On species delimitation, hybridization and population structure of cassava whitefly in Africa.

The Bemisia cassava whitefly complex includes species that cause severe crop damage through vectoring cassava viruses in eastern Africa. Currently, this whitefly complex is divided into species and subgroups (SG) based on very limited molecular markers that do not allow clear definition of species and population structure. Based on 14,358 genome-wide SNPs from 62 Bemisia cassava whitefly individuals belonging to sub-Saharan African species (SSA1, SSA2 and SSA4), and using a well-curated mtCOI gene database, we show clear incongruities in previous taxonomic approaches underpinned by effects from pseudogenes. We show that the SSA4 species is nested within SSA2, and that populations of the SSA1 species comprise well-defined south-eastern (Madagascar, Tanzania) and north-western (Nigeria, Democratic Republic of Congo, Burundi) putative sub-species. Signatures of allopatric incipient speciation, and the presence of a 'hybrid zone' separating the two putative sub-species were also detected. These findings provide insights into the evolution and molecular ecology of a highly cryptic hemipteran insect complex in African, and allow the systematic use of genomic data to be incorporated in the development of management strategies for this cassava pest.

Determination of ultra-low concentrations of gaseous 14C-bearing hydrocarbons produced during corrosion of irradiated steel using accelerator mass spectrometry.

Compound-specific radiocarbon analysis (CSRA) was developed to identify and quantify gaseous 14C-bearing carbon compounds at the pico- to femtomolar concentration range and employed in a corrosion experiment with small specimens of irradiated steel. The approach is based on gas chromatographic separation of single 14C-bearing carbon compounds, their oxidation to 14CO2, sampling with a custom-made fraction collector and quantification by accelerator mass spectrometry (AMS). In addition to CSRA, a method allowing the quantification of the total 14C content of the gas phase was developed and tested. After validation of the two set-ups with standards, the gaseous 14C-bearing carbon compounds produced during alkaline anoxic corrosion of irradiated steel were quantified. Small hydrocarbons (HCs) like methane (14CH4) and ethane (14C2H6) were the only 14C-bearing compounds identified in the gas phase above the detection limit. 14CH4 was the main species (on average 5.4 × 10-14 mol L-1 gas) and contributed >90% to the total 14C content, whereas the concentration of 14C2H6 was much lower (7.9 × 10-16 mol L-1 gas). To our knowledge, this is the first study reporting CSRA of gaseous 14C-bearing HCs produced during anoxic corrosion of irradiated metallic radioactive waste at ultra-low concentrations.

Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L) / Selênio na dieta melhora o sistema de defesa antioxidante de juvenis de Tilápia do Nilo (Oreochromis niloticus L)

Abstract From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Resumo Com o avanço da produção de tilápia nos últimos anos, buscam-se dietas que possibilitem o máximo crescimento, saúde e qualidade do pescado. Neste trabalho foram avaliados parâmetros de crescimento, bioquímicos, sanguíneos e oxidativos de tilápias alimentadas com níveis crescentes de selênio: 0,53, 0,86, 1,04 e 1,22 mg kg-1. Foram utilizados 400 juvenis (peso inicial =36,51 ± 10,88 g), alimentados durante seis semanas. Não ocorreu efeito do selênio no crescimento, nem nos parâmetros bioquímicos e hematológicos dos peixes. Nos parâmetros oxidativos, ocorreu aumento nos níveis de tióis não-proteicos e diminuição de malondialdeído, evidenciando efeitos antioxidantes do selênio. Os níveis de selênio acima de 0.86 mg kg-1 melhoram o sistema antioxidante dos peixes e não compromete os parâmetros bioquímicos, sanguíneos e de crescimento de juvenis de tilápia.

