Using Structural and Diffusion Magnetic Resonance Imaging To Differentiate the Dementias

Dementia is one of the major causes of personal, societal and financial dependence in older people and in today’s ageing society there is a pressing need for early and accurate markers of cognitive decline. There are several subtypes of dementia but the four most common are Alzheimer’s disease, Lewy body dementia, vascular dementia and frontotemporal dementia. These disorders can only be diagnosed at autopsy, and ante-mortem assessments of “probable dementia (e.g. of Alzheimer type)” are traditionally driven by clinical symptoms of cognitive or behavioural deficits. However, owing to the overlapping nature of symptoms and age of onset, a significant proportion of dementia cases remain incorrectly diagnosed. Misdiagnosis can have an extensive impact, both at the level of the individual, who may not be offered the appropriate treatment, and on a wider scale, by influencing the entry of patients into relevant clinical trials. Magnetic resonance imaging (MRI) may help to improve diagnosis by providing non-invasive and detailed disease-specific markers of cognitive decline. MRI-derived measurements of grey and white matter structural integrity are potential surrogate markers of disease progression, and may also provide valuable diagnostic information. This review summarises the latest evidence on the use of structural and diffusion MRI in differentiating between the four major dementia subtypes.     

Burden of asthma among children in a developing megacity: childhood asthma study,Pakistan

Objectives: Global burden of childhood asthma has increased in the past few decades, particularly in low-income countries. In Pakistan, there is a lack of community-based epidemiological studies estimating the burden of asthma among children. This study determined the prevalence and predictors of asthma among children 3–17 years of age in Karachi, Pakistan. Methods: A two-stage community-based representative cross-sectional survey was conducted in Karachi from March 2012 to April 2013 comprising 1046 children aged 3–17 years. Of 7500 clusters, 80 were randomly selected, and of these, 15 children per cluster were enrolled randomly. A translated and pre-tested version of International Study of Asthma and Allergies in Children questionnaire was administered. Results: The overall prevalence of asthma among study participants was 10.2% (95% CI: 8.4–12.0). Asthma was more likely to occur among boys (adj. OR: 2.5, 95% CI: 1.6–4.0), children in the younger age group (3–7 years) (adj. OR: 2.9, 95% CI: 1.7–4.8), those living in households with ill-ventilated kitchens (adj. OR: 1.8, 95% CI: 1.1–3.1), having family history of asthma (adj. OR: 2.3, 95% CI: 1.3–3.9) and those of the Sindhi ethnicity (adj. OR: 2.2, 95% CI: 1.1–4.4). Conclusion: This study is the first robust evidence regarding asthma among children in Pakistan, reporting a high burden in this group. Family history, male gender, Sindhi ethnicity and ill-ventilated kitchen were identified as important predictors of asthma. Targeted preventive measures and intervention studies are required to better understand and reduce the burden of asthma among children in Pakistan.     

Functional interaction with filamin A and intracellular Ca2+ enhance the surface membrane expression of a small-conductance Ca2+-activated K+ (SK2) channel

