Efficacy and ligand bias at the μ-opioid receptor

In order to describe drug action at a GPCR, a full understanding of the pharmacological terms affinity, efficacy and potency is necessary. This is true whether comparing the ability of different agonists to produce a measurable response in a cell or tissue, or determining the relative ability of an agonist to activate a single receptor subtype and produce multiple responses. There is a great deal of interest in the μ-opioid receptor (MOP receptor) and the ligands that act at this GPCR not only because of the clinically important analgesic effects produced by MOP agonists but also because of their liability to induce adverse effects such as respiratory depression and dependence. Our understanding of the mechanisms underlying these effects, as well as the ability to develop new, more effective MOP receptor drugs, depends upon the accurate determination of the efficacy with which these ligands induce coupling of MOP receptors to downstream signalling events. In this review, which is written with the minimum of mathematical content, the basic meaning of terms including efficacy, intrinsic activity and intrinsic efficacy is discussed, along with their relevance to the field of MOP receptor pharmacology, and in particular in relation to biased agonism at this important GPCR.

Novel GPCR paradigms at the μ-opioid receptor

Opioids, such as morphine, are the most clinically useful class of analgesic drugs for the treatment of acute and chronic pain. However, the use of opioids is greatly limited by the development of severe adverse side effects. Consequently, drug discovery efforts have been directed towards improving the therapeutic profile of opioid-based treatments. Opioid receptors are members of the family of GPCRs. As such, the recent GPCR paradigms of biased agonism and allosterism may provide novel avenues for more effective analgesics. Biased agonism (or functional selectivity) has been described for all the opioid receptor family members. Furthermore, the first allosteric modulators of opioid receptors have very recently been described. However, identification and quantification of biased agonism in a manner that is informative to medicinal chemists and drug discovery programmes still remains a challenge. In this review, we examine the progress, to date, towards identification and quantification of biased agonism and allosterism at the μ-opioid receptor in the context of its implications for the discovery of better and safer analgesics.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Morphine-induced internalization of the L83I mutant of the rat μ-opioid receptor

BACKGROUND AND PURPOSE

Naturally occurring single-nucleotide polymorphisms (SNPs) within GPCRs can result in alterations in various pharmacological parameters. Understanding the regulation and function of endocytic trafficking of the μ-opioid receptor (MOP receptor) is of great importance given its implication in the development of opioid tolerance. This study has compared the agonist-dependent trafficking and signalling of L83I, the rat orthologue of a naturally occurring variant of the MOP receptor.

EXPERIMENTAL APPROACH

Cell surface elisa, confocal microscopy and immunoprecipitation assays were used to characterize the trafficking properties of the MOP-L83I variant in comparison with the wild-type receptor in HEK 293 cells. Functional assays were used to compare the ability of the L83I variant to signal to several downstream pathways.

KEY RESULTS

Morphine-induced internalization of the L83I MOP receptor was markedly increased in comparison with the wild-type receptor. The altered trafficking of this variant was found to be specific to morphine and was both G-protein receptor kinase- and dynamin-dependent. The enhanced internalization of L83I variant in response to morphine was not due to increased phosphorylation of serine 375, arrestin association or an increased ability to signal.

CONCLUSIONS AND IMPLICATIONS

These results suggest that morphine promotes a specific conformation of the L83I variant that makes it more liable to internalize in response to morphine, unlike the wild-type receptor that undergoes significantly less morphine-stimulated internalization, providing an example of a ligand-selective biased receptor. The presence of this SNP within an individual may consequently affect the development of tolerance and analgesic responses.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Nosocomial outbreak of hepatitis B virus infection involving two hospitals in the Republic of Ireland

The routes of nosocomial hepatitis B virus (HBV) transmission have changed over the years. Initiatives to prevent transfusion-associated HBV and healthcare worker-to-patient transmission have had a positive impact on these transmission routes. Recent reports of outbreaks of nosocomial HBV have implicated breaches in standard precautions as important causes of HBV transmission. This report describes a nosocomial outbreak of HBV infection in the Republic of Ireland, which occurred between January 2005 and March 2006. The outbreak was detected following identification of a case of acute HBV infection in a patient whose only risk factor was a recent surgical procedure. The extensive multi-agency investigation that followed revealed that the patient was one of five cases of acute HBV infection and that four separate transmission events between infectious cases had occurred in two different hospitals over a 15-month period. A definitive cause for each transmission event was not identified, although lapses in adherence to standard precautions, safe injection and phlebotomy practices could not be ruled out. Two secondary cases of acute HBV infection in community contacts of two of the nosocomial cases were identified. Phylogenetic analysis proved a useful tool in confirming infection with a pre-core HBV mutant and viral transmission between the seven patients. A patient notification exercise involving 1028 potentially exposed patients found no evidence of additional cases of nosocomial HBV infection. These findings highlight the importance of consistent application of standard precautions.

