Characterisation of a sub-20 ps temporal resolution pulse dilation photomultiplier tube

A pulse-dilation photomultiplier tube (PD-PMT) with sub-20 ps temporal resolution has been developed for use with γ-ray-sensitive gas Cherenkov detectors at the National Ignition Facility to improve the diagnosis of nuclear fusion burn history and the areal density of the remaining capsule ablator. The pulse-dilation mechanism entails the application of a time-dependent, ramp waveform to a photocathode-mesh structure, introducing a time-dependent photoelectron accelerating potential. The electric field imparts axial velocity dispersion to outgoing photoelectrons. The photoelectron pulse is dilated as it transits a drift region prior to amplification in a microchannel plate and read out with a digital oscilloscope. We report the first measurements with the prototype PD-PMT demonstrating nominal <20 ps FWHM across a 400 ps measurement window and <30 ps FWHM for an extracted charge up to 300 pC. The output peak areas are linear to within 20% over 3 orders of magnitude of input intensity. 3D particle in cell simulations, which included space charge effects, have been carried out to investigate the device temporal magnification, resolution, and linearity.

Impact of (18)F-FDG PET/CT on the staging and management of follicular lymphoma

Follicular lymphoma (FL) is the most common indolent lymphoma. Despite the evidence-based utilization of fluorine-18 fludeoxyglucose positron emission tomography ((18)F-FDG PET)/CT in aggressive lymphomas, the utility of PET in FL remains controversial and varies across different jurisdictions. The management of patients with FL differs from aggressive lymphomas and is usually reserved for patients with localized disease in whom long-term control may potentially be achieved by involved field radiotherapy, or for symptomatic patients with advanced-stage disease in whom systemic therapy is indicated. There is a growing body of literature supporting the use of PET/CT in initial staging of FL to guide management decisions. In this review, we summarize the existing literature and present cases from our experience to illustrate current knowledge on the potential role of (18)F-FDG PET/CT in FL.

Non-cutaneous melanoma: is there a role for (18)F-FDG PET-CT?

Non-cutaneous melanomas (NCM) are diverse and relatively uncommon. They often differ from cutaneous melanomas in their epidemiology, genetic profile and biological behaviour. Despite the growing body of evidence regarding the utility of positron emission tomography (PET)/CT in cutaneous melanoma, the data on its use in NCM are scarce. In this review, we will summarize the existing literature and present cases from our experience with NCM to illustrate current knowledge on the potential role and limitations of fluorine-18 fludeoxyglucose PET/CT in NCM.

Latent class analysis of co-morbidity in the Adult Psychiatric Morbidity Survey in England 2007: implications for DSM-5 and ICD-11

BACKGROUND

Psychiatric co-morbidity is complex and ubiquitous. Our aim was to describe the extent, nature and patterning of psychiatric co-morbidity within a representative sample of the adult population of England, using latent class analysis.

METHOD

Data were used from the 2007 Adult Psychiatric Morbidity Survey, a two-phase national household survey undertaken in 2007 comprising 7325 participants aged 16 years and older living in private households in England. The presence of 15 common mental health and behavioural problems was ascertained using standardized clinical and validated self-report measures, including three anxiety disorders, depressive episode, mixed anxiety depressive disorder, psychosis, antisocial and borderline personality disorders, eating disorders, post-traumatic stress disorder, attention deficit disorder, alcohol and drug dependencies, problem gambling and attempted suicide.

RESULTS

A four-class model provided the most parsimonious and informative explanation of the data. Most participants (81.6%) were assigned to a non-symptomatic or 'Unaffected' class. The remainder were classified into three qualitatively different symptomatic classes: 'Co-thymia' (12.4%), 'Highly Co-morbid' (5.0%) and 'Addictions' (1.0%). Classes differed in mean numbers of conditions and impairments in social functioning, and these dimensions were correlated.

CONCLUSIONS

Our findings confirm that mental disorders typically co-occur and are concentrated in a relatively small number of individuals. Conditions associated with the highest levels of disability, mortality and cost--psychosis, suicidality and personality disorders--are often co-morbid with more common conditions. This needs to be recognized when planning services and when considering aetiology.

Thermal and Visual Observation of Water and Acetone Oscillating Heat Pipes

A visual and thermal experimental investigation of four oscillating heat pipes (OHPs) was conducted to observe fluid flow of liquid plugs and vapor bubbles in the OHP and its effect on the temperature distribution and heat transfer performance in an OHP. These four OHPs consist of an open loop water OHP, an open loop acetone OHP, a closed loop water OHP, and a closed loop acetone OHP. These copper OHPs were constructed identically with all six turns in the same plane. They were constructed out of 1.65 mm inner diameter copper tubing and copper heat spreading plates in the evaporator and condenser regions. The heat pipes were charged at a filling ratio of about 50%. The results show that the acetone OHP at low power performs better than the water OHP, while at high power the water OHP exceeds the acetone OHP. The experimental results show that both the acetone and water closed loop OHPs had reduced movement in the connecting turn between the two sides. However, in the water closed loop OHP, this prevented circulation altogether. Comparing the water closed loop OHP to the water open loop OHP, their flow patterns were similar. Therefore, improving the flow in this turn should increase the closed loop OHP's performance.

