Accessibility of nucleosomal DNA to V(D)J cleavage is modulated by RSS positioning and HMG1

B and T cell receptor gene assembly by V(D)J recombination is tightly regulated during lymphoid development. The mechanisms involved in this regulation are poorly understood. Here we show that nucleosomal DNA is refractory to V(D)J cleavage. However, the presence of HMG1, a chromatin-associated nonhistone DNA-binding protein, stimulates V(D)J cleavage of nucleosomal templates. This HMG1 stimulation is differentially affected by the rotational or translational positioning of the recombination signal sequence on the histone octamer, with cleavage of the 12 bp spacer RSS showing sensitivity to rotational position and the 23 bp spacer RSS affected by its displacement from the dyad. These results suggest that V(D)J recombination can be modulated by controlling substrate accessibility and cleavage at the level of an individual nucleosome.

Meta-analysis of sentinel node imprint cytology in breast cancer

BACKGROUND

Intraoperative diagnosis of breast cancer metastases in axillary sentinel nodes is desirable to avoid a second operation for lymphadenectomy. Imprint or touch-preparation cytology is a popular technique that has high specificity and a wide range of sensitivity.

METHODS

A systematic search of electronic databases was performed. Included articles were assessed for methodological and reporting quality. Random-effects model pooled estimates of sensitivity and specificity were calculated. Single-variable and multivariable meta-regression analyses were performed for predictors of sensitivity.

RESULTS

Thirty-one studies were included; all were of good methodological quality but reporting quality varied. Pooled sensitivity of imprint cytology was 63 (95 per cent confidence interval (c.i.) 57 to 69) per cent and specificity was 99 (95 per cent c.i. 98 to 99) per cent. Pooled sensitivity for macrometastases was 81 per cent and that for micrometastases 22 per cent. Mean or median primary tumour size (P = 0.004), the prevalence of metastases (P = 0.103) and the proportion of micrometastases (P = 0.022) were significant risk factors in single-variable meta-regression analysis. Only the proportion of micrometastases remained significant in multivariable analysis. Frozen sectioning had better sensitivity than imprint cytology in three of four direct comparisons.

CONCLUSION

Imprint cytology is simple and rapid, and has good sensitivity for macrometastases. The significance of poor sensitivity for micrometastases will be determined by trials investigating their natural history.

A systematic review of the influence of the retail food environment around schools on obesity-related outcomes

The high prevalence of childhood obesity has led to questions about the influence of 'obesogenic' environments on children's health. Public health interventions targeting the retail food environment around schools have been proposed, but it is unclear if they are evidence based. This systematic review investigates associations between food outlets near schools and children's food purchases, consumption and body weight. We conducted a keyword search in 10 databases. Inclusion criteria required papers to be peer reviewed, to measure retailing around schools and to measure obesity-related outcomes among schoolchildren. Thirty papers were included. This review found very little evidence for an effect of the retail food environment surrounding schools on food purchases and consumption, but some evidence of an effect on body weight. Given the general lack of evidence for association with the mediating variables of food purchases and consumption, and the observational nature of the included studies, it is possible that the effect on body weight is a result of residual confounding. Most of the included studies did not consider individual children's journeys through the food environment, suggesting that predominant exposure measures may not account for what individual children actually experience. These findings suggest that future interventions targeting the food environment around schools need careful evaluation.

Regulation of immunoglobulin class-switch recombination: choreography of noncoding transcription, targeted DNA deamination, and long-range DNA repair

Upon encountering antigens, mature IgM-positive B lymphocytes undergo class-switch recombination (CSR) wherein exons encoding the default Cμ constant coding gene segment of the immunoglobulin (Ig) heavy-chain (Igh) locus are excised and replaced with a new constant gene segment (referred to as "Ch genes", e.g., Cγ, Cɛ, or Cα). The B cell thereby changes from expressing IgM to one producing IgG, IgE, or IgA, with each antibody isotype having a different effector function during an immune reaction. CSR is a DNA deletional-recombination reaction that proceeds through the generation of DNA double-strand breaks (DSBs) in repetitive switch (S) sequences preceding each Ch gene and is completed by end-joining between donor Sμ and acceptor S regions. CSR is a multistep reaction requiring transcription through S regions, the DNA cytidine deaminase AID, and the participation of several general DNA repair pathways including base excision repair, mismatch repair, and classical nonhomologous end-joining. In this review, we discuss our current understanding of how transcription through S regions generates substrates for AID-mediated deamination and how AID participates not only in the initiation of CSR but also in the conversion of deaminated residues into DSBs. Additionally, we review the multiple processes that regulate AID expression and facilitate its recruitment specifically to the Ig loci, and how deregulation of AID specificity leads to oncogenic translocations. Finally, we summarize recent data on the potential role of AID in the maintenance of the pluripotent stem cell state during epigenetic reprogramming.