Deletion of the distal COOH-terminus of the A2B adenosine receptor switches internalization to an arrestin- and clathrin-independent pathway and inhibits recycling

BACKGROUND AND PURPOSE

We have investigated the effect of deletions of a postsynaptic density, disc large and zo-1 protein (PDZ) motif at the end of the COOH-terminus of the rat A(2B) adenosine receptor on intracellular trafficking following long-term exposure to the agonist 5'-(N-ethylcarboxamido)-adenosine.

EXPERIMENTAL APPROACH

The trafficking of the wild type A(2B) adenosine receptor and deletion mutants expressed in Chinese hamster ovary cells was studied using an enzyme-linked immunosorbent assay in combination with immunofluorescence microscopy.

KEY RESULTS

The wild type A(2B) adenosine receptor and deletion mutants were all extensively internalized following prolonged treatment with NECA. The intracellular compartment through which the Gln(325)-stop receptor mutant, which lacks the Type II PDZ motif found in the wild type receptor initially trafficked was not the same as the wild type receptor. Expression of dominant negative mutants of arrestin-2, dynamin or Eps-15 inhibited internalization of wild type and Leu(330)-stop receptors, whereas only dominant negative mutant dynamin inhibited agonist-induced internalization of Gln(325)-stop, Ser(326)-stop and Phe(328)-stop receptors. Following internalization, the wild type A(2B) adenosine receptor recycled rapidly to the cell surface, whereas the Gln(325)-stop receptor did not recycle.

CONCLUSIONS AND IMPLICATIONS

Deletion of the COOH-terminus of the A(2B) adenosine receptor beyond Leu(330) switches internalization from an arrestin- and clathrin-dependent pathway to one that is dynamin dependent but arrestin and clathrin independent. The presence of a Type II PDZ motif appears to be essential for arrestin- and clathrin-dependent internalization, as well as recycling of the A(2B) adenosine receptor following prolonged agonist addition.

Audit of performance of size 1.5 ProSeal laryngeal mask airways in infants less than six months undergoing inguinal herniotomy

Many anaesthetists have found the size 1.5 classic Laryngeal Mask Airway unsuitable for use in children under 10 kg, whereas recent studies evaluating the ProSeal Laryngeal Mask Airway (PLMA) show high success rates, even during laparoscopic surgery. Our routine practice has been to use tracheal intubation for inguinal herniotomy in children weighing less than 10 kg. Following the introduction of the PLMA to our hospital, we decided to audit our use of the PLMA 1.5 in this group of patients. We included 20 consecutive infants, aged less than six months and weighing 5 to 10 kg. We recorded patient, anaesthetic and insertion details, device performance data and complications. No aspect of anaesthetic practice was changed by involvement in this audit. The PLMA was inserted successfully at the first attempt in 85% (17/20) of infants. Overall successful insertion occurred in 90% (18/20) and satisfactory airway maintenance was provided for the duration of anaesthesia in 90% (18/20). The mean leak pressure was 24 cmH2O (range 15 to 30 cmH2O). We found the 1.5 PLMA provided a satisfactory airway in 90% of infants. This report adds to the evidence that the PLMA 1.5 can provide a satisfactory alternative to intubation in selected infants.

The effect of protein kinase C and G protein-coupled receptor kinase inhibition on tolerance induced by mu-opioid agonists of different efficacy

Differences in the mechanisms underlying tolerance and mu-opioid receptor desensitization resulting from exposure to opioid agonists of different efficacy have been suggested previously. The objective of this study was to determine the effects of protein kinase C (PKC) and G protein-coupled receptor kinase (GRK) inhibition on antinociceptive tolerance in vivo to opioid agonists of different efficacy. A rapid (8-h) tolerance-induction model was used where each opioid was repeatedly administered to naive mice. Animals were then challenged with the opioid after injection of a kinase inhibitor to determine its effects on the level of tolerance. Tolerance to meperidine, morphine, or fentanyl was fully reversed by the PKC inhibitor 12-(2-cyanoethyl)-6,7,12,13-tetrahydro-13-methyl-5-oxo-5H-indolo(2,3-a)pyrrolo(3,4-c)carbazole (Gö6976). However, in vivo tolerance to [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) was not reversed by PKC inhibition. The novel small-molecule GRK inhibitors beta-adrenergic receptor kinase 1 inhibitor and 2-(8-[(dimethylamino) methyl]-6,7,8,9-tetrahydropyridol[1,2-a]indol-3-yl)-3-(1-methylindol-3-yl)maleimide (Ro 32-0432) did not reverse the tolerance to meperidine, fentanyl, or morphine but did reverse the tolerance to DAMGO. To correlate GRK-dependent DAMGO-induced tolerance with mu-opioid receptor desensitization, we used in vitro whole-cell patch-clamp recording from mouse locus coeruleus neurons and observed that the GRK inhibitors reduced DAMGO-induced desensitization of mu-opioid receptors, whereas the PKC inhibitor had no effect. These results suggest that tolerance induced by low- and moderate-efficacy mu-opioid receptor agonists is dependent on PKC, whereas tolerance induced by the high-efficacy agonist DAMGO is dependent on GRK.

