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  • 1. Adiels, Martin
    et al.
    Mardinoglu, Adil
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab. Chalmers University of Technology, Sweden.
    Taskinen, Marja-Riitta
    Boren, Jan
    Kinetic Studies to Elucidate Impaired Metabolism of Triglyceride-rich Lipoproteins in Humans2015In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 6, 342Article, review/survey (Refereed)
    Abstract [en]

    To develop novel strategies for prevention and treatment of dyslipidemia, it is essential to understand the pathophysiology of dyslipoproteinemia in humans. Lipoprotein metabolism is a complex system in which abnormal concentrations of various lipoprotein particles can result from alterations in their rates of production, conversion, and/or catabolism. Traditional methods that measure plasma lipoprotein concentrations only provide static estimates of lipoprotein metabolism and hence limited mechanistic information. By contrast, the use of tracers labeled with stable isotopes and mathematical modeling, provides us with a powerful tool for probing lipid and lipoprotein kinetics in vivo and furthering our understanding of the pathogenesis of dyslipoproteinemia.

  • 2. Alkner, B.
    et al.
    Norrbrand, Lena
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Tesch, P.
    Neuromuscular adaptations following 90 days bed rest with or without resistance exercise.2016In: Aerospace Medicine and Human Performance, ISSN 2375-6322, Vol. 87, no 7, 610-617 p.Article in journal (Refereed)
  • 3. Alkner, Björn
    et al.
    Jonsson, Lena
    Karolinska Institutet.
    Atling, Åsa
    Tesch, Per
    Resistance exercise maintains quadriceps muscle strength and size during 90 d bed rest.2003In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 35, no 5, 262- p.Article in journal (Refereed)
  • 4. Alkner, Björn
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Tesch, Per
    Effects of 90 d bed rest with or without resistance exercise on knee extensor muscle fatigue2004In: 25th Annual International Gravitational Physiology Meeting, 2004Conference paper (Refereed)
  • 5. Alkner, Björn
    et al.
    Norrbrand, Lena
    Karolinska Institutet.
    Tesch, Per
    Knee extensor and plantar flexor muscle size and function in response to 90 d bed rest with or without resistance exercise2004In: 7th Scandinavian Congress on Medicine and Science in Sports, 2004Conference paper (Refereed)
  • 6. Amon, M.
    et al.
    Debevec, T.
    Keramidas, Michail E.
    Pisot, R.
    Simunic, B.
    Kounalakis, S.N.
    Mekjavic, I.B.
    Effect of intermittent normobaric hypoxic exposure on performance in hypoxic and normoxic environments2008Conference paper (Other academic)
  • 7. Amon, M.
    et al.
    Debevec, T.
    Keramidas, Michail E.
    Simunic, B.
    Pisot, R.
    Kounalakis, S.N.
    Eiken, O.
    Mekjavic, I.B.
    Intermittent hypoxic training2008Conference paper (Other academic)
  • 8. Amon, M.
    et al.
    Keramidas, Michail E.
    Debevec, T
    Kounalakis, S.N.
    Mekjavic, I.B.
    The effect of hypoxic training regimens on pulmonary function2009Conference paper (Other academic)
  • 9. Amon, M
    et al.
    Keramidas, Michail E.
    Kounalakis, S
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Simpson, L
    MacDonald, I
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Mekjavic, IB
    Effect of hypoxia on postprandial blood glucose and insulin response2011Conference paper (Refereed)
  • 10.
    Amon, M.
    et al.
    Jozef Stefan Institute.
    Keramidas, Michail E.
    Jozef Stefan Institute, Slovenia .
    Kounalakis, S.N.
    Hellen Mil Univ, Human Performance Rehabil Lab.
    Mekjavic, I.B.
    Jozef Stefan Institute.
    The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response2012In: High Altitude Medicine & Biology, ISSN 1527-0297, E-ISSN 1557-8682, Vol. 13, no 1, 32-39 p.Article in journal (Refereed)
    Abstract [en]

    The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n=9) or experimental (EXP; n=8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD(NOR); CON and EXP groups) and hypoxic (CIVD(HYPO); F(I)O(2)=0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD(NOR): +0.5°C; CIVD(HYPO): +0.5°C), number of waves (CIVD(NOR): +0.5; CIVD(HYPO): +0.6), and CIVD amplitude (CIVD(NOR): +1.5°C; CIVD(HYPO): +3°C) in both CIVD tests (p<0.05). In contrast, the CON group had an increase in only the CIVD amplitude (+0.5°C; p<0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.

  • 11. Andersson, Jan
    et al.
    Berggren, Peter
    Grönkvist, Mikael
    Swedish Defence Research Agency.
    Magnusson, Staffan
    Svensson, Erland
    Oxygen saturation and cognitive performance.2002In: Psychopharmacology, ISSN 0033-3158, E-ISSN 1432-2072, Vol. 162, no 2, 119-128 p.Article in journal (Refereed)
    Abstract [en]

    The purpose of the experiments was to investigate how inhalation of 100% oxygen affected cognitive performance. A test battery was developed that was designed to capture different aspects of cognitive processes, i.e., perception, attention, working memory, long-term memory and prospective memory. All tests were verbally based, thus reducing cognitive spatial processes to a minimum. In experiment 1, 48 participants volunteered in a complete factorial within-participant design. Two different conditions for type of gas were used, inhalation of 100% oxygen and inhalation of breathing air (approximately 21% oxygen balanced with nitrogen). The inhalation was performed during the 1 min prior to starting each separate test. The instructions for each test were given during the inhalation period. All participants inhaled oxygen or breathing air through a Swedish military pilot mask. Physiological (heartbeats per minute and blood oxygen saturation level) reactions were recorded continuously throughout the session. Participants also completed a mood-state questionnaire before and after the test battery. The results revealed that cognitive performance were not affected by inhalation. Hence, this experiment does not replicate previous findings that suggest that inhalation of 100% oxygen could increase cognitive performance. Another experiment was performed to control for methodological issues. Experiment 2 revealed exactly the same pattern, i.e., inhalation of oxygen did not affect cognitive functioning.

