Association of PET-measured myocardial flow reserve with echocardiography-estimated pulmonary artery systolic pressure in patients with hypertrophic cardiomyopathy

BackgroundPulmonary hypertension (PH) is a known complication of HCM and is a strong predictor of mortality. We aim to investigate the relationship between microvascular dysfunction measured by quantitative PET and PH in HCM patients.MethodsEighty-nine symptomatic HCM patients were included in the study. Each patient underwent two 20-min 13N-NH3 dynamic PET scans for rest and stress conditions, respectively. A 2-tissue irreversible compartmental model was used to fit the segments time activity curves for estimating segmental and global myocardial blood flow (MBF) and myocardial flow reserve (MFR). Echocardiographic derived PASP was utilized to estimate PH.ResultsPatients were categorized into two groups across PASP: PH (PASP > 36 mmHg) and no-PH (PASP ≤ 36 mmHg). patients with PH had larger left atrium, ratio of higher inflow early diastole (E) and atrial contraction (A) waves, E/A, and ratio of inflow and peak early diastolic waves, E/e', significantly reduced global stress MBF (1.85 ± 0.52 vs. 2.13 ± 0.56 ml/min/g; p = 0.024) and MFR (2.21 ± 0.57 vs. 2.62 ± 0.75; p = 0.005), while the MBFs at rest between the two groups were similar. There were significant negative correlations between global stress MBF/MFR and PASP (stress MBF: r = -0.23, p = 0.03; MFR: r = -0.32, p = 0.002); for regional MBF and MFR measurements, the highest linear correlation coefficients were observed in the septal wall (stress MBF: r = -0.27, p = 0.01; MFR: r = -0.31, p = 0.003). Global MFR was identified to be independent predictor for PH in multivariate regression analysis.ConclusionEchocardiography-derived PASP is negatively correlated with global MFR measured by 13N-NH3 dynamic PET. Global MFR is suggested to be an index of PH in HCM patients.</div

Cardiosphere-derived cells demonstrate metabolic flexibility that Is influenced by adhesion status

Adult stem cells demonstrate metabolic flexibility that is regulated by cell adhesion status. The authors demonstrate that adherent cells primarily utilize glycolysis, whereas suspended cells rely on oxidative phosphorylation for their ATP needs. Akt phosphorylation transduces adhesion-mediated regulation of energy metabolism, by regulating translocation of glucose transporters (GLUT1) to the cell membrane and thus, cellular glucose uptake and glycolysis. Cell dissociation, a pre-requisite for cell transplantation, leads to energetic stress, which is mediated by Akt dephosphorylation, downregulation of glucose uptake, and glycolysis. They designed hydrogels that promote rapid cell adhesion of encapsulated cells, Akt phosphorylation, restore glycolysis, and cellular ATP levels

Can probability of genetic mutation be an indicator of clinical relevance?

AbstractNPM1 gene mutation evaluated on a population basis is a valuable and realistic tool to reflect the pathophysiological relevance of cancer. In a comparison of the NPM1 cDNA of human bladder cancer with its consensus sequence, we have found that a higher NPM1 sequence identity in a population is consistent with poor tumor differentiation, advanced tumor stage, and likelihood of recurrence. These data imply that “probability” of NPM1 mutation is an indicator of status of malignancy

Simultaneous technetium-99m/thallium-201 SPECT imaging with model-based compensation for cross-contaminating effects

Simultaneous acquisition of dual-isotope SPECT data offers a number of advantages over separately acquired data; however, simultaneous acquisition can result in cross-contamination between isotopes. In this work we propose and evaluate two frameworks for iterative model-based compensation of cross-contamination in dual-isotope SPECT. The methods were applied to cardiac imaging with Technetium-99m-sestamibi and Thallium-201, and they were compared to a subtraction-based compensation method using a cross-talk estimate obtained from an auxiliary energy window. Monte Carlo simulations were performed to carefully study aspects of bias and noise for the methods, and a torso phantom with cardiac insert was used to evaluate the performance of the methods for experimentally acquired data. The cross-talk compensation methods substantially improved lesion contrast and significantly reduced quantitative errors for simultaneously acquired data. Thallium image normalized mean square error (NMSE) was reduced from 0.522 without cross-talk compensation to as low as 0.052 with model-based cross-talk compensation. This is compared to a NMSE of 0.091 for the subtraction-based compensation method. The application of a preliminary model for crosstalk arising from lead fluorescence x-rays and collimator scatter gave promising results, and the future development of a more accurate model for collimator interactions would likely benefit simultaneous Tc/Tl imaging. Model-based compensation methods provide feasible cross-talk compensation in clinically acceptable times, and they may ultimately make simultaneous dual-isotope protocols an effective alternative for many imaging procedures

