A novel in-lens detector for electrostatic scanning LEEM mini-column

A novel principle of an in-lens detector of very slow electrons is described and the detector efficiency discussed. The detector was built into a coaxial column for a Cylindrical Mirror Analyser for Auger electron microanalysis. In order to obtain a very low energy scanned imaging, a cathode lens was formed between the final electrode of the column and a negatively biased specimen. The signal electrons accelerated within the cathode lens field enter the column and after being mirrored back impact a micro-channel-plate based detector fitted around the optical axis. The acceptance of the detector, expressed as a ratio of the number of electrons impacting the detector to the full emission of a cosine source, was calculated to be 0.86 for 1 eV and 0.985 for 10 eV electrons. Then, the efficiency of conversion into output pulses is 0.35 and 0.31, respectively; these parameters are superior to those of conventional SEM detectors for secondary electrons. Micrographs taken at low energies ranging down to units of eV are presented.

Prisons and public health: emerging issues in HIV treatment adherence

Correctional facilities in the United States are faced with challenges in providing appropriate and timely HIV treatment to incarcerated HIV-infected inmates. Prison and jails, due to their structure, operation, and staff, may present many barriers to HIV treatment and adherence to complicated and expensive HIV treatment regimens. Changes and modifications of prison health care delivery are required to accommodate the needs of HIV-infected inmates. Approaches to improving correctional HIV care and treatment include training health care personnel, prevention education for inmates, increasing access to voluntary HIV testing, comprehensive treatment planning, and continuity of care. Policy changes for correctional systems include adopting current HIV care standards and immediate evaluation for and access to HIV treatment upon entry into the institution. These changes can have a significant impact on the quality of care for inmates, ultimately improving their quality of life and reducing the morbidity and mortality of HIV disease for incarcerated populations.

Psychometric validation of a constipation symptom assessment questionnaire

BACKGROUND

Clinical management of constipation is complicated by the lack of a gold standard for evaluation of symptoms. A constipation symptom assessment instrument, the PAC-SYM, was developed to address the patient perspective on the disorder. Instrument content was based on literature review and results of focus groups.

METHODS

Two hundred and sixteen patients at nine sites participated in a 6-week psychometric evaluation of the PAC-SYM. The final instrument contained 12 items assigned to 3 subscales: stool symptoms, rectal symptoms, and abdominal symptoms. The psychometric properties of this final instrument were assessed.

RESULTS

Internal consistency and test-retest reliability of the final instrument was high (Cronbach's alpha = 0.89; intraclass correlation = 0.75). Concurrent validity was supported by the correlation with both subject and investigator constipation severity ratings (r= 0.68 and 0.72, respectively; P < 0.0001). Scores were moderately correlated with instruments measuring quality of life. Comparison of treatment responders with nonresponders showed the ability of the instrument to differentiate between groups on the basis of clinical severity (t = -6.12, P < 0.0001 ). Scores changed significantly over time among responders, indicating instrument responsiveness.

CONCLUSIONS

The PAC-SYM is internally consistent, reproducible under stable conditions, valid, and responsive to change and provides a comprehensive means to assess the effectiveness of treatment for constipation.

Pharmacoeconomic evaluation in the real world. Effectiveness versus efficacy studies

Pharmacoeconomic data may be obtained within the context of randomised clinical trials (RCTs) and from effectiveness studies in the 'real world'. The differences between the 2 types of study design have implications for the types of data that can be obtained and the interpretation of the resulting findings. Because RCTs are designed to assess the safety and efficacy of pharmaceuticals, and because the study design of RCTs emphasises internal validity over generalisability, the pharmacoeconomic data collected from them are limited. The data may not be applicable to the more heterogeneous patients encountered in actual clinical practice, and cost estimates may be inaccurate because of protocol requirements. Effectiveness studies, in which treatments are studied under real-world conditions, remedy some of these limitations. Generalisability to actual users is generally enhanced in effectiveness designs, but data may be biased in other ways. This brief review compares the 2 study designs as they relate to pharmacoeconomic evaluations in terms of the research questions they address, design differences and their implications for study bias, data collection and data analysis and the generalisability of their results.