Growth and digestive enzymes of silver catfish fed diets containing fruit residue / Crescimento e enzimas digestivas de jundiás alimentados com dietas contendo resíduos de frutas

In fish farming, the use of alternative ingredients has been studied, so that alternative sources can be used to minimize feed costs. This study evaluated the incorporation of grape, orange, guava, and fig residues in diets for silver catfish and its effects on growth, digestive enzymes and body composition. A total of 180 fish (initial mean weight = 22.93±0.75 g) were reared in a recirculation aquaculture system. There was no difference (P>0.05) in the parameters of growth, dry matter, mineral matter, plasma protein, cholesterol, triglycerides, lipase, and trypsin of fish. Glucose levels were higher in fish fed diets containing fig, orange, and grape residue (P<0.05). Lipase activity was higher in fish fed orange residue, compared to guava (P<0.05). Diets containing guava and fig provided more body protein in silver catfish. The fish fed with diet containing orange residue had a higher content of body lipids. It can be concluded that the tested fruit residues can be used in silver catfish feeding.(AU)

Na piscicultura, o uso de ingredientes alternativos vem sendo estudado, de modo que seja possível utilizar fontes alternativas para minimizar custos com a alimentação. Neste estudo, foi avaliada a incorporação de resíduos de uva, laranja, goiaba e figo em rações para jundiá e seus efeitos no crescimento, em enzimas digestivas e na composição corporal. Foram utilizados 180 peixes (peso médio inicial = 22,93±0,75 g), criados em sistema de recirculação. Não houve diferença (P>0,05) nos parâmetros de crescimento, matéria seca, matéria mineral, proteína plasmática, colesterol, triglicerídeos, lipase e tripsina dos peixes. Os níveis de glicose foram maiores nos peixes alimentados com dietas contendo figo, laranja e uva (P<0,05). A atividade de lipase foi maior nos peixes alimentados com resíduo de laranja, comparado com o de goiaba (P<0,05). As dietas contendo goiaba e figo proporcionaram mais proteína corporal nos jundiás. Os jundiás alimentados com dieta contendo resíduo de laranja apresentaram maior teor de lipídeos corporal. Conclui-se que os resíduos de frutas testados podem ser usados na alimentação do jundiá.(AU)

Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L.).

From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Impact of long-term daylight deprivation on retinal light sensitivity, circadian rhythms and sleep during the Antarctic winter.

Long-term daylight deprivation such as during the Antarctic winter has been shown to lead to delayed sleep timing and sleep fragmentation. We aimed at testing whether retinal sensitivity, sleep and circadian rest-activity will change during long-term daylight deprivation on two Antarctic bases (Concordia and Halley VI) in a total of 25 healthy crew members (mean age: 34 ± 11y; 7f). The pupil responses to different light stimuli were used to assess retinal sensitivity changes. Rest-activity cycles were continuously monitored by activity watches. Overall, our data showed increased pupil responses under scotopic (mainly rod-dependent), photopic (mainly L-/M-cone dependent) as well as bright-blue light (mainly melanopsin-dependent) conditions during the time without direct sunlight. Circadian rhythm analysis revealed a significant decay of intra-daily stability, indicating more fragmented rest-activity rhythms during the dark period. Sleep and wake times (as assessed from rest-activity recordings) were significantly delayed after the first month without sunlight (p < 0.05). Our results suggest that during long-term daylight deprivation, retinal sensitivity to blue light increases, whereas circadian rhythm stability decreases and sleep-wake timing is delayed.

Analysis of 14C-bearing compounds released by the corrosion of irradiated steel using accelerator mass spectrometry.

