Bridging the age gap in breast cancer: impact of omission of breast cancer surgery in older women with oestrogen receptor-positive early breast cancer on quality-of-life outcomes

BACKGROUND

Primary endocrine therapy may be an alternative treatment for less fit women with oestrogen receptor (ER)-positive breast cancer. This study compared quality-of-life (QoL) outcomes in older women treated with surgery or primary endocrine therapy.

METHODS

This was a multicentre, prospective, observational cohort study of surgery or primary endocrine therapy in women aged over 70 years with operable breast cancer. QoL was assessed using European Organisation for Research and Treatment of cancer QoL questionnaires QLQ-C30, -BR23, and -ELD14, and the EuroQol Five Dimensions 5L score at baseline, 6 weeks, and 6, 12, 18, and 24 months. Propensity score matching was used to adjust for baseline variation in health, fitness, and tumour stage.

RESULTS

The study recruited 3416 women (median age 77 (range 69-102) years) from 56 breast units. Of these, 2979 (87.2 per cent) had ER-positive breast cancer; 2354 women had surgery and 500 received primary endocrine therapy (125 were excluded from analysis due to inadequate data or non-standard therapy). Median follow-up was 52 months. The primary endocrine therapy group was older and less fit. Baseline QoL differed between the groups; the mean(s.d.) QLQ-C30 global health status score was 66.2(21.1) in patients who received primary endocrine therapy versus 77.1(17.8) among those who had surgery plus endocrine therapy. In the unmatched analysis, changes in QoL between 6 weeks and baseline were noted in several domains, but by 24 months most scores had returned to baseline levels. In the matched analysis, major surgery (mastectomy or axillary clearance) had a more pronounced adverse impact than primary endocrine therapy in several domains.

CONCLUSION

Adverse effects on QoL are seen in the first few months after surgery, but by 24 months these have largely resolved. Women considering surgery should be informed of these effects.

Bridging the age gap in breast cancer. Impacts of omission of breast cancer surgery in older women with oestrogen receptor positive early breast cancer. A risk stratified analysis of survival outcomes and quality of life

Background

Age-related breast cancer treatment variance is widespread with many older women having primary endocrine therapy (PET), which may contribute to inferior survival and local control. This propensity-matched study determined if a subgroup of older women may safely be offered PET.

Methods

Multicentre, prospective, UK, observational cohort study with propensity-matched analysis to determine optimal allocation of surgery plus ET (S+ET) or PET in women aged ≥70 with breast cancer. Data on fitness, frailty, cancer stage, grade, biotype, treatment and quality of life were collected. Propensity-matching (based on age, health status and cancer stage) adjusted for allocation bias when comparing S+ET with PET.

Findings

A total of 3416 women (median age 77, range 69–102) were recruited from 56 breast units—2854 (88%) had ER+ breast cancer: 2354 had S+ET and 500 PET. Median follow-up was 52 months. Patients treated with PET were older and frailer than patients treated with S+ET. Unmatched overall survival was inferior in the PET group (hazard ratio, (HR) 0.27, 95% confidence interval (CI) 0.23–0.33, P < 0.001). Unmatched breast cancer–specific survival (BCSS) was also inferior in patients treated with PET (HR: 0.41, CI: 0.29–0.58, P < 0.001 for BCSS). In the matched analysis, PET was still associated with an inferior overall survival (HR = 0.72, 95% CI: 0.53–0.98, P = 0.04) but not BCSS (HR = 0.74, 95% CI: 0.40–1.37, P = 0.34) although at 4–5 years subtle divergence of the curves commenced in favor of surgery. Global health status diverged at certain time points between groups but over 24 months was similar when adjusted for baseline variance.

Interpretation

For the majority of older women with early ER+ breast cancer, surgery is oncologically superior to PET. In less fit, older women, with characteristics similar to the matched cohort of this study (median age 81 with higher comorbidity and functional impairment burdens, the BCSS survival differential disappears at least out to 4–5 year follow-up, suggesting that for those with less than 5-year predicted life-expectancy (>90 years or >85 with comorbidities or frailty) individualised decision making regarding PET versus S+ET may be appropriate and safe to offer. The Age Gap online decision tool may support this decision-making process (https://agegap.shef.ac.uk/).

Trial registration number

ISRCTN: 46099296.

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Propensity matched study of women >70 with breast cancer comparing surgery or PET

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Unmatched analysis found surgery improves overall & disease-specific survival.

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Matched analysis (stage, age, health, frailty) found similar disease-specific survival

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Surgery led to adverse events in 19% & negative impacts on QoL and physical function

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Less fit women >85 may be offered PET to reduce morbidity, without survival detriment

Simulating long-term and residual effects of nitrogen fertilization on corn yields, soil carbon sequestration, and soil nitrogen dynamics

Soil carbon sequestration (SCS) has the potential to attenuate increasing atmospheric CO2 and mitigate greenhouse warming. Understanding of this potential can be assisted by the use of simulation models. We evaluated the ability of the EPIC model to simulate corn (Zea mays L.) yields and soil organic carbon (SOC) at Arlington, WI, during 1958-1991. Corn was grown continuously on a Typic Argiudoll with three N levels: LTN1 (control), LTN2 (medium), and LTN3 (high). The LTN2 N rate started at 56 kg ha(-1) (1958), increased to 92 kg ha(-1) (1963), and reached 140 kg ha(-1) (1973). The LTN3 N rate was maintained at twice the LTN2 level. In 1984, each plot was divided into four subplots receiving N at 0, 84, 168, and 252 kg ha(-1). Five treatments were used for model evaluation. Percent errors of mean yield predictions during 1958-1983 decreased as N rate increased (LTN1 = -5.0%, LTN2 = 3.5%, and LTN3 = 1.0%). Percent errors of mean yield predictions during 1985-1991 were larger than during the first period. Simulated and observed mean yields during 1958-1991 were highly correlated (R2 = 0.961, p < 0.01). Simulated SOC agreed well with observed values with percent errors from -5.8 to 0.5% in 1984 and from -5.1 to 0.7% in 1990. EPIC captured the dynamics of SOC, SCS, and microbial biomass. Simulated net N mineralization rates were lower than those from laboratory incubations. Improvements in EPIC's ability to predict annual variability of crop yields may lead to improved estimates of SCS.

Sex-specific association between bipolar affective disorder in women and GPR50, an X-linked orphan G protein-coupled receptor

GPR50 is an orphan G protein-coupled receptor (GPCR) located on Xq28, a region previously implicated in multiple genetic studies of bipolar affective disorder (BPAD). Allele frequencies of three polymorphisms in GPR50 were compared in case-control studies between subjects with BPAD (264), major depressive disorder (MDD) (226), or schizophrenia (SCZ) (263) and ethnically matched controls (562). Significant associations were found between an insertion/deletion polymorphism in exon 2 and both BPAD (P=0.0070), and MDD (P=0.011) with increased risk associated with the deletion variant (GPR50(Delta502-505)). When the analysis was restricted to female subjects, the associations with BPAD and MDD increased in significance (P=0.00023 and P=0.0064, respectively). Two other single-nucleotide polymorphisms (SNPs) tested within this gene showed associations between: the female MDD group and an SNP in exon 2 (P=0.0096); and female SCZ and an intronic SNP (P=0.0014). No association was detected in males with either MDD, BPAD or SCZ. These results suggest that GPR50(Delta502-505), or a variant in tight linkage disequilibrium with this polymorphism, is a sex-specific risk factor for susceptibility to bipolar disorder, and that other variants in the gene may be sex-specific risk factors in the development of schizophrenia.