Exposure to peanuts in utero and in infancy and the development of sensitization to peanut allergens in young children

This study attempted to determine the underlying factors that may influence the development of peanut sensitization in young children in South Africa. One of our objectives was to ascertain whether the consumption of peanuts or peanut-containing foods during pregnancy and lactation by mothers from atopic families impacted upon the development of an allergic response to peanuts in the child. Forty-three children between the ages of 0 and 3 yr participated in this study. There were 25 peanut-sensitized subjects and 18 control subjects (children sensitized to milk and/or egg, but not to peanuts). A significant association was found between peanut sensitization and sensitivity to soya (p=0.0002), wheat (p=0.03), and cod fish. We found that mothers who consumed peanuts more than once a week during pregnancy were more likely to have a peanut-allergic child than mothers who consumed peanuts less than once a week (odds ratio=3.97, 98% confidence interval 0.73-24). Peanuts or peanut butter was introduced into the child's diet from a significantly younger age in the peanut-allergic subjects (p<0.03). There was a positive correlation in the peanut-allergic subjects between age of introduction of peanuts and age at the onset of symptoms (r=0.63). Exclusive breast feeding did not protect against the development of peanut sensitization. Peanut allergy is associated with an increased risk of sensitization to other foods. It is more likely to occur if mothers eat peanuts more frequently during pregnancy and introduce it early to the infant's diet. These features highlight potentially avoidable factors that might prevent sensitization.

Magnetic resonance imaging of knee cartilage repair

Cartilage injury resulting in osteoarthritis is a frequent cause of disability in young people. Osteoarthritis, based on either cartilage injury or degeneration, is a leading cause of disability in the United States. Over the last several decades, much progress has been made in understanding cartilage injury and repair. Magnetic resonance (MR) imaging, with its unique ability to noninvasively image and characterize soft tissue, has shown promise in assessment of cartilage integrity. In addition to standard MR imaging methods, MR imaging contrast mechanisms under development may reveal detailed information regarding the physiology and morphology of cartilage. MR imaging will play a crucial role in assessing the success or failure of therapies for cartilage injury and degeneration.

Correlates of disruptive behavior in severely cognitively impaired nursing home residents

This article provides information about correlates of "disruptive behaviors" among nursing home residents with dementia. We used averages of multiple observations for a wide range of behaviors (n = 45) across 11 months to gather this information. We placed behaviors into four separate categories: physically aggressive, physically non-aggressive, vocally agitated, and vocally aggressive. Then, we tested associations between these categories and demographic, cognitive, and health variables. Cognitive status and selected demographic variables were associated with the behavior categories; adding health variables did not improve prediction. Lower cognitive status was associated with more disruptive behaviors. Our findings suggest that cognitive status, but not health variables, predicts disruptive behavior among nursing home residents with dementia.

Hemispheric asymmetries in global and local processing: evidence from fMRI

Functional magnetic resonance imaging (fMRI) was used to explore the brain substrate associated with global and local processing of visuospatial patterns. Systematic differences in activation, consistent with differences observed in reaction time data collected under conditions of visual hemifield presentation, were found in occipitotemporal regions of the right and left hemispheres. Within the right hemisphere, area of activation and fractional signal changes were greater under conditions of global processing than under local processing conditions. In the left hemisphere, activation to global and local input was high and comparable.

Effects of BDNF infusion on the regulation of TrkB protein and message in adult rat brain

Exposure of embryonic CNS neurons to BDNF in vitro causes down-regulation of TrkB protein and mRNA, and an attenuation of functional responses to acute neurotrophin stimulation. In order to investigate ligand-mediated regulation of TrkB in vivo, we infused BDNF into the midbrain, near the periaquaductal grey-dorsal raphe (PAG-DR), or into the olfactory bulb of adult rats. Midbrain infusion of BDNF produced analgesia that was sustained for the duration of BDNF delivery. Analysis of TrkB receptor levels revealed that at the point when the maximal analgesic effect of BDNF was obtained, there was a concommitant 75% decrease in full-length TrkB protein at the infusion site. After discontinuation of infusion, levels of TrkB recovered toward base line. Interestingly, TrkB protein levels were not accompanied by decreased trkB mRNA levels. To determine if BDNF infusion decreased TrkB protein levels in other brain areas and whether trkB mRNA might be down-regulated in the cell bodies of neurons projecting to the infusion site, we infused BDNF into the olfactory bulb. Following a 12-day infusion of BDNF, TrkB protein levels decreased within the bulb to a similar extent as in the PAG-DR. This decrease in receptor protein, however, was not accompanied by decreased trkB mRNA levels in the olfactory cortex, which is afferent to the bulb. Taken together, our data suggest that decreases in TrkB receptor protein at the site of BDNF infusions in the adult brain represent receptor turnover, but this is not associated with altered expression of trkB mRNA or attenuation of the pharmacological effects of BDNF.

