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The ever increasing interest in surface analysis techniques with excellent depth resolution, great detection sensitivity, and good throughput has been a driving force for development of dynamic secondary ion mass spectrometry using low energy primary beams. This work investigated sputtering erosion of Si and emission of secondary ions from Si bombarded by sub-keV O2+ beams at glancing incidence. It was demonstrated that surface roughening remained minimal for 250 and 500 eV O2+ beams at an angle of incidence above 80° but developed rapidly at angles between 60° and 80°. The depth resolution for B and Ge appeared very different at the glancing incidence and changed dramatically in opposite ways as the angle of incidence decreased. The difference in the depth resolution was explained by the different diffusion/segregation behavior between B and Ge during O2+ bombardment. In general, the use of sub-keV O2+ beams at the glancing incidence (above 80°) favored a thinner altered layer, a short surface transient, a minimal apparent shift in depth profiles, a better depth resolution (not for B in Si), a good sputter rate, but a poor yield of the positive secondary ions. To address the issues with the low ion yield, we identified optimal cluster ions for common dopant such as boron and nitrogen. Good sensitivity was achieved for analyses of boron in Si by detecting BO2- as the characteristic secondary ion. A parallel study published elsewhere suggested SiN- as an ideal candidate for detection of nitrogen in ultrathin oxynitride [Z. X. Jiang et al., Surf. Interface Anal. (in press)]. For analyses of thin SiGe films in Si at glancing incidence, detection of Ge+ provided fairly good sensitivity. Applications of an O2+ beam at 250 eV 83° for analyses of shallow boron implant demonstrated superior accuracy in the measured near-surface boron distribution. Also the characterization of thin SiGe films exhibited excellent depth resolving power for Ge in Si although the ion yield of Ge+ was low. [ABSTRACT FROM AUTHOR]

The host's intestinal microbiota contributes to endocrine and metabolic responses, but a dysbiosis in this environment can lead to obesity and insulin resistance. Recent work has demonstrated a role for microbial metabolites in the regulation of gut hormones, including the metabolic hormone, glucagon-like peptide-1 (GLP-1). Muramyl dipeptide (MDP) is a bacterial cell wall component which has been shown to improve insulin sensitivity and glucose tolerance in diet-induced obese mice by acting through the nucleotide oligomerization domain 2 (NOD2) receptor. The purpose of this study was to understand the effects of MDP on GLP-1 secretion and glucose regulation. We hypothesized that MDP enhances glucose tolerance by inducing intestinal GLP-1 secretion through NOD2 activation. First, we observed a significant increase in GLP-1 secretion when murine and human L-cells were treated with a fatty acid MDP derivative (L18-MDP). Importantly, we demonstrated the expression of the NOD2 receptor in mouse intestine and in L-cells. In mice, two intraperitoneal injections of MDP (5 mg/kg body weight) caused a significant increase in fasting total GLP-1 in chow-fed mice, however this did not lead to an improvement in oral glucose tolerance. When mice were exposed to a high-fat diet, they eventually lost this MDP-induced GLP-1 release. Finally, we demonstrated in L-cells that hyperglycemic conditions reduce the mRNA expression of NOD2 and GLP-1. Together these findings suggest MDP may play a role in enhancing GLP-1 during normal glycemic conditions but loses its ability to do so in hyperglycemia.

Background: Pulmonary valve replacement (PVR) is a common operation in patients with congenital heart disease (CHD). As survival with CHD improves, infective endocarditis (IE) is a growing complication after PVR. The aim of this study was to assess the incidence, risk factors, and clinical outcomes of IE after surgical PVR in patients with CHD at our institution., Methods: Retrospective analysis of all cases of surgical PVR performed at Children's Hospital of Wisconsin between 1975 and 2016 was performed. All cases of IE after PVR were identified and clinical and imaging data were obtained by review of medical records., Results: Out of 924 surgical PVRs, there were 19 (2%) cases of IE. The incidence of IE after surgical PVR was 333 cases per 100,000 person-years. The median age at diagnosis of IE was 21 years (range = 1.2-34 years) and the median time from PVR to diagnosis of IE was 9.4 years. The overall freedom from IE after PVR was 99.1%, 96.9%, and 93.4%, at 5, 10, and 15 years, respectively. There was no significant difference in freedom from IE based on valve type, including bovine jugular vein grafts. Patients with IE were more likely to have had a history of multiple PVRs, while length of follow-up after PVR, age at time of PVR, and gender were not significant risk factors. Eleven (58%) cases of IE required surgical intervention, while 8 (42%) were successfully treated with intravenous antibiotics alone. There were no deaths and no recurrences of IE after treatment., Conclusion: The overall risk for IE after PVR is low. There was no association between age or type of pulmonary valve and risk of IE. The majority of cases require surgical intervention, but in general the outcomes of IE after PVR are good with low mortality and risk of recurrence., (© 2018 Wiley Periodicals, Inc.)

Poly(A)+ mRNA from mouse hepatoma ascites cell cytoplasm is characterized by three frequency classes: an abundant frequency class of a limited number of different nucleotide sequences, a less abundant frequency class of a larger number of different nucleotide sequences, and a rare frequency class containing a high number of different nucleotide sequences. [3H]cDNA synthesized on this poly(A)+ mRNA template hybridizes with some of the DNAs of the putative transcribable euchromatin fraction at a significantly faster rate than with total DNA if residual contaminating RNA is not removed. Following NaOH incubation to remove such RNA, the cDNA probe hybridized with essentially the same rate to the euchromatin fractions and total DNA. Nick translation of the nuclease-sensitive sequences of chromatin demonstrated that, even with limited nuclease digestion, the excised sequences rapidly converted to small oligonucleotides. The nick-translatable, small chromatin segments showed no enrichment for transcribable sequences. Chromatin segments, which distribute to the 50S-70S glycerol gradient fractions and which satisfy several of the presumptive criteria for enrichment for transcribable sequences, therefore show no enrichment for sequences complementary to the cDNA for poly(A)+ mRNA.