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At least 1,243 records · Page 69Linked to original sources
PubMed1988

Fura-2 detected myoplasmic calcium and its correlation with contracture force in skeletal muscle from normal and malignant hyperthermia susceptible pigs.

Fura-2 was used to estimate myoplasmic [Ca2+] in intact intercostal muscle fibers from normal and malignant hyperthermia susceptible (MHS) pigs. Small muscle bundles (20-50 fibers) were loaded with the membrane-permeant form of the dye. Resting myoplasmic [Ca2+] were not significantly different in normal and MHS muscles. Halothane produced increases in myoplasmic Ca2+ with associated contractures in MHS muscles, but not in normal muscles. These halothane effects were reversible. Caffeine produced increases in myoplasmic Ca2+ and contractures in both MHS and normal muscles. The threshold concentrations were lower in the MHS muscles. The correlations between myoplasmic [Ca2+] and force in MHS and normal muscles were similar.

Animals↗
PubMed1989

Correction of established capsular contractures with polyurethane implants.

Twelve patients with severe and recurrent capsular contractures following breast augmentation and reconstruction were improved with polyurethane-covered implants. It still has not been established whether these implants prevent or merely delay the onset of contractures, but some of these patients have been followed for over three years and all 12 were improved.

Adult↗
PubMed1989

Capsular contracture after breast reconstruction with the lateral thoracodorsal flap.

Early postoperative manipulation of breast implants in patients who underwent breast reconstruction utilizing a lateral thoracodorsal flap is described. This manipulation did not reduce the rate of firm capsular contracture after the reconstruction with the flap, but only postponed its development. Open capsulotomies, however, yielded stationary soft breasts to a statistically significant extent. The patient's acceptance of the reconstructed breast as a natural part of her own body was high. It was not influenced by the occurrence of firm capsular contracture.

Adult↗
PubMed1991

Activation dependence of isotonic transient in response to step tension reduction in cardiac muscle segment during barium contracture.

To clarify the activation-dependence of dynamic mechanical characteristics of contracting cardiac muscle, we analysed the healthy central segment length (SL) response to step decrease in tension at two different levels of barium contracture (0.2 mM and 0.5 mM Ba2+) in rat papillary muscles with a fixed initial SL. The time course of this response is thought to reflect the kinetics of actin-myosin interaction. The muscle was released stepwise from the steady contracture tension (Tc) to new steady tension levels (Tr) of varying magnitudes at 22 degrees C. The SL responses consisted of four phases at Tr/Tc greater than 0.3. The amplitude of shortening in the second phase, after the initial rapid and minute shortening in the first phase, increased with an increase in amplitude of step tension reduction, and was greater at the higher activation level when compared at an identical amount of Tr/Tc. The fourth phase, after the remarkable lengthening in the third phase, was an extremely slow and minute shortening toward a new steady SL under the new tension. The duration of the second and third phase was quite insensitive to activation level at Tr/Tc greater than 0.85, but became longer at the higher activation level with larger amounts of tension reduction. The velocity measured from the initial quasi-steady SL shortening in the second phase increased significantly with the increase in activation level. These results are discussed in terms of cross-bridge kinetics underlying the isotonic SL transients at two different activation levels.

Animals↗
PubMedDate not supplied

Mitochondrial calcium in hearts subjected to lipid peroxidation with contracture development.

In the present study we have investigated isolated rat hearts perfused with oxygen radicals generated by xanthine oxidase and hypoxanthine. The influence of verapamil (1 mg.1(-1] pretreatment on oxygen radical-induced contracture development and decrease in contractility was examined. In addition, we have measured mitochondrial calcium and magnesium levels in control hearts and hearts perfused with oxygen radicals with and without addition of superoxide dismutase (SOD) and catalase. The presence of oxygen radical-induced lipid peroxidation was confirmed by the increased level of conjugated diens in lipid extracts from oxygen radical-perfused hearts. Verapamil prevented contracture development in hearts perfused with oxygen radicals. Diastolic pressure measured with a left ventricle balloon was at the end of the experiments. 18 +/- 3 mm Hg (mean +/- SEM) with verapamil and 66 +/- 9 mm Hg without (p less than 0.001). Perfusion with oxygen radicals resulted in a reduction in mitochondrial calcium from 14.63 +/- 0.93 to 8.26 +/- 0.61 nmol.mg-1 (p less than 0.001) which was partly reversed by superoxide dismutase and catalase. Mitochondrial magnesium levels were unchanged in all groups.

