Background & objective
Percent whole brain volume change (PBVC) measured from serial MRI scans is widely accepted as a sensitive marker of disease progression in Alzheimer's disease (AD). However, the utility of PBVC in the differential diagnosis of dementia remains to be established. We compared PBVC in AD and dementia with Lewy bodies (DLB), and investigated associations with clinical measures.
72 participants (14 DLBs, 25 ADs, and 33 healthy controls (HCs)) underwent clinical assessment and 3 Tesla T1-weighted MRI at baseline and repeated at 12 months. We used FSL-SIENA to estimate PBVC for each subject. Voxelwise analyses and ANCOVA compared PBVC between DLB and AD, while correlational tests examined associations of PBVC with clinical measures.
AD had significantly greater atrophy over 1 year (1.8%) compared to DLB (1.0%; p = 0.01) and HC (0.9%; p < 0.01) in widespread regions of the brain including periventricular areas. PBVC was not significantly different between DLB and HC (p = 0.95). There were no differences in cognitive decline between DLB and AD. In the combined dementia group (AD and DLB), younger age was associated with higher atrophy rates (r = 0.49, p < 0.01).
AD showed a faster rate of global brain atrophy compared to DLB, which had similar rates of atrophy to HC. Among dementia subjects, younger age was associated with accelerated atrophy, reflecting more aggressive disease in younger people. PBVC could aid in differentiating between DLB and AD, however its utility as an outcome marker in DLB is limited.
•AD showed faster global and regional brain atrophy in comparison to DLB.•Similar rates of global and regional atrophy were found in DLB and HC.•Longitudinal imaging could improve clinical differentiation of DLB from AD.•Atrophy rates might not be a useful marker to track disease progression in DLB.
Dementia; Alzheimer's disease; Lewy bodies; Neuroimaging; Atrophy
Here we implement ultraviolet photodissociation
(UVPD) in an online
liquid chromatographic tandem mass spectrometry (MS/MS) strategy to
support analysis of complex mixtures of lipid A combinatorially modified
during development of vaccine adjuvants. UVPD mass spectrometry at
193 nm was utilized to characterize the structures and fragment ion
types of lipid A from Escherichia coli, Vibrio
cholerae, and Pseudomonas aeruginosa using
an Orbitrap mass spectrometer. The fragment ions generated by UVPD
were compared to those from collision induced dissociation (CID) and
higher energy collision dissociation (HCD) with respect to the precursor
charge state. UVPD afforded the widest array of fragment ion types
including acyl chain C–O, C–N, and C–C bond cleavages
and glycosidic C–O and cross ring cleavages, thus providing
the most comprehensive structural analysis of the lipid A. UVPD exhibited
virtually no dependence on precursor ion charge state and was best
at determining lipid A structure including acyl chain length and composition,
giving it an advantage over collision based methods. UVPD was incorporated
into an LC–MS/MS methodology for the analysis of a number of
structural variants in a complex mixture of combinatorially engineered Escherichia coli lipid A.
Overweight and obesity is a problem in children in particular and determining pathways of transmission is important in prevention. We aimed to examine associations for body mass index (BMI) across three generations of the same families.
Members of 556 families in the Lifeways Cross-Generation Cohort Study 2001–2014.
Community-based study with linkage to health records in the Republic of Ireland.
Employing a novel mixed-method approach which adjusts for age and familial group, BMI correlations were estimated at three ages of the index child, that is, at birth and at ages 5 and 9. Height was also examined for comparative purposes.
Correlation of offspring's BMI with that of the mother increased with age (correlation coefficient 0.15 increasing to 0.28, p value <0.001 in all cases) while no consistent pattern was seen with offspring and fathers. There was an association also with each parent and their own mother. Offspring's BMI was correlated to a lesser extent with that of the maternal grandmother while for girls only there was an association with that of the paternal grandmother at ages 0 and 5 (correlation coefficients 0.25, 0.28, p values 0.02, 0.01, respectively). In contrast, height of the child was strongly associated with those of all family members at age 5, but at birth and at age 9 only there was an association with those of the parents and the paternal grandfather. Correlation of offspring's height with those of the mother and father increased with age.
The results suggest that BMI is predominantly associated with the maternal line, possibly either with intrauterine development, or inherited through the X chromosome, or both, while height is a more complex trait with genetic influences of the parents and that of the paternal grandfather predominating.
