| 1. |
- Jaworowski, Åsa, et al.
(författare)
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Calponin reduces shortening velocity in skinned taenia coli smooth muscle fibres
- 1995
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Ingår i: FEBS Letters. - 1873-3468. ; 365:2-3, s. 167-171
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Tidskriftsartikel (refereegranskat)abstract
- Calponin (4.1-5.9 microM, pig stomach) inhibited maximal shortening velocity (Vmax) by 20-25% with only minor influence on force in skinned smooth muscle from guinea-pig taenia coli activated at different Ca2+ levels and with thiophosphorylation. Similar results were obtained with a fragment of the N-terminal 1-228 amino acids engineered using a mouse cDNA construct (5.4 microM). Both the native calponin and the fragment inhibited actin filament sliding in a graded manner in an in vitro motility assay. We conclude that calponin influences the kinetics of the actin-myosin interaction in the organised smooth muscle contractile system and that engineered fragments of calponin can be used to probe its action in muscle fibres. The effects can be due to an introduction of an internal load during filament sliding, possibly by decreasing the detachment rates and increasing the cross-bridge time spent in the attached state.
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| 2. |
- Murtada, Sae-Il, et al.
(författare)
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Experiments and mechanochemical modeling of smooth muscle contraction : Significance of filament overlap.
- 2012
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 0022-5193 .- 1095-8541. ; 297, s. 176-186
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Tidskriftsartikel (refereegranskat)abstract
- The main function of smooth muscle is to maintain/regulate the size of different hollow organs through contraction and relaxation. The magnitude of the active force during contraction is dependent on the number of attached cross-bridges, which can be linked to the overlap between the thin and thick filaments. The relevance of filament overlap and the active cross-bridges in smooth muscle is investigated through a mechanical model founded on Hill's three-element model. The mechanical model describes a sarcomere-equivalent contractile unit supported by structural observations with a distinct filament overlap and a realistic framework for the filament sliding behavior based on force-velocity experiments. The mechanical model is coupled to the four-state latch-model by Hai and Murphy to capture the electromechanical activation from intracellular calcium concentration to load-bearing cross-bridges. The model is fitted to isometric experiments performed on the pig carotid media and on isotonic quick-release experiments found in the literature. The proposed coupled mechanochemical model with the description of the filament overlap, which has a significant influence on the results, is able to predict isometric experimental data performed at different muscle lengths. The relevance of the filament overlap and the load-bearing cross-bridges is investigated through the model by simulating additional scenarios that has been documented in the literature.
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| 3. |
- Witman, Nevin, 1982-, et al.
(författare)
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Recapitulation of developmental cardiogenesis governs the morphological and functional regeneration of adult newt hearts following injury
- 2011
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Ingår i: Developmental Biology. - : Elsevier BV. - 0012-1606 .- 1095-564X. ; 354:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- Urodele amphibians, like the newt, are the champions of regeneration as they are able to regenerate many body parts and tissues. Previous experiments, however, have suggested that the newt heart has only a limited regeneration capacity, similar to the human heart. Using a novel, reproducible ventricular resection model, we show for the first time that adult newt hearts can fully regenerate without any evidence of scarring. This process is governed by increased proliferation and the up-regulation of cardiac transcription factors normally expressed during developmental cardiogenesis. Furthermore, we are able to identify cells within the newly regenerated regions of the myocardium that express the LIM-homeodomain protein Istet1 and GATA4, transcription factors found in cardiac progenitors. Information acquired from using the newt as a model organism may help to shed light on the regeneration deficits demonstrated in damaged human hearts.
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| 4. |
- Arner, Anders, et al.
