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  • 251. Winter, Reidar
    et al.
    Lindqvist, Per
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Clinical Physiology.
    Sheehan, Florence H
    Test of simulator-based assessment of psychomotor skill in transthoracic echo2018In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 38, no 6, p. 994-999Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: We developed a transthoracic echo simulator that measures technical skill in image acquisition in terms of the deviation angle between an acquired image and the anatomically correct plane for that view. We studied whether this metric reflects the clinical experience of providers.

    METHODS: Attendees at an echo course or at the annual meeting of the Swedish Heart Association were invited to test themselves on the simulator by scanning a mannequin and acquiring four views in 15 min: parasternal long axis (pLAX) in patient 1, apical four chamber and apical long axis (aLAX) in patient 2 and pLAX in patient 3. Their experience with echo was assessed from duration in years and procedure volume in the past year. Image acquisition error was assessed from the deviation angle.

    RESULTS: , P<0·001); both had similar duration of experience (9 ± 8 versus 12 ± 11 years, P = NS). The deviation angle for aLAX (55 ± 37 degrees) was higher than for any other view (P<0·00001). aLAX was the only view whose deviation angle correlated significantly with experience and only with procedure volume (r = -0·357, P = 0·008).

    CONCLUSIONS: These results demonstrate that deviation angle, a novel metric of technical skill in image acquisition, reflects clinical experience. Simulator-based testing provides objective and quantitative assessment that may be of value in the certification of trainees and for maintenance of certification.

  • 252.
    Wählby, Lennart
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Achilles tendon injury: aspects on muscle structure and strength1978Doctoral thesis, comprehensive summary (Other academic)
  • 253.
    Yelhekar, Tushar
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Chloride Homeostasis in Central Neurons2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall aim of the present thesis is to clarify the control of intracellular chloride homeostasis in central neurons, because of the critical role of chloride ions (Cl) for neuronal function. Normal function of the central nervous system (CNS) depends on a delicate balance between neuronal excitation and inhibition. Inhibition is, in the adult brain, most often mediated by the neurotransmitter γ-aminobutyric acid (GABA). GABA may, however, in some cases cause excitation. GABA acts by activating GABA type A receptors (GABAARs), which are ion channels largely permeable to Cl. The effect of GABAAR-mediated neuronal signaling - inhibitory or excitatory - is therefore mainly determined by the Cl gradient across the membrane. This gradient varies with neuronal activity and may be altered in pathological conditions. Thus, understanding Cl regulation is important to comprehend neuronal function. This thesis is an attempt to clarify several unknown aspects of neuronal Cl regulation. For such clarification, a sufficiently sensitive method for measuring the intracellular Cl concentration, [Cl]i, is necessary. In the first study of this thesis, we examined two electrophysiological methods commonly used to estimate [Cl]i. Both methods, here called the interpolation and the voltage-ramp method, depend on an estimate of the Cl equilibrium potential from the current-voltage relation of GABA- or glycine-evoked Cl currents. Both methods also provide an estimate of the membrane Cl conductance, gCl. With a combination of computational and electrophysiological techniques, we showed that the most common (interpolation) method failed to detect changes in [Cl]i and gCl during prolonged GABA application, whereas the voltage-ramp method accurately detected such changes. Our analysis also provided an explanation as to why the two methods differ. In a second study, we clarified the role of the extracellular matrix (ECM) for the distribution of Cl across the cell membrane of neurons from rat brain. It was recently proposed that immobile charges located within the ECM, rather than as previously thought cation-chloride transporter proteins, determine the low [Cl]i which is critical to GABAAR-mediated inhibition. By using electrophysiological techniques to measure [Cl]i, we showed that digestion of the ECM decreases the expression and function of the neuron-specific K+ Cl cotransporter 2 (KCC2), which normally extrudes Cl- from the neuron, thus causing an increase in resting [Cl]i. As a result of ECM degradation, the action of GABA may be transformed from inhibitory to excitatory. In a third study, we developed a method for quantifying the largely unknown resting Cl (leak) conductance, gCl, and examined the role of gCl for the neuronal Cl homeostasis. In isolated preoptic neurons from rat, resting gCl was about 6 % of total resting conductance, to a major part due to spontaneously open GABAARs and played an important role for recovery after a high Cl load. We also showed that spontaneous, impulse-independent GABA release can significantly enhance recovery when the GABA responses are potentiated by the neurosteroid allopregnanolone. In a final commentary, we formulated the mathematical relation between Cl conductance, KCC2-mediated Cl extrusion capacity and steady-state [Cl]i. In summary, the present thesis (i) clarifies how well common electrophysiological methods describe [Cl]i and gCl, (ii) provides a novel method for quantifying gCl in cell membranes and (iii) clarifies the roles of the ECM, ion channels and ion transporters in the control of [Cl]i homeostasis and GABAAR-mediated signaling in central neurons. 