  • 12. Andersson, R. M.
    et al.
    Aizman, O.
    Aperia, A.
    Brismar, Hjalmar
    KTH, Superseded Departments, Physics.
    Modulation of Na+,K+-ATPase activity is of importance for RVD2004In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 180, no 4, 329-334 p.Article in journal (Refereed)
    Abstract [en]

    Aim: This study was performed to examine the role of Na+,K+-ATPase activity for the adaptive response to cell swelling induced by hypoosmoticity, i.e. the regulatory volume decrease (RVD). Methods: The studies were performed on COS-7 cells transfected with rat Na+,K+-ATPase. To study changes in cell volume, cells were loaded with the fluorescent dye calcein and the intensity of the dye, following exposure to a hypoosmotic medium, was recorded with confocal microscopy. Results: Ouabain-mediated inhibition of Na+,K+-ATPase resulted in a dose dependent decrease in the rate of RVD. Total Rb-86(+) uptake as well as ouabain dependent Rb-86(+) uptake, used as an index of Na+,K+-ATPase dependent K+ uptake, was significantly increased during the first 2 min following exposure to hypoosmoticity. Since protein kinase C (PKC) plays an important role in the modulation of RVD, a study was carried out on COS-7 cells expressing rat Na+,K+-ATPase, where Ser23 in the catalytic alpha1 subunit of rat Na+,K+-ATPase had been mutated to Ala (S23A), abolishing a known PKC phosphorylation site. Cells expressing S23A rat Na+,K+-ATPase exhibited a significantly lower rate of RVD and showed no increase in Rb-86(+) uptake during RVD. Conclusion: Taken together, these results suggest that a PKC-mediated transient increase in Na+,K+-ATPase activity plays an important role in RVD.

  • 13. Arvedsen, SK
    et al.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Petersen, L. G.
    Damgaard, M.
    Body height and arterial pressure in seated and supine young males during +2 G centrifugation2015In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 309, no 9Article in journal (Refereed)
    Abstract [en]

    It is known that arterial pressure correlates positively with body height in males and it has been suggested that this is due to the increasing vertical hydrostatic gradient from the heart to the carotid baroreceptors. Therefore we tested the hypothesis that a higher gravitoinertial stress induced by the use of a human centrifuge would increase mean arterial pressure (MAP) more in tall than in short males in the seated position. In short (162-171cm, n=8) and tall (194-203cm, n=10) healthy males (18-41y), brachial arterial pressure, heart rate (HR) and cardiac output were measured during +2G centrifugation, while they were seated upright with the legs kept horizontal (+2Gz). In a separate experiment, the same measurements were done with the subjects supine (+2Gx). During +2Gz MAP increased in the short (22±2 mmHg, p<0.0001) and tall (23±2 mmHg, p<0.0001) males, with no significant difference between the groups. HR increased more (p<0.05) in the tall than in the short group (14±2 versus 7±2 bpm). Stroke volume (SV) decreased in the short group (26±4 mL, p=0.001) and more so in the tall group (39±5 mL, p<0.0001; short vs tall p=0.047). During +2GX, systolic arterial pressure increased (p<0.001) and SV (p=0.012) decreased in the tall group only. In conclusion, during +2Gz MAP increased in both short and tall males with no difference between the groups. However, in the tall group HR increased more during +2Gz which could be caused by a larger hydrostatic pressure gradient from heart to head leading to greater inhibition of the carotid baroreceptors.

  • 14. Baer, R
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Effects of continuous positive- and negative-pressure breathing on the pattern of breathing in man during exercise.1989In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 137, no 2, 301-7 p.Article in journal (Refereed)
    Abstract [en]

    Breathing pattern and static lung volumes were studied in 10 subjects at rest and during incremental-load cycle ergometry under three different conditions, viz. with normal pressure in the airways (control) and during continuous positive- and negative-pressure breathing (CPPB, CNPB) of +15 and -15 cmH2O. End-expiratory, end-inspiratory and mid-expiratory volumes were increased by CPPB and decreased by CNPB; these effects were especially pronounced at rest and during mild exercise. Both at rest and during exercise mean inspiratory flow (VT/TI) was exaggerated by CPPB and attenuated by CNPB. At rest these changes were due mainly to concomitant changes in tidal volume (VT) which was increased by CPPB and decreased by CNPB, while inspiratory time duration (TI) was relatively unaffected by pressure breathing. The transition from rest to loadless pedalling induced an increase in VT but no change in TI in the control condition, whereas in the CPPB and CNPB conditions TI decreased and VT remained unaltered. This CPPB- and CNPB-induced change in the volume-time threshold relationship at the onset of pedalling is attributed to increased stretch receptor activity in the extrathoracic portion of the trachea as a result of the increments in transmural pressure. During the course of exercise there was an inverse relationship between the slope of the VT-TI curve and the mid-expiratory volume in that the slope was greater in the control than in the CPPB condition and greatest during CNPB, suggesting that in exercise hyperpnoea the VT-TI relationship is also determined by pulmonary and/or thoracic wall stretch receptors capable of sensing the absolute lung volume.

  • 15. Baer, R.
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Balldin, U.
    Cardiovascular effects of head-up tilt as affected by a vasopressin analogue1987In: The Physiologist, ISSN 0031-9376, E-ISSN 1522-1202, Vol. 30, no 1 Suppl, S64-65 p.Article in journal (Refereed)
  • 16. Baer, R
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Balldin, U
    Effects of triglycyl-lysine-vasopressin on cardiovascular responses to orthostatic stress.1987In: Clinical Physiology, ISSN 0144-5979, E-ISSN 1365-2281, Vol. 7, no 4, 329-35 p.Article in journal (Refereed)
    Abstract [en]

    The influence of triglycyl-lysine-vasopressin (TGLVP) on cardiovascular responses to orthostatic stress was studied. Arterial pressures, heart rate (HR) and stroke volume (SV) were measured in eight healthy males subjected to 20 min 70 degrees head-up tilt. On different days they received either 0.01 mg/kg b.w. of TGLVP or a corresponding volume of 0.9% saline i.v. after 15 min supine rest. After the drug injection, in supine subjects, HR had decreased from 58 to 50 beats min-1, total peripheral resistance (TPR) was elevated by 29%, systolic (SAP) and diastolic pressure (DAP) had increased by 7 and 8 mmHg, respectively. During tilt, values for HR and SAP were similar with and without TGLVP whereas DAP and MAP were elevated 8 and 7 mmHg, respectively, by the drug. 4-8 min into the tilt, TGLVP caused an 8% sustained curtailment of SV. Both with and without the drug TPR increased by about 30% in response to head-up tilt. Thus, the marked peripheral arteriolar constriction after vasopressin in the supine position was not affected by head-up tilt. Tilting also abolished the drug-induced elevation in SAP, most likely explained by the reduction in SV. Although TPR was markedly increased by TGLVP during head-up tilt, reflected in the behaviour of DAP, the response of SV speaks against any beneficial effect of this drug on orthostatic tolerance in healthy subjects.