Do associations between staff and inpatient feedback have the potential for improving patient experience? An analysis of surveys in NHS acute trusts in England

OBJECTIVE

To examine whether staff feedback on quality, safety and workforce issues is reflected in patient-reported experience.

SETTING

166 NHS acute trusts in England.

PARTICIPANTS

Respondents to the 2006 surveys of adult inpatients and staff in 166 NHS acute trusts in England.

METHODS

Multiple linear regression was used to model the relationship between responses by "frontline" staff and inpatients at trust level. Staff survey items were the explanatory variables and inpatient responses the dependent variables. Adjustments were made for location (London and non-London) and trust type.

RESULTS

69 500 staff and 81 000 patients responded to the surveys. There were several significant associations between staff and patients' responses, including that staff availability of hand-washing materials was positively associated with patient feedback on cleanliness and hand washing by doctors/nurses (p<0.00). It was a significant predictor of patient experience also in several other models. Other significant predictors of patient experience were managerial support, witnessing and reporting of errors (positively associated with patient experience), working extra hours and stress (negatively associated). London trusts performed worse on patient experience than trusts outside London and specialist trusts performed better than other acute trusts.

CONCLUSIONS

Staff feedback was associated with patient-reported experience. Positive staff feedback on availability of hand-washing materials was broadly reflective of positive patient experience. Negative staff experience was reflected in poorer patient experience and vice versa. Although we cannot demonstrate causality, the consistent direction of the findings is indicative of it. Management boards of trusts and clinicians and other staff should monitor and act on the results of their staff surveys. This has the potential for improving quality, safety and patient experience.

Heat Transport Capability and Fluid Flow Neutron Radiography of Three-Dimensional Oscillating Heat Pipes

An experimental investigation into the parameters affecting heat transport in two three-dimensional oscillating heat pipes (OHPs) was implemented. A three-dimensional OHP is one in which the center axis of the circular channels containing the internal working fluid do not lie in the same plane. This novel design allows for more turns in a more compact size. The OHPs in the current investigation is made of copper tubings (3.175 mm outside diameter, 1.65 mm inside diameter) wrapped in a three-dimensional fashion around two copper spreaders that act as the evaporator and condenser. The two OHPs have 10 and 20 turns in both the evaporator and condenser. The 20-turn OHP was filled to 50% of the total volume with a high performance liquid chromatography grade water. Transient and steady state temperature data were recorded at different locations for various parameters. Parameters such as heat input, operating temperature, and filling ratio were varied to determine its effect on the overall heat transport. Neutron radiography was simultaneously implemented to create images of the internal working fluid flow at a rate of 30 frames per second. Results show the average temperature drop from the evaporator to condenser decreases at higher heat inputs due to an increase in temperature throughout the condenser region due to greater oscillations. These large oscillations were visually observed using neutron radiography. As the operating temperature is increased, the thermal resistance is reduced. A decrease in filling ratio tends to create more steady fluid motion; however, the heat transfer performance is reduced.

Ethnic and social inequalities in women's experience of maternity care in England: results of a national survey

OBJECTIVE

To examine ethnic and social inequalities in women's experience of maternity care in England.

DESIGN

A 2007 national survey of women (16 years or over) about their experience of maternity care. Multiple logistic regression analysis, controlling for several maternal characteristics, was used to examine inequalities by ethnicity, partner status and education.

SETTING

Sample of records of 149 NHS acute trusts and two primary care trusts (PCTs) providing maternity services in England.

RESULTS

A total of 26,325 women responded to the survey (response rate 59%). Ethnic minority women were more likely than White British women to access services late, not have a scan by 20 weeks, and experience complications during pregnancy and birth. They were more likely to initiate breastfeeding and say they were treated with respect and dignity. Single women responded more negatively to almost all questions than women with a husband/partner. They were less likely to access care within 12 weeks of pregnancy (OR 0.45, 95% CI 0.39-0.52), have a scan at 20 weeks (OR 0.49, 95% CI 0.39-0.63), attend NHS antenatal classes (OR 0.56, 95% CI 0.49-0.65), have a postnatal check-up (OR 0.67, 95% CI 0.60-0.75), and initiate breastfeeding (OR 0.57, 95% CI 0.51-0.62), and were more likely to experience complications. Women completing education at 19+ years were more likely to access services early (OR 1.21, 95% CI 1.04-1.40), attend antenatal classes (OR 1.48, 95% CI 1.31-1.67), have a postnatal check-up (OR 1.19, 95% CI 1.07-1.32) and initiate breastfeeding (OR 3.88, 95% CI 3.56-4.22) than those completing education at 16 years or younger, and were less likely to experience complications.

CONCLUSIONS

Ethnic minority women, single mothers, and those with an earlier age at completing education access maternity services late, have poorer outcomes, and report poorer experiences across some--though not all--dimensions of maternity care. Ethnic differences were absent or inconsistent between groups for some aspects of care. We recommend these findings are used by commissioners, trusts and healthcare professionals to inform improvements in maternity services for high-risk groups and reduce inequalities.

