Mammalian Comparative Sequence Analysis of the Agrp Locus

Agouti-related protein encodes a neuropeptide that stimulates food intake. Agrp expression in the brain is restricted to neurons in the arcuate nucleus of the hypothalamus and is elevated by states of negative energy balance. The molecular mechanisms underlying Agrp regulation, however, remain poorly defined. Using a combination of transgenic and comparative sequence analysis, we have previously identified a 760 bp conserved region upstream of Agrp which contains STAT binding elements that participate in Agrp transcriptional regulation. In this study, we attempt to improve the specificity for detecting conserved elements in this region by comparing genomic sequences from 10 mammalian species. Our analysis reveals a symmetrical organization of conserved sequences upstream of Agrp, which cluster into two inverted repeat elements. Conserved sequences within these elements suggest a role for homeodomain proteins in the regulation of Agrp and provide additional targets for functional evaluation

Prediction of potential for organ donation after cardiac death in patients in neurocritical state: a prospective observational study

Background Successful donation of organs after cardiac death (DCD) requires identification of patients who will die within 60 mm of withdrawal of life-sustaining treatment (WLST). We aimed to validate a straightforward model to predict the likelihood of death within 60 min of WLST in patients with irreversible brain injury. Methods In this multicentre, observational study, we prospectively enrolled consecutive comatose patients with irreversible brain injury undergoing WLST at six medical centres in the USA and the Netherlands. We assessed four clinical characteristics (corneal reflex, cough reflex, best motor response, and oxygenation index) as predictor variables, which were selected on the basis of previous findings. We excluded patients who had brain death or were not intubated. The primary endpoint was death w Findings We included 178 patients, 82 (46%) of whom died within 60 mm of WLST. Absent corneal reflexes (odds ratio [OR] 2.67, 95% CI 1.19-6.01; p=0.0173; 1 point), absent cough reflex (4.16, 1.79-9.70; p=0.0009; 2 points), extensor or absent motor responses (2.99, 1.22-7.34; p=0.0168; 1 point), and an oxygenation index score of more than 3.0 (2.31, 1.10-4.88; p=0.0276; 1 point) were predictive of death within 60 mm of WLST. 59 of 82 patients who died within 60 min of WLST had DCD-N scores of 3 o Interpretation The DCD-N score can be used to predict potential candidates for DCD in patients with non-survivable brain injury. However, this score needs to be tested specifically in a cohort of potential donors participating in DCD protocols

Spreading depolarisations and outcome after traumatic brain injury: a prospective observational study

Background Pathological waves of spreading mass neuronal depolarisation arise repeatedly in injured, but potentially salvageable, grey matter in 50-60% of patients after traumatic brain injury (TBI). We aimed to ascertain whether spreading depolarisations are independently associated with unfavourable neurological outcome. Methods We did a prospective, observational, multicentre study at seven neurological centres. We enrolled 109 adults who needed neurosurgery for acute TBI. Spreading depolarisations were monitored by electrocorticography during intensive care and were classified as cortical spreading depression (CSD) if they took place in spontaneously active cortex or as isoelectric spreading depolarisation (ISD) if they took place in isoelectric cortex. Investigators who treated patients and assessed outcome were masked to electrocorticographic results. Scores on the extended Glasgow outcome scale at 6 months were fitted to a multivariate model by ordinal regression. Prognostic score (based on variables at admission, as validated by the IMPACT studies) and spreading depolarisation category (none, CSD only, or at least one ISD) were assessed as outcome predictors. Findings Six individuals were excluded because of poor-quality electrocorticography. A total of 1328 spreading depolarisations arose in 58 (56%) patients. In 38 participants, all spreading depolarisations were classified as CSD; 20 patients had at least one ISD. By multivariate analysis, both prognostic score (p=0.0009) and spreading depolarisation category (p=0.0008) were significant predictors of neurological outcome. CSD and ISD were associated with an increased risk of unfavourable outcome (common odds ratios 1.56 [95% CI 0.72-3.37] and 7.58 [2.64-21.8], respectively). Addition of depolarisation category to the regression model increased the proportion of variance in outcome that could be attributed to predictors from 9% to 22%, compared with the prognostic score alone. Interpretation Spreading depolarisations were associated with unfavourable outcome, after controlling for conventional prognostic variables. The possibility that spreading depolarisations have adverse effects on the traumatically injured brain, and therefore might be a target in the treatment of TBI, deserves further research

Inter-site and inter-scanner diffusion MRI data harmonization.

We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the proposed method