Body Mass Index; height; heritability; Intergenerational Relations; Population genetics
Vascular factors are now established risk factors for cognitive decline, both for dementia and its two main subtypes: Alzheimer’s disease (AD) and vascular dementia. Their impact likely goes beyond causing an increase in concurrent vascular pathology, since they have been associated with increasing the risk of degenerative Alzheimer (plaque and tangle) pathology, either by increasing its rate of formation or reducing elimination from the brain, or a mixture of the two. A comprehensive series of reviews published in BMC Medicine, investigates the relationship between AD and cardiovascular diseases and risk factors from a clinical, pathological and therapeutic perspective. Whilst links between vascular factors and AD have clearly been demonstrated at both the clinical and pathological level, the nature of the relationship remains to be fully established and there is a lack of high quality treatment studies examining the extent to which vascular risk modification alters AD disease course. Further longitudinal mechanistic and therapeutic studies are required, especially to determine whether treatment of vascular risk can prevent or delay the onset of AD and/or reduce its rate of clinical progression.
Alzheimer’s disease; Vascular risk; Stroke; Dementia; Risk factors; Prevention; Treatment; Hypertension
Ultraviolet photodissociation (UVPD) mass spectrometry was used to characterize the structures of amphiphilic glycosphingolipids and gangliosides in comparison to collision induced dissociation (CID) and higher energy collision dissociation (HCD) in a high performance Orbitrap mass spectrometer. UVPD produced the widest array of fragment ions diagnostic for both the ceramide base and oligosaccharide moieties. CID and HCD generated mainly glycosidic B/Y and C/Z cleavages of the oligosaccharides moieties and very few informative fragments related to the hydrophobic ceramide base. Several unique cleavages at the sphingoid base and the fatty acid chain occurred upon UVPD, as well as a wider variety of cross ring cleavages (A/X ions), thus affording differentiation of isobaric gangliosides. An LC-UVPD-MS strategy allowed the elucidation of 27 gangliosides among five different classes.
Electrical coupling of photoreceptors through gap junctions suppresses voltage noise, routes rod signals into cone pathways, expands the dynamic range of rod photoreceptors in high scotopic and mesopic illumination, and improves detection of contrast and small stimuli. In essentially all vertebrates, connexin 35/36 (gene homologues Cx36 in mammals, Cx35 in other vertebrates) is the major gap junction protein observed in photoreceptors, mediating rod-cone, cone-cone, and possibly rod-rod communication. Photoreceptor coupling is dynamically controlled by the day/night cycle and light/dark adaptation, and is directly correlated with phosphorylation of Cx35/36 at two sites, serine110 and serine 276/293 (homologous sites in teleost fish and mammals respectively). Activity of protein kinase A (PKA) plays a key role during this process. Previous studies have shown that activation of dopamine D4 receptors on photoreceptors inhibits adenylyl cyclase, down-regulates cAMP and PKA activity, and leads to photoreceptor uncoupling, imposing the daytime/light condition. In this study we explored the role of adenosine, a nighttime signal with a high extracellular concentration at night and a low concentration in the day, in regulating photoreceptor coupling by examining photoreceptor Cx35 phosphorylation in zebrafish retina. Adenosine enhanced photoreceptor Cx35 phosphorylation in daytime, but with a complex dose-response curve. Selective pharmacological manipulations revealed that adenosine A2a receptors provide a potent positive drive to phosphorylate photoreceptor Cx35 under the influence of endogenous adenosine at night. A2a receptors can be activated in the daytime as well by micromolar exogenous adenosine. However, the higher affinity adenosine A1 receptors are also present and have an antagonistic though less potent effect. Thus the nighttime/darkness signal adenosine provides a net positive drive on Cx35 phosphorylation at night, working in opposition to dopamine to regulate photoreceptor coupling via a push-pull mechanism. However, the lower concentration of adenosine present in the daytime actually reinforces the dopamine signal through action on the A1 receptor.
adenosine; A2a receptor; A1 receptor; Cx36; photoreceptor
Transfection of DNA has been invaluable for biological sciences and with recent advances to organotypic brain slice preparations, the effect of various heterologous genes could thus be investigated easily while maintaining many aspects of in vivo biology. There has been increasing interest to transfect terminally differentiated neurons for which conventional transfection methods have been fraught with difficulties such as low yields and significant losses in viability. Biolistic transfection can circumvent many of these difficulties yet only recently has this technique been modified so that it is amenable for use in mammalian tissues.