Down's syndrome and hip arthropathy

We report a case of a 19 year old male with Down's syndrome who presented with severe functional disability and pain secondary to bilateral hip arthritis. He had longstanding developmental dysplasia of the hip (DDH) that had evolved into end stage arthritis. Following a comprehensive assessment and counselling, he underwent bilateral total hip replacements. At last follow up, he had excellent outcome for function and pain relief. This case highlights the good results achievable with aggressive management of musculo-skeletal conditions (especially hip arthropathy) in those with Down's syndrome and the need for increased recognition of these conditions.

The dimensional accuracy of four impression techniques with the use of addition silicone impression materials

OBJECTIVE

The aim of this study was to assess the influence of impression technique selection on the dimensional accuracy of the produced casts.

METHODOLOGY

Four impression techniques (single-stage, two-stage, monophase, and heavy/wash technique) were used to make addition silicone impressions of a phantom head maxillary jaw. The impression materials used were Aquasil, Extrude, and Imprint. Measurements on casts were made for the inter-abutment distances to assess dimensional accuracy.

RESULTS

There was a significant difference (p < 0.05) for the anteroposterior distances with the single-stage technique. The crossarch distances were slightly increased compared with the master model for all techniques, but significant statistical differences were only recorded for the single-stage technique and the monophase technique. The monophase technique demonstrated irregular results. The heavy/wash technique showed no significant differences for all the measurements compared with the standard model.

CONCLUSION

The results suggest that the selection of impression technique is an important factor that can affect the dimensional accuracy of the subsequent models which are used for indirect restorations.

Dopamine depletion results in increased neostriatal D(2), but not D(1), receptor binding in humans

The effect of endogenous dopamine (DA) on neostriatal DA D(1) and D(2) receptor binding potentials (D(1)RBP and D(2)RBP, respectively) in vivo was evaluated with positron emission tomography (PET) and the radiotracers [(11)C]SCH23390 and [(11)C]raclopride, respectively, by comparing the D(1)RBP and D(2)RBP before and after acute DA depletion. DA depletion was achieved by per-oral administration of 4500 mg alpha-methyl-para-tyrosine (AMPT) given in the 25 h prior to [(11)C]SCH23390 PET and of 5250 mg AMPT given in the 29 h prior to [(11)C]raclopride PET. Six healthy subjects completed the protocol. The AMPT treatment decreased plasma levels of the DA metabolite homovanillic acid by 61 +/- 16% (4500 mg; average +/- standard deviation) and 62 +/- 17% (5250 mg), and levels of the norepinephrine metabolite 3-methoxy-4-hydroxyphenethyleneglycol by 58 +/- 7% (4500 mg) and 66 +/- 5% (5250 mg). This AMPT treatment increased D(2)RBP significantly from 3.18 +/- 0.34 to 3.59 +/- 0.30 but no significant change was observed in D(1)RBP (1.64 +/- 0.24 pre AMPT vs 1.70 +/- 0.17 post AMPT). Thus, while DA depletion "uncovers" D(2)receptors, it does not do so for D(1) receptors. The implications of this finding for measuring endogenous DA and its effects on in vivo receptor binding in humans are discussed.

Lower dopamine transporter binding potential in striatum during depression

Previous studies suggest that there is a dopamine lowering process during major depressive episodes (MDE). To investigate this, we measured the dopamine transporter binding potential (DAT BP) in the striatum of depressed and healthy subjects using [(11)C]RTI-32 PET. The DAT, a predominantly presynaptic receptor, decreases in density after chronic dopamine depletion and the BP is proportional to receptor density. In all striatal regions, subjects with MDE had significantly lower DAT BP. Low striatal DAT BP in MDE is consistent with a downregulation of DAT in response to a dopamine lowering process. There was also a strong, highly significant, inverse correlation between striatal DAT BP and neuropsychological tests of dopamine-implicated symptoms in patients (i.e. patients with lower DAT BP performed better). Lower DAT BP itself reduces extracellular clearance of dopamine. Patients who did not decrease their striatal DAT BP failed to compensate for low dopamine and showed greater impairment on dopamine related tests.

Occupancy of serotonin transporters by paroxetine and citalopram during treatment of depression: a [(11)C]DASB PET imaging study

OBJECTIVE

Selective serotonin reuptake inhibitors are commonly used to treat major depression; however, the percentage of serotonin (5-HT) transporter (5-HTT) sites occupied during clinical dosing is unknown. This study measured the proportion of 5-HTT sites blocked during paroxetine and citalopram treatment of depression and assessed the relationship between serum paroxetine levels and the proportion of 5-HTT sites blocked.

METHOD

Twelve medication-free depressed patients completed a 6-week trial of either paroxetine (N=8) or citalopram (N=4). Striatal 5-HTT binding potential was measured with [(11)C]DASB and positron emission tomography, before and after 4 weeks of treatment. The binding potential is proportional to receptor density. Striatal 5-HTT binding potential was measured twice in six healthy subjects and once in 11 healthy subjects.