Modulation of inhibitory autapses and synapses on rat CA1 interneurones by GABA(A) receptor ligands

To determine whether autaptic inhibition plays a functional role in the adult hippocampus, the action potential afterhyperpolarisations (spike AHPs) of CA1 interneurones were investigated in 25 basket, three bistratified and eight axo-axonic cells. The spike AHPs showed two minima in all regular-spiking (5), burst-firing (3) and in many fast-spiking cells (17:28). The fast component had a time-to-peak (TTP) of 1.2 +/- 0.5 ms, the slower TTP was very variable (range of 3.3-103 ms). The AHP width at half-amplitude (HW) was 12.5 +/- 5.7 ms in fast-spiking, 29.3 +/- 18 ms in regular-spiking and 99.7 +/- 42 ms in burst-firing cells. Axo-axonic cells never establish autapses, and the fast-spiking variety showed narrow (HW: 3.9 +/- 0.7 ms) spike AHPs with only one AHP minimum (TTP: 0.9 +/- 0.1 ms). When challenged with GABA(A) receptor modulators, spike AHPs in basket and bistratified cells were enhanced by zolpidem (HW by 18.4 +/- 6.2 % in 10:15 cells tested), diazepam (45.2 +/- 0.5 %, 6:7), etomidate (43.9 +/- 36 %, 6:8) and pentobarbitone sodium (41 %, 1:1), and were depressed by bicuculline (-41 +/- 5.7 %, 5:8) and picrotoxin (-54 %, 1:1), and the enhancement produced by zolpidem was reduced by flumazenil (-31 +/- 13 %, relative to the AHP HW during exposure to zolpidem, 3:4). Neuronal excitability was modulated in parallel. The spike AHPs of three axo-axonic cells tested showed no sensitivity to etomidate, pentobarbitone or diazepam. Interneurone-to-interneurone inhibitory postsynaptic potentials (IPSPs), studied with dual intracellular recordings, had time courses resembling those of the spike AHPs. The IPSP HW was 13.4 +/- 2.8 ms in fast-spiking (n = 16) and 28.7 +/- 5.8 ms in regular-spiking/burst-firing cells (n = 6), and the benzodiazepine1-selective modulator zolpidem strongly enhanced these IPSPs (45 +/- 28 %, n = 5). Interneurones with spike AHPs affected by the GABA(A) receptor ligands exhibited 3.8 +/- 1.9 close autaptic appositions. In three basket cells studied at the ultrastructural level 6 of 6, 1 of 2 and 1 of 2 close appositions were confirmed as autapses. Therefore, in the hippocampus autaptic connections contribute to spike AHPs in many interneurones. These autapses influence neuronal firing and responses to GABA(A) receptor ligands.

Excitatory Connections Between CA1 Pyramidal Cells Revealed by Spike Triggered Averaging in Slices of Rat Hippocampus are Partially NMDA Receptor Mediated

Spike triggered averaging was used to record local circuit connections between pairs of CA1 pyramidal neurons in isolated slices of rat hippocampus. Of 795 pairs of neurons tested, six were connected. These epsps were only partially blocked by 2-amino-5-phosphonovalerate (AP-5), which decreased the amplitude and half width of the epsp, but did not affect the early rising phase. In contrast, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocked all phases of the epsp and combinations of AP-5 and CNQX blocked the epsp almost entirely. These results indicate that these epsps were mediated by both N-methyl-d-aspartate (NMDA) and non-NMDA excitatory amino acid receptors. Moreover, they exhibited a voltage relation typical of neuronal responses to NMDA, increasing in amplitude and duration as the postsynaptic cell was depolarized. These epsps were brief (10 - 90% rise time < 5 ms, width at half amplitude < 20 ms), indicating a proximal location. Increasing presynaptic firing rate (1 - 4 spikes/s) reduced average epsp amplitude by almost 50%. When epsps were evoked by pairs of spikes (interval 3 - 25 ms), a large response to the first spike precluded a large response to the second. No evidence for selective enhancement of the NMDA receptor component by paired spike activation was found. It is concluded that a significant NMDA receptor mediated input to CA1 is provided by local circuit CA1 - CA1 connections and that these synapses can be demonstrated under control conditions.

Coactivation of Local Circuit NMDA Receptor Mediated epsps Induces Lasting Enhancement of Minimal Schaffer Collateral epsps in Slices of Rat Hippocampus

Lasting enhancement of minimal Schaffer collateral epsps in CA1 pyramidal neurons was induced when these epsps were coactivated with putative local circuit N-methyl-d-aspartate (NMDA) receptor-mediated epsps. In transverse slices of hippocampus, minimal epsps were evoked by stimulating the Schaffer collateral/commissural pathway within CA3 stratum radiatum and the local circuit axons were stimulated within CA1 stratum oriens or alveus using fine, two barrel glass micropipettes. Minimal Schaffer collateral epsps were insensitive to d-2-amino-5-phosphonovalerate (AP-5) and displayed conventional voltage relations. Local epsps were sensitive to AP-5 and increased in amplitude and duration with membrane depolarization. High frequency tetanic stimulation of the minimal Schaffer collateral epsps induced no lasting enhancement. However, pairing of the Schaffer epsp with a frequency potentiated local epsp resulted in a delayed, but lasting increase in the Schaffer epsp. When the local epsp did not exhibit frequency potentiation during pairing, no enhancement resulted. When either epsp was contaminated with an ipsp, no lasting increase resulted. When transmission through the alveus was blocked by focal application of local anaesthetic, traditional protocols for long-term potentiation (LTP) induction were relatively ineffective. These results indicate that a significant source of the NMDA receptor activation required for the induction of LTP in the Schaffer collateral input to CA1 derives from local circuit connections between CA1 pyramidal neurons and, moreover, that lasting enhancement can be induced with low frequency activation, at postsynaptic resting potential, in the presence of Mg2+ and with local inhibition intact.

Women's expectations and experiences of childbirth

OBJECTIVE

to explore, describe and understand the expectations during pregnancy and subsequent experiences of childbirth in primiparae.

DESIGN

a qualitative study using a phenomenological approach. Data were collected using unstructured, tape-recorded interviews in late pregnancy and at two weeks post birth.

SETTING

the north of England.

PARTICIPANTS

eight pregnant women, expecting their first baby.

FINDINGS

the women all wanted to take an active part in their labour and the feeling of being 'in control' was the main finding and the 'essence' of this study. This was achieved through support from partners, the positive attitudes of the midwives caring for them during pregnancy and labour, information giving during pregnancy and labour and being able to make and be included in decision making during labour.

IMPLICATIONS FOR PRACTICE

if women are to be empowered by making choices for childbirth and feeling 'in control', then it is important for midwives to explore and discover the wishes and feelings of women in their care so that realistic expectations can be promoted and then hopefully fulfilled.

Mammalian class Sigma glutathione S-transferases: catalytic properties and tissue-specific expression of human and rat GSH-dependent prostaglandin D2 synthases

GSH-dependent prostaglandin D(2) synthase (PGDS) enzymes represent the only vertebrate members of class Sigma glutathione S-transferases (GSTs) identified to date. Complementary DNA clones encoding the orthologous human and rat GSH-dependent PGDS (hPGDS and rPGDS, respectively) have been expressed in Escherichia coli, and the recombinant proteins isolated by affinity chromatography. The purified enzymes were both shown to catalyse specifically the isomerization of prostaglandin (PG) H(2) to PGD(2). Each transferase also exhibited GSH-conjugating and GSH-peroxidase activities. The ability of hPGDS to catalyse the conjugation of aryl halides and isothiocyanates with GSH was found to be less than that of the rat enzyme. Whilst there is no difference between the enzymes with respect to their K(m) values for 1-chloro-2,4-dinitrobenzene, marked differences were found to exist with respect to their K(m) for GSH (8 mM versus 0.3 mM for hPGDS and rPGDS, respectively). Using molecular modelling techniques, amino acid substitutions have been identified in the N-terminal domain of these enzymes that lie outside the proposed GSH-binding site, which may explain these catalytic differences. The tissue-specific expression of PGDS also varies significantly between human and rat; amongst the tissues examined, variation in expression between the two species was most apparent in spleen and bone marrow. Differences in catalytic properties and tissue-specific expression of hPGDS and rPGDS appears to reflect distinct physiological roles for class Sigma GST between species. The evolution of divergent functions for the hPGDS and rPGDS is discussed in the context of the orthologous enzyme from chicken.

