Oscillatory Contractions Research Articles

1P183 A帯滑り運動系と制御系タンパク質を用いた自励振動現象発生機構の解明(筋肉 : 筋蛋白・収縮)

1P183 A帯滑り運動系と制御系タンパク質を用いた自励振動現象発生機構の解明(筋肉 : 筋蛋白・収縮)

1P165 筋収縮系自励振動(SPOC)における外力刺激応答のサルコメア長依存性(筋肉 : 筋蛋白・収縮)

1P165 筋収縮系自励振動(SPOC)における外力刺激応答のサルコメア長依存性(筋肉 : 筋蛋白・収縮)

The mechanism of honokiol-induced and magnolol-induced inhibition on muscle contraction and Ca2+ mobilization in rat uterus.

The effects of honokiol and magnolol extracted from the Magnolia officinalis on muscular contractile responses and intracellular Ca(2+) mobilization were investigated in the non-pregnant rat uterus. Honokiol and magnolol (1-100 micromol/l) were observed to inhibit spontaneous and uterotonic agonists (carbachol, PGF(2alpha), and oxytocin)-, high K(+)-, and Ca(2+) channel activator (Bay K 8644)-induced uterine contractions in a concentration-dependent manner. The inhibition rate of honokiol on spontaneous contractions appeared to be slower than that of magnolol-induced response. The time periods that were required for honokiol and magnolol, at 100 micromol/l, to abolish 50% spontaneous contractions were approximately 6 min. Furthermore, honokiol and magnolol at 10 micromol/l also blocked the Ca(2+)-dependent oscillatory contractions. Consistently, the increases in intracellular Ca(2+) concentrations ([Ca(2+)](i)) induced by PGF(2alpha) and high K(+) were suppressed by both honokiol and magnolol at 10 micromol/l. After washout of these treatments, the rise in [Ca(2+)](i) induced by PGF(2alpha) and high K(+) was still partially abolished. In conclusion, the inhibitory effects of honokiol and magnolol on uterine contraction may be mediated by blockade of external Ca(2+) influx, leading to a decrease in [Ca(2+)](i). Honokiol and magnolol may be considered as putative Ca(2+) channel blockers and be of potential value in the treatment of gynecological dysfunctions associated with uterine muscular spasm and dysmenorrhea.

Troponin C in different insect muscle types: identification of two isoforms in Lethocerus, Drosophila and Anopheles that are specific to asynchronous flight muscle in the adult insect.

The indirect flight muscles (IFMs) of Lethocerus (giant water bug) and Drosophila (fruitfly) are asynchronous: oscillatory contractions are produced by periodic stretches in the presence of a Ca(2+) concentration that does not fully activate the muscle. The troponin complex on thin filaments regulates contraction in striated muscle. The complex in IFM has subunits that are specific to this muscle type, and stretch activation may act through troponin. Lethocerus and Drosophila have an unusual isoform of the Ca(2+)-binding subunit of troponin, troponin C (TnC), with a single Ca(2+)-binding site near the C-terminus (domain IV); this isoform is only in IFMs, together with a minor isoform with an additional Ca(2+)-binding site in the N-terminal region (domain II). Lethocerus has another TnC isoform in leg muscle which also has two Ca(2+)-binding sites. Ca(2+) binds more strongly to domain IV than to domain II in two-site isoforms. There are four isoforms in Drosophila and Anopheles (malarial mosquito), three of which are also in adult Lethocerus. A larval isoform has not been identified in Lethocerus. Different TnC isoforms are expressed in the embryonic, larval, pupal and adult stages of Drosophila; the expression of the two IFM isoforms is increased in the pupal stage. Immunoelectron microscopy shows the distribution of the major IFM isoform with one Ca(2+)-binding site is uniform along Lethocerus thin filaments. We suggest that initial activation of IFM is by Ca(2+) binding to troponin with the two-site TnC, and full activation is through the action of stretch on the complex with the one-site isoform.

ChTX induces oscillatory contraction in guinea pig trachea: role of cyclooxygenase-2 and PGE2.