The combination of ion chromatography (IC) with accelerator mass spectrometry (AMS) was developed to determine the speciation of 14C-(radiocarbon) bearing organic compounds in the femto to pico molar concentration range. The development of this compound-specific radiocarbon analysis (CSRA) of carboxylic acids is reported and the application of the method on a leaching solution from neutron-irradiated steel is demonstrated. The background and the dynamic range of the AMS-based method were quantified. On using 14C-labelled standards, the measurements demonstrate the repeatability of the analytical method and the reproducible recovery of the main target carboxylic acids (i.e., acetate, formate, malonate, and oxalate). The detection limit was determined to be in the mid fmol 14C per L level while the dynamic range of the analytical method covers three orders of magnitude from the low fmol to the mid pmol 14C per L level. Cross contamination was found to be negligible during IC fractionation and was accounted for during eluate processing and 14C detection by AMS. The 14C-bearing carboxylates released from an irradiated steel nut into an alkaline leaching solution were analysed using the CSRA-based analytical method with the aim to check the applicability of the approach and develop appropriate sample preparation. The concentrations of 14C-bearing formate and acetate, the main organic corrosion products, were at a low pmol 14C per L level for convenient dimensions of the alkaline leaching experiment which demonstrates that compound-specific 14C AMS is an extremely sensitive analytical method for analysing 14C-bearing compounds. The content of total organic 14C in solution (TO14C) determined by the direct measurement of an aliquot of the leaching solution agrees well with the sum of the 14C concentrations of the individual carboxylates within the uncertainty of the data. Furthermore, the TO14C content is in good agreement with the calculated value using the corrosion rate determined from the 60Co release and the 14C inventory of the irradiated steel specimen.

Can short-wavelength depleted bright light during single simulated night shifts prevent circadian phase shifts?

In single night shifts, extending habitual wake episodes leads to sleep deprivation induced decrements of performance during the shift and re-adaptation effects the next day. We investigated whether short-wavelength depleted (=filtered) bright light (FBL) during a simulated night shift would counteract such effects. Twenty-four participants underwent a simulated night shift in dim light (DL) and in FBL. Reaction times, subjective sleepiness and salivary melatonin concentrations were assessed during both nights. Daytime sleep was recorded after both simulated night shifts. During FBL, we found no melatonin suppression compared to DL, but slightly faster reaction times in the second half of the night. Daytime sleep was not statistically different between both lighting conditions (n = 24) and there was no significant phase shift after FBL (n = 11). To conclude, our results showed positive effects from FBL during simulated single night shifts which need to be further tested with larger groups, in more applied studies and compared to standard lighting.

Diet selenium improves the antioxidant defense system of juveniles Nile tilapia ( Oreochromis niloticus L.)

Abstract From the advancement of tilapia production in recent years, diets are sought that allow the maximum growth, improving health and fish quality. In this study growth, biochemical, hematological and oxidative parameters were evaluated of tilapia fed with increasing selenium levels: 0.53, 0.86, 1.04 and 1.22 mg kg-1. It was used 400 juveniles (initial weight = 36.51 ± 10.88 g), fed for six weeks. There was no effect of selenium on fish growth, biochemical and hematological parameters. In the oxidative parameters, there was an increase in non-protein thiols and a decrease in malondialdehyde levels, evidencing antioxidant effects of selenium. The diet selenium levels above 0.86 mg kg-1 improved the antioxidant system and does not affect to biochemical, hematological and growth parameters of tilapia juveniles.

Resumo Com o avanço da produção de tilápia nos últimos anos, buscam-se dietas que possibilitem o máximo crescimento, saúde e qualidade do pescado. Neste trabalho foram avaliados parâmetros de crescimento, bioquímicos, sanguíneos e oxidativos de tilápias alimentadas com níveis crescentes de selênio: 0,53, 0,86, 1,04 e 1,22 mg kg-1. Foram utilizados 400 juvenis (peso inicial =36,51 ± 10,88 g), alimentados durante seis semanas. Não ocorreu efeito do selênio no crescimento, nem nos parâmetros bioquímicos e hematológicos dos peixes. Nos parâmetros oxidativos, ocorreu aumento nos níveis de tióis não-proteicos e diminuição de malondialdeído, evidenciando efeitos antioxidantes do selênio. Os níveis de selênio acima de 0.86 mg kg-1 melhoram o sistema antioxidante dos peixes e não compromete os parâmetros bioquímicos, sanguíneos e de crescimento de juvenis de tilápia.