RESULTS

A significant decrease in striatal 5-HTT binding potential was found after either treatment, compared to changes found over a 4-week period in healthy subjects. For patients treated with 20 mg/day of paroxetine (N=7), the mean proportion of 5-HTT sites occupied was 83%. For patients treated with 20 mg/day of citalopram (N=4), the mean 5-HTT occupancy was 77%. 5-HTT occupancy increased in a nonlinear relationship with serum levels of paroxetine such that a plateau of occupancy around 85% occurred for serum paroxetine levels greater than 28 microg/liter.

CONCLUSIONS

During treatment with clinical doses of paroxetine or citalopram, approximately 80% of 5-HTT receptors are occupied. This change in 5-HTT binding potential is greater than the known physiological range of changes in 5-HTT binding potential but may be necessary for some therapeutic effects.

Positron emission tomography quantification of [(11)C]-DASB binding to the human serotonin transporter: modeling strategies

[(11) C]-DASB, namely [(11) C]-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile, is a new highly selective radioligand for the in vivo visualization of the serotonin transporter (SERT) using positron emission tomography (PET). The current study evaluates different kinetic modeling strategies for quantification of [(11)C]-DASB binding in five healthy humans. Kinetic analyses of tissue data were performed with a one-tissue (1CM) and a two-tissue (2CM) compartment model. Time-activity curves were well described by a 1CM for all regions. A 2CM model with four parameters failed to converge reliably. Reliable fits of the data were obtained only if no more than three parameters were allowed to vary. However, even then, the rate constants k(3) and k(4) were estimated with poor precision. Only the ratio k(3)/k(4) was stable. Goodness of fit was not improved by using a 2CM as compared with a 1CM. The minimal study duration required to obtain stable k(3)/k(4) estimates was 80 minutes. For routine use of [(11)C]-DASB, several simplified methods using the cerebellum as a reference region to estimate nonspecific binding were also evaluated. The transient equilibrium, the linear graphical analysis, the ratio of target to reference region, and the simplified reference tissue methods all gave binding potential values consistent with those obtained with the 2CM. The suitability of [(11)C]-DASB for research on the SERT using PET is thus supported by the observations that tissue data can be described using a kinetic analysis and that simplified quantitative methods, using the cerebellum as reference, provide reliable estimates of SERT binding parameters.

A simple method to measure baseline occupancy of neostriatal dopamine D2 receptors by dopamine in vivo in healthy subjects

The effect of endogenous dopamine (DA) on measurement of neostriatal DA D(2) receptor binding potential (D(2)RBP) in vivo was evaluated with positron emission tomography (PET) and the radiotracer [11C]raclopride by comparing the D(2)RBP before and after acute DA depletion. DA depletion was achieved by per-oral administration of 4.5 g alpha-methyl-para-tyrosine (AMPT) given in 25 h. Six healthy subjects completed the protocol. The AMPT treatment increased D(2)RBP significantly from 3.11 +/- 0.25 to 3.68 +/- 0.23 and decreased plasma levels of the DA metabolite homovanillic acid by 71 +/- 11% and levels of the norepinephrine metabolite 3-methoxy-4-hydroxyphenethyleneglycol by 53 +/- 7%. Increase in D(2)RBP correlated with decrease in attentiveness and with increase in errors of commission from Conners' Continuous Performance Test. On AMPT, a significant decrease in subjective happiness scores was observed. The results imply that a noninvasive [11C]raclopride PET protocol coupled with relatively brief administration of a rather low total dose of AMPT resulted in measurable acute DA depletion that might provide estimates of synaptic neostriatal DA concentration.

Influence of L-dopa and pramipexole on striatal dopamine transporter in early PD

BACKGROUND

Animal data indicate that chronic exposure to dopaminergic drugs can alter levels of the dopamine transporter (DAT), which is critically involved in regulation of synaptic dopamine levels. DAT changes could influence the response to therapy in PD.

METHODS

A randomized, assessor-blinded, placebo-controlled clinical trial was performed in subjects with early PD to determine whether L-dopa or pramipexole might regulate striatal DAT binding as measured by PET with [(11)C]RTI-32. Thirty clinically asymmetrical patients were randomly assigned to receive 6 weeks of L-dopa (300/75 mg/d), pramipexole (1.5 mg/d), or placebo; PET studies were performed before and after treatment.

RESULTS

Mean interval change in DAT binding was significantly reduced by 16% to 22% in all striatal regions (caudate, anterior and posterior putamen) of the L-dopa-treated patients, whereas significant changes in the pramipexole-treated patients were limited to the contralateral caudate (-15%), ipsilateral anterior putamen (-14%), and posterior putamen (-20%). In the placebo group there were significant changes in contralateral caudate (-11%) and ipsilateral anterior putamen (-12%). L-dopa and pramipexole produced similar clinical benefit.