For an excitable cell to function properly, a precise number of ion channel proteins need to be trafficked to distinct locations on the cell surface membrane, through a network and anchoring activity of cytoskeletal proteins. Not surprisingly, mutations in anchoring proteins have profound effects on membrane excitability. Ca²⁺-activated K⁺ channels (K_Ca2 or SK) have been shown to play critical roles in shaping the cardiac atrial action potential profile. Here, we demonstrate that filamin A, a cytoskeletal protein, augments the trafficking of SK2 channels in cardiac myocytes. The trafficking of SK2 channel is Ca²⁺-dependent. Further, the Ca²⁺ dependence relies on another channel-interacting protein, α-actinin2, revealing a tight, yet intriguing, assembly of cytoskeletal proteins that orchestrate membrane expression of SK2 channels in cardiac myocytes. We assert that changes in SK channel trafficking would significantly alter atrial action potential and consequently atrial excitability. Identification of therapeutic targets to manipulate the subcellular localization of SK channels is likely to be clinically efficacious. The findings here may transcend the area of SK2 channel studies and may have implications not only in cardiac myocytes but in other types of excitable cells.Small-conductance Ca²⁺-activated K⁺ (SK or K_Ca2) channels are highly unique in that they are gated solely by changes in intracellular Ca²⁺ (Ca²⁺_i) concentration. Hence, the channels function to integrate changes in Ca²⁺ concentration with changes in membrane potentials. SK channels have been shown to be expressed in a wide variety of cells (1–3) and mediate afterhyperpolarizations following action potentials in neurons (1, 4, 5). We have previously documented the expression of several isoforms of SK channels in human and mouse atrial myocytes that mediate the repolarization phase of the atrial action potentials (6, 7). We further demonstrated that SK2 (K_Ca2.2) channel knockout mice are prone to the development of atrial arrhythmias and atrial fibrillation (AF) (8). Conversely, a recent study by Diness et al. suggests that inhibition of SK channels may prevent AF (9). Together, these studies underpin the importance of the precise control for the expression of these ion channels in atria and their potential to serve as a future therapeutic target for AF.Current antiarrhythmic agents target the permeation and gating properties of ion channel proteins; however, increasing evidence suggests that membrane localization of ion channels may also be pharmacologically altered (10). Furthermore, a number of disorders have been associated with mistrafficking of ion channel proteins (11, 12). We have previously demonstrated the critical role of α-actinin2, a cytoskeletal protein, in the surface membrane localization of cardiac SK2 channels (13, 14). Specifically, we demonstrated that cardiac SK2 channel interacts with α-actinin2 cytoskeletal protein via the EF hand motifs in α-actinin2 protein and the helical core region of the calmodulin (CaM) binding domain (CaMBD) in the C terminus of SK2 channel. Moreover, direct interactions between SK2 channel and α-actinin2 are required for the increase in cell surface localization of SK2 channel.Here, to further define the functional interactome of SK2 channel in the heart, we demonstrate the role of filamin A (FLNA), another cytoskeletal protein, in SK2 channel surface membrane localization. In contrast to α-actinin2 protein, FLNA interacts not with the C terminus, but with the N terminus of the cardiac SK2 channel. FLNA is a scaffolding cytoskeletal protein with two calponin homology domains that has been shown to be critical for the trafficking of a number of membrane proteins (15–19). Our data demonstrate that FLNA functions to enhance membrane localization of SK2 channels. Moreover, using live-cell imaging, we demonstrate the critical roles of Ca²⁺_i on the membrane localization of SK2 channel when the channels are coexpressed with α-actinin2, but not FLNA. A decrease in Ca²⁺_i results in a significant decrease in SK2 channel membrane localization. Our findings may have important clinical implications. A rise in Ca²⁺_i—for example, during rapid pacing or atrial tachyarrhythmias—is predicted to increase the membrane localization of SK2 channel and result in the abbreviation of the atrial action potentials and maintenance of the arrhythmias.     

Validation of the Arabic version of the revised Fibromyalgia Impact Questionnaire (FIQR_A) on Jordanian females with fibromyalgia

The aim of this study was to translate and validate the Arabic version of the Revised Fibromyalgia Impact Questionnaire (FIQR_A). Translation of the FIQR followed a worldwide-recognized approach to ensure the accuracy and equivalency of the translation from the English version of the FIQR. Following the translation of the FIQR, 92 women with fibromyalgia completed the FIQR_A, the Arabic Research ANd Development Short Form Health Survey (RAND SF-36), and the Arabic Hospital Anxiety and Depression Scales (HADS). The FIQR_A significantly correlated with RAND SF-36 domains and HADS. The correlations ranged from fair to moderate. For selected outcomes, Bland–Altman plots were consistent with Spearman’s correlations. Test–retest intraclass correlation coefficients were all significant and ranged from moderate to excellent. Internal consistency was found to be excellent. These observations suggest that the FIQR_A is a valid and reliable tool for both clinical practice and research purposes with Arabic speakers globally.     