  • 254.
    Yelhekar, Tushar D.
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Druzin, Michael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Johansson, Staffan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB).
    Contribution of Resting Conductance, GABA(A)-Receptor Mediated Miniature Synaptic Currents and Neurosteroid to Chloride Homeostasis in Central Neurons2017In: eNeuro, ISSN 2373-2822, Vol. 4, no 2, article id e0019Article in journal (Refereed)
    Abstract [en]

    Maintenance of a low intraneuronal Cl- concentration, [Cl-](i), is critical for inhibition in the CNS. Here, the contribution of passive, conductive Cl- flux to recovery of [Cl-](i) after a high load was analyzed in mature central neurons from rat. A novel method for quantifying the resting Cl- conductance, important for [Cl-](i) recovery, was developed and the possible contribution of GABAA and glycine receptors and of ClC-2 channels to this conductance was analyzed. The hypothesis that spontaneous, action potential-independent release of GABA is important for [Cl-](i) recovery was tested. [Cl-](i) was examined by gramicidin-perforated patch recordings in medial preoptic neurons. Cells were loaded with Cl- by combining GABA or glycine application with a depolarized voltage, and the time course of [Cl-](i) was followed by measurements of the Cl- equilibrium potential, as obtained from the current recorded during voltage ramps combined with GABA or glycine application. The results show that passive Cl- flux contributes significantly, in the same order of magnitude as does K+-Cl- cotransporter 2 (KCC2), to [Cl-](i) recovery and that Cl- conductance accounts for similar to 6% of the total resting conductance. A major fraction of this resting Cl- conductance is picrotoxin (PTX)-sensitive and likely due to open GABAA receptors, but ClC-2 channels do not contribute. The results also show that when the decay of GABAA receptor-mediated miniature postsynaptic currents (minis) is slowed by the neurosteroid allopregnanolone, such minis may significantly quicken [Cl-](i) recovery, suggesting a possible steroid-regulated role for minis in the control of Clhomeostasis.

  • 255.
    Yelhekar, Tushar D.
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Druzin, Michael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Karlsson, Urban
    Blomqvist, Erii
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Staffan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    How to Properly Measure a Current-Voltage Relation? -Interpolation vs. Ramp Methods Applied to Studies of GABA(A) Receptors2016In: Frontiers in Cellular Neuroscience, ISSN 1662-5102, E-ISSN 1662-5102, Vol. 10, article id 10Article in journal (Refereed)
    Abstract [en]

    The relation between current and voltage, I-V relation, is central to functional analysis of membrane ion channels. A commonly used method, since the introduction of the voltage-clamp technique, to establish the I-V relation depends on the interpolation of current amplitudes recorded at different steady voltages. By a theoretical computational approach as well as by experimental recordings from GABA(A) receptor mediated currents in mammalian central neurons, we here show that this interpolation method may give reversal potentials and conductances that do not reflect the properties of the channels studied under conditions when ion flux may give rise to concentration changes. Therefore, changes in ion concentrations may remain undetected and conclusions on changes in conductance, such as during desensitization, may be mistaken. In contrast, an alternative experimental approach, using rapid voltage ramps, enable I-V relations that much better reflect the properties of the studied ion channels.

  • 256.
    Yelhekar, Tushar
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Kuznetsova, Tatiana
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Malinina, Evgenya
    Ponimaskin, Evgeni
    Dityatev, Alexander
    Druzin, Michael
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Johansson, Staffan
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology.
    Extracellular Matrix Regulates Neuronal Chloride Concentration via K+-Cl--cotransporter 2Manuscript (preprint) (Other academic)
  • 257. Yu, Fang Fang
    et al.
    Lin, Xia Lu
    Yang, Lei
    Liu, Huan
    Wang, Xi
    Fang, Hua
    Lammi, Mikko J.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB). Institute of Endemic Diseases, School of Public Health of Health Science Center, Xi’an Jiaotong University, Key Laboratory of Trace Elements and Endemic Diseases, National Health and Family Planning Commission, Xi’an 710061, Shaanxi, China.
    Guo, Xiong
    Comparison of T-2 Toxin and HT-2 Toxin Distributed in the Skeletal System with That in Other Tissues of Rats by Acute Toxicity Test2017In: Biomedical and environmental sciences, ISSN 0895-3988, E-ISSN 2214-0190, Vol. 30, no 11, p. 851-854Article in journal (Refereed)
    Abstract [en]

    Twelve healthy rats were divided into the T-2 toxin group receiving gavage of 1 mg/kg T-2 toxin and the control group receiving gavage of normal saline. Total relative concentrations of T-2 toxin and HT-2 toxin in the skeletal system (thighbone, knee joints, and costal cartilage) were significantly higher than those in the heart, liver, and kidneys (P < 0.05). The relative concentrations of T-2 toxin and HT-2 toxin in the skeletal system (thighbone and costal cartilage) were also significantly higher than those in the heart, liver, and kidneys. The rats administered T-2 toxin showed rapid metabolism compared with that in rats administered HT-2 toxin, and the metabolic conversion rates in the different tissues were 68.20%-90.70%.

