Hitchhiker’s Guide to Voltammetry: Acute and Chronic Electrodes for in Vivo Fast-Scan Cyclic Voltammetry

Fast-scan cyclic voltammetry (FSCV) has been used for over 20 years to study rapid neurotransmission in awake and behaving animals. These experiments were first carried out with carbon-fiber microelectrodes (CFMs) encased in borosilicate glass, which can be inserted into the brain through micromanipulators and guide cannulas. More recently, chronically implantable CFMs constructed with small diameter fused-silica have been introduced. These electrodes can be affixed in the brain with minimal tissue response, which permits longitudinal measurements of neurotransmission in single recording locations during behavior. Both electrode designs have been used to make novel discoveries in the fields of neurobiology, behavioral neuroscience, and psychopharmacology. The purpose of this Review is to address important considerations for the use of FSCV to study neurotransmitters in awake and behaving animals, with a focus on measurements of striatal dopamine. Common issues concerning experimental design, data collecti..

A Survey of New Temperature-Sensitive, Embryonic-Lethal Mutations in C. elegans: 24 Alleles of Thirteen Genes

To study essential maternal gene requirements in the early C. elegans embryo, we have screened for temperature-sensitive, embryonic lethal mutations in an effort to bypass essential zygotic requirements for such genes during larval and adult germline development. With conditional alleles, multiple essential requirements can be examined by shifting at different times from the permissive temperature of 15°C to the restrictive temperature of 26°C. Here we describe 24 conditional mutations that affect 13 different loci and report the identity of the gene mutations responsible for the conditional lethality in 22 of the mutants. All but four are mis-sense mutations, with two mutations affecting splice sites, another creating an in-frame deletion, and one creating a premature stop codon. Almost all of the mis-sense mutations affect residues conserved in orthologs, and thus may be useful for engineering conditional mutations in other organisms. We find that 62% of the mutants display additional phenotypes when shifted to the restrictive temperature as L1 larvae, in addition to causing embryonic lethality after L4 upshifts. Remarkably, we also found that 13 out of the 24 mutations appear to be fast-acting, making them particularly useful for careful dissection of multiple essential requirements. Our findings highlight the value of C. elegans for identifying useful temperature-sensitive mutations in essential genes, and provide new insights into the requirements for some of the affected loci

Alternative Splicing in the Differentiation of Human Embryonic Stem Cells into Cardiac Precursors

The role of alternative splicing in self-renewal, pluripotency and tissue lineage specification of human embryonic stem cells (hESCs) is largely unknown. To better define these regulatory cues, we modified the H9 hESC line to allow selection of pluripotent hESCs by neomycin resistance and cardiac progenitors by puromycin resistance. Exon-level microarray expression data from undifferentiated hESCs and cardiac and neural precursors were used to identify splice isoforms with cardiac-restricted or common cardiac/neural differentiation expression patterns. Splice events for these groups corresponded to the pathways of cytoskeletal remodeling, RNA splicing, muscle specification, and cell cycle checkpoint control as well as genes with serine/threonine kinase and helicase activity. Using a new program named AltAnalyze (http://www.AltAnalyze.org), we identified novel changes in protein domain and microRNA binding site architecture that were predicted to affect protein function and expression. These included an enrichment of splice isoforms that oppose cell-cycle arrest in hESCs and that promote calcium signaling and cardiac development in cardiac precursors. By combining genome-wide predictions of alternative splicing with new functional annotations, our data suggest potential mechanisms that may influence lineage commitment and hESC maintenance at the level of specific splice isoforms and microRNA regulation

Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

Future Directions for Global Clinical Neurosurgical Training: Challenges and Opportunities

OBJECTIVE: Expanded access to training opportunities is necessary to address 5 million essential neurosurgical cases not performed annually, nearly all in low- and middle-income countries (LMICs). To target this critical neurosurgical manpower issue and advance positive collaborations developed the Global Neurosurgery 2019: A Practical Symposium, a summit was designed to assemble stakeholders in global neurosurgical clinical education to discuss innovative platforms for clinical neurosurgery fellowships. METHODS: The Global Neurosurgery Education Summit was held in November 2021, with a total of 30 presentations from directors and trainees in existing global neurosurgical clinical fellowships. Presenters were selected based on chain referral sampling from suggestions made primarily from young neurosurgeons in LMIC. Presentations focused on the perspectives of hosts, local champions and trainees on clinical global neurosurgery fellowships and virtual learning resources. This conference sought to identify factors for success in overcoming barriers to improving access, equity, throughput, and quality of clinical global neurosurgery fellowships. A pre-conference survey was disseminated to attendees. RESULTS: Presentations included in-country training courses, twinning programs, provision of surgical labs and resources, existing virtual educational resources, and virtual teaching technologies, with reference to their applicability to hybrid training fellowships. Virtual learning resources developed during the COVID-19 pandemic and high-fidelity surgical simulators were presented, some for the first time to this audience. CONCLUSION: The summit provided a forum for discussion of current challenges and opportunities for developing a collaborative consortium capable of designing a pilot program for efficient, sustainable, accessible, and affordable clinical neurosurgery fellowship models for the future

<i>par-2</i> mutants.

<p>A. DIC time-lapse images of wild-type <i>par-2(or373 </i>ts<i>)</i>, <i>par-2(or539 </i>ts<i>)</i>, and <i>par-2(or640 </i>ts<i>)</i> embryos. The blastomeres in the <i>par-2</i> mutants were of similar size at the two cell stage and initiated mitosis simultaneously, in contrast to the wild type. The <i>par-2(or373 </i>ts<i>)</i> embryo was obtained from a hermaphrodite shifted to the restrictive temperature for 5 hours prior to imaging. The <i>par-2(or539 </i>ts<i>)</i> and par-<i>2(or540 </i>ts<i>)</i> embryos were obtained from hermaphrodites shifted to the restrictive temperature for 30 minutes prior to imaging. Arrows indicate mitotic spindles at the two cell stage. Times in min:sec are given relative to AB NEBD. Scale bar, 10 µm. B. Defect map for individual embryos observed during time-lapse recordings, embryos are listed on the left and phenotypes are listed on the top: 1; Normal one cell embryo; 2; assymetric two cell embyro, 3; asynchronous two cell divisions. In the long upshifts, hermaphrodites were transferred to the restrictive temperature for 5–8 hours. In the short upshifts, embryos were harvested from hermaphrodites transferred to the restrictive temperature for 30 minutes. C. Amino acid alteration in the <i>par-2(or373 </i>ts<i>)</i> mutant. Asterisk indicates the changed residue. Homologous proteins are aligned below the <i>C. elegans</i> protein.</p