Partner violence, social support, and distress among inner-city African American women

This study examined the role of social support in the partner violence-psychological distress relation in a sample of African American women seeking medical care at a large, urban hospital (n = 138). Results from bivariate correlational analyses revealed that partner violence was related to lower perceived social support and greater psychological distress, and lower social support was related to more distress. Furthermore, findings based on path analysis indicated that low levels of social support helped account for battered women's increased distress. Findings point to the need for service providers to screen for partner violence in nontraditional sites, such as hospital emergency rooms, and to address the role of social support resources in preventive interventions with African American battered women.

Viral double-stranded RNA triggers Ig class switching by activating upper respiratory mucosa B cells through an innate TLR3 pathway involving BAFF

Class switch DNA recombination (CSR) from IgM to IgG and IgA is crucial for antiviral immunity. Follicular B cells undergo CSR upon engagement of CD40 by CD40 ligand on CD4+ T cells. This T cell-dependent pathway requires 5-7 days, which is too much of a delay to block quickly replicating pathogens. To compensate for this limitation, extrafollicular B cells rapidly undergo CSR through a T cell-independent pathway that involves innate Ag receptors of the TLR family. We found that a subset of upper respiratory mucosa B cells expressed TLR3 and responded to viral dsRNA, a cognate TLR3 ligand. In the presence of dsRNA, mucosal B cells activated NF-kappaB, a transcription factor critical for CSR. Activation of NF-kappaB required TRIF (Toll/IL-1R domain-containing protein inducing IFN-beta), a canonical TLR3 adapter protein, and caused germline transcription of downstream CH genes as well as expression of AID (activation-induced cytidine deaminase), a DNA-editing enzyme essential for CSR. Subsequent IgG and IgA production was enhanced by BAFF (B cell-activating factor of the TNF family), an innate mediator released by TLR3-expressing mucosal dendritic cells. Indeed, these innate immune cells triggered IgG and IgA responses upon exposure to dsRNA. By showing active TLR3 signaling and ongoing CSR in upper respiratory mucosa B cells from patients with CD40 signaling defects, our findings indicate that viral dsRNA may initiate frontline IgG and IgA responses through an innate TLR3-dependent pathway involving BAFF.

Menstrual blood-loss with intrauterine devices

The effect of three intrauterine contraceptive devices (I.U.D.)-Lippes D, Dalkon Shield, and Copper 7-on menstrual blood-loss has been studied serially by objective methods in 279 women. All the women had a minimum of two cycles following delivery, abortion, cessation of lactation, or previous pill or I.U.D. use. All pads and tampons used for two further menstrual cycles before and for 12 cycles after I.U.D. insertion were collected, and the blood-loss was measured by extracting the haemoglobin by conversion to alkaline haematin. Mean menstrual blood-loss increased with all three devices. The amount of loss, the percentage of women losing more than 80 ml, the decline in haemoglobin concentration, and the incidence of anaemia during the 12 cycles following insertion were all greater among users of the Lippes Loop than of the Copper 7 with generally intermediate values for Dalkon Shield users. The mean increases in blood-loss were: for parous women fitted with the Lippes Loop, 48 ml, with the Dalkon Shield, 34 ml, and with the Copper 7, 18 ml; for nulliparae fitted with the small size of Dalkon Shield, 27 ml, and, with the Copper 7, 19 ml.