(författare)
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Calcium transients and the effect of a photolytically released calcium chelator during electrically induced contractions in rabbit rectococcygeus smooth muscle
- 1998
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Ingår i: Biophysical Journal. - 1542-0086 .- 0006-3495. ; 75:4, s. 1895-1903
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Tidskriftsartikel (refereegranskat)abstract
- Intracellular Ca2+ was determined with the fura-2 technique during electrically induced contractions in the rabbit rectococcygeus smooth muscle at 22 degreesC. The muscles were electrically activated to give short, reproducible contractions. Intracellular [Ca2+] increased during activation; the increase in [Ca2+] preceded force development by approximately 2 s. After cessation of stimulation Ca2+ fell, preceding the fall in force by approximately 4 s. The fluorescence properties of fura-2 were determined with time-resolved spectroscopy using synchrotron light at the MAX-storage ring, Lund, Sweden. The fluorescence decay of free fura-2 was best described by two exponential decays (time constants approximately 0.5 and 1.5 ns) at low Ca2+ (pCa 9). At high Ca2+ (pCa 4.5), fluorescence decay became slower and could be fitted by one exponential decay (1.9 ns). Time-resolved anisotropy of free fura-2 was characteristic of free rotational motion (correlation time 0.3 ns). Motion of fura-2 could be markedly inhibited by high concentrations of creatine kinase. Time-resolved spectroscopy measurements of muscle fibers loaded with fura-2 showed that the fluorescence lifetime of the probe was longer, suggesting an influence of the chemical environment. Anisotropy measurements revealed, however, that the probe was mobile in the cells. The Ca2+-dependence of contraction and relaxation was studied using a photolabile calcium chelator, diazo-2, which could be loaded into the muscle cells in a similar manner as fura-2. Photolysis of diazo-2 leads to an increase in its Ca2+-affinity and a fall in free Ca2+. When muscles that had been loaded with diazo-2 were illuminated with UV light flashes during the rising phase of contraction, the rate of contraction became slower, suggesting a close relation between intracellular Ca2+ and the cross-bridge interaction. In contrast, photolysis during relaxation did not influence the rate of force decay, suggesting that relaxation of these contractions is not determined by the rate of Ca2+ removal or due to an increased Ca2+ sensitivity, but instead is limited by other processes such as deactivation by dephosphorylation or detachment of tension-bearing cross-bridges, possibly regulated by thin filament systems.
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| 5. |
- Balogh, Johanna, et al.
(författare)
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Desmin filaments influence myofilament spacing and lateral compliance of slow skeletal muscle fibres.
- 2005
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 88:2, s. 1156-1165
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Tidskriftsartikel (refereegranskat)abstract
- Intermediate filaments composed of desmin interlink Z-disks and sarcolemma in skeletal muscle. Depletion of desmin results in lower active stress of smooth, cardiac, and skeletal muscles. Structural functions of intermediate filaments in fast (psoas) and slow (soleus) skeletal muscle were examined using x-ray diffraction on permeabilized muscle from desmin-deficient mice (Des–/–) and controls (Des+/+). To examine lateral compliance of sarcomeres and cells, filament distances and fiber width were measured during osmotic compression with dextran. Equatorial spacing (x-ray diffraction) of contractile filaments was wider in soleus Des–/– muscle compared to Des+/+, showing that desmin is important for maintaining lattice structure. Osmotic lattice compression was similar in Des–/– and Des+/+. In width measurements of single fibers and bundles, Des–/– soleus were more compressed by dextran compared to Des+/+, showing that intermediate filaments contribute to whole-cell compliance. For psoas fibers, both filament distance and cell compliance were similar in Des–/– and Des+/+. We conclude that desmin is important for stabilizing sarcomeres and maintaining cell compliance in slow skeletal muscle. Wider filament spacing in Des–/– soleus cannot, however, explain the lower active stress, but might influence resistance to stretch, possibly minimizing stretch-induced cell injury.
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| 6. |
- Gachkar, Sogol, et al.
(författare)
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Aortic effects of thyroid hormone in male mice
- 2019
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Ingår i: Journal of Molecular Endocrinology. - 1479-6813. ; 62:3, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- It is well established that thyroid hormones are required for cardiovascular functions; however, the molecular mechanisms remain incompletely understood, especially the individual contributions of genomic and non-genomic signalling pathways. In this study, we dissected how thyroid hormones modulate aortic contractility. To test the immediate effects of thyroid hormones on vasocontractility, we used a wire myograph to record the contractile response of dissected mouse aortas to the adrenergic agonist phenylephrine in the presence of different doses of T3 (3,3',5-triiodothyronine). Interestingly, we observed reduced vasoconstriction under low and high T3 concentrations, indicating an inversed U-shaped curve with maximal constrictive capacity at euthyroid conditions. We then tested for possible genomic actions of thyroid hormones on vasocontractility by treating mice for 4 days with 1 mg/L thyroxine in drinking water. The study revealed that in contrast to the non-genomic actions the aortas of these animals were hyperresponsive to the contractile stimulus, an effect not observed in endogenously hyperthyroid TRβ knockout mice. To identify targets of genomic thyroid hormone action, we analysed aortic gene expression by microarray, revealing several altered genes including the well-known thyroid hormone target gene hairless. Taken together, the findings demonstrate that thyroid hormones regulate aortic tone through genomic and non-genomic actions, although genomic actions seem to prevail in vivo. Moreover, we identified several novel thyroid hormone target genes that could provide a better understanding of the molecular changes occurring in the hyperthyroid aorta.
