Susan W. Robinson

Psychiatric morbidity after screening for breast cancer.

One hundred and thirty two women with normal breast screening results were interviewed six months after their attendance at the Edinburgh Breast Screening Clinic. Eight percent of women said screening had made them more anxious about developing breast cancer. Thirty eight percent said they were more aware of the disease since screening but they regarded this as advantageous. Seventy percent of the women were still practising breast self-examination. There was no difference in the psychiatric morbidity of the screened sample when compared with a matched random sample community control group. Neither was there any difference in the General Health Questionnaire case rates before and after screening. Screening does not appear to increase the prevalence of psychiatric morbidity. Twenty nine percent of the interview sample were examining their breasts more than once a month--21% once a week or more. However, these frequent self-examiners did not have a greater prevalence of psychiatric morbidity than their matched controls.

A Brassica napus mRNA encoding a protein homologous to phospholipid transfer proteins, is expressed specifically in the tapetum and developing microspores

The E2 cDNA was isolated by differential screening of a Brassica napus library made from anthers of 1.8–4 mm in length. Northern gel and RNA dot blot analysis revealed that the E2 cDNA hybridised to a 0.7-kb mRNA transcript in RNA extracted from anthers and extruded immature microspores. High expression is limited to the microspore development phase. In situ hybridisation indicated that E2 transcript is also expressed within the tapetal cells. The sequence of 658 nucleotides was determined from clone E2B containing one major open reading frame, encoding a putative protein of Mr 12.5 kDa. This protein is cysteine rich, encodes a potential signal sequence and shows high homology with plant phospholipid transfer proteins.

Nitric oxide is an activity-dependent regulator of target neuron intrinsic excitability.

Summary Activity-dependent changes in synaptic strength are well established as mediating long-term plasticity underlying learning and memory, but modulation of target neuron excitability could complement changes in synaptic strength and regulate network activity. It is thought that homeostatic mechanisms match intrinsic excitability to the incoming synaptic drive, but evidence for involvement of voltage-gated conductances is sparse. Here, we show that glutamatergic synaptic activity modulates target neuron excitability and switches the basis of action potential repolarization from Kv3 to Kv2 potassium channel dominance, thereby adjusting neuronal signaling between low and high activity states, respectively. This nitric oxide-mediated signaling dramatically increases Kv2 currents in both the auditory brain stem and hippocampus (>3-fold) transforming synaptic integration and information transmission but with only modest changes in action potential waveform. We conclude that nitric oxide is a homeostatic regulator, tuning neuronal excitability to the recent history of excitatory synaptic inputs over intervals of minutes to hours.

NMDAR‐mediated EPSCs are maintained and accelerate in time course during maturation of mouse and rat auditory brainstem in vitro

NMDA receptors (NMDARs) mediate a slow EPSC at excitatory glutamatergic synapses throughout the brain. In many areas the magnitude of the NMDAR‐mediated EPSC declines with development and is associated with changes in subunit composition, but the mature channel composition is often unknown. We have employed the calyx of Held terminal with its target, the principal neuron of the medial nucleus of the trapezoid body (MNTB), to examine the NMDAR‐mediated EPSC during synapse maturation from P10 to P40. Our data show that the calyx has reached a mature state by around P18. The NMDAR‐mediated EPSC amplitude (and dominant decay τ) fell from around 5 nA (τ: 40–50 ms) at P10/11 to 0.3–0.5 nA (τ: 10–15 ms) by P18. The mature NMDAR‐EPSC showed no sensitivity to ifenprodil, indicating lack of NR2B subunits, and no block by submicromolar concentrations of zinc, consistent with NR1‐1b subunit expression. Additionally, from P11 to P18 there was a reduction in voltage‐dependent block and the apparent dissociation constant for [Mg2+]o (Ko) changed from 7.5 to 14 mm. Quantitative PCR showed that the relative expression of NR2A and NR2C increased, while immunohistochemistry confirmed the presence of NR2A, NR2B and NR2C protein. Although the mature NMDAR‐EPSC is small, it is well coupled to NO signalling, as indicated by DAR‐4M imaging. We conclude that native mature NMDAR channels at the calyx of Held have a fast time course and reduced block by [Mg2+]o, consistent with dominance of NR2C subunits and functional exclusion of NR2B subunits. The pharmacology suggests a single channel type and we postulate that the mature NMDARs consist of heterotrimers of NR1‐1b–NR2A–NR2C.

Genetic variation of basal iron status, ferritin and iron regulatory protein in mice: potential for modulation of oxidative stress.

