A Novel Public MR Image Dataset of Multiple Sclerosis Patients With Lesion Segmentations Based on Multi-rater Consensus

Quantified volume and count of white-matter lesions based on magnetic resonance (MR) images are important biomarkers in several neurodegenerative diseases. For a routine extraction of these biomarkers an accurate and reliable automated lesion segmentation is required. To objectively and reliably determine a standard automated method, however, creation of standard validation datasets is of extremely high importance. Ideally, these datasets should be publicly available in conjunction with standardized evaluation methodology to enable objective validation of novel and existing methods. For validation purposes, we present a novel MR dataset of 30 multiple sclerosis patients and a novel protocol for creating reference white-matter lesion segmentations based on multi-rater consensus. On these datasets three expert raters individually segmented white-matter lesions, using in-house developed semi-automated lesion contouring tools. Later, the raters revised the segmentations in several joint sessions to reach a consensus on segmentation of lesions. To evaluate the variability, and as quality assurance, the protocol was executed twice on the same MR images, with a six months break. The obtained intra-consensus variability was substantially lower compared to the intra- and inter-rater variabilities, showing improved reliability of lesion segmentation by the proposed protocol. Hence, the obtained reference segmentations may represent a more precise target to evaluate, compare against and also train, the automatic segmentations. To encourage further use and research we will publicly disseminate on our website http://lit.fe.uni-lj.si/tools the tools used to create lesion segmentations, the original and preprocessed MR image datasets and the consensus lesion segmentations.     

Acute systemic MK‐801 induced functional uncoupling between hippocampal areas CA3 and CA1 with distant effect in the retrosplenial cortex

The hippocampus and retrosplenial cortex are integrated within a higher‐order cognitive circuit supporting relational (spatial, contextual, episodic) forms of learning and memory. Hippocampal place cells can coordinate multiple parallel representations in the same physical environment. Novel environment exploration triggers expression of immediate‐early genes (IEGs) Arc and Homer1a in spatial context‐specific ensembles of CA1 and CA3 neurons. Less is know about ensemble coding in the retrosplenial cortex (RSC), a region directly connected and functionally coupled to CA1. Hippocampal and retrosplenial damage is found in patients with schizophrenia alongside cognitive deficits affecting relational memory. Systemic administration of non‐competitive NMDAR antagonists such as MK‐801 is used to model psychosis in animals and humans. Acute systemic MK‐801 (0.15 mg/kg) impaired cognitive control in rats and ensemble code for spatial context in CA1. Here, we use expression of immediate‐early genes Arc and Homer 1a to examine ensemble coding in rat CA3 and RSC to test if the effect of MK‐801 extends upstream and downstream of CA1, respectively. Different rats explored the same context twice (A/A), explored two distinct contexts (A/B) or remained in their home cage (CC). In contrast to CA1, MK‐801 did not affect ensemble coding in CA3. Unlike CA3 and CA1, similarity of RSC ensembles active during exploration did not reflect change in spatial context, but MK‐801 (0.15 mg/kg) increased similarity in RSC ensembles active during spontaneous behavior in the home cage. The data provide support for MK‐801‐induced functional uncoupling between CA3 and CA1 and suggest that ensemble coding deficit may extend downstream of CA1. This deficit may reflect hyperassociative state in the cognitive circuit underlying cognitive disorganization in psychosis. © 2016 Wiley Periodicals, Inc.     

Pentapeptide-modified poly(N,N-diethylacrylamide) hydrogel scaffolds for tissue engineering

Poly(N,N-diethylacrylamide) (PDEAAm) hydrogel scaffolds were prepared by radical copolymerization of N,N-diethylacrylamide (DEAAm), N,N'-methylenebisacrylamide and methacrylic acid in the presence of (NH?)?SO? or NaCl. The hydrogels were characterized by low-vacuum scanning electron microscopy in the water-swollen state, water and cyclohexane regain, and by mercury porosimetry. The pentapeptide, YIGSR-NH?, was immobilized on the hydrogel. Human embryonic stem cells (hESCs) were cultured with the hydrogels to test their biocompatibility. The results suggest that the PDEAAm hydrogel scaffolds are nontoxic and support hESC attachment and proliferation, and that interconnected pores of the scaffolds are important for hESC cultivation. Immobilization of YIGSR-NH? pentapeptide on the PDEAAm surface improved both adhesion and growth of hESCs compared with the unmodified hydrogel. The YIGSR-NH?-modified PDEAAm hydrogels may be a useful tool for tissue-engineering purposes.     

Brain Natriuretic Peptide Concentrations After Aneurysmal Subarachnoid Hemorrhage: Relationship with Hypovolemia and Hyponatremia

Background  

Hyponatremia and hypovolemia occur often after aneurysmal subarachnoid hemorrhage (SAH) and are associated with poor outcome. The authors investigated whether brain natriuretic peptide (BNP) is related to hypovolemia and hyponatremia after SAH and whether it can differentiate between hypovolemic and non-hypovolemic hyponatremia.