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.

CrkRS

We have isolated and characterised a novel human protein kinase, Cdc2-related kinase with an arginine/serine-rich (RS) domain (CrkRS), that is most closely related to the cyclin-dependent kinase (CDK) family. CrkRS is a 1490 amino acid protein, the largest CDK-related kinase so far isolated. The protein kinase domain of CrkRS is 89% identical to the 46 kDa CHED protein kinase, but outside the kinase domains the two proteins are completely unrelated. CrkRS has extensive proline-rich regions that match the consensus for SH3 and WW domain binding sites, and an RS domain that is predominantly found in splicing factors. CrkRS is ubiquitously expressed in tissues, and maps to a single genetic locus. There are closely related protein kinases in both the Drosophila and Caenorhabditis elegans genomes. Consistent with the presence of an RS domain, anti-CrkRS antibodies stain nuclei in a speckled pattern, overlapping with spliceosome components and the hyperphosphorylated form of RNA polymerase II. Like RNA polymerase II, CrkRS is a constitutive MPM-2 antigen throughout the cell cycle. Anti-CrkRS immunoprecipitates phosphorylate the C-terminal domain of RNA polymerase II in vitro. Thus CrkRS may be a novel, conserved link between the transcription and splicing machinery.

Children followed with difficulty: how do they differ?

OBJECTIVE

To determine if very low birthweight children followed with ease differ in any perinatal or sociodemographic characteristics, or outcomes, compared with children followed with more difficulty.

METHODOLOGY

Consecutive children of birthweight < 1000 g or with gestational ages < 28 weeks born in 1991 (n = 51) or of birthweight < 1500 g born in 1992 (n = 166) at the Royal Women's Hospital, Melbourne, surviving to 5 years of age, were assessed at 5 years of age, corrected for prematurity. Those who attended on the first mutually agreed appointment without substantial reluctance were considered to have been followed with ease. The remainder were considered to have been followed with difficulty. Outcomes included impairments such as cerebral palsy, blindness, deafness, and low IQ. Children had a disability if they had any of cerebral palsy, blindness, deafness requiring amplification, or an IQ more than 1 SD below the mean.

RESULTS

Of the 217 survivors, 204 (94%) were assessed fully at 5 years of age. Of the 204 children assessed, 153 (75%) were followed with ease, and 51 (25%) with difficulty. Of data available in the perinatal period, significantly fewer children followed with more difficulty came from intact families, and more of their mothers had fewer than 12 years of schooling. More children followed with difficulty had a disability (41% compared with 19%), as they predominantly had lower IQ scores (mean difference in IQ - 12.7, 95% confidence interval - 18.0, - 7.4). The association between difficulty of assessment and both higher rates of disability and lower IQ scores remained after adjustment for significant perinatal and sociodemographic variables.

CONCLUSIONS

Children followed with difficulty can partly be recognized on several sociodemographic characteristics in the perinatal period, and have substantially worse sensorineural outcomes than those followed with ease. In any longitudinal study, the more incomplete the follow up, the lower will be the rate of adverse sensorineural outcome.

Dynamic fibular function: a new concept

Fibular function has long been a point of controversy in the literature. Until recently the fibula's role during gait has been thought of as entirely static. A review of the literature reveals an important dynamic function for the fibula in maintaining ankle mortise stability during weight bearing. Roentgenographic and anatomical studies confirm the hypothesis of progressive distal fibular descent. A taut interosseous membrane and deepened mortise result when be flexors of the foot contract during stance phase. Congenital deformities of the ankle may stem from aberration in the dynamic role of the fibula. Stress fractures and problems resulting from impaired distal migration and synostosis formation are interpreted as disorders of the dynamic role of the fibula.

Arrestin isoforms dictate differential kinetics of A2B adenosine receptor trafficking

Adenosine mediates the activation of adenylyl cyclase via its interaction with specific A(2A) and A(2B) adenosine receptors. Previously, we demonstrated that arrestins are involved in rapid agonist-promoted desensitization of the A(2B) adenosine receptor (A(2B)AR) in HEK293 cells. In the present study, we investigate the role of arrestins in A(2B)AR trafficking. Initial studies demonstrated that HEK293 cells stably expressing arrestin antisense constructs, which reduce endogenous arrestin levels, effectively reduced A(2B)AR internalization. A(2B)AR recycling after agonist-induced endocytosis was also significantly impaired in cells with reduced arrestin levels. Interestingly, while overexpression of arrestin-2 or arrestin-3 rescued A(2B)AR internalization and recycling, arrestin-3 promoted a significantly faster rate of recycling as compared to arrestin-2. The specificity of arrestin interaction with A(2B)ARs was further investigated using arrestins fused to the green fluorescent protein (arr-2-GFP and arr-3-GFP). Both arrestins underwent rapid translocation (<1 min) from the cytosol to the plasma membrane following A(2B)AR activation. However, longer incubations with agonist (>10 min) revealed that arr-2-GFP but not arr-3-GFP colocalized with the A(2B)AR in rab-5 and transferrin receptor containing early endosomes. At later times, the A(2B)AR but not arr-2-GFP was observed in an apparent endocytic recycling compartment. Thus, while arrestin-2 and arrestin-3 mediate agonist-induced A(2B)AR internalization with relative equal potency, arrestin isoform binding dictates the differential kinetics of A(2B)AR recycling and resensitization.