Kinetics of the Formation and Dissociation of Actin Filament Branches Mediated by Arp2/3 Complex

AbstractThe actin filament network at the leading edge of motile cells relies on localized branching by Arp2/3 complex from “mother” filaments growing near the plasma membrane. The nucleotide bound to the mother filaments (ATP, ADP and phosphate, or ADP) may influence the branch dynamics. To determine the effect of the nucleotide bound to the subunits of the mother filament on the formation and stability of branches, we compared the time courses of actin polymerization in bulk samples measured using the fluorescence of pyrene actin with observations of single filaments by total internal reflection fluorescence microscopy. Although the branch nucleation rate in bulk samples was nearly the same regardless of the nucleotide on the mother filaments, we observed fewer branches by microscopy on ADP-bound filaments than on ADP-Pi-bound filaments. Observation of branches in the microscope depends on their binding to the slide. Since the probability that a branch binds to the slide is directly related to its lifetime, we used counts of branches to infer their rates of dissociation from mother filaments. We conclude that the nucleotide on the mother filament does not affect the initial branching event but that branches are an order of magnitude more stable on the sides of new ATP- or ADP-Pi filaments than on ADP-actin filaments

New graduate registered nurses in public health

This presentation investigates the following objectives: 1) to discuss current challenges facing the public health nursing profession; 2) to synthesize existing literature regarding new graduate registered nurses (RNs) in public health; 3) to present the benefits of hiring new graduate RNs with baccalaureate degrees into public health agencies; 4) to utilize existing literature to suggest support measures that will optimize new graduate RNs’ success in public health

An assessment of the polytypic status of the Namib darkling beetles Onymacris unguicularis and Onymacris rugatipennis

Rachel M. Pollard is the winner of the 2014 Michael F. Bassman Honors Thesis AwardThe southern African beetle genus Onymacris (family Tenebrionidae) comprises 14 species, six of which are polytypic. Despite longstanding research on the physiological and behavioral adaptations of these desert beetles, little is known about their evolutionary relationships, particularly regarding the validity of currently recognized subspecies. In this study, I examined the polytypic status of the species Onymacris unguicularis and O. rugatipennis, each composed of two subspecies. The first, Onymacris unguicularis, is restricted to vegetationless dunes and is renowned for an unusual drinking behavior called fog basking. Northern populations—isolated from southern populations by approximately 300 km of duneless land—compose the subspecies O. u schulzeae, which exhibits only minor morphological differences from the southern subspecies, O. u. unguicularis. The second species, Onymacris rugatipennis, also contains two subspecies—O. r. rugatipennis and O. r. albotessellata—which are distinguished by the latter’s white wax bloom on the dorsum. Their ranges are contiguous and slightly overlapping, with O. r. rugatipennis occurring primarily along riverbanks and O. r. albotessellata occurring on dune bases. To assess the validity of the subspecies of O. unguicularis, I analyzed morphological variation in 35 specimens of O. u. schulzeae and 95 of O. u. unguicularis as well as mitochondrial DNA (mtDNA) sequence variation in five O. u. schulzeae and ten O. u. unguicularis. For O. rugatipennis, I examined only mitochondrial DNA sequence variation, generating sequence data for 11 O. r. rugatipennis and 12 O. r. albotessellata. Phylogenetic analysis of the mtDNA data revealed reciprocal monophyly between O. u. unguicularis and O. u. schulzeae, a pattern complementary to their morphological variation. On the basis of congruent phenotypic diversity, geographic delimitation, and genetic variation, I support the recognition of O. u. unguicularis and O. u. schulzeae as valid taxa. Conversely, the limited genetic divergence, absence of phylogeographic structuring, and number of shared haplotypes between O. r. rugatipennis and O. r. albotessellata suggest this species would be better regarded as a monotypic taxon

Videofluoroscopic Evaluation of the Pharynx and Upper Esophageal Sphincter in the Dog: A Systematic Review of the Literature

