Five energy window scatter correction for 111-In µSPECT

Objectives: In preclinical molecular imaging, large interest exists for absolute quantification, since this would allow for an accurate evaluation of disease progression. Photon scatter is one of the limiting factors for quantitative imaging. This study investigates a scatter correction (SC) method using five energy windows (FEW) for 111In µ-SPECT imaging. 111In can be used for in vivo evaluation of tumor selectivity, and hence the potential therapeutic performance, of a tracer. The monoclonal antibody 14C5, labeled to 111In-DOTA, has shown to be a selective tracer for pancreatic cancer. Methods: Our SC method uses 5 energy windows (EW): a 20% main EW around each photopeak, an 8% scatter EW at both sides of the 171keV photopeak and an 8% scatter EW at the left side of the 245keV photopeak. To evaluate the SC method, measurements were carried out on a U-SPECT-II camera (Milabs). A comparison between reconstructed uncorrected and corrected images was performed for the following parameters: (1) point spread function (PSF) of 1mm Ø cylinders in a resolution phantom; (2) contrast recovery for two 8mm Ø cold spots (air & water) in the small animal NEMA image quality phantom; (3) tumor-to-background ratio of a tumor bearing mouse injected with 111In-DOTA-14C5 . Results: The FEW SC gives rise to a mean improvement of 3.8% of the FWHM of the PSF for the cylinders of the resolution phantom. After SC, contrast improved with 4.3% and 2.8% for respectively the air and water filled cold spot of the NEMA phantom. In the preclinical mouse study, SC leads to a significant enhancement of the tumor-to-background ratio from 6.7 to 9.0. Conclusions: The FEW SC method will offer a significant improvement in the absolute quantification of 111In µ-SPECT images

Regularity and asynchrony when tapping to tactile, auditory and combined pulses

This research is carried out with the aim to develop assistive technology that helps users following the beat in music, which is of interest to cohchlear implant users. The envisioned technology would use tactile feedback on each musical beat. However, this raises fundamental questions about uni- and cross-modal perception which are not addressed in similar context in the literature. The aim of this study was i) to find out how well users are able to follow tactile pulses. ii) To gain insights in the differences between auditory, tactile and combined auditory-tactile feedback. A tapping experiment was organized with 27 subjects. They were requested to tap along with an auditory pulse, a tactile pulse and a combined auditory-tactile pulse in three different tempi. An evaluation with respect to regularity and asynchrony followed. Subjects were found to perform significantly better in terms of reqularity and asynchrony for the auditory and auditory/tactile condition with respect to the tactile only condition. Mean negative asynchrony (MNA) for auditory and combined (auditory and tactile) conditions were in the range of previous studies. The MNA’s for the tactile conditions showed a remarkable dependence on tempo. In the 90BPM condition a clear anticipation (-20ms) was reported, for the 120BPM condition the mean was around zero, the 150BPM condition showed a positive MNA (a reaction vs anticipation). An effect that could be encorporated into the design of an assistive technology

Vitreous silica distends in helium gas: acoustic vs. static compressibilities

Sound velocities of vitreous silica are measured under He compression in the pressure range 0-6 GPa by Brillouin light scattering. It is found that the well-known anomalous maximum in the pressure dependence of the compressibility is suppressed by He incorporation into the silica network. This shows that the elastic anomaly relates to the collapse of the largest interstitial voids in the structure. The huge difference between the static and the acoustic compressibilities indicates that the amount of incorporated helium still increases at 6 GPa.Comment: 5 pages, 4 figure

Highlights from the HIV Cure and Reservoir Symposium, 11-12 September 2017, Ghent, Belgium

For the second time, the HIV Cure Research Center (HCRC) at Ghent University organised the HIV Cure and Reservoir Symposium, in Ghent, Belgium, where in this two-day conference, virologists, molecular biologists, immunologists and clinicians presented the most recent achievements in the field of HIV cure, including data on therapeutic vaccines, HIV remission strategies such as 'shock and kill' or 'block and lock', benefits of early ART and potential of haematopoietic stem cell transplant in achieving cure. Furthermore, methods to characterise and quantify the HIV reservoir were discussed along with HIV reservoir characterisation in different body parts, including the central nervous system. An HIV activist and representative of a patients' agency also presented the patients' perspective on HIV cure. This report is a summary of all topics discussed during this symposium

