| 1. |
- Arner, Anders, et al.
(författare)
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Smooth, slow and smart muscle motors.
- 2003
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Ingår i: Journal of Muscle Research and Cell Motility. - 0142-4319. ; 24:2-3, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- Smooth muscle is a slow and economical muscle with a large variability in contractile properties. This review describes results regarding the relation between expression of myosin isoforms and the contraction of smooth muscle. The focus of the review is on studies of the organised contractile system in the smooth muscle tissue. The role of the myosin heavy chain variants formed by alternative splicing in the myosin heavy chain tail (SM1, SM2 isoforms) and head (SM-A SM-B isoforms) regions, as well as the role of essential light chains (LC17a, LC17b isoforms) for the variability of contractile properties are discussed. Smooth muscle also has the ability to alter its contractile properties in response to altered functional demands in vivo, e.g. during hypertrophic growth of urinary bladder, intestine, uterus and vessels and in response to altered hormone levels. These alterations involve changes in myosin expression and altered contractile kinetics. Non-muscle myosin has been shown to have a contractile function in some smooth muscle tissues and recent data on the kinetic properties of non-muscle myosin filaments in smooth muscle tissue are described.
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| 2. |
- Karlsson Wede, Oskar, et al.
(författare)
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Mechanical function of intermediate filaments in arteries of different size examined using desmin deficient mice.
- 2002
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Ingår i: Journal of Physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 540:Pt 3, s. 941-949
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Tidskriftsartikel (refereegranskat)abstract
- Protein composition and mechanical function of intermediate filaments were examined in arteries of different sizes using desmin deficient mice (Des-/-) and their wild-type controls (Des+/+). Using SDS-PAGE gels and Western blots we found a gradient in desmin expression in the arterial tree; the desmin content increased from the elastic artery aorta, via the muscular mesenteric artery to the resistance-sized mesenteric microarteries approximately 150 microm in diameter in Des+/+ mice. Mechanical experiments were performed on the aorta, the mesenteric artery and resistance-sized arteries using wire myographs. For aorta and mesenteric artery, no differences in passive or active circumference- stress relations were found between Des-/- and Des+/+ mice. In microarteries, both passive and active stress were lower in the Des-/- group. In conclusion, large elastic and muscular arteries contain a relatively low amount of desmin, and the desmin intermediate filaments do not seem to play a major role in the mechanical properties of these larger arterial vessels. In the microarteries, where expression of desmin is high, desmin plays a role in supporting both passive and active tension.
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| 3. |
- Löfgren, Mia, et al.
(författare)
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Effects of thyroxine on myosin isoform expression and mechanical properties in guinea-pig smooth muscle.
- 2002
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Ingår i: Journal of Physiology. - : Wiley. - 1469-7793 .- 0022-3751. ; 543:3, s. 757-766
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Tidskriftsartikel (refereegranskat)abstract
- Information on the effects of thyroid hormone on smooth muscle contractile protein expression and mechanical properties is sparse. We have addressed the following questions. (1) Can thyroxine hormone alter myosin isoform composition in smooth muscle? (2) Can a change in myosin isoform composition lead to altered mechanical properties in smooth muscle? (3) Are alterations, if occurring, equal in fast and slow smooth muscle types? Guinea-pigs were treated with thyroxine (T(4)) for 12 days. Control animals were given physiological saline solution. Maximal unloaded shortening velocity (V(max)) was measured in chemically skinned, maximally activated muscle preparations from the aorta and the taenia coli. V(max) increased following thyroxine treatment, by approximately 20 % in the taenia coli. In the aorta, no significant increase in V(max) could be detected. The sensitivity of isometric force to inorganic phosphate (P(i)) was increased in the taenia coli following thyroxine treatment. The expression of mRNA (determined with RT-PCR) for the myosin heavy chain with the seven amino acid insert increased by approximately 70 % in the aorta and about 25 % in the taenia coli following thyroxine treatment. Western blot analysis showed an increase in the inserted myosin heavy chain form in the taenia coli. Expression of mRNA for the myosin essential light chains and the corresponding proteins did not change significantly in either muscle type. No alterations in non-muscle myosin heavy chain isoforms could be detected after thyroxine treatment. In conclusion, thyroxine treatment alters the isoform composition of myosin in fast and slow smooth muscles in vivo. This change is sufficient to increase shortening velocity and sensitivity of isometric force to P(i) in the fast, but not in the slow, smooth muscle type.