A comparison of information retention at an initial orthodontic consultation

The exchange of information is an everyday part of orthodontic treatment. However, the amount of information that is understood and retained, by patients and their parents, is not known. There has been very little research in the area of information retention in dentistry. This has implications with the demands for improved provision of information for patients. This questionnaire-based study, compared the effectiveness of written, verbal, and visual methods of providing orthodontic information. It assessed the retention of this information, by patients and parents, in both the short- and long-term. Twenty-eight patients and their parents, were allocated alternately into one of three groups, receiving written, verbal, or visual information. Short-term retention of knowledge was assessed 10-15 minutes after receiving the information and long-term retention rated by a second questionnaire mailed 8 weeks later. Overall, little difference was found between the three methods. The findings suggested that verbal information should not be given to patients unless supplemented by written and/or visual information, and that parents were more attentive to verbal instructions than their children.

Identification of a novel AU-Rich element in the 3' untranslated region of epidermal growth factor receptor mRNA that is the target for regulated RNA-binding proteins

The epidermal growth factor receptor (EGF-R) plays an important role in the growth and progression of estrogen receptor-negative human breast cancers. EGF binds with high affinity to the EGF-R and activates a variety of second messenger pathways that affect cellular proliferation. However, the underlying mechanisms involved in the regulation of EGF-R expression in breast cancer cells are yet to be described. Here we show that the EGF-induced upregulation of EGF-R mRNA in two human breast cancer cell lines that overexpress EGF-R (MDA-MB-468 and BT-20) is accompanied by stabilization (>2-fold) of EGF-R mRNA. Transient transfections using a luciferase reporter identified a novel EGF-regulated approximately 260-nucleotide (nt) cis-acting element in the 3' untranslated region (3'-UTR) of EGF-R mRNA. This cis element contains two distinct AU-rich sequences (~75 nt), EGF-R1A with two AUUUA pentamers and EGF-R2A with two AUUUUUA extended pentamers. Each independently regulated the mRNA stability of the heterologous reporter. Analysis of mutants of the EGF-R2A AU-rich sequence demonstrated a role for the 3' extended pentamer in regulating basal turnover. RNA gel shift analysis identified cytoplasmic proteins (~55 to 80 kDa) from breast cancer cells that bound specifically to the EGF-R1A and EGF-R2A cis-acting elements and whose binding activity was rapidly downregulated by EGF and phorbol esters. RNA gel shift analysis of EGF-R2A mutants identified a role for the 3' extended AU pentamer, but not the 5' extended pentamer, in binding proteins. These EGF-R mRNA-binding proteins were present in multiple human breast and prostate cancer cell lines. In summary, these data demonstrate a central role for mRNA stabilization in the control of EGF-R gene expression in breast cancer cells. EGF-R mRNA contains a novel complex AU-rich 260-nt cis-acting destabilizing element in the 3'-UTR that is bound by specific and EGF-regulated trans-acting factors. Furthermore, the 3' extended AU pentamer of EGF-R2A plays a central role in regulating EGF-R mRNA stability and the binding of specific RNA-binding proteins. These findings suggest that regulated RNA-protein interactions involving this novel cis-acting element will be a major determinant of EGF-R mRNA stability.

Thyrotropin-releasing hormone and epidermal growth factor regulate iron-regulatory protein binding in pituitary cells via protein kinase C-dependent and -independent signaling pathways

Intracellular iron homeostasis is regulated, in part, by interactions between iron-regulatory proteins (IRP1 and IRP2) and iron-responsive elements (IREs) in ferritin and transferrin receptor mRNAs. In addition to iron, cellular oxidative stress induced by H(2)O(2), nitric oxide, and hypoxia, and hormonal activation by thyroid hormone and erythropoeitin have each been shown to regulate IRP binding to IREs. Hormonal signals, in particular mediated through protein kinase C (PKC), play a central role in the modulation of IRP/IRE interactions since phorbol esters were shown to activate IRP binding (Eisenstein, R. S., Tuazon, P. T., Schalinske, K. L., Anderson, S. A., and Traugh, J. A. (1993) J. Biol. Chem. 268, 27363-27370). In pituitary thyrotrophs (TtT97), we found that thyrotropin releasing hormone (TRH) and epidermal growth factor (EGF) increased IRP binding to a ferritin IRE, dependent on PKC and mitogen-activated protein kinase (MAPK) activity. In contrast, TRH and EGF decreased IRP binding in pituitary lactotrophs (GH3), despite activation of PKC and MAPK. IRP1 and IRP2 levels remained constant and IRP2 binding was predominant throughout. TRH and EGF markedly decreased IRP binding in MAPK kinase inhibitor-treated GH3 cells, whereas, they increased IRP binding in phosphatase inhibitor-treated GH3 cells. IRE-dependent CAT reporter translational expression closely reflected IRP binding to the ferritin IRE in both GH3 and TtT97 cells. Interestingly, ferritin protein levels were regulated similarly by TRH in both cell lines. These data link two different cell receptor systems to common signaling pathways that regulate IRP binding and ferritin expression. Remarkably, for TRH and EGF, these effects may be PKC-dependent or -independent determined by the cell type.

Molecular frequency filters at central synapses

During the 1950s to 70s most of the mechanisms that control transmitter release from presynaptic nerve terminals were described at the neuromuscular junction. It was not, however, until the 1990s that the multiplicity of protein-protein interactions that govern this process began to be identified. The sheer numbers of proteins and the complexity of their interactions at first appears excessive, even redundant. However, studies of identified central synapses indicate that this molecular diversity may underlie a important functional diversity. The task of the neuromuscular junction is to relay faithfully the rate and pattern code generated by the motoneurone. To demonstrate phenomena such as facilitation and augmentation that are apparent only when the probability of release is low, experimental manipulation is required. In the cortex, however, low probability synapses displaying facilitation can be recorded in parallel with high probability synapses displaying depression. The mechanisms are largely the same as those displayed by the neuromuscular junction, but some are differentially expressed and controlled. Central synapses demonstrate exquisitely fine tuned information transfer, each of the many types displaying its own repertoire of pattern- and frequency-dependent properties. These appear tuned to match both the discharge pattern in the presynaptic neurone and the integrative requirements of the postsynaptic cell. The molecular identification of these differentially expressed frequency filters is now just coming into sight. This review attempts to correlate these two aspects of synaptic physiology and to identify the components of the release process that are responsible for the diversity of function.

Double immunofluorescence, peroxidase labelling and ultrastructural analysis of interneurones following prolonged electrophysiological recordings in vitro

Inhibitory hippocampal and neocortical interneurones comprise a physiologically, morphologically and neurochemically heterogenous cell population. To identify the roles each class of interneurone plays within a given circuit it is necessary to correlate the electrophysiological properties of individual cells with their neurochemistry and morphology at both the light and electron microscopic level. However, the optimal conditions required for any one part of the protocol typically compromise the results from another. We have developed a protocol which allows the neurochemical content, gross morphology and ultrastructure details of biocytin-filled neurones to be recovered following long, dual intracellular recordings in thick mature slices maintained in an interface recording chamber, helping define sub-populations which could not otherwise be determined. Dual immunofluorescence is performed by incubating the tissue in monoclonal and polyclonal antibodies simultaneously, prior to visualization of biocytin-labelling with precipitation of a peroxidase reaction product. By using a biotinylated anti-avidin D antibody (Vector Laboratories), the intensity of this precipitation can be enhanced further where necessary. It is envisaged that this protocol can not only help determine the neurochemical content of cells recorded in similar in vivo studies, but that the ability to amplify peroxidase labelling in poorly filled cells is also of interest.

