Developmental changes in prostaglandin E(2) receptor subtypes in porcine ductus arteriosus. Possible contribution in altered responsiveness to prostaglandin E(2).

BACKGROUND: Prostaglandin E(2) (PGE(2)) is important in ductus arteriosus (DA) patency, but the types of functional PGE(2) receptors (EP) in the developing DA are not known. We postulated that age-dependent alterations in EP and/or their subtypes may possibly contribute to the reduced responsiveness of the newborn DA to PGE(2). METHODS AND RESULTS: We determined PGE(2) receptor subtypes by competition binding and immunoblot studies on the DA of fetal ( approximately 75% and 90% gestation) and newborn (<45 minutes old) pigs. We studied the effects of EP receptor stimulation on cAMP signaling in vitro and on term newborn (<3 hours old) DA patency in vivo. Fetal pig DA expressed EP(2), EP(3), and EP(4) receptors equivalently, but not EP(1). In neonatal DA, EP(1), EP(3), and EP(4) were undetectable, whereas EP(2) density was similar in fetus and newborn. Prostaglandin-induced changes in cAMP mirrored binding data. 16,16-Dimethyl PGE(2) and 11-deoxy PGE(1) (EP(2)/EP(3)/EP(4) agonist) produced more cAMP in fetus than newborn, but butaprost (selective EP(2) agonist) caused similar cAMP increases in both; EP(3) and EP(4) ligands (M&B28767 and AH23848B, respectively) affected cAMP production only in fetus. After birth, administration of butaprost alone was as effective as 11-deoxy PGE(1) and 16,16-dimethyl PGE(2) in dilating DA in vivo. CONCLUSIONS: The data reveal fewer PGE(2) receptors in the DA of the newborn than in that of the fetus; this may contribute to the decreased responsiveness of the DA to PGE(2) in newborn. Because EP(2) receptors seem to mediate the effects of PGE(2) on the newborn DA, one may propose that a selective EP(2) agonist may be preferred as a pharmacological agent to maintain DA patency in infants with certain congenital heart diseases.

Significant interaction between the nonprescription antihistamine diphenhydramine and the CYP2D6 substrate metoprolol in healthy men with high or low CYP2D6 activity.

The prototype "classic" over-the-counter antihistamine diphenhydramine was shown to interact with the polymorphic P450 enzyme CYP2D6. This project was undertaken to investigate (1) whether diphenhydramine inhibits the biotransformation of the clinically relevant CYP2D6 substrate metoprolol in vitro and (2) whether this in vitro interaction results in a clinically significant pharmacokinetic and pharmacodynamic drug interaction in vivo. In vitro incubations were carried out with microsomes obtained from lymphoblastic cells transfected with CYP2D6 complementary deoxyribonucleic acid to determine the type and extent of inhibition. We then randomized 16 subjects with genetically determined high (extensive metabolizers) or low (poor metabolizers) CYP2D6 activity to receive metoprolol (100 mg) in the presence of steady-state concentrations of diphenhydramine or placebo. In vitro, diphenhydramine was a potent competitive inhibitor of metoprolol alpha-hydroxylation, exhibiting an inhibitory constant of 2 micromol/L and increasing the Michaelis-Menten constant of metoprolol sixfold. In vivo, diphenhydramine decreased metoprolol oral and nonrenal clearances twofold and metoprolol-->alpha-hydroxymetoprolol partial metabolic clearance 2.5-fold in extensive metabolizers (all P < .05) but not in poor metabolizers (P > .2). Although the hemodynamic response to metoprolol was unaltered by diphenhydramine in poor metabolizers (P > .05), metoprolol-related effects on heart rate, systolic blood pressure, and Doppler-derived aortic blood flow peak velocity were more pronounced and lasted significantly longer in extensive metabolizers receiving diphenhydramine compared with poor metabolizers and extensive metabolizers receiving placebo. We conclude that diphenhydramine inhibits the metabolism of metoprolol in extensive metabolizers, thereby prolonging the negative chronotropic and inotropic effects of the drug. Clinically relevant drug interactions may occur between diphenhydramine and many CYP2D6 substrates, particularly those with a narrow therapeutic index.