New modifications to the accelerator chamber have enhanced the gene gun's firing accuracy and increased its depths of penetration while also allowing the use of lower gas pressure (50 psi) without loss of transfection efficiency as well as permitting a focused regioselective spread of the particles to within 3 mm. In addition, this technique is straight forward and faster to perform than tedious microinjections. Both transient and stable expression are possible with nanoparticle bombardment where episomal expression can be detected within 24 hr and the cell survival was shown to be better than, or at least equal to, conventional methods. This technique has however one crucial advantage: it permits the transfection to be localized within a single restrained radius thus enabling the user to anatomically isolate the heterologous gene's effects. Here we present an in-depth protocol to prepare viable adult organotypic slices and submit them to regioselective transfection using an improved gene gun.
Neuroscience; Issue 92; Biolistics; gene gun; organotypic brain slices; Diolistic; gene delivery; staining
Electrical synapses are abundant in the vertebrate brain, but their functional and molecular complexity are still poorly understood. We report here that electrical synapses between auditory afferents and goldfish Mauthner cells are constructed by apposition of hemichannels formed by two homologs of mammalian connexin36 (Cx36), and that while Cx35 is restricted to presynaptic hemiplaques, Cx34.7 is restricted to postsynaptic hemiplaques, forming heterotypic junctions. This molecular asymmetry is associated with rectification of electrical transmission that may act to promote cooperativity between auditory afferents. Our data suggest that in similarity to pre- and postsynaptic sites at chemical synapses, one side in electrical synapses should not necessarily be considered the mirror image of the other. While asymmetry based on the presence of two Cx36 homologs is restricted to teleost fish, it might also be based on differences in posttranslational modifications of individual connexins or in the complement of gap junction-associated proteins.
electrical transmission; connexin36; auditory; rectification; gap junction
See Dujardin (doi:10.1093/brain/awu218) for a scientific commentary on this article. Nombela et al. present data from the ICICLE-PD study of cognition in newly diagnosed Parkinson’s disease. Consistent with the ‘Dual Syndrome’ hypothesis, impairments in executive function reflect a frontal dopaminergic syndrome modulated by COMT genotype, while visuospatial and memory deficits reflect disruption of temporo-parietal systems modulated by MAPT and APOE.
Parkinson’s disease is associated with multiple cognitive impairments and increased risk of dementia, but the extent of these deficits varies widely among patients. The ICICLE-PD study was established to define the characteristics and prevalence of cognitive change soon after diagnosis, in a representative cohort of patients, using a multimodal approach. Specifically, we tested the ‘Dual Syndrome’ hypothesis for cognitive impairment in Parkinson’s disease, which distinguishes an executive syndrome (affecting the frontostriatal regions due to dopaminergic deficits) from a posterior cortical syndrome (affecting visuospatial, mnemonic and semantic functions related to Lewy body pathology and secondary cholinergic loss). An incident Parkinson’s disease cohort (n = 168, median 8 months from diagnosis to participation) and matched control group (n = 85) were recruited to a neuroimaging study at two sites in the UK. All participants underwent clinical, neuropsychological and functional magnetic resonance imaging assessments. The three neuroimaging tasks (Tower of London, Spatial Rotations and Memory Encoding Tasks) were designed to probe executive, visuospatial and memory encoding domains, respectively. Patients were also genotyped for three polymorphisms associated with cognitive change in Parkinson’s disease and related disorders: (i) rs4680 for COMT Val158Met polymorphism; (ii) rs9468 for MAPT H1 versus H2 haplotype; and (iii) rs429358 for APOE-ε2, 3, 4. We identified performance deficits in all three cognitive domains, which were associated with regionally specific changes in cortical activation. Task-specific regional activations in Parkinson’s disease were linked with genetic variation: the rs4680 polymorphism modulated the effect of levodopa therapy on planning-related activations in the frontoparietal network; the MAPT haplotype modulated parietal activations associated with spatial rotations; and APOE allelic variation influenced the magnitude of activation associated with memory encoding. This study demonstrates that neurocognitive deficits are common even in recently diagnosed patients with Parkinson’s disease, and that the associated regional brain activations are influenced by genotype. These data further support the dual syndrome hypothesis of cognitive change in Parkinson’s disease. Longitudinal data will confirm the extent to which these early neurocognitive changes, and their genetic factors, influence the long-term risk of dementia in Parkinson’s disease. The combination of genetics and functional neuroimaging provides a potentially useful method for stratification and identification of candidate markers, in future clinical trials against cognitive decline in Parkinson’s disease.
Parkinson’s disease; cognition; functional MRI; genetics
To pool clinical trials of similar design to assess overall sensitivity and specificity of ioflupane I123 injection (DaTSCAN or ioflupane (123I)) to detect or exclude a striatal dopaminergic deficit disorder (SDDD), such as parkinsonian syndrome and dementia with Lewy bodies.
