Bandwidth correction for LED chromaticity

The spectral bandwidth formulae of Stearns and Stearns   are generalized for an arbitrary slit function. Correction coefficients are derived in terms of moments of the slit function. Application to model LED spectra measured with a compact, fiber‐coupled spectrometer having bandwidth of order 12 nm, and a nonlinear wavelength scale shows that accurate LED color measurements may be obtained with such an instrument. Fitting of the relatively broad slit function to line spectra for accurate wavelength calibration is also described. Such fitting, coupled consistently with the bandpass correction, improves the accuracy color measurements with a broad‐response spectrometer. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 374–380, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20242     

Isoproterenol evokes extracellular Ca2+ spikes due to secretory events in salivary gland cells

Secretory cells should in principle export substantial amounts of calcium via exocytosis since Ca2+ is sequestered in secretory granules. Based on a new technique for measurements of the extracellular calcium concentration in the vicinity of the cell membrane and on the droplet technique, we have monitored the rate of calcium extrusion from salivary gland acinar cells. Isoproterenol (ISP), a beta-adrenergic agonist and powerful secretogogue, evoked no change in the cytosolic free Ca2+ concentration ([Ca2+]i) but induced vigorous extracellular Ca2+ concentration ([Ca2+]i) spiking. The absence of [Ca2+]i elevation and the pulsatile nature of the changes in [Ca2+]i indicate that these spikes are most likely due to calcium release from secretory granules. The cholinergic agonist acetylcholine (ACh), which induces moderate secretion, evoked a marked rise in [Ca2+]i and a smooth rise in [Ca2+]i, most likely induced by plasma membrane calcium pumps, on which shortlasting [Ca2+]i spikes were superimposed. The rate of ISP-induced calcium efflux was very substantial. The calculated calcium loss during the first 100 s of supramaximal stimulation corresponded to a reduction of the total cellular calcium concentration of approximately 0.4 mM. We conclude that in salivary glands, calcium release via exocytosis is one of the main mechanisms extruding calcium from cells to the extracellular milieu.     

Effect of allowing for ethnic group in prenatal screening for Down's syndrome

We conducted a study to investigate ethnic group differences in levels of serum markers used in screening for Down's syndrome [serum alpha-fetoprotein (AFP), unconjugated oestriol (uE3), total human chorionic gonadotrophin (hCG), free alpha- and free beta-hCG, and dimeric inhibin-A], to estimate the extent to which maternal weight differences between ethnic groups explain these differences, and to estimate the effect of adjusting for ethnic group and maternal weight on screening performance. Serum measurements were taken from women who were screened prenatally for Down's syndrome. AFP, uE3, and hCG concentrations were available from 9462 white, 4215 black, and 4392 South Asian women with singleton pregnancies without Down's syndrome or neural tube defects between 15 and 22 weeks' gestational age. Frozen serum samples were available from a subset of 922 white, 449 black, and 135 South Asian women and were used for measurement of free alpha-hCG, free beta-hCG, and inhibin. Values were expressed as multiples of the median (MOM) for women of the same gestational age. There were statistically significant differences in the serum marker levels between ethnic groups that were not explained by differences in maternal weight. The main differences were found in black women compared with white women; black women had serum AFP levels 22 per cent higher (95 per cent confidence interval 20-24 per cent), total hCG levels 19 per cent higher (16-22 per cent), and free beta-hCG levels 12 per cent (3-21 per cent) higher. The other differences were less than 10 per cent. Adjusting for ethnic group only had a small estimated effect on screening performance: a maximum of about 0.5 per cent extra detection at a 5 per cent false-positive rate. At a fixed risk cut-off level, the false-positive rate will not be materially different between different ethnic groups. Adjusting serum markers for ethnic groups improves Down's syndrome screening performance to a very small extent. It is worthwhile because of its established value in AFP screening for open neural tube defects.     

Global folds of highly deuterated, methyl-protonated proteins by multidimensional NMR

The development of 15N, 13C, 2H multidimensional NMR spectroscopy has facilitated the assignment of backbone and side chain resonances of proteins and protein complexes with molecular masses of over 30 kDa. The success of these methods has been achieved through the production of highly deuterated proteins; replacing carbon-bound protons with deuterons significantly improves the sensitivity of many of the experiments used in chemical shift assignment. Unfortunately, uniform deuteration also radically depletes the number of interproton distance restraints available for structure determination, degrading the quality of the resulting structures. Here we describe an approach for improving the precision and accuracy of global folds determined from highly deuterated proteins through the use of deuterated, selectively methyl-protonated samples. This labeling profile maintains the efficiency of triple-resonance NMR experiments while retaining a sufficient number of protons at locations where they can be used to establish NOE-based contacts between different elements of secondary structure. We evaluate how this deuteration scheme affects the sensitivity and resolution of experiments used to assign 15N, 13C, and 1H chemical shifts and interproton NOEs. This approach is tested experimentally on a 14 kDa SH2/phosphopeptide complex, and a global protein fold is obtained from a set of methyl-methyl, methyl-NH, and NH-NH distance restraints. We demonstrate that the inclusion of methyl-NH and methyl-methyl distance restraints greatly improves the precision and accuracy of structures relative to those generated with only NH-NH distance restraints. Finally, we examine the general applicability of this approach by determining the structures of several proteins with molecular masses of up to 40 kDa from simulated distance and dihedral angle restraint tables.     