Effects of solution pH and electrical parameters on hydroxyapatite coatings deposited by a plasma-assisted electrophoresis technique

Hydroxyapatite (HA) coatings can be deposited using a hybrid process of plasma electrolysis and electrophoresis, called plasma-assisted electrophoretic deposition (PEPD). HA aqueous suspensions with various pH values were prepared using a modified ultrasonic cleaning bath as an agitator/stirrer. Both DC and unbalanced AC power supplies were used to bias the titanium alloy substrate materials employed in this work. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to observe and analyze coating morphology and microstructure. It was shown that the morphology and composition of the calcium phosphate coatings were significantly influenced by solution pH values; the level of "pure" HA in the coatings' composition corresponded to both solution pH and the type of power supply employed. Loss of hydroxyl radials (i.e., dehydroxylation), which degrades the performance of the hydroxyapatite coating in terms of long-term chemical and mechanical stability, can be virtually eliminated by a combination of high pH and unbalanced AC plasma power. In addition, the underlying TiO2 coatings used to support the HA layer (preproduced by plasma electrolysis process) have a nanoscaled (10-20 nm) polycrystalline structure. TEM studies also revealed a dense, continuous amorphous titania layer (10 nm in thickness) at the interface between the Ti alloy substrate and the TiO2 layer, which may play a role in improving the corrosion resistance of the substrate. Such a nanophase TiO2 layer (if used as a coating alone) may also provide a further improvement in osteoinductive properties, compared to a conventional TiO2 coating on the Ti alloy substrate.

Lack of cross-species transmission of porcine endogenous retrovirus infection to nonhuman primate recipients of porcine cells, tissues, or organs

BACKGROUND

Nonhuman primates (NHPs) have been widely used in different porcine xenograft procedures inevitably resulting in exposure to porcine endogenous retrovirus (PERV). Surveillance for PERV infection in these NHPs may provide information on the risks of cross-species transmission of PERV, particularly for recipients of vascularized organ xenografts for whom data from human clinical trials is unavailable.

METHODS

We tested 21 Old World and 2 New World primates exposed to a variety of porcine xenografts for evidence of PERV infection. These NHPs included six baboon recipients of pig hearts, six bonnet macaque recipients of transgenic pig skin grafts, and nine rhesus macaque and two capuchin recipients of encapsulated pig islet cells. Serologic screening for PERV antibody was done by a validated Western blot assay, and molecular detection of PERV sequences in peripheral blood mononuclear cells (PBMCs) and plasma was performed using sensitive polymerase chain reaction and reverse transcriptase-polymerase chain reaction assays, respectively. Spleen and lymph node tissues available from six bonnet macaques and three rhesus macaques were also tested for PERV sequences.

RESULTS

All plasma samples were negative for PERV RNA suggesting the absence of viremia in these xenografted animals. Similarly, PERV sequences were not detectable in any PBMC and tissue samples, arguing for the lack of latent infection of these compartments. In addition, all plasma samples were negative for PERV antibodies.

CONCLUSION

These data suggest the absence of PERV infection in all 23 NHPs despite exposure to vascularized porcine organs or tissue xenografts and the use of immunosuppressive therapies in some animals. These findings suggest that PERV is not easily transmitted to these NHP species through these types of xenografts.

The cloning and expression of a new guanylyl cyclase orphan receptor

A novel membrane form of guanylyl cyclase (GC-G) has been identified through the isolation of a full-length cDNA clone; it is predicted to contain an extracellular ligand binding domain, a single transmembrane segment, and intracellular protein kinase-like and cyclase catalytic domains. That GC-G represents a guanylyl cyclase was confirmed by both transient expression in COS-7 cells and stable expression in H293 cells. Endogenous cyclic GMP concentrations of transfected or stable cells, however, were much higher than control cells, suggesting an inability of the cells to effectively regulate GC-G cyclase activity. Of six Cys residues found within the extracellular domain of guanylyl cyclase-A (GC-A), the receptor for atrial natriuretic peptide, five are conserved within GC-G. Ligands for the other cyclase receptors, nevertheless, failed to stimulate GC-G expressed in transient or stable cells, suggesting that the unknown ligands possess a structure different from the natriuretic peptides or heat-stable enterotoxins. 125I-ANP also failed to bind to H293 cells overexpressing GC-G. Based on Northern hybridization, mRNA for GC-G was predominantly expressed in lung, intestine, and skeletal muscle. Using the candidate gene approach to potentially define function, the gene for GC-G was mapped to the distal region of mouse chromosome 19 (syntenic with human chromosome 10q), but no human genetic defect has been ascribed to the GC-G locus. The finding of a new membrane form of guanylyl cyclase in peripheral tissues suggests the existence of another family or subfamily of ligands that signal through elevations of cGMP.

Restraint and seclusion: a distressing treatment option?

