The CLEAR X-ray emission spectrometer available at the CLAESS beamline of ALBA synchrotron.

The CLEAR X-ray emission spectrometer installed at the CLAESS beamline of the ALBA synchrotron is described. It is an energy-dispersive spectrometer based on Rowland circle geometry with 1 m-diameter circle. The energy dispersion is achieved by the combination of a diced analyzer crystal and a unidimensional detector. A single unconventional dynamically bent analyzer crystal (Si 111) permits a wide energy range to be covered, just by exploiting its different reflections (333, 444, 555, 777, 888): 6-22 keV, with a spectrometer efficiency that decreases above 11 keV because of the Si detector thickness (Mythen, 350 µm), while the relative scattering intensities for the Si 333, 444, 555, 777 and 888 reflections correspond to 36, 40, 21, 13 and 15, respectively. The provided energy resolution is typically below 1-2 eV and depends on the beam size, working Bragg angle and reflection exploited. In most cases the energy dispersion ranges from 10 to 20 eV and can be enlarged by working in the out-of-Rowland geometry up to 40 eV. The spectrometer works in full backscattering geometry with the beam passing through the two halves of the analyzer. The vacuum beam path and the particular geometry allow a typical average noise of only 0.5 counts per second per pixel. The spectrometer is mainly used for measuring emission lines and high-resolution absorption spectra, with a typical scanning time for highly concentrated systems of around half an hour, including several repeats. The intrinsic energy dispersion allows systematic collection of resonant X-ray emission maps by measuring high-resolution absorption spectra. Moreover, it allows spectra to be measured on a single-shot basis. Resonant inelastic X-ray scattering experiments to probe electronic excitations are feasible, although the spectrometer is not optimized for this purpose due to the limited energy resolution and scattering geometry provided. In that case, to minimize the quasi-elastic line, the spectrometer is able to rotate along the beam path. Advantages and disadvantages with respect to other existing spectrometers are highlighted.

Immune complexes and persistent high levels of serum vitamin B12.

INTRODUCTION: Patients with persistent high levels of serum vitamin B12 were often referred to Hematology departments. In this study, characteristic of patients with serum vitamin B12 levels higher than 2500 pmol/L (high B12) were studied. METHODS: Prevalence of high B12 was evaluated during a 10-month period. Samples with high B12 were incubated with polyethylene glycol (PEG) and a new measurement of vitamin B12 was carried out using the supernatant. As a pilot study, 26 frozen samples with high B12 were evaluated for changes in vitamin B12 after PEG. Moreover, a prospective study was carried out during three consecutive months. Size exclusion chromatography was employed to demonstrate the presence of immune complexes (ICs) with plasma vitamin B12-binding proteins in some serum samples with high B12. RESULTS: Prevalence of high B12 was 1.3%. Results from 26 frozen samples and from a prospective study (28 cases) showed that undergoing vitamin B12 treatment was the main cause of high B12. However, ICs were detected in 10 frozen samples and in seven cases (25%) of the prospective study, respectively. Serum vitamin B12 decreased to normal values after precipitation with PEG, and size exclusion chromatography confirmed ICs. An association with autoimmune or hematological disorders was observed. CONCLUSIONS: In patients with repeatedly high B12 levels, ICs were detected in approximately 25% of samples. Precipitation with PEG is an easy method to confirm the presence of ICs and to evaluate serum vitamin B12 levels in these patients.

Bronchial plasma exudation after adenosine monophosphate or methacholine challenge.

