| 161. |
- Kabanshi, Alan, et al.
(författare)
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Occupants’ perception of air movements and air quality in a simulated classroom with an intermittent air supply system
- 2019
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Ingår i: Indoor + Built Environment. - : Sage Publications. - 1420-326X .- 1423-0070. ; 28:1, s. 63-76
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Tidskriftsartikel (refereegranskat)abstract
- The study reported herein builds on occupant response to an intermittent air jet strategy (IAJS), which creates periodic airflow and non-isothermal conditions in the occupied zone. Previous research has highlighted the benefits of IAJS on thermal climate and supports energy saving potential in view of human thermal perception of the indoor environment. In this study, the goal was to explore occupant acceptability of air movements and perceived indoor air quality, and to determine a way of assessing acceptable air movement conditions under IAJS. Thirty-six participants were exposed to twelve conditions: three room air temperatures (nominal: 22.5, 25.5 and 28.5 oC), each with varied air speeds (nominal: <0.15 m/s under mixing ventilation (MV), and 0.4, 0.6 and 0.8 m/s under IAJS) measured at the breathing height (1.1 m). The results show that participants preferred low air movements at lower temperatures and high air movements at higher temperatures. A model to predict percentage satisfied with intermittent air movements was developed, and predicts that about 87% of the occupants within a thermal sensation range of slightly cool (-0.5) to slightly warm (+0.5), in compliance with ASHRAE standard 55, will find intermittent air movements acceptable between 23.7 oC and 29.1 oC within a velocity range of 0.4 – 0.8 m/s. IAJS also improved participants’ perception of air quality in conditions deemed poor under MV. The findings support the potential of IAJS as a primary ventilation system in high occupant spaces such as classrooms.
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| 162. |
- Kalezic, Ivana, et al.
(författare)
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Changes in Tetrodotoxin-Resistant C-Fibre Activity during Fatiguing Isometric Contractions in the Rat
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science, PLoS. - 1932-6203. ; 8:9, s. e73980-
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Tidskriftsartikel (refereegranskat)abstract
- It is by now well established that tetrodotoxin-resistant (TTX-R) afferent fibres from muscle in the rat exhibit a multisensitive profile, including nociception. TTX-R afferent fibres play an important role in motor control, via spinal and supraspinal loops, but their activation and function during muscle exercise and fatigue are still unknown. Therefore, the specific effect of isometric fatiguing muscle contraction on the responsiveness of TTX-R C-fibres has been investigated in this study. To quantify the TTX-R afferent input we recorded the cord dorsum potential (CDP), which is the result of the electrical fields set up within the spinal cord by the depolarisation of the interneurons located in the dorsal horn, activated by an incoming volley of TTX-R muscle afferents. The changes in TTX-R CDP size before, during and after fatiguing electrical stimulation of the gastrocnemius-soleus (GS) muscle have been taken as a measure of TTX-R C-unit activation. At the end of the fatiguing protocol, following an exponential drop in force, TTX-R CDP area decreased in the majority of trials (9/14) to 0.75 +/- 0.03% (mean +/- SEM) of the pre-fatigue value. Recovery to the control size of the TTX-R CDP was incomplete after 10 min. Furthermore, fatiguing trials could sensitise a fraction of the TTX-R C-fibres responding to muscle pinch. The results suggest a long-lasting activation of the TTX-R muscle afferents after fatiguing stimulation. The role of this behaviour in chronic muscle fatigue in connection with pain development is discussed. Accumulation of metabolites released into the interstitium during fatiguing stimulation might be one of the reasons underlying the C-fibres' long-lasting activation.
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| 163. |
- Kalezic, Ivana, et al.