Pooled analysis of three phase 3 and one phase 4 clinical trials. These four trials were selected because they were the four studies used for the US new drug application to the Food and Drug Administration (FDA).
Multicentre, open-label, non-randomised.
Patients with either a movement disorder or dementia, and healthy volunteers.
Ioflupane (123I) was administered.
Images were assessed by panels of 3–5 blinded experts and/or on-site nuclear medicine physicians, classified as normal or abnormal and compared with clinical diagnosis (reference standard) to determine sensitivity and specificity.
Pooling the four studies, 928 participants were enrolled, 849 were dosed and 764 completed their study. Across all studies, when images were assessed by on-site readers, ioflupane (123I) diagnostic effectiveness had an overall (95% CI) sensitivity of 91.9% (88.7% to 94.5%) and specificity of 83.6% (78.7% to 87.9%). When reads were conducted blindly by a panel of independent experts, the overall sensitivity was 88.7% (86.8% to 90.4%) and specificity was 91.2% (89.0% to 93.0%).
In this pooled analysis, the visual assessment of ioflupane (123I) images provided high levels of sensitivity and specificity in detecting the presence/absence of an SDDD. Ioflupane (123I) imaging has the potential to improve diagnostic accuracy in patients with signs and symptoms of a movement disorder and/or dementia.
Trial registration number
Around 30% to 62% of older individuals fall each year, with adverse consequences of falls being by no means limited to physical injury and escalating levels of dependence. Many older individuals suffer from a variety of adverse psychosocial difficulties related to falling including fear, anxiety, loss of confidence and subsequent increasing activity avoidance, social isolation and frailty. Such ‘fear of falling’ is common and disabling, but definitive studies examining the effective management of the syndrome are lacking. Cognitive behavioural therapy has been trialed with some success in a group setting, but there is no adequately powered randomised controlled study of an individually based cognitive behavioural therapy intervention, and none using non-mental health professionals to deliver the intervention.
We are conducting a two-phase study examining the role of individual cognitive behavioural therapy delivered by healthcare assistants in improving fear of falling in older adults. In Phase I, the intervention was developed and taught to healthcare assistants, while Phase II is the pragmatic randomised controlled study examining the efficacy of the intervention in improving fear of falling in community-dwelling elders attending falls services. A qualitative process evaluation study informed by Normalization Process Theory is being conducted throughout to examine the potential promoters and inhibitors of introducing such an intervention into routine clinical practice, while a health economic sub-study running alongside the trial is examining the costs and benefits of such an approach to the wider health economy.
Current Controlled Trials ISRCTN78396615
Fear of falling; Falls; Elders; Community; Randomised controlled trial; Cognitive behavioural therapy; Complex intervention; Normalization process theory
Dementia with Lewy Bodies (DLB) and Parkinson’s Disease Dementia (PDD) together, represent the second most common cause of dementia, after Alzheimer’s disease (AD). The synaptic dysfunctions underlying the cognitive decline and psychiatric symptoms observed throughout the development of PDD and DLB are still under investigation. In this study we examined the expression level of Dynamin1 and phospho-CaMKII, key proteins of endocytosis and synaptic plasticity respectively, as potential markers of molecular processes specifically deregulated with DLB and/or PDD. In order to measure the levels of these proteins, we isolated grey matter from post-mortem prefrontal cortex area (BA9), anterior cingulated gyrus (BA24) and parietal cortex (BA40) from DLB and PDD patients in comparison to age-matched controls and a group of AD cases. Clinical and pathological data available included the MMSE score, neuropsychiatric history, and semi-quantitative scores for AD pathology (plaques - tangles) and for α-synuclein (Lewy bodies).
Changes in the expression of the synaptic markers, and correlates with neuropathological features and cognitive decline were predominantly found in the prefrontal cortex. On one hand, levels of Dynamin1 were significantly reduced, and correlated with a higher rate of cognitive decline observed in cases from three dementia groups. On the other hand, the fraction of phospho-CaMKII was decreased, and correlated with a high score of plaques and tangles in BA9. Interestingly, the correlation between the rate of cognitive decline and the level of Dynamin1 remained when the analysis was restricted to the PDD and DLB cases, highlighting an association of Dynamin1 with cognitive decline in people with Lewy Body dementia.