  • 17. Bali, TC
    et al.
    Kounalakis, SN
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    PlanHab: The effects of 21-day hypoxic confinement and unloading/inactivity on regional body composition and muscle strength2015Conference paper (Refereed)
  • 18. Bense, L
    et al.
    Eklund, G
    Jorulf, H
    Farkas, A
    Balashazy, I
    Hedenstierna, G
    Krebsz, A
    Balazs, G
    Eden Strindberg, J
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Douglas, J
    Perforation of the right main bronchus, detected by HRCT 3D technique2011Conference paper (Refereed)
  • 19. Bense, L
    et al.
    Jorulf, H
    Farkas, A
    Eden-Strindberg, J
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Jokay, A
    Krebsz, A
    Pulmonary gas conducting interstitial pathway2015In: Acta Radiologica Open, ISSN 2058-4601, Vol. 4, no 10, 1-5 p.Article in journal (Refereed)
    Abstract [en]

    In spite of the growing efforts oriented towards revealing different aspects of emphysema, the persistence of the emphysematous or emphysema-like changes (ELCs) is not explored yet in the open literature. In this study we demonstrate the persistence of an ELC for 22 years in a spontaneous pneumothorax (SP) patient which indicates a hitherto unknown gas supply to the ELC. For this purpose we used high resolution computed tomography (HRCT) images processed into three-dimensional (3D) geometry. By the same token, not only a long persistence but also the volume increase of this ELC between 2002 and 2010 was demonstrated. The 3D geometry visualized an aerated interstitial structure between the sites of supposed gas leakage at the wall of the third generation airways and the ELC. This potential gas conducting interstitial pathway is not a continuation and has neither the form nor the structure of a bronchus. The finding suggests that in this patient the intrabronchial gas passes through the bronchial wall and via a gas conducting interstitial pathway reaches the ELC. Despite the availability of the presently employed techniques for at least 15 years, such case and phenomenon have not been described previously. The retrieval of the patient suggests that the findings could be relevant for a considerable proportion of the population.

  • 20. Berg, H. E.
    et al.
    Eiken, Ola
    Swedish Defence Research Agency.
    Muscle control in elite alpine skiing1999In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 31, no 7, 1065-1067 p.Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to determine whether muscle control may be influenced by accelerative forces brought about by the downhill displacement of body mass in combination with the sharp turns during alpine skiing.

    METHODS: Sixteen elite skiers performed either super G (SG), giant slalom (GS), slalom (SL), or freestyle mogul (FM) skiing. Knee and hip joint angles and electromyographic (EMG) activity of the knee extensors were recorded.

    RESULTS: During the course of a turn, the minimum (deepest stance position) knee angle of the outside (main load-bearing) leg ranged from 60 degrees to 100 degrees, where the smallest angle was obtained in the FM event. Among the traditional alpine disciplines, smaller knee angles were obtained in the high-speed events (i.e., knee angle: SG<GS<SL). Knee angular velocity of the outside leg ranged from 15 degrees to 300 degrees x s(-1), with the slower movements in the high-speed disciplines (i.e., knee angular velocity: SG<GS<SL<FM). In all disciplines, EMG activity reached near-maximal levels during the course of a turn. In SG, GS, and SL, but not in FM skiing, a marked predominance of eccentric over concentric muscle actions was observed. The dominance of slow eccentric muscle actions has not been observed in other athletic activities.

    CONCLUSIONS: We believe these results have important implications for the design of specific training models.

  • 21. Berg, H E
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Tesch, P A
    Involvement of eccentric muscle actions in giant slalom racing.1995In: Medicine & Science in Sports & Exercise, ISSN 0195-9131, E-ISSN 1530-0315, Vol. 27, no 12, 1666-70 p.Article in journal (Refereed)
    Abstract [en]

    Joint angular movements and muscle activation (EMG), were determined in male elite racers while performing the giant slalom. Movement cycles averaged 3.5 +/- 0.6 s (left plus right turn), and knee angle ranged 66-114 degrees (180 degrees = straight leg). Knee extensor muscle use was dominated (rectified EMG; P < 0.05) by the leg controlling the outside (downhill) ski during the turn. Time spent while decreasing knee angle (eccentric muscle action) of outside leg averaged 1.0 +/- 0.2 s. This phase was longer (P < 0.05) than the average push-off (concentric muscle action) phase of 0.5 +/- 0.1 s. Moreover, EMG activity of the outside leg during eccentric muscle actions exceeded (P < 0.05) that of concentric actions and was similar to that attained during maximum isometric knee extension in laboratory tests. Knee and hip angular movement ranged 20-50 degrees. Average joint velocities equalled 20-40 degrees.s(-1) during the turning phase. Thus, competitive giant slalom skiing is dominated by slow eccentric muscle actions performed at near maximum voluntary force. Because of their greater ability to generate force, eccentric muscle actions may be warranted or even required to resist the G-forces induced during the turn phase.