(författare)
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Distinctive pattern of c-fos expression in the feline cervico-lumbar spinal cord after stimulation of vanilloid receptors in dorsal neck muscles
- 2004
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Ingår i: Neuroscience Letters. - Amsterdam : Elsevier Science. - 0304-3940 .- 1872-7972. ; 364:2, s. 94-97
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, c-fos expression in the spinal cord has been used as a marker of neuronal activation induced by capsaicin-sensitive sensory afferents from the dorsal neck muscles in cats (n = 6). The number of Fos-immunoreactive neurons, which were revealed using the avidin-biotin-peroxidase method, was significantly increased in the cervical and lumbar spinal cord. In contrast to the control group (n = 3), 2 h after intramuscular capsaicin injection, c-fos expression was more extensive ipsilaterally to the injected side in the C3-C6 segments, and bilaterally in the L4-L6 segments. Most labeled neurons in the cervical spinal cord were small and giant cells, predominantly located in the middle and lateral parts of lamina I and, additionally, at the neck of the dorsal horn (lamina V), i.e., within the zones of termination of high-threshold muscle afferents. The widespread distribution of labeled cells throughout the cervical cord within the intermediate zone (lamina VII) coincided with the sites of last-order premotor interneurons and cells of origin of long crossed and uncrossed descending propriospinal pathways to the lumbar spinal cord. These findings suggest possible mechanisms for spreading of nociceptive signals between cervical and lumbar regions.
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| 164. |
- Kalezic, Ivana
(författare)
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Experimental studies of spinal mechanisms associated with muscle fatigue
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Muscle fatigue is ubiquitous in every day life.Muscle fatigue might be considered as an altered state of motor behaviour, which impairs motor performance. By contrast, muscle fatigue could also be considered a positive phenomenon, which protects muscle tissue from damage that might be incurred to it by overuse. The principal aim of the thesis was to explore some of the mechanisms of muscle fatigue at the spinal level in animal models.The activation of multiple motor units of a single calf muscle may influence contractile properties of its neighbouring, otherwise inactive units, providing evidence for spatial spreading of fatigue between different muscle parts. The release of metabolites, their action on inactive muscle units and the effects of local hypoxia are the most likely causes. Fatigue-induced metabolite shift in the interstitium provokes excitation and/or sensitisation of high-threshold afferent fibers, with complex effects on the spinal premotoneuronal network involved in the modulation of motoneuronal output. This was examined by studing the intrasegmental lamellar distribution of the lumbar spinal interneurons following fatiguing contractions of the triceps surae muscle. Furthermore, fatigue of calf muscles enhanced the activity of fusimotor neurons to these muscles irrespective of the regime of muscle activity (isometric vs. lengthening) in conditions that simulate locomotion. Altered fusimotor activity, through increased or maintained muscle spindle afferent responsiveness may be advantageous, providing support to the skeletomotor activity and enhanced information about muscle periphery to higher nervous centres. The particular effects of interneuronal network at motor input (presynaptic inhibition system) and output (recurrent inhibition system) stages were then addressed. Fatigue of triceps surae muscle induced a suppression of the monosynaptic reflex. The intensity of presynaptic inhibition increased, while the intensity of recurrent inhibition decreased. Post fatigue-evoked changes in monosynaptic reflexes and presynaptic inhibition indicate the possibility that high-threshold afferents inhibit group Ia terminals pre-synaptically, which would allow fatigue-induced signals from the muscle to reduce the relevance of proprioceptive feedback. Besides intrasegmental, intersegmental spreading of nociceptive signals was explored. Activation of sensory afferents from dorsal neck muscles by capsaicin induces powerful activation of interneurons located in the cervical spinal cord, as well as a widespread activation of cells in lumbar spinal cord segments. The results confirm the pivotal role of small diameter muscle afferents in the orchestration of segmental responses to fatigue and show complex interactions that may lead to limited accuracy of motor output. They also depict processes that may be related to, and even become precursors of chronic muscle pain.
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| 165. |
- Kalezic, Ivana, et al.