Analysis of the reconstructibility and noise properties of scattered photons in Tc SPECT

Since scattered photons carry degraded spatial information, scatter is typically considered a source of contamination in SPECT. However, with the advent of scatter modeling methods and reconstruction-based scatter compensation (RBSC), it may be possible to utilize scattered data in a productive manner. In this work we analyze the reconstructibility of scattered photon projection data and investigate the potential for using scattered photons to reduce the noise levels of SPECT images. We have simulated projection data for an elliptical phantom containing three cold rods in a uniform background of Tc-99m activity. A variety of photopeak and scatter energy windows were formed, as well as corresponding RBSC transfer matrices. Each statistically weighted matrix was decomposed using SVD and analyzed in terms of reconstructibility and noise properties. Results indicate that scattered photons contain sufficient information to reconstruct the source activity, but the scatter-only matrices are very poorly conditioned. We have also evaluated several methods of utilizing scattered events via RBSC, and compared them with other, idealized methods of handling scatter. It was found that scattered photons can be used productively when photopeak and non-photopeak data are separated through the use of multiple energy windows. The RBSC methods outperformed ideal scatter subtraction, but fell short of methods which assume perfect discrimination between scattered and primary events. The knowledge gained by this study may help guide future research and lead to better approaches to handling scatter in SPECT

Fast implementations of reconstruction-based scatter compensation in fully 3D SPECT image reconstruction

Accurate scatter compensation in SPECT can be performed by modeling the scatter response function during the reconstruction process. This method is called reconstruction-based scatter compensation (RBSC). It has been shown that RBSC has a number of advantages over other methods of compensating for scatter, but using RBSC for fully 3D compensation has resulted in prohibitively long reconstruction times. In this work we propose two new methods that can be used in conjunction with existing methods to achieve marked reductions in RBSC reconstruction times. The first method, Coarse-Grid Scatter Modeling, significantly accelerates the scatter model by exploiting the fact that scatter is dominated by low frequency information. The second method, Intermittent RBSC, further accelerates the reconstruction process by limiting the number of iterations during which scatter is modeled. The fast implementations were evaluated using a Monte Carlo simulated experiment of the 3D MCAT phantom with Tc-99m tracer, and also using experimentally acquired data with Tl-201 tracer. Results indicated that these fast methods can reconstruct, with fully 3D compensation, images very similar to those obtained using conventional RBSC methods, and in reconstruction times that are an order of magnitude shorter. Using these methods, fully 3D iterative reconstruction with RBSC can be performed well within the realm of clinically realistic times (under 10 minutes for 64 × 64 × 24 image reconstruction)

A covalent p97/VCP ATPase inhibitor can overcome resistance to CB-5083 and NMS-873 in colorectal cancer cells