We examined the possible role of cyclooxygenase (COX) in charybdotoxin (ChTX)-induced oscillatory contraction in guinea pig trachea. Involvement of prostaglandin E(2) (PGE(2)) in ChTX-induced oscillatory contraction was also investigated. ChTX (100 nM) induced oscillatory contraction in guinea pig trachea. The mean oscillatory frequency induced by ChTX was 10.7 +/- 0.8 counts/h. Maximum and minimum tensions within ChTX-induced oscillatory contractions were 68.4 +/- 1.8 and 14.3 +/- 1.7% compared with K(+) (72.7 mM) contractions. ChTX-induced oscillatory contraction was completely inhibited by indomethacin, a nonselective COX inhibitor. Valeryl salicylate, a selective COX-1 inhibitor, did not significantly inhibit this contraction, whereas N-(2-cyclohexyloxy-4-nitro-phenyl)-methanesulfonamide, a selective COX-2 inhibitor, abolished this contraction. Exogenously applied arachidonic acid enhanced ChTX-induced oscillatory contraction. SC-51322, a selective PGE receptor subtype EP(1) antagonist, significantly inhibited ChTX-induced oscillatory contraction. Exogenously applied PGE(2) induced only a slight phasic contraction in guinea pig trachea, but PGE(2) induced strong oscillatory contraction after pretreatment with indomethacin and ChTX. Moreover, ChTX time-dependently stimulated PGE(2) generation. These results suggest that ChTX specifically activates COX-2 and stimulates PGE(2) production and that ChTX-induced oscillatory contraction in guinea pig trachea is mediated by activation of EP(1) receptor.

A帯滑り運動系(Bio-nanomuscle)による筋収縮機構及び自励振動現象機構の解明

A帯滑り運動系(Bio-nanomuscle)による筋収縮機構及び自励振動現象機構の解明

蛍光顕微解析による筋収縮系自励振動(SPOC)メカニズムの解明

蛍光顕微解析による筋収縮系自励振動(SPOC)メカニズムの解明

心筋収縮系の自励振動現象

心筋収縮系の自励振動現象

A chemical kinetic theory on muscle contraction and spontaneous oscillation

From a set of chemical kinetic equations describing the actin-activated myosin ATPase cycle, we show that, in active muscle, the fraction of myosin heads in any given biochemical state is independent of both [ADP] and [P i]. Combining muscle mechanics data of Pate and Cooke, we deduce the muscle state equation in which muscle force is a state variable of the muscle system. The theoretical results are consistent with Baker's experimental data but somewhat different from conventional muscle theory. Based on the muscle state equation with the knowledge of special structure of muscle, we present a physical mechanism which can lead to both contraction and oscillation of sarcomeres. It explains the muscle spontaneous oscillatory contraction in a natural way and agrees well with experimental data. The model will be helpful in studying the oscillatory behavior of cilia and flagella.

Phospholipase-Mediated Inhibition of Spontaneous Oscillatory Uterine Contractions by Lindane in Vitro

Although regulation of uterine contractility is fundamental for parturition, mechanisms by which toxicants modify uterine muscle contractions remain poorly understood. In a previous cumulative concentration-response study, 10 μM lindane (γ-hexachlorocyclohexane) reduced contraction force and 30 μM lindane abolished contractions in Gestation Day 10 rat uterine strips when lindane was added to muscle baths at 10-min intervals. Other studies showed that brief (<10 min) exposures to 10–100 μM lindane inhibit gap junctions and activate phospholipase pathways in rat myometrial cells in culture. Consequently, lindane was used as a prototype toxicant with known uterine activity to investigate the hypothesis that activation of a specific phospholipase pathway provides a mechanistic link between inhibition of uterine contraction and inhibition of myometrial gap junctions. Uterine tissue and cells were pretreated with phospholipase pathway inhibitors to evaluate the role of phospholipase pathways in lindane's actions in the uterus. Concentrations of inhibitors were selected based on previous reports of effective concentrations for the enzyme activity and on pilot toxicity studies of the inhibitors on uterine contraction and gap junction communication. To monitor uterine contractions, longitudinal uterine strips were excised from Gestation Day 10 rats and suspended in isometric muscle baths, consistent with previous experiments. Exposure in vitro for 60 min to 10–50 μM lindane, an effective concentration range for the uterine responses of interest, revealed that 30 μM lindane rapidly abolished contractions. Subsequently, uterine strips were pretreated with phospholipase pathway inhibitors and then challenged with 30 μM lindane, the lindane concentration that elicited maximal inhibition of uterine contraction. Pretreatment with 20–50 μM of the phosphatidylinositol-specific phospholipase C inhibitor 1- O-octadecyl-2- O-methyl- sn-glycerol-3-phosphorylcholine (ET-18-OCH 3) reversed lindane-induced inhibition of spontaneous uterine contractions. Gap junction intercellular communication was monitored by injecting the fluorescent dye Lucifer yellow into rat myometrial cells grown in culture and assessing dye transfer to adjacent cells using epifluorescence microscopy. Similar to uterine contraction, pretreatment of cell cultures with phospholipase C inhibitors (30 μM ET-18-OCH 3, 50 μM tricyclodecan- p-yl-xanthogenate · K [D609] or 50 μM tricyclodecan- p-yl-xanthogenate · K or 2-nitro-4-carboxyphenyl- N,N-dophenylcarbamate [NCDC]) partially reversed inhibition of dye transfer by 100 μM lindane, a lindane concentration previously shown to abolish myometrial Lucifer yellow dye transfer under similar culture conditions. In contrast, pretreatment with 20 μM of bromoenol lactone (BEL) to inhibit the calcium-independent phospholipase A 2 or 100 mM ethanol to interrupt the phospholipase D pathway failed to prevent inhibition of spontaneous uterine contractions and inhibition of Lucifer yellow dye transfer by lindane (100 μM). These data suggest that lindane inhibits myometrial gap junctions and spontaneous oscillatory contractions by a phospholipase C-mediated pathway.