FabR regulates Salmonella biofilm formation via its direct target FabB

Background: Biofilm formation is an important survival strategy of Salmonella in all environments. By mutant screening, we showed a knock-out mutant of fabR, encoding a repressor of unsaturated fatty acid biosynthesis (UFA), to have impaired biofilm formation. In order to unravel how this regulator impinges on Salmonella biofilm formation, we aimed at elucidating the S. Typhimurium FabR regulon. Hereto, we applied a combinatorial high-throughput approach, combining ChIP-chip with transcriptomics. Results: All the previously identified E. coli FabR transcriptional target genes (fabA, fabB and yqfA) were shown to be direct S. Typhimurium FabR targets as well. As we found a fabB overexpressing strain to partly mimic the biofilm defect of the fabR mutant, the effect of FabR on biofilms can be attributed at least partly to FabB, which plays a key role in UFA biosynthesis. Additionally, ChIP-chip identified a number of novel direct FabR targets (the intergenic regions between hpaR/hpaG and ddg/ydfZ) and yet putative direct targets (i.a. genes involved in tRNA metabolism, ribosome synthesis and translation). Next to UFA biosynthesis, a number of these direct targets and other indirect targets identified by transcriptomics (e.g. ribosomal genes, ompA, ompC, ompX, osmB, osmC, sseI), could possibly contribute to the effect of FabR on biofilm formation. Conclusion: Overall, our results point at the importance of FabR and UFA biosynthesis in Salmonella biofilm formation and their role as potential targets for biofilm inhibitory strategies

Underestimated effect of intragenic HIV-1 DNA methylation on viral transcription in infected individuals

Background: The HIV-1 proviral genome harbors multiple CpG islands (CpGIs), both in the promoter and intragenic regions. DNA methylation in the promoter region has been shown to be heavily involved in HIV-1 latency regulation in cultured cells. However, its exact role in proviral transcriptional regulation in infected individuals is poorly understood or characterized. Moreover, methylation at intragenic CpGIs has never been studied in depth. Results: A large, well-characterized HIV-1 patient cohort (n = 72), consisting of 17 long-term non-progressors and 8 recent seroconverters (SRCV) without combination antiretroviral therapy (cART), 15 early cART-treated, and 32 late cART-treated patients, was analyzed using a next-generation bisulfite sequencing DNA methylation method. In general, we observed low level of promoter methylation and higher levels of intragenic methylation. Additionally, SRCV showed increased promoter methylation and decreased intragenic methylation compared with the other patient groups. This data indicates that increased intragenic methylation could be involved in proviral transcriptional regulation. Conclusions: Contrasting in vitro studies, our results indicate that intragenic hypermethylation of HIV-1 proviral DNA is an underestimated factor in viral control in HIV-1-infected individuals, showing the importance of analyzing the complete proviral genome in future DNA methylation studies

Noninvasive assessment of reperfusion and reocclusion after thrombolysis in acute myocardial infarction.

The clinical significance of ST-segment changes and of the time course of appearance in serum of different cardiac proteins has been reviewed for the diagnosis of coronary reperfusion and reocclusion after thrombolysis. In particular, the value of serial 12-lead electrocardiographic (ECG) studies, of Holter monitoring, and of continuous multilead computer-assisted ECG monitoring is compared. Regarding the serum proteins, the clinical significance of reperfusion indices described so far for serum creatine kinase (CK), its isoenzyme serum creatinine kinase MB, the CK isoforms, and myoglobin is reviewed. Emphasis is placed on (1) the calculation method used for deriving the reperfusion indices; (2) the sensitivity and the specificity of the reperfusion indices; (3) the minimum turn-around time needed to produce the reperfusion indices (depending on the practicability of the analytical and calculation methods and their applicability in an em

Climate driven trends in tree biomass increment show asynchronous dependence on tree-ring width and wood density variation

Tree growth is a key ecosystem function supporting climate change mitigation strategies. However climate change may induce feedbacks on radial growth and wood density, affecting the carbon sequestration capacity of forests. Using a mixed modeling technique long-term trends in radial growth, wood density and above-ground biomass, defined as the product of the annual basal area growth with the wood density, of common beech (Fagus sylvatica) and sessile oak (Quercus petraea) in the Belgian Ardennes, were determined and explained using climate drivers of change. This modeling strategy allowed us to determine if the same conclusions can be drawn when only BAI is considered, as is assumed in most carbon sequestration studies, when looking at long-term trends in carbon sequestration. The models indicate that above-ground biomass increment changes over time are more driven by changes in radial growth than by changes in wood density. Nevertheless, the assumption of constant wood density in most carbon sequestration studies is incorrect. Ignoring wood density results in an underestimation of long-term trends in above-ground biomass increment for beech, and an overestimation of above-ground biomass increment for oak. Interesting is that radial growth is mostly driven by climate variables of the current year, whereas wood density is more driven by the climate variables of the previous year. Beech radial growth and wood density is found to be negatively influenced by drought and positively by water availability. Oak radial growth and wood density is negatively affected by late frost and positively by water availability. The findings of this study suggest that radial growth in combination with wood density should be used in carbon sequestration studies as different climate driven long-term trends in radial growth and wood density are found