| 1. |
- Bitaraf, Nazanin
(författare)
-
The electrophysiological response of medial preoptic neurons to hypoxia and development of a system for patch-clamp measurement with full oxygen control
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A stroke is caused by interruption of the blood supply to the brain. Yearly 15 million people around the globe endure a stroke and the costs and suffering for the people involved and the society are immense. The aim of this thesis was to investigate the response to oxygen deprivation in neurons from the medial preoptic nucleus (MPN) that have a high abundance of neuroglobin. The long term goal is to investigate the neuroprotective role of the protein in relation to stroke. Initially, the electrophysiological response of neurons to hypoxic exposure in an open system was assessed with a conventional patch-clamp setup. The first aim was to see how well the conventional system worked and if it needed improvement. Secondly, the MPN had never been investigated regarding oxygen, deprivation; hence the electrophysiological response under hypoxia needed to be investigated. The conventional patch-clamp system only allowed a reduction of the oxygen content to a level of 3-6% but not total control of the cell environment. The medial preoptic neurons showed mainly an increase of their resting membrane potential at hypoxia. The voltage activated Ca2+ and K+ currents displayed a clear attenuation when cells were subjected to hypoxia. Non-L-type Ca2+ channels were affected by hypoxic exposure and one cell indicated participation of Ca2+ activated K+ channels. However, a response could only be seen in approximately fifty percent of the neurons in the open system. This may have been due to the fact that full control of the oxygen around the neurons at hypoxia could not be achieved. A new system with full control of the ambient oxygen had to be developed in order to investigate this. After the conclusions of the first experiments, a system was developed were a labon- a-chip system was combined with the patch-clamp technique. A microfluidic system with a patch-clamp micropipette integrated was combined with optical tweezers for 3D maneuvering of the neurons. The development of patch-clamp in combination with a microfluidic system and optical tweezers allowed for full oxygen control. The experiments showed that the electrophysiological measurements were not affected by the laser when an infrared laser was used. The microfluidic system allowed very good oxygen control reaching levels of 0.5-1.5 % compared to 3-6 % in the open system. In summary, this work suggests that high voltage activated Ca2+ channels, and K+ channels are involved in the hypoxic depolarization of medial preoptic neurons. Full control of ambient oxygen in cell vicinity could be achieved by the combination of microfluidics, patch-clamp and optical tweezers. The results can be used in future studies to better understand the reaction of the brain to oxygen deprivation caused by stroke.
|
|
| 2. |
- Björ, Bodil, et al.
(författare)
-
Cold health impacts in northern Sweden
- 2016
-
Ingår i: International Journal of Circumpolar Health. - : Informa UK Limited. - 1239-9736 .- 2242-3982. ; 75:33200
-
Tidskriftsartikel (refereegranskat)
|
|
| 3. |
- Boschman, J. S., et al.
(författare)
-
Relationships between work-related factors and musculoskeletal health with current and future work ability among male workers
- 2017
-
Ingår i: International Archives of Occupational and Environmental Health. - : Springer Science and Business Media LLC. - 0340-0131 .- 1432-1246. ; 90:6, s. 517-526
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose was to increase job-specific knowledge about individual and work-related factors and their relationship with current and future work ability (WA). We studied cross-sectional relationships between mental demands, physical exertion during work, grip strength, musculoskeletal pain in the upper extremities and WA and the relationships between these variables and WA 11 years later. We used a dataset of a prospective cohort study (1997-2008) among employees of an engineering plant (n = 157). The cohort was surveyed by means of tests and written questions on work demands, musculoskeletal health, WA score (WAS; 0-10), and mental and physical WA. Spearman correlation coefficients and logistic regression analysis were used. Among manual workers, we found weak correlations between grip strength and current and future physical WA. We did not find predictors for future poor WA among the manual workers. Among the office workers, we found that musculoskeletal pain was moderately and negatively related to current WAS and physical WA. More handgrip strength related to better future WAS and physical WA. Musculoskeletal pain (OR 1.67 p < 0.01) and lower handgrip strength (OR 0.91 p < 0.05) predicted future poor WA among office workers. Our results showed cross-sectional and longitudinal relationships between musculoskeletal health and work ability depending on occupation. However, the present implies that predicting work ability in the far future based on health surveillance data is rather difficult. Testing the musculoskeletal system (grip strength) and asking workers' about their musculoskeletal health seems relevant when monitoring work ability.
|
|
| 4. |
- Burström, Lage, et al.