Warfarin use and long-term outcomes in patients with acute myocardial infarction and atrial fibrillation

Warfarin use in patients with acute myocardial infarction (AMI) and atrial fibrillation (AF) remains challenging. We describe use of warfarin up to 1 year after hospitalization among patients with AMI and AF according to stroke and bleeding risk, and identify factors associated with long-term mortality in this population. Patients with AMI and AF who underwent cardiac catheterization during their AMI hospitalization in 1995–2007 were identified from the Duke Databank for Cardiovascular Disease. Warfarin use at discharge, 6 months, and 1 year as well as long-term vital status were assessed by surveys. Rates of warfarin use were presented according to CHADS₂ and CHA₂DS₂VASc stroke and ATRIA bleeding risk scores. Cox proportional hazards modeling was used to determine whether warfarin use at discharge was independently associated with 1-year mortality. A total of 879 patients hospitalized with AMI with AF were identified. Median age was 72 (25th, 75th percentiles: 64, 79), and median follow-up was 4.1 years (1.3, 7.4). The rate of warfarin use at discharge was 24 % and did not differ by CHADS₂, CHA₂DS₂VASc, or ATRIA risk scores. Warfarin use remained similar at 6 months (26 %) and 1 year (27 %). Long-term mortality was high and did not differ by whether warfarin was or was not prescribed at discharge (72 and 71 %, respectively). Factors associated with 1-year mortality were history of heart failure (HR 1.58, 95 % CI 1.32–1.90), higher Charlson comorbidity index (HR 1.19, 95 % CI 1.11–1.28), and older age (HR 1.03 per 1-year increase, 95 % CI 1.02–1.05). Warfarin use at discharge among patients hospitalized for AMI who had comorbid AF was low and remained low at 1 year. Warfarin use at hospital discharge was not associated with either 1-year mortality or long-term mortality.     

C-terminal region of activation-induced cytidine deaminase (AID) is required for efficient class switch recombination and gene conversion