The effectiveness of restraint and seclusion interventions in the nursing management of disturbed and aggressive clients remains questionable. Considerable debate continues regarding the use of these treatment options in psychiatric hospitals. The existing literature suggests that the controversial nature of restraint and seclusion creates a complex dilemma for nurses, which initiates emotional distress. This study specifically explored the emotions and feelings experienced by a group of psychiatric nurses working in Ireland in relation to incidents of restraint and seclusion. A qualitative research approach was employed incorporating focus group discussions. A total of 23 nurses participated in three focus group interviews. The data were analysed using qualitative interpretive analysis. Three themes were created consisting of: (1) the last resort - restraint and seclusion; (2) emotional distress; and (3) suppressing unpleasant emotions. It is suggested that the nurses' experience of restraint and seclusion created a dynamic movement between the release and suppression of distressing emotions. The oscillatory characteristics embedded within the nurses' emotional responses were reminiscent of a model of suffering developed by Morse in 2001. Consequently, this model is incorporated throughout the discussion of the findings to provide a more in-depth description of the emotional distress experienced by the nurses in the study.

Serial studies of immunocompetence of patients undergoing chemotherapy for acute leukemia

Immunocompetence was followed serially for 1 yr from the onset of treatment in 55 adult patients with acute leukemia. The tests used were delayed hypersensitivity responses to a battery of five recall antigens (dermatophytin, dermatophytin 0, candida, streptokinase-streptodornase, and mumps) and in vitro lymphocyte blastogenic responses to phytohemagglutinin and streptolysin 0. There was a strong correlation between immunocompetence at the start of treatment and a good prognosis; 32/39 patients who subsequently entered remission were initially immunocompetent compared to 4/15 who failed to enter remission. In the complete remission group there was a decline in competence starting from 2 to 5 mo after the onset of treatment. In those who remained in remission for 1 yr, competence recovered at 6 mo and remained vigorous thereafter. In those who relapsed before 1 yr, the decline in competence occurred 1 mo before relapse and competence continued to decline progressively during the 1 yr follow-up period. These studies suggest that therapeutic approaches which restore immunocompetence or prevent its decline will improve both the remission rate and the remission duration of patients with acute leukemia.

Iron and atherosclerosis: inhibition by the iron chelator deferiprone (L1)

BACKGROUND

Accumulating evidence suggests that oxidative modification of lipoproteins may play a significant role in atherogenesis. In this study, we hypothesized that the iron chelator deferiprone (L1) would function as an antioxidant and decrease atherosclerosis progression.

MATERIALS AND METHODS

For the in vitro studies, human low-density lipoprotein (LDL) was collected and then subjected to oxidation by either hemin/H2O2 or copper sulfate in the presence of various concentrations of L1. Lag time to oxidation was measured to assess antioxidant activity of L1. In addition, human umbilical vein endothelial cells (HUVEC) were subjected to oxidized LDL in the presence of varying concentrations of L1 to assess the antioxidant cytoprotective ability of L1. For the in vivo studies, rabbits (n = 21) were maintained on a 0.25% by weight cholesterol diet for 10 weeks; 9 rabbits also received twice daily L1 by gavage (total dose = 100 mg/kg/day). Lipid profiles were measured during the study. At 10 weeks, rabbits were sacrificed, and thoracic aorta cholesterol content (TACC) and planimetry were determined to assess atherosclerosis severity.

RESULTS

In vitro, L1 prevented oxidation of LDL and protected HUVEC from the cytotoxic effects of oxidized LDL in a concentration-dependent manner. In vivo, L1 reduced TACC (P = 0.001), while also significantly decreasing total plasma cholesterol (P = 0.003), very-low-density lipoprotein cholesterol (P = 0.01), and LDL cholesterol (P = 0.002) compared to control animals. However, no significant differences between L1-treated animals and controls were evident for the surface area of plaque involvement by planimetry (P = 0.3) or in the serum iron levels (P = 0.3).

CONCLUSIONS

These results confirm that L1 possesses antioxidant activity in vitro and may reduce atherogenesis in vivo.