  • 22. Berg, Hans E.
    et al.
    Eiken, Ola
    Swedish Defence Research Agency.
    Miklavcic, Lucijan
    Mekjavic, Igor B.
    Hip, thigh and calf muscle atrophy and bone loss after 5-week bedrest inactivity2007In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 99, no 3, 283-289 p.Article in journal (Refereed)
    Abstract [en]

    Unloaded inactivity induces atrophy and functional deconditioning of skeletal muscle, especially in the lower extremities. Information is scarce, however, regarding the effect of unloaded inactivity on muscle size and function about the hip. Regional bone loss has been demonstrated in hips and knees of elderly orthopaedic patients, as quantified by computerized tomography (CT). This method remains to be validated in healthy individuals rendered inactive, including real or simulated weightlessness. In this study, ten healthy males were subjected to 5 weeks of experimental bedrest and five matched individuals served as ambulatory controls. Maximum voluntary isometric hip and knee extension force were measured using the strain gauge technique. Cross-sectional area (CSA) of hip, thigh and calf muscles, and radiological density (RD) of the proximal tibial bone were measured using CT. Bedrest decreased (P < 0.05) average (SD) muscle strength by 20 (8)% in knee extension, and by 22 (12)% in hip extension. Bedrest induced atrophy (P < 0.05) of extensor muscles in the gluteal region, thigh and calf, ranging from 2 to 12%. Atrophy was more pronounced in the knee extensors [9 (4)%] and ankle plantar flexors [12 (3)%] than in the gluteal extensor muscles [2 (2)%]. Bone density of the proximal tibia decreased (P < 0.05) by 3 (2)% during bedrest. Control subjects did not show any temporal changes in muscle or bone indices (P > 0.05), when examined at similar time intervals. The present findings of a substantial loss in hip extensor strength and a smaller, yet significant atrophy of these muscles, demonstrate that hip muscle deconditioning accompanies losses in thigh and calf muscle mass after bedrest. This suggests that comprehensive quantitative studies on impaired locomotor function after inactivity should include all joints of the lower extremity. Our results also demonstrate that a decreased RD, indicating bone mineral loss, can be shown already after 5 weeks of unloaded bedrest, using a standard CT technique.

  • 23. Berg, Ulf
    et al.
    Kölegård, Roger
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Fysiska tester i samband med Grundläggande militär utbildning (GMU)2012Report (Other academic)
  • 24. Bergenius, J.
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Brantberg, K.
    The subjective horizontal at different angles of roll-tilt in patients with unilateral vestibular impairment1996In: Brain Research Bulletin, ISSN 0361-9230, E-ISSN 1873-2747, Vol. 40, no 5-6, 385-390 p.Article in journal (Refereed)
    Abstract [en]

    The subjective visual horizontal is mainly dependent on the otolithic system. A group of 11 patients with sudden unilateral vestibular impairment were asked to set a dimly illuminated bar according to their subjective horizontal when they were seated upright and tilted 10, 20, and 30 degrees to the right and left in a completely darkened room (Bias test). The patients were examined within 1 week, after 3 and 6 weeks, and 9 patients consented to the 11-week follow-up. The results were compared with ENG examinations. In the acute stage of the disease all patients, when they were in upright position, set the light bar tilted towards the affected side. At roll tilt to the affected side, 9 of the 11 patients set the light bar in the same direction as their body tilt (undercorrection). At a tilt to the unaffected side 6 of the 11 patients made an undercorrection. For the group of patients the magnitude of undercorrection was larger at tilt to the affected side than to the unaffected side. The patients' ability to correctly align the light bar with the true horizontal gradually improved but was found normal in both upright and tilted positions in only three of the nine patients at the last follow-up. In four of the six patients who still demonstrated pathologic results, these were met only in tilted positions. No significant correlation was found between the intensity of spontaneous nystagmus or the degree of caloric side difference and the deviation in setting of the light bar in upright or tilted positions. The large asymmetric perceptual responses at tilt found at onset might be explained by the two-directional organisation of the utricle.

  • 25.
    Bergh, Ulf
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Danielsson, Ulf
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Värmehandbok för markstridssoldaten2011Report (Other academic)
  • 26. Berglund, B
    et al.
    Gennser, Mikael
    Swedish Defence Research Agency.
    Ornhagen, H
    Ostberg, C
    Wide, L
    Erythropoietin concentrations during 10 days of normobaric hypoxia under controlled environmental circumstances.2002In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 174, no 3, 225-229 p.Article in journal (Refereed)
    Abstract [en]

    Serum erythropoietin levels (s-[epo]), haemoglobin concentration ([Hb]), haematocrit (hct), and ferritin concentration ([fer]) were measured in seven healthy male volunteers (20-23 years) exposed continuously to hypoxia (PO(2) 14 kPa) for 10 days. Serum erythropoietin concentration increased significantly from 9.5 +/- 3.51 to 33.6 +/- 11.64 U L(-1) (P < 0.05) after 2 days of hypoxia. Thereafter, s-[epo] decreased. However, after 10 days s-[epo] was 18.7 +/- 5.83 U L(-1) which was still increased above the pre-hypoxia level (P < 0.05). Serum haemoglobin concentration and hct increased over the 10 days of hypoxia, [Hb] from 152 +/- 8.9 to 168 +/- 9.2 gL(-1) (P < 0.001), and hct from 43 +/- 2.4 to 49 +/- 2.6% (P < 0.001). Ferritin concentration decreased significantly during the hypoxic exposure from 82 +/- 46.9 to 44 +/- 31.7 mmol L(-1) after 10 days (P < 0.01). In conclusion, the initial increase of s-[epo] under controlled normobaric hypoxia was marked, 353%, and levelled off after 5-10 days at 62-97% above normoxia level. There was also a significant increase in [Hb] and hct and a decrease in [fer] after 10 days of exposure to normobaric hypoxia.

  • 27. Bhiwapurkar, M. K.
    et al.
    Saran, V. H.
    Goel, V. K.
    Mansfield, N.
    Berg, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Study of human comfort under thermal and vibratory environment using physiological indices2009In: 16th International Congress on Sound and Vibration 2009, ICSV 2009, 2009, 4376-4383 p.Conference paper (Refereed)
    Abstract [en]

    Besides the vibrations, passenger discomfort is influenced by various other factors such as, the environmental factors of noise, temperature, humidity and visual stimuli, etc. The discomfort can be measured both subjectively and objectively. Rammohan25 studied the influence of backrest support and handgrip contractions on acute metabolic, respiratory, and cardiovascular responses during exposure to whole-body vibration (WBV). In the present work, discomfort of passengers subjected to whole body random vibrations, environmental factors such as temperature, humidity and noise level variations by assessing their effect on various physiological parameters like, Pulse Rate, Respiration Rate, Galvanic Skin Response, Skin Temperature, Heart Rate, Heart Rate Variability and ECG values has been studied. The study was conducted on the three axes vibration simulator developed in the Laboratory, IIT Roorkee, India as a mock-up of a railway vehicle. The simulator room has a controlled temperature and humidity environment and its noise level can also be controlled. A BIOPAC system was used for data acquisition along with various modules for measuring physiological parameters. The mean and standard deviation of physiological parameters, possibly indicating the human comfort or discomforts for the 12 subject is found out. The design of experiment (ANOVA) was employed to quantify the relationships between measured responses and the input factors. The results show that some physiological parameters viz, pulse rate, SKT and HR show variation in vibration condition at 0.6 m/s2. It is also found that all the parameters affected by noise level and temperature show significant variation between no vibration condition and vibration condition.