Role of CA(2+)-activated K+ channels in the regulation of basilar arterial tone in spontaneously hypertensive rats.

1. Ionic channels appear to play an important role in contractile responses of the cerebral arteries and, thereby, contribute to the regulation of cerebral circulation. In the present study, we investigated the role of large-conductance Ca(2+)-activated K+ (BK(Ca)) channels in the regulation of cerebral arterial tone during chronic hypertension. 2. Ring segments of the basilar artery from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were placed in bath chambers and the isometric tension of each ring was measured. 3. Application of inhibitors of BK(Ca) channels, namely tetraethylammonium (TEA; > or = 0.1 mmol/L) and charybdotoxin (CTX; > or = 0.1 nmol/L), produced spontaneous contraction with rhythmic oscillation in the basilar artery from SHR. 4. The oscillatory contraction was not induced by 5-hydroxytryptamine (0.01-10 micromol/L) or depolarization by external high K+ (20-60 mmol/L). 5. The rhythmic contraction was completely abolished by either the removal of external Ca(2+) or the application of nicardipine (10 nmol/L). 6. The oscillation was not affected by the substitution of external Cl(-) by various equimolar anions (i.e. acetate, benezenesulphonate, bromide and isethianate). 7. The amplitude of the oscillation was dose-dependently increased by the vasodilators forskolin and sodium nitroprusside, as well as by stimulation of the endothelium with histamine and acetylcholine, whereas the frequency was decreased. 8. In contrast, the oscillation was eliminated by depletion of Ca(2+) stores by caffeine. Neither TEA (10 mmol/L) nor CTX (10 nmol/L) produced any significant contraction of the basilar artery in WKY rats. 9. These results suggest that BK(Ca) channels may play an important role in regulating the resting tone of the cerebral artery in SHR.

Ca 2+-activated K + channel blockers induce PKC modulated oscillatory contractions in guinea pig trachea

Mechanisms underlying the Ca 2+-activated K + channel (K Ca) blockers-induced oscillatory contractions were investigated in guinea pig tracheal smooth muscle. The mean oscillatory frequencies induced by charybdotoxin (ChTX; 100 nM) and iberiotoxin (IbTX; 100 nM) were 9.8±0.8 (counts/h) and 8.0±1.3 (counts/h), respectively. Apamin (1 μM), a blocker of SK Ca, induced no contraction in guinea pig trachea and did not affect ChTX-induced oscillatory contractions. In Ca 2+ free solution, no ChTX-induced contraction was observed. Nifedipine (100 nM), a blocker of voltage-dependent Ca 2+ channels, and SK&F 96365 (10 μM), a blocker of capacitative Ca 2+ entry, completely abolished ChTX-induced oscillatory contractions. Ryanodine (1 μM) decreased the amplitude, but increased the frequency of the oscillatory contractions. Thapsigargin (1 μM) changed contractions from the oscillatory type to the sustained type. Moreover, the protein kinase C (PKC) inhibitor, bisindolylamaleimide I (1 μM), decreased the amplitude and frequency, but PKC activator, phorbol 12-myristate 13-acetate (1 μM), increased the frequency of oscillatory contractions. These results suggest that K Ca inhibitors-induced oscillatory contractions are initiated by Ca 2+ influx through L-type voltage-dependent Ca 2+ channels. The ryanodine-sensitive calcium release channels in the sarcoplasmic reticulum may play an important role in maintaining the oscillatory contractions. Moreover, PKC activity modulates these oscillatory contractions.