  • 258.
    Yu, Ji-Guo
    et al.
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Sports Medicine.
    Russell, Brenda
    Cardiomyocyte remodeling and sarcomere addition after uniaxial static strain in vitro.2005In: J Histochem Cytochem, ISSN 0022-1554, Vol. 53, no 7, p. 839-44Article in journal (Refereed)
  • 259.
    Zafar, Hamayun
    et al.
    Umeå University, Faculty of Medicine, Department of Odontology. Department of Rehabilitation Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.
    Alghadir, Ahmad H.
    Iqbal, Zaheen Ahmed
    Iqbal, Amir
    Anwer, Shahnawaz
    Alnahdi, Ali H.
    Influence of different jaw positions on dynamic balance using Y-balance test2019In: Brain and Behavior, ISSN 2162-3279, E-ISSN 2162-3279, article id e01507Article in journal (Refereed)
    Abstract [en]

    Background: Jaw sensory‐motor system has been shown to affect static balance of the body. It would be interesting to know whether it can influence dynamic balance as well. The objective of this study is to examine the influence of different jaw positions on dynamic balance using the Y‐balance test.

    Methods: Eighty healthy male participants aged 20–35 years were invited to participate in this study. Dynamic balance was measured by the Y‐balance test in three directions (anterior, posteromedial, and posterolateral) for each leg separately in three jaw positions: resting jaw (control), open‐jaw, and clenched jaw.

    Results: There were no significant differences in reach distances between the different jaw positions except in the posterolateral direction. In comparison with resting jaw position, reach distance was significantly higher in open‐jaw position for the right leg and in clenched and open‐jaw positions for the left leg in the posterolateral direction.

    Conclusions: Although various studies have shown direct or indirect influence of jaw sensory‐motor system on static postural control, results of this study point to limited relation with dynamic postural control among healthy subjects. However, it supports the potential of the jaw sensory‐motor system to affect motor control during functional tasks in patients with postural instability or similar disorders.

  • 260.
    Zashikhin, Andrei
    et al.
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Histology and Cell Biology.
    Sehlin, Janove
    Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Histology and Cell Biology.
    Visceral'naja gladkaja myšečnaja tkan'2001Book (Refereed)
  • 261.
    Ängquist, Karl-Axel
    Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences. Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Anatomy.
    Human skeletal muscle fibre structure: effects of physical training and arterial insufficiency1978Doctoral thesis, comprehensive summary (Other academic)
  • 262.
    Åberg, Anna
    et al.
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gideonsson, Pär
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Vallström, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Olofsson, Annelie
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Öhman, Carina
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Rakhimova, Lena
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Borén, Thomas
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Engstrand, Lars
    Brännström, Kristoffer
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Arnqvist, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    A Repetitive DNA Element Regulates Expression of the Helicobacter pylori Sialic Acid Binding Adhesin by a Rheostat-like Mechanism2014In: PLoS Pathogens, ISSN 1553-7366, E-ISSN 1553-7374, Vol. 10, no 7, article id e1004234Article in journal (Refereed)
    Abstract [en]

    During persistent infection, optimal expression of bacterial factors is required to match the ever-changing host environment. The gastric pathogen Helicobacter pylori has a large set of simple sequence repeats (SSR), which constitute contingency loci. Through a slipped strand mispairing mechanism, the SSRs generate heterogeneous populations that facilitate adaptation. Here, we present a model that explains, in molecular terms, how an intergenically located T-tract, via slipped strand mispairing, operates with a rheostat-like function, to fine-tune activity of the promoter that drives expression of the sialic acid binding adhesin, SabA. Using T-tract variants, in an isogenic strain background, we show that the length of the T-tract generates multiphasic output from the sabA promoter. Consequently, this alters the H. pylori binding to sialyl-Lewis x receptors on gastric mucosa. Fragment length analysis of post-infection isolated clones shows that the T-tract length is a highly variable feature in H. pylori. This mirrors the host-pathogen interplay, where the bacterium generates a set of clones from which the best-fit phenotypes are selected in the host. In silico and functional in vitro analyzes revealed that the length of the T-tract affects the local DNA structure and thereby binding of the RNA polymerase, through shifting of the axial alignment between the core promoter and UP-like elements. We identified additional genes in H. pylori, with T- or A-tracts positioned similar to that of sabA, and show that variations in the tract length likewise acted as rheostats to modulate cognate promoter output. Thus, we propose that this generally applicable mechanism, mediated by promoter-proximal SSRs, provides an alternative mechanism for transcriptional regulation in bacteria, such as H. pylori, which possesses a limited repertoire of classical trans-acting regulatory factors.