Toxic and carcinogenic free radical processes induced by drugs and other chemicals are probably modulated by the participation of available iron. To see whether endogenous iron was genetically variable in normal mice, the common strains C57BL/10ScSn, C57BL/6J, BALB/c, DBA/2, and SWR were examined for major differences in their hepatic non-heme iron contents. Levels in SWR mice were 3- to 5-fold higher than in the two C57BL strains, with intermediate levels in DBA/2 and BALB/c mice. Concentrations in kidney, lung, and especially spleen of SWR mice were also greater than those in C57BL mice. Non-denaturing PAGE of hepatic ferritin from all strains showed a major holoferritin band at approximately 600 kDa, with SWR mice having > 3-fold higher levels than C57BL strains. SDS PAGE showed a band of 22 kDa, mainly representing L-ferritin subunits. A trace of a subunit at 18 kDa was also detected in ferritin from SWR mice. The 18 kDa subunit and a 500 kDa holoferritin from which it originates were observed in all strains after parenteral iron overload, and there was no major variation in ferritin patterns. Although iron uptake studies showed no evidence for differential duodenal absorption between strains to explain the variation in basal iron levels, acquisition of absorbed iron by the liver was significantly higher in SWR mice than C57BL/6J. As with iron and ferritin contents, total iron regulatory protein (IRP-1) binding capacity for mRNA iron responsive element (IRE) and actual IRE/IRP binding in the liver were significantly greater in SWR than C57BL/6J mice. Cytosolic aconitase activity, representing unbound IRP-1, tended to be lower in the former strain. SWR mice were more susceptible than C57BL/10ScSn mice to the toxic action of diquat, which is thought to involve iron catalysis. If extrapolated to humans, the findings could suggest that some people might have the propensity for greater basal hepatic iron stores than others, which might make them more susceptible to iron-catalysed toxicity caused by oxidants.

Regulation of Kv channel expression and neuronal excitability in rat medial nucleus of the trapezoid body maintained in organotypic culture.

Principal neurons of the medial nucleus of the trapezoid body (MNTB) express a spectrum of voltage‐dependent K+ conductances mediated by Kv1–Kv4 channels, which shape action potential (AP) firing and regulate intrinsic excitability. Postsynaptic factors influencing expression of Kv channels were explored using organotypic cultures of brainstem prepared from P9–P12 rats and maintained in either low (5 mm, low‐K) or high (25 mm, high‐K) [K+]o medium. Whole cell patch‐clamp recordings were made after 7–28 days in vitro. MNTB neurons cultured in high‐K medium maintained a single AP firing phenotype, while low‐K cultures had smaller K+ currents, enhanced excitability and fired multiple APs. The calyx of Held inputs degenerated within 3 days in culture, having lost their major afferent input; this preparation of calyx‐free MNTB neurons allowed the effects of postsynaptic depolarisation to be studied with minimal synaptic activity. The depolarization caused by the high‐K aCSF only transiently increased spontaneous AP firing (<2 min) and did not measurably increase synaptic activity. Chronic depolarization in high‐K cultures raised basal levels of [Ca2+]i, increased Kv3 currents and shortened AP half‐widths. These events relied on raised [Ca2+]i, mediated by influx through voltage‐gated calcium channels (VGCCs) and release from intracellular stores, causing an increase in cAMP‐response element binding protein (CREB) phosphorylation. Block of VGCCs or of CREB function suppressed Kv3 currents, increased AP duration, and reduced Kv3.3 and c‐fos expression. Real‐time PCR revealed higher Kv3.3 and Kv1.1 mRNA in high‐K compared to low‐K cultures, although the increased Kv1.1 mRNA was mediated by a CREB‐independent mechanism. We conclude that Kv channel expression and hence the intrinsic membrane properties of MNTB neurons are homeostatically regulated by [Ca2+]i‐dependent mechanisms and influenced by sustained depolarization of the resting membrane potential.

Teachers' Assessments of Primary Children's Classroom Work in the Creative Arts.

Summary The primary aims of this study were to derive a taxonomy of the constructs used by primary teachers in assessing childrens work in visual art, music and creative writing, and to investigate the extent to which these constructs can be used consistently by different teachers. They were operationalized in the form of a series of rating scales derived from repertory grid type analyses of teachers’ descriptions of arts activities and artistic products. In two pilot studies and a main study, which included two in‐service day conferences, teachers from 17 primary schools evaluated childrens products from activities which were operationally defined as either structured or unstructured in each of the three artforms. Statistical analysis of the ratings revealed three clear findings, namely (1) that there was a high level of intercorrelation between individual teachers’ ratings of different pieces of work across all scales, (2) that there was a high level of intercorrelation between the different rating sc...

Essential Role of the AH Receptor in the Dysfunction of Heme Metabolism Induced by 2,3,7,8-Tetrachlorodibenzo-p-dioxin

