Pamela L Shaw

Acetylcholinesterase knockouts establish central cholinergic pathways and can use butyrylcholinesterase to hydrolyze acetylcholine

Acetylcholinesterase is one of the most prominent constituents of central cholinergic pathways. It terminates the synaptic action of acetylcholine through hydrolysis and yields the choline moiety that is necessary for transmitter recycling. Despite these pivotal relationships, mice nullizygous for acetylcholinesterase established all principal anatomical components of central cholinergic pathways. No compensatory increase in the distribution of butyrylcholinesterase was detected. However, both the wild-type and nullizygous mice showed that butyrylcholinesterase enzyme activity extended to all parts of the brain receiving cholinergic innervation and that it could hydrolyze the acetylcholine surrogate acetylthiocholine. As opposed to acetylcholinesterase which was mostly of neuronal origin, butyrylcholinesterase appeared to be mostly of glial origin. These experiments lead to the unexpected conclusion that acetylcholinesterase is not necessary for the establishment of cholinergic pathways. They also show that butyrylcholinesterase can potentially substitute for acetylcholinesterase and that this enzyme is likely to play a constitutive (rather than just back-up) role in the hydrolysis of acetylcholine in the normal brain. The inhibition of butyrylcholinesterase may therefore provide a desirable feature of cholinergic therapies, including those aimed at treating Alzheimers disease.

Monoclonal antibodies that target pathological assemblies of Aβ

Amyloid beta (Aβ) immunotherapy for Alzheimers disease has shown initial success in mouse models of Alzheimers disease and in human patients. However, because of meningoencephalitis in clinical trials of active vaccination, approaches using therapeutic antibodies may be preferred. As a novel antigen to generate monoclonal antibodies, the current study has used Aβ oligomers (amyloid β‐derived diffusible ligands, ADDLs), pathological assemblies known to accumulate in Alzheimers disease brain. Clones were selected for the ability to discriminate Alzheimers disease from control brains in extracts and tissue sections. These antibodies recognized Aβ oligomers and fibrils but not the physiologically prevalent Aβ monomer. Discrimination derived from an epitope found in assemblies of Aβ1–28 and ADDLs but not in other sequences, including Aβ1–40. Immunoneutralization experiments showed that toxicity and attachment of ADDLs to synapses in culture could be prevented. ADDL‐induced reactive oxygen species (ROS) generation was also inhibited, establishing this response to be oligomer‐dependent. Inhibition occurred whether ADDLs were prepared in vitro or obtained from Alzheimers disease brain. As conformationally sensitive monoclonal antibodies that selectively immunoneutralize binding and function of pathological Aβ assemblies, these antibodies provide tools by which pathological Aβ assemblies from Alzheimers disease brain might be isolated and evaluated, as well as offering a valuable prototype for new antibodies useful for Alzheimers disease therapeutics.

Cholinergic nucleus basalis tauopathy emerges early in the aging-MCI-AD continuum

The cholinergic denervation in Alzheimers disease (AD) provides the rationale for treatments with anticholinesterases. The presence of this cholinergic lesion is solidly established in advanced AD. Whether it also exists in early disease remains unsettled. This question was addressed with thioflavin‐S histofluorescence to identify neurofibrillary tangles (NFT) and two tau antibodies (AT8, Alz‐50) to identify pre‐tangle cytopathology in the nucleus basalis, the source of cortical cholinergic innervation. Methods for the concurrent visualization of tauopathy and choline acetyltransferase were used to determine if the cytopathology was selectively located within cholinergic neurons. Five elderly index cases who had died at the stage of mild cognitive impairment (MCI) or early AD were identified by longitudinal neuropsychological and behavioral assessments. They were compared to 7 age‐matched cognitively normal subjects. NFT and AT8 (or Alz‐50) immunostaining in cholinergic nucleus basalis neurons existed even in the cognitively normal subjects. The percentage of tauopathy‐containing nucleus basalis neurons was greater in the cognitively impaired and showed a significant correlation with memory scores obtained 1‐18 months prior to death. These results show that cytopathology in cortical cholinergic pathways is a very early event in the course of the continuum that leads from advanced age to MCI and AD.