  • 263.
    Åström, Charlotte
    et al.
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
    Lindkvist, Markus
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Burström, Lage
    Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
    Sundelin, Gunnevi
    Umeå University, Faculty of Medicine, Department of Community Medicine and Rehabilitation, Physiotherapy.
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Changes in EMG activity in the upper trapezius muscle due to local vibration exposure.2009In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 19, no 3, p. 407-415Article in journal (Refereed)
    Abstract [en]

    Exposure to vibration is suggested as a risk factor for developing neck and shoulder disorders in working life. Mechanical vibration applied to a muscle belly or a tendon can elicit a reflex muscle contraction, also called tonic vibration reflex, but the mechanisms behind how vibration could cause musculoskeletal disorders has not yet been described. One suggestion has been that the vibration causes muscular fatigue. This study investigates whether vibration exposure changes the development of muscular fatigue in the trapezius muscle. Thirty-seven volunteers (men and women) performed a sub-maximal isometric shoulder elevation for 3min. This was repeated four times, two times with induced vibration and two times without. Muscle activity was measured before and after each 3-min period to look at changes in the electromyography parameters. The result showed a significantly smaller mean frequency decrease when performing the shoulder elevation with vibration (-2.51Hz) compared to without vibration (-4.04Hz). There was also a slightly higher increase in the root mean square when exposed to vibration (5.7% of maximal voluntary contraction) compared to without (3.8% of maximal voluntary contraction); however, this was not statistically significant. The results of the present study indicate that short-time exposure to vibration has no negative acute effects on the fatiguing of upper trapezius muscle.

  • 264.
    Öhberg, Fredrik
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Grip, Helena
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Wiklund, Urban
    Umeå University, Faculty of Medicine, Department of Radiation Sciences, Radiation Physics.
    Sterner, Ylva
    Karlsson, J Stefan
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Gerdle, Björn
    Chronic whiplash associated disorders and neck movement measurements: an instantaneous helical axis approach.2003In: IEEE transactions on information technology in biomedicine, ISSN 1089-7771, E-ISSN 1558-0032, Vol. 7, no 4, p. 274-282Article in journal (Refereed)
    Abstract [en]

    This paper presents an assessment tool for objective neck movement analysis of subjects suffering from chronic whiplash-associated disorders (WAD). Three-dimensional (3-D) motion data is collected by a commercially available motion analysis system. Head rotation, defined in this paper as the rotation angle around the instantaneous helical axis (IHA), is used for extracting a number of variables (e.g., angular velocity and range, symmetry of motion). Statistically significant differences were found between controls and subjects with chronic WAD in a number of variables.

  • 265.
    Öhberg, Fredrik
    et al.
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Zachrisson, Adam
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Holmner-Rocklöv, Åsa
    Umeå University, Faculty of Medicine, Department of Radiation Sciences.
    Three-Dimensional Camera System for Measuring Arm Volume in Women with Lymphedema Following Breast Cancer Treatment2014In: Lymphatic Research and Biology, ISSN 1539-6851, E-ISSN 1557-8585, Vol. 12, no 4, p. 267-274Article in journal (Refereed)
    Abstract [en]

    Background: Lymphedema is a common complication following breast cancer treatment, estimated to affect 20% of breast cancer survivors. The condition is associated with a number of symptoms, such as impaired range of motion and anxiety. A wide range of methods for determining the volume of the lymphedematous arm have been described. Circumference measurement (CM) is commonly used in clinics to appraise arm volume, while water displacement (WD) is often used in studies. The aim of the study was to assess the performance of a new method using 3D-technology in comparison to CM and WD. Methods and Results: The study was performed on 25 subjects with lymphedema secondary to breast cancer treatment. Volumetric data from CM, WD, and the 3D-camera were gathered on all subjects. The measurements were performed by two physiotherapists, each subject being measured by one of the physiotherapist. Estimates of differences between the methods was calculated through analyzing the data collected from the three methods using mixed-design analyses of variance. The results indicated a tendency for the 3D-camera to overestimate the volume in comparison the WD by 45.25 mL, 95% confidence interval (CI) -36.31 - 126.82 (p value 0.270). Conversely, CM showed a tendency to underestimate the volume compared to WD (-24.28 mL, CI -99.78 - 51.22, p value 0.521). Thus, no statistically significant difference was found between the methods. Conclusions: The 3D-camera is a viable method for measuring arm volume, performing on level with the established methods WD and CM.

3456 251 - 265 of 265
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