Role of protein kinase C and mu-opioid receptor (MOPr) desensitization in tolerance to morphine in rat locus coeruleus neurons

In morphine tolerance a key question that remains to be answered is whether μ-opioid receptor (MOPr) desensitization contributes to morphine tolerance, and if so by what cellular mechanisms. Here we demonstrate that MOPr desensitization can be observed in single rat brainstem locus coeruleus (LC) neurons following either prolonged (> 4 h) exposure to morphine in vitro or following treatment of animals with morphine in vivo for 3 days. Analysis of receptor function by an operational model indicated that with either treatment morphine could induce a profound degree (70–80%) of loss of receptor function. Ongoing PKC activity in the MOPr-expressing neurons themselves, primarily by PKCα, was required to maintain morphine-induced MOPr desensitization, because exposure to PKC inhibitors for only the last 30–50 min of exposure to morphine reduced the MOPr desensitization that was induced both in vitro and in vivo. The presence of morphine was also required for maintenance of desensitization, as washout of morphine for > 2 h reversed MOPr desensitization. MOPr desensitization was homologous, as there was no change in α₂-adrenoceptor or ORL1 receptor function. These results demonstrate that prolonged morphine treatment induces extensive homologous desensitization of MOPrs in mature neurons, that this desensitization has a significant PKC-dependent component and that this desensitization underlies the maintenance of morphine tolerance.

Involvement of PKC alpha and G-protein-coupled receptor kinase 2 in agonist-selective desensitization of mu-opioid receptors in mature brain neurons

BACKGROUND AND PURPOSE

The ability of an agonist to induce desensitization of the mu-opioid receptor (MOR) depends upon the agonist used. Furthermore, previous data suggest that the intracellular mechanisms underlying desensitization may be agonist-specific. We investigated the mechanisms underlying MOR desensitization, in adult mammalian neurons, caused by morphine (a partial agonist in this system) and DAMGO (a high-efficacy agonist).

EXPERIMENTAL APPROACH

MOR function was measured in locus coeruleus neurons, by using whole-cell patch-clamp electrophysiology, in rat and mouse brain slices (both wild-type and protein kinase C (PKC)alpha knockout mice). Specific isoforms of PKC were inhibited by using inhibitors of the receptors for activated C-kinase (RACK), and in vivo viral-mediated gene-transfer was used to transfect neurons with dominant negative mutants (DNMs) of specific G-protein-coupled receptor kinases (GRKs).

KEY RESULTS

Morphine-induced desensitization was attenuated by using RACK inhibitors that inhibit PKCalpha, but not by other isoform-specific inhibitors. Further, the PKC component of morphine-induced desensitization was absent in locus coeruleus neurons from PKCalpha knockout mice. The PKC-enhanced morphine-induced desensitization was not affected by over-expression of a GRK2 dominant negative mutant (GRK2 DNM). In contrast, DAMGO-induced MOR desensitization was independent of PKC activity but was reduced by over-expression of the GRK2 DNM but not by that of a GRK6 DNM.

CONCLUSIONS AND IMPLICATIONS

In mature mammalian neurons, different MOR agonists can induce MOR desensitization by different mechanisms, morphine by a PKCalpha-mediated, heterologous mechanism and DAMGO by a GRK-mediated, homologous mechanism. These data represent functional selectivity at the level of receptor desensitization.

Cost induced by hip fractures

Hip fracture is the most common fracture in the elderly population. Treating hip fractures is a major burden on the Irish Health system. There is no recent Republic of Ireland study detailing hospital costs for such injuries. A comprehensive analysis of 143 patients admitted with a hip fracture was performed to determine current medical expenditure incurred during acute hospitalization for hip fractures during 2005 in a major university hospital. Costs associated with surgery (implant & theatre costs), laboratory, radiology, physiotherapy and ward were calculated on individual basis. All the hip fractures were above 60 years of age (mean 82 years); average stay in the hospital was 11 days. The mean total hospital expenditure per patient was Euro 9236.01 of which ward costs contributed 55.33%, operative costs 39.82% and investigations 4.83%. The result clearly show that hip fractures have a major economic impact arising from the inpatient treatment, most of which relate to length of hospital stay.