Reduction of bleomycin-induced acute DNA injury in the rat lung by the 21-aminosteroid, U-74389G

OBJECTIVE

To determine whether pretreatment with a 21-aminosteroid, U-74389G, can prevent subsequent DNA injury in bleomycin-exposed lungs.

SUBJECTS

Thirty-six adult male Sprague-Dawley rats.

DESIGN

Controlled animal laboratory investigation of DNA injury in vivo.

INTERVENTIONS

Animals were treated with 21-aminosteroid (10 mg/kg) or vehicle and subsequently received intratracheal instillation of bleomycin (1.75 U) or normal saline.

MEASUREMENTS AND MAIN RESULTS

Twenty-four hours after bleomycin exposure, the 21-aminosteroid-treated animals had decreased evidence of DNA injury, expressed as percentage of DNA fragmentation normalized to the control group (113.5 +/- 6 [SEM] vs. 132 +/- 3.9%, p < or = .05), and activity of the DNA repair enzyme poly ADP-ribose synthetase (3.4 +/- 0.2 vs. 5.6 +/- 0.9 pmol nicotinamide adenine dinucleotide/min/mg protein, p < or = .05). Only bleomycin-exposed (+ vehicle) animals demonstrated significant evidence of increased DNA injury vs. the intratracheal saline-exposed control groups.

CONCLUSIONS

The 21-aminosteroid pretreatment decreases subsequent pulmonary DNA injury induced by bleomycin exposure. This finding is likely due to the 21-aminosteroid's iron-chelating and cell-permeating abilities, and suggests that these agents may be effective in other diseases where iron-dependent free radical reactions occur.

Prenatal dexamethasone administration to premature rats exposed to prolonged hyperoxia: a new rat model of pulmonary fibrosis (bronchopulmonary dysplasia)

OBJECTIVE

To evaluate the postnatal effects of prenatal dexamethasone treatment of preterm rats and to test the hypothesis that prenatal dexamethasone treatment projects against pulmonary oxygen toxicity in the preterm rats and stimulates lung antioxidant enzyme levels in response to hyperoxia.

STUDY DESIGN

We administered dexamethasone (0.4 mg/kg, intraperitoneally), or equivolume saline solution to pregnant rats at 48 and 24 hours before premature delivery at gestation day 21. Both groups of prematurely delivered rat pups were randomly assigned to other > 95% O2 or room air immediately after birth and brief resuscitation.

RESULTS

The hyperoxic survival rates from day 1 through day 14 were similar in both dexamethasone-treated and control preterm O2 groups. At 7 days of hyperoxia, the preterm pups demonstrated similar lung antioxidant enzyme activity and sufactant content responses to high O2 in the dexamethasone-treated and control groups. Lung quantitative morphometry changes were similar (equal degree of inhibition of normal alveolar development) in both groups. Unexpectedly, the lungs of the preterm O2 control rats showed evidence of septal fibrosis and the pups that received dexamethasone-O2 showed even greater severity of septal fibrosis and a greater increase (+50%) of lung hydroxyproline compared with the O2 groups control rats.

CONCLUSIONS

In preterm animals, prenatal dexamethasone administration does not show any of the hypothesized protective effects against hyperoxia or protective biochemical lung changes during prolonged O2 exposure. However, prenatal dexamethasone administration with prolonged exposure of the preterm rat to hyperoxia results in a pulmonary pathologic picture quite similar to bronchopulmonary dysplasia.