Locus coeruleus neurofibrillary degeneration in aging, mild cognitive impairment and early Alzheimer's disease

Neurofibrillary degeneration in the nucleus basalis and a loss of its cortical cholinergic projections are prominent components of the neuropathology in Alzheimers disease (AD). The AD brain is also associated with a degeneration of the noradrenergic projections arising from the nucleus locus coeruleus (LC), but the time course of this lesion is poorly understood. To determine whether the LC displays neurofibrillary abnormalities early in the course of events leading to AD, we examined tissue specimens from seven cognitively normal controls and five subjects at the stages of mild cognitively impairment (MCI) or early AD. Tyrosine hydroxylase immunochemistry was used as a marker of LC neurons while AT8 immunolabeling visualized abnormal tau associated with neurofibrillary tangles and their precursors. Thioflavine-S was used as a marker for fully developed tangles. We found that AT8-positive labeling and thioflavine-S positive tangles were present in both groups of specimens. However, the percentage of neurons containing each of these markers was significantly higher in the cognitively impaired group. The MMSE scores displayed a negative correlation with both markers of cytopathology. These results indicate that cytopathology in the LC is an early event in the age-MCI-AD continuum and that it may be listed among the numerous factors that mediate the emergence of the cognitive changes leading to dementia.

Use of Fetal Cortical Grafts in Hypoxic-Ischemic Brain Injury in Neonatal Rats

In view of numerous studies demonstrating that intracerebral implants of fetal neural tissue can promote functional recovery and structural repair in the damaged brain, the present study examined the potential use of neocortical transplantation in newborn rats that sustained hypoxic-ischemic brain injury. Ischemic insult was induced in Long-Evans, black-hooded 1-week-old rats by unilateral common carotid artery occlusion followed by 2.5 h of hypoxia in 8% O2. One week later, animals received neocortical block transplants. At 2-6 weeks posttransplantation, animals were sacrificed and their brains examined histologically. Transplants survived in over 80% of the animals and the presence of acetylcholinesterase-positive fibers crossing the host-transplant interface provided evidence of transplant integration with the host brain. However, morphometric measurements revealed that the transplants were unable to reduce the hypoxia-ischemia-induced degeneration in the host hippocampus, caudate-putamen, or thalamus. Nonetheless the demonstrated survival of grafts in the neonatal hypoxia-ischemia model suggests a potential therapeutic effect.

Neocortical transplants grafted into the newborn rat brain demonstrate a blood-brain barrier to macromolecules

Vascular permeability was examined in fetal neocortical transplants grafted into the cerebral cortex of newborn rats. Methods based on the histochemical labeling of intravenously administered horseradish peroxidase or on the immunocytochemical demonstration of endogenous immunoglobulin showed the presence of a blood barrier within the transplants.