Hormonal regulation of mRNA stability and RNA-protein interactions in the pituitary

Regulating gene expression from DNA to protein is a complex multistage process with multiple control mechanisms. Transcriptional regulation has been considered the major control point of protein production in eukaryotic cells; however, there is growing evidence of pivotal posttranscriptional regulation for many genes. This has prompted extensive investigations to elucidate the mechanisms controlling RNA processing, mRNA nuclear export and localization, mRNA stability and turnover, in addition to translational rates and posttranslational events. The regulation of mRNA stability has emerged as a critical control step in determining the cellular mRNA level, with individual mRNAs displaying a wide range of stability that has been linked to discrete sequence elements and specific RNA-protein interactions. This review will focus on current knowledge of the determinants of mRNA stability and RNA-protein interactions in the pituitary. This field is rapidly expanding with the identification of regulated cis-acting stability-modifying elements within many mRNAs, and the cloning and characterization of trans-acting proteins that specifically bind to their cognate cis elements. We will present evidence for regulation of multiple pituitary genes at the level of mRNA stability and some examples of the emerging data characterizing RNA-protein interactions.

Facilitation, augmentation and potentiation at central synapses

Release probability (P) appears to be a major factor that influences the pattern of transmitter release. At cortical pyramidal axon inputs onto different classes of target cells, very different release patterns are observed, patterns that correlate with release probability. Simplistically, 'low P' synapses display facilitation and augmentation, whereas 'high P' synapses supplied by the same axon exhibit paired-pulse and frequency-dependent depression. Different combinations of factors probably contribute to release probability at different terminals, during development and under different experimental conditions. The recent advances made by molecular biological studies of the release machinery do, however, provide candidate proteins and protein-protein interactions whose differential distributions might be important factors in determining the patterns of transmitter release.

Does evidenced-based practice medicalise midwifery care? Part 2

In this paper evidence-based care is defined. The evidence to support the provision of care by midwives is presented, as is the evidence to support home birth for those women at low obstetric risk. In conclusion midwives are challenged to be political and use this evidence to support changes to improve the quality of care provided to women and their families.

Does evidenced-based practice medicalize midwifery care? Part 1

In this paper evidence-based care is defined. The evidence to support the provision of care by midwives is presented, as is the evidence to support home birth for those women at low obstetric risk. In conclusion midwives are challenged to be political and use this evidence to support changes to improve the quality of care provided to women and their families.

Neurotransmission: Chemical and electrical interneuron coupling

Recent studies have described the coupling between pairs of neocortical interneurons involving both electrical and chemical transmission; these new results may have important implications for the mechanisms underlying neuronal synchrony and rhythmic activity in the brain.

Differential sensitivity to Zolpidem of IPSPs activated by morphologically identified CA1 interneurons in slices of rat hippocampus

Hippocampal pyramidal cells express several alpha-subunits, which determine the affinity of GABAA (gamma-aminobutyric acid) receptors for benzodiazepine site ligands. This study asked whether inhibitory postsynaptic potentials (IPSPs) elicited by specific interneuronal subclasses were differentially sensitive to the alpha1-preferring agonist Zolpidem, i.e. whether different receptors mediate different inhibitory connections. Paired intracellular recordings in which the presynaptic cell was an interneuron and the postsynaptic cell a CA1 pyramid were performed in slices of adult rat hippocampus. Resultant IPSPs were challenged with Zolpidem, cells filled with biocytin and identified morphologically. IPSPs elicited by fast spiking (FS) basket cells (n = 9) were enhanced more than IPSPs elicited by regular spiking (RS) basket cells (n = 10). At FS basket cell synapses the efficacy of Zolpidem was equivalent to that of Diazepam, while RS basket cell IPSPs are enhanced 50% less by Zolpidem than by Diazepam. Thus, while alpha1 subunits may dominate at synapses supplied by FS basket cells, RS basket cell synapses also involve alpha2/3 subunits. Two bistratified cell IPSPs tested with Zolpidem did not increase in amplitude, despite powerful enhancements of bistratified cell IPSPs by Diazepam, consistent with previous indications that these synapses utilize alpha5-containing receptors. Enhancements of basket cell IPSPs by Zolpidem and Diazepam were bi- or triphasic with steep amplitude increases separated by plateaux, occurring 10-15, 25-30 and 45-55 min after adding the drug to the bath. The entire enhancement was, however, blocked by the antagonist Flumazenil (n = 7). Flumazenil, either alone (n = 3), or after Zolpidem, reduced IPSP amplitude to approximately 90% of control, suggesting that alpha4-containing receptors were not involved.

Optimized RNA gel-shift and UV cross-linking assays for characterization of cytoplasmic RNA-protein interactions

Considerable interest has recently focused on defining the mechanisms involved in the regulation of gene expression at the level of mRNA stability and translational efficiency. However, the assays used to directly investigate interactions between RNA and cytoplasmic proteins have been difficult to establish, and methods are not widely available. Here, we describe a robust method for RNA electrophoretic mobility shift and UV cross-linking assays that allows rapid detection of cytoplasmic RNA-protein interactions. For added convenience to new investigators, these assays use mini-gels with an electrophoresis time of 15-20 min, enabling a high throughput of samples. The method works successfully with many different probes and cytoplasmic extracts from a variety of cell lines. Furthermore, we provide a system to optimize characterization of the RNA-protein complex and troubleshoot most assay difficulties.

Iron-regulatory proteins, iron-responsive elements and ferritin mRNA translation

Iron plays a central role in the metabolism of all cells. This is evident by its major contribution to many diverse functions, such as DNA replication, bacterial pathogenicity, photosynthesis, oxidative stress control and cell proliferation. In mammalian systems, control of intracellular iron homeostasis is largely due to posttranscriptional regulation of binding by iron-regulatory RNA-binding proteins (IRPs) to iron-responsive elements (IREs) within ferritin and transferrin receptor (TfR) mRNAs. the TfR transports iron into cells and the iron is subsequently stored within ferritin. IRP binding is under tight control so that it responds to changes in intracellular iron requirements in a coordinate manner by differentially regulating ferritin mRNA translational efficiency and TfR mRNA stability. Several different stimuli, as well as intracellular iron levels and oxidative stress, are capable of regulating these RNA-protein interactions. In this mini-review, we shall concentrate on the mechanisms underlying modulation of the interaction of IRPs and the ferritin IRE and its role in regulating ferritin gene expression.

Modulation of bistratified cell IPSPs and basket cell IPSPs by pentobarbitone sodium, diazepam and Zn2+: dual recordings in slices of adult rat hippocampus

Simultaneous intracellular recordings from presynaptic Stratum pyramidale interneurons and postsynaptic pyramidal cells in adult rat hippocampal slices were performed to investigate the strength of the modulation of single-axon inhibitory postsynaptic potentials (IPSPs) by the GABAA receptor modulators pentobarbitone, diazepam and zinc. The processing of biocytin-filled interneurons for light microscopy revealed that these single-axon IPSPs were generated by basket cells (n = 33), bistratified cells (n = 18) and axo-axonic cells (n = 2). The IPSPs generated by these three groups of interneurons had amplitudes and widths at half amplitude with similar ranges, but when bistratified cell IPSPs were compared with basket cell IPSPs with similar half widths their rise times were slower. Pentobarbitone sodium (250 microM) powerfully enhanced 13 tested IPSPs generated by all three cell types. Amplitudes were enhanced by 82 +/- 56%, 10-90% rise times by 150 +/- 101% and the widths at half amplitude by 71 +/- 29%. Diazepam (1-2 microM) also increased all IPSPs tested, although the changes were more moderate in basket cell IPSPs (amplitudes increased by 19 +/- 11%, n = 8) than in bistratified cell IPSPs (amplitudes increased by 66 +/- 48%, n = 5). Basket cell IPSP 10-90% rise times and widths at half amplitude were not significantly increased. Bistratified cell IPSP 10-90% rise times were increased by 44 +/- 24% and the widths at half amplitude by 32 +/- 35%. The one tested IPSP generated by an axo-axonic cell was also diazepam-sensitive. Zinc, 250 microM, decreased four out of 10 IPSPs generated by basket cells and four out of five IPSPs generated by bistratified cells. The one tested axo-axonic cell IPSP was zinc-insensitive. These data suggest that IPSPs generated in CA1 pyramidal cells by basket and bistratified cells display different pharmacologies and may be mediated by different receptors or receptor combinations.