Clostridium difficile infection precipitating hemolysis in glucose-6-phosphate dehydrogenase-deficient preterm twins causing severe neonatal jaundice

The incidence of glucose-6-phosphate dehydrogenase deficiency in neonates of immigrant mothers in Canada is increasing. Newborn screening programs in Canada do not screen for this disorder. Infants with G-6-PD deficiency may develop jaundice resulting in kernicterus with devastating sequelae. In this case report, we speculate that Clostridium difficile infection may have triggered severe jaundice in G-6-PD-deficient neonates.

Agonist-selective mechanisms of GPCR desensitization

The widely accepted model of G protein-coupled receptor (GPCR) regulation describes a system where the agonist-activated receptors couple to G proteins to induce a cellular response, and are subsequently phosphorylated by a family of kinases called the G protein-coupled receptor kinases (GRKs). The GRK-phosphorylated receptor then acts as a substrate for the binding of a family of proteins called arrestins, which uncouple the receptor and G protein so desensitizing the agonist-induced response. Other kinases, principally the second messenger-dependent protein kinases, are also known to play a role in the desensitization of many GPCR responses. It is now clear that there are subtle and complex interactions between GRKs and second messenger-dependent protein kinases in the regulation of GPCR function. Functional selectivity describes the ability of agonists to stabilize different active conformations of the same GPCR. With regard to desensitization, distinct agonist-activated conformations of a GPCR could undergo different molecular mechanisms of desensitization. An example of this is the mu opioid receptor (MOPr), where the agonists morphine and [D-Ala(2),N-MePhe(4),Gly-ol(5)]enkephalin (DAMGO) induce desensitization of the MOPr by different mechanisms, largely protein kinase C (PKC)- or GRK-dependent, respectively. This can be best explained by supposing that these two agonists stabilize distinct conformations of the MOPr, which are nevertheless able to couple to the relevant G-proteins and produce similar responses, yet are sufficiently different to trigger different regulatory processes. There is evidence that other GPCRs also undergo agonist-selective desensitization, but the full therapeutic consequences of this phenomenon await further detailed study.

Feasibility of a self-administered geriatric assessment tool for older patients with cancer

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Background: As the population ages, there is an emerging need to develop a geriatric assessment (GA) tool for oncologists to characterize the ‘functional age‘ of older patients in order to tailor treatment, stratify outcomes by factors other than chronological age, and develop interventions to optimize cancer treatment. The GA tool must be easy to administer in order to minimize burden on clinic resources. The goal of this study was to determine the feasibility of administering a brief, comprehensive, self-administered GA tool to older patients before their meeting with the oncologist. Methods: The self-administered GA tool addresses the following domains: functional status, comorbidity, psychological state, nutritional status, and social support. The measures which comprise the tool are brief, reliable, validated, predictive of mortality and morbidity in older patients, and do not require a staff member to administer. Feasibility was assessed by the following parameters: 1) % able to complete the GA tool unassisted; 2) % requiring the assistance of staff members versus non-staff members; 3) overall patient satisfaction; 4) time to complete. Results: 168 (96%) of 175 patients completed the GA tool with a mean age of 76 (range 64–92) with AJCC stages [I (33%), II (17%), III (10%), IV (39%)] across a variety of tumor types. Of the study cohort, 67% were women, 57% were married, and 89% were retired. Median time to complete the GA tool was 13 minutes and mean time was 16 minutes (SD 11, range 3–60). Most completed the GA tool on their own (75%) or received assistance from a friend or family member (20%). Only 4% required assistance from a member of the healthcare team. Patient satisfaction with the GA tool was high: 88% satisfied with the length, 92% reported no difficult questions, and 97% reported no upsetting questions. Based on the assessment scores, the following interventions were offered: referral to a social worker (38%), nutritionist (43%), visiting nurse/home health aide (30%), internist (23%), rehabilitation (13%), ENT (13%), ophthalmology (7%), and psychiatry (5%). Conclusion: This brief, comprehensive, self-administered GA tool is feasible for use in the outpatient oncology setting. Prospective trials are needed to determine the effectiveness of the interventions offered.

No significant financial relationships to disclose.