  • 28. Bjornson, Elias
    et al.
    Boren, Jan
    Mardinoglu, Adil
    KTH, Centres, Science for Life Laboratory, SciLifeLab. KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. Chalmers University, Sweden.
    Personalized Cardiovascular Disease Prediction and Treatment-A Review of Existing Strategies and Novel Systems Medicine Tools2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, 2Article, review/survey (Refereed)
    Abstract [en]

    Cardiovascular disease (CVD) continues to constitute the leading cause of death globally. CVD risk stratification is an essential tool to sort through heterogeneous populations and identify individuals at risk of developing CVD. However, applications of current risk scores have recently been shown to result in considerable misclassification of high-risk subjects. In addition, despite long standing beneficial effects in secondary prevention, current CVD medications have in a primary prevention setting shown modest benefit in terms of increasing life expectancy. A systems biology approach to CVD risk stratification may be employed for improving risk-estimating algorithms through addition of high-throughput derived omics biomarkers. In addition, modeling of personalized benefit-of-treatment may help in guiding choice of intervention. In the area of medicine, realizing that CVD involves perturbations of large complex biological networks, future directions in drug development may involve moving away from a reductionist approach toward a system level approach. Here, we review current CVD risk scores and explore how novel algorithms could help to improve the identification of risk and maximize personalized treatment benefit. We also discuss possible future directions in the development of effective treatment strategies for CVD through the use of genome-scale metabolic models (GEMs) as well as other biological network-based approaches.

  • 29. Bjurstedt, H
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Graded restriction of blood flow in exercising leg muscles: a human model.1995In: Advances in Experimental Medicine and Biology, ISSN 0065-2598, E-ISSN 2214-8019, Vol. 381, 147-56 p.Article in journal (Refereed)
  • 30. Bjurstedt, Hilding
    et al.
    Eiken, Ola
    Karolinska Institutet.
    Graded ischemia in exercising human skeletal muscles: methods and applications1995In: News in Physiological Sciences - NIPS, ISSN 0886-1714, E-ISSN 1522-161X, Vol. 10, 193-197 p.Article in journal (Refereed)
    Abstract [en]

    A method was developed for inducing graded blood flow restriction in exercising large muscle groups in humans. The method holds promise as a means to study local and systemic effects of ischemic exercise. Recent applications include studies on the effects of long-term leg ischemia in endurance training.                                                           

  • 31. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Arterial bubbles following trimix dives2014Conference paper (Other academic)
  • 32. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Direct comparison of audio Doppler ultrasound scores and 2D ultrasound images of venous gas emboli.2010Conference paper (Refereed)
  • 33. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Near maximal venous bubble scores and arterial bubbles with no signs or symptoms of DCS - a case study.2011Conference paper (Refereed)
  • 34. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Predisponerar helium i dykgasen för arteriella bubblor?2014Conference paper (Other academic)
    Abstract [sv]

    Bakgrund: Bubblor i den arteriella cirkulationen observerades första gången vid 10 av 12 exkursioner från heliox- (O2/He) och trimix- (O2/He/N2) mättnad (1).  På senare tid har Ljukovic et al (2) redovisat resultat av trimixdykningar där 5 av 7 dykare uppvisade arteriella bubblor. Visserligen har arteriella bubblor observerats även i samband med nitrox- och luftdykningar men inte i så hög frekvens. Gör heliumgasen att bubblor lättare tar sig igenom lungfiltret?

    Metoder: Dykare undersöktes med kardiellt ekokardiografi efter 251 trimixdykningar och 37 nitroxdykningar med varierande dykprofiler. Dykdjupen varierade mellan 20 – 100 m för trimixdykningarna och 33 – 60 m för nitroxdykningarna. Totalt 43 dykare deltog i trimix- och 19 dykare i nitroxdykningarna. Dykarna undersöktes varje kvart i 2 timmar efter dykningarna. Förekomst av venösa och arteriella bubblor registrerades och skattades enligt Brubakk-Eftedal-skalan (EB).

    Resultat: Totalt observerades arteriella bubblor hos 3/43 dykare efter trimixdykning och hos 3/19 dykare efter nitroxdykning. En av dykarna med arteriella bubblor i nitroxgruppen behandlades för ledbends. Två av dykarna hade arteriella bubblor både efter trimix- och nitroxdykningar. I samtliga fall med artärbubblor observerades också venösa bubblor (EB 2 – 4c).

    Slutsats: Jämfört med tidigare rapporterad incidens av artärbubblor i samband med trimixdykningar är de redovisade resultaten låga. Resultaten för nitroxdykningarna är också låga givet att ca 25% av normalpopulationen har öppetstående foramen ovale. Någon ökad incidens artärbubblor observerades inte med den heliuminnehållande gasen, utan det mest troliga är att förekomsten av artärbubblor beror på mängden venösa bubblor och individuell predisponering att ”läcka” bubblor från den venösa till den arteriella cirkulationen.

  • 35. Blogg, L
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Jurd, KM
    Møllerløkken, A
    Observed incidence of decompression sickness and venous gas bubbles following 18 M dives on RN table 11/Norwegian air diving table2015Conference paper (Refereed)
  • 36. Blogg, S. Lesley
    et al.
    Gennser, Mikael
    Swedish Defence Research Agency.
    Cerebral blood flow velocity and psychomotor performance during acute hypoxia2006In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 77, no 2, 107-113 p.Article in journal (Refereed)
    Abstract [en]

    INTRODUCTION: The physiological effects of hypoxic environments can help determine safe limits for workers where cognitive and motor performance is important. We investigated the effects of a PIO2 of 15 kPa and 10 kPa on medial cerebral artery blood flow velocity (CBFV) and psychomotor performance.