(författare)
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Fatigue-related depression of the feline monosynaptic gastrocnemius-soleus reflex
- 2004
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Ingår i: Journal of Physiology. - London : Cambridge U. P.. - 0022-3751 .- 1469-7793. ; 556:1, s. 293-296
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Tidskriftsartikel (refereegranskat)abstract
- In decerebrate cats, changes in the monosynaptic reflex (MSR) of gastrocnemius-soleus (G-S) motoneurones were studied after fatiguing stimulation (FST) of the G-S muscles. Monosynaptic reflexes were evoked by stimulation of Ia fibres in the G-S nerve and recorded from a filament of ventral root (VR) L7. FST (intermittent 40 s(-1) stimulation for 10-12 min) was applied to the distal part of the cut VR S1. FST reduced MSR amplitudes to 0.64 +/- 0.04 (mean +/-s.e.m.) of the prefatigue values. The suppression remained stable for approximately 25 min and then MSR amplitudes gradually returned towards the normal. To test for the involvement of presynaptic and recurrent inhibition, MSRs were conditioned by stimulation of the nerve to the posterior biceps and semitendinosus (PBSt) muscles or a filament of VR L7, respectively. The intensity of presynaptic inhibition (reduction of the normalized value of MSR amplitude during conditioning) increased from 0.19 +/- 0.02 in prefatigue to 0.44 +/- 0.04 within a 5.3-18.2 min interval after FST, followed by a recovery. In contrast, the intensity of recurrent inhibition first diminished from 0.23 +/- 0.02 in prefatigue to 0.15 +/- 0.01 within 15.6-30.1 min after FST and then gradually recovered. Both primary afferent depolarization and the intensity of antidromic discharges in primary afferents increased with the presynaptic inhibition intensity. These results demonstrate a fatigue-related suppression of Ia excitation of synergistic motoneurones, probably arising from the activation of group III and IV afferents. The effects could in part be due to increased presynaptic inhibition, while recurrent inhibition plays a minor role.
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| 166. |
- Kalezic, Nebojsa
(författare)
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Autonomic reactivity in muscle pain : clinical and experimental assessment
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There are numerous indications of possible involvement of the autonomic nervous system in the genesis of chronic pain. The possibility exists that sympathetic activation is related to motor dysfunction and changes in sensory processing, which have otherwise been implicated in musculoskeletal disorders.The primary aim of the thesis has been to investigate autonomic regulation at rest and in response to laboratory tests of autonomic function in subjects suffering from chronic pain in different localisations (lower back, neck-shoulder and neck-jaw), as well as to study the relations between autonomic regulation, proprioceptive acuity and clinical data. Secondary aim has been to assess autonomic regulation in fit, pain-free subjects in response to experimentally induced pain and in occupationally relevant settings.A total of 194 subjects suffering from chronic pain participated [low back pain (LBP) n=93; non-traumatic neck pain (NT) n=40, Whiplash associated disorder (WAD) n=40, Whiplash with temporomandibular dysfunction (WADj) n=21]. Each chronic pain group was subjected to a battery of autonomic function tests combining cognitive (Stroop Colour-Word conflict tests), physical (handgrip), sensory (unpleasant sound) and motor tasks (chewing tests) as well as the activation of reflex pathways (paced breathing and the orthostatic test) and compared to an age- and gender balanced control group. Autonomic regulation was also assessed in exposure to experimentally induced muscle pain in healthy subjects (n=24) in order to describe acute pain reaction. Further assessment was carried out during monotonous repetitive work and dynamic work in healthy subjects (n=10) and in a three-day monitoring of ambulance personnel (n=26) in occupational settings.Autonomic regulation was evaluated using cardiovascular (heart rate and heart rate variability, local blood flow and blood pressure), respiratory (breathing rate) electrodermal (skin conductance), muscular (trapezius and masseter EMG) and biochemical (insulin, cortisol, catecholamines) variables. Proprioceptive acuity was assessed using active-active repositioning tests. Pain levels were assessed using Visual-analogue or Numerical Rating scales. General health was evaluated through the Short-Form SF-36 Health Related Quality of Life questionnaire and Self-Efficacy Score questionnaires, whereas dysfunction was evaluated using the Oswestry Low Back Pain