Internalization and desensitization of the oxytocin receptor is inhibited by Dynamin and clathrin mutants in human embryonic kidney 293 cells

Oxytocin (OT) has long been used as an uterotonic during labor management in women, and yet responses to OT infusion remain variable and unpredictable among patients. The investigation of oxytocin receptor (OTR) regulation will benefit labor management, because the clinical practice of continuous iv infusion of OT is not optimal. As with other G protein-coupled receptors, it is likely that the OTR internalizes and/or desensitizes upon continuous agonist exposure. The mechanisms by which this might occur, however, are unclear. Here we explore OTR internalization and desensitization in human embryonic kidney cells by utilizing inhibitors of heterologous second messenger systems and recently available mutant cDNA constructs. We report rapid and extensive internalization and desensitization of the OTR upon agonist exposure. Internalization was unaffected by inhibitors of protein kinase C or Ca(2+) calmodulin-dependant kinase II but was significantly reduced after transfection with dominant-negative mutant cDNAs of G protein-coupled receptor kinase 2, beta-Arrestin2, Dynamin, and Eps15 (a component of clathrin-coated pits). Moreover, desensitization of the OTR, measured by a calcium mobilization assay, was also inhibited by the aforementioned cDNA constructs. Thus, our data demonstrate, for the first time, the importance of the classical clathrin-mediated pathway during agonist-induced OTR internalization and desensitization.

The placebo effect in irritable bowel syndrome trials: a meta-analysis

BACKGROUND

Despite the apparent high placebo response rate in randomized placebo-controlled trials (RCT) of patients with irritable bowel syndrome (IBS), little is known about the variability and predictors of this response.

OBJECTIVES

To describe the magnitude of response in placebo arms of IBS clinical trials and to identify which factors predict the variability of the placebo response.

METHODS

We performed a meta-analysis of published, English language, RCT with 20 or more IBS patients who were treated for at least 2 weeks. This analysis is limited to studies that assessed global response (improvement in overall symptoms). The variables considered as potential placebo modifiers were study design, study duration, use of a run-in phase, Jadad score, entry criteria, number of office visits, number of office visits/study duration, use of diagnostic testing, gender, age and type of medication studied.

FINDINGS

Forty-five placebo-controlled RCTs met the inclusion criteria. The placebo response ranged from 16.0 to 71.4% with a population-weighted average of 40.2%, 95% CI (35.9-44.4). Significant associations with lower placebo response rates were fulfillment of the Rome criteria for study entry (P=0.049) and an increased number of office visits (P=0.026).

CONCLUSIONS

Placebo effects in IBS clinical trials measuring a global outcome are highly variable. Entry criteria and number of office visits are significant predictors of the placebo response. More stringent entry criteria and an increased number of office visits appear to independently decrease the placebo response.

The placebo effect in irritable bowel syndrome trials: a meta-analysis

BACKGROUND

Despite the apparent high placebo response rate in randomized placebo-controlled trials (RCT) of patients with irritable bowel syndrome (IBS), little is known about the variability and predictors of this response.

OBJECTIVES

To describe the magnitude of response in placebo arms of IBS clinical trials and to identify which factors predict the variability of the placebo response.

METHODS

We performed a meta-analysis of published, English language, RCT with 20 or more IBS patients who were treated for at least 2 weeks. This analysis is limited to studies that assessed global response (improvement in overall symptoms). The variables considered as potential placebo modifiers were study design, study duration, use of a run-in phase, Jadad score, entry criteria, number of office visits, number of office visits/study duration, use of diagnostic testing, gender, age and type of medication studied.

FINDINGS

Forty-five placebo-controlled RCTs met the inclusion criteria. The placebo response ranged from 16.0 to 71.4% with a population-weighted average of 40.2%, 95% CI (35.9-44.4). Significant associations with lower placebo response rates were fulfillment of the Rome criteria for study entry (P=0.049) and an increased number of office visits (P=0.026).

CONCLUSIONS

Placebo effects in IBS clinical trials measuring a global outcome are highly variable. Entry criteria and number of office visits are significant predictors of the placebo response. More stringent entry criteria and an increased number of office visits appear to independently decrease the placebo response.

Acute coronary syndrome and chronic infection in the Cork coronary care case-control study

OBJECTIVE

To examine the association between chronic infection and cumulative burden of infection and acute coronary syndrome.

DESIGN

The 5C (Cork coronary care case-control) study was a community based case-control study. Patients and controls underwent a standard physical examination and had blood samples taken for serological analysis for Helicobacter pylori (IgG), Chlamydia pneumoniae (IgA, IgM, and IgG), cytomegalovirus (IgG), and herpes simplex virus types 1 and 2 (IgG).

SETTING

Patients were recruited from four hospitals in Cork City and Mallow Town. Controls, individually matched on age and sex, were selected by incident density sampling from the same general practices as the referent case.

MAIN OUTCOME MEASURES

Age and sex adjusted and fully adjusted odds ratios for acute coronary syndrome by seropositivity and by increasing number of infections.

RESULTS

Cases and controls did not differ significantly in seropositivity to C pneumoniae, cytomegalovirus, herpes simplex viruses, and H pylori. In unconditional logistic regression analysis adjusted for age, sex, waist to hip ratio, smoking, physical activity, alcohol consumption, and social class there was no evidence of an increasing risk for acute coronary syndrome with increasing burden of infection.