Alzheimer’s disease; Dementia with Lewy bodies; Parkinson’s disease with dementia; synaptic dysfunction; vesicle recycling; synaptic plasticity; beta amyloid; tau; cognitive impairment
Drug resistance remains a chief concern for malaria control. In order to determine the genetic markers of drug resistant parasites, we tested the genome-wide associations (GWA) of sequence-based genotypes from 35 Kenyan P. falciparum parasites with the activities of 22 antimalarial drugs.
Methods and Principal Findings
Parasites isolated from children with acute febrile malaria were adapted to culture, and sensitivity was determined by in vitro growth in the presence of anti-malarial drugs. Parasites were genotyped using whole genome sequencing techniques. Associations between 6250 single nucleotide polymorphisms (SNPs) and resistance to individual anti-malarial agents were determined, with false discovery rate adjustment for multiple hypothesis testing. We identified expected associations in the pfcrt region with chloroquine (CQ) activity, and other novel loci associated with amodiaquine, quinazoline, and quinine activities. Signals for CQ and primaquine (PQ) overlap in and around pfcrt, and interestingly the phenotypes are inversely related for these two drugs. We catalog the variation in dhfr, dhps, mdr1, nhe, and crt, including novel SNPs, and confirm the presence of a dhfr-164L quadruple mutant in coastal Kenya. Mutations implicated in sulfadoxine-pyrimethamine resistance are at or near fixation in this sample set.
Sequence-based GWA studies are powerful tools for phenotypic association tests. Using this approach on falciparum parasites from coastal Kenya we identified known and previously unreported genes associated with phenotypic resistance to anti-malarial drugs, and observe in high-resolution haplotype visualizations a possible signature of an inverse selective relationship between CQ and PQ.
Metagenomics provides a powerful new tool set for investigating evolutionary interactions with the environment. However, an absence of model-based statistical methods means that researchers are often not able to make full use of this complex information. We present a Bayesian method for inferring the phylogenetic relationship among related organisms found within metagenomic samples. Our approach exploits variation in the frequency of taxa among samples to simultaneously infer each lineage haplotype, the phylogenetic tree connecting them, and their frequency within each sample. Applications of the algorithm to simulated data show that our method can recover a substantial fraction of the phylogenetic structure even in the presence of high rates of migration among sample sites. We provide examples of the method applied to data from green sulfur bacteria recovered from an Antarctic lake, plastids from mixed Plasmodium falciparum infections, and virulent Neisseria meningitidis samples.
metagenomics; Bayesian phylogenetics; microevolution
We examined 99mTc-exametazime brain blood flow single-photon emission computed tomography (SPECT) images using a spatial covariance analysis (SCA) approach to assess its diagnostic value in distinguishing dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). Voxel SCA was simultaneously applied to a set of preprocessed images (AD, n=40; DLB, n=26), generating a series of eigenimages representing common intercorrelated voxels in AD and DLB. Linear regression derived a spatial covariance pattern (SCP) that discriminated DLB from AD. To investigate the diagnostic value of the model SCP, the SCP was validated by applying it to a second, independent, AD and DLB cohort (AD, n=34; DLB, n=29). Mean SCP expressions differed between AD and DLB (F1,64=36.2, P<0.001) with good diagnostic accuracy (receiver operating characteristic (ROC) curve area 0.87, sensitivity 81%, specificity 88%). Forward application of the model SCP to the independent cohort revealed similar differences between groups (F1,61=38.4, P<0.001), also with good diagnostic accuracy (ROC 0.86, sensitivity 80%, specificity 80%). Multivariate analysis of blood flow SPECT data appears to be robust and shows good diagnostic accuracy in two independent cohorts for distinguishing DLB from AD.
Alzheimer's disease; differential diagnosis; dementia with Lewy bodies; perfusion; spatial covariance; SPECT
Cognitive fluctuations are a core symptom in dementia with Lewy bodies (DLB) and may relate to pathological alterations in distributed brain networks. To test this we analysed resting state fMRI changes in a cohort of fluctuating DLB patients (n = 16) compared with age matched controls (n = 17) with the aim of finding functional connectivity (FC) differences between these two groups and whether these associate with cognitive fluctuations in DLB. Resting state networks (RSNs) were estimated using independent component analysis and FC between the RSN maps and the entirety of the brain was assessed using dual regression. The default mode network (DMN) appeared unaffected in DLB compared to controls but significant cluster differences between DLB and controls were found for the left fronto-parietal, temporal, and sensory–motor networks. Desynchronization of a number of cortical and subcortical areas related to the left fronto-parietal network was associated with the severity and frequency of cognitive fluctuations. Our findings provide empirical evidence for the potential role of attention–executive networks in the aetiology of this core symptom in DLB.