Haemopoietic progenitor cell lines generated by the myeloproliferative leukaemia virus: a model system to analyse murine and human lineage-affiliated genes

Multipotential progenitor and stem cells occur with a low frequency in haemopoietic tissue. As a result, it is often difficult to obtain sufficient numbers of cells to undertake many of the assays that would be informative about the molecular events involved in the regulation of lineage-affiliated genes within these multipotent cells. To circumvent this problem, we have used the myeloproliferative leukaemia virus (MPLV) to generate a phenotypically diverse array of haemopoietic progenitors from adult mouse bone marrow and embryonic blood. These cells could be expanded to perform a variety of analyses that would not previously have been possible using analogous primary cells. The validity of these assays was supported by the observation that the phenotype of several MPLV-infected lines was very similar to previously described primary haemopoietic progenitor cells. By using mice transgenic for the human alpha and beta globin gene clusters, we have shown that human genes may also be investigated. In addition, this strategy has a wide potential applicability including the rescue of haemopoietic progenitors from mouse embryos lacking genes critical for their survival as well as the study of any haemopoietic gene for which an appropriate transgenic mouse is available.

Release-independent depression at pyramidal inputs onto specific cell targets: dual recordings in slices of rat cortex

1. Paired intracellular recordings were performed in slices of adult rat neocortex and hippocampus to examine presynaptic depression. A novel form of depression that occurs even in the absence of transmitter release during conditioning activity was observed at a subset of synaptic connections. 2. In each pair studied, a pyramidal neurone was presynaptic and inputs onto a range of morphologically identified postsynaptic target cells were analysed; high probability connections exhibiting the more traditional forms of release-dependent depression, as well as low probability connections exhibiting facilitation, were tested (n = 35). 3. Connections were tested with presynaptic spike pairs and trains of spikes with a range of interspike intervals. Sweeps in which the first action potential elicited no detectable response (apparent failures of transmission) and sweeps in which the first action potential elicited large EPSPs were selected. Second EPSPs that followed apparent failures were then compared with second EPSPs that followed large first EPSPs. 4. Release-independent depression was apparent when second EPSPs at brief interspike intervals (<10-15 ms) were on average smaller than second EPSPs at longer interspike intervals, even following apparent failures and when the second EPSP amplitude at these short intervals was independent of the amplitude of the first EPSP. 5. Release-independent depression appeared selectively expressed. Depressing inputs onto some interneurones, such as CA1 basket-like and bistratified cells, and facilitating inputs onto others, such as some fast spiking neocortical interneurones, exhibited this phenomenon. In contrast, depressing inputs onto 10/10 neocortical pyramids and facilitating inputs onto 7/7 oriens-lacunosum moleculare and 5/5 burst firing, sparsely spiny neocortical interneurones did not.

Dual intracellular recordings and computational models of slow inhibitory postsynaptic potentials in rat neocortical and hippocampal slices

Dual intracellular recordings in slices of adult rat neocortex and hippocampus investigated slow, putative GABA(B) receptor-mediated inhibitory postsynaptic potentials. In most pairs tested in which the interneuron elicited a fast inhibitory postsynaptic potential in the pyramid, this GABA(A) receptor mediated inhibitory postsynaptic potential was entirely blocked by bicuculline or picrotoxin (3:3 in neocortex, 6:8 in CA1, all CA1 basket cells), even when high-frequency presynaptic spike trains were elicited. However, in three of 85 neocortical paired recordings involving an interneuron, although no discernible response was elicited by single presynaptic interneuronal spikes, a long latency (> or =20 ms) inhibitory postsynaptic potential was elicited by a train of > or =3 spikes at frequencies > or =50-100 Hz. This slow inhibitory postsynaptic potential was insensitive to bicuculline (one pair tested). In neocortex, slow inhibitory postsynaptic potential duration reached a maximum of 200 ms even with prolonged presynaptic spike trains. In contrast, summing fast, GABA(A) inhibitory postsynaptic potentials, elicited by spike trains, lasted as long as the train. Between four and 10 presynaptic spikes, mean peak slow inhibitory postsynaptic potential amplitude increased sharply to 0.38, 2.6 and 2.9 mV, respectively, in the three neocortical pairs (membrane potential -60 to -65 mV). Thereafter increases in spike number had little additional effect on amplitude. In two of eight pairs in CA1, one involving a presynaptic basket cell and the other a putative bistratified interneuron, the fast inhibitory postsynaptic potential was blocked by bicuculline revealing a slow inhibitory postsynaptic potential that was greatly reduced by 100 microM CGP 35348 (basket cell pair). The sensitivity of this slow inhibitory postsynaptic potential to spike number was similar to that of neocortical 'pure' slow inhibitory postsynaptic potentials, but was of longer duration, its plateau phase outlasting 200 ms spike trains and its maximum duration exceeding 400 ms. Computational models of GABA release, diffusion and uptake suggested that extracellular accumulation of GABA cannot alone account for the non-linear relationship between spike number and inhibitory postsynaptic potential amplitude. However, cooperativity in the kinetics of GABA(B) transduction mechanisms provided non-linear relations similar to experimental data. Different kinetic models were considered for how G-proteins activate K+ channels, including allosteric models. For all models, the best fit to experimental data was obtained with four G-protein binding sites on the K+ channels, consistent with a tetrameric structure for the K+ channels associated with GABA(B) receptors. Thus some inhibitory connections in neocortex and hippocampus appear mediated solely by fast GABA(A) receptors, while others appear mediated solely by slow, non-ionotropic, possibly GABA(B) receptors. In addition, some inhibitory postsynaptic potentials arising in proximal portions of CA1 pyramidal cells are mediated by both GABA(A) and GABA(B) receptors. Our data indicate that the GABA released by a single interneuron can saturate the GABA(B) receptor mechanism(s) accessible to it and that 'spillover' to extrasynaptic sites need not necessarily be proposed to explain these slow inhibitory postsynaptic potential properties.

Facilitating learning in the community with lecturer-practitioner posts

The purpose of this paper is to present a case study of the perspectives of their role of a group of community lecturer-practitioners and a community teacher, who referred to themselves as 'community facilitators'. A qualitative design was used and data were collected by semi-structured interviews. These were transcribed and content analysis was undertaken. All participants provided a liaison role between the college and the community practitioners, prepared students for their clinical experience and assisted in relating theory to practice. The participants described how they managed the role and how they supported each other. Developing small teams of facilitators may provide a bridge between teachers and practitioners and can serve as a basis for further study of the lecturer-practitioner role.

