A quantitative study of the pixel-shifting,blurring and nonlinear distortions in MRI images caused by the presence of metal implants

Magnetic resonance imaging has found an increasing number of medical applications in recent years due to its technical merits as well as its non-invasive nature. However, its full potential has been severely limited by magnetic susceptibility difference artefacts caused by the presence of ferromagnetic sources such as orthopedic implants, dental work or metallic needles used in neurosurgery. In this study, we propose a method to numerically quantify the distortions resulting from the magnetic susceptibility differences by investigating the phenomena from three perspectives: (1) pixel displacement, (2) blurring and (3) nonlinearity. For this purpose, phantom images obtained from a magnetic resonance scanner were studied. Attempts made to reconstruct an ideal image from its distorted version by appropriately compensating for the three types of distortions yielded encouraging results.     

A density functional theory study on silver and bis-silver complexes with lighter tetrylene: are silver and bis-silver carbenes candidates for SARS-CoV-2 inhibition? Insight from molecular docking simulation

Ribavirin and remdesivir have been preclinically reported as potential drugs for the treatment of SARS-CoV-2 infection, while light silver tetrylene complexes (NHE_Ph–AgCl and (NHE_Ph–AgCl)₂ with E = C, Si, and Ge) have gained significant interest due to their promising applicability on the cytological scale. Firstly, the structures and bonding states of silver–tetrylene complexes (NHE–Ag) and bis-silver–tetrylene complexes (NHE–Ag-bis) were investigated using density functional theory (DFT) at the BP86 level with the def2-SVP and def2-TZVPP basis sets. Secondly, the inhibitory capabilities of the carbene complexes (NHC–Ag and NHC–Ag-bis) and the two potential drugs (ribavirin and remdesivir) on human-protein ACE2 and SARS-CoV-2 protease PDB6LU7 were evaluated using molecular docking simulation. The carbene ligand NHC bonds in a head-on configuration with AgCl and (AgCl)₂, whereas, the other NHE (E = Si and Ge) tetrylene ligands bond in a side-on mode to the metal fragments. The bond dissociation energy (BDE) of the NHE–Ag bond in the complex families follows the order of NHC–Ag > NHSi–Ag > NHGe–Ag and NHSi–Ag-bis > NHGe–Ag-bis > NHC–Ag-bis. The natural bond orbital analysis implies that the [NHE_Ph→AgCl] and [(NHE_Ph)₂→(AgCl)₂] donations are derived mainly from the σ- and π-contributions of the ligands. The docking results indicate that both the ACE2 and PDB6LU7 proteins are strongly inhibited by silver–carbene NHC–Ag, bis-silver–carbene NHC–Ag-bis, ribavirin, and remdesivir with the docking score energy values varying from −17.5 to −16.5 kcal mol⁻¹ and −16.9 to −16.6 kcal mol⁻¹, respectively. The root-mean-square deviation values were recorded to be less than 2 Å in all the calculated systems. Thus, the present study suggests that silver–carbene NHC–Ag and bis-silver–carbene NHC–Ag-bis complexes are potential candidates to inhibit ACE2 and PDB6LU7, and thus potentially conducive to prevent infection caused by the SARS-CoV-2 virus.

Simultaneous inhibition of silver–carbene complexes to ACE2 and PDB6LU7 is conducive for the prevention of SARS-CoV-2 infection: a virtual prediction.     