Estimation of foetal brain dose from I-131 in the foetal thyroid

The ingestion of I-131 by pregnant women can have consequences for the developing foetus, in particular brain function. As the foetal thyroid accumulates iodine from the twelfth week of gestation onwards, the determination of foetal brain dose resulting from such I-131 accumulation is essential. Normal dosimetric methods fail to treat the case of foetus. Using an approximation method based on the MIRD approach, a foetal dose estimation scheme is developed to allow the determination of foetal brain dose from foetal thyroid irradiation. Dose values are obtained for the foetus based on the maternal intake of I-131. It was found that the choice of biokinetic model for the mother/foetus has a large impact on the determined dose estimate.     

Hematopoietic precursor cell exhaustion is a cause of proliferative defect in primitive hematopoietic stem cells (PHSC) after chemotherapy

The aim of the present study is to determine the possibility of measuring the bone mineral density (BMD) around implants by dual energy X-ray absorptiometry (DEXA). Therefore, the trabecular BMD was measured close to 127-600 microns and at a distance from various uncoated and Ca-P-coated implants inserted into the femoral condyle of goals. The implants were left in situ for 12 weeks. In addition, the bone-implant interface was evaluated histologically. For comparative reasons the BMD of non-implanted lateral and medial femoral condyles was also measured. The reproducibility of the measurements, expressed as a coefficient of variation, was found to be 0.44%. Moreover, the regions closest to the implants exhibited a higher BMD than all other regions, and the regions located in the medial condyle showed a higher BMD than the lateral condylar regions. Although the histological sections of the implants in the medial condyle demonstrated more bone contact with the coated than with the uncoated implants, a higher density was measured around the uncoated implants. The results regarding the non-implanted condyles indicated a higher density in the medial than in the lateral condyle. In view of these results, we conclude that BMD around dental implants depends on the location of the implant and that DEXA appears to be an excellent tool for analysing bone-implant reactions.     

Double coupling Edman chemistry for high-sensitivity automated protein sequencing

Capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) is a promising new method for the analysis of protein sequencing products. It gives 10 zmol (1 zmol = 10(-21) mol) limits of detection (3 sigma) for fluorescein thiohydantoin (FTH) amino acids. We have developed a separation for the (FTH)-amino acid products generated from 18 of the 20 coded amino acids. The extremely low volume requirement associated with CE-LIF makes it incompatible with commercial sequencers. For this reason, we have also been developing a miniaturized sequencer that can be more easily coupled to our detection system. Both the CE-LIF system and the miniaturized sequencer are described.     

Factors related to rehospitalization within thirty days of discharge after coronary artery bypass grafting

BACKGROUND: Early rehospitalization after coronary artery bypass grafting (CABG) is an expensive and frequently adverse outcome. Rehospitalization rates after various surgical procedures have been used as an indicator of quality of care. Determining the extent to which rehospitalization rates reflect patient case mix and severity of illness rather than quality of care requires detailed information regarding the patients, the care they received, and the reasons for their rehospitalization. METHODS: We conducted a nested case control study comparing 110 CABG patients who were rehospitalized within 30 days after discharge with 224 control patients. Control patients were randomly selected from patients undergoing CABG during the same time frame as the cases and were matched on age, gender, and priority of surgery. A detailed chart review provided information regarding treatment in the postsurgical period, in addition to the preoperative information collected on all CABG patients as part of an ongoing regional prospective study. RESULTS: The overall rehospitalization rate was 13.8%. The most common reasons for rehospitalization included: wound infection (19%), atrial fibrillation (13%), pleural effusion (11%), and thromboembolic event (10%). Preoperative severity of illness and comorbidity accounted for 24% of the total variance. After adjustment for these factors, discharge hematocrit less than 30% (OR = 2.01, p = 0.018) and several discharge medications including: antiarrhythmics (OR = 3.26, p = 0.047), diuretics (OR = 2.18, p = 0.055), beta blockers (OR = 0.44, p = 0.036), and long length of stay (more than 7 days; OR = 2.09, p = 0.029) were the most important predictors of rehospitalization risk. CONCLUSIONS: Although the reasons for rehospitalization after CABG are heterogeneous and related to patient severity of illness as well as comorbid status, several of the most common are potentially preventable and related to quality of care. Rehospitalization was not related to early discharge.