Characterization of PGE2 receptors in fetal and newborn ductus arteriosus in the pig.

We compared the total density and the relative expression of EP receptor (EP) subtypes in ductus arteriosus (DA) of the newborn with that of the fetal piglet. Saturation binding experiments showed 3-fold less PGE2 receptors in the newborn than in the fetus because of loss of EP3 and EP4 receptors thus explaining, at least partly, the reduced responsiveness to PGE2 of the newborn DA. Displacement experiments showed that the relative proportions of EP2, EP3, and EP4 were similar in the fetal DA but only EP2 was detected in the DA of the newborn pig. Hence, PGE2 effects in the newborn DA seem to be exclusively mediated by EP2 receptors both in vitro and in vivo. These findings may help to propose more specific therapies for regulation of DA's tone in certain newborns for whom conventional therapy is contraindicated.

Partial pressures and nature of products. Application to the photolysis of PH3 and NH3 in the atmosphere of Jupiter and Saturn.

The photolysis of mixtures of gases containing NH3 or PH3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH3, PH3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed.

[Marcus-Gunn Syndrome. Based on a case report]. / Syndrome de Marcus-Gunn. A propos d'un cas.

The Marcus-Gunn syndrome associates an unilateral congenital blepharoptosis and "jaw-winking" synkinesia. We report a 12-year-old girl presenting an unilateral Marcus-Gunn syndrome and discuss the clinic, pathogenesis and treatment of this syndrome.

[Management by objectives: an experience by transfusion and immunology service in Rabat]. / Contractualisation interne : expérience du service de transfusion et d'immunologie de Rabat.

The management by objectives method has become highly used in health management. In this context, the blood transfusion and haemovigilance service has been chosen for a pilot study by the Head Department of the Ibn Sina Hospital in Rabat. This study was conducted from 2009 to 2011, in four steps. The first one consisted in preparing human resources (information and training), identifying the strengths and weaknesses of the service and the identification and classification of the service's users. The second step was the elaboration of the terms of the contract, which helped to determine two main strategic objectives: to strengthen the activities of the service and move towards the "status of reference." Each strategic objective had been declined in operational objectives, then in actions and the means required for the implementation of each action. The third step was the implementation of each action (service, head department) so as to comply with the terms of the contract as well as to meet the deadlines. Based on assessment committees, the last step consisted in the evaluation process. This evaluation was performed using monitoring indicators and showed that management by objectives enabled the Service to reach the "clinical governance level", to optimize its human and financial resources and to reach the level of "national laboratory of reference in histocompatibility". The scope of this paper is to describe the four steps of this pilot study and to explain the usefulness of the management by objectives method in health management.

In vitro characterization of cytochrome P450 2D6 inhibition by classic histamine H1 receptor antagonists.

Classic antihistamines, namely diphenhydramine, chlorpheniramine, clemastine, perphenazine, hydroxyzine, and tripelennamine, share structural features with substrates and inhibitors of the polymorphic cytochrome P450 (CYP) isozyme CYP2D6. Therefore, the current study was undertaken to characterize the in vitro inhibition of CYP2D6 by these commonly used, histamine H1 receptor antagonists. Microsomal incubations were performed using bufuralol as a specific CYP2D6 substrate and microsomes derived from human cells transfected with CYP2D6 cDNA. Reaction velocities were assessed in the absence and presence of antihistamines (20 microM) at 11 substrate concentrations (1, 2.5, 5, 7.5, 10, 15, 20, 25, 50, 75, and 100 microM), as well as at three nonsaturating substrate concentrations (2.5, 5, and 20 microM) and three inhibitor concentrations (5, 20, and 50 microM). In the presence of all antihistamines, the Vmax and KM of bufuralol 1'-hydroxylation were significantly altered, compared with the uninhibited reaction (p < 0.05). Lineweaver-Burke plots suggested competitive inhibition of the reaction by diphenhydramine and mixed inhibition by all other antihistamines tested. Diphenhydramine and chlorpheniramine, with estimated Ki values of approximately 11 microM, were the weakest inhibitors of CYP2D6 in vitro. Whereas tripelennamine, promethazine, and hydroxyzine were similar in their inhibitory capacities (Ki approximately 4-6 microM), clemastine appeared to be significantly more potent, with a Ki of approximately 2 microM. These data demonstrate that classic histamine H1 receptor antagonists, available in over-the-counter preparations, inhibit CYP2D6 in vitro. Furthermore, the CYP2D6-inhibitory concentrations of these antihistamines are in the range of their expected hepatic blood concentrations, suggesting that, under specific circumstances, clinically relevant interactions between classic antihistamines and CYP2D6 substrates might occur.