Patient-level analysis of incident vancomycin-resistant enterococci colonization and antibiotic days of therapy.

Vancomycin-resistant enterococci (VRE) infections are a public health threat associated with increased patient mortality and healthcare costs. Antibiotic usage, particularly cephalosporins, has been associated with VRE colonization and VRE bloodstream infections (VRE BSI). We examined the relationship between antimicrobial usage and incident VRE colonization at the individual patient level. Prospective, weekly surveillance was undertaken for incident VRE colonization defined by negative admission but positive surveillance swab in a medical intensive care unit over a 17-month period. Antimicrobial exposure was quantified as days of therapy (DOT)/1000 patient-days. Multiple logistic regression was used to analyse incident VRE colonization and antibiotic DOT, controlling for demographic and clinical covariates. Ninety-six percent (1398/1454) of admissions were swabbed within 24 h of intensive care unit (ICU) arrival and of the 380 patients in the ICU long enough for weekly surveillance, 83 (22%) developed incident VRE colonization. Incident colonization was associated in bivariate analysis with male gender, more previous hospital admissions, longer previous hospital stay, and use of cefepime/ceftazidime, fluconazole, azithromycin, and metronidazole (P < 0·05). After controlling for demographic and clinical covariates, metronidazole was the only antibiotic independently associated with incident VRE colonization (odds ratio 2·0, 95% confidence interval 1·2-3·3, P < 0·009). Our findings suggest that risk of incident VRE colonization differs between individual antibiotic agents and support the possibility that antimicrobial stewardship may impact VRE colonization and infection.

The influence of the tricyclic antidepressant amitriptyline on periodic limb movements during sleep.

INTRODUCTION: Many antidepressants are associated with periodic limb movements (PLM) during sleep. Although some tricyclic antidepressants, such as amitriptyline, promote sleep and are thus often prescribed as a treatment for sleep disturbances that can accompany depression, it remains unclear whether amitriptyline is associated with PLM. METHODS: 32 healthy males (18-39 years) spent 2 consecutive nights in the sleep lab for polysomnographic recording. During the second night, they received either 75 mg amitriptyline or placebo in a randomized, double-blind, placebo-controlled manner. RESULTS: In subjects receiving amitriptyline but not in subjects receiving placebo, the number of periodic leg movements per h was significantly increased from baseline to intervention night. However, objective polysomnographic sleep parameters (such as the number of awakenings, wake after sleep onset, and sleep efficiency) and subjective sleep perception were not significantly associated with any PLM indices. DISCUSSION: Our findings indicate that amitriptyline can induce or even increase the number of PLM during sleep in healthy subjects. When treating sleep disturbances with amitriptyline, PLM should be considered as a possible cause of insufficient improvement.

Pneumocystis pneumonia in hospitalized patients: a detailed examination of symptoms, management, and outcomes in human immunodeficiency virus (HIV)-infected and HIV-uninfected persons.