Background: Diseases of the pharynx and upper esophageal sphincter can result in debilitating respiratory difficulty, dysphagia or a combination of both. An exact diagnosis is essential to properly prognosticate and guide therapy. Videofluoroscopic assessment of the pharynx and upper esophageal sphincter with or without orally administered contrast material is the diagnostic of choice for many diseases as both anatomic and functional information is gleaned. The purpose of this review is to assess for continuity in imaging protocols across institutions and to record quantitative and qualitative parameters used for analysis of videofluoroscopy of the pharynx and upper esophageal sphincter in dogs.Methods: A systematic literature search was performed including articles published in peer-reviewed veterinary journals involving the topic of videofluoroscopy of the pharynx and upper esophageal sphincter through August 1, 2018. Specifics of study acquisition technique were recorded. Quantitative and qualitative videofluoroscopic parameters were recorded and compared across institutions where appropriate using one-way ANOVA with p ≤ 0.05 being considered significant.Results: Videofluoroscopy of the pharynx and upper esophageal sphincter is performed either in right lateral or standing postures depending on the institution. Bolus size and consistency used during contrast videofluoroscopy of swallowing differs between institutions. Some institutions evaluate videofluoroscopic studies using qualitative criteria while others apply quantitative measures. Reported quantitative measures include inter-swallow interval, swallow rate, jaw cycles per swallow ratio, time to upper esophageal opening, maximal pharyngeal contraction, maximum laryngeal excursion, upper esophageal closure, epiglottic re-opening, and pharyngeal constriction ratio. Measurement outcomes are significantly different between institutions and when bolus size/consistency is variable when assessing healthy dogs.Conclusions: The current peer-reviewed literature on fluoroscopic evaluation of the pharynx and UES in dogs shows a lack of standardization regarding imaging protocol. There is not a standard set of quantitative criteria applied amongst the institutions and there are significant differences in the outcomes obtained from videofluoroscopic assessment of swallowing suggesting significant inter-observer or inter-institutional variability. A consensus statement regarding imaging protocol and what parameters should be used to interpret airway and swallowing videofluoroscopic studies of the pharynx and UES in dogs is needed along with targeted analysis of observer variability

Survey of physics reasoning on uncertainty concepts in experiments: an assessment of measurement uncertainty for introductory physics labs

Measurement uncertainty is a critical feature of experimental research in the physical sciences, and the concepts and practices surrounding measurement uncertainty are important components of physics lab courses. However, there has not been a broadly applicable, research-based assessment tool that allows physics instructors to easily measure students' knowledge of measurement uncertainty concepts and practices. To address this need, we employed Evidence-Centered Design to create the Survey of Physics Reasoning on Uncertainty Concepts in Experiments (SPRUCE). SPRUCE is a pre-post assessment instrument intended for use in introductory (first- and second-year) physics lab courses to help instructors and researchers identify student strengths and challenges with measurement uncertainty. In this paper, we discuss the development of SPRUCE's assessment items guided by Evidence-Centered Design, focusing on how instructors' and researchers' assessment priorities were incorporated into the assessment items and how students' reasoning from pilot testing informed decisions around item answer options.Comment: 23 pages, 11 figures, submitted as part of the Physical Review Physics Education Research Focused Collection on Instructional Labs: Improving Traditions and New Direction

A systematic review and taxonomy of tools for evaluating evidence-based medicine teaching in medical education

Background: The importance of teaching the skills and practice of evidence-based medicine (EBM) for medical professionals has steadily grown in recent years. Alongside this growth is a need to evaluate the effectiveness of EBM curriculum as assessed by competency in the five ‘A’s’: asking, acquiring, appraising, applying and assessing (impact and performance). EBM educators in medical education will benefit from a compendium of existing assessment tools for assessing EBM competencies in their settings. The purpose of this review is to provide a systematic review and taxonomy of validated tools that evaluate EBM teaching in medical education. Methods: We searched MEDLINE, EMBASE, Cochrane library, Educational Resources Information Centre (ERIC), Best Evidence Medical Education (BEME) databases and references of retrieved articles published between January 2005 and March 2019. We have presented the identified tools along with their psychometric properties including validity, reliability and relevance to the five domains of EBM practice and dimensions of EBM learning. We also assessed the quality of the tools to identify high quality tools as those supported by established interrater reliability (if applicable), objective (non-self-reported) outcome measures and achieved ≥ 3 types of established validity evidence. We have reported our study in accordance with the PRISMA guidelines. Results: We identified 1719 potentially relevant articles of which 63 full text articles were assessed for eligibility against inclusion and exclusion criteria. Twelve articles each with a unique and newly identified tool were included in the final analysis. Of the twelve tools, all of them assessed the third step of EBM practice (appraise) and four assessed just that one step. None of the twelve tools assessed the last step of EBM practice (assess). Of the seven domains of EBM learning, ten tools assessed knowledge gain, nine assessed skills and-one assessed attitude. None addressed reaction to EBM teaching, self-efficacy, behaviours or patient benefit. Of the twelve tools identified, six were high quality. We have also provided a taxonomy of tools using the CREATE framework, for EBM teachers in medical education. Conclusions: Six tools of reasonable validity are available for evaluating most steps of EBM and some domains of EBM learning. Further development and validation of tools that evaluate all the steps in EBM and all educational outcome domains are needed

Craniomaxillofacial Trauma in Dogs-Part II: Association Between Fracture Location, Morphology and Etiology.

Treatment of craniomaxillofacial (CMF) trauma in dogs requires a thorough understanding of the CMF skeletal structures involved. The human medical literature has several examples of CMF trauma and fracture classification, including the classically described Le Fort fractures. The recent classification schemes require large studies using computed tomography (CT). In the veterinary medical literature, such studies are lacking. The aims of part II of this retrospective study were to use a large number of CT studies of dogs evaluated for CMF trauma to determine whether specific fracture locations in the CMF region occur concurrently, and whether trauma etiology influences fracture morphology. This information may then be used to form a fracture classification scheme in the future. The medical records and CT studies of 165 dogs over a 10-year period were evaluated. The skeletal location of CMF fractures as well as the severity of displacement and fragmentation of each fracture was recorded. Dogs' demographic data and trauma etiology were also recorded. Fractured portions of the mandible tended to occur with fractures of adjacent bones, with the major exception of symphyseal separation, which occurred simultaneously with fractures of the cribriform plate. Fractures of the maxillary bone were accompanied by many concurrent fractures affecting the majority of the midface, skull base, and cranial vault. When the zygomatic bone was fractured, the other bones comprising the orbit also tended to fracture. Fractures of the relatively superficially located frontal and nasal bones were often accompanied by fractures of the skull base. Fracture etiology influenced fracture morphology such that vehicular trauma resulted in a relatively higher number of severely displaced and comminuted fractures than did other trauma etiologies. This study provides examples of fractures that, when found, should prompt veterinarians to look for additional injuries in specific locations. In addition, it further highlights the need for thorough CT evaluation of the entire CMF region, even when clinically apparent fractures appear relatively superficial

Craniomaxillofacial Trauma in Dogs-Part I: Fracture Location, Morphology and Etiology.

Treatment of craniomaxillofacial (CMF) trauma in dogs often requires a multidisciplinary approach and a thorough understanding of the CMF skeletal structures involved. The aim of this retrospective study was to use a large number of CT studies of dogs evaluated for CMF trauma and to describe fracture location and morphology in relation to demographic data and trauma etiology. The medical records and CT studies of 165 dogs over a 10-year period were evaluated. The skeletal location of CMF fractures as well as the severity of displacement and fragmentation of each fracture was recorded. Patient demographic data and trauma etiology were also recorded. Animal bites accounted for the majority of trauma (50%), followed by unknown trauma (15%), vehicular accidents (13%), and blunt force trauma (13%). Small dogs, <10 kg, and juveniles accounted for the majority of patients (41.8 and 25.5%, respectively). The most likely bone or region to be fractured was the maxillary bone, followed by the premolar and molar regions of the mandible. Up to 37 bones or regions were fractured in any given patient, with an average of 8.2 fractured bones or regions per dog. The most commonly fractured location varied according to trauma etiology. Specifically, vehicular accidents tended to result in more locations with a higher probability of fracture than other trauma types. A major conclusion from this study is that every bone of the CMF region was fractured in at least one case and many cases had a large number of fractured regions. Thus, the need for comprehensive assessment of the entire CMF region, preferably using CT, is underscored

FGF4 retrogene on CFA12 is responsible for chondrodystrophy and intervertebral disc disease in dogs.

Chondrodystrophy in dogs is defined by dysplastic, shortened long bones and premature degeneration and calcification of intervertebral discs. Independent genome-wide association analyses for skeletal dysplasia (short limbs) within a single breed (PBonferroni = 0.01) and intervertebral disc disease (IVDD) across breeds (PBonferroni = 4.0 × 10-10) both identified a significant association to the same region on CFA12. Whole genome sequencing identified a highly expressed FGF4 retrogene within this shared region. The FGF4 retrogene segregated with limb length and had an odds ratio of 51.23 (95% CI = 46.69, 56.20) for IVDD. Long bone length in dogs is a unique example of multiple disease-causing retrocopies of the same parental gene in a mammalian species. FGF signaling abnormalities have been associated with skeletal dysplasia in humans, and our findings present opportunities for both selective elimination of a medically and financially devastating disease in dogs and further understanding of the ever-growing complexity of retrogene biology