CONCLUSIONS

Short-term therapy with L-dopa and, to a lesser extent, pramipexole can modestly down-regulate striatal DAT in patients with early PD. Decreased striatal DAT could increase dopaminergic neurotransmission with potential benefit, but might also play a role in the development of dopamine-related response fluctuations in patients with advanced disease. Our data also suggest caution in interpretation of longitudinal imaging studies employing DAT to assess disease progression and the efficacy of neuroprotective agents.

Serotonin 5-HT1A receptor binding potential declines with age as measured by [11C]WAY-100635 and PET

Positron emission tomography (PET) and [11C]WAY-100635 were used to examine the effect of age on serotonin-1A (5-HT1A) receptor binding potential (BP) in 19 healthy subjects. Regions of interest (ROI) were drawn on the co-registered magnetic resonance imaging (MRI) in orbitofrontal (OFC), dorsolateral prefrontal (DLPFC), anterior cingulate (ACC), lateral (LTC), and mediotemporal (MTC), parietal, occipital and cerebellar cortex, and the raphe nuclei. BP values were calculated using a simplified reference tissue method. In addition, a voxelwise analysis was performed using SPM99. Voxelwise analysis revealed a significant global decrease of 5-HT(1A) BP with age (set level <.001). ROI analysis revealed significant age-related 5-HT(1A) BP decreases in DLPFC (r = -0.56), ACC (r = -0.44), OFC (r = -0.42), LTC (r = -0.40), parietal (r = -0.65), and occipital cortex (r = -0.43), but not in MTC or raphe nuclei. Overall, cortical 5-HT(1A) BP declined by approximately 10% per decade, except for the MTC, where we did not find a significant age effect. Hence, careful age matching may be recommended for future studies using PET and [11C]WAY-100635 to examine 5-HT1A receptors.

Imaging the serotonin transporter with positron emission tomography: initial human studies with [11C]DAPP and [11C]DASB

Two novel radioligands, N,N-dimethyl-2-(2-amino-4-methoxyphenylthio) b enzylamine (DAPP) and (N,N-dimethyl-2-(2-amino-4-cyanophenylthio) benzylamine (D ASB), were radiolabeled with carbon-11 and evaluated as in vivo probes of the serotonin transporter (SERT) using positron emission tomography (PET). Both compounds are highly selective, with nanomolar affinity for the serotonin transporter and micromolar affinity for the dopamine and norepinephrine transporters. Six volunteers were imaged twice, once with each of the two radioligands. Both ligands displayed very good brain penetration and selective retention in regions rich in serotonin reuptake sites. Both had similar brain uptake and kinetics, but the cyano analogue, [11C]DASB, had a slightly higher brain penetration in all subjects. Plasma analysis revealed that both radiotracers were rapidly metabolized to give mainly hydrophilic species as determined by reverse-phase high-performance liquid chromatography. Inhibition of specific binding to the SERT was demonstrated in three additional subjects imaged with [11C]DASB following an oral dose of the selective serotonin reuptake blocker citalopram. These preliminary studies indicate that both these substituted phenylthiobenzylamines have highly suitable characteristics for probing the serotonin reuptake system with PET in humans.

A voxel-by-voxel analysis of [18F]setoperone PET data shows no substantial serotonin 5-HT(2A) receptor changes in schizophrenia

Several postmortem studies have reported regionally localized decreases in serotonin(2A) receptors (5-HT(2A)R) in schizophrenia. This was not confirmed by two recent [18F]setoperone positron emission tomography (PET) studies. In these two studies relatively large regions of interest (ROIs) were used; hence, 5-HT(2A)R changes may have been missed in some brain areas. Therefore, data from one study were analyzed on a voxel-by-voxel basis using Statistical Parametric Mapping (SPM). We also used this method to examine the relationship between 5-HT(2A)R binding potential (BP) and five PANSS-derived factors: negative, positive, activation, dysphoric and autistic preoccupation. Thirteen schizophrenic patients (10 antipsychotic-naïve, 3 antipsychotic-free; 11 M, 2 F; age 31+/-7 years) and 35 age-matched control subjects (15 M, 20 F; age 30+/-7 years) were scanned. The 5-HT(2A)R BP was determined for each voxel using the pseudoequilibrium ratio method on PET data obtained between 65 and 90 min after [18F]setoperone bolus injection. The resulting parametric 5-HT(2A)R BP images were spatially normalized using a ligand specific template. Analyses of covariance were done using SPM99 with age as covariate. In tests for the effect of schizophrenia and for partial correlations between 5-HT(2A)R BP and the five factors, corrected P values <0.05 at cluster or voxel level were considered significant. No significant differences were detected between patients and control subjects, and no significant correlations were observed between 5-HT(2A)R BP and any of the five factors. Thus, in agreement with the previous ROI studies, voxel-by-voxel analysis confirmed the lack of substantial 5-HT(2A)R BP differences between schizophrenic patients and control subjects.