•We report resting state network (RSN) alterations in dementia with Lewy bodies (DLB).•The default mode network was intact in DLB compared to healthy controls (HC).•Fronto-parietal, temporal, and sensory–motor RSNs showed differences (DLB < HC).•The left fronto-parietal network (FPN) correlated with cognitive fluctuations in DLB.•The FPN therefore may be a potential marker for cognitive fluctuations in DLB.
Cognitive fluctuations; Visual hallucinations; Resting state network; Lewy bodies; Dementia
To describe the frequency of mild cognitive impairment (MCI) in Parkinson disease (PD) in a cohort of newly diagnosed incident PD cases and the associations with a panel of biomarkers.
Between June 2009 and December 2011, 219 subjects with PD and 99 age-matched controls participated in clinical and neuropsychological assessments as part of a longitudinal observational study. Consenting individuals underwent structural MRI, lumbar puncture, and genotyping for common variants of COMT, MAPT, SNCA, BuChE, EGF, and APOE. PD-MCI was defined with reference to the new Movement Disorder Society criteria.
The frequency of PD-MCI was 42.5% using level 2 criteria at 1.5 SDs below normative values. Memory impairment was the most common domain affected, with 15.1% impaired at 1.5 SDs. Depression scores were significantly higher in those with PD-MCI than the cognitively normal PD group. A significant correlation was found between visual Pattern Recognition Memory and cerebrospinal β-amyloid 1–42 levels (β standardized coefficient = 0.350; p = 0.008) after controlling for age and education in a linear regression model, with lower β-amyloid 1–42 and 1–40 levels observed in those with PD-MCI. Voxel-based morphometry did not reveal any areas of significant gray matter loss in participants with PD-MCI compared with controls, and no specific genotype was associated with PD-MCI at the 1.5-SD threshold.
In a large cohort of newly diagnosed PD participants, PD-MCI is common and significantly correlates with lower cerebrospinal β-amyloid 1–42 and 1–40 levels. Future longitudinal studies should enable us to determine those measures predictive of cognitive decline.
Clostridial neurotoxins reversibly
block neuronal communication
for weeks and months. While these proteolytic neurotoxins hold great
promise for clinical applications and the investigation of brain function,
their paralytic activity at neuromuscular junctions is a stumbling
block. To redirect the clostridial activity to neuronal populations
other than motor neurons, we used a new self-assembling method to
combine the botulinum type A protease with the tetanus binding domain,
which natively targets central neurons. The two parts were produced
separately and then assembled in a site-specific way using a newly
introduced ‘protein stapling’ technology. Atomic force
microscopy imaging revealed dumbbell shaped particles which measure
∼23 nm. The stapled chimera inhibited mechanical hypersensitivity
in a rat model of inflammatory pain without causing either flaccid
or spastic paralysis. Moreover, the synthetic clostridial molecule
was able to block neuronal activity in a defined area of visual cortex.
Overall, we provide the first evidence that the protein stapling technology
allows assembly of distinct proteins yielding new biomedical properties.
Organotypic brain slices (OTBS) are an excellent experimental compromise between the facility of working with cell cultures and the biological relevance of using animal models where anatomical, morphological, and cellular function of specific brain regions can be maintained. The biological characteristics of OTBS can subsequently be examined under well-defined conditions. They do, however, have a number of limitations; most brain slices are derived from neonatal animals, as it is difficult to properly prepare and maintain adult OTBS. There are ample problems with tissue integrity as OTBS are delicate and frequently become damaged during the preparative stages. Notwithstanding these obstacles, the introduced exogenous proteins into both neuronal cells, and cells imbedded within tissues, have been consistently difficult to achieve.
Following the ex vivo extraction of adult mouse brains, mounted inside a medium-agarose matrix, we have exploited a precise slicing procedure using a custom built vibroslicer. To transfect these slices we used an improved biolistic transfection method using a custom made low-pressure barrel and novel DNA-coated nanoparticles (40 nm), which are drastically smaller than traditional microparticles. These nanoparticles also minimize tissue damage as seen by a significant reduction in lactate dehydrogenase activity as well as propidium iodide (PI) and dUTP labelling compared to larger traditional gold particles used on these OTBS. Furthermore, following EYFP exogene delivery by gene gun, the 40 nm treated OTBS displayed a significantly larger number of viable NeuN and EYFP positive cells. These OTBS expressed the exogenous proteins for many weeks.