Genetic and Environmental Variances of Bone Microarchitecture and Bone Remodeling Markers: A Twin Study

All genetic and environmental factors contributing to differences in bone structure between individuals mediate their effects through the final common cellular pathway of bone modeling and remodeling. We hypothesized that genetic factors account for most of the population variance of cortical and trabecular microstructure, in particular intracortical porosity and medullary size – void volumes (porosity), which establish the internal bone surface areas or interfaces upon which modeling and remodeling deposit or remove bone to configure bone microarchitecture. Microarchitecture of the distal tibia and distal radius and remodeling markers were measured for 95 monozygotic (MZ) and 66 dizygotic (DZ) white female twin pairs aged 40 to 61 years. Images obtained using high‐resolution peripheral quantitative computed tomography were analyzed using StrAx1.0, a nonthreshold‐based software that quantifies cortical matrix and porosity. Genetic and environmental components of variance were estimated under the assumptions of the classic twin model. The data were consistent with the proportion of variance accounted for by genetic factors being: 72% to 81% (standard errors ～18%) for the distal tibial total, cortical, and medullary cross‐sectional area (CSA); 67% and 61% for total cortical porosity, before and after adjusting for total CSA, respectively; 51% for trabecular volumetric bone mineral density (vBMD; all p < 0.001). For the corresponding distal radius traits, genetic factors accounted for 47% to 68% of the variance (all p ≤ 0.001). Cross‐twin cross‐trait correlations between tibial cortical porosity and medullary CSA were higher for MZ (r_MZ = 0.49) than DZ (r_DZ = 0.27) pairs before (p = 0.024), but not after (p = 0.258), adjusting for total CSA. For the remodeling markers, the data were consistent with genetic factors accounting for 55% to 62% of the variance. We infer that middle‐aged women differ in their bone microarchitecture and remodeling markers more because of differences in their genetic factors than differences in their environment. © 2014 American Society for Bone and Mineral Research.     

The effect of three human recombinant hematopoietic growth factors (granulocyte-macrophage colony-stimulating factor, granulocyte colony- stimulating factor, and interleukin-3) on phagocyte oxidative activity

Hematopoietic growth factors not only modulate blood progenitor cell activity but also alter the function of mature phagocytes. Recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF; 1 ng/mL for 60 min) did not stimulate luminol-enhanced chemiluminescence of polymorphonuclear leukocytes (PMNs) in suspension but primed PMN for as much as a 15-fold increase in chemiluminescence in response to f-met- leu-phe (fMLP). Mixed mononuclear leukocytes (monocytes [approximately 20%] and lymphocytes [approximately 80%]; MNL) chemiluminescence was very low even after rhGM-CSF priming, but MNLs added to the PMNs (PMN- MNL) resulted in near doubling of rhGM-CSF-primed PMN fMLP-stimulated chemiluminescence. The enhancing factor(s) from MNLs were inherent rather than induced by the GM-CSF, and purified lymphocytes increased GM-CSF-primed PMN chemiluminescence equal to mixed MNLs. We could not detect cell-free "enhancing factor(s)," but cell-to-cell contact further enhanced rhGM-CSF-primed fMLP-stimulated PMN-MNL oxidative activity by 40%. Polyclonal rabbit anti-tumor necrosis factor (TNF) (but not preimmune serum) decreased both fMLP-stimulated rhGM-CSF- primed PMNs and PMN-MNL chemiluminescence, suggesting that TNF on the PMN surface is enhancing GM-CSF-primed chemiluminescence. GM-CSF priming markedly increased PMN superoxide release (sevenfold), but PMN superoxide release was not further enhanced by the presence of MNLs. Recombinant human granulocyte colony-stimulating factor (rhG-CSF) and interleukin-3 (rhIL-3) displayed much smaller effects on pure PMNs and mixed PMN-MNL chemiluminescence and superoxide release than rhGM-CSF. rhGM-CSF primes PMNs for increased oxidative activity more than rhG-CSF and rhIL-3. Maximal oxidative activity was observed when mixed PMN-MNL were primed with GM-CSF in a cell pellet-promoting cell-to-cell contact. This enhanced activity can be attributed, in part, to both inherent enhancing factor(s) on lymphocytes and PMN-associated TNF induced by GM-CSF.     

A common evolutionary origin for mitochondria and hydrogenosomes.

