Effect of bile salts on lactosylceramide beta-galactosidase activities in human brain, liver and cultured skin fibroblasts

The effect of bile salts on the hydrolysis of lactosylcermide by human beta-galactosidases in vitro was studied using cultured skin fibroblasts, liver and brain tissue. The evidence for two distinct enzymes that can catalyze the hydrolysis of lactosylceramide was observed when the bile salt was changed from pure sodium taurocholate to either crude taurocholate, or pure glycodeoxycholate, taurodeoxycholate or taurochenodeoxycholate. Tissues from patients with Krabbe's disease were found to be deficient in lactosylceramide beta-galactosidase activity (lactosylceramidase I) when pure taurocholate was used in the assay. When crude taurocholate was used in the assay, the Krabbe patients appeared to have normal activity for this enzyme. In place of crude taurocholate the pure salts of glycodeoxycholate, taurodeoxycholate and taurochenodeoxycholate worked even better to stimulate the second lactosylceramide beta-galactosidase activity and GM1 gangliosidosis patients exhibiting little if any activity. Therefore, lactosylcermidase I is stimulated by crude taurocholate or pure glycodeoxycholate, taurodeoxycholate and taurochenodeoxycholate. The use of pure bile salts to assay lactosylceramidase I and II will result in better reproducibility for these enzyme activities between laboratories.     

Tailoring the properties of quantum dotmicropillars by ultrafast optical injection of free charge carriers

We review recent studies of cavity switching induced by the optical injection of free carriers in micropillar cavities containing quantum dots. Using the quantu...     

Mitigation methods for errors in oxygen measurement with redox cycling of materials for hydrogen and syngas production

In the search for new and improved materials for hydrogen and syngas production by solar thermochemical looping, test-reactors are employed which include a temperature controlled sample chamber and adjustable gas flows through or past the sample. The experiments performed in these devices enable researchers to find limiting factors like mass transfer, heat transfer, kinetics, and material durability in a time and cost efficient manner. The devices have proven their utility by their near universal employment by groups seeking and studying new materials. A review of past studies has revealed that the measurement of oxygen partial pressure during the reduction state is key to the evaluation of material productivity, yet the methods for this measurement are varied across different publications and are often given little focus. The majority of O₂ sensing is achieved using a mass spectrometer or gas chromatograph, inferring behavior at the sample from measurements of gas that has traveled for some distance and time. In this paper, we investigate the potential errors which may be introduced by taking a single measurement of oxygen production at the system outlet to infer O₂ production curves, and demonstrate some methods to correct this. We also investigate some of the issues related to including an oxygen sensor near the sample. Issues discussed include temporal delays between sensors, oxygen leakage, sensing an incompletely mixed flow, diffusion, and mixing downstream from the sample. Oxygen entering the system through inlet gas or leakage accounted for the largest source of error, but these errors can be corrected by straightforward methods. Numerical simulations are employed to investigate the mixing of the flow, while diffusion is estimated with an analytical model. During an example experiment, the applied correction methods reduced differences between two sensors' data from 20% to 7%, while the corrections led to a 36% change in calculated total oxygen production from raw to corrected data.     

Non-uniform attenuation correction for myocardial SPET using two Gd-153 line sources

AIM: This study deals with the effect of the non-uniform attenuation correction method on myocardial tomograms of normal subjects. METHOD: A total of 35 patients (20 female, 15 male) without evidence of cardiac disease underwent SPET with and without attenuation correction using a dual head camera and transmission data obtained by two scanning Gd-153 line sources after administration of 400 MBq Tc-99m-tetrofosmin RESULTS: In non-corrected (NC) stress studies the lowest count rates were found in the inferior segments with mean differences in count rates between maxima and minima of 35.8 +/- 10.8%. In attenuation corrected (AC) images the respective segmental differences averaged only 20.9 +/- 3.3% and the images did not show significant count deficiency in the inferior segments. The effects of correction revealed to be sex dependent, but independent of body mass on average. CONCLUSION: AC using the above technique significantly reduces the variability of count rate distribution in normal subjects and improves the preconditions for accurate diagnostic evaluation of coronary artery disease using SPET.     