CONCLUSIONS

The findings do not support an association between specific infectious agents and acute coronary syndrome and do not provide evidence of a burden of infection effect.

Randomized trial to compare the effect of recombinant human FSH (follitropin alfa) with or without recombinant human LH in women undergoing assisted reproduction treatment

Women undergoing intracytoplasmic sperm injection (ICSI) for male factor infertility were randomly assigned to receive ovarian stimulation in a long agonist protocol with a combination of recombinant human FSH (r-hFSH; Gonal-F) and recombinant human LH (r-hLH; Luveris) (n = 212) starting on day 6 of FSH stimulation until human chorionic gonadotrophin (HCG) at a daily fixed dose of 150 IU r-hLH, or with r-hFSH alone (n = 219). There was no significant difference in the number of metaphase II oocytes retrieved (10.3 versus 10.4) in patients treated with r-hFSH and r-hLH versus r-hFSH alone; however, more embryos were transferred in the LH-supplemented group (2.9 versus 2.8, P = 0.037). Overall, the implantation rates were 22.9 versus 27.0% in patients treated with r-hFSH and r-hLH versus with r-hFSH alone respectively (NS). The respective numbers of MII oocytes retrieved in patients <35 or >or=35 years were 11 versus 8.3 (P = 0.010) for patients treated with r-hFSH alone, and 10.7 versus 9.3 (NS) for those given supplemental r-hLH (150 IU) from day 6. Implantation rates in patients <35 years treated with r-hFSH were higher (30.7%) than those receiving r-hFSH and r-hLH, (23.5%) (P = 0.068). In patients >or=35 years, the implantation rates were 21.7% for those patients supplemented with 150 IU r-hLH from day 6 of stimulation versus 15.7% when treated with FSH alone (NS). Younger patients therefore do not seem to benefit from an LH-supplemented ovarian stimulation protocol, but women >or=35 years undergoing assisted reproduction may benefit from using r-hLH in addition to r-hFSH.

Clinical significance of isolated paraventricular cysts on cranial ultrasonography

OBJECTIVES

Isolated paraventricular cysts detected on routine cranial ultrasonography in premature and full term neonates are often incidental findings. The aetiology and clinical significance of these lesions is uncertain. A case control study was designed to attempt to clarify the clinical significance of isolated paraventricular cysts in terms of growth and neurodevelopment.

METHODS

Ten infants with isolated paraventricular cysts on neonatal cranial ultrasonography were identified. These were matched with 10 control infants for sex, gestational age and birthweight. All infants were assessed at a corrected age of 18-31 months for growth and neurodevelopment. Two index infants and their controls were excluded from analysis of psychometric data as the neurodevelopmental assessment tools used were different.

RESULTS

There was no statistically significant difference between the index and control groups in terms of growth, motor and psychometric assessment at follow up.

CONCLUSIONS

The study suggests that isolated paraventricular cysts detected on routine cranial ultrasonography have no prognostic significance. However the study involved a small sample size with limited power of study (power = 0.3). A larger prospective cohort study would help to clarify the clinical significance of this condition.

Prognostic value of placental ultrasound in pregnancies complicated by absent end-diastolic flow velocity in the umbilical arteries

Our objective was to evaluate the utility of gray-scale placental ultrasound for the detection of pathological lesions in the placentas of preterm pregnancies with abnormal fetoplacental blood flow (defined by absent or reversed end-diastolic flow velocities [ARED] in the umbilical arteries) before 32 weeks of gestation. Sixty consecutive structurally and chromosomally normal singleton pregnancies were evaluated. Pre-defined criteria were used to describe placental appearances using gray-scale real-time ultrasound. Proximal uterine artery Doppler waveforms were recorded using pulsed and color Doppler ultrasound. Each patient had a thrombophilia profile. Following delivery, a single perinatal pathologist reviewed each placenta at a gross and microscopic level blinded to the placental ultrasound findings. Placental shape or texture was abnormal on gray-scale ultrasound in 43/59 (73%) and echogenic cystic lesions (ECL) were found in 16 (27%). Uterine artery Doppler was abnormal in 47/60 (78%) cases. Thirty-eight pregnancies were subsequently delivered by planned Caesarean section in the fetal and/or maternal interest (birthweights 540-2300 g, mean gestational age 30.6 weeks) and 21 pregnancies resulted in the vaginal delivery of a stillborn fetus where fetal weight and/or gestational age did not justify Caesarean section (birthweights 85-600 g, mean gestational age 24.9 weeks). ECL had a low positive predictive value for both villous infarcts (63%) and for focal/massive perivillous fibrin deposition (40%). Nevertheless, the combination of abnormal uterine artery Doppler and abnormal gray-scale findings (abnormal placental morphology or ECL) was strongly predictive of stillbirth (17/21; sensitivity 81%, PPV 52%, p = 0.006 Fisher's exact test). Pregnancies with ARED in the umbilical arteries have a high perinatal mortality associated with pathology of the placental villi. Ultrasound examination of the placenta and its maternal blood supply may contribute to the perinatal management of these pregnancies.