BACKGROUND: Pneumocystis jirovecii pneumonia (PCP) is a life-threatening infection for immunocompromised individuals. Robust data and clear guidelines are available for prophylaxis and treatment of human immunodeficiency virus (HIV)-related PCP (HIV-PCP), yet few data and no guidelines are available for non-HIV-related PCP (NH-PCP). We postulated that prevention and inpatient management of HIV-PCP differed from NH-PCP. METHODS: We performed a retrospective case review of all pathologically confirmed cases of PCP seen at the University of Alabama Medical Center from 1996 to 2008. Data on clinical presentation, hospital course, and outcome were collected using a standardized data collection instrument. Bivariate analysis compared prophylaxis, adjunctive corticosteroids, and clinical outcomes between patients with HIV-PCP and NH-PCP. RESULTS: Our analysis of the cohort included 97 cases of PCP; 65 HIV and 32 non-HIV cases. Non-HIV cases rarely received primary prophylaxis (4% vs. 38%, P = 0.01) and received appropriate antibiotics later in the course of hospitalization (5.2 days vs. 1.1 days, P < 0.005). Among transplant patients, NH-PCP was diagnosed a mean of 1066 days after transplantation and most patients were on low-dose corticosteroids (87%) at the time of disease onset. No significant differences in adjunctive corticosteroid use (69% vs. 77%, P = 0.39) and 90-day mortality (41% vs. 28%, P = 0.20) were detected. CONCLUSIONS: Patients who have undergone organ or stem cell transplant remain at risk for PCP for many years after transplantation. In our cohort, patients who developed NH-PCP were rarely given prophylaxis, and initiation of appropriate antibiotics was significantly delayed compared to cases of HIV-PCP. Medical providers should be aware of the ongoing risk for NH-PCP, even late after transplantation, and consider more aggressive approaches to both prophylaxis and earlier empirical therapy for PCP.

Orexin receptor antagonism, a new sleep-enabling paradigm: a proof-of-concept clinical trial.

The orexin system is a key regulator of sleep and wakefulness. In a multicenter, double-blind, randomized, placebo-controlled, two-way crossover study, 161 primary insomnia patients received either the dual orexin receptor antagonist almorexant, at 400, 200, 100, or 50 mg in consecutive stages, or placebo on treatment nights at 1-week intervals. The primary end point was sleep efficiency (SE) measured by polysomnography; secondary end points were objective latency to persistent sleep (LPS), wake after sleep onset (WASO), safety, and tolerability. Dose-dependent almorexant effects were observed on SE , LPS , and WASO . SE improved significantly after almorexant 400 mg vs. placebo (mean treatment effect 14.4%; P < 0.001). LPS (­18 min (P = 0.02)) and WASO (­54 min (P < 0.001)) decreased significantly at 400 mg vs. placebo. Adverse-event incidence was dose-related. Almorexant consistently and dose-dependently improved sleep variables. The orexin system may offer a new treatment approach for primary insomnia.

Observational study of the epidemiology and outcomes of vancomycin-resistant Enterococcus bacteraemia treated with newer antimicrobial agents.

Vancomycin-resistant Enterococcus bloodstream infections (VRE-BSI) are a growing problem with few clinical trials to guide therapy. We conducted a retrospective study of management and predictors of mortality for VRE-BSI at a tertiary-care centre from January 2005 to August 2008. Univariate and multivariable analyses examined the relationship of patient characteristics and antibiotic therapy with 30-day all-cause mortality. Rates of VRE-BSI increased from 0·06 to 0·17 infections/1000 patient-days (P=0·03). For 235 patients, 30-day mortality was 34·9%. Patients were primarily treated with linezolid (44·2%) or daptomycin (36·5%). Factors associated with mortality were haemodialysis [odds ratio (OR) 3·2, 95% confidence interval (CI) 1·6-6·3, P=0·007], mechanical ventilation (OR 3·7, 95% CI 1·3-10·4, P=0·01), and malnutrition (OR 2·0, 95% CI 1·0-4·0, P=0·046). Use of linezolid, but not daptomycin (P=0·052) showed a trend towards an association with survival. In conclusion, VRE-BSI is a growing problem, associated with significant 30-day mortality. Multiple factors were associated with poor outcomes at our hospital.

The Double Sensor-A non-invasive device to continuously monitor core temperature in humans on earth and in space.