IPSPs elicited in CA1 pyramidal cells by putative basket cells in slices of adult rat hippocampus

CA1 basket cells are identifiable by an axonal arbour largely confined to, and spanning, the entire depth of stratum pyramidale where they innervate pyramidal somata and proximal dendrites. Basket cells display a range of electrophysiological properties and the inhibitory postsynaptic potentials (IPSPs) they elicit in pyramidal cells vary widely in duration. To determine whether these parameters are correlated, we used paired intracellular recordings, with biocytin filling, in pyramidal cells of adult hippocampal slices, and studied gamma-aminobutyric acid (GABAA) IPSPs (n = 43) elicited by putative basket cells (n = 35) with axons largely confined to stratum pyramidale in simultaneously recorded pyramidal cells. Fast-spiking interneurons elicited relatively brief IPSPs, while IPSPs elicited by burst-firing cells were amongst the slowest. Regular spiking interneurons elicited fast and slow GABAA IPSPs, but any one interneuron elicited IPSPs with remarkably similar durations in two to four pyramidal targets. However, with different types of target for a single putative basket cell, IPSPs elicited in postsynaptic interneurons were briefer than in pyramidal cells. Vertical oriens cells with somata in stratum oriens and a narrow, sparse axonal arbour in stratum pyramidale in transverse hippocampal slices, elicited IPSPs whose rise times and half widths clustered around intermediate values. Durations of IPSPs in pyramidal cells thus correlate, to a degree, with the physiological properties of presynaptic basket cells. The seven-fold range of durations observed (10-70 ms half widths) may underlie contributions made by different basket cells to hippocampal rhythms of different frequencies.

Continuing education needs of community nurses, midwives and health visitors for supervising and assessing students

The objective of this study was to ascertain the changing educational needs of community nurses, midwives and health visitors in relation to the teaching, supervising and assessing of pre- and post-registration students. A questionnaire was sent to all education institutions providing community nursing experience in England (Whittaker et al. 1997), which allowed identification of three centres for in-depth study. Questionnaires were sent to practitioners (community nurses and midwives, health visitors and school nurses), their managers, and teachers of community courses in the three centres: 314 were returned. Eight semi-structured interviews were undertaken with volunteers in each of the study centres (n = 24). Extensive demands are being made on community staff to provide learning experiences for students on a wide range of courses. Practitioners reported that in order to fulfil their teaching and assessing functions they needed continuing education in matters which would assist them to provide research-based practice and education, teaching and assessing in the community and personal skills, for example assertiveness and counselling. Less than a quarter of practitioners were undertaking continuing education courses. However, opportunities for further academic study varied enormously and most practitioners had to study in their own time at their own expense.

Increased bioactivation of dihaloalkanes in rat liver due to induction of class theta glutathione S-transferase T1-1

A characteristic feature of the class Theta glutathione S-transferase (GST) T1-1 is its ability to activate dichloromethane and dibromoethane by catalysing the formation of mutagenic conjugates. The level of the GSTT1 subunit within tissues is an important determinant of susceptibility to the carcinogenic effects of these dihaloalkanes. In the present study it is demonstrated that hepatic GST activity towards these compounds can be elevated significantly in female and male Fischer-344 rats by feeding these animals on diets supplemented with cancer chemopreventive agents. Immunoblotting experiments showed that increased activity towards the dihaloalkanes is associated with elevated levels of the GSTT1 subunit in rat liver. Sex-specific effects were observed in the induction of GSTT1 protein. Amongst the chemopreventive agents tested, indole-3-carbinol proved to be the most potent inducer of hepatic GSTT1 in male rats (6.2-fold), whereas coumarin was the most potent inducer of this subunit in the livers of female rats (3. 5-fold). Phenobarbital showed significant induction of GSTT1 only in male rat liver and had little effect in female rat liver. Western blotting showed that class Alpha, Mu and Pi GST subunits are not co-ordinately induced with GSTT1, indicating that the expression of GSTT1 is determined, at least in part, by mechanisms distinct from those that regulate levels of other transferases. The increase in amount of hepatic GSTT1 protein was also reflected by an increase in the steady-state level of mRNA in response to treatment with chemopreventive agents and model inducers. Immunohistochemical detection of GSTT1 in rat liver supported the Western blotting data, but showed, in addition to cytoplasmic staining, significant nuclear localization of the enzyme in hepatocytes from some treated animals, including those fed on an oltipraz-containing diet. Significantly, the hepatic level of cytochrome P-450 2E1, an enzyme which offers a detoxification pathway for dihaloalkanes, was unchanged by the various inducing agents studied. It is concluded that the induction of GSTT1 by dietary components and its localization within cells are important factors that should be considered when assessing the risk dihaloalkanes pose to human health.

Assessment of communication impairment and the effects of resective surgery in solitary, right-sided supratentorial intracranial tumours: a prospective study

To assess the effects of solitary, right-sided supratentorial intracranial tumours on language and communication function patients were assessed preoperatively using the Western Aphasia Battery (WAB) and Boston Naming Test (BNT). The impact of resective tumour surgery was evaluated prospectively by a comparison of test scores obtained at pre- and postoperative assessments. The WAB scores in 33 patients revealed that 21% were by definition dysphasic (i.e. Aphasia Quotient < 93.8) and 35% obtained an abnormal Language Quotient. Performance was particularly variable on the written picture description and word fluency WAB subtests. Using the BNT 21% of 47 patients were anomic. The tumours were evenly distributed throughout the frontal, temporal and parietal lobes, but none were in the occipital lobe. Reassessment approximately 6 days after excisional tumour surgery showed that mean scores for the BNT, Aphasia Quotient, and the WAB spontaneous speech and comprehension subtests had improved significantly despite a significant reduction in dexamethasone therapy. This study has demonstrated that right-sided intracranial tumours produce subtle, but specific language deficits of a type more usually associated with left-sided brain dysfunction. The pathophysiological basis of these deficits is unclear, but they are not attributable to either limited education or pre-existing dyslexia. Further studies using a discriminating and comprehensive assessment of language in the right hemisphere are required.

Bb1-3, a transgenic hybrid cell line with erythroid and megakaryocytic differentiation potential that expresses high levels of human gamma-globin and human beta-globin

We have characterized a murine hybrid cell line, Bb1-3, generated by the fusion of mouse primary erythroblasts with MEL cells. It proliferated in serum-free medium and displayed a low level of spontaneous erythroid and megakaryocyte differentiation. Terminal erythroid differentiation could be induced with HMBA and DMSO and was enhanced by serum. Treatment with phorbol esters resulted in a high proportion of megakaryocytes and the expression of megakaryocytic specific lineage markers. Bb1-3 cells contain a human beta-globin transgene that was expressed at levels of 20-50% of the endogenous mouse globin genes. Initially, expression was largely limited to the beta-globin gene but after adaptation to serum free growth, equal expression of both the human gamma- and human beta-globin genes was observed. This cell line provides further evidence that the differentiation potential of mouse erythroleukaemia cells is not restricted to the erythroid lineage and should be useful to study the mechanisms underlying both developmental globin gene regulation and the terminal differentiation of bipotential erythroid/megakaryocytic progenitor cells.

Sequence, catalytic properties and expression of chicken glutathione-dependent prostaglandin D2 synthase, a novel class Sigma glutathione S-transferase

The Expressed Sequence Tag database has been screened for cDNA clones encoding prostaglandin D2 synthases (PGDSs) by using a BLAST search with the N-terminal amino acid sequence of rat GSH-dependent PGDS, a class Sigma glutathione S-transferase (GST). This resulted in the identification of a cDNA from chicken spleen containing an insert of approx. 950 bp that encodes a protein of 199 amino acid residues with a predicted molecular mass of 22732 Da. The deduced primary structure of the chicken protein was not only found to possess 70% sequence identity with rat PGDS but it also demonstrated more than 35% identity with class Sigma GSTs from a range of invertebrates. The open reading frame of the chicken cDNA was expressed in Escherichia coli and the purified protein was found to display high PGDS activity. It also catalysed the conjugation of glutathione with a wide range of aryl halides, organic isothiocyanates and alpha,beta-unsaturated carbonyls, and exhibited glutathione peroxidase activity towards cumene hydroperoxide. Like other GSTs, chicken PGDS was found to be inhibited by non-substrate ligands such as Cibacron Blue, haematin and organotin compounds. Western blotting experiments showed that among the organs studied, the expression of PGDS in the female chicken is highest in liver, kidney and intestine, with only small amounts of the enzyme being found in chicken spleen; in contrast, the rat has highest levels of PGDS in the spleen. Collectively, these results show that the structure and function, but not the expression, of the GSH-requiring PGDS is conserved between chicken and rat.