Animals↗
PubMed1990

Diltiazem and nifedipine reduce the in vitro contracture response to halothane in malignant hyperthermia-susceptible muscle.

The effects of diltiazem (1 microM) and nifedipine (1 microM) were examined separately on the in vitro halothane tests for malignant hyperthermia (MH) susceptibility. Eighteen patients with MH susceptibility were diagnosed as MH-susceptible (MHS) according to the protocol of the European MH Group. In addition, halothane tests were carried out in the presence of either diltiazem (ten patients) or nifedipine (eight patients). These two calcium channel blockers significantly reduced the halothane contracture. Furthermore, in five of the ten MHS patients tested in the presence of diltiazem as well as in five of the eight MHS patients tested in the presence of nifedipine the halothane contracture test could be classified as negative. It is concluded that the presence of clinical concentrations of either diltiazem or nifedipine in the muscle bath affects the in vitro discrimination for MH susceptibility to halothane.

Depression, Chemical↗
PubMed1982

Masseter spasm induced by succinylcholine in children: contracture testing for malignant hyperthermia: report of six cases.

We evaluated six boys who had developed isolated masseter muscle spasm following intravenous succinylcholine. All were receiving halothane by inhalation.l In vitro muscle contracture tests utilizing halothane and caffeine were performed. Four of the six boys had contracture response similar to those of malignant hyperthermia susceptible patients. Rigidity following succinylcholine should prompt the clinician to consider malignant hyperthermia but has been associated with other myopathic conditions as discussed.

Anesthesia↗
PubMed1998

A single mutation that results in an Asp to His substitution and partial exon skipping in a family with congenital contractural arachnodactyly.

Congenital contractural arachnodactyly (CCA) is an autosomal dominant disorder of connective tissue and is characterized by multiple congenital contractures, arachnodactyly, and external ear malformations. Recent investigations indicate that mutations in the fibrillin-2 gene (FBN2) cause CCA. Here, we report a G-->C transversion at nucleotide 3340 (G3340C) of FBN2 in a family with phenotypic characteristics of CCA. The G3340C mutation predicts the substitution of histidine for aspartic acid at amino acid residue 1114 (Asp1114His) and also alters the 5' donor splice site consensus sequence of exon 25. Reverse transcription/polymerase chain reaction and DNA sequence analyses demonstrate that this missense mutation also causes low level in-frame mis-splicing of exon 25 (del exon 25). Consequently, this single point mutation produces a heterogeneous population of mutant fibrillin-2 molecules in a single individual. Despite the complex manifestation of the mutation, it is associated with a relatively mild phenotype. Analysis of FBN2 allele expression in cultured dermal fibroblasts derived from the proband has shown that the mutant allele is preferentially expressed, contributing about 84% of the total transcript. This indicates that an overabundance of mutant transcript does not necessarily correlate with a more severe CCA phenotype.

Aged↗
PubMed2003

Gradual closed correction of equinus contracture using the Ilizarov apparatus.

We treated 16 patients with equinus contracture using the Ilizarov method without open soft tissue release. No hinge was used in seven patients; instead, their ankle joint was used as the hinge (natural hinge; unconstrained construct). In the remaining nine patients, medial and lateral hinges connecting the tibial and foot rings were placed at the center of the talar dome (rotating hinge; constrained construction). We assessed the results in terms of the extent of dorsiflexion, its improvement, and complications. There was little difference between the results in the natural hinge group and the rotating hinge group. The natural hinge system is therefore the method of choice for treating equinus contracture because it is less invasive and simpler. However, particular care is needed during correction to avoid complications such as anterior subluxation of the talus and joint space narrowing. When complications do occur, intervention should be immediate.

Adolescent↗
PubMed1992

Free medial gastrocnemius myocutaneous flap transfer with neurovascular anastomosis to treat Volkmann's contracture of the forearm.