The objective of our study was to establish whether rectal temperature recordings in humans could be replaced by a non-invasive skin temperature sensor combined with a heat flux sensor (Double Sensor) located at the forehead to monitor core body temperature changes due to circadian rhythms. Rectal and Double Sensor data were collected continuously for 24h in seven men undertaking strict head-down tilt bed-rest. Individual differences between the two techniques varied between -0.72 and +0.55 degrees C. Nonetheless, when temperature data were approximated by cosinor analysis in order to compare circadian rhythm profiles between methods, it was observed that there were no significant differences between mesor, amplitude, and acrophase (P>0.310). It was therefore concluded that the Double Sensor technology is presently not accurate enough for performing single individual core body temperature measurements under resting conditions at normal ambient room temperature. Yet, it seems to be a valid, non-invasive alternative for monitoring circadian rhythm profiles.

[Restless legs syndrome, periodic limb movements, and psychopharmacology]. / Restless-legs-Syndrom, periodische Gliedmassenbewegungen im Schlaf und Psychopharmakologie.

Restless legs syndrome (RLS) and the often associated periodic limb movement disorder in sleep (PLMD) frequently occur in the general population as a primary disorder. In addition to organic disease, secondary forms are caused by psychotropic medication. Several antidepressants, antipsychotics, lithium, and opioid withdrawal have been shown to induce or exacerbate RLS and PLMD, while several antiepileptics used as mood stabilizers and some benzodiazepines demonstrate therapeutic potential for treating RLS/PLMD. Systematic or controlled studies for evaluating these side effects still do not exist. Among the antidepressants at higher risk of inducing this disorder are selective serotonin reuptake inhibitors, venlafaxine, and some tetracyclic antidepressants. Under medication with some tricyclic substances, periodic limb movements were observed more often. For some antidepressants with differing transmitter profiles such as bupropion RLS/PLMD ameliorating effects or at least neutral effects (Trazodon, Nortriptylin) have been described in small studies. In case of continued of or newly occurring insomnia a thorough history should be taken to identify a possible RLS/PLMD as an intolerable side effect of treatment. A change in medications should be considered if clinically feasible. In case of RLS/PLMD occurring in psychotic patients switching the antipsychotic and additionally using a second line medication such as antiepileptics or a benzodiazepine should be considered.

Self-reported empathic abilities in schizophrenia.

BACKGROUND: Increasing evidence indicates impairments of empathic abilities in schizophrenia that may impact outcome and course of the disease. While there is consensus on the presence of deficits in 'theory of mind' in this disorder, i.e. cognitive aspects of mental state attribution, the ability to infer emotional experiences of others, i.e. affective empathy, has not been investigated so far. METHODS: We assessed multiple dimensions of empathy in 45 schizophrenic patients and 45 healthy controls, matched for age and gender, with a self-rating instrument, the Interpersonal Reactivity Index (IRI). To control for modulating effects of cognitive deficits, a neuropsychological test battery was employed. RESULTS: Schizophrenic patients showed significantly lower scores in cognitive empathy ('perspective taking': F=12.176, df=1, p=0.001) but more self-related aversive feelings in response to the distress of others ('personal distress: F=16.477, df=1, p<0.001). Self-ratings of affective empathy, i.e. concern for others, did not differ between groups. Results in the domains of empathy were not explained by symptoms or neurocognition as revealed by regression analysis. However, lower scores in 'perspective taking' were found with advancing duration of illness (r=-0.453, p=0.002). CONCLUSIONS: Results indicate reductions of cognitive empathy but relatively preserved emotional empathic abilities in schizophrenia. Although previous studies observed deficits in emotion perception and expression, our findings support the concept of differentially disturbed abilities in cognitive and emotional empathy in schizophrenia.

Association between cerebral glutamate and human behaviour: the sensation seeking personality trait.