Reversal of caffeine withdrawal by ingestion of a soft beverage

Followlng regular use, acute cessation of caffeine is associated with a characteristic withdrawal syndrome. Despite this, caffeine remains popular with its consumers. The aim of this study was to examine the physiologic and psychologic effects of small caffeine doses, administered in the form of a market-leading soft drink, on healthy women who were acutely withdrawn from caffeine. After 48-h abstinence and overnight fast, 11 healthy (22 to 40 years) female volunteers, all regular caffeine users (daily consumption 143 to 773 mg) consumed using a double-blind. randomized, controlled cross-over design either 2 tins of regular or caffeine-free Diet Coke. On both visits a Mars bar was eaten to prevent hypoglycaemia. Thus, the caffeine load was 76 or 10 mg respectively. Following ingestion of regular Diet Coke, there was a l0% fall in middle cerebral artery velocity (95% CI [6%-l4%], p < 0.005 versus caffeine free) and improvement in feelings of pleasure (p < 0.046) and energy (p < 0.037). Intellectual function (4-choice reaction time) was unaffected by caffeine status. On both visits, ingestion of Diet Coke induced a pressor response (maximum rise in systolic pressure +15+/- 2 mm Hg with caffeine and +l2 +/- 2 mm Hg with caffeine-free beverage, both p < 0.001 compared with baseline). In conclusion, in women acutely withdrawn from caffeine, ingestion of a popular soft beverage containing modest amounts of caffeine is associated with demonstrable physiologic and psychologic effects.

Methylation-sensitive, single-strand conformation analysis (MS-SSCA): A rapid method to screen for and analyze methylation

We have developed methylation-sensitive, single-strand conformation analysis (MS-SSCA) as a method of screening for methylation changes. Bisulfite modification converts cytosines to thymines, but methylated cytosines remain unchanged. This modification creates sequence differences between methylated and unmethylated samples, which can be resolved by SSCA. SSCA is 70-95% efficient at detecting single base changes in a fragment. As bisulfite modification of methylated DNA would typically involve several base changes in a fragment, the efficiency of detecting methylation using MS-SSCA could approach 100%. We applied this method to analyze the BRCA1 promoter CpG island in breast cancer samples. About 20% of sporadic breast cancers are hypermethylated at the BRCA1 promoter CpG island. MS-SSCA rapidly detected those tumors that had previously been shown to be methylated by Southern blotting. The variant bands detected by SSCA were analyzed by sequencing and shown to be methylated. MS-SSCA is a simple method for screening large numbers of samples for methylation and can accelerate genomic sequencing, as all bands can be isolated and sequenced directly.

Histological evaluation of repair using a bioresorbable membrane beneath a resin-modified glass ionomer after mechanical furcation perforation in dogs' teeth

Resorbable barriers have been shown both clinically and histologically to produce favorable periodontal regenerative outcomes. The purpose of the present study was to evaluate the histological response to one such resorbable barrier (Atrisorb) when used as a matrix under a resin-modified glass ionomer (RMGI) sealant in the repair of furcation perforations in experimental animals. After anesthesia, pulp extirpation and filling of radicular canals with zinc oxide-eugenol cement, furcal perforations were made in 30 lower premolar (P2, P3, and P4) teeth of labrador dogs with a 1 mm diameter round bur in a conventional handpiece. The perforated teeth were randomly divided into two groups of 15 teeth. Group 1 teeth were treated with RMGI alone and group 2 with the resorbable barrier under RMGI. Six teeth without perforations served as negative controls. Pulp chambers of all teeth were filled with RMGI cement. Animals were sacrificed after 3 months. The teeth and the surrounding structures were processed for light microscopy. There were no differences found between results for glass ionomer alone and barrier with glass ionomer. The conclusion of this study is that placement of a resorbable barrier at the pulp chamber aspect of a furcation perforation did not result in superior healing, compared with the use of resin-modified glass ionomer alone.

Task-independent effect of time on rCBF

Positron emission tomography was used to identify brain regions that showed general increase or decrease in regional cerebral blood flow (rCBF) across time that was task-independent. Twelve male subjects were scanned eight times: the first and last scans were taken while subjects performed a baseline fixation task and the middle six scans were taken while subjects performed a visuomotor activation task. To determine whether there was a consistency across different studies in the regions that showed this time-related change in rCBF two additional datasets were analyzed. There were similarities across all three studies in the regions that showed a monotonic task-independent change in activity. In all three studies there was a general bilateral decrease in rCBF of occipital and temporal areas across scans that might be related to habituation in the visual domain. Increases in rCBF were found in anterior cingulate, postcentral gyrus, and precentral gyrus across studies. It is likely that these changes reflect motor learning and motor program retrieval. This implies that, unless the experimenter controls for time-dependent changes in brain activity, the interpretation of task-related changes in rCBF may be confounded by these monotonic changes in rCBF. We present analytic strategies to identify experimental effects that are independent of nonspecific time effects, which can be used when it is not possible to control these effects through counterbalancing the experimental design. Nonspecific confounds are particularly relevant in functional MRI studies in which the number of scans acquired per study is much larger.