Some articles have reported the use of medial gastrocnemius transfer to repair soft-tissue defects caused by trauma and inflammation (Morris, 1978; Feldman et al., 1978; Arnold and Mixter, 1983). However, we have not found any report describing the use of free medial gastrocnemius myocutaneous flap transfer with neurovascular anastomosis to treat Volkmann's contracture of the forearm. Since 1982, 20 cases of Volkmann's contracture of the forearm have been treated by transfer of medial gastrocnemius flap with neurovascular anastomosis. These 20 patients ranged in age from 6-18 years, with a mean of 10 years. There were 18 males and 2 females. All cases resulted from ischaemia of the extrinsic and intrinsic muscles of the forearm and hand. The most common causes were severe supracondylar fractures or, less frequently, fracture-dislocations of the elbow. Six to twenty months after operation, the transplanted muscles exhibited normal electromyographic potentials, good volume and contractile power with satisfactory functional recovery of the forearms. The deformities of the hand and wrist were also corrected. In this paper we describe the anatomy of the donor site and the operative procedure.

Adolescent↗
PubMedDate not supplied

Structural aspects of the effect of ethyl benzoates on caffeine contracture.

The effect of ethyl benzoate, ethyl o- and p-fluorobenzoate and ethyl o- and p-toluate on the caffeine-induced contracture of frog sartorius muscle was investigated. All drugs with the exception of ethyl o-toluate depressed caffeine-induced contractures. It is proposed that the methyl group in ethyl o-toluate sterically blocks the ester carbonyl group from exerting its inhibitory action. It is further proposed that ethyl o-aminobenzoate exerts its potentiating effect through the lone pair of electrons on the nitrogen atom.

Animals↗
PubMed1979

Depressant effects of phenoxygenzamine on potassium contracture in cat ventricular muscle.

Phenoxybenzamine has been shown to have a depressant action on K+-depolarization contracture in cat ventricular muscle. In the present study, we show that this depressant action is specific for phenoxybenzamine and occurs in the presence of beta-adrenergic receptor blockade with nadolol. K+-contracture is not depressed by phentolamine nor augmented by phenylephrine. Thus, the depressant action of phenoxybenzamine is not mediated by its effects on cardiac adrenergic receptors.

Animals↗
PubMed1987

Defibrotide, an antithrombotic substance which prevents myocardial contracture in ischemic rabbit heart.

Defibrotide, a polydeoxyribonucleotide obtained from mammalian lungs, reduced in a dose-dependent fashion the ischemic contracture due to low perfusion (0.2 ml/min) of isovolumic left heart of rabbit and abolished the irregular rhythm of the heart, thereby restoring the cardiomechanical activity upon reperfusion (20 ml/min). Defibrotide stimulated the release of PG-like material from the heart in a dose-dependent manner without modifying the basal contractility. Both PGE2 and PGI2 (10 ng/ml) have an antiischemic activity on this preparation as shown by the partial reduction of the ischemic contracture and by the improvement of heart contractility upon reperfusion. Indomethacin infusion (1 microgram/ml) completely removed both the antiischemic activity of Defibrotide (400 micrograms/ml) and its ability to increase the generation of prostaglandins in the rabbit heart. These results suggest that Defibrotide has a beneficial influence on ischemic rabbit heart through an increase in prostaglandin synthesis. However other mechanisms not necessarily related to prostaglandin generation, such as a direct effect on membrane function deactivation and mitochondrial Ca2+ overload, should be considered in explaining the antiischemic activity of Defibrotide in the rabbit heart.

Animals↗
PubMed1987

Caffeine contractures in denervated slow-twitch and fast-twitch muscles of the rat.

Caffeine contractures (25 mM) and twitches were registered in vitro (34 degrees C) in normal and denervated soleus and extensor digitorum longus of the rat. Both muscles lost weight progressively after denervation although the loss of weight in soleus muscles was more manifest. Denervated extensor digitorum longus muscles showed an increase in the caffeine contracture tension (expressed in g/g muscle) whereas the response generated by denervated soleus muscles was smaller than the control values. The time to peak of the caffeine responses was shortened in both types of muscles after denervation. Twitches were larger and had a slower time course than in normal muscles, especially in the extensor digitorum longus muscles. These findings suggest that some changes in the excitation-contraction coupling could be responsible for the potentiation of the twitches in denervated muscles.

Animals↗
PubMed1980

Volkmann's ischaemic contracture of the forearm.