Our described methodology of producing OTBS, which results in better reproducibility with less tissue damage, permits the exploitation of mature fully formed adult brains for advanced neurobiological studies. The novel 40 nm particles are ideal for the viable biolistic transfection of OTBS by reducing tissue stress while maintaining long term exogene expression.
Organotypic brain slices; Vibroslicer; Gene gun; Biolistic transfection; Nanoparticles; Tissue slicer
Fluctuating cognition (FC), particularly in attention, is a core and defining symptom in dementia with Lewy bodies (DLB) but is seen much less frequently in Alzheimer's dementia (AD). However, its neurobiological origin is poorly understood. The aim of our study was therefore to characterize perfusion patterns in DLB patients that are associated with the severity and frequency of FC as measured both clinically and using objective neuropsychological assessments.
Spatial covariance analyses were applied to data derived from single photon emission computed tomography (SPECT) HMPAO brain imaging in 19 DLB and 23 AD patients. Patients underwent clinical assessment of their FC and cognitive function as well as objective testing of their attention.
Covariant perfusion principal components (PCs) were not associated with either FC or cognitive or attentional measures in AD. However, in DLB patients, the second PC (defined as DLB-cognitive motor pattern, DLB-PCI2) which was characterized by bilateral relative increases in cerebellum, basal ganglia, and supplementary motor areas and widespread bilateral decreases in parietal regions, positively correlated with poorer cognitive function, increased FC and worse attentional function measured both clinically and neurophysiologically (p < 0.05) as well as with the severity of bradykinesia (p = 0.04).
FC in DLB appears distinct from those seen in AD, and likely to be driven by internal neurobiological perturbations in brain circuitry as evidenced using spatial covariance analyses of cerebral perfusion. FC and certain aspects of attentional dysfunction in DLB may, in part, depend upon both distributed motor and non-motor networks.
attention; Alzheimer’s disease; single photon emission computed tomography; SPECT; imaging
We describe an analysis of genome variation in 825 Plasmodium falciparum samples from Asia and Africa that reveals an unusual pattern of parasite population structure at the epicentre of artemisinin resistance in western Cambodia. Within this relatively small geographical area we have discovered several distinct but apparently sympatric parasite subpopulations with extremely high levels of genetic differentiation. Of particular interest are three subpopulations, all associated with clinical resistance to artemisinin, which have skewed allele frequency spectra and remarkably high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalogue of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in various transporter proteins and DNA mismatch repair proteins. These data provide a population genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist its elimination.
Assistive technology and telecare (ATT) are relatively new ways of delivering care and support to people with social care needs. It is claimed that ATT reduces the need for community care, prevents unnecessary hospital admission, and delays or prevents admission into residential or nursing care. The current economic situation in England has renewed interest in ATT instead of community care packages. However, at present, the evidence base to support claims about the impact and effectiveness of ATT is limited, despite its potential to mitigate the high financial cost of caring for people with dementia and the social and psychological cost to unpaid carers.
ATTILA (Assistive Technology and Telecare to maintain Independent Living At Home for People with Dementia) is a pragmatic, multi-centre, randomised controlled trial over 104 weeks that compares outcomes for people with dementia who receive ATT and those who receive equivalent community services but not ATT. The study hypothesis is that fewer people in the ATT group will go into institutional care over the 4-year period for which the study is funded. The study aims to recruit 500 participants, living in community settings, with dementia or significant cognitive impairment, who have recently been referred to social services.
Primary outcome measures are time in days from randomisation to institutionalisation and cost effectiveness. Secondary outcomes are caregiver burden, health-related quality of life in carers, number and severity of serious adverse events, and data on acceptability, applicability and reliability of ATT intervention packages. Assessments will be undertaken in weeks 0 (baseline), 12, 24, 52 and 104 or until institutionalisation or withdrawal of the participant from the trial.
In a time of financial austerity, CASSRs in England are increasingly turning to ATT in the belief that it will deliver good outcomes for less money. There is an absence of robust evidence for the cost-effectiveness and benefit of using assistive technology and telecare. The ATTILA trial meets a pressing need for robust, generalisable evidence to either justify continuing investment or reappraise the appropriate scale of ATT use.