Desensitization of endogenously expressed delta-opioid receptors: no evidence for involvement of G protein-coupled receptor kinase 2

The involvement of G protein-coupled receptor kinase 2 (GRK2) in the agonist-induced desensitization of delta-opioid receptor-mediated inhibition of cAMP formation in NG108-15 mouse neuroblastomaxrat glioma hybrid cells was investigated. Pretreatment of wild-type cells with the delta-opioid receptor agonist [D-Pen(2,5)]-enkephalin (DPDPE; 100 nM) for as little as 5 min produced marked desensitization of subsequent DPDPE-mediated inhibition of iloprost (300 nM)-stimulated cAMP formation. In NG108-15 cells stably overexpressing wild-type GRK2 or dominant negative mutant GRK2 (DNM GRK2), the DPDPE-induced desensitization of cAMP inhibition was the same as in plasmid-transfected control cells. Pretreatment of wild-type cells with the inhibitors of receptor internalization, concanavalin A (0.25 mg ml(-1)) or hypertonic sucrose (0.4 M), also failed to inhibit DPDPE-mediated desensitization. Finally, in NG108-15 cells stably overexpressing G protein-coupled receptor kinase 6 (GRK6), DPDPE-induced desensitization was significantly increased as compared to plasmid-transfected control cells. These results indicate that GRK2 is unlikely to mediate the desensitization of endogenous delta-opioid receptors in NG108-15 cells, but that other GRKs, such as GRK6, may be more important.

NaCl consumption is attenuated in female KCNE1 null mutant mice

The role of potassium channels in the regulation of NaCl intake has not been investigated previously. One potassium channel, KCNQ1, and its regulator, KCNE1, are expressed in salivary glands and kidneys, and KCNE1 null mutant mice are deficient in KCNQ1 potassium currents. To understand the role of the KCNQ1/KCNE1 channel complex in NaCl taste and intake, we compared the NaCl consumption of KCNE1 +/+ (129/Sv), KCNE1 +/-, and KCNE1 -/- mice using two-bottle intake tests and lick rate tests. Although KCNE1 +/+ and KCNE1 +/- mice exhibited consumption patterns for 75-150 mM NaCl solutions considered typical for 129/Sv mice, the KCNE1 -/- null mutant 129/Sv mice were indifferent to or rejected them. This effect was observed in female mice only, required prior exposure to NaCl solutions, and the extent of rejection was greater after prior exposure to 150 mM NaCl solution than 75 mM NaCl solution. No differences were observed in the avidity for KCl solutions or in lick rates of naive mice for 150 or 300 mM NaCl solutions. These results demonstrate that a single potassium channel gene can influence voluntary NaCl intake. We speculate that disruption of the KCNE1 gene impairs sodium metabolism in female mice drinking high levels of 150 mM NaCl, which causes malaise that becomes associated with NaCl taste, and as a consequence, reduced preference for NaCl.

Rapid agonist-induced desensitization and internalization of the A(2B) adenosine receptor is mediated by a serine residue close to the COOH terminus

The G(s)-coupled rat A(2B) adenosine receptor (A(2B)-AR) was epitope-tagged at the NH(2) terminus with hemagglutinin (HA) and subjected to progressive deletions or point mutations of the COOH terminus in order to determine regions of the receptor that contribute to agonist-induced desensitization and internalization. When expressed stably in Chinese hamster ovary cells, a mutant receptor in which the final 2 amino acids were deleted, the Leu(330)-stop mutant, underwent rapid agonist-induced desensitization and internalization as did the wild type (WT) receptor. However, the Phe(328) and the Gln(325)-stop mutants were resistant to rapid agonist-induced desensitization and internalization. Co-expression of arrestin-2-green fluorescent protein (arrestin-2-GFP) with WT receptor or Leu(330)-stop mutant resulted in rapid translocation of arrestin-2-GFP from cytosol to membrane upon agonist addition. On the other hand, agonist activation of the Phe(328)-stop or Gln(325)-stop mutant did not result in translocation of arrestin-2-GFP from cytosol. A COOH terminus point mutant, S329G, was also unable to undergo rapid agonist-induced desensitization and internalization, indicating that Ser(329) is a critical residue for these processes. A further deletion mutant (Ser(326)-stop) unexpectedly underwent rapid agonist-induced desensitization and internalization. However, activation of this mutant did not promote translocation of arrestin-2-GFP from cytosol to membrane. In addition, whereas WT receptor internalization was markedly inhibited by co-expression of dominant negative mutants of arrestin-2 (arrestin-2-(319-418)), dynamin (dynamin K44A), or Eps-15 (EDelta95-295), Ser(326)-stop receptor internalization was only inhibited by dominant negative mutant dynamin. Taken together these results indicate that Ser(329), close to the COOH terminus of the rat A(2B)-AR, is critical for the rapid agonist-induced desensitization and internalization of the receptor. However, deletion of the COOH terminus also uncovers a motif that is able to redirect internalization of the receptor to an arrestin- and clathrin-independent pathway.