Twenty-three patients with established contractures of the forearm, which were treated by excision of all irreparably damaged muscles, lengthening of the tendons and neurolysis of the median and ulnar nerves, are reported. Fourteen patients were children. Supracondylar fractures of the humerus, all treated by plaster-of-Paris, were associated with 10 contractures. Twelve patients achieved good or normal function of the hand after treatment; 5 had obvious functional disability, 4 achieved only a support function and 2 required forearm amputations. Early treatment improved the functional result. Treatment of displaced supracondylar fractures by traction seemed to be an important prophylactic procedure.

Adolescent↗
PubMed1991

Caffeine rapid cooling contractures and negative force staircase in rat papillary muscle.

In rat papillary muscle, rapid cooling causes membrane depolarization which initiates action potentials that lead to a contraction. This rapid cooling contraction (RCC) can be blocked by TTX, Mn2+, Ni2+ or high K+ superfusion. In the presence of caffeine (0.5-1 mM), the rapid cooling contracture (caffeine-RCC) has an amplitude similar to that of a twitch elicited by field stimulation at 37 degrees C, but is not inhibited by these agents. As the caffeine-RCC appears to be independent of membrane depolarization and Ca influx but can be inhibited by increasing the bathing caffeine concentration to 20 mM, we consider that the amplitude of this contracture gives a good indication of the calcium content of the sarcoplasmic reticulum (SR). In Tyrode containing 1.8 mM Ca an increased stimulus frequency leads to a negative force staircase which is paralleled by a similar decrease in the amplitude of the caffeine-RCC. These effects are lost if the bathing Ca is reduced (0.18-0.45 mM) in a way which can be reversed by isoproterenol (100 nM). In verapamil (2 microM), however whilst the twitch responses may show a steeper dependence upon stimulus frequency, the negative frequency dependence of the caffeine-RCC is also lost. Low external Na+ also inhibits the frequency dependent reduction of the caffeine-RCC. The results suggest that if the amplitude of the caffeine-RCC is a good indication of the SR calcium content, then this Ca store is related reciprocally to membrane Ca current where activation of the Ca channels leads to a depletion of the store whereas inhibition of membrane Ca channels leads to a filling of the Ca store. We propose that on stimulation the size of the Ca influx determines the fraction of Ca released from the SR. This released Ca may be partially extruded from the cell by way of the Na/Ca exchange which acts in competition with the re-uptake mechanism of the SR to control SR Ca content.

Action Potentials↗
PubMed1986

The facilitative actions of Bay K 8644 on norepinephrine and KCl-induced contractures of rabbit aortic rings.

The effect of the calcium channel agonist BAY K 8644 on the ability of KCl and norepinephrine to induce contractions of rabbit aortic rings has been examined in Krebs-Henseleit buffer containing either 4.0 or 6.8 mM potassium. BAY K 8644 (10(-8) to 10(-6) M) alone induced slowly developing aortic contractures which were 10 (at 4.0 mM potassium) or 20 (at 6.8 mM potassium) percent of the maximum obtainable with norepinephrine. These contractions were not observed in every experiment, but were more likely to occur at 6.8 mM (71% at 10(-6) M BAY K 8644) when compared to 4.0 mM (31% at 10(-6) M BAY K 8644) potassium buffer. BAY K 8644, in either potassium buffer, induced a statistically significant shift to the left in the norepinephrine dose-response curve. The norepinephrine dose-response curve was significantly curvilinear in the presence of 3 X 10(-8) M BAY K 8644 (6.8 mM potassium) and 10(-6) M BAY K 8644 (4.0 mM potassium). Similarly, BAY K 8644 induced sinistral shifts in the KCl dose-response curve with a curvilinear function observed at 3 X 10(-7) M BAY K 8644. These data show that BAY K 8644 is capable of inducing aortic contractures at potassium concentrations significantly lower than previously reported. Furthermore, BAY K 8644 facilitates opening of calcium channels by either potassium or norepinephrine. In contrast to others, our data indicates that BAY K 8644 can affect calcium channels activated by norepinephrine. Finally, our data suggest that the alpha and dihydropyridine receptors are capable of interacting and that occupation of one receptor can affect the action of a compound binding to the other receptor.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