Postsynaptic pyramidal target selection by descending layer III pyramidal axons: dual intracellular recordings and biocytin filling in slices of rat neocortex

Paired intracellular recordings in slices of adult rat neocortex with biocytin filling of synaptically connected neurons were used to investigate the pyramidal targets, in layer V, of layer III pyramidal axons. The time-course and sensitivity of excitatory postsynaptic potentials to current injected at the soma, and locations of close appositions between presynaptic axons and postsynaptic dendrites, indicated that the majority of contributory synapses were located in layer V. Within a "column" of tissue, radius < or = 250 microm, the probability that a randomly selected layer III pyramid innervated a layer V pyramid was 1 in 4 if the target cell was a burst firing pyramid with an apical dendritic tuft in layers II/I. If, however, the potential target was a regular spiking pyramid, the probability of connectivity was only 1 in 40, and none of the 13 anatomically identified postsynaptic layer V targets had a slender apical dendrite terminating in layers IV/III. Morphological reconstructions indicated that layer III pyramids select target layer V cells whose apical dendrites pass within 50-100 microm of the soma of the presynaptic pyramid in layer III and which have overlapping apical dendritic tufts in the superficial layers. The probability that a layer V cell would innervate a layer III pyramid lying within 250 microm of its apical dendrite was much lower (one in 58). Both presynaptic layer III pyramids and their large postsynaptic layer V targets could therefore access similar inputs in layers I/II, while small layer V pyramids could not. One prediction from the present data would be that neither descending layer V inputs to the striatum or thalamus, nor transcallosal connections would be readily activated by longer distance cortico-cortical "feedback" connections that terminated in layers I/II. These could, however, activate corticofugal pathways to the superior colliculus or pons, both directly and via layer III.

The utility of the Right Hemisphere Language Battery in patients with brain tumours

The Right Hemisphere Language Battery (RHLB) (Bryan, 1989) was devised to assess the presence of language disorders in patients with damage to the right cerebral hemisphere and to permit an evaluation of the efficacy of therapeutic techniques. To evaluate the utility and sensitivity of the RHLB in patients with solitary right hemispheric brain tumours 20 patients were assessed before and after neurosurgery. Twenty control subjects with no signs or symptoms of brain disease who were undergoing lumbar spinal surgery were also assessed. On six of the seven RHLB subtests there was no significant difference between the scores obtained preoperatively by patients with right hemispheric brain tumours and the control subjects. There was also no significant change in the scores of the patients with tumours before and after resection of the lesion. The RHLB is therefore not recommended for either evaluating communication deficits or for measuring the efficacy of therapeutic techniques in patients with right hemisphere brain tumours. This study does, however, show that there are statistically significant differences between the control and brain tumour groups on the discourse analysis subtest preoperatively. The implications of the study are discussed together with possible reasons for the findings.

CA1 pyramidal to basket and bistratified cell EPSPs: dual intracellular recordings in rat hippocampal slices

1. Dual intracellular recordings in the CA1 region of adult rat hippocampal slices and biocytin filling of synaptically connected cells were used to study the excitatory postsynaptic potentials (EPSPs) elicited in basket (n = 7) and bistratified interneurones (n = 7) by action potentials activated in simultaneously recorded pyramidal cells. 2. Interneurones could be subdivided according to their electrophysiological properties into classical fast spiking, burst firing, regular spiking and fast spiking cells with a rounded spike after-hyperpolarization. These physiological classes did not, however, correlate with morphological type. EPSPs were not recorded in regular spiking cells. 3. Average EPSP amplitudes were larger in bistratified cells (range, 0.5-9 mV) than in basket cells (range, 0. 15-3.6 mV) and the probability of obtaining a pyramidal cell-interneurone EPSP was also higher for the bistratified cells (1:7) than for the basket cells (1:22). EPSP 10-90 % rise times in bistratified cells (0.7-2 ms) and their widths at half-amplitude (3. 9-11.2 ms) were slightly longer than in basket cells (rise times, 0.4-1.6 ms; half-widths, 2.2-9.7 ms). 4. The majority of these EPSPs (6 of 8 tested) increased in amplitude and duration with postsynaptic depolarization, although in two (of 4) basket cells the voltage relation was conventional. 5. All EPSPs tested in both basket (n = 7) and bistratified cells (n = 5) decreased in amplitude with repetitive presynaptic firing. The average amplitudes of second EPSPs elicited within 15 ms of the first were between 34 and 94 % of the average amplitude of the first EPSP. Third and fourth EPSPs in brief trains were further depressed. This depression was associated with an increase in the incidence of apparent failures of transmission indicating a presynaptic locus.

Facilitating pyramid to horizontal oriens-alveus interneurone inputs: dual intracellular recordings in slices of rat hippocampus

1. In adult rat hippocampal slices, simultaneous intracellular recordings from pyramidal cells in CA1 and interneurones near the stratum oriens-alveus border revealed excitatory connections that displayed facilitation on repetitive activation in twelve of thirty-six pairs tested. 2. Postsynaptic interneurones were classified as horizontal oriens-alveus interneurones by the pronounced 'sag' in response to hyperpolarizing current injection, high levels of spontaneous synaptic activity and by the morphology of their somata and dendrites, which were confined to stratum oriens-alveus and their axons which projected to stratum lacunosum-moleculare where they ramified extensively, in the region of entorhinal cortex input to CA1. 3. Excitatory postsynaptic potentials (EPSPs) elicited by single pyramidal cells were 0 to 12 mV in amplitude. Mean EPSP amplitude (single spikes) was 0.93 +/- 1. 06 mV at -70 +/- 2.3 mV (n = 10). The rise time was 1.2 +/- 0.5 ms and the width at half-amplitude was 7.5 +/- 4.7 ms. 4. EPSPs fluctuated greatly in amplitude; the mean coefficient of variation was 0.84 +/- 0.37 for the first EPSP and 0.47 +/- 0.24 for the second. Apparent failures of transmission frequently occurred after first presynaptic spikes but less frequently after the second or subsequent spikes in brief trains. 5. EPSPs displayed facilitation at membrane potentials between -80 mV and spike threshold. Second EPSPs within 20 ms of the first were 253 +/- 48 % (range, 152-324 %) of the mean first EPSP amplitude. Third EPSPs within 60 ms were 266 +/- 70 % (range, 169-389 %) and fourth EPSPs within 60-120 ms were 288 +/- 71 % (range, 188-393 %). Both proportions of apparent failures of transmission and coefficient of variation analysis indicated a presynaptic locus for this facilitation.

Quantal analysis of synaptic processes in the neocortex

The application of fluctuation analysis to studies of synaptic function in the neocortex is discussed. Analysis of failures of transmission has been valuable in indicating whether a presynaptic or a postsynaptic site is responsible for a change in synaptic efficacy. When combined with detailed ultrastructural verification of all synapses involved in an individual cell to cell connection, a reasonable estimate of quantal size and release probability under conditions of low frequency activity can be obtained. However, both the number of available release sites in functional terms and the probability that an action potential (AP) will release transmitter from any given site can vary from AP to AP at higher frequencies. A variety of presynaptic mechanisms that modulate release are now apparent. For example, one mechanism dominates release patterns at one class of connection which is insensitive to absolute firing frequency, but responsive to changes in frequency. At another class of connection, a different mechanism dominates, resulting in high sensitivity to frequency.