Family-based transmission disequilibrium test (TDT) and case-control association studies reveal surfactant protein A (SP-A) susceptibility alleles for respiratory distress syndrome (RDS) and possible race differences

A key cause of respiratory distress syndrome (RDS) in the prematurely born infant is deficiency of pulmonary surfactant, a lipoprotein complex. Both low levels of surfactant protein A (SP-A) and SP-A alleles have been associated with RDS. Using the candidate gene approach, we performed family-based linkage studies to discern linkage of SP-A to RDS and identify SP-A susceptibility or protective alleles. Moreover, we performed case-control studies of whites and blacks to detect association between RDS and SP-A alleles. Transmission disequilibrium test (TDT) analysis revealed that the frequency of transmission (from parent to the offspring with RDS) of alleles 6A(2) and 1A(0) and of 1A(0)/6A(2) haplotype in RDS was increased, whereas transmission of alleles 1A(5) and 6A(4) and of haplotype 1A(5)/6A(4) was decreased. Extended TDT analysis further strengthened the observations made. The case-control studies showed that in whites or blacks with RDS the frequencies of specific genotypes, 1A(0) and 6A(2) or 1A(0), were increased, respectively, but the frequency of specific 6A(3) genotypes was increased in certain white subgroups and decreased in blacks. Regression analysis revealed gestational age (GA) and 6A(3) genotypes are significant factors in blacks with RDS. In whites with RDS, GA and antenatal steroids are important factors. The data together indicate linkage between SP-A and RDS; certain SP-A alleles/haplotypes are susceptibility (1A(0), 6A(2), 1A(0)/6A(2)) or protective (1A(5), 6A(4), 1A(5)/6A(4)) factors for RDS. Some differences between blacks and whites with regard to SP-A alleles may exist.

Survey of ophthalmic conditions in a Labrador community. I. Refractive errors

Of the 745 available members of the population of Nain in Labrador 650 (87%) were screened for refractive errors and ocular disease. Refraction by retinoscopy was done in 553 and axial length measured by an optical method in 514. The results showed that the incidence of low degrees of myopia was higher in Inuit (Eskimos) and those of Mixed Inuit-Caucasian blood in the age groups 10 to 40 than in those over 40. 75% of the myopes came from 20 families in which myopia was present in 2 or more generations. Although there was no significant correlation between the refraction of parents and offspring, there were significant correlations between them for axial length. The axial lenths of the myopic eyes of the Inuit and Mixed populations were significantly longer than emmetropic and hypermetropic eyes. The younger memebers of the population were taller than their parents, and except in female Caucasians axial length showed a significant positive correlation with height. More myopes than emmetropes and hypermetropes achieved grade 8 or more in school. It is suggested that the increased incidence of myopia in the younger age groups might be due to environmental factors interfering with the process of emmetropisation in eyes with a genetic predisposition to myopia by virtue of inheriting a slightlt longer eye. Better nutrition resulting in an increase in stature may also have had some influence.

Evidence of porcine endogenous retroviruses in porcine factor VIII and evaluation of transmission to recipients with hemophilia

Since 1984, unheated porcine clotting factor VIII (Hyate:C) has been used to treat severe bleeding episodes in persons with hemophilia who have antibodies to human clotting factor. We document the presence of porcine endogenous retrovirus (PERV) in plasma samples of pigs and in clinical lots of Hyate:C. Both gag and pol PERV RNA sequences were detected by reverse-transcriptase (RT) polymerase chain reaction in 13 of 13 lots of Hyate:C tested. Among 10 of these lots, RT activity also was detected, which confirms the presence of retroviral particles. To assess the transmission of PERV to Hyate:C recipients, we tested serum specimens from 88 recipients of Hyate:C and 23 noninfused control subjects for anti-PERV antibodies by using a Western blot assay. None of the samples was positive. Our data document that PERV particles are a common contaminant of Hyate:C products and suggest that the risk of PERV transmission from these percutaneous exposures is very low.

An investigation of factors associated with depressive symptoms among a sample of regular ecstasy consumers

AIMS/OBJECTIVES

Methylenedioxymethamphetamine affects the central serotonergic system, and there is some evidence for an association between ecstasy use (drugs sold as methylenedioxymethamphetamine) and depression. The aim of the present study was to investigate the incidence of self-reported depression and associated help-seeking among a sample of regular ecstasy users. A further aim was to examine the correlates of depressive symptomatology in this population.

MATERIALS AND METHODS

100 regular ecstasy consumers (at least monthly use) were interviewed as part of the Ecstasy and Related Drug Reporting System in Tasmania, Australia. Participants were also administered epidemiological measures of depression (Center for Epidemiological Studies Depression Scale) and psychological distress (Kessler Psychological Distress Scale).