G protein-coupled receptor kinases 3 and 6 use different pathways to desensitize the endogenous M3 muscarinic acetylcholine receptor in human SH-SY5Y cells

We have investigated the effects of G protein-coupled receptor kinase (GRK) 3 and GRK6 on the phosphorylation and regulation of the M3 muscarinic acetylcholine receptor (mACh) endogenously expressed in SH-SY5Y cells. Overexpression of GRK3 or GRK6 enhanced M3 mACh receptor phosphorylation after high-concentration methacholine (100 microM, 1 min) addition. However, GRK6 was more potent, increasing receptor phosphorylation even after low (3 microM, 1 min) agonist stimulation. Compared with plasmid-transfected control cells expressing equivalent M3 mACh receptor number, GRK3- or GRK6-overexpressing cells exhibited a reduced phospholipase C activity reflected by a lower accumulation of total [3H]inositol phosphates and Ins(1,4,5)P3 mass. In addition, direct stimulation of G protein activation of phospholipase C (by AlF4(-)) was inhibited in GRK3- but not GRK6-overexpressing cells. Guanosine-5'-O-(3-[35S]thio)triphosphate binding and immunoprecipitation of Galpha(q/11) indicated that acute methacholine-stimulated receptor/Galpha(q/11) coupling was unaffected by GRK overexpression. In contrast, agonist pretreatment of cells for 3 min caused M3 mACh receptor uncoupling from Galpha(q/11), which was markedly enhanced by GRK6 overexpression, particularly at lower agonist pretreatment concentrations. However, the increased M3 mACh receptor phosphorylation seen in clones overexpressing GRK3 was not accompanied by increased receptor-Galpha(q/11) uncoupling. Overall, these data suggest that GRK3 and GRK6 use different pathways to desensitize the M3 mACh receptor. GRK6 seems to act as a classical GRK, inducing increased receptor phosphorylation accompanied by an uncoupling of receptor and Galpha(q/11). Conversely, GRK3 may cause desensitization independently of receptor phosphorylation, possibly via Gbetagamma binding and/or direct Galpha(q) binding via its regulator of G protein signaling domain to inhibit phospholipase C activity.

Agonist-induced internalization of the metabotropic glutamate receptor 1a is arrestin- and dynamin-dependent

At present, little is known regarding the mechanism of metabotropic glutamate receptor (mGluR) trafficking. To facilitate this characterization we inserted a haemagglutinin (HA) epitope tag in the extracellular N-terminal domain of the rat mGluR1a. In human embryonic kidney cells (HEK293), transiently transfected with HA-mGluR1a, the epitope-tagged receptor was primarily localized to the cell surface prior to agonist stimulation. Following stimulation with glutamate (10 microM; 30 min) the HA-mGluR1a underwent internalization to endosomes. Further quantification of receptor internalization was provided by ELISA experiments which showed rapid agonist-induced internalization of the HA-mGluR1a. To determine whether agonist-induced mGluR1a internalization is an arrestin- and dynamin-dependent process, cells were cotransfected with HA-mGluR1a and either of these dynamin-K44A or arrestin-2 (319-418). Expression of either dominant negative mutant constructs with receptor strongly inhibited glutamate-induced (10 microM; 30 min) HA-mGluR1a internalization. In addition, wild-type arrestin-2-green fluorescent protein (arrestin-2-GFP) or arrestin-3-GFP underwent agonist-induced translocation from cytosol to membrane in HEK293 cells coexpressing HA-mGluR1a. Taken together our observations demonstrate that agonist-induced internalization of mGluR1a is an arrestin- and dynamin-dependent process.

Assessment of dietary intake of preschool children living in a homeless shelter

Families with young children are the fastest-growing group among the homeless population. This study was undertaken by nursing students and faculty to learn more about what homeless preschool children were fed and what they ate at one family shelter in the Southwest. Results from the study were shared with the entire shelter staff. Mothers who participated in the study were given information on age-appropriate food preparation and servings. This research reveals the important role nurses can play in documenting and teaching both shelter staff and homeless mothers more about children's dietary needs and the long-term health outcomes of a proper diet.