Current Controlled Trials
Assistive technology; Telecare; Dementia; Randomised control trial; Independence; Community living
Gap junction (GJ) channels composed of Connexin36 (Cx36) are widely expressed in the mammalian CNS and form electrical synapses between neurons. Here we described a novel modulatory mechanism of Cx36 GJ channels that is dependent on intracellular free magnesium ([Mg2+]i). We examined junctional conductance (gj) and its dependence on transjunctional voltage (Vj) at different [Mg2+]i in cultures of HeLa or N2A cells expressing Cx36. We found that Cx36 GJs are partially inhibited at resting [Mg2+]i, thus, gj can be augmented or reduced by lowering or increasing [Mg2+]i, respectively. Similar changes in gj and Vj-gating were observed using MgATP or K2ATP in pipette solutions, which increases or decreases [Mg2+]i, respectively. Changes in phosphorylation of Cx36 or in [Ca2+]i were not involved in the observed Mg2+-dependent modulation of gj. Magnesium ions permeate the channel and transjunctional asymmetry in [Mg2+]i resulted in asymmetric Vj-gating. The gj of GJs formed of Cxs 26, 32, 43, 45 and 47 was also reduced by increasing [Mg2+]i, but was not increased by lowering [Mg2+]i; single channel conductance did not change. We showed that [Mg2+]i affects both open probability and the number of functional channels, likely through binding in the channel lumen. Finally, we showed that Cx36-containing electrical synapses between neurons of the trigeminal mesencephalic nucleus in rat brain slices are similarly affected by changes in [Mg2+]i. Thus, this novel modulatory mechanism could underlie changes in neuronal synchronization under conditions in which ATP levels, and consequently [Mg2+]i, are modified.
Gap junctions in retinal photoreceptors suppress voltage noise and facilitate input of rod signals into the cone pathway during mesopic vision. These synapses are highly plastic and regulated by light and circadian clocks. Recent studies have revealed an important role for connexin36 (Cx36) phosphorylation by protein kinase A (PKA) in regulating cell-cell coupling. Dopamine is a light-adaptive signal in the retina, causing uncoupling of photoreceptors via D4 receptors (D4R), which inhibits adenylyl cyclase (AC) and reduces PKA activity. We hypothesized that adenosine, with its extracellular levels increasing in darkness, may serve as a dark signal to co-regulate photoreceptor coupling through modulation of gap junction phosphorylation. Both D4R and A2a receptor (A2aR) mRNAs were present in photoreceptors, inner nuclear layer neurons, and ganglion cells in C57BL/6 mouse retina, and showed cyclic expression with partially overlapping rhythms. Pharmacologically activating A2aR or inhibiting D4R in light-adapted daytime retina increased photoreceptor coupling. Cx36 among photoreceptor terminals, representing predominantly rod-cone gap junctions but possibly including some rod-rod and cone-cone gap junctions, was phosphorylated in a PKA-dependent manner by the same treatments. Conversely, inhibiting A2aR or activating D4R in daytime dark-adapted retina decreased Cx36 phosphorylation with similar PKA dependence. A2a-deficient mouse retina showed defective regulation of photoreceptor gap junction phosphorylation, fairly regular dopamine release, and moderately down-regulated expression of D4R and AC type I mRNA. We conclude that adenosine and dopamine co-regulate photoreceptor coupling through opposite action on the PKA pathway and Cx36 phosphorylation. In addition, loss of the A2aR hampered D4R gene expression and function.
Campylobacter jejuni is a natural commensal of the avian intestinal tract. However, the bacterium is also the leading cause of acute bacterial diarrhea worldwide and is implicated in development of Guillain-Barré syndrome. Like many bacterial pathogens, C. jejuni assembles complex surface structures that interface with the surrounding environment and are involved in pathogenesis. Recent work in C. jejuni identified a gene encoding a novel phosphoethanolamine (pEtN) transferase, EptC (Cj0256), that plays a promiscuous role in modifying the flagellar rod protein, FlgG; the lipid A domain of lipooligosaccharide (LOS); and several N-linked glycans. In this work, we report that EptC catalyzes the addition of pEtN to the first heptose sugar of the inner core oligosaccharide of LOS, a fourth enzymatic target. We also examine the role pEtN modification plays in circumventing detection and/or killing by host defenses. Specifically, we show that modification of C. jejuni lipid A with pEtN results in increased recognition by the human Toll-like receptor 4–myeloid differentiation factor 2 (hTLR4-MD2) complex, along with providing resistance to relevant mammalian and avian antimicrobial peptides (i.e., defensins). We also confirm the inability of aberrant forms of LOS to activate Toll-like receptor 2 (TLR2). Most exciting, we demonstrate that strains lacking eptC show decreased commensal colonization of chick ceca and reduced colonization of BALB/cByJ mice compared to wild-type strains. Our results indicate that modification of surface structures with pEtN by EptC is key to its ability to promote commensalism in an avian host and to survive in the mammalian gastrointestinal environment.