RESULTS

One quarter (23%) of participants self-reported recent experience of depression, a rate notably greater than the general population. However, only one third of these participants had attended a health professional for this issue. A range of drug use factors (e.g. frequency and quantity of ecstasy use, frequent cannabis or methamphetamine use, intravenous drug use, polydrug use, binge drug use, harmful alcohol use, and elevated psychological dependence scores for ecstasy and methamphetamine) were associated with high levels of depressive symptomatology.

CONCLUSION

These findings are consistent with an association between depressive symptomatology and ecstasy and other drug use. Harm reduction strategies which target drug use factors such as those identified in this study may also aid in the reduction of the experience of depression. Considering the low levels of help-seeking among this population, improving awareness and access to information and treatment for depression may also be important.

Characteristics and in vitro response of thin hydroxyapatite-titania films produced by plasma electrolytic oxidation of Ti alloys in electrolytes with particle additions

Enhanced incorporation of hydroxyapatite nanoparticles in porous titania coating formed by plasma electrolytic oxidation significantly increases surface osteogenic activity.

The enhancement of the biological properties of Ti by surface doping with hydroxyapatite (HA) is of great significance, especially for orthodontic applications. This study addressed the effects of HA particle size in the electrolyte suspension on the characteristics and biological properties of thin titania-based coatings produced on Ti–6Al–4V alloy by plasma electrolytic oxidation (PEO). Detailed morphological investigation of the coatings formed by a single-stage PEO process with two-step control of the electrical parameters was performed using the Minkowski functionals approach. The surface chemistry was studied by glow discharge optical emission spectroscopy and Fourier transform infrared spectroscopy, whereas mechanical properties were evaluated using scratch tests. The biological assessment included in vitro evaluation of the coating bioactivity in simulated body fluid (SBF) as well as studies of spreading, proliferation and osteoblastic differentiation of MC3T3-E1 cells. The results demonstrated that both HA micro- and nanoparticles were successfully incorporated in the coatings but had different effects on their surface morphology and elemental distributions. The micro-particles formed an irregular surface morphology featuring interpenetrated networks of fine pores and coating material, whereas the nanoparticles penetrated deeper into the coating matrix which retained major morphological features of the porous TiO₂ coating. All coatings suffered cohesive failure in scratch tests, but no adhesive failure was observed; moreover doping with HA increased the coating scratch resistance. In vitro tests in SBF revealed enhanced bioactivity of both HA-doped PEO coatings; furthermore, the cell proliferation/morphometric tests showed their good biocompatibility. Fluorescence microscopy revealed a well-organised actin cytoskeleton and focal adhesions in MC3T3-E1 cells cultivated on these substrates. The cell alkaline phosphatase activity in the presence of ascorbic acid and β-glycerophosphate was significantly increased, especially in HA nanoparticle-doped coatings.

'Everything was just getting worse and worse': deteriorating job quality as a driver of doctor emigration from Ireland

BACKGROUND

Medicine is a high-status, high-skill occupation which has traditionally provided access to good quality jobs and relatively high salaries. In Ireland, historic underfunding combined with austerity-related cutbacks has negatively impacted job quality to the extent that hospital medical jobs have begun to resemble extreme jobs. Extreme jobs combine components of a good quality job-high pay, high job control, challenging demands, with those of a low-quality job-long working hours, heavy workloads. Deteriorating job quality and the normalisation of extreme working is driving doctor emigration from Ireland and deterring return.

METHODS

Semi-structured qualitative interviews were conducted with 40 Irish emigrant doctors in Australia who had emigrated from Ireland since 2008. Interviews were held in July-August 2018.

RESULTS

Respondents reflected on their experiences of working in the Irish health system, describing hospital workplaces that were understaffed, overstretched and within which extreme working had become normalised, particularly in relation to long working hours, fast working pace, doing more with less and fighting a climate of negativity. Drawing on Hirschman's work on exit, voice and loyalty (1970), the authors consider doctor emigration as exit and present respondent experiences of voice prior to emigration. Only 14/40 respondent emigrant doctors intend to return to work in Ireland.

DISCUSSION

The deterioration in medical job quality and the normalisation of extreme working is a key driver of doctor emigration from Ireland, and deterring return. Irish trained hospital doctors emigrate to access good quality jobs in Australia and are increasingly likely to remain abroad once they have secured them. To improve doctor retention, health systems and employers must mitigate a gainst the emergence of extreme work in healthcare. Employee voice (about working conditions, about patient safety, etc.) should be encouraged and used to inform health system improvement and to mitigate exit.