[11C]RTI-32 PET studies of the dopamine transporter in early dopa-naive Parkinson's disease: implications for the symptomatic threshold

To estimate the threshold of nigrostriatal dysfunction required for symptomatic Parkinson's disease (PD), we employed [11C]RTI-32 and PET to study the dopamine transporter in striatal subdivisions of 11 L-dopa-naive patients with very early parkinsonism. As compared with the controls (N = 10), the PD group had on the side contralateral to the maximal clinical symptoms, significantly reduced binding in the posterior putamen (-56%) and anterior putamen (-28%), with the reduction in caudate (-12%) not significantly different. To the extent that dopamine transporter binding accurately reflects the number of nigrostriatal dopamine nerve terminals, these findings suggest that the clinical threshold for PD in the middle-age human is approximately 50% loss of dopaminergic innervation to the posterior putamen. Our data also suggest that damage to the putamen component of the striatum is sufficient for the clinical expression of PD.

Thermographic assessment of dentine pin placement

OBJECTIVE

This in-vitro study aimed to examine the change in surface temperature induced by the actions of drills for the placement of dentine pins.

METHODS

Ten decoronated extracted premolar teeth were embedded by the apical tip of their roots in orthoresin. They were held in a bench vice and allowed to reach the ambient temperature of 24 degrees C. A thermal imaging camera, Agema Thermovision 900 series, was positioned 0.05 m perpendicular to the decoronated surface. Sequential recording of a series of images was stored at a rate of three per second during each stage of the pin placement procedure. This included a pilot drill, a channel cutting drill and the pin placement. All pins were 0.675 mm diameter x 2 mm in length and were placed 1 mm from the amelo-dentinal junction using a Kavo handpiece rotating at 4000 rpm.

RESULTS

The mean baseline temperature for the thermally stabilized teeth was 23.9 degrees C. The action of the round pilot drill changed the temperature from baseline by 25 degrees C. The action of the channel drill generated the greatest heat, with a mean maximum temperature recorded during these procedures of 94 degrees C +/- 9 degrees C. The pilot drill produced a mean change from baseline of 31.3 degrees C +/- 17.7 degrees C during pin placement.

CONCLUSIONS

The placement of dentine pins produced a high temperature increase on the surface of the dentine. All stages of pin placement gave rise to an increased temperature, but this was maximal with the channel drill. Further studies are required to determine whether these surfaces temperatures are transferred to the pulpal chamber.

A molecular and evolutionary study of the beta-globin gene family of the Australian marsupial Sminthopsis crassicaudata

Beta-globin gene families in eutherians (placental mammals) consist of a set of four or more developmentally regulated genes which are closely linked and, in general, arranged in the order 5'-embryonic/fetal genes-adult genes-3'. This cluster of genes is proposed to have arisen by tandem duplication of ancestral beta-globin genes, with the first duplication occurring 200 to 155 MYBP just prior to a period in mammalian evolution when eutherians and marsupials diverged from a common ancestor. In this paper we trace the evolutionary history of the beta-globin gene family back to the origins of these mammals by molecular characterization of the beta-globin gene family of the Australian marsupial Sminthopsis crassicaudata. Using Southern and restriction analysis of total genomic DNA and bacteriophage clones of beta-like globin genes, we provide evidence that just two functional beta-like globin genes exist in this marsupial, including one embryonic-expressed gene (S.c-epsilon) and one adult-expressed gene (S.c-beta), linked in the order 5'-epsilon-beta-3'. The entire DNA sequence of the adult beta-globin gene is reported and shown to be orthologous to the adult beta-globin genes of the North American marsupial Didelphis virginiana and eutherian mammals. These results, together with results from a phylogenetic analysis of mammalian beta-like globin genes, confirm the hypothesis that a two-gene cluster, containing an embryonic- and an adult-expressed beta-like globin gene, existed in the most recent common ancester of marsupials and eutherians. Northern analysis of total RNA isolated from embryos and neonatals indicates that a switch from embryonic to adult gene expression occurs at the time of birth, coinciding with the transfer of the marsupial from a uterus to a pouch environment.

In vivo binding of [11C]SKF 75670 and [11C]SKF 82957 in rat brain: two dopamine D-1 receptor agonist ligands

The high affinity benzazepine D1 agonists SKF 75670 and SKF 82957 labeled with C-11 were evaluated in vivo in rats as potential radioligands for imaging dopamine D1 receptors with positron emission tomography (PET). Their in vivo pharmacological profile revealed selective binding for both tracers in rat brain regions rich in D1 receptors such as the caudate-putamen. The more lipophilic [11C]SKF 82957 (6-chloro-[11C]SKF 75670) showed a higher brain uptake (more than 2-fold up to 30 min), higher specific uptake in the striatum and higher signal-to-noise ratio (striatum-to-cerebellum = 3.2 +/- 0.4 for [11C]SKF 75670 and 9.7 +/- 2.5 for [11C]SKF 82957 at 60 min post-injection) as compared to [11C]SKF 75670. Both radiotracers exhibited high specificity and selectivity for D1 receptors, since only D1 competitors but not the D2 antagonist sulpiride or the 5-HT2 antagonist ritanserin reduced significantly their binding the striatum with [11C]SKF 75670 or the striatum and olfactory tubercles with [11C]SKF 82957. Previous reports have shown that only D1 agonists can recognize the functional high-affinity state from the low-affinity state of D1 receptors. [11C]SKF 75670 and especially [11C]SKF 82957 are D1 agonist radioligands that can potentially be used to study in vivo the functional high-affinity state of D1 receptors using PET.

