| 1. |
- Sundberg, DC, et al.
(författare)
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Morphology development of polymeric microparticles in aqueous dispersions. I. Thermodynamic considerations
- 1990
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 41, s. 1425-1442
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Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic analysis of polymer particle morphology highlights the role of interfacial tensions in controlling particle structure. The influence of the surfactant and the nature of the incompatible polymers is seen through their individual and collective effects upon these interfacial tensions. It has been found that by simply changing the type of surfactant used in the emulsion the particle morphology can change from core-shell to hemispherical, in agreement with thermodynamic predictions. Several apparently different morphologies (hemispherical, sandwich, multiple lobes) have been found to coexist at the same time within a single emulsion, suggesting that they may be simply different states of phase separation and not thermodynamically stable, unique morphologies. The thermodynamic analyses are independent of particle size and method of emulsion processing. Experimental evidence shows that the morphology of particles formed via in situ polymerization ( as in a synthetic latex) is controlled by interfacial tensions in the same manner as those particles formed via solvent evaporation from a solution of an incompatible polymer pair ( as in an artificial latex or microencapsulation).
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| 2. |
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| 3. |
- Axelsson, Björn, et al.
(författare)
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Managing by International Travelling
- 1992
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Ingår i: Managing Networks in International Business. - : Gordon & Breach, Philadelphia. ; , s. 93-109
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Eiken, Ola, et al.
(författare)
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Effects of ischaemic training on force development and fibre-type composition in human skeletal muscle
- 1991
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Ingår i: Clinical Physiology. - 0144-5979 .- 1365-2281. ; 11:1, s. 41-49
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Tidskriftsartikel (refereegranskat)abstract
- Force (peak torque) of m. quadriceps femoris was measured during 60 repeated, voluntary dynamic knee extensions in 10 men before and after a 4-week training regimen of one-legged cycle exercise. Biopsies for histochemical analysis were obtained from the lateral vastus muscle after the training period. One leg was trained with the blood flow to the leg muscles reduced by local supra-atmospheric external pressure of 50 mmHg ('Ischaemic leg, I-leg'). Employing the same work-load profile the other leg was trained at normal atmospheric pressure ('Non-restricted-flow leg, N-leg'). In response to I-training, Maximum Peak Torqued (MPT; the highest torque produced in any contraction) and Initial Peak Torque (IPT; the average peak torque of the initial 12 contractions) decreased by 8% (P less than 0.01) and 9% (P less than 0.001), respectively. Final Peak Torque (FPT; the average peak torque of the final 12 contractions) increased by 13% (P less than 0.05) after I-training. No changes in MPT, IPT or FPT occurred following N-training. After training the proportion of slow-twitch fibres was higher (P less than 0.05) and the mean slow-twitch fibre area was larger (P less than 0.05) in the I-than in the N-trained leg. The results indicate that blood flow-restricted training, in contrast to non-restricted-flow training, decreases maximum voluntary dynamic force, possibly by inducing an increase in the share of the muscle cross-sectional area consisting of slow-twitch fibres. That flow-restricted training improves maintenance of force during short-term local exercise may reflect ischaemically induced changes in the metabolic characteristics of skeletal muscle.
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| 5. |
- Esbjörnsson, M, et al.
(författare)
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Muscle fibre types and enzyme activities after training with local leg ischaemia in man.
- 1993
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 148:3, s. 233-41
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Tidskriftsartikel (refereegranskat)abstract
- Eight healthy men performed supine one-legged training on a bicycle ergometer 45 min per leg four times per week for 4 week. The ergometer and lower body were inside a pressure chamber, the opening of which was sealed at the level of the crotch. One leg trained with impeded leg blood flow (I-leg), induced by an increased (50 mmHg) chamber pressure, at the highest tolerable intensity. The contralateral leg trained at the same power under normal pressure (N-leg). Before and after training biopsies were taken from the vastus lateralis of both legs and maximal one-legged exercise tests were executed with both legs. Biopsies were repeated when the subjects had been back to their habitual physical activity for 3 months. Training increased exercise time to exhaustion, but more in the I-leg than in the N-leg. After training, the I-leg had higher activity of citrate synthase (CS), a marker of oxidative capacity, and lower activity of the M-subunit of lactate dehydrogenase isoenzymes. It also had a higher percentage of type-I fibres and a lower percentage of IIB fibres, larger areas of all fibre types and a greater number of capillaries per fibre. It is concluded that ischaemic training changes the muscle metabolic profile in a direction facilitating aerobic metabolism. An altered fibre-type composition may contribute, but is not enough prerequisite for the change.