A survey of community placements for educational programmes in nursing and midwifery

In this paper preliminary findings from the first stage of an English National Board (ENB) commissioned study investigating the educational needs of community practitioners in relation to their responsibilities for student learning are presented. A national postal survey of all educational centres offering nurse and/or midwifery education was undertaken in the latter half of 1993. Information was collected regarding the nature and planning of the community practice components of courses. The main methods of support for practitioners included the provision of the ENB 998/997 courses and liaison meetings between educational centres and community practice areas. Practitioners were often required to both supervise and assess students on practice placements, the length of these placements varying enormously. For those centres offering the mental health and learning disability branches of the Diploma in Higher Education in Nursing Studies (Project 2000), a significant proportion lacked teachers with specialist community qualifications. The investigation took place at a time of great upheaval, with 42% of centres reporting that they were in the process of amalgamation. The findings demonstrate that community nurses and midwives undoubtedly contribute to the education of nurse and midwife students and consequently have educational needs which must be addressed if they are to continue to supervise students.

Synaptic interactions in neocortical local circuits: dual intracellular recordings in vitro

Properties of local synaptic connections in neocortex, studied with dual intracellular recordings in vitro and correlated with cell and synaptic morphology are summarized. The different durations and sensitivities to somatic membrane potential of pyramid-pyramid excitatory postsynaptic potentials (EPSPs) apparently reflect the positions of the synapses on the postsynaptic dendrites. Their time-, frequency- and voltage-dependent properties enable supra-linear summation of several low-frequency inputs arising in the same dendritic region, even if only loosely coincident, but they depress during repetitive firing in any one input. Pyramidal input to classical fast spiking and low threshold spiking interneurones are strikingly different. Here low presynaptic firing rates results in many transmission failures. EPSPs are brief and inputs must be near coincident for summation. However, these synapses display pronounced. frequency-dependent, incrementing facilitation at higher presynaptic frequencies. Once initiated by a brief high-frequency burst, this facilitation is maintained at lower frequencies. GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) arising proximally are of very different durations depending on the type of interneurone activated and can prevent and subsequently synchronize firing in their many postsynaptic partners with very different delays (eg. 10-100 ms). Low threshold spiking interneurones, in contrast, generate brief IPSPs only in more distal dendritic regions and have little effect on somatic excitability acting to shunt input distally.

Activity-dependent properties of synaptic transmission at two classes of connections made by rat neocortical pyramidal axons in vitro

1. To compare the dynamics of synaptic transmission at different types of connection, dual intracellular recordings were made from pairs of neurones in slices of adult rat neocortex. Excitatory postsynaptic potentials (EPSPs) were elicited by single spikes, spike pairs and brief spike trains in presynaptic pyramidal cells and responses recorded in postsynaptic pyramidal cells and in interneurones. 2. Pyramid-pyramid EPSPs were strongly voltage dependent and this resulted in a range of paired pulse effects. At thirty-two of sixty-nine pyramid-pyramid connections, the 2nd EPSP was the same shape as the 1st, indicating minimal interaction between active synapses. In these thirty-two connections, paired pulse depression (PPD) was apparent (2nd EPSP integral 46 +/- 21% of the 1st, at 5-20 ms), which recovered within 60-70 ms. 3. In eleven additional pyramid-pyramid pairs, the 2nd EPSP was also the same shape as the 1st, but paired pulse facilitation (PPF, 149 +/- 32%) decaying within 50-60 ms was apparent. Even these connections displayed frequency-dependent depression, however, as 3rd EPSPs were smaller than 1st EPSPs at intervals < 100 ms. 4. At twenty-five pyramid-pyramid connections, 2nd EPSPs were broader than 1st EPSPs and in sixteen of these, voltage- and NMDA receptor-dependent enhancement was large enough to obscure the underlying PPD. PPD was revealed by postsynaptic hyperpolarization (4 pairs), N-methyl-D-aspartate (NMDA) receptor blockade (3 paris), or if Mg2+ was removed (in the one case studied). If synapse location allowed significant depolarization of one active site by another, voltage-dependent enhancement could produce supralinear EPSP summation and overcome PPD. Third EPSPs were, however, consistently smaller than 1st EPSPs. 5. In striking contrast, profound frequency-dependent facilitation, independent of voltage or NMDA receptors was seen at fifteen connections involving two classes of postsynaptic interneurones. 6. At these pyramid-interneurone connections, facilitation of the 2nd EPSP (655 +/- 380% at 5-20 ms) decayed rapidly, within 50-60 ms. Third and fourth EPSPs showed additional facilitation which decayed more slowly, within 90 ms and 2 s, respectively. Facilitation due to five to six spike trains was still apparent at 3 s. Therefore, once initiated by a brief high frequency spike train, facilitation was maintained at lower frequencies.

Community midwives' and general practitioners' perspectives, of antenatal care in the community

OBJECTIVE

to ascertain who was providing antenatal care in the community in a defined geographical area in the north of England, and whether the care could achieve the government objectives presented in Changing Childbirth (DoH 1993).

DESIGN

a questionnaire was used to obtain demographic information and semi-structured interviews were held with care providers in order to assess the perspective of those providing care.

PARTICIPANTS

a purposive sample of nine community midwives and six general practitioners (GPs).

FINDINGS

the midwife was the professional undertaking most of the antenatal care although in most instances there was a GP available on site if required. GPs saw the midwife as the main provider of care with themselves as 'back up'. Conflict over responsibility for care was an issue in some instances. Whilst changes in antenatal care provision had been, or were about to be made, only one midwife expressed a clear positive feeling towards midwife-led care. Giving women the opportunity for choice provoked an overwhelming feeling of helplessness for midwives. Midwives and GPs believed their education adequately prepared them to provide antenatal care in the community, however, GPs did not attend regular updating sessions.

IMPLICATIONS FOR PRACTICE

whilst it was recognised that midwives are taking increasing responsibility for antenatal care, GPs still believe that overall responsibility lies with them; therefore, there is a need to clarify roles. The majority of midwives expressed reservations about midwife-led care.

Stereotactic biopsy of nonpolar tumors in the dominant hemisphere: a prospective study of effects on language functions

A prospective study of patients undergoing computerized tomography (CT)-guided stereotactic biopsy of nonpolar tumors in the dominant hemisphere was undertaken to determine if stereotactic biopsy caused a deterioration of language functions. Language was assessed using the Western Aphasia Battery (WAB) and the Boston Naming Test (BNT) before and after a biopsy sample was obtained. Of 16 patients studied, five (31%) were dysphasic preoperatively. After the biopsy the Aphasia Quotient (AQ), derived from the WAB, had significantly deteriorated in four (80%) of these patients, whereas in the fifth it remained relatively unchanged. One of these patients with an extensive infiltrating hemispheric oligoastrocytoma subsequently recovered normal language function after radiotherapy. In 10 of the 11 patients who had normal language function preoperatively there were no deleterious changes after biopsy in either the WAB subtest or BNT scores. In the other patient whose WAB score was normal preoperatively, there was a significant deterioration in postoperative AQ. This patient, who declined steroid therapy before and after biopsy, had a glioblastoma multiforme in Wernicke's area. A postoperative CT scan revealed no changes from what was shown on preoperative scan. This clinical study shows that CT-guided stereotactic biopsy of nonpolar tumors in the dominant hemisphere using the Brown-Roberts-Wells system and the Sedan-Nashold biopsy cannula carries a 9% risk (95% confidence intervals 0-26%) of impairing language functions if the patient is not dysphasic preoperatively. If the patient is dysphasic preoperatively, there is a very high risk of aggravating the dysphasia with stereotactic biopsy.

Neuroscience. More than just frequency detectors?

Connection from neuron to neuron in the cortex of the brain becomes less effective with each successive action potential but eventually recovers after the end of the action potential burst. Two new reports, one in this issue ( p. 220 ), present many-neuron models with these properties and show that these neurons respond to large changes in the frequency of individual inputs (they act as frequency detectors) or to simultaneous changes in many inputs (they act as coincidence detectors). In her Perspective, Thomson explains the origin of the modeled properties and discusses the accuracy with which these models mimic the behavior of real cortical cells. Such modeling of many neurons with real properties reveals computational characteristics of the circuit not apparent from analyses of individual cells.