    METHODS: Over 3 sessions, each involving 3 separate test batteries, 13 subjects breathed either 21 kPa PIO2 (control), 15 kPa PIO2, or 10 kPa PIO2. The tests measured reaction time, spatial orientation, voluntary repetitive movement, and fine manipulation. CBFV, PETCO2, PETO2, Sa02, and BP were recorded throughout.

    RESULTS: ANOVA analysis showed that 15 kPa PIO2 did not significantly change psychomotor test performance. The mean number of incorrect responses in the reaction time test significantly increased to 5.6 (SD - 4.0) while breathing 10 kPa PIO2, as did the mean number of errors (7.7 +/- 5.0) in the fine manipulation test. Only 10 kPa PIO2 affected CBFV, causing a significant increase in flow from 50 +/- 6.5 cm x s(-1) to 55 +/- 10.3 cm x s(-1). CBFV significantly increased during three psychomotor tests while breathing air; however, it did not increase further during psychomotor testing in hypoxia.

    DISCUSSION: A PIo2 of 15 kPa did not affect subject performance, and should not cause operational risk. At 10 kPa PIO2, accuracy and vigilance were slightly affected; however, the reduction in oxygenation was not great enough to cause major decrements. CBFV was not a good indicator of mental stress during hypoxia.

  • 37. Blogg, S. Lesley
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    The need for optimisation of post-dive ultrasound monitoring to properly evaluate the evolution of venous gas emboli2011In: Diving and hyperbaric medicine : the journal of the South Pacific Underwater Medicine Society, ISSN 1833-3516, Vol. 41, no 3, 139-146 p.Article in journal (Refereed)
    Abstract [en]

    Audio Doppler ultrasound and echocardiographic techniques are useful tools for investigating the formation of inert gas bubbles after hyperbaric exposure and can help to assess the risk of occurrence of decompression sickness. However, techniques, measurement period and regularity of measurements must be standardised for results to be comparable across research groups and to be of any benefit. There now appears to be a trend for fewer measurements to be made than recommended, which means that the onset, peak and cessation of bubbling may be overlooked and misreported. This review summarises comprehensive Doppler data collected over 15 years across many dive profiles and then assesses the effectiveness of measurements made between 30 and 60 minutes (min) post-dive (commonly measured time points made in recent studies) in characterising the evolution and peak of venous gas emboli (VGE). VGE evolution in this dive series varied enormously both intra- and inter-individually and across dive profiles. Median, rather than mean values are best reported when describing data which have a non-linear relation to the underlying number of bubbles, as are median peak grades, rather than maximum, which may reflect only one individual's data. With regard to monitoring, it is apparent that the evolution of VGE cannot be described across multiple dive profiles using measurements made at only 30 to 60 min, or even 90 min post-dive. Earlier and more prolonged measurement is recommended, while the frequency of measurements should also be increased; in doing so, the accuracy and value of studies dependent on bubble evolution will be improved.

  • 38. Blogg, SL
    et al.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The use of ultrasound bubble detection to develop the Swedish Navy trimix dive tables2015Conference paper (Refereed)
  • 39. Blogg, S.L.
    et al.
    Gennser, Mikael
    Swedish Defence Research Agency.
    Loveman, G.A.M.
    Seddon, F.M.
    Thacker, J.C.
    White, M.G.
    The effect of breathing hyperoxic gas during simulated submarine escape on venous gas emboli and decompression illness2003In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 30, no 3, 163-174 p.Article in journal (Refereed)
    Abstract [en]

    Raised internal pressure in a distressed submarine rapidly increases the risk of decompression sickness (DCS) following submarine escape. The hypothesis that breathing a hyperoxic gas during escape may reduce the risk of DCS was tested using goats. Shallow air saturation and simulated submarine escape dives were carried out either singularly or in combination (saturation, escape, or saturation followed by escape) using air or 60% / 40% oxygen (O2) / nitrogen (N2) mixture as breathing gas during the escapes. Post-surfacing, animals were observed for signs of DCI and O2 toxicity. Precordial Doppler ultrasound was used to score venous gas emboli (VGE) using the Kisman Masurel (KM) scale. Following escape from 2.5 MPa, the rate at which VGE disappeared in the hyperoxic group (n = 8) was significantly faster(p < 0.05) than the air group (n = 7). One case of pulmonary barotrauma with arterial gas embolism occurred in the air group, but no cases of DCS were observed. After saturation at 0.18 MPa followed by escape from 2.5 MPa, DCS occurred in four of 15 animals in the air group and in two of 16 animals in the hyperoxic group. The rate of disappearance of VGE was significantly faster (p < 0.01) in the hyperoxic group. O2 toxicity was not discernible in any of the animals.

  • 40. Blogg, S.L.
    et al.
    Loveman, G.A.
    Seddon, F.M.
    Woodger, N.
    Koch, A.
    Reuter, M.
    Gennser, Mikael
    Swedish Defence Research Agency.
    White, M.G.
    Magnetic resonance imaging and neuropathology findings in the goat nervous system following hyperbaric exposures2004In: European Neurology, ISSN 0014-3022, E-ISSN 1421-9913, Vol. 52, no 1, 18-28 p.Article in journal (Refereed)
    Abstract [en]

    Divers may be at risk of long-term CNS damage from non-symptomatic hyperbaric exposure. We investigated the effect of severe, controlled hyperbaric exposure on a group of healthy goats with similar histories. Thirty goats were exposed to various dive profiles over a period of 5 years, with 17 experiencing decompression sickness (DCS). Brains were scanned using magnetic resonance (MR) imaging techniques. The animals were then culled and grossly examined, with the brain and spinal cord sent for neuropathological examination. No significant correlation was found between age, years diving, DCS or exposure to pressure with MR-detectable lesions in the brain, or with neuropathological lesions in the brain or spinal cord. However, spinal scarring was noted in 3 animals that had suffered from spinal DCS.