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| 6. |
- Kaijser, L., et al.
(författare)
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Muscle oxidative capacity and work performance after training under local leg ischemia
- 1990
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 69:2, s. 785-787
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Tidskriftsartikel (refereegranskat)abstract
- Healthy young men executed supine one-legged cycle training four times per week for 4 wk with legs and the cycle ergometer inside a pressure chamber, the opening of which was sealed by a rubber membrane at the level of the crotch. Each training session started by training one leg under ischemic conditions induced by increased chamber pressure (50 mmHg) at the highest intensity tolerable for 45 min. Then the other leg was trained with the same power profile but normal atmospheric chamber pressure. Before and after the training period, both legs executed one-legged exercise tests under both normal and increased chamber pressure and muscle biopsies were taken from the vastus lateralis. Ischemic training increased performance more than normal training, the difference being greater for exercise executed under ischemic conditions. The difference in performance increase between the legs was paralleled by a greater muscle citrate synthase activity in the ischemically than in the normally trained leg.
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| 7. |
- Mekjavić, I. B., et al.
(författare)
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Perception of thermal comfort during narcosis
- 1994
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Ingår i: Undersea & Hyperbaric Medicine. - 1066-2936. ; 21:1, s. 9-19
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Tidskriftsartikel (refereegranskat)abstract
- We examined the perception of thermal comfort in six male subjects immersed in water at 28 degrees C (study I) and 15 degrees C (study II), breathing either room air (AIR) or a normoxic mixture containing 30% N2O (N2O). Immersions were terminated if esophageal temperature (Tes) decreased by 2 degrees C from resting levels or to 35 degrees C. At regular intervals, subjects rated their perception of thermal comfort on a 21-point scale (thermal comfort vote, TCV; +10 = very, very hot, 0 = neutral, -10 = very, very cold). For similar decreases in Tes from resting preimmersion values (mean +/- SD = -0.90 degrees +/- 0.13 degrees C and -0.92 degrees +/- 0.15 degrees C during the AIR and N2O trials in study I, and -0.90 degree +/- 0.22 degree C and -0.89 degree +/- 0.27 degree C during the AIR and N2O trials in study II), subjects perceived the immersions as less cold during the N2O trials. The median TCVs for the AIR condition of -5 in study I and -7.75 in study II, were significantly lower than those reported by the subjects for the respective N2O conditions (1.75 in study I and -5.5 in study II). It is concluded that behavioral adjustments required for maintaining thermal balance may be diminished during narcosis due to the altered perception of thermal discomfort. Assuming that the effect of inert gas narcosis on thermoregulatory responses is similar to that of N2O, then combined with the significant attenuation of heat gain mechanisms by anesthetic gases, the attenuation of the perception of thermal comfort may represent a significant factor in the etiology of hypothermia observed in compressed air divers.
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| 8. |
- Permadi, H, et al.
(författare)
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Effects of perfluoro fatty acids on peroxisome proliferation and mitochondrial size in mouse liver : dose and time factors and effect of chain length.