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| 4. |
- Löfgren, Mia, et al.
(författare)
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Nonmuscle Myosin motor of smooth muscle.
- 2003
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Ingår i: Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 121:4, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- Nonmuscle myosin can generate force and shortening in smooth muscle, as revealed by studies of the urinary bladder from mice lacking smooth muscle myosin heavy chain (SM-MHC) but expressing the nonmuscle myosin heavy chains A and B (NM-MHC A and B; Morano, I., G.X. Chai, L.G. Baltas, V. Lamounier-Zepter, G. Lutsch, M. Kott, H. Haase, and M. Bader. 2000. Nat. Cell Biol. 2:371–375). Intracellular calcium was measured in urinary bladders from SM-MHC–deficient and SM-MHC–expressing mice in relaxed and contracted states. Similar intracellular [Ca2+] transients were observed in the two types of preparations, although the contraction of SM-MHC–deficient bladders was slow and lacked an initial peak in force. The difference in contraction kinetics thus do not reflect differences in calcium handling. Thick filaments were identified with electron microscopy in smooth muscle cells of SM-MHC–deficient bladders, showing that NM-MHC can form filaments in smooth muscle cells. Maximal shortening velocity of maximally activated, skinned smooth muscle preparations from SM-MHC–deficient mice was significantly lower and more sensitive to increased MgADP compared with velocity of SM-MHC–expressing preparations. Active force was significantly lower and less inhibited by increased inorganic phosphate. In conclusion, large differences in nucleotide and phosphate binding exist between smooth and nonmuscle myosins. High ADP binding and low phosphate dependence of nonmuscle myosin would influence both velocity of actin translocation and force generation to promote slow motility and economical force maintenance of the cell.
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| 5. |
- Löfgren, Mia, et al.
(författare)
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Substrate and product dependence of force and shortening in fast and slow smooth muscle
- 2001
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Ingår i: Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 117:5, s. 407-418
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Tidskriftsartikel (refereegranskat)abstract
- To explore the molecular mechanisms responsible for the variation in smooth muscle contractile kinetics, the influence of MgATP, MgADP, and inorganic phosphate (P(i)) on force and shortening velocity in thiophosphorylated "fast" (taenia coli: maximal shortening velocity Vmax = 0.11 ML/s) and "slow" (aorta: Vmax = 0.015 ML/s) smooth muscle from the guinea pig were compared. P(i) inhibited active force with minor effects on the V(max). In the taenia coli, 20 mM P(i) inhibited force by 25%. In the aorta, the effect was markedly less (< 10%), suggesting differences between fast and slow smooth muscles in the binding of P(i) or in the relative population of P(i) binding states during cycling. Lowering of MgATP reduced force and V(max). The aorta was less sensitive to reduction in MgATP (Km for Vmax: 80 microM) than the taenia coli (Km for Vmax: 350 microM). Thus, velocity is controlled by steps preceding the ATP binding and cross-bridge dissociation, and a weaker binding of ATP is not responsible for the lower V(max) in the slow muscle. MgADP inhibited force and V(max). Saturating concentrations of ADP did not completely inhibit maximal shortening velocity. The effect of ADP on Vmax was observed at lower concentrations in the aorta compared with the taenia coli, suggesting that the ADP binding to phosphorylated and cycling cross-bridges is stronger in slow compared with fast smooth muscle.
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