Direct evidence for in vivo nitroxide free radical production from a new antiarrhythmic drug by EPR spectroscopy

The new Class I anti-arrhythmic agent 2,2,5,5-tetramethyl-3-pyrroline-1-carboxamide derivative, is currently being evaluated in clinical trials in patients with a high risk for cardiac arrhythmias. In this study we show that this antiarrhythmic drug can be chemically converted to the nitroxide free radical analog. Further, using an in vivo Electron Paramagnetic Resonance (EPR) spectroscopy model by detecting free radicals in the distal portion of the tail of an anesthetized mouse, we demonstrate that the drug is oxidized to the corresponding nitroxide. In vitro studies using Chinese hamster V79 cells suggest that the oxidation products of the drug, namely, the hydroxylamine and the nitroxide protect against oxidative damage induced by hydrogen peroxide (H2O2). Taken together, our results suggest that, in addition to the antiarrhythmic effects of the parent drug, sufficient levels of nitroxides may accumulate from the parent drug in vivo to provide antioxidant defense to cardiac tissue that may be subject to ischemia and oxidation-driven injury.

MR imaging of articular cartilage in the ankle: comparison of available imaging sequences and methods of measurement in cadavers

OBJECTIVE

To assess hyaline cartilage of cadaveric ankles using different magnetic resonance (MR) imaging techniques and various methods of measurement.

DESIGN AND PATIENTS

Cartilage thicknesses of the talus and tibia were measured in ten cadaveric ankles by naked eye and by digitized image analysis from MR images of fat-suppressed T1-weighted gradient recalled (FS-SPGR), sequences and pulsed transfer saturation sequences with (FS-STS) and without fat-suppression (STS); these measurements were compared with those derived from direct inspection of cadaveric sections. The accuracy and precision errors were evaluated statistically for each imaging technique as well as measuring method. Contrast-to-noise ratios of cartilage versus joint fluid and marrow were compared for each of the imaging sequences.

RESULTS

Statistically, measurements from FS-SPGR images were associated with the smallest estimation error. Precision error of measurements derived from digitized image analysis was found to be smaller than that derived from naked eye measurements. Cartilage thickness measurements in images from STS and FS-STS sequences revealed larger errors in both accuracy and precision. Inter-observer variance was larger in naked eye assessment of the cartilage. Contrast-to-noise ratio of cartilage versus joint fluid and marrow was higher with FS-SPGR than with FS-STS or STS sequences.

CONCLUSION

Of the sequences and measurement techniques studied, the FS-SPGR sequence combined with the use of digitized image analysis provides the most accurate method for the assessment of ankle hyaline cartilage.

BDNF down-regulates neurotrophin responsiveness, TrkB protein and TrkB mRNA levels in cultured rat hippocampal neurons

Regulation of Trk receptors by their ligands, the neurotrophins, was investigated in dissociated cultures of embryonic day 18 rat hippocampal neurons. Cultures were exposed to brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) or NT-4/5 for 24 h upon plating followed by factor washout. As determined by immunohistochemical staining and phosphotyrosine blotting, the functional responses to acute stimulation with BDNF, NT-3 and NT-4/5, including c-Fos induction and phosphorylation of Trk and extracellular signal-regulated kinase (ERK) proteins, were significantly decreased after 6 days in culture by prior exposure to BDNF. As determined by Western and Northern blot analysis respectively, there was a parallel down-regulation of TrkB protein as well as of trkB and trkC mRNA levels in BDNF-pretreated cultures. Exposure to NT-3 or NT-4/5 at the same concentrations as BDNF did not down-regulate any of the measured cellular responses or TrkB protein and/or trkB and trkC mRNA levels. Regulation of hippocampal neuronal Trkb protein does not appear to be just a development phenomenon, as infusion of BDNF into the hippocampus of adult rats for 6 days produced an 80% decrease in levels of full-length TrkB protein. We thus show that exposure of hippocampal neurons to BDNF, both in culture and in the adult brain, results in down-regulation of TrkB. At least in vitro, this leads to long-term functional desensitization to BDNF, NT-3 and NT-4/5, as well as down-regulation of trkB and trkC mRNA.