- 1993
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Ingår i: Xenobiotica. - 0049-8254 .- 1366-5928. ; 23:7
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Tidskriftsartikel (refereegranskat)abstract
- 1. Male mice were fed a diet containing perfluoro fatty acids of varying chain length (i.e. perfluoroacetic, -butyric, -octanoic and -decanoic acids) at different doses (0.02 or 0.1% w/w of diet) for different periods of time (2-10 days), and effects on liver weight, hepatic mitochondrial protein and hepatic peroxisomal palmitoyl-CoA oxidation, lauroyl-CoA oxidase and catalase were monitored. 2. The greatest effects were obtained with perfluoro-octanoic and perfluoro decanoic acids, while perfluoro acetic acid was inactive. The effects with 0.02% w/w of diet perfluoro-octanoic acid were at least as great as those observed with 0.1%. A more detailed dose-response investigation focused on perfluoro-octanoic acid revealed that maximal effects with this substance could be obtained with a dietary dose of 0.01% for 10 days and that significant changes were also observed with 0.001%. 3. Maximal effects with 0.02% w/w of diet perfluoro-octanoic acid were attained after 6-10 days of feeding. 4. As with other peroxisome proliferators, perfluoro fatty acids increase mouse hepatic peroxisomal fatty acid beta-oxidation more extensively than they increase catalase, thus increasing hepatic oxidative stress. 5. As with other peroxisome proliferators, perfluoro fatty acids increase mouse liver mitochondrial protein. This effect is due primarily to a redistribution of mitochondria from the nuclear to the mitochondrial fraction, caused by an apparent decrease in the mean size of hepatic mitochondria after treatment.
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| 9. |
- Sundberg, C, et al.
(författare)
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Comparison of the potencies of (+)- and (-)-2-ethylhexanoic acid in causing peroxisome proliferation and related biological effects in mouse liver.
- 1994
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Ingår i: Chirality. - : Wiley. - 0899-0042 .- 1520-636X. ; 6:1
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Tidskriftsartikel (refereegranskat)abstract
- Male C57BL/6 mice were exposed to 1% (w/w) (+)- or (-)-2-ethylhexanoic acid or an equimolar mixture of these enantiomers in their diet for 4 or 10 days. A significant increase in liver weight and a 2- to 3-fold increase in the protein content of the mitochondrial fraction were seen in all cases. Peroxisomal palmitoyl-CoA oxidation was increased 2- to 3.5-fold after 4 days of treatment and 4- to 5-fold after 10 days, while the corresponding increases in peroxisomal lauroyl-CoA oxidase activity were 2- to 3-fold and 9- to 12-fold, respectively. Peroxisomal catalase activity was unchanged, whereas the microsomal and cytosolic activities were increased 2- to 3-fold and 6- to 16-fold, respectively. These treatments also induced microsomal omega-hydroxylation of lauric acid 7-fold and soluble epoxide hydrolase activity in the mitochondrial and cytosolic fractions, as well as microsomal epoxide hydrolase activity about 50-100%. The only significant differences observed between the effects of (+)-2-ethylhexanoic acid and its (-)-enantiomer were on peroxisomal palmitoyl-CoA oxidation and lauroyl-CoA oxidase activity after 4 days of treatment. In both these cases the (+)-enantiomer resulted in increases which were 50-75% greater than those seen with the (-)-form.
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| 10. |
- Sundberg, C. J., et al.
(författare)
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Effects of ischaemic training on local aerobic muscle performance in man
- 1993
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Ingår i: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 148:1, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to compare the effects of ischaemic and non-ischaemic training on aerobic performance. In 10 subjects, peak oxygen uptake (peak VO2) and time to fatigue (TTF) for one-legged exercise were measured before and after 4 weeks (4 times week-1) of one-legged training. Each training session started with one leg training for 45 min with 20% blood-flow reduction induced by local application of a supra-atmospheric external pressure of 50 mmHg (ischaemic leg; I-leg). We have previously shown that this decreases leg blood flow by about 20%. The contralateral leg (non-restricted-flow leg; N-leg), serving as a control, then trained with an identical power-output profile for 45 min but without flow restriction. In the I-leg the average training-induced increments in TTF and peak VO2 were 27 and 24%, respectively. In the N-trained leg TTF and peak-VO2 increased 10 and 14%, respectively. Both increments were significantly greater (P < 0.05) in the I-trained leg. Moreover, the performance increase in the I-trained leg was exaggerated (P < 0.05) in the ischaemic test condition, i.e. there was a specificity in the training response. In conclusion, ischaemia acts as an additive stimulus to training leading to an exaggerated increase in endurance and peak-VO2 compared to identical training without blood-flow restriction. The main explanation is probably an enhanced local adaptation in the I-trained leg.
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| 11. |
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