Activation-induced cytidine deaminase (AID) introduces single-strand breaks (SSBs) to initiate class switch recombination (CSR), gene conversion (GC), and somatic hypermutation (SHM). CSR is mediated by double-strand breaks (DSBs) at donor and acceptor switch (S) regions, followed by pairing of DSB ends in two S regions and their joining. Because AID mutations at its C-terminal region drastically impair CSR but retain its DNA cleavage and SHM activity, the C-terminal region of AID likely is required for the recombination step after the DNA cleavage. To test this hypothesis, we analyzed the recombination junctions generated by AID C-terminal mutants and found that 0- to 3-bp microhomology junctions are relatively less abundant, possibly reflecting the defects of the classical nonhomologous end joining (C-NHEJ). Consistently, the accumulation of C-NHEJ factors such as Ku80 and XRCC4 was decreased at the cleaved S region. In contrast, an SSB-binding protein, poly (ADP)-ribose polymerase1, was recruited more abundantly, suggesting a defect in conversion from SSB to DSB. In addition, recruitment of critical DNA synapse factors such as 53BP1, DNA PKcs, and UNG at the S region was reduced during CSR. Furthermore, the chromosome conformation capture assay revealed that DNA synapse formation is impaired drastically in the AID C-terminal mutants. Interestingly, these mutants showed relative reduction in GC compared with SHM in chicken DT40 cells. Collectively, our data indicate that the C-terminal region of AID is required for efficient generation of DSB in CSR and GC and thus for the subsequent pairing of cleaved DNA ends during recombination in CSR.Activation-induced cytidine deaminase (AID) is essential for three different genetic events: class switch recombination (CSR), gene conversion (GC), and somatic hypermutation (SHM), which contribute to Ig gene diversification (1–5). Although AID generates single-strand breaks (SSBs) in the Ig genes, subsequent repair steps for CSR and GC are similar to each other but are distinct from SHM in their mechanistic properties, i.e, in (i) generation of the double-strand breaks (DSBs), (ii) recombination, and (iii) the requirement for uracil-DNA-glycosylase (UNG) for the pairing of the DSB ends (6–10). Despite the similarities between GC and CSR, their repair mechanisms have distinct features: CSR recombination requires nonhomologous end joining (NHEJ), and GC depends on homologous recombination (HR). During CSR, DSB ends normally are joined by classical NHEJ (C-NHEJ), which requires specific repair proteins such as Ku80, XRCC4, or DNA ligase IV (11, 12). In the absence of C-NHEJ, a back-up end-joining pathway called “alternative end joining” (A-EJ), which is reported to be slower and also more error prone than C-NHEJ, joins the broken DSBs ends (13). On the other hand, HR, the most common form of homology-directed repair, requires long sequence homology between donor and acceptor DNA to complete the recombination step by recruiting a distinct set of repair proteins such as RAD54, RAD52, and RAD51 to the break sites (14, 15).Various studies on AID mutations in the N-terminal or C-terminal regions (4, 8, 9, 16–19) have shown that N-terminal AID mutants are compromised for CSR and are defective in SHM, indicating that the N-terminal region of AID is required for DNA cleavage (9, 16, 19). On the other hand, the C-terminal region of AID, which contains a nuclear-export signal and is responsible for AID’s shuttling activity between the nucleus and cytoplasm, is required for CSR-specific activity but not for DNA cleavage activity and SHM (8, 16). Among the series of AID C-terminal mutants examined, two mutants show characteristic features: P20, which has an insertion of 34 amino acids at residue 182 and normal nuclear-cytoplasmic shuttling activity, and JP8Bdel, which has a 16-amino acid truncation at residue 183, accumulates in the nucleus, and shows higher DNA break activity at the donor switch (S) region (16, 17). Although several reports suggest that the C-terminal region of AID is involved in protein stability (20, 21), C-terminal mutants of AID stabilized by fusing the hormone-binding domain of estrogen receptor (ER) also show similar CSR-defective phenotypes (8). Taken together, these data suggest that the DNA cleavage activity and CSR-specific activity depend on different regions of AID (8, 19). In addition, the C-terminal region of AID is essential for the interaction of AID with poly (A)⁺ RNA via a specific cofactor (22). Because CSR requires de novo protein synthesis, we proposed that after DNA cleavage the C-terminal region of AID may be involved in the regulation of the recombination step through generation of a new protein (8, 16, 22).DSBs induced by AID during CSR ultimately are joined by the efficient DNA repair pathway that requires C-NHEJ factors such as Ku70/80 (12, 23). However, in the absence of C-NHEJ, the A-EJ pathway that relies on microhomology can join the broken DNA ends, although this pathway is associated with chromosomal translocations (11, 24). Previously, we reported that JP8Bdel enhances aberrant c-myc/IgH translocations and that it fails to carry out the efficient recombination between donor and acceptor S regions in the IgH locus (8). Therefore, it is important to examine whether the AID C-terminal mutants affect the S–S joining in CSR.In the current work we examined whether the C-terminal region of AID is involved in DNA synapse formation and recombination during CSR in CH12F3-2 and spleen B cells. We also examined the effect of AID C-terminal mutations on GC in chicken DT40 cells, which depends on HR between pseudo V genes and the downstream IgVλ region. Using these CSR- and GC-monitoring systems, we demonstrate that efficient CSR and GC require the C-terminal region of AID for the formation of DSB from SSB and subsequent end synapse. Considering these findings together, we conclude that, in addition to DNA cleavage, AID has a unique function in the generation of DSBs, which is required for S–S synapse formation and joining in CSR and recombination in GC.     

Evidence for zoonotic transmission of species A rotavirus from goat and cattle in nomadic herds in Morocco, 2012–2014

Virus Genes - Species A rotaviruses (RVAs) are a leading cause of diarrhea in children and in the young of a large variety of mammalian and avian host species. The purpose of this study was to...