(författare)
-
A follow-up study of welders’ exposure to vibration in a heavy engineering production workshop
- 2010
-
Ingår i: Journal of Low Frequency Noise Vibration and Active Control. - : Sage Publications. - 0263-0923 .- 1461-3484 .- 2048-4046. ; 29:1, s. 33-39
-
Tidskriftsartikel (refereegranskat)abstract
- Manual work involving vibrating power tools is associated with symptoms that include vascular, neurological and musculoskeletal disorders. This study examines the vibration exposure of welders to determine the change between 1987 and 2008. Vibration measurements on handheld tools were used to evaluate the acceleration and the daily exposure time was determined by subjective rating. From these data, the 8-hour equivalent vibration exposure A(8), has been calculated. During the period, the A(8) decreased from 3.9 m/s2 to 1.9 m/s2. It was concluded that this decrease is the result of fewer vibrating tools and a decrease in daily exposure time. Although the daily vibration exposure has decreased over the study time, for some welders the daily vibration exposure A(8) is still above the action value set by the EU directive on vibration. This means more effort should be spent to decrease vibration exposure.
|
|
| 5. |
- Burström, Lage, et al.
(författare)
-
Absorption of vibration energy in the human hand and arm
- 1994
-
Ingår i: Ergonomics. - : Informa UK Limited. - 0014-0139 .- 1366-5847. ; 37:5, s. 879-890
-
Tidskriftsartikel (refereegranskat)abstract
- A possible basis for the risk assessment for hand-transmitted vibration may be to determine the amount of energy absorbed in the human hand and arm. In the present study, the mechanical energy absorption in the hand-arm system was measured within the frequency range of 4 to 1000 Hz. The study was carried out on ten healthy subjects during exposure to sinusoidal vibration. The influence of various experimental conditions, such as vibration direction (Xh, Yh, Zh), grip force (25-75 N), vibration level (8-45 mm/srms), and hand-arm posture were studied. The outcome shows that the energy absorption in the human hand and arm depended mainly on the frequency and direction of the vibration stimulus. Higher vibration levels, as well as firmer handgrips, resulted in higher absorption of energy. Varying hand-arm postures had only a small influence on the amount of absorbed energy, while the constitution of the hand and arm affected the energy absorption to a larger extent.
|
|
| 6. |
- Burström, Lage, 1954-, et al.
(författare)
-
Acute effects of vibration on thermal perception thresholds
- 2006
-
Ingår i: Diagnosis of injuries caused by hand-transmitted vibration - 2nd International workshop, Göteborg, 2006. - : Springer Science and Business Media LLC.
-
Konferensbidrag (refereegranskat)abstract
- Objective This study focuses on the acute effects of vibration and how vibrations influence the measures of the thermal perception thresholds during different vibration magnitudes, frequencies, and durations.Methods The fingers of ten healthy subjects, five males and five females, were exposed to vibration under 16 conditions with a combination of different frequency, intensity and exposure time. The vibration frequency was 31.5 and 125 Hz and exposure lasted between 2 and 16 min. The energy-equivalent frequency weighted acceleration, according to ISO 5349-1, for the experimental time of 16 min was 2.5 or 5.0 m/s(2) (r.m.s.), corresponding to a 8-h equivalent acceleration, A(8) of 0.46 and 0.92 m/s(2), respectively. A measure of the thermal perception of cold and warmth was conducted before the different exposures to vibration. Immediately after the vibration exposure the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures at every minute for a maximum of 10 min. If the subject's thermal thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min.Results For all experimental conditions and 30 s after exposure, the mean changes of the thresholds compared with the pre-test were found to be 0.05 and -0.67C for the warmth and cold thresholds, respectively. The effect of the vibration exposure was only significant on the cold threshold and only for the first minute after exposure when the threshold was decreased. The warmth threshold was not significantly affected at all. The frequency and the exposure time of the vibration stimuli had no significant influence on the perception thresholds for the sensation of cold or warmth. Increased equivalent frequency weighted acceleration resulted in a significant decrease of the subjects' cold threshold, not the warmth. The thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency weighted acceleration or the unweighted acceleration.Conclusion When testing for the thermotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained the previous praxis of 2 h avoidance of vibration exposure before assessment is recommended.
|
|
| 7. |
- Burström, Lage, 1954-, et al.