The dysfunction of hepatic heme synthesis by 2,3,7,8-tetrachlordibenzo- p-dioxin (TCDD) in mice, enhanced by iron, leads to accumulation of uroporphyrins I and III (uroporphyria) and resembles the human disorder porphyria cutanea tarda (PCT) precipitated by alcohol and estrogenic drugs. Although consequences of TCDD are considered entirely dependent on the aryl hydrocarbon receptor (AHR), this is not proven for uroporphyria. Administration of TCDD (75 microg/kg) caused uroporphyria in susceptible C57BL/6J mice with high-affinity AHR after 5 weeks (>600-fold increase in hepatic uroporphyrins). Transcriptomics showed significant modified gene expressions for intermediary, heme, and iron metabolism as well as for oxidative stress and cell injury. Resistant low-affinity AHR DBA/2 mice (no increase in porphyrins) showed far fewer changes. At this dose of TCDD, persistent up-regulation of some traditional AH battery genes occurred in both strains. Essentiality of AHR was demonstrated with C57BL/6 Ahr knockout mice. Elevation of hepatic uroporphyrins was 964-fold in Ahr (+/+) mice, lower in Ahr (+/-) (60-fold), but undetectable with Ahr (-/-) . Consistent with an oxidative mechanism, iron overload enhanced porphyria as well as general liver injury in Ahr (+/+) and Ahr (+/-) mice but had no interactive effect in Ahr (-/-) . In contrast, when iron-treated mice received, instead of TCDD, the heme precursor 5-aminolevulinic acid (ALA), causing uroporphyia in Ahr (+/+) mice (242-fold rise in uroporphyrins), elevation of uroporphyrins I and III (42-fold) also occurred in Ahr (-/-) mice and was seemingly associated with AHR-independent expression of Cyp1a2. The findings prove that AHR is a key factor in porphyria induced in mice by TCDD. However, in other models of human PCT, participation of AHR may not be an essential requirement.

Protection from Noise-Induced Hearing Loss by Kv2.2 Potassium Currents in the Central Medial Olivocochlear System

The central auditory brainstem provides an efferent projection known as the medial olivocochlear (MOC) system, which regulates the cochlear amplifier and mediates protection on exposure to loud sound. It arises from neurons of the ventral nucleus of the trapezoid body (VNTB), so control of neuronal excitability in this pathway has profound effects on hearing. The VNTB and the medial nucleus of the trapezoid body are the only sites of expression for the Kv2.2 voltage-gated potassium channel in the auditory brainstem, consistent with a specialized function of these channels. In the absence of unambiguous antagonists, we used recombinant and transgenic methods to examine how Kv2.2 contributes to MOC efferent function. Viral gene transfer of dominant-negative Kv2.2 in wild-type mice suppressed outward K+ currents, increasing action potential (AP) half-width and reducing repetitive firing. Similarly, VNTB neurons from Kv2.2 knock-out mice (Kv2.2KO) also showed increased AP duration. Control experiments established that Kv2.2 was not expressed in the cochlea, so any changes in auditory function in the Kv2.2KO mouse must be of central origin. Further, in vivo recordings of auditory brainstem responses revealed that these Kv2.2KO mice were more susceptible to noise-induced hearing loss. We conclude that Kv2.2 regulates neuronal excitability in these brainstem nuclei by maintaining short APs and enhancing high-frequency firing. This safeguards efferent MOC firing during high-intensity sounds and is crucial in the mediation of protection after auditory overexposure.

Decreased expression of the adenomatous polyposis coli (Apc) and mutated in colorectal cancer (Mcc) genes in mouse lung neoplasia

A decrease in the intracellular concentrations of the transcripts for some tumor suppressor genes has been found during murine lung tumorigenesis; for p15INK4b and p16INK4a, this was due to homozygous deletions. We report here a decrease in the mRNA levels of the mutated in colorectal cancer (Mcc) and adenomatous polyposis coli (Apc) genes in mouse lung tumors and some neoplastic cell lines. This was assessed both by northern blotting and reverse transcriptase–polymerase chain reaction of RNA isolated from lung tumors that had been induced by urethane, N‐nitrosodiethylamine, or 3‐methylcholanthrene in (A/J × C57BL/6) F1 or A/J mice. A reduced amount of both Mcc and Apc messages was also seen when two neoplastic cell lines, a spontaneous transformant (E9) and a line derived from a chemically induced solid tumor (82‐132), were compared with two independently derived nontumorigenic cell lines (E10 and C10); E9 was derived from E10, and all of these lines are probably of alveolar type 2 cell origin. A cell line derived from a chemically induced papillary lung tumor probably of bronchiolar Clara cell origin (LM2) had Mcc mRNA levels similar to those of C10 and E10 but reduced Apc mRNA levels. A line (p53‐823) derived from a papillary tumor that arose in a mouse with a mutated p53 transgene had a reduced amount of the Mcc gene product only. These differential changes in the relative amounts of Apc and Mcc messages in LM2 and p53‐823 cells may serve as useful models for studying the regulation of their expression. Both messages had half‐lives of 6–9 h in normal E10 and neoplastic E9 cells, so decreased message stability does not account for these reductions. This is the first report of estimated degradation rates of these mRNAs. Apc and Mcc message content did not vary as a function of growth status of the cell lines. Single‐strand conformation polymorphism analysis did not reveal mutations in Apc coding regions known to have a high mutation frequency in human colon tumors. Loss of heterozygosity of Apc and Mcc was not found in tumors that developed in the F1 mice, implying a lack of allelic deletions. These changes in tumor suppressor gene expression may contribute to the development and maintenance of neoplasia in lung epithelium. Mol. Carcinog. 21:37–49, 1998.