questionnaire, Pain Disability and Neck Disability Index questionnaires, the McKenzie evaluation and primary healthcare diagnoses. Self-reports of pain, stress and exertion were acquired prior to, during and post-testing.Chronic pain subjects were characterised by increased sympathetic and decreased parasympathetic activity as reflected in heart rate (LBP, WAD, WADj), heart rate variability (LBP, WAD, WADj), blood pressure (WADj) and electrodermal activity (LBP). In general, WAD showed more pain and dysfunction than NT, with lower self-efficacy and health-related quality of life. Differential reactivity was observed only in WAD, with increased responsiveness to sensory stimuli (heart rate variability, electrodermal activity), and motor tasks (heart rate) and a decreased response to cognitive challenge (heart rate variability, electrodermal activity). A significant part of WADj subjects showed sensorimotor impairment and low endurance in chewing tests, concomitant with a cardiovascular response that correlated with pain levels. Proprioceptive acuity was not found to be impaired among subjects suffering from chronic pain, and there were no indications of significant individual response specificity. Response to experimentally induced muscle pain in healthy subjects was also characterised by a prominent cardiovascular component. In simulated occupational settings autonomic activation and transient insulin resistance were detected in healthy subjects following monotonous repetitive work, with no similar effects following dynamic exercise. Modest deviations in circadian heart rate variability patterns during workdays were detected in ambulance personnel reporting more pronounced musculoskeletal symptoms, with no such effects on work-free days.Autonomic balance observed in chronic pain subjects was characterised by a trend towards increased sympathetic activity in comparison with pain-free controls. Moderate signs of affected reactivity to autonomic function tests were observed in patients with WAD, however no specific reaction patterns have been observed in any chronic pain group. Correspondence between the intensity of pain and autonomic activity was observed in acute pain and in chronic pain groups characterised by higher pain levels. As indicated by autonomic and neurohormonal changes in the recovery from real and simulated work, further studies with physiological monitoring of the effects of work-related stress are warranted for better understanding of the mechanism of musculoskeletal disorders.
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| 167. |
- Kalezic, Nebojsa, et al.
(författare)
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Cardiovascular and muscle activity during chewing in whiplash-associated disorders (WAD)
- 2010
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Ingår i: Archives of Oral Biology. - : Elsevier BV. - 0003-9969 .- 1879-1506. ; 55:6, s. 447-453
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Tidskriftsartikel (refereegranskat)abstract
- Objective. The present study aimed to elucidate possible physiological mechanisms behind impaired endurance during chewing as previously reported in WAD. We tested the hypothesis of a stronger autonomic reaction in WAD than in healthy subjects in response to dynamic loading of the jaw-neck motor system. Design. Cardiovascular reactivity, muscle fatigue indicies of EMG, and perceptions of fatigue, exhaustion and pain were assessed during standardised chewing. Twenty-one WAD subjects and a gender/age matched control group participated. Baseline recordings were followed by two sessions of alternating unilateral chewing of a bolus of gum with each session followed by a rest period. Results. More than half of the WAD subjects terminated the test prematurely due to exhaustion and pain. In line with our hypothesis the chewing evoked an increased autonomic response in WAD exhibited as a higher increase in heart rate as compared to controls. Furthermore, we saw consistently higher values of arterial blood pressure for WAD than for controls across all stages of the experiment. Masseter EMG did not indicate muscle fatigue nor were there group differences in amplitude and mean power frequency. Pain in the WAD group increased during the first session and remained increased, whereas no pain was reported for the controls. Conclusion. More intense response to chewing in WAD might indicate pronounced vulnerability to dynamic loading of the jaw-neck motor system with increased autonomic reactivity to the test. Premature termination and autonomic involvement without EMG signs of muscle fatigue may indicate central mechanisms behind insufficient endurance during chewing.
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| 168. |
- Kalezic, Nebojsa, et al.