Stimulation of oxyradical production of hepatic microsomes of flounder (Platichthys flesus) and perch (Perca fluviatilis) by model and pollutant xenobiotics

Stimulation of hepatic microsomal NAD(P)H-dependent hydroxyl radical (.OH) production by model compounds, viz. menadione (2-methyl-1,4-naphthoquinone) and nitrofurantoin (N-(5-nitro-2-furfurylidene)-1-aminohydantoin), and pollutant xenobiotics, viz. benzo[a]pyrene (BaP) diones (products of microsomal BaP metabolism), duroquinone (tetramethyl-1,4-benzoquinone--present in pulp mill effluent), and the pesticide lindane (gamma-hexachlorocyclohexane), was examined in flounder Platichthys flesus. Duroquinone was also studied in perch Perca fluviatilis, a freshwater species used in studies of pulp mill effluents in the aquatic environment. Microsomal .OH production was detected by the oxidation of the scavenging agent 2-keto-4-methiolbutyric acid (KMBA), using FeCl3/EDTA as a promotor of the Haber-Weiss reaction (O2- + H2O2 = .OH+OH- + O2). All xenobiotics tested, except lindane, showed synergistic interactions with ferric/EDTA indicative of redox cycling of the xenobiotic. Inhibition of menadione- and nitrofurantoin-stimulated .OH production by superoxide dismutase (50% inhibition) and catalase (80%) indicated respectively the involvement of O2- and H2O2 in .OH production. Maximal rates of KMBA oxidation (Vmax in nmol ethylene/min/mg protein) were similar for NADH and NADPH for menadione (4.58-4.61) and duroquinone (0.26-0.3 [flounder] and 0.93-0.99 [perch]), higher for NADPH than NADH for nitrofurantoin (1.21 and 0.77), and higher for NADH than NADPH for BaP diones, decreasing in the order 1,6-dione (1.12 and 0.14), 3,6-dione (0.75 and 0.25), and 6,12-dione (0.31 and 0.09). Rates for lindane, lacking a redox cycling structure, were low (0.01-0.05). Apparent Km (app. Km) values for xenobiotic were 1-2 orders of magnitude lower for BaP diones than the other compounds. App. Km was lower for NADH than NADPH for 3,6-dione (1.23 and 1.66 microM) and 6,12-dione (0.85 and 1.81 microM), but the reverse of this was found for the 1,6-dione (1.41 and 0.78 microM). App. Km values were almost identical for menadione and duroquinone and lower for NADPH (32-44 microM) than NADH (346-382 microM). The reverse was seen for nitrofurantoin, viz., 76 microM (NADH) and 269 microM (NADPH). Hepatic 1000 g supernatants of P. flesus metabolized BaP to oxyradical-generating products, moreso for beta-naphthoflavone-induced than control fish, and production was reduced by UDP-glucuronic acid for the latter but not the former. The studies indicate a widespread potential for contaminant-stimulated oxyradical generation via redox cycling and other free radical interactions of xenobiotics and their metabolites.

Epidural anaesthesia in von Hippel-Lindau disease. Management of childbirth and anaesthesia for caesarean section

The management of childbirth, including epidural anaesthesia for Caesarean section is described in a patient with von Hippel-Lindau disease. The reasons for the choice of epidural anaesthesia are explained and the anaesthetic significance of the disease is discussed.

Binding of AID to DNA does not correlate with mutator activity

The DNA deaminase activation-induced cytidine deaminase (AID) initiates somatic hypermutation (SHM) and class switch recombination (CSR) by deaminating cytidines to uridines at V region (V) genes and switch (S) regions. The mechanism by which AID is recruited to V genes and S region DNA is poorly understood. In this study, we used the CH12 B lymphoma line to demonstrate that, although S regions can efficiently recruit AID and undergo mutations and deletions, AID neither binds to nor mutates the V gene, thus clearly demonstrating intraimmunoglobulin locus specificity. Depletion of the RNA-binding protein polypyrimidine tract binding protein-2, previously shown to promote recruitment of AID to S regions, enables stable association of AID with the V gene. Surprisingly, AID binding to the V gene does not induce SHM. These results unmask a striking lack of correlation between AID binding and its mutator activity, providing evidence for the presence of factors required downstream of AID binding to effect SHM. Furthermore, our findings suggest that S regions are preferred targets for AID and, aided by polypyrimidine tract binding protein-2, act as "sinks" to sequester AID activity from other genomic regions.