vivo; 2) adrenal responsiveness is increased further between 72 and 100 h of P-ACTH, and activation probably involves changes in ACTH receptor-GTP coupling as well as enzyme activities on the pathway to F biosynthesis.

Adrenal Glands↗

PubMed1982

Activation of adrenal function in fetal sheep by the infusion of adrenocorticotropin to the fetus in utero.

We determined whether ACTH1-24, infused into fetal lambs at a rate that is known to cause premature labor, elicits changes in the responsiveness of the fetal adrenal glands, and alters the pattern of corticosteroid output. Plasma cortisol (F), corticosterone (B) and progesterone (P4) were measured during 72 h of infusion of saline or ACTH (10 micrograms/h) beginning on Day 127 of pregnancy. Adrenals were then dispersed into isolated cells, and the output of F, B and P4 after exogenous ACTH determined in vitro. Plasma concentrations of F and B were higher in ACTH-treated fetuses. The increment in F (5-to 7-fold) was greater than that in B (2-fold) such that the F:B ratio in plasma of ACTH-treated fetuses on Days 2 and 3 of infusion was 2.5 times higher than in controls. After 72 h of infusion, the adrenal weights in ACTH-treated fetuses (741 +/- 38 mg, +/- SEM; n = 4) were greater than in the control animals (349 +/- 11 mg). There was a significant effect of ACTH pretreatment in vivo on F output by isolated adrenal cells in vitro. Mean increments in F output after addition of ACTH1-24 (5000 pg/ml) in vitro rose from 368 +/- 235 pg/50,000 cells in controls, to 64,639 +/- 19,875 pg/50,000 cells after ACTH in vivo. There was no significant effect of ACTH in vivo on B output in vitro; the ratio of F:B output, either in the absence or presence of ACTH in vitro, was significantly higher in cells from ACTH-pretreated fetuses. There was a significant effect of in vivo ACTH on in vitro P4 output. After ACTH treatment in vivo there was an increase in the vitro output ratio of F:P4, but no change in the output ratio of B:P4. We conclude that ACTH treatment of the fetal lamb in vivo results in activation of fetal adrenal function, increased fetal adrenal responsiveness to ACTH, and directed corticosteroid biosynthesis towards cortisol. Our results are consistent with an increase in fetal adrenal 17 alpha-hydroxylase activity after ACTH treatment.

Adrenal Glands↗

PubMed1981

The development of fetal adrenal function.

The response profiles of fetal sheep adrenals to tropic stimulation have been examined ih vivo and in vitro. Isolated adrenal cells from sheep fetuses in early pregnancy (Day 50) reduced cortisol in response to ACTH, dibutyryl cyclic AMP and GTP. The response was minimal on Day 100, but reappeared near term. 17 alpha-Hydroxyprogesterone was converted to cortisol by adrenals of all ages, but pregnenolone and progesterone were converted to cortisol only in early and late, but not mid-pregnancy. These studies suggested that the mid-gestation loss of fetal adrenal responsiveness was associated with post-receptor/adenylate cyclase events and involved loss of 17 alpha-hydroxylase activity. Fetal adrenal function was activated by exogenous ACTH in vivo, and was reflected in an increase in the ratio of cortisol to corticosterone in fetal plasma and in augmented cortisol output in vitro from dispersed fetal adrenal cells. The results were consistent with an effect of ACTH administration on 17 alpha-hydroxylation. Fetal pituitary cells, prostaglandin E2, alpha-MSH and term placental extract are other potential (sources of) corticotropins, although further studies are required to delineate the nature and origin of the active substances, and/or their primary sites of action.

Adrenal Glands↗