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| 7. |
- Liu, Jiao, et al.
(författare)
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Altered Sarcomeric Structure and Function in Woody Breast Myopathy of Avian Pectoralis Major Muscle
- 2020
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The “Woody” or “Wooden” breast disease is a severe myopathy of pectoralis major muscle recently identified within rapidly growing broiler lines all around the world with a prevalence rate around 20%, or even higher. Although of significant ethical and economic impact, little is known regarding the structural and functional aspects of the contractile apparatus in the woody breast muscle. The aim of the present study was to determine physiological properties of the contractile system in the morphologically intact muscle fibers of focally damaged woody breast in comparison with normal muscle fibers to gain insight into the muscle function of the animal and possibly mechanisms involved in the disease development. Muscle samples were taken from woody breast (non-lesioned areas) and normal breast muscles from broilers. Length-tension curves, maximal active stress, maximal shortening velocity, calcium sensitivity, rate of tension development, lattice spacing and muscle biochemical composition were investigated on single skinned fibers. Sarcomeres of woody breast fibers were more compliant, which is very likely related to the wider spacing (18% wider compared to controls) between thick and thin filament. No differences were found in optimal sarcomere length (2.68 ± 0.04 vs. 2.65 ± 0.05 μm) nor in maximal active stress (116 ± 17 vs. 125 ± 19 mN mm–2). However, woody breast fibers had less steep descending arm as shown in length-tension curve. Woody breast muscle fibers had 40% bigger sarcomeric volume compared to controls. Content of contractile proteins (myosin and actin), and maximal shortening velocity were unchanged indicating that the growth in woody breast muscle fiber was associated with synthesis of new contractile units with unaltered kinetics. Calcium sensitivity was decreased in woody breast muscle fibers significantly. In conclusion, the results show that the rapid growth of muscle in woody breast disease is associated with significant structural and functional changes in the pectoralis major musculature, associated with alterations in the mechanical anchoring of contractile filaments.
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| 8. |
- Olofsson, Peder S., et al.
(författare)
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Blood pressure regulation by CD4+ lymphocytes expressing choline acetyltransferase
- 2016
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Ingår i: Nature Biotechnology. - : Nature Publishing Group. - 1087-0156 .- 1546-1696. ; 34:10, s. 1066-1071
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Tidskriftsartikel (refereegranskat)abstract
- Blood pressure regulation is known to be maintained by a neuro-endocrine circuit, but whether immune cells contribute to blood pressure homeostasis has not been determined. We previously showed that CD4(+) T lymphocytes that express choline acetyltransferase (ChAT), which catalyzes the synthesis of the vasorelaxant acetylcholine, relay neural signals(1). Here we show that these CD4(+)CD44(hi)CD62L(Io) T helper cells by gene expression are a distinct T-cell population defined by ChAT (CD4 T-ChAT). Mice lacking ChAT expression in CD4(+) cells have elevated arterial blood pressure, compared to littermate controls. Jurkat T cells overexpressing ChAT (JT(ChAT)) decreased blood pressure when infused into mice. Co-incubation of JT(ChAT) and endothelial cells increased endothelial cell levels of phosphorylated endothelial nitric oxide synthase, and of nitrates and nitrites in conditioned media, indicating increased release of the potent vasorelaxant nitric oxide. The isolation and characterization of CD4 T-ChAT cells will enable analysis of the role of these cells in hypotension and hypertension, and may suggest novel therapeutic strategies by targeting cell-mediated vasorelaxation.
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| 9. |
- Sjuve, Rolf, et al.