Uterine muscle as a potential target of polychlorinated biphenyls during pregnancy

Because of their once-popular commercial uses, improper disposal and environmental persistence, polychlorinated biphenyls (PCBs) are common environmental contaminants found in many designated Superfund sites. Several epidemiology studies associated PCB exposure with decreased length of gestation. Recent laboratory studies, described in this review, examined PCB actions in uterine muscle in order to investigate mechanisms by which PCBs may stimulate early onset of parturition. Because increased frequency, force and coordination of oscillatory uterine contractions are the defining characteristics of parturition, the laboratory studies used uterine muscle tissue and cells to study PCB actions on uterine contraction. Acute in vitro exposures to commercial PCB mixtures and microbially dechlorinated commercial PCB mixtures increased the frequency of spontaneous oscillatory contractions of uteri from pregnant rats. Increased uterine stimulation was observed with PCB mixtures containing increased abundance of lesser-chlorinated, ortho-substituted congeners. Similarly, in vitro exposures to PCB congeners increased the frequency of spontaneous uterine oscillatory contractions in a structurally related manner, with ortho-substitution of four or fewer chlorines associated with increased stimulation. Moreover, inhibitors of phospholipase A2 prevented stimulation of oscillatory uterine contractions by the commercial PCB mixture Aroclor 1242, suggesting involvement of arachidonic acid in the Aroclor 1242-induced stimulation. Acute exposure to a hydroxylated estrogenic PCB inhibited uterine contraction acutely, but a 42-h exposure increased uterine sensitivity to the uterotonic hormone oxytocin in a manner similar to 17β-estradiol, suggesting an estrogenic mechanism by which some PCBs could decrease gestation length. These studies show that PCBs stimulate uterine contraction in vitro, providing biologically plausible mechanisms in support of previous epidemiology findings associating PCB exposure with decreased gestation length. Further conclusions regarding human health should be considered in the context of human exposure and the experimental limitations of the in vitro studies.

Alternative splicing, muscle contraction and intraspecific variation: associations between troponin T transcripts, Ca2+ sensitivity and the force and power output of dragonfly flight muscles during oscillatory contraction

SUMMARYThe flight muscles of Libellula pulchella dragonflies contain a mixture of six alternatively spliced transcripts of a single troponin T (TnT) gene. Here, we examine how intraspecific variation in the relative abundance of different TnT transcripts affects the Ca2+ sensitivity of skinned muscle fibers and the performance of intact muscles during work-loop contraction regimes that approximate in vivo conditions during flight. The relative abundance of one TnT transcript, or the pooled relative abundance of two TnT transcripts, showed a positive correlation with a 10-fold range of variation in Ca2+ sensitivity of skinned fibers (r2=0.77, P&amp;lt;0.0001) and a threefold range in peak specific force (r2=0.74, P&amp;lt;0.0001), specific work per cycle (r2=0.54; P&amp;lt;0.0001) and maximum specific power output (r2=0.48, P=0.0005) of intact muscle. Using these results to reanalyze previously published data for wing kinematics during free flight, we show that the relative abundances of these particular transcripts are also positively correlated with wingbeat frequency and amplitude. TnT variation alone may be responsible for these effects, or TnT variation may be a marker for changes in a suite of co-regulated molecules. Dragonflies from two ponds separated by 16 km differed significantly in both TnT transcript composition and muscle contractile performance, and within each population there are two distinct morphs that showed different maturational trajectories of TnT transcript composition and muscle contractility. Thus, there is broad intraspecific variability and a high degree of population structure for contractile performance phenotypes, TnT ribotypes and ontogenetic patterns involving these traits that affect locomotor performance.

Thickness waves in electroelastic plates

Within the linear theory developed in [J. Struct. Control 5 (2) (1998) 73] for coherently oriented, transversely isotropic electroelastic plates capable of thickness changes, the general boundary-value problem uncouples into a “membrane” problem and a “flexure” problem. When progressive waves for the membrane problem are investigated, the relative propagation condition reveals that three different types of solutions exist involving oscillatory thickness distension and contraction accompanied by in-plane motion. In the special case of no electroelastic coupling in the material response the propagation condition can be explicitly solved; one purely electrical and two purely mechanical waves obtain. A simple argument based on kinematical similarities indicates that the two mechanical waves can be regarded as two-dimensional counterparts of the first equivoluminal and dilatational modes of the three-dimensional Rayleigh–Lamb theory.