Small-molecule inhibitors of p97 are useful tools to study p97 function. Human p97 is an important AAA ATPase due to its diverse cellular functions and implication in mediating the turnover of proteins involved in tumorigenesis and virus infections. Multiple p97 inhibitors identified from previous high-throughput screening studies are thiol-reactive compounds targeting Cys522 in the D2 ATP-binding domain. Thus, these findings suggest a potential strategy to develop covalent p97 inhibitors. We first used purified p97 to assay several known covalent kinase inhibitors to determine if they can inhibit ATPase activity. We evaluated their selectivity using our dual reporter cells that can distinguish p97 dependent and independent degradation. We selected a β-nitrostyrene scaffold to further study the structure-activity relationship. In addition, we used p97 structures to design and synthesize analogues of pyrazolo[3,4-d]pyrimidine (PP). We incorporated electrophiles into a PP-like compound 17 (4-amino-1-tert-butyl-3-phenyl pyrazolo[3,4-d]pyrimidine) to generate eight compounds. A selective compound 18 (N-(1-(tert-butyl)-3-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4-yl)acrylamide, PPA) exhibited excellent selectivity in an in vitro ATPase activity assay: IC50 of 0.6 μM, 300 μM, and 100 μM for wild type p97, yeast Cdc48, and N-ethylmaleimide sensitive factor (NSF), respectively. To further examine the importance of Cys522 on the active site pocket during PPA inhibition, C522A and C522T mutants of p97 were purified and shown to increase IC50 values by 100-fold, whereas replacement of Thr532 of yeast Cdc48 with Cysteine decreased the IC50 by 10-fold. The molecular modeling suggested the hydrogen bonds and hydrophobic interactions in addition to the covalent bonding at Cys522 between WT-p97 and PPA. Furthermore, tandem mass spectrometry confirmed formation of a covalent bond between Cys522 and PPA. An anti-proliferation assay indicated that the proliferation of HCT116, HeLa, and RPMI8226 was inhibited by PPA with IC50 of 2.7 μM, 6.1 μM, and 3.4 μM, respectively. In addition, PPA is able to inhibit proliferation of two HCT116 cell lines that are resistant to CB-5083 and NMS-873, respectively. Proteomic analysis of PPA-treated HCT116 revealed Gene Ontology enrichment of known p97 functional pathways such as the protein ubiquitination and the ER to Golgi transport vesicle membrane. In conclusion, we have identified and characterized PPA as a selective covalent p97 inhibitor, which will allow future exploration to improve the potency of p97 inhibitors with different mechanisms of action

Persistent delirium is associated with cerebrospinal fluid markers of neuronal injury

Delirium is associated with the risk of future long-term cognitive impairment, but the degree to which markers of neuronal injury may be distinct or shared with dementia has yet to be comprehensively described. We investigated CSF biomarkers of dementia, astrocytosis and neuronal damage in a clinical cohort with persistent delirium, comparing them with an outpatient memory clinic sample. Our aim was to determine if different patterns of biomarker changes could implicate specific mechanisms for delirium-related neuronal injury over and above that attributable to comorbid dementia. We recruited 35 participants from the Prince of Wales Hospital, Sydney, Australia. We included inpatients with delirium persisting for at least 5 days (n = 15, 10 with underlying dementia) and participants from outpatient memory clinics (n = 20, 17 with dementia). CSF assays were as follows: amyloid-β42, amyloid-β40, phosphorylated tau181, neurofilament light chain and glial fibrillary acidic protein. We used propensity score matching to estimate effect sizes for each standardized CSF biomarker separately for persistent delirium (irrespective of underlying dementia) and dementia (irrespective of superimposed delirium). Compared with individuals without delirium, persistent delirium was associated with elevated glial fibrillary acidic protein (normalized coefficient per transformed standard deviation, β = 0.85; 95% confidence interval: 0.03-1.68) and neurofilament light chain (β = 1.1; 95% confidence interval: 0.5-1.6), but not phosphorylated tau181. Compared with individuals without dementia, glial fibrillary acidic protein, neurofilament light chain and phosphorylated tau181 were all increased to expected levels in dementia cases, with the former two biomarkers at levels comparable to those seen in persistent delirium [glial fibrillary acidic protein (β = 1.54; 95% confidence interval: 1.05-2.0) and neurofilament light chain (β = 0.65; 95% confidence interval: 0.24-1.1)]. Persistent delirium was linked with changes in CSF biomarkers not necessarily attributable to dementia. These findings support the potential that delirium is associated with direct neuronal injury independent of dementia pathophysiology. Whether this neuronal injury involves astrocyte dysfunction or direct axonal damage are both possibilities. Future work examining acute brain injury in delirium is needed.</p