  • 41. Blogg, SL
    et al.
    Møllerløkken, A
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Response: car wrecks and caution: a lament on getting the facts straight in scientific reporting.2017In: Undersea Hyperb Med, Vol. 44, 492-494 p.Article in journal (Other (popular science, discussion, etc.))
  • 42.
    Botha, Elise M.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Industrial marketing.
    A means to an end: Using political satire to go viral2014In: Public Relations Review, ISSN 0363-8111, E-ISSN 1873-4537, Vol. 40, no 2, 363-374 p.Article in journal (Refereed)
    Abstract [en]

    With the rise of video sharing giants like Youtube and Google Video, coupled with increased broadband connectivity and improved sharing functionality across social networking sites, the role of the viral video has been cemented in many IMC strategies. While most agree about the importance of better understanding viral marketing, there is less agreement about what makes content become viral. While some content gets viewed by millions of people, others struggle to gain viral traction. Content specific, intrapersonal and interpersonal reasons have been proposed for viral marketing success. This paper' focuses on the intrapersonal reasons for content going viral in the context of political satire. More specifically, the role of emotion in the spread of content online, is investigated. Political satire focuses on gaining entertainment from politics. Satire, and specifically political satire, forms part of using humour in advertising and has been influential in shifting public opinion since ancient Greece. This study compares success and unsuccessful viral campaigns that used political satire, by first analysing the online comments that viewers made about the video. Following these findings, an experiment is conducted and the influence of intensity, creativity, humour and utility on virality is modelled, controlling for valence and previous exposure. The findings suggest that, when using political satire in viral campaigns, creativity and the intensity of the emotions felt are key influencing factors in whether videos get "shared" or "liked". Therefore, while many authors contend that particular emotions or positive content has a greater likelihood to become viral, this paper shows that it is not the particular emotion, but the intensity with which that emotion was felt that drives viral success.

  • 43. Brantberg, K.
    et al.
    Bergenius, J.
    Mendel, L.
    Witt, H.
    Tribukait, Arne
    Karolinska Hospital.
    Ygge, J.
    Symptoms, findings and treatment in patients with dehiscence of the superior semicircular canal2001In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 121, no 1, 68-75 p.Article in journal (Refereed)
    Abstract [en]

    Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of the superior semicircular canal. Identifying patients with this 'new' vestibular entity is important, not only because the symptoms are sometimes very incapacitating, but also because they can be treated. We present symptoms and findings in eight such patients, all of whom reported pressure-induced vertigo that increased during periods of upper respiratory infections. Pulse-synchronous tinnitus and gaze instability during head movements were also common complaints. All patients lateralized Weber's test to the symptomatic ear. In some of the patients the audiogram also revealed a small conductive hearing loss. However, the stapedius reflexes were always normal. A vertical/torsional eye movement related to the superior semicircular canal was seen in most of the patients in response to pressure changes and/or sound stimulation. One patient also had superior canal-related positioning nystagmus. Testing vestibular evoked myogenic potentials revealed in all patients a vestibular hypersensitivity to sounds. In the coronal high-resolution 1-mm section CT scans the dehiscence was visible on 1 to 4 sections. Moreover, the skull base was rather thin in this area and cortical bone separating the middle ear and the antrum from the middle cranial fossa was absent in many of the patients. Two of the patients have undergone plugging of the superior semicircular canal using a transmastoid approach and both patients were relieved of the pressure-induced symptoms.

  • 44. Brantberg, K.
    et al.
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital .
    Gentamicin treatment in peripheral vestibular disorders other than Ménière's disease1996In: Journal for Oto-Rhino-Laryngology, ISSN 0301-1569, E-ISSN 1423-0275, Vol. 58, no 5, 277-279 p.Article in journal (Refereed)
    Abstract [en]

    Intratympanic instillation of gentamicin may not exclusively be a treatment for Ménière's disease. We present case reports of successful vertigo control in peripheral vestibular disorders other than Ménère's disease. Cases 1 and 2 illustrate treatment of vertigo attacks caused by vestibular dysfunction in deaf ears. Case 3 illustrates treatment of brief sensations of linear acceleration in a patient who had suffered idiopathic sudden hearing loss a few years earlier. Case 4 illustrates treatment of disabling benign paroxysmal positioning vertigo. Case 5 illustrates treatment of severe and frequent attacks of vertigo in an elderly patient with a medium-sized acoustic neuroma who did not want surgical extirpation of the tumor.

  • 45. Brantberg, K.
    et al.
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital.
    Vestibular-evoked myogenic potentials in patients with dehiscence of the superior semicircular canal1999In: Acta Oto-Laryngologica, ISSN 0001-6489, E-ISSN 1651-2251, Vol. 119, no 6, 633-640 p.Article in journal (Refereed)
    Abstract [en]

    Recently Minor and co-workers described patients with sound- and pressure-induced vertigo due to dehiscence of bone overlying the superior semicircular canal. Identifying patients with this "new" vestibular entity is important, not only because the symptoms can be very incapacitating, but also because they are surgically treatable. We present symptoms and findings for three such patients. On exposure to sounds, especially in the frequency range 0.5-1 kHz, they showed vertical/torsional eye movements analogous to a stimulation of the superior semicircular canal. They also showed abnormally large sound-induced vestibular-evoked myogenic potentials (VEMP), i.e. the short latency sternomastoid muscle response considered to be of saccular origin. The VEMP also had a low threshold, especially in the frequency range 0.5-1 kHz. However, in response to saccular stimulation by skull taps, i.e. when the middle ear route was bypassed, the VEMP were not enlarged. This suggests that the relation between the sound-induced and the skull tap-induced responses can differentiate a large but normal VEMP from an abnormally large response due to dehiscence of bone overlying the labyrinth, because only the latter would produce large sound-induced VEMP compared to those induced by skull taps.

  • 46. Brantberg, K.
    et al.
    Fransson, P A
    Bergenius, J.
    Tribukait, Arne
    Karolinska Hospital.
    Tilt suppression, OKAN, and head-shaking nystagmus at long-term follow-up after unilateral vestibular neurectomy1996In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 6, no 4, 235-241 p.Article in journal (Refereed)
    Abstract [en]

    The functional status of the velocity storage mechanism was studied in patients at long-term follow-up (2 to 4 years) after unilateral vestibular neurectomy. The time constant of the vestibulo-ocular reflex (VORtc), the effect of head tilt on postrotatory nystagmus, optokinetic after-nystagmus (OKAN), and nystagmus after rapid head shaking were studied in 10 patients. In agreement with previous findings, VORtc was found to be short and most patients manifested OKAN, suggesting that unilateral peripheral vestibular loss is associated with a complete loss of storage within the the VOR but only a partial loss of velocity storage for visual input. However, at postrotatory head tilt the VOR time constant was further shortened, supposedly due to discharge of functioning velocity storage. Moreover, most patients manifested nystagmus after head shaking. These findings on tilt suppression and head-shaking nystagmus suggest that velocity storage within the VOR may function even in patients with complete unilateral vestibular lesions.