INTRODUCTION: Brain imaging studies have linked the anterior cingulate cortex (ACC) to motivation, drive, and personality traits like novelty and sensation seeking. Animal studies have shown glutamatergic neurotransmission to be important in ACC function as well as motivated behaviour. However, the role of glutamate in related personality traits like sensation seeking has not been investigated in humans. METHODS: The associations between sensation seeking personality scores and absolute glutamate concentrations in the ACC and the hippocampal region measured by 3-Tesla proton magnetic resonance spectroscopy (1H-MRS) were investigated. RESULTS: ACC glutamate concentration was negatively correlated with the sensation seeking sum score and the experience seeking subscore. A weak negative correlation was also observed between the hippocampal glutamate and the sensation seeking sum score. The reexamination of the glutamate concentration after 4 weeks revealed a similar relationship with sensation seeking. DISCUSSION: Although preliminary, the results are in line with the key role of the ACC for motivation and executive control and with the impact of glutamate on novelty related behaviour observed in animal experiments. The role of the hippocampus for novelty processing is discussed. Glutamate measurement with 1H-MRS may facilitate the understanding of biological underpinnings of personality traits and psychiatric diseases associated with dysfunctions in motivation and drive.

Computed tomography of the human pineal gland for study of the sleep-wake rhythm: reproducibility of a semi-quantitative approach.

PURPOSE: To propose a semi-quantitative computed tomography (CT) protocol for determining uncalcified pineal tissue (UCPT), and to evaluate its reproducibility in modification of studies showing that the degree of calcification is a potential marker of deficient melatonin production and may prove an instability marker of circadian rhythm. MATERIAL AND METHODS: Twenty-two pineal gland autopsy specimens were scanned in a skull phantom with different slice thickness twice and the uncalcified tissue visually assessed using a four-point scale. The maximum gland density was measured and its inverse graded on a non-linear four-point scale. The sum of both scores was multiplied by the gland volume to yield the UCPT. The within-subject variance of UCPT was determined and compared between scans of different slice thickness. RESULTS: The UCPT of the first measurement, in arbitrary units, was 39+/-52.5 for 1 mm slice thickness, 44+/-51.1 for 2 mm, 45+/-34.8 for 4 mm, and 84+/-58.0 for 8 mm. Significant differences of within-subject variance of UCPT were found between 1 and 4 mm, 1 and 8 mm, and 2 and 8 mm slice thicknesses (P<0.05). CONCLUSION: A superior reproducibility of the semi-quantitative CT determination of UCPT was found using 1 and 2 mm slice thicknesses. These data support the use of thin slices of 1 and 2 mm. The benefit in reproducibility from thin slices has to be carefully weighted against their considerably higher radiation exposure.

EXAFS study of U(VI) uptake by calcium silicate hydrates.

Among the different cement minerals, calcium silicate hydrates (C-S-H) are the prime candidates for heavy metal binding because of their abundance and appropriate structure. Immobilization processes of heavy metals by cementitious materials, and in particular C-S-H phases, thus play an important role in multibarrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. In this study, the uptake of U(VI) by C-S-H has been investigated using X-ray absorption fine structure (XAFS) spectroscopy. C-S-H phases were synthesized using two different procedures: One is based on the mixing of CaO and SiO2 solids ("direct reaction" method); for the other one starting solutions of Ca and Si are used ("solution reaction" method). XAFS investigations were carried out on samples doped with U(VI). U(VI) was either sorbed onto previously precipitated C-S-H phases (sorption samples) or added during C-S-H synthesis (coprecipitation samples). The coordination environment of U(VI) in the sorption samples was found to be independent of the procedure used for C-S-H synthesis. A split equatorial oxygen shell (Oeq1: R=2.23-2.27 A; Oeq2: R=2.36-2.45 A), neighboring silicon atoms at short (R=3.07-3.11 A) and long (R=3.71-3.77 A) distances, and neighboring Ca atoms (R=3.77-3.81 and 4.15-4.29 A) were observed for all the samples. The structural parameters resemble those reported for uranophane. The coordination environment of U(VI) in the coprecipitation samples depends on the method used for C-S-H synthesis, and further, the spectra differ from those determined for the sorption samples. UU backscattering contributions were observed in the samples prepared using the direct reaction method, whereas no split equatorial shell appeared in the samples prepared using the solution reaction method.