Nonspecific hyperresponsiveness to adenosine monophosphate is better related to airway inflammation than methacholine. Adenosine induces mast cells and other cells to release inflammatory mediators that produce bronchoconstriction and perhaps other inflammatory effects, such as plasma exudation, which have not been well studied. We compared the plasma exudation effect, as measured in induced sputum, between adenosine and methacholine challenge in healthy and asthmatic subjects. In a cross-over design, 42 subjects were randomly challenged with adenosine or methacholine. After recovery, induced sputum was collected on 2 separate days, 48 to 72 hours apart. In the control group, an additional challenge with saline was performed. Differential cell counts and albumin and alpha2-macroglobulin levels were determined. The sputum volume obtained was sufficient to measure proteins in only 34 subjects: 10 healthy individuals and 24 mild asthmatics. There was a significant difference between adenosine and methacholine in sputum albumin (mean differences: 68[73.4] microg/L in controls, p = 0.039 and 48.0[162.9] microg/L in asthmatics) and cell counts, but only a tendency in alpha2-macroglobulin. PC20 adenosine was better related to eosinophil counts than methacholine (r = -0.44, p = 0.014). Albumin or alpha2-macroglubulin levels were not significantly correlated with baseline FEV1, PC20, or eosinophil counts. Adenosine, but not methacholine challenge, produces a mild airway plasma exudation that does not seem to be relevant to bronchoconstriction. However, this could be relevant, to some supernatant measurements after adenosine challenge.

Optimization of glycemic control by insulin therapy decreases the proportion of small dense LDL particles in diabetic patients.

Small dense LDL particles (B phenotype) are considered to be more atherogenic than large buoyant LDL particles. The influence of glycemic control on LDL particle size and density is still under debate. The aim of this study was to determine LDL subfraction phenotype in both IDDM and NIDDM patients in poor glycemic control compared with that of respective matched control groups. In addition, we evaluated the effect of a 3-month period of optimized glycemic control on this parameter. Thirty-seven IDDM patients and 33 NIDDM patients, together with two respective age-, sex-, and BMI-matched control groups were studied. Non-A phenotype prevalence in IDDM patients before (19%) and after blood glucose optimization (11%) was similar to that of their control group (12%). However, NIDDM patients displayed a higher proportion of the non-A phenotype (51%) than did the control group (28%), but it became closer (30%, P < 0.05) after glycemic control improved. All subjects with non-A phenotype that changed to A phenotype showed triglyceride levels below 1.63 mmol/l and a greater decrease in HbA1c than did subjects whose phenotype did not change (4.9 +/- 1.5 vs. 3.1 +/- 1.4%, P < 0.05). A higher proportion of small dense LDL was observed in NIDDM women than in nondiabetic women (LDL5 10.0 +/- 4.8 vs. 6.3 +/- 1.5%, LDL6 6.1 +/- 2.2 vs. 4.2 +/- 0.8%, P < 0.05) during both stages of glycemic control, but no differences were observed between NIDDM and nondiabetic men. In conclusion, these findings provide new evidence for the relevance of near-normal glycemic control in the prevention of macrovascular disease and could contribute to an explanation of the loss of protection for cardiovascular disease in diabetic women.

[Seasonal variations of lipids and arterial pressure]. / Variación estacional de lípidos y presión arterial.

BACKGROUND: The presence of a seasonal variation in serum lipids and blood pressure is often described in the literature. METHODS: With the aim of analyzing this seasonal influence blood pressure and lipid (total cholesterol and cholesterol corresponding to different lipoprotein, triglycerides and AI and B apolipoprotein families) values were studied over 12 months in 36 normotense healthy males (mean age 36 +/- 6 years), a third of whom presented diverse base lipid alterations. A variance analysis of the relative intraindividual values (to study monthly differences) was carried out and a Student's t test was performed for the absolute values and grouped into two periods (summer and winter) and according to two categories (normal and hyperlipemic). RESULTS: No significant modification was observed in any of the parameters studied with the exception of the intrapersonal variation coefficient of the triglycerides which was significantly higher in the hyperlipemic individuals. CONCLUSIONS: In the population studied no seasonal modification was observed in blood pressure or different lipid concentrations analyzed. The slight variation of temperature observed and the elevated sunstroke in Spain in addition to the youth of the population studied may explain the lack of seasonal variation.