  • 47. Brantberg, Krister
    et al.
    Löfqvist, Lennart
    Westin, Magnus
    Tribukait, Arne
    Swedish Defence Research Agency.
    Skull tap induced vestibular evoked myogenic potentials: an ipsilateral vibration response and a bilateral head acceleration response?2008In: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 119, no 10, 2363-2369 p.Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP).

    METHODS: An electro-mechanical "skull tapper" (that provided a constant stimulus intensity) was used to test the effects of different midline stimulus sites/directions in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=8).

    RESULTS: The standardized midline skull taps caused highly reproducible VEMP. There were highly significant differences in amplitude and latency in both normals and patients depending on site/direction of tapping (suggesting a stimulus direction dependency). Occiput skull taps caused, in comparisons to forehead and vertex taps, larger amplitude VEMP with more pronounced differences between the lesioned and the healthy side in the patients.

    CONCLUSIONS: The present data, in conjunction with earlier findings, support a theory that skull tap VEMP are mediated by two different mechanisms. It is suggested that skull tapping causes both skull vibration and head acceleration. Further, the VEMP would be the sum of the direction-independent vibration-induced response (from the sound-sensitive part of the saccule) and the direction-dependent head acceleration response (from other parts of the labyrinth).

    SIGNIFICANCE: Skull tap VEMP, as a diagnostic test, is not equivalent to sound-induced VEMP.

  • 48. Brantberg, Krister
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Vestibular evoked myogenic potentials in response to laterally directed skull taps2002In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 12, no 1, 35-45 p.Article in journal (Refereed)
    Abstract [en]

    In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that midline forehead skull tap stimulation evokes similar VEMP. In the present study, the influence of skull tap direction on VEMP was studied in 13 normal subjects and in five patients with unilateral vestibular loss. Gentle skull taps were delivered manually above each ear on the side of the skull. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Among the normals, laterally directed skull taps evoked "coordinated contraction-relaxation responses", i.e. skull taps on one side evoked a negative-positive "inverted" VEMP on that side and a positive-negative "normal" VEMP on the other side. Among patients with unilateral vestibular function loss, skull taps above the lesioned ear evoked similar coordinated contraction-relaxation responses. However, skull taps above the healthy ear did not evoke that type of response. These findings suggest that laterally directed skull taps activate mainly the contralateral labyrinth.

  • 49. Brantberg, Krister
    et al.
    Tribukait, Arne
    Karolinska Hospital.
    Fransson, Per-Anders
    Vestibular evoked myogenic potentials in response to skull taps for patients with vestibular neuritis2003In: Journal of Vestibular Research-Equilibrium & Orientation, ISSN 0957-4271, E-ISSN 1878-6464, Vol. 13, no 2-3, 121-130 p.Article in journal (Refereed)
    Abstract [en]

    In recent years it has been demonstrated that loud clicks generate short latency vestibular evoked myogenic potentials (VEMP). It has also been demonstrated that skull tap stimulation evokes similar VEMP. In the present study, the differences between the click-induced and the skull-tap induced VEMP were studied in 18 patients at onset of vestibular neuritis. Gentle skull taps were delivered manually above each ear on the side of the skull and on the forehead midline. The muscular responses were recorded over both sternocleidomastoid muscles using skin electrodes. Abnormal skull tap VEMP were found in the majority of the patients (10/18, 56%). However, only 4/18 (22%) showed asymmetry in the click-induced VEMP. The high percentage of abnormal skull tap VEMP might suggest that this response is not only dependent on the inferior division of the vestibular nerve, because the inferior division of this nerve is usually spared in vestibular neuritis. Moreover, the patients with abnormal skull tap VEMP differed from those with normal VEMP in their settings of the subjective visual horizontal with static head tilt in the roll plane. This might suggest that skull tap VEMP are (also) related to utricular function.

  • 50. Brantberg, Krister
    et al.
    Westin, Magnus
    Löfqvist, Lennart
    Verrecchia, Luca
    Tribukait, Arne
    Swedish Defence Research Agency.
    Vestibular evoked myogenic potentials in response to lateral skull taps are dependent on two different mechanisms2009In: Clinical Neurophysiology, ISSN 1388-2457, E-ISSN 1872-8952, Vol. 120, no 5, 974-979 p.Article in journal (Refereed)
    Abstract [en]

    OBJECTIVE: To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP).

    METHODS: The muscular responses were recorded over both sternocleidomastoid (SCM) muscles using skin electrodes. A skull tapper which provided a constant stimulus intensity was used to test cervical vestibular evoked myogenic potentials (VEMP) in response to lateral skull taps in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=10).

    RESULTS: Skull taps applied approximately 2 cm above the outer ear canal caused highly reproducible VEMP. There were differences in VEMP in both normals and patients depending on side of tapping. In normals, there was a positive-negative ("normal") VEMP on the side contra-lateral to the skull tapping, but no significant VEMP ipsi-laterally. In patients, skull taps above the lesioned ear caused a contra-lateral positive-negative VEMP (as it did in the normals), in addition there was an ipsi-lateral negative-positive ("inverted") VEMP. When skull taps were presented above the healthy ear there was only a small contra-lateral positive-negative VEMP but, similar to the normals, no VEMP ipsi-laterally.

    CONCLUSIONS: The present data, in conjunction with earlier findings, support a theory that skull-tap VEMP responses are mediated by two different mechanisms. It is suggested that skull tapping causes both a purely ipsi-lateral stimulus side independent SCM response and a bilateral and of opposite polarity SCM response that is stimulus side dependent. Possibly, the skull tap induced VEMP responses are the sum of a stimulation of two species of vestibular receptors, one excited by vibration (which is rather stimulus site independent) and one excited by translation (which is more stimulus site dependent).

    SIGNIFICANCE: Skull-tap VEMP probably have two different mechanisms. Separation of the two components might reveal the status of different labyrinthine functions.

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