(författare)
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Physiological reactivity to functional tests in patients with chronic low back pain
- 2007
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Ingår i: Journal of Musculoskeletal Pain. - Binghamton : Haworth Press. - 1058-2452 .- 1540-7012. ; 15:1, s. 29-40
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of the present study was to investigate autonomic regulation at rest and in response to functional laboratory tests in patients with chronic low back pain [CLBP], as well as its possible relations to different characteristics of the clinical picture.Methods: Ninety-three CLBP patients [47 females, 45 males; age 38 +/- 7 years] and 32 healthy normal control subjects [15 females, 16 males: 36 +/- 9 years] participated. Subjects were examined according to the McKenzie procedure, and filled in Short Form 36 and Oswestry Disability Questionnaires in addition to self-reports of pain. An electrocardiogram, finger plethysmogram, respiration, and skin conductance were recorded. Functional tests included the Stroop Color-Word test, orthostatic test, paced breathing, and handgrip. A five-minute baseline recording was followed by four counterbalanced functional tests, separated by two- to three-minute long pauses.Results: An analysis of variance revealed higher baseline heart rate [P=0.011 in females only], low frequency spectral power [P=0.001] and electrodermal activity [P=0.048], and lower high frequency spectral power [P=0.001]. Each functional test evoked a response, without any group differences in physiological reactivity. There were no significant differences with respect to physiological reactivity between subgroups formed on the basis of prior diagnoses, McKenzie evaluation, VAS pain estimates, Short Form 36, and Oswestry Disability Questionnaire data. The patients did not show high levels of individual response specificity.Conclusions: Presented data show that patients with CLBP exhibit increased sympathetic tonus in comparison with the control group, regardless of CLBP patients' level of pain, functional disability, or clinical status indices.
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| 169. |
- Kjeldsen, Ann-Christina, et al.
(författare)
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Training phonological awareness in kindergarten level children : consistency is more important than quantity
- 2003
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Ingår i: Learning and instruction. - : Elsevier. - 0959-4752 .- 1873-3263. ; 13, s. 349-365
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we show that the benefits of phonological training upon reading skills, aptly demonstrated by Lundberg, Frost, and Petersen (Reading Res. Q., 23 (1988) 263), can be obtained even in less favourable conditions featuring a smaller dose of training in a kindergarten culture impregnated by knowledge of phonological awareness and reading. As a consequence, the control group in the present study demonstrated vastly better pre-school reading skills than the one in Lundberg et al. (1988). One experimental group received a training dose of only 60% of that administered by Lundberg et al. (1988). The results replicated those of Lundberg et al. (1988) even for the group with a 60% training dose. A significant gain in word reading was maintained until the end of grade 2 both for mainstream pupils and childrenat- risk. A spelling gain was observed only for children-at-risk in grade 2. It is suggested that training must be strictly systematic in order to be effective. The results are discussed in terms of metacognitive insights into reading that are gained through training in phonological awareness.
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| 170. |
- Kjellgren, Daniel, et al.
(författare)
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Laminin isoforms in human extraocular muscles
- 2004
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Ingår i: Investigative Ophthalmology and Visual Science. - : Association for Research in Vision and Ophthalmology (ARVO). - 0146-0404 .- 1552-5783. ; 45:12, s. 4233-4239
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To determine the laminin isoform composition of the basement membranes (BMs) in the human extraocular muscles (EOMs) and relate it to the fact that EOMs are spared in laminin alpha2-chain-deficient congenital muscular dystrophy. METHODS: Samples from adult human EOMs and limb muscle were processed for immunocytochemistry, with monoclonal antibodies against laminin chains (Ln) alpha1 to -5, beta1 and -2, and gamma1. Neuromuscular junctions (NMJs) were identified with acetylcholinesterase reaction. The capillary density was measured in sections stained with anti-Lnalpha5. RESULTS: The extrasynaptic BM of the EOM muscle fibers contained Lnalpha2, -beta1, -beta2, and -gamma1, and, in contrast to limb muscle, it also contained Lnalpha4 and -alpha5, to some extent. The distinct laminin composition of the EOMs was confirmed by the presence of Lutheran protein, an alpha5-chain-specific receptor not found in limb muscle. At the NMJs, there was increased expression of Lnalpha4 and expression of Lnalpha2, -alpha5, -beta1, -beta2, and -gamma1 was also maintained. The capillary density was very high (1050 +/- 190 capillaries/mm(2)) in the EOMs and significantly (P < 0.05) higher in the orbital (1170 +/- 180 capillaries/mm(2)) than in the global (930 +/- 110 capillaries/mm(2)) layer. CONCLUSIONS: The human EOMs showed important differences in laminin isoform composition and capillary density when compared with human limb muscle and muscles of other species. The presence of additional laminin isoforms other than laminin-2 in the BM of the extrasynaptic sarcolemma could partly explain the sparing of the EOMs in Lnalpha2-deficient congenital muscular dystrophy.
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