Trichomonads are among the earliest eukaryotes to diverge from the main line of eukaryotic descent. Keeping with their ancient nature, these facultative anaerobic protists lack two "hallmark" organelles found in most eukaryotes: mitochondria and peroxisomes. Trichomonads do, however, contain an unusual organelle involved in carbohydrate metabolism called the hydrogenosome. Like mitochondria, hydrogenosomes are double-membrane bounded organelles that produce ATP using pyruvate as the primary substrate. Hydrogenosomes are, however, markedly different from mitochondria as they lack DNA, cytochromes and the citric acid cycle. Instead, they contain enzymes typically found in anaerobic bacteria and are capable of producing molecular hydrogen. We show here that hydrogenosomes contain heat shock proteins, Hsp70, Hsp60, and Hsp10, with signature sequences that are conserved only in mitochondrial and alpha-Gram-negative purple bacterial Hsps. Biochemical analysis of hydrogenosomal Hsp60 shows that the mature protein isolated from the organelle lacks a short, N-terminal sequence, similar to that observed for most nuclear-encoded mitochondrial matrix proteins. Moreover, phylogenetic analyses of hydrogenosomal Hsp70, Hsp60, and Hsp10 show that these proteins branch within a monophyletic group composed exclusively of mitochondrial homologues. These data establish that mitochondria and hydrogenosomes have a common eubacterial ancestor and imply that the earliest-branching eukaryotes contained the endosymbiont that gave rise to mitochondria in higher eukaryotes.     

Extra-pulmonary manifestations in a large metropolitan area with a low incidence of tuberculosis.

BACKGROUND: The increases in extra-pulmonary tuberculosis (EPTB) have been largely due to human immunodeficiency virus co-infection. The rates of EPTB have remained constant despite the decline in pulmonary tuberculosis (PTB) cases. OBJECTIVE: To evaluate covariates associated with EPTB. METHODS: A 4-year cohort of EPTB patients was compared with PTB cases. Enrollees were assessed for TB risk, medical records were reviewed, and Mycobacterium tuberculosis isolates were fingerprinted. RESULTS: We identified 538 EPTB cases (28.6%) in a total of 1878 enrollees. The most common sites of infection were lymph nodes (43%) and pleura (23%). EPTB cases included 320 (59%) males, 382 (71%) patients were culture-positive, and 332 (86.9%) patient isolates were fingerprinted. Fewer EPTB than PTB patients belonged to clustered M. tuberculosis strains (58% vs. 65%; P = 0.02). A multivariate model identified an increased risk for EPTB among African Americans (OR = 1.9, P = 0.01), HIV-seropositive (OR = 3.1, P < 0.01), liver cirrhosis (OR = 2.3, P = 0.02), and age <18 years (OR = 2.0, P = 0.04). Patients with concomitant pulmonary and extra-pulmonary infections were more likely to die within 6 months of TB diagnosis (OR = 2.3, P < 0.01). CONCLUSIONS: African American ethnicity is an independent risk factor for EPTB. Mortality at 6 months is partly due to the dissemination of M. tuberculosis and the severity of the underlying co-morbidity.     

Contrast-based sensorless adaptive optics for retinal imaging

Conventional adaptive optics ophthalmoscopes use wavefront sensing methods to characterize ocular aberrations for real-time correction. However, there are important situations in which the wavefront sensing step is susceptible to difficulties that affect the accuracy of the correction. To circumvent these, wavefront sensorless adaptive optics (or non-wavefront sensing AO; NS-AO) imaging has recently been developed and has been applied to point-scanning based retinal imaging modalities. In this study we show, for the first time, contrast-based NS-AO ophthalmoscopy for full-frame in vivo imaging of human and animal eyes. We suggest a robust image quality metric that could be used for any imaging modality, and test its performance against other metrics using (physical) model eyes.OCIS codes: (010.1080) Active or adaptive optics, (170.3880) Medical and biological imaging, (170.4460) Ophthalmic optics and devices, (330.4875) Optics of physiological systems