(författare)
-
Influence of vibration exposure on tactile and thermal perception thresholds
- 2009
-
Ingår i: Occup Med (Lond). - : Oxford University Press (OUP). - 1471-8405 .- 0962-7480. ; 59:3, s. 174-9
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS: To establish if intermittent exposure to hand-transmitted vibration had the same effect as continuous exposure on the temporary response of finger tactile and thermal perception thresholds. METHODS: Two laboratory experiments were conducted. In each, 10 healthy subjects, five males and five females, participated. The subjects' fingers were exposed to vibration under four conditions with a combination of different periods of exposure and rest periods. The vibration frequency was 125 Hz and the frequency-weighted acceleration was 5 m/s(2). A measure of the tactile or thermal perception was conducted before the different exposures to vibration. Immediately after the vibration exposure, the acute effect was measured continuously for the first 75 s. This was followed by regular measures for a maximum of 30 min. RESULTS: The results showed that combinations of vibration with different periods of exposure and rest periods significantly influenced vibrotactile perception, but not thermal perception. CONCLUSIONS: These findings suggest that intermittent exposure to hand-transmitted vibration might be more beneficial for the response of the finger vibrotactile sensation than continuous exposure. This finding is inconsistent with the evaluation methods in ISO 5349-1 for vibrotactile sensation, but accurate for thermal perception.
|
|
| 8. |
- Burström, Lage, et al.
(författare)
-
Mechanical energy absorption in human hand-arm exposed to sinusoidal vibration
- 1988
-
Ingår i: International Archives of Occupational and Environmental Health. - 0340-0131 .- 1432-1246. ; 61:3, s. 213-216
-
Tidskriftsartikel (refereegranskat)abstract
- A possible basis for risk assessment of human exposure to vibration when using hand-held tools may be to determine the amount of mechanical energy that is absorbed by the hand-arm system. The aim of this investigation was to study the absorption of mechanical energy in the human hand-arm system during exposure to sinusoidal vibration within the frequency range of 20 to 1500 Hz. A handle, specially designed for this type of experiments, was used during the measurements. The influence of various experimental conditions, such as three different hand-arm postures, grip force (25–75 N) and vibration levels (27–53 mm/srms), were studied on eight subjects. The outcome clearly shows that the energy absorption properties of the human hand-arm system are more or less dependent on all of the experimental conditions studied, but mainly to the frequency of the vibration stimuli. Furthermore, the results indicate a non-linear relationship between the energy absorbed and all other variables studies.
|
|
| 9. |
- Burström, Lage, et al.
(författare)
-
Mechanical impedance of the human hand-arm system
- 1989
-
Ingår i: International Journal of Industrial Ergonomics. - : Elsevier BV. - 0169-8141 .- 1872-8219. ; 3:3, s. 235-242
-
Tidskriftsartikel (refereegranskat)abstract
- Summary The mechanical impedance of the hand and arm was studied on ten healthy subjects during exposure to sinusoidal vibration within the frequency range of 2 to 1000 Hz. A special handle for the measurements was constructed. The influence of vibration direction, handle grip, grip force, vibration level, hand-arm posture and sex as well as anthropometric data were studied. The results show that the impedance of the hand-arm mainly depends on the frequency and direction of the vibration stimuli. Higher vibration levels, as well as more firm hand-grips, resulted in higher impedance. Furthermore, the outcome shows that experiments conducted with different hand-arm postures had an active influence on the mechanical impedance. Moreover, the subjects' sex and constitution of the hand and arm affected the impedance to a large extent.
|
|
| 10. |
|
|