Trauma system development in low- and middle-income countries: a review

BACKGROUND Trauma systems in resource-rich countries have decreased mortality for trauma patients through centralizing resources and standardizing treatment. Rapid industrialization and urbanization have increased the demand for formalized emergency medical services and trauma services (EMS and TS) in low- and middle-income countries (LMICs). This systematic review examines initiatives to develop EMS and TS systems in LMICs to inform the development of comprehensive prehospital care systems in resource-poor settings. MATERIALS AND METHODS EMS and TS system development publications were identified using MEDLINE, PubMed, and Scopus databases. Articles addressing subspecialty skill sets, public policy, or physicians were excluded. Two independent reviewers assessed titles, abstracts, and full texts in a hierarchical manner. RESULTS A total of 12 publications met inclusion criteria, and 10 unique LMIC EMS and TS programs were identified. Common initiatives included the integration of existing EMS and TS services and provision of standardized training and formalized certification processes for prehospital care providers, as well as the construction of a conceptual framework for system development through the public health model. CONCLUSIONS There is no single model of EMS and TS systems, and successful programs are heterogeneous across regions. Successful EMS and TS systems share common characteristics. A predevelopment needs assessment is critical in identifying existing EMS and TS resources as a foundation for further development. Implementation requires coordination of preexisting resources with cost-effective initiatives that involve local stakeholders. High-impact priority areas are identified to focus improvements. Financial stresses and mismatching of resources in LMICs are common and are more commonly encountered when implementing a high-income model EMS and TS in an LMIC. Preimplementation and postimplementation evaluations can determine the efficacy of initiatives to strengthen EMS and TS systems.

Using the Bioconductor GeneAnswers Package to Interpret Gene Lists

Use of microarray data to generate expression profiles of genes associated with disease can aid in identification of markers of disease and potential therapeutic targets. Pathway analysis methods further extend expression profiling by creating inferred networks that provide an interpretable structure of the gene list and visualize gene interactions. This chapter describes GeneAnswers, a novel gene-concept network analysis tool available as an open source Bioconductor package. GeneAnswers creates a gene-concept network and also can be used to build protein-protein interaction networks. The package includes an example multiple myeloma cell line dataset and tutorial. Several network analysis methods are included in GeneAnswers, and the tutorial highlights the conditions under which each type of analysis is most beneficial and provides sample code.

Characteristics of Epstein-Barr Virus Envelope Protein gp42

Epstein–Barr virus (EBV) glycoprotein 42 (gp42) is a membrane protein essential for fusion and entry of EBV into host B-lymphocytes. Gp42 is a member of the protein-fold family C-type lectin or lectin-like domains (CLECT or CTLD) and specifically is classified as a natural-killer receptor (NKR)-like CLECT. Literature review and phylogenetic comparison show that EBV gp42 shares a common structure with other NKR-like CLECTs and possibly with many viral CTLDs, but does not appear to exhibit some common binding characteristics of many CTLDs, such as features required for calcium binding. The flexible N-terminal region adjacent to the CTLD fold is important for binding to other EBV glycoproteins and for a cleavage site that is necessary for infection of host cells. From structural studies of gp42 unbound and bound to receptor and extensive mutational analysis, a general model of how gp42 triggers membrane fusion utilizing both the flexible N-terminal region and the CTLD domain has emerged.

Review and evaluation of electronic health records-driven phenotype algorithm authoring tools for clinical and translational research

OBJECTIVE To review and evaluate available software tools for electronic health record-driven phenotype authoring in order to identify gaps and needs for future development. MATERIALS AND METHODS Candidate phenotype authoring tools were identified through (1) literature search in four publication databases (PubMed, Embase, Web of Science, and Scopus) and (2) a web search. A collection of tools was compiled and reviewed after the searches. A survey was designed and distributed to the developers of the reviewed tools to discover their functionalities and features. RESULTS Twenty-four different phenotype authoring tools were identified and reviewed. Developers of 16 of these identified tools completed the evaluation survey (67% response rate). The surveyed tools showed commonalities but also varied in their capabilities in algorithm representation, logic functions, data support and software extensibility, search functions, user interface, and data outputs. DISCUSSION Positive trends identified in the evaluation included: algorithms can be represented in both computable and human readable formats; and most tools offer a web interface for easy access. However, issues were also identified: many tools were lacking advanced logic functions for authoring complex algorithms; the ability to construct queries that leveraged un-structured data was not widely implemented; and many tools had limited support for plug-ins or external analytic software. CONCLUSIONS Existing phenotype authoring tools could enable clinical researchers to work with electronic health record data more efficiently, but gaps still exist in terms of the functionalities of such tools. The present work can serve as a reference point for the future development of similar tools.