Characterization of PGE2 receptors in fetal and newborn lamb ductus arteriosus.

Although the role of PGE2 in maintaining ductus arteriosus (DA) patency is well established, the specific PGE2 receptor subtype(s) (EP) involved have not been clearly identified. We used late gestation fetal and neonatal lambs to study developmental regulation of EP receptors. In the fetal DA, radioligand binding and RT-PCR assays virtually failed to detect EP1 but detected EP2, EP3D, and EP4 receptors in equivalent proportions. In the newborn lamb, DA total density was one-third of that found in the fetus and only EP2 was detected. Stimulation of EP2 and EP4 increased cAMP formation and was associated with DA relaxation. Though stimulation of EP3 inhibited cAMP formation, it surprisingly relaxed the fetal DA both in vitro and in vivo. This EP3-induced relaxation was specifically diminished by the ATP-sensitive K(+) (K(ATP)) channel blocker glibenclamide. In conclusion, PGE2 dilates the late gestation fetal DA through pathways that involve either cAMP (EP2 and EP4) or K(ATP) channels (EP3). The loss of EP3 and EP4 receptors in the newborn DA is consistent with its decreased responsiveness to PGE2.

Building Canada's health research capacity within the framework of the Canadian Institutes of Health Research.

The establishment of the Canadian Institutes of Health Research (CIHR) generated considerable excitement about the capacity for health research in Canada. The long term success of the CIHR will be determined, in part, by its ability to recruit, train and retain a cadre of talented researchers. During a workshop to develop the research agenda for one of the proposed institutes within the CIHR, a national, multidisciplinary group of clinical and basic science research trainees were invited to present their views about the challenges that face Canadian researchers of tomorrow. The objective of this paper is to present the challenges associated with recruiting, training and retaining health researchers, and to identify new opportunities provided by the creation of the CIHR. The present paper concludes with suggestions that may improve the success of researchers and, ultimately, the success of the CIHR.

Prostanoid receptors: ontogeny and implications in vascular physiology.

Prostanoids exert significant effects on circulatory beds. They play a role in the response of the vasculature to adjustments in perfusion pressure and oxygen and carbon dioxide tension, and they mediate the actions of numerous factors. The role of prostanoids in governing circulation of the perinate is suggested to surpass that in the adult. Prostanoids are abundantly generated in the perinate. They have been implicated in autoregulation of blood flow as studied in brain and eyes. Prostaglandins are also dominant regulators of ductus arteriosus tone. The effects of these autacoids are mediated through specific G protein-coupled receptors. In addition to the pharmacological characterization of the prostanoid receptors, important advances in understanding the biology of these receptors have been made in the last decade. Their cloning and the development of animals with disrupted genes of these receptors have been very informative. The involvement of prostanoid receptors in the developing subject, especially on brain and ocular vasculature and on ductus arteriosus, has also begun to be investigated; the expression of these receptors changes with development. Some but not all of the ontogenic changes in these receptors are attributed to homologous regulation. Interestingly, in the process of elucidating their effects, functional perinuclear prostaglandin E2 receptors have been uncovered. This article reviews prostanoid receptors and addresses implications on the developing subject with attention to vascular physiology.