(författare)
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Increased expression of non-muscle myosin heavy chain-B in connective tissue cells of hypertrophic rat urinary bladder
- 2001
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Ingår i: Cell and Tissue Research. - : Springer Science and Business Media LLC. - 1432-0878 .- 0302-766X. ; 304:2, s. 271-278
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Tidskriftsartikel (refereegranskat)abstract
- Expression of the non-muscle myosin heavy chain-B (NM-MHC-B, also denoted as the embryonic smooth muscle myosin heavy chain, SMemb) was examined in rat urinary bladder during growth in response to a partial urinary outflow obstruction. Following obstruction, the weight of the urinary bladder increased more than five-fold within 10 days. Immunohistochemistry with a polyclonal antiserum against the C-terminal sequence of NM-MHC-B revealed very few NM-MHC-B immunoreactive cells in the control urinary bladders. In hypertrophic bladders, the number of NM-MHC-B immunoreactive cells markedly increased. The majority of such cells were found in the interstitium surrounding smooth muscle bundles and also in the subserosal and submucosal layers. Western blot analysis showed that the NM-MHC-B expression was transient; the content of NM-MHC-B immunoreactive material had doubled 10 days after obstruction and then declined towards the control level after 6 weeks. Immunohistochemistry revealed co-localization of NM-MHC-B and vimentin within the same cells. NM-MHC-B did not co-localize with smooth muscle actin, suggesting that the source of NM-MHC-B is not a de-differentiated smooth muscle cell or myofibroblast but a non-muscle cell possibly reacting to tissue distension or stress. The NM-MHC-B-positive cells could have a role in the production of extracellular matrix and growth factors or be involved in modulation of spontaneous contractile activity.
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| 10. |
- van Wieringen, Tijs, 1979-
(författare)
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Intra- and Extracellular Modulation of Integrin-directed Connective Tissue Cell Contraction
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- All blood vessels in the microvasculature are embedded in loose connective tissue, which regulates the transport of fluid to and from tissues. The intersti-tial fluid pressure (IFP) is one of the forces that control this transport. A lowering of IFP in vivo results in an increased transport of fluid from the circulation into the underhydrated connective tissues, resulting in edema formation. During homeostasis, contractile connective tissue cells exert a tension on the connective tissue fibrous network by binding with β1 in-tegrins, thereby actively controlling IFP. During inflammation, the IFP is lowered but platelet-derived growth factor (PDGF)-BB induces an IFP nor-malization dependent on integrin αVβ3. We demonstrate that extracellular proteins from Streptococcus equi subspecies equi modulated cell-mediated and integrin αVβ3-directed collagen gel contraction in vitro. One of these proteins, the collagen- and fibronectin binding FNE, stimulated contraction by a process dependent on fibronectin synthesis. This study identified a pos-sible novel virulence mechanism for bacteria based on the ability of bacteria to modulate the edema response. Another protein, the collagen-binding pro-tein CNE, inhibited contraction and this led to the identification of sites in collagen monomers that potentially are involved in connecting αVβ3 to the collagen network. PDGF-BB and prostaglandin E1 (PGE1) stimulate and inhibit collagen gel contraction in vitro and normalize and lower IFP, respec-tively. We showed that these agents affected both similar and different sets of actin-binding proteins. PDGF-BB stimulated actin cytoskeleton dynamics whereas PGE1 inhibited processes dependent on cytoskeletal motor and adhesive functions, suggesting that these different activities may partly ex-plain the contrasting effects of PGE1 and PDGF-BB on contraction and IFP. Mutation of the phosphatidylinositol 3’-kinase (PI3K), but not phospholipase C (PLC)γ activation site, rendered cells unable to respond to PDGF-BB in contraction and in activation of the actin binding and severing protein cofilin. Ability to activate cofilin after PDGF-BB stimulation correlated with ability to respond to PDGF-BB in contraction, suggesting a role for cofilin in this process downstream of PDGF receptor-activated PI3K. Many proteins can modulate contraction either by affecting the extracellular matrix and cell adhesions or by altering cytoskeletal dynamics. Knowledge on how these proteins might influence IFP is likely to be of clinical importance for treat-ment of inflammatory conditions including anaphylaxis, septic shock and also carcinoma growth.
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