Laser-Induced Nanometer−Nanosecond Expansion and Contraction Dynamics of Poly(methyl methacrylate) Film Studied by Time-Resolved Interferometry

The expansion and contraction behavior of a neat poly(methyl methacrylate) film is induced by 248 nm excimer laser exitation and directly measured by nanosecond interferometry. Above the ablation threshold (1400 mJ/cm2), the film expands during the excitation laser pulse, and after 25% expansion of the thickness, it undergoes fragmentation. Below the threshold, the expansion rate is still high (a few nm/ns), and permanent swelling is observed after transient expansion and succeeding contraction. By decreasing the laser fluence below 800 mJ/cm2, permanent swelling was not observed, and at a few tens of mJ/cm2, novel oscillatory expansion and contraction behavior was successfully detected. The expansion amplitude as a function of laser fluence indicates that the polymer film undergoes phase transition from glass to rubber upon excitation with a fluence higher than 450 mJ/cm2. In the glass state, the interpenetrating structure of the polymer film and associated free volume distribution may be changed upon ir...

Antioxidants prevent gamma-hexachlorocyclohexane-induced inhibition of rat myometrial gap junctions and contractions.

Lindane (gamma-hexachlorocyclohexane) is a commonly used pesticide that bioaccumulates in mammalian adipose tissue. Lindane inhibits gap junctional intercellular communication and oscillatory contractions of pregnant rat myometrium in vitro. The present study investigated the role of oxidative stress in lindane's inhibition of myometrial function in mid-gestation pregnant rat uteri. Lucifer yellow dye was microinjected into cultured myocytes to assess gap junctional intercellular communication. Lindane exposure (100 microM) resulted in a time-dependent, biphasic inhibition of dye transfer. This pattern of inhibition was also seen upon cell exposure to the pro-oxidant, tert-butyl hydroperoxide (100 microM). Lindane's initial and secondary-onset dye transfer inhibitions were reversed by cotreatment and pretreatment with the antioxidants, alpha-tocopherol (25-100 microM), diphenyl-1,4-phenylene diamine (10-30 microM), and superoxide dismutase (100-400 U/ml). D-mannitol (100-300 mM) also reversed lindane's initial dye transfer inhibition. Nitro blue tetrazolium reduction to formazan (measured spectrophotometrically) was elevated upon exposure of cultured cells to lindane or tert-butyl hydroperoxide, indicating the presence of reducing agents. Lipid peroxidation, assessed as thiobarbituric acid-reactive substances, was also elevated in lindane-exposed cell cultures. alpha-Tocopherol reversed this elevation. Finally, uterine contractility was assessed by measuring isometric contractions of uterine strips hung in standard muscle baths. Pretreatment with alpha-tocopherol prevented lindane's abolishment of uterine contractions in vitro. These data support the hypothesis that lindane inhibits uterine contractility and myometrial gap junctions by establishing an oxidative stress environment.

Expression and function of the Drosophila ACT88F actin isoform is not restricted to the indirect flight muscles.

Most higher eukaryotic genomes contain multiple actin genes, yet the sequence differences between isoforms are few. In Drosophila melanogaster it was previously established that one of the six actin genes, Act88F, is expressed only in the indirect flight muscles (IFMs). These muscles are highly specialised for oscillatory contractions to power flight. The implication was that this isoform had tissue-specific properties. In this paper we show using two reporter constructs expressing either beta-galactosidase, Act88F-lacZ, or the green fluorescent protein, Act88F-GFP, that the Act88F promoter is active in a small number of other muscles, including leg (femoral) and uterine muscles. However, the levels of Act88F driven non-IFM expression are much less than in the IFMs. We have confirmed endogenous Act88F gene expression in these other muscles by in situ hybridisation studies. Using null and antimorphic mutants to show decreased walking ability and delayed/reduced oviposition we demonstrated that Act88F expression is functionally important in multiple muscle groups. Since the mutant effects are mild, this supports the expectation that other actin genes are also expressed in these muscles. The Act88F-GFP promoter-reporter also detects Act88F-driven expression in the bristle-forming cells in the pupal wings. The implications of these results for the functions and developmental expression of the Drosophila ACT88F isoform are discussed.

Nanometer–Nanosecond Oscillatory Expansion and Contraction Behavior of Polymer Films Induced by 248 nm Excimer Laser Excitation

Microregional mechanical measurements of a poly[methylmethacrylate) film can be made by a combined probe/measurement laser system, as represented in the picture. The localized nature of the laser systems allow quantification of the degree of expansion and contraction processes, as well as the glass-rubber transition. Such nondestructive techniques lead to the elucidation of polymer morphological dynamics.

Nanometer–Nanosecond Oscillatory Expansion and Contraction Behavior of Polymer Films Induced by 248 nm Excimer Laser Excitation

Microregional mechanical measurements of a poly[methylmethacrylate) film can be made by a combined probe/measurement laser system, as represented in the picture. The localized nature of the laser systems allow quantification of the degree of expansion and contraction processes, as well as the glass-rubber transition. Such nondestructive techniques lead to the elucidation of polymer morphological dynamics.