The statistical power of [15O]-water PET activation studies of cognitive processes

[15O]-Water positron emission tomography (PET) scanning is an important means of investigating the neural correlates of cognitive processes. This study analyses the statistical power of these experiments under usual experimental conditions. Eleven subjects were scanned repeatedly while they undertook an active-baseline task. Using an empirically derived estimate of variance, the statistical power to detect task-induced increases in regional cerebral blood flow was calculated for different values of magnitude of change, number of subjects and probability of Type I error. The results (a) provide an empirical basis for selecting the number of subjects for cognitive studies using [15O]-water PET; (b) illustrate the importance of considering the statistical power of the test, while making a physiological interpretation of the results; and (c) highlight the problems in concluding the non-involvement of a given brain region in a cognitive task, based solely on the results of a PET study.

Effects of groove placement on retention/resistance of maxillary anterior resin-bonded retainers

Debonding of resin-bonded fixed partial dentures has been partly resolved with modification of tooth preparations. Tooth preparations for resin-bonded retainers were completed on a maxillary central incisor, a lateral incisor, and a canine. Fifteen metal replicas were constructed (five of each tooth morphotype). The three tooth morphotypes were then modified with proximal grooves prepared parallel to the long axes, and another 15 metal replicas were prepared. Cast metal retainers were constructed and cemented to the replicas with a resin cement. Tensile shearing dislodging loads were applied at 20 degrees to the long axes of the teeth with a testing machine. The addition of proximal grooves made statistically significant differences in resistance to debonding forces for all three tooth morphotypes (p < 0.01). An increase of 76.7% was seen in dislodging forces for lateral incisors with proximal grooves compared with incisors without grooves.

Absence of residual effects after physiological stimulation of the visual and motor cortex: an [15O]-H2O PET study in humans

Cognitive experiments using positron emission tomography (PET) with [15O]-H2O require multiple scans done at 10 to 12 min intervals. Momose and colleagues reported that regional cerebral blood flow changes in response to visual stimulation do not return to baseline even 15 min after the stimulation. If confirmed, this fact would have important implications for the design and interpretation of PET cognitive studies. The purpose of this study was to determine the temporal course of residual effects following visual and motor stimulation. Six healthy volunteers undertook six scans each. Two scans were done to establish a baseline, one to observe the task induced activation, and three scans to investigate the residual effects at varying intervals after the task. The data were analysed using both statistical parametric mapping and a region of interest analysis. The visual and motor task produced robust activations bilaterally in the occipital cortex and in the contralateral primary motor cortex. There was no evidence for a statistically significant residue effect at any of the three intervals studied (30 s, 3 and 6 min). Our results refute the findings of Momose and colleagues and suggest that the 10-min interscan interval is more than adequate to re-establish a resting baseline.

Sequence of lamprey vitellogenin. Implications for the lipovitellin crystal structure

The amino acid sequence of lamprey vitellogenin has been predicted from the nucleotide sequence of cloned cDNA. The sites of proteolytic cleavage that produce the lipovitellin complex from the vitellogenin have been located by comparing the N-terminal sequences of two lamprey lipovitellin polypeptides with the predicted sequence. These results also confirm that the vitellogenin sequence derived here corresponds to the lipovitellin complex for which the crystal structure has been solved previously. Predictions of secondary structure indicate that the region most likely to correspond to the large alpha-helical domain of the crystallographic model consists of vitellogenin residues 300 to 600. Similar to the lipovitellins of Xenopus laevis, lamprey lipovitellin appears to lack approximately 200 C-terminal residues that are present in vitellogenin. However, the lamprey lipovitellin differs from those of Xenopus and chicken in two respects. First, most of the serine-rich domain that is present as the phosvitin polypeptide in the lipovitellins of the higher vertebrates appears to be lost in the maturation of lamprey vitellogenin to lipovitellin. Second, the domains that constitute the large lipovitellin-1 polypeptide in Xenopus and chicken are present in two polypeptides in lamprey, owing to an additional proteolytic processing event.

Fast neutron radiation therapy for glioblastoma multiforme. Results of an RTOG study

Between January 1977 and September 1980, 166 patients were entered on a RTOG protocol comparing neutron-boost radiotherapy with standard treatment for patients with glioblastomas. Eighty-three patients were randomized to receive a neutron boost and 83 to receive a photon boost after 50 Gy photon, whole-brain irradiation. Of these, six were ineligible and two were cancelled, leaving 158 patients available for analysis. The median survival for the neutron-boost group was 9.8 months, compared to 8.6 months for the photon-boost group. The difference is not statistically significant. Autopsies revealed actively growing persistent tumor in all photon-treated patients compared to no evidence of actively growing tumor in the majority of neutron-treated patients.