Meningitis caused by Streptococcus bovis

Streptococcus bovis was isolated from the CSF of a 66-year-old man with meningitis. His clinical appearance was unusual in that he lacked typical signs and symptoms of pyogenic meningitis. Streptococcus bovis was also recovered from his blood, which suggested that bacterial endocarditis was the source of his CNS infection. He was cured after four weeks of therapy with intravenous penicillin G potassium. This is the fourth reported case of meningitis caused by S bovis. The previous three patients also had endocarditis caused by S bovis. Because of the reported propensity of S bovis to infect heart valves and the frequent association of S bovis bacteremia with malignant gastrointestinal (GI) tract tumors, recovery of this organism form CSF should prompt a search for bacterial endocarditis and occult GI cancer.     

Cytochrome P-450 induction by phenobarbital and 3-methylcholanthrene in primary cultures of hepatocytes

The characteristic hepatocellular changes resulting from phenobarbital administration in vivo, namely an increase in the levels of cytochrome P-450 and proliferation of membranes of the smooth endoplasmic reticulum, have been demonstrated in primary cultures of nonreplicating hepatocytes on floating collagen membranes. Addition of methylcholanthrene to the medium resulted in an increase in cytochrome P-448 within 48 hours, whereas the phenobarbital induction of P-450 required 5 days. These results demonstrate that responses induced in adult liver cells in vivo by phenobarbital can be reporoduced in cultured hepatocytes, contrary to previous reports.     

耶稣之心教堂,慕尼黑

一直到1980年代,使教堂建筑世俗化的努力,使得教堂建筑放弃了自身的主导地位,而和原有的普通建筑结合,建成多功能教区中心,这使许多教堂不再是城市的标志性建筑.今天,我们看到一种力求恢复教堂神圣感的反向潮流.从这个意义上讲,这座教堂是一个不同凡响的工程.尽管这是一栋“单纯”的教堂,它的外形一点都不符合这类建筑的特点：它犹如一个玻璃盒,或是一个飞机库,特别是它那巨大的大门.神圣气氛主要在教堂内营造,并通过光线的照射来强化.建筑师设计了一个“屋中屋”的结构.外部是玻璃幕墙,建筑的透明度从大门到圣坛后墙逐渐递减.大门由432块蓝色玻璃格窗组成刻有圣约翰所描绘的耶稣受难文字,采用怀旧的楔形字体书写.内室由木板条围成,并通过回廊分割.木板条交错布局的方式使更强的光线射到圣坛上.     

Investigating the state-of-the-art in whole-body MR-based attenuation correction: an intra-individual,inter-system,inventory study on three clinical PET/MR systems

Objective

We assess inter- and intra-subject variability of magnetic resonance (MR)-based attenuation maps (MRμMaps) of human subjects for state-of-the-art positron emission tomography (PET)/MR imaging systems.

Materials and methods

Four healthy male subjects underwent repeated MR imaging with a Siemens Biograph mMR, Philips Ingenuity TF and GE SIGNA PET/MR system using product-specific MR sequences and image processing algorithms for generating MRμMaps. Total lung volumes and mean attenuation values in nine thoracic reference regions were calculated. Linear regression was used for comparing lung volumes on MRμMaps. Intra- and inter-system variability was investigated using a mixed effects model.

Results

Intra-system variability was seen for the lung volume of some subjects, (p = 0.29). Mean attenuation values across subjects were significantly different (p < 0.001) due to different segmentations of the trachea. Differences in the attenuation values caused noticeable intra-individual and inter-system differences that translated into a subsequent bias of the corrected PET activity values, as verified by independent simulations.

Conclusion

Significant differences of MRμMaps generated for the same subjects but different PET/MR systems resulted in differences in attenuation correction factors, particularly in the thorax. These differences currently limit the quantitative use of PET/MR in multi-center imaging studies.