The morphology and electrophysiology of leech neurones in vitro: A study using microfabricated devices

1. This thesis considers the possibility of investigating neuronal information processing by making mulitisite recordings either from individual isolated neurones or from small neuronal networks of controlled design. 2. Isolated leech neurones were used (a) to study the effects of isolation on electrophysiological properties (Chapter 2); (b) to provide the first demonstration of the use of planar extracellular electrode arrays to measure electrophysiological properties of individual isolated neurones (Chapter 3); and (c) to investigate the use of topographical features for controlling the outgrowth of neurones in culture (Chapters 4 & 5). 3.The study into the effects of isolation confirmed and extended previous reports which showed that (a) the action potentials recorded from the cell body of isolated Retzius neurones are generally similar to action potentials recorded in vivo and (b) isolation causes an increase in input resistance. 4. The results of an experiment designed to show a correlation between input resistance and the length of processes, suggest that the removal of processes during extraction is not the main cause of the high input resistance of isolated cells. One possibility is that the input resistance is a direct result of a change in membrane properties. 5. This conclusion is supported by the demonstration in isolated neurones of a slow inward transient (known as anomolous rectification) that occurs shortly after the onset of large hyperpolarising current injections. This transient was not observed in dissected ganglia and has not been previously reported in leech neurones. 6. The electrophysiology of isolated nevirones was also explored using extracellular electrode arrays. Specifically the electrode arrays were used to show that: (a) the conduction velocity of action potentials in P cells is faster than that of action potentials in Retzius cells (which correlates with the difference in rise time); (b) the action potentials of isolated neurones propagate from the tip of the extracted process towards the cell body (indicating that the concentration of Na+ channels is greater at the tip of the extracted process than in other regions); and (c) the action potential in the extracted process may have a faster rise time than that in the cell body, suggesting a difference in the average concentration of Na+ channels. 7. The use of extracellular electrode arrays in the above experiments demonstrates: (a) the first multisite extracellular recordings of isolated neurones; (b) the first extracellular recordings made of the electrical activity that results from extracellular stimulation of the same cell; and (c) the feasibility of using these devices to investigate information processing in single cells. 8. In order to control the morphology of single neurones, and the connectivity of groups of neurones, the influence of the substratum in determining the morphology of cultured neurones was investigated. The principal result demonstrates for the first time that topography can influence the outgrowth morphology of large identified invertebrate neurones. The dimensions of the topographical features were similar to those required to align the neurites of much smaller vertebrate neurones. 9. The results also show that: (a) on planar Con A-coated substrata the outgrowth of Retzius neurones tends to be dominated by large lamellae, whereas on leech extracellular matrix (ECM)-coated substrata cells produced an elaborate network of neurites (confirming previous reports), (b) interference reflection microscopy (IRM) revealled that the neurites made a series of very close but intermittent contacts with the substratum, whereas the lamella was characterised by a large region of uniform close contact, and (c) whereas neurites were strongly influenced by topographical features the lamellar-type outgrowth was only partially aligned. 10. Based on these results a new hypothesis (the Topographical Modulating Hypothesis) is presented. The hypothesis proposes that the influence of topographical discontinuities in determining the morphology of neurones, or the orientation of migrating cells, is modulated by the molecular nature of the substrate

The Politics of Environmental Dispute Resolution

Also PCMA Working Paper #17.http://deepblue.lib.umich.edu/bitstream/2027.42/51148/1/380.pd

Beyond Environmental Regulatory Fragmentation: Signs of Integration in the Case of the Great Lakes Basin

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72007/1/j.1468-0491.1995.tb00197.x.pd

A nomenclature for restriction enzymes, DNA methyltransferases, homing endonucleases and their genes

A nomenclature is described for restriction endonucleases, DNA methyltransferases, homing endonucleases and related genes and gene products. It provides explicit categories for the many different Type II enzymes now identified and provides a system for naming the putative genes found by sequence analysis of microbial genome

International consensus conference recommendations on ultrasound education for undergraduate medical students

Objectives: The purpose of this study is to provide expert consensus recommendations to establish a global ultrasound curriculum for undergraduate medical students. Methods: 64 multi-disciplinary ultrasound experts from 16 countries, 50 multi-disciplinary ultrasound consultants, and 21 medical students and residents contributed to these recommendations. A modified Delphi consensus method was used that included a systematic literature search, evaluation of the quality of literature by the GRADE system, and the RAND appropriateness method for panel judgment and consensus decisions. The process included four in-person international discussion sessions and two rounds of online voting. Results: A total of 332 consensus conference statements in four curricular domains were considered: (1) curricular scope (4 statements), (2) curricular rationale (10 statements), (3) curricular characteristics (14 statements), and (4) curricular content (304 statements). Of these 332 statements, 145 were recommended, 126 were strongly recommended, and 61 were not recommended. Important aspects of an undergraduate ultrasound curriculum identified include curricular integration across the basic and clinical sciences and a competency and entrustable professional activity-based model. The curriculum should form the foundation of a life-long continuum of ultrasound education that prepares students for advanced training and patient care. In addition, the curriculum should complement and support the medical school curriculum as a whole with enhanced understanding of anatomy, physiology, pathophysiological processes and clinical practice without displacing other important undergraduate learning. The content of the curriculum should be appropriate for the medical student level of training, evidence and expert opinion based, and include ongoing collaborative research and development to ensure optimum educational value and patient care. Conclusions: The international consensus conference has provided the first comprehensive document of recommendations for a basic ultrasound curriculum. The document reflects the opinion of a diverse and representative group of international expert ultrasound practitioners, educators, and learners. These recommendations can standardize undergraduate medical student ultrasound education while serving as a basis for additional research in medical education and the application of ultrasound in clinical practice

Status of Muon Collider Research and Development and Future Plans

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].Comment: 95 pages, 75 figures. Submitted to Physical Review Special Topics, Accelerators and Beam

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead