Prospectus, March 16, 2005

https://spark.parkland.edu/prospectus_2005/1008/thumbnail.jp

Room 101: The Social SAC

This column looks at the SAC at the University of Bradford (UoB), which is commonly known as Room 101. The column looks at how Room 101 has reacted to the problem of reduced usage as a result of the cancellation of foreign language courses at the UoB, social media making online communication between learners easier, and the availability of online resources which have reduced the perceived importance of SAC resources (such as books and CDs)

Studies in Self-Access Learning Journal Researching the New Room 101: "A Safe Haven for Me to Learn"

To cite this article Allhouse, M. (2014). Researching the new Room 101: "A safe haven for me to learn&quot

Calcium- and myosin-dependent changes in troponin structure during activation of heart muscle

‘The definitive version is available at www3.interscience.wiley.com '. Copyright The Physiological Society. DOI: 10.1113/jphysiol.2008.164707Each heartbeat is triggered by a pulse of intracellular calcium ions which bind to troponin on the actin-containing thin filaments of heart muscle cells, initiating a change in filament structure that allows myosin to bind and generate force. We investigated the molecular mechanism of calcium regulation in demembranated trabeculae from rat ventricle using polarised fluorescence from probes on troponin C (TnC). Native TnC was replaced by double-cysteine mutants of human cardiac TnC with bifunctional rhodamine attached along either the C helix, adjacent to the regulatory Ca2+-binding site, or the E helix in the IT arm of the troponin complex. Changes in the orientation of both troponin helices had the same steep Ca2+-dependence as active force production, with a Hill coefficient (nH) close to 3, consistent with a single co-operative transition controlled by Ca2+ binding. Complete inhibition of active force by 25 μM blebbistatin had very little effect on the Ca2+-dependent structural changes and in particular did not significantly reduce the value of nH. Binding of rigor myosin heads to thin filaments following MgATP depletion in the absence of Ca2+ also changed the orientation of the C and E helices, and addition of Ca2+ in rigor produced further changes characterized by increased Ca2+ affinity but nH close to 1. These results show that, although myosin binding can switch on thin filaments in rigor conditions, it does not contribute significantly under physiological conditions. The physiological mechanism of co-operative Ca2+-regulation of cardiac contractility must therefore be intrinsic to the thin filaments.Peer reviewe

Developing a predictive model for perinatal morbidity among small for gestational age infants

Background: While neonates with birth weight <10th percentile are at increased risk of morbidity and mortality, most of these are constitutionally small and not at increased risk. There are no current strategies that reliably distinguish constitutionally small neonates from small neonates at the highest risk of morbidity, so additional tools for risk stratification are needed. Objective: Our objectives were to identify factors that are independently associated with perinatal morbidity among neonates with birth weight <10th percentile (small for gestational age, SGA) and to create predictive models of perinatal morbidity among SGA neonates based on the timing of information availability. Study design: This secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be, was a nested case-control study. Participants were prospectively enrolled at eight U.S. centers, with data collection occurring at three standard time points during pregnancy and again after delivery. Our analysis included neonates with birth weights 48 h, NEC, sepsis, RDS, mechanical ventilation, retinopathy of prematurity, seizures, grade 3 or 4 IVH, stillbirth, or death before discharge. Cases were SGA neonates that experienced the primary outcome, and controls were SGA neonates that did not. Maternal factors for potential inclusion in predictive modeling were drawn from a broad list of variables collected as part of the NuMoM2B study, including demographic, anthropometric, clinical, ultrasound, social/behavioral, dietary, and psychological variables. Characteristics that were different in bivariate analysis between cases and controls then underwent further evaluation and refinement. Continuous and multi-category variables were assessed using multiple approaches, including as continuous variables, using standard categories (such as for BMI) as well as empirically-derived cut-points identified by receiver-operating characteristics methodology. The approach for each variable that resulted in the best performance was selected for use in modeling. After variable optimization, multivariable analysis was used to derive prediction models using factors known at mid-pregnancy (Model 1) and delivery (Model 2). Results: Of the original cohort, 865 were eligible and analyzed, with 134 (15.5%) experiencing the primary outcome. After bivariable and multivariable analysis, these variables were included in Model 1: BMI, stress level, diastolic blood pressure, narcotic use (all in 1st trimester), and uterine artery pulsatility index at 16-21 weeks. Model 2 added the following variables to Model 1: preterm delivery, preeclampsia, and suspected fetal growth restriction. When models 1 and 2 were empirically tested and compared to predicted performance to demonstrate calibration, observed morbidity rates approximately followed expected rates within deciles. Models 1 and 2 had respective areas under the receiver-operating characteristic curve of 0.72 (95% CI 0.67-0.76) and 0.84 (0.80-0.88), to predict the composite morbidity. Conclusion: Using a deeply phenotyped cohort of nulliparous women, we created two models with the moderate-good prediction of perinatal morbidity among SGA neonates

Differential effects of arginine, glutamate and phosphoarginine on Ca2+-activation properties of muscle fibres from crayfish and rat

The effects of two amino acids, arginine which has a positively charged side-chain and glutamate which has a negatively charged side-chain on the Ca2+-activation properties of the contractile apparatus were examined in four structurally and functionally different types of skeletal muscle; long- and short-sarcomere fibres from the claw muscle of the yabby (a freshwater decapod crustacean), and fast- and slow-twitch fibres from limb muscles of the rat. Single skinned fibres were activated in carefully balanced solutions of different pCa (-log10[Ca2+]) that either contained the test solute (&ldquo;test&rdquo;) or not (&ldquo;control&rdquo;). The effect of phosphoarginine, a phosphagen that bears a nett negative charge, was also compared to the effects of arginine. Results show that (i) arginine (33-36 mmol l-1) significantly shifted the force&ndash;pCa curve by 0.08&ndash;0.13 pCa units in the direction of increased sensitivity to Ca2+-activated contraction in all fibre types; (ii) phosphoarginine (9&ndash;10 mmol l-1) induced a significant shift of the force&ndash;pCa curve by 0.18&ndash;0.24 pCa units in the direction of increased sensitivity to Ca2+ in mammalian fast- and slow-twitch fibres, but had no significant effects on the force&ndash;pCa relation in either long- or short-sarcomere crustacean fibres; (iii) glutamate (36&ndash;40 mmol l-1), like arginine affected the force&ndash;pCa relation of all fibre types investigated, but in the opposite direction, causing a significant decrease in the sensitivity to Ca2+-activated contraction by 0.08&ndash;0.19 pCa units; (iv) arginine, phosphoarginine and glutamate had little or no effect on the maximum Ca2+-activated force of crustacean and mammalian fibres. The results suggest that the opposing effects of glutamate and arginine are not related to simply their charge structure, but must involve complex interactions between these molecules, Ca2+ and the regulatory and other myofibrillar proteins. <br /